The Warminster Municipal Authority Wastewater Treatment Plant, located in Bucks County, Pa., serves a population of about 50,000. It is designed to treat more than 8 million gal of wastewater a day from residential, commercial and industrial users. For nearly a decade, the facility has relied on a highly skilled staff and advanced valve automation to operate at a consistently high efficiency rate. Because of the plant’s superior efficiency, the authority’s customers pay one of the lowest rates in the area.

“Automation and teamwork are what keep things running smoothly around here,” said George Pfeiffer, sewer system superintendent for Warminster Municipal Authority. “We have made a commitment to invest in reliable equipment; provide ongoing training for our employees; do most of our own maintenance; and use automation where it makes economic sense.”

A dependable process

The plant was originally built in 1959 and has been upgraded several times, most recently in 1988. It employs a totally biological A2/O process for wastewater treatment. The main steps in the process include: screening; grit removal and primary settling; A2/O processing and treatment; final clarification; and disinfection by intense UV light.

According to the engineering consulting firm hired by the authority, the totally biological A2/O process has shown that it can accomplish BOD and nutrient removal at a significantly higher process efficiency rate than conventional activated sludge treatment.

The plant discharges its treated water into Little Neshaminy Creek, which is part of the Delaware River system. By maintaining its highly efficient operation, the Warminster facility is doing its part to help keep Little Neshaminy Creek cleaner.

Keeping the environment clean is a top priority for the authority. Wastewater is processed biologically, with none of the chemicals that are typically used, and achieves complete nitrogen removal. Specifically, the process removes CBOD, suspended solids, ammonia as nitrogen, nitrates, nitrites and phosphorus. In 2001, the authority added a third final clarifier that virtually eliminated suspended solid overflows after heavy rainstorms.

“Because the process is totally dependent on biological, rather than chemical treatment, it is necessary that we monitor and carefully regulate every step of the process,” Pfeiffer said. “It’s important to have a dedicated staff of professionals who are well-trained and thoroughly understand their duties. We’ve also invested in cost-effective automation equipment that’s dependable and able to perform well around the clock.”

Key to success

In 1999, the authority approved a SCADA pilot project to see if automated valves would help improve productivity and performance on the primary settling tanks. Previously, a total of 16 telescopic valves were manually operated and needed to be drawn down every four hours, 365 days a year.

Pfeiffer called upon Edwin Elliot and Co. and a local engineering firm to assist with the project. After a careful analysis of appropriate technology, the authority decided to install 16 Rotork IQ electric actuators, a Pakscan two-wire loop and a Pakscan IIS master station for local control at the primary settling tank site. The facility also used an engineering group to help integrate the PLC to SCADA system.

Warminster takes pride in its capability to do as much work in-house as possible. They perform approximately 98% of all maintenance throughout the plant and were able to install this new system easily.

“We did all the wiring and installed the valves, stems and actuators in-house,” Pfeiffer said. “The Pakscan two-wire daisy-chain system was simple to hook up. We saved a tremendous amount of money by doing the work ourselves.”

“From day one the primary tank settling process became more efficient. It was ten-fold better than doing it by hand,” Pfeiffer added. “Now, time and position of the valves are controlled by PLC. We are operating the valves every half-hour now, instead of every four hours as we did when we were doing it manually. More frequent operation lets us control the process better.”

Expanding the concept

Because the automated valves worked so well at the primary settling tanks, the authority decided to apply the same concept throughout the plant. Today, it has Rotork actuators and Pakscan communication systems on all the sludge-handling processes, digesters and centrifuge.

“All in all, we have a total of more than 50 Rotork IQ and AQ actuators with all of them tied to the Rotork Pakscan system,” Pfeiffer said. “The programming is interfaced with our PLC, so it’s easy to tell each actuator what to do and when to do it. Each valve actuator has its own address, so we have maximum control.”

Tim Pattison, plant operator, said, “If there is a problem with the plant processes, I’m able to find the solution to the problem much faster by reviewing the system status rather than checking the valves at each location. The reliability of the plant automation can be summed up in five words—set it and forget it.”

Steve Sweder, plant operator, added,“I have more time to work on other tasks in the plant. I’m not rushed during critical times of the day when our loading and our flows change. Operating approximately 50 valves manually was very labor intense. Now it is much easier with electric actuators.”

Accomplishing goals

Among Pfeiffer’s most important goals were to eliminate violations. “In the mid-1990s, we were nagged by violations during wet weather conditions. Suspended solids and washouts were a real problem,” Pfeiffer explained.

“In 2001, we added a third clarifier to our process. Now, with the third clarifier and our automated valve upgrades, we’ve eliminated the violations,” he said. “Things are running very smoothly, and we don’t have to make radical changes to our process. Today, all we do is make minor adjustments.”

The authority credits the dedication of its staff and the reliability of the Rotork actuators and Pakscan system for the plant’s consistent performance. The combination of a skilled workforce and reliable valve automation has enabled the operation to provide customers with a high level of dependable, environmentally friendly service at a very reasonable cost.