Papers by Mark C M van Loosdrecht
The porosity of spacer-filled feed channels influences the hydrodynamics of spiral-wound membrane... more The porosity of spacer-filled feed channels influences the hydrodynamics of spiral-wound membrane systems and impacts the overall performance of the system. Therefore, an exact measurement and a detailed understanding of the impact of the feed channel porosity is required to understand and improve the hydrodynamics of spiral-wound membrane systems applied for desalination and wastewater reuse. The objectives of this study were to assess the accuracy of porosity measurement techniques for feed spacers differing in geometry and thickness and the consequences of using an inaccurate method on hydrodynamic predictions, which may affect permeate production. Six techniques were applied to measure the porosity namely, three volumetric techniques based on spacer strand count together with a cuboidal (SC), cylindrical (VCC) and ellipsoidal volume calculation (VCE) and three independent techniques based on volume displacement (VD), weight and density (WD) and computed tomography (CT) scanning. The CT method was introduced as an alternative for the other five already existing and applied methods in practice. Six feed spacers used for the porosity measurement differed in filament thickness, angle between the filaments and mesh-size. The results of the studies showed differences between the porosities, measured by the six methods. The results of the microscopic techniques SC, VCC and VCE deviated significantly from measurements by VD, WD and CT, which showed similar porosity values for all spacer types. Depending on the maximum deviation of the porosity measurement techniques from À6% to þ6%, (i) the linear velocity deviations were À5.6% and þ6.4% respectively and (ii) the pressure drop deviations were À31% and þ43% respectively, illustrating the importance of an accurate porosity measurement. Because of the accuracy and standard deviation, the VD and WD method should be applied for the porosity determination of spacer-filled channels, while the CT method is recommended for numerical modelling purposes. The porosity has a linear relationship with the flow velocity and a superlinear effect on the pressure drop. Accurate porosity data are essential to evaluate feed spacer performance in spiral-wound membrane systems. Porosity of spacer-filled feed channels has a strong impact on membrane performance and biofouling impact.
Surface coating of membranes may be a promising option to control biofilm development and biofoul... more Surface coating of membranes may be a promising option to control biofilm development and biofoul-ing impact on membrane performance of spiral-wound reverse osmosis (RO) systems. The objective of this study was to investigate the impact of an amphiphilic copolymer coating on biofilm formation and biofouling control. The coating was composed of both hydrophilic and hydrophobic monomers hydroxyethyl methacrylate (HEMA) and perfluorodecyl acrylate (PFA), respectively. Commercial RO membranes were coated with HEMA-PFA copolymer film. Long and short term biofouling studies with coated and uncoated membranes and feed spacer were performed using membrane fouling simulators (MFSs) operated in parallel, fed with water containing nutrients. For the long-term studies pressure drop development in time was monitored and after eight days the MFSs were opened and the accumulated biofilm on the membrane and spacer sheets was quantified and characterized. The presence of the membrane coating was determined using X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). Results showed that the amphiphilic coating (i) delayed biofouling (a lower pressure drop increase by a factor of 3 and a lower accumulated active biomass amount by a factor of 6), (ii) influenced the biofilm composition (23% lower polysaccharides and 132% higher protein content) and (iii) was still completely present on the membrane at the end of the biofouling study, showing that the coating was strongly attached to the membrane surface. Using coated membranes and feed spacers in combination with advanced cleaning strategies may be a suitable way to control biofouling.
Biocides may be used to control biofouling in spiral-wound reverse osmosis (RO) and nanofiltratio... more Biocides may be used to control biofouling in spiral-wound reverse osmosis (RO) and nanofiltration (NF) systems. The objective of this study was to investigate the effect of biocide 2,2-dibromo-3-ni-trilopropionamide (DBNPA) dosage on biofouling control. Preventive biofouling control was studied applying a continuous dosage of substrate (0.5 mg/L) and DBNPA (1 mg/L). Curative biofouling control was studied on pre-grown biofilms, once again applying a continuous dosage of substrate (0.5 mg acetate C/L) and DBNPA (1 and 20 mg/L). Biofouling studies were performed in membrane fouling simulators (MFSs) supplied with biodegradable substrate and DBNPA. The pressure drop was monitored in time and at the end of the study, the accumulated biomass in MFS was quantified by adenosine triphosphate (ATP) and total organic carbon (TOC) analysis. Continuous dosage of DBNPA (1 mg/L) prevented pressure drop increase and biofilm accumulation in the MFSs during a run time of 7 d, showing that biofouling can be managed by preventive DBNPA dosage. For biofouled systems , continuous dosage of DBNPA (1 and 20 mg/L) inactivated the accumulated biomass but did not restore the original pressure drop and did not remove the accumulated inactive cells and extracellular polymeric substances (EPS), indicating DBNPA dosage is not suitable for curative biofouling control.
