Publications

  • [Show abstract] [Hide abstract]
    ABSTRACT: Landfill leachate requires rigorous treatment to limit environmental impact. Often, granular activated carbon (GAC) filtration is part of the treatment train. Little is known on how a preceding (advanced) oxidation process (AOP) could modify the adsorption properties. As such, different AOPs were compared as preceding step to GAC filtration for treatment of biologically stabilized landfill leachate.
    Journal of Chemical Technology & Biotechnology 02/2014; · 2.50 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Anammox has shown its promise and low cost for removing nitrogen from high strength wastewater such as landfill leachate. A reactor was inoculated with nitrification-denitrification sludge originating from a landfill leachate treating waste water treatment plant. During the operation, the sludge gradually converted into red Anammox granular sludge with high and stable Anammox activity. At a maximal nitrogen loading rate of 0.6 g N l(-1) d(-1), the reactor presented ammonium and nitrite removal efficiencies of above 90%. In addition, a modified Stover-Kincannon model was applied to simulate and assess the performance of the Anammox reactor. The Stover-Kincannon model was appropriate for the description of the nitrogen removal in the reactor with the high regression coefficient values (R2 = 0.946) and low Theil's inequality coefficient (TIC) values (TIC < 0.3). The model results showed that the maximal N loading rate of the reactor should be 3.69 g N l(-1) d(-).
    Environmental Technology 01/2014; 35(9-12):1226-33. · 1.61 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Ozone decomposition in real water is often empirically modelled due to the system complexity. Mechanistic models, however, can be of great value in view of engineering applications. The high number of model parameters often restricts their applicability. In this study, sensitivity analyses were used to determine the most important elementary reactions from a kinetic model and to understand the reaction mechanism. Only seven of the twenty-eight rate constants showed to impact ozone and hydroxyl radical concentrations. Mass-transfer related parameters were of major importance. Ozone decomposition was extremely sensitive to parameters involving dissolved organic matter (DOM) at very low scavenger levels implying that even in “ultrapure” water systems impurities should be considered. To increase the applicability of mechanistic ozonation models, simplification of the elementary radical scheme combined with a more detailed description of reactions involving DOM is needed.
    Ozone: Science and Engineering 05/2013; 35:338–349.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: This study experimentally examined the impact of oxidation on the properties of effluent organic matter (EfOM) using two different oxidation techniques: ozonation and UV/H2O2 treatment. Multiple surrogates for EfOM related to its spectral properties, molecular size, concentration, polarity and biodegradability were used to study the oxidant induced conversions. Spectral calculations as differential absorbance spectra (DAS) and absorbance slope index (ASI) were applied for the first time to describe EfOM oxidation and proved to be useful to unravel differences in working mechanism between ozone and hydroxyl radical (HO) induced transformation of EfOM. Effluent ozonation inherently led to significant HO production as a result of electron transfers between ozone and electron rich moieties of EfOM. HO production increased as function of ozone dose and was strongly correlated to UV absorption at 254 nm (UV254). During the UV moderated process, pseudo steady-state behaviour of the HO concentration was observed. Ozone decomposition was extremely sensitive to EfOM reactivity. Most likely, the degree of dissociation of EfOM controlled its reactivity towards ozone. The pH effect was quantified by calculating the pseudo-first order decay constant for ozone as function of reaction time and pH. Treatment with both processes led to more oxygen rich, less hydrophobic and more biodegradable EfOM.
    Water Research 02/2013; 47(7):2387-2398. · 4.66 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The autotrophic nitrogen removal process (partial nitritation combined with the Anammox process) is a sustainable nitrogen removal technique for nitrogen-rich streams. A modelling and experimental study was performed to define optimal process conditions for the autotrophic nitrogen removal process. Special attention was given to the influence of feeding characteristics on the performance of both the partial nitritation reactor and the Anammox reactor. It was revealed that the feeding regime is an important factor in the successful start-up of the Anammox process. Nitrite concentration peaks at the beginning of a feeding period will lead to an unsuccessful start-up, while a slow input of nitrogen speeds up the process. Feeding regimes are less important in partial nitritation reactors since laboratory results show that slow or fast supply of influent does not influence the growth of ammonium oxidisers.
