Complex Flow Paths Research Articles

Fine particle transport dynamics in response to wood additions in a small agricultural stream

AbstractWood additions to streams can slow water velocities and provide depositional areas for bacteria and fine particles (e.g., particulate organic carbon and nutrients sorbed to fine sediment), therefore increasing solute and particle residence times. Thus, wood additions are thought to create biogeochemical hotspots in streams. Added wood is expected to enhance in‐stream heterogeneity, result in more complex flow paths, increase natural retention of fine particles and alter the geomorphic characteristics of the stream reach. Our aim was to directly measure the impact of wood additions on fine particle transport and retention processes. We conducted conservative solute and fluorescent fine particle tracer injection studies in a small agricultural stream in the Whatawhata catchment, North Island of New Zealand in two reaches—a control reach and a reach restored 1‐year earlier by means of wood additions. Fine particles were quantified in surface water to assess reach‐scale (channel thalweg) and habitat‐scale (near wood) transport and retention. Following the injection, habitat‐scale measurements were taken in biofilms on cobbles and by stirring streambed sediment to measure fine particles available for resuspension. Tracer injection results showed that fine particle retention was greater in the restored compared to the control reach, with increased habitat‐scale particle counts and reach‐scale particle retention. Particle deposition was positively correlated with cobble biofilm biomass. We also found that the addition of wood enhanced hydraulic complexity and increased the retention of solute and fine particles near the wood, especially near a channel spanning log. Furthermore, particles were more easily remobilized from the control reach. The mean particle size remobilized after stirring the sediments was ~5 μm, a similar size to both fine particulate organic matter and many microorganisms. These results demonstrate that particles in this size range are dynamic and more likely to remobilize and transport further downstream during bed mobilization events.

Density-dependent solute transport in a layered hyporheic zone

Hyporheic exchange is affected by bedform geometry, which induces complex flow paths within the bedform. Additional factors that influence flow and solute transport in the hyporheic zone are layered profile sediments and density-driven flow. This study explored the combined effects of these factors on hyporheic exchange through laboratory experiments and numerical simulations involving infiltrating solute displacing less-dense resident water in a layered bedform with a low permeability layer (LPL). The bedform consisted of three horizontal layers, in which the hydraulic conductivity of the middle layer (LPL) was less than that of the top (TL) and bottom layers (BL). The results demonstrated that a previously unexplored combination of mechanisms (density effects and layered bedform) produces irregular spatial patterns of solute transport in the hyporheic zone. For instance, the width of solute plume within the bottom layers becomes narrowed compared with tracer transport. With increasing density contrast between infiltrating solute and resident water, the solute plume becomes much narrower, forming fingers. Numerical modeling further shows that the hydraulic conductivity contrast (HCC) and relative thickness (RT) of the hyporheic zone layers also affect the spatial solute transport patterns. As the hydraulic conductivity contrast or relative thickness increases, the plume becomes much narrower. Horizontal ambient flow (HAF) dominated in the bottom layers, and lateral solute spreading and mixing intensified with a higher hydraulic conductivity contrast and relative thickness. Furthermore, the vertical solute plume was detached by the horizontal ambient flow in the bottom layers with a discontinuous low permeability layer, forming a discontinuous zone of vertical solute transport.

Microchannel fabrication via ultraviolet-nanoimprint lithography and electron-beam lithography using an ultraviolet-curable positive-tone electron-beam resist

In this study, we propose a process to fabricate microchannels for in-situ cell cultivation and observation to facilitate a variety of biological experiments. The fabrication process involved a combination of ultraviolet nanoimprint lithography (UV-NIL) followed by electron-beam lithography (EBL) with a UV-curable EB resist polymer to form micropatterns directly on the imprinted microscale patterns. Here, we demonstrate the fabrication of microscale flow paths and reservoirs by UV-NIL and the subsequent formation of capillary flow paths and cell traps on the order of 2–4 μm by EBL. The UV-NIL/EBL hybrid technique can be used to fabricate complex microfluidic devices and is expected to be useful for lab-on-a-chip applications that require fine and complex flow paths.

