Recycling of concentrated refinery tar residues using bioremediation

The treatment operations undertaken by CELTIC Technologies Ltd from August 1997 to October 1998 at a disused refinery in Scotland, UK, in agreement with the Scottish Environmental Protection Agency are described. Initially, contaminant levels in the raw sludge were ~ 300,000 mg/kg oil hydrocarbons in the range of C₁₀-C₄₀ and 600 mg/kg PAH. Risk-based criteria were agreed for PAH including 6 mg/kg, dibenz(a,h)anthracene; 17 mg/kg benzo(a)pyrene and 5000 mg/kg hydrocarbons (diesel range organics). A total of 7000 cu m of tar was successfully treated and met validation requirements. The project comprised of: rapid on site treatment with no off site disposal; conversion of tar into soil cover for golf course construction; and the absence of environmental impact. In the treatment, the biopiles and the underlying groundwater aquifer were monitored and sampled and results of treatment for 8-10 wk showed typical final mean levels of : 2385 mg/kg alkanes; 42.2 mg/kg total PAH; 4.7 mg/kg benz(a)pyrene; 2.2 mg/kg dibenz(a,h)anthracene.