With ever increasing environmental standards and waste water loading rates, energy consumption for waste water treatment is predicted to rise by over 20% by 2020 in the United States. When considering the resource efficiency of waste water treatment plants factors such as effluent quality, carbon footprint and increasing electricity rates act as a driving force for sustainable design of these facilities. Exergy analysis has been identified in the literature as a powerful tool in the analysis of thermal systems. It enables the resource efficiency of systems to be benchmarked, where the process with the greatest exergy destruction represents the greatest energy efficiency opportunity. The objectives of this research are: (i) calculate the chemical exergy of the relevant process streams within waste water treatment plants; (ii) identify the most suitable parameter to calculate the chemical exergy of organic matter; (iii) identify exergy losses from process streams that could be utilised to produce work. Exergy analysis of three separate waste water treatment plants has been performed. Having identified and measured all the key process input and outputs, a comprehensive exergy analysis has been undertaken. Following an extensive literature review, earlier methods to calculate chemical exergy of organic matter are critically assessed; chemical oxygen demand was identified as the most useful parameter when calculating the chemical exergy of organic matter in waste water. Results for the work indicate that organic matter is the principal contributor to chemical exergy values in waste water treatment plants. Influent organic matter loading rates also greatly impact the exergy destruction rates across a waste water treatment plant.