Third step: Chlorine

After the water has been chemically filtered, it receives its final treatment before it enters the water supply for the City of Bozeman.

Fluoride is added, because fluoride lowers the incidence of cavities in people. Chlorine is also added, to make sure that very hardy pathogens (like the cysts of giardia) are rendered harmless and to help prevent growth of bacteria in the water system.

We visited the Bozeman water treatment plant on January 25, 2001; it was processing about 4 million gallons of water on that day. Rick told us that on hot summer days, demand can rise to 12 million gallons a day - the current operating capacity of the plant.

So we learned that the ecological footprint for water is this:

> the land reserved for the watershed

> the land taken up by creeks, canals, the water treatment plant, the wastewater treatment plant and the water system

> the land needed to produce the energy for running the plants and water system, plus the energy to produce, transport and dispose of the chemicals used in water purification and wastewater treatment

We also learned that the footprint for water is growing. As more and more people use and re-use water, more and more chemicals get added to the water, which may be very expensive to remove. Gill Geesey told us that today, chemicals such as caffeine and hormones (especially estrogen from birth control pills) are not removed from water during water treatment, and concern is growing about the long-term effects of these chemicals in the water we drink every day.

First step: Settling Second step: Filter