Unit 1_Water Technology.pptx WATER QUALITY MODEL

WATER QUALITY MODEL

1. Water Technology/Analysis

2. Water “Water is abundant on earth yet it’s precious”

3. Major Problems in Water Alkalinity Hardness Salinity

4. Hard Water What’s hard water? Practically speaking, presence of : Calcium (Ca 2+ ) ions Magnesium (Mg 2+ ) ions Hardness as calcium carbonate mg/L (ppm) Soft 0-17 Moderately hard (Medium) 60-120 Hard 120-180 Very hard 180 & over

5. “ The soap consuming capacity of water is known as hardness of water .” OR “ Property of water which prevents lather formation of soap ” 2C 17 H 35 COONa + CaCl 2  (C 17 H 35 COO) 2 Ca ↓ + 2NaCl Sodium Sterate Hardness Calcium Sterate (Soluble-Soap) in water (Scum) Note: The Calcium and Magnesium ions reacts with sodium salts of soap to form insoluble scum, which do not have detergent value. Soap are sodium salts of long chain fatty acids. Hardness of Water

6. Types of Hardness There are two types of hardness (a) Temporary or Carbonate Hardness (b) Permanent or non-Carbonate Hardness

7. Temporary or Carbonate Hardness The hardness of water which can be removed by simple boiling. Temporary Hardness is caused by the presence of dissolved bicarbonate of calcium and magnesium . Ca (HCO 3 ) 2 Heat CaCO 3 + H 2 O + CO 2 Calcium bicarbonate Calcium Carbonate Mg(HCO 3 ) 2 Heat Mg(OH) 2 + 2CO 2 Magnesium Bicarbonate Magnesium hydroxide

8. Permanent Hardness The hardness of water which cannot be removed by simple boiling is called permanent hardness. It is due to the presence of chlorides, sulfates of calcium and Magnesium. Note: This hardness can be removed by some external methods i.e. Zeolite Method, Ion Exchange Method, Lime Soda Process etc.

9. Draw backs (or) Disadvantages of Hard Water Domestic Use Industrial Use 1. Washing 2. Bathing 3. Drinking 4. Cooking Textile Industry : wastage of soap Sugar Industry : difficulty in crystallization of sugar Dyeing Industry : imperfect shades or uneven spots Paper Industry Pharmaceutical Industry In Steam generation in Boilers The sticky precipitate adheres on the fabric/cloth and gives spots and streaks. Fe salts stain the cloths. Produces sticky scum on the bath tub and the body Bad to the digestive system and calcium oxalate formation is possible in urinary tracts Requires more fuel and time. Certain foods don’t cook soft and also gives unpleasant taste

10. Degree of hardness Degree of Hardness is expressed in terms of equivalents of CaCO 3 because – CaCO 3 is most insoluble salt in water. The equivalent weight of CaCO 3 is 50(Mol. Wt. 100), which cause ease (=easy) in calculations. Therefore the calculation of the degree of hardness is given by-

11. Parts per million (ppm) or milligram per liter (mg/l) 1ppm=1 part of CaCO 3 equivalence hardness causing substance present in 10 6 parts of water Degrees French ( o Fr ) 1 o Fr = 1 part of CaCO 3 eq per 10 5 parts of water Degree Clarke ( o Cl ) 1 o Clarke= 1part of CaCO 3 equivalent hardness in 70000 parts of water [1ppm = 1 mg/liter = 0.1 o Fr = 0.07 o Cl ] Units of Hardness

12. A water sample contains 408 mg of CaSO 4 per liter. Calculate the hardness in terms of CaCO 3 equivalent. How many grams of CaSO 4 dissolved per liter gives 70ppm of hardness? A water sample was found to contain CaSO 4 80 mg/ litre and MgSO 4 100 mg/ litre . Calculate the hardness of water in ppm, o Fr and o Cl . Numerical based on hardness of water

13. Quiz What is hardness of water? How do you remove temporary hardness? What are the units of hardness of water? What is CaCO 3 equivalent? Why CaCO 3 is taken as standard in calculating hardness of water?