Water Science & Technology, 2009
Models currently used have been developed to describe the storage response in the activated sludg... more Models currently used have been developed to describe the storage response in the activated sludge process. In these models the distribution of the substrate flux between growth and storage is an empirical function. rRNA-structured biomass models are proposed to describe the metabolic status of cells in view of predicting the growth response (dmicro/dt) of cells in activated sludge process. The autocatalytic reaction rate of the synthesis of the PSS component (rRNA) can provide a mechanistic explanation for the growth response and the growth lag phase. The proposed models were able to describe and predict properly the growth response of the biomass in various types of reactor. Such models could be more widely applicable by using intrinsic model parameters. This would be a key improvement for as it would lead to improved models for design.
Water Research, 2010
Linear flow velocity Biofilm streamers Two phase bubble flow Feed spacer channel pressure drop Bi... more Linear flow velocity Biofilm streamers Two phase bubble flow Feed spacer channel pressure drop Biomass cohesion strength Flush Biofouling Nanofiltration Reverse osmosis Drinking water a b s t r a c t Biomass accumulation and pressure drop development have been studied in membrane fouling simulators at different flow regimes. At linear flow velocities as applied in practice in spiral wound nanofiltration (NF) and reverse osmosis (RO) membranes, voluminous and filamentous biofilm structures developed in the feed spacer channel, causing a significant increase in feed channel pressure drop. Elevated shear by both single phase flow (water) and two phase flow (water with air sparging: bubble flow) caused biofilm filaments and a pressure drop increase. The amount of accumulated biomass was independent of the applied shear, depending on the substrate loading rate (product of substrate concentration and linear flow velocity) only. The biofilm streamers oscillated in the passing water. Bubble flow resulted in a more compact and less filamentous biofilm structure than single phase flow, causing a much lower pressure drop increase. The biofilm grown under low shear conditions was more easy to remove during water flushing compared to a biofilm grown under high shear. To control biofouling, biofilm structure may be adjusted using biofilm morphology engineering combined with biomass removal from membrane elements by periodic reverse flushing using modified feed spacers. Potential long and short term consequences of flow regimes on biofilm development are discussed. Flow regimes manipulate biofilm morphology affecting membrane performance, enabling new approaches to control biofouling. (J.S. Vrouwenvelder).
Proceedings of the Water Environment Federation, 2013
Wastewater treatment plants (WWTPs) contribute to global greenhouse gas emissions. Current knowle... more Wastewater treatment plants (WWTPs) contribute to global greenhouse gas emissions. Current knowledge is still insufficient regarding the exact magnitude of the emissions of the powerful greenhouse gas nitrous oxide (N 2 O). Also, the complete N 2 O production mechanisms remain unclear. In order to shed light on N 2 O emissions at real plants, under different weather conditions, continuous field measurements of gaseous nitrous oxide (N 2 O), ammonium (NH 4 + ), nitrate (NO 3 -) and dissolved oxygen (DO) were carried out at the aeration zone of a 750,000 PE wastewater treatment plant. These were complemented with high-frequency lab analyses of important variables at different locations in the plant. N 2 O emissions were analysed by relating it with the aeration flow rate, the DO and other nitrogen-containing components, as well as the influence of dry and wet weather conditions. Spatial differences in N 2 O emissions throughout the aerated zone were also investigated. It could be concluded that ammonia-oxidizing bacteria (AOB) can contribute significantly to N 2 O production compared to the heterotrophic pathway for N 2 O production. Moreover, rather than simply correlating N 2 O production by AOB with DO concentration, the investigation revealed the conditions affecting NH 4 + to be oxidized either more to N 2 O or more to NO 3 -. Under regular dry weather conditions, the measured average N 2 O emission factor at the summer package aeration zone is 0.96% of influent nitrogen load. The N 2 O production by AOB is stimulated by high NH 4 + concentrations, but it is likely that under high DO conditions the fraction of NH 4 + converted to N 2 O is smaller than under low DO conditions while the NO 3 production kept increasing. Under rain events, lower N 2 O emissions were observed.
