污水处理的英文文献翻译
污水处理工业废水回用中英文对照外文翻译文献
污水处理工业废水回用中英文对照外文翻译文献XXX and resource recovery in us industries。
and they are of significant XXX-catalysis has been well established for water recovery and reuse。
chemo-catalysis is only starting to make an XXX-catalytic processes for water reuse。
XXX。
XXX.2.Chemo-XXX reuseChemo-XXX。
including XXX。
One of the most promising ns of chemo-XXX。
XXX。
This process has been shown to be effective in removing COD (chemical oxygen demand) XXX.3.XXX COD removalXXX treatment。
The process involves the use of a XXX can be a metal oxide or a metal complex。
and the oxidizing agent can be hydrogen peroxide。
ozone。
or XXX mild ns。
and the process is XXX.4.XXXXXX (AOPs) such as XXX。
photo-Fenton n。
and electro-XXX include the use of anic frameworks (MOFs) XXX.5.nIn n。
chemo-catalytic processes。
XXX。
XXX。
such as AOPs。
MOFs。
and nanomaterials。
污水处理工业废水回用中英文对照外文翻译文献
(文档含英文原文和中文翻译)中英文资料对照外文翻译Catalytic strategies for industrial water re-useAbstractThe use of catalytic processes in pollution abatement and resource recovery is widespread and of significant economic importance [R.J. Farrauto, C.H. Bartholomew, Fundamentals of Industrial Catalytic Processes, Blackie Academic and Professional,1997.]. For water recovery and re-use chemo-catalysis is only just starting to make an impact although bio-catalysis is well established [J.N. Horan, BiologicalWastewater Treatment Systems; Theory and Operation, Chichester, Wiley,1990.]. This paper will discuss some of the principles behind developing chemo-catalytic processes for water re-use. Within this context oxidative catalytic chemistry has many opportunities to underpin the development of successful processes and many emerging technologies based on this chemistry can be considered .Keywords: COD removal; Catalytic oxidation; Industrial water treatment1.IntroductionIndustrial water re-use in Europe has not yet started on the large scale. However, with potential long term changes in European weather and the need for more water abstraction from boreholes and rivers, the availability of water at low prices will become increasingly rare. As water prices rise there will come a point when technologies that exist now (or are being developed) will make water recycle and re-use a viable commercial operation. As that future approaches, it is worth stating the most important fact about wastewater improvement–avoid it completely if at all possible! It is best to consider water not as a naturally available cheap solvent but rather, difficult to purify, easily contaminated material that if allowed into the environment will permeate all parts of the biosphere. A pollutant is just a material in the wrong place and therefore design your process to keep the material where it should be –contained and safe. Avoidance and then minimisation are the two first steps in looking at any pollutant removal problem. Of course avoidance may not be an option on an existing plant where any changes may have large consequences for plant items if major flowsheet revision were required. Also avoidance may mean simply transferring the issue from the aqueous phase to the gas phase. There are advantages and disadvantages to both water and gas pollutant abatement. However, it must be remembered that gas phase organic pollutant removal (VOC combustion etc.,) is much more advanced than the equivalent water COD removal and therefore worth consideration [1]. Because these aspects cannot be over-emphasised，a third step would be to visit the first two steps again. Clean-up is expensive, recycle and re-use even if you have a cost effective process is still more capital equipment that will lower your return on assets and make the process less financially attractive. At present the best technology for water recycle is membrane based. This is the only technology that will produce a sufficiently clean permeate for chemical process use. However, the technology cannot be used in isolation and in many (all) cases will require filtration upstream and a technique for handling the downstream retentate containing the pollutants. Thus, hybrid technologies are required that together can handle the all aspects of the water improvement process[6,7,8].Hence the general rules for wastewater improvement are:1. Avoid if possible, consider all possible ways to minimise.2. Keep contaminated streams separate.3. Treat each stream at source for maximum concentration and minimum flow.4. Measure and identify contaminants over complete process cycle. Look for peaks, which will prove costly to manage and attempt to run the process as close to typical values as possible. This paper will consider the industries that are affected by wastewater issues and the technologies that are available to dispose of the retentate which will contain the pollutants from the wastewater effluent. The paper will describe some of the problems to be overcome and how the technologies solve these problems to varying degrees. It will also discuss how the cost driver should influence developers of future technologies.2. The industriesThe process industries that have a significant wastewater effluent are shown in Fig. 1. These process industries can be involved in wastewater treatment in many areas and some illustrations of this are outlined below.Fig. 1. Process industries with wastewater issues.2.1. RefineriesThe process of bringing oil to the refinery will often produce contaminated water. Oil pipelines from offshore rigs are cleaned with water; oil ships ballast with water and the result can be significant water improvement issues.2.2. ChemicalsThe synthesis of intermediate and speciality chemicals often involve the use of a water wash step to remove impurities or wash out residual flammable solvents before drying.2.3. PetrochemicalsEthylene plants need to remove acid gases (CO2, H2S) formed in the manufacture process. This situation can be exacerbated by the need to add sulphur compounds before the pyrolysis stage to improve the process selectivity. Caustic scrubbing is the usual method and this produces a significant water effluent disposal problem.2.4. Pharmaceuticals and agrochemicalsThese industries can have water wash steps in synthesis but in addition they are often formulated with water-based surfactants or wetting agents.2.5. Foods and beveragesClearly use water in processing and COD and BOD issues will be the end result.2.6. Pulp and paperThis industry uses very large quantities of water for processing –aqueous peroxide and enzymes for bleaching in addition to the standard Kraft type processing of the pulp. It is important to realise how much human society contributes tocontaminated water and an investigation of the flow rates through municipal treatment plants soon shows the significance of non-process industry derived wastewater.3. The technologiesThe technologies for recalcitrant COD and toxic pollutants in aqueous effluent are shown in Fig. 2. These examples of technologies [2,6,8] available or in development can be categorised according to the general principle underlying the mechanism of action. If in addition the adsorption (absorption) processes are ignored for this catalysis discussion then the categories are:1. Biocatalysis2. Air/oxygen based catalytic (or non-catalytic).3. Chemical oxidation1. Without catalysis using chemical oxidants2. With catalysis using either the generation of _OH or active oxygen transfer. Biocatalysis is an excellent technology for Municipal wastewater treatment providing a very cost-effective route for the removal of organics from water. It is capable of much development via the use of different types of bacteria to increase the overall flexibility of the technology. One issue remains –what to do with all the activated sludge even after mass reduction by de-watering. The quantities involved mean that this is not an easy problem to solve and re-use as a fertilizer can only use so much. The sludge can be toxic via absorption of heavy metals, recalcitrant toxic COD. In this case incineration and safe disposal of the ash to acceptable landfill may be required. Air based oxidation [6,7] is very attractive because providing purer grades of oxygen are not required if the oxidant is free. Unfortunately, it is only slightly soluble in water, rather unreactive at low temperatures and, therefore, needs heat and pressure to deliver reasonable rates of reaction. These plants become capital intensive as pressures (from _10 to 100 bar) are used. Therefore, although the running costs maybe low the initial capital outlay on the plant has a very significant effect on the costs of the process. Catalysis improves the rates of reaction and hence lowers the temperature and pressure but is not able to avoid them and hence does not offer a complete solution. The catalysts used are generally Group VIII metals such as cobalt or copper. The leaching of these metals into the aqueous phase is a difficulty that inhibits the general use of heterogeneous catalysts [7]. Chemical oxidation with cheap oxidants has been well practised on integrated chemical plants. The usual example is waste sodium hypochlorite generated in chlor-alkali units that can be utilised to oxidise COD streams from other plants within the complex. Hydrogen peroxide, chlorine dioxide, potassium permanganate are all possible oxidants in this type of process. The choice is primarily determined by which is the cheapest at the point of use. A secondary consideration is how effective is the oxidant. Possibly the mostresearched catalytic area is the generation and use of _OH as a very active oxidant (advanced oxidation processes) [8]. There are a variety of ways of doing this but the most usual is with photons and a photocatalyst. The photocatalyst is normally TiO2 but other materials with a suitable band gap can be used [9,10]. The processes can be very active however the engineering difficulties of getting light, a catalyst and the effluent efficiently contacted is not easy. In fact the poor efficiency of light usage by the catalyst (either through contacting problems or inherent to the catalyst) make this process only suitable for light from solar sources. Photons derived from electrical power that comes from fossil fuels are not acceptable because the carbon dioxide emission this implies far outweighs and COD abatement. Hydroelectric power (and nuclear power) are possible sources but the basic inefficiency is not being avoided. Hydrogen peroxide and ozone have been used with photocatalysis but they can be used separately or together with catalysts to effect COD oxidation. For ozone there is the problem of the manufacturing route, corona discharge, which is a capital intensive process often limits its application and better route to ozone would be very useful. It is important to note at this point that the oxidants discussed do not have sufficient inherent reactivity to be use without promotion. Thus, catalysis is central to their effective use against both simple organics (often solvents) or complex recalcitrant COD. Hence, the use of Fenton’s catalyst (Fe) for hydrogen peroxide [11]. In terms of catalysis these oxidants together with hypochlorite form a set of materials that can act has ‘active oxygen transfer (AOT) oxidants’ in the presence of a suitable catalyst. If the AOT oxidant is hypochlorite or hydrogen peroxide then three phase reactions are avoided which greatly simplifies the flowsheet. Cheap, catalytically promoted oxidants with environmentally acceptable products of oxidation that do not require complex chemical engineering and can be produced efficiently would appear to offer one of the best solutions to the general difficulties often observed.3.1. Redox catalysis and active oxygen transferThe mechanism of catalytically promoted oxidation with hydrogen peroxide or sodium hypochlorite cannot be encompassed within one concept, however there are general similarities between the two oxidants that allows one to write a series of reactions for both (Fig. 3) [5]. This type of mechanism could be used to describe a broad range of reactions for either oxidant from catalytic epoxidation to COD oxidation. The inherent usefulness of the reactions is that;1. The reactions take place in a two-phase system.2. High pressure and temperature are not required.3. The catalytic surface can act as an adsorbent of the COD to be oxidised effectively increasing the concentration and hence the rate of oxidation.The simple mechanism shows the selectivity issue with this type of processes. The oxidant can simply be decomposed by the catalyst to oxygen gas – this reaction must be avoided because dioxygen will play no role in COD removal. Its formation is an expensive waste of reagent with oxygen gas ($20/Te) compared to the oxidant ($400–600/Te). To be cost competitive with alternative processes redox catalysis needs excellent selectivity.3.2. Technology mappingThe technologies so far described can be mapped [12] for their applicability with effluent COD concentration (measured as TOC) and effluent flow rate (m3 h-1). The map is shown in Fig. 4. The map outlines the areas where technologies are most effective. The boundaries, although drawn, are in fact fuzzier and should be only used as a guide. Only well into each shape will a technology start to dominate. The underlying cost model behind the map is based on simple assertions – at high COD mass flows only air/oxygen will be able to keep costs down because of the relatively low variable cost of the oxidant. At high COD concentrations and high flows only biological treatment plants have proved themselves viable –of course if done at source recovery becomes an option. At low flows and low COD levels redox AOT catalysis is an important technology – the Synetix Accent 1 process being an example of this type of process (see Fig. 5 for a simplified flowsheet). The catalyst operates under very controlled conditions at pH > 9 and hence metal leaching can be avoided (<5 ppb). The activity and selectivity aspects of the catalyst displayed in Fig. 3 can be further elaborated to look at the potential surface species. This simple view has been extended by a significant amount of research [3,4,5]. Now the mechanism of such a catalyst can be described in Fig. 6. The key step is to avoid recombination of NiO holes to give peroxy species and this can be contrasted with the hydrogen peroxide situation where the step may be characterized as oxygen vacancy filled. From both recombination will be facilitated by electronic and spatial factors. The range of application of the process is outlined below. From laboratory data some general types of chemical have been found suitable –sulphides, amines, alcohols, ketones, aldehydes, phenols, carboxylic acids, olefins and aromatic hydrocarbons. From industrial trials recalcitrant COD (nonbiodegradable) and sulphur compounds have been successfully demonstrated and a plant oxidising sulphur species has been installed and is operational.4. ConclusionsWastewater treatment processes are in the early stages of development. The key parameters at present are effectiveness and long term reliability. Many processes operating are in this stage, including the redox Accent TM is a trademark of the ICIGroup of Companies. catalysis systems. However,once proven, redox catalysis offers many advantages for COD removal from wastewater:1. The low capital cost of installation.2. Simple operation that can be automated.3. Flexible nature of the process – can be easily modified to meet changing demands of legislation.Hence it will be expected to develop into an important technology in wastewater improvement.AcknowledgementsThe author is grateful to Jane Butcher and Keith Kelly of Synetix for discussions on this paper. References[1] R.J. Farrauto, C.H. Bartholomew, Fundamentals of Industrial Catalytic Processes, Blackie Academic and Professional, 1997. F.E. Hancock / Catalysis Today 53 (1999) 3–9 9[2] J.N. Horan, Biological Wastewater Treatment Systems; Theory and Operation, Chichester, Wiley, 1990.[3] F.E. Hancock et al., Catalysis Today 40 (1998) 289.[4] F. King, F.E. Hancock, Catal. Today 27 (1996) 203.[5] J. Hollingworth et al., J. Electron Spectrosc., in press.[6] F. Luck, Environmental Catalysis, in: G. Centi et al. (Eds.), EFCE Publishers, Series 112, p. 125.[7] D. Mantzavinos et al., in: V ogelpohl and Geissen (Eds.), in: Proceedings of the Conference on Water Science and Technology, Clausthal-Zellerfeld, Germany, May 1996, J. Int. Assoc. Water Quality, Pergamon, 1997.[8] R. Venkatadri, R.W. Peters, Hazardous Waste Hazardous Mater. 10 (1993) 107.[9] A.M. Braun, E. Oliveros, Water Sci. Tech. 35 (1997) 17.[10] D. Bahnemann et al., Aquatic and surface photochemistry, Am. Chem. Soc. Symp. Ser. (1994) 261.[11] J. Prousek, Chem. Lisy 89 (1995) 11.工业废水回用的接触反应策略摘要：无论从控制污染还是资源恢复的角度，接触反应都是被广泛应用并极具经济效益的。
污水处理工业废水回用中英文对照外文翻译文献
中英文资料对照外文翻译Catalytic strategies for industrial water re-useAbstractThe use of catalytic processes in pollution abatement and resource recovery is widespread and of significant economic importance [R.J. Farrauto, C.H. Bartholomew, Fundamentals of Industrial Catalytic Processes, Blackie Academic and Professional,1997.]. For water recovery and re-use chemo-catalysis is only just starting to make an impact although bio-catalysis is well established [J.N. Horan, BiologicalWastewater Treatment Systems; Theory and Operation, Chichester, Wiley, 1990.]. This paper will discuss some of the principles behind developing chemo-catalytic processes for water re-use. Within this context oxidative catalytic chemistry has many opportunities to underpin the development of successful processes and many emerging technologies based on this chemistry can be considered .Keywords: COD removal; Catalytic oxidation; Industrial water treatment1.IntroductionIndustrial water re-use in Europe has not yet started on the large scale. However, with potential long term changes in European weather and the need for more water abstraction from boreholes and rivers, the availability of water at low prices will become increasingly rare. As water prices rise there will come a point when technologies that exist now (or are being developed) will make water recycle and re-use a viable commercial operation. As that future approaches, it is worth stating the most important fact about wastewater improvement–avoid it completely if at all possible! It is best to consider water not as a naturally available cheap solvent but rather, difficult to purify, easily contaminated material that if allowed into the environment will permeate all parts of the biosphere. A pollutant is just a material in the wrong place and therefore design your process to keep the material where it should be –contained and safe. Avoidance and then minimisation are the two first steps in looking at any pollutant removal problem. Of course avoidance may not be anoption on an existing plant where any changes may have large consequences for plant items if major flowsheet revision were required. Also avoidance may mean simply transferring the issue from the aqueous phase to the gas phase. There are advantages and disadvantages to both water and gas pollutant abatement. However, it must be remembered that gas phase organic pollutant removal (VOC combustion etc.,) is much more advanced than the equivalent water COD removal and therefore worth consideration [1]. Because these aspects cannot be over-emphasised，a third step would be to visit the first two steps again. Clean-up is expensive, recycle and re-use even if you have a cost effective process is still more capital equipment that will lower your return on assets and make the process less financially attractive. At present the best technology for water recycle is membrane based. This is the only technology that will produce a sufficiently clean permeate for chemical process use. However, the technology cannot be used in isolation and in many (all) cases will require filtration upstream and a technique for handling the downstream retentate containing the pollutants. Thus, hybrid technologies are required that together can handle the all aspects of the water improvement process[6,7,8].Hence the general rules for wastewater improvement are:1. Avoid if possible, consider all possible ways to minimise.2. Keep contaminated streams separate.3. Treat each stream at source for maximum concentration and minimum flow.4. Measure and identify contaminants over complete process cycle. Look for peaks, which will prove costly to manage and attempt to run the process as close to typical values as possible. This paper will consider the industries that are affected by wastewater issues and the technologies that are available to dispose of the retentate which will contain the pollutants from the wastewater effluent. The paper will describe some of the problems to be overcome and how the technologies solve these problems to varying degrees. It will also discuss how the cost driver should influence developers of future technologies.2. The industriesThe process industries that have a significant wastewater effluent are shown in Fig. 1. These process industries can be involved in wastewater treatment in many areas and some illustrations of this are outlined below.Fig. 1. Process industries with wastewater issues.2.1. RefineriesThe process of bringing oil to the refinery will often produce contaminated water. Oil pipelines from offshore rigs are cleaned with water; oil ships ballast with water and the result can be significant water improvement issues.2.2. ChemicalsThe synthesis of intermediate and speciality chemicals often involve the use of a water wash step to remove impurities or wash out residual flammable solvents before drying.2.3. PetrochemicalsEthylene plants need to remove acid gases (CO2, H2S) formed in the manufacture process. This situation can be exacerbated by the need to add sulphur compounds before the pyrolysis stage to improve the process selectivity. Caustic scrubbing is the usual method and this produces a significant water effluent disposal problem.2.4. Pharmaceuticals and agrochemicalsThese industries can have water wash steps in synthesis but in addition they are often formulated with water-based surfactants or wetting agents.2.5. Foods and beveragesClearly use water in processing and COD and BOD issues will be the end result.2.6. Pulp and paperThis industry uses very large quantities of water for processing –aqueous peroxide and enzymes for bleaching in addition to the standard Kraft type processing of the pulp. It is important to realise how much human society contributes to contaminated water and an investigation of the flow rates through municipal treatment plants soon shows the significance of non-process industry derived wastewater.3. The technologiesThe technologies for recalcitrant COD and toxic pollutants in aqueous effluent are shown in Fig. 2. These examples of technologies [2,6,8] available or in development can be categorised according to the general principle underlying the mechanism of action. If in addition the adsorption (absorption) processes are ignored for this catalysis discussion then the categories are:1. Biocatalysis2. Air/oxygen based catalytic (or non-catalytic).3. Chemical oxidation1. Without catalysis using chemical oxidants2. With catalysis using either the generation of _OH or active oxygen transfer. Biocatalysis is an excellent technology for Municipal wastewater treatment providing a very cost-effective route for the removal of organics from water. It is capable of much development via the use of different types of bacteria to increase the overall flexibility of the technology. One issue remains –what to do with all the activated sludge even after mass reduction by de-watering. The quantities involved mean that this is not an easy problem to solve and re-use as a fertilizer can only use so much. The sludge can be toxic via absorption of heavy metals, recalcitrant toxic COD. Inthis case incineration and safe disposal of the ash to acceptable landfill may be required. Air based oxidation [6,7] is very attractive because providing purer grades of oxygen are not required if the oxidant is free. Unfortunately, it is only slightly soluble in water, rather unreactive at low temperatures and, therefore, needs heat and pressure to deliver reasonable rates of reaction. These plants become capital intensive as pressures (from _10 to 100 bar) are used. Therefore, although the running costs maybe low the initial capital outlay on the plant has a very significant effect on the costs of the process. Catalysis improves the rates of reaction and hence lowers the temperature and pressure but is not able to avoid them and hence does not offer a complete solution. The catalysts used are generally Group VIII metals such as cobalt or copper. The leaching of these metals into the aqueous phase is a difficulty that inhibits the general use of heterogeneous catalysts [7]. Chemical oxidation with cheap oxidants has been well practised on integrated chemical plants. The usual example is waste sodium hypochlorite generated in chlor-alkali units that can be utilised to oxidise COD streams from other plants within the complex. Hydrogen peroxide, chlorine dioxide, potassium permanganate are all possible oxidants in this type of process. The choice is primarily determined by which is the cheapest at the point of use. A secondary consideration is how effective is the oxidant. Possibly the most researched catalytic area is the generation and use of _OH as a very active oxidant (advanced oxidation processes) [8]. There are a variety of ways of doing this but the most usual is with photons and a photocatalyst. The photocatalyst is normally TiO2 but other materials with a suitable band gap can be used [9,10]. The processes can be very active however the engineering difficulties of getting light, a