Removal of Perchlorate from Ground Water by Hydrogen‐Utilizing Bacteria

Abstract

An autotrophic consortium of bacteria, utilizing hydrogen and bicarbonate as electron and carbon sources, respectively, for the reduction of perchlorate has been enriched. The efficiency of this consortium for perchlorate reduction in a packed‐bed bioreactor is described. The use of hydrogen as an electron source for microbial biodegradation of pollutants in a packed‐bed bioreactor is advantageous because hydrogen does not promote vigorous biomass growth, resulting in less clogging of the system, and hydrogen gas reduces the need for post‐reactor water cleanup. The consortium, comprised of four bacteria, was capable of removing nitrate and perchlorate simultaneously from mineral salts medium in a batch culture. A 120‐mL bioreactor was designed to test the capacity of the consortium to remove perchlorate in a flow‐through system. At a flow rate of 1 mL min−1, perchlorate levels naturally occurring in San Gabriel Valley ground water (0.740 mg L−1) were completely removed to less than 0.004 mg L−1, which is the detection limit. However, as the flow rate was increased, the removal efficiency decreased. Factors affecting the rate of perchlorate removal included nonuniform distribution of biomass in the column, unstable pH of the ground water, and limited delivery of hydrogen to the bacteria. This bioreactor also completely removes perchlorate from ground water at a flow rate of 1 mL min−1 without an added carbon source, presumably using the bicarbonate naturally present in the ground water.

Microbial Degradation of Perchlorate: Principles and Applications

“…Perchlorate degradation has also been achieved in bioreactors using only inorganic amendments. These reactors are sustained by hydrogen gas delivered by pressurization, gas transfer across liquid films, or synthetic membranes (Giblin et al, 2000b;Miller and Logan, 2000;Nerenberg et al, 2002). These hydrogen-based technologies are promising technologies for water treatment because less biomass is produced by autotrophic processes than heterotrophic processes.…”

“…A 120-mL bioreactor packed with Celite R-635 (Celite Corporation, Lompoc, CA) was used to degrade perchlorate with hydrogen (Giblin et al, 2000b). The autotrophic consortium of bacteria was fed a pressurized water stream containing dissolved hydrogen and bicarbonate.…”

Chemolithotrophic perchlorate reduction linked to the oxidation of elemental sulfur

“…Most perchlorate respiring bacteria (PRB) utilize simple organic substrates such as acetate as the electron-donating substrates . Several PRB have been shown to use inorganic electron donors such as H 2 (Giblin et al, 2000;Logan and LaPoint, 2002;Zhang et al, 2002), sulfide (Achenbach et al, 2001;Bruce et al, 1999), and Fe(II) (Achenbach et al, 2001;Bruce et al, 1999).…”

“…Residual organic matter resulting from organic substrate additions can stimulate bacterial growth in water distribution systems and contribute to the formation of disinfection byproducts during chlorination. To overcome these problems, chemolithotrophic perchloratereducing bioreactors utilizing H 2 as an electron donor have been proposed (Giblin et al, 2000;Logan and LaPoint, 2002;Miller and Logan, 2000;Nerenberg and Rittmann, 2004).…”

Reduction of Perchlorate and Nitrate by Microbial Communities in Vadose Soil

“…Although perchlorate is persistent in the environment, studies have proven microorganisms can reduce perchlorate, an electron acceptor, to innocuous chloride and oxygen under anaerobic conditions (5,8,12,16,18,21,22,26,27,36,38,40). A widely accepted perchlorate-reducing pathway (26) All previously isolated perchlorate-reducing bacteria belong to Proteobacteria (8,12,18,21,26,27,36,37,40).…”