In Situ Chemical Reduction (ISCR) Fundamentals related to selection, design and distribution of ISCR technologies at contaminated sites

Transcription

1 In Situ Chemical Reduction (ISCR) Fundamentals related to selection, design and distribution of ISCR technologies at contaminated sites Ravi Srirangam P.E., Ph.D. PeroxyChem Environmental Solutions Design and Application of Insitu Treatment Technologies CT/MA May 2016

2 BASIC PRINCIPLES OF ISCR 2

3 The beginning of ISCR for soil and groundwater applications Started with an interest in Abiotic MNA Rediscovery of McCarty and Vogel Postulated Abiotic Pathways oxidation, reduction, substitution, and dehydrohalogenation reactions occur abiotically or in microbial systems Butler, E., Hayes, K., Kinetics of the transformation of halogenated aliphatic compounds by iron sulfide. Environ. Sci. Technol. 34, Lee, W., Batchelor, B., Abiotic reductive dechlorination of chlorinated ethylenes by iron bearing soil minerals. 1. Pyrite and magnetite. Environ. Sci. Technol. 36, Wilson, J. T. (2003). Abiotic reactions may be the most important mechanism in natural attenuation of chlorinated solvents. Presented at the AFCEE Technology Transfer Workshop, Brooks AFB, San Antonio, TX. 3

4 What is ISCR? Reduction adds electrons to the contaminant (need an electron donor) Oxidation removes electrons from the contaminant (need an electron acceptor) ISCR involves transfer of electrons to contaminants from reduced metals (ZVI, ferrous iron) or reduced minerals (magnetite, pyrite etc.) ISCR of CVOCs occurs via both abiotic as well as abiotic pathways...because both processes occur simultaneously in the subsurface 4

5 Examples of Contaminants Destroyed Chlorinated Solvents PCE, TCE, cis-dce, 1,1-DCE, VC 1,1, 2,2-TeCA, 1,1,1-TCA CT, CF Pesticides Toxaphene, Chlordane, Dieldrin, Pentachlorophenol Energetics TNT, DNT, RDX, HMX, Perchlorate Heavy Metals Examples of Contaminants That Require Organic Amendment to ZVI for Destruction Chlorinated Solvents 1,2-DCA DCM, CM Contaminants Treated via ISCR 5

6 Direct Dechlorination Reactions Reactions: Fe 0 Fe e - 2H 2 O 2H + + 2OH - 2H + + 2e - H 2(g ) R-Cl + H + + 2e - R-H + Cl - 6

7 Half-life (hrs)) Significantly reduced half-lives of CVOCs in the presence of ZVI Requires direct contact with ZVI surface Role of ZVI and DVI (Fe(II) Reaction is abiotic reductive dehalogenation; minimizes/eliminates DCE/VC Typical CVOC Half-lives (Room temperature) ZVI provides a long-term source of DVI to promote indirect chemical reduction of CVOCs (formation of reactive iron and iron sulfide minerals) β-elimination is the dominant pathway (~90%); ZVI generates hydrogen so some biotic reductive reactions are supported PCE TCE cdce tdce 11DCE VC CT TCM 111TCA 112TCA 7

8 ISCR CONFIGURATION AND CASE STUDIES 8

9 Common ISCR Implementation Methods Hydraulic fracturing/injection (120 ft, 37 m) Direct injection (30ft,9m) soil mixing (40 ft, 12 m) Ferox Injection Trailer Overburden Pneumatic Injection Module Nitrogen Gas Source Atomized Slurry in Gas Stream Packer continuous trenching (35 ft, 11 m) Injector Treatment Zone pneumatic fracturing (90 ft, 27 m) 9

10 Expansion of Granular Iron Grain Size Range 0.25 to 2 mm (-8 to +50 US mesh) for trenched PRBs 0.07 to 1.7 mm (-12 to +200 US mesh) for hydraulic fracturing Pneumatic/hydraulic injection (microscale, D90 of 140 micron) mixed into clean soil backfill following excavation of contaminated soils (0.25 to 2 mm) physical mixing of iron and clay into the contaminated zone ( -50 mesh) 10 to 70 micron material in conjunction with other biological amendments-injections Nanoscale materials ( nm) 10

11 Commercial Facility, Mississauga, ON (February 2008) Former dry cleaner Risk-assessment to address source and on-site contamination PRB to prevent off-site migration Continuous trencher Depth of 9 m 125 m long 11

12 First ZVI PRB Installation in the Netherlands Start of trenching Continuous Backfill of Iron/sand Outline of the installed Iron/sand PRB Continuous trencher (CT) was used to install 120 m long PRB, with 0.3 m trench width (1.0 m to 5.5 m bgs). Two 30 m long HDPE wing sections were also installed using the CT. The PRB consisted of a granular iron and sand mix with 40% ZVI (v/v). 12

