Pin-point denitrification for groundwater purification without direct chemical dosing: Demonstration of a two-chamber sulfide-driven denitrifying microbial electrochemical system

Water Research
Sen LinGuanghao Chen

Abstract

The nitrate concentration in groundwater has been increasing over time due to the intensive use of nitrogen fertilizer. Current nitrate removal technologies are restricted by the high operational cost or the inevitable secondary contaminations. This study proposed a two-chamber sulfide-driven denitrifying microbial electrochemical system to denitrify nitrate in its cathode chamber. Instead of conventional organic substrates, sulfide is oxidized in the anode chamber to generate electrons for cathodic denitrification. Long-term performance of this novel system was evaluated over 200 days (100 cycles) of batch-fed operation. With the assistance of anodic microorganisms, sulfide can be directly oxidized to sulfate thus avoiding passivating the anode. Catalyzed by the cathodic microorganisms, complete denitrification was realized with neither nitrite nor nitrous oxide accumulation. Benefiting from the electroautotrophic behavior of the functional microorganisms, high electron utilization efficiencies were achieved, 80% and 85% for the anode (sulfide oxidation) and the cathode (denitrification) respectively. Both observed electrode potentials and microbial analyses revealed that cytochrome c is the crucial electron transfer mediator ...Continue Reading

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