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WATER & WASTE WATER ENGINEERING - water treatment process & units

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WATER & WASTE WATER ENGINEERING - water treatment process & units

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This presentation is made with a view to introduce various units & processes carried out in water treatment plant with various trains or say chains of units to meet Indian Standard criteria.

This presentation is made with a view to introduce various units & processes carried out in water treatment plant with various trains or say chains of units to meet Indian Standard criteria.

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WATER & WASTE WATER ENGINEERING - water treatment process & units

  1. 1. Bhagwan Mahavir College of Engineering and Technology PRESENTATION ON
  2. 2. Prepared by : Ankit Gangani 140060106055
  3. 3. OUTLINE  Introduction  Objectives of water treatment  Conventional water treatment plant layout  Various Methods of purification of water Screening Plain Sedimentation Sedimentation aided with coagulation Filtration Disinfection Aeration Softening
  4. 4. Introduction Water treatment is the process of making water suitable or acceptable for an end-use. It removes existing water contaminants and so reduces their concentration that the water becomes fit for its desired application. The amount & type of treatment process (Treatment Train ) depends upon quality of raw water and various standards required after treatment.
  5. 5. Objectives of water treatment The objectives of water treatment are to produce: Water that is safe for human consumption Water that is appealing aesthetically to the consumer Water at a reasonable cost
  6. 6. Indian Standards for drinking water
  7. 7. Screening Coagulation Flocculation Sedimentation Filtration Disinfection Storage Distribution Raw water Alum Cl2 sludge sludge sludge 7
  8. 8. Functions of Water Treatment Units
  9. 9. Selection of treatment process-Train  The types of treatment required for different sources are given in the following table:
  10. 10.  Removes large solids logs branches rags fish  Simple process may incorporate a mechanized trash removal system  Protects pumps and pipes in Water Treatment Plants
  11. 11. Plain Sedimentation  Sedimentation is the removal of suspended particles by gravitational settling.  Types of Sedimentation Tanks 1) Fill And Draw Type 2) Continuous Flow type
  12. 12. Shape of sedimentation tank 1. Rectangular tank with horizontal flow. 2. Circular tank with radial or spiral flow. 3. Hopper bottom tank with vertical flow.
  13. 13. SEDIMENTATION 13  Water flows to a tank called a sedimentation basin  Gravity causes the flocs to settle to the bottom  It would take a very long time for all particles to settle out and that would mean we would need a very large sedimentation basin.
  14. 14. Sedimentation aided with coagulation Addition of measured quantity of chemicals called coagulants to water and their through mixing ( rapid mixing ). Formation of precipitate which coagulates and forms a flow ( flocculation ) Sedimentation  Sedimentation added with comprises of three step
  15. 15. Coagulants  Aluminum Sulfate Al2(SO4)3  Ferrous Sulfate FeSO4  Ferric Sulfate Fe2(SO4)3  Ferric Chloride FeCl3  Lime Ca(OH)2 Aluminum salts are cheaper but iron salts are more effective over wider pH range 15
  16. 16. Aeration Unit  Work : Diffusion of Air  Removes odour and tastes  Oxidizes iron and manganese, increases dissolved oxygen content in water, removes CO2 and reduces corrosion and removes methane and other flammable gases.  Types of Aerators 1. Gravity aerators 2. Fountain aerators 3. Diffused aerators 4. Mechanical aerators.
  17. 17.  Gravity Aerators (Cascades): In gravity aerators, water is allowed to fall by gravity such that a large area of water is exposed to atmosphere, sometimes aided by turbulence. Aeration Unit
  18. 18.  Injection or Diffused Aerators : It consists of a tank with perforated pipes, tubes or diffuser plates, fixed at the bottom to release fine air bubbles from compressor unit. Time of aeration is 10 to 30 min and 0.2 to 0.4 litres of air is required for 1 litre of water. Aeration Unit
  19. 19.  Fountain Aerators : These are also known as spray aerators with special nozzles to produce a fine spray. Each nozzle is 2.5 to 4 cm diameter discharging about 18 to 36 l/h. Nozzle spacing should be such that each m3 of water has aerator area of 0.03 to 0.09 m2 for one hour. Aeration Unit
  20. 20.  Mechanical Aerators : Mixing paddles as in flocculation are used. Paddles may be either submerged or at the surface. Aeration Unit
  21. 21. Types of Mixing Devices  Mixings basins with baffle walls `
  22. 22.  Mixing Basins Equipped with Mechanical devicies
  23. 23. Flocculation  Flocculation is a slow mixing or agitating process in which the destablished colloidal particles are brought into intimate contact in order to promote the floc formation .  Rate of flocculation depends upon  Types and amount of turbidity  Types of coagulant  Dosages of coagulant  Mean velocity gradient in basin
  24. 24. Clariflocculator Clarifier and flocculator are provided in single unit called clariflocculator. The flocculating chamber is provided in the centre and clarifier component is formed by the peripheral space. Velocity of flow of water around 0.3 m/min. Mechanical scrapper provided to remove sludge.
  25. 25. Filtration The process of passing the water through the beds of such granular material is known as filteraton  Types of Filtration Slow sand gravity filter Rapid sand gravity filter 1. Rapid sand gravity filter 2. Pressure filter
  26. 26. Method of disinfection  Physical method By heat By U.V. rays  Chemical method Oxidizing chemicals Metal ions Alkalis and acids  Minor method Boiling of water Treatment with excess lime Treatment with ozone Treatment with iodine and bromine Treatment with ultra-violet rays Treatment with potassium permanganate
  27. 27. Water softening  Water is said to be hard when it contains relatively large amounts of bicarbonates, carbonates, sulphates and chlorides of calcium and magnesium dissolved in it.  Types of Hardness  Temporary hardness  Permanent hardness
  28. 28. Types of Hardness  Temporary Hardness- caused by dissolved bicarbonates of Ca and Mg. -AKA ‘alkaline or carbonate hardness’  Permanent Hardness – caused by dissolved chlorides and sulphates of Ca, Mg, Fe and Al etc.
  29. 29. Removal of Hardness  Removal of temporary hardness 1. Boiling 2. By adding lime  Removal of temporary hardness 1. Lime-soda process 2. Zeolite process 3. Demineralization or De-ionization process
  30. 30. Disinfection  The filtered water may normally contain some harmful disease producing bacteria in it.  These bacteria must be killed in order to make the water safe for drinking.  The process of killing these bacteria is known as Disinfection or Sterilization.
  31. 31. Methods of Disinfection  Boiling: The bacteria present in water can be destroyed by boiling it for a long time. However it is not.  Treatment with Excess Lime: Lime is used in water treatment plant for softening. But if excess lime is added to the water, it can in addition, kill the bacteria also. Treatment like recarbonation for lime removal should be used after disinfection.  Treatment with Ozone: Ozone readily breaks down into normal oxygen, and releases nascent oxygen. The nascent oxygen is a powerful oxidizing agent and removes the organic matter as well as the bacteria from the water.  Chlorination : The germicidal action of chlorine is explained by the recent theory of Enzymatic hypothesis, according to which the chlorine enters the cell walls of bacteria and kill the enzymes which are essential for the metabolic processes of living organisms.
  32. 32. Reference  Water & waste water Engineering -4th edition By Mahajan Publishing House  http://web.iitd.ac.in/~arunku/files/CVL100/L8.pdf  http://nptel.ac.in/courses/105104102/Lecture%2020.ht m  http://www.sswm.info/sites/default/files/reference_at tachments/SCHUTTE%202007%20Handbook%20for %20the%20Operation%20of%20Water%20Treatment %20Works.pdf

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