Building & Development

Types of On-Site Sewage Management Systems

Septic tank with on-site disposal

Septic tanks provide primary treatment of effluent by allowing a period of time for waste water to remain within the septic tank. During this detention time, bacteria in the tank help to break down the solid wastes and reduce the volume of sludge collecting in the bottom of the tank.

Septic tanks do not remove nutrients and the waste water is not disinfected. Since the effluent is highly infectious it must be applied to land below ground level. 

Absorption systems

Carrying out a Septic Tank Check once a year will help to ensure that your system is operating satisfactorily.

Council also recommends that septic tanks are de-sludged by an authorised contractor every three to five years to ensure that the absorption trench does not become clogged.

Aerated Waste Water Treatment Systems (AWTS)

Aerated waste water treatment systems increase the level of treatment of the waste water through the processes of settling, aeration and chlorination of ultra violet treatment.

Although the treated effluent is of a higher quality than septic tank effluent, most systems do not significantly reduce nutrient levels. Therefore, appropriately designed and maintained effluent disposal areas are necessary.

AWTS systems must be operated continuously, and therefore the power to the system must not be turned off. Servicing of the system is required on a quarterly basis by an Approved Waste Water Treatment Plant Service Contractor

Aerated Waste Water Treatment Systems

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 in environmentally sensitive locations. Mounds are built up above the existing ground level with an amended soil mix, which is then covered with grass, or suitable low-growing perennials.

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.

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.

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