Combined Process Of Coagulation And Biological Technology With Ultrafiltration Membrane For The Treatment Of Micro-polluted Water

The rapid economic growth has caused a gradual deterioration of surface water quality,the drinking water sources have been heavily polluted by the organic matters(OM)and ammonia nitrogen(NH4+-N).Conventional treatment process for the treatment of polluted water could not effectively remove NH4+-N and CODMn,it can not ensure the treated water safety,especially in low temperatures,the ammonia removal rate decreases because of the low growth rate of the nitrifying bacteria.Therefore,needing to research and develop new water treatment to ensure the drinking water safety.A pilot-scale study of combined process of on-line control system which contain coagulation and biological technology with ultrafiltration membrane for micro-polluted water were investigated.And the optimal condition of the biological treatment was investigated through an orthogonal experiment under different temperatures.The results showed:(1)The average removal rate of ammonia nitrogen?permanganate consumption(CODMn)and UV254 were 92.5% ? 59.5% and 80.2%,respectively,when ammonia nitrogen?CODMn and UV254 of raw water were 1.54 to 3.38mg/L?3.12 to 5.58mg/L and 0.184cm-1 to 0.284cm-1;the contribution rate of ammonia removal ? CODMn of coagulation and biological technology unit were 94.0%?67.3%,respectively;UF membrane unit were 6.0%?32.7%,respectively,under water temperature more than 10°C.(2)The average removal rate of ammonia nitrogen?CODMn and UV254 were 87.8% ? 53.5% and 74.3%,respectively,when ammonia nitrogen?CODMn and UV254 of raw water were 1.22 to 2.16mg/L?2.88 to 5.55 mg/L and 0.156cm-1 to 0.340cm-1;the contribution rate of ammonia removal ?CODMn of coagulation and biological technology unit were 94.5%?56.3%,respectively;ultrafiltration membrane unit were 5.5%?43.7% respectively,under water temperature less than 10°C.At the same time,the average removal rate of DOC,Fe and Mn were 41.0%,98.9%,and 96.7%,respectively.Moreover,there was no accumulation of nitrite nitrogen in the reactor,and the effluent turbidity was below 0.1NTU,which could reach evaluation standard of the Urban Water Supply Modernized Waterworks in Zhejiang Province 2013.(3)The optimal condition of the filtration mode and the important operation parameters,including membrane flux?filtration time?physical cleaning time and chemical cleaning cycle were investigated through orthogonal experiment to slow down membrane fouling.The experiments showed that under the optimal conditions,the transmembrane pressure(TMP)increased slowly,and the optimal parameters were found as follows: cross-flow with 0.3m3/h;membrane flux 35L/(m2·h)?water production 50min;air cleaning 50s?combined water and air backwashing 70s?hydraulic cleaning 20s;after six physical cleaning cycles,it was used 100 ppm sodium hypochlorite for chemical cleaning.