catalyst and the effluent efficiently contacted is not easy. In fact the poor efficiency of light usage by the catalyst (either through contacting problems or inherent to the catalyst) make this process only suitable for light from solar sources. Photons derived from electrical power that comes from fossil fuels are not acceptable because the carbon dioxide emission this implies far outweighs and COD abatement. Hydroelectric power (and nuclear power) are possible sources but the basic inefficiency is not being avoided. Hydrogen peroxide and ozone have been used with photocatalysis but they can be used separately or together with catalysts to effect COD oxidation. For ozone there is the problem of the manufacturing route, corona discharge, which is a capital intensive process often limits its application and better route to ozone would be very useful. It is important to note at this point that the oxidants discussed do not have sufficient inherent reactivity to be use without promotion. Thus, catalysis is central to their effective use against both simple organics (often solvents) or complex recalcitrant COD. Hence, the use of Fenton’s catalyst (Fe) for hydrogen peroxide [11]. In terms of catalysis these oxidants together with hypochlorite form a set of materials that can acthas ‘active oxygen transfer (AOT) oxidants’ in the presence of a suitable catalyst. If the AOT oxidant is hypochlorite or hydrogen peroxide then three phase reactions are avoided which greatly simplifies the flowsheet. Cheap, catalytically promoted oxidants with environmentally acceptable products of oxidation that do not require complex chemical engineering and can be produced efficiently would appear to offer one of the best solutions to the general difficulties often observed.3.1. Redox catalysis and active oxygen transferThe mechanism of catalytically promoted oxidation with hydrogen peroxide or sodium hypochlorite cannot be encompassed within one concept, however there are general similarities between the two oxidants that allows one to write a series of reactions for both (Fig. 3) [5]. This type of mechanism could be used to describe a broad range of reactions for either oxidant from catalytic epoxidation to COD oxidation. The inherent usefulness of the reactions is that;1. The reactions take place in a two-phase system.2. High pressure and temperature are not required.3. The catalytic surface can act as an adsorbent of the COD to be oxidised effectively increasing the concentration and hence the rate of oxidation.The simple mechanism shows the selectivity issue with this type of processes. The oxidant can simply be decomposed by the catalyst to oxygen gas – this reaction must be avoided because dioxygen will play no role in COD removal. Its formation is an expensive waste of reagent with oxygen gas ($20/Te) compared to the oxidant ($400–600/Te). To be cost competitive with alternative processes redox catalysis needs excellent selectivity.3.2. Technology mappingThe technologies so far described can be mapped [12] for their applicability with effluent COD concentration (measured as TOC) and effluent flow rate (m3 h-1). The map is shown in Fig. 4. The map outlines the areas where technologies are most effective. The boundaries, although drawn, are in fact fuzzier and should be only used as a guide. Only well into each shape will a technology start to dominate. The underlying cost model behind the map is based on simple assertions – at high COD mass flows only air/oxygen will be able to keep costs down because of the relatively low variable cost of the oxidant. At high COD concentrations and high flows only biological treatment plants have proved themselves viable –of course if done at source recovery becomes an option. At low flows and low COD levels redox AOT catalysis is an important technology – the Synetix Accent 1 process being an example of this type of process (see Fig. 5 for a simplified flowsheet). The catalyst operates under very controlled conditions at pH > 9 and hence metal leaching can be avoided (<5 ppb). The activity and selectivity aspects of the catalyst displayed in Fig. 3 can befurther elaborated to look at the potential surface species. This simple view has been extended by a significant amount of research [3,4,5]. Now the mechanism of such a catalyst can be described in Fig. 6. The key step is to avoid recombination of NiO holes to give peroxy species and this can be contrasted with the hydrogen peroxide situation where the step may be characterized as oxygen vacancy filled. From both recombination will be facilitated by electronic and spatial factors. The range of application of the process is outlined below. From laboratory data some general types of chemical have been found suitable –sulphides, amines, alcohols, ketones, aldehydes, phenols, carboxylic acids, olefins and aromatic hydrocarbons. From industrial trials recalcitrant COD (nonbiodegradable) and sulphur compounds have been successfully demonstrated and a plant oxidising sulphur species has been installed and is operational.4. ConclusionsWastewater treatment processes are in the early stages of development. The key parameters at present are effectiveness and long term reliability. Many processes operating are in this stage, including the redox Accent TM is a trademark of the ICI Group of Companies. catalysis systems. However,once proven, redox catalysis offers many advantages for COD removal from wastewater:1. The low capital cost of installation.2. Simple operation that can be automated.3. Flexible nature of the process – can be easily modified to meet changing demands of legislation.Hence it will be expected to develop into an important technology in wastewater improvement.AcknowledgementsThe author is grateful to Jane Butcher and Keith Kelly of Synetix for discussions on this paper. References[1] R.J. Farrauto, C.H. Bartholomew, Fundamentals of Industrial Catalytic Processes, Blackie Academic and Professional, 1997. F.E. Hancock / Catalysis Today 53 (1999) 3–9 9[2] J.N. Horan, Biological Wastewater Treatment Systems; Theory and Operation, Chichester, Wiley, 1990.[3] F.E. Hancock et al., Catalysis Today 40 (1998) 289.[4] F. King, F.E. Hancock, Catal. Today 27 (1996) 203.[5] J. Hollingworth et al., J. Electron Spectrosc., in press.[6] F. Luck, Environmental Catalysis, in: G. Centi et al. (Eds.), EFCE Publishers, Series 112, p. 125.[7] D. Mantzavinos et al., in: V ogelpohl and Geissen (Eds.), in: Proceedings of the Conference on Water Science and Technology, Clausthal-Zellerfeld, Germany, May 1996, J. Int. Assoc. Water Quality, Pergamon, 1997.[8] R. Venkatadri, R.W. Peters, Hazardous Waste Hazardous Mater. 10 (1993) 107.[9] A.M. Braun, E. Oliveros, Water Sci. Tech. 35 (1997) 17.[10] D. Bahnemann et al., Aquatic and surface photochemistry, Am. Chem. Soc. Symp. Ser. (1994) 261.[11] J. Prousek, Chem. Lisy 89 (1995) 11.工业废水回用的接触反应策略摘要：无论从控制污染还是资源恢复的角度，接触反应都是被广泛应用并极具经济效益的。
污水处理的英文文献翻译(1)
Nutrient removal in an A2O-MBR reactor with sludgereductionABSTRACTIn the present study, an advanced sewage treatment process has been developed by incorporating excess sludge reduction and phosphorous recovery in an A2O-MBR process. The A2O-MBR reactor was operated at a flux of 77 LMH over a period of 270 days. The designed flux was increased stepwise over a period of two weeks. The reactor was operated at two different MLSS range. Thermo chemical digestion of sludge was carried out at a fixed pH (11)and temperature (75℃) for 25% COD solubilisation. The released pbospborous was recovered by precipitation process and the organics was sent back to anoxic tank. The sludge digestion did not have any impact on COD and TP removal efficiency of the reactor. During the 270 days of reactor operation, the MBR maintained relatively constant transmembrane pressure. The results based on the study indicated that the proposed process configuration has potential to reduce the excess sludge production as well as it didn't detonated the treated water quality.Keywords: A2O reactor; MBR; Nutrient removal; TMP1. IntroductionExcess sludge reduction and nutrients removal are the two important problems associated with wastewater treatment plant. MBR process has been known as a process with relatively high decay rate and less sludge production due to much longer sludge age in the reactor (Wenet al., 2004). Sludge production in MBR is reduced by 28-68%, depending on the sludge age used (Xia et al.,2008). However, minimizing the sludge production by increasing sludge age is limited due to the potential adverse effect of high MLSS concentrations on membrane (Yoon et al., 2004). This problem can be solved by introducing sludge disintegration technique in MBR (Young et al., 2007). Sludge disintegration techniques have been reported to enhance the biodegradability of excess sludge (Vlyssides and Karlis, 2004). In overall, the basis for sludge reduction processes is effective combination of the methods for sludge disintegration and biodegradation of treated sludge. Advances in sludge disintegration techniques offer a few promising options including ultrasound (Guo et al., 2008), pulse power (Choi et al.,2006), ozone (Weemaes et al., 2000), thermal (Kim et al., 2003), alkaline (Li et al., 2008) acid (Kim et al., 2003) and thermo chemical(Vlyssides and Karlis, 2004). Among the various disintegration techniques, thermo chemical was reported to be simple and cost effective (Weemaes and Verstraete, 1998). In thermal-chemical hydrolysis, alkali sodium hydroxide was found to be the most effective agent in inducing cell lysis (Rocker et al., 1999). Conventionally, the nutrient removal was carried out in an A2O process. It has advantage of achieving, nutrient removal along with organic compound oxidation in a single sludge configuration using linked reactors in series (Tchobanoglous et al., 2003). The phosphoroes removal happens by subjecting phosphorous accumulating organisms (PAO) bacteria under aerobic and anaerobic conditions (Akin and Ugurlu, 2004). These operating procedures enhance predominance PAO, which are able to uptake phosphorous in excess. During the sludge pretreatment processes the bound phosphorous was solubilised and it increases the phosphorousconcentration in the effluent stream (Nishimura, 2001).So, it is necessary to remove the solubilised phosphorus before it enters into main stream. Besides, there is a growing demand for the sustainable phosphorous resources in the industrialized world. In many developed countries, researches are currently underway to recover the phosphoroes bound in the sludge's of enhanced biological phosphorus removal system (EBPR). The released phosphorous can be recovered in usable products using calcium salts precipitation method. Keeping this fact in mind, in the present study, a new advanced wastewater treatment process is developed by integrating three processes, which are: (a) thermo chemical pretreatment in MBR for excess sludge reduction (b) A2O process for biological nutrient removal (c) P recovery through calcium salt precipitation. The experimental data obtained were then used to evaluate the performance of this integrated system.2. Methods2.1. WastewaterThe synthetic domestic wastewater was used as the experimental influent. It was basically composed of a mixed carbon source, macro nutrients (N and P), an alkalinity control (NaHCO3) and a microelement solution. The composition contained (/L) 210 mg glucose, 200 mg NH4C1, 220 mg NaHCO3, 22一34 mg KH2PO4, microelement solution (0.19 mg MnCl2 4H20, 0.0018 mg ZnCl22H2O,0.022 mg CuCl22H2O, 5.6 mg MgSO47H2O, 0.88 mg FeCl36H2O,1.3 mg CaCl2·2H2O). The synthetic wastewater was prepared three times a week with concentrations of 210±1.5 mg/L chemical oxygen demand (COD), 40±1 mg/L total nitrogen (TN) and 5.5 mg/L total phosphorus (TP).2.2. A2O-MBRThe working volume of the A2O-MBR was 83.4 L. A baffle was placed inside the reactor to divide it into anaerobic (8.4 L) anoxic (25 L) and aerobic basin (50 L). The synthetic wastewater was feed into the reactor at a flow rate of 8.4 L/h (Q) using a feed pump. A liquid level sensor, planted in aerobic basin of A2O-MBR controlled the flow of influent. The HRT of anaerobic, anoxic and aerobic basins were 1, 3 and 6 h, respectively. In order to facilitate nutrient removal, the reactor was provided with two internal recycle (1R). IRl (Q= 1)connects anoxic and anaerobic and IR 2 (Q=3) was between aerobic and anoxic. Anaerobic and anoxic basins were provided with low speed mixer to keep the mixed liquid suspended solids (MLSS) in suspension. In the aerobic zone, diffusers were used to generate air bubbles for oxidation of organics and ammonia. Dissolved oxygen (DO) concentration in the aerobic basin was maintained at 3.5 mg/1 and was monitored continuously through online DO meter. The solid liquid separation happens inaerobic basin with the help of five flat sheet membranes having a pore size of 0.23 pm. The area of each membrane was 0.1 m2. They were connected together by a common tube. A peristaltic pumpwas connected in the common tube to generate suction pressure. In the common tube provision was made to accommodate pressure gauge to measure transmembrane pressure (TMP) during suction. The suction pump was operated in sequence of timing, which consists of 10 min switch on, and 2 min switch off.2.3. Thermo chemical digestion of sludgeMixed liquor from aerobic basin of MBR was withdrawn at the ratio of 1.5% of Q/day and subjected to thermo chemical digestion. Thermo chemical digestion was carried out at a fixed pH of 11(NaOH) and temperature of 75℃for 3 h. After thermo chemical digestion the supernatant and sludge were separated. The thermo-chemicallydigested sludge was amenable to further anaerobic bio-degradation (Vlyssides and Karlis, 2004), so it was sent to theanaerobic basin of the MBR2.4. Phosphorus recoveryLime was used as a precipitant to recover the phosphorous in the supernatant. After the recovery of precipitant the content was sent back to anoxic tank as a carbon source and alkalinity supelement for denitrification.2.5. Chemical analysisCOD, MLSS, TP, TN of the raw and treated wastewater were analyzed following methods detailed in (APHA, 2003). The influent and effluent ammonia concentration was measured using an ion-selective electrode (Thereto Orion, Model: 95一12). Nitrate in the sample was analyzed using cadmium reduction method (APHA, 2003).3. Results and discussionFig. 1 presents data of MLSS and yield observed during the operational period of the reactor. One of the advantages of MBR reactor was it can be operated in high MLSS concentration. The reactor was seeded with EBPR sludge from the Kiheung, sewage treatment plant, Korea. The reactor was startup with the MLSS concentration of 5700 mg/L. It starts to increase steadily with increase in period of reactor operation and reached a value of 8100 mg/L on day 38. From then onwards, MLSS concentration was maintained in the range of 7500 mg/L by withdrawing excess sludge produced and called run I. The observed yields (Yobs) for experiments without sludge digestion (run I) and with sludge digestion were calculated and given in Fig. 1. The Yobs for run I was found to be 0.12 gMLSS/g COD. It was comparatively lower than a value of 0.4 gMLSS/g CODreported for the conventional activated sludge processes (Tchoba-noglous et al., 2003). The difference in observed yield of these two systems is attributed to their working MLSS concentration. At high MLSS concentration the yield observed was found to be low (Visva-nathan et al., 2000). As a result of that MBR generated less sludge.The presently used MLSS ranges (7.5一10.5 g/L) are selected on the basis of the recommendation by Rosenberger et al. (2002). In their study, they reported that the general trend of MLSS increase on fouling in municipal applications seems to result in no impact at medium MLSS concentrations (7一12 g/L).It is evident from the data that the COD removal efficiency of A2O system remains unaffected before and after the introduction of sludge digestion practices. A test analysis showed that the differences between the period without sludge digestion (run I) and with sludge digestion (run II and III) are not statistically significant.However, it has been reported that, in wastewater treatment processes including disintegration-induced sludge degradation, the effluent water quality is slightly detonated due to the release of nondegradable substances such as soluble microbial products (Ya-sui and Shibata, 1994; Salcai et al., 1997; Yoon et al., 2004). During the study period, COD concentration in the aerobic basin of MBR was in the range of 18-38 mg/L and corresponding organic concentration in the effluent was varied from 4 to 12 mg/L. From this data it can be concluded that the membrane separation played an important role in providing the excellent and stable effluent quality.Phosphorus is the primary nutrient responsible for algal bloom and it is necessary to reduce the concentration of phosphorus in treated wastewater to prevent the algal bloom. Fortunately its growth can be inhibited at the levels of TP well below 1 mg/L (Mer-vat and Logan, 1996).Fig. 2 depicts TP removal efficiency of the A2O-MBR system during the period of study. It is clearly evident from the figure that the TP removal efficiency of A/O system was remains unaffected after the introduction of sludge reduction. In the present study, the solubilised phosphorous was recovered in the form of calcium phosphate before it enters into main stream. So, the possibility of phosphorus increase in the effluent due to sludge reduction practices has been eliminated. The influent TP concentration was in the range of 5.5 mg/L. During thefirst four weeks of operation the TP removal efficiency of the system was not efficient as the TP concentration in the effluent exceeds over 2.5 mg/L. The lower TP removal efficiency during the initial period was due to the slow growing nature of PAO organisms and other operational factors such as anaerobic condition and internal recycling. After the initial period, the TP removal efficiency in the effluent starts to increase with increase in period of operation. TP removal in A2O process is mainly through PAO organisms. These organisms are slow growing in nature and susceptible to various physicochemical factors (Carlos et al., 2008). During the study period TP removal efficiency of the system remains unaffected and was in the range of 74-82%.。
污水处理外文翻译---污水的生物处理过程
污水处理外文翻译---污水的生物处理过程XXX to a level where the discharge of effluent will not harm the XXX only needs to be to a required level。
The degree andtype of treatment for a specific XXX。
The degree of treatment often depends on the XXX so that the DO of the receiving water is not depressed too far。
The amount of BOD that must be XXX.XXX。
let's assume a "XXX: BOD ≤ 15mg/L。
SS ≤ 15mg/L。
and P ≤ 1mg/L.XXX-XXX。
Secondary treatment。
on the other hand。
is a logical process that XXX。
Finally。
XXX of physical。
logical。
and chemical XXX。
While there could have been nal effluent standards established。
we will focus on these three for XXX.The third step in XXX grit and sand。
These substances can cause damage to equipment such as pumps and flow meters。
so itis crucial to remove them。
The most common method for removing grit is through a grit chamber。
关于污水处理的英语作文
关于污水处理的英语作文英文回答：Importance of Wastewater Treatment in Protecting Environmental and Human Health.Wastewater treatment plays a pivotal role in safeguarding both environmental and human well-being. Untreated or inadequately treated wastewater can pose significant threats to human health and the environment, leading to water contamination, disease outbreaks, and ecological degradation.Water Contamination: Wastewater contains a complex mixture of pollutants, including pathogenic microorganisms, organic matter, and toxic chemicals. When released into water bodies, these pollutants can contaminate drinking water sources, making them unsafe for human consumption and leading to waterborne diseases such as cholera, typhoid, and gastroenteritis.Disease Outbreaks: Untreated wastewater can create breeding grounds for disease-carrying organisms such as bacteria, viruses, and parasites. These organisms can transmit diseases to humans through direct contact with contaminated water or indirect exposure via contaminated food or drinking water.Ecological Degradation: Wastewater discharge can disrupt aquatic ecosystems by altering water chemistry, increasing nutrient levels, and introducing harmful pollutants. This can lead to eutrophication, resulting in algal blooms, loss of biodiversity, and declines in fisheries.Economic Impacts: The consequences of wastewater contamination extend beyond health and environmental concerns. It can also have significant economic impacts. Contaminated water supplies can lead to costly treatment and purification efforts, and can also reduce tourism and recreational activities that rely on clean water.Benefits of Wastewater Treatment:Wastewater treatment plays a crucial role in mitigating these risks and ensuring the safety and sustainability of our water resources. By removing pollutants from wastewater, treatment plants help to protect public health, the environment, and the economy.Public Health Protection: Wastewater treatment plants use a combination of physical, chemical, and biological processes to remove contaminants from wastewater. These processes effectively reduce the presence of pathogens, organic matter, and toxic chemicals, making the treated water safe for discharge into water bodies or reuse in irrigation or industrial applications.Environmental Protection: Wastewater treatment helps to preserve the integrity of aquatic ecosystems by reducing nutrient pollution and the discharge of harmful chemicals. This prevents eutrophication, supports biodiversity, and ensures the continued productivity of fisheries.Water Resource Conservation: By treating wastewater to a level suitable for reuse or discharge, wastewater treatment plants conserve valuable water resources. This is particularly important in arid or semi-arid regions where water availability is scarce.Challenges and Innovations:Despite the significant benefits of wastewater treatment, there are also challenges that need to be addressed. These include:Energy Consumption: Wastewater treatment processes can be energy-intensive, especially when using conventional technologies. Innovations in energy-efficient technologies are crucial to minimize the environmental footprint of treatment plants.Emerging Contaminants: Over time, new emerging contaminants such as pharmaceuticals and microplastics have been detected in wastewater streams. These compounds can pose unique challenges for traditional treatment methods,requiring research and development of innovative removal strategies.Climate Change: Climate change is expected to affect wastewater treatment infrastructure, particularly incoastal areas vulnerable to sea level rise and storm surges. Adaptation measures are necessary to ensure the resilienceof treatment plants in the face of changing climate conditions.Conclusion:Wastewater treatment is a vital process for protecting environmental and human health, ensuring the safety of our water resources, and supporting economic development. By investing in wastewater treatment infrastructure and continuing to innovate in more efficient and sustainable technologies, societies can mitigate the risks associated with untreated wastewater and create a healthier and more sustainable future.中文回答：污水处理在保护环境和人类健康中的重要性。
污水处理外文翻译带原文
