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The study presented three-dimensional (3D) analysis of water's upward flowing through the vertical pipe under turbulent characteristic considerations. Both numerical constructed and improved the model of 3D for cylindrical coordinates of governing equations for incompressible turbulent flow with the Reynolds Average Navier-Stokes (RANS) model using the improved constants of the (k-e) type. The present model is then compared with a previous study to give the feasibility of the present single-phase turbulent flow parameters. The pipe length is tested to measure how much it affected the turbulent parameters though one of the expected factors is the turbulent time scale. On the other hand, the model is numerically examined to determine the velocity profile, shear rate, and surface deformation of the water domain. While the pressure distribution, turbulent kinetic energy, and turbulent dissipation rate, these parameters are classified as the mechanic's system factors. The simulation is done with wide software used to simulate industrial is COMSOL 5.4 Multiphysics software. The results obtained increased the velocity of three inlet water velocities used ranging from (0.087, 0.105, and 0.123 m/sec) of upward flow. High fluctuation in the water flow moves along the entire pipe length and it can notice the sensitivity to any change in water properties or mechanical properties. The liquid upward flow in turbulent conditions is suffered from many characteristics such them related to liquid properties and others related to the mechanics of the application through the systems. The interaction between the fluid film (fluid boarded the pipe inner diameter) has been observed by the shear rate and liquid surface deformation. [ABSTRACT FROM AUTHOR]

In this paper, the instability of a vertical fluid motion, or throughflow, is investigated in a horizontal bidisperse porous layer that is uniformly heated from below. By means of the order-1 Galerkin approximation method, the critical Darcy–Rayleigh number for the onset of steady instability is determined in closed form. The coincidence between the linear instability threshold and the global nonlinear stability threshold, in the energy norm, is shown. [ABSTRACT FROM AUTHOR]

A plethora of active matter models exist that describe the behavior of self-propelled particles (or swimmers), both with and without hydrodynamics. However, there are few studies that consider shape-anisotropic swimmers and include hydrodynamic interactions. Here, we introduce a simple method to simulate self-propelled colloids interacting hydrodynamically in a viscous medium using the lattice-Boltzmann technique. Our model is based on raspberry-type viscous coupling and a force/counter-force formalism, which ensures that the system is force free. We consider several anisotropic shapes and characterize their hydrodynamic multipolar flow field. We demonstrate that shape-anisotropy can lead to the presence of a strong quadrupole and octupole moments, in addition to the principle dipole moment. The ability to simulate and characterize these higher-order moments will prove crucial for understanding the behavior of model swimmers in confining geometries. [ABSTRACT FROM AUTHOR]

The dynamics of flow of a dielectric fluid in a vertical cylindrical annulus with a fixed temperature difference and an increasing alternating electric tension has been investigated using a direct numerical simulation (DNS). The temperature difference imposed on the cylindrical surfaces induces a radial temperature gradient perpendicular to the ground gravity which generates a baroclinic flow ascending near the hot surface and descending near the cold one. The electric field coupled with the permittivity gradient generates a dielectrophoretic buoyancy force which is a source of vorticity. Above a critical value of the electric tension, the flow bifurcates to a pattern of stationary columnar vortices. These columnar vortices which characterize the thermoelectric convection are not axially invariant, in contrast with classical Taylor columns. They bifurcate to regular wave patterns and then to spatio-temporal chaotic patterns when the electric field intensity is increased. The flow and temperature fields, the kinetic energy and the enstrophy of thermoelectric convective regimes are computed for different values of the electric tension. [ABSTRACT FROM AUTHOR]

In this paper, an attempt has been made to critically examine the flow field inside a cylindrical model vortex chamber type sediment extractor with 1.0 m diameter. Data on velocity distribution along tangential and radial directions have been collected by Programmable Electro Magnetic Shunt (PEMS) meter in a circular cylindrical model of vortex chamber in the laboratory. Data were for wide range of flow rate, water abstraction ratios, vertical, radial and transverse spacing. In this paper only result of one lowest water abstraction ratio that is 8% is presented. The results are presented in the form of graphical representation. Also, the segments with similar flow field have been identified. [ABSTRACT FROM AUTHOR]

To better understand the Wudalianchi intraplate volcanism and mantle dynamics in NE China, we collect abundant teleseismic waveform data during 2008 to 2018 recorded at 259 seismic stations around the Wudalianchi volcano. These stations include 148 WAVESArray portable stations, 66 NECESSArray portable stations and 45 Chinese provincial stations. Our newly deployed WAVESArray makes the station intervals of ~20–30 km around the Wudalianchi volcano. Using the minimum transverse‐energy grid‐search method, we make effective SKS splitting measurements at 192 stations. Our results show that the fast direction in the study region is mainly NW‐SE, but there are obvious contrasts within and between different tectonic units. To the east of the North‐South Gravity Lineament, around the Wudalianchi volcano, our SKS splitting measurements show a southeastward opening U‐shaped pattern in the fast direction and splitting time. Such a pattern of seismic anisotropy could be caused by horizontal and vertical flows in the big mantle wedge due to the deep subduction, long stagnancy, and deep dehydration of the Pacific slab in the mantle transition zone. The horizontal flow in the big mantle wedge could be obstructed by the thicker lithosphere under the Great Xing'an range and disturbed by hot and wet upwelling flow under the Wudalianchi volcano. Around the Nuominhe and Halaha volcanic groups, variations in the splitting parameters may also be associated with lithospheric deformation and delamination, though they are located at the edge of our study region. These results shed new light on the intraplate volcanism and mantle dynamics in NE China. Key Points: Our measurements show a southeastward opening U‐shaped pattern in fast direction and splitting time around the Wudalianchi volcanoSuch a pattern of seismic anisotropy could be caused by the horizontal and vertical flows in the big mantle wedgeHorizontal flow is obstructed by thicker lithosphere under Great Xing'anrang and disturbed by hot upwelling under Wudalianchi volcano [ABSTRACT FROM AUTHOR]

Verification of a groundwater flow model by radiocarbon (14C) data are presented taking into consideration the paleo-hydrogeological changes. Northeastern area of the Great Hungarian Plain was a deep-lying flat area, and its central part (Nyírség) has been uplifted in the last 15,000 years. These geological events have drastically changed the hydrogeological conditions of Nyírség. The groundwater flow system is composed of the Quaternary-Pliocene-Upper Pannonian clastic sediments. Groundwater flow modeling has been performed to define the main lateral and vertical flow directions and velocities controlling the propagation of the environmental radioactive tracer 14C. Solute-transport modeling was used to calculate the 14C activity. The recent steady-state groundwater flow velocity was reduced to a reasonable value characterizing the average flow velocity over the 15 ka simulation period using "trial and error" method. The best fit between the simulated and measured 14C data was achieved by assuming 0.4 flow velocity reduction factor. Results indicate that the present steady-state flow model with this flow velocity reduction factor is capable of reproducing the observed 14C data taking into account the effect of the significant uplift of the part of the land surface in the last 15 ka in NE Hungary. [ABSTRACT FROM AUTHOR]

In this paper, we study the hydrodynamics induced by an ionic polymer metal composite (IPMC) cantilever vibrating in a quiescent fluid. Time-resolved particle image velocimetry is used to measure the velocity field in the vicinity of the vibrating IPMC strip and a control volume analysis is utilized to estimate the thrust production per unit IPMC width. The governing fluid dynamics dimensionless parameters are varied parametrically to ascertain the influence of the Reynolds number, the peak tip displacement to IPMC length ratio, and the IPMC aspect ratio. It is found that the Reynolds number is the dominant parameter in determining the thrust produced by the IPMC, while the relative tip displacement and aspect ratio play secondary roles. An increase in the relative tip displacement has a minimal effect on the produced thrust, while an increase in the aspect ratio results in a mild decrease in thrust production. It is further found that estimating the thrust from the mean velocity field significantly underpredicts the thrust estimate. [ABSTRACT FROM AUTHOR]

