Permeable Reactive Barrier Research Articles

Using CO2 and oxidants for in situ regeneration of permeable reactive barriers for leachate–contaminated groundwater

Groundwater contamination near landfills is commonly caused by leachate leakage, and permeable reactive barriers (PRBs) are widely used for groundwater remediation. However, the deactivation and blockage of the reactive medium in PRBs limit their long-term effectiveness. In the current study, a new methodology was proposed for the in situ regeneration of PRB to remediate leachate-contaminated groundwater. CO2 coupled with oxidants was applied for the dispersion and regeneration of the fillers; by injecting CO2 to disperse the fillers, the permeability of the PRB was increased and the oxidants could flow evenly into the PRB. The results indicate that the optimum filler proportion was zero-valent iron (ZVI)/zeolites/activated carbon (AC) = 3:8:10 and the optimum oxidant proportion was COD/Na2S2O8/H2O2/Fe2+ = 1:5:6:5; the oxidation system of Fe2+/H2O2/S2O82− has a high oxidation efficiency and persistence. The average regeneration rate of zeolites was 72.71%, and the average regeneration rate of AC was 68.40%; the permeability of PRB also increased. This technology is effective for the remediation of landfills in China that have large contaminated areas, an uneven pollutant concentration distribution, and a long pollution duration. The purification mode of long-term adsorption and short-time in situ oxidation can be applied to the remediation of long-term high-concentration organically polluted groundwater, where pollution sources are difficult to cut off.

Cr(VI) removal and mechanism from simulated polluted groundwater by Klebsiella variicola H12-CMC-FeS@biochar assisted permeable reactive barrier

Permeable reactive barrier(PRB) is an attractive technique for in situ polluted groundwater remediation. Klebsiella variicola H12-Carboxymethylcellulose -FeS@biochar (K.variicola H12-CMC-FeS@biochar) was used as filling medium in PRB to remove chromium contamination from simulated groundwater. The results showed that the chromium removal efficiency was 94 %, which was more effective than k. variicola H12 or biochar respectively and the optimal solid-liquid ratio was 30:1. Ionic strength and initial chromium concentration in groundwater have greater influence on the treatment effect. Scanning electron microscopy(SEM) and fluorescence microscopy showed that biofilm covered on the surface of the material. X-ray Photoelectron Spectroscopy(XPS) indicated that most of hexavalent chromium(Cr(VI)) and trivalent chromium(Cr(III)) were adsorbed by k. variicola H12-CMC-FeS@biochar. Cr(III) originated from the reduction of chromium by K. variicola. Furthermore, quantitative real-time polymerase chain reaction(qPCR) results showed that the expression level of ChrA, ChrB and ChrR genes increased, which contributed to relieve cytotoxicity. These changes improved the resistance of k. variicola H12 to Cr(VI), promoting Cr(VI) reduction. In summary, biofilm adsorption and microbe reduction were the two primary ways to enhance the chromium removal efficiency. It provided a new method for treating in-situ groundwater pollution by PRB technology using biochemical materials as mediums.

Remediation potential of mining, agro-industrial, and urban wastes against acid mine drainage

Acid mine drainage (AMD) poses serious consequences for human health and ecosystems. Novel strategies for its treatment involve the use of wastes. This paper evaluates the remediation potential of wastes from urban, mining and agro-industrial activities to address acidity and high concentrations of potentially toxic elements (PTE) in AMD. Samples of these waste products were spiked with an artificially prepared AMD, then pH, electrical conductivity (EC), and PTE concentrations in the leachates were measured. The artificial AMD obtained through oxidation of Aznalcóllar’s tailing showed an ultra-acid character (pH − 2.89 ± 0.03) and extreme high electrical conductivity (EC − 3.76 ± 0.14 dS m−1). Moreover, most PTE were above maximum regulatory levels in natural and irrigation waters. Wastes studied had a very high acid neutralising capacity, as well as a strong capacity to immobilise PTE. Inorganic wastes, together with vermicompost from pruning, reduced most PTE concentrations by over 95%, while organic wastes retained between 50 and 95%. Thus, a wide range of urban, mining, and agro-industrial wastes have a high potential to be used in the treatment of AMD. This study provides valuable input for the development of new eco-technologies based on the combination of wastes (eg. Technosols, permeable reactive barriers) to remediate degraded environments.

