Do we need chemical-water-quality parameters?Water has been called the universal solvent, and chemical-water-quality parameters are related to the solvent capabilities of water. The solvent capability of water makes it an ideal means by which waste products can be carried away from industrial sites and home.The chemical parameters for chemical water quality management as following:
A- Total dissolved solid (TDS ) The TDS is very and quick indication for chemical-water-quality. The material remaining in the water after filtration for the suspended solids analysis is considered to be dissolved. This material/s is left as a solid residue up on evaporation of the water and constituents a part of total solids. Dissolved material results from the solvent action of the water on solids, liquids, and gases. Dissolved substances may be organic or inorganic in nature. Inorganic substances which may be dissolved in water include minerals, metals, and gases, water may come in contact with these substances in the atmosphere, on surface, and within the soil. Dissolved materials normally came from the decay products of vegetation, from organic chemicals, and from the organic gases. TDS measured unit is mg/litre or part per million (ppm) , the approximate analysis for TDS is often made by determining the electrical conductivity of the water.
Alkalinity is defined as the quantity of ions in water that will react to neutralize hydrogen ions. Alkalinity is thus a measure of the ability of water to neutralize acids. The source of alkalinity in the natural water systems include the following:
These compounds result from the dissolution of mineral substances in the soil and atmosphere, and play important role for chemical-water-quality. Phosphates may originate from detergents in waste water discharges and from fertilizers and insecticides from agriculture land. Hydrogen sulfide and ammonia may be products of microbial decomposition of organic material. By far the most common constituents of alkalinity are
in addition to their mineral origin, these substances can originate from carbon dioxide, a constituent of the atmosphere and a product of microbial decomposition of organic material. Alkalinity measurement are made by titration the water with an acid and determining the hydrogen equivalent. Alkalinity expressed as mg/litre as of CaCO3 . Alkalinity measurement are often included in the analysis of natural water to determine their buffering capacity. It’s also used frequently as process control variable in water and waste water treatment.
The Hardness as chemical-water-quality is essential parameter for decision of water treatment process requirment. Hardness is defined as the concentration of multivalent metallic cations in solution. At supersaturated conditions, the hardness cations will react with anions in the water to form a solid precipitate. Hardness is classified as carbonate hardness and noncarbonated hardness, depending upon the anion with which it associates. The hardness that is equivalent to the alkalinity is termed carbonate hardness, with any remaining hardness being called noncarbonated hardness. Carbonate hardness is sensitive to heat and precipitates readily at high temperatures Ca(HCO3)2 →Heat→ CaCO3↓+CO2↑+H2O Mg(HCO3)2 →Heat→ Mg(OH)2 ↓ + 2CO2 ↑ To find out the source of hardness in fact the multivalent metallic ion which most abundant in natural waters are calcium and magnesium, others may include iron and manganese in their reduced states(Fe+ , Mn2+), strontium (Sr2+), and Aluminum(AL3+), the latter usually found in much smaller quantities then calcium and magnesium, and for all practical purposes, hardness may be represented by the sum of the calcium and magnesium ions. Hardness in fact has some impact such as soap consumption by hard waters represent an economic loss to the water users. Lathering does not occur until all of the hardness ions are precipitated, at which point the water has been “softened” by the soap. The precipitate formed by hardness and soap adheres to surfaces of tubes, sinks, and dishwashers and many stain clothing, dishes, and other items. Residues of the hardness-soap precipitate may remain in the pores, so that skin may feel rough and uncomfortable. Boiler scale, the result of the carbonate hardness precipitate may cause considerable economic loss through fouling of water heaters and hot water pipes. Change in pH in the water distribution system may also result in deposits of precipitates. Bicarbonates begin to convert to the less soluble carbonates at pH value above 9.0 Magnesium hardness particularly associated with the sulfate ion, has a laxative effect on persons unaccustomed to it.Magnesium concentrations of less then 50 mg/L (ppm) are desirable in potable water, although many public water supplies exceed this amount. Calcium hardness present no public health problem, in fact hard water is apparently beneficial to the human cardiovascular system. Hardness can be measured by using spectrophotometric techniques or chemical titration to determine the quality of calcium and magnesium ions in the given sample. The analysis for hardness is commonly made on natural waters and on waters intended for potable supplies and for certain industrial uses. Hardness may range from practically zero to several thousand part per million (ppm), a general accepted classification is as follows.
