4A10 Construction Research & Innovation

BioGeoChemistry

Professor Mark DyerTrinityHaus

Hanworth Case Study – Plan (after Dyer 2004)

Diesel Storage Tank (BTEX)

Benzene

Toluene

Ethyl Benzene

Xylene

Solvent Bath (TCE)

Trichloroethene

and

Metal Salts

CN-

Cr VI

MNA : Natural Processes

Source

Groundwater Flow

Monitoring boreholesoDispersion & Diffusion

oSorption

oBiodegradation

LNAPL’s

DNAPL’s

Monitored Natural Attenuation (MNA)

Target

Evidence of Natural Attenuation

Evidence of NATURAL ATTENUATION

oReduction of aqueous concentration with distance (or gaseous)

oShrinking of plume with time

oAppearance of biodegradation by-products (e.g. dechlorination of TCE)

oDepletion of alternative electron acceptors (e.g. oxygen, nitrate, ferric iron, sulphate ions)

PlumeSource

No 1 : Evidence of Biodegradation

Evidence of NATURAL ATTENUATION

oAppearance of biodegradation by-products (e.g. dechlorination of TCE

Plume

Eg. Biodegradation at Philips Factory Zwolle NL

Chlorinated Hydrocarbons

PCE TCE cis-DCE VC Ethene

Aqueous concentration (µg/l)

68,000 17,000 32,000 6,825 3,451

Zwolle NL: Evidence of strong biodegradation

906 (14-15)

0.0

300.0

600.0

900.0

1200.0

0 9 17 33 43 59

week

µm

ol/

l

Ethane

Ethene

VC

cis-DCE

TCE

PCE

906 (14-15)

0%

20%

40%

60%

80%

100%

0 9 17 33 43 59

week

rela

tiv

e c

on

trib

uti

on

(on

mo

lar

ba

sis

) Ethane

Ethene

VC

cis-DCE

TCE

PCE

Presentation of results in relative molar concentration

No2 Depletion of Alternative Electron Acceptors

Evidence of NATURAL ATTENUATION

oDepletion of alternative electron acceptors close to source (e.g. oxygen, nitrate, ferric iron, sulphate ions)

sulphate nitrateferric iron

oxygen

Gradual reduction in redox potential towards the source of pollution due to consumption of electron

acceptors by bacteria

Depletion of alternative electron acceptors

nitrate

ferric iron

Tim

eEg. Progressive depletion of electron acceptors

sulphateferric iron

nitrate oxygen

oxygen

No 3 Reduction in Aqueous Concentration

Evidence of NATURAL ATTENUATION

oReduction of aqueous concentration with distance (or gaseous)

oShrinking of plume with time

PlumeSource

Mechanisms:- Advection, Dispersion and Sorption

Distance or time from source

Rela

tive C

on

cen

trati

on

C

/Co

1.0

0.5

0.0

ADVECTION

Advection, Dispersion and Sorption

Distance or time from source

Rela

tive C

on

cen

trati

on

C

/Co

1.0

0.5

0.0

DISPERSION by tortuously & friction through pore space resulting in relative reduction but no overall reduction in mass of pollutant

Advection, Dispersion and Sorption

Distance or time from source

Rela

tive C

on

cen

trati

on

C

/Co

1.0

0.5

0.0

SORPTION onto soil and organic matter resulting in an overall reduction of aqueous concentration & retardation

Advection, Dispersion and Sorption

Distance or time from source

Rela

tive C

on

cen

trati

on

C

/Co

1.0

0.5

0.0

SORPTION onto soil and organic matter resulting in an overall reduction of aqueous concentration & retardation

Adsorption onto the surface of clay particles or negative charged carboxylic acids (C-COOH) or alcohols (C-OH) for humus colloidAbsorption into organic matter (humus)

Advection, Dispersion and Sorption

Distance or time from source

Rela

tive C

on

cen

trati

on

C

/Co

1.0

0.5

0.0

SORPTION onto soil and organic matter resulting in an overall reduction of aqueous concentration & retardation

Adsorption onto the surface of clay particles for metal ions

Absorption into organic matter for organic pollutants (BTEX)

Adsorption Isotherms

Cs (g/g)

Ceq (g/L)

Linear

Langmuir

Ci

Ceq

Cs = [(Ci – Ceq) x volume of liquid]/weight of soil

Hypothetical Batch Test

Ci (g/L) Ceq(g/L)

Wt (g)

Cs(g/g)

