scholarly journals Phosphate Induced Arsenic Mobilization as a Potentially Effective In-Situ Remediation Technique—Preliminary Column Tests

Water ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 2364
Author(s):  
Martin V. Maier ◽  
Yvonne Wolter ◽  
Daniel Zentler ◽  
Christian Scholz ◽  
Charlotte N. Stirn ◽  
...  
Keyword(s):  
Microbial Activity ◽  
Ph Value ◽  
Surface Complexation ◽  
Contaminated Sites ◽  
Contaminated Site ◽  
Anoxic Conditions ◽  
Arsenic Mobility ◽  
Pump And Treat ◽  
Reducing Conditions

Arsenic (As) contamination of groundwater is commonly remediated by pump and treat. However, this technique is difficult to apply or maintain efficiently because the mobility of arsenic varies depending on the geochemical aquifer conditions. Arsenic interacting with the sediment can cause strong retardation, which is counteracted by ions competing for sedimentary sorption sites like silica, bicarbonate and phosphate. Phosphate competes most effectively with arsenic for sorption sites due to its chemical similarity. To accelerate an ongoing but ineffective pump and treat remediation, we examined the competitive effect of increasing phosphate doses on contaminated aquifer material of different depths and thus under distinct geochemical conditions. In the columns with phosphate addition, significant amounts of arsenic were released rapidly under oxic and anoxic conditions. In all tests, the grade of leaching was higher under anoxic conditions than under oxic conditions. As(III) was the dominant species, in particular during the first release peaks and the anoxic tests. Higher amounts of phosphate did not trigger the arsenic release further and led to a shift of arsenic species. We suggest that the competitive surface complexation is the major process of arsenic release especially when higher amounts of phosphate are used. Commonly arsenic release is described at iron reducing conditions. In contrast, we observed that a change in prevailing redox potential towards manganese reducing conditions in the oxic tests and iron reducing conditions in the anoxic column took place later and thus independently of arsenic release. The reduction of As(V) to As(III) under both redox conditions is presumed to be an effect of microbial detoxification. A loss of sulphate in all columns with phosphate indicates an increased microbial activity, which might play a significant role in the process of arsenic release. Preliminary tests with sediment material from a contaminated site showed that phosphate additions did not change the pH value significantly. Therefore, a release of other metals is not likely. Our results indicate that in-situ application of phosphate amendments to arsenic-contaminated sites could accelerate and enhance arsenic mobility to improve the efficiency of pump and treat remediation without negative side effects. The novelty of this approach is the use of only small amounts of phosphate in order to stimulate microbial activity in addition to surface complexation. Therefore, this method might become an innovative and cost-effective remediation for arsenic contaminated sites.

Study on Degradation of Nitrobenzene in Groundwater by Fenton-Like Oxidation Based on Iron in Aquifer Materials

2011 ◽  
Vol 183-185 ◽  
pp. 516-521 ◽  
Author(s):  
Meng Sun ◽  
Yong Sheng Zhao ◽  
Jun Dong ◽  
Li Li Dong
Keyword(s):  
Hydroxyl Radical ◽  
Contaminated Sites ◽  
Contaminated Site ◽  
Generation Process ◽  
High Efficient ◽  
Good Potential ◽  
Three Stages ◽  
Radical Generation ◽  
Extraction Agent

