EPA-600/2-76-182
July 1976 Environmental Protection Technology Series
POLLUTANT POTENTIAL OF
RAW AND CHEMICALLY FIXED
HAZARDOUS INDUSTRIAL WASTES AND
FLUE GAS DESULFURIZATION SLUDGES
Interim Report
Municipal Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into five series. These five broad
categories were established to facilitate further development and application of
environmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The five series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
This report has been assigned to the ENVIRONMENTAL PROTECTION
TECHNOLOGY series. This series describes research performed to develop and
demonstrate instrumentation, equipment, and methodology to repair or prevent
environmental degradation from point and non-point sources of pollution. This
work provides the new or improved technology required for the control and
treatment of pollution sources to meet environmental quality standards.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/2-76-182
July 1976
POLLUTANT POTENTIAL OF RAW AND CHEMICALLY FIXED
HAZARDOUS INDUSTRIAL WASTES AND
FLUE GAS DESULFURIZATION SLUDGES
Interim Report
by
J. L. Mahloch
D. E. Averett
M. J. Bartos, Jr.
Environmental Effects Laboratory
U.S. Army Engineer Waterways Experiment Station
Vicksburg, Mississippi 39180
Interagency Agreement No. EPA-IAG-D4-0569
Project Officer
Robert E. Landreth
Solid and Hazardous Waste Research Division
Municipal Environmental Research Laboratory
Cincinnati, Ohio 45268
U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
CINCINNATI, OHIO 45268
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DISCLAIMER
This report has been reviewed by the Municipal Environmental Research
Laboratory, U. S. Environmental Protection Agency, and approved for publi-
cation. Approval does not signify that the contents necessarily reflect
the views and policies of the U. S. Environmental Protection Agency, nor
does mention of trade names or commercial products constitute endorsement
or recommendation for use.
11
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FOREWORD
The Environmental Protection Agency was created because of increasing
public and government concern about the dangers of pollution to the health
and welfare of the American people. Noxious air, foul water, and spoiled
land are tragic testimony to the deterioration of our natural environment.
The complexity of that environment and the interplay between its com-
ponents require a concentrated and integrated attack on the problem.
Research and development is that necessary first step in problem
solution and it involves defining the problem, measuring its impact, and
searching for solutions. The Municipal Environmental Research Laboratory
develops new and improved technology and systems for the prevention,
treatment, and management of wastewater and solid and hazardous waste
pollutant discharges from municipal and community sources, for the preser-
vation and treatment of public drinking water supplies, and to minimize
the adverse economic, social, health, and aesthetic effects of pollution.
This publication is one of the products of that research; a most vital
communications link between the researcher and the user community.
This research was supported by the EPA so that the Agency will have
the required data base in the event guidelines become necessary for
stabilization technology. This research will provide data to assist in
making sound engineering decisions for the stabilization technology.
Francis T. Mayo
Director
Municipal Environmental
Research Laboratory
111
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ABSTRACT
This report presents an interim summary of current research dealing with
the effects of chemical fixation on disposal of hazardous industrial
waste residues and flue gas desulfurization (FGD) sludges. Present
research involves both leaching and physical tests of raw and chemically
fixed industrial wastes and FGD sludges. The intent of the study is to
examine the potential environmental impact of raw sludge disposal and
to assess the technical merits of sludge fixation as a disposal pretreatment
process. Both objectives are being accomplished by leachate testing,
which can be evaluated by comparison to the raw sludges and by durability
testing, which reflects the environmental stability of the fixed products.
Major points of discussion within this report are the methods for physical
and chemical analyses, documentation of the various sludge fixation
processes, and a discussion of physical and chemical data that are
presently available. Since the project is only partially completed,
parameters and data have been selected that are representative of
current progress. Physical data include the descriptive parameters for
the raw sludges and engineering properties of the fixed sludges that have
been completed. Chemical properties related to leachate testing
include the descriptive parameters pH and conductivity, plus the pollutants
sulfate and copper.
This report is submitted in partial fulfillment of Interagency Agreement
Number EPA-IAG-D4-0569 between the U. S. Environmental Protection Agency,
Municipal Environmental Research Laboratory, Solid and Hazardous Waste
Research Division (EPA, MERL, SHWRD) and the U. S. Army Waterways Experiment
Station (WES). Work for this report was conducted during the period of
January to August 1975.
iv
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CONTENTS
Foreword iii
Abstract iv
List of Figures vi
List of Tables x
Note xi
Acknowledgments xii
I Introduction 1
II Summary 4
III Methods and Materials 5
IV Residue Fixation 13
V Physical and Engineering Properties 32
VI Chemical Properties 54
VII References 103
V
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LIST OF FIGURES
Number Page
1 Raw and Fixed Residues, Number 100 22
2 Raw and Fixed Residues, Number 200 23
3 Raw and Fixed Residues, Number 300 24
4 Raw and Fixed Residues, Number 400 25
5 Raw and Fixed Residues, Number 500 26
6 Raw and Fixed Residues, Number 600 27
7 Raw and Fixed Residues, Number 700 28
8 Raw and Fixed Residues, Number 800 29
9 Raw and Fixed Residues, Number 900 30
10 Raw and Fixed Residues, Number 1000 31
11 Grain Size Distributions, Raw and Fixed Sludges
(100, 200, and 300) 35
12 Grain Size Distributions, Raw and Fixed Sludges
(400, 500, and 600) 36
13 Grain Size Distributions, Raw and Fixed Sludges
(800, 900, and 1000) 37
14 Grain Size Distributions, Raw and Fixed Sludges (600) . 39
15 Specific Gravities of Common Materials Compared
with Raw and Fixed Sludges 41
16 Porosity and Void Ratio of Soils Compared with
Raw and Fixed Sludges 42
17 Compaction Test, Comparison of Soils with
Residues Fixed by Process B 44
VI
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LIST OF FIGURES (continued)
Number Page
18 Densities of Materials Fixed by Process B,
Before and After Compaction 45
19 Unconfined Compression Test, Comparison of
Sludges Fixed by Process E with Concrete 46
20 Unconfined compression Test, Comparison of
Sludges Fixed by Process E with Soil-Cement 47
21 Stress-Strain Curves, Fixed (E-100, E-400, E-500, and
E-1000) 48
22 Stress-Strain Curves, Fixed Residues (C-200, C-700, and
F-600). . . 49
23 Elasticities of Common Materials Compared
With Fixed Sludges 50
24 Results of Wet-Dry-Brush Test, Process E, 4 Cycles. . . 51
25 Results of Wet-Dry-Brush Test, Process E, 12 Cycles . . 52
26 Leachate pH for Raw and Fixed Residues 59
27 Stability of pH with Time, Raw and Fixed Sludges. ... 60
28 Conductivity vs. Time, Raw and Fixed Residues,
Number 100 62
29 Conductivity vs. Time, Raw and Fixed Residues
Number 200 63
30 Conductivity vs. Time, Raw and Fixed Residues
Number 300 64
31 Conductivity vs. Time, Raw and Fixed Residues
Number 400 65
32 Conductivity vs. Time, Raw and Fixed Residues
Number 500 66
vii
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LIST OF FIGURES (continued)
Number
33 Conductivity vs. Time, Raw and Fixed Residues,
Number 600 67
34 Conductivity vs. Time, Raw and Fixed Residues,
Number 700 68
35 Conductivity vs. Time, Raw and Fixed Residues,
Number 800 69
36 Conductivity vs. Time, Raw and Fixed Residues,
Number 900 70
37 Conductivity vs. Time, Raw and Fixed Residues,
Number 1000 71
38 Sulfate Concentration vs. Time,
Raw and Fixed Residues, Number 100. 75
39 Sulfate Concentration vs. Time,
Raw and Fixed Residues, Number 200 76
40 Sulfate Concentration vs. Time,
Raw and Fixed Residues, Number 300 77
41 Sulfate Concentration vs. Time,
Raw and Fixed Residues, Number 400 78
42 Sulfate Concentration vs. Time,
Raw and Fixed Residues, Number 500 79
43 Sulfate Concentration vs. Time,
Raw and Fixed Residues, Number 600 80
44 Sulfate Concentration vs. Time,
Raw and Fixed Residues, Number 700 81
45 Sulfate Concentration vs. Time,
Raw and Fixed Residues, Number 800 82
46 Sulfate Concentration vs. Time,
Raw and Fixed Residues, Number 900 83
Vlll
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LIST OF FIGURES (continued)
Number
47 Sulfate Concentration vs. Time,
Raw and Fixed Residues, Number 1000 84
48 Copper Concentration vs. Time,
Raw and Fixed Residues, Number 100 86
49 Copper Concentration vs. Time,
Raw and Fixed Residues, Number 200 87
50 Copper Concentration vs. Time,
Raw and Fixed Residues, Number 300 88
51 Copper Concentration vs. Time,
Raw and Fixed Residues, Number 400 89
52 Copper Concentration vs. Time,
Raw and Fixed Residues, Number 500 90
53 Copper Concentration vs. Time,
Raw and Fixed Residues, Number 600 91
54 Copper Concentration vs. Time,
Raw and Fixed Residues, Number 700 92
55 Copper Concentration vs. Time,
Raw and Fixed Residues, Number 800 93
56 Copper Concentration vs. Time,
Raw and Fixed Residues, Number 900 94
57 Copper Concentration vs. Time,
Raw and Fixed Residues, Number 1000 95
58 Cumulative Leaching Rate, Residue 200 97
59 Cumulative Leaching Rate, Copper, Residue 200 (C) . . . 98
60 Cumulative Leaching Rate, Copper, Residue 200(R,A,B,D). 99
61 Incremental Leaching Rate, Copper, Residue 200 (R,A,B);101
62 Incremental Leaching Rate, Copper, Residue 200 (C). . .102
IX
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LIST OF TABLES
Number
1 Chemical Properties 7
2 Sample Preservation for Chemical Properties 7
3 Operating Conditions for HGA 9
4 Process-Residue Assignment Matrix 14
5 Process A - Formulation for Residue Fixation 15
6 Process B - Formulation for Residue Fixation 17
7 Process C - Formulation for Residue Fixation 17
8 Process E - Bench Scale Leachate Data 18
9 Process E - Formulation for Residue Fixation 19
10 Process F - Formulation for Residue Fixation 20
11 Process G - Bench Scale Leachate Data 20
12 Process G - Formulation for Residue Fixation 21
13 Physical and Engineering Properties of Raw and
Fixed Sludges 33
14 Comparison of Physical Properties among Soils,
Raw Sludges and Fixed Sludges 38
15 Chemical Properties of Control Columns 57
16 Analysis of Variance for pH, Residue 100 73
17 Analysis of Variance for Conductivity, Residue 100 . . 74
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NOTE
All measurements in EPA documents are to be expressed in metric units.
In the report, however, implementing this practice adversely affects clarity.
Conversion factors for non-metric units used in this document are therefore
given as follows:
British Metric
1 ft2 0.0929 meters2
1 ft3 0.0283 meters3
1 ft3/min 28.316 1/min
1 gpm 3.785 1/min
1 Ib 0.454 kg
1 ton (short) 0.9072 metric tons
XI
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ACKNOWLEDGMENTS
The assistance of the firms and companies which provided samples of residues
and performed fixation and these samples is gratefully acknowledged. With-
out the continued support of these companies, research projects of this
nature could not be successfully performed.
The guidance and support of Mr. Robert E. Landreth and the Solid and
Hazardous Waste Research Division, Municipal Environmental Research Labora-
tory, U. S. Environmental Protection Agency is greatly appreciated.
This project was conducted at the U. S. Army Engineer Waterways Experiment
Station (WES) under the general supervision of Dr. John Harrison, Chief,
Environmental Effects Laboratory (EEL), and Mr. Andrew J. Green, Chief,
Environmental Engineering Division. The Soils and Pavements Laboratory
(S§PL) provided physical property analyses under the direction of Mr. G. P.
Hale; and the EEL Analytical Laboratory Groups, under the direction of Mr. J.
D. Westhoff and Dr. D. W. Rathburn, provided guidance in selection of chemi-
cal testing procedures as well as chemical analysis of the sludges and
leachates used. Technical support in maintaining and sampling the leaching
facilities was provided by Messrs. Oscar W. Thomas, Johnnie E. Lee, and
Jack H. Dildine.
Director of WES during the course of this study was Col. G. H. Hilt, CE.
Technical Director was Mr. F. R. Brown.
Xll
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SECTION I
INTRODUCTION
BACKGROUND
The promulgation of air and water pollution control legislation has brought
about an increase in the efficiency of equipment designed to remove pollu-
tants from air and water discharge streams. The end product of treatment is
usually a solid material, i.e., sludge or residue, that contains the
removed pollutants in a concentrated form. (The terms residue and sludge
will be used synonymously throughout this report.) Until recently, the
disposal of sludge or residue was not considered an integral phase of the
air or wastewater treatment processes. The realization that improper ,
disposal of these residues may result in an adverse environmental impact
has reinforced the concept that proper environmental management and control
must address all aspects of the environment -- air, water, and land. Since
many residues contain pollutants in high concentrations, they may be
referred to as hazardous because of the precautions required for disposal
or handling.
The disposal of hazardous residues may be accomplished in several fashions.
Incineration is useful as a volume reduction process and for complete
destruction of synthetic compounds such as pesticides. Ocean disposal is
practiced where it is feasible and where the environmental impact may be
demonstrated to be small or none. Recovery and reuse of materials from
residues is practiced when technology is available and there is an economic
incentive. This latter concept is not a disposal operation, per se, but may
be equated to a disposal operation by virtue of eliminating or reducing its
need. Other promising treatment and/or disposal processes for hazardous
wastes have been summarized recently.2 Generally, the main receptor for
most residues is the land through a landfill process, or similar disposal
operations such as ponding or abandoned mine filling.
The practice of land disposal of residues is aimed at eventually returning
all pollutants or materials to the environment. In the case of hazardous
residues, the rate of pollutant migration from the disposal site to the
surrounding air, land, or water may exceed that which is considered environ-
mentally safe. Unsafe conditions may arise because of the pollutant con-
centration and its associated mobility for a particular residue, or through
physical, chemical, or biological interaction of the residues with the
surrounding environment. When land disposal of residues results in adverse
environmental impact, further treatment of the residue may be required.