Injecting freshwater and pumping salt water are effective methods to restore the salt water in a coastal area. Based on a one-dimensional vertical experiment, the variable density flow is simulated under the condition of different injection directions and injection rates of fresh water. A one-dimensional mathematical model of variable density flow and solute transport is established. The mathematical models are solved using the implicit difference method. Fortran code is developed to simulate and verify the vertical flow of variable density flow in different directions. Through both numerical simulation and experimental studies, it is found that the variable density fluid in the direction of reverse gravity is different from that in the direction of gravity. On this basis, the most effective desalination model of salt water is further discussed. It provides a theoretical and technical method for the restoration of salt water in the vertical injection of freshwater. In order to improve the remediation efficiency and reduce the cost in the engineering application, the suitable water injection rate should be ensured, considering the suitable construction time and zone of a study area. [ABSTRACT FROM AUTHOR]

One of the possible ways to improve the operation efficiency of constructed wetlands and to prevent their clogging is the application of earthworms. They have already been successfully applied for vermicomposting and for sludge dewatering and treatment. A few studies have already examined the effect of earthworms on the treatment of wastewater by vertical flow constructed wetlands (VFCWs), but none of them have provided a yearlong research result from an open-air system or compared the effect that different seasons in a temperate climate area can have on these invertebrates. The goal of this research was to estimate the effect that earthworms and plants have on VFCW's operation. Four mesocosms (a filter, a filter with earthworms, a VFCW and a VFCW with earthworms) were built and their influent and effluent water quality was monitored for a period of 1 year. They were fed with wastewater coming from a building of the University of Bologna (Italy). The results have shown that the presence of earthworms in this specific system did not reduce the organic matter content of the substrate, but it has positively influenced plants' growth. However, since neither earthworms nor plants had a statistically significant effect on the effluent quality, it can be concluded that the integration of these invertebrates cannot improve wastewater treatment of vertical flow filters or constructed wetlands. [ABSTRACT FROM AUTHOR]

Abstract Particle-based assays are widely used in many biomedical applications. However, the performance of particle-based systems is often compromised by the carry-over contamination caused by the residual reagents during the liquid-exchange process. We have developed a sieve-through platform that utilizes a porous membrane to sieve out the particles, and an absorbent pad to remove the waste liquid by capillary force. The porous membrane is able to contain the liquid in the reaction chamber, and allows the waste liquid to flow through when it is brought into contact with the absorbent pad. The sieve-through platform is able to effectively remove the waste liquid, thereby achieving a more efficient liquid exchange as compared to the conventional process, and minimizing the carry-over contamination. In this study, we have determined the factors that affect the flow characteristics through the porous membrane on the sieve-through platform. We have shown that the sieve-through platform effectively reduces the carry-over contamination. In addition, we have shown particle-based ELISA on the sieve-through platform for the analysis of proteins and cells. We have further demonstrated the potential of the sieve-through platform for high-throughput analysis by presenting a sieve-array, which allows concurrent analysis of multiple samples in parallel. The sieve-through platform can significantly improve the performance of particle-based systems. Graphical abstract Image 1 Highlights • A unique platform using porous membrane as the bottom of the reaction chamber. • Efficient liquid exchange in particle-based assays by discarding the waste liquid through the porous membrane. • Reduced carryover contamination in both particle-based preparative (solid-phase extraction) and analytical (ELISA) assays. • Easy upscale for potential high-throughput particle-based assays. [ABSTRACT FROM AUTHOR]

Summary: The system of vacuum pressure combined with vertical drains to accelerate soil consolidation is one of the most effective ground improvement methods. The consolidation theories of soft soil improved by vertical drains including void ratio–dependent compressibility and permeability have been widely applied in practice to predict the consolidation behavior. In this paper, analytical solutions of the consolidation of vertical drains are derived incorporating the loss and propagating stage of vacuum pressure. In addition, special solutions are obtained for the cases of instantaneous surcharge loading and staged surcharge loading, based on the general solution. The solution is verified by ignoring the propagating stage of vacuum pressure formation and comparing it with an existing solution. The effects of vacuum pressure loss and propagating stage combined with other parameters are investigated through the ratio between excess pore water pressure and surcharge loading. [ABSTRACT FROM AUTHOR]

The Arbuckle Group is the principal reservoir used for wastewater disposal in Oklahoma. In Osage County—a seismically quiet part of the state—continuous measurements of fluid pressure reveal that pressure in the reservoir is increasing by at least 5 kPa annually and sometimes at a much higher rate. Tidal analysis reveals that fluid level changes lead the local strain tides, with no apparent influence from transient permeability changes; this indicates a response that is inconsistent with flow in a radially extensive, confined reservoir. We investigate whether this is due to vertical flow to the water table, vertical flow within the Arbuckle, or local distortions from fractures. While none of these alternative models can fully explain both the observed tidal phases and amplitude ratios, the observed response to teleseismic waves supports a mechanism related to leakage rather than fracture effects. At this location fluid influx associated with wastewater disposal is offset by migration into surrounding layers, which include the Precambrian basement below. Thus, our findings suggest the need to monitor for changes in the induced seismicity hazard, while pore pressures increase in a leaky disposal reservoir. Plain Language Summary: There is consensus among earthquake scientists that subsurface fluid pressure changes are the principal cause of the manmade (or "induced") earthquakes occurring in Oklahoma and around the globe. This is because greater fluid pressures reduce the clamping pressure that would otherwise prevent a fault from having an earthquake. The leading cause of pressure changes on faults in Oklahoma is the disposal of wastewater related to production of oil and natural gas. Disposing of wastewater is generally done by pumping fluid down boreholes into deep, highly permeable reservoirs, like the Arbuckle. One way for scientists to measure water pressure changes is by lowering specially designed instruments down unused wastewater disposal wells. The paper presents continuous measurements of fluid pressure at an Arbuckle well located in Osage County, Oklahoma. Our findings show an overall trend of fluid pressures increasing over time. The only conceivable source of this increase is due to the injection of wastewater. Furthermore, our findings show evidence that fluids are leaking out of the reservoir at a significant rate. Key Points: The tidal response of the Arbuckle reservoir in Oklahoma is inconsistent with confined, radial flow and shows evidence of leakageTime series show additional signals unrelated to tides and atmospheric pressure, including a robust teleseismic response and long‐term trendsFluid pressure in the Arbuckle is steadily increasing, presumably related to high volume wastewater disposal [ABSTRACT FROM AUTHOR]