Study on Disinfection and Anti –microbial Technologies for Drinking WaterZHU Kun, FU Xiao Yong(Dept. of Environmental Engineering, LAN Zhou Railway University, LAN Zhou 730070, China)Abstract: Disinfection by-products produced by the reaction between chlorine and dissolved organic compounds and other chemicals are considered as a worrying problem in the drinking water treatment process since a series of mutagenic carcinogen substances are formed including trihalomethanes (THMs). Among the tested disinfectants(chlorine , ozone , chlorine dioxide , potassium permanganate , chloramines and hydrogen peroxide etc. ) , chlorine dioxide has proved to be the most feasible and effective oxidant for drinking water treatment and removal of pathogens due to its oxidation efficiency , low cost and simple way of utilization. A series of experiments indicate that chlorine dioxide can significantly restrain production of trihalomethanes (THMs) and control bacteria growth particularly for Cryptosporidium oocysts. The experiments verified that both ozone and chlorine dioxide are absolutely vital to ensure thtion of water storage are destroyed. The paper discusses oxidation capacity of chlorine dioxide, especially for removing petroleum compounds, which is affected by reaction time, gas injection way, and pH of treated water.Key words: disinfection; oxidants; water treatment; pathogens; chlorine dioxideCLC number: X523 Document code: A1 IntroductionChemical and filtration processes are two main methods used in China for treating drinking water meanwhile UV radiation has been used successfully for water treatment with relatively low flow rate. On the individual family level, usually chemical treatment is a feasible alternative. The following guidelines exist for the selection of suitablal of contaminants should be done by decomposition, evaporation or precipitation etc, to eliminate or decrease the toxicity, oxidants or reactionby-products should not be harmful to human health, and the purification processes should be practical and economical. The objective of this paper is to evaluate and discuss available disinfectants for drinking water treatment. The different disinfectants are compared regarding purification efficiencies and application approaches.2 Comparison ofO3 > ClO2 > HOCl > OCl - > NHCl2 > NH2ClReferring to Fiessinger′s [2] suggestion, the properties of these disinfectants are compared in Tab. 1. Chlorine is shown to be an excellent disinfectant to prevent waterborne diseases such as typhoid fever over long periods. Chlorine reacts not only within oxidation, but also by electrophilic substitution to produce a variety of chlorinated organic by - products, particularly trihalomethanes (THMs) and other mutagens. Here THMs mainly refer to chloroform, bromoform, dibromochloromathane and bromodichloromathane etc. Since the 1970`s, the usage of Cl2 in drinking water disinfection has been questioned with ozone being substituted as the preferred disinfectant in the water supply plants. But , ozone could not be introduced to the rural farmer community due to its high costs and short half - life (15～20 min. ) . As with other disinfectants, ozonation also leads to formation of organic by - product s such as aldehyde, ketones, and carboxylic acids, and also mutagenicity may be induced if bromic anion exists.Tab. 1 Comparison of various oxidants- no effect ; + little effect ; + + effect ; + + + largest effectMany studies have pointed out that disinfection is absolutely vital to ensure that any microorganisms arising from fecal contamination of water storage are destroyed. The selection of the available disinfectant s must concern to reduce risk from microbial contamination of drinking water and the potential increase in risk from chemical contamination that result from using any of the disinfectant s. The biocidal efficiency of commonly used disinfectants - ozone, chlorine dioxide, chlorine and chloramines are ranked almost with the same order as the oxidizing capacity, but the stability of those are following the order as [3]:Chloramines > Chlorine dioxide > Chlorine > Ozone3 Purification of organic pollutants by chlorine dioxideAccording to WHO guideline for drinking water quality, much consideration should be paid to benzene homologous compounds; therefore, the study on purification effect s of chlorine dioxide is focused on petrochemical pollutants. A series of experiment s were carried out to simulate the oxidation processes of contaminated water. The polluted solutions were prepared in a dark barrel (10L capacity) of seven kinds of benzene homologous compounds-Benzene , toluene , ethyl benzene , p-phenylmethane, o-phenylmethane, m-phenylmethane and styrene. Samples were taken to determine the initial concentration of the compounds prior to the test s. Standard chlorine dioxide solution was produced from sodium chlorite reacted with HCl solution of 10% [4]. The GR - 16A Gas - chromatograph with FID detector Shenyang LZ-2000 was used for measurement of Cl2, ClO2, ClO-2 and ClO-3[5]. Oil concentrations were determined with an UV -120-20 spectrophotometer (Shimadzu) following the procedure described by APHA [4]. Organic compounds in the water samples were measured with a GC-MS (QP-1000A). ClO2and O3were standardized by iodimetric titration at pH7.For the purpose of chemical disinfection for drinking water, chlorine was instantaneously ignored due to the formation of THMs and other mutagenic substances. The results indicated that potassium permanganate and hydrogen peroxide did not have enough oxidation capability to decompose petroleum contaminant s achieving only 46 %, and 5.7% decomposition of styrene, respectively. Ozone could not be selected due to it s high cost, complex operation and short half-life although it is an excellent oxidant for water treatment. Chlorine dioxide was the next most successful alternative for disinfection. The benefit s include-effective oxidation capacity, algicidal effect and negligible formation of halogenated by-products. Based on economic and operational requirement, the mixing gas method is easily used. The results obtained suggest that disinfection of drinking water with ozone and or chlorine dioxide seems to be a suitable alternatives to the use of NaClO for cont rolling the formation of non-volatile mutagens[6].In the laboratory experiments, the oxidants ozone, chlorine dioxide, potassium permanganate and the mixing gas (mainly contained ClO2 and a certain amount of Cl2, O3 and H2O2) were tested for removal of the petroleum compounds, and results are shown in Tab. 2.Tab. 2 Comparison of oxidation capacity for the various oxidantsA study was conducted to elucidate the decay pathway of monochloramine in thepresence and absence of natural organic matter (NOM) [7]. It was found that natural organic matter acted primarily as a reductant rather than catalyst. This conclusion was verified using a redox balance, and much of oxidizing capacity of monochloramine goes towards NOM oxidation. Cleaning agents and disinfectants from house keeping, hospitals, kitchens are sources of absorbable halogenated organic compounds (AOX) in municipal wastewater. The amount of AOX generated strongly depends on the nature and concentrations of dissolved and solid organic compounds, the concentration of active substances, temperature, pH and reaction time [8] When the mixing gases react with water molecules and organic micro-pollutants, hypochlorous acid is formed by chlorine, chlorite and chlorate ions are produced from chlorine dioxide in a series of redox reactions. The principal reactions are summarized as follows:ClO2+ organic →ClO -² + oxidized organic (1)2ClO -² + Cl2 = 2ClO2 + 2Cl - (2)2ClO -²+ HOCl = 2ClO2 + 2Cl - + OH- (3)2ClO2 + HOCl + H2O = 2ClO - ³ + HCl + 2H+ (4)The rate of chlorate yield can be described by Equation (5):d [ClO3]/ d t = 2 k [ClO2] [HOCl] (5)in which k = 1.28 M/ min at 25 ℃ [9].The stoichiometry of the undesirable reactions that form chlorate in low concentration of chlorite or presents of excess chlorine is given as:ClO -² + Cl2 + H2O = ClO - ³ + 2Cl - + 2H+ (6)ClO - ² + HOCl = ClO - ³ + Cl - + H+ (7)At alkaline conditions:ClO -² + HOCl + OH- = ClO - ³ + Cl - + H2O (8)Typically, chlorine dioxide is used in drinking water treatment and the concentrations are ranging from 0.1 to 2.0 mg/L [10]. However, the relevant by - products of chlorine dioxide treatment-chlorite and chlorate have been found to induce methemoglobinemia in the human body when concentrations are more than 100 mg/L [11]. The oxidation results of the organic contaminants were affected byreaction time. The initial concentrations and removal rate at different times are listed in Tab. 3. It is shown that chlorine dioxide has a very strong oxidation capability including the break down of the benzene ring. There are no other commonly used oxidants to do like this except for ozone.Tab. 3 Removal rate of tested organic compounds at different operating time (at pH7)The injecting method for chlorine dioxide gas into the solution also has an apparent influence on the removal rate. With the indirect method, the gas firstly was dissolved in a certain amount of distilled water, and then added to the tested organic solutions, as a result, removal rates appear lower than for the direct blowing method. The main reason for the difference is due to the conversion and decomposition of chlorine dioxide in the dissolving process before the reaction. It is confirmed from Tab. 3 that the removal rate was proportional to operating time. Since chlorine dioxide showed very strong oxidation capability for organic chemicals but was reduced to chlorite anion according to Equation (4), and the removal rate initially appeared quite high. Then, chlorite keeps the oxidation capacity at a level, which allows decomposition of the organic compounds to continue even though the oxidation reaction gradually became weaker with reaction time. The experiment indicated that pH values significantly influenced the removal rate of the organic compounds. The differences of degradation rates in a variety of pH through indirect input way areshown in Tab. 4.Tab. 4 Degradation rate of benzene homologous compounds with indirect method at different pH (after 15 min)There are, however, some disadvantages with ClO2, such as easy loss from solution due to volatilization, and disproportionation above pH 10 into chlorate and chlorite ions that are of certain oxidation capacity, but reported to be harmful to health if the concentration is too high. Chlorine dioxide was unstable in the solution even though it has a stronger oxidation capability than chlorite and chlorate as the two resulted in anions being dominant in the oxidation processes. The actual concentration of chlorine dioxide depended on the existence of chlorine, chlorite and chlorate whose concentrations were determined by pH values of the solution according to Equations (6) and (8) respectively. Consequently, the pH is the critical controlling factor in the concentrations of chlorine dioxide, chlorite and chlorate. The latter two harmful ions can be removed quite quickly by treatment with a reducing agent such as sulfur dioxide - sulfite ion at pH values of 5～7[10 ,12]. Fe (II) can be used to eliminate chlorite from the water , and the redox reaction is kinetically more rapid at pH 5～7 as well[13]. It was evident that the decomposition in acidic conditions was much better than that in alkaline conditions because a disproportional amount of chlorine dioxide was consumed by the reactions under alkaline conditions. For drinking water treatment, it has been suggested that the mixture of chlorine 0.8 mg/L and chlorinedioxide 0.5 mg/L will achieve disinfection and control THMs formation in preference to use of pure chlorine dioxide[14]. According to USEPA drinking water standard, the residue of ClO2 is limited as 0.8 mg/L that tends to the goal of 0.4 mg/L.4 Control of pathogens with disinfectantsHuman pathogens that are transmitted by water including bacteria, viruses and protozoa. Organisms transmitted by water usually grow in the intestinal tract and leave the body in the feces. Thus, they are infections. Fecal pollution of water supplies may then occur, and if the water is not properly treated, the pathogens enter a new host when the water is consumed, therefore, it may be infectious even if it contains only a small number of pathogenic organisms. Most outbreaks of waterborne diseases are due to breakdowns in treatment systems or are a result of post contamination in pipelines.The microorganisms of concern are those which can cause human discomfort, illness or diseases. These microbes are comprised of numerous pathogenic bacteria, viruses, certain algae and protozoa etc. The disinfection efficiency is typically measured as a specific level of cyst inactivation. Protozoan cysts are the most difficult to destroy. Bacteria and viral inactivation are considered adequate if the requirement for cyst inactivation is met. Therefore, water quality standard for the disinfection of water have been set at microorganisms, usually take the protozoan cysts as indicator, so viruses will be adequately controlled under the same operation conditions required for inactivation of protozoan cysts. The widely found drinking water contamination is caused by protozoan that is a significant intestinal pathogens in diary cattle, likely a source of this outbreak.There are two of the most important protozoa - Cryptosporidium and Giardia cysts those are known to outbreak diseases, frequently are found in nature and drinking water storage ponds. Protozoa form protective stages like oocysts that allow them to survive for long periods in water while waiting to be ingested by a host. Protozoa cysts are not effectively removed by storing water because of their small size and density. Cryptosporidium oocysts have a setting velocity of 0.5 um/s. Therefore, if the water tank is 2 m deep, it will take the oocyst 46 days to settle to thebottom. Giardia cysts are much large and have a great settling velocity of 5.5um/s. It was evident that chlorine and chloramines were ineffective against Cryptosporidium oocysts, which was discovered to be amazingly resistant to chlorine, and only ozone and chlorine dioxide may be suitable disinfectants [15]. The investigations have verified that Cryptosporidium is highly resistant to chorine, even up 14 times as resistant as the chlorine resistant Giardia, therefore methods for removing it in past rely on sedimentation and filtration. Watson′s Law to study protozoan disinfection, reads as follows:K = Cηt (9)In the formula:K ——constant for a given microorganism exposed to a disinfectant under a fixed set of pH and temperature conditions;C ——disinfectant concentration (mg/ L);η——empirical coefficient of dilution ;t ——time required to achieve the fixed percentage inactivation.For the preoxidation and reduction of organic pollutants , the recommended dosages are between 0. 5～2. 0 mg/ L with contact time as 15～30 min depending on the pollutants characteristics in the water. In the case of post - disinfection , the safe dosages of ClO2 are 0. 2～0.4 mg/L. At these dosages, the potential by - products chlorite and chlorate do not constitute any health hazard [16]. The relation between disinfectant concentration and contact time can be established by using Ct products based on the experimental data. From this the effectiveness of disinfectants can be evaluated based on temperature, pH value and contact time. Since Cryptosporidium has become a focus of regulatory agencies in the United States and United Kingdom, the prospects of controlling this pathogen show more considerable. The comparison of the Ct values by using ozone , chlorine dioxide , chlorine and chloramines for Giardia and Cryptosporidium cyst s are listed in Tab. 5[17 ,18 ] , and for some microorganisms disinfection are displayed in Tab. 6[19 ] .Tab. 5 Ct values (mg·min/ L.) for disinfection of Giardia and Cryptosporidium cysts by using 4 disinfectantsTab. 6 Comparison of value intervals for the product Ct (mg·min/ L) for the inactivation of various microorganisms by using 4 disinfectantsThe mean Ct value for ClO2 at pH 7 and 5 ℃was 11. 9 mg·min/ L, and dropped to 5.2 at pH 7 and 25 ℃. High temperatures normally enhance the efficiency of disinfectants while lower temperatures have opposite effects requiring additional contact time or extra quantity of disinfectants. The best performance for ClO2 is at pH 9 and 25 ℃, which yields a Ct product of 2.8 mg·min/ L [20]. Chlorine dioxide appears to be more efficient for Cryptosporidium oocysts than either chlorine or monochloramine. Exposure of oocysts to 1.3 mg·min/ L at pH 7 reduces excystation from 87 % to 5 % in a hour at 25 ℃. Based on this result, Ct product of 78 mg·min/ L was calculated. However, the Ct product for ozone to do this work was examined as 5 - 10 mg·min/ L from observation that excystation decreased from 84 % to 0 % after 5 minutes with the ozone concentration of 1 mg/ L [15]. As with other disinfectants, increasing temperature decreased the Ct values and improved the cysticidal action. Increasing temperature unexpectedly reduced the Ct values from a high of 6.35 mg·min/ L at pH5 to a low of 2.91 mg·min/ L at pH 9[20]. It is generally the rule, that for protozoa ozone is the best cysticide, chlorine dioxide is superior to chlorine andiodine, but chlorine, in overall, is much superior to chloramines [21].Although disinfection efficiency of ozone is higher than chlorine dioxide, this difference can be compensated by the contact time. The experiment indicated that chlorine dioxide could reach the same results for disinfection of coliform bacteria as ozone did if time lasted long enough, which can be seen in Fig. 1. The added concentrations of both of ozone and chlorine dioxide were 2 mg/ L.Control of Cryptosporidium oocysts in potable water requires an integrated multiple barrier approach. Coagulation is critical in the effective control of Cryptosporidium by clarification and filtration. Dissolved air floatation can achieve oocysts removal of 3 logs compared to about 1 log by sedimentation. Dissolved air floatation and filtration provide two effective barriers to Cryptosporidium oocysts with cumulative log removal of 4 to 5 compared to log removals of 3 to 4 by sedimentation and filtration [22].Fig. 1 Comparison of disinfection efficiency between ozone and chlorine dioxide on coliform bacteria5 Tendency of disinfection for drinking waterIn the future, the burden of producing water with low pathogen level and low tastes and odor will be allocated to a combination of steps, including source water protection, coagulation - flocculation - sedimentation, filtration, floatation, membrane processes and adsorption. Some form of terminal treatment with chlorine, chlorine dioxide, ozone, UV, or other agents will also be required. No single step can or should be expected to shoulder the entire burden to controlling a given contaminant. With the development of techniques, new chemical and physical agents will meet tests of practicability for use in water treatment and will reduce pathogens. These may include electromagnetic fields and other forms of treatment with light or sonic energy [23].In light of availability, efficacy, operability and costs, the priority should be given to ultraviolet method among all of the currently utilized disinfection technologies, particularly in developing countries. The medium and low - pressure UV extends tremendous potential promise for adaptation into various scale water supply plants. The researches have validated that extremely low dosage of UV can behighly effective for inactivate oocysts [24]. Furthermore, comparison of medium and low - pressure lamps demonstrated no significant differences. By using low - pressure UV at the dosage of 3 , 6 and 9 mJ/ cm2 , oocyst inactivation levels were yielded between 3.4 and 3.7 log. In the trials of UV in water with turbidity of more than 1 NTU, the ability of medium –pressure was not affected, and high level of oocysts inactivation could still be achieved.6 ConclusionsTo purify drinking water, chlorine dioxide can be chosen instead of chlorine, ozone and other disinfectants because of it s advantages of high efficiency of disinfection, competent stability, low cost and simple utilizing way etc. Both ozone and ClO2 are absolutely vital to ensure that any microorganisms arising from fecal contamination of water storage are destroyed. The utilization of chlorine dioxide has been found to efficiently restrict protozoa growth, to disinfect from bacteria and viruses. Taking the protozoan cysts as indicator in which Cryptosporidium oocysts were solidly resistant to chlorine, but chlorine dioxide may be suitable disinfectants to mutilate. Thus, viruses will be adequately controlled by chlorine dioxide under the same operation conditions required for inactivation of protozoan cysts. The experiment indicated that chlorine dioxide could reach the same results for disinfection of coliform bacteria as ozone did if time lasted long enough although disinfection efficiency of ozone is higher than chlorine dioxide.It is an obvious preference for chlorine dioxide to pragmatically remove oil and benzene homologous compounds in water treatment meanwhile the formation of mutagenic and toxic substances is limited. The degradation rate was proportional to input amount of oxidants and increase of operating time. The dosage input , in overall , is suggested to range between 0. 5～2.0 mg/ L. The effective pH at which reactions occur is in the slightly acid range of 5 to 7 at which formation of chlorite and chlorate is minimized. The chlorine dioxide gas should be injected directly into the treated water body, so that high concentrations of ClO2 can be kept in the solution. Under these conditions, the elimination rate for organic pollutants will be much higher. For the storage system, input dosage of chlorine dioxide concentration should be higherthan that in laboratory studies due to complex pollutants in treated water. References:[1 ] Katz J . Ozone and chlorine dioxide technology for disinfection of drinking water [M]. Noyes New Jersey: Data Corporation, 1980.[2] Fiessinger F. Organic micropollutants in drinking water and health [M] . Publisher, N. Y., U. S. A: Elsevier Sci., 1985.[3 ] Hoff J C , Geldreich E E. Comparison of the biocidal efficiency of alternative disinfectants [C] . In Proceedings AWWA seminar, Atlanta, Georgia, 1980.[4 ] APHA , American Public Health Association. American Water Works Association and Water Pollution Control Federation. Standard Methods for the Examination of Water and Wastewater. (16th Edition) [M]. Washington D. C., 1989.[5] Dietrich A M. Determination of chlorite and chlorate in chlorinated and chloraminated drinking water by flow injection analysis and ion chromatography[J ] .A nal. Chem., 1992, 64:496 - 502.[6] Monarca S. Mutagenicity of extracts of lake drinking water treated with different disinfectants in bacterial and plant tests[J ] . Water Res, 1998, (32):2 689 - 2 695.[7] Vikesland P , Ozekin K, Valentine R L. Effect of natural organic matter on monochloramine decomposition : pathway elucidation through the use of mass and redox balance[J ] . Envi ron. Sci. Tech., 1998, 32 (10):1 409 - 1 416.[8] Schulz S , Hahn H H. Generation of halogenated organic compounds in municipal wastewater [M] . Proc. 2nd Int. Assoc. Water Qual. Int. Conf. Sewer Phys. Chem. Bio. Reactor, Aalborg, Denmark, 1998.[9 ] Aieta E M. A review of chlorine dioxide in drinking water treatment [J]. J. A WWA, 1986, 78 (6): 62 - 72.[10 ] Gordon G Minimizing chlorine ion and chlorate ion in water treatment with chlorine dioxide[J ] . J. A WWA, 1990, 82 (4):160 - 165.[11] Kmorita J D , Snoeyink V L. Monochloramine removal from water by activated carbon[J ] . J. A WWA, 1985, (1):62 - 64.[12] Gordon G, Adam I , Bubnis B. Minimizing chlorate information[J ] . J. AWWA, 1995, 87, (6): 97 - 106.[13] Iatrou A. Removing chlorite by the addition of ferrous iron[J ] . J. A WWA, 1992, 84 (11): 63 - 68.[14 ] Schalekamp Maarten. Pre - and intermediate oxidation of drinking water with ozone, chlorine and chlorine dioxide [J]. J. Ozone Science and Engineering, 1986, 8: 151 - 186[15 ] Korich D G, Mead J R , Madore M S , et al . Effects of ozone, chlorine dioxide, chlorine and monochramine on Cryptosporidium parvum oosyst viability [J]. Applied and Environmental Microbiology, 1990, 56: 1 423 - 1 428.[16 ] AWWA Research Foundation. Chlorine dioxide; drinking water issues, 2nd International Symposium [R]. Houston, TX, 1992.[17] Lykins B W, Griese H G. Using chlorine dioxide for trihalomethane control[J ] . J, A WWA, 1986, 71 (6): 88 - 93.[18] Regli S. Chlorine dioxide , drinking water issues , 2nd International Symposium [ R ] . Houston, TX, AWWA Research Foundation, 1992.[19] Hoff J C. Inactivation of microbial agents by chemical disinfectants[J] . US EPA, 1986.[ 20 ] Rubin A , Evers D , Eyman C , et al . Interaction of gerbil - cultured Giardia lamblia cysts by free chlorine dioxide [J]. Applied and Envi ronmental Microbiology, 1989, 55: 2 592 - 2 594.[ 21 ] Rusell A D , Hugo WB , Ayliffe GA J . Principes and Practice of Disinfection [M]. Preservation and Sterilization. Blackwell Scientific Publications, Oxford, U K, 1992.[22 ] Edzwald J K, Kelley M B. Control of Cryptosporidium from reservoirs to clarifiers to filters [C] . Proc. 1st IAWQ –IWSA Joint Specialist Conf. Reservoir Manage. Water Supply, Prague, Czech, 1998.[23] Haas Charles N. Disinfection in the Twenty - first century[J ] . J. A WWA, 2000, 92 (2): 72 - 73.[24 ] Clancy L , Jenneifer , Bukhari Z , et al , Using UV to Inactivate Gryptosporidium[J ] . J. A WWA, 2000, 92: 97 - 104.饮用水的消毒及杀菌技术研究朱琨伏小勇(兰州铁道学院环境工程系, 甘肃兰州730070)摘要:饮用水处理消毒过程中可产生一系列致癌物质,主要是氯与水中的有机物和其它化学成分反应的结果,其中典型产物有三氯甲烷. 通过对常用消毒剂液氯,臭氧,二氧化氯,高锰酸钾,氯胺及过氧化氢的实验对比,证明二氧化氯是高效,方便,廉价的消毒剂. 它不仅对一般病原菌类有明显的抑制和杀菌作用,对清除难以灭杀的潜原性病毒也有理想的效果. 在净化水中石油类有机物时,二氧化氯的效果受到反应时间,注入方式和pH 值的影响.关键词:消毒;氧化剂;水处理;病原菌;二氧化氯中图分类号:X523 文献标识码:A中文译文：饮用水消毒和杀菌技术的研究朱琨伏小勇（兰州铁道学院环境工程系，甘肃兰州，730070 中国）在饮用水处理过程中，通过氯与溶解性有机物和其他化合物的反应所产生的消毒副产物被看作一个令人担忧的问题，因为一系列诱变致癌的物质组成包括总卤甲烷。
污水处理的英文文献翻译
性 宜 适的用回水及能性理处厂理处水污旦约
刊期术学 8002 5135-4861 NSSI BJA/gro.slanruojcimedaca.www//:ptth4 月 8 年 8002 年 9262 至 1262 第 � � 51 � 7 。 卷 程 工 物 生 洲 非
使复重合适否是其定确以�较比了 行进量质水生再对并估评了行进能 性的 厂理处水污个四对。围范的水 出和水进� �OD �氧解溶和�SDT� 体固 解 溶总 � � SST � 体 固 浮 悬 总 � �DOB�量氧需物生� �DOC�量氧需 学化量测�估评了行进性特水废对 并。定决人的�PTW�桑哈 idaW 和 � �PTR� 的 ahtma� R�PTI� 的德比尔伊 �PTSA�的拉姆萨铝由别分�点特厂 理处 水污个四�中究研项这在 。项选的力引吸有具 极个一是用回的水�中究研项这加 增源资水用可旦约在�此因。 �7002 �yrammA;7002�等 kcinroCcM;5002 � nidadaH 和 ruodB;2002 � 等 heniataB � 旦 约 于 用 地 接 间或接直被将水生再些这��51 过 超至升上将年 03 的来下接在 �水生 再的 raey/ m 万 007 过超的�01 约 3 的水 供总 国全 占。 �年 2002�合混 等 heniataB�水表地的近附游下厂 理处或物植业农制限于用水废收回 �前目。流溪和谷山到水废的理处 过经放排许允准标旦约�时准标合 符数参多很卵虫蠕�菌细菌杆肠大 �体固浮悬总�量氧需学化�量氧需 化生当。节调的放排的境环和用利 再的水对着试尝�5991/398SJ�准 标水生再旦约。 �6002�da'asA;年 2002 � 人 等 heniataB � � PTSA � 厂理处水污 armasA 入流转天/米方 立 322681 中其�天/米方立 214612 为约量水的厂理处些这入流。务服 口人的�65 约为厂理处些这。镇城 和市城要主分部大了盖覆且并�厂 理处水污政市个 32 有旦约在
污水处理英汉翻译资料
1) oilfield wastewater采油废水1.By samples experiment of different batches of microbiological preparations to verifying the effect of the removal rate of CODCr and petroleum hydrocarbon degradation of oilfield wastewater treatment, a method using Victory Blue B1 for detecting the quality of the microbiological preparations of oilfield wastewater treatment was proposed.通过不同批次制剂样品对采油废水的CODCr去除率和石油烃降解效果的检测实验,提出了以维多利亚蓝BI来检测油田废水微生物制剂质量的检测方法。
2.The photoelectrocatalytic degradation of oilfield wastewater containing high content of chlorine was studied in TiO_2 aqueous suspensions.以高压汞灯为光源,考察了在光催化、电氧化、光电催化及光电催化/H2O2体系中降解实际油田采油废水的效率。
3.A catalytic advanced oxidation process based on copper charging activated carbon and DO in wastewater has been studied for polishing oilfield wastewater treated by coagulation sedimentation of which COD could not meet the discharge standard.采用载铜活性炭和废水中溶解氧体系,用催化氧化法深度去除采油废水中的COD。
污水处理工业废水回用毕业论文中英文资料对照外文翻译文献综述
