A new membrane filtration plant challenges the operations staff but yields higher-quality water for a growing Utah community.
When the summer heat arrives in northwestern Utah near Great Salt Lake, the city of Ogden calls on a modern tool to increase its water supply: a membrane filtration plant.
The plant and the team behind it have collected recognition after just two seasons in service from the Northwest Membrane Operator Association. The plant earned the 2016 Outstanding Membrane Plant Award – Large Facility, and Ruston Monson, water production supervisor, received the Operator of the Year award. In addition, Utah Construction and Design gave the plant its 2015 award for Most Outstanding Project for Water.
As the plant was built, the Ogden team incorporated advanced ideas to reduce future costs. There is definitely a future as Ogden, 40 miles north of Salt Lake City, is growing rapidly.
The new plant fits in a tight space; on one side Highway 39 and on the other side the Ogden River. On either side of the road and river are the steep walls of Ogden Canyon. Building began in winter of 2014, when demand for water was low, and continued into spring. The old 1953 vintage multimedia filtration plant kept operating during the project.
The microfiltration plant sits at the foot of Pineview Reservoir and draws from that source and also from Wheeler Creek, which empties into Ogden River just below the reservoir dam. A 36-inch pipe brings water to the plant. Water passes through the main valve and is introduced to a flat-bottom clarifier.
The European design splits the flow in half and introduces water 1 to 2 feet above the bottom of the clarifier. Liquid polymer and ferric chloride are introduced here to create floc. “As the sludge blanket builds, it acts as a filter for particles flowing in with the raw water. This takes up much less space than a traditional unit, and there are no mechanical parts — no chain drive, no paddles,” says Monson, who is also a master plumber. “It uses only gravity.”
After the clarifiers, water enters a vault, on top of which are four pumps (Flowserve) that push it through four 300-micron prefilters (Amiad), and then through the microfiltration membranes (Pall Corporation).
Filtrate comes out through a 36-inch pipe, where chlorine is added for disinfection. It is then blended with water from the city’s wells. The outflow falls into a 36-inch pipe that runs down Ogden Canyon to the city.
Water used for membrane clean-in-place processes and enhanced flex maintenance operations is neutralized in a vault and pumped back to the head of the plant. Unfiltered water from the membranes also flows into the neutralization vault. The result is a plant that reuses 99.9 percent of its processing water, as opposed to the typical 96 percent. “We don’t have a sewer up here, so it is a question of hauling the water away or reusing it,” Monson says.
Each clarifier contains a series of cones that form a low-velocity area in the fluid flow. Solids settle out in the cones, and when sensors determine that the cones are full, the plant computer opens a valve to transfer the sludge to the slurry building. The slurry is mixed to maintain a uniform density and fed through a mechanical screw press (Huber Technology). Dewatered solids are hauled to a recycling site; supernatant is returned to the head of the plant.
Changing to microfiltration was a challenge for the staff. “It’s a more involved process in a way,” Monson says. “The process is more automated. For example, we don’t need an operator to initiate a backwash. But there are more chemicals, more components and more pumps.” The tradeoff is much higher-quality water. Turbidity with the previous system was 0.08 to perhaps 0.12 NTU. Now it’s 0.013 NTU regardless of conditions upstream of the intake.
In addition to two weeks of training by Pall, plant staff members visited membrane plants in Bozeman, Montana, and Park City and Garden City, Utah, to learn about the process and plant operations. “It was very different from what we were used to,” says Monson. “To start with, the terminology was different. We used to be concerned with headloss and time and turbidity. Now we’re talking about transmembrane pressure and permeability. It’s the same essential principles, but a very different way to get the water to the same point.”
The operators saw one highly positive change: The ability to go home at night and be with their families. The plant is so automated that there is no need to staff it around the clock, as was the case with the old plant during its operating season. Instead, operators go home with a laptop that lets them link to the plant SCADA software. They can also link into the security cameras. If there’s a problem, the computer sends a text message alert to the operator on call.
