Reactive Barrier Research Articles

Gallionellaceae in rice root plaque: metabolic roles in iron oxidation, nutrient cycling, and plant interactions.

In waterlogged soils, iron plaque forms a reactive barrier between the root and soil, collecting phosphate and metals such as arsenic and cadmium. It is well established that iron-reducing bacteria solubilize iron, releasing these associated elements. In contrast, microbial roles in plaque formation have not been clear. Here, we show that there is a substantial population of iron oxidizers in plaque, and furthermore, that these organisms (Sideroxydans and Gallionella) are distinguished by genes for plant colonization and nutrient fixation. Our results suggest that iron-oxidizing and iron-reducing bacteria form and remodel iron plaque, making it a dynamic system that represents both a temporary sink for elements (P, As, Cd, C, etc.) as well as a source. In contrast to abiotic iron oxidation, microbial iron oxidation results in coupled Fe-C-N cycling, as well as microbe-microbe and microbe-plant ecological interactions that need to be considered in soil biogeochemistry, ecosystem dynamics, and crop management.

Enhanced Biogenic Sulfidation of Zero-Valent Iron in Columns: Implications for Promoting Dechlorination in Permeable Reactive Barriers.

Biogenic sulfidation of zero-valent iron (ZVI) using sulfate reducing bacteria (SRB) has shown enhanced dechlorination rates comparable to those produced by chemical sulfidation. However, controlling and sustaining biogenic sulfidation to enhance in situ dechlorination are poorly understood. Detailed interactions between SRB and ZVI were examined for 4 months in column experiments under enhanced biogenic sulfidation conditions. SRB proliferation and changes in ZVI surface properties were characterized along the flow paths. The results show that ZVI can stimulate SRB activity by removing excessive free sulfide (S2-), in addition to lowering reduction potential. ZVI also hinders downgradient movement of SRB via electrostatic repulsion, restricting SRB presence near the upgradient interface. Dissolved organic carbon (e.g., >2.2 mM) was essential for intense biogenic sulfidation in ZVI columns. The presence of SRB in the upgradient zone appeared to promote the formation of iron polysulfides. Biogenic FeSx deposition increased the S content on ZVI surfaces ∼3-fold, corresponding to 3-fold and 2-fold improvements in the trichloroethylene degradation rate and electron efficiency in batch tests. Elucidation of SRB and ZVI interactions enhances sustained sulfidation in ZVI permeable reactive barrier.

Removal of Pb from Contaminated Kaolin by Pulsed Electrochemical Treatment Coupled with a Permeable Reactive Barrier: Tuning Removal Efficiency and Energy Consumption.

Lead contamination in soil has emerged as a significant environmental concern. Recently, pulse electrochemical treatment (PECT) has garnered substantial attention as an effective method for mitigating lead ions in low-permeability soils. However, the impact of varying pulse time gradients, ranging from seconds to hours, under the same pulse duty cycle on lead removal efficiency (LRE) and energy consumption in PECT has not been thoroughly investigated. In this study, a novel, modified PECT method is proposed, which couples PECT with a permeable reaction barrier (PRB) and adds acetic acid to the catholyte. A comprehensive analysis of LRE and energy consumption is conducted by transforming pulse time. The results show that the LREs achieved in these experiments were as follows: PCb-3 s (89.5%), PCb-1 m (91%), PCb-30 m (92.9%), and PCb-6 h (91.9%). Importantly, these experiments resulted in significant reductions in energy consumption, with decreases of 68.5%, 64.9%, 51.8%, and 47.4% compared to constant voltage treatments, respectively. It was observed that LRE improved with an increase in both pulse duration and voltage gradient, albeit with a corresponding rise in energy consumption. The results also revealed that corn straw biochar as a PRB could enhance LRE by 6.1% while adsorbing migrating lead ions. Taken together, the present data highlights the potential of modified PECT technology for remediation of lead-contaminated soil, which provides an optimal approach to achieve high LRE while minimizing energy consumption.

