WATER TREATMENT

When the water is turbid, installation of a filtering screen and sand filter unit becomes necessary. The filter chamber may be constructed adjoining the holding tank. There are two types of filter systems: (a) gravity filter where water is pumped into the filter chamber over the surface of the filter bed and allowed to pass through the filter material by gravity to the holding chamber which is located under the filter chamber and (b) reversing filter where water is pumped directly to the space under the filter chamber and pumped upward through the filter to the surface and on to the holding tank. In both systems, the filter chamber usually contains either white sand, charcoal, gravel, or all the three as filter material. The advantage of the reverse system is that water pass slowly through the filter material and the whole surface area of the filter is utilized. It is easy to backwash by spraying water from the surface of the filter and the detritus underneath are easily washed out.