EPA/600/2-87/001
January 1987
DATA REQUIREMENTS FOR SELECTING REMEDIAL ACTION TECHNOLOGIES
HAZARDOUS WASTE ENGINEERING RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U. S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
-------
DISCLAIMER
This Final Report was furnished to the Environmental Protection Agency by
the Alliance Technologies Corporation, (formerly GCA Technology Division,
Inc.), Bedford, Massachusetts 01730, in fulfillment of Contract
No. 68-03-3243, Work Assignment No. 4. The opinions, findings, and
conclusions expressed are those of the authors and not necessarily those of
the Environmental Protection Agency or the cooperating agencies. Mention of
company or product names is not to be considered as an endorsement by the
Environmental Protection Agency.
-------
CONTENTS
Section Page
Introduction 1
Use of this Document 3
Report Format 8
1.0 Surface Seals . 11
2.0 Dust Control 13
3.0 Grading 15
4.0 Revegetation 17
5.0 Diversion/Collection Systems ..... 19
' Dikes and Berms ......... 19
Ditches, Channels, Swales, Diversions,
and Waterways 21
Terraces and Benches . 23
Chutes and Downpipes .......... 25
Seepage/Recharge Basins and Ditches 27
Sedimentation Basins/Ponds 29
Levees and Floodwalls 31
6.0 Subsurface Containment 33
Slurry Walls 33
Grout Curtains 35
Sheet Piling 37
Bottom Sealing 39
7.0 Ground Water Pumping 41
; 8.0 Subsurface Drains 43
9.0 Surface Water/Sediment Containment Barriers 45
Cofferdams 45
Floating Covers 47
Silt Curtains and Booms 49
10.0 Streambank Stabilization 51
11.0 Gas Collection/Recovery 53
Passive Subsurface Gas Control 53
Active Subsurface Gas Control Systems 55
12.0 Excavation/Removal ...... . 57
13.0 Dredging : 59
111
-------
CONTENTS (continued)
Section
Page
14.0 Biological Treatment „ 61
Activated Sludge 61
Trickling Filter 63
Aerated Lagoons 65
Waste Stabilization Ponds 67
Rotating Biological Disks ... 69
Land Application 71
Bioreclamation 73
Permeable Treatment Beds 75
15.0 Chemical Treatment 77
Neutralization 77
Precipitation 79
Oxidation (Chlorination) 81
Hydrolys is 63
Reduction 85
Chemical Dechlorination 87
Ultraviolet/Ozonation 89
Solution Mining (Extraction) 91
16.0 Physical Treatment 93
Flocculation 93
Sedimentation 95
Carbon Adsorption/Activated Carbon . . 97
Ion Exchange 99
Reverse Osmosis 101
Liquid/Liquid (Solvent) Extraction 103
Oil/Water Separation 105
Steam Stripping 107
Filtration 109
Dissolved Air Flotation Ill
17.0 Solids Handling/Treatment 113
Solids Separation 113
Dewatering ...... 115
Solidification/Stabilization 117
18.0 Gaseous Waste Treatment 119
Flaring 119
Adsorption 121
Afterburners 123
19.0 Thermal Destruction (Incineration) 125
Rotary Kiln Incineration ., 125
Fluidized Bed Incineration 127
Multiple Hearth Incineration 129
Liquid Injection Incineration 131
Molten Salt Combustion 133
High Temperature Fluid Wall Reactor/Advanced
Electric Reactor 135
IV
-------
CONTENTS (continued)
Section Page
Plasma Arc 137
Cement and Lime Kilns 139
Pyro lysis 141
Wet Air Oxidation 143
Industrial Boilers 145
20.0 Land Disposal 147
Secure Chemical Landfill . 147
Surface Impoundments/Gravity Separation 149
Deep Well Injection 151
Secure Chemical Vaults ........ ... 153
21.0 Physical Treatment 155
Sewer Cleaning 155
22.0 Sewer Rehabilitation and Repair 157
Sewer Rehabilitation and Repair 157
23.0 Alternate Drinking Water Supplies 159
24.0 Home Water Treatment 161
References 163
-------
ACKNOWLEDGEMENT
This report was prepared by Thomas Nunno, Lisa Wilk, Martin Ohenhauer and
Steven Palmer of Alliance Technologies Corporation under EPA Contract
68-03-3243. Edward Opatken, Hazardous Waste Engineering Research Laboratory,
served as the EPA Project Officer and directed the technical efforts of the
project. Peer reviews or other contributions to the report were provided
by Douglas Ammon, Charles Mashni, Donald Sanning and Robert Stenburg,
Hazardous Waste Engineering Research Laboratory and Clarence demons,
Center for Environmental Research Information.
vi
-------
INTRODUCTION
The National Contingency Plan (NCP) and subsequent guidance documents for
remedial investigations, feasibility studies, and remedial designs set forth
the procedural framework for selecting and implementing remedial responses.
These documents do not specifically address the data requirements for
screening, evaluating, designing, and constructing remedial action
technologies at uncontrolled hazardous waste sites. The purpose of this task
is to define the data requirements for screening remedial action
technologies. This report presents data requirements for screening remedial
action technologies applicable to: air pollution controls, surface water
controls, leachate and ground water controls, gas migration controls,
excavation and removal of waste and soils, removal and containment of
contaminated sediments, in situ treatment, aqueous waste treatment, solids
handling, other direct treatment, land disposal, sewer cleaning and
rehabilitation, and alternative water supplies.
Data requirements for screening remedial action technologies for control
of other site problems should fit into the five step NCP remedial response
process which is presented in Figure 1 and outlined below:
1. Site Discovery or Notification—A release of hazardous substances,
pollutants, or contaminants identified by Federal, State, local
government agencies, or private parties is reported to the National
Response Center (NRC). Upon discovery, such potential sites are
screened to identify release situations warranting further remedial
response consideration. These sites are entered into the
Comprehensive Emergency Response, Compensation and Liability
Information System (CERCLIS); this computerized system serves as a
data base of site information and tracks the change in status of a
site through the remedial response process.
2. Preliminary Assessment and Site Inspection (PA/SI)—The preliminary
assessment involves the collection and review of all available
information and may include offsite reconnaissance to evaluate the
source and nature of hazardous substances present and to identify
the responsible party(s). Depending on the results of the PA, a
site may be referred for further action. Site inspections routinely
include the collection of samples and are conducted to determine the
extent of the problem and to obtain information needed to determine
whether a removal action is needed at the site or whether the site
should be included on the National Priorities List (NPL).
-------
1
SITE DISCOVERY OR NOTIFICATION
PRELIMINARY ASSESSMENT AND
SITE INVESTIGATION REPORTS
HAZARD RANKING SYSTEM PRIORITIES
• DETERMINE GENERAL RESPONSE ACTIONS
• IDENTIFY DATA NEEDS FOR SCREENING
FROM DATA REQUIREMENT FACT SHEETS
• DEVELOP RI/FS WORK PLAN
DEVELOP RI/FEASIBILITY STUDY
INITIATE REMEDIAL ACTION PLAN
Figure 1. National contingency plan procedure.
-------
3. Establishing Priorities for Remedial Action—Sites are scored using
the Hazard Ranking System (HRS) and the data from the PA/SI. This
scoring process is the primary mechanism for identifying sites to be
included on the National Priorities List (NPL), which in turn is the
guide for allocating Superfund monies for cleanups. Sites that
receive a score of 28.5 or greater, will be proposed as candidates
for the NPL. After public comment, these sites may be included on
the NPL.
4. Remedial Investigation/Feasibility Study (RI/FS)—Site
investigations are conducted to obtain information needed to
identify, select, and evaluate remedial action alternatives in the
feasibility study based on technological, public health,
institutional, cost, and environmental factors. The final result of
this step is selection of the most appropriate, cost-effective
solution. In some cases, the FS may show that no further action is
needed.
5. Remedial Action Design and Construction—The actual design of the
selected remedial action is developed, then implemented through
construction.
The approach to screening remedial action technologies discussed in this
report is designed to be used after the site has been listed on the NPL
(step 3), and during the initial stages of the remedial investigation/
:feasibility study (step 4). At this point, sufficient information should be
available to determine the appropriate general response actions that must be
considered. Determination of the appropriate general response action and
remedial technology can provide an opportunity to focus the data needs for
screening remedial action technologies. Therefore, our approach was to
develop data needs for each type of remedial technology catalogued by general
response action. If a site has more than one problem, a common situation, the
user can combine the data needs for the appropriate general response actions.
Screening of remedial action technologies involves technological, public
health, institutional, cost, and environmental factors. The data requirements
discussed in this report address technological issues and acceptable
engineering practices. Given the information in this report, the remedial
action engineer should be able to determine which technologies can be applied
at the site, whether or not they are likely to effectively address the
problem, and an order of magnitude estimate of costs. The screening data will
also help the engineer in the final selection and evaluation process although
additional data, such as pilot scale tests, may be needed after the screening
process has been completed.
USE OF THIS DOCUMENT
Each potentially applicable remedial technology is described in a
two-page summary, or "Fact Sheet." Once the general response actions have
been identified, the engineer can use the Fact Sheet Technology Matrix
presented in Table 1 to locate appropriate technologies and identify
-------
3
O
o
•z,
M
I
o
M
s
CC
H
Q
Cd
fa
M
O
P-.
CO
CO
o
bl
^
M
O
H
en
M
,J
erf
Cd
H
CO
w
1
U
i
I
M
1
iis
••« m a
Hi!
-
ii
•js-s
3SS
1 U
u ! 2 §
ill!
3 ! ° H
illl
* ! MW
o ! u
III
f 3
S£
O
B U
|||I
ssss
O -H
a o
s I*
^ 8 u
O CC •
B
O (•
11
Is!
«
s5.:
^1 s
a
S 0
•3 ** *i
w a o
*J O
3 h
3
B
X
X
X
X
s
*
X
X
o
i
U
U
3
O
«
X
X
M
B
S
U
en
X
.
1
X
c
o
a
00
1
•"
X
g
•0
X
i
m
a
0)
Q
rH
X
U
ra
e
3:
"c
!
o
tA
X
g
m
1
s
s
ui
X
s.
o.
I
0
U
01
u
1
in
X
81
.
in
X
1
•H
CO
C
o
H
i
•o
2
X
w
|
0
(N
1
01
1
in
1
1
CO
c
^
I
(4
>0
CO
^
PL.
V
f
c
g
o
•^
«
•H
^H
3
I
«
*
M
1
<*
X
X
£
o
^
X
s
I
I
•H
^
x
X
.5
1
to
s
X
1
s
n)
C
c
o
0)
o
o
-------
(!)
a
0
w
0
0
o
N — '
,-1
w
,J
PQ
^Q
S
§
U
B4
CATIOH/RES
3
S>
41 1
H i
1 0. h 1
15 S i
i 0] 1
j 0) 01 1
! a c -H i
0 & S ^ |
•d 8.2 !
. o i
1 -H C 1
i i flj « I
jjg£|
HI 00 1
., ! .5 :
1 I *o 5 !
\ ! „ § !
H 1 3 B I
1 3 V 1
! •« H |
s i :
W 0 !
C u i
O 1
C u 1
> « « B i
S C c -a i
S o o u i
O -H 1
o •-* w i
s|s]
J^l I
SI
U 1
fl h I X
3S5 ',
^ « I
.5. :
•S '§ i
2 3 g j
p-l O U 1
01 M M 1
"Sg J
H r-l C 1
-C P4 U 1
|
!
]
i
j
s : !
1 !
s i;
j *•
i
I C
X
;
\
t
Subsurface
P
X
°
,
1
(
I
.
•
<
*
t-
•
•
J
, •
1
X
£-
•
,
•
X
J
'
<
t-
<
X
i
";•
0
«
X
Lagoon ing
t
f
_
X
;
\
.
<
^
X
'(.
1-*
•
(I
•
1
<
X ^<
•r
1
^>
•;
M
•
f
atnation
le Treatme
r-
•r
r» a
•s <
X
•
*J
X
•
-,
;
*-"
u
X
'
•
'
I
r
u
X X
X X
•
I
-
6
'
•0
"
lO U
X
XXX
X X
,
C
S
1
X
Q)
3
•H
JJ
0
0
\*_x
1
I
;
i
-------
*0 |
O X O I
fe !
III!
lH ^ u '
O • I
3 S I
j g
13
0)
C
• H
o
o
-------
-d
a)
g
•H
4J
C
o
o
w
§
i
u
g
1
I
$
o
£
ft
ntamlnated
ter Supplies
d Sewer
nes
S£ S3
5 60
,, as
a u o
wi n co
^ 1
C l-> u
S
» .1
4J T3 fH
1 S5
p V
B
5fi
O
B 4J
1 C c
B C C *D
« O O OT
O -rl
§o
r-4 CO
? i*
> B -l
n3 S
w to C
U X O
*s
h-l O U
s h|
' *S w fi
a a a
B
M >H C
3 £ 5
i
X
K
|
19 Thermal Destruction (Incii
-------
appropriate data needs. For example, if a site requires: (1) excavation and
removal of waste and onsite soils; and (2) surface water controls, the matrix
identifies the following Fact Sheets for consideration.
1. Excavation and Removal of Waste and Soil
1.0 Capping/Surface Sealing
2.0 Dust Control
3.0 Grading
4.0 Revegetation
12.0 Excavation/Removal
2. Surface Water Controls (additional technologies)
5.1 Dikes and Berms
5.2 Channels and Waterways
5.3 Terraces and Benches
5.4 Chutes and Downpipes
5.5 Seepage Basins and Ditches
5.6 Sedimentation Basins/Ponds
5.7 Levees and Flood Wells
9.0 Surface Water/Sediment Containment Barriers
9.1 Cofferdams
9.2 Floating Covers
9.3 Silt Curtains
The user can review the information contained on the Data Requirement
Fact Sheets to: 1) identify the data needs necessary to screen the remedial
technologies; 2) determine why the data is necessary; and 3) obtain
information on approximate costs for data acquisition.
REPORT FORMAT
Each remedial technology is described in appropriate sections of this
report. The individual Fact Sheets are designed to stand alone if necessary.
Each Fact Sheet is structured to display: the technology, its function, a
technical description with an appropriate figure, design criteria, process
limitations, current technology status, associated technologies, and data
needs for screening with approximate costs.
-------
The Type of Control and Function sections provide quick definition of the
application of the selected process to a remedial problem. A general overview
of the process, types of uses, related equipment, and an illustrative figure
are provided in the Description section. This section may also describe
similar applications of the process in other remedial situations.
The Design Criteria and Limitations sections provide information which
should be considered when making decisions on the most applicable technology.
Such considerations involve the efficiency of the process in certain
situations, effects of outside factors such as weather, and recommended scope
of use.
The applicability of a technology to the treatment of hazardous
constituents is provided in the Technology Status section. Included is the
status of the equipment and techniques required. Some processes are
conventional and well demonstrated in application, while others have yet to be
fully proven for remedial actions.
Most technologies are used in concert with other processes to accomplish
treatment. Technologies also listed in this report are listed in the
Associated Technology section. When collecting data to evaluate one process,
it may also be necessary to refer to other Fact Sheets identified in this
section for other related requirements.
Data required for process evaluation is listed in Data Needs for
Screening. This section lists various process data needs, why this data is
required, how it can be collected, and approximate costs. Costs listed in
this section are intended for estimation of total costs only, and have been
rounded to the nearest $50. Costs may also vary with the number of samples,
site-specific requirements, difficulty of sampling, and other factors.
The data needs presented on the Fact Sheets will provide the engineer
with an organized list of information to be collected in order to adequately
evaluate any of the technologies listed for use in remedial programs.
£30b JJUS
-------
-------
1.0 SURFACE SEALS
Type of Control: Surface Water, Leachate, Ground Water
Function: Most commonly used to contain contamination by minimizing surface
water infiltration and erosion; also provides a media for revegetation; less
commonly used as an economical alternative to excavation when extensive
subsurface contamination is present.
Description: Surface seals, also referred to as caps or covers, generally
refer to low permeability barriers which are installed over waste disposal
sites where infiltration needs to be eliminated. A variety of materials can
be used in the construction of surface seals, including: soils, admixtures
(i.e., asphaltic concrete, soil cement bentonite), synthetic geomembranes, and
chemical sealants/stabilizers, though most CERCLA covers should meet the
guidance for multiple layer covers under RCRA under Subtitle C (40 CFR
Part 240).
As diagrammed in Figure 1.0, typical surface seals consist of several layers,
including a top soil layer (for vegetation), buffer soil layer (usually a
sandy soil to protect barrier layer), barrier layer (clayey soil or synthetic
membrane which restricts passage of water or gas), filter layer (intermediate
grain-sized sands used to prevent fine barrier layer particles from sifting
through the coarser buffer layer), and a gas channeling layer (sand and gravel
used to collect or disperse gases produced from the wastes).
2% minimum sldos
.*...» * * + " ' * *
Loam (for Vegetation)
Clay I Barrier! ////////////
-------------- ^POOOOOOOOOOOOOOOC
o_- /~u-nnnM >OOOOOOOOOOOOOOOOC
•SO 'MIL SYNTHETIC
Figure 1.0. Typical surface seal designs.
Source: U.S. EPA 1985b.
Design Considerations; Several materials and designs are available for
capping. Factors influencing the proper selection of materials and design
include: desired functions of cover materials, waste characteristics,
climate, hydrogeology, projected land use, and availability and costs of cover
materials. For more information concerning design considerations for specific
types of caps, refer to Lutton, et al., 1979 or U.S. EPA, 1985b.
Limitations: Surface seals require long-term maintenance. Periodic
inspections should be made for settlement, ponding of liquids, erosion, and
invasion of deep-rooted vegetation. Concrete barriers and bituminous
membranes are vulnerable to cracking, but the cracks can be relatively easily
repaired.
11
-------
Technology Status; Conventional, demonstrated.
Associated Technologies; Grading, diversions, and revegetation.
Important Data Needs for Screening:
Data need
Extent of
contamination
Depth to ground
water table
Availability of
cover materials
Purpose
Cost-effectiveness
of cap vs.
excavation/ removal
May not be effective
in areas with a
high ground water
table
Imp lemen tab i 1 ity
and cost
Collection
method
Sampling and
analysis, site
investigation
Geologic maps,
observation wells,
boreholes, logs,
geologic survey,
piezometers
Site inspection,
site investigation
Costs ($)
100/sample
400
Boreholes,
50/1 in. ft
wells ,
50/vert. ft
Soil
characteristics
- Gradation
- Atterberg limits
- %-Moisture
- Compaction
- Permeability
- Strength
Climate
(precipitation)
Land use
Suitability for
use in cover
- Sieve analysis
- Plasticity tests
- Volume-wt analysis
- Proctor compaction
- Triaxial permeameter
- Triaxial shear,
direct shear
Expected infiltration U.S. NDAA records;
rate; design criteria local records
Selection of proper
cap design
Site investigation,
site inspection
50/Test
50/Test
50/Test
50/Test
50/Test
100-400/
test
50
Nominal
References:
U.S. EPA, 1985b; Ehrenfeld and Bass, 1984; GCA, 1985; U.S.
EPA, 1984.
12
-------
2.0 DUST CONTROL
Type of Control: Air Pollution Control - Particulate Matter
Function: Prevents airborne emissions of contaminants sorbed to soil
particules.
Description: Methods used to control fugitive dusts include chemical dust
suppressants, physical stabilizers, wind screens, water spraying, compaction,
grading, and covering. Chemical dust suppressants are applied (usually
sprayed) to the soil surface and act to strengthen the bonds between soil
particles such that dust formation is inhibited. Wind screens or wind fences
consist of a porous polyester screen or wooden fence, typically 4 to 10 ft
high, which act to deflect and/or slow wind velocity. Wind screens/fences are
designed to lower the wind velocities such that soil movement by wind is
inhibited. Dust emissions can also be controlled by spraying water on the
exposed surfaces, a method commonly used on well-travelled areas. Covering
and grading are described in Fact Sheets 1 and 3, respectively.
Design Considerations: Dust suppressants are a reliable short-term (l to
4 weeks) control measure. However, consideration should be given to the
potential impacts to soil and ground water from the use of certain chemical
dust suppressants which may contain hazardous substances. Examples of
commercially available dust suppressants can be found in U.S. EPA, 19b5b and
Rosbury and James, 1985. Some soil types may not be appropriate for use with
certain chemical suppressants and physical stabilizers. Compatibility of the
suppressant/stabilizer with the soil type should be determine prior to
selection. Compacting the surface with rollers prior to using chemical dust
suppressants or water spraying will increase the effectiveness of these dust
control techniques. Water spraying is more effective for larger grain-sized
particles. -Wind fences/screens are easily transported and installed. Maximum
wind velocity reduction can be effected for distances of one to five fence
heights downstream.
Limitations: Chemical dust suppressants are only effective while the
soil-chemical crust is maintained. If undisturbed by weeds and traffic,
chemical dust suppressants will be 100 percent effective for a period of
approximately 1 to 4 weeks, with declining control efficiencies thereafter.
Wind screens are only partially effective in the control of inhalable (fine)
particulates, and are not effective for particles smaller than 10 micrometers.
Technology Status: Conventional, demonstrated.
Associated Technologies : Excavation and removal, grading, and capping.
13
-------
Important Data Needs for Screening:
Data need
Soil type
(texture)
Soil grain size
distribution
Percent
compaction
Climate
Purpose
Affects suppressant
efficiency
Affects suppressant
efficiency
Affects suppressant
efficiency
Affects wind transport;
Collection
method
Plasticity tests
Sieve analysis
Proctor
compaction
National climatic
Costs ($)
50/test
50/test
50/test
50
Contaminant
nominal
characteristics
Land use
determines effective-
ness of dust
suppressant techniques
Sorption volatility;
effectiveness of dust
suppressant techniques
Need for traffic
control
Sampling and
analysis, CRC
Handbook of
Chemicals and
Physics
Site inspection,
site investigation
50/sample
Nominal
References; U.S. EPA, 1985b; Ehrenfeld and Bass, 1984; U.S. EPA, 1984;
GCA, 1985, U.S. EPA, 1985d.
14
-------
3.0 GRADING
Type of Control: Surface Water, Soil Stabilization
Function; Alters the topography and runoff characteristics of a waste site;
optimizes slope and prepares area for surface sealing and/or revegetation.
Description: Grading refers to techniques used to reshape the surface of a
site in order to manage surface water infiltration and runoff while
controlling erosion. Grading techniques include spreading, compaction,
sacrification, tracking, and contour furrowing. Figure 3.0 illustrates
typical grading equipment.
SlMl-whMl Compactor
" Doi«BU*i •*•-" Limlffl BUde
Front-end Accessories
Figure 3.0. Typical grading equipment.
Source: U.S. EPA 1985b.
Spreading, and compaction are used to optimize a slope in such a way that
surface runoff is increased while infiltration and ponding are decreased,
without increasing erosion. These techniques are used to prevent surface
water runoff from contacting waste, and/or to prepare a site for subsequent
remediation activities. Sacrification, tracking, and contour furrowing are
grading techniques employed to roughen soils in preparation for revegetation.
These techniques slow runoff, thereby increasing infiltration and decreasing
erosion potential.
Design Considerations; Generally, graded slopes should be 3 to 5 percent;
sometimes greater slopes are used to promote more effective drainage, but the
maximum slopes usually do not exceed 33 percent.
15
-------
Limitations: Costs may be excessive if suitable soil for slope optimization
can not be found within a reasonable hauling distance from the site. Also,
periodic regrading and maintenance may be necessary to correct depressions
formed through settlement, compaction and/or eroded slopes.
Technology Status; Conventional, demonstrated.
Associated Technologies; Excavation and removal, capping, revegetation, and
diversion/collection techniques.
Important Data Needs for Screening;
Data need
Purpose
Collection
method
Costs
Climate
Topography
Soil type
Average precipitation
effects selection of
optimum slope
Grading operations
limited for sites with
steep topography; steep
slopes may require
drainage channels and
benches to control
erosion
Affects selection of
optimum slope; fill
material selection
National Climatic
Center (NCC),
local weather
bureau
Site inspection,
site survey,
topography map
50
Plasticity
tests
Survey:
200-300/
acre
(2,500
minimum)
50/test
References: U.S. EPA, 1985; Ehrenfeld and Bass, 1984; U.S. EPA, 1984;
GCA, 1985.
16
-------
4.0 REVEGETATION
Type of Control: Surface Water, Soil Stabilization
Function: Stabilizes soil against erosion due to wind and precipitation,
reduces runoff, improves aesthetic appearance, and in certain cases can treat
contaminated soil and leachate through uptake of waste constituents.
Description: Revegetation refers to the establishment of a vegetative cover
to stabilize the surface of a hazardous waste disposal site. It is frequently
preceded by grading and capping, particularly for final cover system designs
for waste disposal sites. The process of revegetating a site involves the
selection of a suitable plant species, seedbed preparation, seeding/planting,
mulching and/or chemical stabilization, and fertilization arid maintenance.
Various types of grasses, legumes, shrubs, and trees may be used for
revegetation. Important characteristics of these plant species can be found
in Lutton, 1982 and U.S. EPA, 1985b. Generally, grasses provide a quick and
lasting ground cover with dense root systems that anchor the soil and enhance
infiltration. Legumes are most suited for stabilization and erosion control
and enhancing soil fertility (through nitrogen fixation). Shrubs provide a
dense surface cover and tend to be more tolerant of acidic soils and other
disposal site stresses. Trees provide a long-term protective cover and aid in
developing a stable, fertile layer of decaying leaves and branches. Gas
migration controls may be required (Figure 4.0).
Cross-Section End View of Gas Barrier Trench
•fcl •(-/"-- o — •.-.••- ~/? O"*2,\S- -^ ~°
•10'-
V Topsoil
J 1' Subsoil
— Plastic Sheet
PVC Perforated
Vent Pipes
Cross-Section End View of Soil Mound
Figure 4.0 Gas migration controls for vegetation.
Source: U.S. EPA 1985b.
Design Considerations; Temporary stabilization via straw-bale check dams,
mulching, or chemical methods, may be required while vegetation is being
established. Also, in cases where revegetation is to be part of a final cover
system, it is important to consider the expected root system when selecting
the vegetative species, because the roots can interfere with the cover system
(e.g., by penetrating liners, etc.).
17
-------
Des ign Cons id era t ions: Earth fill may be available onsite. Low permeability
clayey soils are best for construction, but compacted sands and gravel may
also be used. Dikes are not recommended for upsloped drainage areas larger
than 5 acres.
Technology Status; Conventional, demonstrated.
Associated Technologies: Capping, revegetation, excavation and removal, site
clearing.
Important Data Needs for Screening:
Data need
Purpose
Collection
method
Costs (tf)
100-yr floodplain
elevation
Soil permeability
Soil type
Site accessibility
Topography
Location of
dike/berm
Low permeability
best for fill
Clayey soils best for
dike/berm construction,
compacted sands and
gravel also effective
Sufficient accessible
area for equipment
Grading operations
limited for sites with
steep topography; steep
slopes may require
drainage channels and
benches to control
erosion
Topography map;
USDA records;
Federal Emergency
Management Agency
(FEMA) Flood Study
Triaxial
permeameter
Sampling and sieye
analysis; plasticity
tests; Proctor
compaction
Site inspection;
site survey; town/
city/county records
records
Site inspection,
site survey,
topography map
Nominal
50/test
50/test
Nominal
Survey:
200-300/
acre
(2,500
minimum)
References: U.S. EPA, 1985a; U.S. EPA, 1985b; U.S. EPA, 1984; U.S. EPA, 1984b;
Ehrenfeld and Bass, 1984' JRB, 1984; Phelps, 1986; Brady, 1974.
20
-------
5.0 DIVERSION/COLLECTION SYSTEMS
5.2 DITCHES, CHANNELS, SWALES, DIVERSIONS, AND WATERWAYS
Type of Control: Surface Water
Functions/Uses: Used to intercept runoff and/or reduce slope length; conveys
runoff from one area to another.
Description: Ditches and channels are depressions or shallow, excavated areas
with V-shaped, trapezoidal, triangular, or parabolic cross-sections, which
intercept runoff or reduce slope length. Earthen channels can be used to
divert runoff from entering the site. Waterways are channels that have been
stabilized with vegetation or stone rip-rap, and are able to collect and
transfer diverted water offsite or to an onsite storage/treatment area. A
diversion is a modified earthen channel that has a supporting dike or berm
along the downhill edge of the channel. Swales are similar to channels except
that their side slopes are not as steep, and they have a vegetative cover for
erosion control. Figure 5.2 shows typical channel design features.
STANDARD DESIGN FOR DRAINAGE DITCHES
2:1 or flatter
Existing ground
TYPICAL DRAINAGE DITCH AT BASE OF DISPOSAL SITE
Jteepflr- d«Pflndent on topography
Outlet H required.
SM item 6 below.
Figure 5.2. Typical channel design features,
Source: U.S. EPA 1985b.
Design Considerations: Channels and waterways are generally designed to
intercept flows from 10 or 25-year storm events, in such a way as to be able
to convey these flows at non-erosive velocities. Wider and shallower channel
cross-sections have lower flow velocity and thus reduced potential for erosion
of channel side slopes. Narrower and deeper channels require stabilization
through vegetation or the use of stone rip-rap to line channel bottoms and
break up flow. Half-round channels, which are constructed of cut corrugated
metal pipe or pre-fabricated asphalt sections, can be placed below grade and
have low maintenance and installation costs.
21
-------
Limitations; Diversions should only be used for slopes of 15 percent or
less. Ditches are designed for short-term use only. Diversions and waterways
are more permanent. For channel slopes greater than 5 percent, vegetation,
mulches, or stone rip-rap may be necessary for stabilization.
Technology Status: Conventional, demonstrated.
Associated Technologies; Revegetation, grading, surface sealing, excavation
and removal, site clearing.
Important Data Needs for Screening:
Data need
Purpose
Collection
method
Costs (ii)
Soil
permeability
Area land use
Climate
Low permeability
preferable
Trees, bushes, stumps,
need to be cleared
Channels & waterways
are better suited for
areas with heavy and/or
frequent rains
Triaxial
permeameters
50/test
Site inspection, 500
site survey
National Climatic
Center (NCC),
local weather
bureau
Nominal
Topography
15 percent or less
slopes required for
diversions; channel
slopes 5 percent need
to be re vegetated
Site inspection,
site survey,
topographic map
200-
300/acre
(2,500
minimum)
References; U.S. EPA, 1985a; U.S. EPA, 1985b; U.S. EPA, 1984a; U.S. EPA,
1984b; Ehrenfeld and Bass, 1984; JRB, 1984; Phelps, 1986;
Brady, 1974.
22
-------
5.0 DIVERSION/COLLECTION SYSTEMS
5.3 TERRACES AND BENCHES
Type of Control: Surface Water
Function: Control erosion by reducing slope length (terraces); intercept and
divert surface water flow (benches).
