v>EPA
United States
Environmental Protection
Agency
Robert S Kerr Environmental
Research Laboratory
Ada. OK 74820
Center for Environmental
Research Information
Cincinnati OH 45268
Technology Transfer
CERI-87-45
Seminar on
Transport and Fate of
Contaminants in the
Subsurface
Slide Copies
-------
FATE AND TRANSPORT
INSTRUCTORS
Physical Processes
Carl D. Palmer
Chemical Processes
Richard L. Johnson
Biological Processes
Joseph M. Suflita
Simulation and Prediction
Joseph F. Keely
OBJECTIVE:
To transfer results from scientific research
concerning natural processes that govern the
transport and fate of ground-water contaminants
from the research community to the regulatory
community.
-------
PHYSICAL PROCESSES
Advection-Dlspersion Theory
Transport in Fractured Media
Non-Aqueous Phase Liquids
Particle Transport & Filtration
Estimation of Transport Parameters
CHEMICAL PROCESSES
Inorganic Contaminants
Behavior of Organics
Laboratory Methods
Field Experiments
Case Histories
-------
BIOTRANSFORMAT1ON PROCESSES
• Microbial Ecology
• Metabolism of Contaminants
• Bioremediation Strategies
• Field and Laboratory Methods
• Case Histories
SIMULATION AND PREDICTION
• Types of Models
• Data Requirements
• Quality Control
• Agency Uses and Needs
• Management Considerations
-------
TRANSPORT AND FATE
PHYSICAL PROCESSES
Session 1
Carl D. Palmer
(Oregon Graduate Center)
CDP-l - 1
-------
WASTE
MONITORING
UNSATURATED WELL
X X / ZONE
WATER
SUPPLY
WELL
AQUIFER
CDP-1 - 2
BREAKTHROUGH CURVE
i.O -
o
I— I
W H
: o.5
o
0.0
CDP-1 - 3
-------
WHY SHOULD WE BE INTERESTED IN DISPERSION?
• Prediction of arrival of an action limit for a
contaminant
• Estimation of the costs for aquifer remediation
• Development of aquifer remediation strategies
CDP-l - 4
h
U
3
Q
Z
c
o
c
DC
Q
MOLECULAR MICRO MACRO
MEGA
REV
MEV
VOLUME
After Glllham »nd Cherry (1982).
CDP-l - 5
-------
ADVECTION-DISPERSION
EQUATION
82C 9C 3C
D 7TT2 - V
9x ~ 9t
Dispersive Advective Change in
Term Term Mass per
Unit Time
CDP-1 - 6
DISPERSION COEFFICIENT
= Dd * Dm
t \
Dispersion Moleculuar Mechanical
Coefficient Diffusion Diffusion
Coefficient Coefficient
CDP-1 - 1
MECHANICAL DISPERSION COEFFICIENT
Dm =av
A
Mechanical Disperslvlty Groundwater
Dispersion Parameter Velocity
Coefficient
CDP-1 - B
-------
MECHANICAL DISPERSION
B
After Cillhaoi and Cherry (198Z).
CDP-1 - 9
-------
MOLECULAR DIFFUSION COEFFICIENT
Molecular
Diffusion
Coefficient
• «v
Free Solution
Diffusion
Coefficient
Tortuosity
Factor
CDP-l -10
10'
10'
10
10
i r i i NIII r i i i inn i i i i inn i i
DL = Longitudingal Dispersion Coefficient
Do" Molecular Diffusion Coefficient
v -Solute Velocity
d • Average Grain Diameter
TRANSITION ZONE
ADVECTION
DOMINATED
DIFFUSION
DOMINATED
DOT
till i nil
Dt-OtV
DL
1111111 i i 11 mi i t ii Inn i i M mi
10
-3
10
-2
-1
10 10
vd/D0
10'
10'
Perklni niul Julmiitun,
CDP-l -11
-------
BREAKTHROUGH CURVE
1
o 0.8
i—i
W H
£S 0.6
w H 0.4
o 0.2
u
0 -
DISPERSION
TIME
CDP-l -12
CONCENTRATION DISTRIBUTION
i
o 0.8
i— i
H
0.6
o 0.2
o
0 -
X
DISTANCE
PLUG
FLOW
ADVECTION
CDP-l -1
-------
ADVECTION AND DISPERSION
OF A CONTAMINANT SLUG
«
w
H
<
^^ i—\
QO O
^r1
pfe
o
K
CJ
t = t
t = t
t = t
X = Xr
X = Xi
X =
CDP-1 -14
ADVECTION-DISPERSION
EQUATION
9
X
to.
8 C
J
Dispersive
Term
j )
v
8x.
V*J
8t
Advective Change in
Term Nfass per
Unit Time
v
= I (v,
CDP-1 -15
-------
10'
10
D.
10"
I t f I I till I I I I HIM I III! III! I I I I I Illl
DT- Transverse Dispersion Coefficient
Do- Molecular Diffusion Coefficient
v - Solute Velocity
d "Average Grain Diameter
TRANSITION ZONE
DIFFUSION
DOMINATED
- Dra
10
-1
ADVECTION
DOMINATED
I I I I illH
DT= fl TV
10
-1
10
10
10'
10
i mi
10
After Parkin* «nd Johnnton (1963).
CDP-1 -16
-------
HYPOTHETICAL CONTAMINANT PLUME
WITH A LARGE TRANSVERSE DISPERSIVITY
WASTE
cc
in
I
o
a.
o
~
After Frind «nd P«ln«r (1980).
CDP-1 -17
HYPOTHETICAL CONTAMINANT PLUME
WITH A SMALL TRANSVERSE DISPERSIVITY
WASTE
a.
u
N
i "-
o
tc
o
CDP-1 -18
-------
DISCREPANCIES BETWEEN THEORY
AND EXPERIMENTAL RESULTS FROM
LABORATORY EXPERIMENTS ARE THE
RESULT OF:
• Immobile Zones of Water
• Solution-Solid Interface Processes
• Anion Exclusion
• Diffusion in or out of Aggregates
CDP-l -19
-------
LONGITUDINAL DISPERSITY VALUES
LABORATORY TESTS
NATURAL GRADIENT
TRACER TESTS
SINGLE WELL TESTS
RADIAL AND
TWO-WELL TESTS
MODEL CALIBRATION
TO CONTAMINANT
PLUMES
0.0001 to 0.01 M
0.01 to 2m
0.03 to 0.3 m
0.5 to 15m
3 to 61 m
After Clllhu and Cherry (1982).
CDP-1 -20
0.10
VI
C£O.OS
Cd
Ou
W
0.00
J~
Longitudinal Dliperslvity
From Sudlcky et «l. (1983)
i 4 i ' ' a 10 T
DISTANCE FROM SOURCE (m)
COP-1 -21
o.so
Longitudinal Dliprmivlly
Vrom Fri-yburj (I01"1)
°-000 io Jb 3<5 45 5i t'i ViJ »b 5'
DISTANCE FROM SOURCE (m)
CDP-1 -22
-------
C0_,
..
-_
-:
z
"
-
i
:
:
I
-
:
-.-
:
Kl
Kg
KG
K4
Ks
i
-
=
:
iiiiiiiiiiiiiiiTuriiiiiiiiiiiiiiiiiiiiiiiiiiiiii
DISTANCE
After Glllham and Cherry (1982).
STATISTICAL INFORMATION
THAT CAN BE OBTAINED
o
z
LLi
3
O
HI
DC
HYDRAULIC CONDUCTIVITY
.,.
LU
OC
DC
O
O
c
0
'u
LAG DISTANCE
CDP-1 -23
CDP-1 -24
-------
ASYMPTOTIC
DISPERSIVITY
TENSOR
0.61 m
0
0
0
0
BORDEN AQUIFER
SUDICKY (1986)
CDP-l -25
TRANSPORT CONCEPTS
Homogeneous Media
Heterogeneous Advection
Advection-Dif fusion
CDP-l -26
-------
DISPERSION
AVERAGE GROUNDWATER
FLOW DIRECTION
13
a.
LU
O
<
oc
I-
v
-"j
HIGHER
PERMEABILITY
LAYERS
AVERAGE GROUNDWATER
FLOW DIRECTION
HIGHER PERMEABILTIY LENSES
CDP-l -27
-------
3
c
j
11
B
111
-
c
EC
C
ADVECTION IN HIGH K LAYERS
ADVECTION IN HIGH K LAYERS
Alter Gillhan et al. (1984).
CDP-1 -28
GROUNDWATER
FLOW
(S,LT
SAND
SILT:
GROUNDWATER
maamamm
FLOW
CDP-1 -29
-------
BREAKTHROUGH CURVES
SHOWING EFFECT OF TRANSVERSE DIFFUSION
o
O r /^ ADVECTION-DISPERSION
ADVECTION-DIFFUSION
EC
Ho,
LU
O
Z
o
o
TRAVEL DISTANCE • 1.0 m
SAND THICKNESS > 0.03 m
GROUNOWATER VELOCITY • 0.10 m/d»y
OISPERSIVITV • 0.001 m
DIFFUSION COEFFICIENT • 1.2 X 10"m*/3
0 10 20 30 40 50
TIME (DAYS)
CDP-l -30
FACTORS CONTRIBUTING TO THE
SPREADING OF CONTAMINANTS
• Diverging Flow Lines
• Three Dimensional Flow
• Variable Source Function
» Temporal Variations in Watertable
n Heterogeneity
CDP-l -31
-------
DENSITY COMPONENT OF FLOW
t t \ \ 1
Velocity Vertical Density Back- Porosity
Component Hydraulic Ground
Due to Conductiviity Density
Gravity
CDP-l -32
EFFECT OF DENSITY
DENSITY OF UNCONTAMINATEI) WATER = J.OOO
NATURAL HOIZONTAL GRADIENT = 0.005
NATURAL VERTICAL GRADIENT = 0.000
vh
vr
DENSITY = 1.000 DENSITY = 1.005 DENSITY = 1.005
= 3 VKv = 5
CDP-l -33
-------
DENSITY DEPENDENT TRANSPORT
AND MONITORING
WASTE
MONITORING
WELL
LOW DENSITY LEACHATE
WASTE
UNSATURATED
MONITORING
WELL
HIGH DENSITY LEACHATE
CDP-1 -34
-------
ADVECTION-DISPERSION
EQUATION
WITH RETARDATION
2
Dae v ac ac
R 3x^ R 9x 9t
Dispersive Advective Change in
Term Term Mass per
Unit Time
R = RETARDATION FACTOR
CDP-l -35
-------
1.00
o
w
0.50
P-J
w
R = 1 / R = 2
R = 4
TIME
CDP-l -16
RETARDATION AND MONITORING
1.2.3 1*2
WASTE DETECTED DETECTED
R - 5
R- 3
R « 2
AQUIFER
1 ONLY
DETECTED
R« 1
', AQUITARD ,
'/////////////'////s
CDP-l -37
-------
IMPORTANCE OF THE UNSATURATED ZONE
• Increases overall length of flow path
• Can have greater sorption capacity than saturated
zone and can thus act as a source of
contamination even after site surface is cleaned
• Can be an zone of significant biodegradation
• Can be a source of metal ions
• It is a pathway for the transport of gases and
volatile organics
CDP-l -38
UNSATURATED FLOW
38
fjr = Specific Water Capacity
6 = Volumetric Water Content
$ = Soil Water Pressure Head
= Hydraulic Conductivity
CDP-l -39
-------
CHARACTERISTIC CURVE
Air Entry Value
i
MAIN
DRAINAGE
CURVE
TENSION .
•^ SATURATION
Residual
Water
Content
MAIN
WETTING
CURVE
w
O
o
W
H
<:
O
I-}
O
PRESSURE HEAD
CDP-l -40
-------
HYSTERESIS
Refers to the observation that the
soil water pressure head is not a unique
function of volumetric water content but
depends on the moisture history of the
soil.
CDP-l -41
CHARACTERISTIC CURVE
SCAN LINES
^- TENSION .
SATURATION
MAIN
DRAINAGE
CURVE
Residual
Water
Content
MAIN
WETTING
CURVE
f-
2
u
H
2
O
u
OJ
O
t-^
Od
H
PRESSURE HEAD
CDP-l -42
-------
10
-1
s
o
E-
H— «
£
CJ
D
Q
O
10
OS
10,
0.10
I '
I ' L
I • I I ' I ' I I 1 1 1 1 1 1 1 1 1 1
0.15 0.20 0.25 0.30 0.35 0.40
VOLUMETRIC WATER CONTENT
CDP-l -43
-------
UNSATURATED ZONE TRANSPORT EQUATION
- «•*]-
6 = Volumetric Water Content
c = Solute Concentration
D = Dispersion Coefficient
q = Volumetric Water Flux
CDP-l -44
UNSATURATED ZONE DISPERSION COEFFICIENT
D = DOT + av(8)
D = Dispersion Coefficient
D0 = Free Solution Diffusion Coefficient
T = Tortuosity Factor
a «= Dispersivity
v(8) - q/8 = solute velocity
6 = Volumetric Water Content
CDP-l -45
-------
VAPOR TRANSPORT
VAPOR
MONITORING
WELL "A"
VAPOR
MONITORING
WELL "B"
c.
u
a
•
CONCENTRATION
VAPOR TRANSPORT
IMPERMEABLE
BOUNDARY
VAPOR
MONITORING
WELL "B"
a
UJ
o
CONCENTRATION
CDP-l -46
CDP-1 -47
-------
FACTORS AFFECTING
VAPOR TRANSPORT
Diffusion
Advection
Density
Cultural Features
Partitioning into Soil Water
Thermal Effects
Chemical Reactions
COP-l -48
-------
TRANSPORT OF GASES
SOIL CONTAINING _
ORGANIC MATTER
CO,
I t
BEDROCK CONTAINING
SULPHIDE MINERALS
SOIL CONTAINING
ORGANIC MATTER ^
BEDROCK CONTAINING
•:':• SULPHIDE MINERALS
CDP-l -49
-------
TRANSPORT OF GASES
SOIL CONTAINING
ORGANIC MATTER ^
02 C02
I t
BEDROCK CONTAINING
SULPHIDE MINERALS
SOIL CONTAINING _
ORGANIC MATTER ^
••
\
BEDROCK CONTAINING
SULPHIDE MINERALS
CDP-l -50
-------
TRANSPORT PROCESSES IN
FRACTURED GEOLOGIC MEDIA
• Advection
• Diffusion
• Dispersion
CDP-l -51
FRACTURED POROUS ROCK
Diffusion
into Roe
Matrix
*
Fracture Flow
t t t
Diffusion
into Rock
Matrix
/t t t t
CDP-l -S3
-------
DISPERSION PROCESSES IN
FRACTURED GEOLOGIC MEDIA
• Velocity Distributions
• Mixing at Fracture Intersections
• Variation in Aperature Width along Stream
Line
• Distribution in Aperature Width across Flow
Path
• Diffusion
CDP-l -53
-------
MODELS FOR TRANSPORT IN
FRACTURED ROCK
• CONTINUUM MODELS
- Single Porosity
- Double Porosity
• DISCREET FRACTURE MODELS
— Deterministic
— Stochastic
• HYBRID MODELS
• CHANNEL MODELS
CDP-l -54
b
B-
JL
A -I -4 I
A i i j i j
Porous
Matrix
'A
Fracture Flow
1 1 1 ttttttttttttttttt
Porous
Matrix
M M M
M
M M M
Fracture Flow
MM* 1111 rm 1111111
Porous
Matrix
CDP-l -55
-------
CUBIC LAW
FRACTURE:
= (2b)3pg/(12/0
EQUIVALENT POROUS MEDIA
= (2b)3pgN/(12B/0
N = number of fractures over B
K = hydraulic conductivity
B = thickness of formation
b = half-width of fracture
/i= fluid viscosity
p= fluid density
CDP-l -56
EQUIVALENT POROUS MEDIA
VEPM= YRf
Rf = 1 + nB/b
CDP-l -57
-------
FRACTURE NETWORKS BEHAVE
LIKE CONTINUA WHEN:
• FRACTURE DENSITY IS
INCREASED
• APERTURES ARE CONSTANT
RATHER THAN DISTRIBUTED
• ORIENTATIONS ARE DISTRIBUTED
RATHER THAN CONSTANT
• LARGER SAMPLE SIZES ARE
TESTED
(J.LONG, 1982)
CDP-l -58
-------
DIFFUSION
Pick's Law:
9C
J, = -nD,
d o
82C
8t
CDP-1 -59
IMPORTANCE OF
MOLECULAR DIFFUSION
Heterogeneous Porous Media
Fractured Media
Vapor Phase Transport
Low Permeability Formations
Barriers and Liners
Residual NAPLs
CDP-1 -60
-------
DOES DETECTION OF
CONTAMINANTS INDICATE
"FAILURE" OF LINER?
MONITORING,
WELL
MOLECULAR DIFFUSION
CDP-l -61
-------
NON-AQUEOUS PHASE
LIQUIDS
(NAPLs)
• Light NAPLs (LNAPLs)
• Dense NAPLs (DNAPLs)
LNAPLs
Gasoline
Heating Oil
Kerosene
Jet Fuel
Aviation Gas
-------
LNAPLs
PRODUCT SOURCE
I tl tt
PRODUCT
ENTERING
SUBSURFACE
TOP OF
CAPILLARY
FRINGE
VATERTABLE
CROUNDWATER
KLOff
CROUNDWATER
FLOW
CDP-1 -64
LNAPLs
PRODUCT SOURCE
HtH
PRODUCT
ENTERING
SUBSURFACE
WATERTADLE
GROUNDffATER
FLOff
GROUNDWATER
FLOW
CDP-1 -65
-------
LNAPLs
PRODUCT
SOURCE
INACTIVE
PRODUCT
AT RESIDUAL
SATURATION
TOP or
CAPILLARY
FRINGE
-v.A
IROUNDKATEn
PRODUCT
AT RESIDUAL
SATURATION
FLOW
CDP-1 -66
-------
DNAPLs
1,1,1 - Trichloroethane
Carbon Tetrachloride
Pentachlorophenols
Dichlorobenzes
Tetrachloroetlrylene
Creosote
DNAPLs
Identified at
4 of top 5
and
10 of top 20
Hazardous Waste Sites
(Plumb and Pitchford, 1985)
CDP-l -67
CDP-1 -68
-------
DNAPLs
MAGNITUDE OF PROBLEM
7 L (10 kg) of TCE can
contaminate 108 L of
groundwater at 100 pbb
COP-l -69
DNAPLs
MOBILITY CAN BE GREAT
• Low Solubility
» High Density
» Low Viscosity
CDP-l -70
-------
DNAPLs
PRIMARY FACTORS
THAT CONTROL MIGRATION
» Type of Solvent
B Volume Released
• Rate of Release
• Area of Infiltration
CDP-l -71
-------
RELATIVE PERMEABILITY
k = k(S „ __Q
r v n" s
= relative permeability
= permeability at Sn
= NAPL saturation
= permeability at
100% saturation
CDP-l -72
NAPL SATURATION
100% Q o
1.0
m
<:
w
^
«
w
cu
w
£
E-
0.0
NAPL
Residual
NAPL
Saturation
Irreducible
- Water
Saturation-
0 Srw 100%
WATER SATURATION
CDP-1 -73
-------
DNAPLs
DNAPLs will not
be Mobile when DNAPL
content is less than
the Residual Saturation
CDP-l -74
Natural
Groundwater
Flux Rate =
10 cm/day
Effective
Groundwater
Flux Rate =
1.7 cm/day
o
Groundwater
Saturated
with TCE
I-*- 1
Residual Satxiration = 20%
Porosity = 0.35
Volume of TCE = 0.07 cubic meters
Mass of TCE = 103 kg
Solubility of TCE = 1100 mg/1
TIME REQUIRED
TO REMOVE TCE
BY DISSOLUTION
= 15.4 YEARS/m
CDP-l -75
-------
DNAPLs
RESIDUAL
TOP OF
CAPILLARY
FRINGE J
WATERTABLE
GROUND-
WATER FLOW
DNAPL SOURCE
tllT+T
DENSE VAPORS
GROUND-
WATER FLOW
LOWER
PERMEABILITY
STRATA
DISSOLVED
CHEMICAL
PLUME
After Feenstra and Cherry, (1987).
DNAPLs
CDP-1 -76
DNAPL SOURCE
t+tt+t
TOP OF
CAPILLARY
FRINGE -
DISSOLVE!
CHEMICAL
PLUME
GROUND-
WATER FLOW
LOWER
PERMEABILITY
STRATA
x
After Fccuatra and Cliorry (1987).
CDP-1 -77
-------
DNAPLs
DNAPL SOURCE
RESIDUAL DNAPL
TOP OF
CAPILLARY
FRINGE .^_
WATERTADLE
'"DISSOLVED
i CHEMIGAI*!!
'•••'•• PLUMED
LOWER
PERMEABILITY
STRATA
CDP-l -78
After Feenstra and Cherry (1987).
-------
TRANSPORT AND FATE
PHYSICAL PROCESSES
Session 2
Carl D. Palmer
(Oregon Graduate Center)
CDP-2 - 1
-------
PARTICLE TRANSPORT
THROUGH POROUS MEDIA
A potential mechanism for the
rapid movement of contaminants
in the subsurface.
"Facilitated Transport"
CDP-2 - 2
TYPES OF PARTICLES
Bacteria and Viruses
Natural Organic Matter
Inorganic Precipitates
Asbestos Fibers
Clay
CDP-2 - 3
-------
FILTRATION MECHANISMS
• Surface Filtration
• Straining
• Physical-Chemical
FILTRATION MECHANISMS
o -
SURFACE gOgOgOgO
FILTRATION O0O°O°O0
gogogogo
o
o
o o
<> « '
STRAINING
qgogqgqg
Sogogogo
PHYSICAL-
CDP-2 - 4
CDP-2 - 5
After HcOowell-Boyer et «1. (1986).
-------
MECHANISMS CONTROLLING THE
TRANSPORT OF MICROORGANISMS
• Straining
• Adsorption
• Sedimentation
• Interception
• Diffusion
• Chemotaxis
• Die-Off
• Growth
CDP-2 - 6
LABORATORY METHODS
• Grain-Size Analysis
» Permeameter
• Consolidation Tests
• Triaxial Cells
• Porosity
• Bulk Density
• Water Content
• Mineralogy
CDP-2 - 7
-------
GRAIN-SIZE ANALYSIS
1. METHODS
Seive
Hydrometer
Settling Tube
Light Scattering Techniques
CDP-2 - 8
GRAIN-SIZE ANALYSIS
2. RESULTS
• Estimate of Local Hydraulic
Conductivity
- Masch and Denny (1966)
- Hazen
- Grain-Size/Porosity Methods
• Estimate Proper Monitoring Well
Slot-Size
COP-2 - 9
-------
PERMEAMETER TESTS
1. METHODS
• Steady Flow
• Transient Flow
2. Results
• Hydraulic Conductivity
CDP-2 -10
-------
TRIAXIAL CELL TESTS
CONSOLIDATION TESTS
RESULTS
• Hydraulic Conductivity
• Specific Storage
• Coefficient of Compressibility
SOILS TESTS
Porosity
Bulk Density
Water Content
CDP-J -12
FIELD METHODS
Slug Tests
Aquifer Tests
Interference Pumping Tests
Time-Series Sampling Tests
Borehole Dilution
Seepage Meters
Fracture Mapping
Geophysical Techniques
Tracer Tests
CDP-2 -13
-------
SLUG TESTS
TYPES
Falling Head Test
Rising Head Test
Bail Test
Pressure/Packer Test
CDP-2 -14
SLUG TESTS
METHODS OF ANALYSIS
• Hvorslev (1961)
• Bouwer and Rice (1976)
• Cooper et al. (1967)
• Nguyen and Pinder (1984)
CDP-2 -15
-------
Ground Surface |«c|
H
KH
Palmer and Paul (1987).
CDP-2 -16
O.8
0.8
0.7
0.6
2"
1 0.4
5.
2
i °"'
£
OJt
0.1(
p
A
•
\
* •
\
^
; \y.=.
-T0-0^7-^<
t=K
3T
*^
\
\
\.
Omln. »
\
A ,
•100 2OO ''^
Time fmirO
CDP-2 -17
Palmer and Paul (1987).
-------
Cooper et al. (1967)
Type Curves
°-9o
Tt/r-
10'
CDP-2 -18
SLUG TESTS
POTENTIAL SOURCES OF ERROR
• Bridging of Seals
• Leaky Joints
• Formation of Low Permeability Skin
• Entrapped Air
• Presence of Fractures
• Stress Release Around Borehole
« Partial Penetration of IVell
• Anisotropy of Formation
« Varying Regional Piezometric Surface
• Boundary Conditions
• Sand Pack Effects
• Uncertainty in Initial Head
• Radius of Influence of Test
• Thermal Expansion
CDP-2 -19
-------
L-V
i «-
r
t/io/«R*i"
wen 2-1
Bail Test * 1
Starling Dale: 9/4/66
T9 s31.BOOn«n.
Time (nwl.)
Palmer and Paul (1987).
CDP-2 -20
We» 1-2
Tim* (mm.)
Palmer nnd Paul (1987).
CDP-2 -21
-------
1.0
T1
HH
0.8
.
£
(Q0.4
LOG K (fm) = 8
EFFECT OF
LOW K SKIN
LOG
SKIN
K(SKIN) = -10
THICK. = 0.0251 m
10
10" 1 10
TIME (DAYS)
From Palmer and Paul (1987).
10'
CDP-2 -22
LOG K(SKIN) s -10
SKIN THICK. •= 0.0251 M
EFFECT OF
LOW K SKIN
'0.0
10.o
_ _ J —I- * III
20.0 30.0
TIME (DAYS)
40.0
50.0
Palmer and Paul (1987).
CDP-2 -23
-------
GEOMETRC MEAN OF TRIAXIAL RESULTS
FOR SrTE 1 AND 2 = -7.68
(std. dev. 0.13)
^ SfTE 1 HYDRAULIC CONDUCUVfTY
£2 srre 2 HYDRAULIC coNoucrivrTY
lil TRIAXIAL RESULTS FOR
SITES 1 AND 2
-8.0
-6.0
From Paul (1987).
CDP-2 -24
-------
AQUIFER TESTS
PARAMETERS
DETERMINED
Hydraulic Conductivity
Specific Storage
Leakance
Anisotropy
Boundaries
Aquitard Diffusivity
CDP-2 -25
AQUIFER TESTS
TYPES OF TESTS
Constant Rate
Constant Head
Variable Rate
CDP-2 -26
-------
AQUIFER TESTS
TYPES OF FLOW
EQUATIONS
Steady-State Flow
Non-Steady State Flow
COP-2 -27
AQUIFER TESTS
TYPES OF AQUIFERS
Confined
Un confined
Semi-Confined (Leaky)
Semi—Unconfined
CDP-2 -28
-------
AQUIFER TESTS IN
FRACTURED ROCK
SINGLE POROSITY
- Same Methods as used for porous media
- Anlsotropy will be Important
Weeks (1969)
Way and McKee (1982)
DOUBLE POROSITY
- Barenblatt(1960)
— Boulton and Streltsova (1977)
CDP-2 -29
DIFFERENTIATING DOUBLE POROSITY MEDIA
FROM SINGLE POROSITY MEDIA
(AFTER GR1NGARTEN, 1984)
W
£2
LOG (t)
CDP-2 -30
-------
TIME SERIES SAMPLING
Can be used in evaluation
of source of contamination.
CDP-2 -31
VMftTER TUBIE
*
WATER TABLE
CDP-2 -32
Keely, J.F., 1982. Chemical Time-Series Sampling.
Ground Water Monitoring Review, Fall, 1982, p. 29-38.
-------
I. SLOW DECLINE. CONSTANT
TIME OR VOLUME PUMPED
II. RAPD DECLINE. CONSTANT
TIME Oft VOLUME PUMPED
ni. SLOW DECLNE, TRANSIENT
TIME OR VOLUME PUMPED
IV. RAPC DECUNE. TRANSIENT
TIME OR VOLUME PUMPED
V. SLOW INCREASE, CONSTANT
TIME OR VOLUME PUMPED
VI. RAPID NCREASE.CON5TANT
TME OR VOLUME PUMPED
VII. SLOW NCREASE. TRANSCNT
TME OR VOLUME PUMPED
Via. RAPID INCREASE. TRANSIENT
TME OR VOLUME PUMPED
From: Keely, J.F., 1982. Chemical Time-Series Sampling.
Ground Water Monitoring Review, Fall, 1982, p.29-38.
CDP-2 -33
-------
BOREHOLE DILUTION
PARAMETERS OBTAINED
Magnitude of Groundwater Flux
Direction of Groundwater Flow
CDP-2 -34
flow-through
conductance
•lectrod*
totclllc
conouctinc*
'w«ll "tctxn
FLOWUNC
WATCH TABLE
CDP-2 -35
From: McLlnn, 1987.
-------
BOREHOLE DILUTION
where
c1 = background concentration
c0 = concentration in injected slug
A = cross-sectional area of borehole
W = volume in borehole section
q = groundwater flux
CDP-2 -36
o
E—
02
E-
2
O
o
u
10 "i_
0.0
EXPERIMENT SBDD.001
q (calc.) = 5.9 cm/s
q (meas.) = 5,7 cm/s
206.0' '
TIME (MINUTES)
400.0
CDP-2 -37
-------
BOREHOLE DILUTION
TYPES OF DEVICES
Radioisotope Devices
Specific Ion Electrode
Devices
Specific Conductance
Devices
Thermal Devices
Resistivity Devices
CDP-2 -38
-------
Seepage Meter
T
Mini-piezometer
r
Plastic Bag
Sediment
CDP-2 -J9
-------
FRACTURE
MAPPING
Orientation
Aperature
Spacing
CDP-2 -40
GEOPHYSICAL METHODS
SURFACE TECHNIQUES
• Gravity Survey
• Infrared Imagery
• Ground Penetrating Radar
• Induced Electrical Polarization
• Resistivity
• Metal Detection
• Magnetometer
• Reflection Seismics
» Electromagnetic Surveys
CDP-2 -41
-------
GEOPHYSICAL METHODS
BOREHOLE METHODS
• Geothermetry
• Electrical
• Acoustic
• Nuclear
CDP-2 -42
-------
GEOPHYSICAL METHODS
BOREHOLE METHODS
• Electrical
- Resistance
- Normal
- Lateral
- Induction
- Self Potential
- Sidewall
- Induced Polarization
CDP-2 -43
GEOPHYSICAL METHODS
BOREHOLE METHODS
• Nuclear
- Natural Gamma
- Gamma-Gamma
- Neutron
- Spectronic Gamma
CDP-2 -44
-------
TRACER TESTS
INFORMATION GAINED
Dispersion
Heterogeneity
Porosity
CDP-2 -45
TRACER TESTS
TYPE OF TESTS
Natural Gradient
Forced Gradient
- Single Well Tests
- Two-Well Tests
Push-Pull
CDP-2 -46
-------
IMPROVED UNDERSTANDING OF
THE FATE AND TRANSPORT OF
CONTAMINANTS IN
HYDROGEOLOGIC SYSTEMS WILL
REQUIRE BETTER
CHARACTERIZATION OF THE
PHYSICAL NATURE OF THE
SUBSURFACE
• Three-Dimensional Monitoring
• Hydraulic Tests
• Tracer Tests
• Use of Geophysical Tools
CDP-2 -47
-------
RESEARCH FRONTIERS
Spatial Variability
Chemical/Physical Interactions
Multiphase Transport
Multicomponent Transport
Tool Development
Particle Transport
Transport in Fractured Rock
Source Identification
Modelling Techniques
Aquifer Remediation
CDP-2 -48
-------
SELECTED REFERENCES
Boulton, N.S. and T.D. Streltsova, 1977. Unsteady flow to a Pumped Well in
a Fissured Water Bearing Formation, Journal of Hydrology, V. 35, pp. 257-
270.
Freeze, R.A. and J.A. Cherry, 1979. Groundwater, Prentice-Hall, Inc.,
Englewood Cliffs, New Jersey, 604 p.
Freyberg, D.L., 1986. A Natural Gradietn Experiment on Solute Transport in
a Sand Aquifer, 2, Spatial Moments and the Advection and Dispersion of
Nonreactive Tracers, Water Resources Research, V. 22, No. 13, p. 2031-2046.
Frind, E.G. and C.D. Palmer, 1980. Parametric Study of Potential
Contaminant Trnasport at the Proposed DELMARVA Power and Light Company Plant
Site, Vienna, Maryland. Maryland Power PLant Siting Program report NHU PPSE
8-15, 98 p.
Frind E.O. and G.E. Hokkanen, 1987. Simulation of the Borden Plume Using
the Alternating Direction Galerkih Technique, Water Resources Research, V.
23. No. 5,p. 918-930.
Gillhnm, R.W. and J.A. Cherry, 1982. Contaminant Migration in Saturated
Geologic Deposits. IN: Recent Trends in Hydrogeology, T.N. Narasimhan,
(Editor), Geological Society of America Special Paper 189, p. 31-62.
Gillham, R.W., E.A. Sudicky, J.A. Cherry, and E.O. Frind, 1984. An
Advection-Dif fusion Conceptfor Solute Tranport in Heterogeneous
Unconsolidated Geological Deposits, Water Resources Research, v. 20, No. 3,
p. 369-378.
Gringarten, A.C., 1984. Interpretation of tests in fissured and
roultilayered reservoirs with double porosity behavior: theory and practice,
J. of Pet. Tech., pp. 549-564.
Gringarten, A.C., 1982. Flow-Test Evaluation of Fractured Reservoirs, IN:
Recent Trends in Hydrogeology, T.N. Narasimhan, (Editor), Geological Society
of America, Special Paper 189, p. 237-263.
Keely, J.F., 1982. Chemical Time-Series Sampling, Ground Water Monitoring
Review, Fall, 1982, p. 29-38.
Long, J.C.S., J.S. Remer, C.R. Wilson, and P.A. Witherspoon, 1982. Porous
Media Equivalents for Networks of Discontinuous Fractures, Water Resources
Research. V. 18, No. 3, pp. 645-658.
Molz, F.J., 0. Guven, J.G. Melville, and J.F.Keely, q986. Performance and
Analysis of Aquifer Tracer Tests with Implications fof Contaminat Transport
Modeling, U.S. E.P.A. Research and Development Report 600/2-86/062, 88p.
Palmer, C.D. and D.G. Paul, Problems in the Interpretation of Slug Test Data
from Fine-Grained Glacial Tills, Focus Conference on Norhtwester
Groundwater Issurs, PortIan, Oregon,May 5-7, 1987, p. 99-123.
-------
Paul, D.G. The Effect of Construction, Installation, and Development
Techniques on the Performance of Monitoring Wells in Fine-Grained Glacial
Tills. M.S. Thesis, Dept. Geol. and Geophys. Sciences, Univ. of Wisconsin-
- Milwaukee, 230 p.
Perkins, T.K. and O.C. Johnston, 1963. A Review of diffusion and
Dispersion in Porous Media. Society of Petroleum Engineering Journal, V. 3,
p. 70-84.
Sudicky, E.A., 1986. A Natural Gradient Experiment in a Sand Aquifer:
Spatial Variability of Hydraulic conductivity and its Role in the Dispersion
Process. Water Resources Research, V. 22, No. 13, p. 2069-2082.
Sudicky, E.A., R.W. Gillham, and E.G. Frind, 1985. Experimental
Investigation of Solute Transport in Stratified Porous Media, 1. The
Nonreactive Case. Water Resources Research, V. 21, No. 7, P. 1035-1041.
Streltsolva-Adams, T.D., 1978. Well Hydraulics in Hertogeneous Aquifer
Formations, IN: Advances in Hydroscience, V.T. Chow (Editor), V. 11, p.