污水处理工业废水回用毕业论文中英文资料对照外文翻译文献综述污水处理工业废水回用毕业论文中英文资料对照外文翻译文献综述Catalytic strategies for industrial water re-useAbstractThe use of catalytic processes in pollution abatement and resource recovery is widespread and of significant economic importance [R.J. Farrauto, C.H. Bartholomew, Fundamentals of Industrial Catalytic Processes, Blackie Academic and Professional,1997.]. For water recovery and re-use chemo-catalysis is only just starting to make an impact although bio-catalysis is well established [J.N. Horan, BiologicalWastewater Treatment Systems; Theory and Operation, Chichester, Wiley, 1990.]. This paper will discuss some of the principles behind developing chemo-catalytic processes for water re-use. Within this context oxidative catalytic chemistry has many opportunities to underpin the development of successful processes and many emerging technologies based on this chemistry can be considered .Keywords: COD removal; Catalytic oxidation; Industrial water treatment1.IntroductionIndustrial water re-use in Europe has not yet started on the large scale. However, with potential long term changes in European weather and the need for more water abstraction from boreholes and rivers, the availability of water at low prices will become increasingly rare. As water prices rise there will come a point when technologies that exist now (or are being developed)will make water recycle and re-use a viable commercial operation. As that future approaches, it is worth stating the most important fact about wastewater improvement–avoid it completely if at all possible! It is best to consider water not as a naturally available cheap solvent but rather, difficult to purify, easily contaminated material that if allowed into the environment will permeate all parts of the biosphere. A pollutant is just a material in the wrong place and therefore design your process to keep the material where it should be –contained and safe. Avoidance and then minimisation are the two first steps in looking at any pollutant removal problem. Of course avoidance may not be an option on an existing plant where any changes may have large consequences for plantitems if major flowsheet revision were required. Also avoidance may mean simply transferring the issue from the aqueous phase to the gas phase. There are advantages and disadvantages to both water and gas pollutant abatement. However, it must be remembered that gas phase organic pollutant removal (VOC combustion etc.,) is much more advanced than the equivalent water COD removal and therefore worth consideration [1]. Because these aspects cannot be over-emphasised，a third step would be to visit the first two steps again. Clean-up is expensive, recycle and re-use even if you have a cost effective process is still more capital equipment that will lower your return on assets and make the process less financially attractive. At present the best technology for water recycle is membrane based. This is the only technology that will produce a sufficiently clean permeate for chemical process use. However, the technology cannot be used in isolation and in many (all) cases will require filtration upstream and a technique for handling thedownstream retentate containing the pollutants. Thus, hybrid technologies are required that together can handle the all aspects of the water improvement process[6,7,8].Hence the general rules for wastewater improvement are:1. Avoid if possible, consider all possible ways to minimise.2. Keep contaminated streams separate.3. Treat each stream at source for maximum concentration and minimum flow.4. Measure and identify contaminants over complete process cycle. Look for peaks, which will prove costly to manage and attempt to run the process as close to typical values as possible. This paper will consider the industries that are affected by wastewater issues and the technologies that are available to dispose of the retentate which will contain the pollutants from the wastewater effluent. The paper will describe some of the problems to be overcome and how the technologies solve these problems to varying degrees. It will also discuss how the cost driver should influence developers of future technologies.2. The industriesThe process industries that have a significant wastewater effluent are shown in Fig. 1. These process industries can be involved in wastewater treatment in many areas and some illustrations of this are outlined below.Fig. 1. Process industries with wastewater issues.2.1. RefineriesThe process of bringing oil to the refinery will often produce contaminated water. Oil pipelines from offshore rigs are cleaned with water; oil ships ballast with water and the result can be significant water improvement issues.2.2. ChemicalsThe synthesis of intermediate and speciality chemicals often involve the use of a water wash step to remove impurities or wash out residual flammable solvents before drying.2.3. PetrochemicalsEthylene plants need to remove acid gases (CO2, H2S) formed in the manufacture process. This situation can be exacerbated by the need to add sulphur compounds before the pyrolysis stage to improve the process selectivity. Caustic scrubbing is the usual method and this produces a significant water effluent disposal problem.2.4. Pharmaceuticals and agrochemicalsThese industries can have water wash steps in synthesis but in addition they are often formulated with water-based surfactants or wetting agents.2.5. Foods and beveragesClearly use water in processing and COD and BOD issues will be the end result.2.6. Pulp and paperThis industry uses very large quantities of water for processing –aqueous peroxide and enzymes for bleaching in addition to the standard Kraft type processing of the pulp. It is important to realise how much human society contributes to contaminated water and an investigation of the flow rates through municipal treatment plants soon shows the significance of non-process industry derived wastewater.3. The technologiesThe technologies for recalcitrant COD and toxic pollutants in aqueous effluent are shown in Fig. 2. These examples of technologies [2,6,8] available or in development can be categorised according to the general principle underlying themechanism of action. If in addition the adsorption (absorption) processes are ignored for this catalysis discussion then the categories are:1. Biocatalysis2. Air/oxygen based catalytic (or non-catalytic).3. Chemical oxidation1. Without catalysis using chemical oxidants2. With catalysis using either the generation of _OH or active oxygen transfer. Biocatalysis is an excellent technology for Municipal wastewater treatment providing a very cost-effective route for the removal of organics from water. It is capable of much development via the use of different types of bacteria to increase the overall flexibility of the technology. One issue remains –what to do with all the activated sludge even after mass reduction by de-watering. The quantities involved mean that this is not an easy problem to solve and re-use as a fertilizer can only use so much. The sludge can be toxic via absorption of heavy metals, recalcitrant toxic COD. Inthis case incineration and safe disposal of the ash to acceptable landfill may be required. Air based oxidation [6,7] is very attractive because providing purer grades of oxygen are not required if the oxidant is free. Unfortunately, it is only slightly soluble in water, rather unreactive at low temperatures and, therefore, needs heat and pressure to deliver reasonable rates of reaction. These plants become capital intensive as pressures (from _10 to 100 bar) are used. Therefore, although the running costs maybe low the initial capital outlay on the plant has a very significant effect on the costs of the process. Catalysis improves the rates of reaction and hence lowers the temperature and pressure but is not able to avoid them and hence does not offera complete solution. The catalysts used are generally Group VIII metals such as cobalt or copper. The leaching of these metals into the aqueous phase is a difficulty that inhibits the general use of heterogeneous catalysts [7]. Chemical oxidation with cheap oxidants has been well practised on integrated chemical plants. The usual example is waste sodium hypochlorite generated in chlor-alkali units that can be utilised to oxidise COD streams from other plants within the complex. Hydrogen peroxide, chlorine dioxide, potassium permanganate are all possible oxidants in this type of process. The choice is primarily determined by which is the cheapest at the point of use. A secondary consideration is how effective is the oxidant. Possibly the most researched catalytic area is the generation and use of _OH as a very active oxidant (advanced oxidation processes) [8]. There are a variety of ways of doing this but the most usual is with photons and a photocatalyst. The photocatalyst is normally TiO2 but other materials with a suitable band gap can be used [9,10]. The processes can be very active however the engineering difficulties of getting light, a catalyst and the effluent efficiently contacted is not easy. In fact the poor efficiency of light usage by the catalyst (either through contacting problems or inherent to the catalyst) make this process only suitable for light from solar sources. Photons derived from electrical power that comes from fossil fuels are not acceptable because the carbon dioxide emission this implies far outweighs and COD abatement. Hydroelectric power (and nuclear power) are possible sources but the basic inefficiency is not being avoided. Hydrogen peroxide and ozone have been used with photocatalysis but they can be used separately or together with catalysts to effect COD oxidation. For ozone there is the problem of the manufacturingroute, corona discharge, which is a capital intensive process often limits its application and better route to ozone would be very useful. It is important to note at this point that the oxidants discussed do not have sufficient inherent reactivity to be use without promotion. Thus, catalysis is central to their effective use against both simple organics (often solvents) or complex recalcitrant COD. Hence, the use of Fenton’s catalyst (Fe) for hydrogen peroxide [11]. In terms of catalysis these oxidants together with hypochlorite form a set of materials that can act has ‘active oxygen transfer (AOT) oxidants’ in the presence of a suitable catalyst. If the AOT oxidant is hypochlorite or hydrogen peroxide then three phase reactions are avoided which greatly simplifies the flowsheet. Cheap, catalytically promoted oxidants with environmentally acceptable products of oxidation that do not require complex chemical engineering and can be produced efficiently would appear to offer one of the best solutions to the general difficulties often observed.3.1. Redox catalysis and active oxygen transferThe mechanism of catalytically promoted oxidation with hydrogen peroxide or sodium hypochlorite cannot be encompassed within one concept, however there are general similarities between the two oxidants that allows one to write a series of reactions for both (Fig. 3) [5]. This type of mechanism could be used to describe a broad range of reactions for either oxidant from catalytic epoxidation to COD oxidation. The inherent usefulness of the reactions is that;1. The reactions take place in a two-phase system.2. High pressure and temperature are not required.3. The catalytic surface can act as an adsorbent of the COD to be oxidised effectively increasing the concentration and hencethe rate of oxidation.The simple mechanism shows the selectivity issue with this type of processes. The oxidant can simply be decomposed by the catalyst to oxygen gas – this reaction must be avoided because dioxygen will play no role in COD removal. Its formation is an expensive waste of reagent with oxygen gas ($20/Te) compared to the oxidant ($400–600/Te). To be cost competitive with alternative processes redox catalysis needs excellent selectivity.3.2. Technology mappingThe technologies so far described can be mapped [12] for their applicability with effluent COD concentration (measured as TOC) and effluent flow rate (m3 h-1). The map is shown in Fig. 4. The map outlines the areas where technologies are most effective. The boundaries, although drawn, are in fact fuzzier and should be only used as a guide. Only well into each shape will a technology start to dominate. The underlying cost model behind the map is based on simple assertions – at high COD mass flows only air/oxygen will be able to keep costs down because of the relatively low variable cost of the oxidant. At high COD concentrations and high flows only biological treatment plants have proved themselves viable –of course if done at source recovery becomes an option. At low flows and low COD levels redox AOT catalysis is an important technology –the Synetix Accent 1 process being an example of this type of process (see Fig. 5 for a simplified flowsheet). The catalyst operates under very controlled conditions at pH > 9 and hence metal leaching can be avoided (<5 ppb). The activity and selectivity aspects of the catalyst displayed in Fig. 3 can befurther elaborated to look at the potential surface species. This simple view has been extended by a significant amount ofresearch [3,4,5]. Now the mechanism of such a catalyst can be described in Fig. 6. The key step is to avoid recombination of NiO holes to give peroxy species and this can be contrasted with the hydrogen peroxide situation where the step may be characterized as oxygen vacancy filled. From both recombination will be facilitated by electronic and spatial factors. The range of application of the process is outlined below. From laboratory data some general types of chemical have been found suitable –sulphides, amines, alcohols, ketones, aldehydes, phenols, carboxylic acids, olefins and aromatic hydrocarbons. From industrial trials recalcitrant COD (nonbiodegradable) and sulphur compounds have been successfully demonstrated and a plant oxidising sulphur species has been installed and is operational.4. ConclusionsWastewater treatment processes are in the early stages of development. The key parameters at present are effectiveness and long term reliability. Many processes operating are in this stage, including the redox Accent TM is a trademark of the ICI Group of Companies. catalysis systems. However,once proven, redox catalysis offers many advantages for COD removal from wastewater:1. The low capital cost of installation.2. Simple operation that can be automated.3. Flexible nature of the process – can be easily modified to meet changing demands of legislation.Hence it will be expected to develop into an important technology in wastewater improvement.AcknowledgementsThe author is grateful to Jane Butcher and Keith Kelly of Synetix for discussions on this paper. References[1] R.J. Farrauto, C.H. Bartholomew, Fundamentals of Industrial Catalytic Processes, Blackie Academic and Professional, 1997. F.E. Hancock / Catalysis Today 53 (1999) 3–9 9[2] J.N. Horan, Biological Wastewater Treatment Systems; Theory and Operation, Chichester, Wiley, 1990.[3] F.E. Hancock et al., Catalysis Today 40 (1998) 289.[4] F. King, F.E. Hancock, Catal. Today 27 (1996) 203.[5] J. Hollingworth et al., J. Electron Spectrosc., in press.[6] F. Luck, Environmental Catalysis, in: G. Centi et al. (Eds.), EFCE Publishers, Series 112, p. 125.[7] D. Mantzavinos et al., in: V ogelpohl and Geissen (Eds.), in: Proceedings of the Conference on Water Science and Technology, Clausthal-Zellerfeld, Germany, May 1996, J. Int. Assoc. Water Quality, Pergamon, 1997.[8] R. Venkatadri, R.W. Peters, Hazardous Waste Hazardous Mater. 10 (1993) 107.[9] A.M. Braun, E. Oliveros, Water Sci. Tech. 35 (1997) 17.[10] D. Bahnemann et al., Aquatic and surface photochemistry, Am. Chem. Soc. Symp. Ser. (1994) 261.[11] J. Prousek, Chem. Lisy 89 (1995) 11.工业废水回用的接触反应策略摘要：无论从控制污染还是资源恢复的角度，接触反应都是被广泛应用并极具经济效益的。
污水处理外文文献
Aerobic treatment of dairy wastewater with sequencing batch reactor systemsXiujin Li,Ruihong ZhangAbstract Performances of single-stage and two-stage se-quencing batch reactor(SBR)systems were investigated for treating dairy wastewater.A single-stage SBR system was tested with10,000mg/l chemical oxygen demand (COD)influent at three hydraulic retention times(HRTs) of1,2,and3days and20,000mg/l COD influent at four HRTs of1,2,3,and4days.A1-day HRT was foundsufficient for treating10,000-mg/l COD wastewater,with the removal efficiency of80.2%COD,63.4%total solids, 66.2%volatile solids,75%total Kjeldahl nitrogen,and 38.3%total nitrogen from the liquid effluent.Two-day HRT was believed sufficient for treating20,000-mg/l COD dairy wastewater if complete ammonia oxidation is not desired.However,4-day HRT needs to be used for achieving complete ammonia oxidation.A two-stage sys-tem consisting of an SBR and a complete-mix biofilm re-actor was capable of achieving complete ammonia oxidation and comparable carbon,solids,and nitrogen removal while using at least1/3less HRT as compared to the single SBR system.Keywords Aerobic,dairy,wastewater,sequencing batch reactor1IntroductionDairy wastewater is currently disposed of mainly through land application with little or no pretreatment in Califor-nia in the United States.Due to increasing awareness of the general public about potential adverse impact of ani-mal wastes on environmental quality and recent develop-ments in environmental regulations for gaseous-emission control and nutrient management,alternative wastewater treatment methods become attractive options for dairy producers.A sequencing batch reactor(SBR)is a biolog-ical treatment reactor that uses aerobic bacteria to degrade organic carbon and remove nitrogen present in the wastewater.If designed and operated properly,it maybecome a promising alternative for treating animal wastewater to control odors and reduce solids and nutrient contents.The SBR treats wastewater in small batches andfits wellwith most animal wastewater collection systems.It is atime-oriented system and operates over repeated cycles offive phases–fill,react,settle,decant,and idle.The major factors that control the performance of SBRs include or-ganic loading rate,hydraulic retention time(HRT),solids retention time(SRT),dissolved oxygen(DO),and influent characteristics such as chemical oxygen demand(COD),solids content,and carbon-to-nitrogen ratio(C/N),etc. Depending on how these parameters are controlled,theSBR can be designed to have one or more of these func-tions:carbon oxidation,nitrification,and denitrification[1,2].Carbon oxidation and denitrification are carried outby heterotrophic bacteria and nitrification is by auto-trophic bacteria.The SBR has been successfully used in the treatment of municipal and industrial wastewater,wherethe high treatment performance resulted in excellent ef-fluent quality[3,4].It is considered to be a suitable systemfor wastewater treatment applications in small communi-ties[5].The SBR is a relatively new technology for agri-cultural applications.Previous research on the SBR foranimal waste was primarily concentrated on swine wastewater treatment.Several researchers[6,7,8]re-ported the performance of SBR in treating swine waste-water with COD and suspended solids(SS)in the range of1,614–2,826mg/l and175–3,824mg/l,respectively.Satis-factory removal of COD and SS from the wastewater was achieved with HRTs of22–30h.Fernades et al.[9]studiedthe SBR for treating highly concentrated swine manurewith about4%total solids(TS).The influent COD,NH3-N,and total Kjeldahl nitrogen(TKN)were as high as31,175mg/l,1,265mg/l,and2,580mg/l,respectively.Their results indicated that above97%COD,99%NH3-N,and93%TKN removal efficiencies were achieved in theliquid effluent at HRTs of6and9days and SRT of over20days.Tam et al.[10]researched SBR for treatment of wastewater from a milking center and reported that the wastewater with919–1,330mg/l COD and15–37mg/lNH3-N could be successfully treated with a HRT of20h. Bioprocess Biosyst Eng25(2002)103–109DOI10.1007/s00449-002-0286-9103Received:2October2001/Accepted:6February2002 Published online:5April2002ÓSpringer-Verlag2002X.Li(&)Department of Environmental Engineering,Beijing University of Chemical Technology,100029,Beijing,ChinaE-mail:lxiujin@Tel.:+86-010-********Fax:+86-010-********R.ZhangBiological and Agricultural Engineering Department, University of California at Davis,CA95616,USAThis research was supported in part by the California Energy Commission and the Agricultural Experiment Station of the University of California,Davis,USA.Studies on the SBR for treating dairy manure are not well documented in the literature.Previous researchfindings about the SBR for treatment of swine manure and other types of wastewater provide valuable references for the treatment of dairy wastewater.However,due to the dif-ferences in the characteristics of dairy wastewater from other types of wastewater,research is needed to develop design and operational guidelines for the SBR in treating dairy wastewater of various characteristics.The objectives of this study are to investigate the effects of wastewater characteristics,HRT,SRT,and organic loading rate on the performance of the SBR system in treating dairy wastewater for carbon and solids removal and nitrogen conversion,and develop design and opera-tional guidelines for the SBR system in single-and mul-tiple-stage configurations.2Materials and methods2.1Dairy manure collection and preparationDairy manure was collected on the Dairy Research Farm of the University of California at Davis.Due to runoff of urine on the feedlot,the collected manure was mainly feces and contained a relatively low content of ammonia nitro-gen.The manure was slurried with addition of water and then screened twice with two sieves with openings of4·4 and2·2mm,respectively,to remove large particles.The screened manure was transported immediately to the laboratory and stored in a freezer at–20°C until use.The TS and COD of the screened manure were30,000–40,000mg/l and35,000–50,000mg/l,respectively.When needed,the stored manure was thawed and then diluted with tap water to obtain a desired COD concentration.Due to relatively low ammonia content of the raw manure as compared to typical levels in the manure collected on dairy farms,urea was added to increase the NH3-N in the prepared manure from100–125mg/l to500–550mg/l.The prepared manure was then put into a50-l feeding tank housed in a refrigerator at4°C for daily use.The feeding tank had an agitator to mix the wastewater during the feeding of the reactors.2.2Experimental setup and operationBoth single-stage and two-stage treatment systems were tested.The single-stage SBR system consisted of an SBR and a solids-settling tank in series.The wastewater wasfirst fed into the SBR for treatment and the effluent of the SBR, including both sludge and liquid,was then discharged into a settling tank,where liquid was separated from sludge by gravity settling and characterized as liquid effluent of the system.The two-stage system consisted of an SBR(first-stage reactor),a solids-settling tank,and a complete-mix biofilm reactor(CMBR)(second-stage reactor)connected in series.The liquid effluent obtained from the solids-set-tling tank was used as influent of CMBR and further treated in the CMBR for achieving complete nitrification.The two-stage SBR-CMBR system is shown in Fig.1.Each system was fed and decanted twice a day for12h in each treatment cycle.All the peristaltic pumps used for feeding and decanting were operated automatically with a digital time controller.The time sequence for different operations during each treatment cycle of the SBR was1–3minfill,11h and4–8min react,40min settle,1–3min decant,and10min idle.The CMBR was operated as a complete-mix reactor and had long SRT provided by the attached growth on the polyethylene pellets placed in the reactor.The plastic pellets had light density(920kg/ m3)and were keptfluidized with the airflow.Each pellet was10mm in diameter and10mm in height,with a cross inside the cylinder and longitudinalfins on the outside, providing a large surface area for bacterial attachment. Thefilling volume of the pellets in total occupied ap-proximately18%of liquid volume(3l)in the reactor.The SBR and CMBR reactors were made from trans-parent acrylic and had a total volume of6l each,with51cm height and12cm diameter.During testing,the liquid vol-ume of each reactor was3l.Each reactor was aerated using pressurized air at a controlledflow rate.In order to mini-mize the water evaporation in the reactor,the air was hu-midified by traveling through water contained in a15-l jar prior to entering the reactor.The air was evenly distributed into the wastewater through four air stone diffusers in-stalled near the bottom of the reactor.All the reactors were initially seeded with the activated sludge obtained from the UC Davis Wastewater Treatment Plant and allowed to ac-climate for about2months before formal experiments were started.It normally took about4weeks for each SBR re-actor to reach a steady state when a new operating condi-tion was introduced.The steady state was defined to be a state when the weekly variations of effluent COD,TS,NH3-N,and pH were less than5%.These parameters were monitored twice a week.The CMBR had been fully accli-mated with dilute dairy wastewater for about6months and had nitrification bacteria well established before being connected with the SBR.The mixed liquor suspended solids (MLSS)in the CMBR was about10,000mg/l,which was calculated from both suspended growth and attached growth solids.In order to determine the ammonia emission from SBR due to aeration,ammonia in the exiting air of SBR was collected by absorbing it in0.3N boric acid solution for 24h under each testing condition.2.3Experimental plan and system performance evaluation The experiment was carried out in two phases.Thefirst phase was for studying the effects