Investigation of hydrolysis acidification process during anaerobic treatment of coal gasification wastewater (CGW): Evolution of dissolved organic matter and biotoxicity

• Published in: The Science of the total environment Vol. 723; p. 137995
• Main Authors: Chen, Zhiqiang, Li, Da, Wen, Qinxue
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 25.06.2020
• Subjects: Biotoxicity; Coal gasification wastewater; Dissolved organic matter; Hydrolysis acidification; Pearson correlation analysis; Pearson correlation analysis; Dissolved organic matter; Coal gasification wastewater; Hydrolysis acidification; Biotoxicity
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2020.137995

Coal gasification wastewater (CGW) contains several types of aromatic pollutants, which impart high biotoxicity and reduce the quality of anaerobic treatment. Two types of hydrolysis acidification processes, namely microaerobic hybrid reactor (HA-1) and upflow anaerobic sludge blanket reactor (HA-2), were developed for pre-treatment before the anaerobic treatment. The changes in the dissolved organic matter and biotoxicity were investigated to comprehensively understand the degradation process. The results showed that HA-2 coupled with an anaerobic reactor achieved a 12.3% and 13.4% higher removal efficiency for chemical oxygen demand and total phenols, respectively, compared with the coupled process with HA-1. Furthermore, HA-2 could transform macromolecules into small molecules more efficiently and produce fewer intermediates. The coupled process with HA-2 preferentially removed complex aromatic substances with absorption wavelengths of 285 and 254 nm, according to the sequential orders interpreted from two-dimensional correlation spectroscopy. In addition, the results of fluorescence excitation-emission-matrix with regional integration analysis revealed that the contents of typical cyclic compounds in CGW, such as phenolic, heterocyclic, and polycyclic aromatic compounds were remarkably reduced by HA-2. In addition, HA-2 reduced the toxic unit value of CGW by 67.5% and increased the resazurin dehydrogenase activity of the sludge by 37.5% during CGW treatment, thus improving the biotoxicity removal and biodegradability. However, the coupled process with HA-2 did not significantly affect the “indirect estrogenic activity” of CGW. A Pearson correlation analysis indicated that spectral indicators, such as UV254 and ΦT,n, presented a high positive correlation with the reduction of acute toxicity and organics. [Display omitted] •DOM transformation during bio-treatment for CGW was for the first time investigated.•EEM-FRI and 2D-COS upon UV–Vis spectra were used for analysis.•UASB reactor achieved a better hydrolysis efficiency compared to microaerobic hybrid reactor.•Obvious “indirect estrogenic activity” after treatment should cause enough concern.•Spectral indicators can be used to indicate DOM and acute toxicity removal.