SheldonThinks Forum

Water from rain or melting snow which does not seep into the ground but just runs off across the land is called storm water runoff. To overcome the water crisis, this water is also treated in many places and used for domestic purposes. The flats in Kerala and Assam are also installing rain water harvesting systems to make use of the abundant rain received in these areas.
 
The storm water needs to be properly treated before domestic use. The media filters used for storm water treatment are generally two chambered with a pretreatment settling basin and a filter bed filled with sand or other absorptive filtering media. In the first chamber the large particles present in the storm water is removed, while the finer particles and other pollutants are removed when the storm water passes through the filtering media in the second chamber. There can be many design variations like the Austin sand filter, Delaware sand filter and multi-chambered treatment train (MCTT).
 
Storm water media filters have a number of advantages. Compared to other filters they are relatively high pollutant removers for sediment and associated pollutants. They find widespread application with sufficient capture volume. Hence they provide significant control of channel erosion and enlargement due to changes to flow frequency relationships resulting from the increase of impervious cover in a watershed.
 
Their disadvantages are that they are more expensive to construct. They also require more maintenance depending upon the sizing of the filter bed. They require greater hydraulic head to operate properly. The filter also gets clogged due to the high solid loads. When constructed with vertical concrete walls they can present aesthetic and safety problems.
 
These filters are best suited for relatively small, impervious watersheds.