Testing of an in situ chemical oxidation treatment on a plume of - - PowerPoint PPT Presentation

› Testing of an in situ chemical oxidation treatment on a

plume of chlorinated aliphatic hydrocarbons:

› Results, conclusions and future possibilities

2

Project Objective

Testing of chemical oxidation – Introduction – Montréal, April 26, 2016

□ The pumping and treatment of a plume of dissolved chlorinated aliphatic hydrocarbons (CAH) is generally a hydraulic confinement method rather than a rehabilitation solution. □ The estimated pumping time for rehabilitating a plume of dissolved CAH can be very long, often on a scale of tens or hundreds of years. □ In order to reduce the pumping times and complete a possible rehabilitation, in situ processes have been evaluated and applied. □ The study reported presents the challenges encountered in the application of one in situ treatment method, chemical oxidation.

Presentation Contents

Testing of Chemical Oxidation – Introduction – Montréal, April 26, 2016 3

• 1. Background

1.

• a. Challenges and context of the sector to be treated
• 2. Chemical oxidation testing

1.

• a. Preparatory testing and hydrogeological characterization
• b. Completion of the injection test
• 3. Evaluation of chemical oxidation treatment effectiveness

1.

• a. Results and geochemical monitoring of the groundwater
• b. Costs associated with the various work
• 4. Conclusion

Background

Chemical oxidation – treatment of an unconfined aquifer

Hydrogeological Context

5 Chemical Oxidation – Background – Montréal, April 26, 2016

Maximum 50 µg/L A A'

Methods available for preventing CAH from migrating off the property

Chemical Oxidation – Choice of Treatment Method – Montréal, April 26, 2016 6

Methods evaluated as of June 2013 □ ¡ ¡Soil-­‑bentonite ¡containment ¡wall ¡ □ ¡ ¡Reac5ve ¡barrier ¡with ¡filtra5ng ¡gates ¡ □ ¡ ¡Chemical ¡oxida5on ¡ □ ¡ ¡Hydraulic ¡confinement

Chemical oxidation with potassium permanganate was selected for the performance of this oxidant in treating the CAH present at the site and for its persistence in the soil.

Objective of Chemical Oxidation Treatment

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□ The main CAH to be treated are trichloroethylene (TCE), dichloroethylene (DCE) and vinyl chloride (VC). □ Trichloroethylene (TCE) is a chlorinated aliphatic hydrocarbon that was mostly used as a metal degreaser. Oxydant TCE

2KMnO4+C2HCl3 → 2CO2 + 2MnO2 + 2K++ H++ 3Cl-

Chemical Oxidation Testing – Treatment Objective – Montréal, April 26, 2016

In situ chemical

• xidation testing

Chemical oxidation – treatment of an unconfined aquifer

In Situ Chemical Oxidation Testing (INCO)

Chemical Oxidation – Work Completed – Montréal, April 26, 2016 9

Work completed: □ Planning ¡of ¡the ¡INCO ¡and ¡installa5on ¡of ¡13 ¡injec5on ¡wells ¡and ¡24 ¡

• bserva5on ¡wells. ¡Soil ¡sampling ¡and ¡piezocone ¡survey. ¡

□ Preparatory ¡tes5ng ¡(2 ¡pumping ¡tests, ¡2 ¡salt ¡tracing ¡tests, ¡30 ¡ permeability ¡tests) ¡ □ Injec5on ¡of ¡potassium ¡permanganate ¡in ¡13 ¡wells ¡ □ Monitoring ¡of ¡injec5on ¡opera5ons ¡(volume ¡injected, ¡flow, ¡pressure, ¡ water ¡level ¡measurements ¡and ¡conduc5vity ¡in ¡the ¡observa5on ¡wells) ¡ □ Monitoring ¡of ¡geochemical ¡condi5ons ¡in ¡the ¡observa5on ¡wells

Results from the Pre-injection Tests

Chemical Oxidation – Results of the Pre-injection Work – Montréal, April 26, 2016 10

□ Impact radius under injection estimated at 10 m □ Natural demand for oxidant 6 g/kg MnO4 □ No presence of organic matter in the soil □ The permeability of the aquifer varies between 10-4 and 10-7 m/s Following the tests, a single phase of injection was conducted from September 27 to October 31, 2014 (~ 400 m3 of permanganate solution pumped into 13 injection wells).

