Backwashing of multi-media filters mainly refers to the interception and adsorption of a certain amount of impurities and stains by the filter material layer after a certain period of use, which makes the water quality of the filters'effluent decrease. The main characteristics are: the water quality of the filters becomes worse after normal filtration, the pressure difference between the inlet and outlet pipelines increases, and the flow rate of a single filter decreases.

反冲洗的原理：水流逆向通过滤料层，使滤层膨胀、悬浮，借助水流的剪切力和颗粒的碰撞摩擦力清洗滤料层使滤层内的污物脱离并随反洗水排出。

The principle of backwashing is that water flows backward through the filter material layer, which expands and suspends the filter layer. The filter material layer is cleaned by shear force of water flow and collision friction force of particles, so that the dirt in the filter layer is separated and discharged with the backwashing water.

反冲洗的必要性

Necessity of backwashing

(1)在过滤过程中，原水中的悬浮物等被滤料层截留吸附并不断地在滤料层中积累，于是滤层孔隙逐渐被污物堵塞，在滤层表面形成滤饼，过滤水头损失不断增加。当达到某一限度时，滤料需进行清洗，使滤层恢复工作性能，继续工作。

(1) In the process of filtration, suspended substances in raw water are intercepted and adsorbed by the filter material layer and accumulated continuously in the filter material layer. As a result, the pore of the filter layer is gradually blocked by dirt, forming filter cake on the surface of the filter layer and increasing the loss of the filter head. When a certain limit is reached, the filter material needs to be cleaned to restore the performance of the filter layer and continue to work.

(2)过滤时由于水头损失增加，水流对吸附在滤料表面的污物的剪切力变大，其中有些颗粒在水流的冲击下移到下层滤料中去，终会使水中的悬浮物含量不断上升，水质变差，当杂质透过滤层时，过滤器失去过滤效果。因此，到一定程度时，需要清洗滤料，以便恢复滤料层的纳污能力。

(2) As the head loss increases, the shear force of water flow on the filtrate surface becomes larger. Some of the particles move to the lower filter media under the impact of water flow, which will eventually cause the suspended matter content in the water to rise continuously and the water quality to deteriorate. When impurities pass through the filter layer, the filter loses its filtering effect. Therefore, to a certain extent, it is necessary to clean the filter material in order to restore the ability of the filter material layer to absorb contamination.

(3)污水中的悬浮物中含有大量有机物，长期滞留在滤层中会导致滤层中细菌微生物富集繁殖，发生厌氧腐败现象，需定期清洗滤料。

(3) Suspended matter in sewage contains a large amount of organic matter. Long-term retention in the filter layer will lead to bacterial and microbial enrichment and reproduction in the filter layer, which will lead to anaerobic corruption. It is necessary to wash the filter material regularly.

反冲洗参数控制和确定

Control and determination of backwashing parameters

(1)膨胀高度：反冲洗时，为了保证滤料颗粒有足够的间隙使污物迅速随水排出滤层，滤层膨胀率应大一些。但膨胀率过大时，单位体积中滤料的颗粒数变少，颗粒碰撞的机会也减少，所以对清洗不利。双层滤料，膨胀率为40％----50％ 。

(1) Expansion height: When backwashing, in order to ensure that there is enough clearance between the filter particles so that the filtrate can be discharged quickly with water, the expansion rate of the filter should be larger. However, when the expansion rate is too large, the number of particles per unit volume of filter material decreases, and the chance of particle collision decreases, so it is not conducive to cleaning. The expansion rate of double-layer filter material is 40%-50%.

注意：在生产运行中，对滤料的填充高度、膨胀高度等随机进行检查，因为正常反洗过程中，会有部分滤料的跑失或磨损，需要进行补充。相对稳定的滤层，有以下优点：确保过滤水质的稳定，保证反冲洗的效果。

Note: In the production and operation, the filling height and expansion height of the filter material are inspected randomly, because in the normal backwashing process, some of the filter material will run away or wear, and need to be supplemented. The relatively stable filter layer has the following advantages: ensuring the stability of the water quality of the filter and ensuring the effect of backwashing.

(2)反洗水量和压力：一般设计要求，反洗水的强度为40 m3／(m2?h)，反洗水的压力≤0．15 MPa。

(2) Backwash water quantity and pressure: General design requirements, the strength of backwash water is 40 m3/(m2?H), and the pressure of backwash water is less than 0.15 MPa.

(3)反洗空气量和压力：反洗空气的强度为15 m ／(m/h)，反洗空气的压力≤0．15 MPa。

(3) Air volume and pressure of backwashing: the strength of backwashing air is 15 m/(m/h), and the pressure of backwashing air is less than 0.15 MPa.

注意：在反洗过程中，通入的反洗空气汇集于过滤器的顶部，大部分应通过双孔排气阀排出。日常生产中。需经常检查排气阀的通畅性，主要表征在阀球升降的自由度上。

Note: In the process of backwashing, the backwashing air is collected at the top of the filter, most of which should be discharged through the double-hole exhaust valve. Daily production. It is necessary to check the patency of exhaust valve frequently, which is mainly characterized by the degree of freedom of ball lifting.

好了，今天的精彩内容就给大家介绍到这里了，如果大家还有疑问欢迎咨询山东多介质过滤器的官网客服人员：http://www.jnlzsb.com

Well, today's wonderful content is introduced here. If you have any questions, please consult the official website customer service staff of Shandong Multimedia Filter: http://www.jnlzsb.com.