Combined biological and abiotic reactions with iron and Fe(iii)-reducing microorganisms for remediation of explosives and insensitive munitions (IM)

Abstract

Military explosives and insensitive munitions (IM) are a significant hazard to all natural and engineered environments. A number of remediation alternatives have been proposed and investigated in detail, and biological remediation has received a large amount of attention because the reactions can be cost effective and transform the contaminants to innocuous end products. Recently, investigators have begun to look at coupled biological and chemical reactions as way to accelerate the rate of explosives and IM transformation in groundwater, surface water, soil, and industrial wastewater. A number of these technologies are predicated on reactions involving iron, and the microorganisms that reduce ferric iron. These mixed “biological–chemical” reactions may be more effective at degrading the contaminants because the strategies do not rely on a single type of reaction or microorganism, but rather a suite of reactions taking place simultaneously or in series and microbial communities that catalyze similar reactions. The technologies investigated have primarily two mechanisms. The first is initially stimulating Fe(III)-reducing microbial activity, with the secondary chemical reactions with ferrous iron (or electron shuttling molecules) actually degrading the explosives or IM. The second approach is initial chemical treatment with zero valent iron followed by engineered or native microbial activity degrading the residual contamination. In both cases the chemistry and biology of the system and the specific contaminants are critical to environmental restoration. This Frontier Review will present recent advances in the field.