Slib, Schlamm, Sludge

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American Water Works Association
Slib,
Schlamm,
Sludge
American Water Works Association Research Foundation 
KIWA Ltd.
Edited by
David A. Cornwall
Hay MM Koppers
American Water Works Association
RESEARCH FOUNDATION
KEURINGSINSTITUUT VOOR WATERLE1DINGARTIKELEN
Disclaimer
This study was funded by the American Water Works Association Research Foundation (AWWARF) 
and Keuringsinstituut voor Waterleidingartikelen (KIWA). AWWARF and KIWA assume no respon 
sibility for the opinions or statements of fact expressed in the report. The mention of trade names 
for commercial products does not represent or imply the approval or endorsement of AWWARF and 
KIWA. This report is presented solely for informational purposes.
Copyright 1990
American Water Works Association Research Foundation
American Water Works Association
6666 West Quincy Ave.
Denver, CO 80235
Printed in USA 
ISBN 0-89867-532-4
Contents
Preface, v
Chapter 1 Regulations, Characteristics, and Analytical
Considerations ....................................................... 1
Introduction, 1
US Regulations, 2
Dutch Regulations, 12
Sludge Characteristics, 20
Currently Used Sludge Handling Techniques, 30
Analytical Techniques, 36
References, 45
Chapter 2 Optimizing Sludge Characteristics and Minimizing
Generation ......................................................... 47
Summary, 47
Introduction, 48
Effects of Current Treatment Methods on Sludge Management, 49
Promising New or Potentially Improved Technologies, 62
Constituent Recovery, 80
Backwash Recycle, 93
References, 106
Chapter 3 Advanced Treatment Technologies ....................... 109
Summary, 109 
Introduction, 112 
Conditioning Considerations, 112 
Mechanical Freeze-Thaw, 116 
Natural Freeze-Thaw, 130 
Advanced Mechanical Techniques, 152 
Mobile Treatment Facilities, 177 
Innovative Treatment Processes, 188 
References, 205
Chapter 4 Toxic Concerns Regarding Water Plant Wastes ........... 209
Summary, 209
Introduction, 210
Source Water Contributions, 211
Water Treatment Chemical Contributions, 214
Treatment Process Impacts, 219
Leaching of Trace Elements From Water Treatment Residuals, 231
References, 265
111
Chapter 5 Beneficial Applications and Innovative Sludge
Disposal Methods ................................................. 267
Summary, 267
Introduction, 268
Beneficial Applications of Sludge, 270
Innovative Sludge Disposal Methods, 283
Conclusions and Research Needs, 300
References, 302
Index, 305
IV
Preface
This book is the result of a joint effort between the American Water Works Associa 
tion Research Foundation and The Netherlands Waterworks Testing and Research 
Institute (KIWA Ltd.). These two prominent water research agencies developed this 
book in order to assist North American and European water utilities with the grow 
ing problem of sludge and sludge disposal.
The book will provide utilities and water companies with the most up-to-date 
information for formulating planning strategies. The authors address potential prob 
lem areas and innovative solutions. It is hoped the document will spur innovative 
planning by utilities throughout the world and thereby help push forward residuals 
technologies and options.
The document is not designed to review past performance of treatment or dis 
posal technologies. Nor is it aimed at currently available technologies, although cer 
tainly many of the areas addressed in this document are ready for application. All 
authors of this manual reviewed the AWWARF publication Handbook of Practice, 
Water Treatment Plant Waste Management and were asked not to repeat informa 
tion in that manual except for key background information. Therefore, one should 
consider the two documents as complements to each other. The Handbook reviews 
performance of treatment methodologies and information on applying those 
methods. The original Handbook contains the following sections:
• regulatory review;
• disposal practices, including
—direct discharge,
—discharge to wastewater treatment plants,
—landfilling, and
—land application;
• characteristics of water treatment plant wastes, including
—computation of quantities,
—physical characteristics, and
—chemical characteristics;
• dewatering methods, including
—thickening,
—conditioning,
—pumping,
—centrifuge,
—pressure filters,
—vacuum filters,
—belt press,
—sand beds, and
—dewatering lagoons; and
• system optimization.
It would be most useful in reviewing information in this joint document to be 
familiar with the Handbook.
Slib, Schlamm, Sludge is divided into five chapters. One author had primary 
responsibility for the chapter, but individual sections of a chapter were written by 
different authors. Each chapter has US and European contributors. In areas where 
there was only a US or Dutch experience, that section primarily represents the one 
viewpoint. In areas where both countries have experience, the section presents both 
viewpoints.
Chapter 1 is an introductory chapter. It includes background Dutch and US 
regulatory information and presents an overview of the characteristics of waste 
produced in each country. Also included is a discussion of analytical techniques, 
including interferences in chemical analyses. The chapter includes a discussion of 
physical characteristics required for successful landfilling of sludge and particularly 
addresses the Dutch experience in the use of shear tests to characterize sludge 
handleability.
Chapter 2 deals with optimizing sludge characteristics (with regard to sub 
sequent treatment) and minimizing sludge generation. It stresses methods within 
the treatment process that can improve dewatering or can minimize sludge produc 
tion. The chapter also addresses conditioning methods that reduce sludge quantities. 
Included are sections on process selection, pellet reactors, dissolved air flotation, 
constituent recovery, and backwash recycle.
Chapter 3 covers advanced treatment technologies. The conditioning and 
dewatering methods that are discussed include mechanical freeze-thaw, non- 
mechanical freeze-thaw, new scroll centrifuges, and diaphragm filter presses. Infor 
mation is also presented on mobile sludge dewatering facilities, cleaning of existing 
lagoons, and innovative treatment devices.
Chapter 4 provides some of the latest information regarding the toxicity of 
water treatment plant wastes. Included is information on the extraction procedure 
(EP) toxicity test, the toxicity characteristics leaching procedure (TCLP), coagulant 
contribution to sludge contamination, and leaching of metals from water treatment 
plant sludges.
Chapter 5 discusses beneficial applications and innovative sludge disposal 
methods. Beneficial applications include disposal solutions that have been 
thoroughly investigated and documented and have been applied on a major scale. 
Included in beneficial applications are soil conditioning with lime softening sludge, 
hydrogen sulfide binding with iron sludge, and application of softening pellets. Inno 
vative disposal methods have been less well investigated or applied only on a limited 
basis. These methods include brickmaking, iron recovery for steel making, land 
application of coagulant sludges, composting, and cement production.
As with any document of this type, a great deal of effort was involved—more 
than anyone who volunteered to undertake the project realized. I would like to 
thank the US authors: Terry Rolan, Ray Lee, Paul King, Nancy McTigue, and Carel 
Vandermeyden, who agreed to work on this effort and, even more importantly, 
stayed to the end. I want especially to thank my Dutch counterpart on this project, 
Hay Koppers. Hay spent much of the summer in the United States working on this 
manual. I also want to thank the European authors: Nico Wortel,Rudy van 
Nieuwenhuyze, Heinz Eckhardt, Marc van Eekeren, Heinz Henke, and Harald 
Martin. Also to be acknowledged are Deutscher Verein des Gas-und Wasser- 
faches e.v. (DVGW) and Studiecentrum voor Water (SVW); these two colleges
assisted KIWA in obtaining the broad European perspective that is given in the 
book.
Final thanks go to Jim Manwaring, AWWARF Executive Director; Thijs Kobas, 
KIWA Managing Director; Rick Karlin, AWWARF Project Officer; and Wim van de 
Meent, KIWA Director of Research, for their support.
David A. Cornwell 
Editor
Contributors to this work include
David A. Cornwell, Ph.D., P.E., Environmental Engineering &
Technology, Inc., Newport News, Va. 
Heinz Eckhardt, Ph.D., ESWE Institute, Wiesbaden, West
Germany 
Heinz A. Henke, P.E., Henke Engineering Office, Wuppertal, West
Germany 
Paul H. King, College of Engineering, Northeastern University,
Boston, Mass. 
Hay M.M. Koppers, P.E., KIWA Ltd., Nieuwegein, The
Netherlands 
Ramon G. Lee, American Water Works Service Company, Inc.,
Voorhees, N.J. 
Harald Martin, P.E., Wuppertal Municipal Works, Wuppertal,
West Germany 
Nancy E. McTigue, Environmental Engineering & Technology,
Inc., Newport News, Va. 
A. Terry Rolan, Department of Water Resources, City of Durham,
Durham, N.C. 
Carel Vandermeyden, Environmental Engineering & Technology,
Inc., Newport News, Va. 
Marc W.M. van Eekeren, P.E., KIWA Ltd., Nieuwegein, The
Netherlands 
Ruud F. van Nieuwenhuyze, P.E., KIWA Ltd., Nieuwegein, The
Netherlands 
Nico C. Wortel, P.E., KIWA Ltd., Nieuwegein, The Netherlands
Vll
1
Regulations, 
Characteristics, and 
Analytical Considerations
Nancy E. McTigue, Environmental Engineering & 
Technology, Inc.
Hay M.M. Koppers, P.E., KIWA Ltd.
David A. Cornwell, Ph.D., P.E., Environmental Engineering 
& Technology, Inc.