250 77.3 20.42 1.69

500 150.57 20.42 3.42

1000 297.04 20.42 6.89

1500 510.1 20.42 9.70

2000 603.05 20.42 13.68

3800 1198.7 20.42 25.48

6000 2300.5 20.42 36.23

9000 3560.7 20.24 53.27

Ci

Ceq

Cs = [(Ci – Ceq) x volume of liquid]/weight of soil

Cs = [(250 – 77.3) x 0.2]/20.42 = 1.69 (g/g)

200 ml of influent

Hypothetical Batch Test

Ci (g/L) Ceq(g/L)

Wt (g)

Cs(g/g)

250 77.3 20.42 1.69

500 150.57 20.42 3.42

1000 297.04 20.42 6.89

1500 510.1 20.42 9.70

2000 603.05 20.42 13.68

3800 1198.7 20.42 25.48

6000 2300.5 20.42 36.23

9000 3560.7 20.24 53.27

Ci

Ceq

Cs = [(Ci – Ceq) x volume of liquid]/weight of soil

Cs = [(250 – 77.3) x 0.2]/20.42 = 1.69 (g/g)

200 ml of influent

Hypothetical Batch Test

Ci (g/L) Ceq(g/L)

Wt (g)

Cs(g/g)

250 77.3 20.42 1.69

500 150.57 20.42 3.42

1000 297.04 20.42 6.89

1500 510.1 20.42 9.70

2000 603.05 20.42 13.68

3800 1198.7 20.42 25.48

6000 2300.5 20.42 36.23

9000 3560.7 20.24 53.27

Ci

Ceq

Cs = [(Ci – Ceq) x volume of liquid]/weight of soil

Cs = [(250 – 77.3) x 0.2]/20.42 = 1.69 (g/g)

200 ml of influent

Hypothetical Batch Test

0

10

20

30

40

50

60

0 500 1000 1500 2000 2500 3000 3500 4000

Ceq (ug/L)

Cs

(ug

/g)

Hypothetical Batch Tests – Partition Coefficient Kd

0

10

20

30

40

50

60

0 500 1000 1500 2000 2500 3000 3500 4000

Ceq (ug/L)

Cs

(ug

/g)

Partition Coefficient Kd Kd = Cs/Ceq

From batch test data Kd = 31.5/2000 = 0.0158 (L/g)

Estimated Partition Coefficient

However Kd can also be calculated using

Kd = Koc x Foc

where: Koc = soil sorption coefficient normalised for total organic contentFoc = fraction of total organic content

Example (see handout tables for Foc and Koc)

Clays Foc = 0.2

Benzene Koc = 87.1 L/kg

Kd = 87.1 x 0.2 L/kgKd = 17.42 L/kg ( or 0.0174 L/g)

SAQ4

Sketch the biotransformation pathway for trichloroethylene to ethene.

Self Assessment Q’s

Self Assessment Q’s

SAQ5(a)Describe the physical, geochemical and biological mechanisms involved in the natural attenuation of petroleum fuels and chlorinated solvents in an aquifer. (b)Explain the different mechanisms involved in absorption and adsorption of organic pollutants to soil particles. Used sketches where applicable to illustrate bonding mechanism and mention relevant minerals. (c)Use the following data from a soil batch test to calculate the sorbed concentration (g/g), plot a linear isotherm and calculate the sorption coefficient Kd . The weight of soil is 40.42g and the volume of the aqueous solution is 200 ml.

Initial Concentration (g/l) Equilibrium Concentration (g/l)

250 77.3

500 150.57

1000 297.04

1500 510.10

2000 603.05

3800 1198.7

6000 2300.5

9000 3560.7

Self Assessment Q’s

SAQ6A spillage of petroleum fuels and chlorinated solvent (trichloroethylene) has taken place at an industrial site. The results from chemical analyses of groundwater samples from 3 boreholes are shown below. Comment on evidence or potential for natural attenuation at each boreholes.

Parameters Borehole 1 Borehole 2 Borehole 3

pH 7.5 7.2 11.0

DOC (%) 4.5 45 3.9

Redox (mV) -150 +139 -160

TOC (mg/l) 23.5 22.0 23.9

Nitrate (mg/l) 4.0 17.0 5.0

Sulphate (mg/l) 25.0 18.0 21.0

Tetrachloroethene (g/l)

39 2250 2150

Trichloroethene (g/l)

130 1900 1800

Cis-dichloroethene (g/l)

6120 125 122

Trans-dichloroethene (g/l)

49 650 625

Vinyl Chloride (g/l) 16300 95 71