Types of wastewater treatment and application (disposal) systems

Types of wastewater treatment and application (disposal) systems

Aerated wastewater treatment system

An aerated wastewater treatment system used at a picnic ground

Onsite wastewater management systems have two main processes - treatment of wastewater to a certain standard, and application of the effluent (treated wastewater) to a land area on your property.

Treatment systems

The most common types of onsite wastewater treatment systems are:

Wastewater can be treated to three standards:

  • Primary - minimal treatment involving flotation and settlement to separate solids and liquids, and disposal of the clarified but still contaminated effluent (such as septic tanks and composting toilets).
  • Secondary - more advanced treatment using air and biological processes to decompose the solids and chlorine to disinfect the liquid to a standard safe for irrigation (such as aerated wastewater treatment systems).
  • Tertiary - highly advanced systems that use air and biological processes as well as membranes and UV disinfection to treat wastewater to a very high standard (such as membrane filtration and advanced aerated wastewater treatment systems).
Ensuring you have the right type of onsite wastewater system for your household size and land features is critical to protecting water quality in the Sydney drinking water catchment.

Application (disposal) systems

Effluent applied to a land area may be utilised (through irrigation) or disposed of (through soil absorption), depending on the type and level of treatment and effluent application system used.

Soil absorption systems do not require highly treated effluent, and wastewater treated in septic tanks and composting toilets can be disposed of in this way. Only water from aerated wastewater treatment systems (including advanced systems with membrane filtration) may be used for surface irrigation, while effluent treated by biological filters may be applied by subsurface irrigation.

The most common types of onsite effluent application systems are:

What you can do

  • Identify what type of onsite wastewater system you have, and understand its service and maintenance requirements.
  • Learn the location of your wastewater treatment system and the layout of your effluent application system, so that you can monitor its performance and identify any leaks, overflows or other problems early.
  • Keep a record of desludgings, inspections and other maintenance.
  • If you are installing a new system, get advice on the right type to meet your needs and get council approval to operate it


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Friday 12 August