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Onsite 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.
These include only sites that produce flows under 5000 litres a day. Systems that handle, or are designed to handle, higher flow rates need an EPA works approval.
Onsite 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.
Regulatory framework for onsite wastewater systems
The Environment Protection Act 1970 (EP Act) sets out the approval process for onsite wastewater systems with flow rates less than 5000 L/day:
- Local government issues a ‘permit to install/alter and use’ for individual treatment systems. To do so, the council will base its decision on the proposed treatment system and the lodged land capability assessment (if applicable).
The council will also consider the proposed end use (indoors and/or outdoors) for the treated effluent.
- The council must refuse to issue a ‘permit to install/alter’ if the system type is not approved by EPA.
EPA approves system types in line with Australian Standards 1546.1 to 1546.4. The four approved types are:
- AS/NZS 1546.1: 2008 – On-site domestic wastewater treatment units – Septic tanks
- AS/NZS 1546.2: 2008 – On-site domestic wastewater treatment units – Waterless composting toilets
- AS 1546.3: 2017 – On-site domestic wastewater treatment units – Secondary treatment systems
- AS 1546.4: 2016 – On-site domestic wastewater treatment units – Domestic greywater treatment systems.
Treatment system brands and models must be certified by an accredited conformity assessment body (CAB) as conforming to the relevant AS. This accreditation is given by JAS-ANZ (the Joint Accreditation System of Australia and New Zealand). As part of a permit application to a council, the applicant will need to include a copy of the certificate of conformity from a CAB.
Vermiculture systems will be certified against AS/NZS 1546.1 and dry composting toilets against AS/NZS 1546.2.
Interim standards for sand filters are included as a technical annex to the Code of practice – Onsite wastewater management (publication 891).
EPA will collate certificates of conformity and maintain a list of valid certificate holders against each treatment system type.
EPA acknowledges there needs to be a transition period for industry following the introduction of the new Australian Standard AS 1546.3:2017 – On-site domestic wastewater treatment units – Secondary treatment systems. We have implemented a phase-in period that will allow companies to continue to sell products while they apply for certification against AS 1546.3:2017. In Victoria, all new systems will need to be accredited against AS 1546.3:2017 from 31 December 2020. This approach is consistent with other Australian jurisdictions.
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 30 September 2020