Social & Preventive Medicine All of the following statements about purification of water are true, EXCEPT: A Level of residual chlorine in water should be 0.5 mg / L B Presence of Clostridium spores indicates recent contamination C Coliforms must not be detectable in any 100 ml sample of drinking water D Coliforms may be detected by multiple tube method and indole production 💡 Explanation All of the following statements about purification of water are true, EXCEPT: ✓ Correct Answer: B. Presence of Clostridium spores indicates recent contamination