357-423.
Sudicky, E.A., J.A. Cherry, and E.O. Frind, 1083. Migraion of Contaminants
in Groundwater at a Landfill: a case study: 4. A natural-gradient
dispersion test. Journal of Hydrology, V. 63, No. 1/2, p. 81-108.
Way, S.C. and C.R. Mckee, 1982. In-situ Determination of Three-
Dimensional Aquifer Permeabilities, Ground Water, V. 20, p. 594-603.
Weeks, E.P., 1969. Determining the Ration of Horizontal to Vertical
Permeability by Aquifer-Test Analysis, Water Resources Research, V. 5,No. 1,
pp. 196-214.
-------
TRANSPORT AND FATE
CHEMICAL PROCESSES
Session 3
Richard L. Johnson
(Oregon Graduate Center)
-------
MAJOR IONS
(NATURAL)
AXIONS CATIONS
chloride
sulfate
bicarbonate
carbonate
sodium
calcium
magnesium
potassium
RU3A1-;
RADIOISOTOPES
(NATURAL)
Uranium
Radium
Radon
238TT 226^ 222
u—'—*- Ra-*- -— Rn
TRACE METALS
(NATURAL)
• Arsenic
• Selenium
• Lead
• Barium
• Cadmium
RIJ3AI-I
-------
WATER QUALITY
PARAMETERS
» TOTAL DISSOLVED SOLIDS • pH
• SPECIFIC CONDUCTANCE • pE (Eh)
• DISSOLVED OXYGEN • ODOR
" AKLAKINITY • TURBIDITY
» ACIDITY • COLOR
RLJ3AI-5
MAJOR IONS
(Anthropogenic)
ANIONS
CATIONS
Cyanide
Nitrate
Phosphate
Hydrogen
RU3A2-2
RADIOISQTOPES
(Anthropogenic)
Uranium
Cesium
Strontium
Ruthenium
Tritium
RU3A2-3
-------
TRACE METALS
(ANTHROPOGENIC)
Mercury
Chromium
Arsenic
Selenium
Lead
Cadmium
RLJ3A2-4
INORGANIC REACTIONS
SOLUBILITY/DISSOLUTION/PRECIPITATION
COMPLEXATION
ION EXCHANGE
OXIDATION/REDUCTION
RADIODECAY
RU3A4-I
-------
OVERSATURAT !D
UNDERSATURA7 -D
RLJ3A4-2
-10
3579
pH
RLJ3A4-3
-------
-10 -
m.J3A4-4
ion poirj
Hyd'ation shell contact Shored hydration Ion contact type
type
OH,
HN
"NH,
monodentoia ligond
0
potydentote liqond
OH,
S,CH2
. H H
AH,
b,demon hgond
CM,
CH,
polynucleor complex
Source: Morel, 1983 (Used with peraissiun)
RLJ3A4-5
-------
Mononucleir Complexes
Addition ofligand
Addition of prolonged ligands
ML.
a _
[ML,]
IMLJ
M •$- ML4£- ML, • • • -5^- ML, •
. - "A - •
ML.
[M][HL|'
Pol)nuclear Complexes
In //.. and */!._ the subscripts n and m denote the composition of [he complex M.L. formed.
(If m •> I, the second subscript (- I) is omitted.]
IM.L.]
Source: Morel, 1983 (Used vith permission)
RLJ3A4-6
S 20
' 22
23
TI9
f« ...
pH
73 BO
~l r~T
. Hq(OH),
10
Salinity V..
Source: Morel, 1983 (Used vith permission)
RLJ3A4-7
-------
I - I . I /"
X O X OH X 0
I I I \H
Mini Coord.n»
i
-------
log S
logC
RLJ3A4-9
METAL ION BINDING TO OXIDE SURFACES
100
UJ
o
UJ
co
DC
80
60
40
20
Fe (III)
123456789
pH
Adapted froa llohl and Stum, 1976
RLJ3A4-14
-------
13
5 7 9 II
pH
KU3A4-17
-5
-10-
13 5 7 9 II 13
DH
RLJ3A4-18
PH
RLJ3A4-19
-------
ORGANICS
(NATURAL)
HUMICS, FULVICS
COAL, PEAT, LIGNITE
PETRO-ORGANICS
RU3B1-1
-------
COOH COOH
HOO
I (Sm)or)
(HC-OH1,
KC'O
RJ-I3B1-2
SOIL ORGANIC MATTER
*
HUMIC MATTER
NONHUMIC MATTER
UNOECOMPOSEO PLANT RESIDUES
TREAT WITH ALKALI
1
1
INSOLUBLE
(HUMIN)
\
SOLUBLE
1
TREAT WITH AGIO
1
PRECIPITATED
(HUMIC ACID)
I
EXTRACT WITH ALCOHOL
I
SOLUBLE
(HYMATOMELANIC ACID)
* I
INSOLUBLE SOLUBLE
*
NOT PRECIPITATED
(FULVIC ACID)
ADJUST pH TO 4.8
I
INSOLUBLE
P-HUMUS
JUJ3B1-3
-------
ORGANICS
(ANTHROPOGENIC)
EPA PRIORITY POLLUTANTS
RCRA APPENDIX IX
POLAR ORGANICS
IONIZABLE ORGANICS
EVERYTHING ELSE
RLJ3B2-1
POLAR AND IONIZABLE COMPOUNDS
ALCOHOLS (ISOPROPANOL)
ANALINES (NITROANALINES)
ACETATES (VINYLACETATE)
AMINES (DIPHENYLAMINE)
THIOLS (TRICHLOROMETHANETHIOL)
FURANS (DIBENZOFURAN)
NITRILES (ACRYLONITRILE)
PHENOLS (CHLORO- AND NITROPHENOLS)
ALDEHYDES AND KETONES (ACETONE)
ACIDS
RLJ3B2-4
-------
ORGANIC REACTIONS
• HYDROLYSIS
• SORPTION
• COSOLVATION
• IONIZATION
• BIODEGRADATION
RLJ3B4-1
RX + HOH ROM + HX
H X
i i
c_c __— _ c=C + HX
GIT
RLJ3B4-3
-------
HYDROLYSIS OF
1,2,4-TRICHLOROBENZENE
100 tj
50
PERCENT
REMAINING
10
D
70°C
.H-7.11
HALF-LIFE - 160 HOURS
50 100
TIME (HOURS)
150
Adopted Iron Ellington «t al. 1986.
RLJ3B4-9
dC
= -KC
In
c
C(0)
IX
= -K1
f-llfe:
C
C(0)
0.5
t • 160 hours
thus, K = 0.69/160
K =4.3x 103 hr"1
RLJ3D4-10
-------
ADVECTION-DISPERSION
EQUATION
WITH FIRST-ORDER DEGRADATION
(IRREVERSIBLE)
_ 92C 9C 9C
D —2 - v— =— - KC
3 x 3 x 31
RU3D4-11
-------
PYRENE
1800
1500
1200
900
600
300
SLOPE
PYRENE
o
oo
PHENANTHRENE
n600
500
400
300
200
100
Kp
PHENAN-
THRENE
i I i I T
0.0 .005 .010 .015 .020 .025
FRACTION ORGANIC CARBON
Adapted from Karlckhoff, 1981
RLJ3B4-12
1200
u.
o
D)
\
O
3
o
H
<
cc
h-
ui
o
z
o
o
D
LU
m
cc
o
800
400 -
1,1,1 -TRICHLOROETH ANE
f
1,1,2,2-TETRACHLOROETHANE
1,2-DICHLOROETHANE
400 800 1200 1600 2000 2400
AQUEOUS CONCENTRATION (ug/L)
Adapted from Chlou ec al.,1981.
RLJ3B4-13
-------
ADVECTION-DISPERSION
EQUATION
WITH LINEAR EQUILIBRIUM
PARTITIONING
9C 9C
- = R -
9x 9x 9t
RLJ3IM-14
-------
McKay and Trudell
1 - 1 - 1 - 1 - 1 - 1 - 1 - 1 - 1 -
LOG OF THE FINAL AQUEOUS CONCENTRATION (PPB)
RLJ3B4-1S
-------
ALKALI LAKE
2.6-DICHLOROPHENOL
2.3,4,5-TETRACHLOROPHENOL
DICHLOROPHENOXYPHENOL
200
DISTANCE (M)
400
RLJ3B4-16
1
o
<
cc
H
LJJ
O
Z
O
o
UJ
UJ
DC
0.9 i
0.8
0.7-
0.6
0.5-
0.4-
0.3-
0.2-
0.1 -
0
CHLORIDE
STANFORD/WATERLOO
TRACER TEST
CARBON TETRACHLORIDE
TETRACHLOROETHYLENE
200
TIME (DAYS)
Adapted from Roberts et »!., 1986.
400
BLJ3D4-17
-------
1000
100 x
Kp 10 -
1 -
0.1
METHANOL-WATER
ANTHRACENE
.1 .2 .3 .4 .5
FRACTION CO-SOLVENT
Adapted fron Nkedl-Klzza et •!., 198S.
HLJ3B4-18
CL
0-H
CL
0,
+ H"
0
RLJ3B4-5
-------
2,4,5-
TRICHLOROPHENOL
i 1 1 1 r
6.0 6.5 7.0 7.5 8.0 8.5
RLJ4D2-5
C
O
Cl-
H
-Cl
—*- Wl OC"
H^
H
364
126
59
8.2
RLJ3B4-20
-------
0
LU
CARBONTETiRACHLORIDE
TETRACHLOROETHYLENE
HEXACHLOROETHANE
DICHLOROBENZEh4E
200 400 600
TIME (DAYS)
RLJ3B4-19
Adapted from Roberts et al. 1986.
-------
LNAPLs
PRODUCT
SOURCE
INACTIVE
PRODUCT
AT RESIDUAL
SATURATION
CROUNOWATER
FLOW
PRODUCT
AT RESIDUAL
SATURATION
GROUND*ATER
no*
LNAPLs
PRODUCT
SOURCE
INACTIVE
R1J3D1-1
TOP OF
CAPILLARY
FRINGE
PRODUCT
AT RESIDUAL
SATURATION
FLOW
PRODUCT X
AT RESIDUAL
SATURATION
GROUNDWATKR
n.ow
RLJ3D1-2
-------
HEART OF
THE PLUME
ANAEROBIC
ZONE
AEROBIC
ZONE
PRISTINE
ZONE
CHEMICAL SPECIES
so
ELECTRON ACCEPTORS
CO.
so
NO.
RU3D1-B
DO
v_^
V)
CO
o
z
<
o
CC
O
WATERLOO "BTX" EXPERIMENT
CHLORIDE
kBENZENE
TOLUENE
O-XYLENE
P-XYLENE
M-XYLENE
100 200 300
TIME (DAYS)
400
Adapted from Patrick and Barker, 1987.
RLJ3D1-7
-------
leart of
the Plume
12-
5 10-
O)
,§ 8-
(0
"5
2-
Anaerobic
Zone
Aerobic
Zone
"Renovated"
Zone
Sulfate
Heart of
the Plume
Anaerobic
Zone
Aerobic
Zone
"Renovated"
Zone
leart of
the Plume
Anaerobic
Zone
Aerobic
Zone
"Renovated"
Zone
Adapted from Wilson et al., 1986.
RLJ3D1-9
-------
o
%^
o
10 -
9 -
8 -
7 -
6 -
5 -
4 -
3 -
2 -
1 -
0 -*•
Fe
O
18
16
14
12
10
8
6
4
2
0
Methane
30O
Heart of
th« Pluma
Anaerobic
Zone
Aerobic
Zone
"Renovated"
Zone
Adapted from Wilson et al. 1986.
WJ3D1-10
-------
LEAD
| = 20 MG/KG SOIL
SOURCE
RLJ3D1-11
B)
Oxygon Infiltration
diffusion
Ground surface
Oxygen
diffusion
' v>
\ ~ *" I Biodegradation
.\ Gasoline I I-
\\diffuslon Unsaturatcd zone
ty
Oxygen
diffusion
Residual
liquid gasoline '
Gasoline
diffusion
Capillary fringe
Liquid gasoline
Dissolved gasoline
Saturated rone
RLJ3D1-12
-------
TOTAL VOLATILE HYDROCARBONS.
n?o E~"T--,
•r-
T
PARTIAL PRESSUflE OXYGEN
Source: Hult et al., 1985.
RLJ3D1-13
- o»o -
PARTIAL PRESSURE CARBON DIOXIDE
•- 1403 •
± 1390-
oeo -
METHANE, pom
Source: Hulc ft al.. 1985.
RLJ3D1-14
-------
DNAPLs
DNAPL SOURCE
ttt+tt
TOP OF
CAPILLARY
FRINGE -
GROUND- ,—K,,
WATER FLOW
DISSOLVED
CHEMICAL
GROUND-
WATER FLOW
LOWER
PERMEABILITY
STRATA
RU3J2-3
UNLINED CREOSOTE POND
PRESSURE-TREATING
FACILITY
R
f
CREOSOTE, PENTA, WATER, AND DIESEL
RLJ3D3-1
-------
PENSACOLA BAY
0 500ft
After Franks ec «!., 1984.
RLJ3D3-2
PENSACOLA BAY
SILT AND
CLAY LENS
After Bacdcckor et al. 19RS.
RLJ3D3-3
-------
CHEMICAL SPECIES
ELECTRON ACCEPTORS
CO.
so
NO,
RLJ3D3-4
CO
111
_l
o
5
5
UPGRADIENT
CONCENTRATIONS
0.2
0.1 -
0
14
PONDS 500
After Baedecker et al.. 1985.
1000
1500
BAY
HJ3D3-5
-------
I-
LU
a.
LLJ
G
15
20
MMOLES/L
10 0
0.1
0.2
TOTAL C02
HYDROGEN
After Ba«decker ec •!., 1985.
FO-J3D3-6
PENSACOLA BAY
NO SULFIDE
MAJOR CONTAMIATED
ZONE
SILT AND
CLAY LENS
HIGH IRON *&
Aftrr Bacdecker *t nl., 19B5.
RU3DJ-7
-------
TRANSPORT AND FATE
CHEMICAL PROCESSES
Session 4
Richard L. Johnson
(Oregon Graduate Center)
-------
GROUNDWATER SAMPLING
• SAMPLING USING MONITORING
WELLS
• SAMPLING USING CORING
TECHNIQUES
• SAMPLING IN THE UNSATURATED
ZONE
RLMA-1
SAMPLING USING MONITORING
WELLS
• WELL PLACEMENT
• WELL DESIGN
• WELL PURGING
• SAMPLING AND STORAGE
RU4AI-1
-------
MULTI-LEVEL
MULTIPLE
COMPLETION
NEST
SAMPLING
LEVELS
PACKERS
RLJ4A1-2
-------
PURGING
GROUT +-
SAND PACK
WELL SCREEN
RLJ4A1-3
SAND PACK +•
WELL SCREEN-
| PURGING
tL
LOW
RIJ4A1-4
-------
GROUT-
SAND PACK
WELL SCREEN-
SAMPLER
FILLING
LOCATIONS
RLJ4A1-5
GROUT *•
SAND PACK-
WELL SCREEN
SAMPLER CONTROL
' LINE
PACKER
SAMPLER
RLMAl-fl
-------
1/iaifi WCH ZERO-DEAD
VOLUME UNION
Exaaple of a saall-diamoCer resorvoir sampler (Johnson ec al. 1987)
-------
SAMPLING USING COR NG
TECHNIQUES
CORING AND SQUEEZING
CORING AND DISPLACEMENT
CORING AND EXTRACTION
CORING FOR MICROBIOLOGY
FREEZE-CORING
RLMA2-I
-------
N2 (UP TO 750 psi )
^
"0" RING SEALS
1/2" STUD
O mL
SYRINGE
"MININERT"
VALVE
QUARTZ FIBER FILTERS /1/16 VALCO
AND STAINLESS STEEL—7 ZERO DEAD-VOLUME
SUPPORT SCREENS FITTING
i 31/2" I
31/2 LONG #17
SYRINGE NEEDLE
RLJ4A2-2
-------
PORE-WATER EXTRACTION
BY DISPLACEMENT
IMMISCIBLE FLUID
/
SAMPLE
CENTRIFUGAL FORCE
*
EXTRACTED
PORE WATER
RLJ4A2-3
Friedrlchs
Condenser
Soxhlet
Extraction
Tube
Flask
-------
40 mL VIAL
- CAP
-WATER AND
METHANOL
•- SOIL
ORGANIC SOLVENT-
WATER
SOIL-
Hi
RLJ4A2-5
UPPER DBWE
ME40 WITH LEFT
THREADED PIN -x
PISTON CABLE
HARDENED DRIVE
SHOE N
"\
SCHEMATIC
INNER CORE BARREL
'(DEDICATED) '
.OUTER CORE BARREL
PISTON WITH RUBBER
WASHERS 8 BRASS
'SPACERS
Source: Zapeco ft «!., 1987.
-------
CORE REMOVED
BY EXTRACTING f
THE PIPE '
COOLANT IN'
FROZEN GROUND
RLJ4A2-7
SAMPLING IN THE UNSATURATED
ZONE
• SUCTION LYSIMETERS
• PAN LYSIMETERS
• VAPOR SAMPLING
R1-M/U-I
-------
SUCTION LYSIMETER
SAMPLE
WITHDRAWL
POROUS CUP
RLJ4A3-2
A
5 ill
•«. x \^_-'
6 RAINFALL
INFILTRATION
PAN
-------
GROUT
mvw.
SAND
VAPOR SAMPLING
PROBES
RLJ4A3-4
SEPTUM
—-SYRINGE
v
GROUND SURFACE
TO PUMP
SOIL GAS
^PROBE
RIJ4A3-G
-------
TO PUMP
v SORBENT
CARTRIDGE
SOIL GAS
PROBE
RLJ4A3-7
TO SAMPLE
PROBE
RLJ4A3-0
-------
EXPERIMENTAL METHODS
-CHEMICAL
• LABORATORY METHODS
• FIELD METHODS
RLJ-lC-1
EXPERIMENTAL METHODS
- LABORATORY
SORPTION • VOLATILIZATION
DIFFUSION • ION EXCHANGE
HYDROLYSIS • DIAGENESIS
COMPLEXATION • DEGRADATION
DISSOLUTION/PRECIPITATION
RLJ4C1-!
-------
TUMBLE
SLOWLY
40 mL VIAL
CAP
WATER WITH
SORBING
COMPOUND
•*- SOIL
RU4C1-2
V
-WATER IN
WATER PLUS
COMPOUND
WATER PLUS
COMPOUND OUT
NON-SORBING
w SORBING
I
VI V2
VOLUME *•
RLMCl-3
-------
f
6cm
lOcm
MININERT VALVE
STAINLESS STEEL
END CAP
TEFLON WASHER
GLASS BEAD
STAINLESS STEEL
SCREEN
GLASS FIBER FILTER
5cm I.D. STAINLESS
STEEL TUBING
THREADED
BRASS ROD
TEFLON WASHER
STAINLESS STEEL
END CAP
EXPERIMENTAL METHODS
- FIELD
SORPTION
DEGRADATION
DIFFUSION
• OTHER REACTIONS
RLJ4C2-1
-------
z
o
H
LJJ
O
Z
o
o
LU
H
LU
cc
1
0.9
0.8-
0.7-
0.6
0.5 1
0.4
0.3-
0.2-
0.1 -
0
CHLORIDE
STANFORD/WATERLOO
TRACER TEST
CARBON TETRACHLORIDE
TETRACHLOROETHYLENE
200
TIME (DAYS)
400
RLJ4C2-2
After Roberts «t «!., 1986.
CARBONTE1RACHLORIDE
TETRACHLOROETHYLENE
HEXACHLOROETHANE
DICHLOROBENZENE
200 400 600
TIME (DAYS)
RU4C2-7
After Roberta ec al., 1986.
-------
WATER TABLE
Cross-Section
INJECTION
PUMPING WELL
n WATER TABLE
FFi
Plan View
Source Johnson, 1984.
0.20
0.18
3 M PUMPING TRACER TEST (R.6P)
TIME t SEC)
5000 6088 7080
1ULJ4C2-4
Source: Johnson, 1984.
-------
1.INJECT 2 .WAIT 3. WITHDRAW
RLJ4C2-5
MATRIX
i.eo
PUSH-PULL.8489.F
e.eo
2.CO 3.00
E SINCE INJECTION (H>
4.00
e.oe
Fraction of •••« recovered during pumping
vomus reildence tine of the tracer in the
ground prior to beginning of punping for thr
Mpo»h-pullH tents using fluorescein.
Source: Johnson, 1984.
-------
RESEARCH FRONTIERS
INDICATOR COMPOUNDS B SOLVENT/CLAY
INTERACTIONS
SORPTION EXPERIMENTS 3 DIFFUSION IN CLAY
PARTICLE TRANSPORT D UNSATURATED ZONE
VAPOR MOVEMENT
• ANALYTICAL METHODS DEVELOPMENT
RIJ4D-1
NDICATOR COMPOUNDS FOR
COMPLIANCE MONITOR NG
• CONSERVATIVE AND NGN-REACTIVE
• UNIQUE TO THE WASTE MATERIALS
• REPRESENTATIVE OE THE WASTE
MATERIALS
-------
COMMON INDICATOR
COMPOUNDS
• Chloride
• Bromide
• TOC
• TOX
• Halogenated Aliphatic
Hydrocarbons
RLJ4D1-2
SORPTION EXPERIMENTS
• K = F(SOIL/WATER)?
• NON-SETTLING PARTICLES
• IRREVERSIBLE SORPTION
• SORPTION OF NON-HYDROPHOBIC
COMPOUNDS
RIJ.JH2-I
-------
2,3,4,5,6,2',5'-HEPTACHLOROBIPYENYL
10'
(ML/G)
10V
102 103 104
SEDIMENT CONCENTRATION
(MG/L)
After Rschwend and Wu, 1985.
RLJ4D2-2
10
CO
CQ 0.1
o
o
Q 0.1
0.01
0.01 _
1000
o
'*~f
CO
Q
100
10
I
1234
10 10 10 10
SEDIMENT CONCENTRATION
(MG/L)
After Cschuend and Wu, 1985.
RLJ4D2-3
-------
CL
0-H
H'
C
G.LT4D2 - 4
PARTICLE TRANSPORT
• MICROPARTICLES, COLLOIDS, AND
MACROMOLECULES
• TRANSPORT OF INORGANICS
• TRANSPORT OF ORGANICS
MJ«D3-1
-------
§ 1-
CD
DC
o
i M-
o
GC
O
0.01
10
100
1000
SOLIDS CONCENTRATION
(MG/L)
RLJ4D3-2
WHEN IS PARTICLE TRANSPORT
OF ORGANICS IMPORTANT?
EXAMPLE:
1. Mass of NSP = 100 mg/L
2. foe of NSP = 0.01
3. therefore, mass of C = 1 mg/L
4. if Koc = 10°, then
mass on NSP = mass in water
5 if Koc = 105, then
mass on NSP = mass in water
10
RLJ4D3-
-------
PRIORITY POLLUTANTS WITH
6
K VALUES GREATER THAN 10
oc
DDE PAHs
DDT TCDD
Aroclor 1260
Toxaphene
hexachlorobenzene
Dioctyl phthalate
RLJ4D3-4
SOLVENT/CLAY INTERACTIONS
PERMEABILITY CHANGES
DIFFUSION
RU404-1
-------
WASTE
ADVECTION AND DIFFUSION
CLAY
AQUIFER
RLJ4D4-2
WASTE
DO ORGANIC SOLVENTS CAUSE
THE CLAY TO SHRINK
AND CRACK?
/\
CLAY
AQUIFER
RLJ4D4-3
-------
DIFFUSION IN CLAY
i DIFFUSION THROUGH LINERS
i RETARDATION
• SOLVENT/CLAY INTERACTIONS
• STEADY-STATE DIFFUSION
i DIFFUSION THROUGH AQUITARDS
RLJ4D5-1
WASTE
CLAY
HIGH CONCENTRATIONS
1 DIFFUSION 1
LOW CONCENTRATIONS
RLJ4D5-2
-------
DIFFUSION
PICKS SECOND LAW:
3C _ „ 82C
9t ~ ~TnDd8x2
FUSION
WITH SORPTION
PICKS SECOND LAW:
_8C _ -TnL)i 82C
81 ~ R 9 x2
RLJ4D5-3
RI.MD5-4
-------
0.2 04 0.6 08 1.0
(a) D-4xlO'6 cm2/s; or D-2xlO"7; or D-?xlO-l
T-5 years
T-100
T-1.000
(b) D-4xlO'6 cm2/s; or D-2xlO'7; or D-2xlO'8
T-15 years T-300 T-3.000
(c) D-MxlO'6 cm2/s; or D-2xlO'7; or D-2xlO'8
T-25 years
T-500
T-5. 000
Source: Johnson ec al., 1987b. RLJ 4D5-5
6
U
— • 9n
RFACE
£»
3 C
uJ
1-
z
O 60
Ul
z
1- 80
O.
UJ
Q
100
RELATIVE CONC
0,2 0.4 0.6 O.S 10
I (_-*_T — g 1 — 1- s.s-.W""'-'1'-*^1"" 1 -*~
'TOLUENE „'£'''
"1 X
Cf
V-- J'
- /T/
/i /
i
i
,
ENTRATION
0 0.2 0.4 0.6 0.8 1.
..I2.,o-1: r"J-----------f '-= - s13-1
TRICHLOROETHENE
1.2-DICHLOROPROPANE
NAPHTHALENE
,' TOC
i 1 i i
:
20
-
40
Sotirri>:Jo1in.iiin ct al.. 1987.
RU'.D5-8
-------
WASTE
NORMALIZED
CONCENTRATION
0 I
CLAY
AQUIFER
0
DIFFUSION
STEADY-STATE
RLJ4D5-10
PICK'S FIRST LAW:
,
d
d9
x
RIJIH5-11
-------
CONTAMINATED
UNCONTAMINATED
AQUIFER 1
i DIFFUSION AND ADVECTION { AQUITARD
T • _, , _—-—v
AQUIFER 2
RLJ4D5-12
SOLVENT
~ *r
RESIDUAL
SOLVENT
AQUIFER 1
DIFFUSION AND ADVECTION
AQUITARD
UNCONTAMINATED
'AQUIFER 2
RLMD5-13
-------
ANALYTCAL METHODS
DEVELOPMENT
• ION CHROMATOGRAPHY
• IMPROVED VOLATILES ANALYSIS
• SUPERCRITICAL FLUID CHROMATOGRAPHY
• MS/MS/MS
• GC/MS/MS
RU4D6-1
UNSATURATED ZONE VAPOR
MOVEMENT
• "PLUME SNIFFING"
• PHYSICAL/CHEMICAL PROCESSES
• MICROBIOLOGICAL PROCESSES
• FLUX TO THE ATMOSPHERE
RU4D7-1
-------
CONG—»
GROUNDWATER FLOW
RLJ4D7-2
IMPERMEABLE CAP
GROUNDWATER PLUME
GROUNDWATER FLOW
RU-lDV-a
-------
CONCENTRATION
UNSATURATED
CAPILLARY
SATURATED
RLJ4D7-4
CONCENTRATION
UNSATURATED
CAPILLARY
SATURATED
RIJ'in7-5
-------
WATERTABLE
FLUCTUATIONS
GROUNDWATER PLUME
GROUNDWATER FLOW
RIJ4D7-6
-------
REFERENCES
Baedecker, M.J. 1985. Proceedings of the Second U.S.G.S. Toxic Waste Technical
Meeting, Cape Cod, MA. October, 1985.
Chiou, C.T., L.J. Peters and V.H. Freed. 1981. Science, 206. 831.
Ellington, J.J., F.E. Stancil, and W.D. Page. 1987. EPA/600/S3-86/046, 122pp.
Gschwend. P.M. and S. Wu. 1985. Environ. Sci. Technol. 1£, 90-96.
Hohl and W. Stumm. 1975. J. Colloid. Interface Sci., 55, 281.
Hult, M.F. and R.R. Grabbe, 1985, Proceedings of the Second U.S.G.S. Toxic
Waste Technical Meeting, Cape Cod, MA, October, 1985.
Johnson, R.L. 1984. Ph.D. Dissertation, Oregon Graduate Center, Beaverton, OR.
Johnson, R.L.. J.F. Pankow, and J.A. Cherry. 1987. Ground Water, 25, 448-454.
Johnson, R.L., J.A. Cherry, and J.F. Pankow. 1987b. Submitted to Environ. Sci.
and Technol.
Karikchoff, S.W. 1981. Chemosphere, 10, 833-846.
Hattraw, H.C. and Franks, B.J. 1984. U.S.G.S. Open File Report 84-466. 93pp.
Morel, F.M.M. 1983. Principles of Aquatic Chemistry. Wiley-Interscience, 446pp.
Nkedi-Kizza, P., P.S.C. Rao and A.G. Hornsby. 1985. Environ. Sci. Technol., 19,
975-979.
Patrick, G.C., J.F. Barker, and D. Major. 1987. Ground Water Monitoring Review,
Winter, 64-71.
Roberts, P.V., M.N. Goltz, and D.M. McKay. 1986. Stanford University Civil
Engineering Technical Report No. 292, 113-123.
Stumm, W. and J.J. Morgan. 1981. Aquatic Chemistry. Wiley-Interscience.
Swallow, K.A. and P.M. Gschwend. 1984. in "Proceedings of the Petroleum
Hydrocarbons and Organic Chemicals in Groundwater Conference", Houston,
TX, November, 1984.
Wlson, B.H., B.E. Bledsoe, D.H. Kampbell, J.T. Wilson, J.M. Armstrong, and
J.H. Sammons. 1986. in "Proceedings of the Petroleum Hydrocarbons and
Organic Chemicals in Groundwater Conference", Houston, TX, November, 1986.
Zapeco, M., S.Vales, and J. Cherry. 1987. Ground Water Monitoring Review,
Summer, 74-82.
-------
TRANSPORT AND FATE
B1OTRANSFORMATION
PROCESSES
Session 5
Joseph M. Suf lita
(University of Oklahoma, Norman)
-------
THE MICROBIAL ECOLOGY GOVERNING
POLLUTANT BIODEGRADATION IN
TERRESTRIAL SUBSURFACE ECOSYSTEMS
BY
Joseph M. Suflita, PhD.
Department of Botany and Microbiology
The University of Oklahoma
Norman, Oklahoma 73019
Su m mary: The first seminar is an introduction to the historical and current
scientific perspectives regarding the microbial ecology of the terrestrial subsurface.
Careful attention is paid to hoy these perceptions evolved. Examples are given of the
diverse types of subsurface microorganisms and microbial communities and their
associated metabolic activities are emphasized. The metabolic principles that govern
pollutant biodegradation in other habitats are extrapolated to subterranian aquifers.
The limits of pollutant biodegradation in aquifers are considered in the context of the
existing environmental conditions, the physiology of the indigenous microfloraand
the chemical structure of the offending materials. Lastly, it is shovn hov these
principles might apply to abioreclamation/bioremediation approach to the clean-up
of contaminated aquifers in either an ia situ or above ground treatment process.
-------
MICROBIBL ECBLOCV
Microbial ecology has sometimes appeared to be the
art of talking about what nobody really knows
about in a language that eoeryone pretends to
understand
Francis E. Clark, USDR-RRS
The Truth About Ground Water Pollution:
Surface
Unsaturated Zone
Saturated Zone
Misconceptions:
• "Living Filter" degrades pollutants
before ground water contamination
occurs
• No microorganisms below surface
soil layers
Facts:
• Pollutants do contaminate aquifers
• Microorganisms do exist in
subsurface
Groundwater contamination
The environmental Issue of the 1980's
• 50X of population depends on groundwater
• 256* growth In demand from 1950-1980
• 1/3 of the large public water systems have
man-made contamination
• 7,741 private, public and industrial wells
have been closed or seriously affected
by contamination
-------
Non-point sources
Agriculture
Road salt
Point sources
Residential septic systems
Leaking underground storage tanks
Surface Impoundments
Landfills
Transportation losses
Groundwater pollution
Contaminated
Wil»r
Supply
Fum«/Expk>»lon
Spill Sit*
Surface
Contamlnatton
.
-------
Types of groundwater pollution
Free product
Most severe
Limited area
Source of soil & water contamination
Contaminated soil
Severity is soil dependent
Follows free product movement
Source of water contamination & fumes
Contaminated water
Lower concentration
Greatest area
High public exposure
Total microblal number} in shallov^uifers
Norm*), OK
St.LouaPtc.ra
Ontjno.C»ft*Jj
Cwoe.TX
Picfcttt OK
C
CD pristine Q conUmiruttd
<
vittr ' 1
sanof
1123456
, )
7 «
log number of cells / gdv or ml
-------
Cor* Retainer Cort Barnl
AdapKr
Hinged Teeth
FIG I Con«| (Jcvtcc
D CD
Cor* Barrel Extruding Block
Hydraulic
Cylinder
-------
Total and uiable bacteria uiith depth
i
0
9
c
0
u
n
t
s
/
9
d
w
10
D total counts
CPU
\
0.2 147 387 457 592 668 777 860
Depth ( feet)
Eucaryotes In the subsurface
10 12 14 16 18 20
cell/gttv
-------
Questions About Subsurface
Microorganisms
• Are they metabolically active?
• How diverse is their metabolism?
• What factors serve to stimulate and/or
limit their growth and activity?
• Can we take advantage of their metabolism
for aquifer remediation?
Metabolic Processes Detected in the Subsurface and Oxygen
Requirements
Metabolic Oxygen Reference
Process Requirement
I B10DEGRADATION OF ORGANIC POLLUTANTS ~
A) Petroleum Hydrocarbons Aerobic 21.46.58.J9.60.61.S2
B) Alkylpyridines Aerobic/Anaerobic 63
C) Creosote Chemicals Aerobic/Anaerobic 26.55
D) Coal Gasification Products Aerobic 52
E) Sewage Effluent Aerobic 53.64.65
F) Halogenated Organic Compounds Aerobic/Anaerobic 21.24.25.46.66.67
G) Nitrilotriacetate (NTA) Aerobic/Anaerobic 67.68
H) Pesticides Aerobic/Anaerobic 25.67.68
Metabolic Processes Detected in the Subsurface and Oxygen
Requirements - Continued
Metabolic
Process
II Nitrification
III Denilrificalion
IV. Sulfur oxidation
V. Sulfur reduction
VI Iron Oxidation
VII Iron Reduction
VIII. Manganese Oxidation
1! Methanogenesis
Oxygen
Requirement
Aerobic
Anaerobic
Aerobic
Anaerobic
Aerobic
Anaerobic
Aerobic
Anaerobic
Reference
69.70.71
55.67.72
73
74.75.7677,
73.79
53.55
79
24.25.53.76
,78
.80.81
-------
i conditions and biotrinsfaraitiom In i polluted iquiftr
u.ir, 1964)
CHEMICAL SPECIES
ELECTRON ACCEPTORS
BIOLOGICAL CONDITIONS
AEROBIC |
HCTEROTncpuci
RESPIRATION |
SUl'ATC
OH
CHj
OM
OH
0
CM
OM
COO
OH
-co,
fttdox Conditions Biod«r,tad»bi 1 Hy LJg Tin* Reljtive Rao R«[.
Aerobic
Denitrifying
Sulfjtt Reducing
Htlhanogenlc
(I) Hopper. 1976, 1978; (2) Bosseri 4 Young, i986; (3) tik 4 Wlddel. 1986;
(4) Smolensk! 4 SuMlta, 1987; (5) Codsy «i il., 198J; (5) Senior 4 Bilba,
1984.
