&EPA
Office of Water &
Waste Management
Washington D.C. 20460
SW802
October 1979
Comprehensive Sludge Study
Relevant to Section 8002(g)
of the Resource Conservation
and Recovery Act of 1976
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COMPREHENSIVE SLUDGE STUDY RELEVANT TO SECTION 8002(g)
OF THE RESOURCE CONSERVATION AND RECOVERY ACT OF 1976
An Executive Summary
This report (SW-802) describes work performed
for the Office of Solid Waste under contract no. 68-01-3945
and is reproduced as received from the contractor.
The findings should lie attributed to the contractor
and not to the Office of Solid Waste.
U.S. ENVIRONMENTAL PROTECTION AGENCY
1979
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This report was prepared by SCS Engineers, Long Beach, California under
contract 68-01-3945. Project Officer in the Office of Solid Waste was
Jon R. Perry.
Publication does not signify that the contents necessarily reflect the
views and policies of the U.S. Environmental Protection Agency, nor does
mention of ccmmercial products constitute endorsement by the U.S. Government.
An environmental protection publication (SW-802) in the solid waste
management series.
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CONTENTS
Preface i i
Figures i i i
Tables iv
Ac know! edgements vi
I. Introduction 1
II. Highlights of Project Findings 3
Pollution Control Sludge 3
Quantities of Pollution Control Sludge 3
Disposal of Sludge 6
Energy Recovery from Sludge 10
Reclamation of Sludge-Damaged Areas 11
III. Capsulated Summary of Project 12
The Pollution Control Laws and their Effect
on Sludge Generation 12
Quantities of Sludge Generated in Response
to Federally Enacted Pollution Control
Legislation 21
An Evaluation of Current Methods of Sludge
Di sposal 49
Energy Recovery from Thermal Reduction of
Sludge 76
Reclamation of Sludge-Damaged Areas 79
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Preface
This report presents results of a survey and study carried out pursuant
to Section 8000(g) of Public Law 94-580, the Resource Conservation and Recovery
Act (RCRA), to evaluate the probable quantities and disposition of sludges
generated as a result of federally enacted pollution control legislation.
Sludge, for the purpose of this report, includes all solid, semisolid,
or liquid residue generated frcm municipal and industrial wastewater and
municipal water supply treatment plants, air pollution control facilities,
and new energy source processes. The three Federal acts considered in the
study are the Clean Air Act (PL 91-604), the Clean Water Act (PL 93-500),
the Safe Drinking Water Act (PL 93-523). The report also assesses the
effectiveness and environmental, health, and economic impacts of the
disposal of these sludges.
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FIGURES
Number Pa<
1 Pollution Control Sludge Generation by Major
Generators as a Result of Implementation of
the Clean Air Act, Clean Water Act, and Safe
Drinking Water Act by EPA Region, 1977 and
1987 (million dry metric tons) 4
2 Total EPA Region Municipal Wastewater Treatment
Sludge Generation for Period 1967-1987 27
3 Distribution of Municipal Water Treatment Sludge
by EPA Region for 1967, 1977, 1980, 1984, and
1987 31
4 National Generation of Water Pollution Control
Sludge for 18 Industries 34
5 Total EPA Region Industrial Wastewater Sludge
Generation for 1977 and 1987 38
6 Total EPA Region Air Pollution Control Sludge
Generated for 1977 and 1987 42
7 Flow Diagram of the Windrow Composting 57
8 Flow Diagram of the Aerated Pile Composting 58
9 Schematic Diagrams of Four Sludge Incinerator
Configurations 65
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TABLES
Number Page
1 Environmental Impacts of Several Sludge
Disposal Alternatives 7
2 Evolution of Drinking Water Regulations Under
Section 1412 of the Safe Drinking Water Act...... 13
3 EPA Regional Municipal Wastewater Treatment Sludge
Generation Totals by Treatment Classification
for Period 1967-1987 25
4 Total Quantity of Municipal Water Treatment
Sludge Generated by EPA Region for the Period
1967-1987 29
5 Industrial Categories Subject to Regulations
Under the Clean Water Act of 1977 32
6 Estimated Wastewater Treatment Sludge Generation
by the Twelve Largest Sludge Producing
Industries for 1967, 1977, and 1987 36
7 Estimated Air Pollution Control (APC) Sludge
Generation by Thirteen of the Largest Sludge
Producing Industries 40
8 Estimated Quantities of Air Pollution Control (APC)
Sludges Requiring Disposal 41
9 Existing Biomass Sources 46
10 Cost Analysis for Land Burial of Wastewater
Solids (1975 dollars) 52
11 Comparison of Alternative Methods for Handling
Secondary Sludge from a Large City 54
12 Value of One Metric Ton of Dry Sewage Sludge
Under Alternative Levels of Nutrient Content
and Commercial Fertilizer Prices 55
13 U.S. Cities Presently Composting Sludge 59
iv
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TABLES (continued)
Number Page
14 Quantities of Sewage Sludge Dumped in the
Atlantic Ocean, 1973-1977 61
15 Summary of Planned and Operating Systems Designed
for Solid Waste and Sludge Co-incineration 73
16 Treatment Options for Specific Contaminants 80
17 Water Treatment Methods 84
18 Soil Treatment Methods 87
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I. INTRODUCTION
In recent years, public concern has focused on the environ-
mental problems facing the nation. In response, Congress has
considered and passed significant environmental legislation,
including The Clean Air Act (PL 91-604), The Safe Drinking Water
Act (PL 93-523), and The Federal Water Pollution Control Act (PL
92-500). Each of these statutes has been instrumental in remov-
ing pollutants from the air and water. The result has been the
production of large quantities of pollution control sludges,
which has, in turn, contributed to a national awakening to the
need for ensuring the safe disposal of these residues.
Recent studies have revealed some of the ramifications of
our present waste disposal methods to the land. There has been
special emphasis on the impacts of landfills, the most common
method of disposal, and on pits, ponds, and lagoons. Improperly
operated sanitary landfills can become breeding grounds for
disease vectors, contribute to ground water pollution, and
degrade the American landscape.
Some problems are minor and easily remedied through proper
design and'operating techniques. However, others, such as
ground water contamination from leachate, can have severe and
long-term implications. It is estimated that between 39 and 50
percent of the U.S. domestic water supply is derived from ground
water sources. When ground water becomes contaminated, removal
of contaminants can be costly and the health of various species,
including man, is endangered.
Replacements for completed land disposal sites are diffi-
cult to locate in urban areas, and transportation costs for
wastes requiring land disposal are expected to rise. Thus, an
increase in the overall costs of land disposal is foreseeable.»
Congress is aware of the needless waste and pollution of
the nation's land resources through inadequate disposal prac-
tices. Recognizing that present disposal methods are notaalways
environmentally or ecologically sound, Congressional interest in
alternative methods of treatment, transportation-, and disposal
of solid wastes, including sludge, has been aroused. In"
addition to finding alternative methods of disp'bsa.l of sludge to
land, a relatively new emphasis has been placed upon the
development of combustion technology as an environmentally sound
method for utilizing sludge as an energy source.
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In passing the Resource Conservation and Recovery Act of
1976 (RCRA), Congress has taken a major step toward controlling
the disposal of wastes to the land. Subtitle H of RCRA promotes
coordination of research and investigation related to improve-
ment in the safe disposal of waste materials. Under Section
8002(g) of Subtitle H, Congress has authorized the EPA
Administrator to conduct a comprehensive study of sludge,
addressing the following areas of concern:
The types of solid waste which are to be identified as
siudge
The extent to which air, water supply, and water pollution
control legislation could result in the generation of
additional quantities of these sludges
The quantities of sludge generated within each state and
by each industry
The methods currently in use to dispose of sludge,
including an evaluation of the efficiency,
effectiveness, and cost of each disposal method
The potential for alternative uses of sludges, such as
agricultural application or energy recovery
t The analysis of available methods for reclaiming areas
which have been used for the disposal of sludge.
The executive summary which follows provides the findings
from a report, "A Comprehensive Sludge Study," prepared by SCS
Engineers, addressing those items as described under Section
8002(g) of RCRA. The report should provide information useful
to Congress, private industry, states, and municipalities in
planning for and developing environmentally sound disposal
methods for pollution control residuals and solid wastes
generated from new energy source processes. It is only through
the broadening of our present knowledge of the sources of
wastes, their composition and quantity, and problems which have
arisen through past disposal practices, that the dangers from
the improper management of solid and hazardous wastes can be
recognized and diminished. Just as important is the need to
discuss new approaches to land disposal, and to identify other
methods for managing large quantities of organic sludges by
exploring the potential for resource conservation through energy
recovery. This report summarizes a study which is an important
step toward that end.
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II. HIGHLIGHTS OF PROJECT FINDINGS
POLLUTION CONTROL SLUDGE
t Pollution control sludge is defined in this report to
include all solid, semisolid, or liquid residue gen-
erated from municipal and industrial wastewater and
municipal water supply treatment plants, air pollution
control facilities, and new energy source processes.
QUANTITIES OF POLLUTION CONTROL SLUDGE
The total quantity of pollution control sludge destined
for disposal in 1977 is estimated to be 83.1 million dry
metric tons.
By 1987, this quantity could triple, with more than
262.3 million dry metric tons of pollution control
sludge generated as a direct result of implementation of
the Federal Water Pollution Control Act (PL 92-500), the
Clean Air Act (PL 91-604) and the Safe Drinking Water
Act (PL 93-523).
The Clean Air Act will have the greatest impact on
additional sludge generation. Air pollution control
sludges are now generated at about twice the rate of
pollution control residuals from all other sources
combined. By 1987, the ratio of these residues could
increase to about 6.5 to 1.
t The quantity of sludge generated in each EPA region by
major generators as a result of implementation of the
Clean Air Act, Clean Water Act and Safe Drinking Water
Act is presented in Figure 1.
The percent of total pollution control sludges destined
for disposal resulting from implementation of each Act
i s:
1977 1987
Safe Drinking Water Act 5 2
Clean Water Act 26 11
Clean Air Act 69 87
Total 100 100
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Total pollution control sludge disposal requirements by
EPA region for 1977 and 1987, in million dry metric
tons, are estimated to be:
EPA Region 1977 1987
I 1.183 1.956
II 4.256 12.086
III 12.988 33.580
IV 18.682 62.212
V 21.505 78.611
VI 11.520 30.629
VII 3.334 16.246
VIII 1.386 10.941
IX 3.556 8.666
X 2.213 3.496
Total 83.1 262.3
Columns do not add due insufficient information regarding
regional distribution of 12 percent of industrial sludges
Four sources generate most of the pollution control
si udge:
Sludge Generation
million dry Percent of
metric tons total sludge
Source _ 1977 _ 1987 1977 1987
Municipal water
treatment facilities 4.075 5.122 5 2
Municipal wastewater ^
treatment facilities 5.748 6.916 7 3
Industrial wastewater
treatment facilities 15.9 23.0 19 8
Air pollution control 57.4 227.3 69 87
*
The figure 5.748 million dry metric tons presented in the above table
represents untreated municipal wastewater sludge, and does not include
approximately 250 thousand dry metric tons of sludge sent to oxidation
ponds. The amount of treated, i.e. . processed by digestion, compos-
ting, and incineration, sludge that ultimately requires
disposal is reported to be approximately 4.0 million dry metric
tons (Metcalf and Eddy, 1978).
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An additional source of pollution control and process
sludges will emerge in the 1980s as operations to obtain
new energy sources (oil shale, etc.) come on line.
DISPOSAL OF SLUDGE
Five methods of sludge disposal currently practiced in
the United States are examined in this report. They
are: land burial, 1andspreading (for agricultural
utilization), composting, incineration, and ocean
di sposal.
Use of various current disposal methods by pollution
control sludge generators is estimated to be:
MUNICIPAL WASTEWATER TREATMENT SLUDGE
Estimated Quantity
(million dry treated
metric tons Percent of
Disposal Method per year) total sludge
Land burial 1.160 29
Incineration * .880 22
Landspreading 1.240 31
Ocean dumping ^ ^ .480 12
Storage lagoons .24(L... 6
Total "OO^ TOO
* Incineration ash for approximately 2.2 million dry metric ton of raw
sludge.
** Lagoons are considered temporary storage; however, in many cases
sludge is placed into lagoons and is never removed.
*** Estimated sludge requiring disposal is 4.00 million dry metric tons
(4.4 million dry English tons). Source: Metcalf and Eddy, 1978.
INDUSTRIAL WASTEWATER TREATMENT SLUDGE
Estimated Quantity
(million dry
metric tons Percent of
Disposal Method per year) total sludge
On-site disposal
to land or lagoons 11.1 - 12.7 70 - 80
Unknown 4.7 20 - 30
Total 15.8 TOO"
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The proper disposal of pollution control sludges in
general does not result in major environmental
problems. However, improper sludge disposal carries
with it risks such as those identified in Table 1.
While some impacts in the table also relate to
industrial pollution control residues, they are more
associated with municipal wastewater treatment sludge
disposal. Very little data are available concerning the
environmental impact of industrial pollution control
residue di sposal.
TABLE 1. ENVIRONMENTAL IMPACTS OF SEVERAL
SLUDGE DISPOSAL ALTERNATIVES
Reported Environmental Impacts of Land Burial Alternative
(-) Landfill gas, i.e., hydrogen sulfide, ammonia, generated.
(-) Leachate contamination of ground water and surface water
(-) Methane and/or hydrogen sulfide and/or ethylene gas
inhibition of plant growth
(-) Nuisances (odor, noise, dust, traffic, visual, land
disturbance and uneven settlement)
(-) Temporary destruction of wildlife habitat
(+) Containment of unwanted materials
Reported Environmental Impacts of Landspreading Alternative
(-) Phytotoxicity
(-) Uptake of heavy metals, particularly cadmium, lead,
molybdenum, selenium
(-) Storm water runoff contamination of surface waters
(-) Salt buildup in soils
(-) Volatilization of mercury, pesticides, polychlorinated
biphenyls, and other organics
(-) Nuisance odors
(-) Generation of aerosols when sludge is sprayed
(+) Increases available soil moisture in arid regions
(+) Increases crop yields and production
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(+) Increases valuable plant nutrients and required trace
metals
(+) Valuable soil conditioner
(+) Reclamation of strip-mined, eroded, or marginal land
Reported Environmental Impacts of Compost
(-) Storm water runoff contamination of surface waters
(-) Reduces nitrogen content of soil
(-) Phytotoxicity (low pH and high metal content)
(-) Uptake of heavy metals by food crops, particularly cadmium
(+) Aesthetic product which can be used safely in urban area
(+) Reduced environmental hazards (reduced pathogens, ammonia,
organic nitrogen, putrescibility, fly, rodent problems)
(+) Can store in the open
(+) More readily useable as a soil conditioner and/or
ferti1i zer
(+) Increase crop yield and production
(+) Reclamation of marginal and despoiled land, preventing
erosion and stabilizing ash pond
(+) Low-sulfur energy resource
Reported Environmental Impacts of Ocean Disposal
(-) Oxygen demanding substances in sludge reduce oxygen
saturation of bottom waters at disposal sites
(-) Alteration of natural sediment character
(-) Selected heavy metal concentrations (lead, cadmium,
chromium) in sediment at disposal site several-fold greater
than background
(-) Inhibition of phytoplankton cell growth and photosynthesis,
possibly due to reduced light intensity and/or toxic
properties of disposed wastes
(-) Enhancement of primary productivity in surface waters due
to increased nutrient levels
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(-) Reduction of benthic species, and of planktonic larvae of
these species in sewage sludge disposal area
(-) Erosion of exoskeleton and appendages, and gill clogging in
lobsters and crabs
(-) High incidence of fin rot in finfish
(-) Blackening of fish gill epithelium by fine suspended solids
(-) Contamination of shellfish by pathogens, heavy metals, and
other toxic substances
(+) Preserves surface land for nondisposal uses
Reported Environmental Impacts of Incineration
(-) Air emissions from combustion (particulates, hydrocarbons),
which can, however, be controlled by high-energy scrubbing
or other State-of-the-art air pollution control devices.
(-) Air emissions of some metals, particularly volatile
mercuric oxide , metallic mercury, and cadmium
(-) Air emissions control operations produce a waste stream
requiring further treatment and/or disposal
(-) Ash requires proper disposal
(+) Near total destruction of most pesticides at 900° C to
980° C
(+) Conversion of organic solids to ash
(+) Minimal odor and noise problems from sludge handling and
combustion.
* Denotes positive or negative environmental impacts.
o On-site land burial costs range from $6 to $159 per dry
metric ton for sludge handling. It is noted that total
land burial costs should also include such widely
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variable costs as hauling and sludge dewatering. q
Hauling cost is directly proportional to transportation
distance; sludge dewatering cost, which averages $67 per
dry metric ton, is a function of technique used.
Landspreadi n'g of sewage sludge can be cost competitive
with land burial. Costs for landspreading dewatered
sludge range from $50 to $210 per dry metric ton, with
dewatering and hauling costs being the variables. Costs
for landspreading liquid sludge range from $20 to $145
per dry metric ton, with hauling costs being the major
variable.
On-site processing cost of composting ranges from $40 to
$56 per dry metric ton, and tends to decrease as the
amount of sludge processed is increased. To make
compost costs comparable to other disposal alternatives,
however, cost factors for dewatering and transportation
must be included.
ENERGY RECOVERY FROM SLUDGE
Municipal sewage sludges and some industrial wastewater
treatment sludges have sufficient energy content with
sufficient dewatering to warrant energy recovery as a
part of the disposal process. The most promising
technologies for achieving cost-effective energy recovery
from sludge are: incineration with heat recovery;
starved air combustion (also termed pyrolysis or thermal
distillation); anaerobic digestion; and co-incineration
and co-pyrolysis or sludge with coal, oil, municipal
solid waste, or other wastes.
None of these energy recovery systems has received
widespread application in the United States. Anaerobic
digestion and co-incineration systems are in the
construction stage in several U.S. cities.
Many conventional multiple hearth furnaces (MHF) and
fluidized bed furnaces (FBF) maintain a high enough
exhaust temperature to justify retrofitting with
boilers/heat exchangers to recover heat.
MHFs operated in the pyrolytic mode do not require
auxiliary fuel, but can use recovered gas to fuel the
afterburners. This could provide an economic benefit
over MHF operation in the conventional mode.
Production of electric power from steam for in-plant use
is already practiced by some industries. This
application is limited to larger sludge incineration
systems due to economies of scale..
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RECLAMATION OF SLUDGE-DAMAGED AREAS
Although numerous examples can be found of degradation or
environmental impacts resulting from improper land
disposal of municipal or industrial sludges, few examples
could be found in which an engineering or economic
evaluation and assessment of alternative mitigation steps
had been performed. There is a need for more
investigation in this area.
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III. CAPSULATED SUMMARY OF PROJECT
THE POLLUTION CONTROL LAWS AND THEIR EFFECT ON SLUDGE GENERATION
The types of solid wastes to be classified as pollution
control sludges are those solid, semisolid, or liquid wastes
generated as a result of the application of pollution control
measures by:
Municipal water treatment facilities
Municipal wastewater treatment plants
Industrial wastewater treatment plants
Air pollution emission control facilities
Existing or proposed new energy source activities.
It is often difficult to distinguish between some process
sludge and pollution abatement sludges. This is particularly
the case with industrial and new energy source sludges. Fre-
quently, processing of raw materials results in the generation
of process waste residues. Wastes such as these may occur as a
distinct solid material such as spent shale, or as a mud or
sludge which accumulates at the bottom of reactor tanks.
