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℃.