Iron, Manganese And Fluoride Questions Flashcards
What is the primary MCL for fluoride?
4
What is the secondary MCL for Fluoride?
2 mg/L
What is the purpose of adding fluoride to water?
To prevent, caries, and cavities
Adding too much fluoride to water will cause?
Mottling your teeth ( staining them brown)
What do you give someone who has swallowed fluoride?
Water or milk?
What is the first symptom of swelling Fluoride?
Vomiting
What is the first symptom of inhaling fluoride?
Nosebleed
If you use sodium fluoride in fluorination, what must be done to the water if the hardness is above 75?
Soften the water
When feeding sodium fluoride with a saturator, above, what water pH will scaling occur?
10 pH
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?
0.65 PPM
In question 10, how many pounds of 100% F ( fluoride) Will be added per day if the WTP treats 10 MGD?
54 lb ( 0.65x10x 8.34)
What is a day tank?
A day tank that holds enough chemicals to feed water produced in a day
What type of pump is used to feed chemicals?
Positive displacement ( piston)
Recommended control limits and fluoride concentrations are based on?
The annual average of maximum daily temperatures
What is the most common fluoride compound used in water treatment?
Hydrofluosilicic acid, sodium fluoride, sodium silcofluoride
When choosing fluoride- pumping equipment, the most important criteria is?
Accuracy
Fluoride doses must never be metered against a?
Negative or suction head?
Fluoride system must be designed with the means to prevent?
Back siphonage and overfeeding
Fluoride systems should be designed by?
An engineer
If an operator gets fluoride on his skin or in his eyes, the recommended first aid is?
Flush with large amount of water for 15 minutes ( eyes- flush and see A doctor)
Never operate a positive displacement pump against ?
Close valves ( especially a discharge valve)
A form of backflow caused by a negative or below atmospheric pressure within a water system is called?
Back siphonage
***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?
Iron Bacteria
***Why is nitric acid added to the sample bottle used to collect iron samples?
To lower the pH to less than 2 to keep the iron in solution
***What chemical is added to iron sample bottles?
HNO3 ( Nitric Acid)
***What is the holding time for iron samples that have not been acidified?
48 hours
***After backwashing a greensand filter, the filter shows a very high pressure loss. what is the cause?
Improper Backwash and or accumulation of greensand fines on filter bed surface
***If the feed water to an ion exchange softening unit has iron and manganese, what will happen during the softening process?
Fe and Mn will be removed
***What will break down the resins in an ion exchange softening unit?
Chlorine
*** Insoluble iron & manganese will cause what problem in ion exchange unit?
Clogging and fouling the resins
** How are ferric hydroxide precipitates removed during water treatment?
Sedimentation and filtration
*** A water system’s well supplies a water that contains dissolved oxygen and iron and manganese. What does this indicate?
Water being drawn from more than one aquifer
*** Where should iron and manganese samples be taken?
As close to the well as possible
*** How can slim growths be controlled in the distribution system?
By maintaining a free chlorine residual
*** How is a proper polyphosphate dosage determined?
Jar test
*** When is the ion exchange unit regenerated?
When hardness appears in the finished water/
or when Fe and Mn appear in the finished water
*** What is used to clean chemical pumps of calcium carbonate scale?
HC1 37% ( hydrogen chloride)
*** 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?
High Alkalinity
*** 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?
Reduce alkalinity feed before chlorine application.
pH should be 6.2- 6.5
*** The effluent from the manganese greensand filter has a higher manganese content than the influent.
What is the likely cause?
insufficient regeneration
*** The effluent from the manganese greensand filter has a higher manganese content than the influent. What action is need by the operator?
Regenerate filter with potassium permanganate( KMnO4 ).
