Bioaugmentation in lab scale constructed wetland microcosms for treating polluted river water and domestic wastewater in northern China

•Bioaugmentation is effective to treat polluted river water and domestic wastewater.•Nutrient in constructed wetlands shows high removal efficiency by bioaugmentation.•Optimal hydraulic retention time was 7 days.•A repeated inoculation in constructed wetland was defined as every 14 days.

Nutrient removal in constructed wetland (CW) microcosms planted with Phragmites and inoculated with a consortium of six denitrifying bacteria was evaluated as a possible treatment for polluted river water (RW) and domestic wastewater (DW) in northern China. Experiments were conducted using the batch-loaded method over a 15 day period. Bio1 (RW with Phragmites inoculated with the bacterial consortium) and Abio1 (DW with Phragmites and bacterial inoculation) showed significant decreases in chemical oxygen demand (CODcr), and increases in total nitrogen (TN), ammonia (NH3–N) and total phosphorus (TP) removal compared with Bio2 and Abio2, i.e., Phragmites without bacteria inoculation. On the 7th day, the removal efficiencies of Bio1 were found to be 75.7% for CODcr, 96.7% for TN, 96.8% for NH3–N and 90.4% for TP in RW microcosms, and 85.7% for CODcr, 75% for TN, 88.6% for NH3–N and 88% for TP in Abio1 DW microcosms. Optimal hydraulic retention time (HRT) was 7 days. We conclude that bioaugmentation in CWs with inoculation repeated every 14 days is a cost-effective measure for nutrient removal of polluted river water.