i. Physical Characteristics
Physical properties of water include
Physical properties of water include
- temperature
- colour
- turbidity
- taste and odours.
Temperature : The saturation levels of dissolved solids, and gases in water and rates of chemical, biochemical reaction depend on temperature. The temperature of surface water is generally at atmospheric temperature. The temperature of ground water will be more or less than that of atmospheric temperature.
Colour : Colour of water is due to both dissolved and suspended solids in water.
Turbidity: These dissolved and suspended solids also determine the extent of turbidity. For drinking water, even slight turbidity is objectionable. Turbidity will also interfere with the action of chlorination which is the principal method of disinfecting water. It can either react with most of the available chlorine or keep pathogenic organisms from being killed by the chlorine. Ground water is usually less turbid than the surface water. Surface waters are frequently high in turbidity where colour is caused by colloidal clay particles. Turbidity is measured by determining the resistance of water to the passage of light through it.
Taste and odour : Decomposition of organic matter in water, dissolved gases such mas hydrogen sulfide and other inorganic compounds contribute to taste and odour of water.
ii. Chemical Characteristics
The chemical characteristics include
Colour : Colour of water is due to both dissolved and suspended solids in water.
Turbidity: These dissolved and suspended solids also determine the extent of turbidity. For drinking water, even slight turbidity is objectionable. Turbidity will also interfere with the action of chlorination which is the principal method of disinfecting water. It can either react with most of the available chlorine or keep pathogenic organisms from being killed by the chlorine. Ground water is usually less turbid than the surface water. Surface waters are frequently high in turbidity where colour is caused by colloidal clay particles. Turbidity is measured by determining the resistance of water to the passage of light through it.
Taste and odour : Decomposition of organic matter in water, dissolved gases such mas hydrogen sulfide and other inorganic compounds contribute to taste and odour of water.
ii. Chemical Characteristics
The chemical characteristics include
- pH
- hardness
- chlorides
- fluorides
- iron and manganese
Hardness and pH are two important characteristics of water.
Hardness : Hardness of water has great implications for process industries and it will be discussed in detail in next section.
pH : Hydrogen ion concentration in water determines the pH value. The hydrogen ion concentration is affected by the ions of dissolved salts and minerals.Other chemicals : Presence of excess amounts of nitrates and fluorides cause adverse health effects. The presence of heavy metals and toxic compounds such as lead, cadmium, chromium and mercury even in low concentrations is detrimental to public health. These tend to accumulate in food chain.
iii. Biological Characteristics
Biological characteristics of water mainly refer to microbiological quality. Knowledge of type of microorganisms present in water is essential for design and operation of water disinfection processes. If pathogens (disease causing micro organisms) are present, they should be killed before consumption of water. It is not feasible to test for all micro organisms that are present in water and indicator organisms are used for detection of pathogens. When water is contaminated with fecal matter, bacteria of the coliform group serve as indicator organisms. Escherichia coli, Aerobacter aerogenes, and Streptococcus pyogenes are found in fecal matter of warm- blooded animals. Their presence in water indicates a strong possibility of sewage pollution. The organisms mentioned will cause only a mild or no disease, although they are indicators of the presence of Salmonella and Shigella, which can cause serious disease. Experience has shown that treatment that will kill the coliforms will kill the pathogens and render the water safe.
Water contaminated with human waste always contains coliforms, and it is likely to contain pathogens excreted by infected individuals in the community. One pathogen of special concern is the virus that causes hepatitis. It will survive in water - evenin 100 o C water for 5 min. If coliforms are not found in the water, we assume that the water is also free of pathogens. When the coliform count is low, there is little chance that pathogens are present in the water.Various testing methods are used to indicate and enumerate the presence of coliforms in water. The number of organisms must be less than 1 in 100 ml. This number is only achievable in treated water. Water must be checked on a daily basis for coliform and chlorine residual. A free chlorine residual of at least 0.2 mg/l must be maintained throughout a water distribution system. This will not always inactivate viruses.
Hardness : Hardness of water has great implications for process industries and it will be discussed in detail in next section.
pH : Hydrogen ion concentration in water determines the pH value. The hydrogen ion concentration is affected by the ions of dissolved salts and minerals.Other chemicals : Presence of excess amounts of nitrates and fluorides cause adverse health effects. The presence of heavy metals and toxic compounds such as lead, cadmium, chromium and mercury even in low concentrations is detrimental to public health. These tend to accumulate in food chain.
iii. Biological Characteristics
Biological characteristics of water mainly refer to microbiological quality. Knowledge of type of microorganisms present in water is essential for design and operation of water disinfection processes. If pathogens (disease causing micro organisms) are present, they should be killed before consumption of water. It is not feasible to test for all micro organisms that are present in water and indicator organisms are used for detection of pathogens. When water is contaminated with fecal matter, bacteria of the coliform group serve as indicator organisms. Escherichia coli, Aerobacter aerogenes, and Streptococcus pyogenes are found in fecal matter of warm- blooded animals. Their presence in water indicates a strong possibility of sewage pollution. The organisms mentioned will cause only a mild or no disease, although they are indicators of the presence of Salmonella and Shigella, which can cause serious disease. Experience has shown that treatment that will kill the coliforms will kill the pathogens and render the water safe.
Water contaminated with human waste always contains coliforms, and it is likely to contain pathogens excreted by infected individuals in the community. One pathogen of special concern is the virus that causes hepatitis. It will survive in water - evenin 100 o C water for 5 min. If coliforms are not found in the water, we assume that the water is also free of pathogens. When the coliform count is low, there is little chance that pathogens are present in the water.Various testing methods are used to indicate and enumerate the presence of coliforms in water. The number of organisms must be less than 1 in 100 ml. This number is only achievable in treated water. Water must be checked on a daily basis for coliform and chlorine residual. A free chlorine residual of at least 0.2 mg/l must be maintained throughout a water distribution system. This will not always inactivate viruses.
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