Septic System Descriptions

On-site Septic system:

A system that exists on your property which collects and treats the combined wastewater from any commercial or residential building before discharging to land, surface water or community collection system.


Wastewater can include water from your sink drains, bathtubs/showers, laundry washing machine, dishwasher and toilets.

Primary treatment:

Primary treatment is performed by using a standard septic tank. The wastewater moves from the plumbing of your building through the inlet of your septic tank. Here it is collected and allowed to settle. This separates the solids from the liquids. During this settling process naturally occurring bacteria begins to break down the organic materials stored in this tank. Pathogens in the waste are not destroyed in this septic tank. As the wastewater settles, it separates into three layers. The top layer is the crust and contains grease, toilet paper and any plastics and/or debris. This layer consists of all lightweight floating solids. The middle layer is the clear zone or liquid layer. This layer consists of water, liquids and suspended solids. Liquid from this layer is moved, via pump or gravity, to dispersal or advanced/secondary treatment. The third and bottom most layer that is collected in a septic tank is the sludge layer. This layer consists of all heavy solids that have collected during the settling of the waste water. During septic tank pump out, the top scum layer and the bottom sludge layer should be removed.

Secondary Treatment:

Secondary treatment is performed in many different ways, such as the AdvanTex® treatment pod or a sand filter. The purpose of secondary treatment is to reduce the biological oxygen demand and remove any pathogenic microorganisms. Secondary treatment also will decrease the total suspended solids. This method of treatment will provide an environment for natural forming organisms to live and aid in the treatment process. Secondary treatment is used to achieve Type 2 effluent.


Disinfection is done using one of two methods; chemical or physical disinfection. Physical methods include the use of ultraviolet light and heat (boiling). Chemical methods include the use of chlorine, bromine or ozone. Disinfection is used, in some systems, to produce Type 3 effluent.

Tertiary Treatment:

Tertiary treatment is performed using many different technologies. The purpose of this form of treatment is to reduce nitrogen and phosphates. These act as fertilizers and can cause some serious environmental issues when they come in contact with bodies of water, such as fish kills and accelerating the growth of algae blooms. Tertiary treatment may be required if the discharge area is close to natural bodies of water such as: lakes, rivers, streams or the ocean.

Soil Absorption:

After the desired level of treatment is achieved, and no community collection is available, the effluent is then, most often, dispersed to a form of soil treatment. Examples of soil treatment are absorption fields, mounds and a shallow trench. Both of these methods disperse the effluent into the land. This process provides further treatment by killing disease causing organisms and removing nutrients. After the effluent passes through approximately one meter of soil, the harmful pathogens will be destroyed. Mounds are used when the soil has high permeability or the system is to be located in an area where there is a high water table. In these conditions, the waste may reach the groundwater before it has received full treatment. A mound is created to add to the vertical separation between the dispersal manifold and the ground water itself. Primary treatment alone is all that is required to produce Type 3 effluent.

Additional information:

A septic system should be located at least 30m from any well used for domestic purposes. New systems are regulated by the Sewerage System Regulation and it is required to be designed, installed and maintained by authorized personnel (ROWP).

Myth: When the tank looks full, it needs to be pumped out.
Reality: Septic tanks operate at a level that is near the top of the tank. This level, which looks full, will vary only slightly through normal operation. The thickness of the crust and sludge layers in comparison with the total depth of the tank is the actual determination of whether your tank needs pumping. Typically the tank should be pumped when the scum and sludge depth occupy half of the total tank depth.