hypochlorite should be used to disinfect the water in the tank trailer. The procedure for preparing and adding the solution to the tank trailer is as follows:

1. Fill the tank trailer half full of water.

2. Prepare a small amount of HTH concentrate by dissolving the required amount of HTH in a canteen cup or other container. In this case, place the 10 ounces of HTH in a l- or 2-gallon bucket of water.

3. Stir the mixture thoroughly. All of the granules will not dissolve. Allow undissolved granules to settle to the bottom of the bucket.

4. Add only the clear concentrate liquid to the tank trailer. By pouring the supematant into the tank trailer slowly, you can see that the settled granules will remain in the bucket.

5. Fill the remainder of the tank with the water to be treated

6. The water now must be agitated to distribute the HTH. In this example, you could simply attach the tank trailer to a vehicle and go for a short drive.

7. The final step is to take a FAC reading 30 minutes after adding the HTH. The reading must be at or above the required ppm. In this example, the FAC must read 100 ppm or higher. If the ppm is not high enough, add more HTH until the desired ppm is maintained.

NOTE

Remember that during superchlorination the FAC may not fall below 50 ppm wihin 4 hours or the whole procedure must be repeated.

After the 4-hour contact time and the tank trailer ppm has stayed above 50 ppm, the trailer is now disinfected. Rinse the tank thoroughly with potable water and then refill it for usage. An occasion may occur when you must use the water that you superchlorinated. If the chlorine ppm is too high, you may use sodium thiosulfate or sodium bisulfate to dechlorinate the water.

Table 2-3 shows water sources and the required chlorine residual.

For further information, see chapter 9 of the Manual for Preventive Medicine, NAVMEDP-50109.

Table 2-3. - Chlorine Residual Chart

Diatomite Water Purification Unit (3000-D)

The 3000-D Water Purification System is portable and completely self-contained, as shown in figure 2-25. The unit purifies turbid and bacteria-polluted water. Particular attention was paid to design and packaging to increase efficiency, mobility, and cost effectiveness. It also provides a trouble-free method of producing potable water at the rate of 3,000 gallons per hour.

The system is constructed in separate modules, interconnected, and mounted in a common chassis. The chassis is not required for operation, but it greatly eases the transportability of the system. The system contains all of the functional apparatus and supplies necessary to process approximately 20,000 gallons of potable water. The user must have a water source and a