Study On The Performance And Mechanism Of Bioelectrolysis Coupled With Biotrickling Filter For The Degradation Of M-Dichlorobenzene Waste Gas

Chlorinated Volatile Organic Compounds(Cl-VOCs)are one of the refractory organic compounds in VOCs,which have the characteristics of great harm to ecological environment,wide source,high toxicity,difficult degradation and easy formation of toxic by-products.The treatment of Cl-VOCs by biotrickling filter(BTF)has attracted much attention due to its mild reaction conditions and no secondary pollution.In recent years,it has become a hot spot for VOCs treatment.However,microbial activity still limits the performance of BTF to a certain extent.As an emerging waste gas treatment technology,bioelectrochemical system(BES)has shown good prospects in the treatment of Cl-VOCs waste gas.In this study,the typical pollutant m-dichlorobenzene in Cl-VOCs was used as the target pollutant,and the microbial degradation system of m-dichlorobenzene was constructed based on the three-stage domestication method.In addition,BES was introduced into BTF to construct a bioelectrolysis coupled biotrickling filter reactor(MEC-BTF),and the possibility of enhancing the removal of m-dichlorobenzene in the waste gas was investigated.The microbial system for efficient degradation of m-dichlorobenzene was constructed by the domestication model of“Primary primer(Chlorobenzene)-Secondary primer(Dichlorophenol)-Tertiary primer(Dichlorobenzene)”.After high-throughput sequencing,it was found that the genus level mainly included:norank f Micropepsacea(19.7%),norank f Chitinophagaceae(15.6%),Rhodanobacter(11.9%),Nakamurella(8.7%)and Mycobacterium(6.7%).The study on the characteristics of microbial strains for efficient degradation of m-dichlorobenzene showed that the optimal environmental conditions were:temperature of 30℃and p H of 7.0.A system of bioelectrolysis coupled with biotrickling filter(MEC-BTF)was constructed to enhance the microbial purification of m-dichlorobenzene waste gas,and a three-level domesticated microbial flora was inoculated.The removal effect of MEC-BTF on m-dichlorobenzene at different applied voltages was investigated.The results showed that the weak electrical stimulation had an enhancing effect on the reactor performance.When the applied voltage was 0.7 V,the performance improvement was the largest,and the removal efficiency of m-dichlorobenzene increased from 65.5%to 94.6%.Weak electrical stimulation created a more favorable redox environment for the growth and enrichment of functional bacteria.In addition,weak electrical stimulation promoted the formation of biofilm and secretion of extracellular polymers in the reactor.High-throughput sequencing results showed that weak electrical stimulation could effectively regulate the bacterial community of biofilm.Functional gene analysis showed that weak electrical stimulation enhanced the abundance of key functional genes and the enhancement was most pronounced when the applied voltage was 0.7 V.Under the optimal applied voltage conditions,the reactor performance was optimized,and the effects of inlet concentration,empty bed residence time(EBRT)and inlet loading rate on the reactor performance were investigated.The MEC-BTF had the highest removal rate(92.8%)at the optimum voltage(0.7 V)when the m-dichlorobenzene inlet concentration was 400 mg/m~3.The MEC-BTF had the best elimination capacity for m-dichlorobenzene when the EBRT was 60 s,with an average elimination capacity of 27.09 g/m~3/h.The high-throughput sequencing results showed that the top five species in relative abundance at the genus level included Rhodanobacter,norank＿f＿Chitinophagaceae,norank＿f＿Micropepsaccae,unclassified＿f＿＿Rhizobiaceae and Mycobacterium.High-throughput sequencing results also showed that weak electrical stimulation enhanced the selective enrichment of electroactive and dechlorinated bacteria spp.In summary,this study constructed a method for the purification of m-dichlorobenzene by bioelectrolysis coupled with biotrickling filter,and revealed the improvement effect and strengthening mechanism of MEC-BTF on the removal efficiency of m-dichlorobenzene,which can provide reference for the application of bioelectrochemical technology to strengthen the purification of Cl-VOCs in BTF.