With more than 300 miles of wastewater collection lines and 167 lift stations, the Utilities Maintenance Division of Marion County in central Florida oversees a sewer infrastructure under constant attack from H2S gas and microbiologically influenced corrosion (MIC). As part of the county’s ongoing sewer line and lift station maintenance programs, utility engineers approved the use of 100 percent solids epoxy coatings specifically designed by Tnemec for use in gravity sewers, force mains and sanitary lift stations.
“Tnemec’s Perma-Shield line of coatings has been approved for both new construction of wastewater treatment facilities and sewer renovation projects in Marion County,” coating consultant Bill Langer acknowledged. “The most recent project involved the rehabilitation of a lift station that included the installation of new ductile iron pipes with interior and exterior linings specifically designed for wastewater immersion and fume environments.”
The pipe manufacturer lined the interior of the 8-inch diameter ductile iron pipe with Series 431 Perma-Shield PL, a 100 percent solids, ceramic epoxy lining that is spray-applied. Series 431 provides a virtually impenetrable barrier to the elevated levels of hydrogen sulfide gas (H2S) and other sewer gases, which can rapidly corrode ductile iron pipes and fittings used in lift stations and wastewater environments.
“The testing data for Series 431 was helpful in demonstrating its superior performance compared to older coating technologies used to protect the interior of pipes and their fittings,” Langer said. “Series 431 was specifically designed for permeation resistance to the higher levels of sewer gases found in today’s collection systems. Permeability resistance is the key measure of a high-performance lining for ductile iron pipe and fittings used in these severe wastewater environments.”
The interior surface of the pipes was prepared by grinding and abrasive blast cleaning to remove all loose annealing oxides, rust, dirt and other foreign matter. After the surface was cleaned of all dust and abrasives, Series 431 was applied using plural component airless spray equipment. “The owner was pleased with the durability and uniform film thickness of the Series 431, which maintained excellent adhesion throughout the installation,” Langer noted.
The exterior of the pipes received two coats of Series 435 Perma-Glaze, a thick-film, 100 percent solids, abrasion-resistant modified polyamine epoxy, which was applied by brush and roller to achieve a total of 40 mils dry film thickness (DFT). Series 435 offers low permeation to H2S gas, protects against microbiologically influenced corrosion (MIC) and provides chemical resistance to severe wastewater conditions found in force mains, gravity sewers and lift stations.
Langer credits the successful completion of the lift station project to a well coordinated effort between the project engineer, the pipe manufacturer and the general contractor. “Tnemec’s history of providing high-performance products to the water and wastewater markets was also instrumental in the final decision to specify the Series 431 epoxy liner for this project,” Langer added. “Tnemec has such a good reputation in this market that it carried a good deal of weight.”