On-site sewerage facility in backyard

A large number of properties across the region are not connected to a reticulated sewerage system. The treatment and disposal of all wastewater generated on these properties must be undertaken by an on-site sewerage facility.


On-site sewerage facility (OSSF)

A large number of properties across the region are not connected to a reticulated sewerage system. The treatment, storing and disposal of all wastewater generated on these properties must be undertaken by an on-site sewerage facility.

The types of on-site sewerage facilities that may be installed are:

  • aerated wastewater treatment system
  • aerobic sand filter system
  • advanced enviro-septic
  • septic tank
  • holding tank
  • composting dry vault system.

On-site sewerage facilities require regular maintenance to ensure they operate safely and effectively. They must be functioning properly to not adversely affect public health, safety or the environment.

A list of the approved treatment systems is available from the Queensland Government website.

Larger onsite systems with over 20 equivalent persons require ERA 63 approval and further monitoring from the Department of Environment, Science and Innovation.

On-site sewerage facilities (OSSF) treat sewage generated on a property in an area not serviced by sewerage infrastructure. A facility may use mechanical, biological and/or filtration methods to treat, store and dispose treated waste through either above- or below-ground disposal systems within a property boundary. OSSF include all types of wastewater treatment and land application such as aerated wastewater sewage treatment plants, sand filter systems, septic tanks, holding tanks and composting dry vault systems.

These systems aim to treat wastewater to:

  • protect public health and safety
  • maintain and enhance environmental quality
  • maintain and enhance community amenity.

Aerated wastewater treatment system

Typically know as an on-site treatment plant (OSTP), these systems are the most common. Wastewater is treated in tanks with multiple chambers with the use of mechanical, biological and filtration methods. Treated wastewater is dispersed to a designated and approved land application area (LAA).

Aerobic sand filter treatment system

This system works like the aerated wastewater sewage treatment plant but uses a primary tank for natural treatment which then undergoes secondary treatment by passing through a carefully graded and layered bed (filter) of sand and/or gravel to pass oxygen to micro-organisms to treat and purify the wastewater. The treated effluent is then discharged to an approved land application area.

Advanced enviro-septic

Advanced enviro-septic (AES) is a passive, non-mechanical wastewater treatment facility. An AES system utilises natural micro-biological process to purify the wastewater to a higher standard effluent. After primary treatment occurs in the septic tank, wastewater enters the AES system circulating through low and high vents surrounded by sand. After treatment, effluent infiltrates into underlying soil within the approved land application area.

Septic tank

A septic tank is a relatively simple design making use of natural processes to treat wastewater. A septic tank will separate solid and liquid waste, forming three levels of waste; scum (oils & grease), wastewater, and sludge (particles that are heavier than water), disposing of wastewater into the approved drainage beds/trenches.

Holding tank

A holding tank is a collection tank that holds untreated effluent when it cannot be treated and disposed of in a land application area on a property. These tanks are required to be pumped out by a licenced liquid waste contractor and disposed at a sewerage treatment facility.

Composting dry vault system

Composting toilets use a process of biological degradation to convert nightsoil into a humus-like substance through the aerobic action of micro-organisms and invertebrates.


Maintenance is required on sewerage facilities but differs depending on the type of system you have. State legislation requires aerobic wastewater sewerage treatment plants to be serviced every three months and sand filter treatment systems annually. Servicing must be completed by a licenced service agent, engaged by the property owner. Service agents are required to carry out maintenance and advise Council on the performance of system.

The effective volume in a septic tank is reduced if the tank accumulates too much sludge and scum, which reduces the amount of separation that can take place. This means not all solids, grease and oils will separate and will pass out of the septic tank into the trenches/beds, potentially clogging the surrounding soil of the trenches/beds. Important maintenance considerations for septic tanks include desludging the septic tank every three to five years by a licenced liquid waste contractor, using septic safe products and maintaining the land application area.

Common complaints that arise can be from overflowing trenches, unpleasant odours, and wastewater flowing into neighbouring properties. These issues and more pose serious health risks to the community and the environment and need attending to immediately. System failures and faults are often caused by one or a combination of the following:

  • lack of system maintenance
  • poor or failed mechanical components
  • harsh household cleaning chemicals, killing essential bacteria
  • excessive use, shock to the system
  • blockages
  • saturated/overflowing land application area
  • incorrect facility design or installation
  • odours from OSSF.

Maintenance for aerated wastewater treatment plants and sand filter systems

Periodic servicing must be completed by a licenced service agent. It is the responsibility of the property owner to engage an agent and maintain a contract for servicing while the system is in use.

Under the Plumbing and Drainage Act 2018 it is required that these systems are serviced. Service requirements are commonly:

  • aerated wastewater treatment plant - every three months
  • sand filter system - every 12 months.

Maintenance for septic systems

If a septic tank accumulates too much sludge and scum, the effective volume of the tank is reduced, which reduces the amount of separation that can take place. This means not all the solids, oils and grease will separate causing solids to pass out of the septic tank and into the drainage beds/trenches. This can clog the soil surrounding the drainage beds/trenches. Common tasks to maintain your septic system include:

  • cleaning the outlet filter every three months
  • desludging the septic tank every three to five years by a licenced liquid waste contractor
  • mowing grass and maintaining land application area.

Maintenance for composting dry vault systems

Periodic cleaning is advised for composting dry vault systems. To keep the compost pile and toilet healthy and clean:

  • add bulking agent regularly (carbon-based material)
  • don’t add foreign objects (e.g. food scraps)
  • don’t use harsh chemical cleaners or soaps
  • clean pedestal, seat, and lid regularly.