of influent characteris-tics,HRT,and corresponding SRT and loading rate on the performance of the single-stage SBR system.The second phase was to evaluate the performance of a two-stage SBR-CMBR system.The two systems were then compared in terms of carbon and solids removal and nitrogen conver-sion efficiencies.With the single-stage SBR system,three HRTs(1,2and 3days)were tested for wastewater of10,000mg/l COD and four HRTs(1,2,3and4days)for wastewater of20,000mg/l COD.For the wastewater of10,000mg/l COD, the corresponding loading rate and SRT for the three HRTs were10,5,and3.3g COD/l/day and8,12,andBioprocess Biosyst Eng25(2002) 10415days,respectively.For the wastewater of 20,000mg/l COD,the corresponding loading rate and SRT for the four HRTs were 20,10,6.7,and 5g COD/l/day and 1.5,3,4,and 6days,respectively.With the two-stage SBR system,2days was used first as the system HRT,with 1day for the first-stage and 1day for the second-stage for both in flu-ents,and then 2.5days was used with 2days for the first stage and 0.5days for the second stage.An air flow rate of 4l/min was applied for all runs,which was able to main-tain dissolved oxygen (DO)in the SBR and CMBR above 3mg/l.The performance of the treatment systems was evalu-ated in terms of carbon and solids removal and nitrogen conversion ef ficiencies.The parameters analyzed included TS,volatile solids (VS),COD,SCOD (soluble COD),TKN,NH 3-N,NO 2-N,and NO 3-N.Two kinds of removal/con-version ef ficiencies were used to interpret the results for carbon and solids removal and nitrogen oxidation.One ef ficiency,E t ,is based on the removal from total ef fluent (including both sludge and liquid ef fluent generated),re-flecting the removal ef ficiency through biological process alone.The other ef ficiency,E l ,was based on the removal from liquid ef fluent,i.e.,supernatant,representing the removal ef ficiency through both biological process and sludge separation.For the single-stage SBR system,the total ef fluent was the ef fluent from the SBR and the liquid ef fluent was the supernatant decanted from the solids settling tank.For the two-stage SBR-CMBR system,the total ef fluent was the combination of sludge from the settling tank and the final ef fluent from CMBR,and the liquid ef fluent was the liquid ef fluent of CMBR.Most of previous research only reports removal ef ficiency from liquid ef fluent (E l ).Actually,E l does not re flect the real capability of a system for removing various constituents from wastewater,because part of these constituents are contained in the sludge that is separated from the liquid ef fluent and discharged as a separate sludge stream.Therefore,E t needs to be used in order to assess the real capability of a system for removing various constituents from wastewater.2.4Sampling and analytical methodsAfter each reactor reached steady state under testing conditions,samples were taken from the in fluent,mixed liquor,total ef fluent,and liquid ef fluent of the reactor three times a week (every other day)for analyses of COD,SCOD,TS,VS,NH 3-N,NO 2-N,NO 3-N,and TKN.The re-moval ef ficiencies,E l and E t ,were calculated based on the data from in fluent,liquid ef fluent,and total ef fluent of the systems.The separation of sludge and liquid in the total ef fluent of the SBR was performed by settling the ef fluent in a 1-l graduated cylinder for 2h and then decanting the liquid fraction above the sludge-liquid interface line.The COD,SCOD,TS,VS,and TKN were measured according to APHA standard methods [11].The COD measured in this study was COD Cr .The pH was measured with an Accumet pH meter (Fisher Scienti fic,Pittsburgh,Pa.).The NH 3-N was measured with a gas-sensing elec-trode and the pH meter.The DO in the reactors wasmonitored on a daily basis with a DO meter (YSI Mode158,Fisher Scienti fic,Pittsburgh,Pa.).The NO 2-N was analyzed with the HACH method,using a DR/2000spectropho-tometer [12].The NO 3-N was measured with a diffusion –conductivity analyzer [13].3Results and discussion3.1Performance of the single-stage SBR system3.1.1Removal of carbon and solidsThe performance data of the SBR for 10,000mg/l COD in fluent COD of 10,000are shown in Table 1.With the increase of HRT from 1to 3days,the COD,SCOD,TS,and VS in the liquid ef fluent became lower,yielding better ef fluent quality due to increased biological conversion and improved sludge settleability,as indicated by the increased removal ef ficiencies (E l and E t ).However,there wasnoboratory setup for a two-stage SBR-CMBR system for dairy wastewater treatmentX.Li,R.Zhang:Aerobic treatment of dairy wastewater with sequencing batch reactor systems105signi ficant difference in terms of carbon and solids rem-ovals and liquid ef fluent quality for the three HRTs.For example,the increase of COD and TS removal ef ficiency E l was 5.1%and 0.3%,and E t was 5.7%and 2.0%,respec-tively,when HRT increased from 1to 3days.Therefore,1-day HRT was believed to be suf ficient for treating the dairy wastewater with 10,000mg/l COD for its satisfactory removal ef ficiency and relatively short HRT.At 1-day HRT,the removal ef ficiency from the liquid ef fluent (E l )was 80.2%for COD,63.4%for TS,and 66.2%for VS.These removals were due to both biological conversion in the SBR and sludge separation in the solids-settling tank.The removal due to biological conversion alone in the SBR,as measured by E t ,was 45.0%for COD,21.4%for TS,and 34.2%for VS.E t was signi ficantly greater than E l ,sug-gesting that the sludge separation after SBR treatment is necessary for achieving signi ficant carbon and solids re-moval from the dairy wastewater.It was found that aerobic treatment greatly enhanced the flocculation and settlea-bility of the solids in the wastewater.Good settleability of sludge was important for achieving high carbon and solids removal ef ficiency.The performance data of the SBR for 20,000mg/l COD in fluent are shown in Table 2.The 1-day HRT was tested first.It was found that it was impossible to control the SRT at a desired level due to fast solids buildup in the reactor and poor solids settleability.When the HRT was increased to 2days,there was signi ficant improvement in the ef fluent quality and increase of removal ef ficiencies.However,when the HRT was further increased to 3days,the changes in the ef fluent quality,COD,and solids removals were not signif-icant.Therefore,2-day HRT was considered enough for COD and solids removal for 20,000mg/l COD in fluent due to its relatively short retention time and high removal ef fi-ciency.At 2-day HRT,the removal ef ficiency E l of COD,SCOD,TS,and VS was 85.7%,67.1%,71.0%,and 70.6%,respectively,and E t was 35.9%,67.1%,22.8%,and 25.6%,respectively.The 4-day HRT was tested for achieving com-plete ammonia conversion.Since ammonia was not com-pletely converted at 2-day and 3-day HRT,longer HRT was needed when complete nitri fication was desired.This will be further discussed in the following nitrogen removal section.The sludge separated from the ef fluent of the SBR contained 4.1–5.9%TS.The lower in fluent COD(10,000mg/l)resulted in better sludge settleability than the higher in fluent COD (20,000mg/l).The sludge volume as the fraction of total ef fluent volume was 5–6%and 13–16%for the lower and higher levels of in fluent COD,respectively.The sludge was composed of not-degraded solids in the wastewater and newly formed bacterial cells.It can be further processed into organic soil amendment through dewatering and composting.Table 1.Ef fluent quality and treatment ef ficiencies of SBR for 10,000mg/l COD in fluentParametersIn fluent (mg/l)1-day HRT 2-day HRT3-day HRT Liquid ef fluent Total ef fluent E l (%)E t (%)Liquid ef fluent Total ef fluent E l (%)E t (%)Liquid ef fluent Total ef fluent E l (%)E t (%)(mg/l)(mg/l)(mg/l)(mg/l)(mg/l)(mg/l)COD 10,0001,9806,50080.245.01,5805,13084.248.71,4704,93085.350.7SCOD 2,9141,4571,45750.050.01,4511,45150.250.21,4281,42851.051.0TS 6,6562,4365,23263.421.42,4765,07962.823.72,4165,09863.723.4VS 5,1081,7243,36166.234.21,5323,24970.036.41,4003,16772.638.0TKN 7801953657553.218535476.354.616533878.856.7TN 78048160738.322.248059838.523.447459639.223.6NH 3-N 51012012076.576.510510579.479.4707086.386.3NO 3-N 0375545NO 2-N 024*******pH8.16.86.76.7Table 2.Ef fluent quality and treatment ef ficiencies of SBR for 20,000mg/l COD in fluentPara-meters In fluent (mg/l)1-day HRT 2-day HRT 3-day HRT 4-day HRTLiquid ef fluent Total ef fluent E l (%)E t (%)Liquid ef fluent Total ef fluent E l (%)E t (%)Liquid ef fluent Total ef fluent E l (%)E t (%)Liquid ef fluent Total ef fluent E l (%)E t (%)(mg/l)(mg/l)(mg/l)(mg/l)(mg/l)(mg/l)(mg/l)(mg/l)COD 20,0004,30013,92078.530.42,87012,82085.735.92,66012,32086.738.4167010,90091.743.3SCOD 6,6603,1973,19752.052.02,1902,19067.167.12,0052,00569.969.912151,21581.881.8TS 12,4424,36710,11564.918.73,6129,60571.022.83,4989,58071.923.033509,19573.124.3VS 10,1043,1427,92268.921.62,9727,51770.625.62,8097,33672.227.424607,05375.729.5TKN 1,14054089952.621.118063884.244.017060085.147.48550092.552.3TN 1,14057393349.718.248491857.519.548891857.219.538888863.020.5NH 3-N 54031031042.642.6828284.884.8808085.285.200100100NO 3-N 020*********NO 2-N 01314013010pH8.08.77.97.87.6Bioprocess Biosyst Eng 25(2002)1063.1.2Nitrogen conversionWith the influent of10,000mg/l COD and1-to3-day HRT,22.2–23.6%of total nitrogen(TN)was lost in the treatment process as indicated by the E t.The losses of TN for the three HRTs were not significantly different.The ammonia collection results showed that the amount of NH3-N volatilized accounted for only2–3%of TN,indi-cating that the ammonia loss through volatilization was small under these operating conditions.The rest of TN loss (approximately20%)might be due to the emission of other nitrogenous gases,such as nitrous oxides(NO and NO2)formed in the nitrification process,and nitrogen gas (N2)formed in the denitrification process.The TKN removal was53.2–56.7%from the total effluent and75–78.8%from the liquid effluent,respectively.The TKN removal mainly resulted from ammonia oxidation.With the influent of20,000mg/l COD and1-to4-day HRTs,the loss of TN was18.2–20.5%.For the1-day HRT, the ammonia collection results showed that ammonia volatilization accounted for16%of TN,indicating that most of TN loss was due to ammonia volatilization.This occurred with the low nitrification rate in the SBR.But ammonia volatilization was insignificant at2-to4-day HRTs,at which the SBR had high nitrification activities. These results might imply that ammonia volatilization could be related to nitrification activity.Little nitrification occurrence at1-day HRT was due to the short SRT of 1.5days.This agrees with thefindings of Prakasam and Loehr[14],who stated that2-day SRT was the minimum for nitrification of poultry wastes.Therefore,HRT was increased to2days and3days,and corresponding SRT were3days and4days.It was found that nitrification was able to sustain in the SBR at both HRTs.At2-day and3-day HRT,the TN and TKN removals were19.5%and44.0–47.4%from the total effluent,and57.5–57.2%and84.2–85.1%from the liquid effluent,respectively.Significant NH3-N was removed,as indicated by removal efficiency of 84.8%for2-day HRT and85.2%for3-day HRT,although there was still80–82mg/l residual NH3-N present in the effluent.It can be seen that there was no significant dif-ference between two HRTs in terms of TN,TKN,and NH3-N removal.Therefore,if complete ammonia oxidation is not required,2-day HRT would be considered efficient for treating20,000mg/l COD influent in terms of both nitrogen removal discussed here and COD and solids removal as mentioned in Sect.3.1.1.Certain amounts of residual ammonia were present in the effluent from20,000mg/l COD influent at2-day and 3-day HRT.This indicates that the nitrification process might have been inhibited in both operation conditions. Nitrification inhibition might be due to possible inhibitions of nitrification bacteria by free ammonia(FA)and free nitrous acids(FNA)and suppression of nitrification bac-teria by more competitive heterotrophic bacteria[15].NH3 was undesirable because of its odor and toxicity to aquatic lives;thus,it needed to be removed from the wastewater. Shammas[16]studied the interaction of temperature,pH, and biomass on the nitrification process and concluded that high nitrification efficiency can only be obtained with either very long detention time or a combination of highsolids concentration and elevated temperature.Therefore,HRT was further increased to4days in order to obtain complete ammonia conversion.It was found that4-dayHRT,corresponding6-day SRT,was enough for complete ammonia conversion,as indicated by zero ammonia pre-sent in the effluent(see Table2).Therefore,it could be concluded that if complete ammonia conversion is desired,4-day HRT would be needed for treating20,000mg/l COD wastewater with540mg/l NH3-N.A track study was conducted in order to further un-derstand the nitrification process in the SBR.The varia-tions of NH3-N,NO2-N,and NO3-N in the SBR during a12-h operating cycle in treating the wastewater of10,000mg/l COD at2-day HRT are shown in Fig.2.Am-monia oxidation mostly occurred in thefirst5h,as indi-cated by the increase of NO2-N and decrease of NH3-N.Since a large amount of ammonia was oxidized in the earlystage of one cycle with high nitrification,the amount of ammonia volatilization may be decreased in contrast tothe condition when nitrification is small as mentionedabove.The relationship between ammonia volatilizationand nitrification activity needs to be further investigated infuture study.The pH could be another factor related to ammonia volatilization.Since higher medium pH in-creased the gas fraction of total ammonia dissolved in the medium,ammonia volatilization could have been highwhen there was little nitrification and pH maintained rel-atively high(approximately8.0),but small when there wasgood nitrification and the pH was decreased(Fig.2).TheNO2-N increased to the peak value about5h later after feeding and then started to decrease,while NO3-N startedto increase slightly.Generally speaking,the variations ofNH3-N,NO2-N,NO3-N,and pH in the SBR during the operating cycle depends on the bioconversion dynamics inthe reactor,initial ammonia concentration,and alkalinityin the wastewater.3.2Performance of the two-stage SBR-CMBR systemAs stated above,a4-day HRT is needed for achieving complete oxidation of ammonia in the dairy wastewaterin107the single-stage SBR.It appears that increasing HRT to achieve complete nitri fication is not cost effective.This led us to explore a two-stage treatment system.Research showed that nitrifying in a separate second-stage aeration system would increase nitri fication rate,due to the more suitable environment provided by a two-stage system than a single-stage system [17].In aerobic treatment,carbon oxidation is carried out by heterotrophic bacteria,while nitri fication is carried out by autotrophic bacteria.The two groups of bacteria are signi ficantly different in physiology,substrate requirement,metabolic characteristics,and growth kinetics.In a single-stage system,both carbon oxidation and nitri fication proceed in one reactor.This forces two groups of bacteria to coexist within the same physical and chemical environment,which is not optimal for either autotrophic or heterotrophic bacteria and makes it dif ficult to achieve optimum carbon and ammonia ually,longer HRT is applied in a single-stage system to balance the slow-growing autotrophic bacteria responsible for nitri fication and fast-growing he-terotrophic bacteria for carbon oxidation.But this is not economical,as mentioned above.A two-stage system could separate carbon oxidation and the nitri fication process and make each process proceed in a separate re-actor.The first-stage reactor is intended mainly for carbon oxidation and enhancement of solids settleability,and the second-stage reactor for providing suitable conditions fornitri fication.Since carbon could be oxidized quickly by fast-growing heterotrophic bacteria,the first-stage reactorcould use a relatively shorter HRT.After the first-stage SBR treatment,the solids settleability is improved as well,the sludge generated is separated and the liquid ef fluent is used as in fluent for the second-stage reactor.Sludge sep-aration would signi ficantly increase the system removal ef ficiency and reduce concentrations of constituents such as COD,TS,and NH 3-N in the in fluent,making it possible to use a shorter HRT,while maintaining a longer SRT for nitri fication in the second-stage reactor.With the opti-mization of environmental conditions and substratecharacteristics for heterotrophic and autotrophic bacteria in separate stages as mentioned above,the overall per-formance of the two-stage system can be improved and overall HRT reduced,as indicated from the performance data presented below.The two-stage system consisted of one SBR as the first stage and one CMBR as the second stage.The CMBR was selected to be the second-stage reactor,because the at-tached bacteria growth supported by the polyethylene pellets were believed to be favorable for nitri fication bac-teria by providing a long SRT.The CMBR was used to treat the liquid ef fluent from the SBR.Both SBR and CMBR were first operated at 1-day HRT,with the system HRT being 2days for treating 10,000mg COD/l and 20,000mg COD/l in fluent,respectively.The 1-day HRT in the CMBR was determined to be the appropriate level,based on preliminary test results.The performance data of the two-stage system are shown in Tables 3and 4.It can be seen that the liquid ef fluent quality and removal ef ficiencies of carbon,solids,and nitrogen from the two-stage system at 2-day HRT were comparable to those from the single-stage SBR at 3-day HRT for both in fluents.This suggests that,based on the HRT,the two-stage system would require 1/3less reactor volume than the single-stage system and therefore appears to have more favorable economics.In addition,the two-stage system allows complete ammonia oxidation in the wastewater as indicated by zero NH 3-N present in the two-stage system ef fluent at 2-day HRT as compared to 70mg/l NH 3-N in the one-stage ef fluent at 3-day HRT.Because with the in fluent of 20,000mg/l COD ammonia volatilization was high in the first-stage SBR at 1-day HRT,Table 3.Performance of two-stage SBR-CMBR system for 10,000mg/l COD in fluent In fluent (mg/l)Stage I:SBR(1-day HRT)Stage II:CMBR (1-day HRT)E l (%)E t (%)Liquid ef fluent Liquid ef fluent (mg/l)(mg/l)COD 10,0001,9801,37486.351.1SCOD 2,9141,4571,01465.265.2TS 6,6562,4362,07668.824.8VS 5,1081,7241,47271.239.1TKN 7801956092.358.0TN 78048143544.224.7NH 3-N 510120 2.599.599.5NO 3-N 037195NO 2-N 0249180pH 8.16.87.9Table 4.Performance of the two-stage SBR-CMBR system for 20,000mg/l COD in fluentIn fluent (mg/l)stage I:SBR (1-day HRT)stage II:CMBR (1-day HRT)E l (%)E t (%)stage I:SBR (2-day HRT)stage II:CMBR (0.5-day HRT)E l (%)E t (%)Liquid ef fluent Liquid ef fluent Liquid ef fluent Liquid ef fluent (mg/l)(mg/l)(mg/l)(mg/l)COD 20,0004,3002,67686.637.028********.543.8SCOD 6,6603,1972,02069.769.7219089086.686.6TS 12,4424,3673,43272.421.83612267078.526.4VS 10,1043,1422,15278.727.029********.532.5TKN 1,14054018084.246.11804096.556.2TN 1,14057350455.823.248443062.321.5NH 3-N 540310 3.099.499.4820100100NO 3-N 020*********NO 2-N 0131341400pH 8.08.77.87.97.4Bioprocess Biosyst Eng 25(2002)108。
污水处理的英文文献翻译(1)
Nutrient removal in an A2O-MBR reactor with sludgereductionABSTRACTIn the present study, an advanced sewage treatment process has been developed by incorporating excess sludge reduction and phosphorous recovery in an A2O-MBR process. The A2O-MBR reactor was operated at a flux of 77 LMH over a period of 270 days. The designed flux was increased stepwise over a period of two weeks. The reactor was operated at two different MLSS range. Thermo chemical digestion of sludge was carried out at a fixed pH (11)and temperature (75℃) for 25% COD solubilisation. The released pbospborous was recovered by precipitation process and the organics was sent back to anoxic tank. The sludge digestion did not have any impact on COD and TP removal efficiency of the reactor. During the 270 days of reactor operation, the MBR maintained relatively constant transmembrane pressure. The results based on the study indicated that the proposed process configuration has potential to reduce the excess sludge production as well as it didn't detonated the treated water quality.Keywords: A2O reactor; MBR; Nutrient removal; TMP1. IntroductionExcess sludge reduction and nutrients removal are the two important problems associated with wastewater treatment plant. MBR process has been known as a process with relatively high decay rate and less sludge production due to much longer sludge age in the reactor (Wenet al., 2004). Sludge production in MBR is reduced by 28-68%, depending on the sludge age used (Xia et al.,2008). However, minimizing the sludge production by increasing sludge age is limited due to the potential adverse effect of high MLSS concentrations on membrane (Yoon et al., 2004). This problem can be solved by introducing sludge disintegration technique in MBR (Young et al., 2007). Sludge disintegration techniques have been reported to enhance the biodegradability of excess sludge (Vlyssides and Karlis, 2004). In overall, the basis for sludge reduction processes is effective combination of the methods for sludge disintegration and biodegradation of treated sludge. Advances in sludge disintegration techniques offer a few promising options including ultrasound (Guo et al., 2008), pulse power (Choi et al.,2006), ozone (Weemaes et al., 2000), thermal (Kim et al., 2003), alkaline (Li et al., 2008) acid (Kim et al., 2003) and thermo chemical(Vlyssides and Karlis, 2004). Among the various disintegration techniques, thermo chemical was reported to be simple and cost effective (Weemaes and Verstraete, 1998). In thermal-chemical hydrolysis, alkali sodium hydroxide was found to be the most effective agent in inducing cell lysis (Rocker et al., 1999). Conventionally, the nutrient removal was carried out in an A2O process. It has advantage of achieving, nutrient removal along with organic compound oxidation in a single sludge configuration using linked reactors in series (Tchobanoglous et al., 2003). The phosphoroes removal happens by subjecting phosphorous accumulating organisms (PAO) bacteria under aerobic and anaerobic conditions (Akin and Ugurlu, 2004). These operating procedures enhance predominance PAO, which are able to uptake phosphorous in excess. During the sludge pretreatment processes the bound phosphorous was solubilised and it increases the phosphorousconcentration in the effluent stream (Nishimura, 2001).So, it is necessary to remove the solubilised phosphorus before it enters into main stream. Besides, there is a growing demand for the sustainable phosphorous resources in the industrialized world. In many developed countries, researches are currently underway to recover the phosphoroes bound in the sludge's of enhanced biological phosphorus removal system (EBPR). The released phosphorous can be recovered in usable products using calcium salts precipitation method. Keeping this fact in mind, in the present study, a new advanced wastewater treatment process is developed by integrating three processes, which are: (a) thermo chemical pretreatment in MBR for excess sludge reduction (b) A2O process for biological nutrient removal (c) P recovery through calcium salt precipitation. The experimental data obtained were then used to evaluate the performance of this integrated system.2. Methods2.1. WastewaterThe synthetic domestic wastewater was used as the experimental influent. It was basically composed of a mixed carbon source, macro nutrients (N and P), an alkalinity control (NaHCO3) and a microelement solution. The composition contained (/L) 210 mg glucose, 200 mg NH4C1, 220 mg NaHCO3, 22一34 mg KH2PO4, microelement solution (0.19 mg MnCl2 4H20, 0.0018 mg ZnCl22H2O,0.022 mg CuCl22H2O, 5.6 mg MgSO47H2O, 0.88 mg FeCl36H2O,1.3 mg CaCl2·2H2O). The synthetic wastewater was prepared three times a week with concentrations of 210±1.5 mg/L chemical oxygen demand (COD), 40±1 mg/L total nitrogen (TN) and 5.5 mg/L total phosphorus (TP).2.2. A2O-MBRThe working volume of the A2O-MBR was 83.4 L. A baffle was placed inside the reactor to divide it into anaerobic (8.4 L) anoxic (25 L) and aerobic basin (50 L). The synthetic wastewater was feed into the reactor at a flow rate of 8.4 L/h (Q) using a feed pump. A liquid level sensor, planted in aerobic basin of A2O-MBR controlled the flow of influent. The HRT of anaerobic, anoxic and aerobic basins were 1, 3 and 6 h, respectively. In order to facilitate nutrient removal, the reactor was provided with two internal recycle (1R). IRl (Q= 1)connects anoxic and anaerobic and IR 2 (Q=3) was between aerobic and anoxic. Anaerobic and anoxic basins were provided with low speed mixer to keep the mixed liquid suspended solids (MLSS) in suspension. In the aerobic zone, diffusers were used to generate air bubbles for oxidation of organics and ammonia. Dissolved oxygen (DO) concentration in the aerobic basin was maintained at 3.5 mg/1 and was monitored continuously through online DO meter. The solid liquid separation happens inaerobic basin with the help of five flat sheet membranes having a pore size of 0.23 pm. The area of each membrane was 0.1 m2. They were connected together by a common tube. A peristaltic pumpwas connected in the common tube to generate suction pressure. In the common tube provision was made to accommodate pressure gauge to measure transmembrane pressure (TMP) during suction. The suction pump was operated in sequence of timing, which consists of 10 min switch on, and 2 min switch off.2.3. Thermo chemical digestion of sludgeMixed liquor from aerobic basin of MBR was withdrawn at the ratio of 1.5% of Q/day and subjected to thermo chemical digestion. Thermo chemical digestion was carried out at a fixed pH of 11(NaOH) and temperature of 75℃for 3 h. After thermo chemical digestion the supernatant and sludge were separated. The thermo-chemicallydigested sludge was amenable to further anaerobic bio-degradation (Vlyssides and Karlis, 2004), so it was sent to theanaerobic basin of the MBR2.4. Phosphorus recoveryLime was used as a precipitant to recover the phosphorous in the supernatant. After the recovery of precipitant the content was sent back to anoxic tank as a carbon source and alkalinity supelement for denitrification.2.5. Chemical analysisCOD, MLSS, TP, TN of the raw and treated wastewater were analyzed following methods detailed in (APHA, 2003). The influent and effluent ammonia concentration was measured using an ion-selective electrode (Thereto Orion, Model: 95一12). Nitrate in the sample was analyzed using cadmium reduction method (APHA, 2003).3. Results and discussionFig. 