Filter - Filter Cycles
Filters remove solids from water. The water flows downward
through the media and is clarified. The solids accumulate in
the media bed.
When the filter begins to clog or when the head loss though the
bed increases, flow rates are dramatically reduced and often
solids “break through“ the filter and water quality
deteriorates. To clean the filter bed, the flow is reversed,
fluidizing the media bed, and is directed to drain. The flow
required is specific to the media. If too much flow is
applied, the bed can be flushed from the tank and if too little
flow is applied, the bed will not fluidize properly and will not
be cleaned. Improper cleaning leads to mud ball formation and
channeling in the filter. The FRF, FMF, and FHF Series all use
nozzle type backwash rate-of-flow controllers. Backwash is made
possible by shifting the Task Masterä
or Task Master IIä
multiport valve so that it allows the water to enter the bottom
of the filter tank and flow upward through the media bed, thus
backwashing filtered solids to drain.
Filter to Waste.
When a filter is returned to service after backwash, the initial
effluent solids concentration from the filter is high. The bed
must be repacked and begin to remove some particulates before it
can become effective. Thus, the first few gallons of a filter
run are usually wasted. This part of the cycle is called
filter to waste.