NIRE-170-1-6
50
If the flow from the relief pipe is excessive make needed
adjustments to the chemical pump discharge flow to reduce relief
pipe discharge flow. Use the safety equipment such as goggles
and gloves when inspecting discharge piping and making
adjustments.
(2) Precautions for Element Chemical Cleaning
a.
Keep the injecting pressure below 10 kPa (100 mbar).
Avoid direct discharge
from the chemical pump to the membrane elements. Too high pressure in the
membrane element will cause damage to the membrane. Please note that injecting
pressure may increase after injecting half of the chemical.
b. Make certain the module is completely submerged in the tank prior to injecting any
chemicals. The liquid level above the module should be maintained at 500 mm or
higher.
c. Elevated chemical cleaning solution temperatures increase the membrane cleaning
effectiveness. However, make certain not to allow the cleaning solution
temperatures to exceed 40 degree C. Conversely, lower cleaning solution
temperatures reduce the effectiveness of the chemical cleaning process. Try to
maintain the cleaning solution temperature as high as possible within the range
below 40 degree C.
d. 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.
e.
If a sodium hypochlorite cleaning is immediately followed by acid cleaning or
in reverse order, make certain that these chemicals never come in contact
with one another in the cleaning tank or piping.
Mixing of the two chemicals will
generate toxic chlorine gas.
f.
If filtrate is used as makeup water for the cleaning solution, there exist the potential
for the formation of insoluble calcium compounds when sodium hypochlorite is
mixed with the filtrate. If a high calcium concentration is expected in the makeup
water, confirm the potential for precipitation by performing a bench-scale sodium
hypochlorite addition test. If a whitish precipitate of calcium forms it is recommend
that tap water be used for the makeup water supply instead of filtrate.
g.
As a result of contacting with hypo solution, some activated sludge nearby
WARNING
!