1D/3D dual carbon-supported Mott-Schottky-type Co-Co2P heterojunctions for pH-universal hydrogen evolution

The rational design of low-cost, efficient, and stable heterojunction catalysts for pH-universal hydrogen evolution is attracting increasing attention towards a sustainable hydrogen economy. Herein, a sequential spatial restriction-pyrolysis route is developed to confine Mott-Schottky-type Co-Co2P heterojunctions embedded in the one-dimensional (1D) carbon nanotube-modified three-dimensional (3D) N,P dual-doped carbon matrix (Co-Co2P@CNT//CM). The synergistic effect between the abundant Mott-Schottky heterointerfaces and the 1D/3D dual carbon confinement system enables fully exposed active sites and facilitated charge transfer dynamics, thus triggering favorable electronic structures of Co-Co2P@CNT//CM. As a result, Co-Co2P@CNT//CM heterojunctions exhibit excellent pH-universal hydrogen evolution reaction (HER) performance with overpotentials of 142, 205, and 262 mV at 10 mA cm−2 in 0.5 M H2SO4, 1.0 M KOH, and 1.0 M phosphate buffer saline (PBS), respectively. The theoretical results demonstrated that the Mott-Schottky effect can induce an oriented interfacial charge exchange between Co and Co2P. This can lower the reactive kinetic barrier and endow Co-Co2P@CNT//CM with ideal hydrogen adsorption free energy, which efficiently drives the production of H2 from electrolytic water.

Behavior of multi-layer permeable reactive barriers for groundwater remediation

This paper aims to evaluate the efficiency of a multilayer configuration of a permeable reactive barrier (PRB) made up of granular mixtures of zero valent iron (ZVI) and lapillus. The latter is a volcanic material used to disperse ZVI particles. A high dispersion of ZVI improves the long-term hydraulic conductivity but can significantly reduce reactivity due to the lower amount of ZVI. In this research, the performance of two different combinations of a two-layer configuration was studied by means of long-term column tests. The first layer, named “pre-treatment layer”, had a thickness of 4 cm and a volumetric ratio (ZVI/lapillus) of 10:90 or 05:95, while the second layer had a volumetric ratio (ZVI/lapillus) of 20:80. A single layer configuration made only of the 20:80 ZVI/lapillus was used as a benchmark. The three tests were performed using a multi-contaminated solution of copper, nickel and zinc. Test results showed an early loss of the hydraulic conductivity in the single layer configuration and an increase of PRB longevity by 68 % in the presence of the pre-treatment layer. The pre-treatment zone containing 10 % ZVI delayed the clogging phenomenon, while the zone with 5 % ZVI ensured both the correct long-term hydraulic behavior and a removal efficiency higher than 77.6 % for Nickel and 99 % for copper and zinc at 23 cm of thickness for at least two months.

PANI/MCM-41 adsorption for removal of Cr(VI) ions and its application in enhancing electrokinetic remediation of Cr(VI)-contaminated soil.

In this study, a polyaniline/mesoporous silica (PANI/MCM-41) composite material that can be used as a filler for permeable reactive barrier (PRB) was prepared by in situ polymerization. Firstly, the adsorption capacity of PANI/MCM-41 on Cr (VI) in solution was investigated. The results show that the prepared PANI/MCM-41 exhibits a significant Cr (VI) adsorption capacity (~ 340mg/g), and the adsorption process is more accurately described by the Langmuir isotherm and pseudo-second-order kinetic model. The thermodynamic functions evidenced that the Cr(VI) adsorption was an endothermic spontaneous process. In addition, adsorption-desorption cycle experiments proved the excellent reusability of the material. Subsequently, the material was utilized as a filler in the PRB for the remediation of Cr(VI)-contaminated soil using electrokinetic-permeable reactive barrier (EK-PRB) technology. The results show that compared with traditional electrokinetic remediation, the use of PANI/MCM-41 as an active filler can enlarge the current during remediation and enhance the conductivity of soil, which increases the removal rates of total Cr and Cr(VI) in soil (17.4% and 10.2%).

