Evaluation of an intermittent-aeration constructed wetland for removing residual organics and nutrients from secondary effluent: Performance and microbial analysis.

This study proposed a novel intermittent-aeration constructed wetland (CW) to resolve the vertical loss of oxygen in tertiary treatment. Compared to the non-aeration CW, the intermittent-aeration CW presented a better removal performance (90.8% chemical oxygen demand, 94.3% ammonia nitrogen, 91.5% total nitrogen and 94.1% total phosphorus) at a dissolved oxygen of 3 mg L and hydraulic retention time of 2 days. It was mainly attributed to the higher abundance and greater diversity of bacterial community due to the oxygen supply. High-throughput sequencing indicated that high abundance of phyla Proteobacteria (35.34%) and Bacteroidetes (18.20%) in intermittent-aeration CW were responsible for simultaneous nitrogen and phosphorus removal. Besides, the dominant families Burkholderiaceae (11.16%), Microtrichales (6.88%) and Saprospiraceae (6.50%) were also detected, which was vital to hydrolyze and utilize complex organic matters. In general, oxygen supply upregulated the metabolism pathways of amino acid and carbohydrate, bringing a greater biodegradation potential for removing contaminants.