Injection of zero-valent iron

Transcription

1 Injection of zero-valent iron Transnational Herk-de-Stad Flanders Coordination Group June 2013 Art Lobs Verhoeve Groep

2 Project s objectives: improve the quality and minimize the pollution of soil and groundwater Problem? chlorinated solvents in soil and groundwater: hard to remediate and risk for health and environment often caused by companies with little capital urban environment poses additional limiting conditions for research and remediation common problem in all European cities How? Develop an integrated approach for remediation of chlorinated solvent pollution in urban areas, encompassing not only technical aspects but also aspects of communciation, socioeconomic and organizational aspects

3 Titel van de presentatie pagina 5

4 CONTENTS Introduction zero-valent iron Objectives project Description location and soil contamination Laboratory testing Injections of iron Monitoring Conclusions Recommendations Additional research

5 Dutch/Belgium international environmental contractor since 1987 Specialities: in-situ remediation, water treatment & irrigation Permeable Reactive Bariers with Granul-X In-situ chemical oxidation Bioheating/Electro-reclamation

6 INTRODUCTION ZERO VALENT IRON PRB (since 1994) 2 Cl Cl C PCE C Cl Cl 1 GRANULAR ca. 1,0-2,5 mm 2Fe 0 + R-Cl + 3H 2 O 2Fe 2+ + R-H + 3OH - + H 2 + Cl - Cl C C C 4 compounds Cl dichloroacetylene Cl H 17 C C H chloroacetylene 14 C C H acetylene Cl H C C trans-dce H Cl 7 3 Cl Cl Cl H Cl H H H C C C C TCE 4 C C cis-dce VC 9 C 18 C ethylene 19 C 2 H 6 ethane Cl H Cl H H H H H 5 Cl Cl C C 1,1-DCE Hypothesized reaction pathways for degradation of chlorinated ethenes during reduction by Fe 0. Reactions 1, 3, 4, 5, 7, 9, 14, 17 and 18 correspond to hydrogenolysis reactions, while reactions 2, 6, 8 and 10 are reductive β-elimination reactions. Reaction 11 proceeds via reductive α-elimination and reactions 13, 15, 16 and 19 are hydrogenation reactions (Arnold and Roberts, 2000). 11 H H

7 INTRODUCTION ZERO-VALENT IRON PRB (since 1994) GRANULAR ca. 1,0-2,5 mm 2Fe 0 + R-Cl + 3H 2 O 2Fe 2+ + R-H + 3OH - + H 2 + Cl - MICRO-SCALE ca. 0,1-100 µm NANO-SCALE ca. <100 nm REACTIVITY SURFACE BASED PROCESS

8 INTRODUCTION ZERO- VALENT IRON PRB (since 1994) injection ironslurry GRANULAR ca. 1,0-2,5 mm MICRO-SCALE ca. 0,1-100 µm INJECTIVITY NANO-SCALE ca. <100 nm REACTIVITY + greater depths possible + beneath buildings - contact with contamination!

9 OBJECTIVES PROJECT Objective: Demonstration of possibilities of microen nano-iron for remediation of chlorinated hydrocarbons in Herk-de- Stad. injection ironslurry ca. 0,85-1 /kg ca. 1,2-1,5 /kg ca. 25 /kg (20% DS) GRANULAR ca. 1,0-2,5 mm MICRO-SCALE ca. 0,1-100 µm INJECTIVITY NANO-SCALE ca. <100 nm REACTIVITY

10 DESCRIPTION LOCATION AND SOIL CONTAMINATION Historical soil and groundwater contamination, mainly PCE Printing business

11 DESCRIPTION LOCATION AND SOIL CONTAMINATION Groundwatertable between 1,5 en 3,5 m-gl Loamy sand up to 15 m-gl Low flow rate: 0,5 m/year Flow direction west (unclear)

12 DESCRIPTION LOCATION AND SOIL CONTAMINATION Contaminated soil volume (> BSN): 7720 m³, 180 m³ source-zone (between 2,5 15 m-gl) Contaminated groundwater volume (>BSN):27000 m³

13 DESCRIPTION LOCATION AND SOIL CONTAMINATION Soil contamination

14 DESCRIPTION LOCATION AND SOIL CONTAMINATION Groundwater contamination

15 DESCRIPTION LOCATION AND SOIL CONTAMINATION Additional soil investigation: updating soil and groundwater contamination with aqualock samplers Highest concentrations: Undeep Soil: 42 mg/kg PCE Groundwater: µg/l PCE