Regulating the FeSx assembly pattern of sulfidated zero-valent iron: All-in-one interface modulation with activated carbon

Specifically designing the heterogeneous interface in sulfidated zero-valent iron (S-ZVI) has been an effective, yet usually overlooked method to improve the decontamination ability. However, the mechanism behind FeSx assembly remains elusive and the lack of modulating strategies that can essentially tune the applicability of S-ZVI further imposes difficulties in creating better-performing S-ZVI with heterogeneous interface. In this study, by introducing powdered activated carbon (PAC) during S-ZVI preparation, S-ZVI/PAC microparticles were prepared to modulate the assembly pattern of FeSx for the applicability and reactivity of the material. S-ZVI/PAC showed robust performance in Cr(VI) sequestration, with 11.16 and 1.78 fold increase in Cr(VI) reactivity compared to ZVI and S-ZVI, respectively. This was attributed to the fact that the introduced PAC could acquire FeSx to enhance the electron transfer capacity matching its adsorption threshold, thus helping to accommodate the transfer of the reduction center to PAC in S-ZVI/PAC. In optimizing the FeSx allocation between ZVI and PAC, the chemical assembly of FeSx on S-ZVI was superior to physical adsorption. Critically, we found that isolated FeSx in the prepared solution was physically adsorbed by the PAC, allowing chemically assembled FeSx on the S-ZVI. This was achieved by controlling the addition sequence of Na2S and PAC, as it effectively controlled the release rate and content of Fe(II) in the preparation solution. S-ZVI/PAC was demonstrated to be extremely effective in simulated wastewater and electrokinetics-permeable reactive barrier (EK-PRB) treatments. Introducing PAC enriches the diversity of sulfidation mechanisms and may realize the universality of the S-ZVI/PAC application scenarios. This study provides a new interface optimization strategy for S-ZVI targeted design towards environmental applications.

Enhancing electrokinetic remediation of TPH-Cr(VI) co-contaminated soils with biochar-immobilized bacteria as biological permeable reactive barriers

The co-contamination soil caused by petroleum pollution poses a significant challenge for remediation. The complexity of pollution composition and interaction increases the difficulty of the remediation process. This study established a methodology that employs biochar-immobilized bacteria to enhance the electrokinetic (EK) remediation technique. A 25-day experiment was conducted in the laboratory to remediate co-contaminated soil with total petroleum hydrocarbons(TPH) (9252.51 mg/kg) and Cr (VI) (147.17 mg/kg). The results indicate that adding biochar-immobilized bacteria leads to the most effective remediation performance in the EK system. Compared to the standalone EK remediation, TPH removal efficiency increased by 22.57 %, and the removal rate of Cr (VI) increased by 53.15 %. The study also examined the response of microbial communities in the remediation system. The study results on microbial diversity reveal that introducing the EK system reduces the diversity of soil microbial communities. In contrast, incorporating biochar-immobilized bacteria impacts the microbial community structure in the soil, enhancing microbial communities’ stability. This study demonstrates the effectiveness of adding biochar-immobilized bacteria in enhancing EK remediation of co-contaminated soil and its impact on microbial community structure.

