PENETRON ARC: A Protective Coating Against Acid Attack in Wastewater Facilities

The pumps at the Nova Piqueri Sewage Pumping Station on the Tietê River in São Paulo, Brazil went online in June 2020. PENETRON ARC, an innovative new acid-activated protective coating that effectively protects concrete structures exposed to highly acidic environments, was successfully applied at the new facility.

The Tietê River rises in the Serra do Mar just east of the city of São Paulo and flows northwest for 700 miles (1,130 km) before ending in the Paraná River. Considered one of the most important economic conduits in the state of São Paulo, it is also known as the most polluted. Sabesp, a Brazilian water and waste management company owned by the state of São Paulo, was mandated in the 1990s to clean up the Tietê River.
 

Slowly Restoring a River

“After more than 20 years, the Tietê River clean-up still has a long way to go, but progress has been made,” notes Cláudio Neves Ourives, Executive Director of Penetron Brasil. “An important part of restoring a healthy river has been the ongoing expansion of sewage treatment capacity across the state. The recent completion of the Nova Piqueri sewage pumping station is part of that process.”

The Barueri wastewater treatment plant, the biggest such facility in Brazil, treats sewage from the city of São Paulo. The Nova Piqueri sewage pumping station, an automated station where sewage passes through a waste crusher and is pumped to a higher elevation to flow to the sewage treatment plant, is part of the Barueri plant upgrade. During the planning phase of the pumping station project, Telar Engenharia e Comércio S.A. (Telar), the project’s general contractor, looked for a way to protect the new concrete structures from the highly aggressive environment found in the aerobic conditions of a sewage treatment plant.
 

Preventing Premature Deterioration

Biodeterioration leads to premature deterioration of reinforced concrete structures from chemical attack, which is a serious concern for the wastewater industry. Sulfur-reducing bacteria in the effluent degrades the organic matter, forming hydrogen sulfide (H2S) as a waste product. The hydrogen sulfide gas is oxidized by sulfur-oxidizing bacteria to form biogenic sulfuric acid. This lowers the pH level on the surface of the concrete, enhancing the spread of sulfur-oxidizing, acid-producing bacteria.

“When concrete in sewer and septic environments is exposed to sulfates and biogenic sulfuric acid attack, deterioration of the concrete matrix and embedded reinforcing steel is accelerated – shortening the lifespan of the structures,” adds Cláudio Neves Ourives.
 

An Innovative New Solution for Concrete Durability

There are many ways to increase concrete’s resistance to acidic environments. Alternative measures include reducing the water/cement ratio (W/C) and increasing the moist curing time, or partially replacing Portland cement with cementitious materials, such as fly ash and ground granulated blast furnace slag. Most are ultimately no match for the acidic conditions and succumb to deterioration over time.

Penetron developed PENETRON ARC, an acid-activated protective mineral coating specifically formulated to provide concrete with acid resistance in aggressive aerobic wastewater environments. Topically applied to concrete surfaces, the protective strength of this coating is activated when exposed to the aggressive acids, especially sulfuric acid, found in wastewater treatment plants.

“When PENETRON ARC reacts to the acids in an aerobic wastewater environment, it is transformed into a dense, acid resistant shell,” says Cláudio Neves Ourives. “This coating protects and prolongs the life of the concrete substrate, even in the harshest conditions.”
 

Penetron System as a Total Solution

Penetron Brasil was also asked to provide a solution for the groundwater at the Nova Piqueri construction site adjacent to the Tietê River. Because the foundation slab of the sewage pumping station alone is 23 m (76 feet) below ground level, a waterproofing solution was needed to resist the hydrostatic pressure at that depth. A combination of PENETRON ARC, PENETRON and PENECRETE MORTAR was used to waterproof and protect the concrete tank walls and foundation slab of the Nova Piqueri sewage pumping station.

“Our Penetron Brasil team ultimately waterproofed the new and existing concrete elements from the high water table and applied a mineral coating as protection from the aggressive sewage environment,” summarizes Cláudio Neves Ourives. “That’s a total solution from Penetron.”