Strategic food waste disposal to improve the C:N ratio and process economy within Danish wastewater treatment plants: process modelling and life cycle assessment

Municipal wastewater treatment (WWT) is a well-established public service that requires expert technical knowledge and good process planning to be cost-effective. One of the key issues of treatment plant operation is the maintenance of optimal carbon to nitrogen ratios, due to the varying composition of influent wastewaters. When these elements are present in imbalanced proportions, the addition of chemical agents or other process control actions might be necessary, thereby increasing operation costs and the risk of process failures. Considering the disposal of domestic food wastes through the sewer network, there is good potential for strengthening this balance and improving process economy, through reduced waste transportation and an increase in local energy recovery. Therefore, the present study aims to investigate how the planned addition of liquid food and source-separated organic household wastes (LFW and SSOHW, respectively) to the WWT network can improve nutrient balances, while reducing plant expenses, environmental impact and human health concerns.