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Accurately assessing the clogging risk of the drainage pipe envelopes is a prerequisite for the reasonable design and proper management of subsurface drainage. However, the current assessment of clogging risk for subsurface drainage envelopes in arid areas mainly focuses on the impacts of single factors such as physical or chemical factors, with less attention given to combined physical–chemical clogging, which is more likely to occur and causes significant harm. Based on the evaluation indicators for physical and chemical clogging risks, this study utilized the entropy weight method to determine the weights of physical and chemical clogging risks, then proposed evaluation indicators for combined clogging risks and generated risk maps of physical, chemical, and combined clogging within the Xinjiang watershed. Furthermore, field excavation and sampling of subsurface drainage pipes were conducted to apply the proposed evaluation indicators for combined clogging risks and analyze the influencing factors. The results show that the combined clogging risk map based on the proposed combined clogging evaluation indicators is consistent with the actual clogging situation in the subsurface drainage system. Both physical and chemical clogging coexisted in the subsurface drainage system in Xinjiang, with a higher mass content of SiO2 than CaCO3 in the clogging substances. The combined clogging risk increased with rises in the drainage temperature and salinity. Under current conditions, the proportions of high, moderate, and low-risk areas of combined clogging risk are 22.10%, 30.37%, and 47.53%, respectively. The high-risk areas are mainly concentrated in Southern Xinjiang, which accounts for 91.7% of the high-risk area. This study can provide technical support for the prevention and control of clogging in subsurface drainage systems for saline-alkali farmland in arid areas.

Clogging is one of the major factors affecting the performance of drip irrigation systems. It can be of a physical, chemical or biological nature but currently no method offers non-destructive field measurements of clogging. The aim is to propose a new method for monitoring and discriminating physical and chemical clogging. It is based on near infrared (NIR) spectroscopy combined with multivariate analysis methods. Kaolinite (physical clogging) and calcium carbonate (chemical clogging) were monitored in a transparent millifluidic cellflow. The evolution of clogging throughout the experiment was monitored by applying a multivariate curve regression – alternating least-squares (MCR-ALS) on absorption spectra. Comparison of the MCR-ALS results with the reference thickness measured by optical coherence tomography (OCT) indicated that absorbance spectroscopy coupled with MCR-ALS allows for accurate monitoring of the clogging thickness of kaolinite and calcium carbonate deposits. The detection of clogging and the monitoring of its thickness in the channel could be performed during both experiments. In addition, based on the spectra, a partial least squares-discriminant analysis (PLS-DA) model was developed to distinguish between the two types of clogging materials. Discrimination between both materials using PLS-DA model was achieved with accuracy greater than 97%. The proposed strategy highlights the potential of NIR spectroscopy coupled with MCR-ALS and PLS-DA methods to monitor the evolution of thickness and nature of clogging in a millifluidic cellflow. These results thus indicate a new methodology for detecting, monitoring and discriminating in situ clogging in the field. • Accurate spectral method for in situ monitoring and discrimination of clogging. • MCR-ALS method allows for clogging quantification with precision around 100 μm. • PLS-DA allows for clogging classification with accuracy greater than 97%. [ABSTRACT FROM AUTHOR]

While utilizing hydrothermal resources, it is necessary to reinject wastewater into the reservoir through reinjection wells to extract heat without mining groundwater. Chemical clogging is a serious problem in the process of reinjection. The precipitation of minerals can lead to reservoir clogging and the reduction of permeability. Therefore, to study the effect of chemical clogging on permeability, the weakly consolidated sandstone of the Neogene Guantao Formation geothermal reservoir in northern Shandong (Eastern China) was taken as the research object. A long-term thermal-hydro-mechanical-chemistry (THMC) coupling reinjection experiment was carried out. The results showed that when the temperature of wastewater was higher than 45 °C, there was a temporary phase of permeability enhancement in the first 10 min of reinjection. However, wastewater with higher temperatures would cause more chemical clogging eventually. XRD and ion analysis results showed that the precipitation of minerals was mainly potash feldspar, illite, calcite, and other carbonate minerals during reinjection. According to the characteristics of low-TDS wastewater in the Guantao Formation, it is recommended to adopt low-temperature wastewater reinjection and reduce the concentration of Ca2+ and Mg2+ in wastewater before reinjection. HIGHLIGHTS Water–rock chemical reactions cause the precipitation of minerals.; Permeability is an important parameter to characterize blockage.; XRD and ion concentration were used to analyze chemical blockage.; There was a temporary phase of permeability enhancement in the first 10 min of reinjection.; Tailwater with higher temperatures will cause more blockage eventually.;

