The viscosity of water changes with temperature. A change of one degree Centigrade in the temperature of
the feed water results in a 3% rate of change (increase/decrease) in membrane throughput6. Throughput,
or flux, describes the hydraulic capacity of water produced by the desalination membrane. Therefore, to
achieve an equivalent production value or throughput, more pressure is applied (in varying increments),
additional reverse osmosis capacity is brought on line, or production decreases. The relative influence that
feed water temperature has on required seawater reverse osmosis (SWRO) pressures, at a fixed average
seawater salinity of 34,000 mg/L (34 parts per thousand, ppt) and a SWRO recovery of 50%, is illustrated in
Figure 3.
4