EPA-670/2-75-049
June 1975
Environmental Protection Technology Series
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VIEW OF LANDSPREADING OF
MUNICIPAL SEWAGE SLUDGE
National Environmental Center
Office of Research and Development
U.S. Environmental Protection Agency
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EPA-670/2-75-049
June 1975
REVIEW OF LANDSPREADING OF
LIQUID MUNICIPAL SEWAGE SLUDGE
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WIRONMENTAL PROTECTION /
CINCINNATI, OHIO 45268
For sale by the Superintendent of Document!, U.S. Government
Printing Office, Waihington, D.C. 20402
U.S. ENVIRONMENTAL PROTECTION AGENCY ^ ro
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REVIEW NOTICE
The National Environmental Research Center--Cincinnati has
reviewed this report and approved its publication. Approval does
not signify that the contents necessarily reflect the views and
policies of the U. S. Environmental Protection Agency, nor does
mention of trade names or commercial products constitute endorse-
ment or recommendation for use.
11
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FOREWORD
Man and his environment must be protected from the adverse
effects of pesticides, radiation, noise and other forms of pollu-
tion, and the unwise management of solid waste. Efforts to
protect the environment require a focus that recognizes the
interplay between the components of our physical environment—
air, water, and land. The National Environmental Research
Centers provide this multidisciplinary focus through programs
engaged in
0 studies on the effects of environmental contaminants
on man and the biosphere, and
0 a search for ways to prevent contamination and to
recycle valuable resources.
This survey of liquid sludge spreading practices was con-
ducted for the Ultimate Disposal Section of the Advanced Waste
Treatment Research Laboratory to evaluate the present status
and the potential of various techniques of sludge spreading on
land for beneficial use and disposal of the sludge. All methods
of disposal of pollutants from water involve some risk of
causing pollution in another area. Only by comparing the
benefits and risks involved in each disposal technique can
rational choices between alternatives be made.
A. W. Breidenbach, Ph.D
Director
National Environmental
Research Center, Cincinnati
ill
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ABSTRACT
The objective of this study was to review and summarize existing inform-
ation regarding landspreading of liquid municipal sewage sludge. An
extensive literature review was conducted and an annotated bibliography
is available as a separate report from the National Technical Information
Service. Emphasis was also given to obtaining information concerning the
number of sewage treatment plants currently using landspreading. A ques-
tionnaire survey of 1909 sewage treatment plants in Federal Regions 2, 3,
4, 5 and 9 was conducted and selected operations were visited.
The information and data gathered during the study are summarized rela-
tive to sludge characteristics, sludge handling and distribution systems,
economics of landspreading, sludge-soil-plant interactions, public
health considerations, land acquisition, and survey of sewage treatment
plants. The survey indicated that about 21 percent of the sewage treat-
ment plants in the study regions are using landspreading on a routine
basis. Of the plants which are using landspreading, 68 percent of them
have been conducting the practice for less than 10 years. Of this 68
percent over 2/3 have begun the practice only within the last 5 years.
This report was submitted in fulfillment of Contract 68-03-0140 by
Battelle Memorial Institute, Columbus Laboratories, under the sponsor-
ship of the Environmental Protection Agency. Work was completed as of
June, 1974.
xv
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CONTENTS
Page
FOREWORD iii
ABSTRACT iv
LIST OF FIGURES vii
LIST OF TABLES viii
SECTIONS
I. CONCLUSIONS 1
II. RECOMMENDATIONS 4
III. INTRODUCTION 5
IV. OBJECTIVES 6
V. SLUDGE CHARACTERISTICS 7
Wastewater Characteristics 7
Treatment Plant Sludges 8
Treatment Plant Control of Pathogens 13
VI. SLUDGE HANDLING AND DISTRIBUTION SYSTEMS 19
Retention Provisions 19
Conveyance Mode and Application Methods 20
Selection of Conveyance Mode 23
VII. ECONOMICS OF LANDSPREADING 24
Treatment Plant Considerations 24
Agricultural Considerations 26
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CONTENTS (Continued)
Page
VIII. SLUDGE-SOIL-PLANT INTERACTIONS 30
Physical Characteristics 30
Mineralogical Characteristics 31
Chemical Characteristics 31
Physiographic Considerations 32
Physical Characteristics of Liquid Sewage
Sludge-Soil Interactions 34
Chemical Characteristics of Liquid Sludge-Soil-Plant
Interactions 36
IX. PUBLIC HEALTH CONSIDERATIONS 41
Movement of Pathogens in the Soil 41
Survival of Pathogenic Organisms in the Soil 43
Potential Health Hazards 47
X. LAND ACQUISITION 49
Obstacles 49
Land Availability 50
XI. SURVEY OF SEWAGE TREATMENT PLANTS IN FEDERAL REGIONS
2, 3, 4, 5, AND 9 52
Questionnaire and Phone Survey 53
Field Visits 63
XII. REFERENCES 89
vi
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LIST OF FIGURES
Number Page
1 Schematic of Sewage Treatment Operations and General
Sludge Characteristics 9
2 Schematic of Existing Sewage Treatment Plants Modified
to Provide Secondary and/or Tertiary Treatment .... 10
3 Questionnaire Used in Mail Survey 55
4 Distribution of Sewage Treatment Plants Using
Landspreading on a Routine Basis 64
vii
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LIST OF TABLES
Number Page
1 Properties of Digester Supernatant 12
2 Bacteria in Sewage Sludge 14
3 Representative Sludge Compositions 15
4 Bacteriological Studies of Sludge Produced in
Plant-Scale Tests of Lime Stabilization 17
5 Average Costs for Ultimate Sludge Disposal 25
6 Effect of Population on Unit Cost of Sludge Disposal . . 26
7 Comparative Costs of Sludge Disposal 27
8 Maximum Sustained Slope vs. Minimum Distance to
Watercourses 33
9 Metals Content of Corn 40
10 Summary of Bacteriological Analyses 43
11 Survival Times of Pathogenic Microorganisms in
Various Media 46
12 Summary of the Mail Survey Response 56
13 Landspreading Survey Results 58
14 Summary of Responses by Individual Plants 59
15 Estimated Operating Costs of Selected Landspreading
Operations
16 Tabulation of Crop Yields and Sludge Application
at Springfield, Illinois
67
viii
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LIST OF TABLES (Continued)
Number
17 Development Costs of Sugar Creek Sludge Disposal Area
at Springfield, Illinois ............... 75
18 Development Costs of Spring Creek Sludge Disposal
Area at Springfield, Illinois ............. 76
ix
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SECTION I
CONCLUSIONS
This report presents a broad overview of landspreading of liquid munici-
pal sewage sludges as an ultimate disposal alternative. Some of the
more significant conclusions drawn from the literature review, the sur-
vey of sewage treatment plants, and the field visits to active land-
spreading operations are presented below.
(1) Land disposal of liquid sewage sludges has been practiced
for many years in the United States under a wide range of
geographic, topographic, climatic, and soil conditions.
Although detailed operating documentation is not readily
available, the practice has been conducted with apparent
success and limited problems.
(2) The principles guiding many of the landspreading operations
appear to have evolved from experience gained with sewage
farm operations and land disposal activities associated
with dried sludge or wastewater effluents.
(3) There is a paucity of easily comparable data specific to
liquid sludge from which the overall economic and environ-
mental benefits and costs can be quantified. Specifically,
data are generally lacking in regard to sludge composition,
application rates, environmental response, and dollar flows.
(4) Most sludge spreading has been done without monitoring the
effects upon the environment. Studies are now under way to
determine the effects of pathogens, nutrients, trace ele-
ments, and other sludge constituents upon soils, water, air,
plants, and animals.
(5) Landspreading is a viable sludge disposal alternative. How-
ever, criteria for site selection and management techniques
need to be developed and disseminated to planning, management,
and operational levels.
(6) While liquid sludge has value as a fertilizer, it is not a
balanced fertilizer for many crops and soil conditions. Its
soil conditioning properties are perhaps more valuable than
its fertilizer content. Data derived from statistically
meaningful experiments are needed to elucidate and quantify
these sludge attributes.
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(7) Generally, each plant's landspreading operation will be
determined by the sludge composition, transportation
factors, soil characteristics, and land use considerations.
The purpose of the landspreading operation—disposal only or
soil improvement—will help to determine the frequency and
rate of application. It will also determine the duration of
a land disposal operation at a given site.
(8) Sludges which contain excessive amounts of trace elements
and pathogens are potentially dangerous to plants, animals,
and public health. Such sludges should not be used as a
fertilizer and/or soil conditioner.
(9) Sludge treatment systems designed to eliminate potential
problems relative to pathogens are both in operation and
research stages. Many problems associated with excessive con-
centrations of metals and other trace elements could be appre-
ciably reduced by enforcement of stricter controls on indus-
trial discharges to municipal sewers. However, elimination of
all metals and other trace elements is not feasible since do-
mestic wastewater contributes a significant amount.
(10) Agricultural land, both cropland and pasture, is most commonly
used for landspreading practices. Where such land is not
readily available, other lands such as abandoned stripmines,
golf courses, parks, highway median strips, forests, orchards,
and airports are being used.
(11) There is more than sufficient land area available for land-
spreading activities. Economical distribution rather than the
capacity of the total system to assimilate the sludge is the
problem.
(12) The most frequently stated objections to landspreading relate
to potential health hazards, nuisances (odors, insects, etc.)
associated with the landspreading operation, and a general
"human waste stigma". These concerns appear to be more a
function of landspreading1s visibility as a disposal method
than a function of real risk to public health. Well planned
public information programs could help to overcome these
objections.
(13) Wastewater treatment plant design efforts, both initial and
retrofitting, must include considerations of what method will
be used for the ultimate disposal of the sludge produced.
(14) Liquid municipal sewage sludge is amenable to land disposal
and can offer a number of benefits (i.e., reduced treatment
plant operating costs, fertilizer value, soil conditioning
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value, supplemental irrigation water) when practiced under
the proper conditions. However, problems can result from in-
appropriate management of this practice. More information
should be obtained and guidelines provided relative to safe
application rates and frequencies and facility management.
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SECTION II
RECOMMENDATIONS
The literature review and field visits to active landspreading opera-
tions suggested the following research needs:
(1) Development of methods based upon sewerage service area
profiles which will allow the estimation of sludge character-
istics and their amenability for land disposal in the liquid
state
(2) Development of practical economic and environmental formulae
and computational techniques which can be utilized by plant
designers and operators to project the costs associated with
landspreading
(3) Intensification of field studies to determine the behavior
and ultimate fate of these constituents under actual operating
conditions, in addition to continuing studies designed to deter-
mine allowable soil and plant concentrations of various sludge
constituents (for example, heavy metals)
(4) Comparison of the effects of advanced wastewater treatment
practices and proposed sludge treatment alternatives to
control pathogens on sludge characteristics relative to their
amenability for landspreading
(5) Development of programs for disseminating information being
developed on landspreading to treatment plant operators, vari-
ous regulatory agencies, and the general public
(6) Performance of an integrated, multidisciplinary study directed
toward an understanding of the complexities of the liquid
sludge-soil-plant interactions
(7) Assessment of the feasibility of adopting regional sludge
collection and disposal schemes as opposed to independently
conducted operations.
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SECTION III
INTRODUCTION
One of the primary objectives of the wastewater treatment process is
the prevention of water pollution by removing the pollutants from sewage
and industrial wastes. The effluent, sludge, and gases produced as by-
products of the treatment process must be either disposed of or util-
ized in an efficient, low-cost fashion without risk to public health
and, also, without undue stress on other components of the environment.
The traditional means of sludge handling and disposal still widely
used today are
• Ocean disposal via barging or pipeline transport
• Dewatering and drying and sale as a fertilizer or disposal
in a landfill
• Incineration
• Lagooning
• Landspreading.
Too often, no attempt is made while disposing of sludge to integrate
the materials into natural systems. Consequently, much of the conven-
tional disposal technology represents a nonbeneficial use of a poten-
tial resource.
The value of human and animal wastes has been recognized for centuries.
For instance, the Chinese and other early civilizations applied human
organic wastes to the land to improve and/or maintain soil fertility.
Many technically advanced European countries including England, France,
Poland, and Germany are applying appropriately treated sewage sludge to
land surfaces.
The practice of landspreading is increasing in popularity in the United
States. Although the initial interests have been directed primarily
toward treated wastewater effluents, particularly in water deficient
regions, there are many situations where the disposal of the liquid
sludge by landspreading is an economical and beneficial solution to the
waste-disposal problem.
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SECTION IV
OBJECTIVES
The objective of this program was to provide a review and summary of
existing information and operational experiences in landspreading of
liquid municipal sewage sludge. There was a dearth of information con-
cerning the amount, procedures, and location of sludge applications to
the land. Major emphasis was thus given to obtaining information con-
cerning unreported landspreading operations currently employed in this
country through a combination questionnaire and telephone survey of all
sewage treatment plants greater than 3.8 x 10 M /day (1 mgd) in Federal
Regions 2, 3, 4, 5, and 9. In addition, plant visits were made to
selected treatment plants and associated landspreading operations.
The collected information was reviewed and summarized with respect to
the following aspects:
Sludge Characteristics
Sludge Handling and Distribution Systems
Economics of Landspreading
Sludge-Soil-Plant Interactions
Public Health Considerations
Land Acquisition
Research Needs
Survey of Sewage Treatment Plants.
Each of these aspects is discussed separately in the following sections
of this report. An annotated bibliography of the significant literature
on landspreading is presented as an appendix to the report.
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SECTION V
SLUDGE CHARACTERISTICS
Sludges from municipal wastewater treatment plants vary markedly in
moisture content, decomposable organic matter, chemical composition,
and microbial populations. Basically, this variability is a result
of the composition of the wastewater constituents and treatment plant
design and operation.
WASTEWATER CHARACTERISTICS
Generally, wastewater characteristics are responsive to (1) the domestic
water system including the water supply source, treatment, and convey-
ance system; (2) inorganic and organic compounds contained in industrial
and domestic wastewaters; and (3) inflow and infiltration into the waste-
water collection system.
Each resident of a community is usually considered as the contributor of
265-380 liters of wastewater per day resulting in the production of 91
grams of sludge per day [1]. These values include residential and in-
dustrial discharges into municipal wastewater.
The composition of municipal wastewaters is highly dependent on the pro-
portion and nature of the community's industrial base. Extremely vari-
able loadings of industrial wastes to municipal sewage systems will
increasingly affect treatment plant operations and ultimately the char-
acteristics of the sludge. Some industrial discharges such as various
food and agricultural industry wastes may increase usable landspread-
ing constituents. However, many discharges associated with chemical
process, metallurgical, mineral products, petroleum, and wood process-
ing industries may contribute undesirable constituents and as a result
may affect sludge disposal practices.
Sludge characteristics are also markedly influenced by the affluency of
the municipal residential area served by the wastewater treatment plant.
The increasing household use of marketed chemical compounds (cleaning
complexes, drugs, etc.) affect sewage treatment operations and, finally,
sludges. The increased use of garbage grinders [2] and disposable paper
products has increased the solids contributed by households.
The residential diet also affects wastewater and sludge characteristics.
As an example, the daily normal digestion and excretion of zinc is
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expected to average about 10 mg/person. The concentration of zinc in
fresh foods ranges from less than one ppm in fruits to 50 ppm in le-
gumes [3]. Higher amounts of zinc are contained in yeast, mushrooms,
and seafoods, with oysters containing as much as 2300 ppm [4],
The design and integrity of the wastewater collection system can also
alter sludge characteristics. Treatment plant operations are affected
by increased loadings (hydraulic and solid) due to captured urban storm-
water runoff (combined sewers and/or groundwater infiltration). Storm-
water runoff reaching the sewage treatment plant often transports vari-
ous "street refuse" (litter, dirt, bird and animal droppings, air pollu-
tion fallout particles, oils, chemical compounds, etc.).
TREATMENT PLANT SLUDGES
Figure 1 is a conceptual schematic diagram of sewage treatment operations
that indicates associated general sludge characteristics. In reality,
sewage treatment plant design alternatives are numerous, particularly for
secondary treatment. In addition, a sewage treatment plant which has
been modified .to provide secondary and/or tertiary treatment is more
likely to resemble the simplistic schematic presented on Figure 2.
Raw sludge usually refers to settled water-borne materials in sedimenta-
tion tanks. Primary sludge exhibits a solids content of about 2.5-5.0
percent. These unstabilized sludges are characteristically highly putres-
cible, with a volatile solids content of 50 to 80 percent, and they con-
tain a high bacterial count [1, 5, 6] . In addition to high concentrations
of fecal coliform bacteria (i.e., Escherichia coli about 10/100 ml) other
intestinal and respiratory tract organisms are present at lower concentra-
tions [ 7]. Organisms which cause such diseases as cholera, typhoid, dys-
entery, etc., are also commonly associated with fecal wastes and may be
present.
Although some measure of decomposition occurs, secondary sludges are un-
stabilized. Biological secondary treatment operations, trickling fil-
ters, or aerated systems produce sludges with total solids content percents
ranging from 5-10 or 0.5-1, respectively. The sludges consist primarily
of floe-forming zooglea bacteria which have entrapped suspended solids and
adsorbed colloidal material. These sludges are highly putrescible, ex-
hibit a high bacteria count, and volatile solids content normally range
from 65-75 percent [1, 5, 6].
The chemicals most commonly used to remove phosphates (lime, alum, and
iron salts) produce sludges ranging in total solids content from 5-15
percent after gravity thickening. Chemical sludges from alum or iron
coagulation produced by operation of a separate tertiary system result
in the formation of sludge material which has a volatile content of
about 10 percent. Such materials are slightly to moderately putrescible
and contain only minor amounts of bacteria. However, these sludges are
not considered of value as fertilizers or soil conditioners. In addi-
tion, the high contents of aluminum or iron may be deleterious to soils.
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Chemical sludges resulting from high pH lime coagulation (separate ter-
tiary system) are nonvolatile and are considered nonputrescible and
essentially bacteria free. The sludge is considered to have some value
as a fertilizer due to its phosphate content, which is slowly released.
The sludge may have some value as a soil conditioner or for pH control.
However, coprecipitated heavy metals content may be high, depending on
the wastewater [j, 5, 8] .
Primary, secondary, or tertiary sludges can be disposed of separately.
However, as depicted in Figure 2, sludges are often in combination.
Newer activated sludge plants often do not use a separate presedimenta-
tion system. Presently, coagulation chemicals are used for phosphorus
removal in conjunction with either primary or secondary treatment.
Because of the bacterial content of unstabilized sludges, putrefaction
results when oxygen is consumed and anaerobic decomposition dominates.
Anaerobic digestion for 10 (high-rate thermophilic) to 30 (standard-rate
mesophyllic) days destroys up to 60 percent of the organic matter. The
gas formed in this process (anaerobic digestion) is 55 to 80 percent
methane, 30-35 percent carbon dioxide, 2-3 percent hydrogen sulfide, and
lesser amounts of nitrogen, carbon monoxide, hydrogen, and other odorous
substances. The sludge gas is often utilized to maintain digester tem-
perature in the optimum mesophyllic range of 32-38 C. Sufficient gas is
often available to meet the normal energy operation demands of the sewage
treatment plant. However, due to seasonal and diurnal variations related
to digester insulation integrity and--more important—the variability
of sludge characteristics, gas production is variable and not considered a
dependable energy source. Thus, the gas is often flared |j, 5, 6, 7] .
In addition to the loss of mass due to gas evolution, a portion of the
liquid phase of the sludge (supernatant liquor) is often drawn off and
recycled to the plant, thus further reducing the volume of the sludge
[L, 5, T| . Some characteristics of digester supernatants are shown in
Table 1. Under anaerobic conditions, 80 percent of the phosphates
present in the sludge can be expected to be solubilized and thus also
be present in the recycled supernatant [9] .
The final product in the case of a well digested sludge is a black
liquid similar in appearance to a crude oil emulsion and it often evolves
a similar odor. A partially digested sludge may produce odors, attract
flies, and contain considerable counts of pathogenic organisms and viable
seeds. Normal digester operation is semicontinuous, and raw sludge is
periodically incorporated with the digester sludge and digested sludge
is withdrawn UL, 5, 7] .
Since anaerobic digestion is subject to process upset due to a variety
of toxic influents, aerobic stabilization (aerobic digestion) is some-
times used. Basically, the process involves aeration of sludge until
destruction of a large portion of the organics has occurred. As opposed
to anaerobic digestion, the production of a stabilized sludge requires
energy for aeration [l, 5, 6, 7] .
