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Abstract: Accurate and reliable predictions of sulfide production in a sewer system greatly benefit formulation of appropriate strategies for optimal sewer management. Sewer systems, rising main systems in particular, are highly dynamic in terms of both flow and wastewater composition. In order to get an insight in sulfide production as a response to the dynamic changes in sewer conditions, several measurement campaigns were conducted in two rising mains in Gold Coast, Australia. The levels of various sulfur species and volatile fatty acids (VFAs) were monitored through hourly sampling for periods ranging from 8 to 29h. The results of these field studies showed large temporal as well as spatial variations in sulfide generation. A dynamic sewer model taking into account the hydraulics and the biochemical transformation processes was formulated and calibrated and validated using the data collected during the four measurement campaigns at the two sites. The model was demonstrated to reasonably well describe the temporal and spatial variations in sulfide, sulfate and VFA concentrations. Application of the model was illustrated with a case study aimed to optimize oxygen injection to one of the two mains studied, which is being used as a means to control sulfide production on this site. The model predicted that, moving the current oxygen injection point to a location close to the end of the sewer line could achieve the same degree of sulfide control with only 50% of the current oxygen use. This study highlighted that the location at which oxygen is injected plays a major role in sulfide control and a dynamic model could be used to make a proper choice of the location. [Copyright &y& Elsevier]

Abstract: Controlling sulfide (H2S) production and emission in sewer systems is critical due to the corrosion and malodour problems that sulfide causes. Chemical dosing is one of the most commonly used measures to mitigate these problems. Many chemicals have been reported to be effective for sulfide control, but the extent of success varies between chemicals and is also dependent on how they are applied. This industry survey aims to summarise the current practice in Australia with the view to assist the water industry to further improve their practices and to identify new research questions. Results showed that dosing is mainly undertaken in pressure mains. Magnesium hydroxide, sodium hydroxide and nitrate are the most commonly used chemicals for sewers with low flows. In comparison, iron salts are preferentially used for sulfide control in large systems. The use of oxygen injection has declined dramatically in the past few years. Chemical dosing is mainly conducted at wet wells and pumping stations, except for oxygen, which is injected into the pipe. The dosing rates are normally linked to the control mechanisms of the chemicals and the dosing locations, with constant or profiled dosing rates usually applied. Finally, key opportunities for improvement are the use of mathematical models for the selection of chemicals and dosing locations, on-line dynamic control of the dosing rates and the development of more cost-effective chemicals for sulfide control. [Copyright &y& Elsevier]