Fenton and Fenton-like reactions are regarded as high efficient methods in advanced treatment of nitrobenzene wastewater but both restrained in degradation of nitrobenzene in groundwater because of the low pH condition( less than 4 ) requirement and other problems such as secondary pollution by the irons in contaminated sites. This paper reports a new Fenton-like technology combined irons extraction from aquifer materials which were found in a nitrobenzene contaminated site in China with hydrogen peroxide catalytic oxidation. The simulate experiments were conducted to investigate the oxidation of nitrobenzene in groundwater by this method under the condition of neutral pH and 8~10°C. The comparison of different extraction agent and production rule of hydroxyl radical were both studied in this research. The results indicated that extraction had hysteresis property because the highest extracting efficiency occurred after 36h. Extraction agent DCB has the highest efficiency, for Fe3+ was 62.92% and Fe2+ was 30.17%. The highest removal efficiency could reach 80.2% while the mole ratio of nitrobenzene to H2O2 was 1:200. Three stages could found in hydroxyl radical generation process, in the first stage hydroxyl radical generated rapidly in 0~30min, then decreased slowly between 30min and 120min, at last the generation tended to be steady after 120h. The results could possess a good potential for application in the treatment of nitrobenzene contaminated groundwater and provide theoretical basis on in-situ chemical remediation technology of nitrobenzene contaminated sites.

In situ Biorestoration of an Oil Contaminated Subsoil

1988 ◽  
Vol 20 (3) ◽  
pp. 255-256 ◽  
Author(s):  
R. van den Berg ◽  
J H. A. M. Verheul ◽  
D. H. Eikelboom
Keyword(s):  
Microbial Activity ◽  
Contaminated Soil ◽  
Degradation Rate ◽  
Fine Sand ◽  
Contaminated Site ◽  
Literature Study ◽  
Limited Mobility ◽  
Gasoline Station ◽  
Oil Components

The feasibility of in-situ biorestoration of contaminated subsoils is being investigated by RIVM in co-operation with TNO. This project is aimed at optimizing the treatment of deeper layers of contaminated soil by enhancing microbial activity. The project consists of a literature study, research at laboratory-scale, detailed research of the selected experimental site and the actual clean-up of the contaminated site. In the literature study it was concluded that in-situ biological treatment offers reasonable prospects, concerning the technical aspects and the final results, but there were still questions about the efficiency of the clean-up of the soil itself. The selected site is a gasoline station, where the soil has been contaminated with gasoline, caused by a leaking tank. At least 30 m of normal gasoline have leaked and about 600 m3 of soil have been contaminated. Several monitoring wells have been placed to get an impression of the quantity and composition of the contamination. The soil consists of medium fine sand, without organic material and contains some clay-loam layers. The groundwater level is at about 2.5 m below the surface. Concentrations of the oil components in the soil(mainly between 1,000 and 5,000 mg/kg) as well as in the groundwater exceed the Dutch reference values which demand treatment of the site. In leaching experiments it was found that only very small quantities of the gasoline can be leached from the soil. Clean-up by percolation only would take at least 4 years. The leached quantity increased with the percolation rate, but was nearly independent of the gasoline concentration. The mobility could not be promoted by the addition of detergents. Numerous laboratory biodegradation experiments have been carried out in order to determine the degradation capacity of the contaminated soil, and to determine to what extent this biodegradation could be stimulated. The conlusions of these experiments are:In the soil there is low microbial activity and also the rate of degradation of the oil is low and constant in time. From mass balance studies it was determined that the degradation rate is determined by the availability of the oil components, which is a function of the dissoiution rate into the water and the volatilization. Availability turns out to be one of the determining aspects for this type of restoration technique.The degradation activity is most enhanced by the addition of seeding material from a landfarm, but is practically not feasible because of the limited mobility of microorganisms in soil.The presence of water and buffering at a neutral pH contribute to an optimal biodegradation rate.Some N and P additions are necessary. However, the C-N-P ratio had a very small influence on the degradation. A C-N-P ratio of 100-10-10 is recommended.As alternative oxygen source, hydrogen peroxide seems suitable, but the use of high concentrations of nitrate led to a decreased degradation.Detergents applied to increase the availability of the oil components did not stimulate the degradation. The degradation rate under stimulated conditions varied between 5 and 40 (mean 10) mg C/kg/day in comparison with an autonomous degradation rate of 3-4 mg C/kg/day. A stimulated clean-up duration of 1.5 years is expected. Column experiments are in progress now and are used to confirm the findings of the laboratory tests. They should also give answers about oxygen limitation and alternative oxygen sources. First examples of the hydrological set-up (infiltration by drains and withdrawal by wells, dimensioned by the desired degradation rate) confirm the feasibility of this project. It is expected that the actual clean-up operation will start in the fall of this year. In-situ treatment offers a very good alternative with advantages over excavation combined with various treatment techniques.

