Experiment

Problem:

The Township of South Stormont brought to our attention that the Long Sault and Ingleside water treatment plants, who obtain raw water from the St. Lawrence River, could not always provide treated water that meets Ontario Drinking Water Quality Objectives. The wells that provide water for Osnabruck Centre have been contaminated with high levels of chlorides from salt and bacteria. Wells south of the Trillium Toad dump have also been contaminated with high bacteria counts. So the question remains: Is the water coming out of our taps safe to drink?

If not, what are the most effective methods we can use to make our drinking water safe if it were contaminated by harmful bacteria?

Hypothesis:

I think the best method of disinfecting our water is with chlorine. Boiling water could also disinfect the water but this method would only be useful for small quantities.

Materials:

    - Raw water sample

    - Test Kits*

    - Sterile measuring containers

    - Hot plate and container suitable for boiling water sample

    - A timer & thermometer

    - Chlorine (5.25% sodium hypochlorite)

    - Municipal Tap Water**

*The test kit referred to in this experiment is called "Water Check" and is manufactured by e.b.p.i.,. in Brampton, Ontario. It is advertised as a ‘Water test for coli forms including E. Coli.’ and sells for $9.95 at local hardware stores.

**Ingleside Municipal water originates from the St. Lawrence River. It is filtered for large debris and then chlorinated at the treatment plant before it is tested by the municipality, declared safe and sent to our homes. This sample should produce a negative result for bacteria from the Test Kits and serve as a control sample for the kit.

Method:

1. A large quantity of water was taken directly form the St. Lawrence river near the municipal intake pipes. The Bag from the test kit was opened. Care was taken not to touch the inside of the bag. A 100 ml sample of water was taken from the sample bucket and poured into the bag. Inside the bag is a powder which when mixed with the water will serve as a growth medium for coli forms if present. Excess air was squeezed from the bag and the top of the bag was rolled around the wire strip and thereby sealed. The test bag was set aside at room temperature. At 22 ºC it is recommended to wait 72 hours for results.

2. A large sample of water was taken from the same river water sample as above. It was placed in a container on the hot plate and allowed to boil for 2 minutes. A 100 ml sample was removed and added to a Test Kit as in the procedure for the first sample.

3. A 500 ml sample of river water was placed in a sterile container along with 1 ml of 5.25% sodium hypochlorite. The chlorine was allowed to stand for 20 minutes, then after gently mixing a 100 ml sample was removed and placed in a Test Kit and treated as the first sample.

4. A 100 ml sample of tap water was placed in the fourth sample kit and placed with the first three kits for a period of 72 hours.

Observations:

All water samples looked clear and clean to begin with. There was no way to know if any one sample was contaminated with harmful bacteria, there were no indicators that would be useful to predict the results without testing.

Results:

Both sample #1 (Raw river water) and sample # 2 (Boiled river water)
tested positive for E. Coli.

Both sample #3 (Water + chlorine) and sample #4 (Filtered tap water)
tested negative for E. Coli.

Conclusions:

My hypothesis that the chemical chlorine would disinfect contaminated water was correct. However my second method of disinfection, boiling, did not produce the desired effect.

Summary:

Water, a necessary part of our lives, can turn deadly without any warning. We assume because it is coming out of our taps that it is healthy. Not so! Even municipal water, as was the case in Walkerton, Ontario in the spring of 2000, can make us sick. Well water can be worse as it is not regularly monitored. In my experiment I showed that water with the chemical chlorine added was safe to drink, however further research will show that this may not always be the safest water either as there can be side effects from the chlorine itself. When camping we always assumed that just bringing water to a boil was enough to kill any bacteria and yet my experiment proved that even boiling under laboratory conditions for two minutes was not enough to kill harmful bacteria. So the question remains, Are you going to drink that water? Are you sure it is safe?

Future Experiments:

Since it is impossible to tell if water is contaminated by smell, taste or appearance it would be useful to have a test kit available in stores that could quickly test water for bacteria. If a test could be developed to give rapid results so a person would not have to wait 24 hours or more to get results, it could save many people from becoming ill or even dying from contaminated water. Currently a person on a private well or even on municipal water, may end up sick before knowing there was a problem with the water. Even though the water has been acceptable up to this point, something as innocent looking as a heavy rainfall could contaminate it by washing contaminated runoff into the source water.

Sources of Error:

1. The test kits that were chosen came in individual packages and they may not have been of consistent quality.

2. The containers /measuring instruments, may have been clean but not sterile.

3. I may have accidentally touched the inside of the kit bag thereby contaminating it.

4. I may not have let the kits incubate long enough to give accurate results.

5. The tests should have been repeated several more times to give more accurate results.