A municipality was conducting a test for pathogens in water across a city. There are 16 samples of water from tanks in different parts of the city, but only 8 testing kits. The lab technician decided to pool together the water samples into 8 bottles labeled A to H.
Tank 1 - Bottle B,D,F,H
Tank 2 - Bottle B,D,F,G
Tank 3 - Bottle B,D,E,H
Tank 4 - Bottle B,D,E,G
Tank 5 - Bottle B,C,F,H
Tank 6 - Bottle B,C,F,G
Tank 7 - Bottle B,C,E,H
Tank 8 - Bottle B,C,E,G
Tank 9 - Bottle A,D,F,H
Tank 10 - Bottle A,D,F,G
Tank 11 - Bottle A,D,E,H
Tank 12 - Bottle A,D,E,G
Tank 13 - Bottle A,C,F,H
Tank 14 - Bottle A,C,F,G
Tank 15 - Bottle A,C,E,H
Tank 16 - Bottle A,C,E,G
If water from a tank has the pathogen, then each bottle containing a sample from it will test positive.
If a bottle test positive, one of the tanks whose water samples were pooled into it contains the pathogen. If a bottle tests negative, then none of the tanks whose water samples were mixed into the bottle has the pathogen.
If bottle C tests positive and bottle E, H, and A test negative, which tank had the pathogen?
Answers
Answer:
The presence of bacteria and pathogenic (disease-causing) organisms is a concern when considering the safety of drinking water. Pathogenic organisms can cause intestinal infections, dysentery, hepatitis, typhoid fever, cholera, and other illnesses. (new screening test for waterborne pathogens).
Sources of Bacteria in Drinking Water:
The Need for Water Testing
Human and animal wastes are a primary source of bacteria in water. These sources of bacterial contamination include runoff from feedlots, pastures, dog runs, and other land areas where animal wastes are deposited. Additional sources include seepage or discharge from septic tanks, sewage treatment facilities, and natural soil/plant bacteria. Bacteria from these sources can enter wells that are either open at the land surface or do not have water-tight casings or caps.
Insects, rodents or animals entering the well are other sources of contamination. Old wells were dug by hand and lined (cased) with rocks or bricks. These wells usually have large openings and casings that often are not well-sealed. This makes it easy for insects, rodents, or animals to enter the well.
Another way bacteria can enter a water supply is through inundation or infiltration by flood waters or by surface runoff. Flood waters commonly contain high levels of bacteria. Small depressions filled with flood water provide an excellent breeding ground for bacteria. Whenever a well is inundated by flood waters or surface runoff, bacterial contamination is likely. Shallow wells and wells that do not have water-tight casings can be contaminated by bacteria infiltrating with the water through the soil near the well, especially in coarse-textured soils.
Older water systems, especially, dug wells, spring-fed systems, and cistern-type systems are most vulnerable to bacterial contamination. Any system with casings or caps that are not water-tight are vulnerable. This is particularly true if the well is located so surface runoff might be able to enter the well. During the last five to 10 years, well and water distribution system construction has improved to the point where bacterial contamination is rare in newer wells.
Step-by-step explanation:
Answer:
Tank Number 6
Step-by-step explanation:
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