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Water Treatment > Filtration Systems > Flashcards

Filtration Systems Flashcards

1
Q

Which is the filtration flow rate through a manganese Greensand pressure filter at 100 C ?

a. 1 to 2 gpm/ft2
b. 2 to 3 gpm/ft2
c. 3 to 5 gpm/ft2
d. 5 to 8 gpm/ft2

A

b. 2 to 3 gpm/ft2

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2
Q

When a filter is ripening, ________.

a. it is need of a backwash.
b. turbidity is just starting to break through.
c. it is becoming more efficient in particle removal.
d. it is beginning to grow algae in the filter bed, walls, and troughs.

A

c. It is becoming more efficient in particle removal.

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3
Q

Virgin Greensand can be regenerated by soaking the filter bed for several hours in a solution of chlorine containing _______.

a. 50 mg/L Cl2
b. 75 mg/L Cl2
c. 100 mg/L Cl2
d. 200 mg/L Cl2

A

c. 100 mg/L

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4
Q

Which role does the action of straining of suspended particles play during filtration?

a. Minor
b. Fair
c. Good
d. Major

A

a. Minor

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5
Q

The turbidity of settlled water before it is applied to the filters, (Post-Sedimentation-Process) should always be kept below?

a. 1 to 2 ntu.
b. 2 to 4 ntu.
c. 5 ntu.
d. 8 to 10 ntu.

A

a. 1 to 2 ntu

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6
Q

Which is the best process for the removal of turbidity?

a. Anion exchange
b. Coagulation, flocculation, seimentation, and filtration
c. Chemical oxidation
d. Granular activated carbon

A

b. Coagulation, Flocculation, Sedimentation, Filtration

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7
Q

If filter run times between backwashes are long, for example one week, because high quality (low turbidity) water is being applied to the filters, which problem could still arise?

a. Mudball formation
b. Air binding and formation of mudballs
c. Extended backwashing due to media becoming too compacted
d. Floc breakthrough

A

d. Floc breakthrough

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8
Q

Gravel displacement in a filter bed from backwash rates with too high of a velocity could eventually cause?

a. compaction of the filter media.
b. loss of media into the backwash troughs.
c. a sand boil.
d. bed shrinkage.

A

c. a sand-boil.

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9
Q

Virgin Greensand __________.

a. does not require regeneration.
b. requires regeneration with potassium permanganate (1 hour soak with 60 grams KMnO4/ft3).
c. requires regeneration with manganese dioxide (2 hour soak with 25% by weight solution of MnO2).
d. requires regeneration with manganese hydroxide (4 hour soak with 200 grams Mn(OH)2/ft3).

A

b. requires regeneration with potassium permanganate (1 hour soak with 60 grams KMnO4/ft3)

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10
Q

Which conventional treatment step is eliminated by direct filtration?

a. Oxidation
b. Aeration
c. Flocculation
d. Sedimentation

A

d. Sedimentation

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11
Q

If crustaceans have clogged the water treatment plant’s filters, which is the most probable solution?

a. Shut down the filters and physically remove them.
b. Shut down one filter at a time and drain; once the crustaceans have died, physically remove them and then repeat process on the other filters.
c. Backwash filters using a very high concentration of ozone in the water.
d. Use a disinfectant that targets the specific organisms in question.

A

d. Use a disinfectant that targets the specific organisms in question.

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12
Q

Which organism can escape coagulation and thus pass through a granular filter?

a. Giardia
b. Entamoeba
c. Cryptosporidium
d. Naegleria

A

c. Cryptosporidium

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13
Q

Reverse Osmosis membranes will compact faster with?

a. higher iron content.
b. higher chlorine contact.
c. higher pressure.
d. higher pH.

A

c. higher Pressure

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14
Q

Which would immediately occur if newly installed manganese greensand was not skimmed of the fines after backwashing and stratification steps were completed?

a. Uneven flow through the bed
b. Cracks would develop in the bed
c. Medball formation
d. Shorter filter runs

A

d. Shorter filter runs

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15
Q

When a filter is operated at normal flow rates, its ability to trap flocculated particles in suspension is a function of _______.

a. effective size multiplied by uniformity coefficient.
b. effective size multiplied by uniformity coefficient divided by media size.
c. media depth and media size.
d. media depth and uniformity coefficient.

A

c. Media depth and Media size.