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The principal method of treatment is creation of a barrier between the
disposal site and the surrounding environment by use of a liner, or fixation
of the residue. The use of liners is a feasible alternative and is justi-
fiable when economics are favorable. Possible problems associated with the
use of liners are unfavorable reactions with the residue (which may cause
deterioration) or improper placement (which results in spot leaks). Fixa-
tion is defined as a process that retards the migration of pollutants from
residues to the surrounding environment. As it is currently applied, fixa-
tion may be considered as the addition of materials that react with the
residues or as an encapsulation process. Encapsulation is very similar to
the use of liners in that a physical barrier is provided against pollutant
mobility. In the use of admixing materials with the residues, either
organic or inorganic materials may be used. In this mode, fixation generally
reduces pollutant mobility through alteration of the chemical and physical
properties of the residue. The chemical alterations are quite complex and
are difficult to explain theoretically; however, the physical alterations
generally take place by decreasing the surface-area-to-volume ratio by
formation of a solidified mass. This latter alteration is advantageous in
retarding pollutant migration through mass transport phenomena. The use
of fixation is particularly desirable in the case of hazardous wastes,
where it assures an environmentally proper disposal. The use of fixation
for treatment also has its associated problems. Since fixation generally
depends on a reaction of additives with the residues, it must be tested
in advance to determine whether the desired reaction will take place and
the proper conditions for reactions (viz. mixing, ratio or reagents, etc.).
Additionally, the rate of leaching of pollutants from fixed materials may
not be determined in advance and must be established by testing. Testing
should consider all possible physical, chemical, and biological properties
that may affect fixed material performance. Furthermore, testing should be
performed over a sufficient time frame to allow prediction of future per-
formance for the life of the disposal system. Realistically, it is not
possible to test all system permutations, but testing should be sufficiently
detailed to place confidence on the reliability of fixation in the field.
The physical durability of the fixed material should be determined. Since
alteration of residue geometry, or physical state, may be a chief advantage
of fixation, adherence to those properties under handling or disposal con-
ditions should be evaluated.
Since additional treatment of residues before disposal represents an added
cost for overall treatment, the economics of fixation processes must also
be considered. If economics are to be considered, they must be defined for
each fixation process and in turn related to the potential application of
that process. Generally, the economics may be represented as a tradeoff
between costs and the degree of hazard associated with a particular residue.
The degree of hazard is directly related to the environmental risk associat-
ed with the disposal operation process for a particular residue. Obviously,
the higher the hazard and its risk for disposal, the higher the cost that
may be associated with treatment.
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PURPOSE AND OBJECTIVES
The U. S. Array Waterways Experiment Station (WES) has undertaken, through
an interagency agreement with the U. S. Environmental Protection Agency,
a study directed at examining the potential utility of fixation processes
for application to various sludges to yield products environmentally
acceptable for disposal. The various sludge categories identified within
the scope of work are residues associated with industrial processes and with
flue gas desulfurization (FGD) systems. The specific objectives of the
study are as follows:
(a) To assess on a laboratory scale the pollution potential, leacha-
bility, and physical durability of selected hazardous industrial residues,
FGD residues, and fixed materials from these categories.
(b) To verify the laboratory data by field studies.
To accomplish these objectives, the study has been divided into three
distinct phases: (1) residue characterization and experimental design,
(2) laboratory testing, and (3) field testing. The first phase of the
study was to serve as background for the remaining phases. This phase is
complete and has been summarized in an earlier project report. Phasing
of the project has been designed to build a sufficient data base on which
to base the evaluation of fixation technology. The pollutant potential of
raw sludges has been included for comparative purposes since it represents
an integral part of this study.
SCOPE OF THIS REPORT
The purpose of this report is to summarize the project results from the
last interim report.^ A majority of this report summarizes fixation of
the residue samples by the processors included in the laboratory program.
Since the purpose of the study is to assess fixation technology, neither
the participating processors nor the sources of sludges will be identified
in this report. The remainder of the report will discuss current progress
in physical testing and leach column testing. The data are limited since
the laboratory program is not complete; consequently, those data presented
are only a portion of the results deemed representative of the project.
Since these data were limited at the time of this report, definite conclus-
ions should not be made from the data presented here until all data is
available.
Determination of process economics for fixation is not possible at this
point in time, but the subject will be addressed in the subsequent project
reports. Assessing the economics of several fixation processes for compara-
tive purposes is difficult because of a number of factors. First, it is
extremely difficult to obtain comparable cost data for a specific residue
category. Second, many fixation processes are offered as services and
capital costs are included in the service cost and not considered separately.
Third, possible productive uses exist for some fixed residues that would
offset processing costs.
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SECTION II
SUMMARY
The purpose of this report is to summarize the project results from the
last interim report.3 The data are limited since the laboratory program
is not complete; consequently, those data presented are only a portion of
the initial nine month results deemed representative of the project.
Fixation of residues is characterized by alterations in geometry (surface
area:volume) and changes in chemical environment. Retarding the leaching
of pollutants by chemical fixation is process-dependent, but appears to
be successful (although leaching rates for copper and sulfate are high
for some residues and would probably exhibit an environmental impact).
Leaching behavior for most samples can be related to a diffusion and/or
solubility mechanism and appear to stabilize in time.
Leaching of copper from both raw and fixed residues was demonstrated for
a majority of the samples tested. In most cases, initial leaching was
above background levels (10 vg/&), and some fixation processes were not
successful in retarding the leaching of copper.
Leachate data for most specimens exhibited high initial concentrations of
sulfate (> 1,000 mg/£), followed by a gradual decrease. The leaching of
sulfates is apparently related to solubility, which depends on the compounds
present in specific specimens, particularly the FGD sludges. Fixation
demonstrated an ability to retard sulfate leaching, but concentrations
were high for certain samples.
Conductivities for leachates were strongly dependent on the type of residue,
but observation of high leachate conductivities for most specimens seemed
to indicate leaching of dissolved solids.
In fixed residues, pH seemed to be dependent on fixation additives,
time, and volume of leaching solution applied. Convergence of leachate
pH for raw and fixed sludges as a function of time appears to demonstrate
that stability of the fixed sludges is a function of the volume of leaching
solution applied. The pH of the leachate (for residue 100) was independent
of the type of leaching solution applied, suggesting that pH was mainly
dependent on the type of residue.
Raw sludges are physically characterized to be fine-grained materials of
low density (40-60 PCF), similar in texture to silt and silt-loam. On
this basis, low shear strength (2-8 PSI) and permeability (< 10~4 cm/sec)
are to be expected, although no laboratory testing was conducted for
verification.
Fixation of sludges results in physical alterations that produce a hardened
mass or a soil-like material characterized by increased dry densities
(1-811 increase) and strength; fixed sludge characteristics are strongly
dependent on the fixation process and type of sludge.
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SECTION III
METHODS AND MATERIALS
LEACHING TEST FACILITY
As mentioned previously, the primary concern in ultimate disposal of sludges
is the rate of pollutant migration to the environment. To effectively
determine the rate of pollutant migration, a leaching test has been devised.
This leaching test is aimed at measuring the rate of pollutant movement.
into an aqueous medium, and has been designed to represent field conditions
as closely as possible. Details of this leaching test system have been
previously documented,3 and will only be summarized for this report. The
principle factors to be considered in constructing a leaching facility
include materials for construction of the system; specifications for sample
preparation; and procedures for performing the leaching tests.
The specifications of material for construction are required to assure that
the equipment may be considered inert with respect to the leach specimen
and leachate. Since adequate information was not available regarding pollu-
tant interaction with materials in this study, high grade plastics were
selected for construction materials. To provide further assurances,
adequate measures were taken to clean all materials and to establish con-
trols for detection of any interactions.
The leaching columns are four inches inside diameter (I.D.) and constructed
to contain a sample volume of approximately 0.35 cubic feet. The inlet
port was placed approximately 1 inch above the top of the sample to main-
tain a fluid head of that height on the top of the sample. The columns
were capped to minimize air contamination. The bottom of the column is con-
structed to collect the leachate through an outlet port. Flow through the
columns is regulated by a stopcock to maintain a fluid velocity of approxi-
mately 1 x 10'5cm/sec. This velocity corresponds to the permability
through a very fine sand. A 3-inch layer of polypropylene
pellets was placed in the bottom of each column to retard movement of
suspended solids from the columns. This technique was used since field
conditions will normally provide similar filtration capacity at the
boundary of the sludge. Some of the fixed sludges assumed a definite
physical shape and demonstrated structural rigidity. These samples were
molded into 3-inch diameter forms, placed in the columns, and the annular
ring filled with polypropylene pellets. This procedure created a dispersed
flow around the columns, similar to field conditions. For all leaching
tests, the specimens are maintained in a saturated flow condition.
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Sample collection was made in 1-gallon polypropylene containers sealed
with parafilm.
Two leaching fluids were used, deionized water saturated with carbon
dioxide, pH 4.5 to 5.0, and deionized water buffered with boric acid, pH
7.5 to 8.0. Boric acid was selected since it is relatively inert and
was used in a low concentration as not to effect the leaching properties
of the samples. The two leaching fluids represent both sides of the pH
scale and should provide some concept of the pH effect on leaching.
Each set of columns was fed from a constant head reservoir. Sample
columns were triplicated for each leaching solution and all columns were
randomly assigned within the test system. All materials for the leach
fluid distribution system were polypropylene or teflon to minimize
exchange reactions during the leaching operation.
Two types of experimental control were exercised for the leaching test.
The first type of control used the raw sludges for each residue category
and was arranged in a similar fashion as the fixed sludges. The second
type of control was within the experimental apparatus and utilized
leaching columns in triplicate with and without the polypropylene filler
beads for each leaching fluid.
Before loading the columns with samples, all materials were washed with
a laboratory detergent followed by a rinse with dilute hydrochloric
acid. The entire leaching apparatus was preleached with deionized water
for a 1-week period at the design flow rate. The columns were loaded
with the sample and initially filled from the bottom with leaching fluid
to minimize air entrapment. No provisions were made to retard biological
activity within the leaching apparatus, since the composition of the
samples is such that biological activity is not expected to occur. The
columns are translucent and observations of flow patterns as well as
possible biological activity can be made.
CHEMICAL PROPERTIES
Chemical properties of the leachates from the raw and fixed residues are
classified into descriptive, organic, metals (cationic), and anionic
analyses. The specific analyses included within these grouping are present-
ed in Table 1. These parameters were selected to describe the chemical
properties of the raw and fixed residues and to include all pollutants of
specific interest within a residue category. All samples are analyzed for
the descriptive parameters at each sampling time. The remaining chemical
parameters were screened in all samples initially and analytical efforts
were selectively reduced to a monitoring level in those cases where pollutant
levels were low or considered insignificant. The ALG performed the bulk
of these analyses and managed contract testing.
Sampling
Sampling for leachates is scheduled for one year in a logarithmic fashion.
Twelve samples are to be analyzed at total elapsed times of 7, 14, 21, 28,
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42, 56, 86, 116, 146, 206, 266, and 356 days. The logarithmic sampling
schedule best reflects leach column performance that would be predicted
by mass transport theory.4 Mass transport theory specifies a diffusion
mechanism between the material surface and leaching solution. Although
other reactions may be occurring, the data are evaluated by laboratory pro-
cedures and represent an "effective" diffusivity for a given pollutant.
Behavior of these systems is generally characterized by a stable or a mono-
tomically decreasing leach rate, approaching some limiting value. In this
context, the initial sampling period becomes more critical than the later
stages of leaching, and is best sampled by a logarithmic procedure.
Subsequent to sample analysis of the descriptive parameters, the samples are
split into aliquots and preserved in relation to the analyses to be perform-
ed on the aliquot. The preservation scheme is described in Table 2. Those
chemical parameters not specifically identified in Table 2 for preservation
are either analyzed immediately after collection or require no preservation.
All samples are held at 4°C until analyses are performed.
TABLE 1. CHEMICAL PROPERTIES
Descriptive
Sample volume
Conductivitya
Metals (cations)
Arsenica ,
O f\
Berrylium »D
Cadmiuma»b
Calciuma>b
Chromium? »b
Coppera»b
Leada>b ,
Magnesium '
Mercuryb
Nickela'b
Seleniumb
Organic
€1
Chemical oxygen demand
1_
Total organic carbon"
Anions
Chloridea
Cyanide0
Fluoridea
Nitratea>b
Nitritea>b
Sulfatea»^
Sulfitea'D
TABLE 2. SAMPLE PRESERVATION FOR CHEMICAL PROPERTIES
Parameter Method
b
Metals (cations) Ultrex nitric acid
Cyanide Sodium hydroxide^
Total organic carbon Hydrochloric acid
Chemical oxygen demand Sulfuric acidb
o
Standard Methods for the Examination of Water and Wastewater, 13th
Edition, American Public Health Association, Washington, D. C., (1971).
Methods for Chemical Analysis of Water and Wastes, U. S. Environmental
Protection Agency, Report No. EAP-625/6-74-003, (1974).
/**
Cyanide in Water and Wastewater, Technicon Industrial Method No. 315-
74W, Technicon Company, (1974).
7
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Sample preservation is used to allow some flexibility in programming the
analytical scheduling to obtain maximum efficiency in the laboratory.
Quality Control
To obtain assurance within the analytical program, an extensive quality
control program has been implemented. This quality control program represents
internal, intralaboratory, and extralaboratory procedures. The intra-
laboratory program includes spiked and reference samples within the column
leachate samples. The internal program includes replicate determination
and spike additions to representative samples. The extralaboratory program
was coordinated between the ALG and the U.S.E.P.A. This assurance program
primarily concentrates on the metals, since these pollutants represent the
major group of interest within the project.
Methods for Chemical Analysis
The methods adopted for chemical analyses were selected by the ALG and
reviewed by the U.S.E.P.A. These are described by reference in Table 1.
The methods employed for metal analyses may be classified into two categories.
All samples are first screened by flame atomic adsorption with the exception
of arsenic, selenium, and mercury. If the results of these analyses are
below detection limits, one replicate from the sample group is analyzed by
atomic absorption using the heated graphite atomizer (HGA). The operating
procedures that have been adopted eliminate the need for further sample
handling to reach lower concentrations and rely directly on analytical pro-
cedures are presented in Table 3. Additionally, a portion of the samples
are analyzed by argon plasma emission spectroscopy. This technique has a
lower sensitivity than flame absorption for most metals, and serves as a
check on oJier procedures. Since the major emphasis of the program lies
with the metal analyses, a considerable effort has been expended to select
techniques which maximize analytical throughput while minimizing sacrifices
in precision and accuracy.
PHYSICAL AND ENGINEERING PROPERTIES
In order to preclude any confusion in regard to the terminology used to
describe the raw and fixed sludges, a brief definition of the properties
and parameters cited herein is included in this chapter. All terms and
tests are in standard use for the description and analysis of soils and/or
concrete. Deviations from standard procedures are also noted within
specific discussions; however, standard testing methods were generally
adhered to for purposes of comparing results with literature values. Tests
were performed on fixed residue specimens after a suitable curing period,
as specified by the respective processors, had elapsed.
