Comparison of different multibarrier concepts designed for treatment of groundwater containing mixed pollutants

A study was set up to develop and evaluate the possibilities of multibarriers for the remediation of groundwater contaminated with mixed pollutants. A multibarrier is a multifunctional permeable reactive barrier in which biological and physicochemical pollutant removal processes can be combined. Different combinations of biodegradation, reductive dehalogenation using zero valent iron and sorption were considered to treat mixed pollutants consisting of heavy metals (As, Zn), aromatics (benzene, toluene, m-xylene) (BTX) and volatile chlorinated compounds (VOCIs, e.g. PCE, TCE). Biodegradation of BTX in batch-systems was found to be negatively influenced by the presence of zero valent iron and other pollutants. Starting from the same aquifer mixture, addition of different electron-acceptors were selected for a different BTX-degrading microbial population as determined by PCR-DGGE. Based on column experiments which simulated different multibarrier concepts, sequential as well as mixed (Fe 0 /bio) multibarriers proved to be suitable for the treatment of the tested pollutant mixture. Good results were obtained with O 2 , NO 3 - , SO 4 2- , Fe 3+ as terminal electron acceptors.