Slide 1: Water treatment Dr p v singh Asst.professor Cert Meerut.. GENERAL INTRODUCTON: GENERAL INTRODUCTON Water is a natural gift on earth It is essential for human, animal and plants. It is used widely for domestic and industrial purpose In nature water is present in abundance 96% of water form ocean, 2.2% form ice 1.2% form ground water HARDNESS OF WATER: HARDNESS OF WATER calcium and magnesium salts are present in rocks are dissolved in water and make it hard. Temporary hardness : it is caused due to presence of bicarbonates of Ca and Mg It can be removed by boiling of water. Ca (HCO 3 ) 2 -------→ CaCO3↓ + H 2 O+ CO 2 ↑ Mg (HCO 3 ) 2 --------→ MgCO 3 ↓ + H 2 O+ CO 2 ↑ Permanent hardness: caused due to dissolution of CaCl 2 ,MgCl2,CaSO4 and MgSO 4 . Can not removed by boiling . Hard water causes: Hard water causes Scale and sludge formation Caustic embrittlement Boiler corrosion Priming and foaming. Treatment of boiler feed water Treatment of boiler feed water : Treatment of boiler feed water Carbonate conditioning: by introducing sodium carbonate CaSO 4 + Na 2 CO 3 → CaCO 3 ↓+ Na 2 SO 4 Phosphate conditioning: By Introducing Tri Sodium Phosphate 2Na 3 PO 4 +3CaCO 3 → Ca 3 (PO 4 ) 3 + 3Na 2 CO 3 Calgon Process: it is known as sodium hexametaphosphate. It forms soluble compound with calcium salt and hence prevent scale and sludge formation Na 2 [Na 4 (PO 3 ) 6 ] <===> 2Na + +[Na 4 P 6 O 18 ] 2- 2CaSO 4 +[Na 4 P 6 O 18 ] 2- →[Ca 2 P 6 O 18 ] 2 - + 2Na 2 SO 4 Water softening process: Water softening process The various process for water softening are used which are as follow : Zeolite process Ion exchange process Reverse osmosis process Lime soda process ZEOLITE ??: ZEOLITE ?? Zeolite is also known as Permutit. The general formula of zeolite: Na 2 OAl 2 O 3 . x SiO 2 . y H 2 O It holds sodium ions loosely that is replaced by calcium or magnesium. It is of two types natural and synthetic . ZEOLITE PROCESS: ZEOLITE PROCESS Slide 9: CHEMICAL REACTIONS Na 2 Z +CaCl 2 → CaZ +2NaCl Na 2 Z +MgCl 2 → MgZ +2NaCl Na 2 Z +CaSO 4 → CaZ +Na 2 SO 4 Na 2 Z +MgSO 4 → MgZ +Na 2 SO 4 Na 2 Z +Ca(HCO 3 ) 2 → CaZ +2NaHCO 3 Na 2 Z +Mg(HCO 3 ) 2 → MgZ +2NaHCO 3 REGENERATION OF ZEOLITE CaZ + 2NaCl→ Na 2 Z +CaCl 2 MgZ + 2NaCl→ Na 2 Z +MgCl 2 ZEOLITE PROCESS: ZEOLITE PROCESS ADVANTAGES Remove almost complete hardness and produce water up to 10ppm hardness. No sludge formation occurs. Method is cheap since zeolite can be reuse. DISADVANTAGES Treated water contains more sodium salt. Method is not useful for treatment of turbid water. Can not remove acidic ions. Capable only for replacing Ca and Mg ions . Slide 11: Ion exchange Resins Ion exchange resins are insoluble,crosslinked,high molecular weight organic polymer with porous structure. The functional group attached to the chain are responsible for exchanging the ions. Cation Exchangers: - Strongly acidic – functional groups derived from strong acids e.g., R-SO 3 H ( sulfonic ). - Weakly acidic – functional groups derived from weak acids, e.g., R-COOH (carboxylic Slide 12: Anionic Exchangers: Strongly basic – functional groups derived from quaternary ammonia compounds, R-N-OH. Weakly basic - functional groups derived from primary and secondary amines, R-NH 3 OH or R-R’-NH 2 OH. ION EXCHANGE RESINS: ION EXCHANGE RESINS CATION EXCHANGER ANION EXCHANGER ION EXCHANGE PROCESS: ION EXCHANGE PROCESS SOFTENING PROCESS: SOFTENING PROCESS Cation exchange reactions 2RH + Ca ++ → R 2 Ca + 2H + 2RH + Mg ++ → R2Mg + 2H + Anion exchange reactions ROH + Cl - → RCl + OH - 2ROH + CO 3 → R 2 CO 3 + 2OH - H + + OH - -----→ H 2 O Slide 16: THANKS !!