Determination of combustibil sulfur content in sewage sludge

Large amounts of sewage sludge are produced at waste water treatment plants and its disposal is an environmental problem. In this context and in accordance with the European Commission communication on the role of waste-to-energy in the Circular Economy, one of the objectives of Romania Waste Management-Strategy Plan for municipal waste, is incineration of the solid waste in dedicated incinerators, with energy recovery. When the incineration of the sewage sludge with energy recovery is chosen as the final path of disposal, the optimal energy gain, have to be correlated with the limits provided of the legislation in force for the air pollution emissions and with the quantities of the waste which must be minimized. The presence of sulfur in sewage sludge has significant implications in incineration processes, due to its transformation at high temperature into SO2 which is released into the atmosphere, and on the other hand, there is a risk of high-temperature corrosion of the pipes and pumps, depending of the molar ratio 2S/Cl. The paper presents a study on the determination of the technological forms of sulfur and total sulfur in sewage sludge to be incinerated. The results obtained show that the total sulfur is mostly represented by the combustible sulfur which is in a proportion of about 88% and the rest of about 12 % is the sulfur remaining in the ash.