Regardless of any physical resemblance to sludge, for the
purpose of this report, these wastes are considered to be
"process sludges" simply because they are generated during a
manufacturing process and not as a result of wastewater pollu-
tion control. This distinction was used as the primary basis
for deciding which sludges would be classified as "pollution
control sludges" and, therefore, included in our inventory of
waste residues generated in response to pollution control
legislation.
Municipal Water Treatment Facilities
The Safe Drinking Water Act of 1974 (SDWA) significantly
extends the influence of the federal government over water sup-
ply, treatment, distribution, and final drinking water quality.
The SDWA prescribes that the EPA promulgate primary and secon-
dary standards regulating two classes of water contaminants:
Primary standards limiting the concentration of contami-
nants which may have an adverse effect on the health of
persons
t Secondary standards controlling parameters, such as odor
and color, which could give "acceptable" water an
undesirable appearance and cause users to switch to a
better looking but less acceptable source.
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It was the intent of Congress that the states take primary
responsibility for assuring the safety of drinking water. To do
so, they must adopt regulations at least as stringent as the
federal regulations and enforce these requirements for all pub-
lic systems serving 25 or more persons, or 15 or more service
connecti ons.
Section 1412 of SDWA sets the framework around which regu-
latory activities are to proceed. The chronology of the regu-
latory strategy is provided in Table 2. The interim primary
regulations under Section 1412(a)(l) set maximum contaminant
levels (MCLs) for ten inorganic chemicals (arsenic, barium,
cadmium, chromium, lead, mercury, selenium, silver, fluoride,
and nitrates), turbidity, coliform organisms, pesticides, herbi-
cides, and radionuclides. Early in 1978, EPA proposed regu-
lations for synthetic organics and trihal omethanes. These
regulations were included under the interim primary drinking
water standards.
TABLE 2. EVOLUTION OF DRIVING WATER REGULATIONS UNDER
SECTION 1412 OF THE SAFE DRINKING WATER ACT
Regulaton
National Interim Primary
Drinking Water Regulations
Revised National Primary
Drinking Water Standards
Secondary Drinking Water
Regulations
Section
Number
Status
1412(b)(2)
1412(b)(2)
1412(b)(5)
1412(c)
Date
March 1975
Proposed
Promulgated January 1976
Effective June 1977
Proposed Fall 1979 (?)
Promulgated Unknown
Effective Unknown
Proposed March 1977
Promulgated Fall 1979 (?)
Compliance with the regulations will result in the genera-
tion of significant quantities of sludge. The pollution control
technologies most commonly used to remove these constituents are
a combination of physical-chemical treatment processes, i.e.,
coagulation, sedimentation, filtration, and adsorption. Thus,
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the SDWA will affect sludge generation by setting standards for
which the most likely treatment techniques to be employed in
bringing systems into compliance will result in the generation
of sludge. Additional sludge production may, however, occur
gradually due to an issuance of variances and exemptions per-
mitted under Sections 1415 and 1416 of SDWA. Variances may be
granted if the poor quality of a system's raw water source and
common technology applied to the raw water cannot effectively
reduce the concentration of the regulated contaminants. Also,
the variance may not result in water quality posing an unrea-
sonable risk to health. It is not anticipated that variances
will play a major role in delaying compliance (and thus reducing
the rate of additional sludge generation). Exemptions are
granted on the basis of compelling factors, including economic
factors, and, like variances, must not allow an unreasonable
risk to the public health. It is likely that many small systems
will apply for exemptions from the regulations. Systems with
exemptions from the interim regulations will have to be in com-
pliance by 1981 for most systems, or by 1983 for systems which
are becoming part of a regional system. Should the regulations
be revised, the systems have seven years (nine years for reg-
ional systems) from the effective date of the regulations to
come into compliance. Assuming that this occurs in 1980, it
could be 1987 before most systems are in compliance with the
revised regulations.
Municipal Wastewater Treatment Plants
Municipal wastewater treatment plants were required under
Section 301(a) of the Federal Water Pollution Control Act (PL
92-500, FWPCA) to provide secondary treatment as a minimum by
July 1, 1977, in order to meet the water quality standards
addressed by Section 303 of the Act. The intent of regulations
under the Act is to set national standards for the minimum
treatment level of municipal sewage, and to let state and inter-
state agencies set water quality standards that might dictate
more stringent levels of treatment. Secondary treatment is
defined as either removing 84 to 89 percent of both 5-day BOD
and suspended solids, or as achieving effluent levels of 30
mg/l (lb/10° Ib) BOD5 and 30 mg/£ (lb/106 Ib) suspended solids.
More stringent treatment, as may be required by some states,
usually refers to tertiary treatment for the removal of addi-
tional suspended solids, heavy metals, or nutrients such as
nitrogen and phosphorus. Secondary treatment will generate
sludge as the BOD and the suspended solids are reduced through
biological action. In states where treatment beyond secondary
is required, more sludge will be generated as BOD, suspended
solids, and other constituents are further reduced.
The sole purpose of the municipal wastewater treatment
facility is pollution control, and all solid and semisolid or
liquid wastes produced by these facilities are considered to be
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"pollution control" sludges. This includes primary settled
sludges and biological sludges produced during secondary treat-
ment. Tertiary sludges include spent coagulant and polymers,
coagulated solids, spent ion exchange resins or spent carbon.
Since the emphasis in this study is to determine the amount of
sludge that will result from the implementation of the FWPCA,
the quantity of sludge generated due to treatment beyond "secon-
dary" is not included in the impact assessment.
Industrial Wastewater Treatment Facilities
The quality of industrial point source discharges is con-
trolled through the Federal Water Pollution Control Act (PL 92-
500) and its amendments. As required under Section 301 of the
Act, EPA established technology-based effluent limitations for
27 industrial point source categories. Such restrictions will
require the removal of large quantities of pollutants from
industrial wastewater effluents, and result in the generation of
considerable volumes of sludge.
Section 301(b)(l)(A) of FWPCA establishes that by July 1,
1977, industrial dischargers to navigable waters (direct dis-
chargers) should control the quality of their effluents through
the application of the Best Practicable Control Technology
Currently Available (BPT). The BPT regulations focus mainly on
the removal of conventional pollutants, i.e., pollutants sus-
ceptible to conventional treatment methods under normal opera-
ting conditions, e.g., BOD5, TSS, pH, oil and grease.
By July 1, 1984, it is required under Section 301(b)(2)(A)
that treatment technologies for the control of conventional pol-
lutants be upgraded to the Best Available Technology Economi-
cally Achievable (BAT). This incremental approach to pollution
abatement is intended to establish a reasonable rate for pro-
gressing toward the national goal of eliminating the discharge
of all pollutants - a national zero discharge policy. This
strategy has been modified somewhat by the 1977 Amendments to PL
92-500. Waiver provisions under Section 301(c) of FWPCA allows
for EPA to relax control requirements for dischargers that can
prove the cost of incremental pollution abatement to be unrea-
sonably excessive for conventional pollutants. Section 307(a)
now requires that the costs for incremental removal of con-
ventional pollutants compare reasonably with costs incurred by
publicly owned treatment works (POTW) in controlling similar
pollutants. Where BAT requirements are shown to be too costly
for a given industry, effluent limitations will be rolled back
to BPT levels until revised BAT limitations are promulgated. At
that time, BAT would be renamed Best Control Technology (BCT).
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Another significant amendment to PL 92-500 deals with EPA
strategy to control the discharge of toxic pollutants in indus-
trial effluents by July 1, 1984. Toxic pollutant control (Sec-
tion 307b) " will require a level of treatment at least equivalent
to BAT and, where justifiable, stricter control (including zero
discharge). At present, toxic pollutant effluent limitations
are being developed for 21 industries. There will be no waiver
provisions for economic reasons.
Implementation of toxics control for direct dischargers
will result in significant increases in sludge production. The
types of constituents to be removed, such as metals and dis-
solved organics, require sludge-producing control technologies,
i.e., coagulation or lime addition and adsorption onto solids
such as carbon. Compounding the problem, in order to effec-
tively remove organics, it is often necessary to remove most of
the BOD and suspended solids from an effluent prior to applying
adsorption technologies. It can be expected that compliance
with 1984 BAT effluent guidelines for control of both toxic and
conventional pollutants will lead to increased sludge genera-
tion. Furthermore, the 21 industries required by FWPCA to
control their toxic discharges will be faced with the problem of
managing large quantities of potentially hazardous wastes.
Rigid pretreatment standards will be included in the toxic
pollutants strategy to protect the treatment operations of POTWs
from toxic discharges by industries into sewers, and also to
ensure the quality of POTW sludge. Under authorization from
Section 307(b) of FWPCA, EPA will set national pretreatment
standards for 21 industries believed to be discharging toxic
pollutants. At the present time, regulations have been pro-
mulgated or have interim final status for eight industries
(electroplating, inorganic chemicals, leather tanning and fini-
shing, nonferrous metals, petroleum refining, steam electric
power plants, timber products, and textile mills). These eight
industries will have three years to attain compliance with the
regulations, and should be in compliance by 1980 pending final
regulations. Regulations for the remaining 13 industries will
be finalized in 1979 and 1980. By 1983, all regulated indus-
tries discharging into POTWs should be controlling all the
substances listed under Section 307(b), as well as other sub-
stances considered to interfere with or pass through publicly
owned treatment works.
Control of toxic pollutants from the effluents of indus-
trial dischargers to POTW will result in a unit sludge genera-
tion, e.g., kg of pollution control sludge produced per 1,000 kg
of product manufactured, roughly similar to that for industrial
direct dischargers. The differences in unit sludge production
are related to the fact that industrial direct discharges are
regulated by fairly rigid national standards, while control of
16
-------
industrial indirect discharges will vary according to require-
ments set by local POTWs.
A new class of pollutants, termed nonconventional/nontoxic,
has been defined, and will be subject to regulatory control by
July 1, 1987. This would include the control of all those
pollutants not addressed under Sections 301 and 307 of FWPCA.
The mandatory level of treatment will be BAT. Waiver provisions
for nonconventional pollutants will be similar to the economic-
based provisions for conventional pollutants, and would include
a consideration of the persistence, acute toxicity, chronic
toxicity, synergistic properties, and bioaccumulative tendency
of substances under review. If pollutants are determined to be
toxic, waiver for economic reasons will not be permitted. Since
this class of pollutant has not yet been defined for individual
industrial waste streams, it is not possible to estimate the
magnitude of the effect that such control would have on addi-
tional sludge production.
Air Pollution Emission Control Facilities
The Air Quality Act of 1967, and its amendments of 1970,
1974, and 1977, established the most recent framework by which
EPA has developed regulations and standards for improving and
protecting the quality of the air. Under authorization of
Section 109 (a)(l) of the Act, EPA has set national ambient air
quality standards (NAAQS) to control the level of hydrocarbons
(HC), sulfur oxides (SOX), total suspended particulates (TSP),
nitrogen dioxide (NOo), carbon monoxide (CO), and photochemical
oxidants for approximately 250 Air Quality Control Regions
(AQCR). The strategy is to set goals for air quality within
AQCRs through stringent secondary air quality standards which
will protect the nation's welfare, and to promote the achieve-
ment of those goals through intermediate compliance with less
restrictive primary air quality standards. Through Section 110
of the Act, EPA has the authority to require each state to
develop State Implementation Plans (SIP), placing the responsi-
bility on individual states for enforcing the primary standards
and, ultimately, the secondary standards. States must set achievable
New Source Performance Standards (NSPS) for 28 industrial point source
categories which are at least as stringent as the NSPS set by EPA under
Section 111 of CAA. For these industries, EPA has set emissions
limitations for seven pollutants, including sulfur dioxide,
nitrogen oxides, particulates, sulfuric acid mist, hydrocarbons..
*The Air Quality Act of 1967 and its amendments are commonly
referred to as the Clean Air Act (CAA).
17
-------
flourides, and carbon monoxide*. In addition to the six crite-
ria po.llutants (Section 109),. ^PA has identified four hazardous
air pollutants and, under the provisions of Section 112, has set
standards to control emissions of asbestos, beryllium; mercury,
and vinyl chloride. Limitations for hazardous air pollutants
apply to both existing and new sources of air pollution.
Provisions of The Clean Air Act and its amendments, which
will have the greatest impact on additional sludge production,
are found in:
t Section 109 establishing National Primary and Secondary
Ambient Air Quality Standards
t Section 110 establishing State Implementation Plans
policies for the Prevention of Significant Deterioration
(PSD), and the requirements for offset in nonattainment
areas
Section ill setting New Source Performance Standards for
industries
Section 112 controlling the emission of hazardous air
pol1utants.
In addition, the influence of the federal energy regulations
requiring certain major air pollutant sources to convert from
oil to coal will have a direct impact on enforcement of the
Clean Air Act, and ultimately on sludge production by the
affected industries.
The 1977 Amendments to the CAA require that states im cur-
rent nonattainment areas must have an approved revised SIP by
July 1, 1979. It is required that primary NAAQS be attained by
December 31, 1982. For photochemical oxidants and carbon mono-
xide, extensions are available in certain cases until 1987.
This requirement is very powerful because it defines a pre-
condition for construction or modification of major emission
sources in nonattainment areas after 1979. The SIPs must also
incorporate the new EPA offset policy, which requires that the
increase in pollution emissions from a new facility must be
offset by a reduction from existing sources. In addition, the
reduction in emissions from existing sources must result in a
net improvement in air quality. The result, depending on the
type of pollutant being controlled, could be an increase in
waste residual generation. At the present time, 40 states are
New sources are not necessarily controlled for all seven
pollutants. In addition, total reduced sulfur (TRS) from
kraft pulp mills, and sulfides from sulfur recovery plants in
the petroleum refining industry, are also controlled.
18
-------
in the process of revising their SIPs, with approval expected to
extend through 1979.
In addition to the problem of nonattainment of the NAAQS is
the problem of noncompliance. Several factors have been identi-
fied as hindering full compliance with SIPs. Those industries
preferring to comply with emission limitations for combustion
sources by switching to cleaner fuels are faced with the problem
of an insufficient supply of low-sulfur fuel. In addition, the
recent federal energy policy legislation has constrained fuel
switching from coal to oil. The 1977 amendments to the Act
state that using untreated "clean fuels" is insufficient to meet
the requirements of the amendments. Since the only proven tech-
nology which will reduce sulfur dioxide levels to acceptable
limits (90 percent reduction) is flue-gas desul furization (FGD)
"scrubbing," it appears that more and more fossi1-fuel-fired
plants will be installing scrubbers. The result of this trend
will be to promote additional sludge generation.
Directly related to this is the current National Energy
Policy (NEP), which will have a significant influence on sludge
generation resulting from air pollution regulations. As nuc-
lear, hydroelectric or unconventional technologies develop to
replace fossil fuels, potential air pollutant emissions - and,
therefore, generated sludges - are reduced. As coal is used to
replace imported petroleum and natural gas, air pollutant emis-
sions and sludge quantities will increase.
In a program under NEP to convert existing oil- and gas-
fired utility plants to coal, more than 100 power plants will
convert to coal by 1985. Although new conversion technologies,
such as coal liquefaction and gasification and oil shale proces-
sing, could alleviate some of the sludge generation problems
arising from coal combustion, the total contribution of such
fuels by 1990 is expected to be small.
Another area for consideration is the prevention of sig-
nificant deterioration (PSD) provisions of the Act included in
the 1977 amendments. The PSD requirements were provided to
ensure nondegradation of existing air quality in clean air
areas. The PSD provisions are to be enforced as components of
the SIP on New Source provisions of the Act. Thus, the effects
of PSD requirements are manifested as changes in the charac-
teristics of sludge generation under the SIP and NSPS provisos.
Of the six criteria pollutants controlled through the
National Ambient Air Quality Standards, only S02 and particu-
lates are removed from gas streams using sludge-generating
technologies. The other four criteria pollutants (HC, N02, CO,
and oxidants) are not amenable to "scrubbing"; therefore, no
sludge is generated from the control of these pollutants.
19
-------
Strategies which have been considered for controlling SC^
and participates emissions are:
Switching to a cleaner fuel, e.g., coal to oil. Due to
changes in the National Energy Policy and a shortage of
relatively clean coal, fuel-switching is no longer a
likely strategy for reducing emissions.
Reducing the effects of existing emissions on nearby
ambient air quality by the use of taller stacks. The
EPA has recently discouraged this strategy, and the
Amendments of 1977 (Section 123) specifically limit the
credit for stack height on any stationary source built
after 1970. Regulations on the design of tall stacks
are to be promulgated in 1978, limiting stack height to
less than two and one-half times the height of the
facility-
Curtailing production to a level which ensures that
limitations will not be exceeded; relocating plant
capacity, or redesigning to reduce emissions. These
strategies are not generally cost-effective or feasible
and, for these reasons, are less tenable than employing
technologies to directly remove pollutants from the
stack gas stream.
Applying available technologies to physically remove
pollutants such as S02 and particulates from the gas
stream. This concept for controlling emissions is not
only tenable^ but currently operative in a wide range of
industries.
The only strategy of those mentioned above which directly
results in additional sludge generation involves the use of
pollution control devices. Most of these devices generate
"pollution control sludges" with characteristics which vary
according to the industrial processes responsible for air pollu-
tant emissions, the pollutants removed, and the technology
employed. The control technologies for S02 and particulates,
which will result in generating additional pollution control
sludges under the CAA, are mentioned below.
Five existing technologies which can reduce SOo emissions
are physical and chemical coal cleaning, coal gasification, coal
liquefaction, fl uidized-bed combustion, and flue-gas desulfuri-
zation. The most common, most highly developed, and most eco-
nomical control technology is flue-gas desulfurization (FGD).
Coal gasification, coal liquefaction, and fluidized-bed com-
bustion are still in the early stages of development. Advanced
physical and chemical cleaning techniques are being thoroughly
investigated and may be employed to a small degree in the near
20
-------
future. However, to the extent that coal cleaning and conver-
sion processes are utilized to meet air emission limitations,
the resultant sludges would have to be ascribed to the CAA.
However, the revisions to the NSPS for fossil-fuel-fired-utility boilers
may require FGD even after the coal is cleaned.
FGD systems can be classified as nonregenerabl e and regen-
erable. The nonregenerable processes, e.g., lime and limestone
scrubbing and the double-alkali method, produce a sludge con-
sisting qf calcium sulfate, calcium sulfite, fly ash and
water. The regenerable processes are designed to recover S02
and recycle the sorbent. Ideally, S02 can be reclaimed as a
marketable by-product such as elemental sulfur, sulfuric acid or
concentrated S02- Regenerable processes have not received
sufficient R&D emphasis, are not currently economically competi-
tive, and are not expected to replace the conventional, non-
regenerative processes in the near future.
Particulate removal technology from flue gas streams is
somewhat better developed than SOo removal, and removal effi-
ciencies are typically higher. Other than the coal conversion
and cleaning techniques referred to above, there are five basic
technologies that can be employed: settling chambers, dry
centrifugal collectors, wet collectors and mist eliminators,
high voltage electrostatic precipitators, and fabric filtration.
It should be pointed out that most of these techniques can and
often do produce fly ash materials which are disposed of as a
solid waste. However, once collected in an aqueous medium, the
ash is generally easy to dewater to facilitate disposal.
