纳米乳化油强化硝酸盐反硝化产气变化研究

Simulation experiments on gas change in enhanced denitrification of nitrate process by nano emulsified oil

为探究纳米乳化油原位修复硝酸盐污染地下水过程中产气对含水介质渗透性的影响,以硝酸盐为目标污染物,采用活性污泥滤液接种,分别以纳米乳化油、吐温80和司盘80为碳源开展硝酸盐降解批实验研究,探讨和评估硝酸盐降解及降解过程中的产气情况.结果显示,纳米乳化油、吐温80和司盘80均能促进硝氮的降解,在实验的100d内,共完成7个周期硝酸盐氮的有效去除,总去除率分别为79.5%、63.8%和68.8%.在硝酸盐氮降解过程中,受厌氧发酵和反硝化作用的影响,各反应体系中均有气体生成,只有活性污泥反应体系中主要产气成分是CO_2,未加碳源和分别加3种碳源的4个反应体系(都添加活性污泥和硝酸盐)中主要产气成分是CO_2、N_2.其中,添加纳米乳化油的反应体系U型管产气量最大,为47.73m L;受碳源厌氧发酵的影响,添加司盘80反应体系总产气量最大,为205.34m L.纳米乳化油反应体系次之,吐温80反应体系最小.根据三氮的变化,结合纳米乳化油反应体系理论与实际产气对比显示,在纳米乳化油强化硝酸盐反硝化过程中,18.8%纳米乳化油厌氧发酵产生CO_2,95.4%硝氮反硝化生成N_2.

To investigate the effects of gas production in the process of in-situ nitrate pollution remediation by nano emulsified oil on aquifer permeability, batch experiments were carried out to evaluate the nitrate degradation and the gas production. In the experiments, the reaction systems were inoculated by activated sludge filtrate and nano emulsified oil, Tween 80, and Span 80 were used as carbon source,respectively. The degradation experiments have been completed for seven cycles in 100 days and the results indicated that the selected carbon sources can enhance nitrate degradation. The total removal rates for systems with nano emulsified oil, Tween 80 and Span 80 were 79.5%, 63.8%, and 68.8%, respectively. Gases were generated in each reaction system due to the anaerobic fermentation and denitrification in the process of nitrate degradation. The main gas component in reaction system with only activated sludge filtrate was CO2. In other systems, the gases were mainly CO2 and N2. The reaction system of nano emulsified oil had the largest gas production in the U-shaped tube, and the volume was 47.73 m L. Affected by anaerobic fermentation, the largest volume of total gas production（205.34 m L） was observed in the system of Span 80 and the smallest occurred in the reaction system with Tween 80. According to mass balance in the transformation processes of nitrogen species and the comparison between the theoretical and actual gas production in nano emulsified oil reaction system, it showed that 18.8% nano emulsified oil generated CO2 through anaerobic fermentation and 95.4% nitrate generated N2 through denitrification in the process of nano emulsified oil enhanced denitrification.