Sewage Lagoon Vs. Septic Field: What's The Difference?

Septic systems rely on either a drain field or sewage lagoon to help process household waste. Although a drain field, sometimes called a septic leach field, is the preferred method, impermeable soils can make installing a drain field impossible. In that case, a sewage lagoon is sometimes used instead. If the term "sewage lagoon" sounds a bit too unpleasant, you can also refer to these waste treatment pools as "residential waste stabilization lagoons."

If you have a septic system, all of the wastewater from your house is collected in an underground septic tank. Inside the tank, solid waste settles to the bottom, while oils, fats, and grease rise to the top. This leaves water in the middle of the tank, but it's not clean water. Even though the solid waste settles out of the water, it still contains potentially harmful bacteria.

To deal with this, the water flows into a drain field outside the septic tank. The drain field is a series of perforated pipes running underground and surrounded by gravel to promote drainage. The water slowly flows out of these pipes, through the gravel and down through the soil below, where microorganisms consume the harmful bacteria. By the time the water from the septic system seeps into the groundwater below, it's bacteria-free and safe for the environment.

Unfortunately, in some places, a drain field simply won't work. The primary reason is that the soil around the septic tank may be impermeable. In this case, the water doesn't percolate through the soil and instead puddles on the ground. Some areas allow septic systems to utilize a sewage lagoon in this situation. When working well and properly maintained, a sewage lagoon can work for up to 30 years.

A sewage lagoon is a pool that is about 3 to 5 feet deep all the way around. Wastewater flows out of the septic tank and into the lagoon rather than into a drain field. In the lagoon, three different processes break down the harmful bacteria in the wastewater.

At the bottom of the lagoon, anaerobic good bacteria that don't need oxygen consume some of the harmful bacteria in the wastewater. On the top of the lagoon, aerobic bacteria that do need oxygen consume some of the harmful bacteria. In the middle, both types of bacteria are hard at work. Sunlight at the top of the lagoon supports algae, which in turn produce oxygen that supports aerobic bacteria in the lagoon.

When properly designed, built, and maintained, sewage lagoons are quite effective at cleaning wastewater. They're inexpensive to install and fairly easy to maintain. Their biggest benefit is that they can allow you to have a septic system where you otherwise might not be able to do so.

There is no hiding the elephant in the room, however; a sewage lagoon is a lake of wastewater on your property. If it's not well maintained or not operating properly for another reason, it can lead to foul odors and mosquito breeding. A lagoon also comes with some municipal rules. Many municipalities, for example, require fencing around sewage lagoons to protect children and animals.

Sewage lagoons require a bit more maintenance than a drain field, although they don't require massive amounts of work. You'll need to keep the grass and other vegetation around the lagoon short and remove any trees or bushes that get too close. For proper functioning, it's imperative that both sunlight and wind reach the lagoon unobstructed.

Don't use herbicides or other chemicals to keep the vegetation at bay, as they can upset the bacterial balance in the lagoon. When mowing or trimming, direct the clippings away from the lagoon. Cattails, duckweed, and other weeds can cause an organic overload, so remove them promptly when you find them at the water's edge or growing within the lagoon.