Clogging Process Research Articles

Dripper clogging: emphasis on the problem and how to minimize impact

Irrigation is a useful tool to achieve a better productivity and quality foods, which contributes to a higher efficient use of agriculture land. Drip irrigation is characterized by higher application efficiency, providing an efficient control of the irrigation depth required. Moreover, it has advantages such as lower evaporation loss and higher crop yields when associated with fertigation. However, dripper clogging is pointed out by several authors as the main limiting factor for a rapid adoption of drip irrigation on a larger scale. Emitter clogging susceptibility depends basically on five parameters: water quality, filtration system, fertilizer quality, labyrinth architectural layout and maintenance procedures. The adoption of chemical treatments helps to control biological agents and precipitates, making it possible to minimize the risk of clogging. This paper aims to understand how drip clogging process occurs, providing scientific arguments and support on the development of a standardized test pattern, making progress in order to identify commercial emitters that are less susceptible to clogging under field conditions.

Clogging and maintenance evaluation of pervious concrete pavements with recycled concrete aggregate

Pervious concrete surfaces are being used more frequently these days because of their environmentally beneficial properties. These include allowing water to infiltrate into the ground and reducing the impact of urban heat island effects. Despite the benefits, these structures also present limitations. The main one comes from the process of pore clogging, reducing their drainage potential and the effectiveness of their hydraulic properties. To circumvent this problem and contribute to the dissemination of the use of pervious concrete paving, this work aims to analyze the loss of infiltration capacity over time, also analyzing cleaning and maintenance methods. Unlike other works available in the literature, the focus of this study is permeable concrete produced with recycled concrete aggregates (RCA). Therefore, periodic infiltration rate tests were performed on an experimental paving subject to the natural clogging process, and five cleaning methods were tested: high pressure water jets with subsequent vacuuming, high-pressure water jets, wetting with subsequent sweeping, sweeping followed by vacuuming, and the application of vacuuming. Through the analysis of the results obtained, it was evident that periodic cleaning is necessary to maximize life of the paving, which should start as soon as the pavement is ready. In addition, it was found that the corrective maintenance needs to be compatible with the types of particles that caused the clogging. Finally, an analytical model was used in order to predict the loss of infiltration capacity over time. This model, based on works available in the literature, allows estimating the suface's residual infiltration rate as well as predicting when the paving will reach a rate considered inadequate.

Different Irrigation Pressure and Filter on Emitter Clogging in Drip Phosphate Fertigation Systems

Irrigation pressures and filters have a significant influence on emitter clogging in drip fertigation systems. Exploring the anti-clogging performance of emitters at different irrigation pressures (80, 90, 100 kPa; 40, 50, 60 kPa) and filters (the disc filter with an aperture of 125 μm, the screen filter with an aperture of 125μm, and the screen filter with an aperture of 200 μm) can provide suitable guidance for the design and operation of drip fertigation systems. The average relative discharge (Dra), the Christiansen uniformity coefficient (CU), and the differential pressure (DP) were analyzed to study the anti-clogging performance of flat emitters (FE) and labyrinth emitters (LE). Meanwhile, the scanning electron microscope and energy dispersive spectrometer were used to observe the surface morphology and chemical composition of clogging substances in filters and emitters. Results showed that the irrigation pressure of 90 and 50 kPa did not cause a significant decrease in Dra, and the Dra of two types of emitters were all great than 95.22%. When the irrigation pressure was 80 and 40 kPa, the Dra decreased significantly (73.48–78.71%, 81.3–83.6% for FE and LE). The CU values of emitters were all greater than 90% except for the irrigation pressures of 80 and 40 kPa. The relative Dra and CU of LE were greater than those of FE, indicating that the LE had a better anti-clogging performance compared with the FE. The decrease in DP reflected an increase in the emitter clogging degree. Meanwhile, irrigation pressures and the interaction between irrigation pressures and filters imposed a significant effect on the CU at a significance level of p < 0.05, p < 0.01, respectively. The clogging process was mainly affected by physical and chemical factors, and the generated clogging substances included phosphate fertilizer, silicate, carbonate, and phosphate precipitations. In conclusion, the best operation mode of phosphate fertilizer in drip fertigation systems was to use the disc filter with an aperture of 125 μm and the LE at the irrigation pressure of 50 kPa. An appropriate irrigation pressure combined with effective filters can reduce emitter clogging while saving water and fertilizer.