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16
Q

Which is the best solution if iron bacteria are causing corrosion problems in the filters?

a. Protect the metal parts of the filters by adding zinc orthophosphate.
b. Optimize the settling process.
c. Superchlorinate
d. Add lime at 50 mg/L to one filter at a time.

A

c. Superchlorinate

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17
Q

A conventional water treatment plant with dual media filters has very cold water in the winter and very warm water in the summer. Which should the operator do to compensate for this temperature change?

a. Use more coagulants in the summer per million gallons.
b. Sustain the same bed expansion without media loss by reducing or increasing backwash flow rate.
c. Increase summer bed expansion and inrease winter backwash flow rates.
d. Increase bed expansion in the winter compared to summer in order to remove turbidity.

A

b. Sustain the same bed expansion without media loss by reducing or increasing backwash flow rate.

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18
Q

How are Reverse Osmosis membranes cleaned once they become fouled?

a. They are soaked in high purity industrial soap for at least 24 hours.
b. They are cleaned with an acid wash.
c. They are cleaned with an acid, then with an industrial soap for 24 hours.
d. They are cleaned first with a high purity industrial soap and then soaked in an acid solution for 3 days.

A

b. They are cleaned with an acid wash.

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19
Q

Which membrane process is use to treat brackish water or seawater?

a. Microfiltration
b. Nanofiltration
c. Reverse osmosis
d. Ultrafiltration

A

c. Reverse Osmosis

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20
Q

The amount of reject water from a reverse osmosis unit is dependent on the number of stages in which the membranes are configured and the __________.

a. feed pressure.
b. amount of cations.
c. amount of cations and anions.
d. pH of the water.

A

a. feed pressure.

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21
Q

Manganese greensand filters can be regenerated by using ____________.

a. a surface wash and an air-water backwash.
b. brine water during backwashing.
c. potassium permanganate solution during backwashing.
d. first a brine solution during the first backwashing cycle followed by potassium permanganate solution for the second backwash cycle.

A

c. Potassium Permanganate solution during backwashing.

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22
Q

Which material is manganese greensand and which is the coating?

a. Quartz sand coated with manganese hydroxide [Mn(OH)2]
b. Garnet sand coated with manganese dioxide [MnO2]
c. Ilmenite sand coated with manganese hydroxide
d. Glauconite sand coated with manganese dioxide

A

d. Glaucoonite sand coated with manganese dioxide.

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23
Q

Which is the layer of solids and biological growth that forms on the top of a slow sand filter?

a. Biosolids film
b. Bio-carbonated scale layer
c. Schmutzdecke
d. Saprophytic layer

A

c. Schmutzdecke

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24
Q

Which filter type utilizes pressure for filtration?

a. Diatomaceous earth filter
b. High-rate filter
c. Rapid sand filter
d. Deep-bed monomedium filter

A

a. Diatomaceous earth filter

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25
Q

Slow sand filter runs can be as long as ________.

a. 3 months.
b. 4 months.
c. 6 months.
d. 1 year.

A

c. 6 months.

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26
Q

Gravity rapid sand filters can have head losses as high as ________.

a. 6 ft.
b. 8 ft.
c. 10 ft.
d. 12 ft.

A

b. 8 feet.

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27
Q

Which group of algae is usually associated with “blinding filters”?

a. Green algae
b. Blue-green algae
c. Pigmented flagellates
d. Diatoms

A

d. Diatoms

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28
Q

Depending on water temperature, which is the typical backwashing flow rate for a manganese Greensand filter bed?

a. 7 to 8 gpm/ft2
b. 8 to 10 gpm/ft2
c. 10 to 12 gpm/ft2
d. 12 to 14 gpm/ft2

A

c. 10 to 12 gpm/ft2

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29
Q

The typical filter run time for a high-rate filter system is ______.

a. 8 hours.
b. 24 hours.
c. 48 hours.
d. 72 hours.

A

b. 24 hours.

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30
Q

Below are four membrane technologies. Which is the correct sequence from larger to smaller pore sizes?

a. Microfiltration, reverse osmosis, ultrafiltration, nanofiltration
b. Microfiltration, ultrafiltration, nanofiltration, reverse osmosis
c. Reverse osmosis, ultrafiltration, microfiltration, nanofiltration
d. Ultrafiltration, microfiltration, reverse osmosis, nanofiltration

A

b. Microfiltration, Ultrafiltration, Nanofiltration, Reverse Osmosis

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31
Q

Optimum water quality in manganese greensand filters can be attained by backwashing and regenerating the greensand before the effluent manganese level goes above _______.

a. 0.02 mg/L.
b. 0.05 mg/L.
c. 0.10 mg/L.
d. 0.12 mg/L.

