Evaluation of a combined treatment to control gaseous phase H2S in sewer

•Designed laboratory scale reactor system simulated the actual sewer system well.•Sulphate Reducing Bacteria (SRB) biofilm was grown on top of the concrete surface.•The combination of pH control and ferrous chloride dosing was better than one alone.•Measured and theoretical H2S (g) concentration were significantly different at pH > 8.

Hydrogen sulphide (H2S) generation in sewer systems is a serious problem. A cost effective means of controlling sewer corrosion has been tested in a laboratory scale sewer model which includes a concrete surface. Traditionally two most practised methods are pH adjusted to >10.5 and ferrous chloride addition at [Fe2+]: [S2−] of 1-1.3:1. When the combined methods were tested in a laboratory scale sewer system, the amount of ferrous chloride required was only at [Fe2+]: [S2−] of 0.1:1 and pH∼8. Further experiments confirmed some oxygen in the water/air space is necessary to achieve an efficient reduction, but the oxygen present in the water (∼1 mg/L) of gravity sewer was found sufficient. This provides a cost-effective means of H2S reduction in the gaseous phase, although testing with real sewer is needed.

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