97 research outputs found
Werkwijze voor het behandelen van ammonia-houdend afvalwater
No full textTreatment of ammonia-comprising waste water comprises: (a) subjecting the waste water to a nitrification treatment using a nitrifying microorganism and adding oxygen, to give a solution comprising an oxidation product of ammonia, and (b) converting the oxidation product of ammonia into nitrogen using a denitrifying microorganism, use of bicarbonate-containing waste water, which is substantially stripped of bicarbonate by the supply of air, and maintaining the pH in the 1st step at \~7.2 by controlling the aeration, part of the ammonia present is converted into nitrite, and in the 2nd step the denitrifying microorganism uses the formed nitrite as oxidant for the remaining ammonia.Applied Science
Growth and metabolism of Anammox Bacteria
No full textThe anoxic ammonium oxidation (anammox) process is the conversion of nitrite and ammonium under anoxic conditions- to form dinitrogen gas. The process is performed by deep-branching Planctomycetes. The startup of the first full-scale anammox reactor in the world is described in Chapter 2. The described full scale reactor was a granular sludge reactor which was optimized for biomass retention. The reactor was scaled up directly from lab-scale to full-scale without the intermediate step of a pilot plant- and the step from lab-scale to full-scale took three years. In the first phase of the startup, quantification of the number of anammox bacteria, which were present in the reactor by quantitative polymerase chain reaction (Q-PCR) was a reliable indicator of growth of the anammox bacteria. The volumetric conversion of 10 kg N/m3/day is high compared to lab-scale systems. In Chapter 3, anammox bacteria were grown as free suspended (planktonic) cells. Even at a Sludge Retention Time (SRT) of 12 days (doubling time 8.3 days) stable operation was possible. The purity of the biomass was estimated to be 97.6%, which was the highest level of enrichment ever achieved for anammox reactors. The addition of hydroxylamine and the subsequent transient production of hydrazine can be regarded as a benchmark for the anammox process. In Chapter 4, the kinetics of the conversion were studied in detail for "Kuenenia stuttgartiensis". Hydrazine accumulated slightly after addition of hydroxylamine and remained low until near completion of the hydroxylamine. At that moment, the hydrazine level suddenly rose to ca. 100 μM, after which it gradually disappeared. The overall reaction was a disproportionation of hydroxylamine into ammonium and dinitrogen gas. The observed sudden accumulation of hydrazine could only be explained by assuming that hydrazine was an intermediate in this process. Two simple mathematical models, based on the continuous turn over of hydrazine during hydroxylamine conversion, were capable of quantitatively explaining the observed phenomena. The production of nitric oxide, another potential intermediate in the anammox process, was studied in combination with the emission of greenhouse gas nitrous oxide (N2O) in a full scale two reactor nitritation anammox process in Chapter 5. The NO and N2O emissions in the nitritation reactor were 0.2% and 1.7% of the nitrogen load respectively and 0.003% and 0.6% for the anammox reactor. The NO emission in the nitritation reactor was higher at higher aeration flows and NO seemed to be produced mainly in the period when the nitritation reactor was aerated. The N2O emission on the other hand seemed to be mainly produced during anoxic periods. Anammox bacteria have a unique cell plan consisting of several membrane-surrounded compartments. In the main compartment, the anammoxosome, the anammox catabolism is hypothesized to take place. Therefore, also the proton motive force is probably generated between the anammoxosome and the riboplasm by which the anammoxosome is surrounded. 31P nuclear magnetic resonance (NMR) spectroscopy was used to evaluate the pH difference over the anammoxosome membrane of "Kuenenia stuttgartiensis" in vivo in Chapter 6. Two compartments with stable pH values of 6.3 and 7.3 respectively were found in actively converting cells. The pH values were independent of the external pH and were visible already upon exposing the cells to anoxic conditions. The lower pH value was assigned to the anammoxosome, whereas the pH of 7.3 was assigned to the riboplasm. The stability of the pH in both compartments is a strong indication that the anammoxosome is the locus of the catabolism and thus functionally resembles the eukaryotic mitochondrion.Applied Science
Sustainability in Inland Shipping: The use of LNG as Marine Fuel
No full textLNG has the potential to reduce echaust gas emissions from vessels. The report explains the basics of LNG: what is it, what are the technical challenges of using LNG as marine fuel, which infrastructure is needed to bunker it and what is the impact on the costs. The report concludes with some measures to assure the succesful adoption of LNG as a marine fuel.Mechanical, Maritime and Materials Engineerin
Variational iteration method for solving multispecies Lotka–Volterra equations
