Assessing toxicity of two industrial zone effluents reaching Kelani River, Sri Lanka

Evaluation of the efficacy of waste treatment technologies of industrial waste is a major challenge for sustainable industrial development world-wide. Hence, new strategies are needed to assess interactive toxic effects of all substances present in the treated waste. This study assessed potential toxic hazards of treated effluents discharged from common wastewater treatment plants of two industrial zones located in the Kelani River basin using Allium cepa (common onion) test system. The results showed that the final effluents of both industrial zones under undiluted and diluted (1:8 v/v) conditions induced cytotoxicity on all occasions, with evidence of significant (p < 0.05) mito-depression in the root meristem and retardation of root growth in A. cepa. Genotoxic hazard of the effluents was evident by frequent increase of nuclear and chromosomal abnormalities, and occasional development of micronuclei in the root meristem. Dilution of the effluents to 1:8 reduced the genotoxic effects generated in A. cepa roots by the final effluents. The results revealed that waste treatment technologies in these two industrial zones need to be upgraded in order to eliminate cytotoxic and genotoxic hazards associated with the treated effluents. The results highlight the importance of incorporating practically feasible bioanalytical tools such as A. cepa root based test system on a regular basis for evaluating the efficacy of waste treatment technologies.