During Water Week 2017, the Water Quality Assn. (WQA)...
Fighting contaminants in ponds and lakes with harsh chemicals can be dangerous, expensive and ineffective, yet the alternative—aeration equipment—can be too expensive to be cost-effective. But if you can catch the power of the wind with a windmill-driven aeration system, you can have the best of both worlds.
Whether due to algae blooms, animal waste or other problematic water chemistry, freshwater lakes and ponds everywhere are becoming perilously contaminated. Managers and owners of ponds, lakes and reservoirs are increasingly turning to aeration to eliminate these problems as an alternative to harsh chemical treatments such as copper sulfate.
Windmill-driven aeration, widely used in agricultural and recreational bodies of water due to its low capital cost and energy freedom, is now becoming increasingly popular in small municipal applications such as water storage, golf courses and public parks.
Aerating the Attica Reservoir
In Attica, N.Y., the water department caught on to wind power almost nine years ago. The 8.5-acre reservoir there, which holds approximately 50 million gal of water, was contaminated with an influx of manganese and iron during the spring and autumn water turnovers.
“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 [suspended particles].”
Krawczyk said the water treatment plant had used copper sulfate at the reservoir as an algaecide until a few years earlier when the Department of Environmental Conservation issued new regulations on its application due to potentially toxic effects on fish, swimmers and the surrounding habitat.
“We did quite a bit of exploration on the Internet and aeration appeared to be the best solution,” Krawczyk said. “Oxidation would solve the manganese problem, and there are harsh chemicals that will provide that, but we didn’t want to use harsh chemicals. Plus, the reservoir is in a remote location, so chemical treatment wasn’t a good solution.”
Air & Water
Constructed in 1928, the Attica reservoir is a man-made lake that is fed by the surface waters of Crow Creek and is located in a wooded area miles away from the water treatment plant. The remote location also made running power to an electric aeration device problematic, although the water department wanted to avoid the cost of energy anyway.
“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 at the reservoir. But either of those choices were going to be brutally expensive and a logistical nightmare. The terrain between the treatment plant and the reservoir is full of big ravines and is just a mess.”
“In the process of researching aeration, I came across the Koenders Windmill website [the parent company of Superior Windmills]. The wind-power aeration solution has made us think differently. I had started researching water problems stemming from iron and manganese, and aeration kept reappearing as one of the best ways to take care of the problem. So we decided to pursue it.”
Krawczyk said the simplicity and efficiencies of the windmill aeration system were very impressive. It was simple to construct and self-install, had relatively few parts and required little maintenance and no electric power. The logistical considerations were not an issue because the system is completely self-contained and ideal for remote locations.
“The windmill aeration system couldn’t be a simpler design,” Krawczyk said. “The wind creates a rotary motion that is converted by the windmill to a reciprocating motion. It pumps a diaphragm and that pumps air into the reservoir. It appeared to be a perfect fit for us.”
The constant aeration windmill keeps the water fresh because it pulls water down from the top, then it sweeps it across the bottom and pushes it up as a column of air, according to Krawczyk. The effect is similar to turnover that is occurring at all times, keeping the water oxygenated.
Height & Footprint
There were two important considerations before making a final decision on the windmill: height and footprint.
“The reservoir is located in a wooded area that is sheltered by trees,” Krawczyk said. “There are not a lot of clearings. We had to keep the windmills at a relatively low height—12 ft—so that we could catch the air currents as they move across the water. 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.”
The other problem was that because the reservoir is contained by an earthen dam that is fairly narrow, the windmill needed to have a relatively small footprint. The bigger the windmill tower, the bigger the footprint, so the 12-ft tower was a good solution for both footprint and height.
The Attica Water Department purchased five windmill aeration systems. Three were installed at the primary reservoir and one was for standby. The fifth windmill was eventually disassembled and converted to a water wheel that continuously flows and aerates water at a secondary reservoir.
Krawczyk has been pleased with the performance of the systems, including the low-maintenance requirements. “We seldom run into any repairs,” he 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 two to three years without having to service them again.”