Expanded application of the Passive Flux Meter: in-situ measurements of 1,4-dioxane, sulfate, Cr(VI), and RDX

2018 ◽  
Author(s):  
Alexander Haluska ◽  
Meghan Thiemann ◽  
Patrick Evans ◽  
Jaehyun Cho ◽  
Mike Annable
Keyword(s):  
Inorganic Ions ◽  
Contaminated Sites ◽  
Chromium Vi ◽  
Reducing Conditions ◽  
Uptake Rates ◽  
Consumption Rates ◽  
Flux Measurements ◽  
Passive Flux Meter ◽  
Ion Species

Passive flux meters (PFMs) have become invaluable tools for site characterization and evaluation of remediation performance at groundwater contaminated sites. To date, PFMs technology has been demonstrated in the field to measure low - to midrange hydrophobic contaminants (e.g., chlorinated ethenes, fuel hydrocarbons, perchlorate) and inorganic ions (e.g., uranium and nitrate). However, flux measurements of a low partitioning contaminant (e.g., 1,4-dioxane, hexahydro-1,3,5-trinitro-s-triazine (RDX)) and reactive ions-species (e.g., sulfate (SO42-), Chromium(VI) (Cr(VI)) are still challenging because of their low retardation during transport and quick transformation under highly reducing conditions, respectively. This study comprises the first application of PFMs for the in-situ mass flux measurements of 1,4-Dioxane, RDX, Cr(VI) and SO42- reduction rates. Laboratory experiments were performed to model kinetic uptake rates and extraction efficiency for sorbent selections. Silver impregnated granular activated carbon (GAC) was selected for capture of 1,4-Dioxane and RDX, whereas Purolite 300A was selected for chromium and SO42-. PFM field demonstrations measured 1,4-Dioxane fluxes ranging from 13.3 to 55.9 mg/m2/day, an RDX flux of 4.9 mg/m2/day, Cr(VI) fluxes ranging from 2.3 to 2.8 mg/m2/day, and SO42- consumption rates ranging from 20 to 100 mg/L/day. These data suggest other low-partitioning contaminates and reactive ion-species could be monitored using the PFM.

Copper(II) removal by natural siderite (FeCO3) from surface and groundwaters

2020 ◽  
Author(s):  
Lisa C. Füllenbach ◽  
Jeffrey Paolo H. Perez ◽  
Helen M. Freeman ◽  
Andrew N. Thomas ◽  
Liane G. Benning ◽  
...  
Keyword(s):  
Ferrous Iron ◽  
Groundwater Remediation ◽  
Low Cost ◽  
Reaction Products ◽  
Solution Ph ◽  
Anoxic Conditions ◽  
Adsorption Mechanisms ◽  
Reducing Conditions ◽  
Reaction Processes

