The use of steelmaking slag for sewage sludge stabilization

The objective of this work was the examination of the stabilization of sewage sludge by the addition of a steel slag (slag), and the investigation of the effect of stabilization time on the properties of the produced mixtures. The used slag was a by-product from steelmaking refining processes in ladle furnaces, the steelmaking slag that presented high calcium content. Four samples were prepared by mixing the slag and sewage sludge in various ratios (2.5-20% on a dry basis) and the mixtures were stabilized for a period of 48 d. Monitoring of the mixtures properties was carried out for the determination of the pH, the moisture content, the pathogens removal rate and the mineralogical phases present. The addition of slag resulted in the increase of mixture pH exceeding 12, the increase of total solids content and the reduction of volatile percentage; these effects were more pronounced at the highest slag dosage. In addition, effective pathogens removal was observed in mixtures containing more than 10% slag, from the early time of mixing, due to the high pH values of the mixtures. It was concluded that this method might have a high potential for the efficient management of two solid waste streams.