INVESTIGATION OF CO-DIGESTION POTENTIAL OF PRIMARY AND SECONDARY SEWAGE SLUDGE FRACTIONS WITH FOOD WASTE

Abstract: Rapid increase in sewage and sewage sludge production paralel to industrialization and urbanization necessitated spreading of anaerobic digestion technology in the last decade. A special interest found its place as co-digestion of food wastes in anaerobic sludge digesters operating in municipal wastewater plants (WWTPs) in place of landfilling as it provides much faster conversion to energy. Municipal WWTPs are comprised of two fractions as primary settling sludge (rich in protein and fatty matter) and secondary (waste biological) sludge mostly bacterial biomass. Each fraction has different a biodegradability character and a potential for separate anaerobic stabilization exists. Co-digestion of food waste with primary and/or secondary sludge fraction has been gaining an increasing interest and appllication in the last years to increase energy yield in anaerobic sludge digesters operating in municipal WWTPs. This study investigated co-digestion of fruit waste with primary and secondary sludge fractions in paralel to control sequential batch reactors to determine biochemical methane potential and alkalinity addition has been found sufficient to eliminate the negative effect on the co-digestion process.