Optimal Selection Of Chemical Phosphorus Removal Agents Enhanced Biological Phosphorus Removal Based On Sanitary Sewage

With the gradually increasing eutrophication trend in China, the state requests thatmunicipal sewage treatment plants should be upgradated and reformed so that the effluent watercan meet the Level-1A standards of Discharge Standard of Pollutants for Municipal WastewaterTreatment Plant (GB18918－2002). The effluent water can hardly reach the standards stably bythe biological phosphorus removal process. Therefore, to improve the efficiency of biologicalphosphorus removal process, chemical measures are often adopted. This experiment studies theoptimal chemical synchronous dephosphorization agents in biological simultaneousdenitrification and phosphorus removal system by synchronous chemical measures. The mainconclusions are as follows:(1) By comparison and analysis of the synchronous dephosphorization effects on thesanitary sewage of5common chemical dephosphorization agents (ferric chloride, ferrous sulfate,aluminium sulphate, aluminium chloride, polyaluminium chloride) added in the process, it isfound that iron-seires chemical dephosphorization agents’ phosphorus removal effects aresuperior to those of aluminium-series ones, among which ferrous sulfate’s removal effect is thebest, whose optimum dosage is: Fe/TP=1.6. And the sequence of the5agents’ inhibitoryeffects on biological phosphorus removal process can be listed from weak to strong as below:ferrous sulfate, ferric chloride, polyaluminium chloride, aluminium chloride, aluminium sulphate.Add in the agent ferrous sulfate for the synchronous precipitation. And it is tested that theaverage TP removal rates before and after the dosage are respectively51.8%and95.5%. Takingthe chemical agent’s phosphorus removal effect on the sewage and its inhibitory effect on thebiologcial process into consideration, it is recommended that ferrous sulfate should be chosen asthe optimal chemical agent for the synchronization precipitation to enhance the biologicalphosphorus removal process, and its optimal dosage is: molar ratio of Fe/TP=1.6. It can helpchemically enhanced biological phosphorus removal process optimization, reduce operatingcosts, improve the urban sewage treatment plants and phosphorus removal.(2) Within the range of1≤Fe/TP≤2.6，Fe/TP has a good correlationship with both theeffluent TP and the effluent PO43-, whose relation formulas respectively are:y=3.620073.99618x+1.05771x2+0.24622x30.09222x4,R2=0.99942;y=2.088652.2529x+0.54334x2+0.16159x30.05464x4, R2=0.99922. Through this correlationship, the proper chemicaldosage can be figured out by its required effluent phosphorus content, providing references forsewage plants’ biological phosphorus removal process aided by chemical measures.