Analysis Of Microbial Commnities Related To Sewage Treatment And Membrane Fouling In The MBR-Worm-Chemical Phosphorus Removal System

The cost of sewage treatment was significantly increased by the sludge treatment and disposal.Thus,the sewage treatment process with simultaneous sewage treatment and sludge reduction has attracted extensive attention.In our previous study,the excess sludge of a membrane bioreactor(MBR)was pumped into a worm-reactor,which reduced the sludge yield,modified the sludge characteristics and alleviated the membrane fouling by the worm predation.To further analyze the relationship between the pollutes removal,membrane fouling controlling and microbial communities,solve the phosphorus release induced by sludge reduction in the MBR-worm reactor,the combined system of MBR and worm reactor was studied in this work.The pollutants removal performance in each unites of the system and the changes of functional communities were observed.The effects of sludge morphology,structure,characteristics and the microbial communities on membrane fouling were analyzed.A combine process of MBR-worm-chemical phosphorus removal was established,the optimal controlling conditions were clarified,and efficient removal of phosphorus from the sewage was achieved.The combined system had better performance of the sewage treatment than that of the conventional MBR.The loads of the chemical oxygen demand(COD),ammonia-nitrogen(NH4+-N)and total phosphorus(TP)of the MBR of the combined system were increased by 0.8 %,3.4 % and 11.3 %,respectively,which resulted from the worm predation.However,the removal efficiencies of the pollutants of the combined MBR were 2.0%,5.2%,1.7% higher than that of the conventional MBR.In the MBR-worm system,the Saprospiraceae,Klebsiella and Dechloromonas related to the proteins degradation,carbohydrate convertion and ammonia oxidization were enriched,which were 4.0%,6.5% and 5.9% higher than that in the conventional MBR.The activity of ammonia oxidizing bacteria(AOB)of the combined process was 11.6% higher than that of the conventional MBR.The membrane fouling performance and mitigation mechanisms in MBR-worm reactor were analyzed.Compared with the conventional MBR,the sludge settleability was increased by 37.8%,the sludge structure was more compact,the activities of the protease were increased by 19.1% in the combine system,which promoted the hydrolysis of the protein as the major pollutants of membrane fouling.The protein of the extracellular polymeric substances(EPS)in the activated sludge mixed liquor and the sludge cake of the combine system were 33.6% and 27.3%,respectively,lower than that of the conventional MBR.In the combine system,the abundance of Zoogloea,?-and ?-proteobacteria secreting the EPS or carbohydrates(etc.colloidal substances)were 4.4%,2.3% and 5.6% lower than that in the conventional MBR,Frankia,Clostridium and Actinomyces(etc.slow growing bacteria)were increased by 55.5%,the abundance of the Firmicutes bacterium,Flavobacterium and Chloroflexus secreting the proteins and polysaccharide hydrolase to degrade soluble microbial products(SMP)and EPS were 14.8%,8.3% and 5.0% higher than that of the conventional MBR.The membrane fouling of the combine system was controlled effectively by the modification of the sludge structure,characteristics and the shifts of microbial communities.The membrane fouling period of the combine system was 2.5 times longer than that of the conventional MBR.The performance of the MBR-worm-chemical phosphorus removal system was analyzed.The TP removal efficiency achieved 20.8 ± 3.3%,which was 19.6% higher than that of the MBR-worm reactor and 16.6% higher than that of the conventional MBR.The TP concentration in the sludge of the worm reactor was decreased by 46.7% and the acid phosphatase activities was increased by 32.8% due to the chemical phosphorus removal.The COD and TP concentrations of the worm reactor supernatant were decreased effectively by the chemical phosphorus removal,resulting in the increased COD and TP loads decreased by 40% and 72%,respectively.Moreover,the protein and carbohydrate concentrations in the SMP were decreased,the particle size of sludge flocs was increased and the filtration and dewatering of sludge was improved by chemical phosphorus removal.Thus,membrane fouling rate of the combine system further decreased.Based on above analysis,the effective domestic sewage treatment and membrane fouling control were achieved in the MBR-worm-chemical phosphorus removal system.This study provided theory and technical support for the development of bio-predation for sludge reduction and MBR.