<p>Anthropological use of land and resources releases vast amounts of waste into surface waters and aquifers. Copper(II) is one of the most widely occurring heavy metal contaminants, introduced into the environment from industrial discharge, landfill leakage, agricultural and mining sources. Common remediation strategies for redox-sensitive Cu(II) are based on adsorption or phytoremediation methods. To experimentally test the efficiency of Cu(II) retention by inorganic redox reaction processes suitable for in situ surface- and groundwater remediation applications, we used siderite (FeCO<sub>3</sub>), which is abundant in anoxic sediments and soils and as a carbonate highly soluble in acidic environments. Its dissolution increases alkalinity and releases highly reactive, redox sensitive Fe(II). This aqueous ferrous iron can act as 1) a precursor for Fe(III) (hydr)oxides in oxic conditions, which are effective sorbents of heavy metals, and 2) a reducing agent under reducing conditions, where it can form a strong redox couple with Cu(II). We investigated the long term (1008 h) removal of aqueous Cu(II) through siderite dissolution batch experiments under oxic and anoxic conditions and monitored changes in the aqueous concentrations of Cu and Fe, pH and the reacted solids morphology over time. Cu adsorption and speciation on the reaction products was determined by X-ray absorption and photoelectron spectroscopies.</p><p>Under oxic conditions, increasing alkalinity led to a rapid increase in solution pH and the precipitation of nanoparticulate goethite and hematite from the released ferrous iron. After 1008 h of reaction, 80 % of the dissolved Cu(II) were removed from solution by sorption, whereby up to >30 % of this sorbed Cu(II) was reduced to Cu(I). Under anoxic conditions, the solution pH increased abruptly and copper uptake occurred more than twice as fast as under oxic conditions. Notably, the released Fe(II) was oxidized by Cu(II) leading to the precipitation of lepidocrocite, while all copper was removed from solution with >70 % of Cu(II) being reduced to Cu(0).</p><p>Our results suggest that 1) redox reactions between aqueous Cu(II) and Fe(II) promote coupled dissolution-precipitation and adsorption mechanisms responsible for Cu(II) removal, and that 2) siderite is a low-cost and effective material that is potentially useful for in situ remediation in either oxygenated or reduced environments.</p>

scholarly journals Expanded Application of the Passive Flux Meter: In-Situ Measurements of 1,4-Dioxane, Sulfate, Cr(VI) and RDX

Water ◽  
2018 ◽  
Vol 10 (10) ◽  
pp. 1335 ◽  
Author(s):  
Alexander Haluska ◽  
Meghan Thiemann ◽  
Patrick Evans ◽  
Jaehyun Cho ◽  
Michael Annable
Keyword(s):  
Inorganic Ions ◽  
Contaminated Sites ◽  
Chromium Vi ◽  
Reducing Conditions ◽  
Uptake Rates ◽  
Consumption Rates ◽  
Flux Measurements ◽  
Passive Flux Meter ◽  
Ion Species

Passive flux meters (PFMs) have become invaluable tools for site characterization and evaluation of remediation performance at groundwater contaminated sites. To date, PFMs technology has been demonstrated in the field to measure midrange hydrophobic contaminants (e.g., chlorinated ethenes, fuel hydrocarbons, perchlorate) and inorganic ions (e.g., uranium and nitrate). However, flux measurements of low partitioning contaminants (e.g., 1,4-dioxane, hexahydro-1,3,5-trinitro-s-triazine (RDX)) and reactive ions-species (e.g., sulfate (SO42−), Chromium(VI) (Cr(VI)) are still challenging because of their low retardation during transport and quick transformation under highly reducing conditions, respectively. This study is the first application of PFMs for in-situ mass flux measurements of 1,4-dioxane, RDX, Cr(VI) and SO42− reduction rates. Laboratory experiments were performed to model kinetic uptake rates and extraction efficiency for sorbent selections. Silver impregnated granular activated carbon (GAC) was selected for the capture of 1,4-dioxane and RDX, whereas Purolite 300A (Bala Cynwyd, PA, USA) was selected for Cr(VI) and SO42−. PFM field demonstrations measured 1,4-dioxane fluxes ranging from 13.3 to 55.9 mg/m2/day, an RDX flux of 4.9 mg/m2/day, Cr(VI) fluxes ranging from 2.3 to 2.8 mg/m2/day and SO42− consumption rates ranging from 20 to 100 mg/L/day. This data suggests other low-partitioning contaminates and reactive ion-species could be monitored using the PFM.

scholarly journals In situ oxalic acid injection to accelerate arsenic remediation at a superfund site in New Jersey

