Deep Bed Filtration Research Articles

Microscale insights into deep bed membrane filtration: Influence of internal surface roughness

Deep bed filtration is widely applied in bioprocessing, virus filtration, and water purification to remove small impurities, such as particles or virus fragments. However, more needs to be understood about the parameters that influence particle capture and deposition. Detailed simulations and microfluidic filtration experiments with straight pores have been widely investigated, yet realistic membrane porosity features such as pore gradients and roughness have not been addressed in detail. The internal membrane morphology is assumed to have a strong effect on filtration performance. Therefore, this study introduces a new microfluidic membrane mimicking device (MMD) and methodology that analyzes spatio-temporal particle collections in a deep bed filtration MMD with gradually decreasing pore size toward the retentate side. The design allows us to systematically tailor an internal filter surface roughness to investigate its influence on differently sized soft particles and the consequences for filtration performance, in particular, particle capture. Optical investigation and quantitative evaluation show enhanced particle–pillar interactions for increased roughness. This results in a reduced penetration depth and reduced particle breakthrough. The modes of capture or filtration phenomena, such as pore blocking, bridging, or dendrite formation, differ significantly between smooth and rough membrane filter structures. In the case of rough inner filter surfaces, those phenomena lead to a less distinct decrease in volumetric flow, allowing a longer filtration process. The microfluidic study offers a detailed investigation of how microscale phenomena influence the filtration process. The results provide a fundamental understanding of microscale filtration effects based on roughness and, hence, motivate a tailoring of the internal membrane filter surface according to the filtration problem at hand.

Study on the operation effect of old and new process replacement based on denitrification deep bed filters

In order to study the effect of replacing old and new processes in denitrifying deep-bed filter, the water quality data before and after equipment upgrading at the same period were collected for comparative analysis. The results show that the new process has a desirable removal rates for COD (93.67%), BOD (96.82%), NH3-N (98.04%) and SS (97.47%) throughout the year, respectively, with the effective and feasible denitrification process. The average TN concentration in effluent was 6.1mg/L after process upgrading, which decreased by 41.69% compared with the same period before process upgrading. The average removal rate was 72.5%, which was much higher than that before replacement (58.8%). In general, the denitrification deep bed filter had a great nitrogen removal efficiency.

Session 25. Oral Presentation for: Deep bed filtration and formation damage by particles with distributed properties

Session 25. Oral Presentation for: Deep bed filtration and formation damage by particles with distributed properties

Deep bed filtration and formation damage by particles with distributed properties

Current models for deep bed filtration describe particles with uniform properties. Yet, the sizes, densities, and mineral composition of particles vary significantly in the same injection well. The aim of this work is to provide an effective mathematical model for water injection of particles with distributed properties and formation damage prediction. We average the set of traditional population balance equations for single-property particles and obtain one upscaled equation. The upscaled equation for particle retention rate contains a non-linear function of suspended concentration, which we call the 'suspension function'. We derive analytical solutions for the upscaled equation for linear (coreflood) and radial (well injectivity) flows. Then we treat lab coreflood data to determine the model suspension function and provide a model for well injectivity prediction. The retention profile for the flow of uniform particles has an exponential form. Frequently reported in the literature, hyper-exponential forms have been hypothetically explained by multiple particle properties. The inverse solution allows revealing the individual filtration coefficients for binary mixtures from total breakthrough concentrations during coreflood. Treatment of the data from lab experiments reveals individual filtration coefficients that belong to common intervals. For the first time, deep bed filtration of particles with distributed properties is upscaled and presented using a single equation that reflects the particle property distribution. This equation provides an effective mathematical model for tuning lab coreflood data, determines the model function, and uses it for injectivity decline prediction.

A Method for Automatic Three-Dimensional Particle Tracing Under Laboratory Conditions Using Dynamic X-Ray Computed Microtomography

AbstractThis paper presents a method for particle tracing in laboratory X-ray micro-computed tomography (µCT) using an adjusted Random Sample Consensus (RANSAC) algorithm combined with least squares ellipse fitting (LSF). For method testing, a setup for the investigation of deep bed filtration (DBF) has been used as an example of a complex process that can be elucidated with such a method. Particle tracking with tomography systems requires high-temporal resolution which can only be achieved with synchrotron radiation computer tomography. Therefore, in this work, it has been demonstrated that instead of particle tracking, particle tracing in opaque systems such as DBF can be performed in laboratory µCT systems. To achieve particle tracing, dynamic µCT scans with a duration between 30 and 110 s combined with an exposure time of 0.13 s/projection were executed and during the scan time the filtration was performed, causing parabola shaped motion artefacts. The developed method exploits the motion artefacts created by the particle motion during the scan. It could be shown that it is possible to trace particles in complex structures within only one 30 s scan. Furthermore, through trace length and time, it is possible to determine the average velocity. Whereby, the accuracy and limits depend on the particle size, particle velocity/data rate and the X-ray attenuation of particle and medium.

