City of Memphis Wastewater Treatment Plant
The T.E. Maxon Wastewater Treatment Plant of the City of Memphis, TN has four, 180-foot diameter primary clarifiers. Clarifiers 1, 2 and 3 were built in 1980 with 54-inch diameter concrete inlet pipes. Looking forward, engineers designed the splitter box that distributes effluent to the clairfiers, to allow a fourth clairfier, which was added in 1996 with a 48-inch diameter concrete inlet.
After 27 years, the floor of Clarifier 2 started shifting enough to affect the operation of the clarifier's scraper arms. Inspections showed that the ground beneath the clarifier needed to be stabilized and the underground inlet pipes for Clarifiers 1 and 2 needed to be repaired.
"Over the years, the concrete pipe was exposed to highly corrosive sewer gases in the constantly moist environment," said Ken Thompson of Layne Inliner, operations manager for Inliner. "The most severe damage was an opening in the crown of one pipe that was approximately seven feet in length and 15 to 18-inches wide. Inlet pipes for Clarifiers 3 and 4 were CIPP lined as a proacive and precautionary measure."
Steve Lindsey, senior pipelines rehabilitation specialist, Jordan, Jones & Goulding, Inc (JJC), designed the pipe project. "Because the inlet pipes run under the clairifiers, excavation and replacement was out of the question," he said. "It was essential to keep the plant running, so the repairs had to be scheduled to coincide with the planned maintenance down times."
No more than two clairfiers could be shut down at any given time and then only for short periods. The plant's maximum flow rate is rated at 160 million gallons per day. The design average daily flow is 90 million gallons.
Seamless Layne Inliner repaired the entire lengths of the four inlet pipes, including the steel discharge elbows that taper out of the splitter box in a 20-foot-long, sweeping 90-degree turn. Layne Inliner used the inversion process to install new, seamless liners into the discharge and pipe.
Each liner section consisted of a special felt tube that was impregnated with a Vipel unsaturated polyester resin in a wet-out facility. AOC chemists engineer CIPP resins to provide consistent wetting, handling and cure characteristics. The wet-out tubes were shipped to the job site in a refrigerated truck to prevent premature resin cure.
As the tube was installed through the splitter box opening, water pressure inside the tube moved it forward while inverting it along the host pipe interior. To effectively cover the damage in the inlet pipe crowns, the liner was designed to be 1.25-inches thick.
After each inversion was complete, the water in the tube was heated to accelerate the reaction that turns the resin into a permanent, chemically stable solid while also being corrosion resistant. Layne Inliner supplied two boiler trucks to shorten the job's total cure cycle and thus minimize clarifier downtime.
Over the course of the project, 680 feet of CIPP rehabilitation was performed. Before a clarifier was brought back on-line, the area where the splitter box connects with the discharge elbow was cleaned and sealed to improve resistance to corrosive wastewater being distributed from the box.
Role / Responsibility
Layne Inliner, LLC (formally known as Reynolds Inliner, LLC) - Prime Contractor; CIPP and miscellaneous rehabilitative measures