Gravity filters are to be used to treat 24000 m3/d of settled effluent at a filtration rate of 200 L/m2.min. The filtrat

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Gravity filters are to be used to treat 24000 m3/d of settled
effluent at a filtration rate of 200 L/m2.min. The filtration rate
with one filter taken out for service for back-washing is not to
exceed 240 L/m2.min. Determine the number of units and the area of
each unit to satisfy these conditions. If each filter is backwashed
for 30 min every 24 h at a wash rate of 960 L/m2.min, determine the
percentage of filter output use for washing if the filter is out of
operation for a total of 30 min/day. What would be the total
percentage of filter output used for backwashing if a surface
washing system that requires 40 L/m2.min if filtered effluent is to
be installed?