Description; Terraces and benches are embankments, or combinations of
embankments, constructed across long or steep slopes. In climates where
rainfall is frequent and/or heavy, benches and terraces are typically
constructed in association with drainage channels so that concentrated surface
flows can be intercepted and transported offsite. Drainage benches may be
seeded, mulched, sodded, rip-rapped, chemically stabilized, or lined with
concrete or grouted rip-rap (the latter two techniques are more costly
alternatives).
SLOPE REDUCTION MEASURES
Swal« or Ditch
1 fl$
•
&&•''•••£?• Reiuw
Figure 5.3. Typical terrace and bench applications.
"Source: U.S. EPA 1985b.
Design Considerations: Benches are generally designed with sufficient height
and width to withstand a 24-hour, 25-year storm. Generally, the spacing
between drainage benches should be more frequent for long, steep slopes with
erodible soil cover. Structures must be stabilized as soon as possible after
grading and compaction.
Limitations: Terraces and benches are an effective control in areas of high
precipitation and can be used for long and steep slopes above, on, or below
disposal sites. Terraces and benches should be periodically inspected,
especially after heavy rainfall events.
23
-------
Technology Status: Conventional, demonstrated.
Associated technologies; Diversions, dikes and berms, ditches, channels,
capping, revegetation.
Important Data Needs for Screening:
Data need
Purpose
Collection
method
Costs
Climate
Topography
Soil type
Soil
permeability
Runoff volumes &
flow velocities
Inspections required
after heavy rainfall
events
Cost-effective for
long and steep slopes
above, on, or below
disposal sites;
steeper slopes require
more benches/terraces.
Closer bench placement
for erodible soil covers
Low permeability
soils preferred
Proper sizing and
placement of terraces/
benches
National Climatic Nominal
Center (NCC),
local weather
bureau.
Topography map, 20U-30U/
site inspection, acre
site survey. (2,500
minimum)
Sampling and 50/test;
sieve analysis; 50/test
plasticity tests
Triaxial 50/test
permeameters
Gauge stations; 400
meters; USDA
records; field
measurements
References: U.S. EPA, 1985a; U.S. EPA, 1985b; U.S. EPA, 1984a; U.S. EPA,
1984b; Ehrenfeld and Bass, 1984; JRB, 1984; Phelps, 1986;
Brady, 1974.
24
-------
5.0 DIVERSION/COLLECTION SYSTEMS
5.4 CHUTES AND DOWNPIPES
Type of Control; Surface Water
Function: Chutes and downpipes are used to convey concentrated flows of
surface water from one level of a site to a lower level without erosive damage.
Description; Chutes (also referred to as flumes) are open channels that have
compacted, smooth linings placed over undisturbed soil or well-compacted
fill. Downpipes (also called downdrains or pipe slope drains) consist of
rigid piping laid in slope areas. Generally, downpipes extend downslope from
earthen embankments (i.e., dikes and berrus) and convey water to stabilized
waterways or outlets at the base of the slope.
Design Considerations; Chutes and downpipes are temporary structures, often
used in conjunction with other technologies, that do not require formal
design. Chutes and downpipes are useful in emergency situations because they
can be quickly constructed.
Limitations; Chutes and downpipes are temporary measures only. Periodic
inspection and maintenance is required, particularly after storm events.
Downpipes are only suitable for 5-acre drainage areas. Chutes are limited to
heads of about 18 ft or less.
Technology Status; Conventional, demonstrated.
Associated Technologies; Channel, diversions, waterways, ditches, dikes and
berms.
25
-------
Important Data Needs for Screening:
Data need
Topography
and local
drainage
patterns
Purpose
For downpipes limited
to 5-acre drainage
areas; chutes limited
to 8 ft heads or less
Collection
method
Topographic map;
site inspection,
site survey
Costs ($)
200-300/
acre
(2,500
minimum)
Climate
Soil type
Soil
permeability
Site size
Inspection and
maintenance
required after
heavy storm events
Clays or compacted
sands and gravels
are preferred
Low permeability
soils are preferred
Needs to be large enough
for installation inspec-
tion, and maintenance
National Climatic 50
Center (NCC) ;
local weather
bureau
Sampling and 50/test
sieve analysis;
plasticity tests;
proctor compaction
Triaxial 50/test
pertneameters
Site inspection; Nominal
site survey; town/
city/county records
References; U.S. EPA, 1985a; U.S. EPA, 1985b; U.S. EPA, 1984a; U.S. EPA,
1984b; Ehrenfeld and Bass, 1984; JRB, 1984; Phelps, 1986;
Brady, 1974.
26
-------
5.0 DIVERSION/COLLECTION SYSTEMS
5.5 SEEPAGE/RECHARGE BASINS AND DITCHES
Type of Control: Surface Water, Ground Water
Function: Intercept runoff and recharge the water downgradient from the site
to minimize ground water contamination and leachate problems.
Description: As shown in Figure 5.5, there are several construction designs
for seepage basins and ditches. Typically, a seepage basin consists of an
excavated basin, a sediment trap, a bypass for excess flow, and an emergency
overflow area. The sidewalls of the basin are constructed of previous
material to allow for recharge.
SEEPAGE BASIN: LARGE VOLUME. DEEP DEPTH TO GROUNDWATER
Seepage basin Overflow
SEEPAGE DITCH
10' (min.)
Bypass
48" min.
18" (max.)
SEEPAGE DITCH WITH INCREASED SEEPAGE EFFICIENCY
SEEPAGE BASIN.- SHALLOW DEPTH TO GROUNDWATER
Dense turf
18" max.
1 10' min.
Figure 5.5. Typical designs for.seepage basins and ditches.
Source: U.S. EPA 1985b.
Design Considerations: Seepage ditches are usually constructed in parallel
with runoff moving through drains set in gravel ditches. Improved percolation
occurs when gravel-filled trenches are constructed along the basin floor.
Dense turf on the basin sidewalls will prevent erosion while permitting a high
infiltration rate.
27
-------
Limitations; Seepage/recharge basins and ditches are susceptible to clogging
(particularly in areas of heavy precipitation) and, therefore, require
periodic monitoring and cleaning. They are not effective in poorly permeable
soils, best used for soils where permeability exceeds 0.9 in./day.
Technology Status: Conventional, demonstrated.
Associated Technologies: Diversions, revegetation.
Important Data Needs for Screening:
Data need
Purpose
Collection
method
Costs ($)
Soil type
(Atterberg
limits)
Soil
permeability
Topography
Climate
Sands and gravels
preferred
Not effective in poorly
permeable soils; best
where permeability
exceeds 0.9 in./day
Presence of dense turf
and vegetation allows
for high rate of
infiltration and
prevents erosion
Areas where frequent and
heavy rainfall occurs are
generally not suitable
Plasticity tests; 50/test
sieve analysis
Triaxial 50/test
permeameter
Topography map; Nominal
site inspection,
site survey
National Climatic 50
Center (NCC) ;
local weather
bureau
References; U.S. EPA, 1985a; U.S. EPA, 1985b; U.S. EPA, 1984a; U.S. EPA,
1984b; Ehrenfeld and Bass, 1984; JRB, 1984; Phelps, 1986;
Brady, 1974.
28
-------
5.0 DIVERSION/COLLECTION SYSTEMS
5.6 SEDIMENTATION BASINS/PONDS
Type of control: Surface Water, Ground Water
Function; Used to control suspended solids entrained in surface flows
(impedes surface runoff carrying solids, allows sufficient time for
particulate matter to settle); used in control of diverted surface runoff.
Description; Sedimentation basins remove suspended solids from waterways
through gravitational settling. A sedimentation basin is constructed by
placing an earthen dam across a waterway or excavated area. It consists of
the basin, a principal spillway, an anti-vortex device, and an emergency
(overflow) spillway. As shown in Figure 5.6, the principal spillway consists
of a vertical pipe (or riser) jointed to a horizontal pipe (barrel) that
extends through the dike and outlets beyond the basin. The riser is topped by
the anti-vortex device which improves the flow of water into the spillway and
prevents floating debris from exiting the basin. Water discharge from the
sediment action basin is typically directed toward an existing, stable
stream. Additional measures (such as impact basin, rip-rap, excavated plunge
pools, and stone facing) may be implemented to protect against scour (erosism).
Design Considerations; The size of the sedimentation basin is dependent upon
the particle size distribution of the suspended solids, the inflow
concentration, the volumetric flow rate, the desired concentration of
suspended solids, and the water flow rate to the pond. Given this
information, the required area of the sedimentation basin can be calculated.
An explanation of the calculation can be found in U.S. EPA, 1985.
TYPICAL DESIGN OF A SEDIMENT BASIN EMBANKMENT
- Anti-vonex Device
Emergency Spillway Crest
MODIFICATION OF CONVENTIONAL SEDIMENTATION POND
TO REDUCE SUSPENDED SOLIDS
Fn« Aggregate*
Cofwtiuclion
SwtdS-niUr
toConcrato
EMBANKMENT
Figure 5.6. Sedimentation basin designs.
Source: U.S. EPA 1985b.
29
-------
Limitations; Regular inspections and maintenance, including periodic
cleanings, are required. Sedimentation basins/ponds perform poorly during
periods of heavy rains. Fine-grained suspended solids and chemicals that are
not sorbed to suspended particulates are not removed by sedimentation
basins/ponds.
Technology Status: Conventional, demonstrated.
Associated Technologies; Waterways, excavation and removal, site clearing.
Important Data Needs for Screening:
Data need
Purpose
Collection
method
Costs ($)
Climate
Land use
Soil/sediraent
characteristics
(Atterberg limits)
Waste
characteristic
Basin siting
and design
Land area needs to be
free of roots, woody
vegetation, large
stones, etc. (sacrifi-
cation may be necessary
Fine-grained
suspended solids
are not removed
Chemicals sorbed to
suspended particulates
are not removed
National Climatic
Center (NCC);
local weather
bureau.
Site inspection;
site survey
Plasticity tests;
sampling and
sieve analysis
Laboratory analysis;
CRC Handbook of
Chem. & Physics
50
400
50/test
Sample
analysis
500/sample
References; U.S. EPA, 1985a; U.S. EPA, 1985b; U.S. EPA, 1984a; U.S. EPA,
1984b; Ehrenfeld and Bass, 1984; JRB, 1984; Phelps, 1986;
Brady, 1974.
30
-------
5.0 DIVERSION/COLLECTION SYSTEMS
5.7 LEVEES AND FLOODWALLS
Type of Control: Surface Water
Function: Flood protection structures in areas subject to inundation from
tidal flow or riverine flooding.
Description: Levees are earthen embankments that create a barrier to confine
floodwaters to a floodway and to protect structures behind the barrier.
Levees are constructed of erosion-resistant, low-permeability soils (i.e.,
clay), or compacted, impervious fill. Floodwalls are similar to levees,
except that they are constructed of concrete. Levees generally require a very
large base width; therefore, in areas where there is limited space and fill
material, concrete floodwalls are preferred. Various designs for levees and
floodwalls are diagrammed in Figure 5.7
TYPICAL LEVEE AT BASE OF DISPOSAL S!
Elavation: Minimum ?
Abova 100 Year Flood
PERIMETER FLOOD PROTECTION STRUCTURE
Compacted ImperaiouB Soil •
Compacted tmpervioua
Soil Levee
Stripping
bnpervioua Groundwater Cutoff Trei
] May Be Required in Certain Soda
Venfy Eating V TO*
Clay Cover Soil (TvP-t
—V Key Into Impefvioue Soa
Figure 5.7. Levees at disposal sites.
Source: U.S. EPA 1985b.
Design Considerations: Levees and floodwalls are generally designed with a
height capable of withstanding a 100-year flood (usually 2 ft of freeboard
above the 100-yr flood elevation). A 10 ft minimum top width is required for
levees to allow access for construction and maintenance equipment.
Availability of fill materials onsite reduces construction cost. Drainage
structures are often needed to drain the area behind the levee or floodwall.
Typically used drainage structures include: diversion ditches, gravel-filled
trenches, tile drains, sumps, and/or pressure conduits. If seepage problems
occur, it may be necessary to construct a compacted impervious core or
sheet-pile cut-off extending below the levee to bedrock. Excess seepage can
be collected with gravel-filled trenches or drains along the interior edge of
the levee or floodwall. Vegetation or rip-rap can be used to protect levee
bank slopes from erosion. Upslope interceptor ditches, diversions, or grassed
waterways may be used to prevent backwater flooding from runoff falling on the
drainage area behind the levee or floodwall.
Limitations:
Levees and floodwalls are most suitable in flood fringe areas or
areas subject to storm tide flooding. They are not suitable for areas with
direct open floodways. Federal Emergency Management Agency (FEMA) regulations
may limit the use or placement of floodwalls and levees. Hydraulic analysis
of the impact of the embankment on flooding characteristics of the waterway
may be required. Flooding from storm runoff behind a levee and/or floodwall
may be a problem; reduced flow storage capacity increases potential for
downstream flooding.
31
-------
Technology Status: Conventional, demonstrated.
Associated Technologies: Ditches, diversions, waterways, sheet piling, gabion
walls.
Important Data Needs for Screening:
Data need
Purpose
Collection
method
Costs ($)
100-year
floodplain
elevation
Site map
Flow patterns
and velocity
Soil type
Soil permeability
Topography
Geologic
chacteristics
Cannot be constructed
in the FEMA-designated
floodway
Levees require large
land areas; floodwalls
can be used in areas
with limited space
Reduced flow storage
capacity increases
potential for down-
stream flooding
Fine-grained clays or
compacted sand and
gravel for levees
Low permeability soils
for levees
Additional drainage
structures may be
required in areas
with steeper slopes
Bedrock suitable for
sheet-pile cut-off
is preferrable
Topography map;
FEMA flood study;
USDA records
Site inspection;
site survey;
town/city/county
records
Gauge stations;
meters; USDA
records; field
measurements
Sampling and sieve
analysis; plasticity
tests
Triaxial
pertneameter
Topography map;
site inspection
site survey
Existing geological
maps, surveys;
bore hole logs
Nominal
Nomina1
400
50/test
50/test
200-300/
acre
Boreholes
50/linear
ft; test
trench:
50/cu yd
References: U.S. EPA, 1985a; U.S. EPA, 1985b; U.S. EPA, 1984a; U.S. EPA,
1984b; Ehrenfeld and Bass, 1984; JRB, 1984; Phelps, 1986;
Brady, 1974.
32
-------
6.0 SUBSURFACE CONTAINMENT
6.1 SLURRY WALLS
Type of Control: Ground Water, Leachate
Function: Contain, capture, or redirect ground water and/or leachate in the
vicinity of a site.
Description; Slurry cut-off walls are low-permeability, fixed walls installed
to contain or divert ground water flow. The slurry maintains trench stability
during excavation, and also prevents fluid losses to the surrounding ground by
forming a filter cake on the trench walls. The primary types of slurry walls
are soil-bentonite slurry walls, cement-bentonite slurry walls, and diaphragm
walls. Soil-bentonite walls are constructed by backfilling the vertical
trench with soil materials (often trench spoils) mixed with a bentonite and
water slurry. Cement-bentonite slurry walls are composed of a slurry of
Portland Cement and bentonite which is allowed to set, thereby forming a
stronger but more permeable wall. Diaphragm walls are reinforced concrete
panels that are either cast in-place or pre-cast and then placed in the
trench. Slurry walls can be configured in a variety of ways. Slurry walls
may either be keyed into the underlying bedrock (key-in walls) to prevent
vertical and/or horizontal movement of contaminants within the aquifer, or
placed to intercept only the upper portion of the aquifer (hanging walls) to
control contaminants which float on top of the ground water. The slurry wall
may be placed upgradient, downgradient, or circumferential to the area of
contamination. Upgradient slurry walls are used to divert uncontaminated
ground water around the site. Downgradient and circumferentially placed walls
are used to contain contaminated ground water (usually for subsequent pumping
and/or treatment).
Design Considerations: Soil-bentonite walls require a larger land area and a
relatively flat topography. Cement-bentonite walls are better suited for more
extreme topographies. Cement-bentonite walls are more permeable than
soil-bentonite walls; permeabilities less than 10~° cm/sec are generally not
achievable with cement-bentonite walls. However, diaphragm walls are much
more costly to install than cement-bentonite walls. Soil-bentonite walls are
the least costly of the slurry wall alternatives.
Limitations: Slurry wall characteristics should be compatible with in situ
soil, ground water, and leachate conditions. The soil-bentonite wall is not
suitable for leachate or contaminated ground water containing strong acids
and/or bases and alcohols. The cement-bentonite wall is not applicable for
wastes or leachate containing chlorinated hydrocarbons, organic acids, or acid
chlorides. The durability of the diaphragm wall decreases over time when
there is continued contact with inorganic salts, acids and bases, and nonpolar
organics.
Technology Status: Conventional, demonstrated; new techniques being developed.
Associated Technologies: Ground water pumping, surface and subsurface
collection, surface sealing, grouting, sheet piling, grout curtains.
• 33
-------
Important Data Needs for Screening;
Data need
Purpose
Collection
method
Costs
Accessibility of
site materials
Topography
Depth to
impermeable strata
Seismic history
Heterogeniety
of subsurface
formation
Soil conditions
Ground water depth,
rate and direction
of flow
Soil chemistry
Chemistry of waste
and ground water
Cost, implementability Site inspection
Soil-bentonite walls
require larger land
area, relatively flat
topography
USGS topography
map; site inves-
tigation; site
survey
Cost, implementability Borings
Ceraent-bentonite
wall not applicable
in areas subject to
seismic activity
Difficult to install
diaphragm wall with
rocky subsurface
material
Suitability for
backfill
Implementab ility
Cement-bentonite wall
unsuited for highly
acidic or high
sodium soil
Compatibility
with wall material
USGS geologic
maps, records,
field surveys,
aerial photos.
Test trench,
geologic maps
Plasticity, size,
permeability tests
Existing geologic
maps, boreholes,
observation wells,
logging & mapping,
piezometers
Soil sampling
and analysis
GW sampling
and analysis
Nominal
Survey:
200-300/
acre
(2,500 rain. )
50/1 in. ft
Nominal
Test
trench,
50/cu yd
50/test
Boreholes,
50/lin. ft
wells,
30/vert. ft
25/test
100-5OO/
sample
References; U.S. EPA, 1985b; Ehrenfeld and Bass, 1984; GCA, 1985;
Anderson and Jones, 1983; Canter and Knox, 1985; Kirk and
Othmer, 1979; Ryan, 1980.'
34
-------
6.0 SUBSURFACE CONTAINMENT
6.2 GROUT CURTAINS
Type of Control: Ground Water, Leachate
Function: Contain or divert ground water by sealing fissures, and other voids
in rock.
Description: Grout curtains are fixed, subsurface barriers formed by
injecting a liquid, slurry, or emulsion under pressure into the ground through
well points. Typically, the grout is injected into pipes arranged in a
pattern of two or three adjacent rows as shown in Figure 6.2. The injected
fluid fills open pore spaces and sets or gels into the rock or soil voids,
thereby greatly reducing the permeability of the grouted area. Particulate
grouts consist of water plus Portland Cement, bentonite, or a mixture of the
two which solidifies within the soil matrix. Chemical grouts consist of two
or more liquids which gel when mixed together. Often, particulate grouts are
used as "pre-grouts" with a second injection of a chemical grout to seal the
finer voids.
SEMICIRCULAR GROUT CURTAIN AROUND WASTE SITE
Vibfiung /
Himmer ...j
.Or,
Tvp-C9*Y
VIBRATING BEAM GROUT INJECTION
Figure 6.2. Grout curtain and vibrating beam injector. ^
Source: U.S. EPA 1985b.
Design Considerations: It is important to test the compatibility of the
wastes with the grouts to ensure an adequate seal. Grout curtains should
extend to bedrock (or impervious layer) to be effective. Since it is
difficult to verify the continuity of the curtain once installed,
implementation of this technique is difficult.
Limitations: Grout curtains are not applicable where heterogeneous geologic
conditions exist (e.g., glacial till). Also, very permeable soils or very
fine-grained soils are not suitable for grout curtains.
Technology Status: Demonstrated.
Associated Technologies: Ground water pumping (well systems), surface and
subsurface collection/drainage systems, surface sealing, slurry or sheet pile
cut-off walls.
35
-------
Important Data Needs for Screening:
Data need
Purpose
Collection
method
Costs
Accessibility
of materials
Soil moisture
content
Soil permeability
Grain Size
distribution
Soil/waste
chemistry
Subsurface
geology
Depth to bedrock
(impermeable
strata)
Depth to ground
water table
Direction and
rate of ground
water flow
Ground water pH,
sulfides, calcium
'Implementability
and costs
Implementability
Not applicable in very
permeable soils
Suitable if through
No. 200 sieve; if 10%
through No. 200 sieve;
then low viscosity
grout material required
Compatibility
with grout
Not suitable for
heterogeneous subsurface
Optimal depth of wall
Implementability
High GW flow
adversely affects
curtain integrity
Integrity of
grout curtain
Site visit/
investigation
Volume-we ight
analysis
Triaxial
permeameter
Sieve
analysis
Sampling and
analysis
Test trench
Existing
geologic maps,
surveys bore-
holes, logging
and mapping
Existing
geologic maps,
observation
wells, boreholes,
logging & mapping
piezometers.
Pump tests;
injection tests;
town/city/county
records
Sampling and
analysis
400
50/test
50/test
50/test
50/test
50/cu.yd.
Boreholes,
50/lin. ft
Boreholes,
50/lin. ft
wells,
50/vert. ft
Wells,
50/vert. ft
100/sample
References; U.S. EPA, 1985b; Ehrenfeld and Bass, 1984; GCA, 1985;
Knox, 1984; U.S. EPA, 1984; JRB, 1984.
36
-------
6.0 SUBSURFACE CONTAINMENT
6.3 SHEET PILING
Type of Control: Ground Water, Leachate
Function: Used to contain or divert ground water flow around or below
contaminated areas; controls hazardous leachate generation for locations where
wastes are in contact with a permanent or seasonal water table.
Description; Sheet piling cut-off walls are constructed by driving lengths of
interlocking steel into the ground with a pneumatic or steam driven pile
driver to form a thin impermeable barrier to ground water flow. Steel is most
commonly used; wood or precast concrete are used, depending on site
characteristics. Figure 6.30 shows various configurations used in
construction of sheet pile walls. Soon after being driven into the ground,
the joint connections fill with fine to medium-grained soil particles which
hinder ground water flow.
Straight Web Type
Arch Web Type
Deep Arch
Web Type
Figure 6.3. Steel piling configurations.
Source: U.S. EPA 1985b.
Design Considerations; Soil type and waste characteristics are important
factors to consider, because there is a high potential for leakage through
interlocking piles. Sheet piles are typically used in loosely packed soils
that predominantly consist of sands and gravels. A penetration resistance of
4 to 10 blows/foot for medium to fine-grained is recommended. To be
effective, sheet piles should extend to bedrock or low-permeability strata.
The maximum depth to which sheet piles can be driven without damaging the
sheet pile wall material is generally 15 feet. The characteristics of the
waste constituents and/or leachate strongly affect the lifetime of the
sheet-pile wall (particularly the pH of the waste material).
37
-------
Limitations: Sheet piles are not be suitable for rocky soils, which could
damage the sheet piles during installation, or for ground water containing
high concentrations of salts or acids.
Technology Status: Conventional, demonstrated.
Associated Technologies; Grout curtains, slurry cut-off walls, ground water
pumping, surface sealing.
Important Data Needs for Screening;
Data need
Purpose
Collection
method
Costs ($)
Depth to bedrock
(impermeable strata)
Grain size
distribution
Compaction
Depth to ground
water table
pH of ground water
and waste
Leachate/ground
water chemistry
Optimal wall depth
Fine- to medium-
grained soil particles
optimum filling
sheet pile joints
Penetration
resistance affects
feasibility
Maximum depth to
which sheet piles
can be effectively
driven is approxi-
mately 15 feet
Sheet pile lifetime
(neutral pH is best)
Compatibility with
sheet pile wall
Geologic maps,
boreholes, logs
Sieve analysis
Proctor
compaction
Geologic maps,
observation wells,
boreholes, logs,
geologic survey,
piezometers.
Sampling and
analysis
Sampling and
analysis
Boreholes-
5U/lin. ft
50/test
50/test
Boreholes-
50/lin. ft
wells
50/vert.
ft
50/test
lUU/sample
References; U.S. EPA, 1985; Ehrenfeld and Bass, 1984; GCA, 1985; Knox, 1984.
38
-------
6.0 SUBSURFACE CONTAINMENT
6.4 BOTTOM SEALING
Type of Control: Ground Water, Leachate
Function: Contain contaminated ground water, direct uncontaminated ground
water flow away from contaminated area, or lower water table inside isolated
area.
Description: Bottom sealing consists of placing a horizontal barrier beneath
the hazardous waste site to prevent downward migration of contaminants.
Possible approaches include grout injection and block displacement. Both of
these techniques are in the developmental stages; some laboratory and field
testing has been performed.
The grout injection technique involves drilling a series of holes across the
site and injecting grout to form a horizontal or curved barrier. The block
displacement method is used to isolate and raise a contaminated block of
earth. A slurry trench or grouting is used to form a barrier around the
perimeter of the block of contaminated earth to be isolated. Grout is then
injected into holes bored through the site. The grouting and slurry pumping
is continued until the contaminated block is displaced and a bottom seal is
formed beneath the block.
Limitations: The block displacement technique is not applicable to areas
where heterogeneous geologic conditions .exist. Also, this technique is not
suitable for ignitable wastes because explosives may be used during
construction.
Technology Status; Developmental, not demonstrated.
Associated Technologies: Slurry cut-off walls, grout curtains, sheet pile
cut-off walls.
39
-------
Important Data Needs for Screening;
Data need
Accessibility of
site materials
Subsurface
geology
Thickness of
subsurface strata
Depth to bedrock
(impervious strata)
Hydraulic
conductivity
Purpose
Costs and
imp leme nt ab i 1 i t y
Not applicable
for heterogeous
subsurface geology
Implementability
Optimal depth of
associated walls
Implementability
Collection
method
Site inspection
site investment
Test trench;
geologic maps
Geologic maps;
boreholes, logging
Geologic maps ;
boreholes; logging
Piezometers ;
pump tests
Costs (it)
Nominal
Test
trench,
50/cu.yd.
Boreholes-
50/lin. ft
Boreholes—
50/lin. ft
Wells-
50/vert. ft
Soil type (texture)
Soil grain size
distribution
Suitability for
backfill
Determine viscosity
of grout material
required
Plasticity tests 50/test
Sieve analysis 50/test
References: U.S. EPA, 1985; Ehrenfeld and Bass, 1984; JRB, 1984.
40
-------
7.0 GROUND WATER PUMPING
Type of Control: Ground Water, Leachate
Function; Contain or remove a contaminant plume or alter direction of ground
water movement; less frequently used to adjust ground water levels.
Description; Ground water pumping involves the extraction of water from, or
the injection of water into wells to manage contaminated ground water. A
series of wells is used for this purpose. The types of wells used for ground
water pumping include: well points, suction wells, ejector wells, and deep
wells, as shown in Figure 7.0. Typical components of ground water well
systems include: casing (to encase the well and pump), screening (to
stabilize the hole, facilitate flow, and keep particles out of the well),
gravel pack (to fill the annular space surrounding the screen), and pumps
(e.g., turbine submersible pump, vertical line shaft pump, and ejector pumps).
Figure 7.0. Ground water pumping wells.
Source: U.S. EPA I985b.
Design Considerations: Wellpoint systems and suction wells are best suited
for shallow, unconfined aquifers where extraction below 22 feet is not
required. Wellpoint systems are effective in most hydraulic situations.
Suction wells tend to perform poorly with low hydraulic conductivities, but
have a higher capacity than wellpoints. Deep wells and ejector well systems
are used for deeper aquifer systems. Deep wells perform best in homogeneous
aquifers with high hydraulic conductivities, and where large volumes of water
are to be pumped. Ejector wells are better suited for heterogeneous aquifers
with low hydraulic conductivities.
Limitations: Operation and maintenance costs for pumping systems are high,
which may limit their use for long term remediation. Long-term pumping may
affect local ground water levels; recharge of the aquifer may be necessary.
Technology Status: Conventional, demonstrated.
41
-------
Important Data Needs for Screening;
Data need
Purpose
Collection
method
Costs
Depth to
impermeable
strata (bedrock)
Subsurface
geology
Soil
permeability
Depth to
water table
Ground water
and leachate
chemistry
Drainage area
of pipes
Waste
viscosity
Drain spacing and
feasibility
Not cost-effective
if substantial hard
rock excavation is
necessary
Drain spacing and pipe
inflow; not suited
for soils with high
permeability
Drain spacing
Selection of
pipe material
(compatibility)
Inflow to pipe
Unsuited for
viscous wastes
Geologic maps;
logs; boreholes
Geologic maps;
boreholes; logs
Triaxial
permeameter
Geologic maps;
observation wells;
boreholes; logs;
piezometers
GW sampling and
analysis
Boreholes-
50/lin. ft
Boreholes-
50/lin. ft
50/test
Wells,
30/vert. ft
100/sample
Site visit/inspect.; Site survey:
site investigation; 200-300/acre
topography map (2,500 min.)
Sampling and
analysis
100/sample
References; U.S. EPA, 1985; Ehrenfeld and Bass, 1984; JRB, 1984.
44
-------
9.0 SURFACE WATER/SEDIMENT CONTAINMENT BARRIERS
9.1 COFFERDAMS
Type of Control: Surface Water, Sediment :
Function: Hydraulically isolates a portion of the water body; can be used to
isolate contaminated surface water for subsequent pumping to treatment
systems, or to isolate uncontaminated surface water for subsequent
dredging/sediment removal operations in the surrounding (contaminated) area.-
Description: Cofferdams are surface water barriers, which are anchored to the
soil/sediment at the bottom of a surface water body. They may be constructed
of various materials including soil, sheet piling (usually black steel, but
galvanized or aluminum coatings are also available), earth-filled sheet pile
cells (single-walled or cellular), and sand bags (for short-term structures).
Pre-assembled (interlocked) sections of sheet piling are also available. The
sheet-piling can be hand-driven using a hand maul or a light pneumatic
hammer. Heavy driving equipment such as a drop hammer, pneumatic pile driver,
or steam pile driver are also used.
Depending upon site conditions, various installation' patterns may be
utilized. In areas where the entire stream channel bed is contaminated, a
pair of cofferdams (upstream and downstream) can be used to isolate the
contaminated area while diverting the stream flow to the temporary channel, as
shown in Figure 9.la. Alternatively, if only a portion of the stream channel
bed is contaminated, a single curved or rectangular cofferdam may be used to
isolate the contaminated area without the necessity of constructing a
temporary diversion channel, as shown in Figure 9.1b.
