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Water treatment process
- 4. SCREENING • screens are used to remove the floating matters. This process is called screening. • screens are generally placed at 30-60º angle, to reduce the velocity of flow and increase the cross-sectional area. • The velocity of flow, sec/0.175.0 mvf
- 5. screens Coarse screens Size: 25-75 mm Fine screens size: 10-3 mm
- 7. • Aeration brings water and air in close contact in order to remove dissolved gases (such as carbon dioxide) • It oxidizes dissolved metals such as iron, hydrogen sulfide, and volatile organic chemicals. • Oxygen is added to water through aeration.
- 8. Air diffusion method Methods of Aeration Cascade method Trickling plates method Spray nozzle method
- 9. screening aeration Plain sedimentation Sedimentation with coagulation Filtration Disinfection Softening Water treatment process SEDIMENTATION
- 10. Sedimentation is a process in which the suspended materials or solids are made to settle by gravity under still water condition Sedimentation Plain Sedimentation (the impurity is separated by natural forces) Sedimentation with coagulation (impurity is removed by some chemicals)
- 11. Continuous Flow Rectangular sedimentation tank Baffles walls
- 12. Radial flow sedimentation tank
- 13. Hopper Bottom Continuous Flow Sedimentation Tank
- 14. Design of Sedimentation Tank The design of sedimentation tank is done based on volume of water to be treated. STEPS: 1. the height of tank H= 3.5 – 6.0m min/30.015.0 mvf 2.Velocity of flow: 3. Capacity of tank: “Detention period: the time between entry and exit of a fluid particle in sedimentation tank.” hourst hourst d d 42 84 Q C td For plain sedimentation: For sedimentation with coagulation : Where, =detention time C= capacity of tank Q= discharge per hour dt
- 15. 4. The L:B is generally taken as 4:1 mD mB 60 12 The diameter of circular tank Width of rectangular tank **Detention time for vertical flow circular tank: Q HDD td 785.0011.02 Where, D=dia of tank H = height of tank
- 17. It is a process in which an insoluble flocculent precipitate is formed by adding certain chemicals for absorbing colloidal matter. Coagulants: the chemicals added to water for forming insoluble precipitate during coagulation process . Some coagulants are: 1. Aluminum Sulphate (Alum): It is reactive in basic water. In acidic water lime is added with ALUM.
- 18. Chemical Reaction of Alum: 1. When water is Basic: 224 323242 6183 2318. COOHCaSO OHAlHCOCaOHSOAl precipitate 2.When water is acidic: OHCaSOOHAlOHCaOHSOAl 2432242 1832318. precipitate • For complete reaction the pH of water should be 6-8.5 • 0.03-0.13 gm Alum is added in 1lit of water
- 19. Feeding Devices for Coagulation 1. Dry feed device: Dey feeding device (a) by toothed wheel, (b) by helical wheel
- 20. 2. Solution feed device Conical plug and float device
- 21. Flocculation The formation od floc in sedimentation tank when coagulants are added into the sedimentation tank is called flocculation • After flocculation water enters the settling tank which is called clarifier • In this operation the floc which has been formed above is allowed to settle
- 22. Optimum Dose Required For Coagulants: It is determined by Jar Apparatus Test 1.Water is taken in every jar 2.Coagulent is added in jar in varying amount. 3.The quantity of coagulant in each jar is noted 4.All the paddles are rotated at 30-40 rpm for 10min. 5. After this speed is reduced and paddles are rotated for 20*-30min. 6. The rotation of paddle is stooped and floc formed In ech jar is noted and allowed to settle. 7. The dose of coagulant which gives best floc is the optimum dose.
- 24. “Filtration is process of passing water through bed of sand or other granular material.” • Filters are used for removing bacteria, color, taste, and odour. • 95-98% suspended impurities are removed by sand filtration following action takes place when water is filtered by sand media. Mechanical Straining Sedimentation and absorption Biological action Electrolytic action
- 25. Filters rapid sand filter Gravity type Pressure type Slow sand (rate of flow is 1/20th or less of rapid sand filter)
- 26. Slow Sand Filter It is consist of following parts:• It is rectangular air tight chamber. The floor has bed slope of 1 in 100 to 1 in 200 towards the central drain. Enclosure Tank: • It is 90-110cm thick. Sand size = 0.2-0.3 mm and Cu=2-3. Filter Media: • It consist of three layers, top layer of sand • Bottom layer of coarse sand • gravel Base Material: • It is below coarse layer which collects filtered water and deliver it to reservoir. Under drain system • Head loss devices, maintaining consistent rate of low devices. appurtenances
- 27. Slow Sand Filter Filter media description : top sand layer thickness = 75- 90cm size = 0.2-0.3mm Bottom sand layer, thickness =30cm, size= 0.3-2 mm Lowermost gravel layer, thickness = 30 cm, size= 2-45mm. daymv /6.34.2 it effectively removes 98-99% bacteria of raw water. It can reduce turbidity upto 1NTU
- 28. • Depth= 2.5 to 3.5m, surface area= 20-50 sq.m Enclosure Tank: • Sand size = 0.35-0.6, Cu=1.5. Filter Media: • It consist of three layers, top layer of sand • Bottom layer of coarse sand • gravel Base Material: • It is below coarse layer which collects filtered water and deliver it to reservoir. Under drain system • Wash water through, Air compressor, rate control device. appurtenances Gravity Sand Filter
- 29. Rapid Sand Filter (gravity type) • It is only suitable when Turbidity of water is less than 30-40ppm. • The filtration rate is 40000lit/m2/day
- 30. Rapid Sand Filter (pressure type) • The pressure may vary from 3 to 7 kg/sq.m • Thickness of filter is 50-60cm and size of sand is 0.35-0.6mm • The rate of filtration varies from 6000- 15000 m3/m2/hour.
- 32. The process of killing the infective bacteria from the water and making it safe to user is called disinfection Physical Methods Boiling: for 15- 20min. Ultra-voilet ray Chemical Methods Chlorination Bromine and Iodine Potassium permanganate Ozone Excess lime treatment
- 33. Chlorination: it is applied in following forms: • It is a process when other treatment is not required. • 0.8mg Cl per lit of water is required Plain Chlorination • 1-2 mg Cl per liter of water is required Super chlorination • It is process of removing Cl from waterDechlorination
- 35. Temporary Hardness By boiling of water Lime process(lime is added to water) Permanent Hardness Lime soda process Zeolite process Methods of softening of water
- 36. Zeolite Process: • Zeolite is complex silicate of zeolite, sodium and aluminum. • It is based on ion exchange process. • the salt od calcium and magnesium present in water converts to sodium salt The reactions are as follows: 32232323 42232324 2232322 42232324 32232324 CONaSiOMgAlSiOAlNaMgCO SONaSiOMgAlSiOAlNaMgSO ClNaSiOCaAlSiOAlNaCaCl SONaSiOCaAlSiOAlNaCaSO CONaSiOCaAlSiOAlNaCaSO