Material Selection for Wastewater Containment

All projects involving short- or long-term exposure to water require durable materials. Even plain water with a neutral pH is a strongly erosive force that slowly breaks down many materials. Using the wrong kind of geomembrane, reinforcement mesh, or concrete could result in an unreliable wastewater containment system. The materials used for various parts of a complex system also need to work together seamlessly without causing reactions or issues between them. If you’re still in the early stages of designing a wastewater containment system from scratch, these benefits and drawbacks of various materials will help you settle on the right choices for your project.

Metal Tanks and Structures

Metal tanks are widely used throughout industrial and processing facilities that generate the majority of the world’s wastewater. While these tanks may work for holding certain chemicals or gathering wastewater as it’s produced, they’re less than ideal for long-term storage, processing, or containment. First, metal tanks and structures can only ever serve as primary containment units. Double-walled metal tanks are less reliable than two-layer lined ponds or double-walled plastic tanks. The corrosion that threatens to weaken a metal tank’s first layer often occurs on the second barrier at the same time, leaving them both equally at risk for leaking. The majority of wastewater mixtures also contain chemicals or produce gases that corrode and weaken metal faster than normal, a problem that occurs with fresh water alone as well.

Rigid Plastic Tanks

Plastic tanks are a better choice than metal for most wastewater products due to their increased chemical resistance. Yet, you can’t assume that all polymers will automatically handle chemical exposure better than metal. Some plastic materials are even more likely to leak or collapse if used to store highly corrosive acids or solvents. Large, rigid tanks with high volumes are also difficult to transport and costly to install. They may require special foundations or reinforced supports to handle their high total weight being placed above grade.

Fiberglass and Other Resins

Fiberglass is another widely used tank material that offers more benefits than metal. It’s far more corrosion resistant than metal and is often resistant to chemicals that cause reactions in plastic materials. The fiberglass reinforcement also allows for these tanks to be thinner than their plastic counterparts. Unfortunately, even a thinner design doesn’t reduce the weight of these tanks very much. They tend to weigh less than metal ones, but still enough to complicate transportation and installation. The reduction in maintenance is an added bonus, but all of these benefits are offered by flexible liners that don’t have any of these drawbacks.

Flexible Geomembranes

For the most scalable, easiest to install, and lowest maintenance wastewater containment solution, stick with a chemical-resistant geomembrane. Materials like reinforced polyethylene (RPE) offer everything you need for wastewater control in an affordable and easy to install package. These liners conform to any space you excavate into the ground or build above grade. If you choose the right material, you don’t have to worry about breakdown due to corrosion or chemical reactions. Even UV exposure is fine with the right geomembrane rated for that kind of installation. Geomembranes are also highly impermeable, ensuring you don’t have to worry about seepage. If you want to use a porous material like concrete in your wastewater storage containment plan, you’ll likely need to combine it with a geomembrane to meet local and federal regulations.

Concrete

Concrete is one of the most widely used materials for primary and secondary containment. Its high strength and durability make it an obvious choice for both above and below ground tanks and ponds. However, concrete alone is not an impermeable barrier for containment. The material is more porous than you might assume from simply looking at it. Tiny openings between the cured cement particles suck water through like a sponge thanks to capillary action. Numerous coatings and liners have been developed over the decades to help concrete become an impermeable containment solution. Pairing an impermeable geomembrane with concrete reduces the drawbacks of the porous surface.

Combination Designs

As mentioned above, concrete and geomembranes are widely used together for a reliable and long-term containment system. Geomembranes are also used to repair or reinforce plastic, fiberglass, and metal tanks that are corroding due to constant contact with the wastewater. Since the polymers used for geomembranes tend to offer better corrosion resistance and react less to chemical exposure, they’re the best option for lining a tank that’s starting to show signs of damage. Lining a pond or tank before it fails can help extend its lifespan significantly and delay the need to replace it right away.

For best results, stick with geomembrane alone or paired with concrete when planning large in-ground ponds and holding pools. Geomembranes are also the most versatile choice for secondary containment since these layers and basins must cover much larger areas than primary containment systems. You’ll find reliable and affordable RPE liners available through BTL Liners that are ideal for all kinds of wastewater containment projects.


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