Onsite Sewage Management
An Onsite Sewage Management System is any system that stores and/or treats wastewater and disposes of the treated effluent on the same property. The main types of OSSM systems in the Singleton Local Government Area (LGA) are septic tanks and aerated wastewater treatments systems.
For more information, visit the NSW Health website.
Types of onsite sewage management systems
There are a number of different on-site sewage management systems available. Each user and site will have different factors which will determine the type of system most suitable for installation.
Septic tank with onsite disposal in evapotranspiration / absorption trenches or beds
These are the most common types of systems. Effluent is settled in a septic tank and then disposed of into trenches or beds. The septic tank pre-treats the wastewater before it goes to the land application system. Three main things happen in the septic tank:
- Solids settle to the bottom of the tank and form a layer of sludge.
- Lighter wastes such as fat and grease float to the surface and form a scum layer.
- Bacteria, which live in the septic tank, help break down the solid wastes and reduce the volume of sludge collecting in the bottom of the tank.
It is important to remember that:
- Septic tanks do not remove nutrients.
- The wastewater is not disinfected and because it is highly infectious it must be applied to land below ground level where bacteria can digest the pollutants and pathogens.
- A poorly operated and maintained septic tank will allow excessive solids to pass to the land application system causing it to clog. This will result in health hazards and a need for expensive reinstatement of the absorption area.
- De-sludging of the septic tank is required every 3-5 years depending on use.
Aerated wastewater treatment systems (AWTS)
Aerated wastewater treatment systems (AWTS) increase the level of treatment of the effluent by aeration and disinfection, so it is suitable for irrigation onto lawns or gardens.
It is important to remember that:
- Although effluent produce is of a higher quality than septic tank effluent, most systems do not significantly reduce nutrient levels. Therefore an appropriately designed and maintained effluent disposal site is necessary.
- AWTS must be operated continuously; power to the system must not be turned off. If AWTS are used at irregular intervals the system might need to be serviced before use.
- Servicing is required every 3-4 months by a Council approved service provider. This cost must be considered when choosing this system.
Sand filters further treat effluent from a septic tank, effluent quality is comparable with that from AWTS. Effluent is pumped through a bed of coarse sand, collected and disposed in shallow subsurface irrigation in lawns or gardens. Sand filters are generally low maintenance systems and can handle surge loads. They may be used to extend the life of the land application system.
Effluent is treated in a septic tank prior to a reed bed. The reed bed further treats the effluent through settlement and nutrient removal. Treated effluent is then distributed into subsurface irrigation a minimum of 300mm below the ground surface. Reed beds can be incorporated into landscaping. Effluent is contained beneath the rock surface of the reed bed. Reeds require some annual pruning / removal.
Onsite sewage management inspections
In accordance with the Council's On-site Sewage Management Strategy, OSSM systems are inspected by Council to determine whether they are functioning satisfactorily. The frequency of inspections is determined on an assessment of risk undertaken by Council.
- High Risk - Inspected once per year;
- Medium Risk - Inspected every three years;
- Low Risk - Inspected every five or more years; and
- Minimal Risk - Self-assessment every 10 years with random Council inspections.
Notification of an inspection of your OSSM will be sent to you approximately two weeks prior to the inspection being conducted. If required, arrangements can be made to conduct the inspection with the owner present. This may be required if the property is usually locked and/or to reduce stress to pets.
If you are selling or buying a property with an OSSM, you may request to have your system inspected by Council by completing a Request for Inspection of an Onsite Sewage Management System form and returning it to Council with the fee. Council will contact the owner to arrange a suitable date and time for the inspection.
Destruction, removal or reuse of OSSM
The NSW Ministry of Health has developed Advisory Note 3 - Revised January 2017, Destruction, Removal or Reuse of Septic Tanks, Collection Wells, Aerated Wastewater Treatment Systems (AWTS) and other Sewage Management Facilities (SMF) which indicates that Council approval is required prior to the installation of any reused septic tank, collection well or Aerated Waste Water Treatment System (AWTS). The Advisory Note also provides guidelines on how to appropriately decommission Onsite Sewage Management Systems.
If you are considering the purchase of a used tank, please check with Council to find out if approval can be granted to reinstall the system. Any system installed must be a current NSW Ministry of Health accredited model.
Onsite sewage management approval
An "Approval to Operate" must be obtained from Council for new on-site sewage management systems prior to commissioning the system. This can be applied for by selecting the relevant box on the Application for s68 Approval - On-site Sewage Management System form.
If you have an existing system that does not have an "Approval to Operate" then it is not registered with Council. You may attempt to register your system and obtain an "Approval to Operate", by lodging an Application for s68 Approval - On-site Sewage Management System form.
Failure to register your system with Council may result in the issue of a penalty infringement notice.
An "Approval to Operate" is valid for one year. Council will send out an extension of your Approval to Operate in July each year, providing that no issues have been identified with your system.