Industrial sand filters are occasionally used in the treatment of sewage as a final polishing stage. In these industrial sand filters the sand traps residual suspended material and bacteria and provides a physical matrix for bacterial decomposition of nitrogenous material, including ammonia and nitrates, into nitrogen gas.
FRP Sand Filter
The FRP sand filter should use a multimedia filtration process. Coarser, lighter media should be at the top of the filter bed capable of capturing large particulate matter. Smaller particles should continue down to the successive lower media levels where particles as small at 25 microns should be retained by finer heavier media. The density differences between the media should allow for layer separation after backwashing.
Since sand filter has to be backwashed with raw water, therefore, rinse step should be provided in backwash sequence. The filters should be designed for manual operation, Non-clogged type, and low-pressure drop and should contain a minimum of five separate layers.
FRP GAC (Granular Activated Carbon) used in this filter should be specially graded for water purification. It should have the capability to adsorb most of the organic chemicals, chlorine, insecticides, pesticide, THMs, TCE and PCBs etc. It should remove odor and gives water a natural taste. The filter should have a Spherical top and bottom ends of the tank should be designed to give uniform flow from both the inlet distribution and outlet collection assemblies. The system should provide adequate distribution to uniformly expand the filter bed during backwash and entire media bed should be utilized during the filter cycle.