The Impact of Advanced Wastewater Treatment Technologies and Wastewater Strength on the Energy Consumption of Large Wastewater Treatment Plants

Wastewater treatment is an energy intensive process often requiring the use of advanced treatment technologies. Stricter effluent standards have resulted in an increase in the number of wastewater treatment plants (WWTPs) with advanced treatment over time. Accordingly, associated energy consumption has also increased. Concerns about lowering operating costs for WWTPs and reducing associated greenhouse gas generation present an incentive to investigate energy use in WWTPs. This research investigated the impact of wastewater strength and the introduction of advanced treatment technologies, to replace traditional technologies on energy use to treat wastewater in WWTPs. Major unit processes were designed for a 100 MGD plant and variables controlling energy were identified and used to compute energy consumption. Except for primary clarification and plate and frame press dewatering, energy consumption computed using fundamental equations are within values in the literature. Results show that energy consumption for dissolved air flotation thickeners, centrifuges, gravity thickeners, and aeration basins are heavily influence by wastewater strength. Secondary treatment and tertiary treatment require a significant amount of energy. Secondary treatment requires 104 times the energy of preliminary treatment, 17 times the energy of solids processing, and 2.5 times the energy of tertiary treatment. Secondary treatment requires 41 times the energy of preliminary treatment, and 7 times the energy of solids processing. The results of this research provide a means of estimating energy consumption in the design and operation phase of a WWTP. By using the fundamental equations and methodology presented, alternative technologies can be compared or targeted for future energy savings implementation. Limitations of the methodology include design assumptions having to be made carefully, as well as assumptions of motor and equipment efficiencies.