The Study Of Co-Substrates Enhanced Degradation Of Polycyclic Aromatic Hydrocarbons By Different Activated Sludge And High Throughput Sequencing Of Sludge Bacteria

Coking wastewater contains various organic matter including polycyclic aromatic hydrocarbons?PAHs?,phenolics,benzene and other substances.Phenol is the main component of COD in coking wastewater and the main carbon source for the microbial utilization in biological treatment process.In order to realize high efficient biodegradation of PAHs,sludge from each process unit?A-O1-H-O₂ process?of a coking wastewater treatment project were chosen as the sources of microorganism;phenol or other substrates were added to study the feasibility of enhanced degradation of PAHs,Analysing the degradation differences of each sludge and find its cause verification t and verify.The main research contents and results were as follows:?1?Activated sludge was collected from an anaerobic tank of a coking wastewater treatment plant to studied the enhanced biodegradation and kinetics of benzo[a]pyrene?BaP?with phenol,glucose,sodium acetate,TritonX-100,and their combinations as cometabolic substrates,respectively.Moreover,the effects of the mentioned four substrates on the degradation processes of the mixtures of naphthalene,phenanthrene,anthracene,fluoranthene,pyrene and BaP were also investigated.The results showed that the addition of enhanced substrates promote the degradation of BaP and there were significant differences occurred in the degradation rates in the presence of different co-substrates.Sodium acetate demonstrated the highest enhancement of degradation for BaP while 39.9% of BaP can be degraded in 30 days.However,27.1% of BaP were removed by phenol which was the slowest among the four different substrates.Compared to single substrate group,the combination of phenol and sodium acetate group had the best performance on the biodegradation of BaP and the degradation rate is 50.0%.In different systems,the biodegradation of BaP are followed the first order reaction kinetics model.In the presence of the six PAHs,sodium acetate still had the best enhancement effect,Within 20 days,the biodegradation rates of naphthalene,phenanthrene,anthracene,fluoranthene,pyrene and BaP are 66.1%,60.7%,43.2%,22.0%,15.5% and 14.7%,respectively.Coking sludge prefer to biodegrade low molecular weight PAHs,such as naphthalene,phenanthrene,anthracene.For high molecular weight PAHs,such as fluoranthene,pyrene and BaP,could be removed relatively less.?2?For phenol can promote the degradation of PAHs by anaerobic sludge.So phenol cosubstrate degradation of BaP and 6 PAHs by sludge from A-O1-H-O₂ process were also studied,and analyse microbial community structure to obtain the related information on degradation ability,influence factors and degrading bacteria group of each sludge,The results showed: phenol can promote the degradation of BaP by kind of sludge,the degradation rate of O₂ tank sludge is higher than O1 in aerobic degradation group,H tank sludge is higher than A in anaerobic degradation group.Relatively small adsorption coefficient,low concentration of pollutants and more abundant microorganism are the reason that O₂,H pool sludge showed stronger biological activity than O1,A.In 6 mixed PAHs degradation system,the degradation rate of 6 PAHs were naphthalene>phenanthrene>anthracene>fluoranthene>pyrene>BaP and the removal rate was positively related with logKow.In addition,the sludge microbial population structure of each sludge has changed both before and after the experiment.compared to O1,the dominant bacteria are Rhodospirillaceae,Comamonadaceae of O₂ tank sludge and their percentage increase;Ignavibacteriaceae,rhodocyclaceae are more abundant in H tank sludge than A;the percentage of comamonadaceae increased before and after the experiment in each tank sludge,These increasing bacteria may be the mainly degradation bacteria genera of BaP.The study of the bacteria diversity in each tank sludge is conducive to the optimization of reaction conditions for efficient removal of BaP.?3?After acquiring sludge difference effect on PAHs degradation,according to the influencing factors,municipal sludge was chosen to investigate the phenol co-substrate degradation,kinetics of BaP and microbial diversity,moreover,Compare municipal sludge with coking sludge to verify this conclusion.Results show that: municipal sludge on the degradation of BaP is better than that of coking sewage sludge on phenol co-substrates conditions,Within 56 d,municipal sludge is able to convert 62.4% of BaP,coking sewage sludge was 37.2%.From the genus level,Bacillus,Pseudomonas,Achromobacter,Sphingomonas sp.Species both exist in the two kinds of sludge and percentage are increased,which may be the mainly degradation bacteria genera of BaP.