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B Exam: Demineralization

front 1

Specific Conductance is the indirect measurement of what parameter?

back 1

TDS

front 2

The TDS is what percent of the specific conductance?

back 2

70%

front 3

What is the pumping pressure used in RO treatment?

back 3

500-1200 PSI

front 4

What is the pumping pressure used in Membrane Softening?

back 4

Usually 100-200 PSI but the range is 100 to 500 PSI

front 5

What is a pretreatment process in RO treatment?

back 5

Add acid (Sulfuric Acid)

front 6

What is the purpose of prefilters?

back 6

Particulate safeguards

front 7

To increase the flow through the membranes in RO treatment, what action is
needed?

back 7

Increase pumping pressure

front 8

When the feed water temperature increases, what happens?

back 8

Product water increases

front 9

What is the TDS content of sea water?

back 9

35,000 mg/L

front 10

When pressure is increased in RO treatment, what reaction happens with the mineral flow?

back 10

Mineral flow is not affected by the PSI increase

front 11

Why is acid added in RO pretreatment?

back 11

Prolong life of cellulose acetate membranes

Ans. Prevent/control scaling

front 12

What is used to clean fouled membranes?

back 12

Ans. Citric Acid
Ans. Bactericide (if there is bacterial fouling)

front 13

When the water pressure must be increased by 15%, what action is needed?

back 13

Clean membranes

front 14

When recovery decreases by 15%, what action is needed?

back 14

Clean Membranes

front 15

What do you call the decline in flow due fouling and membrane compaction?

back 15

Flux Decline

front 16

By arranging the membranes in a Christmas Tree configuration, what recovery percent is normal?

back 16

85% or better

front 17

What type of pump is used for desalination of water?

back 17

Positive Displacement

front 18

What type of pump is used for membrane softening?

back 18

Centrifugal

front 19

If the brine valve is fully closed, what happens to recovery percent?

back 19

100% Recovery and damage to the membranes

front 20

What type of piping is used for desalinating water?

back 20

High grade stainless steel

front 21

To minimize concentration polarization, what action is necessary?

back 21

Create turbulence by varying flow velocity

front 22

In membrane filtration, what type of piping is normally required?

back 22

PVC

front 23

The Membrane Softening WTP is experiencing lower product water flow and higher salt rejection, what is the most likely cause?

back 23

Membrane Compaction

front 24

What action is needed in question 23?

back 24

Membrane replacement

front 25

The MS WTP is experiencing higher product water flow and lower salt rejection. What is the most likely cause?

back 25

Hydrolysis

front 26

What action is needed in question 25?

back 26

Membrane replacement

front 27

The MS WTP is experiencing lower product water flow, lower salt rejection, and higher delta pressure. What is action is needed?

back 27

Clean the membranes

front 28

The WTP treats 4.6 MGD. The product water is 3.5 MGD. What is the recovery percent?

back 28

76% (Product Water divided by Feed flow)

front 29

The RO WTP uses the Christmas Tree configuration for its membranes. The Feedwater flow is 10.0 MGD. The Feed TDS is 1,600 mg/L and product TDS is 210 mg/L. Hardness in the feed is 220 mg/L with finished water hardness of 32 mg/L. What is the plant's recovery percent?

back 29

Ans. 85%

front 30

What is the most common problem found in Electrodialysis (ED)?

back 30

Scaling and fouling of the membranes

front 31

What type of electrical power is used in ED?

back 31

DC

front 32

If feed water is pretreated with chlorine, what action is needed?

back 32

Dechlorination (Chlorine will damage ED membranes)

front 33

In ED, what is the purpose of prefilters?

back 33

Particulate safeguards

front 34

What is the purpose of acid addition to the feed water?

back 34

Prevent scaling

front 35

What is the operating temperature of ED?

back 35

110°F

front 36

When operating temperature of the EDC system increases, what happens to the process?

back 36

Removal Efficiency Increases

front 37

The feed water for an ED system has an iron content of 0.2 mg/L and manganese in excess of 0.4 mg/L. What action is needed?

back 37

Pretreatment to remove iron and manganese

front 38

An RO WTP uses the Christmas Tree configuration for its membranes. It treats 10 MGD with a product water of 8.5 MGD. The feed water has 1,660 mg/L of TDS. The product water has 210 mg/L of TDS. There is no hardness in the product water. What is the rejection percentage for TDS?

back 38

87%

front 39

In RO, what limits recovery percent?

back 39

Desired water quality and solubility of minerals

front 40

Over a period of time there is a gradual deposition of minerals on the membrane. This called?

back 40

Concentration Polarization

front 41

What is a Point-Of-Use or Point-of-Entry device or application?

back 41

A water treatment device located at the entry to a customer's home or a building, or a facility

front 42

What is Cross-Flow Filtration?

back 42

Flow from inside the membrane, flows through the membrane and out of the system

front 43

What is Dead-End Filtration?

back 43

Ans. All solids accumulate on membrane
Ans. Flow can be from outside to inside or vice-versa with no wastestream

front 44

What action is needed by the operator in order to recover the decrease in flow due to membrane fouling?

back 44

By backwashing and cleaning the filter element

front 45

What benchmarks are used to determine RO efficiency?

back 45

Ans. PSI Required and Recovery Percent
Ans. Membrane Integrity

front 46

If the feed water mineral content increases, permeate mineral content will _?

back 46

Increase

front 47

What factors influence the recovery rate?

back 47

Desired product quality and solubility of mineral content

front 48

Why is chlorine added to feed water at an RO plant?

back 48

To prevent biological fouling

front 49

In question 48, Why is chlorine added to feed water at an RO plant. what dosage would the operator use?

back 49

Ans. 1-2 mg/L

front 50

Pretreatment for an ED unit consists of which of the following?

back 50

Removal of iron, manganese, and chlorine residual

front 51

ED compartments losing salt are labeled?

back 51

Dilute

front 52

ED compartments getting salt are labeled?

back 52

Brine

front 53

What determines cartridge filter replacement?

back 53

PSI drop (10 psi)

front 54

If an entire ED unit must be taken offline immediately, what would the operator do?

back 54

Flip the main breaker

front 55

When ED feedwater temperature drops, what happens within the system/

back 55

DC amperage drops