ANALYSIS OF ORGANIC COMPOUNDS CONTENT AND BIOTOXICITY DURING TREATMENT PROCESS OF FLUE GAS DESULFURIZATION WASTEWATER IN A COAL-FIRED POWER PLANT
The complex organic composition of desulfurization wastewater in coal-fired power plants greatly affected the high efficiency and low-consumption operation of zero-emission systems,and there was a certain risk of biological toxicity.The organic components and biological toxicity in the desulfurization wastewater treatment process of a coal-fired power plant were analyzed by field test and simulation experiments in this study.The results showed that the two-stage clarification method and the high-efficiency flocculant method could not effectively remove the organic matter in the desulfurization wastewater,but could reduce the humic acid substances in the wastewater.The reflux of nanofiltration concentrate reduced the proportion of tryptophan and tyrosine protein in the effluent of the regulating tank to 30％,but greatly increased the proportion of humic acid substances to 60％.The molecular weights of the pollutants in the desulfurization wastewater were mainly around 2084 Da and 612 Da,and the molecular weight of the pollutants in the nanofiltration concentrate was slightly smaller than that of the pretreated effluent,which may cause membrane fouling by adsorption and plugging pores.The two-stage clarification method and high-efficiency flocculant method could all remarkably reduce the biological toxicity of the effluent of the regulating tank,and the luminescence inhibition rate of luminescent bacteria decreased from 46.23％to 12.45％and 2.57％,respectively.The nanofiltration concentrate enriched a large number of biological toxic substances such as humic acid,and the luminescence inhibition rate increased to 49.05％.The lower molecular weight of the organic matter in the desulfurization wastewater resulted in higher risk of nanofiltration membrane fouling,and the enrichment of humic acid increased the biological toxicity of nanofiltration concentrate.
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