13 Concentration (ug/l) Concentration (ug/l) Netherlands PRB-February 2007 Results cdce Transect 1 Transect 2 0 Upgradient Downgradient VC Transect 1 Transect 2 0 Upgradient Downgradient

14 Long Term Performance of Commercial Systems Advantages 13 year operating record at oldest commercial facility possible benefits due to hydrogen gas, low Eh conditions (microbial activity) at most sites, if 5 to 8 years can pass before rejuvenation or replacement, then technology is economically attractive Disadvantages Contact -very critical Passivation of Iron surfaces Increasing implementation costs with Depth

15 Engineered ISCR? Simple carbon donors Complex carbon donors/isrm ZVI Engineered ISCR Bacterial inoculation 15

16 Engineered Reductants Engineered ISCR: Amendments that combine chemical reductants (especially ZVI) with materials that stimulate microbial activity (organic carbon in various forms) are available as commercial products. The products include EHC and Daramend (PeroxyChem), ABC + (Redox Tech, LLC), and emulsified zero-valent iron (EZVI) (National Aeronautics and Space Administration). This approach relies on taking advantage of synergies offered by ZVI and organic carbon to further enhance the ISCR mechanism. 16

17 EHC Reagent Composition EHC is delivered as a dry powder and includes: Micro-scale zero valent iron powder(standard ~40%) Controlled-release, food grade, complex carbon (plant fibers) (standard ~60%) Major, minor, and micronutrients Food grade organic binding agent Sustainable Solution o By-product ZVI o Food production by-products 17

18 Mechanisms Zone of Influence Direct Chemical Reduction requires contact with ZVI particle Extended Zone with Biological Reduction and Indirect Iron Effects Bacteria VFAs Nutrients Fe +2 H 2 Fe +2 H 2 H 2 VFAs VFAs Advection and Dispersion Fe +2 H 2 Diffusion between Solid ISCR seams

19 Hypothesized reaction Pathways Biotic PCE Abiotic PCE TCE Cis 1,2-DCE Trans 1,2-DCE VC Ethene Ethane TCE cis1,2-dce VC Ethene Dichloroacetylene Chloroacetylene Acetylene CO 2 CH 4 H 2 O β-elimination Hydrogenolysis Hydrogenation Ethane CO 2 CH 4 H 2 O

20 DESIGN AND IMPLEMENTATION OF ENGINEERED ISCR 20

21 Remediation Strategy Source Area/ Hotspot Treatment Injection PRB for Plume Control Plume Treatment 21

22 Key Design Questions? 1. What should the strategy be based on the site-specific goals? Residual source area treatment / Plume treatment / PRB 2. Which product to use, how much, how frequent? Make up of target contaminants Desired reduction in concentration of CVOCs? Estimated mass of CVOCs Prevailing geochemistry (DO, ORP) Pathways required to treat the suite of CVOCs Product longevity Product distribution under the site-specific geologic/hydrogeologic conditions (depth, geology) Demand from CEAs Site-Specific Design Factor 3. Are other additives required (buffer, bioaugmentation etc.)? Potassium bicarbonate / dolomite SDC-9 / KB-1 22

23 Key Implementation Questions 1. Can the required product be applied in one event or multiple events are required? Available pore volume v/s injected volume 2. Application Method DPT Injection Wells Fracturing Soil Blending 3. ROI and number of injection points? ROI increases with permeability-less injection points ROI increases with high pressure injections 23

24 Key Implementation Questions 1. Distribution of Slurries (all engineered ISCR products contain ZVI) Top Down / Bottom Up for DPT Fracturing (pneumatic/hydraulic) 2. Mixing / Pump Requirements Good mixing to eliminate clogging Positive displacement pumps/ high flow rate 3. Injection Spacing (horizontal/vertical) It is not only about how far you can distribute the reagent 4. Verification of Distribution Magnetic separation Visual inspection of cores 24

25 Methods to Validate ROI Verification of direct product placement: Visual observation of fractures in soil cores. Magnetic separation of ZVI from soil cores. Monitoring of ground deformation using uplift stakes or tilt meters (usually used during fracturing). Extended zone of influence: Groundwater Indicator Parameters (TOC, Fe, geochemical parameters) 25

