Submission Assignment for HSCI 10021 – Environmental Microbiology
Due Date: Sunday, November the 13th, 2022 at 23:59
Please submit individually.
References for PART-A: of Brock Biology
of Microorganisms, 15th Edition AND your own research from water quality websites, other
books, journal articles etc. Answer the questions given below.
Please write in FULL sentences.
PART -A
QUESTIONS (16 marks):
A. Bacterial examination of water: The bacteriological examination of water is performed routinely by water utilities and governmental agencies to ensure a safe supply of water for drinking, bathing, swimming and other domestic and industrial uses. The ‘Membrane Filtration’ (MF) is the method of choice and an easy way to estimate bacterial populations in water. An appropriate water sample volume is passed through a membrane filter with a pore size (0.45 micron) small enough to retain the bacteria present. The filter is placed in a petri dish saturated with a culture medium that is selective for coliform bacterial growth. The petri dish containing the filter is incubated, upside down, for 24 hours at the appropriate temperature (usually 42°C). After incubation, the colonies that have grown are identified and counted using a low power microscope. Coliform colonies will stain blue.
B. Scenario: You work in a water-monitoring laboratory and routinely analyze water
samples collected from six distinct locations in Southern Ontario . You receive water samples in a volume of 500 ml per location and run the microbiological analysis as described above. You filter three water volumes per location: one 100 ml, one 10 ml and one 1 ml sample, respectively.
Submission Assignment for HSCI 10021 – Environmental Microbiology
After filter incubation in the petri dishes with the coliform selection medium you count the grown bacterial colonies and report coliform density as the number of colonies . In the analysis, 24-48 hrs after receiving the water samples, the coliform cfu numbers
are as follows:
Bay Front
Lake Ont.
Lakeside
Park
St.Catharine
Lake Ont.
Burlington
Beach Lake
Ont.
Long Point
Beach Lake
Erie
Private
Water Well
in
Haldimand
Private
Well in
Wainfleet
100 ml 128 46 99 76 0 80
10 ml 25 3 9 12 0 10
1 ml 1 0 1 1 0 2
Questions part A:
1. What is the bacteriological standard for potable and recreational water in Ontario?
2. What is the federal standard for potable water?
3. Would you consider your i) four environmental water samples and ii) two well water samples safe to drink? Why or why not? Explain using the calculated coliform densities in cfu/used ml
for each of the samples and the relevant standards.
4. Which well(s) would you issue a boil water advisory?
5. Are the two tested recreational beaches safe to swim?
6. What is one major limitation of this method of testing the sample?
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