• Clean drinking water is essential to human health.Pouring Water Into a Glass image by Curtis J. Alexander from Fotolia.com
  
  In nature, groundwater is filtered naturally by passing through layers of rock and sand. Humans recreate this process artificially to filter water and they also treat water with chemicals and other methods to make water safe for drinking. You can learn more about water filtration by performing your own experiments.
  
  

Soda Bottle Water Filter

• This experiment can be done at home without specialized equipment. Cut a 2-liter plastic soda bottle in half and place the top upside down in the bottom like a funnel. Layer filter materials like sand, gravel, cotton balls, paper towels and coffee filters into the bottle top. Use paper or something large on the bottom to plug up the mouth of the bottle. Then make some dirty water by adding dirt, oil, food coloring or bits of paper to it. Pour the water through the filter. Examine the water when it comes out and try to see what was removed by each layer in the bottle. Clean out the bottle and try it again with different filter materials. Compare your results to see which filters work best.
  
  

Drinking Water Purification

• Filtering water for drinking must focus on bacterial content in order to produce safe drinking water. For this experiment, you need access to a lab. Collect some water from a lake, pond, ditch or stream. Pass the water through paper towels to remove the large debris from the sample. Examine the diluted sample on Petrifilm and record bacterial content. Treat other samples of the water with filtration methods such as UV light, activated carbon, bleach, steam distillation and boiling. Examine the samples and compare the amount of bacteria present in each sample to the control sample to determine the most efficient method of filtration.
  
  

Fabric Water Filters

• Collect a sample of water from a lake, pond, ditch or stream. You could also make a sample by adding some soil to a tap-water sample. Place equal amounts of your water sample into several test tubes. Prepare the same number of empty beakers by placing a sample of fabric over the top of each beaker and securing it with a rubber band. Use a different type of fabric for each beaker, such as cotton, silk, polyester, canvas and blends. Examine the filtered samples for turbidity (visible particulates) to determine which fabric did the best job of filtering the water.