Heavy Metal Analysis of Wastewater from Tannery Facilities in Kano State

Tannery operations in Kano State, North West Nigeria, generate large volumes of liquid effluent containing heavy metals from chemical processing stages involving chromium salts, dyes, and other auxiliaries. This study analysed the concentrations of heavy metals in wastewater samples collected from tannery effluent discharge points and adjacent surface drainage channels in the Sharada Industrial Area of Kano. Samples were collected in triplicate from six tannery facilities and from three receiving water bodies. Analysis was performed for chromium, lead, cadmium, zinc, copper, manganese, iron, and nickel by atomic absorption spectrophotometry after appropriate digestion. Chromium was the dominant metal contaminant, with effluent concentrations ranging from 18.6 to 124.3 mg/L, far exceeding the Federal Environmental Protection Agency permissible limit of 0.05 mg/L for chromium VI. Lead concentrations in effluent ranged from 2.4 to 11.6 mg/L. Cadmium was detected in all tannery effluents at concentrations between 0.8 and 4.2 mg/L. Surface drainage water concentrations were lower but still substantially above permissible levels at all sampling points, indicating persistent contamination from historical discharges. A strong correlation between chromium concentration and effluent colour intensity was observed. These findings confirm severe heavy metal pollution from Kano tannery operations and emphasise the urgent need for effluent treatment infrastructure investment, chrome recovery systems, and strict enforcement of environmental discharge regulations in the industrial district.

Keywords: heavy metals, tannery wastewater, chromium, Kano State, effluent treatment