11
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Table 1. PROPERTIES OF DIGESTER SUPERNATANT [7]
(Municipal Wastewater Sludge)
_ Item _ Standard rate _ High rate
Total solids
(mg/2) 4,000-5,000 10,000-14,000
Total suspended
solids (mg/Z) 2,000-3,000 4,000-6,000
BOD (mg/A) 2,000-3,500 6,000-9,000
Volatile
solids (mg/ji) 650-3,000 2,400-3,800
Alkalinity
(MO) (mg/4) 1,000-2,400 1,900-2,700
H2S (mg/Ji) 70-90 190-440
NH -Nitrogen
240-560 560-620
pH 7.0-7.6 6.4-7.2
12
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Although digester conditions present pathogenic organisms with a hostile
environment, the conditions are not lethal. The principal bactericidal
effect appears to be related to a natural dieoff with time. Bacterial
concentrations in digested primary sludge and undigested waste activated
sludge are presented in Table 2. The large differences between raw
waste-activated sludges A and B, which were taken 11 days apart, are
not unexpected and probably represent day-to-day fluctuations. Consis-
tent differences between aerobic and anaerobic destruction of pathogens
have not been reported [ 7] .
Included in Table 3 are selected reports of sludge compositions avail-
able in the literature relative to landspreading of liquid sewage sludge.
Elements considered as plant macronutrients (N, P, K, Ca, Mg, and S) are
presented as percent solids (dry weight basis). The major micronutrients
(B, Mo, Fe, Mn, Cu, and Zn) and other elements of potential concern (Cd,
Hg, Ni, Pb, Cr, etc.) to sludge landspreading are presented as parts per
million. The major fertilizer constituents of sludge (N, P, and K) are
usually reported as total nitrogen, P205, and lOjO, and usually range in
value from 2.0-6.0, 2.0-8.0, and 0.2-0.8 percent of dry solids, respec-
tively. Little information relative to the lesser macronutrient (Ca,
Mg, and S) concentrations are presented in the published literature.
As discussed earlier, the heavy metals associated with sewage sludges
arise from various sources. Industrial discharges are probably respon-
sible for the higher concentrations of reported heavy metals, particular-
ly the values reported for Cd, Ni, Pb, and Cr. Even with strict indus-
trial discharge controls, the reduction of heavy metals--specifically,
elements considered as micronutrients, would not be expected to decrease
concentrations much below reported mean values [7]. In addition to ele-
ments which are contained in foods, high concentrations of micronutrients
such as Zn, Cu, and Fe may be considered on a municipal level as non-
point source pollutants.
TREATMENT PLANT CONTROL OF PATHOGENS
Of major concern from a human health standpoint when considering land-
spreading of sludges is the viability of pathogens. Dean and Smith [7]
summarize pertinent research in the area of treatment plant pathogen
control. Major portions of this discussion are included here.
As an alternative to digestion, sludge may be stabilized by adding lime
to a pH near 12 [25]. About one quarter ton of lime is required per ton
of sludge solids. Lime treatment provides a high level of bacterial dis-
infection (Table 4). Viruses are also destroyed by high pH although
tuberculosis bacteria and some parasitic eggs may be more resistant.
High pH inhibits bacterial growth but does not decompose organic matter.
Since most soils and crops are benefited by lime treatment, there should
be many agricultural uses for lime stabilized sludges. A limed sludge
may putrefy in a lagoon as bacterial action at the edges produces C02
and the pH drops. If a limed sludge is dispersed in a well-aerated soil,
13
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Table 2. BACTERIA IN SEWAGE SLUDGE [7]
(per 100 ml)
Raw primary
Trickling filter
Raw WAS
Raw WAS
(thickened) - B
Raw WAS - C
Anaerobic digested
primary
Aerobic digested WAS
Anaerobic digested WAS
Iron primary
Lime primary
pH 9.0
Lime primary
pH 11.5
Fecal coli
(x 106)
11.4
11.5
2.8
20
2.0
0.39
0.66
0.32
32
32
0.014
Salmonella
460
93
74
9,300
2,300
29
150
7.3
460
1,500
<3.0
Pseudomonas
46,000
110,000
1,100
2,000
24,000
34
100,000
1,000
21,000
24,000
<3.0
aste activated sludge.
14
-------
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-------
Table 4. BACTERIOLOGICAL STUDIES OF SLUDGE PRODUCED IN PLANT-SCALE
TESTS OF LIME STABILIZATION TO pH 11.5 [7]
Sludge
Bacterial count (organisms/liter of sludge)
Salmonella Pseudomonas Total aerobic
species aeruginosa count x 10"
Alum-primary
Limed alum-primary
Ferric-primary
Limed ferric-primary
110
None detected
>24,000
None detected
1,300
None detected
610
None detected
41
5.0
190
0.29
17
-------
aerobic organisms will consume the organic matter and no putrescent
odors should be produced.
Pasteurization is being used in Germany and Switzerland for digested
sludge that is to be spread on pastures during the grazing season.
Generally, 25 to 30 minutes heating at 70 C is suggested for destruc-
tion of cysts, oocytes, pathogens, worm eggs,and viruses [26]. Di-
rect steam injection is used because organic fouling and inorganic
scaling on direct heat exchanger surfaces reduce the effective heat
transfer. Recovery of heat from pasteurized sludge by means of vapor
heat exchangers can be used, but it requires a substantial capital in-
vestment. Small plants cannot economically recover the heat of pasteur-
ization. The sludge should be cooled enough to avoid killing vegeta-
tion before it is applied to the land.
Direct steam injection, which raises the temperature above 75 C for 1
hour, is an effective way to destroy pathogens and reduce coliform in-
dicators below 1000 counts per 100 ml [27]. Warm sludge can be applied
to growing grasses if the temperature at the soil surface does not ex-
ceed 60 C. Because evaporative cooling of sprayed sludge can reduce
the temperature significantly, and heat may be lost in transit from
plant to spreading site, direct cooling may not be necessary in most
cases. Adverse effects are not expected if hot sludge is applied to
bare soil before crops are started.
The cost of sludge pasteurization was calculated by Treibel in 1967 for
German conditions [26]. The heat for pasteurization was derived from
the methane gas produced by the anaerobic digestion and heating costs
were not included. The cost of fuel to heat sludge from 15 to 75 C was
estimated at about $4.50 per metric ton (ton) of dry sludge [27]. Be-
cause of shortages and rising costs, the fuel cost to heat sludge from
15 to 75 C has risen to about $20 per ton of dry sludge [28]. On a
solids basis, a cost of between $11 to $22 per ton of dry solids is a.
fair preliminary estimate.
Heat treatment of sludge to improve dewaterability is carried out at
temperatures above 160 C for about half an hour. These conditions will
completely destroy all living organisms. If oxygen is present, some
organic matter may be oxidized. The process is then called wet oxida-
tion. All heat treatment processes increase the concentration of soluble
organic matter and ammonia in the supernatant liquor or "soup". This
soup, although sterile when it is produced, is a rich nutrient broth
that can putrefy if it is allowed to come into contact with bacteria
that are in the air or on container walls. The dewatered sludge is,
however, resistant to putrefaction [29].
Lagoon or other storage for many months is frequently depended upon to
reduce the numbers of pathogenic organisms, particularly those that
cannot multiply outside the human body [30, 31]. Storage may be necess-
ary in any case if sludge is disposed of only part of the year, and
additional storage lagoons can be built into the system to provide more
protection against transmission of disease.
18
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SECTION VI
SLUDGE HANDLING AND DISTRIBUTION SYSTEMS
The technical feasibility of landspreading depends on many factors
which can vary significantly from one operation to another. However,
the major consideration from the operator's standpoint relates to the
economics of the operation. In many cases, due to lack of concise
economic data, the decision to utilize landspreading is intuitive.
However, many operators do perceive the specific importance of (1) pro-
viding ample retention volume(s) to allow for operational irregularities
and (2) selecting the proper sludge conveyance mode(s) and application
method(s) which optimize the individual landspreading system.
RETENTION PROVISIONS
Many sewage treatment plants which utilize landspreading do not have
separate retention provisions for containing the sludge prior to
landspreading. For instance, many plants which employ anaerobic
digestion utilize portions of the digester volume for storage. Where
possible, a secondary unheated digester may provide the required
storage capacity. In anticipation of periods when sludge cannot be
applied to the land, digester withdrawals proceed at an accelerated
rate to ensure the availability of retention volume until the land-
spreading operation can be resumed. The fact that digesters often
serve as retention vessels can lead to potential problems at the land-
spreading site if the sludge withdrawn for landspreading is insuffi-
ciently stabilized and contains high counts of pathogenic microorgan-
isms.
Some sewage treatment plants operate sludge lagoons for either routine
sludge dewatering or as holding reservoirs when landspreading practices
are temporarily interrupted due to adverse weather conditions and/or
unanticipated equipment failure. By contrast, 9-meter-deep inter-
mediate "retention reservoirs" have been expressly designed into the
landspreading operation conducted by Chicago's METRO at their Fulton
County strip mine reclamation site. Other plant appurtenances such
as the sludge wells associated with decommissioned or seasonally
19
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operated vacuum filter dewatering equipment are often utilized to
provide retention volume. In a rare case, even a cell of a secondary
aerated system may be utilized for the retention of liquid sludges
prior to transporting the sludge to the landspreading site.
Extended use of vented sludge wells as holding reservoirs allows time
for additional stabilization. However, open retention vessels may
create odors if the sludges have not been sufficiently stabilized.
Some plant operators have had difficulty in resuspending sludges which
have been retained in lagoons, wells, and secondary unheated digesters
due to long-term gravity separation of the solid and liquid phases of
the sludge.
CONVEYANCE MODE AND APPLICATION METHODS
Tank trucks are most commonly used to convey sewage sludges from small
treatment plants. The major attribute of this sludge haulage mode is
its flexibility. Pipelines are also utilized to transport sludges
over both very short and long distances. Basic to the decision of
committing the required capital expenditure for a sludge pipeline is
the "useful life" of the disposal site and the assurance of land
availability in close proximity to the disposal site. These require-
ments necessitate ownership of sufficient land and public acceptance
of the landspreading operation. Rail tank cars and barges are also
being employed to convey sewage sludges. The city of Chicago has
utilized rail tank cars and is presently conducting the largest and
most extensively engineered sludge landspreading operation to date
involving the use of both barge and pipeline transportation modes.
Application methods such as sub-sod injection (first applications up
to 360 dry tons per hectare per year) and spray irrigation are being
used by Chicago METRO at their Fulton County stripmine reclamation
site. However, most smaller sewage treatment plants that utilize
landspreading discharge sludge directly to the land from tank trucks.
Tank truck associated ridge and furrow and spray irrigation application
procedures are also conducted, particularly when the site is under
cultivation. Irrespective of application method and land use, liquid
sludges are often incorporated into the soil by plowing and discing.
Tank Trucks
The tank trucks utilized for transporting liquid sewage sludges range
in carrying capacity from about 2.3 to 28.4 m . The smaller capacity
trucks (2.3-13.2 m ) are usually straight tank trucks, while the
larger are tractor-trailer rigs. The trucks, either gasoline or
20
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diesel fueled, seldom average more than 1.3 or 1.7 kilometers to the
liter. A straight tank truck designed for hauling and spreading
sludge can be purchased either as a single unit built to specifications,
or the chassis, only,may be purchased for later tank installation.
Vehicles of this type can have a "useful life" exceeding 10 years.
A wide range of tank truck configurations is possible. Some communi-
ties have converted water tanks and installed them on a truck chassis
or even have carried them in a conventional dump truck, thus allowing dual
use of the truck. A few communities have converted gasoline trucks,
and one has even baffled and enclosed the box of a large dump truck
in order to transport liquid sewage sludge. Most of the tank trucks
utilize gravity filling and emptying methods. Some trucks, however,
are equipped with gasoline motor driven pumps for loading and spread-
ing. The pumps can often supply the head of pressure required for
short range spray irrigation. Keeping these sludge pumps primed can
be a problem and constitute an additional energy requirement. As a
general rule, tank trucks also include in-cab sludge release controls.
Tank trucks used for sludge disposal are usually equipped with devices
to increase the area of discharge. The discharge system often con-
sists of a central supplied manifold (>10 cm I.D. input orifice) which
is split into two lateral manifolds with about six to ten output
orifices (>5 cm I.D.). The width of sludge spread in this design is
usually 2.5 to 3 meters). The amount applied depends primarily on
the truck speed, tank volume, and differential discharge control (if
any). With this design, it is possible for the tank truck operator
to produce a uniform spread over the truck run. Other sludge spreader
designs include single open-close orifices and single orifices equip-
ped with splash pans. However, in these cases, the sludge pattern is
considerably less than the width of the truck, and the resulting
pattern impedes uniform incorporation into the soi!0
Tank truck haul schedules are controlled primarily by the crops and
by soil moisture. Once a crop such as corn has germinated, land-
spreading from a tank truck can only reasonably be continued as a
gravity ridge and furrow or a spray irrigation procedure. Application
in grassed fields (pasture and grazing land) does not appear to be
constrained. With exception of some well-packed sandy soils, as soil
moisture increases so do the chances that the tank truck may become
"bogged down". This is a problem in clay soils. Therefore, in order
to extend the time that trucks can operate, high flotation tires are
often used. This practice also somewhat alleviates soil compaction
problems due to heavy wheel loadings. Many landspreading operations
in the North also take full advantage of frozen ground conditions and
continue landspreading of liquid sludge through the winter months.
21
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Pipeline
In some cases sludges are transported via pipeline from separate
sewage treatment plants for processing at a common collection point.
Chicago METRO utilizes a pipeline to transport sludges withdrawn
from barges 11 miles to intermediate land reclamation holding
reservoirs. The present use of sludge pipelines by small sewage
treatment plants is usually restricted to distances less than 2 kilome-
ters and in most cases is directly associated with field application
methods such as ridge and furrow, spray irrigation, flooding, etc.
Due to increasing problems of municipal solid waste disposal (includ-
ing all sludges) and since costs associated with pipeline transport
are quite sensitive to economy of scale, research attention will
continue to focus on aspects which relate to regional waste trans-
port systems [32],
Design and operation of sludge pipelines can be difficult. In some
cases pipelines which experience prolonged freeze periods are both
insulated and heated. Sludges can be reasonably transported up to
a solids content of 10 percent; however, Raynes [33] suggests that
the optimum solids content is nearer 5 percent assuming turbulent
flow. When sludge pumping is intermittent, damage due to gas pro-
duction and blockage due to separation of solids can be avoided by
purging the system.
Sparr [34] conducted a significant review of the technical literature
relative to design and operation of sludge pipelines and concludes
that (1) the head loss caused by the friction of a pipeline conveying
sludge varies directly with the viscosity of the sludge flowing within
it; (2) increasing the velocity of sludge flow within the pipe in
laminar flow decreases the apparent viscosity; (3) increasing the
velocity of sludge flow within the pipe in turbulent flow further
decreases the apparent viscosity of sludge until the true viscosity of
sludge is approached as a limit; (4) reducing the size of coarse
sludge particles reduces the viscosity of the sludge; (5) effective
grit removal is necessary for economical pumping of sludge in a
pipeline; (6) the low velocities experienced in the laminar flow
zone when raw primary sludge is pumped often result in deposition of
grease on the inner periphery of the pipe wall; (7) pumping anaerobi-
cally digested sludge results in lower head loss as a result of
friction than pumping raw primary sludge of the same solids content
(dry basis) and flow condition; (8) flow velocities in the turbulent
flow region tend to prevent deposition of grease within the pipe;
(9) maintaining the operating velocity in the lower portion of the
turbulent flow zone results in maximum economy for pumping sludge
through a long pipeline; (10) little or no grease deposition within
the pipeline has been observed over periods of many years when low-
22
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solids-content activated sludge is pumped; (11) pipeline materials
and linings influence pipeline head losses as a result of differing
friction factors; (12) some pipeline materials and linings such as
glass lining, cement lining, and fiber-glass-reinforced epoxy pipe
resist the adherence of greases more readily than other materials
such as cast iron and steel.
SELECTION OF CONVEYANCE MODE
In determining which transportation mode (pipeline or tank truck) will
be selected to convey sludges from the plant to the site, sludge
characteristics, elevation differences, distance, and sludge volumes
must be considered. The sludge solids concentration is a prime fac-
tor. Given a sludge concentration, there is an optimum associated
pumping velocity. Other characteristics such as high specific gravity,
low temperature, presence of large solid tramp material, and scaling
tendency can adversely influence disposal by pipeline more than truck-
ing. Large differences in elevation between the sewage plant and the
disposal site increase both capital and operating costs for pipelines
and trucking, but pipeline costs would probably be influenced to a
greater extent [35] .
Long distances between the disposal site and treatment plant tend to
favor pipelines. Conversely, shorter distance hauls favor the use
of tank trucks rather than pipelines. Chicago METRO is considering
transporting sludge (275 kilometers) to marginal farmland by pipe-
line. Riddel and Cormack [36] conclude that trucks provide the most
economical means of sludge transport (digested sludge, 3.5 percent
solids) for distances less than 240 kilometers from populations
smaller than 10,000. Rail transport may become competitive for
greater distances. For 40-kilometer hauls, pipelines are economical
for areas with populations greater than 60,000.
Small sludge volumes tend to favor trucking as the mode of transporta-
tion. Cities with populations greater than 1.5 million can pump
sludges continuously [35]. A study by Bechtel Corporation [37] con-
cludes that pipelines are the most economical form of transport for
regional systems involving more than five tons per day of digested
sludge (dry basis). Smaller volumes can also be transported by pipe-
line more economically than by truck; however, the inabilility of the
sewage treatment plant to continue a site-specific landspreading
operation over a long period of time may rule out the pipeline trans-
port alternative.
23
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SECTION VII
ECONOMICS OF LANDSPREADING
The processing and ultimate disposal of sludge at a treatment plant
represents a significant amount of the total expenditures for sewage
treatment. As more investigators consider the alternatives available
for the ultimate disposal of wastewater treatment sludges, land-
spreading in the liquid state emerges as an apparently economical
means of final disposal. While landspreading in the dewatered and
dried state has been a somewhat common practice in the United States for
solids disposal and soil improvement, it requires expensive, time-
consuming and often troublesome dewatering operations. Landspreading
of the liquid sludges, however, eliminates these troublesome aspects,
and hence is receiving renewed attention as a means of economical
solids disposal rather than simply for land and soil improvement.
TREATMENT PLANT CONSIDERATIONS
Literally thousands of tons of sewage sludge are produced daily in the
towns and cities of the United States; and the amounts produced are
increasing along with the population. Also contributing to the growing
volumes of sludge is the application of secondary biological treatment
and chemical treatment methods. Conservative estimates now place the
generation of sewage sludge by U. S. municipal sewage treatment facil-
ities, alone, at about 8.2 million tons per year [38] . As these
volumes increase, so will the problems and cost of sludge disposal.
Therefore, the success and efficiency of a treatment plant, in large
part, may be measured in terms of its ability to provide for ultimate
lisposal of sludge.
The fact that 25-50 percent of sewage treatment plant capital and
>perating costs are attributable to sludge handling and disposal
ittests to the magnitude of this problem. The processing and disposal
)f sludge at a treatment plant thus represent a significant amount of
:he total expenditure for sewage treatment. Dean and Smith [1] report
.hat the cost of sludge treatment and disposal is a function of the
ons of water associated with each ton of solids and that the cost
f dewatering and drying liquid sludge can run as much as $55 per ton
f solids produced.
24
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Burd [39J has reviewed the significant economic data, and points out
that the costs are dependent on plant location and operation factors
which in turn are largely affected by climate, physical environment,
population, esthetics, system complexity and efficiency, and the
characteristics of the wastewater. Unfortunately, there is a scarcity
of complete operating records concerning the costs of land disposal
systems currently in use relative to the size of the plant. Surd's
general review of available economic data, however, yielded average
costs for ultimate sludge disposal. These are presented in Table 5.
Table 5. AVERAGE COSTS FOR ULTIMATE SLUDGE DISPOSAL (1966) |?]
(presented in English units)
Capital and operating costs,
$/dry short ton
System Average Range
A. Composting , ^ Not accurately known
B. Heat drying^ 50 40-55
C. Incineration
(1) Wet combustion 42
(2) Multiple hearth and 30 10-50
fluidized bed
D. Landfilling dewatered sludge 25 10-50
E. Disposal as a soil-conditioner 25 10-50
w/o heat drying (dewatered)
F. Disposal on land as ..a. liquid 15 8-50
soil conditioner
G. Lagooning 12 6-25
H. Barging to sea 12 5-25
I. Underground disposal Unknown, potentially inexpensive
J. Pipline to sea 11
(a)
Gross cost does not account for money received from sale of sludge.
These data indicate that the cost for land disposal of nondewatered
sludges is not much greater than lagooning or ocean disposal.
Ewing and Dick [l6| have also reviewed the costs of land disposal
systems. They state that for a particular plant the costs are a
function of sludge characteristics, type of disposal system, population
served, land costs, and distance to the disposal area. They further
indicate that few actual operating records are available relative to
the cost of land disposal. However, they do report some data on the
effect of population on sludge disposal costs and some estimated
25
-------
costs of land disposal compared with the costs of other alternative
means for disposal. These data are presented in Tables 6 and 7,
respectively. From these data it can be seen that landspreading of
liquid sludge does offer an economical means for sludge disposal.
