Significance of biofilm structure on transport of inert particulates into biofilms

1998 ◽  
Vol 38 (8-9) ◽  
pp. 163-170 ◽  
Author(s):  
S. Okabe ◽  
H. Kuroda ◽  
Y. Watanabe
Keyword(s):  
Molecular Diffusion ◽  
Domestic Wastewater ◽  
Honeycomb Structure ◽  
Convective Transport ◽  
Transport Efficiency ◽  
Particulate Transport ◽  
Fluorescent Microbeads ◽  
Significant Difference ◽  
Rapid Transport ◽  
Biofilm Structure

Evolutional changes in interior structures of mixed population biofilms grown on domestic wastewater were quantitatively analyzed using a cryosectioning technique and an image analysis. Meanwhile, transport of particulates into the biofilms was also experimentally investigated using fluorescent microbeads as tracers to relate the biofilm structure and particulate transport into the biofilm. Microscopic observation of the cryomicrotomy biofilm sections indicated the biofilms were very porous and consisted of interwinded filamentous biomass acting as a framework of the biofilm. A honeycomb structure was often found, which would make the biofilm more resistant to water flow. There were micropores with the diameter of about 10 μm microcolony aggregates attached to filamentous biomass and macropores with the diameter of 20–200 μm in the biomass matrix. These pores did not clog during two months of cultivation. Areal porosity was about 30% in the bottom biofilm and more than 90% in the surface. Significant difference in transport efficiency was not observed for various sizes of microbeads due to the presence of macropores. Therefore, even 10 μm tracer beads could quickly traverse throughout a biofilm 640 μm thick via water channels or macropores and then penetrated into the micropores. Convective transport from the bulk to the bottom biofilm, rather than molecular diffusion, was responsible for this rapid transport. Based on experimental results, it can be concluded that the biofilm structure seems to be well designed to maximize the transport efficiency of substrates and products and the strength of biofilm structure.

scholarly journals Energy Transport, Overshoot, and Mixing in the Atmospheres of Very Cool Stars

2003 ◽  
Vol 210 ◽  
pp. 113-125
Author(s):  
Hans-Günter Ludwig
Keyword(s):  
Energy Transport ◽  
Thermal Structure ◽  
Stability Boundary ◽  
Convective Transport ◽  
Gravitational Acceleration ◽  
Transport Efficiency ◽  
Exponential Decline ◽  
Pressure Scale ◽  
Complex Chemistry ◽  
Convective Overshoot

We constructed hydrodynamical model atmospheres for mid M-type main-, as well as pre-main-sequence objects. Despite the complex chemistry encountered in such cool atmospheres a reasonably accurate representation of the radiative transfer is possible. The detailed treatment of the interplay between radiation and convection in the hydrodynamical models allows to study processes usually not accessible within the framework of conventional model atmospheres. In particular, we determined the efficiency of the convective energy transport, and the efficiency of mixing by convective overshoot. The convective transport efficiency expressed in terms of an equivalent mixing-length parameter amounts to values around ≈ 2 in the optically thick, and ≈ 2.8 in the optically thin regime. The thermal structure of the formally convectively stable layers is little affected by convective overshoot and wave heating, i.e. stays close to radiative equilibrium. Mixing by convective overshoot shows an exponential decline with geometrical distance from the Schwarzschild stability boundary. The scale height of the decline varies with gravitational acceleration roughly as g–1/2, with 0.5 pressure scale heights at log g=5.0.

Transient analysis of macromolecular transport across microvascular wall and into interstitium

1993 ◽  
Vol 265 (3) ◽  
pp. H993-H999 ◽  
Author(s):  
D. Kim ◽  
P. M. Armenante ◽  
W. N. Duran
Keyword(s):  
Molecular Diffusion ◽  
Fluid Velocity ◽  
Calcium Ionophore ◽  
Convective Transport ◽  
Cheek Pouch ◽  
Solute Flux ◽  
Ionophore A23187 ◽  
Transport Parameters ◽  
Macromolecular Transport ◽  
Dextran 70

