Research On Sludge Reduction And Membrane Fouling Control Efficiency Of A~2O-MBR-Worm-bed Coupling System

Worm predation sludge reduction technology utilized the worm on the predation of sludge digestion,through the use of energy in the food chain transmission process to reduce the phenomenon of sludge reduction.Because of characteristics of worm predation sludge reduction technology of low energy consumption,high efficiency and environmental friendliness,this technology has become the key point of research.Researchers combined worm predation reduction technology with sewage treatment systems to achieve efficient synergies between sludge reduction and wastewater treatment.In this paper,the worm bed is coupled with the anaerobic-aerobic-membrane bioreactor(A~2O-MBR)process with high efficiency wastewater treatment.Based on the sludge reduction of A~2O-MBR-worm bed coupling system,the effects of sewage treatment efficiency and membrane fouling on the coupling process were investigated.This study achieved a better sewage treatment efficiency,higher sludge reduction effect and slowed down membrane pollution.In this study,A~2O-MBR,A~2O-MBR-blank worm bed and A~2O-MBR-worm bed system were constructed.After a long period of operation,the A~2O-MBR-worm bed coupling system could achieve 48.4 % reduction.Through the optimization of A~2O-MBR-worm bed coupling system,the effluent quality of sewage treatment system can be improved,and the removal efficiency of total nitrogen and total phosphorus can reach 77 %and 96% respectively.In addition,the return of the worm after the predation of the worm also changed the sludge properties of the aerobic tank.Compared with A~2O-MBR and A~2O-MBR-blank worm bed system,the MLVSS/ MLSS value of A~2O-MBR-worm bed coupling system is reduced.At the same time,the sedimentation performance is weakened and the sludge dewatering performance is improved.The decrease of sludge particle size and sludge viscosity also exacerbates and alleviates the process of membrane fouling respectively.From the TMP results and membrane resistance analysis,we can see that the coupling of worm bed and A~2O-MBR system can effectively alleviate the process of membrane fouling.The mechanism of sludge reduction in A~2O-MBR-worm bed coupling system was analyzed.In the study of sludge reduction mechanism of A~2O-MBR-worm bed coupling system by batch-batch experiment,it was found that the micro-anaerobic blank worm bed could achieve higher sludge reduction effect,and achieve twice sludge reduction with worm bed.Compared with A~2O-MBR system,the sludge reduction rates of the A~2O-MBR-blank worm bed system and the A~2O-MBR-worm bed system were 8.43 % and 13.23 %,respectively.A~2O-MBR-worm bed systemmicro-anaerobic and aerobic alternating environmental conditions also contribute to the occurrence of uncoupling phenomenon,thereby reducing sludge production.In addition,A~2O-MBR-worm bed coupling system with more chronic growth bacteria and predatory bacteria is conducive to the system of sludge reduction.The membrane fouling mechanism of A~2O-MBR-worm bed coupling system was explored.Combined with microscopic examination,it can be found that the A~2O-MBR-worm bed system is more abundant in the three groups,and more advanced organisms such as nematodes and oligosaccharides are found.Analysis of membrane contamination by microbial community using 16 S r RNA high throughput sequencing showed that Proteobacteria was dominant group,and the proportion of total samples in the six samples was over 50 %.At the same level,the relative abundance of the bacteria showed a decreasing trend compared with the sludge mixture in the same system,but had a common dominant species,Dechloromonas.Compared with the three groups,the dominant bacteria of A~2O-MBR-worm bed coupling system were significant,and the relative abundance distribution of the population was concentrated,which indicated that the system had obvious enhancement effect on the abundance of main functional bacteria.In addition,the more abundant Defluviicoccus were found in the samples of the A~2O-MBR system,and the extracellular polymers secreted would aggravate the membrane fouling process and the A~2O-MBR-worm bed system was smaller.