Distillation

The intake water is exchanged from a liquid to vapor (steam). The vapor is then condensed to produce product water.

Reverse Osmosis

Pressure is applied to the intake water, forcing the water molecules through a semipermeable membrane. The salt molecules do not pass through the membrane, and the water that passes through becomes potable product water.

Ranges In Plant Capacity

(Other than off shore oil and gas platforms.) 16 - 112,000 AF/year (One acre-foot is equivalent to 326,000 gallons). This is equivalent to the amount of water that two to three households would consume in one year. In most cases, conversions can not be made directly from gallons per day (gpd) to acre-feet per year (AF/year) since most plants will not operate every day of the year.

Costs

Most sea water plants in California would produce water in the range of $1,300 to $2,200/AF.

Energy Use

2,500 to 12,000 kWh/AF.

Efficiency

(Percent of product water recovery to input flow.)

For every 100 gallons of sea water input, 15 to 73 gallons of fresh water would be produced. The remainder would be waste brine solution and solid wastes.

Water Quality

2 to 500 ppm tds (the recommended California drinking water standard or maximum total dissolved solids level is 500 ppm.)

Plant Size Area

- This varies according to how spread out the design of the plant is. Proposed or existing California plants range from 80 square feet for a 16 AFlyear plant to 7.5 acres for a 5,000 AF/year plant.

Height

Typical distillation equipment 30 to 530 feet. (Typical reverse osmosis equipment 15 to