Comparison of Energy Requirements of Conventional Ozonation and the Aop O3/h2o2 for Transformation of Target Micropollutants in Diverse Water Matrices

We used conventional ozonation and the AOP O3/H2O2 to estimate the required energy to achieve the desired pre-defined level of oxidation of target organic micropollutants by hydroxyl radicals. We used the probe compound para-chloro benzoic acid (pCBA) to assess the fraction of OH available for oxidation of micropollutants. pCBA reacts slowly with O3 but reacts very fast with OH (kOH,pCBA = 5 x 10 Ms). For our investigations we used three lake waters: Lake Zürich (ZH) and Lake Greifensee water (GF) from Switzerland and Lake Jonsvatnet water (NW) from Norway. The DOC concentrations were 1.4, 3.5 and 3 mg/L for ZH, GF and NW waters respectively and alkalinity was 2.7, 3.4 and 0.3 mM correspondingly. The results showed that for 90% pCBA transformation, the O3 consumption was roughly 2 mg/L (40 μM) for ZH and NW waters and approximately 4 mg/L (80 μM) for GF water. Bromate formation in ZH water was much higher than in GF and NW waters and exceeded the EU drinking water standard of 10 μg/L for all examined O3 concentrations, for initial bromide concentration 80 μg/L. The energy requirement to achieve 90% transformation was in the range 6.4 – 12.8 Wh/person/day for conventional ozonation of ZH-water and slightly higher for the use of AOP O3/H2O2. The use of O3/H2O2 however, reduces the required contact times and bromate formation.