INTRODUCTION
Handling and disposing of water treatment process sludge have always been 
important considerations in water treatment. Over the past 10 years, however, the 
problem of where and how to dispose of these residuals has received increased 
attention. More stringent water quality standards for finished drinking water, and 
for receiving water bodies and groundwater underlying surface disposal sites, have 
made the proper disposal of sludges more difficult. Coupled with these more 
stringent regulations has been a decrease in land available for the ultimate disposal 
of sludges.
Residual disposal is a common problem for any plant treating water for drink 
ing purposes. In this book, experiences of utilities in both the United States and The 
Netherlands are discussed. While specific regulations and treatment processes may 
differ between the two countries, the overall problem of environmentally sound
2 SLIB, SCHLAMM, SLUDGE
sludge disposal is the same. The approaches these two countries have used to cope 
with the problem, as well as some of the solutions that have been suggested, may 
help utilities with their sludge problems.
Throughout this report, Dutch and US regulations, current sludge handling 
practices, and advanced and innovative sludge handling methods are described. 
Water Treatment Plant Waste Management (Cornwell et al. 1987) was written as a 
handbook on sludge handling and disposal techniques currently used in the United 
States. That publication should be consulted for background information, as this 
book is designed to supplement that original handbook.
US REGULATIONS
No federal legislation exists that directly governs the handling and disposal of water 
treatment plant sludges in the United States. Instead, applicable regulations are 
found in laws written to protect different parts of the environment, including water, 
soil, and air. On the local level, noise abatement laws can even impact the ultimate 
disposal of sludges. Applicable US federal legislation will be discussed in the follow 
ing section.
Most of the current regulations applicable to water plant sludges can be found 
in two general bodies of legislation, one dealing with surface water quality and one 
dealing with handling of hazardous materials. The first general body of legislation, 
which deals with surface water quality, incorporates the Clean Water Act (CWA), 
passed in 1977, and the Federal Water Pollution Control Act (FWPCA), passed in 
1956. These laws tend to limit direct discharge of wastes into a watercourse as an 
acceptable technology. The second set of regulations, the Resource Conservation and 
Recovery Act (RCRA) and the Comprehensive Environmental Response, Compensa 
tion, and Liability Act (CERCLA), primarily affect land disposal of water plant 
wastes. If the waste contains radioactivity, additional regulations can apply.
Table 1-1 lists the regulatory acts that currently govern the disposal of water 
plant sludges. The two general groups, regulations dealing with water and regula 
tions dealing with waste application to land, will be discussed separately.
Table 1-1 Regulatory Acts Governing Water Plant Waste Disposal
Disposal Option Applicable Regulations
Stream National Pollutant Discharge Elimination System (Clean Water Act [CWA]) 
In-Stream Water Quality Criteria (CWA) 
Discharge Guidance Documents
Wastewater Plant Pretreatment Standards (CWA) 
Landfill Resource Conservation and Recovery Act (RCRA)
Comprehensive Environmental Response, Compensation, and Liability Act
(CERCLA)
State Surface Water Requirements (RCRA)
Low-Level Radioactive Waste Requirements (state, Nuclear Regulatory 
Commission [NRC], Department of Transportation [DOT], United States 
Environmental Protection Agency [USEPA]) 
Land Application Sludge Disposal Regulations (CWA) 
__________________Low-Level Radioactive Waste Requirements (state, NRC, DOT, USEPA)______
Source: Cornwell, D.A. et al. 1987. Handbook of Practice, Water Treatment Plant Waste Management. AWWARF, Denver, 
Colo.
SLUDGE HANDLING AND DISPOSAL 3
Discharge to a Water Body
The CWA was built on a series of laws written since 1912, aimed at federal control 
of the quality of the nation's surface water. Among the federal laws passed were the 
Public Health Service Act of 1912, the Oil Pollution Act of 1924, and the FWPCA of 
1956. It was the FWPCA, as amended in 1972, that began to focus federal efforts on 
a goal of no discharge of pollutants into waterways. This act allowed for the estab 
lishment of national pollutant discharge elimination system (NPDES) permits. It 
also established national water quality goals, for the first time. This law and others 
are summarized in Table 1-2 (Davis and Cornwell 1985).
The CWA strongly endorsed the view that waterborne toxic substances should 
be controlled. The text of the act included a list of 65 substances or classes of sub 
stances that was to be used as the basis for defining toxics. More importantly for 
waste disposal considerations, it further defined the NPDES system. In discharging 
anything, including water plant sludge, to a body of water, a permit must be 
obtained. The standards for the discharge permit were designed to protect aquatic 
and human life.
This requirement to protect the environment led to the establishment of 
in-stream water quality criteria and standards. Criteria are defined as guidelines or 
goals established by the US Environmental Protection Agency (USEPA). Standards 
are the enforceable levels, generally established by the individual states. Allowable 
pollutant concentrations in a discharge can be set to meet the in-stream water 
quality standards, the criteria levels, or other levels as the individual states may 
deem appropriate for a specific water course. The act recognized that technology 
(coupled with economics) may not be sufficiently developed to allow all industrial
Table 1 -2 Federal Laws Controlling Water Pollution
Year Title Selected Elements of Legislation
1948Water Pollution Control Act
1956 Federal Water Pollution 
Control Act
1965 Water Quality Act
1972 Federal Water Pollution 
Control Act (amended)
1977 Clean Water Act
1981 Municipal Waste Treatment 
Construction Grants 
Amendment
Funds for state water pollution control agencies
Technical assistance to states
Limited provisions for legal action against polluters
Funds for water pollution research and training
Construction grants to municipalities
Three-stage enforcement process
States set water quality standards
States prepare implementation plans
Zero discharge of pollutants goal
Best practical treatment and best available treatment
effluent limitations 
National Pollution Discharge Elimination System
permits
Enforcement based on permit violations 
Best available treatment requirements for toxic
substances 
Best conventional treatment requirements for
conventional pollutants 
Reduced federal share in construction grants program
Source: Davis, M. & Cornwell, D.A. 1985. Introduction to Environmental Engineering. Prentice-Hall, Boston, Mass. 
NOTE: The table entries include only the new policies and programs established by each of the laws. Often these 
provisions were carried forward in modified form as elements of subsequent legislation.
4 SLIB, SCHLAMM, SLUDGE
dischargers to meet the desired in-stream levels. The act called for the development 
of guidance documents for industrial discharges, indicating the discharge levels that 
dischargers should be able to meet. The CWA also required individual wastewater 
treatment plants to develop pretreatment standards to govern discharge of wastes 
into the sewer. These pretreatment regulations can affect the discharge of water 
plant wastes into the wastewater plant.
The FWPCA required states to set standards for interstate waters and gave 
them authority to order treatment of wastes from water treatment plants. The CWA 
established a more formal procedure for controlling water treatment plant 
discharges. Water supply was formally declared an industry, and a draft guidance 
document was developed.
The draft guidance document for the water supply industry divided water 
treatment plants into the following three categories:
• Plants that use one of the following: coagulation, oxidation for iron and man 
ganese removal, or direct filtration.
• Plants that use chemical softening procedures.
• Plants that use a combination of the procedures in the above categories.
For each category, the best practical control technology was defined, and allow 
able pH and total suspended solids limitations were established. The limits estab 
lished for water plant discharges ranged from 5 to 10.8 Ib of solids/mil gal (0.6 to 
1.3 g of solids/m ) of water treated, depending on plant capacity. These figures cor 
respond with a suspended solids concentration in the waste stream to be discharged 
of approximately 30-60 mg/L suspended solids, assuming a 2 percent waste dis 
charge of the main stream. Larger plants were held to lower solids discharge levels. 
It did not address liquid-phase waste discharges.
This guidance document did not progress past the draft guidance phase, and it 
is not likely that it will ever be more than a draft document. The USEPA has no 
plans to publish a guidance document pertaining to water plant wastes. Therefore, 
discharge decisions are made either by the regional USEPA offices or by the 
individual states delegated to write their own permits. It is up to the permit writer 
to rule on the best available treatment technology for each plant on a case-by-case 
basis. According to the USEPA, the primary criterion for allowance of direct dis 
charge of water plant sludges is to meet established in-stream water quality stan 
dards at the edge of the mixing zone. As stated by the USEPA,
In developing technology based limitations in permits, a controlled release of 
water clarifier sludge and filter backwash from water treatment plants in a man 
ner which meets water quality standards may in appropriate circumstances be 
constituted to be technology based controls (USEPA 1978).
In-stream water quality criteria and standards are developed by individual 
states (with the use of some federal guidelines). Most states have classified each 
body of water for a designated use and set in-stream quality guidelines appro 
priately. Table 1-3 shows example in-stream water quality criteria and standards for 
several selected compounds. (Since standards vary from state to state, only 
examples can be illustrated.) These quality criteria would apply to solid/liquid waste 
stream water quality standards.