Research Progress of Nanoscale Zero-valent Iron in Removal of Heavy Metals From Groundwater

Groundwater heavy metal pollution has become increasingly serious, receiving widespread attention. Permeable reactive barrier (PRB) is one of the commonly used in situ remediation technologies for groundwater heavy metal pollution. Currently, it has been widely used in engineering practice. Nanoscale zero-valent iron (nZVI) is an emerging remediation material with broad application prospects for groundwater heavy metal pollution. This article summarizes different types of PRB and methods for preparing nZVI. It also introduces the different modifications and effects of nZVI, and elaborates on the relevant problems that need to be overcome in the engineering application of nZVI. This study believes that seeking more affordable modification methods and environmentally friendly modification materials are key issues that need to be addressed in the future.

Remediation of Groundwater Contaminated with Copper Ions by Waste Foundry Sand Permeable Barrier

The permeable reactive barrier (PRB) is one of the promising innovative in situ groundwater remediation technologies, in removing of copper from a contaminated shallow aquifer. The 1:1- mixture of waste foundry sand (WFS) and Kerbala’s sand (KS) was used for PRB. The WFS was represented the reactivity material while KS used to increase the permeability of PRB only. However, Fourier-transform infrared (FTIR) analysis proved that the carboxylic and alkyl halides groups are responsible for the sorption of copper onto WFS. Batch tests have been performed to characterize the equilibrium sorption properties of the (WFS+KS) mix in copper- containing aqueous solutions. The sorption data for Cu+2 ions, obtained by batch experiments, have been subjected to the Langmuir and Freundlich isotherm models. The Langmuir model was chosen to describe the sorption of solute on the solid phase of PRB. COMSOL Multiphysics 3.5a based on finite element method was used for formulation the transport of copper ions in two- dimension physical model under equilibrium condition. Numerical and experimental results proved that the PRB plays a potential role in the restriction of the contaminant plume migration. A good agreement between the predicted and experimental results was recognized with mean error (ME) not exceeded 10 %.

Iron Permeable Reactive Barrier for Removal of Lead from Contaminated Groundwater

The possibility of using zero-valent iron as permeable reactive barrier in removing lead from a contaminated groundwater was investigated. In the batch tests, the effects of many parameters such as contact time between adsorbate and adsorbent (0-240 min), initial pH of the solution (4-8), sorbent dosage (1-12 g/100 mL), initial metal concentration (50-250 mg/L), and agitation speed (0-250 rpm) were studied. The results proved that the best values of these parameters achieve the maximum removal efficiency of Pb+2 (=97%) were 2 hr, 5, 5 g/100 mL, 50 mg/L and 200 rpm respectively. The sorption data of Pb+2 ions on the zero-valent iron have been performed well by Langmuir isotherm model in compared with Freundlich model under the studied conditions. Finite difference method and computer solutions (COMSOL) multiphysics 3.5a software based on finite element method were used to simulate the one-dimensional equilibrium transport of lead through sand aquifer with and without presence of barrier. The predicted and experimental results proved that the reactive barrier plays a potential role in the restriction of the contaminant plume migration and a reasonable agreement between these results was recognized.

Phenol Removal Using Granular Dead Anaerobic Sludge Permeable Reactive Barrier in a Simulated Groundwater Pilot Plant