QUANTITIES OF SLUDGE GENERATED IN RESPONSE TO FEDERALLY ENACTED
POLLUTION CONTROL LEGISLATION
As a direct consequence of pressures to clean up the envi-
ronment, ever-increasing amounts of pollution control sludge are
being generated. In order to appreciate what this can mean in
terms of our future need for safe and environmentally acceptable
sludge disposal, it is necessary to know just how much sludge is
being generated in response to this socially desirable goal.
For this purpose, best possible estimates have been made
quantifying pollution control sludge generation over a 20-yr
span, from 1967 to 1987. This time period has been selected
because most of the significant milestones for regulatory imple-
mentation and compliance will be realized within this time
period. The 1967 baseline year provides an historical per-
spective as a point in time when relatively little federal
pollution control legislation was in force.
-------
Sludge generation will be described under two scenarios.
The first represents minimum implementation of pollution control
regulations (controls to remain at the 1977 level of implementa-
tion). The second provides for maximum implementation and full
compliance by all pollutant generators specified in the regula-
tions. Generators of pollution control sludges belong to five
groups: municipal water treatment facilities, municipal waste-
water treatment facilities, industrial wastewater treatment
facilities, air pollution control systems, and new energy source
operations.
Municipal Wastewater Treatment Sludges
Rather than to develop a range of values representing
possible sludge generation under two scenarios, a direct esti-
mate of sludge quantities was made. The overall approach used
to estimate sludge quantities occurred in three sequential
tasks:
Data source identification and evaluation
t Calculation of sludge quantities from the data base for
the 1976 baseline year
Extrapolation of baseline data to the years 1967, 1977,
1980; 1984, and 1987.
Under provisions of PL 92-500, the Environmental Protection
Agency (EPA) is required to submit to Congress the cost esti-
mates for construction of publicly owned wastewater treatment
facilities. To provide a sound basis for these estimates, a
large-scale survey (the NEEDS Survey) of existing plants was
undertaken by the EPA. Raw data from the NEEDS Survey were used
as input to several computer systems. These data were used
primarily for cost calculations, but are potentially useful for
other purposes, including estimates of sludge quantities. The
NEEDS data file, along with technical information obtained from
the literature, was used as a basis for making calculations.
During the past year, there have been several major amendments
to the acts and revisions in regulatory strategies. Sludge
quantities presented in this report represent regulatory
conditions as they existed prior to April 1978. It should be
noted, however, that information in this report regarding
definitions and regulatory strategies has been updated to
October 1978.
22
-------
Of the 17 unit processes included in the NEEDS Survey, nine
treatment configurations were selected to represent various
degrees of sludge generation. These were grouped as follows:
t Primary treatment - primary sedimentation
Secondary treatment - trickling filters, activated
sludge, sand filter
Tertiary treatment - chemical addition for phosphorus
removal, nitrification, denitrification
Treatment process unknown.
Sludge generation factors (kg or Ib of sludge/capita/day) were
then derived for each configuration, based on the following
assumpti ons:
Sludge is produced by removal of influent solids,
precipitation of dissolved solids, and biological
growth.
Sludges generated by different processes produced
different amounts of solids with different
characteri sties.
t Sludge quantities generated are proportional to flow and
population served.
Sludge was calculated by employing a computerized technique
for mapping plants selected from the data file with the appro-
priate treatments and sludge generation factors. Total sludge
for a given aggregation of plants, e.g., activated sludge plants
in North Dakota, is calculated by multiplying the sludge genera-
tion characteristic^or that group by the group population for
the data base year.
Extrapolation of the 1976 baseline data to the years of
interest was made as follows:
1967 - Sludge values for 1967 were calculated from
population changes on a per state basis. A linear rela-
tion between population and sludge is assumed.
1977 - Same procedure as for 1967.
1980 and 1984 - Both population changes and new
construction were considered. Upgrading to secondary
treatment was assumed.
The NEEDS data file used for this report was a 1976 data base.
23
-------
1987 - Same procedure as for 1967 and 1977. No legisla-
tive impact is applicable during this period.
Total municipal wastewater treatment plant wet ari'd dry
weight sludge generation for the period 1967 to 1987 is pre-
sented in Table 3 . Dry weight sludge values increase only
slightly between 1977 and 1984, when implementation of the
requirement for secondary treatment is to take place. The
values of 5.75 mil t, 6.23 mil t, and 6.69 mil t of sludge for
1977, 1980, and 1984, respectively, represent an overall
increase of about 0.95 mil t. When considered on a wet weight
basis, however, an additional 33.3 mil t of sludge could be
generated. Since roughly 35 percent of all municipal sewage
sludge is presently (1977) being incinerated, approximately 3.74
mil t (dry weight) of sludge are being disposed of to land. If
the fraction of sludge were to remain constant for the next few
years, more than 4 mil t of sludge could require land disposal
by 1984, with more than 2 mil t potentially being incinerated.
Figure 2 shows the distribution of municipal wastewater
sludge by EPA region generated over the period from 1967 to
1987. Region V has by far the greatest production of sludge.
This is consistent with 1977 flow data which show that Region V
also treats the most wastewater. According to data compiled
from the NEEDS Survey, Region V facilities predominantly use
treatment configurations which have large unit sludge generation
characteristics.
Sludge generation by EPA Regions can be grouped into four
ranges for the period 1967 to 1987.
Region 5 = 1.63 mil t - 1.95 mil t
Regions 2,3, and 4 = 0.680 mil t - 1.09 mil t
t Regions 1,6, and 9 = 0.299 mil t - 0.678 mil t
Regions 7,8, and 10 = 0.120 mil t - 0.258 mil t.
Over the next 20 years, the generation of pollution control
sludges will be greatest on the east coast of the United States
and throughout the Great Lakes States. On the west coast, only
Region IX will contribute significantly to national sludge pro-
duction, with about 90 percent of that sludge coming from
California.
*
These values represent., total si udge^generated by treating
wastewater. Additional treatmentsofbsIudge whith may reduce
the quantities of sludge requiring disposal was not considered
In a recent study, Metcalf and Eddy estimated that sludge
destined for disposal in 1977 was 4.00 million dry metric tons
(4.4 dry English tons).
24
-------
TABLE 3. EPA REGIONAL MUNICIPAL WASTEWATER TREATMENT SLUDGE GENERATION TOTALS
BY TREATMENT CLASSIFICATION FOR PERIOD 1967-1987
1
AREA
REGION 1
PRIMARY
SECONDARY
TERTIARY
TOTAL
REGION 2
PRIMARY
SECONDARY
TERTIARY
TOTAL
REGION 3
PRIMARY
SECONDARY
TERTIARY
TOTAL
REGION 4
PRIMARY
SECONDARY
TERTIARY
TOTAL
REGION 5
PRIMARY
SECONDARY
TERTIARY
TOTAL
1977 FLOW
MILLION
CUBIC
METERS
988.3
1303.3
225.1
2516.7
561.1
3918.8
147.1
4627.0
396.2
3622.6
215.8
4234.6
792.7
4618.8
359.9
5771.4
1633.9
8125.7
607.2
10366.8
SLUDGE GENERATION IN THOUSANDS OF METRIC TONS
1967
DRY
76.. 7
201.3
20.9
298.9
44.0
672.1
25.2
741.3
30.8
611.2
38.1
680.1
57.3
622.6
60.2
740.1
126.2
1343.5
162.3
1632.0
WET
1457.2
6335.7
492.0
8284.9
836.7
21308.9
775.5
22921.1
585.8
19171.4
1216.1
20973.2
1088.5
19023.8
1714.5
21826.8
2397.6
42599.2
2386.2
47383.0
1977
DRY
80.0
215.7
22.9
318.5
45.1
682.6
25.5
753.1
32.2
626.0
39.9
698.1
65.6
713.0
71.7
850.4
132.4
1406.1
168.3
1706.9
WET
1519.1
6780.7
534.2
8834.0
856.0
21630.4
786.0
23272.4
611.7
19628.2
1275.1
21515.0
1247.0
21793.7
2056.3
25097.0
2516.3
44583.7
2491.8
49591.9
1980
DRY
41.5
298.9
24.4
364.8
23.1
739;1
26.1
788.4
16.6
670.2
41.1
727.9
35.5
837.9
80.2
953.6
68.5
1569.8
173.2
1811.6
WET
788.9
9175.0
566.3
10530.2
439.2
23288.6
804.1
24531.9
314.5
20932.6
1312.6
22559.7
674.4
25481.1
2306.0
28461.5
1301.7
49384.0
2570.0
53255.6
1984
DRY
0.0
383.3
25.2
408.5
0.0
793.0
26.5
819.5
0.0
717.4
42.2
759.7
0.0,
946.8
85.6
1034.3
0.0
1727.6
177.7
1905.2
WET
0.0
11595.4
585.1
12180.5
0.0
24855.1
817.2
25672.3
0.0
22325.3
1350.3
23675.6
0.0
28726.1
2465.9
31192.0
0.0
53972.1
2633.3
56605.4
1987
DRY
0.0
395.3
26.1
421.4
0.0
806.6
27.0
833.6
0.0
735.2
43.4
778.6
0.0
997.3
90.8
1088.1
0.0
1764.2
181.9
1946.1
WET
0.0
11958.5
604.2
12562.7
0.0
25278.4
830.6
26109.0
0.0
22880.8
1387.0
24267.8
0.0
30198.0
2624.8
32822.7
0.0
55116.3
2694.3
57810.6
ro
ui
-------
TABLE 3. (continued)
AREA
REGIOM 6
PRIMARY
SECONDARY
TERTIARY
TOTAL
REGIOM 7
PRIMARY
SECONDARY
TERTIARY
TOTAL
REGION 8
PRIMARY
SECONDARY
TERTIARY
TOTAL
REGION 9
PRIMARY
SECONDARY
TERTIARY
TOTAL
REGION 10
PRIMARY
SECONDARY
TERTIARY
TOTAL
Grand Total
1977 FLOW
MILLION
CUBIC
METERS
112.9
2283.5
204.7
2601.1
628.7
1134.0
81.1
1843.8
151.9
1137.2
2.5
1291.7
1521.2
2245.7
91.6
3858.6
581.9
1199.9
62.8
1844.6
30956.3
SLUDGE GFNERATION IN THOUSANDS OF METRIC TONS
1967
DRY
7.9
289.0
30.1
327.0
48.3
128.4
11.4
188.2
10.2
110.3
0.3
120.9
110.5
294.5
13.6
418.5
41.3
113.0
7.4
161.6
5308.6
WET
150.5
8589.7
943.9
9684.1
918.5
3366.8
289.9
4575.2
194.1
3088.8
10.4
3293.3
2099.5
8778.5
395.2
11273.3
783.9
3225.5
230.2
4239.6
154454
1977
DRY
9.4
344.5
36.4
390.3
51.3
138.1
12.4
201.8
12.7
136.5
0.4
149.6
126.3
346.0
15.7
488.0
' 48.1
134.7
8.7
191.5
5748.2
WET
178.9
10247.9
1140.2
11567.0
974.4
3618.7
314.8
4907. 9
242.2
3826.9
12.0
4081.1
2399.1
10303.6
457.2
13159.9
913.0
3847.7
273.3
5034.1
167060
1980
DRY
5.0
373.0
38.7
416.7
26.3
182.9
12.1
221.3
6.9
155.9
0.4
163.1
66.8
487.6
16.6
571.1
24.6 ;
182.0
9.0
215.6
6234.1
WET
95.3
11088.0
1210.7
12393.9
499.1
4900.3
306.9
5706.4
130.8
4387.7
12.5
4531.0
1269.3
143SS.8
486.3
16111.5
466.9
5192.6
282.1
5941.6
184023
1984
DRY
0.0
406.0
41.4
447.4
0.0
232.5
12.3
244.7
0.0
178.5
0.4
178.9
0.0
632.6
17.4
650.0
0.0
236.5
9.5
246.0
6694.2
WET
0.0
12059.2
1295.3
13354.5
0.0
6303.2
312.2
6615.4
0.0
5028.6
13.0
5041.6
0.0
18498.7
507.9
19006.6
0.0
6744.1
296.6
7040.7
200384
1987
DRY
0.0
429.9
44.0
474.0
0.0
236.1
12.5
248.6
0.0
189.1
0.4
189.5
0.0
660.3
18.1
678.4
0.0
247.9
9.9
257.8
6916.1
WET
0.0
12772.6
1378.8
14151.4
0.0
6400.9
317.5
'6718.4
0.0
5328.4
13.4
5341.8
0.0
19303.1
529.2
19832.3
0.0
7067.6
310.8
7378.3
206995
Note: Municipal wastewater treatment sludge quantities do not include the contribution
from industrial dischargers.
ro
cr>
-------
2.0-
I .3
i .a
o .5
- 0.421
z
o
(V ~
UJ Ul
uj a
0
2 .0
I .5
1 .0
0 .3
- a.403
UJ
o
a
i-
ll
-------
Municipal Water Supply Sludges
The approach that was used to develop sludge generation
estimates for municipal water supply facilities, was also used
to estimate sludge generated by municipal wastewater facilities
(see page 23). A large data base was compiled using flow, ser-
vice population, and treatment data contained in the EPA
"Inventory of Public Water Supply" (IPWS) computer file.
Although there were some data gaps for flow, the file was
relatively complete for entries pertaining to service population
and treatment type. Most of the missing data were for small
water supply facilities.
Of the 12 treatment classes used in the IPWS file, four are
considered to be sludge generating. These are coagulation, fil-
tration, softening, and iron removal. Sedimentation was not
considered to be a process which generates sludge, but rather a
process which collects sludge generated by another unit opera-
tion. Flow-based unit sludge generation rates were calculated
for 16 of the most common combinations of unit treatment pro-
cesses. In cases where some undetermined split of multiple water
sources (ground, surface) contributed to the water supply, equal
distribution of flow through each treatment chain was assumed.
Total sludge generation was calculated by multiplying the unit
sludge generation for each treatment chain by the per capita
flow employing that type of treatment on a state-by-state basis.
Since the IPWS is a 1974 data base, total sludge generation
values must be extrapolated to other years of interest. Sludge
values for 1967 were calculated on a per state population basis,
and did not take into account new plant construction between
1967 and 1987. A linear relation between population and sludge
generation was assumed. The 1977 values were calculated in the
same manner, using 1977 population statistics. Both population
changes and upgrading of treatment due to the SDWA were con-
sidered in extrapolating data to 1980 and 1984. EPA estimates
of the number of water treatment facilities in violation of
maximum contaminant levels were used to estimate needed treat-
ment modifications. The largest impact was considered to be the
addition of coagulation or filtration. It was assumed that 80
percent of those municipal systems using surface water that do
not presently (1977) use coagulation or filtration will be in
full compliance with the SDWA by 1980, and that by 1984, all of
these systems would be in full compliance. Estimates of 1987
sludge generation were based on projected population increases.
The total quantity of municipal water treatment sludge
generated in the United States during 1967, 1977, 1980, 1984,
and 1987, is presented in Table 4. The current level of sludge
production is 4.08 mil dry t, an increase of 11.1 percent over
1967. By 1984, when all systems should be in compliance with
28
-------
ro
UD
TABLE 4 . TOTAL QUANTITY OF MUNICIPAL WATER TREATMENT
SLUDGE GENERATED BY EPA REGION FOR THE PERIOD 1967-1987
(million dry metric tons)
EPA
Region
I
II
III
IV
V
VI
VII
VIII
IX
X
Sludge Generation
1967
0.037
0.089
0.235
0.690
1.280
0.554
0.212
0.112
0.441
0.024
1977
0.040
0.091
0.242
0.842
1.336
0.637
0.231
0.123
0.503
0.030
1980
0.078
0.166
0.279
0.966
1.378
0.668
0.235
0.131
0.681
0.061
1984
0.090
0.187
0.233
1.041
1.413
0.706
0.242
0.136
0.747
0.073
1987
0.093
0.190
0.300
1.113
1.446
0.743
0.246
0.140
0.775
0.077
Total
3.674
4.075
4.643
4.868
5.123
-------
the drinking water standards, 4.91 mil dry t of sludge is esti-
mated to be produced. This represents a 20.3 percent increase
over'1977 values. Projections for 1987 indicate that sludge
generation could reach 5.12 mil dry t, based on maximum regula-
tory compliance and the current population trends. The addi-
tional sludge generation from 1967 to 1987 is expected to be
about 1.45 mil dry t, or 39.5 percent greater than 1967 pre-
legislation levels. Figure 3 shows sludge production by EPA
region from 1967 to 1987. At the EPA regional level, the
largest quantities of water treatment sludge are generated
across an area extending from the Great Lakes to the Gulf of
Mexico (EPA Regions IV, V, and VI). In the West, only Region IX
produces appreciable quantities of sludge. All other regions
produce comparatively little sludge. Relative sludge generation
remains about the same through 1987. More than 65 percent of
the nation's municipal water treatment sludges are generated by
Regions IV, V, and VI. By adding Region IX values, more than 80
percent of the U.S. total is accounted for.
Industrial Wastewater Treatment Sludges
Sludge production from industrial wastewater pollution
control activities was estimated based on two scenarios. The
first scenario depicts a minimum sludge generation situation
which assumes that no further restrictions on industrial direct
dischargers to navigable waters would be forthcoming beyond 1977
Best Practicable Technology (BPT) requirements. The second
scenario portrays the maximum legislative condition under which
industry will need to employ Best Available Technology (BAT) for
control of conventional and toxic pollutants when discharging to
navigable waters; and control of toxic pollutants when discharg-
ing to publicly owned treatment works (POTW). Under maximum
conditions, the concept of zero discharge was not expanded
beyond what is already established through existing effluent
guidelines. There are no available national data files which
contain useable information on industrial effluents or that
include actual data on quantities of industrial pollution con-
trol sludges. It was therefore necessary to develop a data base
to include all of the industries whose effluents are regulated
under PL 92-500. This data base was compiled predominately from
the EPA Development Document series on effluent limitations for
industrial point sources, the associated economic analyses of
proposed effluent guidelines, EPA hazardous waste studies on 15
industries, and other government-sponsored studies. Department
of Commerce reports were used extensively to develop production
projections. Simple trend analysis was employed where projec-
tions were not obtainable. The development documents, economic
analysis and hazardous waste studies were the major source of
discrete subcategory production-related data.
Wastewater treatment practices and raw wastewater char-
acteristics were defined for 37 manufacturing industries whose
30
-------
2.c -
1 .5
t .0
0.3 -
z
a
(V
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(3
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t~4
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i <
i .5
1 .0
0 .!
0
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o.s
1987
1.113
0 .093
0 . 190
0 .300
0 .
0 .773
0 .
0 .
0.077
1936.
1.4-13
1.041
0 .090
0.137
0.233
0 .70S
0 . 717
0 .242
0 . 135
a .073
1980
1 .373
0 .946
0 .073
a.
0 .279
0 .443
0.431
0 .235
0.131
0 .061
1977.
1 .334
0 .342
0 .24.2
0.0*0 0 .09 1 f I
0.437
0.50*
0 .231
0 . 124
0 .030
1967
I .230
0.490
0.55*.
0 .4,4,1
0.212
I 1
0 . 112
0 .024
t; tit
rv v vi
EPA REGION
/ 1 1 vni :x
Figure 3.
Distribution of municipal water treatment sludge by
EPA region for 1967, 1977, 1980, 1984, and 1987.
31
-------
effluents are regulated under federal discharge standards.
