TREATMENT SYSTEMS

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A septic tank is a small anaerobic digestor. Wastewater (both black and grey) flow into the septic tank. Solids sink to the bottom and form a sludge layer, while scum, oil and grease float to the top. The sludge and scum layers are digested by millions of bacteria and semi-clarified effluent discharges from the tank through the outlet between these two layers. Septic tanks are a passive type treatment system(no moving parts, no power). Septic tanks produce primary treatment effluent which must be discharged underground, typically into shallow gravel trenches.

A septic tank must be pumped out every 3-5 years. Otherwise maintenance requirements are generally low and can be performed by the homeowner.

 Reed beds are a secondary treatment process,  installed after a septic tank, to reduce nutrient loading of the wastewater. The use of a reed bed produces a secondary treated effluent that allows owners to better utilise their wastewater, especially on sites with soil and waterway constraints. 

Maintenance requirements are generally low and can be performed by the homeowner.

For further information on reed beds: https://lismore.nsw.gov.au/files/Reed_Beds.pdf

An Aerated Wastewater Treatment System (AWTS) is a package treatment plant that produces secondary treated effluent. The system is fully automated and includes primary settling, aeration chamber, clarification and disinfection of the effluent. Effluent is pumped from the system.

AWTS units can therefore be used for tricky sites where effluent needs to be treated to a higher level or pumped to higher parts of the property. On most sites they work out to be the most cost effective system to install.

AWTS units do use a small amount of electricity to run the aeration blower and irrigation pump and will require quarterly servicing by an accredited plumber.

An army of worms live in the tank and break down all the organic matter. Food scraps can also be added through the top of the tank.

A greywater treatment system will treat and disinfect wastewater from the laundry and bathroom making it suitable for re-use on the property through subsurface irrigation or surface irrigation on some low risk sites.

A separate treatment system is required for blackwater (toilet and kitchen).

Composting toilets (also known as waterless toilets) significantly reduce the hydraulic and nutrient loading and will reduce the size of the wastewater treatment system required for the property. Composting toilets can be a good option for constrained sites or where water supply is limited. However there is some additional maintenance and periodic disposal of composted solids.