NIRE-170-1-6
48
b. Chemical cleaning with the chemical tank located above the membrane tank
(Fig.VIII-3)
(i)
Confirm that the chemical injection valve is closed.
(ii)
Using the chemical tank, mix the desired amount of chemical solution.
(iii)
Discontinue the filtration process and associated module aeration. Next close
the filtrate valve.
(iv)
Slowly open the chemical injection valve to inject chemicals.
(v)
After injecting the chemical, soak the elements for 1 to 3 hours.
(vi)
Close the chemical injection valve, open the filtrate valve, and start module
aeration. Finally resume the filtration process.
*
When starting up the MBR after a chemical cleaning, some residual cleaning
chemical may be present in the filtrated water for 2 or more filtration cycles. It
is recommended that the filtrate flow be directed back into the raw water tank
until no residual cleaning chemical is detected. Before directing the filtrate
from the raw water tank back to the normal filtrate discharge line, test the
filtrate pH and chlorine concentration.
Fig.VIII-3 Chemical Cleaning with Chemical Tank Located
above Membrane Tank
c. Chemical cleaning with the chemical feed pump and relief piping (Fig.VIII-4)
(i)
Confirm that the chemical feed pump is in the off position, both the chemical
feed valve and the chemical injection valve are in the closed position. To
make certain that the filtrate line does not experience too high pressure,
confirm that the height of relief piping is located at 1 m or less from the
Module
Manifold
Filtrated water
valve
Chemical tank
1,000 mm (=10 kPa) or less
O
p
e
n
Low water level of
Membrane Tank
Chemical
injection valve