Managed aquifer recharge (MAR) is increasingly being adopted to improve water security internationally. However, clogging during MAR remains one of the greatest challenges for sustainable operations. This study examines the effects of iron on biological clogging processes using column experiments and suggests management options. The results indicated that the presence of iron limits the transport of bacteria through the column, and that concentrations <10 mg/L are correlated with increased bacterial growth. Conversely, the increased viscosity of biofilm subsequently limits the transport of iron through the column. Fourier transform infrared spectroscopy and x‐ray photoelectron spectroscopy indicated that large iron‐Pseudomonas sp. flocs formed which occupied the sand pore spaces. The effect of iron induced chemical clogging was most notable in the initial stage of the experiment while bio‐clogging dominated later. There are many recommended values of iron concentration in water recharge, most of them are advised from the point of pollution perspective. Based on these laboratory results, iron concentrations in recharge water for MAR should be <0.3 mg/L to mitigate clogging effects. Furthermore, using non‐corrodible materials for bore screen and pumps, and avoiding external oxidant inputs should be considered to prevent iron related chemical and biological clogging. [ABSTRACT FROM AUTHOR]

This study develops a coupled model of chemical clogging and permeability coefficient of geotextile envelope. Based on the distribution characteristics of crystal precipitates on geotextile envelope and their influence on the permeability coefficient, a permeability coefficient model of an actual geotextile envelope that considers the overlapping effect is developed. Then, the densification effects of geosynthetic fiber hypothesis and the filter cake effect hypothesis are proposed to simulate the processes of increasing fiber diameter after crystal precipitation and the accumulation of crystal precipitates on the surface of geotextile envelope. The crystal precipitation module and permeability coefficient module are coupled, and their experimental values are used to confirm the availability of the model. Results indicate the satisfactory performance of the model. In addition, the parameter sensitivity analysis and trend prediction show that the saturation index SI and solution flow rate V are the main factors that affect the chemical clogging and permeability of geotextile envelope. When the solution conditions are not considered, the sensitivity of geotextile envelope parameter d f increased with the amount of precipitation in crystal precipitation. When the pores of the geotextile envelope are completely clogged, the permeability coefficient of the geotextile envelope will drop sharply, then decline slowly. • A coupled model for chemical clogging and permeability coefficient of geotextile envelope is developed. • The densification effect of geosynthetic fiber and the filter cake effect are proposed to generalize chemical clogging. • The sensitivity of geotextile envelope parameter d f increased with the amount of precipitation. [ABSTRACT FROM AUTHOR]

