Reasons for stacking multi-media filters and solutions
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The bottom of the multi-media filter consists of quartz sand, while the upper part contains anthracite; currently, the anthracite in the upper part is mixed with the quartz sand. I would appreciate some advice from those who are more experienced. Thank you. This post was last edited by li*ch1968 on 2009-4-13 08:31]
It is mostly caused by excessive backwashing intensity and improper operation
The particle size of the bituminous coal in the upper layer (1–2 mm) should be larger than that of the quartz sand in the lower layer (0.5–1 mm), and its density (1.5–1.8) should be lower than that of the quartz sand (2.65)
During backwashing, the intensity of backwashing wasn’t controlled properly; carelessness was shown during the operation..............
It is possible that the backwashing intensity is too high, resulting in an excessive amount of water used for backwashing and thus the formation of chaotic layers； It is also possible that the water distribution system in the lower part of the multi-media filter is uneven, resulting in high backwash water volumes in some areas and low volumes in others, which causes chaotic layering. It is recommended to monitor the expansion height of the filter media during backwashing; if the expansion is excessive, it may be due to an excessive amount of water used for backwashing ； If the expansion height is not significant, it is very likely due to uneven water distribution.
The 5th floor’s explanation is quite comprehensive. One additional point: check whether the filter media is severely damaged; filter media have a certain lifespan, and if a large amount of it is broken, then the filter media will need to be replaced. The typical service life of filter media is around 3 years, and it also depends on the conditions of use.
It is possible that the backwashing intensity is too high, resulting in an excessive amount of water used for backwashing and thus the formation of chaotic layers； It is also possible that the water distribution system in the lower part of the multi-media filter is uneven, resulting in high backwash water volumes in some areas and low volumes in others, which causes chaotic layering. It is recommended to monitor the expansion height of the filter media during backwashing; if the expansion is excessive, it may be due to an excessive amount of water used for backwashing ； If the expansion height is not significant, it is very likely due to uneven water distribution
Check for uneven layering inside the tank; if such unevenness is present, it is likely due to an uneven distribution of the water supply system beneath the filter, resulting in higher backwash water volumes in some areas and lower volumes in others, which causes the uneven layering. If it’s a large-scale disorder in the layering, the main cause is likely improper operation.
It may be due to the high water flow rate during backwashing, as the workers opened the valves too quickly; another possibility is the absence of a distributor at the inlet
It is possible that the backwashing intensity is too high, resulting in an excessive amount of water used for backwashing and thus the formation of chaotic layers； It is also possible that the water distribution system in the lower part of the multi-media filter is uneven, resulting in high backwash water volumes in some areas and low volumes in others, which causes chaotic layering. It is recommended to monitor the expansion height of the filter media during backwashing; if the expansion is excessive, it may be due to an excessive amount of water used for backwashing ； If the expansion height is not significant, it is very likely due to uneven water distribution. Another reason is the clogging and clumping of the filter media. If that’s the case, it can be pickled with hydrochloric acid; I’ve encountered this before.
If the layers have become disordered, it should be possible to re-establish the layers by gradually reducing the amount of water used for backwashing during subsequent backwashing processes~