Bioelectrochemical denitrification on biocathode buried in simulated aquifer saturated with nitrate-contaminated groundwater

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Abstract
Nitrate contamination in aquifers has posed human health under high risk because people still rely on groundwater withdrawn from aquifers as drinking water and running water sources. These days, bioelectrochemical technologies have shown a great number of benefits for nitrate remediation via autotrophic denitrification in groundwater. This study tested the working possibility of a denitrifying biocathode when installed into a simulated aquifer. The reactors were filled with sand and synthetic groundwater at various ratios (10, 50, and 100 %) to clarify the effect of various biocathode states (not-buried, half-buried, and fully buried) on nitrate reduction rate and microbial communities. Decreases in specific nitrate reduction rates were found to be correlated with increases in sand/medium ratios. A specific nitrate reduction rate of 322.6 mg m−2 day−1 was obtained when the biocathode was fully buried in an aquifer. Microbial community analysis revealed slight differences in the microbial communities of biocathodes at various sand/medium ratios. Various coccus- and rod-shaped bacteria were found to contribute to bioelectrochemical denitrification including Thiobacillus spp. and Paracoccus spp. This study demonstrated that the denitrifying biocathode could work effectively in a saturated aquifer and confirmed the feasibility of in situ application of microbial electrochemical denitrification technology.

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