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Van Hulle S.W.H.,Ghent University | Van Hulle S.W.H.,West-Flanders College | Vandeweyer H.J.P.,West-Flanders College | Meesschaert B.D.,Catholic University College of Bruges-Ostend | And 4 more authors.
Chemical Engineering Journal

The anaerobic ammonium oxidation (Anammox) process, discovered 20 years ago, is, in combination with partial nitritation, ideally suited to treat nitrogen rich waste water streams such as digester effluent. In this review the engineering aspects and the practical application of the process are reviewed. The conventional nitrification-denitrification and nitritation-denitritation are also discussed briefly. The environmental conditions affecting the nitrification process, free ammonia and nitrous acid concentration, temperature, pH and dissolved oxygen concentration, are discussed. These conditions can be controlled in such a way that the partial nitritation step produces an Anammox-suited influent. The Anammox reactor conditions should favour the growth of the Anammox organisms in view of their low growth rate and possible inhibition effects. Dissolved oxygen and nitrite concentrations should be kept as low as possible and biomass washout should be limited. If the partial nitritation process and the Anammox process are occuring in the same reactor, care should be taken to the dissolved oxygen concentration, the ammonium load and the nitrite concentration to obtain a sustainable co-existence between aerobic and anaerobic ammonium oxidizers.An overview is presented of the practical implementation of autotrophic nitrogen removal. The process can be accomplished in the same reactor (1-reactor system) or by using 2 separate reactors (2-reactor system). Typically the 1-reactor system is a biofilm or granular reactor where the ammonium oxidizers are active in the outer layers of the biofilm or granule, producing a suitable amount of nitrite for the Anammox organisms that are active in the inner layers. Transport of ammonium and the produced nitrite is governed by diffusion. Finally, the different nitrogen removal processes are compared in terms of operational conditions and a direction for future work is provided. © 2010 Elsevier B.V. Source

Claeys K.,Musculoskeletal Research Unit | Claeys K.,Catholic University College of Bruges-Ostend | Brumagne S.,Musculoskeletal Research Unit | Dankaerts W.,Musculoskeletal Research Unit | And 3 more authors.
European Journal of Applied Physiology

Optimal postural control is an essential capacity in daily life and can be highly variable. The purpose of this study was to investigate if young people have the ability to choose the optimal postural control strategy according to the postural condition and to investigate if non-specific low back pain (NSLBP) influences the variability in proprioceptive postural control strategies. Young individuals with NSLBP (n = 106) and healthy controls (n = 50) were tested on a force plate in different postural conditions (i.e., sitting, stable support standing and unstable support standing). The role of proprioception in postural control was directly examined by means of muscle vibration on triceps surae and lumbar multifidus muscles. Root mean square and mean displacements of the center of pressure were recorded during the different trials. To appraise the proprioceptive postural control strategy, the relative proprioceptive weighting (RPW, ratio of ankle muscles proprioceptive inputs vs. back muscles proprioceptive inputs) was calculated. Postural robustness was significantly less in individuals with NSLBP during the more complex postural conditions (p < 0.05). Significantly higher RPW values were observed in the NSLBP group in all postural conditions (p < 0.05), suggesting less ability to rely on back muscle proprioceptive inputs for postural control. Therefore, healthy controls seem to have the ability to choose a more optimal postural control strategy according to the postural condition. In contrast, young people with NSLBP showed a reduced capacity to switch to a more multi-segmental postural control strategy during complex postural conditions, which leads to decreased postural robustness. © 2010 Springer-Verlag. Source

Vandamme D.,Laboratory Aquatic Biology | Foubert I.,Laboratory Aquatic Biology | Fraeye I.,Laboratory Aquatic Biology | Meesschaert B.,Catholic University College of Bruges-Ostend | And 2 more authors.
Bioresource Technology

Microalgae hold great potential as a feedstock for biofuels or bulk protein or treatment of wastewater or flue gas. Realising these applications will require the development of a cost-efficient harvesting technology. Here, we explore the potential of flocculation induced by high pH for harvesting Chlorella vulgaris. Our results demonstrate that flocculation can be induced by increasing medium pH to 11. Although both calcium and magnesium precipitated when pH was increased, only magnesium (≥0.15. mM) proved to be essential to induce flocculation. The costs of four different bases (sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide and sodium carbonate) were calculated and evaluated and the use of lime appeared to be the most cost-efficient. Flocculation induced by high pH is therefore a potentially useful method to preconcentrate freshwater microalgal biomass during harvesting. © 2011 Elsevier Ltd. Source

Vandamme D.,Laboratory Aquatic Biology | Foubert I.,Laboratory Aquatic Biology | Meesschaert B.,Catholic University College of Bruges-Ostend | Meesschaert B.,Catholic University of Leuven | Muylaert K.,Laboratory Aquatic Biology
Journal of Applied Phycology

Due to their small size and low concentration in the culture medium, cost-efficient harvesting of microalgae is a major challenge. We evaluated the potential of cationic starch as a flocculant for harvesting microalgae using jar test experiments. Cationic starch was an efficient flocculant for freshwater (Parachlorella, Scenedesmus) but not for marine microalgae (Phaeodactylum, Nannochloropsis). At high cationic starch doses, dispersion restabilization was observed. The required cationic starch dose to induce flocculation increased linearly with the initial algal biomass concentration. Of the two commercial cationic starch flocculants tested, Greenfloc 120 (used in wastewater treatment) was more efficient than Cargill C*Bond HR 35.849 (used in paper manufacturing). For flocculation of Parachlorella using Greenfloc 120, the cationic starch to algal biomass ratio required to flocculate 80% of algal biomass was 0.1. For Scenedesmus, a lower dose was required (ratio 0.03). Flocculation of Parachlorella using Greenfloc 120 was independent of pH in the pH range of 5 to 10. Measurements of the maximum quantum yield of PSII suggest that Greenfloc 120 cationic starch was not toxic to Parachlorella. Cationic starch may be used as an efficient, nontoxic, cost-effective, and widely available flocculant for harvesting microalgal biomass. © 2009 Springer Science+Business Media B.V. Source

Peuteman J.,Catholic University College of Bruges-Ostend | Aeyels D.,Ghent University

An averaging result is presented for local uniform asymptotic stability of nonlinear differential equations without requiring a fast time-varying vectorfield. The nonlinearity plays a crucial role: close to the origin, the trajectories vary slowly compared to the time dependence of the vectorfield. The result generalises averaging results which prove stability properties for systems having a homogeneous vectorfield with positive order. The result is illustrated with several examples. © 2010 Elsevier Ltd. All rights reserved. Source

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