-------
Oe;rje«iion of pollutants in in
lerooic jnd tn l methano;emc
biofiH celling IBd-aer. 19341
Aeroeic
Acetitt
CMorobtn;«n«
1 ,*-0
-------
MICROCOSM SAUPtINQ AMAMATUS
i
T»ne*
Stoococt
<&
OjAlJTATlVt ASStSSMEKTS
IkWtM "a
woral C
-------
UTIUTV OF MICROCOSMS
Risk Rssessmont
llJoste Rsslmllatory Capacity of an Enulronment
Transport of a Contaminant
Fete of e Contaminant
A) Identify biodegradable pollutant!
B) examine the effect! of tubstate
concentration on blodegrodotlon
C) determine blodegredatlon
pathway*
0) estimate rate* of
blotrantformatlon
RUBNTHGES OF MICROCOSMS
Repllceble
Uary chemical and physical poromel
Perturbable
Manipulate trophic structure
Control of Inports and exports
Can be time efficient
Ruold field pollution
Rccesslble and Containable
MICROCOSMS
Contalnerlzotlon
Structural and functional disturbance
high Initial costs
high operating costs
high surface to volume ratios
-------
EASE OF EXTRAPOLATION
Mole hill
Mountain
Bocttriol
physiology
MODERATE
Human
phytlology
Surfoc*
microbiology
PROBABLY
EASY
Subiurloc*
microbiology
Factors Influencing Pollutant
Biodegradation
• Existing Environmental Conditions
• Physiology of the Requisite
Microorganisms
• Chemical Structure of the Contaminant
-------
Organic Materials That Persist In Various Habitats
Organic Material
Human Hair
Protolytic
Enzymes
Wood
Microbiol Spores
Oil Deposits
Source
Desert
Cemetery
Permafrost
Soils
Soil/Lagoons/
Peats
Fresh Water
Sediments
Subsurface
Age (Yrs.)
*5x 103
»5x 103
2-20 x 103
3 x 104
4x 108
Environmental Barriers
To Biodegradation
Environmental Barriers
To Biodegradation
-------
Potentially Limiting
Environmental Factors
• pH
• Salinity
• Other Synthetic Chemicals
• Heavy Metals
• Osmotic Pressure
• Hydrostatic Pressure
• Free Water Limitations
• Radiation
Physiological Barriers
To Biodegradation
A contaminant will be a poor substrate if:
• No active microorganism is present, therefore, no
available enzymatic machinery
• Microorganisms present, but...
— Substrate is a poor inducer
— Substrate concentration is too low
— Substrate fails to enter cells
— Cell lacks other essential nutrients
— Inhibition/toxicity of enzymes by substrate or
products
— Other necessary microbes are absent
-------
0 H
II I
O-C-N-CHg
CAR8ARTL
1-NAPHTHOL
4-H,4ftij.|. 3.4-Omifrnrl-
IctMtaM IctrtUA*
CH/OCOOM «
TOM .
-.">?.
•5SX^M°I V«S>COO« I k>
OH
V>l«>UMi>i<> bllulk 1.14 rm»l M^r^^u.M
\ »
-------
Chemical Barriers
To Biodegradation
Effect of Branching
COOH
ClMvag* Points
H2-CH2-CH2-CH2-CHZ-CH2-CH- COOH -
I
Qutttnwy /J
Cirboo Alom/ ^
l-Phtnyld«con« l-Ph»nyl-4-mclhyld«con« l-P(icflyl-4,4-dim«thyl««cone
Uit'ococcui cerilicans H 0 I-N
Uicrococcvs ctntitoat MO 3
tiicrocotcia etnticont H 0. *
Uicrocotcus etnlieaits S-18.2
Uitroceceul eenfitans S-W.I
PsetMtoatoaat atraguioso 119 JWF
PltiHfomooos atrugimaa 191 JWF
Pstijdomonos aeruginoso Sol 20 JS
Wycotacterium pi lei No. 4SI
Uycotocttrium lerluilum No. 389
Mycobotttrium fheaocnieut No. 382
Hfcotecttrium smefmatti No. 422
Nocara.a opoco
Notordia rub'Q
Nocardio trftnnpolit
fioeorgia palffti'omogtntl
Nataraio earollma
2
2
2
2
2
2
2
2
2
2
0 C
0 C
2 1
2 C
2 C
2
2
2
2
2
)
I
I
3
)
The rale of eaierobic monorialobenzwte metabolism exhibited by an enrichment
of Cehalogenating bacteria
P05ITIOH
-DEHM.OGENATION RATE ( umoles / I / hr )-
Cl Br
ORTHO
flfTA
PM1
n.d
0
0
0
4.63
0
1.20
3.70
0.05
050
0.89
0.66
-------
Ease of Biodegradation
Labile
Structural
Analogs of
Natural
Materials
Recalcitrant
Chemicals With
No Natural
Counterpart
Biodegradability
^
3
I
1
I
I
1
4
t
r
*
1
s
1
s
rr
^
5
i
2!
1
EASy
^
r
'
-«
1
1
1
«
b
^
r
^
IV
X
S\
O v
"""
-------
Biodegradation of organic
contaminants
Carbon , ___ ^
_
Hydrogen
Coll Malarial
C, H, N, P, O,
Traca Minerals
C, H, N, P, O,
Traca Minerals
j Carbon
Dioxide,
Water
Bioreclamatlon stimulates this natural process
outside water source
r DIRECTION OF GROUND WATER FLOW
A fa
r* *
INJECTION SYSTEM
f.
[X
\
ZONE OF CONTAMINATION
T T T T T T T ? )
poeumaic recovery
pump
j i i i i i rr
. RECOVERY SYSTEM
1 t t
1 1
What Is In Situ Remediation?
In Situ: "In the natural or original
position"
Remediation: "A process of correcting or
counteracting an evil"
.% In Situ Remediation is the process of
correcting a contamination problem in
the environment in which it occurs
-------
TO SEWER OR
RECIHCULATE
gliJ
II
NUTRIENT
ADDITION
TANK
T COMPRESSOR t*SZL-G-C**-1
COARSE
SAND
PRODUCTION WELL
WATER TABLE-i
'—~ _ SPILLED MATERIALS """"
WATER SUPPLY
-INJECTION WELL
PARGER
CLAY
Air
Compr«it«r ttr
Hydrogtn Pooildt
Tank
ill Addition
Indlirtilon Qilloy
Topptd Hydrocirbont
Walir
Monilodng W«ll
R«co««ry
flduantoges of biorestoration
Can be used to treat some common aquifer pollutants
Enulronmentally sound - complete destruction of contaminant
Utilizes Indigenous microorganisms
Treatment moues tulth the mater
Economical
Bacteria are subject to Inhibitors
Bacteria can potentially plug formations
Incomplete degradation can lead to taste and odor problems
Maintenance Intenslue
Limited to aquifers of high permeability
Long term effects unknown
-------
REFERENCES
1} McKay, D.M., P.V. Roberts and I.A. Cherry, 1985. Transport
pf organic contaminants in qroundwater. ENVIRON SCI TECHNOL,
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-------
14) Kobayashi, H. and B.E. Rittnann, 1982. Microbial Removal
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-------
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31) Norris, R.D. and R.H. Carlson, 1980. The Role of Oxidizing
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243.
35) Fogel, M.M., A.R. Taddeo and S. Fogel, 1986.
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37) Horvath, R.S., 1972. Conetabolign of the Herbicide 2.3.6-
Trichlorobenzoate bv Natural Microbial Populations. BULL
ENVIRON CONT TOX. 7: 273-276.
-------
38) Brunnar, W., S.H. Sutherland and D.D. Focht, 1985.
Enhanced Biodegradation of Polvchlorinated Biohenvlg in Soil bv
Analog Enrichment and Bacterial Inoculation. J ENVIRON QUAL
14: 324-328.
39) Crawford, R.L. and W.W. Hohn, 1985. Microbiological
Removal of Pentachlorophenol from Soil Using a Flavobacterium.
ENZYME MICROS TECHNOL. 7: 617-621.
40) Canter, L.W. and R.C. Knox, 1985. In-Situ Technologies.
In: Ground Water Pollution Cont;r_o_l. Lewis, Chelsea MI p
143.
41) Atlas, R.M. and R. Bartha, 1981. Microbial Ecology;
Fundamentals and Applications. Addison-Wesley Co., Reading.
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42) Cerba, C.P., 1985. Microbial Contamination in the
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and P.L. McCarty, eds. John Wiley and Sons, New York, pp. 53-
67.
43) Matthess, G. and A. Pekdeger, 1985. Survival and Transport
of Pathogenic Bacteria and Viruses. In: Ground Water Quality*
C.H. Ward, W. Giger and P.L. McCarty, eds. John Wiley and
Sons, NY, pp 472-482.
44) Updegraff, D.M., 1982. Plugging and Penetration of
Petroleum Reservoir Rock bv Microorganisms. Proceedings of
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45) Jenneman, G.E., M.J. Mclnerney and R.M. Knapp, 1985.
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46) Wilson, J.T., J.F. McNabb, D.L. Balkwill and W.C. Ghiorse,
1983. Enumeration and Characterization of Bacteria Indigenous
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QUALITY. (C.H. Ward, W. Giger and P.L. Mccarty eds.), John
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49) White, D.C., et al, 1985. piochenical Measures of the
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-------
50) Ghiorse, W.C. and D.L. Balkwill, 1983. Enumeration and
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51) Webster, J.J., 6.J. Hampton, J.T. Wilson, W.C. Ghiorse and
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52) Humenick, M.J., L.N. Bitton and C.F. Mattox, 1982. Natural
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53) Godsey, E.M. and G.G. Ehrlich, 1*78. Reconnaissance for
fljlcrobial Activity in the Maoothv Aquifer. Bav Park. New York.
Four Years After Artifical Recharge. J RES US GEOL SURVEY. 6:
829-836.
54) Ventullo, R.M. and R.J. Larson, 1985, Metabolic Diversity
and Activity of Hatirotrophic Bacteria in Ground Water. ENV
TOXICAL CUEM. 4: 759-771.
55) Ehrlich, G.G., E.M. Godsay, O.F. Goerlitz and M.F. Hult,
1983. Microb^a,! Ecoloorv of a Creosote-Contaminated Aquifer at^
St. Louis Park. Minnesota. DEV IND MICROBIOL. 24: 235-245.
56) Ladd, T.I., R.M. Ventullo, P.M. Wallis and J.H. Costerton,
1982. Heterotrophic Activity and B^odflgradat^gn of Labile and
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57) Harvey, R.W. D.L. Smith and L. George, 1984. Effect of
Organic Contamination Upon Microbial Distribution and
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58) Wilson, J.T., M.J. Noonan and J.F. McNaJab, 1985.
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Wiley and Sons, Inc. New York. pp. 483-498.
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MICROBIOL. 16: 305-312.
61) Raymond, R.L., V.W. Jamison and J.O. Hudson, 1977.
Beneficial Stimulation of Bacterial Activity in Groundvaterg
Containing Petroleum Products. AIChE SYMP SER. 73(166): 390-
404.
-------
62) Lee M.D. andC.H. Ward, 1985. Biological Methods fgr. t
Restoration Of Contaminated Aquifers. ENV TOXICAL CHEM. 4:
721—726 .
63) Rogers, J.E., R.G. Riley, S.W. Li, M.L. O'Mallay and B.L
Thomas, 1985. Microbial Transformation of Alkvlnyridineg in
Groundwater. WAT AIR SOIL POLL. 24; 443-454?
64) Aulanbach, D.B., H.L. Clescari and T.J. Tofflemire 1975
Hater Renovation bv Discharge into Deen Natural Sand FIH-ArV
PROG OF AICh£ CONF.y May 4-87 1975, Chicago, IL. * "™rff •
65) Harvey, R.W., D.L. Smith and L. George, 1984. Effect of
Organic Contamination Upon Hicrobial Distribution ^n"
Heterotroohic Uptake in a Cane Cod. Mass.. AmHf?r- APPL
ENVIRON MICROBIOL. 48: 1197-1202.
66) Wood, P.R., R.F. Lang and I.L. Payan, 1985. Anaerobic
Trana formation. Transport and Removal of Volatile Chlorinated
Organics in Groynd Wa^ag. In: GROUND WATER QUALITY, C.H.
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68) Vantullo, R.M. and R.J. Larson, 1985. Metabolic Diversity
and Activity of Heterotroohic Bacteria in Ground Water. ENV
TOXICAL CHEM. 4: 321-329.
69) Barcelona, M.J. and T.G. Naymik, 1984. Dynamics of a
Fertilizer Plume in Groundwater. ENVIROK SCI TECHNOL. 18:
257-261.
70) Idelovitch, E. and M. Michail, 1980. Treatment Effects and
Pollution Dangers of Secondary Effluent Percolation to
Groundwater. PROG WAT TECH. 12: 949-966.
71) Preul, B.C., 1966. Underground Movement of Nitrogen.
ADVAN WATER POLLUT RES, PROC 3RD INT CONF. pp. 309-328.
72) Lind, A.M., 1975. Nitrate Reduction in the Subsoil. PROC
INT ASSOC WATER POLLUT RES. Copenhagen, Aug. 18-20, 1975. 1:
14.
73) Olson, G.J., G.A. McFeters and K.L. Temple, 1981.
Occurrence and Activity of Iron and Sulfur-Oxidizing
Microorganisms in Alkaline Coal Strip Mine Spoils. MICROS
ECOL. 7: 40-50.
-------
74) van Beak, C.G.E.M. and 0. van der Kooij, 1962. Sulfata-
Reducina Bacteria in Ground Water from Cloaaina and Noncloaaina
Shallow Walla in the Netherlands River Region. GROUND WATER.
20: 298-302.
75) Jacks, G., 1977. The "Amber River:1* An Example of Sulfata
Reduction. PROC 2ND INT SYMP WATER-ROCK INTERACT. Strasburg,
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Producing Bactaria in Groundvatar. ACT PATHOL MICROBIOL SCAND.
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1981. Sulfata-Raducinq Bactaria from Deep Aouifara in Montana,.
GEOMICROBIOL J. 2: 327-340.
79) Hallburg, R.O. and R. Kartinall, 1976. Vyredox - In Si,tu
Purification of Ground Water. GROUND WATER. 14: 88-93.
80) Belyaav, S.S. and M.V. Ivanov, 1983. Bacterial
ftethanogenaia in Under Ground Waters. ECOL BULL. 35: 273-280.
81) Davis, J.B., 1967. PETROLEUM MICROBIOLOGY. Elsttvier Pub.
Co., Anatardan. p. 604.
-------
TRANSPORT AND FATE
BIOTRANSFORMATION
PROCESSES
Session 6
Joseph M. Suflita
(University of Oklahoma, Norman)
-------
MICROBIOLOGICAL PRINCIPLES
INFLUENCING THE BIORESTORATION OF
AQUIFERS
BY
Joseph M. Sufflta, PhD.
Department of Botany and Microbiology
The University of Oklahoma
Norman, Oklahoma 73019
Sum mary: The second seminar briefly considers various treatment options for the
clean-up of contaminated aquifers and shovs hov and why biorestoration techniques
fit into the myraid of pollution mitigation tools. Attention is given to the types of
considerations that must be made before an aquifer biorestoration strategy is
implemented in the field. The example of spilled gasoline in an aquifer is chosen to
help illustrate specifically how chemical, physical and microbiological principles
meld into an overall aquifer treatment strategy. Guidelines for the critical evaluation
of the claims for aquifer restoration are also given with specific suggestions for the
types of information that might be collected to bolster such claims. Particular
attention is also paid to /a situ biorestoration attempts that rely on the inoculation of
desirable microorganisms. Lastly, a perspective on biorelamation techniques is
provided through a consideration of the pratical limitations of the technology. This
then leads to the realization that properly considered. bioreclamaUon is not a panacea
for the many different types of subsurface pollution problems but should prove
valuable under specific sets of circumstances.
-------
Subsurface contamination
Symptoms of
groundwater pollution
» Contaminated water well
- Odor, taste, free product
- Potential health risk
• Fumes
- Explosion risk
- Potential health risk
• Surface water contamination
- Oil seeps, color/odor, fish kills
-------
Fate of a Contaminant
Environment
Movement
Retention
Reaction
Contaminant
Rate Ground Water Flow
Permeability
Soil Type
Organic Content
pH
Redox Conditions
Microbial Communities
Amount of Material
Physical State
Solubility
Viscosity
Surface Tension
Solubility (Lack of)
Ionic Character
Chemical Reactivity
Biodegradability
Mechanisms Affecting Fate
• Movement
— Gravity
— Ground water motion (vertical and horizontal)
— Dissolution
• Retention
— Sorptlon
— Properties of contaminant
• Reaction
— Hydrolysis
— Precipitation
— Oxidation/reduction
— Biological transformation
These mechanisms controlled by chemical properties
of contaminant and subsurface environment
The fate of a contaminant is determined
by its
• Transport
• Reaction with the environment
Remediation is governed by the same
factors
-------
Treatment Options
High
Transport
o
CO
-------
Containment
• If it moves slow, it can be contained
• But, the contaminant persists
• Methods
— Slurry walls
— Clay caps
— Interceptor trenches
— Hydraulic barriers
Extraction
• Easily transported substances
• But, requires surface treatment
— Air stripping
— Carbon
— Reaction
— Discharge
• Methods
— Water
— Venting
Reaction
• Reactive species can be treated in situ
— Chemically - Oxidation, Reduction, Hydrolysis,
Polymerization
— Biologically - Degradation, Mineralization
• Treatment chemicals/nutrients must be transported
• Methods
— Chemical reclamation
— Enhanced bioreclamation
-------
HOUIFfRRCMFDIflTIONCONSIDlllflTIONS
R. Type of Contaminant
phaies, solubility, susceptibility to blodegradatlon
B. Pathways of Blodegradatlon
C. Site Characteristics
hydrology, geology, depth to water table
D. Removal of Free Product
E. System Design
above or below ground
F. Laboratory Inuestlgotlon
eueluation of blodegredatlon
G. Operation of Blostlmuletlon
lab effort to design stimulation, extrapolate to field
H. Monitor Progress
The Ideal Site
• Homogeneous, Permeable Soil
• Single Point Source
• Low Groundwater Gradient
• No Free Product
• No Soil Contamination
• Easily Degraded, Extracted or
Immobilized Contaminant
The Real Site
Solids. Viscous Liquids
(Insoluble Liquids
jLow Solubility Species
(Adsorbent Species
Tension Saturated Zone
f _______________ "_J^-__
Vs _ Free Product '
Light Jnsoluble Liquids ^ Water
Table
Saturated Zone
[•• Groundwater flcw$
Soluble Species
Dense. Insoluble Liquids
-------
Hydrogeologlc Variables That Impact
In-Situ Remediation
• VadoseZone
— Thickness
— Permeability (Horizontal + Vertical)
— Geologic Complexity
— Organic Content
• Saturated Zone
— Type of Aquifer (Composition)
— Thickness of Shallow Aquifer
— Interconnection of Aquifers
— Location of Discharge Area
— Water Table Fluctuations
— Ground Water Flow Rate
Major Classes of Gasoline Components
Hydrocarbon Conroe. Colinga. Jennings.
Class Texas California Louisiana
Alkanes 16.8 18.0 24.5
Cycloalkane 47.1 55.5 38.4
Aromatic 19-5 10.2 15.6
-------
Metabolic Pathways
Alkane Degradation Path
CH3 - (CH2)n - CH3 Alkane
/ Terminal '
H _ / Methyl
HZ° t Group
CH3 - (CH2)n - CH2OH Alcohol ^ OxW«ton ,
+ O, -.. I
"•*>
CH2
J-
2H
CH3 - (CH2)n - CHO Aldehyde
HjO -J-2H
CH3 — {CH2)n - COOH Fatty Acid
/! -Oxidation
CO2 * HjO
Allcyclic Hydrocarbons
OH
-2H
^
Cycloh«xane
O
r^o .
O
0-Caprolactone
V ^
J *k
HjO
Cyclohaxanol Cyclol
COOH
CH2
CH2
CH2 -
1
^-Oxidation '
O
A °^^H
u«o
I
COOH
Adlpic Acid
-------
Aromatic Hydrocarbons
B»m«n«
s-einztn* Oihydrodlol
Cil«chol
• H
rOH
tOH'
'H
2-Hydroxy^it. d»- * elt-Mueonte Acid
Moconie S«nc«l
-------
How does
bioreclarnation
work?
Enhanced bioreclamation
Contaminated aquifer
Contaminated
area
-~~ -tablt
Enhanced bioreclamation
Creating a reaction vessel
R*cycl«d
ground
water
Enhanced bioreclamation
Creating a chemical environment
Recycled
Ground
wat«r —v
Aj
EZS Nutrlont (low
BS Bloactlvo aroa
[El Contaminant
V-^f^^-ii
-------
Enhanced bioreclamation
Managing in situ biodegradation
Recycled
ground
water
Nutrient flow
Bloactlve area
Contaminant
water
Enhanced bioreclamation
Site remediation
Recycled
ground
water —i
Nutrient flow
Bloactlve area
Contaminant
- --.- f "', ^*-'>-*?-.r-v^vcrJ-F-.**r-t'J
-------
Bioreclamation Works Because:
• Hydrocarbon degrading microorganisms
are widely distributed
• Hydrocarbons are essentially natural
substrates
• Over 30 years of basic scientific
information
• Nutrient requirements for metabolism are
well understood
Carbon Adsorption
Circulation Rate
Influent Cone.
(Initial)
Project Timing
Project Costs ($K)
Construction
(Inc. Elect.)
Carbon Replac. (Annual)
Operator (Annual)
50 gpm
80 ppm
10-20 yre.
420-600
90
15
18
100 gpm
40 ppm
10-20 yre.
600-1000
200
15
25
Enhanced Bioreclamation
Circulation Rate
Project Timing
Project Costs ($K)
Design & Startup
Nutrients
Service & Equipment
Operator
50 gpm
8-10 Months
220-290
50-75
90-112
70-88
10-15
100 gpm
4-5 Months
180-241
50-75
90-112
35-44
6-10
Contaminant* treated by
In situ Bloremedlotlon
fl. Hydrocarbons
gotollne
mineral oil
aliphatic piatllclzeri
B. Solvents
methyl chloride
n-butenol
acetone
ethylene glycol
Ijoproponol
letrehydrnftiran
chloroform
C. Other compounds
dimethyl aniline
-------
Flom Characteristics Of flgulfers UJhere
Bloremedlatlon Has Been Tried
Pumping Rote
25-380 (l/mln)
Flow Rate
0.6 - 800 (m/y)
Hydraulic Conductiuity
10"5 - 10"3( cm/sec)
CniTICRL EUflLUBTION OF BIORESTORflTION CLfllMS
Reduction In Substrate Concentration - Mass Balances
Increase In Blomass/Rctlulty
Production of Catabolltes
Consumption of Terminal Electron Receptors
Rdaptatlon / flccllmatlon Phenomena
Blodegradatlon Kinetics
RLl FflCTOBS REIRTIUE TO flPPROPRIRTE RBIOT1C CONTROLS
B
IOO
50-
r
4-Amino-3,5-
dichloro-
benroote
4-Amino-3-
chlorobenzoate
5 15 20 25 30 0 3 6 0 5 20
INCUBATION TIME (DAYS)
-------
o
"o
E
o
o
E
LU
t—
CC
h-
m
Z>
2
_l
7— •
6-
5-
4-
3-
2-
\-
Q-
K
1
\
)
_x,4-NH2-3,5-diCI-BZ
-^3-I-BZ
^3-Br-BZ
ADAPTATION
exPT 3-Bi 3-1 J.J-diCI
A 27 34 39
B 21-24 Z8 29-39
3-F-BZ ^?\^
3-ci-ez ^
PERIOD (DAYS)
4.MMj.3,5(,iCl J.C, j.F
80-69 ISO-170 >|TO
37 129-148 >365
0 4O 80 120 160
- r 1 1 r 1
2OO 240
TIME (DAYS)
SUBSTRATE
COO-
COO"
COO-
ADAPTATION TIME
20 days
23-35 days
39 days
_O
O
E
o
v_
o
1
llJ
<
CC
t-
V)
CO
80 120 160 200
TIME (DAYS)
240
-------
400pM 3-F-BZ
40OpM 4-NH9-3,5-diCI-BZ
20pM 4-NH2-3,5-diCI-BZ
20pM 3-F-BZ
80 120 160 200
TIME (DAYS)
240
BEflSONS FOR LBG PERIOD PRIOR TO BIODEGRflDflTiON
Requirement for bacterial growth
Specific substrate concentration
Need to deplete competing substrates
Nutrient limitations
Need to etichange genetic material
Laboratory artifacts ????
-------
SITE ADAPTATION PERIOD0
I 5 WKS
2 4-5 WKS
3 4-5WKS
4b 4-6 WKS
aaverage of 10 replicates
bstored sample (2yr);slie 2
CRN BIODEGRflDflTIQN BE STIMULRTED ????
VES -- BUT
REQUIRES RN UNDERSTflNDING OF THE
FRCTORS CONTROLLING THE
LflG RNO RDRPTRTION PERIODS
-------
POSSIBLE STIMULRTION RPPRORCHES
CROSS RCCLIMRTION
RNflLOG •ENRICHMENT1
OUERCQMING NUTRIENT LIMITRTIONS
BIOMRSS ENRICHMENT
OUERCOMING ENUIRONMENTRL FRCTORS
OTHERS...
SUBSTRATE TESTED
for CROSS -
ADAPTATION
CO
r^
Cl^x
rffi*
t
C0<
^^^^
C0(
C
coc
C
C|S^O» V*
C0(
C
D-
1
I
>-
L
)-
)-
3-
ADAPTATION
TIME
(WK)
3-8
0.5-4
2- 3
2-3
32-40
TIME(wk) for COMPLETE
DEGRADATION In SEDIMENT
ADAPTED TO:
coo- coo-
2-3 2-3
<.
-------
20
o
3
cf
u
adapted from. I.-S. You and R.
Bortho i982flppl.Enulron.
Mlcroblol. 44:678-681
Days
FIG. 1. Effect of aniline on the mineralization of
OCA (5 u,g/g) in soil. (A) 1.8 mg of aniline added per g;
(B) 0.4 mg of aniline added per g; (C) no aniline added:
(D) poisoned by HgClj. Aniline additions to (A) were
made in three increments on days 0, 18, and 37, up to
the total specified above.
2O
adapted from, I.-S. You andfl
Bortha I982flppl.tnulron.
Mlcroblol. 44: 678-681
Days
F.1G 2 Effect of aniline on the mineralization of
humus-bound DCA in soil. HA-DCA complex (0.5
mg/g) containing 2.5 ng of bound DCA per g was
incubated with (A) and without (B) 1.4 mg of aniline
per g. Aniline was added in two increments on days 0
(0.4 mg) and 12 (1 m«).
-------
40
30
E
•
e
g
t-
10
from, J.T. UJIUon and B.H.
Will on. 1985 flppl. Enulron
Mlcroblol. 49:242-243
All** Vclilllll • I
»«!••«•« vllk All**
5.5
6.5 7.5
Port Volumtt
6.5
FIG. 1. Removal of TCE during passage through unsaturated soil
exposed lo an atmosphere of 0.61* methane (vol/vol) in air.
Selected List Of Organs
Substances Subject To Co-Metabolism
ETHANE
PROPANE
3-CHLOROBENZOATE
2-FLUORO-4-NITROBENZOATE
o- or p-XYLENE
PYRROLIDONE
2,3,6-TRICHLOROBENZOATE
2,4,5-T
DDT
-------
WOULDN'T VOU UJflNT fl PRODUCT THRT:
SUBSTITUTES FOR FERTILIZER flND LIME
GET RID OF EHCESS HERBICIDE RESIDUES
6IUES HIGHER GROWTH VIELDS
MRKES DEPLETED SOILS COME RLIUE
GIUES PLRNTS RN UNEHPLRINED PROTECTION FROM DISERSES
GIUES LUSTER TO GRRIN
SIIRUIURL OF
JunniLflTED INTO SOIL
from Kotznelson, H. 1 94fla,b Soil SCl 19: 21-31, 283-293
OR6HNISM
ffctwocycetet
cellulosae
Bacillus cereuf
Pteudomonfft
f/uoretcenf
ttzolobacter
chroococcum
Manured Soil
Manured and Limed Soil
45
— INCUBRTION (DRYS)
100 0 45 100
NUMBERS PER GRflM DRV SOIL •
24.7 7.7 7.1
8.4 0.1 0
23.2 57.4 49.3
142.8 0 0
200 0,300*0
33.9
2.7 2,2
7.6 0.04 0
86.9 8.6 12.3
175
360
1.1 0
120 0
* relnoculated
-------
:> u (vi ivi t K
100
or
UJ
o
m ai
.01
.001
FECAL
COLIFORM
100
-1- .001
FECAL
STREPTOCOCCUS
10 20 30 0 10 20 30
TIMEtdoys
100
WINTER
T
FECAL
STREPTOCOCCUS
10 20 30 40 50 60 70
Tl ME, days
-------
SELECTED flBlOTIC FflCTORS
LIMITING THE SURUIURL OF
MICROORGRNISMS
fl)pH
B) Temperature
C) Salinity
D) Water
E) Pressure
8
W
o
«t-
O
6
c
o»
o
STRAIN
123
R hizobi um JQ ponicum
8r
Sterile soil
Non-sterile soil
0 10 20 30 40 50
STRAIN
58 6
Sterile soil
Non-sterile soil
0 10 20 30 40 50
TIME (days)
-------
8r-
O
V)
-------
Microbiological Profile of a Soil Treated tuith Inoculonts
Bacteria flctinomycetes Fungi
Treatment CK Litter CK Litter CK Litter
1 • 105 / g Soil
Untreated 31 60 46 100 4 16
Medina 37 32 32 119 6 12
Supernate 39 39 40 100 4 10
EFFECT OF MICROBIRL INOCULRNTS ON SOIL
RESPIRRTION
SOIL
TRERTMENT CHECK PINE LITTER
mg C02 euolued-
Untreated 36 94
Medina 25 94
Supernate 21 97
-------
HflBITflT
RN flBEfl OF UNDEFINED SIZE WITH fl DEGREE OF
UNIFORMITY IN CHRRRCTERISTICS OF ECOLOGICflL
SIGNIFICRNCE FOR RN ORGRNISM. THE 'ffWffW
OF RN ORGRNISM
NICHE
R TERM USED TO DESIGNRTE THE UNIQUE FUNCTIONS
OF RN ORGRNISM IN ITS HflBITflT. THE
•OCCUPffTWNm OF flN ORGRNISM
COMMUNITY
THE ORGRNISMS INHRBITING fl GIUEN HflBITflT
ECOSYSTEM
THE COMMUNITY OF ORGRNISMS IN fl SPECIFIC
ENVIRONMENT RND THE RBIOTIC SURROUNDINGS
WITH WHICH THE ORGRNISMS RRE flSSOCIRTED
HOMEOSTRSIS
THE CflPRCITY FOR R COMMUNITY OF
MICROORGRNISMSTO REMAIN QURLITflTIUELY RND
QURNTITRTIUELY STRBLE UNDER fl UflRIETY OF
BIOLOGICflL RND NONBIOLOGICRL STRESSES
-------
BIQRESTQRRTION
IS NOT fl PflNflCEfl FOR flLL TYPES OF POLLUTflNTS
NEEDS TO BE CONSIDERED RS RNOTHER PRRT OF THE
POLLUTION MITIGRTION RRSENRL
-------
Alexander, M. 1971. Microblal ecology. John Wiley and Sons Inc., New York.
Brown. M. E. 1974. Seed and root bacteHzatlon. Ann. Rev. Phytopath.
12:181-197.
Katznelson, H. 1940 a. Survival of Azotobacter 1n soil. Soil Sc1. 49:21-35
. 1940 b. Survival of microorganisms Introduced Into soil.
Soil Sc1. 49:283-293.
Miller, R. H. 1979. Ecological factors which Influence the success of micro-
Van Donsel, F. J., E. E. Geldreich, and N. A. Clarke. 1967. Seasonal varia-
tions 1n survival of indicator bacteria 1n soil and their contribution tc
storm water pollution. Appl. M1crob1ol. 15:1362-1370. '
Haksman, S. A. and H. B. Woodruff. 1940. Survival of bacteria added to soil
and the resultant modification of soil population. Soil Sci. 50:421-427.
Weaver, R. W., E. P. Dunigan, J. P. Parr and A. E. Hiltbold. , (Eds.) 1974.
Effect of two soil activators on crop yields and activities of soil micro
organisms 1n the southern United States. Southern Cooperative Series
Bull. 189. Texas Agric. Exp. Stn., College Station, Texas.
-------
EPA/600/2-87/008
January 1987
LEAKING UNDERGROUND STORAGE TANKS:
REMEDIATION WITH EMPHASIS ON IN SITU BIORESTORATION
by
J. M. Thomas, M. D. Lee, P. B. Bedient, R. C. Borden,
L. W. Canter and C. H. Ward
NATIONAL CENTER FOR GROUND WATER RESEARCH
Rice University, Houston, Texas 77251
University of Oklahoma, Norman, Oklahoma 73019
Oklahoma State University,Stillwater, Oklahoma 74078
Cooperative Agreement No. CR-812808
Project Officers
Marion R. Scalf and Jerry N. Jones
Applications and Assistance Branch
Robert S. Kerr Environmental Research Laboratory
Ada, Oklahoma 74820
ROBERT S. KERR ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
ADA, OKLAHOMA 74820
-------
coniirrs
i. if ua MOLflorcAi ruunon
1. HUroblal Activity Tn
Mlcroblal processes My b. used to degrade contaminant* In situ by
stimulating th. native mlcroblel popul.tlon. Anoth.r in tUa bloetlmulatlon
34
I.
JJJ IITV BIOLOGICAL TBtATMEVT J4-
1. Mlcroblal Activity In Aoulf.rT J4
Sampling MoIhod• for Subsurface Hlcrobe* ....... 3j
Hlcroblal Number* In th* Subourfac* . . . . 34
Hlcroblal Ecology of th* Subsurface. .... ! ! ! " ' 34
Metabolic Activity of th* Subsurface
Mlcroblal Community Jt
Environmental Factors Which May Limit Blodagradatlon '.'.'.'.'.'. 38
*• BlostlmuUtlon by Addition af Llmltlnit tmtrtente 41
Development, of the la Jit" Blostlaulatlon Procass
with Oxygen Supplied by Air Sparging 41
Application of th* denradatlve .ctlvlty of
iubsurfac* microbe* 4,
Flr»t application of th* blostli.il at Ion oroe««. ....'... 4t
Stjgs In th* biostliBulatlon prooss 43
AddlHonaJL caia hlstorl.s In which oxvuen was supplied
by air spartlnt 4J
Minimum hrdroearbon concentrations achievable fry
In iltu bloitlml.l;(on 41
Treatment trains 4B
'"Alternative Oxygen Sources ". ". 7~~.~'.~~ .~~r~— ;—,-•,—,—<—.—.—,~~.~.",~"5f
Hydror.n puroxlde ". . . . 52
Soil venting 54
-^ Colloidal it* aphrons 59
Summary _of_ Aerobic In Siiu Blo*tl*ulatlon.Proc*as** sf
fTnnovatlve'Procesies .'....'. i 45"
Land treatment 45
Technique* that reduce Interfaelal tension 47
Engymas es en Innovative treatment technique 48
Tr.atment Beds 48
PolsnVlalTor"Anaaroblc'Proc*ss*s."."~r". . '. ." . . ..'.... ,~" ti
Anaerobic degradation pathwaya in the subsurface «9
Anaerobic processes In In eltu blostlmuletlon 70
3. Addition of Sptelallred Mlcroblal Populations to the
Subsurface 71
Genetic Engineering to Enhance Dagradatlve Activity 72
Issues in Cunetlc Engineering of Microbes 73
Seeding Aqu«ou* Environments with Microorganisms 74
Seeding Soil Environments with Microorganisms 74
Seeding the Subsurface with Hlcronrganlems 77
Aqulf.r Remediation Using Inoculation Techniques 78
14. Enrichment of Specific FopuUtlont 81
technique which le not yet denonetreted le th* Inoculetlon of the eub.urfece
with t •Icrobltl population thet hee epeclellted netebollc cepebllltlee.