Abstract Green energy production from natural resources can reduce emissions of greenhouse gases and pollutants from burning of fossil fuels in power plants. Recently, groundwater geothermal energy (GGE) is harnessed by deploying closed- and open-loop heat systems. In open-loop geothermal heat pump systems (OLGHPS), groundwater is reinjected into aquifer after harnessing GGE. Nevertheless, OLGHPS face noxious clogging issue because of elusive chemistry (corrosion or precipitation) of chemical species, principally of iron (Fe), in pipes and aquifers during reinjection process via oxidation reactions. Plethora of filtering materials are available for removal of ions, but these are quite expensive and environmentally unsafe. More recently, low-cost, eco-friendly, green filtering materials gain much interest. These materials can remove ions from groundwater that can minimize clogging in heat exchange systems, injection wells, and aquifer. In the present study, three filtering materials, i.e., wooden charcoal (biomaterial), yamazuna fine sand, and volcanic ash, were tested to estimate their Fe removal capacity. In upward flow mode with minimum oxygen-water contact, serial column (each with 6 ports) experiments were conducted under constant pressure head and constant velocity conditions. Columns were connected to well water having dissolved Fe concentration of 10.85 mg L−1. Sampling was done at the well, column inlets, column’s six sampling ports and column outlets, and samples were analyzed for Fe by atomic absorption spectroscopy. Related tested parameters include pH, EC, temperature, turbidity, porosity, particle diameter, and dissolved oxygen. Volcanic ash showed less Fe removal, while sand filter showed substantial reduction in velocity. Biomaterial (wooden charcoal) displayed higher Fe adsorption capacity compared to other materials that can be ascribed to its surface chemistry and functional groups. Under different flow rates, maximum Fe content of 3.5 g Fe kg−1 dry charcoal was obtained. By considering a safety factor and influence of groundwater composition, it is possible to design a biomaterial-based iron filter system to minimize Fe-induced chemical clogging in OLGHPS which is an eco-friendly, green energy source.

Although riverbank filtration (RBF) has been widely applied in China, the managers do not pay enough attention to the inevitable clogging issues during continuous RBF operation. The RBF site, which is located near the Lalin River, northeastern China, was selected as the study area, and the laboratory column experiments were used to simulate the RBF process and further investigate the physical and chemical clogging. The removal of turbidity (59.4–95.1%), COD (21.9–71.7%), NH4+ (10.9–39.4%), Fe (18.5–64.8%), and Mn (19.8–71.7%) demonstrated the water quality improvement by RBF. Whereas, the significant decrease in permeability (39.6–88.2%) also indicated that the clogging issues could not be ignored during RBF. Among them, the physical clogging-dominated area, chemical clogging-dominated area, and the transition zone were located at 0–12.5%, 37.5–100%, and 12.5–37.5% of the infiltration pathway, respectively. Moreover, the concentration of suspended particle materials, mean size of riverbed sediments, and aquifer media are the major impact factors for physical clogging; the precipitation of soluble constituents and redox reaction and other hydrochemical processes were the major impact factors for chemical clogging. The conclusion of this study can contribute to managers alleviating the clogging issues and improving the effectiveness of the sustainable operation in the local RBF system. [ABSTRACT FROM AUTHOR]

Clogging has garnered growing interest as a significant operational and maintenance concern that affects the sustainable development and implementation of sub-surface flow (SSF) wetlands in wastewater treatment. The existing literature on clogging has been found to have limitations, as none of the studies have provided a comprehensive overview of the entire clogging process, starting from its initiation to remediation. In addition, very few works have addressed the models that were utilized to forecast the occurrence of system clogging. This study primarily focuses on the process of clogging, in widely used SSF wetland systems due to its negative impact on the lifespan of these systems. The article seeks to evaluate different forms of clogging and their developmental mechanisms, as well as the influencing factors. The work thoroughly examines the several techniques used to measure and evaluate clogging. The current review also encompasses the examination of several mathematical models used to predict the clogging of the system. Lastly, it also emphasizes the remediation methods required to resolve clogs. The main objective of this review is to bring all pertinent information on the clogging of SSF wetlands to the attention of prolific researchers with the goal of mitigating system clogging and establishing CW technology as a viable and sustainable alternative for wastewater treatment in the near future. [Display omitted] • The mechanisms of various types of clogging in SSF-CWs have been described. • Factors influencing clogging in SSF-CWs were briefly discussed. • Various methods adapted to measure clogging of wetland beds were highlighted. • Numerical models employed to date, to understand clogging in SSF-CWs were overviewed. • The available remediation techniques to counteract clogging in SSF-CWs were explained. [ABSTRACT FROM AUTHOR]

