Combination of O3/H2O2 and UV for multiple barrier micropollutant treatment and bromate formation control - an economic attractive option

Abstract

Advanced Oxidation Processes (AOP) are known as an effective treatment barrier for micropollutants. Well known AOP combinations are UV/H2O2 and O3/H2O2. This paper will present a more detailed view on how to use the different options combining UV; ozone and H2O2. The focus of this investigation is on treatment effects (reduction of specific contaminats), water matrix, energy consumption and cost calculation (CAPEX, OPEX). The presented data are extracted from extended pilot trials carried out at DUNEA in 2009 and 2010. Dunea (The Netherlands,The Hague) produces drinking water from the Meuse River, which contains a variety of organic micropollutants as a result from upstream activity. Dunea is performing research to extend the current multiple barrier treatment (e.g. pre-treatment, artificial recharge and recovery (ARR), post-treatment) with an advanced oxidation processes (AOP), situated at the pre-treatment location in Bergambacht, before ARR. The degradation of organic micropollutants as a result of advanced oxidation using different combinations of hydrogen peroxide, ozone, low pressure (LP) UV lamps has been assessed by means of pilot-scale (5 m3/h) experiments. The influent was pre-treated river water, with an yearly average UV-transmission of 80% and a DOC concentration of 4 mg/L.The peroxide doses were varied as 0, 5 and 10 ppm, the ozone doses were varied as 1, 2 and 3 g ozone/m3. The UV doses were varied between 300 and 650 mJ/cm2. The installed power for the LP reactor was 0.26 kWh/m3. Atrazine, bromacil, ibuprofen and NDMA were spiked (10-20 µg/L) and used as model compounds. Bromacil was completely (>99%) removed by ozone/peroxide. Atrazine and ibuprofen were good (58% and 85% respectively) removed by O3/H2O2 and NDMA was not (9%) removed by this technique, whereas NDMA showed good (82%) removal by UV/H2O2. Atrazine, bromacil and ibuprofen were degraded by UV/H2O2 at 53, 46 and 59 %, respectively. In addition also combined AOP was tested; spiked water was treated by O3/H2O2 first and let over the LP-UV reactor directly afterwards. All four compounds showed highest degradation during combined AOP treatment. With this combined AOP, lower ozone dose and lower UV dose result in comparable degradation compared to single AOP treatment. For all these techniques a detailed capital expenditure operational expenditure (CAPEX / OPEX) evaluation was carried out based on a daily water flow of 240,000 m3/d. This evaluation resulted in the finding, that the combined AOP is the most economical solution with the best treatment result. Other advantages of the combined AOP are limited by-product formation, especially bromate, and a future barrier against OMPs encompassing a broad spectrum of properties.