Risks of Both Active and Closed Sewage Lagoon

Sewage lagoons, when properly designed, are often in use for two decades or longer before being retired. Eventually, demand changes or renovations become so expensive that new facilities make more sense. Yet, even closed and abandoned sewage lagoons still pose risks to the surrounding environment unless properly built in the first place. Careful design prevents all of the following issues from making a sewage lagoon a nuisance or a health risk. Avoid the potential disease spread or damage that could arise from a poorly designed sewage lagoon by exploring the risks of some installations.

Unpleasant Odors

The least dangerous, but most widespread issue with poorly designed sewage lagoons, is offensive odors. As the bacteria in a waste pond break down the sewage and improve the water quality, they can produce a wide range of gases. A balanced mix of bacteria will make little to no noticeable odor, even when standing close to the water. This is true for aerobic and anaerobic ponds alike. If an anaerobic pond is disturbed for cleaning or sludge measurement, it may produce a slight odor for a short period of time. Any strong or noticeable odors are a clear sign something is out of balance in the sewage lagoon.

Bacterial Spread

If commercial or residential lagoons leak or overflow, the escaping wastewater can carry bacteria and viruses to areas where humans can come in contact with them. Bacteria and viruses picked up by humans, or that enter the drinking water supply, can lead to vomiting, headaches, muscle cramps, and even life-threatening conditions like dysentery and hepatitis. Proper design of a sewage lagoon, regardless of its size or purpose, prevents the risk of any bacteria or viruses escaping the holding area. Berms should surround any drains or overflow areas so that sewage is directed away from occupied areas for safety.

Nitrogen and Phosphorous Overload

When sewage wastewater escapes from a holding pond or lagoon and mixes into the natural water supply, the influx of nutrients often results in negative effects. Sewage is particularly high in nitrogen and phosphorous, which is why the sludge from these lagoons can serve as a potent fertilizer source. If these nutrients flood a body of water that’s not acclimated to them, the result is algae blooms, dead fish and water plant die off. Algae overgrowth dramatically reduces dissolved oxygen levels, leaving water unable to support plant and fish life. Keep sewage out of local waterways until the water has processed enough not to no longer effect stream and lake health. Make sure closed and sealed ponds can’t leak and lose sewage long after being forgotten since it can be hard to track the original source of the runoff.

Mosquito Breeding

Any standing water, exposed to the air, runs the risk of incubating mosquito eggs and larvae over the summer. Sewage lagoons are particularly prone to worsening insect issues in an area, especially when residential ponds are installed just a few hundred feet away from backyards and other gathering areas. Aeration equipment, that breaks up the surface of the water, is the best option for treating mosquitoes. In addition, chemical controls that won’t interfere with proper sewage processing, can also be employed. Natural treatment options like barley straw pellets are rarely an option for these kinds of applications since they’re gradual and won’t provide enough protection for a sewage lagoon.


All sewage lagoons are at risk for flooding, regardless of their size or purpose. Large scale commercial water treatment plants are usually located far from homes and businesses that might be damaged by floods. Unfortunately, residential lagoons need to stay near the homes they serve to effectively drain and process waste. This means that flooding conditions can bring sewage near homes where it poses a health risk. Secondary containment basins and spillways direct sewage in case of floods so that it can’t travel far from the designated area. Make sure any containment basins and barriers are lined are well to prevent seepage.

Falling and Drowning

Even small and shallow lagoon ponds located in backyards pose a slip and fall hazard to anyone traveling through the area. Small ponds are easily hidden by tall grass or weeds until a human or animal has slipped down its banks. Shallow grades on the banks, of no more than 20 percent slope, are essential for allowing guests to climb back out if they stumble into the pond. Deeper anaerobic storage and processing areas need extra protection due to their increased depth and volume. Commercial treatment plants absolutely need fencing and drowning prevention due to the size of the facilities.

Sludge Accumulation

Solid particles settle out of sewage as wastewater processes, becoming sludge that fills the bottom of the pond. All ponds eventually fill up entirely with sludge over time. Careful measuring and timely cleaning of the sewage lagoon is necessary to keep it functioning as designed. Make a plan to deal with the sewage sludge safely and effectively before sizing and installing a particular pond. Even a small lagoon can produce hundreds of pounds of sludge per year from a single home’s sewage supply. This sludge is easily pumped for removal, but it must be disposed of properly at an approved dumping station or sold as fertilizer after further processing.

With the right design and a little attention every month, a sewage lagoon is a low risk way to process waste with minimal energy costs. These systems are easy to visually inspect since they’re one of the few modern waste management designs to work at the surface of the soil rather than deep underneath it. Shop our selection of liners here at BTL Liners to find the right product for your sewage lagoon project.

Liners by BTL

AquaArmor Pond Liner

The most versatile liner on the market today, AquaArmor maximizes protection from harmful UV rays, tear resistance and punctures that cause leaks. Simply the best liner on the market.

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