26 How Far is Substrate Distributed? 26

27 Solid ISCR Design Calculation Steps 1. Calculate quantity of EHC required Hydrogen demand from CEAs and CVOCs in the treatment area Multiply the hydrogen demand by specific hydrogen capacity of EHC (94 g H 2 /kg of EHC), Multiply the theoretical EHC demand by a site-specific design factor (1 to 10) If the calculated demand is less than the default value, use the default value Recommended default values are: 0.15 to 0.25% by wt of soil for plume treatment 0.25 to 1.0% by wt. for source area treatment 0.50 to 1.5% by wt. for a PRB 2. Assess if the quantity estimated can be injected 8 out of 10 times selected dosage is based on default values If required EHC slurry volume is less than 15% of the total porosity in the treatment zone, the quantity can be injected. If more than 15%, multiple injection events may be required spaced 6 months apart. If slurry volume is less than 10%, increase the volume by diluting the slurry to inject at a minimum 10% of the PV. 27

28 Liquid ISCR Design Calculation Steps 1. Calculate quantity of substrate required 1. Hydrogen demand from CEAs and CVOCs in the treatment area Multiply the hydrogen demand by amount of H2 produced per unit quantity of substrate eg: (0.141 HRC, Lactate EHC Liquid, soy bean oil Multiply the theoretical demand by a site-specific design factor (1 to 10) Calculate the required concentration of TOC in pore water. If the calculated concentration is less than the default value, use the default value Recommended default values are: 1,000-5,000 mg/l for plume treatment ,000 mg/l for residual source area treatment 10,000-15,000 mg/l for source area and PRB 2. Assess if the quantity estimated can be injected 8 out of 10 times selected dosage is based on default values If required substrate volume after X dilution is greater than 15% but less than 30% of the total porosity in the treatment zone, the quantity can be injected. If it is more than 50%, the dilution factor can be reduced to inject a concentrated solution or perform multiple applications. If it is less than 15%, increase the volume by diluting the solution or increasing the application rate. 28

29 SOLID-ISCR CASE STUDIES 29

30 EHC Case Study Source Area / Grid Injection Site: Former Dry Cleaner, OR Contaminants: PCE ~ 22,000 ug/l TCE ~ 1,700 ug/l DCE ~ 3,100 ug/l VC ~ 7 ug/l Treatment: 10K lbs (4.5 kg) in 5 days 32 injection pts Target area = 825 ft 2 x 20 ft deep Vertical Interval = 10 to 30 ft bgs Low permeability lithology Large seasonality in GW flow Application rate - 0.6% by wt. to soil Material Cost: $1.24/ft 3, ~$20,000 30

31 Conc. (mg/l) ORP (mv) EHC Case Study Results - Indicator Parameters Conc. (mg/l) Conc. (mg/l) ORP Time post EHC injection (months) Dissolved Oxygen Time post EHC injection (months) Sulfate Methane Time post EHC injection (months) Time post EHC injection (months) NW sampling cluster SW sampling cluster NE sampling cluster SE sampling cluster 31

32 Conc. (ug/l) Conc. (ug/l) EHC Case Study Results Conc. (ug/l) Conc. (ug/l) 30,000 NW sampling cluster 6,000 NE sampling cluster 25,000 5,000 20,000 4,000 15,000 10,000 3,000 2,000 PCE 5,000 1, TCE Time post injections (months) Time post injections (months) 8,000 SE sampling cluster 12,000 SW sampling cluster c-dce 6,000 10,000 8,000 VC 4,000 6,000 2,000 4,000 2, Time post injections (months) Time post injections (months) 32

33 Upstate NY Case Study ISCR pilot and Full scale Injections Manufacturing site with DCE stall historically An ISCR (EHC) pilot test was previously conducted in the CVOC source area in Feb Full scale injections were designed as multiple events spread over 2 years both in the source area and downgradient (PRB) to prevent offsite plume migration Design parameters: The injections were conducted around monitoring wells MW-11, MW-17 and MW-07 in Sep 2011 and Apr 2013 Bioaugmentation was done using SDC-09 at the end of each injection event 33

34 EHC Case Study Results 34

35 EHC Case Study Results 35

36 ISCR PRB- Plume Treatment Site: Confidential Site, KS Contaminant: Carbon Tetrachloride 2600 ft / 800 m plume Treatment: 48K lbs (21.7kgs) EHC PRB Application PRB installed down-gradient of Strategy: source area Installed line of injection points 10 ft / 3 m apart PRB extends width of plume = 270 ft / 90 m long Installed in 12 days using direct inject discharges into small creek Courtesy of Malcolm Pirnie (Arcadis) 36

37 ISCR - PRB <1 < <1 < <1 57<1 27<1 33<1 31<1 29<1 25< <1 < February May October April August March 2005 N <1 6.4 EHC Treatment Zone EHC Treatment Zone Monitoring well and CT Monitoring concentration well and (ug/l) CT concentration (ug/l) Property Line Property Line SCALE IN FEET SCALE IN FEET <1 <

