Energy decarbonisation of wastewater treatment plants in Murcia- case study

Energy is a critical input for wastewater treatment plants (WWTPs) and a major source of greenhouse gas emissions. In the Region of Murcia, Spain, where precipitation is low and water resources are limited, a significant portion of treated wastewater is reused for agricultural irrigation. This necessitates advanced levels of treatment, which are highly energy intensive. According to ISO 50001 guidelines on Energy Management Systems, it is essential for organisations to identify energy-intensive processes, reduce energy wastage, and implement energy-efficient technologies to improve overall energy performance. In line with this, the current study conducts an energy assessment of two WWTPs, Molina de Segura and Alcantarilla. This assessment, referred to as a Low-Carbon Polygeneration System (LCPS) analysis, includes (i) Evaluation of energy consumption and associated emissions, (ii) Identification of energy-intensive treatment stages and equipment, (iii) Assessment of renewable energy generation from sector-specific sources (e.g., hydropower from wastewater flow and biogas from sludge via anaerobic digestion), and (iv) Evaluation of non-sector-specific renewable energy sources such as solar PV. The study further evaluates the techno-economic and environmental feasibility of these decarbonisation strategies through multiple scenarios that reflect both current and projected future conditions. Solar PV is a viable option for energy generation, whereas hydropower technology remains limited due to the low hydraulic head (less than 1 m). The high investment cost of battery storage also restricts its use for energy storage. These challenges could be mitigated by offering incentives, such as renewable energy subsidies to WWTPs.