Potable water assessment – single most important parameter for domestic use For judging the suitability of a water supply for domestic (drinking) purposes, which water quality parameter is considered the most important indicator of safety?

Introduction:
Drinking-water safety hinges on protection against waterborne disease. While many chemical parameters affect aesthetics and long-term health, microbial contamination represents the most immediate risk. Hence, public health practice emphasizes microbiological indicators that signal fecal contamination and the possible presence of pathogens.

Given Data / Assumptions:

• Domestic potable use (drinking, cooking).
• Routine compliance monitoring context.
• Use of indicator organisms to infer sanitary quality.

Concept / Approach:

Coliforms (especially Escherichia coli or thermotolerant coliforms) are used as indicator organisms. Their detection suggests fecal contamination, and thus potential presence of pathogens like viruses, protozoa, and bacteria. While hardness, chlorides, and DO affect taste, scaling, corrosion, or aesthetic acceptability, they are not immediate indicators of infectious disease risk.

Step-by-Step Solution:

Verification / Alternative check:

Guidelines for drinking-water quality consistently require zero detectable E. coli per 100 mL in treated supplies, underscoring priority over hardness or chloride levels.

Why Other Options Are Wrong:

Carbonate and non-carbonate hardness influence taste/scale; chlorides and DO are secondary for domestic acceptability compared with microbial safety.

Common Pitfalls:

Equating ‘‘good-tasting’’ water with safe water; ignoring that clear, odorless water can still be microbiologically unsafe.

Final Answer:

coliform group of organisms