While geomembranes may offer the best combination of durability and flexibility for wastewater containment, they’re not all equally suited for this particular use. Wastewater from a mine or hospital is much more likely to react with liner materials and cause them to breakdown than clean water used to fill in a fishpond. You’ll need to choose a geomembrane that can take on the challenges of containing corrosive and damaging liquid since failure has such as high cost. You don’t want to learn that a certain polymer isn’t a good fit for storing hydrocarbon-rich fracturing waste by discovering a steady leak in your pond or tank. Use these recommendations to find a liner you can count on regardless of the chemical composition of the wastewater.
There are dozens of individual formulations used for making geomembrane liners. However, they tend to fall into a few basic categories based on shared composition or features. Your options are listed here in order of suitability for wastewater contaminant liners.
In general, the best combinations of chemical resistance and durability are found in the polyethylene family of flexible polymer liners. Of course, there’s plenty of variation within this family as well. Reinforced polyethylene (RPE) is the best choice for almost all wastewater applications. It combines both low density polyethylene (LDPE) with high density polyethylene (HDPE) to create a composite that is stronger and more durable than either material alone. The reinforced design also increases tear resistance, prevents wrinkles from forming that crack under the weight of the water, and protects the liner from freeze damage.
Polyvinyl chloride (PVC) may work well as a plumbing material for pipes, but it’s less ideal as a flexible liner for tough wastewater applications. The flexibility of the material is matched only by RPE, but it is much weaker in the chemical resistance category. UV degradation is also a major problem with most PVC liners. Tear resistance is low, unless the PVC is reinforced, which makes it thicker and heavier than similar reinforced polyethylene materials. PVC can also contribute chemical contaminants of its own to the wastewater, complicating efforts to treat it enough for discharge into local waterways.
More accurately known as ethylene propylene diene terpolymer (EPDM), this rubber material comes in thick sheets that are very durable. Yet, the durability is accomplished with a heavy weight that makes shipping and installation difficult, along with stiffness that makes it hard to fit the liner into corners and over edges. EPDM is best known as a roofing material and is only used secondarily as a pond liner. It’s not very UV or chemical resistant, making it a poor fit for most wastewater projects.
Geosynthetic Clay Liners
Geosynthetic clay liners combine open-weave geotextiles or geonets with layers of polymer amended clay. The clay is supposed to swell and expand when water is added to the lined pond or basin, creating a loose but somewhat impermeable barrier. This may work well enough for drainage ditches or low risk ponds, but it’s not reliable enough for use in wastewater containment systems. The clay is too permeable and prone to failure, even when reinforced with a mesh at the core, to use in such a sensitive situation.
Which Material is Best for Wastewater Containment Liners?
Reinforced polyethylene (RPE) is the best all-round liner for wastewater containment purposes. It offers the best combination of chemical resistance, UV resistance, durability, and longevity for its price. Other liners will require costly underlayment or modifications to work well in any modern wastewater application. If a less expensive geomembrane material is chosen to fit into a budget, expect to replace it within a few years and therefore spend any of the money you saved during the first installation.
Impermeability for Hazardous Wastewater
Impermeability is the most important feature for any liner used to contain hazardous materials. Even if you don’t find the wastewater particularly dangerous, the Environmental Protection Agency (EPA) likely disagrees. They base their qualification of hazardous or non-hazardous on risks to humans, animal life, plant life, and the environment. Simply having too much salt or soap mixed into wastewater can turn it from relatively benign to hazardous for fish and plant life. Check that the liners you choose offer the correct impermeability rating before you order, since a slow seepage problem is often not discovered for years.
Exposed vs Covered Installation
Most liners used in wastewater containment will be covered by dirt, sand, gravel, or even concrete. This does more than just hold down the liner. It also protects the polymers from the destructive UV rays of the sun. UV rays weaken the bonds between the particles in a liner, increasing brittleness and encouraging stretching and tears. If you won’t be covering every inch of the liner, you’ll need a product rated for exposed installation. BTL Liner’s ArmorPro, is available in formulations rated for 20 years of exposed use or more. Even if you plan to stick with a fully covered installation, using a product rated for exposure will protect you if the cover material ever moves and leaves the liner exposed to the sun.
Wear and Tear Resistance
Make sure to use a high quality, reinforced liner material when working on a large-scale pond or containment basin. Flexible liners bend easily to fit tighter corner but these tight spaces can make them prone to wrinkling. Smoothing and stretching out the material grows more difficult as the liner gets larger. Reinforced liners are wrinkle resistant because of the addition of the woven reinforcement tape. The material is more likely to roll flat, which is a major improvement since wrinkles are prone to cracking under the weight of a filled pond.
Let BTL Liners help you choose the right product if you’re still unsure what geomembranes work best for wastewater containment. We can discuss chemical resistance and installation ideas with you to develop a plan for your project.