Electric energy consumption (EEC) in groundwater-based drinking water supply systems: analysis and comparison of seven Italian case studies

Drinking water and wastewater services depend on energy: electric energy consumption (EEC) of this sector amounts to 2–3% of global EEC. The attention of the scientific community and of water utilities about this topic is focused on energy optimization of wastewater treatment plants and pumping stages in drinking water supply systems (DWSSs). However, because of increasingly stringent regulations and because of more and more extended water-source pollution, the need for ‘unconventional’ drinking water treatment systems, which are very energy-intensive, will bring treatment to be a key factor in this scenario. Analyzing EEC in seven full-scale DWSSs, we wanted to control EEC in every single stage of the DWSS (withdrawal, drinking water treatment plant (DWTP) and distribution) and to identify opportunities for reducing energy consumption in DWSS, with a special focus on each drinking water treatment process. The most energy-intensive unconventional treatment turns out to be membrane filtration by reverse osmosis (for which specific consumption per cubic meter of pumped water is equal to 0.243 Wh/m3), whereas the most energy-intensive conventional treatment turns out to be air oxidation (specific EEC from 0.012 to 0.087 kWh/m3). The main strategies for energy conservation can be applied both in management and in the design phase.