Reverse osmosis gives Julesburg, Colo., water supply new lease on life
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| Four reverse osmosis pumps remove nitrogen and other impurities from Julesburg, Colo.'s well water. The purified water would leach minerals from the town's ductile iron water pipes, so it must be blended with well water to restore its pH balance. (Photo courtesy of Julesburg Utilities) |
Getting the best performance from a new appliance or system involves a certain amount of trial and error, whether it is a home theater, a lawn mower or—in the case of Julesburg, Colo.—a reverse osmosis water treatment facility.
The town is located in the state's northeast corner, surrounded by farms and feedlots. Nitrates from fertilizer and manure leach into the groundwater, driving the mineral concentration in the town's three wells as high as 16 parts per million, compared to the state limit of 10 ppm. "We've been looking for better water since 1949," admitted Julesburg Utility Manager Allen Coyne, "but it was hard for the town council to justify the kind of investment a water treatment plant required."
State and Federal regulations have a way of forcing hard decisions, however. In 2000, the Colorado Department of Public Health and Environment ordered Julesburg to clean up its water supply.
Point-of-use technology applied on municipal scale
Having accepted the inevitability of change, the council began to weigh options for bringing its water quality up to standard. Those options included digging a new well field or importing higher quality water from the Ogallala Aquifer, but complicated water transfer rights ruled out both alternatives.
Nebraska had high quality water to sell, but not quantity, Coyne recalled. "The state's own water needs took priority, which meant we could be cut back in our use or shut off completely," he said. "Whatever we did, we had to ensure our customers a reliable water supply."
Another possibility was installing point-of-use filters on every metered customer—768 individual units. That approach presented a whole new set of problems. "Only water from indoor taps would meet drinking standards. Filters would have to be changed every six months, so our service technicians would have to be bonded to go into homes. Owners would want to be home when the workers were there," he ticked off the disadvantages. "We didn't want to spend a lot of money to wind up with a system that was so inflexible."
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| The blended water in this 750,000-gal. water tank supplies Julesburg residents with clean, safe water that meets the state's standards for nitrogen concentration. (Photo courtesy of Julesburg Utilities) |
While point-of-use units ultimately proved too expensive and inefficient to pursue, the technology suggested an answer to Julesburg's water treatment woes. Many residents had already installed their own point-of-use reverse osmosis filters to remove the nitrates from their drinking water. "We knew RO was very effective at a residential scale, and we knew that Brighton, Colo., was using RO to treat its water," he said. "Once we started doing the research, it was clear that reverse osmosis was the best way to treat water for the entire town."
Project includes computer-controlled motors, sewer system upgrade
Julesburg selected the Ionics, Inc., four-train brackish water reverse osmosis system to be the heart of its $2.5 million water treatment plant. A USDA Rural Development grant supplied $698,000, and the Colorado Department of Local Affairs contributed a $300,000 Energy and Mineral Impact Assistance grant. The town carries the remaining $1,687,000 debt through Water Resources and Power Development Authority and the USDA.
The system draws water from the town's three wells, each of which is fitted with a 100-hp pump operated by a computer-controlled, variable-speed drive. The four RO pumps are powered by 75-hp motors and 35-hp booster motors.
For every 350 gallons of water the system treats, 250 denitrified gallons are sent to two storage facilities totaling one million gallons, and 100 gallons of highly concentrated water goes to Julesburg's upgraded sewage treatment plant. The town built a $1.7 million package sewer plant to take care of the excess water.
Tinkering with water mix to save electricity, protect water lines
At the storage facility, the purified water is blended with untreated well water. "Our water lines are ductile iron, and purified water sucks the minerals right out of the metal," explained Coyne. "Mixing well water and purified water restores enough of the pH to protect the pipes."
In its first year of operation, the plant sent out a 50-percent treated/50-percent well water mix and had an electrical bill of $42,000. At the council's request, Coyne boosted the ratio to 65/35 the next year and watched the plant's electrical costs go up to $51,000. "For each 5-percent increase in the amount of treated water in the blend, we found there was roughly an 8-percent increase in electrical costs," Coyne estimated.
The plant reduced the mix to 60/40 this year and expects to see a corresponding drop in electrical use. Coyne believes that the 50/50 mix may turn out to offer the best return on water and electricity while protecting the town water lines.
The five-year drought cycle gripping the west must also be factored into water use and operating costs, he pointed out. In 2001, the town used 165 million gallons. The following year—the same year the water plant experimented with a higher treated-water mix—was one of the driest on record, and Julesburg residents used 185 million gallons. "The more water they use, the more we have to make, the higher the operating costs," the utility manager said.
Water bills have gone up in Julesburg, but residents accept it because, on the dry prairie of northeastern Colorado, "the public is smart about water. They understand that safe drinking water comes at a price," noted Coyne.
In the meantime, the utility continues to collect performance data on its RO water treatment plant and fine tune its operation. Adding a new function to a system may increase its energy use, but efficiency can still be part of the package, if you take the time to get to know your equipment.
