100% renewable wastewater treatment plants: Techno-economic assessment using a modelling and optimization approach

Renewable energies are being given increasing attention worldwide, as they are able to reduce the dependence on depletable fossil fuels. At the same time, wastewater treatment is known to be a significantly energy-intensive sector, which could potentially exploit renewable energies conversion in different forms. This study investigated the feasibility to design high renewable share wastewater treatment plants through dynamic simulations and optimization, aiming to move towards greener and energy-wise wastewater remediation processes. The main aim of the work was achieved by integrating photovoltaic systems with wind turbines, multi-energy storage technologies, i.e., batteries and hydrogen systems, and reverse osmosis tertiary treatment to absorb the power production surpluses. It was supposed that, in the newly proposed scenario, most of the plant electricity need would be covered by renewable energy. The optimization problem was multi-objective and found the trade-off solutions between minimizing the net present cost and maximizing the renewable share. In the first part of the study, the model was developed and applied to a medium-scale Italian municipal wastewater treatment plant. Model generalization was successively accomplished by applying the model to different locations and plant scales across the world. For all the investigated scenarios and cases, the optimal system integration was to design a renewable and storage system with a renewable share of 70%, corresponding to the lowest net present cost. The developed model is highly flexible and can be applied to other relevant case studies, boosting for a more sustainable wastewater treatment sector, enhancing at the same time local renewable energy conversion.