The Effect of Oil Dispersants on E.coli Growth

Oil spills are an inevitable occurrence in the world today. A common method of oil spill clean-up uses a dispersant, which is a chemical that speeds up dispersion of oil. The purpose of the experiment was to determine if dispersed oil in salt water had an effect on E.coli growth over multiple generations.

A fish tank was filled with salt water and diesel fuel was poured over the top to form a complete layer. The oil dispersant was evenly sprayed over the top of the slick. The fuel was allowed to disperse for one week. Samples of water were then taken from various areas in the tank and hole-punched filters were soaked in the liquid. The hole-punches were placed three at a time in the first set of petri dishes with E.coli bacteria. The bacteria incubated for twenty-four hours. The bacteria was then scraped from the dishes, diluted in water and then reapplied to a new set of dishes. This was repeated three more times. The same process was done for E.coli without dispersed water. After the fifth generation was grown, the numbers of colonies were counted.

Using a two-sample t-test, it was determined that the number of colonies grown of E.coli with dispersed water applied was significantly different than the number of colonies grown of untreated E.coli. The likelihood of these statistics occurring by chance is almost zero. This means that dispersed oil in salt water did in fact have an effect on E.coli growth over multiple generations.

Research Done By:

Kathryn Amejka
CousinoHigh School

Matthew Forsgren
South LakeHigh School