Interactions Between Microorganisms and Metal Nanoparticles: A New Approach for Groundwater Remediation


Graduate Researchers: Rabiya Shabnam, John McEvoy,Achintya N.Bezbaruah

Project sponsors: USGS/NDWRRI (03/2008-08/2009)


The main objective of this study is to investigate the interaction between iron nanoparticles and microorganisms for groundwater contaminant remediation. The specific objective was to study iron nanoparticle-microorganism interactions in terms of microbial growth and their behavioral changes. The proposed research focuses on encapsulating metal nanoparticles and microorganisms in alginate capsules (reactors) and studying their interactions for the remediation of environmental contaminants using encapsulated microorganism-metal system. Trichloroethylene (TCE) is a halogenated aliphatic organic compound which, due to its unique properties and solvent effects, has been widely used as an ingredient in industrial cleaning solutions and as a universal degreasing agent. TCE, perchloroethylene (PCE), and trichloroethane (TCA) are the most frequently detected volatile organic chemicals (VOC) in ground water in the United States. The EPA has set a maximum contaminant level for trichloroethylene in drinking water at 0.005 milligrams per liter (0.005 mg/L) or 5 parts of TCE per billion parts water. Biological degradation (and possibly mineralization) of TCE remediation under anaerobic conditions has been studied for a number of years. Though individually studied, nanometals and microorganisms have not been used simultaneously in environmental remediation. In current practice, they are used separately and injected into the aquifer after necessary pretreatment. However, if the nanoparticles and microbes can be injected together, there may be considerable technology advantage and better remediation. This work hypothesizes that nanoparticles can reduce a contaminant as the first step in the degradation process and microorganism can preferentially take over the process and reduce/oxidize the degradation byproduct(s) to benign end products or vice-versa. One of the ways of delivering the microbes and the nanoparticles together is to encapsulate them in easily biodegradable biopolymers. Sodium alginate is a carbohydrate-based biopolymer, is a linear polysaccharide, consisting of variable amounts of Β-D-mannuronic acid (M) and its C5-epimer α-L-guluronic acid (G) linked via 1,4-glycosidic bonds. Like DNA, alginate is a negatively charged polymer; imparting material properties ranging from viscous solutions to gel-like structures in the presence of divalent cations (Figure 1) (33), Calcium form a complex with sodium alginate to form a capsule.