EPA-902/9-74-002
PRETREATMENT
AND
ULTIMATE DISPOSAL
OF
WASTEWATER SOLIDS
Sponsored by
U.S. ENVIRONMENTAL PROTECTION AGENCY, REGION II
and
DEPARTMENT OF ENVIRONMENTAL SCIENCE, COOK COLLEGE, RUTGERS UNIVERSITY
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PRETREATMENT AND ULTIMATE
DISPOSAL OF WASTEWATER SOLIDS
U.S. L.T-rcrr.'-Siics! F-foieclion Ap.t'
!*<•-;• on 5, Li;.v.ry (!•'[.-] 2J)
7/'Vest J?.CK-,O- b,;;i;ov.3:J, 12th
Chicago, II. GC60--i-3590
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The contents of these Proceedings do not necessarily reflect
the views and policies of the Environmental Protection Agency, nor
does mention of trade names or commercial products constitute en-
dorsement or recommendation for use.
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PRETREATMENT AND ULTIMATE DISPOSAL OF WASTEMATER SOLIDS
Proceedings of a Research Symposium Cosponsored
by the
United States Environmental Protection Agency, Region II
and the
Department of Environmental Science, Cook College, Rutgers University
Rutgers University
The State University of New Jersey
May 21 and 22, 1974
Edited by
Arnold Freiberger
Research and Development Branch, EPA, Region II
Published by the
United States Environmental Protection Agency, Region II
Gerald M. Hansler, P.E., Regional Administrator
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PRETREATMENT AND ULTIMATE DISPOSAL OF WASTEWATER SOLIDS
Greetings to Conference
Charles E. Hess
Dean of Cook College, Rutaers University
Table of Contents
SESSION 1: A. J. Kaolovsky, Cook College, Chairman
Overview of Sludge Handling and Disposal
J. B. Parrel 1
Elemental Analysis of Wastewater Sludges From 33
Wastewater Treatment Plants in the United States
B. V. Salotto
E. Grossman III
J. B. Farrell
Stabilization of Municipal Sewage Sludge by High
Lime Dose
C. A. Counts
A. J. Shuckrow
J. E. Smith
Thermal Degradation of Sludges
R. A. Olexsey
Page
1
23
73
127
SESSION 2: R. C. Olson, EPA, Region II, Chairman
Thickening Characteristics of Aluminum and Iron
Primary Sewage Sludges
S. W. Hathaway
J. B. Farrell
Dewatering of Physical-Chemical Sewage Sludges
D. J. Cook
197
* Not received in time for publication.
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Table of Contents
(Continued)
Page
Sludge Incinerators in Use Today That Meet The 237
Requirements of State and Federal Regulations
R. L. Kaercher
Economic Considerations for Planning Sewage 245
Sludge Disposal Systems
D. A. Derr
V. Kasper, Jr.
M. Gould
E. J. Genetelli
SESSION 3: E. J. Genetelli, Cook College, Chairman
Future Problems in Sludge Production and Handling 267
Systems
J. V. Hunter
EPA's Position on Ocean Disposal in the New York 283
Bight
R. T. Dewling
R. D. Spear
P. W. Anderson
R. J. Braun
Disposal of Sewage Sludge to Sea: United Kingdom 331
Experience and Practice
J. E. Portmann
Preliminary Summary of Sludge Degradation Studies 349
in a Marine Benthic Environment
W. P. Muellenhoff
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Table of Contents
(Continued)
Session 4: D. J. Baumgartner, EPA, NERC-Corvallis, Chairman
Bioassay Methods and Impact Evaluation of Ocean 391
Disposal Sites
D. Dorfman
J. M. McCormick
Evaluating the Impact of Sludge Discharge to 417
Santa Monica Bay, California
F. K. Mitchell
A Discussion of a Near Field Dispersion Model for 435
Sludge Discharges to Coastal Waters
W. F. Rittall
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Greetings to Conference
Pretreatment and Ultimate Disposal of Wastewater Solids
Dean Charles E. Hess
Cook College, Rutgers University
It is a pleasure to welcome you to the Cook College campus of
Rutgers University, It is very appropriate that you meet on the
campus of a College dedicated to the concern of man and his environ-
ment. As many of you know we had an earlier conference, jointly
sponsored by the Environmental Protection Agency and the College,
dealing with the land disposal of sewage sludge. It is important to
follow that conference with an exploration and evaluation of alternate
methods of pretreating and disposing of waste water solids.
We value the close association between the College and the Environ-
mental Protection Agency. Working together on a wide range of environ-
mental problems we hope through research and extension programs to pro-
vide answers to many of the serious environmental problems facing the
nation's most densely populated state.
I hope that you enjoy your visit to Rutgers University and if we
can do anything to make your stay more enjoyable or rewarding, please
let us know. We are here to serve you.
VI 1
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vm
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OVERVIEW OF SLUDGE HANDLING
AND DISPOSAL *
fcy
J. B. Farrell **
For about 8 years, the Advanced Waste Treatment Research Laboratory,
which is now part of U. S. Environmental Protection Agency's National
Environmental Research Center, Cincinnati, has had an Ultimate Disposal
Section. A primary objective of this group has been to advance the
technology for processing and disposing of the concentrates from muni-
cipal and advanced wastewater treatment processes. It has thus been
our privilege to observe and to take part in the effort to improve the
methods for handling and disposal of wastewater sludges.
As the quality of wastewater treatment has improved, sludge handling
and disposal have become a greater problem. The trend is not expected
to change. As more and more municipalities upgrade facilities to improve
effluent quality, the quantity of sludge will continue to increase.
Table 1 compares sludge production in 1972 with the estimated production
in 1985: the amount of secondary treatment sludge will be almost doubled,
and chemical sludges will be produced in quantity; dewatering costs will
increase more than proportionately because the biological secondary
sludges and several important types of chemical sludges are unusually
difficult to dewater.
* Presented at Research Symposium on Pretreatment and Ultimate Disposal of
Wastewater Solids, Rutgers University, New Brunswick, N.J., May 21-22,
**Acting Chief, Ultimate Disposal Section, Treatment Process Development
Branch, Advanced Waste Treatment Research Laboratory, National Environ-
mental Research Center, U. S. Environmental Protection Agency,
Cincinnati, Ohio 1*5268.
1
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The operations carried out on wastewater sludge are conveniently
divided into treatment operations, such as pumping, thickening,
stabilization, and dewatering; and disposal operations, which include
incineration, landfill, and landspreading. The more important recent
developments in treatment are considered here first.
TREATMENT OPERATIONS
Thickening
If sludges removed from primary and secondary clarifiers are to
be dewatered, their solids content should be as high as possible,
that is, Just short of the point where the "thick" sludge interferes
with the operation of the device used for dewatering. Thickening is
often required. The most commonly used devices are either gravity or
air flotation thickeners. Air flotation thickeners are generally more
expensive to operate, but have advantages in certain cases. There is
less opportunity for sludge to become anaerobic, because residence time
is less than in a gravity thickener and air bubbles that have floated
the sludge provide a reservoir of available oxygen. In secondary
plants where the effluent has nitrified, gravity thickening of waste
activated sludge becomes difficult because the respiring activated
sludge organisms use nitrate as their oxygen source after dissolved
oxygen is consumed. Nitrogen gas is released and this causes a portion
of the sludge to float. If air flotation is utilized instead of gravity
thickening, any tendency of sludge to float will, of course, be advan-
tageous.
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Stabilization
The conventional stabilization processes are anaerobic and aerobic
digestion. The effect of these processes is to reduce odor, reduce the
putrefaction potential of the sludge, and reduce the concentration of
hazardous microbiological organisms. It is interesting to separate
these positive results and consider other means by which they can be
carried out. Table 2 measures a number of processes against these
characteristics. It is evident that none of the processes do all
things veil. Further study of Table 2 indicates that certain combina-
tions of processes would be effective, for example, anaerobic digestion
followed by pasteurization. These two processes have been carried out
in sequence in Germany (l) to treat sludge used on pasture lands during
the summer months. Radiation has recently been used following anaerobic
digestion (2), again in Germany and for the same purpose.
Costs of combined treatment are additive. Recently, however,
there has been interest in the use of anaerobic or aerobic thermophilic
digestion. These processes can be operated at 60° C and destroy
pathogenic microorganisms. They effectively combine pasteurization and
stabilization into a single process, and economies can result.
Most stabilization processes adversely affect supernatants and
filtrates from subsequent dewatering operations: anaerobic digestion
and heat treatment produce supernatants rich in nutrients and BOD;
supernatant from heavy chlorination is high in chloramines and possibly
chloro-organic compounds; and supernatant from lime treatment is high
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in pH. Cost of processing supernatants must be considered in the total
cost of processing.
Processes such as digestion and heat treatment reduce the mass of
sludge to be treated in subsequent operations. These changes in mass
are a cause of great confusion in the literature when costs of complete
processing sequences are compared. Costs are most often presented as
dollars per ton of dry solids without specifying whether the basis is
the sludge mass before or after processing. An unequivocal way of
comparing costs of alternative processing sequences for a given waste-
water is to base costs on equal wastewater flow (e.g., ^/lOOO gal.
of wastewater).
Dewatering
Filtration—The continuous rotary vacuum filter is the most commonly
used device for dewatering wastewater sludges. Three different types
are used: the drum (cloth on drum, cake removed by doctor blade), cloth
belt (cloth belt winds off drum, sharp bend causes cake to drop off,
both sides of belt are washed, and cloth returns to drum), and coil
(filter surface comprises two layers of tightly coiled springs, other-
wise similar to belt type).
A new type of drum filter, utilizing top-feed, has been developed
by the Rexnord Corporation for the City of Milwaukee under an EPA grant
(see Figure l). Gravity assists in depositing coagulated solids, which
are denser than water, onto the drum surface. Gravity also assists in
removing cake from the filter surface, so air blowback to loosen cake
is not needed, and the doctor blade is nearly superfluous.
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Centrifuges—Solid-howl continuous conveyor-type centrifuges are
the most popular centrifugal device used for sludge dewatering. Cake
solids contents are similar to those obtained with vacuum filters.
These devices are also excellent classifiers. They are being used
with tertiary (3) and primary lime sludges (k) to classify organic and
most mineral solids except calcium carbonate into the centrate. The
cake is then high in calcium carbonate, which can be calcined and
recovered as CaO.
Basket-type centrifuges are being used to thicken aerobically
digested sludge. This type of centrifuge will be used to remove solids
from the centrate from Los Angeles County's solid-bowl conveyor-type
centrifuges (5).
Other Methods—Filter presses are receiving considerable interest
in the United States, particularly now that high cake solids is becoming
important. At Cedar Rapids, Iowa (6), a filter press has been installed
that uses a precoat of sludge incinerator ash and a body feed of
incinerator ash, lime, and ferric chloride. Vertical presses, used
at several plants in Japan, offer very speedy cake discharge. Precoat
is not needed because a section of the filter cloth is washed during
each cycle. The cloth advances one frame at each discharge cycle.
Thus, a section of cloth is washed after having performed a number of
filtrations equal to the number of frames. Ca(CH)2 and Fed? are the
usual conditioning agents with this filter at Japanese plants.
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Belt filters have been used extensively in Europe and are being
marketed in the United States. They combine gravity drainage with
mechanical pressure after a cake has been formed. The Carter* belt
filter, presented schematically in Figure 2, illustrates the principle.
The capillary suction filter developed by Westinghouse with the
financial support of EPA combines capillary suction dewatering with
mechanical pressure. A simplified sketch of the original research
unit is presented in Figure 3. Sludge is placed on a dry belt of a
foamed porous material, which removes moisture from the sludge by
capillary action. A contact roll rides directly on -toe partially
dewatered sludge layer and applies mechanical pressure. Water is
forced from the sludge into the porous belt. The sludge cake transfers
to the smooth-surfaced contact roll where it is collected and removed.
The porous belt, now free of sludge, is washed and squeezed dry.
Activated sludges, which can seldom be dewatered to over 15 percent
solids, can be dewatered to over 18 percent solids at high rates with
this device.
Conditioning
Very few sludges can be filtered without additives of some kind.
Lime and ferric chloride continue to be used, particularly when odors
are a problem or when improperly digested sludge is to be landfilled.
The use of organic polymeric conditioning agents continues to grow.
* Mention of manufacturer's names does not constitute EPA endorsement.
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The most rapid gains, however, have been made by heat conditioning.
Sludge heated to 200° C (392° F) for under an hour, in the presence
of air or without air, loses its gelatinous nature and becomes easily
filterable, generally without chemicals. A substantial portion of the
sludge, however, is solubilized and the filtrate must be recycled to
biological treatment.
Heat treatment is a satisfactory means for conditioning sludge.
Whether or not it is the most cost-effective depends on the situation.
The process requires a higher degree of operating skill than is
ordinarily available at wastewater treatment plants. It causes odors
that are sometimes extraordinarily difficult to eliminate. The
additional cost of biologically treating the filtrate (and handling
the increased biological sludge generated) should be charged to the
process. Even for plants with temporary excess capacity, the loss in
capacity caused by the need to process recycle streams must eventually
be borne by the wastewater treatment plant. In Great Britain, where
effluent quality requirements are more stringent than those in the
United States, separate treatment of the supernatant is needed. At one
facility, supernatant is being biologically treated by separate activated
sludge treatment, which is followed by activated carbon to remove
residual COD. At another plant, the entire supernatant will be con-
centrated by flash evaporation and the concentrate then incinerated.
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DISPOSAL OPERATIONS
Hazardous Substances
Disposal of sludge is turning out to be the pivotal question in
wastewater processing. Sludges contain the concentrated wastes of a
community. It is reasonable to expect that objectionable materials
may be present in sufficient concentration to be hazardous. The
degree of hazard will, of course, depend on the intended means of
disposal.
Some typical concentrations of hazardous substances found in
sludge are presented in Table 3. The hazardous substances are toxic
metals, toxic organic chemicals, and pathogenic microorganisms. The
concentration and quantities of these contaminants clearly limit
disposal options. For example, the high concentrations of pathogens
in raw sludge virtually prohibit disposal to landfill or to agricultural
land. Sludge with a high PCB concentration should not be applied to land
if there is a possibility of leaching. Sludge with high mercury content
may be suitable for disposal to a landfill but not for incineration.
There appears to be no foolproof disposal method suitable for all
sludges.
The type of disposal chosen by a community is a commitment not
easily changed. Increasing knowledge of hazards, or a change in the
nature of the community's wastes, may indicate that the wastewater
sludges contain too high a concentration of certain materials for the
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method of disposal practiced. Two things are necessary—the community
should have a current knowledge of the concentrations of hazardous
materials in its sludge, and it should have ordinances which allow
it to prohibit disposal into its collection systems not only wastes
which affect the quality of wastewater processing but also hazardous
wastes which are not "neutralized" by the disposal method and are a
threat to the environment.
The conventional disposal methods are ocean disposal, landspreading,
landfill, and incineration. A discussion of ocean disposal is beyond
the scope of this presentation. It appears at this time, however,
that disposal of sludge solids by outfalls or by dumping will diminish
in coming years, and that the level of hazardous materials in their
sludges will have to be reduced by communities continuing to use these
procedures.
Land Application
The use of stabilized sludge to fertilize agricultural land or
reclaim marginal land is a conserving use which has been practiced
for many years. Chicago plans to dispose of a major portion of their
sludge by this means (7)• Coastal cities are considering it as an
alternative to ocean disposal. Attention has been called to possible
hazard to crops and to human health from a gradual buildup of toxic
metals in soil to which sludge has been applied over a number of
years (8). The U. S. EPA is currently studying suggested guidelines
for land application of sludge.
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It is likely that some restrictions will be placed on the practice
of land spreading. Suggestions have been made to limit both the con-
centrations of metals such as Cd, Cu, Zn, and Ni in the sludge and
the maximum loading of sludges on the land (8), or the maximum
loading of the metals on the land (9). Knowledge of effects of metals
in sludge on crops is sparse, which makes preparation of reasonable
guidelines difficult. It is expected, however, that for communities
with an unusually high industrial component in their wastewater,
recommended application rates may be too low for this method to be
competitive with alternative disposal means.
Landfill
Disposition to landfill is the most common way to get rid of
sludge. Sometimes the landfill is a properly operated sanitary
landfill for disposal of solid wastes and sludge. Often the landfill
is an uncovered dumping site inside the plant grounds. Small plants
often dispose of their sludge to unprotected sites outside their plant
limits--sometimes in flood plains and often without cover.
Little attention has been paid to the disposal techniques practiced
by small plants. Disposal to sanitary landfills may be impractical
because of distance or because sludges are banned from the landfill,
and operators often resort to what is essentially uncontrolled dumping.
The EPA is sponsoring work by the U. S. Department of Agriculture to
develop a method for operating a private sludge landfill in an
ecologically satisfactory way with the use of simple farm machinery.
10
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A properly operated sanitary landfill is an excellent place to
dispose a sludge high in metals or persistent organic compounds. The
site should be located where groundwater contamination is not possible,
and any leachate should be collected and treated.
Incineration
When properly carried out, incineration is a satisfactory means
of disposing of the great majority of hazardous sludges. Particulates
must be contained by modern scrubbing equipment, and temperature-time
characteristics must be adequate to decompose thermally stable organic
compounds. Sludges containing mercury are an exception because mercury
vaporizes upon incineration and is not captured satisfactorily by
conventional scrubbers. Even mercury can be captured, however, if the
flue gases are brought to room temperature and filtered (10). A major
problem with incineration is poor operation; this can be corrected by
good operating procedures and modern control devices.
Trends in Disposal
There has probably not been a more difficult time for forecasting
disposal trends. The picture is very negative for ocean disposal,
although changes are possible. Land application will be subjected to
guidelines—guidelines that will recommend reduced application rates and
require more land; landfill is satisfactory, but suitable sites are
dimishing rapidly; incineration would appear to face a promising
future except that the high cost of fuel, added to the cost of air
pollution control equipment, has escalated the total cost.
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Promising areas for the future, which are nov being seriously
investigated, are co-incineration and co-pyrolysis of sludge with
solid waste. These methods will not require supplemental fuel.
Co-pyrolysis may produce usable fuel gas and char. When estimating
future disposal trends (Table l), incineration and pyrolysis increase
from 25 percent in 1972 to 35 percent in 1985. Much of this gain will
be from new methods of co-incineration and co-pyrolysis.
Certainly disposal costs, as a proportion of wastewater treatment
costs, will rise. The benefit will be a more secure environment for
now and for the future.
END
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LITERATURE CITED
1. Triebel, W., "Experiences with Sludge Pasteurization at Niersverband:
Techniques and Economy," Intern. Res. Group on Refuse Disposal (IGRD)
Inform. Bull. No. 21-31, Aug. 1964-Dec. 1967, pp. 330-390.
2. Suss, A., Ma'tsch, H., Bosshard, E., Schurmann, G., and Luscher, 0.,
Kerntechnik 3£, Jahrgang (197M, No. 2, pp. 65-70, "An Experimental
Irradiation Facility for the Sterilization of Sewage Sludge."
3. South Tahoe P.U.D., "Advanced Wastewater Treatment as Practiced at
South Tahoe," pub. U. S. EPA, 17010 ELQ 08/71 (Aug. 1971), Avail.
NTIS, No. PB 204 525.
h. Parker, D. S., Zadick, F. J., and Train, K. E., "Sludge Processing for
Combined Physical-Chemical-Biological Sludges," pub. U. S. EPA,
EPA-R2-73-250 (July 1973).
5. Parkhurst, J. D., Rodrigue, R. F., Miele, R. P., Hayashi, S. T.,
"Summary Report: Pilot Plant Studies on Dewatering Primary Digested
Sludge," pub. U. S. EPA, EPA-670/2-73-0^3 (Aug. 1973).
6. Gerlich, James W., "Pressure Filtration of Waste Water Sludge with
Ash Filter Aid," pub. U. S. EPA, EPA-R2-73-231 (June 1973).
7. Dalton, F. E., and Murphy, R. R., J.W.P.C.F., _{£, No. 7, 1^89-1507
(1973)) "Land Disposal IV: Reclamation and Recycle."
8. Chaney, R. L., "Crop and Food Chain Effects of Toxic Elements in
Sludges and Effluents," in Proc. of Joint Conf. on Recycling Municipal
Sludges and Effluents on Land, July 9-13, 1973 > Champaign, 111., pub.
Natl. Assn. of State Univ. and Land Grant Colleges (Wash., D.C.).
9. Page, A. L., "Fate and Effects of Trace Elements in Sewage Sludge
When Applied to Agricultural Lands—A Literature Review Study,"
pub. U. S. EPA, EPA-670/2-7^-005 (Jan. 1971*).
10. Perry, R. A., Chem. Eng. Progress, 70, No. 3, 73 (197M, "Mercury
Recovery from Process Sludges."
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TABLE 1
TRENDS IN PRODUCTION AND DISPOSAL
OF MUNICIPAL WASTEWATER SLUDGE
1972 1985
Popul. Dry tons**. Popul. Dry tons
SLUDGE TYPE (mill.) per year (mill.) per year
Primary (0.12 lb/cap-da)* 145 3,170,000 170 3,720,000
Secondary (0.08 lb/cap-da) 101 1,480,000 170 2,480,000
Chemical (0.05 lb/cap-da) 10 91,000 50 455,000
Percent Percent
DISPOSAL METHODS
Landfill 40 40
Utilized on land 20 25
Incineration 25 35
Ocean (dumping and outfalls) 15 0
* Ib x 0.454 = kg
** ton x 0.908 = metric ton
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TABLE 2
ATTENUATION EFFECT OF WELL-CONDUCTED TREATMENT PROCESSES
ON STABILIZING WASTEWATER TREATMENT SLUDGES
PROCESS
Anaerobic digestion
Aerobic digestion
Heavy chlorination
Lime treatment
Pasteurization (70° C)
Radiation
Heat treatment (195° C)
DEGREE OF ATTENUATION
Pathogens
fair
fair
good
good
excellent
excellent
excellent
Putrefaction
Potential
good
good
fair
fair
poor
poor
poor*
Odor
good
good
good
good
poor
fair
poor*
* good for filter cake
15
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TABLE 3
APPROXIMATE CONCENTRATION LEVELS OF SUBSTANCES
IN MUNICIPAL WASTEWATER SLUDGES
Sludge parameter
% Volatile solids
% Ash
Metal concentration
(rag/kg dry solid)
Cd
Zn
Cu
Ni
Hg
Bacterial content
(per 100 ml liquid sludge)
Fecal coliform
Salmonella
Pseudomonas aeruginosa
Organic compounds
(mg/kg dry solids)
Polychlorinated biphenyls
Chlordane
DDT
Dieldrin
Raw primary
72.0
28.0
11 x 106
460
46,000
Digested primary
52.6
4?.4
30
1,950
1,000
350
5
0.4 x
29
34
n.d.* to 105
3 to 30
n.d. to 1
0.1 to 2.0
* n.d. = not detectable
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Figure 1. Drum-Type Vacuum Filters
"Overview of Sludge Handling and Disposal"
by
J. B. Farrell
17
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00
TOP FEED
BOTTOM FEED
DRUM-TYPE VACUUM FILTERS
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Figure 2. Schematic of Carter Belt-Filter Press
"Overview of Sludge Handling and Disposal"
by
J. B. Farrell
19
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LIQUID SLUDGE
ro
SCHEMATIC OF CARTER
BELT-FILTER PRESS
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Figure 3. Schematic of Research Capillary Dewatering Unit
"Overview of Sludge Handling and Disposal"
J. B. Farrell
21
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1X5
ro
Sludge Feed
Cake
Filtrate
Sludge
Cake
Sludge
Compression
Roller
Capillary Dewatering Section
Belt & Screen Motion
Porous
Belt
Screen
Belt
Sludge
Cake
Screen
Wash
Figure 3. Schematic of research capillary dewatering unit
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ELEMENTAL ANALYSIS OF WASTEWATER SLUDGES FROM
33 WASTEWATER TREATMENT PLANTS IN THE UNITED STATES*
by
B. Vincent Salotto
Ernst Grossman III
Joseph B. Farrell**
Abstract
Sludges, principally of the digested type, from 33 municipal wastewater
treatment plants in the United States have been analyzed for 21 metals,
Nitrogen, Phosphorus, and Sulfur. The BTU value of some sludges was also
determined. Atomic absorption method was used for the determination of metals
in sludge. No detectable amount of beryllium was found in any sludge sample
analyzed and although very toxic, it evidently does not present a commonly
encountered hazard in the disposal of sludge.
Mathematical analysis of the data indicated that the distribution of
heavy metals in sludge is approximately log-normal. This behavior is charac-
teristic of all sludge types analyzed thus far. Levels of metals in essen-
tially domestic sludges were found to correspond closely to the 25th percentile
distribution of metals in all sludges reported. Comparison of the levels of
metals in the United States sludges with corresponding levels in Scandinavian
sludges show higher levels in the U. S. sludges. Variation of any particular
metal in sludges of a particular wastewater treatment plant was much less
than in sludge samples taken from different plants.
* Presented at Research Symposium on Pretreatment and Ultimate Disposal of
Wastewater Solids sponsored by the Environmental Protection Agency and the
Department of Environmental Science, Rutgers University, New Brunswick,
New Jersey, May 21-22, 1974.
** Research Chemist, Physical Science Technician, and Acting Chief, Ultimate
Disposal Section, Treatment Process Development Branch, AWTRL, National
Environmental Research Center, EPA, Cincinnati, Ohio 45268.
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The data collected are not sufficient to permit analyses of various
groupings of data so that the effect of factors such as industrial mix,
composition of the water supply, and the type of treatment can be identified.
As more data become available, such effects will be investigated. In the
near future, major emphasis of continuing work will be to more accurately de-
fine the composition of sludges produced by secondary treatment plants
processing municipal wastewaters from domestic sources.
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INTRODUCTION
The Ultimate Disposal Section of the U. S. Environmental Protection
Agency's Advanced Waste Treatment Laboratory, NERC-Cincinnati, has been
analyzing wastewater sludges for metals content for the past two and a half
years. The major purpose of this effort has been to determine for various
sludge types the kinds and levels of metals, especially toxic metals, in
sludge. Such interest on the part of EPA is in response to the national
interest in the impact of metals on the environment. The treatment and dis-
posal of municipal wastewater sludge, which is the primary concern of the
Ultimate Disposal Section, results in a residue which is disposed to land,
sea, or soil. One of the disposal means which may be limited by the presence
of high concentrations of toxic metals in the sludge is the use of digested
sludge as a fertilizer on agricultural land. It is essential to have adequate
knowledge of the concentrations of metals found in sludge in order to estab-
lish reasonable loadings of sludge on the land.
Initial impetus for the study of hazardous substances in wastewater
sludges came as a result of the formation of an EPA task force in the summer
of 1971. The task force was organized to determine the effects of sludge
incineration on air and land environment. Although emphasis then was on air
pollution, data about the sludges to be disposed were still of prime impor-
•tance. The results of the EPA task force have been published in 1971 which
showed wide variation of metal content of sludge (1), and occasionally high
levels of pesticides and polychlorinated biphenyls (2).
Municipal wastewater sludges contain a large proportion of cellulose
and fecal matter; they also contain a great variety of other undesirable
organic and inorganic wastes from household and business activities, including
25
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in some cases street runoff. Metal concentrations in wastewater vary from
plant to plant, from region to region, and from season to season. Usually,
the wastewater received by a wastewater plant represents a mixture of domestic
and industrial waste flows. Ordinarily, it is not possible to determine the
domestic or industrial component in a wastewater solely on the basis of the
metal analysis. For example, copper and zinc come from both domestic and
industrial sources. The presence of cadmium does not necessarily indicate an
industrial waste because it also may come from household piping and street
runoff (from auto tire wear). Similar cases can be cited for other metals.
The industrial component in a wastewater is best determined by a detailed
investigation of the contributors to the wastewater system.
The fate of metals through wastewater treatment processes depends to a
large extent on the chemistry of the metal, the type of biological system
employed, and the efficiency of each process step. An investigation of the
receipt and fate of metals through wastewater treatment was conducted by this
laboratory nine years ago (3). The wastewater treatment plants were surveyed
for four metals: chromium, copper, nickel, and zinc. Table 1 shows data
taken from that study of incoming and outgoing concentrations of the four
metals at each of the wastewater treatment plants. The last column shows for
'each metal at each plant the percent of the total incoming metal removed by
processing and immobilized in the sludges. Removal of any particular metal
was not uniform from plant to plant. For example, at Grand Rapids, Michigan,
16 percent of the total copper going through the plant was removed by the
sludge, but at the plant at Richmond, Indiana, the sludge removed 73 percent
of the copper. These data do not support the generally held belief that the
26
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greater part of the metal load going through a uastewater plant will end up
in the sludge. Metal removal from a process stream by sludge is an incom-
pletely understood mechanism; evidently many factors, peculiar to any one
plant and area served, must be studied before one can predict the fate of
metals through the process. Further information on the effects of metals
on biological wastewater treatment processes may be obtained from past pub-
lications of this laboratory (4).
