Electrical Stimulation On Aerobic Sludge Acclimation For Treatment Of Phenol-containing Wastewater

Electro-assisted biological technology(EABT)is a new wastewater treatment technology.EABT could be used to enhance the treatment effect of pollutants by microorganisms in a suitable voltage range.Traditional sludge acclimated period is too long,meanwhile,the aerobic sludge acclimation process,the metabolic activity and microbial community structure characteristics of aerobic biofulm microorganisms under electrical stimulation arerarely reported yet.Therefore,in this thesis,phenol was used as a target pollutant,single-chamber bio-electrochemical reactors(BERs)packed with conductive biofilm carriers were built to treat phenol containing wastewater using intermittent and continuous electrical stimulation modes.The mechanism of electric stimulation on aerobic sludge acclimation was studied.On this basis,the electro-enhanced treatment of phenol-containing wastewater was achieved by using the aerobic attached microorganisms formed under the electric stimulation.The main results of this paper are as follows:(1)Compared with the non-conductive foam,when the conductive carbon felts were used as the biofilm carrier,the microbial degradation efficiencies of phenol were significantly improved.When the applied voltages were 0.8,1.0 and 1.2 V,the electrical stimulation could promote the removal efficiency acclimated effect of sludge acclimation.When the concentration of phenol was 500 mg/L,the acclimation time of sludge was shortened from 16 days to 8 days,compareding with that the control system.According to the analysis of phenol degradation rate of suspended and attached microorganisms,compared with the control group,when the applied voltage was 0.8 V with the intermittent electrical stimulation mode,the effect of electrical stimulation was more obvious.For example,the ratio of phenol degradation rate constant of attached microorganisms was 1.27 ± 0.11,while the degradation rate constant ratio of unit biomass of suspended sludge was 1.80 ± 0.7.(2)Under short-term electrical stimulation,the suspended microorganisms were mainly Actinobacteria and Proteobacteria at the phylum level,while the attached microorganisms were mainly Proteobacteria and Bacteroidetes.At the family level,the main families were Microbacteriaceae and Burkholderiaceae,and their relative abundance ranged from 1.56-77.15% and 7.09-58.43%,respectively.At the genus level,compared with that of non-conductive foam biofilm carriers,the relative abundance of Cupriavidus and Acidovorax on conductive biofilm carriers decreased by 8.36% and 8.99%,respectively.The relative abundance of Macellibacteroides increased by 32.48%,indicating that the conductive material changed the microbial community structure and increased the proportion of functional microorganisms.Thereby,a high phenol removal efficiency could be achieved when the applied voltage was 0.8 V,especially with the intermittent electrical stimulation mode.It was mainly due to the enrichment of a special microorganisms related with genera of Cloacibacterium(14.41%)and the proportion of each genus was relatively uniform.(3)In the long-term operation under the electrical stimulation,when the applied voltage was 0.8 V,and the concentration of phenol was 800 mg/L,the phenol removal efficiency could reach 92.69 ± 7.60%,which was much higher than that of the control group(50.97 ± 5.26%).However,when the applied voltage was 0.4 V,the effect of electrical stimulation on the phenol removal efficiency was not significant(54.51 ±4.09%).The long-term operation further demonstrated that a high phenol removal efficiency could be achieved with applied voltage of 0.8 V conducted with intermittent electrical stimulation mode.This effect may be due to the enrichment of functional microorganisms at the genus level,such as Janthinobacterium,Flavobacterium,Cloacibacterium,flute bacteria Diaphorobacter,and Pseudomonas Comamonas,which were higher than that in the control group.In addition,the abundance of Janthinobacterium and Flavobacterium at anode was increased by5.71% and 0.59%,respectively,compared with that at cathode,which further explained the best treatment effect was acheived when applied voltage was 0.8 V.