Quality Water Treatment, Inc.

School Experiments

The Story of Water
How Drinking Water is Treated
Water Treatment Experiments
More Science and Water Links

Water: As Old as the Earth

Water has been on earth since the planet was formed. In fact, the water you are drinking today is the same water dinosaurs drank! Water evaporates, condenses into droplets, and falls as rain over and over again in a never-ending cycle. This cycle is known as the hydrologic cycle. Water keeps moving and changing from a solid to a liquid to a gas, over and over again.

Clean water, like the air we breathe, is essential for life on earth. Every plant and animal needs water. Without water, there would be no life on our planet.

Water: A Scarce Resource

We often take water for granted. When we have plenty of water we don't think about where it comes from or how we use it. But, even though 80% of the surface of the earth is covered with water, there is a limited supply of useable water on our planet. Most of the water on earth is salt water. Humans cannot drink this water and it is too difficult and expensive to remove the salt. Less than 1% of all water on earth is fresh water that we can actually use.

Sources of Water

Throughout history our greatest cities have been built near large water sources - oceans, rivers, lakes and springs. Water is necessary not only for drinking, but for agriculture, transportation and manufacturing as well. Water found at the surface of the earth is called surface water but it can also be found underground. This water, called groundwater, can be found in the cracks and crevices of stone and in spaces between gravel and sand. There is 30 times more water under the ground than there is in all the world's rivers and lakes.

You can understand this better by filling a glass completely full with sand then slowly pouring water from a measuring cup into the glass. The water goes into the spaces between the grains of sand. How much water can you pour in? The results will amaze you.

After a storm some of the rainfall runs into lakes and streams. But some of the water seeps into the ground. This groundwater may remain for several years in the same place it first collected or it may travel underground as much as hundreds of miles away. There is groundwater almost everywhere, even under the desert. Many groundwater reserves, known as aquifers, have taken as many as 30,000 years to accumulate. If all of the water underground were pumped to the surface, there would be enough to cover the earth with 100 feet of water!

Even with so much groundwater, in many places it is being used more rapidly than it can collect. That is what is happening in the western United States. Farmers are using millions and millions of gallons of groundwater for irrigating their crops. They are using the water faster than the water can be replenished so many wells are running dry. This is why many communities are enacting laws to regulate and limit the use of water.

Go to The Edwards Aquifer for more information.

Water: The Universal Solvent

Everything is made of atoms. An atom is the smallest particle of an element, like oxygen or hydrogen. Atoms join together to form molecules. A water molecule has three atoms: two hydrogen (H) atoms and one oxygen (O) atom. That's why water is also called H2O.

Water is an unusual substance because it is dipolar: the water molecule has one negatively charged atom on one side of the molecule and two positively charged atoms on the other side. This dipolarity allows water molecules to be attracted to one another: the two hydrogen atoms of one molecule are attracted to the one atom of oxygen of another water molecule.

A solvent is a liquid that can dissolve other substances. Water is the most common solvent in nature. Because of the dipolarity of water, which allows water molecules to attach themselves together, the molecules in water can also attach themselves to the molecules of other substances and keep them dissolved in the water. This is why many minerals are found in water.

For a discussion on acidity and alkalinity, see Chem4Kids, acids and bases.

Water Pollution

Chemicals are essential for making all kinds of thing that improve our lives: medicines, food, fabrics and plastics for example. But whenever chemicals are used, waste is also produced. One of the biggest challenges we face is disposing our waste products.

For decades, chemical wastes were released into our rivers and lakes. Because this polluted the rivers and lakes, laws were passed making this practice illegal. There is no good way of disposing of these wastes. At one time, chemical wastes were pumped into man-made lagoons. But water evaporates from lagoons and the chemicals become more and more concentrated. Eventually these concentrated chemicals seeped into the groundwater where they cannot be easily removed.

At one time we tried disposing of chemicals by placing them in steel drums and burying the drums. Unfortunately, the drums rusted or the chemicals ate holes in the drums. Then the chemicals leaked into the ground and caused pollution.

Sometimes, hazardous chemicals are disposed of by incineration or burning them is special facilities. This is not only very expensive but unpopular as well. Very few people would want dangerous chemicals being burned in their community.

Today, many chemical waste producers are finding ways not only to reduce the amount of wastes by recycling the chemicals they use. Unfortunately, some waste products, such as radioactive wastes, cannot be recycled, incinerated or otherwise disposed of. These chemicals are sealed in ceramic containers which don't rust or leak and placed in caves deep underground where they will remain forever, but they still don't go away.

As the population of the world grows, our goal must be to use less and to recycle what we use. Our planet is blessed with a bounty of water, but, as with all resources, we must use it wisely.

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How Drinking Water Is Treated

Water treatment is the process of making water potable or suitable for drinking. Because it is a good solvent, water picks up all sorts of natural pollutants. In nature, water isn't always clean enough to drink. Our municipal water supply is treated several ways before it is considered potable or safe to drink. To be potable, water must be free from:

disease-producing bacteria
dissolved minerals
pollutants
substances which give water an unpleasant taste or odor.

Commercial Water Treatment Process

There are several processes that raw water undergoes at a treatment plant. They are:

Intake: water is taken form the source. Logs, fish and plants are screened out at the intake and the water is drawn into the treatment plant.
Coagulation and Flocculation: Aluminum sulfate (alum), polymers and/or chlorine are added to the water. These kill germs, improve taste and odor, and help settle solids still in the water. The alum and other chemicals added to the water cling to particles in the water. This is called coagulation. It causes the particles to stick together to form larger particles called floc.
Sedimentation: The water and floc particles flow into a sedimentation basin. Here the floc settle to the bottom and are removed from the water.
Filtration: From the sedimentation basin, the water flows through filters. Filters are made of layers of sand and gravel. The filters are used to remove any remaining particles left in the water.
Disinfection: A small amount of chlorine is added to the filtered water to free it of harmful microorganisms.
Storage: The water is placed in a closed tank or reservoir called a clear well. The water then flows into the distribution system.

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Water Treatment Experiments

1. Equipment and ingredients you will need:

One gallon bucket
Several clear drinking glasses
Backyard soil or Fuller's earth (available at any hardware store)
Soup ladle
Small funnel
Glass wool (available at pet stores)
Baking soda
Powdered alum (available in drug stores)
Packaged dry yeast
Molasses
Household bleach

2. Making "dirty" Water

You will begin by making dirty or turbid water which will then be cleaned. To make turbid water, simply add soil from your backyard to water. If the soil doesn't contain enough clay, you can purchase a substance known as Fuller's earth. You will stir the dirt into the water to form a suspension.