-------
Table 3. OPERATING CONDITIONS FOR HEATED GRAPHITE ATOMIZER (HGA)
Element
Be Cd Cr Cu Mg Mi Ni Pb Zn As
Wave length, ran 234.9 228.8 357.9 324.7 285.2 279.5 232.0 283.3 218.9 193.7
Drying:
/
Temp, °C 125 120 120 125 125 120 120 120 120 120
Time, sec 30 40 30 50 30 40 50 30 40 50
Charring:
Temp,°C 1200 400 1250 950 1200 1100 1200 500 400 1200
Time, sec 40 30 60 80 30 60 45 60 40 45
Atomizing:
Temp, °C 2800 2000 2600 2700 2000 2400 2500 2000 2500 2700
Time, sec 7 10 7 7 5 5 7 7 5 7
-------
Physical Properties
The following physical properties tests were performed during this study to
determine the physical properties of the sludges:3
a. Grain size analysis
b. Specific gravity of solids
c. Bulk density
d. Dry density
e. Water content
f. Porosity/void ratio
g. Permeability
Grain Size Analysis-The grain size distribution of raw and fixed sludges
was determined by hydrometer analysis. The hydrometer analysis is described
in Appendix V of Engineer Manual (EM) 1110-2-1906^ and in American Society
for Testing Materials (ASTM) designation D 422-19.6 This method, based on
Stoke's Law, involves preparation of a suspension of sludge particles in
water; measurement of the specific gravity of the suspension at specified
time intervals; and correlation of settling velocity, particle diameter, and
time in order to determine the distribution of grain sizes. The results of
this test are plotted to give a particle size distribution curve and are
used to assign the sludges a soil classification according to the Unified
Soil Classification System (U.S.C.S.),5 and according to the textural classi-
fication system employed by the U. S. Department of Agirculture (U.S.D.A.).
Specific Gravity-While there are three types of specific gravity defined
for use in soils engineering, only the specific gravity of solids (Gs)
applies to fine-grained material such as the FGD sludges. The specific
gravity of a sludge is determined by dividing the unit weight of sludge by
the unit weight of water. The test procedure as well as the soils definition
are found in EM 1110-2-1906,5 Appendix IV, and in ASTM D 854-58.6
Bulk Density-The bulk density is the air-dried unit weight, and is deter-
mined by weighing a sample of sludge of known volume and dividing the weight
in pounds by the volume in cubic feet. Bulk density differs from dry density
in that bulk density includes the weight of any interstitial water, while
dry density is determined only after the water has been driven off by oven
drying. The procedure for determining sample volume and weight can be
found in Appendix II of EM 1110-2-190.5
Dry Density-The dry density or dry unit weight is defined as the weight
of oven-dried sludge solids divided by the entire volume of sludge; and is
generally expressed in pounds per cubic foot. Standard procedures for deter-
mining the weight and volume are presented in EM 1110-2-1906, Appendix II.5
10
-------
Water Content-The water content, or moisture content, as the terms are
interchangeable, is defined as the weight of water divided by the weight of
dry solids in a sludge sample and is expressed as a percentage. A sludge
sample of known weight is dried in an oven, and the weight loss is attributed
to loss of interstitial water. This weight loss (water) divided by the
weight of the dry sludge is the water content. Water content is determined
by the method presented in EM 1110-2-19065 Appendix I and in ASTM D 2206-19.6
Porosity/Void Ratio-The void ratio of a specimen of sludge is defined as
the ratio of the volume of the voids in the specimen to the volume of the
solids in the specimen. Porosity is defined as the ratio of the volume of
the voids of the specimen to the total volume of the specimen. Void ratio,
e, is expressed as a decimal, while porosity, n, is expressed as a percent-
age. Porosity and void ratio are related to each other by the following
equations:
n = {e/(l + e)} x 100%
e = n/(l - n);
and the pore volume within any specimen of known volume may be determined by
by either of the following equations:
Vy = n x VT/100%
Vy = e x VT/(1 + e),
where V = pore volume, and
VT = total volume of specimen.
The standard procedure for determining void ratio and porosity are found in
EM 1110-2-1906, Appendix II.5
Permeability-The permeability of a sample is defined as the fluid
velocity which will pass through the sample under a given set of hydraulic
conditions. The procedure for conducting the permability test is currently
under investigation.
Engineering Properties
In order to classify the fixed sludges according to their engineering prop-
erties, a number of standard engineering tests were performed on selected
fixed sludges. These tests included the 15-blow compaction test, unconfined
compression test, and cycles of wetting and drying.
15-Blow Compaction Test-The 15-blow compaction test simulates the com-
pactive effort that might be expected from passing equipment over a placed
landfill, while the Standard Proctor Compaction Test simulates the higher
compactive effort required for fill placed in roadways and in dams. The
15-Blow Test was selected because it is felt that this compactive effort
(> 400 FT-LB/CF) is more representative than that of the Standard Test
11
-------
(12,200 FT-LB/CF) of the compaction that would be achieved for most of the
productive uses of the fixed residues. A study conducted at the WES (Mis-
cellaneous Paper 4-269) concluded that the maximum dry density was 3.4%
higher for the standard test than for the 15-blow test. The 15-blow com-
paction test involves subjecting samples of sludge at different, known water
contents to a specified compactive effort. After application of the com-
pactive effort, the dry density of each sample is determined. The results
of this test are presented in a graph of dry density versus water content.
From this graph, the maximum dry density and optimum moisture content are
determined. Test procedures appear in EM 1110-2-1906, Appendix VI5 and in
ASTM D 698-70.6
Unconfined Compression Test-The unconfined compression test is used to
determine the uniaxial, unconfined compressive strength of a cohesive or
cemented material. A cylindrical specimen is prepared and loaded axially
until failure. The test results are presented as a graph of compressive
stress versus axial strain. The compressive strength is taken as the peak
compressive stress sustained by the sample. The modulus of elasticity (E),
defined as the slope of the stress-strain curve, may also be determined from
the results of the unconfined compression test. The standard testing pro-
cedure, found in Appendix XI of EM 1110-2-1906,5 was followed except that a
height-to-diameter ratio of 2.0 was used instead of 2.1.
Wet-Dry-Brush Test-This test is designed to evaluate the durability of
fixed sludges by subjecting samples to 12 test cycles; each consisting of
wetting, drying, and brushing operations. Results are presented as percent
weight lost during the test. The standard wet-dry-brush test procedure is
given in ASTM D 559-57." Modifications to this procedure included the use
of specimen diameters of three inches instead of four, and specimen heights
of either four or six inches instead of 4.5 inches.
12
-------
SECTION IV
RESIDUE FIXATION
BACKGROUND
During Phase one of the project, nine fixation processes identified as A-1
were selected as candidates for the program. A matrix was prepared assign-
ing each process to either an industrial waste or FGD residue category, or
both. A sufficient sample of each residue type was obtained from its res-
pective source for the laboratory testing program. An aliquot of each
sample was provided to each processor for evaluation at their laboratory
according to the assignment matrix mentioned previously. The purpose for
preliminary evaluation by the processors was to determine compatability
between the fixation process and residue category and to establish optimum
admixture ratios for each residue. Processors E and G delegated respon-
sibility for this latter task to WES under the present program. The results
of these evaluations will be discussed separately in this section.
After this preliminary evaluation phase, two processors, H and I, declined
further participation in the project, generally for logistical reasons.
The remaining processors agreed to fix the residues according to the assign-
ments presented in Table 4. Process D, initially assigned to all residue
categories, was eventually confined to one residue because of economic con-
siderations. The remaining deletions occurred because the processors felt
their fixation method would not be successful given a particular residue
category. It is interesting to note that with the exception of one pro-
cessor, all deletions occurred within the industrial residue categories.
Speculation as to why these deletions were made cannot presently be made
from a theoretical basis due to the complexities inherent in the fixation
process chemistry and lack of specific information regarding certain processes.
At the conclusion of this preliminary evaluation task, the remaining pro-
cessors were scheduled to perform fixation for the laboratory and physical
testing at WES. This arrangement was made to allow project personnel to
observe the actual fixation procedure and to maintain a degree of quality
control consistent with all fixation methods. All fixation procedures
included within the program required a curing time for their product. At
the end of the curing time, the processors were invited to certify that
fixation was adequate, and in some cases, to prepare samples for subsequent
testing.
13
-------
Table 4. PROCESS-RESIDUE ASSIGNMENT MATRIX
Processes
Sludge category
100a
200^
300^
400a
50 of
600.
700.
800i
900f
10001
A
xb
X
X
X
X
X
t
X
X
X
B
X
X
X
X
X
X
"t
X
X
X
C D
X, X
td
X
t
t
E
X
X
X
X
X
F
X
t
t
X
t
G
X
X
X
X
X
fSludge 100 = FGD, lime process, eastern coal.
X = Sludge actually fixed by processor and placed in column.
^Sludge 200 = Electroplating.
t = Sludge evaluated by processor but not fixed for this study.
^Sludge 300 = Nickel/cadmium battery.
Sludge 400 = FGD, limestone process, eastern coal.
feludge 500 = FGD, double alkali process, eastern coal.
vSludge 600 = FGD, limestone process, western coal.
~!"Sludge 700 = Inorganic pigment.
^Sludge 800 = Chlorine production, brine sludge.
i^ludge 900 = Calcium fluoride.
Sludge 1000= FGD, double alkali, western coal.
GENERAL PROCEDURES <
Residue samples obtained for the laboratory study were partitioned into
several aliquots. A portion was used for preliminary evaluation by the pro-
cessors, a portion was used for raw sludge chemical and physical testing, a
portion was utilized for fixation, and the remainder of the sample was saved
for supplementary testing. Sludge samples were stored in sealed, plastic
containers under room conditions. Partitioning of one sample was adopted to
minimize heterogeneity between sample usages which would hamper comparative
evaluation of test data. All sample aliquots were mixed by a Lightning Mixer
in required batch sizes prior to their use.
The fixation processes utilized in this project result in products which
fall into two distinct groupings. The first group is a soil-like material
which is highly variable in particle size and the second is a solid, continu-
ous material. The procedure utilized for the first group consisted of fixing
in a container and molding in square molds containing adequate volume for
the fixed sample (48 x 48 x 3.5 inches). The molds were covered, and after
curing the fixed sample was broken into smaller particle sizes and loaded
into the columns. The second group of samples were molded in 3-inch dia-
meter, paraffin lined tubes, 4 feet in length. Shorter tube lengths were
-------
used in some cases for convenience. After curing, the tubes were stripped
and the resultant cores were placed in columns for chemical testing or
subjected to physical tests. Specific deviation from these procedures will
be discussed under sample fixation.
SAMPLE FIXATION
The intent of this report section is to discuss the actual procedures
utilized for fixation of the residues by process category. Included for
each process is a discussion of the process plus the details relating to
fixation as performed at WES. All weights presented in the succeeding
tables for sludges are as wet weight, and for the remaining compounds on
an as received basis.
Process A-Process A, which is patented, uses flyash and a lime additive
to produce a pozzolan product. Fixation was performed on all sludges except
700. Bituminous flyash was used for the eastern coal FGD sludges, 100, 400,
and 500, and for the industrial sludges; whereas, sub bituminous flyash was
used for western coal FGD sludges 600 and 1000. The availability of flyash
at power plants producing scrubber sludges is one advantage of this process.
A fixed product with a high solids content (80%) is considered optimum, and
dewatering the sludge often reduces the amount of flyash required, parti-
cularly for the scrubber sludges. All sludges that could be dewatered by
decantation were dewatered at WES.
The sludges and fixation agents were mixed using a 5 cubic foot mortar mixer.
The fixed product was then placed into cylindrical molds, covered, and
allowed to cure for 30 days. Inspection of the fixed specimens revealed that
curing in the molds under a dry environment had produced cracks, a situation
which the processor felt was not representative of this process; therefore,
a decision was made to repeat the fixation process. Because of time limita-
tions and convenience to the processor the second fixation was conducted at
the processor's laboratories. In this case, the specimens were placed in
shorter tubes (3 in. x 16 in.) and cured under humid conditions to prevent
drying. The fixed specimens were then shipped to WES for chemical and
physical testing. The processor chose not to reveal the specific additive-
to-sludge ratios for proprietary reasons; however, the percent of dry sludge
solids for each fixed specimen is presented in Table 5. These mixes are
slightly different from larger scale preparations because of the need to
work with small molds. In a field scale operation placement and consolidation
of the sludges would likely be done with construction equipment, hence,
requiring a stiffer, lower moisture content mix.
Table 5. PROCESS A-FORMULATION FOR RESIDUE FIXATION
Residue category Percent dry sludge solids
100 49
200 25
300 21
15
-------
Table 5.-(continued)
Residue category Percent dry sludge sol ids
400 49
500 49
600 57
800 41
900 37
1000 35
Process B-Process B, which is patented, uses two additives to produce
a soil-like material. The proportions of reagents used determine the
hardness of the fixed product. The hardness of the end product is deter-
mined either by ultimate use or the quantity of reagents required to affect
pollutant immobilization. In most cases a soil-like material, which is
more economical, is produced.
The sludge and reagents were mixed in 9 to 14 gallon batches using a Lightning
Mixer. This provided mixing equivalent to that produced by prototype equip-
ment which includes an aerated, continuously stirred reactor and a series of
recirculating and transfer pumps designed to provide complete mixing of the
reagents and sludge. The solids, volumes of sludge, and weight of additives
for the nine fixed sludges are given in Table 6. Molds 4 feet square by
3.5 inches were used to hold the fixed sludge for curing. A polyethylene
cover was used during the curing period (12 days) to prevent excessive
drying. The fixed specimens were broken into smaller particle sizes and
placed in the column without compaction.
Process C-Process C uses an organic resin plus other additives in a
polymerization process to form a solid rubber-like material. The organic
resin is a patented product. Table 7 describes the formulation used for
each batch of fixed material prepared. The reagents were manually mixed
with the sludge using a paddle stirrer. The mixture was then immediately
poured into cylindrical molds after mixing and allowed to cure.
Process D-Process D is an encapsulation method utilizing a resin to
form an agglomerate which is subsequently surrounded by a 0.25- inch
plastic jacket fused to the agglomerate. The process requires a dry
residue for fixation which was provided by WES to the processor's laboratory.
Fixation was performed outside WES because of the specialized equipment
needed to produce fixed samples.
The fixed residue samples provided to WES were cylindrical in shape, 3
inches in diameter and 4 inches in height, each containing approximately
250 grains of dry residue. These cylinders were used as received for all
chemical and physical testing.
