Performance evaluation of hybrid treatment wetland for six years of operation in cold climate

New insights for enhancing the performance of constructed wetlands at low temperatures

Constructed wetlands (CWs) have been widely utilized for various types of wastewater treatment due to their merits, including high cost-effectiveness and easy operation. However, a few intrinsic drawbacks have always restricted their application and long-term stability, especially their weak performance at temperatures under 10 °C (low temperatures) due to the deterioration of microbial assimilation and plant uptake processes. The existing modifications to improve CWs performance from the direct optimization of internal components to the indirect adjunction of external resources promoted the wastewater treatment efficiency to a certain degree, but the sustainability and sufficiency of pollutants removal remains a challenge. With the goal of optimizing CW components, the integrity of the CW ecosystem and the removal of emerging pollutants, future directions for research should include radiation plant breeding, improvements to CW ecosystems, and the combination or integration of certain treatment processes with CWs to enhance wastewater treatment effects at low temperatures.

Treatment for domestic wastewater from university dorms using a hybrid constructed wetland at pilot scale

A hybrid constructed wetland (CW) system was operated at pilot scale to evaluate the treatment of domestic wastewater from university dorms in Hubei province, China. The hybrid system consisted of an integrated vertical flow constructed wetland (IVF CW) (a down-flow VF CW and an up-flow VF CW) and a horizontal subsurface flow constructed wetland (HSF CW). The influent for the hybrid CW containing chemical oxygen demand (COD), total phosphorus (TP), total nitrogen (TN), and ammonium nitrogen (NH₄⁺-N) with mean concentrations of 152, 0.75, 18.9, and 8.9 mg L^-1, respectively, was purified by the hybrid CW system to achieve mean removal efficiencies of 59.0% COD, 82.8% TP, 57.7% TN, and 79.2% NH₄⁺-N over a 9-month period. The nitrification intensity of the media in the down-flow VF CW was the highest compared to the other CWs, whereas the denitrification intensity of the media in the HSF CW was significantly higher than the IVF CW. The abundance of nitrifying bacteria in the media of the IVF CW was higher than in the HSF CW, while a higher abundance of denitrifying bacteria was found in the HSF CW compared to the IVF CW, suggesting that the HSF CW was more suitable for the growth of denitrifying bacteria.