Exergy Analysis: A Comparison of Source Separation Systems and Conventional Treatment Systems

Abstract

Exergy analysis and material balances are useful to describe resource use in different systems. In this study, three different sewerage systems are analyzed: a conventional system with biological nitrogen removal, a conventional system in combination with source separation of urine, and a treatment system with source separation of urine and feces. The influence of factors such as the size of the system, access to farmland, and concentration of collected urine is studied. The study shows that total exergy consumption is least for the system with source separation of urine and feces and greatest for the conventional wastewater treatment system. The primary difference results from the amount of methane gas that is produced by each alternative. Another conclusion is that a significant portion of exergy consumption in the source separation system is the transport and spreading of urine.