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14 Cards in this Set
- Front
- Back
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Through ordinary exposure to air, soil and effluents, surface waters usually acquire harmless, saprobic microorganisms. TRUE/FALSE
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TRUE. The most prominent water borne pathogens are the protozoans, Giardia and Cryptosporidium, the bacteria, campylobacter, Salmonella, shigella, Vibrio and Mycobacterium; and hapatitis A and Norwalk viruses.
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Which Enteric bacteria are most useful in the routine monitoring of microbial pollution?
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Gram neg rods called coliforms and enteric streptococci, which survive in natural waters, but do not multiply there.
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EPA standards for water sanitation are based primarily on the levels of coliforms. How can you describe them?
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Gram neg, lactose fermenting, gas producing bacteria such as E. coli, Enterobacter and Citrobacter.
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Fecal contamination of marine waters that poses a risk for GI disease is more readily correlated with Gram positive cocci, primarily, Enterococcus. TRUE/FALSE
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TRUE. occasionally, coliform bacteriophages and reoviruses(Norwalk) are good indicators of fecal pollution.
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List two water quality assay tests?
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Standard plate count- small sample of water is spread over the surface of a solid medium. The number of colonies that develop provide an estimate of the total viable population.
Level of dissolved oxygen- water having high levels of organic matter and bacteria will have a lower O2 content because of consumption by aerobic respiration. |
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What is the most probable number procedure?
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It detects coliforms by a series of presumptive, confirmatory and completed tests. After 24 hours of incubation, the tubes are evaluated for gas production. A positive test for gas formation is presumptive evidence of coliforms, negative for gas means no coliforms.
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When a test is negative for coliforms, the water is considered generally fit for human consumption. TRUE/FALSE
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TRUE. However,municipal waters can have a maximum of 4 coliforms per 100ml, private wells, even higher.
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There is no acceptable level for fecal coliforms, enterococci, viruses or pathogenic protozoans in drinking water. TRUE/FALSE
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TRUE. if the coliform level of recreational waters reaches 1,000 coliforms per 100ml, health departments usually bar its usage.
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Regarding water and sewage treatment, how does water treatment begin?
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With the impoundment of water in a large reservoir such as a dam or catch basin that serves the dual purpose of storage and sedimentation.
Overgrowth of cyanobacteria and algae that add undesirable qualities to the water is prevented by pretreatment with CuSO4(O.3ppm). |
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What is the next process of water purification?
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The water is pumped to holding ponds or tanks, where it undergoes further settling, aeration and filtration. Water is filtered first through sand beds or pulverized diatomaceous earth to remove residual bacteria, viruses and protozoans and then through activated charcoal to remove organic contaminants.
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What is the final step inwater treatment?
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Chemical disinfection by bubbling chlorine gas through the tank until it reaches a concentration of 1-2 ppm(some plants use chloramines).
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What is sewage?
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It is the used wastewater draining out of homes and industries that contains a wide variety of chemicals, debris and microorganisms.
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Sewage treatment requires several phases. What are they?
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The primary stage separates out large matter, the secondary stage reduces remaining matter and removes some toxic substances. The tertiary stage completes the purification process.
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What are anerobic digesters?
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When sludge is formed in the secondary phase, further digestion is carried out by microbes in sealed chambers called bioreactors or anarobic digesters. the digesters convert components of the sludge to swamp gas, primarily methane with small amounts of H2, CO2, and other volatile compounds. Swamp gas can be burned to provide energy to run the sewage processing facility.
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