The common multi-media filters used in water treatment are anthracite quartz sand magnetite filter, activated carbon quartz sand magnetite filter, activated carbon quartz sand filter, quartz sand ceramic filter, etc.

多介质过滤器的滤层设计，主要考虑的因素为：

The main factors to be considered in the design of multi-media filter are as follows:

1、不同滤料具有较大的密度差，保证反洗扰动后不会发生混层现象。

1. The density difference of different filter media is large, which can ensure that there will be no mixing layer after backwashing disturbance.

2、根据产水用途选择滤料。

2. The filter material is selected according to the purpose of producing water.

3、粒径要求下层滤料粒径小于上层滤料粒径，以保证下层滤料的有效性和充分利用。

3. The particle size of the lower filter material is required to be smaller than that of the upper filter material to ensure the effectiveness and full utilization of the lower filter material.

事实上，以三层滤床为例，上层滤料粒径，有密度小的轻质滤料组成，如无烟煤、活性炭；中层滤料粒径居中，密度居中，一般为石英砂组成；下层滤料由粒径更小，密度的重质滤料组成，如磁铁矿。由于密度差的限制，三层介质过滤器的滤料选择基本上是固定的。上层滤料起粗滤作用，下层滤料起精滤作用，这样就充分发挥了多介质滤床的作用，出水水质明显好于单层滤料的滤床。而对于饮用水，一般禁止使用无烟煤，树脂等滤料。

In fact, taking the three-layer filter bed as an example, the upper filter material has the largest particle size and is composed of light filter materials with low density, such as anthracite and activated carbon; the middle filter material has a medium particle size and a medium density, which is generally composed of quartz sand; the lower layer is composed of heavy filter material with the smallest particle size and the largest density, such as magnetite. Due to the limitation of density difference, the selection of filter material for three-layer media filter is basically fixed. The upper filter material plays the role of coarse filtration, and the lower filter material plays the role of fine filtration, thus giving full play to the role of multi-media filter bed, and the effluent quality is obviously better than that of the single-layer filter bed. For drinking water, it is generally forbidden to use anthracite, resin and other filter materials.

多介质过滤器主要由过滤器体、配套管线和阀门构成。

The multi-media filter is mainly composed of filter body, matching pipeline and valve.

其中过滤器体主要包括以下组件：简体；布水组件；支撑组件；反洗气管；滤料；排气阀(外置)等。

The filter body mainly includes the following components: cylinder; water distribution component; support component; backwashing gas pipe; filter material; exhaust valve (external), etc.

滤料的选择依据

Selection basis of filter material

(1)必须有足够的机械强度，以免在反冲洗过程中很快地磨损和破碎；

(1) It must have enough mechanical strength to avoid rapid wear and breakage in the process of backwashing;

(2)化学稳定性要好；

(2) The chemical stability is good;

(3)不含有对人体健康有害及有毒物质，不含有对生产有害、影响生产的物质；

(3) It does not contain harmful and toxic substances to human health, and does not contain substances harmful to or affecting 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。

(4) The selection of filter media should try to use the filter materials with high adsorption capacity, pollution interception capacity, high water yield and good effluent quality.

在滤料中，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，孔隙大，便于正洗工序中，滤后水顺利通过；同样，反洗工序中，反洗水和反洗空气等能顺利通过。常规配置中，卵石分为四种规格，铺垫方式为自下而上先大后小。

In the filter material, pebbles mainly play a supporting role. In the process of filtration, due to its high strength, stable spacing, and large pores, it is convenient for the filtered water to pass smoothly in the forward washing process; similarly, in the backwashing process, the backwashing water and air can pass smoothly. In the conventional configuration, the pebbles are divided into four specifications, and the paving mode is from bottom to top, first large and then small.