Attempts to collect operating cost data by visiting active landspread-
ing operations were made as part of this research program. For the
most part, these attempts confirm the lack of readily available, com-
plete, and reliable cost accounting regarding the landspreading opera-
tions. At best, these data (presented in a later section of this
report) reflect a wide variation of operating costs, ranging from a
low of $2.57 per dry ton to a high of $149 per dry ton.
Table 6. EFFECT OF POPULATION ON UNIT COST
OF SLUDGE DISPOSAL (1970)
(presented in English units)
Population,
millions
0.125
0.25
0.5
1
2
4
Cost of incineration,
$/dry short ton
67
57
49
42
35
30
Cost of land disposal,
$/dry short ton
30
17
11
8
5
4
AGRICULTURAL CONSIDERATIONS
The literature is replete with examples of the benefits to be derived
•from landspreading of liquid sludges. Most significant among these
benefits are those that relate to the growth-promoting ingredients
contained in the digested sludge, specifically, nitrogen, phosphorus,
potassium, and certain trace elements. Essentially, the solids por-
tion of the sludge (approximately 3-6 percent) contains most of the
nitrogen and phosphorous, while the liquid portion (approximately
94-97 percent) contains most of the potassium. Therefore, to retain
the complete fertilizer content and thus realize the greatest benefit
from sludge, it must be applied in the liquid form. Also, when
applied in the liquid form, the sludge provides a source of supple-
mental irrigation water.
In addition to providing certain fertilizer requirements as mentioned
above, digested sludge can offer a number of other plant-and-crop-
growth-promoting features, such as
26
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Table 7. COMPARATIVE COSTS OF
SLUDGE DISPOSAL (1970)
(presented in English units) [l6]
Estimated cost,
Method $/dry short ton
Incineration 50
Wet-air oxidation 42-50
Multiple-hearth 30-57
Fluidized-bed 30
Drying: fertilizer sale 45
Lagooning
Pumping 7-49
Trucking 5% sludge 18
Trucking 10% sludge 12
Disposal at sea
Pumping 11
Barging 5% sludge 12
Barging 10% sludge 9
Land application
Landfill 25
Heat-dried sludge 50
Dewatered sludge 25
Liquid sludge 15
Strip-mine reclamation 16
27
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• Increased humus content of the soil
• Increased soil fertility
• Increased water holding capacity of the soil
• Improved soil structure.
The majority of the information available on the fertilizer and soil
conditioning value of liquid sludge is qualitative in nature and
states essentially that additions of liquid sludge result in increased
plant growth. Little quantitative data can be found. Furthermore,
what data are available are not easily compared due to the incomplete
nature of the data and due to differences in the sludge characteristics,
soil conditions, experimental design parameters, and local environ-
mental conditions.
It is generally agreed that liquid sludge is an economical fertilizer
and soil conditioner for the farmer, especially when a municipality
furnishes the sludge free of charge and then also pays the cost of
transporting and applying the sludge to the farmer's field. However,
it is believed that farmers would not be willing to purchase and/or
apply the large quantities of sludge required to obtain a crop response
comparable to that produced by a much lesser quantity of commercial
inorganic fertilizer. For example, studies conducted by Larson, et al
[22] are indicative of the amounts of sludge required to produce crop
yields equivalent to those produced by commercial fertilizers. On
sandy Minnesota soils, a 168 ton per hectare application of sewage
sludge was required to produce a corn yield about equal to that ob-
tained with 1.12 ton per hectare of a 20-10-10 fertilizer. When com-
paring the growth of barley on replicate plots fertilized with liquid
sludge and commercial ammonium phosphate (16-20), Merz [15] found that
best growth was obtained with ammonium phosphate applied at a rate of
448 kilograms per hectare. Although sludge loading rates of 56 to 112
tons per hectare resulted in improved plant growth, a loading rate of
224 tons per hectare was required to produce a growth equal to that
obtained with the ammonium phosphate.
In a recent article, Sabey, et al [40], stated that—disregarding the
soil conditioning properties of liquid sludge-~land application of
sewage sludge for its fertilizer value is not economical when compared
with commercial inorganic fertilizers. Evans [41] suggests that liquid
sludge cannot compete with commerical fertilizers, since (a) not enough
sludge is produced to meet all fertilizer needs and (b) commercial
fertilizers are relatively cheap and sludge can become expensive if
long transportation distances are involved.
While liquid sludge contains the major and minor nutrients required
for plant growth, it is not necessarily a balanced fertilizer for
many crops and soils. The sludge composition will vary depending on
the wastewater composition and the sewage treatment and sludge
28
-------
stabilization processes. Normally, the sludge is low in potassium,
medium in available nitrogen, and high in phosphorus. Nevertheless,
under the conditions mentioned above (i.e., delivered and applied
on fields at no cost to the farmer), liquid sludge can be an economical
and satisfactory fertilizer supplement and soil conditioner. Through
the addition of organic matter, sludge amended soils have been shown
to improve markedly with regard to fertility, water holding capability,
humus content, and tilth. Thus, the soil conditioning properties of
sludge are perhaps more important than its fertilizer content. This
attribute of sludge makes it an effective agent for use in soil main-
tenance programs or in the reclamation of marginal lands which have
been depleted of organic matters through misuse. Here again, however,
little comparable data are available to adequately quantify the value
of sludge.
29
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SECTION VIII
SLUDGE-SOIL-PLANT INTERACTIONS
One of the major factors in land spreading of liquid sludge is the
land itself, especially the upper horizons of the soil in which plants
grow. A well engineered landspreading operation must recognize the
limitations of the soil and then design for the maximum utilization
of the assimilative capacity of a soil such as its filtration, biologi-
cal degradation and absorption properties. The ultimate benefit de-
rived from the purifying and assimilating capacity of soil is the
establishment of favorable plant cover. This inevitably depends on
the three closely related factors—the triad of liquid sludge properties,
land and soil properties, and plant nutrient requirements.
The sludge properties have been covered already in an earlier section
of this report. This section will discuss the general physical,
mineralogical, and chemical characteristics of the soil, physiographic
considerations, physical characteristics of liquid sludge-soil inter-
action, and chemical characteristics of liquid sludge-soil-plant
interactions.
PHYSICAL CHARACTERISTICS
Physical characteristics such as grain size, bulk density, and porosity-
together with past performance experience—are helpful in predicting
soil permeability. The sizes of soil particles, which range from fine
gravel to clay, determine its texture. The texture of the soil influ-
ences the flow and retention of soil water, the circulation of air,
and the rate of chemical reactions within the soil. The structure of
the soil is determined by the grouping or arrangement of the soil
grains or formation of soil granules, blocks, or plates in loamy or
finer textured soils, as opposed to coarse-textured soils where each
soil particle seems to function separately. Favorable structure in
fine textured soils is essential to the satisfactory movement of water
and air and plant root penetration. It also provides for adequate
food supply.
30
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Bulk density is influenced by structure, texture, and compactness,
It is directly related to the porosity of the soil, for the reduction
of the space between soil particles reduces the volumes of pore spaces
and hence, the capacity of the soil to allow free movement of air,
water, and plant roots.
The rate at which water percolates into the soil (or rate of infiltra-
tion) is influenced by soil properties and hydraulic slope. Water
standing on gravelly or coarse sandy soils percolates into the soil
rapidly. On fine-textured clay soils, water may collect and stand on
soils with little infiltration. Furthermore, infiltration rate is
usually higher at the beginning of a rain or irrigation than it is
several hours later [42].
Permeability is the measure of flow in any direction and is influenced
by the moisture content of the soil, the physical properties of the soil
such as size and shape of pore spaces, and the specific weight and
viscosity of the soil water.
MINERALOGICAL CHARACTERISTICS
Quartz commonly dominates sand and silt fractions of the soil. Also
found in these fractions are feldspars, micas, gibbsite, hematite, etc.
The clay fraction also contains some of these minerals, but the more
important group is that of the layer silicates. A typical example is mont-
morillonite. It possesses a high cation exchange capacity which is caused
by (a) isomorphous substitution and (b) ionization of hydroxyl groups
attached to silicon of broken tetrahedron planes. The negative charges
created in the former are distributed more uniformly on interlayer
surfaces, whereas the latter are at corners and on edges. Water and
polar organic molecules, such as glycols, polyglycols, polyglycol e..hers,
and some proteins can be sorbed in the interspaces of the layer silicates
to cause swelling [43J.
Also important in the mineral characterization of clay fraction or whole
soil are the hydrated complexes of iron, aluminum, and manganese. The
cation exchange capacity of the clay soil is decreased by the formation
of these positive charge nonreplaceable hydroxy cation interlayers.
CHEMICAL CHARACTERISTICS
Sand and silt, which are dominantly quartz, are generally quite inactive
chemically. The most active part of soil is the colloidal fraction,
namely clay and humus. These two fractions are the common sites of soil
chemistry (ion exchange and physical adsorption) and soil microbiology.
31
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Soil microbiology is important in humus formation. As organic tissue
is incorporated into a moist warm soil, it is immediately attacked by
a host of different soil organisms. The easily decomposed compounds
quickly succumb, yielding simple soluble products, while the resistant
materials are only modified from the original plant and animal tissues.
Also present in the amorphous, colloidal humus fraction are compounds
synthesized within microbial tissues which remain as the organisms die.
The colloidal fractions of humus are made up of carbon, hydrogen,
oxygen, nitrogen, sulfur, and phosphorus rather than silicon, oxygen,
aluminum, and iron, as in case of clay. The negative charges arise
from exposed -COOH and -OH groups from which the hydrogen may be
replaced by cation exchange. The cation exchange capacity of humus
far exceeds that of clay,.
PHYSIOGRAPHIC CONSIDERATIONS
The physiographic characteristics of the land are extremely important
considerations in landspreading, as they can either aggravate or ameli-
orate the potential for ground and/or surface water contamination.
While the potential for groundwater contamination exists, it does not
appear to be a serious hazard if sludges are applied properly. Con-
cern for contamination of surface waters via runoff from sludge amended
soils, however, is valid. Several factors must be considered in an
assessment of potential contamination of surface waters via localized
runoff from the sludge spreading site. The most significant of these
factors are the slope of the land, the soil permeability, the distance
to the water course, and vegetative cover.
Generally speaking, the land should be level enough to minimize surface
water runoff. Troemper [44] noted that when applying sludge to an
area of land by flooding, sludges with a reasonably high solids con-
centration (5 to 6 percent) would run readily down a gentle slope.
The Interdepartmental Committee on Sludge Disposal, Toronto, Ontario,
Canada [45], has suggested interim guidelines for the disposal of
sewage sludge on northern and southern Ontario agricultural lands.
These interim guidelines relate the maximum sustained slope to the
minimum distance to the water course and are shown in Table 8..
32
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Table 8. MAXIMUM SUSTAINED SLOPE VS. MINIMUM DISTANCE
TO WATERCOURSES [45]
(presented in English units)
Maximum Minimum distance to watercourse
sustained For sludge application dur- For sludge application
slope ing May to Nov., inclusive during Dec, to Apr., inclusive
0 to 37o 200 ft. 600 ft.
3 to 6% 400 ft. 600 ft.
6 to 9% 600 ft. No sludge to be applied
Greater No sludge to be applied No sludge to be applied
than 97o unless special conditions
exist
Some optimum characteristics and management procedures for land to be
used for the disposal of sewage sludge were suggested by Bell [35].
These characteristics are for land which would receive heavy sludge
applications (i.e., approaching the limits of vegetative cover to
remove the nutrients contained in the sludge) under Ontario, Canada,
climatic conditions. Bell suggests that, if the slope of the land is
greater than 3 percent, the soil should be reasonably permeable to
enhance absorption of surface water and thereby inhibit runoff. A
permeability coefficient of at least 10" cm/sec was suggested and it
was indicated that soils possessing coefficients of a least 10 cm/
sec would exhibit good drainage quality. Flach [46] indicates that
the degree of soil limitations.are slight when the soil permeability
is within a range of 4.2 x 10 to 4«2 x 10 cm/sec. Soil limita-
tions are considered severe when permeabilities are less than 1.4 x
10 cm/sec or greater than 1.4 x 10 cm/sec.
To reduce the potential of contaminating surface waters with runoff
or with percolating groundwater, the sludge disposal site should be
sufficiently remote from surface water courses. However, to recommend
a single minimum distance from a water course which would be valid
for all sludge spreading sites would not be practical<> The required
distance is based upon the peculiarities of individual sites.
The selection of vegetative cover can also influence the potential
for contamination of surface waters, as certain plants are superior to
others from the viewpoint of stabilizing the soils and controlling
erosion and surface water runoff. For example, most grasses would be
superior to crops such as soybeans or corn in the control of runoff.
However, this aspect would have to be weighed against the plant
characteristics relative to nutrient uptake and amenability to
fertilization with liquid sludge. Those harvested plants which are
capable of efficiently removing the nutrients contained in sludge
would be valuable in reducing the possibility of nutrients accumulating
33
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to the extent that they could pollute surface and groundwater or cause
soil toxicity problems.
PHYSICAL CHARACTERISTICS OF LIQUID
SEWAGE SLUDGE-SOIL INTERACTION
When liquid sludge is spread on the land, two soil improvement prac-
tices are simultaneously.being accomplished, irrigation and fertili-
zation. The dual benefits are possible because the liquid sludge is
made up of both liquid and solid phases with each phase containing
plant nutrients. The quality of the sludge can have direct effect
on the physical properties of the soils upon which it is deposited.
Soil structure and texture, depth of liquid sludge on soil surface,
temperature of liquid sludge and soil, and moisture content of soil
may influence the intake of the water phase of the sludge. Usually»
lower infiltration rates are experienced with fine-textured soil
than with coarse-textured soil. When enough sludge is applied, seal-
ing of the^soil surface with sludge solids takes place regardless of
the soil texture. The infiltration capacity of the soil is restored
by drying of the sludge.
Because of the low plasticity and cohesion of the sludge humus,
liquid sludge may alleviate the unfavorable structural characteristics
caused by a high proportion of clay. It imparts to sandy soils some
chemical reaction sites for nutrient exchanges and promotes soil
aggregation. For example, digested sludge applied on a sandy soil and
Cheshire loam soil at the rate of about 67 tons per hectare increased
field moisture capacity, noncapillary porosity, and cation exchange
capacity from 3 to 23 percent, organic matter content from 35 to 40
percent, total nitrogen up to 70 percent, and soil aggregation from
25 to 600 percent [12]. It was observed that greater benefits occur
in sandy soil than in loams.
Another physical characteristic of liquid sludge-soil interaction is
the rate of dewatering of the sludge. This is influenced by both the
soil properties and climate or weather conditions, such as the intake
rate and infiltration rate of the soil and the rate of sludge drying
caused by convective and radiative heat transfer [47,48]. The weather
factors controlling the evaporation rate of free water from soil sur-
faces are the amount of rainfall, the humidity, air velocity, and tem-
perature. It has been reported that by varying temperatures, humidity
differences, and flow rates of air over a broad range of values when
sludge temperatures were low and the air humidity was high, the rate
at which digested sludge dried by convective heat transfer was only
about one-half the rate of evaporation from a free water surface.
However, when sludge temperatures were high and air humidity was low,
the rate of convective drying of digested sludge approached the rate
of evaporation from a free water surface.
34
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An investigation of the factors determining the dewatering rate of
digested sludge on soils showed that, when sludge is first applied on
soils, dewatering of the sludge is fairly constant and the rate
depends on filtration of water into soils and water lost evapora-
tion. When the water content of sludge has been reduced to about 80
percent by weight, further drying of the sludge is by evaporation
alone. [30]
The rate of infiltration of sludge liquid depends on the initial soil
moisture content and solids content of the sludge. The higher the
soil moisture and sludge solids contents, the lower is the rate of
infiltration.
Thomas and Law [49] have reviewed the use of the soil as a waste-
water treatment method and report that many wastewater treatment
systems have been plagued with the problem of physical clogging of
the soil and subsequent loss in infiltration rate. Under heavy sludge
application rates, similar clogging problems might be encountered.
Generally, Thomas and Law suggest that soil clogging is related to
the frequency and rates of application and that clogging has not been
noticed with frequencies which permit the soil to dry between applica-
tions.
McGauhey and Krone [50] have also looked at the problem of soil clogging
in somewhat greater detail. Their conclusions, which appear to relate
to landspreading of liquid sewage sludge, were that the principal mech-
anism of soil clogging is due to physical phenomena, but that biologi-
cal and chemical factors may also play a role in soil clogging. The
primary physical factors involved were reported to be compaction from
loads imposed on the soil surface from landspreading equipment, or
from "smearing" of the soil surface by treatment of the site following
landspreading, i.e., plowing and discing associated with agricultural
activities at the site. They also suggest that the interparticle
spacing of larger, lower grains of the soil may become blocked by migra-
tion of fine grains of soil from the upper zone.
The biological aspects of soil clogging were indicated to be related to
anaerobic conditions which would develop under conditions of frequent,
heavy applications of wastewater. Causes cited here were that (a) organic
slimes were created by anaerobic bacteria which could clog the soil, (b)
fine particles of precipitated ferrous sulfide resulting from anaero-
bic degradation of sulfides could create a layer on the surface which
inhibits infiltration, and (c) anaerobic conditions could permit the
accumulation of lignins, waxes, tannins, cutins, and fats which are
resistant to degradation by anaerobic bacteria.
As mentioned earlier, soil clogging problems relative to the land-
spreading of liquid sewage sludge should not be an extremely great
problem except under conditions of prolonged, frequent, heavy appli-
cations of liquid sludge. Generally speaking, these conditions would
tend to be the exception rather than the rule as most landspreading
activities are conducted by plants in the 3.8-19 x 103 m3/day (1-5
mgd) size cla-ss. Normally, these plants appear to have sufficient
35
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amount of land area available to enable the sludge applications to be
rotated from site to site, thereby providing adequate time for the
various sites to recover and maintain the aerobic conditions necessary
to prevent soil clogging.
CHEMICAL CHARACTERISTICS OF LIQUID
SLUDGE-SOIL-PLANT INTERACTIONS
About 90 to 99 percent of the sludge is water, and the remaining solids
normally range in organic content from 50 to 70 percent. The addition
of water to cropland as supplemental irrigation in dryer climates or
during prolonged precipitation free periods in other regions is cer-
tainly conducive to plant growth. Assuming that 90 to 99 percent of the
sludge is water, the disposal of 56 dry tons/ha/year of sludge would
amount to a yearly supplemental water input of 5 to 50 cm. The soil
permeability, moisture content, and regional evapotranspiration
are the major hydraulic factors to be considered. When the soil
becomes saturated, runoff occurs which can transport contained sludge
constituents to surface waters. The supplemental water associated
with landspreading of sludge, like precipitation, also recharges the
soil mantle, and thus can transport soluble constituents to the ground-
water.
The application of sludge to the soil increases the organic content of
the soil or the soil humus. Humus is in a dynamic state, being decom-
posed continuously by microorganisms. It contains almost all major
and minor plant nutrients, and its colloids have the property of ad-
sorbing the soluble nutrients, thus preserving them from loss through
leaching,and making them available to plants. For example:
KAlSi000 + H humus HAlSi»00 + K humus
JO- JO
microcline acid silicate adsorbed K
Hence, the potassium is changed from a molecular to an adsorbed form,
making it readily available to higher plants. It has been reported that
the base exchange capacity of soils is directly related to the organic
matter content [51].
Sewage sludge also contains considerable quantities of bases (calcium,
magnesium, and sodium). Calcium and magnesium are also important
trace plant nutrients. High applications of most sludges will tend to
buffer the pH of soils. This is particularly of value to very acid
soils such as acid mine spoil banks. Although of little plant food
value, sodium is of importance since it assists in chemical changes
which take place in the soil. In soils rich in clay and humus, the
sodium cation liberates certain plant nutrients, including calcium,
magnesium, potassium, and phosphorus. In light soil, sodium tends to
hold moisture and aid capillary attraction. However, in municipal
sludge calcium exceeds sodium so that no deleterious effects are
expected from applying sludge to the land.
36
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Liquid sludge as applied to the land contains major fertilizing ele-
ments (nitrogen, phosphorus, and potassium). The dry weight percentage
of each, as earlier discussed, depends on the sewage and sludge treat-
ment plant operations. Nitrogen, phosphorus, and potassium content of
sludge can normally vary from 2 to 6 percent total N, 2 to 8 percent
P 0 , and 0«,2 to 0.8 percent K?0 on a dry weight basis.
Both mineral and organic nitrogen are contained in sludges. Part of the
organic nitrogen of raw sludges is converted by digestion to mineral
forms. The mineral nitrogen in digested sludge is mostly in the form
of ammonium ions with small amounts of nitrite and nitrate ions. Much
of the ammonium ion concentration can be lost through volatilization
if the sludge is not immediately incorporated into the soil [7,16,22,27,
35,57].
