Sand filtration removes most inorganic substances from water, primarily iron (Fe), ammonia (NH3) and manganese (Mn), remaining after passing through the cartridge filter. At least two sand filters, which contain several layers of quartz sand particles of different granulations, are usually installed in the sand filtration system.
The water flowing through the sand layers must be adequately saturated with oxygen molecules. Without a sufficient amount of dissolved oxygen in the system there is no oxidation of undesirable metals on the surface of the sand particles, so it is not uncommon to see an aerator (air blower) or injectors installed in front of the sand filters on the preparation water tank.
Another important factor that affects the efficiency of a sand filtration system is microbiological bacteria. In order for microbiological bacteria to fully settle and develop in the system, it sometimes takes several months of continuous trial operation of the system. The growth of bacteria in the tank can be accelerated artificially by adding biological fertilizer.
Like all other water treatment systems, sand filters are fully automated. The system is programmed to regenerate or “rinse” itself once a day, so the same quartz sand can be used in the system for a longer period of time.