These industries are identified in Ta.ble 5. From this data
base, unit sludge generation factors were calculated for nearly
700 individual waste streams for which effluent standards have
been promulgated or proposed. Total sludge production was then
calculated on a dry weight basis by multiplying unit sludge gen-
eration for 1967, 1977, 1980, 1984, and 1987, by annual indus-
trial production. Corresponding wet weight values were esti-
mated from sludge dry weight.
TABLE 5. INDUSTRIAL CATEGORIES SUBJECT TO REGULATIONS
UNDER THE CLEAN WATER ACT OF 1977
Industry SIC Code
Feedlots 02
Meat products 201
Dairy products 202
Canned and preserved fruits and
vegetables 203
Grain mills 204
Sugar products 206
Textiles 22
Paper and allied products 26
Inorganic chemicals 281
Plastics and synthetics 282
Paint manufacture 283
Organic chemicals 2865, 2869
Pesticides 287
Carbon black 289
Petroleum refining 2911
Paving and roofing materials 295
Rubber processing 30
Leather tanning and finishing 31
Iron and steel 3312
Glass 32
Primary nonferrous metals 333
Electroplating 34
The following assumptions were made in estimating or
projecting sludge generation for 1967, 1977, 1980, 1984. and
1987:
The level of treatment in practice prior to compliance
with BPT requirements was used to estimate the 1967
level of treatment. Since this is an historical year,
minimum and maximum conditions do not apply.
Unit sludge generation factor is defined as the number of units
of sludge generated per 1,000 units of production.
32
-------
The majority of direct dischargers were already treating
at BPT levels in 1977, thus full compliance with BPT was
assumed in making calculations. Since 1977 is an
historical year, minimum and maximum scenarios were not
used.
Under minimum conditions, unit sludge generation for
1980, 1984, and 1987 was assumed to be equivalent to the
1977 value. That is, more stringent controls than BPT
for all dischargers were rolled back to BPT levels.
Under maximum conditions, eight industries (identified
in the CWA Amendments of 1977) will be subject to
pretreatment standards for indirect dischargers by
1980. Although 13 additional industries will be in
compliance with these standards by 1984, no standards
have been developed for these industries as yet. No
additional regulation was calculated for indirect
dischargers for 1984 and 1987. Industrial direct
dischargers were assumed to be in full compliance with
BAT standards by 1984. Unit sludge generation for
direct dischargers for 1980 was assumed to be equal to
1977 values, and 1987 unit sludge generation was assumed
to be equal to 1984 values.
Figure 4 presents estimates of national generation of water
pollution control sludges for 18 industries under minimum and
maximum scenario conditions. Of tne industries represented in
the figure, 12 manufacturing industries produce an estimated 97
percent of U.S. water pollution control sludges. The two lar-
gest sludge producers, the iron and steel (SIC 3312) and the
inorganic chemical industries (SIC 281), together generate an
estimated 42 percent or 6.89 mil t (dry wt) of this slud.ge. The
group of four industries ranking next highest in sludge genera-
tion (paper (SIC 26), paving and roofing (SIC 295), electroplat-
ing (SIC 34), and sugar products (SIC 206)) accounts for an
estimated 41.2 percent or 6.7 mil t (dry wt) of the national
total. The remaining 31 industries surveyed contribute 16.8
percent or 2.75 mil t (dry wt).
Total sludge generation for the nation's 12 largest sludge-
producing industries for 1967, 1977, and 1987, is provided in
Table 6. The current (1977) level of sludge generation is
approximately 16 mil dry t (over 52 mil wet t). By 1987, indus-
trial dischargers could generate as much as 23.0 mil t of sludge
(more than 104 mil t, wet weight). In the course of 20 years,
from 1967, a period with limited federal discharge regulations,
to 1987, a period with a complex federal regulatory system,
industrial sludge generation can be expected to increase more
than threefold.
33
-------
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i
IRON INORGANIC PAPER PAVING ELECTRO- SUGAR MEAT PHOSPHATE TEXTILES
AND STEEL CHEMICALS AND AND PLATTN6 PR3SUCT5 MANUFACTURE
(BLAST FURNACES ALLIED ROOFING
AND STEEL MILLS PRODUCTS ' -.-.»,.,.
Figure 4. National generation of water pollution control
siudge for 18 industries.
34
-------
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PETROLEUM NON- ORGANIC PLASTICS
REFtNINC FERROUS
METALS
(PRIMARY)
DAIRY
LEATHER =537;.
CICES
*VALUES REPRESENT SLUDGE GENERATED IN TREATING WASTEWATER
DESTINED FOR DIRECT DISCHARGE TO NAVIGABLE WATERS.
tCARBON ADSORPTION IS A RECOMMENDED TREATMENT TECHNOLOGY,
HOWEVER, THESE VALUES DQ NOT INCLUDE WEIGHT OF SPENT
ACTIVATED CARBON.
Figure 4 (continued)
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35
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TABLE 6. ESTIMATED WASTEWATER TREATMENT SLUDGE GENERATION
BY THE TWELVE LARGEST SLUDGE PRODUCING INDUSTRIES
FOR 1967, 1977, AND 1987
SIC
Code Industry
3312 Iron and steel
(steel making)
201 Inorganic chemicals
26 Paper and pulp
295 Paving and roofing
34 Electroplating
206 Sugar products
201 Meat productsf
201 Phosphate manufacture
22 Textiles
206 Organic chemicals
333 Non-ferrous metals
(primary)
2911 Petroleum refining
Total Sludge Generation (106 t)
1967
Dry Weight
0.71
0.63
1.16
1.46
0.91d
1.25
0.309
0.16
0.05
0.05
0.13
0.07
Wet Weight
__
1.26
3.32
18. 2d
~"
--
1.04
0.16
0.70
1977
Dry Weight
3.41
3.48
1.93
1.08
1.32
1.63
0.83
0.60
0.33
0.14
0.29
0.09
Wet Weight
__
6.96
5.52
__
26.4
12.2
0.44
0.90
1987a
Dry Weight
4.50 (5.45)
3.98 (4.10)
2.41 (3.52)
2.34 (2.34)
1.75e
1.70 (1.70)
0.99e
0.76 (0.77)
0.38 (1.30)
0.36 (0^38)
0.41 (0.51)
0.13 (0.18)
Wet Weight
7.96 (8.20)
6.89 (10.1)
--
35. Oe
--
--
14.0 (48.0)
1.14 (1.21)
1.30 (1.80)
TOTALr
6.96
>25.0
15.9
>52.0
19.7 (23.0) >66.3 (>104)
aMinimum scenario values (maximum scenario values).
bExcludes sludges generated by indirect dischargers to POTW.
°Job and captive shops (Battelle Columbus data, 1976).
d!975 data.
e!983 data.
Environmental Quality Systems, Inc., data, 1976.
91971 data.
Totals for wet weight are given as the lowest estimate.
-------
On a regional scale, (Figure 5) most of the industrial
sludges in the U.S. are generated along a sector extending from
the Great Lakes to the Gulf of Mexico. EPA Regions IV and V are
by far the largest producers of pollution control sludges in the
nation (46.9 percent) with about 3.35 mil dry t and 2.92 mil dry
t, respectively, currently (1977) being generated. Both of
these regions will remain the leading generators through 1987,
with sludge quantities increasing to about 4.43 mil dry t in
Region IV and to about 4.13 mil dry t in Region V. The least
amount of sludge is currently (1977) being generated in the
western United States (12.9 percent) by EPA Regions VII, VIII,
and IX, and in the northeastern United States by EPA Region I.
Relatively speaking, medium quantities of sludge (0.734 mil dry
t - 1.99 mil dry t) are being generated in EPA Regions II (5.4
percent), III (10.1 percent), VI (14.8 percent), and X (9.8
percent). It is anticipated that by 1987, the distribution of
sludge produced will not change; however, quantities of sludge
produced in each region will increase over the entire country.
Air Pollution Control Sludges
Sludge production from APC devices was estimated using the
following procedure:
Industries which produce significant regulated air
pollution emissions were identified using both the EPA
compilation of Air Pollutant Emission Factors (AP-42),
and National Emissions Data Systems production rates,
and were grouped by SIC Code:
- Kraft pulping (SIC 2611)
- Paint pigment mixing (SIC 2816)
- Hydrofluoric acid manufacturing (SIC 2819)
- Sulfuric acid manufacturing (SIC 2819)
- Phosphate fertilizer (SIC 2874)
- Petroleum refining (SIC 2911)
- Concrete products (cement) (SIC 3241)
- Brick manufacturing (SIC 3251)
- Castable refractory (SIC 326)
- Gypsum (SIC 3275)
- Lime (SIC 3295)
- Ceramic clay (SIC 3295)
- Mineral wool (SIC 3296)
- Iron and steel (SIC 3312)
- Gray iron foundry (SIC 3321)
- Primary copper (SIC 3331)
- Primary lead (SIC 3332)
- Primary zinc (SIC 3333)
- Primary aluminum (SIC 3334)
- Secondary aluminum (SIC 3341)
- Brass and bronze (SIC 3341)
- Secondary lead (SIC 3341)
37
-------
ON CONTROL SLUDGE GENERAT
ILLION DRY METRIC TONS)
O *- N U 4> Ul Ov
4
0 .50*
0.3SO "
I
t * 1 1 i ri
i
30
4"
I
'
f. 126
I Z .923
pii
III
HIM '
EH'
0 . »21
0.319
2.072
1 .993
0 .575
0.270
0.203 B==I
P===J f 1
IV V VI VII VIII
987CMAXIMUM)
977(HISTORIC)
= 1987
= 1977
1.315
3 .856 i .299
[|
IX
III
X
EPA REGION
O
Q.
Figure 5. Total EPA region industrial wastewater sludge
generation for 1977 and 1987.
38
-------
- Secondary zinc (SIC 3341)
- Electric utility (SIC 4911)
- Incineration processes (SIC 4953)
t Significant pollutants emitted and methods used for
their control were identified for each industry.
Uncontrolled pollutant emission factors (UPEF) were
obtained for processes used by each industry. A unit
sludge generation factor was developed (kg dry sludge
produced per thousand kg of product), based on UPEF and
control efficiency.
Sludge production was calculated by multiplying unit
sludge production for each process and type of control
equipment by the fraction of production in compliance
using that process. Production data for air pollution
sources were obtained from the National Emission Data
System (NEDS) computer data file. Data were available
on a state-by-state basis for the 1977 baseline year.
National sludge production estimates for the 13 largest
sludge-producing industries for 1977 and 1987 are summarized in
Table 7. The values presented represent the total quantity of
sludge generated by air pollution control devices. Because
current industrial practices include the extensive recovery of
these waste residuals, the actual quantity of sludge requiring
disposal is considerably less than those values presented in
Table 7.
While total APC sludge generation is estimated to be 110.9
mil dry t (1977) and 377.7 mil dry t (1987), that portion des-
tined for disposal is considerably less. Values for APC sludges
destined for disposal are presented in Table 8. Of the 13 major
generators of APC sludge, five practice extensive recycle or
reuse of APC waste residues. These industries include: brass
and bronze (SIC 3341), concrete products (SIC 3241), paving
(asphalt cement) (SIC 2951), gypsum (SIC 3275), and phosphate
fertilizer (SIC 2874). In addition to these, the iron category
of the iron and steel industry (SIC 3241), and the secondary
lead industry (SIC 334) all practice extensive recycle or reuse.
The resource conservation measures described above reduced
APC sludge disposal requirements by nearly 50 percent in 1977.
It is possible that at least 40 percent of the APC sludge pro-
jected for 1987 could be used beneficially through recycle or
reuse.
Regional distribution of APC sludges occurs in a pattern
similar to the distribution patterns for each of the other cat-
egories of pollution control sludge generators. As shown in
Figure 6, EPA Regions III, IV, V, and VI produce the most
39
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TABLE 7 . ESTIMATED AIR POLLUTION CONTROL (ARC)
SLUDGE GENERATION BY THIRTEEN OF THE
LARGEST SLUDGE PRODUCING INDUSTRIES
(.million dry metric tons)
SIC
Code
4911
3341
3241
281
3312
2951
3241
2611
2911
3321
333
3275
2874
Total Sludge Generation
Industry
Electric utility
Brass and bronze
Concrete products
(cement)
Inorganic chemicals
Iron and steelmaking
Paving (asphalt cement)
Clay products
(lime and ceramic clay)
Kraft paper pulping
Petroleum refining
Gray iron foundries
Primary non-ferrous metals
(smelting and refining)
Gypsum
Phosphate fertilizer
TOTAL #
1977
39.779
14.161
18.172
5.086
8.202
6.545
4.368
4.295
3.506
1.486
0.957
0.725
0.478
110.960
1987*
196.993
84.718
36.911
10.522
11.269
9.419
9.580
8.038
4.316
2.203
1.731
1.141
0.831
377.673
NOTE:
The content of this table includes sludges recycled back into the manu-
facturing process.
*Maximum scenario values.
"''Includes hydrofluoric acid manufacturing and sulfuric acid manufacturing.
^Excludes secondary lead. Production data for this category is conflicting.
Current practices include recycling of APC sludge to process.
40
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TABLE 8. ESTIMATED QUANTITIES OF AIR POLLUTION
CONTROL (APC) SLUDGES REQUIRING DISPOSAL
(million dry metric tons)
SIC
Code
4911
281
2611
2911
3312
3321
3295
333
Total Sludge Generation
Industry
Electric utility
Inorganic chemicals
Kraft pulping
Petroleum refining
Steelmaking
Gray iron foundries
Ceramic clay
Primary non-ferrous metals
(refining only)
TOTAL SLUDGE TO DISPOSAL
1977
39.779
5.086
4.295
3.506
2.568
1.486
0.442
0.233
57.388
1987*
196.993
10.522
8.038
4.316
4.227
2.203
1.023
0.360
227.282
NOTE:
The content of this table represents sludge generated by the eight largest
APC sludge producing industries. Only sludges destined for disposal are
included.
*Maximum scenario values.
41
-------
z
o
a:
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Hi 075
~_l I- so
CO !£
_J ^S
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G£ ft:
\- Q 30
Z
O Z
U O 15
_
O _J
I-H M
i- s:
71 .093
15.539
55.581
8 . 318
0 . 938 2.673
0 .464
Illlllllllllllll 19 87 (MAX I MUM)
I |1977(HISTORIC)
0.421 = 1987
0.319 = 1977
15.481
2.693
10.037
0 .629
6.357
1 . 878
1 . 346
0 .692
I I
I I I
IV V VI
EPA REGION
VI I
VIII
IX
_
o
Q.
Figure 6.
Total EPA region air pollution control sludge
generated for 1977 and 1987.
42
-------
sludge. About 80 percent of the nation's ARC sludge disposal
requirement is and will continue to be associated with these
regions.
New Energy Source Sludges
Four new energy sources were examined to determine the
extent of total sludge (process and pollution control sludges)
generated by these emerging technologies. Our definition of
sludge used here has been broadened to accommodate limitations
in the data on waste stream characteristics. Such data is not
yet obtainable since development of new energy sources is just
beginning to commence. All four new energy source technologies
will result in operations which generate solid and/or liquid
waste streams requiring subsequent management. Those new
sources of energy include:
Coal gasification
t Biomass
Geothermal
t Oil shale.
The following provides a brief description of each energy
source and the quantity and characteristics of waste residuals
expected to be generated during energy recovery processes.
Gasification--*
The coal gasification process consists of several opera-
tions which will produce solid waste. Coal pretreatment/pre-
paration operations involve crushing and sizing of coal to be
supplied as feedstock to the gasifier. Solid waste from this
operation consists primarily of rock and mineral matter and
undersized coal fines rejected by the sizing equipment. This
material is either landfilled, consumed on site as a fuel,
or briquetted for use as gasifier feedstock. Solid waste gener-**
ation based on design estimates for the coal preparation process
ranges from 1,440 to 164,000 t/yr.
During the gasification process, coal is combusted at high
temperatures in the presence of a steam/air or steam/oxygen
mixture, or with a fluxing agent such as dolomite. Solid wastes
generated during gasification consist primarily of hot ash. The
ash is comprised primarily of mineral matter, slag, coal feed
additives and unreacted coal. The chemical composition, as well
as the stability, determines disposal options. Over 180,000
t/yr ash are generated by one 250 billion BTU facility.
* only pilot operations exist at this time
** Plant size - 250 billion BTU/stream day.
43
-------
The gas product generated from the gasification process
must be purified to remove particul ates, tars, oils, anci acid
gases. These constituents are collected dry by cyclones or
electrostatic precipitators, or wet during the quenching and
acid gas removal process. In addition to these solids, some
pollutants removed in the solvent blowdown stream may have to be
treated prior to disposal.
Emissions from coal gasification operations include par-
ticulates, SOo and hydrocarbons. Particulate emissions origi-
nate mainly as dust from coal crushing and sizing operations and
during the gasification process. This material is composed
primarily of mineral matter, and may be collected in a wet or a
dry mode. Captured solid waste from the collectors is either
disposed of in a landfill, used as a fuel, or sold as a by-
product.
Desulfurization of quenching operations emissions can be
accomplished using wet limestone scrubber systems. The control
of sulfur emissions creates limestone sludges from the desul-
furization unit. This sludge contains calcium hydroxide, cal-
cium carbonate, calcium sulfate and calcium sulfite, spent
catalysts, absorbents, and various by-products. Where efficient
particulate removal is not performed upstream of the scrubber,
such sludges also contain large quantities of coal ash.
The two methods of disposal of FGD sludge are (1) dewater-
ing and subsequent disposal in a landfill, and (2) ponding. On
a dry weight basis, combined sludge and ash waste will be about
2.5 times the normal coal ash disposal tonnage produced by a
conventional coal-fired utility. Large disposal facilities will
be needed to handle these sludges. For example, a 1,000 MW unit
over a 20-yr lifetime will require about 221 ha (0.5 sq mi) of
land for disposal, assuming a wet sludge containing 50 percent
solids ponded to a depth of 9 m (30 ft).
Two methods currently used to reduce the hydrocarbon con-
tent of gaseous waste streams include (1) oxidizing hydrocarbons
to C02 and water, and (2) adsorption onto activated carbon.
Neither method results in significant sludge generation.
Liquid waste streams come from gas quenching and acid gas
removal operations, and wet scrubbers located downstream in the
process. Evaporation ponds have been used for wastewater treat-
ment in a number of preliminary designs for coal gasification
plants. However, evaporation ponds require substantial land
area, are not generally effective in areas with evaporation
rates of less than 50 cm (20 in), and can contaminate ground-
water if used over a period of years.
44
-------
Biomass Conversion--
There are approximately 754 mil t (831 mil tons) of indus-
trial, municipal, and agricultural wastes available each year
for conversion to some type of fuel. The fuel value of
thesewastes, estimated at 14.4 x 1015 BTUs, represents about gO
percent of the total energy consumption of the United States.
Biomass conversion processes convert the organic fraction
of urban wastes, agricultural residues, and terrestrial and
marine energy crops to synthetic fuels. Available data indicate
that from 40 to 60 percent of the input material to a biomass
conversion facility can be converted to energy. However, large
quantities of process waste residues are associated with large-
scale bioconversion operations.
The four technologies most used at present are: pyroly-
sis/incineration, anaerobic digestion, thermal/chemical con-
version, and hydrogen production. All of these require some
sort of air or water pollution emissions control, and can be
expected to produce pollution control sludges in response to
regulation under either the Clean Water Act or the Clean Air
Act.
Existing sources of biomass for conversion to energy are
listed in Table 9. With the exception of secondary municipal
sewage sludge, pollution control sludges are not presently used
as feedstock to any great extent. For the most part, existing
feedstock from industry has been limited to process wastes.