Iven In the presence of «n Indlgeneoui population which 1* tccllmted to the
orgenlc contuln.nl*, degredatlon My b* United et high contenlnent
concentration* or by io*e environmental factor. Addition of electron
ecceptort. euch a* oxygen, and Inorganic nutrient!, typically nitrogen,
phoaphorua. end trace eietaU, auy provide the alcroflora with eaaentlal
nutrlenti that are Halting In the pretence of high concentrations of
pollutants. Inoculation of a specialized laleroblal population My reduce
the tl»e required for acclimation to the contaminants and/or allow th*
renoval of recalcitrant eontamlnanti. Related process** such as the
eddttlon of bloeculslfUrs or eurfeetsnts to Increese the avalleblllty of
subsurface contaminants to th* mleroflor* can alao be u**d. Uh*n
applicable, biological processes may offer th* advantage of partial or
complete deatructlon of the contaminants rather than slnply transferring th*
pollution to another phase of the environment.
Technologies for bloreatoratlon of polluted aquifer, hav* resulted from
recent research Indicating that aubsurface mlcroorgsnlsma exist, are
•etebollcally active and often nutritionally divan*. A review, publlihad
by Dunlep and HcMabb (1473) of the Robert S. Kerr Environmental R*ae*rch
Laboratory, addressed subsurface biological activity In relation to ground
water pollution end Initiated most of th* research In this area . Before
publication of the review, the concept of biological activity below the
rhlroepher* had not been widely received. Hlcroblologlsta ware skeptical
sbout biological activity In the subsurface becaus* of ollgotrophlc
condition, below the rhliosphere (Leenh**r *t *l., 1974) and an early study
which had Indicated that mlcroblel number* decreesed preclpltouely with
depth (Uakaman, 19UK
Sampling Hethod* for Subsurface Mlcrob.a—
A document that described aaapllng methods for subsurface ulcroorganlaauj
was published In 1977, by the Knvlronmentel Protection Agency (DunUp et
al., 1977). Th* method for procuring a representative aampl* of unconsoll-
datad aubaurfac* soil has since been modified (Wilson *t el., 1981). A soil
•ample la collected by flrat drilling a borehole to e dealred depth with an
aug*r and than taking th* sample with a core barrel. After sample
procurement, th* cor* le extruded through a it.rll. paring device that
remove* the outer layar of soil thst hae come In contact with the cor*
barrel. The remaining .oil core Is thus uncontamlnated by the sampling
procedure and representative of the aubaurfac*.
Investigation* of mlcroblel activity In the subsurface conducted prior
to the development of the sampling techniques were equivocal beeauae of the
potential for contamination during sample procurement. In addition, many of
the Investigation* were conducted using u*ll wator Instead of core
materiel. Recent evidence suggests that the majority of aubcurface
microorganisms are associated with soil particles (Harvey et al., 1984). In
addition, well water may contain microorganisms that are artlfacta of the
well becaua* of cubsurface contamination during well installation and
changea In water quality around the wall.
35
-------
HlcrobUl dumber. In the Sub.urface--
H.thod. to .nuMrat. th. .ub.urfac. mlcroflora al.o hav. ba.n
developed. Il.ctron .Uroacopy. vl.bl. count*, .plfluore.c.nc. nlcro.copy.
and Me*ur»..nt« of bloche.lcal co.pon.nt. have been uaed to ..tlMt.
•Icroblal blo«.« (Chlor.. «nd B.lkwlll. 1985; Chlor*. and B.lkwlll. 198J;
Ull.on «t al.. 1983; S.lth et ml.. 1*84; Stetienb.eh et •!.. 1»B4; Snlth «t
el.. 1985; Balkwlll tnd Chlor*., 1985; Bon. and Balkwlll. 198«; W.beter et
• 1., 1985; Whit. «t al.. 1983; Hoo. «nd Sehw.l.furth, 1982; Ihrlleh «t ml.,
1983; P.derle et «t.. 1984). In contr..t to Uek.iaan'. .tudy (1914) which
r.port.d th.t .Icroblal number, declined with depth, unlforn population
level, around IO*-10T cella/g dry poll. .eaaured by eplfluore.eence
•Icro.copy. w«r. reported for profll.. of uncontamln.t.d .hallow aquifer.
(Chlor.e .nd Salkwlll. 198S; U.b.t.r «t »!.. 1985; Ullion »t ml.. 196J;
Chlora. and Balkvlll. 1983; Balkwlll and Chlor... 1985; Bon. and B.lkwlll.
im). How.v.r. baet.rla In a chalk aquifer (consolidated) wer.
aporadlcally dlatrlbot.d with d.plh (To-l.r «t ml., 198S). Clo»«
•xuluatlon of th. .ubiurf.c. ttrat. Indlcat... patehln.ja of, bact.rlal
population.; »a«pl.» fro. th. top of th. un.aturat.d ion. of an •«•'"'•"
aqulf.r yl.ldwl th. hlfh.ft count, wh.r... tho«. fro* b.drock and confining
lay.ra yU>ld»d th» low.ft total counts (B.loln .t al., 198»).
MUroblal Ecology of th. Sub.urfac.-- '
B.et.rla .r. th. predominant for* of •lcroor»anli» oba.rv.d In th.
•ubturfac. although a f»w hlgh.r llf. fon.. h.v. b..n d.t.ct.d (Ull.on .t
.1.. 198J; Chlor.. «.d Balk-Ill. 1985; whit. »t .1.. 1983). Sow •uc.ryotlc
for., which may b. fung.l «por.. or y.a.t c.lll h.v. b..n obi.rv.d In th.
upp.r 10 m of a .oil profit. (Chlor.. and Balkwlll, 1983; Hoo. and
Schw.l.furth. 1982; F.d.rl. .t »!.. 1984J. Baet.rla. prototoa. and fungi
h.v. b..n d.t.et.d In ...pi., of ground w.t.r eoll.et.d from on.-y.ar-old
w.ll. (Hlr.ch .nd «.d..-Rohkohl. H83). In addition. . .low-growing aao.ba
hat b..n l.olat.d and eultur.d fro« th. ground wat.r Int.rfac. of an
unconta»lnat.d .oil (B.lkwlU and Chlor... 1985; B.loln .t .1.. 1984).
H.tabollc Activity of th. Sub.urf.c. Mlcrobl.l Coi««.nlty--
org.nlc .att.r that .nt.r. th. unconla»lnet.d .ub.urf.c. 1. u.u.lly th.
.or. r.fr.ctory hu«lc .ub.t.nc.. which r..l.t d.gr.datlon whll. p.rcol.tlng
through th. biologically .ctlv. .oil ion.. Th. organic mat.rlal av.ll.bl.
for n.tabolla. by th. .ub.urfac. .Icroflora 1. lU.ly to b. In low
conc.ntr.tlon and difficult to d.gr.d.. Th. majority of »leroorg.nl.«.
pr.i.nt In .uch nutrl.nt-poor .nvlrotw.nt. .r. g.n.r.lly ollgotrophlc.
Ch.ract.rUatlon of th. .ub.urf.c. .leroflor. Indlc.t.. th.t th. baet.rla
ar. u.u.lly .ull.r «1.0 vm In .!«•) than tho.. In .utrophle
.nvlrom.«nt. and both Cra. po.ltlv. and n.jatlv. c.ll typ.. ar. P"""'
(Chlor.. and Balkvlll. 1983; Wll.on .t .1.. 1983; Chlor.. and Balkwlll
198S). Cra« po.ltlv. for., pr.do.lnat. In .any uncontanlnat.d .oil.. Tn.
Pr.do.ln.nc. of .Mil. coccold c.ll. and h.nc. a l.rg. .urf.c. to yolu«
ratio for .nh.ne.d nutrl.nt upt.k.. 1. . llk.ly nwchanl.. for .urv val In an
ollgotrophlc .nvlronm.nt .uch aa th. uncontanlnat.d .ub.urfae. (Ull.on .t
.1 19»3> In eonlrait, tubfurfac. toll eontanlnat.d with er.o.ot. wa.t.
w.i found to contain mor. bloi«.. and a gr.at.r proportion of Cra- n.j.tlv.
to Cram po.ltlv. .Icrob.. wh.n co^)ar.d to uncontaalnat.d .oil fro. th. .a»*
.It. (Smith .t .1.. 1985; S.lth .t al.. 1984).
Studio h.v. .l.o Indicated 'that .any lub.urf.c. nleroorg.nl... .r.
aatabolIcally actlv*. Of th. tot^l c.ll count, about 0.01 to 50 p.rc.nt can
b. r.cov.r.d by plating on .olid madia and .bout 1 to 10 p.rc.nt .xhlblt
r.aplr.Lory activity mua.ur.d by th. reduction of 2-(p-lodoph*nyl)
-l-p-nltroph.nyl)-5-ph.nyl t.tr.xolltua chlorld. by cytochro.*. (B.lkwlll and
Chlor... 1985; W.b.tnr .t .1., 1985). Hlerobl.l activity. ..a.ur.d by th.
hydrolyal. of fluor.ic.ln dlac.tat., d.clln.d with d.pth In th. un.aturat.d
ion. of Ultl.ol. .nd Alfl.ol. (r.d.rl. .t al., 1984); how.v.r,
2-(p •lodoph.nyl)-3-(p-nltroph.nyl)-5-ph.nyl t.tr.zollu. chlorld. r.ductlon
varl.d gr.atly b.tw.an .trata of a .oil profll. obtaln.d fro. • .hallow
aqulf.r (B.loln *t al., 1984).
H.ny .ub.urfac. nlcroorg.nl.m. ar. nutritionally dlv.r.. (Tabl. 2-3).
Slmpl. aub.tr.t.. .uch a. gluco.., glutualc acid, arglnln., a .Ixtur. of
anlno acldi, and a .ynth.tlc compound, nltrllotrlac.tle .eld. w.r.
.In.rallt.d In aaatpla. of uncontaminated ground wat.r (L.r.on and V.ntullo,
1983). Polar iolv.nt. .uch ai ac.ton., liopropanol, ..thanol, eth.nol. and
t.rt-butanol .l.o h.v. h..n r.port.d to d.gr.d. ..roblcally by .ub.urfac.
•Icroorganl.aa (Wovak .t al., 19A4; Jhav.rl and Haizacca. 1983). More
challenging contajalnant. th.t are a.roblcally d.grad.d by .ub.urf.c.
•Icroorg.nl.n. Include th. ..thyl.t.d b.ni.n.., chlorlnat.d benzene. (Kuhn
•t al., 1985). chlorlnat.d phenol. (Sufllta and Miller, 1985). .nd ..thyl.n.
chlorld. (Jhav.rl and Mazzacca. 1983). Highly llpophlllc coapound. .uch a*
naphthal.n.. ..thylnaphthal.n... dlb.nzofuran, fluor.n., and phen.nthr.n.
ar. al.o blotran.formed In th. .ub.urf.c. (Ull.on .t .1.. 1985; L«e and
Uard. 1985).
Th. .leroflora In .on. uncont.mlnat.d .oil* r.qulr. llttl. or no
accll.atlon p.rlod to d.grad. many x.noblotlc.. For .xuapl., tolu.n.,
chlorob.nz.n*. and broBOdlchloronethan. war. blotran.form.d In
uncontaialnat.d .oil, but not 1.2 dlchloro.than., 1,1,2-trlchloroethanc,
trlchloroethylen*. and tetrachloro.thyl.n. (Ull.on et al.. 1983). B.ni.n..
tolucn. and th* xylcn. l*om«r> ware found to d.grad. In unconta.ln.ted
lub.urfac* loll. (Bark.r and Patrick, 1984). In addition, atethenol (80-100
pp.) waa d.gr.d.d co.pl«t.ly aft.r two .onth., wba£mam_t«^rt-butaijo_l__d.grad.d
•uch .lower In two uncontamlnated ana.roble aqulfar. (Uhlt. ct al., 198O.
In contra.t to report, of degradation of xenoblotle. In uncontamlnated
.all, long period, of eccllwatlon to .ub.urf.c. pollutant, auy b. required
bafor. blod.gradation can occur. Wll.on .t al. (1985) r.port.d d.gr.datlon
of naphthal.n., 1-m.thyl naphthalene, 2-methyl naphthalene, dkbenzofuren and
fluor.n. at 100-1000 yt/1 In .ub.urf.c. .oil In th. plun. of contamination
froa a crao.ot. wait, pit; how.var, degradation of th... compound, wa* not
ob.erved In'uncontanlnated .oil fro. the «•»• .Ite. The tl.e end
concentration required for acclimation of the .Icroflora to aubaurface
pollutant, arc unknown. Spain and Van Veld (1983) r.port.d a thrv.hold
concentration of 10 ppb for adaptation to p-nltrophenol In .aople. of
..dlnant and natural water. A better undent.ndlng of acclliutloit proc.....
nay nxplaln why Boa. chemical, p.r.l.t In th. .ub.urfac. .yen though they
have been reported to degrad. in laboratory culture, and .ample, of water
and .oil.
34
37
-------
TABU
J.J. OICAJIIC COHPOOWOS THAT KAVI MM SHOW* TO BC BIOOICIUDABLt IH
Till SUBSURTACI
Compound
Soil from
Contaminated
Area
Aerobic Reference
Natural Compound*
glucote
glutamlc acid
arglnlne
Solvent*
ecetone
ethenol
liopropanol
tert-butanol
•ethano!
no
ye*
ye*
broi»odlchloro»»t»HU»e no
Aromatic*
benzene
xylene
methylated bentene* ye*
chlorinated benzene*
chlorinated phenol* y*»
naphthalene *••
dlbenzofuran
fluorene
phenanthrene
toluene no
ehlorobencane
r.«t.r, ,
»nvlrow*.nt«l
,ub.urr.e. ors.nlc
R.c.UUr.ne. of co-pound,
'ye*
»••
ye*
ye*
ye*
ye*
ye*
Ltrton end Ventullo,
mi
Jhaverl and
Mazzaece. 1983
Uov»k at al.. 148*
Ullton at el..
B«rk«r «nd Patrick,
148)
Kuhn «t tl. . 198S
Sufllt. »nd Miller.
1485
Wilton «t «1., 1485;
L*« md Wird. 148S
Ullion «t *!., 1483
r..ult fro-
. ln.«..lbll lly
in Ih. iub>urf>c<> alto >rf*ct> blodagrtdaUon. Traniport li dltcuattd In
detail In Sactlon II. P.
Blod»(r>d>tlon of many organic pollutanta In th« aubiurfaca Bay b*
lUltad by Iniufflclant oxygan. Alaxandar (1980) raportad that avan tha
MttbollH of cirbohydrttai aay ba Inhibited In o>cyjen-d«pletad
•nvlronnant*. Laa and Ward (198S) found that tha rata and axtant of
blotranafornatlon of naphthalene, 2-nethyl naphthalene, dlbenxofuran,
fluorene, and phenanthrena ware (ratter In oxygenated ground water than In
oxygen-depleted weter. Contrary to funeral theory that complete degradation
(•Inerallzatlon) of hydroearbona require! nolecular oxygen, oore recant
ra*earch tuggetti that alternate ptthwiyt axltt uudar anaerobic condition!.
Kuhn et al. (198S) reported Mineralization of xylene* In aaaplea of river
alluvlua under denitrifying condltloni. In addition, benzene, toluene, the
xylenea, and other alkylbenzenea were netabollzed In Bethinogenlc river
lUuvtun that had been contanlntted with landfill leachate (Ullton and Reea,
1985); Mineral Izatlon of toluene wai confirmed by adding l4C-labellad
toluene and nvaiurlng the anount of **COj produced. Crblc-Callc and
Vogel (148») alao reported •Inorellzatlon of toluene and benzene under
anaerobic condition* by a oathanogenle consortium aecllBeted to ferulate.
Further teata Indicated that water aupplled the oxygen that la flrat
Incorporated Into the toluene and benzene ring (Vogel and Crblc-Celle, 1484).
The pretence of oxygen Bay Inhibit the blodegradatlon of Many
halogtnalad aliphatic conpoundt In the lubturface. Degradation of
trlhaloeuthanea, trlchloroethylene, and tetrachloroethylene did not occur l«
eeroblc cultures of aewage bacteria; however, the trlhaloaethanei were
degraded anaeroblcally by ialxed culture* of nethanogena (Bouw*r et al.,
1981). In addition. Bouwer and McCtrty (1983b) reported that chloroform.
carbon tetrachlorlda and bronlnated trlhaloaethanei, but not chlorinated
benzene* , ethylbenzene, or naphthalene were blotranifomed under
denitrifying condition*.
In addition to oxygen, other nutrient* nay Holt the blodegradatlon of
ortmlc pollutant* In the *ub*urf*c*. Inorganic nutrient*. *ueh a* nitrogen
and phoiphoroui, «ay be Uniting when the ratio* of carbon to nitrogen or
phoaphoroua exceed that necexery for nlcroblel proceaee*. On the other
hend. the pretence of aulfata nay Inhibit otathanogenlc coniortl* that hive
been reported to dehalogenete and mineralize many chlorinated aromatic
coopoundt (Sufllt* and Glbion. 1985; Sufllta and Miller. 1985).
The effect of lubitrat* concentration on blodegredatlon of organic
compound* In aurfaca tollt and wttert he* been documented (Alexander,
19S5). Threihold* below which degradation 1* (low or doe* not occur may
•xltt for compound* that are readily biodegradable at higher
concentration*. Boethllng and Alexander (1979) reported thet let* thtn 10
percent of 2.4-dlchlorophenoxy*cet*t* at concentration* of 22 pg/ol and 2.2
ng/ml we* mineralized In atream water wherea* about 8O percent wa*
•Inerallzed et higher concentration* of 0.22 and 22 iig/ml. On the other
hand. •lcroorg*nl*m* may be Inhibited or killed by high concentration* of
organic pollutant* that reault from Injection well* end haterdou* wavte
•Itea. Lee (19Bt) reported thet glucoae mineralization wa* Inhibited In
38
39
-------
subsurface .oil h..vll» cont.»ln.t.d with cr.o.otes how.«r. glucose we,
.lr,.r.lU.d In uncont«ln.t.d and .lightly eont«ln.t.d cor. -t.rlal fro.
th. same lit*.
Oth.r factor* .uch a. .orpllon. pH .nd temperature may .1" .ff.ct
blod.gr.d.tlon of pollut.nl. In th. .ub.urf.c.. Many of th. organ c
compound. eonta.ln.tlng th. .ub.urf.c. .r. highly llpophlllc. Th. .
compound. are .orb.d b, .oil -or. .trongly than th. more ky«"P»ille
(Hutchl*. .t .1.. »«)• Sorptlon «y .nhanc. •>«8«-.d.tlon by
"
ssss-srs-jsisr srs-rsss/s: ss
nuUn.c.v.nglng In uncont»ln.t.d aqulf.r. which .r. g.n.r.lly
olUotrophl" n^.r. .orptlon «, compete with the .leroflor. foe
.ub.urf.e. pollutant* th.t .r. c.l«tl».ly nydrophoblc.
s
• pH of t.O than 5.0.
b.t«.n p.tral.u- hydroe.rbon d.jr.d.lloa »nd t«p.r.tur..
In .unury. th. .ub.urf.e. .nvlron».nt eonl.ln. «lerob.. th.t
..ny of trSw"le co^ound. th.t eont-ln.t. ,round w.t.r Th.
"crooc,.nl.« In uneont»ln.t.d .,ulf.r. .r. UV.ly »« *« »»JJ
Th. «.Jorlty of th. •UroorBtnUiu «r. ...ocl.t.d with .oil p.rtlcl..
cf .d.pt.d popul.tlon.. .nvlron-nt.l f.etor. .uch ..
blod.tr.d.tlon of .ub.urf.e. poUut.nt..
40
2. Blo.tlmul.tlon by Addition of Llmltlnit HutrUnt.
D«v.lopB.nt of th. £n Situ Blo.tlnul.tlon Proe... with Oicrt.n Supplied
by Air Sp.rflni-•
Appllcitlon of th. dittr.d.tlv. .etlvlty of aubturf.e. »terob.«- -Th.
pot.ntl.l for blod.gr.d.tlon of org.nlc compound. In conta«ln.t.d .qulf.r.
w.. flr.t r.port.d In 1971. B.et.rl. e.p.bl. of dugr.dlni hydror.rbon. u.r«
obi.rv.d In *n .r*. cont.mln.ted with g.iolln.i haw.v.r. blod.gr.datlon of
the B.'olin. w*. 1 tailed by th. >v.liability of oxygen. Btn.r.1 nutrl.nt*.
.nd hydroc.rbon .urf.ca *r«. (WLHltme and Wilder. 1971). Ullllui. end
Wilder (1971) .uBKvited Hist th.i. hydroc.rbon-d.fir.dlnE becterl. could b.
u.ed to clem th. .qulf.r of r.cldu.l ti.ollne; however, concern w..
*xpr....d th.t b.et.rl.l growth would plug the well .nd formation. O.vl. et
.1. (1972) recommended cupplylng th. Indigenous mlcroflor. vlth nutrl.nt.,
oxytcn, .nd eoliture r.th.r tli.n Inoculetlng th. (ub.urf.c. with comerlc.l
biologic.1 product* .uch ** drl.d b.eterl.l culture.. Oxyjta-limited
d.fr.d.tlon of hydrocarbon, w.. reported by McKee et .1. (1972) In .tudie*
de.lgned to Investigate the f.t. of geiollne trapped In th. pore .pece of
..nd eoluBA*. S.v.r.l .p.elel of Pt.udoaon.. .nd Arthrobacter were liolited
fro* ground w.ter. ...ocl.ted with • (..ollne oplll .nd uce.2 in the coluen
experiment.. Th. tot.l number of ge.olln. degr.dlng becterle In the ground
w.t.r numbered ov.r 50,000 cells/ml In th. containln.t.d zone, but lei. than
200 cell./ml h.d be.n found In the uncontenln.ted woll. «n4 In wells where
ga.olln. h.d not b..n detuctttd for . y..r. Th.'pr.s.nc. of high number, of
g..olln..d.gr.dlng becterl. w*. augge.ted .. an Indicator of cleanup
progrea*. In th. column study, the b.ct.rl. rapidly degraded th. gasoline
in th. con. of aeration but .lowly degrad.d that in th. saturated zone. In
a similar itudy, Litchfleld and Clark (1971) •iium»r.t*d hydrocarbon-degrading
bact.rl. in ground wat.ra from 12 .ita. which wore contaminated with
petroleum. The number* of hydrocarbon-degrading b.ctarla ranged from 10*
to 10* colls/ml, with similar nunbar. of both aerobic and mlcroaerophllle
organisms, in ground waters containing more than 10 ppm hydrocarbon. Hydro-
carbon-degrading bacteria were found in ground water from all 12 site.;
however, on a stt« by sit. bail*, there were no relationships between the
type* of organisms, the type of petroleura contamination, th. geological
characteristic), or the geographical location of th. sit*.
Application of th. dvgradatlv. capacity of aub.urfac. microorganism, to
r.itoro gasoline-contaminated ground w.t.r was fir.t demonstrated by
t.ymond, J.nl.on, Hudson ind coworker. .t Sunt.ch (L«. and Ward, 1983). In
1974. Raymond (1974) received . p.t.nt on . process deslgn.d to remove
hydrocarbon contaminants from ground waters by stimulating th* Indigenous
•icrobl.l population with nutrients and oxyg.n. Oxygen .nd nutrient, are
Introduced Into the formation through injection wells and production well.
w.r. used to circulate them through th. aquifer. Placement of the well, was
dependant on th. «res of contamination and the poroilty of th. formation.
but usually no closer than 100 ft .part. Th. nutrl.nt amendment consl.t. of
nitrogen, pho.phoruc, .nd other inorganic ..Its, a. required, et
concentration* of O.OOS to 0.02 percent by weight; oxyg.n wa* supplied by
sparging air Into th. ground wnt.r. Th. proceos wa* projected to require
about six months to achieve degradation of 90 percont of the hydrocarbons If
th. growth rat. of th. microorganisms wa* 0.02 g/L par d.y. Th. number* of
41
-------
b«ct»rlnl oil* were expected to return to anblent Iwele oncu the addition
of nutrient* was terminated. The proceie wa* expected to be mac* efficient
In totting ground water contaminated with leio thin 40 pfm of gaiollne.
First application of the blast Imitation proee«s--A pipe line le*k In
Ambler. Pennsylvania was tin Mrtt site where Raymond's patent on
biorestorstlon was demonstrated. An estimated 380,000 L of high octane
gasolln* had leaked Into t highly fractured dolomite outcrop underlaid by
quartzlte (Reymond et al.. 19)5). Depth to the water table ranged from 9.7
to 30.i • In the 4t nonltorlng walli Installed tt the lite. Before
blorestoretlon was attempted, conventional pump and treat technologic* were
u**d a* remedial action. Containment of the gasoline was exhlaved by
continuously puaplng water from well* located In the splli area. About
738,000 L of the gasoline wa* recovered by physical method*; however, the
recovery prograa wa* Incomplete end approximately 119.000 L of reildual
gasolln* remained. The concentration of dissolved gaiollne In the withdrawn
ground water averaged lei* th»n 5 pp». The tine required for restoration of
the aquifer using thl* punp and treat technique we* estimated to be more
than 100 yeart.
Problem* In analyzing the concentration of re*ldual hydrocarbon* during
the puiap and treat phaie were later attributed to the presence of
hydrocarbon degrading bacteria (Raymond et al.. 1475). A program deilgned
to lnv*itlg«t« the potentlel for blodegradatlon of the gasoline by the*e
organism* wee then Initiated. A laboratory atudy Indicated that aupplements
of elr. Inorganic nitrogen, and phosphate salts could Increase the nunbers
of hydrocarbon-degrading bacteria by one thoussnd-fold . Blodegrade-
tion of 1 liter of gatollno was estimated to require 44 g of nitrogen. 22 g
of phosphorus, and 730 g of oxygon. However. Bauhr and Corpcloglu (1985)
estimated that degradation of a pound (0.63 liter) of gasoline requires
3.5 g of uxygen. Batch addition of the nutrlonts worked ss well ss
continuous addition and was more cost-effective; however, high concentra-
tions of nutrients nay osnotlctlly shock the microorganisms (Raymond et •!.,
197*). Oxygen was supplied by sparging elr Into the wells using pslnt
tpray«r-type compre**ors and Carboundum dlffusers with a flow ret* of 0.06
n^/mln. As a result, the bscterlil population Increased from sbout 103
to 107 cells/ml. High bacterial counts mirrored location* of high
ga*ollne concentration* at th« alte (Raymond et at.. 1975).
During the bloatlnulatlon progrim at the Ambler. Pennsylvania «lte. 32
cultures of bacteria that actively metabolized gasoline were Isolated «nd
characterized; the Isolates Included specie* of the genera Hocardla.
pledgeuccu*. Aclnetubacter. rlavpbecterlua. and Paoudomona*; some cultures
could not be Identified. Studle* were conducted to determine the metabolic
capabilities of these l*olstes (Janlaan et si.. 1976). The date suggested
that the Hocardla cultures were largely responsible for the degradetlon of
the aliphatic hydrocarbons wherea• thoie from the genu*, Pieudomona*.
degraded the aromatic*. Branched paraffins, oleflns, or cyclic alkanes did
not support the growth of eny Isolate. Co-oxidation may have played a major
role In the blodegradatIon of these organic*. An alternative hyyothe*!* 1*
that the bacteria capable of degrading thege compound! wera not Isolated.
The lack of mlcroblal growth on some types of hydrocarbons may result from
the toxlclty or structure of the substrate. Strslght chain allphatlcs which
srs las* than 10 carbon* In length can be toxic whereas longer chain* and
branched ajkanes ere often resistant to mlcroblal attack (Sufllta, 1985).
Substitutions on sromatlcs that sre biodegradable may render them recal-
citrant. Muddleston et al. (1986) gave the following order for petroleum
hydrocarbon constituents, in ordur of decreasing blodegradablllty: linear
alkenes CiO-19« gees* €2.4. ilkene* Cj.o,, brenched alkenes Cjj,
alkenes Cj_n, branched alkenes, uromitles, and cycloalkanes.
The bioreclamation prograa conducted by Suntech it Ambler. Pennsylvania.
was rtesonsbly successful. During the period of nutrient addition, the
concentration of gasoline In the ground weter did not decline; however
gssoltne could not be detected In ground water 10 months later (Raymond et
al., 1976). A thousand-fold Increase In the number* of total end
hydrocarbon-degrading bacteria we* observed In ground water from many well*
(Raymond et al.. 1975). The waters from some wells exhibited foaming
because of high mlcrubla) numbers and associated •xopolyssccharldea. Counts
of mlcroorgsnlsms determined one yeer efter nutrient addition was terminated
Indicated thet the mlcroblal population had declined. Eitlmate* based on
the amount of nitrogen end phosphorus removed from the nutrient solution
suggested that between 88.400 and 112,400 L of gasoline were degraded.
However, this estimate was not particularly accurate because sone of the
nutrients nay have been adsorbed by soil or lost from the bloetlnulstlon
are* by dilution. In addition, the eatlmstes were baled on dlacrete samples
rather than composited simple*. I.erge quentltle* of nutrient* were ueed In
this project; approximately /9 metric tons of food grade resgents were
purchased.
Steps In the blostlsiulstlun process—The Ambler. Pennsylvania site csse
history is an example of the blostlmulatlon process. The basic step*
involved In an in situ bloreftoratIon program are the following: 1) lite
Investigation; 2) free product recovery; 3) mlcroblal degradation
enhancement study; 4) system design; S) operation; and 6) monitoring (Lee
end Ward, 1986). The first step in the process is to define thv
hydrogeology and the extent of contamination of the site. Important
hydrogeologlc characteristics include the direction and rete of ground water
flow, the depthe to the water table and to the contaminated zone, the
specific yield of the aquifer, and the heterogeneity of th» soil. In
addition, hydraulic connections between aquifer*, potential recharge and
dlicharge arua*. and fluctuation* in the water table must be considered.
Th« sustainable pumping rate must also be determined (Roux, 1965; Brown et
si., 1985s). These parameters can be determined by surveying the existing
-------
data for that lit* and region, resonnslssanee by experienced hyrtro-
geologlsts, geophysical surveys, excavation of lot pita, and Inataltatlon
of boreholes and monitoring well* (Josephson. 1963). Low dissolved oxygen
concentration* may Indicate an active xon« of hydrocarbon blodegradatlon
(Chtffce and Uelmer, 1983). The typal and concentration! of contaminants It
al«o Important (Brown et ml., 1985a). The type of remedial action chosen
depend! on the tine elapied clnce the iplll, the ereel extent of
contamination, the nature of contaminants and whether the contamination la
acute, chronic, or periodic. The urgency for action and the treatment level
thet »utt be achieved will depend on the potential for contamination of
drinking water or agricultural water well*.
After defining the elte hydrogeology. the next step It recovery of free
product. Depending on tho characteristics of the aquifer and eontsmlnants.
free product can account for a* much •• 91 percent of the spilled
hydrocarbon (Brown et ml., 1985s). The remaining hydrocarbon, which le
•orbed to the »oll and dissolved In the ground water, may account for 9 to
40 percent of the total hydrocarbon (pilled; the majority le usually torb*d,
however, the dlnolved phaee le the mo it difficult to treat. Tho pure
product can be removed using techniques described In sections II B.2. an D.
Physical recovery often accounts for only JO to 40 percent of the spilled
hydrocarbon before yields decline (Ysnlga and Mulry, 1985).
Prior to In situ treatment. * laboratory study Is conducted to determine
the nutrient requirements that will enable the Indigenous microorganisms to
efficiently degrade the contaminants (Lee and Ward. 198Sb). Kaufman (1984)
suggested th»t thdie laboratory studies csn provide e reliable basis for
field trials; however, the studies must be performed under conditions that
almulete the field. For example. Kuhlneler and Sunderltnd (1984) conducted
a laboratory Investigation of the unsaturatedT tone using samples saturated
with ground water. Clearly, the results of their study do not represent the
fate of the organlcs In the unsaturated tone. A chemical analysis of the
ground water provides little Information about the nutrient requirements of
the mlcroflora (Raymond et al., 1978). However, the chemistry of the site
will affect the nutrient forauletlon. For example, large quantities of
oxygen may be consumed to oxidize reduced Iron (Hallberg and Hartlnell,
1974). In addition, nutrients may sorb onto soils, especially silts and
clays and be unavailable to the mlcroflore (BrubaVor and Crockett, 1984).
Limestone and high mineral content soils and ground waters will also affect
nutrient availability by reacting with the phosphorus.
Nutrient requirements are usually site specific. Wltrogen and
phosphorus were required at the Ambler lite (Raymond et al., 1974a);
however, the addition of aimonlum sulfate. mono-end dlaodlua phosphate.
itagncilum sulfate. sodlu* carbonate, calcium chloride, manganese sulftte,
and ferrous sulfate was required si other sites (Raymond st al., 1978;
Klnugh et ml., 1983). The fora of the nutrient may also be Important;
uimonlum nitrate was less efficient than sjaaonlum sulfsle In one aquifer
system.
Laboratory atudles conducted to determine appropriate nutrient
formulations can be performed using a number of techniques. An Increese In
44
the number of total and hydrocarbon degrading bacteria has boen used to
Identify limiting nutrients In a factorial t>xparlm«ntal design (Raymond at
al., 1974, 1978). However, an Increase In nlcroblal numbers does not
demonstrate that the substrate of Interest Is being used. Batch culture
techniques designed to measure the disappearance of the contaminant
(riathman end Clthens, 1985) and electrolytic resplroneter studies designed
to measure the uptake of oxygen slso have been used (riathsan et al.,
DBS). The result* of another laboratory Investigation Indicated thst
dissolved oxygen was the primary factor limiting blodegradatlon of aroutlc
contaminants at a wood creototlng alte rather than Inorganic nutrients (Lee,
1984). Blotrenafornatlon studies which measure the disappearance of the
contaminants or silnartllzatlon studies which Indicate the complete
destruction of the compound to ctrton dioxide and water will confirm that
the contaminant* are being degraded. Controls to detect abiotic
transformation of the pollutants and tests to detect toxic effects of the
contaminants on th* mlcroflora should be Included (Flathman et al., 19S4).
A system for Injection of nutrients Into the formation and circulation
through the contaminated portion of the aquifer oust be designed and
constructed (Lee and Ward, 198Sb). The aye-tern usually Includes Injection
and production welle and equlpnunt for the addition end mixing of the
nutrient solution (Raymond, 1978). A typical systea Is shown In Figure
2-1. Plscement of Injection and production wells may be restricted by the
presence of physical atructures. Wells should be screened to auconaodete
ssasonal fluctuations In the level of the water table. Air can b« supplied
with carborundum dlffusers (Raymond et al., 1975), by sueHer dlffusers
constructed from a ehort piece of OuPont Vlaflo tubing (Raymond et al..