We studied the dynamics of macromolecular transport across the microvascular wall in the hamster cheek pouch using intravital microscopy and digital video-image analysis. We used fluorescein isothiocyanate-dextrans of 70,000 and 150,000 Da (FITC-Dextran 70 and 150, respectively) as tracers. We applied our mathematical model and our in vivo calibration to determine the diffusion coefficient (D) and the average fluid velocity (V) in the microvascular wall and in the interstitium from the experimental data. The value of D for FITC-Dextran 70 was 0.90 +/- 0.04 x 10(-11) cm2/s in the wall and 1.29 +/- 0.05 x 10(-8) cm2/s in the interstitium. In both regions, V was 2.05 +/- 0.05 x 10(-8) cm/s. The transport parameters for FITC-Dextran 150 were 0.27 +/- 0.02 x 10(-11) cm2/s, 0.55 +/- 0.05 x 10(-8) cm2/s, and 1.71 +/- 0.48 x 10(-8) cm/s for D in the wall and interstitium and V, respectively. The topical application of either calcium ionophore A23187 (7 x 10(-7) M) or bradykinin (5 x 10(-7) M) increased D for FITC-Dextran 70 and 150 2-fold and V 10-fold relative to their control values. We used these values to quantify the relative importance of the diffusive and convective mechanisms in the total solute flux. Molecular diffusion dominates convective transport in both the microvascular wall and the interstitial space.

Single Idealized Cracks: A Tool for Understanding Fractured Glass Block Leaching

2008 ◽  
Vol 1107 ◽  
Author(s):  
Laure Chomat ◽  
Frédéric Bouyer ◽  
Stéphane Gin ◽  
Stéphane Roux
Keyword(s):  
Molecular Diffusion ◽  
Convective Transport ◽  
Glass Block ◽  
Transport Mechanisms ◽  
Realistic Condition ◽  
Glass Model ◽  
Gravity Driven ◽  
Original Device ◽  
Glass Leaching

AbstractWithin the scope of the long term behaviour of the R7T7 glass, which is the French nuclear glass, leaching and its coupling with transport mechanisms is studied. Experiments carried out on a SON 68 glass (inactive R7T7 type glass) model cracks in static basic conditions show a strong coupling between solution transport and glass leaching, depending on crack aperture. Moreover, gravity driven convective transport was evidenced for vertical model cracks, whereas only molecular diffusion was detected for horizontal model cracks under the same alteration conditions. In addition, an original device was developed to study the influence of temperature gradients on alteration kinetics as a convective driving force. These experiments show conclusively that thermally- or gravity-induced convective flow must be taken into account, even if such convective effects have not been established experimentally in neutral condition, which is more realistic condition for geological storage. A modeling, based on a porous geochemical software (HYTEC) accounting for both chemistry and transport, has been successfully applied to describe alteration within simple silicate glass cracks. It will be extended to study SON 68 glass model cracks, and more complex fracture networks.

Detailed Numerical Comparison of Laminar Burning-Speed of Stratified Hydrogen-Air and Methane-Air Mixture with Corresponding Homogeneous Mixture Using Open-Source Code

2020 ◽  
pp. 1-17
Author(s):  
Mohammad Sadik Rizvi
Keyword(s):  
Equivalence Ratio ◽  
Molecular Diffusion ◽  
Transport Model ◽  
Lewis Number ◽  
Homogeneous Mixture ◽  
Chemical Effect ◽  
Diffusion Effect ◽  
Flammability Limit ◽  
Significant Difference ◽  
Laminar Burning Speed

Abstract Detailed numerical study of laminar burning speed for fuel-air mixture is conducted using laminarReactingLMFoam solver which is a modified version of reactingfoam solver based on OpenFoam code. It accounts for detailed mixture averaged transport property calculation for reacting flow using low-Mach number governing equations. Effect of various equivalence ratio gradients is studied on stratified hydrogen-air and methane-air mixture with mixture-averaged transport model and unity Lewis number for all species and corresponding laminar burning speed is compared with homogeneous mixture. For both the fuel-air mixture, rich to lean stratified mixture resulted in a higher laminar burning speed and no significant difference was noticed for lean to rich stratified mixture when compared to homogeneous mixture at same local equivalence ratio. Increased burning speed is explained based on higher burnt gas temperature and molecular diffusion of lighter species from burnt gas referred to “Chemical Effect” in this study. Effect of thermal and molecular diffusion from the burnt gas on laminar burning speed is studied for stratified and homogeneous mixture using mixture-averaged transport model and unity Lewis number for all species. It is shown that molecular diffusion effect from burnt gas (“Chemical Effect”) are more prominent as compared to thermal diffusion effect. Extension in lean flammability limit for stratified mixture of both the fuel is shown based on higher heat release rate as compared to homogeneous mixture and extension in flammability limit for stratified mixture is explained based on higher Chemical Effect from burnt gas.

