Unit ii introduction to water supply scheme
- 1. UNIT –II INTRODUCTION TO WATER SUPPLY SCHEME a) Introduction to water supply scheme: b) Water intake structures: c) Quantity:
- 2. WATER IS THE BASIC NEED OF ALL LIVING BEING NECESSITY OF WATER Drinking, cooking, washing, bathing, sanitary purpose. Industrial Processes, Steam generation. Swimming pools, water games(parks). Ornamental displays like fountains. Watering lawns, gardens and roads. For modern applications such as air conditioners, dish washers, washing machines etc. For extinguishing fires Irrigation purposes.
- 3. WATER SUPPLY SCHEME : VARIOUS PHASES Selection of source Collection and conveyance of raw water Treatment of water Pumping and storage of water in ESR Distribution of water DATA TO BE COLLECTED FOR WATER SUPPLY SCHEME 1. Source of water 2. Quantity of water required - - Population to served - - Water demands- domestic, public, industrial - - Design period 3.Quality of water 4. Survey data 5. Map or plan of town or city and 6. Acquisition of land & compensations
- 4. COMPONENTS OF WATER SUPPLY SCHEME Water Source Intake Structure Pumping Unit Rising/ falling main Treatment Units ESR Distribution System
- 5. LAYOUT OF WATER SUPPLY SCHEME Source Intake Well Jack Well Aeration Clarifier Sand filter Disinfection Distribution Storage Tank ESR
- 6. DESIGN PERIOD Future estimated period of number of years for which provision is made in designing the capacities of various components/units of water supply scheme is called as design period. DESIGN PERIOD FOR VARIOS COMPONENTS OF WTP Sr. No Components Suggested design Period 1. Dam, Weir, Intake Structure, Reservoir, penstock pipe 30 – 35 Years 2. Treatment units- aerator, clarifier, filter 20 – 30 Years 3. Distribution System a) Pipe less than 300 mm Dia. 30 Years b) Pipe More than 300 mm Dia. 20 – 25 Years
- 7. CONVEYANCE OF WATER Selection of material for Pipe Carrying capacity of the pipe Durability of the pipe Type of water to be conveyed Availability of funds Repair and maintenance cost Types of Pipes 1.Cast iron: Available in length of 3-6m Advantages: Moderate cost highly resistant to corrosion, Strong,, easy jointing, withstanding high internal pressure long life (100 Yrs.) Service connections easy
- 8. Disadvantages :Very heavy and difficult to transport, brittle easily cracks, cannot used for pressure more than 7 kg/cm2. they are fragile (delicate ). 2. Steel pipe: Made from steel bars, by hot or cold process. mostly used for main lines where pressure is high and diameter requirement is more. Advantages: strong, light weight and withstand higher pressure than cast iron pipes, cheap, easy to construct and can be easily transported. Disadvantages: Cannot withstand external loads, affected by corrosion, difficult to make connections, and maintenance are costly.
- 9. 3. Cement lined Cast Iron Pipes: Mortar lining of 1:1 proportion is applied . Thickness of lining 5 – 6 mm. Advantages: more life, Easily constructed on site and factories, least coefficient of expansion, not affected by force of buoyancy. Disadvantages : Repairs are very difficult, difficult to make connection, due to heavy weight transportation and laying costs are high.
- 10. 4. Plastic Pipes: Made from synthetic resins of high molecular weight. Polymerized from simple compounds by heat, pressure and catalysis. Plastic pipes and tubes are manufactured from a number of polymerization products such as polythene, polypropylene,, poly vinyl chloride and cellulose acetate butyrate. Advantages - corrosion resistant , light weight and economical, Cheaper, easy to handle and transport, good electrical insulators, adequate strength, durable and unaffected by weather. Disadvantages : Coefficient of expansion is high, low resistance to heat.
- 11. 5.Wrought iron and galvanized iron pipes: Manufactured by rolling flat plates of wrought iron to the proper diameter and welding the edges. These pipes are usually protected by coating them with a thin film of molten zinc. Easily cut, threated, lighter in weight. More costly , less durable. 6. Cement concrete pipes: PCC up to heads of 7m. RCC up to head of 60m. For higher heads prestressed concrete pipes are sed. NP1,NP2,NP3 – non-reinforced or non-pressure pipes. used for drainage lines, irrigation etc. P1,P2,P3 – Reinforced concrete pipes. Pressure they withstand may be 2.0 kg/cm2(20 m), 4.0 kg/cm2 (40m) and 6.0 kg/cm2(60m).
- 12. Advantages: resists the external loads and backfill loads, maintenance cost is less, no corrosion, pipe can be cast at site, no transportation cost. No expansion joints. Disadvantages: Tensile cracks, leakage problem , repair is difficult, handling is difficult. 7. Copper and lead pipes: made from copper and lead, costly, soft and bend easily
- 13. VALVES: various appurtenances are use to isolate and drain pipe sections for test, installation, cleaning and repair. Valves are one of the important device provided to stop and regulate the flow of water in the course of ordinary operations and in an emergency. VALVES ARE USED TO SERVE THE FOLLOWING PURPOSES: To control the rate of flow of water Release or admit air into the pipeline Prevent or detect the leakage Meet the demand during emergencies Make the distribution system more efficient. FACTORS CONSIDERED IN THE SELECTION OF VALVES: purpose and operation, capacity required, head loss and rate of flow, cost, availability, etc.
- 14. TYPES OF VALVES Sluice or gate valve Air relief Valve Reflux valve Relief valve Altitude Score Valve SLUICE VALVE: These are also known as gate for stop valve. They are used in distribution system. Spacing of these valves may be between 150 to 300 meters. Also placed at street corners or where two pipelines intersects. AIR RELIEF VALVE: Air relief valves are installed at high points of distribution piping to provide an exit for entrapped air. They are also used to discharge air when a main is being filled and to admit air when it is being emptied.
