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Ion Trapping of Amines in Protozoa: A Novel Removal Mechanism for Micropollutants in Activated Sludge
- Source :
- Environmental sciencetechnology. 52(1)
- Publication Year :
- 2017
-
Abstract
- 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.
- Subjects :
- 0301 basic medicine
010501 environmental sciences
Wastewater
Photochemistry
01 natural sciences
Ion trapping
Waste Disposal, Fluid
Cell membrane
03 medical and health sciences
chemistry.chemical_compound
medicine
Environmental Chemistry
Amines
0105 earth and related environmental sciences
biology
Sewage
Chemistry
Vesicle
Acridine orange
General Chemistry
biology.organism_classification
Fluorescence
Kinetics
030104 developmental biology
medicine.anatomical_structure
Activated sludge
Environmental chemistry
Protozoa
Amine gas treating
Water Pollutants, Chemical
Subjects
Details
- ISSN :
- 15205851
- Volume :
- 52
- Issue :
- 1
- Database :
- OpenAIRE
- Journal :
- Environmental sciencetechnology
- Accession number :
- edsair.doi.dedup.....b8efbe136d432b0a9b42e829aaf9808d