The toxicity of leather tanning wastewater from a traditional tannery (TT), which is based on vegetable tannin (VT), was compared with wastewater from a tannery combining the use of chromium-based tanning (CT) with VT-based tanning operations. Wastewater samples from a TT and a CT plant as well as from five sewer sampling points were collected in Marrakesh, Morocco, and the concentrations of VT and some selected inorganics were measured. A set of bioassays were used to test wastewater toxicity in sea urchin (Paracentrotus lividus) embryos and sperm, in Daphnia magna, and in marine microalgae (Dunaliella tertiolecta). Toxicity end points included: (1) developmental defects, embryonic mortality, sperm fertilization success, and offspring damage in sea urchins; (2) D. magna immobilization; and (3) algal growth rate inhibition. Toxicity tests on TT and CT effluents (TTE and CTE) were run at dilutions ranging from 0.1% to 2% (sea urchins and algae) or up to 12% in D. magna. Parallel bioassays were run on VT extract (VTE) at nominal tannin concentrations ranging from 0.1 to 10 mg l–1. The results showed higher toxicity of CTE compared with TTE. CTE toxicity in sea urchins and algae showed concentration-related trends, whereas TTE exerted hormetic effects at levels of 0.1% to 0.2% and toxic effects at levels ‡1%. The same trends were observed for VTE, suggesting a prevailing role of tannin in TTE-associated effects. The moderate wastewater toxicity of VT-based tanneries might prompt interest in the VT tanning process.
|Titolo:||Wastewater Toxicity of Tannin- Versus Chromium-Based Leather Tanneries in Marrakesh, Morocco|
|Data di pubblicazione:||2007|
|Digital Object Identifier (DOI):||10.1007/s00244-006-0181-5|
|Appare nelle tipologie:||1.1 Articolo in rivista|