Biological remediation of polychlorinated biphenyls (PCB) in the soil and sediments by microorganisms and plants

Abstract

It is a known fact that the environment is suffering from severe contamination as a result of various uncontrolled activities of man and chemicals in the biosphere. This acute and diffuse contamination of air, soil and water by metals, chemicals and metalloids causes wide environmental concerns, which if left unchecked will be detrimental to man and organisms. Biological methods for cleaning of the environment especially the soil have been receiving increasing attention for the past two decades. Bacteria and fungi have been the natural detoxification agent for contaminants in the environment. Recently, research has shown that with the combination of plants and microorganism in the right proportions and technique, detoxification of environmental contaminants will produce a desirable and better result and most importantly the natural environment will not be affected as some of the processes are environmentally friendly. However, the hydrophobic organic molecules such as polychlorinated biphenyls (PCBs) tend to be much less responsive to bioremediation strategies. The wide spread presence of this compound and others in the prominent group known as persistent organic pollutants (POP’s), that share common chemical, toxicological and environment properties continues to increase in the environment, even with the various measures taken to control its presence in the environment. This review focuses on the possible trends of remediation of PCBs in the environment and the methodologies applied. It also reviews the merits and demerits of using plants and microorganisms as biological detoxification agents. This will highlight the possible improvement measures on the combination of plants and microorganisms in bioremediation, thereby filling the gap left behind by the conventional methods of remediation with its enormous limitations and disadvantages. Key words: Bioremediation, phytoremediation, PCB, biodegradation, environmental pollution, rhizodegradation, thermal and chemical/physical process, dechlorination, contaminated soil, oxidative dechlorination/reductive dechlorination.