A

b. 0.05 mg/L.

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32
Q

Granular media filters should remove suspende solids including iron and manganese greater than ______.

a. 10 µm.
b. 15 µm.
c. 20 µm.
d. 25 µm.

A

a. 10 µm.

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33
Q

Which filter media material is given an abrasive number?

a. Garnet
b. Activated carbon
c. Sand
d. Greensand

A

b. Activated Carbon

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34
Q

Which is the typical filtration rate for high-rate filters?

a. 0.5 to 2.0 gpm/ft2
b. 3.0 to 12.0 gpm/ft2
c. 15.0 to 20.0 gpm/ft2
d. >25.0 gpm/ft2

A

b. 3.0 to 12.0 gpm/ft2

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35
Q

After backwashing and stratifying newly installed manganese greensand, approximately which percentage of the greensand should be skimmed off?

a. 3%
b. 5%
c. 8 to 9%
d. 12 to 15%

A

c. 8 to 9%

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36
Q

The media in a slow sand filter is ________.

a. stratified fine.
b. stratified medium.
c. stratified coarse.
d. unstratified.

A

d. Unstratified.

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37
Q

Clumping of filter media or Ion exchange resin is caused by ___________.

a. electrostatic charges.
b. media or resin breakdown, respectively.
c. temperature and pH of the clay in the water.
d. iron and manganese oxides reacting with the coagulant.

A

a. electrostatic charges.

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38
Q

Backwash water is what percentage of the totaled filtered water in a conventional rapid sand filter system?

a. 1%
b. 2 to 4%
c. 5 to 6%
d. 6 to 10%

A

b. 2 to 4%

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39
Q

Why does anthracite always stay on top of sand during backwashing?

a. Because the grain sizes are smaller
b. Because it is lighter and less dense
c. Because of its shape
d. Because of its porosity

A

b. Because it is lighter and less dense

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40
Q

The length of filter runs for manganese greensand filters can be increased by _________.

a. adding a high molecular weight polymer filter aid.
b. keeping the pH above 9.0 and lowering it after filtration.
c. keeping the pH below 7.3 and raising it after filtration.
d. adding a layer of anthracite above the greensand.

A

d. adding a layer of anthracite above the greensand.

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41
Q

Which is the most common type of valves used on filters?

a. Gate
b. Globe
c. Butterfly
d. Ball

A

c. Butterfly

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42
Q

Manganese greensand removes manganese and iron by a combination of ________.

a. adsorption and oxidation.
b. adsorption and absorption.
c. adsorption and precipitate screening.
d. absorption and precipitate screening.

A

a. adsorption and oxidation.

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43
Q

Which is the best means to remove Giardia Lamblia?

a. Coagulation, flocculation, and filtration
b. Ion exchange
c. Powdered activated carbon
d. Activated alumina

A

a. Coagulation, flocculation, and filtration

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44
Q

Which is the best method for removing Trihalomethanes precursors?

a. Reverse osmosis
b. Powdered activated carbon
c. Lime softening
d. Aeration and stripping

A

a. Reverse osmosis

45
Q

Reverse Osmosis membranes will compact faster _______.

a. with higher iron content.
b. with higher temperature.
c. with higher chlorine.
d. if the pH is greater than 8.5.

A

b. with higher temperature.

46
Q

Which is the best method for the removal of arsenic (+3)?

a. Reverse osmosis
b. Coagulation, sedimentation, and filtration
c. Cation exchange
d. Activated alumina

A

a. Reverse osmosis

47
Q

Which is the filtration rate for filters with granular activated carbon as a medium?

a. 0.5 to 1.0 gpm/ft2
b. 2.0 gpm/ft2
c. 4.0 gpm/ft2
d. 5.0 to 6.0 gpm/ft2

A

b. 2.0 gpm/ft2

48
Q

When manganese greensand filters are run in the continuous regeneration mode [continuous regeneration of the MnO2 (s) surfaces], the free chlorine residual in the filter effluent should be kept at ______.

a. 0.50 mg/L.
b. 1.00 mg/L.
c. 1.20 mg/L.
d. 1.75 mg/L

A

a. 0.50 mg/L.

