环境污染与治理知识点

环境污染与治理

环境：是相对于某一事物来说，是指围绕着某一事物（通常称为主体）并对该事物会产生某些影响的所有外界事物（通常称其为客体），即环境是指相对并相关于某项中心事物的周围事物。

Biosphere：The entire part of earth's land, soil, water & atmosphere in which living organism are found is called biosphere。The combined area lithosphere, hydrosphere of & atmosphere is known as biosphere. Ecological footprint：The amount of biologically productive land and water needed to indefinitely supply the people in a given area with renewable resources。Also includes the land and water necessary to absorb and recycle wastes and pollution。（Per capita ecological footprint：Average ecological footprint of an individual in a given area）。

Sustainable living：The ability of the earth’s various natural systems and human cultural systems and economies to survive and adapt to changing environmental conditions indefinitely."（可持续发展被定义为：“能满足当代人的需要，又不对后代人满足其需要的能力构成危害的发展。提出可持续发展的四大支柱是经济、社会、环境和文化，只有四个方面协调发展，才能实现可持续发展）。（太阳能、生物多样性、化学循环）

自然资本（natural capital）：Our lives and economies depend on energy from the sun and natural resources and natural services (natural capital) provided by the earth.

水的自然循环和人为循环：

Important Contaminants Of Concern In Wastewater Treatment ：Suspended solids (SS)：Lead to the development of sludge deposits and anaerobic conditions when untreated wastewater is discharged into the aquatic environment. Nutrients (P, N2&C)：When discharged into the aquatic environment, these nutrients

can lead to the growth of undesirable aquatic life. When discharged in excessive amounts on land, they can also lead to the pollution of groundwater.

Priority pollutants ：Organic and inorganic compounds selected on the basis of their known or suspected carcinogenicity, or high acute toxicity. Many of these compounds are found in wastewater

Refractory organics ：These organics tend to resist conventional methods of wastewater treatment. Typical examples include surfactants, phenols, and agricultural pesticides.

Heavy metals：Heavy metals are usually discharged to wastewater from commercial and industrial activities and have to be removed if the wastewater is to be reused. Dissolved inorganics：Inorganic constituents such as calcium, sodium, and sulfate are added to the original domestic water supply as a result of water use and may have to be removed if the wastewater is to be reused.

Characteristics Of Wastewater

Physical Characteristics（Total Solids：Analytically the total solids content of a wastewater is defined as all the matter that remains as residue upon evaporation at 103 to 105°C. Odors：Wastewater may contain either odorous compounds or compounds that produce odor during the process of wastewater treatment.Temperature：The temperature of water is a very important parameter because of its effect on Chemical reactions and reaction rates in treatment process. Aquatic life. Color：Color of industrial wastewater varies according to the type of industry. Most colored matter is in a dissolved state.. Turbidity：Turbidity, a measure of the light-transmitting properties of water, is another test used to indicate the quality of wastewater discharges and natural waters with respect to colloidal and residual suspended matter.）

Inorganic Matter：Nitrogen & Phosphorus，Sulfur，Heavy Metals.

Biological Characteristics ：Pathogenic organisms like slaughterhouses others have molds and fungi as starch and yeast factories.Biological information is needed to assess the degree of treatment of the wastewater before its discharge to the environment.

Natural Purification (Self Purification)：When wastewater is discharged into the river or stream, the BOD of mix increases initially and DO level starts falling.

As river water travels further BOD gradually reduces and DO increases and reaches its saturation level.Thus river gets purified on its own. This phenomena is known as self purification of stream.

环境容量(The self purification capacity)：一定水体在规定的环境目标下所能容纳污染物质的最大负荷量。

ACTIONS INVOLVED IN SELF PURIFICATION OF STREAMS：1. DILUTION、2. DISPERSION DUE TO CURRENT、3. SEDIMENTATION、4. OXIDATION、5. REDUCTION、6. TEMPERATURE、7. SUNLIGHT

氧垂曲线：When pollutional load is discharged into the stream, DO goes on reducing. This process is known as deoxygenation. It depends upon organic matter present and temperature.The variation or depletion of DO is represented graphically by deoxygenation curve.

