V. V. SchifanoSchifano, C. MacLeod, C. MacLeodArcadisArcadis GeraghtyGeraghty & Miller International Inc. (UK)& Miller International Inc. (UK)

A.W.L. A.W.L. DudeneyDudeney, R. , R. DudeneyDudeneyImperial College, London (UK)Imperial College, London (UK)

Remediation of Soils Contaminated with Remediation of Soils Contaminated with Petroleum Hydrocarbons Petroleum Hydrocarbons Using Quicklime MixingUsing Quicklime Mixing

Outline of PresentationOutline of Presentation

• Introduction

• Objectives

• Experimental Study

• Results

• Conclusions

IntroductionIntroduction

• Why Quicklime? • Mechanisms of Stabilisation/Solidification

• Adsorption on (CaOH)2 and other precipitates

• Encapsulation into the CSH/CAH cementitious matrix

• Physical entrapment within the soil macro-aggregates voids

• Thermal Effects• Volatilisation

• Degradation in alkaline, O2 rich environment

• Drying of soils and improvement of mechanical properties

ObjectivesObjectives

• To examine the effects of Quicklime mixing on the a) concentration and b) leachability of petroleum hydrocarbons compounds in clayey soils

• To evaluate the effects of variables such as soil type, moisture content and quicklime content on a) and b).

Experimental StudyExperimental StudyMaterials

• Natural contaminated samples of London clay (45% sand; 35% silt; 20% clay; w = 27 – 36%; wl= 43 – 61%; wp = 17 –22%) from Petrol Filling Station in Hampshire.

• Artificial samples of Sand and Kaolinite to which Petrol and Diesel were added.

• Quicklime (Limbase 60, Buxton Lime Industries Ltd).

Experimental StudyExperimental StudyMethods

• BS methods for Moisture Content, AtterbergLimits, pH

• Chemical Analyses on TPH working group• GRO by GC-FID

• EPH Accelerated Solvent Extraction in + GC-FID

• Leachates by DIN 34-414 (CO2 saturated water at pH 5.6; water to solid 10:1).

Experimental StudyExperimental StudyPreparation of Samples

• Dry mixed Sand and kaolinite

• Added Distilled Water and Petrol (3g/kg) and Diesel (3g/kg)

• Homogeneise by hand-mixing (stainless steel spatula/rod on glass plate or plastic dish)

Experimental StudyExperimental Study

Preparation of Samples

• Stored in Refrigerator for one week during which samples were periodically mixed

• Quicklime added and hand-mixed

• Samples stored in sealed plastic containers at room temperature

Experimental StudyExperimental StudyPreparation of Samples: a) London Clay

____________________________Sample w CaO pH____________________________LC1U 32 0 7.71LC1A 32 5* 11.37LC1B 64* 5* 11.51LC2U 32 0 7.75LC2A 32 5* 11.35LC2B 32 10* 11.67LC2C 32 20* 12.72LC2D 64* 5* 11.34____________________________________Note: w=moisture content; * estimated value

Experimental StudyExperimental StudyPreparation of Samples: b) Sand/Kaolinite Samples

Sample Sand Kaol. w CaO G/D% % % % mg/kg

O 90 10 24 0 6000P 75 25 29 0 6000Q 50 50 40 0 6000R 50 50 60 0 6000S 50 50 20 0 6000A 90 10 24 5 6000B 90 10 24 10 6000C 90 10 24 20 6000D 75 25 29 10 6000E 50 50 40 10 6000F 50 50 60 10 6000G 50 50 20 10 6000

Note: G/D = Gasoline/Diesel.

Experimental StudyExperimental Study

Upon Mixing with Quicklime

• Temperature, pH, moisture content, Atterberg Limits

• Concentrations of Petroleum Hydrocarbons in Soils

• Concentrations of Petroleum Hydrocarbons in Leachates

ResultsResultsTemperature Changes during quicklime mixing: Sand Samples

0

20

40

60

80

100

120

140

160

0 5 10 15 20 25 30 35 40 45 50 55 60 65

Time (minutes)

Tem

pera

ture

(ºC

)

Beakerw=5%, CaO= 15%

Beaker w=10%, CaO 30%

Open Tray w=15%, CaO 45%

Table 4. Pre- and Post-Treatment pH of K/S Mixtures______________________________________________________SAMPLE A B C D E F GTime (days)______________________________________________________t=0 5.5 5.5 5.5 5.6 5.5 5.4 5.3t=1 12.3 12.3 12.3 - - - -t=3 - - - 12.3 12.1 12.8 12.2t=7 12.3 12.3 12.5 12.6 12.5 12.5 12.5t=15 12.6 12.5 12.5 12.2 12.4 12.4 12.6t=30 12.6 12.6 12.7 12.6 12.6 12.6 12.7_______________________________________________________

ResultsResults

ResultsResults

Table 4. Pre- and Post-Treatment Moisture Content, w (%), of Kaolinite / Sand Mixtures__________________________________________________________SAMPLE A B C D E F GTime (days)__________________________________________________________t=0 24 24 24 29 40 60 20t=1 20 13 7 - - - -t=15 19 13 8 18 29 48 12t=30 19 13 8 18 28 45 12___________________________________________________________

