This document summarizes a study evaluating amendments to improve the effectiveness of biowalls used for groundwater remediation at sites with high sulfate concentrations. The biowall at Altus Air Force Base in Oklahoma was experiencing reduced performance due to sulfide toxicity. Laboratory tests evaluated different iron sources that could be combined with emulsified vegetable oil amendments to precipitate sulfide and buffer toxicity. Field tests at a pilot biowall compared vegetable oil alone to vegetable oil combined with ferrous lactate and nano hematite. Preliminary results are being analyzed to assess enhancement of reductive dechlorination from the iron additives and determine if they should be included in biowall rejuvenation at high-sulfate sites.