Water - I: Sources and purification of water MCQs

Answer: Contact carrier→ get infection from case Paradoxical carrier→ get infection from another carrier Pseudo carrier- carry avirulent organisms Reference: Park's Preventive and social medicine, 27th edition, Chapter Principles of Epidemiology & Epidemiology methods.

Explanation: The standard public health guideline for effective disinfection of drinking water via chlorination is a free residual chlorine level of 0.5 parts per million (ppm) after a contact time of at least 1 hour . (Option B,C and D ruled out) This combination ensures that a sufficient concentration of the disinfectant has been in contact with the water long enough to inactivate pathogenic microorganisms. Key Takeaways: The benchmark for effective well water chlorination is 5 ppm free residual chlorine after 1 hour of contact.

The correct amount of beaching powder required to disinfect 455 L of water with a chlorine concentration of 3 mg/L is approximately 6 grams. Horrock's apparatus first shows the 3rd cup blue, indicating a chlorine concentration of 3 mg/L. Volume of water to be treated = 9100 Liters. If it takes 6gm to disinfect 455L Then how much does it take to disinfect 9100L Amount of bleaching powder required = (6*9100)/455 = 54600/455 = 120 grams Therefore, option A (120 grams) is the correct choice. In summary, the correct amount of bleaching powder required to disinfect 9100 Liters of water with a chlorine concentration of 3 mg/L, as indicated by the Horrock's apparatus, is approximately 120 grams. Reference: Park's Preventive and social medicine, 27th EDITION Pg 855

Explanation: Target (Option A): This is a specific, quantifiable measure of progress towards an objective, not the ultimate desired state itself. Mission (Option B): This describes the core purpose and fundamental reason for an organization's existence, not the future health state it aims to achieve. Plan (Option D): This is a detailed blueprint outlining the specific actions, timelines, and resources required to accomplish objectives.

As population numeration is done from 8-28th February and stopped on 1 st march. The point at which the numeration is completed is called as Census Stop or moment at 00:00 hrs of 1 st March Why the other options are not correct: 5th June (Option C): World environment day 1st July (Option B): While July 1st is used to measure the mid-year population 1st January (Option D): January 1st is too early in the year