The use of food waste as a carbon source for on-site treatment of nutrient-rich blackwater from an office block

Abstract

ABSTRACTWastewater from office blocks is typically dominated by blackwater and is therefore concentrated and nutrient-rich. A pilot plant was operated for 260 days, receiving 300 L d−1 of wastewater directly from an office building to determine whether nutrient removal could be achieved using food waste (FW) as a supplemental carbon source. The pilot plant consisted of a 600 L prefermenter and a 600 L membrane bioreactor that was operated as a sequential batch reactor in order to cycle through anoxic, anaerobic and aerobic phases. The influent wastewater Chemical Oxygen Demand (COD)/N/P was, on average, 1438/275/40 mg L−1, considerably higher than typical municipal wastewater. Treatment trials on the wastewater alone showed that the COD was only marginally sufficient to exhaust nitrate, and initiate anaerobic conditions required for phosphate removal. The addition of 15 kg d−1 of macerated FW increased the average influent COD/N/P concentrations to 20,072/459/66 mg L−1. The suitability of FW as a carbon source was demonstrated by denitrification to NOx-N concentration of <1 mg L−1 during the biological nutrient removal (BNR) cycles. N removal was limited by nitrification. FW also induced the anaerobic phase within the BNR cycles necessary for P removal. The final average COD (non-recalcitrant)/N/P effluent concentrations under FW supplementation were 7/50/13 mg L−1 which equates to 99%, 89% and 80% COD/N/P removal, respectively, meeting the highest nutrient removal efficiency standards stipulated by state jurisdictions for on-site systems in the USA.