Now in large-scale water treatment projects, multi-media filters play an increasingly important role, but if we are careful, we will find that sometimes the filter media in the filter will occur coagulation phenomenon, the following Shandong multi-media filter manufacturers will give us an analysis of the reasons for this!
(1) If the contamination on the surface of the filter layer can not be removed effectively within a certain period, in the subsequent backwashing process, if the distribution of backwashing air is not uniform, the expansion height will be uneven. With the rubbing of the backwashing air, where the rubbing amount is small, the oil contamination and other impurities on the surface of the filter material can not be removed effectively. After entering the next normal filtering cycle, the local load will increase. Large impurities will sink from the surface into the interior, the pellets will gradually increase, and at the same time extend to the filter filling depth, until the whole filter fails.
Note: In actual operation, uneven backwash air often occurs, mainly due to perforation of bottom gas distribution pipeline, blockage or damage of local filter cap or deformation of grid pipe spacing.
(2) The surface of the filter layer has small particles, less chance of collision and less momentum when backwashing, so it is not easy to clean. Attached sand particles tend to form small mud balls. When the backwash is finished, the mud ball enters the lower filter material and moves to the depth with the growth of the mud ball.
(3) The oil contained in the raw water, which is intercepted in the filter, washed back and the residual part, accumulated over time, is the main factor leading to the filter material hardening. When to carry out backwashing can be determined according to the water quality characteristics of raw water and the water quality requirements of effluent, using the criteria of limited head loss, effluent quality or filtration time.
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