除磷工艺构型已基本成型； – 实践证明：在推流系统的首段设置一部分非曝气区域
是实现强化生物除磷的重要条件。
❖ 20世纪70年代末 – 微生物学方面的研究得到加强；从活性污泥中分离到
除磷菌；发现不动杆菌起重要作用。 – Fuhs 和 Chen: 发现厌氧段存在对产生短链脂肪酸的必要
性，并假设不动杆菌需要短链脂肪酸进行生长和好氧吸 磷。但并未把释磷和吸磷联系起来。
Concentration of VFAs
Adequate concentration of VFAs is beneficial. Low VFA concentration reduces the P release in anaerobic zone, resulting in corresponding low P uptake in aerobic zone.
• Under aerobic conditions: – aerobes find little BOD left – anaerobes inactive – PAOs oxidize previously stored BOD
• PAOs selected for by anaerobic conditions: – produces fermentation products they need – limits competition from other aerobes
5Ca2+ + 3PO43- + OH- ↔ Ca5(PO4)3(OH)(s) (羟磷灰石 ， Hydroxyapatite)
But when add lime to water:
Ca(OH)2 ↔ Ca2+ + 2OHOH-+ HCO3- ↔ H2O + CO32Ca2+ + CO32- ↔ CaCO3(s)
DO
In P release, consumes VFAs (2.3g COD/g O2) and limit the
formation of VFAs; In P uptake, rate decreases if DO is too low.
Nitrate
O2
Settling phase Effluent
Return sluge
Anaerobic PO4
Aerobic / Anoxic
Waste sluge Settling phase
Bulk liquid
Biomass
HAc PHA Poly-P GLY
PO4 Poly-P
GLY
PHA
PO4 GLY PHA
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
secondary treatment
❖ Polymers may be added to enhance removal
除磷技术
Chemical Precipitation (P315-318) Reactions Form Insoluble Phosphates
Reaction with lime:
So required dose of lime depends on alkalinity – once carbonate used up, get P removal
除磷技术
Chemical Precipitation
Advantages – reliable – low levels of P in effluent possible – retrofit for existing plant likely possible
污水深度处理与回用
(3)磷的去除
磷循环
Global Phosphorus Cycle
Weathering: 侵蚀/风化 Burial: 沉积
磷循环
The Land Phosphorus Cycle
除磷技术
Chemical Precipitation
❖ Precipitate h – Lime - Ca(OH)2 – Alum - Al2(SO4)3 – most common
– ~1980 – largely agreed it was biological
Organisms
• Now generically called “Phosphate Accumulating Organisms” (PAOs) – if fed acetate, show similar behaviour for P release and uptake – require oxygen for growth (aerobic) – PAOs store P internally as polyphosphate – maximum P accumulation: 100-150 mgP/g VSS (10-15%)
除磷技术
Enhanced biological Phosphorus Removal
Other Parameters affecting BPR process
Parameters
Optimal range/value and comments
Carbon source
BOD/P 15-20; BOD/N≥4-5
Reactions with Aluminium and Iron:
Al3+ + PO43- ↔ AlPO4(s) Fe3+ + PO43- ↔ FePO4(s)
But in practice – takes ~2 moles Al or Fe per mole P – e.g., Al3+ + 3OH- ↔ Al(OH)3(s)
除磷技术
Enhanced biological Phosphorus Removal
Essential Condition: Anaerobic/aerobic Cycling
Selective Advantage of PAOs
Anaerobic!
• Under anaerobic conditions: – aerobes can’t utilize BOD – anaerobes ferment BOD; little energy available – PAOs take up and store fermentation products
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!
除磷技术
Enhanced biological Phosphorus Removal
method (or other aluminium compounds) – Iron - FeCl3 or Fe2(SO4)3
❖ Add – before primary – in aeration tank – before secondary settling – separate unit process after
除磷技术
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?)
Problem – digestion (especially anaerobic) may re-release P
投加氯化铁除磷
除磷技术
Biological Phosphorus Removal
Assimilation
• Cells are 1-2% P (dry weight) • Removing biomass removes P
▪ P storage is not “luxury uptake” of the nutrient ▪ It is energy storage ✓ Anaerobic conditions: PAOs release P from polyphosphate, utilizing the energy
for uptake and storage of organics ✓ Aerobic conditions: PAOs utilize the stored organics, and take up P to produce
the polyphosphate for energy storage
❖ 20世纪80年代初，Rensink –首次阐释释磷与吸磷的关系；
❖ 此后 –生化模型的发展
除磷技术
Enhanced biological Phosphorus Removal
Influent
PO4 HAc
Anaerobic PO4
HAc
Poly-P
PHA
Aerobic CO2
PO4
PHA Poly-P
High Loaded Plug Flow System