Full-scale investigation of in-situ iron and alkalinity generation for efficient sulfide control.

Author(s) Pikaar, I.; Flugen, M.; Lin, H.W.; Salehin, S.; Li, J.; Donose, B.C.; Dennis, P.G.; Bethke, L.; Johnson, I.; Rabaey, K.; Yuan, Z.
Journal Water Res
Date Published 2019 Dec 15

Hydrogen sulfide induced corrosion of concrete sewer pipes is a major issue for wastewater utilities globally. One of the most commonly used methods to combat hydrogen sulfide is the addition of ferric chloride. While a reliable and effective method, ferric chloride is acidic causing OH&S concerns as well as alkalinity consumption in sewage. This study investigates, under full-scale field conditions, an alternative method for sulfide control by in-situ electrochemical generation of iron ions using sacrificial iron electrodes. This method concomitantly produces alkalinity through cathodic OH generation, rather than consumption. The gaseous hydrogen sulfide concentrations at the discharge wet well of a real-life rising main (length: ∼1 km in, diameter: 150 mm) decreased from 173 ppm to 43 ppm (90 percentile of peak values), when a current of 0.86 A/m of sewage was applied. The 90 percentile peak HS value was further reduced to 6.6 ppm when the applied current was increased to 1.14 A/m sewage. Moreover, methane generation was almost completely inhibited from 25.3 ± 1.46 mg COD/L to 0.06 ± 0.04 mg COD/L. The overall cell voltage remained constant throughout the experimental period clearly showing the stability of the process. Detailed characterization of the down-stream sewer pipe biofilm revealed the complexity of the iron chemistry as the in-situ produced iron ions undergo transformation into a variety of iron species. Overall, this study demonstrates that in-situ generation of iron and alkalinity is an effective alternative method for hydrogen sulfide control in sewers.

DOI 10.1016/j.watres.2019.115032
ISSN 1879-2448
Citation Water Res. 2019;167:115032.

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