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Step 1: Close all influent and effluent valves
Step 2: Open the valve to the uppermost filter layer
Step 3: Increase the flow rate to 4800 mL/min
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Allow enough time for this layer to now fluidize (~30 seconds).
Step 5: Simultaneously close the middle valve and open the lowermost valve
Once the bottom layer of the filter is fully fluidized, back wash can begin.
Step 6: Wait
The filter must now be allowed to back wash. The water level inside the filter column will rise until it flows over the effluent weir. The sand will remain at ~30% expansion, which is lower than the effluent weir height. The sand will remain in the filter column while the trapped particles are pushed out over the effluent weir. Allow the filter to backwash until effluent water appears clear of particles (~7 minutes).
Return filter to filtration mode
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Step 8: Open all influent and effluent valves
Step 9: Close valve to distribution tank, open an effluent waste valve
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