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Water Treatment Processes:- Coagulation , Flocculation, Filtration by Kalpesh Solanki
- 1. 03/28/17 water treatment1 Presented by :- Prof. Kalpesh Solanki Major Clean Up Water Treatment Processes:- Coagulation , Flocculation, Filtration
- 2. Course Content Introduction Water treatment process or Methods Coagulation and flocculation Filtration
- 3. Introduction Why it isneeded? To kill all pathogenic germs, which are harmful to human health To remove the unpleasant and objectionable taste and odours from the water To remove dissolved gases ,colour of water To make water fit for domestic, industrial, and commercial uses. To remove micro organism and colloidal matters To remove hardness of water 03/28/17 water treatment 3
- 4. Raw water collection 03/28/17water treatment 4
- 5. Initial Stages Screening -the removal of any floating objects like leaves, branches, fishes , weeds, etc. from the water.
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- 7. 03/28/17 water treatment7 Sedimentation: Removal of Suspended matters having higher specific gravity than water and also fine suspended matter.
- 8. 03/28/17 water treatment8 Aeration – Dissolving oxygen into the water to remove smell and taste, promote helpful bacteria to grow, and precipitate nuisance metals like iron and manganese.
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- 10. 03/28/17 water treatment10 Spray aerators
- 11. Major Clean Up •Coagulation and flocculation - causes the agglomeration and sedimentation of suspended solid particles through the addition of a coagulating agent (usually aluminum sulfate and/or iron sulfate) to the raw water along with a polymer to help form a floc. • Filtration- Remove Micro-organism and colloidal matter • Disinfection---Pre-chlorination and dechlorination - mostly to kill algae that would otherwise grow and clog the water filters. Also kills much of the remaining unprotected bacteria. • Softening- To remove hardness
- 12. 03/28/17 water treatment12 COAGULATION & FLOCCULATION Removal of colloidal substances from water Potable water requirements: health, aesthetics, economic Colloids Size of colloids - light waves Brownian motion Stability of colloids
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- 14. 03/28/17 water treatment14 Theory of coagulation Coagulation is the destabilization of colloids by addition of chemicals that neutralize the negative charges The chemicals are known as coagulants, usually higher valence cationic salts (Al3+ , Fe3+ etc.) Coagulation is essentially a chemical process Ionic layer compression Adsorption and charge neutralization Entrapment in a flocculent mass
- 15. 03/28/17 water treatment15 Relative coagulating power Na+ = 1; Mg2+ = 30 Al3+ > 1000; Fe3+ > 1000 Typical coagulants Aluminum sulfate: Al2(SO4)3.14 H2O Iron salt- Ferric sulfate: Fe2(SO4)3 Iron salt- Ferric chloride: Fe2Cl3 Polyaluminum chloride (PAC): Al2(OH)3Cl3
- 16. 03/28/17 water treatment16 Aluminum Chemistry 1 mole of alum consumes 6 moles of bicarbonate (HCO3 - ) Al2(SO4)3.14 H2O + 6HCO3 - ⇔ 2Al(OH)3↓+ 6CO2 + 14H2O + 3SO4 -2 •If alkalinity is not enough, pH will reduce greatly •Lime or sodium carbonate may be needed to neutralize the acid. •(Optimum pH: 5.5 – 6.5) With alum addition, what happens to water pH? Al2(SO4)3.14 H2O ⇔ 2Al(OH)3↓+ 8H2O + 3H2SO4 -2
- 17. 03/28/17 water treatment17 Alkalinity calculation Al2(SO4)3.14 H2O + 6HCO3 - ⇔ 2Al(OH)3↓+ 6CO2 + 14H2O + 3SO4 -2 594 mg 366 mg If 200 mg/L of alum to be added to achieve complete coagulation. How much alkalinity is consumed in mg/L as CaCO3? 594 mg alum consumes = 366 mg HCO3 - 200 mg alum will consume = (366/594) x 200 mg HCO3 - = 123 mg HCO3 - Alkalinity in mg/L as CaCO3 = 123 x (50/61) = 101 mg/L as CaCO3
- 18. Al3+ species as afunction of pH 03/28/17 water treatment 18
- 19. 03/28/17 water treatment19 Iron Chemistry FeCl3+ 3HCO3 - ⇔ Fe(OH)3↓+ 3CO2 + 3Cl- With iron salt addition, what happens to water pH? (Wider pH range of: 4 – 9; Best pH range of 4.5 – 5.5) 1 mole of FeCl3 consumes 3 moles of bicarbonate (HCO3) If alkalinity is not enough, pH will reduce greatly due to hydrochloric acid formation. Lime or sodium carbonate may be needed to neutralize the acid. Lime is the cheapest.
