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How does a septic system work?

Septic tank systems

If your property isn’t connected to the municipal sewerage system, the treatment and disposal of wastewater must occur on your property, through an on-site septic system that includes a septic tank. Septic tanks should be regularly inspected, to ensure that the system continues to function effectively in treating septic waste matter so that it is not a health risk for neighbouring homes. To ensure your treatment plant keeps working properly, it is important to understand how your septic system works.

What happens in a septic system?

A septic system consists of some main components, which biologically convert sewage and other organic waste matter into effluent that, depending on the treatment, can be reused for specific purposes. The main components of a septic system include:

Drainage pipes

Drainage pipes connect the toilets, showers and sinks of a home to a septic tank. The wastewater can be transported by air pressure if necessary, however, the force of gravity is often utilised to move the wastewater down along the pipes to the tank for treatment. Kitchen sink pipes are sometimes fitted with a grease trap, which prevents fats and greases from entering the septic system. A grease trap is generally a rectangular container, which sorts the fat solids from the wastewater before it is taken to the septic tank.

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How does a septic tank work?

Once the biowaste is collected in the septic tank it undergoes ‘primary’ treatment, as the waste is sorted into sludge, wastewater and scum, based on its density. Sludge is the heaviest waste product, as it is composed of organic solids, so it collects at the very bottom of the tank. Wastewater is lighter than sludge but heavier than scum, so it sits under a layer of scum that floats at the top of the tank and above the pile of sludge at the bottom.

Diagram of a septic tank
Diagram of a septic tank

As seen in the septic tank diagram, once the waste is sorted into its three main types, the wastewater is then extracted from the tank through the outlet pipe for further treatment or disposal. The tank is also fitted with inspection pipes, which allow qualified plumbers to inspect critical parts of the septic tank design. Depending on the system, the septic tank will treat different types of waste. For example, some systems only treat blackwater but home plant sewage systems treat both blackwater and greywater.

Absorption trench

After the ‘primary’ treatment, the effluent is transported to the absorption trench for secondary treatment, either from gravity or an electric motor. The absorption trench consists of a sand filter, which catches any leftover septic solids from the effluent. The trench also includes a gravel filter which promotes an oxygenated environment for anaerobic bacteria to thrive in, which are good bacteria that digest and break down the septic waste. After the effluent has been treated again, it is then ready to be disposed of.

Disposal area

The disposal area for a septic tank is generally a sand mound or a trench, to ensure the clarified effluent is not released above ground. In saying this, the radius in which a sprinkler in a pump well system discharges water is also considered a ‘disposal’ area.

AWTS systems

Aerated wastewater treatment systems are another type of septic system that include a few different design components, like an anaerobic pump. The pump releases oxygen into another compartment of the septic tank, creating an artificial oxygenated environment for the anaerobic bacteria to break down solids in the effluent.

Your local septic system specialists

If you are looking for a professional septic system installation, repair or inspection service, get in touch with Express Wastewater Solutions. We specialise in carrying out high-standard septic system services on a range of different types of systems. Our team of professionally trained plumbers understand the importance of having an on-site sewage system that your family can count on to keep effectively working 24/7, which is why we want to help you. Contact us today about your home septic system by calling 1300 722 517 or by completing our online booking form.