1,2,3-TCP Remediation in Groundwater: Biological Reduction and Chemical Reduction using ZVZ

Transcription

1 1,2,3-TCP Remediation in Groundwater: Biological Reduction and Chemical Reduction using ZVZ Melissa Schmitt, Senior Engineer Eric Suchomel, Senior Engineer Geosyntec Consultants

2 Why is 1,2,3-Trichloropropane an Emerging Concern For Groundwater? Man-made compound typically found at: Ag-chem facilities, Chemical manufacturing/storage facilities, Military bases Supply wells, particular those in agricultural areas Often low-concentration, nonpoint source groundwater contaminant Relatively low vapor pressure Low K oc, unlikely to sorb to soil Classified as a likely or potential human carcinogen

3 Current Regulatory Climate - Federal No Federal Maximum Contaminant Level (MCL) Included in EPA s Third Unregulated Contaminant Monitoring Rule (UCMR 3) Sampling of public water systems from Reporting limits during testing potentially high relative to regulatory levels 1,2,3-TCP was detected above reporting limit (0.03 µg/l) in 1.3% of systems and above 1x10-4 cancer risk threshold (0.04 µg/l) in 1.1% of systems Listed on 2015 Draft Contaminant Candidate List 4 for regulatory determination (CCL4)

4 Current Regulatory Climate - State 1,2,3-TCP regulatory levels low relative to other VOCs (e.g., PCE MCL is 5 µg/l) California: Part per trillion goals µg/l Public Health Goal (OEHHA; est. 2009) Draft MCL Expected Hawaii: State MCL of 0.6 µg/l (est. 2011) Minnesota: Health Risk Limits (HRL) (est. 2013): µg/l Cancer HRL 0.7 µg/l Non-Cancer HRL New Jersey: Drinking Water Quality Institute Recommendation to Department of Environmental Protection (est. 2009): 0.03 µg/l Suggested MCL* *Based on practical quantitation limit of analytical method Other states coming soon?

5 Current Status of Groundwater Remediation Practice Groundwater ex situ treatment is costly Common VOC removal methods less effective for 1,2,3-TCP Long GAC residence time required for removal Advanced oxidation processes may also be effective In situ remediation is most effective but not widely tested Potentially costly for dilute plumes Includes: Biological Reduction (ISBR) Chemical Oxidation (ISCO) Chemical Reduction via Zero Valent Metals (ISCR)

6 1,2,3-TCP Degradation Pathway Primary pathway observed for ISBR and ISCR Abiotic in the presence of cysteine or sulfide OH allyl mercaptan, S-allyl mercaptocysteine, and allyl sulfides allyl alcohol

7 Advances in ISBR of 1,2,3-TCP Since 2000 Biostimulation at numerous sites; mixed results and unknown/unclear degradation mechanism and pathway ~2010 Dihaloelimination of chlorinated propanes by Dehalogenimonas recognized (Bowman et al, 2012) 2014 Commercially-available testing of Dehalogenimonas 2014-Present Developed better understanding of biological degradation pathway Pathway evaluated at higher concentrations (500-5,000 µg/l) Degradation products transient in water and rarely observed

8 Advances in ISBR of 1,2,3-TCP KB-1 Plus Evaluation: Bioaugmentation culture containing Dehalogenimonas Culture is capable of dihaloelimination of 1,2,3-TCP without advanced acclimation Size of inoculum for effective degradation of 1,2,3-TCP is similar to that of chlorinated ethenes/ethanes

9 1,2,3-TCP Conc. (µg/l) Logarithmic scale DHG % Increase KB-1 Plus Evaluation: Practical Lower Concentrations 10,000 1, Time (Days) 10 ppb 50 ppb 100 ppb 1000 ppb 5000 ppb ppb 1, Treatments 10 ppb 50 ppb 100 ppb 1,000 ppb 5000 ppb 10,000 ppb Degradation of TCP at varying concentrations and corresponding growth of Dehalogenimonas

10 1,2,3-TCP Concentration (mmols/bottle) KB-1 Plus Evaluation: Optimal ph Range Time (Days) ph 5 ph 6 ph 7 ph 8 Media Control Degradation of 1.5 mg/l TCP by KB-1 Plus at ph values from 5 to 8

11 ISBR - Case Study # 1 Direct push injections of a slow-release electron donor (HRC TM ) Successful long-term reduction of TCP (and dichloropropane [DCP]) Pilot led to full-scale implementation Understanding of remedial mechanisms remained unclear Recent Dehalogenimonas testing inconclusive ~9 years after full-scale injections

12 ISBR - Case Study # 2 Former agricultural chemical wholesale facility Constituent Max Site Conc. State Goal 1,2,3-TCP 72 µg/l µg/l (PHG) 1,2-DCP 680 µg/l 5 µg/l (MCL) Nitrate (as N) 1,800 mg/l 10 mg/l (MCL) Sulfate 415 mg/l 250 mg/l (Secondary MCL) Treatability study elements Biostimulation with lactate and emulsified vegetable oil (EVO) Bioaugmentation with KB-1 Plus Biostimuation alone unsuccessful, promising results with KB-1 Plus bioaugmentation