16
-------
Table 6. PROCESS B--FORMULATION FOR RESIDUE FIXATION
Residue
Category
100
200
300
400
500
600
800
900
1000
Percent
solids
37.9
34.0
41.2
35.7
43.3
32. la
59.7
44.9
39.6
Volume
fixed
(gallons)
28
28
23
28
27
25
20
28
25
Weight of additives
(Ib/gal of sludge)
1.80
1.10
0.90
1.80
2.10
2.10
1.80
0.90
1.80
^ewatered from 13.4% TS to 32.1% TS for fixation.
Table 7. PROCESS C-FORMULATION FOR RESIDUE FIXATION
Residue category
Item 200 70C
Weight of sludge (g) 4800 4800
Weight of additives (g) 2400 2880
Process E-Process E uses two readily available commercial materials
(additives) to convert waste sludge into a hardened mass similar to concrete.
This particular processor has not devoted extensive research toward this
process because of its conventional nature and the expense of the process,
which may prevent wide application in the field for large volumes of
sludge.
A representative of the company visited WES and furnished guidance on
the method for determining the optimum formulations for fixation of the
five FGD sludges. Laboratory preparation of specimens for evaluation of
the leaching characteristics was demonstrated. The procedure used for
determining the optimum formulation is as follows:
a. Mix small samples (100-200 g) of each sludge with various combina-
tions of additive A and B.
b. Pour each fixed specimen into a mold and allow the specimens to
cure two days.
c. Place each specimen in a 1500 ml beaker, add 1000 ml deionized
water', and stir slowly for 24 hours.
17
-------
d. Analyze the leachate for calcium, sulfates, and conductivity.
e. Select the optimum formulation based on minimum leachability and
integrity of the sample (specimens which disintegrated upon contact with
water were discarded).
A minimum of twelve sludge-additive A, B, combinations for each sludge
were evaluated. Results for the six best combinations are presented in
Table 8. The optimum formulation was based strictly on minimum leachability
without regard to economic considerations.
Fixed samples for the column study were prepared in 20 gallon batches.
Mixing was produced with a Lightening Mixer, except for sludge 500, where
a 4 cubic foot concrete mixer was used. The processor had suggested that
a concrete mixer be used for mixing the reagents with the sludge; however,
the Lightning Mixer provided more efficient blending of the materials.
Conditions for fixation of the five sludges are given in Table 9. After
thoroughly mixing the reagents with the sludge, the mixture was poured
into cylindrical molds and allowed to cure for four weeks at room conditions
before testing.
Table 8. PROCESS E-BENCH SCALE LEACHATE DATA
Additive A Additive B
Sludge -sludge -sludge Calcium Sulfate
number ratio ratio (ppm) (ppm)
Conductivity
Cymhos/on)
100
100
100
100
100
100
400
400
400
400
400
400
500
500
500
500
500
500
600
600
600
600
600
600
0.33
0.34
0.42
0.43
0.50
0.52
0.31
0.32
0.31
0.39
0.40
0.38
0.20
0.20
0.20
0.50
0.50
0.50
0.20
0.20
0.40
0.50
0.50
0.50
0.33
0.51
0.42
0.26
0.25
0.17
0.08
0.16
0.31
0
0.08
0.15
0.10
0.20
0.40
0
0.10
0.20
0.35
0.60
0.35
0.20
0.35
0.50
2300
5200
1900
2000
1800
2100
240
240
190
240
220
250
130
120
610
170
120
160
83
83
30
100
55
48
800
210
660
658
668
598
510
166
186
212
268
185
710
781
565
700
610
540
57
42
39
37
37
34
NA
NA
NA
NA
NA ,
,03x10;
,99x10;
, 68x10;
,02x10;
, 58x10:
2.11x10:
5.
4.
5.
4.80x10:
20xio:
95x10;
ooxio:
5.
4.
1.
1.
1.
1.
1.
20x10.::
20xio::
06xio:;
I2xio:;
02x10:;
31x10^
11x10,
0.99x10'
18
-------
Table 8.-(continued)
Additive A Additive B
Sludge -sludge -sludge Calcium Sulfate
number ratio ratio ' '
Conductivity
fumhos/cnO
1000
1000
1000
1000
1000
1000
0.40
0.50
0.50
0.60
0.60
0.60
0.10
0.10
0.25
0.10
0.25
0.40
*•* * -f- ,
NA
NA
NA
NA
NA
NA
805
542
438
390
344
394
5.59x10^
5.10x10^
4.62x10::
4.60x10:;
4.52x10^
4.41x10
, No analysis.
All 1000 samples included 0.25 parts water per part sludge.
Table 9. PROCESS E-FORMULATION FOR RESIDUE FIXATION
Sludge
no.
100
400
500
600
1000
Weight of
sludge
db)
145
160
193
160
121
Additive A
-sludge
ratio
0.50
0.31
0.50
0.40
0.60
Additive B
-sludge
ratio
0.25
0.31
0.20
0.35
0.40
Water-
sludge
ratio
0
0
0
0
0.25
Mixing Type
time of
(min) mixer
10 Lightning
10 Lightning
45 Concrete
15 Lightning
15 Lightning
Process F-Process F mixes a patented additive, designated herein as
Reagent F, with a sludge at optimum pH to settle the solids in the slurry.
The solid mass cures in the presence of the supernatant for approximately
30 days, forming a hardened clay-like material.
Table 10 lists the formulations and fixation data for sludges 100 and 600.
The pH adjustment was performed and Reagent F, a dry powder, was added
slowly and allowed to mix thoroughly with the sludge. The fixed samples
were poured into cylindrical molds. All the tubes were then enveloped
in polyethylene tents to maintain a humid environment for curing the
specimens. The relatively large amount of free liquid which accompanied
the fixed solids in the tubes resulted in some leakage of liquid through
the walls of the mold thereby reducing the amount of free supernatant
over the samples. This loss of liquid would not occur under field
conditions; however, the samples remained moist and cured to the satisfact-
ion of the processor.
19
-------
Process G-Process G is a fixation technique in which waste sludge
is mixed with an additive which is a waste product from a manufacturing
industry, and the pH of the mixture is adjusted to an optimum value. An
advantage of this process is that the additive and the compound used to
adjust pH are both normally waste materials The processor evaluated
various combinations of materials in his own laboratory and then chose
the two most promising mixtures (labelled a and b) for bench-scale
demonstration at WES. After the fixed specimens had cured to a constant
weight (20 to 30 days) they were leached with deionized water for 72
hours. The conductivity was periodically measured during the leaching
process and reached an equilibrium after 24 hours. The results of
leachate analysis after 72 hours are given in Table 11. The best mixture
was selected on the basis of minimum leachability of calcium, cadmium,
and sulfates. Table 12 describes the fixation conditions for the five
sludges fixed at WES. The fixed sludges were cured in 20 x 3 inch
cylindrical molds for ten weeks prior to testing.
Table 10. PROCESS F-FORMULATION FOR RESIDUE FIXATION
Sludge number
Item 100 600
Total weight (Ib) 229 276
Percent solids 36 40
Percent reagent F 10 10
Wt. reagent F. (Ib) 8.5 11
Final pH 12.9 12.4
Mixing time (min) 30 30
Table 11. PROCESS G-BENCH SCALE LEACHATE DATA
Sludge Calcium Sulfate Cadmium Specimen
number (mg/1) (mg/1) (yg/1) weight (g)
lOOa 500 3250 0.8 160
lOOb 490 2400 1.1 143
400a 380 1760 1.8 140
400b 490 3850 2.6 118
500a 510 4400 3.8 164
600a 470 3750 5.0 129
600b 510 3960 3.3 130
lOOOa 500 7000 5.5 161
lOOOb 450 6000 6.0 146
20
-------
Table 12. PROCESS G-FORMULATION FOR RESIDUE FIXATION
Sludge
number
100
400
500
600
1000
Weight.
sludge
(lb)
74
55
58
50
84
Weight
additive
(lb)
74
55
58
50
84
Final
wt. (lb)
223
178
288
190
360
Percent
solids
36
13
46
20
38
SAMPLE DESCRIPTION
To visualize the effect of fixation upon selected residues, a photographic
record has been prepared for comparison. This record is presented for
residue categories 100 through 1000 in Figures 1 through 10, respectively.
The effect of fixation on physical characteristics is obvious, the
resultant reduction in surface area to volume ratio should intuitively
provide superior chemical performance during leach testing. Most materials
seem to possess reasonable structural properties on the basis of appearance;
physical properties will be discussed in detail in a subsequent section.
21
-------
SLUDGE NO. I 1OO
PROCESS F
Figure 1. Raw and fixed residues, Number 100.
-------
••
SLUDGE NO.I2OO
PROCESS C
Figure 2. Raw and fixed residues, Number 200.
-------
SLUDGE NO. 1300
PROCESS A
Figure 3. Raw and fixed residues, Number 300.
-------
SLUDGE NO. 400
•
PROCESS E
PROCESS G
Figure h. Raw and fixed residues, Number
-------
r.
LUDGE• HO.I500
i
RAW SLUDGE ^ —< PROCESS B
PROCESS A
PROCESS G
Figure 5- Raw and fixed residues, Number 500.
-------
SLUDGE NO. 1600
•
Figure 6. Raw and fixed residues, Number 600.
-------
SLUDGE NO. 700
.
•
Figure 7. Raw and fixed residues, Number TOO.
-------
SLUDGE NO. 800
Figure 8. Raw and fixed residues, Number 800.
-------
SLUDGE NO. 900
Figure 9- Raw and fixed residues, Number 900.
-------
SLUDGE NO.11000
•V
PROCESS G
Figure 10. Raw and fixed residues, Number 1000.
-------
SECTION V
PHYSICAL AND ENGINEERING PROPERTIES
BACKGROUND
One approach to the characterization of chemically fixed hazardous sludges
involves the evaluation of their physical and engineering properties, as
determined by standard tests. Physical properties describe the particle
structure of the sludge, while engineering properties are used to evaluate
the sludge as a mass and to predict its reaction to applied loads. An
evaluation of the effects of the fixation processes on the properties of
the sludges is made possible by conducting physical and engineering properties
tests on samples of sludges both before and after treatment with the chemical
fixing agents, and comparing the results. Furthermore, the properties of the
fixed sludges may be compared with regard to the type of treatment process
used. Additional characterization of the fixed sludges is possibly by com-
paring the properties of the sludges with typical values of the properties
of other, more familiar materials such as soil-cement, concrete, soils, and
some common mineral and rock types.
The purpose of this section is to characterize chemically fixed sludges as
fully as possible by evaluating the physical and engineering properties of
the sludges. The properties of the raw sludges are presented first for com-
parative purposes. The physical and engineering properties of the fixed
sludges are presented next according to the procedure utilized. The last
part of this section deals with potential productive uses of fixed sludges;
however, more detailed investigations are necessary before the potential of
the fixed sludges for productive uses can be fully evaluated. The physical
and engineering properties presented herein are the result of standard tests
which have been discussed previously (Section III); consequently, these
properties reflect only those characteristics determined by these tests.
PROPERTIES OF RAW SLUDGES
Physical properties of the untreated sludges are determined by conducting
eight standard tests, the results of which appear in Table 13. The R-
designated materials are the raw sludges, while the remaining are fixed
sludges, each bearing the specific fixation processes prefix letter
designation. In comparison with soils, the raw sludges are generally of low
density, with the exception of R-300; and except R-200, all are of low water
content. The specific gravities however, are comparable to soils, indicating
that structural rearrangement of the particles should result in densities of
32
-------
TABLE 13. PHYSICAL AND ENGINEERING PROPERTIES OF RAW AND FIXED SLUDGES
oo
oo
PHYSICAL PROPERTIES
ENGINEERING PROPERTIES
IS-Blow
compaction test
Bulkb
Specific* density
Material gravity (lb/cf)
R-100 2.45 51.7
R-200 3.27 63.5
R-300 3.99 157.2
R-400 2.73 63.1
R-500 2.90 52.3
R-600 2.67 89.0
R-700 3.00 55.5
R-800 2.82 64.3
R-1000 2.95 47.4
B-100 2.68 77.0
B-200 2.94 87.1
B-300 3.75 93.2
B-400 2.98 79.4
B-500 2.94 90.8
B-600 2.75 79.6
B-800 2.88 105.9
B-900 2.76 86.2
B-1000 2.81 81.5
C-200 1.81 75.4
C-700 1.80 65.7
E-100 2.64 101.4
E-400 2.73 82.7
E-500 2.77 99.3
E-1000 2.67 82.7
F-600 2.60
Oven-dryb
unit wt
(lb/cf)
50.0
42.4
153.1
61.1
47.1
85.8
50.9
57.4
45.3
41.4
44.1
47.1
36.2
52.2
40.7
80.6
52.0
47.1
50.2
43.2
89.5
76.1
88.2
82.0
_ — —
Waterb
content
(*)
3.3
49.6
2.7
3.2
11.0
3.7
9.1
12.1
4.6
85.9
97.6
97.9
119.5
74.0
95.6
31.4
65.7
73.0
50.2
52. 0
13.0
8.7
12.6
0.9
"* "" ""
Porosityb
(*}
67.3
79.2
38.5
64.2
74.0
48.5
72.8
67.4
75.4
75.3
76.0
79.9
80.5
71.6
76.3
55.2
69.8
73.2
55.6
38.5
45.7
55.4
49.0
50.8
_ __
Voidb
ratio
2.059
3.815
0.627
1.789
2.844
0.943
2.679
2.067
3.065
3.041
3.162
3.970
4.139
2.516
3.218
1.231
2.313
2.724
1.251
1.601
0.801
1.240
0.961
1.033
_ _ _
Wet-dry
1 wt.loss
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
c
c
15.80
15.00
10.85
6.60
"" *"""
Max dry
density*
lb/cf
NA
NA
NA
NA
NA
NA
NA
NA
NA
41.0
46. S
74.3
48. S
49.5
40.4
73.6
59.8
49.8
NA
NA
NA
NA
NA
NA
"
Optimum
moisture
content3
i
NA
NA
NA
NA
NA
NA
NA
NA
NA
91.0
86.5
47.0
74.0
72.0
89.8
39.1
53.8
75.0
NA
NA
NA
NA
NA
NA
198
Uhconfined compression test
Undrained
shear
strength
frsi)
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
374
154
1,287
360
1,110
687
396
Unconfined
compressive
strength
(psi)
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
747
309
2,574
719
2,220
1,374
— — _
Modulus
elasticity^*1
(psi)
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
17,000
10,000
450,000
126,000
310,000
245,000
— — -
Coefficient
of
permeability
(on/sec)
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
?Value determined from one specimen.
