Removal Efficiency And Biotransformation Mechanism Of Ppcps From Landfill Leachate By Aerobic Activated Sludge

In recent years,emerging pollutants represented by pharmaceuticals and personal care products(PPCPs)have become a research hotspot in the field of environment.PPCPs are frequently detected in surface water,groundwater and other environments,posing a threat to human health and ecological security.Landfill leachate is high-concentration organic wastewater produced in the landfill process and it is a source of PPCPs pollution that cannot be ignored.The activated sludge method is the most conventional sewage treatment process,and is widely used in the treatment of landfill leachate.However,the removal efficiency and pathway of most PPCPs by activated sludge are still unclear,and the mechanism of microbial action on PPCPs remains to be studied.Therefore,this study used landfill leachate treatment liquid as the research substrate to explore the removal efficiency of activated sludge on PPCPs and the mechanism of microbial transformation.Firstly,the removal efficiency and transformation pathway of 10 kinds of PPCPs by activated sludge were studied.Set the initial concentration of PPCPs to 100 μg/L,after 120 h of activated sludge treatment,the removal rates of 9 PPCPs,except carbamazepine,exceeded80%;adsorption and biodegradation were the main pathways of PPCPs conversion;The adsorption of PPCPs by activated sludge conformed to a quasi-first-order kinetic model,and the adsorption rate was mainly affected by the diffusion speed of PPCPs in the sludge particles;Biodegradation kinetics studies showed that the biodegradation of single-ring compounds was faster than compounds containing complex polycyclic rings.Secondly,selecting ibuprofen and naproxen as representatives,16 S r RNA gene sequencing technology was used to explore the influence of PPCPs on microbial population structure.Under the selective pressure of ibuprofen and naproxen,α diversity increased after slightly decreased,and the response of microorganisms to PPCPs stress had the potential to restore.The community differentiation of activated sludge was mainly affected by PPCPs treatment time,and there was no significant difference between different concentrations.PPCPs changed the species composition and abundance of microorganisms.Proteobacteria and Gemmatimonadetes were significantly enriched under the selective pressure of PPCPs,while Gemmatimonas,Hyphomicrobium,and SWB02 were the dominant bacteria genus under pressure of PPCP.After the treatment of ibuprofen and naproxen,the structure of microbial co-occurrence network became more complicated,the microbial connection became closer,and the community became more stable.Finally,the occurrence characteristics and host bacteria of ibuprofen and naproxen degradation genes in activated sludge were explored by metagenomic sequencing technology,and the metabolic pathways and functional microorganisms of ibuprofen and naproxen were revealed.Several metabolic pathways of ibuprofen and naproxen were found in activated sludge microorganisms,and the metabolism of PPCPs was diverse.Proteobacteria,Burkholderiaceae,Thaurea were the main hosts of PPCP degradation genes.Many families(genus)such as Burkholderiaceae and Haliea played a role in the initial metabolism of ibuprofen,but only the two families(genus)Dongia and Z2-YC6860 played a role in the initial metabolism of naproxen.The degradation of PPCPs may be accomplished by a variety of microorganisms.In this study,the removal efficiency and kinetics of PPCPs by activated sludge were studied based on the actual landfill leachate treatment solution,which provided a theoretical basis for evaluating the operation efficiency of the landfill biological treatment system and the ecological risk of effluent.Using high-throughput sequencing technology to elucidate the mechanism of microorganisms on PPCPs from a molecular perspective and reveal the functional microbes of activated sludge has important practical significance for regulating the microbial composition of sludge,optimization of degradation performance and improvement of landfill leachate treatment efficiency.