Iron, Manganese And Fluoride Questions

Question 1

What is the primary MCL for fluoride?

Answer 1

4

Question 2

What is the secondary MCL for Fluoride?

Answer 2

2 mg/L

Question 3

What is the purpose of adding fluoride to water?

Answer 3

To prevent, caries, and cavities

Question 4

Adding too much fluoride to water will cause?

Answer 4

Mottling your teeth ( staining them brown)

Question 5

What do you give someone who has swallowed fluoride?

Answer 5

Water or milk?

Question 6

What is the first symptom of swelling Fluoride?

Answer 6

Vomiting

Question 7

What is the first symptom of inhaling fluoride?

Answer 7

Nosebleed

Question 8

If you use sodium fluoride in fluorination, what must be done to the water if the hardness is above 75?

Answer 8

Soften the water

Question 9

When feeding sodium fluoride with a saturator, above, what water pH will scaling occur?

Answer 9

10 pH

Question 10

How many PPM of fluoride must be added to the finish water if the raw water fluoride content is 0.15 PPM and the desired fluorite limit is 8 ppm?

Answer 10

0.65 PPM

Question 11

In question 10, how many pounds of 100% F ( fluoride) Will be added per day if the WTP treats 10 MGD?

Answer 11

54 lb ( 0.65x10x 8.34)

Question 12

What is a day tank?

Answer 12

A day tank that holds enough chemicals to feed water produced in a day

Question 13

What type of pump is used to feed chemicals?

Answer 13

Positive displacement ( piston)

Question 14

Recommended control limits and fluoride concentrations are based on?

Answer 14

The annual average of maximum daily temperatures

Question 15

What is the most common fluoride compound used in water treatment?

Answer 15

Hydrofluosilicic acid, sodium fluoride, sodium silcofluoride

Question 16

When choosing fluoride- pumping equipment, the most important criteria is?

Answer 16

Accuracy

Question 17

Fluoride doses must never be metered against a?

Answer 17

Negative or suction head?

Question 18

Fluoride system must be designed with the means to prevent?

Answer 18

Back siphonage and overfeeding

Question 19

Fluoride systems should be designed by?

Answer 19

An engineer

Question 20

If an operator gets fluoride on his skin or in his eyes, the recommended first aid is?

Answer 20

Flush with large amount of water for 15 minutes ( eyes- flush and see A doctor)

Question 21

Never operate a positive displacement pump against ?

Answer 21

Close valves ( especially a discharge valve)

Question 22

A form of backflow caused by a negative or below atmospheric pressure within a water system is called?

Answer 22

Back siphonage

Question 23

***A WTP starts receiving complaints concerning red water in the distribution system. The water system is using a greensand filter to remove iron and manganese. What is the most likely cause for the red water?

Answer 23

Iron Bacteria

Question 24

***Why is nitric acid added to the sample bottle used to collect iron samples?

Answer 24

To lower the pH to less than 2 to keep the iron in solution

Question 25

***What chemical is added to iron sample bottles?

Answer 25

HNO3 ( Nitric Acid)

Question 26

***What is the holding time for iron samples that have not been acidified?

Answer 26

48 hours

Question 27

***After backwashing a greensand filter, the filter shows a very high pressure loss. what is the cause?

Answer 27

Improper Backwash and or accumulation of greensand fines on filter bed surface

Question 28

***If the feed water to an ion exchange softening unit has iron and manganese, what will happen during the softening process?

Answer 28

Fe and Mn will be removed

Question 29

***What will break down the resins in an ion exchange softening unit?

Answer 29

Chlorine

Question 30

*** Insoluble iron & manganese will cause what problem in ion exchange unit?

Answer 30

Clogging and fouling the resins

Question 31

** How are ferric hydroxide precipitates removed during water treatment?

Answer 31

Sedimentation and filtration

Question 32

*** A water system’s well supplies a water that contains dissolved oxygen and iron and manganese. What does this indicate?

Answer 32

Water being drawn from more than one aquifer

Question 33

*** Where should iron and manganese samples be taken?

Answer 33

As close to the well as possible

Question 34

*** How can slim growths be controlled in the distribution system?

Answer 34

By maintaining a free chlorine residual

Question 35

*** How is a proper polyphosphate dosage determined?

Answer 35

Jar test

Question 36

*** When is the ion exchange unit regenerated?

Answer 36

When hardness appears in the finished water/

or when Fe and Mn appear in the finished water

Question 37

*** What is used to clean chemical pumps of calcium carbonate scale?

Answer 37

HC1 37% ( hydrogen chloride)

Question 38

*** The effluent from a manganese filter has a brownish-yellow color and has a high iron and manganese content. What is the most likely cause?

Answer 38

High Alkalinity

Question 39

*** The effluent from a manganese filter has a brownish-yellow color and has a high iron and manganese content? What action should the operator take?

Answer 39

Reduce alkalinity feed before chlorine application.

pH should be 6.2- 6.5

Question 40

*** The effluent from the manganese greensand filter has a higher manganese content than the influent.
What is the likely cause?

Answer 40

insufficient regeneration

Question 41

*** The effluent from the manganese greensand filter has a higher manganese content than the influent. What action is need by the operator?

Answer 41

Regenerate filter with potassium permanganate( KMnO4 ).