Although there may be some potential for using biological
sludges from the food industry (SIC 20), from feedlots (SIC 02),
or from the timber industry (SIC 24), there are few, if any,
efforts at this time to investigate the feasibility for con-
verting the biomass in industrial pollution control sludges to
fuel .
Geothermal Energy--
Geothermal energy is heat energy derived from steam or hot
water extracted from wells extending deep into the earth's sur-
face (geysers). The energy derived from geothermally heated
fluids is used to drive low-pressure turbines to produce elec-
tricity. The Pacific Gas and Electric Company Geysers, located
in California, is the only geothermal field currently producing
electric power in the United States. This vapor-dominated
system has the capacity to generate approximately 500 MW of
electricity (an amount sufficient to supply a city of about
500,000 persons). PG&E expects future expansion at this site to
reach a peak of around 1,800 MW by 1985.
Assuming all usable wastes are converted to methane.
+ Cumulative plant capacity is projected to reach 773 MW in
1978 and 909 MW in 1979.
45
-------
Table 9 Annual production of organic wastes in U.S.
(Source: USDA 1978 report "Improving Soils With Organic Wastes)
Total Production
Organic Waste 1,000 dry tons Percent of total
Animal manure
Crop residues
Sewage sludge and septage
Food processing
Industrial organic
Logging and wood
manufacturi ng
Municipal refuse
175,000
431 ,087
4,369
3,200
8,216
35,714
145,000
21 .8
53.7
0. 5
On
. 4
1f\
. 0
4.5
18.1
Total 802,586 100.0
The Imperial Valley in .California promises to be the next
major source of geothermal energy in the United States. This
would be the first liquid-dominated electric generating facility
to be operated commercially. The U.S. Bureau of Reclamation and
the Office of Saline Water are currently conducting a pilot pro-
ject to test the feasibility of producing desalinated water from
various sites in the Valley. Generating capacity from these
sites is estimated to be 20,000 to 30,000 MW, or more than 40-60
times that being produced at the PG&E facility.
The San Diego Gas and Electric Company and the U.S. Depart-
ment of Energy currently have a geothermal 10 MW binary fluid
power test facility in the Imperial Valley at Niland, Cali-
fornia. This geothermal source produces highly saline fluids
w-hich may preclude its development into a major power source.
The steam from wells consists of about four percent by
weight noncondensable gases (H2S, C02, CH4, and NHo), trace
amounts of the radioactive nobfe gas, radon, entrained solids,
and B, Na, Mg, Al, Si, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn, As, Sr,
Hg, and Pb. Most of the solid material picked up in the system
settles to the bottom of the cooling tower to produce a "process
solid waste residual" requiring disposal. Of the noncondensable
gases, concern over the emission of hazardous HoS gas from the
jet gas ejectors to the cooling towers has resulted in treatment
of cooling water with ferrous sulfate to precipitate H2S as
solid sulfur. Cooling tower water is filtered to remove the
particulate sulfur, and the residue is disposed of in a land-
fill. Chemical analyses of H2S oxidized sludge at the PG&E
facility show a dry weight composition of 62.7 percent sulfur,
18.5 percent iron, 16.6 percent oxygen and hydrogen, and 2.2
46
-------
percent other constituents. The sludge has a moisture content
of 50-70 percent. PG&E estimates that the total HoS sludge
production estimated for 1978 is 45 t/day (16,000 t/yr). This
quantity should more than double by 1985 if PG&E realizes an
anticipated generating capacity of 1,800 MW.
PG&E estimates that sludge generated from the Geysers
facility (including cooling tower sludge), will reach 65.6 t/day
(23,616 t/yr) in 1979 and 150 t/day (54,000 t/yr) by 1985.
The geothermal systems proposed for the Imperial Valley
will rely on heated water (liquid-dominated) rather than
steam. These fluids are typically highly mineralized, with
total dissolved solids content ranging from 10,000 to 250,000
ppm. Concentrations of undesirable minerals in spent geothermal
fluids have traditionally been disposed of to nearby surface
water, resulting in a high degree of chemical and thermal pollu-
tion. The emerging solution to the disposal problem is to dis-
pose of spent geothermal fluids by reinjecting them into a
producing formation through productive wells or holes drilled
for that purpose. Most of the chemical pollutants return to
their source and the fluid supply in the reservoir is replen-
ished, thus reducing the chance of surface -subsidence caused by
continuous fluid withdrawal from a subterranean reservoir.
Reinjection is expensive, however, and there is the addi-
tional risk of plugging the geologic formation with various
types of solid matter from the injection fluid. There are also
regulations in California that prohibit the discharge of waste
fluids with high dissolved solids content into either surface
waters or shallow aquifers. In addition, provisions under
Section 1421 of the Safe Drinking Water Act require permits for
injection activities. These restrictions are currently being
addressed by storing spent geothermal brines in plastic lined
evaporation ponds.
As an alternative, dissolved solids content of the brines
could be reduced through treatment of brine wastes prior to
reinjection. Based on an estimated flow of 150 mgd (567.,750
m /day) for a 1,000 MW liquid-dominated plant and a 50 percent
removal efficiency, an impressive 1 to 27 million tons/yr
ofpollution control sludge could be expected to be generated for
brines containing 10,000-250,000 ppm dissolved solids.
Oil Shale--
Currently, diminishing supplies of oil and natural gas have
brought about a renewed interest in tapping the enormous U.S.
shale oil reserves in Wyoming, Utah, and Colorado. Commercial
interest in developing this resource has been thwarted for a
variety of economic, political and technological reasons.
Unfortunately, a mining operation of tremendous proportions
would be required to supply even ten percent of the current U.S.
47
-------
oil requirement. A mining endeavor of this magnitude would
result in over 1.5 million tons of oil shale being mined each
day. Since only a small fraction of the shale is recoverable as
oil, a considerable amount of solid waste as spent shale would
require disposal. By the late 1980's, when oil shale pro-
duction is expected to exceed one million barrels per day,
spent shale generation could approach 1.3 million tons per
day or 420 million tons per year. It is estimated that
40-50 percent of this material will have to be disposed of
to land, posing a monumental disposal problem.
Most of the oil derived from oil shale is produced by ther-
mal decomposition of kerogen, a solid organic substance which
"cements" the marlstone rock together. When heated to about
550°C, pyrolyis occurs, and the kerogen decomposes to produce a
mixture containing hydrocarbons, water, and carbon oxides. This
mixture is roughly equivalent to crude oil. The crude product
is refined in much the same manner as petroleum- to yield gaso-
line, jet fuel, heating oils, and other products. Western oil
shale fields could produce 600 million barrels of oil from high-
grade shale (averaging 25 or more gallons of oil per ton),
andcould yield an additional 1.2 billion barrels of oil from
low-grade shale (averaging 15-20 gallons of oil per ton).
Commercial extraction of oil shale may be accomplished from
surface retorts where oil shale is removed from the mines prior
to pyrdlysis, or in situ by fracturing the shale formation and
applying heat to the fractured zone.
Spent shale from surface retort operations may possess
characteristics which impact public health or the environment if
not disposed of properly. Spent shale not only contains sub-
stantial levels of soluble salts which could ultimately leach
out to contaminate nearby water supplies, but also contains
significant quantities of polycondensed organic matter formed
during pyrolysis. Thus, the potential presence of carcinogenic
or mutagenic organics is not unreasonable.
48
-------
Although in situ retorting leaves spent shale within the
mines, there is still potential for ground water contamination
due to leaching. In addition, operations for recovery of off
gases and wastewater may not be as effective as those used
during surface operations.
The long-term aspect of oil shale leaching must be con-
sidered in any large-scale development. Further investigations
are currently underway to provide a better definition of the
magnitude of this and other problems.
A variety of solid process wastes may be produced during
retorting and on-site crude oil upgrading. These include shale
fines from crushing and sizing operations, shale oil cake
produced during on-site upgrading of the crude oil and spent
coal from hydrotreating, sulfur recovery and arsenic removal
operations. Although these wastes represent a small fraction of
the solid waste generated compared to spent shale, they may
contain highly toxic substances such as arsenic or organics.
Wastewaters originate from a variety of sources:
Retort water
Wastewater from upgrading operations if integrated with
retorting operations
Waste/effluents from air emission control systems
Cooling water and boiler blowdown
Wastewater from raw water treatment systems.
Treatment of these effluents is expected to involve several unit
processes or operations in order to achieve water quality suit-
able for reuse or discharge. Processes that may be used to
treat wastewater include primary settling or dissolved air flo-
tation for removal of suspended matter, ammonia stripping,
biological treatment and carbon adsorption for dissolved
organics removal, and chemical coagulation or lime softening and
filtration to reduce heavy metals.
Disposal of the highly polluted retort water by subsurface
injection into previously retorted shale zones or into deep
wells will fall under restrictions encountered in state codes
and will be subject to permit provisions under Section 1421 of
the Safe Drinking Water Act.
AN EVALUATION OF CURRENT METHODS OF SLUDGE DISPOSAL
The vast quantities of various pollution abatement sludges
presently generated, as well as the increased amount projected
49
-------
for the future due to the Clean Air Act, Clean Water Act, and
Safe Drinking Water Act, require environmentally acceptable dis-
posal. On the other hand, the scheduled termination of ocean
dumping undoubtedly will increase the necessity of land-based
alternatives, namely, landfilling, land spreading, composting,
and pyrolysis/incineration.
Landfilling of Sludges
Landfilling is a method for disposal of solid waste on land
without creating nuisances or hazards to public health and
safety, or to the environment. Engineering principles are
judiciously applied in order to confine wastes to the smallest
practical volume, and to provide cover with a layer of earth at
the conclusion of each day's operation or at more frequent
intervals if deemed necessary.
A U.S. Environmental Protection Agency inventory found that
29 percent of treated municipal sludges and 22 percent of the incin-
erator ash are landfilled . State and local agencies differ in
their regulations for the acceptability of municipal sludge. In
many states, sludges must be dewatered before they can be dis-
posed to landfills. In other states where regulations permit,
landfilling of sludge with solid waste is a common practice.
Appropriate management of landfill activities can result in
the leveling of eroded, irregular, or low land to increase its
usefulness, and at the same time can assure a very low occur-
rence of infectious and parasitic diseases. On the other hand,
poor management of operations involving landfilling of
sewagesludges can result in more damage than benefits. Some of
the adverse effects of improperly managed landfills are:
Contamination of ground and/or surface water bodies
Spreading of diseases from vector contact
Explosion hazards from methane gas
Inhibition of plant growth due to poor venting of
methane, hydrogen sulfide, or ethylene gases
Poor public acceptance due to nuisances, i.e., odors,
noise, dust, traffic, and land disturbance.
Landfilling costs consist of the initial capital investment
costs and operating costs. The total cost of operating a land
* Source: Metcalf and Eddy, 1978,
50
-------
burial site will depend, to a large extent, on the terrain in
which the operations are conducted. Generally, if the area is
open and reasonably level, the cost of operation can be mod-
erate. If, on the other hand, operations involve filling a
swamp, bog, or similar area where material-hand!ing operations
are considerably more difficult, the cost will of necessity be
higher. Frequently, one of the primary reasons for increased
costs is the type of equipment required to operate satisfac-
torily in the selected location.
Table 10 presents estimated costs of wastewater sludge
disposal by land burial at a rate of 100 t/day for a large
metropolitan city. These estimates include the cost of sludge
treatment and transportation ($50.03/dry t), but exclude moni-
toring costs. In general, on-site land burial cost ranges from
$73 to $226 per dry t, including average costs for dewatering.
Landspreading of Municipal Sewage Sludge and Wastewater
Currently, 10,958 dry t/day (12,058 dry tons/day) is left for
disposal after being processed, 31 percent of which is disposed
of by landspreading. Implications of 1andspreading include
recycling nutrient resources to crop lands, reclamation of
despoiled lands or just simply an ultimate disposal method.
Proper management of landspreading sludge on cropland will:
t Improve soil physical properties, e.g., promote soil
aggregation and soil moisture
Improve soil chemical properties, e.g., increase
nutrient retention capacity which preserves loss of
plant nutrients by leaching
Supply additional plant nutrients, e.g., nitrogen,
phosphorus, potassium, etc.
Increase crop yields.
A major concern in landspreading of sludge on cropland is
the enrichment of heavy metals, particularly cadmium, to plant
tissues and, consequently, to human food chains. As a preventa-
tive measure, soil pH should be maintained in the range of 6.5
to 7.0, and the rate of sludge application must be carefully
calculated so that heavy metal concentration will not exceed the
limit recommended in the guidance provided in the Sludge Techni-
cal bulletin, and Section 4004 (RCRA) and Section 405 (CWA)
guidelines when promulgated.
Source: Metcalf and Eddy, 1978,
57
-------
TABLE 10. COST ANALYSIS FOR LAND BURIAL OF
WASTEWATER SOLIDS (1975 dollars)
Item Trenching Landfil1i ng
$/dry t
Capital cost 18.40 14.86
Operating cost 39.96 37.81
Total cost* 58.36 52.67
Note: These costs are based on a site located in
Philadelphia, Pennsylvania.
Monitoring cost is excluded.
When sludge 1andspreading is used for reclamation purposes,
the sludge is applied for its organic content. For instance,
strip-mined lands invariably have had the topsoil completely
removed. As a result, the exposed surface is usually completely
void of organic material and plant life. Reclamation utilizes a
considerably larger quantity of sludge, e.g., 200-400 t/ha in
comparison to 3-10 t/ha when applied to cropland. However,
reclamation activities usually cease after a good, rich top
layer of soil has been developed. Those individuals involved
with soil reclamation are usually less conservative than the
farmer, who must protect his soil for future use.
Sludge may also be applied to land for no other beneficial
purpose than that of disposal. These programs are designed so
that disposal sites may be utilized for many years without a
loss or decrease in the soil's ability to assimilate sludge.
Generally, there are no future agricultural plans for the plot
of land. The primary concern is that the neighboring properties
and ground water supplies do not become polluted, and that nui-
sance odors do not develop.
Municipal sewage wastes are viewed by society as having a
negative value, since costs must be incurred to get rid of
them. Applying sewage sludges to land produces goods with a
positive social value by the beneficial recycling of water and
nutrients back to the land. This added value acts to reduce the
net cost of disposal.
A substantial portion of the cost of sludge application to
land is the transporting cost. It is an economical disposal
alternative when the application site is close to the treatment
plant. Another major cost factor is the handling cost. The
sludge can be handled as a liquid, slurry, or solid, and hand-
ling costs are incurred differently in each situation. Table 11
52
-------
shows estimated costs for various sludge-handling systems that
might be used by a large city (greater than 1 million popu-
lation). Total costs for dewatering, transporting and applying
operations range from $50 to $210 per dry t.
The direct economic benefits of sludge application to crop-
land may be estimated by considering the value of sludge as a
substitute for commercial fertilizer, principally by comparing
the nitrogen, phosphate, and potassium content of each. Esti-
mates of the dollar value of sludge for six different nutrient
levels are compared against commercial fertilizer prices in
Table 12.
The costs of sewage sludge disposal generally exceed the
value of sludge as a commercial fertilizer substitute. Using
current fertilizer prices and the median nutrient content for
sludge, the benefits to the user would be $26/dry t ($23/dry
ton). The value of sludge, however, may be reduced drastically
if it contains excessive concentrations of heavy metals.
Indirectly, the economic impact of sludge 1andspreading
could be positive if the local land market potential is promoted
through increased crop production. On the other hand, the eco-
nomic impact would be negative if landspread areas were aes-
thetically displeasing and the practice contributes heavy metals
and organic contaminants to the food chain.
Sewage Sludge Composting
Composting is a biological process for stabilizing and
treating organic waste. Interest in sewage sludge composting
has recently increased in the United States as a result of
several factors:
Legislative actions prohibiting or restricting water and
air pollution (Water Pollution Control Act Amendments of
1972; Marine Protection, Research, and Sanctuaries Act
of 1972; Air Quality Act of 1967).
Interest in waste recycling and public awareness of the
need for a clean environment
Improvements in composting technology
Increased costs of sludge disposal by incineration and
other methods, and the need to more effectively utilize
nonrenewable resources.
In the United States, there are several methods used for
composting sludge. A mechanical sludge composting process was
developed and tested by the Eimco Corporation in 1968. The
53
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TABLE 11. COMPARISON OF ALTERNATIVE METHODS FOR
HANDLING SECONDARY SLUDGE FROM A LARGE CITY
System description
Costs (dollars per dry metric ton)
De- Transpor- Appli-
watering tation cation Total
1. Lagooning and later ex-
cavation, then trucking to
site 32 km (20 miles) distant,
where it is dumped and later
plowed into the soil at 15%
solids.
2. Lagooning and later ex-
cavation, then 160 km (100
miles) rail haul to site at 15%
solids, then dilution and plow-
ing into soil at 10% solids.
3. Vacuum filtration to 25%
solids, then truck haul to site
32 km (20 miles) distant, where
it is dumped and later plowed
into the soil at 25% solids.
4. Vacuum filtration of 55% of
sludge to 25% solids, then mix-
ing with remaining 45% of sludge
at 3%. 160 km (100 miles) rail
transportation at 15% solids,
then dilution and plowing in at
10% solids.
5. Pipelining for 20 years at
5% solids for 32 km (20 miles)
then lagooning, later excavation
and plow application at 10%
solids.
6. Same as 5,
(100 miles).
except for 160 km
7. 160 km (100-mile) barging of
8.0% material after vacuum filtra-
tion of 20% of total and mixing
with remaining 80%, followed by
application to land.
$16.54
$14.66
16.54
17.64
9.92
16.54
16.54
8.82
8.82
8.82
3.75
$22.05 $53,25
22.05 47.40
22.05 48.51
22.05 40.80
22.05 42.34
18.74
3.86 ' 20.67
22.05 57.33
22.05 46.58
Source: Arthur D, Little, personal communication.
54
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TABLE 12. VALUE OF ONE METRIC TON OF DRY SEWAGE SLUDGE UNDER
ALTERNATIVE LEVELS OF NUTRIENT CONTENT AND COMMERCIAL FERTILIZER PRICES
Value of Nutrients in Sludge
N = $0.66/kg, P205 = $0.44/kg N = $0.44/kg, P205 = $0.33/kg
Nutrient Content ICO = $0.24/kg K20 = $0.18/kg
High (N = 6.4%, $54 $40
P0 =8.7%
Medium (N = 5%, 35 26
P205 = 5.25%
K0 = 0.54%)
tn P 0 = 5 25%
en 25 3-"*
2
Low (N = 3.5%, 17 11
P205 =1.8%
K20 = 0.24%)
pproximately 30% of total N and 100% of P20s and K20 would be available for crops
-------
Agricultural Research Service at Beltsville, Maryland, has
demonstrated two other processes for stabilizing sludge:
A windrow process that composts digested sludge
A forced aeration process for composting raw or digested
siudge.
Flow diagrams of these two processes are shown in Figures 7 and
8. Ongoing composting projects in various cities in the United
States are listed in Table 13.
Composted sludges (also called composts) are more attrac-
tive for landspreading than digested sludges because they:
o Decrease the solubility of heavy metals and/or dilute
the concentration of these metals in the sludge
o Avoid odors usually associated with sewage sludge
o Inactivate weed seeds
o Greatly reduce animal and human pathogens
o Reduce moisture content and, thereby, the weight to be
hauled
o Make the material of a size and consistency to facili-
tate even application, a factor of special significance
when used on lawns or .pasture.
