Metering Pump Reduces Chemical Costs While Improving Safety & Efficiency

Advocates of the latest technologies often tout the benefits of being an early adopter: greater attention from the vendor, the opportunity to serve as an industry trendsetter and access to the newest, most accurate solutions. One recent example is at a wastewater treatment plant in the Lakehaven Utility District, located in the state of Washington, an early adopter of a pump manufacturer’s new metering pump. This peristaltic pumping technology has aided Lakehaven in reducing chemical costs at its Lakota plant by 15 to 20 percent, while improving overall efficiency, ease of use and worker safety in the process. The district is using the pumps for sodium hydroxide (caustic) and poly-aluminum chloride (PAX) applications.

Utility Seeks Upgrade for Greater Safety

Lakehaven Utility District is a municipal corporation in the state of Washington that serves about 112,000 customers. The Lakota activated sludge plant processes 10 million gallons per day. “At the Lakota plant, we were using peristaltic pumps with a traditional tube element design,” explained Chris McCalib, wastewater operations manager at the Lakehaven Utility District. He added, “They were certainly fine from a dependability standpoint, but to gather feedback for example dosage rates, you had to pull the information out of the machine and send it into the plant’s control system to be generated. There was no local display or functionality at the pump.” Of additional importance was the provision of operator protection from a caustic or PAX spill in the event of a tubing failure. Lakehaven’s local safety protocol required that its peristaltic pumps be installed in a special containment area with Plexiglas enclosures. The new metering pump was a good solution for Lakehaven. Because of the way the plant is designed, not much engineering was needed for the installation. It was a simple drop-in replacement that would provide a cost-effective solution for its problems. Furthermore, the metering pump offered a further level of operator safety.

The Metering Pump

The metering pump is not a typical peristaltic pump because of its specialized pump head. The sealed, long-life, consumable peristaltic pump head is designed to enhance safety and simplicity while reducing the cost of ownership when compared to other pump types. This has eliminated the safety concerns that Lakehaven had previously faced. In addition to delivering performance, the pump is simple to maintain with long maintenance intervals. When the tubing exceeds its operational life, the pump signals an operator that it is time to change the sealed pump head. It is an economical, single component replacement that is completed in seconds without tools, special rebuild kits or chemical exposure.

Savings for Lakehaven

After selecting the Lakota plant as the site for the metering pump installation, Lakehaven then proceeded with a trial period. Lakehaven’s McCalib reported, “Following the application and performance trials, the pump met our criteria for success and has been operating flawlessly ever since.” Lakehaven enjoyed several features that offered opportunities for process improvements in the installation and the utility pump application. In addition, Lakehaven installed the metering pump in a second application to meter from 250-gallon totes, tapping into the pump’s “barrel bar” feature—a function that calculates drawdown based on the pump’s metering accuracy and sounds an alarm when a source barrel is getting low. McCalib explained that Lakehaven installed the metering pumps in the Lakota location because the plant had problems pumping from a tote. Operators could not shut off the pumps mid-process, which made knowing when to change the tote difficult. Occasionally, totes would drain completely. At other times, an operator would change a tote that was 20 percent full. McCalib credits the metering pump barrel bar feature with a 15 to 20 percent reduction in chemical costs, giving operators the ability to meter properly without wasting chemicals or running dry.

Response to Market Need

The metering pump was engineered in response to a market need for a simple yet accurate and reliable metering pump to reduce chemical waste and improve process efficiency. The key advantage of the metering pump range compared to traditional solenoid or stepper motor-driven diaphragm metering pumps is that it offers linear flow performance regardless of typical fluctuations in the suction or discharge pressure conditions. Rooted in peristaltic technology, the metering pump also has no internal ball valves to clog or corrode when metering chemicals with suspended solids and will not vapor lock when metering chemicals such as sodium hypochlorite. This aspect also reduces the ongoing costs by eliminating the need for typical ancillary pump equipment—such as backpressure valves, pulsation dampeners, strainers and float switches. The benefits of the metering pump extend beyond the pump head. The full color thin-film transistor display gives operators access to all the required performance details. Several auto-control options are available to suit a broad range of user applications, including:

• Manual control only
• Automatic with full analog speed control and feedback, relay outputs and supervisory control and data acquisition level inputs
• PROFIBUS network control

Fitted with an impact resistant display cover and National Electric Motor Association 4X enclosure, the metering pump can withstand aggressive chemical environments. McCalib attests to the success of the pump. “Since the initial installation, we’ve purchased another metering pump because the pump works so well for our facility.” McCalib is now looking at this metering pump as the solution for replacing the plant’s older pump technology.