Adapting a denitrifying biocathode for perchlorate reduction

Abstract

Perchlorate is widely used as a propellant in the aerospace and defense industries, and is of environmental concern due to its high mobility and inhibiting effect on thyroid function. An ideal treatment approach is bioreduction to chloride via dissimilatory perchlorate-reducing bacteria (PCRB). PCRB are ubiquitous in the environment, and are mainly facultative anaerobes and denitrifiers. Previous research suggests that PCRB may grow using a cathode as an electron donor, although this research was performed in a half cell with exogenous electron shuttles. We investigated a functioning MFC with a denitrifying biocathode for perchlorate reduction, as a means to confirm the existence of biocathode-utilizing PCRB and the possibility of perchlorate remediation without added shuttles. The biocathode was initially run with 20 mgN/L nitrate. The perchlorate concentration was increased stepwise from 0.1 mg/L to 20 mg/L, while the nitrate concentration was decreased from 20 mgN/L to 5 mgN/L. The maximum perchlorate removal was 12 mg/L-d, contributing 64% to the 0.28 mA produced by the cell. Given the lack of soluble electron donor in the medium, the extent of perchlorate reduction, and the improvement of perchlorate reduction over time, these tests strongly suggest PCRB are utilizing the cathode as an electron donor without exogenous electron shuttles.

Description of the novel perchlorate-reducing bacteria Dechlorobacter hydrogenophilus gen. nov., sp. nov. and Propionivibrio militaris, sp. nov.

“…BER technology (Thrash et al 2007) and hydrogen-based reactors (Miller and Logan 2000; Nerenberg et al 2002) are examples of treatment alternatives that have already enriched for novel organisms. A remarkable number of BER options exist (Thrash and Coates 2008), and new reactors using these as well as the application of microbial fuel cell technology (already shown capable of stimulating nitrate-reducing microorganisms (Clauwaert et al 2007)) for perchlorate bioremediation (Shea et al 2008) should lead to even more disparate isolates.…”

Bioelectrochemical systems for efficient recalcitrant wastes treatment

“…36,62,76,79,80 Similarly, the electrochemically active microbial consortia initially inoculated from municipal wastewater treatment plants and enriched with acetate as the electron donor can also change its composition and be adaptive to another contaminant. These results showed the bacterial diversity among electrochemically active microbial consortia as well as the bacterial various pathways for the degradation of different recalcitrant substances, 55,62,81,82 although in another case the dominant species were nearly unchangeable with the shift of substrates. 69 Thus, analysis and comparison of the phylogenetic diversity of the microorganisms within complex BESs is necessary to provide a significant insight into community dynamics which significantly affect the performance of BESs.…”

Enhanced nitrogen removal in bio-electrochemical systems by pH control

“…Recently, there has been an increased interest in replacing abiotic cathodes with biocathodes in which living microorganisms enhance the reduction catalysis (He and Angenent 2006). With regard to the multiplicity of the possible bacterial reduction reactions, several types of biocathodes with different types of oxidants have successfully been demonstrated in microbial fuel cells or microbial electrolysis cells ranging from O 2 reduction (Clauwaert et al 2007b;Rabaey et al 2008) and denitrification (Clauwaert et al 2007a;Gregory et al 2004;Virdis et al 2008) to dechlorination and H 2 evolution (Aulenta et al 2008;Rozendal et al 2008a;Shea et al 2008). Little is known about the microbiology in biocathodes and how the biocatalysts retrieve electrons from the cathode (Clauwaert 2009;He and Angenent 2006).…”