A study on the relationship between biodegradability enhancement and oxidation of 1,4-dioxane using ozone and hydrogen peroxide

Advanced oxidation involving O-3/H2O2 was used to eliminate 1,4-dioxane and to enhance the biodegradability of dioxane-contaminated water. Oxidation experiments were carried out in a bubble column reactor operating in fed-batch. The rate of dioxane removal and enhancement in biodegradability was investigated at hydrogen peroxide to ozone ratios between 0 and 0.6 mol:mol and pH between 5 and 11. A theoretical model was also applied to predict the experimental data and to investigate the effects of dioxane concentration, pH, and H2O2 concentration. The model predictions fit the experimental data well and there was a linear correlation between dioxane oxidation and BOD enhancement. At low dioxane concentrations, the oxidation rate was first order and it gradually approached zero order with increasing dioxane concentration. Also, the biodegradability of the solution increased with pH up to about 9 and it stayed constant with further pH increase. Hydrogen peroxide initially enhanced dioxane removal and biodegradability enhancement of the solution. However, at H2O2:O-3 ratios greater than about 0.4-0.45 mol:mol, i.e. about 2.90 mM for H2O2 concentration, H2O2 had negative impacts and resulted in reduced dioxane removal and biodegradability increase. (C) 2004 Elsevier Ltd. All rights reserved.