Landspreading of composted sludges provides the same
advantageous effects as would the landspreading of digested
sludge. Although landspreading of composted sludge presents
less of a human health risk than non-composted sludge, the
cost is almost equal to incineration. However, compost can
be used as a fuel which can be stored, transported, and burned.
It is estimated that one ton of compost would equal the energy
from a ton of coal, or 246 (65 gal) of No. 2 fuel or 226 m3
(8,000 ,ft3) of natural gas.
On-site processing cost of composting is subject to econ-
omies of scale ranging from $56/dry t ($51/dry ton) for a munic-
ipality of 100,000, to $40/dry t ($30/dry ton) for a city of
500,000, not including dewatering costs. Costs are expected to
continue decreasing as production capacity increases. Com-
posting is land-intensive, requiring a hectare for about every
30,000 people or for every 6.72 dry t (1 ac for every 3 dry t)
of sludge processed. Composting is also labor-intensive, with
56
-------
COMPOST
01
SLUDGE
(1 VOLUME)
WOODCHIPS
(3 VOLUMES)
DAYS
WINDROW
COMPOSTING
t
biniiiiiiiiiii
WOODCHIP RECYCLING
Figure 7. Flow diagram of the windrow composting.
-------
CJ1
00
SLUDGE
(1 VOLUME)
WOODCHIPS
<2 VOLUMES)
21 DAYS
30 DAYS
SCREENING
WOODCHIP
RECYCLING
Figure 8. Flow diagram of the aerated pile composting.
-------
TABLE 13. U.S. CITIES PRESENTLY COMPOSTING SLUDGE
City
Danger, ME
Camden, HY
Chicago, IL
Durham, MM
Stratford, CN
Washington, D
Los Angeles,
CA
,7l Type Composting
Population^' oF Process
(xlO3)
38
TOO
3,173
12
49
.C.2,000
2,717
Waste
Raw S.S.
Primary (raw)
S.S.
Digested S.S.
Raw S.S.
Primary and
Activated S.S.
Digested S.S.
Digested S.S.
AP9
AP
AP
AP
AP
AP, Wd
W
Year
Operation
Started
1975
1978b
1977
1975
1974
1975
1972
Output
(xlO3 dry
t/yr)
2.26
__
0.52
31.26
2.08C
20.0
54.7
Sale
Price
($/yd3)
$/n.3
4.00
0
0
0
1.52
_ Point of Soje
P Taiit Dell v e r ed"
Yes
Yes
Mo
Yes
Yes
Yes
No
tlo
No
No
No
No
Type of Custorti
Private
Citizen
Yes
Yes
No
__
No
No
Govt. P
Agency
Yes
No
Yes
__
Yes
No
ter
rlvaCe
Company
No
No
Mo
No
Yes
aAerated pile process.
'W plant has only been operating since May 1978, so the marketing information is not available.
^here is no customer yet, the City and University of Bridgeport jointly operate a green house and potting soil
project. A marketing plan may be forthcoming.
TJindrow process.
eFac111ty located in BeHsv11le, Md.
-------
40 percent of the costs going for labor. Municipalities should
not view the composting of sewage sludge as a potential money-
maker, but rather as a means of reducing sludge disposal costs.
Ocean Disposal
Under current practices, large-scale disposal of pollution
abatement sludges is restricted to municipal sewage sludge. One
small-scale pilot project investigating ocean disposal of air
pollution control sludges ( stabi 1 i zed ^scrubber sludge and fly
ash) in Long Island Sound, has been under study since 1977.
Ocean disposal of sewage sludge and other waste materials
is currently regulated by the Marine Protection Research and
Sanctuaries Act of 1972 (PL 92-532, MPRSA), and Sections 402 and
403 of the Clean Water Act of 1977 (PL 95-217, CWA). The MPRSA
controls the dumping of sewage sludge from vessels or barges,
while the CWA regulates the disposal of sewage sludge into the
marine environment from ocean outfalls. The ocean disposal
section of this report evaluates both ocean disposal and ocean
discharge practices.
Currently, ocean dumping of sewage sludge occurs at two
disposal sites (excluding dredged material), accounting for
nearly 70 percent of the total waste material dumped in the
ocean. Both disposal sites are located along the Atlantic
Coast. One site, located approximately 19 km (12 mi) from the
Long Island, New York and New Jersey shorelines, receives sewage
sludge from the New York-New Jersey metropolitan areas (New York
Bight Apex). A second site is located 93 km (58 mi) from the
mouth of Delaware Bay, and southeast of Cape May, New Jersey.
This site receives sewage sludge from Philadelphia, arid, prior
to 1977, received sludge from Camden, New Jersey. Table 14
summarizes the amount of sewage sludge annually dumped on the
Atlantic Coast since 1973 from these two operations.
Discharge of sewage sludge through ocean outfalls is prac-
ticed by several coastal communities. The quantities discharged
and the characteristics of the sludge vary considerably between
communities. Both raw sewage sludge and anaerobically digested
sludge is discharged through ocean outfalls. One large urban
area which discharges its waste-activated and digested sludge
through a marine outfall is Los Angeles, California. Unlike
many other ocean discharge operations, the Los Angeles situation
has been carefully monitored since 1973, recording not only the
amounts of sludge discharged, but also the observed environ-
mental and public health impacts which can be associated with
this sludge disposal practice. During 1977, nearly 58,000 dry
metric tons of sewage sludge were discharged into Santa Monica
Bay, a portion of the Southern California Bight.
60
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TABLE 14. QUANTITIES OF SEWAGE SLUDGE DUMPED IN THE
ATLANTIC OCEAN, 1973-1977 ^
(in approximate wet metric tons)
1973 4,443,300
1974 4,544,100
1975 4,570,900
1976 4,779,900
1977 4,656,500
Assuming five percent solids content.
The MPRSA was intended to minimize or end all ocean dumping
of waste materials (vis., dredged material) by April 23, 1978.
Existing dumpers who were unable to meet the 1978 deadline,
could receive interim permits after that date if they were able
to provide implementation schedules adequate to allow phasing
out of ocean dumping or compliance with all requirements of a
special permit by December 31, 1981. Provisions of the CWA also
call for a ceasing of ocean discharge of sewage sludge by 1981.
The identification of specific environmental impacts asso-
ciated with ocean sewage sludge disposal is confounded by the
separation of natural perturbations with waste disposal
effects. For example, samples collected from sewage-stressed
areas may or may not be significantly different from expected
natural equilibria and variations in these equilibria. Factors
ultimately affecting species abundance include effects from
chemicals released from wastewater emissions, food supply,
predation, and interspecific and intraspecific competition. In
many instances, it is difficult to determine whether observed
responses by benthic organisms are due to chemical changes in
the habitat or physical impacts (e.g., suffocation by
particulate matter).
The highly variable volumes and characteristics of dumped
and other waste materials which reach the New York Bight Apex
directly or indirectly (e.g., river outflows, sewage treatment
plant and raw sewage outfalls, industrial outfalls, and dredge
spoil disposal at a dump site within a few kilometers of the
sewage sludge dump site), make it extremely difficult to relate
the direct effects of sewage sludge dumping on the sediment and
water quality of the Bight Apex, and thereby on the biota.
Observed impacts at the sewage sludge dump site can, at best, be
defined in terms of the sum effect of all wastes disposed in the
area.
61
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The task of identifying environmental effects of sewage
sludge disposal is somewhat easier for the Philadelphia and Los
Angeles disposal sites. Only sewage sludge is disposed at these
sites, and the impacts of its disposal are not masked by con-
taminants from other sources. Recent research by the EPA at the
Philadelphia dump site has found sediment accumulations of
organic carbon, metals characteristic of the sludge waste, PCBs,
and coprostanol (a steroid biochemical which is excreted from
the intestines of warm-blooded animals, and is indicative of
sewage pollution). Areas of sewage sludge deposition typically
extend to the south of the release site, and northeast in a
large swale.
Even though metal concentrations in the sediment exceed
background levels, these elevated concentrations have remained
the same since first sampled in 1975. Accumulations of heavy
metals in scallops and clams collected from the disposal site,
as well as mortalities in the Mahogany Clam, have been linked
with sludge disposal. Determinations of tissue-level concentra-
tions of metals in commercially important fish species have not
been reported. Black necrotic lesions in crabs have also been
observed.
Surveys of the sediment field off the Los Angeles City
Sludge Outfall have reported an area with sludge-like char-
acteristics covering less than 2 knr (1 mi^ ). Benthic macro-
faunal studies of the outfall area have not shown any net
average effect of the outfall on the benthos. Efforts to find
pollution indicator species in the outfall area have failed to
determine the presence of a single species which would ade-
quately indicate any one set of conditions or excessive amounts
of waste discharge. Occurrence of a few bottom fish species was
rare, although one species of bottom fish and several species of
Rockfish appear to be positively attracted to the nutrient-
enriched area near the outfall. Despite observed fluctuations
in fish abundance in the outfall area, it has not been clearly
demonstrated that these fluctuations are the result of either
conditions at the sewage sludge discharge site, natural causes,
or both. Incidence of fin erosion and skin tumors has been
reported in fish collected from the outfall area, although the
disease is also present in fish populations sampled from several
nondischarge areas off Los Angeles and other Southern California
counties.
Sewage sludge is a potential carrier of bacterial and viral
pathogens from human and other animal intestinal tracts. Trans-
mission of these pathogens to man through ocean disposal can
occur either through exposure during contact recreation, e.g.,
beach or ocean swimming, or through consumption of contaminated
seafood. .'
62
-------
At present, no immediate health hazard has been observed to
occur from contact recreation as the result of sewage sludge
disposal at any of the three sites discussed in this report.
Incidents of high coliform counts and of floatables with high
coliform levels in New York beach waters, have been attributed
to sewage sludge dumping. However, the major source of the
coliforms and particles has been shown by numerous EPA studies
to originate in outflow from the Hudson River or from nonpoint
shoreline discharges.
It is well known that shellfish concentrate microorganisms
in their tissues. Health hazards implicit in the consumption of
contaminated seafood are, therefore, much greater than those
associated with contact recreation.
In 1970, the presence of high concentrations of coliform
bacteria forced the FDA to close a portion of the New York Bight
Apex to shellfishing in the immediate area of the sewage sludge
disposal site. In 1972, the boundaries of the closed area were
extended. Contamination of the shellfish in this area has not
been shown to be a result of sewage sludge dumping alone. In
fact, bacterial contamination from onshore sources has been doc-
umented as a major contributory factor. In 1976, the FDA closed
an area in the vicinity of the Philadelphia sewage sludge dis-
posal site to shellfishing as the result of coliform contamina-
tion from the sludge. No incidents of shellfish contamination
have been recorded in Santa Monica Bay as a direct result of
sludge discharge.
The costs associated with ocean disposal of sewage sludge
are both direct and indirect. Direct costs include construc-
tion, operation, and maintenance costs of sludge pretreatment
facilities, as well as transportation costs, and environmental
monitoring costs in the disposal area. Indirect costs can be
incurred from the effects of sludge disposal in the ocean.
Indirect costs include decreased recreational use, closure of
areas to both fishing and shellfishing, prohibition of the sale
of products due to contamination, and biological effects on
mortality, growth, and reproduction rates of commercially
important marine resources. Estimates of direct costs for ocean
disposal by barge dumping range from $29/dry metric ton to
nearly $50/dry metric ton. The difference is largely a function
of barging distance. Direct costs for discharge of sewage sludge
at Los Angeles is approximately $20/dry metric ton.
It is considerably more difficult to assign a dollar value
to the indirect costs of ocean disposal of sewage sludge. Few
studies have been performed which evaluate the indirect costs.
One estimate of the impacts of the FDA closure of the shell-
fishing area near the Philadelphia dump site cites an annual
loss of 120,000 bushels of ocean quahogs with a dockside value
63
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of $360,000. The capitalized value of this lost resource has
been set at $5.6 mill ion.
Combustion of Pollution Control Sludges
Combustion is an alternative disposal method for disposal
of organic sludges. This method of disposal is most prevalent
in the disposal of municipal sewage sludge, although certain
organic industrial sludges are sometimes disposed of in this
manner.
Current Sludge Combustion Technology--
Thermal processing units, or incinerators, which are cur-
rently used on the municipal scale for sludge disposal include:
Multiple hearth furnaces (MHF)
Fluidized bed furnaces (FBF)
Cyclone furnaces
Rotary kiln incinerators.
Altogether, an estimated 400 sludge incinerators are
currently operating in the United States, burning an estimated
35 percent of all municipal sewage sludge. Figure 9 displays
each of the four incinerator configurations listed above.
An estimated 85 to 90 percent of all sludge incineration
in the United States is performed using multiple hearth
inci nerators (1).
Their wide acceptance is due primarily to their ability to
accept sludges with low solids content, thereby limiting the
amount of preprocessing required. They have also proven reli-
able, are simple in design and operation, and are relatively
insensitive to minor variations in feed rate.
As the name implies, the multiple hearth furnace (MHF)
consists of a series of vertically stacked circular hearths
enclosed in a refractory shell. Each hearth is equipped with
rotating rabble arms to agitate the sludge and move it to a
series of openings leading to the next hearth below. The
multiple hearth design consists of, from top to bottom, (Fig.
9) (1) a drying zone; (2) a combustion zone; and (3) a cooling
zone. As the sludge is fed in at the top, it is dried on the
first series of hearths by hot combustion gases. The dried
sludge is then moved to the next series of hearths, where
volatile and fixed carbon are burned. On the bottom hearths,
theremaining ash is cooled by incoming combustion air and
then discharged to storage for subsequent land disposal. Odor
control is inherent to the MHF design. Although some States
require a minimum of 1400 F gas discharge temperature from
the furnaces, normally produced in an, afterburner; distillation
of odors from sludge does not occur until 80 to 90 percent
of the moisture has been evaporated by which time the sludge
64
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FEED
SLUDGE
COOLING AIR
DISCHARGE
MULTI-HEARTH SLUDGE INCINERATOR
AFLOAT ING-
DAMPER
RABBLE ARM STACK
EACH HEARTH GAS
ROTATING
HEARTH
CROSS SECTION OF A CYCLONE
FURNACE
CROSS SECTION OF A FLUID BED REACTOR
BURNER
FLUIOIZING AIR
INLET
COMBUSTION
AIR
ROTARY KILN FURNACE
(SIMPLIFIED SCHEMATIC)
Figure 9.
Schematic diagrams of four sludge incinerator
configurations .
65
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is already in the combusting zone (3). State-of-the-art
air pollution controls for the MHF are the venturi and
impingement scrubbers, with an associated operating cost
of four to five percent of the cost of furnace operation (2,
3).
The fluidized bed furnace (FBF) gained acceptance in the
mid-1960s for the incineration of municipal sewage sludge. FBF
systems currently account for an estimated five to ten percent
of the municipal sludge incinerated in the United States.
The FBF consists of a vertical refractory-lined cylindrical
shell containing a bed of graded sand at the bottom. The sand
is preheated, then fluidized by low-pressure combustion air.
Sludge is added directly to the turbulent bed and burned.
Unburned volatiles escape to the freeboard zone, where a
retention time of several seconds ensures burnout. The ash
flows with the combustion gases to the air pollution control
device, which is commonly a cyclone followed by a wet scrubber.
The FBF concept is in many ways superior to the MHF.
Because the fluid bed serves as a heat sink, less auxiliary
fuel (if any) is required for start-up and batch feed opera-
tions. Less excess air is required due to the highly turbulent
mixing of air and sludge in the bed, thereby further reducing
energy consumption. The high temperature of the freeboard zone
may also eliminate the need for a separate afterburner, which
in turn also reduces fuel consumption. The principal problems
with operating FBF systems have been in feed system and
control (size limitations due to sludge distribution constraints,
and over drying of sludge prior to injection), and air
pollution control system used. Because a FBF is designed to
be nonagglomerating, i.e., feed residue does not become part
of the bed material, much of the ash is instead entrained
in the exhaust and must be removed.
The cyclonic furnace consists of a single rotating hearth
enclosed in a refractory-lined shell. Sludge is deposited on
the perimeter of the hearth and directed toward the center as it
rotates by a fixed series of plows (see Figure 9). Unlike the
MHF and FBF, combustion air is injected tangentially above the
hearth. Combustion gases and volatiles form a vortex and spiral
upward to the exhaust duct; ash falls out of the centerhole into
a quench tank for final disposal.
The cyclonic furnace was originally designed for small-scale
application, although larger units are now commercially avail-
able. It has found widespread application abroad. No cyclonic
sludge furnaces are operating in the United States at the
present time.
66
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The cyclonic furnace is mechanically simple and has a low
capital and operating cost. Its principal drawback is in the
feed system being used, which is similar to the that of the
FBF system (2).
The rotary kiln incinerator is a rotating inclined cyclin-
drical furnace which agitates the feed as it moves down an
incline. The ash and exhaust gases are typically discharged at
the lower end of the furnace, although some kilns employ
countercurrent flow for combustion air. Baffles are installed
throughout the length of the kiln to agitate the sludge. Unlike
other applications of the rotary kiln, however, chains,
knockers, and other anti-stick devices are not thought to be
required for all sludge incinerators.
Several rotary kiln sludge incinerators are currently in
operation in the United States (3), and similar units have found
successful application in drying and incinerating other liquid
and solid wastes. Advantages of the rotary kiln furnace include
the availability of a wide range of throughput capacities, sim-
plicity of design, and relatively maintenance-free operation.
Disadvantages associated with the use of rotary kiln sludge
incineration systems are inadequate control over air supply,
universal need for an afterburner, tendency for sludge
cake to ball up during movement down the kiln, and a minimum 65
percent solids feed required for autogenous combustion (3).
Other incinerator configurations are availabe for sludge
incineration, but most are either in the developmental stage,
are not directly applicable to sludge alone, or else have
not been commercially accepted in the United States. The
success of the multiple hearth incinerator can be attributed in
part to its operating flexibility, lack of odor, air pollution
control capability, and wide range of capacity. However, more
energy-eficient systems such as the fluidized bed should see
increased application in the future.
The principal environmental concerns associated with sludge
incineration are air emissions and ash disposal. Uncontrolled
particulate emissions from an' MHF and a FBF averages 33 and 45
pounds per ton of sludge burned, respectively (4). Adequate
control of particulates can be achieved using a high-energy
venturi scrubber and, in some cases, with impingement scrubbers.
Other devices such as electrostatic precipitators and filter
are expected to find application on sludge incinerators in the
near future. Similarly, emissions of metals (particularly
mercury) are routinely controlled either by the scrubber or in
the ash matrix. Gaseous emissions are not considered a problem.
Organics (PCB, DDT, etc.) are present only in trace quantities
in the feed and are normally destroyed in the incineration
process (4)- Collected fly ash is disposed of to lagoons (with
effluent treatment) or to sanitary landfills; no episodes of
67
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ground water contamination, specifically from sludge ash dis-
posal to land, were identified in the literature.
The cost of sludge incineration varies substantially,
primarily as a function of the following:
Feed sludge characteristics (percent solids, and
volatile solids content)
Incinerator configuration and capacity
Auxiliary fuel requirements.
Because most sewage sludges are not being sufficiently
dewatered by mechanical means to provide autogenous combustion,
sludge combustion must be preceded by further thermal drying
within the incinerator system; this requires a net input of
energy in the form of auxiliary fuel (typically natural gas or
oil). However, fuel consumption can be minimized for a given
incinerator through (1) thorough mechanical dewatering prior to
incineration; and (2) maximizing the amount of volatile solids
available .
