Group Members: Diana Samaroo, Ralph Alcendor, Urmi Ghosh-Dastidar, Muhammad Ali Ummy
Title of Activity: Chemical and Biological Analysis of Water Quality
Location/outside partner: Beach-front at Brooklyn Bridge
Detailed Description of Activities (supplemental to Group 2 Agenda)
Activities (working template)
- Collect water samples from two locations, stagnant and flowing, at the Brooklyn Bridge Park. Participants will decide sampling area.
- Collect water samples from City Tech or bottled water.
- Measure the temperature of the water sample collected.
- Return to City Tech P304 where the following test will be conducted
- pH – using a pH meter
- Microbial contamination – using phenol red dextrose tubes and phenol red broth.
Procedure
pH reading
To determine the pH of samples collected, follow the following steps.
Note: The pH meter is calibrated and ready to use. However, ensure that the pH reading is around 7 ( the probes are stored in pH 7 buffer).
- Rinse the probe in distilled water.
- Insert the probe into the water specimen.
- Swirl the container and wait until the reading stabilizes.
- Record the displayed reading.
- Give the probe a final rinse and return it to the calibration buffer or continue measuring the pH of other samples.
Microbial level
To measure microbial levels we will use the Colony Forming Unit (CFU) method.
Samples will be collected two days prior. 1 ml of each sample will be used to prepare a 10 fold serial dilution using phenol red glucose broth and nutrient agar plates. This dilution will be carried out to observe the minimum number, usually one, of bacteria in the water sample. All inoculated tubes will be incubated and fermentation and growth will be observed 48 hrs later. (More to come)
Interpretation of results;
Growth or no growth – Nutrient agar plate
Number of colonies – Nutrient agar
Number of different colonies – nutrient agar
Red media - no fermentation
Yellow media – fermentation
Bubble or gas in the upside tube – gas production
To determine the most probable number of bacteria within each sample,
- Observe the change in color of each tube and record the number of positive tubes in each set (3 tubes). The order of positive and negative results in each set is important.
- 2. Use the 3-tubeThe number of positive tubes are then used to determine the number of inoculums in each sample using the 3-tube MPN Table.
- 3. Record your
Part II: Chemical Analysis of Water Quality
The following quality control tests will be performed with the collected water samples.
Using a multipurpose test strip, assess the level of hardness, pH and iron (HPI)
Using a second multipurpose test strip, assess the level of nitrate and nitrite (NN)
Instructions for test strip use:
1) Insta-Test Analytic Nitrite (NO2) & Nitrate (NO3) Strips
Using a cup-size sample, immerse strip for 2 seconds and remove with pads face up. DO NOT SHAKE OFF EXCESS WATER. Wait 60 seconds and immediately compare to color chart.
Use one strip for each water sample. (You will use a maximum of three strips).
(Keep wet fingers out of test strip bottle)
Results: Based on the color chart you will report the level of nitrite and nitrate in the water samples as: 0 ppm, 0.5 ppm, 1 ppm, 5 ppm, 10 ppm.
ppm: part per million
Think about the following: Why should the levels of nitrate and nitrite be regulated?
Read the following:
http://www.freedrinkingwater.com/water-contamination/nitrates-nitrites-contaminants-removal-water.htm
2) Insta-Test: Hardness, Wide Range pH and Total Iron