Effect of interparticle dipolar interaction on pore clogging during microfiltration.

We present numerical investigations on the clogging of adhesive particles carrying electric dipoles at pore scale using an adhesive discrete element method (DEM). Based on the simulation results, the long-range dipolar interaction is reported to promote the clogging process, which is quantified by the bulk permeability, the penetrating particle number, and the particle capture efficiency. A clogging phase diagram is constructed in terms of the Stokes number (St) and the adhesion parameter (Ad) for both neutral and polarized particles. The influence of the dipolar interaction on the clogging-nonclogging transition is then described by the shifted boundary on the diagram. Also, the cake structure is characterized by different mathematical descriptions. A looser structure is formed with the increase of both the short-range adhesion and the long-range dipolar interaction. More ordered structures, such as particle chains, are observed in the presence of the stronger dipolar interaction. Furthermore, fluid stress is found to be essential in the compression and restructuring of the cake structure. Finally, a schematic representation of the cake structure is established, which provides a general physical picture showing the relationship between the cake structure and the particle-scale interactions.

Impact of biological clogging and pretreatments on the operation of soil aquifer treatments for wastewater reclamation

Globally, sustainable water management is required to minimize water security, and soil aquifer treatments (SATs) are widely applied in wastewater reclamation. Clogging problems limit the sustainable operation of SATs (i.e., the decrease of infiltration rate), and Physical clogging has been widely studied. However, the effect of biological clogging on the operation of SATs is still unclear. Thus, this study focuses on the effects of biological clogging in an SAT system and demonstrates that the clogging process in an SAT column. In this study, the infiltration rate in the A2O ​+ ​NaN3 water column decreased slightly, to 6–7 ​cm/h with an average rate of 0.01 ​cm/h per month after 240 ​d, compared with an average rate of 0.3 ​cm/h per month in the columns fed by filtered A2O water. The fastest reduction in infiltration rate, caused by biological clogging, occurred in the first 60 ​d and corresponded to the highest reduction in hydraulic conductivity of 0–2.5 ​cm layer. For alleviating clogging, this study illustrated that removing suspended solids from A2O water by filtration helped reduce approximately 25% of polysaccharides and heterotrophic bacteria. In comparison, pre-ozonation of A2O water helped to reduce approximately 70% of the biomass in the surface layer of the A2O ​+ ​O3 column. Thus, ozonation of wastewater effluent helps control biological clogging in SAT.

Exploring the clogging process in coarse soil deposits in a dam foundation

Exploring the clogging process in coarse soil deposits in a dam foundation

Evolution of water migration in porous asphalt due to clogging

Porous asphalt is a commonly used material for permeable pavement. However, porous asphalt will inevitably result in void structure clogging and affect its drainage function in the road service period. Most studies focus on macroscopic permeability but ignore microscopic seepage behavior in void structure, which is unfavorable for the understanding of the change in the permeability of porous asphalt. In this study, we described the microscopic water migration of the porous asphalt with the seepage depth, seepage velocity, and seepage path, and clarified the void structure evolution and the water migration characteristics variation during the clogging. On this basis, we explored the impact of the size of clogging particles and the void content of porous asphalt on the variation of water migration. The data demonstrate that water migrates and branches along the void structure of porous asphalt under the action of inertia force. The deposition of clogging particles in the void hinder the migration of water and restrict the water distributary. However, the clogging process does not affect the dominant effect of inertia force on water migration. Water migration is more impeded by small particles due to their more significant water absorption effect. The increased void content of porous asphalt can reduce the effect of clogging on the void structure. This research can help us understand the evolution of water migration characteristics at a micro-level.