Some states have established maximum allowable concentrations in the dis 
charge. These limits generally apply if they are more stringent than the allowable 
discharge that will meet the in-stream water quality criteria. For example, Illinois 
does not allow a discharge of greater than 15 mg/L fluoride (F). Barium discharge is 
required to be less than 2 mg/L, even if the 1-mg/L in-stream standard could be met
SLUDGE HANDLING AND DISPOSAL 5
Table 1 -3 Example In-Stream Water Quality Guidelines and Standards
Compound
Arsenic (dissolved)
Barium
Beryllium
Cadmium
Chloride
Chromium
(hexavalent, dissolved)
(trivalent, active)
(TOTAL)
Copper
Cyanide, free
Fluoride
Hydrogen sulfide
Iron, total soluble
Lead
Manganese, total
soluble
Mercury
Nickel (total)
Nitrate (as N)
Phenol
Selenium
Silver
Sulfate
TDS
Zinc
Aldrin
Chloride
Endrin
Heptachlor
Lindane
Methoxychlor
Toxaphene
DDT
Chloroform
Radioactivity
Ra226,Ra2*8
Gross alpha particle
activity (excluding
radon and uranium)
Guidelines
Aquatic Life 
Chronic Criteria
Fresh 
VgIL
72
130
el.16 (ln(hardness)) - 3.841
7.2
eO.819 (In(hardness)) + .537
2.0
4.2
2.0
1000
el.34 (ln(hardness)) - 5.245
0.00057
eO.76 (ln(hardness)) + 1.06
1.0
35
o.iel.72 (In(hardness)) - 6.52
47
0.03
0.0043
0.0023
0.0038
0.08
0.03
0.013
0.001
1240
Example 
Standards
Salt 
WS/L
63
12
54
4
23
0.57
2.0
8.6
100
0.1
7.1
1.0
54
0.023
58
0.003
0.004
0.0023
0.0036
0.0016
0.03
0.0007
0.001
Stream Used 
Human for Potable 
Health* Water 
\ig/L mg/L
2.2ng/L
3.7ng/L
10.0
170
20.0
50
146ng/L
13.4
3500
10
50
5000
0.074 ng/L
0.46 ng/L
1.0
0.28 ng/L
0.71 ng/L
0.024 ng/L
0.19
0.05
1.0
0.01
250
0.05
1.0
1.4
0.3
0.05
0.05
0.002
10
0.001
0.01
0.05
250
500
5.0
0.0002
0.004
0.10
0.005
0.1
5pCi/L
15pCi/L
Source: Cornwell, DA. et al. 1987. Handbook of Practice, Water Treatment Plant Waste Management. AWWARF, Denver, 
Co/o.
NOTE: Guideline values are from USEPA, Water Quality Criteria Documents, Federal Register, Nov. 28, 1980, Vol. 45, 
No. 231, 79318. Standards are selected from various state regulations and do not reflect any one state's regulations.
* Values given are the ambient water quality criterion for protection of human health for noncarcinogens, and for car 
cinogens the value is the risk of one additional case of cancer in 1 million persons.
6 SLIB, SCHLAMM, SLUDGE
through dilution. Wisconsin has set maximum discharge levels of radium (soluble) in 
liquid wastes as follows:
Ra226 Ra228
30 30
< 1 pCi/L
These regulations apply to discharge from a water plant to a storm sewer or to 
a surface body of water. They also apply to an effluent from a wastewater treat 
ment plant.
Discharge to wastewater treatment plants is generally governed by the 
individual plant's pretreatment regulations. There may also be some specific 
guidelines provided by state agencies. Wisconsin has limited the discharge of radium 
to a sewer as
Ra226 Ra228
400 800
< 1 pCi/L
In addition, the total amount of radiation released/to the sewer system cannot 
exceed1.0 Ci/year.
The CWA, through its NPDES permit system, in-stream water quality stan 
dards, discharge guidance documents, and pretreatment standards, provides the 
regulatory framework for the disposal of water plant sludges to waterways. Because 
states can interpret and apply these regulations differently, the type of disposal that 
is actually permitted will vary greatly from state to state. For example, certain 
states will allow direct discharge of alum sludge to streams, while others will allow 
it only with pretreatment, while other states will prohibit it completely.
Land Application
Disposing of water plant sludges by applying them to land, whether by landfilling or 
beneficial application, is governed by numerous laws. Unlike laws pertaining to 
water, most of these laws have been passed quite recently.
The CWA authorized the establishment of criteria for land application of 
sludges. These criteria are designed for wastewater sludges and only provide general 
guidelines for water plant wastes. When considering landfilling of dewatered solids 
from water treatment plants, RCRA and solid waste requirements govern. The 
RCRA defines hazardous waste and establishes the guidelines for its safe treatment, 
storage, and disposal.
The Solid Waste Disposal Act was passed in 1965, and the RCRA was passed 
in 1970. The RCRA states that the emphasis of waste management disposal should 
be on recovery and recycle of materials and not on disposal. It was designed to meet 
disposal needs resulting from the CWA and the Clean Air Act. The statutes of those 
two acts require the removal of hazardous substances from air emissions and water 
discharges. These statutes, however, did not assure that the disposal of the waste 
materials generated would be environmentally sound. The intent of RCRA was to 
provide that assurance. The five major elements of RCRA are
• federal classification of hazardous waste;
• cradle to grave manifest system;
• federal standards to be followed by generators, treaters, disposers, and storers 
of hazardous wastes;
SLUDGE HANDLING AND DISPOSAL 7
• enforcement of federal standards; and
• authorization of states to obtain primacy for implementation of the regulations.
Currently, the only way that a water plant waste could be classified as hazard 
ous, and so fall under the requirements of RCRA, is by failing the extraction proce 
dure (EP) toxicity test. Basically, the test is a measure of defined constituents that 
are present or will leach from the water plant waste. For a liquid waste, the con 
stituents are measured directly. For a solid waste, the waste is held at pH 5.5 for 
several hours under defined procedures. If the liquid or extract from the waste con 
tains concentrations greater than defined levels, then it is hazardous. Table 1-4 
shows the defined contaminants for the EP toxicity test and their maximum allowed 
values. Those constituents and the levels are 100 times the maximum contaminant 
level (MCL) as stated in the Safe Drinking Water Act (SDWA).
However, the EP toxicity test is being replaced by the toxicity characteristic 
leaching procedure (TCLP). This procedure increases the number of compounds 
regulated and lowers the acceptable limit. Table 1-5 shows the TCLP limits. 
Generally speaking, water plant sludges do not fail the EP toxicity test. However, it 
is possible for sludges to fail the TCLP test.
With the Technical Sewage Sludge Regulations originally proposed in February 
1989, USEPA has moved away from leachate testing for evaluation of land applica 
tion, landfilling, and surface disposal (Federal Register 1989). These regulations 
involve the determination of total metal (and selected organic) concentrations fol 
lowed by modeling to determine the groundwater impact. The regulation is aimed at 
keeping groundwater impacts at below the MCL levels. The effect of these proposed 
regulations on the water industry is to have some states look at water plant sludges 
more carefully, particularly in terms of metal content and groundwater impacts.
Another set of regulations that could affect land disposal of water plant wastes 
is the Comprehensive Environmental Response, Compensation, and Liability Act 
(CERCLA) of 1980. This piece of legislation provides authority for the removal of 
hazardous substances from improperly constructed or operated sites not in com 
pliance with RCRA. The RCRA regulations are concerned only with the handling of
Table 1 -4 Denned Contaminants and Maximum Allowed Values for EP Toxicity Test
Maximum
Concen. 
Contaminant mg/L
Arsenic 5.0
Barium 100.0
Cadmium 1.0
Chromium 5.0
Endrin 0.02
Lead 5.0
Lindane 0.4
Mercury 0.2
Methoxychlor 10.0
Selenium 1.0
Silver 5.0
Silvex 1.0
Toxaphene 0.5 
2,4-D__________________________________________ 10.0
Source: Cornwell, DA. et al. 1987. Handbook of Practice, Water Treatment Plant Waste Management. AWWARF, Denver, 
Colo.
8 SLIB, SCHLAMM, SLUDGE
wastes at existing or new facilities, while CERCLA governs the cleaning of aban 
doned disposal sites.
A noteworthy aspect of the CERCLA regulations is that they allow cleanup 
costs to be assessed against the user of the land disposal facility based on a volume- 
use basis. The waste itself need not have directly caused the problem. For example, 
if a water utility disposed of its sludge at a private landfill that also accepted other 
industrial wastes that contaminated the groundwater, the water utility could be
Table 1 -5 Toxicity Characteristic Contaminants and Regulatory Levels
Contaminant
Regulatory
Threshold
Level
mg/L
Arsenic
Barium
Cadmium
Chromium
Lead
Mercury
Selenium
Silver
Endrin
Lindane
Methoxychlor
Toxaphene
2,4-D
2,4,5-TP
Chlordane
Heptachlor (and its hydroxide)
Benzene
Carbon tetrachloride
Chlorobenzene
Chloroform
1,2-Dichloroethane
1,1-Dichloroethylene
Methyl ethyl ketone
Tetrachloroethylene
Trichloroethylene
Vinyl chloride
1,4-Dichlorobenzene
Hexachlorobenzene
Hexachlorobutadiene
2,4-Dinitro toluene
Hexachloroethane
Nitrobenzene
Pyridine
o-Cresol
Trt-Cresol
p-Cresol
Pentachlorophenol
2.4.5-Trichlorophenol
2.4.6-Trichlorophenol
5.0
100.0
1.0
5.0
5.0
0.2
1.0
5.0
0.02
0.4
10
0.5
10
1.0
0.03
0.008
0.05
0.5
100
6.0
0.5
0.7
200
0.7
0.5
0.2
7.5
0.13
0.5
0.13
3.0
2.0
5.0
200
200
200
100
400
2.0
Source: Federal Register. 1990. 40 CFR 261, 55:61:11805 (March 29).
