Degradation kinetics of naphthalene by anaerobic sludge and analysis of the bacterial biodiversity

For efficient biological treatment of naphthalene in the industrial wastewater,activated anaerobic sludge was collected from a wastewater treatment plant of petroleum industry,and domesticated with naphthalene,naphthalene and lactate as electron donors,respectively.When the removal efficiency of naphthalene reached more than 90% in a domestication cycle,degradation kinetics were investigated in batch reactions with naphthalene,naphthalene and lactate as electron donors,respectively.Meanwhile,the microbial DNA was extracted from the sludge with high naphthalene removal efficiency,the 16S rDNA clone library was built up,and the bacterial community was analyzed.The results indicated that the degradation rate of naphthalene in reaction with naphthalene as the sole electron donor was much lower than that with naphthalene and lactate as electron donors.In both domestication modes,the naphthalene concentration and the time followed the first order reaction kinetics model and the kinetic constant K were 3.5×10-3 h-1 and 16×10-3 h-1,respectively.In addition,phylogenetic analysis indicated that the bacterial communities in naphthalene and lactate co-metabolism sludge were mainly composed of Deltaproteobacteria,Thermotogae,Bacteroidetes,Chloroflexi and Unclassified bacteria.Deltaproteobacteria was the main phylum in the sludge.In mature anaerobic activated sludge,Desulfobulbus sp.and Kosmotoga accounted for 24.2% and 21.0%,respectively.Smithella,Syntrophobacter and Levilinea were also found in the bioreactor.The study of the bacteria diversity in the anaerobic sludge is conducive to the optimization of reaction conditions for efficient removal of naphthalene.