Table 4. Post-Treatment Liquid Limit, wl (%),of Kaolinite / Sand Mixtures______________________________________________________SAMPLE A B C D E F GTime (days)______________________________________________________t=0 23 23 23 23 34 34 34t=1 24 27 29 - - - -t=3 - - - 36 52 57 -t=7 26 28 29 37 52 51 47t=15 26 29 30 38 52 60 48t=30 26 28 29 36 52 61 44______________________________________________________

ResultsResults

ResultsResultsTable 4. Pre- and Post-Treatment Plastic Limit, wp (%), of Kaolinite / Sand Mixtures______________________________________________________SAMPLE A B C D E F GTime (days)______________________________________________________t=0 18 18 18 16 23 23 23t=1 19 21 21 - - - -t=3 - - - 25 31 34 28t=7 22 22 22 22 30 32 28t=15 21 20 20 23 31 34 28t=30 18 20 19 24 31 35 28______________________________________________________

ResultsResults

• Changes in moisture content, liquid limit, plastic limit and pH of the treated sample A-G, occurred rapidly upon quicklime mixing (first determination after 1 day), then continued at a much lower rate.

• The largest changes in liquid and plastic limit occurred in the sample with the largest initial moisture content (sample F).

_______________________________________________________COMPOUND LC1U LC1A LC1BCaO 0 5 5W 32 32 64

Concentrations (mg/kg)Benzene 0.03

_________________________________________________________________________________COMPOUND LC2U LC2A LC2B LC2C LC2DCaO 0 5 10 20 5W 32 32 32 32 64_________________________________________________________Benzene 0.02

London Clay Samples Concentrations (mg/kg)ResultsResults

Hydrocarbon content in London Clay samples LC2U (without quicklime) and LC2B (with 10% quicklime)

0.01

0.1

1

10

100

Benz

ene

Tolue

neEth

ylben

zene

Xylen

esMT

BEAli

phati

csC5

-C6

C6-C

8C8

-C10

C10-C

12C1

2-C16

C16-C

21C2

1-C35

Arom

atics

Ec8-E

c10

Ec10

-Ec1

2Ec

12-E

c16

Ec16

-Ec2

1Ec

21-E

c35

Con

cent

ratio

n (m

g/K

g)

LC2U

LC2B

K/S Samples Concentrations (mg/kg)_________________________________________________________________

O(t=0-30) A(t=1) A(t=17) A(t=30)

Benzene 0.33-0.02

K/S Samples Concentrations (mg/kg)________________________________________________________________SAMPLE O(t=0-30) B(t=1) B(t=17) B(t=30)_______________________________________________________________Benzene 0.33-0.02

K/S Samples Concentrations (mg/kg)____________________________________________________________________________SAMPLE O(t=0-30) C(t=1) C(t=17) C(t=30)

__________________________________________________________________________Benzene 0.33-0.02

K/S Leachates Concentrations (µg/l)_________________________________________________COMPOUND O(t=30) B(t=1) B(t=30)Benzene

K/S Samples ResultsResults

Total Petroleum Hydrocarbons in Leachate after one month from CaO mixing

1

10

100

1000

10000

O (t=30) A (T=30) B (T=30) C (T=30)

All samples 90% sand, 10% kaolinite. O control sample.

Samples A, B, C mixed with 5, 10 and 20% CaO

respectively

Con

cent

ratio

n(u

g/l)

ControlTreated Samples

ConclusionsConclusions

• Changes in Atterberg Limits followed the same behavior as typically reported in the literature for uncontaminated kaolinite clays. Therefore, it can be concluded that the large initial concentrations of petroleum hydrocarbon compounds present in sand/kaolinite mixtures did not inhibit the occurrence of reactions responsible for Atterberg Limit changes in the soil samples

• Mixing soils with quicklime resulted in a rapid decrease of concentration of petroleum hydrocarbon compounds measured in all samples of London clay and artificial sand/kaolinite mixtures.

ConclusionsConclusions

• The decreases in BTEX and Light Aromatics and Aliphatics can be explained as mostly due to volatilisation due to temperature increases.

• The decreases of heavy hydrocarbons is though to be in part due to encapsulation of the compounds in clay macro-aggregates and fixation of the compounds within the matrix of the pozzolanic reaction products and in part to other unknown degradation processes.

• Quicklime mixing caused a progressive reduction in the hydrocarbon leaching. After 30 days from mixing, the leachate concentrations were near or below analytical method detection limits.

ConclusionsConclusions

• The study has confirmed quicklime mixing as a promising on site treatment method for high to low plasticity clayey soils, contaminated with petroleum hydrocarbon using various mixing water and quicklime contents.

Outline of PresentationIntroductionObjectivesExperimental StudyExperimental StudyExperimental StudyExperimental StudyExperimental StudyExperimental StudyExperimental StudyResultsResultsResultsResultsResultsResultsLondon Clay Samples Concentrations (mg/kg)London Clay Samples Concentrations (mg/kg)London Clay Samples Concentrations (mg/kg)K/S Samples Concentrations (mg/kg)K/S Samples Concentrations (mg/kg)K/S Samples Concentrations (mg/kg)K/S Leachates Concentrations (mg/l)K/S Samples