Remediation of Perchlorate, NDMA, and Chlorinated Solvents Using Nanoscale ZVI Neal Durant, Evan Cox GeoSyntec Consultants Wei-xian Zhang - Lehigh University Sandra Dworatzek - SiREM Scott Neville, Chris Fennessy Aerojet RTDF PRB Workshop Niagara Falls, New York October 16, 2003 ndurant@geosyntec.com
Technology Overview Project Motivation Presentation Outline Demonstration Project: California Site Bench test approach Bench test results Pilot test plan R&D Needs
Nanoscale ZVI Technology Overview Typical diameter < 100 nm Specific surface area: 33.5 m 2 /g (vs. < 1 m 2 /g for commercial Fe powder) Treatment rates 10 to 100 times faster than ZVI powder Addition of noble metal (< 1% wt.) dramatically increases treatment rates 100 nm Ease of deployment: Direct injection into wells Ex situ slurry reactors (e.g., GAC, zeolite) Fixed to membranes
Nanoscale ZVI: Compounds Treated Chloroethenes PCE, TCE, cdce, VC Chloromethanes CTET, Chloroform Chlorobenzenes Organochlorine pesticides (e.g., Lindane) PCBs N-nitrosodimethylamine (NDMA) Cr VI, As V, Pb II - Perchlorate, NO 3 Everything else treated by granular ZVI, except > 10x faster
Nanoscale ZVI In Situ Approaches Plume-Wide Remediation Monitoring or Remediation Wells Groundwater Flow
Nanoscale ZVI In Situ Approaches Plume-Wide Remediation NZVI Injection Into Existing Wells Groundwater Flow
Nanoscale ZVI In Situ Approaches Plume Containment via PRB Nano-ZVI Injection Points Mobile Nano-ZVI Zone Dispersed Nano-ZVI
Project Motivation Perchlorate (ClO 4 ) is a national threat to drinking water Produced, handled, or used in at least 44 states Present in groundwater supplies in > 18 states Detected in water supplies of > 15 M people in CA, AZ, NV Incidence of ClO 4 detection continues to increase ClO 4 is highly soluble and generally un-reactive in groundwater Plumes are frequently large and deep Conventional ex situ treatment technologies (e.g., ion exchange) carry high capital cost
Project Motivation ClO 4 plumes often contain N-nitrosodimethylamine (NDMA), and chlorinated solvents (especially at rocket test sites) Few (if any) conventional technologies can treat all these compounds at once Nanoscale ZVI has potential to treat these compounds simultaneously, in situ However, subsurface transport and longevity of NZVI poorly understood
Project Motivation Moore et al. (2003) demonstrated abiotic dechlorination of ClO 4 in presence of granular and powder ZVI, and Concluded that rates were too slow for application for site remediation But, Did not examine nanoscale ZVI
Project Motivation Gui et al. (2000) demonstrated effective abiotic dechlorination of NDMA in presence of granular ZVI, and Nickel-ZVI; Transformation rates have not been reported for Nano-ZVI
Technology Demonstration: Treatment of ClO 4, NDMA, Chloroethenes, and Nitrate at Aerospace Site Sacramento, California
Demonstration Objectives Phase I: Bench Test (On-going) Confirm treatability Determine site-specific Nano-ZVI loading requirements Estimate site-specific transformation rates Determine treatment capacity (reactive longevity) under site-specific conditions Measure retardation and transport of Nano-ZVI in aquifer columns Phase II: Pilot Test (Planned) Nano-ZVI delivery and performance in active recirculation cell Nano-ZVI delivery and performance in passive PRB
Example Batch Reactors Control 5 g/l Nano Fe
Optimal Loading Tests (ongoing) Objective: estimate optimal range for NZVI loading concentration Set-up Separate batch reactors treated with either 0, 0.5, 1, 5, or 10 g/l Nano-ZVI 25% aquifer sediment slurry in site groundwater React for 48 hours Measure contaminant remaining Only tested chloroethenes and NDMA so far
Preliminary Results Determination of Optimal Loading for Chloroethene Treatment 0.60 0.50 0.40 Chloroethene remaining after 48 hours in batch reactors (25% sediment slurry) as a function of NZVI loading /L) (mg 0.30 0.20 Optimal NZVI loading range TCE 1_1-dce 0.10 0.00 0 2 4 6 8 10 12 g/l Nano Fe
Preliminary Results Determination of Optimal NZVI Loading For NDMA Treatment 100 75 NDMA remaining after 48 hours in batch reactors as a function of NZVI loading ug/l 50 25 Optimal NZVI loading range 0 0 2 4 6 8 10 12 g/l Nano Fe