1978), or by dlffusers spaced along air lines burled In the Injection lines
(Klnugh et al., 1983). The site of the compressor and the number of
dlffusers are determined by the extent of contamination and the time allowed
for treatment (Raymond. 1978). nutrients also can be circulated ualng en
Infiltration gallery (Figure 2-2); this method provides an additional
advantage of treating the reslduel gesollne that may be trapped In the pore
spaces of tlie unsaturated zone (Brenoel and Brown, 1985). Oxygen also can
be supplied using hydrogen peroxide, otone. or soil venting (see vectlon on
alternative oxygen sources). Well Installation should be performed under
the direction of a hydrogeologlst to ensure adequate circulation of the
ground water (Le* and Ward, 1985b). Produced water csn be recycled to
reclrculate unused nutrients, avoid disposal of potentially contaminated
ground water, and avoid the need for makeup water.
Inorganic nutrients can be added to the subsurface once the eystem Is
constructed. Continuous Injection of the nutrient solution Is labor
Intensive,but provides a more constant nutrient supply than a discontinuous
process. Continuous addition of oxygen le recommended because the oxygen Is
likely to be a limiting factor in hydrocarbon degradation.
The performance of the system and proper distribution of the nutrients
can be monitored by measuring the organic, Inorganic, end bacterial levels
(Lee and Ward, 1985b). Carbon dioxide levels are also an Indicator of
mlcroblal activity In the formation (Jhaverl and Hatzacca, 1985). Depending
on the eharcterlstlcs of the nutrient* end soil, nutrients can be removed
45
-------
TO SEWER OR
RECIRCULATE
— —I AIR
ri COMPRESSOR
II
NUTRIENT
(ADDITION
COARSE
SAND
PRODUCTION WELL
WATER TABLE-
SPILLED MATERIALS -
WATER SUPPLY
-INJECTION WFLL
SPARGER
tt//Jt't
CLAY
figure 2-1. Typical schematic for aerobic subsurface bloreatoratlon.
I Addition
InfMlnlion O«M«l»
Tcsppsd M»d(oe»bon»
Figure 2-2. Uae of Infiltration gallery for reclrcul.tlon of water end
nutrient* In in situ blorestoretlon.
fro* lolutlon by sorptlon onto loll (Brubsker .nd CrocVett. 1*86). About 90
percent of the ammonium end phosphate end 70 percent of the hydrogen
peroxide edded to • sandy toll with low calcium. magnesium. and Iron was
recovered. After paaeage of a nutrient solution through • eoliuui pack»d
wllh • city ioll thit h*d high ctlclua tnd Msn*ilun but low Iron and
chlorld* Uv*l*. 100. 44 «nd 2S p«re*nt of th* unaonlun, phoiphat*. end
hydrofan pcroxld* w*r« r«eov«r*d, r*ip«ctlv*ly. How«v«r, «ft«r p««t>s* of •
nutrUnt tolutlon throuth • column pick.d with • city ioll hl|h In c»lelu«.
«*in»ilu», and chloride, but low In Iron, TS, 100; and IS percent of the
unonlun, photphttc, tnd hydrogen peroxide, retpect Ively, were recovered.
Both ioll end ground water itaplei thould be collected end tntlyxed to fully
evaluate the treatment ef feetlvenei* (Roux. 1985). Raymond et al. (197$)
reported that the matt difficult problaa In optlnltlng nlcroblal growth ID
the A»bler reaervolr va» the dlitrlbutlon of nutrlentf , which wa* Bade
difficult by the heterogeneity of the doloalte formation.
Additional ta«e h(ttorl»» In wblth oxygen wa« eqpplled by »tr
tpinttnn — {n. iltu bloreitoratlon hai been largely uied to treet gaiollne
fplll* and with reasonably good tuccaa*. However, many of the report* on |n
•ttu bloreatoratlon lack aufflclent data to fully judge the overall
effectlveneaa end coata aaaoelated with the proceie.
In e high permeability land aquifer contanlnated with hydrocarbon* In
Hlllvllle. Hew Jeney, the in iltu bloreatoratlon prograa we* *ucce*aful In
rearavlng free product, but reildual hydrocarbon wa* found at the lilt
•aapllng period (Raymond et al., 1978). The nutrient aolutlon waa Moved
through the formation at ratea of 6 to 14 ft/day, but dliaolved oxygen we*
rapidly coniuaed and did not Increase In *on* of th* naln well* at all.
However, analysts of cor* material collected from the aquifer Indicated that
the concentration of gasoline had not changed substantially during the
blostlsulatlon program. During th* Initial treatment process. Inadequate)
dissolved oxygen level* led to the mlcrobl*! formation of phenol, but th*
phenol level* declined as store aerobic condition* were achieved. A ten to
on* thousand-fold Increase In th* number of gasollne-ut 11 lilng bacteria was
noted In the area with the highest gasoline level*. Th* clesnup met th*
state requirement of removal of the free gasoline and wa* subsequently
•topped.
At a gasoline spill In La Grange, Oregon, nine month* of treatment by
iQ iltu bloresloret ton and a vapor elimination program succeeded In removing
the free product and mitigating the vapor problem* at two restaurants
(Hlnugh et al.. 1)81); however, the concentration of gasoline In the pit* In
th* blorestorstlon treatment area still rsnged from 100 to SOO ppta In the
majority of the samples. After an additional three month* of treetment. the
dissolved organic level* In the ground water had decreased from en average
of 20 ppm to !••• than S ppm In th* majority of th* samples.
relessed from s pipeline spill of gasolln* temporarily closed an
elementary school (Suntcch, 1978). A punplng will wa* ussd to maintain th*
water table below the school's foundetlon end physical recovery we* used to
remove two-third* of th* gasoline. An enhanced blod*gradatlon program was
Initiated by circulating nutrient* and oxygen through th* formation for *lx
47
-------
month*. After the cleanup, hydrocarbons could not be detected and the fumes
that had threatened the icliool had been el Imlneted.
Minimum h^drosacbofLConcent ratlona »chl«v»bU by in altu blostlmulatlon-
The minimum concentration of hydrocarbon that on be echloved by in sj_tu
blorestorstlon is unknown and la moat likely lit* specific. A natural
gradient field tttt In a candy Canadian aquifer required 434 day> to reduce
1.000 to 2,400 ppb of benzene, toluene, and tha xylene l«om«ra to balow the
detection llmlta (1 to 2 ppb) In tha abaanca of addad nutrlanti and oxygan
(Barker and Patrick. 116*). Tha dlatrlbutlon of dissolved oxygen In tha
plume waa heterogeneous and probably controlled blodegradatlon of tha
aromatic*.
Janaan at al. (1481) euggeeted that tha Indlganoua mlcroflura ahould ba
abla to reduce tha concentration of hydrocarbon* balow 1 ug/L whan tha
Initial hydrocarbon concentration is lei* than 10 ng/L and adequate
quantities of nutrlenta and oxygen ar« auppllad. Tha results of batch
experiment* utlng ground water from hydrocarbon-contaminated aquifer* ihouad
that th* native mleroflora could generally reduce the concentration* of
toluene, benzene, xylene. trlaiathyl benzene, naphthalene, methyl naphthalene,
blphenyl. ethyl naphthalene, and dimethyl naphthalene from a rang* of 400 to
1.100 t>g/L to lea* than 1 wg/L within a week In tha preaenea of oxygen
and nutrlenta. however, phenanthrene and toluene pereleted at higher
concentration* In two of tha ground watera after Incubation for alx day*.
Th* concentration of tree* level organic* In an aquifer may be reduced
by providing a primary substrate that aupport* mlcroblal growth and allow*
th* organlim* to act upon th* trace level organic* ea aecondary substrates
(Bouwer. 1984). Th* concentration of tha trace organic or «econd*ry
•ubitrat* 1* thought to b* below the minima* eubetrete concentration
(S,,!,,) required to support ailcrobial growth (Rlttnan and Kobayaahl,
1982). Th* S,,in concept waa developed to describe llmltatlona related to
tranaport of organic* Into a blofllai and the subsequent kinetic* of
reaction. There are leveral example* of Swjn. A reactor fad laboratory
grcd* water containing O.S9 a>g/L TOC waa able to reduce acetate below the
Smln value (0.01 mg/L) for acetate. Shlmp end Pfaender (1985)
demonstrated that addition of fatty acid*, carbohydrates and am I no acid*
enhanced th* ability of mixed mlcroblal population! to degrade *ubatltuted
phenol*. The** data suggest that th* addition of naturally occurring
substrates "ay enhance th* blodegradatlon potential of some xenoblotlea.
However, the addition of a primary *ubatr*t* euy not eupport the removal of
some compound*. A blofllm aupported by thyialne could utilise alanlne and
acetate, both coonon metabolite*, but not phenol and galactoie (Rlttman and
Kobayashl. 1982).
Treatment traini—In many hydrogeologlc ayitem* which become
contaminated froi* leaking underground storage tank*, a remediation process
•ay b* mo complex in term* of contaminant behavior and alte characterlatIc*
that no on* system or unit will neat all requirements. Very often. It li
necessary to combine several unit operation*. In aerie* and sometimes In
parallel, into one treatment procen train In order to effectively reator*
ground water quality to a required level (Ulleon et al., 198»). Exaieples of
treatment trains Include: j
(1) physical containment with product removal and surface treetment;
(2) product removal with unaaturated zone flushing followed by In situ
chemical treatment;
(3) physical containment with in, *_ltu physical/chemical treatment; and
(4) product removal followed by jjj situ biological treatment.
Physical containment through barriers and hydrodynamlc controla alone
merely act aa temporary plume control measuraa. However, hydrodynamlc
processes must also be Integral part* of any withdrawal and treatment or in
situ treatment meaaure*. Moat reavedlctlon projecta where enhanced
bloreatoratlon ha* been applied have started by removing heavily
contaminated soils. This waa usually followed by Installing pumping iyetarns
to remove free product floating on tha ground water, before bloreitoratlon
enhancement measure* were Initiated to degrade the more diluted portions of
the plume.
There are numerous proven lurfaca treatment proceaae* available for
treating a variety of organic and Inorganic waatewatere. However,
regardless of the source of ground water contamination and the remediation
measures anticipated, the limiting factor is getting the contemlneted
subsurface material to the treetment unit or units, or In the case of In
tltu processes, getting the treatment process to th* contaminated material.
The key to success Is a thorough understanding of tha hydrogeologlc and
geochemlcal characteristics of the area. Such an understanding will permit
full optimization of all possible remedial actions, maximum predictability
of remediation effectlveneoa, minimal remediation coata, and more reliable
coat satlmataa (Ullson et al., 1984).
The role of blorestoration In combination treatment schemes it often
difficult to aasass. Yaniga at al. (1985a) described the cleanup of a
gasoline spill In which an air atrlpper waa used to reduce the contaminant*
in the withdrawn ground water and to aupply oxygen before the water we*
recirculated to the aquifer via an infiltration gallery. Before
reclrculetlon. ammonium chloride, eodium monophosphate, sodium dlphoaphate.
iron lulfate. and manganese lulfat* were added In slug batches to tha
treated water. Additional oxygen wes supplied by sparging air into the
wells. Aa a reault, the dissolved oxygen Increased from a range of 0-3 to
5-10 pom; th* hydrocarbon degrading bacteria Increased from 10*-103 to
10J-10* celle/ml with Just oxygen addition by air stripping and tpsrglns
and then Increaaed to 10* eel la/ml with nutrient addition and additional
oxygan. Brown et al. (1985b) Identified another gasoline contaminated
aquifer which wee treated unlng air sparging. An estimated 25.000 to JO.OOO
gallona of gaaollna entered a 20 ft thick coarse grain sand and fine gravel
aquifer. Recovery of free product accounted for 18,500 gallons of tha
spilled gasoline; however, an estimated 10,000 gallons wa* *orbed to th*
•oil at concentration* of 2,000 to 3.OOO ppm and 30 to 40 ppm we* dlieolved
in'the ground water. The concentration of gaaollna waa reduced to lee* than
JO ppm In th* *oll and leg* th*n 1 ppm In th* ground water by air sparging.
48
49
-------
Only 1 to 2 ppm of dlaiolved oxygen could be achieved in the wella by tlr
aparglng.
1 ipill of four *olventa--mathylan* chloride, n-butinol, acetone, and
dimethyl anlllne--lnto • glacial till aquifer waa withdrawn and treated by
mn activated aludge proceae. allowed to aettle, and then recharged into tht
«ubeurf«c» through injactlon tranche* after being aerated and anendad with
nutrltnta (Jhaverl and Heztacca. 1981). The recharge water contained
orgenlam* acclimated to the tolventa In addition to a nutrient amendment
containing nltroten, phoiphate, nagnoaltim, tulfcto, carbonate, manganeia,
and Iron. Additional oxygen waa eupplled to the aquifer ualng a aeriea of
injection welli. Removal efficiencies of laethylene chloride, n-butanol, and
acetone were greater than 91 percent and the dimethyl aniline level* were
reduced by greater then 91 percent In the ebove ground treatment. The
concentration* of the folventi In the reaultlng effluent decreaaed to 0.04
•e/L for n-butanol. 0.92 a\g>L for mathylene chloride, 0.18 og/L for dimethyl
aniline, end 1.12 mg/L for acetone tram initial concentratlona of 19.1,
31.5, 2.9. and 38.6 wg/L, reapectively. Baaed upon COD and ga*
chromalography analytla. the plume wa* reduced In alia by 90 percent after
three yeara of operation (Jhaverl and Mectaeea. 1981). The COO waa reduced
from 100 to 20 mg/L In one Monitoring well. Baaed on the rate of ground
water flow, thl» reduction In COD colnclded'wlth the expected arrival time
of the treated ground water at that well. Elevated levela of carbon dioxide
In ground water collected from the treatment sane*. In comparison to thoa*
obeerved in uneontanlnated and decontaminated wella, auggeated that Jjj >Uu
bloreatoratlon wa* occurring. However, the solvent* ware detected in the
ground water beyond the projected date for completion of the project and the
Hew Jaraey Departavant of Environmental Protection atandard* had not been
achieved after three yeara of operation.
rlattuun at al. (198S) and Quince et al. (1985) dlacuaaed cleanup of a
iMthylene chloride aplll uaing phyalcal and biological above-ground
treatment proceiaea and in altu biological treatment, following aand
filtration to reaiove partlculatei, air atrlpplng, combined with a heat
exchanger to improve atripplng efficiency, waa initially uaed to treat the
withdrawn ground water and the water waa uaed to fluah the aoll (Quince et
al., 198}). Air (tripping reatoved about 98 to 99.9 percent of the sethylen*
chloride In the withdrawn water. The concentration of nathylene chloride In
th* ground water wa* reduced by 97 percent In on* downatraaoi monitoring
well. Biological treataent wia uled to further reduce the concentration of
the methylene chloride after addition of anoonla and phoaphate. An
activated aludge unit wae aeeded with acclimated organlim* from a waatawater
treatment plant receiving methylene chloride and theae organlam* were uaed
to Inoculate the loll (rlathiun et al. 198S). After 41 day* of la ai^u
blologlcsl troatnent, the concentration of mathylen* chloride In ground
«*ter fron a monitoring well 20 ft from the aplll declined from 192 to i ppm
and lit ppm chloride waa releaaed; however, It could not be determined
whether the edded bacteria or Indlgenou* mlcroflora or both were Involved In
mathylena chloride degradation. Both air itrlpplnf, and biological treatment
rtooved 99.9 percent of the Initial amount of methylene chloride present
during the four nontha of field operation. The concentration of methylen*
.n.1hyi.n. in -
about 4.000 gallon, of coo ng w.Ur trill I1"'!" UI?B fr°" kh' lo" of
(flathmen et .1.. 1984). The unaetur.^ "*" §Urf"* Ilo"*« ^
concentration* o .thy .„. «?„""? ^ K ""* "" cont«->"«t«d with
glycol In th; around !J * " 4>'°° "«/k« io11
^^^
si
-------
Wlnegardner and Quince (1914) documented two additional eaaa hlatorlet
of in allu bloreetoratlon that Involvad addition of acclimated bactarla.
The Mr»t caae hlatory deacrlbed the cleanup of a train derailment which
releaaad a leml-eoluble aliphatic hydrocarbon plaitlelzer. Recovery well!
were uaed to collect the plaatlclter fro* the aubeurt'ace. Later, (urface
recharge and ehallow Injection were used to flufh the plaatlclzer out of the
•oil; thl* treatment reduced the peak concentration of greater than 2.000
ppm In a wldeapread area to a ouch amallar zone after 70 daya, In addition
to reducing, the concentration of the plaatlelzer throughout the contaminated
area. Air atrlpplng and carbon adaorptlon were mod initially; however,
thece technique! were replaced by biological treateent ualng activated
iludge. The water treated by activated iludge wai uied ai an Inoculant to
Introduce the acclimated bacteria into the lubiurface to enhance ^n altu
bloreitoratlon. The concentration of the plattlclzer in the recovered water
waa reduced from approximately 1,700 to 400 ppia after clarification;
however, the Importance of each component In the treatment proceaa could not
b.e determined.
The aecond eaae hlatory- Involved contamination of a glaetel kaaie depoalt
of aand. gravel, allt, and clay with chloroform from a leaking pipeline.
Ground water we* withdrawn end treated with a nixed »edle prefllter, an
activated a'.udge bloreactor and lettllng vestal, and a heated air itrlpper.
The effluent from the activated aludge bloreactor waa used aa an inoculant
for bloreitoratlon. The effluent from the air (tripper wai discharged Into
a proceii aewer or into the lubiurface. A forced fluihlng/recovery tyitem
waa uaed to enhance the recovery of th« chloroform. Biological treatment
followed the phyalcal recovery; however, treatawnt effeetlvenaaa. waa not
dlacuaaed.
Sumary of Aerobic In Situ Bloatlaulatlon Proceaaea—
There are a mimber of advantages and dltadvantege* in utlng in altu
bloreitoratloii (Table 2-4). Compound! ranging from petroleum hydrocarbon!
to iolvcnta have been treated by in aitu bloreatoratlon (Table 2-S). Unlike
MJI; aquifer remediation techniques, In. altu bloreclamatlon can often treat
conlaninanti that are aorbed to loll or trapped in pore ipacai. In addition
to treatment of the aaturated zone, organic! held In the unaeturatcd and
capillary zone can be treated when an infiltration gallery or aoll fluihlng
la uiad. Blodegradatlon In the lubiurface can be enhanced by increailng the
concentration of dleaolved oxygen, through the uae of hydrogen peroxide,
ozone, or a colloidal dlaparalon of air (colloidal gae aaphrona). Complete
blodegradatlon (mineralization) of organic compound! uaually produce! carbon
dioxide, water, and an Increaae In cell rnaaa. However, Incomplete degrada-
tion (blotranaformatlon) of organic material! can produce byproduct! that
are more toxic than the parent molecule. An example of blotraniformatlon li
the degredatlon of leopropanol to acetone at * hazardoui waate alte
deacrlbed by Flathoan and Clthent (1965). The level! of acetone Increaaed
Initially, but decllnnd after moat of the liopropenol waa removed. In eltu
bloreatoratlon may rely on tne blodegradatlon potential of the indlgenoua
59
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TABLE 2-4. ADVANTAGES AMD DISADVANTAGES Of B1ORESTORATJOH
(J. I. B. Associates, 1982; rang and Bye, 1979)
TABLE 2-J. COHTAHrMANTS TREATED BY ijl SITU BIOST1KULATIOM
Advantages
C«n be used to treat hydrocarbon* and certain organic compounds.
e*pocielly water-soluble pollutant* and low levels of othar
compoundi that would b« difficult to remove by othar Mthodi
tnvlrowentally aound bacauto It doc* not uaually generate waata
product* and typically results In complete d*(radatlon of tha
contaminants
Utllltaa th* Indigenous mlcroblal flora and doa* not Introduce
potentially hanaful organisms
Fait, lafa and generally economical
Treatment moves with th* ground w*t*r
Good for ihort-tam treatment of organic contaminated ground water
Dliadvantagat
Can ba Inhibited by haavy metal* and *om* organic*
Bacteria can plug tha toll and raduc* circulation
Introduction of nutrlantt could advarialy iffaet natrby *urf*e* water*
Residue* atay caui* ta*t* and odor problaau
Labor and aalntanance raqulraa*nt* may ba high, •ipaclally for Inng
tan* traatnant
Long tarm affact* ara unknown
Kay not work for aquifer* with low paraaabllltla* that do not parnit
adaquata circulation of nutrlanti
Contaminant*
Tr*itit*nt Daicrlptlon
Rafaranc**
high oetan*
ga*otlna
giiolln*
gaiolln*
gnolln*
gaiolln*
g**olln*
g**olln*
g**olln*
unlttdad gaiollna
•Inaral oil
hydrocarbon*
gatolln*
air *pirglng with nitrogen
•nd phoiphoru* addition
air (pargtng with complete
•Ix of Inorganic*
air iparglng with addition of
conplat* Inorganic nutrient
•olutlon
ilr aparglng and addition of
nutrient*
dltiolvad oxygan supplied by
an air itrlpper and iparglng;
nutrient* alto added
dlnolvad oxygan luppllad by
an air itrlpper
hydrogen peroxide plu*
nutrients
Initial treatment utllltcd air
(tripping; hydrogen peroxide
u**d later with tha nutrient
formulation
hydrogen peroxide supplied
the oxygen
withdrawn water treated with
ocone and relnflltrated
toll venting uied to supply
oxygen to unaaturated zone
(Continued)
Raymond et el.. 197$
Raymond et el., 1»>S
Janlson et al. . 1*1}
Jamison et el..
Raymond et el.. 1«7I
Hlnugh et el.. 1*81
Suntech. 19/8
Yanlga et si.. 198)*
Yanlga et el.. 198Sb
Brown et el.. 19BSb
Yanlga and Ifcilry.
1984
Ysnlga, 1982
Brown et el.. l»«Sb
Yanlga et •!.. 198Sb
Brown and Herri*,
1986
Hagel et al.. 1982
Xuhlraaler and
Sunderland. 198i
61
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TABLE 2-5. (Continued)
Contaminants
wist* solvents
and alkane*
methyl chloride,
n-butanol.
dimethyl aniline,
acetone
•cthylane
chloride
ethylene glycol
liopropanol and
tetrahydrofuran
cllphttlc
hydrocarbon
plastlclzer
chlorofona
Treatment Description
References
nutrient! plus hydrogen
peroxide
withdrawal and treatment by
an activated iludge proceat
and recharge of aerated
nutrient-laden water.
withdrawal and treatment with
air stripping followed later
by treatment In an actlveted
sludge unit and recharge
treataient following withdrawal
with *thylen*-d*gridlng
bacteria and nutrlentt and
then recharge
treatment In an above ground
reactor with addition of
acclimated microbes to the
aquifer along with nutrient*
activated iludge and recharge
of acclimated bacteria and
nutrients
activated iludge bloreactor
with the bacteria Innoculated
into the tubsurface
Brown et al.. 198Sb
Uestray el al.. 1985
Brenoel and Brown.
1985
Brown et al., 198i
Jhaverl and
Hazzacca. 1983
Jhiverl and and
Hazzacc*. 1985
Quince, et al., 1985
Flathman et al.. 1985
Plathnan et al., 1985
Flathnan and Caplan,
1985
Flathnan and Clthena.
1985
Ulnegardner and
Quince. 1984
Ulnegardner and
Quince. 1984
subsurface mlcroflora which usually contains few pathogenic organisms unless
the aquifer ha* been contaminated with waetewaters (Keewlck. 1984). The
time required to treat subsurface pollution using In, situ blorestoratlon can
often be faster than some withdrawal and treatment procedure*. A gasoline
•pill In Axbl.r. Pennsylvania, was remediated In 16 month* using in ejtij
bioreetoretlon wherea* pump and treat techniques were estimated to require
100 year* to reduce the concentration* of gasoline to potable level*
(Raymond et al.. 1974). Jn situ bloreetoratlon can alio cost less than
(2
other remedial options. Flithman end Clthens (1985) estimated that the coat
of IQ situ blorestoratlon would be iMe-Mfth of that for excavation and
dlepoeal of soil contaminated with Isopropanol and tetrahydrofuran end In
addition would provide an ultimate disposal solution. Th« areal zone of
treatment using blorestoratlon c*n be larger than other remedial
technologic* because the treatment move* with the plum* and can reach aree*
which are otherwise Inaccessible.
There are also disadvantages to in situ btorestoretlon program*. Hany
organic compounds In the subsurface are resistant to degredetlon. In situ
bloreatoratlon requires an acclimated population; however, adapted
population* may not develop for recent spills or recelcltrant compound*.
Heavy metal* end toxic concentration* of organic* may inhibit mlcroblal
activity and preclude the us* of the Indigenous nlcroflora for In situ
bloreatoratlon at some alias. One option In this Instance would be to
remove the Inhibitory substances end then seed the subsurface with
appropriately adapted • Uroorganiimi; however, the benefiti to adding
microorganism* to the subsurface are itlll undemonstrated. The formation
and Injection well* s\sy clog from profuse mlcroblal growth which results
from the addition of oxygen and nutrient*. In on* bloitlmulatlon project,
mlcroblal growth produced foanlng In the well cuing* (Raymond at al..
197ia).. fn addition, the hydrodynamics of the restoration program muet be
properly managed. The nutrients added aust be contained within the
treatment tone because the profusion of Inorganic* Into untirgeted ar*a* csn
result in eutrophlcatlon. High concentration* of nitrate cen render ground
water unpotable. Hetabollte* at pertlel degradation of organic compound*
may Impart objectionable tastes and odor*. For example, the Incomplete
degradation of gaiolln* under low dissolved oxygen conditions resulted In
phenol production; phenol wss then degreded when nor* aerobic conditions
wire achieved (Raynond et al.. 1978). Blostloulstlon project* require
continuous monitoring and maintenance for successful treatment; whether
these requirement* are greater then those for other remedial ectlona Is
debatable. The process rsiults In Increased alcrobial bloraass which could
decompose and release undesirable metabolite*. In addition, mlcroblal
growth can exert an oxygen demand that may drive the system anaerobic end
result In the production of hydrogen sulfld* or other objectionable
byproducts. The long tern effects of bloraitoratlon are unknown. In ittu
bloreitoretlon 1* difficult to Implement In low permeability aquifers In
which perfualon of nutrients and oxygen Is slow or negligible; however, many
la »ltu physical and chualcal remediation processes are subject to the aana
restrictions. The success of in j_U_u treatment scheme* In low permeability
aquifers depend* on transporting the nutrient* to the mlcroflora or the
active agent .to the contaminants. The process has been used in different
hydrog*ologle*l»formatlona (Table 2-6).
Potential problem* for any aquifer restoration program Include
reversible adsorption of the contaminants, poor delineation of the plume,
inadequate siting of the recovery lystom, pollution at depth, high costs,
treating and disposing of large amount* of pollutants, constraints on ground
water pumping, acease to the contaminated area, end substantial quantities
•f pollutant* In the vadose zone (Schmidt. 1983). To decrees* the ovpens*
of ail aquifer cleanup, llyer (198S) advocated a policy of life cycle dealgn
41
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TA»Lt 2-t. TYFIS Of AQUIFIRS WHIR! JIT JJJU BIOST1HUI.ATIOM HAS BUM UTftmO
Aquifer Dvicrlption
flow Characteristic*
Ref erence
hl(h permeability
delimit*
medium to eotrte **nd
•lluvlil fan depoelt of
• •nd. grav*l, and eobbl**
with 'ion* clay and (lit
poorly eorted mixture
of bouldtri, pebble*,
cobble*, i*nd. vllt and
clay
perched u«t«r table In
un*tratlflad, unaorted
layer of clay, (lit*.
(tndi, gnveli, and
cobble* above • clay
layer
tank vault filled with
pea (ravel lurrounded
by (and and iandy clay
•irate
glacial outwaah composed
of lilt, land, and
(ravel
coarae tanda and gravel
ehale and illtitone
coari* tand with treater
than 5* (ravel
flaelal till composed of
•and, gravel, and bouldera
in a tllty clay matrix
connected to a fractured
landitone
pumpln( rat* of 2*5
to 371 L/nln
pujnpln| rat* of <$
to 151 L/mln
flow of J.4 m/day
hydraulic conductivity
of 9.4x10-* to
1.7xlO-Jcm/**c
punplng rat* of 3t to
to 57 L/mln
flow rat* In excel*
100 «/yr
pumping rate of 151
L/nln
hydraulic conductivity
of 6.8x10-* to
1.5xlO-J«m/**e
hydraulic conductivity
of 2.1 em/*ee
punplng rat* of 48 L/mln
(radlent of 0.015 to
0.02 */•; flow of 0.41
to 0.91 m/yr
Raymond et .1.. 1974
Raymond at al., 197S
JanIfon et al., 1975
JamI ton et al.. 1971
Raymond et al., 1984
Mlnu|h et at., 1911
Jhaverl and Maxzaeea,
1981
Jhaverl and Matiacca,
1985
Quince et al., 1985
riathman et al., 1985
Ueitray et al.. 1985
Brown et al., 1985b
Brenoel and Brown,
1*85
Brown and Xorrle. 19B*
Ma(*l et al., 1982
Brown et al., 1985b
Yanlga et al., 1982
Yenlga et al., 1985b
Yanlga and Hulry, 1984
Yanl(a et al., 1985b
for ramedlel action* In which COM of the equipment could b. recycled end
uaed at other lite*. An extnple of thli tyitem wee propoeed to r»««dlete
contaminated (round water fro* a Gulf Coait hasardou* waat* cite. The
(round water contained high concentratlona of phenol and *nou(h dliaolved
•olid* (15,000 M'U to be contldered a brine. The treatment ayiten
conilfted of two activated elud(e unit*, a fixed fllo-eetlvet*d tludge unit,
a dual *>*dl* filter, and a carbon adaorptlon column. The component! of the
treatMAt lyitea could be eeelly changed to accoaodat* the chan(e In
concentration of the contaminant* during the clean up proof*.
Potential for Anaerobic rroceeie*--
AnatrgbU denradatlon pathway* In th« »ub»urt*ej--AnaerBhte proce.tei
are Important In the lubiurfac* environment becauee oxy(*n mey be depleted
In contanlnated asulfer* *• a raiult of a.eroblc mlcroblal activity. However.
low level* of oxygen will lupport *ome ml'croblal activity. One* the
dltiotved oxygen content In (round wtter decline* •• • reiult of mlcroblal
activity, replacement depend* on recharge, retention from toll ga**e. and
mixture with oxygentted water* lurroundlng the organic plum* (Borden and
Badlent. 1986; Borden et al., 1984).
De(radatlon of • variety of compound* under anaerobic condition* ha*
been demonttrated to occur In equlfere and laboratory experiment* utlng
•ub*urf*c* material*. However, anterobloil* may retard the d*(r*dation of
many compound* (Hutchln* at al., 1985). The *equ*nc* of nlcroblal procenei
thtt occur a* *nv1ronmente1 condition* change from aerobic to ena*roblc In
the aubiurfec* uiually follow* the pattern of aerobic reeplrttion,
denltrlfIcttlon, mangtn*** and Iron reduction, eulfate reduction, and
finally mathan* formation (Bouwer, 1985; Down**, 19(5). Wet energy
production decrease* a* the redox potential deer***** (Down**, 1985).
Bouuer and HcCarty (1983ail981b) denon*trated difference* In the degradation
of organic compound* under different redox potential*; chloroform and
1,1,1-trlchlorotthylene were degraded by methinogenlc, but not denitrifying
bacteria. Ihrllch et al. (1982; 1981) reported the degradation of
phenolic*, but not polynuclear aromatic* *uch a* naphthalene, under
m*thtno(*ntc condition*. Recently Kuhn et al. (1985) documented renoval of
tetrachloroethylene, the xylene leomer*, and dlchlorobenzen* l*om*r* under
denitrifying condition*. Wilton and R*** (1985) *how*d that d*(radatlon of
benzene, ethylbeniene, toluene, and o-rylene occurred In methtnogenlc
•qulfer materiel from a landfill, although the prucete we* (low compared to
aerobic pathwaya. The concentration of toluene had b**n reduced by 87
percent after r.lx week*, however, (tor* than 20 percent of the benzene.
ethylbenzene, and o-xylene added to th* mlcroco*m* perilited beyond 40
week*. In the time (tudy, trlchloroethyl*n* and ttyrene degraded under
iniaroblc condltlun*, wharei* chlorobentene perdited. Sufllt* and Clbeon
(1985) reported that 11 of 19 halogenated l*om*r* of benzotte, phenol, and
phenoxyecetate pertlited at concentration* greater than 90 percent of that
Initially added to aubiurfac* material* collected from a *ulfat*-r*duclng
zone; however, only 3.4-dlchlorobenzen* remained at concentration* greater
thin i percent of that originally added to methanoganlc (ample* collected
dovngrtdient of th* *ulfat* reducing ton*. Maximal numbar* of
(ulfate-reduclng end meth*nog*nlc becterle are found at redox potential* of
-100 to -150 and -250 to -350 mV. respectively (Van tngera, 197B).
Hilogenated aliphatic* *uch a* trlchloroethylene, tetrtchloroethylene.
carbon t*trachlorld*. and 1,1,1-trlchloroethene can be mineralized or
d*halo(enated under reducing condition* (Ptrion* at al., 1985) to
potentially more ttfxlc compound* luch •* vinyl chloride (Vogel and HcCarty.
1915; Wood et al.. 1985).
•hallow baaln containing
•and and pet gravel
flow of 27 to 38 L/mln
rl*thm*n and Clthen*.
1985
-------
....rpe »roce..e. In tn .Itu blo.tlauUtlon- -Anaerobic pro «ay
be of potential u.e In in altu blore.toretlon proca..... Th. redox
pot.ntl.l would b. ..l.ctlv.ly .dju.ted to favor th. degradation of a
particular contaminant. In addition to adjuatlng the redox potential, th.
pll of the tround water could b. adju.t.d to the neulr.l or alkaline
condition, required for .ulf.t. reduction, meth.nog.n..!.. and "•"•"y
denltrlfUatlon. Ana.roble degradation of organic compound, would probably
r.qulr. 1.1. Inorganic nutrl.nt .upplw.nt.tlon b.eau.e 1... energy .nd
th.r.fore blomaa. 1. produe.d (Rlttman .nd Kobey.hl. 1982). Betteraan
(1983) .dd.d nllr.t. to ground w.t.r contaminated with hydrocarbons In en
itt.ept to promote d.nltrlflcatlon. Th. contenlneted aquifer eon.let.d of
in 8 to 10 meter thick l.y.r of «»nd which contained .on. .lit end cl.y b.d.
and . ground w.t.r flow of 4 ./day. Th. w.t.r w.. wllhdr.wn fro. . d.eper
uncont.mln.t.d .qulf.r. ..rated. p....d through . ..nd filter, .nd am.nd.d
with nitrate «t 300 mg/L b.for. b.lng r.ch.rg.d to th. .hallow .qulf.r.
Pho.ph.t. -I. not .dd.d b.c.u.. It w.. not limiting. Th. author, .ugge.t.d
th.t anaerobic d.gr.d.tlon accounted for th» removal of 7.S ton. of
Sn^rton -tthln . p.rlod of 120 d.y.. Hemov.l of 1 « of th. hydroc.rbon
required 3.3 »8 of nltr.t. (B.tt.man .nd Werner. 1984). Th. «.u«centr.tlon
of aliphatic, declined .lowly fro. 1.5 to about 0.7 «8/L where., th. total
.rornatU. declined fro. 5.5 «/L down to about 1.5 .S/L In .pproxlm. aly on.