On-Line Hemodiafiltration with Pre- and Postdilution: A Comparison of Efficacy

1997 ◽  
Vol 20 (2) ◽  
pp. 81-90 ◽  
Author(s):  
P. Ahrenholz ◽  
R.E. Winkler ◽  
W. Ramlow ◽  
M. Tiess ◽  
W. Müller
Keyword(s):  
Molecular Weight ◽  
Theoretical Description ◽  
Convective Transport ◽  
Small Molecular Weight ◽  
Dialysate Flow ◽  
Significant Difference ◽  
On Line ◽  
The Impact

Since the introduction of on-line substituate preparation, high substituate rates (Qs) in pre- and postdilution for hemodiafiltration (HDF) procedures can be realized. During postdilution HDF (POD-HDF) and additional convective removal is possible, but in vivo Qs is limited to approx. 1/3Qb (bloodflow). With predilution HDF (PRD-HDF) higher Qs and therefore high convective transport rates by ultrafiltration can be reached. On the other hand the blood concentration is diminished by predilution. Further decrease of the diffusive transport is caused by reduced dialysate flow Qd due to separation of the substituate from the dialysate (Fresenius 4008 On-Line HDF, Gambro AK100 Ultra). The theoretical description of the combined diffusive-convective transport is limited to 1-dimensional models and small UF-rates. Therefore for practical and theoretical purposes the assessment of the efficacy of on-line PRD-HDF and POD-HDF in different molecular weight ranges is desirable. By means of in vitro experiments the effective clearances Keff of hemodialysis (HD, dialyzer: Fresenius F60) for urea, creatinine, vitamin B12 and inulin were compared with measured and theoretical Keff of POD- and PRD-HDF. The theoretical expectation is confirmed that Keff for small molecular weight substances decreases slightly with PRD-HDF and increases for larger molecules. In the case of POD-HDF Keff for small molecular weight substances increases slightly and strongly for larger molecules. In vivo experiments were performed to measure the real substance removal from patient's blood and to figure out the impact of dialysate flow (collection of the used dialysate during the 1. treatment hour and concentration measurements for urea, creatinine, phosphate, ß2-MG). The results show that the substraction of Qs from Qd reduces Keff for urea, creatinine and phosphate but not for ß2-MG. PRD-HDF with Qd = 500 ml/min is significantly less effective for small molecules than HD. There is no significant difference of Keff for urea, creatinine, phosphate during HD and PRD-HDF with Qd = 800 ml/min, but a significant increase of 10-15% for POD-HDF Keff for ß2-MG increases by 75% for PRD-HDF and 95% for POD-HDF compared with HD (Qd = 500 ml/min).

Determination of Granites' Mineral Specific Porosities by PMMA Method and FESEM/EDAX

2006 ◽  
Vol 985 ◽  
Author(s):  
Marja Siitari-Kauppi ◽  
L. Penttinen ◽  
M. Siitari-Kauppi ◽  
U. Alanso ◽  
M. Garcia-Gutierrez ◽  
...  
Keyword(s):  
Diffusion Coefficients ◽  
Molecular Diffusion ◽  
Total Porosity ◽  
Mineral Surfaces ◽  
Quartz Crystals ◽  
Apparent Diffusion Coefficients ◽  
Significant Difference ◽  
Apparent Diffusion ◽  
The Matrix ◽  
Granite Samples

