Enhanced self-powered system with graphene oxide modified electrode for simultaneous remediation of nitrate-contaminated groundwater and river sediment

Abstract

Simultaneous in situ remediation of malodorous organic sediment and nitrate-contaminated groundwater was achieved with a novel, enhanced, self-driven three-chamber bio-electrochemical system with Graphene Oxide (GO) modified electrodes. It has been successfully improving the electron transfer efficiency and self-purification ability by the special configuration combining surface water, sediment with underground water. The upper part can be regarded as a Sediment Microbial Fuel Cell (SMFC). The organic sediment serves as available carbon source to provide electrons for the microbes coated on the anode instead of potential pollutants. The lower part is the Biofilm Electrode Reactor (BER). Electrons were synchronously obtained from the loaded biofilm to reduce nitrate. The electricity generated from the upper part was applied directly to the lower part as electrical stimulation to enhance bacterial denitrification of the system. The electron conduction efficiency was further improved by graphene oxide modifying. With a maximum power density of 14.21 W/m2, as well as the voltage outputs ranging from 700 mV to 900 mV, nitrate removal was accelerated with less accumulation of intermediates compared with the controls without graphene oxide. The maximum output power was increased by 1.5 times and the nitrate removal efficiency (in 10 h) was increased from 89.13 ± 1.4% to 99.9 ± 0.1% after the modification. The organic matter in the sediment decreased by 78% after 270 days simultaneously. Sequencing of the microbial community showed that Geobacter and Anaerolinina were enriched in the anode. And theα-proteobacteria were enriched in the four experimental groups and had a good effect on nitrate removal especially in the C-GO-SSG system (Carbon felt anode-Graphene Oxide Modified cathode equipped Surface-water Sediment and Groundwater System) after 270 days operation. These results demonstrate that the C-GO-SSG system can be further used to remediation of sediment and groundwater with improved efficiency.