Microbial community structure analysis of a pilot-scale membrane bioreactor for dairy farm wastewater
This study was conducted to explore the evolution of the microbial community structure within a pilot-scale membrane bioreactor(MBR)for treating high-strength wastewater from dairy cattle farms under different operating parameters.The microbial compositions,diversity,and distribution of dominant microbiota were characterized under five operating conditions formed by various sludge retention times(SRT),hydraulic retention times(HRT),and aeration modes(continuous aeration,three types of intermittent aeration).The pollutant removal effects under different conditions were also compared.The results showed that the optimal operating parameters for conducting MBR treatment on high-strength dairy wastewater were:SRT of 30 d,HRT of 96 h,intermittent aeration of 15 min on/10 min off,resulting in removal efficiencies of 97.0%±0.5%for chemical oxygen demand(COD),90.4%±1.3%for ammonia nitrogen(NH+4-N),85.5%±1.8%for total nitrogen(TN),and 89.6%±5.6%for total phosphorus(TP).In the treated effluent,the concentrations of four water quality indexes were found to be(224±56),(45±8),(105±19)mg·L-1,and(4±2)mg·L-1,respectively.The COD concentration of some of the treated effluents met the standard for irrigation water quality during the entire operation period.This highly efficient and stable removal of organic matter,nitrogen,and phosphorus was attributed to the diversity and stability of MBR microorganisms.The dominant phyla of denitrifying and phosphorus-removing bacteria,including Proteobacteria,Firmicutes,and Bacteroidetes,collectively represented 85.2%of the total bacterial community.The effectiveness of high-efficiency nitrogen and phosphorus removal in wastewater was found to be closely associated with both the species and the relative abundance of these denitrifying and phosphorus-removing bacteria.The combined relative abundance of three predominant classes,namely Gammaproteobacteria,Bacteroidia,and Clostridia,comprised 81.2%of the total,with Gammaproteobacteria demonstrating the highest relative abundance at 57.3%.This high abundance of Gammaproteobacteria,a functional phosphorus-removing bacterial class,contributed to the noteworthy reduction of TP concentration in the treated effluent.Ottowia,the dominant denitrifying bacterial genus,exhibited a relative abundance of 54.8%,leading to significant improvements in nitrogen removal efficiency.The MBR system had demonstrated considerable efficacy in the treatment of high-concentration dairy wastewater.The effectiveness of MBR in pollutant removal was intricately linked to the composition of their predominant bacterial communities.Specifically,an increased relative abundance of key bacterial taxa within these communities enhanced the overall performance of MBR and improved the quality of the treated effluent.
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维普
