Brackish Water and Excessive Total Dissolved Solids (Secondary MCl: 500 ppm; 1000 ppm in California)

Water can acquire excessive dissolved mineral content by evaporation, as in the case of Colorado River water being directed through the desert in aqueducts to Southern California; by flowing through deposits of soluble salts, as in the true alkaline waters that are full of sodium sulfate or sodium carbonate; and by sea water intrusion, as is seen in all coastal areas. These waters are not merely unpalatable; they are actually unhealthful until the excess dissolved material is removed. In an extreme case, such as drinking sea water, it can be fatal. That is because of osmotic pressure, which deserves its own discussion.