The 'chlorine demand' of a water sample is defined as:

• A The amount of chlorine required to kill all pathogenic bacteria in the sample
• B The quantity of chlorine consumed only by organic matter during contact
• C The residual chlorine present at the consumer's end of a piped supply
• D The difference between the amount of chlorine applied and the residual chlorine remaining after a given contact period ✓

Explanation

Chlorine demand equals the dose applied minus the residual remaining after a stated contact time, because chlorine is consumed by organic matter, ammonia, iron, manganese and other reducing substances. It is not a bactericidal endpoint, and it is broader than consumption by organics alone since ammonia and inorganic reducers also exert demand. Breakpoint chlorination is reached once this demand is fully satisfied.

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.