16 DESCRIPTION LOCATION AND SOIL CONTAMINATION

17 1. Stability micro-iron slurry LABORATORY TESTING - supplier: Gotthart Maier Metallpulver, Germany - particle: 0-80 µm - rapid sedimentation in mixing vessel, injectiontubing and in the soil immediately after injectionpoint - reduce sedimentation by adding increase viscosity no particles, soluble biostimulation (biological reductive degradation)

18 LABORATORY TESTING 2. Injection and distribution of micro- en nano-iron - supplier Nano iron: NANO-IRON, Tsjechië - particle size: nm Before injection After injection

19 LABORATORY TESTING 3. Reactivity 0,4 g nfe 0 60 ml + TCE 0,4 g mfe 0 60 ml + TCE - 60 ml + TCE TCE concentratie (µg L 1 ) ,5 1 1,5 2 2,5 3 tijd (dagen) blanco nano ijzer micro ijzer Ln (C/C 0 ) 0 0,5 1 1,5 2 2,5 3 y = 0,1885x R² = 0,9989 y = 0,8371x R² = 0, ,5 1 1,5 2 2,5 3 tijd (dagen) T 1/2 (micro iron) = 88 u T 1/2 (nano iron) = 20 u nano ijzer micro ijzer 1,2 DCE concentratie (µg L 1 ) ,5 1 1,5 2 2,5 3 tijd (dagen) blanco nano ijzer micro ijzer

20 IRONINJECTIONS MIP soundings - contamination between mainly 2,0 en 8,0 m-gl

21 IRONINJECTIONS Injections - 3 injections per irontype - distance between: app. 2 m - from 2 up to 8 m-gl - 25 L per 0,5 m Nano-iron - ca L slurry - 10 g Fe 0 / L Micro-iron - ca L slurry - water/glycerol: 60/40-50 g Fe 0 / L

22 IRON INJECTIONS

23 IRON INJECTIONS

24 IRON INJECTIONS

25 IRON INJECTIONS

26 IRON INJECTIONS

27 IRON INJECTIONS

28 IRON INJECTIONS Liners and monitoring wells - in the middle of each injection triangle - diverse depths - no injected iron visible

29 RESULTS MONITORING Injections executed in march Monitoringrounds: 3 days after injection: geochemistry 2 weeks after: geochemistry and VOC 1 month after: geochemistry and VOC 3 months after: geochemistry and VOC 5 months after: 4 drillings, geochemistry and VOC 6 months after: geochemistry 10 months after: geochemistry and VOC

30 Concept pilottest RESULTS MONITORING

31 Redox potential (mv) RESULTS MONITORING (micro)

32 Redox potential (mv) RESULTS MONITORING (nano)

33 RESULTS MONITORING (micro)

34 RESULTS MONITORING (nano)

35 Prior laboratory test CONCLUSIONS - Reactivity and injectivity nano-iron better - Increase of injectivity micro-iron with additive Iron injection & monitoring - Injection of Micro : possible with additive (glycerol) - Injection of both types iron succesful - No (additional) iron detected in soil samples - radius of influence: limited (15 cm) - Downstream only influence for Micro glycerol (confirmed: increasing DOC in 319 en 1002)

36 CONCLUSIONS - In both injection zones: low redoxpotential and [O2] in combination with high concentration of degradation products of PCE iron injections stimulate natural degradation? - Cost-price: Nano = 2 x more expensive than Micro + glycerol This pilot experiment shows no benefit to the more expensive iron

37 RECOMMENDATIONS - Full scale remedation with iron injections = less suitable limited radius of influence a dense grid of injections injected product high costs & breakthrough of the - Iron injections = suitable for the creation of geochemical conditions for natural degradation conditions (toxic on sites with onsuitable geochemical on sites with high concentrations of pollution for the bio-population)

38 Latest monitoring - Consumption of DOC ADDITIONAL RESEARCH - Degradation of PCE was determined, stagnation to the level of 1,2 DCE Indicates: natural degradation absence of suitable microbial community for further degradation to ethene (via vinylchloride) Additional research planning: end of May - Injection of bacterial strain (Dehalococcoides ethenogeneses) - Complete degradation to ethene / ethane? monitoring during 9 months - Results additional research: view website of Citychlor in the future

39 Thank you! Verhoeve Groep Belgium Art Lobs