In the process of water treatment, filtration generally refers to the process of using quartz sand, anthracite and other granular filter material layer to intercept suspended impurities in water, so as to make water clear. The main function of filtration is to remove the suspended colloidal impurities in water, especially the micro particles and bacteria that can not be removed by precipitation technology. BOD5 and COD also have a certain degree of removal effect. In the industrial circulating water treatment system, the multi-media filter is used to remove the impurities in the sewage, adsorb oil, etc., and make the water quality meet the requirements of recycling.

(1)滤料的机械强度一定要好防止在反冲洗过程中很快地破碎和磨损；

(1) The mechanical strength of the filter material must be better to prevent it from breaking and wearing quickly in the backwashing process;

(2)滤料的化学稳定性要好

(2) The chemical stability of filter material is better

(3)配套管线和阀门。其中多介质过滤器体又包括①简体；②反洗气管；③布水组件；④支撑组件；⑤滤料；⑥排气阀(外置)等。

(3) Matching pipelines and valves. The multi-media filter body also comprises a cylinder body; ② Backwash the trachea; ③ Water distribution components; ④ Support components; ⑤ Filter media; ⑥ Exhaust valve (external), etc.

过滤器体；滤料的选择依据：滤料不应该含有对人体健康有害的有毒物质，不应含有影响生产，对生产有害的物质；

Filter body; The selection basis of filter material: the filter material should not contain toxic substances harmful to human health and production;

(4)滤料的选择，应尽量采用吸附能力、截污能力大、产水量高、出水水质好的滤料。其中的卵石，主要是起支撑作用，在过滤工艺过程中，因其强度高，相互之间的间距缝隙稳定，即孔隙大，便于正洗工序中，滤后水顺利通过；反之反洗工序中，反洗水和反洗空气等顺利通过。常规配置中，卵石分为四种规格，铺垫方式，先大后小。

(4) The selection of filter materials should try to use the filter materials with high adsorption capacity, high sewage interception capacity, high water yield and good effluent quality. In the process of filtration, because of its high strength, the gap between them is stable, that is, the pores are large, which is convenient for the smooth passage of filtered water in the washing process; On the contrary, in the backwashing process, the backwashing water and air pass smoothly. In the conventional configuration, the pebbles are divided into four specifications, and the paving method is large first and then small.

滤料的粒径和装填高度之间的关系：滤床的高度和滤料的平均粒径的比值为800～1ooo(设计规范)。滤料的粒径的大小和过滤精度相关。

The relationship between the particle size of filter media and the loading height: the ratio of the height of filter bed to the average particle size of filter media is 800 ~ 1OOO (design specification). The particle size of filter media is related to the filtration accuracy.