Before revision: The backwash sequence would typically be: Close inlet valve Isolate controller Allow water to drain down Close outlet valve Start air blower Open air inlet valve Air scour for 0-10 minutes Stop air blowers Close air valve Wait 30 seconds Start washwater pumps Open upwash valve slowly Open wash out valve Wash water for 0-10 minutes Close upwash valve Raise washwater weir Open surface flush inlet, Surface flush for 0-5 minutes Close washout valve Lower washwater weir Bring controller into service Open inlet valve when filter is full The byproduct of backwashing is sludge which is either tankered away or is run to waste .
After revision: The backwash sequence would typically be: Close inlet valve Isolate controller Allow water to drain down Close outlet valve Start air blower Open air inlet valve Air scour for 0-10 minutes Stop air blowers Close air valve Wait 30 seconds Start washwater pumps Open upwash valve slowly Open wash out valve Wash water for 0-10 minutes Close upwash valve Raise washwater weir Open surface flush inlet, Surface flush for 0-5 minutes Close washout valve Lower washwater weir Bring controller into service Open inlet valve when filter is full The byproduct of backwashing is sludge .