Study On The Performance And Mechanism Of Trimethoprim Degradation By Anaerobic Biological System Enhanced By Photoelectric Stimulatio

The residual antibiotics in the environment lead to the accumulation of antibiotic resistance genes（ARGs）and drug-resistant antibiotics resistant bacteria（ARB）.If the residual antibiotics can’t be handled and controlled in effectively,the estimated annual increase in antibiotics-resistant deaths worldwide by 2050 will exceed 10 million.Therefore,the removal and mineralization of antibiotics are urgent.Microbial fuel cell（MFC）and photocatalysis fuel cell（PFC）have the characteristics of environmental friendliness,low energy consumption,no secondary pollution and so on.They can convert chemical energy in wastewater into electrical energy to realize pollution treatment and energy generation simultaneously.In addition,studies have shown that these two technologies have the ability to degrade antibiotic wastewater,but MFC requires too long domestication time,and PFC has high requirements on photocatalytic materials.In recent years,the photocatalytic coupled microbial fuel cell（PMFC）has become a research hotspot in the treatment of emerging pollutants such as antibiotics.In this study,trimethoprim（TMP）was used as the target pollutant,and three different types of photocatalytic anodes based on Ti O₂ were prepared.Three systems of PMFC,PFC and MFC were constructed.Then the degradation efficiency,transformation pathway and toxicity removal of TMP in the three systems were studied.Furthermore,the functional microbial community structure and accumulation of ARGs in MFC and PMFC systems were compared.The conclusions are summarized as follows:（1）The optimal conditions for MFC to degrade TMP and total organic carbon（TOC）were determined as resistance 1000Ω,p H 7.0 and 25 m M PBS.At the same time,the TMP removal efficiency of the three treatment systems was compared under these conditions.It was found that PMFC system had better performance in TMP removal efficiency,TOC removal efficiency and products toxicity removal.TMP degradation efficiency increased by4.8%and 6.0%at PMFC system,compared to MFC and PFC respectively,indicating that the photoelectric catalytic coupled anaerobic biodegradation system could degrade TMP effectively.（2）The photocatalytic anode of PFC reactor was prepared with sol-gel,sol-hydrothermal and 001-type Ti O₂ as photocatalyst and nickel foam as substrate.The characterization results show that 001-type Ti O₂ photocatalytic material has the best photo-generated charge separation efficiency.The PFC reactor with 001 Ti O₂ as photocatalytic anode also showed the optimal performance of TMP removal,which could degrade 93.56%TMP within 72 h.However,the TOC removal efficiency was only 11.76%,which indicated that the degradation of TMP transformation products by PFC was incomplete.In addition,cyclic experiment results showed that the sol-hydrothermal photocatalytic material was the most stable,after 4cycles（480 h）of continuous use,the degradation rate of TMP decreased only 7.56%and remained at 84.59%.（3）The transformation products of TMP in MFC,PFC and PMFC systems were analyzed by UPLC-QTOF-MS,and their degradation paths were speculated.Results showed that the reaction occurred during TMP degradation,including hydroxylation,demethoxylation,deamination and breaking the methylene bridge.The pathway M291→M140→M123→M137only occurred in MFC system,while the pathway M291→M307→M305→M197/M123 only occurred in PFC system.It was speculated that the decyclization and deamination reactions of imidazole only occurred in PMFC system during the degradation of TMP,indicating that the photoelectric catalytic coupling system could achieve further conversion of TMP transformation products compared single system.（4）The high-throughput sequencing analysis was used to analyze the microbial community structure of the anode biofilms from MFC and PMFC.Results showed that Proteobacteria and Betaproteobacteria were the highest abundance at the phylum and class levels,respectively.At the genus level,the electrochemically bacteria genera（EAB）Geobacter and Geothrix achieved the greatest enrichment in PMFC reactor,with 2.35%and2.23%,respectively,which were improved compared to the MFC reactor（1.14%and 0.18%）,indicating that the photoelectrocatalytic coupled microbial system can promote the enrichment of EAB in the bioanode.Moreover,more nitrate-reducing bacteria（NRB）was founded in PMFC reactor,which may be due to the imidazole ring-opening and deamination reaction of TMP under photocatalysis,resulting in the production of nitrogen-containing compounds more suitable for NRB metabolism.（5）The composition of ARGs on the anodic biofilm of MFC and PMFC was analyzed by metagenomic sequencing analysis.Results showed that there were 8 major kinds of ARGs in PMFC and MFC reactors.Sulfonamide antibiotics ARGs were the most significantly increased ARGs after domestication.The relative abundance in PMFC and MFC was 15.86%and 20.04%,respectively.And sul1 and sul2 were typical sulfonamide-like ARGs subtypes,which had a strong positive correlation with Acinetobacter and Aquamicrobium.By comparing the accumulation of ARGs in the closed-circuit and open-circuit MFC,it was found that the accumulation of ARGs in the open-circuit condition was significantly slower than that in the closed-circuit environment,presumably because the micro-electric field existing in the closed-circuit environment promoted the replication and propagation of ARGs.PMFC system reduced the accumulation of ARGs compared to MFC during degrading TMP.