臭氧氧化对常减压装置电脱盐二级出水的作用机制

Action mechanism of ozonation on biological effluent of electro-desalting unit in atmospheric-vacuum distillation facility

探究了臭氧氧化对常减压装置电脱盐二级出水中有机物的转化与降解作用,结合常规指标分析并采用超滤分子质量分布、气相质谱-色谱联用仪等手段对臭氧氧化前后的水质进行分析,并对比分析臭氧氧化对后续生物活性炭进一步吸附降解废水中有机物的作用。结果表明,当二级出水COD均值为39.7 mg/L、臭氧投加量为20 mg/L、单柱停留时间为40 min时,臭氧氧化对COD的平均去除率为19.8%,对UV254的平均去除率为30.9%。臭氧氧化可有效将含有不饱和键的大分子有机物转化为易生物降解的小分子物质,改变有机物结构,并降解一部分小分子物质,使废水中分子质量小于1 kD的有机物所占比例从69%提升至87%。相较于将二级出水直接进行生物活性炭的吸附降解,臭氧预氧化可将COD去除率提升11.4%,将UV254的去除率提升19.0%。

The effect of ozonation on the transformation and degradation of organic compounds in biological effluent of electro-desalting unit in an atmospheric-vacuum distillation facility is investigated. Combining with conventional index analysis,ultrafiltration molecular weight distribution(MWD）,gas chromatography-mass spectrometer and other measurements are used to analyze water quality before and after ozonation. Besides,the influence of ozonation on subsequent adsorption and degradation of organic compounds in wastewater by biological activated carbon(BAC） are compared and analyzed. The results show that the average removal rates of COD and UV254 are 19. 8% and 30. 9%,respectively when the average COD in biological effluent is 39. 7 mg·L-1,the ozone dosage is 20 mg·L-1 and the residence time of single column is 40 min. The unsaturated bonds-containing macromolecular organics can be converted effectively into biodegradable small molecules by means of ozonation. And the ozonation can change the structure of organics,degrade parts of small molecules and change the MWD of wastewater and increase the percentage of small molecules(1 kD） from 69% to 87%.Compared with treating the biological effluent by BAC directly,the removal rates of COD and UV254 of wastewater that is pretreated by ozonation before treated by BAC increase by 11. 4% and 19. 0% in average respectively.