Aerated Wastewater Treatment Systems (AWTS) – Secondary Treatment

These days, the AWTS is the most common type of system installed, because the quality of the final effluent is treated to a very high quality. This means that these systems present a much lower risk to the health of your family, neighbouring properties and our local waterways. And because the quality of the effluent is excellent, the water is dispersed just below the surface of the ground, so effectively, you are reusing the treated effluent to water your gardens and lawns.  

These types of systems can be installed on any property, including those with rock, sand, high-water table areas, steep gradients, and limited space and they are the preferred system in an environmentally sensitive areas. 

How do I care for my Aerated Wastewater Treatment System (AWTS)?

Septic Tank Services

Your AWTS MUST be serviced every 3 months by an accredited and licenced plumber. This is a requirement of state and local government authorities.  It is also in your best interest to maintain your asset. Just like it is for your car, regular servicing is critical to the proper functioning and longevity of your septic system and it helps to:

  • protect your septic system;
  • reduce the severity of system faults and the cost of repairs; and
  • protect the health of you, your family and the local environment.

Reduce your use of cleaning products

Harsh cleaning products, especially bleach and antibacterial products will kill the good bugs in your system and it will stop the helpful digestion process of the wastewater. This will put pressure on your effluent field and will cause odours.

Wherever possible, use biodegradable liquid detergents and NEVER flush solids down your drains (food scraps, sanitary napkins, nappies, wet wipes, etc).

Desludge / Septic Tank Clean

It is critical to have your septic system desludged by an accredited liquid waste contractor every 3 years (on average). Why? Because over the years, the layer of sludge in your Septic Tanks will accumulate. If there is too much sludge in your system, the solids will exit your Tank and block up your irrigation filter, putting lots of pressure on your pumps, and eventually, the solids will block the pipework in your subsurface irrigation field, which is expensive to replace!

Clean your irrigation filter

If your AWTS pumps to subsurface irrigation, you will most likely have an irrigation filter, which is the last line of defence to trap solids before they flow through to your irrigation field. If this filter gets blocked, it will put a lot of pressure on your submersible pump, which is expensive to replace if it breaks down. A blocked filter is also the most common cause of the system’s alarm. We recommend cleaning this filter fortnightly. Watch our videos on how to do this.

Avoid shock loads of water

Try and spread out your loads of washing over the week to avoid shock loads of water entering the system all at once. If too much water enters the tank at once, it may result in solids being pushed out to your absorption trenches.

Sometimes you can’t avoid shock loads, because you’re having a party or have people staying with you for the weekend. In these situations, it might be a good idea to have your system desludged before the upcoming event.

If you feel your system is constantly being overloaded, ie you have a busy household and you feel that the system is undersized for your family’s needs, contact SSA to discuss your options on 1800 800 333.

Cleaning an irrigation filter

How does an Aerated Wastewater Treatment System (AWTS) work?

  1. All wastewater from your bathrooms, kitchen and laundry is collected in the Septic Tank (or Primary Chamber).  In this tank, the wastewater settle out into three separate layers:
    – The fats, oils and grease (FOGs) float to the surface and create a thin layer of ‘scum’;
    – The liquids or effluent in the middle; and
    – The solids will eventually settle on the bottom of the tank as a layer of ‘sludge’ 
  2. As more water enters the system from the house, the existing effluent that has undergone ‘Primary’ treatment, gets pushed into the second chamber or ‘Aeration Tank’. Here, the effluent is aerated with oxygen by an aeration pump in order to help the ‘live’ microbes in the water to digest and breakdown the breakdown the organic waste.
  3. A third chamber is for additional clarification, as the solids are returned to either the septic chamber or the aeration chamber for further treatment before irrigation can happen.
  4. In many systems the effluent undergoes disinfection by a Chlorinator which removes any remaining harmful bacteria, viruses and pathogens, producing clean, safe water.
  5. When the final chamber fills up to a certain level, it will engage a float switch which will automatically engage an irrigation pump to send the final treated effluent out to your irrigation field.

Benefits of AWTS

Quality of effluent is excellent

Suitable for properties with tight acces

Suitable for sites with rock or highwater table 

Effluent can be used to water your grass and gardens


Homeowners guide to an AWTS