Table of Contents
In this article, we will discuss the impurities in water.
1. Introduction
Pure water cannot be found in nature even rainwater which is pure at the instant of originating contains gases, dust and other substances as it passes through the atmosphere.
The ultimate or primary source of water is water as it comes to the earth surface which is already impure rain passing through the atmosphere further picks up the organic and suspended matter as of surface runoff and portion of rainwater which percolates into the ground as groundwater dissolves several salts and minerals, organic and inorganic matter while infiltrating into subsurface strata.
The water thus tapped from surface and ground source may contain undesirable and excess substances as termed as impurities which may be classified as follows.
2. Impurities in Water
Various impurities may be present in water which is classified by two methods as follows.
1. Classification on the basis of properties or characteristics of impurities
a) Physical impurities
b) Chemical impurities
c) Bacteriological impurities
a) Physical impurities
The presence of physical impurities in water affects physical characteristics such as colour, odour, taste and turbidity. Colour, odour and taste in water are due to the presence of organic matter, minerals, microorganisms etc. Turbidity in water is chiefly due to suspended matters whereas colloidal also liable for turbidity.
b) Chemical impurities
The presence of chemical impurities in water affects the chemical salts of minerals, characteristics of water such as PH, solids, hardness, alkalinity, chloride, nitrogen etc. The presence of chemical impurities may cause various types of diseases.
c) Bacteriological impurities
The presence of the bacteriological impurities affects the bacteriological characteristics of water such as pathogenic microorganisms. (Salmonella), non-pathogenic (E-coli) Bacteriological impurities present in water causes diseases in humans.
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2. Classification on the Basis of the State of Presence/Occurrences
a) Suspended impurities
b) Dissolved impurities
c) Colloidal impurities
a) Suspended impurities
These impurities are a dispersion of solid particles resulting in turbidity in water. Suspended impurities include silt, clay, algae, fungi, organic and inorganic matters, mineral matter etc.
These impurities remain in suspension due to the same specific gravity as that of water. Suspended impurities are macroscopic and cause turbidity in water. The concentration of suspended matter in water is measured by turbidity. Suspended impurities can be removed by settling or by filtration.
b) Dissolved impurities
Water is a very good solvent and can dissolve all that it comes in contact with the salts to The dissolved impurities may contain organic compounds, inorganic salts, gases etc. The amount of dissolved solids is normally expressed in and magnesium in water causes bad taste, hardness, alkalinity, alkaline PPm. Salt of calcium etc.
Iron oxide and manganese when dissolved cause odour, taste, red or black or brown colour, produce stain’s on cloth in laundries and plumbing fixtures in buildings. Gases like O2 and CO2 causes corrosiveness and H2S causes the smell of rotten egg. Dissolved impurities is in a liquid having only one phase so such impurities can be removed only by phase change such as Precipitation, adsorption, distillation.
c) Colloidal impurities
These impurities are so small that they cannot be removed by an ordinary filter and are not visible to the naked eye. These are a dispersion of particles in water with electrically charged and remain in continuous motion and do not settle due to the same charge.
These colloidal impurities are generally associated with organic matter containing bacteria and are the chief source of epidemics. Colour in water is normally due to colloidal impurities. Their quantity is determined by colour tests. Their quantity is determined by colour tests. The size of colloidal impurities is between 10-3 mm to 10-6 mm. Colloidal can be removed from water by coagulation and sedimentation than filtration.
