GDM ist eine einfache, wartungsfreie Technologie für die Trinkwasserversorgung ohne Elektrizität und Chemie.
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Boues granulaires aérobies. État de l'art de la recherche actuelle et future
Les boues granulaires aérobies offrent plusieurs avantages pour le traitement biologique des eaux usées municipales par rapport au procédé à boues activées conventionnels. Cependant, malgré un nombre croissant d’applications industrielles et municipales, notre recul sur les boues granulaires aérobies reste limité. L’EPFL et l’Eawag ont évalué au cours des dernières années les mécanismes, performances et limites des systèmes de boues granulaires aérobies. Dans cet article, nous résumons notre compréhension des facteurs influençant les propriétés des boues granulaires aérobies et fournissons une appréciation globale de cette nouvelle technologie.
Derlon, N.; Layer, M.; Morgenroth, E.; Adler, A.; Gelb, A.; Holliger, C. (2018) Boues granulaires aérobies. État de l'art de la recherche actuelle et future, Aqua & Gas, 98(1), 14-19, Institutional Repository
Membranes d'ultrafiltration. La présence de biofilms: un avantage pour stabiliser le flux et augmenter la qualité du perméat
L’utilisation de systèmes composites combinant une couche biologique (le biofilm) supportée par une barrière physique (la membrane) a de multiples avantages pour le traitement des eaux (production d’eau potable, recyclage des eaux grises). Cet article présente comment tirer profit de la microbiologie des biofilms afin d’améliorer la qualité du perméat et faire fonctionner des systèmes membranaires à flux constant pendant plusieurs années, et ce sans maintenance.
Derlon, N.; Pronk, W.; Morgenroth, E. (2018) Membranes d'ultrafiltration. La présence de biofilms: un avantage pour stabiliser le flux et augmenter la qualité du perméat, Aqua & Gas, 98(5), 30-35, Institutional Repository
Formation of aerobic granules for the treatment of real and low-strength municipal wastewater using a sequencing batch reactor operated at constant volume
This study aimed at evaluating the formation of aerobic granular sludge (AGS) for the treatment of real and low-strength municipal wastewater using a column sequencing batch reactor (SBR) operated in fill-draw mode (constant volume). The focus was on understanding how the wastewater upflow velocity (VWW) applied during the anaerobic feeding influenced the sludge properties and in turn the substrate conversion. Two different strategies were tested: (1) washing-out the flocs by imposing high wastewater upflow velocities (between 5.9 and 16 m h−1) during the anaerobic feeding (Approach #1) and (2) selective utilization of organic carbon during the anaerobic feeding (1 m h−1) combined with a selective sludge withdrawal (Approach #2). A column SBR of 190 L was operated in constant volume during 1500 days and fed with real and low-strength municipal wastewater. The formation of AGS with SVI30 of around 80 mL gTSS−1 was observed either at very low (1 m h−1) or at high VWW (16 m h−1). At 16 m h−1 the AGS was mainly composed of large and round granules (d > 0.63 mm) with a fluffy surface, while at 1 m h−1 the sludge was dominated by small granules (0.25 < d < 0.63 mm). The AGS contained a significant fraction of flocs during the whole operational period. A considerable and continuous washout of biomass occurred at VWW higher than 5.9 m h−1 (Approach #1) due to the lower settling velocity of the AGS fed with municipal wastewater. The low sludge retention observed at VWW higher than 5.9 m h−1 deteriorated the substrate conversion and in turn the effluent quality. High solid concentrations (and thus solid retention time) were maintained during Approach #2 (VWW of 1 m h−1), which resulted in an excellent effluent quality. The study demonstrated that the formation of AGS is possible during the treatment of real and low-strength municipal wastewater in a SBR operated at constant volume. Low wastewater upflow velocities should be applied during the anaerobic feeding phase in order to ensure enough biomass retention and efficient substrate removal.
Derlon, N.; Wagner, J.; Ribeiro da Costa, R. H.; Morgenroth, E. (2016) Formation of aerobic granules for the treatment of real and low-strength municipal wastewater using a sequencing batch reactor operated at constant volume, Water Research, 105, 341-350, doi:10.1016/j.watres.2016.09.007, Institutional Repository
Effect of particulate organic substrate on aerobic granulation and operating conditions of sequencing batch reactors
The formation and application of aerobic granules for the treatment of real wastewaters still remains challenging. The high fraction of particulate organic matter (XS) present in real wastewaters can affect the granulation process. The present study aims at understanding to what extent the presence of XS affects the granule formation and the quality of the treated effluent. A second objective was to evaluate how the operating conditions of an aerobic granular sludge (AGS) reactor must be adapted to overcome the effects of the presence of XS. Two reactors fed with synthetic wastewaters were operated in absence (R1) or presence (R2) of starch as proxy for XS. Different operating conditions were evaluated. Our results indicated that the presence of XS in the wastewater reduces the kinetic of granule formation. After 52 d of operation, the fraction of granules reached only 21% in R2, while in R1 this fraction was of 54%. The granules grown in presence of XS had irregular and filamentous outgrowths in the surface, which affected the settleability of the biomass and therefore the quality of the effluent. An extension of the anaerobic phase in R2 led to the formation of more compact granules with a better settling ability. A high fraction of granules was obtained in both reactors after an increase of the selection pressure for fast-settling biomass, but the quality of the effluent remained low. Operating the reactors in a simultaneous fill-and-draw mode at a low selection pressure for fast-settling biomass showed to be beneficial for substrate removal efficiency and for suppressing filamentous overgrowth. Average removal efficiencies for total COD, soluble COD, ammonium, and phosphate were 87 ± 4%, 95 ± 1%, 92 ± 10%, and 87 ± 12% for R1, and 72 ± 12%, 86 ± 5%, 71 ± 12%, and 77 ± 11% for R2, respectively. Overall our study demonstrates that the operating conditions of AGS reactors must be adapted according to the wastewater composition. When treating effluents that contain XS, the selection pressure should be significantly reduced.
