Interactive Primary Newsletter 21
Earth and Space     Materials from Earth
Describe how solids of different sizes can be separated		Level C
‘Water, water everywhere and not a drop to drink' In Scotland we are fortunate in that we have lots of water in our lochs and reservoirs. However drinking water directly from our reservoirs may give rise to risks of infection or disease. There are many odd items found in reservoirs from innocuous tree debris to unseen water borne bacteria. What does our water authority do to make sure our water is safe and drinkable? One of the first tasks is to remove the more obvious contaminants, such as debris like leaves, twigs, small stones, etc. This is the easy bit. All that is needed is a coarse filter. The next stage requires more filtering through a bed of aggregate, mixed rock and stones. When the water has passed this stage chemicals are added to help precipitate (sink to the bottom) any particles still remaining. Then the final stage, the addition of further chemicals to help keep any nasties at bay. Thence onwards to our taps and cisterns. You can obtain a free interactive CD (West Region Water Quality Review" from Tania Richards , Public Relations Officer, SEPA .
Explain how evaporation and filtration can be used in the separation of solids from liquids		Level D