Measuring Techniques to Monitor the Application of Nano-Sized Zero-Valent Iron for Subsurface Remediation

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1 Measuring Techniques to Monitor the Application of Nano-Sized Zero-Valent Iron for Subsurface Remediation Erfordernis und Möglichkeiten der Sanierungsbegleitung und Überwachung beim Einsatz von Nano-Eisen Kolloquium Stuttgart, October 7 th 2010 Jürgen Braun, Norbert Klaas University of Stuttgart, Germany Motivation for Injecting Colloidal Zero Valent Iron ZVI reacts with a wide variety of contaminants Low cost for installation Possible under buildings No limit to depth of injection (except economic) Semi-Passive method After all iron is used (or activity ceases), new injection possible Innovative method Kolloquium 2010 October 7 th Stuttgart 2

2 Open Questions Transport - What transport distances are achievable under field conditions? Distance between injection wells - What influences / controls the transport distances and iron distribution? Pre-treatment, rate-, concentration- and duration of injection - How to determine / prove injected iron concentrations in the aquifer? Duration of injection Reactivity What is the longevity of nano/micro-iron colloids? How much nano/micro-iron is necessary? Monitoring Short term: Location of nano/micro-iron after injection? Long term: When is a re-injection necessary? Kolloquium 2010 October 7 th Stuttgart 3 Currently Applied Measuring Techniques measurements of flow rate water level oxidation reduction potential (ORP) dissolved oxygen (DO) ph specific conductance temperature total dissolved iron in monitoring wells geophysical measurements ground penetrating radar geomagnetic and geoelectric mapping contaminant concentration reduction In observation wells In soil / aquifer samples Kolloquium 2010 October 7 th Stuttgart 4

3 New Measuring Concept / Metal Detector test setup nzvi particles are small but still ferromagnetic Detection by measuring the inductance of coil Simple metal detector principle 2006 Digital recording of signal Detector Electronics Measuring Coil Sand filled pipe Sliding construction Kolloquium 2010 October 7 th Stuttgart 5 New Measurement Technology for Nano-Iron Modified Mine Detection Apparatus 2007 Detection of Chances in magnetic susceptibility Comparative measurement before and after injection of nano iron Uses commercially available mine detection apparatus High temporal and spatial resolution Objective, quantitative reading Kolloquium 2010 October 7 th Stuttgart Fig: Inst. Dr. Foerster 6

4 1-D Flow and Transport Experiments Experimental setup was created to investigate various factors influencing the transport of Nano-Iron in the sub-surface An automated measurement method with high spatial and temporal resolution was developed for scanning columns Kolloquium 2010 October 7 th Stuttgart 7 New Measurement Technology for Nano-Iron / Calibration Kolloquium 2010 October 7 th Stuttgart 8

5 Impact of Iron Suspension Concentration Kolloquium 2010 October 7 th Stuttgart 9 1-D Flow and Transport Results Transport of nano-iron is function of: Age of the suspension (Aggregation stage, Particle Size) Pre-treatment (Bi-metal, Dispersing, Surfactants) Aquifer Material (Grain size distribution) Concentration of nano-iron suspension (Optimal around 10 g/l) Flow Velocity (Sedimentation is a function of shear rate) Kolloquium 2010 October 7 th Stuttgart 10

6 2-D Depth Averaged Radial Flow Field Experiment 60 triangular container to simulate the injection in a confined aquifer In-situ sensors record Fe 0 -break through curves at different locations during the injection Realistic field flow velocities and concentrations v 3D drawing of the container (r: 2 m, α: 60, h: 0.6 m) Kolloquium 2010 October 7 th Stuttgart 11 Kolloquium 2010 October 7 th Stuttgart 12

7 Dual Coil Electro Magnetic Measuring Technique nzvi particles are ferromagnetic Magnetic flux density B is connected to the magnetic field strength H by the susceptibility of nzvi (χ nzvi ) and the permeability of vacuum (μ 0 ) Sine wave signal through one coil induces a voltage in a second coil Kolloquium 2010 October 7 th Stuttgart 13 Different generations of measuring sensors 1 st concept, uncoated, 2 generations coated, 1 st concept for field Kolloquium 2010 October 7 th Stuttgart 14

8 2-D Depth Averaged Radial Flow Experiment In-situ dual-coil sensors record Fe 0 -break-through curves due to the change in the magnetic susceptibility of the medium inside the sensor during the injection Kolloquium 2010 October 7 th Stuttgart 15 Quantitative Measurement and Qualitative Observation t = 200 s L = 2 m t = 700 s t = 3600 s Tracer Suspension Water t = 6300 s Magnetic susceptibility measured during the injection experiment Four sequential images of the cross sectional glass plate Kolloquium 2010 October 7 th Stuttgart 16

9 Quantitative Measurement Proved by Chemical Analysis Tracer Suspension Water Magnetic susceptibility measured during the injection experiment Results of chemical analysis derived from hydrogen production after adding acid (HCl) Kolloquium 2010 October 7 th Stuttgart 17 Monitoring System Concept Development of Direct Push Sensor for injection monitoring & Longevity sensors combined with observation wells Kolloquium 2010 October 7 th Stuttgart 19

10 Monitoring System Concept Slave CAN bus Slave CAN bus Slave CAN bus PC live view of break through curves CAN bus SPI Slave CAN bus Slave Master Data logger (long-term) Sensor 19 Sensor Sensor Kolloquium 2010 October 7 th Stuttgart 20 Conclusions New measuring technique for break trough curves of ZVI 2 m Transport of nano sized iron colloids in radial flow field proven to be possible under field realistic conditions Qualitative observation but also Quantitative measurement Kolloquium 2010 October 7 th Stuttgart 21

11 Current Work & Outlook Comparison of different Fe 0 colloids, varying: Size (nm-µm) Composition of formulation (additives) Production costs Long term experiments in columns Extension of chemical and transport experiments to directly measure effects in the source zone Measuring technique development for field application Field tests to support laboratory findings Kolloquium 2010 October 7 th Stuttgart 22 Thank you for your attention! Funding for the presented work was provided by: The EU in the 7th Framework Programme FP7 ENV AQUAREHAB The State of Baden-Wuerttemberg, Germany Project number: / , BUT 013