2014 ◽  
Vol 11 (5) ◽  
pp. 525 ◽  
Author(s):  
Karen Wovkulich ◽  
Martin Stute ◽  
Brian J. Mailloux ◽  
Alison R. Keimowitz ◽  
James Ross ◽  
...  
Keyword(s):  
New Jersey ◽  
Oxalic Acid ◽  
Solid Phase ◽  
Sediment Cores ◽  
Pilot Scale ◽  
Contaminated Site ◽  
Superfund Site ◽  
Superfund Sites ◽  
Pump And Treat

Environmental context Arsenic is one of the most common contaminants at US Superfund sites; therefore, establishing techniques to accelerate As remediation could benefit many sites. In a pilot scale study, we determined that addition of oxalic acid to the subsurface has the potential to increase arsenic release from sediments and possibly improve remediation efficiency by pump and treat techniques. Because pump and treat remediation can require many decades to sufficiently decrease contaminant levels, methods for improving remediation could lead to substantial savings in time and resources. Abstract Arsenic is a prevalent contaminant at a large number of US Superfund sites; establishing techniques that accelerate As remediation could benefit many sites. Hundreds of tonnes of As were released into the environment by the Vineland Chemical Co. in southern New Jersey during its manufacturing lifetime (1949–1994), resulting in extensive contamination of surface and subsurface soils and sediments, groundwater, and the downstream watershed. Despite substantial intervention at this Superfund site, sufficient aquifer clean up could require many decades if based on traditional pump and treat technologies only. Laboratory column experiments have suggested that oxalic acid addition to contaminated aquifer solids could promote significant As release from the solid phase. To evaluate the potential of chemical additions to increase As release in situ and boost treatment efficiency, a forced gradient pilot scale study was conducted on the Vineland site. During spring and summer 2009, oxalic acid and bromide tracer were injected into a small portion (~50m2) of the site for 3 months. Groundwater samples indicate that introduction of oxalic acid led to increased As release. Between 2.9 and 3.6kg of As were removed from the sampled wells as a result of the oxalic acid treatment during the 3-month injection. A comparison of As concentrations on sediment cores collected before and after treatment and analysed using X-ray fluorescence spectroscopy suggested reduction in As concentrations of ~36% (median difference) to 48% (mean difference). Although further study is necessary, the addition of oxalic acid shows potential for accelerating treatment of a highly contaminated site and decreasing the As remediation time-scale.

scholarly journals Full-scale application of ELS® microemulsion Technology for the Treatment of an Aquifer Contaminated with perchloroethylene and trichloroethylene via Ehnanced Reductive Dechlorination

2020 ◽  
Author(s):  
Alberto Leombruni ◽  
Federica Morlacchi ◽  
Linda Collina ◽  
Daniel Leigh ◽  
Mike Mueller
Keyword(s):  
Electron Donor ◽  
Source Area ◽  
Organic Substrate ◽  
Low Flow ◽  
Innovative Technology ◽  
Effective Electron ◽  
Chlorinated Organics ◽  
Pump And Treat ◽  
Reducing Conditions