A Study on Flow Characteristics and Flow Uniformity for the Efficient Design of a Flow Frame in a Redox Flow Battery

As global environmental problems are worsening, the efficiency of storage systems for renewable energy are gaining importance. The redox flow battery (RFB), a promising energy storage system (ESS), is a device that generates or stores electricity through reduction–oxidation reactions between active materials constituting electrolytes. Herein, we proposed a flow frame design that reduces flow resistance in the flow path and causes uniform flow distribution in the electrode to develop an efficient redox flow battery. Through computational fluid dynamics (CFD) and experimental verification, we investigated the flow characteristics and flow uniformity inside the conventional redox flow battery cell. An analysis of the flow characteristics of the conventional flow frame revealed a non-uniform distribution of the flow discharged to the electrodes, owing to the complex (branched) flow path geometry of the inlet channel. To address this problem, we proposed a new flow frame design that removed and integrated bifurcations in the flow path. This new design significantly improved flow uniformity parameters, such as the symmetry coefficient ( C s y m ), variability range coefficient ( R i ), and maximum flow rate deviation ( D m ). Ultimately, we decreased the pressure drop by 15.3% by reducing the number of flow path bifurcations and chevron repositioning.

Impact of Riparian and Stream Restoration on Denitrification in Geomorphic Features of Agricultural Streams

HighlightsDenitrification enzyme activity (DEA) was measured in stream sediments of restored and unrestored agricultural streams.Nitrate, sediment characteristics, riparian vegetation, and geomorphology influenced DEA.Pools at restored sites had lower organic carbon, coarser sediment textures, and lower denitrification potential.Restoration strategies should increase organic carbon and residence times through complex flowpaths.Abstract. Agricultural land use, channel modifications, and riparian vegetation composition can affect instream denitrification by altering geomorphic features, such as sediment texture, organic matter, retention time, and hyporheic exchange. Stream and riparian restoration is widely implemented in agricultural watersheds to mitigate excess nutrient export to sensitive downstream waters; however, the cumulative impact of channel reconstruction and altered channel and near-stream morphology on nitrogen dynamics remains poorly understood. We measured denitrification enzyme activity (DEA) and environmental variables (e.g., water chemistry, sediment texture, and organic matter) in different geomorphic features in agriculturally influenced streams in North Carolina with varied channel and riparian zone characteristics. Our results indicate that denitrification is primarily influenced by increased transport of nitrate (NO3-) to the streams in wetter months. Secondarily, structural factors, including riparian vegetation and stream geomorphology, impact denitrification by controlling the distribution of sediment texture and organic carbon. In the newly restored stream, we observed coarser streambed sediments and low sediment organic carbon, especially in scour pools constructed downstream from cross-vanes. Lower DEA was observed in restored pools (39.1 ng N g-1 dry mass h-1) compared to naturally occurring pools (70.7 to 278.1 ng N g-1 dry mass h-1). These results highlight the need for restoration strategies to be directed at increasing organic carbon and residence times through complex flowpaths (e.g., meanders, root wads, artificial woody debris dams). Keywords: Denitrification, Freshwater, Nitrogen, Restoration, Riparian, Stream, Water quality.

A study in fractional diffusion: Fractured rocks produced through horizontal wells with multiple, hydraulic fractures

The spatiotemporal evolution of transients in fractured rocks often displays unusual characteristics and is traced to multifaceted origins such as micro-discontinuity in rock properties, rock fragmentation, long-range connectivity and complex flow paths. A physics-based model that incorporates transient propagation wherein the mean square displacement of the diffusion front follows a nonlinear scaling with time is proposed. This model is based on fractional diffusion. The motivation for fractional flux laws follows from the existence of long-range connectivity that results in the mean square displacement of fronts moving faster than predicted by classical models; correspondingly, obstructions and discontinuities, local flow reversals, intercalations, etc. produce the opposite effect with fronts moving at a slower rate than classical predictions. The interplay of these two competing behaviors is quantified. We simulate transient production in a porous rock at the Theis scale as a result of production through a horizontal well consisting of multiple hydraulic fractures. Asymptotic solutions are derived and computations verified. The practical potential of this model is described through an example and the movement of fronts under the constraints of this model is demonstrated through the new expressions developed in this work. We demonstrate that this model offers a potential avenue to explain other behaviors noted in the literature. Though this work is developed in the context of applications to the earth sciences (production of hydrocarbons, extraction of geothermal resources, sequestration of radioactive waste and other fluids, groundwater flow), a minimal change in the Nomenclature permits application to other contexts. Ideas proposed here are particularly useful in the context of superdiffusion in bounded systems which until now, in many ways, has been considered to be an open problem.

