Enhancing Reductive Dechlorination of Chlorinated Ethenes and Ethanes in a Natural Treatment System

• Main Author: Burda, Caroline
• Other Authors: Pardue, John
• Format: Others
• Language: en
• Published: LSU 2009
• Subjects: Engineering Science (Interdepartmental Program)
• Online Access: http://etd.lsu.edu/docs/available/etd-09022009-114608/

Chlorinated solvent contamination continues to plague sites around the world. In many cases, lower chlorinated daughter products build up and remain in ground waters and soils. A Bio-Filter/Phytobed (BFP) system has been developed to replace a traditional pump and treat technology currently operating at the ReSolve Superfund site in North Dartmouth, MA. Pilot scale testing at the facility displayed a significant acclimation period prior to microbial dechlorination, as well as delayed degradation of chlorinated ethanes. Microcosm studies suggest that acidic conditions, possibly created by the peat mixture used to construct the bio-filter, inhibited bacterial growth. The neutralization of trench pH appeared to coincide with the start of chlorinated solvent degradation in pilot scale studies. In subsequent microcosm studies, lactate, hydrogen, and acetate were added to promote bacterial growth and enhance reductive dechlorination, yet lactate failed to enhance the degradation capabilities of either chlorinated ethenes or ethanes. In an effort to increase the availability of hydrogen, larger concentrations of hydrogen gas in the headspace replaced the lactate. Although the hydrogen eliminated chlorinated ethane lag time, the degradation rates remained lower than desired. However, the addition of acetate successfully stimulated chlorinated ethane degradation and increased degradation rates. Recommendations for the final design include the use of carbon filtration and a two trench BFP system. A life cycle analysis depicting the BFP system as a more sustainable remediation technology as compared to the currently operating pump and treat system is included.