- 20. Mixing device 03/28/17 watertreatment 20 1- Mixing basins with baffle walls 2- Mixing basin with mechanical devices (Rapid mixing)
- 21. 03/28/17 water treatment21 • Rapid or Flash mixing is the process by which a coagulant is rapidly and uniformly dispersed through the mass of water. This process usually occurs in a small basin immediately preceding or at the head of the coagulation basin. Generally, the detention period is 30 to 60 seconds and the head loss is 20 to 60 cms of water. Here colloids are destabilized and the nucleus for the floc is formed. Slow mixing brings the contacts between the finely divided destabilised matter formed during rapid mixing.
- 22. Coagulation aim 03/28/17 watertreatment 22
- 23. What is Flocculation? 03/28/17water treatment 23 Flocculation is the agglomeration of destabilized particles into a large size particles known as flocs which can be effectively removed by sedimentation or flotation.
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- 26. 03/28/17 water treatment26 Why coagulation and flocculation? Various sizes of particles in raw water Particle diameter (mm) Type Settling velocity 10 Pebble 0.73 m/s 1 Course sand 0.23 m/s 0.1 Fine sand 0.6 m/min 0.01 Silt 8.6 m/d 0.00010.0001 (10 micron)(10 micron) Large colloidsLarge colloids 0.3 m/y0.3 m/y 0.000001 (1 nano)0.000001 (1 nano) Small colloidsSmall colloids 3 m/million y3 m/million y Particle diameter (mm) Type Settling velocity 10 Pebble 0.73 m/s 1 Course sand 0.23 m/s 0.1 Fine sand 0.6 m/min 0.01 Silt 8.6 m/d 0.00010.0001 (10 micron)(10 micron) Large colloidsLarge colloids 0.3 m/y0.3 m/y 0.000001 (1 nano)0.000001 (1 nano) Small colloidsSmall colloids 3 m/million y3 m/million y Colloids – so small: gravity settling not possible GravItysettlIng
- 27. Fe species asa function of pH 03/28/17 water treatment 27
- 28. 03/28/17 water treatment28 Hydraulic Flocculation • Horizontally baffled tank Plan view (horizontal flow) • Vertically baffled tank L Isometric View (vertical flow) L W H The water flows horizontally. The baffle walls help to create turbulence and thus facilitate mixing The water flows vertically. The baffle walls help to create turbulence and thus facilitate mixing
- 29. 03/28/17 water treatment29 http://www.environmental-center.com/magazine/iwa/jws/art4.pdf Hydraulic Flocculation
- 30. Hydraulic flocculators 03/28/17 watertreatment 30
- 31. 03/28/17 water treatment31 Hydraulic flocculators: simple technology
- 32. 03/28/17 water treatment32 Flocculators integrated with settling
- 33. 03/28/17 water treatment33 Flocculators integrated with settling
- 34. 03/28/17 water treatment34 Flocculators both sides of settling
- 35. Clarifier • After FlocculationWater enters the settling tank which is commonly called Clarifier. Clariflocculator In modern practice, flocculator and clarifier are provided in one unit called Clariflocculator in which chamber is provided in the center and clarifier compartment is formed by the periferical space. 03/28/17 water treatment 35
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- 38. Filtration 03/28/17 water treatment38 The process of passing the water through the bed of such granular materials is known as filtration. Types of filter 1- The slow sand gravity filter 2- Rapid sand filter
- 39. Slow sand filtersare used in water purification for treating raw water to produce a potable product. They are typically 1 to 2 metres deep, can be rectangular or cylindrical in cross section and are used primarily to treat surface water. Filter through a 3 to 5 foot deep bed of unstratified sand flow rate 0.05 gallons per minute per square foot. Biological growth develops in the upper surface of the sand is primarily responsible for particle and microbe removal. Effective without pretreatment of the water by coagulation flocculation‑ . Periodically clean by removing, cleaning and replacing the upper few inches of biologically active sand. 03/28/17 water treatment 39
