The so-called water cushion layer refers to a certain height of space between the surface of the resin layer and the water inlet device. This space is occupied by water during operation or backwashing, so it is called a water cushion.
The water cushion of the fixed bed device has two functions
Provide expansion space for the resin during backwashing. The exchange bed is backwashed and the resin fully expands under the impact of the backwash water. At this time, due to the collision of the resin particles and the impact of the backwash water, the dirt surrounding the surface of the resin particles will be affected. The mud peeled off and was carried away by the backwash water. At the same time, in order to prevent the fine resin particles from being carried away by the water, a suitable buffer space is reserved.
The backwash filter water cushion can slow down the erosion of the resin layer surface by the water flow, and to a certain extent, can make the water flow evenly distributed on the cross section of the exchange bed. The height of the water cushion layer is generally equivalent to 60%-10% of the height of the resin layer