    Water S.A 07/2011; 37(3):289-294. · 0.88 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Numerous mechanistic models describing the UV/H2O2 process have been proposed in literature. In this study, one of them was used to predict the behaviour of a full-scale reactor. The model was calibrated and validated with non-synthetic influent using different operational conditions. A local sensitivity analysis was conducted to determine the most important operational and chemical model parameters. Based on the latter, the incident UV irradiation intensity and two kinetic rate constants were selected for mathematical estimation. In order to investigate changes of the NOM content over time, some time delay was considered between calibration and validation data collection. Hydrogen peroxide concentration, the decadic absorption coefficient at 310 nm (UVA310, as a surrogate for natural organic matter) and pH could be satisfactorily predicted during model validation using an independent data set. It was demonstrated that quick real-time calibration is an option at less controllable full-scale conditions. The reactivity of UVA310 towards hydroxyl radicals did not show significant variations over time suggesting no need for frequent recalibration. Parameters that determine the initiation step, i.e. photolysis of hydrogen peroxide, have a large impact on most of the variables. Some reaction rate constants were also of importance, but nine kinetic constants did show absolutely no influence to one of the variables. Parameters related to UV shielding by NOM were of main importance. At the conditions used in this study, i.e. H2O2 concentrations between 0.5 and 4 mM, hydraulic residence times between 90 and 200 s and alkalinity concentrations between 2.5 and 6 mM, competitive radiation absorption by NOM was more detrimental to the micro pollutant removal efficiency than hydroxyl radical scavenging. Hydrogen peroxide concentration was classified as a non-sensitive variable, in contrast to the concentration of a micro pollutant which showed to be very to extremely influential to many of the parameters. UV absorption as a NOM surrogate is a promising variable to be included in future models. Model extension by splitting up the UVA310 into a soluble and a particulate fraction seemed to be a good approach to model AOP treatment of real (waste)waters containing both dissolved and particulate (suspended) material.
    Chemical Engineering Journal 06/2011; 171(1):113-126. · 3.47 Impact Factor
  • Source
    Communications in agricultural and applied biological sciences 01/2011; 76(1):181-4.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The autotrophic nitrogen removal process (partial nitritation combined with the Anammox process) is a new and sustainable nitrogen removal technique for nitrogen rich streams. A modeling study was performed to define optimal process conditions on two reactor configurations: a single oxygen limited partial nitritation reactor and a single Anammox reactor and to investigate the influence of feeding characteristics on the performance of the Anammox reactor. The simulations revealed that the feeding regime is an important factor in the successful startup of Anammox reactors. Nitrite concentration peaks in the beginning of a feeding period will lead to an unsuccessful start-up while a slow input of nitrogen fastens up the process. Feeding regimes are less important in partial nitritation reactors since lab results show that slow or fast supply of influent does not influence the growth of partial nitrifiers.
    01/2011;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The autotrophic nitrogen removal process (partial nitritation combined with the Anammox process) is a new and sustainable nitrogen removal technique for nitrogen-rich streams. A modelling study has been performed to define optimal process conditions (temperature, oxygen supply, pH and biomass retention) and to investigate the influence of chemical oxygen demand, nitrogen loading rate and hydraulic retention time on three alternative reactor configurations: a single oxygen-limited partial nitritation reactor, a single Anammox reactor, and a combination of partial nitritation and Anammox in a single reactor. The model applied was compared to experimental data from the literature and gave good agreement for all three reactor configurations. The simulations revealed that a system with separated partial nitritation and Anammox offered a wider range of optimal process conditions than a one-reactor system. The key factors in the successful operation of partial nitritation were found to be control of aeration, ammonium loading rate and temperature. Heterotrophs remained present in all three reactor systems and it was confirmed that interaction between heterotrophs and Anammox and between heterotrophs and ammonium oxidizers was possible.
