Field assessment of guar gum stabilized microscale zerovalent iron particles for in-situ remediation of 1,1,1-trichloroethane

A pilot injection test with guar gum stabilized microscale zerovalent iron (mZVI) particles was performed at test site V (Belgium) where different chlorinated aliphatic hydrocarbons (CAHs) were present as pollutants in the subsurface. One hundred kilograms of 56 μm-diameter mZVI (~ 70 g/L) was suspended in 1.5 m3 of guar gum (~ 7 g/L) solution and injected into the test area. In order to deliver the guar gum stabilized mZVI slurry, one direct push bottom-up injection (Geoprobe) was performed with injections at 5 depths between 10.5 and 8.5 m bgs. The direct push technique was preferred above others (e.g. injection at low flow rate via screened wells) because of the limited hydraulic conductivity of the aquifer, and to the large size of the mZVI particles. A final heterogeneous distribution of the mZVI in the porous medium was observed explicable by preferential flow paths created during the high pressure injection. The maximum observed delivery distance was 2.5 m. A significant decrease in 1,1,1-TCA concentrations was observed in close vicinity of spots where the highest concentration of mZVI was observed. Carbon stable isotope analysis (CSIA) yielded information on the success of the abiotic degradation of 1,1,1-TCA and indicated a heterogeneous spatio-temporal pattern of degradation. Finally, the obtained results show that mZVI slurries stabilized by guar gum can be prepared at pilot scale and directly injected into low permeable aquifers, indicating a significant removal of 1,1,1-TCA

Injection of guar gum micro-sized zero-valent iron via direct push - field study

Within the FP7 AQUAREHAB project (GA 226565), injectable micro-sized zerovalent iron particles (mZVI) were developed and evaluated for in-situ chemical reduction of chlorinated aliphatic hydrocarbons (CAHs). mZVI particles have good reactive properties and a longer life-time than nano-sized particles (nZVI), but need to be stabilised during injection to prevent sedimentation in storage vessels and injection tubes. Earlier we reported on a field scale injection of guar gum stabilized mZVI that was performed in November 2011 as a joined endeavour of several AQUAREHAB partners. More recently, April 2013, an additional larger scale pilot test was performed at another CAH-contaminated site in Belgium, where findings of the first test and numerous lab scale tests were used to work out an improved approach. At a PCE contaminated test site, 250 kg of mZVI was injected as 5 m³ of 0.45% guar gum stabilized suspension via direct push between 2 and 8 m bgs. The mZVI was injected in a test area of 3 by 6 m via 6 high pressure injections (MIP-IN technology) targeting a radius of influence of 0.5 m. Multilevel monitoring wells were installed at different distances around the injection point, along with temperature sensors and devices specifically developed to detect magnetic particles via measurement of electromagnetic susceptibility. Groundwater samples were taken before the injection and during several months after the injection. After the injection, also several undisturbed soil core samples were collected to evaluate the presence of mZVI (via susceptibility measurements & chemical analyses) and guar gum. The aim of the field test was: (1) to evaluate the feasibility to prepare guar gum stabilised slurry at a larger scale, (2) to evaluate the injectability of the within AQUAREHAB developed mZVI, (3) to determine the radius of influence of the injection, (4) to document the impact of the mZVI on the pollutant concentrations, and (5) to study the fate and added value of the guar gum after the injection. This paper presents the results of the followed approach, as well as some practical considerations related to lessons learne

