Treatment of winery wastewater by ozone-based advanced oxidation processes (O 3, O 3/UV and O 3/UV/H 2O 2) in a pilot-scale bubble column reactor and process economics

Abstract

The effectiveness of different ozone-based advanced oxidation processes (O 3, O 3/UV and O 3/UV/H 2O 2) on the treatment of winery wastewater was investigated in a pilot-scale, bubble column reactor. At the natural pH of the wastewater (pH 4) the effectiveness of each AOP followed the sequence: O 3/UV/H 2O 2 > O 3/UV > O 3 > UV-C. The rate of chemical oxygen demand (COD) and total organic carbon (TOC) removal were enhanced by operation at neutral (pH 7) and at alkaline pH (pH 10). The underlying chemistry involved in each of the AOPs is discussed and correlated with the observed reactivity. The rate of ozone consumption in the reactor with the O 3/UV and O 3/UV/H 2O 2 processes was in the range of 70–95% during the experiments, suggesting an effective use of the ozone supplied to the system. In all the experiments the disappearance of the winery wastewater organic load was described by pseudo-first-order apparent reaction kinetics. The fastest rate constant (6.5 × 10 −3 min −1), at the natural pH of the wastewater, was observed with the O 3/UV/H 2O 2 process under optimised oxidant dose (COD/H 2O 2 = 2). An economic analysis of the operating costs of the AOPs processes investigated revealed the O 3/UV/H 2O 2 to be the most economical process (1.31 Euro m −3 g −1 of TOC mineralised under optimised conditions) to treat the winery wastewater.