A bug's life on the toxic waste heap

Bacteria are a remarkable form of life. No matter how dangerous the pollution, no matter how severe the environment, members of their extensive family are there, thriving and multiplying on whatever chance provides them.

For this reason they hold great promise as a way to clean up pollution, an approach known as bioremediation. It involves the use of living organisms to reduce or eliminate environmental hazards caused by toxic chemicals and hazardous wastes.

Researchers at the National Microelectronics Research Centre (NMRC) and the Department of Electrical Engineering at University College Cork are involved in an EU-funded project that will attempt to speed up the bioremediation process. It involves finding ways to keep the bacteria as happy and comfortable as possible to encourage them to get on with their important work.

"Bioremediation, although well proven at this stage, typically takes 12 months or more to produce acceptable levels of progress," said Dr Bill Lane, transducers group director at the NMRC. The Cork group, in partnership with researchers and companies in Britain and the Netherlands, are designing a fully automated system that will greatly speed up bioremediation, bringing improvement in months rather than years.

"Accelerated land remediation will result in huge cost savings by shortening the time a company must wait before building on previously contaminated land," Dr Lane said. "These land sites are worth huge amounts of money if they could be cleaned up. The actual cleanup bill for any of these sites runs into the millions." Fast remediation therefore makes financial as well as environmental sense.

"What we are doing is developing a football pitch-sized reactor," Dr Lane explained. "The aim is to find an optimum set of conditions that would speed up the remediation. Mostly what we are trying to do is control oxygen and pH [acidity] in the pile."

The team has started small with an experimental reactor, a fully contained tank measuring about three metres tall and a metre-and-a-half wide. The plan would be to move on to a site the size of a typical suburban back garden and finally a largescale test site the size of a pitch.

The most likely approach would involve moving polluted soil aside on a site to allow the placement of a semi-permeable cloth, "geotextile", to form a barrier underneath, Dr Lane explained. A temporary structure would then be erected above the pile so that temperature, oxygen, moisture levels and gas emission could be controlled.

The NMRC's role is to develop sensors that can measure conditions in and around the pile, and instruments that can deliver this information. Sensors would also monitor any effluent discharged by the pile.

The Department of Electrical Engineering in turn is developing "algorithms", mathematical software that can interpret the information so that conditions in the pile can be regulated.

"As you raise the temperature, the bioremediation activity goes much faster," Dr Lane said, "but there are limits. The temperature you choose is also linked to the moisture levels in the pile and its chemical condition." The plan he said was to optimise the environment and not to optimise the particular species of bacteria used. These, he added were "relatively standard" and were chosen on the basis of the pollution involved.

"Basically you are talking about a computerised system," Dr Lane said, running 24 hours a day and without human operators. An array of chemical and other sensors would provide constant feedback to the computer system overseeing the reactor. This in turn would raise or lower temperatures, add moisture and generally keep the bacteria working hard.

The NMRC has already provided sensors and instrumentation for the test rig, which is in operation in the UK. A quick scale up is planned, however, and by the end of this three-year project in 2003, one of the commercial partners, Response Environmental of Rotherham, is to have a fully working system.

"The aim for the [company] at the end of it is they would go out and trial it on small sites," Dr Lane said.

The NMRC was established in 1981 and is the largest information and communication technologies research centre in Ireland, with a staff of 200 and research facilities valued at more than £80 million.