Water Treatment Process

Southern Water takes water from several different sources including underground aquifers, rivers and surface water reservoirs.

The level of treatment the water undergoes before being pumped into supply depends on where it comes from.

Generally water from aquifers is already of high quality because it has been filtered through many layers of chalk or sand and needs only disinfection with chlorine.

Water from rivers and reservoirs contains a range of substances which need to be removed through several processes.

This is how a typical water treatment plant works:

1. Screening
Water drawn from rivers and reservoirs is passed through screens to remove any floating debris such as leaves, twigs or plants.

2. Auto-Coagulation
The water is then pumped to contact tanks where a chemical coagulant is automatically added. This helps solid material in the water to settle.

3. Clarification
The water is then fed into clarifier tanks where the settled solid material in the water settles and is removed in the form of sludge.

4. Disinfection
Following coagulation and clarification the water is disinfected using carefully controlled amounts of chlorine.

5. Filtration
The water flows into rapid gravity filters where it passes through layers of anthracite, sand and gravel about 1.5 metres deep. Carbon filters can also be used to remove tiny traces of pesticide which occur in river water.

6. Chlorination
A final check is made on the chlorine levels and additional chlorine added before the water is pumped into supply.

7. Tap Water
Exceptionally high quality water flows through water mains via covered storage reservoirs to your taps.

Your water source.
You can find out yours by entering your postcode in the Where I Live section.