A Change of Mixers Makes a Big Treatment Difference for a Small-Community Clean-Water Plant

Not in Winfield, Kansas, where a replacement mixer with a four-pole motor has yielded substantial energy savings and a promise of longevity

A Change of Mixers Makes a Big Treatment Difference for a Small-Community Clean-Water Plant

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In the Kansas city of Winfield they know a thing or two about energy.

Since 1904, Winfield has been a public power community. Its residents are stockholders, and the profits go to support vital services such as police, fire, streets and parks. At the local wastewater treatment facility, Clint Gregor also knows a thing or two. He has worked there since it was commissioned in 1996.

“We’re a top-three power user here,” says Gregor. “Energy takes up 30% of our budget, and in today’s world, we have to look at power consumption more than ever.”


While energy costs are firmly in the industry spotlight, Gregor’s driving factor for continuous improvement is total cost of ownership. Return on investment has been in focus of late due to the prohibitive cost of maintaining some of the plant’s mixers.

The 1.5 mgd plant serves a population of 12,000. A 7.5 hp direct-drive mixer in the anoxic zone of a 26-foot-deep aeration tank continued to have issues, causing unplanned downtime. Repair bills were running high. “Being quoted around $8,000 to repair a mixer that costs $10,000 gets your attention,” says Gregor.

“We did everything we could to keep it going, but eventually it was all chewed up beyond repair. The cost of having the copper rewound on a direct-drive mixer or replacing an impeller seemed sky-high. Everything seemed geared to making the mixer almost a throwaway piece of equipment.

“This can’t be right. The work couldn’t be undertaken by a local repair shop. That added to our costs, and then we were given lead times of anything between 18 and 20 weeks, which was totally unacceptable.”


Effective mixing in the anoxic zone was important to nutrient removal. Keen to find an alternative mixer that would give the best total cost of ownership, while also being energy efficient, Gregor found help from local supplier, Fluid Equipment. Representative Jeff Ubben recommended a Landia mixer that he said would give 20-plus years of reliable service.

“It was a very different but far better construction compared to what we had,” Gregor observes. “The mixer that failed had a 16-pole motor. The new one was just a four-pole, which would be much better for controlling speeds. These were just the first signs that despite what some people say in the industry, not all mixers are the same.”

Although it has a much lower speed and considerably less horsepower than the previous mixer, Gregor reports that the new unit provides equally good mixing, if not better. Additionally, installation was easy and cost-effective because it was possible to use the existing guide rail.


Gregor notes that the new mixer’s propellers are sturdy and therefore heavier, but overall it is relatively light and easy to service, with a motor about half the size of the failed unit.

The City of Winfield was established in 1870 by the American military commander and political candidate Winfield Scott (1786-1866). Known as Old Fuss and Feathers for his insistence on proper military etiquette, he was also called the Grand Old Man of the Army for his many years of service.

That adherence to high standards and commitment to the job prevail today in Winfield. Gregor and his team work to meet ever-stricter permit requirements prescribed by the U.S. EPA and the Kansas Department of Health and Environment to protect the Walnut River, which was declared an Outstanding National Resource Water in the late 1990s.

Persistence in best practice is paying off for Winfield, as after one year the new mixer was using half the energy of its predecessor.

“Total cost of ownership is best,” says Gregor. “This mixer will soon pay for itself. We also know that because of the way it is designed and the way the company behind it operates, we won’t be held to ransom for heavy repair bills and very expensive replacement parts.

“The amp draw is less than half of the old drive mixer, so we were confident in making significant energy savings as well as longevity. In our adjacent tank we have another mixer that is coming to the end of its days, and when it needs to go, we’ll be replacing it with a Landia mixer.”


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