Multi-species toxicity evaluation of a chromium-based leather tannery wastewater

This study focused on a comparative evaluation of wastewater from a chromium-based tannery in Izmir (Turkey). Two sampling campaigns included raw wastewater (R), the effluents of coagulation/flocculation process (CF), biological treatment (B) and dried sludge (DS). Samples were analyzed for their metal contents. A set of toxicity endpoints were tested by sea urchin (Paracentrotus lividius and Sphaerechinus granularis) for the endpoints of acute embryotoxicity, developmental defects, changes in sperm fertilization success and transmissible damage from sperm to the offspring. Furthermore, algal growth (Selenastrum capricornutum) inhibition and Daphnia magna immobilization tests were performed according to standard procedures. The sea urchin bioassay results showed that raw wastewater toxicity is enhanced by the physico-chemical treatment and is decreased by the biological treatment for both samples. Confirming the data from a previous study, a concentration-related toxicity was exerted by effluent or sludge samples according to the following rank: DS > CF > R > B. On the other hand, offspring quality was not affected by sperm exposure to any wastewater or to sludge samples. However, D. magna was immobilized for both samples by the ranking of R > CF > B while algal growth inhibition was caused in a different order for the samples. Overall results suggest submitting the CF effluent to biological treatment which absorbs the toxic content of the wastewater in leather tanning industry; however, the sludge containing toxic components must be handled very carefully.