In Situ, Low Temperature Thermal Remediation of LNAPL with ...In-Situ Thermal Bench Test: Results 7 Contaminant Mobility test oil sheen appeared at temperatures of approximately 60°C

“Insert” then choose “Picture” – select your picture.

Right click your picture and “Send to back”.

The world’s leading sustainability consultancy

In Situ, Low Temperature Thermal Remediation of LNAPL with Pesticides and Other

Recalcitrant CompoundsRemTech 2017, Banff Springs Hotel and Conference Centre

October 11, 2017Presented by - Jay Dablow, ERM, Inc., Irvine, CA, USA

James Baldock, ERM, Oxford, UK;

Joanne Dinham, ERM, Manchester, UK ,and

Kathryn Johnson, ERM, Edinburgh, UK.

The business of sustainability

© Copyright 2017 by ERM Worldwide

Group Limited and/or its affiliates

(‘ERM’). All Rights Reserved. No part

of this work may be reproduced or

transmitted in any form or by any

means, without prior written

permission of ERM.


Background

2

■ The Site has been used since the late 1960’s

for the manufacture of wood preservatives,

damp proofing chemicals and specialist

coatings

■ The Site comprises two main buildings

(offices and laboratory, which remain in use

and a central area comprising mainly storage

and disused offices)

■ The Site is bounded by a railway line to the

south beyond which lie residential properties.

A river is located approximately 500m

downgradient of the site.

The clients goals for the Site include:

• Establish the current environmental status with respect to the presence and

significance of historic soil and groundwater contamination; and

• Manage potential liabilities associated with these impacts in the context of UK

contaminated land legislation


■ The Site is underlain by Made Ground (typically <1m thickness), sands and gravels, and

Chalk.

■ Both the sands and gravels and Chalk form unconfined aquifers with relatively high

permeability.

■ Lower permeability silts and clays are present towards the top of the sands and gravels in

some parts of the Site.

■ Soil source zones appear to correlate well to the main areas where chemicals were

previously used, stored or disposed.

■ Multiple overlapping plumes are present, beneath and downgradient of the source areas,

although impact from a more limited range of compounds has been identified within the

Chalk.

■ Likely that the recent channel identified within the centre of the Site may be influencing

contaminant migration towards the south-west corner of the Site.

■ The dominant controlling mechanism for contaminant migration into the Chalk is likely to be

contaminant properties (those which sink) or be related to preferential flow through

soakaways.

Geology and Hydrogeology

3


4

Properties and Distribution of Selected Contaminants

Contaminant Physical

state

Molecular weight

Water solubility

Log KOC VapourPressure

Henry's Law Constant

mg l-1 25oC cm3 g-1 Pa Pa m3 mol-1 (25oC)

Aldrin solid 364.91 0.02 5.34 1.35E-02 50.3Dieldrin solid 380.91 0.2 3.59 4.18E-08 5.88gamma HCH solid 290.82 7.3 3.07 3.70E-03 0.375>C10-C12 Aliphatics liquid 3.40E-02 5.40 63.83>C12-C16 Aliphatics liquid 7.60E-04 6.70 4.86Benzene liquid 78.11 1780 1.83 6240 557Tetrachloroethene liquid 165.83 225 2.43 1010 1730

Environment Agency 2008 SR7 Compilation of da ta for priority organic pollutants for derivation of Soil Guideline Values

PPDB: Pesticide Properties Data Base http://sitem.herts.ac.uk/aeru/projects/ppdb/index.htm

TPHCWG Vol 3

KOC - organic carbon partition coefficient

http://sitem.herts.ac.uk/aeru/projects/ppdb/index.htm


Conceptual Site Model

Not to scale

625m

Chalk

Permeability: 2 to 192m/day

Top of Chalk identified 5 to

8.5m bgl

Gravels

Permeability: 0.2 to 0.7 m/day

4 to 7.5m thickness

River

Off-site

current

and

former

industrial

land uses

Made Ground

Historical Sources: Kerosene

and Dieldrin

Main surface water

receptor

Main groundwater

receptor at risk: Chalk

Vertical migration of Dieldrin

into Chalk

5

Future potential leaching of

COCs into Gravels

Mobile LNAPL causing enhanced transport of

COCs within Gravels


Initial Remedial Concept

6

■ Mass removal

■ Limited LNAPL in wells

■ circa 8,000kg mass (mostly Kerosene).

■ Pesticides (dieldrin) solubilized in carrier oil

■ Remedial options appraisal identified limited mass recovery

options

■ Excavation requiring building demolition

■ Thermal considered most applicable, but target temperature challenges

■ Boiling points:

■ Kerosene 150ºC (minimum)

■ Dieldrin 350ºC!

