Biosorption of heavy metals in automobile panel workshop effluent using Bacillus safensis LAU13

Abstract

Heavy metals are natural constituents of the environment, but improper application for human activities has altered their geochemical compositions and biochemical balance. There is a need to remediate heavy metals released into natural resources through anthropogenic activities. This study centres on remediation (by biosorption) of Mn²⁺, Co³⁺, Cu²⁺, Fe²⁺, Zn²⁺, Hg²⁺, Se⁴⁺, Cr³⁺, Pb⁴⁺ and Cd²⁺ from wastewater obtained from automobile panel workshop, Ogbomoso, Nigeria using Bacillus safensis LAU13 inoculum. Initial concentrations of heavy metals in the effluent samples after digestion were determined through Atomic Absorption Spectrometry (AAS). The glucose-enriched wastewater samples were autoclaved, the inoculums cultured and subjected to bio-treatment using 250, 500, 750 and L dosages of Bacillus safensis LAU13 inoculum, a Gram-positive, mesophilic, spore-forming, aerobic and chemo- heterotrophic bacterium. Optical density of inoculated samples was determined through a spectrophotometer and the growth monitored for 48 h. Residual pellets were subjected to Scanning Electron Microscopy (SEM). Results showed that 100% removal was achieved for Mn²⁺ and Co³⁺. Cr³⁺ was reduced to a very minimal concentration, Zn²⁺, Cu²⁺, Pb⁴⁺and Se⁴⁺ were above average in the remediation. Fe²⁺and Cd²⁺ were remediated below average but very low remediation of Hg²⁺ with less than one per cent removal. Optical density increased significantly showing rapid growth of microorganisms irrespective of glucose supplement, and 250 L inoculum dosage has the optimum performance. SEM micrographs indicate certain accumulated aggregates taken as remediated heavy metals. The study confirmed the efficiency of the biosorption technique as an alternative to the conventional treatment methods of huge cost, and high precipitates and slurry. Bacillus safensis LAU13 is therefore recommended as a bio-remediating agent in treating automobile workshop effluents with high amounts of manganese, cobalt, chromium, zinc, copper, lead and selenium.