A Beginners Guide to Sewage Treatment Plants

A Beginners Guide to Sewage Treatment Plants

If your property is not able to connect to the mains sewerage infrastructure, your most cost effective and environmentally friendly “off mains” option is a packaged sewage treatment plant. In simple terms, a sewage treatment plant is a below ground vessel which treats the incoming effluent to an environmentally acceptable quality. This treated water can be legally discharged to flowing surface waters or in ground soakaway following applicable exemptions or consents.

How do they work?

Nearly all sewage treatment plants use the same 3 stage principle to treat the influent; primary settlement, biological treatment, final settlement.

  • Stage 1 – The influent enters the primary settlement chamber where the solids sink to the bottom of the chamber where they form a sludge which is periodically removed by a tanker.
  • Stage 2 – The remaining liquid moves forward to the biological treatment zone. In this biozone, air containing oxygen is introduced to the liquid to encourage the growth of aerobic bacteria (found naturally in the sewage) by allowing them to breath. Most treatment plants also use media in the biozone which provides a large surface area for the same bacteria to cling to and grow.
  • Stage 3 – Finally the treated effluent moves into the final settlement chamber where the calm allows biological material to settle at the bottom for periodic removal or further treatment. The remaining settled liquid then flows out to surface waters or ground soakaway.


How do they differ to septic tanks?

A septic tank relies on anaerobic bacteria digestion, the by products of which are large amounts of carbon dioxide and methane which is responsible for the familiar pungent smell associated with a septic tank.

A sewage treatment plant uses an aerobic process with the forced introduction of oxygen. This promotes the growth of aerobic bacteria to digest the sewage. The by product of the aerobic process is carbon dioxide, water and biomass.

The aerobic process in a sewage treatment plant is much faster and produces a much higher quality effluent.

The outfall from a sewage treatment plant can be legally discharged to surface waters, however it is illegal to allow septic tank effluent to discharge to surface waters.


How to install them?

Here at Cotterill Civils, we supply a complete range of sewage treatment plants, accommodating the needs and wants of a very diverse range of properties or applications. Regardless of whether you’re looking for a sewage treatment plant to suit 6 people or 500 people, you’re sure to find exactly what you’re looking for here!

We will help you size and get to the most appropriate, cost effective and compliant solution. Uniquely, as installers as well as merchants, there is no one in the industry better placed to serve your requirements than us.
Why do you need to maintain them?

Sewage treatment plants, like any other system, need to be maintained to ensure trouble free operation, compliance and longevity.

Regular maintenance involves periodic sludge removal and checks of the mechanical and electrical components such as compressors, motors, pumps and control panels.


Why choose a sewage treatment plant?

A sewage treatment plants allows you to dispose of your wastewater efficiently, ensuring that there are minimal negative impacts on the environment. We will always advise you to choose a treatment plant over a septic tank or cesspool due to its huge environmental benefit and compliance.

If you need to know more about sewage treatment plants, don’t hesitate to get in touch with our team of experts.

Call us on 0121 351 3230 today. We know sewage treatment.