Now that you’ve explored the challenges of storing produced water from wineries and some of the common sources of it, it’s time to consider specific design parameters. A well-designed, produced water system will result in affordable and effective treatment and reuse opportunities. Alternatively, a lack of preparation will lead to a produced water system that is costly, odor-producing, and difficult to manage. Ponds are generally the best storage unit for winery process water, but some parts of the system may also require tanks if you intend to treat the water for reuse. Learn the basics of designing produced ponds for wineries to ensure you’re starting off on the right foot.
Storage or Treatment?
The first question, that guides the design of any produced water pond, is whether it’s solely for storage or if it will also function as a treatment unit. Many wineries build sewage connections or septic systems to discharge their wastewater almost immediately, but a storage pond prevents even this kind of system from getting overwhelmed during periods of heavy use. Simple storage ponds must be drained in some way every few weeks, to months at the most, to avoid bacterial growth and waste build-up that leads to odors and other issues. Treatment ponds can hold water for much longer periods thanks to the active or passive breakdown of waste. However, they almost all require some kind of extra equipment or special design to become more effective than simple storage ponds. Consider the higher cost and greater effort required for treatment ponds before assuming you’re going to build a number of them. The winery may need both types to handle the high output of crush season.
Ponds vs Tanks
After deciding on the extent of water treatment you’re comfortable handling on-site at the winery, you’ll need to choose between ponds and tanks for holding the majority of the volume. Ponds are generally a better choice for holding and treating water on a winery for a wide range of reasons.
Exposure to Sun and Air
When evaporation is specified as part of the treatment or discharge process, you’ll definitely want the open design and large surface area of a shallow pond rather than a deep and enclosed tank. Tanks are limited in their evaporation rate, even when designed for open installation. Exposure to the sun and air is also part of many treatment processes, encouraging beneficial bacteria to break down waste and improve the water quality.
Aeration Options
Aeration is one of the most popular options for treating winery produced water, because it’s affordable to operate and easy to implement in a wide range of ponds. It’s generally harder to add aeration equipment to tanks due to their rigid walls, deep and narrow shapes and corners with lack of flow. Shallow and wide ponds already enjoy natural aeration effects when water blows over the surface and it’s relatively easy to increase the dissolved oxygen rate with strategically placed pumps and diffusers.
Anaerobic Control
Most treatment methods for produced water from wineries involves plenty of oxygen, but some techniques call for anaerobic digestion instead. In these cases, it may make sense to use enclosed tanks for at least part of the treatment plan. However, you’re also free to use ponds for this kind of low-oxygen processing by simply adding matching covers over the top. Tightly sealed covers keep oxygen and extra rainwater out, creating an anaerobic environment in even the largest treatment pond.
Secondary Containment
Ponds and tanks themselves are forms of primary containment, but they both require secondary containment to protect the winery’s buildings and land from damage if there’s a spill. Tanks can be built with a double-walled design to contain leaks, but this kind of containment is limited in volume and very expensive. It’s far more affordable to create water-tight basins under the tanks to capture any lost liquids. If you’re already excavating and lining a pit or basin, you might as well use it for storage instead of having to buy tanks too. Ponds are easily designed with secondary containment built right in through the use of double-layer liners that trap water before it can reach the soil.
Combining Both
In most wineries, aiming to treat wastewater on site, it’s necessary to install both tanks and ponds. This is true whether the water is to be discharged somewhere or reused for irrigation. Even when ponds are used for aeration and long-term storage, tanks are still necessary for clarification and settling. These steps help both dissolved and suspended solids sink to the bottom where they’re easier to collect and remove. Doing this in a smaller tank reduces the need for sludge removal in a large pond where it’s expensive and could damage the liner. Many specialty micro screens and other filtration units also function better in the higher pressure of a small tank. Don’t be afraid to combine both types of produced water storage to create a custom system that works well for your winery.