»H^ Th. r.t. of d.clln. In th. conc.ntr.tlon of xyl.n. «.. -.ch «Jow.r
th« th*t of b.n«.n. .nd tolu.n.. W.t.r «.. InJ.ct.d dur ng th. t.at which
r..ult.d In a rl.. In th. l.v.l of th« hydrocarbona a« w.ll .. th. w.t.r
Ubl. tnto th. un..tur.t.d «n«,. Th.r. w.. .n ov.r.ll 40 p.rc.nt r.ductlon
In th. conc.ntr.tlon of hydroc.rbon .. . r..ult of th. ^"t"nk(,''""":o„
n.ufflcl.nt information wa. provld.d to d.t.r,ln. If «"»[°bl<^ "^ °"
w.. r..pon.lbl. for th. r.«ov.l of th. cont-ln.nt. or If th. r«oval w..
du. to th. oxyg.n Introdue.d wh.n th. InJ.ctlon w.t.r w.. ..r.t.d b.for. It
w.. r.ch.rc*d Into th. ahallow aqulfar.
of low eone.ntr.tlon. of organic compound, und.r
n condition., with ac.t.t. .dd.d at hl*h"'°nC^";'°",;;)i
.ub.tr.t.. haa b..n d.non.trat.d (Bouw.r. 1985). "'f.rty (1985)
oropd . .ch«« to tr..t cont«,ln.t.d ground w.t.r .n..roblc.lly U.lng th.
p"«ry .ub.tr.t. conc.pt. Th. .y.t.» con.l.t. of .n .bov. •"""* «"«'
to which .ub.tr.t. and nutrl.nt. ar. .dd.d. a w.ll caalnj b «"ctoj
op.r.t roblc.lly Ilk. . trickling fllt.r .nd th. •«»««• «•
ground r..ctor 1. u..d to d.v.lop .n .ccll-t.d population Th.
tro. th. .bov. ground r.actor 1. InJ.ct.d Into th. w.ll ca.lng b or..ctor to
Introduc. accllLt.d i.lcrob.. Into th. .qulf.r or .nh.nc. adaptation of th..
£££. mul.tlon to th. cont«ln.nt. One. th. ««»-jJ-^uUtl
-------
••thod, r.comblnant DMA technology 1* ui*d to chant* th* g*n*tle structure
of th* mlcroorg.nl.m (Kllbane, 198i). The genetic itructure 1. changed by
Inserting • DMA fragment, often • pla.mld that cod*, (or a .pacific
d.gr.datlv* pathway. Into another organl.*. A pl.inld It • ploe* of DMA
that exl.t. Independently from th. cell', chromoio... (Blri*, 1981). The
•xtr.-chromo.om.l DMA e»n be tr.n.formed fro* on* b.ct.rlum to mother by
conjugation, trantductlon, or trtnifonutlon. Multiple degrtdatlve
c.pabllltle* can be pieced on > .Ingle pi.amid th*t will ellow the org.nlcm
to degrade «n array of cocpound* or complete th* degradation of •
nonbiodogradable molecule. Cenetlc engineering e«n be uied to .t.blllie th*
degradatlve trait* coded by th* plaamld, incr**** th* number of plaamldi In
a call, amplify enzyme production and activity. InvoV* cultlpl* degradatlve
tralti, or produce • novel d*|r*d*tlv* pathway (Pierce, 1912). In addition,
organism* with different *ub*trat* affinltlei, pH optima, or degradation
ratal can be faahloned (John*ton and Robln.on, 1982a>.
Cen.tlc tnsln**rlni to Inhanc* D.gr.datlv. Activity—
Genetic engineering ha* been ueed to enhance th* degradation of th*
recalcitrant peillelde, 2.*,5- trlehlorophenoxyeeetlc acid (2',4,J-T).
Blodetradatlon of th* peitlclde 1* u.ually vary alow (Kllban* *t *!.,
W2). A mixed culture of •teroorganlau that ui*t 2.A.S-T ai • •ole. ctrbon
and energy iourc* wai obtained by a technique called pla.mld-a.ilited
mol.cul.r breeding (Kellog at el'., 19S1). The technique Involve*
tnoculatlnt a cheeMttat with mUroorgenl i»i fro* i variety of hatardoui
wait* tltei and org.nlim* that carry an array of plaimld. that cod* for
degradation of ipeclflc x.noblotle*. A pure culture that could uie 2,*,)-T
ai a lole carbon and energy *ourc* w«« liolated from the nixed population
and tentatively Identified ai Pieudomonai cepacte (Kllbane et al., 1981).
In addition, the culture, designated £. cepacla AC1100, wai reported to
oxldlte many chlorophenoli. Degradation of both 2.4-dlehloroph.noxyee.tle
acid (2,4-D) and 2,4.5-T wa* expreued In another itraln of g. fjpacla after
conjugal tranifcr of two planld fro* an ftlcalUen** entroehjt *p. that
degraded loae chlorinated phenoxy herbicide* (Choial at •!., 1985). An
Inoculut) of 2 X 107 celli/s of {.. c«P*cta AC1100 degraded 9S percent of ,
the 1,000 »c/L 2,«.5-T added to loll at 25 percent molftur* and Incubated at
30-C (Chatterje* et •!.. 1«S2). Lea* 2.4.S-T we* renoved with • inalUr
Inoculun *li* and different t*«p*r*tura* and aiolitura content*. Tn
addition, th* 2.4.S-T degrading bacteria did not turvlve In toll without
2,«,$-T or when the concentration of the compound had been depleted (Kllban*
et al., H83). Pl*ld trial* to determine the effectlveneai of the
2,4,5-T-degradlng bacteria have not bean conducted.
Colaruotolo et al. (198Sa) received a patent for -mlcroblal degradation
of obnoxlou* organic waitei Into Innocuous material*." The procei* Involv**
liolatlon of "IcrobUl cultural froa lampl** of coll and leachat* from a
haiardoui wait* lit* by enrichment culturlng end then application of th*
purified itraln* In the field to remove th* contanlnanta. Hlcroorganliiu
capable of degrading eelected lioaer* of chlorotoluene. dlchlorotoluen*. and
dUhlorobenioate were liolated. Conjugation and tranaformatlon experiment!
were conducted to trantfer the plaiold DMA, which conferred th* ability to
degrede tome chloroaromatlci. fro* th* original laolatea to another
organl**. Th* pat*nt clelaed that the organliea could be uied to
72
.««!« ? rh f ' T «ont«ln.nt. In th. air. .In.r.m. toxic
organlei In the leachete from a che-mlcal landfill and thereby reduce the
coneentratloni of noxloui eh.«le«l*4
Inue* In Genetic engineering of Microbe* —
Org.nl..* that can not .aitly exchang. th.lr g.n.tlc Information with
r" '"i "' r"" •»1r«««1-"«" •' "tlvlty In nont.rg.t are..; .nd 5)
d.tanalnallon of let rlik level, acc.ptabl. to th. public (Joyc. 1983)
Many icl.ntliti argu. that th* engineered org.nl. « 1, not radically
dlff.r.nt from that which If genetically unaltered. Th. rele.ae of
gen.tteally engineered org.nlimi into th* environment 1. of great concern
•nd lorn, tl.e .iy *i.pi. b.for. th... .,.,.,,1.,,. ,r. u..d , ^J ,,,„"£.
.urvlvablllly of g.n.tlc.lly alt.r.d org.nl... In th. env rodent l,'.l« of
°
.oil
w.r. add.d to fanpU. of ..w.g., l.k. w.t.r
'
ai.n » ..
(Liang *t .1.. 1982). Son. of th. antltaot le-r..l.t.nt .train, reached
iteady-.tat. conc.ntr.tlon. In l.k. wat.r .nd ..w.g.; how.v.r a" .train.
d.clln.d in th. ..11 after a period of on. month. PJfudomon» . r.In" h!t
degrade 2 «-dlchloroph.nol and p. nltroph.nol were "
*n
. rop.no were u by
*nrlch.,nt culturln, t.chnl,u... The ability of th. l.ol.t.^o d.jr.J.
0 lnoeuut-d int°
of .
conc.ntr.tlon of th. t.rg.t compound required to .upport
.'"nt blotird*r T r* l!"JUnE- T°Xle °f •ntl-1«<""«» .ub.tnc*. .uch
b .r!f i K T "* f°U"d '" "nlr •"v»«-o."..nt.. High d.n.lty inocul. e^y
be gracad by pr.d.tor. and the d.gradatlv* capacity ..v.r.ly decre.a.d if
the growth rat. of th. Introduced org.nl.m. ll *loi. In adjltlon .
•ntur' cont«' •' '"• organlam with th. pollutant will be
to achieve In th* lubiurfae*.
with mo« ^"r
-------
TABLE 2-8. HEASOHS WlfY IlfTHODUCBD ORCAMISKS PAIL TO PUHCTION IK THK
(Goldstein »t «i.
1. The concentration of the compound ie too low
2. The environment contains «ome substance or organisms that Inhibit
growth or activity, Including predators
3. Tha Inoculated organism uses oome other organic other than the one It
WBS selected to metabolize
«. The organic la not accessible to the organUn
containing the microorganisms. To avoid problems encountered with
inoculation of foreign organisms Into the environment, samples from the
contaminated environment can be collected, microorganism that can degrade
the pollutants can be cultured by enrichment techniques or genetically
engineered, and finally the specialized population can be relntroduced Into
the environment from which they came (Omenn. 1964). In addition, genetic
manipulation of ollgotrophic bacteria with high affinity enryae systems may
be advantageous because these enzyme systems will allow the organism to
attack low concentrations of organic pollutants (Johnston and Robinson.
1982b).
Seeding Aqueous Environments with Microorganisms—
Tnoculants of specialized microorganisms have been used In treatment of
contaminated water. Atlas and Bartha (1973) tasted several commercial
bacterial preparations and found that the Inocula were ineffective In
treating oil spills In the marine environment. However, the addition of
fertilizer and a bacterial aeed Isolated from an estuarlne environment
Increased petroleum degradation In a saline but not In a freshwater pond
(Atlas and Busdosh. 1975). After six weeks. 50 percent of the oil remained
In the saline pond. The lack of activity In the freshwater pond suggests
that the inoculum should b« cultured from an environment similar to that
being treated. Colwo11 and WalVer (1977) suggeated that aeedlng would be
unsuccessful In environments such as the ocean; however, contained spills
and lagoons may be amenable to such treatment. Cutnlek and Bocenberg (1977)
staled that "there ie no evidence to support lha claim that "seeding" oil
•licks with microorganisms reduces oil pollution by stimulating petroleum
blodegradatlon."
Seeding Soil Environments with Hlcroorganlsas—
The efficacy of Inoculating soil with acclimated bacteria to remove
selected contaminants was tested In a bar lea of experiments (Uetzel nt el..
1981) using experimental chambers set up In groenhouoea. The contaminants,
74
« not successful in ^1^.^^ ' "««•» °< the
1.jr,d«Llon of the C*l* c« . !°U '"thtly increased the
.oil. amended with f ertm^on? °U>. »' "-"-nes ln co.pari.on "o
lack of enhancenent
ba
75
-------
r.,ult of tn.d.«U»t. appliealon of th. Inoculu.. It.. km °' or*tnl'"
Ittv.atlgatlon.
(H.rtln.on
to 20 pee.nt.
, io> e.ll./f
ob..rv.d .t
i 1 i x
• 1*
1 (HB6) »ug»»»t«d
" .^ i« b. u..d to tr..t
b.lo« th. thr.«hUld of
•« -;.:: •."Si"" "~
•yit.a u.lnt two fluid film r.icto^. In *.rl.i w«« th.n propo*.d; th. flrit
rcictor would r.duc. high eonc.ntratlont of PCP »nd th. i.cond roctor would
COntlln orgSnlin* th.t Could r«mow«'PCP to low Uv»l«. Th. contort lum w..
•bl. to r.no«. PCP to l.t* th.n 1 vt/L wh.n th. Initial concentration*
w.r. Lit thin 1
74
S..dln( th. Subfurf.c. with Hlcroorginl.*.— -
Inoculation of b.et.rl. Into th. .ub.urf.c. for blor.itor.tlon h.i b..n
Mt with io>. lucctii, but th. contribution of th. Introduced b.et.rl. to
th. ov.r.lt el.tnup c«n not b. r.idllx d.t.raln.d. In Bo.t c.*.*, th. rol.
of th. Introdue.d b.et.rl. In d.gridttlon pf th. contulntntt e.n not b.
d.t.rnln.d b.etut. ipproprlat. control ploti w.r. not Incorporit.d Into th.
.xp.rlB.nt.l d.ilfn and th. rxulti w.r. not qu.ntltttlv.ly iM.fur.d
throughout th. court, of th. pro J act. Th. blgg.it conc.rn of Inoculation
Into th. tubiurf.c. ti .muring contact b«tw..n th. ip.el.llt.d e.ll. and
th. t.rg.t contaminant*. Th. c.ll* may b. fllt.r.d out of th. p.rfu.lng
lotutlon or §orb«d onto toll b.for. r..chlng th« contiuiln.nt* (Bouwar,
1484). In addition, normal dla-off nty control th. taovwaant and .pr.ad of
bacl.rl. In w.ll-*ort.d aand, gr.v.li, (ractur«d rock, and kar.tle llna.ton*.
rtleroblal novaa^nt through th. lubiurf.c. d.p.nd* on th.
characttrlitlc* of th. .oil and nlcroorganl*!.*. Only 1 parcant of an
Inoculuia of a P*audoaiona« (tr.ln ptn.d through . 2-lnch aanditona cor.
•ftar w.thing with 12) por. volun.* (J.nnmun *t .1., 1984). P.n.tr.tlon of
bactarla Into .anditon. cor.* with hydraulic conductlvlti.* gr.at.r than 100
•lllldarcta* wai rapid; how.v.r, p.n.tr.tlon In cor.* with hydraulic
conductlvlti.* b.low 100 nlllldarcl.l wai flow (J.nnaaan .t .1., 1965).
Hot 11. bactarla nov.d thr.. to .Ight tlm.. faatar than nouotll. bact.rl*.
Hag.dom (I9S4) *una.rlc.d th. r.ault* of i.l.ct.d itudl.* on th. oaxliiu>
dlatanc* th.t microorganism* inovad In varlou. .oil.: 19.1 « In 27 weak. In
a fin. land; 10.7 • In a land and aandy clay In eight w«.k*: 24.4 • In a
fin. and coar*. i.nd (tin. of tr.v.l not r.port.d); 30. 5 • In . a.nd and pea
gr.v.l iqulf.r In 35 hour*; 0.6 to 4 m In a fin. ..ndy loaa (tlia. of tr.val
not r.porttd); 457.2 • In . coar*. graval a. conducted. The formation mult bit permeable enough to p.rfu*. nutrient*
and th. Inoculum through th. tone of contamination.
77
-------
Aquifer 8*aodl»tlon Ualng Inoculation Techniques- -
Inoculation of microorganisms Into the subsurface haa been unud In
aquifer remediation In conjunction with wastewtter treatment processes.
These esses are summarized In Table 2-9. A representative system 1« shown
In figure, 2-3. In on« case study, 7.0OO gallons of acrylonltrile was
spilled in a metropolitan area from a leaking rail ear (Uallon and Oobb«.
1980). The receiving aquifer contained ilgnlfleant amount« of allt and clay
and hence waa rather impermeable. Initial treatment Involved withdrawal and
treatment of the ground water by air stripping. After the concentration of
acrylonltrlle had declined to nontoxlc levcla, mutant bacteria were seeded
Into the eoll. The concentration of acrylonltrlle declined from l.OOO ppo
to nondetectable level* (Unit of detection 2OO ppb) within one month;
however, the role at the bacterial seed In aerylonltrlle degradation could
not b« determined.
Quince and Cardner (19B2a; 1982b> documented the cleanup of 100.000
gallons of various organic compounds. Including ethylene glycol and propyl
ecetate, over a 250.000 square foot ar«a. The soil consisted of a thick
sllty clay that extended to a depth of nor* than iO feet; migration of the
organics Into the main aquifer was prevented by the structure of the
formation. Containment and recovery of the organic* were Halted to the
perched water table located In the upper eley layer. The contaminated
ground water was withdrawn and treated by elarlfIcstlon. aeration, and
granular activated carbon. A blostlnulstlon program with specialized
bacteria, nutrlente. and air was Initiated after the levels of the
contaalnanti had decreesed from 2.0OO-10.0OO ppm to less than 2OO ppm.
During treatment, the concentration of ethylene glycol was reduced from
1.200 to less than SO mg/L. propyl acetate was reduced fron 500 ng/t. to less
than SO mg/L, end the total concentration of >pltl«d compounds declined from
34,OOO to lee» than 100 ag/t.. The resulting concentretlons of contaolnanta
were acceptable to the regulatory agencies.
Quince and Cacdix«r <1982s; 19B2b) dotuswntsd lh» cleanup of • number of
organic chemicals Including dlchlorobefliene. swthylene chloride, and
trlchloroethane that contaminated the subsurfece as a result of a spill froe
leaking tenkers. The treatment scheme Included recovery of product with a
vacuum system, soil flushing. »lr stripping, and then Inoculation of
conaerclel hydrocarbon-degrading bacteria Into an above ground reactor
followed by recharge of the affluent Into the subsurface. A commercial
nlcroblal Inoculum seeded Into the above ground reector slgnlfIcsntly
decreased the concentrations of the organic contaminants after 3« hour* of
exposure. The operation was terminated after a 9S percent reduction In the
organic levels was achieved. The Injected hydrocarbon dsgnders were
expected to complete the blodegradatlon In sUui however, the rol« of the
added bacteria was not demonstrated.
An accidental spill of 130,000 gallons of organic chenlcels entered e
IS fool thlcV shallow uneonflned aquifer and resulted In total contaminant
levels as high as 10.000 ppo (Ohneck and Cardner. 1982). A drinking water
aquifer we* separated from the eontenlnuted tone by SO to to feet of sllty
tlay. The contaminated ground water was withdrawn and treated by
clarification, granular activated carbon adsorption, and air stripping. A
76
TABLB 2-».
Compound
acrylonltrlle
phenol and
ehlorophanol
ethylene glycol and
propyl acetate
dlchlorobenzene,
dlchloromethene.
and triehloroethane
unidentified organic
compound s
formaldehyde
OT1LII1BO ,„,„„,„,.„
Treatment Description
Reference
mutant bacteria added after
concentrations had been
reduced by etr-strlpplng
initial treatment by
adsorption onto CAC
followed by Innoculatlon
with mutant bacteria
treatment above ground
and later with epecl.lU.d
bacteria,
Initial treatment with
air stripping and then
Innoculatlon with a hydro-
carboii-degredtng bacteria
hydrocarbon-degrading
bacteria added after levels
reduced by CAC and sir
stripping
commercial dagrader added to
above ground treatment system
formed from call ballast
Walton and Dobbs, 1980
Walton and Dobbs, 1980
Quince and Cerdner
1982s and b
Quince and Cerdner.
19B2a and b
Ohneck and Gardner.
1982
Sikes et al.. 1984
«Uh hydro*.ro0n Se^.dlng b«!.rla llT I ""'J-"1 •»«- -•• «-"<«.d
the vsdos. zone A^" result fh ' " """-ients. Md Injected Into
..U cor. were "educed " '' " "" "n^^' 1" on.
-ter were
J9
-------
omecrwN OF GROUND WATER now
INJECTION SYSTEM
/ T
2ONE Of CONTAMINATION
I T I T T T T T
Tl I 1 I i . i J
RECOVERY SYSTEM
t t
fl»ur« I-J. Combination of cbovo «round tr*«tMnt with In .ttu
blor**toratton. ^"^
Ineorporallon of blolotlc«l tr.ttMnt Inlo th. r..tor.Uon pro§r« d.cr.n.d
th« v«d by • ».euu« ln»ck .nd JiO cubic ytrdi o( loll v.r. .x.vat.d
t.l/ U •llllon (•lion* of w.l.r w.. collected. Th« w.t.r w««
tr.«t.d with hrdro(«n »*co»ld» to r.Ooc. th« concentration of
forMld.lijrd. fro. JO.OOO-iO.OOO to SOO-l.OOO ppn by onldttlon. S** S.ctlon
ir.D. for Mr* d«UU« of th* u>* of hydro(*n p.roxld. In thU c»*« itudy
Ttio f.«.lbllltr of la sliu btolotlc.l d«(r*d*tlon of the r.««lnln(
foruldehyde u.lni t cwiewrcUl becterUl Inocultn v«* then lnveitU»t»d. A
«o«n«reiel inoculu* th«t contained .p.cl.lly cultured •Icroorsenicne u.i
«ho«en (or the project. The btolo(tcel treatment lytteei eontUted of e
the
for^ldehyd.
of th, /orM,d.h
th.r concede that proving the
rd. d.fr.d.Uon w^ld "
•««•; a
The author. ,UM..t th.t
J "«lo§ietl activity.
"ltroo«-»"'l— In
" •<""*«• »»• «1. of
lwd. d.lr.d.tlon could not b.
-------
TRANSPORT AND FATE
SIMULATION AND
PREDICTION
Session 7
Joseph F. Keely
(Oregon Graduate Center)
-------
MODELING APPROACHES
• Conceptual
• Physical
• Analog
• Mathematical
TYPES OF MODELS
i Flow models
i Transport models
Multi—phase models
Chemical reaction models
Parameter identification
models
Data manipulation models
Resource management models
-------
MODEL
DIMENSIONALITY
• 1,2,3-D spatially
• Steady—state or
transient
• Non-dimensional
CONCEPTUAL MODELS
Definition:
An organizational framework for
observations and ideas, that conveys
an impression of causes and effects
of the observations.
Example:
Integration of the natural processes
that affect the movement of a specific
contaminant in a particular setting,
for assessment or prediction purposes.
-------
CONCEPTUAL FLOW
MODELS
• Confined (artesian)
flow
• Unconfined
(water-table) flow
• Fractured rock flow
• Multi-phase flow
• Unsaturated (vadose)
zone flow
-------
CONCEPTUAL
TRANSPORT MODELS
• Advection—dispersion
• Diffusion dominated
• Advection dominated
• Advection-diffusion
• Discrete fracture
• Dual porosity, MING
» Multi-phase
-------
CONCEPTUAL
MULTI-PHASE MODELS
» Unsaturated (vadose)
zone
• Salt-water intrusion
• Immiscible phases
(NAPL's)
• Compositional
simulators
CONCEPTUAL CHEMICAL
MODELS
• Equilibrium speciation
• Mass transfer
• Mass balance
• Kinetic rate
• Graphical relationships
-------
INTEGRATED
CONCEPTUAL MODELS
• Transport and speciation
• Transport and kinetics
• Well-mixed reactor cells
• Density dependent
transport
OTHER CONCEPTUAL
MODELS
• Inverse parameter i.d.
• Data input & output
*
• Statistical methods
• Resource management
• Economics
-------
PHYSICAL MODELS
Definition:
A scaled replica of a real—world
system, simplified and idealized for
practical considerations.
Examples:
"Sand-tank" artificial aquifers,
laboratory column experiments, and
biological microcosms.
ANALOG MODELS
Definition:
A contrivance that imparts insights
regarding cause & effect relationships
•within one physically distinct system
to those of another physically distinct
system.
Example:
Electric-analog model for water-
supply wellfield management, using
resistors for permeability, capacitors
for storage effects, etc.
-------
MATHEMATICAL MODELS
Definition:
A collection of equations that relate
input parameters and variables to
quantified outputs, based on specific
assumptions and simplifications of the
real-world system being modeled.
Example:
The Konikow-Bredehoeft contaminant
transport model that employs a finite
difference formulation for the flow
field and a method-of-characteristics
formulation for transport predictions.
FORMS OF
MATHEMATICAL MODELS
• Analytical - closed form
solutions
H Numerical - iterative
solutions
• Semi-analytical - mixed
form
• Computer - any form,
codified
-------
STATISTICAL BASES OF
MATHEMATICAL MODELS
• Deterministic (spatially &
temporally fixed
inputs and outputs)
• Stochastic (probabilistic inputs
and/or outputs)
• Geostatistical (spatial
interpolation)
» Statistical (regression,
correlation)
-------
EPA/600/2-86/062
July 1986
PERFORMANCE AND ANALYSIS OF AQUIFER TRACER TESTS
WITH IMPLICATIONS FOR CONTAMINANT
TRANSPORT MODELING
Fred J. Molz, Oktay Giiven, Joel G. Melville
Civil Engineering Department
Auburn University, AL 36849
and
Joseph F. Keely
Robert S. Kerr Environmental Research Laboratory
U.S. Environmental Protection Agency
P.O. Box 1198, Ada, OK 74820
CR-810704
Project Officer
Joseph F. Keely
Robert S. Kerr Environmental Research Laboratory
Ada, OK 74820
ROBERT S. KERR ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
ADA, OK 74820
-------
DISCLAIMER
The Information In this document has been funded wholly or In part
by the United States Environmental Protection Agency under assistance
agreement number CR-810704 to Auburn University. It has been subject to
the Ayency's peer and administrative review, and It has been approved
for publication as an EPA document.
11
FOREWORD
The U.S. Environmental Protection Agency was established to coordinate
«d»1n1str»t1o« of the nwjor Federal programs desired to protect the quality
of our environment.
An luportant part of the Agency's effort Involves the search for
Information about environmental problems, management techniques and new
technologies through which optimum use of the Nation's land and water resources
"n be assured and the threat pollution poses to the welfare of the American
people can be minimized.
EPA's Office of Research and Development conducts this search through a
nationwide network of research facilities.
As one of the
the Robert S. Kerr Environmental Research
til srs
.
Me soil .^.subsurface environment, for the protection of this resource.
This report contributes to that knowledge which Is essential In order
for EPA to establish and enforce pollution control standards which ,«
reasonable, cost effective and provide adequate environmental protection for
the American public.
Clinton U. Hall
Director
Robert S. Kerr Environmental
Research Laboratory
111
-------
Abstract
Due to worsening national problems, hydrologlsts are being asked to
Identify, assess or even anticipate situations Involving groundwater con-
tamination, and a large fraction of the regulation activities of the U.S.
Environmental Protection Agency Is In the groundwater area. In both regula-
tion and assessment. Increasing use 1s being made of complex mathematical
models that, are solved with the aid of a digital computer. Typically, such
models are collections of partial differential equations that contain a
number of parameters which represent aquifer physical properties and must be
measured 1n the field. Of the various parameters Involved, the hydraulic
conductivity distribution 1s of najor Importance. Other parameters such as
those relating to sorptlon, hydrodynamlc dlspersloon, and chemical/biologi-
cal transformation are Important also, but hydraulic conductivity 1s more
fundamental because combined with head gradient and porosity It relates to
where the water Is moving and how fast. Therefore, this communication 1s
devoted mainly to the conceptualization and measurement of hydraulic
conductivity distributions and the relationship of such measurements to
dispersion (spreading) of contaminants 1n aquifers.
For the most part, contemporary modeling technology Is built around
two-dimensional models having physical properties, such as transm1ss1v1ty,
that are averaged over the vertical thickness of the aquifer. In such a
formulation, the major aquifer property related to contaminant spreading 1s
forced to be longitudinal d1spers1v1ty. This 1s not due to any fundamental
theoretical limitation. The major limitation 1s that dependable and
economical field approaches for measuring vertically-variable hydraulic
iv
conductivity distributions are not available. In the absence of such data,
one his no choice In a modeling sense but to use sows type of vertically-
averaged advection-dlsperslon approach built around full aquifer longitudi-
nal dispers1v1t1es.
In order to begin to overcome this limitation, a series of single-well
and two-veil tracer tests were performed at a field site near Mobile,
Alabama, and a major objective of this communication 1s to describe these
tracer tests and discuss some practical implications of the results with
regard to modeling of contaminant dispersion In aquifers. The tests utilize
wmilevel sampling wells which have to be designed and Installed carefully.
Tracer test results along with theoretical studies suggest that the follow-
ing working conclusions are warranted.
I. Local longitudinal hydrodynamlc dispersion plays a relatively
unimportant role 1n the transport of contaminants 1n aquifers.
Differential advectlon (shear flow) in the horizontal direction
is much nore Important.
II. The concept of full-aquifer dlsperslvlty used in vertically-
averaged (areal) models will not be applicable over distances of
Interest in most contamination problems. If one has no choice
but to apply a full-aquifer dispersion concept, the resulting
dlsperslvlty will not represent a physical property of the
aquifer. Instead, it will be an ill-defined quantity that will
depend on the size and type of experiment used for its supposed
measurement.
III. Because of conclusion II. It makes no sense to perfor. tracer
tests aimed at measuring full-aquifer dispersivlty. If an areal
-------
model it used, the modeler will end up adjusting the dlsperilvlty
during the calibration process anyway. Independent of the
measured value.
IV. Vhen tracer tests are performed, they should be a fined at
determining the hydraulic conductivity distribution. Both our
theoretical and experimental work have indicated that the vari-
ation of horizontal hydraulic conductivity with respect to
vertical position Is a key aquifer property related to spreading
of contaminants.
V. Two- and three-dimensional modeling approaches should be utilized
which emphasize variable advectlon rates In the horizontal
direction ana* hydrodynamlc dispersion In the transverse direc-
tions along with sorptlon and mlcrobial/chemlca! degradation.
VI. In order to handle the more advectlon-dominated flow systems
described In conclusion V, one will have to utilize or develop
numerical algorithms that are more resistant to numerical
dispersion than those utilized in the standard dispersion-
dominated models.
Much of contemporary modeling technology related to contaminant trans-
port may be viewed as an attempt to apply vertically homogeneous aquifer
concepts to real aquifers. Real aquifers are not homogeneous, but they are
not perfectly stratified either. What Is being suggested, therefore. 1$
that the time may have arrived to begin changing from a homogeneous to a
vertically-stratified concept when dealing with contaminant transport.
realizing fully that such an approach will be Interim In nature and not
vl
totally correct. Field calibration will still be required. However, the
performance and simulation of several single- and two-well tracer tests
suggests that the stratified approach 1s much more compatible with valid
physical concepts, and at least In some cases results In a mathematical
model that has a degree of true predictive ability.
An obvious Implication of the study reported herein 1s that any type of
groundwater contamination analysis and reclamation plan will be difficult.
expensive and probably unable to meet all of the desired objectives in a
reasonable tine frame. Therefore, one can not overemphasize the advantages
of preventing such pollution whenever it is feasible.
-------
CONTENTS
Foreword in
Abstract iv
Figures *
Tables xii
1. Introduction 1
EPA's Site-Specific Modeling Efforts 2
EPA's Generic Modeling Efforts 3
Subsurface Transport Models 4
The Hydraulic Conductivity Distribution 6
The Mechanisms of Dispersion 9
Simulation of Advectlon-Dlsperslon Processes II
2. Types of Tracer Tests 18
3. Design and Construction of Multilevel Sampling Wells 23
4. Performance and Results of Single-Well and Two-Mel 1
Tracer Tests at the Mobile Site 37
Single-Hell Test 44
Two-Well Test 52
5. Computer Simulation of Single-Well and Two-Well
Test Results 61
Simulation of Sinyle-Well Tests 61
Simulation of Two-Well Tests 68
6. Discussion and Conclusions 79
References 86
ix
-------
FIGURES
Number
I Hypothetical velocity distribution
2 Schematic diagram of contaminant concentrations
3 Vertical cross-sectional diagram of single well
8
9
10
test
4 Two-welt test geometry in a stratified aquifer
5 Various types of multilevel sampling systems
et al. multi-level sampling/observation well
11 Diagram of a completed multilevel sampling well
12 Diagram Illustrating the scheme for
13
14
the
effects °f drmin»
•>*"«
system used ,B th. single- and two-we., trace
Page
. 14
. IS
. 19
. 22
. 25
. 26
. 27
. 29
, 31
32
33
34
36
15 Diagram of the subsurface hydrologic system at the Mobile site .... 39
16 P1t(le9|tob?ledsHe9 "*""* assoc1ated ««th P"Plng wells at
17 ';:,'£ '"M "! Xl*'-*™** «? •«"•« M».11e
43
18 Broil I de concentration In the Injection/withdrawal well (12) 46
19 Bromide concentration breakthrough curves at the seven
levels of well £3 during experiment K4 47
20 Electrical conductivity breakthrough curves at various
levels of well E3 during experiment H
48
21 Inferred normalized hydraulic conductivity distribution 53
22 Injection well tracer concentration versus time during the
first 80 hours of the two-well test 56
23 Measured tracer concentration versus 'time in the withdrawal
well during the two-well test 57
24 Measured and predicted breakthrough curves at the 7 levels
of observation well E3 59
25 Normalized hydraulic conductivity distribution inferred from
travel times Measured during the two-well test 60
26 Hydraulic conductivity profile 63
27 Unsteady injection concentration during the Pfckens and Grlsak
(1981) single-well field experiment 64
28 Comparison of SUAOM results with field data for the flow-weighted
concentration from an observation well one meter from the
injection-withdrawal well 66
29 Comparison of SWAOH results with field data for the flow-weighted
concentration from an observation well two meters from the
injection-withdrawal well 67
30 Comparison of SWADH results with field data for the concentration
leaving the injection-withdrawal well 69
31 Results of various simulations of the two-well test
32 Calculated tracer concentration versus time in the withdrawal
well
73
76
33 Comparison of measured and calculated tracer concentration
versus time in the withdrawal well 78
34 Preliminary results of four single well tests performed at the
Hoblle site 83
xi
-------
TABLES
Number
1
Page
Two-
49
71
Introduction
Due to worsening national problems and potential problems relating to
Industrial waste disposal, municipal waste disposal, radioactive waste dis-
posal and others, there 1s Increasing pressure on hydrologlsts to Identify,
assess or even anticipate situations involving groundwater contamination.
In order to meet these demands, subsurface hydrologists have turned
Increasingly to the use of complex mathematical models that are solved with
the aid of a digital computer. Some of the principal areas where
mathematical aw dels can now be used to assist 1n the management of EPA's
groundwater protection programs are:
(1) appraising the physical extent, and chemical and biological
quality, of groundwater reservoirs (e.g., for planning purposes),
(2) assessing the potential Impact of domestic, agricultural, and
industrial practices (e.g., for permit Issuance, EIS's, etc.),
(3) evaluating the probable outcome of remedial actions at hazardous
waste sites, and of aquifer restoration techniques generally,
(4) providing exposure estimates and risk assessments for
health-effects studies, and
(5) policy formulation (e.g.. banning decisions, performance
standards).
These activities can be broadly categorized as being either site-specific or
generic modeling efforts, and both categories can be further subdivided into
point-source or nonpolnt-source problems. The success of these efforts
depends on the accuracy and efficiency with which the natural processes
controlling the behavior of groundwater, and the chemical and biological
species 1t transports, are simulated. The accuracy and efficiency of the
simulations, in turn, are heavily dependent on the applicability of the
xii
-------
assumptions and simplification adopted In the model(s), and on subjective
judgments made by the modeler and management.
EPA's Site-Specific Modeling Efforts
Whether for permit Issuance, Investigation of potential problems, or
remediation of proven contamination, site-specific models are necessary for
the Agency to fulfill Us mandate under a number of major environment:!
statutes. The National Environmental Policy Act (1970) stipulates a need to
show the Impact of major construction activities 1n Environmental Impact
Statements and potential Impacts are often projected by the use of
mathematical models. The Underground Injection Control (UIC) program, which
originated In the Safe Drinking Water Act (1974) (SDWA) and Is now subject
to provisions of the Resource Conservation and Recovery Act (1984 Amend-
ments) (RCRA). requires an evaluation of the potential for excessive
pressure build-up and contaminant movement out of the Injection zone.
Mathematical models are the primary mechanism for the required evaluation,
due In part to the difficulty of Installing monitoring wells several
thousand feet deep.
UIC also calls for determinations of which aquifers serve, or could
serve, as underground sources of drinking water (USDW's), based on a lower
quality limit of 10,000 ppm total dissolved solids. Here, modeling has been
found to be a useful adjunct to gathering and Interpreting field data, such
as In the U.S. Geological Survey's efforts to assist EPA In determining
USDW's (e.g., the RASA program). Another SDHA program, for the designation
of Sole Source Aquifers (SSA), has frequently employed the use of models for
establishing and managing water-quality goals. Designation of the Spokane
Valley - Ratbdrwt Prairie SSA. for Instance, Included an evaluation of
nonpolnt-soureei of nitrates with a groundwater model developed for EPA by
the USGS.
