Biodegradation of oily sludge in Norwegian soils

Abstract

The degradation rate of oily sludge in soil under Norwegian conditions has been studied in field experiments during a 32 months' period. The experimental plots were added 0, 200, 400, and 600 kg N per ha. In uncultivated soil the oil content was reduced by respectively 4, 9, 22, and 26% during the first 9 months. In the same period the corresponding biodegradation in cultivated soil were 10, 15, 39, and 45%. At the end of the experiment only minor differences between the two different soil types were found. The mean degradation in percent was now 35, 50, 74, and 83, respectively. The optimum temperature for oil degradation in soil was found to be about 18°C. About 2/3 of the optimum activity was retained at 12°C. No leaching of oil or lead through soil columns infiltrated with oily sludge could be observed. A close relationship between oil content of the soil and the rate of water infiltration was found. Due to the extremely high content of lead in this oily sludge, a second application of sludge could not be recommended.