Novel 3-D T-Shaped Passive Micromixer Design with Helicoidal Flows

Laminar fluid flow and advection-dominant transport produce ineffective mixing conditions in micromixers. In these systems, a desirable fluid mixing over a short distance may be achieved using special geometries in which complex flow paths are generated. In this paper, a novel design, utilizing semi-circular ridges, is proposed to improve mixing in micro channels. Fluid flow and scalar transport are investigated employing Computational Fluid Dynamics (CFD) tool. Mixing dynamics are investigated in detail for alternative designs, injection, and diffusivity conditions. Results indicate that the convex alignment of semi-circular elements yields a specific, helicoidal-shaped fluid flow along the mixing channel which in turn enhances fluid mixing. In all cases examined, homogenous concentration distributions with mixing index values over 80% are obtained. When it is compared to the classical T-shaped micromixer, the novel design increases mixing index and mixing performance values by the factors of 8.7 and 3.3, respectively. It is also shown that different orientations of ridges adversely affect the mixing efficiency by disturbing the formation of helicoidal-shaped flow profile.

Elementary Pore Network Models Based on Complex Analysis Methods (CAM): Fundamental Insights for Shale Field Development

This paper presents insights on flow in porous media from a model tool based on complex analysis methods (CAM) that is grid-less and therefore can visualize fluid flow through pores at high resolution. Elementary pore network models were constructed to visualize flow and the corresponding dynamic bottomhole pressure (BHP) profiles in a well at reservoir outflow points. The pore networks provide the flow paths in shale for transferring hydrocarbons to the wellbore. For the base case model, we constructed a single flow path made up of an array of pores and throats of variable diameter. A passive ganglion (tracer) of an incompressible fluid was introduced to demonstrate the deformation of such ganglions when moving through the pores. The simplified micro-flow channel model was then expanded by stacking flow elements vertically and horizontally to create complex flow paths representing a small section of a porous reservoir. With these model elements in place, the flow transition from the porous reservoir fluid to the wellbore was modeled for typical stages in a well life. The dynamic component of the bottomhole pressure (BHP) was modeled not only during production but also during the drilling of a formation (with either balanced, underbalanced or overbalanced wellbore pressure). In a final set of simulations, the movement of an active ganglion (with surface tension) through the pore space was simulated by introducing a dipole element (which resisted deformation during the movement through the pores). Such movement is of special interest in shale, because of the possible delay in the onset of bubble point pressure due to capillarity. Capillary forces may delay the reservoir to reach the bubble point pressure, which postpones the pressure-drop trigger that would lead to an increase of the gas–oil ratio. The calculation of the estimated ultimate recovery (EUR) with an erroneous assumption of an early increase in the gas–oil ratio will result in a lower volume than when the bubble point delay is considered.

Investigation of Cryogenic Chilldown in a Complex Channel Under Low Gravity Using a Sounding Rocket

To realize high-performance cryogenic propulsion systems, the chilldown sequence has to be improved. Because the chilldown is carried out under low gravity, the effect of gravity on the two-phase flow, especially at low flow rate, should be investigated. To understand the physics under low gravity, an experiment was conducted using a sounding rocket. Two identical test sections with different mass flow rates simulated part of a turbopump, each of which has a complex flowpath including slits and a dead end. Using liquid nitrogen, the flight experiment obtained data of temperatures, pressures, void fractions, and video frames of liquid motion. Then, the flight experiment data were compared to the ground data taken under normal gravity, revealing that the slits played an important role in the chilldown process and that the test sections were quickly chilled down under low gravity. The slits of the test sections formed liquid jets, and their behaviors were different from those in the ground experiment. In the flight experiment, the jets easily reached the dead end of the test sections and cooled down the whole walls due to the increase in inertia and wettability; however, such behaviors were hardly observed in the ground experiment. The difference between the ground and flight is significant at lower flow rate.

Transport of perfluorocarbon tracers in the Cranfield Geological Carbon Sequestration Project

AbstractA field‐scale carbon dioxide (CO2) injection pilot project was conducted by the Southeast Regional Carbon Sequestration Partnership (SECARB) at Cranfield, Mississippi. Two associated campaigns in 2009 and 2010 were carried out to co‐inject perfluorocarbon tracers (PFTs) and sulfur hexafluoride (SF6) with CO2. Tracers in gas samples from two observation wells were analyzed to construct breakthrough curves. In this work, we present the field data and numerical modeling of the flow and transport of CO2, brine, and tracers. A high‐resolution static model of the formation geology in the detailed area study (DAS) was used to capture the impact of connected flow pathways created by fluvial channels on breakthrough curves and breakthrough times of PFTs and SF6 tracers. We use the cubic‐plus‐association (CPA) equation of state, which takes into account the polar nature of water molecules, to describe the phase behavior of CO2–brine‐tracer mixtures. Our simulated results show good agreement for the 2009 tracer campaign in Cranfield, while a larger discrepancy emerges by 2010. The combination of multiple tracer injection pulses with detailed numerical simulations proves to be a powerful tool in constraining both formation properties and how complex flow paths develop over time. © 2018 Society of Chemical Industry and John Wiley & Sons, Ltd.