SLUDGE HANDLING AND DISPOSAL 9
liable for cleanup based on its volume use of the landfill, even if its sludge did not 
cause the problem.
Land application guidelines for water plant sludges generally do not exist, 
although some states have set maximum metal content limits for land application. 
Land application is usually governed by sewage sludge regulations for metal load 
ings. Table 1-6 shows the federal guidelines for maximum cumulative loadings for 
sewage sludges, depending on soil type.
The biggest impact of alum or iron water plant sludges on land is a reduction 
of the equilibrium phosphorus concentration (EPC). The EPC is the amount of phos 
phorus immediately available to plant roots. As a general rule, a maximum loading 
of 10 to 20 tons/acre (2.2 to 4.4 kg/m ) of water plant sludge is required to prevent 
phosphorus deficiencies. Sludge and soil analyses are required to determine the site- 
specific proper loading rate.
The American Water Works Association Research Foundation has concluded a 
project that determined the conditions under which land application of water plant 
sludges is appropriate (AWWARF 1990). Until an adequate data base exists for 
water plant sludge, regulatory agencies will continue to use the existing criteria that 
relate primarily to sewage sludges.
The criteria used by the commonwealth of Pennsylvania are probably typical 
for most regulatory agencies and will be discussedhere. In Pennsylvania, treatment 
residuals to be land applied must be subjected to the same analytical procedures 
required for sewage sludge. This consists, at a minimum, of the parameters listed in 
Table 1-7. Regulations currently under development in Pennsylvania make a distinc 
tion between agricultural utilization and land reclamation, where the former per 
tains to applications involving a beneficial effect on selected crop growth (i.e., 
orchard grass, oats, barley, etc.). Land reclamation is defined as the application/dis 
posal of sludge to establish vegetative growth and/or restore or enhance the soil 
productivity of surface-mined areas or other lands.
Agricultural utilization. Following are the key provisions of the regulations 
governing agricultural utilization in Pennsylvania.
1. Sludge cannot be applied during periods of precipitation or when the ground 
is saturated, covered with snow, or frozen.
Table 1 -6 Maximum Cumulative Amount of Metal Suggested for Agricultural Soils With Sewage 
Sludge
Soil Cation Exchange Capacity 
meq/100g
Less than 5 5-15 Greater than 15
Maximum Amount of Metal 
Metal Ib/acre
Cadmium
Copper 
Lead
Nickel
Zinc
5
125 
500
50
250
10
250 
1000
100
500
20
500 
2000
200
1000
Source: United States Environmental Protection Agency. 1978. Sludge Treatment and Disposal: Sludge Disposal. Vol. 2. 
MERL, EPA 625:4-78:012.
NOTE: Ib/acre x 0.1 = g/m2 .
10 SLIB, SCHLAMM, SLUDGE
Table 1-7 Analyses Required for Land Application of Sewage Sludge
Moisture content Cyanide
Percent total nitrogen Sodium
Percent total ammonium Cadmium
Percent organic nitrogen Zinc
Percent phosphorus Copper
Percent potassium Nickel
BOD (biological oxygen demand) Lead
pH Chromium
Mercury 
Molybdenum
Source: Dixon, K. & Lee, R. 1989. A Residuals Management Strategy for the Perm-American Water Company. Presented at 
AWWA/WPCF Joint Residuals Management Conference, San Diego, Calif., (Aug. 13-16, 1989).
2. The rate of application shall be controlled by the most stringent of the fol 
lowing three factors:
a. Nitrogen loading—available nitrogen shall not exceed 75 percent of the 
selected crop uptake specified in Table 1-8.
b. Trace metals—the annual application rate based on trace metal con 
centrations in the sludge cannot exceed the limits specified in Table 1-8.
c. Hydraulic limit—the annual application rate shall not exceed 30,000 
gal/acre (2.8 cm/year). Daily application shall not exceed 5000 gal/acre (0.5 cm/day).
3. Site life is calculated based on a maximum accumulation of trace metals, as 
specified in Table 1-8. A soil analysis must be conducted after 30 dry tons 
sludge/acre (6.6 kg/m ) have been applied. The results must be evaluated in terms of 
the toxicity limits. Sludge can only be applied to suitable soils with a minimum 
depth of 20 in. (0.5 m) to bedrock and/or the seasonal high water table and 4 ft 
(1.2 m) to the permanent groundwater table.
Soil pH is to be 6.5 or greater prior to application and must be maintained at 
6.5 or greater during the operational life of the site and for two years following the 
final application.
Radioactive Wastes*
Water plant wastes containing radium could come under the authority of three 
federal agencies: the Nuclear Regulatory Commission (NRC), the USEPA, and the 
Department of Transportation (DOT). None of these agencies, however, directly 
regulate this type of waste. The ultimate authority for regulation of water plant 
wastes containing radium lies with the individual states.
The NRC is responsible for regulating the licensing, generation, containment, 
and disposal of radioactive material. The NRC does not, however, regulate radium 
waste unless it is associated with nuclear fuel. The NRC has developed design 
criteria for the disposal of radium-containing uranium mill tailings, which can pro 
vide technical guidelines to utilities that must dispose of radium-containing water 
plant wastes.
The USEPA's authority in this area has been limited to avoid overlap with 
NRC authority. The extent of USEPA involvement with radioactive wastes is shared 
responsibilities with NRC for uranium mill tailings.
*The material in this section is taken from Corn well et al. (1987).
SLUDGE HANDLING AND DISPOSAL 11
Table 1-8 Agricultural Utilization Control Factors
Nitrogen Uptake by Selected Crops 
Crop
Corn
Corn silage 
Grain sorghum 
Wheat
Oats
Barley 
Orchard grass 
Brome grass 
Tall fescue
Bluegrass
Maximum Trace Element Loading Rate
Element
Cadmium
Copper 
Chromium
Lead
Mercury 
Nickel
Zinc
Crop Yield 
per acre
120 bu
140 bu
32 tons 
4 tons 
60 bu
80 bu
100 bu
100 bu 
6 tons 
5 tons 
3.5 tons
2 tons
Maximum 
Loading Rate 
Ib/acre
1.0
20 
20
20
0.2 
4.0
40
Nitrogen Uptake 
Ib/acre
150
185
200 
250 
125
186
150
150 
300 
166 
135
200
Lifetime
Maximum Loading 
Rate 
Ib/acre
3
60 
60
60
0.6 
12
120
Source: Dixon, K. & Lee, R. 1989. A Residuals Management Strategy for the Penn-American Water Company. Presented at 
AWWA/WPCF Joint Residuals Management Conference, San Diego, Calif., (Aug. 13-16, 1989). 
NOTE: Ib/acre x 0.1 = g/m2 .
The DOT regulates the shipment of any radioactive waste. The DOT is a pos 
sible regulatory authority if the waste is shipped off site for disposal. The waste can 
be considered radioactive by DOT if (1) a state authority has designated the waste 
as radioactive or (2) the radioactivity exceeds DOT-established levels. The DOT 
defines a radioactive waste as a material that has a specific activity of over 2000 
pCi/g (dry weight). It is unlikely that any water plant sludge would exceed this 
level. However, if a state designates a waste as radioactive, then DOT regulations 
apply. In such cases, shipment must be according to 49 CFR Part 172.392, which 
requires that the waste be packaged in leak-proof containers with acceptable levels 
of external radiation and transported in appropriately marked vehicles.
Specific regulations, other than those relating to transportation, are left to the 
state agencies. South Dakota, for example, has regulations that require the water 
plant to be licensed as a generator of radioactive material.
Wisconsin has set the following criteria for landfilling of sludges containing 
radium:
• Solid waste containing 2 pCi/g (dry weight) or less of Ra can be landfilled in 
approved sanitary landfills.
12 SLIB, SCHLAMM, SLUDGE
• Solid waste containing greater than 2 pCi/g but less than or equal to 50 pCi/g 
(dry weight) of Ra can be disposed of in selectively approved sanitary 
landfills. The waste must be mixed with stabilizing solid waste so that the
nnc o o
concentration of Ra averaged over any area of 1075 ft (100 m ) will not 
exceed background levels by more than 5 pCi/g, averaged over any 6-in. (15-cm) 
thick soil below the surface.
• Solid waste containing over 50 pCi/g requires specific agency review.
• The radium-containing waste should be disposed of in its own trench with 
separate liner and leachate collection/treatment system.
Illinois has similar regulations governing water plant wastes containing 
radium, with some additional restrictions to assure that the release of radon is less 
than 5 pCi/m2 • s.
