Biodegradability of Selected–Oil Spill Dispersants Commonly Used in Nigeria

Abstract

The study investigates the biodegradation of two oil spill dispersants: ‘Eco-Remover’ which was obtained from the Nigerian National Petroleum Corporation (NNPC), Port Harcourt and a locally made unapproved ‘Rigwash,’ obtained from an industrial chemical store at Trans-Amadi, Port Harcourt. The setups were monitored at two weeks interval over 42-days period at room temperature (approximately 30°C) on a static shake-flask system. The physico-chemical parameters of the samples were analyzed using standard chemical methods such as the atomic absorption spectrophotometry, Gas Chromatography (GC-FID) and the titrimetric technique. The result of primary biodegradation rate revealed that the mixture of Eco-Remover, seawater and crude oil (L2) was the highest degraded at 77.1%, followed by Eco-Remover and seawater combination (L1) at 4.39%. K1 (a mixture of seawater and Rigwash) and K2 (a mixture of crude oil, seawater and Rigwash) degraded at 1.22% and 1.19% respectively. The result also indicated that K1 had an adverse effect on crude oil. Analytical Profile Index of bacterial isolates revealed a total of Five genera found growing on the samples. Among them, Bacillus, Pseudomonas and Kocuria were dominant and possess the potential to utilize dispersants and/or crude oil as the only carbon sources. The fungal isolates include: Aspergillus niger (18.0%), Cladosporium carionii (8.20%), Fusarium oxytoca (4.92%), Myxomycete spp. (13.1%), Fusarium spp. (3.28%), Penicillium spp. (3.28%), Phoma spp. (8.20%), Pleurotus pulmorarius (8.20%), Rhizopus spp. (3.28%), Talaromyces flavus (9.84%), Trichoderma longibrachiatum (6.56%), T. polysporum (4.92%) and Verticillium spp. (8.20%). Analysis of variance at confidence limit P ≤ 0.05 showed that there was significant difference in the biodegradation of each dispersant or their combination with crude oil. The implication of this study establishes that Eco-Remover is more biodegradable than Rigwash ‘dispersant’. However, there is need for further studies on their application in the field to confirm the outcome of this laboratory observations.