| Anthraquinone compounds widely exist in industrial dye wastewater. Their stable structure, biotoxicity and other characteristics resulted in the increased difficulty of wastewater treatment. Biological treatment is widely applied due to its low cost, simple operation and environmental friendliness. In this paper, the co-metabolic degradation of anthraquinone compounds by a newly isolated Rhodococcus pyridinivorans GF3 was studied. The degradation products of four kinds of anthraquinone compounds were analyzed using high performance liquid chromatography-mass spectrometry (HPLC-MS) and fourier transform infrared spectroscopy (FTIR). According to the above analysis, the possible degradation pathways of anthraquinone compounds by strain GF3 were proposed. These studies provide the theory basis for the application of strain GF3.The co-metabolic biodecolorization of 1-amino-anthraquinone-2-sulfonic acid (ASA-2) was studied. The results showed that, among additional nutrients, peptone had the most significant accelerating effect on ASA-2 biodecolorization. Further experiment demonstrated that many amino acids could accelerate ASA-2 biodecolorization, and L-leucine had the most significantly accelerating effect on ASA-2 decolorization and cell growth. The optimal environmental conditions for ASA-2 bio-decolorization with L-leucine as co-metabolic carbon source were pH 7.5-8.5,30? and 150?200 r/min. Under the optimal conditions, strain GF3 could completely decolorize 20?500 mg/L ASA-2. The decolorization kinetics of ASA-2 by strain GF3 could be described by Andrew's equation. During the process of ASA-2 decolorization, strain GF3 could tolerate 30 g/L NaCl,2 g/L of NaNO3 and 3 g/L Na2SO4. When sodium succinate was used as a co-metabolic carbon source, strain GF3 not only could decolorize ASA-2, but also could remove nitrogen by aerobic denitrification. The optimal conditions were C/N 15, pH 7.5,30? and 200 r/min. Under the optimal conditions, the decolorization percentage of ASA-2 reached 95.5% in 44 h. Meanwhile, the removal percentage of total nitrogen was over 88.2%. During this process, low concentration NO2--N was accumulated and removed. NO3-N could be finally transformed to nitrogen gas, N2O was not detected.When L-leucine was used as a co-metabolic carbon source, the degradation processes of ASA-2 and other anthraquinone compounds (1-amino-4-bromoanthraquinone-2-sulfonic acid (ABSA), anthraquinone-2-sodium sulfonate (AQS) and anthraquinone-2-carboxylic acid (AQC)) were analyzed. Using HPLC, HPLC-MS and FTIR, the degradation end products of the above four kinds of anthraquinone compounds were analyzed, and the degradation pathways were proposed. The results showed that the decolorization percentage of 107.6 mg/L ASA-2 could reach over 95.4% in 30 h under the optimal conditions, and TOC removal percentage was 61.9%. UV-Visible spectra analysis showed that the characteristic absorption peaks of ASA-2 totally disappeared and a new characteristic absorption peak at 340 nm appeared when the red color of ASA-2 aqueous solution faded to be colorless. The degradation end product of ASA-2 was proposed to be 3-amino-4-sulfophthalic acid. The formed intermediate product catechol was further degraded by catechol 2,3-dioxygenase, and eventually mineralized. Strain GF3 could also degrade 100 mg/L ABSA, AQS and AQC. Their degradation percentages reached over 90.1%,98.9% and 94.3%, respectively. UV-Visible spectra analysis showed that the characteristic absorption peaks of ABSA, AQS and AQC totally disappeared with their complete degradation. For ABSA degradation, two new characteristic absorption peaks at 351 nm and 265 nm appeared. The degradation pathways of the four kinds of anthraquinone compounds were proposed. Anthraquinone rings cleaved to catechol and the corresponding original-functional-groups-containing phthalic acid. The formed catechol was further mineralized by strain GF3. |
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