Biodegradation of oily sludge in Kuwait soil.

Soil microorganisms were not inhibited by mixing oily sludge in soil up to 8.7% (w/w) oil (15% sludge). Adding NH 4 (+) and phosphate increased microbial activity. Microbial activity was also affected by seasonal variation. Thermotolerant microorganisms were more predominant during the summer. After 29 months, 72%, 84%, and 83% of the soil was degraded in fertilized soils dosed with 2.9, 5.8 and 8.7% oil, respectively.