Water Research, 2009
Feed spacer channel pressure drop Biofouling NMR MRI Membrane Flux Hydrodynamic conditions NF RO ... more Feed spacer channel pressure drop Biofouling NMR MRI Membrane Flux Hydrodynamic conditions NF RO Drinking water a b s t r a c t Biofouling was studied in full-scale and pilot-scale installations, test-rigs and membrane fouling monitors by conventional methods as well as Magnetic Resonance Imaging (MRI). Independent of permeate production, the feed spacer channel pressure drop and biomass concentration increased similarly in a nanofiltration pilot installation. In the presence of a feed spacer the absolute feed channel pressure drop increase caused by biomass accumulation was much higher than when a feed spacer was absent: in both spiral-wound nanofiltration and reverse osmosis systems biofouling is dominantly a feed spacer problem. This conclusion is based on (i) in-situ visual observations of the fouling accumulation, (ii) in-situ non-destructive observations of the fouling accumulation and velocity distribution profiles using MRI, and (iii) differences in pressure drop and biomass development in monitors with and without feed spacer. MRI studies showed that even a restricted biofilm accumulation on the feed channel spacer influenced the velocity distribution profile strongly. Biofouling control should be focused on the development of low fouling feed spacers and hydrodynamic conditions to restrict the impact of biomass accumulation on the feed channel pressure drop increase. (J.S. Vrouwenvelder).
Journal of Membrane Science, 2010
A three-dimensional (3D) computational model describing fluid dynamics and biofouling of feed cha... more A three-dimensional (3D) computational model describing fluid dynamics and biofouling of feed channels of spiral wound reverse osmosis and nanofiltration membrane systems was developed based on results from practice and experimental studies. In the model simulations the same feed spacer geometry as applied in practice and the experimental studies was used. The 3D mathematical model showed the same trends for (i) feed channel pressure drop, (ii) biomass accumulation, (iii) velocity distribution profile, resulting in regions of low and high liquid flow velocity also named channeling. The numerical model predicted a dominant biomass growth on the feed spacer, consistent with direct in situ observations on biofouling of spiral wound membrane modules and monitors using Magnetic Resonance Imaging (MRI). The model confirms experimental results that feed spacer fouling is more important than membrane fouling. The paper shows that mathematical modeling techniques have evolved to a stage that they can be used hand-in-hand with experiments to understand the processes involved in membrane fouling.
Journal of Membrane Science, 2008
There is a substantial need for novel measurement techniques that enable non-invasive spatially r... more There is a substantial need for novel measurement techniques that enable non-invasive spatially resolved observation of biofouling in nanofiltration (NF) and reverse osmosis (RO) membrane modules. Such measurements will enhance our understanding of the key design and operational parameters influencing biofilm fouling. In this study we demonstrate the first application of nuclear magnetic resonance microscopy (NMR) to a spiral wound reverse osmosis (RO) membrane module. The presented NMR protocols allow the extraction of the evolution with biofouling of (i) the spatial biofilm distribution in the membrane module, (ii) the spatially resolved velocity field and (iii) displacement propagators, which are distributions of molecular displacement of a passive tracer (in our case, water) in the membrane. From these measurements, the effective membrane surface area is quantified. Despite the opaque nature of membrane design, NMR microscopy is shown to be able to provide a non-invasive quantitative measurement of RO membrane biofouling and its impact on hydrodynamics and mass transport. Minimal biofilm growth is observed to have a substantial impact on flow field homogeneity.