Highlights • Methane formation potential of primary treatment units is 5.1–7.3 L CH 4 /(p∙d). • Methane is removed completely for surface loads of up to 19 g CH 4 /(m2∙d). • Oxidation via nitrate is of minor importance for methane removal. • Methane oxidation causes production of EPS. Abstract Most types of subsurface flow constructed wetlands include pretreatment units for separation of particulate matter. Due to long retention times of the settled sludge in pretreatment units of small constructed wetlands (CWs), anaerobic degradation processes occur and cause methane emissions into the environment. To minimize methane emissions, small-scale trials were carried out, in order to investigate whether vertical subsurface flow CWs (VF wetlands) are suitable for removal of methane and whether it can be utilized to improve the denitrification rate of VF wetlands. The results show that methane was completely removed for surface loads of up to 19 g CH 4 /(m2·d). Based on mass balancing, 2% of the fed methane was oxidized with nitrate while 22% were oxidized with oxygen. The major part was attributed to biomass build-up. A correlation between effluent COD load and removed methane load was observed. Published literature indicates that COD accumulation is a result of production of extracellular polymeric substances. Low methane loads have only a slight impact on COD accumulation. It is expected that typical methane loads resulting from pre-sedimentation units may cause effluent COD concentrations to increase by up to 20% for municipal wastewater treatment with VF wetlands. Hence, combined wastewater treatment and methane oxidation was successfully demonstrated, but enhanced denitrification could not be achieved. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Froude number correlates gas holdup and mass transfer in the bubble column. • Energy dissipation rate can be described as a function of Froude number. • Average energy dissipated correlates the growth of K. veneficum. • CO 2 mass transfer limits the growth of K. veneficum at low energy dissipation. • A model for the influence of dissipated energy on cell growth is proposed. Abstract The shear-sensitive marine algal dinoflagellate Karlodinium veneficum was grown in a cylindrical bubble column photobioreactor with an internal diameter of 0.044 m. Initial liquid height varied from 0.5 to 1.75 m, superficial gas velocities from 0.0014 to 0.0057 ms−1, and nozzle diameter from 1 to 2.5 mm. Computational fluid dynamics was used to characterize the flow hydrodynamics and energy dissipation rates. Experimental gas holdup and volumetric mass transfer coefficient strongly depended on the liquid height and correlated well with the Froude number. Energy dissipation near the head space (ED top) was one order of magnitude higher than the average energy dissipation in the whole reactor (ED whole), and the value in the sparger zone (ED spar) was one order of magnitude higher than ED top. Cultures of K. veneficum were limited by CO 2 transfer at low ED whole and severely stressed above a critical value of ED whole. [ABSTRACT FROM AUTHOR]

Highlights • The The influence of seepage flow pulsations to oscillatory mode of instability is studied. • It is shown that the control of flow patterns available and it is most efficient at the natural frequency of oscillatory motion. • The parametric resonance or nonmonotonous effect at multiple frequencies is not observed. Abstract The paper is devoted to the investigation of the linear stability of homogeneous pulsating vertical seepage of mixture through horizontal porous layer with solute immobilization. The mixture flow through porous medium is studied within the standard Darcy-Boussinesq approach taking into account the solutal convection. The immobilization of solute particles by solid matrix of medium is described by the mobile/immobile media (MIM) model with second-order kinetics. It was shown earlier that the immobilization leads to oscillatory mode of convective instability due to transition of solute from the mobile phase to immobile one. This means that immobilization effect on the flow pulsations should be non-trivial. The equations for the convection with immobilization are derived, the regime of homogeneous filtration is obtained and its stability is investigated. The neutral curves in the parameter space are plotted. The effect of homogeneous filtration stabilization under intensification of external seepage and dynamics interphase exchange is studied. It is found that the effect of pulsations is significant in the case when frequency of pulsations is close to the natural frequency of instability. The parametric excitation of convection is not observed. [ABSTRACT FROM AUTHOR]

Highlights • An experimental study on the characteristics of two phase flow on a large piping system is performed. • Flow regime analysis for both horizontal and vertical pipe flow is performed. • Two phase parameters including void fraction and pressure are presented. • Frictional pressure drop model and drift flux model are evaluated using the data. • The elbow effect on the flow structure and flow parameters is discussed. Abstract An experimental study of the characteristics of air-water two-phase flow in a piping system with an inner diameter of 152.4 mm is presented. Both horizontal and vertical pipes (with the lengths of 15.09 m and 6.42 m) are included in the system and two 90-degree elbows are used for their connections. 71 flow conditions are performed in this experiment, covering plug, slug, pseudo slug, and stratified flow for the horizontal flow, and bubbly, cap bubbly, churn turbulent, and falling film/annular flow for the vertical flow. Detailed flow regime analysis for the flow regimes of the horizontal and vertical pipe flow and the effects of the elbow on the flow regime transition are discussed. The flow regime maps proposed generally agree with the existing maps. A significant flow regime shift in the vertical section is also observed and discussed. The area averaged void fraction development is presented and a sharp drop of void fraction in vertical downward test section is observed which results from the kinematic shock phenomenon. The result of the frictional pressure drop is discussed, and it agrees with the Kim et al.'s correlation. With the database, the drift flux model for Goda et al.'s vertical downward flow is evaluated. Large difference has shown at low void fraction which may indicate further modeling investigation. [ABSTRACT FROM AUTHOR]

Abstract We present a novel vertical flow-based paper immunosensor for the rapid and sensitive electrochemical and colorimetric detection of influenza H1N1 viruses using a different pore size (DP) sample pad. The DP sample pad consisted of two different pore size papers: larger pores (diameter: 11 µm) facing the inlet, and smaller pores (diameter: 0.45 µm) facing the conjugate pad. This sample pad offered moderate and uniform flows, and hence concentrated horseradish peroxidase tagged antibodies (HRP-Abs)-H1N1 complexes from 40 µL of sample volumes on a conjugate pad for 2 min after sample injection, thereby providing fast detection (6 min for both detection methods) with 100 µL of flushing afterwards, high sensitivity, and the simplicity of the sensor. The filtration characteristics of the DP sample pad were evaluated using fluorescent beads, indicating that only small-sized bio-particles such as viruses can pass through the sample pad. Sandwich immunoreactions of HRP-Ab-H1N1-Ab were performed on the gold paper electrode of the immunoStrip, which was determined by electrochemical impedance spectroscopy (EIS) measurements. Simultaneously, the color signal of free HRP-Ab captured on the colorimetric zone was obtained using a scanner, and the intensity was analyzed using ImageJ. This immunosensor detected H1N1 virus concentration as low as 3.3 plaque forming units (PFU)/mL (phosphate buffer saline; PBS) and 4.7 PFU/mL (saliva) by EIS, and 1.34 PFU/mL (PBS) and 2.27 PFU/mL (saliva) by the colorimetric method. Furthermore, integrating these two detection methods can reduce false results with double assurance, and this device can provide a simple and economical on-site detection platform. Highlights • The first paper immunosensor using a double pore size (DP) sample pad. • The first vertical flow assay-based, sandwich ELISA-type paper immunosensor for the detection of influenza viruses. • Dual (electrochemical and colorimetric) detection methods to provide double assurance. • The DP sample pad offered fast detection (~6 min), high sensitivity (the limit of detection <5 PFU/mL), and the simplicity. • The DP sample pad also acted as a filter to pass only small-sized particles. [ABSTRACT FROM AUTHOR]

Abstract Currently, the standard method for identifying biological agents of potential threats to national security and public health, such as pathogens, virus, and toxins, mainly rely on microbiological cultivation. This method is time-consuming and it requires sophisticated equipment and well-trained personnel, which are often unavailable in remote areas or at point-of-need. Therefore, an alternative rapid, simple, and sensitive method for detecting bio-threat agents is in crucial need. We report a paper-based Vertical Flow Immunoassay (VFI) device that can overcome these limitations. The VFI device utilizes a nanoporous nitrocellulose membrane encapsulated in a stainless steel filter holder. As the sample is pushed through the membrane, which is pre-functionalized with capture antibody, a sandwich assay is formed and colorimetric signal is generated to reflect the presence of target antigens. Through theoretical analyses of antigen-antibody binding process inside a porous membrane, we identified two critical factors – membrane pore size and sample flow rate that can be optimized to improve the assay sensitivity. Then, the effects were demonstrated through experimental studies using Burkholderia pseudomallei (the causative agent of melioidosis) as a model pathogen. The B. pseudomallei VFI was based on an immunoassay targeting the B. pseudomallei surface capsular polysaccharide (CPS). The experimental results agreed well with the theory showing that increasing the flow speed (up to 1.06 mm/s) and reducing the membrane pore size (down to 0.1 µm) could improve the sensitivity by at least 5 times. The VFI's limit-of-detection for CPS spiked in buffer solution was determined to be 0.02 ng/mL. The developed VFI shows great potential as a point-of-care tool for detection of bio-threat agents in a variety of clinical and resource-restricted conditions. Graphical abstract fx1 Highlights • Paper-based vertical flow device was developed to detect bio-threat pathogens. • Limit-of-detection for B. pseudomallei surface capsular polysaccharide was 0.02 ng/mL. • Sample flow rate and membrane pore size was studied in theory and experiment. • Multiplexing diagnostic of melioidosis and anthrax was demonstrated. [ABSTRACT FROM AUTHOR]

