| 摘要 |
A filter bed filled with active carbon granules cleans descending water for removal from under the bed base when the upper section of the bed is satd. with insoluble material, water flow is reversed, with flushing water rising through holes in the bed base. Because of the inwardly inclined shape of the side walls and an inserted displacement member, the cross-sectional area of the bed's surface is about 20-50% less than near its base, and hence the flushing water speed increases from its initial entry value, and near the surface is sufficient to fluidise the carbon granules, while leaving the lower granules at rest. The fluidised granules are removed through a lateral conduit. Only the heavily soiled upper granules are removed, and this without a separate fluidising grid for the top of the bed as in a known device. The lightly soiled lower granules are removed subsequently and used as the upper layer to a base of fresh granules. |