Average value determined from three specimens.
'Tangent of "straight" portion of stress-strain curve.
NA -- Not applicable.
-------
the same magnitude as those of soils. The high porosities of the sludges
give an indication of how loosely packed the sludge particles are; in fact,
the total volume of most samples included more than 60 percent voids.
On the basis of the grain size distributions, Figures 11-13, the raw sludges
were classified as silt (ML) under the Unified Soil Classification System;
and as silt and silt loam with the U.S.D.A. system. While no engineering
properties tests were conducted on raw sludge samples, general characteristics
may be predicted. The grain size distributions for the raw sludges show that
a high percentage of the particles pass the number 200 sieve usually indica-
tive of low permeability (< 10~4cm/sec). Strength is also expected to be low.
Soils of low density are generally so loosely packed that little intergranular
friction is developed, and shear strengths are correspondingly low in the
absence of cementation.
Prior to treatment, sludges were characterized by low densities and low water
content, leading to the anticipation of low shear strength (2-8 psi) and low
permeability. (< 10~4 cm/sec). Porosity is high and improvement in the quality
of the sludges should be accomplished by restructuring the particle matrix
to provide a tighter packing arrangement. Comparison of the physical prop-
erties of the raw sludges to soils is presented in Table 14.
PHYSICAL PROPERTIES OF FIXED SLUDGES
Grain Size Distribution and Soil Classification
The grain size distribution of nine sludges treated with process B and of
one sample treated with process F were determined. Each fixed sludge was
given a soil classification of either silt (ML) or silty sand (SM) under the
U.S.C.S system. Sludges fixed with process B were classified loam, or fine
sandy loam under the U.S.D.A system. The grain size curves of the fixed
sludges were plotted on the same graphs as the curves for the corresponding
raw sludges, as shown in Figures 11-13 and Figure 14.
Comparison of the grain size curves for sludges fixed with process B with
those of raw sludges, Figure 11-13, shows that the process had little effect
on the distribution of particle sizes. Particle sizes of the fixed sludges
remain in the same range as those of the raw sludges. It was anticipated
that identical treatment (B) of all sludges might result in some change in
particle size. The change in gradation, though slight, was not uniform for
all sludges fixed with treatment B. There was no change for sludges 500
and 800; the curves for raw and treated sludges plot almost together, crossing
in several places. Treatment of some sludges, though, resulted in a finer
gradation than the corresponding raw sludges (100, 400, and 600); and the
other treated sludges, B-200, B-300, B-900, and B-1000, proved to have a
coarser gradation than the corresponding untreated sludges. All B-treated
sludges remain, however, similar to the raw sludges in texture, and are similar
to silty soils.
-------
U. S- STANDARD SIEVE OPENING IN INCHES
'
U. S. STANDARD SIEVE NUMBERS
I tO 1416 20 30 40 to 70 100 140
SLUDGE 100
GRAIN SIZE JN MILLIMETERS
SLUDGE 200
U,S STANDARD SIEVE OPENING IN INCHES
U. S. STANDARD SIEVE NUMBERS
"
t J
~T "
_j *
__i .
1
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6 *
— -
•-
+
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6
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BJBD
ffii
GRAIN SIZE IN WLUMETERS
Figure 11.
SLUDGE 300
Grain size distributions, raw and fixed sludges
(100, 200, and 300).
-------
U S. STANMKD SIEVE OPCNMG IN INCHES
GRAIN SIZE IN MILLIMETERS
SLUDGE 400
SLUDGE 500
GRAIN SBE IN MILLIMETERS
SLUDGE 600
Figure 12. Grain size distributions, raw and fixed sludges
(400, 500, and 600).
36
-------
GRAIN SIZE IN MILLIMETERS
SLUDGE 800
GRAIN SIZE IN MILLIMETERS
SLUDGE 900
SLUDGE 1000
Figure 13. Grain size distributions, raw and-fixed sludges
(800, 900, 1000).
37
-------
TABLE 14. COMPARISON OF PHYSICAL PROPERTIES AMONG
SOILS, RAW SLUDGES, AND FIXED SLUDGES
Properties
Materials
MaximumNaturalOptimum
Dry Water Moisture
Specific Porosity Void Density Content Content Permeability
Gravity I Ratio (PCF) (%) (%) (on/sec)
Well-graded dense sand
Soft inorganic clay
Soft organic clay
R-100
R-200
R-300
R-400
R-500
R-600
R-700
R-800
R-900
R-1000
B-100
B-200
B-300
B-400
B-500
B-600
B-800
B-900
B-1000
2.65
2.70
2.60
2.45
3.27
3.99
2.73
2.90
2.67
3.00
2.82
2.74
2.95
2.68
2.94
3.75
2.98
2.94
2.75
2.88
2.76
2.81
30
55
75
67.3
79.2
38.5
64.2
74.0
48.5
72.8
67.4
70.0
75.4
75.3
76.0
79.9
80.5
71.6
76.3
55.2
69.8
73.2
0.43
1.2
3.0
2.059
3.815
0.627
1.789
2.844
0.943
2.679
2.067
2.334
3.065
3.041
3.162
3.97
4.139
2.516
3.218
1.231
2.313
2.724
138
112
100
41.0
46.5
74.3
47.2
49.5
40.4
73.6
59.8
49.8
16
45
110
3.3
49.6
2.7
3.2
11.0
3.7
9.1
12.1
5.3 '
4.6
85.9
97.6
97.9
119.5
74.0
95.6
31.4
65.7
73.0
12 10"i
20 10"?
30 10'6
91.0
86.5
47.0
84.0
72.0
89.8
39.1
53.8
75.0
38
-------
SIZE IN MllUMETEHS
0,01 0.005
U. S. STANDARD SIEVE OfCWNG IN INCHES
SLUDGE 600
U.S. STANDARD SIEVE NUMBERS
GRAIN SIZE IN MILLIMETERS
SLUDGE 600
U, SSTUIDMO S1EVI
GRAN SIZE IN MILLIMETERS
SLUDGE 600
Figure 1^. Grain size distributions, raw and fixed sludges
(600).
39
-------
Specific Gravity
In general, treatment of the sludges resulted in little change in specific
gravity. Some values were slightly higher after treatment, and some were
slightly lower, but changes were not process-dependent. Treatment of sludges
200 and 700 with process C resulted in specific gravities considerably
(40 to 50 percent) lower than those of the raw sludges. All specific gravi-
ties are reported in Table 14. Values remain in the range of common minerals
and soils, as shown in Figure 15 and in Table 14.^>9
Bulk Density
Bulk density, or air-dry unit weight, did not exhibit as wide a range of
values after treatment as before treatment. The range of values for all
treated sludges is 65.7 LB/CF to 105.9 LB/CF, while for raw sludges values
ranged from 47.4 LB/CF to 157.2 LB/CF. There were some large reductions, as
well as some increases, in bulk density resulting from treatment; but none
appeared to be dependent upon the type of treatment process.
Dry Density
Dry density, oven-dry unit weight, was generally lower after treatment by
process B, considerably higher after fixation by process E, and not process-
dependent with process C. The dry densities of sludges fixed by process E are
in the range of light-weight clays and silts. All values of dry density for
fixed sludges are presented in Table 13.
Water Content
A large increase in water content resulted from treatment of sludges by pro-
cess B. Water contents for B-treated sludges ranged from 2 to 37 times those
of the raw sludges. One of the fixed sludges, C-200, experienced only a
slight increase in water content (0.6%) while C-700 had a sevenfold increase.
Sludges with process E remained at low water contents in the range of the
raw sludges. All water contents are shown in Table 13.
Porosity/Void Ratio
Porosity and void ratio, reported in Table 13 remained about the same after
fixation with process B. Processes C and E resulted in lower values of
porosity and void ratio. Comparisons of sludges, raw as well as fixed, with
soils in terms of void ratio and porosity are presented in Figure 16^ and
Table 14.9>10
Permeability
At the time of this report, no permeability data were available.
ENGINEERING PROPERTIES OF FIXED SLUDGES
Three standard engineering properties tests were conducted on selected fixed
sludges. The 15-Blow Compaction Test was conducted on nine samples of sludges
ko
-------
1.51
2.5-
6
O
a
Q_
4.5J
- HALITE
- GRAPHITE
- GYPSUM
- KAOLINITE
^QUARTZ
- DOLOMITE
FLUORITE
HORNBLENDE
3.5- -DIAMOND
AZURITE
SIDERITE
- CORUNDUM
-C-700
x
-R-IOO
N
kl
-B"ionR'60Qj E-IOOO
i&Afr40<*. E'40(i
^ E?§00~B-900 S'6
B-IOOO
600
I — B-800
R_500
=.B-400
B-200, B-500
R-700
R-IOQO
R-200
UJ
QC
B-300
R-300
Figure 15. Specific gravities of common materials
compared with raw and fixed sludges.
-------
c
fr
ro
)
0.
1
33
POROSITY,
0.50 0.60 0.67
OTTAWA
SAND
i
UNIFORM SILT
I
SANDY OR SILTY CLAY
1
WELL-GRADED
GRAVEL, SAND,
SILT, CLAY
MIXES
i
CLAY (30 50% CLAY SIZES)
I
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j
III
II
COLLOIDAL CLAY (-0
r
c
r
<1 3)
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3 0(
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r
n cor
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(
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0.71 0.75 0.78 0.80
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t
(
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t
0.5
1.0
1.5
2.0 2.5
VOID RATIO, e
3.0
3.5
Figure l6. Porosity and void ratio of soils compared with
raw and fixed sludges
4.0
4.5
-------
fixed with process B to determine the density-moisture relationships of the
fixed sludges. The compressive strengths of specimens of sludges treated by
processes C, E, and F were determined by performing the Unconfined Compression
Tests. Durability of sludges fixed with processes C and E was determined by
the wet-dry-brush test.
Compaction Test
Results of the compaction test, reported in Tables 13 and 14 and in Figure 17,
show that sludges fixed with process B exhibit low dry densities and high
optimum moisture contents (CMC), when compared to basic soil types. The
high values of CMC might be partially attributed to the presence of hydrates
within the sludge matrix. A comparison of the dry densities of sludges fixed
with process B before and after the application of the compactive effort of
the 15-blow compaction reveals that in some cases (B-300, B-400, and B-900)
a more dense material resulted. Furthermore, samples B-100 and B-600 were LS
unaffected by the test; and two samples, B-500 and B-800 had higher densities
before the compactive effort. This comparison, presented in Figure 18
indicates that some difficulty may be anticipated in field compaction of cer-
tain fixed sludges.
Unconfined Compression Test
The compressive strengths of samples of sludges fixed with processes C, E,
and F were determined by an unconfined compression test. Additionally, the
modulus of elasticity was determined from the stress-strain curve for each
sludge treated. Sludges fixed with processes C or E lost their soil consist-
ency and became quite hard; undergoing a cementation process. Compressive
strengths of sludges fixed with process E, Table 14, are comparable to those
of low strength concrete (3000 psi at 28 days). Figures 19 and 2012'1-3 show
comparisons between concrete and sludges fixed by process E, and between soil-
cement and samples fixed by process E, respectively. The stress-strain curves
also show that sludges fixed with process E are brittle; failure occurred at
low strains. Sludges fixed with processes C and F however, failed at very
high strains indicating an elastic consistency, though compressive strengths
were lower than the sludges fixed with process E. Figures 21 and 22 show
the stress-strain curves for fixed sludges. These curves were used to deter-
mine the modulus of elasticity, E, of the samples. In this case, E was deter-
mined to be the tangent of the "straight" portion of the stress-strain curve,
as illustrated in Figure 23.14 The values for E are reported in Table 13.
Wet-Dry-Brush Test
This test of durability was performed on samples fixed by processes C and E.
The sludges fixed by process E performed fairly well, as compared to the
sludges fixed by process C, which failed during the first cycle. Figures 24
and 25 show the samples after 4 and 12 cycles respectively. The weight loss
determined for samples fixed by process E are reported in Table 13.
-------
120
100
h
U.
D
U
V)
z
Ul
Q
IT
D
40 60 80
WATER CONTENT, %
100
120
Figure 17« Compaction test, comparison of soils with
residues fixed by process B
-------
100 200 300 400 500 600 800 900
TYPE SLUDGE FIXED WITH PROCESS B
1000
LEGEND
O MAXIMUM 7j (15-BLOW COMPACTION TEST)
D 7d (PRIOR TO COMPACTION TEST)
Figure 18. Densities of materials fixed by process B,
before and after compaction.
-------
3000
0.5
1.0
AXIAL STRAIN, %
1.5
2.0
Figure 19-
Unconfined compression test, comparison of
sludges fixed by process E with concrete.
Notes: 1. Solid Lines Are Typical Stress-
Strain Curves for Concrete of Compressive
Strength Shown. 2. Each Sludge Curve Is
Average of 3 Specimens. 3. Compressive
Strength of Concrete Determined After 28 Days
of Curing.
-------
3000
2500
2000
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AXIAL S1KAIN, %
1.5
2.0
RESIDUE E-100
RESIDUE E-400
liOOO
3000
1000
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0.5
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AXIAL STRAIN, %
1.5
2.0
2OOO
1500
500
°O 1.0
AXIAL STRAIN,")
1.
2.0
RESIDUE E-500
RESIDUE E-1000
Figure 21. Stress-strain curves, fixed sludges (E-100,
, E-500, and E-1000).
1*8
-------
AXIAL SIXAIN, %
300
100
10
AXIAL S1HAIN, %
RESIDUE C-200
RESIDUE C-700
flftO ,-f.
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AXIAL ST1AIN, %
RESIDUE F-600
Figure 22. Stress-strain curves, fixed residues (C-200, C-700,
and F-600).
-------
4.0
3.5
3.0
CO
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O
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CO
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UJ
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AXIAL STRAIN, € , IN/IN
DEFINITION SKETCH
E-IOO
E-500
E-IOOO
E-400
C-700
C-200
Figure 23- Elasticities of common materials compared
with fixed sludges.