The present study was carried out to develop rapid field-based immunoassays for onsite detection of Classical swine fever virus (CSFV) antibody in clinical serum sample. Purified CSFV antigen was coated onto nitrocellulose membranes housed in a plastic module with layers of absorbent filter pads underneath. Following addition of serum to be tested appearance of a red dot indicated the presence of antibodies to CSF virus in the sample tested. A total of 240 serum samples collected from different areas of North Eastern States of India were tested for the presence of CSFV antibody by Indirect ELISA, Dot ELISA and Vertical flow through test. The result of the Indirect ELISA could be obtained within 2.5 hours whereas the result in case of Dot ELISA and Vertical Flow through test was obtained within 1 hour and 15 minutes respectively. Dot- ELISA and Vertical flow through test could equally detect the CSFV antibody in samples possessing 1:4 and above ELISA titre. The specificity and sensitivity of Dot-ELISA and vertical flow through test after comparison with Indirect ELISA indicated 100% specific and 84.28% sensitive. These tests have the potential to be used as a field-based kit to assess the serodiagnosis of CSFV. [ABSTRACT FROM AUTHOR]

The German Association for Water, Wastewater and Waste e.V. (DWA) has published a new standard for the dimensioning, construction, and operation of constructed wetlands for treatment of domestic and municipal wastewater. The changes to the standard are based on a wide range of experience gained in recent years in Germany and Europe. For the first time ever, the standard has been officially translated and published in English. This paper summarizes the new standard for secondary treatment of domestic wastewater with classical one-stage unsaturated vertical flow (VF) wetlands, VF wetlands with lava sand for treatment of wastewater from combined sewer systems, and actively aerated VF and horizontal flow (HF) flow wetlands. Two-stage unsaturated VF wetlands treating raw wastewater (French VF wetlands), are also included in the new standard. HF wetlands are no longer described in the standard for secondary treatment of domestic wastewater. This does not exclude their application. Existing HF wetland systems in Germany may continue to be operated so long as effluent parameters are met and proper operations and maintenance is ensured. This paper gives an overview of the new design standard, including key information on wastewater type and loading, as well as primary attributes of each wetland design. [ABSTRACT FROM AUTHOR]

In Austria, single-stage vertical flow (VF) wetlands with intermittent loading are a state-of-the-art technology for treating domestic wastewater. They are designed according to the Austrian design standard with a specific surface area of 4 m² per person (i.e. 20 g COD/(m²·d)) and thus demand a bigger amount of land to treat the same amount of wastewater compared to intensified technical treatment systems. In order to reduce the amount of land needed, a modified design for VF wetlands has been proposed. The modified design has a specific surface area of 2.5 m² per person (i.e. 32 g COD/(m²·d)) and it has been shown to be able to meet the Austrian effluent requirements. To allow higher organic loading, more loadings per day but lower volume of a single loading, a constant loading interval, and increased number of openings per m² are applied. A simulation study using the HYDRUS Wetland Module was carried out to compare the treatment efficiencies of single-stage VF wetlands with classical and modified design. Data from a classical Austrian single-stage VF wetland was used for calibration of the model using the standard parameter set for the CW2D biokinetic model. The influent COD fractionation was calibrated to adapt to the wastewater. The simulations showed a good performance of the modified design compared to a classical VF wetland for COD removal with COD effluent concentrations in winter (effluent water temperature of 4.5 °C) of 35 and 29 mg/L, respectively. The simulation study showed that during high-loading events the VF wetland with modified design has lower maximum NH4-N effluent concentrations. Single-stage VF wetlands with modified design seem to be very effective and allow application of higher organic loads compared to single-stage VF wetlands with classical design. [ABSTRACT FROM AUTHOR]

Abstract A pilot-scale vertical flow constructed wetland (VFCWs) system was designed, implemented and operated for one year for the treatment of dye-rich real textile effluent. Brachiaria mutica was vegetated to develop VFCWs in which five different textile effluent degrading endophytic bacteria were inoculated. These bacteria were screened based on their dye degrading and plant growth promoting capabilities. The system's performance was evaluated by monitoring physicochemical parameters, nutrients removal, heavy metals reduction, detoxification potential, and persistence of endophytic bacteria in the plant rhizo- and endosphere. Although VFCWs were able to remove a majority of the pollutants from the wastewater, bacterial augmentation further enhanced the remediation efficiency. The system promoted an increase in dissolved oxygen up to 188% and, concomitantly, a substantial decrease in the chemical oxygen demand (81%), biochemical oxygen demand (72%), total dissolved solids (32%), color (74%), nitrogen (84%), phosphorous (79%), and heavy metals [Cr(97%), Fe(89%), Ni(88%), Cd(72%)] was recorded. Wastewater treated with VFCWs augmented with bacteria was found to be non-toxic and inoculated bacteria showed persistence in the root and shoot interior of B. mutica. Conclusively, VFCWs proved to be an effective methodology for treatment of textile effluent whereas its smaller size with high efficiency is an advantage for field-scale applications. Graphical abstract Unlabelled Image Highlights • A pilot-scale endophyte-assisted VFCWs were engineered to treat real textile effluent. • Endophytes augmentation increased removal of organic and inorganic pollutants. • Inoculated bacteria displayed persistence in the root and shoot of Brachiaria mutica. • This study recommends field-scale application of endophyte-assisted phytoremediation. [ABSTRACT FROM AUTHOR]

Abstract A laboratory-scale vertical flow constructed wetland system was designed and monitored to compare nitrogen removal rates and pathways from both saturated and unsaturated zones under a hydraulic loading rate and influent total nitrogen concentration of 1.5 m3/m2.d and 508 mg/L respectively. Weekly measurements of the concentrations of nitrogen compounds, chemical oxygen demand, temperature, dissolved oxygen, oxidation-reduction potential, and hydrogen ion concentration were taken throughout the study. At the end of the experiments, PCR analysis of 16S rRNA gene sequencing was performed to identify microbial communities in the unsaturated and saturated parts of the system. The nitrogen compounds were removed from the system after 182 days, with similar total nitrogen removal efficiencies (94% and 93%) for the unsaturated and saturated zones respectively. Heterotrophic nitrification/aerobic denitrification was the major pathway responsible for the removal of nitrogen compounds. Adsorption into the gravel bed also contributed to ammonium removal. Proteobacteria were the dominant bacterial strains involved in nitrogen transformation and accounted for 80% of the total bacteria in the unsaturated zone and 60% in the saturated zone. With little difference in the concentration removal efficiencies of the unsaturated and saturated zones, a more effective design would be an entirely saturated wetland as the total mass removal of nitrogen depends on the water volume stored, which at full saturation in this design was seven times greater per unit wetland volume than the unsaturated zone. Highlights • Nitrogen decay is similar in unsaturated and saturated zones of the wetland. • Nitrate is lost by heterotrophic nitrification and aerobic denitrification. • Nitrite is also lost by heterotrophic nitrification and aerobic denitrification. • Ammonium loss occurs by heterotrophic nitrification and biofilm adsorption. • Saturated water content is seven times greater than the unsaturated water content. [ABSTRACT FROM AUTHOR]