“The new system gives us many more resources to see and adjust what’s happening in the plant,” Monson says. “With the previous system, as soon as an alert came in over a cellphone we were driving to the plant. Now we head for the plant only if the remote operation can’t fix a problem.” The project includes a new high-speed fiber-optic data line running to the plant for connections to the SCADA system and out to the internet.
Skills make a difference
The team members who keep the system running are Jay Lowder, public works director; Kenton Moffett, P.E., water utility manager; Monson; Brett Hawks, master electrician and operator; Jordan Hendrix, journeyman electrician and operator; and Todd Stevens, Bryson Church and Chris Callahan, operators.
“I’ve been told by the drinking water people from the state that with our source water, the way our plant is, where it’s positioned, and the piping below it, we have one of the most complex systems they’ve seen,” Monson says.
Since the membrane plant runs only seasonally, there is a challenge in starting it up and shutting it down every year. But this is also an opportunity, because it allows downtime for maintenance.
“We really stand out in having some well-qualified technical tradesmen on staff,” Monson says.
In hiring, the department looked deliberately for people with trade skills. Having skilled people on hand is a great advantage. “You have to bid for every bit of electrical work, and treatment plants have so many components, plumbing and electrical, that you’re always bringing in outside contractors,” says Monson. “If you have your own licensed professionals in-house to perform that work at that high technical level, it saves a great deal of money. We’re fortunate to have them.”
There is nothing wrong with the skills of outside contractors, Monson says, but having licensed professionals on staff brings a faster response to problems: “One day a transformer started to go bad. When transformers start to hum, they usually only get worse. This was right in the middle of construction on the membrane plant, and that transformer supplied electricity to the entire property.”
Because electricians were on staff, they could immediately diagnose the problem in the 480-volt, 90-amp transformer. The utility had its own electricians replace the transformer as soon as the building schedule allowed.
It was a similar story when a heating element in one of the clean-in-place tanks failed. Staff electricians jumped on the problem, pulled the old element out, and wired the new one in. Over the years, having licensed tradesmen on staff has saved the utility about $150,000.
The technical skills aren’t deployed only at the membrane plant. The team members perform other jobs in the water distribution system, such as wiring pumps.
There is more to the new membrane plant: a sleek building with plenty of windows to let in natural light, and a minimalist control room with a few computer screens and a 70-inch monitor. But the real advantage is what goes on beyond the control room windows: Providing the city of Ogden with clean water to grow.
Growth drives demand
The membrane filtration plant is not the only water source for Ogden, an expanding city at the foot of the Wasatch Mountains in central Utah. About 13 miles northeast, the city draws from six deep wells that supply water year-round. The city owns and maintains the wells, which are on U.S. Forest Service property.
“In most of Ogden, landscape irrigation is with potable water, so in the warmer summer months consumption goes quite high,” says Ruston Monson, water production supervisor at the membrane plant. After the watering season (mid-May to mid-October), usage shuts down.
The wells add 13 mgd to the membrane plant’s 13.5 mgd capacity. A 24-inch line carries well water down Ogden Canyon to the city and provides backup for membrane plant water in case of a problem with the 36-inch line from the plant to the city.
The driver for all this water production is growth. The area around Ogden is a prime location for skiing, hiking, biking, boating, and other recreation. “It’s really an outdoor enthusiast community,” Monson says. “There’s a lot of new commercial growth as well.”
Ogden, 40 miles north of Salt Lake City, is attractive to people who like the area but don’t want the complications of big-city living. Ogden’s population according to the 2010 census was 82,825; for 2015 the Census Bureau estimated 85,444, a 3 percent increase in five years.
The membrane plant is not at capacity, and there is room for more. The design allows for expansion to 17 mgd. Says Monson, “We’re going to drill more wells also, and we’re in the earliest stages of that process.”