Transformation of Chloroform in Constructed Wetlands

Abstract

Chloroform is a volatile organic contaminate widely detected in groundwater, surface water and wastewater effluent, thus its fate in the natural treatment systems is of great importance to the environment and human’s health. In this study, the transformation processes were studied for six model constructed wetlands (CWs), for treating chloroform in the secondary effluent. Contaminate fate was investigated in the respective water, plant, litter, gravel and atmosphere. Results showed that sorption and biodegradation were the main chloroform removal processes in litter-added CWs, while sorption and plant uptake were the primary contributors to chloroform removal in planted CWs. Volatilization flux of chloroform was always low (2.0–2.5 %) in CWs likely due to the limitation of water–air transfer via diffusion in the SSF CWs. Overall, this study makes the quantitative evaluation of chloroform distribution (i.e. aqueous phase, gaseous phase, vegetation, and bed substrate) and multiple removal pathways (i.e. destructive versus nondestructive processes) in CWs. This will benefit for opening the “black box” of the treatment processes and make people better understand the transformation of trace volatile organic pollutants in natural treatment systems.