Summary: A three‐dimensional (3D) multi‐phase numerical model of proton exchange membrane fuel cell (PEMFC) is built. The catalyst layer (CL) spherical agglomerate model is used to replace traditional homogenous model, which can predict the concentration loss in PEMFC more accurately. Utilizing this multi‐phase model, the PEMFC with 3D fine mesh flow field is investigated at length, and the liquid water distribution in 3D flow field is qualitatively compared with the experimental image in previous literature. It is found that the 3D fine mesh flow field can improve the reactant gas supply from flow field to porous electrodes significantly and facilitate liquid water removal in PEMFC simultaneously. Therefore, it reduces the concentration loss of PEMFC effectively without increasing the pumping power loss thanks to the greatly increased mass transfer area between gas diffusion layer (GDL) and flow field and vertical flow design of hydrogen and air, which also make the reaction rate distribution in CL more uniform. However, the decreased contact area between GDL and bipolar plate in 3D flow field may decrease PEMFC performance at the current densities where ohmic loss is dominated, but its effect is insignificant. A comprehensive three‐dimensional (3D) multi‐phase computational fluid dynamics numerical model is developed, in which the spherical agglomerate model of catalyst layer is introduced to better reflect the concentration loss in proton exchange membrane fuel cell (PEMFC). Utilizing this model, the PEMFC with 3D fine mesh flow field is simulated in detail, and the liquid water distribution in 3D fine mesh flow field is qualitatively compared with the experimental image in previous literature. [ABSTRACT FROM AUTHOR]

Highlights • Effect of pipe size on drift-flux analysis for horizontal flow is insignificant. • Gas phase moves slower than the liquid phase in horizontal bubbly flow. • Horizontal plug and slug flows are relatively more homogeneous than bubbly flow. • Differences are observed for C 0 and 〈〈 V gj 〉〉 between current work and these in TRACE for vertical flow. • Correlations modified from vertical flow cannot predict void fraction well for horizontal flow. Abstract The current work seeks to perform the one-dimensional drift-flux analysis for horizontal gas-dispersed flow, to provide closure models for void fraction and to investigate the relative motion between gas and liquid phases. A reliable experimental database for void fraction and bubble velocity is first established over a wide range of flow conditions for bubbly, plug and slug flows in different pipe sizes, due to the limitations of existing database. It is found that the effects of flow regime and pipe size on the drift-flux analysis are insignificant. The drift velocity is found to be negative in horizontal bubbly flow. This is consistent with the conclusion by the 〈 α 〉–〈 β 〉 analysis, where the slope is found to be greater than one. This indicates that the gas phase moves slower than the liquid phase in horizontal bubbly flow. The analysis also indicates that the horizontal plug and slug flows are relatively more homogeneous than horizontal bubbly flow. As such, the homogeneous flow model can predict the void fraction better for plug and slug flows. The current drift-flux analysis provides closure relations for C 0 and 〈〈 V gj 〉〉 that can be employed in TRACE, while existing closure relations are developed for vertical flow and cannot be used for horizontal flow prediction. In addition, various void fraction models in literature are evaluated. It is found that the correlations modified from vertical flow generally cannot predict the void fraction well for horizontal flow. The correlations for plug and slug flows by Franca and Lahey, and Lamari underestimate the void fraction, which may be because these correlations are developed for relatively low j f conditions, while the current work focuses on conditions at j f greater than 2.0 m/s. [ABSTRACT FROM AUTHOR]

This comment on Hitchman and Rowe first deepens their introduction by distinguishing adiabatic and diabatic tilting of vorticity. Then, it strengthens their interpretation by emphasizing that momentum must be vertically transported with reference to isentropic levels to yield the potential vorticity (PV) dipoles. Moreover, it points out a flaw in their PV budget analysis and proposes a remedy for the flaw. Their convective momentum transport paradigm and the vorticity tilting paradigm reinterpret the same physical process. However, they counted one physical process twice by associating the two paradigms with two different terms. As an attempt to remedy the flaw, this comment associates the reinterpretation of the two paradigms with a transformation of the PV equation; their paradigm corresponds to a flux form. With the proposed remedy, their paradigm can be more easily translated to advances in convective parameterization because of its horizontal locality. [ABSTRACT FROM AUTHOR]

The object of this study was to investigate the effect of saturated zone depth (SZD) and plant on the removal of organics and nitrogen in four continuous-feed vertical flow-constructed wetlands (VFCWs). Three VFCWs were planted with Iris pseudacorus and operated at different SZDs (19, 51, and 84 cm), and the other one was non-planted and operated at 51 cm SZD. The VFCWs were operated with an organic loading rate (OLR) of 79 g chemical oxygen demand (COD) m−2 day−1, a total nitrogen loading rate (NLR) of 11 g N m−2 day−1, and a hydraulic loading rate (HLR) of 0.35 m3 m−2 day−1. Simultaneous transformation of ammonium and nitrate occurred in all of the four systems. In the planted bed with 51 cm SZD, suitable conditions for nitrification and denitrification could be created and the best performance for total nitrogen (TN) removal was realized via simultaneous nitrification and denitrification (SND), achieving TN removal efficiency of 67.4-80.3%. Higher ammonium nitrogen (NH4+-N) and COD removal efficiency was obtained in the system operated with 19 cm SZD, whereas higher NO3−-N removal could be achieved in the bed with 84 cm SZD. With the same SZD of 51 cm, the planted VFCW performed preferable removal of COD, NH4+-N, and TN in comparison with the non-planted one. All the VFCWs showed high removal efficiencies for total phosphorus (> 60.15%). Adsorption of phosphorus was primarily observed in the top and upper-middle layers filled with carbon burn slag. It has been proved that the partially saturated VFCW operated with continuous feed could achieve good performance in removal of organic matter and nitrogen by SZD adjustment to develop appropriate aerobic and anoxic regions. [ABSTRACT FROM AUTHOR]

In order to investigate the potential of vertical flow constructed wetlands (VFCWs), a 24.5 m2 surface area filled with gravel and planted with Heliconia psittacorum, was implemented as an experimental system for domestic wastewater treatment in southern Brazil. The aims of the study were to (i) evaluate the performance of a full scale system septic tank (ST) and VFCW for decentralized domestic wastewater treatment, and (ii) identify the influence of Heliconia for hydraulic characteristics and consequent performance of the VFCW. The applied load rates in the VFCW were, on average, 10 g biochemical oxygen demand (BOD) m−2 day−1, 4 g NH4+-N m−2 day−1 and a hydraulic loading rate (HLR) of 60 mm day−1. Physicochemical analyses of wastewater treatment were carried out through grab sample methodology, for 5 months. Additionally, hydrodynamic tests were performed during plant development using rhodamine. The study demonstrated the viability of the system for decentralized wastewater treatment in Brazil, with average removal efficiencies of 78% for chemical oxygen demand (COD) and 84% for total suspended solids (TSS), according to national effluent discharge regulations. In spite of media's large size, the VFCW achieved good average removal efficiencies. The tracer test results showed that the VFCW average hydraulic detention time increased as plants grew. This may have occurred due to interception of wastewater applied on the macrophyte's leaves as well as a reduction in filter media permeability caused by the spread of roots and rhizomes. These results indicate that the plants played an important role in increasing wastewater contact time in wetlands with high hydraulic conductivity such as a gravel VFCW. [ABSTRACT FROM AUTHOR]

