| Industrial wastewater（such as petroleum or pharmacy wastewater）contains phenol and phenol derivatives,which can inhibit microorganisms and is difficult to treat by activated sludge process.Bioenhancement technology is a method to improve the efficiency of microorganisms by purifying bacteria and promoting the expression of key genes,so as to promote the degradation of refractory substances.It has been widely used for the lab-scale treatment of the phenol compound and polycyclic aromatic hydrocarbons（PAHs）,due to the high cost-effectiveness.In this study,phenol is used as the target pollutant and the acetate is selected as the substrate to promote the degradation of phenol by the bioco-metabolism,in which is one way of the bioenhancement.The influence factors of acetate concentration,dissolved oxygen（DO）,and temperature on phenol degradation are explored to achieve the operational optimization.Besides,the variations of microbial structures and the difference among the co-metabolic systems are also investigated through the high-throughput sequencing,and the dominant bacterial genera in different systems are identified.The aerobic activated sludge of domestic sewage treatment plant was inoculated in a sequencing batch reactor（SBR）,and the system was stabilized after 64 days.At 20℃,the removal efficiency of phenol at low concentration(300 mg·L-1)reached about 97.00%.However,the removal efficiency was low when treating high concentration(≥500 mg·L-1)phenol.The addition of acetate enhanced the degradation of phenol.When the concentration of acetate was 100 mg·L-1,the removal of phenol at medium concentration(500 mg·L-1)was increased by 11.21%.However,due to the strong inhibition of high concentration(1000mg·L-1)phenol on the microorganisms,the removal of phenol at high concentration only increased by 2.51%.The high-throughput sequencing analysis showed that the relative abundance of Azotobacter and Bdellovibrio in the samples before and after treatment occupied 12.97%and 9.08%,respectively.It indicated that these bacteria might have the ability to resist phenol toxicity or degrade phenol.With the addition of acetate,the relative abundance of Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium and Ottowia reached 10.64%and 8.34%,respectively,indicating these two bacterial genera could play an important role in co-metabolism system.The concentration of acetate,DO and the temperature have significant effects on the degradation of phenol in the cometabolic system.The removal efficiency of phenol was improved by increasing the acetate concentration.When DO was 1.5 mg·L-1 at 20℃,acetate of 100 mg·L-1 was optimal for treatment of medium and high concentration phenol wastewater,and the removal efficiency was increased by 11.21%and 2.51%,respectively.But the high concentration of acetate made no significant promotion for the degradation of phenol,because much acetate consumed DO,resulting in the competition for DO among the microorganisms.The performance of co-metabolism was also enhanced by increasing DO and temperature.When 100 mg·L-1 acetate was added as the substrate,under the temperature of 20℃and DO of 1.5 mg·L-1,the removal efficiency of phenol wastewater at high concentration was only 3.78%.However,when the temperature increased to 26℃,with DO of 5 mg·L-1,the removal efficiency reached to 84.17%.This is because the increase of DO and temperature enhances the activity of microorganisms,thus improving the performance of cometabolic system.In this study,the degradation of phenol wastewater at medium and high concentration is improved significantly by means of biological co-metabolism.This work provides a novel process for the degradation of phenol wastewater,and also promotes the research of bioenhancement technology. |
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