Clogging Phenomena Research Articles

Clogging of Leachate Drains in Landfills due to Biochemical Precipitation: a Literature Review

Objective: Review the relevant literature and analyze the causes that lead to the clogging of leachate drains in landfills due to biochemical precipitation. Theoretical Framework: Although leachate drainage systems have greatly evolved in terms of performance, clogging can occur in all designs due to physical, biological, and chemical mechanisms. Method: To investigate the issue of clogging in leachate drainage systems, an extensive literature review was conducted through consultations on relevant websites. National and international technical papers were sought, as well as regulations from environmental agencies of different countries. Results and Discussion: The removal of Chemical Oxygen Demand (COD), primarily in the form of acetic acid, transforms this stronger acid into weaker acids such as carbonic acid, which results in an increase in the pH of the environment. The concentration of carbonate also increases, consequently accelerating the precipitation of calcium carbonate. These precipitates are usually mixed with the biofilm and exhibit very characteristic shapes and structures. Research Implications: The lifespan of a vertical landfill can be strongly determined by the clogging phenomena in the leachate drainage system. Therefore, the monitoring of this system must be carried out with great care. Originality/Value: This review stands out for addressing a relevant and underexplored topic, especially in the national technical literature. Understanding the processes that can lead to clogging of the leachate drainage system is of interest to everyone working in the field, particularly those who design and/or operate a landfill.

Stratified structure of membrane clogs observed in full scale cross-flow tubular ultrafiltration (UF) system: Fouling characterization and a proposed two-stage formation mechanism

Membrane fouling remains a significant challenge in wastewater treatment, hindering both efficiency and lifespan. This study reports a distinct phenomenon of stratified membrane clogging observed in a full-scale cross-flow tubular ultrafiltration (UF) system treating sludge anaerobic digestion (AD) reject water. The distinct stratified structure, comprising inner and outer layers within the cake layer, has not been previously described. This research involved characterizing the filtration performance, analyzing membrane clog composition, and proposing a two-stage formation mechanism for the stratified clogs. It was revealed that higher inorganic and lower organic content in the outer layer compared to the inner layer. Acid and alkali treatments demonstrated the effectiveness of combined cleaning strategies. A mathematical model was developed to determine the critical conditions for stratified clog formation, influenced by membrane flux and cross-flow velocity (CFV). It is proposed that outer layer forms through long-term selective deposition, while the inner layer results from short-term dewatering within limited tubular space. High CFV (>2.5 m/s) prevents inner layer formation. Critical conditions for stratification occur at a flux of 18 L/m2/h with a CFV of 0.1 m/s or 65 L/m2/h with a CFV of 0.35 m/s. This study contributes a novel understanding of stratified membrane clogging, proposing a two-stage formation mechanism and identifying critical conditions, which provides insights for effective fouling control strategies and maintenance of operational efficiency for membrane systems.

A Strategic NH3-Dosing Approach for the Minimization of N2O Production During NH3-SCR Reactions over Cu-SSZ-13 Catalysts

The undesired production of N2O during NH3-SCR reactions is investigated over a reference commercial Cu-CHA catalyst. Steady-state experiments performed in the 150–500 °C temperature range exhibit a bimodal trend in the N2O formation profile, confirming the existence of two different reaction mechanisms occurring at low and high temperatures. Focusing on a low-to-medium T-range, N2O production, usually ascribed to NH4NO3 formation and decomposition, increases with the NO2/NOx ratio. However, an excess of NO2 leads to a decrease in the N2O release due to ammonium nitrate deposition and catalyst clogging phenomena. Steady-state and dynamics experiments show the promoting effect of both NH3 feed concentration and NH3 storage on N2O production at T > 200 °C. Surprisingly, N2O decreases with increasing NH3/NOx ratio at lower temperature. A novel approach based on the strategic injection of NH3 is also applied to mitigate the N2O formation while maintaining high deNOx activity. Remarkably, complete NOx conversion and ~ 11% N2O saving are achieved (with inlet NO2/NOx = 0–0.5) at temperatures exceeding 200 °C; in addition, a peculiar behavior is observed in the N2O profile, which increases and decreases when adding and removing NH3 from the feed, respectively. Notably, the opposite trend is observed in the N2O profile at 200 °C. When under Standard SCR conditions, this so far unreported observation challenges the NH4NO3 formation route for N2O and suggests the existence of different controlling phenomena at different temperature regimes: i) the Cu/redox chemistry at T ≤ 200 °C and ii) the NH3 storage at higher temperature, ideally up to 300 °C.