Recycling sludge to the environment by landspreading is an especially
attractive method of disposal because it returns nutrients such as nitrogen,
phosphorus, and potassium back to the soil. This method has been in use
for centuries in several countries around the world, and is almost an ideal
recycling method. There is lately much concern that metals in the sludge
may accumulate in the soil to levels where they either are toxic to crops
directly, or are taken up by the crops and become hazardous to man or animals
that consume them. Webber (5) has documented some of the effects of metals.
The group of metals generally regarded as toxic are boron, cadmium, cobalt,
chromium, copper, mercury, nickel, lead, and zinc. Cadmium is of great
interest now because recent statistical studies indicate that an increase in
the body burden of cadmium may increase the incidence of heart disease (6).
The amount of metals a sludge may safely contain and the rate at which
sludge may be applied to the land depend on many factors relating to soil
condition, climate, crop type, and agricultural practices. Dotson (?) and
Chaney (8) have provided guidance and suggestions. Pluch research must be
done before accurate predictions of metal uptake by crops can be made.
Despite the incompletely developed state of knowledge, it is evident that
27
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the metal content of sludges must be known so that at the least the quantities
of metals in the sludges being applied to the land are known.
Generally, wastewater sludge is a brown to blackish, amorphous, hetero-
geneous, non-Newtonian liquid containing dissolved, colloidal, and suspended
solids. Its physical, chemical, and microbiological properties are largely
dependent on source of the waste, type of treatment producing the sludge,
and sludge-handling steps. Descriptive names for various type sludges refer
to the degree of stabilization or treatment. For instance, a digested or
digester sludge refers to a sludge stabilized by the anaerobic or aerobic
digestion procedure. Unstabilized sludges such as primary or waste activated
are referred to as raw sludges. Water content of sludges can range from as
little as 55 to 99.9 percent. It contains humus-type organic material, carbon,
nitrogen, phosphorus, sulfides, and major constituent metals such as silicon,
sodium, potassium, calcium, magnesium, aluminum, and iron. It contains a
host of minor or trace metals such as boron, chromium, cobalt, copper, cadmium,
lead, manganese, nickel, silver, and zinc. A trace metal can be present in
concentrations as high as 11,000 mg/Kg in the sludge on a dry basis. This
translates to 1.1 percent and is evidently no longer present in "trace"
amount.
COLLECTION AND ANALYSIS OF SLUDGES
From the summer of 1971 to January 1974, about 100 sludge samples have
been analyzed for content of metals and other constituents such as volatile
solids, nitrogen (1KN), phosphorus, sulfur, and heat of combustion. These
samples have been collected from 33 wastewater treatment plants in 13 states
of the U. 5. (see Fig. 1 and Table 2). They are not in any manner broadly
28
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representative of wastewater sludge around the country; nor have they been
selected according to a prearranged schedule. The analysis program was
commenced in response to the study by the EPA task force of the effects of
sludge incineration on land and air (1). Locations mere chosen at sites thought
to be suitable for incineration tests. Later sampling concentrated on the
Eastern Seaboard where the practice of ocean disposal was being questioned.
Also a sampling program was originated by the EPA regional staff in California
and by the Ultimate Disposal staff in Ohio, where it was convenient for this
laboratory group to collect samples.
The treatment plants sampled range in size from small plants in urban
communities (about 0.1 mgd) to large plants in the larger cities such as
Baltimore and Philadelphia (about 150 mgd). Some plants such as those along
the New York-New Jersey coastal tier area employ primary treatment only,
disposing or barging the digested sludge to an ocean dumping area. Waste-
water treatment plants with secondary aeration facilities produce waste-
activated sludges. Most plants employ anaerobic digestion of their sludge
so that a great percentage of samples received for analysis were digested
sludge.
A variable number of sludge samples were submitted by the 33 treatment
.plants. Some plants submitted one sample; others such as the Hillcreek
Plant in Cincinnati, Ohio, submitted 25 samples. To provide for equal sta-
tistical treatment of the data from the 33 plants, the results of the analyses
of any one plant were averaged and treated as one entry from that plant.
Obviously, no averaging was needed in those cases in which only one sample
of sludge was submitted.
29
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Routine tests on sludge were performed according to Standard Methods (9).
The heat of combustion tests were done using a Parr* bomb apparatus. A
pretreatment technique was employed in the analysis of metals in the sludge.
This step was necessary in order to convert metal forms to ionic soluble
forms capable of determination by the atomic absorption procedure. Analysis
proceeded using a weighed and dried sludge sample. A combination of nitric
and sulfuric acids was used to completely decompose the sample except for
residual silicious material that all sludge samples contain. As a final
step in the digestion procedure, a few milliliters of perchloric and nitric
acid mixture were used to clear and remove the last traces of charred organic
matter. There is nothing new about this pretreatment step except that other
laboratories may use other combinations of acids to decompose the sludge
sample. A reagent blank was carried through the metals analyses in order
to minimize errors due to contamination from glassware and reagents. Metal
concentrations in the blank were low, indicating no gross contamination from
reagents and glassware used in the procedure.
A method of standard addition was made to determine the percent recov-
eries of metals. The test gives valuable information as to losses of metals
either through volatilization or interferences. This was done by adding
known concentrations of metals standards to sludge samples and determining
the total metal content of the sludge. Thus, knowing the total and metal
content originally determined in the sludge sample, one could calculate the
amount of added metal recovered by the procedure. The standards contained
cadmium, copper, mercury, manganese, nickel, load, and zinc, and were
Mention of products and manufacturers is for identification only and does
not imply endorsement by the United States environmental Protection Agency.
30
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determined in the presence of other metals normally found in sludge. The
percent recoveries of metal standards added to a Little Miami Uastewater
Treatment Plant sludge sample, Cincinnati, Ohio were as follows:
Metal Added
Cadmium
Copper
Manganese
Nickel
Lead
Zinc
Original
Concentration
in the iludge*
mg/Kg
150
1500
300
400
600
3800
Amount
Added
mg/Kg
500
1000
500
500
1000
3500
Total
Metal
Found
mg/Kg
650
2500
850
850
1500
7620
Standard
Recovery
mg/Kg Percent
500
1000
550
450
900
3820
100
100
110
90
90
109
Original analysis of digested sludge sample from Little Miami
Wastewater Treatment Plant, Cincinnati, Ohio
As can be seen from the percent column, recoveries were in the range of 90-
110 percent, which indicates an accuracy of -10 percent in results of analyses.
Because of the volatility of mercury and its compounds, sludge samples
for detorminations of mercury were treated differently from samples used for
analyses of the other metals. A weighed and dried sample of the sludge was
cold-digested with a solution of sulfuric, nitric acids, and potassium per-
manganate overnight in a stoppered, Erlenmeyer flask. This treatment decom-
2+
poses the sludge sample and converts mercury forms to Hg without loss of
mercury. Subsequent analysis by the vapor atomic absorption procedure (10)
determines as little as 0.5 mg/Kg mercury concentration in a dried sludge
sample.
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The regular atomic absorption procedure for most metals generally does
not warrant reporting results less than 100 mg/Kg (ppm). Since cadmium often
falls below this concentration, an improved procedure had to be adopted for
this important element. Consequently, to determine cadmium content of sludges,
a graphite furnace was used in conjunction with the atomic absorption spectro-
photometer to report concentrations as low as 10 mg/Kg. For the more common
elements in sludge, concentrations were substantially greater than 100 mg/Kg,
so the graphite furnace was not needed.
All metal analyses in this paper are reported on a dry basis of sludge
because of the variable wet condition of the sludge samples as received by the
laboratory. Results are shown as milligram of metal per kilogram of dry sludge.
This appears to be a universally acceptable method of reporting as it is
identical to reporting on a part per million basis.
Much remains to be done in improving and developing analytical methods
for the determination of metals in sludge. The lack of uniform methods or
analysis is directly traceable to the complex nature of the sludge medium.
I/an Loon, et al (11) have written an excellent discussion about the analyses
of sludge.
STATISTICAL APPROACH
As can be anticipated from the above discussion, which pointed out the
wide variety of plants sampled, concentrations of individual metals varied over
wide ranges. It was necessary to investigate the bost moans for indicating:
a) the central tendency of the data,
b) deviations of the dispersion of data points from the central tendency.
The first steps attempted in the analysis of the data utilized a graphical
method. Tho data points were first tabulated in the order of ascending
32
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concentrations and a cumulative frequency distribution was calculated for
any particular metal. These results were plotted on normal probability paper,
which would yield a straight line if the distribution were normal. Both con-
centration and logarithm of concentration were plotted on normal probability
paper. The distribution of the logarithm of concentration was tested, because
a logarithmic normal distribution (log-normal) is commonly encountered in
analytical work when the concentrations being measured are small (near zero)
and the samples are heterogeneous. With the nature of the distribution
established, a computer was used to calculate 25th, 50th, 75th, 90th and 95th
percentile values, arithmetic mean concentration and standard deviation, and
logarithmic mean concentration and its associated standard deviation. The
antilog of the logarithmic mean was calculated giving the familiar geometric
mean. The computation of the antilog of the standard deviation gave the spread,
which is a multiplying and dividing factor for the geometric mean. This is
quite different from the standard deviation of an arithmetic distribution which
is an added and subtracted factor. Results of analyses reported as less than
the detectalbe limit of the analytical method were not included in the calcu-
lation of the means and standard deviations of the arithmetic and logarithmic
distributions. Generally, the number of samples excluded from the tabulation
was about 10 percent of the total. If more than 30 percent of the total num-
ber of entries were reported as less than some stated value, the statistical
parameters were not calculated for that particular metal. On the other hand,
the calculation of the median and the various percentiles for any particular
metal did include values above and below a specified limit of analysis.
Thus, the comparison of the median with the other means shows the influence
33
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of the less-than-detected values. The median is always an important statistic
in a distribution because it is unbiased (by definition it is always the mid-
point of a distribution). Unfortunately, the measure of dispersion used with
the median (such as the range or modifications of the range) are not as use-
fully related as the standard deviation to the nature of the distribution.
This reduces the value of the median as a statistic. Nevertheless, because
of its unbiased nature and simplicity the median is generally determined along
with the other more sophisticated measures of central tendency.
METALS IN SLUDGE
Distribution of Metals Found in Sludge—In all the tabulations which follow,
sludges are shown as two types. Eighty of the 100 samples analyzed were di-
gested sludges and the remainder were the raw or primary unstabilized sludges.
Digested sludge is the most important because this is the most common type
of stabilized sludge disposed to the land.
Cumulativ/e distributions of the frequency of occurence versus both concen-
tration and logarithm of concentration were plotted for each of the 21 metals.
The distribution of logarithm of concentration showed a closer approach to
linearity than concentration, indicating that concentration is log-normally
distributed. Frequency histograms of the logarithm of concentration are shown
in Figures 2 through 7 for 4 metals—cadmium, copper, lead and zinc. As the
curves illustrate, the distributions are not skewed when presented on this
basis, and approximate the typical bell shape of a normal distribution.
Calculations of statistical indices were made for about 21 metals in
digested sludge samples. The three measures of central tendency are presented
for 13 metals in Table 3 to illustrate how each statistical approach can give
34
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different results. Note that for each particular metal the arithmetic mean
is greater than the geometric mean, which in turn is greater than the median.
The most bias is shown in the arithmetic mean when compared to the median.
This is undoubtedly due to the effect of a few high values. On the whole
the geometric mean was much closer than the arithmetic mean to the median for
any particular metal, and thus appears to be a better measure of central ten-
dency. This conclusion is supported by the fact that the log-normal distribu-
tion fits the data. The geometric mean and the median should then be identical,
except for some displacement which results because "less-than-detectable"
points have been included in the calculation of the median but not in the
calculation of the geometric mean.
The spread associated with the geometric mean was greater for some metals
such as cadmium, chromium, and manganese than for others. This is an indica-
tion that these metals are not ordinarily found in domestic wastewater but are
occasionally introduced (probably from industrial sources) in relatively high
concentrations.
The metals concentration data for digested sludges are presented in Table
4 as percentiles. The non-linear nature of the distribution can be seen by
comparing the concentration "step" from the 25th to the 50th percentile with
the 50th to the 75th. If the distribution were arithmetic, these steps would
be equal. In all cases, the 50th to 75th percentile step is the greater,
indicating a peak in the distribution at some concentration below the 50th
percentile.
Tho 3 measures of central tendency are shown for metals in raw or unsta-
bilized sludge in Table 5. As was the case of the averages in digested sludge,
the geometric mean and median are better measures of central tendency than
is the arithmetic mean.
35
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The geometric mean levels of metals concentration in raw or unstabilized
sludge are compared in Table 6 to the concentrations in digested sludge.
Concentrations of chromium, copper, lead and zinc were higher in digested
sludge than in raw sludge. This is an expected result because organic matter
is volatilized during anaerobic digestion leaving metals behind in a more
concentrated form. However, concentrations of some other metals were higher
in raw sludge than in digested sludge. The most probable cause of this
anomaly was the fact that the sludge samples were not from the same plants.
The average concentrations shown thus far are based on analyses of samples
from 33 plants. Obviously as more samples from more wastewater plants are
examined in our future research, the accuracy of the averages will be improved
as the base is broadened.
Toxic and some nontoxic metals have been included in this study to make
reporting of metals in sludge as complete as possible. Some metals have not
been reported either because the data base was insufficient or because some
metals such as iron and aluminum simply do not present any hazard or toxicity
to plants and man. In the former class are such metals as arsenic, barium,
beryllium, molybdenum, and antimony. Beryllium is of special interest because
of its reported high toxicity to man (12). Although the analytical detection
limit was low for this metal as compared to other metals (less than 2 mg/Kg),
beryllium was not detected in any of the analyzed 102 sludge samples. It
appears at this point that beryllium in sludge presents little or no problems
in sludge disposal.
Comparison of Data of This Study with Other Sourcos—Dean and Smith (13) have
presented a tabulation of geometric mean metals concentrations which includes
36
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information taken from the U. S. literature and from Scandinavian sources
(14, 15) as well as from the present investigation. U S. metal levels are
higher than the levels in Denmark and Sweden. In Table 7, their tabulation
is reproduced but data from this laboratory have been updated to include
additional data and results for cadmium. Swedish and Danish national averages
of 8 toxic metals tend to agree with each other. Similarly, U. S. literature
values and results from the present investigation agree, but are generally at
a higher level than the Scandinavian results. Some reasons for this are ob-
vious such as the fact that there is a greater level of industrial activity
in the typical community in the United States.
Dean and Smith (13) have shown that both the Scandinavian and U. S. data
follow a log-normal distribution. This was also found to be true in this
study, and it appears that the log-normal distribution is characteristic of
metals concentrations in sludge. The log-normal characteristic is probably
attributable to two factors. First, the sampled communities vary widely
among themselves. The result is a variation which is large compared to the
mean. The distribution is bounded on one side only (because concentrations
are never less than zero). This combination of effects generally forces a
distribution to be skewed. Second, there are a few dominating influences
.which are probably log-normally distributed; for example, the proportion of
industrial wastes in the wastewater flow. Consequently, skewness of the pro-
portion of industrial wastes in relation to the other sources of the waste-
water flow leads to skewness of the distribution of any particular metal in
the waste sludge. The good fit of the metals data to a log-normal distribu-
tion should be considered an empirical observation with little theoretical
37
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justification. Moreover, it has been consistently observed in this study and
other investigations (13) and can be used with confidence.
Toxic Metals in Sludge—Chaney has proposed that sludge application to agri-
cultural* land is a reasonable practice provided a) there is a good benefit:
risk ratio, and b) metals loadings are limited to permit continued general*
farming. He has analyzed a number of sludges and has presented a listing
of the reasonably attainable minimum toxic metal content. Higher than minimum
quantities are attributed to industrial pollution. He states that these metal
contents are attainable and reasonable for digested sludge, and that sludges
with higher toxic metal content should not be applied to agricultural land.
Chaney!s tabulation is presented below:
Element Content
Zinc < 2,000 ppm
Copper < 800 ppm
Nickel < 100 ppm
Cadmium < 0.5$ of Zn
Boron < 100 ppm
Lead < 1000 ppm
Mercury < 15 ppm
Of those metals, cadmium is the major threat to human health. Chaney (8)
states that the only apparent way to be sure that the cadmium in a food crop
grown on a sludge or effluent-treated soil will not be a potential food-chain
hazard is to reduce the cadmium content of sludges to 0.5 percent of the zinc
* Emphasis is Chaney's
38
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content. In this way, zinc excess (at about 500 ppm zinc in leaves) would
injure the crop before the zinc or cadmium content of the crop constituted
a health hazard.
Chaney's recommended concentrations are compared with the data obtained
in this study in Table 8. Median (i.e. 50th percentile) and 25th percentile
concentrations are shown for the data from the 33 plants as well as median
concentrations for domestic sources. The "domestic source" plants were
selected from the 33 plants on the basis of location away from industrialized
areas and on size of the plant. It is interesting to note that the 25th
percentile concentrations and the domestic source concentrations coincide
very closely. Empirically, it can be said that the domestic source and the
25th porcentile compositions are essentially the same.
The median concentrations obtained in the present investigation exceed
Chaney's values for 5 out of 7 metals, but the domestic sources and the
25th percentile values are exceeded by Chaney's for about half of the metals.
The absolute magnitude of Chaney's values for any given metal, however, do
not match well with the domestic source or the 25th percentile.
There are threefold differences in the values for boron, mercury, and
nickel, fledian, domestic source, and 25th percentile compositions show
•cadmium to zinc ratios of 1.12$, 0.79$, and 0.91$, which substantially exceed
Chaney's recommended value of 0.5$. There appear then to be substantial dif-
ferences between Chaney's sludge "free of industrial pollution" and the pres-
ent study's "domestic source" .sludge. ThB differences probably arise from
differences in the geographical area covered and the types of plants se-
lected for the samples.
39
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If the metals content of a sludge is to be compared against a standard
composition—consider the median composition—the probability that the concen-
trations of each metal will be less than or equal to the median will be ap-
preciably less than 50 percent. To illustrate this point, the over 100 sludge
sample analyses (from 33 plants) were compared against Chaney's standard
composition and against the 25th percentile composition. Only 1 sludge met
Chaney's standard composition and 3 sludges met the 25th percentile composi-
tion. It is evident that very few sludges will meet even a 25th percentile
composition. A 75th percentile composition would exclude about 50 percent of
the sludges, and would serve the purpose of excluding sludges with a high
proportion of industrial wastes.
One implied problem in the above discussion is the definition of "domes-
tic source." A city can be considered a domestic source even if its waste-
water contains the discharges from the small businesses that serve the needs
of the city. If there is a substantial industrial discharge, it no longer
can be considered a domestic source. A survey of domestic sources should
be geographically diverse and should include large as well as small balanced
communities. It should not overrepresent wastewater plants serving surburban
areas which sometimes receive only household wastewater. When a large number
of plants are surveyed without detailed knowledge of each community served,
a significant contribution from industrial sources cannot be ruled out. On
the other hand, a high concentration of certain metals may indicate an unusual
domestic activity and is not prima facie evidence of an industrial discharge.
Variation of Nptals in Sludgs Somplos from Cincinnati's Millcrsek Plant—The
experiments with digested sludge from the Millcreek Uastewater Treatment Plant
40
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were undertaken to establish the extent of variation in metals content of
sludge from a given plant. This was done by collecting a digested sludge
sample from the treatment plant each day for a period of three weeks. Each
sample was analyzed for metals content, and the geometric mean and spread was
calculated for 11 metals. These results are shown in Table 9. Recall that
the spread is a dividing and multiplying factor. For example, dividing and
multiplying the chromium geometric mean value of 3360 mg/Kg by 1.30 gives
a spread of approximately 2590-4370 mg/Kg. A spread of 1.00 indicates no
deviation at all. The percent of data not detected is shown to indicate that
in most cases 90 or more percent of the analytical results were included in
the computation of the geometric means.
Geometric mean composition and spread for the Millcreek sludges are com-
pared with the values obtained for the 33 plants (Table 3) in Table 10. Metal
concentrations in the flillcreek sludge are higher than for the 33 plants and
reflect the industrial activity in the Millcreek Valley region of Cincinnati.
The spreads are much lower for the Millcreek data than the spreads for the
33 plants. The Millcreek spreads are a "within-plant" variation, which includes
analytical and sampling error as well as actual changes in the sludge. The
spreads for the 33 plants represent a "between-plant" variation, which is
•evidently much larger than the within-plant variation. The results indicate
satisfactory precision of the analytical work. A sampling frequency of about
once every two weeks ought to be satisfactory to obtain a knowledge of metals
content of sludge from any one plant. This same conclusion may not hold true
when raw sludge is sampled because the averaging effect obtained when sludge
is held in a well-mixed digester for a residence time of two weeks is not pres-
ent. Because of low variability of within-plant measurements, care must be
41
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taken in including them in a survey to establish between-plant variability.
In this and in the Scandinavian (14, 15) studies, this difficulty was avoided
by averaging analyses at a given plant and using them as a single entry in the
data array. One advantage, which should not be overlooked, is that within-
plant measurements help to more accurately establish the constituent charac-
teristics of a sludge from any given plant.
Estimating Metal Concentrations in the Influent Stream to a Wastewater Plant—
Having arrived at average concentrations of metals in sludge, one can make
a rough estimate of the concentrations of the common metals found in wastewater
influent streams. A knowledge of the average sludge production is needed for
this calculation. Fair and Geyer (16) estimate that an average of 890 pounds
of dry digested sludge solids are produced from treating one million gallons
of uastewater. This is equivalent to 0.107 gram of digested sludge per liter
of raw wastewater. Assume that 70 percent of each of the 8 toxic metals in
Table 3 is removed in the sludge. The calculation is illustrated for zinc
which has a median concentration of 2.78 mg/Kg (Table 3):
Metal removed from wasteuater = Metal found in sludge
(1 liter) (0.70) (x mg/l) - (0.107 gram) (2.78 mg/g)
x = 0.424 mg/l estimated zinc concentration in raw wastewater
Calculated concentrations of other metals based on median concentrations in the
sludge shown in Table 3 are as follows:
42
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Metal Concentration
tng/1
Cadmium 0.005
Chromium 0.170
Copper 0.190
Mercury 0.001
Manganese 0.060
Nickel 0.060
Lead 0.130
Zinc 0.420
The calculated values show that, in order to detect metals such as cadmium,
mercury, manganese, and nickel in raw wastewater, very sensitive analytical
procedures must be used because concentrations of these metals are very low.
This calculation procedure may be reversed, and used to estimate metal content
of sludge. The approximate nature of the calculation should be recognized.
ADDITIONAL SLUDGE PARAMETERS
In addition to the metal analysis, nitrogen, phosphorus, sulfur, volatile
solids, and heat of combustion were determined on sludge samples. An oxygen
•bomb calorimeter procedure was used to determine the heat of combustion of sludge
(17). Geometric mean values of these constituents are shown in Table 11.
The average heat of combustion of raw primary sludge, as expected, was higher
than that of digested sludge, due to the higher percentage of volatile organic
matter in raw primary sludge. Phosphorus and sulfur, on the other hand, are
concentrated in the digested sludge, since these constituents are only partially
lost during anaerobic digestion. Nitrogen concentration is lower in digested
43
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sludge than in raw primary sludge, probably due to the conversion of nitrogen
forms to soluble or volatile forms of nitrogen such as NH.-N and NI-L-IM.
CONCLUSIONS
The following conclusions can be drawn from this investigation:
1. In metal analysis of sludges, the distribution of the concentration
values of any one particular metal is characteristically log-normal.
2. Concentrations of toxic metals in sludges from 33 wastewater plants
in the United States are higher than those found in the sludges of two
Scandinavian countries.
3. Levels of metals found in domestic sludge are higher than those
recommended to be added to agricultural soil.
4. Within-plant variation of any one metal in sludge samples from a
single plant is much less than the variation of the same metal in
between-plant sludges.
ACKNOWLEDGEMENTS
The collection, analysis, and evaluation of sludge analyses data called
for the help and cooperation of many people. Thanks first go to all the
superintendents, sanitary engineers, and operators of the 33 wastewater treat-
ment plants who submitted sludge samples to the EPA Advanced Waste Treatment
Research Laboratory. The assistance of personnel of NERC-RTP-Raleigh, EPA
Regions II, III, and IX, who collected samples from some of the plants, is
gratefully appreciated. The assistance of Dr. Robert B. Dean was especially
helpful in the statistical evaluation of the data.. Thanks go also to Mrs.
Patricia Tutt who performed some of the laboratory tests and transmitted the
44
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data to IBM cards. Finally, the investigation would not have been possible
without the assistance of the chemists of the analytical group, AWTRL, who
performed the atomic absorption determination of the metals.
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LITERATURE CITED
1. U, S. Environmental Protection Agency Task Force, "Sewage Sludge Incinera-
tion," Report No. R2-72-040, NTIS No. PB-211 323 (Aug. 1972).
2. Farrell, 3. B., and Salotto, B. U., "The Effect of Incineration of Metals,
Pesticides and Polychlorinated Biphenyls in Sewage Sludge," pp. 186-198
in Proc. Nat. Symp. on Ultimate Disposal of Wastewaters and their Residuals,
Univ. of North Carolina, April 26-27, 1973, pub. Water Resources Res.
Inst., North Carolina State University (June 1973).
3. Barth, E. F., English, 3. N., and Salotto, B. U., "Field Survey of Four
Municipal Wastewater Treatment Plants Receiving Metallic Wastes," JWPCF
.37(8): 1101 (1965).
4. U. S. Public Health Service, "Interaction of Heavy Metals and Biological
Sewage Treatment Process," No. 999-WP-22, DHEW (May 1965).
5. Webber, 3., "Effects of Toxic Metals in Sewage on Crops," Water Pollution
Control (Great Britain) _71_(4):404 (1972).
6. Friberg, L., Piscator, M., and Nordberg, G., "Cadmium in the Environment,"
pub. by CRC Press, Cleveland, Ohio, 1971.
7. Dotson, G. K., "Some Constraints of Spreading Sewage Sludge on Cropland,"
pp. 67-79 in Proc. of the Conference on Land Disposal of Municipal
Effluents and Sludges, Rutgers University, New Brunswick, N. 3., March 12-
13, 1973, EPA-902/9-73-001, pub. U. S. EPA.
8. Chaney, R. L., "Crop and Food Chain Effects of Toxic Elements in Sludge
and Effluents," pp. 129-141 in Proc. of the Joint Conference on Recycling
Municipal Sludges and Effluents on Land, July 9-13, 1973, pub. National
Association of State Universities and Land Grant Colleges, Champaign,
Illinois.
9. APHA, AWWA, WPCF, "Standard Methods for the Examination of Water and Waste-
water," 13th edition, New York, APHA, 1971.
10. Kopp, 3. F., Longbottom, M. C., and Lobring, L. B., "Cold Vapor Method
for Determining Mercury," JAWW.fl 64(1);2D (Jan. 1972).
11. U an Loon, J. C., Lichwa, J., Ruttan, D., and Kinrade, J., "The Determina-
tion of Heavy Metals in Domestic Sewage Treatment Plant Wastes," Water,
Air, and Soil Pollution (Netherlands) 2_:473, 1973 (Printed in English).
12. "Toxicity of Beryllium," Kettering Lab., University of Cincinnati, Final
Technical Engineering Report, Report No. ASD-TR-62-7-665, April 1962.
13. Dean, R. B., and Smith, 3. E., Jr., "The Properties and Composition of
Sludges," EPA NERC-Cincinnati, Presented at the Seminar on Methodology
for Monitoring the Marine Environment, University of Washington, Seattle,
Washington, Oct. 16-18, 1973.
46
-------
14. Christiansen, H., "Content of Some Heavy Metals in Sludge Samples from
Swedish Treatment Works," in 8th Scandinavian Symposium on Disposal of
Wastes, Skokloster, April 25-27, 1972 (in Swedish).
15. Pauly, H., "Metal Content of Sludge from Danish Treatment Works Which Do
Not Have Wastes from Industry," in 8th Scandinavian Symposium on Disposal
of Wastes, Skokloster, April 25-27, 1972 (in Danish).
16. Fair, G. M., Geyer, 0. C., and Okum, D. A., "Water and Wastewater
Engineering," Vol. 2, New York, D. C. Wiley and Sons, 1968.
