Towards Energy Self-Sufficiency in Municipal Wastewater Treatment Plants

Wastewater treatment plants (WWTPs) are among the most energy-intensive components of urban infrastructure. In light of the revised EU directive on municipal wastewater treatment, which targets energy neutrality by 2045, effective energy management in this sector is becoming essential. This article reviews the current knowledge regarding energy consumption in WWTPs and analyses opportunities to increase their energy self-sufficiency by reducing energy demand and recovering energy. Key factors influencing energy consumption are discussed, including facility size, the range of technological processes used, automation level, and equipment condition. Attention is given to aeration systems, which account for the largest share of electricity consumption, and the possibilities for their modernization and optimization using energy-efficient diffusers and advanced process control systems. The potential for recovering chemical energy from sewage sludge is analyzed, with emphasis on anaerobic digestion and co-digestion with other organic wastes. Alternative sludge conversion methods, such as incineration, pyrolysis, gasification, and hydrothermal carbonization, are also presented. The analysis is complemented by technologies for recovering physical energy from wastewater, including the use of thermal energy via heat pumps and hydraulic energy from wastewater flow. The findings indicate that achieving energy self-sufficiency in WWTPs requires site-specific, hybrid solutions combining energy savings with selective energy recovery, considering technical and economic conditions.