Treatment of micropollutants from landfill leachate by using advanced oxidation methods

In this thesis, detecting of sixteen micropollutants selected from polyaromatic hydrocarbon, pesticide, phthalate and surfactant groups in the leachate of Konya Aslım solid waste storage area and removal of them by Fenton oxidation (FO), ozone oxidation (OO), supercritical water oxidation (SCWO) and consecutive treatment processes including chemical precipitation, Fenton oxidation and ozone oxidation were investigated. In addition, oxidation by-products formed after treatment were determined qualitatively. Samples were analyzed by gas chromatography mass spectrometry (GC-MS) after extracted according to EPA 3510C method. High amount of phthalate and phenol type micropollutants were found in raw leachate. While di(2-ethylhexyl)phthalate (DEHP) and di-n-octylphthalate (DNOP) were found in the range of 12.5- 242 µg/L and 0-180 µg/L respectively, octylphenol (OP) and nonylphenol (NP) were determined in the range of 6.09-38.2 µg/L and 2.66-5.48 µg/L respectively. The concentrations of PAH (except naphthalene) and pesticides did not exceed 1.5 L µg/L. According to the results obtained, all of the processes used in treatment were determined highly effective in the removal of phthalates, pesticides and surfactants. While investigated DEHP and DNOP belong to phthalates group were removed over 90 % by Fenton and SCWO separately, eliminated 70% by ozone oxidation. However, removal of butyl benzyl phthalate (BBP) which was not detected in some leachate samples taken, has been very low compared to the other two phthalate (for Fenton 60%, for SCWO 35%). Although naphthalene removed 100% by Fenton processes, removal of PAHs with three or more benzene rings were found as inefective in the same process. Unlike Fenton process, ozone oxidation was found very efficient for the removal of PAHs with two or three benzene rings. Removal rates of napthalene (NAP), anthracene (ANT) and floranthene (FL) by ozone oxidation were determined as 100%, 100%, 90% respectively. Although SCWO process decreased the COD values of leachate up to 98%, it has been also determined that formation mechanisms of PAHs can occur rather than removal of them under uncontrolled conditions due to high pollution content of leachate. Oxygen equivalent required for complete minerilization of organic compound (DOD) and super critical conditions are important parameters in SCWO treatment. Removal efficiencies of NAP, AN, FL were obtained as 97%, 95%, 87% respectively in the treatment conditions. All used oxidation treatment processes for the removal of investigated pesticides were observed highly effective and their removal rates were achieved up to 100%. For surfactants, while the removal efficiencies of NP were found as 99%, 95%, 98% for FO, OO and SCWO processes respectively, OP removals were determined as 96%, 80% and 98% for the same treatments. The removal efficiencies of PAHs with three or more benzene rings were increased up to 83% and 100% by combined treatment. While higher molecular weight intermediates occurred in Fenton process, ozone oxidation produces lower molecular weight intermediates. High amount of benzaldehyde was found in the samples which was treated by super critical water oxidation. However, final products such as chrysene and pyrene having four or more benzene rings also formed at 450-500oC in supercritical water oxidation process which were not detected in raw leachate. Keywords: Fenton oxidation, leachate, micropollutant, ozonation, pesticide, phthalates and surfactants, polyaromatic hydrocarbons, super critical water oxidation.