Field injection of microscale zerovalent iron for groundwater remediation

In the framework of the research project AQUAREHAB (FP7 - G. A. Nr. 226565), a pilot injection test of guar gum stabilized microsized zerovalent iron has been designed and performed under low pressure in a CAHs contaminated site in Belgium, characterized by fine sand (hydraulic conductivity in the order of 2•10-5 m/s) and an effective velocity equal to 0.005 m/day (1). The field application was aimed to overcome those critical aspects which hinder mZVI particles field injection, mainly due to ZVI-based colloidal suspensions instability. A shear thinning guar gum solution (2 g/l) was selected as an environmentally friendly stabilizer. The relevant properties of the iron slurry (iron particles size and concentration, polymeric stabilizer type and concentration, slurry viscosity) were designed in the laboratory based on several tests (namely iron reactivity tests towards contaminants, sedimentation tests and rheological measurements).The slurry preparation was successfully up-scaled to the field application, allowing a fast preparation of large volumes (1 m3 at a time) of slurry with good dissolution of guar gum and effective dispersion of mZVI. Since the injection regime of iron slurries depends on subsurface geotechnical parameters, aquifer hydraulic conductivity, and fluid properties, a specific injection well and monitoring strategy have been developed in order to achieve high discharge rates and radii of influence, and a more homogeneous distribution of the iron particles through low pressure injection. The injection well has been designed and sealed in order to sustain average to high discharge rates, preventing the daylighting of the product. Moreover the well has been hydraulically tested by means of innovative water and guar gum step rate tests in order to determine the most suitable injection rate for the iron slurry. The injection of 50 kg of microsized iron particles (BASF, Germany), dispersed in 5 m3 of a 2 g/l guar gum suspension, was performed at a discharge rate of 1.5 m3/h. The monitoring of the process has been conducted measuring injection rate and pressure as well as iron concentration by means of a magnetic susceptometer. After the injection, the iron distribution in the subsurface was determined through liners extraction and the iron concentration measured both via non-invasive magnetic susceptibility measurements and chemical analysis. Even if the field test was specifically designed to inject in a permeation regime, or on the threshold between permeation and fracturing, the results of monitoring injection pressure and iron distribution proved that particles migration in the porous medium occurred via preferential flow. Results will be presented as well as considerations about critical aspects related to injection via permeation

Injection of guar gum micro-sized zero-valent iron via direct push – field study

Within the FP7 AQUAREHAB project (GA 226565), injectable micro-sized zerovalent iron particles (mZVI) were developed and evaluated for in-situ chemical reduction of chlorinated aliphatic hydrocarbons (CAHs). mZVI particles have good reactive properties and a longer life-time than nano-sized particles (nZVI), but need to be stabilised during injection to prevent sedimentation in storage vessels and injection tubes. Earlier we reported on a field scale injection of guar gum stabilized mZVI that was performed in November 2011 as a joined endeavour of several AQUAREHAB partners. More recently, April 2013, an additional larger scale pilot test was performed at another CAH-contaminated site in Belgium, where findings of the first test and numerous lab scale tests were used to work out an improved approach. At a PCE contaminated test site, 250 kg of mZVI was injected as 5 m³ of 0.45% guar gum stabilized suspension via direct push between 2 and 8 m bgs. The mZVI was injected in a test area of 3 by 6 m via 6 high pressure injections (MIP-IN technology) targeting a radius of influence of 0.5 m. Multilevel monitoring wells were installed at different distances around the injection point, along with temperature sensors and devices specifically developed to detect magnetic particles via measurement of electromagnetic susceptibility. Groundwater samples were taken before the injection and during several months after the injection. After the injection, also several undisturbed soil core samples were collected to evaluate the presence of mZVI (via susceptibility measurements & chemical analyses) and guar gum. The aim of the field test was: (1) to evaluate the feasibility to prepare guar gum stabilised slurry at a larger scale, (2) to evaluate the injectability of the within AQUAREHAB developed mZVI, (3) to determine the radius of influence of the injection, (4) to document the impact of the mZVI on the pollutant concentrations, and (5) to study the fate and added value of the guar gum after the injection. This paper presents the results of the followed approach, as well as some practical considerations related to lessons learned

Low pressure injection of guar gum stabilized microscale zerovalent iron particles: a pilot study

In the framework of the research project AQUAREHAB (FP7 - G. A. Nr. 226565), a pilot injection test of guar gum stabilized microsized zerovalent iron (mZVI) was designed and performed under low pressure in a CAHs contaminated site in Belgium. Since the injection regime of iron slurries depends on subsurface geotechnical parameters, aquifer hydraulic conductivity, and fluid properties, a specifically designed injection well was installed and a monitoring set-up developed in order to achieve high discharge rates and radii of influence, and a likely homogeneous distribution of the iron particles through low pressure injection. The injection well was designed and sealed in order to sustain average to high discharge rates, preventing the daylighting of the product. Moreover it was hydraulically tested by means of innovative water and guar gum step rate injection tests in order to determine the most suitable injection rate for the iron slurry. A subsequent injection of 50 kg of microsized iron particles (BASF, Germany), dispersed in 5 m3 of a 2 g/l guar gum suspension, was performed at a discharge rate of 1.5 m3/h. The monitoring of the process was conducted measuring injection rate and pressure as well as iron concentration by means of a magnetic susceptometer. After the injection, the iron distribution in the subsurface was determined through liners extraction and the iron concentration measured both via non-invasive magnetic susceptibility measurements and chemical analysis. The field test was specifically designed to inject in a permeation regime, or on the threshold between permeation and fracturing. A radius of influence in the order of 1 m was obtained. The presence of mZVI particles was detected up to 1.7 m from the injection point