Accurately assessing the clogging risk of the drainage pipe envelopes is a prerequisite for the reasonable design and proper management of subsurface drainage. However, the current assessment of clogging risk for subsurface drainage envelopes in arid areas mainly focuses on the impacts of single factors such as physical or chemical factors, with less attention given to combined physical–chemical clogging, which is more likely to occur and causes significant harm. Based on the evaluation indicators for physical and chemical clogging risks, this study utilized the entropy weight method to determine the weights of physical and chemical clogging risks, then proposed evaluation indicators for combined clogging risks and generated risk maps of physical, chemical, and combined clogging within the Xinjiang watershed. Furthermore, field excavation and sampling of subsurface drainage pipes were conducted to apply the proposed evaluation indicators for combined clogging risks and analyze the influencing factors. The results show that the combined clogging risk map based on the proposed combined clogging evaluation indicators is consistent with the actual clogging situation in the subsurface drainage system. Both physical and chemical clogging coexisted in the subsurface drainage system in Xinjiang, with a higher mass content of SiO 2 than CaCO 3 in the clogging substances. The combined clogging risk increased with rises in the drainage temperature and salinity. Under current conditions, the proportions of high, moderate, and low-risk areas of combined clogging risk are 22.10%, 30.37%, and 47.53%, respectively. The high-risk areas are mainly concentrated in Southern Xinjiang, which accounts for 91.7% of the high-risk area. This study can provide technical support for the prevention and control of clogging in subsurface drainage systems for saline-alkali farmland in arid areas. • Risk evaluation indicators for combined clogging of subsurface drainage were proposed. • Risk maps of physical, chemical, and combined clogging in Xinjiang were generated. • The combined clogging risk increased with rises of drainage temperature and salinity.. [ABSTRACT FROM AUTHOR]

Green energy production from natural resources can reduce emissions of greenhouse gases and pollutants from burning of fossil fuels in power plants. Recently, groundwater geothermal energy (GGE) is harnessed by deploying closed- and open-loop heat systems. In open-loop geothermal heat pump systems (OLGHPS), groundwater is reinjected into aquifer after harnessing GGE. Nevertheless, OLGHPS face noxious clogging issue because of elusive chemistry (corrosion or precipitation) of chemical species, principally of iron (Fe), in pipes and aquifers during reinjection process via oxidation reactions. Plethora of filtering materials are available for removal of ions, but these are quite expensive and environmentally unsafe. More recently, low-cost, eco-friendly, green filtering materials gain much interest. These materials can remove ions from groundwater that can minimize clogging in heat exchange systems, injection wells, and aquifer. In the present study, three filtering materials, i.e., wooden charcoal (biomaterial), yamazuna fine sand, and volcanic ash, were tested to estimate their Fe removal capacity. In upward flow mode with minimum oxygen-water contact, serial column (each with 6 ports) experiments were conducted under constant pressure head and constant velocity conditions. Columns were connected to well water having dissolved Fe concentration of 10.85 mg L−1. Sampling was done at the well, column inlets, column's six sampling ports and column outlets, and samples were analyzed for Fe by atomic absorption spectroscopy. Related tested parameters include pH, EC, temperature, turbidity, porosity, particle diameter, and dissolved oxygen. Volcanic ash showed less Fe removal, while sand filter showed substantial reduction in velocity. Biomaterial (wooden charcoal) displayed higher Fe adsorption capacity compared to other materials that can be ascribed to its surface chemistry and functional groups. Under different flow rates, maximum Fe content of 3.5 g Fe kg−1 dry charcoal was obtained. By considering a safety factor and influence of groundwater composition, it is possible to design a biomaterial-based iron filter system to minimize Fe-induced chemical clogging in OLGHPS which is an eco-friendly, green energy source. [ABSTRACT FROM AUTHOR]