At the same time oxygen gets added into the stream through various processes such as photosynthesis, rains etc.The curve representing oxygen gaining process is known as Reoxygenation or reaeration curve.In a running polluted stream deoxygenation and reaeration processes go hand in hand.

Euthophication（富营养化）：由于氮、磷等植物营养物质含量过多而引起

的水质污染现象，一般发生在湖泊、江河、海湾等缓流水体中。Natural Eutrophication

And Cultural Eutrophication。

点源污染：(point source pollution)：以点状的形式集中排放的工业废弃物或从污水处理厂排放的工业废水。

非点源污染：(non-point source pollution)：从田间和果园冲刷下来的农药、化肥和畜禽养殖产生的废水，通过径流进入河流、湖泊或渗入地下水。

废水处理分级：

Physical Unit Operations ：Treatment methods in which the application of physical forces predominates. Screening, mixing, flocculation, sedimentation, flotation, filtration, and gas transfer are typical unit operations.

Chemical Unit Processes：Treatment methods in which the removal or conversion of contaminants is brought about by the addition of chemicals or by other chemical reactions.Precipitation, adsorption, and disinfection are the most common examples used in wastewater treatment.

Biological Unit Processes ：Treatment methods in which the removal of contaminants is brought about by biological activity.Biological treatment is used primarily to remove the biodegradable organic substances(colloidal or dissolved) and nutrients (nitrogen & phosphorus) from wastewater.

Basically, these substances are converted into gases that can escape to the atmosphere and into biological cell tissue that can be removed by settling.

水的物理处理：1、格栅，格栅的基本结构是由一组平行设置的栅条所组成的框架，主要是去除一些大块的固体悬浮物和漂浮物。2、沉淀，沉砂池，可分为平流式、旋流式和曝气沉砂池三大类。3、离心分离，物体高速旋转时产生离心力场利用离心力分离废水中密度与水不同的悬浮物的处理方法；４、气浮，气浮法是利用高度分散的微细气泡作为载体去黏附废水中的污染物利用其密度小于水的特性，使其上浮到水面，从而实现固液或液液分离的过程，又称气泡浮上法。５、过滤，过滤是用来分离悬浮液，获得清净液体的单元操作。在水处理中，过滤一般是指以石英砂等粒状颗粒的滤层截留水中悬浮杂质，从而使水获得澄清的工艺过程。６、隔油，ＡＰＩ、ＣＰＩ。

水的化学处理：１、中和处理的目的是中和废水中过量的酸或碱，使中和后的废水呈中性或接近中性，以满足下一步处理或外排的要求。２、Oxidation/Reduction、Oxidants （Oxygen(O2).Chlorine (Cl2).Sodium hypochlorite (NaClO).Calcium hypochlorite (Ca(ClO)2).Potassium permanganate(KMnO4).Hydrogen peroxide(H2O2).）are used in wastewater treatment as a first step in the removal of heavy metals to oxidize organics or as a last step in a treatment process, to oxidize odoriferous compounds such as hydrogen sulphide or to oxidize inorganics such as cyanide and for disinfection.３.Chemical precipitation in wastewater treatment involves the addition of chemicals to alter the

physical state of dissolved and suspended solids and facilitate their removal by sedimentation.凝聚是指胶体被压缩双电层而失去稳定性，发生相互聚集的过程；絮凝是指脱稳胶体聚结成大颗粒絮体的过程；混凝则是凝聚和絮凝的总称。

Active Sludge：can be defined as "a mixture of microorganisms which contact and digest biodegradable materials (food) from wastewater.细菌在活性污泥的生物量中占９５％，利用污水中蛋白质、碳水化合物等进行生长，为了较好的保证活性污泥的生物降解进程，控制细菌的生长成为关键（细菌的生长曲线、合成（Anabolism）和分解代谢（Catabolism））。

Aerobic Biological Treatment，95% of the BOD is reduced during this stage。Conventional Activated Sludge system contains a tank for wastewater aeration followed by a settler and a solids recycle line.

