Fast Growing Water Plant Quickly Shifts to VLT® AQUA Drive
Located in one of the fastest growing regions in the U.S., the Benton/Washington Regional Public Water Authority (BWRPWA) broke ground in 1996 for a water treatment facility serving northwest Arkansas and eastern Oklahoma. Today, it operates as a wholesaler, providing up to 24 million gallons of drinking water per day to sixteen municipalities and other entities. To be a cost-effective water provider, the Authority operates pumps at varying speeds, night and day—which is why BWRPWA saw a lot of value in the Danfoss VLT® AQUA Drive, variable frequency drive.
“We’re selling water to many different customers,” says Jeremy McCrary, maintenance foreman for BWRPWA. “To provide a potable water supply as cost-effectively as possible, we need to be up and running at all hours. That’s why when the variable frequency drive for one of our 500-hp pumps went down, I was glad Danfoss had a fast solution.”500-hp drive moves up to 13 million gallons per day
As a water wholesaler, the BWRPWA draws water from nearby Beaver Lake then completes the treatment process at the plant. From there, a vertical pump transports the water to various storage tanks. The water is then distributed to suppliers who operate their local systems and bill customers.
“Our operation is pretty straightforward,” says McCrary. “We pump water into storage. We’re not dealing with sophisticated control strategies. We just want to make sure our storage tanks are filled as cost effectively as possible.”
During the summer months, that means minimizing pumping during peak hours when electricity is more expensive. As much as possible, the plant shifts heaviest electricity use to off-peak hours.
“In peak electrical demand periods, we switch to onsite generated power, allow the tanks to draw down and throttle the pump back to about 60 percent capacity to minimize electric costs,” he emphasizes. “But then at hours when electrical demand is lower, we run those pumps hard at 100 percent to catch up until the storage tanks are full.”
That strategy worked fine until one of BWRPWA’s three pumps went down due to a variable frequency drive (VFD) failure. “We run two 500-hp pumps and one 1,000-hp pump,” says McCrary. “When the 500-hp drive went down, we had to find a solution fast.”
McCrary contacted Fleming Controls and Power Specialties in nearby Bryant, Ark., for advice. Fleming Vice President Scot Eisenhauer made a recommendation that McCrary didn’t expect.
Eisenhauer explains: “We provide field and bench repair services as well as sales, design, programming and installation of AC and DC drives. Over the years, we’ve been very impressed with Danfoss drives. In this case we recommended that the old VFD be replaced by the Danfoss VLT® AQUA Drive.”
At first McCrary was skeptical. “I knew that Danfoss VFDs were used in HVAC systems,” he says. “But I didn’t know they had VFD products for water and wastewater applications.”