Permeable Reactive Barriers (Proceedings of the International Symposium held at Belfast, Northern Ireland, March 2004). IAHS Publ. 298, 2005, 75-81.

1 TNO Environment, Energy and Process Innovation, Department of Environmental Biotechnology, PO Box 342, 7300 AH Apeldoorn, The Netherlands

2 DAF Trucks, The Netherlands

3 BAM-NBM, The Netherlands

Abstract A pilot remediation with a biological treatment zone is performed at a site contaminated with chloroethenes and chloroethanes. This paper describes two different water circulation systems that were installed at the site for the infiltration of various compounds to enhance the degradation of the contaminants. Our experiences in the operation and performance of both bioscreen systems are given. Elaborate monitoring—of contaminants inclusive degradation products, hydrogen, sulphate and fatty acids—was essential to adjust the operation of the two bioscreens and the electron donor infiltration regime. The results show that both chloroethenes and chloroethanes are degraded in the two bioscreens. In the best working bioscreen, concentrations of cis-DCE dropped from 15 mg l^-1 to 10 µg l^-1. VC concentrations initially increased from 1500 to 3300 µg l^-1, followed by a decrease to less then 1 µg l^-1. Concentrations of 1,1-DCA and 1,2-DCA dropped from 1 mg l^-1 to 100 µg l^-1 and 10 µg l^-1, respectively.

Key words bioscreen; chlorinated solvents; groundwater remediation