Biodegradability of unused lubricating brake fluids in fresh and marine ecosystem.
The biodegradability of four unused lubricating brake fluids (Total brake fluid, Allied brake fluid, Oando brake fluid and Ate brake fluid) was carried out in fresh and marine water obtained from Isiokpo stream and Bonny river of the Niger Delta, South South Nigeria. Biodegradability, of the brake fluids were obtained after a 56 day period of incubation monitored at 2 weeks intervals using the percentage ratio of Biological Oxygen Demand (BOD) to Chemical Oxygen Demand (COD). Olive oil was used as the positive control while sodium azide served as the negative control. The results obtained showed the following rate of biodegradability in fresh water and marine water; Total brake fluid (20, 2.3 percent), Allied brake fluid (40%, 1%), Oando brake fluid (44%, 2.5%), and Ate brake fluid (13.3%, 2.1%). Statistical analysis using ANOVA, showed that there was significant difference (P<0.05) in the percentage mineralization of Allied brake fluid in both fresh and marine water sources. Biodegradability of the brake fluids was higher in fresh water than in the marine water. Results obtained from the viable bacterial and fungal counts (TVC) indicated higher total heterotrophic bacterial (THB) count than total fungal (TF) counts and higher hydrocarbon utilizing bacteria (HUB) counts than Hydrocarbon Utilizing Fungi (HUF) counts. Characterization and identification tests revealed that a microbial consortium comprising of the following genera; Bacillus, Pseudomonas, Proteus, Escherichia, Micrococcus, Arthrobacter, Enterobacter and Citrobacter was implicated in the biodegradation process in fresh water, while Bacillus, Pseudomonas, Staphylococcus, Enterobacter and Citrobacter was implicated in the marine water source. Similarly, the moulds encountered from the fresh water were, Aspergillus, Fusarium, Penicillium, Geotricum and Cladosporuim. The yeast was candida species. In marine water, the moulds were Aspergillus and Fusarium. Physicochemical parameters monitored were pH, salinity, BOD, COD, SO42- and PO43-. The study indicates that the lubricating brake fluids which are petroleum based were not readily biodegradable in fresh and marine aquatic ecosystems, hence research into production of biobased lubricating oils that are environmentally friendly, cost effective and efficient in performance is highly recommended.
Key words: Biodegradation, Mineralization, Lubricating Oils, Biodegradability, Brake fluids.