CHAPTER 9 WATER TREATMENT AND PURIFICATION

As a Utilitiesman, you are responsible for ensuring that an adequate supply of safe water is available for domestic and fire protection uses. In meeting this responsibility you must consider several factors, such as the selection of a water source, ways to develop the water source, contaminants you may encounter, and methods you can use to remove these contaminants. In this chapter, each of these considerations is discussed.

WATER SOURCE SELECTION

You must consider three factors for a water source: quantity, quality, and reliability.

SOURCE QUANTITY

Water sources developed for military use are referred to as water points. Water points are classified as follows:

1. Surface water (streams, lakes, and rivers)

2. Groundwater (wells and springs)

3. Seawater

4. Rain, snow, and ice

When selecting a water source, you must consider the amount of water available and what the demand is for water.

The amount of water that collects in any surface source depends on the amount of precipitation, the size of the drained area, geology, ground surface, evaporation, temperature, topography, and artificial controls. The available water at a source can be estimated by using some simple calculations. To calculate the quantity of water (gallons per minute) flowing in a stream, use the following formula:

Q = 6.4 x A x V.

Q = Quantity of water in gallons per minute (gpm).

6.4 = A constant - There are 7.5 gallons of water per cubic foot. However, because of error in stream measurement, 7.5 has been reduced to 6.4.

A = The area of the stream in square feet obtained by multiplying the width times the average depth of the stream.

V = The velocity of the stream in feet per minute obtained by measuring the time it takes a floating object to travel a known distance.

An example of this calculation would be a stream having an average depth of 2 feet and a width of 16 feet, and a twig is noted to flow at 13.3 feet per minute. To find the amount of water flowing in the stream, you should work the equation as follows:

Q= 6.4 x A x V

Q= 6.4 x (2 x 16) x 13.3

Q= 6.4 x 32 x 13.3

Q = 2,723.84 gpm

To calculate the quantity of water in a lake or pond having little or no runoff, multiply the