49
Q

The sorption kinetics and sorption capacity of Mn(11) by MnOx(s)- coated filter media increase with ________.

a. increasing solution pH.
b. decreasing alkalinity.
c. increasing alkalinity.
d. decreasing temperature.

A

a. increasing solution pH.

50
Q

Direct filtration is used to treat raw water that has average turbidities ________.

a. below 10 ntu.
b. up to 25 ntu.
c. 40 to 50 ntu.
d. above 50 ntu.

A

b. up to 25 ntu.

51
Q

Diatomaceous earth filters _________.

a. have a relatively high installation cost.
b. have relatively high operating costs.
c. are used only for water with low turbidity.
d. produce very little backwash sludge.

A

c. are used only for water with low turbidity.

52
Q

Besides regenerating manganese greensand beds, potassium permanganate will also regenerate _________.

a. anthracite filter beds.
b. granular activated carbon beds.
c. pyrolusite filter beds.
d. polystyrene upflow clarifier media beds.

A

c. pyrolusite filter beds.

53
Q

Why is there a limited effect of organic absorption when granular activated carbon (GAC) is used as a filter medium above the sand layer?

a. GAC has a low porosity
b. GAC repels much of the organics due to the attached coagulants
c. Backwashing does not remove the organics absorbed over time nor does it regenerate the GAC
d. The water being filtered has limited contact time with the GAC

A

d. The water being filtered has limited contact time with the GAC

54
Q

An advantage of a variable declining-rate filtration system is that _________.

a. it does not require a loss-of-head indicator.
b. it does not require a rate-of-flow controller.
c. individual filters keep a constant filtration rate.
d. flow rate changes do not impact the system.

A

b. It does not require a rate-of-flow controller.

55
Q

Which is the most probable solution if Chironomids can be seen in the finished water?

a. Increase chlorination and backwash
b. Isolate distribution area, superchlorinate, flush mains and customer lines
c. Add powdered activated carbon to the filters, then backwash
d. Use chloramines, or, if already using, temporarily increase by 100%

A

a. Increase chlorination and backwash

56
Q

When should core samples be collected from filters using granular activated carbon?

A

At the time of installation and every six months thereafter.

57
Q

A flocculant is required for iron removal if most of the iron passes through a _______ filter membrane

A

5 µm

58
Q

Which would be the most probable solution to control algae in the water plant if the algae were clogging the filters?

A

Use activated carbon.

59
Q

Which bed expansion during backwashing must be achieved for filters using granular activated carbon?

A

50%

60
Q

The cartridge filters that are sometimes used immediately between reverse osmosis units should be replaced when the difference in pressure between the inlet and outlet gauges reaches?

A

15 psi

61
Q

After granular activate carbon (GAC) has all adsorption sites filled, which option should be taken?

A

Replace or reactivate the GAC.

62
Q

The cross section of the (repeating) layers in an electrodialysis membrane would be as follows;

A

Cation permeable membrane, plastic spacer, anion permeable membrane.

63
Q

An electrodialysis system will operate at temperatures as

high as _______.

A

1100 F

64
Q

In the operation of an electrodialysis system, the most commonly encountered problem is _______.

A

Scaling or membrane fouling.

65
Q

Backwashing rate procedures should be reassessed to determine the cause of granular activated carbon loss if the loss per year exceeds ________.

A

2 inches

66
Q

What will most probably cause taste and odors, slime, and filter clogging?

A

Blue-green algae

67
Q

Why can rapid sand filters handle filtration rates compared to slow sand filters?

A

Coarser sand

68
Q

What filter has an unstratified media distribution?

A

Slow sand filters

69
Q

Point-of-use activated carbon filters are most effective for removing _________.

A

Chlorine

70
Q

An operator should record filter _______ measurements, condition, and depth of media on a _______ basis.

A
  • bed expansion
  • quarterly basis
71
Q

What are absolute ratings based on with regard to membranes?

A

Largest pore opening

72
Q

How are manganese greensand beds regenerated?

A

Backwashed with permanganate solution.

73
Q

What is the primary advantage of placing a properly sized anthracite cole layer over manganese greensand?

A

Longer filter run times.