This study investigates the performance of granular dead anaerobic sludge (GDAS) bio-sorbent as permeable reactive barrier in removing phenol from a simulated contaminated shallow groundwater. Batch tests have been performed to characterize the equilibrium sorption properties of the GDAS and sandy soil in phenol-containing aqueous solutions. The results of GDAS tests proved that the best values of operating parameters, which achieve the maximum removal efficiency of phenol (=85%), at equilibrium contact time (=3 hr), initial pH of the solution (=5), initial phenol concentration (=50 mg/l), GDAS dosage (=0.5 g/100 ml), and agitation speed (=250 rpm). Fourier transform infrared (FTIR) analysis proved that the carboxylic acid, aromatic, alkane, alcohol, and alkyl halides groups are responsible for the bio-sorption of phenol onto GDAS.A 2D advection-dispersion, solved numerically by computer solutions (COMSOL) Multiphysics 3.5a software which is based on the finite element method, has been used to simulate the equilibrium transport of phenol within groundwater. This model is taking into account the pollutant sorption onto the GDAS and sandy soil which is represented by Langmuir equation. Numerical and experimental results proved that the barrier plays a potential role in the restriction of the contaminant plume migration. Also, the barrier starts to saturate with contaminant as a function of the travel time. A good agreement between the predicted and experimental results was recognized with root mean squared error not exceeded the 0.055.

Ball-milled sulfide iron-copper bimetals based composite permeable materials for Cr (VI) removal: Effects of preparation parameters and kinetics study

Zero-valent iron (ZVI) and modified ZVI have been investigated extensively for groundwater remediation. However, ZVI based powder was difficult to be applied directly as permeable reactive barrier (PRB) materials due to their low water permeability and usage rate. In this study, sulfide iron-copper bimetal was prepared by ball milling, which is environment-friendly without second contamination. The optimal preparation parameters of sulfide iron-copper bimetal for Cr(VI) removal were determined (Cu/Fe ratio (w/w), 0.018; FeS/Fe ratio (w/w), 0.1213; ball milling speed, 450 rpm; ball milling time, 5 h). A composite permeable material was prepared by sintering a mixture of sulfide iron-copper bimetal, sludge, and kaolin. The parameters for composite permeable material preparation including sludge content and particle size, and sintering time were optimized, which were 60%, 60–75 mesh, and 4 h, respectively. The optimal composite permeable material was characterized by SEM-EDS, XRD, and FTIR. The results demonstrated preparation parameters can affect the hydraulic conductivity and hardness of composite permeable material. High sludge content, small particles size, and moderate sintering time resulted in high permeability of composite permeable material and were beneficial for Cr(VI) removal. The dominant Cr(VI) removal mechanism was reduction, and the reaction followed pseudo-first order kinetics. Conversely, low sludge content and large particle size, and long sintering time lead to low permeability of composite permeable material. Chromate removal was mainly by chemisorption following pseudo-second order kinetics. The hydraulic conductivity and hardness of the optimal composite permeable material achieved 1.732 cm/s and 50, respectively. The results of column experiments indicated that its Cr(VI) removal capacity was 0.54 mg/g, 0.39 mg/g and 0.29 mg/g at pH 5, 7 and 9, respectively. The ratio of Cr(VI) to Cr(III) on composite permeable material surface was similar under acidic and alkaline conditions. This study will provide an effective reactive material of PRB for field application.

Degradation of 1,2-dichloroethane in real polluted groundwater by using enriched bacterial consortia in aerobic and anaerobic laboratory-scale conditions

The aim of this work was to gain insights about the feasibility of chlorinated solvents removal through biostimulated and bioaugmented biological processes in laboratory-scale permeable reactive barriers (PRBs) under anaerobic and aerobic conditions. The experimental plant consisted of two Plexiglas cylindrical columns filled with silica sand and fed with real groundwater contaminated by chlorinated solvents (mainly 1,2-dichloroethane, 1,2-DCA, at a concentration of 20 mg l−1). Column A simulated a PRB containing poly-β-hydroxybutyrate (PHB) powder as electron donor and worked under anaerobic conditions; in Column B an inlet air flow rate ensured aerobic conditions. Both columns were inoculated with dechlorinating bacterial consortia obtained by enrichment cultures from the same contaminated groundwater. Results from Column A showed that PHB can be fermented and used as a slow-releasing carbon source for sustaining reductive dechlorination, as revealed by acetate production up to 267 mg l−1 and 100% 1,2-DCA removal. The microbial community detected in Column A at the end of the experimental period was mainly enriched in sulfate reducing bacteria that could act as both fermenting and dechlorinating agents. Column B showed a slight lower 1,2-DCA removal efficiency (98%) likely related to the establishment of aerobic (co)metabolic processes.