Optimal Loading Tests Summary of Preliminary Results Nano-ZVI effective treatment agent for TCE, NDMA TCE and perchlorate are driver compounds (loading requirement for TCE >> NDMA) Optimal Nano-ZVI loading requirement: 2 to 5 g/l
Transformation Rate Tests Objectives (1) estimate ClO 4, chloroethene, and nitrate transformation rates in the presence of 10 g/l Nano-ZVI (2) compare rates for commercial and laboratory synthesized NZVI Set-Up Duplicate reactors, sampled at various intervals for 27 days 25% aquifer sediment slurry in site groundwater Included control reactors (sediment + water, w/o Nano-ZVI) Initial concentrations: ClO 4 = 14 ppm; TCE= 2 ppm; nitrate = 20 ppm
Transformation Rate Tests Controls Control ( no Nano-ZVI) Treatment ef fi ciency ( C/Co) 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 TCE cdce 1,1-DCE Nitrate Perchlorate 0 5 10 15 20 25 30 Days
Transformation Rate Tests Lehigh Nano-ZVI Lehigh NanoZVI (10 g/l) Treatment efficiency (C/Co) 1.2 1.0 0.8 0.6 0.4 0.2 0.0 TCE cdce 1,1-DCE Nitrate Perchlorate 0 5 10 15 20 25 30 Days
Transformation Rate Tests Lehigh Nano-ZVI Lehigh NanoZV I (10 g/l) 150 2000 Perch lorate and Chl oroethene Concentrat ion (um) 100 50 Perchlorate Tota l Chloroethene Chloride 1900 1800 1700 Chl or i de ( um ) 0 0 200 400 600 800 1600 Hours
Transformation Rate Tests Toda Nano-ZVI Toda NanoZVI (10 g/l ) Treatment ef fi ciency ( C/Co ) 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 ClO 4 (14 ppm) + HgCl 2 (250 ppm) 0 5 10 15 20 25 30 Days TCE cdce 1,1-DCE Nitrate Perchlorate
Transformation Rate Tests Comparison of Nano-ZVI Performance for Chloroethenes Toda NanoZVI ( 10 g/l) 0.5-0.5 Lehigh NanoZVI ( 10 g/l) LN (C/Co) -1.5-2.5-3.5-4.5-5.5-1 k TCE = 0.023 hr k 11DCE = 0.0178hr k NO3 = 0.0175 hr k cdce = 0.0036 hr 0 50 100 150 Hours -1-1 -1 LN ( C/Co ) TCE 0.5 cdce 0.0 1,1-DCE -0.5-1.0 Nitrate -1.5-2.0-1 k NO3 = 0.071 hr -2.5 k 11-DCE = 0.0674 hr -1-3.0 200 k TCE 250 = 0.05 hr -1 k cdce = 0.034 hr -3.5-4.0-1 TCE cdce 1,1-DCE Nitrate 0 10 20 30 40 50 60 Hours
Transformation Rate Tests Comparison of Nano-ZVI Performance for Perchlorate Toda NanoZVI ( 10 g/l) Perch l orate (mg/l ) 16.0 14.0 12.0 10.0 8.0 6.0 4.0 2.0 0.0 k ClO4 = 0.0873 mg/l-hr k ClO4 = 0.0504 mg/l-hr 0 200 400 600 Hours Perch l orate (mg/l ) 16.0 14.0 12.0 10.0 800 8.0 6.0 4.0 2.0 0.0 Lehigh NanoZV I (10 g/l) k ClO4 = 0.0507 mg/l-hr 0 200 400 600 800 Hours
Transformation Rate Test Summary of Observed Transformation Rates Toda Nano-ZVI Lehigh Nano-ZVI Constituent Zero Order (mg/l-hr) First Order (hr -1 ) Half- Life (d) Surface-Area Normalized Rate Coefficient (L/hr/m 2 ) Zero Order (mg/l-hr) First Order (hr -1 ) Half- Life (d) Surface-Area Normalized Rate Coefficient (L/hr/m 2 ) Perchlorate 0.0504 0.0507 TCE 0.023 1.3 6.57E-05 0.050 0.6 1.49E-04 1,1-DCE 0.018 1.6 5.09E-05 0.067 0.4 2.01E-04 c-dce 0.004 8.0 1.03E-05 0.034 0.8 1.01E-04 Nitrate 0.018 1.7 5.00E-05 0.071 0.4 2.12E-04
Transformation Rate Test Summary of Preliminary Findings Nano-ZVI treats chloroethenes, ClO 4, NDMA, and nitrate in Site groundwater; ClO 4 is rate-limiting step. Lehigh Nano-ZVI degraded chloroethenes 2 to 3 times faster than Toda Nano-ZVI. Why? Lehigh material has fewer impurities (i.e., oxides) Degradation of ClO 4 was preceded by lag period for both for Toda NZVI and Lehigh NZVI Why? Possible that anions competitively inhibited ClO 4 sorption to Nano-ZVI (this is a critical first step)
Transformation Rate Test Summary of Preliminary Findings Lag period to onset of ClO 4 degradation was shorter for Toda NZVI (2 to 5 days) than for Lehigh NZVI (5 to 8 days) Why? Mixed oxide/zvi content of Toda-NZVI is more favorable for dechlorination of perchlorate (Moore et al. 2003)
Aerospace Site Pilot Test Plans Direction of Groundwater Flow Passive Treatment Demo Layout Active Treatment Demo Layout IW IW IW Treatment Building IW (3 day) (3 day) (5 day) (10 day) (1 day) (3 day) (5 day) EW (15 day)
Aerospace Site Potential Approach for NZVI delivery
Research and Development Needs Cost effective approaches for particle synthesis/manufacture Field studies evaluating Nano-ZVI particle transport and reactive longevity Laboratory evaluation of relationship between particle shape and transport characteristics Evaluation of optimal modes for particle delivery Rigorous performance and cost comparison with in situ bioremediation (for perchlorate and chloroethenes)