摘要
在饮用水深度处理中,采用臭氧化技术后,产生可能对人体有高致癌性的溴酸盐副产物。目前对溴酸盐的控制方法有多种,氨抑制溴酸盐就是其中方法之一。但是,目前研究者仅针对水中NH4+研究的相对较多,而气相氨无人研究。因此,本课题提出一种新方法,通过气相氨和液相氨对溴酸盐抑制作用的比较来探索气相氨对于溴酸盐的抑制效果。
论文首先研究了逆向流鼓泡柱实验,结果表明:两种情况下,气相氨对溴酸盐的抑制率在52%-60%,液相氨(氯化铵)则为53%-62%,气相氨和液相氨对溴酸盐的抑制率接近,气相氨对液相氨没有优势。对于出水氨氮浓度的变化情况,气相氨的氨氮浓度有波动,但波动幅度不大,出水氨氮浓度的变化范围在0.030-0.166mg/L;加氯化铵氨氮浓度也有所波动,但波动范围不大,出水氨氮浓度的变化范围在0.030-0.165mg/L。同时实验还考察了氨氮浓度沿柱方向变化情况,结果为:气相氨为逐渐降低,而液相氨则为逐渐升高。
改变进水方式,论文继续对同向流鼓泡柱实验进行了研究,结果表明:气相氨对溴酸盐的抑制率在60%-71%,而加入液相氨(硫酸铵)对溴酸盐的抑制率在55%-62%;与液相氨生成溴酸盐量相比,气相氨比液相氨减少20%-32%,气相氨比液相氨有更好的抑制效果。在不改变其它条件的情况下:增加氨氮浓度,气相氨和液相氨抑制溴酸盐的效果都增强;而分别增加溴离子浓度和臭氧浓度,气相氨和液相氨对溴酸盐的抑制率都有所降低,但降幅不大。若保持臭氧浓度不变,同时改变溴离子浓度和氨氮浓度也即N/Br(摩尔比)不变,这种情况对抑制溴酸盐的影响没有规律性。对于出水氨氮浓度变化则是变化幅度都不大,气相氨出水氨氮浓度比液相氨出水氨氮浓度低;氨氮浓度沿柱体方向的变化情况为:气相氨先升高后降低,液相氨为逐渐升高。
基于以上实验结果可知,采用同方向进水进气的方式,气相氨比液相氨对溴酸盐有更好的抑制效果,与液相氨生成溴酸盐量相比,气相氨比液相氨减少20%-32%;气相氨可通过调节氨气流量来控制氨气的投加量,这样就可以实现实际工程中的在线控制。
Ozone-based technology has been applied widely in the drinking water treatment. But it may create a high carcinogenic bromate by-product for human body. Bromate has a variety of control methods at present and ammonia is one of them. However, researchers have just many studies for NH4 +relatively at present, gas phase ammonia is currently no studied. Therefore, this issue presents a new method to explore inhibition effect of bromate for gas phase ammonia through the comparison of gas phase ammonia and liquid phase ammonia on bromate inhibition.
At first, paper studies the reverse-flow bubble column experiment and results show: bromate inhibition rate of gas phase ammonia is 52%-60% and bromate inhibition rate of liquld phase ammonia (ammonium chloride) is 53%-62%. Gas phase ammonia and liquild phase ammonia have a similar bromate inhibition rate. So gas phase ammonia is not for the advantages of liquid phase ammonia in bromate inhibition. For the changes in effluent ammonia concentration, concentration of gas phase ammonia has volatility, but the volatility is not high and the effluent ammonia concentration is in the range of 0.030-0.166mg/L. Liquid phase ammonia concentration is also fluctuate but the fluctuation is little and effluent ammonia concentration is in the range of 0.030-0.165mg/L. In the meantime, experiment also examines the change of ammonia concentration along the column direction and its experiment results is that gas phase ammonia is gradually reduced, while liquid phase ammonia is then gradually increased.
Paper continues to study bubble column experiment with the same flow and the experiment results show that bromate inhibition rate of gas phase ammonia is 60%-71%, while bromate inhibition rate of liquid phase ammonia (ammonium sulfate) is 55%-62%. Compared with the bromate generated by liquid phase ammonia, the bromate generated by gas phase ammonia is reduced by 20%-32%. So gas phase ammonia has a better bromate inhibition effect than that of liquid phase ammonia. Without changing the other conditions, increasing ammonia concentration, inhibition effect of bromate by gas phase ammonia and liquid phase ammonia are both enhanced; increasing concentration of bromide ion and ozone respectively, bromate inhibition rate of gas phase ammonia and liquid phase ammonia has been lower, but drop a little. If the ozone concentration is unchanged while concentration of bromide ion and ammonia is changed, that is N / Br is unchanged, bromate inhibition effect in this condition has not regularity. For the effluent ammonia concentration, its magnitude of change is not large. Generally, the effluent ammonia concentration of gas phase ammonia is lower than that of liquid phase ammonia. Ammonia concentration change along the bubble column direction is first increased and then decreased for gas phase ammonia, while liquid phase ammonia is gradually increased.
Based on the above results, we can conclude that gas phase ammonia inhibition effect on the bromate is better than that of liquid phase ammonia in the direction of water intake using the same way. Compared with the bromate generated by liquid phase ammonia, the bromate generated by gas phase ammonia is reduced by 20% -32%. Gas phase ammonia can be controlled by regulating the flow of ammonia dosage, so that it can achieve on-line control in the actual project.
引文
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