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Item Characterizing the structure of aerobic granular sludge using ultra-high field magnetic resonance(IWA Publishing, 2020-08) Kirkland, Catherine M.; Krug, Julia R.; Vergeldt, Frank J.; van den Berg, Lenno; Velders, Aldrik H.; Seymour, Joseph D.; Codd, Sarah L.; Van As, Henk; de Kreuk, Merle K.Despite aerobic granular sludge wastewater treatment plants operating around the world, our understanding of internal granule structure and its relation to treatment efficiency remains limited. This can be attributed in part to the drawbacks of time-consuming, labor-intensive, and invasive microscopy protocols which effectively restrict samples sizes and may introduce artefacts. Timedomain nuclear magnetic resonance (NMR) allows non-invasive measurements which describe internal structural features of opaque, complex materials like biofilms. NMR was used to image aerobic granules collected from five full-scale wastewater treatment plants in the Netherlands and United States, as well as laboratory granules and control beads. T1 and T2 relaxation-weighted images reveal heterogeneous structures that include high- and low-density biofilm regions, waterlike voids, and solid-like inclusions. Channels larger than approximately 50 μm and connected to the bulk fluid were not visible. Both cluster and ring-like structures were observed with each granule source having a characteristic structural type. These structures, and their NMR relaxation behavior, were stable over several months of storage. These observations reveal the complex structures within aerobic granules from a range of sources and highlight the need for non-invasive characterization methods like NMR to be applied in the ongoing effort to correlate structure and function.Item Heterogeneous diffusion in aerobic granular sludge(Wiley, 2020-08) van den Berg, Lenno; Kirkland, Catherine M.; Seymour, Joseph D.; Codd, Sarah L.; Van Loosdrecht, Mark C. M.; de Kreuk, Merle K.Aerobic granular sludge (AGS) technology allows simultaneous nitrogen, phosphorus, and carbon removal in compact wastewater treatment processes. To operate, design, and model AGS reactors, it is essential to properly understand the diffusive transport within the granules. In this study, diffusive mass transfer within full‐scale and lab‐scale AGS was characterized with nuclear magnetic resonance (NMR) methods. Self‐diffusion coefficients of water inside the granules were determined with pulsed‐field gradient NMR, while the granule structure was visualized with NMR imaging. A reaction‐diffusion granule‐scale model was set up to evaluate the impact of heterogeneous diffusion on granule performance. The self‐diffusion coefficient of water in AGS was ∼70% of the self‐diffusion coefficient of free water. There was no significant difference between self‐diffusion in AGS from full‐scale treatment plants and from lab‐scale reactors. The results of the model showed that diffusional heterogeneity did not lead to a major change of flux into the granule (<1%). This study shows that differences between granular sludges and heterogeneity within granules have little impact on the kinetic properties of AGS. Thus, a relatively simple approach is sufficient to describe mass transport by diffusion into the granules.Item Characterization and quantification of structure and flow in multichannel polymer membranes by MRI(2019-01) Schuhmann, S.; Simkins, Jeffrey W.; Schork, N.; Codd, Sarah L.; Seymour, Joseph D.; Heijnen, M.; Saravia, F.; Horn, H.; Nirschl, H.; Guthausen, G.Polymeric multichannel hollow fiber membranes were developed to reduce fiber breakage and to increase the volume-to-membrane-surface ratio and consequently the efficiency of filtration processes. These membranes are commonly used in ultrafiltration and are operated in in-out dead-end mode. However, some of the filtration details are unknown. The filtration efficiency and flow in the multichannel membranes depend on filtration time and are expected to vary along spatial coordinates. In the current work, in-situ magnetic resonance imaging was used to answer these questions. Velocities were quantified in the feed channels to obtain a detailed understanding of the filtration process. Flow and deposits were measured in each of the seven channels during filtration of sodium alginate, which is a model substance for extracellular polymeric substances occurring in water treatment. Volume flow and flow profiles were calculated from phase contrast flow images. The flow in z-direction in the center channel was higher than in the surrounding channels. Flow profiles variate depending on the concentration of Ca2+, which changes the filtration mechanism of aqueous solutions of sodium alginate from concentration polarization to gel layer filtration.Item Low-Field Borehole NMR Applications in the Near-Surface Environment(2018-01) Kirkland, Catherine M.; Codd, Sarah L.The inherent heterogeneity of the near subsurface (<200 m below the ground surface) presents challenges for agricultural water management, hydrogeologic characterization, and engineering, among other fields. Borehole nuclear magnetic resonance (NMR) has the potential not only to describe this heterogeneity in space nondestructively but also to monitor physical and chemical changes in the subsurface with time. Nuclear magnetic resonance is sensitive to parameters of interest like porosity and permeability, saturation, fluid viscosity, and formation mineralogy. Borehole NMR tools have been used to measure soil moisture in model soils, and recent advances in lowfield borehole NMR instrumentation allow estimation of hydraulic properties of unconsolidated aquifers. We also demonstrate the potential for low-field borehole NMR tools to