■ Only applicable heating method to volatilize both ISTD

■ Thermal remediation questions for bench testing

■ Are temperatures even achievable?

■ Is there an alternate thermal mass removal mechanism


In-Situ Thermal Bench Test: Results

7

■ Contaminant Mobility test

■ oil sheen appeared at temperatures of approximately 60°C after 24 hours of heating;

■ visual observations of contaminant release from the soil into the water

■ greater contaminant mobility observed at 100°C.

■ Post heating, soil concentrations appeared to increase from baseline concentrations;

■ not expected;

■ likely due to pre-test concentrations being under reported due to analytical interference caused by the

presence of both pesticides and hydrocarbons in the same sample.

■ Results

■ At 70ºC Dieldrin and C10 - C28 TPH concentrations of liquids increase significantly, suggesting

mobilization of both carrier oil and pesticide (solubilized) via the heating process.

■ At 100ºC concentrations of both compounds remain above baseline, but significantly lower.

■ The decrease may reflect a combined mass removal mechanism

■ Volatilization for the TPH compounds at 100ºC, since Dieldrin’s boiling point is nearly four times the temperature

attained during the test.

■ Mobilization of TPH and Dieldrin

■ Both compounds could be recovered at lower temperatures via mobilization of solubilized NAPL and

limited volatilization of TPH.


Thermal Bench Test Results

8

0

20

40

60

80

100

120

140

160

180

0

10000

20000

30000

40000

50000

60000

20 70 100

Die

ldri

nC

on

cen

trati

on

µ

g/l

TP

H C

on

cen

trati

on

µ

g/l

Temperature °C

C6-C10 C10-C28 Dieldrin


Thermal Model: Methodology and Objectives

9

■ The results from bench test suggested that a target temperature of

between 70ºC and 100ºC would be sufficient to remove the COCs.

■ Temperatures can be accomplished via steam injection.

■ A thermal model was created using PC based PetraSim™ software to

estimate the following design parameters for implementation of steam

injection system in the upper margins (contaminated area) of the

saturated zone:

■ Mass and energy balance;

■ Energy consumption;

■ Prediction of heating duration;

■ Sensitivity to heating and extraction well spacing including number of

heater wells, energy cost and duration.


ISTD Heating Models

10

Model 1:

■ 4m spacing (36 wells)

■ SVE wells at 6m spacing

Model 2:

■ 3m spacing (64 wells)

■ SVE wells at 6m spacing

SVE

ISTD


ISTD Model Results (3m spacing)

11

Made Ground

Clay

Silt

Chalk

Gravel

Note: X- Cross Section through the

centre of the heating zone

1 month

Vadose

ZoneAfter 3 months:

• Range in target zone = 130 – 200oC

• Vadose zone = ~ 170oC

• Saturated zone = ~ 130oC

Not high enough for ISTD

2 month

3 month

Vadose

Zone

Saturated

Zone

Vadose

Zone

Saturated

Zone


Model Input Parameters – Steam Injection Well Configuration

12

Remedial system well configuration:

■ Soil Vapour Extraction (SVE) well:

■ 6 m Radius of Influence

■ 3.5 m depth

■ 0.5 – 3.5 m screened section (3 m)

■ Steam Injection Well:

■ 6 m Radius of Influence

■ 3.5 m depth

■ 2.5 to 3.5 m screened section. (1 m)

SVE

Steam


Steam Injection Model Results

13

Note: X- Cross

Section through

the centre of

the heating

zone

1 month

2 month

3 month

After 3

months the

saturated and

unsaturated

zones are

predicted to

reach a

temperature

of 100°C

Water Table


Model Conclusions

14

■ Maximum heat achievable in the unsaturated zone is 150°C (3m

spacing)

■ After 3 months, temperature stabilizes and does not increase above the

maximum predicted

■ Implication: Kerosene can potentially be volatilized, but dieldrin

cannot

■ Are there benefits to the closer spaced/higher temperature ISTD

approach?


Effect on Remedial Strategy

15

■ TTT reduced from 150°C to 70ºC

■ Change in methodology meant steam rather than ISTD could be used to

heat the subsurface (less wells and energy)

■ Lowest carbon footprint heating approach developed using the model:

0

500,000

1,000,000

1,500,000

2,000,000

2,500,000

3,000,000

Model 1 Model 2 Model 3

ISTD: 3m heater well

spacing

150 – 200ºC

ISTD: 4m heater well

spacing

130 – 170ºC

Steam injection

<100ºC


Enhanced ISTR Implementation

16

■ Rental steam boiler

■ Piping Layout

■ Treatment compound

■ Vapor extraction system – Vapor phase GAC

■ GW extraction system - Liquid phase GAC

■ NAPL recovery


Heating Progress (3 April – 31 May 2017)

17


Remediation Performance Evaluation (Area 4)

18

Project Endpoint Evaluation Endpoint

Achieved?