Determination of fan height based on FDM nozzle temperature field analysis—an example of babbitt alloys

In this paper, the phenomenon of nozzle clogging or drooling droplets in the process of FDM metal 3D printing of tin-based Babbitt alloys was evaluated by simulation to assess the effects of different heights of cooling fans on the printer’s nozzle cooling module, and the optimal height of the fans was determined. Based on the thermal analysis results, a thermodynamic coupling analysis was carried out to analyze the thermodynamic changes of the nozzle at a given temperature. Finally, the printing trials of tin-based Babbitt alloy were carried out using self-developed forming equipment to verify the accuracy of the theory. The results show that the print quality can be effectively improved by controlling the heat dissipation module of the printer nozzle. The printed material exhibited a uniform and fine microstructure in the 3D printing trials of tin-based Babbitt alloy.

Influence of coarse aggregate granulometry on clogging in pervious concrete

The phenomenon of clogging in pervious concrete (PC) has been one of the main causes of the hydraulic useful life reduction. This phenomenon begins with the partial or total clogging of the pore network and consequently the reduction of the permeability coefficient. Considering that the porous network of the PC is directly related to the aggregate used, the present work aims to evaluate the influence of granulometry on the clogging of the PC. The results showed that the largest aggregate size (D_max=19 mm) favors the hydraulic properties of the material. However, the variation of the granulometry grading distribution (poorly graded and single-sized) does not generate a significant difference in such results. In terms of clogging, there was a marked effect on the type of the granulometry grading distribution, the use of poorly graded aggregates led to a lower permeability reduction due to clogging when compared to PCs with single-sized aggregates.

Щодо надійності технологічного процесу подрібнення пожнивних решток

The article is devoted to finding ways to solve the problem of increasing the reliability of the technological process of shredding crop residues using shredding rollers with operating parts in the form of knife drums. The research presents a review and analysis of existing types of machines for shredding crop residues equipped with driven and non-driven active operating parts with their advantages and disadvantages. The ways and methods that should be considered when solving problems of improving the quality of grinding and reliability of this technological process are formulated. The article presents the content and methods of conducting experimental field studies of the process of shredding crop residues by a drum with knives installed on its surface at a certain angle of deflection between adjacent rows and with a shift of the line of row blades relative to the axis of the drum itself. It is proved that at certain values of these parameters, it is possible to achieve a significant increase in the reliability of the technological process, to virtually eliminate the negative phenomenon of clogging of the inter-row space with particles of plant stems and soil. The rational values of the angles of the knives on the surface of the chopping drum, substantiated in this work, allow increasing the intensity of chopping crop residues as a result of reducing the distance between the rows of knives. Thus, the approximate length of the particles of chopped plant stems can be reduced from 21.4 cm to 17.4 cm, without negative consequences for the reliability of the technological process.

A novel water content sensor design and its application for in-situ water content measurement inside the flow channel of PEMFC

In-situ water content detection in proton exchange fuel cell (PEMFC) is of great importance to its water management. In this study, flexible thin film water content microsensor (WCMS) were fabricated and deployed for real-time measurement of water distribution inside the channel of proton exchange membrane fuel cells. The effect of inserting WCMS on the cell performance was confirmed to be negligible. Besides, three WCMS were used to monitor the variation of water distribution in the upstream, midstream, and downstream of the flow channel, respectively. The experimental results show that the WCMS can efficiently detect the change of water content inside the fuel cell in real time. The co-occurrence phenomenon of water column clogging in the flow channel and degradation of cell performance were observed. This work provides a novel design of WCMS and its application on the water content distribution inside flow channel of fuel cells.