monitor field-relevant biogeochemical processes like biofilm accumulation and microbially induced calcite precipitation at laboratory and field scales. Finally, we address some remaining challenges and areas of future research, as well as other possible applications where borehole. NMR could provide valuable complementary data.Item NMR investigation of water diffusion in different biofilm structures(2017-09) Herrling, M. P.; Weisbrodt, Jessica; Kirkland, Catherine M.; Williamson, Nathan H.; Lackner, S.; Codd, Sarah L.; Seymour, Joseph D.; Guthausen, G.; Horn, H.Mass transfer in biofilms is determined by diffusion. Different mostly invasive approaches have been used to measure diffusion coefficients in biofilms, however, data on heterogeneous biomass under realistic conditions is still missing. To non-invasively elucidate fluid–structure interactions in complex multispecies biofilms pulsed field gradient-nuclear magnetic resonance (PFG-NMR) was applied to measure the water diffusion in five different types of biomass aggregates: one type of sludge flocs, two types of biofilm, and two types of granules. Data analysis is an important issue when measuring heterogeneous systems and is shown to significantly influence the interpretation and understanding of water diffusion. With respect to numerical reproducibility and physico-chemical interpretation, different data processing methods were explored: (bi)-exponential data analysis and the Γ distribution model. Furthermore, the diffusion coefficient distribution in relation to relaxation was studied by D-T2 maps obtained by 2D inverse Laplace transform (2D ILT). The results show that the effective diffusion coefficients for all biofilm samples ranged from 0.36 to 0.96 relative to that of water. NMR diffusion was linked to biofilm structure (e.g., biomass density, organic and inorganic matter) as observed by magnetic resonance imaging and to traditional biofilm parameters: diffusion was most restricted in granules with compact structures, and fast diffusion was found in heterotrophic biofilms with fluffy structures. The effective diffusion coefficients in the biomass were found to be broadly distributed because of internal biomass heterogeneities, such as gas bubbles, precipitates, and locally changing biofilm densities. Thus, estimations based on biofilm bulk properties in multispecies systems can be overestimated and mean diffusion coefficients might not be sufficiently informative to describe mass transport in biofilms and the near bulk.Item Peclet number dependent superdiffusive hydrodynamic dispersion in a site percolation porous media measured by NMR(2017-04) Seymour, Joseph D.; Codd, Sarah L.; Kimmich, RainerThe displacement time dependent hydrodynamic dispersion in a model 2D site percolation structure is measured using PGSE NMR. The data indicate superdiffusive scaling of the mean squared displacement at high Peclet numbers, where advective transport dominates, consistent with classic percolation scaling concepts. The time scaling of the mean squared displacement is shown to vary with the Peclet number demonstrating a dependence on the changing dynamics.Item Anomalous fluid transport in porous media induced by biofilm growth(2004-11) Seymour, Joseph D.; Gage, Justin P.; Codd, Sarah L.; Gerlach, RobinMagnetic resonance measurements of the transition from normal to anomalous hydrodynamic dispersion in porous media due to biological activity are presented. Fractional advection-diffusion equations are shown to provide models for the measured impact of biofilm growth on porous media transport dynamics.Item Magnetic resonance microscopy of biofilm structure and impact on transport in a capillary bioreactor(2004-04) Seymour, Joseph D.; Codd, Sarah L.; Gjersing, Erica L.; Stewart, Philip S.Microorganisms that colonize surfaces, biofilms, are of significant importance due to their role in medical infections, subsurface contaminant remediation, and industrial processing. Spatially resolved data on the distribution of biomass within a capillary bioreactor, the heterogeneity of the biofilm itself and the impact on transport dynamics for a Staphylococcus epidermidis biofilm in the natural growth state are presented. The data demonstrate the ability of magnetic resonance microscopy to study spatially resolved processes in bacterial biofilms, thus providing a basis for future studies of spatially resolved metabolism and in vivo clinical detection.Item Magnetic resonance microscopy analysis of advective transport in a biofilm reactor(2005) Gjersing, Erica L.; Codd, Sarah L.; Seymour, Joseph D.; Stewart, Philip S.In this article we present magnetic resonance microscopy (MRM) characterization of the advective transport in a biofilm capillary reactor. The biofilm generates non-axial flows that are up to 20% of the maximum axial velocity. The presence of secondary velocities of this magnitude alters the mass transport in the bioreactor relative to non-biofilm fouled reactors and questions the applicability of empirical mass transfer coefficient approaches. The data are discussed in the context of simulations and models of biofilm transport and conceptual aspects of transport modeling in complex flows are also discussed. The variation in the residence time distribution due to biofilm growth is calculated from the measured propagator of the motion. Dynamical systems methods applied to model fluid mixing in complex flows are indicated as a template for extending mass transport theory to quantitatively incorporate microscale data on the advection field into macroscale mass transfer models.Item Magnetic resonance microscopy of biofilm and bioreactor transport(2006-02) Codd, Sarah L.; Seymour, Joseph D.; Gjersing, Erica L.; Gage, Justin P.; Brown, Jennifer R.