Optimization of the wastewater treatment plant: From energy saving to environmental impact mitigation.

This paper outlines a multi-objective, integrated approach to analyze various possibilities for increasing energy efficiency of the largest Italian wastewater treatment plant (WWTP) at Castiglione Torinese. In this approach, wastewater and sludge treatment units are thoroughly investigated to find the potential ways for improving the energy efficiency of the system. Firstly, a multi-step simulation-based methodology is proposed to make a full link between treatment processes and the energy demand and production. Further, a scenario-based optimization approach is proposed to find the nondominated and optimized performance of the WWTP. The results prove a potential to save up to 5000 MWh of the annual energy consumption of the plant, in addition to improve the effluent quality through operational changes only. Even for what concerns the sludge line a model was proposed for the optimization of the energy recovery from the processes that in a WWTP are devoted to the management of sewage sludge. The obtained results show that the introduction of an advanced thickening stage and sludge pre-treatment would have a positive impact on the energy and greenhouse gas balance of the plant.