13 1,2-DCP, Propene, & Propane (mmols/bottle) 1,2,3-TCP (mmoles/bottle) 1,2-DCP, Propene, & Propane (mmols/bottle) 1,2,3-TCP (mmoles/bottle) ISBR - Case Study # 2 EVO Amended/KB-1 Plus Bioaugmented Time (Days) ,2-DCP Propene Propane Bioaugmented with KB-1 Plus (TCP) 1,2,3-TCP Lactate Amended/KB-1 Plus Bioaugmented Time (Days) ,2-DCP Propene Propane Bioaugmented with KB-1 Plus (TCP) Amended with Lactate 1,2,3-TCP

14 ISBR Conclusions & On-Going Research In situ bioremediation can be effective, but results are variable Removal mechanisms difficult to interpret Abiotic versus biotic degradation can be difficult to determine Non-target donor demands (particularly sulfate) may be limiting factor in applicability Work is ongoing to further advance TCP bioremediation, including: Field implementation of bioaugmentation Evaluating practical lower concentration limits for TCP ISBR Refining evaluation of ph ranges over which degradation occurs Conducting Gene-Trac Dhg testing at sites where biostimulation alone was successful

15 Advances in ISCR of 1,2,3-TCP Use of zero valent metals has been evaluated and applied at TCP sites (bench- and pilot-scale) since at least the mid-2000 s Several types of zero valent metals formulations have been assessed for TCP remediation: Zero Valent Iron (ZVI), Zero Valent Zinc (ZVZ), proprietary mixtures of ZVI and other compounds (e.g., EHC ) Remediation implemented in several ways: Injection (liquid or slurry formulations) through temporary or permanent injection points Placement of solids permeable reactive barriers

16 Comparison of TCP Degradation by ZVI and ZVZ Kinetics of TCP degradation by ZVZ and ZVI Figure format Surface area normalized rate constant (k SA ) vs. mass normalized rate constant (k M ) Good for complex comparisons of kinetics Reactivity increases up and to the right Observations Both ZVZ and ZVI produce relevant degradation rates, but ZVZ rates significantly faster than ZVI Sarathy, Tratnyek, et al., 2010

17 ZVZ Field-Scale Column Testing Initial laboratory bench-scale batch and small column testing of ZVZ conducted with positive results Field-scale column testing conducted with different zinc/sand mixtures to support remedy design Reactors Two 5-Gallon Pails in Series 25% Zn64 Dust/75% Sand 33% Zn1210 Powder/67% Sand 67% Zn1210 Powder/33% Sand 100% Zn1210 Powder

18 ZVZ Field-Scale Column Results All Zn1210 columns met 1,2,3-TCP treatment goal Treatment efficiency declined over 12 weeks of operation Hydrogen gas produced Effluent dissolved zinc (0.04 to 0.20 mg/l) was below secondary MCL (5 mg/l) Time (weeks) Salter-Blanc, Suchomel, et al., 2012

19 ZVZ Pilot Study Military facility located in Southern California 1,2,3-TCP present in source well at concentrations up to 10 µg/l, eventual remedial objective for 1,2,3-TCP expected to be 0.5 µg/l Pneumatic fracturing injections completed in July 2014 injected ~14,000 pounds of Zn1210 Main issues surfacing, process challenges (pump plugging, etc.)

20 ZVZ Pilot Study Initial Results TCP degradation by ZVZ ongoing over year of post-injection monitoring No observed impacts to groundwater flow or secondary water quality impacts

21 On-Going ISCR Research Additional post-injection characterization work at pilot study site planned for 2016: Advance soil borings to evaluate distribution of ZVZ within injection area Collect performance monitoring data to evaluate long-term efficacy of ZVZ Pilot study expansion may be considered as element of site-wide groundwater remedy

22 Conclusions/Summary 1,2,3-TCP is an emerging challenge Low levels with long dilute plumes Relatively high toxicity -> Low regulatory levels Degradation pathway not well understood until now On-going advances in situ remediation provides more robust remedial technology alternatives for consideration

23 Team & Acknowledgements Geosyntec Consultants Melissa Schmitt, PE Eric Suchomel, PhD, PE Rula Deeb, PhD, PE SiREM Sandra Dworatzek Jeff Roberts Phil Dennis Jennifer Webb Oregon Health and Science University Paul Tratnyek Alexandra Salter-Blanc James Nurmi Naval Facilities Engineering Command Theresa Morley Nancy Ruiz Research at Oregon Health & Science University (OHSU) is funded by Strategic Environmental Research and Development Program (SERDP) Grant No. ER Commeralization by Geosyntec Consultants is funded by private clients and the Navy Environmental Sustainability Development to Integration (NESDI) Program Project # 434