Mass Transfer Velocity Research Articles

Vacuum ammonia stripping from liquid digestate: Effects of pH, alkalinity, temperature, negative pressure and process optimization

High ammonia-nitrogen digestate has become a key bottleneck limiting the anaerobic digestion of organic solid waste. Vacuum ammonia stripping can simultaneously remove and recover ammonia nitrogen, which has attracted a lot of attention in recent years. To investigate the parameter effects on the efficiency and mass transfer, five combination conditions (53 °C 15 kPa, 60 °C 20 kPa, 65 °C 25 kPa, 72 °C 35 kPa, and 81 °C 50 kPa) were conducted for ammonia stripping of sludge digestate. The results showed that 80% of ammonia nitrogen was stripped in 45 min for all experimental groups, but the ammonia transfer coefficient varied under different conditions, which increased with the rising of boiling point temperature, and reached the maximum value (39.0 mm/hr) at 81 °C 50 kPa. The ammonia nitrogen removal efficiency was more than 80% for 30 min vacuum stripping after adjusting the initial pH to above 9.5, and adjustment of the initial alkalinity also affects the pH value of liquid digestate. It was found that pH and alkalinity are the key factors influencing the ammonia nitrogen dissociation and removal efficiency, while temperature and vacuum mainly affect the ammonia nitrogen mass transfer and removal velocity. In terms of the mechanism of vacuum ammonia stripping, it underwent alkalinity destruction, pH enhancement, ammonia nitrogen dissociation, and free ammonia removal. In this study, two-stage experiments of alkalinity destruction and ammonia removal were also carried out, which showed that the two-stage configuration was beneficial for ammonia removal. It provides a theoretical basis and practical technology for the vacuum ammonia stripping from liquid digestate of organic solid waste.

Numerical Study of the Influence of the Type of Gas on Drag Reduction by Microbubble Injection

In this work, a novel numerical method for studying the influence of gas types on drag reduction by microbubble injection is presented. Aimed at the microbubble drag reduction (MBDR) process for different types of gases, the mass transfer velocity of different types of gases in the gas–liquid phase is defined by writing a user-defined function (UDF), which reflected the influence of gas solubility on the drag reduction rate. An Eulerian multiphase flow model and the Realizable k−ε turbulence model are used for numerical calculation. The population balance model is used to describe the coalescence and breakup phenomena of the microbubble groups. Henry’s theorem is used to calculate the equilibrium concentration of the microbubble mixed flow. The interphase mass transfer rate of the microbubble injection process for different types of gases is studied by using permeation theory. The local mass fraction of the mixed flow is solved by the component transport equation. It is found that the larger the solubility of the gas, the lower the efficiency of MBDR. When the volume flow rate of the same type of gas is the same but the injection speed is different, the larger the solubility of the gas is, the greater the difference in the drag reduction ratio.

Local processes with a global impact: unraveling the dynamics of gas evasion in a step-and-pool configuration

Abstract. Headwater streams are important sources of greenhouse gases to the atmosphere. The magnitude of gas emissions originating from such streams, however, is modulated by the characteristic microtopography of the riverbed, which might promote the spatial heterogeneity of turbulence and air entrainment. In particular, recent studies have revealed that step-and-pool configurations, usually found in close sequences along mountain streams, are important hotspots of gas evasion. Yet, the mechanisms that drive gas transfer at the water–air interface in a step-and-pool configuration are not fully understood. Here, we numerically simulated the hydrodynamics of an artificial step-and-pool configuration to evaluate the contribution of turbulence and air entrainment to the total gas evasion induced by the falling jet. The simulation was validated using observed hydraulic features (stage, velocity) and was then utilized to determine the patterns of energy dissipation, turbulence-induced gas exchange and bubble-mediated transport. The results show that gas evasion is led by bubble entrainment and is mostly concentrated in a small and irregular region of a few square decimeters near the cascade, where the local gas transfer velocity (k) peaks at 500 m d−1. The enhanced spatial heterogeneity of k in the pool does not allow one to define a priori the region of the domain where the outgassing takes place and makes the value of the spatial mean of k inevitably scale-dependent. Accordingly, we propose that the average mass transfer velocity should be used with caution to describe the outgassing in spatially heterogeneous flow fields, such as those encountered in step-and-pool rivers.