Temporary sh«jt-pil«; • , ,
remove after pipeline construction
Diversion
channel;
excavate, place
corrugated metal
: pipe or similar
conduit
Riprap tor
outiat protection
Figure 9.la. Streamflow diversion
using two cofferdams.
Source: U.S. EPA 19855
Figure 9.Ib.
Streamflow diversion
using single cofferdams,
Source: U.S. EPA 19855.
45
-------
Design Considerations; Sheet—pile cofferdams are typically constructed of
black steel sheeting with a 5 to 12 gauge thickness and a 4 to 40 ft length.
Factors affecting the selection of dimensions include: stream depth, stream
flow velocity, and the characteristics of the soil/sediment beneath the
surface water body. In general, the length of the exposed sheeting should be
roughly equivalent to the driven length (i.e., unexposed, anchored into soil),
with an additional 1 to 3 feet of freeboard above the water surface. It may
be necessary to have a longer anchored length if there is a significant layer
of soft, muddy, or unconsolidated sediments overlying the stable soil stratum.
Limitations: Areas enclosed by cofferdams may require dewatering (e.g., in
areas of high precipitation). Flow velocities in the area adjacent to the
cofferdam will increase, thereby potentially causing bed scour and bank
erosion if bank reinforcement measures are not deployed. Underlying bedrock
may hinder the sheet-pile driving operations.
Associated Technologies: Dredging, dewatering, diversions, streambank
stabilization.
Important Data Needs for Screening;
Data need
Soil/sediment
characteristics
Purpose
Longer, anchored
length for sheet-
pile for soft,
muddy or unconsol-
idated sediments
Collection
method
Volume-weight
analysis,
grain size
distribution,
plasticity tests
Costs ($)
50/test
(each)
Geologic
conditions
Dimensions and stream
flow of surface
water body
Climate
Area of
contamination
Underlying bedrock
may hinder sheet
pile-driving operations
Influences instal-
lation configuration
and resulting costs
Dewatering of area
contained by
cofferdam may be
required
Influences of
installation config-
uration, and
resulting costs
Existing geologic
maps; geologic
surveys; bore
hole logs.
Boreholes,
50/lin. ft
Site investigation, 400
field measure-
ments, maps
National Climatic 50
Center (NCC) ;
local weather
bureau
Sampling and 100/
analysis sample
References; Brady, 1974; GCA, 1985; JRB, 1984; U.S. EPA, 1984b; U.S. EPA,
1985a; U.S. EPA, 1985b.
46
-------
9.0 SURFACE WATER/SEDIMENT CONTAINMENT BARRIERS
9.2 FLOATING COVERS
Type of Control: Surface Water, Air Pollution Control
Function; A temporary measure used to prevent overtopping of a waste lagoon
prior to final closure; mainly used to cover drinking water supply
reservoirs. Also controls voltile air emissions.
Description; A floating cover consists of a synthetic liner placed over an
impoundment. The liner is held up by floats, and anchored at the edges of the
impoundment. The synthetic liner consists of a 36-mil or 45-mil thick,
reinforced Hypalon, chlorinated polyethylene (CPE), or XR-5 material. The
material must be tested for compatibility with the waste prior to use. Two
basic types of floating cover designs are used. The most commonly used
configuration, shown in Figure 9.2a, consists of a large center float with
several smaller floats attached perpendicularly to the center float.
Rainwater is directed to a sump around the perimeter of the floating cover.
The rainwater collected in the sump is periodically drained or pumped.
Perimeter Sump A^—^
Floating
Cow -
M«t«n»l
Floating
Cover
Figure 9.2a.
Schematic plan of
a patented globe
floating cover.
Source: U.S. EPA, 1985b.
Figure 9.2b.
Cross-section of a
floating cover incor-
porating the patented
Burke design.
Source: U.S. EPA 1985b.
Another type of configuration, shown in Figure 9.2b, directs rainwater through
channels in the middle of the cover. The channels consist of sand-filled
tubes held at constant depth by floats on either side of the channel.
Perforated collection tubes are connected above and parallel to the sand
tubes. The collection tubes drain the rainwater off the cover.
47
-------
Design Considerations: Depending on the characteristics of the waste, it may
be necessary to include a gas collection system in the cover design. An
example of a typical gas collection system is diagrammed in Figure 9.2c.
Gases are channeled beneath the floating cover to an air chamber which is
connected to a manifold pipe so that gases can be pumped and collected.
Floating Cover
1
Flexible Gas
Collection
Figure 9.2c. Cross-section of a gas collection system design.
Source: U.S. EPA 1985b.
Limitations: Floating covers are temporary (interim) measures until final
closure actions are taken.
Technology Status; Conventional, demonstrated.
Associated Technologies; Land disposal.
Important Data Needs for Screening;
Data need
Purpose
Collection
method
Costs ($)
Waste
characteristics
Climate
If gases are released,
need a collection
system; selection of
compatible liner
Frequent heavy storms
may cause problems;
need adequate drainage
for the cover top;
selection of appro-
priate configuration
Sampling and 100/
analysis sample
National Climatic 50
Center (NCC);
local weather
bureau.
References; Brady, 1974; GCA, 1985; JRB, 1984; U.S. EPA, 1984b;
U.S. EPA, 1985a; U.S. EPA, 1985b.
48
-------
9.0 SURFACE WATER/SEDIMENT CONTAINMENT BARRIERS
9.3 SILT CURTAINS AND BOOMS
Type of Control; Surface Water, Sediment
Function: Used to contain suspended sediments during dredging operations
(silt curtains), and to contain contaminants that float (booms).
Description; Silt curtains are
low permeability floating barriers
that extend vertically from the
surface of the water to a
specified depth. A silt curtain
is comprised of a flexible skirt
(made of polyester-reinforced PVC,
nylon-reinforced PVC, or KEVLAE/
polyester blend), a ballast chain
to keep the skirt in a vertical
position, a tension cable to
absorb stress caused by currents,
and anchored lines to hold the
curtain in place. End connectors
are used to attach two or more
curtain sections. Silt curtains
can have several possible con-
figurations (maze, instream,
U-shaped, circular, and elliptical)
as shown in Figure 9.3, depending
upon the specific surface water
body conditions.
Legend:
D Mooring Buoy
X Anchor
Single Anchor
or Piling
Booms are similar to silt curtains,
and are used to confine contaminants
that float (i.e., specific gravity
less than 1). Booms tend to decrease
advection, dispersion, and photolysis
development configurations processes,
and may increase volatilization.
Design Considerations; The maze con-
figuration, illustrated in Figure 9.3,
is generally not recommended. The in-
stream, U-shaped configuration is suit-
able for rivers or other water bodies
where the current does not reverse.
Circular or elliptical configurations
are more suitable for open waters and
areas with reversing tides. Silt cur-
tains are typically used for small
dredging and capping operations where
frequent curtain movement does not occur.
Curtain Movement Due \
to Reversing Currents
" 'U-Shaped
Anchored On-Shore
Circular or Elliptical
Estuary
V
Figure 9.3
Typical silt curtain
development
configurations.
Source: U.S. EPA,
49
-------
Limitations: Surface wave action and (strong) currents limit the
effectiveness of silt curtains. Silt curtains are generally not effective
when used in open waters, or where currents exceed one knot, or in areas
exposed to high tides and large waves. Booms are most effective immediately
following a release (i.e., before the contaminant plume has dispersed), and
are frequently used as an emergency measure to contain oil spills.
Technology Status; Conventional, demonstrated.
Associated Technologies: Dredging, capping.
Important Data Needs for Screening;
Data need
Purpose
Collection
method
Costs
Water depth
Tidal flow
Stream/current
flow velocity
Bottom sediment
characteristics,
quantity and type
of material
in suspension
Silt curtains not suit-
able for large depths
Surface wave action
limits effectiveness;
not suitable for open
oceans, high tides,
or large waves
Strong currents limit
effectiveness;
unsuitable when
current exceeds 1 knot
Compatibility with
barrier material
Field
measurements
Gauge
measurements
400
400
Gauge
measurement s
Sampling and
analysis
400
100 /
sample
References; Brady, 1974; GCA, 1985; JRB, 1984; U.S. EPA, 1984b; U.S. EPA,
1985a; U.S. EPA, 1985b.
50
-------
10.0 STREAMBANK STABILIZATION ,
Type of Control: Surface Water, Leachate
Function: Prevents bank undermining and erosion from stream flow and from
surface runoff. Applicable to areas where bank erosion poses a threat of
introducing contaminated materials to a surface water body.
Description; Various methods of stabilizing streambanks are available.
Surface water diversion trenches or berms constructed on the upslope edge of
the streambank intercept upslope runoff and prevent it from running over the
streambank. Sheet piling walls, rip-rap, gabion walls, or other revetment of
the bank itself prevent erosion of the bank by the stream.
Sheet piling walls consist of interlocking sheet piles driven into the ground
along the edge of the stream such that the height of the wall is approximately
equivalent to the height of the bank. The space between the wall and the bank
is backfilled, thereby creating a new bank which prevents contact between the
water and the bank soils.
Rip-rap is comprised of large pieces of rock which cover the streambank and
reduce or prevent contact between water and soils. Sometimes grouting issued
to seal the rip-rap material.
Gabion walls are a series of chain link steel mesh boxes filled with stones.
These stone-filled boxes are then placed and/or stacked along the bank to
prevent contact of water with the bank. It may be necessary to construct a
stable foundation to support the gabion wall.
Design Considerations: Common construction equipment can be used in
construction of sheet piling walls, gabion walls, or rip-rap along a
streambank. Depending on the size of the stream and the steepness of the
bank, barges may be needed to provide a working surface for the equipment.
Limitations: A stable foundation (i.e., consolidated soils or bedrock) along
the stream bank is necessary in order to prevent undermining by the stream and
eventual failure. However, sheet piles should not be considered for use with
rocky soils which could damage the sheet pile units during installation. -•-•
Technology Status: Conventional, demonstrated.
Associated Technologies: Dredging, surface water/sediment containment
barriers (e.g., cofferdams), diversions (e.g., trenches, berms), sheet piling.
51
-------
Important Data Needs for Screening;
Data need
Purpose
Collection
method
Costs
Soil characteristics
(of streambank)
Geologic
characteristics
Site
accessibility
Hydrogeologic
characteristics
-100-yr floodplain
-Flow velocity
-Surface runoff
Selection of stabili-
zation technique
Stream bank construc-
tion requires a stable
foundation to prevent
undermining and
eventual failure
Barge and/or crane
may be required for
access
Applicability
of stabilization
technique
Plasticity
tests
Existing geologic
map; geologic
survey; bore
hole logs
Site inspection;
site survey;
town/c ity/county
records
USGS records;
FEMA flood study;
topography map
50/test
Boreholes-
30/lin. ft
Nominal
Nominal
References; Brady, 1974; GCA, 1985; JRB, 1984; U.S. EPA, 1984b; U.S. EPA,
1985a; U.S. EPA, 1985b.
52
-------
11.0 GAS COLLECTION/RECOVERY .
11.1 PASSIVE SUBSURFACE GAS CONTROL
Type of..Control: Gas Migration
Function: Prevents subsurface migration of landfill-generated gases beyond the
landfill property line. •
Description: Passive gas control systems alter subsurface gas flow paths
without using mechanical components. Generally, subsurface flow is directed to
points of controlled release through the use of high permeability systems,
while flow paths to protected areas are blocked through'the use of low
permeability systems. High permeability .systems consist of trenches or wells
excavated at the boundary of the landfill and backfilled with a highly
permeable material (e.g., coarse, crushed stone), as shown in Figure 11.la.
Gas flow is directed to the trench area because its higher permeability is more
conducive to gas flow than the surrounding less permeable areas. Low
permeability systems, consisting of clay-lined or synthetic-lined trenches are
used to block the paths of diffuse gas flow (see Figure 11.ID). Gases will
then travel through either the ground surface between the barrier and the
landfill or through the surface of the landfill. Often, high permeability and
low permeability systems are used in combination to control subsurface.gas flow.
4" PVC, VENT PIPE-
(SPACE @ SO'iO.C.l,
4" PVC PERFORATED COLLECTOR
(CONTINUOUS)
MONITORING
DRAINAGE PROBE
SWALE
ANY CONVENIENT WIDTH
Figure 11.la.
Passive gas control
using a permeable trench.
Source: U.S. EPA, 1985b.
Figure 11.Ib. Passive gas control
synthetic membrane.
Source: U.S. EPA 198i>b.
Design Considerations: The maximum recommended depth for the trench is
3 fee.t. Trench effectiveness is improved by constructing a low permeability
system at the perimeter of the high permeability trench to prevent migration
past the high permeability trench. Migration underneath the trench can be
prevented by extending the trench to bedrock (or impervious strata).
Installation of riser pipes and capping of the landfill further facilitates gas
movement by enhancing the trench as the path of least resistance.
Limitations: Infiltration of precipitation and/or runoff limits the
effectiveness of trench vents. If capping is not employed in conjunction with
passive trench vents, then the trenches should not be located in areas of low
relief (a slope can be constructed along the trench to control runoff).
53
-------
Periodic monitoring of subsurface gas samples collected from probes installed
in the protected area is required. Passive systems generally require little
operation and maintenance.
Technology Status: Conventional, undemonstrated at hazardous waste sites
(primarily used to control methane at municipal landfills).
Associated Technologies: Capping, diversions.
Important Data Needs for Screening:
Data need
Topography
Soil
characteristics/
permeability
Geologic character-
istics (type of sub-
surface strata, pH,
temperature, depth
to bedrock)
Purpose
Trench placement
to avoid surface
runoff infiltration
Effectiveness of sub-
surface gas transport;
vapor flux
Presence of rock
strata may limit
effectiveness
Collection
method
Topographic map;
site inspection;
site survey
Triaxial
percneameter
Geologic maps;
boreholes, logs
Costs
Survey:
2UU-30U/acre
(2,500 min. )
3U/test
Boreholes-
DU/lin. ft
Climate
Depth to
ground water
Waste
characteristics
(composition,
moisture content)
Less effective in
areas with high
rainfall or prolonged
freezing temperatures
Presence of perched
water table may limit
effectiveness
Trench placement
Natl. Climatic 50
Center (NCC) ;
local weather
bureau
Geologic maps; Boreholes-
piezometers; bO/lin. tt
observation Wells-
wells; boreholes 50/vert. ft
Microorganisms present Trench placement
(gas-producing)
Oxygen
availability
Vapor flux
Sampling & ana-
lysis, includ-
ing volume
weight analysis
Sampling and
analysis
COD analysis;
BOD analysis
iU/test
IDU/sample
5U/test
5U/test
References; U.S. EPA, 1985b; JRB, 1984; Ehrenfeld and Bass, iy»4.
54
-------
11.0 GAS COLLECTION/RECOVERY
11.2 ACTIVE SUBSURFACE GAS CONTROL SYSTEMS
Type of control: Gas Migration, Air Pollution
Function: Controls subsurface migration of landfill-generated gases; prevents
offsite migration of subsurface gases.
Figure 11.2.
Active gas extraction.
Source: U.S. EPA, 1985t>.
PLAN VIEW
GAS EXTRACTION WELL
CONTROL VALVE \
GAS COLLECTION
HEADER
Description; Active perimeter
gas control systems use mechanical
means to alter pressure gradients
to redirect the paths of subsurface
gas flow. As shown in Figure 11.2,
major components generally include:
gas extraction wells, gas collection
headers, vacuum blowers or compressors,
and gas treatment or utilization
systems.
Gas extraction wells can be installed
in the landfill or in the soil area
surrounding the landfill. They are
normally drilled to either the depth of
the seasonally low ground water table or
to the base of the landfill. A pipe,
which is solid at the top and perforated
at the level where the gas is to be
collected, is set in crushed gravel (or
other permeable material). The area
surrounding the pipe at the top of the
well is sealed with concrete or clay.
The upper portion of the pipe is con-
nected to a gas collection header. The
gas collection header is connected to
several extraction wells spaced at
regular intervals. Vacuum blowers or
compressors are used to create a negative
pressure area, which causes gases to be
drawn up from the extraction well. The
gases may subsequently be treated and
released to the atmosphere, or recovered
for use as fuel.
Design Considerations: Applicable where site conditions allow drilling
through landfilled material to the required depth. Well spacing is a critical
factor in the design of the systems. Typically, 100 ft spacing is used.
However, appropriate spacing depends upon several factors, including:
landfill depth, type of waste, moisture content of waste and surrounding
soils, percent compaction of waste, grain-size distribution of surrounding
soil, stratigraphy, and soil permeability.
\NATURAL
GROUNDS
DEPTH
VARIES
GROUNDWATER
BASE OF
MONITORING PROBE
ISPACE Ig 100'±)
MONITORING
PROBE
55
-------
Limitations: Limiting factors include: presence of free-standing leachate
(i.e., saturation) or impenetrable materials within the landfill. Not
sensitive to freezing or saturation of surface or cover soils.
Technology Status; Conventional, undemonstrated (primarily used to control
methane at municipal landfills).
Associated Technologies: Capping.
Important Data Needs for Screening:
Data need
Purpose
Collection
method
Costs
Subsurface
geology
Depth to
ground water
Soil
permeability
Waste
Constituents
Difficult installation
with rocky strata
Selection of
drilling depth
for extraction wells
Effectiveness limited
with low permeability
soils
Selection of appro-
priate well spacing
and appropriate
subsurface gas control
technology
Geologic maps; Boreholes-
boreholes, logs 5U/lin. ft.
Geological maps; Boreholes-
logs, Piezo- 50/lin. ft;
meters, observa- Wells-
tion boreholes 50/vert. ft,
Triaxial
permeameter
Sampling and
analysis
50/test
100/sample
Moisture content
of waste and soil
Percent
compaction of waste
Soil grain site
distribution
Well— spacing
Well-spacing
Well-spacing
Volume-weight
analysis
Proctor
compaction
Sieve
analysis
50/test
50/test
50/test ,
References: U.S. EPA, 1985b; JRB, 1984; Ehrenfeld and Bass, 1984.
7 03
': TO
56
-------
12.0 EXCAVATION/REMOVAL
Type of Control; Surface Water
Function; Removes (generally by mechanical digging) contaminated surface and
subsurface soils for subsequent treatment and/or disposal.
Description: Mechanical equipment such as a backhoe (hydraulically-powered
digging unit), a crane-mounted dragline (crane-fitted with a drag bucket and
connected to a boom by a cable), and a clamshell bucket (similar to a dragline,
but able to dig at depths of 50 ft or more), are generally used to excavate
solids and thickened sludge material; examples of these types of equipment are
shown in Figure 12.0. During excavation activities, the excavated material is
either contained onsite for treatment, storage, or disposal, or is loaded
directly into trucks for transport offsite for treatment, storage, or disposal.
TYPICAL BACKHOLE
DRAGLINE
CLAMSHELL BUCKET
Figure 12.0.
Examples of commonly used excavating equipment.
Source: U.S. EPA, 1985b.
The major types of excavating techniques are casting and loading, hauling,
pumping, and industrial vacuum loading. Loading and Casting is the most
commonly used excavation technique. The equipment generally used for this
technique includes: backhoes, bulldozers, and front-end loaders. Hauling
excavation techniques are used when wastes are to be transported to onsite
and/or offsite areas. Typical equipment used for excavation hauling includes:
scrapers, haulers, bulldozers, and front-end loaders.
Pumping is used to remove liquids and sludges from ponds, waste lagoons, and
surface impoundments. The liquid wastes are then either pumped to an onsite
treatment system or a tank truck for transport offsite to a commercially
operated treatment facility. The two major types of pumps are dynamic pumps
(i.e., centrifuge pumps), and displacement pumps (i.e., reciprocating or rotary
pumps). Industrial vacuum loaders can be used in large-scale cleanup operations
to remove soil or pools of liquid waste. Vacuum loaders can be vehicle-mounted
or portable skid-mounted.
57
-------
Design Considerations; The site must be accessible to heavy equipment used for
excavating the contaminated materials.
Limitations: Excavation is not well-suited for materials with a low solids
content. Dewatering techniques may need to be employed in conjunction with
excavation. Excavation is generally not cost-effective for large areas of
contamination (but alternative control technologies are not always available).
Technology Status; Conventional, demonstrated.
Associated Technologies: Dewatering, subsurface and surface water barriers,
diversions, grading, capping, revegetation.
Important Data Needs for Screening;
Data need
Purpose
Collection
method
Costs
Waste
characteristics
Nature and
extent of
contamination
Not suited for
materials with a low
solids content, may
need to employ
dewatering techniques
Determines
feasibility and
cost-effectiveness
TSS analysis;
TDS analysis
Sampling and
analysis
50/test
100/sample
Topography
Geologic
characteristics
Soil/sediment
percent—moisture
content
Accessibility to
heavy equipment
Difficulty of
excavation
Dewatering may
be necessary
Site inspection,
site survey;
town/city/county
records
Geologic maps;
borings, logs
Volume-weight
analysis
Nominal
Boreholes-
50/lin. ft.
50/test
Climate
Frequent and heavy
rains lower efficiency
National Climatic
Center (NCC);
local weather
bureau
50
References; GCA, 1985c; Ehrenfeld and Bass, 1984; U.S. EPA, 1985a;
U.S. EPA, 1985b.
58
-------
13.0 DREDGING
Type of Control: Surface Water, Sediment
Function: Used to recover contaminated sediments beneath a water body (i.e.,
contaminants that have been deposited in, or adsorbed by sediments in natural
water bodies).
Description: The choice of method; mechanical, hydraulic, and pneumatic,
depends on the size of the water body, flow rates, and sediment
characteristics. Diversion techniques and dredge spoil management
technologies are used in conjunction with dredging operations. Mechanical
dredging is used for smaller water bodies with depths of 10 ft or less, and
stream flows of 2 ft/sec or less. Mechanical dredging equipment includes
backhoes, crane-mounted draglines, bucket loaders, and clamshell buckets.
Mechanical dredging can be performed directly in-stream or on barges.
Typically, mechanical dredging is performed in conjunction with water body
diversion techniques.
Figure 13.0.
Example of mechanical dredging equipment.
Source: U.S. EPA, 1985b.
Hydraulic dredging is performed in-stream using specialized floating equipment
and removes sediments using a cutting and/or suction apparatus. The material
is collected and suction-removed through a floating pipeline to land-based
temporary storage, dewatering, treatment, and/or disposal facilities.
Hydraulic dredging can be used in several types of water bodies and waste
impoundments, and effectively removes liquid, slurries, semi-solid sludges,
and sediments.
Pneumatic dredges are very similar to hydraulic dredges. Pneumatic dredges
have a pump that operates on compressed air and hydrostatic pressure to draw
sediments to the collection head and through the transport piping. Examples
of pneumatic dredges include the airlift, the pneuma, and the oozer.
Pneumatic dredges, are able to yield denser slurries than conventional
hydraulic dredges with lower levels of turbidity and solids resuspension.
However, pneumatic dredges have lower production rates (maximum of 390 cu.
yd/hour).
Design Considerations: Dredge spoil management is usually required prior to
final disposal. If a pumping system transports the dredged sediments, booster
pumps are used for distances greater than 0.5 miles.
59
-------
Limitations; In-stream sediment dredging activities can cause resuspension of
sediment particles in the water; therefore, barriers and diversions should be
used to prevent uncontrolled downstream transport of contaminated sediments.
Technology Status: Conventional, demonstrated.
Associated Technologies; Surface water/sediment containment barriers,
diversions, pumping, sedimentation.
Important Data Needs for Screening;
Data need
Purpose
Collection
method
Costs
Nature and extent
of aquatic
ecosystem
Geologic
characteristics
Topography/site
accessibility
Dimensions of
water body
Stream flow
velocity
Phys. and chem.
characteristics
of the waste
Phys. and chem.
characteristics
of soil/sediment
Climate
Some ecosystem disrup-
tion, particularly in
wetlands; fill place-
ment and revegetation
may be required
Near surface bedrock
and large boulders; may
restrict cofferdams as
barriers during mechan-
ical dredging operations
May limit the type
and size of dredging
equipment
Mechanical dredging is
used for smaller water
bodies with depths of
10 ft or less
Mechanical dredging best
suited for stream flows
of 2 ft/sec or less
Protective measures may
be required
Selection of dredging
techniques
Frequent and heavy
rains lower efficiency
Wetlands
assessment
Existing geologic
maps; geologic
survey; bore
hole logs
400-1,000
Borehole s-
50/lin. ft
Site inspection; Nominal
site survey; town/
city/county records
Field 400
measurements
Stream gauge 400
measurements,
USGS records.
Sampling and 100/
analysis sample
Sieve analysis; 50/test
volume-weight
analysis ,
National Climatic 50
Center (NCC); local
weather bureau
References: GCA, 1985c; Ehrenfeld and Bass, 1984; U.S. EPA, 1985a; U.S. EPA,
1985b.
60
-------
14.0 BIOLOGICAL TREATMENT
14.1 ACTIVATED SLUDGE
Type of Control: Direct Waste Treatment (Aqueous Treatment)
Function: Used to aerobically break down organic wastes in aqueous waste
streams through the activity of microorganisms. This technology is most
efficient in removing alcohols, phenols, phthalates, cyanides, and ammonia.
Description: Activated sludge processes break down organic wastes in aqueous
streams by aerobic oxidation and hydrolysis, and separate into a liquid
effluent and a concentrated biomass sludge. As diagrammed in Figure 14.1,
aqueous wastes are placed in a tank equipped with an aeration device. Sludge
with air or pure oxygen pumped into the tank through nozzles or mechanical
aerators. The aerated sludge/waste mixture is transferred to a clarification
unit where the sludge biomass and treated aqueous waste are separated by
sedimentation. Treated effluent is discharged from the process. A portion of
the sludge is returned to the aeration unit to provide a continuing source of
microorganisms. Excess sludge is periodically removed from the tank for
disposal.
Wastewater
Influent
Aerator
Clarifier
Wastewater Effluent
Recycled Sludge
Sludge Residue
Figure 14.1.
Activated sludge system diagram.
Source: ADL, 1976.
Factors affecting the removal efficiency of activated sludge systems include:
the type of organics present, type of aeration, retention time, pH. level and
waste loading. Because of the importance of a near neutral pH, most systems
employ an equalization tank and pH adjustment as pretreatment steps.
Performance of the system is typically determined by BOD or COD removal
efficiency. In hazardous waste applications, the removal of specific
compounds is often the required performance criteria. Existing activated
sludge treatment plants have been used to treat leachate from hazardous waste
facilities. Removal efficiencies of up to 65 percent have been achieved in
studies conducted on landfill leachate.
Design Considerations; Design parameters for activated sludge treatment are:
BOD and toxic constituent removal rate, detention time in the aeration unit,
jclarifier surface area and design, nutrient requirements to sustain biological
activity, and sludge production.
61
-------
limitations: Some heavy metals and some organic compounds at concentrations
above a few ppm are toxic to activated sludge organisms. Pre-treatment
processes may be required. Activated sludge processes may have difficulty in
removing highly chlorinated organics, aliphatics, amines, and aromatic
compounds from wastewater.
Technology Status: Conventional, well demonstrated.
Associated Technologies; Pre-treatment pH adjustment, sludge filtration,
incineration, land disposal.
Important Data Needs For Screening:
Data need
Purpose
Collection
method
Costs ($)
Gross organic
components (BOD,TOG)
Specific organic
constituents
Influent pH
Effluent
requirements
Suitability for
treatment
Suitability for
treatment
Effect on
efficiency and
microorganisms
Design criteria
Sampling and
analysis
Organic
pollutant scan
Sampling and
analysis
Regulatory
assessment
100/sample
1,500-2,OOO/
sample
Nominal
Variable
References; Ehrenfeld, 1983; Kosson, 1985.
62
-------
14.0 BIOLOGICAL TREATMENT
14.2 TRICKLING FILTER
Type of Control; Direct Waste Treatment (Aqueous Treatment)
Function: Used to decompose organic matter in aqueous liquid wastes with less
than 1 percent suspended solids. Most efficient in removing alcohols,
phenols, phthalates, cyanides, and ammonia.
Description: Liquid aqueous wastes are sprayed over a bed of rocks or
synthetic media upon which a slime of microbiological organisms is grown. The
microbes decompose organic matter aerobically at the outer slime surface by
natural updrafts of air through the bed. Anaerobic decomposition may occur
within the microbial mass adjacent to the trickling bed media. Design factors
which influence the removal efficiency of this system are: type, number,
size, and configuration of the filter units used, recycling of effluent,
pre- and post-treatment, and BOD of pollutant load.
PUMP STATION
RECIRCULATION
RAW WASTEWATER
\
PRIMARY
CLARIFIER
1
i.
*t_j*
HICH RATE. '
ROCK MEDIA
TRICKLING
FILTER
i
FINAL
CLARIFIER
1
I/ten cmnnr
"trrLUlNI
I
I
1
1
J: I
RAW SLUDGE
RECIRCULATION
Figure 14.2. Trickling filter treatment system.
Source:
Design Considerations: Design parameters for trickling filters include:
size, type, number and configuration of the filters, pollutant BOD load, waste
constituents and volume, necessity for pre- and post-treatment, hydraulic
load, recirculation method, and sludge generation rate. Secondary design
considerations may be associated with clarifier requirements, nutrient needs
of the system, bed depth, and media type.
Limitations: A disadvantage of trickling filters is the requirement for very
uniform waste composition, flow rate and a consistent temperature aDove
0 degrees C. Odors from the filter and flies can be a problem. Clogging and
surface ponding in the filter can result from inadequate liquid flow through
the system. If the filter must be covered for odor control, forced air
ventilation is often necessary.
Technology Status: Conventional technology, as yet undemonstrated for the
treatment of hazardous wastes. The use of mixed microbial populations in
'soils to biodegrade leachate from hazardous waste lagoons has been
investigated. This method involved the use of soil as the microbial growth
media rather than the usual filter design.
63
-------
Associated Technologies: Activated sludge treatment, filtration,
incineration, land disposal.
Important Data Needs For Screening:
Data need
Purpose
Collection
method
Costs ($)
Gross organic
components (BOD,TOG)
Influent
temperature
Waste volume
Suitability for
treatment
Effect on
efficiency and
mic roorgani sms
Adequate treatment
capacity
Sampling and
analysis
Process
management
Site survey
processes
100/sample
Nominal
Variable
References; Ehrenfeld, 1983; Kosson, 1985.
64
-------
14.0 BIOLOGICAL TREATMENT
14.3 AERATED LAGOONS
Type of Control; Direct Waste Treatment (Aqueous Treatment)
Function; Used to aerobically break down hazardous organic wastes in lagoons
(surface impoundments) through microbial oxidation, and photosynthesis. This
technology is most efficient in removing alcohols, phenols, phthalates,
cyanides, and ammonia.
