Biological Perchlorate Reduction in Packed Bed Reactors Using Elemental Sulfur

Abstract

Sulfur-utilizing perchlorate (ClO 4 -)-reducing bacteria were enriched from a denitrifying wastewater seed with elemental sulfur (S 0 ) as an electron donor. The enrichment was composed of a diverse microbial community, with the majority identified as members of the phylum Proteobacteria. Cultures were inoculated into bench-scale packed bed reactors (PBR) with S 0 and crushed oyster shell packing media. High ClO 4 concentrations (5-8 mg/L) were reduced to <0.5 mg/L at an empty bed contact time (EBCT) of 13 h. Low ClO 4concentrations (60-120 µg/L), more typical of contaminated groundwater sites, were reduced to <4 µg/L at an EBCT of 7.5 h. PBR performance decreased when effluent recirculation was applied or when smaller S 0 particle sizes were used, indicating that mass transfer of ClO 4 to the attached biofilm was not the limiting mechanism in this process, and that biofilm acclimation and growth were key factors in overall reactor performance. The presence of nitrate (6.5 mg N/L) inhibited ClO 4 reduction. The microbial community composition was found to change with ClO 4availability from a majority of Beta-Proteobacteria near the influent end of the reactor to primarily sulfur-oxidizing bacteria near the effluent end of the reactor.

The Family Helicobacteraceae

“…It is the type strain of the only species within this genus. Sequences with high homology to S. kujiense have also been detected in the ironand sulfur-rich freshwater nature reserve De Bruuk in The Netherlands (Haaijer et al 2008), an Athabasca oil sands reservoir in western Canada containing severely biodegraded oil (Hubert et al 2012), meromictic lake sediments (Nelson et al 2007), chemoclines (Hubert et al 2012), sulfidic caves and springs (Porter and Engel 2008), anoxic bottom waters of a volcanic lake in Iceland, a water well field adjacent to the North Saskatchewan River in Canada (Medihala et al 2012a), and other autotrophic denitrification conditions (Sahu et al 2009;Zhao et al 2011).…”

Simultaneous removal of perchlorate and nitrate in a combined reactor of sulfur autotrophy and electrochemical hydrogen autotrophy

“…Although H 2 is a good energy substrate for ClO 4 À and NO 3 À reduction, it is difficult to handle in bulk quantities and is publicly perceived to represent a significant disaster threat due to its inherent explosive nature. Granular sulfur (S 0 ) in packed bed bioreactors has been successfully used as an electron donor in the autotrophic reduction of ClO 4 À and NO 3 À [20, [23][24][25][26]. As granular S 0 is insoluble in water, it can provide a slow-release supply of electron on demand and offer low expense cost as well as low maintenance cost.…”

“…As granular S 0 is insoluble in water, it can provide a slow-release supply of electron on demand and offer low expense cost as well as low maintenance cost. The stoichiometric equations for the S 0 autotrophic reduction of ClO 4 À and NO 3 À are respectively shown as follows [24,26] …”

Autotrophic perchlorate reduction kinetics of a microbial consortium using elemental sulfur as an electron donor

“…The S 0 pellets as the electron donor can eliminate the issues associated with organic residuals, provide a slowly released supply of electron on demand, offer lower expense cost as well as lower maintenance cost, and produce little excess biomass. Batch experiments and packed-bed reactors utilizing S 0 as the electron donor have been proven to be efficient for perchlorate reduction (Boles et al 2012;Ju et al 2007;Sahu et al 2009). As we all know, the kinetic parameters of microbial perchlorate reduction are essential to design biological treatment systems, as well as to predict and evaluate their performance.…”