Surface Ponds vs Underground Treatment and Discharge
The majority of wineries in many parts of the world, including British Columbia and Southern France, still lack advanced produced water handling systems. These facilities tend to rely on simple methods of underground discharge that allow water to directly flow into the ground. Wineries that are more concerned about their effect on the environment may add in a level of underground treatment such as a septic tank that allows some solids to settle out first.
Neither of these options compares to the treatment power offered by surface ponds. While underground treatment can offer some anaerobic improvements, it’s much more difficult to routinely test the mixture to see how it’s progressing. The water’s quality also improves more slowly, than on the surface, due to the lack of exposure to sun and fresh air. While underground holding and treatment tanks can solve odor issues by keeping them trapped underground, they also disguise the signs of incomplete or poor waste treatment. Bringing the produced water to the surface, where issues can be seen and smelled, will encourage the entire winery team to work together to improve its quality.
How Irrigation Ponds Differ from Produced Water Ponds
While it may be possible to reuse produced water as a form of irrigation for thirsty grape vines, don’t assume that an irrigation pond can double as a holding space for wastewater. Irrigation ponds are generally designed to hold fresh water that’s either diverted from a nearby water source or pumped out of the ground from a well. They typically don’t require any treatment equipment, like aeration, to keep water quality high since the turnover rate ensures the supply is refreshed on a regular basis. Even if the produced water you need to store will be used within a few weeks as irrigation water, it can develop a lot of quality issues during that time. You’ll likely need to add at least basic aeration equipment to maintain the current level of quality or better while using the supply up; which alters the design significantly from a simple irrigation pond.
Make sure the liner you choose for any produced water ponds is rated for wastewater applications and not just irrigation. The same acidity, salinity, and high level of dissolved solids that can make this produced water challenging to reuse for irrigation also have an effect on the liner material. Durable and chemical resistant liners will hold up through years of exposure to acidic and salty solutions without delaminating or developing pinholes.
Odor Control Measures
It’s a common misconception that any form of produced, wastewater has to smell. These odors are generated by specific bacteria and the production of certain gases during the decomposition of chemical and organic compounds. Careful handling and treatment of the produced water will keep smells to a minimum and prevent them from interrupting tourist’s use of the winery. Increasing evaporation, speeding up the nitrogen cycle, encouraging the growth of certain bacteria, and limiting solids mixed into the wastewater all go a long way in controlling odor. The very design of the pond itself also plays a role. While shallow ponds, with large surfaces areas, are generally recommended for their evaporation assistance, some depth is needed to keep odors under control. Finding the perfect balance for odor control usually means settling on a final depth of between 3 to 5 feet and routinely dredging the pond to keep it at that level.
Choosing a Liner
Every produced water, storage pond requires a liner. Some states allow wastewater storage ponds on wineries to be built without liners or only with a layer of natural clay. Even if this is allowed by local and state environmental codes, it leaves you vulnerable to paying fines and fees later. Regulations may allow for a design that leaks. If there’s an environmental effect traced back to your winery’s runoff, it doesn’t typically help that you followed the regulations on pond design. You will still have to pay for remediation and may have to redesign your storage system. Instead, start with a flexible and impermeable liner that will reliably contain the produced water. Here’s what you need to know to make the right choice.
Material Options
There is a wide range of polymers, used for pond liners, sold across different industries. Only a few of the materials are appropriate for winery produced water. Thanks to the acidity, salinity, and chemical composition of this mixture, many common materials like polyvinyl chloride (PVC) are a less than ideal choice. Don’t forget that these wastewater ponds are generally installed with the liner exposed to the surface in order to keep the pond easy to dredge and clean as needed. This means the liner will need a high UV resistance; another feature that’s hard to find from PVC liners.
Low-density and high-density polyethylene (LDPE and HDPE) have good chemical resistance, but they vary in durability and flexibility. LDPE is more flexible and easier to install, but it’s not as durable in general as HDPE. Reinforced polyethylene (RPE) is the best choice for lining produced water ponds in wineries, because it combines all the best features of other polyethylene products. It offers superior chemical resistance, durability, flexibility, and a lower weight than other liner products. These features significantly speed up installation. Despite being lighter and thinner, RPE liners are as tough or tougher than other materials available for lining wastewater ponds.