Description: Aerated lagoons break down aqueous organic wastes by aerobic
oxidation and hydrolysis as diagrammed in Figure 14.3. An aerated lagoon is
very much like a eutrophic lake. The lagoon is equipped with an aeration
device, or aeration may be provided by wind action and algae. The aerator
provides movement of the liquid to cause mixing with air. The oxygen supplied
by aeration is used by the microorganisms to oxidize organic matter to carbon
dioxide. Algae use carbon dioxide for photosynthesis which, in turn provides
more oxygen. Secondary clarification can be carried out in a lagoon by
physical and chemical means.
Nutrient Feed
, Mechanical Aerators
(optional)
Liquid Effluent
Secondary Clarifiers
(Concrete)
Excess Sludge
Figure 14.3. Aerated lagoon (surface impoundment),
Source: Ehrenfeld, 1983.
Factors effecting the removal efficiency of aerated lagoon systems include:
the type of organics present, type of aeration, detention time, depth, and BOD
levels. Lagoons can typically handle BOD levels of 200-500 mg/1; systems with
anaerobic digestion can handle somewhat higher levels. Performance of the
system is typically determined by BOD or COD removal efficiency, usually in
the range of 60-90 percent. Often, lagoons are used to polish low BOD
effluent from activated sludge or trickling filters before discharge.
Design Considerations: Design parameters for aerated lagoons are:
composition of wastes to be treated, volume of wastes to be treated, BOD
removal rate, detention time in the lagoon, surface area of the lagoon,
effluent limitations, local weather, and sludge generation rate to determine
the need for secondary clarification.
65
-------
Limitations: Some heavy metals and some organic compounds at concentrations
above a few ppm are toxic to microorganisms. If such toxic substances are
present in sufficiently high concentrations, pre-treatment processes may be
required to remove them. Impoundments are most efficient during warm weather;
cold weather or ice formation significantly reduce efficiency, and requiring
longer detention times. To reduce excess sludge generation, suspended solids
in the influent must be kept below 1.0 percent. There may be odor from
chemical volatilization.
Technology Status: Conventional, well demonstrated.
Associated Technologies: Pre-treatment pH adjustment, activated sludge,
trickling filters, sludge filtration, incineration, land disposal.
Important Data Needs for Screening:
Data need
Purpose
Collection
method
Costs ($)
Gross organic
components (BOD, TOG)
Specific organics
Dissolved heavy
metals
Temperature
Priority pollutant
analyses (organics,
metals, pesticides,
CN, phenols)
Waste volume
Waste strength for
treatment duration
Suitability for
treatment
Toxic impact
Feasibility
in climate
Suitability for
treatment, toxic
impact assessment
System capacity
Effluent requirements Design criteria
Sampling and
analysis
Organic
pollutant scan
Sampling and
analysis
Meterological
data
Sampling and
analysis
Varies with
waste stream
Regulatory
assessment
100/sample
1,500-2,000/
sample
900-1,200/
sample
Nominal
1,300-1,5007
sample
Variable
0-50,000
Variable
References; Ehrenfeld, 1983; Kosson, 1985.
66
-------
14.0 BIOLOGICAL TREATMENT
14.4 WASTE STABILIZATION PONDS
Type of Control: Direct Waste Treatment (Aqueous Treatment)
Function; Used to aerobically break down hazardous organic wastes in lagoons
(surface impoundments) through microbial oxidation, and photosynthesis. This
technology is most efficient in removing alcohols, phenols, phthalates,
cyanides, and ammonia.
Description; Stabilization lagoons break down aqueous organic wastes by
aerobic oxidation and hydrolysis of the wastes. The lagoon is not equipped
with an aeration device; mixing and aeration are provided by wind and algal
action. The oxygen supplied by mixing is used by the microorganisms to
oxidize organic matter to carbon dioxide. Algae use the carbon dioxide for
photosynthesis which, in turn provides more oxygen. This type of lagoon is
usually shallow, from 0.3 to 0.6 meters in depth. Secondary clarification
can be carried out in a lagoon by physical and chemical means or in a
secondary clarification unit as shown in Figure 14.4.
Nutrient Feed
Liquid Effluent
Secondary Clarifiers
(Concrete)
Excess Sludge
Figure 14.4. Stabilization lagoon (surface impoundment)
Source: Ehrenfeld, 1983.
Factors affecting the removal efficiency of lagoon systems include: the type
of organics present, type of aeration, detention time, depth, and BOD levels.
Lagoons can typically handle BOD levels of 200-500 mg/L; systems with
anaerobic digestion can handle somewhat higher levels. Performance of the
system is typically determined by BOD or COD removal efficiency, usually in
the range of 60-90 percent.
Design Considerations: Design parameters for stabilization lagoons are:
nature of the wastes to be treated, volume of wastes to be treated, BOD
removal rate, detention time in the lagoon, surface area of the lagoon,
effluent limitations, local weather, and sludge generation rate to determine
the need for secondary clarification.
67
-------
Limitations: Some heavy metals and some organic compounds at concentrations
above a few ppm are toxic to microorganisms. If such toxic substances are
present in sufficiently high concentrations, pre-treatment processes may be
required to remove them. Impoundments are most efficient during warm weather;
cold weather or ice formation will significantly reduce efficiency, requiring
longer detention times. To reduce excess sludge generation, suspended solids
in the influent must be kept below 1.0 percent. There may be odor from
chemical volatilization.
Technology Status; Conventional, well demonstrated.
Associated Technologies: Pre-treatment pH adjustment, activated sludge,
trickling filters, sludge filtration, incineration, land disposal.
Important Data Needs for Screening:
Data need
Purpose
Collection
method
Costs ($)
Gross organic
components
(BOD, TOG)
Specific organics
Dissolved heavy
metals
Temperature
Waste volume
Waste strength,
treatment duration
Suitability for
treatment
Toxic impact
Feasibility in
climate
Adequate treatment
volume
Effluent requirements Design criteria
Sampling and
analysis
Organic
pollutant scan
Sampling and
analysis
Meteorological
data
Capacities of
processes
producing wastes
Regulatory
assessment
100/
sample
1,500-2,000/
sample
900-1,200/
sample
Nominal
Variable
Variable
References; Ehrenfeld, 1983; Kosson, 1985.
68
-------
14.0 BIOLOGICAL TREATMENT
14.5 ROTATING BIOLOGICAL DISKS
Type of Control: Direct Waste Treatment (Aqueous Treatment)
Function: Rotating biological discs (RED) are used to aerobically break down
organic wastes in aqueous waste streams through the activity of
microorganisms. This technology is most efficient in removing alcohols,
phenols, phthalates, cyanides, and ammonia.
Description: RED processes facilitate aerobic oxidation and hydrolysis, and
separate wastes into a liquid effluent and a concentrated biomass sludge in a
secondary clarifier (Figure 14.5). Aqueous wastes are first subjected to
primary treatment, then pumped in a tank equipped with the RBD. A series of
discs, 2-3 meters in diameter, coated with a microbial film, rotate through
troughs containing effluent. About 40-50 percent of the disc area is immersed
in the effluent, while the remainder of the disc exposes the microbial film to
the atmosphere. The shearing motion of the disc through the effluent keeps
the biological floe from becoming too dense. Discs are usually arranged in
series in groups of four. The aerated sludge/waste mixture is transferred to
a secondary clarification unit.
Bio-SurfUnits
Primacy Treatment
Secondary Clarifw
Figure 14.5. Rotating biological disk system diagram.
Source: Ehrenfeld, 1983.
Factors effecting the removal efficiency of RBD systems include: the type and
concentration of organics present, waste volume, discrotational speed, media
surface area exposed and submerged, and pre- and post-treatment facilities.
Like other biological treatment units, RBDs are temperature sensitive and
removal efficiency falls with temperature. RBD systems, like activated sludge
units, are typically designed to remove between 85 to 90 percent of wastewater
BOD load.
Design Considerations: Design parameters for RBD treatment systems are:
organic and hydraulic loading, design of disc train(s), rotational velocity,
tank volume, media area submerged and exposed, detention time in the unit,
primary treatment and secondary clarifier capacity, and sludge production.
69
-------
Limitations: Some heavy metals and some organic compounds at concentrations
above a few ppm are toxic to microorganisms. If such toxic substances are
present in sufficiently high concentrations, pre-treatment processes may be
required to remove them. RED processes may have difficulty in removing highly
chlorinated organics, aliphatics, amines, and aromatic compounds.
Technology Status: Conventional, not demonstrated. Activated sludge
treatment plants have been used to treat leachate from hazardous waste
facilities. Since RED systems should be capable of treating the same types of
wastes as activated sludge or aerated impoundment systems, they should be able
to treat similar types of hazardous wastes.
Associated Technologies; Primary treatment, secondary clarification, sludge
filtration, incineration, land disposal.
Important Data Needs for Screening:
Data need
Purpose
Collection
method
Costs
Gross organic
components (BOD,TOG)
Priority pollutant
analyses (organics,
metals, pesticides,
CN, phenols)
Temperature
Waste volume
Waste strength,
treatment duration
Suitability for
treatment, toxic
impact assessment
Feasibility
in climate
System capacity
Effluent requirements Design criteria
Sampling and
analysis
Sampling and
analysis
Sampling and
analysis
Varies with
waste stream
or hydrogeological
investigation
Regulatory
assessment
100/sample
1,300-1,5007
sample
Nominal
Variable
0-50,000
Variable
References: Ehrenfeld, 1983; Kosson, 1985.
70
-------
14.0 BIOLOGICAL TREATMENT
14.6 LAND APPLICATION
Type of Control; JLn situ Treatment
Function: Direct application of biodegradable wastewater onto land for
microbial decomposition.
Description; Ground level application is conducted by pipe distributors,
under pressure, in which liquid wastewater discharges 15-30 cm above the
ground. There are currently four common modifications on the distribution
system: high and slow rate irrigation, overland flow, and rapid
infiltration. Figure 14.6 illustrates irrigation and over land flow. The
waste constituent separation and conversion occurs through filtration and
oxidation by physical, chemical or biological means. High/slow rate land
treatment irrigation is the application of wastewater to crops where effluent
percolation depth and vegetation are critical components. Overland flow
treatment consists of vegetated, sloped terraces and relatively impermeable
runoff ditches. After percolation, more than 50 percent of the applied
wastewater. is then returned for reuse or secondary treatment. Rapid
infiltration is the high rate application of wastewater to rapidly permeable
ground tables such as sand or loam where treatment occurs through the soil
matrix.
SPHAr O
SURFACE
APPLICATIOh
EVAPORATION
BRASS ADD VECEIATIVE LITTER
{_
AA A
A h J\ t
AA A
i A A A
A A A
SLOPE
VARIABLE
-SEEP
PERCOLATIOK
(a) IRRIGATION
RUNOFF
COLLECTION
(b) OVERUND FLOVf
Figure 14.6.
Land application techniques.
Source: Ehrenfeld, 1983.
Design Considerations; Prior to process selection or implementation, the
following factors must be determined: application techniques, preapplication
techniques, preapplication treatments, soil type and permeability, topography,
depth to ground water, wastewater characteristics, and climatic restrictions
such as number of days above freezing, annual rainfall, etc.
Limitations: Critical limitations of land application include siting (soil
characteristics, land use conflicts, etc.), and potential environmental
pollution (soil sealing, runoff, plant poisoning, etc.).
71
-------
Technology Status; Land application is a proven removal method for biological
oxygen demand, suspended solids, and nutrients.
Associated Technologies: Excavation and removal, revegetation, dikes and
berms, terraces and benches, ditches and diversions.
Important Data Needs for Screening:
Data need
Purpose
Collection
method
Costs ($)
Soil permeability
Soil type
Topography,
site area
site accessibility
Priority pollutant
analysis
pH of wastewater
Determine type of Triaxial
treatment permeater
Detemine crop cover,
harvesting and use,
if any
Selection of area
large enough for
installation
100
Sampling and sieve 150
analysis,
plasticity tests
Site inspection 150-250/
site survey; acre
area records
Determine toxicity to GC/MS/AAS
plants and food chain
Determine adequacy pH probe
for plants
(6.4-8.4)
1,100
Nominal
References; Overcash, 1981; U.S. EPA, 1977.
72
-------
14.0 BIOLOGICAL TREATMENT
14.7 BIORECLAMATION
Type of Control; _In situ Treatment
Function: Technique for treating zones of contamination by microbial
degradation.
Description: Two general types of bioreclamation systems include
injection/extraction wells and gravity flow (subsurface drains). A typical
injection and recovery system, illustrated in Figure 14.7, extracts ground
water downgradient of a contamination zone and reinjects it upgradient.
In situ aeration supplies oxygen directly while nutrients are added inline by
way of mixing tanks. Subsurface drains are limited to depths of 40 feet or
less under conditions of moderately low permeability. A typical collection
drain would be a lined trench, 10 feet deep by 4 feet wide, whose length would
encompass the hypothetical ground water plume. Construction would be in such
a manner that reinjected water flows out of the downgradient side of the well.
Nutrients c
in-line * i
Oxygen Source
^
In-situ j_
Aeration
v' //vy \j ™^^rv/^^fWf*r*ff/3rf-t:**/t*
Soil Flushing
Injection
Well
Groundwater
r*»
leaehate- Plume
^f^Kfrf^WVfiff'V^v^ffVt*t'if^^^^^jf^
Aeration
Well Bank
Aeration Zone
Direction of Groundwate'r Flow ^—N
Extraction Well
Figure 14.7. Treatment of contaminated ground water with the
bioreclamation technique.
Source: EPA, 1985b.
Design Considerations: Prior to implementation it is recommended that a
thorough site hydrogeological and geochemical investigation be conducted.
Data to be determined include size, flow rate, and chemical composition of the
contaminated plume. Other factors affecting microbial size and activity
include pH, temperature, soil permeability, and degree of water saturation.
73
-------
Limitations: The operating period will depend on the biodegradation rate and
potential of the contaminants and the amount of recycle. Under adverse
hydrogeological conditions of excessively long operating periods, other
aquifer restoration methods may be more appropriate.
Technology Status; Aerobic bioreclamation has been demonstrated to be
effective at more than 30 organic spill sites (U.S. EPA, October 1985).
Although not yet tested at hazardous waste sites, the method should prove
effective if the organics are amenable to biodegradation and aquifer hydraulic
conductivity is sufficiently high.
Associated Technologies: Excavation and removal, drainage structures,
injection/extraction wells and ground water pumping.
Important Data Needs for Screening:
Data need
Purpose
Collection
method
Costs ($)
Gross organic
components (BOD,TOG)
Priority analysis
Microbiology cell
enumerations
Waste strength
treatment duration
Identify refractory and
biodegradable
compounds, toxic
impac t
Determine existence of
dominant bacteria
BOD5 test;
TOG analyzer
Sampling and
analysis
Bacterial aerobic
heterotrophic
plate counts
50/sample
1,300-1,5007
sample
50/test
Temperature
Dissolved oxygen
pH
Nutrient analysis
NH3, N03, P04, etc.
Feasibility
in climate
Rate of reaction
Bacteria preference
Nutrient requirements
In situ
water quality
monitoring
D.O. meter
pH meter
Field test kits
Lab analysis
100/sample
point
10 /sample
10/sample
100/sample
References; U.S. EPA, 1985a; U.S. EPA, 1985b; Flatham, et al., 1986;
Pope Scientific, Inc. 1976.
-------
14.0 BIOLOGICAL TREATMENT
14.8 PERMEABLE TREATMENT BEDS
Type of Control: In situ Treatment
Function: Used to produce a nonhazardous soluble product or a solid
precipitate upon adequate contact between treatment agents and contaminated
ground water or leachate.
Description: As shown in Figure 14.8, permeable treatment beds are
essentially excavated trenches placed perpendicular to contaminated ground
water flow. The beds are filled with a reactive, permeable medium to behave
as an underground reactor. Currently, four types of reactive media can be
feasibly utilized in permeable beds, i.e., limestone or crushed shell,
activated carbon, glauconitic green sands, and synthetic ion exchange resins.
Limestone or crushed shell have been shown by a laboratory study (Artiola and
Fuller, 1979) to be effective in neutralizing acidic ground water and removing
heavy metals such as cadmium, iron and chromium. The effectiveness of
limestone as a barrier depends primarily on the pH and volume of the solution
passing through the limestone (Artiola and Fuller, 1979). Activated carbon
has the capability of removing nonpolar organic compounds, while glauconitic
green sands have the potential for the removal of 60 to 90 percent of many
heavy metals (e.g., copper, mercury, nickel, arsenic, cadmium). Zeolites and
synthetic ion exchange resins are also effective in removing heavy metals, but
short lifetimes and high costs make them unattractive.
Figure 14.8. Permeable treatment bed.
Source: EPA, 1982.
Design Considerations: In addition to plume characteristics, soil
permeability, waste characteristics (pH, volume of solution) and reaction rate
should be determined to select the proper reaction medium and bed design.
75
-------
Limitations; Permeable treatment beds are only applicable to relatively
shallow ground water tables since the trench must be constructed down to the
level of an impermeable strata. Also, due to short life (resulting from
saturation of bed materials, plugging of bed with precipitates and short life
of treatment materials), high cost, and reactivation difficulties, permeable
beds are feasible only on a temporary basis.
Technology Status: Permeable treatment beds are in the conceptual stage for
use at hazardous waste sites; many potential difficulties currently affect
implementation.
Associated Technologies; Excavation and removal ditches, channels or
trenches, land disposal.
Important Data Needs for Screening;
Data need
Purpose
Collection
method
Costs ($)
Depth to bedrock
Plume cross section
Define extent of bed Soil borings 50 ft.
Define extent of bed Ground water 50 ft.
sampling wells
Hazardous constituent Define reactive media Full pollutant scan 1,100
Hydraulic gradient
Soil permeability
Define bed residence Monitoring well, 50 ft.
time ground water
elevation
Define bed residence Triaxial 100/test
time permeater
References; U.S. EPA, 1985a; U.S. EPA, 1985b.
76
-------
15.0 CHEMICAL TREATMENT
15.1 NEUTRALIZATION
Type 'of Control: Direct Waste Treatment, Aqueous Treatment, _In situ Treatment
Function: Used to adjust basic or acidic wastewater to a neutral pH.
Description: Neutralization adjusts a waste stream to an acceptable pH level
for discharge (usually between pH 6.0 and pH 9.0). Neutralization may also be
used as a pre- or post-treatment step with other treatment processes. The
adjustment of pH is done by adding alkaline wastes or chemical reagents to
acidic streams^and vice versa. Figure 15.1 shows a three-stage neutralization
system schematic including initial neutralization, equalization and final
adjustment. The system consists of a multiple compartment, concrete basin,
lined or coated with a corrosive-resistant material (e.g., acid brick).
Mixers installed in each compartment provide adequate contact between the
waste and neutralizing agents, which increases reaction times. In the first
stage, the neutralizing agent is added to the waste. Equalization takes place
during the second stage where further mixing occurs, allowing time for the
neutralization reactions to stabilize. In the final stage, additional
neutralizing agent may be added to insure that the pH of the waste stream is
properly adjusted. In situ neutralization techniques involve injecting dilute
acids_or bases into the ground water (see Section 15.8 - Solution Mining) to
optimize pH for further treatment (e.g., biodegradation, oxidation,
reduction), or to neutralize basic or acidic plumes that do not require
further treatment.
NEUTRALIZING CHEMICAL
LK,
-INCOMING WATER
pH MEIER CONTROLLER >
STAKE 1:
IN [TIA1,
NEUTRALI-
ZATION
STAGE 2:
EQUALI-
ZATION
STACK :<
FINAL
ADJUST-
MKHT
NEUTBALIZ
FUD
X.
J^
\
\
(
^^
1
^>
t
(
^~
\
s
NEUTRALIZED WAI
Figure 15.1.
Flow diagram for neutralization process.
Source: U.S. EPA.
77
-------
Design Considerations: The factors to be considered when choosing the most
suitable reagent include: purchase cost, neutralization capacity, reaction
rate, storage and feeding requirements, and neutralization products. The most
common acidic reagents are sulfuric acid and hydrochloric acid. The most
common alkaline reagents are various limes and sodium hydroxide. Reagents
used in neutralization of untreated wastes may be quite corrosive, it is
important to select compatible plant construction materials.
Limitations: Hazardous air emissions can be produced from the neutralization
of certain hazardous waste streams (e.g., wastes containing sulfide salts).
Feed tanks should be totally enclosed to prevent the release of acid fumes.
Technology Status; Conventional, demonstrated.
Associated Technologies: Carbon adsorption, ion exchange, air stripping,
oxidation, reduction.
Important Data Needs For Screening:
Data need
Purpose
Collection
method
Costs ($)
Expected average,
variations in daily
wastewater flow rate
Wastewater acidity
or alkalinity
pH of wastewater
Volume of waste to be
neutralized; system
size requirements
Reagent requirements
Reagent requirements
H model
Sampling and
analysis, GC/MS
Sampling and
analysis
400
900-1,000
(10 or more
samples)
10/sample
References: Ehrenfeld and Bass, 1984; U.S. EPA, 1980.
78
-------
15.0 CHEMICAL TREATMENT
15.2 PRECIPITATION
Type of Control: Direct Waste Treatment, Agueous Treatment, In situ Treatment
Function: A physiochemical process in which some or all of a substance is
removed from wastewater by conversion to an insoluble (solid) form.
Description: Precipitation is a treatment technique used for removal of heavy
metals including zinc, cadmium, chromium, copper, lead, manganese, mercury,
phosphate, sulfate, and fluoride. It involves alteration of the ionic
equilibrium to produce insoluble precipitates that can easily be removed by
sedimentation or filtration. Removal of metals as hydroxides or sulfides is
the most common precipitation application in wastewater treatment. Generally,
lime or sodium sulfide is added to the wastewater in a rapid mixing tank, along
with flocculating agents. As depicted in Figure 15.2, the precipitation
initiation step is typically followed by flocculation and sedimentation or
filtratipn. Flocculation describes techniques whereby precipitate particles
become agglomerated. Sedimentation is used to separate the liquid and solid
phases via settling in a basin (for further descriptions of these associated
technologies see Section 16.2- Flocculation, Section 16.3 - Sedimentation, and
Section 16.13 - Filtration).
FLOCCULATION
PRECIPITATING CHEMICALS—,
FLOCCULATING AGENTS
INLET LIQUID STREAM
SEDIMENTATION
OUTLET LIQUID
STREAM
Figure 15.2.
Precipitation process.
Source: EPA, 1985.
Design Considerations: Precipitation treatment can either be a batch or
continuous operation. A mixing tank is sized based on wastewater flow and
precipitation chemical/wastewater contact time required. Flocculation tank.
sizes are based on flow and retention time. Sedimentation tank size is based
on laboratory experiments to determine the settling rate. The solubility of
metal hydroxides and sulfides is greatly affected by pH, therefore, proper
control of pH is essential for favorable performance of precipitation techno-
logies. Neutralization techniques can be used to aid in the control of pH..
Limitations: Precipitation is inhibited by the presence of organic
constituents that form organometallic complexes with metals. Cyanide may also
complex with metals, reducing the efficiency of the precipitation process.
Variable flow rates, pH, and metal concentrations can make precipitation
reactions difficult to control.
79
-------
Technology Status; Conventional, demonstrated.
Associated Technologies; Neutralization, flocculation, sedimentation,
filtration.
Important Data Needs For Screening:
Data need
Purpose
Collection
method
Costs ($)
Variations in daily
wastewater flow rate
Implementability;
precipitation is
inefficient with
highly variable
flow rates
Flow monitoring;
stream guaging
Variable
Wastewater
characteristics
pH of wastewater
Settling rate
Reagent requirements,
precipitable consti-
tuents, interfering
species, sludge
production rate
Reagent requirement
and reaction success
Sedimentation tank
size
Sampling and
analysis,
GC/MS
Sampling and
analysis
Lab. analysis,
Imhoff cone test
900-1,000
(10 or more
samples)
10/sample
Variable
References; U.S. EPA, 1985; Ehrenfeld and Bass, 1984; U.S. EPA, 1980.
80
-------
15.0 CHEMICAL TREATMENT
15.3 OXIDATION (CHLORINATION)
Type of Control; Direct Waste Treatment, Aqueous Treatment, In situ Treatment
Function; Uses chlorine in wastewater treatment to oxidize cyanides to
cyanates and ultimately to carbon dioxide and nitrogen.
Description; Chlorine as elemental or hypochorite salt is a strong oxidizing
agent in an aqueous solution. Chlorination of alkaline cyanide-containing
wastes involves a two-stage process to remove cyanide. In the first stage,
cyanide is oxidized to the less toxic cyanate ion. During the second stage,
cyanates are oxidized to nontoxic bicarbonates and nitrogen. Figure 15.3
presents a two stage reactor, a configuration often used to minimize size or
retention time by optimizing the reaction stages through pH control. During
both stages, caustic and chlorine are added to act as the oxidizing agent.
Caustic Chlorine Caustic Chlorine
Wastewater
orme Caustic Chlor
pH -\-9-11
Mixer
pH -v 8.5
Mixer
Cyanide
Free Wastewater
Stage 1
Stage 2
Figure 15.3.
Two-stage chlorination reactor.
Source: Ehrenfeld and Bass, 1984.
Design Considerations: Requirements include vessels with agitators, storage
vessels, and chemical metering equipment. Some instrumentation is required to
determine pH and degree of completion of the oxidation reaction. The pH must
be closely monitored to avoid development of acid conditions. Reagents must
also be added in small amounts to avoid violent reactions.
Limitations; Excess chlorine may react with other constituents in the
wastewater to form hazardous compounds. Another limitation is the potential
hazard of storing and handling chlorine gas.
81
-------
Technology Status; Conventional, demonstrated.
Associated Technologies: Ultraviolet/ozonation, oxidation.
Important Data Needs for Screening:
Data need
Collection
Purpose method
Costs ($)
Variations in daily
wastewater flow rate
Variations in
contaminant
concentrations
Climate
pH
Volume of water
to be oxidized
Reagent requirements
to minimize formation
of other hazardous
compounds
Adequate temp, for
reaction to proceed
Suitable pH necessary
for reaction to
proceed
Flow monitoring,
stream gauging
Sampling and
analysis,
GC/MS
National Climatic
Center (NCC),
Local weather
bureau
Sampling and
analysis
Variable
900-1,000
(10 or more
samples)
10-20
10/sample
References: Ehrenfeld and Bass, 1984; GCA, 1985.
lion
82
-------
15.0 CHEMICAL TREATMENT
15.4 HYDROLYSIS
Type of Control: Direct Waste Treatment, Aqueous Waste Treatment, In situ
Treatment
Function; JEn situ degradation on amines, carbonates, alkyl halides, sulfuric
arid sulfonic acid esters, phosporic and phosponic acid esters, nitriles, and
pesticides typically via acid- or base-catalyzed reactions.
Description: Hydrolysis involves the displacement of a functional group on an
organic molecule with a hydroxyl group from water. The reaction can be
represented as follows:
RX
H20
ROH + HX
where R is the organic group, and X is the leaving group. Hydrolysis of
organic compounds can result from a neutral reaction with water, or it can be
catalyzed in the presence of an acid or a base. An alkali can also function
as a stoichiometric reactant. A typical hydrolysis unit appears in
Figure 15.4.
Clean Ale
To Exhaust
Settling Tank
Air Pump
Figure 15.4. Hydrolysis unit.
Source: Kiang and Metry, 1982.
Design Considerations: Performance characteristics will be specific at each
site. Factors which affect performance are temperature, pH, the homogeneity
of the waste mixture, the availability of the waste constituents to react with
the detoxifying agent, and the ability to mix waste and the detoxifying
agent. Mixing is achieved by utilizing stirrers for surface impoundments or
ultivators for landfills.
Limitations: The waste to be treated should be isolated from waste which is
not compatible with the treatment reagent to prevent the formation of toxic
byproducts. Environmental conditions of concern include pH and water
temperature. Another limitation is the need for numerous, closely spaced
injection wells, even in coarse-grained deposits.
83
-------
Technology Status: Developmental. The basic methods using hydrolysis to
treat hazardous waste have been developed and applied in an industrial
setting. However, application at uncontrolled sites has been limited.
Associated Technologies: Neutralization.
Important Data Needs For Screening:
Data need
Purpose
Collection
method
Costs U)
Wastewater average
and variable flow
rates
Wastewater
analysis
Soil permeability
Soil type
Geohydrologic
site survey
pH of wastewater
Climate
Volume of water
to be treated
Constituents appli-
cable to technology,
reaction rate
Permeable soils
best
Clay soils difficult
to decontaminate
Establish potential
for constituent
contamination and
well placement sites
Reagent requirements
Determine suitable
and and water
temperature
H model
Sampling and
analysis,
GC/MS
Triaxial
permeater
Sampling and
sieve analysis,
plasticity test,
proctor compaction
Site survey
Sampling and
analysis
National Climatic
Center (NCC),
Local weather
bureau
250/day
900-1,000/
10 samples
50/test
50/test
Variable,
5,000-50,000
50/test
50/test
References:
EPA, 1974; EPA, 1983; EPA, 1985; EPA, 1985; EPA (Treatability
Manual Vol. Ill), 1981; GCA , 1986; (Hazardous Waste Processing
Technology) Kiang and Metry, 1982.
84
-------
15.0 CHEMICAL TREATMENT
15.5 REDUCTION
Type of Control; Direct Waste Treatment, Aqueous Treatment, In situ Treatment
Function: Lowers the oxidation state of metals (primarily hexavalent
chromium, mercury, and lead) to reduce toxicity or solubility, or to transform
waste 'to a form which can be easily handled.
Description; Reduction is accomplished by addition of a reducing agent, which
lowers the oxidation state of a substance. Base metals such as iron,
aluminum, zinc, and sodium compounds, are commonly used as reducing agents.
Sulfur compounds may also serve as effective reducing agents. A flow diagram
for a typical reduction process is presented in Figure 15.5. Initially, the
pH of the waste is adjusted to an appropriate level for efficient reduction to
occur (e.g., pH 2 to 3 for sulfur dioxide treatment of chromium). Following
pH adjustment, the reducing agent is added. The solution is then mixed to
provide adequate contact between the reducing agent and the waste. Upon
completion of the reduction reaction, the reduced solution is typically
subjected to additional treatment to settle or precipitate the reducing
agent. Filtration may be used to improve separation. The effluent stream is
typically acidic and must be neutralized prior to discharge
Acid Reducing Agent
Wastewatsr
pH = 2-3
Reduced
Figure 15.5.
Reduction process schematic.
Source: Ehrenfeld and Bass, 1984.
Design Considerations; Reduction can be performed using simple, readily
available equipment and reagents. Equipment requirements include: storage
vessels for the reducing agents and wastes, metering equipment for both
stream's (flow control), contact vessels with agitators to provide suitable
contact of reducing agent and waste, and monitoring instrumentation (i.e., pH
meter, and oxidation-reduction potential electrode). Laboratory and
pilot-scale tests should be performed for complex waste streams containing
other potentially reducible compounds in order to determine appropriate feed
rates and reactor retention times.
