Minimum recommended dose of “free” residual chlorine in water for routine chlorination (in mg/L)-
Correct Answer: 0.5 mg/L for a contact period of 1 hr.
Description: (A) (0.5 mg/L for contact period of 1 hr) (663 - Park 22nd)Residual chlorine:* Presence of free residual chlorine (Minimum recommended concentration = 0.5 mg/LQ]for a contact period of at least 1 hourQ is essential to kill bacteria and viruses.* The point at which chlorine demand of the water is met is called the "break-point". If further chlorine is added beyond the break point, free chlorine (HOCI & OCI) begins to appear in water in proportion to added dose of chlorine.* Free residual chlorine provides a margin of safety against subsequent microbial contamination (during storage and distribution).* Dose of chlorine to be applied - Chlorine demand of specific water + Free residual chlorine (0.5 mg/L).Principles of chloriantion:* Water to be chlorinated should be clear and free from turbidity.* Chlorine demand of water (Difference between the amount of chlorine added to water and amount of residual chlorine remaining at the end of a specific period of contact (usually 1 hour), at a given temperature and pH of the water) should be estimated.CHLORINATION* Horrock's apparatus: Designed to estimate the chlorine demand** of water and to find out the dose of bleaching powder required for disinfection of water. Indicator solution is starch iodide**.(i) Berkefeld filter - used for filtration of water on small scale.(ii) Double rod method - is used for chlorination of well.(iii) Chloroscope - is used for measuring residual chlorine level.* Ortho-tolidine test - is used to detect chlorine in water.*** Colour produced after a lapse, 15-20 minute is due to action of both free and combined chlorine*** In fresh bleaching powder available chlorine is 33%.* Disinfecting action of chlorine on water is mainly due to Hypochlorous acid*** Chlorine acts best when pH is around 7* One tablet of chlorine is effective to disinfect 20L of water.* Drawback of ozone as water disinfectant is No residual germicidal effect.**** Temporary hardness of water is primarily due to the presence of calcium and magnesium bicarbonates.* Permanent-hardness is due to calcium and magnesium sulphate, chloride and nitrates.* Recommended hardness of water 50-50 meq/L softening is recommended when hardness exceeds 3 mEq/L (50 mg per liter of CaCO3 in one litre of water).High Yeild Points1. Test of pasteurised milk is - phosphatase test, standard plate count, colliform test (Eijkman test or indole production)Coliform test for water contamination2. HAV-C is most prevalent in India (HAV-A in world wide)3. Light index in living room is 8% (kitchens - 10%)4. Floods, tsunamis are associated with maximum death in disasters (hydrological disasters)5. ASHA - accredited social health activist6. Zero incidence is - elimination of disease7. I. Most common cancer in males in India - oro-pharyngeal ca (aero-digestive ca)II. Most common cancer in males in world - Lung CaIII. Most common cancer in female in India - Cervical CaIV. Most common cancer in female in world - Breast CaV. Most common STD in India - chlamydial infection (viral - HPV, protozoal - trichomonas vaginalis)8. Vagabond's disease is pediculosis corporis caused by body louse9. Anopheline culcifacies - main vector for rural and periurban areasAnopheline - stephensi - responsible for malaria in urban and industrial areas10. Multidrug treatment in TB is given inI. Prevent emergence of peristersII. Prevent relapseIII. Prevent emergence of resistanceIV. Shorten the duration of treatment11. A) Sociology - study of human relationships and human behavioursB) Social psychology - psychology of individuals living in human societyC) Anthropology - study of physical, social and cultural history of man12. Triage - consists of rapidly classifying the injured and the likelyhood of their survival with promp medical intervention.Four colour code system (red - high priority treatment or transfer; yellow - medium priority; green - ambulatory patients; black - dead or moribund patients)13. Disease under international surveillance (WHO)I. RabiesV. SalmonellosisII. MalariaVI. Human influenzaIII. PoliomyelitisVII. Louse bom typhusIV. Relapsing feverfever14. Acculturation means "culture contact" when there is contact between two people with different types of culture.15. Green house effect: is the process by which absorption and emission of infrared radiation by gases in the atmosphere warm a planet's lower atmosphere and surface.Green house gases include-I) Natural - CO2, nitrous oxide, methane, ozone, water vapourII) Non-natural gases - hydroflurocarbons, perflurocarbons, sulphur hexafluoride
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