Assessment of Biosorption Capacity of Sugarcane Bagasse and Cultures of Aspergillus flavus And Trichophyton species in Removal of Heavy Metals from Refinery Effluent

Abstract

Most refinery effluents have been reported to consist of a variety of hazardous substances, heavy metals included. This poses a serious health hazard, as well as a threat to the ecosystem. This study was carried out with the aim of testing the ability of two fungal isolates: Trichophyton species and Aspergillus flavus in removal of Nickel (Ni), Mercury (Hg) and Arsenic (As) from effluent of the Kaduna Refinery and Petrochemical Company (KRPC), with sugarcane bagasse serving both as growth medium and as a component of the experimental biosorbents. The physicochemical properties of the effluents were determined following standard procedures. The performances of the experimental sorbents in the removal of the heavy metal ions were also determined using fixed bed sorption columns. It was observed that the raw refinery effluent was highly turbid (111NTU) with high electrical conductivity (717µS/cm) and chemical oxygen demand (874.10mg/l). Arsenic (As) was not detected, while a higher than the permissible limits of Nickel (1.149mg/l) and Mercury (484.780mg/l) was detected. The optimum time of Ni and Hg uptake by all the treatments was observed to be 1hr after the start of the experiment, and equilibrium was reached between 5-6hrs and at 4hrs for Nickel and Mercury adsorption respectively. Sugarcane bagasse proved to be a suitable medium for growth of fungi as well as removing heavy metal ions from refinery effluent. It was observed that both fungal isolates as well as the sugarcane bagasse had the ability to remove Ni and Hg ions from refinery effluent with more than 90% efficiency. The unsterilised and un-inoculated sugarcane bagasse removed more Hg ions (97.6%) than the fungal cultures, while in Ni ions removal, the sterilised sugarcane bagasse inoculated with Aspergillus flavus had the highest performance (97.1%). Data analysis carried out using one-way Analysis of Variance (ANOVA) showed a significant difference between the performance of the sorbents in the removal of Ni ions (p=0.00), while no marked difference was observed  statistically (p>0.05) between the performance of un-inoculated sugarcane bagasse in removing  and adsorbing the heavy metal ions from solution with that of the sugarcane bagasse inoculated with the test fungal isolates used in this study both separately and as co-culture, as each of the sorbents proved to be very efficient. It was therefore concluded that the refinery effluent consisted of physicochemical properties including turbidity, electrical conductivity, and chemical oxygen demand, as well as heavy metals Ni and Hg, most of which were found to be higher than the permissible limits; while As was not detected. Sugarcane bagasse and fungal isolates (A. flavus and Trichophyton species) were also found to be very effective in removing Ni and Hg ions from the effluent.

Key Words: refinery effluent; heavy metals; sorbents; Aspergillus flavus; Trichophyton species; physicochemical properties