The procedure for manganese dioxide removal is the same
as the procedure for iron oxide removal, except that anhydrous sodium bisulfite is
added to the solution rather than oxalic acid (see the manufacturer's instructions for the
To remove algae growths, add a 12.5 percent hypochlorite
solution to the tank volume after filling the tank to the proper level (see the
manufacturer's instructions for the proper amounts to use for units of different sizes).
Check the piping and valves and appurtenant equipment twice a
year, including the body-feed equipment. Make any adjustments the manufacturer's
instructions indicate are necessary.
Clean and paint all exterior surfaces, if necessary.
Ion-Exchange Equipment. Ion-exchange maintenance schedule is
summarized in Table 37.
Operating Conditions. Determine the operating condition of the softener
each quarter. Refer to operating records and make such tests and meter readings as
are necessary to determine the following information:
Flow Rate. Natural ion exchangers can operate satisfactorily at a
flow rate of 5 gpm per square foot (3.5 Lps/sq m); synthetic resins operate at a rate of
6 to 7 gpm per square foot (4 to 5 Lps/sq m). Rates higher than these cause
undesirable head loss through the bed and bed packing. Adjust the controls of the flow
rate each quarter.
Backwash Rate. The rate of backwash should be 6 to 8 gpm per
square foot (4 to 6 Lps/sq m) of bed surface. Rates below this value do not clean the
bed properly. Rates too high wash some of the resin out of the softener and reduce its
softening capacity. Adjust the flow rate control to produce the best backwash rate each
Pressure. Each quarter, check operating records for any change in
the difference between inlet and outlet pressure. Any change in head loss through the
softener indicates a problem. A decrease in pressure drop may indicate improper valve
closure or a channelized bed. An increase in pressure drop may indicate a valve not
completely opened, a dirty bed, clogged gravel, or a clogged underdrain system.
Softening Efficiency. Each quarter, check the records to determine
the softening capacity between the regeneration periods. Compare the current amount