Capacity of various single-stage constructed wetlands to treat domestic sewage under optimal temperature in Guangzhou City, South China

Less seasonal temperature variation in humid tropical and subtropical climate makes unique wastewater and removal performance of constructed wetlands (CWs) in South China. Nine single-stage CWs consisting of surface flow (SF), horizontal subsurface flow (HF) and vertical flow (VF) units vegetated with Canna indica or Thalia dealbata, as well as unvegetated filters were operated over 33 months (September 2013 to May 2016) to assess their removal capacity for domestic sewage and to evaluate the key influencing factors (i.e. vegetation, flow type, and temperature) in South China. The evaluation of the results indicated that these systems had great removal capacity of nutrient and organic matter. The average influent concentration of TN, NH4-N, TP and COD was 29.3, 23.3, 2.6 and 142.1 mg L-1, respectively. Removed load of TP, NH4-N, and COD were higher in VF CWs. Removed load of TN was higher in HF CWs. Influent loads positively influenced the removed loads of pollutants. Flow type had the greatest impact on removed load, followed by the temperature, and vegetation had minimal impact. VF (unvegetated) - HF (vegetated) could be the model of purification of domestic sewage by CWs in South China