<prompt> All of the following statements about purification of water are true except -Presence of Clostridial spores indicate recent contamination of waterColiforms must not be detectable in a ny 100 ml sample of drinking waterSodium thiosulphate is used to neutralize chlorineColiforms may be detected by multiple tube method indole production  <response>: Spores of Clostridium are capable of surviving in water for a longer time than the coliform group of organisms. The presence of Clostridium spores in the absence of coliform group suggest faecal contamination occurred at some remote time. Parks Textbook of Preventive and Social Medicine, 25th edition, Page No. 781 