Beating the Gremlins

A UV disinfection system helps a plant meet a provincial disinfection mandate once a remedy is found for electrical voltage fluctuations.
Beating the Gremlins
Rick Kokiw, with the Hallett 30 UV reactors from UV Pure Technologies, worked with Ross Galbraith at Metcon Sales and Engineering and Mark Houghton at UV Pure Technologies on the system installation.

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A mandate from Manitoba Conservation and Water Steweardship required water treatment plants to use microfiltration or some form of primary disinfection other than chlorination.

Rick Kokiw, a Class II operator hired by the town of Rossburn to oversee the water treatment plant, preferred chlorine dioxide, but felt the cost would overwhelm the 550 town residents. “I wanted a solution that was simple, cost-competitive, and easy to maintain,” he says. “When I saw the Hallett 30 UV reactors from UV Pure Technologies at a water conference last year, I figured this was the way to go.”

The Rossburn plant was the first of three in the province to use the system. The manufacturer helped Kokiw adapt the system to account for an electrical anomaly related to the plant’s remote location. Once that was done, the units performed as designed and have done so ever since.

Keeping it simple

The plant draws from two wells producing 35,000 gpd; treatment consists of greensand filtration and softening. The filters reduce iron and manganese in the raw water from 1.0 mg/L or more to 0.04 to 0.10 mg/L.

Two part-time people do the daily testing and backwash, adjust the dosing pumps, and check the chemical levels for the feed pumps. “We don’t have an annunciator system, so we check the plant twice a day,” says Kokiw.

He located and built the headworks for the system where it would require the least pipe work. The best location also was a tight one. A welding shop fabricated a 3- by 2- by 6-foot-high frame for the four 9- by 8- by 32-inch-high reactors, mounted two per side and back-to-back.

Testing first

The NSF/ANSI 55 Class A UV units are effective against E. coli and other bacteria, Cryptosporidium and Giardia cysts, and most viruses. The UV lamps are mounted outside the process stream; the bulbs are mounted in air, and the energy is focused on the water column. Dual sensors monitor both lamp intensity and water quality.

Elliptical reflectors provide 360-degree coverage to destroy pathogens. The lamps can be replaced in minutes without draining the system, and an automatic stainless steel wiper system prevents quartz fouling.

Before the 30 gpm disinfection units arrived from distributor Metcon Sales and Engineering in Concord, Ont., Kokiw tested the single-phase 120/220-volt power supply and saw nothing wrong. “The reactors came with surge protectors, so we didn’t anticipate a problem with the utility’s normal voltage fluctuation of up to 5 volts,” says Kokiw. The water plant has no power factor correction capacitors to prevent voltage fluctuations.

Upon delivery of the units, Kokiw took them home, mounted them to the frame, built the manifolds and pretested the system, then disassembled everything and reassembled it at the plant. “I had just enough room to install ball valve manifolds and tees between the backs of the reactors,” he says. “They enable me to access each unit for repairs.”

He didn’t use solenoids because they are more complicated than ball valves: “I wanted a system simple enough that anyone with basic instructions could operate it,” he says.

He drilled into the plant’s concrete floor and bolted down the tall, top-heavy frame. Then he cut into the mainline going to the reservoir, installed two tees with a bypass valve between, ran the flexed stainless steel bellows hoses to the units, and plugged them in.

Correcting issues

Initially, Kokiw had an electrician wire the units so that they ran only when the plant produced water. When drawing from the first well, the net flow was 67 gpm across the three reactors. Drawing from the second well increased the flow to 79 to 90 gpm.

In about three weeks, the system’s sensing diodes began signaling tube problems. Mark Houghton, director of Canadian engineering sales at UV Pure, attributed the alarms to cycling the bulbs on and off too frequently.

“Tying the reactors to the three-phase pumps surged the tubes and ballasts when the pumps activated,” says Kokiw. “The reactors should run full-time and lamp life is then about a year. When the alarm signals reduced lamp intensity, I can turn off the reactor, switch on a standby unit, and order a set of tubes.”

After a second ballast failure, Kokiw determined that voltage fluctuation was to blame — lows average 105 volts when the distribution pumps activated. “The undulating power tripped an internal ballast switch,” says Kokiw.

Houghton had the answer: an uninterruptible power supply (UPS) from American Power Conversion. Since Kokiw installed the UPS in mid-December, the reactors have run perfectly. “It was a trial-and-error learning experience for all of us,” says Kokiw. The plant now complies with the primary disinfection mandate.



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