Wagner, J.; Weissbrodt, D. G.; Manguin, V.; Ribeiro da Costa, R. H.; Morgenroth, E.; Derlon, N. (2015) Effect of particulate organic substrate on aerobic granulation and operating conditions of sequencing batch reactors, Water Research, 85, 158-166, doi:10.1016/j.watres.2015.08.030, Institutional Repository
Linking composition of extracellular polymeric substances (EPS) to the physical structure and hydraulic resistance of membrane biofilms
The effect of extracellular polymeric substances (EPS) on the meso-scale physical structure and hydraulic resistance of membrane biofilms during gravity driven membrane (GDM) filtration was investigated. Biofilms were developed on the surface of ultrafiltration membranes during dead-end filtration at ultra-low pressure (70 mbar). Biofilm EPS composition (total protein, polysaccharide and eDNA) was manipulated by growing biofilms under contrasting nutrient conditions. Nutrient conditions consisted of (i) a nutrient enriched condition with a nutrient ratio of 100:30:10 (C: N: P), (ii) a phosphorus limitation (C: N: P ratio: 100:30:0), and (iii) a nitrogen limitation (C: N: P ratio: 100:0:10). The structure of the biofilm was characterised at meso-scale using Optical Coherence Tomography (OCT). Biofilm composition was analysed with respect to total organic carbon, total cellular mass and extracellular concentrations of proteins, polysaccharides, and eDNA. 2D-confocal Raman mapping was used to characterise the functional group composition and micro-scale distribution of the biofilms EPS. Our study reveals that the composition of the EPS matrix can determine the meso-scale physical structure of membrane biofilms and in turn its hydraulic resistance. Biofilms grown under P limiting conditions were characterised by dense and homogeneous physical structures with high concentrations of polysaccharides and eDNA. Biofilm grown under nutrient enriched or N limiting conditions were characterised by heterogeneous physical structures with lower concentrations of polysaccharides and eDNA. For P limiting biofilms, 2D-confocal Raman microscopy revealed a homogeneous spatial distribution of anionic functional groups in homogeneous biofilm structures with higher polysaccharide and eDNA concentrations. This study links EPS composition, physical structure and hydraulic resistance of membrane biofilms, with practical relevance for the hydraulic performances of GDM ultrafiltration.
Desmond, P.; Best, J. P.; Morgenroth, E.; Derlon, N. (2018) Linking composition of extracellular polymeric substances (EPS) to the physical structure and hydraulic resistance of membrane biofilms, Water Research, 132, 211-221, doi:10.1016/j.watres.2017.12.058, Institutional Repository
The effect of different aeration conditions in activated sludge – side-stream system on sludge production, sludge degradation rates, active biomass and extracellular polymeric substances
On-site minimization of excess sludge production is a relevant strategy for the operation of small-scale and decentralized wastewater treatment plants. In the study, we evaluated the potential of activated sludge systems equipped with side-stream reactors (SSRs). This study especially focused on how the sequential exposure of sludge to different aeration conditions in the side-stream reactors influences the overall degradation of sludge and of its specific fractions (active biomass, extracellular polymeric substances (EPS), EPS proteins, EPS carbohydrates). We found that increasing the solid retention time from 25 to 40 and 80 days enhanced sludge degradation for all aeration conditions tested in the side-stream reactor. Also, the highest specific degradation rate and in turn the lowest sludge production were achieved when maintaining aerobic conditions in the side-stream reactors. The different sludge fractions in terms of active biomass (quantified based on adenosine tri-phosphate (ATP) measurements), EPS proteins and EPS carbohydrates were quantified before and after passage through the SSR. The relative amounts of active biomass and EPS to volatile suspended solids (VSS) did not changed when exposed to different aeration conditions in the SSRs, which indicates that long SRT and starvation in the SSRs did not promote the degradation of a specific sludge fraction. Overall, our study helps to better understand mechanisms of enhanced sludge degradation in systems operated at long SRTs.
Habermacher, J.; Benetti, A. D.; Derlon, N.; Morgenroth, E. (2015) The effect of different aeration conditions in activated sludge – side-stream system on sludge production, sludge degradation rates, active biomass and extracellular polymeric substances, Water Research, 85, 46-56, doi:10.1016/j.watres.2015.08.002, Institutional Repository