MANAGEMENT OF PERCHLORATE CONTAMINATION USING GASEOUS ELECTRON DONOR TECHNOLOGY

Perchlorate has been widely used as an oxidizer in rocket fuel and has potential human health effects associated with the interference of iodide uptake in the thyroid gland. Due to its persistence and high solubility in the environment, perchlorate contamination is long-term and extremely difficult to manage. While ex-situ remediation technologies such as excavation, bioremediation, thermal treatment, and soil washing have been proven capable of treating perchlorate-contaminated shallow or saturated soil, few techniques have been identified as effective long-term solutions for perchlorate contamination in the vadose zone. Gaseous electron donor injection technology (GEDIT) is an innovative in situ bioremediation technique that involves injection of gaseous electron donors into the soil to stimulate anaerobic bioremediation of perchlorate. In our studies, bench-scale microcosm tests and pilot studies were conducted at former munitions manufacturing sites to demonstrate GEDIT for in situ bioremediation of perchlorate in vadose zone soil. Hydrogen and liquefied petroleum gas (LPG) were chosen as the primary electron donors in these tests. The tests were performed to investigate the impacts of electron donor dosages, moisture contents, and soil types on the success of GEDIT. Results indicate significant perchlorate degradation under many conditions. In addition to perchlorate reduction, the results also showed that GEDIT stimulated the biological degradation of nitrates and can potentially stimulate degradation of chromium (VI), uranium and technetium. The results of these studies and implications for full-scale application will be discussed.