85
-------
Limitations: Currently, there are not any practical methods for the reduction
of organic wastes; reduction treatment methods are generally limited to
metals. Another problem is the potential for introducing additional hazardous
ions into the solution. Wastes containing high concentrations of contaminants
may make reduction a cost-prohibitive option.
Technology Status: Conventional and demonstrated for industrial
applications. However, in situ application at uncontrolled hazardous waste
sites has been limited.
Associated Technologies; Oxidation, neutralization, precipitation.
Important Data Needs For Screening:
Data need
Purpose
Collection
method
Costs ($)
Variations in daily
wastewater flow rate
Wastewater analysis
for contaminants
pH of wastewater
Volume of water to
be treated
Reagent requirements
Reagent requirement
reaction success
Flow monitoring,
stream gauging
Sampling and
analysis,
GC/MS
Sampling and
analysis
Variable
900-1,000
(10 or more
samples)
10/sample
References: U.S. EPA, 1985, U.S. EPA, 1980; Ehrenfeld and Bass, 1984.
13GB
•":sw
.W ™ 0
86
-------
15.0 CHEMICAL TREATMENT
15.6 CHEMICAL DECHLORINATION
Type of Control: Direct Waste Treatment, Aqueous Waste Treatment, In situ
Treatment
Function; Uses chemical reagents to break apart chlorinated molecules, or
rearrange their structure, to form less hazardous compounds.
Description: Dechlorination techniques have been developed for the treatment
of oils and liquid wastes. Conventional techniques involve filtering the
liquid waste, and then transferring it to a reactor tank. In the reactor
tank, a reagent (usually a sodium reagent) is mixed with the waste. Following
dechlorination of the waste, the mixture is usually centrifuged and filtered.
Effluent streams typically consist of the treated material, a salt (e.g.,
sodium chloride), a polyphenyl and/or a hydroxide (e.g., sodium hydroxide).
Processes for in situ treatment of soils and solids are under development.
These processes generally involve adding a sodium reagent to the waste. The
reaction of the waste with the reagent results in the formation of a solid
polymer, which is subsequently filtered out as shown in Figure 15.6. A
variation of this technique involves excavating the contaminated soil,
extracting the contaminant from the soil with a solvent, and dechlorinating
the resulting extract.
DRUM PUMP
RESERVOIR VALVE
VENT
r
*-~ -— —
^> < <
-------
Limitations; Most of the dechlorination techniques have been developed for
PCB-containing wastes. Some testing has been performed on dioxin-containing
wasteSj with promising results. Although dechlorination techniques could
potentially be used for other chlorinated compounds, their use has been
limited.
Technology Status: Chemical dechlorination of aqueous wastes has been
demonstrated. In situ applications are in the developmental stage.
Associated Technologies: Oxidation, reduction, neutralization.
Important Data Needs for Screening;
Data need
Purpose
Collection
method
Cost ($)
Wastewater average
and variations of
daily flow rate
Wastewater and
soil analysis
Soil type
Volume of water to
be processed
Reagent
requirements;
implementability
Not as effective
in clayey soils
Help model
Sampling and
analysis;
GC/MS
Plasticity
tests; sieve
analysis
400
900-1,0007
(10 samples)
50/Test
Hydrogeo logic
site survey
Site area/
extent of
contamination
Establish potential
for migration
Feasibility and
cost-effectiveness
of implementation
Existing
records and
surveys; site
survey
Site invest;
sampling and
analysis
Minimal for
existing
information
100,000
for full
survey and
invest. ;
900-1, OOO/
10 samples
References; GCA, 1985a; Berry, 1981; Peterson, 1986.
88
-------
15.0 CHEMICAL TREATMENT
15.7 ULTRAVIOLET/OZONATION
Type of Control: Aqueous Treatment
Function: Uses simultaneous application of ultraviolet light and ozone for
the oxidation of chlorinated hydrocarbons, chlorinated aroraatics, pesticides,
and phenolic compounds.
Description: Ultraviolet (UV) radiation is electromagnetic radiation having a
wave length shorter than visible, but longer than x-ray radiation. UV
radiation causes rearrangements of molecular structures such that new chemical
compounds result. Ozone (03) is an unstable, highly reactive oxidizing
agent. Ultraviolet-activated ozone has been shown to be successful in the
degradation of certain organics.
Conventional UV ozonolysis techniques utilize a liquid-phase reaction. Ozone
gas is bubbled into liquid waste or a liquid solution containing the
contaminant. The mixture is then exposed to UV radiation in a mixing tank.
The UV radiation not only degrades the contaminant directly, but also causes
the ozone to be split into free oxygen, which further oxidizes the contaminant.
Design Consideration; Some key design parameters include: ozone dose rate,
ultraviolet light dosage, and retention time. Ozone dosage is expressed as
either ppm or pounds of ozone/pound of contaminants. Retention times range
from 10 minutes to 1-hour, and ultraviolet light dosages range from 1 to
10 watts/liter.
Limitations: UV/ozonation is generally restricted to wastewaters with a
1 percent or lower concentration of hazardous contaminants. In addition,
since ozone is a non-selective oxidant, the waste stream should contain
primarily the compound of concern. If other oxidizable compounds are present,
they will exert an additional demand for ozone. Since supplying ozone at a
sufficiently fast rate can be difficult when treating concentrated wastes,
this treatment method is not generally used for wastes which contain high
levels of hazardous components. The waste to be treated should also be
relatively free of suspended solids. A high concentration of suspended solids
can impede the passage of ultraviolet radiation, and the waste treatment
efficiency will be adversely affected.
89
-------
Technology Status; Conventional, undemonstrated
Associated Technologies: Oxidation.
Important Data Needs for Screening:
Data need
Purpose
Collection
method
Costs
Expected average,
variations in daily
wastewater flow rate
Concentration of
oxidizable organics
Climate
pH
System capacity
Determine reagent
requirements;
Adequate temperature
for reaction to
proceed
Suitable pH necessary
for reaction to
proceed
Volume of flow
rate measurement
Sampling and
analysis,
GC/MS
National Climatic
Center (NCC),
Local weather
bureau
Sampling and
analysis
Variable
(0-10,000)
900-1,000
(10 or more
samples)
Nominal
Nomina1
References; GCA, 1985; Ehrenfeld and Bass, 1984; GCA, 1984.
90
-------
15.0 CHE MI CAT, TREATMENT
15.8 SOLUTION MINING (EXTRACTION)
Type of Control: Direct Waste Treatment, Aqueous Waste Treatment
Function: Removes and/or treats hazardous waste constituents by application
of a solvent to a waste solid or sludge, and collection of the leachate at
well points.
Description; As diagrammed in Figure 15.8, water or an aqueous solution is
injected through an injection well point into the area of contamination.
Sorbed contaminants are mobilized into solution via solubility, formation of
an emulsion, or a chemical reaction with the flushing solution. The resulting
leachate is pumped to the surface for removal, recirculation, or onsite
treatment and re injection. Typical flushing solutions include water, dilute
acid solutions, and/or complexing and chelating agents. Water is generally
used to flush water-soluble or water-mobile organics. Solubilities and
octanol/water partition coefficients (which can be used to estimate water
solubilities), are available for a number of compounds in Lyman, et al., 1982;
and CRC, 1986.
Dilute acid solutions (e.g., sulfuric, hydrochloric, nitric, phosphoric, and
carbonic acid) are widely used in industrial treatment/recovery processes to
extract metal ions by dissolving basic metal salts (e.g., hydroxides, oxides,
carbonates). For in situ treatment, weak acids (e.g., dihydrogen phosphate,
acetic acid) should be used because of the toxicity of many of the stronger
acids. Stronger dilute acid solutions (i.e., sulfuric acid) may be used if
the soil or leachate is sufficiently alkaline to neutralize it. Acid
solutions can be used to flush basic organic contaminants such as amines,
ethers, and anilines.
Complexing and chelating agents, such as citric acid, EDTA, and DTPA, may be
used to remove heavy metals. For metals which are strongly adsorbed to
manganese and/or iron oxides, reducing agents can be used to release the heavy
metal into solution. Chelating agents or acids can then be used to retain the
metals in solution. Examples of these types of treatment combinations include:
hydroxylamine with a dilute acid solution, and sodium dithionite/citrate.
Surfactants can improve the effectiveness of solution mining techniques by
enhancing the solubilities of aqueous solutions, and creating more effective
transport. Various surfactants and their specific uses are presented in U.S.
EPA, 1985.
WITHDRAWAL WELL
Figure 15.8.
Solution mining using injection/withdrawal wells (cross-section).
Source: EPA, 1985.
91
-------
Design Considerations: Injection and withdrawal wells must be designed and
placed such that contamination of surrounding ground water with extracting
solvents and extracted material is prevented.
Limitations; Solution mining is not suitable for treating soils and leachate
which are contaminated at low levels, or which are contaminated with complex
waste mixtures. Additionally, it is generally not practical to treat large
volumes of contaminated solids by this method.
Technology Status; This technology has been used extensively by the chemical
processing and mining industries. However, its use for in situ treatment of
hazardous waste is very limited. EPA has developed a mobile soils flushing
system which has been tested on PCB-contatninated and dioxin-contaminated
soils. A more complete description of this mobile system and the results of
pilot tests can be found in U.S. EPA, 1983.
Associated Technologies: Precipitation.
Important Data Needs for Screening:
Data need
Purpose
Collection
method
Costs ($)
Wastewater volume and
aquifer response
characteristics
Waste analysis
(volatile and semi-
volatile organics)
Soil organic content
Soil permeability
Soil type
Volume of water for
treatment, feasibility
of pumping/extraction
Extraction efficiency
of various solvents;
presence of consti-
tuents which are in-
compatible with solvent
Adsorption potential
of soil
Permeable soils
best
Clay soils are
more difficult
to contaminate
Hydrogeologic
modeling
Sampling and
analysis,
GC/MS
Variable
(10,000-10,000)
1,200/sample
Sampling and
TOG analysis
Triaxial
permeameter
Sampling and
sieve analysis;
plasticity test;
proctor
compaction
50/sample
50/test
50/test
References: EPA, 1983; EPA, 1985a; EPA, 1985b; EPA, 1985c; EPA, 1981; GCA,
1986; Kiang-Metry, 1982; GCA, 1985; Ehrenfeld and Bass, 1984.
92
-------
1
16.0 PHYSICAL TREATMENT
16.1 FLOCCULATION
Type of Control:
and Treatment
Direct Waste Treatment (Aqueous Treatment), Solids Handling
Function: Agglomerates fine suspended particles in an aqueous waste stream to
larger, more settleable particles prior to sedimentation or other treatment;
used primarily for the precipitation of inorganics (i.e., removal of metals as
hydroxides or sulfides).
Description; Flocculation is a process which uses chemical and physical means
to agglomerate small, unsettleable suspended particles into larger, more
settleable particles. Initially, a flocculating agent is added to the waste
stream. This step is followed immediately by rapid mixing to disperse the
flocculating agent. The flocculating agent chemically induces destabilization
of the repelling forces between the particles. After this step, the waste
stream is mixed more slowly to allow for contact between the small particles.
The non-repelling particles agglomerate into large, more settleable particles.
Following flocculation, the agglomerated particles are usually removed from
the liquid by sedimentation (see Section 16.2) or subjected to further
treatment (Figure 16.1).
FLOCCULATION
SEDIMENTATION,
Fig'ure 16.1.
Typical flocculation system.
Source: U.S. EPA, 1985b.
Design Considerations: The flocculation process can be easily integrated into
more complex treatment systems, and uses readily available and easily operated
equipment (i.e., chemical pumps, metering devices, and mixing and settling
tanks). Selection of the proper flocculating agent should be made on the
basis of laboratory tests. Several types of flocculating agents may be used,
including: alum, lime, iron salts, (ferric chloride, consisting of
1-ong-chain, water-soluble polymers such as polyacrylamides).
Limitations: Flocculation is not suitable for highly viscous waste streams,
which tend to inhibit settling of solids. The performance and reliability of
flocculation is significantly reduced for wastes with highly variable flow
rates, composition, and pH.
93
-------
Technology Status: Conventional, demonstrated.
Associated Technologies: Precipitation, sedimentation, filtration, dissolved
air flotation.
Important Data Needs for Screening:
Data need
pH of waste
Viscosity of
waste stream
Sludge flocculation,
settling, and dewater-
Purpose
Selection of
flocculating agent
Affects settling of
agglomerated solids;
high viscosity not
suitable
Selection of
flocculating agent
Collection
method
pH analysis
Viscosity
Laboratory
scale tests
Costs ($)
50/test
50/test
300
ing characteristics
Leachate
variability
Not suitable for
wastes with highly
variable pH, flow,
and composition
Laboratory
tests; sampling
and analysis
100/sample
References; Ehrenfeld and Bass, 1984; JRB, 1984; Sundstrom and Klei, 1979;
U.S. EPA, 1980a; U.S. EPA, 1985b.
94
-------
16.0 PHYSICAL TREATMENT
16.2 SEDIMENTATION
Type of Control: Direct Waste Treatment (Aqueous Treatment), Solids Handling
and Treatment
Function; Removes suspended solids from an aqueous waste stream.
Description; Sedimentation occurs by using gravitational forces to allow
suspended solids in an aqueous solution to settle. The apparatus used for
sedimentation includes a basin to maintain the aqueous waste to be treated in
acquiescent state, a means of directing the aqueous waste to the basin that is
able to maintain a relatively quiescent state, and a means of physically
separating the liquid and the settled particles (i.e., either removing the
settled particles, or removing the liquid). The sedimentation system can be
designed as either a batch or a continuous process. The settling vessel can
be a lined surface impoundment, a conventional settling basin, or a clarifier
(usually circular). Figure 16.2 diagrams these design configurations.
Sedimentation basins and clarifiers are typically designed with built-in
solids removal devices such as a sludge scraper and/or a sludge draw-off
mechanism.
Overflow Discharge Weir
Accumulated Settled Panicles
Periodically Removed by Machinical Shovel
Circular Clarifier
Settling Zone
Revolving Collection
Mechanism
Circular Baffle
Annular Overflow Weir
Ouuet Liquid
Settling Panicles
Sealed Panicles ! Collected and Periodically Removed
| Sludge Drawoff
Sedimentation Basin
Inlet Zone -\
Inlet Liquid
Settled Particles Collected
and Periodically Removed
Baffles to Maintain
'"Quiescent Conditions
.^Settling Panicles Trajecti
Belt-Type Solids Collection Mechanism
Figure 16.2. Representative types of sedimentation.
Source: U.S. EPA, 1985b.
Design Considerations: Important considerations in the design of a
sedimentation system include: the ability to contain surges in flow, and
allowing time for settling. Baffles are often installed to maintain quiescent
conditions and to prevent reentrainment of settling particles. Particle
removal is dependent upon basin depth, detention time, flow rate, surface
area, and particle size.
95
-------
Limitations: Sedimentation is limited to the removal of suspended solids
which are heavier than water (i.e., specific gravity >1). This technique is
not suitable for wastes containing emulsified oils. The solids and/or liquids
resulting from sedimentation generally require further treatment.
Sedimentation is frequently used as a pretreatment step for many chemical
processes (e.g., carbon adsorption, filtration).
Technology Status: Conventional, demonstrated.
Associated Technologies: Precipitation, flocculation, biological treatment,
carbon adsorption, ion exchange, air or steam stripping, reverse osmosis,
filtration, and dredging.
Important Data Needs for Screening:
Data need
Purpose
Collection
method
Costs
Viscosity of
aqueous waste
Oil and grease
content of
waste stream
High viscosity hinders
sedimentation
Not applicable to
wastes containing
emulsified oils
Viscosity
analysis
Oil and grease
analysis
50/test
50/test
Specific gravity
suspended solids
Performance tests
Must be > 1 for
sedimentation to occur
To predict performance
for flocculating
particles
Density analysis, 50/test
or observation
Laboratory-scale 300
settling tests
References; Ehrenfeld and Bass, 1984; JRB, 1984; Sundstrom and Klei, 1979;
U.S. EPA, 1985b.
-------
16.0 PHYSICAL TREATMENT
16.3 CARBON ADSORPTION/ACTIVATED CARBON
Type of Control; Direct Waste Treatment (Aqueous Treatment), Gaseous Waste
Treatment
Function; Used to remove dissolved organic compounds from contaminated ground
water; effectively treated compounds include chlorinated pesticides, phenols,
aliphatic chlorinated hydrocarbons, and aromatics (such as benzene, toluene,
and xylene); effective and reliable means of removing low-solubility organics
over a broad concentration range.
Description: Carbon adsorption can be designed for either column or batch
applications, but ground water treatment is usually performed with columns.
In column applications, adsorption involves the passage of contaminated water
through a bed of activated carbon which selectively adsorbs the hazardous
constituent (adsorbate) onto the carbon (adsorbent). When the activated
carbon has been utilized to its maximum adsorptive capacity (exhaustion
"spent"), it is then removed for disposal, destruction, or regeneration.
Design Considerations; Design factors affecting removal efficiencies
include: carbon exhaustion (usage) rate, contact time, hydraulic loading
rate, and column size. Adsorption efficiencies are affected by both the
characteristics of the hazardous constituent and the characteristics of the
aqueous waste streams in which they are contained. Characteristics of the
hazardous constituent which affect adsorption include polarity, molecular
weight, solubility, and molecular structure. In general, non-polar, high
molecular weight organics with limited solubility are preferentially
adsorbed. Structurally, branched-chain compounds are more readily adsorbable
than straight-chain compounds. Characteristics of the aqueous stream which
affect adsorption efficiency include: pH, temperature, suspended solids
concentration, and oil and grease concentration. Generally, the compound will
adsorb at the pH which imparts the least polarity to the molecule. Adsorption
is an exothermic process, and therefore increased adsorption will occur as
temperatures increase.
Limitations: To prevent clogging, it is necessary that the suspended solids
concentration of the aqueous stream be less than 50 ppm, and the oil and
grease concentration should be less than 10 ppm. Often, pretreatment
techniques (e.g., granular filtration or sedimentation) are used in
conjunction with carbon adsorption.
Technology Status; Conventional, demonstrated.
Associated Technologies; (Granular) filtration, reverse osmosis,
sedimentation, biological treatment, air stripping.
97
-------
Important Data Needs for Screening:
Data need
Purpose
Collection
method
Costs ($)
Biological
organisms
in leachate
Leachate TSS
concentration
Leachate oil
and grease
concentration
Leachate
components, and
characteristics
Can aid in treatment
through biodegrada-
tion, or can hinder
operation via clogging
or odor generation
Should not exceed
50 ppm; may need
pretreatment
Should not exceed
10 ppm; may need
pretreatment
Treatability via
carbon adsorption
Sampling and 100/sample
analysis
TSS analysis
Oil and grease
analysis
GC/MS
analysis;
CRC Handbook
of Chemistry
and Physics
50/test
50/test
approximately
100/sample
References:
Ehrenfeld and Bass, 1984; GCA, 1985a; JRB, 1984; Kaufman, 1982;
Lyman, 1980; Troxler, et al., 1983; Sundstrom and Klei, 1979;
U.S. EPA, 1980a; U.S. EPA, 1985b.
98
-------
16.0 PHYSICAL TREATMENT
16.4 ION EXCHANGE
Type of Control: Direct Waste Treatment (Aqueous Treatment)
Function; Used to remove cationic and anionic metallic elements, halides,
cyanides, nitrates, carboxylics, sulfonics, and some phenols.
Description: Ion exchange is a reversible process in which an interchange of
ions occurs between a solution and an essentially insoluble solid in contact
with the solution. Toxic ions are removed from the aqueous phase by being
exchanged with the relatively non-toxic ions held by the ion exchange
material. The exchange material can consist of natural clays or zeolites; or
synthetic resins are more commonly used. The extent to which removal of
anions and/or cations occurs depends on the nature and volume of the ion, the
type of resin and its saturation, and the ion in the contaminated aqueous
solution. Ions with a higher charge will form more stable salts with the
exchanger than those with a lower charge; thus allowing for selective removal
of polyvalent species from a solution of monovalent species.
The ion exchange process may be operated using a batch or continuous
technique. In a batch process, the ion exchange resin is stirred with the
waste until the reaction is complete. The spent resin is removed by settling
and is subsequently regenerated and reused. In a continuous process, the
exchange material is placed in a bed or packed column, and the waste is passed
through it. As diagrammed in Figure 16.4, various modes of operation are
possible with the continuous technique, including: concurrent fixed bed,
countercurrent fixed bed, and countercurrent continuous. Often, exchange
columns are used in a series.
Cotmlercurronl Fined Bed
HtGtNfcHAltON
Continuous Counlercuitent
HLGfNERAIION
Figure 16.4.
Ion exchange systems.
Source: U.S. EPA, 1985b.
Design Considerations: Important factors to consider in the design of an ion
exchange system include: selection of appropriate resin to remove
contaminants of concern, optimization of column flow-through rates, and
determination of required regeneration rate. Laboratory scale experiments are
generally performed to aid in the selection of the proper design parameters.
99
-------
Limitations; Ion exchange is not suitable for removal of high concentrations
of exchangeable ions (above 2,500 mg/L) because the resin material is rapidly
exhausted during the exchange process and costs for regeneration become
prohibitively high. Pretreatment of the wastewater is often necessary to
remove any constituents which would adversely affect the resin. Certain
organics (e.g., aromatics) become irreversibly sorbed by the resin. Oxidants
(such as chromic or nitric acid) can also damage the resin.
Technology Status; Conventional, demonstrated.
Associated Technologies: Filtration, carbon adsorption, air stripping,
sedimentation.
Important Data Needs for Screening;
Data need
Purpose
Collection
method
Costs ($)
Leachate
characteristics
TDS concentration
Resin selection
TDS should be
2,500 mg/1 for
efficient operation
TSS concentration Suspended solids
clog resin
Treatability
study
Flow through rate
and resin regenera-
tion frequency
Sampling and
analysis
TDS
TSS analysis
Laboratory
scale trial
100/sample
50/test
50/test
300
References; Ehrenfeld and Bass, 1984; GCA, 1984; GCA, 1985a; JRB, 1984;
Skoog and West, 1979; Sundstrora and Klei, 1979; U.S. EPA,
1980a; U.S. EPA, 1985b.
100
-------
16.0 PHYSICAL TREATMENT
16.5 REVERSE OSMOSIS
Type of Control; Direct Waste Treatment (Aqueous Treatment)
Function: Used to remove dissolved organic and inorganic materials, and to
reduce the concentration of soluble metals, total dissolved solids (TDS) and
total organic carbon (TOG).
Description: The process of reverse osmosis involves filtering the
contaminated water through a semi-permeable membrane at a pressure greater
than the osmotic pressure caused by the dissolved materials in the water.
Operating pressures generally range from atmospheric to 1,500 psi* The
semi-permeable membrane is typically fabricated either in the form of a flat
sheet (plane) or tube. As shown in Figure 16.5, the wastewater (feed) flows
over the surface of the membrane. Treated water passes through microscopic
pores in the membrane. The concentrated waste stream passes over the membrane
to further treatment or disposal.
Fend * •'. ' ' • .''.'.' '.'-'•• ',• '. '.'.•'.'.'• '.'.'.•^.'.'.Concentrate
Membrane
Support .
Figure 16.5. Membrane processes using a pressure driving force in
(a) plane, and (b) tubular designs.
Source: GCA, 1985b.
Design Considerations: The amount of material which can be removed using the
reverse osmosis technique is dependent on the membrane type, operating
pressure, and the specific contaminant of concern. Multicharged cations and
anions are easily removed from the wastewater with this technique. However,
most low molecular weight dissolved organics are not removed or are only
partially removed with this method. Selection of the proper membrane material
and configuration is essential. Cellulose acetate membranes are used most
commonly, but other types are available. Factors to consider in selecting a
membrane type include: cost, ease of fabrication, serviceability, and
resistance to variations in leachate properties (pH, temperature, etc.).
Limitations: Colloidal and organic matter can clog the membrane surface, thus
reducing the efficiency of the process. Biological growth may form on a
membrane fed an influent containing biodegradable organics. Low-solubility
salts may precipitate on the membrane and reduce the level of product water.
Pretreatment techniques (e.g., TSS removal, pH adjustment, oil and grease
removal, and removal of oxidizers) may be necessary. Reverse osmosis is not a
suitable treatment technique for wastes containing high concentrations of
organics since the membrane may dissolve in the waste. Residual chlorine
oxidizes polyamide membranes; dechlorination pretreatment may be required.
101
-------
Technology Status: Conventional, undemonstrated. Reverse osmosis has not
been widely used for the treatment of hazardous wastes.
Associated Technologies: Carbon adsorption, chemical precipitation,
filtration, sedimentation.
Important Data Needs For Screening:
Data need
Purpose
Collection
method
Costs ($)
Treatability
study
Waste
constituents
Leachate
variability
Leachate pH
TSS
Biological
organisms
in leachate
Residual
chlorine
Optimize design
parameters
Not suitable for most
low molecular weight
dissolved organics;
also not suitable for
high concentrations
of organics
Pretreatment (e.g.,
equalization) required
if pH, temp., TSS
change rapidly
Membrane operation
is limited to
certain pH ranges
Suspended solids
should be 10 to
prevent plugging
of membrane
Organic films reduce
permeability
Oxidizes polyamide
membranes
Laboratory-
scale trial
Sampling and
analysis,
(GC/MS)
Sampling and
analysis
pH analysis
TSS analysis
Sampling and
analysis
Sampling and
analysis
300
100/sample
50/test
50/test
50/test
100/sample
100/sample
References: Ehrenfeld and Bass, 1984; Fair, et al., 1968; GCA, 1984; GCA,
1985a; JRB, 1984; Sundstrom and Klei, 1979; U.S. EPA, 1980a;
U.S. EPA, 1985b.
102.
-------
16.0 PHYSICAL TREATMENT
16.6 LIQUID/LIQUID (SOLVENT) EXTRACTION
Type of Control: Direct Waste Treatment (Aqueous Treatment)
Function: Used to separate the components of a liquid solution by contact
with another immiscible liquid for which the impurities have a high affinity.
Description: The liquid/liquid extraction process generally involves three
basic steps: solvent extraction, solute removal from the extracting solvent,
and solvent recovery from the treated stream (raffinate). The process can be
operated continuously. A simplified flow diagram of the liquid/liquid
extraction process is presented in Figure 16.6. The extraction step involves
bringing the liquid waste feed and the solvent into intimate contact to allow
solute transfer either by forced mixing or by countercurrent flow caused by
density differences. Various types of solvent extraction unit designs can be
used, including: a single-stage combination mixing/settling unit, several
single-stage units in series, or a multi-stage unit which uses counter current
flows within a single device (e.g., a column or differential centrifuge). Two
output streams are released from the extractor; the solute-laden solvent, and
the treated stream (raffinate). Usually, a secondary solvent extraction, or a
distillation step must be performed on the extracting solvent to remove the
solute so that the solvent can be either disposed or recycled.
UWWEATED
WASTE WATER
TREATED
•WATER
MFFINATE
$01 VENT « SOLUTE
SOLVENT
MAKE-UP
Figure 16.6.
Flow diagram for liquid/liquid extraction.
Source: U.S. EPA, 1980.
Design Considerations: Design is specific to the solute being recovered and
the characteristics of the waste stream. Criteria for solvent selection
include: low cost, high extraction efficiency, low solubility in the
raffinate, easy separation from the solute, adequate density difference with
raffinate, no tendency for emulsion formation, non—reactive, and
non-hazardous. It is difficult to find a solvent that will meet all the
desired criteria, and therefore, some compromise is generally made.
103
-------
Limitations: Liquid/liquid extraction systems seldom produce an effluent
suitable for direct discharge to surface waters. Therefore, the process
usually requires the use of other unit processes such as distillation or
stripping to effectively recover solvent and solute from the two effluent
streams. Valuable products can be recovered using a liquid/liquid extraction
process. However, in some cases process costs may limit the actual
applications for solvent recovery.
Technology Status: Liquid/liquid extraction is a proven method for the
separation of liquid components of a waste. It has also been demonstrated as
a solvent recovery technique.
Associated Technologies; Steam distillation, air or steam stripping.
Important Data Needs for Screening;
Collection
Data need Purpose method Costs ($)
Waste stream Selection of GC/MS 900
characteristics appropriate solvent
(e.g.,solvent
immiscibility,
flow rate, etc.)
Choice of solvent Design for optimum Lit. search; Nominal
recovery lab test
Distribution Design for optimum Lit. search Nominal
coefficient extraction
References: King, 1980; U.S. EPA, 1977; U.S. EPA, 1980.
104
-------
16.0 PHYSICAL TREATMENT
16.7 OIL/WATER SEPARATION
Type of Control; Direct Waste Treatment (Aqueous Treatment)
Function; Remove oil and grease from wastewater by utilizing the difference
in terminal velocities that can exist between substances of different
densities.
Description; Oil/water separation is accomplished through the use of a
gravity oil separator, which consists of a separation chamber and a skimming
system. The standard oil/water separation unit is the API separator, which is
based upon design standards published by the American Petroleum Institute. As
diagrammed in Figure 16.7, the oil and any other floating matter (e.g.,
grease) rise to the top of the separation chamber after a sufficient retention
time, while the liquid (i.e., water) flows continuously out of the chamber. A
system of scrapers and rotating drums is used to remove the oil that floats to
the surface. A secondary skimmer pulls a belt vertically through the water to
skim the floating oil, which is subsequently scraped off and collected.
Coalescing techniques can be used to increase the amount of oil removal from
the liquid medium (i.e., water); thereby improving the efficiency of
separation. Coalescing involves the addition of a coagulant (coalescing
medium) which causes oil droplets to accumulate on the medium and rise to the
surface as larger droplets. In situations where a stable oil-in-water
emulsion is encountered prior to gravity separation, an emulsion breaking step
is required. This step is achieved through chemical (interactive charge
neutralization, precipitation, etc.) or thermal (water evaporation) means.
BAFFLE
EFFLUENT
BOTTOM SLUDGE COLLECTOR
OFTEN INCLUDED
Figure 16.7. Oil/water separator.
Source: U.S. EPA, 1980a.
Design Considerations; Oil/water separators can be operated as batch vats, or
as continuous flow-through basins, depending upon the volume of waste to De
treated. Information on specific gravity, overflow rates, viscosity, presence
of additional constituents, etc., should be obtained so that the system can t>e
designed to effectively separate the oil from the water. These factors are
used to determine proper retention times, to select coalescing agents, and to
select appropriate emulsifying techniques (if needed).
105
-------
Limitations: Variable wastewater characteristics such as flow, temperature,
and pH can adversely affect process performance. Also, if oil skimmings can
not be reused, then they will require subsequent treatment and/or disposal.
