Removing the hazardous

Treating petroleum sludge and oil spills: a case study

An oil spill or oil in waste discharged into the sea from refineries, factories or shipping contains poisonous compounds. These poisons are a danger to all the plant and animal wildlife in the area, and can pass into the food chain and eventually be eaten by humans

Oil spill cleanup approaches include treating with chemicals, using physical barriers to contain the oil, and pumping the collected oil away from the site into storage tanks.

Some bacteria and other microorganisms in the environment can break down oil into harmless small molecules in a natural, slowly-occurring process called bioremediation. This can be sped up by:

  • adding nutrients to the water in the area of the spill
    • this provides the naturally-occurring bacteria in the ocean with increased nutrients, increasing their rate of reproduction and therefore the rate of oil breakdown
  • adding oil-digesting bacteria to the water in the area of a spill.

Researchers are also working to genetically engineer effective oil-digesting bacteria that are well suited to the environmental conditions of the ocean. They could be used to speed up the bioremediation process in future oil spill disasters.

Oil-eating bacteria - work sheet [PDF 34kb | 3 pages]

After the Exxon Valdez oil tanker crashed off the shore of Alaska in 1989, spilling its contents all over the area, one of the biggest contributors to cleaning up the environment were Pseudomonas bacteria. Scientists found that by enriching the contaminated area with oxygen and waste water, the bacteria present were provided with the nutrients needed to flourish, thereby encouraging breakdown of the oil's hydrocarbons.

Cleaning up arsenic

By adding genes to common weeds, scientists have created a new tool for cleaning up arsenic in the soil. Although very small doses of arsenic and other heavy metals are essential for good health, high levels are toxic to animals and humans.

The researchers added two bacterial genes to the commonly-used laboratory plant Arabidopsis thaliana . The first gene helps convert arsenic from soil to a form that can be 'sucked up' and stored. The second gene helps the plant detoxify heavy metals and accumulate the molecules in its leaves.

The use of plants to clean the earth is called phytoremediation. Plants are cheap and use solar power! Researchers are now using larger plants that can take up more arsenic to make the process more practical.

Land mines

Land mines are explosives laid just below the surface of the ground. They are triggered when someone steps on them, causing terrible injuries, often to innocent people farming land that used to be old battlefields.

Researchers have been genetically engineering plants that could detect explosives housed in a land mine, and then fluoresce, highlighting the presence of a land mine.

This was successfully trialled in 1999, but it has limitations and some environmental concerns. Whether or not it is successful, the trial highlights that new science and technologies can be applied to a wide variety of problems.

In 2004, Danish plant scientists started working on a similar project. But, instead of fluorescing, the genetically modified plant changes colour. Called RedDetect, the plant can sense nitrogen dioxide gas — which leaks from landmines — in the soil and change colour from green to red when growing on or in near proximity of landmines. The red colour is caused by anthocyanins, the same pigmentation you can see in autumn leaves. The plants are still undergoing tests.

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Get that barnacle off my boat!

Boat with barnacles

Centre for Marine Biofouling and Bioinnovation at the University of NSW

Anything that is left in the sea for a while will start to become colonised with marine life. The colonisation of submerged surfaces by living organisms is called marine biofouling. A common example is barnacles attached to the hulls of ships.

Biological fouling can occur on a range of surfaces, from ship hulls to the walls of houses and the interior of water pipes. It results in increased fuel consumption, corrosion, breakdown of materials and buildings, the transport of introduced pests and many other problems worldwide. Biofouling also harbours pathogens.

The major focus of fouling and antifouling technologies has been in the marine shipping industry, where fouling is estimated to cost more than $5 billion per year.

Other than repeated cleaning of surfaces, by far the most common commercial approach to fouling control is to coat surfaces with antifouling paints that contain heavy metals (copper or tin).

The main problems with these coatings are the environmental effects of the heavy metals they release. The most commonly used paints in the marine environment for the past 30 years, tributyltin-based coatings, are in the process of being banned by the International Maritime Organization.

Copper-based paints are also banned in some parts of Europe. House paints also typically contain toxic antibacterial or antifungal compounds to inhibit microbial fouling.

Australian scientists are working to develop novel approaches to the control of unwanted biofouling and corrosion on submerged surfaces and building walls using biotechnology. These approaches are based on the incorporation of metabolically active bacteria (living paints) or enzymes into coatings. This technology can also be used to incorporate bacteria into a ‘biocement’ which inhibits fouling.

The bacteria in the paint will release natural products (enzymes) that prevent the organisms that cause fouling from adhering to the surface. Enzymes are capable of catalysing the reaction to degrade any attaching organisms or fouling species.


Scientists are now using bacteria such as Thiobacillus ferroxidans to leach copper from mine wastes, improving recovery rates and reducing operating costs. The process has also allowed extraction from low grade ores. Worldwide, 25% of all copper is produced through bioprocessing.

Bioprocessing is also used to economically extract gold from very low‑grade sulphidic gold ores, once thought to be worthless. In 2006, a species of bacteria was reported to be found living on the surface of gold grains collected in Australia. The bacteria – named R. metallidurans – can survive in the presence of dissolved gold that would kill most other bacteria. It could be very useful in discovering or producing more gold.

Nuclear site cleanup

In 1999, scientists in the United States developed a new variety of microbe capable of eating waste materials at nuclear sites and rendering them less harmful.

The modified microbe, based on the radiation-resistant bacteria Deinococcus radiodurans , can dispose of the toxic heavy metals and organic chemicals commonly found at weapons production sites where normal bacteria cannot survive.