M2U1 Coagulation and Flocculation

Question 1

first process in the wwt plant to remove a significant fraction of organic particulate matter

Answer 1

primary treatment

Question 2

principal form of primary treatment

Answer 2

sedimentation

Question 3

consists of grease, oil, plastic, leaves, rags, hair, and other floatable materials

Answer 3

scum

Question 4

constitute the backbone processes in most water and advance wwt plants

Answer 4

coagulation and flocculation

Question 5

DBP

Answer 5

disinfection by products

Question 6

coagulating agent used by egyptians to clarify water

Answer 6

almonds

Question 7

coagulating agent used by Romans and used in municipal water treatment in England

Answer 7

alum

Question 8

NOM

Answer 8

natural organic matter

Question 9

particulate and dissolved organic matter when collected is called

Answer 9

NOM (natural organic matter)

Question 10

treated to remove natural organic water

Answer 10

surface water

Question 11

treated to remove hardness, or iron or manganese

Answer 11

groundwater

Question 12

T/F
The object of coagulation (and subsequently flocculation) is to turn the small particles into larger particles called flocs

Answer 12

true

Question 13

addition of one or more chemicals to condition the small particles for subsequent processing by flocculation

Answer 13

coagulation

Question 14

the
process of aggregation of the destabilized particles and precipitation products.

Answer 14

flocculation

Question 15

5 properties of colloids why they are suspended in water

Answer 15

1. Electrokinetic Properties
2. Hydration
3. Brownian Movement
4. Tyndal Effect
5. Filterability

Question 16

most important electrical property of the colloidal and suspended particles

Answer 16

surface charge

Question 17

Four principal ways or Electrokinetic Properties

Answer 17

1. Ionization
2. Adsorption
3. Isomorphous replacement
4. Structural imperfections

Question 18

accept or donate protons

Answer 18

ionization

Question 19

a solute becomes bound to the solid surface

Answer 19

adsorption

Question 20

Under geologic conditions, the metal in a metal oxide is replaced
by a metal atom with a lower valence.

Answer 20

isomorphous replacement

Question 21

In the formation of the mineral crystal, bonds are broken on the edge of the crystal. These lead to development of surface charge.

Answer 21

Structural imperfections

Question 22

Colloidal particles that have water-soluble groups on their surface such as hydroxyl, carboxyl, amino, and sulfonic exhibit high affinity for hydration and cause a water film to surround the particles.

Answer 22

hydration

Question 23

Colloids exhibit a continuous random movement caused by bombardment by the water molecules in the dispersion medium

Answer 23

brownian movement

Question 24

Colloidal particles have an index of refraction different from water, light passing through the dispersion medium and hitting the particles will be reflected.

Answer 24

tyndall effect

Question 25

colloidal particles can be readily removed by ultrafiltration but require coagulation prior to their efficient removal by ordinary filtration

Answer 25

filterability

Question 26

Mechanisms of coagulation

Answer 26

1. adsorption and charge neutralization 2. entrapment of particles in precipitate 3. adsorption and bridging between particles

Question 27

Hydrolyzed metal salts, prehydrolyzed metal salts, and cationic polymers have a positive charge. They destabilize particles through charge neutralization.

Answer 27

adsorption and charge neutralization

Question 28

With doses exceeding saturation for the metal hydroxide, aluminum and iron salts form insoluble precipitates and particulate matter is entrapped in the precipitate. This type of destabilization has been described as sweep coagulation

Answer 28

entrapment of particles in precipitate

Question 29

Other sites on the polymer chain extend into solution and adsorb on surfaces of other particles, thus creating a “bridge” between the particles. This bridge results in a larger particle that settles more quickly and forms a more dense sludge.

Answer 29

adsorption and bridging between particles

Question 30

A solution that resists large changes in pH when an acid or base is added or when the solution is diluted is called

Answer 30

buffer solution

Question 31

law of mass action

Answer 31

Le Chatelier’s principle

Question 32

defined as the sum of all titratable bases down to about pH 4.5

Answer 32

alkalinity

Question 33

serves as a measure of buffering capacity

Answer 33

alkalinity

Question 34

T/F The greater the alkalinity, the greater the buffering capacity.

Answer 34

True

Question 35

series of steps involved as dosage increases

Answer 35

1st: aquocomplexes 2nd: hyrodroxocomplexes 3rd. hyroxometal polymer 4th: aluminum hydroxide precipitates

Question 36

Two important factors in coagulant addition

Answer 36

pH and dose

Question 37

means of reducing disinfection byproducts

Answer 37

NOM removal

Question 38

recommended technique for removing NOM.

Answer 38

enhanced coagulation

Question 39

PACl

Answer 39

Polyaluminum Chloride

Question 40

primary coagulant when turbidity and alkalinity are high

Answer 40

cationic polymers

Question 41

They are used in waters that have low concentrations of particles and, thus, have few nucleating sites to form larger floc

Answer 41

coagulant aids

Question 42

They are added after the coagulants are added and the particles are already destabilized.

Answer 42

flocculant aids

Question 43

most commonly used chemical because of its lower cost

Answer 43

lime

Question 44

it does not increase water hardness

Answer 44

soda ash

Question 45

a measure that directly depends on the pH scale

Answer 45

basicity

Question 46

how much acid is needed to lower the pH into a significant acid value; also known as the buffering capacity of a water body.

Answer 46

alkalinity

Question 47

Process Steps of Coagulation and Flocculation

Answer 47

1. Flash Mixing 2. Coagulation 3. Flocculation

Question 48

T/F Flash mixing typically lasts a minute or less. If the water is mixed for more than 60 seconds, the mixer blades will shear the newly forming floc back into small particles

Answer 48

True

Question 49

T/F Gentle mixing brings the fine particles formed by coagulation into contact with each other; typically lasts for about 30-45 minutes

Answer 49

true

Question 50

often has a number of compartments with decreasing mixing speeds as the water advances through the basin

Answer 50

flocculation basin

Question 51

Types of Colloidal Systems

Answer 51

Type I: High colloidal concentration, low alkalinity (pH 4-6). Type II: High colloidal concentration, high alkalinity. Type III: Low colloidal concentration, high alkalinity. Type IV: Low colloidal concentration, low alkalinity

Question 52

intended to simulate the coagulation/flocculation process in a water treatment plant

Answer 52

jar test

Question 53

function of the power input into the water

Answer 53

velocity gradient, G

Question 54

The difference in velocity between adjacent layers of the fluid

Answer 54

velocity gradient

Question 55

Dispersion of the coagulant into water

Answer 55

flash or rapid mixing

Question 56

most important factor affecting particle-removal efficiency

Answer 56

flocculation

Question 57

most important physical factor affecting coagulant efficiency

Answer 57

rapid mix

Question 58

used to separate the flocculation basin compartments

Answer 58

baffle wall