Physico-Chemical Properties and Microbial Community of Soils Polluted by Tannery Effluents at the Nigerian Institute of Leather and Science Technology Zaria, Nigeria

Abstract Tannery effluent is a wastewater containing complex toxic chemical compounds affecting the environment and the exposed organisms. This study is aimed to evaluate the physicochemical parameters and microbial composition of soil contaminated by tannery effluents.The results showed that the contaminated soil recorded highest levels of chromium and ammonia in site C, which ranges from a minimum of 0.40mg/g to a maximum of 0.43mg/g and lowest concentration of 0.60 to a maximum of 0.70mg/g respectively.Similarly, sulphide ranges from 0.40 mg/g concentration to 0.44mg/g in the same site. The recorded values exceeded the tolerable levels of <0.1, 0.2 and 0.2 mg/g for chromium, ammonia and sulphide respectively, set by Federal Ministry of Environment. Additionally, the results revealed variety of bacteria inhabiting the contaminated soil, such as Bacillus cereus, Bacillus subtilis, Proteus mirabilis, Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli, Serratia marcensces, and Streptococcus pyogenes. Moreover, the fungal species analysed in the contaminated soil includes Aspergillus niger, Aspergillus flavus, Aspergillus fumigatus, Penicillium notatum, Mucor pusillus and Fusarium sporotrichioides. High counts of bacteria and fungi were recorded in the soil contaminated with tannery effluent. The viable soil microbialcounts were found in the range of 7.90±1.60 – 8.00±0.70 ×105cfu/g and 1.50±0.10 – 1.2±0.20 × 104cfu/g for the bacteria and fungi, respectively.The presence of these chemical substances and microorganisms in the contaminated soil samples poses a potential threat to environmental sustainability. Future research should focus on sustainable waste disposal solutions and evaluate the long-term ecological impacts of tannery-related pollution. Keywords: Microorganism, physicochemical parameters, polluted soil, Tannery effluent