Low pressure injection of guar gum stabilized microscale zerovalent iron particles: a pilot study

In the framework of the research project AQUAREHAB (FP7 - G. A. Nr. 226565), a pilot injection test of guar gum stabilized microsized zerovalent iron (mZVI) was designed and performed under low pressure in a CAHs contaminated site in Belgium. Since the injection regime of iron slurries depends on subsurface geotechnical parameters, aquifer hydraulic conductivity, and fluid properties, a specifically designed injection well was installed and a monitoring set-up developed in order to achieve high discharge rates and radii of influence, and a likely homogeneous distribution of the iron particles through low pressure injection. The injection well was designed and sealed in order to sustain average to high discharge rates, preventing the daylighting of the product. Moreover it was hydraulically tested by means of innovative water and guar gum step rate injection tests in order to determine the most suitable injection rate for the iron slurry. A subsequent injection of 50 kg of microsized iron particles (BASF, Germany), dispersed in 5 m3 of a 2 g/l guar gum suspension, was performed at a discharge rate of 1.5 m3/h. The monitoring of the process was conducted measuring injection rate and pressure as well as iron concentration by means of a magnetic susceptometer. After the injection, the iron distribution in the subsurface was determined through liners extraction and the iron concentration measured both via non-invasive magnetic susceptibility measurements and chemical analysis. The field test was specifically designed to inject in a permeation regime, or on the threshold between permeation and fracturing. A radius of influence in the order of 1 m was obtained. The presence of mZVI particles was detected up to 1.7 m from the injection poin

Pilot Scale Injection of Guar Gum Stabilized Micro-sized Zero-valent iron via Hydro-fracturing

Within the FP7 AQUAREHAB project, injectable micro-sized zero-valent iron particles (mZVI) are being developed and evaluated for in-situ chemical reduction of Chlorinated Aliphatic Hydrocarbons (CAHs). mZVI particles have good reactive properties and a longer life-time than nano-sized particles (nZVI). In contrast to nZVI, mZVI suspensions need to be stabilised to prevent sedimentation in storage vessels and injection tubes. Here we report on a field scale injection of guar gum stabilized mZVI that was performed in November 2011 as a joined endeavor of several AQUAREHAB partners. At the test site (located in Belgium) a TCE and 1,1,1-TCA contamination is present at 4-11 m bgs. The aquifer has a relatively low permeability and the gradient is very small resulting in an estimated groundwater velocity of approximately 10 m per year. Different injection techniques and approaches were considered. Based on the site characteristics, the final pilot test was performed with direct push injection (Geoprobe) at 5 depths (1 location) at high pressure to induce fracturing. Multilevel monitoring wells were installed at different distance around the injection point, along with temperature sensors and devices specifically developed to detect magnetic particles via measurement of electromagnetic susceptibility. In total, 100 kg of mZVI was injected suspended in 1.5 m³ of guar gum (6 g/l) slurry. The objectives of the field test were: - To evaluate the preparation procedure and injectability of guar gum stabilized mZVI - To understand the pressure range developed during the injection - To test the applicability of the newly developed monitoring probes - To determine the vertical and horizontal distribution of mZVI particles in the subsurface after injection - To evaluate the reactivity of mZVI after the injection A short overview of the approach followed is described in this pape

Pilot Scale Injection of Guar Gum Stabilized Micro-sized Zero-valent iron via Hydro-fracturing