Son* of the most difficult site-specific problems facing the Agency
involve hazardous waste sites falling under the purviews of RCRA and
CERCU/Superfund. Associated with most of these sites Is a complex array of
chenlcal wastes and the potential for groundwater contamination. Their
hydrogeologlc setting, usually •ppt.r quite complicated when examined at the
sule appropriate for technical assessments and remediation efforts (e.g..
100's to 1000's of feet). Groundwater models are used to assist In the
organization and Interpretation of data gathered during remedial Investiga-
tions, the prediction of potential contaminant transport pathways and rates
of migration, the setting of Alternate Concentration Limits, the design and
Carlson of remedial alternatives, and the evaluation of the performance
of final C.s bullf) design, at hazardous waste sites. They are also used
to help determine the adequacy of monitoring and compliance networks, and to
determine the feasibility of meeting clean-up targets.
Ej>A's Generic Modeling Efforts
There are a number of Instances where the Agency has limited data or
other constraints, such that site-specific modeling 1s not feasible. As a
result, many decisions are made with the assistance of generic modeling
efforts. Generic efforts utilize analytical models, as opposed to numerical
models, to a much greater degree than occurs In site-specific efforts. This
1, , logical consequence of the simplified mathematics of analytical models.
-------
the significantly greater data requirements of numerical models, and the
higher costs of numerical simulations.
The Agency has many statutory responsibilities which benefit from
generic modeling, Including the estimation of potential environmental
exposures, and their Integration with dose-response nodeIs to yield
health-based risk assessments. These are necessary, for example, 1n Issuing
compound-specific rulings on products subject to pre-reglstratlon require-
ments under the Toxic Substances Control Act and the Federal Insecticide,
Fungicide, and Rodentldde Act. More generalized policy formulation
activities also benefit from generic modeling efforts. Examples Include
making policy decisions about land disposal 'banning,' preparing Technical
Enforcement Guidance Documents (I.e., for monitoring network designs), and
'dellstlng' under RCRA.
Subsurface Transport Models
The most common types of modern groundwater transport models are a
collection of partial differential equations and other mathematical/physical
relationships that embody our best understanding of the system of Interest,
which 1n the present context 1s an aquifer. Virtually all groundwater
models contain a number of parameters, which are simply numbers or functions
that represent the physical and chemical properties of an aquifer and the
aqueous solution that It contains. In order to apply a model to a
particular problem situation, one must specify all the parameters (length,
width, thickness, hydraulic conductivity, dlsperslvlty. retardation
coefficient, etc.) that pertain to that particular system. This Is what
distinguishes one system from another In the application of a mathematical
model.
In the actual process of using a mathematical model, the user puts all
necessary Information Into the model (geometry, physical properties. Initial
and boundary conditions), and a computer 1s employed to rapidly solve the
resulting equations which generates the model output. Output, for example.
might include a predicted contaminant concentration distribution 10 years In
the future. Presently, this predictive process 1s far from satisfactory
(Konikow. 1986). Our understanding of all the physical and chemical
phenomena Involved is Imperfect, and there are 1n»ense difficulties In
measuring and specifying all of the required Input data. If accurate
Information 1s not put Into a mathematical model, one cannot expect accurate
information to come out.
Over the past decade, a significant number of scientists have concluded
that the single most Important barrier to developing an Improved ability to
simulate groundwater contamination problems 1s our Inability to measure.
specify and, therefore, understand the type of hydraulic conductivity
distribution that occurs in natural aquifers (Smith and Schwartz. 1981).
This is not to say that other parameters such as those relating to sorptlon.
hydrodynamic dispersion and chemical/biological transformations are not
Important. It is simply that the hydraulic conductivity 1s more
fundamental, because together with the hydraulic head distribution and
porosity, it is the physical property that relates to where and how fast the
groundwater 1s moving. If one does not have the ability to specify the
location of a parcel of water at a given time, one can hardly specify what
-------
^
'• "ing on chemically and Mo10fla|1, (.
-un c,Mon „ deyot
* distribution, and «, r.1ltlon,Mp „
to dUp.r,1on (,Pr,.ding) of
The Hydraulic Conduct^*,. Bi..-ft,,,t|njL
Heasurement of hydraulic conductivity ,. difficult beeme of
location „.... belw, «. ,„„„„ ,urfa
"•"Ml aquifers. (It f. not uftcowm)fl
• '"tor of ,0 or more w „„,„„ Qf ^ ^ -f ^ ^ ^
variation, and the unique physic.!, chemical and biological environments
found in the subsurface. It 1, difficult or Impossible to study spatial
variability In a definitive ».y with laboratory experiment,.
According to Philip (1980) field heterogeneity can be classified as
either deterministic or stochastic. Deterministic heterogeneity refers to
hydraulic conductivity variations that are sufficiently ordered to be
characterized by , set number of measurements, although In practice the
measurements may be difficult to make. Stochastic heterogeneity refer, to
nydr.ullc conductivity changes that are essentially random. maMng It
Pointless to try to measure then ,11. However. even tne$e
on scale of observation (problem size), because variations that can be
viewed collectively as stochastic on a sufficiently large scale (regional
scale) My have to be treated as deterministic on a smaller scale such as a
site-specific scale. In addition, stochastic variations are often embedded
In systematic trends (I.e., random variations within discrete strata).
Since a complete characterization of the spatial distribution of
hydraulic conductivity and hence a complete description of all the details
of the flow field In an aquifer are practically Impossible, various
stochastic convection-dispersion models for solute transport have been
proposed In recent years (e.g., Gelhar and Axness, 1983; Winter. 198Z).
While these models may be useful under certain conditions, they also have
various limitations. Detailed discussions of the capabilities and
limitations of these models nay be found In Gelhar et al. (1979). Hatheron
and deHarsily (1980), Gelhar and Axness (1983), Dagan (1984). and Sposlto.
Jury and Gupta (1986). As reviewed In detail In the recent paper by
Sposlto. Jury and Gupta (1986). all such models Involve a conceptual
collection (ensemble) of statistically similar aquifers rather than a
specific real aquifer. Consequently, these stochastic models provide
results which are averages over the collection and, therefore, not directly
applicable to a single aquifer. In addition, only under very Halted
conditions can measurements In a single real aquifer be related even
conceptually to the statistics of a collection of aquifers that contains the
real aquifer as one of Its members. Essentially, the real aquifer must be
statistically homogeneous on the average and ergodlc (rieuman, 1982; Sposito,
Jury and Gupta, 1986). Without going Into details here, It Is sufficient to
-------
»X that such a condition is very restrictive and does „„, all(jw
to have the type of genera, variability and persistent hydraulic conduc-
tivity trends that we thieve are essential to understanding contaminant
transport. Part1CU,arly In site-specific situation, Invoking re,at1ve1y
s-ort trave, distances. For these reasons and others. Sposlto. Jury and
C«PU (1986, conceded that -.«,, TOre theoret1ca, „„.„„ f§ ^^ ^
the stochastic convection-dispersion TOdel does not yet warrant unqualified
u« .s a too, for physically ^ quantitative appHcatlons of so,ute
transport theory to the management of so,Ute movement at f,.,d scales."
I" order to circumvent the fundamental difficulties of the stochastic
convection-dispersion approach discussed In the previous paragraph and to
-------
familiar to almost everyone. However, as Illustrated 1n Figure 1, nany
different phenomena contribute to the dispersion process 1n aquifers. The
horizontal extent of the hypothetical tracer plume In Figure 1 Is determined
mainly by the elapsed travel time and the difference between the maximum and
minimum values of the horizontal advectlve velocities. These velocity
variations result primarily from the variations of hydraulic conductivity.
Dilution within the plume and along the plume boundaries Is caused by
pore-scale mixing (local hydrodynan/lc dispersion) due In part to molecular
diffusion, velocity variations wlthlr, each pore, and the overall tortuosity
of the flow path. In the hypothetical situation depicted 1n Figure 1, there
Is an overall trend of hydraulic conductivity Increase from the top towards
the bottom of the aquifer. Four minor trends, resulting In hydraulic
conductivity peaks In both the upper third and bottom third of the aquifer.
are evident also, with the lower peak being more pronounced. The plume
concentration distribution 1$ determined to a large extent by these trends.
In addition, there are "wobbles" In the concentration distribution caused by
seepage velocity components In all directions at a scale smaller than the
scale of the minor trends noted above. Thus the actual concentration
distribution of the plune Is determined by a combination of strata-scale
advectlve effects arising from the nonunlform velocity distribution and
pore-scale mixing effects caused by the concentration differences within the
plume and the basic nature of pore-scale flow. This pore-scale effect Is
most pronounced at the plume boundaries because the concentration gradients
are largest there. In addition, wobbles In the concentration distribution
at an Intra-stratum scale could, after a sufficient travel time, result In a
type of semi-local mixing, which some researchers have called macro-
dispersion (Gelhar and Axness. 1983). As the plume travels further
10
downstream, the concentration gradient, In the transverse direction would be
gradually smoothed out due to both hydrodynamlc dispersion and seepage
velocity components In the tran,ver,e direction and a somewhat well-mixed
condition would develop at each stre.nulse station over the whole depth of
the aquifer after a sufficiently long travel tine. However, the time
required for this behavior could be very large (see. e.g., Gelhar et al..
1979; Matheron and deHarslly. 1980; Molz et al. 1983; Guven et al.. 1984).
In many site-specific situation,, such large tr.vel time, are usually not
involved, and variation, of concentration over the depth of the aquifer are
expected to be an Important consideration when dealing with particular
site-specific problem,.
Simulation of Advect1onH)1sper,1on Processes
Historically, the field of subsurface hydrology developed mainly In
response to groundw.ter supply problems. To solve such problems there was
often little need to develop detailed Information concerning the spatial
variability of hydraulic conductivity within a given aquifer. Knowledge of
the average tr.nsmlsslvlty and stor.tlvlty of the aquifer was adequate along
with specification of the vertical aquifer boundaries (water table or
confining layers) and In some case, the lateral boundaries. For these
condition,. one-d1men,1onal, horizontal, transient flow 1n a confined
homogeneous aquifer may be written a, (Freeze and Cherry. 1979)
»2h S »h (1)
where x - length In the direction of flow, t • time, h • hydraulic head. S -
storatlvlty and T - tr.nsmlsslvlty. Typically, the average S and T values
would be determined by a pumping test utilizing fully-screened, fully-
penetrating pumping and observation wells (Freeze and Cherry. 1979).
11
-------
More recently, when societal trends shifted from groundwater supply to
groundwater contamination problems, it seemed logical to work with the
contaminant transport version of equation (1). For steady horizontal flow
but transient (time changing) dispersion of a conservative solute in a
confined aquifer, this equation is given by (Freeze and Cherry. 1979)
" + V»'DL;7 <2>
-here c » solute concentration, V « uniform seepage velocity and DL • longi-
tudinal dispersion coefficient. DL is given by the product «LV. where «L 1s
the longitudinal dlsperslvlty. which represents the random local mixing
properties of the aquifer. But what happens if one attempts to blindly
apply equation (2) to the situation depicted in Figure 1? First of ,11. one
would have to work with some average horizontal velocity. V. an average
concentration. E. and some type of apparent or effective dispersion coeffi-
cient, Of, which we will call the "full aquifer" dispersion coefficient.
«th these assumptions, solutions of equation (2) would predict tracer
distributions similar to those shown in Figure 2. Comparison of the
predicted distributions (which, as a result of the assumptions are uniform
In the vertical direction) with the more realistic distribution (Figure IB)
shows this approach to be generally unsatisfactory. A lot of useful
Information has been lost by not incorporating the vertical distribution of
hydraulic conductivity. This example highlights the problem that results
-hen attempting to solve groundwater contamination problems with approaches
found to be useful In water supply problems. Two-dimensional versions of
equation (2) are the so-called area! advectlon-dlsperslon models; they are
based on the same vertically-averaged approach and thus suffer from the same
limitations.
12
If one considers explicitly the vertical variation of hydraulic conduc-
tivity for the transport problem Illustrated In Figure 1 with flow, V(z),
parallel to the stratification 1n a horizontal stratified aquifer, the
governing equation becomes {Molz, Guven and Melville, 1983)
(3)
»x
where c « c(x,z,t) • concentration distribution, z = vertical coordinate, OT
• OTV(Z) » transverse (vertical) dispersion coefficient, DL •
-------
(A)
^3»
^
Hypolhelicol i
/Velocity
"••^ j Dislribulion
^ *^ i
^^^ 1
1 i -y *T, Jjjjjjjjii , , , \
/Tracer al
Tlme-0
4-
Tracer Dislribulion
al Time >0
Figure 1. Part (A) show, a hypothetical velocity distribution and an Initial
distribution of tracer while part (B) shows how the tracer would
be dispersed by the moving groundwater at several different scales.
Three common mechanisms of pore scale dispersion (velocity variation
within a pore (a); flow path tortuosity (6), and molecular diffusion
due to concentration differences (Y) ) are Illustrated also.
14
(A)
\\\\\\\\\\\\V\\\
Tracer at
time=0
Tracer al later
limes I, and I25
(B)
A
Displacement
Figure 2. Schematic diagram showing the Inherent lack of vertical
contaminant concentration structure resulting from
vertically-averaged transport models (part A) and
the resulting plots of concentration versus distance
(part B).
!'
-------
*« to a combination of local nixing. DT
-------
Types of Tracer Tests
It Is generally agreed that tracer tests are currently the rest relia-
ble field methods for obtaining data to describe dispersion 1n groundwater.
Most tracer tests can be placed In two major categories—natural gradient
and forced gradient. As the name Implies, natural gradient tests Involve
various means of placing an Inert, non-adsorbing chemical (tracer) In an
aquifer and allowing It to move with the natural groundwater flow (Sudlcky,
Cherry and Frlnd. 1983). Stanford University, In cooperation with the
University of Waterloo, has recently completed a detailed natural gradient
test soon to be reported In Hater Resources Research. Herein we are con-
cerned mainly with forced gradient tests which employ pumping wells
(Injection and/or withdrawal) to move a tracer through the test aquifer.
Normally, the selected pumping rates are such that the resulting hydraulic
gradients are much larger than the natural gradient. For this reason,
forced gradient tests are much shorter In duration than natural gradient
tests. The most common types of forced gradient tracer tests are single-
well tests and two-well tests. Over the past two years, both types have
been performed at the Mobile site (Molz et al., 1985, 1986). and both types
have been studied In some theoretical detail relative to their analysis and
Interpretation In stratified aquifers (G'uven et al., 198S, 1986). The
stratified aquifer assumption represents the simplest aquifer Idealization
having a horizontal hydraulic conductivity distribution that depends on the
vertical coordinate (Guven. Molz and Melville, 1984).
Shown In Figure 3 Is a typical configuration for a single-well test.
The term "single-well* represents the fact that only one pumping well Is
required In order to perform the test. As detailed In Guven et al. (1985),
an observation well with multilevel samplers Is required In order to obtain
18
INJECTION
WITHDRAWAL
ONFINING LAYER
INJECTION-
WITHDRAWAL
WELL
OBSERVATION
WELL
WITH
MULTILEVEL
SAMPLERS
LOWER CONFINING LAYER
Figure 3. Vertic.l cro.s-seccion.l di.gr.. showing single-weH
ce»t geometry.
19
-------
tracer travel time data at several vertical positions In the aquifer. One
or more such observation/sampling wells may be used In any particular tracer
test. Actual test performance Involves the Injection of water having a
known concentration of tracer, C
-------
Injection well
(source)
Withdrawal well
(sink)
Multi-Level
Observation
Vertical section in x-z plane
Figure 4. Two-well Celt geometry In a str.lifted aquifer.
22
node, the water produced from the withdrawal well Is wasted at a safe
distance from the test area. A separate water supply, usually a well In the
sane aquifer but sufficiently far from the two test wells, so that
negligible hydraulic Interference occurs, provides the Injection water. The
Injection tracer concentration In this case Is C1nJ(t) • C1r)(t).
For the two-well tests discussed herein, observation wells containing
Isolated multilevel samplers are Installed between the Injection well and
the withdrawal well In order to sample the tracer concentration at different
elevations In the aquifer during the experiment. From the tracer arrival
times at several Isolated sampling points In a multilevel sampling
observation well, the variation of horizontal hydraulic conductivity In the
vertical my be Inferred (Plckens and Grlsak, 1981). As will be described
In more detail later, the Inference assumes that the aquifer Is perfectly
stratified and of constant thickness and porosity In the vicinity of the
test wells.
Design and Construction of Multilevel Sampling Wells
As explained In the previous section, the most unique aspect of the
single- and two-well tests that we are discussing Is the use of one or more
multilevel sampling wells to obtain tracer travel time data at different
elevations In the study aquifer. This changes the objective of the tests
from attempting to determine a number for the so-called full aquifer longi-
tudinal dtsperstvlty of (which we believe Is rather meaningless at the scale
of practical tracer tests) to one of gathering Information about the advec-
tlon pattern In the aquifer, which In most situations will dominate the
early tracer dispersion process as Illustrated In Figure 1. (Field evidence
In support of this statement will be presented later.) Because of the
emphasis on obtaining accurate tracer travel times at Isolated elevations In
23
-------
the study aquifer, It 1s vital that multilevel sampling wells be constructed
so that dependable data are obtained. Unfortunately, a satisfactory
solution to the multilevel sampling well construction problen 1s not yet
available.
Shown 1n Figure 5 are three multilevel sampling well types. In recent
tracer tests with which the authors are concerned, various versions of type
! have been attempted. Type I and related types have appeal because of the
convenient vertical location of the sampling zones, and the potential
economy of Installation. Illustrated 1n Figure 6 1s the multilevel sampling
system described by Plckens et al. (1978) and later used In single- and
two-well tracer tests (Plckens and Grlsak, 1981). The systeo was designed
for shallow water table applications and was usually forced Into position
using a high pressure water jet (Plckens et al., 1978). Identical or
similar systems have been utilized or tested by other research groups
(Stanford University. Tennessee Valley Authority, personal communications).
For the Plckens et al. (1978) system to perform acceptably, the study
aquifer must collapse around the sampler and make good contact so that
spurious high vertical permeability pathways are not created along or near
the aquifer-sampler boundary (Fig. 14). Apparently, this was not a problem
in the clean sandy aquifer studied by Plckens and Grisak (19E1). However,
In more cohesive aquifers with lower vertical hydraulic conductivities and
higher vertical head gradients, problems have been observed (Tennessee
Valley Authority, personal communication).
Moltyaner and Killey (1986) have developed an automated multilevel
sampling system designed for use with radioactive tracers. This system,
which uses a dry access well monitoring technique, is illustrated In Figure
7. With this arrangement Moltyaner and Killey (1986) made the equivalent of
24
t ;
n
X
o
a
a
V
L
II
r
,
-------
•to vacuum
flask
Surface
PVC pipe
Screen
Figure 6. Pickens et »1. multi-level sampling/observation well.
Steel
Casing
(6")
Packer
.Grout
Slots
/
\
j ! ! %olld PVC
r
Pipe (4")
AQUIFER
^Removable PVC
Insert Pipe 12")
: ::
!! !!
The Insert will
Contain all
Instrumentation
-------
750.000 point measurements using computer-controlled probe placement and
data aqulsltlon. which illustrates one of the tremendous labor-saving >J\an-
tages associated with the use of radioactive tracers.
Presumably, the dry access tube(s) could be Implaced using a variety of
drilling techniques, each of which would have a different effect on the
tube-aquifer boundary. If the tubes were jetted Into th<- study aquifer or
placed 1n augsr holes with the Idea of having the formation collapse around
them, then the saw potential vertical leakage problem discussed previously
would seem to exist. If thick drilling mud were used, however, and the
access tube placed 1n a ntd-llneti hole. 1t would seem that the potential for
spurious vertical leakage would be diminished greatly.
Molz et al. (1985) describe the design and construction of a multilevel
sampling well system for use with chemical tracers In a variety of confined
and unconflned aquifers. The actual sampling system Is not perfected and
should be viewed as a prototype. However, it appeared to work In a satis-
factory manner at the Mobile site.
As shown in Figure 0. the screened portions of the multilevel observa-
tion wells are not of a standard design. The screens themselves are com-
posed of 91 cm (3') slotted sections alternating with 213 cm (71) solid
sections. Although 5 slotted sections are shown In Figure 8 for purposes of
Illustration, the actual screens contained 7 slotted sections.
As also shown in Figure 8, a 5.1 cm (2") diameter PYC Insert was
constructed with slotted and solid portions that matched with those of the
observation well screen. The insert was designed to hold any wires, tubing,
or Instrumentation that Ultimately would be placet) in an observation well.
Composed of threaded 3.05 m (10') sections, the inserts extended all the way
to the land surface. In order to Isolate the various sampling zones, the
28
Steel
casing
(6")
29
-------
Inierts were fitted externally with cylindrical annular Inflatable packers
as Illustrated In Figures 9 and 10. After the required probes, tubing and
wires were placed within the Inserts, the sampling sections were Isolated
Internally with illlcone rubber plugs. The complete Insert was constructed
on the surface, then placed 1n the well, using a crane, positioned and the
packers inflated. After Installation, each Isolated 91 cm <3') sampling
zone appeared as shown In Figure 11. A conductivity probe was placed near
the zone center, and two lengths of vacuum tubing connected the sampling
zone to the surface. This tubing rould be used with peristaltic pumps to
mix the contents of the sampling zone and to obtain groundwater samples for
analysis as Illustrated In Figure 12.
In designing the multilevel sampling wells for use at the Mobile site,
the drilling and well development process illustrated In Figure 13a,b was
visualized. After removal of the drilling equipment, the drilling mud and
disturbed aquifer material are mixed significantly as shown 1n Figure 13a.
The cleaning and development procedure then was to pump and surge the wells
until the water was clear and devoid of drilling mud and fine material. As
shown in case (b), Figure 13, this procedure probably left some drilling
mud adjacent to the solid casing segments and a disturbed (perhaps more
permeable) aquifer material near the slotted segments where samples were to
be collected. Such mud remnants would not be left behind (see Figure 13c)
if a fully slotted screen had been used. The potentially beneficial effects
of a partially slotted (segmented) screen with respect to a fully slotted
screen, and a vertical leakage path possible In the fully slotted case, are
illustrated further in Figure 14. The drllHno mud remnant adjacent to the
solid portion of the screen may result In a barrier to vertical flow that 1s
very desirable. For the fully slotted screen, very little inud remains after
30
Figure 9.
Multil.v.1 ...pit., -ell with sampling zone, l.ol.t.d with
inflit.blt packers and illlcone rubber plug..
31
-------
Top View
Packer M l|;i
\ i I I'll
J [I
Side View
Tubing To
Surface
4" PVC
Packer
! crSlotted
Section
2" PVC
Figure 10. Details concerning the geometry and Installation
of Inflatable packers. The packers were Inflated
with water.
32
•
-------
Peristaltic
xPump Drive
To Sample
Tubing
.Clamps
rom
Sampling
Zone
To Sampling-^.
7nnn ^^
Zone
Figure 12. Diagram Illustrating the scheme for causing mixing In Che various
(solaced sampling tones and obtaining samples Cor Laboratory
analysis.
34
35
-------
packtr
Col segmented
('b') fully.slotted
Figure 14.
36
development and a disturbed aquifer material of possibly higher permeability
would result along the entire length of screen.
The most thought out and best designed multilevel sampling system from
a vertical Integrity viewpoint of which the authors are aware appears to be
the multiple port system manufactured by Uestbay Instruments, Ltd. of Van-
couver. B.C. In Us present configuration, however, the system 1s suited
for groundwater monitoring but not tracer testing which requires the ability
to sample rapidly and simultaneously from a number of elevations. Lack of a
solution to the vertical Integrity problem valid In a broad range of aquifer
types coupled with the unavailability of economic, dependable and flexible
commercial equipment Is a major Impediment to the practical application of
most types of multilevel tracer testing.
Performance and Results of Single-Well and Two-Well
Tracer Tests at the Mobile Site
Using the multilevel sampling wells described 1n the previous section,
a series of single-well and two-well tracer tests were performed at the
Mobile site over the past two years. The major purpose of these tests was
to measure the tracer travel times between an Injection well and one or more
multilevel sampling wells. Subject to several assumptions to be discussed
later In this section, the resulting travel time data allows one to Infer a
vertical distribution of horizontal hydraulic conductivity. He view the
experiments to be described as the simplest and most convenient tracer tests
which yield some Information about the variation of aquifer hydraulic
properties with respect to the vertical position In the aquifer. The basic
experimental plan was to conduct a series of single-well and two-well tests
at different locations In an attempt to build up a three-dimensional picture
of the hydraulic conductivity distribution. He did not attempt to make
point measurements or nearly point measurements as was done by Plckens and
37
-------
GHsak (1981). Our objective was to average tracer travel times over a
suitable aquifer thickness. Thus the Inferred hydraulic conductivity
distribution that results may be viewed as being based on a type of spatial
average.
The project site fs located In a soil borrow area at the Barry Steam
Plant of the Alabama Power Company, about 32 km (20 ml) north of Mobile,
Alabama. The surface zone Is composed of a low-terrace deposit of Quater-
nary age consisting of Interbedded sands and clays that have, In geologic
time, been recently deposited along the western edge of the Mobile River.
These sand and clay deposits extend to a depth of approximately 61 m (200
ft) where the contact between the Tertiary and Quaternary geologic eras Is
located. Below the contact, deposits of the Miocene series are found that
consist of undlfferentlated sands, sllty clays and thin-bedded limestones
extending to an approximate depth of 305 m (1000 ft). The study formation
1s a confined aquifer approximately 21 m (69 ft) thick which rests on the
Tertlary-Quaternarty contact.
Except for the well diameters. Figure 15 Is a vertical section scale
drawing of the subsurface hydrologlc system at the Mobile site. Included 1n
the drawing are 3 pumping wells (El. 12 and E10) and 4 multilevel observa-
tion wells (E5. E3, E7 and E9) all situated at approximately the same
vertical plane. (A schematic plan view showing the wells El and 12 and the
supply well S2 is given In Figure 17). The study aquifer 1s well confined
above and below by clay-bearing strata that probably extend laterally for
several thousand feet or more, and the natural piezometric surface of the
confined aquifer at the test site 1s at a depth of 2 to 3 m (6 to 10 ft)
below the ground surface. In experiments performed to date, vertical
hydraulic gradients within the aquifer have been small. A medium to fine
38
O
a i > i
39
-------
sand containing approximately 3 percent silt and clay by weight composes the
main aquifer matrix at well E3. (At other locations in the aquifer the
fines vary from II to 151 by weight.) When E3 was constructed, moderately
disturbed cores were obtained at 7 locations throughout the depth of the
study aquifer using a Shelby tube. The resulting particle size and
distribution data, which we believe are accurate'despite the moderate
disturbance, are presented in Table 1. Further details concerning
aquifer/aquitard hydraulic and other physical properties nay be found In
P»rr et al. (1983).
The pumping wells are constructed of 20.3 cm (8") steel casings with
15.2 on (6") stainless steel, wire wrapped screens and are grouted from the
top of the study aquifer to the land surface. As illustrated in Figure 16,
the piping and valve system associated with each pumping well Is designed so
that the well can be used for Injection or withdrawal of tracer solution.
In the single-well test to be reported in detail herein, tracer solution was
injected through well 12. As illustrated In Figure 17, supply water was
obtained from a well (SZ) screened in the study aquifer about 244 m (800 ft)
east of 12. This separation was sufficiently large so that the hydraulic
effects of S2 pumping did not affect the tracer experiments in the vicinity
of 12. Concentrated tracer solution was mixed in a 4800 liter (1270 gal)
tank and added to the 10.2 en (4 in) pipeline connecting S2 and 12 using a
metering pump. The pipeline travel distance from the metering pump to the
study aquifer was at least 160 m (525 ft) which was more than sufficient to
Insure complete mixing of the tracer. It was assumed that the plezometHc
head distribution in the Injection well screen was uniform with depth since
the screen diameter was 15.2 cm (6 in) which resulted in a maximum average
vertical fluid velocity in the screen of 0.84 m/s (2.75 ft/s) (during
40
Table 1. Particle sUe distribution data for the seven disturbed cor*S
obtained during construction of well E3.
Depth of Core
(m)
40.2
43.3
46.6
49.7
52.7
56.1
59. 1
——————
°60
(m)
0.46
0.36
0.58
0.46
0.49
0.59
0.94
— ... i- "™ '
D30
(on)
0.35
0.26
0.45
0.27
0.28
0.44
0.56
--
• — "••" •"— '
D10
(«o)
0.21
0.13
0.21
0.12
0.15
0.26
0.19
__
Percent Passing
1200 Sieve
(I)
1.8
1.4
3.0
5.6
3.5
1.2
3.8
— _ —
41
-------
4'Pipe ond Fittings-^
MOTOR
Drive Shofb
Tracer
Tank
Instrument
Trailer
Figure 17.
Dlagraat ihouing tht IB*in features of the surface hydraulic system
used In the single- and two-we 11 tracer tests at the Mobile site.
Figure 16.
Piping and valvlng schema associated with
pumping wells at the Mobile site.
42
43
-------
experiment 14). Thus the maximum velocity head was only 0.037 m (0.12 ft)
and the head losses due to friction along the 21 m (69 ft) length of screen
would be less than 0.10 m (0.33 ft). These totals when compared to the
Injection head of approximately 3 m (9.8 ft) are consistent with the
assumption of constant head In the well screen Interior.
A* discussed In detail by Molz et al. (1985), several preliminary tests
were conducted with the objective of assessing the vertical Integrity of tha
multilevel sampling wells and the effect of mixing the water within each
sampling zone which was approximately 0.91 m (3 ft) high. It was concluded
that sample zone Isolation was adequate for tec's which were to follow.
There was a significant difference between breakthrough curves at the seven
sampling zones depending on whether sample zone mixing was Induced. There-
fore, It was concluded that mixing within each Isolated sampling zone Is
desirable. For a sampling zone of finite length It Is possible for the
tracer to enter the zone anywhere along the slotted length and then be
recorded depending on unknown natural nixing and probe position. Imposed
mixing forces an Integration effect causing tracer concentration to be more
representative of the entire length of the sampling zone. (This relates
back to the moving average concept discussed previously.) Without Imposed
mixing, the effective sampling length 1n the vertical direction Is unknown.
Single-Well Test
The first complete single-well tracer test conducted at the Mobile site
was labeled "experiment 14" and utilized the multilevel sampling well E3
(Figure 15). To start the experiment, supply groundwater without tracer was
Injected Into 12 until the Initial transients disappeared and a steady
Injection rate resulted (approximately 2 hours). Then at time zero tracer
was added to the Injection water, and the actual test Initiated. Shown 1n
44
Figure 18 are the bromide concentrations measured 1n 12 (Injection/
withdrawal well), while the concentration breakthrough curves measured 1n E3
(multilevel sampling well) are shown 1n Figure 19. (Hater samples were
obtained fro. the Injection/withdrawal well using a faucet In the pipeline.)
During the experiment tracer solution at an average concentration of 242
•g/1 was injected at the rate of 0.915 m3/m1n (242 gpm) for the first 32
hours. This Injection rate, without tracer added to the water, was
maintained for the next 22 hours at which time Injection was halted. One
hour and 15 minutes later withdrawal pumping was Initiated at the rate of
1.19 m3/m1n (314 gpm) and continued for two weeks so that virtually all
tracer was removed from the system. Note that Figure 18 contains both
injection and withdrawal data while Figure 19 contains only Injection
breakthrough data.
Table 2 contains the time for 501 of breakthrough for each level based
on the electrical conductivity measurements for experiment 14 shown 1n
Figure 20 and the concentration data shown In Figure 19. With the probable
exception of level 1. the concentration data look quite good. On the
average, the arrival times based on electrical conductivity lag those based
on concentration by about 2 hours. (We will refer to this as the "two-hour
rule" later on.) This 1s largely due to the fact that the electrical
conductivity of the supply water, which Is ultimately mixed with tracer. Is
lower than that of the native groundwater In the vicinity of 12 by about
16*. caused In part by water chemistry changes Induced by previous aquifer
thermal energy storage experiments at the same site (Molz et .1.. 1983).
Thus as the tracer solution approaches a conductivity probe, the reading
will decrease Initially even though the bromide concentration Is Increasing.
The net effect of this Interaction 1s to cause the electrical conductivity
45
-------
300n
240
§ 180-
O
z
o
0 120
CD
60-
30 60 90
TIME (HOURS)
120
Figure 18. Bronlde concentration In Che Injection/withdrawal well (12)
during experiment H1*. Tracer Injection ended at t»32 hours;
Injection ended »t t-54 hours. Withdrawal began at t»55.25
houri.
46
too
= 1*0
"i leo
e 140
• i to
— 100
Z .0
; .0
Level I
Level 2
~—to—io 40 »o To to 10 40
Time (hr»)
too
110
1*0
140
I tO
IOO
.0
*o
40
to
Level 4
Level 9
Level 7
o to10 to ao 40 o io to 10 to »o^40 to
Tim* (hr«)
Figure 19. Bromide concentration breakthrough curves at the
seven levels of well E3 during experiment #4.
47
-------
1
1
1
1
u
1
E
^J
i
u
i
400
380
360
340
320-
300-
28O-
260-
240-
•«e«^UK
1
380.
360.
340
320-
300-
280-
260-
240.
£*•
AJO '
j^*«^% t
• & y
n ' >
? ! i
/ i I
f Level / ?
Y ^ V* / ,
? 0-9-W V*
ki
TkM (hril
Ftgur. 20. EUctrleal conductivity breakthrough curve, .t vrlou,
leveli of well E3 during experiment #4.
Table 2. Sampling zone elevations, arrival tines for fifty percent break-
through, apparent dlspersfvlty values and Inferred normalized hydraulic
conductivity values for experiment 14.
Level
t
1
2
3
4
5
6
7
Mid-Zone
Elevation
-40.7 m
-43.8 m
-46.6 m
-43.3 m
-52.9 •
-56.0 m
-59.0 m
Arrival Times
from
Concentration
Measurements
33.4 hr?
24.3 hr
20,5 hr
14.0 dr
19.0 hr
8.0 hr
32.4 hr
Arrival times
Normalized Apparent from normalized
Hydraulic Dlsper- Electrical Hydraulic
Conductivity slvlty Conductivity Conductivity
Measurements
0.24
0.33
0.39
0.57
0.44
1.00
0.25
0.07+0.01 m
0.18+0.02 m
0.17+0.06 m
0.12+0.04 m
0.32_+0.08 m
0.50+0.03 m
0.04^0.01 m
29.0 hr
27.3 hr
—
16.0 hr
21.8 hr
10.0 hr
33.2 hr
0.34
0.37
--
0.63
0.46
1.00
0.30
43
-------
data to overestimate the actual mid-rise arrival time. Presumably, this
could be corrected by adding additional Ions, other than bromide, to the
supply water. However, we did not attempt this because the probe recordings
were used mainly to orient ourselves qualitatively as to what was happening
In the subsurface. Ultimately, calculations of normalized hydraulic
conductivity were based mainly on arrival times deduced from concentration
data measured In the laboratory. The results of both are shown In Table 2
mainly for comparison and Information purposes.