Inferring catchment flow path responses using a data-driven model: an exploratory study based on a generalized additive model

ABSTRACTIdentifying physical catchment processes from streamflow data, such as quick- and slow-flow paths, remains challenging. This study is designed to explore whether a flexible nonparametric regression model (generalized additive model, GAM) can be used to infer different flow paths. This assumes that the data relationship in data-driven models is also a reflection of catchment physical processes. The GAM, using time-lagged flow covariates, was fitted to synthetic rainfall–runoff data simulated using simple linear reservoirs. Partial plots of the time-lagged covariates show that the model could differentiate simple and more complex flow paths in simulated synthetic data with short and long memory systems and varying between dry and wet climates. Further analysis of data from real catchments showed that the model could differentiate catchments dominated by slow flow and by quick flow. Therefore, this study indicates that GAM can be used to identify catchment storages and delay processes from streamflow data.

Investigation of fabrication of hollow plate with complex flow paths for the breeding blanket by explosive weld

The breeding blanket, which contains a large quantity of hollow structures with complex flow paths, is one of the core parts of the fusion reactor. Fabrication of the hollow plate is the most fundamental and difficult process because such kind of hollow plate is restricted by severe requirements of the special application environment from being manufactured by the regular welding and HIP technology. This thesis manufactures the hollow plate with complex flow paths by milling the groove, filling the mould and the explosive welding, and analyzes the interface by mechanical shearing, bending test, bond interface analysis and SEM scanning, and then tests the pressure resistance of flow paths within. The result indicates that the weld interface form a metallurgic bonding without impurity elements with the strength of 478MPa, the weld joint may endure 135° of bending, and the flow paths within are tight enough to resist 7MPa of pressure.

A Comparative Hydraulic Analysis of Conventional- and Reverse-Circulation Primary Cementing in Offshore Wells

Summary Reverse-circulation primary cementing (RCPC), a technique in which cement is pumped down the annulus, has historically been used for specialized cases as an alternative to conventional-circulation primary cementing (CCPC), in which cement is pumped down the casing and circulates up the annulus. As the potential application of this placement technique has extended to deep water, traditional conventional hydraulic analysis is insufficient because of the complex flow path required by deepwater RCPC. The focus of this study is to provide a hydraulic analysis of this flow path, to determine causes of apparent equivalent-circulating-density (ECD) reductions, and to provide operators and well engineers with simple tools to estimate the changes in ECDs throughout the casing annulus. Investigations of the specific hydraulic considerations of RCPC have been explored and evaluated since its first applications. This analysis builds upon previously published case studies and evaluations of hydraulics for traditional RCPC in which fluids are directly injected into the annulus from surface. By use of a graphical analysis, the hydraulics of deepwater RCPC, which requires an unconventional-flow path to divert flow from the work string into the annulus below the seafloor, is evaluated and compared with conventional placement. The results of this study can be used for an initial determination of whether RCPC will produce the desired results for a specific wellbore geometry. By developing expressions for the pressure in the casing annulus for both conventional and reverse circulation, an analytic equation for the critical depth can be derived, assuming a constant pressure drop per unit length in the casing annulus. This study also evaluates the cause of pressure differences between conventional and reverse placement and the relationship of frictional-pressure drops, hydrostatic effects, and the elimination of applied lift pressure. If the ECD is reduced at the bottom of the hole and increased at the previous casing shoe, then there is a point between those two where the pressures in conventional and reverse circulation are equal. A critical depth analysis has previously been performed for traditional RCPC applications. For deepwater applications that take into account the unconventional-flow path, analysis in this study shows that well geometry and location of a weak zone in the formation affect which placement method results in the lowest ECDs in a targeted area. For deepwater RCPC to be effective, the weakest part of the formation should be below the determined critical depth of the well.

