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

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.