Discharge Flow of Spherical Particles from a Cylindrical Bin: Experiment and DEM Simulations

A series of the DEM simulations of the outflow of wooden spheres from a flat-bottomed container was reported, considering the maximum diameter to arrest the flow. Numerical simulations of the discharge process were performed, and the micro-mechanics of the discharged particles were described. The effect of the sliding friction coefficient between particles, rolling friction coefficient, and modulus of elasticity of particles on the clogging process was investigated. The results of the simulations of the mass flow rate of spheres have shown a fairly close agreement with the experimental results. The real particles of wood were not perfectly spherical, their properties were anisotropic, and their frictional properties were non-homogenously distributed on the surface. Nevertheless, these deviations from ideal conditions did not produce a considerable discrepancy in the results. No direct relationship between the interparticle friction and the clogging was found; however, a relationship between the stability of the dome formed at flow arrest and the rolling friction was observed. An increase in Young’s modulus of particles by two orders of magnitude did not affect the clogging process, but a slightly higher probability of clogging was found for softer particles.

Enzymatic analysis in bank filtration sites as a tool for assessing biological clogging — A column study

Bank filtration (BF) for water treatment presents a limited efficiency due to clogging. This columns study ran for 34 days and was intended to evaluate biological clogging by using homogeneous and poorly graded filter material and different grain sizes. In parallel, filtered water quality and hydraulic parameters were monitored daily to show the clogging process's effect on these parameters. PVC columns were filled with fine sand (d10 = 0.16 mm), medium sand (d10 = 0.44 mm) and coarse sand (d10 = 1.33 mm). Fluorescein diacetate (FDA) and triphenyltetrazolium chloride (TTC) were used to estimate microbiological activity in the filter media, and their results were compared to organic matter content and dissolved oxygen concentration. It was observed a greater hydraulic conductivity (K10) reduction of 98% and greater content of fluorescein (10.68 μg·g−1), dehydrogenase (1.86 μg·g−1·h−1), and organic matter (0.13%) in the first 5 cm of the filter media by using fine sand as filter material, followed by medium and coarse sand. Fluorescein and dehydrogenase accumulated concentrations were greater at coarse sand (4.80 μg·g−1 and 1.075 μg·g−1·h−1, respectively), followed by medium and fine sand. Homogeneous filter media with higher specific porosity favors the presence and distribution of organic fractions and enzymatic activity at greater depths. Enzymatic activity seems to be limited by nutrient availability and dissolved oxygen concentration. Biological clogging seems to be influenced by factors such as grain size distribution and hydrodynamic effects. FDA and TTC showed to be an interesting tool for biological clogging monitoring at bank filtration sites.

Dual-model experiment uncovers self-organized criticality in porous clogging process

Numerical models simulate random and flux-based clogging processes, resulting in channelization criticality.

Injection related issues of a doublet system in a sandstone aquifer - A generalized concept to understand and avoid problem sources in geothermal systems