Analysis of gas flow and PM movement characteristics inside diesel particulate filter channel

Based on experimental data from engine after-treatment tests, the diesel particulate filter (DPF) microscopic channel model was constructed using UG, and the accumulation of particulate matter (PM) in the deep bed filter layer and carbon deposit layer was analyzed through computational fluid dynamics (CFD). A comprehensive study was conducted on the exhaust gas flow characteristics and PM movement within the DPF channel, and focus on the effects of PM distribution type on capture and regeneration characteristics. The results show that with the increase in particle size in the exhaust, the distribution of PM concentration along the axial position of the channel shows a trend of gradually shifting from 0.2 to 0.25 m (rear section) to 0.125–0.2 m (front section). In particular, PM with 1 μm particle size has a large motion inertia, which is easy to move out of the airflow and deposit in the middle part of the channel. For PM in the front and middle sections of the channel, the airflow obstruction is relatively small, but the heat transfer loss is large, which is not beneficial for PM regeneration in the rear section. Therefore, with the distribution of LID, PD-1, and PD-2, the regeneration efficiency is relatively low, at 50.84%, 55.01%, and 54.59%, respectively.

Retention profiles of multiparticle filtration in porous media

A one‐dimensional deep bed filtration model of a polydisperse suspension or colloid in a porous medium is considered. The model includes a quasilinear system of 2n equations for concentrations of suspended and retained particles of n types. The problem is reduced to a closed 3 × 3 system for total concentrations of suspended and retained particles and of occupied rock surface area, which allows an exact solution. The exact solution to the n‐particle problem is derived, the existence and uniqueness of the solution are proven, and the solution in the form of a traveling wave is obtained. The retention profiles (dependence of the deposit concentration on the coordinate at a fixed time) of different size particles and the total profile are studied. It is shown that the profile of large particles decreases monotonically, while the profile of small particles is nonmonotonic. Conditions for the monotonicity/nonmonotonicity of the intermediate particle profiles and the total profile are obtained. The maximum point of the small particles profile tends to infinity with unlimited growth of time, and the maximum points of nonmonotonic profiles of intermediate particles are limited. The asymptotical expansion of the maximum points of nonmonotonic profiles is constructed.

Oily water treatment using particles of crushed dates seeds as a deep bed filtration material

There is a common consensus among petroleum companies that oily water produced from oil and gas wells creates a formidable challenge for humans, water, air, and soil owing to its hazardous content. Therefore, oily water treatment is an inevitable requirement in the development plans.This study reviewed the existing treatment methods for the treatment of oily water associated with oil production, emphasizing deep bed filtration. Furthermore, an experimental investigation of the suitability and efficiency of using crushed date seeds for oily water treatment was conducted. Moreover, the challenges affecting the optimal performance of treatment methods and recommendations for the future development of this technology were discussed.The results showed that the surface of crushed date seeds was highly oil-wet. As a filtration material, these seeds demonstrated almost 95% oil removal efficiency, indicating that the efficiency of crushed date seeds is comparable with that of the existing materials used in the industry, such as nutshell crushed particles. It is worth noting that date seeds are abundantly available, especially in the Arab regions, are cheap, and can be recycled as deep bed filtration media.

Deep bed filtration model for cake filtration and erosion

Deep bed filtration model for cake filtration and erosion

Pressurised sand bed filtration model: Set up and energy requirements for a filtration cycle

Rapid deep bed filtration is a common process of drip irrigation systems to prevent emitter clogging. The particle retention in the porous media increases the pressure difference between the filter's inlet and outlet. Commercial operational instructions preset a threshold value of this pressure difference to define the end of a filtration cycle. Accurate particle retention models may contribute in the determination of this setpoint to improve the energy efficiency of a filtration cycle. A two-step method was developed to calibrate a phenomenological particle retention model with transient data of the filter pressure drop, and retained mass in different media slices at the end of the filtration cycle. The first step used the vertical profile of accumulated mass in the media to fit the input parameters of the specific deposit rate equation. The second step applied the pressure data to find the input parameters of the pressure drop equation. The use of constant values of the input parameters provided reasonable results for all tests. When the end of the filtration cycle was set by applying a threshold pressure drop, both particle mass accumulation and removal efficiency decreased as the flow rate increased. By using the threshold pressure drop criterion, the energy consumption in a filtration cycle also decreased as the flow rate increased, but the energy consumption per unit of filtered water volume increased. For high setpoint pressure drop values, a minimum of the energy consumption per unit of filtered water volume as a function of the flow rate was found.

