Pretreatment Of Excess Sludge By Dielectric Barrier Discharge And Its Gas Production In Anaerobic Digestion Process

With the popularization of sewage treatment and the expansion of sewage plants in China,the output of sludge has further increased accordingly,and resource utilization has become an urgent problem to be solved.Anaerobic digestion has become an important direction for sludge treatment and disposal.But hydorlysis is recognized as the rate-limiting step in the anaerobic digestion.It has become a research hotspot to increase the hydrolysis rate through pretreatment technology,and then improve anaerobic digestion capacity.Dielectric barrier discharge(DBD)is an emerging advanced oxidation technology with the advantages of high efficiency and no secondary pollution,but its impact on sludge hydrolysis is not yet clear.In this work,the change of soluble organic matter in the process of DBD pretreatment of sludge was investigated,the mechanism of cracking sludge was analyzed,and the performance of subsequent anaerobic digestion was explored,which provided guidance for DBD technology for sludge anaerobic digestion.Firstly,different discharge powers were used to study the sludge dehydration performance and the change of extracellular polymeric substance(EPS).The results showed that with the increase of discharge power,the capillary suction time increased,and the particle size decreased.Dehydration performance was worse.With the increase of discharge power,the concentration of protein and polysaccharide in EPS increased significantly,and the maximum reached 136.4%and 99%,respectively.DBD pretreatment destroyed the dense structure of tightly bound extracellular polymeric substance(TB-EPS),so the concentration of polysaccharides and proteins in soluble extracellular polymeric substance(S-EPS)increased.Tryptophan-like proteins in S-EPS had increased greatly.And Tryptophan-like proteins can be easily consumed by microorganisms as biodegradable organic matters.Secondly,the release rule of cellular material in sludge and the mechanism of DBD cracking sludge were investigated.The results showed that the increasing of discharge power could significantly enhance the decomposition of sludge and promote the release of soluble organics within cells into the outer spaces.Soluble chemical oxygen demand of the sludge supernatant increased almost linearly with the reaction time,the discharge power increased from 40 W to 70 W,and the solubilization degree of organic components increased from 3.41% to 22% after 20 minutes of pretreatment.Total nitrogen(TN)and total phosphorus(TP)also showed an upward trend.The release rate of TN increased from 33.8% to 51.6%,and the release rate of TP increased from 0.94% to 18.08%.It was confirmed that the process of DBD decomposing sludge was a combination of electric field,free radicals and ozone.Finally,the performance of anaerobic digestion of sludge and microbial community distribution were explored,and the results showed that the hydrolysis rate was accelerated and the gas production was increased by 51.8%.The main phylums of anaerobic fermentation were Bacteroidetes and Firmicutes.The main methanogens were Methanospirillum,Methanomassiliicoccus and Methanoculleus.Dielectric barrier discharge pretreatment can significantly improve the hydrolysis effect of excess sludge.The further development and application of this technology can provide an effective pretreatment method for sludge recycling.