Hydrolysis and acidification of activated sludge from a petroleum refinery

The cost-effective treatment of activated sludge that is generated by refining petroleum is a challenging industrial problem.In this study, semi-continuous stirred tank reactors(CSTRs) containing petroleum refinery excess activated sludge(PREAS)were used to comparatively investigate hydrolysis and acidification rates, after the addition of heneicosane(C_(21)H_(44))(R1)and 1-phenylnaphthalene(C16 H12)(R2) to different and individual reactors. Operation of the reactors using a sludge retention time(SRT) of 6 days and a pH of 5.0, resulted in the maintenance of stable biological activity as determined by soluble chemical oxygen demand(SCOD), volatile fatty acids(VFAs) production and oil removal efficiency. The optimum conditions for hydrogen production include a SRT of 8 days, at pH 6.5. Under these conditions, hydrogen production rates in the control containing only PREAS were 1567 mL/L(R0), compared with 1365 mL/L in Rl and 1454 mL/L-PREAS in R2.Coprothermobacter, Fervidobacterium, Caldisericum and Tepidiphilus were the dominant bacterial genera that have the potential to degrade petroleum compounds and generate VFAs. This study has shown that high concentrations of heneicosane and 1-phenylnaphthalene did not inhibit the hydrolytic acidification of PREAS.

Efficient ozonation of reverse osmosis concentrates from petroleum refinery wastewater using composite metal oxideloaded alumina

Novel Mn–Fe–Mg-and Mn–Fe–Ce-loaded alumina（Mn–Fe–Mg/Al2O3 and Mn–Fe–Ce/Al2O3） were developed to catalytically ozonate reverse osmosis concentrates generated from petroleum refinery wastewaters（PRW-ROC）. Highly dispersed 100–300-nm deposits of composite multivalent metal oxides of Mn（Mn^2＋）, Mn^3＋,and Mn^4＋, Fe（Fe^2＋）and Fe^3＋ and Mg（Mg^2＋）, or Ce（Ce^4＋） were achieved on Al2O3 supports. The developed Mn–Fe–Mg/Al2O3 and Mn–Fe–Ce/Al2O3 exhibited higher catalytic activity during the ozonation of PRW-ROC than Mn–Fe/Al2O3, Mn/Al2O-3, Fe/Al2O3, and Al2O3. Chemical oxygen demand removal by Mn–Fe–Mg/Al2O3-or Mn–Fe–Ce/Al2O3-catalyzed ozonation increased by 23.9% and23.2%, respectively, in comparison with single ozonation.Mn–Fe–Mg/Al2O3 and Mn–Fe–Ce/Al2O3 notably promoted áOH generation and áOH-mediated oxidation. This study demonstrated the potential use of composite metal oxide-loaded Al2O3 in advanced treatment of bio-recalcitrant wastewaters.

Laboratory studies of rice bran as a carbon source to stimulate indigenous microorganisms in oil reservoirs

There is a great interest in developing cost-efficient nutrients to stimulate microorganisms in indigenous microbial enhanced oil recovery（IMEOR） processes.In the present study,the potential of rice bran as a carbon source for promoting IMEOR was investigated on a laboratory scale.The co-applications of rice bran,K2HPO4 and urea under optimized bio-stimulation conditions significantly increased the production of gases,acids and emulsifiers.The structure and diversity of microbial community greatly changed during the IMEOR process,in which Clostridium sp.,Acidobacteria sp.,Bacillus sp.,and Pseudomonas sp.were dominant.Pressurization,acidification and emulsification due to microbial activities and interactions markedly improved the IMEOR processes.This study indicated that rice bran is a potential carbon source for IMEOR.

Rapid aerobic granulation using biochar for the treatment of petroleum refinery wastewater

Aerobic granular sludge technology has great potential for the treatment of petroleum refinery wastewater.However,strategies to shorten the granulation time and improvement the stability still need to be developed.In this work,biochar was prepared from waste petroleum activated sludge(biochar-WPS) and used in a sequencing batch reactor for the treatment of petroleum refinery wastewater.Biochar-WPS presented the surface area of 229.77 m2/g,pore volume of 0.28 cm3/g,H/C and O/C atomic ratios of 0.42 and 0.21,respectively.The porous structure and a high degree of hydrophilicity were found to facilitate microbial colonization and adhesion as well as particle aggregation.Application of biochar-WPS resulted in the formation of more substantial and stable aerobic granules(~66% of granules> 0.46 mm diameter) 15 days earlier compared with the control.The addition of biochar-WPS enhanced the average removal efficiency of chemical organic demand(~3%),oil(~4%)and total nitrogen(~10%) over the control.Increased microbial richness and diversity were observed within the formed granules and had an increased(~4%) proportion of denitrifying bacteria.These results indicate that an aerobic granulation mechanism using biochar-WPS is a feasible option for the treatment of petroleum refinery wastewater.