media failure
Filter Media, produced to a recognized standard and correctly
placed into a well designed filter, will last for at least 15 years.
Many treatment works have media well over 20 years old.
Filter media, itself, rarely fails. It is the system that fails. Failure may
be divided into three main symptoms.
| Loss of Anthracite | |
| Backwash rate too high | |
| Weir not high enough | |
| Water with anthracite spilling over the weir during air scour. | |
| Siphon placed too close to the surface of the media. | |
| Loss of Sand | |
| Broken nozzle | |
| Hole in the filter floor | |
| Contamination of the filter media | |
| Caused by the failure of the backwash system. | |
| Inadequate airscour | |
| Uneven airscour | |
| Inadequate bed expansion [in summer this may be caused by higher water temperatures] | |
| Low backwash rate | |
| Uneven filter media bed | |
| Uneven backwash | |
| Blockage of the underdrain system or nozzles | |
| Mudballing at the interface between the sand and anthracite of a multimedia filter | |
| Water quality failure | |
| Contamination of the filter media | |
| Run times too long | |
| Complete filter media failure with water spouts through the bed | |
Each of these primary causes of filter media failure may
themselves be the result of a multitude of secondary causes.