No full textAbstractThis paper applies the variational iteration method to multispecies Lotka–Volterra equations. Comparisons with the Adomian decomposition and the fourth-order Runge–Kutta methods show that the variational iteration method is a powerful method for nonlinear equations
Approximate analytical solutions of systems of PDEs by homotopy analysis method
No full textAbstractIn this paper, the homotopy analysis method (HAM) is applied to obtain series solutions to linear and nonlinear systems of first- and second-order partial differential equations (PDEs). The HAM solutions contain an auxiliary parameter which provides a convenient way of controlling the convergence region of series solutions. It is shown in particular that the solutions obtained by the variational iteration method (VIM) are only special cases of the HAM solutions
New exact solutions of sixth-order thin-film equation
No full textAbstractThe
G′G-expansion method is used for the first time to find traveling-wave solutions for the sixth-order thin-film equation, where related balance numbers are not the usual positive integers. New types of exact traveling-wave solutions, such as – solitary wave solutions, are obtained the sixth-order thin-film equation, when parameters are taken at special values
Electromagnetic effects in anti-Hermitian media with gain and loss
No full textFunding Information: L.F. was partly supported by DoinQTech, Jane and Aatos Erkko Foundation. L.F. and M.S.M. thank X. Wang, M. Nyman, and B. Zerulla for their invaluable help with numerical simulations. Also, L.F. wishes to acknowledge the support of Carsten Rockstuhl. Publisher Copyright: © 2024 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Incorporating both gain and loss into electromagnetic systems provides possibilities to engineer effects in unprecedented ways. Concerning electromagnetic effects in isotropic media that have concurrently electric and magnetic responses, there is, in fact, a degree of freedom to distribute the gain and loss in different effective material parameters. In this paper, we analytically scrutinize wave interactions with those media, and, most importantly, we contemplate the extreme scenario where such media are anti-Hermitian. Considering various conditions for excitation, polarization, and geometry, we uncover important effects and functionalities such as lasing into both surface waves and propagating waves, conversion of evanescent source fields to transmitted propagating waves, full absorption, and enhancing backward to forward scattering ratio. We hope that these findings explicitly show the potential of anti-Hermiticity to be used in optical physics as well as microwave engineering for creating and using unconventional wave phenomena.Peer reviewe
Method of treating ammonia-comprising waste water
No full textThe invention relates to a method of treating ammonia-comprising waste water in which the bicarbonate ion is the counter ion of the ammonium ion present in the waste water. According to the invention half the ammonium is converted into nitrite, yielding an ammonia- and nitrite-containing solution, and in the second step the nitrite is used as oxidant for the ammonia. In the method according to the invention the conversion of half the ammonia into nitrite occurs automatically, providing a method which requires fewer controls. Also, the method according to the invention requires no external additiveApplied Science
Watertovenaars: Delftse ideeën voor nog 200 jaar Rijkswaterstaat
No full textEen bundel artikelen met inspiratie voor Rijkswaterstaat voor de ontwikkeling in de volgende 200 jaar. Watertovenaar of tovenaarsleerling? (K. d'Angremond, P. Huisman en G.I. Schiereek) De oudste deltawerken: dammen en duikers uit het begin van de jaartelling (T. de Ridder) Een erfenis uit de Bataafse periode (W.M. de Jong) Wat eerst: wonen, water, wegen of welvaart? (T.M. de Jong) Een nieuwe rol voor de waterstaatsingenieur (F.M. Sanders) De terugkeer van de stedenbouwkundige discipline (V.J. Meyer Water (P. Huisman, K. d'Angremond en G.J. Schiereek) Dynamische buffers in autosnelwegen (D. Westland en P.H.L. Bovy) Op de automatische piloot door de Randstad? (R. van der Heijden, V. Marchau, E. Molin en K. van Wees) Niet bruggen bouwen, maar zelf brug zijn (B. Enserink, M.P.M. van der Ploeg, WAH. Thissen en G.J. de Vreede) Nederland als vervoersemplacement? (M.P.C. Weijnen, W.A.H. Thissen en E.F. ten Heuvelhof) Immobilisatie van gevaarlijk afval (Ch.F.Hendriks) Dubbel verduurzamen van wegconstructies (A.A.A. Molenaar) Innovatie van de geometrische infrastructuur (P.J.G.Teunissen) Radarhoogtemetingen en de (voorname) rol van Delft (M. Naeije) Een hoog(water)standje (T. Rientjes, C. van den Akker en P. van der Veer) Naar één beslismodel voor de veiligheid (J.K. Vrijling en J. Stoop) De betrouwbaarheid van dijken (A. Verruijt) Windgolven, een fascinerend fenomeen (L.H. Holthuijsen en J.A. Battjes) Mijn droom: het railvaartuig (B. Boon) Een waterfilm in plaats van wielen (A. van Beek) Uren worden minuten (E.A.H. Vollebregt, H. Jansen en M.R.T. Roest) Een kwestie van schuiven (R.Brouwer, A.Hof en J. Schuurmans) Energie door vergisting van slib (M.S.M. letten en M.C.M. van Loosdrecht) Nóg een poldermodel: hoge-sterkte beton (J.C. Walraven) Atollen voor de Noordzeekust (J. Kristinsson) Van maker naar regisseur (H.A.J. de Ridder
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