Biofilm characteristics, microbial community structure and function of an up-flow anaerobic filter-biological aerated...

The biofilm characteristics, microbial community structure and function in a lab-scale up-flow anaerobic filter-biological aerated filter (UAF-BAF) driven by COD/N ratio were investigated. Results showed that the TN removal rate of system reduced from 68.7% to 50.6% with COD/N ratio ranging from 10 to 3. Biofilm characteristics analysis indicated that the biomass, biofilm thickness, polysaccharide and protein contents in extracellular polymeric substance and dehydrogenase activity from biofilm in the UAF-BAF declined with the decrease of COD/N ratio. The biofilm structure visualized by confocal laser scanning microscopy displayed that the total cells and EPS content decreased as the COD/N ratio downshifted. 16S rRNA sequencing illustrated that Zoogloea and Pleomorphomonas were the major contributors to TN removal in the UAF, with dramatically decreasing abundance. Functional prediction indicated that the genes involved in nitrogen metabolism and nitrate reductase (EC 1.7.99.4) also decreased, which was responsible for the decrease of TN removal. This study provided insights into understanding of the biofilm structure and underlying ecological function in the UAF-BAF, which would help to regulate wastewater biofilm and improve process performance.