The processes that affect the form of nitrogen in soils (mineralization,
nitrification, denitrification, immobilization , fixation, adsorption,
volatilization, cation exchange, convection, dispersion, and plant up-
take) are extremely complex and may take place concurrently [12] „ The
fate of nitrogen in the sludge which is added to the soil is basically
dependent on the levels of oxygen in the soilo Organic nitrogenous
compounds are decomposed to ammonia by hydrolytic and oxidative mechan-
isms of numerous heterotrophic microorganisms. With normal soil con-
ditions, ammonia in turn is converted by aerobic autotrophic bacteria
into nitrites and nitrates. The nitrate form may be absorbed by plants
or lost in leaching while ammonia is adsorbed by clay or humus par-
ticles. If anaerobic conditions are created in soil in the presence
of carbon, denitrifying bacteria, and the proper temperature, denitri-
fication of nitrates occurs with the usual evolution of nitrogen gas to
the atmosphere. Studies show that in the sludge-soil environment, the
rate of denitrification is independent of nitrate concentration, but
denitrification proceeds at a slower rate then in a sludge environment
alone [52].
The amount of nitrogen removed from the soil by plants is variable, with
losses consisting of the nitrogen contained in the harvested crop since
the rest returns to the soil as humus. The harvest of a good corn crop
can remove 168 to 280 kilograms of nitrogen per hectare from the system.
Some grasses can use more nitrogen. Annual application rates of sludge
range from as low as 6.7 to as high as 359 tons per hectare of sludge
solids. Twenty-two and one-half to thirty-three and one-half tons of
Chicago sludge per hectare per year are required to supply the nitrogen
needs of nonleguminous crops [53].
Many authors contend that the nitrogen is the first component that limits
sludge application rates. If nitrate-nitrogen is applied or formed in
amounts greater than can be removed by harvested plant uptake, denitri-
fication, and microbial use, the excess nitrates can potentially contami-
nate ground and/or surface waters by leaching or runoff. Furthermore,
excess nitrogen can also cause a high nitrate content in certain crops.
Nitrate poisoning can result from the consumption of green forage which
contains in excess of 0.3 percent nitrate (dry basis) [35],
37
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Phosphorus is present in the sewage sludge in both organic and inorganic
forms. The soluble phosphate is directly utilized by plant roots or
adsorbed by mineral clay and humus particles. Phosphate in excess of
crop needs is strongly held to the soil particles [45] and thus will
remain as a valuable soil resource. Although phosphate concentrations
in groundwater are virtually unknown, the soil capacity is not infinite.
Phosphate pollution of surface water may be caused by soil erosion.
Most of the potassium content of sludge is in solution. Part of the
potash is used by plants and the rest is absorbed by soil colloids or
lost through leaching. Excessive quantities of available potassium in
the soil tend to prolong the season of growth and thus delay the matur-
ing of the crop J52J . However, the large amounts of cations in sludges
can depress plant uptake of potassium. Because sludge contains rela-
tively little potassium, even heavy applications of sludge may not
provide sufficient potassium for optimum plant growth.
Sewage sludges contain an abundance of micronutrients, i.e., iron, man-
ganese, boron, copper, zinc, molybdenum, etc. Small applications of
sludge would normally be sufficient to correct any soil deficiencies.
However, large quantities of microelements applied to soils may inter-
act and induce deficiencies and/or toxicities. For example, high con-
centrations of zinc and copper have been reported as being responsible
for the exhaustion of sewage-irrigated soil. It is also observed that
high concentrations of one micronutrient could lead to deficiency of
another. For example, the high concentration of molybdenum in lime-
rich soils of the Paris sewage farm was considered partly responsible
for the lack of manganese [54]. Upon review of published information
related to the nature and effects of minor elements in sewage sludge
amended soils, Page [72] reports that (1) the surface horizons of these
soils are enriched in.trace elements, with the extent of enrichment
depending upon the composition of the sludge and the amount applied,
(2) with the exception of sandy or very acid soils, a high percentage
of trace elements (Ag, Ba, Cd, Co, Cr, Hg, Mn, Ni, Pb, Sn, and Zn)
associated with the sludge organics are retained in the tillage layer,
(3) plant yields and concentration of trace elements in the plant are
dependent basically upon soil pH and the plant species, and (4) under
certain conditions, the concentration of trace elements (Mo, Se, and Cd)
can possibly reach levels which are sufficient to cause toxicities to
livestock.
In addition to those heavy metals in sludge which are considered to
be essential micronutrients, others such as chromium, mercury, cadmium,
lead, and nickel may be beneficial to crop nutrition in certain con-
centrations, but there are limits to the concentrations that can be
tolerated in agricultural soils. The organic matter and fine inor-
ganic soil particles chelate or adsorb many metals such as zinc, copper,
38
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and nickel [?] . Some authors indicate that a principal factor in re-
tention of heavy metals is sorption of hydrous oxides of manganese and
iron. Generally, maintaining oxidizing soil conditions and the pH
neutral to slight alkalinity aids in immobilizing metals [53] «
Although little metal migration in the soil is expected under normal
conditions, the capacity of the soil to retain these elements must be
limited 16] . Groundwater contamination through leaching is a poten-
tial problem; however, erosion of metal-bearing soil particles in
surface water appears more probable 2]] . The use of agricultural lime
has been shown to immobilize most metals and reduce their availability
to plants.
The absolute quantity of the metals added to the soil by landspreading
of liquid sewage sludges may have little relation to the concentration
that is available to plants. Factors including pH, organic matter, and
other metals in the sludge and soil _influence the availability of
metals to plants. King and Morris '20| concluded that the application
of anaerobically digested sludges (higher than average in heavy metals)
had little effect on in-vivo digestibility of the Bermuda grass (Cyndon
dactylon/L. Pers) forage. Applications did increase concentrations of
N and Na in the plants but had little or no effect on yields. Rye
(Secale cereole Lc) yields were reduced when the sludge application
exceeded about 112 dry tons per hectare per year. Reduced yields were
probably due to high levels of Zn and Cu in the forage, rather than
deficiencies of N, P, K, Ca, or Mg or high levels of Mn, B, Mo, or Al
[13].
There appears to be a paucity of information relative to maximum toler-
able concentrations.of micronutrient and other trace elements in crops
and animals. Accumulation of heavy metals in the soil from repeated
sludge applications must also be considered. Conn [55] reports that
copper and zinc soil concentrations in excess of 100 and 300 ppm,
respectively, are toxic for plant growth. A report by Dean, et al [56]',
indicates that soil concentrations of nickel and zinc above 100 to 10
ppm, respectively, are toxic separately with respect to seed germination
of tomatoes. The paper also indicates that 1000 ppm copper has little
effect, while toxic effects can be pronounced below a composite concen-
tration of 100 ppm of Zn, Cu, and Ni. The data shown in Table 9 are
perhaps indicative of the increasing concentrations of heavy metals in
the leaf and grain portions of corn under various application rates [53].
Sludge- borne metals applied to soils are not as readily toxic to plants
as the same metals applied singly as a salt solution.
Discussions are often included in the literature relative to seed
germination inhibition resulting from landspreading of freshly digested
sludge. Hinesly and Sosewitz [18] concluded that corn and soybean
39
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Table 9. METALS CONTENT OF CORN
(ppm oven dry basis) [53]
(presented in English units)
Rate of sludge (a)
application
(inches per week)
0
1/4
1/2
1
Zinc
58.0
85.0
137.8
212.0
Copper
Leaf
8.9
9.0
10.2
8.7
Nickel
2.8
1.3
2.6
4.3
Cadmium
3.3
3.0
5.3
11.6
Grain
0
1/4
1/2
1
88.8
93.0
127.0
152.3
5.2
6.3
5.2
5.6
2.28
3.03
2.18
3.08
0.30
0.60
0.79
1.03
(a) 136 tons of sludge solids per acre applied in U years at the maximum rate.
germination was inhibited partly because of the ammonium or ammonia
content of fresh, anaerobically digested sludge. However, a paper by
Molina, et al [57], states that inhibition of seed germination is not
caused wholly by salt concentration nor the oxygen reduction potential
of the medium. Other hypotheses to account for the observed phenome-
non suggest that manganese or entrained digester gases such as H_S
may be the causative factor. The problem, however, is apparently
avoided if the liquid sludge is stored in the open for a few weeks or
landspreading practices are interrupted during seed germination. With
respect to corn and soybeans, no associated problems have been observed
during plant maturation.
40
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SECTION IX
PUBLIC HEALTH CONSIDERATIONS
The incidence of disease transmission, particularly Shistosomiasis,
associated with the "night soil" crop fertilization in China and the
epidemics of typhoid fever in other parts of the world attributed to
the consumption of raw vegetables irrigated with raw sewage have
caused a general aversion to the use of even treated human waste
products in the United States. The most recent incident of disease
transmission in the United States which could be attributed to the consump-
tion of foodstuffs grown on a sewage farm reportedly occurred in
1919. The consumption of blackberries or vegetables grown on the
farm were believed to have caused typhoid fever in eight employees [58] .
That most such outbreaks can be attributed to either the use of raw,
untreated sewage or unsanitary food preparation and handling practices
is generally not considered by the layman. Hence a "human waste stig-
ma" has developed and acts as a constraint to the widespread acceptance
and utilization of land disposal of treated wastewater sludges. The
following sections summarize the significant literature on landspread-
ing of liquid sludge relative to public health considerations along the
following lines: occurrence and movement of pathogens in the soil, sur-
vival of pathogens in the soil, and health hazards posed to humans and
animals.
MOVEMENT OF PATHOGENS IN THE SOIL
The potential for contamination of groundwater by pathogenic micro-
organisms is dependent on the ability of the pathogens to survive and
move through the soil system. A number of factors including the types
of soil involved, the number of microorganisms applied to the soil sur-
face, and the many different kinds of microorganisms contained in both
the soil system and the applied wastes all combine to complicate an
assessment of pathogen movement in soils. Furthermore, there is a defi-
nite paucity of information on this subject specific to microorganisms
introduced into the soil system through the application of liquid sludges.
The majority of the research work in this area to date has been in con-
junction with the disposal of wastewater effluents to the soil. Never-
theless, this work might well serve as an indicator of the behavior of
pathogenic organisms applied to the soil via liquid sludges, albeit som-
what conservative as the amounts of water applied would be considerably
greater in the disposal of wastewater effluents. In addition, land
treatment systems for wastewater effluents are normally confined to
41
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single site areas and involve much more frequent and heavier applica-
tions of water. Pathogens are more concentrated in sludge than they
are in wastewater, but sludge stabilization processes kill most of the
pathogens. So, the concentration of viable pathogens may be either
higher or lower in sludge.
Much has been written on the various aspects which govern the movement
of bacteria and viruses through the soil systems. McGauhey and Krone
[50] and Krone [58] have comprehensively and critically reviewed the
work of numerous investigators representing many scientific disciplines
in order to assemble and interpret pertinent data on the use of soil as
a wastewater treatment system. Generally, the conclusions of this re-
view indicate that the movement of microorganisms through granular soils
will not normally exceed more than 30.5 m laterally and that groundwater
contamination should not be a serious hazard in granular, unfissured
rock. For the most part, the information presented in this section
summarizes the significant findings of McGauhey and Krone as they re-
late to the movement of bacteria and viruses through the soil systems.
Concerning the movement of viral pathogens, little information was re-
ported in the literature until recently. However, the presence of
viruses in sewage has been amply documented. For instance, one study
isolated 150 viruses during the examination of 1,018 sewage samples. Of
those identified, 31 were identified as ECHO, 4 as Polio, and 76 as Cox-
sackie. Thus, the possibility of survival and movement of viruses in
the soil and percolating water is an important question.
«.
One of the most significant studies relative to the movement of viruses
in percolating waters and soil was contained in the report of the Santee
Project near San Diego, California. Here, sewage was examined for vi-
ruses at each phase of treatment, i. e., raw sewage, activated sludge
effluent, oxidation pond effluent, and effluent from six sand and gravel
percolation beds. Reoviruses, Adenoviruses, and several types of Polio,
ECHO, and Coxsackie viruses were identified at all times in the primary
and secondary effluents, sometimes in the oxidation pond effluent, but
never in the percolate from the soil system. Most recent data from the
Santee Project were also reviewed by McGauhey and Krone. The data re-
flect composite samples taken each day of a 10-day sampling period from
sampling wells located 122 meters downstream from the sand and gravel
percolation beds. The percolation beds were 457 meters (1,500 feet)
long and the flow rate in the gravel was about 61 meters in 2 days. The
samples were analyzed for coliform bacteria, fecal coliforms. and fecal
streptococci, and the results are presented in Table 10. The data indi-
cate an impressive removal of bacteria by a very coarse medium.
On the basis of their review, McGauhey and Krone concluded that "both
biological antagonisms and physical removal of cells characterize the
change in bacterial quality of water percolating through a soil system;
and that the soil system is a quite efficient device for removing bac-
teria".
42
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Table 10. SUMMARY OF BACTERIOLOGICAL ANALYSES [50]
(Coliform, Fecal Coliform, and Fecal Streptococci)
All results are MPN/100 ml.
Sampling Station
Oxidation
pond
200-ft
well
400-ft
well
Interceptor
trench
Coliform bacteria
No. of samples
Maximum
Minimum
Median
Fecal coliform
No. of samples
Maximum
Minimum
Median
Fecal streptococci
No. of samples
Maximum
Minimum
Median
29
11 M£
330,000
1.1 M
29
1.3 M
4,500
210,000
29
490,000
450
4,500
29
3,300
<180
780
29
35,000
78
2,800
28
22,000
20
560
29
200
<180
29
54,000
2
20
29
3,300
<180
30
9,200
2
48
28
110
29
230
1.8
6.8
M = million.
Only one high result.
SURVIVAL OF PATHOGENIC ORGANISMS IN THE SOIL
In general, the occurrence and numbers of human pathogens in domestic
sewage is a function of the general health of an area and of the shedding
rate of various pathogens by infected humans. The bactericidal effects
of sludge digestion are inhibitory, not necessarily lethal. Consequently,
while present-day normal sewage treatment processes reduce the numbers of
pathogenic organisms, they do not produce completely pathogen-free
sludges.
With the practice of land disposal of liquid sewage sludge becoming more
popular and widespread, the survival of pathogenic organisms in the soil,
water, and on crops grown in sludge amended soils assumes increasing
importance. This is especially true when one considers the many types of
land to which sludge is being applied. Cropland, pastureland, woodland
areas, highway median strips, and even public parks and golf courses are
recipients of sludge. Consequently, the possibility that pathogenic
43
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organisms contained in sludges could contribute to an uninterrupted
human and/or animal disease cycle bears investigation.
That sewage sludge should be applied to the land with caution has been
recognized for many years. For instance, in 1935 Tanner [59] stressed
the importance of the persistence of pathogens by stating that "an
important factor in epidemiology is the longevity of pathogenic bacteria
in nature, for upon such longevity rests the ability of various agents
such as foods to disseminate communicable diseases". While much appears
in the literature concerning the pathogenic aspects of land disposal of
sewage sludges, most of this information pertains to sludges which have
been dewatered and either air dried or heat dried. The heat used for
drying normally accomplishes the destruction of pathogenic microorgan-
isms, while the long periods required to air dry the sludges are suffi-
cient to also result in pathogen destruction. On the other hand, little
has been published regarding the survival or persistence of pathogens
introduced into the soil system via the application of liquid sewage
sludges.
Rudolphs, et al [60] conducted an extensive review of the literature
on the occurrence and survival of pathogens in soil, water, and on vari-
ous types of vegetation irrigated or fertilized with sewage and sewage
sludges. This review considered the most common intestinal pathogens
which could cause disease by ingestion of contaminated raw vegetables or
fruit--specifically the bacteria of three genera of the family Enterobac-
teriaceae: Salmonella, Eberthella, and Shigella.
Generally, the significant conclusions of this review were that fruits
and vegetables grown on sewage irrigated or sludge amended soils can be
contaminated with pathogenic microorganisms. Furthermore, the viability
of these pathogens ranged from a few hours to several months. Among the
factors which could influence the survival of pathogens in the soil and
on vegetation, the following are the most significant:
(a) Type of organism - Escherichia coli, Eberthella typhosa, and
Mycobacterium tuberculosis appear to be most resistant
(b) Temperature - lower temperature increases survival time
(c) Moisture - longevity is greater in moist soils than in dry
soils
(d) Type of soil - neutral, high-moisture-holding soils favor sur-
vival
(e) Organic matter - the type and amount of organic matter present
may serve as a food or energy source to sustain the microorgan-
isms
(f) The presence of other microorganisms can have an antagonistic
effect on the pathogens.
44
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Dunlop [61] also reviewed the survival of pathogens and cited numerous
examples of the variable survival rates of microorganisms in soil,
water, and on crops. Table 11 presents a portion of the data extracted
by Dunlop from the literature.
While extensive, the above reviews were not specific to soils which had
been treated with liquid municipal sewage sludge. More recently, how-
ever, Kenner, et al [6], investigated specifically the persistence of
pathogens in liquid sludge amended soils. The studies were conducted
using two agricultural sites in Pennsylvania; St. Marys and Penn Town-
ships. Neither site contained fecal, coliforms, Pseudomonas aeruginosa,
or Salmonella sp. prior to sludge application. Application rates and the
type of sludge applied were as follows: St. Marys - anaerobically di-
gested, activated sludge at the rate of 6.1 cm; Penn Township - anaero-
bically digested, activated sludge at the rate of 4.1 cm. Bacteriologi-
cal assays of the sludges indicated that the St. Marys site received
1.8 x 10' fecal coliforms, 56,000 Ps. aeroginosa, and 414 Salmonella si
per sq ft, while the Penn Township site received 2.5 x 10/ fecal coli-
forms, 3.78 x 10 Ps. aeruginosa, and 5,678 Salmonella sp. per sq ft.
Weekly soil samples from each site were analyzed over the period April 2,
1968, to August 27, 1968. For the St. Marys site, Salmonella sp. were
not detected throughout the study and Ps. aeruginosa was detected only
initially. Fecal coliforms, however, were still detectable at 21 weeks
(192 per gram). Samples from the Penn Township site, however, showed
22 fecal coliforms per gram at 18 weeks, Ps. aeruginosa at 16 weeks, and
Salmonella sp. up to 10 weeks.
Kenner also considered the effects of weather during late fall and winter
months (November, 1969-June 8, 1970) on pathogen survival. Three plots
of grass-covered ground were treated with (1) anaerobically digested pri-
mary sludge, (2) undigested primary activated sludge, and (3) undigested
secondary activated sludge concentrated to 4 percent solids. The sludges
were applied on November 5, 1969, at a rate of 4.1 cm, yielding the follow-
ing number of pathogens per .093 m (1.0 sq ft):
Fecal Ps. Salmonella
coliforms Aeruginosa sp.
Plot 1. Anaerobically digested
primary sludge
Plot 2. Undigested primary
activated sludge
Plot 3. Undigested secondary
activated sludge (4 percent)
1.48 x 107 1,
8
300
1.09 x 10 41,600
7.57 x 10 75,700
1,098
2,800
352,000
45
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Table 11. SURVIVAL TIMES OF PATHOGENIC MICROORGANISMS IN VARIOUS MEDIA [61]
Organism
Ascaria ova
Cholera vibrios
Endamoeba
histolytica
cysts
Enteroviruses
Hookworm larvae
Leptospira
Salmonella typhi
Salmonella, other
than typhi
Shigella
Tubercle bacilli
Medium
Soil
Soil
Plants *• fruits
Spinach, lettuce
Cucumbers
Nonacid vegetables
Onions, garlic,
Oranges, lemons,
Lentils, grapes
Rice, dates
River water
Soil
Tomatoes
Lettuce
Roots °f bean plants
Soil
Tomato & pea roots
Soil
River water
Soil
Dates
Harvested fruits
Apples, pears, grapes
Strawberries
Soil
Soil
Soil
Pea plant stems
Radish plant stems
Soil
Lettuce & endive
Soil
Soil
Lettuce
Radishes
Soil
Soil
Soil
Cress, lettuce & radishes
Lake water
Soil
Vegetables
Tomatoes
Soil
Potatoes
Carrots
Cabbage & gooseberries
Streams
Harvested fruits
Market tomatoes
Market apples
Tomatoes
Soil
Grass
Sewage
Soil
Type of
application Survival time
Not stated 2.5 years
Sewage "P to 7 years
AC(a) 1 month
AC 22-29 days
AC 7 days
AC 2 days
Infected feces hours to 3 days
AC 8-40 days
AC 8 days
AC 18-42 hours
AC 18 hours
AC At least 4 days
AC 12 days
AC 4-6 days
Infected feces 6 weeks
AC 5-6 days
AC 15-43 days
AC 68 days
AC 3 days
AC 24-48 hours
AC 6 hours
AC 74 days
AC 70 days
AC at least 5 days
AC 14 days
AC 4 days
AC up to 20 days
AC 1-3 days
AC 2-110 days
AC . Several months
Infected feces 18 days
Infected feces 53 days
Infected feces 74 days
AC 5-19 days
AC 70-80 days
AC 3 weeks
AC 3-5 days
AC 15-70 days
AC 2-7 weeks
AC Less than 7 days
Sprinkled with 40 days
Domestic sewage
Sprinkled with 40 days
Domestic sewage
Sprinkled with 10 days
Domestic sewage
Sprinkled with 5 days
Domestic sewage
Not stated 30 min-4 days
AC Minutes-5 days
AC At least 2 days
AC At least 6 days
AC 2-7 days
AC 6 months
*C 14-49 months
? 3 months
? 6 months
AC ' artificial contamination
46
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At approximately weekly intervals, 2-inch deep soil samples were taken
and the number and kind of pathogens surviving determined. The maximum
number of days which the pathogens survived are summarized as follows:
Fecal Ps. Salmonella
coliforms Aeruginosa sp.
