Abstract

The effect of inorganic fertilizer (NPK agricultural fertilizer) on biodegradation of soil (5 kg) contaminated with crude oil (50 g) was investigated for seven weeks. Four different test options were prepared namely; (i) 100 g of contaminated soil + 30 g of NPK agricultural fertilizer; (ii) 100 g of contaminated soil + 60 g of NPK agricultural fertilizer; (iii) 100 g of contaminated soil + 90 g of NPK agricultural fertilizer; and (iv) 100 g of contaminated soil only (control). The microbial degradation was monitored by the measurement of total heterotrophic count (THC), hydrocarbon utilizing bacterial count (HUB) and gravimetric loss of the crude oil with time. At the end of the seven weeks of incubation, the THC of 6.9x10⁷, 9.0x10⁷, 1.03x10⁸ and 3.1x10⁷cfu/g were recorded for test options (i), (ii), (iii) and (iv), respectively. The hydrocarbon utilizing bacterial counts (HUB) were 1.68x10⁵, 1.63x10⁵, 1.9x10⁵ and 4.8x10⁴ cfu/g for tests options (i), (ii), (iii) and (iv), respectively. The corresponding gravimetric hydrocarbon losses were 40.0, 50.52, 36.84 and 29.47% for test conditions (i), (ii), (iii), and (iv), respectively.  The results of the study suggest that addition of inorganic fertilizer (especially 60 g NPK agricultural fertilizer) will further enhance microbial utilization of hydrocarbons.

Key words: Biodegradation, crude, NPK agricultural fertilizer.