Hydrolytic Acidification Of Oil Refinery Waste Activated Sludge

With the continuous development of oil industry,petroleum wastewater emission is increased and the production of oil refinery waste activated sludge increases every year.The composition of oil refinery waste activated sludge is very complex,it contains lots of persistent organic pollutants and petroleum,benzene series and heavy metals,which lead to the poor biodegradability and strong biological toxicity.Therefore,reasonabl and effective treatment of oil refinery waste activated sludge has become a hot and difficult problem in the field of environment.Two-phase anaerobic digestion consists of hydrolytic acidification and methanogenesis stages,which shows better stability,shorter retention time and greater methane production rate in comparison with conventional single-phase anaerobic digestion.Due to the hydrolysis acidification process of macromolecular organic matter(lipid,protein and petroleum)in oil refinery waste activated sludge is slow,the hydrolysis acidification stage is considered to be the limitary phase of the whole process of anaerobic digestion.In this study,CSTR reactors were applied under 55±1? condition to investigate acid-producing ability,hydrolytic proprety,gas production and sludge reduction rate of hydrolytic acidification of oil refinery waste activated sludge by changing the SRT,pH and with the specific pollutants.The optimal hydrolytic-acidogenic condition of volatiles fatty acids(VFAs)production and hydrogen production were subsequently determined.Due to large amounts of petroleum exsist in oil refinery waste activated sludge,oil content and its organic composition were analyzed before and after hydrolytic acidification.At last,the microorganism communities under different conditions were investigated by high-throughput sequencing analysis,in order to research the hydrolytic-acidogenic effect of oil refinery waste activated sludge from microbial point of view.The results showed that the optimum hydrolytic-acidogenic condition of gas production was pH of 5.5 and SRT of 2 days,about 0.425L/L·d of biogas were producted,and the hydrogen content was 80%.The optimum hydrolytic-acidogenic condition of VFAs production was pH of 5.0 and SRT of 8 days,about 1056.95 mg/L of VFAs were produced.At this condition,the hydrolytic proprety and sludge reduction rate were also best.The oil content and its organic composition in sludge under initial condition,optimum condition of hydrogen production and VFAs production were analyzed in this study.Petroleum in oil refinery waste activated sludge was degraded in varying degrees during the hydrolytic-acidogenic process,and alkanes were easily biodegradable substances.More than 65% of petroleum was degraded under the optimum condition of VFAs production.Part of specific pollutants were degraded in the hydrolytic acidification process,and compared with heneicosane,1-phenyl naphthalene was easier biodegradable by hydrolytic-acidogenic microorganisms.Fervidobacterium,Coprothermobacter,Exilispira,Blvii28 and Tepidiphilus were the dominant bacterial genus under optimum condition of hydrogen production.Coprothermobacter,Fervidobacterium,Caldisericum and Tepidiphilus were the dominant bacterial genus under optimum condition of VFAs production.Coprothermobacter,Fervidobacterium,Caldisericum and Tepidiphilus were the main genus to degrade petroleum compounds in oil refinery waste activated sludge.