The in situ treatment of TCE and PFAS in groundwater within a silty sand aquifer

2021 ◽  
Vol 31 (2) ◽  
pp. 7-17
Author(s):  
Rick McGregor ◽  
Ye Zhao
Keyword(s):  
Silty Sand ◽  
Sand Aquifer

scholarly journals The Effect of Heterogeneity on the Distribution and Treatment of PFAS in a Complex Geologic Environment

2021 ◽  
Vol 2 ◽  
Author(s):  
Rick McGregor ◽  
Leticia Benevenuto
Keyword(s):  
Activated Carbon ◽  
Hydraulic Conductivity ◽  
Emerging Contaminants ◽  
Fractured Rock ◽  
Ion Exchange Resin ◽  
Subsequent Treatment ◽  
Silty Sand ◽  
Aquifer System ◽  
Pump And Treat

Per-and polyfluoroalkyl substances (PFAS) have been identified as emerging contaminants of concern in the environment in a wide variety of media including groundwater. Typically, PFAS-impacted groundwater is extracted by pump and treat systems and treated using sorptive media such as activated carbon and ion exchange resin. Pump and treat systems are generally considered ineffective for the remediation of dissolved phase contaminants including PFAS but instead are considered applicable for plume containment. An alternative to pump and treat is in-situ treatment. The demonstrated use of in-situ treatment for PFAS-impacted groundwater is limited with only colloidal activated carbon (CAC) being shown to effectively attenuate PFAS over short and moderate time periods. Active research topics for the in-situ treatment of PFAS include the effect of heterogeneity on the distribution of the CAC, the lifespan of the CAC itself, the effect of competitive adsorption/absorption, and the effect of other geochemical conditions on the removal process. This study looked at the effect of heterogeneity on the distribution of CAC and subsequent treatment of PFAS at a site with a multiple aquifer system. The site’s geology varied from a silty sand to sand to fractured bedrock with all three units being impacted by PFAS and benzene (B), toluene (T), ethylbenzene (E), and xylene (X). Parameters evaluated included the distribution of the CAC as well as the subsequent treatment of the PFAS and BTEX. Results of groundwater sampling indicated that the PFAS detected within the groundwater were treated effectively to below their respective reporting limits for the duration of the 1-year test in both the silty sand and sand aquifers. The PFAS in the fractured rock aquifer showed a different treatment profile with longer carbon chained PFAS being attenuated preferentially compared to the shorter carbon chained PFAS. These results suggest that competitive sorptive reactions were occurring on the CAC within the fractured rock. Analysis of the unconsolidated aquifer materials determined that direct push injection of the CAC was effective at delivering the CAC to the target injection zones with post-injection total organic carbon (TOC) concentrations increasing by up to three orders of magnitude compared to pre-injection TOC concentrations. Heterogeneity did have an impact on the CAC distribution with higher hydraulic conductivity zones receiving more CAC mass than lower hydraulic conductivity zones.

The Use of the Dynamic Cone Penetrometer for Quality Control of Compaction Operations

2013 ◽  
Vol 10 ◽  
pp. 49-64
Author(s):  
Moshe Livneh ◽  
Noam A. Livneh
Keyword(s):  
Quality Control ◽  
Silty Sand ◽  
Granular Soils ◽  
Cone Penetrometer ◽  
Clayey Soils ◽  
Falling Weight Deflectometer ◽  
Dynamic Cone Penetrometer ◽  
Additional Testing ◽  
Falling Weight

The use of a new quality control (QC) and quality assurance (QA) specification involving Dynamic Cone Penetrometer (DCP) testing in concert with conventional moisture and density testing is becoming more and more frequent in various parts of the world. The need for this additional testing is essential, as the regular in-situ density tests cannot alone ensure the compliance of the layers constructed with the compaction requirements. Recent analyses of the correlation between the DCP testing and the California Bearing Ratio CBR testing show that QC and QA DCP testing is adequate to verify compaction, stability and vertical uniformity in both cohesive and granular soils. Two examples of DCP usage in two Israeli earthwork projects, one of clayey soils and the other of silty-sand soils, indicate the benefits of this usage along with, though for the clayey example only, Falling Weight Deflectometer (FWD) testing.