1 presents data of MLSS and yield observed during the operational period of the reactor. One of the advantages of MBR reactor was it can be operated in high MLSS concentration. The reactor was seeded with EBPR sludge from the Kiheung, sewage treatment plant, Korea. The reactor was startup with the MLSS concentration of 5700 mg/L. It starts to increase steadily with increase in period of reactor operation and reached a value of 8100 mg/L on day 38. From then onwards, MLSS concentration was maintained in the range of 7500 mg/L by withdrawing excess sludge produced and called run I. The observed yields (Yobs) for experiments without sludge digestion (run I) and with sludge digestion were calculated and given in Fig. 1. The Yobs for run I was found to be 0.12 gMLSS/g COD. It was comparatively lower than a value of 0.4 gMLSS/g CODreported for the conventional activated sludge processes (Tchoba-noglous et al., 2003). The difference in observed yield of these two systems is attributed to their working MLSS concentration. At high MLSS concentration the yield observed was found to be low (Visva-nathan et al., 2000). As a result of that MBR generated less sludge.The presently used MLSS ranges (7.5一10.5 g/L) are selected on the basis of the recommendation by Rosenberger et al. (2002). In their study, they reported that the general trend of MLSS increase on fouling in municipal applications seems to result in no impact at medium MLSS concentrations (7一12 g/L).It is evident from the data that the COD removal efficiency of A2O system remains unaffected before and after the introduction of sludge digestion practices. A test analysis showed that the differences between the period without sludge digestion (run I) and with sludge digestion (run II and III) are not statistically significant.However, it has been reported that, in wastewater treatment processes including disintegration-induced sludge degradation, the effluent water quality is slightly detonated due to the release of nondegradable substances such as soluble microbial products (Ya-sui and Shibata, 1994; Salcai et al., 1997; Yoon et al., 2004). During the study period, COD concentration in the aerobic basin of MBR was in the range of 18-38 mg/L and corresponding organic concentration in the effluent was varied from 4 to 12 mg/L. From this data it can be concluded that the membrane separation played an important role in providing the excellent and stable effluent quality.Phosphorus is the primary nutrient responsible for algal bloom and it is necessary to reduce the concentration of phosphorus in treated wastewater to prevent the algal bloom. Fortunately its growth can be inhibited at the levels of TP well below 1 mg/L (Mer-vat and Logan, 1996).Fig. 2 depicts TP removal efficiency of the A2O-MBR system during the period of study. It is clearly evident from the figure that the TP removal efficiency of A/O system was remains unaffected after the introduction of sludge reduction. In the present study, the solubilised phosphorous was recovered in the form of calcium phosphate before it enters into main stream. So, the possibility of phosphorus increase in the effluent due to sludge reduction practices has been eliminated. The influent TP concentration was in the range of 5.5 mg/L. During thefirst four weeks of operation the TP removal efficiency of the system was not efficient as the TP concentration in the effluent exceeds over 2.5 mg/L. The lower TP removal efficiency during the initial period was due to the slow growing nature of PAO organisms and other operational factors such as anaerobic condition and internal recycling. After the initial period, the TP removal efficiency in the effluent starts to increase with increase in period of operation. TP removal in A2O process is mainly through PAO organisms. These organisms are slow growing in nature and susceptible to various physicochemical factors (Carlos et al., 2008). During the study period TP removal efficiency of the system remains unaffected and was in the range of 74-82%.。
污水处理英文文献
1.Introduction污染的重要来源造成水体富营养化的地表水农村地区的农业面源-(提尔曼etal.源污染物,2002年)。
这些有氨氮径流和污染物被抬进地表水在下雨事件,造成水体富营养化(提尔曼etal.杂志,2001;Panetal.,2010年)。
另一个重要的源引起eutrophicationis 弥漫性污染物(通常由当地生活污水排放社区)流入下游的洪水在农村地区(提尔曼etal.,2002年)。
因此,这是很重要的,同时去除从土壤和水体污染物(污水)在农村地区。
基于生态工程等多种措施之一提出了农业有氨氮污染控制。
例如,biopond系统,构建多层次sorsoil-infiltration缓冲区域,人工湿地系统(Rodeetal.常常被运用,2009年)。
可是,这些技术集中在治疗而非预防农业有氨氮污染。
此外,传统的污水处理设施ocollect明显处于adequatet(USEPA和治疗有氨氮污染物,1989年9月初版。
一个系统收集去除污染物从复杂residentiale农田区域同时要考虑到目前为止,各种技术处理农村家庭废水已经提出来了。
这些可以概括为四组。
第一个是基于soil-filtration,包括slow-infiltration land-treatment系统(Schaub etal.,1982),rapidsoil-infiltration系统(Huthins sand-filter etal.,1983年),系统(Urynowiczetal.,2007年),人工湿地(侗etal.,2005年),capillary-barrier渗透系统(Yangetal.,2004年),和earthworm-amended过滤器(Nahmanietal.土壤Costelloand,2007年;Lamberti,2009年)。
这些condgroup是biotoilet系统使用比较广泛的在日本(AngelandNaoyuki,2005)。
一篇 污水 处理 英文 论文
TREATMENT OF DOMESTICWASTEWATER BY ENHANCEDPRIMARY DECANTATION AND SUBSEQUENT NATURALLYVENTILATED TRICKLING FILTRATIONLINPING KUAI, WIM KERSTENS, NGUYEN PHU CUONGand WILLY VERSTRAETECentre for Environmental Sanitation, Faculty of Agricultural and Applied Biological Sciences,University of Gent, Coupure links 653, 9000 Gent, Belgium(* author for correspondence, e-mail: willy.verstraete@rug.ac.be)(Received 16 January 1998; accepted 22 June 1998)Abstract. To treat household wastewater, a sequence of ‘primary decantation–trickling filter percolation’ was applied in a lab-scale designed treatment system. Poly-electrolyte was used as coagulant toenhance the primary treatment and charcoal was used as carrier material in the trickling filters. Oxy-gen was supplied to the trickling filters by means of natural ventilation. In the labscale system, theenhanced primary stage removed more than 91% of the suspended solids (SS), and 79% of the totalchemical oxygen demand (CODt). The subsequent trickling filtration brought a complete nitrificationto the wastewaters at a volumetric loading rate (Bv) of 0.7–1.0 g CODt L−1 d−1.Onaverage,theconcentrations of the CODt and SS in the final effluents were about 55 and 15 mg L−1 respectively.With respect to phosphate, physico-chemical removal was the dominant process. About 46–62% oftotal P was removed from the tested wastewaters. The integrated treatment system also achieved a fairdegree of hygienisation. The numbers of total coliforms, fecal coliforms and fecal streptococci weredecreased by 2–4 log units. The sludge production of the entire treatment system was about 1.7%(v/v) of the treated wastewater. Only primary sl udge was produced; secondary sludge produced in thetrickling filters was negligible. The cost savings in terms of minimization of sludge production andaeration energy are estimated to be substantial (i.e. some 50%) relative to a conventional activatedsludge system.Keywords: charcoal, coagulation, cost evaluation, household wastewater, nitrification, pathogenremoval, poly-electrolyte, sedimentation, small-scale, trickling filter1.Introduction2.Water pollution in many developing regions causes serious problems. Often thepopulation is living in small villages which are scattered in the countryside. Theincrease of the population and the improvement of people’s daily life in these areasresult not only in an increase of the volume of wastewater, but also in a changeof the wastewater composition which tends to contain more chemicals such asdetergents. Change of the nightsoil system to the flush toilet brings about 90% ofthe nightsoil into wastewater (Ukita et al., 1993). Direct discharge of nightsoil intolocal waters endangers the hygienic quality. Although no systematic epidemiological studies have been conducted in developing countries, it is generally assumedWater, Air, and Soil Pollution 113: 43–62, 1999.© 1999 Kluwer Academic Publishers.Printed in the Netherlands.44LINPING KUAI ET AL.that the direct discharge of raw nightsoil is responsible for a high risk of infectiousdisease transmission in many rural regions of the developing countries (Schertenleib, 1995). Water shortage in arid and semi arid areas can necessitate the reuseof wastewater for local irrigation (Mandi et al., 1993). Treatment of this potentialresource is imperative to avoid sanitary risks before re-use (Hespanhol, 1990).The main objective of wastewater treatment is to dispose the treated effluentwithout causing an adverse impact on the ecosystem of the receiving water body.For this reason sewage treatment always includes the reduction of the concentrationof at least one of the four most important constituents of sewage: (1) suspendedsolids; (2) organic matter; (3) nutrients (notably nitrogen and phosphorus); and(4) pathogenic organisms (Van Haandel and Lettinga, 1994). Up to now, the western model of sewage treatment is the dominant one leading the environmental technological development over the world. However, the techniques which havebeen developed to achieve high levels of N and P removal, might not be applicablein many developing countries because of limited financial and energy resourcesavailable (Larsen and Gujer, 1997; Netter et al., 1993). Yet, since agriculture re-quires a substantial amount of water and nutrient input, safe reuse of treated sewagein these regions can free high quality water for other purposes and can supplementchemical fertilizers. Efficient use of resources will lead to a minimal increase ofentropy and will require an active rather than a reactive approach (Larsen andGujer, 1997). It is therefore of importance in many developing areas to treat sewageto the extend that it can be safely reused on the land. If the wastewater has to bedischarged to the local water-bodies, it should be treated so that the quality ofthe receiving water can be maintained at a level for safe drinking with no risk ofpathogens, no bad smell, no depletion of O2 and no toxicity from NHC4 or NH3.Hence, removal of pathogens and organic matter, in addition to achieving a highlevel of nitrification are essential.Centralized sewage treatment plants are generally not suitable for rural areas.Collection of domestic wastewater and transport to a distant treatment plant isexpensive at low population density (Netter et al., 1993; Paulsrud and Haraldsen,1993). On-site treatment using small scale wastewater treatment plants is the mostcost-effective alternative. The treatment technology for small wastewater streamsshould be based on locally available and serviceable materials and equipments thatare simple and economical to operate. Those low technical skills needed are the most appropriate ones (Ødegaard, 1997). A primary settling tank combined witha t rickling filter based on natural materials and natural ventilation might be anappropriate solution for water pollution control in most rural areas, especially indeveloping countries. The small-scale treatment unit designed for individual house holds or small communities can be compact and closed without causing negativeimpact on the landscape and without producing noise or odors. It can handle fluctuations in hydraulic and organic loads without variation in removal efficiencies(D’Antonio et al., 1997).TREATMENT OF DOMESTICWASTEWATER 45TABLE IThe main characteristics of the two types of wastewater(Average Standard deviation)Parameter UnitThe MHWThe SHWCODtmg L−1 500.0±376 2865.0±3822CODs mg L−1 161.0±42 205.0±134SS mg L−1 673.0±425 2555.0±3103Total N mg L−1 41.0±13 204.0±161Kj-N mg L−1 41.0±13 202.0±161NHC4 -N mg L−1 30.0±1063.0±28NOx−-N mg L−1 0.0 2.03Total Pmg L−1 8.0±3 26.0±13PO3C4 –Pmg L−1 4.0±3 13.0±4pH 7.2±0.4 7.7±0.3The purpose of our research was to develop a treatment process that will guarantee the technical asibility in rural areas, taking into consideration factors suchas the construction and maintenance costs, the availability of construction materialsand equipment, the limitation of land for anindividual household, the productionof noise and odor as well as specialized labor and skills, especially for developingcountries.2. Materials and Methods2.1. WASTEWATERTwo types of domestic wastewaters were tested in the experiments. One was amultiple households wastewater (MHW) obtained from a municipal wastewatertreatment plant located in Gent, Belgium. The other was a single household wastewater (SHW) collected from a family living in the rural area of Avelgem, Belgium.The wastewater samples were taken generally once a week from the sites andstoredat 4 C in the lab before feeding. The main characteristics of the wastewaters aregiven in Table I. The SHW was about 3 times more concentrated than the MHWbecause the water consumption of the family was relatively low and rainfall wasnot entering the wastewater collecting system. Instead of 180 L per inhabitantequivalent (I.E.) per day, discharged to the municipal wastewater treatment plant,the family only discharged maximally 70 L (I.E.)−1d−146LINPING KUAI ET AL.2.2EXPERIMENTS2.2.1. Integrated Treatment of the Multiple Households WastewaterThe process diagram used for the treatment of the MHW is illustrated in Figure 1.The lab-scale integrated system consisted of an influent tank of 30 L, a primarysettling tank of 6 L and a na turally ventilated trickling filter of 2.5 L. To enhancethe natural aeration, as illustrated in Figure 2, the trickling filter was modified basedTREATMENT OF DOMESTICWASTEWATER 47on a conventional trickling filter by placing a net column inside to improve the O2supply. This inner net column was made with PVC and about 80% of the wall areawas holes with 1 cm in diameter. The dimensions of the modified trickling filterwere 1.0 m in height, 0.08 m in diameter of the outside PVC column and 0.056 mof the inside net column. A commercial charcoal (Charbon de bois Epure, S. A.Delhaize, Brussels, Belgium) was used as carrier material, it was grinded toparticles with diameter of about 2 cm before use. Aeration occurred via natural contactwith air entering through the inside net column. Supplemental forced aeration wasnot imposed.The raw MHW was batch fed into the influent tank once a day. It was pumpedsemi-continuously from the influent tank into the primary settling tank in upwarddirection, i.e. 10 min every 15 min. During the pumping period, the influent was si-multaneously mixed by a mixer to avoid accumulation of solids in the influent tank.Chemical coagulation was not applied in the primary stage. The supernatant fromthe primary settling tank automatically flowed into the subsequent trickling filterby gravity force. It percolated over the carrier in downward direction. Operation ofthe trickling filter was started at a low loading rate. The loading rate was increasedstep-wise during the first few weeks depending on the removal e fficiencies of totalchemical oxygen demand (CODt) and NHC4 -N. After an adaptation period of 4weeks, the flow rate was controlled around 25 L d−1, and the HRTs (hydraulicretention time) of the primary settling tank and the trickling filter were 5.8 and2.4 hr, respectively. The volumetric loading rate (Bv) of the trickling filter wasabout 1.0 g COD L−1d−1corresponding to 0.35 g Kj-N L−1d−1(based on theCODt and Kj-N concentrations of the outflow from the primary settling tank). During the whole experimental period, the integrated treatment system was operated atroom temperature varying around 20 C.2.2.2. Integrated Treatment of the Single Household Wastewater2.2.2.1. (a). Primary Coagulation and Sedimentation Tests Before operation ofthe integrated treatment system, a jar test using chemical coagulation and sedimentation to pre-treat the highly concentrated wastewater was carried out. Polyelectrolyte (Praestol BC 611, ChemischeFabrik Stockhausen Gmbh, Krefeld, Germany) was used as the coagulant. Five different dosages of poly-electrolyte, namely0, 2.5, 5, 7.5, 10 mg L−1, were tested. The wastewater sample (800 mL) and theneeded amount of the poly-electrolyte stock solution (1 g L−1) were added into1000 mL beakers. After mixing at 250 rpm for 2 min, the mixed liquors wereallowed to settle for 30 min and the supernatants were taken for analyses. The testswere performed twice with samples obtained at two different times.2.2.2.2. (b). Operation of the Integrated T reatment System The process diagramof the integrated system operated for the SHW was similar to the one used for theMHW treatment. However, the individual treatment units were slightly different.The volume of the influent tank and the primary settling tank were smaller, only48 LINPING KUAI ET AL.10 and 4 L, respectively. The employed trickling filter was a conventional tricklingfilter constructed with a PVC column with a total volume of 2 L, 1.0 m in heightand 0.05 m in diameter. The detailed structure is demonstrated in Figure 1. Freshcharcoal, grinded and sieved to a particle size of about 2 cm, was used as carriermaterial. On the top of the trickling filter, a layer of 10 cm of crushed stones with0.5 to 1 cm in diameter, was placed in order to improve the influent distribution.About 8 small holes, with 1 cm in diameter each, were scattered on the wall of thePVC column close to the bottom. Aeration occurred via contact with air enteringthrough the aeration holes.Based on the results of the primary coagulation and sedimentation tests, chemical coagulation was applied in the primary treatment stage for this highly con centrated SHW. The raw SHW and about 5 mg L−1of poly-electrolyte (PraestolBC 611) were batch added into the influent tank once a day. They were mixed inthe influent tank and pumped into the primary settl ing tank in upward direction simultaneously, for 10 min in every 15 min. The consequential treatment procedureswere similar to those applied for the MHW treatment. After an adaptation periodof 4 weeks, the flow ratewas controlled around 10 L d−1. The Bv of the tricklingfilter fluctuated around 0.7 g CODt L−1d−1which was about 30% lower than theone applied for the MHW treatment. The nitrogen loading rate was about 0.3 gKj-N L−1d−1. The HRT was about 9.6 hr in the primary settling tank and 4.8 hr inthe trickling fil ter. The primary sludge was removed at intervals from the primarysettling tank, e.g. once every two weeks. The system was also operated at roomtemperature around 20 C.2.3. ANALYSESThe routine analyses were carried out once a week unless stated otherwise. Theinfluent and effluent samples were collected proportionally everyday and stored at4 C until analyses. The parameters of COD, Kj-N (Kjeldahl-N), NHC4 -N, NOx -N,andPt (total P) were determined in accordance to the Standard Methods (APHAet al., 1992). Total coliform (TC), fecal coliform (FC) and fecal streptococci (FS)were enumerated by plate count techniques as described by Kersters et al. (1995).3. ResultsThe treatment performance of the laboratory integrated systems were monitoredby determining the removal of (1) suspended solid; (2) organic materials (CODt);(3) nutrients (N and P); and (4) pathogenic organisms (TC, FC and FS).TREATMENT OF DOMESTICWASTEWATER 49TABLE I IThe results of the jar tests on the raw SHW3.1. CODt AND SS REMOVAL3.1.1. Primary Jar Tests to Pre-Treat the SHW by Coagulation and SedimentationThe results of the jar tests by coagulation and sedimentation are described in Table II. For the concentrated SHW, simple sedimentation gave an insufficient andunstable removal of COD t which varied from 23 to 73%. The poly-electrolyteshowed to be highly effective to enhance the CODt removal. By adding 5 mg L−1of poly-electrolyte, the removal percentage of CODt increased to 93%.3.1.2. The Integrated SystemThe change of the CODt concentrations during the whole experimental period areshown in Figure 3. The influent CODt and SS in both types of wastewaters variedconsiderably. For the SHW, up to 15700 mg L−1of CODt was measured in week15 coupled with a high SS concentration of 11200 mg L−1. The variation of theMHW was slightly lower because the wastewater was taken after a grit chamberwhere large particles had already been removed. However, as shown in Figure 3,the influent CODt was still often up to 1000 mg L−1, which was 2 times as high asi tsmean value.The high CODt mainly resulted from the high SS concentration. The primarytreatments removed the major part of CODt and SS from both types of wastewaters.As indicated in Table III, although in the treatment of MHW, poly-electrolyte wasnot used in the primary stage, straight-forward sedimentation still removed 79% ofCODt and 91% of SS, leaving a stable CODt concentration in the effluent rangingfrom 80 to 250 mg L−1. For the SHW, combination of chemical coagulation andsedimentation could even remove up to 95% of CODt and 99% of SS, respectively.Fluctuation of the loading rates was successfully smoothed. The effluent after theprimary stage had a relatively stable concentration of CODt, mostly between 100to 200 mg L−1.The subsequent trickling filters polished the outflows from the primary settlingtanks to a high quality. The final effluents of the MHW and SHW contained a lowCODt concentration of 55 and 50 mg L−1as well as a low SS concentration of 17and11mgL−1in average, respectively.50 LINPING KUAI ET AL.Figure 3.The concentration of CODt in the different process stages. A) The multiple households wastewater; B) The single household wastewater.In total, the entire processes removed respectively about 98% of CODt and 99%of SS fromthe SHW, and about 89% of CODt and 98% of SS from the MHW.3.2. REMOVAL OF NITROGENThe concentrations of nitrogen compounds in the different treatment processes areindicated in Figure 4. The removal percentages are listed in Table IV. As shown inTable IV, for both types of wastewaters, the pri mary treatments were shown sufficient for organic N removal but not for NHC-N removal. For the MHW, the singlesedimentation stage removed about 15% of the Kj-N which was totally due to theremoval of organic N. Of the residual Kj-N in the outflow, 9% was contributedby organic N. For the SHW, about 69% of Kj-N was removed in which only 3%was due to the removal of NHC4 -N. The primary coagulation and sedimentationremoved almostall the organic N.Of the residual Kj-N in the outflow, only 1.6%came from organic N.The trickling filters converted the residual Kj-N mainly to NO−x -N by means ofnitrification. Figure 5 shows that the two trickling filters were all characterized bya start-up period of about 3 weeks with a limited efficiency of nitrification for bothtypes of wastewaters. Significant decrease of NHC4 -N concentration and increase ofNO−x -N concentration in the effluents of the trickling filter occurred simultaneouslyfrom week 3 onwards. After an adaptation period of about 4 weeks, the removalrates of NHC4 -N in the trickling filters increased to 0.30 and 0.25 g NHC4 -N L−1Figure 4.The change of N concentration in the different treatment stages. A) The multiple householdswastewater; B) The single household wastewater.d−1for the MHW and SHW, respectively. On average, about 60% of NHC4 -N wasconverted to NOxN from the MHW and 75% from the MHW.The total N removal was different for the two types of wastewaters. For theMHW, the entire system removed about 49%of total N, in which 15%was removedby the primary sedimentation and another 34% was contributed by the tricklingfilter as partial denitrification occurred in the reactor. The final effluent of theMHW contained 3 mg L−1ofKj-Nand18mgL−1of NO−x -N. For the SHW,the primary coagulation and sedimentation processes removed about 69% of theotal N. However, only a very limited removal of total N, about 2%, was achievedTREATMENT OFin the trickling filter. The final effluent of the SHW contained about 14 mgL−1ofKj-Nand46mgL−1of NO−x -N, respectively.3.3. REMOVAL OF PHOSPHORUSor both types of wastewaters, removal of total phosphorus (Pt) was stable duringhe whole experimental period. As shown in Table V, Pt was mainly removed inhe primary stage. Physico-chemical removal of Pt was the dominant pathway. Inotal, the removal of Pt was about 49% from the MHW and 62% from the SHW.The residual Pt in the final effluents was about 4 and 10 mg L−1, respectively.3.4. HYGIENEThe removal of pathogens from the two wastewaters by the integrated treatmentas quite similar. As shown in Table VI, a fair degree of hygienisation was achieved.n total, the numbers of total coliforms (TC), fecal coliforms (FC) and fecal streptococci (FS) were reduced by 2–4 log units. The reduction was mainly broughtbout by the trickling filters.TREATMENT OF DOMESTICWASTEWATER 553.5. SLUDGE PRODUCTION3.5.1. Primary SludgeThe MHW was less concentrated than the SHW and chemical coagulation wasot imposed in the primary stage. Therefore, sedimentation of the MHW did notprodu ce much sludge. In the first 2 months, the volume of the sludge accumulatedin the primary settling tank increased slowly to 4 L. After that, increase of thesludge volume did not proceed. During the whole operational