Salt Tolerance Domestication And Microbial Community Analysis Of Activated Sludge In Propylene Oxide Saponification Wastewater

Epoxy propane wastewater with high temperature, high salinity, high pH and highsuspended solids is a kind of difficult treatment industrial wastewater. With the constantlyincrease of industrial dosage of epoxy propane every year, the effective governance of epoxypropane wastewater become the focus of research at home and abroad. At present domesticepoxy propane wastewater treatment is primarily using a biological method by cooling,sedimentation and aeration to reach the national wastewater discharge standard. One of themain key is to rely on the degradation of organic pollutants in wastewater by themicroorganisms of the activated sludge. But in general, wastewater with high concentration ofchlorine is toxic to microorganisms. It is mainly because high osmotic pressure of waste waterdestroys cell membranes and enzymes and the metabolism of strains is also affected. So epoxypropane wastewater must be diluted to reduce the chloride ion concentration for wastewatertreatment, which results in a large amount of water waste. In order to save resources andreduce energy consumption, it is necessary to improve the tolerance to salinity of activatedsludge by sludge domestication.In this experiment, activated sludge in epoxy propane wastewater was firstly domesticatedby gradient domestication method. The concentration of chloride ions was gradually increasedfrom11000mg/L to20000mg/L. After the adjustment period, the COD, pH and other indexesof outer drainage all descended obviously and reached to the natio nal standard,except fornitrogen content. It was assumed that this may be associated with the changes of microbialcommunity structure in activated sludge.By three methods of molecular biology: Terminal restriction fragment lengthpolymorphism analysis(T-RFLP),gene library construction and Denaturing Gradient GelElectrophoresis (DGGE), activated sludge microbial community structures were analyzed.The three samples expressed in S1, S2, S3, represent the activated sludge of different chlorideions concentration:18000mg/L(blast aeration sampling),18000mg/L (contact oxidation poolsampling),22000mg/L(blast aeration sampling),respectively. Firstly the metagenome of threesamples were extracted. In T-RFLP analysis, the diversity indexes of S1including Margalefindex、Shannon index、Pielou index and Simpson index were proved to be the highest. On the contrary, the diversity indexes of S3were the lowest. Through Phylogenetic the Assignment onlineanalysis Tool, it was indicated that the dominant bacteria common to the three samples were Bacteroidetes,Firmicutes and Proteobacteria and Chloroflexi was dominant peculiar to the S3sample.To construct the16SrDNA library, the DNA of S3was used as the template. Through thetransformation, screening and identification of the genome, it was found that Chloroflexi(79%)in S3accounted for absolute advantage, following by Proteobacteria (19%),Acidobacteria (1%) and uncultivated bacteria (1%).And through the analysis of the DGGEbands and sequence alignment, advantage bacterium of S3were Chloroflexi (61.092%),Proteobacteria (15.241%) and uncultivated strains (9.68%).By the three methods the results showed that the advantage bacterium in the communitywere mainly Chloroflexi and Proteobacteria. In T-RFLP analysis, it was indicated thatFirmicutes were the dominated bacterium.Jointly,uncultured bacterium were detected by themethods of16SrDNA library and DGGE. The above confirmed microbial community structureof activated sludge was complex and diverse. However, the three methods used in thisexperiment did not find nitrobacterium as the dominant bacteria in activated sludge system. Itwas conjectured that experimental methods might impose restrictions on the result ornitrobacterium took up small percentage in the system.It was reported that Pseudomonas and Bacillus which occupied a certain proportion in theactivated sludge microbial community were affirmed to be the efficiency strains of degradingammonia nitrogen and aerobic Bacillu., Chloroflexus had the function of the degradation oforganic chloride. These researches pointed out the direction for the next experiments.