purification of water Flashcards
what are the types of purification of water?
1- large scale
2- small scale
what does water treatment method depend on?
1- the nature of the water
2- desired standard of water quality
what are the divisions of large scale purification?
1- storage
2- filtration
3-disinfection
what are the different aspects of storage?
1- biological
2- chemical
3- physical
describe the physical aspect of storage
the impurities are able to settle down, allowing the water to be clearer
describe the chemical aspect of storage
aerobic bacteria oxidize organic matter such as ammonia into nitrates
describe the biological aspect of storage
bacterial count drops
what does large scale filtration do?
removes 98-99% of bacteria
what are the types of large scale filtration?
1- mechanical
2- biological
what disinfectants are used in large scale purification?
1- ultraviolet radiation
2- chlorination
3-ozonation
how does UV radiation works?
exposure of thick layer of water to uv radiation
what are the advantages of using ultraviolet radiation?
1- short exposure time
2- doesn’t produce taste or odor
3-no foreign matter introduced
what are the disadvantages of using ultraviolet radiation?
1-no residue left incase of recontamination
2- expensive
3- no test to access progress
types of chlorination methods in large scale purification
1- chlorine gas: irritating to the eye
2-chloramine
3-perchloron
what are the chlorination properties?
1-oxidizes iron, hydrogen sulfide and manganese
2-destroys taste and odor producing constituents of water
3-controls algae and slime organism
4-acts as a better disinfectant when water PH is 6.5 to 8.5
why does chlorine act as a better disinfectant when water PH is 6.5-8.5?
1-water contains hypochlorous acid and hypochlorite ion and together are called free chlorine
2-hypochlorous acid is the most effective disinfectant therefore a lower PH preferred
what are the principles of using chlorine?
1- contact time of at least an hour
2-estimate the chlorine demand
3-know the recommended concentration of free residual chlorine
define chlorine demand of water
• the difference between amount of chlorine added to water and the amount of residual chlorine remaining after a specific contact time at a given PH and temperature
define free residual chlorine
The chlorine concentration of water that is available for rapid action
what is the recommended concentration of free residual chlorine?
0.5 mg per liter
how much ozone gas concentration is required for ozonation?
1.5 mg per liter
what are the criteria’s, for a substance to be used as disinfectant?
1-destroyes microorganism within contact time
2- does not leave product of reaction which could make water toxic or change its color
3-disinfectant able to be left as residue
4-disinfectant can be detected easily to see progress
what are the division of small scale purification?
1- boiling
2- filtration
3- disinfection
what are 6 substances used for disinfection in small scale purification
1- iodine
2- potassium manganate
3-bleach powder
4-chlorine solution
5- chlorine tablet
6-high test hypochlorite
what is hypochlorite?
a compound with calcium and 60-70% chlorine
what occurs with candle filter?
- remove bacteria but not the filter passing virus
- cleaned regularly due to buildup of impurities
what are the types of filter?
- ceramic filters
: berkefeld filters
:katadyn filters
:pastuer chamberland
advantages and disadvantages of using iodine
1-contact time of 20-30 min: used as backup/emergency disinfectant
2- active molecule
: thyroid active- synthesis of thyroid hormones
* too much thyroid hormone leads to disease
3- expensive
disadvantages of potassium manganate
1-only kills cholera vibrio [ a bacterium]
2-alters smell, color and odor of water
what is an example of ceramic filters?
Pasteur Chamberland
