Aerated Wastewater Treatment Systems (AWTS)
An AWTS is like a small-scale sewage treatment plant for your property. It provides secondary and advanced treatment of domestic wastewater, making it suitable for irrigation use on your land. It must be installed by a licensed plumber.
How it Works
Wastewater flows through a series of chambers:
- Primary chamber – solids settle and form sludge; scum floats to the top.
- Aeration chamber – air is added to support bacteria that break down waste.
- Clarification chamber – further solids settle out.
- Disinfection – treated water is chlorinated.
- Disposal – water is pumped to the land application area.
Aerobic Sand Filter Systems
An Aerobic Sand Filter is another type of treatment system that uses natural processes and sand filtration to treat household wastewater.
How it Works
- Wastewater first enters a primary sedimentation tank, where solids settle and break down.
- Effluent then moves into a dosing tank, where it is pumped into a sand filter.
- As the water passes through layers of sand and crushed rock, it is filtered and treated.
- The clean water collects at the base, is disinfected, and then sent to the land application area.
Land Application Areas
Treated wastewater must be disposed of within a designated land application area using one of the following methods:
- Irrigation
- Surface irrigation: sprayed above ground
- Sub-surface irrigation: drippers in shallow trenches
- Covered surface irrigation: drippers covered with mulch or woodchip
- Evapotranspiration-Absorption Systems
- Trenches or beds designed to absorb and evaporate water
- Elevated sand mounds constructed above ground level
The disposal method depends on the level of treatment the wastewater has received.
Maintenance Responsibilities
Regular maintenance is essential to ensure your system operates safely and efficiently. Poorly maintained systems can pose health risks and harm the environment. Key maintenance tips include:
- Avoid overloading the system with too many users
- Use only septic-safe and non-antibacterial cleaning products
- Never flush foreign objects like nappies or sanitary pads
- Desludge tanks every 3–5 years using a licensed contractor
- Keep the land application area mowed and maintained
- Protect the disposal area from vehicle traffic
- Keep your household plumbing in good condition
- Prevent the system from creating any odours or health risks
Servicing Requirements
Under the Plumbing and Drainage Act 2018, regular servicing of your on-site treatment system is mandatory.
- AWTS must be serviced every 3 months
- Aerobic Sand Filters must be serviced every 12 months
Servicing must be carried out by a licensed service agent according to the manufacturer’s instructions and Council permit conditions. All faults must be repaired promptly.
Council Reporting Requirements
After each service, the licensed agent must provide a report:
- A copy must be given to the property owner
- Another copy must be submitted to Council
Council keeps a register of all OSSFs and tracks ongoing compliance. If a system is not serviced as required, Council may take enforcement action and apply penalties.
Maintenance Requirements
Regular maintenance is mandatory under the Plumbing and Drainage Act 2018 to ensure system performance and protect health and the environment.
| System Type | Maintenance Interval |
|---|---|
| AWTP | Every 3 months |
| Sand Filter | Every 12 months |
| Septic Tank | Desludge every 3–5 years |
| Composting Toilet | Inspect and manage compost regularly |
| Greywater Diversion | Clean filters every 3 months |
| Greywater Treatment Plant | Per manufacturer’s instructions |
Owners must use licensed service agents and maintain service records.
Risks of Poor Maintenance
Untreated or mismanaged wastewater can:
- Spread disease (bacteria, viruses, parasites)
- Contaminate groundwater and waterways
- Cause odours, insect issues, or soil degradation
Council monitors OSSFs to ensure compliance with: