April 2009, Vol. 21, No.4
Attica Reservoir Utilizes Wind Power
Problem: Reservoir contaminated with manganese and iron.
Solution: Wind-powered aeration.
The Attica reservoir sits quietly in a wooded area of New York state, miles from the nearest water treatment plant. The man-made lake, constructed in 1928, is fed by surface water from Crow Creek. Beneath the reservoir’s surface brewed a problem of frequent manganese and iron contamination, which plagued the waters for almost 9 years.
“The condition was worst during the fall months when turnover would stir up iron and manganese that naturally occur in the reservoir,” said Brian Krawczyk, chief operator at the Attica Water Plant. “But when there was high manganese and iron content and we treated the water with chlorine, we would get red-water problems and constant turbidity.”
The 3.4-ha (8.5-ac) reservoir holds approximately 189,250 m3 (50 million gal) of water. Each spring and autumn during the water turnovers, the reservoir would become contaminated. The water treatment plant used copper sulfate as an algacide until about 15 years ago, when the New York State Department of Environmental Conservation issued new regulations.
After researching alternative treatment options, Attica Water Plant management decided that oxidation was the best solution. “Oxidation would solve the manganese problem, and there are harsh chemicals that will provide that,” Krawczyk explained. “But we didn’t want to use harsh chemicals.”
Aeration was another option, but the reservoir’s remote location would make it difficult to use an electric aeration device, and the Attica Water Department wanted to avoid the logistical hassle and cost of providing energy to the reservoir.
“We considered other options as well,” Krawczyk said. “We had a couple of air compressors at the water treatment plant and weighed the possibility of running air lines from the compressors all the way back to the reservoir. Another option was to run power back there and house the compressors there at the reservoir. But either of those choices was going to be brutally expensive and a logistical nightmare. The terrain between the treatment plant and the reservoir is full of big ravines.”
During his research, Krawczyk discovered another option, wind-powered aeration. After the Attica Water Department decided to pursue the option, Krawczyk was tasked with finding the right company to supply the aeration unit. This company was Koenders Windmill, parent company of Superior Windmills (Regina, Saskatchewan).
The wind-powered aeration system was self-contained, required little maintenance, and required no electric power, which worked well at the remote location. “The wind creates a rotary motion that is converted by the windmill to a reciprocating motion,” Krawczyk explained. “It pumps a diaphragm, and that pumps air into the reservoir.”
The system keeps the water fresh by pushing air to the bottom of the reservoir; the air then rises in bubbles to circulate the water. The result is constant turnover of the water to keep it continuously oxygenated.
The systems come in two sizes: 3.7 m tall (12 ft tall) with a 1.5-m (61-in.) base or 6 m tall (20 ft tall) with a 2.5-m (97-in.) base. Before installing the wind-powered aeration unit, the Attica Water Department had to determine the correct height necessary for maximum efficiency of the system. Since the reservoir is located in a wooded area and is contained by a fairly narrow earthen dam, the height of the system and size of the system’s base had to be limited. Because of these restraints, plant management decided to install the 3.7-m windmill to catch air currents that move across the water.
The Attica Water Department purchased five windmill aeration systems, installing three at the primary reservoir and holding two for backup purposes. “Even though the reservoir is located in a bowl, and there is not a whole lot of air moving in the area, just a relatively light breeze will keep the windmills spinning,” Krawczyk said. Krawczyk estimates that the windmills are turning approximately 75% of the time. They produce a volume of air that ranges from 0.04 to 0.08 m3/min (1.5 to 3 ft3/min) at 14 km/h (9 mph).
“We seldom run into any repairs,” Krawczyk said. “We just grease the pivots each year. We recently replaced the diaphragms and check valves, which was simply routine service. We will probably go for 2 to 3 years without having to service them again.”
The windmills cost between $1000 and $2000 each. The Attica Water Department spent approximately $4500 in total for the five systems. While the department has conducted no studies to determine if there has been payback for the systems, they were the most cost-effective solution for their problem, Krawczyk said. “In water quality, the difference was incredible,” he said.
For more information, see www.superiorwindmill.com, or contact Superior Windmills at (888) 821-5533 or firstname.lastname@example.org.