Thermal-alkaline Hydrolysis-two Phase Anaerobic Digestion/Aerobic Digestion Process Of Urban Sludge:Efficiency And Change Of Antibiotic Resistance Genes

Antibiotic resistance genes?ARGs?are a new type of environmental pollutant that is abundantly present in sludge.Therefore,in addition to considering the removal effect of conventional pollutants?VS,TS,etc.?of the sludge treatment technologies,we should also pay attention to the changes of ARGs in excess sludge.It could provide reference for the selection of subsequent sludge disposal methods.In this study,two kinds of bio-stabilization methods for the treatment of urban sludge,thermal-alkaline hydrolysis-mesophilic two-phase anaerobic digestion?taMTPAD?and thermal-alkaline hydrolysis-conventional aerobic digestion?taCAD?,were investigated.The running results and seven high-frequency detection genes before and after the operation of two kinds of bio-stabilization methods were explored in this study.And the correlation between ARGs and microbial community structure were also be studied.In this paper,the sludge was pretreated by thermal alkaline hydrolysis.The results showed that the concentration of nutrients?sCOD,TN,TP,etc.?in the supernatant of sludge was significantly increased after thermal alkaline hydrolysis.As the temperature and pH increased,the cracking effect of the sludge became better.However,the cracking effect of the thermal alkaline hydrolysis was not much different from the mesophilic alkaline hydrolysis.Considering the nutrient dissolution effect,energy consumption and ARGs control effect,it was determined that pH=11,T=70?,t=1h was the suitable pretreatment condition of sludge.The taMTPAD process showed strong stability under three different tHRTs of 20d,16d and 10d.At tHRT=20d,the VS removal rate was the highest and the control effect on ARGs was the best.However,at tHRT=10d,the VFA and sCOD accumulation of the acidogenic phase,and the daily gas production and methane production of the methanogenic phase was the largest,but the control effect on ARGs was the worst.The thermal-alkaline hydrolysis could significantly improve the acid production capacity of the acidogenic phase,the gas production capacity of the methanogenic phase and the VS removal rate of two-phase anaerobic digestion system,but thermal-alkaline hydrolysis could also cause some ARGs to rebound.The pH of taCAD process was close to neutral,which was more suitable for microbe growth and reproduction.At HRT=10 d,the thermal-alkaline hydrolysis could significantly improve the VS and TCOD removal rate of the CAD process,and could effectively reduce the VS/TS value.Increasing the aeration rate had no significant effect on the VS removal rate of the four reactors,but could increase the TCOD removal rate.Thermal alkaline hydrolysis can significantly improve the NH₃-N removal efficiency of the CAD process,but it also brings higher sCOD and TP in supernatant.The results of ARGs test showed that when Q_b=0.5L/min,prolonging HRT was beneficial for CAD to reduce ARGs.Adding thermal alkaline hydrolysis and shortening HRT might cause some ARGs to rebound.For the case of Q_b=2L/min,although some ARGs in the taCAD group were different from the raw sludge,the variation was not large.