Monitoring of industrial effluent ecotoxicity in the greater Thessaloniki area

The aim of this work was the assessment of the toxicity of various industrial effluents by a battery of bioassays in order to investigate their potential impact during co-treatment of industrial and municipal wastewaters in an activated sludge plant. The battery test included three test-species as indicator organisms: the protozoan unicellular organism Tetrahymena thermophilla, the crustacean Daphnia magna and the marine photobacterium Vibrio fischeri. The results obtained from the bioassays showed highly toxic effluents originating from processes such as metal coating, chemical and dyeing plants. Daphnia magna exhibited the highest sensitivity, while Tetrahymena thermophilla appeared as the most tolerant species. The response of each organism varied from hormesis affects up to 100% mortality for samples collected from food industry effluents. A specific relation between the chemical analysis data and the bioassay results was not observed. The Student–Newman–Keuls statistical analysis showed that the mean values of bioluminescence inhibition of Vibrio fischeri and mortality/immobilization of Daphnia magna were overlapping for the cases that the organisms were exposed to metal coating and chemical industrial effluents, while in the case of Tetrahymena thermophilla the overlapping mean values included metal coating, chemical and paper industries. Distinctively low mean values were observed for distilleries and food effluents for the cases of low mean values were observed for wastewaters from paper industries and distilleries.

The examination of the toxicity properties of industrial effluents was performed in this study, by using a combination of physicochemical analyses and bioassays aiming to the assessment of their effect on activated sludge treatment plants and the receiving ecosystems. Industrial effluent samples were collected from six types of production plants and their toxic properties were evaluated by using three test species: Vibrio fischeri, Daphnia magna and Tetrahymena thermophilla. Physicochemical analyses revealed the variation of the samples composition due to the complicated nature of the corresponding production processes. Bioassay results showed a high variation of toxic properties of the samples to the test species: high toxicity effects were observed from samples collected from the metal coating industries, while samples collected from distilleries, showed the lowest toxicity properties. The use of battery of bioassays is required in combination with physicochemical analyses for an integrated monitoring of the industrial effluent properties.