Gongye shui chuli (May 2024)
Variations in dissolved organic matter during wastewater treatment in natural gas purification plants
Abstract
Dissolved organic matter (DOM) is a pivotal determinant for wastewater discharge compliance standards. A comprehensive analysis of the molecular composition of DOM is imperative for its efficient removal. In this study, wastewater from a natural gas purification plant was investigated. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) and three-dimensional excitation-emission-matrix spectra (3D-EEMs) were employed to analyze the fluorescence properties, molecular composition, mass-to-charge ratio, and molecular transformations of DOM during the oxidation process at molecular level. The 3D-EEM results indicated wastewater was dominated by humic substances, followed by fulvic acid substances. O3/H2O2 oxidation reduced the fluorescence intensity of humic substances, while DOM degradation was constrained by the reaction characteristics of ozone with electron-rich organic compounds. In contrast,the O3/H2O2-Fenton combined oxidation significantly reduced the overall fluorescence intensity, and effectively removed humic-like substances. FT-ICR MS results revealed that O3/H2O2 oxidation removed part of CHO and CHON type DOM, while the removal efficiency for CHOS and CHONS types was less pronounced. Polycyclic aromatic and highly unsaturated compounds were transformed into aliphatic compounds by ozone, with increase of the oxygen content of CHO type DOM. O3/H2O2-Fenton oxidation exhibited superior removal efficiency for CHOS and CHONS type DOM, which almost eliminated polyphenolic compounds and generated DOM with lower oxygen content and higher saturation. Furthermore, the combined oxidation process significantly mitigated ultrafiltration membrane fouling with removing a substantial portion of reversible and irreversible fouling.
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