Effects of single and combined ozonation with hydrogen peroxide or UV radiation on the chemical degradation and biodegradability of debittering table olive industrial wastewaters

Chemical oxidation of debittering table olive wastewaters using ozone alone and combined with hydrogen peroxide or UV radiation has been studied. The effect of oxidant concentrations on COD, BOD, TC (total carbon), aromatic content and colour of wastewaters has been observed. COD reduction of 80 or 90% can be reached with ozone doses between 3 and 4 g in the presence of 10−3 M initial hydrogen peroxide concentration (2.4 g at the conditions investigated) or 254 nm UV radiation while moderate reductions of TC can be achieved (between 40 and 60%). Both the aromatic content and colour nearly completely disappear with less than 0.5 g of ozone applied. Along the reaction pH of wastewaters diminishes from 12 to 7.5. Biodegradability of wastewaters, measured as BOD/COD, increases from 0.16 (untreated wastewaters) to nearly 0.7 or 0.8 when using ozone combined with hydrogen peroxide (2.95 g O3 fed during 2 h and 2.4 g H2O2 initially charged) or UV radiation (3.98 g O3 fed during 2 h and 2.65×10−6 Einstein s−1) as the oxidising systems, respectively.