Van Alexons, age 8  of Phoenix, Arizona

How is lake water made purer for drinking?

There may be fish and even weeds in the lake. You wouldn't dream of drinking it. Yet when it reaches your house! that water is safer than fresh rainwater: The purifying job is done at the water works.  Machines work day and night. Experts hover around, testing all the time. The water that runs through the pipes into the bath tub is the same excellent quality as the water you drink.

Duke water is usually purified in three stages The first job is to sift out bits of floating debris. The water is. allowed to stand quietly in large tanks or basins. This process is called sedimentation: Solid bits of stuff settle in a sediment at the bottom of the water.

Sedimentation can be speeded up with certain chemicals.  When added to the standing water, these chemicals swell up and form a fine jelly, As the jelly sinks, it carries floating solids with it. This process is called flocculation. Floceulation is helpful. when the water is very full of debris, though it is not always necessary.

Step two is filtration. Still finer particles are sifted and filtered through the half clean water. The job is done with gravel and sand. A deep layer of gravel is put into a large trough. A layer of sand is strewn on top of the gravel. The water is led in gently onto the sand and allowed to stand.

A water mainwith porous opening runs through the gravel at the bottom of the filter tank. The water seeps its way down through the sand. The clear liquid can get through, but the tiny floating particles are trapped and left behind in the grains of sand.` The gravel takes out still more particles along with loose grains of sand. The clean, clear water seeps into the water pipes below.

This water looks pure and clean enough to drink. But it is not pure enough to satisfy the experts. They know that microbes too small to be seen may still be present‑ some of them dangerous. This process calls for constant  checking with slides and microscope. Just enough chlorine gas is used to put an end to the microbes. It oxydizes them to death by slow burning. The tests show just how much chlorine to use. Of course, it is never enough to harm a person. The strong‑smelling gas is forced into the pipes at a controlled rate. When properly done you cannot even taste it.

The water is now pure and safe.  But lake water sometimes gives another problem. Tiny algae plants often leave a musty flavor even after, they have been removed from the water. This taste is removed if chlorine dioxide is used in purifying the water. It will freshen up the taste; of the water. However, the taste does not make the water unsafe. Once in a great while you are told. to boil water from the pipes before drinking. This is when floods have contaminated the pure water from the water works.

Andy says, let’s go fix a long cool drink of water., We know, for sure that it is safe and pure. It is refreshing and enjoyable.. besides which, it is very good for us.