CHAPTER 7 WATER TREATMENT

LEARNING OBJECTIVE: Recognize methodology used for water treatment and purification; understand and identify types of water treatment equipment, treatment processes, and water testing procedures.

Water is never absolutely pure. Impurities in water vary from dissolved gases, chemicals and minerals, to suspended matter, like disease germs and dirt. Some impurities can be seen and some cannot; others can be detected by taste or odor or only by laboratory tests. This chapter explains the water cycle, the quality of water, the chlorination equipment, the water treatment quality control and water testing procedures. Water treatment is vital to the health and well-being of the troops. Improper treatment of water can allow the spread of infectious intestinal diseases and skin fungus. The unit commander and the Navy Medical Service share responsibility of ensuring a supply of pure water in the Seabees. As a Utilitiesman, you will perform major duties involving the treatment and purification of water, so it is safe to use for drinking, cooking, and bathing.

Figure 7-1. - The hydrologic cycle.

THE WATER CYCLE

LEARNING OBJECTIVE: Understand the hydrologic cycle and sources of water.

Water is circulated from the oceans to the atmosphere by a series of processes and then to the surface of the earth and beneath it. This is known as the water cycle, or hydrologic cycle (fig. 7-1). An understanding of the occurrence of groundwater is based on a general knowledge of these processes and their relationships to each other. Basically, the cycle consists of the following processes:

Evaporation of water from oceans

Condensation of the water to produce cloud formations

Precipitation of rain, snow, sleet, or hail upon the land surface

Dissipation of the water by direct runoff into lakes and streams

Seepage, or infiltration, of rainwater or melted snow into the soil and then into underlying rock formations

Movement of water through the openings in the rocks and at the surface through springs, streams, and lakes

Direct evaporation

The cycle usually does not progress through a regular sequence and may be interrupted or short- circuited at any point. Moisture that condenses over the ocean may fall into it as rain. Rain that falls upon a heavily forested area soon may return to the atmosphere by direct evaporation or through transpiration by plants. Jungle-covered islands of the Southwest Pacific are known to produce more evaporation than adjacent areas of ocean. Water that seeps into the soil may be retained for a time by soil capillarity, or other means, before moving downward through the unsaturated zone to become a part of the groundwater.

As the rainfall and water cycle repeats itself, depending upon climatic and other conditions, a water supply is built up that can be captured and used for a