Ion Trapping of Amines in Protozoa: A Novel Removal Mechanism for Micropollutants in Activated Sludge,Environmental Science & Technology

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Ion Trapping of Amines in Protozoa: A Novel Removal Mechanism for Micropollutants in Activated Sludge
Environmental Science & Technology ( IF 10.8 ) Pub Date : 2017-12-13 00:00:00 , DOI: 10.1021/acs.est.7b03556
Rebekka Gulde ₁ , Sabine Anliker _{1,

2} , Hans-Peter E. Kohler _{1,

2} , Kathrin Fenner _{1,

2,

3}

Affiliation

To optimize removal of organic micropollutants from the water cycle, understanding the processes during activated sludge treatment is essential. In this study, we hypothesize that aliphatic amines, which are highly abundant among organic micropollutants, are partly removed from the water phase in activated sludge through ion trapping in protozoa. In ion trapping, which has been extensively investigated in medical research, the neutral species of amine-containing compounds diffuse through the cell membrane and further into acidic vesicles present in eukaryotic cells such as protozoa. There they become trapped because diffusion of the positively charged species formed in the acidic vesicles is strongly hindered. We tested our hypothesis with two experiments. First, we studied the distribution of the fluorescent amine acridine orange in activated sludge by confocal fluorescence imaging. We observed intense fluorescence in distinct compartments of the protozoa, but not in the bacterial biomass. Second, we investigated the distribution of 12 amine-containing and eight control micropollutants in both regular activated sludge and sludge where the protozoa had been inactivated. In contrast to most control compounds, the amine-containing micropollutants displayed a distinctly different behavior in the noninhibited sludge compared to the inhibited one: (i) more removal from the liquid phase; (ii) deviation from first-order kinetics for the removal from the liquid phase; and (iii) higher amounts in the solid phase. These results provide strong evidence that ion trapping in protozoa occurs and that it is an important removal mechanism for amine-containing micropollutants in batch experiments with activated sludge that has so far gone unnoticed. We expect that our findings will trigger further investigations on the importance of this process in full-scale wastewater treatment systems, including its relevance for accumulation of ammonium.

中文翻译：

原生动物中胺的离子捕集：活性污泥中微量污染物的新型去除机理

为了优化从水循环中去除有机微量污染物，了解活性污泥处理过程的过程至关重要。在这项研究中，我们假设在有机微污染物中含量很高的脂肪胺通过原生动物中的离子捕集被部分地从活性污泥的水相中除去。在医学研究中已广泛研究的离子捕获中，含胺化合物的中性物质扩散穿过细胞膜，并进一步扩散到真核细胞（如原生动物）中存在的酸性囊泡中。由于强烈阻碍了在酸性囊泡中形成的带正电物质的扩散，因此它们被困住了。我们通过两个实验检验了我们的假设。第一的，我们通过共聚焦荧光成像研究了活性污泥中荧光胺a啶橙的分布。我们在原生动物的不同区室中观察到了强烈的荧光，但在细菌生物质中却没有。其次，我们研究了常规活性污泥和原生动物已被灭活的污泥中12种含胺和8种对照微污染物的分布。与大多数对照化合物相比，与被抑制的污泥相比，含胺的微污染物在非被抑制的污泥中表现出明显不同的行为：（ii）偏离从液相中去除的一级动力学；（iii）固相含量更高。这些结果提供了有力的证据，表明原生动物中发生了离子捕获，并且这是迄今为止尚未引起人们注意的使用活性污泥进行批处理实验中含胺微污染物的重要去除机理。我们希望我们的发现将触发对此过程在大规模废水处理系统中的重要性的进一步调查，包括其与铵盐积累的相关性。

更新日期：2017-12-13

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