Area 4: • The thermal system successfully operated for

up to 20 weeks;

• or until asymptotic mass recovery (of Total

Petroleum Hydrocarbons (TPH) and/or total

Drins) is demonstrated, whichever is the sooner

• Mass recovery has reached

asymptotic conditions

• Total system operational time was 20

weeks

Yes

Area 4:• In the event that Drin mobilisation is not

reflective of the results of the pilot studies then

conditions are created to enable the

application of In-Situ Chemical Oxidation

(ISCO)

• ISCO success demonstrated through the

creation of conditions conducive to oxidation

processes and additional mass destruction of

Drins is demonstrated to the extent

reasonably practicable

• Dieldrin concentrations have been

detected within the recovered NAPL

and liquid at concentrations greater

than detected during the bench scale

testing, demonstrating success.

• ISCO implemented in two isolated

hot spots (Ara 3 and 4S). Conducive

oxidation conditions demonstrated.

Yes


1.0

10.0

100.0

1000.0

10000.0

25/01/17 14/02/17 06/03/17 26/03/17 15/04/17 05/05/17 25/05/17 14/06/17 04/07/17 24/07/17

Mass R

eco

very

(kg

)

Date

Vapour Mass Recovery Dissolved Phase Recovery LNAPL Recovery Total Recovery

Steam Off Steam On Steam Off Steam On Steam Off

Total Mass Recovered/Removed (Area 4)

19

Asymptotic

recovery

achieved

Mass composition is mainly TPH (kerosene) –

4,160kg recovery estimated.

Circa 7.5kg of mass is OCPs (recovered as

free, dissolved phase and ‘sludge’)


In Situ Chemical Oxidation – Activated Persulfate

■ In-Situ Chemical Oxidant (ISCO)

■ ISCO injection undertaken in

northern site area (7 – 22 June

2017)

■ ISCO injection undertaken in

southern site area (27 June – 12

July 2017)

■ Activation via sodium hydroxide

■ Field monitoring (pH, conductivity,

ORP, DO and temperature in

observation wells) carried out

during injection and into early

August

20


Remediation Performance Evaluation (Area 3/4S)

21

Project Endpoint Evaluation Endpoint

Achieved?

Area 3:• Where ISCO is deployed, groundwater

conditions are demonstrated to be

conducive to oxidation processes and

mass destruction of Drins is

demonstrated to the extent reasonably

practicable

• Significant changes from pre-injection

negative ORP to positive ORP recorded,

proving effective oxidant injection.

Yes

Area 4S:

• Where ISCO is deployed,

groundwater conditions are

demonstrated to be conducive to

oxidation processes and mass

destruction of Drins is demonstrated

to the extent reasonably practicable

• Significant changes from pre-injection

negative ORP to positive ORP recorded,

proving effective oxidant injection (see

measurements in observation wells MW1 –

MW5, Figure 3)

Yes


ORP Field Monitoring Data (Area 3)

22

-200.0

-100.0

0.0

100.0

200.0

300.0

400.0

6-Jun-17 13-Jun-17 20-Jun-17 27-Jun-17 4-Jul-17 11-Jul-17 18-Jul-17 25-Jul-17

OR

P (

mV

)

MW6 Top MW6 Middle MW6 Bottom MW7 Top

MW7 Middle MW7 Bottom MW8 Top MW8 Middle

MW8 Bottom MW9 Top MW9 Middle MW9 Bottom

MW10 Top MW10 Middle MW10 Bottom

Injection Period

■ ORP shows an increasing positive trend following ISCO injection in all monitoring wells (successful oxidant delivery)

■ Low dieldrin concentrations detected both pre- and post oxidant injection. Concentrations remain at <0.005mg/l


-200.0

-100.0

0.0

100.0

200.0

300.0

400.0

22-Jun-17 29-Jun-17 6-Jul-17 13-Jul-17 20-Jul-17 27-Jul-17

OR

P (

mV

)

MW1 Top MW1 Middle MW1 Bottom MW2 Top

MW2 Middle MW2 Bottom MW3 Top MW3 Middle

MW3 Bottom MW4 Top MW4 Middle MW4 Bottom

MW5 Top MW5 Middle MW5 Bottom

ORP Field Monitoring Data (Area 4S)

23

Injection Period

■ ORP shows an increasing positive trend following ISCO injection in all monitoring wells (successful oxidant delivery)

■ Low dieldrin concentrations detected both pre- and post oxidant injection. Concentrations remain at <0.03mg/l

Documents

In Situ, Low Temperature Thermal Remediation of LNAPL with ...In-Situ Thermal Bench Test: Results 7 Contaminant Mobility test oil sheen appeared at temperatures of approximately 60°C