Removal of hexavalent chromium using zero-valent magnesium in a continuous flow system

Zero-valent magnesium (ZVM) is a powerful and beneficial material for the reduction of Cr6+ to Cr3+. To the best of our knowledge, no work has been conducted on the removal of Cr6+ from water using ZVM in a continuous flow system. Therefore, the aim of this research was to study the reduction of Cr6+ in a column with a thin ZVM layer working in continuous mode. In particular, the process kinetics were investigated using different types of Mg0 particles (powder, grit and turnings) under several operating conditions. In this regard, the effects of the inlet Cr6+ concentration and pH of the inlet solution on the process performance were studied. In addition, the influence of co-existing ions was investigated, and the material longevity was assessed. The smallest ZVM particles (powder) showed the greatest reactivity, reaching efficiencies between 78 and 100 %, followed by magnesium grit and turnings. For all the materials applied, increasing efficiencies were detected with decreasing chromium concentrations. Acidic conditions of the influent promoted the pollutant removal and the highest removal rates were achieved at pH 3. However, magnesium powder was able to guarantee satisfactory efficiencies even at pH 5 and 7, with abatements from 63 to 92 %. The presence of sulfate and nitrate did not significantly affect the process performance. Based on the collected data, a modified first-order kinetic law was formulated, resulting in an equation useful for the design of continuous systems such as reactive permeable barriers. The exhaustion tests proved a satisfactory durability of the reactive material.

Permeable Concrete Barriers to Control Water Pollution: A Review

Permeable concrete is a class of materials that has long been tested and implemented to control water pollution. Its application in low-impact development practices has proved its efficiency in mitigating some of the impacts of urbanization on the environment, including urban heat islands, attenuation of flashfloods, and reduction of transportation-related noise. Additionally, several research efforts have been directed at the dissemination of these materials for controlling pollution via their use as permeable reactive barriers, as well as their use in the treatment of waste water and water purification. This work is focused on the potential use of these materials as permeable reactive barriers to remediate ground water and treat acid mine drainage. In this respect, advances in material selection and their proportions in the mix design of conventional and innovative permeable concrete are presented. An overview of the available characterization techniques to evaluate the rheology of the paste, hydraulic, mechanical, durability, and pollutant removal performances of the hardened material are presented and their features are summarized. An overview of permeable reactive barrier technology is provided, recent research on the application of permeable concrete technology is analyzed, and gaps and recommendations for future research directions in this field are identified. The optimization of the mix design of permeable reactive concrete barriers is recommended to be directed in a way that balances the performance measures and the durability of the barrier over its service life. As these materials are proposed to control water pollution, there is a need to ensure that this practice has minimal environmental impacts on the affected environment. This can be achieved by considering the analysis of the alkaline plume attenuation in the downstream environment.

Redox trapping of arsenic in hyporheic zones modified by silicate weathering beneath floodplains

Groundwater containing high concentrations of dissolved arsenic (As) and iron (Fe(II)) discharges to rivers across the Ganges-Brahmaputra-Meghna delta. Observed Fe(III)-oxyhydroxide (FeOOH)–As deposits lining the riverbanks of the Meghna River may have been created by bidirectional mixing in the hyporheic zone (HZ) from ocean tides. This process has been named the Natural Reactive Barrier (NRB). Sedimentary organic carbon (SOC) is deposited annually on floodplains. Floodwaters that infiltrate through this layer may chemically transform the groundwater prior to discharging through the HZ in ways that influence the capture and retention of As in the NRB. The goal of this study is to understand how the interaction of these two scales of river-groundwater mixing influence the fate of As trapped within an NRB. Monitoring wells were installed to 1–17 m depth, up to 100 m distance from the river's edge during the dry season on the East (Site 1) and West (Site 2) sides of the river. They were sampled during the dry season (January) under gaining river conditions. The physical properties and elemental composition of the sediment was described by hand observation and hand-held X-Ray Fluorescence (XRF), respectively. Mixing with river water was quantified using the sum of charge of major cations (TC). Site 1 has a sloping bank that is only partially inundated during the wet season. The aquifer is composed of homogeneous sand. Site 2 is flat and therefore fully inundated in the wet season. The aquifer is composed of sand with thin (1–20 cm thick) clay layers. Both sites generate the dissolved products of FeOOH-reduction coupled to organic carbon oxidation, and silicate weathering beneath the floodplain. These products are dissolved Fe, As, silica, bicarbonate, calcium and phosphate. This chemistry is conducive to the formation of crystalline iron oxide minerals such as goethite which may co-precipitate with As, trapping it long-term.