Plot 1. Anaerobically digested
primary sludge 147 119 56
Plot 2. Undigested primary
activated sludge 147 147 112
Plot 3. Undigested secondary
activated sludge (4 percent) 133 91 77
All of the above data suggest that pathogens can and do survive for vary-
ing periods in both the sewage sludge and the soils on which the sludge
is spread.
POTENTIAL HEALTH HAZARDS
As pointed out earlier in this report, pathogenic organisms can and do
survive the sewage treatment process and sludge digestion and can remain
viable for varying lengths of time in the soil and on the vegetation
growing on the soil. Therefore, whenever liquid sludge is handled, wheth-
er in transporting the material to lagoons for disposal or spreading the
liquid sludge on land as part of a soil improvement program, the potential
always exists for these pathogens to contribute to human and animal dis-
ease. The available information relative to public health hazards in-
volved with land disposal of sludge leads to the belief that the risk to
public health is slight.
For instance, Ewing and Dick [16] state that there is a great deal of pub-
lic concern stemming primarily from an uncertainty of the fate of patho-
genic agents and subsequent health hazards associated with land disposal
practices. They also point out, however, that no incidence of disease
transmission has been traced to sludge-disposal activities. In a review
of the West Herfordshire sludge disposal operation, Seabrook [63] points
out that public health officials do not feel the landspreading operation
which disposes of 340 x 10^ m of liquid digested sludge per year on
firm, easily drained gravel soils is a threat to public health. Stone
[64] investigated numerous farms used for the disposal of sewage wastes
in California and reported no particular difficulty with plant, animal,
or human disease transmission. Sabey, et al [40], reported that where raw
sewage is utilized, the health hazards are prevalent; but where well-
digested sludge is used few if any health hazards are posed.
47
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Most of the above discussion is concerned with the potential for trans-
mission of diseases through the consumption of foodstuffs grown on
waste-amended soils. That some pathogens can survive the sludge diges-
tion process and remain viable in the soil for periods up to several
months has prompted the general recommendation that liquid sludges should
not be applied to root crops or crops intended for human'consumption in
the raw form. Adherence to this recommendation undoubtedly is responsible
for the lack of public health problems in the United States relative to
the land disposal of liquid sewage sludges.
Pastureland and farmland used to grow forage crops is frequently used
as a land disposal site, and this is a practice which appears to present
little problem from the standpoint of disease transmission via livestock
grazing on such fields. Numerous studies have been reported [64J con-
cerning the application of digested sludge and even raw sewage to pasture-
land, with no adverse effects accruing to the livestock.
Regarding pathogenic contamination of ground and surface waters, it has
been reported that bacteria do not travel laterally more than 30.5 meters
through granular soils, that complete removal of E. coli was noted in
about 4.9 meters of dune sands, and viruses were removed in a 0.61 meter
bed of clean sand at moderate rates of application over a 7-month period.
Generally, then, groundwater contamination by pathogens may not be as
much of a potential hazard as surface water contamination via surface
erosion resulting from direct runoff from the sludge spreading operation
or surface water runoff induced by snowmelt or rainfall. With careful
site management, surface runoff can be controlled to essentially elimin-
ate erosion. The important considerations along these lines have been
discussed in the section on physiographic considerations.
It must be pointed out, however, that because of the variations of condi-
tions that affect landspreading (i.e., quality of the sludge, general
levels of public health prevailing in the area, site characteristics,
soil characteristics, etc.), an evaluation of each active or proposed
land disposal operation should be made before attempting to quantitatively
predict the potential health hazards from a given operation. Also, there
are means of disinfecting sludge prior to landspreading. The methods
include long-term storage, pasteurization, addition of lime, and disin-
fection with chlorine or other chemicals; these have been considered in
a previous section of this report.
48
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SECTION X
LAND ACQUISITION
Since landspreading utilizes the land as a means of ultimate disposal,
adequate amounts of suitable land must be continually available to
accept the quantities of liquid sludge generated at the wastewater
treatment plants. Both the literature review and the survey conducted
as part of this program revealed a wide range of land types currently
utilized to receive the liquid sludge. The most common land type by
far is agricultural, both cropland and pastureland. Other types en-
countered included public parks, golf courses, airports, abandoned
strip mines, cemeteries, plant grounds, highway median strips, wood-
lands, and landfill operations (both active and abandoned). Others
were encountered, but not with the frequency of those listed above.
This section will review the problems of acquiring sufficient amcunts
of suitable land from two viewpoints: obstacles to land acquisition
and land availability.
OBSTACLES
Two obstacles can prevent acquisition of land for sludge spreading.
There are public fears of alleged health hazards and potential nuisances
associated with landspreading and the high cost and scarcity of suitable
land areas. Each of these objections would appear to be of a social
nature both in implication and solution. For instance, one individual
[65] reports that resistance is offered by people who simply do not want
wastes used around them regardless of how helpful or ecologically safe
they are. The static provided by such groups may be more limiting to
landspreading than economic or technological factors.
Esthetic effects can also promote adverse public reaction to spreading
"of liquid sludges on the land. Generally, the major esthetic problem
stems from odors generated at the site resulting from spreading of in-
adequately stabilized sludges. Along this line, Stone [66] reports
that prior to the adoption of sludge digestion, some English sludge
farms had notorious reputations for odor production. The resulting
public opposition persisted even after sludge digestion eliminated most
of the problems. This prompted Stone to conclude that "such is the
power of the human mind over matter that complaints of disgusting stench
49
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and revolting conditions are made which bear no relation to sensory ex-
perience". A similar experience was noted [65] in regard to a planned
sludge spreading operation in Illinois. One individual complained of
the "terrible, horrible stink of the sludge" before sludge spreading
was started.
Probably the most frequently stated objection to land disposal of
liquid sewage sludge relates to potential health hazards. These con-
cerns are felt by some [67] to be more a function of land treatment's
visibility as a disposal method than a function of real risk to public
health. While many individuals readily accept the use of farmyard ma-
nures, they have a reluctance to regard properly treated and utilized
human wastes in the same way [66]. Although potential for disease
transmission via a carefully managed landspreading operation is quite
low, this information must be communicated to the general public in
attempts to allay fears of disease transmission. Meanwhile, this "human
waste stigma" can be a very real constraint to the acquisition of ade-
quate amounts of suitable land areas.
Although small communities can usually find suitable land for sludge
disposal at no cost to the treatment plant operation, there are instances
where the purchase of land would be desirable to enable complete control
over the operation and to ensure continuity of the practice. The new
Federal Water Pollution Control Act Amendments of 1972 under Title II,
"Grants for Construction of Treatment Works", Section 212(2) (2), now
permits acquisition of the land that will be an integral part of the
waste treatment process or will be used for ultimate disposal of residues
resulting from such treatment [68].
LAND AVAILABILITY
Each landspreading activity should be examined on the basis of the goals
intended for the particular operation, i.e., a disposal operation only
or a disposal operation as part of a soil improvement program. The fre-
quency and rate of application and the type and amount of land required
(and hence its availability) are largely influenced by the ^stated objec-
tive.
If one considers the total amount of land potentially available for use
in sludge disposal activities in the United States, it would appear that
the nation's land resources need be in no danger from sludge disposal.
For instance, on the basis of 1965 data, some 1.3 million hectares of
land have been disturbed by surface mining activities [67]. Six states
were reported as containing over 40,500 hectares each which required
reclamation. These are
50
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• Pennsylvania 92,900 hectares
0 Ohio 69,500 hectares
« Florida 58,100 hectares
a Texas 55,200 hectares
» West Virginia 45,100 hectares
0 California 43,100 hectares.
These six states account for more than 31 percent of the total United
States population. In addition, most major United States cities are
located within 16 kilometers of such areas, which is within the limits
that sludges can be economically transported by truck, rail, or pipe-
lines
With regard to agricultural land, Carlson J70] states that such land
will be used more and more for waste disposal, either in conjunction
with cropping or replacing cropping for utilization as disposal sites
only. The United States presently has some 144 million hectares of
cropland, over 410 million hectares of forest and range land, and 205
million hectares of nonagricultural land. On an assumed worst case,
Carlson further estimates that all of our decomposable municipal wastes
could be disposed of on less than 5 percent of our cropland without harm
to the resource. Distribution rather than the capacity of the total
system to assimilate the wastes becomes the problem.
51
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SECTION XI
SURVEY OF SEWAGE TREATMENT PLANTS
IN FEDERAL REGIONS 2, 3, 4, 5, and 9
The comprehensive literature survey conducted as an integral element
of this program revealed the existence of a large body of written
matter on land disposal systems and techniques relative to waste
water effluents, organic composts, and both liquid and dried sewage
sludge. As a whole, however, the major portion of the information
relative to land disposal of liquid sewage sludges can be placed in a
category best described as "how we are conducting our landspreading
operation". As such, this information relates primarily to the
mechanics of individual landspreading operations,many of which are
located in Europe and England. While most European operations are
associated with raw sewage farms, surveys have shown that approxi-
mately 40 percent of all municipal treatment works in England are
now using landspreading for the disposal of liquid digested
sludges [63].
Until recently, however, the practice of landspreading of liquid
sewage sludge was not widely observed in the United States. Rather,
these sludges were often treated as "waste products" of society and,
accordingly, were disposed of with too little attention given to
their potential usefulness or resource value. Now, however, this
practice is increasing in popularity in the United States. Although
the initial interests were directed primarily toward the liquid
portion of treated sewage in water deficient regions, there are many
situations where the disposal of the liquid sludge by landspreading
may offer an ultimate and an economical solution to the waste disposal
problem while at the same time providing for a beneficial use of
resources which might otherwise be wasted.
Since the vast majority of active landspreading activities are not
reported in the open literature, a literature review will not yield
an accurate estimate of the proportion of U. S. sewage treatment
plants which are routinely disposing of their liquid sludges via
landspreading. Furthermore, an examination of the most recent in-
ventory of municipal waste facilities [71] , while providing information
on sludge treatment and disposal methods, does not yield a reliable
estimate of the extent to which landspreading is currently practiced
in the United States. Also, most state agencies either do not compile
such information, or are just beginning to assemble the information!
and therefore cannot readily provide it.
52
-------
An integral element of this program was, therefore, to obtain a
relatively accurate estimate of the proportion of the United States
sewage treatment plants routinely using landspreading for the disposal
of liquid sludges. Consequently, a combination mail and phone survey
was conducted involving all sewage treatment plants, 3.8 x 1CH m3/d
-------
o o
consideration all plants smaller than 3.8 x 10 tn/day and (2) elimi-
nation of those communities and facilities listed in the 1968
inventory that were being served by other communities or facilties.
The reasoning behind the eliminating of smaller plants involved con-
siderations of the ability to collect data. Also, many of the plants
with design inflow less than 1 mgd are package plants and essentially
unmanned. Therefore, it was felt that the response to a mail and/or
phone survey from the less than 3.8 x 103 tn3/day plants would not
warrant the effort of contact and, further, that available data from
these operations would be severely limited. It was further concluded
that serviced communities could be more expeditiously contacted by
surveying the parent organization.
The screening process yielded 1,909 plants stratified by Federal
Region and plant size as follows:
Plant
size ,
103 m3/day
3.8-38.0
38-380
> 380
Total
Region
2
247
38
12
297
3
270
26
6
302
4
466
40
3
509
5
444
82
9
535
9
211
51
4
266
Total
1,638
237
34
1,909
A copy of the questionnaire mailed to the above population is shown in
Figure 3. As the primary objective of the mail survey was to obtain
an estimate of the number of plants using landspreading in the five
Federal Regions of interest, the decision was made to keep the ques-
tionnaire short and simple in order to elicit the highest possible
response.
Table 12 summarizes the results of the mail survey. Briefly, a 40
percent response to the mail survey was achieved, with the best re-
sponse (55 percent) coming from Region 5. The remaining Regions
responded in the following percentages: Region 2-28 percent,
Region 3-35 percent, Region 4-32 percent, and Region 9-38
percent.
Based upon the actual number of responses, the percent response to
each of the categories of Question 1 of the questionnaire are
summarized as follows:
1A. Landspreading is used on a routine basis - 25 percent
IB. Landspreading has not been used - 57 percent
1C. Landspreading was used, but discontinued - 7 percent
54
-------
Form Approved
OMB No. 158-S 72024
Name of Facility
Address
Name and Phone Number of Person Responding
1. Check the one which best describes your plant's operation with respect
to landspreading of liquid municipal sewage sludge.
[| a. Landspreading is currently used on a routine basis.
[| b. Landspreading has not been used.
j| c. Landspreading was used, but has been discontinued.
[I d. Landspreading will be used in the future.
jI e. Landspreading was considered, but rejected.
2. If you checked la, please answer the following:
a. How many years has your plant used landspreading?
b. How is landspreading presently conducted at your plant?
II By plant personnel. || By contract hauler. (_J As a give-
away operation. || Other (please specify)
c. What means are used to transport the sludge to the landspreading
site? (~~| Tank Truck [ [ Pipeline Q Barge | | Railroad
II Other (please specify)
d. Distance to landspreading site. miles
e. What kind(s) of land is used for the landspreading operation?
[I Farmland |[ Abandoned strip mine || Parks \\ Highway
median strips || Other (please specify)
f. What type(s) of spreading equipment is used? [| Tank Truck
|~1 Spray Irrigation Q Sprinkler Irrigation Q Irrigation Pipe
II Sub-sod Injection |[ Other (please specify)
FIGURE 3. Questionnaire Used in Mail Survey
55
-------
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ID. Landspreading will be used - 8 percent
IE. Landspreading was considered, but rejected - 3 percent
Because the problem of nonrespondents is characteristic of all data-
gathering schemes utilizing mail surveys, a follow-up phone survey
was conducted in an attempt to develop a more accurate estimate of „
plant landspreading operations. All plants with greater than 380 x 10 /
m /day volume within the five Federal Regions were contacted. Since the
mail response from Regions 2 and 5 was lowest and highest, respectively,
follow-up phone calls to randomly selected nonrespondents were initially
concentrated in these regions to verify the mail survey results.
An analysis of the two samples (e.g., phone and mail survey) by region
and plant size indicated that the samples were statistically different.
In all cases, it was the mail survey which suggested the higher esti-
mate of the percentage of treatment plants that are using landspreading
on a routine basis. On this basis, it was decided that follow-up
phone calls to a sample of nonresponding plants in Regions 3, 4, and 9
would be conducted to further increase the confidence on the survey
estimates of plants using landspreading in these three regions. The
results of the completed mail and phone survey are included in Table
13.
Of the 987 respondents to the survey, 225 (22.8 percent) are currently
using landspreading on a routine basis. Applying the survey results
on a region-by-region basis to the total population sampled suggests
that about 400 plants (21 percent) are presently practicing landspreading,
Utilization of landspreading of liquid sewage sludge is most dominant
in Region 5 (Ohio, Indiana, Illinois, Michigan, Minnesota, and
Wisconsin). The survey indicated thattthe percentage of plants using
landspreading is least in Region 2 (New York and New Jersey). The
characteristic plant Size using landspreading in the regions surveyed
is less than 380 x 10 /m /day. Figure 4 demonstrates the geographic
distribution of those plants which responded as using landspreading.
Table 14 summarizes the results of the mail and phone survey by
individual plants. Briefly, the summary table indicates that the
majority of the plants which responded as using landspreading are
secondary activated sludge plants in the (3.8-19.0) x 10 m /day size
class. Utilization of plant personnel to conduct transport and
spreading operations constitutes normal practice. With the exception
of Chicago, Illinois, no transport systems involving barges or rail-
road tank cars were identified. The use of pipeline sludge transport
systems identified in the survey are for the most part restricted to
those less than 1.6 kilometers in length. The most common transport
system involves the use of a tank truck with the distance to the land-
spreading site being normally less than 16 kilometers one way.
57
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Some operations are being conducted on a trial basis, while other
sewage treatment plants have utilized landspreading longer than 40
years. Data gathered via the survey reveals that landspreading is
indeed growing in popularity and utilization. An examination of the
survey responses, which included the number of years that land-
spreading has been practiced by the various sewage treatment plants,
reveals that 68 percent of the plants responding have been conducting
landspreading for less than 10 years. Of this 68 percent, over two-thirds
have begun the practice only within the last 5 years.
Tank trucks are the predominant method of spreading liquid
sewage sludge. Other spreading methods utilized are pipe, spray
and sprinkler irrigation. Sub-sod plow-down injection and ridge
and furrow methods are also utilized.
The survey indicates that the lands utilized for landspreading are
predominantly agricultural. Parks, airports, golf courses, abandoned
landfills, and strip mines, among others, are also utilized. In one
case--San Leandro, California — about 3.8 x 103 m3/day of liquid sewage
sludge is spread by the Highway Department on median strips.
FIELD VISITS
The purpose of the field visits was to attempt to obtain pertinent
unreported data relative to landspreading and to prepare case history
write-ups based upon observations of the operations and interviews
with the plant personnel. The types of data deemed most pertinent
to the landspreading operations included the type and amount of land
used, the kind of waste water treatment employed, the quantity and
quality of sludge, the type of sludge stabilization used, the con-
veyance system, distance to the site, sludge application rates, soil
and crop response, and the costs of disposal.
Accordingly, 26 plants in six states were selected for visitation as
follows:
Number of plants visited
3.8-38 3.8-38
State Region X1Q3 m3/day X1Q3 m3/day
California
Florida
Illinois
Minnesota
Ohio
Wisconsin
9
4
5
5
5
5
3
3
-
5
3
4
2
1
1
—
3
1
63
-------
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64
-------
These states and plants were considered representative of the extremes
of population, climate, topography, and soils which would be encoun-
tered throughout the five Federal Regions of interest to this study.
The following discussion provides an overview of the information
obtained during the plant visits and also presents some conclusions
drawn from observation of the various operations and interviews
with plant personnel. The first conclusion drawn from these visits is
that plant economics are the primary driving forces behind most
decisions to utilize landspreading. Those aspects of landspreading
that offer a more trouble-free operation are also involved, but,
nevertheless, economics remains the prime mover even though detailed
cost figures were not always available to substantiate this fact. The
often repeated benefits of liquid sludge (i.e. - fertilizer value,
soil conditioning, source of supplemental water, etc.) were reiterated
by most plant operators, but, again, there was essentially no data
beyond empirical judgments to add credence to these claims.
Generally speaking, information was readily available on such
operational aspects as the type of influent (i.e. - percent domestic
vs percent industrial), the type of wastewater treatment used, the
quantity of sludge disposed of, the conveyance system used, distance
to landspreading site(s), the type(s) of land used, and the methods
of obtaining land. However, data relative to the most significant
aspects of the operation - i.e., the amount of land and sludge
application rates used, crop and soil response, and the costs of
disposal — x\rere generally lacking or, at best, incomplete.
The normal practice is to have a number of sites available for
utilization in order to rotate sludge applications and to assure
continuity of the operation during adverse weather conditions.
However, sufficient records are not kept at most treatment plants
to enable a determination of the loading rate at which sludge is
applied to the individual sites. As a rule, the records show only
the total amount of sludge taken from the plant.
In most instances, soil and/or crop response was reported to be good.
However, this is based primarily on observation alone, as only two
of the plants visited (Springfield, Illinois, and Moorhead,
Minnesota) have conducted studies along these lines. Most plant
operators indicated that such information is not solicited from the
farmers who are receiving the sludge.
As discussed in a previous section of this report, the quality of
the sludges should be an important consideration in the planning and
design of a landspreading operation. However, no extensive sludge
analyses were encountered beyond those required for plant operation or
by the various state agencies -- specifically, total dissolved solids,
volatile solids, and pH.
