What Is a Septic Tank?

A septic tank is a buried, water-tight container that collects sewage, wastewater, and effluent from domestic and agricultural sources. Septic tanks are used to treat wastewater and effluent at the house or property level, rather than relying on treatment plants located in most towns and cities. Typically, the wastewater and effluent flows from the house or agricultural site through a piping system, eventually arriving at the septic tank. The septic tank serves as an anaerobic (does not require oxygen) environment in which organic matter, including solids and other material, are broken down. The excess water and any remaining liquid is then discharged into a leaching field or drain field, where it can further dissipate into the ground.

How Does a Septic Tank Function?

When wastewater and effluent enter a septic tank, the tank divides it into the three distinct layers. The top layer, known as the scum layer, is comprised of lighter materials like oil, grease and other organic solids, such as hair and food particles.

The middle layer, known as the effluent layer, is mostly liquid, as well as some of the broken down solids. This layer is the most contaminated, and is therefore the key layer in septic tank treatment.

The bottom layer is composed of denser materials like substrate and grit, which settle on the bottom of the tank. This layer helps the tank maintain an aerobic environment, while also working to support the breakdown of the organic materials.

In the process of breaking down the organic solids, bacteria and other microorganisms consume and decompose the material. This process results in the release of gases and the formation of biodegradable material that sets at the bottom of the tank. This material must be removed on a regular basis to ensure the tank is functioning properly.

Approximately two-thirds of the liquid is eventually discharged into a leach or drain field. The leach or drain field serves as a filter that allows the liquid to be further cleansed of remaining material and pollutants as it slowly moves into the soil.

Benefits of Using Septic Tanks

Septic tanks are a great way to treat wastewater, effluent, and organic materials when connection to a main sewage line is not available. Not only do they offer homeowners with a way to manage the waste generated on their property, they can also provide added treatment when municipal wastewater treatment plants are at capacity. Septic tanks are also favored since they are typically cheaper to install than connecting to a main effectively line, and they require less maintenance when compared to municipal wastewater treatment plants.

They also serve to contain any existing contamination that may be present in the undeveloped or agricultural land. Additionally, unlike using a standard cesspool or seepage pit, which are open containers that can release confined sewage directly into the ground, septic tanks can help to further prevent soil contamination or pollution, especially when used in combination with a leaching or drain field.