1. Finding Total Coliforms and Enterococcus in Water
Samples from Cidra in the River Arroyata
Alejandra González and Angeline Figueroa
RISE
Abstract
Waters in the world are contaminated by different pathogens. In Puerto Rico,
the waters contain coliforms which are a type of bacteria and they are divided into
two groups, total coliforms and fecal coliforms. Enterococcus is another type of
bacteria that affect our waters and they can be a hazard for the health of people and
animals. For this project we wanted to know if there was presence of total coliforms
and enterococcus in the waters of the river Arroyata in Cidra, Puerto Rico. Since
fecal coliforms are endemic in the waters of Puerto Rico they were going to be
present in the samples taken from the river, unless the samples were treated against
fecal coliforms.
Introduction
Coliforms are broad class of bacteria found in our environment, including the
feces of man and other warm-blooded animals.The presence of coliform bacteria in
drinking water may indicate a possible presence of harmful, disease-causing
organisms. There are two types of Coliforms, fecal and total. Total coliforms are
bacteria that are found in the intestines of animals and in the environment, while
fecal coliforms are found only in the intestines of animals and these are endemic in
the waters of Puerto Rico and they are used to know the presence of pathogenic
organisms. Enterococcus is a genus of lactic acid bacteria, which are the ones that
are used for example in yogurt. Two species are common commensal organisms in
the intestines of humans: E. faecalis andE. faecium, some infections caused by
Enterococcus include urinary tract infections, bacteremia, bacterial endocarditis,
diverticulitis, and meningitis.Our question for this project was if we were going to
be able to find total coliforms and enterococcus in the waters of the river Arroyata
in Cidra. The hypothesis to this question would be that yes, we are going to be able
to find coliforms and enterococcus in the mentioned river. Since fecal coliforms are
endemic in the waters of Puerto Rico we are sure that they will show in our results.
Materials and Methods
The samples were collected on May 3, 2013 from the River Arroyata in Cidra,
Puerto Rico. We collected six samples of one hundred milliliters, two for each
section of the river. The first four samples were collected near the town and the last
two a bit far from the town. Before each collection we measured the temperature

2. and conductivity with a multimeter and the turbidity utilizing a turbidmeter. In
addition, there was used a GPS to identify the latitude and longitude from were the
sample were collected, the sample number to identify each sample with its place of
collection and to record the time of the collection. The samples were identified as
follow: the first two, from the first section of the river, were numbered 66, the third
and forth from the second section, were 69 and the last two from the third section,
were 70.
After the collection we brought the samples to the laboratory to prepare
them for the analysis process. The samples were divided into two groups of three.
For the first three, we pouredColilert substrate and the Enterolert substrate was
added to the other group of three samples. The Colilert is to identify fecal and total
coliforms and the Enterolert to identify enterococcus bacteria. These substrates are
detectors that have nutrients indicator that will be metabolized by the bacteria
resulting in a change in color in the water sample if result positive to the bacteria
mentioned before. For instance, if the test resulted positive for total coliforms the
water will change from clear to yellow. And, if the same sample is put under
ultraviolet light the ones that change from yellow to light violet resulted positive for
fecal coliforms. For the enterococcus test, the water will change from green to blue if
resulted positive for that bacteria. The next step was to pour each water samples
with substrates in six quantity trays(one for each sample) and then seal them with
the quantity tray sealer.After that, the samples were incubated for twenty-four
hours, the one with Colilert at 35-Celsius degrees and the one with Enterolert at 41-
Celsius degrees.
The next day we took out the quantity trays from the incubator to analyze
them. For the total coliform test, we observed how much water in the quantity trays
were changed to yellow, for the fecal coliforms we put the under ultraviolet light
and see the amount of water that changed to light violet and for the enterococcus we
observe how much water changed to blue.
Results
It was difficult to have an accurate number of bacteria inone hundred
milliliters of water due to the method utilized, so the results are the most probable
number (MNP) of bacteria that one hundred milliliters of water could contain.
For the test of the total coliforms the three samples (66, 69 and 70) resulted
in the same amount of that bacteria 2,419.6MNP. The fecal coliforms test resulted in
a different amount: the 66 samples had 307.8MNP, the 69, 172.6 and the 70, 210.5.
Finally, for the enterococcus test resulted in diverse number of bacteria too: the 66
samples 344.8, the 69 had 579.4 and the 70 had 156.5

3. *-Conductivity is a way to measure ions dissolved in a water body. As low the
conductivity is fresher is the water. Conductivity should range from 150 to 500
micromhos per centimeter (mhos/cm) to consider the water as pure.
*-Turbidity is measured at nephelometric turbidity units (NTU) and we can see turbidity
in the color of the water.
Conclusion
Based on the results we could deducethat the conductivity was slightly higher
than the normal ranges, which are 150 to 500mhos/cm. This indicates that the water is not
too pure for its use. Considering that there are many factors that altered the conductivity,
such as temperature, these results can vary making the water to be in the ranges of fresh
water.Also, that the turbidity resulted with an NTU lower than the range, which is
10NTU. This quantity of turbidity indicates that the water is plenty pure, because it does
not have too much organic and inorganic material. We were able to obtain positive results
in the six samples. In other words, we did find fecal and total coliforms and enterococcus
bacteria in the water of the riverArroyata in Cidra, Puerto Rico. Consequently, we were

4. able to measure the water quality of three different section of the river, so we can
conclude that as far as we moved to collect the samples from the town was less bacteria.
With all the gathered information we will be able to orient people on how to drink
purified water and the dangers of ingesting water that has not been treated against
pathogens, campaigns can be also an option to tell more people to help keep our waters
cleaned.
Literature Cited
http://www.bfhd.wa.gov/info/coliform.php (Public Health of US)
http://www.gobierno.pr/NR/rdonlyres/BA0D6158-5A70-449A-B385-
D55F654720A8/0/EstandaresCalidadAgua.pdf (Junta de Calidad de Ambiental de Puerto
Rico)