Many anaerobic conversions proceed close to ther-modynamic equilibrium and the microbial groups i... more Many anaerobic conversions proceed close to ther-modynamic equilibrium and the microbial groups involved need to share their low energy budget to survive at the thermodynamic boundary of life. This study aimed to investigate the kinetic and thermodynamic control mechanisms of the electron transfer during syntrophic butyrate conversion in non-defined methanogenic communities. Despite the rather low energy content of butyrate, results demonstrate unequal energy sharing between the butyrate-utilizing species (17 %), the hydrogenotrophic methanogens (9–10 %), and the acetoclastic methanogens (73– 74 %). As a key finding, the energy disproportion resulted in different growth strategies of the syntrophic partners. Compared to the butyrate-utilizing partner, the hydrogenotrophic methanogens compensated their lower biomass yield per mole of electrons transferred with a 2-fold higher biomass-specific electron transfer rate. Apart from these thermodynamic control mechanisms , experiments revealed a ten times lower hydrogen inhibition constant on butyrate conversion than proposed by the Anaerobic Digestion Model No. 1, suggesting a much stronger inhibitory effect of hydrogen on anaerobic butyrate conversion. At hydrogen partial pressures exceeding 40 Pa and at bicarbonate limited conditions, a shift from methanogenesis to reduced product formation was observed which indicates an important role of the hydrogen partial pressure in redirecting electron fluxes towards reduced products such as butanol. The findings of this study demonstrate that a careful consideration of thermodynam-ics and kinetics is required to advance our current understanding of flux regulation in energy-limited syntrophic ecosystems.
Understanding the factors that determine the spatial and temporal biofilm development is a key to... more Understanding the factors that determine the spatial and temporal biofilm development is a key to formulate effective control strategies in reverse osmosis membrane systems for desalination and wastewater reuse. In this study, biofilm development was investigated at different water temperatures (10, 20, and 30 C) inside a membrane fouling simulator (MFS) flow cell. The MFS studies were done at the same crossflow velocity with the same type of membrane and spacer materials, and the same feed water type and nutrient concentration, differing only in water temperature. Spatially resolved biofilm parameters such as oxygen decrease rate, biovolume, biofilm spatial distribution, thickness and composition were measured using in-situ imaging techniques. Pressure drop (PD) increase in time was used as a benchmark as to when to stop the experiments. Biofilm measurements were performed daily, and experiments were stopped once the average PD increased to 40 mbar/cm. The results of the biofouling study showed that with increasing feed water temperature (i) the biofilm activity developed faster, (ii) the pressure drop increased faster, while (iii) the biofilm thickness decreased. At an average pressure drop increase of 40 mbar/cm over the MFS for the different feed water temperatures, different biofilm activities, structures, and quantities were found, indicating that diagnosis of biofouling of membranes operated at different or varying (seasonal) feed water temperatures may be challenging. Membrane installations with a high temperature feed water are more susceptible to biofouling than installations fed with low temperature feed water.
Environmental technology, Jan 25, 2016
In the last decade, autotrophic nitrogen removal technologies based on anammox metabolism have be... more In the last decade, autotrophic nitrogen removal technologies based on anammox metabolism have become state of the art in urban and industrial wastewater treatment systems, due to their advantages over traditional nitrogen removal processes. However, their application is currently limited to the treatment of warm wastewater (25-40°C) mainly due to the low growth rate of the anammox bacteria. The extension of the application field to wastewater characterized by lower temperatures (8-20°C), such as those typical for municipal sewage, allows the design of treatment systems with a net energy production. In this study, the distribution and bacterial community structure of a lab-scale single-stage partial nitritation/anammox (PN/A) granular sludge bioreactor operating at low temperatures was analysed using next-generation sequencing techniques. The presence of ammonium-oxidizing bacteria and anammox bacteria was found, but the appearance of other bacterial species shows a complex microbia...
Water research, 2010
Phosphate limitation as a method to control biofouling of spiral wound reverse osmosis (RO) membr... more Phosphate limitation as a method to control biofouling of spiral wound reverse osmosis (RO) membranes was studied at a full-scale installation fed with extensively pretreated water. The RO installation is characterized by (i) a low feed channel pressure drop increase and (ii) low biomass concentrations in membrane elements at the installation feed side. This installation contrasted sharply with installations fed with less extensively pretreated feed water (and therefore higher phosphate concentrations) experiencing a high-pressure drop increase and high biomass concentrations in lead elements. Membrane fouling simulator (MFS) studies showed that low phosphate concentrations (approximately 0.3 microg P L(-1)) in the feed water restricted the pressure drop increase and biomass accumulation, even at high substrate (organic carbon) concentrations. In the MFS under ortho-phosphate limiting conditions, dosing phosphonate based antiscalants caused biofouling while no biofouling was observe...
