“Encouraged” bacteria cleaning up more effectively after oil spills
Imitating nature along the shoreline
Here at Brattørkaia in Trondheim, Norway, researchers have assembled a comprehensive “oil library” which they use in this type of research. The properties of the oils have been accurately measured and recorded, and this enabled the researchers to select the perfect oil for their experiment.
“The oil we chose is produced in large volumes on the Norwegian shelf, and is thus ideal for simulating a realistic scenario involving the accumulation of oil on a Norwegian shoreline,” explains Netzer. “We then tried to simulate what happens in nature when oil becomes stranded,” he says.
Sixteen tanks were filled with sediments, together with naturally-occurring bacterial flora, oil, and seawater. The researchers also simulated the action of the tides by replacing the seawater and thus ensuring that there was an adequate supply of oxygen and nutrients. What then happened in the tanks was carefully recorded. After a month of observations, however, only minor amounts of contaminants had been removed.
Biological analyses the most sensitive
Chemical and biological analyses carried out afterwards produced approximately the same results.
“However, we noted that the biological approaches, which analyze the concentrations of bacteria, their DNA, and oxygen consumption, were very sensitive and provided us with a great deal of information. Chemical approaches have to be very advanced in order to achieve the same detection thresholds” says Netzer.
“Even the results of the bacterial experiments were obviously disappointing”, he explains. “But the biological results indicated that we were on the right track, and this gave us the idea to give nature a helping hand. We already knew that the bacteria would reproduce — and thus be more effective in their work — if they were provided with additional nutrients. In nature, bacteria flourish best in the presence of high concentrations of phosphates and nitrogen,” says Netzer.
The problem is that the natural concentrations of these substances are insufficient,” he says.
So the researchers decided to give them a little supplement.
They also increased the water temperature, reduced the oxygen concentration and extended the duration of the experiment. The tidal regime was also adjusted, so that now there was a 12-hour interval (instead of the previous three) between the introductions of new water to the tanks.
The release notes that this produced results. After one month, the researchers got their clear and unambiguous answers.
Analyses revealed that the extra nutrients had enabled the bacteria to work more effectively in breaking down the oil. At the same time, the increase in temperature, reduced oxygen concentration and adjustment of the tidal cycle produced no significant effect.
“We think that the data obtained from these experiments will be of considerable importance to the oil companies — not least because they are now expanding their activities into environmentally-sensitive areas in and around the Barents Sea,” says Netzer. He now envisages the introduction of a new weapon in the battle to clean up after oil spills.
“We believe that in time we will be able to make capsules which can attach themselves to rocks along the shoreline. These will provide the bacteria with ideal growing conditions by releasing nutrients as and when needed,” says Netzer.
