Under the Resource Conservation and Recovery Act (RCRA), the U.S. Environmental Protection Agency (EPA) is authorized to require secondary containment systems for aboveground storage systems (ASTs) containing chemicals used in water and wastewater treatment. According to 40 Code of Federal Regulations (CFR) Protection of the Environment part 264.193(b), “Secondary containment systems must be designed, installed and operated to prevent any migration of wastes or accumulated liquid out of the system to the soil, ground water, or surface water at any time during the use of the tank system…”
The federal regulation further states that, “Secondary containment systems must be at a minimum constructed of or lined with materials that are compatible with the wastes to be placed in the tank system and must have sufficient strength and thickness to prevent failure owing to pressure gradients (including static head and external hydrological forces), physical contact with the waste to which it is exposed, climatic conditions, and the stress of daily operation (including the stresses from nearby vehicular traffic).”
A variety of chemicals are used in drinking-water treatment for coagulation and flocculation, pH adjustment, corrosion control, sequestering, disinfection and oxidation, fluoridation, defluoridation, softening, taste and odor control, and as dechlorinators and antioxidants. Chemicals are used in wastewater treatment for coagulation, precipitation, oxidation and advanced oxidation, ion exchange, and neutralization and stabilization, which can be applied to wastewater during cleaning.
Tnemec offers a line of chemical-resistant, fiberglass mat reinforced vinyl ester and 100 percent solids epoxy linings in 65 and 125 mils dry film thickness (DFT) for secondary containment systems in water and wastewater environments. “These are thick, monolithic, fiberglass reinforced lining systems designed to contain chemical spillage for up to 72 hours,” according to Vaughn O’Dea, Director of sales, Tnemec Water and Wastewater Treatment. EPA regulations require spillage removal within 48 hours or in as timely manner as possible.
In addition to protecting against harsh chemicals, ChemBloc linings resist thermal cycling, impact and abrasion, O’Dea noted. Specific products include Series 237SC ChemBloc, a modified amine epoxy; Series 239SC ChemBloc, a modified novolac amine epoxy; and Series 252SC ChemBloc, a novolac vinyl ester. Each lining is available in two-component containment kits, which are easily mixed and roller-applied for fiberglass reinforced mat systems that specify 65 mil thickness. The linings are also available in three-component mortar containment kits that include a Part C (aggregate) for trowel-applied mortar/fiberglass reinforced applications requiring 125 mils thickness. “The fiberglass reinforced mortar is typically used for applications where thermal shock or more aggressive chemicals are considerations,” O’Dea shared.
Specifications for secondary containment systems linings usually include the use of primers or resurfacers to reduce outgassing, which is caused by voids and bugholes in both new and repaired concrete secondary containment systems. Series 201 Epoxoprime, a modified amine epoxy, is the primer specified for use with Series 237SC and Series 239SC mat-reinforced amine epoxy systems, while Series 251SC ChemBloc, a novolac vinyl ester, is the specified primer for Series 252SC.
At the 8.5 million gallons per day wastewater treatment plant in Salisbury, Md., three concrete containment areas measuring 40 feet by 40 feet with a three-foot high curbing used Tnemec’s modified novolac amine epoxy to protect the substrate from harsh chemicals, abrasion and thermal cycling. After the concrete was blast cleaned, the surface voids were filled in with Series 218 MortarClad, a modified epoxy cementitious resurfacer, followed by a prime coat of Epoxoprime and a trowel-applied basecoat of novolac amine epoxy.
While the basecoat was still wet, the fiberglass mat was laid into the surface and saturated with additional novolac amine epoxy until the mat was wet out. Additional coats of the novolac amine epoxy were added to the initial coat after it cured to achieve the desired thickness. A final topcoat of Series 282 Tneme-Glaze, a chemical- and solvent-resistant novolac epoxy glaze coat, was roller-applied for added protection.
“With the various system choices we offer, the ChemBloc line covers a majority of the chemicals and concentrations typically being stored for water and wastewater treatment,” O’Dea said. “The primary reason for choosing one of these lining systems over another is based on the chemical solutions in storage and the concentrations of those solutions.”
Once a new lining system has cured, inspection of the lining should include high voltage spark testing in accordance with NACE SPO188 Discontinuity (Holiday) Testing of Protective Coatings to determine the presence and number of discontinuities. “It’s always advisable to perform holiday testing following coating application to ensure you are achieving a monolithic barrier protection in a secondary containment system,” O’Dea added.