17. "Oxygen Bomb Calorimetry and Combustion Methods," Moline, 111., Parr
Instrument Company, Technical Manual No. 130, Dec. 1966.
47
-------
TABLE 1
FATE OF HETALS THROUGH SEWAGE TREATMENT PROCESS
(a)
Bryan, Ohio, Activated Sludge
Metal
Chromium
Copper
Niokel
Zinc
Influent Sewage, (mg/l) Final Effluent, (mq/l)
Average
0.8
0.2
0.05
2.2
Range
0.6-1.1
0.2-0.3
0.03-0.1
1.4-3.0
Average
0.2
0.1
0.05
0.2
Range
0.2-0.3
0.04-0.1
0.03-0.1
0.2-0.3
Percent
Immobilized
in Sludge,
-
(a)
Grand Rapids, Michigan, Activated Sludge
Chromium
Copper
Nickel
Zinc
3.6
1.4
2.0
1.5
0.7-5.6
0.7-2.4
1.3-3.4
0.6-2.5
2.5
1.6
1.8
0.8
1 .0-3.3
0.4-2.9
1.0-2.5
0.6-1 .2
40
16
12
58
Richmond, Indiana, Activated Sludge
Chromium
Copper
iJickel
Zinc
0.8
0.2
0.03
0.3
0.2-2.1
0.1-0.4
0.01-0.1
0.1-0.5
0.2
0.07
0.02
0.1
0.01-0.5
0.04-0.2
0.01-0.03
0.1-0.2
82
73
78
85
Rockford. Illinois. High-Rate Trickling Filter
Chromium
Copper
Nickel
Zinc
1.8
1.4
0.9
2.7
0.5-2.9
0.6-3.3
0.2-1.9
1.2-3.4
1.2
1.0
0.9
1.3
0.6-1.5
0.5-3.6
0.5-1.4
0.8-1 .7
37
23
Q
53
Data taken from report of E. F. Barth, et al (3).
48
-------
TABLE 2
UASTEUATER TREATMENT PLANT LOCATIONS
ARIZONA
PHOENIX
TUCSON
CALIFORNIA
BARSTOU
CARSON
FRESNO
LOS ANGELES
MISSION BAY
MONTEREY
OXNARD
SAN FRANCISCO
SAN LORENZO
SAN MATED
TAHOE
HAWAII
PEARL CITY
INDIANA
INDIANAPOLIS
I QUA
CEDAR RAPIDS
MARYLAND
BALTIMORE
NEVADA
LAS VEGAS
RENO
NEU1 JERSEY
BERGEN COUNTY
ESSEX COUNTY
MIDDLEBORO
N.W. BERGEN COUNTY
PASSAIC VALLEY
NORTH CAROLINA
GREENSBORO
OHIO
CINCINNATI
COLUMBUS
DAYTON
PENNSYLVANIA
IMORRISTOUJN
PHILADELPHIA
VIRGINIA
LORTON
WASHINGTON
EDMONDS
LYIMNWOOD
49
-------
TABLE 3
AVERAGE CONCENTRATIONS OF METALS
IN DIGESTED SLUDGE
(ALL FIGURES MG/KG DRY SLUDGE BASIS)
METAL
SILVER
BORON
CADMIUM
CALCIUM
CHROMIUM
COBALT
COPPER
MERCURY
MANGANESE
NICKEL
LEAD
STRONTIUM
ZINC
ARITHMETIC
MEAN STD.DEV.
(+ and -)
250
430
75
36,500
1,860
350
1,590
10
1,300
680
2,750
520
4,210
230
310
104
23,800
1,920
220
1,670
18
2,290
620
2,350
670
3,800
GEOMETRIC
MEAN STD.DEV.,
(r and X)(a
190
380
43
31,100
1,050
290
1,270
6.5
475
530
2,210
290
2,900
1.99
1.58
2.47
1.77
3.22
1.88
1.95
2.34
3.67
1.88
1.82
2.70
2.40
MEDIAN
50%
VALUE
100
350
31
30,000
1,100, x
<100^ '
1,230
6.6
380
410
830
175
2,780
(a)
(b)
Standard deviation of the geometric mean is a ratio and has no units,
The symbol "<" indicates less than.
50
-------
TABLE 4
QUARTILE DISTRIBUTION OF METALS
IN DIGESTED SLUDGE
(ALL FIGURES MG/KG DRY SLUDGE BASIS)
NETAL
SILVER
BORON
CADMIUM
CALCIUM
CHROMIUM
COBALT
COPPER
MERCURY
MANGANESE
NICKEL.
LEAD
STRONTIUM
ZINC
PERCENTILE GROUPING
PERCENT EQUAL TO OR LESS THAN STATED VALUE
25%
<100
300
15
22,800
395
<100
900
5.1
160
300
<500
100
1,640
50$
100
350
31
30,000
1,100
<100
1,230
6.6
380
410
830
175
2,780
75/o
230
450
67
45,200
2,700
260
2,120
8.5
770
550
2,000
340
5,000
90/o
430
490
80
49,000
4,000
500
2,970
11
4,860
1,170
2,770
1,490
9,880
95$
450
870
140
58,800
5,820
520
4,310
12
6,080
1,720
4,370
1,790
11,100
NO. OF
TREATMENT
PLANTS
23
13
18
23
23
23
24
22
24
24
24
22
24
51
-------
TABLE 5
AVERAGE CONCENTRATIONS OF METALS
IN RAW SLUDGE
(ALL FIGURES PIG/KG DRY SLUDGE BASIS)
METAL
SILVER
BORON
CADMIUM
CALCIUM
CHROMIUM
COBALT
COPPER
MERCURY
MANGANESE
NICKEL
LEAD
STRONTIUM
ZINC
ARITHIMETIC
MEAN STD.DEV.
(+ and -)
490
880
30
13,800
1,370
700
860
15
1,310
580
1,380
190
1,960
370
410
15
7,830
1,400
770
550
23
2,860
540
775
75
1,000
GEOMETRIC
MEAN STD.DEV. /a
(f and X)
355
775
27
11,700
940
410
740
8.2
460
420
1,150
175
1,740
2.51
1.67
1.53
1.82
2.75
2.32
1.67
2.54
3.32
2.12
1.95
1.45
1.66
MEDIAN
50$
VALUE
<100
805
20
13,900
750
240
660
5.5
200
335
1,150
CIOO
1,880
''Standard deviation of the geometric mean is a ratio and has no units.
52
-------
TABLE 6
COMPARISON OF METALS IN RAW
TO METALS IN DIGESTED SLUDGES
(ALL FIGURES MG/KG DRY SLUDGE BASIS)
METAL
SILVER
BORON
CADMIUM
CHROMIUM
COBALT
COPPER
MERCURY
MANGANESE
NICKEL
LEAD
STRONTIUM
ZINC
RAW SLUDGE
GEOMETRIC MEAN
355
775
27
940
410
740
8.2
460
420
1,150
175
1,740
DIGESTED SLUDGE
GEOMETRIC MEAN
190
380
43
1,050
290
1,270
6.5
475
530
2,210
290
2,900
53
-------
TABLE 7
COMPARISON OF METALS IN UNITED STATES
SLUDGES WITH F1ETALS IN SCANDINAVIAN SLUDGES
(ALL FIGURES MG/KG DRY SLUDGE BASIS)
METAL
CADMIUM
CHROMIUM
COPPER
MERCURY
MANGANESE
NICKEL
LEAD
ZINC
THIS
STUDY
U. S. <<>>
SOURCES
DANISH^
DATA
SWEDISH^
DATA
GEOMETRIC MEAN CONCENTRATIONS
43
1,050
1,270
6.5
475
530
2,210
2,900
69
840
960
28
400
240
480
2,600
10
110
340
7.8
350
37
470
2,600
9.8
170
^*~}r\
670
5.8
400
65
220
1 ,900
(a) SEE REFERENCE 13
(b) SEE REFERENCE 14
(c) SEE REFERENCE 15
54
-------
TABLE 8
TOXIC METALS CONTENT OF DOMESTIC SLUDGE
(ALL FIGURES MG/KG DRY SLUDGE BASIS)
TOXIC METAL
BORON
CADMIUM
CHROMIUM
COPPER
MERCURY
MANGANESE
NICKEL
LEAD
ZINC
THIS STUDY
AUERAGE , v
33 PLANTS1'3''
MEDIAN
350
31
1,100
1,230
6.6
380
410
830
2,780
DOMESTIC v
SOURCE*1 '
MEDIAN
300
14
300
700
6.8
100
300
<500
1,700
25TH , .
PERCENTILE (C)
300
15
395
900
5.1
160
300
<500
1,640
CHANEY'S.v
DATA(d)
100
<10
—
<800
<15
_-
ClOO
<1,000
<2,000
(a) SEE DATA OF TABLE 3
(b) AVERAGE BASED ON ANALYSES OF SLUDGES FROM PLANTS RECEIVING DOMESTIC WASTES
(c) SEE DATA OF TABLE 4
(d) SEE REFERENCE (8)
55
-------
TABLE 9
AVERAGE CONCENTRATION AND SPREAD OF METALS
IN SLUDGE SAMPLES FROM THE MILLCREEK PLANT
IN CINCINNATI, OHIO
METAL
SILVER
CADMIUM
CHROMIUM
COBALT
COPPER
MERCURY
MANGANESE
NICKEL
LEAD
STRONTIUM
ZINC
PERCENT NOT
DETECTED
5
10
0
5
0
0
0
5
0
0
0
GEOMETRIC
MEAN
MG/KG
190
130
3,360
515
3,550
1.8
2,360
1,590
6,980
2,220
10,700
SPREAD
('- and X)
1.24
1.51
1.30
1.07
1.31
1.60
1.59
1.17
1.49
1.07
1.22
56
-------
TABLE 10
COMPARISON OF VARIATIONS OF METALS IN SLUDGES
ONE PLANT US. MANY PLANTS
(MEAN EXPRESSED IN UNITS OF MG/KG)
METAL
SILVER
CADMIUM
CHROMIUM
COBALT
COPPER
MERCURY
MANGANESE
NICKEL
LEAD
STRONTIUM
ZINC
MILLCREEK
PLANT
CINCINNATI, OHIO
MEAN X SPREAD(a)
190 X 1.24
130 x 1.51
3,360 x 1.30
515 x 1.07
3,550 x 1.31
1.8 x 1.60
2,360 x 1.57
1,590 x 1.17
6,980 x 1 .49
2,220 x 1 .07
10,700 x 1.22
AVERAGE
33 PLANTS
MEAN X SPREAD(a)
190 X 1.99
43 x 2.47
1,050 x 3.22
290 x 1.88
1,270 x 1.95
6.5 x 2.34
475 x 3.67
530 x 1.88
2,210 x 1.82
290 x 2.70
2,900 x 2.40
(a)The spread is here expressed as the antilog of the geometric
standard deviation.
57
-------
TABLE 11
AVERAGE CONCENTRATIONS OF OTHER CONSTITUENTS
IN PRIMARY AND DIGESTED SLUDGE
(MG/KG EXCEPT WHERE NOTED)
CONSTITUENT
NITROGEN
PHOSPHORUS
SULFUR
% us (a)
BTU/LB(b)
PRIMARY SLUDGE J
GEO. MEAN
X SPREAD
80,000 x 4.32
9,070 x 2.04
3,100 x 3.33
74.4 x 1.12
7,910 x 1.10
MEDIAN
32,000
7,650
5,590
75
8,040
DIGESTED SLUDGE
GEO. MEAN
X SPREAD
37,100 x 2.64
16,700 x 1.60
6,010 x 2.09
51.9 x 1.24
5.850 x 1.14
MEDIAN
25,800
17,800
6,550
54
5,760
(a)PERCENT VOLATILE SOLIDS
(b)HEAT OF COMBUSTION EXPRESSED AS BTU/LB
58
-------
en
10
L V >
~~ >
FIGURE 1-LOCATIONS OF WASTEWATER TREATMENT PLANTS
IN THE UNITED STATES SUBMITTING SAMPLES.
-------
0.400
en
o
0.300
iu
:D
O
Lii
u-
UJ
0.200
0.100
0.00
till
.94 1.241.541.842.142.442.74
LOG10 PPM CONCENTRATION
FIGURE 2 -HISTOGRAM OF CADMIUM IN DIGESTED SLUDGE,
-------
L9
-n
RELATIVE FREQUENCY
SURE 3 -HISTOGRAM OF COPPER IN PRI^l
LOG-jo PPM CONCEMTRATIO
c
•
c
c
jo
Ol
o
ro
O
N)
b
O
CO
0
CO
CO
0
CO
O)
o
i^ ^^ ^^ ^^ «^
^ Ik NJ CO 4^
3 O O O O
D O 0 0 O
1 i I i
(0
r-
o
o
m
-------
ro
0.400
O 0.300
ID
O
UJ
£ 0.200
(U
h-
<
0.100
0.00
J I
2.60 2.80 3.00 3.20 3.40 3.60 3.80 4.00
•
LOG10 PPM CONCENTRATION
FIGURE 4 -HISTOGRAM OF COPPER IN DIGESTED SLUDGE.
-------
0.400
GO
0.300
yj
13
o
yj
£
LU
>
h-
<
UJ
cc
0.200
0.100
0.00
i i i i
1.86 2.16 2.46 2.76 3.06 3.30 3.60 3.90
LOG10 PPM CONCENTRATION
FIGURE 5-HISTOGRAM OF LEAD IH PRIMARY SLUDGE,
-------
O-)
0.400
O 0.300
UJ
:D
O
iu
UL 0.200
us
ec
0.100
0.00
J I
I I
2.35 2.55 2.75 2.95 3.15 3.35 3.55 3.75
LOG10 PPM CONCENTRATION
FIGURE 6 -HISTOGRAM OF ZINC IN PRIMARY SLUDGE
-------
0.400
O 0.300
Z
L'J
13
O
LI]
E 0.200
LLJ
S 0.100
0.00
2.25 2.55 2.85 3.153.453.754.054.35
LOG10 PPM CONCENTRATION
FIGURE 7-HISTOGRAM OF ZINC IN DIGESTED SLUDGE
-------
FIGURE 1-LOCATIONS OF WASTEWATER TREATMENT PLANTS
IN THE UNITED STATES SUBMITTING SAMPLES.
-------
0.400
0.300
u
D
O
u
cc
in
0.200
0.100
0.00
I I I I
.94 1.24 1.54 1.84 2.14 2.44 2.74
LOG10 PPM CONCENTRATION
FIGURE 2 -HISTOGRAM OF CADMIUM IN DIGESTED SLUDGE.
-------
89
RELATIVE FREQUENCY
Q
DO
m
CO
I
o
o
DO
O
o
"0
TJ
m
•o
33
LOG-io PPM CONCENTRA
C
•
C
ro
en
O
10
•
^j
O
10
b
0
CO
•
0
CO
CO
o
CO
O)
o
o o o o
> L> io CO *
5 O O O O
5 O O O O
1 I I i
O
O
m
-------
69
RELATIVE FREQUENCY
O
C
3)
m
O
o
DO
O
o
"D
•o
m
DO
g
O
m
(/)
m
a
o
o
m
o
•
o
o
o
•
o
o
o
fo
o
o
o
CO
o
o
o
•
ft
o
o
to
b)
o
to
bo
a
CO
b
o
8
O O
O co
H 00
DO O
± S
o o
-------
RELATIVE FREQUENCY
O
DO
m
01
i
o
o
3D
O
Tl
I"
m
>
o
LOG10 PPM CONCENTRA
c
_, c
r* c
00
O)
to
•
O)
to
•
^
0)
go
•
>4
0)
CO
b
O)
CO
CO
0
CO
b)
0
CO
(O
o
o o o o
^ ^^ • • «
3 IL 10 CO ^
D O O O O
D O O O O
I i i I
-
DO
(A
O
O
m
-------
0.400
O 0.300
m
D
O
LLI
£ 0.200
LU
LJJ 0.100
QC
0.00
I I I
2.35 2.55 2.75 2.95 3.15 3.35 3.55 3.75
LOG10 PPM CONCENTRATION
FIGURE 6 -HISTOGRAM OF ZINC IN PRIMARY SLUDGE
-------
RELATIVE FREQUENCY
Tj
O
C
3D
m
*>i
I
o
o
O
-n
N
z
o
D
O
m
o>
m
o
0)
LOG10 PPM CONCENTRAT
<
i
(
to
fo
en
10
en
en
10
00
en
CO
en
CO
en
CO
en
6
en
CO
en
Dm ...
Lt. 10 CO £h
D O O O O
D O O O O
I 1 1 1
o
O
m
-------
STABILIZATION OF MUNICIPAL SEWAGE SLUDGE
BY HIGH LIME DOSE
by
C. A. Counts1
A. J. Shuckrow2
J. E. Smith3
June 1974
PACIFIC NORTHWEST LABORATORIES
BATTELLE MEMORIAL INSTITUTE
P. O. Box 999
Richland, Washington 99352
Research Engineer, Water and Waste Management Section,
Battelle-Northwest
2Manacjer Water and Waste Management Section, Battelle-
Northwest
3Sanitary Engineer, AWTRL, National Environmental Research
Center, EPA, Cincinnati, Ohio, 45268
73
-------
STABILIZATION OF MUNICIPAL SEWAGE SLUDGE
BY HIGH LIME DOSE
by
C. A. Counts
A. J. Shuckrow
J. E. Smith
INTRODUCTION
Sludge treatment and ultimate disposal represent a major
portion of municipal wastewater treatment costs. Generally
efforts in this area have been directed towards minimizing
the volume of sludge requiring disposal and reducing the
potential for producing nuisance conditions and public health
hazards during and after disposal. Processes such as
anaerobic digestion, aerobic digestion, and incineration have
been used extensively for sludge stabilization. However, each
of these processes adds significantly to the cost of waste-
water treatment and none totally eliminates the residue which
requires disposal.
The use of sewage sludge on cropland is limited by several
factors which are of particular concern to environmentalists
and public health officials: the nitrogen content of the
sludge, the concentration of metals and other trace elements,
and the survival of pathogens. Treatment of sludge to reduce
its pathogen content and, therefore, its potential for intro-
ducing pathogens into cropland was a major concern of this
program.
Historically, lime has been used to treat nuisance condi-
tions resulting from open pit privies and the graves of
deceased domestic animals. The scope of the program followed
from the work of Farrell, et al.,1 at the Lebanon, Ohio,
wastewater treatment plant. In that work, Farrell and his
74
-------
co-workers were concerned with developing a treatment technique
for processing that portion of the plant's sludge production
which exceeded its digester design flow. In the Lebanon study,
lime addition to the sludge was found to be effective in both
deodorization and disinfection. The current program was
designed as an investigation of the pertinent operating para-
meters for lime stabilization of sludges and the subsequent
effects of application of the lime treated sludges directly
to cropped lands.
SCOPE OF THE PROGRAM
The two major objectives of this program were: 1) to
determine the degree of stability produced in sludges by
the addition of large amounts of lime, and 2) to determine the
effects of spreading lime stabilized sludges on land used for
crop production. Initial work to achieve the first objective
was accomplished through bench scale laboratory studies
designed to aid in selection of pilot plant equipment and
operational parameters. The majority of the work in this
part of the study, however, was conducted on a larger pilot
scale. Work on the second objective was accomplished in
small scale greenhouse studies and on larger outdoor plots
which received varying amounts of sludge. After sludge
application, the outdoor plots were cultivated and cropped
using standard agricultural techniques.
DISCUSSION OF MAJOR FINDINGS
Laboratory Work
Bench scale laboratory studies were conducted to develop
basic information on the lime stabilization process itself and
to develop data for use in design and operation of a pilot
plant. These bench scale studies were concerned with:
75
-------
1. lime requirements to achieve specified pH levels
within a range from pH 11.0 to 12.4,
2. time dependency of the lime/sludge reaction, and
3. pathogenic bacteria and obnoxious odor reduction as a
function of pH and contact time between the lime
and the raw sludge.
Unless otherwise noted, all sludge used in the laboratory
studies was a mixture of primary sludge and trickling filter
humus and was taken from the digester feed line at the Richland,
Washington municipal sewage treatment plant.
Laboratory studies were conducted at the beginning of the
program to determine the lime dose required to raise the pH to
a specified level. The results from these studies were used
in design and operation of the pilot plant facility which was
used to produce lime stabilized sludges for use on the plots
in outdoor growth studies.
The pH levels chosen for investigation were 11.0, 11.2,
11.4, 11.6, 11.8, 12.0, and 12.4. One liter raw domestic
sewage sludge samples with known total solids concentrations
were dosed with a 100 mg Ca(OH)2/ml lime slurry and mixed
with a paddle stirrer until the change in pH reached equil-
ibrium. Lime dose and the resulting pH were then recorded.
This procedure was repeated until the specified pH level was
reached. Sludges with different total solids concentrations
were treated in this same manner to develop data on the lime
dose required to raise pH to specified levels in sludges with
different solids contents.
The results from these studies are shown in Figure 1.
These results indicate that total solids concentration affects
the lime dose required to raise the pH to a specified level.
As can be seen from Figure 1, the lime requirements increased
as total solids concentration increased. This variation in
lime requirements is probably caused by a combination of
76
-------
/
Q 1.0% SOLI OS
iW SOLI OS
Q 3.0% SOLI OS
• 3.5% SOLIDS
4.4% SOLIDS
I « /
V2/
2000
4000 6000
Ca(OH)z DOSE (mg/l)
8000
10.000
FIGURE 1. LIME DOSES REQUIRED TO RAISE pH IN SLUDGES
WITH DIFFERENT SOLIDS CONCENTRATIONS.
-------
factors including: 1) difficulty in establishing good mixing
patterns in the thicker sludges, and 2) chemical demand caused
by reaction of the hydroxyl ions with dissolved CO-, bicarbonate
alkalinity, and organic materials (neutralizing organic acids,
hydrolysis, saponification). A low shear, paddle mixing tech-
nique was used to prevent homogenization of the sludge.
Difficulty in establishing good mixing patterns in the sample
container was encountered with the higher solids concentration
sludges. This difficulty with establishing good mixing
patterns in the thicker sludges could possibly have prevented
intimate contact between the lime slurry and the liquid phase
component of the sludge. Thus, a dissolution of Ca(OH)2
introduced into the sludge would be hindered and more lime
would be required to elevate the pH of the system. The lime
demand would also increase as solids content increased since
more organic matter would be introduced with a concomitant
increase in the hydroxyl ion requirement for neutralizing
organic acids and reactions involving hydrolysis and saponifi-
cation.
From this discussion, it appears that the lime dose
required to raise the pH of a given sludge to a specified
level would be significantly influenced by the chemical
characteristics and the solids concentration of the sludge
and by the technique used to mix the lime and sludge.
Previous work on lime-sludge systems has shown that a pH
decay is experienced as the treated sludge ages.1'2'3 Decay
from high pH levels to lower levels can change the system
environment from one hostile to microbial survival to one
suitable for organism existence and growth. Therefore,
laboratory studies were undertaken to define the extent of
pH decay experienced in sludges after lime treatment.
78
-------
A sludge sample with total solids concentrations of 4.4
percent was collected and divided into one liter batches
which were then lime treated to pH levels of 11.0, 11.2, 11.4,
11.6, 11.8, 12.0, and 12.4. pH decay in each of these samples
was monitored over a 24 hour time period. Results from this
study are shown in Figure 2.
As can be seen from the results, pH decay was observed
in all samples as the lime treated sludges aged. However,
the degree of decay significantly decreased when the initial
value of a sample was 12.0 or greater.
This decay is believed to be caused by the sludge chemical
demand exerted on the hydroxyl ions supplied in the lime
slurry. Many of the reactions which exert this demand probably
proceed slowly in this type of system (non-optimal chemical
reactor), and thus pH decays slowly as hydroxyl ions enter
into chemical reactions. The degree of decay probably
decreases as initial pH increases because of the extremely
large quantities of lime required to elevate pH to 12.0 or
greater. Large concentrations of both hydroxyl ions and
undissociated Ca(OH)2 are supplied in the slurry. Therefore,
at high pH, sufficient OH~ species are present in the system
to allow chemical reactions to proceed without an attendant
decrease in pH. In summary, pH decay depends upon both the
quantity of lime added and the total solids concentration of
the sludge.
A major portion of this program was concerned with
definition of the effects of high lime dose on the pathogen
populations in sewage sludges. Therefore, a laboratory study
was conducted in which mixed primary and secondary sludges
with a total solids content of 4.4 percent was lime treated
to various pH levels within the 11.0 to 12.4 range. Labora-
tory beakers containing the lime treated sludge were allowed
to stand open to the atmosphere at room temperature, and
79
-------
00-
o
TT
C_
Q.
£
£
13
11 <
9
7
13
_ PH0=- 11.0
"~%>-o^ TS=4.4%
-
p!H0. 11.2
... TS=4.4%
9
7
13
11 '
9
7
13
ll'
9
7
>0^— o
-
™"
pHQ. 11.4
r TS-4.4%
~~~*
pH0: 11.6
k TS=4.4%
" °~0-o_
-
, , , i
5 24
ELAPSED TIME (HRS)
Q.
£
£
a
11'
9
7
13
4
11
9
7
11
9
7
•^*V\^
pH0* 11.8
— TS - 4.47.
^ pH0= 12.0
— TS-4.4T.
- pH0= 12.4
'__ TS=4.4%
1 1 1 1
24
ELAPSED TIME (HRS)
FIGURE 2. LIME-SLUDGE pH REACTION TIME
DEPENDENCY FOR 4.4% SLUDGE SOLIDS
-------
samples for bacteriological analysis were collected after
lime-sludge contact times of one and twenty-four hours. The
microorganisms chosen as indicators of pathogen response to
lime treatment were fecal coliform, fecal streptococci,
Salmonella species, and Pseudomonas aeruginosa. Bacteriologi-
cal methods used for determination of Salmonella species and
Pseudomonas aeruginosa were developed by Kenner, et al.1*
The membrane filter technique and plate count technique,
both described in Standard Methods,5 were used to count fecal
coliforms and fecal streptococci, respectively.
Results from these studies are shown in Tables 1 and 2.
After one hour of contact time, pathogen reductions were
observed in the lime treated sludges at all pH values within
the range under study. In general, the degree of reduction
increased as pH increased with consistently high pathogen
reductions occurring only after the pH reached 12.0. Fecal
streptococci appeared to resist inactivation by lime treatment
particularly well at the lower pH values in the study range.
However, at pH 12.0 these organisms were also inactivated
after one hour of contact time.
An increase in pathogen counts was usually observed in
the samples taken after twenty-four hours of contact time.
It should also be noted that the pH of the lime-sludge
system usually decreased during this time period. Work done
by Paulsrud and Eikum3 on lime stabilization of sewage sludges
in Norway showed that pH could be maintained at high levels
by overdosing the system with Ca(OH)2. This procedure provides
surplus lime to the system so that chemical demand does not
cause a significant decrease in pH. For sludge which is to be
spread on agricultural land, addition of excess quantities of
lime in some cases might harm crop production.
81
-------
TABLE 1
EFFECT OF LIME ON FECAL COLIFORM AND FECAL STREPTOCOCCI
AT 4.4% SLUDGE SOLIDS CONCENTRATION
Initial '
pH Value
6.8*
6.8*
11.0
11.0
11.0
11.0
11.2
11.2
11.2
11.2
11.4
11.4
11.4
11.4
11.6
11.6
11.6
11.6
111. 8
11.8
11.8
11.8
12.0
12.0
12.0
12.0
12.4
12.4
12.4
12.4
Lime
Contact
Time
(hrs)
1
1
24
24
1
1
24
24
1
1
24
24
1
1
24
24
1
1
24 '
24
1
1
24
24
1 '
1 •
24
24
pH When
Sample
Taken
10.3
10.3
8.6
8.6
10.6
10.6
8.7
8.7
10.7
10.7
9.2
9.2
11.1
11.1
9.5
9.5
11.5
11.5
9.9
9.9
11.8
11.8
10.6
10.6
12.1
12.1
11.4
11.4
Fecal Coliform
per 100 ml
i.eoxio7
2.03xl07
3.65xlO<
4.35xl04
2.87x10*
3.25xl04
3.72x10*
2.70x10*
1.70x10*
1.37x10*
1.63x10*
2.10x10*
3.20xl04
4.95x10*
5.15x10*
5.03x10*
2.55x10*
3.80x10*
6.65x10*
3.48x10*
5.34x10*
5.77x10*
3.70x10*
2.25x10*
1.15x10*
2.20x10*
2.70x10*
5.35x10*
7.13x10*
7.78x10*
Fraction of
Original
Remaining
2.01x10-3
2.40xlO-3
1.58xlO~3
1.79x10-3
2.05x10-3
1.49x10-3
9.37x10-*
7.55x10-*
8.90x10"*
1.16x10-3
1.76x10-3
2.09x10-3
2.84x10-3
2.77x10-3
1.40x10-3
2.09x10-3
3.66x10-3
1.92xlO~J
2.94x10-3
3.18x10-3
..2.04x10-3
1.24x10-3
6.34x10-3
1.21xlO"3
1.49x10-3
2.95x10-3
3.93xlO"3
4.28x10-3
Fecal Streptococci
per 100 ml
4.13xl07
4.67xl07
5.37x10'
6.50x10?
