1. Lab #3 Titlle: Water Sampling Testing and Statistical Application
Dr. Javier Arce
From this laboratory, I learned the basics of taking water samples. The procedure
consists of first, letting water run for 2 to 3 minutes to clean the pipes. To take the water
sample you need a 100ml sterilized bottle. As soon as possible, put the water in a cooler
at 40 ° C and then take it to the refrigerator in the laboratory. An important tip is to
measure the temperature instantly after taking the water sample. This is done to
determine if the sample has the appropriate conditions for organism to live. When
analyzing samples, there are several steps too. First, use a substrate that interacts with E.
coli and another that interacts with Total Coliforms (you can also use a substrate that
interacts with both of them). Pour 100ml of water in the Quanty- Tray and label time,
number of sample, and date. After that, place the Quanty- Tray in the Quanty-Tray sealer.
Now, it is ready for placement in the incubator for 24 hours at 35° Celsius. We can
conclude that Sample #2 was positive to Total Coliforms and to E. coli. The Total
Coliforms are 231MPN and the E.coli is 2MPN. As a continuation of the lab, we used
Excel to analyze data given by Dr. Arce and create charts. This includes calculating the
mean, average, standard deviation or variance.