Tracer travel time data alone does not enable one to calculate an
absolute value of hydraulic conductivity. To calculate such a value for the
general nonhomogeneous case, one must know the flow path, porosity and
hydraulic head distribution along the flow path In addition to the travel
time. It was not feasible to measure all these quantities during our tracer
tests. However. If one approximates the real aquifer In the test vicinity
with a perfectly stratified aquifer of constant porosity and horizontal
layering, then for a fully penetrating Injection well the Darcy velocity at
the elevation of each sampling zone will be horizontal and proportional to
the hydraulic conductivity at that level. Thus the following equations can
be written
stRjR/t
(6)
where K, • horizontal hydraulic conductivity at the 1th level, B(R) >
•/(dh/dr) where • Is the porosity and dh/dr Is the hydraulic gradient at
radius R, v. • seepage velocity at the 1th level, R • constant radial
distance between the Injection well and a particular multilevel sampling
well. t. • tracer travel time between the two wells at the 1th level, T •
SO
aquifer transmlsslvtty, and Q - Injection flowrate. At any particular
level, t. It taken as the time between the start of tracer Injection and
when SOI of breakthrough occurs. In any given experiment there will be a
minimum arrival time. t^. which corresponds to the layer with the largest
hydraulic conductivity. KMX, and from equation (6)
Forming the ratio of equations (6) and (7), one arrives at what can be
called the normalized hydraulic conductivity
'mln
(7)
(8)
It Is also possible to calculate the ratio K,/R • t/t,, where the "bar"
notation Indicates average values (Plckens and Grlsak, 1981). R could then
be equated, as a first approximation, to the hydraulic conductivity obtained
from a fully penetrating pumping test, as K • T/B where T Is the trans-
mlsslvlty and 8 Is the aquifer thickness. This would enable explicit values
to be calculated for each Kf.
Me would like to re-emphasize that the simple equations (6) through (P)
all result from the "stratified aquifer" approximation which many hydrolo-
glsts may consider too Idealized to represent a real aquifer. There Is
certainly some merit to this viewpoint. However, the only other practical
alternative that we see at the present time Is to make the usual assumption
of a homogeneous or statistically homogeneous aquifer and go after a full-
aquifer dlsperslvlty which, as discussed 1n the Introduction. Is a much
worse approximation. Kore will be said about this later.
51
-------
Based on equation (8). Figure 21 resulted which Is a plot of normalized
hydraulic conductivity '*/*-,,,) »5 determined from the concentration data of
experiment 14. Since the concentration data for level 1 are not consistent
with that from the other levels (perhaps a tubing leak?), we used the
electrical conductivity data and the 2-hour rule (see page 22) to provide an
Improved estimate of the level 1 relative permeability. At this level the
electrical conductivity data were normal In appearance and resulted In the
level 1 value on the curve shown 1n Figure 21. The results displayed
Indicate the presence of a high permeability zone In the bottom third of the
aquifer, along the line connecting E3 and 12. This result Is consistent
with the findings from previous thermal energy storage experiments at the
Mobile site which Indicated the presence of a high permeability zone,
although at a slightly higher elevation In the aquifer (Molz et al., 1983;
Buscheck et al., 1983).
In displaying the data of Figure 21, It was decided to simply draw
straight lines between the points where hydraulic conductivity was known or
measured. In doing this use was made of nine points—the top and bottom of
the aquifer, where the clay confining layers force the permeability to
essentially zero, and the seven sampling points where tracer travel times
were recorded.
Two-Well Test
As described previously, a two-well test may be used with one or more
multilevel sampling wells to obtain tracer travel time Information similar
to that obtained with a single-well test. However, the two-well test 1s
generally performed on a larger scale and, therefore. Is more time
consuming. At the Mobile site our single-well tests lasted about 5 days,
while the two-well tests required 30 to 35 days followed by a month or more
52
.1 .2 .3 .4 .5 .6 .7 .8 .9 I
K/Kmax
Figure 21. Inferred nor».lix«d hydraulic "nd
based on the results of experiment
aquifer 'assumption.
and the
53
-------
of withdrawal to remove til remnant, of tracer. Generally speaking, single-
well tests are suited for relatively low cost but wall scale hydraulic
conductivity measurements because only a single pumping well Is required. A
two-well test 1n the non-reclrculatlng node requires at least 2 pumping
well* but provides the advantage of being able to move water relatively
rapidly over larger travel distances.
Another aspect of a two-well test which was exploited In the present
study Is that It offers a convenient vehicle for testing tracer transport
prediction capability. In several of our experiments at the Mobile site we
chose to employ the single-well test as t means for Inferring the hydraulic
conductivity distribution 1n a relatively stall aquifer region between an
Injection well and a multilevel observation well (maximum tracer travel
distance of 5.5 n (18 ft)). The two-well test was then used to test
predictions over a relatively large aquifer region (minimum tracer travel
distance of 38.3 • (126 ft)) based on the vertical distribution of
horizontal hydraulic conductivity Inferred fro« the single-well test. This
procedure helps to define what Is actually being measured during a
single-well test and over what travel distances such a measurement might
have meaning. It also provides valuable Insight concerning fundamental
properties of the flow field which was established during the experiments.
Predictions of two-well test outcomes based on single-well test results sre
discussed In the next section entitled 'Computer Simulation of Single-Well
and Two-Well Test Results."
At this time 1n the project, 2 two-well tests have been performed at
the Mobile site. The pairs of pumping wells used In the first and second
tests, respectively, were E1-I2 and I2-E10. Both tests were done In the
non-reclrculatlng mode with El and 12 used as Injection wells In the first
54
test and second test, respectively. Herein, only the E1-I2 test will be
described In detail.
Preparation for the execution of a two-well test Is similar In
philosophy to that for a single-well test. The first step Is to establish
the flow field between the Injection and withdrawal wells using groundwater
without tracer. As Illustrated In Figure 17. the piping between El and IZ
was valved off. and a pump In well S2 was used to Inject water Into El.
Simultaneously, a pump 1n 12 withdrew water which was then wasted.
Discharges were measured with standard turbine-type water meters and only
Blnor valve adjustments were required 1n order to get the Injection and
withdrawal rates essentially equal and to maintain equality throughout the
test. Following flow field establishment, tracer Injection was Initiated
simply by turning on the metering pump (n the line connecting the tracer
tank to the S2-E1 pipeline (Fig. 17). The E1-I2 test was performed within
the geo«wtry Illustrated previously In Figure 15. Both the Injection well
(El) and withdrawal well (12) have 15.2 cm (6") diameter stainless steel
screens that fully penetrate the study aquifer. The observation wells (E5
and E3) are constructed of PVC pipe as described In the discussion of
multilevel sampling well design and construction.
The test began (tracer Injection Initiated) at 9:50 AM on August 31,
1984 and continued until 8:00 AM on October 2, 1984. Injection and
withdrawal rates averaged 0.946 m3/m1n (250 gpm) and, typically, were equal
to within less than II. Tracer was added to the Injection water during the
first 76.6 hours of the experiment which resulted 1n the Injection
concentration versus time function shown In Figure 22. After approximately
70 hours, tracer began to appear In the withdrawal well. As shown In Figure
23. the withdrawal concentration versus time function was complex, and
65
-------
-j
X
C7I
e
~~
0
"5
•t=
0)
u
o
U
ffl
200
ISO
160
140
120
too
SO
60
40
20
O
*^-y
~~x../-v--x
•
•
-
0 10 20 30 40 30 60 70 80
Time (Mrs.)
Figure 22.
Injection well tracer concentration versus
time during the first 80 hours of the two-well teat.
56
NOIlVaiN3DNOD
57
-------
measurable tracer concentrations persisted throughout the 32.5 day
experiment. The peak concentration occurred rather early In the experiment
(-210 hours), and the curve had a well-defined 'till" that was still 15S of
the peak value (-40 tines the background value of 0.1 anj/1) when the
experiment was terminated. Conputer simulations (see below) Indicated that
the tailing wi.« due to the late arrival of tracer being brought to the
withdrawal well along the flow lines which follow the longer and larger arcs
between the Injection well and the withdrawal well shown In Flgi-re 4.
Throughout the experiment, data wvre collected at the two multilevel
observation wells shown In Figure 15. There were seven 0.9 it (3 ft) long
Isolated sampling tones In each well that were kept continuously nixed using
peristaltic pumps on the surface, just as In the previously described
single-well test. The peristaltic pumps were used also to obtain samples
for analysis. Shown In Figure 24 (lines connecting dots) are breakthrough
curves for the seven Isolated levels In well E3. The data for well E5 1s
not shown because It was Invalidated by the presence of drilling mud that
was Inadvertently left In the formation during the well construction process
(Moll et al., 1985).
A tracer travel time analysis similar to that described for the single-
well test and embodied in equations (6), (7), and (8) can be applied to the
two-well test (Pickens and Grisak, 1981). When this is done, using the
experimental data In Figure 24, the normalized hydraulic conductivity
distribution shown In Figure 25 results. Although there are some
differences, this distribution Is quite similar to that shown In Figure 21
which resulted from the single-well test.
S
,
MO
110
100-
«o
.0
40
EXPERIMENTAL DATA
NUMERICAL MODEL
LEVEL 2
JOO 190 400 490 SOO S90 100 • 200 ISO IOC HO 400 490 900 190
TIME (HR)
too
110
no-
no
110
100
to
to
• 0
10
LEVEL 3
Y
LEVEL 4
i LEVEL 5
I O tOO 900 «00 900 «00 100 200 900 400 900 190 tOO 290 900 990
TIME (HR)
= 100
4» 110-
I 110-
g .40-
P .10-
4 100-
& M
S to
z «<>
o to-
LEVEL C
LEVEL 7
100 190 tOO 190 900
190 tOO 190 900 990 400 490 900
TIME (HR)
Figure 24. Measured (lines connecting dots) and predicted (full
lines) breakthrough curves at the 7 levels of observa-
tion well E3.
58
59
-------
•' -2 .3 .4 .5 .6 .7 .8 .9
(K/l
Figure 25. Normalized hydraulic conductivity distribution
inferred from travel times measured during the
tvo-uell test.
60
Computer Simulation of Single-Hell and
Two-Well Test Result?
The schematic diagram of tracer dispersion drawn 1n Figure 1 represents
an advection-dominated process. One of the objectives of the research
reported In this communication Is to develop some Indication of how much
Information concerning tracer dispersion Is actually contained In normalized
hydraulic conductivity distributions similar to the type determined In
single-well and two-well tracer tests subject to the stratified aquifer
approximation. Moreover, when such Information is put Into a mathematical
model, how much of the dispersion process due to true hydrodynamic
dispersion and other factors, such as spatial variations of hydraulic
conductivity not allowed In the stratified aquifer assumption, 1s left
unaccounted for? To begin to answer this question for aquifers where the
required Information Is available, computer simulations for various experi-
ments were developed which explicitly considered the vertical variation of
horizontal hydraulic conductivity as determined by single-well or two-well
tracer tests. Predictions of the computer models, which were made without
"calibration* of any model parameters, were then compared with actual field
results.
Simulation of Single-Well Tests
The first field tracer tests studied In this manner were the single-
well tests performed by Pickens and Grlsak (1981). This particular test was
chosen for analysis because of the availability of very detailed data on
hydraulic conductivity, local dlsperslvlty and concentration distributions
from the test. The computer model that was developed 1s called SHADH
(Falta, 1984; Guven et al., 1985). It takes Into account depth-dependent
advection in the radial direction and local hydrodynamlc dispersion In the
61
-------
vertical ind radial directions (Guven et al.. 1985). The model Is based on
the equation given by
(9)
where r Is the radial coordinate, C • Clr.z.t) Is the tracer concentration,
ur • V'*' Is the radial seepage velocity, Dp • DQ + <>rIUR| 1s the radial
dispersion coefficient, DV • 0Q + 0VIUPI ** the vertical dispersion coef-
ficient. DQ Is the effective molecular diffusion coefficient, and ar and oy
are the radial and vertical local dlsperslvltles.
The very detailed single-well tracer dispersion experiment of Interest
was performed In a shallow unconflned aquifer. A volume of 95.6 cubic
meters of tracer-labeled water was Injected Into an 6.2 m thick aquifer at a
rate of 3.2 m /hr for a period of 30 hours and then withdrawn at the same
rate. Withdrawal began Immediately at the end of Injection. The
previously-described samplers were located In the aquifer at observation
stations 1, 2. 3, 4 and 6 • from the Injection-withdrawal well. From the
relative tracer arrival times at different elevations 1n the observation
wells, a radial hydraulic conductivity distribution In the vertical
(expressed as Kj/K) was calculated. Additionally, Plckens and Grlsak (1981)
estimated the local longitudinal dlspersfvlty at each sampling point and
found the values to be fairly constant with an average magnitude of about
0.007 m. The K/K distribution Inferred from the breakthrough data at the
observation well at a distance of 1 m from the Injection-withdrawal well In
test SHI was used In the SWAOH simulation. This profile Is shown 1n Figure
26. The actual unsteady Injection concentration, shown 1n Figure 27, was
used 1n the simulation (Plckens. 1983, personal communication), along with
local radial and vertical dfsperslvltles of 0.007 m. The value used for the
62
depth
from
upper
confining
loyer
(metert)
I
U
I.O
2.0
3.0
4.0
5.0
6.0
7.0
8.0
(
• 1 * ' 1 1
=L (r-lm|
1
1 .
,1
1 .
1
,1
1 .
1
1
1
- . . 1 . . i , • • • •
) 1.0 2.0
K/R
Figure 26. Hydraulic conductivity profile measured by
8 Plckens ind Crl.ak (1981 ) and used In the present
calculations.
63
-------
1.5
1.0-
C(t)
0.5-
0.0-
•EXPERIMENTAL DATA
[PICKENS, PERSONAL
COMMUNICATION, 1983]
INJECTION
•
•
•
%
-RECOVERY
0 10 20 30 40 50 60
TIME (HOURS)
""'• "•
64
radial dlsperslvlty Is based on the observations, but the value used for the
vertical dlsperslvlty Is arbitrary and It was chosen simply as a possible
upper limit for this quantity In this case as discussed In more detail by
G'liven et al. (1985). The effects of the well radius and molecular diffusion
were neglected. The porosity value used In the calculations was 0.38 as
given by Plckens and Grlsak (1981, page 1197).
In Figures 28 and 29. the actual flow-weighted breakthrough curves from
observation wells located 1 and 2 m from the Injection-withdrawal well
respectively (Plckens and Grlsak, 1981b) are shown along with the flow-
weighted breakthrough curves calculated by SHADH. (The flow-weighted
concentration. C Is defined as C • /J (K(z)/R)Cdz/B. where B 1s the aquifer
thickness.) In Figure 29, the wavy appearance of the computed curve for a
tine greater than about 10 hours 1s due to the unsteady Injection
concentration used In the simulation. The experimental concentration versus
time data Measured at the Injection-withdrawal well is shown in Figure 30
along with the results of the SHADM simulation using the unsteady Input
concentrations. The early part of the experimental data seems to show a
large amount of scatter; however, this part of the curve Is closely modeled
by SWADM using the actual unsteady Injection concentration. The later part
of the breakthrough curve Is underestimated by SWADM. The reasons for this
are not clear. One possible contributing factor could be the presence of
small-scale, three-dimensional, very-low-permeablllty lenses embedded in the
aquifer, which the present model does not take into account. These lenses
could act as temporary storage zones for the tracer which may diffuse into
these zones during injection and then move out slowly during withdrawal,
leading to larger concentrations during withdrawal than predicted by SWADM.
Another possible contributing factor for the behavior noted above is that
65
-------
i.oo
0.75
0.50
0.25
0.00-
• EXPERIMENTAL DATA
[PICKENS AND GRISAK. I 98 I ]
NUMERICAL RESULT
ar*av-o.oo7m
0 5 TO 1520 25 30
TIME (HOURS)
Figure 28. Compaction of SWADH results with field data for the
flow-weighted concentration from an obtervatlon well
one meter from the Injection-withdrawal well.
66
I.OO-
0.75-
0.50-
0.25-
0.00
.EXPERIMENTAL DATA
'(JPICKENS AND GRISAK, 1981 ]
— NUMERICAL RESULT
Otr *dum O.007m
10 15 20
TIME (HOURS)
25
30
Figure 29.
from the injection-
67
-------
according to the measured data, approximately 2.5 percent rite tracer was
shown to have been withdrawn than was Injected. While this Is certainly not
a large experimental error for a field experiment (In fact It is quite
small). It 1s enough to have significantly changed the slope of the later
part of the curve If that Is where the.error occurred. Since a mass balance
was not satisfied perfectly during this experiment, the net area under the
experimental curve Is greater than the area under the calculated curve.
However, In obtaining the results shown In Figures 28, 29, and 30. no "model
calibration" of any type was performed. Only parameter values measured by
Plckens and Grlsak (1981) were utilized. The resulting curves represent
very accurate simulations which Indicate an advection-domlnated dispersion
process with local dlsperslvltles approaching those neasured 1n the
laboratory. As also discussed 1n more detail by Kolz et al. (1983) and
G'liven et al. (1984), It Is clear that 1f a full-aquifer dlsperslvlty were
calculated from these data It would not represent a physical property of the
aquifer.
Simulation of Two-Well Tests
To date, simulations have been performed for two separate two-well
tests, the Plckens and Grlsak (1981) test and the Mobile test described In a
previous section. Only the Mobile two-well test simulation will be pre-
sented In detail because the conclusions are similar to those that result
from simulation of the Plckens and Grlsak (1981) test but are somewhat more
significant because of the larger scale of the experiment.
In our simulation of the E1-I2 two-well test we chose to employ the
single-well test as a means for Inferring the hydraulic conductivity
distribution in a relatively small aquifer region between the injection well
and a multilevel observation well. The two-well experiment was then used to
63
1.0-
0.8-
0.6
0.4
0.2
0.0
Q=3.2m3/hr
B=8.2m
V, =9 5.6m3
oEXPERIMEMTAL
DATA
[PICKENS AND GRISAK.
NUMERICAL
RESULT
"iv*o7*}nr
1-6
VOL. WITHDRAWN / VOL. INJECTED
69
-------
7et1on -«.
V" TMI proen>Z)> Wh ..... "d " 4re the «-rt««t.. .ion, and nor*,, to , local
streanllne, and , is the vertical coord.nate. ,. this syste. the
transformed advectlon-dlsperslon equation Is given by
00,
70
Table 3. Two-well test parameters supplied to CeoTrans, Inc. for their
3-d1nens1on«1 simulations based on the advectlon-dlsperslon equation.
(Mornllzed Hydraulic Conductivity Distribution)
Layer f
(1)
12
11
10
9
8
7
6
S
4
3
2
1
Layer Layer
Center (z.) Thickness
20.4 n 2.40 m
17.97 2.46
15.62 2.24
13.37 2.2S
11.50
10.00
8.50
7.00
5.50
.50
.50
.50
.50
.50
4.00 1.50
2.50 1.50
0.87 1.75
Normalized Cond.
(Xtz^/K^)
0.15
0.31
0.34
0.38
0.48
0.57
0.51
0.44
0.72
1.00
0.65
0.25
(Additional Parameters)
Longitudinal dlsperslvlty 0.15 m
Transverse (horizontal) dlsperslvlty 0.05 m
Transverse (vertical) dlsperslvlty 0.01 m
Tracer Injection time 3.19 days
Total Injection time 32.5 days
One-half well spacing 19.14m
Radius of Injection and production wells 0.08 m 3
Injection and production rates :.. 0.9464 m /mln
Porosity 0.35
Aquifer thickness 21.6 B 2
Molecular diffusion coefficient 1x10 ' m Is
Screen location (Injection well) Fully penetrating
Screen location (Withdrawal well) Fully penetrating
E3 observation well coordinates (x-13.56 m. y • 0)
71
-------
where DS> Dn and DZ are principal components of the hydrodynamlc dispersion
tensor In the longitudinal, transverse and vertical directions, respective-
ly, and hj and h? are the scale factors of the curvilinear coordinate system
(Huyakorn et al.. 1986a). The dispersion coefficients are defined as
U/8
U/t
U/l
(Ha)
(lib)
(lie)
where QZ 1s the vertical dlsperslvlty. and U Is a function of s, n and z.
Solution of equation (10) enables one to predict the tracer concentration 1n
the production well as a function of time and also the tracer concentrations
as functions of time at each level In the multilevel observation well E3.
The actual Information supplied to GeoTrans 1s listed In Table 3. The
Cartesian coordinates listed are based on Figure 4.
The second model used to simulate the two-well test 1s called the
two-well advectlon model (TWAM) and was developed at Auburn University
(Falta. 1984; Giiven et al., 1986). A Lagranglan solution method is used In
this Model based on the travel times of tracer along various flow lines from
one well to the other. In this model, it Is assumed that the aquifer is
horizontal, confined, of constant thickness and porosity, and perfectly
stratified 1n the vicinity of the test wells. TWAM takes Into account the
depth-dependent advectlon 1n the horizontal planes, but neglects completely
any local hydrodynamic dispersion. Thus any simulations resulting from
application of TVAM will yield dispersed concentration distributions based
solely on differential advectlon, which is also called shear flow (Fischer
et al.. 1979).
Shown In Figure 31 are the results of the 3-dimenstonal dispersion
simulation and the advectlon simulation using the model called THAU (G'uven
et al,, 1986). Both models do a remarkably good job of predicting the
n
NOIiVHlN3DNOO
i
-------
recovery concentrations during the two-well test. Since the two Independent
predictions agreed quite well, one can conclude that local hydrodynamlc
dispersion played a very minor role In determining the time distribution of
tracer concentration In the withdrawal well. The entire experiment, which
Involved estimated travel distances over individual flow paths ranging from
38.3 m to about 90 m in the most permeable layer, was highly advection-
dominated. The dominant role of advectlon in the two-well test was also
noted earlier by Hoopes and Harleman (1967) for the case of a homogeneous
aquifer.
We would like to emphasize that no prior calibration was done In order
to arrive at the results shown in Figure 31. All of the Information
supplied to our subcontractor is listed In Table 3. They did not know the
result of the experiment they were attempting to simulate. With the excep-
tion of the dlsperslvity values and the porosity, all of the information
contained 1n Table 3 was measured directly In the field or calculated from
field measurements. The dispersivlty values were chosen arbitrarily to have
relatively small finite values because the 3-D model would develop numerical
dispersion and/or excessive CPU tine problems if the dispersivlty got too
close to zero. Porosity was measured in the laboratory on disturbed core
samples obtained from well E3 during drilling operations. The seven samples
were compacted lightly and the porosity measured based on the determination
of solids specific gravity and saturated water content. The average for
well E3 was 0.41. It was reasoned that this value would likely be higher
than the undisturbed 1n-s1tu values, so an effective porosity of 0.35 was
chosen prior to any simulations. The 3-D model result in Figure 31, based
on the 0.35 porosity value, was obtained from a single computer run which
74
required 8.5 hours of CPU time on a Prime 550-2 minicomputer (Huyakorn et
al.. 1986b). Runs at Auburn University based on identical data using TWAK
(Falta, 1984; Guven et al.. 1986) were performed independently of the
GeoTrans run.
The calculated withdrawal concentration functions in Figure 31 were
obtained from a flow-weighted average of the concentrations along the
withdrawal well screen and thus is a vertically Integrated quantity. A
comparison between concentration breakthrough curves measured at the 7
discrete levels of observation well E3 and those predicted by the 3-D model
are shown in Figure 24. At levels 2. 4. 5. and 6. the agreement is good,
while at levels 3 and 7 it is poor. A valid comparison cannot be nade at
level 1 because of an apparent leak in the tubing used to obtain the level 1
samples (Molz et al., 1985). The mixed results of Figure 24 are not unex-
pected because one would not expect the normalized hydraulic conductivity
distribution shown 1n Figure 21 to remain completely Invariant in a fluvial
aquifer over the 38.3 a separation between the Injection and production
wells. However, 1t is significant that the Integrated prediction (Figure
31) remains quite good.
The prediction of concentration versus time 1n the withdrawal well is
sensitive to the normalized hydraulic conductivity distribution. Shown In
Figure 32 is the withdrawal concentration breakthrough that would result if
one assumed a homogeneous aquifer with a normalized hydraulic conductivity
of unity throughout. In such a situation, one would observe a longer travel
time for the first arrival of the tracer at the withdrawal well and a much
higher peak concentration than was realized during the actual experiment.
However, the general behavior of the tall of the curve does not appear sen-
sitive to the details of the normalized hydraulic conductivity distribution.
75
-------
so
49
<
O
z
o
4O
30
20
I 5
10
8
o o
o
? o
4O 10 l2Ot«OZOQZ402403ZO 3*0 400 440 410)20910 «00 840 *«0 720 7«O
TIME (hrs.)
Figure 32. Calculated tracer concentration versus time In the withdrawal
well based on an assumed homogeneous! isotroplc aquifer with
no local dlsperslon(circles) shown together with the results
of the present two-well test (full line).
76
A good fit to the data results If one assumes a full-aquifer longitudinal
dispcrslvlty of 4 m (Huyakorn et al., 1986b).
Further understanding of the Implications of the data and computations
contained In Figures 24 and 31 can be obtained by selecting a normalized
hydraulic conductivity distribution so that the computed and measured
breakthrough curves of Figure 24 are made to agree with each other as far as
peak arrival times are concerned. (Essentially, this 1s equivalent to using
the two-veil test Itself to estimate the normalized hydraulic conductivity
distribution.) This was discussed previously, and the distribution shown In
Figure 25 was obtained. There Is not a- tremendous difference between the
normalized hydraulic conductivity distributions shown In Figures 21 and 25.
but the Figure 25 conductivity values In the upper half of the aquifer are
smaller. A TNAM simulation of the withdrawal well concentrations based on
the Figure 25 distribution Is shown 1n Figure 33. While the rising limb of
the breakthrough curve 1s not simulated as well, there 1s closer agreement
between the data and computations for the falling 11mb than was obtained
previously (Figure 31) using the normalized hydraulic conductivity distribu-
tion shown In Figure 21. Overall, the simulations shown In Figures 31 and
33 are of comparable quality.
The single-well and two-*e!1 test simulations discussed In this section
pertained to different aquifers In widely separated locations. The
single-well test was performed In a clean, sandy, glaclofluvlal aquifer (n
Canada, while the two-well test was performed In a fluvial, low-terrace
deposit containing sand with appreciable amounts of clay. Both simulations
were quite accurate In an Integrated sense and consistent with an advectlon-
doalnated (shear flow) dispersion process. When advection was considered
77
-------
§3
'-4 U
° ? •
hi C in
VON
u e
« «
£2 S
U M C
•H « S
« a o
3 >« *J
isa
•-< e u
u — o
« a
NOIJ.VHiN3DNOD
78
txplleltly. 1«rg«, sctle-dcpendent, full-aqulftr dtsperslvltles were not
required.
Olicunlon «nd Concluilorn
In the recent past, some hydrologlsts advocited the use of single-well
or two-well tracer dispersion tests as a means for measuring full-aquifer
longitudinal dlsperslvlty. However, our analyses of single- and two-well
tests In stratified aquifers Indicate that If this Is done, the resulting
nuaber will have little physical meaning. In the case of single-well tests,
the full-aquifer breakthrough curves measured 1n observation wells are
determined nalnly by the hydraulic conductivity profile In the region
between the Injection-withdrawal well and an observation well If the travel
distance between the Injection-withdrawal well and the observation well Is
typical of noit test geometries. Thus, Information about the conductivity
profile Is necessary for meaningful test Interpretation. The relative
concentration versus time data recorded at the Injection-withdrawal well
Itself Is primarily a measure of the combined local and (perhaps?) semi-
local dispersion which has taken place during the experiment. Of course,
the effects of such dispersion will depend In part on the hydraulic
conductivity distribution In the aquifer, and In part on the size of the
experiment. As the size of the experiment Increases, the effects of local
vertical dispersion will become larger compared to the effects of local
radial dispersion (G'uven et al.. 1985).
The two-well test simulations show that the concentration versus time
breakthrough curve measured at the withdrawal well would be very sensitive
to variations of the hydraulic conductivity In the vertical. Without the
use of multilevel observation wells, the test would give little useful
Information about the hydraulic or dispersive characteristics of the
79
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aquifer, such as aquifer stratification or values of local dispersivitles.
Factors such as the length of the injection period, the use of recircula-
tion, and the physical 512e of the experiment all have a strong effect on
the breakthrough curve measured at the withdraw! well, making the interpre-
tation of field results difficult, unless aquifer stratification is measured
and properly taken into account (Giiven et al., 1986).
Based on the above observations and the large values for full-aquifer
d1spers1v1t1es that consistently result from calibrated areal groundwater
transport models, we believe that the following working conclusions are
warranted.
I. Local longitudinal hydrodynaailc dispersion plays a relatively
unimportant role in the transport of contaminants 1n aquifers.
Differential advection (shear flow) In the horizontal direction
is much more important.
II. The concept of full-aquifer disperslvity used in vertically-
averaged (areal) models will not be applicable over distances of
Interest in most contamination problems. If one fas no choice
but to apply a full-aquifer dispersion concept, the resulting
disperslvity will not represent a physical property of the
aquifer. Instead, it will be an ill-defined quantity that will
depend on the size and type of experiment used for its supposed
measurement.
III. Because of conclusion II. it makes no sense to perform tracer
tests aimed at measuring full-aquifer dispersivity. If an area!
model Is used, the modeler will end up adjusting the dispersivity
during the calibration process anyway, Independent of the
measured value.
SO
IV. When tracer tests are performed, they should be aiced at determin-
ing the hydraulic conductivity distribution. Both our theoretical
and experimental work have Indicated that the variation of horizon-
tal hydraulic conductivity with respect to vertical position 1s a
key aquifer property related to spreading of contaminants.
V. Two- and three-dimensional modeling approaches should be utilized
which emphasize variable advectlon rates in the horizontal
direction and hydrodynasilc dispersion 1n the transverse direc-
tions along with sorptlon and microbial/chemlcal degradation.
VI. In order to handle the more advection-donlnated flow systems
described In conclusion V. one will have to utilize or develop
numerical algorithms that are more resistant to numerical
dispersion than those utilized 1n the standard dispersion-
dominated models.
As discussed in the Introduction, much of our contemporary modeling
technology related to contaminant transport may be viewed as an attempt to
apply vertically homogeneous aquifer concepts to real aquifers. Real
aquifers are not homogeneous, but they ere not perfectly stratified either.
What we are suggesting, therefore, is that the time may have arrived to
begin changing from a homogeneous to a vertically-stratified concept when
dealing with contaminant transport, realizing fully that such an approach
will be Interim 1n nature and not totally correct. However, our performance
and simulation of several single- and double-well tracer tests suggests that
the stratified approach 1s much more compatible with valid physical con-
cepts, and at least in some cases, results 1n a mathematical model that has
a degree of true predictive ability. Nevertheless, real-world applications
will undoubtedly require calibration, which in the stratified approach would
31
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Involve varying the hydraulic conductivity distribution r«th«r than the
longitudinal dlsptrtlvlty. The btneflt If that when calibrating the K
distribution, one It dealing with the physical property that probably
dominates the dispersion process.
The change fro* a vertically-homogeneous to a vertically-stratified
approach will not be easy from a field measurement viewpoint nor will It be
Inexpensive. The work of Plckens and Grlsak (1981) and the work described
herein has developed some prototype technology and methodology for obtaining
the type of Information shown In Figure 34. This figure presents the
results of a preliminary analysis of all single-well tests to date that have
been performed at the Mobile site and analyzed In the vertical plane shown
In Figures 15 and 34. The mean locations In the aquifer where the tests
took place are Indicated In the bottom half of the figure.
Examination of the K/Km(x plots 1n Figure 34 reveal some Interesting
trends. A high hydraulic conductivity zone In the bottom third of the
aquifer Is evident In all four of the tests. A similar high hydraulic
conductivity zone appeared In the top third of the aquifer during the E5-E1
test and the E10-E9 test, but not In the two tests conducted In the vicinity
of 12. If one attempted to "fit* a stratified mathematical model to the
situation Illustrated In Figure 34, the strict definition of a stratified
aquifer could not be maintained. As a practical necessity, one would have
to postulate a "local" or "quasistratlfied concept" wherein flow was
generally horizontal on the average with the vertical distribution of
horizontal hydraulic conductivity gradually shifting from one distribution
to the other. There are, however, other considerations that may make the
"approximately stratified" Idealization work better than expected. While
the Imposed flow was observed to be locally stratified In the present
82
K/K
'max
y.-y. 7. ';.;/.; A
/.:.Y.;.v -;-
/'////////////////
-40 -30 -20 -10
i
/////////// /////s/s
1 1 1 > 1
0 10 20 30 40
rigurt 34.
Horizontal Distance (m)
PrtllBinary results of four single veil ccict
p«r(oroMd at Che Mobil* lit*. All ftacloni shown
•re situated at approximately the sane vertical
plan*.
83
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experiments and In the experiments of Plckens and GHsak (1981), this does
not necessarily mean that the aquifer hydraulic conductivity distribution Is
also stratified around the localities where the tests were performed; areal
variations of hydraulic conductivity could still be present at each level of
the aquifer around a test veil. However, an overall stratified flow pattern
could still develop In a confined aquifer even 1f the hydraulic conductivity
distribution Is not perfectly stratified. This Is because the flow Is
forced to be horizontal on the average In a confined aquifer, and a quasi-
stratified flow may develop along various flow paths In response to the
effective average value of the hydraulic conductivity at each level of the
aquifer along the flow path, as observed 1n the field experiments discussed
above. This behavior seems to be supported also by the results of some
ongoing numerical solute transport experiments presently being performed »t
Auburn University. In a three-dimensional numerical experiment 1n a
confined aquifer with a completely random computer-generated synthetic
hydraulic conductivity distribution. It was observed, swnewhat surprisingly.
that a quasistratlfled flow field developed along the entire travel path of
a contaminant slug Introduced numerically into the aquifer, which resulted
In considerable longitudinal spreading (shear flow dispersion) of the
contaminant plume.
A question that should be considered further relates to the practical
feasibility of performing the tracer tests required by the stratified
approach. In most situations we view tracer tests as feasible technically
but only marginally feasible In a routine practical sense. As discussed In
the section on multilevel sampling wells, the unavailability of widely
accepted commercial equipment is a major practical Impediment. However.
that problem may disappear In the near future, and the need to consider
84
vertical aquifer property variations 1s very real. As Illustrated by the
field work of Ostensky, Winter and Williams (1964). the use of full-aquifer
dispersion concepts to nodel what Is essentially a shear flow dispersion
process does not result in a conservative estimate of contaminant concentra-
tions. Instead, the noilel Induces a large amount of artificial mixing which
often leads tc an unreallstically-rapld dilution of a contaminant plume.
Such an analysis at a site In central Wyoming concluded that the 1000 og/1
sulfate contour line was located at a maxlmun distance of about 450 m
downgradlent from the source. However, further study by Osiensky et al.
(1984) which considered the structure of the fluvial aquifer In more detail
showed that there were portions of the aquifer 1020 m downgradlent that
contained sulfate concentrations in excess of 5000 my/1. Occurrence of this
kind of potential mistake can be minimized only by including more
Information about the actual geometry and hydraulic conductivity
distribution regardless of whether a vrathenatical nodel is part of the
analysis. The Interin stratified aquifer approach to tracer test analysis
and modeling discussed herein is meant to be a step in that direction.
One obvious implication of our study is that any type of groundwater
contamination analysis and reclamation plan will be difficult, expensive and
probably unable to meet all of the desired objectives in a reasonable time
frame. This reinforces the t1m«-honored saying that O.OZ83 kg (1 oz) of
prevention Is worth 0.4114 kg (1 Ib) of cure, which in the case of
groundwater pollution Is probably an understatement. One can not over-
emphasize the advantages of preventing such pollution whenever It is
feasible.
85
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88
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TRANSPORT AND FATE
MANAGEMENT
CONSIDERATIONS
Session 8
Joseph F. Keely
(Oregon Graduate Center)
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