ABSTRACT
D e s a l in a t io n p e r f o r m e d b y reverse osmosis involves the use of a syn thetic semi-membrane and a high-pressure hydraulic pump. The heart of the process is the semipermeable membrane. The membrane is pene trable by certain molecules and impenetrable by others. Reverse osmo sis is a physical process in which a proportion of water from a pressur ized supply is forced through a semipermeable membrane to become product water leaving behind almost all of the impurities in the re maining water. The salt ions in the reject and excess fluid are dis charged from the system as brine. In 1994, in Saudi Arabia, 1126 desalination plants of both brackish and seawater (IDA, 1994) at 15 sites were in operation producing a total of 0.4 X 106 m3/d of potable water. All the reverse osmosis plants operating in Saudi Arabia are designed on a specific seawater analysis as the salinity of seawater varies from coast to coast along the Arabian Peninsula. The salinity, in terms of total dissolved solids (TDS) around the Al-Khobar-Al-Azizia coast is the highest, i.e., between 65,000 and 70,000 mg/L. Table 1 shows an analysis of seawater. Usually, reverse osmosis plants are designed for seawater salinity in the range of 35,000-50,000 ppm. The permeation behavior for a constant TDS feed has been well studied and reported (DuPont, 1987). However, it is not known how a membrane
Table 1. Analysis of sea-, raw and product water.