Important Data Needs for Screening:
Data need
Purpose
Collection
method
Costs
Temperature
Viscosity
Specific gravity
Pollutant analysis
Settable solids
Determine rise rate
of oil globules
Thermometer
Determine susceptibi- Viscometer
lity to oil separation
Determine stream
density
Determine presence of
auxiliary pollutants
Determine amount of
residual sludge
Baume test
GC/MS
Field test
Nominal
Nominal
Nominal
1,100
50
References: U.S. EPA, 1977; GCA, 1980; U.S. EPA, 1980a.
106
-------
16.0 PHYSICAL TREATMENT
16.8 STEAM STRIPPING *
Type of Control: Direct Waste Treatment (Aqueous Treatment)
Function; Used to remove volatile components from an aqueous waste stream by
passing steam through the waste. Steam stripping is essentially steam
distillation of the waste with the volatile components ending up in the
distillate. This technology is most efficient in removing volatile organic
compounds, water-immiscible compounds, hydrogen sulfide, and ammonia.
Description: Steam stripping processes involve a batch still, an overhead
vapor line, a condenser, a condensate receiver, and a gravity separator.
Steam is admitted through a perforated pipe in the bottom of the still to
provide maximum contact with the waste. The steam provides the heat of
vaporization to the waste. All vapor blown through the liquid is then passed
out of the unit with the product and the nonvolatile impurities remain behind
in the still. The vapor stage is passed through the condenser unit to return
it to liquid state and then the stripped product is collected in the
condensate receiver. Gravity separation may be employed to separate liquids
with similar boiling points and different densities.
Figure 16.8.
Steam stripping system diagram.
Source: ADL, 1976.
Factors affecting the removal efficiency of steam stripping systems include:
the type of volatile organics present, concentration of volatile components,
and wastewater flow. Removal efficiencies of volatile organic compounds from
wastewaters range from 10 to 99 percent.
Design Considerations: Design parameters for steam stripping systems are site
specific. Considerations for this type of system include wastewater flow,
steam requirements, height and diameter of stripping column and air emission
control.
107
-------
Limitations: Steam stripping processes pose problems in air pollution control
if volatile components remain in the leachate. Through the use of various
types of emission control technologies, these problems can be minimized.
Technology Status: Conventional, well demonstrated.
Associated Technologies; Air emission controls, carbon adsorption,
incineration, land disposal.
Important Data Needs for Screening;
Data need
Purpose
Collection
method
Costs ($;
Gross organic
components
Specific organic
components
Leachate analysis
Column packing
Process Size
Effluent
requirements
Suitability for
treatment
Suitability for
t reatment
Gas flow
efficiency
Calculation
of pressure drop
Calculation of
necessary column
length
Design criteria
Sampling and
analysis
Organic
pollutant scan
Sampling and
analysis
Manufacturer1 s
data
Capacities of
processes
producing wastes
Regulatory
assessment
100/sample
1,500-2,0007
sample
Nominal
Nominal
Variable
Variable
References; Ehrenfeld, 1983; McCabe, 1976.
108
-------
16.0 PHYSICAL TREATMENT
16.9 FILTRATION ,
Type of Control: Direct Waste Treatment (Aqueous Treatment)
Function: Used to remove suspended solids from the aqueous phase; often
employed as pre-treatment technique (intermediate process) or as a final
polishing step.
Description: Filtration is a physical process whereby suspended solids are
removed from solution by forcing the fluid through a porous medium. Granular
media filtration is commonly used for treating aqueous waste streams. The
filtration apparatus typically contains sand (or sand with anthracite or coal)
which is supported by an underdrain system that collects the filtrate
(Figure 16.9). As the filtration process proceeds, suspended particles become
trapped on top of, and within the bed, which gradually reduces the efficiency
of the process. Eventually, it becomes necessary to regenerate the filter
media by means of a back-washing (scouring) technique. During this step, the
underdrainage system doubles as a water distribution system. Back-washing
water rises into the filter bed in the reverse direction of the original flow
causing the filter bed to become fluidized. Commonly used methods for
scouring the filter media include: high-velocity x^ash, surface scour, air
scour, and mechanical scour. During the scouring process the solids become
dislodged from the sand and are discharged in the spent wash cycle. The bed
is then allowed to resettle. The coarser, heavier grains tend to settle at
the bottom while the finer, lighter grains remain at the top.
Figure 16.9. Typical filtration bed.
Source: U.S. EPA, 1985b.
Design Considerations: Various modifications to the filtration bed may be
employed, including dual-media filtration (bed consists of anthracite
underlain by sand), and multi-media filtration (bed consists of several layers
of different materials). Commonly used filter materials include: natural
silica sand, crushed anthracite, (hard) coal, crushed magnetite (ore), and
garnet sands.
109
-------
Filtration systems can consist of multiple compartment concrete or steel units
aligned horizontally or vertically. The flow through the filtration units
occurs by using the available head from the previous treatment unit, or by
pumping to a flow-split box and then using the effects of gravity to allow
flow to the filter cells. Pressure filters use pumping to increase the
available head.
Limitations; High solids content (100 to 200 mg/L) in the waste to be treated
may cause clogging of the filtration media. Granular media filtration is
often preceded by sedimentation to reduce suspended solids loading on the
filter. Another limitation of granular media filtration is that it is only
marginally effective in treating colloidal size particles; particles can be
made larger by flocculation. Also, the liquid effluent resulting from
filtration may contain hazardous materials necessitating further treatment.
Technology Status: Conventional, demonstrated.
Associated Technologies; Carbon adsorption, ion exchange, reverse osmosis,
air stripping, biological treatment, precipitation, flocculation,
sedimentation, dissolved air flotation.
Important Data Needs For Screening:
Data need
Purpose
Collection
method
Costs ($)
Leachate TSS
concentrat ion
Leachate TDS
concentration
Performance
tests
Water
solubility
of waste
constituents
High concentration
of suspended solids
(100 to 200 mg/1)
may cause clogging,
decreasing efficiency
Effluent may require
further treatment
Optimization of
design criteria
Applicability,
feasibility
TSS analysis
50/test
TDS
analysis
Laboratory-
scale tests
CRC Handbook
of Chemical and
Physics; U.S.
EPA Treatability
Manual
50/test
300
Nominal
References:
Fair, et al., 1968; Ehrenfeld and Bass, 1984; GCA, 1985b; JRB,
1984; Sundstrom and Klei, 1979; U.S. EPA, 1980a; U.S. EPA, 1985b.
110
-------
16.0 PHYSICAL TREATMENT
16.10 DISSOLVED AIR FLOTATION
Type of Control; Direct Waste Treatment (Aqueous Treatment)
Function: Removes insoluble, suspended fine particulates or globules of oils
and greases from an aqueous phase.
Description; Dissolved air flotation involves saturating the aqueous waste
mixture with air at high pressures (25 to 70 psi). The pressurized wastewater
is kept at this pressure for 0.5 to 3.0 minutes in a retention chamber, and is
then transferred to a flotation chamber which is under atmospheric pressure.
The rapidly reduced pressure causes small air bubbles to rise to the surface.
These bubbles carry the fine particles and small oil and grease globules to
the surface. A skimmer is used to remove the surface particulates and
globules.
EFFLUENT
SLUDGE REMOVAL MECHANISM
SLUDGE
DISCHARGE
RECIRCULATION ft RECYCLE FLOW
PUMP
AIR FEED
REAERAT10N PUMP-» RETENTION TANK
AIR DISSOLUTION
RECYCLE FLOW
Figure 16.10. Flow diagram of dissolved air flotation process.
Source: U.S. EPA, 1980a.
Design Considerations: With more uniform distribution of water and bubbles,
the flotation unit can be shallower. Typically, depths of effective flotatior
units range from 4 to 9 feet. The sweeping action of the air bubbles can
often be enhanced by the addition of surface active chemicals and pH
adjustments. Other modifications include the use of nitrogen instead of air
in order to reduce fire hazards.
Limitations: Dissolved air flotation is only suitable for treating wastes
which have a specific gravity close to that of water (i.e., 1.0). Waste
streams containing volatile organic constituents may require additional air
emission controls.
Ill
-------
Technology Status: Conventional, demonstrated.
Associated Technologies: Chemical precipitation, f locculation, filtration.
Important Data Needs For Screening:
Data need
Specific
gravity
of waste
Waste
constituents
Purpose
Process suitable
for specific
gravity near 1.0
Volatile organic s may
require additional
air emission controls
Collection
method
Viscometer
Sampling and
analysis
Costs ($)
50/test
100 / sample
References: Fair, et al., 1968; Ehrenfeld and Bass, 1984; GCA, 1985b;
JRB, 1984; Sundstrom and Klei, 1979; U.S. EPA, 1980a;
U.S. EPA, 1985b.
112
-------
17.0 SOLIDS HANDLING/TREATMENT
17.1 SOLIDS SEPARATION
Type of Control; Direct Waste Treatment (Solids Handling and Treatment)
Function; Used to separate solids from slurries and/or to classify
contaminated soils or slurries according to grain size.
Description: Various techniques are available for solids separation,
including sieves and screens, hydraulic and spiral classifiers, cyclones,
settling basins, and clarifiers. Settling basins and conventional clarifiers
are described in Section 16.2. Sieves and screens are constructed of bars,
woven wire, or perforated plate surface (see Figure 17.la). The waste is
passed through the screen or sieve, and particles of a specified (by design)
size range are retained by the screen or sieve. Classifiers are used to
separate soils/sediments according to grain size. Separation occurs due to
differences in settling velocities. Hydraulic classifiers are typically used
to separate sand and gravel from slurries. Spiral classifiers are primarily
used to separate clay and silt from the sand and gravel fractions. An example
of a classifier is shown in Figure 17.Ib.
Cyclones and hydroclones use centrifugal forces to separate solids which are
more dense than water (greater than 1.0 g/L). The slurry is fed into the unit
at rate sufficient to create a spiral. The liquid and fine particulates spin
out through the overflow outlet while the larger solids to move via
centrifugal force to the outside of the wall and then to exit through the apex
at the bottom of the unit.
Vanes
Self-Adjusting Feed Baffle
Feed In!
Screen Retainer
Owsize Discharge
Figure 17.la. Wedge bar screen.
Source: U.S. EPA,
1985b.
Discharge
Collecting Flumes
Figure 17.Ib. Hydraulic classifier.
Source: U.S. EPA,
1985b.
113
-------
Design Considerations: Different types of solids separating techniques are
often used in combination for handling large volumes of solids. The most
appropriate solids separation method depends upon several factors including
the following: volume of contaminated soils, composition of soils or
sediments (gradation, percent clays, percent total solids), types of dredges
or excavation equipment used (determines the feed rate to solids separation,
and the percent-solids for slurries), and site location and surroundings.
Limitations ; The available land area and ultimate or present land use may
limit the type of system that can be utilized.
Technology Status: Conventional, demonstrated.
Important Data Needs for Screening;
Data need
Purpose
Collection
method
Costs,
Volume of
soil/sediment
to be treated
Soil/sediment
grain size
distribution,
total solids
Land use
Selection of
appropriate
technology
Selection of
appropriate
technology
Available land
area
Site Nominal
investigation
report
Sieve 50/test
analysis
Site inspection, Nominal
site visit
Type of
equipment
available
Selection of
solids separation
technology
Telephone calls
to vendors
Nominal
References; E.G. Jordan, 1985; Ehrenfeld and Bass, 1984; GCA, 1985a;
Sundstrom and Klei, 1979; U.S. EPA, 1980a; U.S. EPA, 19«5b,
114
-------
17.0 SOLIDS HANDLING/TREATMENT
17.2 DEWATERING
Type of Control; Direct Waste Treatment (Solids Handling and Treatment)
Function: Facilitates the handling and disposal of sediments; often used to
remove liquids from dredge spoils.
Description: Dewatering is the process of removing liquids and concentrating
suspended solids in sludges without changing the chemical characteristics of
the waste. Several methods are available for dewatering sludges. The method
chosen depends upon the volume of slurry (waste), solids content of the slurry
(waste), the sludge characteristics, available space, subsequent treatment/
disposal operations, and costs. Typical units are dewatering beds, vacuum
pumping, vacuum filtration, pressure filtration, centrifugation, and thermal
drying. Some of the equipment used for these techniques is illustrated in
Figure 17.2.
GRAVITY THICKENER
ICMMM •IAMI
ROTARY VACUDM FILTER
BELT PRESS
IMAL
LGt
inn
C«
QRAVITV
fTAGt
,-J^Lr
==-.,=,0.
1 n n n ©
S.\ ">".•-. 0 •:. 0 ,.: U;... U-v y'r
^ .« «'M^
'^} \*ss
AUTOMATIC VALVt
Figure 17.2. Various types of dewatering equipment.
Source: U.S. EPA, 1985b.
Design Considerations: Sludge conditioning techniques (i.e., chemical
conditioning, and sludge thickening methods), and management of dewatered
sludge (i.e., transportation , disposal, and/or incineration) are usually
considered in conjunction with dewatering. It is often necessary to
pre-filter a sediment before employing dewatering equipment because some
dewatering techniques can only process fine-grained silts.
115
-------
Limitations; Centrifugation and thermal drying must be performed at special
processing facilities. Drying beds are the most economical dewatering method
(with the exception of gravity drainage), but the drying bed technique
requires more time and more land area than other dewatering methods.
Further treatment to fixate or solidify the wastes may be necessary before the
solids are able to meet requirements for disposal. Also, the liquids
generated during dewatering generally contain hazardous constituents and will
usually require additional treatment.
Technology Status; Conventional, demonstrated.
Associated Technologies: Dredging, excavation, surface water and sediment
containment barriers, diversions, transport, land disposal.
Important Data Needs for Screening:
Data need
Purpose
Collection
method
Costs ($)
Topography/site
accessibility
Physical and
chemical char-
acteristics of
sludge/sediment
Site area
Land use
Climate
Waste
c harac teri s t ic s
Need access
for equipment
Select technique
Drying beds often
require a large area
Drying beds may emit
unpleasant odors,
depending on waste
characteristics
Frequent and heavy
rains may hinder
operations
Selection of
dewatering technique
Site inspection Nominal
site survey town/
city/county records
TSS, TDS 50/test
analyses
Site inspection,
site survey,
town/city/county
records
Site inspection
town/c ity/c ounty
records
Natl. Climatic
Center (NCC);
local weather
bureau
Sampling and
analysis
Nominal
Nominal
50
100/sample
References: E.G. Jordan, 1985; Ehrenfeld and Bass, 1984; GCA, 1985a;
Sundstrom and Klei, 1979; U.S. EPA, 1980a; U.S. EPA, 1985b.
116
-------
17.0 SOLIDS HANDLING/TREATMENT
17.3 SOLIDIFICATION/STABILIZATION
Type of Control; Direct Waste Treatment (Solid Handling and Treatment)
Function; Alters the physical and/or chemical state of the hazardous
constituents within the soil rendering them less leachable, less toxic, and
more easily handled, transported, and disposed.
Description; Solidification processes include: cementation, pozzolanic
(silicate-based) cementation, sorbents, vitrification, thermoplastic binding,
and organic polymer binding (surface microencapsulation). Each of these
processes results in the formation of a hardened mass, which is generally
stable and inert. The solid mass is easier to handle and/or dispose.
Cement-based processes involve the mixing of Portland cement with a
soil/slurry. This mixture hardens to form a rock-like mass which incorporates
the hazardous constituents into the crystalline structure. Pozzolanic or
silicate—based solidification consists of reacting lime with fine—grained
silaceous (pozzolanic) materials and water to produce a concrete-like mass.
Disposal of solidified hazardous waste from the pozzolanic process may
require a specially designed landfill that will contain and remove any
leachate produced. Sorbents are natural or synthetic solid materials which
are used to eliminate free liquid, which in turn improves the handling
characteristics of the waste. Commonly used sorbents include: fly ash, kiln
dust, vermiculite, bentonite, activated carbon, Hazorb, and Locksorb.
Vitrification involves combining wastes with molten glass typically at
temperature of 1350°C or greater. The melt is cooled to a stable,
non-crystalline solid.
Both thermoplastic binding and organic polymer binding (also called surface
microencapsulation) were developed as disposal methods for radioactive
wastes. Thermoplastic binding involves the use of bitumen, paraffin, and
polyethylene to bind the waste material. Organic polymer binding uses
polymer-forming organic chemicals, such as urea and formaheldehyde, to
physically encapsulate the wastes by sealing them in an organic binder or
resin.
Design Considerations: Important design factors include: selection of
appropriate solidification agent, solidification mixing ratios, curing time,
and volume increase of solidified product. Specific design factors are based
on the specific waste being treated. Vitrification is often more effective
than other solidification techniques, but is very costly and requires
specialized equipment.
117
-------
Limitations; Solidification processes are more successful with inorganics;
organics do not tend to be amendable to solidification. Some types of wastes
interfere with solidification processes. Sulfates and borates tend to
interfere with cementation and pozzolanic processes. Nitrates, chlorates,
perchlorates, and organic solvents tend to interfere with thermoplastic
binding processes. Certain metal salts will interfere with organic polymer
binding processes. Additionally, there may be a loss stability of any
solidified product over the course of several freeze/thaw cycles; research in
this area is currently being conducted.
Technology Status: State-of-the-art solidification/stabilization methods are
rapidly advancing as manufacturers develop new processes.
Important Data Needs for Screening:
Data need
Purpose
Collection
method
Costs ($)
Soil properties
Waste
characteristics
constituents,
pH, TOG, etc.
Treatability
studies
Climate
Compatibility with
solidification agent
Selection of
appropriate solidifi-
cation agent
Suitability for
solidification
May be a loss of
stability with several
freeze/thaw cycles
Soil sampling
and analysis
Sampling and
analysis
Laboratory
studies
Natl. Climatic
Center (NCC),
local weather
bureau
100/sample
50/test
400
50
References; E.G. Jordan, 1985; Ehrenfeld and Bass, 1984; GCA, 1985a;
Sundstrom and Klei, 1979; U.S. EPA, 1980a; U.S. EPA, 1980b;
U.S. EPA, 1985b
118
-------
18.0 GASEOUS WASTE TREATMENT
18.1 FLARING
Type of Control; Direct Waste Treatment, Air Pollution Control
Function: Thermally oxidizes gaseous wastes into less harmful products.
Description: Flaring is a combustion technique which exposes wastes to an
open flame. A flare consists of an ignition chamber in which an ignitable gas
is allowed to combust in a controlled air environment. Gases are ignited by a
pilot burner. With flaring, no special features are used to control
temperatures or combustion time; supplemental fuels may, however, be needed
to sustain continuous combustion. Equipment such as flame sensors, pilot
flames, automatic sparkers (to attempt reignition upon loss of flame), and
alarms (to alert operators to performance problems) are frequently used to
monitor the flaring operation. Shields may be used as windbreaks for
containing the flame and to prevent it from blowing out.
Design Considerations; The diameter and height of the flare stack and the
number of flares required are determined by the flow rate of the waste/fuel.
For proper mixing of gas and air, and also for adequate safety, the flare
stack should be designed such that the flame is contained within the body of
the flare stack. The air/gas ratio is influenced by the oxygen content of the
gas.
Limitations; Supplementary fuels may be required to sustain continuous
combustion with gases that have a low heating value. Due to the large
quantities of natural gas which are consumed in the flaring process, operating
costs are high. Flaring systems perform inconsistently because they have
minimal control mechanisms. Destruction and removal efficiencies (DREs)
required by current regulations generally can not be attained with flaring,
with the possible exception of gaseous waste streams consisting of simple
hydrocarbons (e.g., fuel tank emissions, landfill methane gas, etc.).
Technology Status: Conventional and demonstrated technique. However, flaring
is more commonly used to dispose of fumes from oil and gas refineries,
digestor gas from sewage treatment plants, and landfill gas (methane) from
municipal landfills. Flaring is generally applicable to hazardous wastes.
Associated Technologies: Thermal destruction (incineration).
119
-------
Important Data Needs for Screening;
Data need
Purpose
Collection
method
Costs
Heat content
of waste
Waste
constituents
Performance
tests
Should be
100 Btu/cu. ft.
Iraplementab ility,
capacity
Adequacy of
destruction and
removal efficiencies
Btu analysis
Sampling and
analysis
Bench or
pilot tests
50/Test
100/sample
300
References; Bonner, 1981; Ehrenfeld and Bass, 1984; GCA, 1984; GCA, 1985a;
U.S. EPA, 1985b.
120
-------
18.0 GASEOUS WASTE TREATMENT
18.2 ADSORPTION
Type of Control; Direct Waste Treatment, Air Pollution Control
Function: Used to remove organic compounds and some inorganic compounds from
gaseous waste streams.
Description: Adsorption involves the transfer of contaminants from a gas (or
liquid) to an adsorbent. Various types of adsorbents can be used, including
activated carbon (see Section 16.4), and resins. Adsorption systems for the
treatment of gaseous waste streams generally consist of containerized beds of
adsorbent. The waste stream flows through the bed, leaving behind
contaminants which become sorbed to the adsorbent material. This process
continues until the adsorbent material reaches capacity and needs to be
replaced or regenerated. Multiple adsorbent beds are often used so that
operation can be continuous while adsorbent material is being regenerated or
replaced.
Design Considerations; Carbon adsorption is used to control volatile
hydrocarbons, sulfur-related emissions, mercury, vinyl chloride, halogenated
organics, and radioactive materials. It is widely used as an air pollution
and odor control technique with solvent recovery/reuse systems. Although
applicable, resins are less frequently used for treating gaseous waste
streams. Resins tend to be used for aqueous waste streams.
Limitations; The adsorbent material eventually reaches capacity and must
either be disposed of in an appropriate landfill or regenerated via heating or
solvent washing. Upon reaching capacity, the adsorption process slows or
stops, and some contaminants may be released (through desorption) back to the
waste stream.
Technology Status; Conventional, demonstrated.
121
-------
Important Data Needs for Screening;
Data need
TSS
concentration
Btu content
of waste stream
Leacbate
components
Purpose
Usage rate
for adsorbent
Need for
supplementary fuel
Treatability
via adsorption
References: Bonner, 1981; Ehrenfeld
Collection
method
TSS analysis
Btu analysis
Sampling and
analysis
and Bass. 1984: GCA,
Costs ($)
50 /sample
50/saraple
100/sample
1984; GCA. 1985a:
JRB, 1984; Kaufmann, 1982;' Lyman, 1980; McGaughey, et al.,
1984; Sundstrora and Klei, 1979; Troxler, et al., 1983; U.S. EPA
1980a; U.S. EPA, 1985b.
122
-------
18.0 GASEOUS WASTE TREATMENT
18.3 AFTERBURNERS
Type of Control; Direct Waste Treatment, Air Pollution Control
Function: Most frequently used in conjunction with thermal destruction
(incineration) technologies to remove vapor-phase residuals.
Description; Afterburners are secondary incinerators for combustion of gases
resulting from incineration (via the techniques described in Section 19.0). A
supplemental fuel is added to the gas steam to generate the high temperatures
necessary to decompose (in the presence of oxygen) the hazardous constituents
present in the stream to carbon dioxide, water, and other combustion products.
Design Considerations: Afterburners are only applicable to gaseous waste
streams that can be oxidized at temperatures of 870°C or less at retention
times of 0.5 to 1.0 seconds. Catalysts may be used to lower oxidation
temperatures to 540 to 870°C.
Limitations: Afterburners should only be used for gaseous waste streams which
will not produce undesirable oxidation products. Scrubbers may be required to
further control air emissions.
Technology Status: Conventional, demonstrated.
Associated Technologies; Thermal destruction (incineration).
Important Data Needs for Screening:
Data need
Purpose
Collection
method
Costs
Concentration
of waste
constituents
Volume of
gas to be
treated
Destruction
efficiencies
Feasibility,
capacity
Feasibility,
capacity
Suitability of
technology
Sampling and
analysis
Site investigation
report
Bench or
pilot—scale tests
100/sample
Nominal
1,200
References: Bonner, 1981; Ehrenfeld and Bass, 1984; GCA, 1984; GCA, 1985a;
McGaughey, et al., 1984; U.S. EPA, 1985b.
123
-------
-------
19.0 THERMAL DESTRUCTION (INCINERATION)
19.1 ROTARY KILN INCINERATION
Type of Control: Direct Waste Treatment
Function: Uses high temperature oxidation under controlled conditions to
destroy organic constituents in liquid, gaseous, and solid waste streams;
preferred incineration method for treating mixed hazardous solid residues.
Description: Rotary kiln incinerators are refractory-lined cylinders fueled
by natural gas, oil, or pulverized coal. As shown in Figure 19.1, the kiln is
mounted at a slight angle from the horizontal. Rotary kiln incinerators are
typically used in conjunction with an afterburner and a wet scrubber emission
control system.
FLUE GAS
OXIDATION ftFten- SCRUBBER
CHAMBER BURNER
ASH
REMOVAL
MECHANISM
T
LIQUID
HOLDING
TANK
STACK
A
— ii —
-~
LEGEND: •
1. INFLUENT WASTE
2. COMBUSTION AIR
3. FLUE GAS
A. RESIDUALS
5. SCRUBBER WATER
6. FUEL
Figure 19.1.
Rotary kiln incinerator schematic.
Source: U.S. EPA, 1985b
Wastes are injected (fired) at the top of the rotating kiln. The rotation
creates turbulence and improves combustion. An afterburner is connected to
the discharge end of the kiln and is used to complete the gas-phase combustion
reactions.- Following this stage, a wet scrubber emission control system may
be employed to prevent the emissions of inorganic acids to the atmosphere.
Design Considerations: The rotary kiln typically has a length-to-diameter
ratio between 2 and 10; a peripheral rotational speed ranging from 1 to 5 rpm;
an incline ratio ranging from 1/16 to 1/4 in./ft.; operating temperatures
ranging from 1500 to 3000°F; and residence times varying from a few seconds
to several hours (depending on the waste characteristics). Varying the
rotational speed and the operating temperatures can be used to alter residence
times and combustor air mixing. Auxiliary fuel systems may be required to
bring the kiln up to the desired operating temperatures. Various types of
auxiliary fuel system may be used including: dual-liquid burners designed for
combined waste/fuel firing, or single-liquid burners equipped with a pre-mix
system. Both cocurrent and countercurrent firing designs may be used; liquid
wastes can be fired at either the feed or discharge end of the kiln.
125
-------
Rotary kiln incineration is not suitable for treating waste
streams which have a high concentration of inorganics. Rotary kiln
Limitations:
incinerator systems are susceptible to thermal shock, require careful
maintenance, need additional air due to leakage, have a relatively low thermal
efficiency, high particulate emissions, and a high cost for installation.
Technology Status; Conventional. Demonstrated for use with wastes containing
PCBs, dioxins, tars, obsolete munitions, polyvinyl chloride, solvent
reclamation stillbottoms.
Associated Technologies: Afterburner, scrubbers.
Important Data Needs for Screening:
Data need
Purpose
Collection
method
Costs ($)
Waste
constituents
Heat content
of waste
Waste feed TSS
concentration
Not suitable for
treating waste
streams with a
high concentra-
tion of inorganics
Need for
auxiliary fuel
May require pre-
treatment to
avoid clogging
of the nozzles
Sampling and
analysis UCAP)
Btu analysis
TSS analysis
100/
sample
5U/test
50/test
References; Bonner, 1981; Ehrenfeld and Bass, 1984; GCA, 1984; GCA, 1985a;
Hitchcock, 1979; Metcalf and Eddy, 1972; McGaughey, et al.,
1984; U.S. EPA, 1980a; U.S. EPA, 1985a.
126
-------
19.0 THERMAL DESTRUCTION (INCINERATION)
19.2 FLUIDIZED-BED INCINERATION
Type of Control: Direct Waste Treatment
Function: Uses high temperature oxidation under controlled conditions to
destroy organic constituents in liquid, gaseous, and solid waste streams;
typically used for slurries and sludges.
Description; As diagrammed in Figure 19.2a, the fluidized bed incinerator
consists of a vertical refractory-lined cylindrical vessel containing a bed of
inert granular material (typically, sand) on a perforated metal plate. The
granular bed particles are fluidized by blowing low velocity air upward
through the medium. The rate of air movement is directly proportional to the
particle size, and acts to suspend the bed in a fluid-like manner. Combustion
occurs within the fluidized material. Auxiliary fuel is often injected into
the bed. Heat is transferred from the bed to the wastes (which are generally
in the form of slurries or sludges). The solid materials in the waste become
suspended fine particulate matter and are separated in a cyclone when exhaust
gases pass through an afterburner to destroy vapor-phase residuals.
A recently developed modification of this technique, is the circulating
fluidized-bed combustor (Figure 19.2b) which utilizes contaminated soil as the
bed material and uses an air flow three to five times greater than the
conventional system. The increased air flow causes increased turbulence which
allows for efficient combustion at lower operating temperatures, and precludes
the use of an afterburner.
FLUE
CAS
PROCESS STEAM
FOR HEATING
BURNER
HAKE-OP SATO
COMBUSTOR
Figure 19.2a. Fluidized-bed Figure 19.2b. Circulating bed
incinerator. combustor.
Source: U.S. EPA, 1985b. Source: U.S. EPA, 1985b.
127
-------
Design Considerations: The diameter of the fluidized bed unit typically
ranges from a few meters to 15 meters. Operating temperatures normally range
from 450°C to 980°C, and are limited by the softening point of sand which is
1100°C. Residence times are generally on the order of 12 to 14 seconds for a
liquid hazardous waste. Problems caused by low ash fusion temperatures can be
avoided by keeping operating temperatures below the ash fusion level, or oy
using chemical additives to raise the fusion temperature of the ash.
Limitations; Operating costs are relatively high (in particular, electric
power costs). Regular preparation and maintenance of the fluid bed must be
performed. It is often difficult to remove residual materials from the bed.
The fluidized-bed incineration technique is not well-suited for irregular or
bulky wastes, tarry solids or other highly viscous wastes, or wastes with a
fusible ash content. Formation of eutectics (compounds with low melting or
fusion temperatures) can be a problem. Wastes containing bulky or irregular
solids may require pretreatment in the form of drying, shredding, and sorting,
prior to entering the incinerator.
Technology Status; Fluidized-beds have been used to treat municipal
wastewater treatment plant sludge, oil refinery waste, pulp and paper mill
waste, pharmaceutical waste, phenolic waste, and methyl methacrylate.
Pilot-scale demonstrations have been performed for other hazardous wastes
(including PCBs and dioxins).
Associated Technologies; Afterburner.