Clogging phenomenon in Pervious Concrete (PC): A systematic literature review

Pervious concrete (PC) has gained important ground in civil construction in recent years due to its advantages in managing surface runoff. Numerous studies have been developed to characterize the material mechanically and hydraulically and verify compliance with standards. However, there are still some gaps in the knowledge about the hydraulic behavior of PC over time and how its properties vary with the materials that may accumulate in the internal pores. This last phenomenon is known as clogging and is one of the main factors to cause the loss of hydraulic serviceability of this material. This hinders its diffusion around the world since the process of this phenomenon is neither completely known nor contemplated in the standards. Therefore, considering these gaps in knowledge, this review intends to clarify the most important aspects of the phenomenon of clogging and contribute to the knowledge of the mechanism of permeability decrease of the material. Moreover, this paper seeks to identify which variables influence permeability variation over time and to present the models proposed to predict permeability degradation in PC, as well as some maintenance methodologies to permeability recovery. • Porosity change during clogging is essential for the prediction of PC permeability. • Clogging is related to obstruction of the pores and loss of permeability. • The slow clogging rate is the most damaging for the hydraulic performance. • Clogging models are viable to predict the degradation of hydraulic performance. • The permeability recovery is linked to the type of cleaning method implemented.

Influence of the number of levels and system age on greywater treatment in a green wall

The use of green walls for greywater treatment represents a great opportunity to reduce potable water consumption and achieve multiple benefits. This study aims to analyse the efficiency of a pilot scale open-air green wall and evaluate its durability over time. The green wall consists of two modular panels (P1 set up in 2020, and P2 in 2018), each including nine pots organised in three independent columns. Coconut coir (80%) and perlite (20%) were used as filter media for three ornamental plant species (Carex morrowi, Hedera helix, Lonicera nitida). Each column was individually fed in batch mode with 24 Lday−1 (hydraulic loading rate - HLR 740.8 Lm−2 day−1) of greywater from January to March 2021. 190 water samples were analysed for 13 physical-chemical parameters. Both panels exhibited very good removal efficiencies for TSS (P1: 97.4 ± 4.6%, P2: 89.1 ± 13.8%), BOD5 (P1: 98.8 ± 2.4%, P2: 94.5 ± 9.2%), COD (P1: 78.5 ± 5.2%, P2: 80.1 ± 4.2%), TN (P1: 49.2 ± 30.4%, P2: 48.0 ± 23.31%), MBAS (P1: 92.7 ± 3.8%, P2: 75.3 ± 8.0%). P1 reached satisfying pollutants removal after two levels, while P2 showed higher variability and frequent clogging phenomena, needing three levels (e.g., cumulative BOD5 removal along the three levels in P1: 45.2 ± 36.2% | 86.5 ± 14.8% | 98.8 ± 2.4%; in P2: 16.5 ± 20.8% | 51.8 ± 32.3% | 94.5 ± 9.2%). This highlighted that the third level of P2 was necessary to guarantee good performances after over 2 years of operation. This study confirmed that green walls have high potential in greywater treatment also in challenging conditions (i.e. winter climate, high HLR and operating times), opening to further studies devoted to extending their lifetime.

