Reverse Osmosis, SCADA, Automation Drive Excellence For A South Dakota Plant

Technology helps a water system in rural South Dakota operate efficiently, deploy effective treatment methods and deliver quality customer service.
Reverse Osmosis, SCADA, Automation Drive Excellence For A South Dakota Plant
The Clay Rural Water System team includes, from left, Tom Hollingsworth, operations supervisor; Phil Iverson, operator; Janice Lyso, accounting/bookkeeping; Rob Ganschow, operator; and Greg Merrigan, system manager.

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The Clay Rural Water System in southeast South Dakota covers 735 square miles and has a population of around 5,100 — less than 10 people per square mile.

Yet the system includes some of the latest water utility technologies — reverse osmosis, a sophisticated SCADA system and a two-way automated meter reading network that records water usage on an hourly basis.

Team members Tom Hollingsworth, operations supervisor; Phil Iverson and Rob Ganschow, operators; and Greg Merrigan, system manager; supported by office manager Donna Henriksen and accountant Janice Lyso, have used that technology — plus good old-fashioned operations skill — to earn the system a Decade of Drinking Water Excellence Award from the South Dakota Department of Environment and Natural Resources.

“The award was based on our record of sampling, source water protection and operator certification,” says Merrigan, “plus our record of compliance over the last 10 years.”

One system

The Clay Rural Water System was formed out of a desire among residents to obtain better-quality water and work together as a rural community, according to the utility’s website. In the early 1970s, a countywide survey on water quality and quantity led to formation of a steering committee to explore a central system. The water system was incorporated on July 21, 1975. Member sign-ups, engineering and construction followed, and in fall of 1980 the system was fully operational.

Today, the system consists of two drinking water treatment plants and 1,400 miles of distribution lines (1/2 to 8 inches) providing fresh, clean drinking water through 2,275 connections. The water treatment plant in Wakonda, designed to produce 880 gpm, uses a combination of softening and filtration. Raw water comes from two 140-foot-deep wells, each with 1,200 gpm capacity. The water is aerated to reduce taste and odor, then dosed with lime, soda ash and coagulants to soften it and settle out solids.

A 25-ton tank (TOMCO2 Systems) supplies carbon dioxide to a Wallace & Tiernan carbonation process (Evoqua Water Technologies) that adds CO2 to lower pH. The flow then passes through four General Filter gravity sand filters (WesTech Engineering). Finished water is chlorinated and fluoridated before delivery by four Layne high-service pumps to an in-ground reservoir (A. O. Smith) and then to the clearwell and distribution system. About 300,000 gallons are delivered in bulk to the communities of Wakonda and Gayville. “We supply it to a vault on the edge of the communities, and they distribute it through their own lines,” Merrigan explains.

At the Wynstone plant, about 20 miles south of Wakonda, source water is also drawn from two wells 300 feet deep, each with 350 gpm capacity. Treatment is quite different. The current equipment had to be installed within the tight footprint of what had been a small treatment plant in a housing development before the agency expanded into that part of the county in 2005.

“This plant is located next to the Missouri River,” Merrigan says. “Reverse osmosis was the choice because the reject water could be discharged by permit into the Missouri, and because the RO units [Harn R/O Systems] don’t take up much space. It was a perfect setting.”

A separate portion of the raw water at Wynstone passes through General Filter pressure filters (WesTech Engineering). The RO and pressure-filtered flows are blended and sent on to aeration, caustic addition for pH control, chlorination and fluoridation. A pair of high-service pumps (Layne) push the water to a 250,000-gallon elevated storage tank. It then flows by gravity to customers, including four housing developments and a number of farms — about 20 percent of Clay Rural Water’s connections.

About 20 percent of the water passes through the pressure filters and the rest through the RO membranes. “If we ran 100 percent through RO, the water would be too pure,” Merrigan says. “By splitting the flow, we get the right balance of hardness and salinity.”

