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CIPP Provides Timely Solution for Treatment Plant

30 April 2009

Cured-in-place pipe (CIPP) technology from Reynolds Inliner provided a timely and cost-effective solution for damaged pipe at a wastewater treatment plant near the Mississippi River.

Vipel polyester resin from AOC contributed to the project’s success.

The T.E. Maxson Wastewater Treatment Plant of the City of Memphis, Tennessee, has four, 180-foot (55-meter) diameter primary clarifiers. Clarifiers 1, 2 and 3 were built in 1980 with 54-inch (137-centimeter) diameter concrete inlet pipes. Looking forward, engineers designed the splitter box that distributes influent to the clarifiers to allow for a fourth clarifier, which was added in 1996 with a 48-inch (122-centimeter) 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 a constantly moist environment,” said Ken Thompson, Operations Manager for Reynolds Inliner. “The most severe damage was an opening in the crown of one pipe that was approximately 70 feet (21.3 meters) in length and 15 to 18 inches (38 to 46 centimeters) wide. Inlet pipes for Clarifiers 3 and 4 were CIPP-lined as a proactive, precautionary measure.”

Steve Lindsey, Senior Pipelines Rehabilitation Specialist, Jordan, Jones & Goulding, Inc. (JJG), designed the pipe project. “Because the inlet pipes run under the clarifiers, 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 planned maintenance downtimes.”

No more than two clarifiers could be shut down at any given time and for only short periods. The plant’s maximum flow rate is rated at 160 million gallons per day (605.7 million liters per day). The design average daily flow is 90 million gallons (340.7 million liters).

Reynolds 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 (6-meter) long, sweeping 90-degree turn. Reynolds 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 (32 millimeters) thick.

After an inversion was complete, the water in the tube was heated to accelerate the resin cure, and Reynolds supplied two boiler trucks to shorten the job’s total cure cycle and thus minimize clarifier downtime.

The total linear feet of CIPP rehabilitation performed by Reynolds Inliner was 680 feet (207.3 meters). 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.