Stronger Bacteria, Faster Remediation: Using Nutrients to Achieve Complete Enhanced Reductive Dechlorination (ERD)
Dr. Juan Fausto Ortiz-Medina, Research Associate, EOS Remediation
Enhanced reductive chlorination (ERD) through bioremediation is an effective and affordable approach to remove chlorinated compounds such as perchloroethylene (PCE) and trichloroethylene (TCE) from groundwater. ERD is typically achieved by injecting a carbon substrate to stimulate growth of dechlorinating bacteria, either native or added through bioaugmentation. While this approach is successful at some sites, lower-than-expected dechlorination rates and undesirable accumulation of intermediate daughter products such as cis-dichloroethylene (cDCE) and vinyl chloride (VC) can occur if other macro- and micronutrients are not present in adequate amounts. In this presentation, we will review the importance of adding an optimal amount of nutrients, such as fixed nitrogen and vitamin B12, to achieve complete ERD and further conversion of cDCE and VC to ethene. To further illustrate this importance, we will present results from a field site where bioaugmentation, along with the addition of emulsified vegetable oil (EVO) and a pH buffer stimulated fast PCE reduction to cDCE, but further conversion to ethene was limited. Pilot tests showed that nutrient addition resulted in a rapid decline in cDCE and VC, with concentration of dechlorinating bacteria increasing from 3 to 40,000 copies/mL and VC reductase genes increasing from 0.2 to 1,460 copies/ml in 2 months. Full-scale injection of nutrient supplements reduced cDCE and VC levels by over 99%, leading to ethylene detection throughout the site. Therefore, the concentration of nutrients on site must be considered to attain complete ERD when biostimulation and bioaugmentation strategies are implemented.
Dr. Fausto Ortiz-Medina joined EOS Remediation in 2020. His responsibilities as Research Associate include the research and development of new technologies for in situ remediation, performance analysis of implemented treatments, and quality testing of current products to guarantee their expected effectiveness. He holds a bachelor’s degree in Biotechnology Engineering from Instituto Tecnologico y de Estudios Superiores de Monterrey (ITESM, Mexico), a MS in Environmental Science and Engineering from King Abdullah University of Science and Technology (KAUST, Saudi Arabia), and a PhD in Civil Engineering from North Carolina State University (NCSU, USA).