Septic tank with trenches
The tank separates solids, and the liquid soaks into the soil through trenches or beds. There are few moving parts, but it needs pump-outs every few years and suitable soil.
AWTS (aerated wastewater treatment system)
Air is pumped through the wastewater to treat it further, and the treated water is usually irrigated. It needs power and regular servicing, commonly quarterly. See how to choose an AWTS.
Sand filter
Wastewater from a septic tank passes through a sand bed for extra treatment before disposal. It's sometimes used where soils or site constraints need more treatment than trenches alone.
AES (advanced enviro-septic) type systems
These are proprietary systems that treat wastewater in pipes laid in a sand bed. Like any system, they must be an approved type.
Who decides?
A site and soil evaluation, the system design and Toowoomba Regional Council approval decide what can be installed. Ask a licensed provider to explain the options for your site. See new systems and council approvals.
Related
Sources: Business Queensland – On-site sewage facilities · Toowoomba Regional Council – On-site sewerage facilities. General guidance only; check with council or a licensed provider for your property.