Mixed plumes of chlorinated organics and oxidized metals are a common contaminant at many sites. The oxidized metals can be mediated by the establishment of moderately reducing conditions. The chlorinated organics have been demonstrated to be degradable by specific dechlorinating microrganisms in anaerobic environment such as Dehalococcoides sp. Enhanced biological dechlorination requires the presence of an effective electron donor to provide molecular hydrogen (H2) to completely degrade chlorinated ethenes. Distribution of the electron donor results in the biologically mediated establishment of highly reducing conditions in the treatment zone. This process also results in the reduction and precipitation of the oxidized metals via sulphate-reducing conditions. Peroxychem LLC has developed an innovative electron donor, ELS® Microemulsion Reagent (ELS) for in situ treatment of chlorinated organics and metals. This substrate has been successfully applied at numerous sites to address a variety of contaminants. ELS® is an organic electron donor composed of an easily fermentable organic substrate based on lecithin, and designed to enhance in situ anaerobic bioremediation aquifers contaminated by organochlorine compounds and heavy metals such as hexavalent chromium Cr[VI]. The product is easy to mix, dilute and inject into the subsurface. Once in the groundwater, indigenous microorganisms utilize ELS to rapidly generate highly reducing conditions, favoring biotic dechlorination reactions and the reduction of oxidized metals such as Cr[VI]. This innovative technology was successfully applied to a former manufacturing site in the center of Italy, where groundwater was historically contaminated with Tetrachloroethylene (PCE > 5.5 milligrams per Liter; mg/L), Trichloroethylene (TCE > 2 mg/L), 1,2-Dichloroethene (1,2-DCE > 1 mg/L) and, to a lesser extent, Vinyl Chloride (VC) and 1,2-Dichloropropane (DP). A pump-and-treat system (P&T) installed in the source was active as a source containment measure and to speed up the overall groundwater remediation. However, there was concern that the pumping could affect the ELS treatment effectiveness because of the increased groundwater flow velocity and the potential for removal of the injected bioremediation substrate. To mitigate this potential some wells were switched off the flow rates of others was adjusted to ensure compatibility with the planned product injection. In particular, an upstream low-flow-rate pump and treat system was maintained over the ELS® treatment period, primarily to delay the fast-downstream diffusion of the amendments in the aquifer, thus enhancing the source treatment. Following the calibration of the P&T system, approximately 4,900 kg of ELS® concentration was injected under high pressure at 51 locations into the source area. In about 12 months from injection of ELS® Microemulsion into the groundwater in the main source area, concentrations of PCE, TCE and the recognized catabolites, such as DCE and VC, rapidly reduced, compared to the pre-treatment concentrations, until they reached the statutory national limits (CSC D.lgs 152/06) in the main monitoring piezometers of the area, also highlighting the establishment of clear and enhanced biotic reducing conditions. No rebound effects have been observed in the next three years of monitoring.

scholarly journals Air Concentrations of Gaseous Elemental Mercury and Vegetation–Air Fluxes within Saltmarshes of the Tagus Estuary, Portugal

Atmosphere ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 228
Author(s):  
Rute Cesário ◽  
Nelson J. O’Driscoll ◽  
Sara Justino ◽  
Claire E. Wilson ◽  
Carlos E. Monteiro ◽  
...  
Keyword(s):  
Leaf Area ◽  
Elemental Mercury ◽  
Ambient Air ◽  
Tagus Estuary ◽  
Contaminated Site ◽  
Gaseous Elemental Mercury ◽  
Mercury Flux ◽  
Sarcocornia Fruticosa ◽  
Air Concentrations

In situ air concentrations of gaseous elemental mercury (Hg(0)) and vegetation–atmosphere fluxes were quantified in both high (Cala Norte, CN) and low-to-moderate (Alcochete, ALC) Hg-contaminated saltmarsh areas of the Tagus estuary colonized by plant species Halimione portulacoides (Hp) and Sarcocornia fruticosa (Sf). Atmospheric Hg(0) ranged between 1.08–18.15 ng m−3 in CN and 1.18–3.53 ng m−3 in ALC. In CN, most of the high Hg(0) levels occurred during nighttime, while the opposite was observed at ALC, suggesting that photoreduction was not driving the air Hg(0) concentrations at the contaminated site. Vegetation–air Hg(0) fluxes were low in ALC and ranged from −0.76 to 1.52 ng m−2 (leaf area) h−1 for Hp and from −0.40 to 1.28 ng m−2 (leaf area) h−1 for Sf. In CN, higher Hg fluxes were observed for both plants, ranging from −9.90 to 15.45 ng m−2 (leaf area) h−1 for Hp and from −8.93 to 12.58 ng m−2 (leaf area) h−1 for Sf. Mercury flux results at CN were considered less reliable due to large and fast variations in the ambient air concentrations of Hg(0), which may have been influenced by emissions from the nearby chlor-alkali plant, or historical contamination. Improved experimental setup, the influence of high local Hg concentrations and the seasonal activity of the plants must be considered when assessing vegetation–air Hg(0) fluxes in Hg-contaminated areas.

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