65
-------
Accurate operational costs for sludge disposal were difficult to
obtain, as many of the plants visited did not maintain separate
records for the cost of sludge disposal. For instance, labor is an
important function in determining the cost of the sludge disposal
operation. In many instances, the personnel who conduct the sludge
disposal operation also serve in other capacities around the plant.
It was not a normal practice to record separately the amount of time
an individual devoted to sludge disposal. The available cost
estimates obtained from the plants visited are presented in Table 15.
As a whole, the plant personnel interviewed were relatively pleased
with their landspreading operations and reported no major problems
or complaints. Although accurate cost recording was not the rule,
most were convinced of the economics of landspreading when compared
with alternative means of sludge disposal - i.e. vacuum filters,
centrifuges, sand-drying beds, etc. In fact, numerous idle vacuum
filters and abandoned sand-drying beds were noticed during the plant
visits. Also, several of the plants were either undergoing expansion
and upgrading at the time of visitation, or were awaiting funds for
expansion and upgrading. More often than not, the plans called for
a continuation of the landspreading operation under the new scheme.
Case History Write-Ups
California Plants
Bakers field - The digested sludge containing 5 percent total solids
(50 percent volatile) is pumped to a 2.4-hectare, 3-meter-deep ditch
0.4 kilometers from the plant. Occasionally, some of the
sludge is mixed with plant effluent and used for irrigation of
adjacent grass and farmland. The average monthly sludge output is
about 303 m . No other data were available.
Oceanside - Sludge from the anaerobic digester containing 5 percent
total solids is currently being dumped into a plastic film-lined
canyon 3 kilometers from the plant. This is being done as part
of an experimental program sponsored by EPA to study, among other
things, the leachate characteristics from a bed comprised of alternate
layers of trash (garbage) and sewage sludge.
The plant operation produces two to four 11.4-m^ truckloads every
week. The canyon landfill has caused some occasional nuisance odors,
apparently because of insufficient time of retention of sludge in the
digester. The canyon is close to a public school and some industrial
plants.
Prior to disposing of the liquid sludge ia this canyon landfill, the
sludges were disposed of in 1-meter-deep ditches. However, under the
orders of the Water Quality Control Board of San Diego County, this
practice was discontinued since the water table was only 1.5 meters
below grade.
66
-------
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67
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San Juan Capistrano - The sludge produced in the anaerobic digesters of
the 8.7 x l63 m3/day plant together with that generated in the activated
sludge units is first thickened in a flotation thickener and then sent
through two continuous solid bowl Bird centifuges. The resulting sludge
containing 29 percent total solids is transported to an elevated hopper
using a series of belt conveyers. The sludge accumulated in the hopper
is spread over a 0.2 hectare plot adjacent to the plant. Approximately
23 m3 of sludge are accumulated daily.
This plant faces problems in disposing of its sludge. Spreading of
thinner sludge (about 5 percent total solids) was done on grassland
11 kilometers from the plant using a tank truck. This operation
was discontinued, however, as a result of an order by the Orange County
Health Department. Apparently,the grassland was located on a flood-
plain. For some time after the discontinuation of the spreading opera-
tion, the thin sludge was hauled to a nearby plant where sludge thick-
ening and incineration facilities were available. The plant operator is
now in the process of working out an agreement with a private contractor,
whereby the 20 percent sludge will be rmoved from the plant site for
later processing to produce a rich topsoil. The tentative cost of the
latter operation was put at $7.65/m3.
Santa Barbara - The anaerobically digested sludge from this 38 x 103m3/day
plant contains 5 percent total solids (70 percent volatiles) and is
currently being hauled 92 kilometers to a private farm. Prior to the
application of liquid sludge, the land is disced and after several
sludge applications it is rotary tilled. The high sodium and chloride
contents in the liquid portion of the sludge preclude its use to irri-
gate fruit crops. The cost of transporting 32.0 x 103 m3 (1,598 dry
tons) of sludge produced per year is reported to be about $230,000.
Additionally, the sum of $45 per 22.7 m truckload ($63,400 per year)
is paid to the owner of the farmland, bringing the total cost of the
operation to about $293,400 per year. This amounts to disposal costs
of $183.63/dry ton ($9.17/m3).
Saugus (Los Angeles County District 26~) - Liquid sludge from this 11.4
x 103 nrVday plant's anaerobic digesters averaging 3 percent solids
(65 percent volatile) and pH of 7.0 is hauled away by a private contrac-
tor to a farm located 16.1 kilometers from the plant. A 15.1 m3 tank-
trailer truck is used to transport eight loads over a period of 10 hours
per day 5 days per week. The truck (with driver) is rented for $20.50/
hour. In addition, the farmer is paid $3.50/truckload for preparing
the land prior to sludge spreading (i.e., discing to a depth of 15 cm).
The land to which sludge is applied on a rotating basis is used to grow
mainly corn and melons. Prior to planting, the land is rotary tilled to
a depth of 45.7 cm. The total land area receiving regular applications
of liquid sludge is about 24.3 hectares. Plant personnel reported that
application of liquid sludge to the cultivated land has reduced nitrogen
fertilizer requirements by one-half.
68
-------
Using the above data, costs for the operation are estimated to be
$64.22/ton and $1.92/m3.
Soil and crop response were reportedly good, but no data were avail-
able to quantify this observation. No environmental monitoring is
conducted.
Florida Plants
Qcala - Landspreading of anaerobically digested sludge averaging about
8.9 percent solids (40-45 percent volatile) with a pH value of 7.3 has
been practiced at this 13.2 x 10 m /day plant for the past 15 years.
The sewage influent is composed of approximately 90 percent domestic
wastes and 10 percent industrial wastes from a citrus processing plant
and a slaughterhouse. The sludges are produced for digestion by plain
sedimentation and trickling filters. Prior to the initiation of the
landspreading operation, vacuum filters were used to dewater the sludge
and the dried product was spread on the land.
Two tank trucks (7.57 m^ and 11.4 m^ capacities) are used to haul and
spread the liquid sludge on privately owned pastureland within 19-21
kilometers of the plant. The hauling operation consists of six trips per
day five days per week throughout the year.
In most cases, local farmers have requested that liquid sludge be spread
on their pastures after observing the results of sludge applications on
other farms. When sludge is requested in a new area, the plant per-
sonnel will contact the neighboring landowners and explain the nature of
the operation. In general, public reaction to the landspreading opera-
tion has been favorable, with only an occasional complaint regarding
odors.
Cattle are normally left in the fields during the landspreading opera-
tion; however, they will avoid the sludged areas for some 3-5 days after
spreading. Pasture response to the liquid sludge is apparently good
and application rates were estimated to be on the order of 74.8 m-V
hectare. At these application rates, no crust formation has been
noted.
Environmental response monitoring is not conducted nor are operational
costs maintained separately from other plant operating costs.
St. Petersburg - Anaerobically digested sludges averaging about 2.5
percent solids (70 percent volatile) and a pH of about 7.1 have been
disposed of via landspreading for the past 2 years. Four sewage treat-
ment plants (two primary and two activated sludge plants) treat
essentially 100 percent domestic sewage. The sludges are produced for
anaerobic digestion by primary and secondary (activated) sedimentation.
Essentially all the sludge disposed of via landspreading comes from the
two activated sludge plants (109 x 10 m /day).
69
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Conventional sand-drying beds had been used to dewater the sludges,
however, when the plants were converted to activated sludge systems,
problems were encountered in dewatering the sludges on the sand beds.
Consequently, the decision was made to utilize a combination lagoon/
landfill and landspreading for the disposal of liquid digested sludge.
The initial attempt at landspreading involved ridge and furrow applica-
tion to a field adjacent to the Southwest Plant grounds. The minimum
cost estimates for this method were reported to be $38.60/ton and re-
quired a minimum of 8 hours to treat 0.4 hectare of ground. This
method was thus abandoned due to its high cost of operation, and a 10.9
nH tank truck (diesel) was purchased to haul and spread the liquid
sludge. A pressurized line running from the digester to the sand beds
was tapped and a valve arrangement installed for loading the truck.
Sludge discharge from the truck is by gravity flow, and a spreader bar
assures an even distribution of the sludge.
3 3
On the average, some 1.8 x 10 m of liquid sludge are disposed of each
month via the following scheme. Approximately 20 percent of the liquid
digested sludge is disposed of via landspreading. The remaining 80 per-
cent is hauled to a city-owned lagoon/landfill operation by a 30 m
tractor-trailer unit.
«.
Presently, all of the liquid digested sludge disposed of through land-
spreading is being used to build up the extremely sandy soils for
planned golf courses and park areas. Application rates were estimated
to be on the order of 28 m /ha. Although no problems were reported re-
garding the landspreading operation, the plant personnel speculated that
the "human waste stigma" might hamper a more widespread adoption of
landspreading.
No environmental response monitoring is conducted nor are data routinely
kept on the costs of sludge disposal via landspreading. The tank truck,
however, was purchased new in 1972 at a cost of $33,000 and has since
logged some 25,740 kilometers hauling liquid sludge. During the periods
when sludge is being hauled an average of 143 m /day are disposed of via
landspreading on sites within 8 kilometers of the plant site.
Tallahassee - Anaerobically digested sludges averaging about 4.5 percent
solids (55-60 percent volatile) from three activated sludge sewage treatment
plants (30.3 x 10-* m-^/day total) have been disposed of via landspreading
for the past 14 years. The influent sewage is essentially composed of
95 percent domestic wastes and the sludges are produced for digestion
by plain sedimentation and both low-rate and high-rate trickling fil-
ters. Sand drying beds were used to dewater the sludge before land-
spreading was adopted.
70
-------
Presently, city-owned land surrounding the airport is being used for the
landspreading operation. Some 810 hectares of land are available at
this site, but only 85 hectares are currently used for landspreading.
The soils of the area are extremely sandy and were reported to be approx-
imately 12.2 meters deep. Two tank trucks (9.08 and 15.5 m^ capacities)
are used to haul and spread the sludge.
Good grass growth is being maintained on the sandy soils and the plant
management is considering growing hay on the site for harvest and sub-
sequent sale to local farmers. About 1,562 tons of sludge solids have
been spread at the site over the past 8 months. However, the amount
of land over which this was spread was not known, so application rates
could not be determined. Plant personnel indicated they attempted to
obtain application rates of approximately 56 tons/ha/year.
Operation and maintenance costs for the trucks were reported to be on
the order of $0.10/kilometer.
While the operators considered landspreading to be the best available
and most economical means of sludge disposal, the operation is presently
being conducted under a temporary State permit until another means of
disposal is selected. Tentative plans are to dewater the sludge in a
centrifuge to 10 percent solids and then dispose of it in a landfill.
3 3
Winter Park - The sewage entering this 17 x 10 m /day activated sludge
plant is composed of essentially 100 percent domestic wastes. The
sludges produced by plain sedimentation are anaerobically digested and
normally range from 1.3-1.5 percent solids (77 percent volatile). Land
disposal of liquid sludge has been practiced here for 5 years. Prior
to landspreading, sand beds were used to dewater the liquid sludge.
The beds were abandoned when sludge volumes became too great for the
beds to handle in rainy weather.
3
With the decision to use landspreading, two 9.5-m tank trucks (diesels)
were purchased. These, however, are not tank trucks in the normal sense
of the word. Rather, they are dump trucks which have been modified to
serve as tank trucks. The modification included the installation of
gasketed covers on the beds, leak proofing the beds,and installation of
a spreader bar and discharge-valve arrangement. Loading of the truck is
by gravity flow directly from the digester. Sludge discharge is by
gravity flow. In the event that the landspreading operation would be
discontinued, very little work would be required to restore the original
dump truck configuration. Each truck is equipped with high flotation
tires to facilitate movement in the area's sandy soils.
An interesting situation was encountered at this plant relative to
hauling sludge across county lines. Winter Park is located in Orange
County near the Seminole County line. The initial landspreading opera-
tion was conducted on somewhat poor pastureland in Seminole County not
far from the Winter Park plant. With the increased grass growth promoted
71
-------
by the liquid sludge, the rancher was able to substantially increase
the number of cattle grazed on this land. For some unexplained reason,
Seminole County officials elected to halt the hauling of sludge into
their County. Legal action taken by the ranch owner was to no avail,
and since the landspreading activity was discontinued, the rancher's
herd has reportedly decreased in number by approximately three-fourths.
With the loss of this convenient site, the plant management approached
a local orange grove owner and obtained his permission to apply the
liquid digested sludge to an extremely large grove located about 22
kilometers from the plant. The landspreading operation is now con-
ducted 5-7 days/week throughout the entire year. The liquid sludge
dries rapidly on the sandy soils (reported to vary between 0.6-3.0
meters in depth), and posttreatment of the site in the form of discing
is conducted by the grove owner.
No pre- or postoperational monitoring of soil or crop response is
conducted, anda sludge analysis beyond that mentioned above was not
available. Also, operational costs and sludge application rates were
not recorded.
Illinois Plants
Springfield - (The following description of the Springfield land-
spreading operation is an abstract of a soon-to-be-published paper by
A. P. Troemper, Executive Director, Springfield Sanitary District. The
abstract aptly summarizes the Springfield activated secondary sewage
treatment operation and is included herein with the permission of Mr.
Troemper.) Since 1965 the Springfield Sanitary District has been ex-
permenting with disposal of liquid anaerobically digested sludge by
irrigation of agricultural land. A 2.8-hectare test plot of poor crop-
land was utilized for this purpose. Certain conclusions were possible
as a result of these studies: (1) while considerable variation (due to
climatic conditions) in results may be expected from one year to an-
other, the disposal method is economically feasible, (2) sludge should
be applied to land utilized for growing crops rather than uncropped
land, (3) soil moisture is a great limiting factor in this method of
sludge disposal, (4) while application of sludge to the land by flood-
ing is possible, this method results in numerous problems (spray appli-
cation seems more desirable), (5) crops utilized on the disposal area
should have a high demand for N and P, and (6) storing of sludge in
lagoons for later distribution has not proven practical.
During 5 years of this period for which good records are available, an
average of 51.6 tons of dry solids equivalent were applied per acre each
year. Corn was grown on the test plot as well as on an adjacent area
used for comparative purposes. No fertilizer was used other than sewage
sludge. Average production on the test plot was 7.13 nP per hectare
(81.9 bushels per acre) and on the adjacent land 57.5, or an increase in
72
-------
yield of 42 percent (Table 16). An economic analysis was made based on
the increased yield as opposed to the costs of land plus improvements.
The difference, considered to be the cost of sludge disposal, averaged
$2.71 per ton of dry solids.
Based on results obtained, the Sanitary District is constructing a dis-
posal area to handle all of the anaerobically digested sludge at the
existing treatment works and is also constructing a similar area to
dispose of all aerobically digested sludge at a new treatment works.
Both of these developments will provide for screening or comminution of
the sludge, permanent pumping facilities, permanent distribution facil-
ities to allow spraying the sludge during the entire year, and an under-
drainage system to collect and return the leachate to the treatment
plant. Each area is about 14.2 hectares in size. Development costs of
the areas are presented in Tables 17 and 18. It is anticipated that the
future disposal cost will approximate the cost of disposal during the
experiment.
Minnesota Plants
3 3
Anoka - The Anoka Wastewater Treatment Plant is a 9.5 x 10 m /day
plant and is part of the Metropolitan Sewer Board of the Twin Cities
Area. The treatment given the wastewater consists of (1) screening,
(2) grit removal, (3) primary sedimentation, (4) conventional activated
sludge with contact stabilization, (5) secondary sedimentation, and (6)
aerobic digestion. Currently, the liquid sludge is hauled to a large
drying bed at the city landfill and dewatered. Eventually, the dried
sludge will be bulldozed out of the beds and used to reclaim low-value
land.
They practiced landspreading of liquid sludge for 13 years, but dis-
continued the operation. Though they had no problem with the operation,
they changed from landspreading to drying beds when the management of
the treatment plant changed. The City of Anoka originally built the
plant, but it was sold to the Metropolitan Sewer Board (7 counties
around the Twin Cities area). At this time, the jxLant was changed from "
A trickling filter""to an activated sludge plant and the sludge volume
doubled, i.e., the sludge composition went from 7 percent to 3.5 solids*
The plant superintendent believes that it is less expensive to operate
the drying beds than the landspreading operation with the present system.
3
They formerly used a 3.8-m tank truck to spread the liquid sludge on a
golf course. The operation was fairly satisfactory with few complaints.
With the increase in liquid sludge volume, they would have had to pur-
chase a 15.1-m tank truck and increase their storage capacity. Studies
were made by the plant personnel and it was concluded that drying beds
would be more economical.
Detroit Lakes - The Detroit Lakes Wastewater Treatment Plant is a 3.8
to 4.9 x 10J m^/day plant that treats 100 percent domestic sewage.
The primary and secondary sludges produced by sedimentation and high-rate
73
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74
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Table 17. DEVELOPMENT COSTS OF SUGAR CREEK SLUDGE DISPOSAL
AREA AT SPRINGFIELD, ILLINOIS [44] (BID PRICES
OF LOW BIDDERS ON PROJECT)
(Presented in English Units)
$ 50,022.00
Pumping station
Structure (est. 1/3 of $94,932) $31,644.00
Equipment (est. 1/3 of $36,072) 12,026.00
Sludge comminutor 6,352.00
Total pumping station
Sludge distribution
1,820 of 8 in. C.I. force main at $9.90 18,018.00
5,735 ft of 6 in. C.I. force main at $7.05 40,431.75
8 in. valves - 8 at $250 2,000.00
6 in. valves - 44 at $175 7,700.00
Fittings - 9,415 lb at $0.60 5,649.00
Spray nozzles - 6 at $440 2,640.00
Total sludge distribution system
76,438.75
Disposal area underdrainage
23,610 ft of 4 in. perforated PVC pipe at $2.00 47,220.00
1,300 ft of 6 in. perforated PVC pipe at $2.64 3,432.00
640 ft of 8 in. perforated PVC pipe at $4.00 2,560.00
Underdrainage pump pit & controls 6,593.00
Total underdrainage system
59,805.00
Miscellaneous
4,000 ft of woven wire stock fence at $2.00
Electrical (1/20 of $253,700 - total plant
elect, bid)
Total miscellaneous
Total development cost (exclusive of land)
$206.950.75
8,000.00
12,685.00
20,685.00
$206,950.75
$5,792.07 per acre development
cost of disposal area
35.73
Land cost
2,075 ft x 750 ft = 35.73 acres
35.73 at $750 per acre land cost =
Total disposal area cost
26,797.50
$233,748.25
= $6>542-07 ?er acre total cost of
disposal area
75
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Table 18. DEVELOPMENT COSTS OF SPRING CREEK SLUDGE DISPOSAL
AREA AT SPRINGFIELD, ILLINOIS [44] (BID PRICES OF
LOW BIDDERS ON PROJECT)
(Presented in English Units)
Screening and pumping of sludge
Structure
Equipment
Total screening and pumping
Sludge distribution
6,456 ft 6 in. C.I. force main at $3.25
900 ft underdrain return at $8.56
25 spray irrigation headers and risers at
$321.00
2 spray nozzles at $496.00
Total sludge distribution system
Disposal area underdrainage
35,500 ft 4 in. perf. PVC pipe at $2.50
1,300 ft 6 in. perf. PVC pipe at $3.25
2,475 ft 12 in. perf. PVC pipe at $8.30
Underdrain lift station
Underdrain lift station equipment
Total underdrainage system
Miscellaneous
Pipe and foot bridge relocation
Revision and adjustment of bridge
Pipe supports and braces on bridge
Electrical (1/20 of $134,939 - total plant
elect, bid)
Total miscellaneous
Total development cost (exclusive of land)
$203,169.95 =
30
= $6,772.33 per acre development
cost of disposal area
Land cost
20 acres at $459.96 per acre
10 acres at $500.00 per acre
Total land cost
Total disposal area cost
$203,169.95 + 14,199.20
30
$ 6,275.00
15.768.00
20,962.50
7,704.00
8,025.00
992.00
88,750.00
4,225.00
20,542.50
2,657.00
8,294.00
10,523.00
365.00
1,340.00
6,746.95
= $7,245.63 per acre total
cost of disposal area
$ 22,043.00
37,683.50
124,468.50
18.974.95
$203,169.95
9,199.20
5,000.00
14,199.20
$217,369.15
76
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trickling filters are anaerobically digested and sent to peat bog
lagoons. There are numerous peat bogs in the area, and the City of
Detroit Lakes uses these for sludge disposal. In the operation they
dig the bog out and use the soil as fill for the side banks on the
lagoon. As the lagoon fills and drys out, grass and trees grow. They
then shift to a new peat lagoon. Eventually, the lagoon returns to
meadowland .
Fergus, Falls - The Fergus Falls Wastewater Treatment Plant is a 7.9 x
10^ m^/day plant that treats about 6.1 x 1CH m /day (76 percent) domes-
tic sewage and 1.9 x 10 m /day (24 percent) industrial sewage. The
sludges produced by sedimentation and high-rate trickling filters are
anaerobically digested. Normally, the solids content of the digested
sludge is about 3.5 percent.