AbstractOver extended periods, long-lived radionuclides (RN) or activation products within geologic disposal sites may be released from the fuel and migrate to the geo/biosphere. In the bedrock, contaminants will be transported along fractures by advection and retarded by sorption on mineral surfaces and by molecular diffusion into stagnant pore water in the matrix along a connected system of pores and micro-fissures.The objective of this paper was to determine the connective porosity and mineral-specific porosities for three granite samples by 14C methylmethacrylate (14C-PMMA) autoradiography. Scanning electron microscopy and energy-dispersive X-ray analyses (FESEM/EDAX) were performed in order to study the pore apertures of porous regions in greater detail and to identify the corresponding minerals. Finally, the porosity results were used to evaluate the diffusion coefficients of RNs from previous experiments which determined apparent diffusion coefficients for the main minerals in three granite samples by the Rutherford Backscattering technique.The total porosity of the Grimsel granite (0.75%) was significantly higher than the porosities of the El Berrocal and Los Ratones granites (0.3%). The porosities of the Grimsel granite feldspars were two to three times higher than the porosities of the El Berrocal and Los Ratones granites' feldspars. However, there was no significant difference between the porosities of the dark minerals. A clear difference was found between the various quartz grains. Quartz crystals were nonporous in the El Berrocal and Los Ratones granites when measured by the PMMA method, but the quartz crystals in the Grimsel granite showed 0.5% intra granular porosity. The apparent diffusion coefficients calculated for uranium diffusion within Grimsel granite on different minerals were very similar (210-13 ± 0.5 m2/s), but differences within both Spanish granites were found from one mineral to another (9 ± 110-14 m2/s in feldspars and 4.5 ± 0.510-14 m2/s in quartz) - always presenting lower diffusion values than in the Grimsel granite.

scholarly journals Occurrence of antimicrobial-resistant Escherichia coli in sewage treatment plants of South India

2020 ◽  
Vol 10 (1) ◽  
pp. 48-55 ◽  
Author(s):  
Yerabham Praveenkumarreddy ◽  
Masato Akiba ◽  
Keerthi Siri Guruge ◽  
Keshava Balakrishna ◽  
Kalwaje Eshwara Vandana ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Antimicrobial Resistance ◽  
South India ◽  
Sewage Treatment ◽  
Domestic Wastewater ◽  
Global Network ◽  
Resistance Pattern ◽  
Sewage Treatment Plants ◽  
E Coli ◽  
Significant Difference

Abstract Antibiotics received by sewage treatment plants may be the causative factor in spreading antibiotic resistance bacteria in the aquatic environment. The current study investigates the distribution of antimicrobial-resistant Escherichia coli (E. coli) in four sewage treatment plants (STPs) in South India receiving hospital and domestic wastewater in different proportions. A total of 221 E. coli isolates were checked for antimicrobial resistance against 16 antimicrobials. Among the antimicrobials tested, ampicillin (AMP) and cefazolin (CFZ) showed resistance between 20% and 90%, nalidixic acid (NAL) and ciprofloxacin (CIP) showed resistance between 15% and 75% and chloramphenicol (CHL) showed resistance between 2% and 20%. Based on the observations, there is no significant difference between the wastewater inlet and outlet, suggesting that treatment process was not effective in reducing the resistance. In conclusion, the trends of antimicrobial resistance pattern show that the levels of resistance were slightly higher in hospital wastewater than domestic wastewater. This article has been made Open Access thanks to the generous support of a global network of libraries as part of the Knowledge Unlatched Select initiative.

scholarly journals Penggunaan Serat Kelapa untuk Pengolahan Limbah Cair Domestik

2020 ◽  
Vol 17 (2) ◽  
pp. 81
Author(s):  
Hajimi Hajimi ◽  
Salbiah Salbiah ◽  
Susilawati Susilawati
Keyword(s):  
Waste Water ◽  
Waste Water Treatment ◽  
Treatment Plant ◽  
Domestic Wastewater ◽  
Waste Water Treatment Plant ◽  
P Value ◽  
Coir Fiber ◽  
Coconut Fiber ◽  
Significant Difference ◽  
Coconut Coir

The oil and fat content in domestic wastewater is an element that can cause pollution of water bodies and inhibits the continued process in the Waste Water Treatment Plant. For this reason, efforts should be made to eliminate the womb in wastewater by filtration. In this study the filtration process uses a laboratory scale that is making a waste water solution from a mixture of water with various types of cooking spices that are fried using cooking oil and butter. The purpose of the study was to analyze the effectiveness of coconut fiber as a filter for waste oil (fat) in domestic wastewater. The research starts from the process of making coconut fiber and filtration tanks until it continues to the filtration treatment process. The results showed there were significant differences in oil (fat) levels in domestic wastewater between before and after filtration using coconut coir fiber media with a thickness of 20 cm, 40 cm and 60 cm, which obtained the value of p (p-value) ≤ value α (0 , 05), i.e. 0.019, 0.02 and 0.006. There is no significant difference in effectiveness between variations in thickness of coconut coir fibers as a filtration media against decreasing levels of oil (fat) in domestic wastewater, where a p-value of 0.073> α (0.05) is obtained. The effectiveness of each reduction is 89.24 (thickness 20 cm), 0.02 (thickness 40 cm) and 0.006 (thickness 60 cm). Coconut fiber is effective as a filtration media for treating domestic wastewater that contains oil (fat). It is recommended to conduct further research by increasing the residence time of wastewater in the filtration bath.

