Sand filters use relatively coarse sand and other granular media to remove particles and impurities that have been trapped in a floc through the use of flocculation chemicals - typically salts of Aluminium or Iron. Water and flocculant flows through the filter medium under gravity or under pumped pressure and the flocculated material is trapped in the sand matrix.
   The filter controller allows automatically backwash by timer, which can avoid from any human mistakes from manually cleaning