Rainfall effects to the performance of subsurface flow constructed wetlands in leachate treatment

Abstract

Constructed wetlands have gained wide acceptance as a wastewater treatment practice. Rainfall effect needs to be taken into account in designing local constructed wetlands particularly in tropical countries. This study was carried out to evaluate the effects of tropical climate (rainfall) towards the performance of horizontal subsurface flow constructed wetlands (HSFCW) planted with local plant, Typha angustifolia for landfill leachate treatment. The performance of the constructed wetlands was evaluated using seven parameters i.e nitrate, phosphorus, ammonical nitrogen, chromium, cadmium, biochemical oxygen demand (BOD5) and chemical oxygen demand (COD). Two pilot scale constructed wetlands reactors were used in the experiments. Performance of HSFCW in leachate treatment was evaluated with comparison to a blank reactor (without plants) serving as control. Experiments were run under artificial “monsoon rainfall intensity” in Malaysia. Results show that rainfall effects towards the performance of wetlands in leachate treatment vary from parameter to another (-1% to 41% enhancement) depending on the characteristic of each parameter. All parameters except chromium have better performance in leachate treatment after rainfall. Rainfall effects (increasing of removal efficiency) are more critical in control reactor as compared to the vegetated reactors.