Combined Membrane-High Rate Algal Pound For Advanced Treatment Of Municipal Wastewater Treatment Plant Effluent

The rapid urbanization of China made a sharp increase in sewage from urban production and living in recent years,so there are more and more municipal wastewater treatment plant.But the treatment by municipal wastewater treatment plant can not eliminate pollutants in sewage completely,some municipal wastewater treatment plant effluent even did not meet the standard.The massive emissions of sewage would make the eutrophication become more serious.It is necessary to take measures to treat the municipal wastewater treatment plant.The characteristics of sewage treatment plant effluent are low C/N and high content of nitrogen and phosphorus,the conventional means can not remove the content of nitrogen and phosphorus in sewage effectively.HRAP is a kind of aerobic stabilization pond,it can get carbon sequestration from CO₂in the air,which gives it an advantage in deal with municipal wastewater treatment plant effluent.A combined high rate algal pond and membrane separation process was applied for advanced treatment of municipal wastewater treatment plant effluent.The results showed that,during June and July,under the conditions of 4 days HRT,the inflow concentration of COD_Crvary from20.91 to 72.55 mg/L,NH₄⁺-N vary from 0.74 to 2.85 mg/L,TN vary from7.01 to 10.15 mg/L,TP vary from 0.35 to 0.52 mg/L,the average effluent concentration of COD_Cr,NH₄⁺-N,TN and TP was 14.00,0.65,0.90 and0.05 mg/L respectively,which could reach the II,III,III and II level of surface water quality standards,respectively.The combined high rate algal pond and membrane separation process showed great effect in enhance municipal wastewater treatment plant effluent.During August,under the conditions of 2 days HRT,the inflow concentration of COD_Crvary from 28.74 to 44.11 mg/L,NH₄⁺-N vary from 1.04 to 2.68 mg/L,TN vary from 6.91 to 10.15 mg/L,TP vary from0.37 to 0.48 mg/L,the average effluent concentration of COD_Cr,NH₄⁺-N,TN and TP was 16.37,0.94,2.51 and 0.12 mg/L respectively.The COD_Cr,NH₄⁺-N and TP reach the II,III and III level of surface water quality standards,respectively,the TN can not reach the V level of surface water quality standards.Under 2 days HRT,the removal efficiency of every water quality index declined,especially TN.During November,under the temperature of 10～20^oC,the inflow concentration of COD_Crvary from 30.36 to 46.73 mg/L,NH₄⁺-N vary from 1.44 to 2.79 mg/L,TN vary from 8.16 to 10.15 mg/L,TP vary from0.36 to 0.47 mg/L,the average effluent concentration of COD_Cr,NH₄⁺-N,TN and TP was 22.97,1.15,4.24 and 0.12 mg/L respectively.The COD_Cr,NH₄⁺-N and TP reach the IV,IV,and III level of surface water quality standards,respectively.Under the temperature of 10～20^oC,the removal efficiency of every water quality index declined,especially TN.The average effluent concentration of TN can not reach the V level of surface water quality standards.The applied ceramic and stainless steel membrane could effectively separate alga as well as colloidal and macromolecules from water.The separation rate of alga was more than 90%.The ceramic membrane was relatively easy to be polluted and needed frequent cleaning since the average pore size was quite small.Stainless steel membrane was preferred while taking filtration efficiency and system stability into consideration.