Microorganisms Agent Bioaugmented The Biological Aerated Filter For Advanced Treatment Of Refractory Refinery Wastewater And Microbial Community Analysis

This work aimed to investigate and evaluate the removal of COD and NH₄⁺-N from refinery wastewater in a novel biological aerated filter(BAF)bioreactor,using nut shell activated carbon with high porosity and large specific surface area as a supporting material,in conjunction with microbial agents that can strengthen the BAF in order to improve the efficiency of refining wastewater treatment,Furthermore,microbial community structure analysis was conducted between the upgraded system and the original system to interpret their different performances and the potential mechanisms involved in the bioaugmentation process.Eventually,the wastewater discharge reached the first-level discharge standard of the new discharge standards(GB 31570-2015).The results are as following:1.According to the conventional water quality analysis,the chemical oxygen demand(COD)of the refinery wastewater of the secondary sedimentation tank after the biochemical treatment of the anoxic-aerobic activated sludge process(A/O)is98±20 mg/L,the ammonia nitrogen(NH₄⁺-N)is 17±3 mg/L,p H is 7.68-8.31,and the biochemical oxygen demand(BOD₅)is 25±5 mg/L,etc.Gas quality analysis has determined that the main pollutants in the wastewater from the refinery secondary sedimentation tank are long-chain alkanes(46.35%),esters(31.18%)and benzenes(17.41%).2.After 180 r/min and 28°C enrichment and acclimatization in a 250 m L shake flask,Using n-icosane(naphthalene)with concentrations of 200 mg/L,400 mg/L,600mg/L,800 mg/L,and 1,000 mg/L as the sole carbon source and energy substance,4strains of biodegradable long-chain alkanes(n-icosane)and a large number of intermediate metabolite systems have been separated and purified,and 3 strains of biodegradable benzene ring(naphthalene)and a large number of intermediate metabolite systems have been separated and purified.7 strains named FS-01?FS-07.After 180 r/min and 28°C constant temperature shaking culture for 5 days in a250 m L shake flask,The strains FS-01,FS-02,FS-05,and FS-07 showed higher degradation activity when cultured in refinery wastewater with an initial COD concentration of 1260±110 mg/L,which reduced the COD concentration by 48.6%,45.5%,41.7%,38.6%.The identification results of 4 strains showed that FS-01 is Pseudomonas sp.,FS-02 is Bacillus thuringiensis,FS-05 is Microbacterium oxydans,and FS-07 is Acinetobacter junii.The 4 strains were arbitrarily combined to form 10kinds of composite community and added to the screening medium.As a result,the composite bacteria's degradation rate of COD was higher than that of a single strain.Among all the community,the bacterial population consisting of FS-01 and FS-02had the highest degradation rate,reaching 67.9%.3.Carried out a small-scale study on 1.2 L BAF advanced treatment of refining wastewater.By comparing the treatment effects of various indicators of wastewater from coconut shell,apricot shell and peach shell activated carbon,when the mean COD and NH₄⁺-N of the influent were 98 mg/L and 17.1 mg/L,it was found that coconut shell activated carbon can remove more than 32%of COD and about 95%of NH₄⁺-N.The effects of temperature,dissolved oxygen(DO),and hydraulic retention time(HRT)on the removal rate of major pollutants were explored.The optimized BAF reactor temperature,DO and HRT were determined,which were 30±1°C,3.5mg/L,and 6 h,respectively.4.Bioaugmenting the BAF with Pseudomonas sp.FS-01 and Bacillus sp.FS-02,the bacterial community of the biofilms from the two BAF systems was analyzed by Illumina Mi Seq sequencing.Through the rarefaction curves,principal coordinate analysis(PCo A),and analysis of bacterial community components,the differences of the community in the system before and after bioaugmentation were analyzed.The results showed that a stable and diverse microbial community structure was formed in both systems.The predominant genera in BAF1 were Nitrospira,an unranked member of the Anaerolineaceae,and an unclassified member of the Rhizobiales,while the dominant genera in BAF2 were Pseudomonas,Bacillus,and an unranked member of the Anaerolineaceae.Bioaugmentation accelerated the transformation of the bacterial community structure,Pseudomonas sp.FS-01 and Bacillus sp.FS-02quickly become dominant strains.when the mean COD and NH₄⁺-N of the influent were 98 mg/L and 17.1 mg/L,the average effluent COD and NH₄⁺-N were 31.8 mg/L and 0.4 mg/L.Bioaugmentation can improve the COD remove efficiency by 35%in relation to only adding sludge.The main indicators are better than the latest national first-level emission standards(GB 31570-2015).