The Efficiency of Thermal-Alkaline Hydrolysis-Conventional Aerobic Digestion Process of Excess Sludge and the Change of Antibiotic Resistance Genes

In order to evaluate the efficiency of the Thermal-Alkaline Pretreatment-conventional aerobic digestion (taCAD) process and evaluate its ecological risk initially, the changes of physicochemical characteristics of sludge before and after thermal alkaline hydrolysis(TAH), as well as the changes of conventional indicators and antibiotic resistance genes(ARGs) of conventional aerobic digestion (CAD) and Thermal-alkaline hydrolysis-conventional aerobic digestion(taCAD) under different aeration rates (Qb=0.5，2 L/min) and solids retention time (SRT) (10 , 20 d) were tested . The results showed that under the conditions of TAH at pH=11, T=70℃ and t=1 h, a large amount of intracellular substances were released from sludge cells, and the content of sCOD, polysaccharides and protein in supernatant could reach Tens of times the number of raw sludge. When the SRT of CAD was 10 d, TAH could increase the VS removal rate by 113.9%(Qb=0.5 L/min), 160.5%(Qb=2 L/min) and TCOD removal rate by 234.6%(Qb=0.5 L/min), 83.3%(Qb=2 L/min). TAH could also significantly improve the oxidation capacity of NH3-N of CAD system, but it would increase the sCOD and TP in reactor. Reducing the amount of aeration, extending the SRT of CAD was beneficial to the reduction of ARGs, while TAH could lead to the rebound of part of ARGs in CAD. Correlation analysis and microbial community structure analysis showed that the ARGs transmission pathway in CAD system was mainly based on gene horizontal transfer (HGT) . This study preliminarily evaluated the ecological environment risk of taCAD and provided a theoretical basis for the selection of subsequent sludge disposal methods.