Merrigan and the staff are pleased with the RO units. “We add an antiscalant and that’s it,” he says. “The units have operated for seven years and work very well.” He says Harn has been very helpful and anticipates having to acid clean the units only once every five years or so.

Filter backwash water is discharged to lagoons at the Wynstone plant. At Wakonda, lime sludge is pumped to drying lagoons, and a contractor trucks the dewatered material to farms as a soil amendment. “There’s always a demand for it here,” says Merrigan. “It is very beneficial.”

The entire Clay Rural Water network of plants and distribution lines is managed by an Allen-Bradley SCADA system (Rockwell Automation) so that operators can monitor and control processes on their laptop computers and iPhones. That’s important to a rural system that measures 30 miles top to bottom and 25 miles wide. “We used to run the ‘milk route’ three times a week, but now we only travel it once a week,” says Merrigan. “While we’ve invested heavily in SCADA, the result is a huge cost savings in operations. We’re really spread out.”

Making it better

Life has not been without challenges for the Clay Rural Water team. A drought in 2007 stressed the system to its capacity and prompted the leadership to hire an engineering firm to study the plants and distribution system. The review identified some $3 million in potential improvements. That was beyond the agency’s financial capabilities, but the timing was right because it coincided with the launch of the American Recovery and Reinvestment Act of 2009. Clay Rural Water applied for stimulus funds and received $1.3 million in grants and loans over the next two years, enough to implement several “shovel ready” projects, including:

  • Two new booster stations and additional pumping capacity at the Wakonda plant.
  • A new well to replace two soon-to-be abandoned wells at the Wakonda plant.
  • Interconnects with neighboring communities to provide emergency water if needed.
  • Looping of distribution lines in remote areas so that customers are served by two-way flows, rather than just one-way.

The improvements have helped. “In 2012, we had another dry year, but we were able to keep up without any problems,” says Merrigan. Perhaps the biggest improvement was automated reading. In the early days, customers took their own meter readings, calculated their bills and sent in their payments. Or they simply made estimates and paid the bill. Customers didn’t find that inconvenient, says Merrigan, because “they knew what it was like in the days before the rural water system.”

Gradually, however, customers changed; new users preferred to get a statement in the mail, pay for their usage, and avoid the nuisance of reading the meter. Last spring, Clay Rural Water was changing out the old meters and adopting a fixed-base system (Sensus) that will record data at the user’s end every hour and communicate it to antennas on three of the system’s water towers. Each antenna is connected to a data collector that forwards the data via the Internet to a server in the main office, where reports will be generated every morning and bills prepared.

The transition to the new system was to be complete by the end of 2014. “We’ve spent about $700,000 on the new system and made it work within our rate structure,” Merrigan says.

Shutting down leaks

Besides customer convenience and more accurate readings, the AMR system will help the system deal with leaks, which have numbered about 25 per year. The area’s clay soil easily absorbs moisture and expands during the rainy season, then dries out and contracts, so the ground is always moving. “Some areas have a high water table as well, which can make it difficult to locate leaks,” Merrigan says. The utility’s goal is to keep water loss below 15 percent.

“Because we are reading meters every hour, the new system will enable us to pinpoint leaks on the customer side and alert them to a problem,” Merrigan says. “It will allow us to provide a higher level of customer service.” It’s just one more advantage of making technology work for a small water agency.  

More Information

A. O. Smith - 800/527-1953 - www.hotwater.com

Evoqua Water Technologies, LLC - 815/623-2111 - www.evoqua.com

Harn R/O Systems Inc. - 941/488-9671 - www.harnrosystems.com

Layne/Verti-Line - 913/371-5000 - www.lvlpump.com

Rockwell Automation - 414/382-2000 - www.rockwellautomation.com/industries/water

Sensus - 800/638-3748 - www.sensus.com

Tomco2 Systems - 800/832-4262 - www.tomcosystems.com

WesTech Engineering, Inc. - 801/265-1000 - www.westech-inc.com



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