A spillage of red diesel oil (heating oil) from a holding tank located on Derwent Island in Lake Derwentwater, Cumbria, has been successfully treated using Microbac's oil degrading bacterial cultures. The spill occurred in the Lake District National Park and a major concern was contamination of the lake water. The main problem associated with the work was access to the island which was via a small rowing boat. This precluded the use of conventional techniques for treating contaminated land (i.e. removal of the soil) and, even in Microbac's case, the use of a conventional size Bioreactor was impossible.
After assessment of the site and extensive sampling and analysis to determine the extent of the spill, Microbac designed a treatment system to contain and treat the spill, which incorporated a small, specially constructed Bioreactor. The unit was located at the top of the water gradient, with a plastic lined sump prepared at the lower part of the contaminated area, to collect the oily leachate from the site. Water and biodegradable emulsifier were piped from the Bioreactor to a variety of injection points in the contaminated area. This was followed by an adapted bacteria/nutrient mix. Surplus water contaminated with diesel oil was then leached from the soil down the sloping gradient and collected in the sump, from where it was pumped back through the Bioreactor and recycled over the contaminated area. This system allowed the degradation of the diesel oil in both the Bioreactor and in the soil.
After 70 days, total hydrocarbon levels in the soil were reduced to less than 1 mg/l at all sampling points and visual inspection of the site showed no sign of diesel contamination in the soil and an absence of an soil sheen in the collection sump. Contamination of Lake Derwentwater was successfully prevented.