A meso-scale constructed wetland for the remediation of chlorobenzene contaminated groundwater

Rising groundwater levels in Bitterfeld, Germany, will transport organic contaminants near the ground surface in the future, so that the construction of near-natural wetlands may present an effective remediation approach. A 2 x 6 in pilot plant was built to investigate the fate of monochlorobenzene (MCB), one of the main pollutants at the site, in a wetland system. MCB concentrations were reduced from similar to 10-15 mg l(-1) at the inlet to similar to 1-3 mg l(-1) after passage through the soil filter. A zonation in the vertical and horizontal direction was apparent for MCB, sulfate, iron(II) and pH. Aerobic MCB-degrading microbial communities were enriched from the pilot plant and showed degradation of MCB in microcosms down to oxygen-limited conditions of 0.5 mg O-2 l(-1). Volatilization may also constitute a significant process as indicated by the results of active and passive gas sampling at the surface of the soil filter. Overall, constructed wetlands have a high potential for the remediation of chlorinated solvents, but more research is needed to move away from a black box approach and understand the relevant attenuation processes.