As per BIS (Bureau of Indian Standards) and WHO guidelines for drinking water quality, the permissible limit of total coliform in treated piped water supply is:

• A Less than 10 per 100 mL
• B Less than 5 per 100 mL
• C Less than 50 per 100 mL
• D Zero (absent) per 100 mL ✓

Explanation

WHO guidelines and BIS IS:10500 standards mandate that total coliforms should be absent (zero) per 100 mL in treated drinking water entering the distribution system. Any detectable total coliform in piped drinking water indicates inadequate treatment or post-treatment contamination. Thermotolerant (faecal) coliforms must also be absent; their presence directly indicates faecal contamination.

Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.