Carbon emissions affected by real-time reservoir operation: a hydrodynamic modeling approach coupled with air-water mass transfer

Air-water diffusive carbon fluxes (e.g., CO2 and CH4) in reservoirs, particularly those dammed in river valleys, are the major pathway of reservoir carbon emissions. Hydrodynamic conditions caused by real-time reservoir operation could potentially affect air-water transfer of these greenhouse gases (GHGs), yet still under explored. Here, we proposed an estimation method of gross carbon emissions based on a computational fluid dynamic (CFD) modelling approach. The model assumed that air-water mass transfer was primarily regulated by surface turbulence, and disregarded contributions from biogeochemical processes as well as seasonality of meteorological parameters (i.e., wind speed and direction; air temperature). Through the hydrodynamic modeling, reservoir water level, flow velocity, surface turbulence, and air-water transfer velocity of carbon fluxes were elaborated. Gross carbon emissions were integrated by the carbon fluxes in each discrete cell and time under real-time reservoir operation. The Xiangjiaba Reservoir (XJB), located in the upper Yangtze Basin, was selected as the case of the study. Based on daily hydrological data in 2018, such as reservoir inflow, outflow and water level, the gross CO2 and CH4 emissions in the reservoir were approximately 6.7 Gg and 5.6 Mg. Variations of daily water level and discharge induced by reservoir operation could evidently affect carbon emissions. In particular, when reservoir initiated its impoundment, the discharge could be the probably critical factor that affected mass transfer velocity and carbon emissions in the reservoir. Our model could provide a new vision for evaluating the effect of real-time reservoir operation on carbon emissions.

Impact of Arrhenius activation energy on MHD nanofluid flow past a stretching sheet with exponential heat source: A modified Buongiorno’s model approach

Nanofluids have a wide range of applications in biological research. They are employed in targeted medication administration, hyperthermia (for cancer treatment) and differential diagnostics like magnetic resonance image (MRI). In light of these medical applications, the impact of an external magnetic field and an exponential heat source on the dynamics of [Formula: see text]–[Formula: see text] over a nonlinearly stretched surface has been investigated. A realistic modified Buongiorno model has been used which includes the effects of reaction rate, Biot number and activation energy. The boundary value problem governing the model is solved on MATLAB R2022a using the solver, BVP5C. Further, the consequences of different parameters on rate of heat transfer coefficient (Nusselt number), rate of mass transfer coefficient (Sherwood number), drag coefficient, velocity, temperature and volume fraction profile are observed graphically. It is noted that volume fraction and uniform heat source intensity have a positive effect on the Nusselt number and negative effect on Sherwood number. The effects of thermal radiation and magnetic field on volume fraction profile are, respectively, positive and negative. The current physics of flow across a vertical stretching surface is expected to serve as the foundation for various medical science, engineering and technology applications.

Analytical modeling of mass transfer dynamics, velocity, heat transfer and enthalpy in a gas-liquid combustible mixture

The article studied the distribution of the droplet and temperature over the volume of the combustion chamber when liquid fuel was injected into it. The study showed that the portable mass in the combustion chambers and temperatures are directly proportional. Compiled systems of dynamic equations describing mass transfer, motion, heat transfer and enthalpy at the beginning inside the chamber phase and during combustion inside the chamber. Mathematically modeled a gasoline-hydrogen-air mixture with the mass transfer method. With this simulation, pressures are determined at the beginning inside the chamber phase and during combustion inside the chamber, taking into account the newly introduced enthalpy coefficient of gas kHg and steam kHp phase media.

Автоматизоване розпаралелювання програми моделювання внутрішньочастинкової дифузії й абсорбції в неоднорідних нанопористих середовищах

Heterogeneous media consisting of thin layers of particles of forked porous structure with different physical-chemical properties are widely used in science-intensive technologies and priority sectors of industry, medicine, ecology, etc. Such layers are distributed systems of pores consisting of two main spaces: micro- and nanopores of particles and macropores and cavities between particles. Mass transfer in the system of heterogeneous media causes two types of mass transfer: diffusion in macropores, owing to interparticle space, and diffusion in the system of micro- and nanopores inside particles of the heterogeneous medium. Intraparticle space has a higher level of adsorptive capacity, and at the same time, has a lower velocity of diffusion intrusion in comparison with interparticle space. In modeling concentra- tion and gradient fields for various diffusible components, an important scientific problem is the identification of kinetic parameters of a transfer, predetermining mass transfer velocity on macro- and micro levels, and also equilibrium conditions. The results of designing and parallelization of a program implementing a Crank-Nicolson scheme using algebra-algorithmic specifications represented in a natural- linguistic form are given. The tools for automated design, synthesis and auto-tuning of programs were applied that provided the translation of algebra-algorithmic schemes into source code in a target programming language and its tuning for execution environment to increase the program performance. Numerical distributions of values of diffusion coefficients for intraparticle transfer along coordinate of medium thickness for various time snapshots were obtained. Based on the results of the identification, the models were checked for adequacy and numerical modeling and analysis of concentration and gradient fields of mass transfer were carried out. The experiment results of auto- tuning the software implementation demonstrated high multiprocessor speedup on test data input.