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- 41. Microbial Reductions bySlow Sand Filtration • Effective in removing enteric microbes from water. • Virus removals >99% in lab models of slow sand filters. – Up to 4 log10; no infectious viruses recovered from filter effluents • Field studies: – naturally occurring enteric viruses removals • 97 to >99.8 percent; average 98% overall; • Comparable removals of E. coli bacteria. – Virus removals=99 99.9%;‑ – high bacteria removals (UK study) • Parasite removals: Giardia lamblia cysts effectively removed – Expected removals ~ 99%
- 42. Rapid sand filters 03/28/17water treatment 42 Rapid sand filtration is a purely physical drinking water purification method. Rapid sand filters (RSF) provide rapid and efficient removal of relatively large suspended particles. Two types of RSF are typically used: Rapid gravity Rapid pressure sand filters
- 43. 03/28/17 water treatment43 •The biggest disadvantages of slow sand filter is that it requires large area due to slow filtration rate. •This Requirement make it uneconomical for places where land is very costly in urban area. In order to reduce requirement of space and to increase the rate of filtration , a lot of research conducted which finally led to the developed of rapid sand filter.
- 44. 03/28/17 water treatment44 Rapid sand filters have filter rates 40 times those of slow sand filters. The major parts of a rapid sand filter are: • Filter tank or filter box • Filter sand or mixed-media • Gravel support bed • Under drain system • Wash water troughs • Filter bed agitators
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- 46. 03/28/17 water treatment46 PRESSURE FILTERS Pressure filters fall into two categories: pressure sand and diatomaceous earth filters. Pressure filters are used extensively in iron and manganese removal plants. A pressure sand filter is contained under pressure in a steel tank, which may be vertical or horizontal, depending on the space available. As with gravity filters, the media is usually sand or a combination of media, and filtration rates are similar to gravity filters. Groundwater is first aerated to oxidize the iron or manganese, and then pumped through the filter to remove the suspended material.
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- 48. Construction rapid sandfilter 03/28/17 water treatment 48 1- Enclosure tank 2- Filter Media 3- Base material 4- Under Drainage system 5- Other appurtenances
- 49. Enclosure tank 03/28/17 watertreatment 49 Rectangular in plan Constructed either of masonary or of concrete , coated with water proof material Depth- 2.5 to 3.5 m surface area- 10 to 50 m2 length to width ratio 1.25 to 1.35
- 50. Filter media 03/28/17 watertreatment 50 It consist sand layer -60 to 90 cm in depth Effective size of sand varies from 0.35 to 0.6 mm finer sand be used
- 51. Base material 03/28/17 watertreatment 51 Graded gravel total depth varies from 45 to 60 cm Divided in to 4 to 5 layers Size (mm) Depth (cm) 2 to 5 5-8 5 to 12 5-8 12 to 20 8-13 20 to 38 8-13 38 to 65 13-20
- 52. Under drainage system 03/28/17water treatment 52 Purpose: It collect the filtered water uniformly over the area of gravel bed. It provides uniform distribution of backwash water without disturbing the gravel bed and filter media.
- 53. Types of underdrainage system 03/28/17 water treatment 53 1- Manifold and lateral System
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- 55. 03/28/17 water treatment55 Wheeler system
- 56. 03/28/17 water treatment56 Leopald system
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- 58. 03/28/17 water treatment58 THANK YOU