7.33x10;
7.50xl07
8.50x10?,
8.50x10'
7.70xl07
7.50x10'
6.43xl07
6.57xl07
8.47xl07
8.57xl07
4.47xl06
4.53xl06
8.30xl07
8.33xl07
8.33xl06
8.50xl06
8.27xl06
8.70xl06
3.27xl05
3.37xlOs
3.09xl06
2.50xl06
7.20xl05
7.87xl05
2.61xl06
*2. 55x106
Fraction of
Original
Remaining
1.22
1.47
1.66
1.70
1.93
1.93
1.75
1.70
1.46
1.49
1.93
1.95
0.10
0.10
1.89
1.89
0.19
0.19
0.19
0.20
7.43x10-3
7.66xlO"3
0.07
0.06
0.02
0.02
0.06
0.06
*Raw Sludge
-------
TABLE 2
EFFECT OF LIME ON SALMONELLA SPECIES AND PSEUDOMONAS AERUGINOSA
AT 4.4% SLUDGE SOLIDS CONCENTRATION
Initial
pH Value
6.8*
6.8*
11.0
11.0
11.0
11.0
11.2
11.2
11.2
11.2
11.4
11.4
11.4
11.4
11.6
11.6
11.6
11.6
11.8
11.8
11.8
11.8
12.0
12.0
12.0
12.0
12.4
. 12.4
12.4 .
12.4
Lime
Contact
Time
(hrs)
1
1
24
24
1
1
24
24
1
1
24
24
1
1
24
24
1 '
1
24
24
1
1
24
24
1
1
24
24
pH When
Sample
Taken
10.3
10.3
8.6
8.6
10.6
10.6
8.7
8.7
10.7
10.7
9.2
9.2
11.1
11.1
9.5
9.5
11.5
11.5
9.9
9.9
11.8
11.8
10.6
10.6
12.1
12.1
11.4
11.4
Samonella •
Species
per 100 ml
10,800
5600
1080
220
340
340
340
340
440
260
22
320
560
260
44
98
220
52
260
98
220
34
4
9
28
28
16
14
40
66
Fraction
of Original
Remaining
0.13
0.03
0.04
0.04
0.04
0.04
0.05
0.03
2.68x10-3
0.04
0.07
0.03
5.37x10-3
0.01
0.03
, 6.34x10-3
0.03
0.01
0.03
4.14xlO-3
4.88X10"4.
l.lOxlO"3
3.41x10-3
3.41x10-3
1.90x10-3
1.66xlO"3
4.88x10-3
8.05x10-3
Pseudoroonas
Aeruginosa
per 100 ml
2800
8600 '
144
128
7000
1400
28
28
-------
An important factor in any stabilization process is the
ability to significantly reduce the obnoxious odor producing
potential of the sludge. Odors usually result from anaerobic
decomposition of the sludge organic content. Conventional
methods of reducing the odor producing potential in sludge are
based on controlled biochemical degredation of the sludge
organic matter (aerobic and anaerobic digestion) or total
destruction of the organic matter (incineration). The lime
stabilization process achieves reductions in odor producing
potential by creating a high pH, hostile environment in the
sludge, thus eliminating or suppressing the growth of
microorganisms that could produce nuisance conditions.
Tests to quantitatively measure odor are subject to in-
accuracies since test panels of supposedly unbiased, randomly
selected people are usually required. However, since no other
standard tests were available, the threshold odor number test
described in Standard Methods5 was used in this study to
measure odor in raw and lime treated sludges. Threshold odor
number is defined as the greatest dilution of the sample with
odor-free water which yields the least perceptible odor. The
tests were conducted on mixtures of primary and secondary
sludge which had been lime treated to pH levels of 11.0, 11.2,
11.4, 11.6, 11.8, 12.0, and 12.4. The threshold odor numbers
of the treated samples were compared to those of sludge samples
which had received no treatment. Sludge samples with total
solids concentrations of 2.0 and 4.4 percent were used.
Samples were tested after one and twenty-four hour contact
times.
The results from this study are shown in Table 3. In
both cases, the threshold odor number of the raw sludges was
found to be 8000 while that of the treated samples usually
ranged from 800 to 1330. This data indicates that lime
treatment does have a deodorizing effect. Qualitative
84
-------
TABLE 3
THRESHOLD ODOR NUMBERS FOR TREATED AND UNTREATED
SLUDGES WITH DIFFERENT SOLIDS CONCENTRATIONS
Threshold Odor Numbers
oxuuyt; Aype
and pH Level
Total Solids=2.0%
6.8 (Untreated)
11.0
11.2
11.4
11.6
11.8
12.0
12.4
Total Solids=4.4%
6.8 (Untreated)
11.0
11.2
11.4
11.6
11.8
12.0
12.4
1 Hr Contact
8000
1000
1000
1000
1000
1000
1000
1000
8000
1330
1330
1330
1330
800
800
1330
% Reduction
88
88
88
88
88
88
88
83
83
83
83
90
90
83
24 Hr Contact
8000
8000
1000
1000
1000
1000.
1000
1000
8000
4000
1330
4000
1330
800
1330
1330
% Reduction
0
88
88
88
88
88
88
50
83
50
83
90
83
83
-------
observations in the laboratory substantiate this finding.
The intense putrid odors liberated from the sludge samples
at the commencement of each test changed to relatively
innocuous humus-like odors after lime treatment.
This deodorizing effect is not permanent, however.
Surplus amounts of lime added to the sludge can retard pH
decay and reoccurance of nuisance conditions. Further, if
the lime stabilized sludge is incorporated into the soil,
odors should no longer be a problem.
Pilot Plant Work
After development of pilot plant design and operational
parameters, construction of the pilot facility commenced.
The process flow scheme was quite simple since it basically
consisted of a sludge-lime mixing vessel and contact tank
to provide the desired contact time. Process control was
maintained by periodically monitoring pH of the discharge from
the sludge-lime contactor. Air diffusion mixing was used to
eliminate the blade fouling problems which were observed
during laboratory studies.
Sludge flows ranging from 3 to 5 gpm were treated during
pilot plant operations. Lime dose required to achieve the
desired sludge pH was monitored routinely and recorded. This
allowed optimization of lime feed to minimize process operating
costs from the lime usage standpoint. For the most part,
influent consisted of a mixture of primary and secondary
sludge from the Richland, Washington municipal trickling filter
plant. This mixture of sludges was pumped directly from the
line which feeds the Richland plant's anaerobic digesters.
Additional work was carried out using raw primary sludge and
trickling filter secondary sludge separately, and on mixed
sludges prethickened with gravity settling.
86
-------
The results from studies to determine the lime dose
required to achieve a specified pH level, pathogen reductions
resulting from lime treatment, and the effect of lime treat-
ment on sludge thickening characteristics will be discussed.
In order to optimize chemical feed during pilot plant
operations, the lime dose applied to the raw sludge was varied
and system pH response was observed. The system was allowed
to come to equilibrium after each dose change and pH was
recorded. The results from this study are shown in Table 4.
Average system pH for the series of daily rnns ranged from
12.2 through 12.4, and at no time during the runs did pH fall
below the desired 12.0 level. The average lime dose ranged
from 4.2 to 5.7 g Ca(OH)2 per liter of sludge, and the average
overall pilot plant studies was 4.9 g/£. The daily average
lime dose expressed as grams Ca(OH)2 per kilogram of raw
sludge total solids ranged from 102.2 through 207.8, and the
overall average was 141.9. These lime doses are considered
the minimum required to maintain pH at or above the desired
level (pH>12.0) during sludge processing. However, since
excess lime was not added to the system, slight pH decay with
time would be expected to occur. Paulsrud and Eikum3 deter-
mined that the lime dose required to maintain sludge pH
greater than 11.0 for fourteen days varied considerably with
the type sludge being treated and prior chemical treatment.
Regression analysis of pilot plant operating data resulted
in the following equation which related the required lime dose
and the sludge total solids concentration:
Lime Dose = 4.2 + 1.6 (TS)
where: Lime Dose is expressed as grams Ca(OH)2 per liter
of sludge
TS = total solids fraction in the sludge
87
-------
TABLE 4
SUMMARY OF PILOT PLANT OPERATING DATA
oo
CO
Mo. of Process
Control
Checks Made
1
2
3
4
% S
7
8
9
10
Averages
July 24
July 25
July 26
July 31
August 1
Ca(OH)2
Dose
gA
2.4
3.8
4.2
4.8
4.6
4.9
gAg*
£1.5
97.4
107.7
123.1
117.9
125.6
pH
12.0
12.1
12.2
12.3
12.3
12.3
Ca (Oil) 2
Dose
.?/.*
4.9
4.9
4.9
4.9
4.8
4.8
4.S
4.6
4.4
gAg*
144.1
144.1
144.1
144.1
141.2
141.2
132.4
135.3
129.4
pH
12.4
12.3
12.3
12.3
12.3
12.4
12.4
12.3
12.1
Ca(OH)2
DOSC
If-
4.2
4.3
4.4
4.8
S.2
5.2
5.4
5.7
6.4
gAg*
120.0
122.9
125.7
137.1
148.6
146.6
154.3
162.9
182.9
PH
12.0
12.1
12.2
12.2
12.3
12.3
12.3
12.2
12.2
Ca(OII)2
Dose
g/»
4.8
5.1
S.4
5.8
5.6
5.4
S.4
5.3
gAg*
123.1
130.8
138.5
148.7
143.6
138.5
138.5
135.9
pH
12.2
12.3
12.3
12.3
12.4
12.4
12.4
12.4
Ca(OU)2
Dose _„
g/t gAg* J_
4.6 135.3 12.3
4.8 141.2 12.3
4.7 138.2 12.3
4.7 138.2 12.3
4.7 138.2 12.3
4.2 105.5 12.2
4.7 139.5 12.3 5.1 144.8 12.2
5.4 137.2 12.3
4.7 138.2 12.3
•Gran* Ca(OH)j per kilogram total solid* in the raw sludge.
August 6
Mo. of Process Ca(OH)2
Control Dose
Checks Hade
1
2
3
4
5
6
7
a
. 9
10
Averages
. I/1
4.9
4.9
4.9
4.9
5.0
S.O
4.9
S.O
4.9
5.3
5.0
g/kg*
140.0
140.0
140.0
140.0
142.9
142.9
140.0
142.9
140.0
151.4
142.0
PH
12.3
12.4
12.3
12.2
12.4
12.4
12.3
12.3
12.2
12.3
12.3
August 7
Ca(0ll)2
Dose
fr"
4.4
4.4
4.6
4.6
4.8
4.8
4.4
4.6
g/kg*
200.0
200.0
209.1
209.1
218.2
218.2
200.0
207.8
pH
12.2
12.2
12.3
12.4
12.4
12.4
12.4
12.3
August 8
Ca{Oll>2
Dose
-2£L
4.4
4.4
4.7
4.8
S.O
S.O
S.O
4.8
g/kg*
125.7
125.7
134.3
137.1
142.9
142.9
142.9
135.9
PH
12.3
12.3
12.3
12.3
12.3
12.3
12.3
12.3
August 13
Ca(OH>2
Dose
"?/*
6.3
6.1
5.8
5.7
5.5
5.5
5.3
5.2
5.6
5.8
5.7
g/kg*
218.8
174.3
165.7
162.9
157.1
157.1
151.4
148.6
160.0
165.7
166.2
PH
12.4
12.4
12.4
12.4
12.}
12.3
12.3
12.3
12.3
12.4
12.4
August 14
Ca(OH)2
Dose
g/*
4.7
4.8
4.5
5.0
5,0
5.4
5.3
5.2
5.2
5.0
g/kg*
95.9
97.9
91.8
102.0
102.0
110.2
108.2
106.1
105.1
102.2
pH
12.1
12.3
12.3
12.3
12.3
12.4
12.4
12.4
12.4
12.3
•Grios Ca(OK)2 per kilogram total solids in the raw sludgo
-------
This equation suggests that the greatest portion of the lime
requirement is associated with the liquid phase and only a
small fraction of the lime demand is dependent upon the solids "
concentration. It should be recognized, however, that the
above equation describes only the initial lime demand and
does not take pH decay with time into account.
Data used to derive the relationship were obtained during
pilot plant operation when lime dose was adjusted to maintain
a pH range between 12.2 and 12.4 and lime-sludge contact time
was 30 minutes. Lime Dose is defined as the amount of lime
required to satisfy the chemical demand present in the sludge
and to provide the hydroxyl ion concentration necessary to
raise the pH to the desired level. The total sludge chemical
demand is a combination of the demand present in the liquid
phase and that present in the solid phase. The demand present
in the sludge liquid phase is largely governed by the reaction
of the lime with dissolved C02 and bicarbonate ion. This
demand is probably satisfied with relatively short lime-sludge
contact time. The solids demand is characterized by much
slower reactions of hydroxyl ions with organic materials in the
sludge (neutralizing organic acids, hydrolysis, and saporifica-
tion) so that this demand may be exerted over long periods of
time (hours or days). This long term demand exerted by the
sludge solids causes the pH decay discussed earlier and may
account in part for the greater lime doses required to reach
pH 12.4 in the laboratory jar tests than in the pilot plant
study. In the jar tests, system pH was allowed to equilibrate
after each incremental lime dose, so that several hours were
usually required to reach pH 12.4. During this time period,
hydroxyl ions were satisfying liquid and solids demand as
well as elevating pH. In the pilot plant study, the sludge
received slug doses of lime to elevate and maintain pHXL2.0
after a 30 minute sludge-lime contact time. Therefore, in the
89
-------
laboratory tests, more time was available for reaction with
organic material in the sludge solids and thus more lime was
required in the pilot plant study. In conclusion, the lime
dose required to achieve pH>12.0 is significantly affected
by the chemical demand exerted by the chemical components in
the sludge liquid and solid phases, and the long term chemical
demand is a function of the sludge total solid concentration.
The results derived in this study also indicate that the
lime dose required to maintain the pH at or above the desired
level will be affected by the natural variability of sludge
chemical composition and by any type of sludge treatment which
alters the sludge chemical makeup. Therefore, in practice,
lime dose requirements would have to be determined for each
specific sludge to be treated.
During pilot operations, studies were made of the reduc-
tions in pathogenic organisms achieved by lime treatment in
the pilot process. Once again the indicator organisms used
were fecal coliforms, fecal streptococci, Salmonella species,
and Pseudomonas aeruginosa. Typical results from these
studies are shown in Table 5 and 6.
These results show that significant pathogenic bacteria
reductions can be achieved in sludges which have been continu-
ously lime treated to pH>12.0. Reductions of fecal coliforms
and fecal streptococci were consistently greater than 99 per-
cent. Salmonella species and Pseudomonas aeruginosa appear
to be almost totally inactivated by lime stabilization.
Studies to determine the effect of lime treatment on sludge
settling characteristics were conducted on sludge processed in
the pilot process. One liter samples of raw and lime treated
sludges were placed in graduated cylinders and allowed to
settle for a specified length of time. The sludge volume at
the sludge-supernatant interface was read and recorded
90
-------
TABLE 5
FECAL COLIFORM AND FECAL STREPTOCOCCI IN UNTREATED AND TREATED SLUDGE SAMPLES
(PILOT RUNS MADE ON MIXED PRIMARY SLUDGE AND HUMUS UNLESS OTHERWISE NOTED)
Initial
pH Value
July 25, 1973
Untreated
Sludge
6.2
6.2
Treated
Sludge
12.2
12.2
July 31, 1973
Untreated
Sludge
5.9
5.9
Treated
Sludge
12.0
12.0
Lime
Contact
Time
(hrs)
0.0
0.0
0.5
0.5
(1)
0.0
0.0
0.5
0.5
pH when
Sample
Taken
6.2
6.2
12.2
12.2
5.9
5.9
11.7
11.7
Fecal Coliform
per 100 ml
4.95 x 10'
3.70 x 10'
500
<1000
5.20 x 10.
5.45 x 10'
1.00 x 10"
2.50 x 10^
Fraction
of Original
Remaining
1.16 x 10
9.25 x 10"
1.87 x 10
4.69 x 10
-4
-4
Fraction
Fecal Streptococci of Original
per 100 ml Remaining
5.00 x 10,
5.50 x 10
100
0
1.89 x 10,
1.88 x 10
200
0
1.90 x 10
0.0
-5
1.06 x 10
0.0
-5
(1)Primary sludge
-------
TABLE 5 (Cont'd.)
FECAL COLIFORM AND FECAL STREPTOCOCCI IN UNTREATED AND TREATED SLUDGE SAMPLES
(PILOT RUNS MADE ON MIXED PRIMARY SLUDGE AND HUMUS UNLESS OTHERWISE NOTED)
to
Initial
pH Value
Lime
Contact
Time
(hrs)
August 8, 1973 (2)
Untreated
Sludge
6.1 0.0
6.1 0.0
Treated
Sludge
12.3 0.5
12.3 0.5
August 14, 1973 (3)
Untreated
Sludge
6.2 0.0
6.2 0.0
Treated
Sludge
12.2 0.5
12.2 0.5
pH when
Sample
Taken
6.1
6.1
12.3
12.3
,6.2
6.2
12.2
12.2
Fecal Coliforra
per 100 ml
4.5 x 10
3.6 x 10
<1000
<1000
9.25 x iOi
6.35 x 10'
<1000
500
Fraction
of Original
Remaining
<2.47 x 10
<2.47 x 10
-5
-5
<1.28 x 10
6.41 x 10
-5
-6
Fecal Streptococci
per 100 ml
9.23 x 10
8.46 x 10l
560
33
6
2.24 x 10-
1.60 x 10'
100
170
Fraction
of Original
Remaining
6.33 x 10
3.73 x 10
-5
-6
5.21 x 10
8.85 x 10
-6
-6
(2)Humus
(3)Thickened mixed sludge
-------
TABLE 6
SALMONELLA SPECIES AND PSEUDOMONAS AERUGINOSA IN UNTREATED AND TREATED SLUDGE SAMPLES
(PILOT RUNS MADE ON MIXED PRIMARY SLUDGE AND HUMUS UNLESS OTHERWISE NOTED) '
CJ
Initial
pH Value
July 25, 1973
Untreated
Sludge
6.2
6.2
Treated
Sludge
12.2
12.2
July 31, 1973
Untreated
Sludge
5.9
5.9
Treated
Sludge
12.0
12.0
Line Contact
Time (hrs)
0.0
0.0
0.5
0.5
(1)
0.0
0.0
0.5
0.5
Ph when
Sample
Taken
6.2
6.2
12.2
12.2
'
5.9
5.9
11.7
11.7
Salmonella
Species Fraction
MPN per of Original
100 ml Remaining
5200
5400
0 0.0
0 0.0
6800
7800
0 0.0
0 0.0
Pseudomonas
Aeruginosa
MPN per
100 ml
34,000
22,000
0
0
<320,000
<320,000
0
0
Fraction
of Original
Remaining
*
0.0
0.0
0.0
0.0
(1)Primary sludge
-------
TABLE 6 (Cont'd.)
SALMONELLA SPECIES AND PSEUDOMONAS AERUGINOSA IN UNTREATED AND TREATED SLUDGE SAMPLES
(PILOT RUNS MADE ON MIXED PRIMARY SLUDGE AND HUMUS UNLESS OTHERWISE NOTED)
Initial
pH Value
August 8, 1973
Untreated
Sludge
6.1
6.1
Treated
Sludge
12.3
12.3
August 14, 1973
Untreated
Sludge
6.2
6.2
Treated
Sludge
12.2
12.2
Lime Contact
Time (hrs)
(2)
0.0
0.0
0.5
0.5
(3)
0.0
0.0
0.5
0.5
pH when
Sample
Taken
6.1
6.1
6.2
6.2
12.2
12.2
Salmonella
Species
MPN per
100 ml
2600
7000
0
0
10,800
7000
0
0
Pseudomonas
Fraction Aeruginosa
of Original MPN per
Remaining 100 ml
22,000
15,800
0.0 0
0.0 0
56,000
56,000
0.0 0
0.0 0
Fraction
of Original
Remaining
0.0
0.0
0.0
0.0
(2)Humus
(3)Thickened mixed sludge
-------
periodically. The sludge samples were also gently stirred
periodically to eliminate the effect of bridging among sludge
particles. Typical results from these tests are shown in
Figures 3-6.
In all but one instance, sludge settling characteristics
were enhanced by lime treatment. This phenomena is probably
caused by the formation of floe which settles better than the
dispersed sludge particles in the raw sludge. The supernatants
recovered from these tests were clear and had total solids
concentrations ranging from 0.1 to 0.3 percent and 0.5 to 0.7
percent in the raw sludge and treated sludge supernatants,
respectively. The higher total solids concentrations from the
treated sludge supernatants are caused by the high concentra-
tions of dissolved Ca(OK)~ introduced in the lime slurry and
from increases in dissolved organic concentration caused by
hydrolysis and saponification reactions.
These results indicate that lime treatment of sludges
prior to thickening operations would enhance the effectiveness
of the thickener. Removal of a portion of the sludge liquid
phase would reduce the overall volume of the sludge which
must receive further treatment or removal from the treatment
plant. If the thickened, lime treated sludges were to be
applied to agricultural land, removal of a portion of the
liquid phase would reduce the volume of sludge to be transported
to the disposal site. The high pH conditions created by lime
treatment would also prevent odor production in thickeners
enabling the use of longer residence times which would improve
the effectiveness of the thickener.
Growth Studies
The phase of the program dealing with the effects of
spreading lime stabilized sludges on land used for crop produc-
tion involved both greenhouse studies and larger scale outdoor
plot studies.
95
-------
10
JULY 25. 1973
MIXED PRIORY/SECONDARY SLUEGE
INITIAL SLUDGE SOLIDS CONC.. 3,4%
o RAW SLUDGE
LI ME TREATED SLUDGE
120 150 200 240
SETTLING TIME. MINUTES
FIGURE 3. EFFECT OF LIME TREATMENT ON SLUDGE SETTLING CHARACTERISTICS - 6/25/73
-------
vo
g
13
C-
o
o
t/0
<
o
1COO [
930
960
940
920
900
8SO
860
840
820
800
,1
JULY 31 1973
PRIMARY SLUDGE
INITIAL SLUDGE CONC. =3.9%
o RAW SLUDGE
A LIME TREATED SLUDGE
I I
I I I
40 80 1?0 160 200
SETTLING TIME. AM MUTES
240
2SO
FIGURE 4. EFFECT OF LIME TREATMENT ON SLUDGE SETTLING CHARACTERISTICS - 6/31/73
-------
CO
AUGUST?, 1973
SECONDARY SLUDGE
INITIAL SLUDGE SOLIDS CONC.-2.2*
o RAW SLUDGE
LI ME TREATED SLUDGE
120 160 2CO
SETTLING TIME, MINUTES
FIGURE 5. EFFECT OF LIME TREATMENT ON SLUDGE SETTLING CHARACTERISTICS - 7/7/73
-------
AUGUST 14, 1973
THICKENED MIXED SLUDGE
INITIAL SLUDGE. SOLIDS CONC.=4.9%
o RAW SLUDGE
LIME TREATED SLUDGE
30 120 ICO 200
SETTLING TIME. MINUTES
250
FIGURE 6. EFFECT OF LIME TREATMENT ON SLUDGE SETTLING CHARACTERISTICS - 7/14/73
-------
The greenhouse studies were designed to provide information
on the response of plants grown in various sludge-soil mixtures.
These studies also yielded information which was used in
design of the outdoor plot studies. The outdoor plot studies
were conducted during the summer of 1973 at the Washington
State University Irrigated Agriculture Research and Extension
Center in Prosser, Washington.
For the greenhouse studies, anaerobically digested and
lime stabilized raw sludges in liquid form were applied to
small outdoor plots at five application rates ranging from
11 to 220 metric tons per hectare (5 to 100 tons per acre).
The sludges dewatered by the mechanisms of draining and evapora-
tion, and the sludge solids were left on the surface of the
plots. After the sludge dried, the solids were spaded into
the underlying soil to approximately plow depth, 20 cm (8
inches). Sludge-soil mixtures from each were placed in pots
and barley growth was carried out. This technique for sludge
application had the advantage of very closely simulating
conditions encountered in large scale sludge spreading opera-
tions.
The sludge-soil mixtures were placed in clay flower pots
and readied for use. A set of control pots was prepared for
use in comparing plant growth characteristics and soil response
to sludge application. The control set, which contained only
soil with no sludge additions, received optimum additions of
chemical fertilizer during the actual plant growth phase of
the studies. Barley was sown in the pots and the growing
plants maintained through a full growth cycle as indicated
by the formation of grain heads.
After the full growth cycle, the plant material and sludge-
soil mixtures were subjected to analyses. The plant tissue
was weighed to determine the mass yield and then chemically
analyzed for available micro- and macronutrient content. The
100
-------
sludge-soil mixtures were analyzed both before and after plant
growth for available micro- and macronutirent content, pH,
permability with water, hydraulic conductivity, and field
capacity.
The results from analyses of the physical characteristics
of the sludge-soil mixtures used in the greenhouse studies
are shown in Table 7. The soil used for mixture with sludge
was classified as a Rupert sand which is very porous. Addition
of sludge to the soil appears to have reduced the soil's
permeability with water. This would be expected in a sandy
soil since the sludge organic matter acts to retain moisture.
No well defined trend developed which would correlate perme-
ability with the amount of sludge applied. In general, perme-
ability appears to be reduced after plant growth. This could
possibly be caused by biodegradation of the coarse organic
components in the sludge to finer humus-like material which
would fill pore spaces between larger sand particles.
The pH values in the sludge-soil mixture were usually
lower after plant growth than before. This phenomenon is
believed to be caused by C0~ buildups resulting from biological
activity in the soil.
The field capacities of the sludge-soil mixtures were
observed to be lower in the samples taken after plant growth
than in those taken before the barley was planted.
The results obtained from analyses of sludge-soil mixtures
for available macro- and micronutrients before and after the
plant growth are shown in Table 8. In general, the results
show increases in available nutrient concentrations in the
sludge-soil mixtures as sludge application rates increased.
A decrease in available nutrient concentrations apparently
occurs during plant growth. This decrease is probably caused
by nutrient uptake in the growing plants. Sludge application
to the soil at rates as low as 11 metric tons dry solids per
101
-------
TABLE 7
PHYSICAL CHARACTERISTICS OF SOILS BEFORE AND AFTER
BARLEY GROWTH IN THE GREENHOUSE STUDY
o
PO
Sludge/Soil Type and
Sludge Application Rate
Intrinsic Permeability
with Water - K' ,
(cm2)
(tons dry solids/acre)
Control
100% Rupert Sand (RS)
Mixed Primary
Humus and RS
5
30
55
80
100
Pre-Gro
3.91xlO~8
3.36x10"?.
1.91xlO~*
3.67x10"?
2.33x10"*
4.82x10"°
Post-Gro
1.44xlO"8
9.91x10"!!
1.70x10 "*
1.84x10"?.
1.73x10""
2.85xlO~8
Digested Sludge and RS
5
30
55
80
100
Primary Sludge and RS
5
30
55
80
100
Humus and RS
5
30
55
80
100
2.45x10 °
1.51x10"°
1.57x10"°
1.91xlO~p
3.97xlO~*
2.05x10"!
2.46x10"*
2.77x10"*
4.30x10"*
2.68x10"°
2.60x10"!
2.32x10 *
5.09xlO~"
4.42x10"*
2.22x10 *
1.31x10 p
2.58xlO~*
3.50x10"*
2.53x10"*
3.88xlO~*
6.86xlO"p
1.06x10"?
2.58x10"*
3.14x10"*
3.26x10"*
1.22x10"?.
2.02x10"*
5.38x10"*
4.35xlO~°
4.26x10"*
Hydraulic
Conductivity - K
(cm/sec)
Prc-Gro Post-Gro
•w.
4.61x10
-3
1.74x10
-3
Pre-Gro Post-Gro
1.00
3.96x10"?.
2.25x10,
4.34x10",
2.75x10,
5.69xlO~J
2.90x10"?.
1.78x10,
1.85x10":?
2.25x10,
4.69xlO"J
2.42x10"?.
