Breeding And Application Of Microflora In The Biochemical Treatment Of Dyeing Wastewater

With the rapid development of dyeing industry,azo dyes,anthraquinone dyes,and triphenylmethane dyes have become the three most widely used dyes due to their stable structure and good fixing effect.At the same time,it has also become one of the difficult industrial wastewater.Therefore,the key issue in the treatment of dyeing wastewater was the degradation of dyes.As the main method of biological treatment of dyeing wastewater,the activated sludge method has the disadvantages of low decolorization efficiency and unstable properties.It was necessary to replace the sludge or supplement functional microorganisms periodically to optimize and repair the community structure.Due to the synergy between microorganisms,the microflora has a better dye decolorization effect than single strains.However,most of the current research on the microflora was limited to the decolorization of a certain type or class of dyes,and the degradation of the broad spectrum was relatively low.In this study,we obtained high-degradable and broad-spectrum microflora through domestication and breeding.The decolorization stability and degradation pathways of dyes were studied,and the microbial agents prepared were initially used in dyeing wastewater.(1)In order to obtain a microflora with high dye decolorization ability and broad-spectrum degradation,activated sludge was domesticated and enriched in a stable operation aeration device.High-throughput sequencing confirmed that the microflora was composed of Enterococcus,Proteus,Escherichia-Shigella,etc.Compared with the original activated sludge,the community structure has changed greatly.The decolorization ratio of 400mg·L^-1Reactive Blue 194,400 mg·L^-1Disperse Blue 56,and 400 mg·L^-1Basic Violet 14 by the microflora were 96.2%,92.3%,and 97.4%.Under different temperature(20-50°C),pH(4-10)and salt concentration(0-60 g·L^-1),the decolorization ratio of dyes were more than60%.Six dyes with different structures of 400 mg·L^-1were selected to study the decolorization efficiency of the microflora,and the decolorization ratio of 5 dyes all over 95%.In the concentration range of 300-1200 mg·L^-1for mixed dyes,the decolorization ratio after48 h of the microflora treatment reached over 90%,and the decolorization efficiency was significantly improved compared with that of single strains.(2)The dye degradation process of the microflora was investigated.Through the kinetic analysis of the dye degradation process,the degradation of Reactive Blue 194 and Disperse Blue 56 approximately conformed to the first-order kinetic equation,and the degradation of Basic Violet 14 approximately conformed to the zero-order kinetic equation.UV-Vis analysis determined that the degradation of dyes by the microflora was decolorization rather than adsorption.During the dye degradation process,the activity levels of azoreductase,laccase,lignin peroxidase and manganese peroxidase increased significantly.Based on GC-MS analysis,the possible degradation pathways of dyes by microflora were proposed.The phytotoxicity test confirmed that dyes were degraded into low-toxicity small molecules but not fully mineralized.Compared with the reported decolorizing bacteria,it has a higher broad spectrum of dye degradation.(3)Based on the dye decolorization effect,the bacterial agent preparation and application study were carried out on the obtained microflora.Under the condition of 4%inoculation amount,it was determined that the stirring speed was 300 r·min^-1and the aeration rate was1.25 v·v^-1m^-1as the optimal solution.Under oxygen conditions,the best feed medium carbon-to-nitrogen ratio was 6:1,and the OD₆₀₀can reach 24.8,which was 40.9%higher than that of unfed batch culture,and there was no significant change in the decolorization ratio of dyes.The microflora was cultivated in 50 L and 1000 L fermenters,and OD₆₀₀was 26.4 and32.8.Compared with the fed-batch culture in the 5 L fermentor,its biomass increased by 6.5%and 32.3%.The microflora culture medium and carrier were compounded to prepare solid inoculum.After adding 0.2 g·L^-1bacterial agent to dyeing wastewater for 48 h,the total peak area of organic pollutants was relatively reduced by 91.4%,wastewater decolorization ratio and COD removal ratio reached 69.7%and 68.9%,the sludge settling performance(SV₃₀)increased by 44.3%.Therefore,the selected microflora can optimize and repair the community structure in the treatment system,laying the foundation for its application in the actual dyeing wastewater.