Biological Treatment of Residual DNAPL Following Physical Source Treatment

Often the successful treatment of ground water contaminated with chlorinated solvents is hindered by the existence of high concentrations of contaminants in the form of dense non-aqueous phase liquid (DNAPL). This DNAPL acts as a continuing source of dissolved phase contamination protracting cleanup times and escalating costs of site remediation. DNAPL can exist in the subsurface as a massive volume, which can be located and treated using advanced physical or chemical technologies. More often however, the DNAPL exists as a discontinuous and dispersed contaminant phase sorbed onto the aquifer matrix. This is often referred to as residual DNAPL. Residual DNAPL can develop as the result of a product release, where high concentrations of contaminant moved through the aquifer system, or it can be the end result of a mechanical or chemical treatment of a larger DNAPL body.


The use of biological treatment to stimulate the desorption, dissolution and degradation of residual DNAPL has been demonstrated in the laboratory and in well documented field applications. Specifically, the use of slow release electron-donor substrates such as Hydrogen Release Compound (HRC) to stimulate anaerobic dechlorination has shown excellent results in the rapid removal and degradation of chlorinated contaminants such as TCE. Advantages to this biological approach are many.