2.90x10,
3.27x10,
5.07x10,
3.16xlO~J
3.07x10"?.
2.74x10",
6.01x10,
5.22x10,
2.62xlO"J
1.17x10"^
2.00x10,
2.17x10":}
2.04x10 ,
3.36xlO~J
1.54x10":*
3.04x10,
4.13xlO~:(
2.99x10",
4.58xlO~J
8.09x10"*
1.25x10",
3.04x10",
3.70x10",
3.85xlO~J
1.44x10"^
3.39x10"^
6.36x10",
5.14x10",
5.04xlO"J
0.86
0.49
0.94
0.60
1.23
0.63
0.39
0.40
0.49
1.01
0.53
0.63
0.71
1.10
0.69
0.66
0.59
1.30
1.13
0.56
0.38
0.25
0.43
0.47
0.44
0.72
0.33
0.66
0.89
0.64
0.99
0.18
0.27
0.66
0.30
0.84
0.31
0.74
1.38
1.11
1.09
1. Ratio of the hydraulic conductivity of the sludge-soil mixture (Km) to that of the
control (KC) before the growth cycle.
2. Soil pH measured in water.
3. 1/3 bar percentage.
Field Capacity of
Mixture3 (% of
soil dry wt.)
Pre-Gro Post-Gro Pre-Gro Post-Gro
PH of
Mixture^
7.6
7.8
8.1
8.5
10.6
10.2
7.0
6.5
6.7
6.8
6.8
7.8
7.6
7.9
8.1
10.0
6.1
7.6
8.1
8.1
8.1
8.2
7.3
6.8
6.6
6.3
6.7
7.6
7.6
7.6
7.7
7.7
5.5
9.1
9.4
13.9
15.9
11.4
8.6
13.3
15.2
15.6
16.1
7.6
8.4
10.7
14.9
15.0
4.6
7-1
8.9
10.2
9.6
5.3
6.8
8.2
12.4
11.1
9.2
4.2
5.4
4.2
6.4
5.5
7.9
8.5
8.0
8.1
8.3
8.2
8.3
8.0
8.0
8.0
7.7
13.2
13.2
16.1
20.2
3.5
5.6
4.4
4.4
6.4
-------
TABLE 8
MACRO- AND MICRONUTRIENT CONCENTRATIONS IN SLUDGE-SOIL MIXTURES
BEFORE AND AFTER BARLEY GROWTH IN THE GREENHOUSE STUDY
Sludge/Soil Type and
Sludge Application Rate
(tons dry solids/acre)
Control
100% Rupert Sand (RS)
Nitrate-N (ppm)
Pre-Gro Post-Gro
37
Phosphorus (ppm) Potassium (ppm) Sulfur (ppm)
Pre-Gro Post-Gro Pre-Gro Post-Gro Pre-Gro Post-Gro
100
280
106
10
Magnesium (ppm) Calcium (ppm)
Pre-Gro Post-Gro Pre-Gro Post-Gro
108
144
360
320
Mixed Primary and
Secondary Sludge and RS
5 13
30 43
55 25
80 2
100 2
9
88
125
175
275
13
41
60
78
50
200
210
190
210
240
150
110
120
150
120
9
50
48
0
0
s
26
33
0
24
120
132
120
120
132
120
96
108
132
132
520
2160
2200
3040
3080
720
1900
2400
2800
2300
o
CO
Digested Sludge and RS
5
30
55
80
100
19
35
3
1
1
2
1
7
23
4
18
40
85
46
116
11
56
104
110
122
240
240
240
190
190
150
80
100
80
80
44
140
150
200
210
12
23
120
185
120
120
132
120
120
132
120
96
96
120
96
460
540
560
680
720
420
520
560
600
600
Primary Sludge and RS
5
30
55
80
100
11
36
34
1
2
1
14
2
1
2
16
60
125
225
220
20
104
69
130
110
170
210
240
240
240
120
110
100
110
120
0
46
57
0
0
3
25
16
27
48
120
120
132
120
120
120
120
96
96
120
600
1660
2100
2760
2640
460
920
1320
1800
2040
Humus and RS
5
30
55
80
100
19
4
15
1
2
2
3
2
2
26
15
60
150
200
250
16
59
130
244
244
200
190
210
290
290
140
110
30
SO
100
12
12
39
60
0
4
4
9
30
44
120
120
108
144
168
120
96
132
132
144
520
1120
1460
1660
2000
560
1600
1460
2200
2080
-------
TABLE 8 (Cont'd.)
MACRO- AND MICRONUTRIENT CONCENTRATIONS IN SLUDGE-SOIL MIXTURES
BEFORE AND AFTER BARLEY GROWTH IN THE GREENHOUSE STUDY
Sludge/Soli Type and
Sludge Application Rate
(tons dry solids/aero)
Control
lOOt Rupert Sand (RS)
Sodium (ppra)
Iron (ppm)
Manganese (ppm)
Boron (ppm)
Copper (ppm)
Zinc (ppn)
Pro-Gro Po3t-Cro Pre-Cro Poat-Oro Pro-Cro Pont-Gro Pro-Cro Post-Gro Pro-Cro Pont-Cro Pre-Cro Poat-Cro
75
33
68
73
37
26
0.5
0.5
Mixed Primary and
Secondary Sludge and RS
S 50 44 197 42 95 102 0.4 0.6 8
30 87 55 210 106 70 63 0.6 0.7 10
55 110 67 217 117 180 140 0.6 1.0 9
80 112 112 245 103 85 70 0.5 0.8 11
100 142 105 • 177 208 137 133 0.5 0.5 12
6
7
12
10
9
2
27
26
SO
68
7
21
26
37
2$
Digested Sludge and RS
S 27 23 288 56 84 52 0.8 0.6 7 10 , 8 15
30 80 95 310 60 90 86 1.1 0.7 11 12 46 38
55 90 85 211 187 76 102 1.4 1.1 10 6 68 88
80 145 77 214 210 66 140 1.7. 1.3 9 8 33 125
100 160 93 186 200 83 92 1.3 1.5 13 12 172 105
Primary Sludge and RS
5
30
55 .
80
100
52
30
140
76
126
67
(3
85
112
107
53
70
93
112
312
47
57
100
60
94
40
65
93
130
100
105
88
115
105
95
0.8
0.9
0.9
0.8
0.5
0.4
1.0
0.5
0.9
0.6
11
9
12
10
14
6
11
7
9
12
3
30
26
70
48
7
27
20
30
40
Humus and RS
5
30
55
80
100
28
33
122
207
237
43
40
113
86
120
108
88
96
300
420
85
96
105
80
106
85
97
83
70
100
110
62
105
72
55
0.4
0.7
0.9
1.0
1.1
0.5
1.2
0.6
0.8
0.9
9
12
11
10
12
7
12
12
9
2
10
22
40
37
5
10
18
36
34
-------
hectare (5 tons dry solids per acre) significantly increased
the concentrations of available calcium and iron in the mix-
tures. The increase in calcium concentration was expected
because of the lime added to the sludges. Application of mod-
erate to high amounts of sludge caused significant increases
in the concentrations of available phosphorus, sodium,
manganese, and zinc.
Results from the study of barley weight gains are shown
in Table 9. The control pots which received only chemical
fertilizer yielded plants which averaged only 4.7 grams each.
However, the addition of sludge to the soils significantly
affected the yield. The sludge-soil mixtures made from mixed
primary sludge and humus, primary sludge alone, and humus alone,
applied at the lowest rate of 11 metric tons dry solids per
hectare (5 tons dry solids per acre) all yielded less plant
material than the control pots which received only chemical
fertilizer. The mixture made from Rupert sand and digested
sludge applied at 11 metric tons dry solids per hectare (5
tons dry solids per acre) produced plants whose average weight
exceeded that of the control by almost 2.5 times. The mixtures
made from mixed sludge and digested sludge applied to Rupert
sand all produced increasing plant material yields as the sludge
application rates increased from 66 through 176 metric tons
dry solids per hectare (30 through 80 tons dry solids per acre).
Plant yield decreased for each of these sludge-soil types when
the application rate reached 220 metric tons dry solids per
hectare (100 tons dry solids per acre). The mixtures made
from primary sludge and humus applied to Rupert sand produced
increasing plant yields as sludge application rates increased
through 220 metric tons per hectare (100 tons per acre).
These results indicate that sludge addition to poor soils
would increase productivity and therefore would be beneficial.
The addition of large amounts of lime to the sludges did not
appear to produce any detrimental effects.
105
-------
TABLE 9
BARLEY WEIGHT GAINS FROM THE GREENHOUSE STUDY
Sludge/Soil Type and
Sludge Application Rate
(tons dry solids/acre)
Control
100% Rupert Sand (RS)
Mixed Primary Sludge
and Humus and RS
5
30
55
80
100
Digested Sludge and RS
5
30
55
80
100
Primary Sludge and RS
5
30
55
80
100
Humus and RS
5
30
55
80
100
Total Total Weight of
Number All Plant Tissue Produced
Plants (grams)
16 74.8
16 67.0
16 158.6
15 200.1
15 252.6
16 206.5
14 162.1
15 211.6
17 253.2
16 309.4
15 219.2
16 36.1
14 122.8
16 144.5
17 122.2
17 176.4
15 41.2
16 122.2
16 175.6
14 238.6
16 297.2
Average Weight of
Tissue in Each Plant
(grams/plant)
4.7
4.2
9.9
13.3
16.8
12.9
11.6
14.1
14.9
19.4
14.6
2.3
8.8
9.0
7.2
10.4
2.8
7.6
11.0
17.0
18.6
Yield Ratio*
(grams/gram)
1.00
0.89
2.12
2.83
3.57
2.74
2.47
3.00
3.17
4.13
3.11
0.49
1.87
1.91
1.53
2.21
0.60
1.62
2.34
3.62
3.96
'Calculated as grams plant tissue from the sludge-soil mixtures per gram plant tissue from the
control pots.
-------
Results from analysis of macro- and micronutrient content
of the barley grown in this study are shown in Table 10. The
total nitrogen and phosphorus levels in the plants grown in
the test pots which contained sludge-soil mixtures were
consistently lower than in the plants grown in the control
which contained only soil. These results cannot be interpreted
as indicating a nitrogen or phosphorus deficiency in the soils
which received sludge treatment since plant production in
these pots generally exceeded that in the control pots. The
calcium concentration in plant tissues from pots which received
sludge applications was higher than in the plant tissue from
the control pots. Zinc concentration was considerably higher
in the tissue of plants grown in pots which received digested
sludge than in any of the other plant tissues tested.
In order to further evaluate the short term effects of
spreading lime treated sludge on crop land, larger scale crop
growth studies were conducted on outdoor plots at the Washington
State University Irrigated Agriculture Experiment and Extension
Center in Prosser, Washington. The soil at the site was
classified as Warden silt loam. The site had not been used for
any agricultural experiments during the preceding year. Five
0.04 hectar (0.1 acre) plots were used: one control plot
received no sludge (only application of optimum fertilizer
requirements); two plots received applications of anaerobically
digested sludges at rates equivalent to 22 and 88 metric tons
dry solids per hectare (10 and 40 tons per acre); and two
plots received lime treated mixed primary sludge and humus
at the same application rates used for the digested sludge.
Buffer zones were provided between plots to assure individual
plot integrity during sludge spreading operations, plant
growth, and harvesting operations. The sludge was transported
to the site by a contracted septic tank service man. Even
distribution of the sludge on the plots was accomplished by
use of a splasher plate attached to the tank truck discharge
port.
107
-------
TABLE 10
MACRO- AND MICRONUTRIENTS IN BARLEY TISSUE FROM THE GREENHOUSE STUDY
(ALL SLUDGES LIME TREATED EXCEPT THE DIGESTED SLUDGE)
Sludge/Soil Type and
Sludge Application Rate Total N
(tons dry solids/acre) (%)
Control
100% Rupert Sand (RS) 4.1
Phosphorus Potassium Sulfur Magnesium Calcium Sodium Iron Manganese Boron Copper Zinc
(») (%) C%) (%) (%) (%) (ppm) (ppra) (ppm) (ppm) (ppm)
1.14
3.10
0.32
0.98
0.75
0.58
478
36
31
11
31
O
00
Mixed Primary and
Secondary Sludge and RS
5 1.2
30 1.3
55 1.6
80 1.5
100 1.9
Digested Sludge and RS
5 ' 1.9
30 2.6
55 3.2
80 3.9
100 3.2
Primary Sludge and RS
5 1.4
30 2.1
55 2.1
80 2.0
100 2.7
Humus and RS
5 1.2
30 2.6
55 2.5
80 3.0
100 3.2
0.45
0.62
0.51
0.46
0.52
0.42
0.56
0.52
0.59
0.51
0.44
0.39
0.39
0.55
0.42
0.50
0.45
0.70
0.54
0.42
3.48
4.32
3.60
3.23
3.41
0.32
0.49
0.38
0.34
0.43
0.37
0.44
0.45
0.45
0.44
1.12
1.23
1.20
1.45
1.25
0.21
0.26
0.38
0.63
0.58
450
700
800
433
445
68
73
98
122
120
14
16
16
24
21
11
16
14
11
12
70
107
93
68
74
4.40
3.40
2.82
2.55
2.38
0.40
0.40
0.41
0.36
0.39
0.37
0.45
0.45
0.41
0.38
0.92
1.50
1.68
1.68
1.50
0.59
0.75
0.95
1.20
1.00
800
820
550
950
550
60
102
215
221
187
23
34
55
50
45
14
19
21
23
21
92
450
500
550
500
0.21
0.26
0.38
0.63
0.58
0.59
0.75
0.95
1.20
1.00
0.38
0.70
0.85
0.70
1.00
0.38
0.75
0.85
0.95
1.00
450
700
800
433
445
800
820
550
950
550
1250
428
475
415
500
650
950
550
600
700
4.00
3.75
3.41
3.87
3.05
0.35
0.39
0.48
0.50
0.49
0.41
0.41
0.37
0.37
0.38
1.15
1.20
1.37
1.12
1.25
0.38
0.70
0.85
0.70
1.00
1250
428
475
415
500
55
44
60
53
65
16
19
14
13
15
13
13
11
14
14
70
77
84
110
90
4.00
3.60
3.55
3.23
3.00
0.31
0.36
0.40
0.40
0.40
0.38
0.37
0.40
0.43
0.43
0.87
1.20
1.55
1.55
1.75
0.38
0.75
0.85
0.95
1.00
650
950
550
600
700
44
97
145
138
135
20
27
31
25
21
9
15
15
16
16
57
62
84
95
79
-------
After sludge application, the plots were allowed to dry
and were then prepared for planting. Samples for analyses of
soil physical and chemical characteristics were taken at this
time. Sudan grass, an annual pasture grass adapted to Eastern
Washington State, was used as an indicator plant. Maintenance
of the plots during plant growth mainly involved periodic
application of irrigation water and was carried out by the
staff of the WSU Experiment Center. In early autumn when danger
from frost damage was imminent, the grass was harvested. The
yield from each plot was recorded, and plant matter and soil
samples were collected for analyses. These samples were sub-
jected to the same tests as conducted on the plant tissue and
soil samples from the greenhouse studies.
The results from analyses of physical characteristics of
soils before and after Sudan grass cultivation are shown in
Table 11. Intrinsic permeability with water slightly improved
in the soils from all plots during the growth study. The
greatest improvements occurred in the plots which received
sludge application of 88 metric tons dry solids per hectare.
A slight decrease in soil pH was observed in the samples
collected after the Sudan grass was harvested.
Field capacity varied slightly between the beginning and
the end of the growth study. No general trend could be
established and the variations in most cases were not signifi-
cant.
The results from analysis of macro- and micronutrients in
the outdoor plots before and after plant growth are shown in
Table 12. Increases in the nutrient concentration resulted from
the application of sludges at the rate of 88 metric tons dry
solids per hectare.
109
-------
TABLE 11
PHYSICAL CHARACTERISTICS OF SOILS BEFORE AND AFTER
SUDAN GRASS CULTIVATION IN THE OUTDOOR PLOT STUDIES
Sludge/Soil Type and
Sludge Application Rate
Control
100>. Harden Silt
Loan(KSL)
Intrinsic Permeability
Hydraulic
3'
Digested
and WSL
10
L.i.7,e Treated 10
and KSL
Digested
and KSL
40
Lixe Treated 40
with Water - K'w
(cm2)
Pre-Gro
7.25xlO~9
8.70xlO"9
1.81xlO~8
4.57xlO~8
5.95xlO~8
Post-Gro
7.98xlO"9
9.43xlO"9
1.96xlO"8
5.22xlO"8
6.60xlO"8
Conductivity - K ™ /r
(cm/sec) c
Pre-Gro
8.56xlO~*
1.02X10"3
2.14xlO~3
5.39xlO"3
7.02xlO~3
Poat-Gro
9.42xlO"4
l.llxlO"3
2,31xlO~3
6.16xlO~3
7.79xlO~3
Pre-Gro
1.0
1.2
2.5
6.3
8.2
Post-Gro
1.1
1.3
2.7
7.2
9.1
PH Of
Mixture4
Pre-Gro
6.7
6.6
7.3
6.6
8.0
Post-Gro
6.5
6.3
6.8
6.7
6.8
of Mixture5 '
(% of soil dry wt.)
Pre-Gro
22
25
28
28
32
Post-Gro
23
24
30
26
34
1. Control plot received recommended chemical fertilizer application instead of sludge.
2. Lir-e treated sludge was a mixture of primary sludge and trickling filter humus.
3. Ratio of the hydraulic conductivity of the sludge/soil mixture (1^) to that of the
control (Kc) before the growth cycle.
4. Soil pK measured in water.
5. 1/3 bar percentage.
-------
TABLE 12
MACRO- AND MICRONUTRIENT CONCENTRATIONS IN OUTDOOR
PLOTS BEFORE AND AFTER THE OUTDOOR GROWTH STUDY
Sludge Type and
Nitrate-N (ppm) Phosphorus (ppm)
Potassium (ppm)
Sulfur (ppm)
Magnesium (ppm)
Calcium (ppm)
Application Hate
(tons dry solids/acre)
ControlA
Digested 10
Lime Treated8 10
Digested 40
Lime Treated 40
Sludge Type and
Application Rate
(tons dry solids/acre)
ControlA
Digested 10
n
Lime Treated 10
Digested 40
Lime Treated 40
Pre-Gro
2
25
84
63
87
Sodium
Pre-Gro
66
66
88
110
110
Post-Gro
12
19
6
7
15
(ppm)
Post-Gro
33
40
33
40
40
Pre-Gro
26
33
43
56
104
Iron
Pre-Gro
21
28
32
44
45
Post-Gro
29
32
26
132
180
(ppm)
Post-Gro
40
52
54
73
70
Pre-Gro
340
360
280
460
460
Post-Gro
300
220
180
270
300
Mangnnese (ppm)
Pre-Cro
9
13
14
27
23
Post-Gro
16
49
82
93
110
Pre-Gro
5
15
22
58
54
Boron
Pre-Gro
0.3
0.4
0.4
0.6
0.5
Post-Gro
6
10
7
16
17
(ppm)
Post-Gro
0.5
0.5
0.4
0.7
0.7
Pre-Gro
216
216
228
252
216
Copper
Pre-Gro
10.0
1.5
1.7
2.9
1.5
Post-Gro
168
180
180
192
180
(ppm)
Post-Gro
1.1
2.5
2.6
8.8
6.0
Pre-Gro
1320
1280
1600
1600
2160
Zinc
Pre-Cro
18.5
11.5
12.0
30.0
15.0
Post-Gro
960
• 960
1140
1240
1560
(ppm)
Post-Gro
4.2
16.5
14.8
68.0
50.0
Control plot received optimum chemical fertilizer application instoad of sludge.
Q
Lime treated sludge was a mixture of primary and secondary sludge.
-------
The average maximum plant heights and the green tonnage
yields resulting from growth of the Sudan grass are summarized
below.
Test Plot
Control (no sludge)
Digested Sludge
22 metric tons dry solids/hectare
88 metric tons dry solids-hectare
Lime Stabilized Sludge
22 metric tons dry solids/hectare
88 metric tons dry solids/hectare
HEIGHT
cm in
66 26
YIELD
117
132
89
132
46
52
35
52
m. tons/ tons/
hectare acre
11.77
20.35
24.20
17.16
25.96
5.35
9.25
11.00
7.80
11.80
The Sudan grass growth on the plots which received sludge
applications was more luxurient than on the control plot which
received only an optimum application of chemical fertilizer.
For the plots which received 22 metric tons dry solids per
hectare, the grass reached heights of 117 cm (46 inches) with
digested sludge applied and 89 cm (35 inches) with lime
stabilized sludge applied. The grass which received lime
treated sludge had a yellowish tinge while the grass in the
digested sludge plot had a healthy dark green appearance. In
each of the plots which received 88 metric tons dry solids per
hectare of digested and lime stabilized sludge, the grass grew
to a height of 132 cm (52 inches). The plants in both of
these plots exhibited dark green, healthy appearances.
Results from analysis of Sudan grass for macro- and micro-
nutrient content are shown in Table 13. These results indicate
that the amount of nutrients concentrated in the plant tissue
112
-------
TABLE 13
MACRO- AND MICRONUTRIENT CONCENTRATIONS IN
SUDAN GRASS TISSUE FROM OUTDOOR GROWTH STUDY
Sludge Type * Nitrate P K S Kg Ca Na Fe Mn B Cu Zn
Application Rate Nitrogen Phosphorus Potassium Sulphur Magnesium Calcium Sodium Iron Manganese Boron Copper Zinc
(tons dry solids/acre)
Control1
Digested
Lime Treated2
Digested
Line Treated2
10
10
40
40
ppm
800
100
0
600
500
%
.5
.47
.52
.48
.42
%
3.05
3.20
2.85
2.75
2.37
t
.24
.19
.14
.15
.16
%
.40
.41
.42
.44
.42
%
.52
.77
.80
1.00
.95
t
.06
.09
.22
.10
.09
ppm
370
530
1800
640
1850
ppm
48
34
55
40
38
ppm
7.0
7.0
9.5
8.0
7.5
P?m
10.5
11.0
8.5
12.0
6.5
ppn ._
66
80
50
50
34
1. Control plot received recommended chemical fertiliser application instead of sludge.
2. Lime treated sludge was a mixture of primary and secondary sludge.
-------
is independent of the amount or type of sludge applied to the
land in which the plants are grown. Also, there were no
indications of buildup of excessive amounts of nutrients in
the plant material with the exception of calcium and iron
which did show concentration increases over those in the chemi-
cally fertilized control plot.
DESIGN AND COST CONSIDERATIONS
Process Design
Based upon this work, it appears that the two most
important process variables which must be considered are pH
and contact time. Results indicate that the lime dose to the
raw sludge should be sufficiently high to initially attain
pH>12.0. Moreover, the lime dose should be high enough to
prevent significant pH decay during storage. In the labora-
tory and pilot plant work conducted in this program, short
term (one hour) lime-sludge contact at pH>_12.0 provided
excellent reduction in viable pathogenic bacteria populations,
but upon storage pH was subject to decay. Therefore, in
practice, excess lime should be added to maintain the desired
pH level during storage.
The lime dose required to achieve and maintain high pH
levels will vary considerably among different types of sludges;
and even for the sludge produced at a specific treatment plant,
the required dose will probably be subject to temporal varia-
tions. The quantity of lime required to achieve the desired
condition in any particular sludge can be determined easily
in the laboratory. Sludge samples of a known volume can be
titrated with a lime slurry until the desired pH level is
achieved. Sludge samples dosed with the minimum lime addition
required to reach the desired pH and others dosed with increas-
ing multiples of this amount could then be stored and pH
decay observed over a period of time.
114
-------
By using this procedure, a good indication of the lime dose
required to achieve and maintain the desired conditions could
be obtained. A full scale process can be designed with auto-
matic process control equipment.
A possible process flow scheme is shown in Figure 7. The
process flow is basically the same as that used in the pilot
plant operated for this study. The main variations are provi-
sions for automatic process control and the capability for
adding excess lime in the sludge-lime contactor.
Process operation consists of introducing sludge into a
mixing vessel where lime slurry is added. The pH level of the
sludge in this vessel is continuously monitored and lime slurry
addition automatically altered when the pH deviates from the
setpoint. Sludge whose pH had been elevated to the desired
level is continuously passed from the mixing vessel to a sludge-
lime contactor. This contactor is also mixed and the excess
lime required to prevent pH decay is added at this point.
The quantity of excess lime is a specified multiple of the
dose being added in the sludge-lime mixing vessel. This lime
feed system provides positive process control since lime addi-
tions in the mixing vessel vary in accordance with temporal
variations in sludge chemical demand. The addition of excess
lime to maintain desired conditions is directly tied to the
lime dose added in the mixing vessel.
Process Costs
Cost estimates for a lime stabilization process must be
based on laboratory and pilot plant information. Lime costs
may be easily and accurately estimated from chemical dose data
from laboratory and pilot plant work. The chemical cost esti-
mates made in this section were based on a hydrated lime cost
of $22 per metric ton ($22 per short ton). Operating and
maintenance (O&M) costs were estimated as shown below.
115
-------
Ca(OH)2
SLURRY
kSTORAGE
NO. 2
Ca(OH>2
SLURRY
FEED
PUMP
NO. 1
Ca(OH>2
SLURRY
FEED
PUMP
pH MONITOR
AND RECORDER
RAW SLUDGE
SLUDGE/
CKOH)2
MIXING
VESSEL
STABILIZED SLUDGE
TO THICKENER.
STORAGE, OR
IMMEDIATE DISPOSAL
FIGURE 7. LIME STABILIZATION PROCESS CONCEPTUAL FLOWSHEET
-------
COSTS
($/metric ton sludge solids)
Electricity , $0.76
Operating Labor 4.32
Maintenance Labor 1.22
Repair Materials 0.44
Other Operating Costs
(not included above) 0.26
Total Estimated O&M Costs $7.00
The $0.26 included under "Total Operating Costs" was added to
account for sludge pumping and mixing costs which would have
been excluded otherwise. For a 37,850 m /day (10 MGD) sewage
treatment plant which produces a total sludge flow of approxi-
mately 255 m /day (67,000 gal/day), the total capital cost of
a lime stabilization process would probably be less than $8000.
This cost includes tankage, piping, chemical feed system, and
automatic control instrumentation. This cost is too small to
be financed by a bond issue and would probably be paid directly
from an account set to finance such low cost improvements of
municipal facilities. Since capital costs are considered
insignificant, the major cost of the lime stabilization process
would be O&M costs which, as stated above, would amount to
approximately $7.00 per metric ton of sludge solids treated.
From his work in Ohio, Farrell1 estimated that lime addi-
tion to an alum primary sludge cost an average of $4.95 per
metric ton sludge solids. By adding the O&M costs developed
previously to this chemical cost, a total O&M cost estimate
of $11.95 per metric ton sludge solids was obtained. Farrell1
also found that iron primary sludges had an average lime cost
of $2.50 per metric ton sludge solids. Therefore, total O&M
costs in this case would be about $9.50 per metric ton sludge
solids. The amount of lime applied to the sludges in this
117
-------
study was, in general, the minimum dose required to raise pH
to 11.5. Excess lime to maintain pH above a specified level
was not added.
O&M cost estimates based on the work done by Paulsrud
and Eikum3 were also developed for comparison purposes.
The dose required and the estimated costs for lime stabiliza-
tion of various types of sludges are summarized in Table 14.
The recommended lime doses are those required to maintain
pH>11.0 in sludges stored for fourteen days at 20°C. The
total estimated O&M costs using these recommended lime doses
range from $9 to $19 per metric ton sludge solids. These
results indicate that treatment costs will be mainly dependent
on chemical requirements which will vary with the type of
sludge being treated and the chemical pretreatment history
of the sludge.
Process costs developed from the results of this program
agree with those developed from the results of the other
investigators. Chemical cost estimates were based on an
average lime dose of 150 g Ca(OH)2/kg sludge total solids
required to achieve pH>_12.0 and maintain that level for one
hour. Lime costs in this case were found to be $3 per metric
ton sludge solids, so that estimated total O&M costs would be
$10 per metric ton sludge solids.
