Water treatment

Question 1

What is the process of clarification?

Answer 1

coagulants are added to percipitate out small particles and microorganisms (occurs before filtration

Question 2

What does chlorine dissolve in water to form?

Answer 2

hypochlorous and hydrochloric acids

Question 3

How does chlorine kill bacteria and organisms?

Answer 3

It forms hypochlorous and hypochloric acids which denature proteins

Question 4

What is the most common chlorine source

Answer 4

sodium hypchrorite (NaOCl)

Question 5

Name two gases commonly found dissolved in water?

Answer 5

O2 and CO2

Question 6

What are 3 metal ions found in water?

Answer 6

Ca2+, Mg2+, and Na+

Question 7

Name a significant drawback of using chlorine that results from water containing chlroine being exposed to sunlight

Answer 7

chlorine forms radicals when irradiated

Question 8

What does air stripping remove from water?

Answer 8

gaseous or low boiling points substances (like volatile organic chemicals (VOCs))

Question 9

How does air stipping work?(describe the process)

Answer 9

water is sprayed down a tower against an air updraft

Question 10

What is an advantage of air stripping?

Answer 10

inexpensive

Question 11

Name 3 drawbacks of air stripping

Answer 11

• pollutes the air (dissolved gases and low boiling point substances are now realeased into the air)
• doesnt kill microorganisms
• not long lasting (VOCs can redissolve)

Question 12

How is ozone prepared?

Answer 12

it is prepared by passing high voltage discharge through dry air

Question 13

Ozone is ____ O molecules bonded together

Answer 13

three

Question 14

Name an advantage of ozonation

Answer 14

there is no chemicals left in the water

Question 15

Name 3 drawbacks of ozonation

Answer 15

• more expensive than chlorination
• ozone cannot be stored and transported so it must be made on site
• ozone is an oxidizing agent so it isnt very effective on susbtances that prefer reduction

Question 16

How does UV radiation kill microorganisms?

Answer 16

damages the DNA of the microorganism (the energy breaks secondary and primary structures)

Question 17

What are two advantages ti UV radiation?

Answer 17

• no chemicals or additives left in the water

- very reliable

Question 18

Name two disadvantages of UV radiation

Answer 18

• microorganisms are killed but because there is no chemical additives they can be reintroduced
• the chamber that the water is treated in must be transparent to UV

Question 19

Hardness is a measure of the “____” content in water

____ ____

Answer 19

mineral

dissolved ions

Question 20

What is the dominant contributer to water hardness in freshwater systems?

Answer 20

Ca2+

Question 21

What is the result of the formation of “scum”?

Answer 21

Soap will not lather properly

Question 22

How is soap scum formed

Answer 22

the hydrophilic head of water is attracted to the Ca2+. The combination of the soap and Ca2+ in insoluble in water and so the soap does not lather

Question 23

What is “scale”?

Answer 23

deposits of CaCO3

Question 24

The dissolution of CaCO3 is ____ (Endothermic/exothermic)

Answer 24

exothermic

Question 25

What is the result of the dissolution of CaCO3 being exothermic

Answer 25

Heat causes the CaCO3 to precipitate

Question 26

Are metal carbonates soluble in water? Are carbonate soluble in water?

Answer 26

Metal carbonates are soluble in water and carbonates are insoluble in water

Question 27

A ____ agent can be used to prevent scum

Answer 27

sequestering

Question 28

How do sequestering agents prevent soap scum?

Answer 28

the sequestering agent isolates/surrounds the cation

Question 29

Name 3 sequestering agents

Answer 29

TPP 5-
EDTA 4-
Hydroxycarboxalates

Question 30

Name 2 non chemical additive water softening methods

Answer 30

• purification by distallation

- purification by ion exhange