Lacking of electron donor generally causes the low denitrification performance of constructed wetlands (CWs). Montmorillonite supported nanoscale zero-valent iron immobilized in sodium alginate (SA/Mt-NZVI) as novel electron donor-acceptor compounds were added in the denitrification zone of vertical flow constructed wetlands (VFCWs) to enhance the nitrogen removal. The key factors of the SA/Mt-NZVI dosage, the hydraulic retention time (HRT) of VFCWs, and the C/N ratios of influent were explored. SA/Mt-NZVI significantly improved the nitrogen (NO 3 − -N) removal efficiency in VFCWs. When the optimal dosage of SA/Mt-NZVI was set as 2 g and the C/N was set as 6, the highest NO 3 − -N removal efficiency was improved by 32.5 ± 1.0%. The microbial community analysis of by 16S rRNA had revealed that Proteobacteria and Bacteroidetes at phylum level and Betaproteobacteria , Gammaproteobacteria , and Alphaproteobacteria at class level played an important role in nitrogen removal. [ABSTRACT FROM AUTHOR]

Abstract Constructed wetlands (CWs) is an effective way to removal nitrogen (N) from swine wastewater, which accompanying with the process of ammonia (NH 3) volatilization. However, the removal pathway of NH 3 volatilization has adverse impacts on the natural biogeochemical cycle of N. Here, this paper presents the first attempt to investigate the potential use of clinoptilolite in reducing NH 3 volatilization in integrated vertical-flow constructed wetlands (IVCWs) treating swine wastewater. The NH 3 volatilization flux was measured via steady-state chambers. Results showed that the removal rate of TAN (total ammonia nitrogen, NH 3 and NH 4 +-N) in clinoptilolite system was 96.1%, where 93.01% of that was removed by substrate adsorption, it was significantly higher (p < 0.05) than that in quartz sand system (29.6%). Moreover, the microporous structure of zeolite is not conducive for the growth of denitrifying microorganisms. The NH 3 volatilization flux covered a range of 0.02–3.00 mg N m−2 h−1, which was lower than the reported date. Furthermore, the proportion of NH 3 volatilization in Clite was 0.99%, which was obviously lower (p < 0.05) than that in control (9.01%), and the ammonia volatilization quantities decreased by 180.7% in this study. Results suggest that clinoptilolite plays an important role in reducing NH 3 volatilization to the atmosphere. [ABSTRACT FROM AUTHOR]

Providing the most effective solution for protection of the bed downstream of hydraulic structures constitutes an important field of research. In addition, for safe and cost-effective designs, it is important to be able to predict the maximum scour depth downstream of hydraulic structures. The study reported in this paper examined the effectiveness of two types of countermeasures – a bed sill and riprap – to reduce the maximum scour depth adjacent to horizontal rigid aprons. For tests with the bed sill located downstream of the apron, two distinct scour holes were formed upstream and downstream of the sill, with respective maximum scour depths of ds1 and ds2. The results show that a bed sill can reduce ds1 and ds2 by up to 23% and 47%, respectively, compared with the maximum scour depth for the no-sill condition. However, when the erodible bed between the apron and the bed sill was replaced by riprap, ds1 and ds2 decreased by up to 53% and 90% respectively. Variations of the other characteristic scour hole lengths, including the maximum extension of the scour hole and the maximum height of the mound, were also studied and an attempt was made to examine any geometrical similarities in the scour hole profiles under different conditions. [ABSTRACT FROM AUTHOR]

Empirical evidence of planets in gas-rich circumstellar discs is required to constrain giant planet formation theories. Here we study the kinematic patterns which arise from planet–disc interactions and their observability in CO rotational emission lines. We perform 3D hydrodynamical simulations of single giant planets and predict the emergent intensity field with radiative transfer. Pressure gradients at planet-carved gaps, spiral wakes, and vortices bear strong kinematic counterparts. The isovelocity contours in the CO(2-1) line centroids |$v$| ○ reveal large-scale perturbations, corresponding to abrupt transitions from below sub -Keplerian to super -Keplerian rotation along with radial and vertical flows. The increase in line optical depth at the edge of the gap also modulates |$v$| ○, but this is a mild effect compared to the dynamical imprint of the planet–disc interaction. The large-scale deviations from the Keplerian rotation thus allow the planets to be indirectly detected via the first moment maps of molecular gas tracers, at Atacama Large Millimetre/submillimetre Array angular resolutions. The strength of these deviations depends on the mass of the perturber. This initial study paves the way to eventually determine the mass of the planet by comparison with more detailed models. [ABSTRACT FROM AUTHOR]

The technology of vertical flow constructed wetlands -- French system for treating raw wastewater depends on several hydraulic factors, one of them being the duration of the pulse feeding and the resulting instantaneous hydraulic loading rate. This paper analyses two scenarios in the same system, the first of a faster feeding by pump and the second of a slower feeding by siphon, both with instantaneous hydraulic loading rate values lower than the literature recommendations. The system treated raw wastewater from a population equivalent of 100 p.e. in Brazil, and was comprised by only the first stage and two units in parallel. The shorter duration of feeding time and higher instantaneous hydraulic loading rate were associated with significantly higher chemical oxygen demand and total Kjeldahl nitrogen removal efficiencies, but with no significant differences in terms of biochemical oxygen demand (BOD) and suspended solids (SS). Oxygen concentrations and redox potential in the effluent were evaluated, together with the effluent flow rate profiles. The removal efficiencies were associated with the accumulation of solids in the upper part of the filter resulting from seven years of operation and to the operating hydraulic conditions, which are important elements in the performance of the system. [ABSTRACT FROM AUTHOR]

A pilot-scale hybrid constructed wetland with vertical flow and horizontal flow in series was constructed and used to investigate organic material and nutrient removal rate constants for wastewater treatment and establish a practical predictive model for use. For this purpose, the performance of multiple parameters was statistically evaluated during the process and predictive models were suggested. The measurement of the kinetic rate constant was based on the use of the first-order derivation and Monod kinetic derivation (Monod) paired with a plug flow reactor (PFR) and a continuously stirred tank reactor (CSTR). Both the Lindeman, Merenda, and Gold (LMG) analysis and Bayesian model averaging (BMA) method were employed for identifying the relative importance of variables and their optimal multiple regression (MR). The results showed that the first-order–PFR (M 2 ) model did not fit the data ( P  > 0.05, and R 2  < 0.5), whereas the first-order–CSTR (M 1 ) model for the chemical oxygen demand (COD Cr ) and Monod–CSTR (M 3 ) model for the COD Cr and ammonium nitrogen (NH 4 −N) showed a high correlation with the experimental data ( R 2  > 0.5). The pollutant removal rates in the case of M 1 were 0.19 m/d (COD Cr ) and those for M 3 were 25.2 g/m 2 ∙d for COD Cr and 2.63 g/m 2 ∙d for NH 4 -N. By applying a multi-variable linear regression method, the optimal empirical models were established for predicting the final effluent concentration of five days' biochemical oxygen demand (BOD 5 ) and NH 4 -N. In general, the hydraulic loading rate was considered an important variable having a high value of relative importance, which appeared in all the optimal predictive models. [ABSTRACT FROM AUTHOR]