    Environmental Technology 11/2010; 31(12):1311-24. · 1.61 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In 2003, the Flemish Water Supply Company (VMW) extended its drinking water production site in Kluizen (near Ghent, Belgium) with a combined ozonation and biological granular activated carbon (BGAC) filtration process. Due to this upgrade, biostability increased, less chlorination was needed and drinking water quality improved significantly. The aim of this study was to describe the full-scale reactor with a limited set of equations. In order to describe the ozonation process, a model including key processes such as ozone decomposition, organic carbon removal, disinfection and bromate formation was developed. Kinetics were implemented in WEST® and simulation results were compared to real data. The predicting performance was verified with a goodness-of-fit test and key parameters were determined through a local sensitivity analysis. Parameters involving optical density (both rate constants and stoichiometric coefficients) strongly affect model output. Some parameters with respect to bromate and bacteria showed to be only, but to a large extent, sensitive to their associated concentrations. A scenario analysis was performed to study the system's behavior at different operational conditions. It was demonstrated that the model is able to describe the operation of the full-scale ozone reactor, however, further data collection for model validation is necessary.
    Chemical Engineering Journal 03/2010; 157(2-3):551-557. · 3.47 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The aim of this study was to evaluate the use of nanofibre microfiltration membranes, spun by an innovative electrospinning technique, in water filtration applications. As such, this study bridges the gap between developments in electrospinning techniques for the production of flat-sheet membranes and the application of these membranes in water filtration. Three different applications were examined. Firstly, the use of the membrane (functionalised or non-functionalised) for the removal of pathogens was investigated. Secondly, the electrospun flat-sheet membranes were applied for wastewater treatment in a laboratory-scale submerged membrane bioreactor (MBR). In addition to these applications, physical properties such as clean water permeability (CWP) and strength were also examined. The tests showed that the electrospun membranes can be used for water filtration applications, but that further improvements are necessary before these membranes can be practically employed. In particular, the level of functionality and the properties of irreversible fouling require further research.
    Water S.A 01/2010; 36(1):151-156. · 0.88 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The aim of this study was to evaluate the use of nanofiber microfiltration membranes, spun by an innovative electrospinning technique, in water filtration applications. As such, this study bridges between developments in electrospinning techniques for the production of flat sheet membranes and the application of these membranes in water filtration. Three different applications were examined. First, the use of the membrane (functionalized or non-functionalized) for the removal of pathogens was investigated. Second the electrospun flat sheet membranes were applied in a lab scale submerged membrane bioreactor (MBR). Third, the electrospun membranes were applied as stand-alone filter for water treatment. Next to these applications, physical properties such as clean water permeability (CWP) and strength were also examined. The test showed that the electrospun membranes can be used for water filtration applications, but that further research is necessary towards irreversible fouling properties and level of functionalisation.
    Desalination. 01/2009; 249(3):942-948.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Music festivals and other temporary events, such as bicycle races, lay a heavy burden on the surrounding environment. Treatment of the wastewater originating from such events is necessary if no municipal treatment plant is available. This study demonstrated that activated carbon is a performant technique for the treatment of wastewaters originating from these temporary events. Freundlich isotherms and maximum operational linear velocity (6 m/h) were determined on a lab-scale set-up. A pilot-scale set up was used to treat part (5%) of the total volume of the Dranouter Music Festival shower wastewater. On average 90% removal of COD and suspended solids concentration was obtained. Application of the activated carbon filter resulted in the fact that the local discharge limits were met without operational problems.
    Water Science & Technology 02/2008; 58(8):1653-7. · 1.10 Impact Factor

18 Following View all

58 Followers View all