Treatment of tannery effluent from Sharada Industrial Estate in Kano, Nigeria with porous clays

Abstract

The tannery industry plays a significant role economically, but it negatively hampers the environment by elevating the concentration of pollutants during the tanning process. The geochemical and mineralogical properties of two Nigeria clay samples were studied by Atomic Absorption Spectrophotometer (AAS) and X-ray diffractometer respectively. Clay samples were obtained from Ozanagogo and Otor-Edo in Delta State, coded OZ and OT respectively. Column clay packed with pebbles in a ratio of 1:4 was used for the purification/removal of pollutants using batch method. Results revealed that the pH of the treated effluents increased from 3.7 to 6.9 and 8.2. Turbidity values reduced from 63.00 NTU to 0.2 NTU and 0.5 NTU, while COD values dropped from 877.00 mg/L to 2.71 mg/L and 15 mg/L, and BOD values decreased from 350.00 mg/L to 0.71 mg/L and 5.00 mg/L. A reduction in chloride levels from 2650.00 mg/L to 97 mg/L and 102.00 mg/L was also observed, while treatment of the effluents brought the bacterial count from 1.9x10⁸ to nil, using both clay samples. The mineralogical study revealed that kaolinite was the most abundant clay mineral in both clay types, while hematite was the least abundant in both samples. This paper studied the use of locally sourced material (clays) in treating tannery effluent, and compared the values of the treated effluent with WHO, SON and NESREA standards for drinking water. This study has shown that the porous clay method is an effective purification system using cost-effective, locally-sourced materials and a simple decentralized treatment method.