The Influence Of Ambient Condition On Biological Phosphorus Removal And Paos’ Responding Mechanism In SBR

Enhanced biological phosphorus removal(EBPR) technology had been widely used in municipal wastewater treatment due to its outstanding economic advantage. But the phosphorus effluent concentration of effluent of urban sewage treatment plant was not easy up to the standard because biological phosphorus removal performance was not stable. The problem was to solve engineering practice were the stability and the high efficiency of biological phosphorus removal. Design and engineering operating regulation had some blindness because phosphorus removal mechanisms and the impact factors were unclear. It was difficult to ensure a stable and efficient operation of biological phosphorus removal system because of blindness design.By changing the operation and ambient conditions(feeding mode, concentration of phosphorus and sludge retention time etc.), this thesis studied the relationship of COD and intracellular poly-β-hydroxyalkanoate(PHA) and studied the relationship of PHA and biological phosphorus removal. The purpose of the study was to reveal effects of ambient factors on biological phosphorus removal and PAOs’ responding mechanism so that managers could improve control ability of biological phosphorus removal in engineering practices.The synthetic wastewater was used to study the phosphorus removes in A/O-SBR( anaerobic/aerobic-SBR),A/A/O-SBR( anaerobic/anoxic/aerobic-SBR) and A/A-SBR(anaerobic/anoxic-SBR) systems. This paper discussed the effects of phosphorus feeding modes, phosphorus concentration and sludge retention time on PHA’s synthesis and biological phosphorus removal efficiency as well as their responding mechanisms.The results obtained from the study are shown as follows.(1)Feeding mode of anaerobic no phosphorus and anoxic phosphorus helps A/A-SBR to start.(2)Sludge retention time can change PAOs’ intracellular PHA composition. Prolonged sludge retention time can improve the utilization rate of external carbon source, increase the content of PHA, improve proportion of PHV in PHA, and shorten the essential aerobic time of uptaking phosphorus. When the sludge retention time was respectively 12 d and 20 d, external carbon source utilization rate reached 34% and 74%. When the sludge retention time was 12 d, 20 d and 48 d, PHA synthesis in the sludge were respectively 26.9mg PHA/g VSS, 51.9mg PHA/g VSS and 73.9 mg PHA/g VSS; and the proportion of PHV in PHA were respectively 31%, 58% and 68%; and respectively aerobic 60 min, 45 min and 30 min phosphorus concentration reached 0.5mg/L.(3)Extracellular polymeric substances(EPS)saves a certain amount of phosphorus. Different processes have different EPS phosphorus removal abilities. In A/O-SBR phosphorus removal system, extracellular polymeric phosphorus presents periodic variation. At the end of the reaction, EPS phosphorus recovers to the initial levels. Sludge retention time can be the distribution rates of phosphorus changing in intracellular and extracellular polymeric substances of activited sludge. When the sludge retention time of 12 days, the 40% of all stored in the sludge phosphorus exists in EPS. When the sludge retention time of 20 days, only 20% of all stored in the sludge phosphorus exists in EPS, and the remaining 80% exists in intracellular.The following conclusions obtained by experiment:(1)Because of different phosphorus removal mechanism, feeding mode of anaerobic no phosphorus and anoxic phosphorus helps A/A-SBR to start and stable operation.(2)PHA consumption and sludge phosphorus uptaking is nonlinear correlation. If COD of influent is 450mg/L, consumpting each gram PHA activated sludge can absorb phosphate up to 0.88 grams, and each gram activated sludge can uptake phosphate up to 0.45 grams. When the phosphorus load is too high, by adjusting the anaerobic time can improve the biological phosphorus removal efficency.(3)Prolong sludge retention time can improve the utilization of external carbon source rate, increase the content of PHA in the sludge, and increase proportion of PHV in PHA. longer sludge retention time A/O-SBR phosphorus removal system not only can run stably, but also reduces the production of excess sludge.(4)Different biological phosphorus removal systems because of different operating conditions have different extracellular polymeric substances phosphorus contents. Extracellular polymeric substances phosphorus removal is secondary. Its main function is to mitigate the impact of high phosphorus load in water and to regulate the phosphate concentration of the outside of the cell membrance at the time of anaerobic phosphorus releasing and aerobic phosphorus uptaking. Sludge retention time can be the distribution rates of phosphorus changing in intracellular and extracellular polymeric substances of activited sludge.