A comparison of approximate capital and operating costs
for various sludge stabilization processes is shown in Table 15,
PROCESS APPLICATIONS
There are several situations where application of the
lime stabilization process could be advantageous. Small treat-
ment plants which do not produce large quantities of sludge
and have access to land for disposal by spreading could cer-
tainly use a simple, reliable, and inexpensive sludge treat-
ment process. Another possible strategy, as suggested by
118
-------
TABLE 14
O&M COSTS FOR LIME STABILIZATION
Type of Sludge
(g Ca(OH)2/kg SS)
Lime
Costs
($/metric ton)
Total2
O&M Costs
($/per metric ton)
Primary sludge
Septic tank sludge
Biological sludge
Al-sludge
(Secondary precipitation)
Al-sludge
(Secondary precipitation
+ Prim, sludge (SSAI:SSPRIM
= 1:1)1
Fe-sludge
(Secondary precipitation)
100 -
100 -
300 -
400 -
250 -
350 -
150
300
500
600
400
600
2.00
2.00
6.00
8.00
5.00
7.00
- 3.00
- 6.00
- 10.00
- 12.00
.
- 8.00
- 12.00
9.00
9.00
13.00
15.00
12.00
14.00
- 10.00
- 13.00
- 17.00'
- 19.00
- 15.00
- 19.00
1SS = suspended solids.
2Sum of lime cost and $7.00 O&M cost estimated previously.
-------
TABLE 15
APPROXIMATE CAPITAL AND OPERATING COSTS FOR
VARIOUS SLUDGE STABILIZATION PROCESSES
ro
o
O&M Cost
Capital Cost
Total Cost
Anaerobic Digestion
$ per Metric Ton
Dry Solids
7.00
24.00
31.00
Multiple Hearth
Incineration
$ per Metric Ton
Dry Solids
12.00
23.00
35.00
Lime
Stabilization
$ per Metric Ton
Dry Solids
10.00
Insignificant
10.00
-------
Paulsrud and Eikum,3 is for small treatment plants to use
lime stabilization as a preparatory step for sludge storage.
The stored, lime treated sludge would be periodically hauled
away to larger facilities for further treatment and/or disposal.
For plants which utilize digestion and do not have excess
digester capacity, lime treatment may provide a satisfactory
means of stabilizing sludge prior to ultimate disposal.
Sludge flows in excess of digester capacity could be bypassed
to a separate lime treatment facility. Another option would
be to use existing digesters to thicken lime treated sludge
prior to dewatering or disposal.
Lime stabilization could also be used as a stop-gap
technique when digesters or other sludge treatment processes
temporarily are not working. In this context, lime stabiliza-
tion would be used as an emergency backup process. In a
temporary process, sludge pH could be manually monitored on a
periodic basis and the lime dose adjusted as required.
Alternatively, if sludge were being hauled away regularly by
tank truck, lime could be injected into the sludge as it was
pumped into the truck. This technique was tried during the
course of this program and was found to work quite well. The
septic tank truck used to haul and spread lime treated sludge
on the outdoor plots used a vacuum system for sludge loading.
A vacuum was taken on the truck tank and sludge was pulled
into the tank. The technique used to inject lime slurry
into raw sludge as it was being loaded into the tank was
quite simple. A suction line with a one-half inch ball valve
for slurry metering was attached to an existing threaded
opening in the tank sludge loading port. Then, when suction
was applied, both sludge and lime slurry were pulled into the
tank. Mixing occurred at the point of slurry injection and
during transport to the outdoor plots. Composite samples
were taken during sludge spreading operations and were found
to be at pH of 12.2. This technique of lime addition could
easily be applied for lime stabilization during emergency
operations.
121
-------
SUMMARY AND CQNSLUSIONS
A process for producing lime stabilized sludge was
developed and operated successfully at pilot scale. Signifi-
cant reductions in pathogen populations and obnoxious odors
resulted from lime treatment. Growth studies, both in a green-
house and on outdoor plots, indicate that disposal of lime
stabilized sludge on cropland would have no detrimental effects,
On the basis of laboratory, pilot plant, and crop growth
studies, the following major conclusions were drawn.
Laboratory Studies
• Lime dose required to raise the pH of a given sludge to a
specified level was significantly influenced by the
chemical characteristics of the sludge and by the tech-
nique used to mix the lime and sludge. The required
amount of lime to elevate pH of a mixed primary and
trickling filter sludge to 12.4 was found to vary from
4 to 10 g/£ as the sludges total solid concentration
varied from 1.0 to 4.4 percent.
• The chemical demand for lime exerted by the chemical
components of the sludge caused a pH decay over time;
although an oversupply of OH ions by addition of
excess Ca(OH)2 can retard this decay.
• Significant reductions in indicator and pathogenic
bacteria were achieved by lime treatment of sludge to
pH>12.0.
• Lime treatment had a deodorizing effect on sludge.
The threshold odor numbers in a sludge with a 2.0 per-
cent total solid concentration was reduced by 88 per-
cent at pH>11.2. An 83 percent threshold odor number
reduction was attained in a lime treated sludge with a
4.4 percent total solid concentration at pH>11.6.
122
-------
Pilot Plant Studies
• The lime dose required to achieve pHXL2.0 is signifir
cantly affected by the chemical demand exerted by
the chemical components in the sludge liquid and solid
phases, and the long term chemical demand is a
function of the sludge total solids concentration.
• Continuous processing of the sludge to pHXL2.0 reduced
the pathogenic bacteria and indicator organism popula-
tion by >99 percent.
• Lime treatment significantly improved the sludge's
settling characteristics.
Growth Studies
• In a silt loam type soil, application of sludge appeared
to increase permeability with water; whereas, sludge
application to a sandy soil appeared to decrease
permeability.
• Application of lime treated sludge did not significantly
increase soil pH. The pH level of the soil-sludge
mixtures was lower after plant growth than before.
• Application of lime treated sludge to cropland did
increase the concentration of nutrients available
to plants.
• Application of the proper amount of lime treated
sludge appeared to improve soil productivity as indi-
cated by mass of plant material produced.
• Excessive concentration of nutrients by plants did
not appear to be a problem. The concentration of iron
was consistently higher in the soils which received
sludge applications.
123
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ACKNOWLEDGMENTS
This work was funded by the Ultimate Disposal Research
Program Branch, EPA National Environmental Research Center,
Cincinnati, Ohio, under Project No. 68-03-0203.
124
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REFERENCES
1. Farrell, J. B., J. E. Smith, S. W. Hathoway, and R. B. Dean,
"Lime Stabilization of Primary Sludges at 1.15 MGD," Journal
Water Pollution Control Federation, 46, 1, p. 113, 1974.
2. Doyle, C. B., "Effectiveness of High pH for Destruction of
Pathogens in Raw Filter Cake," Journal Water Pollution Control
Federation, 39, 8, p. 1403, 196TI
3. Unpublished Data. B. Paulsrud and A. S. Eikum, Norwegian
Institute for Water Research, P. 0. Box 333, Oslo, Norway,
April 1974.
4. Kenner, B. A., G. K. Dotson, and J. E. Smith, Jr., "Simul-
taneous Quantitation of Salmonella Species and Pseudomonas
aeruginosa," EPA, National Environmental Research Center,
Cincinnati, Ohio, September 1971.
5. Standard Methods for the Examination of Water and Wastewater,
13th Edition, published by the American Public Health
Association, American Water Works Assoication, and the
Water Pollution Control Federation, 1971.
125
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126
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THERMAL DEGRADATION Of SLUDGES*
by
Robert A. Olexsey**
INTRODUCTION
To a sanitary engineer, a simplified wastewater treatment plant resembles
the process outlined in Figure 1. Hydraulically, it is a steady state, steady
flow process. "X" gallons of relatively pure water come in and "X" gallons of
relatively more pure water go out.*** Along the way, by-products in the form of
>
semi-solid contaminants are discharged.
The specialist in ultimate disposal is primarily concerned with the
handling and disposal of these semi-solid materials collectively known as
sludge. To an "ultimate disposalist" the same wastewater treatment plant
could be schematically depicted as in Figure 2. This analogy to a sludge
factory is appropriate. Sludge is a material manufactured at the treatment
plant. The raw materials are sewage and any chemicals that may be added at
the plant. The manufacturing processes are the various treatment steps
such as sedimentation, aeration, and advanced waste treatment. At the sludge
factory, the relationship between the sludge product and the effluent by-
product is not an obscure one. The larger the quantity of product manu-
factured, the higher the quality of the by-product discharged.
From a manufacturing engineering standpoint, we are concerned with pro-
ducing as much sludge as possible as quickly and efficiently as possible and
* Presented at Symposium on "Pretreatment and Ultimate Disposal of Waste-
water Solids" sponsored by EPA Region II and Department of Environmental
Science, Rutgers University, New Brunswick, New Jersey, nay 21-22, 1974.
** Mechanical Engineer, Ultimate Disposal Section, Treatment Process Develop-
ment Branch, Advanced Waste Treatment Research Laboratory, National
Environmental Research Center, U. S. Environmental Protection Agency,
Cincinnati, Ohio 45268.
***English to Metric unit conversions in Table 8 at end of text.
127
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then disposing of this sludge as rapidly and economically as possible. From
a manufacturing engineering standpoint it would seem a paradox to produce
a product whose fate is to be swiftly destroyed. However, such is the nature
of the material produced at the sludge factory that even in today's booming
commodity market, it can safely be statod that the world's poorest man would
be he who has cornered the sludge market. Although some of sludge's relatives
in the waste family, most notably solid waste, have been attracting increased
attention as potential sources of energy and materials, sewage sludge remains
>
a material of negative economic value. \
\
So alien is this concentration on sludge production and disposal that
as recently as 1967 the WPCF Manual of Practice for Sewage Treatment Plant
Design devoted a total of 30 pages out of 375 to the topic of sludge disposal (1)
Lately, however, we have come to realize that sludge handling absorbs 35
percent of the capital costs and 55 percent of the annual operation and
maintenance costs of a wastewater treatment plant (2) . These cost shares
would increase significantly if disposal were universally carried out in a
proper manner.
Since the only certainty our disposalist is faced with is a larger
quantity of sludge to deal with tomorrow than today, he will naturally seek
out methods that will promptly put today's sludge out of sight and cut of
mind. Although land disposal of sewage sludge remains the most common method
*
of application, there are increasing pressures on the disposalist to employ
on-site reduction and disposal methods. The cost of land is certainly one
of these factors. Health concern is obviously another. However, the
unquantifiable desire simply to get rid of the stuff is probably the main
driving force that pushes our disposalist to seek alternatives, often more
expensive, to land disposal. Most oftun these alternatives take tha form
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of some type of thermal processing or thermal degradation technique.
INCINERATION
Below is a list of some properties that are typical of most sewage
sludges. The most notable parameter is that raw sewage sludge, as dirty as
it may appear, is still essentially water. Also, this sludge, particularly
the secondary component, has such an affinity for its water, that it clings
tenaciously to it.
>
1. Greater than 95 percent water
2. Fierce inclination to retain water
3. Difficult to handle
4. Odorous at operational temperatures
5. 30 percent or greater nonvolatile materials
in solids
6. Corrosiv/e to incinerator construction materials
and air pollution control equipment
After carefully assessing this information and having performed a rig-
orous engineering analysis of the merits of the process we decide to dispose
of the sludge in a most practical manner: we burn it. At least we have been
burning it. Since 1935, when the first sewage sludge incinerator was installed,
incineration has grown in usage so dramatically that it now accounts for over
25 percent of the tonnage of sludge produced in the United States (4,5). In
1974, this translates into approximately 1.3 million tons of sludge incinerated
and by 1985 the current trend points toward a figure of over 4.0 million tons
incinerated (5). Table 1 highlights the projected growth of incineration as
a sludge disposal medium. Note that a large contribution to the percentage
129
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increase in sludge incineration can be expected to come from the densely popu-
lated coastal areas that hav/e been extensively utilizing ocean disposal. In
fact, sludge incineration has become such a way of life that it has become
almost axiomatic in consulting engineering circles to recommend sludge in-
cineration for treatment plants serving over 15,000 people (6).
Since incineration will continue to gain prominence as a sludge disposal
method, let us discuss it. Theoretically, sludge incineration can be defined
as: "A thermal degradation process through which the organic fraction is
>
converted to carbon dioxide and water vapor and the inorganic fraction to
an in off 'ensive ash in an environmentally acceptable manner for the purpose
of volume reduction and solids sterilization (?). Unfortunately, and all
too often, a practical definition of sludge incineration could be: "A basical-
ly uncontrolled process for converting a single medium pollution problem into
a three media pollution problem with the use of a minimum of thermal efficien-
cy at a maximum of cost." Although incineration facilities are seldom designed
in this manner they are often operated under less than optimal design condi-
tions.
Assuming our disposalist is undaunted by the negative aspects of sludge
incineration and he proceeds on his course, he very quickly encounters a
fact of life that firemen have handed down from generation to generation from
antiquity: water doesn't burn. Remembering that raw sludge is received
in a mixture that is 95 percent water, in order to burn the 1.3 million tons
of municipal sewage sludge that will be burned this year, 25 million tons,
or 50,000,000,000 (50 billion) pounds, or 6 billion gallons of retained water
must be dealt with. It's no wonder that people will go to such exotic means
to settle out, pump out, filter out, press out, flush out, dry out, squeeze
130 .
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out, boil out and even freeze out the water. In fact, such is the intensity
of the dewatering campaign that plants will spend from $5 to $35 for every
dry ton just to remove about 80 percent of the water (8,9).
Despite its operational shortcomings, environmental side effects, and
high cost, incineration has its attractions. It alters the problem by
changing the offensive mass into a less offensive mass of smaller volume.
It will provide an immediate resolution of the problem tomorrow as well as
today. Although it is not an ultimate disposal technique, it does prolong
the usefulness of the land areas as a disposal site. Although the incinerator
is a depreciable asset, it is not a depletable resource. When the land area
has accommodated its capacity it is finished as a disposal site. When the
incinerator has accommodated its hour's capacity, it is ready for the next
hour's problem. Finally, many communities simply have no other viable option.
If asked why they incinerate sludge, they would respond: "Because it's there."
THE MULTIPLE HEARTH
Having decided on combustion as the most reasonable approach to our
disposal problem, we must now decide what to burn our sludge in. Mostly,
we burn it in a multiple hearth furnace. In 1972, there were about 125
multiple hearth sludge incinerators operational in the United States, out of
a total of approximately 220 installations incinerating sludge (10,11).
A typical multiple hearth incinerator looks like the unit described
in Figure 3 (12). If the design looks quaint, it's because multiple hearths
have been around since 1889 when the first successful unit for roasting py-
rite ore was built (13).
The furnace consists of a refractory-lined cylindrical steel shell.
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Inside the shell are a number of annular hearths stacked horizontally at a
fixed distance above one another. A centrally located cast iron shaft runs
the full height of the furnace and supports two or four cantilevered rabble
arms above each hearth. Each arm contains several rabble teeth that rake
sludge spirally across the hearth, below the arms, as the arms rotate with
the central shaft. The sludge, optimally in excess of 25 percent solids, is
fed in at the periphery of the top hearth. It is then raked by the rabble
teeth towards the center to an opening through which it falls to the next
hearth. Here the sludge is rabbled outward to the periphery and so on down
the furnace. The sludge and gas streams move countercurrent to one another,
the sludge passing down the furnace and eventually becoming ash and the com-
bustion air moving upward over each hearth and exiting as flue gas at the top
hearth (14).
There are three operating zones in a multiple hearth: sludge is dried;
it is burned; it is cooled. Gas temperatures range from 800° F on the top
hearth, to 1650° F on the burning hearths, to 300° F on the bottom hearth (15)
Multiple hearth units come in sizes ranging from 3 feet in diameter
and 4 hearths to over 22 feet in diameter with 12 hearths (7,16). Hearth
areas range from 85 square feet to 3100 square feet. At 25 percent solids,
a rule of thumb for hearth loading is 8 pounds of wet sludge per hour per
square foot of hearth area (16).
*•
Volume reduction achievement in the multiple hearth incinerator is
typically in the 90 percent range (10,12,17). The following list describes
the type of chemical content of ash that can be expected (17).
132
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Content Percent of Total
Silica (SiO ) 25-30
Alumina (Al) 10-13
Iron Oxide (Fe 0 ) 9-10
£. O
Magnesium Oxide (FlgO) 2-2.8
x
Total Calcium (CaO) 30-37
Available CaO 1-2
Phosphorous Pentoxide (P 0 ) 7-10 *
£. w
Loss on Ignition 0.5-1.0
Ash handling systems can be wet or dry, but there is an increasing tendency
to use the hydraulic handling lagoon approach because of the dust problems
associated with the pneumatic handling-landfill approach.
Figure 4 is a flow and equipment diagram for a multiple hearth incinera-
tion system (17). Thermal efficiency of the unit is enhanced by the recycling
of the exhaust air used to cool the working parts of the furnace. However,
to ensure complete thermal oxidation, excess air to the extent of 100 per-
cent over stoichiometric is often supplied. The diagram in Figure 4 does
not include an afterburner for exhaust gas deodorization. In the literature
one body of opinion holds that this deodorization is not necessary (18).
It is stated that odor-producing compounds are not distilled from the sludge
on the top hearths, and there is much reference to the "thermal jump"
phenomenon that prohibits this distillation (17,19). However, since a mal-
functioning thermal jump has been a difficult thing to explain to neighbors,
conservative design practice has been to incorporate an afterburner arrange-
ment to ensure that the gases are heated to a temperature of 1400° F (12,20,21).
133
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The best thing that can be said about a multiple hearth is that it
works, which is the best thing that can be said about any machine. It is
simple in operation, of proven durability, and is flexible enough to burn
fluctating loadings of a wide variety of materials, including grib, screen-
ings and skimmings.
THE FLUIDIZED BED
If we do burn sludge but do not burn it in a multiple hearth, we most
likely do it in a fluid bed.reactor. Fluid bed technology was originally
developed for catalyst recovery in oil refining operations (20). Fluid bed
incineration was first applied to sewage sludge disposal in 1962 (22). By
1972 there were over 25 fluid bed sludge disposal installations in the U. S.(10),
Figure 5 is a cross section of a vertical fluid bed unit (20). This is the
most common type, although "flatter" horizontal types are also used.
The fluid bed unit utilizes a bed of inert materials capablo of com-
pletely oxidizing all the organic material in the sludge. The technique is
based on the principle that when solids are suspended in an upward moving
stream of gases, the mixture possesses the characteristics of a liquid. The
properties of this fluidized bed in terms of mixing and heat transfer are
utilized to effect both rapid mixing and almost instantaneous drying and in-
cineration of the organic material in the sludge (23).
For combustion of sludges, suspension of the relatively fine particles,
normally less than 1/4 of an inch, of the solid material is effected in a
stream of rising gas in the cylindrical reaction vessel. The v&locity of
the gas flow is regulated so that a vigorous mixing action is maintained
in the fluidized bed. Bed temperature is normally maintained at 1300° to
134
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1500° F to insure complete oxidation and destruction of odors (24).
Figure 6 is a schematic for a fluid bed system (23). The sludge can
be either injected into the bed area as shown in the diagram or pneumatically
sprayed in a controlled dispersion pattern into the "freeboard" zone above
the bed material. The material that constitutes the bed material is generally
silica sand or some other inert material inserted into the reactor at initial
startup and replenished periodically. However, the bed could be made up
of inorganic materials from the sludge feed, so long as these materials do not
>
melt at operating temperatures and prevent fluidization of the bed. By
varying the velocity of the air stream, the operation of the furnace can be
adjusted so that these inorganic materials are either entrained in the ex-
haust gases or retained in the bed itself (24).
Although the bed has to be preheated to 1250° F before the sludge can
be introduced at startup, the bed does serve as an excellent heat capacitor (12).
In one series of tests it was found that a bed that had been shut down at
1400° F lost only 8° F per hour (25). The bed itself has a heat capacity of
16000 BTU/cubic foot, which is another way of saying that the sludge dries
and burns pretty quickly (26). Due to the high exit gas temperatures of
1400° F, the thermal efficiency of a fluidized bed is generally lower than
that of a multiple hearth unit. One study found the thermal efficiency of the
fluid bed furnace to be 40 percent as opposed to 55 percent for the multiple
hearth unit without an afterburner (27) . Thermal efficiency can be improved
through the addition of an inlet air preheater that operates off waste heat
from the exhaust gases and preheats the incoming air to 1000° F (28). However,
since these preheaters can represent as much as 15 percent of the capital
135
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investment of the plant, and since maintenance costs for the preheating
systems have been formidable, these optional subsystems have most often been
deleted from fluid bed installations in the cheap fuel era (20,29) . Operating
pressure in the bed area approximates 2 psi and fluid bed units have demon-
strated the capability to operate at excess air rates of as low as 20 percent
over stoichiometric (12,30).
Fluid bed furnaces for sludge combustion are commercially available
in freeboard diameter (O.D.) sizes ranging from 4 to 16 feet with functional
t
cross sectional areas of from 3 to 150 square feet (11). Sludge handling
capacities can vary from about 200 to 2000 Ib. of dry solids per hour at
25 percent solids and operational units have accommodated as much as 3400
dry pounds per hour at feeds averaging 50 percent solids (23). However, fluid
bed utilization has been confined primarily to smaller installations, probably
because the fluid bed represents a relatively new entrant in the sludge in-
cineration equipment field (10).
The most prominent advantages of the fluidized bed combustor are simpli-
city of operation, since the reactor has no moving mechanical parts, and odor-
free operation. Also, the violent motion of the bed and high temperature
operation prevent the formation of clinkers in the form of metallic salts that
are an operational nuisance to many multiple hearth facilities (20). An his-
toric disadvantage has been the difficulties experienced in achieving a proper
solids fluidizing distribution in the larger sized units (31).
OTHER MODES OF INCINERATION
Of less importance, because they are less widely applied are the flash
dryer-incinerator, the rotary kiln, and the cyclone furnace.
136
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Figure 7 is a flow diagram for a flash drying and incineration system (32) .
There are currently about 50 of these installations in the United States, but
their numbers are declining (10). The process was first applied to the drying
of sewage sludge in 1932 and was very popular in the 1950's (11,33).
As is evidenced from Figure 7, the process is more complex than conven-
tional incineration. There are really two subsystems: one for drying and
one for burning the sludge. In the drying cycle, the wet sludge is mixed
with previously dried sludge to reduce the moisture content of the whole mix-
>
ture to about 35 percent (21). The mixture then meets hot gases at approximately
1100° F from the incinerator (or burner) and is then fed to a cage mill (12,
21)• By the time the sludge leaves the cage mill it has been dried to a mois-
ture content approximating 10 percent in a matter of seconds (20). The drying
gases then carry the sludge particles upward to the cyclone where centrifugal
action separates them. The dried sludge is then discharged through an air-
lock with a portion going back to the mixer while the remainder is either
burned or used as a fertilizer (21).
It is this flexibility in end use that accounted for the flash dryer's
popularity. However, in recent years, the market for dried sludge as a
fertilizer has been depressed to the point where operational costs cannot be
recovered. If the fertilizer cannot be sold, then the advantage of flexi-
bility has disappeared and what its left is an expensive incineration system.
In fact, since most installations were constructed for drying without inciner-
ation, operational costs have been pushed upward because pure fuel has been
used to dry the sludge (10,11). Even with limited heat recovery potential,
the proposition is a costly endeavor.
Less widely used is the rotary kiln, depicted schematically in Figure
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8 (34). It operates similarly to the multiple hearth in that sludge is dried
in the upper area and burned in the lower region. Like the flash drier, it
has been used most widely for sludge drying but has been also applied to
combustion of sludge uiith refuse. Units are available in sizes ranging up
to 2400 Ib/hr capacities (35). A rotary kiln unit has demonstrated the flexi-
bility to dispose concurrently of liquid tars, solid wastes, and chemical
wastes (36).
The newest type of commerically available incinerator is the cyclonic
reactor, represented pictorially in Figure 9 (37). The principle of the cyclone
furnace is to use a vertical cylindrical combustion chamber designed so that
the air velocity and the physical.locations of the air inlets impart a rapid
spinning motion to the column of gas inside the chamber. Due to this spin-
ning motion, centrifugal force effects a separation of cold dense air from
the hot, light combustion products. A central vortex is created that is so
hot that all organic matter is destroyed before the gas stream leaves the
chamber. Particulate matter is thrown outward to the walls and retained in-
side the furnace by centrifugal force.
The best application for the cyclonic reactor is for smaller treatment
;
plants because of their simplicity of operation. The largest unit commer-
cially available is 25 feet in diameter with a capacity of 7 tons per hour (38).
Operation is in the odor-free temperature range and the relatively clean
•<
nature of the exhaust gas is particularly conducive to the use of a heat
exchanger to recover waste heat (39). Cyclone furnaces have accommodated
sludges with solids contents as low as 13 percent with considerable addition
of auxiliary fuel (38).
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WHAT GOES IN
Figure 10 describes a sludge processing system and what goes in and comes
out of it. We mill discuss these inputs and outputs for a sludge incinerator.
Three commodities go into a sludge disposal system: money, sludge, and
fuel. These three are interrelated, but we will discuss each separately.
COSTS
Mostly, what goes into a sludge disposal system is money. Costs of
»
incineration are of three types: preparation, capital, and operational (40) .
Preparation costs are those incurred in preparing the sludge fur incineration
and include capital and operational costs for thickening, transporting, de-
watering, and storing. Capital costs are construction costs amortized over
20 years at 7 percent. These are fixed costs and must be paid whether we
operate or not. Operational costs include labor, maintenance, fuel, and
equipment requirements for operating the incinerators and are equivalent to
variable costs incurred in a production facility.
First, let us put incineration costs into perspective with other disposal
methods. Incineration is expensive, as is shown below (41):
Total Costs
Method ($/Dry Ton)*
1. Disposal as liquid soil conditioner 20
2. Dewatered sludge as soil conditioner 32
3. Heat drying 64
4. La.gooning 15
5. Landfilling dewatered sludge 32
6. Barging to sea 15
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7. Pipeline to sea 14
8. Incineration 32
* Cost figures do not include any credit for sale of
products or by-products.
Cost figures include preparation costs such as dewatering and digestion but
do not include costs for land which may vary widely. No offsetting compen-
sation is made in the cost figures for revenue for the sale of products such
>
as soil conditioner from heat drying operations because any such credits could
not be universally applied. In addition, no costs are included for disposing
of incinerator ash since no firm cost data are available.
For comparison purposes we will assume that, regardless of the combus-
tion process chosen, sludge preparation costs will be identical. This is not
completely true since the newer fluid bod installations tend to use centri-
fuges for dewatering whereas the older multiple hearth complexes rely pri-
marily on vacuum filters (11). However, average dewatering costs will be
close to $12 per ton and handling and storing processes will be similar.
From Table 2 for a multiple hearth plant, without exhaust gas deodoriza-
tion, capital costs can range from $22 per dry ton for a 10 TPD plant to about
|8 per dry ton for a 100 TPD plant. Operational costs of from $8 to $13 per
ton give total costs for multiple hearth incineration of from $16 to $35 per
dry ton exclusive of deodorization and dewa£ering. When the $4 to $10 per
ton costs for deodorization are added, the costs accelerate to $20 to $45
per ton.
Cost data for fluid bed units are more elusive, but there are references
to total costs of from $33 to $52 per dry ton for small plants (43). Data
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for larger plants are inconclusive, but indications are that costs are
competitive with the multiple hearth installations (23). A key factor is
the installation of the inlet air preheater, which will increase capital
costs but decrease variable operating costs because of decreased fuel con-
sumption. This lever relationship would tend to indicate that the preheater
may be a good investment at the larger plants and a function of fuel costs
and availability at the smaller plants.
Where sale of the dried product is not possible, heat drying is simply,
not economical. It has been estimated that incinerating sludge in a system
designed for drying and/or incineration would require an increase in basic
unit co:5ts of 17 percent and thati under the least favorable market conditions,
from 25 to 40 percent of the annual sludge production must be sold to justify
selection of an incineration-drying cycle over straight incineration (44).
SLUDGE
Presently, about 75 percent of the U. S. population is serviced by
sewage treatment plants. Sixty-five percent of the sewage from these plants
is treated to the secondary level and only 2 percent is treated to the ter-
tiary level (45). Current Federal standards call for total secondary treat-
ment by 1977 and escalate to no pollutant discharge by 1985 (46).
Even partial implementation of the Federal standards will greatly affect
sludge disposal technology if only by influencing the sheer quantities of
material:? to be handled. Secondary treatment doubles the amount of sludge
generated by primary treatment alone (47). Advanced waste treatment produces
25 percent more sludge than secondary treatment.
In addition, these greater quantities of sludges will be harder to work
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with. Whereas primary sludge is generally received with a moisture content
of 95 percent, activated sludge is frequently 98 percent or more moisture
(48). Volatile content, or fuel value, of the sludge can also be expected to
suffer as more inert chemicals appear in the sludge mixtures with the use
of advanced treatment processes.
FUEL
In 1974, fuel is the topic of the year and fuel is an increasingly
>
important aspect of sludge combustion. In fact, the new prominence of fuel
as a design and operational parameter will probably cause many people to take
a hard look at conventional sludge incineration.