Abstract This paper reports a numerical investigation on the effect of cavity geometry on fuel transport and mixing processes in a scramjet combustor with a single rear-wall-expansion cavity. The numerical solver and the LES methods were validated against available experimental data and the numerical results were shown in good agreement with the experiments. Effect of the cavity rear wall height on the non-reacting flow fields was then investigated. It was found that the vertical flow velocity of the region located right after the expansion wave starting from the cavity leading edge was increased significantly towards the cavity when lowering the rear wall height, leading to an enhanced fuel entrainment into the cavity. Subsequently, at a larger cavity expansion ratio, the mixture inside the cavity became more fuel-rich, giving rise to a deteriorated mixing environment. In addition, the cavity recirculation zone was further compressed and the turbulent flow and scalar dissipation inside the cavity would be enhanced, which were likely the reason causing the ignition failures and poor flame stabilizations. An optimal cavity expansion ratio for the maximum fuel entrainment was found in the present rig. [ABSTRACT FROM AUTHOR]

Highlights • Three pilot-scale VFCW systems (CW1, CW2 & CW3) with recirculation arrangements of 25, 50 and 75% were operated to treat dairy wastewater. • The average concentration of pollutants in the influent was recorded as: BOD (323.0 ± 139.3 mg L−1); TP (37.6 ± 13.3 mg L−1); NH 4 -N (68.9 ± 13.5 mg L−1) and TN (114.9 ± 22.6 mg L−1) during the study period. • Recirculation arrangement resulted in an increase of 10.0–19.3% TN removal from all CW systems. • Maximum average purification rates of TSS (99.3%), BOD (97.8%), TP (97%), TN (50.5%) and NH 4 -N (50.7%) were achieved in CW3 with 75% recirculation. • OTR value of all three CW systems ranged from 27.0 to 54.4 g O 2 m−2 d−1 before recirculation showed an increase after recirculation and was found between 79.6 and 154.8 g O 2 m−2 d−1. [ABSTRACT FROM AUTHOR]

Highlights • Two hybrid constructed wetlands fed with the same wastewater were investigated. • Performance of opposite configurations of beds was compared. • Vertical flow bed at the beginning of treatment provides better removal efficiency. Abstract Recent years have seen an increasing interest in hybrid constructed wetland (HCW) systems for domestic sewage treatment. This paper is focused on kinetics of removal of the main pollutants occurring in wastewater i.e. organics expressed as chemical oxygen demand, biochemical oxygen demand and total nitrogen. The purpose of the article is to compare different HCW configurations in terms of mass removal rates (MRR) and removal rate coefficients (k A and k v). Analysed data have been collected at two wetland systems, each composed by two subsurface flow beds: horizontal flow (HF) and vertical flow (VF). Reliable evaluation was achieved by using the same composition of influent wastewater in both HCWs. Performance of opposite configurations HF + VF vs. VF + HF was compared after each stage and the overall HCW system. The average mass removal rates of COD, BOD 5 and TN in both systems were similar, respectively: 2.30, 0.98 and 0.40 g m−2 d−1. However, removal rates differ between single wetland beds after each treatment stage. [ABSTRACT FROM AUTHOR]

Recent progress in nuclear thermal-hydraulics simulations has been largely focused on coupling with other computational packages, improved closure models for subcooled boiling and for bubbly flows, and the development of higher-fidelity simulation capabilities (Kulesza et al., 2016). While high-fidelity 3D simulation is important for model validation, scientific understanding, and some design calculations, it can be prohibitively expensive for system design applications or applications involving large geometries. Thus, there is also a need for practical, simplified approaches for those applications. The two-fluid model strikes a balance between detail and computational resources, but requires the accurate specification of several key constitutive models. These include (1) interfacial forces, (2) interfacial area concentration, (3) two-phase turbulence, and (4) wall and bulk boiling and condensation. In many modern CFD packages, uncertainties in the local interfacial area concentration can have strong effects on the ability to predict the other key parameters. This paper demonstrates that the drag force in 3D CFD can be formulated in much the same way as in 1D system analysis codes and that this approach can be used to formulate a model for interfacial area concentration. The method is also applied to two-group approaches to consider the difference in transport properties for different bubble size classes. This approach may open a method to calculate the interfacial forces without the need for interfacial area transport equations. This reduces the number of differential equations and avoids the modeling challenges associated with bubble breakup and coalescence kernels and the need to specify the inlet interfacial area concentration a priori . The new method is expected to decouple the effects of interfacial area uncertainty and calibrated coefficients, and should provide reasonable local bubble diameters for both group-1 and group-2 bubbles. The approaches proposed in this study are applicable to two-phase flow simulations in rather simple geometries such as upward two-phase flow in vertical channels. In view of many applications for upward two-phase flow in vertical channels, including nuclear reactor systems, the proposed methods are considered useful. [ABSTRACT FROM AUTHOR]

An up-flow vertical flow constructed wetland (AC-VFCW) filled with ceramsite and 5% external carbon source poly(3-hydroxybutyrate-hydroxyvalerate) (PHBV) as substrate was set for nitrogen removal with micro aeration. Simultaneous nitrification and denitrification process was observed with 90.4% NH 4 + -N and 92.1% TN removal efficiencies. Nitrification and denitrification genes were both preferentially enriched on the surface of PHBV. Nitrogen transformation along the flow direction showed that NH 4 + -N was oxidized to NO 3 − -N at the lowermost 10 cm of the substrate and NO 3 − -N gradually degraded over the depth. AmoA gene was more enriched at −10 and −50 cm layers. NirS gene was the dominant functional gene at the bottom layer with the abundance of 2.05 × 10 7  copies g −1 substrate while nosZ gene was predominantly abundant with 7.51 × 10 6 and 2.64 × 10 6  copies g −1 substrate at the middle and top layer, respectively, indicating that functional division of dominant nitrogen functional genes forms along the flow direction in AC-VFCW. [ABSTRACT FROM AUTHOR]

A duplex constructed wetland (duplex-CW) is a hybrid system that combines a vertical flow (VF) CW as a first stage with a horizontal flow filter (HFF) as a second stage for a more efficient wastewater treatment as compared to traditional constructed wetlands. This study evaluated the potential of the hybrid CW system to treat influent wastewater containing diesel range organic compounds varying from C 7 – C 40 using a series of 12-week practical and numerical experiments under controlled conditions in a greenhouse (pH was kept at 7.0 ± 0.2, temperature between 20 and 23° C and light intensity between 85 and 100-μmol photons m −2 sec −1 for 16 h d −1 ). The VF CWs were planted with Phragmites australis and were spiked with different concentrations of NH 4 + -N (10, 30 and 60 mg/L) and PO 4 3- -P (3, 6 and 12 mg/L) to analyse their effects on the degradation of the supplied petroleum hydrocarbons. The removal rate of the diesel range organics considering the different NH 4 + -N and PO 4 3- -P concentrations were simulated using Monod degradation kinetics. The simulated results compared well with the observed database. The results showed that the model can effectively be used to predict biochemical transformation and degradation of diesel range organic compounds along with nutrient amendment in duplex constructed wetlands. [ABSTRACT FROM AUTHOR]

Annular flow is one of the most important multiphase flow regimes primarily because of its presence in extensive industrial applications,such as steam generators, evaporators, condensers and boiling water reactors. There is a great need to have specific techniques capable of extracting characteristics of annular flow pattern via experiment and/or modelling, which is essential to understand specific annular flow phenomena. The intention of developing a mathematical decomposition method for flow regime recognition comes from the fact that each regime is characterised by unique dynamic behaviour. The direct approach with Proper Orthogonal Decomposition (POD) was previously introduced by Lumley, which required a very large amount of relevant data from experimental multiphase and process conditions is necessary. The presented approach is to apply POD on a large amount of tomograms for identification of annular flow pattern in a gas-liquid two phase flow, which also provides a new method to extend the current evaluation procedure of Electrical Impedance Tomography (EIT) for imaging of air-water pipeline flows.The paper demonstrates the capability of the proposed method with a study on annular flow patterns in vertical pipeline. [ABSTRACT FROM AUTHOR]

