Acute toxicity of abattoir and saw-mill effluents to juvenile-sizedClarias gariepinus

Abattoir and saw-mill effluents are one of a variety of industrial wastes released into inland freshwater systems in developing countries like Nigeria. For a better understanding of chronic toxic effects of these effluents, a series of static short-term bioassays were conducted to evaluate the acute toxicity of composite mixtures of abattoir and saw-mill effluents (50:50 v/v) to juvenile-sized Clarias gariepinus. The physicochemical parameters of these effluents were measured using standards methods. Effluent concentrations of 20.0, 40.0, 60.0 and 80.0% and control series (0.0%) were utilized as exposures and the 96 h survivorship was subjected to probit analysis. The mean 96 h LC50 value of 49.00 ± 0.01 mg/l was computed from the probit plot while all the physicochemical parameters analysed, except temperature, were not within permissible limits specified by the National Environmental Standards and Regulations Enforcement Agency. In view of the potential impacts on aquatic life and environmental quality, the regulated discharge of this industrial waste water into aquatic systems is recommended.