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Septic Tanks Vs Sewage Treatment Plants

Septic Tanks Vs Sewage Treatment Plants

If you are a property owner with an off-mains drainage system, i.e. drainage systems that are not connected to the main public sewer system, you may have been faced with the choice between installing a septic tank or a sewage treatment plant.

As off-mains drainage systems are not maintained or serviced by local authorities, it is down to you as the property owner to ensure that your systems are properly working and maintained. While the systems are not wildly different from one another, there are some key elements that should be considered when deciding between the two.

Here is Aqua Rod South West’s guide to septic tanks vs sewage treatment plants.

Main Differences


The main differentiating factor between septic tanks and sewage treatement plants is the use of mechanical components. Septic tanks do not use any kind of electrical or moving parts, meaning they do not need power to operate.

Sewage treatment plants on the otherhand, use an air blower system alongside a pumping system to circulate oxygen around the tank. This encourages the growth of bacteria  which breaks down contaminants in the water, cleaning it. Due to the fact that sewage treatment plants utilise electricity, they need to be connected to a reliable source of power.


Another key difference between the two methods of liquid waste removal, is their disposal of waste. Septic tanks simply separate waste from waste whereas sewage treatment plants, as the name implies, treat the wastewater.

This treatment takes place by encouraging bacteria to breakdown the waste, degrading carbon and nutrients and effectively removing them from the water.

This means that while the water that leaves a sewage treatment plant isn’t exactly drinkable, it is much cleaner and environmentally friendly than that expelled from a septic tank.

Watercourse Discharge

Under current legislation in the UK, septic tanks are no longer allowed to discharge to a watercourse. Instead they must feed into a soakaway system of drainage field. Due to the efficiency of sewage treatment plants however, they are able to discharge water straight to a local watercoarse.


Regarding reliability, sewage treatment plants are less likely to encounter problems than septic tanks. However they do require annual maintenance from specialists such as Aqua Rod South West to ensure they are running smoothly and correctly.

Why Treat Sewage? 

There are a number of reasons that sewage is treated; mainly, sewage treatment is a method of purifying used water that is contaminated by bacteria and waste. Treating sewage allows it to be safely returned to the water cycle without damaging the environment or through contamination.

Professional Repair, Installation & Maintenence By Aqua Rod South West

If you’re considering the installation of a sewage treatment plant or septic tank, or require maintenance and repair work, Aqua Rod South West’s friendly and experienced team can help.

Don’t hesitate, get in touch today! Send us an email at or call us on 01209 861 099.

Published by: David Parkes on: May 17th 2022