Installation

At permanent naval activities, the installation of distillation equipment will be designed by engineers and improvements to the system can be made over a long period of time. In the tactical field environment, it will be the Utilitiesman supervisor who must consider various factors for the installation of distillation equipment. These are as follows: l potable water demand l Site location l Site drainage l Security . Fire protection

The demand for potable water will determine the number of distillation units, the need for storage facilities, operating hours, and so forth. You must determine the population you will be serving. Keep in mind that your water point may supply many units in an area, not just your organization.

The site location for distillation equipment must be upstream of any source of contamination. You must consider ocean currents that may change with wind direction, weather conditions, the season of the year, or tidal action. It is not efficient use of personnel or equipment if you have to relocate because the wind changed direction.

The site must also be relatively flat with a gradual slope toward the ocean. You also must allow for' maximum tidal action. In many areas the tide may rise and fall several feet, depending on the season of the year. Build low platforms to keep your equipment out of the sand and to allow air to circulate underneath tanks to prevent rot. These platforms also prevent punctures of the storage tanks by sharp objects and provide a stable working area for operating personnel.

The importance of providing adequate drainage at any water point cannot be overemphasized. Wastewater from filters, leakage from tanks, and spillage from distribution points can render a water point inoperable as well as creating an unsanitary condition.

Your water point may or may not be located in the vicinity of friendly forces. Denying the enemy information about your water point by using overhead concealment and camouflage may be necessary as well as guarding against ground attacks and sabotage with a defensive plan. Any adverse effect, from thirst to disease, the enemy can have on a water point will affect the well-being of the force using it. It will be considered in the plans of the enemy.

Distillation equipment cannot produce water quickly enough to be used for fire protection. Do not permit your treated water to be used for this purpose except in extreme emergencies. Raw water should be used whenever possible.

REVERSE OSMOSIS

The use of reverse osmosis water purification equipment by the military has produced potable water from the sources available in a combat field environment. The reverse osmosis water purification unit (ROWPU) is capable of treating freshwater, brackish water, and seawater.

Additionally, the unit is capable of treating water contaminated with chemical, biological, and radiological warfare agents. When using the unit to treat water contaminated by CBR agents, you must use the equipment in conjunction with auxiliary ion exchange and carbon adsorption units.

The ROWPU used by the NCF is capable of producing 600 gph of product water from freshwater sources and 400 gph of product water from seawater at 70F. The rate of water production in the ROWPU depends upon the operating pressure, normally 350 to 550 psig for freshwater and 750 to 950 psig for seawater. Temperature affects the rate of flow. Cold water decreases the flow, while warm water increases the flow.

NOTE: Maximum operating water temperature of the ROWPU feedwater is 120F. Water temperatures above this figure may damage the membranes within the reverse osmosis modules.

Reverse osmosis (RO) is a purification process in which filtered water is pumped against a semipermeable membrane under great pressure. The membrane allows product water to pass through while rejecting impurities, both dissolved and suspended. You must use an extremely high pressure for a usefull volume of water to pass through a unit membrane. The reverse osmosis process is shown in figure 9-13(A). Reverse osmosis may appear to be nothing more than a filtering process, but there are distinct differences. In filtration, the entire liquid stream flows through the porous filter medium and no chemical changes take place between the feed and the filtrate. In RO, the feed flows parallel to the semipermeable membrane with a fraction of it passing through a given membrane area; dissolved ionic and organic substances are rejected by the membrane and, in this case, drained off as a brine.

Figure 9-13(A).-Reverse osmosis process.

The following explanation is the flow process through the 600 gph ROWPU. As you read through this section, refer to the flow diagram in figure 9-13(B). Water is delivered to the ROWPU through the raw water pump. Upon entering the unit, it goes through the multimedia filter. This filter removes small and large solids. From the multimedia filter, the water is picked up by the booster pump that pushes the water through the cartridge filter. The cartridge filter takes out suspended solids that passed through the multimedia filter. From the cartridge filter, the water is picked up by the RO pump that pushes the water under high pressure through the pulse dampener and into the RO elements. The RO elements remove dissolved minerals and other bacteria that passed through the filters. The product water leaving the last element receives enough chlorine to kill any remaining bacteria.

Figure 9-13(B).-Water flow through the 600 gph ROWPU.

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