Wetland water quality assessment of eco-engineered landscaping practices: a case study of constructed wetland parks in Hangzhou

Abstract

Urban constructed water quality treatment (WQT) wetlands are often applied to be integrated with ecological engineered landscaping (EEL) measures for wastewater treatments. This study aims to identify the interrelationships between the hydrological factors and pollutant removal contributions of typical WQT wetlands at each WQT stage, i.e., subsurface flow wetlands (SSF), vertical flow wetlands (VF), free surface flow wetland (FSF), floating wetland island (FWI), aeration ponds (APs), and ornamental ponds (OPs) in four typical wetland parks in Hangzhou, China. Water quality indices (WQIs) of wetland parks have been monitored. Interactive comparisons and correlations between hydrological indicators and WQIs (i.e., pH, DO, NH3-N, CODCr, and TP) are developed, while the removal contribution of each WQI was explained. It is found that each stage had heterogeneous effects on wastewater treatment due to various geo-ecological factors, including hydraulic conditions, plant type, and microbial microenvironment, whereas the temperature of waterbodies affected WQT performances at full sites in all seasons. Three corresponding EEL guiding principles were derived, i.e., optimising the EEL measures, adapting planting methods, and incorporating multifunctional design and adaptive management. The findings will be helpful for improving the efficacy of WQT stages as one of the potential ecosystem services provided by wetland parks.