If you’ve managed an industrial wastewater treatment system you know each treatment process is critical to ensure sufficient treatment of wastewater. You also know that treatment of industrial wastewater can be very energy intensive.
Industrial wastewater treatment systems use pumps to convey wastewater, mixers to agitate tanks, compressed air for various applications, sensors and electronics to monitor treatment parameters, and electrical panels that house system controls and electrical components. If there’s a way to improve energy efficiency this can result in significant cost savings.
Here are just three ways to save energy (and money) at your industrial wastewater treatment system. If you are interested in specific recommendations for your facility contact us and ask about our Energy Use Assessment Services.
- Improve Process and Component Efficiency
Each industrial wastewater treatment process is comprised of individual components that consume energy during operation (pumps, mixers blowers, etc.). When looking for ways to save energy it is important that you identify changes that improve overall system efficiency. This means looking at both energy efficiency and process efficiency improvements.
Process efficiency improvements include projects that will increase overall operational efficiency. Pumping wastewater can be energy intensive and pumping systems typically have many areas for efficiency improvements. Ways to improve a pumping system’s operational efficiency can include reducing the hours of operation for pumps, reducing the load (work) of the motors, and controlling motors using variable frequency drives (VFD). Using a VFD to control motor speed actually decreases the energy efficiency of the motor, because a motor’s energy efficiency is a function of motor speed, but increases overall system efficiency. A VFD improves system efficiency by reducing power consumption proportional to the demand; it runs the pump slower and faster based on the requirements of the system. Thanks to the affinity laws1 this reduces overall electricity requirements and can improve system functionality.
One way to improve individual component efficiency is to upgrade equipment motors. Every electrically controlled mechanical component (pumps, mixers, blowers, etc.) use motors; however, not all motors are created equal. Motors that are designed with energy efficiency in mind are known as premium efficiency motors (aka high efficiency motors). These motors typically last longer, run cooler, and use less energy than National Electric Manufactures Association (NEMA) B motors of the same size. According to the Department of Energy premium efficiency motors are particularly cost effective when annual operation exceeds 2,000 hours, utility rates are high, motor repair costs are a significant fraction of the price of a replacement motor, or electric utility motor rebates are available2.
- Reduce Compressed Air
Compressed air is very common at industrial wastewater treatment systems and is used due to its convenience; however, compressing air is energy intensive and inefficient. When possible, it is more energy efficient to replace compressed air with electrically powered equipment. This can include switching from using air operated double diaphragm (AODD) pumps, used for transferring wastewater, to using centrifugal pumps or electrically powered AODDs. AODDs area also typically used for dosing treatment chemicals; however, this can be done more efficiently by chemical metering / dosing pumps. When it is not used for pumping, compressed air is typically used for mixing. Whenever possible, mixing should use a mechanical mixer or high efficiency blower.
- Find & Repair Compressed Air Leaks
Compressed air is often used by a variety of industrial wastewater process components integral to the overall system including air operated diaphragm pumps (for wastewater transfer, chemical dosing, etc.) and pneumatic actuated control valves. If you cannot eliminate the use of compressed air, it is critical to periodically perform a compressed air leak assessment to find and repair leaks.
Compressed air leaks typically occur at tubing connections and small orifices, and can cost a significant amount if left uncorrected. According to the Department of Energy, leaks at an average plant can account for 20-30% of the plants compressed air compressor output3. An air leak through an orifice of just 1/4” can lead to an additional annual cost of over $6,778 at 80 psig.
Energy providers offer to subsidize the costs associated with performing a compressed air leak survey and repairs. Loureiro is an approved vendor of the Connecticut and Massachusetts Utilities, and eligible companies can receive the following incentives:
- Eversource CT – Up to 50% of the survey cost and at least 50% of the repair cost
- United Illuminating CT – Up to 50% of the survey cost and at least 50% of the repair cost
- National Grid MA – Up to 100% of survey cost and at least 50% of repair cost
- Eversource MA – Up to 50% of the survey cost and at least 50% of the repair cost
Find out how much you could be saving in energy costs by scheduling a Compressed Air Leak Survey today.
Improving overall system and component efficiency, reducing compressed air usage, and repairing leaks in compressed air systems can lead to significant reductions in energy consumption and cost. Since wastewater treatment systems involve energy intensive pumping, mixing, and measurement processes, small improvements can result in high cost savings.
- Elsevier – Science Direct. Affinity Law. sciencedirect.com/topics/engineering/affinity-law
- United States Department of Energy. Energy Tips – Motor Systems. 2012. energy.gov/sites/prod/files/2014/04/f15/whentopurchase_nema_motor_systemts1.pdf
United States Department of Energy. Energy Tips – Compressed Air. 2004. www.energy.gov/sites/prod/files/2014/05/f16/compressed_air3.pdf