A three-dimensional (3D) computational model describing fluid dynamics and biofouling of feed cha... more A three-dimensional (3D) computational model describing fluid dynamics and biofouling of feed channels of spiral wound reverse osmosis and nanofiltration membrane systems was developed based on results from practice and experimental studies. In the model simulations the same feed spacer geometry as applied in practice and the experimental studies was used. The 3D mathematical model showed the same trends for (i) feed channel pressure drop, (ii) biomass accumulation, (iii) velocity distribution profile, resulting in regions of low and high liquid flow velocity also named channeling. The numerical model predicted a dominant biomass growth on the feed spacer, consistent with direct in situ observations on biofouling of spiral wound membrane modules and monitors using Magnetic Resonance Imaging (MRI). The model confirms experimental results that feed spacer fouling is more important than membrane fouling. The paper shows that mathematical modeling techniques have evolved to a stage that they can be used hand-in-hand with experiments to understand the processes involved in membrane fouling.
Applied microbiology and biotechnology, Apr 2015
In this study, the impact of the hydrogen partial pressure on lactate degradation was investigate... more In this study, the impact of the hydrogen partial pressure on lactate degradation was investigated in a coculture of Desulfovibrio sp. G11 and Methanobrevibacter arboriphilus DH1. To impose a change of the hydrogen partial pressure, formate was added to the reactor. Hydrogen results from the bioconversion of formate besides lactate in the liquid phase. In the presence of a hydrogen-consuming methanogen, this approach allows for a better estimation of low dissolved hydrogen concentrations than under conditions where hydrogen is supplied externally from the gas phase, resulting in a more accurate determination of kinetic parameters. A change of the hydrogen partial pressure from 1,200 to 250 ppm resulted in a threefold increase of the biomass-specific lactate consumption rate. The 50 % inhibition constant of hydrogen on lactate degradation was determined as 0.692 ± 0.064 μM dissolved hydrogen (831 ± 77 ppm hydrogen in the gas phase). Moreover, for the first time, the maximum biomass-s...
Biotechnology and bioengineering, Mar 2016
The syntrophic cooperation between hydrogen-producing acetogens and hydrogenotrophic methanogens ... more The syntrophic cooperation between hydrogen-producing acetogens and hydrogenotrophic methanogens relies on a critical balance between both partners. A recent study, provided several indications for the dependence of the biomass-specific growth rate of a methanogenic coculture on the acetogen. Nevertheless, final experimental proof was lacking since biomass-specific rates were obtained from a descriptive model, and not from direct measurement of individual biomass concentrations. In this study, a recently developed quantitative PCR approach was used to measure the individual biomass concentrations in the coculture of Desulfovibrio sp. G11 and Methanospirillum hungatei JF1 on lactate, formate or both. The model-derived growth yields and biomass-specific rates were successfully validated. Experimental findings identified the acetogen as the growth-limiting partner in the coculture on lactate. While the acetogen was operating at its maximum biomass-specific lactate consumption rate, the...
INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY, Jan 2014
A bacterial consortium that accumulated more than 90 % (w/w) polyhydroxybutyrate (PHB) from lacta... more A bacterial consortium that accumulated more than 90 % (w/w) polyhydroxybutyrate (PHB) from lactate was selected in a laboratory-scale bioreactor with a 'feast-famine' regime. Bacterial strain YD T , representing a dominant species in this enrichment, was isolated and characterized. Analysis of the 16S rRNA gene sequence revealed that the isolate is a member of the class Gammaproteobacteria, forming an independent phylogenetic lineage. The closest relative of the isolate was Plasticicumulans acidivorans TUD-YJ37 T , with 94 % 16S rRNA gene sequence similarity. Strain YD T was an obligate aerobe with large, ovoid, Gram-negative cells, motile by means of a polar flagellum. It utilized a relatively broad spectrum of substrates (e.g. carbohydrates, fatty acids) as carbon and energy sources. The temperature range for growth was 20-45 6C, with an optimum at 40 6C; the pH range was pH 6.0-8.0, with an optimum at pH 7.0. The major respiratory lipoquinones were Q-8 (91 %) and Q-7 (9 %). The polar lipids consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylmonomethylethanolamine and an unidentified aminolipid. The predominant fatty acids in the membrane polar lipids were C 16 : 1 v7c, C 16 : 0 and C 18 : 1 v7c. The G+C content of the genomic DNA was 68.5 mol%. On the basis of the phenotypic, chemotaxonomic and phylogenetic data, the isolate is proposed to represent a novel species in the genus Plasticicumulans, for which the name Plasticicumulans lactativorans sp. nov. is proposed. The type strain is YD T (5DSM
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Papers by Mark C M van Loosdrecht