Nonlocal Diffusion in Fractured Rocks

Summary Space–time fractional diffusion in a linear, bounded region is considered. An analytical expression for the pressure distribution in the bounded region is derived in terms of the Mittag-Leffler function and the Laplace transformation. Comparisons with numerical solutions indicate excellent agreement. A convenient expression that incorporates a combination of Dirichlet and Neumann boundary conditions, particularly suitable for rapid computations, has been elusive until now. Responses that may be expected in nanoporous reservoirs that are usually produced through horizontal wells containing multiple hydraulic fractures are deduced. It is shown that the existence of obstacles, discontinuities, and other complex flow paths in fractured reservoirs express themselves in the form of power-law declines, whereas long-range interactions reflective of rapid communication, interestingly, express themselves as exponential declines. An understanding of the simultaneous influences of these two effects is the purpose of this study. The application to the “trilinear” model often used to evaluate well performance in shales is demonstrated.

Scaling Roughness Effects on Pressure Loss and Heat Transfer of Additively Manufactured Channels

Additive manufacturing (AM) with metal powder has made possible the fabrication of gas turbine components with small and complex flow paths that cannot be achieved with any other manufacturing technology presently available. The increased design space of AM allows turbine designers to develop advanced cooling schemes in high-temperature components to increase cooling efficiency. Inherent in AM with metals is the large surface roughness that cannot be removed from small internal geometries. Such roughness has been shown in previous studies to significantly augment pressure loss and heat transfer of small channels. However, the roughness on these channels or other surfaces made from AM with metal powder has not been thoroughly characterized for scaling pressure loss and heat transfer data. This study examines the roughness of the surfaces of channels of various hydraulic length scales made with direct metal laser sintering (DMLS). Statistical roughness parameters are presented along with other parameters that others have found to correlate with flow and heat transfer. The pressure loss and heat transfer previously reported for the DMLS channels studied in this work are compared to the physical roughness measurements. Results show that the relative arithmetic mean roughness correlates well with the relative equivalent sand grain roughness. A correlation is presented to predict the Nusselt number of flow through AM channels, which gives better predictions of heat transfer than correlations currently available.

Variations on thermal transport modelling of subsurface temperatures using high resolution data

Although streambed dynamics are known to be complex and three-dimensional, flux within the subsurface is often estimated with simplified models for convenience, despite the errors this incurs. While three-dimensional (3D) models have the advantage of being able to capture complex flow paths within the subsurface, they are also more data intensive, requiring a detailed knowledge of both thermal and hydraulic streambed properties. Temperature data are relatively easy to acquire at a high resolution within a natural stream environment; however, it is typically more difficult to capture hydraulic head measurements at this same resolution, making it difficult to apply appropriate boundary conditions to 3D models in order to estimate streambed fluxes from heat tracer techniques alone. In this study, we examine the consequences of the lack of detailed head data for parameterizing boundary conditions. We tested the abilities of three 3D heat and water transport models with increasingly complex boundary conditions to match observed thermal patterns and predict streambed fluxes. All three models showed similar spatial patterns of high and low fluxes. The amplitude of predicted daily temperature variation at a depth of 0.25 m and 0.5 m below the streambed was generally within 0.1 °C (i.e. within sensor error) of observed, while all three models typically underestimated daily temperature variation in advective areas at a depth of 0.1 m. The results of this study suggest that 3D heat transport models of streambeds may be more limited by the low sensitivity of hydraulic conductivity to small temperature variations than by the lack of detailed hydraulic head data for parameterizing boundary conditions.

Identifying hydrologic flowpaths on arctic hillslopes using electrical resistivity and self potential

Shallow subsurface flow is a dominant process controlling hillslope runoff generation, soil development, and solute reaction and transport. Despite their importance, the location and geometry of these flow paths are difficult to determine. In arctic environments, shallow subsurface flow paths are limited to a thin zone of seasonal thaw above permafrost, which is traditionally assumed to mimic the surface topography. We have used a combined approach of electrical resistivity tomography (ERT) and self-potential (SP) measurements to map shallow subsurface flow paths in and around water tracks, drainage features common to arctic hillslopes. ERT measurements delineate thawed zones in the subsurface that control flow paths, whereas SP is sensitive to groundwater flow. We have found that areas of low electrical resistivity in the water tracks were deeper than manual thaw depth estimates and varied from the surface topography. This finding suggests that traditional techniques might underestimate active-layer thaw and the extent of the flow path network on arctic hillslopes. SP measurements identify complex 3D flow paths in the thawed zone. Our results lay the groundwork for investigations into the seasonal dynamics, hydrologic connectivity, and climate sensitivity of spatially distributed flow path networks on arctic hillslopes.

