Energy consumption in anaerobic and aerobic based wastewater treatment plants in Italy

The aim of this study is to carry out an experimental investigation on electricity consumption in wastewater treatment plants in Italy based on aerobic and anaerobic digestion wastewater treatment plants (WWTP). The data refer to plants managed by two major water resources management companies in Italy, Hera and Acquedotto Pugliese (AQP). The survey makes use of statistical tools for data analysis of 202 urban wastewater treatment plants. In order to extend the reliability of the survey, electricity consumption data were analysed through three specific energy demand indicators: kWh/m(3), kWh/PE.year, kWh/kgCOD(removed) referred to each plant. The results show that anaerobic systems are advantageous in terms of electricity consumption per m(3) as they achieve more than 50% saving with values ranging from 1.02 kWh/m(3) for aerobic plants, instead of 0.43 kWh/m(3) for the anaerobic ones. Differences have been found in terms of anaerobic digestion efficiency between the data concerning the plants in northern Italy - Hera Company with an average of 0.33 kWh/m(3)- and those in Apulia - AQP company with an average of 0.53 kWh/m(3). Aerobic systems showed more energy consumption also for HERA-managed WWTP. If anaerobic digestion were implemented on all the AQP WWTP, energy savings should be of approximately 16% and approximately 42% if related to HERA anaerobic-based WWTP average performance.