Following Part (I) of the current study, which presents the experimental results of the elbow effects on two-phase flow parameters in bubbly flow, Part (II) develops models and correlations to predict the evolution of these parameters across and downstream of 90° vertical-upward and vertical-downward elbows. To quantify the length requires for the effects of the elbows to dissipate (or the dissipation length), the strength of elbows is defined as the variance of the local void fraction distribution. The axial development of the elbow-strength is modeled by an exponential function of the axial development length based on the experimental data. Then, the dissipation length of the elbow is determined by characterizing the evolution of the elbow-strength parameter. The elbow-strength parameter is also used to correlate the void-weighted bubble velocity and covariance terms in the interfacial area transport equation (IATE). The two-phase pressure drop across vertical elbows is modeled with a modified Lockhart-Martinelli correlation which considers the additional pressure drop induced by elbows. To evaluate the above developed models and correlations, they are implemented into the IATE applicable to the elbow-influenced region. The established IATE together with the available IATE of different flow orientations in straight channels are implemented to predict the interfacial area transport from the vertical-upward to horizontal to vertical-downward two-phase flow across elbows. It is found that the interfacial area concentration predictions are in good agreement with the experimental data with an average absolute percent difference of ±6% throughout the test section. The individual contributions to the interfacial area concentration transport due to each source and sink term in the IATE are discussed, demonstrating that the models and correlations developed for the two-phase flow parameters in elbow regions are reliable. [ABSTRACT FROM AUTHOR]

This study performs experimental investigation on two-phase bubbly flow through 90° vertical elbows going from vertical-upward to horizontal and horizontal to vertical-downward orientations. The elbows have an inner diameter of 50.8 mm and a radius of curvature of 152.4 mm. A detailed database for local and global two-phase flow parameters in different flow orientations and across vertical elbows is established with a state-of-the-art four-sensor conductivity probe, a pressure transducer, and a high-speed video camera. The evolution of void fraction, interfacial area concentration, bubble velocity, and two-phase pressure drop along the axial development length in different orientations and across elbows are presented. It is observed that elbows create secondary flow and cause redistribution of the bubbles, which significantly affect the development of two-phase flow parameters. The effects occur across the elbows and remain for a significant length downstream. The effects on the void fraction distribution downstream of the elbow are discussed in detail for both elbow orientations. Characteristic differences in the elbow effects due to the elbow orientation are observed. For the vertical-upward elbow, a similar trend in the evolution of the void fraction distribution is observed for all flow conditions investigated while two different trends are observed downstream of the vertical-downward elbow. It is found that the effects of the vertical-downward elbow dissipate faster than that of the vertical-upward elbow. The elbow effects on interfacial area concentration, bubble velocity, and two-phase pressure drop are also discussed. The evolution of the interfacial area concentration is similar to that of the void fraction evolution in the straight pipe sections. However, it increases significantly across both elbows due to the promotion of the bubble breakup induced by the secondary flow. The void-weighted area-averaged bubble velocity is subject to significant changes across and immediately downstream of the elbows due to the redistribution of the bubbles. Additionally, the two-phase pressure gradients across the vertical-upward and vertical-downward elbows are approximately 1.5 and 2 times of that in the straight pipe sections. [ABSTRACT FROM AUTHOR]

Among different decentralized wastewater treatment systems, constructed wetlands are particularly robust, reliable and cost-effective technologies. However, traditional treatment wetland designs have a limited capacity to remove total nitrogen. The recirculating vertical-flow constructed wetland (RVFCW) system is a novel modification of the vertical flow wetland (VFW), allowing for increased denitrification by circulating the nitrified effluent back into a recirculation tank, where it is mixed with primary treated wastewater. Microcosm experiments were conducted to investigate the effects on nitrogen removal of mixing recirculated VFW effluent with raw wastewater after different degrees of primary treatment, with and without attached growth media. The results show that the inclusion of attached growth media in the first chamber of the recirculation tank resulted in enhanced total nitrogen removal. The microcosms that contained a mixture of raw wastewater and VFW effluent showed denitrification efficiency of 83% after 48 h of contact time. An increase in the denitrification efficiency (up to 99.5%) was observed in microcosms that also contained attached growth media. The majority of nitrate-N (NO 3 -N) removal was achieved in the first 24 h. Inclusion of media increased the denitrification efficiency after 48 h contact time from 36 to 93% and from 31 to 88% in microcosms containing VFW effluent mixed at a ratio of 3:1 with wastewater after 1 and 2 days residence time in a septic tank respectively. It was inferred that the lower the degree of pre-treatment of wastewater into which the recirculated VFW effluent was mixed, the greater is the denitrification rate and thereby the lower TN concentration in the effluent. [ABSTRACT FROM AUTHOR]

In this study, a laboratory-scale system combined a vertical flow constructed wetland (VF) with a horizontal flow constructed wetland (HF), which was used to treat the secondary effluent of a wastewater treatment plant. Removal efficiencies of 67.02%, 89.80%, 90.31% and 75.38% were achieved by the system for chemical oxygen demand (COD), ammonium nitrogen (NH4+-N), total nitrogen (TN) and total phosphorus (TP), respectively. The VF showed much higher average loading rates of COD, TP, NH4+-N and TN (7.96 g/m²/d, 0.076 g/m²/d, 0.31 g/m²/d and 0.99 g/m²/d) than in HF (0.65 g/m²/d, 0.016 g/m²/d, 0.25 g/m²/d and 0.50 g/m²/d), during the stable operation period. Biodegradation played a major role in pollutant removal, especially for COD and TN. The results of bacterial community analysis indicated that heterotrophic denitrifying bacteria (Hydrogenophaga and Flavobacterium) were the dominant contributors for nitrogen removal in the VF, while heterotrophic denitrifying bacteria (Rhodobacter, Flavobacterium and Dechloromonas) and the autotrophic denitrifying bacteria Sulfurimonas played the principal roles for nitrogen removal in the HF. Redundancy analyses showed that COD and NH4+-N were the important factors affecting the distribution of nitrogen removal bacteria in the VF, while pH, dissolved oxygen and oxidation-reduction potential were the key factors influencing the distribution of nitrogen removal bacteria in the HF. [ABSTRACT FROM AUTHOR]

Abstract: This proposed technique allows sensible and numerically stable behavior in multilayer analytic element models when layers dewater. When saturated thickness approaches zero in an unconfined or fresh/salt interface domain, the domain transitions to a very thin confined domain with a minimum saturated thickness M. M is an adjustable input parameter, so you can make the horizontal flow in dewatered domains negligibly small by making the minimum saturated thickness very small. Vertical flows can pass through a dewatered domain, whether it is near the surface or at depth. For example, recharge may pass through a shallow dewatered layer to a deeper layer that is not dewatered. This approach is examined in detail in an example multilayer model of mine dewatering. [ABSTRACT FROM AUTHOR]

Freshwater ecosystems are confronted with multiple chemical, biological and physical stressors. Co-occurring stressors commonly result in additive responses, but non-additive interactions may also occur, hindering our predicting capacity. Despite growing interest in multiple stressor research, the response of freshwater communities to co-occurring chemical and climate change-related physical stressors remains largely unexplored. Here, we used a microcosm approach to evaluate the effect of the combined action of chemical and physical stressors on river biofilms. Results showed that additive responses dominated, whereas 14.5% of all responses were non-additive (75% antagonisms and 25% synergisms). Among these non-additive interactions, physical stressors dominated over chemicals and drove the overall responses. Overall, the occurrence of these non-additive interactions, together with the dominance of the climate-change related physical stressors, might lead to unexpected responses as a result of climate change. [ABSTRACT FROM AUTHOR]