DUTCH REGULATIONS
According to an estimate produced by the Dutch Ministry of Housing, Physical Plan 
ning and Environment (MHPPE), the annual quantity of wastes produced in The 
Netherlands in 1982 was close to 65 million tons. This includes approximately 
45 million tons of contaminated river sediments. The problem of disposing of this 
waste continues to grow. Dutch water companies are involved in this problem in two 
ways: on the one hand, they are themselves waste producers, while on the other 
hand, they have an interest in maintaining a clean environment.Consequently, in 
addition to their legal obligations, the water companies have a moral duty to process 
and dispose of their waste products as efficiently and in as environmentally clean a 
manner as possible. The following legal documents cover the disposal of wastes 
(Zeilmaker 1987):
• Nuisance Act (NA)—waste activities within institutions;
• Nuclear Power Act (NPA)—waste regulations contained in specific laws, such 
as those for radioactive waste;
• Mining Legislation—mining wastes;
• Chemical Waste Act (CWA)—chemical waste and used oil;
• Waste Product Act (WPA)—all waste products that are not chemical wastes;
• Surface Water Pollution Act (SWPA) and Seawater Pollution Act (SPA)—dis 
charge and dumping of waste into surface water and seawater; and
• Soil Protection Act (SoPA)—storage/disposal of waste in or on the ground.
In addition to these documents, provincial and municipal regulations play an 
important role, either in "joint authority" on the basis of the legislation listed above 
or "autonomously" on the basis of provincial or municipal legislation. However, these 
regulations will not be discussed here. Only the SWPA, WPA, CWA, and SoPA will 
be addressed. Attention will be paid to a number of central issues relating to the 
current problem of waste disposal. Until the 1970s, the NA, which dates from 1875, 
was the only law by which danger, harm, or nuisance to the environment caused by 
dumping or storing of waste materials could be prevented or limited. In the 1960s 
and 1970s, the need to tackle environmental problems relating to water, air, soil, 
radiation, noise, and waste was realized. This realization led to narrowing the scope 
of the NA, and the creation of a series of new, sectoral environmental laws.
SLUDGE HANDLING AND DISPOSAL 13
Surface Water Pollution Act/Seawater Pollution Act
The first problem to be dealt with was the increase in environmental pollution due 
to the discharge of waste products to the sea and to fresh surface water. The Oil 
Pollution of Seawater Act was passed in 1958, followed in the 1960s and 1970s by 
the SWPA and the SPA. The SWPA prohibits introduction of wastes, or polluted or 
harmful substances into surface water without a license from the relevant 
authorities. If a license is granted, a suitable application method must be used. 
Conditions can be attached to a license for the disposal of wastewater into surface 
water in order to protect the interests for which the requirement of a license was 
originally imposed. The following stipulations are often included in discharge 
licenses:
• the wastewater must not contain toxic substances in quantities and/or con 
centrations that might harm the biological ability of the surface water to clean 
itself;
• the wastewater must not contain fats or oils;
• the wastewater must not contain flammable, explosive, or radioactive 
materials; rapidly precipitable or floating particles; organic solvents; or coarse, 
firm substances; and
• the wastewater must not contain any materials that will cause the surface 
water to change color, taste, or smell.
The policy according to which licenses are granted, therefore, precludes the 
direct discharge of sludge into surface water. The sludge has to be separated from 
the water to be discharged and disposed of in an appropriate manner.
The prescribed values for effluent quality are not always uniform, and can 
differ according to the water quality standards for the water into which the waste is 
to be discharged. Table 1-9 provides an overview of some widely used quality 
requirements in The Netherlands.
Sewer discharge regulations. For discharge into municipal sewer systems, 
the Sewer Discharge Regulations should be followed. These state that
• discharge must not cause any blockage or damage to the sewer system and 
related installations. The most commonly applied quality criteria regarding 
sewer discharge of water utility sludge with respect to this point are
— acidity: 6.5<pH<10
— temperature: <86°F (30°C)
— sulfate content (mg/L): <300.
Table 1-9 Dutch Quality Requirements Regarding Wastewater Discharge From Water Treatment 
Plants Into Surface Water
Parameter Discharge Requirements
Iron content, mgIL Fe Usually <5, occasionally <2 
Suspended solids, mg/L <30 
Settleable solids,* ml/L <0.3 
Acidity 6.5 < pH < 8.5 
COD (chemical oxygen demand), mg/L O% <20 
Nitrogen,t mg/L ___ __________________ <1
Source: Koppers, H.M.M. 1982. Production, Handling and Disposal of Water Plant Sludges. KIWA Report 67. KIWA, 
Rijswijk, The Netherlands. 
*According to Imhoff. 
fKjeldahl nitrogen.
14 SLIB, SCHLAMM, SLUDGE
The sludge should have good flow properties. This will be generally satisfied 
when the dry solids content is below 2 %w/w.
• there must be no negative influence upon the functioning of the sewage 
purification installation, nor upon the quality of the wastewater sludge. This 
refers to the concentration of organic and inorganic contaminants in the dis 
charged waste.
A series of levies and contributions are charged in order to offset the costs of 
implementing SWPA. The level of these is based upon the organic and inorganic 
burden of the wastewater in question.
Chemical Waste Act/Waste Product Act
The problem posed by the responsible handling of chemical waste products and used 
oil became evident during the 1970s. In view of the urgency of the problem, it was 
decided in 1972 that a specific bill should be drawn up to address the different types 
of waste products. The result was the CWA (1976). At the same time, a new, general 
law on waste products was passed (the WPA) in 1977. The two laws underwent a 
staged introduction beginning in 1977 and 1979, respectively, and both were the 
product of the national government's policy on waste products.
The purpose of these policies was to ensure proper management and control of 
waste streams. Methods of achieving this include minimizing the generation of 
waste, promoting useful or beneficial application of waste products, and disposing of 
waste products in an efficient and responsible manner. These objectives include the 
concept of efficiency, something that is unique in environmental hygiene legislation. 
Efficiency is an important criterion in the assessment of provincial waste disposal 
plans, and the granting of licenses and exemptions. The elements of efficiency 
include continuity, capacity, and diversity in disposing of waste and in handling 
techniques.
In addition to these functions, the CWA and WPA provide the organizational 
framework for the efficient disposal of waste products. Central government plays the 
leading role in the enforcement of the CWA, while the WPA is more decentralized in 
structure, with the provinces taking responsibility for coordination and issuing 
licenses, and the municipalities fulfilling the executive function. In addition to this, 
the latter also have regulatory authority with respect to domestic waste. The WPA 
is based upon the system of provincial plans for the disposal of a number of specifi 
cally named waste products. The plan provides the key to the province's waste 
product policy.
Assessment of license applications is carried out based on this plan. The mini 
ster has established guidelines that provide a foundation for the policy vision to be 
set out in the provincial plans. The minister has also established two technical 
guidelines based on the WPA, with regard to the incineration of waste products and 
control of ultimate disposal by landfilling.
With regard to the storage and disposal of waste products in or on the ground, 
the guidelines ensure that the measures taken to protect the soil and the surface 
water from pollution satisfy the following basic criteria:
• direct contact between the waste products and the soil, or ground and surface 
water should be avoided;
• thespread in the soil of polluted water from the waste products should be 
avoided;
• the situation whereby the products are placed in or on the ground should be 
controllable, and should remain so in the future; and
SLUDGE HANDLING AND DISPOSAL 15
• regular inspection should be made of the site and of the effectiveness of the 
provisions made.
These points are intended to obey the principle of isolation, control, and inspec 
tion (ICI). That is, the measures to be taken should ensure that the dumping area is 
isolated from the surrounding environment, and that the situation is controllable 
and will remain so, whereby provisions to allow inspection are absolutely essential. 
These provisions are discussed in greater depth in the guidelines.
Quality of sludge. Water utility sludge is viewed as a waste product with a 
composition that is comparable to that of, for example, contaminated river sedi 
ments, dredge spills, or sludge produced by the treatment of wastewater. Thus, all 
naturally occurring elements are to be found in the sludge, together with non- 
natural materials in higher or lower concentrations. If waste products of this kind 
are stored or disposed of in or on the ground without any type of protection, chemi 
cal and/or biological processes will eventually cause substances to be released into 
the soil in an unchecked and uncontrolled manner, and in potentially contaminating 
quantities. It is necessary, therefore, that such waste be dumped or stored on the 
ground in an environmentally responsible manner. The ICI principles referred to 
previously should be applied in all cases.
The landfill owner, usually local or provincial, determines whether or not the 
waste product will be accepted based on various criteria. The most important 
criteria for evaluating the material include the following:
• composition of the waste product, particularly with respect to the organic and 
inorganic contaminant concentrations as compared to regulatory threshold 
levels stated in the CWA;
• leaching capability at a pH of 4.0. The leachate quality is generally compared 
to reference standards for groundwater, as shown in the Guidance Manual for 
Soil Decontamination (1988) (see Table 1-10); and
• handleability of the waste products. In the case of wastewater plant sludges, 
the most important factors are dry solids concentration and sludge consistency.