- 15. REFLUX VALVE: It is also known as check valve or Non- return valve. This valve allows the water to flow in one direction only. They are placed in water pipes which obtain water directly from the pump. when the pump is stopped ,they the in the pipe dose not rush back and damage the pump. It consists of flat disc, pivoted so that it is forced open when flow of water is in one direction and forced shut against a seating when flow tries to reverse. PRESSURE RELIEF VALVE: also known as automatic cutoff valve or safety valve. They are located at those points where pressure is likely to be maximum. When pressure in line increases above preset value, the valve operates automatically, and the pressure is reduced.
- 16. ALTITUDE VALVES : These valves are mainly used on those lines which supply water to elevated tanks or stand pipes, to automatically control the flow into and out of an elevated storage tank or standpipe to maintain desired water level elevations. These valves close automatically when the tank is full and open when the pressure on pump side is less than on the tank side of the valve. SCORE VALVE: Also known as blow off or washout valve. Located either at dead ends or at lowest points in the mains. Provided to remove the sand and grit deposited in the pipelines.
- 19. INTAKE STRUCTURES Intake structures are the structures used for admitting water from the surface sources and conveying it further to the treatment plant. It is masonry or concrete structure with an aim of providing relatively clean water, free from pollution, sand, grit and objectionable material. Factors Governing Location of Intake As far as possible, the site should be near the treatment plant so that the cost of conveying water to the city is less. The intake must be located in the purer zone of the source to draw best quality water from the source, thereby reducing load on the treatment plant. The intake must never be located at the downstream or in the vicinity of the point of disposal of wastewater.
- 20. The site should be such as to permit greater withdrawal of water, if required at a future date. The intake must be located at a place from where it can draw water even during the driest period of the year. The intake site should remain easily accessible during floods and should not get flooded. Moreover, the flood waters should not be concentrated in the vicinity of the intake. It should have good foundation, further expansion can be possible, river flow should not get obstructed.
- 21. TYPES OF INTAKE Submerged Exposed Wet Dry Constructed entirely under water. Such intake are used to get supply from lake. It is in the form of tower or well constructed near bank of river or away from bank. These are very common due to ease in its operation. A wet intake is that type of intake tower in which the water level is practically the same as the water level of the sources of supply. There is no water in the water tower. Water enters through port directly into the conveying pipes. The dry tower is simply used for the operation of valves.
- 22. River Intake Reservoir Intake Lake Intake Canal Intake
- 31. VARIOUS TYPES OF CONSUMPTION/DEMANDS Domestic consumption Industrial and commercial demand Public demand Fire fighting demand.
- 32. Domestic consumption: the water required for actual household activities is known as domestic demand. It includes water required for drinking, cooking, bathing, washing flushing of toilets etc. Details of Domestic consumption Purpose Water consumption ( lit/capita/day) Drinking Cooking Cleaning of utensils and house Washing of clothes Flushing of water closets(W.C.) Bathing TOTAL 5 5 20 20 30 55 135
- 33. Industrial and Commercial Demand: Industry requires large quantity of water for manufacturing, cooling operation, steam generation, for processing and sanitation. This is known as industrial demand. Commercial demand includes water required for private offices, restaurants, cinema halls motor garages and small scale industries. This demand can be expressed per capita demand ,by dividing the industrial demand by the population of the area. Details of Industrial and commercial Demand ACTIVITY DEMAND(lit/capita/day) Factories Offices Restaurants/seat Hotels/person Cinema/seat 30-45 45 70 180 15
- 34. Public Demands: It includes water required for washing of roads, cleaning of public sewers, watering of parks, gardens water fountains, swimming pools, flushing of water closets and urinals, hospitals, hotels, schools and colleges. This demand is about 5 percentage of total demand. Details of Public Demands ACTIVITY DEMAND Public gardens Street washing Sewer cleaning Hospitals Hotels Schools(without boarding) Schools(with boarding) 1.4 lit/m2/day 1.0 lit/m2/day 4.5 lit/head/day 340 - 450 lit/bed/day 135 lit/head/day 45 lit/head/day 135 lit/head/day
- 36. FACTORS AFFECTING PER CAPITA DEMAND IN A COMMUNITY People's habits Industrialization Public Services Climatic conditions Systems of water supply Meter system System of drainage Availability of supplementary sources Distribution pressure Cost of water
- 37. POPULATION FORECASTING 1. Arithmetic Increase Method: This method is generally applicable to large and old cities. In this method average increase of population per decade is calculated from the past records and added to the present population to find out population of next decade. This method gives a low value and is suitable for well settled and established cities. Pn = P + n x i Pn = Population after n decade P = Present population, n = Nos of decades i = Average increase in population
- 38. 2. GEOMETRIC INCREASE METHOD In this method percentage increase in population from decade to decade remains constant. Therefore, the average value of percentage increase in population is calculated and the future population are calculated at this rate. This method gives much higher value and mostly applicable for growing towns and cities having vast scope for expansion. Pn = P( 1 + r/100)n Where r = Average percentage rate of population increase P = Present population Pn = Population after n decade
- 39. 3. INCREMENTAL INCREASE METHOD This method is the combination of arithmetic increase method and geometric increase method. Hence ,combines the advantages of both methods and gives satisfactory results. In this method, average increase per decade is first calculated and to this average of net incremental increase once for every future decade is added. Pn = P + n x i + n(n + 1)/2 x I Where I = Average incremental increase i = Average increase per decade n = Nos of decades
- 40. Decreasing rate of increase method Graphical comparison method Graphical extension method