Reinforced Design
RPE liners’ reinforced design helps them outperform other materials. All flexible liner materials are made from solid sheets of material, but only reinforced designs feature a woven tape or thread core to stabilize them. Adding reinforcement dramatically increases the tear and rip resistance of the liner, which is especially valuable during the installation process. Without reinforcement, liners are prone to catching on any leftover rocks, roots, or uneven soil. The resistance also carries through to protect the liner from crease and wrinkle damage over time. When large wrinkles are left in non-reinforced material during lining, the folds become cracks and tears after the weight of the water has a chance to press down on it for years on end. Reinforcement not only helps the material resist this form of damage, it makes it easier to work out wrinkles and creases during installation by increasing the lay-flat factor of the liner.
Underlayment
Installing an underlayment is a good idea to protect any liner and extend its life, even if it’s made with RPE. Underlayments are thick layers of non-woven material that aren’t designed to hold water. They’re often made of matted fiber materials that resemble felt. Much thicker than the liner itself, the underlayment is designed to cushion it and keep it separated from the soil. This protects the liners during installation if the soil is rough. It also offers long-term protection from roots and rocks that rise due to the freeze-thaw cycle.
Designing Storage Ponds for Second Uses
While produced water storage ponds need to be designed with their primary use in mind, they can also serve secondary purposes with the right features. As long as the water quality remains high and there are no odor issues, a produced winery pond can serve as a decorative water feature or even a recreational attraction. Allowing visitors to rent paddle boats or take gondola tours of the pond won’t hurt its function, but obviously it’ll require some careful planning of water treatment to maintain a high enough quality. If you don’t want to add extra treatment just to let guests get close to the pond, consider locating it at a distance where it can add to the visual appeal of the landscape without any odor risks.
Access for Treatment Equipment
It’s not enough to plan for the space required for water treatment equipment and processing units. Don’t forget about adding easy access for maintaining and repairing this equipment as well. Buried drains and filters are known for being difficult to access in wastewater ponds; produced water ponds are no exception. If heavy equipment will be needed to lift and replace extra-large pumps or filtration units, make sure they’re located where it will be easy to access without damaging the liner or the banks.
Bank Designs for Wastewater Storage and Treatment
Banks are the most fragile part of any pond, but it’s especially true for wastewater storage ponds. A small pond has relatively little water movement at the surface, but large ponds develop significant wave action due to wind effects on the surface. The constant effect of waves lapping at the banks causes constant erosion unless the surface is properly lined. Yet even with liners, steep and badly designed banks can still collapse from destabilization occurring under the surface. Designing the ideal banks starts with determining the ideal angle of repose for the particular soil you’re working with. Each soil has a different angle of repose, but most textures fall somewhere around 30 degrees as an ideal angle for pond banks. This angle slows down water rolling over the surface so it can’t carry soil into the pond and cause erosion. It’s also stable enough that soil under the liner shouldn’t shift and leave voids that can easily collapse and rip the material.
Sludge and Sediment Removal
Thanks to the high amount of organic material mixed into winery produced water, there’s a constant accumulation of sludge and sediment in any ponds used to hold it. Even with the addition of extra settling and clarifying tanks, these ponds tend to accumulate larger amounts of sludge than other types of holding areas. Exposed liners are easily damaged during the sludge removal process until the pond is built with these processes in mind. Creating concrete lined dredging zones allows heavy equipment to move in and out of the pond as needed to keep the depth at just the right level. Some busy wineries may need to dredge more than once a year to keep up with the sludge, so don’t underestimate the need for safe access to the entire space with heavy machinery.
Many of the finer details of produced water pond design depend largely on the local conditions, including average annual rainfall amounts and soil quality. A design that would work well for a small winery with sandy soil might not function properly when built in a rainy area with clay soil and a larger scale of waste. But no matter the specific details of the final pond, a long lasting, quality product from BTL Liners is the best way to keep it lined and free from leaks.
