In post disaster phase, for ensuring safe water supply, it is advisable to have a Residual Chlorine Level of
**Core Concept**
The residual chlorine level in water is crucial for ensuring its safety for consumption, especially in post-disaster situations where water treatment infrastructure may be compromised. The World Health Organization (WHO) recommends a minimum residual chlorine level of 0.5 mg/L to 1 mg/L to effectively inactivate pathogens and prevent waterborne diseases.
**Why the Correct Answer is Right**
The correct answer is based on the concept of disinfection byproducts (DBPs) and the balance between pathogen inactivation and DBP formation. A residual chlorine level of 0.5 mg/L to 1 mg/L is considered optimal as it effectively inactivates pathogens such as Giardia and Cryptosporidium, while minimizing the formation of DBPs, which are known carcinogens. This balance is achieved by maintaining a sufficient chlorine concentration to ensure water safety without exceeding the maximum allowable limit.
**Why Each Wrong Option is Incorrect**
**Option A:** A residual chlorine level of 0 mg/L is not sufficient to ensure water safety, as it would not inactivate pathogens, increasing the risk of waterborne diseases.
**Option B:** A residual chlorine level of 2 mg/L or higher may lead to the formation of excessive DBPs, which could pose health risks to consumers.
**Option C:** A residual chlorine level of 0.1 mg/L is too low to effectively inactivate pathogens, making it an inadequate choice for ensuring safe water supply.
**Clinical Pearl / High-Yield Fact**
In post-disaster situations, it is essential to conduct regular water quality testing to ensure that the residual chlorine level is within the recommended range. This can be achieved by using portable water testing kits or collaborating with local water treatment authorities.
**Correct Answer: C. 1 mg/L**