74
Q

What are the primary reasons that more small water systems are installing pressure filters?

A

Because installation and operating costs are low.

75
Q

Microfiltration is considered to be intermediate between ________ based on pore size.

A

Ultrafiltration and multimedia granular filtration

76
Q

Manganese greensand filters remove iron and manganese by a combination of both __________.

A

adsorption and oxidation.

77
Q

What is the major advantage of GAC over anthracite?

A

Better adsorption of organics.

78
Q

Air binding is caused by pressure in the filters _______ than atmospheric pressure, and it can cause ________ flow.

A
  • lower
  • resistance to
79
Q

What filter types would be best for direct filtration?

A

Monomedium filters

80
Q

Point-of-use activated carbon filters are not usually effective in removing ___________.

A

Inorganic chemicals.

81
Q

What is the disadvantage of direct filtration compared to conventional treatment?

A

It must be carefully monitored to prevent turbidity breakthrough.

82
Q

The term “schmutzdecke” is affiliated with which type of filter system?

A

Slow sand filtration.

83
Q

Which of the following processes is NOT combined in a

solids-contact basin

A

Reverse Osmosis

84
Q

What is the patented filter underdrain system called that uses a series of perforated vitrified clay blocks with channels to carry the water?

A

Leopold filter bottom

85
Q

Comparisons of filters should not be based on ________, because they very from manufacturer to manufacturer, but should be based on _________.

A
  • nominal ratings
  • absolute ratings
86
Q

Manganese greensand filtration is used to remove _______?

A
  • Manganese
  • Iron
  • hydrogen sulfide
87
Q

What is a patented filter underdrain system called that uses small porcelain spheres of various sizes in conical depressions?

A

Wheeler bottom

88
Q

Greensand grains are typically ________ than silica sands, so the ________ can quickly become ________.

A
  • smaller
  • head loss
  • excessive under a heavy load
89
Q

What pressure differential breaks up both the MnO2(s) and the glauconite mineral sand grain, which causes fines that reduce filter run times?

A

8 psi

90
Q

What type of underdrain system may or may not have a

gravel pack at its base?

A

False floor system.

91
Q

Membranes made of Teflon (polytetrafluoroethylene)

have _________ oxidant resistance.

A

high

92
Q

Why should an operator NOT add extra untested material

to a multimedia filter?

A
  • Specific gravity may be different.
  • Because the effective size may be different.
93
Q

What must the effluent ntu for a slow sand filter be kept at during operation?

A

Less than 1.0 ntu

94
Q

What is an advantage for installing a pressure filter in a

small water system

A

Air binding will not occur.

95
Q

The pH range for a manganese greensand filter for removing iron and manganese should be adjusted to a range of ________.

A

6.2 - 6.8 pH

96
Q

Monomedium filter media is ________ than a conventional filter because the media is ________.

A
  • deeper
  • coarser
97
Q

Filtration alone can be used after oxidation of iron and manganese if the concentration of the metals is below about ________.

A

5 mg/L

98
Q

It is recommended that an operator record the results of

solids retention analysis before and after backwashing

on a _______ basis.

A

yearly

99
Q

When a backwash is occurring, what should the operator do?

A
  • Hose down the walls.
  • Sample the floc.
  • view rate of rise.
100
Q

What is “glauconite” used for in the water industry?

A

Naturally occurring material that makes up greensand.

101
Q

A filter be is usually completely fluidized at just

________ expansion.

A

20%

102
Q

Filters will remove particulate matter by _________.

A

Mechanical Straining and adsorption.

103
Q

After iron and manganese precipitates are formed by the oxidation process, they are usually removed by ________.

A

Filtration

104
Q

The primary reason filters are difficult to clean is because _________.

A

Sticky floc adsorbs to the media.

105
Q

In a slow sand filter, once the sand layer is reduced to a depth of ________, new sand should be added to bring the filter bed back to the original depth.

A

2.0 ft

106
Q

Surface wash systems for filters agitate the top ________ of the media.

A

2 inches

107
Q

Patented backwashable pleated membrane filters have been designed specifically for the removal of _________

A

Iron

108
Q

What is the purpose of the graded gravel below the sand

in a multimedia filter

A
  • To support the underdrain system.
  • To support the sand bed.
  • To prevent sand from entering the underdrain.

Water Treatment (16 decks)

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