With a view to, among other things, the stability and water balance of the 
disposal cell and also to restricting the volume/weight dumped, the sludge should be 
tendered in dewatered form, generally as a near-solid. For example, in West Ger 
many when sludge from a water utility is dumped in a landfill together with domes 
tic waste, a dry solids content of at least 35 %w/w (LAGA 1979) is usually 
demanded. Sludge with a lower dry solids content can be incorporated into a dis 
posal cell provided it is landfilled in the right proportion with the other waste. In 
The Netherlands, the ratio adopted between domestic waste and wastewater sludge 
dewatered with the aid of centrifuges and belt-filter presses varies by weight from 
5:1 to 10:1 (STORA 1989). A larger proportion of sludge has a detrimental effect on 
the bearing capacity and stability of the spoil. In the United States, this ratio tends 
to vary between 4:1 and 10:1. In Switzerland, where sewage sludge is landfilled 
together with domestic refuse, the proportion of sludge in a disposal cell may not 
exceed 15 percent by volume (Working Group EC 1988).
With regards to landfill dumping practices, the general opinion is that a dry 
solids requirement (indirect) is not a sufficient means of characterizing the handling 
or dumping qualities of a sludge. The need to describe the landfill dumping quality 
characteristics of sludge other than the dry solids content is increasing, since a 
steadily larger quantity of wastewater sludge is expected to be disposed of by 
landfilling in the future. A start has been made in West Germany and Switzerland, 
and consequently in The Netherlands, to define and determine the physical
16 SLIB, SCHLAMM, SLUDGE
Table 1-10 Reference Standards (B Values*) for Groundwater
Reference Standard (B Value) 
Component
Ammonium-N 1000
Arsenic 30
Barium 100
Bromide 500
Cadmium 2.5
Chromium 50
Cobalt 50
Copper 50
Cyanide (total-complex) 50 
EOC1 (extractable organic halogen) 15
Gasoline 40
Lead 50
Mercury 0.5
Mineral oil 200
Molybdenum 20
Nickel 50
Phosphate-P 200
Tin 30 
Total aromatic hydrocarbons 30
Total PAHs 10
Total PCBs 0.2 
Total pesticides (organo-chlorine) 0.5 
Zinc . 200
Source: Guidance Manual for Soil Decontamination. 1988. Ministry of Housing, Physical Planning and Environment, 
Staatsuitgeveij, The Hague, The Netherlands (4th ed., Nov. 1988).
*B values indicate that if values listed are exceeded, then further investigation is needed.
characteristics of the sludge for proper landfilling of a sludge by resorting to soil 
mechanics (STORA 1989; Moller et al. 1985).
Shear stress has been adopted as a parameter for sludge consistency, which is 
a reliable yardstick of physical characteristics of the sludge for proper landfilling. 
Shear stress can be easily measured, with easily reproduced results, using a motor 
vane. (See the section on analytical techniques at the end of this chapter.) A shear 
stress of at least 10 kN/m2, as determined with the aid of the vane apparatus, has 
been taken as a provisional limit value or working hypothesis for physical charac 
teristics of the sludge for proper landfilling.
The WPA and CWA explicitly prohibit the disposal or storage of waste products 
in or on the ground unless a license or exemption has been granted. This applies to 
the ultimate disposal of chemical wastes covered by the CWA. The WPA also 
provides for the possibility of a complete ban on specific categories of waste product. 
As yet, however, no such categories have been designated.
The WPA places a strong emphasis upon the granting of licenses by the 
province for setting up waste handling facilities (e.g., waste incinerators and con 
trolled landfill facilities). In so doing, the criterion for granting a license is, in addi 
tion to that of efficiency, "the importance of protecting the environment." This 
criterion is broader than simply the aspects of danger, harm, and nuisance, and 
includes considerations of landscape, ecology, and organization.
SLUDGE HANDLING AND DISPOSAL 17
It should to be noted that the WPA and CWA do not apply to the discharge of 
waste products to surface water as does the SWPA. Also, the section on licensing 
contained in the WPA has only been partially put into operation. It does not yet 
apply to actions such as the retention, storage, or movement of waste (whether or 
not on the company's own premises) or any type of handling or destruction of waste 
materials other than construction debris. For the time being, activities of this kind 
will continue to be covered by the NA. This also applies to the self-governed dump 
ing on the company's own site, for instance, of "self-produced" waste products. The 
WPA does not cover activities of this sort on a company's own property, but the 
necessary measures would be taken under the terms of the NA and, in time, 
the SoPA.
Neither the WPA nor the CWA contains a definition of what a waste product 
is, because the concept is subjective and its content subject to change. In practice, 
the lack of a legally binding definition often gives rise to a good deal of debate.
The definition of chemical waste used by the CWA consists of those waste 
products that are made up in whole or in part of specific chemical substances or that 
are created as a result of particular chemical processes. A description of these is 
contained in the Chemical Waste Act Substances and Processes Order, which came 
into effect on Aug. 1, 1979.This order includes three appendices in list form: a list 
of substances (split into four classes), a list of processes, and a list of exceptions.
The list of exceptions includes regulatory threshold levels for the four classes of 
substances. This means that a particular waste product will not be subject to the 
provisions of the CWA if the concentration of that product falls below the limit for 
that particular class. The threshold levels are 50; 5000; 20,000; and 50,000 mg/kg 
dry solids for a variety of specified substances. Table 1-11 provides an overview of 
the list of substances.
A national survey in 1983 revealed that 50 percent of the Dutch water com 
panies are producing sludge with an arsenic content that exceeds the regulatory 
threshold level for this element (50 mg/kg). The sludges from these water companies 
should be considered as chemical waste as envisaged by the CWA (Koppers 1985). 
This is shown in Figure 1-1.
Waste products to which the CWA applies can only be disposed of either by 
burial, with exemption from the prohibition on landfill dumping, or by handing them 
over to a third party. This third party might be any of the following:
• a body that holds a license under the terms of the act to store, process, or 
destroy these products;
• a body that holds an exemption from the prohibition on landfilling, allowing 
them to dispose of the products in or on the ground ultimately;
• a body that holds an exemption under the terms of the SPA, which allows them 
to dump or incinerate the products at sea;
• a foreign body with which it has been agreed that the waste products be 
exported to their country.
Soil Protection Act
During the period that the WPA and CWA have been in effect, the problem of pollu 
tion, decontamination, and protection of soil became so pressing that the SoPA came 
into effect on Jan. 1, 1987.
The objective of the SoPA is to regulate activities that can harm soil quality, 
particularly those with an irreversible or incurable effect upon one or more soil 
functions.
18 SLIB, SCHLAMM, SLUDGE
Table 1-11 List of Substances and Regulatory Threshold Levels From the Substances and 
Processes Order Chemical Waste Act
Category A (threshold level: 50 mg/kg dry solids) 
Antimony and antimony compounds 
Arsenic and arsenic compounds 
Beryllium and beryllium compounds 
Cadmium and cadmium compounds 
Chromium and chromium compounds 
Mercury and mercury compounds 
Selenium and selenium compounds 
Tellurium and tellurium compounds 
Thallium and thallium compounds 
Inorganic cyanide compounds (cyanides) 
Metal carbonyles 
Polycyclic aromatic compounds 
Halogenated formates of aromatic rings, 
like polychlorinated biphenyls and 
polychlorinated terphenyls and derivates 
of these substances
Category BI (threshold level: 5000 mg/kg dry solids) 
Chromium (III) compounds 
Cobalt compounds 
Copper compounds 
Lead compounds 
Molybdenum compounds 
Nickel compounds 
Tin compounds 
Vanadium compounds 
Tungsten compounds 
Silver compounds
The next organic compounds: 
Organic halogen compounds 
Organic phosphor compounds 
Organic peroxides
Organic nitro- and nitroso compounds 
Organic azo- and azoxy compounds
Nitriles
Amines
(iso- and thio-) cyanates
Phenol and phenolic compounds
Mercaptans
Category BII (threshold level: 5000 mg/kg dry solids)
Asbestos
Cutting, grinding, and roll oil (emulsions)
Halogensilanes
Halogen-containing substances causing acid 
vapors when brought in contact with water 
or damp air such as chlorosulfur, silicon tetra- 
chloride, aluminum chloride, titanium 
chloride
Hydrazine(s)
Category BII (continued)
Explosives as described in the Dangerous
Substances Act 
Fluorine 
Chlorine 
Bromine
Ferrosilicon and alloys of this substance 
White phosphor 
Manganese silicon 
Lead
Category C (threshold level: 20,000 mg/kg dry solids) 
Ammonia and ammonia compounds 
Inorganic peroxides 
Barium compounds 
Fluorine compounds 
Phosphor compounds 
Bromates, (hypo-) bromites 
Chlorates, (hypo-) chlorites 
Aromatic hydrocarbons 
Organic silicon compounds 
Organic sulfur compounds 
lodates
Nitrates, nitrites 
Sulfides 
Zinc compounds 
Salts of per acids 
Acid halogens, acid amides 
Acid anhydrides
Category D (threshold level: 50,000 mg/kg dry solids)
Aluminum
Zinc )
Titanium > Only in powder or dust form
Zirconium )
Lithium
Sodium
Potassium
Calcium
Magnesium
Sulfur
Inorganic acids
Metal hydrogensulfates
Oxides and hydroxides, except when these 
substances form chemical bonds with: 
hydrogen, carbon, silicon, iron, aluminum, 
titanium, manganese, and magnesium
Calcium carbide
Aluminum carbide
Hydrides
Nitrides
Alkanes and cycloalkanes
Organic oxygen compounds
Organic nitrogen compounds
Source: Substances and Processes Order of May 26, 1977. Statute Book 435. (Based on subsections 1 and 3 of section 1, 
Chemical Waste Act, with the latest amendment of Mar. 17, 1988.) Statute Book 145. The Hague, The Netherlands.
