Modeling the impact of food wastes on wastewater treatment plants

Food waste (FW) enriched with readily biodegradable organics can enhance biological nutrient removal (BNR), and biogas production. This study conducted extensive wastewater treatment simulations using BioWin software to predict the impact of food waste on nutrient removal, biogas generation, and energy balance. A total of 114 scenarios were tested to simulate different treatment technologies i.e. conventional activated sludge, Modified Ludzack-Ettinger (MLE), anaerobic-anoxic-aerobic (A2O), Bardenpho, and 2nd generation BNR technologies. The simulations also included sidestream treatment for nitrogen removal, as well as mainstream partial nitrification based on BNR. The results showed that FW addition enhanced nitrogen removal and decreased effluent nitrogen for BNR processes by 3.6-7.9 mg/L for MLE, 0.6-1.3 mg/L for A2O, and 1-2.3 mg/L for Bardenpho. In addition, FW addition decreased net operational cost by 26%-63% for BNR processes operating at mainstream conventional dissolved oxygen (DO) of 2 mg/L, 24%-78% for partial nitrification system, 29%-54% for sidestream, and 23%-76% for sidestream with mainstream partial nitrification process. The total net energy benefit considering both the net change in aeration energy and methane energy for a typical 37,854 m³/d or 10 MGD plant increased with FW addition by 3300-7900 kWh/d with a variation between BNR types, due to a substantial increase in methane production. Carbon diversion scenarios showed that the higher primary treatment efficiencies decreased the net operational cost and increased net energy gain.