Bioremediation of insulating oils

Bioremediation is the process whereby naturally occurring micro-organisms are used to digest chemicals into harmless products such as carbon dioxide, water and microbial biomass. A wide range of chemicals can be degraded in this way including oils and greases. However, the time scales over which this degradation can occur can vary enormously due to limitations imposed by various factors. These factors include numbers of organisms present, nutrient levels, heat, moisture, oxygen levels within the soil and the complexity of the contaminant that needs to be degraded. For example, linear compounds are more easily degraded than ring compounds. Soils generally contain around 10⁶ micro-organisms per gram, but this needs to be boosted to a level of 10⁸ per gram ideally by natural multiplication over a period of time. The increase can be achieved through the addition of selected microbes, however, their rate of increase in population is not always as high as that of the indigenous microbe population. The microorganisms are most effective under particular conditions, for example in the presence of nutrients such as nitrogen and phosphorous and at temperatures of 20-25°C. Bioremediation can be carried out in two ways, ex-situ and in-situ