Д.Г. Віленський — відомий український ґрунтознавець і геоботанік, організатор галузевого науково-освітнього процесу

Goal. To reveal the main milestones of the life and creative path, to summarize the most important scientific achievements of the talented agricultural scientist, one of the organizers of higher branch education and research in the Ukrainian SSR D.G. Vilenskyi. Methods. General scientific — analysis, synthesis, classification; historical — problem-chronological, comparative-historical, retrospective, biographical. Results. It is proved that D.G. Vilenskyi contributed to the establishment of leading institutions of higher agricultural education — Kharkiv Agricultural Institute named after H.G. Rakovsky and Kyiv Engineering and Reclamation Institute. He published the first textbook in the Ukrainian SSR «Botany» (1928) in the state language for higher and secondary educational institutions and the first textbook «History of soil science in Russia» (1958). On the initiative of the scientist, a large-scale interuniversity work was started — the natural zoning of the territory of the USSR for agriculture. It was established that D.G. Vilenskyi made efforts to organize the All-Ukrainian Research Institute of Agro-Soil Science and Chemical Agriculture, as well as the Ukrainian Institute of Applied Botany. For his great achievements in the field of soil science, he was elected president of the International Commission for Classification of Geography and Soil Mapping. Conclusions. The most significant scientific assets of D.G. Vilenskyi is the establishment of the phenomenon of clogging, the development of new indices of genetic horizons of soils — H, E, I, R, etc., preparation of the first soil maps of Ukraine, pioneering geobotanical studies of reclaimed drained soils, authorship of soil maps of the USA, Canada, individual regions and districts of the USSR, development of methods of soil research and large-scale soil mapping. It was established that D.G. Vilenskyi contributed to the popularization of the achievements of domestic science as a member of the editorial board (1930–1949), and editor (1934–1939) of the journal «Soil Science».

Carbon emissions, techno-economic and machinability assessments to achieve sustainability in drilling Ti6Al4V ELI for medical industry applications

In the last decade, cryogenic machining has made a significant impact as a sustainable machining technique, demonstrating machinability improvements in terms of tool life, surface quality of machine parts, low environmental effects and reduced cost of overall machining operation. A near-to-dry machining technique, Electrostatic Minimum Quantity Lubrication (EMQL) has also emerged as a sustainable machining technique, which is an environmentally-friendly alternative to the flood machining process. Although these coolant/lubrication strategies have been studied extensively, there is no direct comparison of both these machining techniques in the aspects of ecology, economy and machining performances. In this novel study, cryogenic liquid carbon dioxide (LCO2) and EMQL techniques are used for high-speed drilling of Ti6Al4V ELI (extra low interstitial) grade, and the sustainability and machinability assessment of these techniques are evaluated which can help medical implant manufacturing industries to implement these techniques as an economic and sustainable replacement of the conventional cooling/lubrication techniques. Ti6Al4V ELI is widely used in the medical industry for Hip and Knee joint endoprosthesis, bone screws, collar bone and dental implants. The sustainability aspects were evaluated in terms of carbon emission and cost analysis of the processes. It was found that the EMQL cutting condition exhibited 27.69% higher carbon emission and 67.60% higher cost of machining operation compared to cryogenic LCO2 cutting condition. Moreover, the tool life experienced when machining using cryogenic LCO2 cutting condition was at least 4 times higher than tool life found when using the EMQL cutting condition. The surface roughness of the workpiece material was higher (56.40%) when using the EMQL coolant. These results were attributed to adhesion wear and chip clogging phenomena which were found to be the main factors for reduced tool life and higher surface roughness in EMQL cutting condition. Therefore, from this study, it can be concluded that cryogenic LCO2 coolant performs significantly better compared to EMQL coolant, providing improved machinability of the titanium workpiece and superior sustainability of the cutting operation.

Direct optical observation of DNA clogging motions near controlled dielectric breakdown silicon nitride nanopores

With the advantages of simple equipment and in-situ preparation of nanopores, the CBD method has been widely concerned by researchers. In this work, a fluorescence platform was set up to directly observe the λ-DNA motions near the CBD prepared different kinds of SiNx nanopores. At first, for the one nanopore film, the λ-DNA post-translocation motion was observed. Then, for the multiple nanopores film, the current modulation phenomena of each nanopore after the DNA clogged the pores was observed. When the distance of asymmetric pores is less than the length of λ-DNA, the larger nanopores are easy to be blocked preferentially by considering the tug-of-war on λ-DNA; when the asymmetric porous distance is larger than the DNA two polymer length, due to the forming a folded structure, the smaller nanopores are preferentially blocked. These results reveal that the clogging phenomena during the DNA translocation analysis for the nanopores are varied, and it should be considered for CBD-prepared nanopores.