SLUDGE HANDLING AND DISPOSAL 19
100 -
Regulatory Threshold Level
200 300 400 
Arsenic Concentration, mg/kg dry solids
500 600
Source: Koppers, H.M.M. 1985. Wasserwerksschlamm: ein zuscitzlich.es Problem fur die Versorgungsunternehmen in den 
Niederlanden. GWF-Wasser/Abwasser, 126:10:513.
NOTE: The vertical axis shows the regulatory threshold level for arsenic (50 mg/kg dry solids). Seven surface water and 107 
groundwater treatment facilities produce sludge with an arsenic content of more than 50 mg/kg dry solids.
Figure 1-1 Arsenic content in sludges from groundwater (•) and surface water (A) treatment 
facilities in The Netherlands.
Within the framework of the act, official orders will be produced containing 
rules for a number of categories of soil-endangering activities. The water companies 
must take into account these orders (currently being drawn up) during storage or 
useful application of their sludge, with regard to:
• the storage and disposal on and in the ground of raw, auxiliary, and waste 
materials. Local sources of contamination, such as storage and landfill areas 
for sludge in particular, will have to comply with ICI criteria formulated within 
the framework of the SoPA;
• the use of organic fertilizers (compost and organic soil) other than animal 
manure;
• product requirements with regard to building materials.
With regard to the agricultural application of water utility sludge, the following 
should be noted. Water plant sludge as a soil improver/fertilizer can, in principle, 
only be applied to soil in conjunction with sludge produced by wastewater purifica 
tion plants and other waste products, if the composition of the mixture satisfies the 
relevant quality requirements. The mixing of sludge from water purification plants
20 SLIB, SCHLAMM, SLUDGE
with other products, including water plant sludge, is only permitted for processing 
into compost or organic soil.
If waste is used as compost, such use must not introduce larger quantities of 
heavy metals and arsenic into the soil than would use of sludge from wastewater 
purification plants. The composition requirements set out in Table 1-12 apply to 
compost made up of a mixture of waste products. The values listed in Table 1-13 
apply to the amount of compost allowable.
There are no limits to the use of organic soil. The structure and properties of 
organic soil must be more or less the same as that of naturally occurring soil. 
Organic soil should, however, be the same as the natural soil, as far as structure 
and properties are concerned.
Table 1-14 shows the maximum permissible heavy metal content for black 
earth/organic soil in relation to the clay fraction smaller than 2 microns and the 
organic fraction.
Finally, the regulations as a whole regarding the storage and disposal of sludge 
on-site of a water treatment plant,as well as the removal of sludge off site of the 
plant, are summarized in Figure 1-2.
SLUDGE CHARACTERISTICS
Characteristics of Sludges Produced in the United States*
Treatment plants in the United States can be broadly divided into four general 
categories. First are those treatment plants that coagulate, filter, and oxidize a sur 
face water for removal of turbidity, color, bacteria, algae, organic compounds, and 
often iron and/or manganese. These plants generally use alum or iron salts for 
coagulation and produce two waste streams. The majority of the waste produced 
from these plants is sedimentation basin (or clarifier) sludge and filter backwash 
wastes.
The second type of treatment plant practices softening for the removal of cal 
cium and magnesium by the addition of lime, sodium hydroxide, and/or soda ash. 
These plants produce clarifier basin sludges and filter backwash wastes. On 
occasion, plants will practice both of the above treatment technologies. It should be 
noted that softening plant wastes can also contain trace inorganics, such as radium, 
that could affect proper handling.
The third type of plant is designed to remove specifically trace inorganic sub 
stances, such as nitrate, fluoride, radium, and arsenic. These plants use processes 
such as ion exchange, reverse osmosis, or adsorption. They produce liquid wastes or 
solid wastes, such as spent adsorption material.
The fourth type of treatment plant produces air-phase wastes, which are 
produced during the stripping of volatile compounds.
Coagulation waste streams. Coagulation of surface waters is by far the 
most commonly used water supply treatment technology in the United States. These 
waste streams make up the majority of the plant wastes produced by the water 
industry, probably in the range of 70 percent of the total waste produced. These 
wastes are also some of the more difficult wastes to treat. Figure 1-3 is a schematic 
of a conventional coagulation treatment process, showing the typical waste products.
Some water plants have a presedimentation step that is generally used only 
when the raw water source is high in settleable solids. Often no chemical is added
*The material in this section was taken from Cornwell et al. (1987).
SLUDGE HANDLING AND DISPOSAL 21
Table 1-12 Maximum Permissible Heavy Metal Content in Compost Made Up of a Mixture of 
Waste Products
1987-91 1991-95 1995-* 
Component mg I kg dry solids mg I kg dry solids mg I kg dry solids
Arsenic
Cadmium
Chromium
Copper
Lead
Mercury
Nickel
Zinc
25
5
300
500
600
3
60
1300
25
2
200
300
200
2
50
900
no value
1
60
60
180
0.7
30
240
Source: Adapted from Bill-Order: Quality of Remaining Organic Fertilizers. Statute Book 209, Oct. 27, 1988. (Based on 
subsection 2 of section 1, subsection 1 of section 2, and section 6 of the Fertilizer Act.) Statute Book 598, 1986. The Hague, The 
Netherlands.
*1995- : indicative values.
Table 1-13 Maximum Permitted Amounts of Compost Prepared From a Mixture of Waste 
Products
Amount of Compost 
tons dry solids I ha
Application Point
Grassland 
Farmland 
Green maize field 
Natural land 
Parks/sports fields
1987-95
Prohibited 
12* 
12* 
Prohibited 
12*
1995-
Prohibited
t 
t 
Prohibited
t
Source: Adapted from Bill-Order: Quality of Remaining Organic Fertilizers. Statute Book 209, Oct. 27, 1988. (Based on 
subsection 2 of section 1, subsection 1 of section 2, and section 6 of the Fertilizer Act.) Statute Book 598, 1986. The Hague, The 
Netherlands.
NOTE: ton/ha x 900 = Ib/acre.
*Amount used over four years.
tNot yet known.
Table 1-14 Maximum Permissible Heavy Metal Content in Black Earth/Organic Soil Until 1995
Permissible Content 
Component mg/kg dry solids
Arsenic 15 + 0.4 (L + H)*
Cadmium 0.4 + 0.007 (L + 3H)
Chromium 50 + 2L
Copper 15 + 0.6 (L + H)
Lead 50 + L + H
Mercury 0.2 + 0.0017 (2L + H)
Nickel 10 + L 
_______Zinc_____________________________50 + 1.5 (2L + H)___________
Source: Adapted from Bill Order: Quality of Remaining Organic Fertilizers. Statute Book 209, Oct. 27, 1988. (Based on 
subsection 2 of section 1, subsection 1 of section 2, and section 6 of the Fertilizer Act.) Statute Book 598, 1986. The Hague, The 
Netherlands.
*L = percent clay fraction smaller than 2 microns; H = percent organic material (maximum H-value is 15 percent).
22 SLIB, SCHLAMM, SLUDGE
Discharge To WWTP; 
CWA Exemption No
Discharge to Surface 
Water; SWPA Permit
Discharge To CWA
Licensee, e.g.,
Landfill
CWA Exemption; 
ICI Principles NA or WPA Permit; ICI Principles
Discharge to WWTP/
Surface Water;
Discharge Permit,
e.g., SWPA
NA Permit 
ICI Principles
SoPA Rules
Legend
WWTP = Wastewater treatment plant SWPA = Surface Water Pollution Act 
NA = Nuisance Act ICI Principles = Isolation, Control, Inspection 
WPA = Waste Product Act SoPA = Soil Protection Act 
CWA = Chemical Waste Act
* Only in consultation with Ministry of Housing, Physical Planning, and Environment
Source: VEWIN (Netherlands Water Works Association). 1986. Memorandum Concerning Disposal of Water Treament Plant 
Sludges. VEWIN, Rijswijk, The Netherlands.
Figure 1 -2 Dutch regulations regarding storage and disposal of wastes.
prior to presedimentation, although an oxidant or small amount of polymer may be 
added. It is generally accepted that as long as coagulant is not added and, therefore, 
the solids are essentially only those settled from the raw water, then these solids 
can be discharged back to the watercourse on a controlled basis. Due to this 
handling, and the very site-specific nature of this waste stream, presetting solids 
will not be specifically addressed here.
