Study On Microbial Community Structure And Settling Performance Of Activated Sludge

In this paper,the activated sludge samples collected from four wastewater treatment plants in Xinjiang were analyzed in winter,and the microbial community structure of activated sludge was analyzed by high throughput sequencing technology.At the same time,the laboratory SBR reactor was operated.The aerobic sludge from oxidation ditch of Aletai sewage treatment plant was collected as inoculum sludge.The experimental water was artificially prepared simulated wastewater.The reactor was run for 234 days.The sludge samples of the SBR reactor were collected,the microbial community structure of activated sludge was analyzed.The extracellular polymers(EPS)were extracted from the activated sludge samples,and the relationship between the extracellular polymer and the sludge settling performance was analyzed.The main research results are as follows:(1)The main dominant phyla in all the samples are Proteobacteria(26.7~48.9%),Bacteroidetes(19.3~37.3%),Chloroflexi(2.9~17.1%)and Actinobacteria(1.5~13.8%)in activated sludge from wastewater treatment plants.The average proportion of Flavobacteriaceae,Saprospiraceae,and Tetrasphaera in bulking sludge was 8.3%,12% and 5.2% respectively,while the average ratio of non bulking sludge was 1.2%,5.7% and 0.1%,respectively.The main filamentous bacteria that cause sludge bulking are Saprospiraceae,Flavobacterium and Tetrasphaera.RDA analysis showed that influent BOD5,DO,water temperature and influent ammonia nitrogen had great influence on bacterial community structure.(2)Proteobacteria(39.9%~81.9%)and Bacteroidetes(13.9%~28.1%)are the most important bacterial phylum in activated sludge from SBR.Norank_f__Anaerolineaceae(9.7%),norank_f__Saprospiraceae(8.6%),and unclassified_f__Comamonadaceae(6.8%)are the main bacterial genera in the inoculated sludge,and norank_o__Rhinosporideacae(97.9%)under Ichthyosporea is the main fungal genus.The proportion of Thiothrix and norank_f__Saprospiraceae was 26% and 16.5% in the bulking sludge samples,which decreased to 0.18% and 7.7% in the non bulking sludge samples.Zoogloea accounted for 12.9% of non sludge bulking samples and increased to 66.2% in bulking sludge samples.The main cause of filamentous bulking is the proliferation of Thiothrix and norank_f__Saprospiraceae.The main cause of non filamentous bulking is the proliferation of Zoogloea.The results of PLS-DA also showed that the bacterial community structure changed greatly after the activated sludge was frozen and the carbon source was changed.(3)In all levels of EPS,TB-EPS content is the most,followed by LB-EPS,while S-EPS content is the least.Polysaccharides were the main components in S-EPS and LB-EPS,and proteins in TB-EPS were the major components.Before sludge freezing treatment,sodium acetate was a single carbon source stage.The SVI value of sludge was positively correlated with total EPS,and positively correlated with PN content and negatively correlated with PS content.After sludge freezing treatment,sodium acetate and glucose were used as carbon sources respectively,the SVI value and EPS content of the sludge were negatively correlated,and negatively correlated with PN and PS contents.