Removal of refractory organic matter from landfill-contaminated groundwater by a permeable reactive barrier coupled with an Fe0/PMS advanced oxidation system

Advanced oxidation technology based on peroxymonosulfate (PMS) has attracted much attention because of its good degradation and even mineralization of refractory organic matter, but it is less used in the removal of refractory organic matter from landfill-contaminated groundwater (CGW). In this study, an Fe0/PMS advanced oxidation system-based permeable reactive barrier (Fe0/PMS-PRB) has been employed to remove refractory organic matter from landfill leachate CGW. The results show that the Fe0/PMS system offers a significantly higher removal efficiency of organic matter, especially humus, from CGW than other control systems. The main active oxygen species are SO4•─ and HO•, which can facilitate electron-transfer, carbonylation, electrophilic addition, decarboxylation, and other pathways to effectively degrade various refractory organic substances (e.g., bisphenol A, diclofenac acid, and ciprofloxacin). The pseudo-first-order reaction rates reached 0.1083, 0.3030, and 0.0641 min−1, respectively, effectively reducing the bio-toxicity of the effluent. Based on observations by scanning electron microscopy, X-ray diffraction analysis, and X-ray photoelectron spectroscopy, a reaction mechanism was proposed, which involves homogeneous oxidation, heterogeneous oxidation, adsorption, and precipitation of Fe0. In long-term seepage tests, under conditions of an Fe0 loading of 0.7 g, a PMS concentration of 0.8 mm, and a hydraulic retention time of 15 min, after running for 10 pore volumes, the removal extents of aromatic organic matter and total organic carbon from the CGW by the Fe0/PMS-PRB reached 79.01 % and 68.25 %, respectively. Therefore, Fe0/PMS-PRB can effectively remove refractory organic matter from CGW and has good application prospects.

Characteristics of Zinc Adsorption onto Biochars Derived from Different Feedstocks

Human activities such as the discharge of urban sewage, garbage, and industrial waste have seriously affected the quality of groundwater sources for human consumption. The potential for using biochar as a reactive medium in a permeable reactive barrier (PRB) was explored for Zn-contaminated groundwater treatment in this study. Four different types of biochar produced from wood, coconut shell, rice straw, and fruit shell were used. The production temperature of these biochars were 600 °C, 550 °C, 500 °C, and 500 °C, respectively. The samples were coded with the initials of the biochar source and the production temperature as WD600, CS550, RS500, and FS500. The results of various batch adsorption studies show that equilibrium solution pH has a great effect on the maximum adsorption capacity in the pH range of 2–7. The adsorption of Zn on biochars follows the Freundlich model and fits well with the pseudo-second-order model. The fixed-bed column test data were well fitted to the Dose–Response model. The adsorption capacities of WD600, CS550, RS500, and FS500 were 24.91, 15.87, 9.25, and 46.71 mg/g, respectively. The removal rate of FS500 can reach a maximum of 98.87%. FS500 is considered to be a potential reaction medium for treating Zn-contaminated groundwater in a PRB system. This work provides a new option for converting biomass waste into an adsorbent for zinc in wastewater. The results of this study are expected to provide a solid theoretical basis for the further application of biochar in groundwater pollution remediation.

Study on Cu- and Pb-contaminated loess remediation using electrokinetic technology coupled with biological permeable reactive barrier

