Microbes for cleaning PCB pollution

Microbes for cleaning PCB pollution

April 30, 2010

Degradation of PCB involves two main mechanisms, performed by different microbes. Microbes adapted to cold conditions were found in sediment from Hammerfest in significant numbers.

PCB pollution

Polychlorinated biphenyls (PCBs) are a group of compounds comprising of two benzene rings with up to ten chlorine atoms attached. After the discovery of their serious toxic properties PCB production and use was banned.

However, due to their stable nature widespread pollution of sediments of harbors, rivers, and lakes has resulted both from production waste and the disposal of PCB-containing products.

Mapping of PCB pollution for harbor sediments in Norway has identified several heavily contaminated sites, including Storvatn lake in Hammerfest.

Digging up the sediment for off-site treatment is difficult because of the low contaminant concentration and large volume of sediment.

Can microbes degrade PCB?

There are two groups of microbes which are involved in PCB biodegradation. One group removes the chlorine atoms from PCBs in the absence of oxygen.

Once the chlorine is removed another group breaks down the carbon-carbon bonds of PCB in the presence of oxygen.

However, the biodegradation processes are very slow or do not occur in nature, due to the lack of adequate nutrients or presence of inhibition factors, such as low temperatures.

Introducing commercial foreign microbes are not desirable since they will be out competed by local microbes which are well adapted to the local condition.

Local microbes

Norut Narvik has carried out a preliminary study to investigate the potential of using local microbes for treatment of PCB contaminated sediment of Storvatn lake.

The samples were provided by ASCAS. The two groups of microbes which are involved in PCB degradation were found in the contaminated sediment in significant numbers.

Nutrient requirements

Biodegradation studies were performed to test the effect of nutrient addition on the degradation activity of the local microbes. Nitrogen with other nutrients was supplemented to the contaminated sediment which was spiked with PCB118.

After 90 days at 10 °C, the PCB118 concentration did not reduce in the sediment added with only nitrogen. But PCB118 concentration reduced by 43, 77 and 80 % in the presence of rapeseed oil, iron and organic acids respectively, together with nitrogen.


Both groups of PCB-degrading microbes are abundant in Storvatn sediment and adapted to the cold conditions. Their degradation activity can be enhanced by addition of suitable nutrients.

However, further investigations of the microbes, the degradation mechanisms and optimisation of the nutrient supply are necessary.

The low contamination level, uneven distribution, accessibility and complexity of PCBs will present challenges for the practical implementation of the biodegradation. However these initial results are encouraging.


Microbes for cleaning PCB pollution


Research Scientist Nga Dang Phuong, Norut Narvik

Research Scientist Ross Wakelin, Norut Narvik