Aerated wastewater treatment systems (AWTS)

Aerated wastewater treatment systems (AWTS)

AWTS schematic

Typical schematic of an AWTS

AWTS treat wastewater to a secondary standard (a higher standard than septic tanks and composting toilets), so that the effluent can be used for irrigation on your property. AWTS use several pumps and are more complicated than septic tanks, and require more frequent maintenance.

Wastewater is treated in several compartments. The first is similar to conventional septic tanks, where solids settle to the bottom and scum floats to the top. The partially clarified wastewater flows into a second compartment where it is mixed with air to assist bacteria to further break down solids.

A third compartment allows further settling of solids and a final chlorination compartment allows disinfection. The treated effluent, treated to a secondary standard, is then usually pumped away for surface or subsurface irrigation in a dedicated area or paddock, although chlorine is not ideal for irrigation. Secondary treated effluent can also be disposed of via other methods including absorption trenches and beds.

Advanced aerated systems use membrane filters, and UV disinfection instead of chlorination, to treat wastewater to an even higher (tertiary) standard, free of chlorine which is better for irrigation.

Membrane filtration involves passing the wastewater through very fine membrane pores that filter out most particles, nutrients and diseases, producing very clear effluent at the same time it is treated by UV disinfection.

Common problems with aerated wastewater treatment systems are:

  • power disruptions can cause pump burn out and system failure
  • stormwater accessing the tank because the tank is too low or run-off is not diverted
  • intermittent or low wastewater loads resulting in lower level of treatment
  • no service agreement with a qualified service provider for regular inspections.

Effluent (treated wastewater) from aerated wastewater treatment systems may be released onto your property through:

  • amended soil mounds
  • sand mounds
  • absorption trenches and beds
  • evapotranspiration absorption beds
  • subsurface irrigation
  • surface irrigation.


Tuesday 17 May
2,573,926 ML
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1,335 ML
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Tuesday 17 May