Formatted Title
Enhancing Microbial Bioremediation of Tertiary Butyl Alcohol in Groundwater Using Permeable Fill Borings
Background/Objectives
Increasing tertiary butyl alcohol (TBA) concentrations in groundwater was observed at a gasoline service station, preventing the site from achieving State Water Resources Control Board (SWRCB) case closure. A sustainable and effective technology was sought to achieve long-term remediation of TBA in the groundwater and SWRCB case closure.
Approach/Activities
In August 2020, six permeable fill borings (PFBs) consisting of a mixture of gypsum and rhyolite gravel were advanced at the site. Gypsum is a commonly available, naturally occurring mineral consisting of hydrated calcium sulfate (CaSO4·2H2O). The expectation was for the gypsum to provide a long-term source of dissolved sulfate (SO4) to the groundwater to be available as an electron acceptor for microorganisms to cultivate an oxidation-reduction reaction, thereby enhancing the breakdown of residual hydrocarbons. The goal of the PFBs is to accelerate biodegradation that is already occurring at the site by stimulating the growth of sulfate-reducing bacteria through the addition of the gypsum gravel blend into the saturated zone.
Results/Lessons Learned
An increase in SO4 and low dissolved oxygen and oxidation-reduction potential values were observed in the treatment area following the permeable fill boring installation. Decreases in TBA concentrations were observed in the same area over the same period. The limited data thus far suggest that the permeable fill borings demonstrated efficacy over the last 2 years. Initial treatment results were used to achieve SWRCB case closure. Results from this site suggest the technology can be used as a sustainable and effective remediation for hydrocarbon contamination.