period of 5 months,there was no need to discharge sludge from the primary settling tank. For the SHW,the primary coagulation and sedimentation stage produced about 1.7% (v/v) ofsludge relative to the total flow of the raw wastewater. The sludge produced wasregularly withdrawn from the primary settling tank once every two weeks. Thewaste sludge was a mixture of under-flow and skimmed floating material and hada concentration of 40 to 50 g SS L−1.3.5.2. Secondary Sludge Secondary sludge produced in the trickling filters was negligible for the two typeso f wastewaters. This was reflected by the low SS concentrations in the effluents;a secondary decanter was not necessary. The two test-runs revealed that the integrated system was stable in operation over an observation period of more than 5months under the given lab-scale conditions. Clogging was never experienced inthe trickling filters.4. Discussion4.1. COAGULATION AND SEDIMENTATIONIn practice, both the quantity and quality of wastewater can vary drastically. It iswell known that the smaller the population, the more pronounced the variation.Whereas larger cities exhibit a variation factor, defined as maximum load/meanload of 1.5–2, the factor may be as high as 5 in small domestic residential areas(Markus, 1997). Therefore, the dynamics of flow and load variations ask for equalization and pretreatment. Especially, when applying high rate treatment systemswith short retention times such as trickling filters and rotating biological contactors, a stable loading rate is an important prerequisite for satisfactory treatmentperformance. Pretreatment also ensures the high quality of the final effluent. Itcan effectively remove the recalcitrant COD fraction as this fraction is mainlyassociated with particles and colloids (Yoshimasa and Yoshihiko, 1997; Rustenet al., 1997).In the treatment of theMHWwith the integrated system, during the first 3 weeksof operating, the COD removal by the simple sedimentation step was not as goodas the one combined with coagulation in the treatment of the SHW (Figure 3).However, from week 4 onwards when enough amount of sludge was accumulated56 LINPING KUAI ET AL.in the primary settling tank and the sludge bed had built up, increase of the CODtremoval was observed. This fact indicated that the sludge bed could serve as asorption layer capturing particles and colloids effectively.For the SHW, the primary jar tests with coagulation and sedimentation showedthat for the concentrated SHW, simple sedimentation was insufficient and unstableto buffer the high variation of the wastewater (T able II). This poor and variableperformance was mainly due to the poor settling characteristics of the SHW.Whenthe wastewater contained much toilet wastes, which also happened frequently during the experimental period, it became very turbid with colloids and settled poor ly.Yet, by adding 5 mg L−1of poly-electrolyte, the removal of the CODt increasedto 93%. This clearly indicated that combination of coagulation and sedimentationwas necessary to ensure a high and stable performance of the primary settling tank.During the operation of the integrated treatment system, the high performance andthe considerable equilibrium capacity of the primary coagulation and sedimentation processes were furtherconfirmed (Figure 3). Not only did it remove about79–95% of CODt, but also absorbed the peak CODt, which varied from 240 to15800 mg L−1. Consequently, the influence of a shock load to the downstreamtrickling filter was alleviated and a high performance was guaranteed.The hydraulic retention time of about 6–10 hr in the two primary settling tankswas relatively long compared with a normal primary settling time of 1–2 hours.The reason of applying the large primary settling tanks was to make them functionboth as primary sludge separation and sludge storage tanks. Long time retention ofsludge in the primary settling tanks, especially in the case of the MHW treatment,resulted in sludge hydrolysis and digestion. Because of sludge hydrolysis and digestion, the sludge production was reduced and a slightly increase of the NHC4 –Nconcentration in the effluent, from 30 to 32 mg L−1, was observed (Figure 4).4.2. TRICKLING FILTERA trickling filter purifies wastewater through physical filtration/adsorption and bi ological degradation. Generally, at least two biological processes are involved ina trickling fil ter, i.e. COD degradation and nitrification. In some cases, partialdenitrification occurs simultaneously (Bertanza, 1997).During the experimental period of 5 months, the effluent CODt from the twotrickling filters remained below 70 mg L−1. Mostly, they were below 60 mg L−1.Without a secondary decanter, the SS concentration in the effluents was around10–20 mg L−1, which indicated that sludge production in the trickling filters wasnegligible. Based on the above fact, backwashing of the trickling filters was notnece ssary. In comparison, a survey of 43 small Norwegian activated sludge plantswith co-precipitation showed a median effluent COD concentration of 70 mg L−1 andSSof24mgL−1(Rusten et al., 1997). The nitrification capacity in the two testruns reached 0.2–0.3 g Kj-N L−1d−1at a Bv of 0.7–1.0 g COD L−1d−1(Figure 4).It was equivalent to or even higher than that in a conventional activated sludgeTREATMENT OF DOMESTICWASTEWATER 57system working at a low loading rate (Muller et al., 1995). Similar results werereported by Netter et al. (1993). However, the latter authors applied a loading rateto the biofilter of only 0.1–0.2 g COD L−1d−1and forced aeration was supplied.An important aspect of the biological processes in a trickling filter is the oxygensupply. In theory, oxygen diffusion from gas to liquid, and then from liquid tobiomass surface is much slower than diffusion from gas phase to biomass surfacedirectly (Tijhuis, 1994). Biomass in a trickling filter can only gain oxygen from airin the open spaces. Gas transport i s the limiting process in all types of biologicallyactive filters (Schwager and Boller, 1997). The trickling filters used in this work,especially the modified one with an inner net column, created good conditions for air supply. The low hydraulic loading rate, obtained by not applying recirculation, avoided liquid flooding. Without liquid resistance, high efficiency of oxygentransfer was ensured. Therefore, the oxygen supply, based solely on the naturalventilation through the aeration holes or the inner net was satisfactory. The latterwas demonstrated by the efficient COD removal, the negligible sludge productionand the effective nitrification.Charcoal has been widely used as an adsorbent in the wastewater treatment (Abeet al., 1993; Funke et al., 1994; Abe et al., 1993; Khalfaoui et al., 1995) because itssurface characteristics are similar to those of granular activated carbon. However,its application as carrier material in a biofilm reactor was scarcely reported. Besideshaving many essential properties, such as a high specific surface area and a highvoid ratio, being durable and light-weight, a maxtrixto be used for sewage treatment in rural areas should also be cheap and locally available. Charcoal, the supportused in the tested trickling filters, fulfilled the abov e requirements. It can be easilycrushed to a required particle size, i.e. 2 to 3 cm. The low density of charcoal, lessthan 1 kg cm−3, makes it more favorable than other materials such as crushed rock,slag etc. With many micro-pores on the surface, charcoal provides good conditionsfor micro-organisms to attach. Fresh charcoal is also a good adsorbent which canaccumulate sufficient organic matter and nutrients for biomass to grow. During thefirst few weeks before the biofilm builds up, the adsorption can also c ompensate theinsufficient biodegradation of COD. Therefore, it can ensure a low effluent CODduring the whole experimental period (Figure 3).In a nitrifying trickling filter, removal of total N can occ ur through the simultaneous denitrification in the anoxic micro-zones within the biological floc (Bertanza,1997). As noted in Table IV, the two trickling filter test-runs showed differentperformance for total N removal from the two types of wastewaters. During thetreatment of the SHW, the trickling filter only converted NHC4 -N to NOx -N withoutdenitrification. However, in the treatment of the MHW, trickling filtration is considered to remove 34% of the total N by means of denitrification. The differencewas due to two factors. One was the different loading rates (Bv) applied to the two trickling filters. The former was treated under a low Bv, e.g., 0.7 g COD L−1d−1,while the latter was treated at a relatively high Bv of 1.0 g COD L−1d−1. The higherBv might create more anoxic micro-zones in the filter which allow denitrification58 LINPING KUAI ET AL.to occur. The other factor was the different ratio of CODt:Kj-N in the influents ofthe two trickling filters. The former had a ratio of 2.2, while the latter had a ratio of3.3. The higher COD:Kj-N ratio resulted in the higher denitrification driving force(Watanabe, et al., 1995).Drawbacks of the system are the absence of an effective denitrification and Premoval. In regions where local soil is poor in nutrients and agricultural fertilizersare relatively expensive or scarce, the so treated sewage could be used for irrigationand fertilization. In industrialized countries however, further improvement of thedenitrification and P removal processes is necessary in order to make this integratedsystem acceptable for implementation in rural areas.4.3. HYGIENEPrimary or secondary wastewater treatment systems generally have poor disinfecting capacity. According to Block (1982) and Farrell et al. (1990), the removalefficiency of fecal coliforms (FC) can only reach 60 to 99% in a con ventionalactivated sludge or a biofilm process. Tremblay et al. (1996) reported that about56% reduction of FC was observed in their trickling bio-filtration process. Our twotrickling filter test-runs disinfected the wastewater fairly well after the adaptationperiods. They reduced the total coliforms (TC), fecal coliforms (FC) and fecalstreptococci (FS) by 2–4 log units. The residual TC in the effluents was less than1000 TC per 100 mL (Table VI). According to the guidelines of microbiologicalquality for irrigation posted by the World Health Organization (WHO), i.e. <1000TC per 100 mL, the treated wastewaters can be used for irrigation of all cropswithout further disinfection (Janssens and Verstraete, 1996; Ghrabi et al., 1993).The main principle of disinfection by a biological process is believed to be basedon sorption, die-off and the predation of micro-organisms by macro-organisms.The high variety of macro-organisms in the trickling filters might be the majorcontributor to the good effect of disinfection. However, the disinfection appearedsimultaneously with nitrification. This fact was in good agreement with the findingsof Lens et al. (1994). The good disinfection effect of their peat。
污水处理英文文献英语
Oxidize the ditch craft in dirty water handle of application and developmentCaiZhi一jun(Foshan City Shunde District Environmental EngineeringBranch Foshan Guangdong 528000)【Abstract 】Setanaerobic, naoxic section Carrous oxidation ditch with biologicla nitrogen and phosphoru sremoval capabilitie, is curren dythe mainstream of city life process of sewage treatme nt, This article descirbes the structure of Carrousel oxidation ditch, porcess and design problems d uring the oper-ation and the corresponding solutions．【Keywords】Carrousel；Oxidationditch；Phosphorusnadnitrogenremoval；Structure；Mechanism1. ForewordOxidize the ditch( oxidation ditch) again a continuous circulation spirit pond( Continuous loop r eactor), is a live and dirty mire method a kind of to transform.Oxidizing the dirty water in ditch ha ndles the craft be researched to manufacture by the hygiene engineering graduateschool of Hollan d in the 50'sof20centuriessuccess.Since in 1954 at Dutch throw in the usage for the velY first nme .secause its a water fluid matter good, circulate the stability and manage convenience etc. techniqu e characteristics, already at domestic and international and extensive application in live the dirty w ater to is dirty to manage aquecustv with the industy[1].Current application than oxidize extensively the ditch type include:The ( Pasveer) oxidizes the ditch, the (Carrousel) oxidizes the ditch, ( Orbal) oxidizes the ditch, the type of T oxidizes the ditc h( three ditch types oxidize the ditch), the type of DE oxidizes the ditch to turn to oxidize the ditch with the Integral whore.these oxidize the ditch because of the difference of esse in construction wi th circulating, therefore each characteristics[2].This text will introduce construction, mechanism, e xistent problem and its latest developments that Carrousel oxidize ditches primarily.2. The Carrousel oxidizes the construction of the ditchThe Carrousel Oxidize the ditch to be researched to manufacture by Dutch DHV company deve lopment in 1967.0xidize the last the companyofDHVinfou ndationoftheditchin theoriginal Carrous el to permited specially the company EIMCO to invent again with its patent in the United States C arrousel 2000 system realizes the living creature of the higher request takes off the nitrogen with d ividedbythefunctionof.Therehasbeen in the world up to now more than 850 Carrousels oxidize the ditch with the Carrousel 2000 system are circulating From diagram therefore[3].The Carrousel oxidizes the ditch the usage the spirit of that definite direction control with shak e up the device, face to mix with the liquid deliver the level speed, from but make drive the liquid of admixture that shake up is in oxidize ditch shut match outlet circulate nowrnererore oxidize the ditch have the special hydraulics flows the ,current complete mix with the characteristics of the ty pe reactor, have the characteristics that push the flow type reactor again, the ditch inside exsrts obviously of deliquescence oxygen density steps degree.Oxidizing the ditch cross section is rectangle or trapezoids, the fiat surface shape is many for oval, the ditch internal water is deep general for2.5 -4 .5 m , the breadth is deep compare for 2:1, also have the deep wate r amount to 7 ms of, ditch inside average speed in water current is 0.3 mS/ s.ostorze ditch spirit admixture equipments cont ain surface spirit machine, the spirit of turn to brush or turn the dish and shoot to flow the spirit m achine, pipe type spirit machine with promote take care of type spirit machine etc., match with in r ecent years usage still contain underwater push machine[4~6].3. The Carrousel oxidizes the mechanism of the ditch3.1 The Carrousel oxidizes the ditch handles dirty and aqueous principleThe at the beginning common Carrousel oxidizes the dirty water In inside In craft of the ditch di rect with dirty mire In reflux together enteroxidize theditch system.The surface spiritmachinemake sfuse In the liquid of admixture the density of the oxygen DO increases about 2 the 3 mgsl t.uncer this kind of well the term of the oxygen, the microorganism gets the enough deliquescence oxygen comes and go to divided by the BOD;At the same time, the ammonia were too oxidized nitrate wi th second nitrate, this time, mix with the liquid be placed in the oxygen appearance.In the spirit ma chine downstream, after water current be become by the swift flow appearance of the spirit Distric t oP even flow the appearance, the water current maintainsin theminim umcurrentvelocity,guarante eingthe liveand dirty mire be placed in the floats the appearance.( average current vercctvs-o.a msl s)Oxldlze microbially the process consumed to fuse theoxygenin thewater,until thevalueofDOdecl inesforzero, mixing with the liquid report the anoxia appearance.versa nitric that turn the function through anoxia area, mix with the liquid enter to have the oxygen area, completing once circulatin g.That system inside, the BOD declines the solution is a continuous process, the nitric turns the fu nction to turn with the versa nitric ~e function ta ke place in same pond.Because of structural restri ct, this kind of oxidize the ditch although can then valid whereabouts BOD,divided by the phosph orus take off the nitrogenous ability ltmrtedt".3.2 The Carrousel oxidizes the ditch divideds by the phosphorus takes off the nitrogenous inf luence factor.Affecting the Carrousel oxidizes the ditch divideds by the phosphoric factor is dirty mire, nitrat e density and quality densities primarily.The research expresses, being total and dirty mire as 11% that a hour biggest phosphorus 4% with deal is its fuck dirty mire deal within live and dirty mire, k eep for the the germ physical endowment measures, but when dirty mire over 15 d hour dirty mire the Inside is biggesttocontain theobviousdescentindealIn phosphorus,canning not reach the biggest divideding by the result of phosphorus on the contrary.Therefore, prolong persistently the dirty mi re (for example 20ds,25ds,30ds) is to have no necessary, proper choose to use within the scope of 8~ 15 d.At the same time, high nitrate density with low quality density disadvantage in divided by the process of phosphorus .4. The Carrousel oxidizes problem and solution methods of the ditch esse.Though the Carrousel oxidizes the ditch has a water fluid matter good, the anti-pounds at the b urthen ability strong, divided by the phosphorus take off the nitrogen efficiency. But, in physically of movement process, still exstts a series of problem.4.1 Dirty mire inflation problemWhen discard the aquatic carbohydrate more, the N, P contains the unbalance of deal, the pH value is low, oxidizing the dirty mire in inside in ditch carries high, fuse the oxygen density the shor tage, line up the mire not etc. causes easily dirty mire ingerm in form in silk inflatlon;Not the dirty mire in germ in form in silk inflation takes place primarily at the waste water water temperature is lower but the dirty mire carries higher hour.The microbial burthen is high, the germs absorbed the large quantity nourishment material, is low because of the temperature, metabolism the speed is sl ower, accumulating the rises large quantity is high to glue sexual and many sugar materials, makin g the surface of the live and dirty mire adhere to the water to increase consumedly, SVI the value i s very high, becoming the dirty mire inflation.Cause that aim at the dirty mire inflation, can adopt the different counterplan:From the anoxia, water temperature high result in of, can enlargement tolerance or lower into the water measures to alleviate burthen, or the adequacy lowers the MLSS( control dirty mire reflux measure), making n eed the oxygen measures decrease.It the dirty mirecarrieshigh, can increaseMLSS, toadjusttheburt hen, necessity4.2 Foam problemBecauseentering totakethe greaseoflarge quantityinthewater, handling system can't completely and availably its obviation, parts of greases enriches to gather in in the dirty mire, through turn to brush the oxygen agitation, creation large quantity foam;The mire is partial to long, the dirty mire is aging, and also easy creation toam.Sprav topourthewaterordivided bywiththesurfacetheof do aw ay with the foam, in common use divided by the an organism oil, kerosene, the oil of stncon, thro w deal as 0.5~ 1.5 mgsl L.Pass to increase dirty mire in pond in spirit in density or adequacies let up the tolerance of ,also can control the foam creation effectively.When contain the live materia! i n surface in the waste water more, separate with the foam easily and in advance method or other m ethods do away with.Also can consider to increase to establish a set of dlvideding by the oil device moreover.But enhance most importantly the headwaters manage, reducing to contain the oil over t he high waste water and other poisonous waste water of into[llJ.4.3 Float the problem on the dirty mireWhen contain in the waste water the oil measures big, whole system mire quality become light , can't like to control very much in operate process its at two sink the pond stop over time, resultin g in the anoxia easily, producing the corrupt and dirty mire ascend to float;When spirit time over l ong, take place in pond the high degree nitric turn the function, making nitrate density high, at two sink the versa nitric in easy occurrence in pond turn the function, creation nitrogen spirit, make di rty mire ascend f1oat;Moreover, contain the oil in the waste water?Take place thedirtymire ascendafterfloating should pauseenter water, broke off or dirty mire in clearance, judge the clear reason, adjust the operation.The dirty mire sinks to decline the sex bad, can throw to add of oagulate or sloth materials, the improvement precipitates the sex;Suchas entert he watercarries big let upintothe water measures or the enlargement reflux measures.Sucn as the di rty mire grain small lower the spirit machine turn soon.If discovers versanitricturning,shouldletup thetolerance,enlarge the reflux or row the mire measures;1f discover the dirty mire is corrupt, shou ld enlargement tolerance, the clearance accumulates the mire, and try the ameliorative pond intern al water dint term!':"4.4 Current velocity is not all and the dirty mire sinks to accumulate the problemIn Carrousel oxidize ditch, for acquiring its special admixture with handles result, mix with liq uid must with certain current velocity is in ditch circulate flow.Think generally, the lowest current velocity should should attain for an average current velocity for, doing not take place sinking acccmutetmq 0.3~0.5 msl s.The spirit equipments that oxidize the ditch is general to turn to brush for t he spirit of to turn the dish with the spirit of , turning to brush of immerse to have no depth for 25 0 ~300 mms, turn the dish immerse to have no depth for 480"'530 mms.With oxidize the ditch wat er the deep(3.0~3.6 ms) comparing, turn to brush occupied the deep 1 / 1 0~ in water 1/12, turned t he dish to also occupy the 1/6'" only 1/7, therefore result in to oxidize the ditch upper part current velocity bigger{ roughly 0.8"'1.2 ms, even larger}, but the bottom current velocity is very small( e specially at the water is deep 2/3 or 3/4 below, mix with the liquid has no current velocity almost), causing ditch bottom large quantity accumulate the mire( sometimes accumulate the mire thicknes s amount to a 1.0 ms), the valid capacity that reduced to oxidize the ditch consumedly, lowered to handle result, affected a water fluid matter[13].Moreover, pass in the spirit on board swim to establish the underwater push machine can also t urn to the spirit of the liquid of admixture that brush the bottom low speed area circulates to flow t o rise positive push function, from but the solution oxidizes the problem that low and dirty mire in current velocity in bottom in ditch sink accumulates,Establish the underwater push machine useds for exclusivelythe push mixs withtheliquidcan make movementmethod that oxidize the ditch much more vivid, this for economy energy, lift the high-efficiency having the very important meaning[14].5. The Carrousel oxidizes the development of the ditchBecause the dirty water handles standard inside to divided by the phosphorus take off the nitro genous request more and more strict, the development that Carrousel further oxidized the ditch to also get.Current, the research and application includes morely below two category type:Tiny bore spirit type Carrousel 2000 systems, Carrousel 3000 system.5.1 TIny bore spirit type Carrousel 2000 systemTiny bore spirit type Carrousel 2000 tiny bore in adoption in system spirit( provide oxygen equi pments as the drum breeze machine), the tiny bore spirit machine can produce the diameter of larg e quantity as a surface for or so and small spirit steeping, this consumedly increases spirit bubble a ccumulates, undering the certain circumstance in capacity in pond make the oxygen transfer the gr oss measures aggrandizement.( if deep increment in pond, its spread the quality efficiency will be higher)Produce the technique ability of the factory house according to the current drum breeze ma chine, the valid waterof thepond is deepbiggestamountingtoa8 ms, therefore can select by examina tions according to the different craft request the fit water is deep.The tradition oxidizes the ditch p ushes to flow is to make use of to turn to brush, turn a disc or pour the umbrella type form machin e realizes of, its equipments utilization is low, the motive consumes big.TIny bore spirit type Carro usel 2000 systems then adopted the underwater pushes the way that flow, rises to dive the propelle r the leaf the motivation that round creation the direct function namely in the of water, at push to fl ow the function to can keep dirty mire from sinking to decline effectively again at the same time.A s a result, the adoption dives the propeller since lower the motive consume, making mire water got again to mixs with adequately.5.2 Carrousel 3000 systemCarrousel 3000 systems are in the Carrousel 2000 systems are ex-to plus a living creature the c hoice the area.That living creature choice area is a craft to make use of high organism carries to sie ve germ grow, repress silk form germ increase, increase each pollutant do away with the rate, after ward principle together Carrousel 2000 syste m.Carrousel 3000 system of bigger increases to express at:An is to increased the pond deep, can a mount to 7.5"'8 ms, united at heart circle type, the pond wall uses totally, reducing to cover the are a, lowering to build the price to increases to bear the low temperature ability at the same time;( ca n amount to 7 'C )Two is the liquid of admixture that spirit equipments that skillful design, the for m machine descends to install to lead to flow ,the anoxia of take out, adopt the underwater propell er solution current velocity problem;Three is to used the advanced spirit controller QUTE.( it adop t the much aer kind of changing the deal control mode)f our is to adopt the integral whole turn the design, starting from the center, Including below wreath form consecuuon craft unu.eoter the well of waterwiththecent watermachine thatused for the liveand dirty mire in reflux;Difference from fo ur-part the choice pond that cent constitute with !X oxygen pond.This outside is a Carrousel to hav e three spirit machine with a prepare versa nitric turn the pond 2000 system.( such as figure 2 sho w)Five is tube line that the design that the circular integral whole turn to make oxidize the ditch do not need additionally, can immediately realize dirty mire in reflux allotment in different craft unit[ [17].6. ConclusionThe Carrousel oxidizes the ditch because of having the good a phosphorus takes off the nitroge n ability, anti-pounds at the burthen ability with circulate to manage the convenience etc. the adva ntage, having got the extensive application.But because of technological development with social advance, that craft is necessarily will exaltation getting further.The author thinks:The carrousel oxi dizes the future research direction of the ditch will now of main below several aspects.1 Combination living creature method, research with develop the living creature model carrouse l oxidize the e this can not only increases the microorganism gross of the unit reactor meas ures, from but increases the organism carries, but also living creature oneself the inside that have p laces the AI the system of 0 enhances to take off the nitrogen result[[18].2 Increases continuously the Carrousel oxidize the microbial activity in Inside in crtcn.scr exa mple throw to add the EM in oxidize ditch with single mind the germ grow, throws in that the salt of Iron make the microorganism tame the live char in iron, devotion in living creature to become t he torrnation to strengthen the germ gumregiment and increases to bear the toxicity pound at etc..3 Increasing the Carrousel oxidizes the ditch equtpments function with supervise and control the technique.Function that increases form machine, underwater propeller, reduce to maintain the w orkload; Making use of DO, etc. of ORP many targets supervises and control the technique and ch anges the technique of is from now on the carrouseloxidizes ditchsciencecirculatenecessarilyfromi troad.4 Increasing the Carrousel oxidizes the ditch resistant to cold and bear toxicity can, reduce to co ver the area to build the price with the engineering.Theoretical application, deep pond in water po wer term with the research of the craft function is to lowers the engineering builds the price and in creases resistant to cold bear the toxicity can wait to provide the possible direction. 【References】[1] Xia Shibin, Liu Junxin. An innovative integrated oxidation ditch with vertical circle for domestic wastewater treatment. Process Biochemistry, 2004, 39(4):1117[2] X, Hao; Doddema, H. J.; van Groenestijn, J. W. Use of contact tank to enhance denitrification in oxidation ditches. Water Science and Technology, 1996, 34(1-2):195~202.1~1117.[3] 汪大，雷乐成。
