Abstract
Pumping groundwater from arsenic (As)-contaminated aquifers exposes millions of people, especially those in developing countries, to high doses of the toxic contaminant. Previous studies have investigated cost-effective techniques to remove groundwater arsenic by stimulating sulfate-reducing bacteria (SRB) to form biogenic arsenian pyrite. This study intends to improve upon these past methods to demonstrate the effectiveness of SRB arsenic remediation at an industrial site in Florida. This study developed a ferrous sulfate and molasses mixture to sequester groundwater arsenic in arsenian pyrite over nine months. The optimal dosage of the remediating mixture consisted of 5 kg of ferrous sulfate, ~27 kg (60 lbs) of molasses, and ~1 kg (2 lbs) of fertilizer per 3785.4 L (1000 gallons) of water. The remediating mixture was injected into 11 wells hydrologically upgradient of the arsenic plume in an attempt to obtain full-scale remediation. Groundwater samples and precipitated biominerals were collected from June 2018 to March 2019. X-ray diffraction (XRD), X-ray fluorescence (XRF), electron microprobe (EMP), and scanning electron microscope (SEM) analyses determined that As has been sequestered mainly in the form of arsenian pyrite, which rapidly precipitated as euhedral crystals and spherical aggregates (framboids) 1–30 μm in diameter within two weeks of the injection. The analyses confirmed that the remediating mixture and injection scheme reduced As concentrations to near or below the site’s clean-up standard of 0.05 mg/L over the nine months. Moreover, the arsenian pyrite contained 0.03–0.89 weight percentage (wt%) of sequestered arsenic, with >80% of groundwater arsenic removed by SRB biomineralization. Considering these promising findings, the study is close to optimizing an affordable procedure for sequestrating dissolved As in industry settings.
Highlights
Arsenic (As) contamination of groundwater is one of the most pervasive health hazards worldwide [1]
Arsenic was measured above the site clean-up standard in 14 of the 23 (61%) of the wells, with the contamination plume likely located in the northwest section of the site (Figure 2a; Table S4)
It was found that untreated groundwater entered the site and increased arsenic in the eastern and southern areas of the site after three months
Summary
Arsenic (As) contamination of groundwater is one of the most pervasive health hazards worldwide [1]. While geogenic arsenic contamination is well known in regions like the Bengal Basin, anthropogenic sources of arsenic contamination, common at industrial and agricultural sites in developed regions, can be a threat to groundwater quality [8,9]. Arsenical herbicides and pesticides have been phased out beginning in the 1980s and barred from use by the U.S.A. Environmental Protection Agency (EPA) in 2009 [12], legacy contamination from industrial manufacturing sites and extensive field applications still pose a threat to groundwater quality today. Environmental Protection Agency (EPA) in 2009 [12], legacy contamination from industrial manufacturing sites and extensive field applications still pose a threat to groundwater quality today Given this dilemma, the development of As-remediation techniques is of high importance world-wide
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