Energy benchmarking of industrial wastewater treatment plants: A case study of activated sludge systems in Isfahan, Iran

Abstract Wastewater treatment plants (WWTPs) using the activated sludge process are widely recognized as significant energy consumers within the water cycle. As a result, it is essential to assess energy consumption and implement solutions for reducing and optimizing it. Energy benchmarking (EB) is a method used to compare and evaluate the energy efficiency of a system to identify opportunities for improvement and enhance energy efficiency. This study aims to evaluate the energy consumption of selected 10 activated sludge operating industrial WWTPs in Isfahan province, Iran. EB of the WWTPs was done using various methods, including normalization, multiple logistic regression, and ordinary least squares. The plants were ranked based on the aggregated scores from different methods using weighted averaging. The results showed that the IWW8, IWW1, and IWW6 plants had the best energy performance. Also, it was found that the aeration unit and effluent pump station accounted for the largest share of energy usage with an average of 68% and 13%, respectively. A positive correlation was found between key performance indices (KPIs) and factors like plant age, design capacity deficiency, and blower power to flow rate ratio that validate the ranking results. Finally, energy saving measures were introduced and prioritized for each of the studied WWTPs based on the BM results and detailed site visits, with a focus on enhancing the aeration system efficiency.