Everything You Need To Know About Covered Lagoons

Everything You Need to Know About Covered Lagoons

Lagoons are a cost-effective and popular way to treat water. Many people utilize the advantages of covered lagoons for wastewater, using them to treat large communities or homes. You can find lagoons on farms to treat the endless amounts of waste that cows and pigs produce, or you could see one in someone's backyard, acting as a private source of water treatment that can be siphoned back to water plants in an irrigation system. Even cities build lagoons to help them efficiently treat wastewater from citizens.

Whatever your reason for building and maintaining a covered lagoon, it's a complex system requiring adequate knowledge. It's essential to understand all the different aspects of lagoons, from the chemical decomposition process to their general uses and maintenance.

Covered lagoons are incredibly effective and work uniquely, breaking down bacteria and suspended solids in an anaerobic process. Here's everything you need to know about them.

What Are Lagoon Systems?

Lagoon systems are deep, pond-like basins that can treat wastewater. A lagoon uses time as its primary factor in decomposition. The waste in the lagoon undergoes a series of biological and chemical processes, effectively treating the water through natural methods.

This is a broad definition of lagoon systems. In a real-life situation, you'll have to tailor your lagoon to fit your location's specific needs. To build and construct a lagoon, you'll first have to prep the area and determine the various factors that go into maintaining one.

A few things you should keep in mind if you're determining whether to build a lagoon:

  • Soil type: The type of soil used in your lagoon will have various effects on its biological and chemical processes, so you should determine this before you start building. Depending on the location, some lagoons may require the bottom of the basin to be lined with clay or another material to prevent leaks into the groundwater. Make sure you identify the best soil for this step to avoid contamination and regulatory violations.
  • EPA regulations: Every area has different laws — ensure you know the land laws before you start building a lagoon system. These protections are established to emphasize safety and cleanliness, and referencing them can help you construct an effective, well-built lagoon that won't create problems for you.
  • Climate: Be aware of the local climate before you build your lagoon. Factors such as temperature and the amount of sunlight will play a significant role in the lagoon's biological processes. The type of lagoon you're building should also align with your area's climate — some lagoons are better suited for warmer weather with plenty of sunlight so the water doesn't freeze, and others may excel in the cold.
  • Available land: The amount of land you'll need is a simple box to be checked off, but it may be the most important. Lagoons can often be large, vast basins of water with great depths.
  • Type of wastewater: You'll want to consider the composition of your wastewater before you attempt to treat it with your lagoon. If you plan on recycling this water and using it to water crops, for instance, you may need to rid the treated lagoon water of disease-causing bacteria to meet regulatory standards.

A lagoon is a more general term used to label a wastewater treatment strategy. The definition of a deep body of water using natural processes to break down waste generally applies to all lagoons. Still, specific types of lagoons also fit under this umbrella definition.

What Are the Different Types of Lagoons?

You should match your lagoon type to the environment surrounding it and the goal it should accomplish. The two main lagoon categories are aerobic and anaerobic. Aerobic simply refers to the involvement of oxygen, whereas anaerobic denotes the absence of oxygen.


Aerobic lagoons require oxygen in the wastewater treatment process. Aerobic lagoons are commonly used in one of two ways:

Naturally Aerobic

Naturally aerobic lagoons use natural processes to cleanse the water. To achieve this breakdown, these lagoons are usually much shallower than others. Sunlight penetrates the lagoon's depths along with oxygen carried in from the wind and surrounding air, combining to create an effective cleansing process.

Because of the need for adequate sunlight and warmer water, naturally aerobic lagoons are better suited for hotter climates. If the water freezes, the natural treatment process ceases to exist, so it's vital to find a suitable climate to keep the water at the correct temperature.

Treatment ranges for these lagoons are typically shorter — adequate cleaning can be completed in anywhere from three to 50 days. Shallowness can cause problems in these types of lagoons, resulting in weeds sprouting on the bottom. To counter this growth, naturally aerobic lagoons should be paved or lined. However, algae and aerobic bacteria are positive growths in these lagoons, aiding in the treatment process.

Artificially Aerated

Whereas naturally aerobic lagoons use sunlight and naturally occurring oxygen to treat water, aerated lagoons use aeration systems to add oxygen to the water. These lagoons often require significant amounts of energy to power this aeration, resulting in more costs. However, these costs are offset by the efficiency and quickness with which the water is treated — aerated lagoons are often smaller and require less time for treatment.

Aerated lagoons are also usually less expensive to run than mechanical water treatment processes, and if the lagoon uses wind-driven energy, this can lower costs significantly. Because of their small sizes and short detention times, aerated lagoons serve well in many small communities.


Anaerobic lagoons act as a counter-strategy to aerobic ones, eliminating oxygen from the treatment process — anaerobic literally means "without oxygen." Anaerobic lagoons institute a unique but effective technique for breaking down and treating waste. They split between two more types — covered and uncovered.

Uncovered Anaerobic Lagoon

Uncovered anaerobic lagoons are just as they sound — lagoons without a cover, using the absence of oxygen as the main driver for treatment. However, uncovered lagoons can often pose problems as they rely on a thin crust forming on the surface to keep odors and gases in. If this crust breaks, it could emit greenhouse gases and expose an unpleasant smell.

Covered Anaerobic Lagoon

A covered anaerobic lagoon is generally considered the better option between the two. Covered lagoons use a manmade cover to keep gases in. These lagoons are in widespread use and are great at effectively treating wastewater.

What Is a Covered Lagoon?

A covered lagoon is one of the best lagoon types for various reasons. Like other lagoons, this type is a large, earthen basin that treats wastewater. Covered lagoons use the absence of oxygen to break raw sewage down into other compounds that you can siphon out of the lagoon as effluent. The lagoon is covered with a strong material such as high-density polyethylene (HDPE) to trap gases and odors.

