Study On The Mechanism Of Enrichment Of Halophilic Bacteria And Intensified Treatment Of High-salt Printing And Dyeing Wastewater

Dyeing wastewater,with huge volumes of toxic and highly colored substance,characterized by multiple components,high concentrations of chemical oxygen demand?COD?and low biodegradability,is a typical high-salt industrial wastewater,which is recognized as one of the most difficult high-concentration organic wastewater in the world.Hydrolysis acidification process is the most effective pretreatment method to remove pollutants from printing and dyeing wastewater.This method can significantly improve the follow-up treatment efficiency.It has the characteristics of eco-friendly,chemical consumption is the lowest and energy-saving.It is a treatment method of printing and dyeing wastewater with broad application prospects.In the present research,simulated dyeing wastewater with different salinity was treated by hydrolytic acidification,and hydrolytic acidification was biologically enhanced.The effects of salinity and bioaugmentation on hydrolytic acidification were explored by testing the conventional physical and chemical properties indicators that characterize the effect of hydrolytic acidification;high-throughput sequencing was used to detect microbial flora in hydrolysis acidification ponds at different treatment stages,and to explore the effects of salinity and biological reinforcement on microbial diversity and community structure in hydrolysis acidification ponds;Fourier Transform Infrared Reflectance Spectroscopy?FTIR?and Gas Chromatography-mass Spectrography?GC-MS?analysis of dyeing wastewater before and after hydrolytic acidification were carried out to infer the decolorization pathway and mechanism of hydrolytic acidification for treating Acid Scarlet GR azo dye.The main conclusions are follows:?1?The dyeing wastewater containing azo dye Acid Scarlet GR was treated by hydrolytic acidification.With the increase of salinity,the dye removal rate,COD removal rate and VFAs production decreased continuously.This indicated that higher salinity inhibited the microbial activity in the hydrolytic acidification tank,but had no obvious effect on the degree of hydrolytic acidification.?2?The dye removal rate,COD removal rate and VFAs production were all higher after bioaugmentation by direct addition,which indicated that biological bioaugmentation could improve the hydrolytic acidification effect of microorganisms and the degree of hydrolytic acidification,and had a positive effect on the degradation of printing and dyeing wastewater.?3?High-throughput sequencing of microbial communities in hydrolysis acidification ponds at different treatment stages showed that salinity and biological reinforcement had a great impact on the diversity of microbial communities in hydrolysis acidification ponds.The increase of salinity decreases the diversity and richness of microorganisms in hydrolysis acidification ponds,which may be due to the inhibition of salinity on the viability of some bacteria.Bioaugmentation improves the diversity of microorganisms in hydrolysis acidification ponds,which may be due to the introduction of more new genera of bacteria adapted to high salinity and azo dye environment.?4?The results of high-throughput sequencing showed that both salinity and bioaugmentation had great influence on the microbial community structure in hydrolysis acidification pond.At 1%and 3%salinity,the microbial community structure in hydrolysis acidification pond was similar.The main degrading bacteria might be Desulfobulbus and Lachnospiraceae.At 5%salinity,the community structure changed greatly compared with 1%and 3%salinity,and the main degrading bacteria might be Bacteroides and Pectinatus.The structureofmicrobialcommunitychangedobviouslyafterbioaugmentation,Erysipelatoclostridium and Marinobacterium may be the main degrading bacteria,which indicated that the introducted bacteria can inhibit or promote the growth of indigenous bacteria in the hydrolysis acidification pond.?5?FTIR analysis and GC-MS analysis of dyeing wastewater before and after hydrolysis acidification treatment showed that acidic scarlet 73 was degraded after hydrolysis acidification.Combined with FTIR and GC-MS analysis,the degradation pathway and mechanism of acidic scarlet 73 were deduced as follows:?i?cleavage of-N=N-double bond and formation of poly?aniline?macromolecule and intermediate product;?ii?desulfonation of SO^3-on sulfonated aromatic amine;?iii?break of benzene and naphthalene rings and formation of diethylamine and acetamide.The results show that aromatic amines which are difficult to degrade under anaerobic conditions are degraded.It is worth noting that the aromatic amines which are easy to accumulate and difficult to degrade under anaerobic conditions are degraded.Printing and dyeing wastewater contains high salinity,which can inhibit the biological activity and degradation of hydrolytic acidifying bacteria.Through domestication and screening of moderate halophilic bacteria?groups?,it can provide bacterial resources for biodegradation of high-salinity printing and dyeing wastewater;through bio-enhancement,it can improve the effect of hydrolytic acidizing treatment,and provide theoretical basis for the practical application of hydrolytic acidizing process;through deduction of degradation mechanism,it can provide high-efficiency halophilic bacteria resources further discovery of degrading bacteria and their functional genes provides basic data.