A review on constructed wetlands in Beijing-Tianjin-Hebei region of China: Application in water treatment, problem, and practical solution

Constructed wetlands (CWs) are commonly employed in developing countries for wastewater treatment, owing to their environmental, economic, and social advantages. CWs remove pollutants through natural processes, offering ecosystem services and recreational benefits. However, the efficiency of pollutant removal varies due to factors such as low winter temperatures and the complexity of wastewater composition. This review examines the development and application of CWs in the Beijing-Tianjin-Hebei region of China. The relationship between CW type and wastewater treatment efficiency is explored, along with factors influencing CW performance. Based on monitoring data from 27 field-scale CWs, Hybrid Constructed Wetlands demonstrated the highest removal rates for COD (43.48 %), TN (44.79 %), and TP (51.50 %). Vertical Flow Constructed Wetlands achieved the highest NH3-N removal rate (71.25 %). Substrate selection, plant species, hydraulic retention time, and pollutant loading rates all influence CW performance. These variations in pollutant removal efficiency are primarily attributed to low dissolved oxygen, low C/N ratios, and ambient temperature. Pollutant removal efficiency can be enhanced through strategies such as intermittent aeration, tidal flow operation, supplementation with electron donor substrates, selection of cold-tolerant plants, augmentation of cold-tolerant microbes, insulation material cover, and clogging remediation. These strategies help increase pollutant removal rates and promote the sustainable operation of CWs.