REHAMOS - Rehabilitation of a combined hexavalent chromium and VOC groundwater contamination : pilot tests with injection of molasses on large scale

Many sites in Flanders have been identified as definitely or potentially contaminated by mainly mineral oils, heavy metals and organic contaminants such as chlorinated hydrocarbons (CAHs), the former being carcinogenic, mutagenic and embryotoxic for humans and need to be removed from groundwater. The beneficiary wanted to remedy the groundwater of its polluted site in Sint-Truiden with the application of molasses substrate injection. The project successfully demonstrated the benefits of this remediation technique on such a scale and collected extensive data indicating that the injection of molasses had significant environmental benefits - no emissions, no nuisance for surrounding areas - and economic benefits – it was cost effective compared to conventional remediation techniques. Full-scale molasses injection into the aquifer at the Tenneco Automotive Europe site in Sint-Truiden induced a significant reduction of the CrVI and trichlooretheen (TCE) mixed pollution present in the groundwater, by anaerobic bioremediation processes. The areas that have been treated for the longest periods show almost complete de-chlorination to ethene and ethane (both harmless) and chromium levels. However, many monitoring wells within the plume remediation area still show high levels of dichloroethylene (DCE) and VOC.