污水深度处理与回用：(3)磷的去除
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Enhanced biological Phosphorus Removal
High Loaded Plug Flow System
Uptake beyond need for balanced growth – Originally called “luxury uptake” • First noted: – 1959 in India – 1961 in USA – unintentional – conventional activated sludge, high loading
Disadvantages – cost of chemicals – substantial additional sludge production – chemical sludge reuse or disposal may be more difficult – may need to adjust pH – may affect the biological processes
But when add lime to water:
Ca(OH)2 ↔ Ca2+ + 2OHOH-+ HCO3- ↔ H2O + CO32Ca2+ + CO32- ↔ CaCO3(s)
Reactions with Aluminium and Iron:
Al3+ + PO43- ↔ AlPO4(s) Fe3+ + PO43- ↔ FePO4(s)
Potential Biomass Production: BOD*YH/1.42=300*0.63/1.42=133 mg VSS/L < 600 mg VSS/L
Effective P removal through assimilation is not practical!
P Removal Technologies
污水深度处理与回用
(3)磷的去除
2015年6月15日
Global P Cycle
Global Phosphorus Cycle
Weathering: 侵蚀/风化 Burial: 沉积
Land P Cycle
The Land Phosphorus Cycle
“Open” Human P Cycle
P Removal Technologies
Enhanced biological Phosphorus Removal
Initial Findings
❖ All plants with enhanced P removal were conventional activated sludge with long plug flow reactors and high loadings (why?)
“Open” Human Phosphorus Cycle
Depletion
Eutrophication
P Removal & Recovery
Forms of P in WW
Forms of Phosphorus in Wastewater (Influent)
(Detergents) Target: TP≤0.5 mg/L (Major Fo百度文库m)
P Removal Technologies
Chemical Precipitation
Advantages – reliable – low levels of P in effluent possible – retrofit for existing plant likely possible
P Removal Technologies
Chemical Precipitation (P315-318)
Reactions Form Insoluble Phosphates
Reaction with lime:
5Ca2+ + 3PO43- + OH- ↔ Ca5(PO4)3(OH)(s) (羟磷灰石 ， Hydroxyapatite)
But in practice – takes ~2 moles Al or Fe per mole P – e.g., Al3+ + 3OH- ↔ Al(OH)3(s)
So required dose of lime depends on alkalinity – once carbonate used up, get P removal
❖ Add – before primary – in aeration tank – before secondary settling – separate unit process after secondary treatment
❖ Polymers may be added to enhance removal
C118H170O51N17P (31/2671=1%)
For typical municipal wastewater: BOD=300 mg/L, TP=6 mg/L
Complete P removal through assimilation: Production of Biomass required : 6/0.01=600 mg VSS/L
P Removal Technologies
Chemical Precipitation
❖ Precipitate with – Lime - Ca(OH)2 – Alum - Al2(SO4)3 – most common method (or other aluminium compounds) – Iron - FeCl3 or Fe2(SO4)3
Problem – digestion (especially anaerobic) may re-release P
投加氯化铁除磷
P Removal Technologies
Biological Phosphorus Removal
Assimilation
• Cells are 1-2% P (dry weight) • Removing biomass removes P
High Loaded Plug Flow System
Uptake beyond need for balanced growth – Originally called “luxury uptake” • First noted: – 1959 in India – 1961 in USA – unintentional – conventional activated sludge, high loading
Disadvantages – cost of chemicals – substantial additional sludge production – chemical sludge reuse or disposal may be more difficult – may need to adjust pH – may affect the biological processes
But when add lime to water:
Ca(OH)2 ↔ Ca2+ + 2OHOH-+ HCO3- ↔ H2O + CO32Ca2+ + CO32- ↔ CaCO3(s)
Reactions with Aluminium and Iron:
Al3+ + PO43- ↔ AlPO4(s) Fe3+ + PO43- ↔ FePO4(s)
Potential Biomass Production: BOD*YH/1.42=300*0.63/1.42=133 mg VSS/L < 600 mg VSS/L
Effective P removal through assimilation is not practical!
P Removal Technologies
污水深度处理与回用
(3)磷的去除
2015年6月15日
Global P Cycle
Global Phosphorus Cycle
Weathering: 侵蚀/风化 Burial: 沉积
Land P Cycle
The Land Phosphorus Cycle
“Open” Human P Cycle
P Removal Technologies
Enhanced biological Phosphorus Removal
Initial Findings
❖ All plants with enhanced P removal were conventional activated sludge with long plug flow reactors and high loadings (why?)
“Open” Human Phosphorus Cycle
Depletion
Eutrophication
P Removal & Recovery
Forms of P in WW
Forms of Phosphorus in Wastewater (Influent)
(Detergents) Target: TP≤0.5 mg/L (Major Fo百度文库m)
P Removal Technologies
Chemical Precipitation
Advantages – reliable – low levels of P in effluent possible – retrofit for existing plant likely possible
P Removal Technologies
Chemical Precipitation (P315-318)
Reactions Form Insoluble Phosphates
Reaction with lime:
5Ca2+ + 3PO43- + OH- ↔ Ca5(PO4)3(OH)(s) (羟磷灰石 ， Hydroxyapatite)
But in practice – takes ~2 moles Al or Fe per mole P – e.g., Al3+ + 3OH- ↔ Al(OH)3(s)
So required dose of lime depends on alkalinity – once carbonate used up, get P removal
❖ Add – before primary – in aeration tank – before secondary settling – separate unit process after secondary treatment
❖ Polymers may be added to enhance removal
C118H170O51N17P (31/2671=1%)
For typical municipal wastewater: BOD=300 mg/L, TP=6 mg/L
Complete P removal through assimilation: Production of Biomass required : 6/0.01=600 mg VSS/L
P Removal Technologies
Chemical Precipitation
❖ Precipitate with – Lime - Ca(OH)2 – Alum - Al2(SO4)3 – most common method (or other aluminium compounds) – Iron - FeCl3 or Fe2(SO4)3
Problem – digestion (especially anaerobic) may re-release P
投加氯化铁除磷
P Removal Technologies
Biological Phosphorus Removal
Assimilation
• Cells are 1-2% P (dry weight) • Removing biomass removes P