Water-Energy Nexus: A Pathway of Reaching the Zero Net Carbon in Wastewater Treatment Plants

The water-energy nexus, together with the need for sustainable management of these interconnected resources, has attracted growing attention from the scientific community. This paper focuses on this nexus from the point of view of the energy that is required by wastewater treatment plants, which are intensive energy consumers and major emitters of greenhouse gases. The main objective of the study is to investigate the possible use of a wastewater plant’s internal chemical, potential, and kinetic energy, and the addition of external renewable technologies with a view to achieving clean energy consumption and reducing greenhouse gas emissions. For this purpose, an analysis is made of the feasibility of introducing alternative technologies—anaerobic digestion, hydraulic turbines, wind turbines, and photovoltaic modules— to meet the plant’s energy needs. The plant chosen as case study (Jinamar plant, Canary Islands, Spain) has an energy consumption of 2956 MWh/year, but the employed methodological framework is suitable for other plants in locations where the renewable energy potential has previously been analyzed. The results show that a renewable energy production of 3396 MWh/year can be obtained, more than enough to meet plant consumption, but also confirm the need for an energy storage system, due to seasonal variability in energy resource availability. In terms of climate change mitigation, the emission of 2754 tons/year of greenhouse gases is avoided. In addition, the economic viability of the proposed system is also confirmed.