The unit processes involved in the SBR（Sequential Batch Reactor）and conventional activated-sludge systems are identical. Aeration and sedimentation/clarification are carried out in both systems. However, there is one important difference. In conventional plants, the processes are carried out simultaneously in separate tanks, whereas in SBR operation the processes are carried out sequentially in the same tank.

As currently used, all SBR systems have five steps arecommonly carried out in sequence as follows:

1-fill.2-react (aeration).3-settle (sedimentation/clarification). 4-draw (decant).5-idle.

A unique feature of the SBR system is that there is no need for a return activated-sludge (RAS) system. Because both aeration and settling occur in the same chamber, no sludge is lost in the react step, and none has to be returned from the clarifier to maintain the sludge content in the aeration chamber.

Trickling Filter “Biological Air Filters”（生物接触氧化法）：

The trickling filter consists of a bed of a highly permeable medium to which microorganisms are attached and through which wastewater is percolated or trickled

Rotating Biological Contractor (生物转盘）：Consists of a series of closely spaced plastic circular disksDisks are submerged in wastewater and rotated slowly through it.Operation, biological growths become attached to the surfaces of the disks and form a slime layer over the entire wetted surface.

Rotating Biological Contractor

Tertiary Treatment：Nitrogen and Phosphorus Removal、Disinfection Nitrification (conversion to Nitrate)Denitrification (conversion to N2 gas)

硝化和反硝化（反硝化的要求：Need low (no) oxygen (< 1 mg/L)、Need carbon source (BOD in Wastewater)、Neutral pH (pH 7)、Conc of nitrate）。

Primary sludge usually have strong odors，Secondary sludge have high concentration of microorganism

Pathogens

Goals of treatments are:Reduce odors、Disinfection、Remove water reduce volume、Decompose organic matter

过程：浓缩—有氧处理——厌氧处理（堆肥）—稳定

人工湿地（Constructed Wetland）：Replicate the naturally occurring process of a natural wetland. Surface Flow和Subsurface Flow（Horizontal Flow Bed、Vertical Flow bed、Hybrid Flow bed）

Atmosphere Pollution：occurs when the air contains gases, dust, fumes or odor in harmful amounts.

Primary Pollutants: Harmful chemical that directly enters the air as a result of human activity. These are deforestisation burning of fossil fuel industrialization warfare etc.

Secondary pollutants :These result from chemical reactions between two or

more air components.

EPA uses six "criteria pollutants" as indicators of air quality：臭氧、一氧化

碳、硫氧化物、氮氧化物、颗粒物、铅

PM2.5比PM10危害更大。了解这六种污染物的危害

四大环境挑战：Green house effect、Ozone depletion、Photochemical smog、Acid rain（了解其危害）。

The important devices to remove PM：

Gravity settling chamber:These are the oldest and simple type of particulate collector .

Particles size 40-100μm in diameter are readily collected by this technique.

The efficiency is very poor on fine dust and decrease as the load increases.

Having the large physical size, but they are inexpensive and reliable .

Cost of equipment is very low and very easy to maintain.

Cyclones：Cyclones use centrifugal forces for removing the fine particles. They are also known as centrifugal or inertial separators.

The cyclone consists of a vertically placed cylinder which has an inverted cone attached to its base. The particulate laden gar stream enters tangentially at the inlet point to the cylinder.

Centrifugal force is utilized to separate the particulate matter.

It can remove 10 to 50 μm particle size.

Electrostatic Precipitators (ESPs) ：An ESP is a particle control device that uses electrical forces to move the particles out of the flowing gas stream and onto collector plates.

The ESP places electrical charges on the particles, causing them to be attracted to oppositely charged metal plates located in the precipitator. 99% efficiency.Can remove particle size range of 0.1 μm to 1 μm.

