There are various wastewater systems on the market for you to choose from. New technologies are also emerging. Purchasing, installing and maintaining a waste water treatment system can be a significant up-front investment. There will be ongoing maintenance costs. Talk to us before you purchase a system.

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Treatment standards
Selecting a system
Types of wastewater systems

Treatment standards

Wastewater can be treated to three standards

Primary - minimal treatment (septic tanks and composting toilets) where solids and liquid separate. Waste is still contaminated.

Secondary - treatment using air and biological processes to decompose the solids, and chlorine to disinfect the liquid to a standard safe for irrigation (but not on vegetable or herb gardens).

Tertiary - advanced systems that use air and biological processes, as well as membranes and UV disinfection, to treat wastewater to a high standard.

Selecting a system

The ultimate choice will depend on a range of factors such as the zoning of the land, the size of the site, soil characteristics as well as ongoing maintenance costs. Choose a system that best suits your needs.

Onsite disposal systems treat wastewater to a certain standard and apply it to a dedicated area of land within the property boundary. Systems must be selected, sited, designed, constructed, operated and maintained so that surface waters are not contaminated by any flow from both land application areas and / or treatment systems.

Types of wastewater systems

Pump-out systems

Pump-out systems are used in locations where there is insufficient land available for on-site disposal. The effluent is held in a collection well and removed by a council approved waste water contractor. Off-site systems such as pump-out involve the preliminary on-site treatment in a septic tank, followed by collection and transport to a centralised wastewater management facility.

Offsite disposal costs are high. For this reason pump-out or off-site disposal options are only considered where there is no other alternative. If you have access to the sewer you will need to connect.

Septic tank and absorption trenches

Septic tanks provide primary treatment of effluent by allowing a period of time for waste water to remain within the septic tank. Bacteria in the tank then helps to break down the solid wastes and reduce the volume of sludge collecting in the bottom of the tank. Carrying out a septic tank check once a year will help to ensure that your system is operating satisfactorily. Depending on load, septic tanks may need to be desludged every two or three years. Septic tanks do not remove nutrients and the waste water is not disinfected.

Soil absorption trenches release effluent into the soil at a depth that cannot be reached by the roots of most small shrubs and grasses. Soil absorption trenches are not recommended on the sandstone plateau, or in sensitive areas, as they may lead to contamination of surface and ground water.

Septic tanks (with associated trenches) are still the most common type of treatment system. But there are now more advanced technologies in place.

Composting toilet systems

Composting toilet systems can be used in place of septic tank systems, with the solid and liquid wastes being separated. The dry composted material must be removed annually and buried below ground. More information on these systems can be found in the Composting Toilet Guide.

Aerated Waste Water Treatment Systems (AWTS)

Aerated waste water treatment systems increase the level of treatment through the processes of settling, aeration and chlorination of UV treatment. Although the treated effluent is of a higher quality than septic tank effluent, most systems do not significantly reduce nutrient levels.

AWTS require regular maintenance, usually 4 services per year. Additional services are generally required to restart pumps. Services usually take between 1/2hr to 1hr to complete. Service reports must be lodged with the Council.

Irrigation and soil absorption

These systems can be used to further treat wastewater that has undergone primary or secondary treatment before land application.

Sand filters

Sand filters are usually used with septic tanks to further treat the effluent. Effluent is pumped through a bed of coarse sand, collected and disposed of in shallow subsurface irrigation in lawns or gardens.

Reed beds

Reed beds are also used in conjunction with septic tanks to further treat the effluent through settlement and nutrient removal. Treated effluent is then distributed into subsurface irrigation a minimum of 300mm below the ground surface.


Mounds may be used with septic tanks or in conjunction with AWTS systems. Mounds are built up above the existing ground level with an specific soil mix, which is then covered with grass, or suitable low-growing perennials.

Forms and Resources