Study On The Influence Characteristics And Mechanism Of Electrocoagulation On The Operation Effect Of MBR System

Membrane bioreactor（MBR）,as a new type of wastewater treatment technology currently favored in the field of water treatment and resource reuse in the current environment,has the advantages of stable effluent water quality,low energy consumption,automation,compact structure and small footprint,etc.,application and research are becoming increasingly widespread.However,to improve the effect of the MBR system in the process of operation and solve the problem of serious membrane fouling,there are still many problems that need to be studied,such as,in the process of cleaning and operation require a lot of energy and chemicals,there are high energy consumption,potential secondary pollution,and high cost,serious membrane fouling problems affect running effect,which will inevitably become the main obstacle of the MBR and its further development.The scientific combination of MBR system and electrocoagulation（EC）can not only achieve the purpose of mitigating membrane fouling,but also improve the effect of operation treatment.Relevant research has been paid much attention to.This study intends to deeply explore and realize the research on the influence characteristics and mechanism of MBR system under electric field drive,this paper carried out relevant research and obtained the following research results:（1）In this experimental study,different power supply conditions were set to explore the influence of electrocoagulation on the operation effect of membrane bioreactor.There were five power supply conditions,including 1V,3V,5V constant voltage and 0.15 A constant current provided by the direct current（DC）power supply,and 18V/10W fluctuating voltage of the solar panel.The EC actuated by constant current of 0.15 A from DC power source and undulate voltage from 18 V/10 W solar panels could mitigate the membrane fouling obviously with 14 and 20 days of operation times,comparable with the operation of the membrane bioreactor under other conditions,the membrane fouling phenomenon during operation is significantly reduced.This was the result of the combined effect of the effective electrocoagulation on sludge expansion suppression and the reduction of sludge filtration specific resistance（SRF）.After electrocoagulation was applied to the membrane bioreactor,proper power supply conditions could well inhibit the sludge bulking caused by filamentous bacteria.Another reason for the reduction of membrane fouling was the reduction of proteins and polysaccharides in SMP and LB-EPS of sludge and filter cake layer.（2）The electrocoagulation driven by electric field could not only reduce membrane fouling,but also improve the removal efficiency of pollutants in wastewater,the removal effect of PO₄^3-was the most obvious.In this study,the removal efficiency of simulated wastewater on NH₄⁺-N without power supply was 42.2%,while the removal efficiency of NH₄⁺-N was more obvious in the presence of electrocoagulation,the removal efficiency was 62.87%～86.84%,basically higher than 80%;The removal effect of TOC was maintained at a high level of more than 90%in all operation stages;The removal rate of PO₄^3-in wastewater without power supply was only 3.72%,but as the voltage increased,the removal effect gradually strengthened,under the condition of a constant voltage of 5 V provided by DC voltage,the average removal rate of PO₄^3-was92.45%.This result was related to the amount of Fe²⁺released,so the experimental results of fluctuating voltage conditions in solar panels were different.（3）Under the condition of electrocoagulation,biological characteristics would be changed.The OTU quantity of activated sludge showed no significant difference from the initial sludge when the electric field condition was not applied.After the application of electrocoagulatio conditions,the number of OTU and ACE index decreased continuously,and then stabilized at a lower level,but the overall difference of Shannon index was not significant.This indicated that community diversity could be maintained well although the community richness of EC-MBR decreases during the operation.Electrocoagulation could embed filamentous bacteria in sludge particles,and then eliminate its impact on membrane fouling.Based on the results of biological sequencing,the relative abundance of bacterial populations was analyzed from the phylum,family,and genus levels,which further revealed the conclusion of membrane fouling,and also showed that the filamentous bacteria were not eliminated by electroflocculation,but were embedded into the sludge particles by flocculant.Although the relative abundance of filamentous bacteria was high,its effect on membrane fouling was reduced.