This study proposes a concept and presents a workflow to examine potential reasons for low injectivity of sandstone aquifers. Injection related problems are a major challenge for the sustainable utilization of geothermal waters. In order to completely understand and avoid the geothermal reinjection problems, potential problem sources acting on different scales should be taken into consideration. Thus, in the workflow, possible problem sources are considered on regional, reservoir and local scale and categorized into 1) effect of regional hydraulics (potential presence of overpressure and upward flow) 2) inadequate reservoir performance (limited extent, low permeability and performance) and 3) local clogging processes (particle migration, mineral precipitation, microbial activity). Hydraulic conditions are characterized by defining the pressure regime and the direction of vertical driving forces. The reservoir properties are given by determining the grain size and the size of the reservoir layers, as well as the permeability and the transmissivity of the reservoir and the capacity of the injector. Physical, chemical, and biological clogging processes are investigated by specifying the rock properties and determining particle content of the fluid; by analysing the type, probability and amount of the scaling and estimating the potential for corrosion; and by evaluating the possibility of biofilm formation. The concept and the workflow were first tested on a geothermal site (Mezőberény, SE Hungary, installed in 2012) that had to stop operation because of unsuccessful reinjection. The low injectivity of the well is a consequence of several separate problems and their interaction: Reservoir properties are insufficient due to low permeability and transmissivity of the reservoir and the limited vertical and horizontal extension of the sandstone bodies. Precipitation of carbonates, iron and manganese minerals is predicted in hydrogeochemical models and observed in solid phase analysis. Microbial material is produced from the particularly high organic content of the produced thermal water. Injection problems due to hydraulic effects are not expected since the regional pressure regime is slightly subhydrostatic. In summary, reservoir properties determine a low injectivity, which is further decreased to a critical level by the clogging processes. The proposed generalized concept guides a detailed reservoir and geothermal system analysis which is essential for a sustainable geothermal operation.

The critical behavior of the clogging process in a porous medium

Flows through porous media can carry suspended and dissolved materials. These sediments may deposit inside the pore-space and alter its geometry. In turn, the changing pore structure modifies the preferential flow paths, resulting in a strong coupling between structural modifications and transport characteristics. Here, we compare two different models that lead to channel obstruction as a result of subsequent deposition. The first model randomly obstructs pore-throats across the porous medium, while the second model always blocks the pore-throat with the highest flow rate. By subsequently closing pores, we find that the breakdown of the permeability follows a power-law scaling, whose exponent depends on the obstruction model. The pressure jumps that occur during the obstruction process follow a universal power-law distribution with the same scaling exponent as the avalanche size distribution of invasion percolation. The fact that this exponent is also independent of the model suggests that the clogging processes and invasion percolation may belong to the same universality class.

Numerical simulation and industrial application of nozzle clogging in bilateral-port nozzle

In this study, an inclusion deposition model was used to simulate the nozzle clogging process in industrial casting. The concepts of inclusion parcel and inclusion magnification factor were introduced in the model, which could be applied to an industrial-scale nozzle clogging simulation. The simulation results were verified using the results from the industry study. The results show that nozzle clogs were formed with Al-O and Al-O-Ce inclusions of diameter 5–10 μm. The nozzle clog formed initially at the nozzle bottom and was deposited on the nozzle wall during the casting process. The volume fraction of the nozzle clog in the nozzle was 52.26% at the end of the casting process. The velocity magnitude in the nozzle increased during casting. The 5 μm Al-O and Al-O-Ce inclusions cause more deposition. The number of the deposited Al-O and Al-O-Ce inclusions were similar.

The contribution of colloidal aggregates to the clogging dynamics at the pore scale

During the filtration of colloidal dispersions by a membrane, pores often get clogged by the suspended particles. Knowing the shape and size of the particles that cause this clog would be a great help to membrane users since they could then choose the ideal filtering device. Microfluidic technology enables the fabrication of model membranes or filters that are transparent, which allows for measuring the particle geometrical features that deposit either at the surface of the pores or on top of the fouling layer that has already formed. However, the use of microfluidic filters have been confined to the study of clog formation at the pore scale, overlooking the influence of the dynamics of the particle deposition on the clogging process. We have recently shown that looking precisely at what is deposited and how this is captured inside the pore provides new insight into the clogging process. In particular, we have found that a minute concentration of aggregates in a supposedly monodisperse dispersions are mainly responsible for pore fouling. In this paper, we use the same imaging technique to determine the entire clogging process for different types of monodisperses dispersions under various flow conditions, DLVO interactions with the pore walls, and confinements. We show that the way clogs form is appear complex but is also quite systematic in the fact that aggregates are the building blocks of the clog. Pores are clogged by progressive accumulation of aggregates with the average size of the aggregate required to cause the blockage increasing with increasing flow velocity. This work demonstrates that particle size and shape distributions of the feeding dispersion must be determined to understand which physical mechanisms are at play during the clogging process.