50
-------
SLUDGE TESTING
E- 100
SPECIMENS 1-3
SLUDGE TESTING
E- 500
SPECIMENS 1-3
SLUDGE TESTING
E- 1000
SPECIMENS 1-3
SLUDGE TESTING
E- 400
SPECIMENS 1-3
-
SLUDGE TESTING
C- 200
SPECIMENS 1-3
SLUDGE TESTING
C- 700
SPECIMENS 1-3
Figure 2U. Results of wet-dry-brush test, processes E and C, k cycles
-------
SPECIMEN SPECIMEN SPECIMEN
2 3
E-100
SPECIMEN
1
SPECIMEN
2
E-400
SPECIMEN
3
SPECIMEN
1
SPECIMEN
2
E-500
SPECIMEN
3
SPECIMEN SPECIMEN SPECIMEN
' 2 3
C-200
SPECIMEN
1
SPECIMEN
2
C-700
SPECIMEN
3
SPECIMEN
1
SPECIMEN
2
E-1000
SPECIMEN
3
Figure 25. Results of wet-dry-brush test, processes E and C, 12 cycles
-------
PRODUCTIVE UTILIZATION OF FIXED SLUDGES
On the basis of the currently available data, speculation may be made regard-
ing the productive usage of fixed sludges. The possibility of productive use
of fixed sludges is of merit since it would offset treatment costs. The
sludges treated with process B may find use as sanitary landfill cover and in
other landfill applications, though shrinkage, swelling, cracking and erosion
may be problem areas on the basis of data presented herein. Sludges fixed
by processes C and E become quite hard, and this may lead to their utilization
as a substitute for low strength concrete. Such substitution might include
using these fixed sludges as roadway base courses, runway and taxiway aprons
and shoulders, or molding into useful shapes such as bricks, blocks, or drain
tiles.
53
-------
SECTION VI
CHEMICAL PROPERTIES
GENERAL COLUMN BEHAVIOR OF SAMPLES
Chemical properties are being investigated through the use of leaching
columns which has been described earlier.^ The leaching columns are
constructed of translucent plastic which allows routine observation of
the samples during the leaching period. During the current study period,
certain physical changes in sample behavior within the leaching columns
have been observed. The purpose of this subsection is to relate these
observations to possible chemical and/or physical properties of the raw
or fixed residues.
Leaching Solution
The rate of fluid application to the leaching columns is controlled to
an approximate fluid velocity range of 10~^ to 10"6 on/sec. This control
has generally been achieved for all samples of fixed residues, due to
flow patterns established for these leaching columns. The control of
permeability for the raw sludges columns has been more difficult since
their permeabilities are a function of the residue category and not
control methods. For some of the residues (e.g. 200 and 300), the
permeabilities appear to be extremely low which resulted in difficulties
in collecting adequate sample volumes for analysis. Permeabilities of
the raw sludges will be determined by independent testing to obtain
comparative values for all residue categories. The obvious implication
to environmental impact is that residues which possess low permeabilities
will produce low volumes of leachate. Depending on the concentrations
of pollutants in the leachates and quantities of sludge disposed, a low
volume of leachate production suggests that ponding may be an environmentally
suitable disposal method. Permeabilities of the fixed specimens are
lower than the raw sludges; consequently, the laboratory design for
leach testing reflected this fact. The use of a system in which the
fixed specimens are surrounded by a more porous medium is similar to
what would be expected under field conditions. The fixed residue would
be exposed to less water in the field than an equivalent amount of raw
sludge because of a reduced permeability and surface area exposed.
Permeability also has a bearing on the performance of specimens in leaching
columns if pollutant mobility is motivated primarily by a diffusion
mechanism.^ For a diffusion mechanism, a high leach solution flow will
produce a maximum leaching in terms of mass of pollutant per unit time;
-------
whereas a low leach solution flow (or static test) results in a maximum
concentration of a pollutant per unit time. Thus, the choice of a continuous
versus static leach test is made on the basis of which bound (maximum) con-
trols. Each of these alternatives has an associated environmental impact,
but for toxic pollutants the latter condition would prevail in most cases.
In this study the fluid velocity for the leaching has been adjusted to the
minimum rate feasible under present limitations of the experimental facilities.
Due to limitations of the hardware, it was difficult to regulate fluid
velocity of the leaching solutions precisely. The volume of sample collected
is measured and velocities may be calculated assuming constant flow during
the sampling period. Spot checks of leach fluid velocities for the facility
have demonstrated variations between columns. The effect of these variations
upon leachate quality has not been determined; it, however, is probably
minimal for the range of rate used in this study.
Physical Characteristics
During the period covered in the report, several physical alterations were
noted for certain specimens in the leaching columns. Generally, there have
been color changes exhibited by some of the raw sludge samples. The degree
of color change is inconsistent between replicates and usually is evident
only in the top few centimeters of the solids. At this time, it is unknown
whether these qualitative changes are a function of chemical or biological
actions. The former is more suspect because most of the residues currently
tested lack sufficient organic carbon to support biological growth. Addi-
tionally, most residues contain chemical constituents that would be detri-
mental to most microorganisms. The effect of these subtle quality changes
are probably not of the extent that could be quantitated by the present
analytical program.
The specimens for residue 400 fixed by process B demonstrated an obvious
physical deterioration during the leach testing. Process B results in a
product with a coarse particle distribution resembling a soil-like material.
The deterioration for these specimens was manifested by a gradual consoli-
dation of the particles into a gelatinous mass. This physical change was
almost complete at the end of 90 days exposure in the leaching column and was
uniform for all replicates. This obvious physical change was equated to
process failure for this residue; consequently, this particular residue was
reprocessed and the testing program initiated again. Reprocessing was
accomplished by adjusting the additives/residue ratio and appears to have
been successful.
Specimens for residue 400 fixed by process E demonstrated a swelling reaction
upon exposure to the leaching solutions. Specimens fixed by process E are
molded into cylindrical shapes for testing. In this case the swelling was
so severe that the leaching column was ruptured. The swell reaction was
assumed to be complete at this point and the specimens were loaded into
new columns and testing continued; no additional swell reaction has been
observed. The swelling reaction has not been observed for other processes.
This particular reaction is being investigated in detail to determine
its possible implications to engineering properties.
55
-------
The physical changes noted during the present testing program have been
documented for their possible effect on process performance. Ultimately,
this information should be related to quantitative data available from leach
testing to ascertain performance effects. Some of these physical changes
are probably related to process control for fixation of specific samples;
therefore, they may not necessarily reflect on optimum process performance.
Conversely, some physical changes may be related to testing procedures and
these would be significant in interpreting process performance.
CHEMICAL PROPERTIES
General Chemical Characteristics
The chemical properties of the raw and fixed sludges were investigated by
leaching columns. The chemical properties of leachates discussed within this
report include pH, conductivity, sulfate, and copper. These parameters were
selected as being representative of the leaching data available. Two leaching
solutions were used and all specimens were tested in triplicate. Column
assignments were made at random throughout the system and control (blank)
columns were included. Replication allows determination of the error for a
given sample, while inclusion of blanks allows establishment of background
noise for the analytical tests and assessment of general system reliability.
Data for the blank columns have been included within the specific results
presented in this section but are summarized for the pH 4.7 leaching solution
in Table 15. This data demonstrates that background levels for the parameters
discussed are very low. These results are reported as the means for the
replicate control columns. Data from the control columns may be utilized
in two ways. First, since it represents background for the chemical properties,
it may be used to establish whether leach rates are significantly different
from those of the control columns. For the data from columns containing
fixed samples, this is particularly important to determine whether leaching
of a given chemical is actually occurring. Second, the control columns are
assigned randomly throughout the system; therefore, low levels for analyzed
parameters indicate high system reliability (i.e., no feeder line leaks or
crossflow). For the chemical properties included in this report, the system
reliability is high.
Volumetric leach rates (leach solution fluid velocity) for the columns are
important for assessing mass leach rates (mass of pollutant leached per
unit time). In most cases the volumetric leach rates for the raw residues
are lower than those for the fixed residues. This means that interpretation
of leach data on the basis of pollutant concentration (equal leachate con-
centrations for raw and fixed specimens) indicates mass leach rates for
fixed specimens are higher, implying that presentation of leach data in
terms of concentration is conservative for the fixed samples. Comparison
of raw and fixed sludges in a field disposal operation by the above manner
must also consider the relationship to the natural event producing the
leachate. If rainfall or water influx into the disposal area produces
leachate, the volumes produced from fixed residues may be smaller than
those produced from raw sludges because of reduced permeability and the
-------
geometric scale factor between laboratory and field situations. For small
volumes of fixed sludge, the control will lie in the permeability of the
material surrounding the sludge, but for large volumes (or areas) control will
lie with the permeability of the fixed residue. In summary, for laboratory
studies mass leach rates may conceivably be higher for fixed sludges than
raw sludges, but interpretation of these results in terms of environmental
impact in the field must consider differences in the physical configurations
of these two systems. An advantage of presenting data in terms of mass
leach rates is that the problem of variable volumetric leach rates is
eliminated. Presentation of concentration gives more readily understandable
data, especially in terms of potential environmental impact, and this method
will be used preferentially in this report.
Table 15. CHEMICAL PROPERTIES OF CONTROL COLUMNS
Parameter Mean Value
pH 5.6 units
Conductivity 97 umhos/cm
Sulfate 8.0 mg/1
Copper 6.6 yg/£
A critical problem in understanding potential environmental impact of residue
disposal is the chemical and physical form of the material being leached.
This is particularly true for the metals which may be transported as soluble,
complexed, or colloidal species. The philosophy behind the present study is
to assess pollutant movement from a disposal site containing either raw or
fixed sludges. The disposal site is defined as that region containing the
residue and excluding all surrounding areas. In this case, it is feasible
that a majority of the pollutants leached from the columns are not in the
soluble form. This fact may be confirmed by noting that the solubilities
for some metals in an alkaline pH are far below the detection limits of
analytical procedures employed.
For the copper data presented in this report this means that most of the
metal is being transported in the complexed or colloidal state. The
environmental impact of these species is not well defined; consequently,
the overall impact of these leaching tests may only be indirectly determined.
Additionally, since most of the specimens exhibit complex chemical properties,
antagonistic and synergistic effects must be addressed.
Descriptive Parameters
The descriptive parameters included in the chemical properties are pH and
conductivity. The pH of the leaching solution is directly related to the
solubility of the metal pollutants and conductivity is proportional to the
dissolved solids present in the leachate. These parameters were measured
to give an overview of the chemical status with respect to the leachates.
57°
-------
An analysis of these parameters by residue category should result in partial
understanding of the basic behavior for the system.
gH-Plots of pH by sludge category for raw and fixed specimens are present-
ed in Figure 26. These plots are based on mean values for all leachate repli-
cates, over the present sampling period, from the pH 4.7 buffered leach solu-
tion. The plots are intended to present a spatial representation of pH for
comparative purposes between all samples.
The displacements with respect to the raw sludge location on a given plot
are consistent for all but one residue category. An ordered arrangement can
be made between processes relating this displacement to increasing pH. This
ordering with respect to pH results inB>E>F>A>D>C for the res-
pective processes. An exception to this ordering occurs for sludge 500 where
E > B > A; in this case the locations for E and B are nearly equal, Figure 26.
The relative position of the raw sludges with respect to the above ordering
is related to the pH of the raw residues. Those residues characterized
by a high pH (> 12), result in an ordering ofR>B>E>F>A>D>C.
All remaining residues result in an ordering B>E>F>A>R>D>C.
Because the ordering is consistent between all sludges, it would tend to
imply that the effect of the processes is consistent between all residues.
The concept would tend to greatly simplify evaluation of fixation processes
for different types of residues.
For all residues except 300 and 500 the latter ordering presented above may
also be related to fixation methodology. Processes B, E, F, and A essentially
utilize inorganic additives and lie above the position for the raw residue, R.
Process D, an encapsulation process, and process C, which utilizes an organic
additive, both lie below the position for the raw residue, R. Generally, one
effect of fixation processes utilizing inorganic additives seems to be eleva-
tion of pH. The relationship of process D with respect to ordering probably
does not relate to a specific effect on leachates since it is an encapsulation
process. The relationship for process C to ordering cannot be related speci-
fically to an organic process.
The above data implies that a predominant effect on leachate solutions by
fixation may lie with pH changes. This concept should be related to observed
pollutant mobility, particularly for the metals which are less mobile at a
high pH due to formation of insoluble hydroxides. The effect of fixation
upon leachates is more complex than stated above, but the pH effect is one
which can be documented by observed data.
Stability of pH Measurements-If the concept of fixation motivated pH
changes on leachate behavior is accepted, the stability of these effects
should be documented. The stability of these effects is important because
of potential implications on disposal and longevity of the fixation process.
An example of the pH stability exhibited by one of the fixation processes
is presented in Figure 27. It can be observed that the pH of the raw
residue is fairly stable with respect to time. In contrast the pH of the
fixed residue is initially distinct from the raw residue but the curve is
converging with raw residue. This behavior is obviously related to elution
58
-------
vn
(
RESIDUE
CATEGORY
too
200
300
400
500
600
700
800
900
1000
PH
> 1 2 3 4 5 6 7 8 9 10 II 12 13 1-
1 1 1 1 1 1 1 1 1 1 1 1 1
RAW SLUDGE A
FIXATION PROCESS JJ H
A
V V V V
C DAB
A
v 9
A B
4
V V V
A E B
A
V V V
A BE
A
V V VV
AF EB
A
V
C
A
V V
A B
A
V V
A B
1 1 1 1 1 1 1 1 1 1 A 1 1 1
V V V
A E B
Figure 26. Leachate pH for raw .and fixed residues.
-------
14
12
10
I
Q.
-D O-
50
LEGEND
A FIXED SLUDGE
D RAW SLUDGE
i i i
100 150
ELAPSED TIME, days
200
250
Figure 27. Stability of pH with time, raw and fixed sludges.
60
-------
and the volume of leaching solution applied. These data have been observed
for other specimens, but do not necessarily reflect the behavior of all
systems tested to date.
If the convergence of the pH curves, Figure 27, represents realistic behavior
for the leaching systems, then there exists some time at which the pH for
the raw and fixed residues will be similar. At this point the leach behavior
of the two systems should be similar if the pH effect predominates for a
given fixation process. Observance of this type of behavior can be related
to quantities of leach solution applied and a calculation of the time for
convergence may be made. If the pH effect is not predominant, then this
behavior will not be observed.
Conductivity-The conductivity of the leachate is a function of the
dissolved solids present and is presented by residue in Figures 28-37, res-
pectively. The data presented are the means for all replicates of the pH
4.7 leaching solution. The conductivities for the raw sludges appear to
be highly variable as a function of time, but the trends are either stable,
(residues 100, 200, 300, 400, 500, and 900) or decreasing (residues 600, 700,
800, and 1000). The conductivities for the fixed residues are also variable,
but generally appear to be decreasing with time. The above noted behavior
is consistent with theoretical behavior which would predict decreasing con-
ductivity (dissolved solids) in the leachates as a function of time. The
rate at which the conductivity decreases is a function of available material
for dissolution and the application rate for leaching solutions. Those
residue categories exhibiting a stable conductivity as a function of time
are characterized by more available solids for dissolution than those
residues demonstrating a decreasing conductivity. The rate of conductivity
decrease is related to the state of materials with respect to dissolution.
