First Full‐Scale In Situ Propane Biosparging for Co‐Metabolic Bioremediation of 1,4‐Dioxane

1,4‐Dioxane is an emerging contaminant of environmental concern, probable human carcinogen, and it can result in diffuse groundwater plumes and is not readily treated using common remedial techniques (e.g., via air stripping or granular activated carbon). In situ bioremediation of 1,4‐dioxane has been studied at the bench‐scale and pilot‐scale. This work documents the full‐scale application of in situ propane biosparging for the treatment of 1,4‐dioxane. The subject site is located at Vandenberg Space Force Base in California. Installation of the full‐scale treatment system came after several pilot tests (e.g., Lippincott et al. 2015), stable isotope testing (Bell et al. 2016), and rebound testing conducted from 2012 to 2016. The full‐scale propane biosparge system supplies air and propane at an average of 5 kg (11 pounds) of propane per day to a network of 97 biosparge wells, or 52 g (0.11 pounds) of propane per day per biosparge well. Additionally, a bioaugmentation culture and macronutrients were delivered to the subsurface. After approximately 6 months of operation, 1,4‐dioxane was reduced at up to 99.2%, with an average global reduction of 64.1% (excluding two anomalous monitoring wells) across a treatment area of approximately 30.5 by 61 m (100 by 200 ft). Nearly 100 propane biosparge locations were installed at Vandenberg Space Force Base in California in the first full‐scale application of in‐situ co‐metabolic bioremediation of 1,4‐dioxane in groundwater.