Comparative bacteriological and mycological assessment of wastewaters from gold-mining and pharmaceutical sites in Minna, Niger State Nigeria

Abstract

The global increase in human population has led to severe human activities like gold mining and pharmaceutical industries which in turn alters the unique nature of the environment. This study was carried out to ascertain the microbial composition of the wastewater samples collected from a gold mining site and pharmaceutical site in Minna, Niger State, Nigeria. Wastewater samples were subjected to microbial analysis using standard serial dilution and culture techniques, followed by biochemical characterization of bacterial isolates and morphological identification of fungal isolates. The results obtained  shows higher microbial loads in gold mining wastewater compared to pharmaceutical effluent, with total bacterial counts of 3.0 × 10⁴ CFU/mL and 2.6 × 10⁴ CFU/m L, respectively, and total fungal counts of 2.1 × 10⁴ CFU/mL and 1.1 × 10⁴ CFU/mL. Nine bacterial species were identified, including Gram-positive isolates (Bacillus sp., Staphylococcus aureus, Micrococcus sp., Corynebacterium sp., and Enterococcus sp.) and Gram-negative isolates (Pseudomonas sp., Enterobacter sp., Salmonella sp., and Escherichia coli). Fungal isolates comprised five species: Mucor sp., Penicillium sp., Aspergillus sp., Fusarium sp., and Rhizopus sp. The distribution of isolates varied across sites, with Salmonella and Enterobacter restricted to mining wastewater, and Corynebacterium and E. coli restricted to pharmaceutical wastewater. The coexistence of opportunistic and pathogenic microorganisms indicates significant environmental and public health risks, including the potential spread of antimicrobial resistance and mycotoxin contamination. These findings underscore the urgent need for improved wastewater treatment and monitoring strategies to mitigate pollution burdens from industrial and mining activities in Minna.