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How to make a water filter | Do Try This At Home | We The Curious


H2O. One simple molecule is essential to life on Earth, and all you have to do is turn a tap and it
just appears as if by magic. Well, magic is just another name we give to engineering, and today we’re going to show you how this trick is done. In the UK, the average person uses roughly one hundred and fifty litres of water every single day. But how does that water get to your home? Today, we’re going out into Bristol and
the South West of the UK to investigate. After the rainwater has fallen, it needs to
be collected from a variety of different sources including rivers, springs, wells and boreholes. The water from nearby natural springs is piped
here, to Cheddar Reservoir. This man-made reservoir has a capacity of 6 billion litres
of water. Now although this raw water looks clean, the quality is nowhere near good enough to come out of your tap at home. Behind me you can see a series of filters
which help to clean the water. The top layer is called the ‘schmutzdecke’, which – as well as being fun to say – contains all sorts of microbiological organisms which help to clean the water. But what you can’t see a few meters beneath the surface are layers of sand and gravel. The water filters down through these layers and it removes the small particles and algae. To see how this process works for yourself,
you can make your own water filter at home… All you need is a two litre plastic bottle,
a coffee filter, cotton wool balls, gravel and sand. Cut the bottle in half, and make a hole through the centre of the cap. Flip the top half upside-down and place the filter inside. Add the cotton balls on top, followed by sand, and gravel. Now take your filter and place it in the bottom half of the bottle and you’re ready to go. So we collected a jar of dirty water, let’s see if our filter works. As each layer gets finer, it filters out smaller and smaller particles Even even though our home-made water filter has gotten rid of most of the dirt, It’s no-where near as good as the filters that a water company uses. And there are still be microscopic organisms in the water which are small enough to fit through the filter. So we would have to boil this water in order to kill those organisms and make it sterile. But boiling water requires a lot of energy.
So water companies use a more high-tech method… Water is passed through pipes like these which contain high intensity ultra-violet lights. This UV light disinfects the water; killing micro-organisms by breaking down the molecular bonds in their DNA. Next, the colour, taste, acidity, and hardness of the water has to be controlled. We’re here with Alan Cook of Bristol Water. Hi Alan So, how do you control the water quality? Bristol Water monitors the samples that we get from all of these plants 24 hours a day, 7 days a week. But quite often we actually monitor them in real-time. So we have turbidity meters, pH, we look for most metals. And we can tell in real time when the plants are not operating properly and when they are. So what’s going in and out of water here in the plant? Well obviously we’re taking away any impurities. We put acids and alkalis in to the water to adjust the pH. We’re obviously monitor turbidity and we also put chlorine in at the end. We add chlorine to the water to keep it disinfected through the distribution network. At the end of the network, we want about 0.1 parts per million. So a lot of work then goes into a glass of water? Absolutely, yeah. After the water has been cleaned and treated, it’s pumped to an underground reservoirs like this one. which is built at the highest point in a local area. The reason for this is because water is really heavy, so it’s really expensive to move around. Instead of using pumps to push it to your house, we use gravity to pull it down instead. When you turn on your tap at home, the level of water in the udnerground reservoir drops down. But your house is just one of a network of thousands connected to the reservoir. Using the force of gravity helps regulate the pressure of the water through the whole network of pipes. So, it doesn’t matter if one tap is on, or hundreds; the pressure is always the same. In just the Bristol area there’s over six-thousand
three-hundred kilometres of pipes underneath our feet That’s enough pipe to stretch from here to China! Ninety-eight percent of the water in those
pipes is used for processes like washing, sanitation, irrigation, and fire-fighting. Only two percent is used for human consumption. So the next time you’re enjoying a glass
of water, remember the phenomenal amount of engineering which helps to keep you from going thirsty. Cheers! It’s pretty good! [laughing] If you enjoyed this video, hit the like button and share it around or click on my glass of water to subscribe. Check out how to make instant ice-cream in this video. And if we’ve inspired you to try science home, send us your pictures and videos on Facebook or Twitter. Thanks for watching! So using the force of… Ooh I’ve got a bug in my ear! Eewww Oh I see it! [laughter] It’s a spider in my ear! [shrieking]

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