Microbe–Mineral Interaction-Induced Microorganism-Augmented Permeable Reactive Barriers for Remediation of Contaminated Soil and Groundwater: A Review

Microbe–Mineral Interaction-Induced Microorganism-Augmented Permeable Reactive Barriers for Remediation of Contaminated Soil and Groundwater: A Review

Crushed construction and demolition waste as reactive media in permeable reactive barriers to immobilize Pb(II) and Cd(II) from landfill leachate

This study evaluates the effectiveness of using crushed construction and demolition waste as reactive media for applying in Permeable Reactive Barriers to treat contaminated groundwater by landfill leachate. Modern analytical methods such as SEM and EDX were used to analyze the physicochemical properties of crushed demolition waste, demonstrating that the material has a porous structure on the surface that is suitable for thetargeted heavy metal adsorption. For ion Pb2+ , the maximum adsorption amount of 114.05 mg/g was for 1-3 mm fraction and 105.05 mg/g for 3-5 mm fraction. Similarly, ion Cd (II) achieves the maximum adsorption capacity of 8.43mg/g with 1-3mm and 6.26mg/g with 3-5mm fraction. Simultaneously, this paper investigates the impact of additional parameters such as time and pH on the adsorption efficiency of the materials.

Optical In Situ Monitoring of Acid Mine Drainage Remediation: Laboratory and Model Investigation

AbstractA permeable reactive barrier (PRB) can be deployed to remediate acid mine drainage. The performance of a PRB material under different boundary conditions (pH, flow velocity, and sulfate concentration) was investigated in a series of column experiments applying in‐situ optical sensing methods for pH and oxygen detection. The reactive material consisted of organic components (compost, wood, and coconut shell) mixed with calcium carbonate and fine gravel. The input concentrations were around 1000 mg/L for iron and 3000 mg/L for sulfate, and the pH value was 6.2. The remediation efficiency of iron was 14.6% and of sulfate 15.2%, but was expected to scale up when moving to a field‐site PRB with greater thickness. The iron and sulfate removal was influenced by decreasing the flow velocity and increasing the sulfate input concentration and the pH value. In an experiment with low pH boundary conditions (pH = 2.2), acidity was neutralized in the PRB by calcium carbonate during an experiment duration of 47 days. The modeling program MIN3P was used to create a simulation of the laboratory experiments. This helps to design parameters, for example, the residence time in the PRB, which is necessary for close to 100% remediation efficiency. This study shows the application of optical oxygen and pH monitoring in PRBs. In this context, they can be used to monitor the stability of a PRB for the remediation of acid mine drainage (AMD).

Behavior of heavy metals and natural radionuclides along the Moroccan phosphogypsum carbonation process with several alkaline reagents

Phosphogypsum (PG) is the main by-product from the phosphoric acid (PA) production industry being the PA production the basic raw material for producing the modern fertilizers. Because of its high calcium and sulfate content, it is important to emphasize that ecological benefits come from recycling and eventually converting PG into value-added compounds are obtained. This work aims to remedy the environmental problems associated to the large quantities of PG generated in Morocco. Furthermore, three procedures for PG conversion into Ca(OH)2, CaCO3, Na2SO4, K2SO4 and (NH4)2SO4 using hydroxide aqueous mediums were studied. The impurity traces contained in the PG were generally found to be completely transferred into the final calcite. The sulfates produced here are recommended for the use as a fertilizer (K2SO4 and (NH4)2SO4) and in the manufacture of detergents (Na2SO4), and the obtained calcite could be used in cement production, concretes, permeable reactive barriers for pollutants removing, etc.