Those residue categories which show rapidly decreasing conductivities, residues
800 and 1000 (Figures 35 and 37), possess contaminants which are more soluble
than the remaining residues. As a consequence the pollutants are leached
from the columns rapidly and the measured conductivities reflect this release
rate.
The relationship between conductivities for the raw and fixed specimens for
a particular residue are of interest for comparative purposes. In some cases
conductivities for the fixed materials are equivalent to conductivities of
the raw residues, (e.g., residues 100, 500, 600, 700, 800, and 900). This
indicates that fixation does not substantially affect the conductivities of
the leachates. In other cases, (e.g., residues 200 and 300) the conductivi-
ties are improved by fixation. In the case of process D, encapsulation, the
conductivity is not significantly different than that of the effluents from
the control (blank) columns. The converse of the above represents the third
situation (e.g., residues 400 and 1000) where the conductivities of the
leach solutions increased as a result of fixation. For residue 400, Figure
31, this would seem to indicate that the additives utilized in fixation were
responsible for deterioration in leachate conductivity. This fact may also
be responsible for stability of the fixed leachates for the first case
through selective retention of some contaminants, but release of compounds
associated with the fixation additives. For residue 1000, Figure 37, the
leachates from the fixed residues demonstrate a significantly higher conduc-
61
-------
150,000
100,000
o
-C
E
10,000
u
o
o
o
1000
100
PROCESS A
PROCESS B
PROCESS E
PROCESS F
RAW SLUDGE
I I I
40
80 120 160
ELAPSED TIME, days
200
240
Figure 28. Conductivity versus time, raw and fixed residues:
Number 100.
62
-------
150,000
100,000
>-
t-
o
§
o
10,000
1000
100
A
A
•
7
D
LEGEND
PROCESS A
PROCESS B
PROCESS C
PROCESS D
RAW SLUDGE
J_J L
40
80 120 160
ELAPSED TIME, days
200
240
Figure 29- Conductivity versus time, raw and fixed residues:
Number 200.
-------
150,000
100,000
10,000
>-
K
>
O
O
o
o
1000
100
— \
40
LEGEND
& PROCESS A
A PROCESS B
D RAW SLUDGE
I I
80 120 160
ELAPSED TIME, days
200
240
Figure 30.
Conductivity versus time, raw and fixed residues:
Number 300.
-------
150,000
100,000
I
ft
o
H
>
o
o
o
o
10,000
1000
100
A PROCESS A
A PROCESS B
O PROCESS E
T PROCESS G
0 RAW SLUDGE
40
80 120 160
ELAPSED TIME, days
200
240
Figure 31. Conductivity versus time, raw and fixed residues:
Number 1*00.
-------
150,000
100,000
E
o
(0
o
i 10,000
K
>
o
o
o
1000
100
LEGEND
A PROCESS A
A PROCESS B
O PROCESS E
D RAW SLUDGE
I I
40
80 120 160
ELAPSED TIME, days
200
240
Figure 32. Conductivity versus time, raw and fixed residues:
Number 500.
66
-------
150,000
100,000
E
o
-------
150,000
100,000
E
o
in
o
_c
E
10,000
o
o
o
o
1000
100
Figure
LEGEND
• PROCESS C
D RAW SLUDGE
I I
40
60 120 160
ELAPSED TIME, days
200
240
Conductivity versus time, raw and fixed residues:
Number 700.
68
-------
150,000
100,000
10,000
>
I-
>
H-
O
O
o
1000
LEGEND
A PROCESS A
A PROCESS B
D RAW SLUDGE
100
40
60 120 160
ELAPSED TIME, days
200
240
Figure 35.
Conductivity versus time, raw and fixed residues:
Number 800.
-------
150,000
100,000
10,000
>-
K
>
U
Q
O
O
1000
100
LEGEND
A PROCESS A
A PROCESS B
0 RAW SLUDGE
40
60 120 160
ELAPSED TIME, days
200
240
Figure 36. Conductivity versus time, raw and fixed residues:
Number 900.
70
-------
150,000
A PROCESS A
A PROCESS B
0 PROCESS E
0 RAW SLUDGE
100
Figure 37-
80 120 160
ELAPSED TIME, days
200
240
Conductivity versus time, raw and fixed residues:
Number 1000.
71
-------
tivity than the raw leachate after the initial leaching period. This observa-
tion may be related to the ability of the fixed residues to retain a certain
portion of the readily soluble compounds in the raw sludge, but is subject
to a threshold release rate upon leaching. This is a definite advantage for
fixation because the environmental impact of leaching at a decreased rate for
a particular residue is probably lessened.
Conductivity is proportional to dissolved solids in the leachates, but no
quantitative relationship exists for the specimens tested. Conductivity does
reflect the general quality of the leachates; consequently, it should be
related to the release patterns of other pollutants. The observation that
most leacnates demonstrated relatively high conductivities indicates that they
are leaching dissolved solids and may have an environmental impact.
Analysis of Descriptive Data
To reinforce the conclusions stated previously and to analyze the effect of
experimental design upon leachate behavior, the data from a selected residue,
100, was subjected to an analysis of variance. The design used included all
replicates for six time periods, two leaching solutions, and four sludge
treatments (one raw and three fixed). This design constituted a repeated
measure testing on all these descriptive parameters.15,16
The results of analysis of variance for pH are presented in Table 16. The
most significant sources of variance are residue, treatment, time, treatment-
time interaction, and treatment-leachate-time interaction. These results
would tend to confirm the conclusion that there is a definite pH effect upon
residue fixation and that this effect is a function of time (pH convergence
on sustained leaching). The sources of variance representing leaching
solution applied, treatment-solution interaction, and time-solution interaction
possess only one significant term. This fact implies that leachate behavior,
with respect to pH, is independent of the leaching solutions used in this
experiment. Since most of the raw and fixed residues demonstrate a strong
buffering capacity, the effect of pH in the leaching solution upon column
effluent is small and would support the practice of leach testing with one
solution. The difference between the two leaching solutions used in this
experiment is not great (e.g., pH 4.7 vs. pH 7.7); therefore, these effects
may become significant if leaching solutions of extreme pH ranges were
utilized.
72
-------
Table 16. ANALYSIS OF VARIANCE FOR pHL Residue 100
Source
Residue treatment (s)
Leaching solution (L)
Time(T)
SxL
SxT
LxT
Error
SxLxT
Error
Sum
of
squares
242.1
14.3
12.1
6.2
17.9
2.1
45.5
12.9
28.3
Sum
of
freedom
3
1
5
3
15
5
16
15
80
Fa
28.35***
5.00*
6.80***
0. 74ns
3.37***
1.18ns***
2.42**
Probabilities for significance
P < 0.001
**, P < 0.01
*, P < 0.05
ns, not significant
The results of the analysis of variance on conductivity are presented in
Table 17 and may be directly related to the results displayed in Figure 28.
The sources represented by treatment, time, and treatment-time interaction
are significant. This tends to validate the conclusion that fixation affects
the conductivity of the leachate and this effect is a function of time. The
sources of variance represented by leaching solution-treatment interaction,
and solution-time interaction are not significant. These results are similar
to those for pH, and demonstrate that leachate quality, as measured by con-
ductivity, is independent of the leaching solution used in this experiment.
73
-------
Table 17. ANALYSIS OF VARIANCE FOR CONDUCTIVITY: RESIDUE 100
Source
Residue treatment (S)
Leaching solution (L)
Time (T)
SxL
SxT
LxT
Error
SxLxT
Error
Sum
of
squares
4.87x10*?
9.41x10°
1.97x10°
8.62xlO«
2.17x10®
6.38x10
11.8x10 7
1. 94x10 '
1.59xl08
Degrees
o£
freedom
3
1
5
3
15
5
16
15
80
pa
22.0***
1.28ns
19.84***
0.39ns
7.29***
0.64ns
0.65ns
Probabilities for significance
***, P < 0.001
**, P < 0.01
*, P < 0.05
ns, not significant
The statistical analysis presented in this section relates to only one residue
category and represents a limited sampling. While the results of this analysis
support those conclusions previously discussed for residue 100, it is not
appropriate at this time to imply that similar analyses would support other
conclusions. It is noteworthy that the effect of leaching solution used in
this experiment does not significantly affect results for the descriptive
parameters. This indicates that the inherent properties of the specimens
dominate the chemical properties of leaching. If this relationship holds for
the remaining chemical properties, it will significantly reduce the testing
required.
Sulfate-The sulfate concentrations in the column leachates are presented
by residue category in Figures 38-47, respectively. Sulfate was selected
for presentation in this report since it represents a major anionic species
present in the residues, particularly the FGD sludges. The data for the raw
sludges, except 300 and 700, show high concentrations of sulfate in the
leachates (concentrations which exceed those desirable for normal water
quality). In these cases the sulfate concentrations are stable with respect
to time or demonstrate a decrease. This fact is possibly coupled to the solu-
bilities of the sulfate compounds existing in the residues, the more soluble
forms being leached at a high, rapid rate, and the less soluble forms being
limited by solubility to a relatively stable leach rate. Those residues
reflecting the former condition include 800 and 1000, and those reflecting
the latter include 100, 200, 400, 500, 600, and 900. Both 800 and 1000,
Figures 45 and 47, are characterized by fairly stable leach rates for sulfate
after a high initial leach rate. This is presumably related to transition
from a soluble sulfate form, which is readily leached, to a form which is leach-
ed at a solubility limited rate. The plots for residues 300 and 700, Figures 40
and 44, are highly variable and do not exhibit any trends which appear to be
significant.
-------
50,000
10,000
tr
E
•>
IL)
1000
100
10
Figure 38.
t
H
*~*~w
— I
i v
— i
— \
— i
— i
/ \
/ \
LEGEND
A PROCESS A
A PROCESS B
0 PROCESS E
• PROCESS F
D RAW SLUDGE
-fe-e-
I I
I
I I
40
80 120 160
ELAPSED TIME, days
200
240
Sulfate concentration versus time, raw and fixed residues;
Number 100.
-------
50,000
10,000
o>
E
*
Id
5
U.
_l
D
V>
1,000
10
Figure 39-
It
II
H—?*
— I
I
I
— I
LEGEND
A PROCESS A
A PROCESS B
• PROCESS C
V PROCESS D
D RAW SLUDGE
40
80 120 160
ELAPSED TIME, days
200
240
Sulfate concentration versus time, raw and fixed residues:
Number 200.
-------
50,000
10,000
1,000
13
OT
100
10
A
A
D
LEGEND
PROCESS A —
PROCESS B
RAW SLUDGE
-jJ—-1-A--1—L
40
80 120 160
ELAPSED TIME, days
200
240
Figure kO. Sulfate concentration versus time, raw and fixed residues:
Number 300.
77
-------
50,OCX)
10,000
IT
E
tn
1000
100
10
• •
= 8
LEGEND
A PROCESS A
A PROCESS B
O PROCESS E
D RAW SLUDGE
I I
1
40
SO 120 160
ELAPSED tlME, days
200
240
Figure Ul. Sulfate concentration versus time, raw and fixed residues:
Number
78
-------
50,000
10,000
cr
E
^
Id
§
D
1000
= !,' V^
100
10
_ i
!i x
:
r^<.
LEGEND
A PROCESS A
A PROCESS B
0 PROCESS E
D RAW SLUDGE
40
60 120 160
ELAPSED TIME, days
200
240
Figure U2. Sulfate concentration versus time, raw and fixed residues:
Number 500.
79
-------
50,000
10,000
cr
E
1000
100
tof ^°-
n
E S
\— i ^>
"— — n n — -
; ^
—
LEGEND
10
t
-
1 1
A
A
0
1 1
PROCESS A —
PROCESS B _
PROCESS F
RAW SLUDGE _
1 1 1
40
80 120 160
ELAPSED TIME, days
200
240
Figure k3. Sulfate concentration versus time, raw and fixed residues:
Number 600.
80
-------
50,000
iopoo
IT
E
**
UJ
V)
1000
100
10
1
_J
\
\
2
I
h- I '
i I
h- I I
I I
I I
I I
I I
-*t-
II
i
LEGEND
PROCESS C
RAW SLUDGE —
I i J I L
40
80 120 160
ELAPSED TIME, days
200
240
Figure UU. Sulfate concentration versus time, raw and fixed residues;
Number TOO.
81
-------
50,000
lopoo
tr
E
LJ
1000
100
10
40
LEGEND
u
—
I
1 1
\
\
\
\
\
\
\
1 V
A
A
0
1
PROCESS A _
PROCESS B
RAW SLUDGE _
1
80 120 160
ELAPSED TIME, days
200
240
Figure 1*5- Sulfate concentration versus time, raw and fixed residues:
Number 800.
82
-------
50,000
iopoo
1000
u
_J
100
10
LEGEND
A PROCESS A
4 PROCESS B
D RAW SLUDGE
I i I i L
il i
40
80 120 160
ELAPSED TIME, days
200
240
Figure k6. Sulfate concentration versus-time, raw and fixed residues:
Number 900.
83
-------
50,000
PROCESS A
PROCESS B
PROCESS E
RAW SLUDGE
80 120 160
ELAPSED TIME, days
200
240
Figure Uj.
Sulfate concentration versus time, raw and fixed residues:
Number 1000.
-------
Examination of Figures 38-47 demonstrates that fixation seems to be effective
in retarding sulfate mobility from the residues. The retardation is in
relationship to the sulfate mobility exhibited by the raw sludges. Most of
the fixed specimens were characterized by sulfate leaching, in many cases
at high concentrations, at a rapidly decreasing rate (e.g., Figure 42).
This behavior indicates that very soluble forms of sulfate are not retained
by fixation, and are initially leached from the fixed residues.
Some of the sulfate leach data for fixed residues, Figures 38, 39, 41, and
43, demonstrate a decline in sulfate concentration in the leachate initially
but appear to be increasing at the latter stages of leaching. This observa-
tion cannot be confirmed since there is not sufficient data at present to
reestablish a trend. If a trend is established, it may be related to a shift
in equilibrium resulting in increased sulfate availability. A possible shift
in equilibrium has been noted earlier with respect to the temporal pH shift.
Copper-Copper data are presented in this report as an example of the
leachate behavior for a metal. The results for copper are presented by residue
category in Figures 48-57, respectively. Reported values are the means of all
replicates. Except for low level (< 20 ppb) data for the raw residues the
leaching of copper is stable or data well behaved for all residues. Well-
behaved leaching is defined by a decreasing concentration versus eluted volume.
