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
mixed bed deioniser
consist of single cylinder containing an intimate mixture of strongly acidic cation exchanger and strongly basic anion exchanger
advantages of mixed bed deionizer
1) water containing high acidity and alkalinity can be purified
2) water with low residual hardness is obtained
3) the softened water is completely free from all the salts
desalination
process of removing extra common salt from water
principle of reverse osmosis
when a P higher than osmotic P is applied externally, osmosis takes place in opposite direction
osmosis
passage of solvent molecules from a lower conc region to higher conc region through a semi permeable membrane
ultra filtratiion membrane
used for RO process
advantages of ultrafiltration membrane
1) low capital cost
2) removes colloidal silica
3) removes ionic, non ionic, colloidal and high molec weight organic impurities
applns of ultrafiltration membrane
prodn of purified drinking water
purifying water for mixing beverages, ice making, cooking
potable water
water safe to drink
sedimentation with coagulation
removing fine suspended and colloidal impurities
chemical methods of disinfection
addn of potassium permanganate addn of bleaching powder using chloramine addition of O3 addn of liq Cr
phy methods of disinfection
simple boiling
passing UV
passing sun light
advantages of chlorination
effective and economical requires less space for storage stable introduces no salt impurities most ideal
disadvantages of chlorination
excess -> unpleasant taste and odour
- > irritation
- > precipitates other ingredients present
break point of chlorination
addn of Cl to the point tht it kills all and completely destroys impurities
advantages of disinfectation by UV
environment friendly highly effective no toxic byprods removes other org and toxic contaminants very less contact time improves taste
advantages of O3 disinfection
O3 sterilizes, bleaches, decolourises and deodurises
effective and rapid
chemical free
no regrowth
disadvantages of O3 disinfection
expensive
special mixing techniques
saturation level of O2
max conc of dissolved O2 that would be present in water at a specific temp in the abs of other factors
winkler method
to measure dissolved O2 level in fresh water systems
factors affecting DO
climate altitude dissolved or suspended solids amt of nutrients org wastes groundwater flow type and no. of organisms in water body
Biochem Oxygen Demand
amt of O2 req for biochem oxdn of org matters present in a sewage under aerobic condn at 20oC for 5 days
chemical oxygen demand
o2 req for complete oxdn of org matter present in sewage in the presence of strong chem oxidising agents