The formation and deposition of tufa precipitate from the leachate of the recycled concrete aggregate (RCA) within fibers of a nonwoven geotextile, as can potentially occur in a transportation infrastructure drainage system, is simulated in a laboratory environment. Two sets of modified column tests were conducted in this study with cycles of wetting and drying for 1 year in order to study the rate of RCA tufa precipitation. Results of measured changes in the infiltration capacities showed that, even with precipitated tufa, the RCA/geotextile system serviceability remains similar to the virgin aggregate (VA)/geotextile system at the end of the 12-month testing. Evaluation of the deposited tufa precipitation within geotextile samples showed that RCA tufa is dominated by calcite and gypsum minerals. Estimated quantities of RCA tufa deposition by existing models developed for natural environments, showed that they either grossly overestimate the observed behavior (calcite model) or underestimate it (gypsum model). Image analysis technique and chemical calculations based on leached dissolved solids were utilized successfully to develop models to predict the precipitation of RCA tufa in macroscales during the service life of a subdrain. [ABSTRACT FROM AUTHOR]

The chemical clogging of geotextiles filters is a common issue, which threatens the safety of engineering projects. To reduce the chemical clogging of nonwoven geotextiles and enhance their drainage capability, a polyurethane foam was innovatively placed under the nonwoven geotextiles in this paper. A series of column tests were conducted to study the mechanism of the polyurethane foam to reduce the chemical clogging of the nonwoven geotextile filters in tailings caused by ferrous iron. In addition, the influence of the concentration of Fe2+, hydraulic gradient and thickness of the tailings specimen on the chemical clogging of the polyurethane foam and nonwoven geotextiles was examined. Less chemical clogging of geotextiles caused by polyurethane foam was observed and the related mechanism was firstly explained. The polyurethane foam under the geotextile reduced the contact between the geotextile and air. As a result, the chemical clogging of the geotextile was alleviated, which increased the drainage capability of the geotextiles. A high water saturation of the polyurethane foam would help to a reduce the extent of the chemical clogging of the geotextile. The chemical clogging characteristics of geotextiles and polyurethane foam under different concentrations of Fe2+ and hydraulic gradients were observed. [ABSTRACT FROM AUTHOR]

Drip irrigation is an important way to alleviate the global water shortage. However, the emitter-clogging issue of drip irrigation directly affects irrigation uniformity and operation efficiency, even disabling the whole system and reducing crop production. Currently, with the widespread use of saline water and large-scale utilization of fertigation, the issue with the chemical clogging of emitters has become more prominent. The poor uniformity of irrigation and fertilization distribution caused by emitter clogging results in salt damage and fertilizer loss due to the complex clogging mechanism. However, no extensive information on chemical clogging is available. Herein, we surveyed the latest research on chemical clogging caused by saline water irrigation and fertigation in drip irrigation systems and described the clogging mechanisms of the emitter by analyzing the key factors, clogging rules, and substances. We also present a framework of the control technologies for clogging based on physical, chemical, and biological methods. Finally, we present the current challenges of fertigation with saline water and technical trends of emitter clogging in the drip irrigation system. To conclude, the efficient integration of these three methods is critical to prevent and eliminate chemical clogging.