Liquid holdup modeling analysis in horizontal gas–liquid slug flow

In slug flow, the wetted wall fraction and liquid holdup of the liquid film section are key parameters affecting the mass transfer and radial velocity distribution of the liquid film, the friction pressure drop, the momentum transfer between the two phases, and heat transfer characteristics. A modified wetted wall fraction and liquid holdup model based on the modified apparent rough surface (MARS) model is proposed in this study, which considers the friction coefficient and shear stress on the gas–wall, liquid–wall and gas–liquid interfaces and introduced the modified average interface velocity of the liquid film. Air–water slug flow experiments were in a 50 mm diameter acrylic glass pipe equipped with a high-speed camera. The edge detection operator was optimized to obtain the wetted wall fraction and liquid holdup at the liquid film section based on image analysis technology. A comparative analysis of the model performance shows that the mean absolute percentage error (MAPE) of the wetted wall fraction model is 9.4%, and the 96.1% relative deviations are within the ±20% error band. The MAPE of the liquid holdup model is 8.04%, and 93.4% relative error is within the ±25% error band. The modified MARS model has good prediction ability for the wetted wall fraction and liquid holdup of the gas–liquid slug flow.

Numerical Study of Non-Newtonian Fluid in a Cavity with Corrugated Bottom Wall Using Buongiorno’s Mathematical Model

A 2-dimensional computational analysis is carried out for a time dependent double diffusive mixed convection flow using non-Newtonian nanofluid. A square-shaped cavity with a corrugated bottom wall is taken with higher temperature and concentration on the top wall. The physical model under consideration is represented by a set of governing equations and solved using the Galerkin weighted residual method based on Finite Element Analysis. Solutions are done for 4 controlling parameters such as Richardson number (Ri = 0.1 - 15), Lewis number (Le = 0.5 - 3), and thermophoresis parameter (Nt = 0.2 - 0.9), and Brownian motion parameter (Nb = 0.2 - 1.0) at different values of τ. For the aforementioned parameters, heat and mass transfer rates, temperature distributions, velocity distributions, and mass distributions in terms of isotherm, streamlines, and iso-concentration are graphically presented. It has been observed that for higher values of Ri, both Nuav and Shav increased while Le decreased for higher values of Nt at any fixed time. It is worth noting that the considered parameter exhibits consistent behavior after a while. HIGHLIGHTS The numerical analysis of non-Newtonian nanofluid with a corrugated bottom wall and a sliding upward wall is performed using Buongiorno's mathematical model The effect of the Richardson number, Lewis number, Brownian motion, and thermophoresis parameters on different dimensionless time periods is addressed The heat and mass transfer rate is increased as the Richardson number, Lewis number, Brownian motion, and thermophoresis parameters increase in value GRAPHICAL ABSTRACT

INTENSIFICATION OF THE ABSORPTION OF OXYGEN BY WATER USING A ROTOR-PULSATING APPARATUS

One of the important components of the quality of food products is the quality of water used. A common way to remove unwanted impurities from water is aeration, i.e. the oxidation of chemical compounds in water by oxygen. Aeration devices with mechanical energy input in comparison with other groups of devices, namely with energy input with gas phase and with liquid phase, have low power consumption and additional mixing of the processed medium. The work presents a study of oxygen absorption in water in an experimental setup with rotor-pulsating apparatus for water treatment in beverage production technology. In this paper, the energy and technological parameters of aeration of a model aqueous solution of a certain concentration of sodium sulfide in an experimental setup with a rotor-pulsating apparatus as an aerator are determined. The experimental aeration setup allows conducting research in several modes and consists in particular of a vessel, a rotor-pulsating apparatus, two ejectors - one at the entrance to the rotor-pulsating, the other at the outlet, the recirculation pipeline. Air from the atmosphere enters each of the ejectors through a separate air duct. The aeration of the studied water took place in the recirculation mode for 20 minutes. Determination of the oxygen mass transfer rate is determined by the iodometric titration method on the rate of oxidation of sodium sulfite. Experiments were conducted without using a catalyst. It is determined that when placing the ejector unit at the rotor-pulsating apparatus inlet at the angular rotor unit velocity of 240.02; 270.18, and 300.02 s-1, the oxygen mass transfer rate is 1.39; 1.49 and 1.73 kg m3/h. At the location of the ejector unit at the outlet of the rotor-pulsating apparatus, the velocity of the oxygen mass transfer under the same conditions is 1.17; 1.36 and 1.63 kg m3/h respectively. However, the power consumption of the second scheme exceeds the power consumption by the first scheme by 50%.

