Study On Influencing Factors And Control Strategies Of Activated Sludge Sedimentation Performance

Activated sludge process is the mainstream technology of urban wastewater treatment,but the sewage treatment effect and sludge settling performance are easy to be troublesome,the result is that the effluent water quality becomes worse or sludge bulking,which makes it difficult to manage the sewage treatment system.This paper is based on the WWTP of Aletai and SBR reactor.Using illumina high-throughput sequencing to studied the microbial community composition from the WWTP of Aletai and change of the microbial community composition in SBR reactor after adding an anaerobic step.To explored the relationship between treatment effect,sludge settlement performance and the microbial community composition from the WWTP of Aletai.At the same time,the EPS of SBR reactor was extracted and monitored.The influence of the change of EPS on the sludge settleability performance was investigated.The main results of this paper are as follows:(1)The sludge has been domesticated for a long period of time by the low temperature,the bacteria were selected to adapt to the low water temperature.The decrease of water temperature will not seriously affect the bacteria community of the activated sludge.The richness and diversity of the bacteria were small.The dominant bacteria in the seeding sludge were Proteobacteria,Bacteroidetes,Chloroflexi,Actinobacteria and Firmicutesat phlum level,norank_f__Saprospiraceae,norank_f__Anaerolineaceae,Candidatus_Microthrix,Dokdonella and Albidiferax at genus level,which play the important role in the WWTP of Aletai.(2)The changes of water inlet pollutants and external environment make the structure of the bacteria community in the activated sludge system change constantly.The decrease of water temperature did not significantly affect the normal growth and proliferation of the nitrogen-removing bacteria in the sludge.It will not lead to a decrease in the relative abundance of phosphorus accumulating bacteria.(3)In activated sludge in SBR reactor,the filamentous bacteria expand,and by adding a 30 min step of anaerobic stirring after the water inflow,the sludge bulking was rapidly inhibited after 10 running cycles.(4)The proliferation of Thiothrix,norank_o__sphingothales and Trichosporon is the main microbial that causes the swelling of the filamentous bacteria in this experiment.The addition of anaerobic step is beneficial to the proliferation of Candidatus_Competibacterr,Defluviicoccus,Candidatus_Accumulibacter and norank_k__Fungi,and the proliferation of these microbial also facilitates the settleability of the sludge.(5)After adding anaerobic sludge the concentration of EPS increased from 84.4 mg/gMLSS to 104.0 mg/gMLSS,the concentration of protein increased from 60.2 mg/gMLSS to 74.8 mg/gMLSS rapidly,promote the settlement of activated sludge,SV fell from 92% to 39%,the SVI value fell from 222 ml/g to 74 ml/g.The structure of bacteria and fungi in sludge was significantly changed after adding anaerobic step,and the change of dominant bacteria and fungi increased the concentration of EPS and promoted the recovery of sludge settleability.