Electrochemical caustic generation from sewage

• Published in: Electrochemistry communications 2011-11, Vol.13 (11), p.1202-1204
• Main Authors: Pikaar, Ilje, Rozendal, René A., Yuan, Zhiguo, Rabaey, Korneel
• Format: Article
• Language: English
• Subjects: Applied sciences; Caustic; Chemistry; Electrochemistry; Exact sciences and technology; General and physical chemistry; Kinetics and mechanism of reactions; Other wastewaters; Polarity switching; Pollution; Sewage; Sewer corrosion; Wastewaters; Water treatment and pollution
• ISSN: 1388-2481; 1873-1902
• DOI: 10.1016/j.elecom.2011.08.044

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/cm 2. 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. ► Caustic was successfully produced from sewage at a coulombic efficiency of 53±8%. ► Polarity switching was successful to overcome problems with scaling. ► The use of spacers did not increase the caustic recovery.