If compost begins to produce nasty odours, the system is not working correctly and will need to be addressed.


Poorly treated and maintained on-site treatment facilities can release contaminates such as waterborne pathogenic microorganisms into the environment potentially causing harm to the health of humans and the environment. Impacts of poorly treated effluent include:

  • soil contamination
  • waterbodies and groundwater contamination
  • public health risks
  • impacts to ecosystems and organisms.

Be a good neighbour

Effluent must be disposed of within the property boundary from which it was generated and treated. It is an offence to dispose of effluent into neighbouring properties, gutters, waterways, or an area where it could run off into waterways.

Ensure your land application area sprinklers remain in the approved locations to ensure run off does not occur or effluent is not sprayed in neighbouring properties.


  • Carry out regular maintenance on on-site sewerage facilities (OSSF) using an approved servicing agent. It is an offence if your OSSF is not maintained regularly by an approved service agent.
  • Use only recommended biodegradable products.
  • Avoid contact with the effluent and irrigation sprays.
  • Call your service agent when you are encountering problems with your system such as alarms and/or smells.
  • Conserve water and avoid overloading the system. Fix leaking taps and running toilets as soon as they are discovered.
  • Use toilet paper that disintegrates easily.
  • Keep a detailed record about your treatment plant, including model number, service agent, records of service visits, maintenance performed and parts replaced.
  • Become familiar with how your own particular system operates and the way it looks, sounds and smells when it is working correctly. This way, you may be able to identify problems before they become serious and alert your service agent to anything unusual.
  • Ensure your OSSF tank lids are properly sealed to prevent entry of mosquito and other vermin.


  • Put food scraps, milk or oil down the sink.
  • Dispose of any products containing ammonia, acids, disinfectants, bleaches and chemicals such as paints, thinners, pesticides etc. into household plumbing fixtures as it will kill the bacteria which operate the system.
  • Have vehicles and/or play equipment in the designation land application area (sprinkler/trench zones)
  • Allow roof or surface water to enter the system as it will overload the system.
  • Allow foreign objects such as plastic or rubber products, cloth, rags, sanitary napkins, bones, metal, glass and tea leaves or coffee grounds to enter the system as they may cause blockages.
  • Switch off the system to save power.
  • Cover tanks with earth, concrete, pavers, pine bark, mulch or other material which could interfere with access for maintenance or enter the tank when lids are opened.
  • Allow anyone to park on or drive over any part of the system.
  • Make or allow unauthorised repairs or alterations to your system without approval from Council.
  • Use garbage grinders unless the on-site sewerage facility is designed to cope with this waste.

We're upgrading to a new simplified system for onsite treatment plant monitoring and compliance called WasteID. This system will be rolled out across the Region in 2024.

What is WasteID?

WasteID provides a new interactive QR code tag. The secure WasteID tag simplifies the requirements for registering and servicing each onsite treatment plant. The cloud-based WasteID register is integrated with Council’s own data bases and IT systems.

How does WasteID work?

An authorised service agent uses their smart device to scan the WasteID tag. The device and other details are automatically loaded, so the applicable service results can be entered. The tester’s GPS location is checked against that of the device and a Form 11 is automatically generated.

Key benefits:

  • simplified system
  • real-time data
  • interactive platform
  • automatic scheduling of servicing
  • electronic test results (Form 11) to service agent, property owner and Council immediately.

Greywater is the wastewater generated from baths, showers, washbasins and laundries.

Common effluent disposal (CED) is in place in Crows Nest and parts of the Cambooya township. Each household will have a common septic tank but instead of disposing of treated effluent through trenches on the property, it is connected to the reticulated sewerage system. This conveys the sewage to either a centralised wastewater treatment plant or to a lagoon sewage treatment facility.

It is the responsibility of the property owner to ensure the maintenance of their CED tank.

You will require Council approval to install or alter an on-site sewerage facility or greywater facility.

One of the important aspects when installing an OSSF is the requirement for a thorough site and soil evaluation to be undertaken as part of the process of obtaining approval for effluent disposal within the property. It is essential for the evaluator to select the most suitable on-site effluent disposal facility for the property and engage the best environmental practices to support property design. The quality of effluent from an on-site sewerage facility is a key consideration to determine how sewage effluent is to be controlled and disposed of within the property.

Before lodging an application to install an on-site sewerage facility, it is recommended that the property owner consults with a site and soil evaluator to discuss the options available for effluent disposal within the property.

The following documents are required for an unsewered plumbing application to Council.

  • Form 1 Plumbing Application
  • Site and soil evaluation
  • Onsite sewerage facility design
  • Drainage design (applicable for a new structure)

To read more, please visit submit a plumbing and drainage application.

On-site treatment facilities must be decommissioned correctly to ensure the facility does not pose a future risk to the public or health of the environment.

A plumbing permit is required prior to any work associated with decommissioning an onsite treatment facility. To read more, visit plumbing and drainage applications.

On-site sewerage facilities must comply with and are assessed under:

  • Plumbing and Drainage Act 2018
  • Queensland Plumbing and Wastewater Code 2019
  • Standards Australia AS/NZS 1546 and AS/NZS 1547
  • Council Policies and Guidelines.


More Information 

For further specific information, contact the Plumbing team on 131 872 or visit your nearest Customer Service Centre.