About Water

• Water treatment
• Safety
• History of water
• Water Cycle
• Waste water treatment
• Uses of water
• Pollution

Main Content

Waste water Treatment

Waste water has to be cleaned before it can be put back into the rivers or the sea. Waste water is cleaned at the waste water treatment works. Here you can find out more about how this is done.

What happens to the water we use?

When you use water you make it dirty. We call this waste water. Sometimes you will hear it called sewage.

Waste water from our toilet, wash hand basin and kitchen sink all goes into underground pipes below the house. These pipes join up with pipes from other houses and with pipes from factories, offices and pavements. All these pipes go into larger pipes called sewers. This is where the word sewage comes from.

The sewers take all the waste water to the treatment works. Even the waste water from toilets can be cleaned there. It goes through five different stages.

The five stages of waste water treatment

Stage 1: Screens trap rubbish like rags, bits of wood and plastic.

Stage 2: Stones and grit are removed so they don't damage machinery.

Stage 3: The waste water rests in these tanks where any solids in the water sink to the bottom. The solids make a slimy mud called sludge. The sludge is pulled out into other tanks to be treated and made harmless. It can be used to make the soil better for growing plants or for burning to make electricity.

Stage 4: Good bugs (bacteria) grow in the tanks. They eat up any chemicals and other waste which could harm plants and animals.

Stage 5: The waste water is allowed to rest again. Large stirrers gently mix the liquid and the left over bits sink to the bottom of the tank.

Now that the treated waste water is much cleaner, it can be poured back in the river or the sea.

To see how the machines work go to the Waste water Treatment Works in the interactive games section.