Although the electrokinetic (EK) remediation has drawn great attention because of its good maneuverability, the focusing phenomenon near the cathode and low removal efficiency remain to be addressed. In this study, a novel EK reactor was proposed to remediate Cu and Pb contaminated loess where a biological permeable reactive barrier (bio-PRB) was deployed to the middle of the EK reactor. For comparison, three test configurations, namely, CG, TG-1, and TG-2, were available. CG considered the multiple enzyme-induced carbonate precipitation (EICP) treatments, while TG-1 considered both the multiple EICP treatments and pH regulation. TG-2 further considered NH4+ recovery based on TG-1. CG not only improved Cu and Pb removals by the bio-PRB but also depressed the focusing phenomenon. TG-1 causes more Cu2+ and Pb2+ to migrate toward the bio-PRB and aggravates Cu and Pb removals by the bio-PRB, depressing the focusing phenomenon. TG-2 depressed the focusing phenomenon the most because Cu2+ and Pb2+ can combine with not only CO32− but PO43−. The removal efficiency of Cu and Pb is 34% and 36%, respectively. A NH4+ recovery of about 100% is attained.

Effect of leachate contamination in municipal solid waste on clay liner characteristics

Landfill leachate is generated as a consequence of water percolation through the solid waste, oxidation of the waste, and corrosion of the waste. Under-designed landfill sites allow the leachate to easily pass through the soil strata. To identify the effect of contaminants on the engineering properties of the clay liner, a pilot-scale lysimeter was developed. Experiments on two types of soils polluted with leachate were conducted which included silty clay and soil enhanced by chemical stabilization. Lime and silica fume are used as reactive barriers in landfill earthen liners. The leachate generated was monitored periodically and sampled for (pH, Electrical conductivity, Chemical oxygen demand, Chloride, Total dissolved solids, and total suspended solids). Lime (L), silica fume (SF), and lime-silica fume (L-SF) mix have been used for stabilizing soil. Three percentages were used for lime (2%, 4% and 6%) and three percentages were used for silica fume (3%, 5% and 7%) and the optimum percentage of silica fume (5%) was mixed with the proportions of lime. The optimum lime values are 4% from the research and 5% for silica fume. Soil samples were analyzed over a maturation period of 135 days for each run to identify the chemicals and their effect on the soil characteristics. The plasticity index of the stabilized soil continues to decline until it reaches 36% over the 135 days of the maturing period. Furthermore, an increase in silty clay soil hydraulic conductivity was observed from 3.3 × 10−6 cm/sec to 5 × 10−6 cm/sec at 135 days of maturation. Whereas there is a sharp decrease in hydraulic conductivity to achieve a maximum value in the stabilized soil (1.25 ×10−10 cm/sec). Based on laboratory test results, it can be concluded that soil stabilization can improve the geotechnical properties of landfill earthen liners due to pozzolanic reactions.

Wastewater Treatment in Central Asia: Treatment Alternatives for Safe Water Reuse

Due to water scarcity and ready availability, treated wastewater in Central Asia is increasingly reused and seen as a valuable resource, requiring effective management with particular care for human health, environmental protection, and water security. Due to limited technical and economic support and poorly developed regulatory systems, many cities have inadequate wastewater treatment infrastructure. Improved wastewater effluent management is paramount due to its relationship with surface and groundwater quality used for drinking and agricultural irrigation. This paper presents a brief review of the published literature reporting on current wastewater treatment technologies and effluent composition, with particular attention paid to reuse needs. The impact of these practices on water quality is further assessed from information and reports gathered from various sources on the quantity and quality of surface waters and groundwaters. Finally, alternatives to current wastewater treatment practices in Central Asia will be explored with a particular emphasis on the removal of contaminants of emerging concern, including biological treatment systems, adsorption, advanced oxidation processes, and managed/unmanaged aquifer recharge techniques based on permeable reactive barriers, aiming to increase the availability and quality of surface waters and groundwaters for safe water reuse.

