Bioremediation of Total Soluble Salt of Tannery Effluent Using Halophilic Microbial Consortium

Abstract

Tannery effluent is known to contain large amount of dissolved salt (such as NaCl) used in the preliminary preservation of hides and skin, which is known to be highly soluble and stable in nature, difficult to eliminate and toxic in nature, thereby being a burden to the environment (ecosystem) and human health. The aim of this study is to isolate halophilic organisms from Nigerian Institute of Leather and Science Technology, Zaria tannery dumpsite using selective media. The isolated microbes were characterized microscopically and biochemically using standard methods. The microbes isolated include; Staphylococcus aureus, Bacillus sp, Pseudomonas aeruginosa, and Saccharomyces cerevisiae. The isolates were used for the bioremediation of total soluble salt in the tannery effluent. Before the tannery effluent treatment, physicochemical parameters such as temperature, pH, colour, Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), chloride content, conductivity, total dissolved solid (TDS) and salinity were determined using standard procedures. The bioremediation of tannery effluent was carried out using the isolated organisms individually and in combination. The highest remediation was observed in the combination of microbial consortium, followed by Saccharomyces cerevisiae, Staphylococcus aureus, Pseudomonas aeruginosa and Bacillus sp. The temperature of the effluent ranges between 27.4°C to 27.6°C before the bioremediation, which increased to between 28.4°C and 32.3°C after remediation. Majority of the physicochemical parameters analyzed recorded drastic decrease especially the salinity (7.10 ppt to 1011 ppm), conductivity (1788 µS to 1407 mS), colour (faint ash to ash), BOD (942 mg/l to 1156 mg/l), COD (1239 mg/l to 508 mg/l), chloride content (181.9 mg/l to 579.8 mg/l), pH (6.3 to 9.1) and TDS (8.20 ppt to 1322 ppm) respectively. Most of the physicochemical parameters are above the Federal Environmental Protection Agency (FEPA) and Ethiopian Environmental Protection Authority (EEPA) standard safe limit viz; pH (6.9), Conductivity (2500 µScm−¹), BOD5 (50 mg/l and 200 mg/l), COD (500 mg/l). However, temperature (<40 and 40°C) and chloride content (1000 mg/l and 600 mg/l) are within the acceptable limits. Also, there is significant difference (P= 0.000 at 0.005 level of significance) between the chloride content of the tannery effluent before the bioremediation and the chloride content after ten days bioremediation. Thus, it is recommended to use these organisms in combination to remedy total dissolved salt efficiently than in single. Halophiles can be used in bioremediation of total soluble salt in tannery effluent. It is recommended that natural halophilic microbes should be used in the remediation of total soluble salts in preference to chemicals, which may contain heavy metals that cause toxicity and threat to the environment (ecosystem) and human health.