BackgroundThis Study
Data Collected
Analysis/Conclusions
Methods & Materials
BackgroundFecal coliform testing is the most widely accepted water quality and water standards test for the EPA (Standard Methods, 1995). These standards entail that drinking water counts for fecal coliform be no more than 0 colonies for every 100ml filtered. For total body contact during the swimming season, the EPA standard is set at maximum count of 200 colonies per 100ml filtered. For total body contact during the non-swimming season, the EPA regulation is set at a maximum of 2000 colonies for every 100ml filtered (EPA Website 2001).
Fecal coliform bacteria are naturally present in the lower intestinal tract of humans and other warm-blooded animals, but are uncommon in unpolluted waters(Lecture Notes). Due to both point and non-point source discharge into small creeks such as Shermans, fecal coliform have become present in many Pennsylvania stream systems. Fecal coliform bacteria itself is not a direct health hazard to humans. Pathogens that live and feed in the same environment as fecal coliform bacteria are the true health hazard. By way of fecal coliform, pathogens enter the water, and it is at that point that human health is in jeopardy (Methods Primer, 1998). These pathogens include viruses, dangerous sub-species bacteria and other human infectious diseases(Methods Primer). Testing for fecal coliform is done simply to indicate whether harmful pathogens, which are present where fecal coliform is found, exist. Due to fecal coliforms short life span in an aquatic system, they are also excellent indicators of recent and nearby contamination (EPA Website-2001).
This study is a combination of three students studies: Alex Hoffmeier, Stephanie Pye, and Carrie Kress
Alex focused his study study on a popular site named the Delville dam swimming hole. It is located near the town of Shermans Dale in the Shermans Creek. He chose this site due in part to the surrounding land use and because it is a swimming hole that is popular to both locals and Dickinson students. A gradually sloping agricultural field meets one bank of the swimming hole. A small wooded area surrounds the opposite bank along with residential houses.
Stepanie Pye followed the EPA five-day swimming water standard test for fecal coliform. She collected her data at the end of swimming season in early Fall of 2001.
The goal of this study is two fold. First, to attempt to find a correlation between the flow of the stream and the number of fecal coliform bacteria counted. The second is to compare the three sets of data. Because her Stephanie's data is taken during the swimming season, and Alex and Carrie's is taken after the swimming season,we attempted to find a correlation between number of colonies counted and the difference in the time of season.
After comparing the number of colonies counted to the flow of the stream, it is very hard to find a true correlation between the two. On Oct 19, the flow was very high, yet the number of colonies counted was only 4 col/10ml or about 40col/100ml (Fig 1). The following week, Oct 26, the flow dropped by 7 taking it down to 38, yet the colony count turned out 221 col/100ml (Fig 2). On Oct 31, the flow increased to 42, yet the colony count was 71 col/ 100ml (Fig 3). Finally, on Nov 10, with the flow still at 42, the colony count was strangely 6 col/100ml (Fig 4). Though variability can be expected when conducting fecal coliform studies, my data for this correlation must be refuted.
After comparing my data to Stephanie’s, it is again very difficult to conclude a correlation between the numbers of colonies counted compared to the different times of season. Because the first two days of her data were not taken at base flow (Fig’s 5-7), comparison of those days to my data is meaningless. Though, the data does separately illustrate that there is correlation between heavy rainfall, increased flow and the increased coliform count in the creek. Stephanie’s data shows that after the storm, the flow increases immensely along with the coliform count (Fig’s 5-7). On Sep 28, when the flow returns to normal, the coliform count is also drastically reduced (Fig 8). Her data demonstrate the true relationship between coliform count and flow in a creek. The only comparable data I have to Stephanie’s is my Oct 26 sampling (Fig-2) and her Sep 28 (Fig-8). In both of these sampling’s the stream flow are the same at 38 and the colony count is extremely precise at 221 col/100ml to Stephanie’s 237 col/100ml.
On the dates of Oct 19, Oct 26, Oct 31 and Nov 10 I traveled to the Delville dam swimming hole to collect water samples for fecal coliform tests. Each water sample was collected in the late afternoon, and the weather for each day was relatively unvarying. There were no major rainstorms or other natural occurrences during the course of this time.
- Samples were collected with two sanitary swirl-bags filled with the swimming hole water (each bag containing approximately 400ml of water).
- A standard autoclave was used to sanitize all instruments used in the filtration process.
- A membrane filtration machine was used to filter the water samples.
- An incubator set at 45.5 degrees Celsius was used for incubation of petri dishes.
- A dissecting microscope was used to count the formed bacterial colonies.
Procedure
The Membrane Filtration technique is recommended by the Standard Methods Manual because it is highly reproductive, can test relatively large samples of water, and yields numerical results more rapidly than the multiple-tube procedure. Though, there are limitations with testing waters with high turbidity or noncoliform bacteria (Standard Methods,1995).
(For use of Membrane Filtration Device, Procedure taken from Aquatic’s Lab Manual, Wilderman 2001)
1. Prepare petri dishes with Fecal Coliform medium onto Absorbent
Filter Paper.
2. Place a sterile glass filter holder with cork into
empty flask.
3. With sterile forceps, load a pre-sterilized membrane
grid, side up, and evenly centered on to the filter holder support base, then
clamp the sterile funnel into position.
4. Pour sample (for samples
less than 15ml follow dilution procedure) into sterile funnel and turn on the
vacuum pump.
5. Turn off pump when all of the water has been filtered
through.
6. Rinse funnel three times with dilution water making sure
that the sides of the filter funnel are washed.
7. Remove filter
membrane with the forceps and transfer to petri dish.
8. Center the
filter, grid-side up, on the medium soaked absorbent pad. Be sure not to trap
air under the filter paper. Bacteria will not colonize properly.
9.
Cover petri dish tightly, label each, and place dish in the incubator upside
down
10. Record time of incubation.
Counting the Colonies:
1. After twenty-four hour incubation period, remove
petri dishes from the incubator.
2. Place each dish under a dissecting
microscope.
3. Count all light-dark blue dots on the petri dish.
4.
Calculate the number of colonies.
Materials
- Swirl Bags
- Vacuum Pump
- Pipette Tips (25ml)
- Electric Pipette
Machine
- Filter Funnel
- Glass Filter
- Forceps