TABLE 4 CONTINUED
Constituent
or property Source or cause Effects
Fluoride (F) Dissolved in small to minute Fluoride in drinking water reduces the incidence of tooth decay quantities from most rocks when the water is consumed during the period of enamel calcificaand soils. Added to many tion. However, it may cause mottling of the teeth, depending on the waters by fluoridation of mu- concentration of fluoride, the age of the child, amount of drinking nicipal supplies, water consumed, and susceptibility of the individual. (Maier, F. J., 1950, Fluoridation of public water supplies, Jour. Am. Water Works Assoc., vol. 42, pt. 1, p. 1120-1132). Nitrate (NO8) Decaying organic matter, sew- Concentration much greater than the local average may suggest m age, fertilizers, and nitrates pollution, USPHS (1962) drinking-water standards suggest a limit d in soil. of 45 ppm. Waters of high nitrate content have been reported to be the cause of methemoglobinemia (an often fatal disease in in- W fants) and therefore should not be used in infant feeding. Nitrate has been shown to be helpful in reducing inter-crystalline cracking of boiler steel. It encourages growth of algae and other organisms which produce undesirable tastes and odors.
Dissolved solids Chiefly mineral constituents USPHS (1962) drinking-water standards recommend that waters dissolved from rocks and soils. containing more than 500 ppm dissolved solids not be used if other Includes some water of crys- less mineralized supplies are available. Waters containing more tallization, than 1,000 ppm dissolved solids are unsuitable for many purposes. Hardness as CaCO, In most waters nearly all the Consumes soap before a lather will form. Deposits soap curd on ,1.
hardness is due to calcium and bathtubs. Hard water forms scale in boilers, water heaters, and magnesium. All of the metal- pipes. Hardness equivalent to the bicarbonate and carbonate is lications other than the alkali called carbonate hardness. Any hardness in excess of this is metals also cause hardness. called non-carbonate hardness. Waters of hardness up to 60 ppm are considered soft; 61 to 120 ppm, moderately hard; 121 to 180 ppm, hard; more than 180 ppm, very hard.