Slow sand filters

SLOW SAND FILTERS

• These filters are also called slow sand gravity filters as water passes through the filter media under the force of gravity (water standing over the filter bed is exposed to the atmospheric pressure
• They are used to remove a larger percentage of impurities and bacteria from water (as compared to rapid sand filters)
• The only drawback of these filters is that the yield is very less as compared to rapid sand filters and thereby require large areas of land for comparatively large yields and hence are more expensive
• In modern treatment plants, they are replaced by rapid sand filters and the resultant supplies are disinfected
• A detailed description of slow sand filters can be found at this link