Effects of electric potential and organic loading on the removal of hydrogen sulfide emitted from wastewater sediments using a submerged electrochemical oxidation system

Hydrogen sulfide (H2S), commonly generated by the anaerobic decay of organic substances in wastewater sediments, is a main odorous compound in domestic sewer networks. In this study, a submerged electrochemical oxidation system (SEOS), in which electrodes were applied directly to wastewater sediments, was tested to reduce H2S. To evaluate the SEOS performance, a series of experiments were conducted using a laboratory-scale closed batch reactor and a full-scale manhole under various electric potentials applied to the SEOS and organic concentrations in terms of COD. In the batch test, the concentration of H2S in the headspace dropped to its detection limit within 30 min when an electric potential greater than 10 V was applied. In addition to the H2S reduction, the COD concentration in the liquid phase was gradually reduced due to the electrochemical oxidation of organic contents, and the oxidation-reduction potential rapidly increased to higher than −100 mV. In the full-scale test with a continuous stream of wastewater with high COD concentrations, the concentration of H2S in the headspace decreased to less than 1 ppmv at an applied electric potential of 10 V and a specific power input (SPI) of 1.0 kW/kg-COD. Both the electric potential and SPI were found to be key operating parameters, and these parameters must be carefully selected to achieve both effective H2S removal and high energy efficiency simultaneously. The SEOS may be a feasible alternative for solving odor-related problems in domestic sewer networks.