M2U1 Coagulation and Flocculation Flashcards

1
Q

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

A

primary treatment

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2
Q

principal form of primary treatment

A

sedimentation

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3
Q

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

A

scum

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4
Q

constitute the backbone processes in most water and advance wwt plants

A

coagulation and flocculation

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5
Q

DBP

A

disinfection by products

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6
Q

coagulating agent used by egyptians to clarify water

A

almonds

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7
Q

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

A

alum

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8
Q

NOM

A

natural organic matter

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9
Q

particulate and dissolved organic matter when collected is called

A

NOM (natural organic matter)

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10
Q

treated to remove natural organic water

A

surface water

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11
Q

treated to remove hardness, or iron or manganese

A

groundwater

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12
Q

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

A

true

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13
Q

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

A

coagulation

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14
Q

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

A

flocculation

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15
Q

5 properties of colloids why they are suspended in water

A
  1. Electrokinetic Properties
  2. Hydration
  3. Brownian Movement
  4. Tyndal Effect
  5. Filterability
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16
Q

most important electrical property of the colloidal and suspended particles

A

surface charge

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17
Q

Four principal ways or Electrokinetic Properties

A
  1. Ionization
  2. Adsorption
  3. Isomorphous replacement
  4. Structural imperfections
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18
Q

accept or donate protons

A

ionization

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19
Q

a solute becomes bound to the solid surface

A

adsorption

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20
Q

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

A

isomorphous replacement

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21
Q

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

A

Structural imperfections

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22
Q

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.

A

hydration

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23
Q

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

A

brownian movement

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24
Q

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

A

tyndall effect

25
Q

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

A

filterability

26
Q

Mechanisms of coagulation

A
  1. adsorption and charge neutralization
  2. entrapment of particles in precipitate
  3. adsorption and bridging between particles
27
Q

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

A

adsorption and charge neutralization

28
Q

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

A

entrapment of particles in precipitate

29
Q

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.

A

adsorption and bridging between particles

30
Q

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

A

buffer solution

31
Q

law of mass action

A

Le Chatelier’s principle

32
Q

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

A

alkalinity

33
Q

serves
as a measure of buffering capacity

A

alkalinity

34
Q

T/F

The greater the alkalinity, the greater the buffering capacity.

A

True

35
Q

series of steps involved as dosage increases

A

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

36
Q

Two important factors in coagulant addition

A

pH and dose

37
Q

means of reducing disinfection byproducts

A

NOM removal

38
Q

recommended technique for removing NOM.

A

enhanced coagulation

39
Q

PACl

A

Polyaluminum Chloride

40
Q

primary coagulant when turbidity and alkalinity are high

A

cationic polymers

41
Q

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

A

coagulant aids

42
Q

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

A

flocculant aids

43
Q

most commonly used chemical because of its lower cost

A

lime

44
Q

it does not increase water hardness

A

soda ash

45
Q

a measure that directly depends on the pH scale

A

basicity

46
Q

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

A

alkalinity

47
Q

Process Steps of Coagulation and Flocculation

A
  1. Flash Mixing
  2. Coagulation
  3. Flocculation
48
Q

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

A

True

49
Q

T/F

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

A

true

50
Q

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

A

flocculation basin

51
Q

Types of Colloidal Systems

A

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

52
Q

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

A

jar test

53
Q

function of the power input into the water

A

velocity gradient, G

54
Q

The difference in velocity between adjacent layers of the fluid

A

velocity gradient

55
Q

Dispersion of the coagulant into water

A

flash or rapid mixing

56
Q

most important factor affecting particle-removal efficiency

A

flocculation

57
Q

most important physical factor affecting coagulant efficiency

A

rapid mix

58
Q

used to separate the flocculation basin compartments

A

baffle wall