There’s hardly a more corrosive environment to be found than that of wastewater treatment plants, particularly dewatering rooms where the presence of high humidity and grit make steel and concrete surfaces ripe for corrosion.
Freshly applied coatings protect against corrosion and provide a near pristine appearance for the grit dewatering room at the new Fort Wayne Wastewater Treatment Plant. Photo Courtesy of the Sherwin-Williams Co.
There’s hardly a more corrosive environment to be found than that of wastewater treatment plants, particularly dewatering rooms where the presence of high humidity and grit make steel and concrete surfaces ripe for corrosion. While corrosion has many causes, a key cause in wastewater facilities is hydrogen sulfide gas created during the breakdown of organic waste. In addition to its flammability, the gas ultimately produces sulfuric acid, which is highly corrosive to steel, concrete and non-ferrous metals.
For the city of Fort Wayne, IN, planning for its new multi-million dollar headworks facility required detailed specifications for all the coatings used on interior surfaces. Howard Painting of Defiance, OH, was selected to do the bulk of the painting work at the site. The company is known throughout the Midwest as one of the top specialists for coating water treatment and wastewater treatment plants. It has worked extensively with more than 500 water and wastewater treatment facilities.
“The conditions at these facilities are very aggressive: they demand very high-performing, corrosion-resistant coatings,” said Joseph Howard, president of Howard Painting.
The main challenge of the project was the new grit dewatering room. The large, three-story room has a footprint of over 80 by 60 feet. Equipment includes vortex separators, cyclone separators, grit washing basins, conveyors and large, roll-off containers that hold the concentrated grit once it has been separated from the water. The room is designed so trucks can enter and back up to the grit roll-off containers for loading.
The new headworks facility replaces the original that was built in 1939. According to Bill Maxwell, project manager, engineering support services for the City of Fort Wayne, much of the city’s original equipment had been updated over the years, but the physical configuration of the old structure was unsuited for the increased flows that have been projected. The new treatment plant is licensed to process up to 60 mgd and can be expanded to up to 120 mgd.
Since the processes taking place in the dewatering room may release hydrogen sulfide, Howard Painting applied corrosion-resistant systems that would protect surfaces and machinery from this very aggressive environment. It was crucial to marry the surface with the coating best suited to protect it.
The room’s concrete floor is often subjected to grit spilled from tanks, abrasion from truck traffic and exposure to hydrogen sulfide gas. To protect the concrete surface, ArmorSeal® 1000 HS from Sherwin-Williams was applied. The heavy duty coating is a two-component polyamide epoxy formulated for chemical and industrial environments. In addition to its resistance to alkalis, abrasion, corrosion and chemical attack, the coating dries rapidly to a high-gloss finish.
Ceilings and walls in the grit dewatering room also required a protective finish to ward off damage from humidity, abrasion and hydrogen sulfide gas. Sherwin-Williams Macropoxy® 646 was selected for its high film build (up to 10 mils in one coat) and high solids. The coating’s properties allow it to be used both as a primer and topcoat, another time-saving measure that benefits the contractor and plant management.
Macropoxy 646 also was used in other areas of the plant including concrete block walls and ceilings as well as ferrous metal piping throughout the building.
For pipes that transport gases and sludge through the system, Sherwin-Williams D™ Acrylic Coating was applied to the exterior insulation portion of the pipes in colors that designated their contents - orange for gas and brown for sludge - for safety, identification and troubleshooting purposes. The finish is a 100 percent acrylic emulsion waterborne coating that is especially formulated for new construction and industrial maintenance applications. It dries quickly, can be used over many types of surfaces, has low odor and offers early moisture resistance.
The new Fort Wayne Wastewater Treatment Plant celebrated its inaugural use early this summer and so far all has gone well.
“We really have an impressive facility that will be able to service this community for many years to come,” Maxwell said.