Research On The Performance Of Self-cleaning Activated Bio-filter For Advanced Treatment Of Municipal Sewage

On account of water resource shortage and water pollution are severe in our country, the sewage discharge standard is becoming more strict, thus advanced wastewater treatment technology has been research hotspot, and has been widely applied. Based on the traditional sand filter, self-cleaning activated bio-filter was improved for the advanced sewage treatment application to improve the sewage treatment effect, and make the effluent reach the recycling standard to be in favour of conservation of water resources. Self-cleaning activated bio-filter has the functions of both filtration and biodegradation, with low investment cost, simple management, continuous sand washing, no need stopping to backwash, and assisted chemical dephosphorization, it can also achieve good dephosphorization effect. Through pilot-scale experiment, the removal efficiencies of SS, COD, TN, NH3-N, TP in wastewater for self-cleaning activated bio-filter used in advanced sewage treatment is investigated, in order to apply it to engineering practice.In this paper, the filtration performance of self-cleaning activated bio-filter was sudied. The equipment could achieve the optimal filtering performance in the working condition as 80 cm of the filter layer height, 4 ~ 6m/h of the filtering velocity, 10~12mm/min of sand circulation rate, the average removal rate of SS was 65%. In the optimal filtering condition, the maximum removal rate of COD, TN, NH3-N, TP were 15%, 7%, 12% and 5%, respectively. Therefore, relying solely on the filtration is no ability of the removal of organic matter.Biological startup experiment was carried out further, the dosage of carbon source, methanol, was 40mg/L. In the initial stage of mature biofilm, the average removal rate of COD, TN, TP were 45.8%, 46.7% and 10.2%, respectively. The stable removal rate of COD, TN implied the biofilm was mature. The influence of gas to water ratio and hydraulic load to the removal efficiency of COD, SS, TN were analyzed, it was determined the optimum gas to water ratio was 2:1, the optimum hydraulic loading was 5~6m3/(m2 ·h).On account of the poor dephosphorization effect of self-cleaning activated bio-filter, the dephosphorization ability assisted chemical dephosphorization was studied. Using aluminum sulfate and polyaluminum chloride as coagulant, the best dosage were 66mg/L and 40mg/L, which could ensure that the effluent TP concentration was less than 0.5mg/L. Polyaluminum chloride was suggested as the optimal coagulant. Thus, chemical dephosphorization can obviously improve the dephosphorization ability of self-cleaning activated bio-filter.