Removal of taste and odor causing compounds in drinking water by peroxone process

Istanbul's main drinking water source, İSKİ Asia-1 Reservoir, faces algal blooms at certain times of the year depending on temperature increase and nutrient concentration. Algal-derived compounds, such as geosmin and 2-methylisoborneol, give earthy-musty taste and odor to drinking water even at quite low concentrations (>10 ng/L) and cause consumer complaints. To prevent the loss of consumer reliability, water authorities are seeking ways to solve this problem by not only searching for the most efficient removal process of these compounds from water, but also by improving management of the watershed. Istanbul Water and Sewerage Administration (İSKİ) has previously searched for solutions in order to preserve the basin and improve the reservoir's quality. Despite all the precautions and remediation attempts, eutrophication in the reservoir could not be avoided. Therefore, a proper treatment process for the removal of the algal-derived compounds was necessary. Peroxone Process is one of the most effective treatments in advanced oxidation processes. In this process, through a series of reactions, the interaction between ozone and hydrogen peroxide produces hydroxyl radical at a certain molar ratio. In comparison to ozone alone, there is an increased production of hydroxyl radical for the removal of pollutants. This increase leads to a more effective oxidation process and can be easily adapted to İSKİ Asia-1 Water Treatment Plant's existing preozonation unit. In this study, the optimum H2O2:O3 molar ratio for the specific water source was determined in laboratory by using a batch reactor and the optimum contact time for the optimum ratio was found. Moreover, changes in dissolved ozone concentration with time was determined with and without hydrogen peroxide to observe the difference. Ozone concentration in the gas phase was measured both at the entrance of the reactor and in off-gas. Finally, comparisons were made regarding the consumption of ozone and hydrogen peroxide. Results of the study indicates that, compared to ozone alone, Peroxone Process is more effective for removing the 2-MIB and Geosmin compounds. Results show that the effect of the temparature in ozone solubility is highly important. This temparature effect is crutial for the removal of the compounds. Consumed ozone is found to be higher in peroxone experiments than ozone alone experiments. The outcomes of this study indicate that the Peroxone Process can be easily adapted to the existing İSKİ Asia-1 Water Treatment Plant. Before applying the Peroxone Process to the full-scale plant, a pilot-scale study is recommended.