14. FAQ Why does soap do not give lather with hard water? What do you understand by hardness of water? What are the different units of hardness of water? Write relationship between them? A water sample contains 408 mg of CaSO 4 per liter. Calculate the hardness in terms of CaCO 3 equivalent.

15. Recap 1. Major Problems in Water 4. Units of Hardness

16. Boiler Feed Water “The water mainly used in boilers for steam generation is known as boiler feed water”. For such water we need some specification: Hardness should be below 0.2 ppm Its caustic alkalinity (due to OH - ) should be in the range of 0.15 – 0.45 ppm. Its soda alkalinity (due to CO 3 2- , HCO 3 - ) should be in the range of 0.45 – 1.0 ppm. Excess of above impurities cause the following problems- Problems Scale and Sludge Caustic embitterment Priming and Foaming Boiler corrosion

17. Boiler problems 17 1. Scale Boiler wall water Hard adherent coating on inner walls of boiler Scales are hard deposits firmly sticking to the inner surface of the boiler. Scale may be formed inside the boiler due to decomposition of calcium-bicarbonate [ Ca (HCO 3 ) 2 ].

18. Boiler wall Slimy loose precipitate called sludge suspended in water 1. Sludge water Sludge is a soft, loose and slimy precipitate formed within the boiler. It can be easily scrapped off with a wire brush.

19. II. Priming and foaming Foaming Foaming- It is the production of continuous foam or hard bubblers in boilers. Foaming is due to the presence of substance like oil in boiling water. Priming- It is the process in which some particles in water are carried along with the steam. The resulting process is called as wet steam or carry over. The process of formation of wet steam in boilers is called as priming. Causes of Priming, Presence of dissolved salts High velocity steam due to sudden boiling Improper boiler design Priming

20. III. Caustic embitterment Boiler corrosion which takes place due to presence of highly alkaline water in boiler is known as caustic embrittlement IV. Boiler corrosion Degradation or destruction of boiler materials (Fe) due to the electrochemical attack is called boiler corrosion Na 2 CO 3 + H 2 O NaOH + H 2 O Na 2 CO 3 + H 2 O 2NaOH + H 2 O 2NaOH + Fe Na 2 FeO 2 + H 2 O 3Na 2 FeO 2 + 4 H 2 O 6 NaOH + Fe 3 O 4 + H 2

21. Prevention of scale formation Internal conditioning methods - of boiler water to prevent scale formation Colloidal conditioning – spreading of organic compounds like tannin, agar gel Carbonate conditioning – addition of carbonate compound Phosphate conditioning – addition of phosphate compound Calgon conditioning – addition of sodium hexa meta phosphate Scale formation can be avoided by adding organic substances like kerosene, tannin, agar-agar etc. These substances get coated over the scale forming precipitates, thereby yielding non-sticky and loose deposits similar to sludge which can be removed by blow down operation . 1. Colloidal conditioning

22. 3. Phosphate conditioning Scale formation can be prevented by adding sodium phosphate to the boiler water which reacts with the hardness producing ions and forms easily removable phosphate salts of respective ions 3CaCl 2 (Boiler water) + 2 Na 3 PO 4 Ca 3 (PO 4 ) 2 + 6 NaCl Calcium chloride Sodium phosphate calcium phosphate (non adherent and can be removed by blow down method) 2. Carbonate conditioning CaSO 4 (Boiler water) + Na 2 CO 3 CaCO 3 + Na 2 SO 4 Calcium sulfate Sodium carbonate calcium carbonate (non adherent loose sludge and can be removed by blow down method) Caution: Excess Na 2 CO 3 can result in caustic embrittlement

23. Calgon conditioning is a most useful method to remove hardness products (i.e. scale & sludge) from boiler. In this process the Graham’s salt is used. Graham’s Salt is also known as Calgon (sodium hexa metaphosphate). Calgon ( sodium hexa metaphosphate ) is soluble in water and it converts the impurity like CaCO 3 , CaSO 4 into soluble complex compound, which will remain in dissolved form in water. This property helps to remove the scale and sludge. 4. Calgon conditioning

