How much water can be disinfected with a tablet of 0.5 gm chlorine?

Appeared in: IGNOU PB Bsc Nsg Entrance-2017

Explanation

The standard recommended dosage for household water purification is one 0.5 g chlorine tablet for every 20 litres of clear water.
This dosage is designed to effectively kill most bacteria, viruses, and other pathogens, making the water safe for consumption after a recommended contact time of at least 30 minutes.
This information is a key public health guideline for ensuring safe drinking water in community and emergency settings, as confirmed by sources like Park's Textbook of Preventive & Social Medicine.

Option A: Using a 0.5 g tablet for only 5 litres would result in over-chlorination. While this would disinfect the water, it would likely have a strong, unpleasant taste and smell, and it is an inefficient use of the tablet.
Option B: While disinfecting 10 litres with a 0.5 g tablet is effective, it is not the standard capacity. This represents half the recommended volume, leading to inefficient use of resources.
Option C: Disinfecting 15 litres is less than the tablet's full, recommended capacity. The standard public health guideline specifies 20 litres to ensure optimal and economical use of the resource.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Water purification dosage as background academic context rather than a clinical decision trigger.
Nurses play a crucial role in community health education, teaching families how to make water safe for drinking using simple methods like chlorination to prevent waterborne diseases like cholera, typhoid, and dysentery.
In disaster or emergency situations, nurses must be able to quickly instruct large groups on correct water purification techniques to prevent outbreaks of disease.
What if the water is cloudy or turbid? The nurse should instruct the community to first filter the water through a clean cloth to remove sediment before adding the chlorine tablet. If filtration is not possible, the chlorine dose should be doubled (two 0.5 g tablets for 20 litres).

How to Approach the Question

Identify the core question: It asks for the volume of water disinfected by a specific amount of chlorine (0.5 g tablet).
Recognize this as a factual recall question related to community health nursing and public health standards.
Recall the standard guidelines for water chlorination at the household level.
The standard dosage is one 0.5 g tablet for 20 litres of clear water. Scan the options and select the one that matches this established fact.

Concept Tested & Keywords

QTSVfJArIV1h2W6-9bshsW

E6 Parks TextBook of Preventive & Social Medicine part 2 — Subpart B (pp 233-449 of 464) p. 34-36

Practise the full IGNOU PB Bsc Nsg Entrance-2017

Attempt every question from this paper in a timed mock, then review the full solution for each one.