The Basics of Sewage Lagoons

All sewage lagoons share some features, although the specific mechanisms of water treatment can vary greatly between designs. Commercial and residential lagoons tend to vary the most since they are different in size and treatment amount. When comparing them within their own categories, you’ll find that the same basic processes are at work across the field. All sewage lagoons hold wastewater for a few days at a minimum, so it’s essential to keep them from seeping or leaking into the surrounding soil during that time. Understand the important design elements necessary for all sewage lagoons, regardless of size or category, to ensure your wastewater management process works properly.

How Do Sewage Lagoons Work?

Lagoons are a surface-level treatment option for processing sewage wastewater into a cleaner water that is safe to reuse or discharge. A sewage lagoon can convert the blackwater supplied by a community into a steady supply of safe irrigation water to keep crops growing in dry climates without the need for drilling and pumping wells. In areas where the soil isn’t conducive to underground septic systems with buried field lines, open air lagoons are used at the residential and community level for easy processing with little equipment or extra work. Natural bacteria break down the solid and liquid waste mixed into the water, improving its safety and condition over time. Eventually, the water is clean enough to treat further, use in some way, or release into the surrounding environment without damaging it. Sewage lagoons are used as part of all traditional and modern wastewater treatment plants, and they’re also widely used as replacements for septic systems or informal cesspits that aren’t as tightly controlled.

Where are These Lagoons Used?

Sewage lagoons are found at more than just wastewater treatment plants. Other important uses of these holding and treatment ponds include:

  • Livestock farms and concentrated feeding operations that generate thousands of gallons of liquid manure when cleaning out barns and structures
  • Hotels and other hospitality businesses located in remote areas where no common sewage or septic services are available
  • Industrial and manufacturing facilities that produce wastewater high in chemicals and other hazardous compounds
  • Food processing plants, especially meat and slaughtering facilities, that produces a greasy and caustic mix of wastewater that is prone to bacterial overgrowth
  • Municipal storm water management areas, especially where there’s a risk of open or closed sewage systems overflowing during rainstorms and hurricanes
  • Treatment for wastewater from bathroom facilities at amusement parks and public recreation areas far out in the wilderness.

There’s a lot of overlap in design requirements and chemical reaction concerns between sewage lagoons and other wastewater holding ponds. Regardless of the exact mixture of chemicals and water held in the pond, all of these structures require a reliable, impermeable liner that can handle the corrosive nature of the mixture.

Important Design Elements for Sewage Lagoons

There’s more to building a reliable and safe lagoon than just putting in a flexible geomembrane liner. These design elements are essential for all sewage lagoons, regardless of the processing method or the style of discharge. Pay close attention to the following design elements to build a lagoon that won’t fail and risk damaging the environment or harming someone’s health.

Proper Angle for Bank Slope

Steep banks are too likely to suffer from erosion over time and collapse eventually, creating risk for leaks and reducing the total volume of the lagoon. Yet, extremely low sloped banks require so much earth moving and grading that it’s impossible to fit into most project budgets. Finding the correct angle of the bank depends on the size and shape of the pond, but most lagoons need an angle around 15 to 20 degrees to prevent erosion and remain stable. Loose soils may call for a slightly more reclined angled, even with the help of a geomembrane liner. This angle prevents both erosion from runoff flowing into the pond and from wave action caused by wind along the surface of the water.

Total Depth and Surface

For natural aerobic or aerated ponds, depth is usually a maximum of only three to five feet. This ensures that air and sunlight penetrate to the depths to maintain a certain speed of decomposition and processing. Anaerobic ponds need a depth beyond this point, reaching up to 20 to 30 feet deep on a commercial scale, in order to keep the water cooler and to establish oxygen-free zones. Large surface area is important for naturally and artificially aerated lagoons since the water must make contact with the air to evaporate and stay oxygenated.

Overflow Protection

Spillways, overflow sensors, drainage pipes, and dam reinforcements all prevent dangerous conditions during a flood. Sewage lagoons can easily top their banks in routine rainfall events if not properly designed with extra space for rising waters. Make sure impermeable liners are used over any spillways and other overflow areas to direct sewage runoff to where it’s safe to discharge rather than allowing it to soak into the ground around the lagoon.

Fences and Signs

Due to the hazards of the wastewater contained in the lagoon, all of these ponds should feature clear signage at the very least to warn adults about the hazards. Of course, signs don’t help with the animals and children that are also attracted to these bodies of water. Fences and secure locking gates are recommended for all sewage lagoons; even relatively shallow and small ones installed for residential use. In fact, fencing is even more important for these features since they’re usually near homes where children and pets are playing.

Why Lagoons Need Liners

Without a liner, a sewage lagoon can’t reliably contain the wastewater stored within it. Seepage occurs with any material that isn’t watertight and impermeable, which includes many materials for lining like concrete and clay. Soil is naturally prone to seepage due to the gaps between individual particles of soil. Geomembranes are most commonly used as impermeable liners due to their flexibility. As long as you select a high-quality liner that can withstand the chemical compounds and corrosive nature of the sewage, it should make the ideal impermeable barrier to control seepage and runoff in a lagoon.

The basics of sewage lagoons may remain similar across the various industries, but each specialty requires a different approach. Don’t stop at determining the basic parameters of the lagoon system. Dive into the specifics of the wastewater treatment system needed for your particular need. If you need advice product or installation advice, you can always ask for help from our expert team here at BTL Liners.


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