ABSTRACT
This chapter provides a description of energy conservation measures (ECMs) that have been used in the wastewater treatment industry. I have chosen to focus on the wastewater industry in particular because it is a much larger user of energy than the water treatment industry; however, the reader should understand that the ECMs discussed in this chapter can also be applied to water treatment operations. Energy is used throughout the wastewater treatment process; however, pumping and aeration operations are typically the largest energy users. Energy costs in the wastewater industry are rising due to many factors, including (USEPA 2008):
• Implementation of more stringent effluent requirements, including enhanced removal of nutrients and other emerging contaminants of concern that may, in some cases, lead to the use of more energy-intensive technologies
• Enhanced treatment of biosolids, including drying/ pelletizing
• Aging wastewater collection systems that result in additional inflow and infiltration, leading to higher pumping and treatment costs
• Increase in electricity rates
As a consequence of these rising costs, many wastewater facilities have developed energy management strategies and implemented energy conservation measures. Accordingly, this chapter describes ECMs being employed in wastewater treatment plants by
• Providing an overview of conventional ECMs with regard to pumping design, variable frequency drives (VFDs), and motors
• Providing detailed information on ECMs related to the design of aeration systems and automated aeration control, including conventional control based on dissolved oxygen (DO) measurements and emerging control strategies, in addition to discussing innovative and emerging technologies for automated control of biological nitrogen removal
• Describing innovative ECMs related to blower and diffuser equipment, including a summary of various blower types such as single-stage centrifugal, highspeed turbo, and screw compressors in addition to new diffuser technology
• Providing a discussion of ECMs for advanced technologies (ultraviolet disinfection, membranes, and anoxic zone mixing) and presenting full-scale plant test results where available (USEPA, 2010)
Pumping operations can be a significant energy draw at wastewater treatment plants (WWTPs), in many cases second only to aeration. Pumps are used for many applications. At the plant headworks, they may be used to provide hydraulic head for the downstream treatment processes. Within the plant, they are used to recycle and convey waste flows, solids, and treated effluent to and from a variety of treatment processes. Pumps are also found in remote locations in the collection system to help convey wastewater to the plant.