Development of an eco-friendly mobile plant for car wash wastewater recovery

The global increase in the number of vehicles has a negative impact on the sustainable development due to the increased energy consumption, noise, and air pollution, as well as the increased water consumption used for car wash. The car wash is one of the main after-sale services in the automobile sector. If car wash wastewater (CWW) could be reused, fresh water customarily used in car washing could be preserved. To achieve this goal, it is necessary to implement ?on-site? wastewater treatment systems (i.e. at car wash stations). In this research, a novel pilot plant is developed for ?on site? treatment of CWW. This pilot plant presents combined methods. It consists of three innovative modules: a multipurpose reactor (for coagulation/flotation, aeration/oxidation), deep bed filter (for filtration), and a two-stage bed coalescer (for coalescence filtration). In all these units packing materials are very light (expanded polystyrene (EPS) and polyurethane (PU)) and therefore energy consumption is significantly low. The pilot plant has a simple and light construction, so that it can be easily moved. It has shown very high COD reduction efficiency as well as removal efficiencies of suspended solids, and oil/grease, thus exhibiting high potentials for water recovery at car wash stations.

Nontarget Screening and Fate of Emerging Per- and Polyfluoroalkyl Substances in Wastewater Treatment Plants in Tianjin, China.

Wastewater treatment plants (WWTPs) are typical point sources of per- and polyfluoroalkyl substances (PFAS) released into the environment. The suspect and nontarget screening based on gas chromatography or liquid chromatography-high resolution mass spectrometry were performed on atmosphere, wastewater, and sludge samples collected from two WWTPs in Tianjin to discover emerging PFAS and their fate in this study. A total of 40 PFAS (14 neutral and 26 ionic) and 64 PFAS were identified in the atmosphere and wastewater/sludge, respectively, among which 5 short-chain perfluoroalkyl sulfonamide derivatives, 4 ionic PFAS, and 15 aqueous film-forming foam-related cationic or zwitterionic PFAS have rarely or never been reported in WWTPs in China. Active air sampling is more conducive to the enrichment of emerging PFAS, while passive sampling is inclined to leave out some ultrashort-chain PFAS or unstable transformation intermediates. Moreover, most precursors and intermediates could be enriched in the atmosphere at night, while the PFAS associated with aerosols with high water content or particles enter the atmosphere easily during the day. Although most emerging PFAS could not be eliminated efficiently in conventional treatment units, deep bed filtration and advanced oxidation processes could partly remove some emerging precursors.

Quantitative analysis of colloid retention and pore fluid flow in monolithic, open-porous media by X-ray computed microtomography and magnetic resonance velocimetry

X-ray computed microtomography (μCT) is a state-of-the-art technique for the experimental investigation of colloidal transport and retention in porous media. However, quantitative analysis of the amount of retained particles in laboratory CT scanners is problematic due to the polychromatic spectrum of the X-ray sources used, so such investigations are predominantly carried out in synchrotron based scanners. Synchrotron sources are expensive to operate and the measurement time at these facilities is severely limited, so that extensive parameter studies cannot usually take place here.In this work, we present an experimental investigation of deep bed filtration processes in a laboratory scale, conducted in porous, monolithic ceramics, including the quantification of retained particles. Experimental insights were given by an innovative combination of μCT and magnetic resonance velocimetry (MRV). Image analysis was carried using a novel approach for detection and quantification of even very low concentrated colloidal depositions, hereby correcting for beamhardening artifacts. Axial deposition profiles are presented, revealing a hyper-exponential behavior, thus indicating unfavorable attachment conditions and a transport-length dependent distribution of the filter efficiency kf. Due to the monolithic, porous media, further evaluation of colloid deposition is based on individual pore objects. It was found that not all pores contributed equally to colloid deposition, numerous pores even remained empty. It is very likely, that those pores are not well incorporated in the porous network and thus cannot be reached by fluid flow. The structural data of the porous media and colloidal depositions was correlated with 3D velocity information. It could be shown that the filter efficiency for particle retention is a function of time and axial position of the individual pore, and changes over the duration of the process. At a certain point in the filtration process, the rate of change of the volumetric particle fraction per pore becomes negative, predominantly at the media's inlet, while it remains positive throughout deeper pore layers. Thus, the rate of change is governed by a complex relocation process along the porous medium.