24. 4. Calgon conditioning continue…. Na 2 [Na 4 (PO 3 ) 6 2Na + + [Na 4 P 6 O 18 ] 2- sodium hexa meta phosphate 2CaSO 4 (Boiler water) + [Na 4 P 6 O 18 ] 2- [Ca 2 P 6 O 18 ] 2- + 2Na 2 SO 4 Calcium Sulfate Soluble complex ion of calcium - can be removed easily Calgon tablets are used in the cleaning of washing machine drums

25. Quiz What is boiler feed water? What are the requirements for Boiler feed water? What is priming and foaming? Boiler corrosion due to use of highly alkaline water is called_______ What is scale and sludge?

26. FAQ What do you mean by boiler feed water? Explain the calgon conditioning method of descaling? Define the following terms: Priming and Foaming Caustic embrittlement Sludge and Scales.

27. Softening of hard water (External treatment of Boiler Feed Water)

28. Zeolite ( Permutit ) method of Softening of water Zeolite is a Hydrated Sodium Alumino Silicate, capable of exchanging its sodium ions with hardness producing cations in water. Porous Structure of zeolite The general chemical structure of zeolite is given below Na 2 O.Al 2 O 3 . x SiO 2 . y H 2 O ( x = 2-10 and y = 2-6) Micro pores of Zeolite

29. Process of softening by Zeolite method Zeolite can be simply represented as Na 2 Ze, where Ze represents insoluble radical which holds sodium ions loosely. When hard water is passed through Zeolite, Ca 2+ and Mg 2+ ions are retained by zeolite as CaZe and MgZe . Na 2 Ze + Ca (HCO 3 ) 2 CaZe + 2NaHCO 3 Na 2 Ze + Mg(HCO 3 ) 2 MgZe + 2NaHCO 3 To remove temporary hardness To remove permanent hardness Na 2 Ze + CaCl 2 CaZe + 2NaCl Na 2 Ze + MgSO 4 MgZe + Na 2 SO 4 Regeneration of Zeolite Bed CaZe (or) MgZe + 2NaCl Na 2 Ze + CaCl 2 or (MgSO 4 ) Washings drained Regenerated Zeolite Used Zeolite 10% brine solution Hardness water Scale formation After some time zeolite bed gets exhausted. Which is regenerated by using NaCl Solution (10% Brine Sol NH 4 Cl + NaOH → NaCl + NH 4 OH)

30. Zeolite softener Zeolite bed Gravel Hard water in Injector NaCl storage Softened water To sink Hard water spray

31. Disadvantages / Limitations / Demerits of Zeolite process If the water is turbid than output is reduced. Treated water contains more sodium salts. The process cannot be used with highly acidic water. Advantages / Merits of Zeolite process It automatically adjust itself according to hardness of water. Soft water of 10-15 ppm can be produced by this method The equipment is cheap and occupies less space It does not require more time and skill

32. A Zeolite softener was 80% exhausted, when 10,000L of hard water was passed through it. The softer required 200L of NaCl solution of strength 50 gm NaCl / L of solution. What is the hardness of water? The hardness of 50,000 liters of a sample of water was removed by passing it through a Zeolite softener. The softener was than required 200 liters of NaCl Solution containing 125 gm/liter of NaCl for regeneration. Calculate the hardness of sample of water. Numerical based on Zeolite process

33. Numerical based on Zeolite process A zeolite bed, on softening 7000 litres of hard water, required 60 litres of 10% NaCl solution for regeneration. Calculate the hardness of water in ppm. A water sample having hardness 250 ppm was softened by zeolite process. The exhausted zeolite bed required 50 litres of 15% NaCl solution for regeneration. Calculate the quantity of water softened using the zeolite bed An exhausted Zeolite softener was regenerated by passing 150 L of NaCl solution, having a strength of 150gm/L of NaCl . If the hardness of water is 600 ppm. Calculate the total volume of water that is softened by this softener.

