Opportunities to improve energy use in urban wastewater treatment: a European-scale analysis

Wastewater treatment is an essential public service that has a major impact on energy use in the urban water cycle, so that it is receiving increasing attention in the growing area of studies on the Water-Energy Nexus. Understanding the current energy use for wastewater is an essential step to design reliable policies to promote a more efficient use of resources. This paper develops a pan European estimation of electricity use for the treatment of wastewater that is based on a single-plant dataset covering the whole continent. Prediction of electricity use has been performed after the calibration of a statistical model that uses minimal but robust parameters and that accounts for economies of scale. Different scenarios of improvements of energy use efficiency have been investigated to understand the possible reductions in electricity consumption at the continental scale. The overall wastewater treatment plant (WWTP) electricity use in Europe (only plants with no less than 2,000 PE have been considered) was estimated at 24,747 GWh per year that is about the 0.8% of the electricity generation in the EU-28. Small plants (less than 50,000 PE) represent almost 90% of the total, but process only 31% of the PE, while they absorb 42% of electricity use. Plants from mid to very large size, being only the 10% of the plants, process about 70% of the PE with 58% of the total electricity use. If all plants that use more than the current average were shifted to the average value, the saving would be slightly more than 5,500 GWh/year. With highly stringent targets of efficiency improvement, saving of about 13,500 GWh/year could be expected. Further considerations on the emerging role of WWTPS as energy and material producer are finally discussed.JRC.D.2-Water and Marine Resource