Thermodynamic analysis and assessment of a municipal wastewater treatment system: A field study on sewage treatment

This paper is a field study on thermodynamic analysis and assessment of an actual municipal wastewater treatment facility. The system operation is described and a methodological approach based on the energy and exergy analyses is provided to assess the performance of a complex wastewater treatment system. Since the specific exergy value of the sludge is increased through treatment process, a new exergy based parameter, net exergy ratio (NExT), is defined to reflect the renewable and sustainable nature of the process. The system treats nearly 222,000 m³ domestic wastewater per day by using the primary and secondary treatments. The NExT values for primary and secondary treatments are found as 2.81 and 1.31, respectively. When the sludge outputs of both processes are considered as waste, the exergetic efficiencies of subsystems in the actual municipal wastewater treatment plant (WWTP) can be obtained as 57.4% for primary treatment system (PTS) and 29.7% for secondary treatment system (STS).