Softener Systems Flashcards
Lime will precipitate noncarbonate hardness from the water,
but it also forms noncarbonate salts that cause
noncarbonate hardness. what are these salts?
CaSO4
&
CaCl2
In the lime-soda ash softening process, smaller plants find
that _______ is less expensive to purchase; regardless
of the size of the plant, ________ needs to be mixed long
enough because it dissolves rather slowly.
- calcium hydroxide
- lime
Because lime slurries have a _______ and a _______ in
water, calcium carbonate will _______ on anything the
slurry touches.
- high pH
- low solubility
- precipitate
After water has been softened, it is close to pH 11; thus,
it needs to be stabilized by a process known as
recarbonation. What small amount of hardness chemical
is formed and what is precipitated in this process?
- calcium bicarbonate
and
- magnesium carbonate
What two major problems will improperly stabilized
softened water cause?
Scale deposits
or
Corrosive water
How is hardness expressed in the ion exchange process?
Grains/gal
How is magnesium noncarbonate hardness removed?
With lime then soda ash
The excess lime-softening process is used so that _______
will precipitate out of the water.
Magnesium hydroxide
Preoxidation has been shown to improve _________.
Floccculation, Sedimentation, Filtration
What is conventional treatment?
Coagulation, Flocculation,
Sedimentation, and Filtration
What type of flash-mixing process gives the best
mixing and control?
Mechanical mixers
The lime-softening process used in removing iron works in
the pH range of ________.
10pH to 11pH
What plant-operating factor could make a difference in
the proper development of floc?
Inadequate flocculation time.
When sodium fluoride solutions are used with hard water,
insoluble compounds of ________ can form.
calcium and magnesium fluoride
Lime should be added to the water being treated with
as _______ a distance between the feeder and
the water as possible.
short
