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membrane.
(4)
Circulate the chemical for a fixed time.
(5)
Stop the chemical feed pump.
(6)
Drain the chemical and rinse the cleaning line and the module thoroughly with
product water.
Take appropriate measures to prevent the mis-
operation or accidents that could cause the
chemicals to get into the product water. Check
the piping and correctly position of each valve
before starting the chemical cleaning.
(7)
The standard conditions for chemical cleaning are shown in Table 5.
The concentration and the circulation time shown in Table 5 should be
observed. Otherwise the membrane module may get damaged and/or
the life of membrane may be shortened.
The cleaning temperature should be 20 to 40 degree C.
The circulation flow rate for each type of the module is as follows.
HFU-2020AN: 50 L/min (13 gpm)
HFU-1020AN: 20 L/min (5.3 gpm)
Table 5. Standard conditions for chemical cleaning
Pollutants
Chemicals
Maximum
Concentration
Circulation
Time (hr)
Inorganic substances
Citric acid *
6)
3.0 wt%
1 - 3
Organic substances
Sodium hypochlorite
3,000 mg/L
as chlorine
(10 < pH < 12)
1 - 3
