<prompt> Loss of Head is:Death of a head of a familyIncreased resistance to filtration in a sand filter related to filtration capacityDeath of a head in village panchayatDeath of a school teacher who is also a healthy worker of a school  <response>: RAPID SAND OR MECHANICAL FILTERSFiltration removes the remaining alum not removed by sedimentation. As filtration proceeds, the suspended impurities and bacteria clog the filters resulting in their reduced efficiency called loss of head.BackwashingRapid sand filters need frequent washing daily or weekly, depending upon the loss of head. Washing is accomplished by reversing the flow of water through the sand bed, which is called backwashing. It helps in dislodging the impurities and cleaning up the sand bed. Essentials of preventive and community dentistry Soben Peter 5th edition 