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、截留在滤层上表层的污物，如果在一定周期内，不能有效地去除，在随后的反洗过程中，如果反洗空气的分布不均匀会导致膨胀高度不均匀，随着反洗空气的搓动，搓动量小的地方，滤料表面的油污等杂质不能有效去除，在投入下一正常滤水周期后，局部负荷增大，杂质会从表面沉入内部，球团逐渐增大，并同时向过滤器的填充深度内延伸，直整个过滤器失效。

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.

备注：实际运行中，反洗空气不均匀的现象经常出现，主要是由于底部布气管道的穿孔、局部滤帽的堵塞或损坏或是栅管间距的变形等原因引起。

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、滤层的表面滤料颗粒细小，反冲洗时相互碰撞机会少，动量小，所以不易清洗干净。附着的砂粒易结成小泥球。当反冲洗结束滤层重新级配时，泥球就进入下层滤料中，随着泥球的长大不断向深处移动。

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、原水中所包含的油，截留在过滤器内，经反洗并残余部分，日积月累，是导致过滤器滤料板结的主要因素。何时进行反洗可根据原水的水质特点和出水水质要求，采用限定水头损失、出水水质或过滤时间等标准来确定。

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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