Image

Credit: Photo: ITT Flygt

The wastewater treatment plant in Fort Atkinson, Wis., processes 2.7 mgd.
Image

Credit: Photo: ITT Flygt

Flyght Pump being hoisted for inspection.

The fibrous material carried in residential influent typically was composed of feminine and household products, and rubber gloves commonly reached the plant from industrial connections. Several major food plants also contribute grease—even after onsite pretreatment—which serves as a binding agent for the fibrous matter. Add the wear evident on the original pump impellers and the stage was set for problems.

Pumps fitted with ITT Flygt's N impeller have since corrected the problem. The impeller is suited for wastewater flows with fibrous solids. The semi-open, self-cleaning design keeps the leading edges of the impeller vanes unobstructed, where fouling often sets the stage for clogging. The leading edges pass across a stationary relief groove that clears any snared fibrous solids, grease, or sludge, creating a self-cleaning flow path through the pump.

“We invested in the new N pump technology because we've experienced excellent reliability from Flygt pumps used elsewhere throughout the plant and in the lift stations of our collection system,” said Christensen. “Some have been operating here for 25 or 30 years. The upgrade at the digester wet well also had to be compatible with the existing operational design.

“The N pump upgrade has achieved the desired results,” he said. “The N pump has delivered the needed reliability and thus far fully eliminated the clogging problem.

— Steve London is a Lansdale, Pa.-based business writer.