LEACHING ASPECTS OF OIL SLUDGE BIODEGRADATION IN SOIL1

Abstract

Efficient disposal of waste oil sludges by biodegradation in soil (“land farming”) requires management practices that include fertilizer addition. The effect of such practices on soil leachate quality was studied in lysimeter columns containing 5 percent (wt/wt) hydrocarbon in a soil-sand mixture. Fertilizer was added in various formulations at a carbon:nitrogen and carbon:phosphorus ratio of 200:1 and 2640:1, respectively. As expected, undegraded hydrocarbons did not appear in the leachate, nor was phosphate eluted from the limed soil-sand mixture. A very moderate increase in total organic carbon of the leachate occurred due to hydrocarbon biodegradation. When nitrogen was applied as urea or as a urea-paraffin adduct, 23 and 19 percent of the added nitrogen were eluted in the leachate, respectively. No nitrogen appeared in the leachate when nitrogen was applied as urea formaldehyde. The above results and additional cited reports indicate that judiciously located and operated land-farming sites are not likely to endanger underground aquifers.