scholarly journals Removal of Pathogens from Domestic Wastewater Using Small-Scale Gradual Hydroponics Planted with Duranta erecta, Addis Ababa, Ethiopia

2022 ◽  
Vol 2022 ◽  
pp. 1-9
Author(s):  
Solomon Tibebu ◽  
Abebe Worku ◽  
Kenatu Angassa
Keyword(s):  
Heterotrophic Bacteria ◽  
Addis Ababa ◽  
Control Unit ◽  
Domestic Wastewater ◽  
Experimental Unit ◽  
Small Scale ◽  
Hydroponic System ◽  
Control Units ◽  
Significant Difference ◽  
And Control

This study aimed to evaluate the treatment potential of gradual hydroponics planted with Duranta erecta in the removal of pathogens from domestic wastewater. Two experimental and control units were configured in series. Each unit contains three bioreactors and was arranged in a cascaded configuration. The two experimental units used both plant and media, but the two control units used only media to treat the wastewater. Gravel and polyester sponge were used as media. Experimental unit 1 and control unit 1 used gravel as media; however, experimental unit 2 and control unit 2 used polyester sponges as media. The experiment was operated at hydraulic retention times of 1, 3, 5, and 7 days in a continuous mode. The performance of the hydroponic system was evaluated by characterizing the influent and effluent quality using standard methods. At optimum hydraulic retention time (7 days), the average removal of experimental units 1 and 2 was 98.7% and 89.8% for heterotrophic bacteria, 96.2% and 86.8% for total coliform, and 92.9% and 84.0% for fecal coliform, respectively. Analysis of variance showed that there was a significant difference P < 0.05 between the two experimental and control units in removing pathogens, but no significant difference P > 0.05 was observed between the two experimental units and between the two control units. Heterotrophic bacteria and coliforms were satisfactorily removed from domestic wastewater via a gradual hydroponic system. Hence, the hydroponic treatment system planted with Duranta erecta has a promising potential in the removal of pathogens from domestic wastewater in developing countries including Ethiopia.

Tailoring of highly efficient nitrifying biofilms in fluidized bed for ammonia-rich industrial wastewater treatment

2000 ◽  
Vol 42 (3-4) ◽  
pp. 357-362 ◽  
Author(s):  
S. Tsuneda ◽  
T. Miyoshi ◽  
Y. Aoi ◽  
A. Hirata
Keyword(s):  
Fluidized Bed ◽  
Industrial Wastewater ◽  
Domestic Wastewater ◽  
Nitrifying Bacteria ◽  
Nitrification Rate ◽  
Fish Analysis ◽  
Ammonia Oxidizing Bacteria ◽  
High Concentration ◽  
Stepwise Reduction ◽  
Biofilm Structure

We proposed two tailoring methods for efficient nitrifying biofilms on particles which are expected to be used in fluidized bed in nitrogen removal processes for industrial wastewaters. The first method was examined with gradual reduction of the hydraulic retention time in continuous feeding reactor to form biofilm with high nitrification ability. As a result, nitrification rate was successfully improved mainly due to acclimation of nitrifying bacteria to higher loading. The second tailoring method for nitrifying biofilm started with the biofilm which had been previously constructed in synthetic domestic wastewater containing high concentration of NH4+-N as well as various biodegradable organic compounds. Stepwise reduction of C/N ratio in inlet wastewater was performed during one month simultaneously with observation of microbial population dynamics in the biofilm using fluorescent in situ hybridization (FISH) analysis. As a result, this acclimation process promoted occupation of the biofilm by ammonia-oxidizing bacteria and resulted in making suitable biofilm structure for nitrification of ammonia-rich industrial wastewater. Moreover, it is confirmed that this new tailoring method greatly shortened required time to obtain nitrifying biofilms.

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