Peristaltic pump with heat and mass transfer of a fractional second grade fluid through porous medium inside a tube

In magnetic resonance imaging (MRI), this MRI is used for the diagnosis of the brain. The dynamic of these particles occurs under the action of the peristaltic waves generated on the flexible walls of the brain. Studying such fluid flow of a Fractional Second-Grade under this action is therefore useful in treating tissues of cancer. This paper deals with a theoretical investigation of the interaction of heat and mass transfer in the peristaltic flow of a magnetic field fractional second-grade fluid through a tube, under the assumption of low Reynolds number and long-wavelength. The analytical solution to a problem is obtained by using Caputo's definition. The effect of different physical parameters, the material constant, magnetic field, and fractional parameter on the temperature, concentration, axial velocity, pressure gradient, pressure rise, friction forces, and coefficient of heat and mass transfer are discussed with particular emphasis. The computed results are presented in graphical form. It is because the nature of heat and mass transfer coefficient is oscillatory which is following the physical expectation due to the oscillatory nature of the tube wall. It is perceived that with an increase in Hartmann number, the velocity decreases. A suitable comparison has been made with the prior results in the literature as a limiting case of the considered problem.

Thermally Radiant Williamson Nanofluid Flow Over a Permeable Stretching Sheet with Viscous Dissipation and Joule Heating Effects

The present paper focuses on the study of an incompressible flow of a steady two-dimensional electrically conducting thermally radiant Williamson nanofluid over a permeable stretching sheet with viscous dissipation and joule heating effects. The governing partial differential equations are reduced to a couple of nonlinear ordinary differential equations by using suitable transformation equations; these equations are then solved numerically with the use of the conventional fourth-order Runge Kutta method accompanied by the shooting technique. Graphical results of the flow, temperature, and nanoparticles volume fraction profiles are displayed. Effects of the physical parameters on velocity, temperature, nanoparticles volume fraction, skin friction coefficient, and the rates of heat and mass transfer are investigated. The results indicate that the velocity ratio parameter enhances the skin friction coefficient, the velocity profile, and the rate of heat transfer whereas it minimizes the rate of mass transfer. On the other hand, increasing the values of the mass suction parameter results in both the velocity and the temperature boundary layer thickness decrease whereas increasing the mass injection enhances both the velocity and the temperature profiles; but it vigorously enhances the rate of heat transfer. The non-Newtonian parameter fosters the rate of heat transfer whereas it lessens both the velocity and rate of mass transfer of the nanofluid.

Blasius and Sakiadis flow of a Casson hybrid nanofluid over a moving plate

ABSTRACT It is generally known that adding a particular amount of nanoparticles to a traditional liquid improves its thermal conductivity. The cause of this dramatic improvement is yet unclear. As a result, determining the proper thermal impact of particles at the nanoscale requires understanding the kinematics of nanoparticle suspension. Bearing this in mind, the primary goal of this research is to investigate thermophoretic particle deposition on a Blasius-Sakiadis flow of a Casson hybrid nanoliquid flow over a moving plate. In this case, a 50% Ethylene glycol (EG) carrier liquid is used to suspend copper and silver nanoparticles. The governing equations are reduced to ordinary differential equations (ODEs) using appropriate similarity transformations. Then these ODEs are solved using the fourth-fifth order Runge–Kutta Fehlberg's technique (RKF-45) with the shooting methodology. The influence of various non-dimensional factors on involved fields is then discussed in depth using appropriate graphs. The results show that for both Blasius and Sakiadis flows, rise in values of the radiation parameter increase fluid heat transfer. Furthermore, for both Blasius and Sakiadis flows, an increase in the thermophoretic coefficient and thermophoretic parameter degrades the liquid's mass transfer and thermophoretic diffusive deposition velocity.