污水处理-英文文献4
污⽔处理-英⽂⽂献4Desalination 231 (2008) 20–260011-9164/08/$– See front matter ? 2008 Elsevier B.V. All rights reservedat The 4th IWA Conference on Membranes for Water and Wastewater TreatmentMay 15–17, 2007, Harrogate, UK*Corresponding author.Upgrading and retrofitting of municipal wastewater treatmentplants by means of membrane bioreactor (MBR) technologyCh. Brepols a , E. Dorgeloh b , F.-B. Frechen c , W. Fuchs d , S. Haider e , A. Joss f ,K. de Korte g , Ch. Ruiken g , W. Schier c *, H. van der Roest h , M. Wett i , Th. Wozniak jaErftverband, Bergheim, GermanybPrüf- und Entwicklungsinstitut für Abwassertechnik (PIA) an der RWTH Aachen, Germany cDepartment of Sanitary and Environmental Engineering - DESEE, University of Kassel, Germany Tel. +49 (561) 8043817; Fax+49(561)8043642;email:*******************************University of Natural Resources and Applied Life Sciences – Vienna, Department IF A-Tulln,Institute for Environmental Biotechnology, Tulln, AustriaeH2Office Abwassertechnik, Wien, AustriafEAWAG — Swiss Federal Institute of Aquatic Science and Technology, Duebendorf, SwitzerlandgDWR — Dienst Waterbeheer en Riolering, Amsterdam, The Netherlands hDHV —Consultancy and Engineering, Amersfoort, The Netherlands iSüddeutsche Abwasserreinigungs-Ingenieur GmbH, Ulm, Germanyjwws consulting, Reutlingen, GermanyReceived 17 May 2007; accepted revised 20 November 2007AbstractIn the future, upgrading of existing wastewater treatment plants (wwtps) will become the more challenging task than erection of wholly new plants, as most of the plants (e.g. necessary in Germany) do exist already. Since some time, MBR technology has been taken into consideration and has been realised as an alternative for wwtp upgrading.This paper gives an overview about some relevant preconditions, basic upgrading concepts and examples of already upgraded wwtps using MBRtechnology.Keywords: Municipal wastewater treatment; Upgrading; MBR technologydoi:10.1016/j.desal.2007.11.035Ch. Brepols et al. / Desalination 231 (2008) 20–26211. IntroductionMany wwtps suffer from an inadequate level of treatment provided. There are several reasons for the need of retrofittedand/or upgraded equip-ment, such as expiry of lifespan, the increase of wastewater flow or load or higher treatment stan-dards due to a change of legal framework. In gen-eral, no standard solutions for the upgrading of wastewater treatment systems are available and the transfer of a certain measure from one case to another is limited. In fact, the optimum answer in each individual case is largely site-dependent. Accordingly, there is a broad spectrum of mea-sures that might be employed. In most cases it is not a singular action to be taken, but the upgrad-ing will incorporate a set of different interlocking components both at the drainage system and the wastewater treatment plant.The MBR process is an emerging advanced wastewater treatment technology that has been successfully applied at an ever increasing num-ber of locations around the world. It involves a suspended growth activated sludge system that utilizes microporous membranes for solid/liquid separation as a substitute of the conventional sec-ondary clarifier. MBR technology has not only attracted increasing interest for the set up of new wastewater treatment systems but also it has high potential looking at upgrading tasks of already existing wwtps.2. Considerations for the choice of MBR technologySince membrane filtration allows raised sludge concentrations, the activated sludge tank volume can be significantly reduced. In combination with the option to convert the secondary clarifier, that is no longer required as a sedimentation tank, as an additional activated sludge tank, the treatment capacity of the existing plant can be largely ex-tended. That way it is possible to upgrade exist-ing wwtps from simple carbon removal to BNR systems just using the already existing volume.Therefore favourable conditions for the choice of MBR technology are given, where retrofitting of the existing plant by the conventional activated sludge (CAS) process would demand for substan-tial extension of the activated sludge volume. As well, where limitations due to insufficient effi-ciency of the secondary clarification basin exist, particularly however, where both problems have to be solved.MBR technology should also be considered if high effluent criteria such as removal of suspended solids or absence of pathogens have to be met. Examples are discharge into small creaks as well as into bathing water or other sensitive areas.Due to the small space requirement the MBR offers special advantages if the given location holds no or only a limited amount of area in re-serve. Moreover, the small footprint allows a com-plete indoor installation in a building designed to blend in with its surrounding environment and such to address issues of visual amenity, odour or noise.Another distinct advantage of MBR technol-ogy is direct utilisation of the effluent for reuse purposes. The water reuse potential includes irri-gation of agricultural land, recharge of aquifers or river flow replenishment. On several occasions this was the major decision criteria to opt for MBR technology.With the choice of the MBR special attention should be paid to the fact that the investment costs are largely correlated with the hydraulic peak flow. This parameter determines the total membrane surface area which needs to be installed. There-fore, accompanying measures to minimize wet weather flow or to harmonise resultant wastewa-ter largely contribute to cost effectiveness of the MBR approach. One option for dealing with high wet weather peaks is to use the former secondary clarifier as storage volume. Another option is hy-brid systems where the conventional system is used as a backup to treat the inflow volume that exceeds the hydraulic membrane capacity. An al-ready realised hybrid concept designs the MBR22Ch. Brepols et al. / Desalination 231 (2008) 20–26line to treat the dry weather flow at the maximum.The inflow volume beyond dry weather condi-tions is treated conventionally.3. Modification of the operation mode using the MBR approachWith the change of sludge/treated wastewater separation from gravity settling to membrane fil-tration the following process configurations are available:3.1. MBR with or without a separate filtration chamberWith upgrading of wwtp as a pure MBR pro-cess the question is to be cleared whether exist-A: substitution of the sedimentation tank by a separate filtration chamberB: sedimentation tank: change of utilisation as biological volumeC: change of flow scheme and immersed membranes within the biologyinitial Fig. 1. Upgrading variations using MBR technology.ing sedimentation tanks can be included sensibly in the future concept of utilisation. According to the structural state it can be possible to use these tanks as an additional biological volume. Also the suitable installation and operation of the mem-brane modules either in activated sludge tanks or in separated filtration chambers depends on the quality of the respective structural situation. At this point wide engineering space is given. Fig. 1shows some possible variations.3.2. Hybrid systems The combination of the CAS process and the MBR process is understood as the hybrid proce-dure. Fig. 2 shows two basic operation concepts of hybrid processes (among other hybrid systems).Ch. Brepols et al. / Desalination 231 (2008) 20–2623Besides, a fullness of mixing variations is pos-sible. The flow concept of the sludge streams be-tween both biological units at parallel operation mode or serial operation mode can be operated separately or combined according to the local cir-cumstances (grey arrows in Fig. 2). In the latter case possible differences are to be taken into con-sideration concerning the sludge qualities, in par-ticular, the quality of sedimentation and the MLSS concentrations.3.3. Other processesBeside the combination with the CAS process also combinations with other wastewater treat-ment procedures are possible, e.g. with SBR tech-nology [1] or with pond technology. Today SBR technology integrating membrane technology as separation process is used at industrial applica-tions or at package plants. Applications combin-ing pond technology and MBR technology are op-parallelserialFig. 2. Basic operation concepts of the hybrid procedure.erated at wwtp St. Peter ob Judenburg, Austria and at wwtp Ihn, Germany.3.4. MBR process with low MLSS concentration In cases when available sedimentation volume is used as additional biological volume, the amount of total biological volume increases to a degree, that clearly exceeds the usual volume de-mand of a conventional MBR process with ap-propriate MLSS concentrations ranging from 10kg/m3 to 15 kg/m3. Dimensioning the MLSS concentration both the available biological vol-ume and the guarantee of the aerobic SRT have to be taken into consideration. Usually this dimen-sioning ends up with less MLSS concentration in the range of 5–7 kg/m3 [2,3] compared with con-ventional MBR operating circumstances. If such a draught can be realised, the usual disadvantages (sensibility compared to impact load, reduced al-pha value) could be overcome by MBR process24Ch. Brepols et al. / Desalination 231 (2008) 20–26to a great extent. Beside the anyway raised efflu-ent quality other advantages of this upgrading concept can be named: considerable biological reserve capacities for future extension;smaller place consumption compared to a con-ventional upgrading concept.Some manufacturers of membrane modules recommend not falling short of a given MLSS concentration directly at the membrane or within a separated filtration chamber. Thus, the suitabil-ity of the respective membrane modules for the “low MLSS operation mode” is to be clarified. Nevertheless, by the construction of a separate filtration chamber optimal MLSS concentrations at the membrane and within the biological zone can be adapted accordingly.3.5. MBR in combination with anaerobic sludge stabilizationUp to now most municipal MBR plants are dimensioned with aerobic simultaneous sludge stabilization. In principle the MBR process also can be combined with anaerobic sludge stabiliza-tion. Some single studies assume dependence be-tween increasing fouling potential and increasing F/M-ratio or rather decreasing SRT [4–6]. A final statement cannot be met yet. If the MBR process is dimensioned with a short SRT, hence, possible intensified fouling effects have to be considered.If the MBR process is dimensioned with a long SRT, slightly reduced digester gas production can be expected. A possible process variation features the digestion of only primary sludge. Thus, in an upgrading situation the cost intensive new build-ing of digestion volume can be avoided.4. Experiences from full-scale applicationsThe full version of DWA WG KA-7.4 report includes all subsequently mentioned wwtps:?wwtp St. Peter ob Judenburg, Austria ?wwtp Schilde, Belgium ?wwtp Eitorf, Germanywwtp Bergheim-Glessen, Germanywwtp Brescia, Italywwtp Viareggio, Italywwtp Heenvliet, Netherlandswwtp Rietliau, SwitzerlandUpgrading of wwtps by means of MBR tech-nology is not a question of special membrane types. The above mentioned plants are equipped with usual and well known hollow fibre mem-branes as well as with flat sheet membranes.In the following two plants out of the above mentioned are now introduced more detailed. Besides, the German wwtp Bergheim-Glessen is an example for a complete process rearrangement. The Swiss wwtp Rietliau shows a hybrid solu-tion.4.1. wwtp Bergheim-Glessen, GermanyIn the case of the wwtp Bergheim-Glessen MBR technology is used to meet advanced re-quirements caused by the discharge of wastewa-ter to sensitive wetland. Upgrading occurs at the existing location using extensively already exist-ing constructions. Treatment efficiency will be rapidly increased by introducing MBR technol-ogy. Hence, in addition, the wastewater of a neighbouring, smaller wwtp, likewise in the need of upgrading, is led across, treated and afterwards led back. Thus, the wwtp load is raised from 5,000p.e. nowadays to 9,000 p.e. Wastewater quantity to be treated from now on amounts to 900,000 m3/a. Fig. 3 illustrates the flow diagram.The mechanical pre-treatment is completely renewed consisting of three units: screening (gap size 6 mm), aerated grit chamber and grease trap, sieving (mesh geometry, gap size 1 mm). The existing oxidation ditch furthermore will be used as activated sludge volume. SRT should amount about 25 d, MLSS concentration is dimensioned with only 8 kg/m3. In time of maximum inflow HRT amounts to 6 h. The membrane modules are installed in four separated filtration chambers.Ch. Brepols et al. / Desalination 231 (2008) 20–2625Fig. 3. Flow diagram of wwtp Bergheim-Glessen.Sludge treatment and simultaneous precipitation are taken over from the today’s continuance. The plant is scheduled to be commissioned in late 2007.4.2. wwtp Rietliau, SwitzerlandUpgrading was necessary to meet the effluent requirements (DOC: 10 mg/l, BOD: 10 mg/l, P total: 0.2 mg/l, SS: 5 mg/l) especially according parameter SS which was unachievable by the former wwtp concept. An upgrading of the treat-ment capacity from 41,400 p.e. up to 44,000 p.e. also would have been accomplished by depth fil-tration as a fourth treatment step. Caused by small space availability the hybrid solution was evalu-ated as an economically more favourable way. Shortage of space is due to the wwtp location in the midst of the residential area W?denswil, 100m far from the bank of the Lake of Zurich. Fig. 4 shows the flow diagram.Wwtp Rietliau was commissioned in Novem-ber 2005. The treatment process is subdivided into two lines. Each, the MBR line and the conven-tional process line, treat half of the incoming wastewater. Sludge of both treatment lines is not mixed. All wastewater is treated by the existing mechanical pre-treatment units (screen, grit cham-ber and grease trap, primarysedimentation). In addition, the inflow from the primary sedimenta-tion to the MBR line is led through a sieve con-sisting of hole geometry with 1 mm gap size.The MBR line consists of two sub-lines. Aero-bic and anoxic volumes of the MBR process are dimensioned the way, that in times of maximum inflow the minimum HRT within the biological zone prior to the filtration chambers does not fall below30min.Better effluent quality concerning the conven-tional process line also is achieved caused by the less hydraulic load of the secondary clarifiers. Thus, the requirements that have to be met by the mixture of both effluent streams can be guaran-teed.5. ConclusionsThe presented upgrading concepts raise no claim to completeness and thus reveal the wide spectrum of supposable measures. Many of them are under investigation and appropriate findings can be expected to be reported soon. However, the chosen upgrading concept must meet the claim to bedemand-oriented according the wastewater-sided requirements and the load situation,economical in view of annual costs (operating expenses and net debt service).Besides, various other, not only process-re-lated, but also nonmonetary and monetary hardly assessable aspects are to be followed and to weigh in each individual case which do not admit a stan-26Ch. Brepols et al. / Desalination 231 (2008) 20–26conventional activated sludge process Fig. 4. Flow diagram of wwtp Rietliau.dard approach concerning the handling of the planning task.Altogether MBR technology provides several promising perspectives in view of upgrading wwtps. The different options introduced provide an overview of the bunch of possibilities the op-timal solution can be selected from. As with all other upgrading options which in general are in-dividual solutions, special importance lies on the adequate diligence of the planning engineer. Nev-ertheless the increasing number of full scale ap-plications presents a sound and ever growing de-cision basis.References[1]J. Krampe and Kh. Krauth, Das Sequencing BatchReactor-Membranbelebungsverfahren. 4. ATSV, Aachen, 2001.[2]W. Schier, An exemplary approach for the integra-tion of new sizing procedures and new purification technologies for the performance of wwtps, Scripts W ATER ? W ASTEW ATER ? W ASTE of Department of Sanitary and Environmental Engineering —DESEE and Department of Waste Engineering ofthe University of Kassel, issue 22, Kassel Univer-sity Press, 2003.[3] F.-B. Frechen, W. Schier, M. Wett and A. Waldhoff,The non-conventional low MLSS MBR technology, IWA Specialty Conference Water Environment –Membrane Technology (WEMT), Seoul, Korea, 2004.[4] A. Drews, M. V ocks, V. Iversen, B. Lesjean and M.Kraume, Fouling in Membranbelebungsreaktoren: Erfahrungen beim Betrieb mit diskontinuierlichem Schlammabzug, Chemie Ingenieur Technik, 77 (2005) 593–599.[5] A. Pollice, A. Brookes, B. Jefferson and S. Judd,Subcritical flux fouling in membrane bioreactors —a review of recent literature. Desalination, 174(2005) 221–230.[6]M. Wett, Fouling behaviour of a submerged mem-brane bioreactor for domestic waste water and its influence to the process efficiency, Scripts WATER ? W ASTEWATER ? W ASTE of Department of Sani-tary and Environmental Engineering — DESEE and Department of Waste Engineering of the University of Kassel, issue 26, Kassel University Press, 2005.[7]Water Environment Federation, Upgrading and Ret-rofitting Water and Wastewater Treatment Plants, Manual of Practice No. 28, McGraw-Hill, USA, 2004.。
污水处理 英文文献3 翻译
丹宁改性絮凝剂处理城市污水J.Beltrán-heredia，J.ánche z-Martin埃斯特雷马杜拉大学化学工程系和物理化学系,德埃娃儿，S / N 06071，巴达霍斯，西班牙摘要一种新的以丹宁为主要成分的混凝剂和絮凝剂已经过测试用以处理城市污水。
TANFLOC 证实了其在浊度的去除上的高效性（接近100%，取决于剂量），并且近50%的BOD5和COD 被去除，表明TANFLOC是合适的凝集剂，效力可与明矾相媲美。
混凝絮凝剂过程不依赖于温度，发现最佳搅拌速度和时间为40转/每分钟和30分钟。
多酚含量不显著增加，30%的阴离子表面活性剂被去除。
沉淀过程似乎是一种絮凝分离，所以污泥体积指数和它随絮凝剂剂量的改变可以确定。
证明TANFLOC是相当有效的可用于污水处理的混凝絮凝剂。
关键词: 基于丹宁的絮凝剂城市污水絮凝天然混凝剂1．简介人类活动是废物的来源。
特别是在城市定居点，来自家庭和工业的废水可能是危险有害的产品[ 1 ]，需要适当的处理，以避免对环境[ 2 ]和健康的影响[ 3,4 ]。
2006年12月4日联合国大会通过决议宣布2008为国际卫生年。
无效的卫生基础设施促使每年220万人死于腹泻，主要在3岁以下儿童，600万人因沙眼失明，两亿人感染血吸虫病，只是为了给出一些数据[ 5 ]。
显然，他们中的大多数都是在发展中国家，所以谈及城市污水，必须研究适当的技术来拓宽可能的处理技术种类。
在这个意义上，许多类型的水处理被使用。
他们之间的分歧在于经济和技术特点上。
了摆脱危险的污染[ 6 ]，一些令人关注的论文已经发表的关于城市污水处理的几种天然的替代方法，包括绿色过滤器、化学初步分离、紫外消毒[ 7 ]和多级程序[ 8 ]。
几个以前的文件指出了城市污水管理[9,10]的重要性。
这种类型的废物已成为社会研究的目标，因为它涉及到几个方面，都与社会结构和社会组织[11 ]相关。
根据这一维度，必须认识到废水管理作为发展中国家的一种社会变化的因素，事关污水处理和生产之间的平衡，是非常重要的，一方面，人类要发展，另一方面，显而易见。
- 1、下载文档前请自行甄别文档内容的完整性，平台不提供额外的编辑、内容补充、找答案等附加服务。
- 2、"仅部分预览"的文档,不可在线预览部分如存在完整性等问题,可反馈申请退款(可完整预览的文档不适用该条件!)。
- 3、如文档侵犯您的权益，请联系客服反馈,我们会尽快为您处理(人工客服工作时间：9:00-18:30)。
非洲生物工程卷。
7（15），第2621至2629年2008年8月4/AJB ISSN 1684-5315 2008学术期刊约旦污水处理厂处理性能及水回用的适宜性无论是在城市还是农村环境，水资源的更有效地利用都有一个增长的趋势。
在约旦，水的需求增加，水资源短缺，导致人们对废水回用产生了兴趣。
在这项工作中，分别测定四个废水处理厂的水质特点，并对废水特性进行了评估。
在选定的污水处理厂中测量其进出水水质的生化需氧量，化学需氧量，总悬浮固体，总溶解固体，氨氮，和溶解氧。
经过处理后的出水水质与约旦的标准进行了比较。
结果表明：在约旦城市废水中的生化需氧量，化学需氧量，总悬浮固体，NH4等污染物的浓度很高，所以它是一个较大的浪费。
评估了四个污水处理厂的性能，常规和改良活性污泥表现出良好的性能，而低水质则是通过稳定塘产生的。
活性污泥污水处理厂的出水水质符合约旦标准。
为了防止其对人类健康和环境的影响，在重复使用前，二级出水需要进行深度处理。
关键词：废水，处理厂，水回用，废水特点，废水处理，约旦前言约旦人口迅速增加，在1950年到2006年从58万增长到560万。
这一增长导致每年提高 3.1％的增长速度，并且从1948年巴勒斯坦连续移民，90年代从1967年科威特开始移民（统计处2006年）。
约旦多年来一直面临着水资源短缺的问题，提高水资源的利用效率作为其努力的重要组成部分，从而来处理水资源短缺的问题。
总平均降水总量约为8.5 × 109立方米/年，但这一数量的92％是通过蒸发损失掉的（铝Zboon，2002）。
耗水量的增加，是人口增长和发展项目的必然结果，而水资源的有效利用却是年复一年的被限制。
在2000年，每年的需水量，估计为1100万立方米，而从各种渠道的可供水量（地表水和地下水）却小于850 万立方米，这表明了250万立方米的缺水问题。
这种水资源的短缺同时也影响了个人消费。
例如，在1998年耗水量约为160m3/capita/y，预计在2020年将下降到90m3/capita/y，这是一个非常低的比较对于人均消费水平在1000立方米/年（铝Zboon，2002）城市农业需水量占总用水量的73％，而22％的水是用于国内需求，只有5％是用于工业部门（WAJ，2006）。
这种水资源的需求增加与限制相结合导致水资源的可利用量的发展。
目前，世界各地的废水资源的再利用促进了废水有限水资源和二级污水处理废水技术（Janga等。
2005年，西蒙，2006）的发展。
污水处理的主要目的是为了阻止对河道的污染，并保护人类的健康和环境（梅特卡夫和埃迪，1991年）。
再生水回用是国际的实践项目。
再生水应用于土壤，耕地的边缘地区，以及在各设施，灌溉，工业，以及地面补给水上（Kalavrouziotis和Apostopoulos，2007; Bushnak，2003;Salgot等，2006;恩斯特等人，2007年）。
污水处理厂的废水再生回用的集成和安全应用决定了环境发展的全面计划，该计划将考虑所有这些参数的相对重用，定性的表征废水以及检查物理化学性质和所有环境对土壤，植物的申请，建筑安装，管道（Kalavrouziotis和Apostopoulos，2007; Salgot等人，2006年;。
Magalha等，2005）的影响。
由于水分亏缺表现的越来越明显，废水回用，水资源保护和开发是中东国家地区发展战略的一部分。
此外，这些国家在这方面的经验已经证明了水资源的重复利用程序的可行性（Bataineh等，2002;Jemali和Kefati，2002; Alatiri等人，2002）。
污水的特性很大程度上取决于污水收集系统的类型（合并式或分开式）、工业废水进入下水道，应用废水的处理技术、国内淡水质量、和消费者的生活水平。
所要求的水处理程度取决于测定接收溪流、湖的有益用途，并针对不同用途进行回用。
因为，再生水的特点对于评估和回用是必要的。
在约旦有23个市政污水处理厂，并且覆盖了大部分主要城市和城镇。
这些处理厂为约56％的人口服务。
流入这些处理厂的水量约为216412立方米/天，其中186223立方米/天转流入Asamra污水处理厂（ASTP）（Bataineh等人，2002年;Asa'ad，2006）。
约旦再生水标准（JS893/1995）尝试着对水的再利用和环境的排放的调节。
当生化需氧量，化学需氧量，总悬浮固体，大肠杆菌细菌，蠕虫卵很多参数符合标准时，约旦标准允许排放经过处理的废水到山谷和溪流。
目前，回收废水用于限制农业植物或处理厂下游附近的地表水（Bataineh等混合，2002年）。
占全国总供水的约10％的超过700万m3/year的再生水，在接下来的30年将上升至超过15％，这些再生水将被直接或间接地用于约旦（Bataineh等，2002;Bdour和Hadadin，2005;McCornick等，2007;Ammary，2007）。
因此，在约旦可用水资源增加这项研究中，水的回用是一个极具有吸引力的选项。
在这项研究中，四个污水处理厂特点，分别由铝萨姆拉的（ASTP）伊尔比德的（ITP），Ramtha的（RTP），和Wadi哈桑（WTP）的人决定。
并对废水特性进行了评估，测量化学需氧量（COD），生物需氧量（BOD），总悬浮固体（TSS），总溶解固体（TDS）和溶解氧（DO），进水和出水的范围。
对四个污水处理厂的性能进行了评估并对再生水质量进行了比较，以确定其是否适合重复使用。
材料与方法被指定的污水处理厂将要处理约旦约90%的生活污水，大约是200多万居民（Bataineh等。
2002年）的生活污水。
ASTP作为稳定塘处理工艺，如表2。
由于ASTP是约旦最大的污水处理厂并且处理和收集超过76％的城市污水，大部分的环境研究集中在这个厂，所以要提高其效率，就必须采取必要的行动。
该工厂总面积181公顷，包括三个平行的车间（Asa'ad，2006），有两种好氧池，四个兼性厌氧池塘，每个车间有四个成熟的池塘。
在干燥的天气下，有超过总量的80％的水从处理厂流入到扎尔卡河电厂。
河流里的水含有高浓度的有机物质，无机矿物质，盐（铝Zboon，2002）和重金属。
在其它污水处理厂如ITP，RTP 和WTP，则是以活性污泥操作作为不同的模式，如表2。
为了确定选定的污水处理厂的废水的特点，从2005年6月到2006年3月，每周从进水和出水中选择样本。
在Al -哈森学院环境实验室按照标准方法（美国公共卫生协会，1985）对样品进行了分析。
在定义市政污水的特点时，生化需氧量和悬浮物是最重要的参数。
总溶解固体，氨氮和溶解氧作为废水再利用的适宜性的指标。
样本在收集时必须非常仔细，以避免鼓动或与空气接触。
用300毫升容量的玻璃瓶并且带有磨口玻璃塞子，将喇叭形口清洗，烘干，然后等待样本的使用。
样品越快运到实验室对分析越有利。
如果之前延误分析预期，样品应在标准方法下，根据建议的程序储存。
稀释后，样品的BOD5在20℃孵育5天，在孵化期溶解氧浓度的变化是根据BOD5的测量以确定其浓度。
用闭管回流的方法来确定化学需氧量的浓度。
培养管用带有挥发性的H2SO4清洗.然后将样品管放置在一个带有保温功能的蒸煮锅中，将蒸煮锅预热到150℃，然后回流2个小时。
在消化后期，冷却样品温度到室温。
滴定过程，样本的颜色从青色改变到红棕色。
为了确定TSS和TDS，用一个（2微米直径的衡量标准）玻璃纤维滤器过滤样本。
在一个干燥的重量盘上将滤液蒸干到180o C。
重量盘质量的增长就代表TDS的质量。
滤波器的余数被槁在105o C。
在重量方面增长的滤波器代表总悬浮固体。
结果与讨论进水的生化需氧量，化学需氧量和悬浮物浓度的平均值分别是880mg/l，1946mg/l，795mg/l（见表3）。
基于这些标准，凡污染物浓度远远高于国际标准，约旦就会将其列为一个强大的废水资源。
ASTP，ITP，RTP和WTP这些污水处理厂的设计是为了使BOD5的浓度分别达到520mg/l，600mg/l，800mg/l和1000mg/l（WAJ，2006年）。
应用和设计之间的这种变化值将导致污水处理厂的性能发生意外恶化。
图1显示了选定的污水处理厂的BOD5值。
可以看出，BOD5值范围从140mg/l到12mg/l，其中ASTP 的BOD5值是最高的。
ITP，RTP和WTP表1：约旦的废水处理厂*ř=应用水力负荷/设计水力负荷×100％。
污水处理厂的污水符合约旦的再生废水排放标准，所以使其流入溪流，供地下水，灌溉公园，灌溉蔬菜水果，树木有使用，并用于饲料作物的再生水回用。
ASTP的出水水质不符合约旦的标准，水排放到溪流地下水回灌，并灌溉公园或无限制灌溉，所示如图1。
从工厂排出的污*ř=应用水力负荷/设计水力负荷×100％。
图1。
比较出水BOD和约旦标准，联合材料：标准排放到溪流，JS2：对于蔬菜标准。
JS3：标准饲料作物，JS4：灌溉公园，JS5：标准的鱼塘。
JS6：标准地下水补给。
其他：其他用途约旦标准。
水Wadi al - Dhlil，符合在AlSukna扎尔卡河位置这水是混合携带其它支流来改善其质量但在用情况下，污染物浓度仍然高于允许的浓度限度。
处理厂图2。
比较出水BOD和约旦标准，联合材料：标准排放到溪流，JS2：对于蔬菜标准。
JS3：标准饲料作物，JS4：灌溉公园，JS5：标准的鱼塘。
JS6：标准地下水补给。
其他：其他用途约旦标准。
处理厂图3。
比较出水BOD和约旦标准，联合材料：标准排放到溪流，JS2：对于蔬菜标准。
JS3：标准饲料作物，JS4：灌溉公园，JS5：标准的鱼塘。
JS6：标准地下水补给。
其他：其他用途约旦标准。
类似的，从污水处理厂流出的污水的BOD5值是由COD和氨氮值获得的，分别如图2和图3所示。
从ITP，RTP和WTP污水处理厂流出的。