The Organic Pollutant Characteristics of Lurgi Coal Gasification Wastewater before and after Ozonation

The effluent of distilled and extracted Lurgi coal gasification wastewater has been found to have low biodegradability and high toxicity, which inhibits further biodegradation. However, ozonation enhances the biodegradability and reduces the toxicity of this effluent, enabling further biological treatment and increased removal of organic materials. In this study, the dissolved organic matters in Lurgi coal gasification wastewater were isolated into six classes by resin adsorbents, after which TOC, UV254, UV-Vis, and 3D EEM were employed to quantitatively and qualitatively analyze organic materials in each part of the fractionated samples. The HoA and HiN fraction accounted for large amounts of the Lurgi coal gasification wastewater, and their TOC values were about 380.21 mg·L−1 and 646.84 mg·L−1, respectively. After ozonation, the TOC removal rates of HoA and HiN reached 42.85% and 67.13%, respectively. The UV254 of HoA was basically stable before and after ozonation, while that of HiN increased continuously because a portion of the humic macromolecular organic materials in HoA was oxidized to HiN. Additionally, UV-Vis analysis revealed that the larger molecular organics of HoA were oxidized during ozonation, resulting in high biodegradability. Finally, the 3D EEM spectra indicated that the macromolecular organics were oxidized to smaller molecules with the degradation of soluble microbial by-products.