While it’s clear that any ponds used for holding winery wastewater will need lining, many owners and managers aren’t sure what that entails. The lining process can seem intimidating even before project managers begin the process of selecting the right material. From permeable woven geotextiles to impermeable membranes that can last decades, there are a lot of options for flexible liner materials. Many of the products marketed to winery owners for wastewater ponds are actually better suited for small, recreational or decorative installations only. Others are far more chemical resistant than wine waste calls for, resulting in an overpriced treatment system. Get just the right type of liner with this guide to making your selection.
State and Regional Requirements
Start by checking out the specific codes and laws applying to waste handling in your state, region, and county. Watershed protection areas often extend through multiple counties and apply to farmers, including vineyard owners, in all of them. These laws are designed to protect waterways first and soil health second, so you’ll generally find some mention of liner requirements in them. Many states, even those with specific codes for winery wastewater like California, only specify the use of an impermeable liner material in any holding ponds or containment basins for tanks. They won’t tell you which material is most resistant to acidic residues or easy to clean when dredging is needed. You’ll have to dig deeper to find out more.
The Importance of Impermeable Barriers
Impermeable barriers are mandated by most state codes because they’re the only way to keep water from migrating through the soil around the pond. Even bentonite clay and other natural products commonly sold to seal ponds aren’t secure enough for waste products. Wastewater can damage the environment, so it can’t be allowed to seep out of a pond. Seepage occurs because even the slickest clay soil is made of tiny particles that only fit so tightly together. Loose soils tend to have a lot of gaps, while compacted and thick clay soils have smaller gaps. Still, even clay allows water to slowly seep through these openings. Only a high quality, flexible liner will truly control this constant loss of water through the ground. Even concrete isn’t impermeable without the addition of a base liner.
Concrete vs Flexible Liners
Speaking of concrete, many ponds require at least some concrete for stability along the banks and sides. It also helps prevent damage from heavy equipment entering and exiting the pond for the routine dredging required for winery wastewater management. However, don’t treat the concrete as the primary liner for the pond. It’s not a full impermeable liner. Spray-on coatings wear off after a few years and can become damaged by heavy equipment. Laying down a flexible liner for the pond before concrete is poured creates the ideal combination of seepage control and protection from damage from above. Older concrete lined ponds can also be renovated with the addition of an impermeable layer over the surface instead.
Which Flexible Liner Material is Best for Winery Wastewater?
Winery wastewater isn’t going to be used for drinking or raising fish, so it doesn’t require a potable water or fish safe liner. Yet, you still need to select the right material for its construction since some materials just aren’t fit for the challenging installation. Here are some of the most common, pond liner materials you’ll find on the market and how they stack up for containing winery wastewater undergoing treatment.
High Density Polyethylene
High density polyethylene (HDPE) is a widely used polymer. It is flexible, but is stiffer than low density polyethylene, reinforced polyethylene or polyvinyl chloride, making it difficult to fit into tight corners. It’s a common choice for lining wastewater containment basins, but it is less forgiving when used for ponds with tight sides and greater depths. HDPE is tear resistant and better for handling heavy equipment traffic than low density polyethylene, but still not as strong as reinforced polyethylene. It’s only a good choice if reinforced materials aren’t available.
Low Density Polyethylene
Low density polyethylene (LDPE) overcomes the stiffness of HDPE while still offering good chemical resistance against acids. Yet its lower resistance to sheering and tearing makes it a poor choice for winery waste ponds that will be cleaned with heavy equipment. Dredging may cause the liner to tear after only a few years of use. Burying it under concrete can help, but the weight of the concrete may pose a problem for this less durable liner. Reinforced polyethylene solves this problem while retaining all of these benefits.
To combine the strength, flexibility, and chemical resistance of both types of polyethylene in one package, look for reinforced polyethylene (RPE) liners. Many of the industry leading liners from BTL Liners fall into this category. Reinforcement allows for a thinner and more flexible sheet while providing superior tear and rip resistance to HDPE alone. Most of these products are made from combined layers of both polyethylene varieties to ensure a combination of their best traits. The reinforcement design is what takes it over the top by ensuring a long-life through durability. Make sure to get a UV resistant product if you’re planning for an exposed installation since the sun’s rays still break down polyethylene nearly as much as another polymer.
Some of the other liners we sell here at BTL Liners are made from reinforced polypropylene (RPP) instead. RPP is another popular option for lining winery wastewater ponds because it’s very chemical resistant, especially against highly acidic waste. Pure pomace and high strength juice residues won’t cause this liner to peel or develop holes. RPP is also good for containment areas where high volumes of less concentrated waste could leak. It’s often less expensive than RPE, making it a complement for projects that need both high and low risk containment.
Polyvinyl chloride (PVC) is a common pond liner material. While they may work fine for certain applications, they’re not a great fit for wineries. First, the PVC offers less chemical resistance in most formulations than RPE or other products. PVC is also known for leaching chemicals into the water unless you use a more expensive fish safe formula. Those chemicals could react with your soil or plants if you’re planning to reuse wastewater for irrigation. Don’t let the liner you choose for your ponds affect the health of your overall operation.
The Question of Seams
Seam sealing is one of the trickiest parts of pond installation. Even if you plan to have a team of professionals handle the installation, designing the pond to minimize seams will better ensure its success in the long run. Finding a manufacturer who offers custom sizes to fit your project’s needs is the best way to do this. Wider rolls and folded sheets allow you to cover multiple acres worth of soil without having to seal dozens of seams. For smaller holding ponds, it’s often possible to create a single seamless sheet that can be installed in place by hand or by machine. RPE is one of the easier materials to seal on site as needed, so choose it to make sure your seams don’t develop leaks that are hard to find while the pond is filled.
Installing Aeration and Filtration Equipment
Most winery wastewater ponds will involve some level of treatment, even if the water is intended for discharge rather than reuse. Every piece of filtration or aeration equipment installed in the pond must either fit over the surface or rise through the liner and create a penetration. Minimize penetrations through the liner to control the number of places where you’ll need to check for leaks. Each opening through the liner is a potential leak later. Most winery aeration equipment is easily installed floating on the surface or over the edges of a pond instead, reducing the equipment installed along the bottom.
Impermeable Liners vs Natural Clay Liners
As discussed above in the section about impermeability, natural clay products like bentonite aren’t generally a good fit for wastewater control. The clay particles are still too prone to seepage to truly control the loss of water. Even if your state and county regulations allow for the use of this kind of liner, it’s also not likely worth the cost and upkeep. Bentonite must be applied in very thick layers of 12 to 16 inches to form a barrier that holds any water back. This can add up to multiple tons of material to cover a full-sized wastewater storage pond. With the need to replenish the layer with new clay every three to 10 years, you’re looking at a lot of work just to maintain a barrier that isn’t truly waterproof. Sticking with a polymer liner is a lot easier in the long run.