Fate of Chlorinated Benzenes in Laboratory Peat and Pozzolana Filters

The removal of chlorinated benzenes (CBs) from the compartments and from polluted industrial sites is of great public interest for the decontamination of polluted water and for the protection of the environment. Biological degradation could be considered as a feasible process to eliminate these compounds from the environment as soil or groundwater. A research program in progress since the year 2007 was initiated to investigate the capacity of eco-remediation of CB-contaminated groundwater using a pilot-scale subsurface flow constructed wetland. In order to assess the removal efficiency of these compounds and to evaluate the biological activities, column experiments were performed. The fate of three CBs was investigated by feeding spiked tap water through laboratory columns filled with two different solid-state materials: peat and pozzolana. In order to stimulate biological activity, organic matter coming from aged vertical flow constructed wetland was added to the media. Concentrations of CBs in water effluent and in air and biological activities were monitored during 4 months. At the end of the experimental period, CB concentrations in the depth of columns were determined and a mass balance was calculated for the CBs. Removal efficiencies of the laboratory columns were >98% in the peat columns and situated around 87% to 95% in the pozzolana columns, indicating the suitability of the experimental systems for the removal of CBs. Higher effluent CB concentrations from the pozzolana columns were detected. Concentration of CBs in ambient air indicates that volatilization was low. ATP monitoring, reduction of tetrazolium violet, and exopolysaccharide determination indicated considerable biological activity with variations according to column depth and carrier material.