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On-site wastewater management systems (commonly known as septic tanks) are used on residential, community and business premises. They treat, then recycle or dispose of:
- greywater, which comes from showers, baths, hand basins, washing machines, laundry troughs and kitchens
- blackwater, which is toilet waste (from water-flush, incineration or dry composting systems)
- sewage, which is combined greywater and blackwater.
On-site wastewater treatment systems must perform effectively and be well managed to minimise risks to public health and the environment. The requirements on them depend on the source of the wastewater, site constraints, treatment method and the quality of effluent needed for the end uses of the treated water:
- Wastewater treated to primary quality is only suitable for disposal below ground via soil absorption trenches, mounds and evapo-transpiration beds or trenches.
- Wastewater treated to secondary quality can also be dispersed to land via pressure-compensating subsurface irrigation.
- Greywater treated to advanced-secondary quality can be used in the home for flushing toilets and in washing machines. It can also be used for surface and subsurface irrigation.
Permit for constructing, installing or altering OWMS
A permit from council is required to construct, install or alter an OWMS with flow rates of sewage not exceeding 5000 L on any day.
Systems that can treat more than 5000 L per day need an EPA works approval (unless an exemption applies).
From 1 July 2021 this will be a development licence and operating licence (unless an exemption applies).
Assessment standards for on-site wastewater treatment plants
The requirement for an on-site wastewater treatment plant to meet the appropriate standards set by EPA will continue under the Environment Protection Act 2017 (as amended) (the Act). The new legislation will be in operation from 1 July 2021.
An on-site wastewater treatment plant type must be assessed by a body accredited under the Joint Accreditation System of Australia and New Zealand or any other accreditation body approved by the Authority (assessment body). The assessment body must certify the treatment system as conforming with the relevant Australian and New Zealand standard (appropriate standard):
- AS/NZS 1546.1: 2008, On-site domestic wastewater treatment units, Part 1: Septic tanks
- AS/NZS 1546.2: 2008, On-site domestic wastewater treatment units, Part 2: Waterless composting toilets
- AS 1546.3:2017, On-site domestic wastewater treatment units, Part 3: Secondary treatment systems
- AS 1546.4:2016 On-site domestic wastewater treatment units, Part 4: Domestic greywater treatment systems
Transitional arrangements will also apply to previously issued certificates that have not expired by 1 July 2021.
The following table summarises the ‘appropriate standards’ and ‘transitional arrangements’ for different types of treatment plants:
|Types of on-site wastewater treatment plants||Transitional arrangements for previously issued certificates that have not expired at 1 July 2021||Appropriate standard from 1 July 2021|
|Septic tanks (and vermiculture systems)||Certificates issued against AS/NZS 1546.1 2008 will continue to be valid until they expire.||AS/NZS 1546.1: 2008, onsite domestic wastewater treatment units, Part 1: Septic tanks|
|Waterless composting toilets||
Certificates issued against AS/NZS 1546.2 2008 will continue to be valid until they expire.
|AS/NZS 1546.2: 2008, onsite domestic wastewater treatment units, Part 2: Waterless composting toilets|
|Secondary treatment systems||
Certificates issued against AS 1546.3:2017 will continue to be valid until they expire.
Certificates issued against AS/NZS 1546.3:2008 will continue to be valid for 2 years from commencement (that is, to 30 June 2023), or earlier if the expiry date in the certificate is earlier.
|AS 1546.3:2017, onsite domestic wastewater treatment units, Part 3: Secondary treatment systems|
|AS 1546.3:2017, onsite domestic wastewater treatment units, Part 3: Secondary treatment systems
(Note: Sand filters will no longer be assessed by councils against the interim standards for sand filters under the Code of Practice – onsite wastewater management publication 891).
|Domestic graywater systems||Certificates issued against AS 1546.4 2016 will continue to be valid until they expire.
Certificates issued against NSW Health: Domestic Greywater Treatment Systems Accreditation Guidelines February 2005 that do not expire by 1 July 2021 will continue to be valid until the date of expiry on the certificate.
AS 1546.4:2016 onsite domestic wastewater treatment units, Part 4: Domestic greywater treatment systems.
(Note: AS 1546.4:2016 was adopted in the legislative framework on 21 November 2016).
Please note that in highly exceptional circumstances relating to innovative on-site wastewater treatment plants, an exemption from these requirements may be granted to a permit applicant by EPA under section 459 of the Act.
EPA collates certificates of conformity and maintains a list of certificate holders against each treatment plant type.
Guidance on onsite wastewater management
- Code of practice – Onsite wastewater management (publication 891)
- Victorian land capability assessment framework (Word 1.1MB; Municipal Association of Victoria)
- EPA has worked with the City of Casey through the OPLE program to develop a video on maintaining septic systems under 5000L. For further information about your septic system, contact your local council.
Reviewed 23 April 2021