Accuracy and Computational Efficiency of 2D Urban Surface Flood Modelling Based on Cellular Automata

There is an emerging abundance of freely available high resolution (one meter or less) LIDAR data due to the advent of remote sensing, which enables wider applications of detailed flood risk modelling and analysis. Digital terrain surface data often comes in raster form, i.e., a square regular grid, and often requires conversion into a specific computational mesh for two-dimensional (2D) flood modelling that adopts triangular irregular meshes. 2D modelling of flood water movement through urban areas requires resolution of complex flow paths around buildings, which requires both high accuracy and computational efficiency. Water distribution and wastewater systems in the UK contain over 700,000km of water distribution and sewer pipes, which represents a large risk exposure from flooding caused by sewer surcharging or distribution pipe breaks. This makes it important for utilities to understand and predict where clean or dirty water flows will be directed when they leave the system. In order to establish risk assessment many thousands of simulations may be required, calling for the most computational efficient models possible.Cellular Automata (CA) represents a method of running simulations based on a regular square grid, thus saving set-up time of configuring the terrain data into an irregular triangular mesh. It also offers a more uniform memory pattern for very fast modern, highly parallel hardware, such as general purpose graphical processing units (GPGPU). In this paper the performance of the CADDIES [1], a CA platform and associate flood modelling software caFloodPro, using a square regular grid and Von Neumann neighbourhood, is compared to industry standard software using triangular irregular meshes for similar resolutions. A minimum time step is used to control the computational complexity of the algorithm, which then creates a trade-off between the processing speeds of simulations and the accuracy resulting from the limitations used within the local rule to cope with relatively large time steps. This study shows that using CA based methods on regular square grids offers process speed increases in terms of 5-20 times over that of the industry standard software using irregular triangular meshes, while maintaining 98-99% flooding extent accuracy.

Theoretical studies of MHD flows in support to HCLL design activities

Theoretical studies are performed to predict magnetohydrodynamic flow pattern and pressure drop in typical geometric components of the liquid metal manifold for a HCLL blanket module. The interaction of the flow with the strong magnetic field that confines the fusion plasma is analyzed by asymptotic techniques and by numerical simulations. The flows in feeding and draining manifolds are electrically coupled to each other via leakage currents which may cross the common wall that hydraulically separates both channels. This results in complex flow paths in the manifold and in additional pressure drop.

Cleaner production of basic chromium sulfate – with a review of sustainable green production options

Ferrochromium and chromium based compounds are produced worldwide from chromite ore. Chrome chemicals are from chromium based compounds. Basic-chromium-sulfate (BCS) is a chrome chemical mostly required as main tanning agent in chrome tanning process in leather industry and also to synthesize other chromic compounds. During the preparation of basic-chromium- sulfate, sodium dichromate containing chromium (VI) is reduced to chromium (III) by sulfur-di-oxide in a packed tower at a chemical process industry (B&M Chemicals, India) where the BCS is produced at suboptimal efficiency due to inefficient (suboptimal) absorption of sulfur-di-oxide (as the gas enters the tower at a higher temperature) followed by reaction. Improper reduction leads to the presence of unconverted chromium (VI) that imparts toxicity, not only through product basic-chromium- sulfate but also through leather and articles produced using this chemical. Design and operating conditions of the packed bed absorber were found and effects of pH, temperature and concentration of SO2 on the performance of absorption were studied. The reaction is favored at pH 4. The overall efficiency of conversion in the tower is increased from 70% to 80% by operating the column at optimal operating conditions obtained using response surface method. Dispersion is achieved by random packing that provides complex countercurrent flow path resulting in greater probability of entraining gas inside the tower. Profiles of basic chromium sulfate are obtained along the height of the tower by solving mathematical models of the reactive absorption process. Chromium (VI) is 99% reduced to chromium (III) in the product. Leached residues and liquid wastes are treated with either ferrous sulfate or sodium sulfide to convert chromium (VI) to chromium (III) to provide sustainable technology. Treated solid waste is stored before safe disposal in hazardous landfill facility. As chromium (VI) is highly toxic, several sustainable methods are suggested to eliminate it from effluent to provide cleaner and sustainable production environment in the industry.