Modeling and Simulation of Cadmium Removal from the Groundwater by Permeable Reactive Barrier Technology

The removal of cadmium ions from simulated groundwater by zeolite permeable reactive barrier was investigated. Batch tests have been performed to characterize the equilibrium sorption properties of the zeolite in cadmium-containing aqueous solutions. Many operating parameters such as contact time, initial pH of solution, initial concentration, resin dosage and agitation speed were investigated. The best values of these parameters that will achieved removal efficiency of cadmium (=99.5%) were 60 min, 6.5, 50 mg/L, 0.25 g/100 ml and 270 rpm respectively. A 1D explicit finite difference model has been developed to describe pollutant transport within a groundwater taking the pollutant sorption on the permeable reactive barrier (PRB), which is performed by Langmuir equation, into account. Computer program written in MATLAB R2009b successfully predicted meaningful values for Cd+2 concentration profiles. Numerical results show that the PRB starts to saturate after a period of time (~120 h) due to reduce of the retardation factor, indicating a decrease in percentage of zeolite functionality. However, a reasonable agreement between model predictions and experimental results of the
 total concentration distribution of Cd2+ species across the soil bed in the presence of zeolite permeable reactive barrier was recognized.

Removal of hexavalent chromium pollutant and mechanism by heat-treated natural pyrite as an efficiency reactive media for permeable reactive barrier

Removal of hexavalent chromium pollutant and mechanism by heat-treated natural pyrite as an efficiency reactive media for permeable reactive barrier

Novel material from immobilization of magnesium oxide and cetyl trimethyl ammonium bromide nanoparticles onto waterworks sludge for removing methylene blue from aqueous solution

Utilizing the waterworks sludge byproduct in the treatment of wastewater contained methylene blue dye is one approach that has been taken in an effort to lessen the difficulties that are associated with managing such byproduct. The prime aim of this work is manufacturing of novel sorbent from co-precipitation of magnesium oxide nanoparticles on the surfaces of waterworks sludge in the existence of cetyl trimethyl ammonium bromide surfactant. Surfactant 0.04 g/50 mL, dose of sludge 2 g/50 mL, and pH 12 were the most efficient preparation parameters to remove 75.31% of adopted dye. The adsorption studies were conducted under various conditions of contact time (0–240 min), concentration of dye (10–300 mg/L), sorbent mass (0.05–1.5 g), and solution pH (3–12). The best values of batch parameters were identical to the highest percentages of contaminant removal. Results proved that the magnesium oxide nanoparticles are attached to the sludge surfaces. Freundlich and pseudo-second-order models have perfectly described sorption results with 59.92 mg/g maximum sorption capacity. The breakthrough curves can be accurately described by the Bohart-Adams model. The outputs of continuous tests have been paved the way for future usage of the prepared sorbent in the field permeable reactive barrier technology.

Development of an advanced machine learning model to predict the pH of groundwater in permeable reactive barriers (PRBs) located in acidic terrain

This paper presents a comprehensive study of various Random Forest (RF) models for predicting increments of pH in groundwater treated by permeable reactive barriers (PRBs). This study uses data collected over 16 years from two PRBs installed in acid sulfate soils. The hyperparameters of the Random Forest have been optimised using three powerful optimisation algorithms: the Whale Optimisation Algorithm, the Tunicate Swarm Algorithm, and the Jellyfish Search Optimizer. The results show that the RF-Jellyfish Search Optimiser was the most accurate model for predicting pH increment in the downgradient. This model could predict pH increments for 80 data points as well as another PRB with a different reactive material. The model was also compared with a finite difference flow model from literature. The results showed that the RF-Jellyfish Search Optimizer was more accurate with the coefficient of determination and root mean square error values of 0.954 and 7.04, compared to 0.942 and 10.27 obtained from the finite difference model. Overall, the novel intelligent technique introduced in this study effectively predicts pH increments in treated groundwater and can also be applied to different PRBs.