Coffee grounds modified zero-valent iron for efficient heavy metal removal

Surface modification is one of the most important approach for improving the reactivity of zero-valent iron. In this study, waste coffee grounds (CG) were chosen to modify zero-valent iron through a mechanochemical method. The synthesized CG-ZVI exhibited a 166 times faster Cr(VI) removal rate. Structural characterization and ATR-FTIR analysis indicated that CG modification endowed ZVI with abundant carboxylic acid groups, and accelerated the adsorption of Cr(VI) via the complexation effect of CG-COOH···HCrO4−. Moreover, the polyphenolic substances from CG-ZVI, as an electron shuttle, accelerated the electron transfer from the iron core to generated surfaced bound Fe2+, resulting in high efficiency of Cr(VI) removal. In addition, CG-ZVI selectively removed Cr(VI) in the presence of anions (Cl−, NO3−, SO42−) and acted as a permeable reactive barrier material for in situ treatment of heavy metal-contaminated water. This work demonstrates that CG modification can function as an excellent candidate for perfecting the reactivity of ZVI. More importantly, it opens up a new way for the utilization of discarded CG.

Performance expectation of coal waste in permeable reactive barrier for removal of cadmium considering contamination level and pore water velocity

The effectiveness and longevity of permeable reactive barriers (PRBs) depend on the performance of the reactive materials and the subsurface environment. The relationship of the groundwater velocity on performance of coal waste for the heavy metal removal was reported in our previous study. In this study, we investigated the performance and longevity of coal waste as a PRB material for the removal of Cd considering subsurface environmental conditions such as contamination level and groundwater velocity. The artificial groundwater contaminated by Cd were prepared with various concentrations ranging from 10 to 100 mg L−1. Lab-scale column experiments were conducted using coal waste filled columns by injecting the artificial groundwater. The breakthrough curves were analyzed advection dispersion equation coupled with equilibrium sorption model to determine the retardation factor. The Cd breakthrough curves exhibited different retardation with respect to the contamination levels. The Cd transport was more retarded as the contamination level lowered. The relationship between the retardation factor and the contamination levels could be explained with empirical equations based on non-linear sorption isotherms. By adopting the velocity dependency of sorbent performance in our previous study, transport of Cd within coal waste was simulated under various subsurface environmental conditions to construct the longevity function. The function could be used for the longevity prediction of coal waste as a PRB material considering groundwater velocity and contamination level in subsurface environment.

Assessment of a new rigid wall permeameter for the slurry like barrier materials: zeolite example

Areas vulnerable to catastrophic disasters such as hurricane, landslide and earthquake require ready and sustainable solutions for the post-pollution scenarios. Clinoptilolite type zeolite re- sources of Türkiye can serve economical and sustainable solutions as a quick response. While the studies on compacted zeolite-bentonite mixture at optimum water content for the landfill liners applications or dry zeolite-sand mixtures in permeable reactive barrier (PRB)s are com- mon, the slurry form of zeolite emplacement at subsurface reactive barriers has not received an attention by the researchers. In this context, this experimental study presents the prelimi- nary findings on one-dimensional consolidation and hydraulic conductivity tests performed on crushed zeolite samples S1 and S2 with fine contents of 33 and 84%, respectively. The results indicate that S2 has a higher compression index than S1, without a significant change in swelling index attributed to less than 4% clay contents. A self-designed rigid wall type per- meameter was used to study on reconstituted slurry like materials under the benefit of back pressure saturation without the consolidation during testing that encountered in flexible wall permeameter. Falling head – rising tail water procedure was adopted under the back pressure in between 200 and 700 kN/m2. S2 samples reconstituted under 25, 50, 100 and 200 kN/m2 show a gradual decrease in kv from 3×10-8 to 2×10-9 m/s. Previous observations on the sample of S1 revealed 8 times higher kv values under the same σv'. Since the fine content of zeolite limits kv, the proposed permeameter will be beneficial to determine the proper grain size dis- tribution of fill materials considering the barrier height and in-situ stress conditions before the environmental studies with leachate.

Funnel and Gate Permeable Reactive Barrier Configuration for Contaminated Groundwater Remediation – Designing, Installation, and Modeling: A Review

Funnel and Gate Permeable Reactive Barrier Configuration for Contaminated Groundwater Remediation – Designing, Installation, and Modeling: A Review