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Department of Civil Engineering
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IMPORTANCE OF WATER Basic need to have a life is water, air, food, shelter, etc. Without food human can survive for a number of days, but water is such an essential element that without it he cannot. Pindar said, "Best of all things is water". The microorganisms found in surface waters and wastewater. USE (a) for drinking and cooking (b)for bathing and washing (c)for watering of lawns and gardens (d)for heating and air-conditioning systems (e)for growing of crops (f)for street washing (g)for fire fighting (h) for recreation in swimming pools, fountains and cascades (i) for steam power and various industrial processes, etc.
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SOURCES Of WATER a)SURFACE SOURCE All sources of water can be broadly classified as follows : (a)Surface sources. These can be further divided as : (i)Streams (ii)Lakes (iii)Ponds (iv)Rivers (v) Reservoirs (vi) Stored rain water and cisterns.
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Sources of Water
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Under ground Sources of Water
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Infiltration Gallery
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IMPORTANCE AND NECESSITY OF WATER SUPPLY SCHEMES For any living being water, air, food, shelter, etc. are the primary needs, for which water has the greatest importance. Pindar said, "Best of all things is water". Everywhere water is required for various purposes : (a) for drinking and cooking (b) for bathing and washing (c) for watering of lawns and gardens (d) for heating and air-conditioning systems (e) for growing of crops (f) for street washing (g) for fire fighting (h) for recreation in swimming pools, fountains and cascades (i) for steam power and various industrial processes, etc.
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IMPORTANCE AND RELIABILITY OF WATER WORKS Water is good carrier of disease germs, and may be responsible for water-borne diseases. Therefore, water which is required by the public should be wholesome and must be free from pathogens, poisonous substances and excessive amount of mineral and organic matter. The water-borne diseases fall into five categories according to the nature of organism causing diseases viz. bacteria, protozoa, worms, viruses and fungi. The water-borne diseases are typhoid fever, paratyphoid fever, bacillary dysentery, and cholera. Therefore, it is very important that water works must remove all the impurities and bacteria from the water and make it wholesome. Water works must provide reliability in the supply of required quantity of water to each consumer at every time. For the reliability of water works it is necessary that the source of water supply should be permanent.
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RELATIVE ORDER OF RELIABILITY FOR WATER WORKS: (a) The water should be taken from permanent (never falling) surface or ground source, from where it can be distributed to the city under gravitation force only. (b) The water should be taken from sufficient large impounding reservoirs, from where it can also flow under force of gravity to the city. (c) The water should be taken from impounding reservoirs at low level, from where it can be pumped to the city. (d) The water should be taken from tube-wells, from where it can be pumped. The reliability of water works also depends on design, construction and maintenance of works for collecting and distributing the water.
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ESSENTIALS OF WATER SUPPLY ENGINEERING (a) The most important thing under water supply schemes is the selection of source of water, which should be reliable and have minimum number of impurities. (b) After the selection of source of water, the next step is to construct intake works to collect it and carry upto treatment plants. At the treatment plants this water will be treated. (c) Types of treatment processes directly depend on the impurities in water at the source and the quality of water required by the consumers. (d) When the water is treated, it is stored in the clear water reservoir, from where it will be distributed to the consumers. (e) The distribution system depends on the elevation of clear water reservoir and the elevation of the distribution area. In low level areas water will directly flow under gravitational force, but for high level areas elevated tanks or pumping will be required.
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DESIGN PERIOD The number of year for which the designs of the water works have been done is known as design-period. This period should neither be too short nor too long. Mostly water works are designed for design periods of 20-30 years, which is a fairly good period.
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Following factors should be kept in view while fixing the design period: (a) Funds available for the completion of the project. If more funds are available the design period shall be less. (b) Life of the pipe and other structural materials used in the water supply scheme. Design period in no case should have more life than the components and materials used in the scheme. (c) As far as possible the design period should be nearly equal to the materials used in the water supply works. (d) Rate of interest on the loans taken to complete the project if rate of interest is less, it will be good to keep design period more. But if the interest rate is very high, the design period should be small. (e) Anticipated expansion rate of the town.