34. Quiz What is the formula of Zeolite? What is the another name of zeolite __________ is used for regeneration of Zeolite Softner . Give the limitations of Zeolite Process.

35. FAQ State the Zeolite process for the removal of hardness of water? Discuss its merits over soda-lime process.  A Zeolite softener was 80% exhausted, when 10,000L of hard water was passed through it. The softer required 200L of NaCl solution of strength 50 gm NaCl / L of solution. What is the hardness of water?

36. Ion-Exchange resin Ion exchange resin Ion exchange resins are insoluble, cross linked, long chain polymers having functional groups responsible for the “ion-exchange” properties.

37. Types of Ion Exchange Resins: Two types Cation Exchange Resins Anion Exchange Resins These resins containing acidic functional groups (i.e. -COOH, -SO 3 H etc.) which are capable of exchanging their H + ions with Hardness producing cations . These are denoted by R – H + . Example- Zeocarb , Dowex-50 etc. These resins containing basic functional groups (i.e. quaternary ammonium group) which on hydrolysis becomes capable of exchanging their OH - ions with hardness producing anions. These are denoted by R + OH – . Example- Dowex –3, Amberlite – 400 etc.

38. Structure of Cation and Anoin exchange resins R = CH 3 Cation exchange resin Anion exchange resin

39. Water Softening The hard water is passed first through cation exchange column, which removes all the cations (like Ca 2+ , Mg 2+ etc.) from it and equivalent amount of H + ions are released from this column to water. Now hard water is passed through anion exchange column, where all the anions like Cl - , SO 4 2- etc. are removed from water and equivalent amount of OH- ions are released from this column to water. H + and OH – ions (released from cation and anion exchange columns) get combined to produce water molecule.

40. Regeneration of ion exchange resins R 2 Ca 2+ + 2H + (dil. HCl (or) H 2 SO 4 ) 2 RH + + Ca 2+ (CaCl 2 ,washings) R 2 SO 4 2- + 2OH - (dil. NaOH ) 2 ROH - + SO 4 2- (Na 2 SO 4 , washings) Regeneration of Cation exchange resin Regeneration of Anion exchange resin cation exchange resin is treated with acid ( dil HCl or dil H 2 SO 4 ) and anion exchange resin is treated with a base ( NaOH ) solutions to regenerate these resins

41. Ion exchange purifier or softener Cation exchange Resin Anion exchange Resin Gravel bed Hard water Injector Alkaline solution for regeneration of resin Soft water Wastages to sink Wastages to sink Acid solution for regeneration of resin pump

42. The process can be used to soften highly acidic or alkaline waters It produces water of very low hardness of 1-2ppm. So the treated waters by this method can be used in high pressure boilers It removes both types (cationic & anionic) of hardness impurities. The setup is costly and more expensive Chemicals are required. It requires more time and space. If turbidity is present output is reduced. Advantages Disadvantages

43. Comparison of Zeolite Process and Ion Exchange process Zeolite Process Ion Exchange Process Advantages It automatically adjust itself according to hardness of water. Soft water of 10-15 ppm can be produced by this method The equipment is cheap and occupies less space It does not require more time and skill Disadvantages If the water is turbid than output is reduced. Treated water contains more sodium salts. The process cannot be used with highly acidic water. Advantages The process can be used to soften highly acidic or alkaline waters It produces water of very low hardness of 1-2ppm. So the treated waters by this method can be used in high pressure boilers It removes both types (cationic & anionic) of hardness impurities. Disadvantages The setup is costly and more expensive Chemicals are required. It requires more time and space. If turbidity is present output is reduced.

44. Quiz What are ion exchange resins? Give their types. Why Ion exchange process is called demineralization or deionization? Why Ion Exchange process is better than Zeolite process? __________ is used for regeneration of cation exchange resin. __________ is used for regeneration of anion exchange resin. What are the limitations of Ion Exchange process?