Sludge incineration in general is capital intensive, but
there is also some variation between the capital costs of the
principal state-of-the-art designs. The following is a com-
parison of the range of capital costs for the MHF, FBF, and
cyclonic incinerators (2):
Capital
Configuration
MHF
FBF
Cyclonic
5 mq
1.2-2
0.9-1
1.0-1
d_
.0
.1
.3
Plant
J_S
1 .
1 .
1 .
Cost
(HMSf
Capacity
mgd
4-2.2
0-1 .4
1-1 .6
SO
1 .
1 .
mg
5-2
3-1
1 .5
1
.4
.6
*8ased on a 1977 survey.
These figures show a substantial economy of scale for all
configurations. For example, a factor of ten increase in capa-
city results in only a 20 to 50 percent increase in capital
cost.
A major component of sludge incineration costs, relative to
either operating cost or capital amortization, is the cost of
auxiliary fuel. All systems require some fuel for start-up, and
systems incinerating low solids content sludge require con-
tinuous fuel addition to sustain combustion. Unit costs for
sludge incineration (excluding dewatering costs) can range from
an estimated $45 per dry metric ton to $180 per dry metric ton.
It should be noted, however, that sludge dewatering costs can
exceed incineration costs.
68
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New Techniques for Thermal Reduction of Sludge--
Despite the widespread acceptance of sludge incineration as
a means of ultimate disposal, the high costs of auxiliary fuel
and air pollution control have prompted research into alter-
native means of thermal sludge reduction. Two such alternatives
are currently receiving the most attention:
Starved air combustion (pyrolysis)
t Co-incineration and co-pyrolysis with other solid
wastes, particularly municipal solid waste.
Starved air combustion (also termed pyrolysis and thermal
distillation) is the application of heat to organic matter in an
oxygen-deficient atmosphere. The resulting decomposition of
organics produces three process streams which are suitable for
use as a fuel: (1) a low-BTU gas composed of methane, hydrogen,
carbon monoxide, and carbon dioxide; (2) a liquid (oil) composed
of heavier organic compounds; and (3) an ash residue, or "char"
which contains up to 30 percent combustibles and ten percent
fixed carbon (2).
Starved air combustion appears to have several distinct
advantages over conventional incineration. Because less
combustion air is required (40 percent versus 150-200
percent for incinerators), (1) the amount of auxiliary fuel
required for air preheating is reduced; (2) particulate emis-
sions are reduced due to reduced internal gas velocities; and
(3) furnace or reactor volume required is reduced for a given
rate of sludge addition (or conversely, a given incinerator
would have an increased capacity as a pyrolytic reactor).
Particulates emitted from starved air systems are typically
larger than those of incinerators, thereby simplifying air
pollution control and treatment of the scrubber effluent.
Starved air operation can be adequately controlled
(5).
Another distinct advantage to starved air sludge combustion
is that it can be performed using some existing incinerator con-
figurations, and does not require a special reactor. Most of
the incinerator configurations discussed earlier have the
potential for starved air operation. The MHF has received the
most attention in starved air sludge combustion research due to
the large number of MHFs already in operation. A recent test of
starved air operations at a full-scale MHF showed that auto-
genous sludge pyrolysis can be achieved. Modifications made to
the MHF to accommodate starved air combustion included the
following (5):
Addition of an afterburner - required to burn off by-
product pyrolytic gas prior to discharge to the
atmosphere
69
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Addition of combustion air flow controls and other
necessary instrumentation
Reduction of fan speed or correction of damper position
to reduce the flow of combustion air
Design review and modification to venturi scrubber to,
maintain high efficiency under reduced air flow
conditions
A general review of furnace system and upgrading with
replacement of remote instrumentation
* Location and repair of possible air leaks to the
combustion chamber.
The gaseous fuels produced from starved air operation can
be used directly, sold for use elsewhere, or combusted in the
afterburner, followed by waste heat recovery. ,,
These and other research findings regarding starved air
combustion are encouraging. Strong research efforts being
conducted by the major incinerator manufacturers should result in
the widespread implementation of starved air sludge combustion
within the next five to ten years, primarily through the
conversion of existing MHF systems.
Disadvantages to starved air incineration do exist, most of
which should be resolved through additional research. For
retrofit systems, the addition of an afterburner may be pre-
cluded due to space limitations. More instrumentation will be
required than for a standard incinerator, although system
control is easier. Gaseous emissions from the furnace are
higher, so bypassing the remainder of the system should not
occur without afterburning. The char and oil by-products, if
not used, present a waste disposal problem. Char disposal to
landfills may encounter more severe restrictions than disposal
of incinerator ash, due to the significant volatiles and organic
content of the char.
Co-incineration and co-pyrolysis of sludges with other
combustible wastes is another attractive means of sludge
disposal. The combination of sludge with a waste fuel which
itself will sustain combustion can drastically reduce the
auxiliary fuel requirements. The primary candidate for combined
thermal processing with sludge in most communities is municipal
solid waste, although wood waste, bagasse, rice hulls, and
agricultural wastes, among others, could also be used where
available.
The use of solid waste incinerators to incinerate sludge
along with mixed refuse has met with only limited success in the
70
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United States. Most of the problems center around an inability
to properly mix the materials as received, and improper design
for burning the sludge fraction completely. Solid wastes
incineration itself fell into disfavor years ago due to the
stringent requirements and associated high cost of air pollution
control. With the advent of more sophisticated processing
systems for solid waste, coupled with the potential for energy
recovery, a variety of incinerator systems are now in operation.
Co-incineration systems can be categorized as either solid
waste incinerators which can also accept small volumes of sewage
sludge, or sludge incinerators which accept solid waste (usually
as a supplementary .fuel). Systems falling into the first
category are more common, possibly because the optimal feed mix
more closely represents the proportion of solid waste and sludge
generated in a typical community.
A variety of techniques has been employed for drying and
burning sludge in solid waste incinerators, including:
t Incineration of a sludge filter cake and solid waste
mixture on a grate
t Drying of sludge using solid waste incineration exhaust
gases and/or by-product steam, followed by dry sludge
addition to the solid waste feed
Direct wet sludge injection into a solid waste
i nci nerator
t Flash evaporation of sludge in a solid waste
i nci nerator.
All of these methods have been employed on a full scale,
but only a few remain in operation at the present time. None
are operating in the United States, although all of these
techniques were employed at one time. In Europe, where there
are approximately 200 solid waste-fired steam-generating incin-
erators, an estimated twenty of these systems also burn
sludge. All systems employ sludge drying by steam and/or
flue' gas followed by solids addition to the furnace (1).
Processed solid waste is used as a supplementary fuel in
MHF sludge incinerators at six European facilities. In these
systems, shredded refuse is added either at the top hearth
(drying zone) or the middle hearths (combustion zone). Refuse-
to-sludge addition ratios of as high as 3:1 have been reported
(6). In the United States, no MHFs are known to burn solid
waste regularly. A test burn of refuse-derived fuel (RDF) in a
MHF was performed in Concord, California (5). The unit was
modified to accept sludge and RDF, and was operated in both the
incineration and pyrolysis mode. The test was considered
71
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successful, as continuous autogenous operation was achieved in
both modes. Similar systems are being designed for at least two
locations (!)
Test burns of solid waste with sludge in fluidized bed
furnaces have been conducted in the United States and Europe
with good results. The most notable of these tests was per-
formed in Franklin, Ohio, where sludge was burned in an FBF
along with hydropulped organic solid waste from the Black-
Clawson Hydras Hydrasposal process. Refuse processing
(shredding to a one-inch to three-inch size) is essential for
FBF use, as large inorganic particles, e.g., cans, bottles,
etc., tend to settle in the bed and defluidize it. However, in
comparison to sludge-fired systems where bed sand is entrained
in the flue gas and must be replaced, supplementary refuse
actually increases the amount of bed material through retention
of metals and glass. A full-scale FBF co-incineration system
(sludge and RDF) is presently under construction in Duluth,
Mi nnesota.
In summary, co-incineration of sludge and municipal solid
waste is technically and economically feasible, and should see
increased application within the next decade. Table 15 des-
cribes four full-scale U.S. systems currently planning to
recover energy from combined processing of sludge and RDF (7).
Co-pyrolysis of sludge and refuse has been shown to be
technically feasible. Using an MHF, the Concord, California,
test actually demonstrated that pyrolysis was superior to
incineration in the full-scale test unit. Product gases con-
tained 130 BTU/DSCF, and the RDF feed rate could be increased
substantially over that of incineration (1). None of the
European systems currently operate in the pyrolytic mode.
Substantial research has been performed toward the develop-
ment of pyrolytic systems for solid waste disposal, and several
such processes are available commercially. Among these
are the Union Carbide PUROX (8) process, the Occidental/Garrett
flash pyrolysis process, the Monsanto Landgard process, and the
Carborendum Torrax process. Most of these and other pyrolysis
processes have been tested using a sewage sludge/RDF mixture,
and reported results have been promising. Union Carbide
recently performed an extensive test program of sludge/solid
waste co-pyrolysis at its 350-ton-per-day plant in South
Charleston, West Virginia. Results of the test indicated that
sludge can be processed efficiently and cleanly at a ratio of
0.75 with solid waste and without major system modifications.
Much higher substitution rates would be expected to result in a
lower gas yield, due to the associated high moisture content of
the sludge feed (20 to 25 percent solids sludge filter cake was
used in the test). Union Carbide estimates the cost of sludge
disposal using the PUROX system to be approximately $100 per dry
72
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TABLE 15. SUMMARY OF PLANNED AND OPERATING SYSTEMS DESIGNED FOR SOLID WASTE AND SLUDGE COINCINERATION(7)
CA>
Location
Duluth.
Minnesota
llarrlsburg.
Pennsylvania
Pompano Beach,
Florida
Wilmington,
Delaware
Key Participants
Western Lake Superior
Sanitary District
(operators); Consoer,
Towns end & Associates
(engineers)
City of llarrlsburg;
Gannett. Glemtng,
Corddry and Carpenter,
Inc. (designers)
Waste Management, Inc.;
Energy Research *
Development Administra-
tion; Jacobs Engineer-
ing Co. (designer)
Delaware Solid Waste
Authority; EPA;
Raytheon Service Co.
Process
Shredding; magnetic separation;
air classification; secondary
shredding; fluldized bed incin-
eration of RDF and sludge
Water-wall combustion; bulky
waste shredding (steam driven);
magnetic separation; sewage
sludge burning
Shredding; air classification;
magnetic and other mechanical
separation; anaerobic digestion
of air classified light fraction
with sewage sludge
Shredding; air classification;
magnetic and other mechanical
separation; froth flotation;
aerobic digestion
Output
RDF; ferrous metals; steam
for heating and cooling of
plant and to run process
equipment
Steam for utility-owned
district heating system and
for city-owned sludge dry-
Ing system; magnetic metals
Methane
Ferrous metals; non-ferrous
metals; glass; RDF; humus
Reported
Capacity
400 TPD
municipal
solid waste;
340 TPD of
301 solids
sewage sludge
720 TPD
50-100 TPD
100U TPD muni-
cipal solid
waste copro-
cessed wi th
350 TPD of
20% solids
digested
sewage sludge
Reported
Capital Costs
(millions of $)
19
8.3
3.1
51k
9 from EPA. OSW;
16 from EPA,
Water Prog. ; 6
from State match-
Ing grants;
remainder from
the Authority
through sale of
revenue bonds
Status
Under con-
struction;
project
startup b>
April 1979
Operational
since October
1972; steam
main comple-
tion by Octo-
ber 1978;
sludge drying
facilities
completion by
mid-1979
Dedicated
Hay 2. 1978;
in shakedown
Contract
signed August
10, 1978 with
Raytheon Ser-
vice Co. ;
groundbreaking
expected by
September 1979
-------
ton at a 0.05 substitution ratio with refuse. The addition of
several sludge drying steps prior to pyrolysis were estimated to
reduce the cost of sludge disposal by up to 80 percent (9).
Sludge pyrolysis and codisposal with solid wastes do pre-
sent some different environmental problems than conventional
incineration, each of which can be controlled with state-of-the-
art technology. Problems identified in the literature and tests
discussed previously include:
Changes in air pollutant emission characteristics when
burning mixed fuels rather than the design feed (sludge)
t Significant levels of combustible organics in pyrolytic
char, which may require disposal if no users can be
1ocated
t Increases in the level of organics in incinerator
residue when certain forms of sludge are added
(particularly unground filter cake)
Treatment of sidestreams that may not have been
generated by the original sludge treatment system or
combustion system.
Air pollutant emissions from operating and test codisposal
systems can be adequately controlled. Gaseous emissions from
pyrolysis are required to be subject to a minimum 1,400° F,
1/2-second afterburner residence time in many states, (which
normally may be sufficient for destruction of volatile gases
and trace amounts of pesticides and PCBs.) High-energy venturi
scrubbers are an accepted system for control of oarticulate
and trace metals.
Residue quality varies with each codisposal system. Some
co-incineration and pyrolysis systems generate a residue with
significant organic content, consisting of either fixed carbon
(char) or unburned feed material. Such residues may be sub.iect
to more stringent landfill requirements than ash. Slaa-
ging pyrolysis systems, on the other hand, generate a
slag which may be disposed of at a debris landfill. In addi-
tion, elutriation tests on PUROX slag generated from solid waste
pyrolysis have shown the elutriate to be of similar quality to
that of co-pyrolysis with sludge (9).
Pyrolysis and co-incineration both generate sidestreams
from wet scrubbing and mechanical dewatering. Scrubber side-
streams are high in dissolved COg, suspended and dissolved
solids, and low in pH. A reduction in suspended and dissolved
solids and pH adjustment are necessary before the water can be
recycled or discharged. Treatment of sludge filtrate is
necessary to reduce the normally high levels of BOD and TKN.
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REFERENCES FOR"DISPOSAL OF POLLUTION CONTROL SLUDGES BY
COMBUSTION
1. Sussman, D. B. and H. W. Gershman. Thermal methods for the
codisposal of sludges and municipal residues. Presented at
the Fifth National Conference on Acceptable Sludge Disposal
Techniques, January 31-February 2, 1978. SW-686, U.S.
Environmental Protection Agency, Washington, D.C., 1978.
2. Sieger, R. B. and P. M. Maroney. Incineration-pyrolysis of
wastewater treatment plant sludges. Prepared for the
Environmental Protection Agency Technology Transfer Design
Seminar for Sludge Treatment and Disposal, 1977.
3. Schroeder, W. H. Principles and practices of sludge incin-
eration. Presented at the Sludge Handling and Disposal
Seminar, Calgary, Alberta, February 16-18, 1977. 40 p.
4. Culp/Wesner/Culp Clean Water Consultants. Air pollution
aspects of sludge incineration. EPA/625/4-75/009,
Environmental Protection Agency, Cincinnati, Ohio, Office
of Technology Transfer, June 1975. 21 p. (Available from
National Technical Information Service (NTIS) as PB-259
457).
5. Brown and Caldwell, Consulting Engineers. Solid waste
resource recovery full scale test report. For Central
Contra Costa Sanitary District. Vol. 1. Walnut Creek,
California, March 1977.
6. Niessen, W., A. Daly, E. Smith, and E. Gilardi. A review
of techniques for incineration of sewage sludge with solid
wastes. EPA-600/2-76-288, Roy F. Weston, Inc., West
Chester, Pennsylvania for Municipal Environmental Research
Laboratory, Cincinnati, Ohio, September 1976. 235 p.
7. Resource recovery operations and activities surveyed in new
report. Solid Wastes Manage., 21:59-62, December 1978.
8. Camp, Dresser & McKee. Phase 1 report of technical
alternatives to ocean disposal of sludge in the New York
City-New Jersey Metropolitan Area. With Alexander Potter
Associates for Interstate Sanitation Commission. Boston,
Massachusetts, June 1975.
9. Union Carbide Corporation. The codisposal of sewage sludge
and refuse in the Purox System. EPA-600/2-78-198, Linde
Division, Tonawanda, New York for Municipal Environmental
Research Laboratory, December 1978. 176 p.
75
-------
ENERGY RECOVERY FROM THERMAL REDUCTION OF SLUDGE
Energy conservation has become a major concern of gov-
ernment and industry. As large consumers of fossil fuels,
sludge incinerators have been the subject of numerous investi-
gations of energy conservation and recovery feasibility.
Several municipal sludge incineration heat recovery systems are,
in fact, in operation at the present time. Heat recovery
experience from industrial sludge incineration is presently
lacking.
Energy recovery from sludge incinerators can be either
direct or indirect. Approximately 80 to 90 percent of the
energy lost during incineration is as sensible heat in the flue
gas, with the remainder as radiation losses and minor losses to
the ash and to furnace leakage. Direct energy recovery refers
to recovery of the sensible heat, as preheated combustion air or
steam. Indirect recovery refers to the production of an
alternate energy form, particularly a fuel product, suitable for
on-site use or for sale.
Direct Energy Recovery
Direct energy recovery is common among sludge incinera-
tors. Multiple hearth furnaces (MHF) draw combustion air from
the bottom, or cooling zone, where heat is exchanged between the
hot ash and cooler combustion air. In addition, air preheaters
located in the stack are common.
Gas-to-water heat transfer systems are the most common
direct energy recovery systems used by industry. Even so, only
five waste heat boiler systems were installed on MHFs by 1978.
In general, a practical limit for waste heat boiler operation is
a 1,000 F exhaust gas temperature. Sludge incinerators exhaust
gas temperatures typically range from 500° F to 900° F without
afterburners and before the scrubber. However, some state regu-
lations require a 1/2-second residence time at 1,400° F for
sludge incinerator exhaust. The high fuel consumption rate in
the associated afterburner renders waste heat recovery economi-
cally attractive, particularly for large incineration systems.
The production of electric power from steam for in-plant use is
also practiced in industry, but would generally be limited to
larger sludge incineration systems due to governing economies of
seale.
Specific parameters which enter into the evaluation of
direct waste heat recovery feasibility include the following:
Temperature and other characteristics of the exhaust gas «
Characteristics of the fly ash and other particulate
carryover
76
-------
Type of exhaust system and associated exhaust load
t Space available for boiler/heat exchanger retrofit
Steam demand profile and boiler system reliability.
Co-incineration of sludges with municipal solid waste may
significantly reduce the auxiliary fuel requirement, thereby
further increasing the cost-effectiveness of energy recovery.
Most solid waste will by itself sustain autogenous combustion at
high temperatures. Most solid waste incinerators designed and
constructed in recent years therefore include a waste heat
recovery system. Large-scale incinerators employ the waterwall
concept, where the waste heat boiler is located in the com-
bustion zone for more efficient energy recovery. The dewatering
and co-incineration of sludge in such an incinerator was dis-
cussed previously (see page 71), and appears to be technically
feasible for relatively low sludge feed rates. Here energy
recovery is achieved through both sludge drying and steam
production.
Aside from the advantage of conserving fuel, direct energy
recovery also reduces water consumption in the scrubber system.
Exhaust gas cooling is normally one of several functions of the
scrubber. By cooling the gases in a waste heat boiler (to 500°
F from 1,000 to 1,400°), less water is lost to evaporation, and
less effluent needs to be treated for recycle or discharge.
