Study on the use of NADH fluorescence measurements for monitoring wastewater treatment systems

Fluorescence measurement of intracellular nicotinamide adenine dinucleotide (NADH) provides information about the physiological response of microbes towards changing conditions in their environment and has been suggested to be useful for the control of wastewater treatment plants. In this study, the practical usefulness of such measurements was evaluated from batch experiments with a commercially available NADH sensor in a bench scale reactor. The sensor was linear in the NADH concentration, robust, almost maintenance free, and hardly sensitive to floc size distribution. Measured fluorescence intensity proved to depend strongly on the concentration of active heterotrophic biomass. The NADH level was supposed to be dependent on the ratio of electron donor/electron acceptor availability inside the cells; however, neither acetate nor ammonium addition was reflected by the measurement signal.A jump wise NADH signal change was observed at complete oxygen or nitrate depletion as also reflected by bends in the redox curve. In the near zero concentration ranges of oxygen and nitrate (0.1-0.5mg/l) the signal changes only slightly in the opposite direction to the redox trend.     

Aerobic granular sludge in a sequencing batch reactor

In a laboratory scale sequencing batch reactor (SBR) granules were cultured under aerobic conditions. To enhance the growth of granular sludge the SBR was operated with very short sedimentation and draw phases resulting in the washout of slow settling biomass. Fast settling granules were retained in the reactor and thus had an advantage over flocs with a slower settling velocity. After 40 days of operation granules were the dominant form of microbial aggregates in the reactor, even though some pin-point flocs remained in the system. Granules taken from the reactor were stored for weeks without disintegrating. After about 130 days of operation the granule quality and COD-removal worsened. The reasons for that are yet to be investigated.     

Platelet procoagulant surface as an essential parameter for the in vitro evaluation of the blood compatibility of polymers

Thrombus formation at an artificial surface in contact with blood is the result of the interplay of two tightly linked biological systems, namely blood platelets and blood coagulation. While initiation of the overall process is thought to originate from proenzyme-enzyme conversions at the artificial surface, propagation of the process is only possible when a suitable phospholipid surface is available. The outer leaflet of the plasma membrane of activated platelets is such a surface; it containts negatively charged phospholipids which are normally present in the inner leaflet of the membrane. An examination of the thrombogenicity of materials, therefore, should include a quantitative assay for procoagulant sites at an artificial surface. In the present study we have evaluated polymers, exposed to platelet-rich plasma, for their procoagulant properties by using two sets of assays. With the one set, markers of blood coagulation were assayed (recalcification time of platelet rich plasma and kallikrein-C1-Inhibitor complex formation) and with the other set the surfaces were analysed for platelet adherence and procoagulant sites utilising annexin V, which has a high affinity for negatively charged phopholipids. For the polymers, the fastest rate of contact activation, as determined from kallikrein-C1-Inhibitor generation, was found with polyethylene. In spite of that, the conventional partial thromboplastin time (PTT) could not reveal differences between the various materials. However, when clotting was performed with platelet-rich plasma, it was found that the polymers differed significantly in their clot promoting activities. The shortest clotting time (5 min) was found with polyethylene (PE), and polyvinyl chloride (PVC) gave the longest clotting time (10 min). These findings closely correlated with the amount of procoagulant sites generated at the platelet-rich plasma-polymer interface.     

Metabolic modelling of full-scale biological nitrogen and phosphorus removing wwtp's.

This paper evaluates the experiences with modelling full-scale biological phosphorus and nitrogen removing wastewater treatment plants. For the simulation, we used a metabolic phosphorus model integrated in ASM2d, further referred to as TUDP-model. It was found that the metabolic model for bio-P removal can be applied for modelling full-scale wwtp's, without extensive parameter adjustments. A stepwise modelling approach was proposed. Only three specific parameters were calibrated. Two parameters, the inert fraction in the influent and the actual anoxic sludge fraction will need calibration for all systems. Parameter sensitivity analyses showed that the sensitivity of operational data, often considered as known input data, is high. The model kinetics were found less sensitive. This will in general be the case for all low-loaded wwtp's recorded in their pseudo-steady state. Based on mass balance calculations, operational data and measurements were evaluated. Since all terms on a phosphorus balance can be measured, errors in operational data (e.g. SRT and flow rates) become very apparent in P-removal models (ASM2d, TUDP). We suggest using the P-balance in general for wwtp modelling, as a check on data consistency. This study showed that considering operational data per definition as known input data is not justified. Therefore, operational data should be evaluated, or considered in model calibration over the use of kinetic and stoichiometric parameters.     

Murine IgG1 complexes trigger immune effector functions predominantly via Fc gamma RIII (CD16)

Previously, we have demonstrated that phagocytosis of IgG1-coated particles by macrophages in vitro is impaired by deletion of Fc gamma RIII in mice, suggesting that IgG1 may interact preferentially with Fc gamma RIII. In the present study, the biologic relevance of this observation was addressed by triggering various effector functions of the immune system in Fc gamma RIII(-/-) mice, using panels of mAbs of different IgG subclasses. Both binding and phagocytosis of IgG1-coated sheep or human erythrocytes by Fc gamma RIII(-/-) macrophages in vitro were strongly impaired, indicating that the impaired ingestion of complexed IgG1 by Fc gamma RIII(-/-) macrophages is due to a defect in binding. An in vivo consequence of the defective phagocytosis was observed by resistance of Fc gamma RIII-deficient mice to experimental autoimmune hemolytic anemia, as shown by a lack of IgG1-mediated erythrophagocytosis in vivo by liver macrophages. Furthermore, trapping of soluble IgG1-containing immune complexes by follicular dendritic cells in mesenteric lymph nodes from Fc gamma RIII(-/-) mice was abolished. Whole blood from Fc gamma RIII(-/-) mice was unable to induce lysis of tumor cells in the presence of IgG1 antitumor Abs. Finally, IgG1 mAbs proved unable to mount a passive cutaneous anaphylaxis in Fc gamma RIII(-/-) mice. Together, these results demonstrate that IgG1 complexes, either in particulate or in soluble form, trigger in vitro and in vivo immune effector functions in mice predominantly via Fc gamma RIII.     

Rate-based modelling of SO2 absorption into aqueous NaHCO3/Na2CO3 solutions accompanied by the desorption of CO2

A rate-based model of a counter-current reactive absorption/desorption process has been developed for the absorption of SO₂ into NaHCO₃/Na₂CO₃ in a packed column. The model adopts the film theory, includes diffusion and reaction processes, and assumes that thermodynamic equilibrium among the reacting species exists in the bulk liquid. Model predictions were compared to experimental data from literature. For the calculation of the absorption rate of SO₂ into NaHCO₃/Na₂CO₃ solutions and concomitant CO₂-desorption, it is important to take into account all reversible reactions simultaneously. It is clear that the approximate analytical based model cannot be expected to predict the absorption rates under practical conditions because of the complicated nature of the reactive absorption processes. The rigorous numerical approach described here only requires definition of the individual reactions in the system, and subsequent solution is independent of specific assumptions made, or operational variables like pH or compound concentrations. As an example of the flexibility of this approach, additional calculations were conducted for SO₂ absorption in a phosphate-based buffer system.     

The rotating disc as a device to study the adhesive properties of endothelial cells under differential shear stresses

Hemocompatibility can be conferred on a biomaterial by covering this material with a monolayer of endothelial cells. The endothelial cell is an epithelial cell of mesenchymal origin, that features a specific phenotype with homotypic intercellular interactions and with specialized cell-matrix interactions. These interactions are mandatory to the normal barrier function and the non-thrombogenicity of the endothelial monolayer and are maintained in vivo at shear stresses ranging from 10^-5 to 10^-3 N cm^-2. The endothelial monolayer grafted on a biomaterial should meet similar requirements. We have constructed a rotating disc device to investigate the effects of differential shear stresses on cell-cell and cell-matrix interactions in a monolayer of endothelial cells grafted on a disc-shaped biomaterial. The range of shear stresses that are being applied by the device vary from 0–10^-4 N cm^-2 to 0–2×10^-3 N cm^-2. In a series of experiments with discs of plasma discharge treated polycarbonate (PC) that are coated with fibronectin, it has been shown that a monolayer of endothelial cells grafted on these discs starts to lose intercellular contacts and cell-fibronectin interactions at shear stresses of 10^-4 N cm^-2. Coating of the PC discs with a complex extracellular matrix, synthesized by arterial smooth muscle cells in culture, prior to endothelial cell seeding results in the formation of a monolayer, which retains its integrity at shear stresses up to 2×10^-3 N cm^-2.     

Phenidone-ascorbic acid development in electronmicroscopic autoradiography

Phenidone-ascorbic acid development in electronmicroscopic autoradiography, using Ilford L4 as photographic emulsion and microdol-x as reference developer. Grain yield and efficiency were studied on pale gold section of uniformly labeled tritium methacrylate. For determination of the resolution, a radioactive line source was prepared by cross-sectioning of an epon-embedded film of tritium labeled albumin. The spatial relationship between silver grains and silver bromide crystals was investigated by shadowing the emulsion with platinumcarbon before development. In shadowed autoradiographs both, silver grains and silver bromide crystal were visible. Phenidone was about twice as sensitive as microdol-x and had a half distance value (Salpeter et al., 1969) of 175 mm. Most of the silver grains of both developers were located within the perimeters of their parent silver bromide crystals. In the case of phenidone more than 80% of the excited crystals gave rise to just one silver deposit. These parameters, together with grain size and shape, and counting feasibility make phenidone a useful developer for quantitative EM-autoradiography.     

Application of direct fluid flow oscillations to improve mixing in microbioreactors

This article describes an active mixing method for a microbioreactor that was designed, simulated, tested, and successfully implemented. By applying a varying pressure to a microchannel looping tangentially into a cylindrical microreactor an oscillating fluid flow was shown to occur. Such an oscillating fluid flow improved mixing, both by diffusion and convection. The oscillating fluid flow has a large impact on the ratio between the diffusion domain and the convection domain. A good match was obtained between experimental mixing results, computational fluid dynamics simulation results and the results of a simplified mixing model thus demonstrating the potential of simulation on improving the design of microreactors. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

Material‐Auswahlbox zur Herstellung fortgeschrittener Polymermembranen für die Wasseraufbereitung

Within the framework of the MABMEM research project, new high‐performance membranes are being developed for sustainable water management. The performance of the membranes will be evaluated in comparative and standardized fouling tests as well as in terms of the removal of trace impurities on a laboratory scale. Seven candidates are currently being tested in demonstrator trials with real‐water matrix in a waterworks for the direct treatment of dam water without prior coagulation over a period of 6 months. Subsequently, the new membrane materials will be operated with the effluent of a wastewater treatment plant.