Predation influences the structure of biofilm developed on ultrafiltration membranes |
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Authors: | Derlon Nicolas Peter-Varbanets Maryna Scheidegger Andreas Pronk Wouter Morgenroth Eberhard |
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Affiliation: | a Eawag, Swiss Federal Institute of Aquatic Science and Technology, Überlandstrasse 133, P.O Box 611, CH-8600 Dübendorf, Switzerland b Institute of Environmental Engineering, ETH Zürich, 8093 Zürich, Switzerland |
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Abstract: | This study investigates the impact of predation by eukaryotes on the development of specific biofilm structures in gravity-driven dead-end ultrafiltration systems. Filtration systems were operated under ultra-low pressure conditions (65 mbar) without the control of biofilm formation. Three different levels of predation were evaluated: (1) inhibition of eukaryotic organisms, (2) addition of cultured protozoa (Tetrahymena pyriformis), and (3) no modification of microbial community as a control. The system performance was evaluated based on permeate flux and structures of the biofilm. It was found that predation had a significant influence on both the total amount and also the structure of the biofilm. An open and heterogeneous structure developed in systems with predation whereas a flat, compact, and thick structure that homogeneously covered the membrane surface developed in absence of predation. Permeate flux was correlated with the structure of the biofilm with increased fluxes for smaller membrane coverage. Permeate fluxes in the presence or absence of the predators was 10 and 5 L m−2 h−1, respectively. It was concluded that eukaryotic predation is a key factor influencing the performance of gravity-driven ultrafiltration systems. |
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Keywords: | Ultrafiltration Predation Biofilm structure Permeate flux Optical Coherence Tomography (OCT) Confocal Laser Scanning Microscopy (CLSM) Gravity-driven membrane (GDM) filtration |
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