Downloads
Types of Systems
The Septic Tank
The septic tank is the most basic part of an on site waste water management system, and most of the following types of systems (apart from aerated and specialised systems) will comprise a septic tank that will treat waste waters to a 'primary' level.
A healthy septic tank is a living ecosystem wherein micro-organisms prosper in the right concentrations to properly digest and treat the incoming waste water.
NB: A septic tank will not kill bacteria / viruses and other pathogenic organisms, and extreme caution should be taken to avoid contact with people, clothes, food and pets. Wash your hands after coming into contact with a septic tank.
NB: A septic tank contains flammable gasses as a by-product of bacterial action, and thus naked flames should never be used in close proximity to a tank.
The contents of a healthy septic tank should form three layers:
- Scum Layer
A layer of greases, fats and oils that floats to the top of the tank (as it is less dense than the liquid effluent) and plays a part in the prevention of odour escaping and air entering the underlying layers. - Effluent Layer
The layer of clear/clarified waste water that will flow out of the tank junction or outlet pipe as new waste water flows in. - Sludge Layer
A layer of bio-solid materials that decants to the bottom of a tank (as it is denser than the liquid effluent) and can build up to levels that hinder adequate tank function, especially if it reaches the same level as the outlet pipe.
After 'primary' treatment in the septic tank, the effluent will flow (or be pumped) to a dispersal mechanism such as absorption trenches or soil mounds for further treatment of nutrient and pathogen contents.
Absorption Trench Systems
There are several types of absorption trench; however, in general the clarified effluent layer of a septic tank will drain into a sub-soil trench to allow for natural soil processes to kill off bacteria and cycle nutrients.
This can be a slow process and thus it is important to prevent overloading the absorption trenches with effluent at any given time. Care should be taken to ensure that water use is monitored and influxes of waste water to the septic tank are not excessive at any one time - one way to achieve this is to ensure that showers / baths, dishwashers, washing machines and laundry equipment are not being used at the same time.
Hazards are created when effluent is not being treated adequately in sub-soil layers, and can leach to the surface (or even groundwater sources) through sub-soil pathways into areas of human contact, creeks or vegetation in the area.
NB: The most common cause of trench failure is neglecting to have the septic tank desludged or pumped-out at regular intervals.
A brochure on absorption systems, as well as the fact sheet on 'Do's and Don'ts of Absorption Trenches' may be downloaded at right..
Aerated Wastewater Treatment Systems (AWTS)
AWTS are systems that employ methods beyond general septic tanks to treat waste water to a 'secondary' level for sub-soil or surface irrigation dispersal fields.
Aerated systems must be serviced at a minimum interval of once every three (3) months by a licensed service provider, and the maintenance / service reports provided to Council.
Like general septic tanks, sludge and scum layers can build up to levels that hinder proper function, and thus desludging or pumping-out of the system still applies, and should be undertaken as recommended by your maintenance service provider.
Irrigation systems must be sized appropriately to provide adequate dispersal of treated effluent, and must function to prevent the concentration of effluent at any one point, to assist in the facilitation of adequate hydraulic and nutrient cycling as well as to allow for soil treatment processes.
Irrigation lines should ideally be positioned 100mm below the soil surface and employ high quality drip emitters. In some unique situations it may be appropriate to employ surface irrigation using sprinklers should the effluent be treated to an acceptable level. Additionally, vegetation used for transpiration purposes within the irrigation dispersal field must be tolerant of high water and high nutrient conditions to facilitate adequate cycling and treatment of these elements.
Irrigation systems should be installed and maintained by adequate service professionals, which can be found in the Yellow Pages.
The fact sheet on 'Do's and Don'ts of Absorption Trenches' should be read for irrigation areas, as most of the same points apply.
Pump-Out Systems
Pump-out systems are dedicated systems that do not disperse waste on site. These systems may employ a single tank (for the holding and settling of waste water) or a dual tank setup (one for the settling of waste and the second for holding of clarified effluent for pump-out).
Pump-out systems are 'pumped-out' by licensed service providers, which can be found in the Yellow Pages. Blue Mountains City Services provides a pump-out service, and the contractual agreement form may be downloaded at right. Council prompts residents to seek out as many service providers as possible, and does not recommend any one service provider over another.
Properties with a pump-out system must enter into a contractual agreement with a licensed service provider, and Council must be informed of this agreement.
The frequency of pump-outs is dependant upon the frequency of use, the number of persons using the system, and the size of the tank/s.
NB: Due to the relative ease at which these tanks can become full prior to a pump-out by a service provider, household water usage should be moderated and stringently monitored to prevent overloading the system pre-maturely.
Other System Types
There are now several other types of waste water dispersal and treatment systems on the market, such as Constructed Wetlands, Evaporation Mounds, Sand Filters, Composting Toilets, and specialised Packaged Treatment Plants.
These types of systems are all very specific in their use and function, and should be thoroughly researched prior to potential use on your property.
Regardless of the type, the system must have a 'Certificate of Accreditation' issued from the Department of NSW Health.
NB: Council will not approve a system for use that is not in receipt of such an accreditation certificate.
A current list of accredited SMF's can be viewed on the Department's website: www.health.nsw.gov.au.
Frequently Asked Questions
A 'Frequently Asked Questions' fact sheet may be downloaded at right.
The Department of Local Government's 'Septic Safe Guide' contains a quick and easy do-it-yourself check for assessing the health of your system.
For any further questions related to On Site Sewage Management (OSSM) programmes or connection to sewer, please do not hesitate to call an Environmental Health Officer in Council on (02) 4780 5000.