The principal disadvantages of direct energy recovery are
the potential for damage to the heat exchanger by corrosive or
particulate-1aden exhaust gases, and limitations on the use of
the steam or power product due to poor quality or variable sup-
ply and reliability. Corrosion is thought to be more severe
from the combustion of solid waste than from that of sewage
sludge; combustion of other pollution control sludges, however,
may produce more corrosive gases than municipal sludge depending
on their composition and combustion properties. Similarly,
particulate emissions from conventional sludge incinerators are
much less than from solid waste incinerators. Fluidized bed
sludge incinerators do emit a higher particulate load than MHFs,
and carryover of the bed material (sand) has been shown to erode
in-stack preheaters.
The fuel value of both sludge and solid waste is highly
variable when compared to fossil fuels, particularly within the
same batch. The resultant steam production profile will fluc-
tuate unless supplementary fuel or state-of-the-art control is
used to stabilize it. To date, waste heat boilers applied to
sludge incinerators have produced steam for heating and other
selected in-plant uses. Solid waste, on the other hand, has
been used as both a primary and supplemental fuel for steam
electric power generation.
77
-------
Indirect Energy Recovery
The term indirect energy recovery, as it is used here,
refers to the production of a fuel from waste which can be used
in-plant or sold for use elsewhere. Indirect energy recovery is
a function of pyrolysis and not of incineration, as pyrolysis
systems have the potential for producing a gaseous, liquid,
and/or solid fuel by-product.
As noted previously, pyrolysis of sewage sludge has been
implemented only on a test basis at several full-scale sludge
incinerators. Emphasis on all test scales has been toward the
production of a low BTU gas and combustible char, although a
liquid fuel can also be produced under the proper operating con-
dition. Bench-scale tests of sludge pyrolysis have produced by-
product gases with heating values ranging from approximately 300
BTU to over 700 BTU. Recent tests at a full-scale MHF produced
a product gas from sludges alone containing 54 BTU/DSCF. The
char product can contain up to 30 percent of the combustibles
contained in the original solid feed. The char has little
potential as a salable fuel due to its high ash content, par-
ticularly char resulting from co-pyrolysis with solid waste.
The char is instead burned in slagging pyrolysis systems.
Extensive testing of sludge co-pyrolysis in solid waste
pyrolysis systems has been limited to the PUROX system. Test
batches containing from 6.6 percent to 23.3 percent sludge in
solid waste were processed in the PUROX reactor. At these
addition ratios, product higher heating values from solid waste
alone were unaffected by the sludge addition.
In summary, the recovery of energy from the thermal
processing of municipal sludges can be accomplished by several
technically feasible approaches. Many conventional MHF and FBF
systems with afterburners maintain a high enough exhaust temp-
erature (before scrubbing) to justify addition of waste heat
boilers. Air preheaters in these systems are already common,
and are either of the in-stack or countercurrent air flow
design. Pyrolysis of sludge to produce fuel gas has also been
tested on the pilot and full scale, and has been shown to
produce by-product gases ranging from 300 BTU/SCF to 700 BTU/SCF
on the bench scale, and 54 BTU/SCF on the full scale. Operation
of MHFs in the pyrolytic mode, using the by-product gases to
fuel the afterburner, may be more economical than the conven-
tional incineration mode.
Full-scale co-pyrolysis and co-incineration systems are in
the early stages of testing and implementation. Co-incineration
of sludge in solid waste heat recovery incinerators is success-
fully practiced in Europe and more recently in the United
States. The use of solid waste (specifically refuse-derived
fuels) in sludge incinerators is not as well developed, but
78
-------
studies have shown that there is great potential for this
practice due to proven technical feasibility and the large
number of MHFs in the United States. Co-pyrolysis has been
successfully tested on the full scale in both sludge incin-
erators and solid waste pyrolytic reactors, although no
continuous co-pyrolysis systems are in operation in the United
States.
RECLAMATION OF SLUDGE-DAMAGED AREAS
Improper sludge and solid waste disposal has resulted
in a variety of adverse environmental impacts. Documented
cases show where the escape of contaminants has so degraded
potable ground water aquifers, or created other hazards
detrimental to the public health, safety, and welfare, that
the sites were condemned and closed down. The economic
dislocations in some instances were significant.
Examples were found of degradation or environmental
impacts resulting from disposal of municipal or industrial
sludges. However, few examples could be found where an engi-
neering or economic evaluation and assessment of alternative
mitigation steps had been performed. Even fewer examples could
be found of actual site reclamation or mitigation.
The three different stages involved in the reclamation of
any sludge-damaged disposal site are:
The identification of the problem and correlation of the
documented problem with the sludge disposal facility
A documented engineering study supported by monitoring
and analytical results, as well as a practical assess-
ment and economic evaluation of alternative approaches
for rectifying the situation
The actual reclamation, mitigation, or abandonment of
the site as dictated by the engineering study.
Reclamation Techniques
Processing--
Si udge-damaged soils and waters can be treated either in
place or after removal, depending on the type and extent of the
contamination. Table 16 summarizes the types of treatments
possible for a variety of contaminants.
In general, waters damaged by sludge cannot be treated in
place; only floating materials on surface waters can be effec-
tively removed without removing the water. For large water
bodies and flowing streams, neither treatment in place nor
removal of water is necessarily effective. Only relatively
79
-------
TABLE 16. TREATMENT OPTIONS FOR SPECIFIC CONTAMINANTS
Contaminant
Acidity/ water
Alkalinity Jo,, (ln.place)
soil (excavated)
Arsenic water
soil (In-place)
sol] (excavated)
Beryl Hun water
soil (In-place)
soil (excavated)
CatatiM water
soil (In-place)
soil (excavated)
Chlorinated water
Hydrocarbons .. ,. . .
soil (In-place)
soil (excavated)
Chromium water
soil (In-place)
soil (excavated)
Adsorption
tt
c
1
-
Biological
Treatment
+
i
1
u.
f §
0<
+
+
k
1
»
u.
IJ
U_l
.
-
i
Chem. Flxatii
Silicates
+
+
++
t
i
r*
11
Ul/l
+
++
Trea
£
Chemical
Neutral 1zat1i
tt
nent
|
Chen. Qxidatl
Hydrolysis
t
-
+
Hetnc
a
li
on
d
a
1$
|5S
U f U
*+
&
ex
J's
»
+
«
M-
£*
*fm *&
U "XI
CQ
I/I
a.
i
|§
+
+t
Distillation
++
»+
+*
++
+.+
Encapsulatloi
++
«
+*
tt
*+
*»
Ion Exchange
+
+t
+
Incineration
tt
e
a
Landfill. Sei
*+
t+
tt
*t
*»
++
1
+
M
M
C
I
+
+
+
+
c
o
«g
1
I
o
I/I
+
+
»
++ Proven acceptable
+ Theoretically acceptable
CO
- Possibly acceptable, but resulting treatment
efficiency may not be very high.
A blank means not applicable or not enough Information.
-------
TABLE 16' (continued)
Contanlnant
Cyanides Mater
soil (In-place)
soil (excavated)
Lead Mater
soil (In-place)
soil (excavated)
Mercury Mater
soil (In-place)
soil (excavated)
Nitrogen Mater
Species fojl (,n.pllce)
soil (excavated)
Oil and Mater
Grea" soil (In-place)
soil (excavated)
Organic Mater
Solvents fo|1 (|n.place,
soil (excavated)
Adsorption
+
_
t+
ft
Blodegradatlon
-
-
.
-
Biological
Treatnent
+
+
.
+
o
u.
II
+
Chem. Flxatlon-
L1BK
-
.
Chem. Fixation-
Silicates
-
++
**
-
Treatment,
jj
t
++
+
t*
Chemical
Neutralization
Chem. Oxidation/
Hydrolysis
++
t
++
+
-
i
.
*
Met!
Chem. Precipita-
tion - Alum
*
_
ol
Chem. Precipita-
tion - Ferric
Chloride
Chem. Precipita-
tion - Line
f
i
II
+f
o
1 Distillation
+
**
t+
+t
Encapsulation
+*
+t
+*
*t
++
+
1
c
o
4-t
t+
+
Incineration
+
++
+
*+
+*
Ji
»
t
r
r-
++
+t
+*
++
++
+t Proven acceptable
+ Theoretically acceptable
I
t
Reverse Osmosis
+
t
*
t
g
| Solvent Extractl
t
*
i
t
CD
- Possibly acceptable, but resulting treatment
efficiency nay not be very high.
A blank weans not applicable or not enough Information.
-------
TABLE 16 (continued)
00
tv
Contaminant
Phenols water
soil (In-place)
soil (excavated)
Phosphates water
soil (in-place)
soil (excavated)
PCB's water
soil (In-place)
sol] (excavated)
Selenium water
soil (tn-ptace)
soil (excavated)
Sul fides water
soil (In-place)
soil (excavated)
Adsorption
4-f
tt
s
Blodegradatlc
.
-
-
4
Biological
Treatment
t
+
i
1
b.
II
t
J.
O
ft
X
C
II
,1
Chem. F1xat1c
Silicates
-
-
-
T
i
O
L
":*
eatn
S
Chemical
Neutral Izetic
nt H
g
Chem. Qxidati
Hydrolysis
+
.
+
+
-
*
t
thai
a
fl
J" c
o
ft
h
1
4
O-
**~ 8
i
|g
i
!*
ii
Distillation
+t
+t
Encapsulatloi
«
*+
o
tt
**
I
s
+
t
*
Incineration
«*'
++
t
|
f"
tt
+t
*+
S
t
14
IA
Reverse Osmo!
t
+
g
g
«
+
t
it Proven acceptable
* Theoretically acceptable
- Possibly acceptable, but resulting treatment
efficiency way not be very high.
A blank means not applicable or not enough Information.
-------
small, confined water bodies are actually amenable to treatment.
For other contaminated waters, the only option is to remove the
source of the contamination and allow the water body to purify
itself naturally. Thus, the only truly treatable water bodies
are small lakes and ponds and confined ground water aquifers.
In both cases, except for surface contamination, removal and
treatment is far more effective than in-place treatment. Com-
plete detoxification is difficult to achieve with in-place
decontamination and, if the contaminant is a heavy metal or
refractory organic, contaminated sludges or sediments are pro-
duced which can serve as a source for future damage.
Many of the treatment methods available for treating con-
taminated water are listed in Table 17. There is a great deal
of literature on water and wastewater treatment, so a lengthy
discussion of the options is not needed. The table lists the
information needed by a decision maker.
Often, removal and treatment of the liquid will not com-
pletely alleviate a water contamination problem. If a surface
water body has been contaminated for any length of time, the
sediments are probably contaminated too, and it might be nec-
essary to dredge out the bottom sediments and treat them sep-
arately. A damaged ground water aquifer may be evidence of a
contaminated soil. If the soil cannot be removed and treated,
the water contamination problem is likely to continue. Whether
or not the source of the contamination is contaminated soil, one
option is to pump out the aquifer, treat the water, allow it to
filter back into the aquifer, and continue the cycle until the
water reaches a low, steady-state concentration of the con-
taminant. The soil may still be contaminated but the soluble
fraction will have been leached out. Contamination may continue
indefinitely, but at a relatively low level.
Contaminated soils (and sediments) are another problem, and
treatment methods are not nearly as standard or routine as those
for water. In the past, damaged soil areas have frequently been
abandoned with little thought to reclamation. Recently, experi-
ence has revealed a number of inherent hazards in simple aban-
donment, i.e., ground or surface water contamination, plant up-
take, vector transport to people. Consequently, increasing
attention has been focused on reclaiming or otherwise detoxi-
fying damaged soils. However, the state of the art is not very
advanced.
The first decision is whether to treat in-place or to
remove and treat. Treating in-place is far less costly, but
generally less efficient than removal. Moreover, neither method
is particularly applicable to deep (>2 m) damage. Because of
the expense, in-place treatment is generally used, with mediocre
results. One possibility is to attempt to leach the contaminant
into ground water, which can then be pumped out and treated. If
83
-------
TABLE 17. WATER TREATMENT METHODS
Treatment
Method
Carbon
Adsorption
Major
Treatable Cost Cost
Contaminants Elements Range ($)
0
Any organic compound, Carbon. 1,000-2,500/1,000 m
some metals to a Pressure vessels. 10,000-50,000
lesser extent Electrical power. 5-10/1,000 m3
Advantages
High efficiency removal
of organics.
Carbon regeneration
economical if volume
treated exceeds
-4,000 m3/day.
Available in portable
units.
Disadvantages
Suspended matter
should be fil-
tered out before
treatment to pre-
vent fouling.
If carbon regen-
eration is not
practiced,
exhausted carbon
becomes a sol id
waste disposal
problem.
Regeneration can
nearly double
capital costs.
Chemical
Neutrali-
zation
Chemical
Oxidation
a) Ozone
b) Chlorine
Acidity/Alkalinity
Organics, Cyanide,
Sulfide
Treatment tank
(200 m3).
Chemicals - lime
sulfuric acid.
Chemical feed
equipment.
Ozonator and con-
tactor.
Electrical power.
Contact-tank
(200 m3)I
Chlorine
15,000-30,000
2-10/1 ,-000 m3,
1-25/1,000 mj
2,000-5,000
16,000-50,000
150-300/1,000 m3
15,000-30,000
1-10/1,000m3
Strong oxidant.
Chlorine can be
purchased in bulk.
Neutralization
chemicals are
themselves
hazardous.
High energy costs.
Ozone is hazardous
and must be
generated on-site.
Hazardous to use.
-------
TABLE 17. (continued)
00
01
Treatment
Method
Chemical
Precipitation
a) Lime
b) Alum
c) Ferric
chloride
d) Soda ash
Distillation
Ion Exchange
Treatable
Contaminants
Heavy metals, ionic
organics; other conta-
minants may be sorbed
by the precipitate.
Any non- volatile
compound or
contaminant.
Any ionic material ;
primarily metals and
inorganic anions.
Major
Cost
Elements
Contact tank (200 m3)
Lime
Alum
Ferric chloride
Soda ash
Still and steam
generator.
Electric power.
Chemicals.
I.E. resin beds.
Regenerant chemicals.
Electrical power.
Cost
Range ($)
15,000-30,000
1-5/1,000 m3
5-20/1,000 m3
2-10/1,000 m3
1-10/1,000 m3
50,000-500,000
3
100/1 ,000 m-%
5-10/1,000 mj
2,000-15,000 ,
40r 110/1, 000 mj
10-15/1,000 m3
Advantages
Relatively inexpensive
with few excessive
capital or operating
expenses.
Pure effluent.
Excellent for low
levels or soluble
inorganics.
Disadvantages
Sludge disposal
requirement.
High costs.
Must be carefully
designed to meet
the specific site
Reverse Osmosis Any soluble material.
Membrane modules.
Membrane replacement.
Chemicals.
Electrical power.
2,000-10,000 ,
50-100/1,000 mj
15-20/1,000 m3,
75-100/1,000 m3
Available in portable
units.
High removal effi-
ciency. Available
in portable units.
conditions.
Pretreatment needed
to remove suspended
matter.
Organic contami-
nants may degrade
the membranes.
Pretreatment
required to reduce
suspended solids.
-------
the ground water aquifer is part of a drinking water supply,
this procedure is not recommended. Thus, in this case, it
becomes necessary to attempt to immobilize the contaminant,
usually in-place with the addition of a chemical fixation
agent. However, there is virtually no way to control the reac-
tion and the results are often unpredictable. Deep damage over
an aquifer is the most insidious and least treatable situation
that can be faced, and few satisfactory solutions are available
at present.
The options for dealing with contaminated surface and shal-
low soils are more numerous and better documented. The choice
between treatment in-place and removal should be based on the
extent and concentration of the damage and the potential for
harming nearby surface or ground water supplies. In general, a
small damaged area, a high contaminant concentration, and/or a
high water table, mean removal and treatment. Otherwise, in
most cases, in-place treatment will suffice.
There are seven basic treatment methods for contaminated
soils: chemical neutralization, chemical oxidation/reduc-
tion/hydrolysis, chemical fixation, encapsulation, solvent
extraction, biodegradation, and incineration. The choice will
depend on the type of contaminant, the volume of soil, the
moisture content of the soil or sediment, and whether or not the
soil must be excavated. Table 18 presents a brief summary of
these soil treatment methods.
86
-------
TABLE 18. SOIL TREATMENT METHODS
Treatment
Method
Treatable
Contaminants
Major
Cost
Elements
Cost
Range ($)
Advantages
Disadvantages
Biodegradation
Chemical
Fixation
Organics in soil
too deep for
excavation
Divalent cations,
other inorganics
to some extent
Injection wells and
pumps.
Nutrient chemicals.
Chemicals.
Chemical injection
in place.
Mixing equipment
for excavated soils.
Chemical Acidity/Alkalinity Surface application
Neutralization (in-place) and mixing.
Chemicals.
oo
'Encapsulation
Incineration
Landfill ing
Solvent
Extraction
Any
Organics, Cyanide,
Nitrogen compounds
Any contaminated
soil/semi-solid
Organics, Water
soluble inorganics
Encapsulating
material (resin,
concrete, asphalt).
Incinerator
(250-500 Ib/ha).
Auxiliary fuel.
Transportation.
Process tank.
Chemicals.
1,000-6,000/well
5-10/m3 soil
100-50Q/m soil
2-10/m2 (surface
area)
1,500-7,500
2-10/r/ (surface
area)
5-50/m2
20-500/m3 soil
10,000-25,000
10-100/m3 soil
0.30-2.25/m -km
6,000-16,000
25-250/m3 soil
Only way to speed up
degradation of inac-
cessible organic
contaminants.
Immobilizes heavy
metals and certain
other constituents.
Commercial portable
units.
More reliable than
most in-place
treatment.
Can be used on any
contaminated soil.
Complete detoxifica-
tion of susceptible
contaminants.
Simple, low-cost
disposal method.
Treated soil can be
returned to
excavation.
Uncontrollable pro-
cess with many
variables.
Unpredictable results.
Contaminants still
in soil and may be
leached in future.
In-place treatment
may be incomplete.
Treatment chemicals
are hazardous.
Encapsulated material
requires disposal.
High capital and
operating costs;
possible air
pollution.
May require treat-
ment with several
solvents. Process
economics may require
solvent recovery/
redistillation.
00 00
O O1
ro o
-------
EPA REGIONS
U.S. EPA, Region 1
Solid Waste Program
John F. Kennedy Bldg.
Boston, MA 02203
617-223-5775
U.S. EPA, Region 2
Solid Waste Section
26 Federal Plaza
New York, NY 10007
212-264-0503
U.S. EPA, Region 3
Solid Waste Program
6th and Walnut Sts.
Philadelphia, PA 19106
215-597-9377
U.S. EPA, Region 4
Solid Waste Program
345 Courtland St., iM.E.
Altanta, GA 30308
404-881-3016
U.S. EPA, Region 5
Solid Waste Program
230 South Dearborn St.
Chicago, IL 60604
312-353-2197
U.S. EPA, Region 6
Solid Waste Section
1201 Elm St.
Dallas, TX 75270
214-767-2734
U.S. EPA, Region 7
Solid Waste Section
1735 Baltimore Ave.
Kansas City, MO 64108
816-374-3307
U.S. EPA, Region 8
Solid Waste Section
1860 Lincoln St.
Denver, CO 80295
303-837-2221
U.S. EPA, Region 9
Solid Waste Program
215 Fremont St.
San Francisco, CA 94105
415-556-4606
U.S. EPA, Region 10
Solid Waste Program
1200 6th Ave.
Seattle, WA 98101
206-442-1260
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