External Requirements
Standard Seawater:
Seawater with TDS of 35,000 mg/l (ppm) is considered as "standard seawater" since this constitutes by far the
largest amount of water worldwide. The composition is nearly the same all over the world (see table 1)
TABLE 1: "Standard Seawater" Composition
Calcium
410 mg/l
Silica
0.04 - 8.0 mg/l
Magnesium
1,310 mg/l
Chloride
19,700 mg/l
Sodium
1,900 mg/l
Sulphate
2,740 mg/l
Potassium
390 mg/l
Fluoride
1.4 mg/l
Barium
0.05 mg/l
Bromide
65 mg/l
Strontium
13 mg/l
Nitrate
< 0.7 mg/l
Iron
< 0.02 mg/l
Bicarbonate
152 mg/l
Manganese
< 0.01 mg/l
TDS = 35,000 mg/l
pH = 8.1
The actual TDS content may, however, vary within wide limits from e.g. the Baltic Sea with 7,000 ppm to the
Red Sea with up to 45,000 ppm. The actual composition can be proportionally estimated from the "standard
seawater" composition.
Be aware that seashore wells depending on the soil, influx from island, etc. can often have salinity and
composition quite different from that of a sample taken from the sea itself.
In seawater treatment the limiting factor is of a physical nature, i.e. the osmotic pressure caused by the high
TDS.