Dealing with hydrogen sulfide induced problems downstream of sewer rising mains

The problems that arise from hydrogen sulfide formation in sewer rising mains are often dealt with by adding chemicals. The most commonly used chemicals are sodium hydroxide and magnesium hydroxide, ferric (or ferrous) chloride, calcium nitrate and oxygen. As there is a lack of tools to evaluate and compare dosing strategies, it is hard to identify the most appropriate dosing chemical in terms of investment and operating costs. As a consequence, chemical selection is often done ad-hoc. In this study, the average dosing costs (operating and capital) of these chemicals is assessed by simulations with a dynamic mathematical model, describing the transformations of sulfide, carbon and nitrogen in a sewer rising main. Based on the results of the simulations, and other parameters, a systematic approach to selecting dosing products for sewer rising mains is outlined.