| In recent years,China’s water ecological treatment and protection work has been deepening,and valley harnessing has become the focus of national water environment protection work.For the key river valley or the important water source protection areas,the first grade A standard implemented by the surrounding urban sewage treatment plants can no longer meet the requirements,which urgently requires urban sewage treatment plants to improve the discharge standard according to local conditions.According to the characteristics of the tail water of the urban sewage treatment plant,this paper puts forward the "coral sand biological aerated filter(BAF)/activated coke adsorption filter" combined action unit.Through the experimental study,the removal effect of CODCr,NH4+-N,TN,TP under several different working conditions was analyzed,and the better operating conditions were found out,which provides a reference for the application of coral sand biological aerated filter/activated coke adsorption filter in the advanced sewage treatment.(1)In the experiment,coral sand BAF and ceramsite BAF were started by continuous culture after inoculation of activated sludge.After stable operation,the treatment effects of two BAFs on CODCr,NH4+-N and TN under different hydraulic loads were compared,and the feasibility of coral sand as BAF filler was investigated.The results show that coral sand BAF is better than ceramsite BAF in TN treatment,and coral sand is suitable for BAF filler of advanced tail water treatment process of urban sewage treatment plant.(2)The BAF process of coral sand was studied,including the effects of A/O volume ratio,hydraulic load,air-water ratio and reflux ratio on BAF.Based on the analysis of the test results,the key process parameters such as A/O volume ratio,hydraulic load,gas water ratio and reflux ratio were determined.(3)When the ratio of A/O volume ratio was 1:1,the hydraulic load was 0.60m3/M2·h,the reflux ratio was 200%,and the ratio of air to water was 5:1,the average removal rate of pollutants in the tail water can reach CODCr was 70.95%,NH4+-N was 80.21%,TN was 47.70%and TP was 30.78%.The average effluent concentrationcan reach 11.74mg/L for CODCr,0.85mg/L for NH4+-N,7.16mg/L for TN and 0.303mg/L for TP.(4)Through the study of the removal effect of pollutants when the hydraulic load of the activated coke adsorption filter was 0.40m3/m2·h,0.60m3/m2·h and 0.80m3/m2 h respectively,the more appropriate hydraulic load of the activated coke adsorption filter was determined.The test shows that the activated coke adsorption filter has a better removal effect when the hydraulic load is 0.60m3/m2·h.At this time,the average removal rates of CODCr,NH4+-N,TN and TP by the combined process were 24.06%,25.26%,21.13%and 38.26%respectively,and the average effluent concentration were10.13mg/L,0.64mg/L,6.26mg/L and 0.193mg/L respectively.(5)When A/O volume ratio was 1:1,hydraulic load was 0.60m3/m2·h,gas water ratio was 5:1,and reflux ratio was 200%,the average removal rate of pollutants by the combined process in the tail water can reach CODCr was 77.09%,NH4+-N was 88.87%,TN was 56.06%and TP was 57.22%.The average effluent concentrationcan reach 10.18mg/L for CODCr,0.53mg/L for NH4+-N,6.36mg/L for TN and 0.192mg/L for TP.CODCr,NH4+-N and TP in the effluent meet the class Ⅳ of "Environmental quality standards for surface water"(GB3 83 8-2002),TN meets the requirements of quasi class Ⅳ water quality standard.The results show that coral sand BAF/activated coke adsorption filter was a kind of combined technology which can meet the requirements of tail-water advanced treatment,with good treatment effect and low investment cost. |
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