Important Data Needs for Screening:
Data need
Purpose
Collection
method
Costs ($)
Ash content
of waste
Viscosity of waste
Solids content
of wastes
Not suitable for
wastes with a fusible
ash content
Not suitable for
highly viscous wastes
Wastes with irregular
or bulky solids may
require pretreatment
Dry ash analysis 50/test
Viscosity tests 50/test
TSS analysis 50/test
References: Earner, 1985; Bonner, 1981; Ehrenfeld and Bass, 1984; Freeman,
1985; GCA, 1981; GCA, 1984; GCA, 1985a; McGaughey, et al.,
1984; Rasmussen, 1986; Rickman, 1985; U.S. EPA, 1980a;
U.S. EPA, 1985a; Vrable, et al., 1985.
128
-------
19.0 THERMAL DESTRUCTION (INCINERATION)
19<3 MULTIPLE HEARTH INCINERATION
Type of Control; Direct Waste Treatment
Function; Uses high temperature oxidation under controlled conditions to
destroy organic constituents in liquid, gaseous, and solid waste streams
(including sludges and tars); best suited for hazardous sludge destruction.
Description; As diagrammed in Figure 19.3, a multiple hearth incinerator
consists of refractory-lined circular steel shell, a rotating central shaft, a
series of solid flat hearths, a series of hearth-mounted rabble arms with
teeth, an air blower, fuel burners on the walls, an ash removal system, and a
waste feed system. Additionally, side ports for fuel injection, liquid waste
burners, and an afterburner are often included.
AIR
FLUE CAS
ASB
SLOTS*
Figure 19.3. Multiple hearth incinerator.
Source: U.S. EPA, 1985b.
Design Considerations; Operating temperatures generally range from 1400 to
1800°F. Residence times can be up to several hours long.
Limitations; Multiple hearth incineration is highly susceptible to thermal
shock and is not suitable for treating highly chlorinated organics or other
wastes requiring high temperatures for destruction. Gases and bulky solids
are not readily treated by this method. Solid waste often requires
pretreatment methods such as shredding and sorting. Wastes containing ash
129
-------
which fuses into large rock-like structures are not suitable for destruction
via multiple hearth incineration. Operating and maintenance costs are high.
Operating costs may be reduced by using liquid or gaseous combustible wastes
as an auxiliary fuel. However, control of the firing of supplemental fuels is
difficult.
Technology Status: Conventional, demonstrated.
Associated Technologies: Afterburners.
Important Data Needs for Screening:
Data need
Purpose
Collection
method
Costs
Waste form
Waste
constituents
Ash content
Solid wastes usually
require pretreatment
»
Not suitable for wastes
requiring high des-
truction temperatures
Fusible ash not
suitable
Observation
Sampling and
analysis
Dry ash
content
Nominal
100/sample
50/test
References: Bonner, 1981; Ehrenfeld and Bass, 1984; GCA 1984; GCA, 1985a;
Hitchcock, 1979; Metcalf and Eddy, 1972; McGaughey, et al.,
1984; U.S. EPA, 1980a; U.S. EPA, 1985a.
130
-------
19.0 THERMAL DESTRUCTION (INCINERATION)
19.4 LIQUID INJECTION INCINERATION
Type of Control: Direct Waste Treatment
Function: Uses high temperature oxidation under controlled conditions to
Description: As diagrammed in Figure 19.4, the general components of a liquid
injection incineration system include: burner, primary combustion chamber
secondary (unfired) combustion chamber, quench chamber, scrubber, and stack.
hoJi^on^ninjerCr^n j-ncinerator svstem can be configured either vertically or
horizontally With the vertical configuration, the incinerator acts as its
own stack and a portion of the stack may serve as a secondary combustion
aSSSX/^l1!*011^1^110^™?0" 3re C0nnected to * ««ck. and are better
suited for tall stacks than the vertically configured system. To ensure
efficient combustion, the liquid must be atomized prior to entering the
combustor. Atomization is typically accomplished either mechanically through
rotary cup or pressure atomization systems, or via gas fluid nozzles using
high pressure air or steam. Waste feed storage and blending tanks aid in
maintaining a steady, homogeneous waste flow.
FLUE GAS
FEED
STEAM WATER
WATER
LIQUID WASTE
FUEL
AIR
Figure 19.4.
Liquid injection incineration system.
Source: U.S. EPA, 1985b.
Design Considerations: Combustion chamber residence times generally range
from 0.5 to 2.0 seconds. Operating temperatures depend on the waste type and
q^rementS' but tvPically range from 650 to 1750°C (or 1200 to
The heat capacity (Btu) of the waste liquid must be adequate for
ignition and incineration, or a supplemental fuel must be added. Liquid
injection incinerators are highly sensitive to waste composition and flow
changes. Therefore, storage and mixing tanks are necessary to ensure a
reasonably steady and homogeneous waste flow.
131
-------
Limitations; Particle size in slurries is a critical factor for successful
operation because the burners are susceptible to clogging by particulate or
caked material at the nozzles. The use of liquid injection incinerators is
limited to wastes which can be atomized. Also, heavy metal wastes and wastes
which have high inorganic content are not suitable for treatment via liquid
injection incineration.
Technology Status; Conventional, demonstrated. Liquid injection incinerators
can be used to destroy virtually any pumpable waste or gas and have been used
to destroy PCBs, solvents, still reactor bottoms, polymer wastes, and
pesticides.
Associate Technologies: Afterburner.
Important Data Needs for Screening;
Data need
Purpose
Collection
method
Costs ($)
Viscosity of
wastes
Percent-moisture
content
Waste
constituents
Particle size
Viscosity of greater
than 10,000 SSU
required in order
to be pumpable
Not suitable for
wastes with a high
moisture content, or
for wastes that
cannot be atomized
Not suitable for
wastes with high
inorganic content
Large particles
may clog nozzles
Viscometer
Volume-weight
analysis
Sampling and
analysis
Sieve analysis
50/test
50/test
50/test
50/test
References; Bonner, 1981; Ehrenfeld and Bass, 1984; GCA, 1984; GCA, 1985a;
McGaughey, et al., 1984; U.S. EPA, 1978a; U.S. EPA, 1980a;
U.S. EPA, 1983a; U.S. EPA, 1985a.
132
-------
19.0 THERMAL DESTRUCTION (INCINERATION)
19.5 MOLTEN SALT COMBUSTION
Type of Control; Direct Waste Treatment
Function; Uses high temperature oxidation under controlled conditions to
destroy organic constituents in liquid and solid waste streams; effective for
chlorinated hydrocarbons including PCBs, chlorinated solvents, and malathion.
Description; Molten salt combustion occurs primarily in a bed of molten
alkali metal salts. Air and waste (in the form of liquids, free-flowing
powders, sludges, and/or shredded solid waste) are injected into the bed.
Wastes subjected to the molten salt process undergo catalytic destruction when
they contact the hot molten salt which is maintained at temperatures ranging
from 1382 to 1832°F. As diagrammed in Figure 19.5, hot gases rise through
the molten salt bath, pass into a secondary reaction zone, and finally through
an air emission control system before being discharged to the atmosphere.
TBAGHOUSE
SALT DISPOSAL
Figure 19.5. Simplified flow schematic of molten salt destruction.
Source: U.S. EPA, 1985b.
Design Considerations: Auxiliary fuel may be required when wastes do not have
a sufficient heat content to maintain combustion temperatures.
133
-------
Limitations: The molten salt process is not suitable for wastes with a high
ash content (greater than 20 percent) or high chlorine content, which must be
removed in the purge system. Spent salt needs to be landfilled if it is not
regenerated.
Technology Status: Developmental.
Associated Technologies: Thermal destruction (incineration).
Important Data Needs for Screening:
Data need
Purpose
Collection
method
Costs ($)
Waste
constituents
Heat content
of waste
Ash content
of waste
Chlorine
content of
waste
Applicability
Need for
auxiliary fuel
Not suitable for
wastes with greater
than 20 percent
ash content
Not suitable for
wastes with high
chlorine content
Sampling and.
analysis
Btu test
Dry ash content
Sampling and
analysis
100/sample
50/test
50/test
100/sample
References; Bonner, 1981; Freeman, 1985; GCA, 1984; GCA, 1985a; Johanson,
et al., 1983; McGaughey, et al., 1984; U.S. EPA, 19b5a.
134
-------
19.0 THERMAL DESTRUCTION (INCINERATION)
19.6 HIGH TEMPERATURE FLUID WALL REACTOR/ADVANCED ELECTRIC REACTOR
Type of Control: Direct Waste Treatment
Function; Uses high temperatures to quickly pyrolyze organic wastes to their
elemental state.
Description: As diagrammed in Figure 19.6,
the process occurs in a reactor consisting
of a tubular core of refractory material.
Thermal radiation (in the near infrared
region) supplied by large electrodes in
the jacket of the vessel are used to heat
the reactor to temperatures of 4000 to
5000°F (2200 to 2300°C). Prior to
allowing the waste feed (in solid, liquid,
or gaseous form) to enter the reactor,
nitrogen (an inert gas) is fed into the
reactor and forms a gaseous blanket which
serves to isolate the waste feed from the
reactor core walls, thereby preventing
damage to the refractory material.
The resulting thermal radiation causes
pyrolysis (as opposed to oxidation) of
the organic constituents in the waste
feed. At these high temperatures,
inorganic compounds melt and are fused
into vitreous solids. Most metal salt-
sare soluble in these molten glasses and
thus become locked up in a solid
solution (vitrified beads). Following
pyrolysis in the reactor, the granular
solids and gaseous reactor emissions are
directed to a post-reactor zone (PRZ)
where radiative cooling occurs. The
granular solid material (e.g., treated
solid) is then collected in a sealed
insulated collection vessel, while
the cooled gases are collected in a
baghouse.
Design Considerations: Post-treatment
in the form of an activated carbon bed
may be required to remove products of
incomplete pyrolysis (PIPs) from
gaseous emissions. Depending on the
required destruction and removal
efficiency, post-treatment is generally
not required for granular solids.
!J • Brrtiom»>«rPon
Figure 19.6.
Cross-section of a
typical high-
temperature fluid-
well reactor.
Source: U.S. EPA 1985b.
135
-------
Limitations: The process is not suitable for treating gases or bulky,
irregular solids. Soils need to be dried and sized (approximately 10 mesh)
before being fed into the reactor.
Technology Status; Developmental; demonstrated on a pilot scale for dioxin
and PCBs.
Associated Technologies: Carbon adsorption.
Important Data Needs for Screening:
Data need
Collection
Purpose method
Costs ($)
Soil grain
size distribution
Percent-moisture
content of soils
Soils need to
be less than 10 mesh
Soils need to
be relatively
dry for efficient
combustion
Sieve analysis
Volume-we ight
analysis
50/test
50/test
References: Bonner, 1981; Boyd, 1986; Freeman, 1985; GCA, 1984; GCA, 1985a;
Lee, et al., 1984; McGaughey, et al., 1984; Roy F. Weston, Inc.,
1985; U.S. EPA, 1985a.
136
-------
19.0 THERMAL DESTRUCTION (INCINERATION)
19.7 PLASMA ARC
Type of Control; Direct Waste Treatment
Function; Used to destroy either liquid or solid wastes by pyrolyzing them
into combustible gases.
Description: The plasma arc process functions by contacting the waste feed
(in the form of liquids or solids) with a gas which has been energized into
its plasma^state by an electrical discharge. A schematic of the process is
shown in Figure 19.7. The plasma torch acts as an electrode and the hearth at
the bottom of the reactor acts as the second electrode. The discharge of
electricity between the two electrodes causes the centerline temperatures in
the plasma to reach 90000°F. A small amount of gas is introduced into the
centerline region through the torch, and is ionized. The ionized gas
molecules transfer energy to the waste to cause pyrolysis of the waste.
Design Considerations; There are some technological limitations on the size
of the plasma reactor that restrict industrial-scale use.
POWER
PLASMA AIR
TROUGH COOLING
WATER
LIQUID INJECTION PROBE
WATER COOLING
Figure 19.7.
Plasma reaction vessel schematic,
Source: U.S. EPA, 1985b.
137
-------
Limitations; Pretreatment techniques, such as blending and filtering, may be
necessary to achieve the correct viscosity and to prevent clogging of the feed
nozzle. The plasma arc process is not suitable for treating gaseous wastes.
Technology Status; Developmental. The technique has been demonstrated at the
pilot-scale.
Associated Technologies; Filtration.
Important Data Needs for Screening;
Data need
Collection
Purpose method
f Costs ($)
Waste form
Viscosity of
waste
Not suitable for
gaseous wastes
Not suitable
for highly
viscous wastes
Observation
Viscometer
Nominal
50/test
References; Bonner, 1981; Freeman, 1985; GCA, 1984; GCA, 1985a;
McGaughey, et al., 1984; U.S. EPA, 1985a.
138
-------
1
19.0 THERMAL DESTRUCTION (INCINCERATION) '
19.8 CEMENT AND LIME KILNS
Type of Control; Direct Waste Treatment (Physical Treatment)
Function: Used to destroy waste oils, solvents, and chlorinated organics and
to recover available heat value from the wastes. Kiln temperatures are
usually higher (2700°F) and gas residence time longer (6 to 10 seconds) than
in conventional incinerators. Kilns provide adequate destruction of wastes
with efficiencies of up to 99.9999 percent having been recorded.
Description; Cement and lime kilns operate as a waste incinerator by
introducing a waste/air mixture as a secondary fuel into the flame produced Dy
a burner powered by virgin fuel as shown in Figure 19.8. Many kilns are coal
fired though some use fuel oil or a coal/coke mixture. The fuel/waste flame
is directed at the cement mixture or lime in a rotating drum and heats it as
it passes down the kiln. The exhaust gas from the process is often passed
through a cyclone centrifugal separator or electrostatic dust precipitator
then to a baghouse collection system for the removal of suspended
particulates. Tests have been conducted using waste oils, chlorinated
solvents, and PCB contaminated liquids. Conventional pollutants such as CO,
NOX Total hydrocarbons, and S02 seem to be independent of the inclusion of
hazardous wastes in the fuel. Increased particulate emissions may be expected
with higher chlorine content wastes, but kilns equipped with precipitators
should experience no problems. HC1 emissions may vary with waste components ,
introduced and would require specific attention.
Ground Feed (Dry)
Mutticlone
tttt
Hot Coal, Primary Air -
Secondary Air -
Waste Fuel, Air •
Gases—•- \ Exhaust
Kiln (560 ft) ___ Soljds Gas *"
'Clinker (1.750TPD)
Fan
Figure 19.8.
Cement kiln incineration system.
Source: Mourningham, 1985.
Factors affecting waste destruction efficiency of a cement of lime kiln
include: waste components, volume viscosity, moisture content, BTU value, ash
content, and particulate size, waste stream composition, and required air
emission controls.
139
-------
Limitations; Cement kiln incineration may pose problems in air pollution
control. In the event of an upset, air quality standards may be violated. In
general, kilns produce higher NOX concentrations than conventional
incinerators due to kiln burner design, not waste characteristics. Kilns may
also experience problems with particulate and HC1 emissions for wastes with
high chlorine concentrations.
Technology Status; Conventional, well demonstrated.
Associated Technologies: Air emission controls, electrostatic dust
precipitation, incineration, land disposal.
Important Data Needs for Screening;
Data need
Purpose
Collection
method
Costs ($)
Waste identification Suitability for
treatment
Waste. Btu value/ Suitability for
treatment
Chlorine content Suitability for
treatment
Available waste
volumes
Emission
requirements
Process capacity
Design criteria
Sampling and,
analysis
Bomb
calorimeter
Sampling and
analysis
Market analysis
Regulatory
assessment
100/satnple
45/sample
30/sample
Nominal
Variable
References: Ehrenfeld, et al., 1983; Mournigham, et. al., 1985.
140
-------
19.0 THERMAL DESTRUCTION (INCINERATION)
19.9 PYROLYSIS
Type of Control; Direct Waste Treatment, Solids Handling
Function: Used to destroy organic wastes in solids, liquids, and sludges by
pyrolyzing them into combustible gases.
Description: Pyrolysis is accomplished in an oxygen deficient atmosphere. A
pyrolytic incineration system principally consists of a pyrolyzer and a fume
incinerator. The pyrolyzer is used to decompose the wastes, and the
incinerator destroys the resultant organic compounds. Temperatures in the
pyrolyzer range from 1000 to 1700°F. During pyrolysis, volatile compounds
in the waste are driven off, forming a combustible gas consisting of
hydrocarbons, hydrogen, and carbon monoxide. Inorganic constituents (i.e.,
salts and metals) will form a solid char in the pyrolyzer, which must be
removed from the pyrolyzer prior to introducing additional untreated wastes.
Combustible gases from the pyrolyzer are directed to the fume incinerator
where organics are destroyed via incineration (rotary kiln or multiple hearth
incineration).
Design Considerations; Pyrolysis is only applicable to wastes containing pure
organics.
Limitations: Pyrolysis systems are usually designed for specific wastes and
can not be readily adaptable to a variety of wastes. Pyrolysis of
chlorophenols. and chlorodibenzofurans can lead to the formation of
chlorodibenzofurans and chlorodibenzo-p-dioxins.
Technology Status: Developmental.
Associated Technologies: Thermal destruction (incineration).
Important Data Needs for Screening: ,
Data need
Purpose
Collection
method
Costs ($)
Waste
constituents
Not suited for
inorganics; also
certain chlorinated
organics produce
hazardous PIPs.
Sampling and
analysis
100/sample
References: Bonner, 1981; Freeman, 1985; GCA, 1984; GCA, 1985a; McGaughey,
et al., 1984; U.S. EPA, 1985a.
141
-------
-------
19.0 THERMAL DESTRUCTION (INCINERATION)
19.10 WET AIR OXIDATION
Type of Control: Direct Waste Treatment, Solids Handling
Function:_ Uses high temperature oxidation under controlled conditions to
destroy dissolved or suspended organic waste constituents; used primarily to
treat concentrated waste streams containing organic (e.g., pesticides,
herbicides, etc.) and oxidizable inorganic wastes, and wastes with a high
chemical oxygen demand/biological oxygen demand (COD/BOD) ratio (i.e., not
readily ammenable to biological treatment).
Description; Aqueous phase oxidation of organic constituents is achieved at
temperatures in the range of 350 to 650°F, and pressures ranging from 300 to
3,000 psi. The elevated pressures are used to keep the water in the liquid
state so that the oxidation reactions can proceed at lower temperatures.
As diagrammed in Figure 19.10, liquid waste is pumped, using a high-pressure
pump, into the system and mixed with compressed air (or oxygen). The
air-waste mixture passes through a heat exchanger before entering the reactor
where oxygen in the air reacts with the organic constituents in the waste.
Residence time in the reactor varies from 30 minutes to 2 hours. The
oxidation reactions cause the reactor temperature to rise. Following
oxidation, the gas and liquid phases are separated. The hot liquid is
recirculated through the heat exchanger to heat the new incoming wastes,
before being discharged from the system. Gases are discharged to a baghouse
filter and then to the atmosphere.
WASTB.
CAS
STORAGE
TANK
SEPARATOR
OXIDIZED 1
U«UID 1
PUMP
-£vWW\A^-
HEAT EXCHANGER
Jr
REACTOR
Figure 19.10.
Flowsheet of wet air oxidation.
Source: U.S. EPA,A 1985b.
143
-------
Limitations: The wet oxidation process is not suitable for inorganics or for
wastes containing low concentrations of organics. The process has not yet
been developed for treating large volumes of waste.
Technology Status; Developmental.
Associated Technologies; Biological treatment, scrubber, afterburner.
Important Data Needs for Screening:
Data need
Purpose
Collection
method
Costs ($)
Waste volume
COD/BOD of
the waste
Haste
constituents
Not suitable for large
volumes of waste
Applicability;
high COD/BOD ratio
more efficiently
treated via pyrolysis
than biodegradation
Not suitable for
inorganics or low
concentrations of
organics
Site investigation
report
COD analysis,
BOD analysis
Sampling and
analysis
(ICAP, GC/MS)
Nominal
50/test
100/sample
References; Bonner, 1981; Freeman, 1985; GCA, 1984; GCA, 1985a; McGaughey,
et al., 1984; U.S. EPA, 1985a.
144
-------
19.0 THERMAL DESTRUCTION (INCINERATION)
19.11 INDUSTRIAL BOILERS
Type of Control; Other Direct Treatment
Function; Industrial boilers may be used to destroy waste oils, solvents, and
other flammable, non-halogenated organics to recover available heat value from
the wastes. Large boilers used for power generation with capacities larger
than 10 million BTUs/hour have the greatest potential for use in hazardous
waste destruction processes.
Description; Industrial boilers can operate as waste incinerators by
introducing wastes as supplemental fuel for the flame produced by a burner
powered by virgin fuel. Many boilers are coal fired though some use fuel oil
or natural gas. Most boilers are capable of accepting any moderately
halogenated liquid organic waste stream. It is possible to burn up to
3 percent halogenated wastes, but usually because of corrosive waste streams,
only approximately 1 percent halogens are burned. A large boiler using
organic wastes to replace 25 percent of the feed would consume approximately
500 gal/day of waste. Studies have indicated that approximately 10 percent of
the feed is more typical in most applications. Under RCRA, the regulations
and process performance standards for hazardous waste incineration do not
apply to the use of combustible hazardous wastes as fuel in energy recovery
operations such as power voilers. That makes the disposal of some waste
streams in industrial boilers very attractive especially considering the
energy value obtained. EPA has estimated that approximately 3.5 million tons
of hazardous wastes were disposed of in this manner in 1981. An industrial
boiler and a boiler circulation diagram are shown in Figure 19.lla and 19.lib,
respectively. Factors affecting waste destruction efficiency of an industrial
boiler include: halogen content, volume, viscosity, moisture content, Btu
value, and ash content.
STEAM SOOT BLOWER SAFETY-VALVE
OUTLET CONNECTION CONNECTION
Steam outlet -^
Slowdown
Sludge-
Figure 19.12a. Industrial boiler.
Figure 19.12b. Circulation flow.
145
-------
Design Considerations; Design parameters for industrial boiler systems
include: availability of appropriate waste streams, supply rate, consistency
of waste stream composition, and required air emission controls.
Limitations; The use of industrial boilers for incineration may pose problems
in air pollution control. It may be difficult to obtain high efficiencies of
combustion depending on the type of fuel, waste, etc. Wastes with high
halogen content or corrosive in nature may damage the boiler.
Technology Status: Conventional, well demonstrated.
Associated Technologies; Air emission controls, electrostatic dust
precipitation, land disposal.
Important Data Needs for Screening:
Data need
Waste identification
Waste Btu value
Chlorine content
Available waste
volumes
Effluent
requirements
Purpose
Suitability for
coincine ration
Suitability for
treatment
Suitability for
coincine ration
Process capacity
Design criteria
Collection
method
Sampling and
analysis
Bomb
calorimeter
Sampling and
analysis
Market analysis
Regulatory
assessment
Costs ($)
100/sample
45 /sample
30/sample
Nominal
Variable
References; Basilico, et al., 1985; Shields, 1961; U.S. EPA, 1985b.
146
-------
20.0 LAND DISPOSAL
20.1 SECURE CHEMICAL LANDFILL
Type of Control: Land Disposal/Storage
Function: Used to provide a long-term, environmentally secure repository for.
the disposal of hazardous materials for which no alternative treatment or
disposal alternative exists. Most efficient in the disposal of dewatered
sludges, solid materials, contaminated soils, etc.
Description: Secure chemical landfills are a disposal technology with design
and operating standards identified by the EPA. Landfill cells are constructed
to contain drummed solid wastes or bulked solids in segregated areas for
long-term storage. Each cell of a landfill is constructed with a bottom liner
overlying a low permeability base material, covered with several feet of clay
or other protective material. This is covered by another liner and protective
layer. A diagram of the construction of a RCRA landfill is shown in
Figure 20.10. Wastes are placed in the cell and surrounded by clay or earth
and placed in layers until the cell is full. Once full, the cell is closed
and covered according to RCRA regulations with more clay, synthetic liners and
surface vegetative cover to limit erosion. Other provisions of a secure
chemical landfill include leachate collection systems within the cell liners,
containment and treatment systems for the leachate, gas venting, leak
detection systems, and closure/post-closure care requirements. Current RCRA
regulations also define other conditions and requirements for the operation of
a secure chemical landfill.
. KEY (USED TO HOLD LINER IN PLACE
AHO FOR CLOSURE 3EALINO WITH
SYNTHETIC LINER IN CAP}
0RAINAOE (WALK
IN-SITU TREATMENT
SECONDARY UNDERDRAW
nSlMAKYUKDERORAIN-5'
..uni/m.u.! -
g- »AHD/aRAVEL WHIMUM Of 1 FEET) _
reU^»»ME<'tJ^re^afr^v»m^Mfc«i^^pf^iei>u^,t^j^
MONtTonma weu. *
(IDENTIFlfO BY ftUB-aURFACC EXPLORATION)
"I,
WATER TABLE
Figure 20.1. Secure chemical landfill design.
Source: Raboczynski, 1985; U.S. EPA, 1985c.
147
-------
Design Considerations: Design parameters for secure chemical landfills
include: waste types and compatibilities, volume of wastes, local topography,
depth to ground water, ground water flow rate and use, flood zones, subsurface
conditions such as geological structures, soil permeability, etc., and
distance to populated areas.
Limitations; Despite comprehensive maintenance and monitoring, secure
chemical landfills may release contaminants to the environment. Materials
released from stored wastes may adversely react with clay or synthetic liners
causing gaps in the integrity of the cell. Liner damage caused by animal,
geologic, or other actions, may contribute to accidental releases. Improperly
maintained or installed liners, leachate collection systems, or caps also add
to the risk of release.
Technology Status; Conventional, well demonstrated. Minimum technology
requirements of the 1984 RCRA Hazardous and Solid Waste Amendments for liners
and leachate systems may affect the use of this technology for onsite
applications.
Associated Technologies; Wastewater treatment, capping/surface sealing, dust
control, grading, revegetation, diversion/collection systems.
Important Data Needs for Screening;
Data need
Purpose
Collection
method
Costs ($)
Waste
characteristics
Property survey
Local geology
Waste volume
RCRA construction
requirements
Suitability for
storage
Suitability of
area for landfill
Subsurface
structures and
ground water levels
System
capacity
Design criteria
Sampling and
analysis
Topographic maps
Sfcate
geological
survey data
Capacities of
processes
producing wastes
Regulatory
assessment
100/sample
Nominal
Nominal
Variable
0-50,000
Variable
References: Ehrenfeld, 1983; Raboczynski, 1985; Muteh, 1984.
148
-------
20.0 LAND DISPOSAL
20.2 SURFACE IMPOUNDMENTS/GRAVITY SEPARATION
Type of Control: Land Disposal/Storage
Function: Used to store or to pre-treat a variety of industrial wastes. An
impoundment may be a natural topographic feature, a man-made excavation, or
diked area. Impoundments can be used for the temporary storage of sludges,
wastewaters, and wastes stored in waste piles. Waste piles may be stored in
surface impoundments to meet the regulatory requirements for leachate
collection. Waste may be stockpiled before or after treatment or while
awaiting disposal.
Description: Surface impoundments may be constructed above, below or
partially in the ground with surface dimensions greater than depth.
Impoundments should be lined with an appropriate synthetic liner and are
designed to contain an accumulation of wastes with free liquids. Although
estimates of capacity vary, studies indicate impoundments vary in size from
0.1 to 5,300 acres. Although there is variation among state requirements, the
most common is the requirement for the use of a liner to prevent seepage. The
criteria in liner selection are permeability, hydrological conditions, and
waste characteristics and compatibility. Buffer zones and monitoring wells
are also used to protect adjacent ground water. Wastes stored in impoundments
may separate into various layers depending on liquid content, solubilities,
densities, and chemical composition. It may be possible to use a surface
impoundment as a pre-treatment step in disposal of some types of materials.
Thick Layer
Compacted Low Permeability Soil
Natrve Soil Foundation
\
Liner
(compacted soil)
Figure 20.2. Surface impoundment.
Source: U.S. EPA, 1985c.
Design Considerations: Design parameters for surface impoundments include:
waste types and compatibilities, volume of wastes, local topography, depth to
ground water, ground water flow rate and use, flood zones, subsurface
conditions such as geological structures,.soil permeability, etc., and
distance to populated areas.
149
-------
Limitations; Despite comprehensive maintenance and monitoring, surface
impoundments may release contaminants to the environment. Materials released
from stored wastes may adversely react with clay or synthetic liners causing
gaps in the integrity of the impoundment. Liner can be damage caused by
animal, geologic, or other actions, may contribute to accidental releases.
Technology Status; Conventional, well demonstrated. Minimum technology
requirements of the 1984 RCRA Hazardous and Solid Waste Amendments for liners
and leachate systems may affect the use of this technology for onsite
applications.
Associated Technologies: Wastewater treatment, capping/surface sealing, dust
control, grading, revegetation, division/collection systems.
Important Data Needs for Screening:
Data need
Waste
characteristics
Property survey
Local geology
Waste volume
RCRA construction
requirements
Purpose
Compatibility
Suitability of
area for lagoon
Subsurface
structures and
ground water levels
System
capacity
Design criteria
Collection
method
Sampling and
analysis
Topographic
maps
State
geological
survey data
Capacities of
processes
producing wastes
Regulatory
assessment
Costs ($)
100/sample
Nominal
Nominal
Variable
0-50, 000
Variable
0-50,000
References; Ehrenfeld, 1981; U.S. EPA, 1978b; U.S. EPA, 1983b;
U.S. EPA, 1983c; U.S. EPA, 1985c.
150
-------
20.0 LAND DISPOSAL
20.3 DEEP WELL INJECTION
Type of Control; Land Disposal/Storage
Function: Used to isolate certain types of wastes by injecting them in liquid
form or mixed with a stabilizing material, deep underground into rock strata
or salt domes. This technique has long been used by the petroleum industry
for the disposal of pumping wastes and brines in well fields. It is an
economical technique, but is very site dependent relative to the subsurface
geological structure of the receiving strata.
Description: A deep-well injection system consists of a disposal zone, a well
and surface storage and a pre-treatment facility. The injection well itself
consists of an injection tube and a casing. Most wells in current use operate
at approximately 300 psi, are in the area of 1,200 m deep, and can dispose of
up to 400 gpm/well. The disposal zone must be located below any potable water
aquifer and isolated from them by thick, relatively impervious strata such as
dolomite or limestone as illustrated in Figure 20.3. Wastes injected may be
mixed with cement or other stabilizing material to immobilize it after
injection. The annular space between the injection tube and the casing can be
filled with oil or fresh water to help detect leaks. Vertical migration of
the wastes may take place by mean of natural fractures such as faults,
abandoned wells, etc. Wastes most suited to deep well injection could be
various heavy tnetals which could be precipitated to an insoluble form or
chelated before mixing with a stabilizing agent and injection. Other
chemically compatible stabilizers could be used with other types of wastes if
required. Polymers mixed with wastes could be injected prior to
polymerization.
Figure 20.3 Deepwell injection system. Source: Stow, 1985.