Sewage sludge itself is autocombustible at approximately 30 percent
solids content for a mixture of equal parts of primary and secondary sludge
(20). Dry raw volatile sewage solids have an average heating value approxi-
mating 10,000 BTU/lb (7). Since volatile solids can range from 60 to 80
percent of total solids by weight, a "typical" sludge has a heating value of
from 6,000 to 8,000 BTU/lb. of dry solids. Values for various sludges are
presented in Table 3 (7). Digestion and the presence of grit, ground garbage,
and grease can alter the heating value of sludges.
Sludges cannot always be dewatered to achieve a solids content in excess
of 30 percent. In fact, obtaining a 20 percent solids cake with secondary
sludge is often a formidable task. Under these circumstancss, additional
heat from auxiliary fuel must be added to the'furnace to evaporate the
excess moisture in the sludge. This auxiliary fuel is normally No. 2 oil
or natural gas.
Fuel requirements for combusting a 25 percent solids sludge in a multiple
hearth furnace without exhaust gas deodorization can be calculated as 28
142 .
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gallons of No. 2 fuel oil per dry ton of sludge (49). In actual practice,
because of variations in solids contents, types of sludges, and operational •
efficiencies, the national average can be estimated at roughly 50 gallons
per dry ton of sludge (50). With the increased use of secondary and tertiary
treatment in the endeavor to attain projected discharge standards, average
fuel consumption may very well double to 100 gallons per dry ton by 1985,
if the present trend continues.
When fuel oil was plentiful at 12 cents per gallon, the economic burden
imposed by fuel consumption was merely painful. In fact, rather than upgrade
dewatering practices or invest in such items as heat exchangers to utilize
waste heat, most plants simply chose to use more and more fuel in place of
more efficient operation. With oil at 25 cents per gallon and rising, the
economic pains become acute. With oil and gas perhaps unavailable, operation
simply becomes impossible.
WHAT GOES OUT
The incinerator's two main products are ash and emissions in the form
of exhaust gases. The ash portion was discussed earlier. Ash constitutes
about 10 percent of the furnace feed and contains less than 1 percent com-
bustible matter in the form of fixed carbon (17). The ash makes an adequate
landfill material.
Aside from odors, which may or may not -exist, the products of sludge
combustion are essentially steam, carbon dioxide, and small amounts of
particulate emissions and oxides of nitrogen and sulfur. The water vapor
does not represent a hazard but cooling the exhaust gases to 110° F will
eliminate the steam plume if this is desirable (17).
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Tabla 4 summarizes the results of stack gas sampling for particulates
NO , SO , and visible emissions from four incineration sites (51). These
s\ £.
data are from tests on three units with multiple hearths and one with a fluid
bed.
All were equipped uith impingement type wet scrubbers. The figures
represent ranges of sampled emissions under a variety of operating conditions.
Average values would indicate that low energy wet scrubbers are an adequate
,air pollution control device and that sewage sludge incinerators so equipped
are not a significant source of SO , NO , and particulate emissions. This is
^ X
further exemplified by the fact that the same study found that maximum parti-
culate emissions were 2.83 Ibs/hr and 4.8 Ibs per day per ton incinerated.
Average values were much lower.
Table 5 is an excerpt from the results of analyses for metals concentra-
tion in input sludges and the resultant ash from three incinerators (52).
If the metals go into the incinerator and do not come out in the ash, they
must go into the scrubber as fly ash or vapor. The study further found that
mercury apparently is totally vaporized into the stack gases and that lead
appears in higher concentrations in the fly ash than it does in the bottom
ash. Although much further study is needed, current technology would indicate
that control of lead emissions is largely a function of particulate removal
efficiency and control of mercury is dependent on the ability of authorities
to regulate mercury discharge into receiving sewers.
Proposed EPA new source performance standards concentrate primarily on
control of particulate emissions and opacity. Process weight regulations
would limit emissions to 1.3 Ib/ton of dry sludge (0.65 g/kg), based on a dry
charging weight of 1000 Ib/hr (53). The lower efficiency impingement scrubbers
144
-------
are adequate to meet opacity standards of 20 percent and the process weight
regulations but do not represent the best control technology (53,54). Manu-
facturers of the high energy venturi scrubbers will guarantee outlet concen-
tration of less than .030 gr/dscf (54).
ALTERNATIVES
We have painted a picture of incineration as a costly alternative to
other sludge disposal techniques. We have shown that incinerators can repre-
sent a substantial capital investment; that they consume about one-fifth as>
much fuel as they do sludge; that they can contribute to air pollution if not
properly operated and that control of this air pollution can be very costly.
We have also described some of the aspects of incineration that make it
attractive, particularly its speed and compactness. We have outlined the
manner in which the advantages of incineration have manifested a definite
trend towards incineration as a sludge disposal technique. Although incinera-
tion will continue to be an important part of the overall sludge disposal
spectrum, increasing cost, fuel, and environmental pressures have prompted
a search for disposal options that possess the advantages of on-site disposal
and minimize the disadvantages.
PYROLYSI5
Pyrolysis is the destructive distillation of organic materials under
pressure and heat in the absence of oxygen. It is the process that is
used to produce coke from coal and charcoal from wood. Through the pyrolysis
process, the organic portions of waste are reformed into lower molecular
weight compounds. These compounds can be in the form of a combustible gas,
tar and oil, and a solid "char" which also has an appreciable heating
value (55).
145
-------
Figure 11 is a flow diagram for a simple pyrolysis system (56). The
"pyrolyzing" process is carried out in an externally heated closed reactor
chamber. Process temperatures can be as low as 500° C (932° F) or in excess
of. 900° C (1652° F) at atmospheric pressures. At the lower temperatures the
reaction product is predominantly solid and at higher temperatures, gas is
more prevalent (57). The vo.latdle gases can bo siphoned off and used to
heat the reaction chamber. The process can be thermally self-sustaining >
providing the heating value of the waste is high enough.
Tar and heavy oils are collected in a tar trap and additional heavy oils
and liquors are condensed out of the product stream. Traces of heavy oil
mists are collected in electrostatic precipitators. Gases are scrubbed clean
of acids and sulfides and then returned to the retort to fuel the pyrolyzer,
collected as product, or flared (57).
("lost of the research and development activity in the field of waste
pyrolysis has been directed towards the processing of municipal solid waste.
Although no full-scale waste pyrolysis plants are currently operating, there
are plans to demonstrate several commercially developed processes for munici-
pal waste pyrolysis in the United States. Perhaps the most ambitious of these
plants is planned for Baltimore, where 1000 tons per day of shredded wastes
will be processed in a rotary kiln unit as described in Figure 12 (58).
The system is not a pure pyrolytic operation since some air is introduced
into the combustion chamber. Gases produced in the reactor will be used
to fuel a boiler that will produce 200,000 pounds of saleable steam per hour.
The 200 ton per day plant under construction in San Diego is outlined
in Figure 13 (59). Product yields in San Diego will be a high viscosity fuel
V
146
-------
oil, a char, and a medium BID gas that mill be used to fuel the reactor.
A third system, being demonstrated by the manufacturer in South
Charleston, West Virginia, is depicted in Figure 14 (60). This 200 ton per
day plant will convert unshredded refuse into a low BTU gas and a slag in
a vertical shaft furnace. Slagging is accomplished through the introduction
of oxygen into the lower portion of the furnace.
Although development of pyrolytic techniques for sewage sludge has not
•kept pace with that for solid wastes, some research has been initiated in ,
this area. Pyrolysis of bovine waste has been performed at 900° C (1652° F)
in the laboratory unit described earlier (Figure 11). For this test the cow
manure was dried to 3.6 percent moisture content, although fresh manure con-
tains over 75 percent moisture. As presented in Table 6 the pyrolysis opera-
tion yielded a gas fraction of 38.5 percent of feed, an oil fraction of 5.8
percent, and a char residue of 36.3 percent (61).
Successful pyrolysis of sewage sludge alone will depend on the ability
of the reaction to generate enough fuel to dry the incoming sludge to a
moisture content approaching 5 percent. A more likely implementation will
be pyrolysis of sewage sludge in conjunction with solid waste.
Since technology for pyrolysis is in a relatively infant state and
since hardware and operational characteristics are not on a firm basis, cost
data on pyrolysis cannot be considered reliable. One estimate places capital
and operating costs of pyrolysis tentatively at about two-thirds that of
pollution-free incineration (62).
Pyrolysis does have the definite advantage that air pollution control
requirements are minimized. If the process can be shown to be self-sustain-
ing, fuel consumption is not the economic burden that it is in incineration
147
-------
processes.
Combined Incineration with Solid Waste
A possible solution to the fuel problem may be found by combining the
incineration operations of municipal solid waste and sewage sludge. Solid
waste makes a good fuel, having a heating value approaching 5,000 BTU/lb
as shown in Table 7 (50). Refuse is a universal commodity found in all commu-
nities at generation rates proportional to sewage sludge. It has a sulfur
content well bslow 1 percent (63). The circumstances that tend to push
communities toward incineration of sludge also work in favor of refuse in-
cineration so that the two are often practiced in parallel. Potential
economic advantages may be realized in confining capital investments to a
single installation. The additional heating value and solids content
provided by the solid waste may enable the combustion of a wetter sludge
cake and result in lower costs for dewatering.
The major consideration in co-incineration is what to burn the material
in. Good solid waste incinerators tend not to be well suited for combusting
materials with high moisture content. Conversely, incinerators that adequately
process sludge cannot cope with the much larger quantities and physical
irregularities presented by solid waste.
Combined incineration of refuse and sludge has had limited application
in the United States. The most common approach has been the utilization of
the waste heat from refuse combustion to dry the sludge before it enters
the incinerator. Such a system is described in Figure 15. A similar system
has been employed in Waterbury, Connecticut, since 1957, where 300 tons per
day of refuse and sludge are incinerated (64). Other attempts at combined
incineration have been made at smaller towns in Wisconsin and Pennsylvania.
148
-------
Unfortunately, the limited cost information has shown the processes to be
expensive, with 1957 costs for Uaterbury quoted at $26 per dry ton of sludge
(21). One of the Wisconsin cities, Neenah, reported auxiliary fuel consump-
tion of about 25 gallons of oil per dry ton of sludge. However, the co-
incineration process was considered economical because it reduced the cost
of hauling the material to a landfill site (65). Co-incineration has also
been practiced with success in a rotary kiln unit in Louisvillfi, Kentucky,
and in a fluid bed at Franklin, Ohio. >
In Europe, where fuel has always been expensive, co-incineration has
been practiced for years. Although recently many plants have converted to
refuse combustion for steam production, plants are still operating in England,
Germany, and Sweden. Installations have ranged from multiple hearths to
rotary kilns.
Although combined incineration has not been overly successful, it probably
merits a closer look in the United States. It is conceivable that a well-
designed and operated co-incineration plant could yield lower overall refuse
and sludge disposal costs than a separate incineration program that involves
heat or fuel recovery from the solid waste.
Wet Oxidation '
Figure-16 depicts a thermal processing technique that alleviates the
need for mechanical dewatering of sludges (20,66). Wet oxidation is a process
whereby organic wastes dissolved or suspended in water are converted to water,
carbon dioxide, small amounts of low molecular weight organic acids, and
a very small amount of fine inorganic ash (67). Since 1912, wet oxidation
has been proposed as a means for disposal of spent liquors from paper-pulp
149
-------
mills. However, commercial application in the paper-pulp industry did not
take place until 1959. The process was first applied to sewage treatment
for sludge digestion and disposal in 1960. By 1972, there had been 17
plants constructed for sewage treatment and five installed for the treatment
of paper-pulp-mill and other industrial wastes (68).
The process is conducted with an excess of oxygen at temperatures
ranging from 300° F to 600° F in a pressure vessel which maintains the water
.as a liquid. Air overpressure can range from 50 to 300 psi with resultingt
operating pressures from 600 to over 3,000 psi (66,67). Feed solids concen-
trations can be as low as one percent but optimal operation is experienced
with sludges thickened to from 3 to 6 percent (20,69).
Wet oxidation has evolved into two separate processes with two distinct
functions. As a disposal process, wet oxidation at temperatures and pressures
at the high ends of the operating ranges can accomplish a 90 percent reduction
of putrescible solids. However, maintenance of the high temperatures and
pressures has made continuous operation difficult and the process has been
costly.
Operation at lower temperatures and pressures is in reality a form of
heat treatment. Exposing the sludge to heat and pressure coagulates the
solids and breaks down the gel structure. This reduces the water affinity
of the sludge solids and enables production of filter cakes of up to 50 percent
solids content (66). The solid residue is sterile but a strongly oxygen-
demanding liquor is formed (68). Disposal of this effluent poses a substantial
problem.
Although wet air oxidation does not qualify as a completely new technique
and has suffered from cost and reliability problems, it is an area of much
150
-------
potential. With continued development, the process could become a viable
disposal technique that emits no air pollutants and is self-sufficient from
a fuel standpoint.
Conclusion
For the disposalist who must deal daily uiith the output of the sludge
factory, thermal processing of sewage sludge is a disposal option that should
be approached objectively. For smaller communities sludge combustion will
most probably be the most expensive disposal technique. Large cities that
are faced with the prospect of transporting sludge long distances to land
disposal sites may find combustion to be a more attractive venture. The aesthe-
tic and convenience advantages of on-site disposal must be weighed against the
environmental, fuel-consumptive, cost aspects of incineration. Improvements
in or alternatives to the sludge incineration process may, in the near future,
solve all the problems associated with current thermal processing techniques,
but since each new development also produces its own new problems, life prom-
ises to remain interesting in the realm of sludge disposal.
151
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NOTES AND REFERENCES
1. "Sewage Treatment Plant Design," Doint Committee of ASCE and WPCF, 1967.
2. Presecan, N. L., "Sludge Disposal: Are We Solving the Problem?" Deeds
and Data, WPCF (Oct. 1971).
3. Russel, Robert A., "Theory of Combustion of Sludge" in "Sludge Concentra-
tion—Filtration and Incineration," Continued Education Series No. 113,
University of Michigan, Ann Arbor, pp. 380-382 (1964).
4. Groen, M. A., "Sludge Drying and Incineration at Dearborn, Michigan,"
Sewage and Industrial Wastes, 3J_(12), pp. 1432-1434 (Dec. 1959).
5. EPA, Municipal Pollution Control Division, Office of Environmental
Engineering, Program Review, Duly 17, 1973.
6. Balakrishnan, S., Survey of consulting engineers by personal communica-
tion, Resource Engineering Associates, Walton, Connecticut, 1968.
7. Owen, M. B., "Sludge Incineration," Proc. of the ASCE, San. Engrg. Div.-
Proc. Paper No. 1172 (Feb. 1957).
B. Simpson, G. D., and Sutton, S. H., "Performance of Vacuum Filters," in
"Sludge Concentration—Filtration, and Incineration," Continued Education
Series No. 113, University of Michigan, Ann Arbor (1964).
9. Albertson, 0. E., and Guidi, E. Dr., "Centrifugation of Waste Sludge,"
. Dour. WPCF, 41(4) (1969).
10. "Sludge Handling and Disposal," Phase I, State of the Art, Stanley
Consultants, November, 1972.
11. Installation lists provided by four manufacturers of sewage sludge
incinerators.
12. Burd, R. S., "A Study of Sludge Handling and Disposal," FWPCA Grant No.
PH-86-66-32, May 1968.
13. Nichols Herreshoff Bulletin No. 233.
14. Unterberg, W., Sherwood, R. 3., and Schneider,- G. R., "Computerized Design
and Cost Estimation for Multiple Hearth-Sludge Incinerators," EPA Contract
No. 14-12-547, Duly 1971.
15. Sebastian, F. P., and Isheim, M. C., "Advances in Incineration and Resource
Reclamation," May, 1970.
16. Sebastian, F. P., and Cardinal, P. D., "Solid Waste Disposal," Chemical
Engineering, 75_(22), pp. 112-117, October 1968.
17. Sebastian, F. P., "Advances in Incineration and Thermal Processes,"
September 1971.
152
-------
18. Sawyer, C. l\l., and Kahn, P. A., "Temperature Requirements for Odor
Destruction in Sludge Incineration," Jour. WPCF. _32(12), pp. 1274-1278
"(1960).
19. Harris, S. M., "Incineration-Multiple Hearth Furnaces," Water and Sewage
Works, Aug., 1967.
20. Balakrishnan, "5., Williamson, D. E., and Okey, R. W., "State of the Art
Review on Sludge Incineration Practice," Water Pollution Control Research
Series 17070 Oil' 04/70, April, 1970.
21. Nickerson, R. D., "Sludge Drying and Incineration," Dour. WPCF 32(1),
pp. 90-98 (1960).
22. Albertson, D. E., "Low Cost Combustion of Sewage Sludges," Presented at
the 1963 Annual Meeting of the Water Pollution Control Federation, >
Seattle, Wash., Oct. 8, 1963.
23. Ducar, G. 3., and Lewin, P., Mathematical Model of Sewaqe Sludqe Fluidized
Bed Incinerator Capacities and Costs, FWPCA Contract No. 14-12-415,
Sept., 1969.
24. McGill, D. L., and Elbridge, M. Smith, "Fluidized Bed Disposal of Secon-
dary Sludge High in Inorganic Salts," Proc. of 1970 National Incinerator
Conference, May, 1970.
25. Sohr, W. H., et al., "Fluidized Sewage Solids Combustion," Water Works
and Wastes Engrq., .2(9), pp. 90-93 (1965).
26. Millward, R. S., and Booth, P. B., "Incorporating Sludge Combustion into
a Sewage Treatment Plant," Water and Sewage Works, 115, pp. 169-174
. Nov., 1968.
27. "Study of the Thermal Efficiency of Sewage Sludge Incinerators,"
Environmental Equipment Division. Nippon Gaishi K. K., Dec., 1970.
28. "Sludge Disposal by Dewatering and Combustion," Anon., Water and Wastes
Engineering. .4(10), pp. 64-67 (Oct. 1967).
29. Walter, L. H., Millward, R. S., "Sludge Disposal by the Fluosolids
System." Presented at the 16th University of Kansas San. Engrg. Conf.
(1966).
30. "The Dorr-Oliver FS Disposal System," Bulletin No. 6051, Dorr-Oliver, Inc.
Stanford, Connecticut, 1965.
31. Burgess, 3. V., "Developments in Sludge and Waste Incineration," Process
Biochemistry, B_ (1), pp. 27-28 (Jan. 1973).
32. McEven, M. M., "The C-E Raymond Flash Drying and Incineration System,"
presented at Nebraska Water Pollution Control Assn., Omaha, Nebraska,
March 2, 1965.
153
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33. "The C-E Raymond Flash Drying and Incineration System for Sewage Sludge
Disposal," Bull. No. FD-60, Combustion Engineering, Inc., Chicago,
Illinois.
34. Foster, W. S. "Hoiu to Give Incinerators Half a Chance,"The American City
(3uly-Aug.,197l).
35. Ferrel, Dames F., "Sludge Incineration," Pollution Engineering (Mar., 1973).
36. Novak, Rudy G., "Eliminating or Disposing of Industrial Solid Waste,"
Chemical Engineering, Oct. 5, 1970, pp.78-82.
37. Stribling, 3. B., "Sludge Incineration by Cyclone Furnace," Effluent
and Water Treatment Journal, Aug., 1972, pp. 395-400.
3o. Stnbling, 3. B., "The Cyclone Furnace for Waste Incineration," Process*
Biochemistry, Jan., 1973, pp. 29-34.
39. Hubbard, P. T., Albertson, 0. E., "The Type CRFS Disposal System," Dorr-
Oliver Techical Reprint No. 607-P, 1967.
40. MacLaren, 3. W., "Evaluation of Sludge Treatment and Disposal,"
Canadian Municipal Utilities (May, 1961).
41. Costs are taken from date in Ref. 12 for 1968 updated to 1973 by adjust-
ment from ENR Indices for 1968 and 1973.
42. Costs are from Ref. 10 for 1972 updated to 1973 by adjustment from ENR
Indices for 1972 and 1973.
43. Costs are from Refs. 22 for 1963 and 25 for 1965 adjusted to 1973 from
ENR Indices for those respective years.
44. Quirk, T. P., "Economic Aspects of Incineration vs. Incineration-Drying,"
Jour. WPCF. 36(11) pp. 1355-1367 (1964).
45. EPA, Office of Water Programs Survey, June, 1972.
46. Federal Water Pollution Control Act Amendments of 1972, October, 1972.
47. McCabe, 3., and Eckenfelder, W. W., "Advances in Biological Waste
Treatment," Pergamon Press, 1963.
48. Dean, R. B., and Smith, 3. E.} 3r., "The Properties and Composition of
Sludges," presented to the Seminar on Methodology for Monitoring the Marine
Environment, Seattle, Washington, Oct. 16-18, 1973.
49. Smith, Robert, "Incineration of Organic Sludges," EPA In-House Memorandum,
Sept. 17, 1972.
154
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50. Olexsey, R. A., and Farrell, 3. B., "Sludge Incineration and Fuel
Conservation," News of Environmental Research in Cincinnati, EPA-NERC-
Cincinnati, May 3, 1974.
51. Environmental Protection Agency Task Force Report, "Sewage Sludge
Incineration," Report No. EPA-R2-72-040 (Aug. 1972), NTIS PB 211323.
52. Farrell, 3. B., and Salotto, B. \l., "The Effects of Incineration on
Metals, Pesticides and Polychlorinated Biphenyls in Sewage Sludge,"
presented at National Symposium on Ultimate Disposal, Durham, N. C.,
April 1973. Published in Proceedings, pp. 186-198.
53. "New Source Performance Standards: Municipal Sewage Treatment Plants,"
EPA, 40 CFR 60, 1973.
54. Background Information on Proposed New Source Performance Standards: >
Sewage Treatment Plants, Office of Air Quality Planning and Standards,
EPA, Research Triangle Park, N. C., Dune 1973.
55. Schlesinger, M. D., Sanner, U. S., and Wolfson, D. E., "Pyrolysis of
Waste Materials from Urban and Rural Sources," in Proceedings of the
Third Mineral Waste Utilization Symposium, March 1972.
56. Banner, W. S. and Wolfson, D. E., "Pyrolysis of Municipal and Industrial
Wastes," U. S. Bureau of Mines, Feb. 1971.
57. Sanner, W. S., Ortuglio, C., Walters, 3. G., and Wolfson, D. E.,
"Conversion of Municipal and Industrial Refuse into Useful Materials
by Pyrolysis," U. S. Bureau of Mines Investigation 7428, Aug. 1970.
58. City of Baltimore, "Demonstration of a Pyrolysis Resource Recovery
Solid Waste Management Systems," Application for Demonstration Grant to
EPA, Duly 1972.
59. County of San Diego, "San Diego County Solid Waste Resource Recovery
. Project," Application for Demonstration Grant to EPA, Duly 1972.
60. "Solid Waste Disposal Resource Recovery," Union Carbide Bulletin,
F-3698.
61. Schlesinger, M. D., Sanner, W. S., and Wolfson, D. E., "Energy from
the Pyrolysis of Agricultural Wastes," U. S. Bureau of Mines, 1973.
62. Milkovich, D. D., "What's Happening to Pyrolysis?" Pollution
Engineering, Mar.-Apr. 1972.
63. Kaiser, E. F., "Chemical Analyses of Refuse Components," in Proceedings
1966 National Incinerator Conference, New York, 1966.
155
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64. Cross, F. L., Dr., Drago, R. 3., amd Francis, H. E., "Metal and
Particulate Emission from Incinerators Burning Sewage Sludge and Nixed
Refuse," in Proceedings of 1970 National Incinerator Conference, ASME,
May 1970.
65. Clinton, M. 0., "Experience with Incineration of Industrial Waste and
Sewage Sludge Cake with Municipal Refuse." No year.
66. Zimpro Division, Sterling Drug, Inc., "Low Cost Oxidation of Sewage
Sludge," Technical Paper Identification No. 651, Undated.
67. National Materials Advisory Board, Materials for Wet Oxidation Processinq
Equipment (Shipboard), Publ. IMMAB-312, National Academy of Sciences,
Dec. 1973.
68. Barber-Colman Company, Technical Note: Summary of the Technology of iiiet
Oxidation, TNRRS 72-1, April 3, 1972.
69. Ettelt, G. A., and Kennedy, T. 3., "Research and Operation Experience
in Sludge Deu/atering," 3our. WPCF 38(2), Feb. 1966.
156
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TABLE 1: TRENDS IN SLUDGE DISPOSAL
NODE
GENERATION
LAND APPLICATION
OCEAN DISPOSAL
INCINERATION
QUANTITY (DRY TONS/DAY)
1972 1985
11,000 28,000
6,600 16,000
1,650 0
2,750 12,000
PERCENT OF TOTAL
1972
100
60
15
25
1985
100
60
0
40
157
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TABLE 2; AVERAGE U. S. 1973 COSTS FOR MULTIPLE
HEARTH INCINERATION (S/DRY TON)*
PLANT SIZE
10 TPD 100 TPD
CAPITAL (AMORTIZED) 22 8
OPERATIONAL JK3 _§_
TOTAL (NO DEODORIZATION) 35 16
DEODORIZATION .10. _4
TOTAL (WITH DEODORIZATION) 45 20
* DOES NOT INCLUDE DEWATERING COSTS.
158
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TABLE 3; HEATING VALUES OF SONE SLUDGES
BTU/LB OF
(MATERIAL COMBUSTIBLES (#) COMBUSTIBLES
GREASE AND SCUN
RAW SEWAGE SOLIDS
FINE SCREENINGS
GROUND GARBAGE
DIGESTED SLUDGE
GRIT
88.5
74.0
86.4
84.8
59.6
33.2
16,750
10,285
8,990
8,245
5,290
4,000
159
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TABLE 4: EMISSIONS FROM FOUR SEWAGE SLUDGE INCINERATORS
EMISSIONS
MINIMUM MAXIMUM
% C02 - \IOL% (DRY BASIS)
% EXCESS AIR (TEST POINT)
S02 (PPM)
N0x (PPM)
HC1 (PPM)
PARTICULATE - FILTER (GR/SCFD)
PARTICULATE - TOTAL (GR/SCFD)
SLUDGE FEED TO FURNACE (LB DS/HR)
STACK FLOW RATE (SCFM)
2.2
366.0
.0127-
.0170-
10.2
51.0
1.97 - 14.28
11.47 - 271.63
.621 - 11.9
.0766
.0859
221.8 - 1710.0
1170 - 10290
160
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TABLE 5; METAL TO FIXED SOLID RATIO FROM THREE
INCINERATORS (MG/G)
ELEMENT
PLANT A
SLUDGE ASH
PLANT B
SLUDGE ASH
CADMIUM
CHROMIUM
COPPER
IRON
LEAD
MERCURY
0.37
2.0
2.6
18.0
5.8
9.0*
0.20
0.3
1.3
8.9
0.7
n.d.
n.d.
2.9
2.5
12.0
7.0
20.0*
0.58
0.5
1.7
11.0
0.85
n.d.
0.31
0.7
1.6
50.0
2.0
6.0*
PLANT C
SLUDGE ASH
0.6
1.6
13.0
1.0
n.d. - NOT DETECTED
* - MICROGRAMS/GRAM
161
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TABLE 6; BOVINE WASTE PYROLYZED AT 900° C
ULTINATE ANALYSIS, UT.
C
H
0
N
S
ASH
FEED*
41.2
5.7
33.3
2.3
0.3
17.2
RESIDUE
49.4
0.4
0.4
1.1
0.3
48.4
YIELDS
GAS
OIL
AQUEOUS
RESIDUE
UT. % OF FEED PER TON OF FEED
38.5 13,940 CU.FT.
5.8 13.0 GAL.
15.9 38.3 GAL.
0.15 (NH,) 65.8 LB
o
36.3 726.0 LB
HEATING VALUES
FEED (BTU/LB)
GAS (BTU/CU.FT.)
RESIDUE (BTU/LB)
7,110
450
7,290
* DRIED TO A 3.6$ MOISTURE CONTENT
162
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TABLE 7; COMPARATIVE HEATING VALUES OF PERTINENT FUELS
HEATING VALUE RATIO OF FUEL VALUES
FUEL (BTU/LB) TO VALUE FOR MO.2 OIL
NO. 2 OIL
NO. 6 OIL
NATURAL GAS
BITUMINOUS COAL
WOOD (AIR DRIED)
GREASE AND SCUF1
SLUDGE (DRY VOLATILES)
DIGESTED SLUDGE
DIGESTER GAS
MUNICIPAL REFUSE
(20$ MOISTURE)
19,600
17,500
22,800
13.600
5,500
16,700
10,000
5,300
15,400
4,900
1.00
0.89
1.16
0.69
0.28
0.85
0.52
0.27
0.79
0.25
SOURCES: PERRY'S CHEMICAL ENGINEER'S HANDBOOK, 4TH EDITION;
A STUDY OF SLUDGE HANDLING AND DISPOSAL, R. S. BURD;
CHARACTERISTICS OF MUNICIPAL REFUSE, E. KAISER.
