For decades, water pollution has caused major crises worldwide. A significant amount of water contamination is caused by illegally deposited chemicals and sewage in rivers and lakes. (MacGregor 41) Recently, scientists have been turning to more natural and aesthetically pleasing methods of water purification. In particular, the purification of water through absorption of pollutants by plants has begun to be investigated. (Pries 58) This can be applied to the many complaints regarding the elimination of natural wetlands throughout Canada. By constructing wetlands with the ability to filter water, new habitats are also being created, replacing the destroyed natural wetlands.

This experiment is an investigation of the efficiency of a constructed wetland filtration system in the removal of E. coli bacteria, since deadly cultures of this bacteria are often found in sewage. By building several wetland models, each containing a different species of plant, and testing them periodically for E. coli, I was able to determine whether or not this method of water purification is successful.

The rate at which two types of water plants, Arrowhead and Giant Bur-reed, absorbed the bacteria were compared. Twelve of each plant were planted in 4L of sterilized soil in two separate containers. A third container was filled with soil also, although it did not contain any plants. 3L of water were added to each of the containers and a pump was installed for each one. The containers were left under grow lights twelve hours each day for about three weeks.

Next, each of the containers was inoculated with 3mL of Luria Broth (a mixture of sodium chloride, pectin and yeast extract), containing the bacteria. Samples were taken at 24 hour intervals and plated within an hour after they were taken. Colonies visible in the dishes were counted within another 24 hours.

The hypothesis was correct: much of the E. coli placed into the artificial wetland models was removed from the water. Both containers with plants showed substantial decreases in E. coli content within the first 24 hours. Of the containers with plants, the rate of decrease in E. coli was greater in Model A, which contained the Giant Bur-reed plants.

However, the bacteria levels decreased at the greatest rate in Model C, which did not contain any plants. After a final sample was taken, it was concluded that there were two possible explanations: first, that the bacteria attached itself to the soil, and either multiplied until it was forced to spread back into the water, or simply detached itself from the soil; second, that the bacteria remained on the soil, and the colonies that appeared on the plates were another type of bacteria that had grown in the water.

The results of this final sample did support the first theory (that the bacteria had attached itself to the soil). The second theory (the colonies that appeared on the plates were another type of bacteria) is also quite possible, however there are no results to prove that it occurred. To conclude, it is quite possible that the E. coli attached itself to the soil and multiplied, although with the given data, this can only be speculated. Therefore, the amount of E. coli in the soil of each of the containers is difficult to determine.