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.