Coupling of Zerovalent Iron and a Slow-Releasing Carbon Source for the In Situ Biological Degradation of 1,2-DCA in Contaminated Aquifers

摘要

Background/Objectives. During the last two decades permeable reactive barriers (PRBs) have been established as robust alternatives to traditional pump-and-treat approaches for groundwater remediation. PRBs are successfully used to in situ treat a wide variety of reducible contaminants, ranging from heavy metals to halogenated hydrocarbons. Zerovalent iron (ZVI) is currently the most frequently employed reactive agent, especially for treating plumes polluted by chlorinated hydrocarbons, particularly chlorinated ethenes and ethanes. Notwithstanding, PRB-ZVI technology is affected by some operational problems, such as the long-term decrease of performance, due to losses of ZVI reactivity and/or of porosity, and the ZVI inability to chemically reduce some less chlorinated compounds, e.g., chloromethane (CM), dichloromethane (DCM) and 1,2-dichloroethane (1,2-DCA). Among them, 1,2-DCA, a carcinogenic compound, is of particular concern because it is one of the most widespread groundwater contaminants. On the other hand, it has been largely demonstrated that most of these compounds are more easily degraded via biological reductive dechlorination, provided the presence of specific microorganisms and available electron donors (which is usually the limiting factor in the natural reductive biodegradation processes). Development of composite materials obtained by the combination of consolidated chemical reactive media with a releasing carbon source is raising increasingly growing interest by researchers to extend treatment to recalcitrant compounds in complex mixtures and/or to enhance microbial activity in a synergistic action.