Bioremediation of a Crude Oil Polluted Tropical Mangrove Environment

A combination of bioaugumentation with hydrocarbon utilizing indigenous bacteria, biostimulation with agricultural fertilizer (NPK 15:15:15) and tilling were employed as remedial options for 20 weeks in a crude oil polluted tidal plain dominated by mangrove ( Rhizophora , Laguncularia and Avicenia ) vegetation. Soil moisture rose from 48.5% prior to remediation to 60.48% four weeks after treatment and dropped to 48.22% after remediation. Other physicochemical parameters of soil such as total hydrocarbon (1.22 to 0.20ppm), organic carbon (18.14 to 8.85%) and carbon/nitrogen ratio (91 to 25) dropped during the remediation period. Total Nitrogen (0.20 to 0.36%) increased during the remediation period. The total heterotrophic bacteria (THB) count increased in treatment options A (biostimulation, bioaugumentation and tilling), B (bioaugumentation and tilling) and D (biostimulation and tilling). The THB count of option C1 (double control), C2 (control) and E (tilling alone) were fairly constant throughout the remediation period. There was however an increase in the hydrocarbon utilizing bacterial counts for all treatment options throughout the remediation period. This increase was greater in option A, B and D. Option A (84%) and option D (82%) recorded higher levels of hydrocarbon loss (P> 0.01) than the other four options B (76%), C1 (36%), C2 (65%) and E (63%). Option B also recorded a significantly higher level of hydrocarbon loss (P>0.01) than C1 , C2 and E while that of C1 was significantly lower than C2 and E. The addition of limiting nutrients (biostimulation) with tilling (option D) is a preferred remedial option for a crude oil polluted soil in a tropical mangrove environment @ JASE