Prediction on Filtration Period of Granular Bed Filter Used in Purifying Produced Water in Oil Field

Summary The granular bed filter can purify the water produced in the crude oil production process by adsorbing oil droplets and suspended solids. A regeneration operation is needed to clean the granular media and recover filtration capacity after a certain operation duration. Currently, filtration models are mainly used for one type of particle removal, with few applications in the filtration system of produced water containing oil droplets and suspended solids. However, the different deposition morphologies of oil droplets and suspended solids in the filter bed can affect the prediction of the filtration process. In this work, we develop a transient filtration model based on the multiphase system transport equations coupled with the filtration rate and momentum exchange equations to predict simultaneously the effluent concentration and the pressure drop buildup, which considers the effect of deposition morphologies of oil droplets and suspended solids on filtration behaviors. The model hypothesizes that particle removal occurs through deep bed filtration mechanisms, and initial filtration coefficients are predicted by trajectory analysis without relying on experimental data. After that, we propose a method for predicting the filtration period, and analyze the effect of particle size and water temperature on the filtration process. Results show that the filtration process can be divided into two major stages—the main filtration zone migration, followed by the saturation front migration. With an S-shape increase in the effluent concentration, the pressure drop of the filter bed increases in a parabolic shape. When the diameter median of suspended solids is 5 μm, and the water temperature is 20°C, the filtration period was determined to be 24 hours to meet both water quality and maximum usable pressure drop of 20 kPa. With the increase in non-Brownian suspended solid size, the interception and gravitational forces increase the removal efficiency of suspended solids, which results in a slight decrease in the removal efficiency of oil droplets and an increase in the pressure drop of the filter bed. As the water temperature increases, the viscosity of the produced water decreases, and the oil droplets and suspended solids are more easily removed, but the pressure drop of the filter bed increases. In this work, we provide new ideas and methods to properly design, operate, and manage filters in a sustainable and energy-efficient way.

Enhanced oil-water emulsion separation through coalescence filtration utilizing milkweed fiber: a sustainable paradigm.

Over the past few years, the environment and public safety have suffered due to the detrimental effects of oily industrial effluents. Natural fibers have gained popularity for their affordability, reusability, and effectiveness in separating oil from oily wastewater. Milkweed fibers were characterized using FTIR (Fourier transform infrared spectroscopy), SEM (scanning electron microscopy), and contact angle techniques. With four porosities (0.90, 0.92, 0.95, and 0.98), deep bed coalescence filters were built at three different filter bed heights (10 mm, 20 mm, and 30 mm). Using milkweed coalescence filtering technology, a novel oil separation method is described along with a method to calculate oil film thickness following emulsified oily water saturation. By combining a bed height of 30 mm and a porosity of 0.98, a maximum oil separation of 99.73% and an optimized D50 droplet ratio were achieved. Throughout a prolonged operational period lasting 250 min, the filter bed, possessing a depth of 30 mm and a porosity of 98%, exhibited no discernible fouling indications. Following five cycles, the milkweed filter bed measuring 30 mm in depth and featuring a porosity of 98% displayed an impressive oil separation efficiency of 91.5%. This study found that using a milkweed deep bed filter, coalescence filtering effectively removes oil from oily effluent. Furthermore, milkweed is a natural and biodegradable fiber that is easy to dispose of after use and does not harm the environment.

Theoretical model and numerical simulation of high-gravity backwashing process for deep bed filter in oilfield

With the large-scale application of polymer flooding technology, the polymer concentration in produced water is increasing, which leads to incomplete regeneration of filter media by gravity field hydraulic backwashing technology only. In this study, the high-gravity backwashing technology is constructed by coupling gravity field and swirl field, which promotes the development of the oilfield. Based on the cascade theory, this paper establishes a mathematical expression of radial collision force in the high-gravity backwashing process in the vortex tube and solves a mathematical equation of high-gravity backwashing velocity gradient G based on the efficient zone of collision force action. Meanwhile, based on the discrete element method and computational fluid dynamics theory, the inter-particle collision regulation of the high-gravity backwashing process is simulated by the coupled FLUENT-EDEM method, and the high-efficiency zone of the backwashing process is verified. In this high-efficiency zone, the theoretical and simulated values of velocity gradient G for different high-gravity values match well, with differences ranging from –5.8 % to +7.1 %, indicating that the theoretical model of high-gravity backwashing is correct. When the high-gravity value is 210–240 g, the total impulse of the filter bed per unit time reaches a great value, and the backwashing velocity gradient G is 3047.1 s−1, which is much larger than the G value of combined air-water backwashing. The high-gravity backwashing technology breaks through the technical bottleneck of low efficiency in the action of the gravity field. It enriches and develops the gravity field hydraulic backwashing technology of the filter bed.