Numerical investigation on interfacial characteristics of steam bubble condensation in subcooled water

Numerous direct-contact condensation (DCC) and boiling issues are numerically investigated with the Lee model under an assumed constant mass transfer coefficient through trial and error. A new mass transfer coefficient correlation is proposed, and the accuracy of the correlation is confirmed via comparison to Kim and Park’ experimental results from steam bubble injected vertically into a flow channel with diameter of 4.9 mm and subcooled temperature of 12 K in this work. The established correlation reveals that a fixed mass transfer coefficient value throughout the whole bubble condensation process is unreasonable and may cause solution divergence. Moreover, values of the mass transfer rate and velocity at the steam-water interface are explicitly derived at several moments. The results demonstrate that the mass transfer rate causes velocity fluctuations at the steam-water interface, and these velocity fluctuations promote bubble deformation, which in turn affects the condensation mass transfer rate.

Modelling Miniature Microbial Fuel Cells with Three-dimensional Anodes

Microbial fuel cells (MFCs) exploit the metabolic activity of electroactive microorganisms for oxidation of organic compounds and extracellular electron transfer to an external electrode. the technology is associate with very slowreaction rates, resulting in low current densities. Anodes with high specific surface should be used to increase the overall electricity generation. Carbon-based 3D materials, with high surface per unit of volume, are largely used anode materials in MFCs, although may show significant lack in efficiency due to mass transfer limitations, concentration gradients, velocity distribution and resistivity of the material. Consequently, the concomitant effect of several parameters should be assessed and quantified to design highly performing MFCs implementing 3D anode materials. In this work, miniature MFCs with 3D anodes are mathematically modelled to quantify the effect of operative parameters on performance. The model combines equations of charge conservation, mass transport phenomena, hydrodynamics, and kinetics of the involved processes under transient conditions, and provides 3D profiles with time of velocity, biofilm thickness, substrate concentration, current density and potential. The solution predicts a laminar flow, as it was expected with the low flow rates used. The concentration profiles show the consumption of substrate in the anode, with low values of local concentrations depending on organic load in the feed stream. The model also provides a versatile tool to optimise the operative conditions of the system, managing the flow arrangements to maximise either substrate removal or electricity generation.

Coupling VOF interfacial mass transfer model with RSM approach in LLE systems: Developing the new correlations for mass transfer, aspect ratio and terminal velocity

The performance of liquid-liquid extraction (LLE) systems is determined by terminal velocity and extraction fraction. Several parameters and their interactive effects influence the performance. In the present study, the response surface methodology(RSM) approach has been used to investigate the parameters' effects and their complicated interactions in hydrodynamics and mass transfer. Hydrodynamic and mass transfer simulations of a single droplet system have been carried out using the VOF method and close agreements have been attained in comparison with experimental data. Subsequently, the RSM and central composite design methods were employed in terminal velocity, aspect ratio, and extraction fraction modeling. The drop diameter, density ratio, and viscosity ratio have been chosen as the effective hydrodynamic parameters in the terminal velocity and aspect ratio. The mentioned hydrodynamic parameters, partition coefficient, and diffusivity ratio have been chosen as the mass transfer variables. The suggested quadratic models of terminal velocity(R2 = 0.99) gives accurate predictions in high Re numbers, while the previous correlations could not. The new general quadratic model of aspect ratio having included the viscosity ratio as an effective parameter, can be used in the wide range of material properties with high accuracy (R2 = 0.95), while the previous correlations have not included the viscosity ratio. The new quadratic model of mass transfer with high accuracy (R2 = 0.99), includes partition coefficient and its interactive effects with diffusivity ratio and hydrodynamic parameters which have not been considered yet. More additionally, the developed model could be applied in every LLE system regardless of the mass transfer resistance existence in the drop/continuous phase or both. Finally, the ANOVA showed that the partition coefficient and viscosity ratio are the most effective parameters in mass transfer, hence the reduction in the partition coefficient along with the reduction in viscosity ratio would help to reach the better mass transfer performance. At the final stage, the optimized conditions have been presented.

