Surfactant Combined With Co-metabolism Substrate Enhancing M-xylene Biodegradation By Microecological Bacteria System

As an important component of BTEX,m-xylene is insoluble in water and poor in biodegradability.Irregular emissions of m-xylene can seriously harm human health and ecological environment.In this paper,activated sludge from coking wastewater treatment plant was used as the bacterial source and m-xylene was selected as the target pollutant.m-Xylene microecological bacteria system was constructed based on multi-substrate progressive acclimation pattern and then was identified.The optimal conditions for the growth of m-xylene microecological bacteria system were determined.At the same time,the effects of surfactants on the growth of microecological bacteria system and m-xylene biodegradation were investigated,and the mechanism of action among m-xylene,surfactants and microecological bacteria system during m-xylene biodegradation was explored.On this basis,the co-metabolism substrates were further added to study the effects of co-metabolism substrates on the growth of microecological bacteria system and m-xylene biodegradation,and the optimal co-metabolism substrate was optimized.The results of the study were as follows:The m-xylene microecological bacteria system was constructed through the multi-substrate progressive acclimation pattern of “inducible substrate(toluene)-intermediate substrate(3-methylcatechol)-target substrate(m-xylene)”.After identification,Pseudomonas sp.and Myroides sp.were dominant among the acclimated m-xylene microecological bacteria system on Genus level,which were accounted for 38.3 % and 26.9 %,respectively.The optimal temperature and p H for m-xylene biodegradation were 30 ? and 7,respectively.The microecological bacteria system had better tolerance to m-xylene with an initial concentration of less than or equal to 200 mg/L.The mineralization efficiency was 76.9 % when m-xylene was completely degraded by microecological bacteria system.In view of the low solubility of m-xylene,the nonionic surfactant Tween 80(C24H44O6)and anionic surfactant SDS(C12H25SO4Na)were selected to study the enhancement of m-xylene biodegradation.For Tween 80,when the Tween 80 concentration was less than critical micelle concentration(CMC),there was only carbon source competition effect between Tween 80 and m-xylene in the system.When the Tween 80 concentration was equal to CMC,the carbon source competition effect between the two substrates in the system was stronger than the solubilizationeffect of Tween 80.When the Tween 80 concentration was greater than CMC,the solubilization effect of Tween 80 in the system occupied a clear advantage,while the carbon source competition effect between carbon source substrates was weak.For SDS,when the SDS concentration was less than CMC,there was only carbon source competition effect between SDS and m-xylene in the system.When the SDS concentration was equal to CMC,the solubilization effect of SDS in the system was stronger than the carbon source competition effect between the two substrates.When the SDS concentration was greater than CMC,the toxicity effect of SDS to microecological bacteria system was the strongest in the system,followed by the solubilization effect of SDS,and the carbon source competition effect between the substrates was the weakest.The experimental results showed that compared with SDS with the concentration of CMC,Tween 80 with the concentration of 2 CMC could provide the better degradation performance of m-xylene.Benzene,toluene and ethylbenzene were selected as co-metabolism substrates to study the m-xylene biodegradation in the presence of surfactant.When 50 mg/L toluene was added as the co-metabolism substrate,the growth and reproduction of microecological bacteria system was the best,and the bacterial density reached 1.925g/L under steady state.At the same time,the m-xylene could be completely degraded within 48 hours.Compared with 100 mg/L benzene and 100 mg/L ethylbenzene as co-metabolism substrates,the completely degradation time was shortened by 12 h and24 h,respectively.In addition,compared with the other two co-metabolism substrates,50 mg/L toluene ccould also be completely degraded within the shortest time.However,the preferential use of m-xylene and toluene as carbon sources by microecological bacteria system would lead to the low consumption of Tween 80.