The coagulation process itself generates most of the waste solids. Generally, a 
metal salt (aluminum or iron) is added as the primary coagulant. In addition to the 
coagulant, other solids-producing chemicals, such as powdered activated carbon, 
polymer, clay, lime, or activated silica, may be used. These added chemicals will all 
produce waste solids. They are usually removed, along with the solids in the raw 
water, in a sedimentation tank or clarifier. In areas with very good raw water 
quality, sedimentation basins are occasionally omitted and the solids are removed by 
filtration only. This process, commonly known as direct filtration, is usually used for 
waters with low and constant turbidity and requires low levels of coagulant. All 
solids removed in this process are collected with filter backwash water. Table 1-15 
shows reported chemical characteristics of an alum coagulant sludge.
The quantity of solids produced depends on the raw water quality and chemical 
addition. The volume of sedimentation basin sludge produced depends on both the 
characteristics of the solids and the mechanism by which solids are removed from
SLUDGE HANDLING AND DISPOSAL 23
c
Chemical ° 
Additions
Raw >
oagulant Aid PAC 
xidant pH Adjustment 
Oxidant 
Coagulant
C
Coagulant Aid
1 1 
1 i —————— i 1
' 1 ^\ '^- T -^
Water *~ *"
X/^
v
VJ
1 
1
*
1 ,
1.
Dagulant Aid
d_ 1x ±
™
N
\
s
1
0 
Fi
1 
1
±3
<idant Corrosion 
ter Aid Control 
pH Adjustment 
Oxidant
_
r > r
Finished
Water
V
Products Coagulant Filter Backwash Sludge Waste
Pre-Settling 
Basin
Rapid 
Mix Flocculation Clarifier Filters
Source: Cornwell, DA. et al. 1987. Handbook of Practice, Water Treatment Plant Waste Management. AWWARF, Denver, 
Co/o.
Figure 1-3 Waste-producing processes in coagulation plants.
the basin. Many basins, particularly older ones, do not have a mechanical means of 
removing the solids and must be manually cleaned. In these basins, the solids are 
stored for extended periods of time and allowed to accumulate to some 
predetermined level.Periodically, the basin is drained and often washed out with a 
fire hose. Obviously for these basins, the cleaning frequency is a function of the 
volume of sludge produced and available storage volume in the basins. Manual 
cleaning results in batch production of sludge and makes subsequent sludge han 
dling more difficult. In most situations, it is desirable to retrofit the basins with 
continuous-sludge-removal equipment, which may be difficult to accomplish due to 
basin configurations. However, producing a fairly continuous and consistent flow of 
sludge to the sludge treatment process is often a critical factor in successful 
dewatering. Appropriate sludge removal in combination with flow equalization must 
be well planned.
The second major waste stream produced is from the batch process of back- 
washing the filters. The solids collected on the filters are those remaining after 
sedimentation or caused by the addition of a filter aid or formed by oxidation of 
perhaps iron or manganese. In a direct filtration process, these are the only solids 
produced. The volume is a function of the amount of water used for backwashing. 
This waste stream is produced at very high flow rates for short periods of time, and 
again proper equalization is required.
Another waste product that is occasionally produced in a coagulation-based 
plant is spent granular activated carbon (GAG). This GAG is sometimes used in the 
filters or in post-filtration. When used for taste and odor removal, the carbon is 
disposed of after its capacity is exhausted or returned to the manufacturer for
24 SLIB, SCHLAMM, SLUDGE
Table 1-15 Reported Chemical Characteristics of an Alum Coagulant Sludge
Parameter Concentration
Total solids (TS) 0.1-27%, by weight
Volatile solids 10-35% of TS
Suspended solids 75-99% of TS
pH 5.5-7.5
BOD 30-6000 mg/L
COD 500-27,000 mg/L
Aluminum 4-11% of TS as Al (limited data)
Iron 6.5% of TS (one sample)
Manganese <0.005-5% of TS
Arsenic <0.04% of TS
Cadmium <0.005% of TS
Individual heavy metals <0.03% of TS
Total Kjeldahl nitrogen 0.7-1200 mg/L as N
Phosphate 0.3-300 mg/L as P
Total plate count ________________ 30-300,000/mL
Source: Given, P.W. & Spink, D. 1984. Alum Sludge: Treatment, Disposal, and Characterization. Proc. 36th Ann. Conv. 
Western Canada Water and Sewage Conf.
regeneration. When its use is for continuous low-level organics removal, then the 
carbon is usually regenerated on-site, with essentially no waste stream.
Softening waste streams. Wastes produced from softening plants represent 
the second major waste product produced by the US water industry. Fortunately, 
softening wastes are generally more easily dewatered than coagulant wastes, 
although the presence of some trace inorganics may make proper disposal difficult. 
There are many variations of the softening process. Chemical addition, flow pro 
cesses, and the subsequent waste quantities and characteristics are all dependent on 
raw water hardness, alkalinity constituents, and the desired finished water quality. 
Since softening is generally used to improve the chemical characteristics and 
aesthetics, rather than the potability of the finished water, subjective decisions can 
be made as to the final desired quality. One factor that enters into that decision 
process is the effect on sludge handling and costs.
Softening is accomplished either by chemical precipitation of the calcium and 
magnesium or by the use of ion exchange resins. The former, traditionally called 
lime-soda ash softening, is by far the most widely used softening process. In this 
method, lime is added for the removal of carbonate hardness supplemented with the 
use of soda ash for noncarbonate hardness removal if required. From the standpoint 
of sludge economics, it is desirable to leave as much magnesium hardness in the 
water as considered acceptable. Often the final magnesium hardness can be allowed 
to remain around 40 mg/L as CaCOs, or slightly higher, and not have an adverse 
effect on home water heaters. The less magnesium in the sludge, the easier it is to 
dewater.
Figure 1-4 is a rather simplified softening plant schematic. Several variations 
of Figure 1-4 are used to obtain the desired water quality and minimize costs. In 
softening plants, there are usually two waste streams produced: the settled solids 
from the clarifier and the backwash wastes. Some plants will add a polymer or 
metal salt to aid in the removal of fine precipitates, color, or turbidity present in the 
original water. Again, from a sludge viewpoint, the addition of metal salts should be
SLUDGE HANDLING AND DISPOSAL 25
Raw 
Water
)xidant Coagulant Aid 
ime Coagulant 
oda Ash
Coagulant
f*> ^T
>,ntrl
^
Coagulant Aid c 
Coagulant
hr+i \ f •*-
N S
\
O, Oxidant Fluoride 
Filter Aid Corrosion 
Control
f •^rti >
Ox
U. >'—> —*
1
dant
f
Waste 
Products
Softening 
Sludge
Backwash 
Waste
Rapid 
Mix
Reaction 
Zone Clarifier Recarbonation Filtration
Source: Cornwell, D.A. et al. 1987. Handbook of Practice, Water Treatment Plant Waste Management. AWWARF, Denver, 
Colo.
Figure 1-4 Waste-producing processes in softening plants.
held to a minimum in order to reduce sludge treatment costs. The use of polymers 
and slurry recirculation can help minimize the use of these coagulants.
In many plants, the reaction zone and clarifier are combined into a single 
solids contact unit. In these plants, sludge can be fairly uniformly withdrawn from 
the sludge blanket, and a consistent suspended solids concentration and flow rate 
can be maintained. Plants that have separate clarifiers are often equipped with 
scrapers for sludge removal. Although not quite as easy to control as the sludge 
blanket units, the separate clarifiers can produce a fairly consistent sludge. As with 
coagulation plants, filter backwash water is produced at high flow rates for short 
periods of time. Filter backwash water may require equalization basins prior to 
treatment or discharge.
When water is softened by ion exchange, the water containing the hardness is 
passed through a column containing the ion exchange material. The hardness in the 
water exchanges with an ion from the ion exchange material. Generally, the ion 
exchanged with the hardness is sodium, thus
Ca(HCO3)2 + 2NaR = CaR2 + 2NaHCO3 (1-1)
where R represents the solid ion exchange material. By the above reaction, calcium 
(or magnesium) has been removed from the water and replaced by an equivalent 
amount of sodium; i.e., two sodium ions for each divalent cation removed. The 
exchange results in essentially 100 percent removal of the hardness from the water 
until the exchange capacity of the ion exchange material is reached. When the ion 
exchange resin becomes saturated, "breakthrough" is said to have occurred because 
the hardness is no longer removed. At this point, the ion exchange material is 
regenerated. During regeneration, the hardness is removed from the material by
26 SLIB, SCHLAMM, SLUDGE
passing water containing a large amount of Na+ through the column. The mass 
action of having so much Na+ in the water will cause the hardness of the ion 
exchange material to enter the water and exchange with the sodium; thus
CaR2 + 2NaCl = 2NaR + CaCl2 (1-2)
The ion exchange material can now be used to remove more hardness.
This regenerant material is the wastewater stream that requires disposal. It 
contains the excess or leftover NaCl and the ions removed—CaCb and MgCte. 
Economics dictate that a readily available location be used for disposal of this brine. 
Therefore, most large plants that utilize ion exchange softening are located in 
coastal communities, and ocean brine disposal is practiced. Ion exchange has been 
used in small water supply systems in other parts of the country and wastes have 
most often been discharged