To ensure a lack of dissolved oxygen, covered lagoons are usually deeper than most, generally ranging between 8 and 15 feet. They also typically take longer to work than other lagoons, as the process involves a slow breaking down of organic compounds. Treatment generally takes around 20 to 150 days. They aren't heated, and they need to stay relatively cool without freezing for optimum efficiency. Like with other lagoons, the treatment process ceases to work if the water freezes.

How Does a Covered Lagoon Work?

A complex microbial process is involved in treating water in a covered lagoon. In a basic overview, raw wastewater, or influent, enters the lagoon near the bottom. With the lack of dissolved oxygen, the waste breaks up into two sections — a thick bottom layer and a liquid layer. The bottom layer is slowly processed and broken down into two main compounds, which are methane and carbon dioxide.

At the deep depths of a covered lagoon, anaerobic conditions remain stable and work against volatile organic compounds. The top layer usually consists of scum, grease and other materials floating in the water. The layer at the bottom of your lagoon will eventually accumulate and have to be cleaned out.

From a microbial perspective, the treatment process operates at two different levels — acid formation and methane production. During the acid phase, bacteria convert complex organic compounds into simple organic compounds. Simply, bacteria in covered lagoons transform carbs, fats and proteins into organic acids.

The methane stage involves two steps. In the first step, known as acetogenesis, bacteria transform organic acids to acetate, hydrogen gas and carbon dioxide. Then, methanogenic organisms known as "methane formers" convert the acetate, hydrogen gas and carbon dioxide into methane gas.

The methane step relies mainly on the lagoon's external factors — primarily temperature. If the temperature isn't ideal, this could slow or inhibit the process, creating issues with treatment. This is why it's so essential to pick the correct climate and type of lagoon for your location. Something as simple as the temperature can dictate a complex microbial process in the dark depths of your lagoon.

The ideal temperature for a covered lagoon digester ranges between 77 to 104 degrees Fahrenheit (25 to 40 degrees Celsius), with a pH level between 6.6 to 7.6 and alkalinity ranging from 1,000 to 5,000 mg/L. Water that gets too cold or drops below freezing will make the treatment process suffer, and a pH level that falls below 6.2 will stop the methane production process altogether.

Once the water is treated, it is siphoned off as effluent for other uses, whether that be into other treatment systems or a recycled water system that transfers to irrigation.

What Are Covered Lagoons Used For?

Because of their large size and slow treatment process, covered lagoons are popular choices for cattle owners and those who run farms. The vast landscapes and lack of residential homes offer an ideal space for a covered lagoon. Covered lagoons are also cheaper and less expensive to build and maintain, making them ideal for individuals looking to cut costs but retain effectiveness.

Because covered lagoons produce methane, you can also use them to heat buildings, power engines and generate electricity. Methane production improves covered lagoons' overall value, as they can treat water and power buildings.

Covered lagoons are often involved in a series of treatment systems. One lagoon may bridge into several others, cleansing the water at each step to ensure safe, effectively treated effluent.

A great example of an effective covered lagoon system is at Royal Farms in Tulare, California. In this system, cattle manure is flushed from the pens into a three-cell covered lagoon system where this influent is treated. The covered lagoons successfully reduce odor and provide a natural way to break down raw wastewater.

Royal Farms recovers heat from the engine generators to warm nursery barns, and they use the final irrigation effluent as barn flush water and irrigation water for crops. The generated electricity covers energy costs, and any remaining is sold.

Royal Farms is an excellent display of the value in building a covered lagoon, as it can be a versatile tool to treat your water and power your facility.

Advantages and Disadvantages of Anaerobic Lagoons

Anaerobic covered lagoons offer various advantages and disadvantages. Depending on your situation, location and climate, you'll want to determine which benefits are most rewarding and which disadvantages would be most detrimental.

Some anaerobic lagoon advantages include:

  • Cost-effectiveness: A covered lagoon is a great way to reduce costs and maintain an effective wastewater treatment strategy. You won't need to use additional energy to power your lagoon.
  • Additional value: Methane biogas creates channels for electricity to power buildings. Electricity can power facilities and heat buildings, and any excess amounts can be sold for profit.
  • Odor control: A cover allows you to trap unpleasant odors underneath, keeping them out of the surrounding environment.

Covered lagoons can also bring several disadvantages, such as:

  • Time: The treatment process often takes longer than other strategies. You'll rely on natural microbial processes to break down organic matter, which is often a methodical, drawn-out procedure.
  • Size: You will need a lot of land to build a covered lagoon, and this is often unattainable in residential areas. Constructing the lagoon can also introduce several impediments, including land and EPA regulations.
  • Dependent on external factors: Climate and temperature will have a considerable impact on your lagoon. If one of these isn't a good match for your lagoon, it could pose significant problems to the biological processes occurring underneath the surface.
  • Cleaning: Anaerobic lagoons split influent into layers. The bottom layer is dark and thick. This layer will eventually accumulate and require you to clean it out. An excessive accumulation of this layer can result in poor lagoon performance and amplified odors. Luckily, there are professional services that can help with anaerobic lagoon cleaning.

Contact Bristola for Anaerobic Lagoon Cleaning Solutions

At Bristola, we provide an innovative submersible robotic cleaning system that offers solutions to all of your covered lagoon cleaning needs. Our process eliminates common cleaning disadvantages like system downtime and human exposure hours. Instead, we increase water quality, carbon reduction and facility efficiencies, all with zero-human entry for a safer and quicker process. You can keep your system running while we clean out your lagoon. Contact us today to get more information on our solution!