Ferric Oxide-Containing Waterworks Sludge Reduces Emissions of Hydrogen Sulfide in Biogas Plants and the Needs for Virgin Chemicals

Ferric oxide-containing waterworks sludge can be used to reduce the formation of hydrogen sulfide during anaerobic digestion. The ferric compound is reduced biochemically in digester and forms insoluble pyrite sludge. Virgin chloride often solve problem. Since 2013, Sydvatten AB has supplied a growing number digestion plants Sweden with ferric-containing dewatered derived from drinking water treatment plant Ringsjöverket limit sulfide. At waterworks, added enhance coagulation organic matter source water. formed this process landfilled, but also recycled biogas production order decrease concentration. In study, use for removal digesters was technically economically evaluated via case studies 13 full-scale Sweden. Compared fresh chloride, operational costs are by up 50% using quality high its content metals low or very low, especially when compared requirements different certification standards biosolid reuse applied addition containing iron dissolved good alternative producing biogas. It one step closer circular economy, as replacing virgin chemicals by-product saves energy materials reduces carbon footprint waterworks.