Which is a valid backwash timing indicator for a rapid sand filter?

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Multiple Choice

Which is a valid backwash timing indicator for a rapid sand filter?

In rapid sand filtration, the bed gradually collects solids, which makes it harder for water to pass through. That increased resistance shows up as higher headloss across the filter. When headloss climbs to a set limit, it means the media is sufficiently clogged and needs backwashing to restore porosity and flow. So an increasing headloss is the reliable signal to initiate backwash. A decrease in headloss would indicate the bed is cleaner or has just been backwashed, not when to backwash next. A rise in pH isn’t a dependable indicator of filter clogging. A decrease in influent flow may happen for other reasons and doesn’t directly reflect the filter’s clogging state.

In rapid sand filtration, the bed gradually collects solids, which makes it harder for water to pass through. That increased resistance shows up as higher headloss across the filter. When headloss climbs to a set limit, it means the media is sufficiently clogged and needs backwashing to restore porosity and flow. So an increasing headloss is the reliable signal to initiate backwash.

A decrease in headloss would indicate the bed is cleaner or has just been backwashed, not when to backwash next. A rise in pH isn’t a dependable indicator of filter clogging. A decrease in influent flow may happen for other reasons and doesn’t directly reflect the filter’s clogging state.

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