Analysis On Phosphorous Removal Performance And Efficiency Of Municipal Wastewater Treatment Plants

The enhanced biological phosphorus removal process has the characteristics of high phosphorus removal efficiency,economy,and sustainability,and is widely used in urban sewage treatment plants.However,in practical engineering applications,it has been found that the phosphorus removal effect of the enhanced biological phosphorus removal process is difficult to maintain stability.Adopt chemical dephosphorization agent to improve the efficiency of dephosphorization.However,the effect of chemical phosphorus removal agents on biological phosphorus removal systems is not yet clear.Therefore,further exploration of the phosphorus removal performance and efficiency of urban sewage treatment plants is of great significance for the efficient and stable phosphorus removal of urban sewage treatment plants.This paper takes the three,fourth,fifth and tenth sewage treatment plants under the Xi’an Wastewater Co.Ltd.as the research object.Through the investigation of the incoming and outgoing water quality,the analysis of the phosphorus concentration in the main operation unit,the sludge release Phosphorus absorption activity determination,functional microbial population analysis,and the analysis of phosphorus in the treatment system,etc.,to explore the effectiveness of biological phosphorus removal in urban sewage treatment plants.The main conclusions are as follows:（1）The third,fourth,fifth,and tenth sewage treatment plants in Xi’an from September to December have an average TP of 8.22 mg/L,3.86 mg/L,6.47 mg/L,4.39 mg/L,and COD/TP The ratios are 78.18,64.56,57.80,77.27.The BOD/COD values of the fourth and fifth sewage treatment plants are relatively high,at 0.6 and 0.55,respectively.Although the treatment process of each sewage treatment plant is different,the effluent after treatment meets the Class A discharge standard,and the TP of the third,fourth,and tenth sewage treatment plants meets the surface class IV water discharge standard.（2）The dephosphorization effect of the selective tank with oxidation ditch is better than that of the A²/O process.Separate A²/O process effluent TP is difficult to reach the level A standard and must be chemically strengthened;while the pond with oxidation ditch effluent TP can be stabilized（3）The contribution of the third sewage treatment plant biological pool dephosphorization and sedimentation flocculation of the secondary sedimentation tank to the removal of total phosphorus in the influent was 5.2 mg/L and 0.03 mg/L;The contribution of phosphorus removal to the removal of total phosphorus in the influent was5.52 mg/L and 0.25 mg/L,respectively;the contribution of phosphorus removal by the tenth sewage treatment plant biological pool and chemical phosphorus removal to the removal of total phosphorus in the influent were 4.31 mg/L and 0.52 mg/L.（4）The rate of phosphorus release/phosphorus absorption of activated sludge in each sewage treatment plant is good and above,among which the rate of phosphorus release and phosphorus absorption of the fourth sewage treatment plant is the largest,being 7.32mg P·g VSS^-1·h^-1,6.16,respectively mg P·g VSS^-1·h^-1,the phosphorus release rate and phosphorus absorption rate of the fifth sewage treatment plant are the smallest,respectively 4.35 mg P·g VSS^-1·h^-1,3.81 mg P·g VSS^-1·h^-1.The third sewage treatment plant has a lowΔP/ΔHAc value of 0.3,indicating that there are more heterotrophic bacteria in the sludge that compete with the phosphorus-accumulating bacteria for carbon sources.There is room for improvement in the phosphorus removal capacity of each sewage treatment plant.（5）Long-term addition of chemical phosphorus removal agents has a negative impact on the phosphorus release capacity of phosphorus accumulating bacteria,which will weaken the phosphorus removal capacity of activated sludge.（6）Fluorescence in situ hybridization analysis showed that the proportion of phosphorus accumulating bacteria in the activated sludge of the third,fourth,fifth and tenth sewage treatment plants was 10.22%,9.00%,11.72%and 10.89%,respectively.The third,fourth,and tenth sewage treatment plants have the same proportion of glycan bacteria,both of which are around 2%.The fifth sewage treatment plant had the highest proportion of glycan bacteria,at 4.10%.（7）The total phosphorus in the inlet water of the third sewage treatment plant is mainly removed by enhanced biological phosphorus removal（phosphorus accumulating bacteria）and microbial proliferation（non-phosphorus accumulating bacteria）,which account for54.55%and 42.96%respectively;Total phosphorus in water is jointly contributed by chemical precipitation,enhanced biological phosphorus removal（phosphorus accumulating bacteria）and microbial proliferation（non-phosphorus accumulating bacteria）.The proportions of the three are 7.72%,41.68%and 50.60%,respectively.In the tenth sewage treatment plant,the proportions of the three are 9.45%,29.06%,61.49%and 8.83%,39.26%and 51.92%respectively.The content of chemical phosphorus components in the remaining sludge of the sewage treatment plant with chemical dephosphorization agent added is higher than that of the sewage treatment plant without dosing phosphorous depletion agent...