Energy-Efficiency Index in Industrial Wastewater Treatment Plants Using Data-Envelopment Analysis

The reduction of energy consumption in industrial wastewater treatment plants (IWTPs) is an important issue because of global warming, fossil-fuel scarcity, and high energy cost. This paper studied the energy-efficiency index (EEI) of 79 IWTPs across Iran and discussed the impact of different factors on it. Data-envelopment analysis (DEA) was used, in which an efficiency score of 0-1 was allocated for every IWTP. Maximum potential saving, in terms of energy consumption and of CO2 emissions, was measured. It was found that 73.4% of IWTPs had poor energy efficiency, with EEIs lower than 0.3, and only 2.6% of IWTPs achieved an EEI of higher than 0.7. Each effective variable on the EEI of IWTPs, such as treatment plant age and size, COD removal, process type, pumping station, and aeration method, had their own effect on EEI, energy consumption, and CO2 emission. According to the results, the improvement of the EEI of IWTPs will result in 72.9% savings in energy cost, and about 52.8 t less CO2 will be emitted into the atmosphere annually. Therefore, upgrading the EEI of all IWTPs in the world can significantly reduce both energy costs and CO2 emission. The results contribute to energy management in IWTPs. (C) 2019 American Society of Civil Engineers.