Tanks For Everything
[email protected]

What Are The 3 Stages of Sewage Treatment?

UPDATE: We are open for orders and advice. Most deliveries are still being made from stock. Some lead times are extended; contact us on 0117 244 4099 if you need an item quicker than the specified delivery time as we may be able to improve on this date. Thank you for your support!

All domestic properties create wastewater, from flushed toilets to drained sinks, to washing machines. All of this water goes into a wastewater system. If you have a property that cannot be connected to the mains sewage system, it is important to find an alternative, and getting a septic tank is one option. Another is to get a sewage treatment system.

Sewage treatment systems can be put anywhere that there is space and an electricity supply that can be used to power it. It works through a series of processes that cleanse the dirty water, resulting in water that is clean enough to be discharged into a drainage area, or even streams and ditches without causing any environmental harm.


There are three main parts to the treatment of sewage to make it clean enough to discharge into the local area. However, before the treatment begins, it is important to remove any larger items in the waste. Any materials that have the potential to block the system or pipes are removed – materials such as nappies, baby wipes, leaves, plastic, or sanitary products, for example.

Primary Treatment

The primary treatment refers to the first chamber in the sewage treatment system. The wastewater enters the chamber – or settlement tank – where the solids are allowed to settle on the bottom of the tank, and grease and oil rise to the top.

The grease and oil can normally then be scraped off the top of the water, whilst the sludge that has settled at the bottom can be gathered by scrapers and then disposed of.

Secondary Treatment

The secondary treatment occurs in the next chamber of the system. The water that remains from the first chamber flows into the second. This water still contains pieces of sludge and particles that did not separate in the first phase.

In the second chamber, air is pumped into the water, which helps the bacteria that are present to break down any organic matter, cleaning the water. The more the bacteria break down, the cleaner and purer the water becomes. This is known as ‘aeration’.

There are other filtering processes that can be used instead of aeration – biofiltration – a process that uses sand, trickling, and contacting filters to ensure that any sediment is filtered out of the water, and oxidation ponds – often used in warmer climates and uses natural water bodies such as lagoons, passing the water through the lagoon and then retaining it for a few weeks afterwards, for example.

This is the most rigorous part of the water treating process.

Tertiary Treatment

The tertiary treatment is the final part of the water treatment process. It aims to remove any inorganic substances that are still present in the water. Viruses, bacteria, and substances like phosphorus and nitrogen can be removed and, if required, this step can be used to make the water suitable for drinking.

Once that the water is cleaned through a sewage treatment system, it can be discharged safely into local areas such as ditches, streams, and watercourses.

Monday 8th August 2022
© Tanks For Everything Limited 2022
Responsive web design by Cotswold Web Services