The filter effluent manganese values are higher than the filter inlet
water, yet
the iron content is low and the filter effluent is
clear. What is the problem with
the greensand filter?
Manganese being leached from the greensand media
Which polyphosphate chemical is more effective at lower dosages?
Sodium metaphosphate
Why is lime sometimes added to water that is being aerated?
Increase pH and help remove CO2
Looking at the plumbing fixtures to see if stains are present is a
good way to
tell what?
If iron or manganese are present
What is the recommended detention time to allow the continuation of
iron
oxidation after aeration?
30-60 minutes
Iron can be oxidized by aerating the water to form insoluble ferric
hydroxide.
This reaction is accelerated by an increase in what?
•Aeration SCFM
•pH
•CO2
•Dissolved oxygen
Why must chlorine be fed along with polyphosphate?
To prevent iron bacteria from growing
In oxidation of iron using aeration, an increase in pH has what
effect on the
reaction?
Accelerates the reaction
Problem with the manganese greensand filtration system. The effluent
is
turbid with a yellow to brown color. The effluent iron and
manganese results
are high. What is the cause of the filter problem?
The lime dose ahead of the filter is too high
Potassium permanganate is often used with what type of filtration media?
Manganese zeolite or manganese greensand
Pink colored filtered water from a greensand filter is an indication of what?
The permanganate dose is too high
Why should chlorine never be fed ahead of the polyphosphate?
The chlorine will oxidize the iron and manganese causing
insoluble
precipitates to form too soon
Manganese greensand filters can be operated in three
modes:
continuous regeneration, catalytic regeneration and what
other method?
Intermittent regeneration
Which chemical is effective in oxidizing iron and manganese to insoluble
oxides?
Potassium permanganate