Structure characterization of the clogging process of coarse fibrous filter media during solid particle loading with X-ray micro-computed tomography

Fibrous nonwoven filters are widely used in various air filtration applications. Coarse filters are typically used to protect and extend the lifetime of high-efficiency filters. However, unlike high-efficiency filters, limited work had been carried out to study the evolution of filtration properties and filter structures during the clogging process of coarse fibrous filters due to the lack of non-invasive and non-destructive structural characterization techniques. In this study, a coarse nonwoven filter media with a 94.52% mean porosity value was fabricated. The filtration properties of the studied coarse filter, including pressure drop and filtration efficiency, were found to increase along with the particle loading. The X-ray micro-computed tomography (XMCT) was used to non-invasively characterize the 3D structures of clean and particle-loaded fibrous nonwoven coarse filters at different clogging stages. Although the surface area scanned by XMCT (research of interest, 600*600 µm2) was a tiny spot on the whole filter media, this surface area exhibited good representativeness of the average structural properties of the whole filter media, e.g., porosity in this study. Depth profiles of local porosity and particle solidity across the full thickness of filter XMCT image indicated that at the beginning of particle loading stages, particles were captured and trapped by the top part of filter thickness, which was corresponded to the reported clogging process of high-efficiency filters. Then particles could be found across the full filter thickness. However, during the transitioning from the depth filtration stage to the surface filtration stage, clogging with high particle solidity was found in the bottom part of filter thickness. As more particles were loaded, clogging was found in both the middle and bottom parts. After that, the top part would be clogged, and the surface cake would start forming thereafter. This is the first report of the clogging process of the fibrous nonwoven coarse filter. Pore diameter distribution derived from the pore skeleton network via skeletonization of the 3D particle-loaded filter structures also described the same structure evolution during dust loading.

Clogging Model for Coarse and Fine Filtering Cloths of Filtering Cylindrical Elements, Preventing Sedimentation of Mechanical Impurities in Their Gap

In this paper we propose a method for preventing sedimentation of solid particles in the lower part of the gap between filtering cylindrical elements of coarse and fine purification by increasing the size of the meshes and total thickness of the first downstream gas flow layers of the fine filtering element in excess of the maximum diameter of solid particles. Experimental corroboration for the proposed method showed absence of solid particles’ sedimentation in the lower part of the gap between filtering cylindrical elements of coarse and fine purification and clogging of their meshes. As a result of the experiments, we found that the maximum sedimentation of mechanical impurities inside the first screens of the fine filtering cloth is achieved when their meshes’ size and screens’ thickness are, respectively, equal to three and two and a half maximum diameters of a solid particle. We developed a mathematical model that describes the clogging dynamics of filtering elements, where pressure losses in the first section with constant mesh sizes of all screens and in the second section with a sequential decrease in mesh sizes have different clogging rates and therefore are calculated separately from each other. The clogging process at each section of the multilayer filter cloth is represented as a successive decrease in the effective screening area of the screen meshes. The mathematical model makes it possible to prevent the sedimentation of mechanical impurities in the gap between gas filter elements of coarse and fine purification and allows to analytically determine the clogging degree at any time of operation, depending on the pressure losses’ values.

