Study On The Mechanism Of Heavy Metal Passivation And Antibiotic And Resistance Gene Reduction In Sludge Composting

Antibiotics,heavy metals,and their resistance genes in urban sludge are factors that hinder the recycling and utilization of sludge resources.If not effectively treated,they will pose a threat to the environment and human health.Composting has a significant effect on reducing and blunting the above harmful substances,and its process has high economic benefits,is simple,and easy to operate.This article systematically studied the reduction and blunting of typical antibiotics and heavy metals during aerobic composting of sludge.In addition,metagenomic analysis was used to analyze the relative abundance of antibiotic resistance genes(ARGs),heavy metal resistance genes(MRGs),and changes in related microbial diversity.The main results of this study are as follows:(1)High-temperature aerobic composting of sludge exhibits good removal effects on tetracycline,ciprofloxacin,and sulfamethoxazole,with removal rates of antibiotics exceeding 75% in different treatments,except for sulfamethoxazole in the low-concentration mixed addition treatment,which has a relatively low removal rate(48.1%).Comparison shows that the removal rate of antibiotics is positively correlated with the concentration and removal rate of ARGs.The removal rates of ARGs were 27.54%(control group),64.33%(high-concentration antibiotic addition treatment),and 48.52%(low-concentration antibiotic addition treatment).Redundancy analysis(RDA)showed that ARGs are significantly influenced by microorganisms such as Proteobacteria in Deferribacteres and Bacteroidetes and environmental factors such as temperature,total organic carbon(TOC),and water content.(2)Exchangeable heavy metals are highly bioavailable and can directly affect the toxic effect of heavy metals on organisms.Composting can effectively reduce it,and the addition of biochar can further promote the blunting of heavy metals.The range of exchangeable content reduction of Mn,Pb,Cu,Zn,and Cr is 17%-61.6%.The addition of biochar at 400℃ had a better effect on the blunting of heavy metals,especially for Mn and Cu.The addition of biochar can also increase the p H of the compost heap,not only promoting the rapid maturation of compost but also having a certain nitrogen-fixing function.In addition,biochar addition increased the overall relative abundance level of MRGs,with a range of enhancement of 16.4%-120.4%.RDA showed that MRGs are significantly influenced by environmental factors such as Tenericutes in Firmicutes,Actinobacteria,and Gemmatimonadetes and TOC and water content.This study achieved fast reduction of residual antibiotics and their resistance genes in urban sludge through composting and effectively blunted heavy metals through the addition of biochar.This not only provides new ideas for reducing the ecological risks of harmful substances from the source of urban sludge but also provides theoretical and data support for the harmless and resourceful utilization of urban sludge.