At one time, the sludges were dewatered on drying beds; however, these
were removed in 1959. Since that time all of the digested sludge has
been spread on farm fields and a city-owned golf course. The sludge is
spread on the golf course in the winter and the farm in summer.
The secondary digester acts as the holding tank for the sludge prior to
withdrawal for landspreading. An 8.3-m tank truck is used to haul and
spread the sludge. Normally, 6 loads per day are hauled by one full-
time operator. In the summer the sludge is applied to about 18.2 hect-
ares, 8.1 hectares of pasture, and 10.1 hectares that are. planted in corn
the following year. The application is made on alternate years on the
pastureland and the cornfield. The distance to the golf course is 11
to 13 kilometers and 10 to 11 kilometers to the farm. A rough cost
estimate was supplied by the plant superintendent as follows:
Labor = $540/no
, ton
3 days — §
Dry tons = 45.4 m /day x 21.75 mo x .035 x m =34.6 dry tons/mo
Labor « 1/2 total cost
S/ton = A « $31.00/ton dry solids.
34.6 tons/mo J
The farmer plows and discs the soil at no expense to the plant. The
plant superintendent is satisfied with the operation. They have had no
major problems or complaints, although they have had some odor problems.
An interview was held with the local farmer regarding his feeling about
the operation. He indicated that the best results were obtained on grass
and hay. He could not notice any difference in his corn yield. There
are no odors except at the time of spreading. His main complaint is
that 6 to 8 applications are required to fertilize the soil and the
trucks pack the ground so that it is difficult to plow.
77
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Moorhead - The Moorhead Wastewater Treatment Plant is«a 17 x 10 m /day
activated sludge plant that treats about 11.4 x 1CP m /day of domestic
wastewater. The only industry in the area is a creamery that contri-
butes about .38 x 1CH m /day. Primary and secondary sludges produced
by sedimentation and high-rate trickling filters are anaerobically di-
gested (15 days at 35 C) and held in an unheated secondary digester
for ultimate disposal to the land.
The anaerobically digested sludge, containing about 2 percent solids,
is hauled by two tank trucks to a 130-hectare city-owned farm which is
rented to a farmer. The land is used for small grain farming and the
usual crops are winter wheat and barley with some soybeans and sugar-
beets.
3
One truck, a 1972 model, can haul 13.2 m while an older truck, a 1966
model, can haul 11.4 mr. Each truck is equipped with a specially de-
signed spray bar so that the sludge is distributed equally over an
8-foot wide path as the truck moves slowly through the field.
The land to which the sludge is applied is very flat and lies approxi-
mately 6 kilometer's northeast of the City of Moorhead and about 10
kilometers from the plant. The topsoil is a Lacustrine silt and clay
containing enough decomposed organic matter to make it dark brown to
black. This type of topsoil on the flat terrain restricts runoff
of the sludge and promotes infiltration into the soil.
Sludge is hauled throughout the year, since the ground is frozen enough
in the winter to support the loaded truck. Plant personnel use snow-
plows to clear a path in the snow when necessary. In wet weather the
sludge is held in an unheated secondary digester until it can be applied
to the fields. In emergency situations old drying beds are available
for dewatering the sludge. Application rates are about 5.56 m tons/ha/
year. Currently, they do not have quantitative information about crop
response. They have had no adverse community reaction and are pLeased
with their operations.
Over the past few years a much greater demand for the digested sludge
has come about as more and more farmers in the Moorhead area want their
land amended with the sludge. Soil samples were taken on the city-
owned farmland in the fall of 1972 and analyzed by the staff at North
Dakota State University. The results of these tests showed an increase
in soil nutrients where the sludge was applied when compared with the
nutrient status of no-sludge treated soils of the same type. The re-
sults are tabulated below:
78
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No-sludge amendment Sludge amendment
1972 Crop - soybeans 1972 Crop - summer fallow
Rate of appl. - none Rate of appl. - 5.8 tons/hectare
pH - 7.3 PH - 7.2
Nitrogen (N) - Nitrogen (N) -
16.8 kilograms/hectare 168 kilograms/hectare
Phosphorus (P20.j) - Phosphorus ^Or) -
53.9 kilograms/hectare 78.6 kilograms/hectare
Potassium (K^O) - Potassium (K20) -
583 kilograms/hectare 583 kilograms/hectare
Some typical operational cost data were available for the months of
September and October, 1972. These are summarized below:
Sept.
Oct.
Sludge
hauled
103 m3
3. 44
3.59
Cost
Percent
solids
1.84
1.44
Dry
tons
63
51.7
Labor
721
724
Fuel
93
118
Maint.
125
125
Deprec.
242
242
Inter-
est
114
114
Insur-
ance
26
26
$/
dry ?/_
Total
1,321
1,349
ton
20.80
26.09
«*
.38
.38
St. Cloud - The St. Cloud Wastewater Treatment Plant was designed for 13.2 x
103 m-Vday capacity but is being.operated at between (24.6 to 32.2) x
1(H m /day. The plant design includes primary and secondary (trickling
filter) sedimentation. The plant lies south of town, so the truck does not
go through the congested part of the city. Part of the sludge disposal city-
owned site is leased to a private farmer at $12.35 per hectare plus a per-
centage of the crop. The city also purchased the necessary farming equipment
(the cost of its use is incorporated in the lease cost to the farmer). Prior
to the landspreading operation the site was barren farmland with extremely
sandy soils. Since then, large amounts of sludge have been applied and incor-
porated into the soil and the site is now reasonably productive farmland.
The principal crops grown are corn, soybeans, and alfalfa. Crop re-
sponse is very good without the use of supplementary fertilizers. The
farmer had the highest soybean yield in the area in 1972. The corn
yield was also excellent (an adjacent farmer tried to grow corn for
silage but plants grew only 35.6 cm tall).
The wet weather is not much of a problem. Sandy soils are well drained.
Under extremely wet conditions, the farmer plows furrows perpendicular
to the road (the field slopes away from the road) and liquid sludge is
unloaded into these furrows and plowed under at a later time. In winter
the city uses a snowplow to make a path in the field wide enough for the
79
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truck to dump the sludge. Often, there are .91 to 1.2 meters of snow
on the frozen fields.
The equipment used is an International tractor (gasoline fueled) with
27.6-m^ and 11.4-m^ trailer tanks. Both tractor and trailer are
equipped with tandem axles. Single axle units did not work out well.
The 11.4-m-^ trailer is rarely used except when load limits are imposed
on the roads. The landspreading operation is conducted by one full-
time driver who is held responsible for the truck. The sludge normally
contains 2.5 to 5 percent solids and is stored in an unheated secondary
digester prior to being loaded into the trailer. About five 27.6-m3
loads per day are spread on the farm in a normal 5-day work week.
The city will build a new 68-76 x 10-^ m^/day plant on 2.8 hectares of
the 122-hectare site so that future landspreading will be adjacent to
the plant. They are very pleased with landspreading and have encoun-
tered no major problems. Prior to the adoption of landspreading in
1958, drying beds were used to dewater the sludge. Dewatering was
slow because of cool, humid weather, and the sludge sometimes required
years to reach the desired degree of dryness. Sludge removal by hand
with shovels was necessitated by the glass covering of the drying beds.
Inasmuch as this procedure was expensive and the dry sludge was spread
on fields and a golf course anyway, it was decided to try liquid sludge
spreading.
Ohio Plants
Defiance - This 15.1 x 10-* m^/day secondary treatment plant treats
about 50 percent domestic wastes and 50 percent industrial wastes and
has utilized landspreading for the disposal of anaerobically digested
sludges (5-7 percent solids) for about 2 years. Approximately 151 m^
week are hauled away by a contractor in two 15.1-m^ tank trucks at a
cost of $1.72/nr. Assuming an average of 6 percent solids, this
amounts to about $28.6/dry ton.
The liquid sludge is spread on a 31.6-hectare cattle pasture owned by
the contractor. The tile-drained field located 16 kilometers from the
plant has outlets to the Auglaize River. Plans are being made to moni-
tor the underdrainage for fecal coliforms, phosphates, nitrates, and
phenols.
The city has also purchased a 9.1-m^ tank truck and has agreed to pay
a local farmer $1.66/m^ to spread the sludge on his cropland. The
plan includes monitoring of crop yields and soil response.
Lancaster - At this 38 x 10 nrVday plant the sludges produced from pri-
mary and secondary (low-rate trickling filters) sedimentation are an-
aerobically digested. The liquid-digested sludge normally averages about
4.75 percent total solids (53 percent volatile) and has a pH value of
80
-------
6.7-6.8. Domestic wastes were estimated to account for 80-85 percent
of the sewage influent.
Landspreading has been practiced since 1961 on 25.9 hectares of farmland
adjacent to the treatment plant. The land, purchased by the city for
the disposal of liquid digested sludge, continues to be cultivated by a
local farmer. Sand-drying beds were once used but were abandoned
because of high costs and operational problems. A vacuum filter was
installed, but similar problems with the vacuum filter led to the
decision to adopt landspreading. The vacuum filter, however, is
maintained in an operational state and utilized when weather conditions
preclude landspreading. When the vacuum filter is used, the filter cake
is stockpiled at the plant and made available to the public. If weather
permitted spreading of all the sludge, some 12.6 irH would be applied via
a 4.2-m3 tank truck to the 25.9-hectare field.
During the nongrowing season, liquid sludge is applied to all 25.9 hect-
ares at an annual application rate estimated to be about 11.1 tons/ha.
During the growing season, however, sludge is applied to only 12.95
hectares, yielding an annual application rate of 22.2 tons/hectare. The
remaining 12.9 hectares are farmed by a local farmer via the following
rotation scheme. The center of the field is farmed one year with
sludge applied to the perimeter area. During the following year sludge
is applied to the center portion where the perimeter is farmed. Sludge
application ceases on the portion to be farmed immediately after plow-
ing.
In 1972, 6.5 hectares each of field corn and popcorn were planted. Since
the city does not receive any income from this operation, no data were
available on crop yields. It was reported, however, that the farmer
produces a marketable commodity. It was also believed the fanner util-
ized supplemental fertilization, but no data were available on the amount
or type used.
Operational monitoring at the site is not conducted and a sludge analysis
beyond that mentioned above was not available. Furthermore, the costs of
the landspreading operation are not recorded.
Plans are under way to upgrade and expand the treatment plant, and
landspreading will be continued as the preferred means of sludge
disposal.
Sidney - Anaerobically digested liquid sludges from this 7.6 to 1C)3 m^/da
activated sludge plant have been spread on farmland for 14 years. Inflow
to the plant was estimated to be about 50 percent domestic wastes and 50
percent industrial wastes, with the industrial input stemming from an
aluminum ore reduction plant. The sludge normally contains about 3.5
percent solids and the following detailed sludge analysis was available.
All values are in mg/JL,
81
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TKN - 770 Mn - 16
NH3 73 NA - 245
P - 3,300 Cr - 47
K - 62 Fe - 296
Al - 2,400 Ca - 960
Cu -25 Zn - 148
Mg - 275 S04 - 26
They are presently experimenting with a Calgon polymer (WT 3000) to
further concentrate the solids to 6 percent.
Presently, the landspreading operation is conducted by plant personnel
using a 7.6-m^ tank truck. The sludges are hauled to 11 farms located
within 2 to 10 kilometers of the plant site, but they are presently
seeking additional farmland. Soil and crop response data were not
available, but some farmers are reported to have indicated increases
^ "-i *^
in annual corn yields of about 1.74 m-Yhectare. About 34 x 10J m
of liquid sludge were hauled to farmland in 1972 at a rate of about
114 nrVday. No exact cost accounting is conducted relative to the
landspreading operation, but the plant superintendent estimated daily
costs to be about $36.55/day. This figure reflects only labor and
fringe benefits and fuel costs, as depreciation and maintenance costs
were not available. Using these figures, 1972 hauling costs were about
$10,965 or $9.19/dry ton of solids ($0.32/m3). A contract hauler had
been used occasionally at a rate of $1.06/m3. The plant personnel had
also tried sub-sod injection of the liquid sludge, but gave up this
practice because (1) it was too slow, (2) if the soil is very stony
the injectors would jump out of the ground, and (3) if the soil is
frozen, sub-sod injection cannout be used. Spray irrigation was also
suggested , but this method was rejected by the State EPA.
The plant and landspreading operations have been experiencing some bad
public relations lately due to the construction of some expensive homes
on the farmland above the plant and in and along the areas where sludge
is being spread. They do not expect the problem to improve, thus they
are seeking new landspreading sites. No pre-or postsite environmental
studies have been conducted. However, prior to its use, each site must
be checked and approved by a sanitarian from the County Health Depart-
ment.
Springfield - Landspreading of liquid sludges has been used at this
94.6 x 10^ itrVday plant for the past 10 years. The sewage influent
82
-------
is approximately 85 percent domestic wastes and the sludges produced
by sedimentation and high-rate trickling filters are anaerobically
digested. A typical sludge from this plant has a solids content
of 8.6 percent (40 percent volatile) and a pH of 7.0. The plant has an
operational vacuum filter, but it has not been used since landspreading
was determined to be a cheaper and more easily managed sludge disposal
method.
3
When the vacuum filter operation was discontinued, a 11.4-m tank truck
(diesel) equipped for gravity-flow discharge and spreader bar distri-
bution was purchased and a special dock constructed to facilitate load-
ing. The loading arrangement consists of a 10-cm counterweighted
loading boom, an electrically operated switch located at the outlet for
operator convenience and control, and a 2.65-m /min centrifugal pump to
pump the sludge into the truck directly from the secondary digesters.
Through personal contact with local farmers and a news release in the
local paper relative to the benefits of liquid digested sludge, adequate
amounts of agricultural land were obtained for sludge disposal. At the
present time, ten farms with land either in "soil bank" or planted in
forage crops are available for sludge disposal on a rotating basis. The
hauling distance to the farms most often used is approximately 16 kilo-
meters round-trip, with the round-trip to other farms being about 29 kilo-
meters .
During periods when weather does not permit landspreading, the sludges
are disposed of in a 4.9 hectare lagoon located on the plant grounds.
When dry, the sludge cake is removed for disposal in a city landfill.
Data relative to the landspreading operation (i.e., costs, application
rates, etc.) have not been routinely recorded to date. However, 6 years
of records (1967-1972) were available for the amount of sludge spread
on the land and the amount of sludge pumped to the lagoon. These records
show that some 40 percent (41 x 10^ m3) were disposed of to the land while
60 percent (64 x 10 m ) were lagooned.
In the absence of explicit operational data, some crude estimates of the
cost of this landspreading operation were prepared using 4 years of data
from the Springfield plant and operation and maintenance costs obtained
from another landspreading operation which used a similar tank truck.
These are summarized as follows:
Sludge $/
hauled Percent Dry Costs $/ dry
10-^ nH solids tons Labor Fuel Maint. Deprec. Total m ton
24.9 8.6 2,359 12,056 536 2,400 4,384 19,376 0.58 9.05
83
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Sludge application rate data were not available, as records are not kept:
regarding the amounts of sludge hauled to each site. No soil or crop
response information was available, nor is any environmental monitoring
of the site being conducted. Essentially, the truck driver and farmer
use their own judgment as to the sludge applications.
Xenia - Landspreading of liquid sludges has been utilized by Xenia's
two 3.8 x 10 m-Vday sewage treatment plants for about 13 years. Both
anaerobically and aerobically digested sludges are being disposed of via
landspreading. The sludges which are anaerobically digested at the Glady
Run Plant are derived from primary and secondary (activated sludge) treatment
operations. The Ford Road Plant sludges are from sedimentation from
an activated sludge system.Typically, the sludges average about 2.3-3.5
percent solids (69-74 percent volatile) and have an average pH of 7-7.2.
The sewage input to these plants is essentially 100 percent domestic
wastes. Although a vacuum filter has been installed at the Glady Run
Plant and provisions have been made for a vacuum filter at the new Ford
Road Plant, landspreading of liquid sludges continues to be the method
of disposal.
Presently, the sludge is spread on farmland used to grow field corn,
wheat, and forage crops and on pastureland used for cattle grazing. Dur-
ing the growing season the liquid sludge is hauled extensively to pas-
turelands with the cattle remaining in the fields during the spreading
operation. Thus far, only two farmers have complained about the sludge
and discontinued its use. The reasons advanced for this discontinuance
were that the sludge contained too many weed seeds and that the sludge
killed the ants in the field. At the present time, ten farms are being
utilized to receive the digested sludge. These farms were obtained pri-
marily through advertisements in the local newspaper.
One full-time driver is employed to haul the sludges from both of the
city's plants using an over-the-road tractor-trailer unit with a tank
capacity of 11.4 m^. This is a cumbersome unit for use in the fields
so it frequently gets stuck and must be towed out with other city-owned
equipment. Maintenance costs and driver qualifications are also higher
for this type of unit than for operation of a normal tank truck.
The landspreading operation is conducted throughout the year. However,
during adverse weather conditions the sludges are disposed of with no
further attention on old sand-drying beds at an abandoned sewage treat-
ment plant. Plant personnel conservatively estimated that 3.8 x 10^ m^
of sludge were disposed of in this fashion during the wet weather of
1972. The environs along the transportation route are essentially rural
when hauling to the farmlands. However, when hauling to the abandoned
treatment plant, the route is through the main business district and
residential areas.
Two years of operational data were available and are summarized as
follows:
84
-------
Sludge $/
hauled Percent Dry Costs $/ dry
1Q3 m solids cons Labor Fuel Maint. Deprec. Total m ton
1971 8.69 3.5 304 7,696 236 271 2,400 10,603 1.22 34.89
1972 15.7 3.5 550 6,698 442 1,304 2,400 10,843 .69 19.72
No environmental site monitoring is conducted nor are data available
relative to sludge application rates, soil and crop response, etc.
3 3
Zanesville - The sewage influent to this 94.6 x 10 m /day primary treat-
ment plant is essentially 90 percent domestic wastes and 10 percent in-
dustrial wastes which stem from a metal plating firm and a slaughter-
house. The sludges are anaerobically digested and the solids content
averages about 10 to 13 percent. Prior to the initiation of land dis-
posal of the liquid digested sludge, a vacuum coil filter was utilized
to dewater the sludge. The sludge cake was then stockpiled and made
available free of charge to the general public.
The decision to utilize land disposal of the liquid sludge was made be-
cause of excessive maintenance problems associated with the coil filter
in the form of stretching of the coils and, even more troublesome, prob-
lems associated with clogging of the filters with livestock hair from
the slaughterhouse operation. Although operational, the coil filter
has not been used since the landspreading was initiated. The filter
well, however, is utilized to store digested sludge for transfer to a
6.1 m3 tank truck which was purchased to transport and spread the sludge.
A self-priming centrifugal pump mounted on the tank truck provides for
both suction to fill the tank truck and pressure to discharge the sludge.
Various city-owned or leased sites such as municipal parks, football
fields, abandoned city landfills, treatment plant grounds, and a 1.6-
hectare weed field adjacent to the plant are used for the landspreading
operation. Liquid sludge application to the park areas is restricted
to the nonrecreational seasons and excellent grass cover was noted at
all such sites. Occasionally, farmland or abandoned strip mine areas
are also utilized. In fact, a very good example of land reclamation
with liquid sludge was encountered here. About 3 years ago, approxi-
mately 3.8 x 10^ m of sludge were applied to a strip-mined area
which was then seeded. Even with no further sludging, the area has con-
tinued to exhibit sufficient grass growth to support cattle grazing.
One other attempt at land reclamation was noted in that grass seed was
added to a load of liquid sludge and the mixture applied to an abandoned
landfill. Although grass cover was obtained, this practice has not been
utilized since.
The 1.6-hectare field adjacent to the plant receives approximately 75
percent of the plant's sludge output. Based upon an average of 4 years'
data, sludge application rates to this field run about 309 tons/ha/year.
85
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However, this is a sludge disposal operation, only, as the field does not
produce a crop. Ready access to this level 1.6-hectare field enables the
land disposal operation to be conducted throughout the year even in ex-
tremely wet weather conditions.
Four years of operational data for this land disposal operation are sum-
marized as follows:
Sludge $/
hauled Percent Dry Costs $/ dry
10-^ m solids tons Labor Fuel Maint. Total m ton
1969
1970
1971
1972
5.84
5.39
5.67
4.78
10.0
13.0
12.4
12.4
584 1,753
700 1,170
702 1,430
592 1,436
133
168
230
221
362
457
360
331
2,248
1,795
2,020
1,988
.39
.33
.36
.42
3.85
2.57
2.88
3.35
No pre- or postoperational site monitoring is conducted, and data relative
to an extensive sludge analysis and sludge application rates other than as
estimated above are not recorded. The plant is presently being expanded
and upgraded and the present plans call for a continuation of the land
disposal activities.