In some cases the data are variable for raw sludges, Figure 52, but there is
insufficient data for this case to determine a probable trend. The suggested
water quality limit for copper is 1.0 mg/£^0 g^ oniy One raw residue, Figure
49, demonstrated a leachate that exceeds this standard in a consistent manner.
The leachate behavior for the fixed residues exhibited three definite patterns.
All fixation processes demonstrated leaching of copper in some manner. For
some of the residue categories the fixed specimens possessed well-behaved
leaching characteristics and the concentration of copper decreased to low levels
rapidly. A low level of copper would be approximately 10 ppb, which is below
the detection limit of conventional flame atomic absorption, and is probably
not environmentally significant since copper is a required micronutrient.
Furthermore, levels of copper below 10 ppb are probably not significantly
different from blank columns, Table 15. In the case of residues 100, 400, 700,
and 800, the leaching of copper is equivalent to, or slightly greater than the
raw sludges, but appears to be increasing with time. This fact again alludes
to the apparent pH shift which is occurring for fixed residues with respect to
time. In the case of residue 200, an interesting observation may be made
regarding the different types of fixation processes. Process B is performing
roughly equivalent to the raw sludge, process D in a superior fashion, and
process C in a fashion worse than the raw sludge. This divergence in process
behavior for a particular residue demonstrates the effect of fixation process-
ing on leaching properties of a product.
To present a more complete understanding of the leaching behavior for copper,
the data for residue 200 are presented as mass leach rates.4 The mass leach
rates were evaluated by use of the following equations:
85
-------
5.0
o.
Q.
UJ
ft
8
.100
.010
LEGEND
A PROCESS B
O PROCESS E
• PROCESS F
D RAW SLUDGE
.001
40
80 120 160
ELAPSED TIME, days
200 240
Figure ^8. Copper concentration versus time, rav and fixed residues:
Number 100.
86
-------
IOO.O
10.0
a
a.
ac
u
a.
o
.100
.010
-
\
i
4 L.I
40
V
D
LEGEND
PROCESS B
PROCESS C
PROCESS 0
RAW SLUDGE
80 120 160
ELAPSED TIME, days
200
240
Figure k9. Copper concentration versus time, raw and fixed residues:
Number 200.
87
-------
5.0
a
a.
ft
8
1.0
-
.100
— \
.010
.001
Figure 50.
LEGEND
A PROCESS A
A PROCESS B
D RAW SLUDGE
I
40
8O 120 160
ELAPSED TIME, days
200
240
Copper concentration versus time, raw and fixed residues
Number 300.
-------
5.0
1.0
Q.
Q.
£E
Ul
ft
o
o
.100
.010
.001
A
e n
/1
/1
LEGEND
A PROCESS A
A PROCESS B
O PROCESS E
0 RAW SLUDGE
40
SO 120 (60
ELAPSED TIME, days
200 240
Figure 51. Copper concentration versus time, raw and fixed residues:
Number UOO.
89
-------
a
a.
u
a.
.100
LEGEND
A PROCESS A
A PROCESS B
O PROCESS E
D RAW SLUDGE
.001
40
SO 120 160
ELAPSED TIME, days
200
240
Figure 52. Copper concentration versus time, raw and fixed residues:
Number 500.
90
-------
5.0
1.0
= ?
—_ |
_ I
_ I
— I
Q.
a.
cc.
u
8
.100
.010
.001
LEGEND
A PROCESS B
O PROCESS E
• PROCESS F
D RAW SLUDGE
40
60 120 160
ELAPSED TIME, days
200
240
Figure 53. Copper concentration versus time, raw and fixed residues:
Number 600.
-------
10.0
e7
—i /i
1.0
a
a.
cr
u
a
ft
o
.100
.010
.001
LEGEND
• PROCESS C
D RAW SLUDGE
40
60 120 160
ELAPSED TIME, days
200 240
Figure 5^. Copper concentration versus time, raw and fixed residues:
Number 700.
-------
10.0,
1.0
Q.
Q.
.100
o
u
.010
LEGEND
A PROCESS A
A PROCESS B
0 RAW SLUDGE
.001
40
80 120 160
ELAPSED TIME, days
200
240
Figure 55. Copper concentration versus time, raw and fixed residues:
Number 800.
93
-------
5.0
1.0
a
a.
.100
.010
.001
I I
LEGEND
A PROCESS A
A PROCESS B
D RAW SLUDGE
I I I
40
BO 120 160
ELAPSED TIME, days
200
240
Figure 56. Copper concentration versus time, raw and fixed residues:
Number 900.
-------
Q.
Q.
••
IT
Ul
O
PROCESS A
PROCESS B
PROCESS E
RAW SLUDGE
.010
.001
60 120 160
ELAPSED TIME, days
200
240
Figure 57. Copper concentration versus time, raw and fixed residues:
Number 1000.
95
-------
V versus
A s
o
Cb) ^n versus (E tn)1/2
A
o
^ * an . V . 1_ versus (t - t
A s t
o n
Where: a = Species mass lost during leaching period, (mg)
Ea = Sum of all a
n n
A = Initial species mass in column, (mg)
V = Volume of specimen, (cm )
2
S = Exposed surface area, (cm )
t = Duration of leachant renewal period
n r
Et = Sum of t
n n
The first two equations, (a) and (b), present the data as cumulative amounts
of any species lost for a leaching period. In this fashion, the total
amount of any particular species lost for a leaching period may be deter-
mined graphically. The third method (c), presents results for each leaching
period separately; therefore, it has the advantage of not being dependent on
past analysis, eliminating any cumulative bias due to experimental errors.
Note that methods (a) and (c) include the volume to surface area ratio in
the presentation of results. This technique assumes that the surface area
to volume ratio is one of the controlling factors for leaching and also
allows comparison of results among columns using different fixation techniques.
In this manner, the success of the applied fixation techniques may be com-
pared graphically. Volume to surface area ratios were approximated from
sample geometry and the additives of fixation were assumed to add no copper
to the residue (mass dilution).
Cumulative leach rates are plotted against time and the square root of time
in Figures 58-59 and 60, respectively. Figures 58-59 include the exposed
volume to surface area term within the cumulative fraction leached. Compari-
son between the leaching properties of the raw and fixed sludges may be made
from these plots, but some caution must be exercised in doing so. The
effect of the volume to surface area ratio for the plots will be pronounced
when comparing data from the raw sludges against the fixed. The plots of
cumulative leach rates for method (a), Figures 58-59, demonstrate that
leaching is approaching an equilibrium point, as characterized by the tendency
to approach constant values for fraction cumulatively leached. The plots
of cumulative leach rates for method (b), Figure 60, have the advantage of
96
-------
u
*
UJ
OC
U
IT
bJ
Q
UJ
O
g
I
u.
u
10'
10'
3 id8
I01
LEGEND
A PROCESS A
A PROCESS B
D RAW SLUDGE
20 40 60 80 100
ELAPSED TIME, days
120
140
Figure 58. Cumulative leaching, rate, copper: Residue 200 (c)
versus time (R,A,B).
97
-------
£
u
UJ
-------
3 XIO'2
i r
2XIO-2
i xicr
•PROCESS C
IX 10'
Figure 60.
2 4
SQUARE ROOT OF TIME, (days
Cumulative leaching rate, copper: Residue 200
versus square root of time.
99
-------
assuming a linear form. The assumption of a linear form permits calculation
of an "apparent" leach rate from the slopes of these plots. The results
of this calculation result in an ordering for leaching of B < R < B < C.
This ordering may be compared to that obtained from the concentration data,
Figure 49 which results in D"< B < R < C. In making this comparison, it
should be noted that the total mass of pollutant (e.g. copper) present in
the leached samples is much greater for the raw sludges than for the fixed
specimens; consequently the cumulative fraction leached would be expected to
be low in relation to the fixed specimens. These observations are not con-
sistent with the ordering presented for pH (C < D < R < B) demonstrating the
effect of sample geometry upon evaluation of leaching data. This inconsist-
ency may, in the case of D, be related to the fact that D is an encapsulation
process and does not behave in the same manner as the other processes with
respect to leaching. The point of agreement between pH and copper leaching
may be related to the pH effect discussed previously.
The incremental leach rates are plotted in Figures 61 and 62. These data
include the elapsed time between column sampling periods and consequently
are not subject to cumulative errors as were the previous plots, Figures
58-60. The data for all residues, fixed and raw, are reasonably well
behaved. These plots also indicate that leaching is approaching a stable
state and demonstrate the effect of surface area alteration.
100
-------
UJ
t-
o:
i
u
UJ
o:
u
z
PROCESS A
A PROCESS B
D RAW SLUDGE
40 60 80 100
TIME, (t-tn/2), days
Figure 6l. Incremental leaching rate, copper: Residue 200 (R,A,B).
101
-------
10'
E T
I
o
UJ
tr
I
ui
i
10'
ro-
10"
\/
_*__
f--.
LEGEND
PROCESS C
20 40 60 80
TIME, (t-tn/2), days
100
120
140
Figure 62. Incremental leaching rate, copper: Residue 200 (c).
102
-------
SECTION VII
REFERENCES
1. Lazar, E. C., "Summary of Damage Incidents from Improper Land Disposal,"
Proceedings of the National Conference on Management and Disposal of
Residues from the Treatment of Industrial Wastewater. February 5-5, (1975),
Washington, D. C. ~~~~
2. Landreth, R. E., Promising Technologies for Treatment of Hazardous
Wastes, U. S. Environmental Protection Agency, Report No. EPA-670/2-74-
088, (1974).
3. Mahloch, J. L., Progress Report on Chemical Fixation of Hazardous Waste
and Air-Pollution-Abatement Sludges, U. S. Army Waterways Experiment
Station, January (1975).
4. Godbee, H. W. and Joy, D. S., Assessment of the Loss of Radioactive
Isotopes from Waste Solids to the Environment; Part I:Background and
Theory, Oak Ridge National Laboratort, Report No. ORNL-TM-4333, Oak
Ridge, Tennessee, (1974).
5. Laboratory Soils .Testing, Engineer Manual 1110-2-1906, U. S. Army Office,
Chief of Engineers (1972).
6. Annual Book of ASTM Standards, Parts 11 and 12, American Society for Test-
ing and Materials, Philadelphia, PA, (1973).
7. The Unified Soil Classification System, Technical Memorandum No. 2-357,
Bol., I, U. S. Army Engineer Waterways Experiment Station, Vicksburg, MS,
(1950).
8. Hough, B. K., Basic Soils Engineering, 2nd Edition, Ronald Press, New
York, (1960).
9. Terzaghi, K., and Peck, R. B., Soil Mechanics in Engineering Practice,
2nd Edition, John Wiley and Sons, New York, (1967).
10. Leet, L. D., and Jusdon, D., Physical Geology, Prentice Hall, 4th Edition,
Englewood Cliffs, NH, (1971).
11. Notes for Earthwork Inspector's Course, Soils and Pavements Laboratory,
U. S. Army Engineer Waterways Experiment Station, (1973).
12. Winter, G., et al, Design of Concrete Structures, 7th Edition, McGraw-
Hill, New York, (1964).
103
-------
13. Unconfined Compressive Strength of Soil-Cement Mixtures, Technical
Memorandum No. 198-1, U. S. Army Engineer Waterways Experiment Station,
Vicksburg, MS, (1942).
14. Jastrzebski, Z. D., Nature and Properties of Engineering Materials, John
Wiley and Sons, New York, (1959).
15. Sokal, R. R. and Rohlf, F. J., Biometry, W. H. Freeman, San Francisco,
(1969).
16. Dixon, W. J., ed., BMD-Biomedical Computer Programs, University of
California Press, Berkeley, (1971).
17. Davis, T. R. A., Burg, A. W., Butters, K. M., and Wadler, B. D., Water
Quality Criteria Data Book, Volume 2 - Inorganic Chemical Pollution of
Freshwater, U. S. Environmental Protection Agency, Report No. 18010-
DPV-07/71, (1971).
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/2-76-182
3. RECIPIENT'S ACCESSIOWNO.
4. TITLE AND SUBTITLE
POLLUTANT POTENTIAL OF RAW AND CHEMICALLY FIXED
HAZARDOUS INDUSTRIAL WASTES AND FLUE GAS DESULFURIZA-
TION SLUDGES - INTERIM REPORT
5. REPORT DATE
July 1976 (Issuing Date)
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
8. PERFORMING ORGANIZATION REPORT NO.
J. L. Mahloch, D. E. Averett, M. J. Bartos, Jr.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Environmental Effects Laboratory
U.S. Army Engineer Waterways Experiment Station
Vicksburg, Mississippi 39180
EHE624 COS
11. CONTRACT/GRANT NO.
IAG-D4-0569
12. SPONSORING AGENCY NAME AND ADDRESS
Municipal Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
13. TYPE OF REPORT AND PERIOD COVERED
Interim Jan. - Aug. 1975
14. SPONSORING AGENCY CODE
EPA-ORD
15. SUPPLEMENTARY NOTES
Robert E. Landreth, Project Officer 513/684-7871
16. ABSTRACT
This report presents an interim summary of current research dealing with the
effects of chemical fixation on disposal of hazardous industrial waste residues and
flue gas desulfurization (FGD) sludges. Present research involves both leaching and
physical tests of raw and chemically fixed industrial wastes and FGD sludges. The
intent of the study is to examine the potential environmental impact of raw sludge
disposal and to assess the technical merits of sludge fixation as a disposal pre-
treatment process. Both objectives are being accomplished by leachate testing, which
can be evaluated by comparison to the raw sludges and by durability testing, which
reflects the environmental stability of the fixed products.
Major points of discussion within this report are the methods for physical and
chemical analyses, documentation of the various sludge fixation processes, and a dis-
cussion of physical and chemical data that are presently available. Since the project
is only partially completed, parameters and data have been selected that are repre-
sentative of current progress. Physical data include the description parameters for
the raw sludges and engineering properties of the fixed sludges that have been com-
pleted. Chemical properties related to leachate testing include the descriptive
parameters pH and conductivity, plus the pollutants sulfate and copper.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Wastes, Stabilization, Leaching, Sludge,
Ground Water, Permeability, Pollution,
Sulfates, Sulfites
Leachate, Solid Waste
Management, Flue Gas
Cleaning, Chemical
Stabilization (Fixation)
13B
3. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (ThisReport)
UNCLASSIFIED
21. NO. OF PAGES
117
20. SECURITY CLASS (Thispage)
IJNrT.ASSTFTF.n
22. PRICE
EPA Form 2220-1 (9-73)
105
*USGPO: 1976 — 657-695/5468 Region 5-11
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