Water disinfection for preventing water-borne diseases: Which of the following agents or methods are valid for destroying pathogenic bacteria in potable water?

Introduction:
Effective disinfection removes or inactivates disease-causing microorganisms in water. Multiple technologies can achieve this, each with strengths and limitations.

Given Data / Assumptions:

• Goal: Destroy pathogenic bacteria.
• Typical municipal treatment context.
• Common disinfectants considered: chlorine, ozone/iodine, and UV.

Concept / Approach:
Disinfection works via chemical oxidation (chlorine, ozone, iodine) or physical mechanisms (UV damaging microbial DNA). Selection depends on source water quality, cost, and residual needs.

Step-by-Step Solution:
Step 1: Chlorine is widely used, effective, and provides a residual.Step 2: Ozone is a powerful oxidant yielding rapid inactivation but no lasting residual.Step 3: UV irradiation inactivates microorganisms physically and avoids chemical taste.Step 4: Therefore, all three can be valid disinfection methods.

Verification / Alternative check:
Many treatment trains combine these methods, e.g., UV or ozone primary, chlorine for residual.

Why Other Options Are Wrong:
Single-method statements exclude other proven methods; boiling is effective in emergencies but is not the only valid engineered method.

Common Pitfalls:
Assuming residual is required from the primary step; UV and ozone may be followed by low-dose chlorine to maintain residual.

Final Answer:
All of the above