臭氧氧化在乙醇SBR出水资源化中的应用研究

Application of ozone oxidation in recycling sequencing batch reactor activated sludge process effluent for ethanol fermentation

为节约水资源,降低生产成本,该研究提出将序批式活性污泥法(sequencing batch reactor activated sludge process,SBR)出水回用于乙醇生产拌料工序。实验结果表明,SBR出水直接回用将导致乙醇发酵被抑制,对SBR出水进行臭氧氧化处理20 min后,SBR出水回用乙醇发酵的抑制性完全解除。研究证明NO_(2)-是SBR出水中的主要抑制物,当NO_(2)-质量浓度达到5 mg/L时就会对发酵产生抑制,表现为酵母细胞数减少且死亡率升高,细胞形态被破坏,对葡萄糖的利用率降低。转录组学研究结果表明,酵母细胞经NO_(2)-胁迫处理后,三羧酸循环与磷酸戊糖途径通量减小,使细胞代谢被抑制,生命活动减弱,因而抑制乙醇发酵。

After treatment with the method of sequencing batch reactor activated sludge process(SBR),the waste liquor from fuel ethanol production is still difficult to meet the emission standards.In order to conserve water and decrease the production costs,a reused SBR effluent in the ethanol production process was proposed.The result showed that the direct reuse of SBR effluent the yeast cell numbers and ethanol production decreased by 46.2%and 54.8%compared to the use of tap water,indicating that the ethanol fermentation has been inhibited.But the ethanol fermentation indicator was the same as the control after the SBR effluent was treated by ozone,indicating that ozone treatment can completely eliminate the inhibitory effect on ethanol fermentation.Further analysis of the inorganic ion content in the SBR effluent revealed that after treated by ozone oxidation,the concentrations of most inorganic ions had no significant change,except nitrite ions concentration,which decreased from 104.83 mg/L to 0 mg/L.Moreover,the assay of adding nitrite ions in ethanol fermentation showed that nitrite was the main inhibitory component in the SBR effluent.The inhibition of fermentation occurred when nitrite concentration reached 5 mg/L,which can be represented as the decreased yeast cells,the increased death rates,the destroyed cell morphology,and the decreased glucose utilization rates.These results suggest that nitrite is the major inhibitor in ethanol fermentation,and ozone oxidation can completely promote the conversion of nitrite into nitrate.Transcriptomics results showed that after treated with 100 mg/L nitrite,the tricarboxylic acid cycle and pentose phosphate pathway in yeast cells were downregulated significantly,which leads to inhibition of cell metabolism and the diminished life activity,thus resulting in the inhibition of ethanol fermentation.