Evaluation of Slow Release Substrates for Anaerobic Bioremediation

A variety of food-grade organic substrates were evaluated to identify materials that could be used to support long-term anaerobic bioremediation processes in the subsurface. In this work, the rate and extent of biogas production was used as an indicator of the potential for substrate fermentation to H₂ and acetate, the primary electron donors used in reductive dechlorination. The rate and extent of biogas (primarily CO₂+ CH₄) evolution varied widely between the different substrates. For many of the substrates, biogas generation declined to very low levels within 100 days of substrate addition. However, a few substrates including several vegetable oils and sucrose esters of fatty acid (SEFAs) did support biogas production for extended time periods. Column studies demonstrated that both soybean oil and a SEFA could support sulfate reduction, methanogenesis and reductive dechlorination of perchloroethene (PCE) to cis-dichloroethene (cis-DCE) for over 14 months. The slower degradation rate of the SEFAs could be used to control substrate degradation rate in the subsurface, increasing substrate lifetime and reducing the required reinjection frequency.