<prompt> Which of the following is not true about water quality estimation -Chlostridium spores indicate recent contaminationNot more than 5 samples should have coliformsSodium thiosulfate added to neutralize chlorineColiforms must not be detected in 100 ml sample  <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 