| The petrochemical industry is an important pillar industry in China,accounting for about 10.8% of the total industrial output value.Meanwhile,the amount of wastewater from the petrochemical industry remains high,with annual emissions up to 3.55 billion tons,which is the highest in the whole industry.Due to the complicated petrochemical production process,long processes and different material components,the petrochemical wastewater quality fluctuates greatly,the pollutant types are numerous and the composition is complex.In recent years,with the continuous increase of the proportion of processing heavy crude oil,the biotoxicity and biodegradation difficulty of the refining wastewater have been increasing,and the wastewater quality has been deteriorating.At present,the biochemical treatment stage is the core treatment process.Aerobic granular sludge technology derived from the conventional activated sludge process with simultaneous decarbonization and denitrification has stood out in many biochemical treatment processes.It shows good sludge settling performance,large biomass,high treatment loading and dense granular sludge structure,which can withstand the impact of toxic and harmful substances showing a good application prospect.In this study,taking advantages of aerobic granular sludge technology and in consideration of the shortcomings in the treatment of refining wastewater,bioaugmentation was used to construct a microbial consortium with the function of petroleum degradation and immobilized onto the carrier,and then added it into the sequencing batch reactor(SBR)to cultivate aerobic granular sludge.The effects of the immobilized bacteria carrier on aerobic granulation,reactor performance and microbial community were evaluated,aiming to provide a theoretical basis for the rapid formation of aerobic granular sludge and stable operation of the SBR system.The results showed that the petroleum-degrading consortium(Brevundimonas sp.Y1,Bacillus sp.Y2,Microbacterium sp.Y4,Rhodococcus sp.Y5,Bacillus sp.Y6,Bacillus sp.Y7,and Planococcus sp.Y8)at the ratio of 2:1.5:1.5:1.5:2:1:2 has the best petroleum degradation efficiency,reaching 55.06%.It can be found that the biochar and activated carbon immobilized petroleum-degrading consortium can promote the granulation of aerobic sludge.Compared to the control reactor,the reactors immobilized petroleum-degrading consortium basically achieved aerobic granulation within 10 days,and the granular sludge with a sludge particle size greater than 0.45 mm accounted for69.11% and 84.24%,respectively.The formed granules were ellipsoidal with a rough surface and complete structure.It was observed that bacteria,filamentous microorganism were adhered on the surface of the sludge.In addition,the reactor with immobilized petroleum-degrading consortium showed good pollutant removal performance,with the average COD removal efficiency higher than 98%.The addition of biochar and activated carbon-immobilized petroleum-degrading consortium can alleviate the biological toxicity of refining wastewater,provide suitable environmental conditions for the survival of microorganisms,and improve the nitrogen removal performance.Biochar and activated carbon immobilized petroleum-degrading consortium in the reactor,the composition of microbial communities was relatively small,with similar microbial community.The content of petroleum-degrading consortium was higher than that in other reactors.The study confirmed that immobilization of petroleum-degrading consortium by porous carbon carriers were not easy to lose,has high biological stability and strong tolerance to refining wastewater.This study provides a new insight for the treatment of refining wastewater by bioaugmentation aerobic granular sludge. |
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