Drinking water hygiene What is the principal public health concern associated with the presence of bacteria in potable (drinking) water supplies?

Introduction / Context:
Safe drinking water is defined primarily by its microbiological quality. While aesthetic parameters such as taste, odour, and colour are important to consumers, regulatory frameworks focus foremost on eliminating pathogenic microorganisms that cause waterborne diseases like cholera, typhoid, and dysentery.

Given Data / Assumptions:

• Potable water refers to treated water entering distribution systems.
• “Presence of bacteria” means potential presence of pathogens or indicator organisms (e.g., coliforms).
• Aesthetic issues are secondary to health protection.

Concept / Approach:
Human pathogens transmitted via water include bacteria, viruses, and protozoa. Even when turbidity and odour are acceptable, the presence of pathogenic bacteria can cause outbreaks. Therefore, disinfection (e.g., chlorination, UV) and barriers (coagulation, filtration) target microbial safety first. Indicator tests (total coliforms, E. coli) serve as proxies for pathogen intrusion.

Step-by-Step Solution:

Verification / Alternative check:
Epidemiological data link bacterial contamination to gastrointestinal illness; WHO and national standards emphasise pathogen removal and residual disinfectant maintenance.

Why Other Options Are Wrong:

• Turbidity / Bad odour / Bad taste and colour: Important but primarily aesthetic; they can accompany contamination but are not the core health risk.
• Scaling of pipes: A water chemistry issue, not directly related to bacterial presence.

Common Pitfalls:
Equating clear water with safe water; pathogens can be present even when appearance and odour are acceptable.

Final Answer:
Disease