  Tannery wastewater contains large amounts of pollutants that, if directly
discharged into ecosystems, can generate an environmental hazard. The present
investigation has focused the attention to the remediation of wastewater
originated from tanned leather in Tunisia. The analysis revealed wastewater
with a high level of chemical oxygen demand (COD) of 7376 mgO2/L. The
performance in reduction of COD, via electrocoagulation (EC) or UV photolysis
or, finally, operating electrocoagulation and photolysis in sequence was
examined. The effect of voltage and reaction time on COD reduction, as well as
the phytotoxicity were determined. Treated effluents were analysed by UV
spectroscopy, extracting the organic components with solvents differing in
polarity. A sequential EC and UV treatment of the tannery wastewater has been
proven effective in the reduction of COD. These treatments combined afforded
94.1 % of COD reduction, whereas the single EC and UV treatments afforded
respectively 85.7 and 55.9 %. The final COD value of 428.7 mg/L was found
largely below the limit of 1000 mg/L for admission of wastewater in public
sewerage network. Germination tests of Hordeum Vulgare seeds indicated reduced
toxicity for the remediated water. Energy consumptions of 33.33 kWh/m3 and
314.28 kWh/m3 were determined for the EC process and for the same followed by
UV treatment. Both those technologies are yet available and ready for scale-up.