Wisconsin Plants
Beaver Dam - The sludges produced by sedimentation and low-rate trickling
filters are anaerobically digested at this 16.8 x 10^ m /day plant. The
sewage influent was estimated to be 70 percent domestic wastes and 30
percent industrial wastes. The liquid digested sludge normally contains
about 6.4 percent solids (41 percent volatile) and has a pH value of 7.2-
7.3. Prior to the use of landspreading, open-drying beds were employed
to dewater the sludge, which was then given away to the general public.
However, climatic conditions would not allow adequate drying and the de-
cision was made to switch to landspreading for the disposal of liquid
sludge.
Land was secured by personal contact with local farmers, or, in some cases,
farmers would request the liquid sludge after observing the beneficial
effects on other fields. The land utilized includes both pastureland and
cropland. Soil and crop response data are not solicited from the farmers,
nor is any environmental monitoring conducted.
A 5.7-m tank mounted in the bed of a dump truck is used to haul and
spread the liquid digested sludge. The truck is obtained from the City
86
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Motor Pool as needed at a cost to the plant of $3/hour. The plant per-
sonnel try to spread the sludge within 8 kilometers of the plant.
Operational data available for 1971 are summarized as follows:
Sludge
hauled
103 m3
Percent
solids
Dry
tons
Truck
rental
costs
Labor
costs
Total
cost
$/
$/
dry
ton
3.91 6.4 250 1,707 2,077 3,784 .97 15.11
3 3
DePere - At this 11.4 x 10 m /day plant primary and waste activated
sludges undergo anaerobic digestion prior to being disposed of via
landspreading by a contract hauler at a cost of .11)^ /liter. The liquid
digested sludge averages 3.6 to 3.9 percent solids (50-55 percent vola-
tile) and has an average pH value of 6.9. While the influent to this
plant is primarily of domestic origin, it has a high industrial BOD load-
ing stemming primarily from a dairy products operation.
Prior to using landspreading, open sand beds were used to dewater the
sludge. Increased sludge volumes and drying problems led to the decision
to dispose of the sludge via landspreading in the liquid state. The con-
tract hauler owns an 8.9-hectare field which includes a 4.45-hectare la-
goon. When weather permits, the contractor spreads the liquid sludge on
a 4.5-hectare plot which will eventually be planted in field corn.
During those periods when weather does not permit landspreading (spring
and winter months, primarily), the sludge is disposed of in the 4.45-
hectare lagoon.
3 3
About 312 m of sludge are hauled each week. A 20.8 m tanker is used by
the contractor to haul five loads/day, 3 days/week. This amounts to some
16.14 x 103 nP/year (614 dry tons/year). At the rate of .1Q6£ /liter the
cost of disposal would be $17,056/year or $1.06/m3 ($28.66/dry ton).
It was reported that while the State Department of Natural Resources does
not require operational monitoring of the site, it must approve the land-
spreading site prior to its use.
3 3
Kaukauna - This 9.46 x 10 m /day activated sludge plant treats essential-
ly domestic wastes and has practiced landspreading of anaerobically di-
gested liquid sludge for the past 3 years. The sludge from the primary
clarifiers and the waste activated sludge from the final clarifiers under-
go both primary and secondary digestion. The resulting liquid sludge
averages 4.8 to 6.2 percent solids (42-50 percent volatile) and has a pH
value of 7. A vacuum filter was previously used to dewater the sludge,
which was then hauled to a landfill. Upon the recommendation of their
consulting engineers, the plant management abandoned the vacuum-filter
87
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3
and now dispose of the liquid sludge on nearby farmland. A 3.8-m gaso-
line tank truck was purchased and modified to haul liquid sludge by re-
moving the tank partitions.
The landspreading sites are privately owned farms used to grow field corn
and forage crops. Some pastureland is also used. This land was secured
through personal contact with the local farmers. While no soil or crop
response data were available, it was reported that tomato seeds contained
in the sludge were an occasional problem to the farmers and that supple-
mentary fertilizers were most probably used.
Only one complaint was expressed regarding the landspreading operation.
On one occasion sludge was spread near a public park and children play-
ing in the park area got into the wet sludge right after it was spread.
Numerous complaints were received from the parents of those involved.
Under adverse weather conditions the sludge is disposed of in a sludge
lagoon located on the plant grounds. For a normal year, however, about
80 percent of the sludge is spread on farms.
Some operational data were available for 1972 and are summarized as
follows:
Sludge
hauled
103 m3
Percent
solids
Dry
tons
Labor
cost
Fuel
cost
Ma int.
cost
Total
cost
$/
m3
$/
dry
ton
1.59 5.6 89 1,251 187 696 2,134 1.34 24.01
3
Oshkosh - Landspreading of liquid sludges was initiated at this 37.9 x 10
m /day plant in April, 1973, as an interim measure during construction of
a new plant which is scheduled for operation in mid-1974. During this
construction period only primary (chemically assisted) treatment was pro-
vided. Prior to initiating this temporary landspreading operation, sand
drying beds were used to dewater the sludge. Construction activities have
removed the sand beds, thereby necessitating landspreading as a means of
sludge disposal.
88
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SECTION XII
REFERENCES
1. Fair, G. M., J. C. Geyer, and D. A. Olkun. Water and Wastewater
Engineering, Vol. 10 Water Supply and Wastewater Removal, Vol. 2.
Water Purification and Wastewater Treatment and Disposal„ New
York, John Wiley & Sons, Inc, 1968.
2. Anderson, M. S. Comparative Analyses of Sewage Sludges. Sewage
and Industrial Waste. _28:132-135, 1956.
3» Bertrand, G. and B. Benson. The Control of Zinc in the Principal
Foods of Vegetable Origin. Bui Soc Sci Hyg Aliment. JL6:457-463,
1928, and Ann Inst. Pasteur 43:386-393, 1929 (Abstract from Bibl
Minor Elements, 4th ed. _1:938. 1948).
4. Hegsted, D. Mark, John M. McKibbin, and Cecil K. Drinker. The
Biological, Hygenic and Medical Properties of Zinc and Zinc
Compounds. Supplement No0 179 Public Health Report, U. S. Public
Health Service. Washington, D. C. 1945.
5. Steel, E. W. Water Supply and Sewerage. New York, McGraw-Hill
Book Company, 1960.
6. Subcommittee on Utilization of Wastewater Sludge. Utilization of
Municipal Wastewater Sludge, WPCF Manual of Practice, No. 2. 1971.
7. Dean, R. B. and J. E. Smith. Properties of Sludges. (Presented at
EPA-USDA-Universities Workshop. Urbana. July 9-13, 1973.)
8. Cornell, Rowland, Hayes, Merryfield, and Hill. Wastewater Treat-
ment Study Vol. 1 and 2. Ruton, Virginia, 1972.
9. Convery, J. J. Treatment Techniques for Removing Phosphorus from
Municipal Wastewaters. Environmental Protection Agency, Water
Quality Office. Water Pollution Control Research Series, 17010.
January 1970. 38 p.
89
-------
10. Tatlock, Mo w. The Economic Preparation and Sale of Digested
Sludge as Commercial Fertilizer. Sewage Works Journal. _4:519-
524, 1932.
11. Anderson, M. S. Fertilizing Characteristics of Sewage Sludge.
Sewage and Industrial Wastes. .31(4):678-682, 1959.
12. Lunt, H. A. The Case for Sludge as a Soil Improver. Water and
Sewage Works. j.00(8) :295-301, 1953.
13. King, L. D. and H. D. Morris. Land Disposal of Liquid Sewage
Sludge. II-The Effect on Soil pH, Manganese, Zinc, and Growth
and Chemical Composition of Rye (Secole cereale L.). Journal
Environmental Quality. _1(4):425-429, 1972.
14. Anderson, M. S. Economic Potential in Utilization of Organics
Wastes. Agricultural Chemicals. (2):30-33; (3):41-42, 113-114,
1959.
15. Merz, R. C. Utilization of Liquid Sludge. Water and Sewage
Works. _106:489-493, November 1959.
16. Ewing, B. B. and R. I. Dick. Disposal of Sludge on Land, Water
Quality Improvement by Physical and Chemical Processes. Austin,
University of Texas Press, 1970.
17. Stone , A. R. Disposal of Sludges on Land. The Institute of
Sewage Purification, Journal and Proceedings:Part 5, paper 3.
1962.
18. Hinesly, T. D. and Ben Sosewitz. Digested Sludge Disposal on
Crop Land. Journal Water Pollution Federation. .41(5, pt. 1):
822-830, May 1969.
19. Goldstein, J. Transporting Wastes to Build Soils. Compost
Science, p. 22-24, September-October 1970.
20. King, L. D. and H. D. Morris. Land Disposal of Liquid Sewage
Sludge. I-The Effect on Yield, In Vivo Digestibility, and
Chemical Composition of Coastal Bermuda Grass (Cynodon dactylon
L. Pers). Journal Environmental Quality. J.(3):325-329, 1972.
21. Andersson, A. and K. 0. Nilsson. Enrichment of trace elements
from Sewage Sludge Fertilizer in Soils and Plants. Ambio.
1(5):176-179, October 1972.
90
-------
22. Larson, W. E., C. E. Clapp, and R. H. Dowdy. Interim Report on
the Agricultural Value of Sewage Sludge. Metropolitan Sewer
Board, St. Paul, Minnesota. November 1972.
23. VanLoon, J. C. and J. Lichwa. A Study of the Atomic Absorption
Determination of Some Important Heavy Metals in Fertilizers and
Domestic Sewage Plant Sludges. 4(L):l-8, 1973.
24. Grant, G. M. Preliminary Analysis of Urban Wastes. Marine
Science Research Center, Technical Report, State University of
New York, Stony Brook, New York. March 1970.
25. Farrell, J. B., J. E. Smith Jr., S. W. Hathaway, and R. B. Dean.
Lime Stabilization of Chemical-Primary Sludges. Journal Water
Pollution Control Federation. 4-6 (1, st. 1): 113-122, January
1974.
26. Treibel, W. Experience With Sludge Pasteurization at Niersver-
band; Techniques and Economy. International Research Group on
Disposal (IRGRD). Information Bulletins Numbers 21-31. August
1964-December 1967.
27. Dotson, G. K., R. B. Dean, and G. Stern. Cost of Dewatering and
Disposing of Sludge on the Land. Chemical Engineering Progress
Symposium Series, 129, AIChE, Water. 1*972.
28. Personal Communication with Mr. G. K. Dotson, Ultimate Disposal
Research Group, National Environmental Research Center, Environ-
mental Protection Agency, Cincinnati, Ohio.
29. Mayrose, D. T. and J. J. Walsh. Heat Conditioning of Sewage
Sludge--Dorr-Oliver's Farrar System. (Presented at the New York
Pollution Control Association Meeting. January 1973.)
30. Hinesly, T. D., 0. C. Braids, and J. E. Molina. Agricultural
Benefits and Environmental Changes Resulting from the Use of
Digested Sewage Sludge on Field Crops. U. S. Environmental
Protection Agency. Solid Waste Demonstration Grant G-06-00080,
An Interim Report on a Solid Waste Demonstration Project.
1971.
31. Koser, A. The Use of Sewage and Sewage Sludge in Agriculture
from the Point of View of Veterinary Hygiene. Schr -Reih
Kuratoriums Kulturbauw No. 16. 1967.
91
-------
32. Thompson, T. L., P. E. Snoek, and E. J. Wasp. Economics of
Regional Waste Transport and Disposal Systems. Chemical
Engineering Progress Symposium Series. J57(107):413-422, 1970.
33. Raynes, B. C. Economic Transport of Digested Sludge Slurries.
Journal Water Pollution Control Federation. ^2:1379, 1970.
34. Sparr, A. E. Pumping Sludge Long Distances. (Presented at the
43rd Annual Conference of Water Pollution Control Federation,
Boston, Massachusetts. October 4-9, 1970.)
35. Bell, R. M. Sewage Sludge Disposal. Ontario Water Resources
Commission-Division of Plant Operations. November 1971.
36. Riddell, M.D.R. and J. W. Cormack. Selection of Disposal Methods
for Wastewater Treatment Plants. Proc. 10th Sanitary Engineering
Conference, University of Illinois. Bulletin 65(115):131, 1968.
37. Technical Aspects of Pipelining of Waste Materials, Bechtel
Corporation. Federal Water Pollution Control Administration
Waste Management Study. 1969.
38. Keckroth, C. Here Come the Sludge: Are You Really Ready for It?
Water Wastes Engineering. November 1971.
39. Burd, R. S. A Study of Sludge Handling and Disposal. Federal
Water Pollution Control Administration. Publication WP-20-4.
May 1968.
40. Sabey, B. R., J. Danford, and H. H. Champlin. Denver Sewage
Sludge Recycled on the Land. Compost Science. J.4(l):4-6, Janu-
ary-February 1973.
41. Evans, J. 0. Ultimate Sludge Disposal and Soil Improvement.
Water Wastes and Engineering. June 1969.
42. Israelsen, 0. W. and V. E. Hansen. Irrigation Principles and
Practices. New York, John Wiley & Sons, Inc., 1965.
43. Hajek, B. F. Chemical Interactions of Wastewater in a Soil
Environment, Journal of Water Pollution Control Federation.
.41(10): 1775-1786.
44. Personal Communication with Mr. A. P. Troemper, Executive
Director, Springfield Sanitary District, Springfield, Illinois.
92
-------
45, The Interdepartmental Committee on Sludge Disposal. Interim
Guidelines for Disposal of Sludge by Land Application. Toronto,
Ontario, Canada. 1972.
46. Flach, K. W. Land Resources. (Presented at EPA-USDA Universities
Workshop. University of Illinois, Urbana. July 9-13, 1973.
47. Quon, J. E. and G. B. Ward. Convective Drying of Sewage Sludge.
International Journal of Air and Water Pollution. _9:311-322,
1965.
48. Quon, J. E. and T. A. Tamblyn. Intensity of Radiation and Rate
of Sludge Drying. Journal of Sanitary Engineering Division,
Proceedings of the American Society of Civil Engineering.
.91(SA2):17-31, April 1965.
49. Thomas, R. E. and J. P. Law, Jr. Soil Response to Sewage
Effluent Irrigation. (Presented at the Symposium on the Use of
Sewage Effluent for Irrigation. Louisiana Polytechnic Institute,
Ruston. July 1968.)
50. McGauhey, P. H. and R. B. Krone. Soil Mantle as a Wastewater
Treatment System. Berkeley, California. University of California
SERL Report No. 67-11. 1967. 201 p.
51. McGeorge, W. T. The Base Exchange Property of Organic Matter in
Soils. 2nd International Congress Soil Science. _3:111, 1930.
52. Skulte, B. P. Agricultural Values of Sewage. Sewage and Indus-
trial Waste. _25:1297-1303, November 1953.
53. Dotson, G. K. Constraints to Spreading Sewage Sludge on Cropland,
Advanced Waste Treatment. U. S. Environmental Protection Agency.
May 1973.
54. Rohde, G. The Effects of Trace Elements on the Exhaustion of
Sewage-Irrigated Land. Journal and Proceedings, Institute of
Sewage Purification. (6):581-585, 1962.
55. Conn, R. L. Liquid Sludge as a Farm Fertilizer. Compost
Science. (5-6):24-25), May-June 1970.
56. Dean, K. C0, R. Havers, and E. G. Voldez. Utilization and
Stabilization of Solid Wastes. Proceedings Ontario Industrial
Wastes Conference, June 1969.
93
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57. Molina, J.A.E, 0. C. Braids, T. D. Hinesly, and J. B. Cropper.
Aeration-Induced Changes in Liquid Digested Sewage Sludge. Soil
Science Society of America Proceedings. J35:60-63, 1971.
58. Krone, R. B. The Movement of Disease Producing Organisms Through
Soils. Louisiana Polytechnic Institute. (Presented at the
Symposium on the Use of Sewage Effluent for Irrigation. Ruston.
July 1968.)
59. Tanner, F. W. Public Health Significance of Sewage Sludge When
Used as a Fertilizer. Sewage Works Journal. (7):611-617, July
1935.
60. Rudolphs, W., L. L. Falk, and R. A. Ragotzkie. Literature Review
on the Occurrence and Survival of Enteric, Pathogenic, and Rela-
tive Organisms in Soil, Water, Sewage, and Sludges, and On Vege-
tation. Sewage and Industrial Wastes. (22), September 1950.
61. Dunlop, S. G. Survival of Pathogens and Related Disease Hazards.
Louisiana Polytechnic Institute. (Presented at the Symposium on
the Use of Sewage Effluent for Irrigation. Ruston. July 1968.)
62. Kenner, B. A., G. K. Dotson, and J. E. Smith, Jr. Persistence of
Pathogens in Sludge Treated Soils. EPA-NERC, Cincinnati, Ohio.
Internal Report. September 1971.
63. Seabrook, B. L. Irrigating with Liquid Digested Sludge. Compost
Science. .14(1): 26-27, January-February 1973.
64. Stone, R. Land Disposal of Sewage and Industrial Wastes. Sewage
and Industrial Wastes .25(4), 1953.
65. Winski, J. M. Chicago's Use of Sewage Sludge in Effort to Make
Strip-Mined Areas Fertile Again Stirs Controversey. The Wall
Street Journal, December 1, 1972.
66. Stone, A. R. Land in Sewage Purification. Journal of the Insti-
tute of Sewage Purification. _4:417-424, 1960.
67. Elazar, D. J., J. Schlesinger, J. Lockard, B. A. Stevens, and
R. M. Stevens. Green Lands-Clean Streams; Converting Sewage
Into Valuable Green Growth and Pure Water Through Land Treatment.
Temple University, Center for the Study of Federalism, Philadel-
phia, Pennsylvania. (Draft), 1972. 184 p.
94
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68. 92nd Congress, 2nd Session, Federal Water Pollution Control Act
Amendments of 1972. Report No. 92-1465. September 28, 1972.
69. Dalton, F0 E., J. E. Stein, and B. T. Lyman. Land Reclamation—
A Complete Solution of the Sludge and Solids Disposal Problem.
Journal Water Pollution Control Federation. 40(5):717-896, May
1968.
70. Carlson, C. W. and J. D. Menzies. Utilization of Urban Wastes
in Crop Production. Bioscience. ^1(12):561-564, June 1971.
71. U. S. Environmental Protection Agency, Office of Water Programs.
Inventory of Municipal Waste B'acilities: A Cooperative State
Report. 10 Vols. Environmental Protection Agency No. OWP-1.
1971.
72. U. S. Environmental Protection Agency, Office of Research and
Development. Fate and Effects of Trace Elements in Sewage Sludge
when Applied to Agricultural Lands: Environmental Protection Agency
No. 670/2-74-005. January 1974.
95
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1 REPORT NO.
EPA-670/2-75-049
3. RECIPIENT'S ACCESSIOI*NO.
4. TITLE AND SUBTITLE
REVIEW OF LANDSPREADING OF LIQUID MUNICIPAL SEWAGE
SLUDGE
5. REPORT DATE
June 1975; Issuing Date
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Thomas E. Carroll, David L. Maase, Joseph M. Genco,
and Christopher N. Ifeadi
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Battelle Memorial Institute
Columbus Laboratories
505 King Avenue
Columbus, Ohio 43201
10. PROGRAM ELEMENT NO.
1BB043; ROAP 21ASE; Task Oil
11. CONTRACT/K»»«X NO.
68-03-0140
12. SPONSORING AGENCY NAME AND ADDRESS
National Environmental Research Center
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
The objective of this study was to review and summarize existing information
regarding landspreading of liquid municipal sewage sludge. An extensive literature
review was conducted and an annotated bibliography is available as a separate report
from the NTIS. Emphasis was also given to obtaining information concerning the
number of sewage treatment plants currently using landspreading. A questionnaire
survey of 1909 sewage treatment plants in Federal Regions 2, 3, 4, 5, and 9 was
conducted and selected operations were visited. The information and data gathered
during the study are summarized relative to sludge characteristics, sludge handling
and distribution systems, economics of landspreading, sludge-soil-plant interactions,
public health considerations, land acquisition, and survey of sewage treatment plants
The survey indicated that about 21 percent of the plants in the study regions are
using landspreading routinely. Sixty-eight percent of the plants using landspreading
have been conducting the practice for less than ten years. Of this 68 percent, over
two-thirds have begun the practice only within the last five years.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
:. COSATI Field/Group
Sludge disposal
Operating costs
Public health
Sewage treatment
Surveys
Environmental effects
Landspreading
Sludge characteristics
Sludge handling
Soil conditioners
13B
18. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (This Report)
UNCLASSIFIED
21. NO. OF PAGES
106
20. SECURITY CLASS {Thispage)
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (9-73)
96
U 5 GOVERNMENT PRINTING OFFICE I975-&57-593/5389 Region No. 5-II
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