The purification is done by filtering the water to remove the majority of suspended solids. Once the majority of the suspended solids are removed, high pressure forces the water through a semipermeable membrane. A maximum of 600 pounds psi is used for fresh and brackish water, and a maximum of 900 pounds psi is used for salt water. Chemicals are added to the product water to kill bacteria.

SUPPORT EQUIPMENT. - The self-contained skid-mounted ROWPU unit requires a portable generator capable of providing 30 kilowatts of power (fig. 2-29).

Other supportable equipment includes the following: portable onion skin bladders (3,000 gallons), as shown in figure 2-30, or collapsible water tanks (3,000 gallons); four frame-mounted, portable, electrical motor-driven water pumps with hoses and fittings; water test equipment (TDS meter, color comparator, etc.); and an operating supply of chemicals (chlorine, sodium hex, polymer, and citric acid).

WATERFLOW THROUGH THE ROWPU. - you read through the next 18 items listed, refer to the flow diagram in figure 2-31.

1. This is the water source that you are going to purify through the ROWPU.

2. The strainer is attached to the end of the intake hose to keep rocks, leaves, and any other foreign objects from entering the pumps and filters.

3. The first of the two pumps that draw water from the water source and pump the water to the ROWPU.

4. The second of the two pumps that draw water from the water source and punp the water to the ROWPU.

5. The polymer pump adds a polyelectrolyte solution to the raw water. The polymer causes coagulation of small floating particles. This enables the filters to remove the particles.

6. The sodium hex pump adds a solutionof sodium hexametaphosphate to prevent scaling of the filters.

7. The multimedia filter is the first actual filter that the raw water goes through.

8. After the water has been filtered, the booster pump draws the water and forces it through the cartridge filter.

9. As the water goes through the cartridge filter, tiny particles that were not filtered out by the multimedia filter are filtered out.

10. The reverse osmosis (RO) pump increases the filtered water pressure and forces the water through the RO elements (semipermeable membranes)

11. The pulse dampener is simply a ball-shaped device that reduces the shock caused by the piston action of the pump.

Figure 2-29. - Generator skid-mounted.