Can you answer question 19-24 ? 9. In the bacteriological examination of water,

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Can you answer question 19-24 ? 9. In the bacteriological examination of water, direct tests are not carried out to assess the presence of pathogens, because a. b. 20. The primary habitat of coliforms is th 21. Coliforms serve as good indicators of possible presence of pathogens, because a. b. d. 22. The size of water sample required for chemical analysis is. for bacteriological analysis, it i. . bottles should be used for collection of samples for bacteriological examination of water. 24. Specially prepared bottles containing are used to collect water samples from a municipal tap for bacteriological analysis. This is to

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Ans-(19) Waterborne pathogens and related diseases are a major public health concern worldwide, not only by the morbidity and mortality that they cause, but by the high cost that represents their prevention and treatment. These diseases are directly related to environmental deterioration and pollution. Despite the continued efforts to maintain water safety, waterborne outbreaks are still reported globally. Proper assessment of pathogens on water and water quality monitoring are key factors for decision-making regarding water distribution systems’ infrastructure, the choice of best water treatment and prevention waterborne outbreaks. Powerful, sensitive and reproducible diagnostic tools are developed to monitor pathogen contamination in water and be able to detect not only cultivable pathogens but also to detect the occurrence of viable but non-culturable microorganisms as well as the presence of pathogens on biofilms. Quantitative microbial risk assessment (QMRA) is a helpful tool to evaluate the scenarios for pathogen contamination that involve surveillance, detection methods, analysis and decision-making. This review aims to present a research outlook on waterborne outbreaks that have occurred in recent years. This review also focuses in the main molecular techniques for detection of waterborne pathogens and the use of QMRA approach to protect public health.

Ans(20) Coliforms can be found in the aquatic environment, in soil and on vegetation; they are universally present in large numbers in the feces of warm-blooded animals.

Ans(21)

What are coliforms?

Coliforms are a broad class of bacteria found in our environment, including the feces of man and other warm-blooded animals. The presence of coliform bacteria in drinking water may indicate a possible presence of harmful, disease-causing organisms.

Why use coliforms to indicate water quality?

Drinking water must be free of disease-causing organisms called pathogens. Pathogens can be viruses, protozoa or bacteria. Waterborne pathogens cause diseases such as hepatitis, giardiasis, and dysentery. To actually test water for specific harmful viruses, protozoa and bacteria is very time consuming and expensive. In addition, not all water laboratories are equipped and approved to do the testing required. Therefore, testing water for specific organisms is limited to investigating specific waterborne disease outbreaks. Coliform bacteria are used as water quality indicators for two main reasons:

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For sampling chlorinated wastewater effluents add sufficient Na2S2O3 to a clean sample bottle to give a concentration of 100 mg/L in the sample. In a 120-mL bottle 0.1 mL of a 10% solution of Na2S2O3 will neutralize a sample containing up to 15 mg/L residual chlorine. For drinking water samples, the concentration of dechlorination agent may be reduced: 0.1 mL of a 3% solution of Na2S2O3 in a 120-mL bottle will neutralize up to 5 mg/L residual chlorine. See Table 9060:I for preparation of sodium thiosulfate solutions. Where possible, determine normal residual chlorine before sampling at a new site (e.g., pool water may contain a higher chlorine level than normal) to enable laboratory to prepare an adequate amount of dechlorination agent per sample bottle. Discard turbid (bacterial growth) 10% sodium thiosulfate stock solutions. Loosely cap bottle and sterilize by either dry or moist heat, as directed (Section 9040) and perform sterility checks as noted in Section 9020B.5d. Presterilized plastic bags or bottles containing Na2S2O3 are available commercially

Sampling Procedures-- Maintain consistent sampling procedures. When the sample is collected, leave ample air space in the bottle (at least 2.5 cm) to facilitate mixing by shaking, before examination. Reject sample bottles that are overfilled and request resampling or, alternatively, add overfilled samples to a larger sterile sample bottle in the laboratory to assure adequate mixing. Keep sampling bottle closed until it is to be filled. Remove cap or stopper, if used, as a unit. Do not place cap down on any surface. Avoid external contamination during sample collection and do not contaminate inner surface of stopper or cap and bottle neck. Fill container without rinsing, replace stopper or cap immediately, and secure hood, if used, around neck of bottle. Systematically plan to collect samples that are representative of the water being tested. When planning sample collection activities, consider temporal, spatial (horizontal and vertical), and hydrodynamic conditions (e.g., wet versus dry weather and seasonal lake turnover effects). Sampling frequency and the number of samples to be collected will depend on ultimate data usage needs.

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