Convective Stability of a Net Mass Flow Through a Horizontal Porous Layer with Immobilization and Clogging

Solutal convection in a horizontal layer filled with porous media with horizontal seepage of a mixture is investigated considering the solute immobilization and clogging. A flow through porous media is modelled within the standard Darcy–Boussinesq model, and the immobilization process is described by the mobile/immobile media (MIM) approach. To describe the clogging process, the present model takes into account and the dependence of media permeability on porosity within the Carman–Kozeny equation. The presence of immobile (or adsorbed) particles of the solute decreases the porosity of media, and porous media become less permeable. The variation of porosity is modelled by a linear function of solute concentration in the immobile phase. We consider the case of high solute concentrations, in which the immobilization is described by the nonlinear MIM (mobile/immobile media) model. As a result, it was shown that the immobilization leads to the stabilization of the homogeneous filtration regime and to slowing down of the perturbation dynamics. The stability maps were plotted in a wide range of system parameters. The results showed that for some specific value of clean media porosity the system becomes most unstable and dynamics of perturbations (frequency of oscillations) is most intensive. This value corresponds to the minimal effect of porosity change to variation of permeability due to the immobilization.

Pore-Scale Simulations of Particles Migration and Deposition in Porous Media Using LBM-DEM Coupling Method

This paper studies the migration and deposition of suspended particles in porous media. This problem results from the fact that during the operation of a groundwater source heat pump, the recharging process will contribute to the impairment of soil permeability. A coupling lattice Boltzmann method, discrete element method and immersed moving boundary method were used to investigate the migration of particles in porous media. The DKT (Drifting, Kissing, Tumbling) phenomena were employed to validate our program. The coupled effects of concentration, flow rate and pH on the clogging mechanism of the porous media were analyzed. Results show that, due to the repulsive barrier between the particles and porous media, there is a critical velocity. At a low flow rate, the deposition ratio increases with the increase in velocity. Beyond the critical velocity, the deposition ratio decreases when the velocity increases due to higher shear force. Permeability impairment increases with the increase in concentration, especially in the low flow rate condition. Changes in pH mainly affect the repulsive barrier. For a low flow rate, the decrease in repulsive barrier greatly promotes the deposition of particles. Under the condition of favorable deposition, the increase in flow rate reduces the deposition phenomenon. Under the condition of unfavorable deposition, the lower flow rate condition has a lower deposition ratio. The process of particle deposition and the dynamic motion after deposition were observed such as particles gliding over the surface. Accumulated particles in the downstream form bridges and hinder fluid flow. At a high flow rate, strong shear force is more capable of destroying bridges and recovering permeability. Adsorbed particles glide on the surface of the grain and deposit in the downstream. This paper aims to help understanding of the micro-events of particle deposition and the clogging process.

Effects of chemical precipitation on the permeability of geotextile envelopes for subsurface drainage systems in arid areas

This paper focuses on the effects of chemical precipitation on the permeability of geotextile envelopes for a subsurface drainage system in arid areas by conducting precipitation experiments of the geotextile in static or flowing solution. The results show that the precipitation process is not significantly promoted or inhibited by the network structure of geotextile. The precipitates in the form of rhombus wrap around the fiber surface. The number of geotextile pores with the smaller diameters decreases significantly after precipitation experiments. As the increase of the area density of precipitates (ΔR), the variation of the pore area (ΔS) and the variation of permeability coefficient (ΔK) of the geotextile decrease rapidly at first and then slowly. The ΔK and ΔS VS ΔR data were best fitted with logarithmic trend line. This study provides a preliminary reference for quantifying the chemical clogging process of geotextile envelopes in arid areas.

Solutal convection in a horizontal porous layer with clogging at a high solute concentration

The authors study the transport of solute particles in a horizontal layer of a porous medium taking into account the clogging process for a wide range of solute concentrations. On the basis of the most popular and experimentally confirmed MIM model with saturation of the immobile phase, a closed equation system describing such transport is derived. The concentration dependence of porosity is described within the Kozeny-Carman model. The criteria for the transition to the popular model of weak clogging, when the solute concentration is significantly lower than the porosity of the medium, are considered. It is shown that the basic state for the model does not correspond to the classical linear distribution of mobile solute. The convective instability of horizontal seepage with respect to two dimensional perturbations is studied. The critical curves in the space of problem parameters are obtained.