Looking to save energy within your municipality? Start with the wastewater treatment plant. Wastewater facilities account for 35% of a typical municipal energy budget with electricity consumption accounting for 25-40% of the plant’s operating budget. By assessing the facility and implementing energy efficient equipment and strategies, you can substantially lower energy costs. Along with upgrading lighting to LED and optimizing HVAC units, wastewater treatment plants can utilize unique strategies to help your municipality save money.
· Variable frequency drives: VFDs adjust the motor speed of a pump, fan, or blower to meet the demand fluctuations. To reduce stress on the motor, variable frequency drives allow for a “soft-start” which gradually brings the motor to the appropriate speed while also reducing maintenance costs. VFDs are reliable and easy to operate and can reduce pump energy usage by 30-50%. While the initial cost of a VFD may be high, the payback is generally around 3 years.
· Cogeneration: Methane gas, a by-product produced during anaerobic digestion, can be used to power cogeneration engines or fuel cells to produce electricity. The waste heat from electric generation can be recovered to heat work spaces and digesters. The electricity generated on-site can be used during peak hours of the facility to reduce the cost associated with purchasing electricity from the grid.
Fine bubble aeration: Aeration energy is typically the largest energy consumer in activated sludge plants. The most efficient plants utilize fine bubble aerators, which are more efficient at transferring oxygen to the fluid. This can reduce aeration energy by 20-35%. For sludge reuse, all plant processes produce sludge at varying rates. This sludge is commonly landfilled, wasting a potential resource. However, through additional digestion through aerobic or anaerobic processes, harmful pathogens can be removed, called sludge stabilization, resulting in a waste material typically high in phosphorus and nitrogen content. This stabilized sludge can then be sold as fertilizer, supplementing a plant’s operating budget, and helping local growers.
· Energy efficient pumps and motors: Motors on pumps and blowers can account for 80-90% of the plant’s energy cost. While energy efficient motors are only slightly more efficient, their failure rate is much lower. Consider replacing motors if they are used more than 8,000 hours per year. Likewise, ensure your pump system is efficient by sizing pumps to meet usage requirements, utilizing low loss components, and designing a pipe-system layout to reduce pressure drops.
Getting started is easy. Schedule an energy assessment for your wastewater treatment plant with the Smart Energy Design Assistance Center (SEDAC). SEDAC, a public-private partnership between 360 Energy Group and the University of Illinois at Urbana-Champaign, provides no-cost energy assessments, in partnership with the Illinois EPA Office of Energy*, to publicly-owned wastewater treatment plants. For more information or to fill out an application, visit sedac.org/wastewater.
*Funding provided in whole or in part by the Illinois EPA Office of Energy. This program is in partnership with the U.S. Dept. of Energy Sustainable Wastewater Infrastructure of the Future (SWIFT) Accelerator for energy efficiency in wastewater treatment.