Analysis of Volume Fraction and Convective Heat Transfer on MHD Casson Nanofluid over a Vertical Plate

The numerous industrial and engineering applications of Casson nanofluid is due to the superiority of its thermophysical properties. Tomatoes paste, engine oil, soup etc., are examples of Casson fluid and when nanometer-sized particles are suspended in such Casson fluid, it becomes Casson nanofluid. This paper considers a natural convective magnetohydrodynamics flow of Cu-engine oil nanofluid across a convectively heated vertical plate. The effects of self-heating of the fluid (measured by the Eckert number), internal conductive resistance to external convective resistance (measured by the Biot number), magnetic field strength, volume fraction of the nanoparticles on the temperature and velocity of mass and heat transfer of Casson nanofluid is analysed. An appropriate model governing the flow of Casson nanofluid is formulated as a system of nonlinear partial differential equations. The natural convection boundary condition is included. To solve the problem, an appropriate similarity transformation is used to reformulate the system as a system of nonlinear ordinary differential equations. The shooting technique is used to convert the boundary problem to initial value problems before Runge-Kutta method, with the Gills constants, is used to solve the reformulated problem. The results are depicted as graphs. Flow velocity is found to increase as the base fluid becomes more Casson and as nanoparticle volume fraction increases. It is also found that increasing Eckert number, Biot number and magnetic field strength causes an increase in the flow temperature.

Flow of Electrically Conducting Williamson Fluid with Cattaneo-Christov heat flux due to Permeable Sheet

An analysis is presented for the flow of non-Newtonian Williamson fluid due to permeable sheet. The recent modification of Fourier’s law of heat conduction, i.e. Model of Cattaneo-Christov heat flux is studied in present article to analysis the heat flux. The permeable sheet undergoes suction and the effect of Soret and Dufour is also investigated The governing boundary layer equations are transformed into a non-dimensional form using appropriate set of transformation and the resulting non-linear coupled system of ordinary differential equations are solved using robust Homotopy Analysis method. The influence of physical parameter affecting the velocity of fluid, heat and mass transfer are discussed and outputs are expressed in figures and tables. Some interesting results are found from the study that the velocity profile is decelerating with increase in magnetic parameter. Increasing Darcy number accelerates the flow due to a corresponding rise in permeability of the regime and concomitant decrease in Darcian impedance.

The Microstructure Evolution and Mass Transfer in Mushy Zone during High-Pressure Solidifying Hypoeutectic Al-Ni Alloy

The mushy zone of hypoeutectic Al-1.5 wt% Ni alloy during high-pressure synthesis was obtained by changing the structure of the graphite heater. Meanwhile, the evolution of the microstructure was investigated. The results demonstrated that three distinguished zones were successfully generated along with the direction of the temperature gradient, including the fully melted area consisting of the columnar dendrite. The mushy zone is composed of an α-Al phase, bulk β-Al3Ni phase, and a eutectic microstructure as well as a non-melted, solid region. In addition, the mass transfer velocity and the time required for the liquid pool to migrate through the mushy zone during thermal-stable treatment under different high pressures were also analyzed. The results showed that the mass transfer was greatly inhibited, and the minimum time required for a liquid droplet to go through the whole mushy zone at 1 GPa and 3 GPa was 746 h and 5523 h, respectively.

Nitrate Removal Across Ecogeomorphic Zones in Wax Lake Delta, Louisiana (USA)

AbstractHuman activities have increased nitrate export from rivers, degrading coastal water quality. At deltaic river mouths, the flow of water through wetlands increases nitrate removal, and the spatial organization of removal rates influences coastal water quality. To understand the spatial distribution of nitrate removal in a river‐dominated delta, we deployed 23 benthic chambers across ecogeomorphic zones with varying elevation, vegetation, and sediment properties in Wax Lake Delta (Louisiana, USA) in June 2018. Regression analyses indicate that normalized difference vegetation index is a useful predictor of summertime nitrate removal. Mass transfer velocity were approximately three times greater on a vegetated submerged levee (13 mm hr−1), where normalized difference vegetation index was greatest, compared to other locations (4.6 mm hr−1). Two methods were developed to upscale nitrate removal across the delta. The flooded‐delta method integrates spatially explicit potential removal rates across submerged portions of the delta and suggests that intermediate elevations on the delta—including submerged levees—are responsible for 70% of potential nitrate removal despite covering only 33% of the flooded area. The channel network method treats the delta as a network of river channels and suggests that although secondary channels are more efficient than primary channels at removing received nitrate, primary channels collectively contribute more to overall removal because they convey more of the total nitrate load. The two upscaling methods predict similar rates of nitrate removal, equivalent to less than 4% of nitrate entering the delta. To protect coastal waters against high nitrate loads, management policies should aim to reduce upstream nutrient loads.