A NEW METHOD FOR IN-SITU REMEDIATION OF PFAS

IN SOIL AND GROUNDWATER

Anders G. Christensen, M.Sc, Expertise Director

Jacqueline A. Falkenberg, PhDNIRAS A/S, ALLERØD, DENMARK

Ian Ross, PhD & Jake Hurst, M.Sc, Allan Hornemann, PhDARCADIS UK & USA

17-03-2016 Renare Mark Vårmöte 2016

A NEW METHOD FOR IN-SITU REMEDIATION OF PFAS IN SOIL AND GROUNDWATER

Anders G. Christensen, M.Sc, Expertise Director

Jacqueline A. Falkenberg, PhDNIRAS A/S, ALLERØD, DENMARK

Ian Ross, PhD & Jake Hurst, M.Sc, Allan Hornemann, PhDARCADIS UK & USA17-03-2016 Renare Mark Vårmöte 2016

Background

Scope of the work

Laboratory work using the TOP Assay

Laboratory test with the ScisoR® method

Results

Conclusions & Outlook

AGENDA

PFAS: A large family of compounds

• Perfluorooctane sulfonate (PFOS)

• Perfluorooctanoic acid (PFOA)

• Other PFAS ranging from 2 to 16 carbon chains

• Precursors compounds exist as “Dark Matter”

• C6 chemistry generally replacing C8 PFAS

Fluorotelomers replace PFOS/PFOA but some form PFOA, PFHA etc.

Unique surface-active properties –bind to organic carbon, clays, silts

Transition to air water interface –stratify in solution

Non-reactive, stable, persistent

Bioaccumulative

Some evidence of causing endocrine disruption

Extreme persistence

PFAS CHARACTERISTICS

AEROBIC BIOTRANSFORMATIONPFAA’S AS DEAD END DAUGHTER PRODUCTS

Currently options are limited to excavation (no final solution, concentrated in another phase)

Landfilling introduces challenges since PFAS will become constituents of leachate (landfill leachate is not typically being evaluated for e.g. PFOS)

No proven techniques available for the biological or chemical breakdown

Incineration, high temperatures (> 1000 °C) are needed to cleave the stable C-F-bonds

Immobilization with GAC or commercial products (soil mixing).

Solidification (e.g. cement) is a yet unproven long-term option

Site characterisation is complex and requires high resolution sampling to build a robust site conceptual model

PFAS SOIL REMEDIATION

There is a need for new/alternative methods !

SCOPE OF THE WORK

Develop a comprehensive yet cost effective analytical methods to assess the true content of the PFAS compounds (“Dark Matter”) in soil & groundwater prior to (any) lab scale experiments

To evaluate the presence of “Dark Matter” on impacted soil and groundwater from a fire training site. Are the current “standard” methods missing out a large fraction of PFAS?

Provide proof of process for the new ScisoR® technology –demonstrate mineralisation of PFOS

Demonstrate to what extent the ScisoR® technology is effective in PFAS destruction in bench scale experiments using site soil and groundwater

Evaluate the need for improvements in the standard analytical procedures used

TOP ASSAYDIGEST PFAS PRECURSORS AND MEASURE THE HIDDEN MASS

Analytical tools fail to measure the hidden PFAS precursor mass, the TOP assay solves this

Microbes slowly biotransform simpler PFAA’s (e.g. PFOS / PFOA) from PFAS (precursors) over 20+ years

Need to determine precursor concentrations

Too many PFAS compounds and precursors –so very expensive analysis (if possible)

This analytical method mimics years of microbial action using conventional oxidation over a few hours

Then measure simpler PFAS’s using analytical method

Done in addition to LCMSMS to provide difference between precursor and free PFCA & PFSA concentrations

TOTAL OXIDISABLE PRECURSOR (TOP) Assay on Composite Samples

• Significant increase in perfluorinated carboxylic acids and sulphonic acids (PFAAs) following TOP assay representing the hidden mass of PFAS present which will produce additional PFAA’s including PFOS as dead end daughter products;

• Sum PFAS increase of 248% in soils and 195% in groundwater using TOP assay;

• Demonstrates matrices impacted with AFFF contain a greater mass of PFAS than identified by conventional analysis with LCMSMS (EPA Method 537).

