How much bleaching powder is required to disinfect 1000 liters of water?

Haryana CHO - 2022

Community Health Nursing

Easy

Appeared in: Haryana CHO - 2022

Explanation

The standard recommended dose for disinfecting clear water is 2.5 grams of bleaching powder per 1000 liters.
This dosage is calculated to satisfy the water's chlorine demand and leave a free residual chlorine level of at least 0.5 mg/L for safety.
Fresh bleaching powder typically contains about 33% available chlorine, and the 2.5g dose provides approximately 0.7 mg of chlorine per liter.
A minimum contact time of 60 minutes is required for the chlorine to effectively kill harmful microorganisms.

Option A: 0 grams is likely an insufficient dose (under-dosing) for 1000 liters of water. It may not be enough to meet the chlorine demand and leave the required 0.5 mg/L of free residual chlorine, leading to incomplete disinfection and risk of waterborne diseases.
Option B: 0 grams is an excessive dose (over-dosing) for 1000 liters of clear water. This would result in a very high level of residual chlorine, making the water unpalatable (unpleasant taste and smell) and potentially causing irritation.
Option D: 5 grams is more than the standard recommended dose for clear water. While it would likely disinfect the water, it would probably result in an unnecessarily high level of residual chlorine, affecting the taste and smell of the water.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Water Disinfection Dosage Calculation as background academic context rather than a clinical decision trigger.
Proper water disinfection is a cornerstone of public health, critical for preventing outbreaks of waterborne diseases such as cholera, typhoid, dysentery, and gastroenteritis.
Nurses in community health settings must be able to educate families and communities on simple, effective water purification methods like chlorination, especially during emergencies like floods or in areas with unsafe water supplies.
What if? - If the water is visibly muddy or turbid, the chlorine demand increases significantly. In this case, the standard 2.5g dose would be insufficient. The water should first be filtered or allowed to settle, and the correct bleaching powder dose must be determined using a Horrocks' apparatus to ensure effective disinfection.

How to Approach the Question

Identify the keywords in the question: 'bleaching powder', 'disinfect', and '1000 liters of water'.
Recognize this as a factual recall question based on public health guidelines for water safety.
Recall the standard dose of bleaching powder required for water purification.
The established guideline for relatively clear water is 2.5 grams of bleaching powder per 1000 liters.
Compare this standard value with the given options.
Select the option that matches the recalled fact, which is 2.5 gms.

Concept Tested & Keywords

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E6 Parks TextBook of Preventive & Social Medicine part 2 — Subpart B (pp 233-449 of 464) pp. 34-36, 33-35