45. FAQ Discuss the Ion-Exchange or deionization or demineralization process for the treatment of hard water with its advantages and disadvantages.

46. When two solutions having different concentration are separated by a semi-permeable membrane, flow of solvent molecules from the lower concentration to higher concentration takes place, until the concentration becomes equal on both sides. This phenomenon is called Osmosis . Or “ Osmosis is the movement of pure water to solution.” In Reverse Osmosis the above process of Osmosis is reversed by applying the external hydrological pressure (14.5 – 38.7 atm ) on solution side (higher conc ). Reverse Osmosis

47. It is simple and reliable process. Purification through RO removes all impurities of water. It operates comparatively at low temperature. The energy requirement is 30% lower than distillation process. The semi-permeable membrane has a lifetime of about 2years & it can be easily replaced within a few minutes. Advantage of Reverse Osmosis (RO) process

48. A major problem with RO process is to find membrane strong enough to withstand the high pressure applied on it. Disadvantage of Reverse Osmosis (RO) process Treatment of waste water, Desalination, In pharma industry In regeneration of minerals Applications

49. Quiz What is reverse osmosis process? What are drawbacks of Reverse osmosis process? Why Reverse osmosis is the best process for water softening?

50. FAQ What do you mean by Reverse osmosis? Explain its process and advantages?

51. Lime soda process It is a process in which Lime (Ca(OH) 2 ) and soda (Na 2 CO 3 ) are added to the hard water to convert the soluble calcium and magnesium salts to insoluble compounds by a chemical reaction. The CaCO 3 and Mg(OH) 2 so precipitated are filtered off and removed easily. It is further divided in to two types Cold lime soda process Hot lime soda process

52. Water Softening Lime removes temporary hardness, permanent hardness of (Mg 2+ ), CO 2 , mineral acids, bicarbonates of Na and K, and NaAlO 2 or alums. Removal of temporary hardness of Ca 2+ Ca (HCO 3 ) 2 + Ca (OH) 2  2CaCO 3 + 2H 2 O Removal of Temporary hardness of Mg 2+ Mg(HCO 3 ) 2 + 2Ca(OH) 2  Mg(OH) 2 + 2CaCO 3 + 2H 2 O Removal of Permanent hardness of Mg 2+ MgCl 2 + Ca (OH) 2  Mg(OH) 2 + CaCl 2 MgSO 4 + Ca (OH) 2  Mg(OH) 2 + CaSO 4 Removal of CO 2 CO 2 + Ca (OH) 2  CaCO 3 + H 2 O Removal of acids 2HCl + Ca (OH) 2  CaCl 2 + 2H 2 O H 2 SO 4 + Ca (OH) 2  CaSO 4 + 2H 2 O Removal of bicarbonates of Na + and K + 2NaHCO 3 + Ca (OH) 2  CaCO 3 + Na 2 CO 3 + 2H 2 O 2KHCO 3 + Ca (OH) 2  CaCO 3 + K 2 CO 3 + 2H 2 O Removal Fe +2 and Al +3 [These may be present in water as permanent hardness or may be added as coagulants] FeSO 4 + Ca (OH) 2  CaSO 4 + Fe(OH) 2 Al 2 (SO 4 ) 3 + 3Ca(OH) 2  3CaSO 4 + 2Al(OH) 3  Reaction with NaAlO 2 or Alum NaAlO 2 + 2H 2 O  Al(OH) 3 + NaOH [Where, NaOH is equivalent to ½ Ca(OH)­ 2 ] 2NaOH + Ca +2  Ca(OH) 2 + 2Na + Amount of lime required for softening (L) = [Temporary hardness of Ca 2+ + 2 x Temporary hardness of Mg 2+ + permanent hardness of Mg 2+ + CO 2 + ½ HCl + H 2 SO 4 + ½ NaHCO 3 + ½ KHCO 3 + FeSO 4 + 3 x Al 2 (SO 4 ) 3 – ½ NaAlO 2 ] in terms of CaCO 3 equivalents x x kg  

