Characteristics of water

CHARACTERISTICS OF WATER

1. PHYSICAL chacteristics: Physical analysis of water is carried out to determine its physical characteristics. The different parameters with respect to water supply are listed below.
1. Temperature: Temperature of water has no practical significance as it cannot be controlled. However, temperature between 10℃ and 25℃ is desirable. At higher temperatures, the solubility of gases (O2) decreases.
2. Colour: Dissolved organic matter from decaying vegetation or inorganic materials such as coloured soils may impart colour to water. Excessive growth of algae or aquatic microorganisms may impart colour to water. Colour in water does not necessarily mean that the water is harmful to humans, but it may adversely affect the colour of clothes being washed in such water. Moreover, it is objectionable from aesthetic and psychological point of view.                                             Colour can be detected by the naked eye. However, it is measured by comparing colour of water sample with Nessler tubes that contain solutions of different colour intensities. Standard unit of colour is produced by 1 mg of platinum cobalt dissolved in 1 litre of distilled water. By this scale, the maximum permissible limit for colour for domestic supplies is 20ppm.
3. Taste & Odour: Dissolved organic matter or inorganic salts or gases (H2S, CH4, CO2, O2) may impart taste and odour to water. Mineral substances like NaCl, iron compounds, carbonates and sulphates of other elements impart taste and odour to water. Tastes imparted by dissolved oxygen and dissolved carbondioxide are desirable. Taste and odour in water is measured by odour intensity or threshold odour number which represents the dilution ratio at which the odour is hardly detectable. The number of times the sample is diluted represents the threshold odour number. For public water supplies the threshold odour number is 1 and should never exceed 3.
4. Turbidity: Turbidity is measured using an instrument called turbidimeter.Jackson Turbidimeter and Baylis turbidimeter were used in the past and have been replaced by Nephelometer. In this instrument, light intensity is measured at right angles to the incident light. The units of turbidity in nephelometer are Nephelometric Turbidity Units (NTU)
5. Solids: The total amount of solids (suspended and dissolved) present in water can be determined gravimetrically.
2. CHEMICAL characteristics
1. Inorganic minerals: As the run-off travels to join the surface water bodies, it contacts rocks and soils and dissolves inorganic minerals which enter into natural waters.
1. Major cations: Major cations found in natural waters include Ca2+, Mg2+, Na+, K+. Calcium contributes to hardness. Magnesium is not as abundant as calcium. Other constituents include Al, B, Fe, Mn, P, etc.
2. Major anions: Major anions include Cl-, SO3-, CO32-, HCO3-, F- and NO3-
2. Carbonates
1. Carbonate equilibrium: The Carbonate-bicarbonate system is the most important chemical system in natural waters. It provides the buffering capacity essential for maintaining the pH of natural water systems
3. pH and Alkalinity: Alkalinity is defined as the capacity of natural water to neutralize acid added to it.
4. Acidity:
5. Inorganic indicators of water quality
1. Hardness:
2. Total Dissolved Solids (TDS):
3. Conductivity:
4. Sodium Adsorption Ratio:
6. Radionuclides:
7. Organic materials
1. Natural Organic Matter:
2. Man-made Organics:
3. Organic Carbon:
4. Inorganic Carbon:
5. Total Carbon:
6. Biological Oxygen Demand (BOD):
7. Chemical Oxygen Demand (COD):
8. Dissolved Gases:
3. MICROBIOLOGICAL characteristics:
4. BIOLOGICAL characteristics: