PCE Removal Options

The problem:  Groundwater at the Modesto Superfund site is impacted with high concentrations (up to 6 mg/L) of tetrachloroethene (PCE).  The client sought to evaluate four potential remediation options:  in situ chemical oxidation using potassium permanganate (KMnO₄); in situ reduction using micro-scale zero-valent iron (ZVI); anaerobic bioremediation using EHC®; and anaerobic bioremediation using 3D-Microemulsion (3DME).

How PRIMA helped:  PRIMA performed batch and column tests to evaluate the ability of each remediation option to destroy PCE, assess the effect of treatment on secondary water quality, and obtain information needed for full-scale design.  Secondary water quality parameters monitored included arsenic (which could be mobilized under anaerobic conditions), hexavalent chromium (which could form during in situ chemical oxidation), and formation of daughter products (a potential issue for both biodegradation and ZVI).  Design parameters measured included KMnO₄ soil oxidant demand, rate constants for PCE degradation by ZVI, and estimation of reagent dose requirements.  Because all treatments effectively destroyed PCE, PRIMA recommended that secondary effects, implementability, and the cost of treatment be used to identify the best remediation option for the site.