Backwashing is performed when which conditions exceed limits?

Backwashing is performed when which conditions exceed limits?

• A. Headloss, turbidity, or time exceeds limits.
• B. During routine operation.
• C. After chemical dosing.
• D. When filter ripening completes.

Answer: (A)

Backwashing is performed when the filter shows signs that it’s losing its ability to filter effectively. The usual signals are the headloss across the filter rising beyond its limit, the filtered water’s turbidity increasing beyond what’s allowed, or the time since the last backwash reaching a preset limit. When any of these limits are exceeded, reversing the flow to clean the bed restores pore space, reduces the pressure drop, and improves filtration performance. Backwashing during routine operation isn’t appropriate because it interrupts production and wastes water. It isn’t tied to chemical dosing, which is a pretreatment step for coagulation. Ripening is the period after a backwash when the bed re-stabilizes and begins filtering again; backwashing starts that process, not waiting for it to complete.

Backwashing is performed when the filter shows signs that it’s losing its ability to filter effectively. The usual signals are the headloss across the filter rising beyond its limit, the filtered water’s turbidity increasing beyond what’s allowed, or the time since the last backwash reaching a preset limit. When any of these limits are exceeded, reversing the flow to clean the bed restores pore space, reduces the pressure drop, and improves filtration performance.

Backwashing during routine operation isn’t appropriate because it interrupts production and wastes water. It isn’t tied to chemical dosing, which is a pretreatment step for coagulation. Ripening is the period after a backwash when the bed re-stabilizes and begins filtering again; backwashing starts that process, not waiting for it to complete.