05
Commercial Filter Manual |
AIR SCOUR BACKWASH
Waterco SPDD and MPD series nozzle plate vessels may use air assisted backwash.
SM/SMD/SMDD and M/MD series, custom air scour laterals and 2”ARV must be included to allow
air assisted backwash.
Please consult Waterco prior to ordering vessels so that suitable vessels can be quoted and
constructed.
There are two options of air scour backwashing available;
1.
Air only followed by water flush
2. Air + water
Waterco does not recommended using air OR air and water at the same time without suitable
design by a qualified hydraulic engineer.
Air velocity is generally 50m3/m2/hr or 3-5 CFM/ft2 depending on method, and provides a more
efficient backwash method saving up to 25% water per backwash.
The time taken to backwash various types of media will vary, depending on;
1.
If the backwash is air scour assisted
2. The debris, density or content of collected material
3. The media type
4. The backwash velocity
5. If flocculants are used
As a general guide, backwashing using a velocity of 36-48m3/m2/hr or 15-20 US gpm/ft2 may take
between 3-5 minutes depending on media loading. Additionally backwashing while injecting air
requires a reduction in backwash flow rate of 30-50% to prevent loosing the media.
NOTE: Up-flow filtration should only be performed if the vessel has been specifically designed
for this use. Please consult Waterco prior to ordering vessels for up flow use.