Degradation of trichloroethylene vapors by micrometric zero-valent Fe[sbnd]Cu and Fe[sbnd]Ni bimetals under partially saturated conditions

The degradation of trichloroethylene (TCE) vapors by zero-valent Iron-Copper (Fe–Cu) and Iron-Nickel (Fe–Ni) bimetals with 1%, 5% and 20% weight content (%wt) of Cu or Ni was tested in anaerobic batch vapor systems carried out at ambient room temperature (20 ± 2 °C) under partially saturated conditions. The concentrations of TCE and byproducts were determined at discrete reaction time intervals (4 h-7 days) by analyzing the headspace vapors. In all the experiments, up to 99.9% degradation of TCE in the gas phase was achieved after 2–4 days with zero-order TCE degradation kinetic constants in the range of 134–332 g mair−3d−1. Fe–Ni showed a higher reactivity towards TCE vapors compared to Fe–Cu, with up to 99.9% TCE dechlorination after 2 days of reaction, i.e., significantly higher than zero-valent iron alone that in previous studies was found to achieve comparable TCE degradation after minimum 2 weeks of reaction. The only detectable byproducts of the reactions were C3–C6 hydrocarbons. Neither vinyl chloride or dichloroethylene peaks were detected in the tested conditions above their method quantification limits that were in the order of 0.01 g mair−3. In view of using the tested bimetals in horizontal permeable reactive barriers (HPRBs) placed in the unsaturated zone to treat chlorinated solvent vapors emitted from contaminated groundwater, the experimental results obtained were integrated into a simple analytical model to simulate the reactive transport of vapors through the barrier. It was found that an HPRB of 20 cm could be potentially effective to ensure TCE vapors reduction.

Passive removal of sulphate and heavy metals from acid mine drainage using sewage sludge and fly ash

This study aims to calculate the removal efficiency (%RE) of metals and sulphate and the constant rate of sulphate reduction from acid mine drainage (AMD) based on passive treatment principles named permeable reactive barrier (PRB) in batch test prior column test. Three media mixtures containing a variety of domestic sewage sludge (SE), mess hall compost (CO), cocopeat (CP), and fly ash (FA) were simulated. All reactive materials are solid waste from other operating units. M1 and M2 were contains organic and inorganic waste, M3 was only contain organic waste. The AMD was collected from a copper mining waste rock dump of which contained high sulphate, metals, and low pH. Batch tests were conducted in a series of glass bottles in an anaerobic chamber, and sub-samplings were taken on days 0, 7, 14, and 28. At the end of treatment, it indicated that M1 mixture resulting in the highest sulphate (SO4 2-) removal (44%), highest alkalinity generation of 1431 mg/L (as CaCO3) and %RE of Al, Cd, Co, Cu, Fe, and Zn were expected to be 100%, Ni 82%, Se 57%, and Mn 98%. Additional of FA for treatment such in M1 and M2 releasing more As in the final result compare to M3 that only contain organic substrates. The primary mechanism controlling the reaction from the M1 was a combination of sulphide precipitation enhanced by Sulphate Reducing Bacteria (SRB) activities supported by pH buffering and hydroxide precipitation. The sulphate reduction mechanism assumed to be the first-order reaction with highest rate constants found as 0.0208 d−1 from M1 reactors, 0.0144 d−1, 0.0161 d−1 for M2 and M3 respectively.

MIL-100(Fe)@cotton fiber as permeable reactive barrier for heavy metal contaminated soils: Preparation, performance and mechanism

Due to their toxicity and serious threat to human health and the environment, heavy metals in soil have drawn attention on a global scale. In our research, a new material MIL-100(Fe)@cotton fiber (CM100) was prepared by using waste cotton fiber as a substrate and loading MIL-100(Fe) particles by in-situ growth under green and mild preparation conditions. Its morphological characteristics and adsorption mechanism were investigated. It was used as a barrier to study the remediation characteristics of electrokinetic-permeable reactive barrier (EK-PRB) under different electrolytes. Results showed that CM100 was able to remove Pb2+ and Cd2+ with efficiencies of 96.1% and 78.7%, respectively. The adsorption is in accordance with the pseudo-second-order kinetic model and is dominated by chemisorption. Under different electrolyte compositions, the remediation efficiencies of CM100 and EK-PRB on heavy metal soils reached more than 90.0%. When the electrolyte was KCl/citric acid (CA), it could regulate soil pH and promote the migration of metal ions, which increased the remediation efficiency to 98.0%. Experimental results demonstrate that CM100/EK-PRB can effectively remediate heavy metal soil, and this study also provides a reference for the resource utilization of waste textiles.