Soil Composite Groundwater Composite

248% increase

195%increase

SCISOR REACTION MECHANISMS

ScisoR chemistry remain commercially sensitive with further research into reaction mechanisms in progress

A range of oxidising & reducing free radicals and reactive species likely involved including SO4, O2

-, solvated electrons

Proposed mechanism for PFOA destruction via sulfate radical oxidation by Katsuna and Hori (2007)

SO4 more powerful direct e- transfer oxidant than OH

Loss of COF2

as perfluorinated chain‘unzips’

Measured as fluoride (HF pka ~3.17)

unzipping ‘cycle’ continues along perfluorinated chain

Novel ScisoRactivation may enable similar mechanisms for oxidative pathways for PFOS in addition to reductive pathways

PFOS DESTRUCTION & FLUORIDE MASS BALANCE DURING SCISOR®

Replicate Data. Error bars are % Standard Error of Measurement (SEM)

• 10 mg/L PFOS starting concentration

• 3 replicate data sets

• 83 to 90% PFOS destruction after 14 days

• 71% to 118% fluoride released from PFOS during SCISOR

• Overall fluoride mass balance (remaining fluoride in PFOS + fluoride released to solution)

− 86% to 126% of theoretical

• All treated samples were blind spiked with 10 mg/L fluoride

− 80% to 99% spike recovery

• Spike analyses demonstrate ion measured is fluoride, results are quantitative

• Longer reaction times and repeat applications of ScisoR will cause complete destruction of PFOS

PFOS DESTRUCTION WITH SCISOR USING SITE GROUNDWATER

• Destruction of PFOS up to 68% after 14 days - site specific reaction kinetics and residual ScisoRreagents indicate further destruction will occur with extended reaction period

• PFOS precursor breakdown will be producing additional PFOS throughout the reaction period

• Full destruction will likely occur over a longer time period and/or via repeat applications of ScisoR

0

50

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3.5 days 7 days 14 days

[PFOS] Low ScisoR

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50

100

150

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250

3.5 days 7 days 14 days

[PFOS] Medium ScisoR

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50

100

150

200

250

3.5 days 7 days 14 days

[PFOS] High ScisoR

TOTAL PFAS MASS AFTER SCISORAPPLICATION TO SOIL COMPOSITE

• Destruction/reduction of multiple PFAAs after 21 days - site specific reaction kinetics and residual ScisoR reagents indicate further destruction will likely occur with extended reaction period

• Total PFAS mass reduced by between 55% and 75% in soil and groundwater

• Complete destruction of all compounds will likely occur over a longer time period and/or via repeat applications of ScisoR

55% Reduction

67% Reduction75% Reduction

Baseline

CONCLUSION & OUTLOOK

• The analytical methods used show:

– Total PFAS concentrations have increased by up to 240% as a result of transformation of hidden PFAS precursors

– PFOS concentrations have increased by up to 200% as a result of transformation of hidden PFAS precursors

– the new analytical tools (TOP assay etc.) are essential to characterise impacts from PFAS

• The ScisoR technology has been proven to mineralise PFOS when present as a single compound (spiked)

• The ScisoR technology has been shown to reduce PFOS in the site soil and groundwater samples significantly and to reduce other common PFAS compounds

• More research by ARCADIS on the ScisoR process are underway

• ScisoR can potentially be applied for :

- In Situ remediation of PFAS impacted source areas

- Regeneration of PFAS saturated granular activated carbon (GAC)

- Soil mixing to destroy PFAS either on-site or in-situ

Visit us at our booth and get a copy of a poster with more information

QUESTIONS ?