53. Water Softening Soda reacts with permanent hardness of Ca 2+ CaCl 2 + Na 2 CO 3  CaCO 3 + 2NaCl CaSO 4 + Na 2 CO 3  CaCO 3 + Na 2 SO 4 [It also reacts with CaCl 2 and CaSO 4 formed by removal of acid, Fe 2+ , Al 3+ to form CaCO 3 .] Amount of Soda required for softening (S) = [permanent hardness of Ca 2+ + permanent hardness of Mg 2+ + ½ HCl + H 2 SO 4 + FeSO 4 + 3 x Al 2 (SO 4 ) 3 – ½ NaHCO 3 – ½ KHCO 3 ] in terms of CaCO 3 equivalents x x kg  

54. Types of Lime Soda Process Cold Lime Soda Process Chemicals are added to hard water at room temperature. Raw water and calculated amount of chemicals are continuously added from the top with continuous stirring. Coagulants also added to fasten the precipitate formation. Precipitate Formed settles down at the bottom.

55. cold lime soda softener Hard water feed Chemicals ( soda+lime+coagulant ) feed Softened water Sedimented sludge (CaCO 3 , Mg(OH) 2 Stirrer Wood fiber filter

56. Types of Lime Soda Process Hot Lime Soda Process Chemicals are added to hard water at 80 o C temperature. Raw water and calculated amount of chemicals are continuously added from the top. Since the reaction takes place at higher temperature, no or very less coagulant is required. Sludge Formed settles down at the bottom.

57. Hot Lime soda Process Hard water feed Chemicals feed (lime and soda) Super heated steam Reaction tank Precipitated sludge (CaCO 3 , Mg(OH) 2 Sludge outlet Filtered soft water Soft water Filtration tank Fine sand layer Coarse sand layer Gravel layer

58. Advantages of Lime soda process Disadvantages of Lime soda process Disposal of large amount of sludge (insoluble precipitates) poses a problem This can remove hardness to the extent of 15ppm which is not good for boilers It is very economical compared to other methods Iron and manganese salts are also removed by this process It increases the pH of the softened water hence corrosion is minimized also pathogenic bacteria

59. Calculation of lime and soda required for the softening of hard water by the lime soda process Hardness producing substance Chemical reaction with lime and soda Need Permanent Hardness Ca Salts Mg salts Temp. Hardness Ca (HCO 3 ) 2 Mg(HCO 3 ) 2 Acids HCl H 2 SO 4 HCO 3 - FeSO 4 NaAlO 2 CaCl 2 + Na 2 CO 3 CaCO 3 + 2NaCl MgSO 4 + Ca (OH) 2 Mg(OH) 2 + CaSO 4 CaSO 4 + Na 2 CO 3 CaCO 3 +Na 2 SO 4 Ca (HCO 3 ) 2 + Ca (OH) 2 2CaCO 3 + 2H 2 O Mg(HCO 3 ) 2 + 2Ca(OH) 2 2CaCO 3 + Mg(OH) 2 + 2H 2 O 2H + + Ca (OH) 2 Ca 2+ + 2H 2 O Ca 2+ + Na 2 CO 3 CaCO 3 + 2Na + HCO 3 - + Ca (OH) 2 CaCO 3 + H 2 O + CO 3 2- Fe 2+ + Ca (OH) 2 Fe(OH) 2 + Ca 2+ Ca 2+ + Na 2 CO 3 CaCO 3 + 2Na + NaAlO 2 + H 2 O Al(OH) 3 + NaOH S L + S L 2L L/2+S/2 L/2 – S/2 L+S L/2

