What should be the amount of Free Residual Chlorine in drinking water?

Raj. CHO -2020

Community Health Nursing

Easy

Appeared in: Raj. CHO -2020

Explanation

The recommended range of 0.5 to 0.8 mg/L for free residual chlorine ensures effective and continuous disinfection of drinking water.
According to public health standards, a minimum free residual chlorine level of 0.5 mg/L for one hour is essential to kill bacteria and viruses.
This level provides a margin of safety against potential recontamination as water travels through the distribution system to the consumer.
The effectiveness of chlorination is optimal at a water pH around 7.

Option A: A concentration of 0.25 mg/L is considered the minimum acceptable level at the consumer's tap but is not the ideal target for the water supply system as it may not provide a sufficient safety margin against recontamination.
Option C: A concentration of 1.0 mg/L is higher than necessary for routine disinfection and can lead to unacceptable taste and odor, causing consumers to reject the water.
Option D: A concentration of 2.0 mg/L is a very high dose used for shock treatment or superchlorination of water sources, not for potable water meant for direct consumption.

Visual 1: Infographic - A chart showing the different levels of free residual chlorine and their corresponding applications (e.g., routine, emergency, superchlorination).
Visual 2: Diagram - An illustration of a DPD (N,N-diethyl-p-phenylenediamine) colorimetric test kit, showing the color change that indicates the presence and concentration of residual chlorine.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Water Purification and Disinfection Standards as background academic context rather than a clinical decision trigger.
Nurses in community settings must be knowledgeable about safe drinking water standards to educate families and communities, especially in rural or underserved areas.
During outbreaks of waterborne diseases like cholera or typhoid, nurses are key in implementing and advising on emergency water disinfection procedures.
What if? If a community reports a sudden increase in gastrointestinal illnesses, a nurse should immediately consider water contamination as a possible cause and advocate for testing of the local water supply, including residual chlorine levels.

How to Approach the Question

Identify the core question: The question asks for the standard recommended amount of a specific chemical (Free Residual Chlorine) in drinking water.
Recognize this as a factual recall question based on public health guidelines.
Evaluate the options based on standard knowledge of water treatment. Think about the purpose of residual chlorine: it needs to be strong enough to kill germs but not so strong as to be unpalatable or harmful.
Eliminate the extremes: 0.25 mg/L seems too low for a safety margin, and 1.0-2.0 mg/L seems too high for routine consumption.
Select the option that represents the established safe and effective range for public water supplies, which is 0.5 to 0.8 mg/L.

Concept Tested & Keywords

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