Chemical oxidation for mitigation of UV-quenching substances (UVQS) from municipal landfill leachate: Fenton process versus ozonation

UV-quenching substance (UVQS), as an emerging municipal solid waste (MSW)-derived leachate contaminant, has a potential to interfere with UV disinfection when leachate is disposed of at publicly owned treatment works (POTW5). The objective of this study was to evaluate and compare two chemical oxidation processes under different operational conditions, i.e. Fenton process and ozonation, for alleviation of UV254 absorbance of a biologically pre-treated landfill leachate. Results showed that leachate UV254 absorbance was reduced due to the UVQS decomposition by hydroxyl radicals (center dot OH) during Fenton treatment, or by ozone (O-3) and center dot OH during ozonation. Fenton process exhibited a better treatment performance than ozonation under their respective optimal conditions, because center dot OH could effectively decompose both hydrophobic and hydrophilic dissolved organic matter (DOM), but O-3 tended to selectively oxidize hydrophobic compounds alone. Different analytical techniques, including molecular weight (MW) fractionation, hydrophobic hydrophilic isolation, UV spectra scanning, parallel factor (PARAFAC) analysis, and fluorescence excitation-emission matrix spectrophotometry, were used to characterize UVQS. After either oxidation treatment, residual UVQS was more hydrophilic with a higher fraction of low MW molecules. It should be noted that the removed UV254 absorbance (Delta UV234)was directly proportional to the removed COD (ADD) for the both treatments (Fenton process: Delta UV254 = 0.011 Delta COD; ozonation: Delta UV254 = 0.016 Delta 00D). A greater Delta UV254/Delta COD was observed for ozonation, suggesting that oxidant was more efficiently utilized during ozonation than in Fenton treatment for mitigation of the UV absorbance. (C) 2016 Elsevier Ltd. All rights reserved.