The final step in the purification of water on a large scale is?

Daman & Diu Staff Nurse - 2018

Community Health Nursing

Easy

Appeared in: Daman & Diu Staff Nurse - 2018

Explanation

Disinfection is the final stage in large-scale water treatment, following filtration.
Its primary purpose is to eliminate any remaining pathogenic microorganisms (bacteria, viruses) that were not removed in previous stages.
Chlorination is the most common method, which not only disinfects but also provides a 'residual' protective effect against re-contamination in the distribution system.
This step is crucial for ensuring the water is microbiologically safe for public consumption.

Option A: Boiling is not used for large-scale water purification due to its high energy cost and logistical impracticality for treating millions of liters of water.
Option C: Storage is one of the initial steps in water treatment, allowing for natural sedimentation of heavy particles.
Option D: Filtration is a critical intermediate step that precedes disinfection. It removes suspended particles that could otherwise shield pathogens from the disinfectant.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Steps of large-scale water purification as background academic context rather than a clinical decision trigger.
Understanding water purification is fundamental to community health nursing. Nurses play a vital role in educating communities about water safety to prevent waterborne diseases like cholera, typhoid, hepatitis A, and diarrheal diseases.
A key concept in public health is 'residual chlorine'. The small amount of chlorine left in the water after disinfection protects it from re-contamination as it travels through pipes to homes. Nurses may need to explain this to address community concerns about the taste or smell of chlorine.
What if a community's water supply is compromised after a flood? The nurse's priority is to advise residents on immediate household water safety measures, such as boiling water for at least one minute or using chlorine tablets, until the municipal supply is declared safe again.

How to Approach the Question

First, identify the key phrases in the question: 'final step' and 'large scale'. This immediately sets the context for municipal water treatment, not household methods.
Second, mentally list or recall the standard sequence of large-scale water purification: Storage, Filtration, and then Disinfection.
Third, evaluate each option against this sequence and scale. 'Boiling' is small-scale. 'Storage' is an initial step. 'Filtration' comes before the final step.
Fourth, conclude that 'Disinfection' is the only option that fits the criteria of being the 'final step' in a 'large-scale' process, designed to ensure microbiological safety before distribution.

Concept Tested & Keywords

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E6 Parks TextBook of Preventive & Social Medicine part 2 — Subpart B (pp 233-449 of 464) pp. 28-30, 31-33