A former solvent recycling site in Florida impacted with PCE/TCE/TCA now has only a DCE/vinyl chloride plume in a shallow aquifer. Previously, enhanced bio using EVO was implemented as a barrier at the site boundary in 2005. Analysis of the results prior to a 5-year review led me to recommend injection in the high concentration area due to slow ground water flow. The geology was conducive to using direct push technology, however, the 2nd injection was hindered by the inability to use anaerobic site ground water as make-up water.
Innovation turned hydrant water anaerobic and included buffer, pH adjustment and bioaugmentation. VOC losses were significant as documented in the 5-year review in 2010. Monitoring in April 2011 indicated losses for DCE ranged from 20-75% with no ethene production. Abiotic reactions may be removing DCE and vinyl chloride due to generation of FeS minerals in the subsurface (Plaines et. al. 2013).