In order to study the chemical clogging and its effect on hydraulic performance of trickle irrigation system, four treatments includes compensating emitters (Netafim and Micro-Flapper), non-compensating emitters (Mehr and Goldani), three treatment of flow rates that includes 8, 4 and 2 lph (liters per hour) were selected and tested using Karoun river’s water in No. 1 research farm of Shahid Chamran University of Ahvaz. The experiment was conducted in a Completely Randomized Block Design (CRBD) and irrigation was performed in 31 times with irrigation frequency for two days, at pressure of 1.5 bar. The results showed that decreasing of flow rate of Micro-Flapper emitter with 8 and 4 LPH flows is higher than the other treatments and this decreasing is significante at the five percent. Also the Micro-Flapper emitter with 2 lph flows has the lowest decreasing of flow rate. Based on field observations, herniation of silicon diaphragm that used in Micro-Flapper emitters with 8 and 4 lph flows is the main reason for the reduction of flow rate and high values of CV, qvar and qd. So in this particular case the Chemical sediment did not impose a major effect. Turbulent regime of water at the outlet is the reason of resistance against the chemical clogging in the Micro-Flapper emitter with 2 lph flows. In Netafim emitter with 8 and 4 lph, despite having the significant clogging in five percent signification level have a minimal values of CV, qvar and qd and high values of EU and CU. In this experiments, the treatment which had the lowest coefficient of manufacturing Variation, was accounted to it the lowest coefficient of variation of flow rate and the highest Emission Uniformity of variation. In most treatments during the Irrigation, values of CV, qvar and qd increased and values of EU and CU decreased. According to the results presented, the Goldani emitter with 8 gph flows is rated and selected as the top emitter in both terms of resistance against the chemical clogging and hydraulic performance parameters than other emitters.

Copyright of Irrigation & Drainage is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the unlikely case of CO 2 leakage from a storage reservoir, it is desirable to close the leak efficiently and permanently. This could be done by injecting a reactive solution into the leak path, thereby immobilizing migrating CO 2 by consuming the gas and forming solid reactants. With regard to permanent closure, it is important to consider materials that are stable in the long-term, ensuring permanent CO 2 containment. Numerical modelling was applied to assess the feasibility of injecting calcium-rich water as a CO 2 -reactive solution to form calcite. A scenarios analyses of key parameters showed that the success of leakage remediation can be up to 95% when carefully balancing the injection rate and distance versus the permeability and leakage rate. [ABSTRACT FROM AUTHOR]

Calcium carbonate (CaCO 3) fouling process in dripper prototypes was studied in the absence and presence of suspended solid particles (SSP) at concentrations of 125 and 500 mg L−1. Eleven flat and non-pressure-compensating dripper prototypes were evaluated. Five prototypes (Model A) present flow with well-developed vortices, whereas the other six prototypes (Model B) present more uniform flow with undeveloped vortices. Water with hardness of 200 and 300 mg L−1 as CaCO 3 was used in the experiments. The dripper prototypes operated for 200 h, and the discharge variation rate (Dra) was determined every 40 h. Images of the interior of the labyrinths were acquired to investigate the fouling patterns. The mass of material fouling the labyrinth of the prototypes was determined and correlated to the geometric parameters of the labyrinths. The deposited material was analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The SSP directly influenced the CaCO 3 fouling processes. In the absence of SSP, heterogeneous nucleation was dominant in the prototype walls and occurred uniformly throughout the labyrinth, interfering directly in the Dra of the model B prototypes. The model A prototypes were more resistant to clogging and did not clog during the experiments. Once added to the water, the SSP functioned as an effective competitor of CaCO 3 nucleation and growth sites; thus, heterogeneous nucleation started occurring preferably on the SSP surface, reducing the fouling in the labyrinth walls. The prototypes that clogged in the tests in the absence of SSP were resistant to clogging in the SSP concentration of 500 mg L−1. The presence of SSP changed the crystal habit of CaCO 3 , and it precipitated in the form of calcite. The nucleation of CaCO 3 directly on the SSP surface is interesting from the point of view of clogging processes, and drippers with better sediment transport capacity are beneficial. • Clogging of drippers due to suspended solid particles (SSP) and CaCO 3 was investigated • SSP reduced the fouling of CaCO 3 on the walls of labyrinths • SSP favored heterogeneous nucleation on the surface of the solid particles • SSP completely modified the morphology of CaCO 3 precipitates • Labyrinths of higher sediment transport capacity were more resistant to clogging [ABSTRACT FROM AUTHOR]