38 LIQUID ISCR CASE STUDIES 38

39 E-ZVI Case Study 39

40 Baseline Concentrations 40

41 Approach (cont.) 41

42 Injection design 42

43 December 2004 TCE Contours Depth Feet April 2008 TCE Contours Depth Feet TCE Concentration (ppb) 10,000 ppb 1,000 ppb 100 ppb 10 ppb Treatment Area TCE Groundwater Cleanup Target Level is 3.0 ppb Monitoring Well with Screen Interval Multi-Chamber Monitoring Well 43 Case Study #3 Patrick AFB, Florida RITS Spring 2009: EZVI Treatment of Chlorinated Solvents

44 Concord NWS Case Study Enhanced Reductive Dechlorination Pilot Test: An Enhanced Reductive Dechlorination (ERD) pilot test was previously conducted in the TCE source area from 2011 to The ERD pilot test used buffered emulsified vegetable oil substrate which was augmented with dechlorinating microbial consortium (SDC-9 ). ISCR Pilot Study: The test was conducted in the TCE source area wells (S29MW01 and S29MW03) not affected by the ERD pilot test. The aquifer was first primed for substrate distribution by fracturing the aquifer using the ELS and bioaugmentation solution. Following confirmation of fracture development, ZVI suspended in guar was injected into the interval followed immediately by the lactate, ELS solution and bioaugmentation culture. Monitoring was then conducted to verify the degradation of TCE. 44

45 Standard Units mv Analytical Results ISCR vs Biotic Only Treatment Comparison ph S29MW10 - Biotic Only S29MW11 - Biotic Only S29MW01 - ISCR S29MW03 - ISCR ISCR vs Biotic Only Treatment Comparison Oxidation-Reduction Potential S29MW10 - Biotic Only S29MW11 - Biotic Only S29MW01 - ISCR S29MW03 - ISCR Days Days 45

46 Analytical Results 46

47 Concord NWPS Total Chlorinated Ethenes 47

48 Half Life (hours) Amended and Unamended Field Half Lives Amended and Unamended Field Half Lives 10,000 5,736 5,736 6,648 6,648 6,648 2,112 2,112 1, CHC (field application rate by weight) PCE (10%) PCE (0.5%) TCE (10%) TCE (1%) TCE (0.5%) Vinyl Chloride (10%) Vinyl Chloride (1%) Anaerobic Natural Attenuation Rates (Alvarez & Ilman, 2006) Injected PRB Field Half Life Trench PRB Field Half Life Granular ZVI (Abiotic) Carbon Tetrachloride (0.5%) Chloroform (0.5%) Engineered ISCR-treated plumes degrade with half lives one to two orders of magnitude faster than that seen under anaerobic natural attenuation

49 Latest Developments 1. Integrated Emulsified Lecithin + ZVI Full-scale application at Concord NWS in Ferox Plus by Hepure ZVI plus emulsified vegetable oil (SRS) 3. Magnetic Susceptibility Analysis Allows us to determine the capacity of the aquifer to intrinsically support abiotic ISCR 4. Combined Remedies Sequential ISCO/ISCR (Klozur Persulfate /EHC) ERH/ISCR (CDMSmith, Hunters Point Naval Shipyard) 49

50 Bench, Pilot, and Design Optimization Tests 1. Bench tests typically recommended only for unique combination of CVOCs, CVOCs that have not been tested before, CVOCs concentrations outside the previously tested range or unique geochemical conditions (e.g. high sulfate) 2. Pay close attention to how you scale up from bench test data (i.e. the ratio of water to soil used in the bench is usually skewed compared to what it is in the aquifer) 3. Perform pilot test to answer questions around distribution, injectability, and full-scale design 4. Pilot test must be small enough to be cost effective, and add value to the full-scale, at the same time broad enough to collect sufficient data. As a general rule, be prepared to collect a lot more data in the pilot then you will during full-scale application 50

51 Lessons Learned 1. Geochemistry is important but it is relatively easy to overcome limiting geochemical conditions 2. It is important to know where the majority of the target contamination resides.specially for source and residual source areas 3. Distribution is the key to success, so engage a qualified injection contractor during the design phase 4. Adopt newer site characterization tools to optimize implementation and achieve desired goals 5. Employ recommended injection pumps, mixing equipment and procedures 6. Allow flexibility in the design to address unforeseen conditions in the field 51

52 Reference Documents CHAPTER 10 IN SITU CHEMICAL REDUCTION FOR SOURCE REMEDIATION Paul G. Tratnyek,1 Richard L. Johnson,1 Gregory V. Lowry2 and Richard A. Brown3 B.H. Kueper et al. (eds.), Chlorinated Solvent Source Zone Remediation, doi: / _10, # Springer Science+Business Media New York

53 Questions??? Ravi Srirangam P.E., Ph.D. Technical Manager, Environmental Solutions PeroxyChem, LLC One Commerce Square 2005 Market Street, Suite 3200 Philadelphia, PA P: