Septic Tanks vs Sewage Treatment Plants

What’s The Difference Between Septic Tanks and Sewage Treatment Plants?

Both septic tanks and sewage treatments are installed and utilised for properties which cannot be connected to a mains sewage system. UK building regulations state, that if possible, properties must be connected to the mains sewage system, so it is worth confirming that your property doesn’t fall into these realms. If certain, the legislation changes to septic tanks back in 2020 bust also be considered, as these regulations have a drastic impact on the type of septic tanks homeowners can have on their properties, as well as where these systems can be installed. We do recommend that anyone considering the installation of sewage systems should discuss this with a specialist, and our team at Trent’s Drains is happy to help you through this process. 

Assessing the existing sewage system

Before considering any changes, it’s crucial to understand the current sewage system of the property. This knowledge helps avoid complications and ensures a smooth transition to a new system.

What is a septic tank?

A septic tank functions as a subterranean wastewater treatment system designed to handle both residential and commercial wastewater. It is typically employed by individuals and businesses that lack access to centralised sewage systems. This impermeable reservoir for wastewater employs biological decomposition to segregate sludge and scum, effectively treating the wastewater before facilitating its secure disposal through a jet vac tanker.

When utilising a septic tank, some aspects need to be taken into consideration such as the installation restrictions in Groundwater Source Protection Zones, and the discharge limitations on the tanks which have to comply with the building Regulations or BS 6297. There are also specific location requirements which need to be fulfilled such as the distance from buildings, boundaries, watercourses, and vehicle-trafficked areas. There’s a strict prohibition of direct discharge into watercourses under the new environmental legislation, therefore it is crucial that the property owners can adhere to all criteria as well as the property and the surrounding areas are carefully inspected. 

septic tank system function diagram

What are sewage treatment plants?

Sewage treatment plants work in a similar way to septic tanks, however, they involve mechanical components requiring a permanent electrical supply for operation.

What are the main differences between a septic tank and a sewage treatment plant?

The first distinctive difference is that sewage treatment plants require a constant electrical supply as they have mechanical components which are necessary for an efficient operation. On the other hand, septic tanks operate without a power supply and rely on time and chemical reactions to separate waste.  From a construction perspective, typically a sewage treatment plant has three zones, the primary and secondary settlement chamber, and a third settlement chamber. A septic tank on the other hand has only two zones. The first zone is designed for the heavier solids to settle, and the second zone allows the settlement of finer solids.

From a functionality perspective, a septic tank only separates waste, whereas a sewage treatment plant actually provides wastewater treatment, so the wastewater leaving a treatment plant is cleaner than the one from a septic tank, making them more environmentally friendly.

There are a number of key points to consider whether septic tanks or sewage treatment plants are the best choice for your property, and hopefully the above guide has answered most of your questions! The team at Trent’s Drains are dedicated to serving the local community as well as the wider area of the South West, Wales and beyond, and we are here to answer any questions you may have about wastewater solutions.  Get in touch with the team today.

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