The Inner Workings of Lagoons

Septic lagoon or holding pond for sewage

Introduction

When regular maintenance is completed, septic systems and portable toilet rentals can be a breeze. Although these two things may seem very different, they are both methods of waste collection. Both require the proper maintenance and waste removal to continue functioning at their optimal level. But what happens to the waste once it has been removed from your tank or portable toilet? We know that lagoons store waste but how does nature decompose and treat the waste?

Let us journey through the waste treatment process so that we can properly understand and respect nature’s methods.

Filtration & Pre-Treatment

Once you have entered the lagoon, you will come upon a series of large ponds. If they are in good condition, they should be bright green in color. There will be one pond however, that will look slightly muddier. This is due to the constant discharge being added to it. This pre-treatment pond is used as a temporary waste storage area.

Some waste treatment systems have a screen that the waste must go through prior to entering the pre-treatment area. This keeps unwanted items such as toys, rocks and other non-biodegradable objects from entering the system.

The Treatment Process

Anaerobic Decomposition       

The waste treatment system used in lagoons is often like that of septic systems. The main difference is that there are multiple ‘pools’ that have an open surface area. As the waste enters the system, the sludge (aka the solids) settles to the bottom. The anaerobic bacteria (bacteria that does not need oxygen) begin to decompose the sludge, transforming it into harmless biproducts. This process produces methane and is the main reason for the disagreeable odor associated with lagoons.

Aerobic Decomposition 

The wastewater has now risen to the surface and is receiving oxygen through photosynthesis and wind movement. This oxygen fuels the aerobic bacteria, giving them energy to break down the organic material into simpler and safer substances. This decomposition process can be seen in the bacteria and algae present in the lagoon. It is also why the bright green color is a sign of health.

Natural Disinfection

A healthy lagoon is quite effective in its ability to naturally disinfect the waste. Not only are the bacteria breaking down the harmful material, but the ultraviolet light from the sun also aids in the removal and death of the microorganisms. In fact, it has been found that the decomposition process occurring at lagoons naturally removes 99.99% of the harmful E. Coli bacteria.

Temperature Variations

Both anaerobic and aerobic decomposition processes are very temperature sensitive. As the temperatures drop and ice is formed, the transmission of oxygen is minimized and the bacteria slow down to conserve energy. This decrease in activity is a large part of why it is not recommended to pump septic systems in the winter. As winter fades and spring arrives, the bacteria begin to stir, and waste treatment begins again.

Discharge

Once the waste has been treated, there a multiple different discharge methods that are dependent on a couple of different factors. Some lagoons discharge annually, while others discharge seasonally. This method is meant to minimize the effect on the streams receiving the treated water. Many times, there are certain seasons where discharge is allowed, such as spring, when there is a higher water content, or winter, when the biological activity has slowed.

Other lagoons have continual discharge or no discharge. When there is no discharge, the lagoon is dependent on evaporation. This type of discharge is typically used in warmer climates, when the evaporation is continually occurring year-round. The continuous discharge lagoons often have multiple different combinations of ponds that allow a thorough treatment prior to the water being released.

Different Types of Lagoons

There are four main types of lagoons that are often mixed and matched for the optimum waste treatment. The types used depend on the environment and space available.

Facultative Lagoon

This lagoon is the most widely used with sludge and wastewater naturally separating and being decomposed by bacteria. They are typically 1.2m to 2.5m deep and can be used as single ponds or following aerated or anaerobic lagoons.

Aerated Lagoon

An aerated lagoon includes a mechanism that keeps waste moving and is consistently adding more oxygen. This allows more aerobic decomposition to occur. These ponds are classically 2m to 6m deep and require less space than the following pond. Having the Facultative lagoon after an aerated one allows the suspended particles to settle and the microorganisms to complete the treatment process more efficiently.

Aerobic Lagoon

Aerobic lagoons are reserved for warmer climates. They work by using primarily photosynthesis and aerobic decomposition. This is effective due to the shallow depth of the pond. They are typically only 0.30m to 0.45m deep, allowing the sunlight to penetrate the entire depth. This is also why they are not used in colder climates, as the waste would freeze and halt the treatment process.

Anaerobic Lagoon

These lagoons are mostly used for industrial waste or as pre-treatment ponds. With a depth of 2.5m to 5m, the organic matter tends to be much more concentrated. Due to this concentration, all biological activity is anaerobic and requires the waste to transfer to an aerated or a facultative pond for continued treatment. Odor is also a common issue with these lagoons, although the thick layer of scum formed by the bacteria often helps.

Desludging

Over the years, sludge will often begin to accumulate and will have reached a proper microbiological quality. This accumulation is because of the higher waste concentration, and the slower rate of anaerobic activity. The colder climate also affects this accumulation, since there are multiple months where biological activity is slowed to a near stop.

Desludging removes the remaining waste using sophisticated equipment. This remaining waste can be disposed of in multiple different fashions, depending on your location. In some places, such as in Ontario, the waste can be spread on agricultural fields. Other times it is dumped into a landfill or placed in an additional lagoon for further treatment.

Conclusion

And there you have it. The entire journey that is undertaken by the waste when it is collected from your property. Natural processes are powerful forces that allow us to continue to offer our services at the highest level possible. Whether you had rented a portable toilet or had your septic system pumped out, the lagoon allowed nature to treat the waste in such a manner that it was safe to release.

We hope that you were able to learn something from this blog! For more information on our services or other blogs, please check out our website.

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Call of the Wild Sanitation

October 9, 2024

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