Multimedia filter is a process of clarifying water by using one or several filter media to remove suspended impurities effectively by passing turbidity water through granular or non-granular materials with a certain thickness under certain pressure. But we will find that there will be the phenomenon of filter material hardening in use. Today, Shandong Multimedia Filter Xiaobian will give you an analysis of the reasons, hoping to help you all!
1. If the contamination on the surface of the filter layer can not be removed effectively within a certain period, the uneven distribution of the air in the subsequent backwashing process will lead to uneven expansion height. With the rubbing of the air in the backwashing process, where the rubbing momentum is small, the oil contamination and other impurities on the surface of the filter material can not be removed effectively. After putting into the next normal filtration cycle, the local load will increase, the impurities will sink from the surface into the interior, the pellets will gradually increase, and extend to the filling depth of the filter at the same time, 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 fine 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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