An on-site wastewater system is a system used for the on-site collection and management of wastewater generated at the premises where:
the wastewater collected and managed is predominantly:
human waste either alone or in combination with water
water that has been used in washing, laundering, bathing or showering
water containing food or beverage waste
a combination of the above
some or all of the wastewater is reused or disposed of by means other than disposal to a Community Wastewater Management System or SA Water sewerage infrastructure and includes any associated irrigation or other system for the disposal of the wastewater on land other than that from which the wastewater is collected.
Toilet water, greywater and some kinds of trade waste are all considered as “wastewater” and can cause disease if not treated correctly to prevent a risk to public health.
In many areas of the state, wastewater is directed to a sewer.There are many other areas where on-site wastewater systems are the only option for wastewater collection, treatment and reuse. These include:
Septic tanks connected to soakage trenches and aerobic wastewater treatment systems which then irrigate the recycled water produced on that site. There are many other types of these systems which can be found in the Onsite Wastewater Systems Code (PDF 111KB) or Australian Standard 1547
Septic tanks which treat the water before it goes into a community wastewater management scheme (CWMS) drain.
Grey water systems which either divert the greywater to a sub-surface disposal area or treat the water to a suitable level for irrigation.
Approval must be given before installing or altering an onsite wastewater system by the relevant authority. In most cases this is the local council and will be processed by the council’s Environmental Health Officer. Larger systems, greater than 40 EP (effective persons), and those in areas not covered by local government administration are processed by SA Health.Application requirements are detailed in Onsite Wastewater Systems Code (PDF 111KB).
A 40 EP system will receive 6000L/day or have a biochemical oxygen demand (BOD5) of 2000g/day.Systems receiving more than this will require referral to SA Health.Details on sizing the system can be found within the Onsite Wastewater Systems Code (PDF 111KB).
It is recommended that you discuss the proposed installation with the appropriate officers in the early stages of planning a property development. There may be important design considerations that need to be identified before planning decisions are made. If you have any questions regarding the approval process or are unsure how to size your system, contact your local council or SA Health's Wastewater Management Section on (08) 8226 7100 for further advice.
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