Treatment of real winery wastewater by wet oxidation at mild temperature

Abstract

This study explores the treatment of high-strength real winery wastewater (COD0≈35g/L, TOC0≈11g/L) by wet oxidation processes. Wet air oxidation (WAO), catalytic wet air oxidation (CWAO), H2O2-promoted CWAO, wet peroxide oxidation (WPO) and catalytic wet peroxide oxidation (CWPO) were the options tested using different carbon-based catalysts, viz. activated carbon, carbon black and graphite. Their suitability was analyzed in terms of polyphenol, chemical oxygen demand (COD) and total organic carbon (TOC) abatement upon 4h reaction time. The results showed that hydrogen peroxide was the unique oxidant capable of achieving an effective reduction of the organic load. The graphite tested was the most active catalyst, most probably due in great part to its Fe content (0.4wt.%), resistant to leaching.CWPO with that graphite was tested at different conditions following the evolution of COD, TOC and ecotoxicity. The best results were obtained by using graphite at 5g/L, the original pH of the wastewater (3.8), 125°C and the stoichiometric amount of hydrogen peroxide distributed in stepwise additions. Under those conditions, 80% COD and TOC removals with 85% of hydrogen peroxide efficiency were achieved after 4h reaction time, giving rise to colorless effluents of very low Microtox ecotoxicity.