Water Technology Flashcards
hard water
which doesnt produce a ready and permanent lather with soap solution
what causes hardness of water
presence of dissolved salts of Ca, Mg and some other heavy metals
what causes temporary hardness
presence of bicarbonates of Ca, Mg and other heavy metals, carbonates of Fe and bicarbonate of sodium
how can hardness of water be removed
simple boiling
what causes permanent hardness
presence of chloride and sulphate of Ca, Mg, Fe and other heavy metals
parts per million
number of parts of CaCO3 equivalent hardness present in 10^6 parts of water
milligram per litre
number of milligrams of CaCO3 equivalent hardness present in 1 L of water
clarkes degree
number of parts of CaCO3 equivalent hardness present in 7000 parts of water
frenche degree
number of parts of CaCO3 equivalent hardness present in 10^5 parts of water
why is conc of dissolved impurities present in water usually expressed in terms of equivalents of calcium carbonate salt
1) molec weight is 100 and equivalent weight 50, convenient for calc
2) CaCO3 is most insoluble substance formed during water treatment
troubles in boilers
1) scale and sludge formation
2) caustic embrittlement
3) boiler corrosion
4) priming and foaming
external treatment method
removing hardness producing salts from water outside the industrial equipment
polymer ion exchange process
external treatment method in which temporary and permanent hardness can be removed
2 types of ion exchange resins
cation
anion
differentiate between cation exchange resin and anion exchange resin
cation: contains acidic functional grps RH2 eg. sulphonated coal Dowex-50 anion: contains basic func grps R(OH)2 eg. phenol formaldehyde Dowex-3