Fabric Filters：Fabric filters, or bag houses, remove dust from a gas stream by passing the stream through a porous fabric. The fabric filter is efficient at removing fine particles (up to 1μm) and can exceed efficiencies of 99% in most applications. There are four commonly used control technologies for gaseous

pollutants: Absorption（吸收）, Adsorption（吸附）, Condensation（冷凝）, and Incineration (combustion)（燃烧）

固体废弃物：Municipal solid waste (MSW) is generated from households, offices, hotels, shops, schools and other institutions. The major components are food waste, paper, plastic, rags, metal and glass, although demolition and construction debris is often included in collected waste, as are small quantities of hazardous waste, such as electric light bulbs, batteries, automotive parts and discarded medicines and chemicals.

Waste management concept：The 3Rs(Reduce, Reuse, Recycle)

Waste management is the

Collection、Transport and handling、Recycling 、Disposal and monitoring of waste materials.

Treatment and disposal of solid waste：Composting（Composting by trenching

、Open windrow composting、Mechanical composting）、Anaerobic digestion 、Incineration、Landfilling、Pyrolysis、Recycling

土壤：Soil is the thin layer of organic and inorganic materials that covers the Earth's rocky surface.Soil is composed of particles of broken rock that have been altered by chemical and mechanical processes that include weathering and erosion.

土壤污染：It is defined as the build-up in soils of persistent toxic compounds, chemicals, salts, radioactive materials, or disease causing agents, which have adverse effects on plant growth and animal health.Soil pollution is also caused by means other than the direct addition of xenobiotic (man-made) chemicals such as agricultural runoff waters, industrial waste materials, acidic precipitates, and radioactive fallout.

污染原因：Seepage from a landfill

Discharge of industrial waste into the soil

Percolation of contaminated water into the soil

Rupture of underground storage tanks

Excess application of pesticides, herbicides or fertilizer

Solid waste seepage

Deforestation and soil erosion

Biodegradation-the use of living organisms such as bacteria, fungi, and plants to degrade chemical compounds。Bioremediation（生物修复）–process of cleaning up environmental sites contaminated with chemical pollutants by using living organisms to degrade hazardous materials into less toxic substances

生物修复条件：It requires the control and manipulation of microbial processes in surface reactors or in the subsurface.The contaminants can be biodegraded in situ or removed and placed in bioreactor (at or off the contamination sites).

To isolate microbes that can degrade or eat a particular contaminant

To provide the conditions whereby it can do this most effectively, thereby eliminating the contaminant

In situ bioremediation is when the contaminated site is cleaned up exactly where it occurred. It is the most commonly used type of bioremediation because it is the cheapest and most efficient, so it’s generally better to use. There are two main types of in situ bioremediation: intrinsic bioremediation and accelerated bioremediation. Ex Situ Bioremediation which is when contaminated land are taken out of the area to be cleaned up by the organisms. This type of bioremediation is generally used only

when the site is threatened for some reason, usually by the spill that needs to be cleaned up.

Ex situ bioremediation is only used when necessary because it’s expensive and damaging to the area, since the contaminated land is physically removed.

Phytoremediation（植物生物修复）is the use of living green plants for in situ risk reduction and/or removal of contaminants from contaminated soil, water, sediments, and air.

Advantages of bioremediation ：

Bioremediation is a natural process and is therefore perceived by the public Bioremediation is useful for the complete destruction of a wide variety of contaminants.

Instead of transferring contaminants from one environmental medium to another, for example, from land to water or air, the complete destruction of target pollutants is possible.

Bioremediation can often be carried out on site, often without causing a major disruption of normal activities.

Bioremediation can prove less expensive than other technologies that are used for cleanup of hazardous waste

Disadvantages of bioremediation ：

Bioremediation is limited to those compounds that are biodegradable. Not all compounds are susceptible to rapid and complete degradation.

There are some concerns that the products of biodegradation may be more persistent or toxic than the parent compound.

Biological processes are often highly specific. microbial populations, suitable environmental growth conditions, and appropriate levels of nutrients and contaminants.

Bioremediation often takes longer than other treatment options.

附录：各章节的重难点