Study On Co-pricipitation Or Post-pricipitation Chemical Phosphorus Removal Process In Urban Sewage Treatment Plant

To protect the surface water environment quality,the state gradually improve effluent water quality requirements of sewage treatment plant.In order to reduce the content of total phosphorus in effluent water,chemical phosphorus removal are usually accompanied to ensure that the effluent water up to the standard.In this study,taking Long Wangzui sewage treatment plant as the research object,analysised the existing biological phosphorus removal process.In chemical phosphorus removal process optimization as the main research targets.Based on actual operation research in sewage plant,according to the biological pool inflow water and effluent water quality,using phosphorus equilibrium analysis methods to analyze the effect of biological phosphorus removal.and calculate the theory of phosphorus formulaof effluent water.The necessity of the chemical phosphorus removal was expounded.Then analyzed dosing point and quantity of chemical phosphorus removal process,throughtest in laboratory experiments.Obtained the best dosing point and quantity of coagulant dosage model.At last the formula of quantity of sludge was studied.All of these provides the necessary technical guidance for actual wastewater plant chemical phosphorus removal.Through this paper the following results are obtained.（1）By analysising the inflow and effluent water quality of Long Wangzui sewage treatment plant,biological phosphorus removal effect is obvious in biological pool.There is an obvious phenomenon of the release and absorption of phosphorus in anaerobic tank and aerobic tank.75%of biological pool effluent water meet the requirements of first level A discharge standard.By analyzing the balance of phosphorus,the average of the percentage of phosphorus balance is 97.2%,TP in inflow water is mainly removed by drainning excess sludge,which takes 90%of TP removal amount.（2）Based on the biological phosphorus removal equilibrium theory,the early stage of the utilization rate of COD analysis results and sludge age calculation assumes,established theoretical calculation formula of effluent TP as follows:（?）Actual operation results show that the theoretical calculation of TP and actual TP quantity in effluent water is relatively close,the formula can be used to forecast effluent phosphorus content according to the biological pond water situation.lay foundation for chemical phosphorus removal research.（3）Use of laboratory experiment of phosphorus removal,it is known that,synchronization coagulant dosage process function by coagulation and precipitation chemical phosphorus removal mechanism.In the subsequent coagulating sedimentation process,phosphorus mainly exists in the form of solubility,its main removed by the chemical precipitation method.the treatment effect and utilization rate of coagulant are relatively low.When the PAC dosing quantity of 2 mg/L,the TP removal amount in synchronization coagulant dosage process is 0.12 mg/L,and in rear process,coagulant dosage process was 0.08 mg/L.TP removal amount in synergism sedimentation process is about 1.7 times to the amount of subsequent coagulating sedimentation process.（4）Chemical phosphorus removal results shows that the existing form of TP and chemical phosphorus removal in wastewater has close ties to the quantity of PAC.Non soluble TP accounted for about 60%of the TP in inflow water,its mainly exists in the form of effluent SS biological phosphorus and colloid or particle state phosphorus,it is easy to be removed through flocculation.（5）According to different biological pond effluent TP content and components,the PAC dosing quantity model is as follows:When TP in biological pond effluent water less than 1 mg/L,TP removal of 1mg/L on average about need dosing PAC about 12 mg/L,dosing quantity formula as follows:M₁=12k（p_e-.047）Q/1000When TP in biological pond effluent water more than 1 mg/L,DTP removal of 1mg/L on average about need dosing PAC about 81.5 mg/L,dosing quantity formula as follows:M₂=k[12p_g+815.（p_s-.047）]Q/1000Validation of the model show that it can be used to estimate of chemical phosphorus removal dosing quantity.（6）Learning process of phosphorus sludge quantity has the following four sources,deposition of suspended solids in raw water,deposition of impurities in coagulant,Reaction products of coagulant and solubility substance,coagulant hydrolysis.The amount of sludge production can use the type to calculate.S_理论=S₁+S₂+S₃+S₄=(SS_in-SS_ef)+0.86M+（35）DTPDosing PAC sludge yield have important relationship with the TP composition of raw water,.When TP mainly exist in the solubility TP,flocculation method as the main means to remove TP,raw water of suspended solid deposit proportion is the largest,when solubility TP content is higher,in addition to the flocculant with low content of solubility substance reacts to precipitate,the other three all have important effects on sludge yield.