What it means
Filtration is a polishing step, not a substitute for failed coagulation. As particles accumulate in the filter bed, headloss increases and effluent quality can decline. Operators monitor turbidity, headloss, filter run time, and backwash performance.
What operators watch
- Filtered-water turbidity is a critical finished-water quality indicator.
- Headloss rise helps determine when a filter needs backwashing.
- Backwashing must expand and clean the media without washing it out.
Common exam traps
- Thinking filters remove dissolved chemicals by default.
- Missing the relationship between coagulation performance and filter run length.
- Confusing filter-to-waste with normal production.
Field example
A filter that reaches terminal headloss quickly may point to poor coagulation, excessive loading, mudball formation, or an incomplete backwash.
