Very hard water is not desirable for many domestic uses; it will leave a scaly deposit on the inside of pipes, boilers, and tanks. Hard water can be softened at a fairly reasonable cost, but it is not always desirable to remove all the minerals that make water hard. Extremely soft water is likely to corrode metals, although it is preferred for laundering, dishwashing, and bathing. Ground water, especially if the water is acidic, in many places contains excessive amounts of iron.
Iron causes reddish stains on plumbing fixtures and clothing. Like hardness, excessive iron content can be reduced by treatment. A test of the acidity of water is pH, which is a measure of the hydrogen-ion concentration. The pH scale ranges from 0 to A pH of 7 indicates neutral water; greater than 7, the water is basic; less than 7, it is acidic. A one unit change in pH represents a fold difference in hydrogen-ion concentration. Briefly, explain why the pH of deionized water is typically found to be around 6.
Write the net ionic equation for the removal of calcium ions by precipitation with carbonate in the lime-soda process. See the introduction to Experiment 2 for a discussion of net ionic equations.
Could sodium ions be removed in the same way as magnesium ions in the lime-soda process i. Briefly, explain your reasoning. Brown, Lemay, and Buster. Chemistry: the Central Science , 7th ed. The authors thank Dewey Holten Washington University for many helpful suggestions in the writing of this tutorial. Louis, MO Natural color of 10 units or less usually goes unnoticed and even in larger amounts is harmless in drinking water.
Color is objectionable in the use of water for many industrial purposes, however. It may be removed from water by coagulation, sedimentation, and activated carbon filtration. However, it may cause mottling of the teeth depending on the concentration of fluoride, the age of the child, the amount of drinking water consumed, and the susceptibility of the individual.
A small number of minerals comprise nearly the entire mass of sandstone aquifers. The average sandstone, as determined by F. Clarke , The data of geochemistry, fifth ed. Limestone and dolomite aquifers are primarily calcium carbonate and calcium magnesium carbonate, respectively, but impure ones may contain as much as 50 percent noncarbonate constituents such as silica and clay minerals.
Quartz, the main constituent of sandstones, is the least reactive of the common minerals and, for all practical purposes, can be considered nonreactive except in highly alkaline solutions Roedder, E.
Clays have been demonstrated to react with highly basic or highly acidic solutions. Clay minerals are common constituents of sedimentary rocks. Roedder stated that sandstones containing less than 0. Clay minerals are known to reduce the permeability of sandstone to water as compared with its permeability to air Johnston, N.
Sweeney, , Effect of clays on the permeability of reservoir sands to various saline water, Bureau of Mines Report of Investigations ; Land, C. Baptist, , Effect of hydration of montmorillonite on the permeability of water-sensitive reservoir rocks, Journal of Petroleum Technology October. The degree of permeability reduction to water as compared with air is termed the water sensitivity of a sandstone by Baptist and Sweeney.
The following characteristics of groundwater give it certain advantages over surface water. Groundwater usually contains no suspended matter. Groundwater, very rarely contains pathogenic bacteria; generally it contains microbes native to the formation, unless contaminated by human activity Michael J. Schieders, Water Systems Engineering Inc. Groundwater is clear and colorless unless tainted with humic material. The temperature of groundwater is relatively constant and is equivalent to, or greater than, the mean air temperature above the land surface.
Temperatures can be altered by human influence. Corrosiveness Water that attacks metal is said to be corrosive. Manganese Dissolved from some rocks and soils, and not so common as iron, manganese chemical symbol Mn has many of the same objectionable features as iron.
Calcium and magnesium Dissolved from practically all solids and rocks, but especially from limestone, dolomite, and gypsum, calcium Ca and magnesium Mg are found in large quantities in some brines. Sodium and potassium Dissolved from practically all rocks and soils, sodium Na and potassium K are also found in ancient brines, sea water, some industrial brines, and sewage. Bicarbonate and carbonate Generated by the action of carbon dioxide in water on carbonate rocks such as limestone and dolomite, bicarbonate HCO 3 - and carbonate CO 3 -2 produce an alkaline environment.
Sulfate Sulfates SO 4 -2 are dissolved from rocks containing gypsum, iron sulfides, and other sulfur compounds.
Chloride Chlorides Cl - are dissolved from rocks and soils. Aluminum Aluminum Al is derived from bauxite and other clays. Silica Dissolved from practically all rocks and soils, silica SiO 2 is generally found in small amounts from 1 ppm to 30 ppm. Iron Extremely common, iron Fe is dissolved from practically all rocks and soils. Nitrate Sources of nitrate NO 3 - are decaying organic matter, legume plants, sewage, nitrate fertilizers, and nitrates in soil.
Dissolved solid refer to any minerals, salts, metals, cations or anions dissolved in water. Total dissolved solids TDS compr ised inorganic slats principally calcium, magnesium, potassium, sodium, bicarbonates, chlorides , and sulfates and some small amounts of organic matter that are dissolved in water.
Background of total dissolve solids. Total dissolved solids or TDS contains of minerals, nutrients that have dissolved in water.
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