Electrochemical caustic generation from sewage

Sewer corrosion caused by hydrogen sulfide generation represents a major issue in sewer management. One commonly used approach for mitigation is the periodic dosing of caustic to the sewer. This creates elevated pH levels that inactivate/kill sulfate reducing bacteria (SRB) present in the biofilms on the sewer pipe. In this study, we investigated the in-situ electrochemical generation of caustic from sewage. The average coulombic efficiency for caustic generation was 53 ± 8% (n = 10) at a current density of 10 mA/cm². The average required cell voltage input was 5.2 ± 0.7 V. Over time, this voltage increased due to a membrane fouling associated increase of the ohmic resistance of the cell. Switching the polarity of the electrodes every four hours was effective to control this fouling and thus retain a stable voltage requirement. This process constitutes a promising reagent-free method for sulfide abatement in sewers.