LNAPL source zone delineation using soil gases in a heterogeneous silty-sand aquifer

2016 ◽  
Vol 192 ◽  
pp. 20-34 ◽  
Author(s):  
Grégory J.V. Cohen ◽  
Florie Jousse ◽  
Nicolas Luze ◽  
Patrick Höhener ◽  
Olivier Atteia
Keyword(s):  
Silty Sand ◽  
Source Zone ◽  
Sand Aquifer ◽  
Soil Gases

scholarly journals In situ diagnostic assessment for the infiltration rate of the northern Gaza wastewater infiltration basins

2020 ◽  
Vol 9 (1) ◽  
pp. 175
Author(s):  
Mazen Abualtayef ◽  
Thaer Abushbak ◽  
Ahmed Abu Alnoor ◽  
Hassan Al-Najjar
Keyword(s):  
Gaza Strip ◽  
Sewage Treatment ◽  
Intervention Strategy ◽  
Diagnostic Assessment ◽  
Silty Sand ◽  
Sieve Analysis ◽  
Infiltration Capacity ◽  
Infiltration Rates ◽  
Groundwater Aquifer

The Northern Gaza Emergency Sewage Treatment (NGEST) is addressed as a promising water management intervention strategy to maintain the sustainability of groundwater aquifer in the Gaza Strip. This study assesses the current operational status of the north-ern Gaza wastewater infiltration basins located at NGEST project. In situ diagnostic assessment was performed at two spots (A) and (B) located inside the basin (3). The results of sieve analysis and bulk density indicate that the soil at the spot (B) is finer than of spot (A) where the contents of the fine material and bulk densities were 13% and 1544 kg/m3 at the spot (A) and 23.7% and 1544 kg/m3 at the spot (B). In terms of the infiltration capacity, the nature of soil at the spot (A) exhibits better initial and saturated infil-tration rate in comparison to the soil at the spot (B), where the initial and saturated infiltration rates were 2.88 and 0.43 for spot (A) and 0.29 and 1.73 meters per day for spot (B), respectively. Thus, the diagnostic assessment for the northern Gaza wastewater infil-tration basins indicates that the soil classification is silty sand and the infiltration rates range between about 3 and 0.3 meters per day.  

Radiostrontium Migration from a 1953-54 Liquid Release to a Sand Aquifer

1987 ◽  
Vol 22 (1) ◽  
pp. 107-128 ◽  
Author(s):  
R.W.D. Killey ◽  
J.H. Munch
Keyword(s):  
Field Experiments ◽  
Reaction Times ◽  
Fission Products ◽  
Leading Edge ◽  
Distribution Coefficients ◽  
Linear Increase ◽  
Pore Waters ◽  
Plume Front ◽  
Sand Aquifer

Abstract Aqueous ammonium nitrate solutions containing a variety of fission products were released to an infiltration pit overlying a sand aquifer in the early 1950’s. Almost all of the undecayed 137Cs and 154Eu are still retained within the 5 m thick unsaturated zone beneath the pit. Radiostrontium, however, has moved up to 350 m through the hydrogeologically simple and fast-moving groundwater flow system; the inventory of the aquifer plume’s 90Sr content is in good agreement with the estimated initial release. Data from 6 determinations of plume front position yield a linear increase in distribution ratios for 90Sr at the leading edge, from 0.8 to 4.8 mL·g−1 between 1955 and 1983. Mean Kd’s between 3 and 9 mL·g−1 have been determined from short-term laboratory and field experiments, and the rate of advance of the plume front is expected to reach a steady state within this range. Analyses of 340 contaminated sands and associated pore waters from various locations in the plume provided in situ distribution ratios with a log mean of 12.9 mL·g−1, and with no significant variations between sediments that have been in contact with 90Sr for from 10 to 28 years. Differences between plume front distribution coefficients and the in situ values observed in older portions of the plume are explained primarily by kinetically slow chemisorption onto secondary oxide coatings on the sand surfaces. This reaction apparently has half-reaction times for both sorption and desorption of less than 2 years, and hence can be treated as an equilibrium process in long-term studies. A substantial conflict remaining in the data, however, is the rate of advance of the centre of mass of the plume. Most of the radiostrontium in the aquifer la apparently moving at a much slower rate than the log mean in situ distribution ratio would predict - one explanation for this discrepancy is that 90Sr movement is greatly retarded by volumetrically small sandy silt strata that have much higher sorption capacities than the fine to medium sands that dominate the overall aquifer sampling. A simple, conservative, model that assumes equilibrium sorption of radiostrontium predicts acceptable concentrations of radiostrontium in surface waters at the CRNL property boundary.

