Use of a Non-Toxic Magnetite-Rich Industrial Waste to Reductively Dechlorinate Perchloroethylene Contaminated Groundwater

Perchloroethylene (PCE) is a widespread groundwater contaminant in industrialized countries. Degradation of this dense non-aqueous phase liquid (DNAPL) chlorinated solvent using traditional methods, such as ‘pump and treat', is a lengthy and onerous process that often does not permit to meet environmental criteria. Enhanced natural attenuation using magnetite-rich particles is a promising means of remediation in a rapidly evolving domain. The purpose of this experiment was to evaluate the effect of sub-micrometric magnetite-rich particles incorporated into a vegetable oil-based emulsion on the biodegradation of PCE contaminated groundwater under anaerobic environments. Samples of the oil-based emulsion containing 25% magnetite-rich particles were added to PCE contaminated groundwater in 500 ml reactors. Initial PCE concentrations were 586 ppb and presence of by-products such as 50 ppb of trichloroethylene (TCE) and 35 ppb of cis-dichloroethylene (cDCE) indicated the existence of dehalogenating bacteria in the contaminated water. After 3 weeks, PCE was totally degraded as TCE concentrations rose from 50 to 346 ppb. After an additionnal 3 weeks, TCE concentrations fell to 3 ppb as cDCE concentrations rose from 37 to 273 ppb. Two other batch reactors, one being operated with emulsion but without magnetite (EM1) and the other being the control, show that EM1 enhanced dechlorination of PCE. However, addition of magnetite-rich particles further accelerates the process. The results indicate that reductive dechlorination through indigenous anaerobic microbes in the contaminated water is stimulated by the addition of sub-micrometric magnetite-rich particles. Future analyses will determine effectiveness of magnetite-rich oil-based emulsion to fully degrade PCE to non-toxic end products such as ethylene, water and carbon dioxide.