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Sources of Drinking Water

	Sources of Drinking Wate Water for drinking and domestic use may be obtained from natural sources like surface water, groundwater and rainwater. Surface water Streams, rivers and lakes are the major sources of surface waters. Usually these sources fulfil1 the requirements of municipal supplies. Water in these sources originate partly from groundwater outflows and partly from rainwater which flows over the terrestrial areas into the surface water bodies. Outflows from groundwater brings in the dissolved solids.
The surface run off contributes turbidity, organic matter and pathogenic organisms. Usually in surface water bodies, the dissolved mineral particles will remain unchanged while the organic impurities are degraded by chemical and microbial action. In slow-flowing or impounded surface waters sedimentation of suspended solids occurs naturally. Due to the lack of nutrients microorganisms wil1 die off.
Although clear water from rivers and lakes requires no treatment, on taking into account the risk of incidental contamination, it is better to practice chlorination. Unpolluted surface water of low turbidity may be purified by slow sand filtration alone. Alternatively, rapid sand filtration followed by chlorination can be practiced. When the turbidity of water is too high, in addition to slow sand filtration a pre-treatment like sedimentation, rapid sand filtration, or both can be used. When colloidal particles are present sedimentation can be improved by chemical coagulation and flocculation. Thus, depending upon the impurities present in surface waters the required treatment process may vary.
Groundwater Wells and springs constitute groundwater supplies. Groundwater mostly originates from infiltrated rainwater which after reaching the aquifer flows through the underground. Groundwater provides water to meet the requirements of individual household supplies as well as municipal supplies. The treatment processes also differ in these two cases with simply boiling the water before use for household supplies. However, municipal supplies require one or more treatment processes depending upon the impurities found in the water. A little contamination of groundwater occurs from organic and inorganic soil particles, animal and plant debris, fertilizers, pesticides, microorganisms, etc. as it flows through the soil layers. In spite of this contamination, infiltration causes partial removal of suspended particles including microorganisms. Organic substances are also degraded by oxidation. Partial removal of microorganisms occurs by the death of cells due to lack of nutrients.
	Thus, properly withdrawn groundwater will be free from turbidity and pathogenic microorganisms. It is important to select the location of groundwater supply at a safe distance from other sources of contamination like septic tanks. If done so, groundwater will be of high quality and can be used directly without any treatment. If the organic content of groundwater is high, oxygen will be consumed for the oxidation of organic matter. The resulting oxygen depleted water will dissolve iron and manganese from the underground. Aeration is required for the removal of these substances. Other suspended solids are removed by sedimentation with or without the aid of coagulation and flocculation. Sand filtration is practiced for the removal of fine particles including microorganisms. By sand filtration about 99 percent removal of bacteria can be achieved. Chlorination is employed as the final treatment process before distribution. Rainwater Rainwater run off from roofs can be collected and stored for domestic use. Rainwater will be of high quality and the only possible source of contamination is airborne microorganisms that too will be present in very low numbers. During collection the first flush of water of a day has to be diverted away from the storage tank since it may contain dust, bird droppings etc. It is important to protect the stored rainwater from contamination and from the entry of mosquitoes. This method is mainly used for household supplies and hence boiling the water is the only treatment.

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Disinfecion Drinking Water Chemical Disinfection Chemical Disinfection by Chlorine Chemical Disinfection by Ozone Chemical Disinfecion by Pottassium Permanganate Chemical Disinfection by Halogens Physical Disinfection by UV Radiation Germicidal Efficiency

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