Environmental Monitoring of Effluents from Tannery Industries in Kano State, North West Nigeria

The leather tanning industry in Kano State, one of Nigeria's oldest and largest, generates high-strength effluents containing chromium, sulphides, ammonia, and organic matter that are frequently discharged into Challawa Creek and neighbouring water bodies. This study conducted systematic environmental monitoring of tannery effluents and their impact on receiving water quality in three tannery clusters in Kano State. Effluent samples were collected from discharge points of eight tanneries over three consecutive months, and receiving water samples were collected upstream and at three downstream intervals. Parameters monitored included total chromium, pH, chemical oxygen demand, biochemical oxygen demand, total suspended solids, ammonia nitrogen, and sulphide concentration. Results showed total chromium concentrations in effluents ranging from 42 to 186 milligrams per litre, far exceeding NESREA permissible limits of 0.5 milligrams per litre for water discharge. Biochemical oxygen demand in effluents averaged 1,840 milligrams per litre. Receiving water quality deteriorated markedly downstream of tannery discharge points, with dissolved oxygen falling below detectable limits at the most impacted stations. Chromium accumulation in sediments at downstream stations presented long-term ecological risk. The study recommends urgent regulatory intervention requiring installation of chromium recovery and effluent treatment systems, technical support for adoption of cleaner chrome-free tanning technology, and enhanced NESREA enforcement capacity for the Kano tannery sector. Keywords: tannery effluent, chromium, Kano State, water pollution, leather industry.