(572a) Biological Treatment of Perchlorate by Autotrophic Organisms Attached to Zero-Valent Iron

In the past decade, there has been increasing concerns about the contamination of groundwater with novel pollutants. These include gasoline compounds such as methyl tert-butyl ether (MTBE) and tert-butanol (TBA), inorganics such as perchlorate, antibiotics and endocrine disruptors, or other toxics such as 1,4 dioxane, N-nitrosodimethylamine (NDMA), polybrominated diphenyl ethers (PBDEs), etc. In many cases, these compounds are present a very low concentrations, and effective treatment presents many technological and economical challenges. Of the different options, biological treatment is often a very promising alternative to conventional treatment. It usually converts the contaminants to harmless compounds without generating secondary contaminants or other by-products. Biological treatment requires low energy input, it is often environmentally friendly and fits well in the need for sustainable development. We recently developed and demonstrated a new treatment process for the treatment of perchlorate (ClO4-) contaminated groundwater. Treatment relies on the reduction of ClO4- by autotrophic organisms attached to zero-valent iron (ZVI). The process can be conducted in an ex-situ vessel (pump and treat) or possibly below grade in a biobarrier setup. As iron corrodes, hydrogen is slowly released and used as a source of energy for the attached perchlorate-reducing bacteria. The effects of selected parameters (flow, perchlorate concentration, inoculum, etc.) on the process was investigated. Effective treatment of perchlorate was observed at liquid residence times as low as 15 min. In most cases, non-detect (i.e., <3 ppb) effluent concentrations were observed. Closure of the chloride balance was accomplished. Fundamental and applied aspects of the process will be presented, and implications for field treatment will be discussed.