Understanding the Role of Coiform Bacteria in Water Contamination Research

Water Coliform Contamination Assignment

Introduction

Coliform bacteria, a type of bacteria found in soil, vegetation, and in the feces of animals and humans, are often used to gauge water supply contamination by intestinal parasites and pathogens (Treyens 2009). Although there are multiple means by which a water source can become contaminated, one way coliform and other bacteria can enter a water supply is through the reduced pressure and/or suction of water lines, which can introduce polluted water and soil into pipes (Treyens 2009). Therefore, the construction of a well system (adherence to construction codes, the presence of backflow prevention devices, etc.) can significantly impact the amount of coliform bacteria present in the water supply, as the quality of the system can determine if contaminated materials enter the water (Treyens 2009). Although most strains of coliform bacteria will not sicken the average individual, testing for coliforms is used as a safety precaution as coliforms are indicators of the presence of pathogens that can cause illnesses (Treyens 2009).

We hypothesized that the water supplies of older buildings, and thus older construction systems, would have higher frequencies of coliform contamination. We predicted that the bathroom sinks of Kennedy (built in 1925) would have a higher coliform contamination frequency than that of the bathroom sinks of Frazier-Jelke (built in 1968), which in turn would have a higher coliform contamination frequency than that of the bathroom sinks of Barret Library (built in 2005).

Methods

Water samples were collected by turning on the respective faucet and allowing the water to drip directly into the collection container. 100 mL of each of the three undiluted water sources was plated on a TSA (total bacterial count) and VRBA (violet red bile salts agar) plate, which was then spread evenly over the plate surface using a sterile spreader. A 1:10 dilution of each water source was made by combining 100 mL of the undiluted water with 900 mL of deionized water in an Eppendorf tube. After shaking the solution, 100 mL of the 1:10 dilution for each of the three water sources was plated on a TSA and VRBA agar plate. All plates were incubated at 37˚C for 25 hours.

After 25 hours, the number of colonies present on each plate were counted, and the CFU/mL for each plate was calculated by multiplying the number of colonies by the dilution factor, and then dividing by the number of mL plated.

Results

Table 1. Raw Data. The number of colonies and CFU/mL of undiluted and 1:10 dilutions of three water sources on TSA and VRBA agar plates.

Water Source Agar Plate Dilution # of Colonies CFU/mL

2nd floor Kennedy women’s bathroom sink TSA Undiluted 0 0

1:10 0 0

VRBA Undiluted 0 0

1:10 0 0

Frazier-Jelke women’s bathroom sink TSA Undiluted 0 0

1:10 0 0

VRBA Undiluted 0 0

1:10 0 0

Ground floor Barret Library women’s bathroom sink TSA Undiluted 0 0

1:10 0 0

VRBA Undiluted 0 0

1:10 0 0

Interpretations/Discussion

Our hypothesis stated that the water supplies of older buildings would have higher frequencies of coliform contamination than the water supplies of the newer buildings. Therefore, we predicted that the coliform contamination frequency would be greater in Kennedy than Frazier-Jelke than Barret Library. Our results indicated no bacterial growth whatsoever at any of the three water sources. Therefore, our hypothesis was not supported because all three locations had the same frequency of coliform contamination (which was none).

Although our hypothesis was not supported, these results indicate that the sink water in the Kennedy, Frazier-Jelke, and Barret Library bathrooms are free of coliform, which indicates that the water sources are being treated properly. Although we intended to test water from water systems of different ages, it is possible that the buildings share the same construction system, although the buildings were built in different years, and that the infrastructure is not old enough to have any breakdown or maintenance problems.

Future directions of this research may include testing the water supplies of residential areas in the surrounding neighborhood, or the water supplies of Robertson Hall, which is currently being built, or Briggs, which is undergoing construction. Because the spigots of sinks are often a point of entry for contamination, future research may test areas that are not cleaned as regularly and where there is an increased number of people living in a small area, by allowing faucets of dorm room sinks, shower heads, and bathtub faucets to drip into collection containers to determine if the areas around the faucet have coliform contamination.

Conclusion

The raw data of our results did not support our hypothesis because each of our three water sources had 0 CFU/mL at both dilutions on both types of plates, TSA and VRBA, meaning that all three water sources had no incidences of coliform contamination. These results refute our hypothesis because we had anticipated the water supplies of the older buildings to have a higher coliform contamination frequency than the water supplies of the new buildings, but instead none of the water was contaminated with coliform.