This study evaluates the long-term performance of two types of geotextiles that were used for 18 years in drainage trenches to stabilize slopes in the French Alps. The flow rate analysis of each trench enabled estimating an average permittivity at trench scale of between 10 −5 and 10 −6 s −1 . After exhuming the geotextiles, their hydraulic and mechanical properties were assessed. The hydraulic tests performed on geotextiles alone gave permittivities greater than 10 −3 s −1 . Gradient ratio tests were performed on undisturbed soil/geotextile/drainage specimens and gave results in the order of 10 −8 s −1 . The aged specimens were examined using scanning electron microscopy. Quantifying the overall performance of the geotextile filter is complicated because of the brittleness of the calcite crust and the subsequent difficulty of characterizing undisturbed interfaces. Various possible explanatory mechanisms involved in the deterioration of trench performance were reviewed: filter cake blinding, internal clogging and downstream chemical clogging. Existing analytical models were used in order to predict the loss of hydraulic performance due to each of these clogging mechanisms. By comparing the measured permittivities to the calculated permittivities, we demonstrated that chemical clogging due to calcite precipitation on the downstream face of the geotextiles was probably the preponderant mechanism responsible for the poorer performance of geotextile filters at trench scale. [ABSTRACT FROM AUTHOR]

Abstract: This study focuses on coupling geochemistry with geo-hydraulics to enable time-dependent modelling of the remediation of acidic groundwater using an alkaline permeable reactive barrier (PRB). Chemical clogging due to secondary mineral precipitates reduces the porosity and hydraulic conductivity of the reactive medium. The governing equations are incorporated into commercial numerical codes, MODFLOW and RT3D. An original algorithm was developed for RT3D to simulate geochemical reactions occurring in the PRB. The results and the model predictions are in agreement, confirming that the hydraulic conductivity reduction due to mineral precipitation occurs at the start of permeation and continues until halfway through the testing phase. [Copyright &y& Elsevier]

Drip irrigation is an important way to alleviate the global water shortage. However, the emitter-clogging issue of drip irrigation directly affects irrigation uniformity and operation efficiency, even disabling the whole system and reducing crop production. Currently, with the widespread use of saline water and large-scale utilization of fertigation, the issue with the chemical clogging of emitters has become more prominent. The poor uniformity of irrigation and fertilization distribution caused by emitter clogging results in salt damage and fertilizer loss due to the complex clogging mechanism. However, no extensive information on chemical clogging is available. Herein, we surveyed the latest research on chemical clogging caused by saline water irrigation and fertigation in drip irrigation systems and described the clogging mechanisms of the emitter by analyzing the key factors, clogging rules, and substances. We also present a framework of the control technologies for clogging based on physical, chemical, and biological methods. Finally, we present the current challenges of fertigation with saline water and technical trends of emitter clogging in the drip irrigation system. To conclude, the efficient integration of these three methods is critical to prevent and eliminate chemical clogging. [ABSTRACT FROM AUTHOR]

An extensive array of deep, large diameter wells is required to locally dewater the aquifers in the Rhenish lignite mining district in Germany, some of which are anoxic. The performance of the wells is often influenced by the precipitation of metal hydroxides, such as FeOOH or MnOOH, which causes well clogging. A laboratory study was undertaken to gain a general understanding of the clogging processes and to create a basis for testing and developing techniques that could possibly prevent or reduce the loss of well efficiency. The chemical genesis of Fe-hydroxide incrustations in a well screen section was reproduced in an experimental model under controlled boundary conditions. In the model, the clogging process was accelerated by modifying the pH and Fe concentration relative to the in situ values. The effect of clogging on the hydraulic situation in the gravel material was quantified by measuring the hydraulic head in the section of the annular gravel pack. Increases in the hydraulic gradient up to 75 % were measured. Analysis of the gravel material using a sequential extraction procedure after the experiment yielded Fe contents up to 5.4 g kg. According to X-ray diffraction, the incrustations mainly consist of 6 line ferrihydrite and lepidocrocite. [ABSTRACT FROM AUTHOR]

