We investigated the effects of the application of wastewater sludges on microbial degradation of crude oil. the experiments were carried out in four beach simulating tanks. In each tank, filled with gravel and seawater, crude oil was added on the surface of seawater. Dehydrated-wastewater sludge, liquid-wastewater sludge and synthetic fertilizers were added in tanks A, D and C, respectively. In tanks A and D, sharp increases in the bacterial number and the oxygen consumption occurred immediately while the increases in tank C was slower. The concentration of nitrogen was high during first few weeks and later decreased in tanks A and D. The synthetic nitrogen fertilizer was maintaining the nitrogen concentration above 1 mg l−1 for the whole experimental period. These observations indicated that the effect of the synthetic nitrogen fertilizer was more enduring than those of the liquid and dehydrated sludges. However, higher concentrations of phosphorous were supplied by both the liquid and dehydrated sludges than by the synthetic phosphorous fertilizer. No significant differences were observed between the biodegradation rates of crude oil in each amended tank. Thus, it was concluded that the wastewater sludges are useful as fertilizers for crude oil bioremediation. © 1999 Taylor &amp
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