Applying deep bed filtration theory to study long-term impairment of fracture conductivity caused by reservoir fines

This paper examines conductivity/permeability impairment of hydraulically-created fractures owing to intrusion of reservoir fine particle. The blockage of fracture network by the reservoir fines will cause productivity loss. Understanding the mechanism upon which the fracture conductivity is reduced owing to intrusion of reservoir fines is essential for operation design and accurate prediction of stimulation performance in reservoirs with unconsolidated sand pockets.In this study, the deep bed filtration network model is used to study transport and distribution of the intruded reservoir particles into a propped fracture plane. The fracture plane was discretized into a series of flow bed elements/units wherein transportation and distribution of particles and capturing coefficient were determined. The bilinear flow model was adopted to explain particulate flow transport into the fracture plane from disrupted sand pockets.An experimental approach was further used to validate the model predictions. A sensitivity analysis was performed to study impacts of proppant size, production/flow rates, fluid viscosity, and the fracture length on the long-term fracture conductivity damage caused by intrusion of reservoir fines. It is anticipated that the approach presented in this paper can immensely contribute to development of a computationally viable method to study productivity impairment due to fines migration and selection of candidate wells for refracturing operation.

A sustainable water vortex-based air purification for indoor air quality

High-efficiency particulate air (HEPA) filters are widely used in air purifiers to trap particular matter. However, from an environmental and economic standpoint, HEPA filters have a low cumulative clean mass and consume many resources for replacement or disposal after use. Herein, we present a water-vortex-based air purification method. The water vortex generated by a rotating impeller can efficiently capture particular matter of any size, owing to the increased surface area and circulation of water. Furthermore, the captured particular matters settle to the bottom due to the centrifugal force, enabling the water vortex-based air purifier to maintain 90% of its air purifying performance even after trapping 7.0 g of particular matters. On the other hand, a HEPA filter decreased its performance to less than 50% after trapping 3.5 g of particular matters because the HEPA filter captures particular matters by a deep-bed filtration mechanism.

A dual-geometry pore-size-resolved model to predict deep-bed loading in a wall-flow filter

A gasoline particulate filter (GPF) is an effective wall-flow technology for gasoline engine particulate matter (PM) emission control via deep-bed filtration through porous ceramic walls within a honeycomb channel structure. An analytical filter model is desired to understand its efficiency and pressure drop under engine operating conditions and, thereby, reduce the development costs for meeting emission regulations and engine performance targets. Most existing models either oversimplify the filter geometry or do not offer good predictions in the soot loading regime. The present work treats the deep bed regime as two co-existing filters with different geometries based on their natural morphologies, one that describes the porous wall and the other for the fiber structure created by soot deposition. Both models are dynamic to account for changes in pore size distribution and soot dendrite growth during loading. Model validation by 12 sets of experimental filter loading data shows that it provides reasonable predictions of both filter efficiency and pressure drop during deep-bed loading for different GPF wall-flow filters under various operating conditions. Scanning electron microscopy (SEM) confirms model predictions for the unit collector size of the dendritic filter formed by soot deposition. Numerical simulation using GeoDict was also carried out to validate the model predictions on particle deposition location. The model is used to investigate the evolution of pore-size-resolved aerosol flow, filtration efficiency, mass loading, and particle packing density during loading. The impact of porosity, mean pore size, and pore size distribution on filter loading performance is studied. The results suggest that increasing porosity, narrowing pore size distribution, and increasing mean pore size can improve filter performance, offering pathways for future filter optimization.

A multi-scale framework for modeling transport of microplastics during sand filtration: Bridging from pore to continuum.

The fate and transport of microplastics (MPs) during deep bed filtration were investigated using combined laboratory experiments and numerical modeling. A series of column experiments were conducted within the designated ranges of six operating parameters (i.e., size of the MP and collector, seepage velocity, porosity, temperature, and ionic strength). A variance-based sensitivity analysis, the Fourier amplitude sensitivity test, was conducted to determine the priority in affecting both the attachment coefficient at the pore scale, and the subsequent stabilized height of the breakthrough curve at the continuum scale, which follows non-monotonic trends with singularity in the size of MP (i.e., 1µm). Finally, Damkohler numbers were introduced to analyze the dominant mechanisms (e.g., attachment, detachment, or straining) in the coupled hydro-chemical process. The robustness of conceptual frameworks bridges the gap between pore-scale interactions and the explicit MPs removal in the continuum scale, which could support decision-making in determining the priority of parameters to retain MPs during deep bed filtration.