Influence of interfacial tension, temperature and recirculating time on the 3D properties of ice particles in jet A-1 fuel

Icing in aircraft fuel systems remains a serious issue for aviation safety and security. It is linked to the geometrical properties of the ice particles formed in situ, which are themselves highly sensitive to the operating parameters of the fuel system. In this work, an experimental campaign was conducted with a fuel-icing bench to explore the impact of the interfacial tension (γ), the sampling temperature (θ) as well as the recirculation time of the particles in the injection loop (τ). For this purpose, a new sampling method has been defined, tested and validated, using paraffin oil (PO) as an impregnation product for ice particles. The specimens were prepared, set up in a cryogenic cell and then scanned using X-ray Micro-Computed Tomography (μCT). Image processing and analyses allowed computation of the 3D properties at 5 μm resolution. The impregnation with PO revealed satisfying results in terms of physical separation of ice particles (more than 66%), especially for the smallest ones (⩽200 μm), thus limiting the sintering phenomenon over time. The decrease in γ values showed a slight tendency to form smaller particle size distributions widths (PSDw). The observed influence of θ was minor due to its interference with τ, which proved to have the strongest effect on particle size and morphology. Thus, the increase in τ promoted the formation of smaller PSDw with modes ~ 100 μm. The elongation (Ee) and flatness (Ef) form factors showed significant tendencies (⩾40%) towards rounded and spherical shapes for all ice specimens. The mean curvature distributions showed a trend towards convexities either by decreasing γ or increasing τ values. This study illustrates the complex impact of process parameters on the geometric properties of ice particles in jet fuel. The obtained results may be useful for further testing of filter clogging phenomena or numerical simulation and modeling studies.

Dynamics of DNA Clogging in Hafnium Oxide Nanopores.

Interfacing solid-state nanopores with biological systems has been exploited as a versatile analytical platform for analysis of individual biomolecules. Although clogging of solid-state nanopores due to nonspecific interactions between analytes and pore walls poses a persistent challenge in attaining the anticipated sensing efficacy, insufficient studies focus on elucidating the clogging dynamics. Herein, we investigate the DNA clogging behavior by passing double-stranded (ds) DNA molecules of different lengths through hafnium oxide(HfO2)-coated silicon (Si) nanopore arrays, at different bias voltages and electrolyte pH values. Employing stable and photoluminescent-free HfO2/Si nanopore arrays permits a parallelized visualization of DNA clogging with confocal fluorescence microscopy. We find that the probability of pore clogging increases with both DNA length and bias voltage. Two types of clogging are discerned: persistent and temporary. In the time-resolved analysis, temporary clogging events exhibit a shorter lifetime at higher bias voltage. Furthermore, we show that the surface charge density has a prominent effect on the clogging probability because of electrostatic attraction between the dsDNA and the HfO2 pore walls. An analytical model based on examining the energy landscape along the DNA translocation trajectory is developed to qualitatively evaluate the DNA–pore interaction. Both experimental and theoretical results indicate that the occurrence of clogging is strongly dependent on the configuration of translocating DNA molecules and the electrostatic interaction between DNA and charged pore surface. These findings provide a detailed account of the DNA clogging phenomenon and are of practical interest for DNA sensing based on solid-state nanopores.