Design Considerations: Design parameters for deep well injection include:
waste types and compatibilities, volume of wastes, local geology, injection
system and rate, monitoring systems, surrounding land use and water supplies,
and current regulatory status.
151
-------
Limitations; The most significant limitation to injection is lack of
comprehensive knowledge of underground conditions without which long term
confinement of the wastes can never be certain. Technical and operational
difficulties exist in the pre-treatment of wastes for injection and in
ensuring proper installation and maintenance of the well itself.
Technology Status; Conventional, well demonstrated in the petroleum and
nuclear industries. Use of this technology for the treatment of hazardous
wastes is divided into class I and class IV wells. Class I wells inject
wastes below an aquifer used as a potable source. Class IV wells inject
wastes into the same strata as the aquifer. The use of Class IV wells has
recently been banned.
Associated Technologies: Excavation and removal, equalization,
neutralization, stabilization, filtration.
Important Data Needs for Screening;
Data need
Purpose
Collection
method
Costs ($)
Waste
characteristics
Property survey
Local geology
Location of
potable water
aquifer(s)
Waste volume
RCRA construction
requirements
Suitability for
injection
Suitability of
area for site
Subsurface
structures and
ground water levels
Potential for
contamination
System
capacity
Design criteria
Sampling and
analysis
Topographic
maps
State
geological
survey data
State
geological
survey data
Capacities of
processes
producing wastes
Regulatory
assessment
100/sample
Nominal
Nominal
Nominal
Variable
0-50,OOU
Variable
References; Overcash, 1981; Stow, 1985; U.S. EPA, 1977; GCA, 1985b.
152
-------
20.0 LAND DISPOSAL
20.4 SECURE CHEMICAL VAULTS
Type of Control; Land Disposal/Storage
Function: Used to provide an interim, environmentally secure repository for
the storage of hazardous materials for which no alternative treatment or
disposal alternative presently exits. Most efficient in the disposal of
dewatered sludges, solid materials, contaminated soils, incinerator ash, etc.
Description; Secure chemical vaults have recently been developed to provide a
technology for long term storage for materials that cannot be further reduced
or destroyed and need to be isolated from the environment. The vault is an
above-ground structure designed to separate hazardous materials from the
environment without the problems and concerns associated with below-ground
landfills. Material stored in vaults would be more easily accessible in the
future if a reclamation or destruction technique is developed. The vault may
be constructed of concrete for the outer containment structure and have
several internal liners, each with leachate collection system as shown in
Figure 20.4. Leachate monitoring and collection would be more reliable since
no pumps would be required, only gravity collection and flow to an outside
containment and treatment area. The vault itself could be visually inspected
for any leakage since it is above ground. Once full, the vault would be
capped by synthetic liners and provided with a runoff control system. Vents
could be added if required. Vaults could be constructed to the necessary size
and number for the application. A vault 1-1/2 acres in size and 25-feet high
will provide approximately 45,000 cu. yds of capacity.
-HI .-,|| 14- Storm Water
- II '.' N U Collection
•|J Cap Monitoring
L° CvcTBm
Compacted, Stabilized
Wast:
Monitorinj Systems
Original 6rade
Clay or Concntt futiary
Lner(Baa)
Figure 20.4. Secure Chemical Vault.
Source: Philipbar, 1985.
153
-------
Design Considerations: Design parameters for secure chemical vaults include:
waste types and compatibilities, volume of wastes, local topography, runoff
control, liner leak detection systems, containment and treatment system for
leachate.
At present, storage as would be provided by a vault is
Limitations;
considered "interim" and cannot be long term. As with a secure chemical
landfill, the vault is intended only to provide storage for a certain time and
at present is not a disposal method. The construction of vaults may present
licensing problems in certain areas since it is intended as long term storage
and would require post-closure monitoring and care.
Technology Status; Conventional, not well demonstrated. One type of vault
was patented in 1984. Minimum technology requirements of the 1984 RCRA
Hazardous and Solid Waste Amendments for liners and leachate systems may
affect the use of this technology for onsite applications.
Associated Technologies; Wastewater treatment, capping/surface sealing, dust
control, collection systems.
Important Data Needs for Screening:
Data need
Waste
characteristics
Property survey .
Local geology
Waste volume
RCRA construction
requirements
Purpose
Suitability for
storage
Suitability of
area for vaults
Subsurface
substructures and
ground water levels
System
capacity
Design criteria
Collection
method
Sampling and
analysis
Topographic
maps
State
geological
survey data
Capacities of
processes
producing wastes
Regulatory
assessment
Costs ($)
100/sample
Nominal
Nominal
Variaole
0-50,000
Variable
References; Ehrenfeld, 1983; Philipbar, 1985.
154
-------
21.0 PHYSICAL TREATMENT
21.1 SEWER CLEANING
Type of Control; Contaminated Water Supplies and Sewer Lines
Function: Used to remove deposits and debris from pipes to improve flow rate.
and capacity. Cleaning is usually necessary prior to any inspection and/or
repair work on water or sewer lines, and may also be necessary if the line has
been contaminated. Techniques for cleaning and inspection are generally
applicable to water lines which are usually smaller than sewer lines.
Description; Sewer cleaning procedures involve the use of several types of
equipment, or the combination of two or more procedures. Mechanical scouring
techniques such as powered "snakes" which .pull or push scrapers, augers, or
brushes through the line are shown in Figure 21.la. Bullet shaped plastic
balls lined with scouring strips called "pigs" are hydraulically propelled at
high velocity to scour the inner surface of the pipes. Hydraulic scouring can
also be accomplished by running high pressure hoses into the sewer lines
through manholes and flushing out a section of pipe with very high pressure
water. Some systems include a directional nozzle. This technique is often
used following mechanical scouring. Bucket cleaners can be used to dredge
grit or contaminated soil from sewer lines. Winches pull sewer balls or
"porcupine" scrappers from manhole to manhole through the sewer pipe. It is
also a useful technique for obtaining samples from the line as illustrated in
Figure 21.Ib. Suction devices or vacuum trucks are also used in sewer
cleaning operations.
Figure 21.la
Powered Snake.
Source: U.S. EPA, 1985b,
Figure 21. Ib
Powered Bucket Cleaner,
155
-------
Factors affecting the removal efficiency of cleaning equipment include: the
type of material present, equipment type availability, access to the
contaminated area, and configuration of the pipes to be cleaned. Removal of
some types of hazardous constituents may be difficult if they have sorbed into
the pipe itself.
Design Considerations; Design parameters for sewer cleaning systems are site
specific. Considerations for this type of system include the type of material
to be removed, accessibility, method of disposal and operator safety.
Limitations; Size of pipes may limit the use of some types of inspection and
cleaning equipment that can be used. Pipes with diameters of less than
48 inches cannot be entered by workmen. Determining which section(s) of pipe
are contaminated and planning logistics of implementation may also be
difficult in some cases.
Technology Status; Well demonstrated for conventional uses, less so for
hazardous applications.
Associated Technologies; Excavation/removal, land application, activated
sludge, incineration, land disposal.
Important Data Needs for Screening:
Data need
Purpose
Collection
method
Costs ($.)
Contaminant
composition
Determine
removal and
disposal method
Sampling and
analysis
100/sample
Location and area
contaminated
Leakage points
Ground water
infiltration points
Planning and
logistics
Areas to be
repaired
Areas to be
repaired
Inspection
of pipes
Inspection
of pipes
Inspection
of pipes
100-150/hr
100-150/hr
100-150/hr
References; Ehrenfeld, 1983; U.S. EPA, 1985b.
156
-------
22.0 SEWER REHABILITATION AND REPAIR
Type of Control; Contaminated Water Supplies and Sewer Lines
Function: Several techniques can be used to relign, remove, or seal pipes
that are in contact with contaminated substances or water. This will prevent
further contamination of the water or sewer line and help to prevent ground
water infiltration.
Description: Sewer and water lines can be rehabilitated by several types of
procedures. Sliplining, or insertion of a new pipe inside an existing pipe is
shown in Figure 22.1. This technique usually involves the insertion of a
flexible liner pipe of slightly smaller diameter inside the damaged or
contaminated pipe. Polyethylene is the most commonly used material. A
similar process called "inversion lining" uses a flexible lining material that
is thermally hardened inside the larger pipe after installation. Inversion
lining is a process using a flexible liner inserted into the damaged or
contaminated pipe and then thermally hardened once in place. Service
connections are reopened by a camera-guided cutter after hardening. This,
technique is often used where excavation is impractical such as near large
trees or below heavily travelled streets. Chemical grouts are commonly used
for sealing leaking joints in otherwise sound sewer pipes. Small holes and
radial cracks can also be repaired in this fashion. A grout is a
low-viscosity liquid which cures to a form-fitting solid. Commonly used
grouts include acrylamide gels, acrylate polymers, and polyurethane gels. If
the pipes are so badly damaged or contamined that no rehabilitation is
possible, it may become necessary to excavate and remove all of the pipe and
replace it.
.WINCH ASSEMBLY
MIH. OF
12 X LINER MIN. OF
DIAMETER 2.5 XD
VREMOTE MANHOLE
OR ACCESS PIT
_CABLE ATTACHED
TO GUIDE CONE
PIPE SUPPORT •
ROLLER
Figure 22-1. Sewer sliplining.
Source: U.S. EPA, 1985b.
There is little information on the use of these techniques for control of
hazardous contaminants. Factors that could adversely affect the performance
and reliability of such repairs are : incompatibility of the contaminants and
the sealing material, and permeability of the repair materials to the
pollutant(s).
157
-------
Design Considerations: Design parameters for sewer rehabilitation are site
specific. Considerations for this type of system include the type of
contaminant, location of the area of pipe in question, accessibility,
disruption of service or traffic and costs involved.
Limitations; Size of pipes may limit the use of some types of inspection,
cleaning, and repair equipment that can be used. Pipes with diameters of less
than 48 inches cannot be entered by workmen. Determining which section(s) of
pipe are contaminated and planning logistics of implementation may also be
difficult in some cases. The type of contaminant involved needs to be
considered relative to the remedial action planned. Slip-lining requires that
the pipe itself be relatively round since the lining pipe must be moved
through it. Chemical grouting cannot be used to strengthen weak pipes or
where the pipe is severely cracked or has large voids outside the pipe joint.
Technology Status; Well demonstrated for conventional uses, less so for
hazardous applications.
Associated Technologies; Excavation/removal, diversion/collection, ground
water pumping, sewer cleaning, incineration, land disposal.
Important Data Needs for Screening;
Data need
Purpose
Collection
method
Costs ($)
Contaminant
composition
Location and area
contaminated
Leakage points
Compatibility of
sealant/repair
material
Ground water
infiltration
points
Determine
removal and
disposal method
Planning and
logistics
Areas to be
repaired
Determine type
of sealant/repair
to be used
Areas to be
repaired
Sampling and
analysis
Inspection
of pipes
Inspection
of pipes
Manufacturer's
data
Inspection
of pipes
100/sample
10U-150/hr
100-15U/hr
100-150/hr
References: Ehrenfeld, 1983; U.S. EPA, 1985b.
158
-------
23.0 ALTERNATE DRINKING WATER SUPPLIES
Type of Control: Alternate Drinking Water Supplies
Function: The selection of alternate sources of drinking water may be a
satisfactory solution to community water quality problems. This may also help
prevent further contamination of the water or sewer lines. Use of bottled
water is also a possibility in some applications.
Description: New water supplies may have to be selected for a community if
the existing source(s) becomes contaminated. Many communities have existing
facilities with alternate sources. The new supply should be located within a
reasonable distance from the community and should be free of contaminants.
If it is not, transportation or treatment costs may make the use of the
alternate source as expensive as removing the contaminant from the original
source. The use of bottled water is relatively costly and is usually only
used for drinking and food preparation. Even though it is more costly, the
delivery of bottled water to ensures all affected residents have safe drinking
water. The use of bottled water is most commonly used as a temporary,
emergency response to a contaminated source.
Design Considerations: Design parameters for alternative water supplies are
site specific. Considerations include: possible contaminants in the
alternate source, location of the source, distribution system(s) available,
contamination of the distribution system, development cost of new reservoir,
or development of new ground water wells.
Limitations; Availability and economics are the two prime factors in the
development of an alternate source. If the source to be used is too far from
the community, it may be either too expensive or impractical (or both) to use
it as an alternative. Also, the cost of developing new impoundments,
treatment systems, sludge disposal, and/or distribution systems may be
prohibitive.
Technology Status: Conventional, well demonstrated.
Associated Technologies: Excavation/removal, diversion/collection, ground
water pumping, sewer cleaning, pipe replacement, incineration, land disposal.
159
-------
Important Data Needs for Screening:
Data need
Purpose
Collection
method
Costs (.$)
Water quality
Location of new
source
Distance to
new source
Required treatment
of new source
(if any)
Expected duration
of need
Determine
suitability
for use
Planning and
logistics
Distribution
system
Determine type
of treatment
needed
Source selection
Sampling and
analysis
Topographical
maps
Topographical
maps
Water quality
criteria
Possibility for
remediation of
original source
100/sample
Nominal
Nominal
Variable
Variable
References; Ehrenfeld, 1983; U.S. EPA, 1985b.
160
-------
24.0 HOME WATER TREATMENT
Type of Control: Contaminated Water Supplies
Function: Point of use or home water treatment systems can be an option that
is technically feasible for the removal of contaminants and may be the most
economical alternative under some situations. Most units are reported to be
most effective for the removal of organic compounds.
Description: There are a variety of devices available now designed for use in
the home or office for the removal of contaminants at the point of use.
Claims have been made for the removal of undesirable tastes, odors,
purification, filtration of suspended matter, and removal of various types of
VOCs. Installations are generally of three types: line bypass, where
separate faucets are provided for treated and non-treated water;
faucet-mounted, where all water through the faucet is treated; whole-house,
where all water is treated. Most common home units involve the use of some
type of small carbon adsorption units to accomplish the purification claimed.
Several studies have concluded that these types of filters may provide a
medium for bacterial growth. Since the small home units are not specifically
designed for removal of VOCs, and generally do not provide the contact time
necessary for effective removal their use for this purpose at this time is
questionable. Home water distillation units have been shown to be extremely
effective in reducing concentrations of inorganic materials, bacteria, and
suspended matter. Efficiency in removal of VOCs is not well documented.
Since these might evaporate with the water, they may also recondense with the
product. As with the carbon units, there is insufficient data to make
conclusions as to effectiveness of treatment.
Other point of use systems include; activated alumina, reverse osmosis, ion
exchange, ozonation, and ultraviolet irradiation. Reverse osmosis and ion
exchange are most commonly used where more stringent water quality standards
must be met such as hospitals, laboratories, etc.
Design Considerations: Design parameters for home water purification systems
include:selection of units appropriate for the contaminant(s) of concern,
appropriate hydraulic capacity, and maintenance criteria and schedules.
Limitations; Activated carbon units may provide potential for excess
bacterial growth, have short-lived effectiveness for some contaminants, could
possibly release contaminants after exhaustion of the carbon, and do not
indicate exhaustion. Distillation units may be ineffective in the removal of
VOC compounds. Reverse osmosis units need high water pressure and flow rates.
Technology Status: Conventional, well demonstrated.
Associated Technologies; Filtration, chlorination, ultraviolet/ozonation,
carbon adsorption, ion exchange.
161
-------
Important Data Needs for Screening:
Data need
Purpose
Collection
method
Costs
Water quality
Purification
criteria
Installation
requirements
Expected volume
of need
Determine
purification
method
Type of system
needed
Determine
system
Equipment
selection
Sampling and
analysis
Manufacturers
data
Manufacturer's
data,
applicability
Manufacturer' s
data
lUO/sample
Nominal
Variable
Variable
References: Ehrenfeld, 1985; U.S. EPA, 1985b.
162
-------
Artiola, J., and W. H. Fuller.
Chromium Attenuation in Soils.
No. 4. pp. 503-510. 1979.
REFERENCES
Effects of Crushed Limestone Barriers on
Journal of Environmental Quality. Vol. 9,
Ehrenfeld, J. , and J. Bass. Evaluation of Remedial Action Unit Operations at
Hazardous Waste Disposal Sites. Noyes Publications, New Jersey. 1984.
Ball, W. P., et al. Mass Transfer of Volatile Organic Compounds in Packed
Transfer Aeration. Journal of the Water Pollution Control Federation,
pp. 127-135. 1984.
Basilico, J. et al. Assessment of Incineration as a Treatment Method for
Liquid Organic Hazardous Wastes. Background Report II: Assessment of
Alternative Technologies. U.S. EPA March 1985.
Earner, H. E., J. S. Chartier, H. Beisswenger, and H. W. Schmidt. Lurgi
Corporation. Application of Circulating Fluid Bed Technology to the
Combustion of Waste Materials. Environmental Progress, 4(2): 125-130. May
1985.
Berry, R. I. New Way to Destroy PCBs.
August 18, 1981.
Chemical Engineering 88(16): 37^1.
Bonner, T. A., et al. Engineering Handbook for Hazardous Waste Incineration.
Prepared for U.S. EPA, Cincinnati, Ohio. SW-399 June 1981.
Boyd, J. , H. D. Williams, and T. L. Stoddard. Destruction of Dioxin
Contamination By Advanced Electric, Reactor. Preprinted Extended Abstract of
Paper Presented Before the Division of Environmental Chemistry, American
Chemical Society, 191st National Meeting. New York, New York: Vol. 26,
No. 1. April 13-18, 1986.
Brady, N. C. The Nature and Properties of Soils, 8th edition.
Publishing Company, Inc., New York. 1974.
Macmillan
California Air Resources Board. Technologies for the Treatment and
Destruction of Organic Wastes as Alternatives to Land Disposal. 1982,
Cantor, L. W. and R. C. Knox. Ground Water Pollution Control.
Publishers Inc. Michigan. 1985.
Lewis
Chillingworth, M., et al. Industrial Waste Management Alternatives and Their
Associated Technologies/Processes, Volume IV. GCA Corporation/Technology
Division. GCA-TR-80-80-G. February 1981.
Crittenden, J. C., G. Friedman, D. W. Hand, and M. Dobrzelewski. Design of
Fixed Beds to Remove Multicomponent Mixtures of Volatile Organic Chemicals.
Paper submitted for presentation at the 1985* AWWA Meeting, Washington, D.C.
June 23-27, 1985.
163
-------
E. C. Jordan Company. Corrective Measures for Releases to Surface Water.
Final Report prepared under subcontract to GCA Corporation/Technology Division
for the U.S. EPA-OSW, Land Disposal Branch, under EPA Contract No. 68-01-6871,
Work Assignment No. 51. GCA-TR-85-66-G. August 1985.
Arthur D. Little, Incorporated. Handbook for Evaluating Remedial Action
Plans. Final Report prepared for U.S. EPA-ORD, MERL, under EPA Contract
No. 68-01-5949. PB84-118249. EPA-600/2-83-076. August 1983.
Fair, G. M., J. C. Geyer, and D. A. Okun. Water and Wastewater Engineering,
Volume 2: Water Purification and Wastewater Treatment and Disposal.
John Wiley and Sons, Inc., New York. 1968.
Flathman, P.E., and J.A. Caplan. Cleanup of Contaminated Soils and Ground
Water Using Biological Techniques. Paper presented at the Hazardous Waste and
Hazardous Materials Conference, Atlanta, Georgia. 1986.
Freeman, Harry M. U.S. EPA-HWERL, Thermal Destruction Branch. Project
Summary: Innovative Thermal Hazardous Waste Treatment Processes.
EPA-600/S2-85/049. 1985.
GCA Corporation, Technology Division. Final Report: Technology Overview -
Circulating Fluidized Bed Combustion. Prepared for U.S. EPA, Office of
Research and Development, under EPA Contract No. 68-02-2693. GCA-TR-81-91-G.
June 1982.
GCA Corporation, Technology Division. Final Report: Technical Assessment of
Treatment Alternatives for Wastes Containing Halogenated Organics. Prepared
for U.S. Environmental Protection Agency, Office of Solid Waste, Waste
Treatment Branch, under EPA Contract No. 68-01-6871, Work Assignment No. 9.
GCA-TR-84-149-G. October 1984.
GCA Corporation, Technology Division. Identification of Remedial
Technologies. Detailed Review Draft Report prepared for U.S. EPA, Office of
Waste Programs Enforcement, under EPA Contract No. 68-01-6769, Work Assignment
No. 84-120. GCA-TR-84-109-G(0). March 1985a.
GCA Corporation, Technology Division. Corrective Measures for Releases to
Ground Water from Solid Waste Management Units. Draft Final Report prepared
for U.S. EPA-OSW, Land Disposal Branch, under EPA Contract No. 68-01-6871,
Work Assignment No. 51. GCA-TR-85-66-G. August 1985b.
GCA Corporation, Technology Division. Corrective Measures for Releases to
Soil from Solid Waste Management Units. Draft Final Report prepared for U.S.
EPA-OSW, Land Disposal Branch, under EPA Contract No. 68-01-6871, Work
Assignment No. 51. GCA-TR-85-66-G. August 1985c.
Gross, R. L., and S. G. Termaath. Packed Tower Aeration Strips
Trichloroethylene from Ground Water. Presented at the 1984 Summer National
Meeting of the American Institute of Chemical Engineers. August 1984.
Hitchcock, D. A.
86(11): 185-194.
Solid Waste Disposal: Incineration.
May 21, 1979.
Chemical Engineering,
164
-------
Johanson, J. G., S. J. Yosim, L. G. Kellog, and S. Sudar. Elimination of
Hazardous Waste by the Molten Salt Destruction Process. In: Incineration and
Treatment of Hazardous-Waste, Proceedings of the Eighth Annual Research
Symposium. EPA-600/9-83-003. April 1983.
JRB Associates. Methodology for Screening and Evaluation of Remedial
Responses. Draft Report prepared for U.S. EPA-MERL, Cincinnati, Ohio, and
U.S. EPA-OERR, Washington, D.C. March 16, 1984.
Kaufmann, H. G. Granular Carbon Treatment of Contaminated Ground Water
Supplies. Second Annual Symposium on Aquifer Restoration and Ground Water
Monitoring, sponsored by the National Well Water Association. 1982.
Kiang, Y. and A. A. Metry. Hazardous Waste Processing Technology Ann Arbor
Science Publishers Inc. Michigan. 1982.
Kirk and Othmer.
Inc., New York.
Chemical Grouts, Volume 5, pp. 368-874.
1979.
John Wiley & Sons,
Kosson, D.C. et al., Development and Application of Onsite Treatment
Technologies for Sludge Filled Lagoons. In: International Conference on New
Frontiers for Hazardous Waste Management EPA-600/9-85/025 September 1985.
Lee, Kenneth W., William R. Schofield, and D. Scott Lewis. Mobile Reactor
Destroys Toxic Wastes in "Space". Chemical Engineering. April 2, 1984.
Lutton, R., G. Regan, and L. Jones. Design and Construction of Covers for
Solid Waste Landfills. EPA-600/12-79-165. 1979.
Lutton, R. Evaluating Cover Systems for Solid and Hazardous Waste. U.S. Army
Engineers Waterways Experiment Station. Prepared for U.S. EPA, Municipal
Environmental Research Laboratory, Cincinnati, Ohio. SW-867. 1982.
Lyman, W. J. Applicability of Carbon Adsorption to the Treatment of Hazardous
Industrial Wastes. Carbon Adsorption Handbook. Ann Arbor Science Publishers,
Inc., Ann Arbor, Michigan. 1980.
McCabe, W. L. and J. Smith.
Edition. McGraw-Hill, Inc.
Unit Operations of Chemical Engineering, Third
New York. 1976.
McCarty, P. L., et al. Volatile Organic Hazardous Constituents Removal by Air
Stripping. American Water Well Association Seminar Proceedings: Controlling
Organics in Drinking Water. San Francisco. June 1979.
Metcalf & Eddy, Inc. Wastewater Engineering: Collection, Treatment, and
Disposal. McGraw-Hill Book Company, New York. 1972.
Mournigham, R.E., et al. Hazardous Waste Incineration in Industrial
Processes: Cement and Lime Kilns. In: Proceedings: International
Conference on New Frontiers for Hazardous Waste Management. U.S.
EPA-600/9-85/025 September 1985.
165
-------
Muteh, R.D. et al. Recent Advances in Secure Landfill Technology. Paper •
presented at Hazardous Wastes and Environmental Emergencies, Houston, TX 1984.
Overcash, et al. Design of Land Treatment Systems for Industrial Wastes, 2nd
edition, Ann Arbor Science Publishers, Inc. 1981.
Peterson, R., et al. Comparison of Laboratory and Field Test Data in the
Chemical Decontamination of Dioxin Contaminated Soils Using the Galston PKS
Process. Presented before the Division of Environmental Chemistry, American
Chemical Society. April 1986.
Phelps, R. GHR Engineering Corporation. Telephone Conversation with T. J.
Nunno, GCA/Technology Division. Re: Topographical Survey Costs.
March 14, 1986.
Philipbar, W.B. Environmental Vault - A New Concept in Land Storage. In:
Proceedings: International Conference on New Frontiers for Hazardous Waste
Management. EPA/600/9-85/025 September 1985.
Pope Scientific, Inc. Menomonee Falls, Wisconsin, Bio-oxidation of Sewage and
Industrial Wastes: An Annotated Computerized Bibliography. 1976.
Raboczynski, R.W. Advanced Secure Chemical Landfill Design. In:
International Conference on New Frontiers for Hazardous Waste Management.
EPA-600/9-85/025 September 1985.
Rasmussen, George P. Waste-Tech Services, Inc. Another Option: Onsite
Fluidized-Bed Incineration. Hazardous Materials & Waste Management Magazine.
January-February 1986.
Rickrnan, William S. GA Technologies, Inc. Circulating Bed Incineration of
Hazardous Wastes. Chemical Engineering Progress, March 1985.
Roberts, P. V., G. D. Hopkins, C. Munz, and A. A. Riojas. Evaluating Two
Resistance Models for Air Stripping of Volatile Organic Contaminants in a
Countercurrent, Packed Column. Environmental Science & Technology,
19(2): 164-173. 1985.
Rosbury, K. D., and S. C. James. Control of Fugitive Dust Emissions at
Hazardous Waste Cleanup Sites. In: Proceedings of the Eleventh Annual
Research Symposium on Land Disposal of Hazardous Wastes. EPA-600/9-85-013.
April 29 - May 1, 1985.
Roy F. Weston, Inc., and York Research Consultants. Times Beach, Missouri:
Field Demonstration of the Destruction of Dioxin in Contaminated Soil Using
the J. M. Huber Corporation Advanced Electric Reactor. Weston Project
No. 255-01-01. February 11, 1985.
Ryan, C. R. Slurry Cut-Off Walls Methods and Applications. Geo-Con, Inc.,
Pittsburgh, Pennsylvania. March 1980.
Shields, C.D. Boilers Types, Characteristics and Functions McGraw-Hill. 1961.
166
-------
Shilling, R. D. Air Stripping Provides Fast Solution for Polluted Well
Water. Pollution Engineering. February 1985.
Skodg, D. A., and D. M. West. Fundamentals of Analytical Chemistry, 3rd
Edition. Holt, Rinehart, and Winston Publishers, New York. 1979.
Stow, S.H. et al. Waste Disposal by Hydrofracture and Application of the
Technology to the Management of Hazardous Wastes. In: Proceedings:
International Conference on New Frontiers for Hazardous Waste Management.
EPA/600/9-85/025. September 1985.
Sundstrom, D. W., and H. E. Klei. Wastewater Treatment.
Englewood Cliffs, New Jersey. 1979.
Prentice-Hall, Inc.,
Swanson, M. L., J. Dollimore, and H. H. Schobert. University of North Dakota,
Energy Research Center. Supercritical Solvent Extraction. Prepared for U.S.
Department of Energy. DOE/FE/60181-96. June 1984.
Thagard Research Corporation Irvine, California. Mobile High Temperature
Fluid Wall Reactor. Draft Report Prepared for U.S. EPA-MERL, Cincinnati,
Ohio. 1984.
Troxler, W. L., C. S. Parmele, and G. A. Barton. Survey of Industrial
Applications of Aqueous Phase Activated Carbon Adsorption for Control of
Pollutant Compounds from Manufacture of Organic Compounds. Prepared by IT
Enviroscience for the U.S. EPA Office of Research and Development.
EPA-600/2-83-034. 1983.
U.S. EPA. Physical, Chemical, and Biological Treatment Techniques for
Industrial Wastes. Vol II. NTIS Report PB 275 287. 1977.
U.S. EPA. Office of Research and Development. At-Sea Incineration of
Herbicide Orange Onboard the M/T Vulcanus. Prepared by TRW Inc., Redondo
Beach, California. EPA-600/2-78-086. April 1978a.
U.S. EPA Manual for Evaluating Contamination Potential of Surface
Impoundments EPA 570/9-78-003. 1978b.
U.S. EPA. Treatability Manual, Volume III: Technologies for Control/Removal
of Pollutants. EPA-600/8-80-042c. July 1980a.
U.S. EPA. Guide to the Disposal of Chemically Stabilized and Solidified
Waste. Washington, D.C. SW-872. September 1980b.
U.S. EPA. Office of Research and Development. At-Sea Incineration of
PCB-Containing Wastes Onboard the M/T Vulcanus. Prepared by TRW Inc., Redondo
Beach, California. EPA-600/7-83-024. April 1983a.
U.S. EPA. Surface Impoundment Assessment National Report. EPA-570/9-84-002
1983b.
U.S. EPA. Office of Technology Assessment. Technologies and Management
Strategies for Hazardous Waste Control. EPA. March 1983c.
167
-------
U.S. EPA. Soil Properties, Classification, and Hydraulic Conductivity
Testing. Draft Technical Resource Document for Public Comment. SW-925.
March 1984a.
U.S. EPA. Review of In-Place Treatment Technologies for Contaminated Surface
Soils, Volume 1: Technical Evaluation. EPA-540/2-84-003a. September 1984b.
U.S. EPA. Modeling Remedial Actions at Uncontrolled Hazardous Waste Sites.
EPA/540/2-85/001. April 1985a.
U.S. EPA. Handbook for Remedial Action at Waste Disposal Sites (Revised).
EPA/625/6-85/006. October 1985b.
U.S. EPA. Minimum Technology Guidance on Double Liner Systems for Landfills
and Surface Impoundments — Design, Construction and Operation. Draft
Guidance. EPA-530/SW-85-014. Second version. May 24, 1985c.
U.S. EPA. Handbook; Dust Control at Hazardous Waste Sites. EPA-540/2-85-003.
November 1985d.
Vrable, D. L., D. R. Engler, and W. S. Rickman. Application of Transportable
Circulating Bed Combustor for Incineration of Hazardous Waste. Presented at
HAZMAT 1985, West Long Beach, California. December 1985.
•frU.S. GOVERNMENT PRINTING OFFICE : 1987-748-121/40690
168
------- |