MINERALIZATION OF ORGANIC COMPOUNDS IN WASTEWATER BY O3/H2O2 AND O3/OH- ADVANCED OXIDATION SYSTEMS
Sustainable process-product development & green chemistry
Environmental Engineering & Management (T1-3P)
Keywords: Ozonation, Wastewater, Advanced oxidation technologies, Oxidation, Water treatment
Municipal and industrial wastewaters usually contain certain organic compounds persistent or with limited biodegradability. Advanced oxidation processes (AOP) provide an effective mineralization rate by enhancing the production of hydroxyl radicals and are intended to remove the dissolved organic carbon in order to meet discharge regulations or for water reuse. The aim of this work was the study of reaction conditions leading to a high degree of organics removal in municipal and industrial wastewaters from conventional biological treatment units. A prescribed amount of naproxen was added to the raw waters after filtering to provide a source of a pollutant with a high direct ozonation rate. The ozone decomposition reactions were carried out in semicontinuous mode using a 5L jacketed reactor whose temperature was controlled by a Polystat thermostatic regulator. The temperature of the liquid inside the reactor was also monitored throughout the experiment. Ozone was produced by a corona discharge ozonator (Ozomatic SWO100) fed by oxygen. The gas containing ozone was bubbled into the liquid with a total gas flow of 240 NL/h. The pH of the reaction mixture was automatically controlled by pumping small amounts of diluted sodium hydroxide. The concentration of ozone in the liquid was monitored using a Rosemount 499AOZ amperometric sensor equipped with Pt 100 RTD temperature compensation and checked against the Indigo Colorimetric Method (SM 4500-O3 B). The concentration of ozone in gas was determined with a non-dispersive UV Photometer Anseros Ozomat GM6000 Pro calibrated and tested against a chemical method. Total organic carbon was measured with a Shidmazu TOC-VCSH apparatus.
The organic content measured as TOC could be completely removed in O3/H2O2 experiments in which a repeated series of hydrogen peroxide injections were performed. Under alkaline conditions in the absence of hydrogen peroxide, a certain amount of residual organic content (2-3 ppm of TOC) was observed. A part of it may be explained by low weight carboxylic acids which evolution was followed by Ionic Chromatography (Dionex DX120). The concentration of ozone was practically constant after an initial period opf about 10 min. Initial parameters: municipal wastewater (TOC = 9.3 ppm, DQO= 130 ppm); industrial wastewater (TOC = 2.9 ppm, DQO = 97 ppm). Naproxen added: 12 ppm (8.76 ppm as TOC).
Presented Monday 17, 13:30 to 15:00, in session Environmental Engineering & Management (T1-3P).
