Drinking water softeners

NaCl(s) + X2+(aq) XCl2(aq) + 2Na+(aq) Water softened by this method contains extra sodium ions. Explain why people with hypertension (high blood pressure) should avoid drinking water softened by this type of ion exchange. 

Water softened in this way contains an increased concentration of Na . Although Na does not form precipitates or cause other problems associated with hard-vwiter cations, individuals concerned about their sodium intake, such as those who have high blood pressure (hypertension), should avoid drinking water softened in this way. 

Groundwater generally has a stable composition, but it is often too hard for use as process water or drinking water. Softening is necessary in many cases. Nanofiltration is here a competitive alternative for lime softening a comparison between both for application in Florida by Bergman (1995) showed that for lime softening operation and maintenance... 

Sodium alumiaate is used ia the treatment of iadustrial and municipal water suppHes and the use of sodium alumiaate is approved ia the clarification of drinking water. The FDA approves the use of sodium alumiaate ia steam generation systems where the steam contacts food. One early use of sodium alumiaate was ia lime softening processes, where it iacreases the precipitation of ions contributing to hardness and improves suspended soHds removal from the treated water (17). Sodium alumiaate reacts with siHca to leave very low residual concentrations of siHca ia hot process water softeners. Sodium alumiaate is often used with other chemicals such as alum, ferric salts, clays, and polyelectrolytes, as a coagulant aid (18,19). 

Water purification and recycling is now a major industry.The method of treatment depends on the source of the water, the use envisaged and the volume required. Luckily the human body is very tolerant to changes in the composition of drinking water, and in many communities this may contain 0.5 gl or more of dissolved solids (Table 14.7). Prior treatment may consist of coagulation (by addition of alum or chlorinated FeS04 to produce floes of Al(OH)3 or Fe(OH)3), filtration, softening (removal of... 

Uses The highest value inorganic acid marketed in the U.S. and second in value to sulfuric acid. Used primarily for the preparation of salts used as fertilizers (ammonium and calcium salts), water softeners and detergents, animal feeds, and baking powder. Food-grade phosphoric acid is used to acidify soft drinks, e.g.. Coca Cola. Organic phosphates are used in flame retardants. 

Lime is used in drinking water treatment to control pH, soften water, and control turbidity. Lime, in combination with sodium carbonate, is used to precipitate the major bivalent... 

Water is the most abundant compound on earth. Seawater, which accounts for 97.3% of the world s water supply, contains 3.5 mass % of dissolved salts. Purification of drinking water involves preliminary filtration, sedimentation, sand filtration, aeration, and sterilization. Hard water, which contains appreciable concentrations of doubly charged cations such as Ca2+, Mg2+, and Fe2+, can be softened by ion exchange. Water is reduced to H2 by the alkali metals and heavier alkaline earth metals, and is oxidized to O2 by fluorine. Solid compounds that contain water are known as hydrates. 

NF is used when high molecular weight solutes have to be separated from a solvent. It is effective in the production of drinking water, especially in the case of water softening. Compared to RO, a lower retention is found for monovalent ions. But very recently [9], it has been found that NF separates the ions of the same valency for a selective defluorination of brackish water. RO and UF have shown, respectively, solution-diffusion and convection mass transfers. In NF, a synergism between both can be observed but strongly depends on the operational conditions (pH, ionic strength, flow rate, transmembrane pressure) and on the membrane material used. 

An ion exchange water softener adds significant amounts of sodium to the water. Thus, it may not be the best choice for drinking water. This is especially true for people on sodium-restricted diets. 

Sodium is present in soils and water as NaCl. In arid environments, NaCl accumulates in the surface and groundwater owing to irrigation and high evapotranspiration. Other activities such as road salting and water softening may also contribute NaCl to natural waters. For additional information on human health effects and drinking water levels, see Shelton (1989). 

A city water plant can remove total hardness for about 1/4 the cost of the individual home owner. Usually, only the hot water line is connected to the water softener to hold the cost down and to keep the sodium content of drinking water as low as possible. This is important for people with high blood pressure or who are hypertensive. 

Sodium ions may naturally be present in drinking water if the supply is brackish, like many water sources in Central Asia and the Middle East. Above about 300-400 ppm of sodium chloride, the water is unpalatable on account of its chloride content, and special purification measures, such as reverse osmosis (see below Section 6) are required. Naturally soft water frequently contains sodium rather than the hardness cations calcium and magnesium, while water softening artificially in domestic water softeners has the hardness cations replaced by sodium (see below Section 5). Even though... 

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