On-Site Wastewater Systems
The City of Mitcham includes some areas which are not serviced by the SA Water sewer network. Properties that are not serviced by SA Water sewer must have their own on-site systems to dispose/treat wastewater generated on the site. Un-sewered areas include are found in Belair, Crafers West, Bellevue Heights, Eden Hills, Upper Sturt, Bedford Park, Mitcham, Hawthorndene, Coromandel Valley, Blackwood, Leawood Gardens and Brownhill Creek.
There are various types of on-site wastewater systems and it is recommended you research different systems and select a wastewater system suited to your location. On-site systems (new installations and alterations) must go through an application process and be formally approved by Council’s Environmental Health team before being installed. There are two main types of on-site wastewater treatment systems: septic tanks and aerobic systems. Both septic tanks and aerated wastewater treatment tanks must be pumped out at least every four years by a licensed contractor to remove the solids.
A septic tank system collects waste from the house via an inlet pipe at one end of the tank. The tank is divided into two chambers and as the waste enters the first chamber the solids settle to the bottom and the scum floats to the top. The settled solids are anaerobically digested by bacteria reducing the volume of solids. The liquid effluent moves through to the second chamber where further settlement occurs, and then excess liquid moves out the outlet pipe to the soakage area. The soakage area requires an engineer's report to determine soil conditions and the area required for soakage. This is also dependent on the amount of waste generated by the property.
Waste in the septic tank that is not decomposed eventually builds up and requires removal by a licensed contractor. The recommended de-sludging frequency for septic tanks is every four years.
Properly designed septic tank systems should be odour free, apart from the periodic pumping out. Septic tanks are a primary treatment system which means the waste cannot be utilised on gardens and must be disposed of in the underground soakage area.
Aerobic Wastewater System (AWTS)
Aerobic systems while similar to septic tanks use aerobic processes for decomposing the waste rather than an anaerobic process. Unlike the septic tank waste which is primary treated, aerobic wastewater systems treat the waste to a secondary level which allows wastewater to be re-used on gardens and lawns as irrigation.
The aerobic system works by effluent entering the first chamber and large solids settling out (similar to a septic tank). The second chamber involves an aeration stage where aerobic bacteria digests the biological wastes in the wastewater. After it leaves the second chamber it goes through a disinfecting stage whereby (usually) chlorine tablets are mixed with the water to produce a secondary treated waste, which is then discharged to the soakage area or can be used to irrigate lawn or garden area. As effluent from AWTS can be discharged to surface level or used in a sprinkler system it needs to be of adequate quality; a Biochemical Oxygen Demand (BOD) less than 20mg/L, and Total Suspended Solids (TSS (SS)) less than 30 mg/L.
Aerobic Systems are also required to have quarterly services carried out by qualified technicians, and service reports submitted to the local authority.
Types of Aerobic Wastewater Treatment Systems:
- Ozzi Kleen
- Aqua Nova
For further information on wastewater systems visit the SA Health Website.
Changes to the Regulations and Codes for Wastewater Management in South Australia
On 16 June 2013 the new SA Public Health Act 2011, SA Public Health (Wastewater) Regulations 2013 and On-site Wastewater Systems Code commenced. All wastewater applications received after this commencement date will be assessed under the new legislation.
Key Changes in the New Legislation
A Wastewater Engineers assessment report will be necessary for all sites (including aerobic wastewater treatment systems installations). Requirements of the report include (but are not limited to) type of system, site and soil details, the size of disposal/recycled water area required (note that the 200m2 irrigation requirements has been removed, and the area is to be determined by the engineer). For full details of what is required in the wastewater engineers report visit SA Health.
Certificates of compliance (COCs) are required to be submitted for all work undertaken in areas where the local council is the relevant authority. COCs must be submitted to Council within 28 days of completion of work.
Persons servicing wastewater systems (such as aerobic wastewater treatment systems) will be required to complete a training course. The 3 day course is now being offered by TAFE SA at the Regency Park School of Plumbing. For further information call TAFE SA on (08) 8348 4206.
Plumbers will be required to install irrigation systems connected to wastewater treatment systems, and provide a COC for this work.
Properties required to submit a wastewater application can find the application from here.
Fees for 2020/2021 are as follows:
- Administration fee $115
- Inspection Fee where the relevant authority is the Council $128
- Application to alter waste control system (administration and one inspection) $228
- Application to install a waste control system to existing building (administration and two inspections) $348
- Application to install a new waste control system (administration and three inspections) $468
- Additional fee for installation or alteration of an on-site wastewater system that exceeds 10 equivalent person $23.70
- Free for additional inspections $128
Below is a checklist of the information required when submitting an application to install or alter an on-site wastewater system.
All new on-site wastewater system applications should include:
- Site and soil report in accordance with either section 8 or 9 of the On-site Wastewater Systems Code 2013
- Detailed site and underfloor plumbing layout plans (in duplicate) drawn to scale.
Site plans must include:
- Allotment dimensions
- Contours indicating natural ground fall
- Proposed location of sanitary drains, buildings, and all other structures as well as components required by AS/NZS 3500
- Position of the proposed on-site wastewater system (including land application systems), showing compliance with all setback distances and all required pipework and appurtenances within the system
- Details of any site modifications, for example benching, cutting and filling, and how this impacts on the proposed system
- Location of any structures or proposed future structures and/or vegetation either on the subject allotment, or on other land which may be affected by the installation of the proposed wastewater system
- Details and locations of any diversion measures to collect surface or migrating subsurface water
- Details and location of storm, surface and roof water disposal.
Underfloor plumbing plans must include:
- The intended use of the building and all the rooms within it
- The method of connecting the internal sanitary plumbing fixtures of a building to the external sanitary drainage system, including the:
- Location of the sewer drain
- Size and grade of sewer drain
- Location of inspection openings
- Location of inspection shafts
- Junctions and bends
- Position of overflow relief gully and the means of maintaining the water seal
- Size of waste pipes
- Size of vents
- An indication of whether fixtures are trapped or untrapped AND
- Any non-standard fixtures.
Please Note the information required when applying for an alteration to an existing system will be dependent upon the type of alteration being proposed.
For your system to continue to operate efficiently, ongoing maintenance is important. Please click on the links for maintenance information provided by SA Health.
For further information about on-site wastewater systems, please contact the Environmental Health Team on 8372 8888.