Treatment of coking wastewater by a novel full-scale microaerobic-anoxic-oxic (M/A/O) system: performance and microbial community analysis.

The aim of this study was to investigate the relationship between system removal performance and microbial community structure in a novel full-scale microaerobic-anoxic-oxic (M/A/O) system for coking wastewater (CWW) treatment. The results showed that 93% of chemical oxygen demand (COD) and 99% of NH4+-N removal efficiency were achieved via the M/A/O process, meanwhile, main organic pollutants in CWW, including phenolic compounds, heterocyclic compounds and polycyclic aromatic hydrocarbons were basically removed. Four dominant phyla of Proteobacteria, Firmicutes, Bacteroidetes and Nitrospirae were demonstrated to be distributed in the system and played significant roles in the M/A/O biological treatment process. The major function of the M process was to partly remove the biodegradable substances such as phenols and hydrolyze the refractory contaminants such as N-heterocyclic compounds to improve the biological oxygen demand/COD (BOD5) ratio and release ammonia. This work illustrated the structure and function of the microbial community in the M/A/O system and provided a new choice for high-strength CWW treatment.