Toxicity of effluents

Abstract

Reliable characterisation of the hazardous properties of effl uents is an important step in water quality management. A “chemical-specific” approach, based on measurements of individual chemicals or chemical groups, has been shown to have limitations particularly in complex mixtures of chemicals such as effl uents. This study shows the importance of direct toxicity assessment of wastewater samples using a toxicity test. Data obtained by direct testing were compared to the toxicity predicted using key toxic compounds data. Toxicity of wastewater samples from tannery and chemical industries as well as key toxic chemicals were assessed using the water flea Daphnia magna. The toxicity predicted from the levels and toxicities of wastewater components was found to be unreliable due to under- or over-estimation of the experimentally determined toxicity. For this reason, direct toxicity measurement is more appropriate for the effective and reliable assessment of effluent quality.

Keywords

• toxicity
• Daphnia magna
• direct toxicity assessment
• chemical industry
• tannery wastewater
• toxic unit