Effects Of Mixed Liquid Temperature On The Overall Performance And Its Mechanism Of An Anoxic/Aerobic Process For Treating ABS Resin Wastewater

ABS resin production wastewater is discharged at temperature as high as 40~60?,and contains high concentration of suspended solids,latex and toxic organic pollutants.The wastewater is mainly treated with combined process of the coagulation/air flotation and biological anoxic/aerobic(A/O)process,which is affected significantly by the high temperature of wastewater.In this study,the effects of mixed liquid temperature on the overall performance of A/O process and microbial community variation of activated sludge were investigated.The main conclusions were as follows:The mixed liquid temperature in the range of 25~45? significantly affect the pollutants removal performance of A/O process,the optimum performance was got at 25~30? and the effluent quality deteriorate significantly at 45?.With the influent COD concentration of 800~1150 mg/L,TN of 80~123 mg/L,ammonia nitrogen of 20~81 mg/L and TP of 1~11.75 mg/L,at the stable operational stage,the reactors' effluent COD concentrations at 25,30,35,40 and 45? were stable at 95 mg/L,94 mg/L,137 mg/L,194 mg and 231 mg/L,respectively.The effluent TN concentrations at 25,30,35,40 and 45? were stable at 16.69mg/L,17.90mg/L,17.90mg/L,22.56mg/L and 67.17mg/L,respectively.The effluent NH4+-N concentrations at 25,30,35,40 and 45? were stable at 0.70 mg/L,1.09mg/L,1.74mg/L,2.49 mg/L and 55.44mg/L,respectively.The effluent TP concentrations at 25,30,35,40 and 45? were stable at 0.50mg/L,0.50mg/L,0.70mg/L,1.40mg/L and 3.46mg/L,respectively.Overall,the A/O reactors demonstrated a good removal performance on the organic nitriles and the aromatic toxic organic pollutants detected in ABS wastewater at 25~45?.With the increase of temperature,the EPS of activated sludge decreased,the soluble microbial product increased,the filamentous bacteria increased,the sludge sedimentation performance degraded.As a result,the increase of soluble and suspended organic matter related to microbial was the main reason leading to higher effluent COD.When the temperature was increased above 35?,the high temperature resulted in the high concentration of free ammonia(FA),which inhibited the NOB and resulted in NO2--N accumulation.When the temperature was increased above 42.5?,the AOB was inhibited significantly and resulted in the effluent NH4+-N increased significantly.Quick temperature increase of mixed liquid from 25? to 40? resulted siginificant shock on the removal efficiency of organic matter,nitrogen and phosphorus in a short period of time.The reactor got similar pollutant removal performances at stable operation stage with two temperature increase mode.One mode was quick temperature rise from 25? to 45? directly,and another one was quick rise from 25? to 40? first and then slowly linear temperature increase to 45?(1?/8d and 2.5?/8d).Consistent with wastewater treatment performance,as the temperature was increased to 42.5 ? and above,in the activated sludge,the relative abundance of Firmicutes and Deinococcus-Thermus were increased siginificantly,while the relative abundance of Acidobacteria and Nitrospirae were decreased siginificantly.Proteobacteria,Bacteroidetes,Chloroflexi and Chlorobi were the major phylum during the whole period of the temperature was increased from 25? to 52.5?.