The water cycle

How we collect water

Considering the water cycle is truly a cycle, there's no real starting point, but if we had to pick somewhere to begin our exciting journey we'd probably say the sun.

Before we can extract the water from rivers, reservoirs and boreholes there are three main steps in the cycle - evaporation, condensation and precipitation:

Evaporation

The sun heats up the water from the oceans where it evaporates and rises into the air as water vapour. The vapour then rises into the earth's atmosphere, along with water transpired from plants and evaporation from the soil. Ask your pupils to think about what happens to a puddle when the sun comes out.

Condensation

As the water vapour rises, the colder temperatures cool the vapour so that it condenses to form water droplets in clouds. Clouds are formed when water droplets and pieces of dust join together in the atmosphere. If it's warm outside ask your pupils to think about why water forms on the outside of a glass when you pour cold water into it. If it's a cold day you could always ask them why water droplets appear on the inside of the window.

Ask for copies of our Water Project booklet to hand out to your pupils - there's fun scientific experiments, puzzles to keep them busy on a rainy day and bite sized facts. Phone a member of the Community Affairs team on 01274 692 548 to order yours.

Precipitation

As the water vapour condenses the air can't hold it anymore so it falls back to earth as rain, sleet, snow or hail. The word precipitation comes from Latin and means "falling". Try asking your pupils to remember the name of this process the next time it rains.

Here's a fun experiment you can try in the classroom - 'The water cycle in a jar'

You'll need:

1. A glass or clear plastic jar
2. A small plant
3. A handful of soil, sand and gravel

What to do:

1. Set up your jar with a layer of gravel in the bottom, followed by a layer of sand and a layer of soil.
2. Put your plant into the soil, water it well and screw on the lid.
3. Put the jar in a sunny place and see how the water cycle works - magic!

The water your pupils drink today has been around pretty much as long as the earth has! That means that a Tyrannosaurus Rex, King Arthur or Winston Churchill might have drunk the same water many years ago.

Sources of water

It's our job to ensure there's always enough water available for everyone in Yorkshire to use. We use water from three sources - on average 45% comes from reservoirs, 33% from rivers and 22% from groundwater.

Which water supply we use is all dependent on location, location, location - the hills of west Yorkshire make an ideal home for reservoirs, whereas in the north we tap into the river network and the flatter east is more at home using groundwater.

A lot goes on at our water treatment works to make your water safe for drinking. The extent of the treatment varies depending on where we collect the water from - if it's from a borehole the water usually only requires minimal treatment, if it's from lowland river sources and upland reservoirs it will go through a tougher treatment process.

When water reaches our works it will normally go through the following stages to remove the "baddies":

Screening

The water passes through a huge metal strainer to remove things like leaves and twigs.

Flocculation

Approved chemicals are added to act like a magnet for smaller impurities like dirt, natural colour and bacteria. The chemicals form a sort of jelly called floc.

We've developed an interactive guide to water treatment including cool sound effects and animations.  Pupils can follow a gang of baddies on their doomed journey through the water treatment works. 

You can request your copy by phoning us on 01274 692548. 

Clarification

The floc has to be taken out of the water, so air is bubbled through the tanks to make the floc float to the surface to form a blanket, where it is scraped off. This process is called Dissolved Air Flotation or DAF for short. At some works that don't have DAF, the floc instead sinks to the bottom of the tanks and is taken away - this process is called sedimentation.

Filtration

The clarified water is passed through filters filled with layers of sand and gravel to remove any final traces of the floc and metals such as iron and manganese. These filters are cleaned regularly, every one to two days.

Ask for some of our Education Resource Packs - packed full of great ideas for lessons as well as A3 posters for your classroom.  Please phone us on 01274 692548.  

Ozonation

Ozone is a gas which is a powerful oxidant and is used at a few of our water treatment works.  It is bubbled through the water to remove any traces of pesticides or similar compounds.

Download our fun water cycle poster (1mb)

Granular Activated Carbon

Granular Activate Carbon is used in filter beds to remove the by-products of ozonation, as well as traces of any other substances which may also be found in the water.

Chlorination

Chlorine is then added to the water. This kills off any microbes that may still be present. A small amount of chlorine is left in the water as it travels to your home to ensure the water at your tap is of the highest possible quality.

We've only given you the basics of water treatment here.  If you'd like to know more about how you can include this subject in your lesson plans, download our Science Pack - there's exciting water facts and fun, interactive experiments. 

Download Science Pack (901 kb)  

If you'd like to learn more about how we treat Yorkshire's water why not book a class trip to one of our water treatment works - click here for details.

How we treat Yorkshire's waste water

Getting water into your home and school is only half the story. Once it has been used, it's up to us to collect and treat Yorkshire's waste water and return it safely to the environment.

Collecting waste water

We've a network around 20,000 miles of underground pipes, collecting the raw sewage from the region's homes, liquid waste from industry, and rainwater that falls on roofs and roads. After water's been used it enters a waste pipe, travels into a drain, then into a sewer pipe that joins others to form something we call a trunk sewer.

Eventually it reaches one of over 600 waste water treatment works across the region where we improve the water before putting it back in the environment.

Treating waste water

At our treatment works the waste water goes through six key stages before it's good enough to be released into rivers and the sea:

1. Screening
We remove debris and large objects such as wood, rags and paper by passing the waste water through specially designed metal grids called screens.

2.  Primary treatment 
Sewage is transferred into large tanks called settlement tanks where most of the remaining solids sink to the bottom forming sewage sludge.  Most of the sludge produced can either be spread onto farmland to improve soil quality or is burned in an incinerator which can be used to generate renewable energy used to power the waste water treatment works - poo power as we like to call it.

Discover more about poopower in the classroom - download our guide to how human waste can help generate electricity. Key stages two and three. 

Download Poo Power booklet (145 kb)   

3. Secondary treatment - stage one
The liquid sewage flows on to stage three which involves biological treatment. Here, the sewage is trickled over filters of stone containing billions of "goodie" micro-organisms which feed on the "baddies" and remove any organic pollutants.

Print out our comic style poster to put up in your classroom explaining how we treat waste water. 

Download poster (1 mb)  

Alternatively, we can send you copies in our school Education Resource Packs.  Phone us on 01274 692548 for details

4. Secondary treatment - stage two
Sometimes the sewage is mixed with the micro-organisms in a tank.  Oxygen is bubbled into the tank so that the "goodies" can breath and go to work.

5. Final treatment
Finally, the sewage enters our settlement tanks where any remaining micro-organisms and sludge sink to the bottom.  We also zap the waste water with ultra-violet light to kill of any surviving "baddies".

Returning water to local rivers and sea

It's important for our environment that the water we use is returned safely to the rivers and the sea. Many of our rivers are cleaner now than since the industrial revolution over 100 years ago. This is because we've been hard at work updating and modernising many of our waste water treatment plants in the region.

We also play a massive part in improving Yorkshire's coastal bathing waters thanks to a multimillion-pound investment in our waste water treatment in these areas. 

To see how we're encouraging biodiversity and putting rivers back at the heart of communities in Yorkshire visit our Riverlife page.

If you'd like to learn more about how we're helping keep Yorkshire's coastal waters clean, take a trip to the seaside.