Septic tank vs aerated treatment system: what is the difference?

All the wastewater from your toilets, showers, kitchen and laundry flows into the tank.

Once inside, heavier waste sinks to the bottom and forms sludge. Fats and lighter material float to the top. Bacteria slowly break down some of that waste, while the liquid between the layers flows out to the disposal field.

This provides a basic level of treatment, called primary treatment. The soil in the disposal field then does much of the remaining treatment work.

The tank does not hold every litre until it gets emptied. Water keeps moving through it as you use your plumbing. What builds up over time is the sludge, which needs to be removed by a sucker truck.

Sometimes, yes. It might be considered old school, but a simple system can still be the right fit.

A traditional septic tank is generally cheaper to buy than a system with extra treatment equipment. There are fewer moving parts, and the treatment process does not need electricity. A pump may still be needed to move the liquid to the disposal field.

It can suit some farmhouses, rural properties and baches where the soil and disposal area can safely handle the liquid leaving the tank. WaterFlow still supplies conventional septic tanks because there are situations where they make sense.

But having a big paddock is only part of the picture. If the ground stays wet or drains poorly, a basic septic system may not be suitable.

WaterFlow supplies both.

Concrete tanks are strong and heavy, so access for delivery and lifting equipment matters.

Plastic tanks are lighter, making them easier to transport and install on some properties with difficult access.

Both do the same basic job. The material affects how the tank is installed, but it does not change a conventional septic tank into a higher-treatment system.

An aerated system adds more treatment before the wastewater leaves the tanks.

After the solids first settle, the liquid moves into another chamber where air is added. This helps bacteria grow and consume more of the waste. Remaining particles are then allowed to settle before the treated water is sent to the disposal field.

EconoTreat is WaterFlow’s aerated treatment range. It provides advanced secondary treatment, which simply means it removes significantly more of the waste than a conventional septic tank does.

The benefit is cleaner water going onto your property, with less treatment left for the soil to do. And you never have to get it sucked out!

Yes. Both systems need somewhere suitable for the liquid to go.

With a conventional septic tank, this may be a soakage bed or trenches in suitable soil. More thoroughly treated wastewater can also be distributed through fine drip irrigation pipes.

That can give you more flexibility in how the disposal area fits into your property. For example, drip lines can follow the shape of a suitable planted area. They need cleaner wastewater because their small outlets can become blocked.

A better treatment system does not remove the need for enough land. It changes the quality of the water reaching it.

A traditional septic tank needs its sludge removed periodically, usually every few years. How often depends on the tank, how much it is used and its maintenance requirements.

An aerated system needs regular servicing to check the air supply, pumps, filters and treatment process. 

Aeration is not the only way to give wastewater more treatment.

Worm-based systems use worms and other living organisms to break down waste. WaterFlow’s NaturalFlow and BioPod ranges use this approach, with different designs and treatment capabilities.

NaturalFlow’s treatment process does not need electricity and, under normal operation, does not need the ongoing septic pump-outs associated with a traditional tank. It still needs proper care, and a pump may be required to move the treated water, depending on the property.

That is why it is worth looking beyond a simple choice between “old septic” and “modern aerated”. There are different ways to do the job.

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With an aerated system, you are paying for more treatment equipment and cleaner wastewater leaving the tank. You also need to allow for electricity and regular servicing.

With a traditional septic tank, the equipment is simpler and usually cheaper. However, the disposal field and installation still contribute to the total price.

Ask for a quote that includes the full setup. A low tank price tells you very little if the earthworks and disposal field are still to come.

If a traditional septic tank can safely do the job on your property, it can be a practical, lower-cost choice.

If the wastewater needs more treatment before it reaches your land, an aerated or worm-based system may be more suitable. The next step is to work out which process fits your property, power supply and maintenance needs.

At WaterFlow, we offer conventional septic tanks, EconoTreat, NaturalFlow and BioPod. We can explain which options will work for your place and what each will involve, so you know what you are buying and why.