Figure 37
Effect of Feed Water Temperature on Pumping Energy
The example in Figure 3 is for seawater with a salinity of 34,000 mg/L. Because salinity is variable around
the coastal United States (and around the rest of the world), the required driving pressure and associated
energy needed to produce the same throughput (flux) for different salinities will vary accordingly. A general
“rule of thumb” is that the net driving pressure needed to produce an equivalent amount of permeate will
increase (or decrease) by about 11 psi (0.76 bar) for each 1000 mg/L (1 ppt) incremental change in feed
water salinity. Figure 4 illustrates how salinity varies around the coastal United States.
According to the National Oceanic and Atmospheric Administration (NOAA), the 3-Zone Average Annual
Salinity Digital Geography in Figure 4 was developed using geographic information system (GIS)
technology, and are the average annual salinities found in certain estuaries along the coastal United
States. The mapped areas include the entire Atlantic, Gulf of Mexico, and Pacific coasts of the United
States.