Within the FP7 AQUAREHAB project, injectable micro-sized zero-valent iron particles (mZVI) are being developed and evaluated for in-situ chemical reduction of Chlorinated Aliphatic Hydrocarbons (CAHs). mZVI particles have good reactive properties and a longer life-time than nano-sized particles (nZVI). In contrast to nZVI, mZVI suspensions need to be stabilised to prevent sedimentation in storage vessels and injection tubes. Here we report on a field scale injection of guar gum stabilized mZVI that was performed in November 2011 as a joined endeavor of several AQUAREHAB partners. At the test site (located in Belgium) a TCE and 1,1,1-TCA contamination is present at 4-11 m bgs. The aquifer has a relatively low permeability and the gradient is very small resulting in an estimated groundwater velocity of approximately 10 m per year. Different injection techniques and approaches were considered. Based on the site characteristics, the final pilot test was performed with direct push injection (Geoprobe) at 5 depths (1 location) at high pressure to induce fracturing. Multilevel monitoring wells were installed at different distance around the injection point, along with temperature sensors and devices specifically developed to detect magnetic particles via measurement of electromagnetic susceptibility. In total, 100 kg of mZVI was injected suspended in 1.5 m³ of guar gum (6 g/l) slurry. The objectives of the field test were: - To evaluate the preparation procedure and injectability of guar gum stabilized mZVI - To understand the pressure range developed during the injection - To test the applicability of the newly developed monitoring probes - To determine the vertical and horizontal distribution of mZVI particles in the subsurface after injection - To evaluate the reactivity of mZVI after the injection A short overview of the approach followed is described in this paper

Development of Groundwater Rehabilitation Technologies with Injectable Fe-based Materials - AQUAREHAB WP5

Within the AQUAREHAB project WP5 focused on the development of groundwater rehabilitation technologies with injectable Fe-based micro- (100 nm < d < 100 µm) and nanoscale particles (< 100 nm). The idea was to inject small sized particles into the subsurface where they spread over a certain distance before sedimenting or attachment to the aquifer matrix. They then either directly react with the present contaminants or build a permeable reactive zone where the dissolved contaminants (plume) are being degraded.The advantage of this technology is that installing these zones or barriers via injection is fairly inexpensiveand not intrusive (in other words, the beneficial usage of the site is not disturbed by remediation efforts). Within the last four years, two strategies were pursued: (1) The use of reducingFe-based particles for reductive dehalogenation of chlorinated solvents. This technology is based upon the state of the art technology of reactive permeable barriers. Hence, the research could be based upon a strong foundation and, as planned, resulted in the successful demonstration on two field sites; (2) Application ofiron oxide particles as electron acceptors for oxidative biodegradation of BTEX contaminants. This technology was totally novel, hence it did not yield a field application within the frame of AQUAREHAB. Nevertheless, the outcomes of AQUAREHAB facilitated the development of this approach to a point where field applications were ready for application. Both approaches were accompanied by the development of monitoring technologies and ecotoxicology studie

Development of Groundwater Rehabilitation Technologies with Injectable Fe-based Materials – AQUAREHAB WP5

Within the AQUAREHAB project WP5 focused on the development of groundwater rehabilitation technologies with injectable Fe-based micro- (100 nm < d < 100 µm) and nanoscale particles (< 100 nm). The idea was to inject small sized particles into the subsurface where they spread over a certain distance before sedimenting or attachment to the aquifer matrix. They then either directly react with the present contaminants or build a permeable reactive zone where the dissolved contaminants (plume) are being degraded.The advantage of this technology is that installing these zones or barriers via injection is fairly inexpensiveand not intrusive (in other words, the beneficial usage of the site is not disturbed by remediation efforts). Within the last four years, two strategies were pursued: (1) The use of reducingFe-based particles for reductive dehalogenation of chlorinated solvents. This technology is based upon the state of the art technology of reactive permeable barriers. Hence, the research could be based upon a strong foundation and, as planned, resulted in the successful demonstration on two field sites; (2) Application ofiron oxide particles as electron acceptors for oxidative biodegradation of BTEX contaminants. This technology was totally novel, hence it did not yield a field application within the frame of AQUAREHAB. Nevertheless, the outcomes of AQUAREHAB facilitated the development of this approach to a point where field applications were ready for application. Both approaches were accompanied by the development of monitoring technologies and ecotoxicology studies