Energy recovery and saving in municipal wastewater treatment engineering practices

Abstract

Municipal wastewater treatment (MWT) plays a critical role in safeguarding aquatic ecosystems but is highly energy intensive. Assessing the energy recovery and saving potential of MWT technologies is essential to propel the sustainable transformation of this sector. Prioritizing practical viability, this study compiled data from 50 real-world cases, including both full-scale engineering projects and pilot studies, to systematically evaluate the energy recovery and saving potential of different technologies. The effectiveness of these technologies was systematically assessed by comparing their theoretical and practical energy densities. The results indicate that anaerobic digestion for methane production is so far the most efficient method for chemical energy recovery. Among various energy-saving strategies, water source heat pumps were identified as an effective approach for substantial energy savings. However, it is important to recognize that the heat energy, calculated solely on the basis of the temperature difference in wastewater, cannot be directly compared with the electrical energy recovered from other conversion processes. The role of heat energy in energy saving needs to be carefully reassessed and repositioned. This study provides valuable guidance for future energy optimization and the sustainable transformation of MWT practices. Reshaping the currently energy-intensive municipal wastewater treatment (MWT) practices is urgently needed. This study systematically assessed the energy recovery and saving potential of different technologies, providing valuable guidance for future optimizations of MWT practices.