60. Lime requirement for softening T.H = temporary hardness P.H = Permanent Hardness Soda requirement for softening Molecular weight of lime = 74 Molecular weight of soda = 106 Molecular weight of CaCO 3 = 100 Therefore, 100 parts by mass of CaCO 3 are equivalent to 74 parts by mass of Ca(OH) 2 106 parts by mass of Na 2 CO 3 in terms of CaCO3 equivalents T.H of Ca 2+ + 2 x T.H of Mg 2+ + P.H of Mg 2+ + CO 2 + ½ HCl + H 2 SO 4 + ½ NaHCO 3 + ½ KHCO 3 + FeSO 4 + 3 × Al 2 (SO 4 ) 3 - ½ NaAlO 2 100 = 74 × vol. of water × 100 10 6 % purity of lime in terms of CaCO3 equivalents P.H of Ca 2+ +P.H of Mg 2+ + ½ HCl + H 2 SO 4 + FeSO 4 + 3 × Al 2 (SO 4 ) 3 - ½ NaHCO 3 - ½ KHCO 3 100 = 106 × vol. of water × 100 10 6 % purity of soda kg kg

61. Numerical based on Lime-soda Process Calculate the amount of lime and soda required for softening 15000 litres of water which analysed as follows: temporary hardness = 20ppm, permanent hardness of Ca = 15ppm, and permanent Magnesium hardness = 10ppm. Water sample was found to contains following salts: CaCl 2 = 55.5 mg/l, SiO 2 = 20.0 ppm, NaHCO 3 = 12.6 mg/l, KCl = 250 mg/l, MgSO 4 = 48 mg/l, CO 2 = 2.2 ppm, Fe 2+ = 2.0 ppm, Al 2 (SO 4 ) 3 = 10.0 ppm and Mg(HCO 3 ) 2 = 43.8 mg/l Calculate the quantity of lime (85% pure) and soda (95% pure) for softening 50,000 litres of water. A water sample was found to contains the following salts in mg/l: CaSO 4 = 20.4, MgCl 2 = 9.5 and HCl = 7.3 Calculate the quantity of lime (85% pure) and soda (80% pure) required for softening 80,000 litres of water. What would be the total cost of chemicals if lime and soda are Rs . 9 and Rs . 35 per Kg?

62. Calculate the quantity of lime and soda for softening 50,000 litres of water containing the following salts per litre – Ca(HCO 3 ) 2 = 9.2 mg; Mg(HCO 3 ) 2 = 7.9 mg; CaSO 4 = 15.3 mg; MgSO 4 = 15 mg; MgCl 2 = 3 mg and NaCl = 4.3 mg. Ans. L= 1.17 kg, S = 1.426 kg Calculate the amount of lime (74% pure) and soda (92% pure) required for softening 20,000 litres of water containing salts in mg/l- MgCO 3 = 84, MgCO 3 = 40, MgCl 2 = 95, CaCl 2 = 111, Mg (NO 3 ) 2 = 37, KCl = 30. Ans. L= 7.3 kg, S = 5.2 kg Calculate the amount of lime (92% pure) and soda (98% pure) required for softening 30,000 litres of water containing salts - Ca(HCO 3 ) 2 = 40.5 ppm; Mg(HCO 3 ) 2 = 36.5 ppm; CaSO 4 = 34 ppm; MgSO 4 = 30 ppm; CaCl 2 = 27.75 ppm and NaCl = 10 ppm. Ans. L= 2.413 kg, S = 2.433 kg Numerical based on Lime-soda Process

63. Quiz What are the formula of Lime and soda used in water softening process. Which process is better Hot or Cold Lime soda process? What are limitations of Lime soda process? Give the formula for calculating amount of Lime and Soda required.

64. FAQ Discuss the hot Lime-Soda process for the treatment of hard water with its advantages over cold Lime-Soda process.  Water sample was found to contains following salts: CaCl 2 = 55.5 mg/l, SiO 2 = 20.0 ppm, NaHCO 3 = 12.6 mg/l, KCl = 250 mg/l, MgSO 4 = 48 mg/l, CO 2 = 2.2 ppm, Fe 2+ = 2.0 ppm, Al 2 (SO 4 ) 3 = 10.0 ppm and Mg(HCO 3 ) 2 = 43.8 mg/l. Calculate the quantity of lime (85% pure) and soda (95% pure) for softening 50,000 liters of water.