The public health service standard recommended a max. of 500 ppm of hardness in drinking water. No maximum limit been set by EPA standard.
The fluoride chemical-water-quality is considered from health point view. Generally associated in natural with a few types of sedimentary or igneous rocks. Fluoride is seldom found in appreciable quantities in surface water and appears in ground water in only a few geographical regions. Fluoride is a toxic to humans and other animals in large quantities, while small concentration can be beneficial. Approximately 1.0 mg/L (ppm) in drinking water help to prevent dental cavities in children, in fact during formation of permanent teeth, fluoride combines chemically with tooth enamel, resulting in harder, stronger teeth that are more resistant to decay. Excessive intakes of fluoride can result in discoloration of teeth if fluoride concentration more then 2 mg/L (ppm), also excessive dosages of fluoride can also result in bone fluorosis and other skeletal abnormalities, that happen when concentration of fluoride more then 5 mg/L (ppm)
The metals presence in water affect negatively on the health of human being so chemical-water-quality testing is a must befor deciding for human use. All metals are soluble to some extent in water, while excessive amounts of any metal may present health hazards, only those metals that are harmful in relatively small amounts are commonly labeled toxic, other metals fall in to the non toxic group. Sources of metals in natural waters include dissolution from natural deposits and discharges of domestic, industrial, or agricultural waste waters. chemical-water-quality measurement for metals in water is usually made by atomic absorption spectrophotometry. Additionally to the hardness ions, calcium and magnesium, other non toxic metals commonly found in water including:
chemical-water-quality shows the toxic metals which are harmful to humans and other organisms in small quantities. Toxic metals that may be dissolved in water include:
Through chemical-water-quality testing there is many organic materials are soluble in water. Organic in natural water systems may come from natural sources or may result from human activities. Most natural organics consist of the decay products of organic solids, while synthetic organics are usually the result of waste water discharges or agricultural practices. Dissolved organic in water are usually divided into two broad categories
The details of chemical-water-quality results shown below
Measurement of non biodegradable organic is usually by the chemical oxygen demand(COD)test. Non biodegradable organics may also be estimated from a total organic carbon(TOC) analysis. Both COD and TOC measure the biodegradable fraction of the organics. So the BOD must be subtracted from the COD or TOC to quantify the non biodegradable organics. Specific organic compound can be identified and quantified through analysis by gas chromatography.
Nutrients are elements essential to the growth and reproduction of plants and animals, and aquatic species depend on the surrounding water to provide there nutrients. Those required in most abundance by aquatic species are carbon, nitrogen, and phosphorus. By chemical-water-quality measurment the Carbon is readily from many sources. Carbon dioxide from atmosphere, alkalinity, and decay products of organic matter all supply carbon to the aquatic system. Although a few biological species are able to oxidize nitrogen gas, nitrogen in the aquatic environment is derived primarily from sources other than atmospheric nitrogen, that is the advantage of chemical-water-quality. Nitrogen is constituent of points, chlorophyll, and many other biological compounds. Up on the death of plants or animals, complex organic matters is broken down to simple forms by bacterial decomposition. Proteins, for instance, are converted to amino acids and farther reduced to ammonia(NH3). If oxygen is present, the ammonia is oxidized to nitrite (NO2-) and then to nitrate (NO3-). The nitrate can then be reconstituted into living organic matter by photosynthetic plants. Other source of nitrogen in aquatic systems include animal waste, chemical(chemical fertilizers), and waste water discharges. Nitrogen from these sources may be discharged directly into streams or may enter water ways through surface runoff or ground water discharge. Phosphorus appears exclusively as (PO43-) in aquatic environments. There are several forms of phosphates, including orthophosphate, condensed phosphate, and organically bound phosphats. Phosphate is also a constituent of animal waste and may become incorporated into the soil in grazing and feeding areas. Runoff from agricultural areas is a major contributor to phosphate in surface water. Municipal waste water is another major source of phosphate in surface water, other sources include industrial waste in which phosphate compounds are used for such purposes as boiler water conditioning. Phosphate are not toxic and do not represent a direct health threat to human or other organism. Phosphate are measured colorimetrically, and the unit in mg/L (ppm) as phosphorus.
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