Chemical Oxidation Effectiveness (north sector)

Chemical Oxidation – Chemical Oxidation Effectiveness– Montréal, April 26, 2016 11

1 10 100 1000 Concentration TCE (ug/l) Date d'échantillonnage

TCE au nord du fossé (site 13PI03)

13PI03 14TRC07 14TRC08 14TRC09 14TRC10 14TRC11 14TRC12

Avant l'injection Après l'injection Avant l'injection Après l'injection Avant l'injection Après l'injection

6 m of hydraulic load 6 litres/minute 23 m3 of solution

Chemical Oxidation Effectiveness (south sector)

Chemical Oxidation – Chemical Oxidation Effectiveness – Montréal, April 26, 2016 12 1 10 100 1000 Concentration TCE (ug/L) Date d'échantillonnage

TCE au sud du fossé

14PI07 14PI11 14PI12 14PI14 14TRC22 14TRC23 14TRC24 14TRC25 13PZ602

Avant l'injection Après l'injection

4-9 m of hydraulic load 5 - 8 litres/minute 10-20 m3 of solution

Pe-pH Conditions

13 Chemical Oxidation – Chemical Oxidation Effectiveness – Montréal, April 26, 2016

Results

Chemical oxidation – treatment of an unconfined aquifer

Follow-ups on Groundwater Quality

Chemical Oxidation – Results of the Chemical Analyses – Montréal, April 26, 2016 15

□ Several groundwater quality follow-ups were conducted in the 8 months following the injection of permanganate. □ Iron and manganese are present naturally in high concentrations in groundwater (iron 20-100 mg/l and manganese 0.07-0.8 mg/l) □ Potassium (K) was detected in the observation wells following the INCO up to a radius of 6 m, but the oxidant MnO4

• did not penetrate any further than

2 m. □ The identical redox conditions before and after the injection demonstrate that the elevated DCO in this aquifer consumes the oxidant very quickly before it can react with the CAH.

Extent of the Plume – Zone to be Treated

Chemical Oxidation – Extent of the Plume – Montréal, April 26, 2016 16

2013 2015 300 µg/L 100 µg/L 50 µg/L 50 µg/L

Results of the Chemical Oxidation Evaluation

Chemical Oxidation – Evaluation of the Treatment Method – Montréal, April 26, 2016 17

□ ¡ ¡In situ demand for oxygen greater than what was estimated in the laboratory

□ A more limited action radius than expected □ Precipitation of the oxidizing solution in the soil □ A more extended contaminated zone is probable Need to inject a larger volume of solution and to densify the network of injection wells. Involves much higher costs to treat the targeted zone.

Cost Associated with the Work

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Work Main Costs Ratio Injection test including the preparatory work Detailed characterization of the aquifer, injection trailer, development

• f injection wells, oxidant

1 Application of the in situ

• xidation at full scale

with 3 injection phases Development of 50 injection wells to cover the entire zone to be treated and the oxidant 2.2 Hydraulic confinement Development of wells and the pumping station 0.6

Chemical Oxidation – Costs Associated with the Work – Montréal, April 26, 2016

Lessons drawn from the tests and future possibilities

Chemical oxidation – treatment of the unconfined aquifer

Knowledge Acquired from the Aquifer

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□ Aquifer range where all the CAH concentrations are located □ Concentrations in TCE, DCE, VC □ Extent of the zone to be treated/confined □ Hydraulic properties of the aquifer (permeability, anisotropy, drainage speed) □ Geochemistry of the aquifer and groundwater matrix This knowledge has made it possible to better understand the site and to plan a hydraulic confinement system that is appropriate to the hydraulic context.

Chemical Oxidation – Knowledge of the Aquifer– Montréal, April 26, 2016

Future possibilities for reducing pumping times

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□ Activated colloidal coal coated in biodegradation-stimulating compounds (BOS 100TM , PlumeStopTM) could be used to stop the CAH plume and treat it. □ It would be preferable to stimulate CAH biodegradation in a reductive environment (anaerobic). To achieve this, we would need to understand the geochemical conditions and use the best electron donor for these conditions (e.g. nitrates, sulfates or Fe). However, the costs could be significant if using these products.

Chemical Oxidation – Future Possibilities – Montréal, April 26, 2016

Conclusions

Chemical oxidation – treatment of the unconfined aquifer

Conclusion – Chemical Oxidation

Chemical Oxidation – Conclusion – Montréal, April 26, 2016 23

□ Detailed hydrogeological knowledge of the area to be treated is required to ensure the effectiveness of the chemical oxidation. □ The quantity and quality of the hydrogeological data could involve a considerable but necessary investment. □ Other in situ treatment methods could be considered, but the costs are higher. □ Connecting the unconfined aquifer to the hydraulic confinement system is the least costly and preferred option for this site.