Cleaning waste water | Secondary | Education | Dwr Cymru Welsh Water
Dwr Cymru Welsh Water
Education Secondary Cleaning waste water

What is wastewater?

This is the water poured down the drain after washing dishes, taking a bath or flushing the toilet. In fact, wastewater includes all types of used water. The waste water contains a variety of substances, some dissolved and some in the form of solids which will float, sink or stay suspended in the water.

  • Domestic water from baths, washing up, toilets etc.
  • Industrial waste water from factories.
  • Rainwater that runs off roofs, roads and paved areas.

Wastewater collection

Collecting this enormous amount of wastewater and getting it to a treatment works is a major engineering task requiring a vast network of sewers spreading out to virtually every home, office, shop, school and factory in the country.

In the region covered by Welsh Water alone, this amounts to approximately 36,000km of sewers and drains.

Sewage network types

There are two main types of sewage network:

Combined sewers – single pipes which carry both domestic and industrial ‘foul’ water as well as surface rainwater.

Separate sewers – one pipe that carries ‘foul’ water and another pipe that carries rainwater run-off.

Wherever possible, separate sewers are preferred because rainwater and ‘foul’ water can be kept apart and rainwater can be easily discharged directly to rivers or the sea, or to soak into the ground.

Sometimes the sewers can be blocked and this can lead to sewage flooding.

Sewer and drain blockages can cost our customers hundreds of pounds to clear, cause flooding to their homes and gardens, or pollute local streams.

Let's Stop The Block

Wet wipes (including those labelled as “flushable”), disposable nappies and sanitary products are the main items that cause problems; but kitchen oil, fats and grease can also lead to major blockages. These items should not be disposed of down the drain. Around half of all sewer blockages are caused by the wrong things being flushed down the toilet or poured down the kitchen sink.

Welsh Water’s campaign called Let’s Stop the Block raises awareness about what can and cannot be flushed down toilets and put down drains. There is lots of information about the campaign below including our short film about loo Loo’s nightclub.

Wastewater treatment

The purpose of wastewater treatment is to remove enough impurities from the wastewater to enable it to be returned safely to a river or the sea where it can again become part of the natural water cycle.

The process by which wastewater is cleaned is made up of be a series of stages including screening, settlement and use of microbes to remove suspended solids in the water. Full details can found in our detailed downloadable information sheets at the bottom of the page.

Turning Poo Into Power

It’s hard to believe that wastewater and sewage could be used to light our homes, we call this Poo Power!

Poo Power uses a biogas rich in methane which is removed from the treatment of wastewater and sewage to drive the turbines. The biogas, predominantly comprising of methane, is produced when bacteria feed on human and animal waste. This process is known as anaerobic digestion and it is a great way to produce green energy, as well as getting rid of waste and the micro-organisms that lurk in it. One of the simplest ways of describing anaerobic digestion is the ‘farting’ of millions of tiny bugs within the waste, which produces the biogas.

Positively, when the biogas is burnt for generating electricity far less carbon dioxide is released than when fossil fuels are burnt.

Did you know?

  • It takes the poo of 100,000 people to generate 51kW of electricity, enough for 500 light bulbs.

Downloads and information sheets

Waste Water

Wastewater Process

Click here to view

Careers at Welsh Water

Waste Maze

Click here to view