Optimization of grading guard systems for trapping of particulates to prevent pressure drop buildup in gas oil hydrotreater

A new approach to optimize grading guard systems for gas oil hydrotreating reactor based on the phenomenon of clogging of catalyst beds with microparticulates and coke deposits was developed. Pellets with different shapes have been tested to obtain dynamic dependencies of filter coefficient and pressure drop buildup. The experiments were performed in the trickle-flow regime with different ensembles of microparticulates having sizes from 15 to 165 μm. The observed effect of a filter cake formation was characterized in terms of average porosity of the interface beds and it was introduced in simulations plugging of catalyst bed. Estimation of the growth of coke deposits was made using modified Voorhies’s equation and experimental samples obtained in the microreactor under hydrotreating process conditions using foulants of industrial gas oil hydrotreater. The analysis of coked samples was carried out using TGA. Based on the discrete model and experimental data, optimization procedure of grading guard systems was carried out using brute force search. All combinations of schemes of guard-beds were compared using integrated hydrodynamic resistance as a criterion. It was shown that an optimized scheme of guard-beds can reduce hydrodynamic resistance as compared to the schemes without guard-beds or with non-optimized guard-beds.

Investigation of discharge characteristics of rod-shaped particles in a hopper: Experimental and numerical studies using polygonal/polyhedral DEM

In this work, the discharge of numerous polygonal particles in a hopper was investigated numerically and experimentally. To this end, a polygonal/polyhedral DEM model is proposed and implemented to simulate hopper operation in 2D and 3D. The results of a conservation test show that the proposed algorithm conserves energy better than the CP algorithm owing to its straightforward contact calculation. The model then is adopted to simulate the discharge of rod-shaped particles in hopper. Lab-scale experiments were also conducted for DEM model validation. To evaluate the influence of particle shape, outlet opening, and discharge slope angle, rod-shaped particles with triangular, square, pentagonal, and hexagonal cross-sections were used in the experiments and simulation. The results show that the discharge rate of non-spherical particles was significantly affected by the shape of particles, and inter-particle packing property was found to have stronger influence than rolling-related properties, such as roundness or moment of inertia. Conditional clogging phenomena of particles were observed, and the tendency of particle clogging was enhanced by high initial loading, narrow outlet opening, and low slope angle of the hopper outlet. The criteria conditions of particle clogging from experiments were satisfactorily reproduced in the simulation. Although the discharge rate increased with increasing initial loading, the discharge rate saturated at over M = 30 kg owing to the so called Janssen’s effect. The discharge corresponding to the change in particle shape and initial loading was in good agreement between the simulation and experimental results. The comparison of 2D/3D simulation shows that the experiments and simulations successfully minimized the 3D effect.

Production and characterization of copper periodic open cellular structures made by 3D printing-replica technique.

Additive manufacturing by 3D printing comprises a set of methods for production of 3D objects starting from a CAD file. Advantages of additive manufacturing combine high manufacturing resolution, a reduction of waste material, and the possibility of computer‐aided design (CAD). When applied to the manufacturing of structured catalyst substrates, the latter enables the optimization of transport properties of the catalyst support. Despite several methods have been introduced for a variety of materials, copper, well known for its high thermal conductivity, is still difficult to be handled. In this work, a novel approach for the additive manufacturing of copper periodic open cellular structures (POCS) is proposed and investigated. It consists in the use of the replica manufacturing procedure starting from resin supports produced by 3D printing stereolithography. Micrometric high purity copper powder was effectively dispersed using a liquid medium based on organic components; the resulting slurry was used for the washcoat deposition on the resin supports. Structures with diamond unit cell shape (cell size of 2.5 mm and void fractions in the 0.8‐0.9 range) were washcoated by dip‐spin coating. Homogeneous washcoat layers were obtained without occurrence of cell clogging phenomena. Optimized thermal treatment procedure was assessed for sintering the copper POCS. The resulting matrices preserved the morphology of the original structure, reaching a resolution in the range of 70 to 120 μm. These materials can eventually be used as catalyst supports for heat‐transfer limited applications (eg, steam reforming of methane), where copper‐based substrates were demonstrated to be an effective solution for process intensification.

