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Arsenic remediation by formation of arsenic sulfide minerals in a continuous anaerobic bioreactor.

ABSTRACT: Arsenic (As) is a highly toxic metalloid that has been identified at high concentrations in groundwater in certain locations around the world. Concurrent microbial reduction of arsenate (As(V) ) and sulfate (SO4 (2-) ) can result in the formation of poorly soluble arsenic sulfide minerals (ASM). The objective of this research was to study As biomineralization in a minimal iron environment for the bioremediation of As-contaminated groundwater using simultaneous As(V) and SO4 (2-) reduction. A continuous-flow anaerobic bioreactor was maintained at slightly acidic pH (6.25-6.50) and fed with As(V) and SO4 (2-) , utilizing ethanol as an electron donor for over 250 d. A second bioreactor running under the same conditions but lacking SO4 (2-) was operated as a control to study the fate of As (without S). The reactor fed with SO4 (2-) removed an average 91.2% of the total soluble As at volumetric rates up to 2.9?mg As/(L?·?h), while less than 5% removal was observed in the control bioreactor. Soluble S removal occurred with an S to As molar ratio of 1.2, suggesting the formation of a mixture of orpiment- (As2 S3 ) and realgar-like (AsS) solid phases. Solid phase characterization using K-edge X-ray absorption spectroscopy confirmed the formation of a mixture of As2 S3 and AsS. These results indicate that a bioremediation process relying on the addition of a simple, low-cost electron donor offers potential to promote the removal of As from groundwater with naturally occurring or added SO4 (2-) by precipitation of ASM.

SUBMITTER: Rodriguez-Freire L

PROVIDER: S-EPMC4729605 | biostudies-literature | 2016 Mar

REPOSITORIES: biostudies-literature

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Arsenic remediation by formation of arsenic sulfide minerals in a continuous anaerobic bioreactor.

Rodriguez-Freire Lucia L Moore Sarah E SE Sierra-Alvarez Reyes R Root Robert A RA Chorover Jon J Field James A JA

Biotechnology and bioengineering 20150918 3

Arsenic (As) is a highly toxic metalloid that has been identified at high concentrations in groundwater in certain locations around the world. Concurrent microbial reduction of arsenate (As(V) ) and sulfate (SO4 (2-) ) can result in the formation of poorly soluble arsenic sulfide minerals (ASM). The objective of this research was to study As biomineralization in a minimal iron environment for the bioremediation of As-contaminated groundwater using simultaneous As(V) and SO4 (2-) reduction. A con ...[more]

PMID: 26333155

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Project description:BackgroundChain elongation forms a new platform technology for the circular production of biobased chemicals from renewable carbon and energy sources. This study aimed to develop a continuous methanol-based chain elongation process for the open-culture production of a new-generation biofuel precursor and potential platform chemical: n-valerate. Propionate was used as a substrate for chain elongation to n-valerate in an anaerobic open-culture bioreactor. In addition, the co-production of n- and iso-butyrate in addition to n-valerate via, respectively, acetate and propionate elongation was investigated.Resultsn-Valerate was produced during batch and continuous experiments with a pH in the range 5.5-5.8 and a hydraulic retention time of 95 h. Decreasing the pH from 5.8 to 5.5 caused an increase of the selectivity for n-valerate formation (from 58 up to 70 wt%) during methanol-based propionate elongation. n-Valerate and both n- and iso-butyrate were produced during simultaneous methanol-based elongation of propionate and acetate. Propionate was within the open-culture preferred over acetate as a substrate with 10-30% more consumption. Increasing the methanol concentration in the influent (from 250 to 400 mM) resulted in a higher productivity (from 45 to 58 mmol C/L/day), but a lower relative product selectivity (from 49 to 43 wt%) of n-valerate. The addition of acetate as a substrate did not change the average n-valerate productivities. Within the continuous bioreactor experiments, 6 to 17 wt% of formed products was methane. The microbial community during all steady-states in both methanol-based elongation bioreactors was dominated by species related to Clostridium luticellarii and Candidatus Methanogranum. C. luticellarii is the main candidate for n-valerate formation from methanol and propionate.Conclusionsn-Valerate was for the first time proven to be produced from propionate and methanol by an open-culture bioreactor. Methanogenic activity can be inhibited by decreasing the pH, and the n-valerate productivity can be improved by increasing the methanol concentration. The developed process can be integrated with various biorefinery processes from thermochemical, (bio)electrochemical, photovoltaic and microbial technologies. The findings from this study form a useful tool to steer the process of biological production of chemicals from biomass and other carbon and energy sources.

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Arsenic remediation by formation of arsenic sulfide minerals in a continuous anaerobic bioreactor.

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Arsenic remediation by formation of arsenic sulfide minerals in a continuous anaerobic bioreactor.

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