purification of water

Question 1

what are the types of purification of water?

Answer 1

1- large scale
2- small scale

Question 2

what does water treatment method depend on?

Answer 2

1- the nature of the water
2- desired standard of water quality

Question 3

what are the divisions of large scale purification?

Answer 3

1- storage
2- filtration
3-disinfection

Question 4

what are the different aspects of storage?

Answer 4

1- biological
2- chemical
3- physical

Question 5

describe the physical aspect of storage

Answer 5

the impurities are able to settle down, allowing the water to be clearer

Question 6

describe the chemical aspect of storage

Answer 6

aerobic bacteria oxidize organic matter such as ammonia into nitrates

Question 7

describe the biological aspect of storage

Answer 7

bacterial count drops

Question 8

what does large scale filtration do?

Answer 8

removes 98-99% of bacteria

Question 9

what are the types of large scale filtration?

Answer 9

1- mechanical
2- biological

Question 10

what disinfectants are used in large scale purification?

Answer 10

1- ultraviolet radiation
2- chlorination
3-ozonation

Question 11

how does UV radiation works?

Answer 11

exposure of thick layer of water to uv radiation

Question 12

what are the advantages of using ultraviolet radiation?

Answer 12

1- short exposure time
2- doesn’t produce taste or odor
3-no foreign matter introduced

Question 13

what are the disadvantages of using ultraviolet radiation?

Answer 13

1-no residue left incase of recontamination
2- expensive
3- no test to access progress

Question 14

types of chlorination methods in large scale purification

Answer 14

1- chlorine gas: irritating to the eye
2-chloramine
3-perchloron

Question 15

what are the chlorination properties?

Answer 15

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

Question 16

why does chlorine act as a better disinfectant when water PH is 6.5-8.5?

Answer 16

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

Question 17

what are the principles of using chlorine?

Answer 17

1- contact time of at least an hour
2-estimate the chlorine demand
3-know the recommended concentration of free residual chlorine

Question 18

define chlorine demand of water

Answer 18

• 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

Question 19

define free residual chlorine

Answer 19

The chlorine concentration of water that is available for rapid action

Question 20

what is the recommended concentration of free residual chlorine?

Answer 20

0.5 mg per liter

Question 21

how much ozone gas concentration is required for ozonation?

Answer 21

1.5 mg per liter

Question 22

what are the criteria’s, for a substance to be used as disinfectant?

Answer 22

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

Question 23

what are the division of small scale purification?

Answer 23

1- boiling
2- filtration
3- disinfection

Question 24

what are 6 substances used for disinfection in small scale purification

Answer 24

1- iodine
2- potassium manganate
3-bleach powder
4-chlorine solution
5- chlorine tablet
6-high test hypochlorite

Question 25

what is hypochlorite?

Answer 25

a compound with calcium and 60-70% chlorine

Question 26

what occurs with candle filter?

Answer 26

• remove bacteria but not the filter passing virus
• cleaned regularly due to buildup of impurities

Question 27

what are the types of filter?

Answer 27

• ceramic filters
  : berkefeld filters
  :katadyn filters
  :pastuer chamberland

Question 28

advantages and disadvantages of using iodine

Answer 28

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

Question 29

disadvantages of potassium manganate

Answer 29

1-only kills cholera vibrio [ a bacterium]
2-alters smell, color and odor of water

Question 30

what is an example of ceramic filters?

Answer 30

Pasteur Chamberland