Copyright of Grundwasser is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract: The radial collector well, an important water drainage construction, has been widely applied to the tailings dam. Chemical clogging frequently occurs around the vertical shaft in radial collector well due to enough dissolved oxygen and some heavy metals in groundwater flow of tailings dam. Considering the contribution of water discharge from both vertical shaft and horizontal screen laterals and chemical clogging occurring around vertical shaft well, a new model was developed on the basis of Multi-Node Well (MNW2) package of MODFLOW. Moreover, two cases were calculated by the newly developed model. The results indicate that the model considering chemical clogging occurring around the vertical shaft well is reasonable. Owing to the decrease in hydraulic conductivity caused by chemical clogging, the groundwater level in dam body increases constantly and water discharge of radial collector well declines by 10–15%. For ordinary vertical well, it decreases by 30%. Therefore, chemical clogging occurring around radial collector well can arouse increases of groundwater level, and influence dambody safety. [Copyright &y& Elsevier]

The clogging of drainage facilities, which reduces the permeability coefficient, raises the phreatic line, and increases the possibility of seepage damage, seriously impacts the safety of tailings dams. The core cause of clogging is the oxidation of active minerals or ions and the formation of gelatinous materials. These materials, the most typical of which are active iron minerals (such as pyrite or ferrous ions), are adsorbed in the percolation passage to block the flow of liquid. This paper aims to study the effect of ferrous ions on the hydraulic conductivity of fine tailings. First, we introduce a new apparatus based on the column experiment to examine the permeation characteristics of fine tailings. Second, a systematic experimental study was conducted to obtain the effect of ferrous ion content, nonwoven geotextile layer number, and specimen height (reflecting the length of the seepage path) on the tailings permeability ratio using this apparatus. Third, scanning electron microscopy (SEM) was performed on selected geotextile samples that underwent filtration to assess the clogging mechanism. The results show that the ferrous ions were oxidized to form the low solubility iron(III) oxide-hydroxide (Fe(OH) 3), which was deposited or adsorbed in the percolation channel and caused chemical clogging. Meanwhile, in the case of more geotextile layers or slower seepage rates, the blockage of the fine tailings formed faster in the penetration experiment. According to the results of the SEM, there were glue coverings on the fiber surface, and ultrafine tailings particles (−10 μm) were adsorbed, adhered and deposited on it and formed a chemical-physical clogging. • Clogging formation is more sensitive to ferrous ions content in the tailings sample. • Geotextile thickness (or number of layers) has a significant impact on the formation of clogging. • The ultrafine particles (−10 μm) are more easily adsorbed, banded, and even encapsulated by colloidal compounds. • Clogging formation seems to be dependent on the hydraulic environment. [ABSTRACT FROM AUTHOR]

Characteristics and deposition pattern of clogging material on cylindrical drip emitters was studied using non-destructive methods of evaluation. Two sets of four cylindrical emitter samples were collected from farm lands. One set of sample emitters was analyzed using Computed Tomography (CT). Other set was dissected and the clogging material extracted was analyzed using Energy Dispersive X-Ray Fluorescence (EDXRF) and X-Ray Diffraction (XRD). CT scans revealed the geometric properties of emitters and the spread of clogging material on the emitter surface. EDXRF analysis found statistically significant inverse relationship between the proportion of physical clogging and chemical clogging materials. XRD analysis indicated presence of physical and chemical clogging materials in their crystalline forms. Emitters having transverse flow path and the boundary optimized with curvature found with the least deposition of physical clogging materials. Corresponding proportion of chemical clogging (as Ca) was found to be much higher. All the samples were found with more clogging material closer to the outlets. Efforts to optimize emitter geometry shall also take into account the outlet area optimization and chemical clogging for obtaining best results., (© 2020 Published by Elsevier Ltd.)