Traction Limits for Tracked Vehicles Crawling the Sea Bottom

1971 ◽  
Vol 93 (2) ◽  
pp. 717-727 ◽  
Author(s):  
C. J. Nuttall
Keyword(s):  
State Of The Art ◽  
Soil Strength ◽  
Silty Sand ◽  
Tracked Vehicles ◽  
Sea Floor ◽  
Sea Bottom ◽  
Art Methods

State-of-the-art methods in regular use for the calculation of the maximum soil-limited net traction of tracked vehicles ashore are briefed. A few simple caveats in applying these to similar vehicles crawling on the sea floor are suggested. Results of limited preliminary tests with a small single-tracked machine in submerged natural silty sand, with supporting in situ soil strength measurements, are presented and commented in context.

scholarly journals Hydromechanical behaviour of a silty sand from a steep slope triggered by artificial rainfall: from unsaturated to saturated conditions

2013 ◽  
Vol 50 (1) ◽  
pp. 28-40 ◽  
Author(s):  
Francesca Casini ◽  
Victor Serri ◽  
Sarah M. Springman
Keyword(s):  
Mechanical Behaviour ◽  
Water Retention ◽  
Stress Path ◽  
Steep Slope ◽  
Silty Sand ◽  
Water Retention Curve ◽  
Retention Curve ◽  
Hydromechanical Behaviour ◽  
Water Contents

This paper presents an experimental investigation aimed at studying the hydromechanical behaviour of a silty sand from a steep slope in Ruedlingen in the northeast of Switzerland, where a landslide-triggering experiment was carried out. The hydromechanical behaviour of the statically compacted Ruedlingen silty sand has been studied under saturated and unsaturated conditions, beginning with different initial void ratios and water contents. The specimens were prepared in the laboratory using static compaction, to reproduce the mean dry density and mean water content expected in natural unsaturated in situ conditions, thus promoting specimen homogeneity and test repeatability. The choice of compaction parameters was supported by a detailed physical and microstructural investigation to produce laboratory specimens with a similar microstructure to that of the natural soil. The aim of the work was to characterize the mechanical behaviour of the soil at different gravimetric water contents in a triaxial stress path apparatus and to link the mechanical behaviour with the soil-water retention curve obtained under suction-controlled conditions with different void ratios. Soil specimens with three different gravimetric water contents were exposed to conventional isotropically consolidated drained and undrained stress paths for the water phase and to stress paths simulating in situ anisotropic compression followed by a decrease of mean effective stress at constant axial load. The radial deformation of the unsaturated specimens was measured with a laser device installed in a triaxial stress path cell. Results have been interpreted using a Bishop stress approach, evaluating the suction through the water retention curve. A simple equation has been proposed to model the compressibility behaviour of the soil tested, which depends on the parameter χ and the stress ratio η. Possible unstable response along the stress path analysed has been investigated by means of second-order work and the validity of a unified framework has also been verified under unsaturated conditions.

Field Tests of Buried Pipe Installation Procedures

1996 ◽  
Vol 1541 (1) ◽  
pp. 97-106 ◽  
Author(s):  
Mark C. Webb ◽  
Timothy J. McGrath ◽  
Ernest T. Selig
Keyword(s):  
Field Tests ◽  
Silty Sand ◽  
Crushed Rock ◽  
Soil Conditions ◽  
Soil Behavior ◽  
Buried Pipe ◽  
Inside Diameter ◽  
Diameter Pipe ◽  
Low Strength

Full-scale field tests to evaluate pipe-soil interaction during backfilling were conducted on the campus of the University of Massachusetts at Amherst. The program consisted of 14 tests, with each test including concrete, plastic, and metal sections. In addition to pipe type, installation variables included in situ soil conditions, trench width, backfill material including controlled low-strength flowable material, haunching effort, and compaction methods. Test trenches were excavated under undisturbed in situ soil conditions. Eleven installations were conducted with 900-mm (inside diameter) pipe, and three installations were conducted with 1500-mm (inside diameter) pipe. Pipe and soil behavior was monitored during backfilling. Measurements included pipe shape, pipe strains, pipe-soil interface pressures, soil density, soil stresses, and soil strains. The pipes were buried to a cover depth of 1.2 m and were then excavated to inspect the pipe bedding and haunches. The results indicated significant variations in pipe behavior caused by installation practices. The rammer compactor produced greater backfill density than did the vibratory plate compactor with the same number of coverages and produced higher residual lateral soil stresses that contributed to better overall pipe performance during backfilling. The silty sand backfill tripled the peaking deflection during sidefill compaction compared with that with angular crushed rock backfill, but the former was more sensitive to deviations from good installation practice. Backfill compaction in the region from the spring line to 30 degrees below the spring line has a significant positive effect in mitigating poor bedding and haunching conditions. Pipe tests with controlled low-strength material for backfill performed very well.

An in-situ study of the occurrence and rate of denitrification in a shallow unconfined sand aquifer

1986 ◽  
Vol 83 (3-4) ◽  
pp. 251-268 ◽  
Author(s):  
M.R. Trudell ◽  
R.W. Gillham ◽  
J.A. Cherry
Keyword(s):  
In Situ Study ◽  
Sand Aquifer
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