Technology Upgrade Improves Efficiency of Water Distribution
Palmyra is a community of about 3,500 people near the Mississippi River in northeastern Missouri. A water treatment plant and elevated tank were built in the early 1970s...
Palmyra is a community of about 3,500 people near the Mississippi River in northeastern Missouri. A water treatment plant and elevated tank were built in the early 1970s to serve the community's growing needs. This expanded a system that already had an existing elevated tank (Dickerson Street) and ground storage tank (GST).
In the early 1990s, an additional water tower was added to support the growth of an Industrial park on the edge of town. The water distribution system now comprises two high service pumps at the plant, three elevated tanks and a ground storage tank.
In 2003, a major project was initiated by Don Lloyd, the superintendent of utilities, and Jeff Schneider, plant supervisor, to better use the capacity and improve the overall efficiency of the system.
Added Capacity Creates Problems
The addition of the Industrial park elevated tank, while it added capacity to the system, also created a few problems. The entire distribution system and levels in each tank were driven from the high service pumps at the plant. In order to maintain levels at the industrial park tank, the plant had to produce and pump enough water to fill the plant tank, ground storage tank, and the Dickerson Street tank.
The elevations of the various tanks also caused several problems. Because of its distance from the rest of the system, it was impossible to completely fill the Industrial park tank. In addition to the unused capacity, this also caused the water pressure to be lower in that part of town. Because the ground storage tank was the low point of the system, the water from this tank did not "turnover" as new water passed over it on the way to the industrial park.
To address these challenges, Palmyra turned to the engineering firm of Poepping, Stone, Bach & Associates (PSBA). PSBA came up with a plan that called for adding control valves at each individual tank and a booster pump station at the ground storage tank. PSBA then turned to Hydro-Kinetics of Saint Louis to provide the valves, pumps and a Healy-Ruff control system. (Interesting note – a Healy-Ruff control system installed in 1973 is still running the plant.)
"Healy-Ruff really helped us on the front-end of this project," said Charlie Bach of PSBA. "They did a site visit, developed a design concept for the control system and coordinated all the radio communication issues. Because of their expertise in water and wastewater applications, they were able to apply the right control algorithms as well as design a user-friendly system."
The new control system consists of a Micro V-PAC RTU and a level transducer at each tank, which regulates the valve to control the tank levels. Each RTU communicates back to the water plant. A Micro V-PAC also controls the new booster pump station. At the plant, a Master V-PAC with a graphical, touch-screen interface provides control of the high service pumps as well as serving as a CTU providing supervisory control and an interface to the entire system.
The new system gives Palmyra an infrastructure that would make it easy to expand and upgrade as they add new sites or add a PC-based SCADA system.
The project was subject to some skepticism–around town and in the plant.
"There were many people who told us it would never work," said Superintendent Lloyd. Also, although the plant staff was interested in improving their operations, they were somewhat concerned about adapting to the new technology.
A Master V-PAC with a graphical, touch-screen interface provides control of the high service pumps.
"We were used to running the system by using the pressure gauge on the original Healy-Ruff control panel as a stopping point. The mark on the gauge (61 PSI) was the maximum pressure we could achieve at the plant," Schneider said. "When they told us about the new system, we were a little intimidated by the technology and were not sure how accurate it would be.
"Once we switched over the new system, we went out and physically measured the tank levels to check on the accuracy of the level readings – they were within inches. Also, it took just a few hours to fill the industrial park tank – which had never been completely filled before."
In addition to improving the system operations, there was an overall average improvement in water pressure from 61 to 74 PSI in the system. It also gave the town 150,000 gallons of additional capacity for future growth.
Palmyra has also seen cost savings. In order to keep the system "fully charged" the water plant needed to produce/pump water an average of 9.5 hours a day. With the new ability to individually control each tank, only 6.5 hours a day of production are required. This nearly one-third reduction in production requirements has dramatically reduced the need for overtime, while increasing the time available for other projects. It has also reduced energy consumption. Additional benefits include reduced equipment maintenance and extended equipment life due to the reduction in daily run-time.
"I never thought I'd see the day when we could get water out of the overflow pipe at the industrial park tank," said Schneider with a smile.
"The morning after we switched over to the new system, I got several calls from around town telling me how much better the water pressure was in their showers that morning. That makes us feel pretty good," added Lloyd.