Experimental assessment of clayey layers for clogging of TBM in Tabriz subway lines, Iran

Clogging phenomenon is defined as the excessive adhesion of clayey particles to drilling equipment that adversely affect machine efficiency. This study involves the clogging potential of clayey soil and rock samples collected from Tabriz subway lines that were tested by laboratory experiments. In order to achieve the objectives of this study, a series of analyses were carried out including sieve analysis, hydrometer, Atterberg limit, slake durability, direct shear, modified direct shear test on the soil/steel interface, and piston pullout apparatus. According to USCS, the studied samples are classified as CL and CH. The clay minerals of the samples are mainly montmorillonite and illite. According to the exist diagrams and classifications based on Atterberg limits, consistency index and adhesion stress, samples are classified as medium to high risk for clogging. The maximum clogging occurrence is possible in the moisture content between 20 and 52% (IC < 0.75). The results proved that water content is a key parameter in adhesion stress variation and clogging behavior of clayey materials. The results of the direct shear test on clay/clay and clay/steel interface indicate that with increasing water content, the cohesion of soil decreases and tangential adhesion to the steel surface tends to increase. Based on piston pullout test, the normal adhesion stress of samples increased to a peak value at IC = 0.65 to 0.75. The results obtained in this study indicate a moderate to high risk of clogging in the mechanized excavation of subway lines in the study area while encountering clayey layers.

Groundwater monitoring for assessing artificial recharge in the Mediterranean coastal aquifer of Korba (Northeastern Tunisia).

Groundwater (GW) artificial recharge with treated wastewater (TWW) is seen as a promising technical solution to overcome groundwater overexploitation and seawater intrusion and to ascertain future water resources availability. While these introduced recharge systems have shown positive impacts in many areas across the world, their effective contribution to GW recharge is still not well quantified in water-stressed regions such as Tunisia. The scarcity of on-site data with accurate temporal and spatial measurements and resolution in such areas hinders the clear assessment of these recharge systems' performances. This article presents an approach based on the on-site monitoring of groundwater level and salinity measurements and recharge rate records spanning over the 6-year period to investigate the performances of a wastewater-based recharge system located in the Korba-El Mida site in Tunisia. The analysis showed that the artificial recharge did not have an impact on groundwater level. Controversially, a decrease in water salinity in and around the study site was observed. Findings emphasize on the weak wastewater volumes applied to the recharge system and the clogging phenomena that occurred in the pool and in the vadose zone. Furthermore, analyzing the information over a short period of time could be misleading as the results of a 6-year period of monitoring show clearly that the way the site was managed and the local conditions have a role in understanding and interpreting the results even if the artificial recharge was appropriately designed.

Hydraulic behavior variation of pervious concrete due to clogging

During the rainfall, different types of sediments are transported (organic and inorganic) and can end up decreasing the hydraulic efficiency of Pervious Concrete (PC). This phenomenon is known as clogging and occurs naturally in the PC due to its high area exposed to the weather. This study aims to identify and characterize the phenomenon of clogging in PC with natural aggregates and recycled aggregates, subjected to three types of sediment: two types of sand (Sand 1 and Sand 2, respectively) and a mixture of sand and clay (S + C). Besides, this research aims on proposing a maintenance plan to avoid loss of functionality of structures produced with PC. To fulfil these aims, the constant head permeability test will be adapted to evaluate the variation of permeability (k) during the clogging process. The results show that PC with recycled aggregates have the best hydraulic performance when compared with PC with natural aggregates. The results present values of 17.5 % and 19.6 % of porosity, and 6.2 mm/s and 10.0 mm/s of permeability for natural and recycled aggregates, respectively. Regarding clogging phenomenon, natural aggregate PC presents permeability reductions of 50 % (Sand 2), 60 % (S + C) and 70 %, (Sand 1) whereas in the case of recycled aggregate the maximum reduction was 30 % (S + C), 40 % (Sand 1) and 50 % (Sand 2). These results show the hydraulic advantage of implementing the use of recycled aggregates for PC production. On the other hand, the results show that a maintenance cycle of 5 years would make possible an increasing of the hydraulic life of PC independently of the type of aggregate used.