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WATER DEMANDS (i) Domestic water demand. (ii) Commercial and Industrial demand. (iii) Fire-demand. (iv) Demand for public uses. (v)Compensate losses demand.
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1. DOMESTIC WATER DEMAND Quantity of water required in the houses for drinking, bathing, cooking, washing etc. The quantity of water required for domestic use mainly depends on the habits, social status, climatic conditions and customs of the people. In India on an average, the domestic consumption of water under normal condition is about 135 liters/day/capita as per IS : 1172-1171. In developed countries this figure may be as high as 350 liters/day/ capita. The increase in water consumption in developed countries is mainly due to use of air coolers, air conditioners, maintenance of lawns, automatic household appliances such as home laundries, dishwashers etc.
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AVERAGE DOMESTIC WATER CONSUMPTION IN AN INDIAN CITY.
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COMMERCIAL AND INDUSTRIAL DEMAND Commercial building and commercial centers include office building, warehouse, stores, hotels, shopping centres, health centres, schools, temples, cinema houses, railway and bus stations etc. The water requirements of commerical and public places may be upto 45 litres/ day/capita. The quantity of water required by industries are also expressed in terms of per capita demand. The water required by factories, paper mills, clothe mills, cotton mills, breweries, sugar refineries etc. comes under industrial use. The quantity of water demand for industrial purposes is around 20 to 25% of the total demand of the city. Most of the big industries, universities and institutions generally have their own water supply arrangements from the private tube-wells.
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As per IS ; 1172-1963 Indian Standard Code of Basic Requirements for Water Supply, Drainage and Sanitation
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FIRE DEMAND Fires generally break in thickly populated localities and the industrial area, and cause serious damages of properties and sometimes lives of the people are lost. Fire may take place due to faulty electric wires by short circuiting, fire catching materials, explosions, bad intention of criminal people or any other unforeseen mishappenings. If fires are not properly controlled and extinguished in minimum possible time, they lead to serious damages and may burn the cities. All the big cities have full fire-fighting squads. As during fire-breakdowns large quantity of water is required for throwing it over the fire to extinguish it, therefore provision is made in the water works to supply sufficient quantity of water or keep as reserve in the water mains for this purpose. In the cities fire-hydrants are provided on the water mains at 100 to 150 m apart. Fire brigade men immediately connect these fire-hydrants with their engines and start throwing water at very high rate on the fire.
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The minimum water pressure available at fire hydrants should be of the order of 1.0 to 1.5 kg / cm 2 and should be maintained even after 4 to 5 hours of constant use of fire hydrant. Quantity of Water The quantity of water required for fire fighting is generally calculated by using the following empirical formulae. (a). National Board of Fire Under writers Formula: Where Q = Quantity of water required in litres/min. P = Population of the town in thousands. Above formulae used when population of the town is upto 2 lakhs. When the population of the town is more than 2 lakhs, the provision of 54,600 litres/min is made with extra provision of 9,100 to 36,400 litres/min. for a second fire.
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b)Freeman formula: For Indian conditions Kuichling's formula gives satisfactory results. For residential cities generally the following fire demand should be adopted (i)For town having low building 2200 litres /minute (ii)For town having higher buildings 4500 litres /minute (iii)For costly colonies or valuable market and public places 7650 to 13,500 litres/minute. / (iv)For three-storeyed density populated colonies upto 27,000 litres/minute. Where Q = Quantity of water required in litres/min P is population in thousand c)Kuichling’s Formula : d)Buston's formula :
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FORECASTING POPULATION After design period is fixed, the next step is to determine the population. The population are increased by births, decreased by deaths, increased by migration and increased by annexation. The correct present and past population can be obtained from census office. The future development of the town mostly depends on trade expansion, development of industries and surrounding country, discoveries of mines, construction of railway stations etc.
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STANDARD METHODS OF FORECASTING POPULATION i.Annual rate of increase method. ii.Arithmetical increase method. iii.Geometrical increase method. iv.Incremental increase method. v.Decreasing rate method. vi.Simple graphical method. vii.Comparative graphical method. viii.Master plan method ix.The logistic curve method. x.The apportionment method.
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