Shifts in microbial community structure and diversity in a novel waterfall biofilm reactor combined with MBBR under light and dark conditions

In this study, a novel, low-cost, easy-maintenance and effective waterfall aeration biofilm reactor (WFBR) was designed to treat wastewater with MBBR. The chemical oxygen demand (COD), nitrogen removal efficiency, and the microbial community structure in this novel system were evaluated for 70 days under light and dark conditions. The COD and ammonium nitrogen (NH(3)–N) removal efficiency remained at approximately 90% and 100% respectively after 25 days, even if the influent substrate concentration and illumination condition changes. High-throughput sequencing was used to investigate the composition and function of the microbial community in different fillers in the treatment system. Dark padding, illuminate carrier and fabric play the good performance in nitrogen nitrification, denitrification and fixation respectively. The major classes present were Betaproteobacteria (30.2% on average), Cytophagia (19.8%), Gammaproteobacteria (11.7%), Alphaproteobacteria (11.2%), Sphingobacteriia (5.1%), Flavobacteriia (2.6%), Deltaproteobacteria (2.4%), Verrucomicrobiae (0.7%), Chloroplast (0.6%) and Clostridia (0.5%). These results could provide important guidance for the improvement of MBBR or other tradition wastewater treatment process, and could also enrich our theoretical understanding of microbial ecology.