Role o e of I InSi Situ B Bioremediation f n for MGP GP Sites - - PowerPoint PPT Presentation

Role o e of I In–Si Situ B Bioremediation f n for MGP GP Sites

By

Mike M Marley, L L.E. E.P. (marley@xdd-llc.com)

Pres esen ented ed to to:

MEA Environmental Learning Summit September 15 – 17, 2014 Hyatt Rosemont, Rosemont, IL

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Be Benef efits o

• f Bi

Biorem emed ediat ation

• Because mo

most contaminants biodegrade

• Biodegradation can accelerate dissolution

and reduce cleanup time

– Rate is a function of availability

• “True In-Situ” Remedy
• Biodegradation in some form is commonly a

component of a multi-technology site remedial strategy

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Aerob

• bic vs. Ana

naerobic D Degradatio tion

(when you have a a c cho hoice) e)

• Aerobic reactions are faster but the rate difference is not often

significant;

– Anaerobic rates can be increased with site condition enhancements;

• Less Regulatory monitoring for aerobic pathways;
• Solubility limits for oxygen delivery;

– Can add much more nitrate and sulfate – higher solubility;

• Should confirm site specific applicability with microcosm studies;

– E.g. – native, mainly anaerobic, bacteria may not always degrade the contaminant of interest – In some cases, mainly chlorinated contaminants, it may be necessary to add bacteria (bioaugmentation)

Is s Biore remediation a appro ropri riate: G Goals s

• Not Appropriate

– Significant source mass reduction goal – High ring PAHs treatment (6-ring and above)

• Due to low solubility
• Appropriate

– Limited source reduction or lighter end source materials – Plume control

• Natural
• Active

– Chlorinated compounds – Access issues limit in-situ or excavation alternatives

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Is Bioremediation a n app ppropr priate: e: G Geochemistry

• Not Appropriate

– No dissolved oxygen – if desire aerobic biodegradation

• Add oxygen e.g. biosparging

– pH : >8 or <6

• Unless buffer aquifer

– No Dehalococcoides

• Chlorinated compounds only
• Need to bioaugment

– Devoid of nutrients or trace minerals (not uncommon in high contaminant mass source areas)

• Add nutrients / minerals

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Bench Test, Pilot Testing, and Design More Than Just the Biology

Characterization:

• Geology/target layers
• Accurate source impact

level assessment

• NAPL

Design:

• Bench Test
• Modeling to achieve risk

closure levels

• Injection Strategy
• Donor / Acceptor mass

sufficient for contaminant mass

Pilot Testing:

• Confirm injection and

extraction rates

• Optimize full-scale grid

Full Scale:

• Effective Design
• = Results

Critical for Success

• Treatability studies can minimize potential field failures

– avoids incurring significant and unnecessary costs – benefits project schedule

• Success or failure is a direct result of understanding

– contaminant mass and its architecture (i.e. distribution in site specific geology) – impacts of the site geochemical and biological conditions on biodegradation potential e.g.

• no DHC present in site soils (again for chlorinated compounds)
• insufficient nutrients or inappropriate pH
• unacceptable by-products

– appropriate reagent formulations and dosages

• Be careful designing based solely on previous successes or

failures…..every site can be different

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Pr Pre-Design / n / Lab T b Treatab ability Services

Plume C Cont

• ntainment – Na

Natural

• Natural biodegradation processes can control off-

site migration of MGP plumes.

• MNA analysis can be used to evaluate current

conditions at the site and determine the effectiveness of natural containment.

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Mann-Kendall A Analys ysis S Summary T ry Table

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• Off-site migration has been

controlled though natural biodegradation processes.

• Exceedences of VOC and

PAH Preliminary Regulatory Guidelines (PRGs) are limited to the site.

Plume C Cont

• ntainment – Ac

Active ve

• Due to cost of source treatment, XDD is seeing

more Utilities looking at plume containment using biodegradation

– Predominantly dissolved components leaving source area – Bio-barriers can be cost effective alternative

• Most we have seen are aerobic for PAHs and BTEX due to rapid

degradation rates i.e. relatively short treatment zone

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Summary

• Biodegradation is often a component of site remedial /

closure strategy and in some cases is used as a stand-alone approach

• Need to understand site specific conditions and goals

– Treatability studies whether in the laboratory (most common) or in the field provide key information for technology viability and design

• In many cases the natural site bacteria just need tweaking
• f their environment, but in some cases you will need to

add select bacteria to achieve the remedial goals

• Appropriate use of the technology can reduce overall

project costs and monitoring duration

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