163
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TABLE 8; CONVERSION FACTORS FOR UNITS
USED IN THIS PAPER
FROM (ENGLISH) TO (METRIC) MULTIPLY BY
GALLONS LITERS 3.785
TONS (SHORT) KILOGRAMS 907.184
POUNDS KILOGRAMS D.453
FEET METERS 0.305
SQUARE FEET SQUARE CENTIMETERS 929.030
CUBIC FEET CUBIC METERS 0.028
SQUARE INCHES SQUARE CENTIMETERS 6.452
BTU'S CALORIES - - 252.000
GRAINS GRAMS 0.065
FOR TEMPERATURES: TO CONVERT FROM FAHRENHEIT (°F) TO CELSIUS (°C):
°C = (°F - 32) X 5/9
164
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FIGURE 1. WASTEWATER TREATMENT PLANT
RAW MATERIAL
SEWAGE
PROCESSING
PRODUCT
TREATMENT
EFFLUENT
en
BY-PRODUCT
SOLIDS
ORGANICS
GRIT
GREASE
SCUM
SLUDGE
-------
FIGURE 2. SEWAGE SLUDGE FACTORY
RAW MATERIAL
en
cr>
SEWAGE
PROCESSING
TREATMENT
PRODUCT
SLUDGE
BY PRODUCT
EFFLUENT
-------
en
COOLING AIR DISCHARGE
FLOATING DAMPER
SLUDGE INLET
FLUE GASES OUT
RABBLE ARM xj
AT EACH HEARTH^
DRYING ZONE
COMBUSTION
ZONE
COOLING ZONE
ASH
DISCHARGE
COMBUSTION
AIR RETURN
RABBLE ARM
DRIVE
COOLING AIR FAN
FIGURE 3. TYPICAL SECTION:
MULTIPLE HEARTH INCINERATOR
-------
WET
SLUDGE
IN
cr>
oo
5F
RECYCLED
CONVEYOR*
COOLING AIR
r
?
CENTRAL
SHAFT
^>
f
REJECTED COOLING AIR
t
COOLING ( -
AIR FROM { )
FAN* /*^\
MHF EXHAUST GAS
-H
~
-«H
JAS
PRECOOLJER f
*"wAT?if~
AUXILIARY
f= FUEL PRE
1 x COOL
~l 0 )
XX \
\
AMBIENT COMBUSTIC
AIR FROM BLOWER*
ADJUSTABLE PORTS /
H
SCRUBBER
EXIT GAS"
t
INDUCED
DRAFT FAN*
WET
SCRUBBER
AND DOORS
'I1
DISCHARGE
DRAIN FOR
SCRUBBER AND
PRECOOLER
WATER
* ELECTRIC MOTOR DRIVE
** PUMP WITH MOTOR DRIVE
SCRUBBER
WATER
FIGURE 4. MHF FLOW AND EQUIPMENT DIAGRAM
-------
SIGHT GLASS
EXHAUST r*-
ACCESS
ifflffflifflli
PREHEAT BURNER
SAND FEED
FLUIDIZED
SAND
PRESSURE TAP
:: -^THERMOCOUPLE
SLUDGE INLET
FLUIDIZING AIR
" INLET
FIGURE 5.
TYPICAL SECTION OF A FLUID BED REACTOR
(DORR-OLIVER, INC.)
169
-------
FROM ~
PLANT
^cr CENTRIFUGE
CENTRATE
WASTE FEED &
DEWATERING SYSTEM
SCREW FEEDER
PLENUM
BLOWER
FIGURE 6. -
SYSTEM COMPONENTS FOR FB REACTOR
170
-------
FIGURE 7. FLASH DRYER-INCINERATOR
f
INCINERATOR
FUEL
i r
ASH
FAN
o
CYCLONE
DRY SLUDGE
MIXER
HOT FLUE GAS
I
O
SLUDGE CAKE
CAGE
MILL
-------
CHARGING
CHUTE
UNDERFIRE
AIR DUCTS
TO EXPANSION CHAMBER
AND GAS SCRUBBER
RESIDUE CONVEYORS
FIGURE 8. ROTARY KILN INCINERATOR
-------
-------
FIGURE 10. BLACK BOX CONCEPT FOR A SLUDGE
DISPOSAL SYSTEM
.EMISSIONS
SLUDGE
INCINERATION
PLANT
FUEL
RESIDUE
-------
01
FIGURE 11. PILOT PLANT PYROLYSIS SYSTEM
LEGEND
1. THERMOCOUPLE
2. ELECTRIC FURNACE
3. RETORT
4. TAR TRAP
5. TUBULAR CONDENSER
6. ELECTROSTATIC PRECIPITATOR
7. AMMONIA SCRUBBER
8. ACID PUMP
STEAM
9.CARBON DIOXIDE SCRUBBER
10. CAUSTIC PUMP
11. LARGE WET-TEST METER
12. DRYING TUBE
13. LIGHT OIL CONDENSER
14. SMALL WET-TEST METER
15. GAS SAMPLE HOLDER
SAMPLE COCK FOR
H2S AND NH3 TESTS
HEATING
ELEMENTS
H2SO4 NaOH NaOH
EXCESS GAS
IS FLARED
50-1
20-1
GEARED
SHAFT
TO Btu AND
sp gr RECORDERS
-Ba»
n
DRAINS
-------
4,800,000 Ib
STEAM FOR SALE
(200,000 PPH)
A 633,600 gol
J fWATER
RECEIVING
SHREDDING
STORAGE
1000 T
AIR
BOILER
GPM)
GAS
PURIFIER
FUEL-
i
KILN
SCRUBBER
"U-
CHEMICAL
TREATMENT
TANK
i
RECIRC.
PUMP
M--4—- ,
I.D. FAN
1
THICKENER
UNDERFLOW
QUENCH
TANK
DEHUMIDIFIER
t
I
AIR
FLOTATION
MAGNETIC
SEPARATION
GASES TO ATMOSPHERE
T
THICKENER
& FILTER
T
WATER
IRON GLASSY CARBON
70T AGGREGATE CRAR
FIGURE 12. LANDGARD FLOW SHEET; BASIS - 1000 TONS FEED
176
-------
FIGURE 13. BLOCK DIAGRAM OF THE GR&D SOLID WASTE RECYCLING PROCESS
AS-REC'D
REFUSE
25%
MOISTURE
PRIMARY
SHREDDING
AIR
CLASSIFICA
TION
NON-MAGNETIC METALS INORGANIC
DIRT & DEBRIS-* 1 RECOVERY
(TO LANDFILL) OPERATIONS
8 WT. % '
DRYING
I I
SECONDARY
SHREDDING
WATER
(TO SEWER)-*-
9 WT. %
MATERIALS AVAILABLE FOR SALE
WT. % OF AS-RECEIVED REFUSE
MILLION B.T.U. PER TON
____!_j___
PYROLYSIS
OPERATION
PRODUCT
RECOVERY
OPERATION
GASES
CHAR
MAGNETIC GLASS
METALS
7% 5%
(OIL & CHAR)
25%
5.3
7%
1.44
-------
FIGURE 14. INPUTS AND PRODUCTS OF PUROX SYSTEM
00
0.2
TONS
OXYGEN
^J
\
f
FURNACE
GAS
GAS
CLEANING
TRAIN
I
0.22 TONS 0.03 TONS RECYCLE
GLASS AND METAL
0.7 TONS
FUEL GAS
1
WASTEWATER
0.28 TONS
-------
FIGURE 15. SIMPLIFIED SYSTEM FOR COMBINED INCINERATION
SOLID WASTE
Id
FAN
COOLED GAS
o
HOT FLUE GAS
SLUDGE CAKE
O
DRY SLUDGE
INCINERATOR
SLUDGE DRYER
-------
SLUDGE
STORAGE
TANK
SLUDGE
REACTOR
AIR COMPRESSOR
BIOTREATMENT
(OPTIONAL)
SOLIDS
SEPARATION
STERILE
LIQUID
(SETTLING,
FILTRATION OR
CENTRIFUGATION) STERILE
INOFFENSIVE
SOLIDS
PQ
STEAM-
GENERATOR
(OPTIONAL)
POWER
RECOVERY
(OPTIONAL)
CATALYTIC
n>nr „ COLORLESS
PURIFIER EXHAUST
SEPARATOR GAS
j;/.-:^'^l SLUDGE
V///A OXIDIZED SLUDGE
| | GASES
FIGURE 16.
FLOW DIAGRAM FOR CONTINUOUS WET AIR OXIDATION
180
-------
FIGURE 1. WASTEWATER TREATMENT PLANT
RAW MATERIAL
SEWAGE
PROCESSING
TREATMENT
PRODUCT
EFFLUENT
00
BY-PRODUCT
SOLIDS
ORGANICS
GRIT
GREASE
SCUM
SLUDGE
-------
FIGURE 2. SEWAGE SLUDGE FACTORY
RAW MATERIAL
CO
SEWAGE
PROCESSING
TREATMENT
PRODUCT
SLUDGE
BY PRODUCT
EFFLUENT
-------
00
CO
COOLING AIR DISCHARGE
FLOATING DAMPER
SLUDGE INLET
FLUE GASES OUT
RABBLE ARM
AT EACH HEARTH
DRYING ZONE
COMBUSTION
ZONE
COOLING ZONE
ASH
DISCHARGE
COMBUSTION
AIR RETURN
RABBLE ARM
DRIVE
COOLING AIR FAN
FIGURE 3. TYPICAL SECTION:
MULTIPLE HEARTH INCINERATOR
-------
CO
WET
SLUDGF
IN
RECYCLED
COOLING >
•^
CONVEYOR*
MR
COC
AIR
FAN
n
?
CENTRAL
SHAFT
^
JUNG /Q
FROM V w
Xs-
f
f
X
REJECTED COOLING AIR SCRUBBER A
EXIT GAS~|J "
MHF EXHAUST GAS
— 1
*
«^-
f AS
DISCH
^ ] /^ INDUCED
( O 1 DRAFT FAN*
PRECOOLER / ] / \
^^^__—— — J m ^
"WATER I
AUXILIARY SCRUBBER
F= FUEL PRE_ WET .-^
. rnoiFP ^rpiiRRFD WATER
K°) l
s~\ \
X
AMBIENT COMBUSTION \ /
AIR FROM BLOWER* AND j f
ADJUSTABLE PORTS AND DOORS Ml
H DRAIN FOR
ARGE ( SCRUBBER AND
DDcrrt/'M CD
WATER
* ELECTRIC MOTOR DRIVE
** PUMP WITH MOTOR DRIVE
FIGURE 4. MHF FLOW AND EQUIPMENT DIAGRAM
-------
SIGHT GLASS
EXHAUST
PRESSURE TAP
PREHEAT BURNER
»=!**
THERMOCOUPLE
=7 -fl SLUDGE INLET
4
-j FLUIDIZING AIR
f"1"
INLET
FIGURE 5.
TYPICAL SECTION OF A FLUID BED REACTOR
(DORR-OLIVER, INC.)
185
-------
FROM ~
PLANT
L^ CENTRIFUGE
CENTRATE
WASTE FEED &
DEWATERING SYSTEM
SCREW FEEDER
PLENUM
BLOWER
FIGURE 6.
SYSTEM COMPONENTS FOR FB REACTOR
186
-------
FIGURE 7. FLASH DRYER-INCINERATOR
INCINERATOR
00
FUEL
ASH
FAN
o
CYCLONE
DRY SLUDGE
MIXER
HOT FLUE GAS
O
SLUDGE CAKE
CAGE
MILL
-------
CHARGING
CHUTE
i?
UNDERFIRE
AIR DUCTS
OVERFIRE
AIR DUCTS
DRYING
TO EXPANSION CHAMBER
AND GAS SCRUBBER
RESIDUE CONVEYORS
FIGURE 8. ROTARY KILN INCINERATOR
-------
-------
FIGURE 10. BLACK BOX CONCEPT FOR A SLUDGE
DISPOSAL SYSTEM
.EMISSIONS
SLUDGE
INCINERATION
PLANT
FUEL
RESIDUE
-------
i-D
FIGURE 11. PILOT PLANT PYROLYSIS SYSTEM
LEGEND
1. THERMOCOUPLE
2. ELECTRIC FURNACE
3. RETORT
4. TAR TRAP
5. TUBULAR CONDENSER
9.CARBON DIOXIDE SCRUBBER
10. CAUSTIC PUMP
11. LARGE WET-TEST METER
12. DRYING TUBE
13. LIGHT OIL CONDENSER
6. ELECTROSTATIC PRECIPITATOR 14. SMALL WET-TEST METER
7. AMMONIA SCRUBBER 15. GAS SAMPLE HOLDER
8. ACID PUMP
-TCA SAMPLE COCK FOR
iltAm H2S AND NH3
^M
I '
HEATING
ELEMENTS
H2SO4 NaOH NaOH
EXCESS GAS
IS FLARED
OR
ESTS"~~~- ^
1
!
n
i
fc i
,ooL!
50-1 jT
20-1 X
GEARED Y
SHAFF
i -D-Ol
^s
1
i •—
f 13
TO Btu AND
sp gr RECORDERS
DRAINS
-------
4,800,000 Ib
STEAM FOR SALE
(200,000 PPH)
BOILER
633,60_p_g^l
fWATER
^(440
GPM)
RECEIVING
SHREDDING
STORAGE
1000 T
AIR
GAS
PURIFIER
FU|L_-
AIR
KILN
SCRUBBER
"U—
I I
CHEMICAL
TREATMENT
TANK
RECIRC.
PUMP
I.D. FAN
DEHUMIDIFIER
I
I
I
I
LJ
THICKENER
UNDERFLOW
QUENCH
TANK
t
I
AIR
FLOTATION
MAGNETIC
SEPARATION
GASES TO ATMOSPHERE
I
THICKENER
& FILTER
IRON
70T
GLASSY
AGGREGATE
170T
T
WATER
CARBON
CHAR
SOT
FIGURE 12. LANDGARD FLOW SHEET; BASIS - 1000 TONS FEED
192
-------
FIGURE 13. BLOCK DIAGRAM OF THE GR&D SOLID WASTE RECYCLING PROCESS
oo
AS-REC'D
PRIMARY
SHREDDING
AIR
CLASSIFICA
TION
REFUSE
25%
MOISTURE
NON-MAGNETIC METALS INORGANIC
DIRT & DEBRIS-* j RECOVERY
(TO LANDFILL) OPERATIONS
8 WT. % I
DRYING
I I
SECONDARY
SHREDDING
WATER
(TO SEWER)-^-
9 WT. %
PYROLYSIS
OPERATIONS-
PRODUCT
RECOVERY
OPERATION
MATERIALS AVAILABLE FOR SALE
WT. % OF AS-RECEIVED REFUSE
MILLION B.T.U. PER TON
t
GASES
CHAR
MAGNETIC GLASS
METALS
7% 5%
(OIL & CHAR)
25%
5.3
7%
1.44
-------
FIGURE 14. INPUTS AND PRODUCTS OF PUROX SYSTEM
0.2
TONS
OXYGEN
FURNACE
1.01
TONS
GAS
GAS
CLEANING
TRAIN
J
0.22 TONS 0.03 TONS RECYCLE
GLASS AND METAL
0.7 TONS
FUEL GAS
WASTEWATER
0.28 TONS
-------
FIGURE 15. SIMPLIFIED SYSTEM FOR COMBINED INCINERATION
SOLID WASTE
FAN
COOLED GAS
o
..
en
HOT FLUE GAS
SLUDGE CAKE
O
DRY SLUDGE
INCINERATOR
SLUDGE DRYER
-------
SLUDGE
STORAGE
TANK
SLUDGE
AIR COMPRESSOR
BIOTREATMENT
(OPTIONAL)
SOLIDS
SEPARATION
REACTOR
STERILE
LIQUID
(SETTLING,
FILTRATION OR
CENTRIFUGATION) STERILE
INOFFENSIVE
SOLIDS
CATALYTIC
GAS
PURIFIER
STEAM-
GENERATOR
(OPTIONAL)
POWER
RECOVERY
(OPTIONAL)
SEPARATOR
COLORLESS
EXHAUST
GAS
v.v!.V.'?.l SLUDGE
AIR
OXIDIZED SLUDGE
GASES
STEAM _
FIGURE 16.
FLOW DIAGRAM FOR CONTINUOUS WET AIR OXIDATION
196
-------
THICKENING CHARACTERISTICS OF ALUMINUM
AND IRON PRIMARY SEWAGE SLUDGES *
by
Steven W. Hathaway and Joseph B. Farrell **
INTRODUCTION
The need for phosphate removal to control eutrophication in certain
receiving waters has been well documented (l). In virtually all cases
phosphate removal is accomplished by addition of chemical precipitants such
as lime and Al or Fe salts. The effectiveness of phosphate removal can be
accurately predicted and reliable methods are available for design of the
water-handling facilities (l). However, there is insufficient information
on which to base the design of equipment for processing the sludges produced
by phosphate removal processes. This is particularly true for processes in
which Al or Fe salts are used as the precipitating agents.
Average quantities of sludge produced and limited information on dewater-
ing of the sludges produced by phosphate removal processes have been presented
by Adrian and Smith (2). Burns and Shell (3) have reported on pilot plant
investigations during which phosphate was precipitated by addition of lime,
alum, and ferric chloride to a reactor-clarifier. Their results were
incomplete, but further work is in progress. Van Fleet et al (I)-), in what
is probably the most authoritative publication to date, described the
properties of sludge produced in plant-scale tests of phosphate removal
* Presented at Research Symposium on Pretreatment and Ultimate Disposal
of Wastewater Solids" sponsored by EPA Region II and Department of.
Environmental Science, Rutgers University, New Brunswick, New Jersey,
May 21-22,
** Research Chemist and Acting Chief, respectively, Ultimate Disposal Section,
Treatment Process Development Branch, AWTRL, National Environmental Research
Center, EPA, Cincinnati, Ohio 45268.
197
-------
processes in the Province of Ontario, Canada. Nevertheless, there is a
dearth of information on dewatering rates obtainable with most dewatering
devices and on the effect of process variables on performance.
One clear indication from the limited information available is that
primary sludges which result when Al or'Fe salts are added to the primary
clarifier (referred to herein as Al-primary or Fe-primary sludges) do not
thicken to as high a solids content as do conventional primary sludges.
Vacuum filter yields are low, probably at least partially because the
sludge to be filtered has a low solids content. The interdependence between
thickening and dewatering indicated that thickening characteristics should
be explored before investigating performance of dewatering devices. The
objective of this investigation, then, is to define the thickening character-
istics of Al-primary and Fe-primary sludges by means of standard gravity
thickening and air flotation measurements.
MATERIALS AND METHODS
Duplicate Treatment Units—To compare the thickening characteristics
of the chemical sludges it was necessary to produce a consistent and
reliable source of sludge. Depending on the raw wastewater entering the
plant, the sludge produced in a pilot unit may change its character hourly.
Therefore, duplicate units were set up to produce two types of chemical
sludge under identical flow and equipment design conditions.
Figure 1 represents the treatment system used in this study. It
consists of two duplicate primary clarification units that receive the
same sewage feed. The duplicate system allowed flexibility of operation:
198
-------
each unit could be run at different dose levels of the same chemical, or with
different chemicals; or one unit could be dosed with chemical and the other
with no chemical (run as a conventional primary treatment plant). Each unit
was fed raw macerated sewage at a rate of 20 liters per min. (5 gpm) into
the chemical mixing and coagulation tank. The chemically-treated sewage then
overflowed to the primary clarifier. The lower section of the clarifier was
conically shaped to facilitate sludge removal. The overflow rate was set
at a low value, 20 m^/m2-day (500 gallons/ft2-day), so that the sludge level
could be maintained below the weir. Sludge was withdrawn once daily from
each clarifier and stored for the thickening experiments in a holding tank.
The table below shows the target metal to phosphorus atomic ratios
(M/P) and the levels at which the chemicals, alum (A^SO^'l^I^O) and
ferric chloride (FeClO, were charged to the wastewater to produce the
sludges required in the investigation. Chemical dose levels are based on
the average P level of 8.0 mg/1. An anionic polymer (2 A 2, Atlas Chemical
Co.*) was used only when the units were dosed with chemical.
Polymer (mg/l) Al (mg/l) Fe (mg/3
Control 0 00
M/P = 1.2 0.5 8.^ 17.1
M/P = 2.0 0.5 lU.O 2T.O
* Mention of a trade name or manufacturer does not indicate EPA endorsement.
199
-------
Gravity Thickening—Gravity thickening of the chemical sludges was
studied in bench-top thickening tests using two-liter cylinders as settling
columns. Each cylinder was equipped with a three-pronged vertical gate
stirrer which rotated at 1 rpm. This rotation was equivalent to a peri-
pheral tip speed of 25 centimeters per minute. Sludge was initially
placed in the cylinder to the two-liter mark and, with the gate rotating,
allowed to settle for 2^ hours. If a polymer was to be used, it was
added to the sludge in the cylinder before the settling test and mixed by
inverting the cylinder several times. Readings of the level of interface
between sludge and supernatant were taken at short intervals of about
10 minutes for a period of about four hours. A final reading was taken
at the 24-hour period.
The method of determining the gravity thickening characteristics of
a sludge utilizes a graphical method illustrated in Figures 2, 3, and k.
The procedure followed is essentially the same as that outlined by Dick (5),
except that the settling velocity vs. sludge concentration curve is obtained
from one instead of several settling tests. Gravity-thickening character-
istics for each sludge tested were defined by a single settling test.
Interface level as a function of time obtained in the settling test were
plotted as shown in Figure 2. At any point along this curve, settling
velocity can be calculated from the slope, which is estimated from a tangent
line. Average concentration of solids in the settling sludge can be cal-
culated from the original solids concentration and volume and the new vplume
at that point. The settling velocity can then be plotted against the solids
concentration as shown in Figure 3. From this curve, selected points are
200
-------
taken to calculate solids flux and are plotted against solids concentration
(Figure k). The thickening rate (solids flux) at a given thickened sludge
concentration is predicted from this curve (Figure 4) by selecting the
solids concentration on the abscissa, and drawing an operating line tangent
to the flux curve. The intersection of the operating line with the ordinate
gives the maximum solids flux through the thickener at the selected thickened-
sludge concentration. Dick (5) explains the theoretical basis of the method.
Dissolved Air Flotation Thickening—Figure 5 is an illustration of the
Komline-Sanderson pilot-scale air flotation thickener used in these experi-
ments. Fresh water was pressurized to TO psi with air. The pressurized
water and chemically-conditioned sludge were then fed into the injection
nozzle and into the flotation chamber. The air bubbles entrapped the
sludge solids and floated them to the top (6). The thickened sludge was
manually scraped into a tank for storage. The underflow (separated liquid)
was removed near the tank bottom and exited into the drain. The surface
o o
area of the thickener was 0.093 m (1.0 ft ). The recommended solids
loading was 10 kg/m2-hr (2 Ib/ft2-hr) and the hydraulic loading had to be
within 1,500 to U,000 ml/min. In order to reduce the complexity of the
experimentation, the initial solids concentration of the sludge was con-
trolled to about 8,000 mg/1 in all experiments by diluting with effluent.
Polymer conditioning of the sludge was essential for all of the flota-
tion tests except for raw primary sludge flotation. The polymer was made
up in a 0.1 percent aqueous solution (l mg/ml) and fed into the sludge
feed line Just before the sludge entered the flotation unit.
201
-------
RESULTS AMD DISCUSSION
General Observations—The sludges produced by the addition of alum or
ferric chloride to the raw sewage were drastically different from those
produced by conventional treatment processes. The conventional primary
sludge was very fibrous and appeared lumpy. The solid particles were, for
the most part, discrete particles suspended in a liquid medium. Although
produced from the same sewage, the Al and Fe-primary sludges were not
fibrous or lumpy. The chemical sludge was very homogenous with no
apparent separation from the liquid phase. An analogy to this observa-
tion can be envisioned by comparing the conventional sludge to a chunky
vegetable soup and the chemical sludge to an homogenous pea soup. The
volume of alum and iron sludges was greater than that of the conventional
primary sludge, and the mass was increased by the chemical compounds
formed and by the additional suspended solids removed by chemical treatment.
Gravity Thickening Characteristics—The gravity thickening character-
istics of primary sludges formed by high and low dose levels of Al and Fe
were investigated. The high metal sludges were obtained at a metal to
phosphorus ratio of 2.0 and the low metal sludges at a ratio of 1.2. During
the experiments, phosphorus (P) and suspended solids (SS) removals were
a'cceptable as is indicated by the average results shown below:
jo P Removal ^ SS Removal
High Al 75 6k
High Fe 80 Jk
The higher removals with Fe would tend to produce a poorer settling sludge
because more fine solids are present. However, the difference was small so
202
-------
the anticipated effect should not be large enough to invalidate a comparison
of the two types of sludges.
Preliminary results showed that "both the Al and Fe-primary sludges
settled very slowly to low solids content sludges. Exploratory experiments
showed that dilution of the sludges with effluent and addition of polymer
caused substantial increases in thickening rate (i.e., loading rate of
solids per unit area). Consequently, the effect of dilution and polymer
addition were investigated in some detail.
The effect of diluting the high Al and high Fe sludges (i.e., produced
at M/P = 2.0) with effluent is shown in Table 1. Without dilution, thicken-
ing rates are extraordinarily low. Dilution with effluent caused an order-
of-magnitude change in the rate of thickening of the Al-primary sludge and
a modest increase for the Fe-primary sludge. No explanation for this large
difference in effect is apparent.
The data shown in Tables 2 and 3 reveal the effect of polymer addition.
Even without dilution, polymer addition increases thickening rates for both
sludges to useful levels. With dilution of the sludge with effluent as well
as polymer addition, the rate increases still more for both the Fe-primary
sludge as well as the Al-primary sludge.
Experiments were also conducted with Al and Fe-primary sludges produced
at a low level of metal addition (M/P = 1.2). Average phosphorus and sus-
pended solids removals are shown below:
jt P Removal j> SS Removal
Low Al 60 60
Low Fe 70 60
203
-------
The lower chemical dose, P-removal, and SS-removal would be expected to
produce a less mineralized sludge with lower fine-solids content than was
obtained at the higher dose (M/P = 2.0). Results of thickening tests are
shown in Table k. Polymer was used in all tests. Surprisingly enough,
results do not differ significantly from those obtained with the high
metal doses.
A summary of the effects of polymer addition and dilution on the
chemical-primary sludges is presented in Table 5« Ranges of solids
content and thickening rate are presented. The experimental conditions
(a testing period of several months and a high daily variability between
different sludges) invalidated somewhat the meaning of comparisons between
the results of different treatments. Nevertheless, the following con-
clusions can be reasonably made, because they are substantiated by
significant patterns in the data obtained.
a. Al-primary and Fe-primary sludges have extremely low thickening
rates, even when the solids concentration leaving the thickener
is low. Conventional gravity thickening appears to be inadequate
for these sludges.
b. Dilution of Al-primary sludges with effluent before thickening
produces a dramatic increase in the thickening rate and increases
thickened solids concentration. This effect of dilution on
Fe-primary sludges is substantial but thickening rate is still
not brought up to practicable levels.
c. Addition of polymers substantially increases the thickening rate and
thickened solids concentrations for both Al and Fe-priiaary sludges.
Rates are increased to practicable levels.
204
-------
d. When both dilution and polymer addition (b and c above) are
vised, the thickening rates of Al and Fe-primary sludges are
unusually high, well above the rates obtained when polymer
alone is used.
e. The measured solids concentration achieved by gravity thicken-
ing, even under the best conditions, did not exceed 5 percent
for either sludge type. This is a reasonable concentration for
a feed to a vacuum filter but is substantially lower than the
concentration achieved by thickening conventional primary
sludges.
The large effect of polymer addition on the thickening rate achieved in
these experiments was not surprising. The use of polymers to improve gravity
thickening is well known. The improvement is evidently related to the
flocculating effect of the polymer on the sludge particles. Dilution of
sludges has been used by others (6) to improve gravity thickening, although
the mechanism by which thickening is improved is not clear. The very large
improvement in thickening rate with Al-primary sludge was unexpected. No
explanation of the poorer performance with Fe-primary sludge is readily
apparent.
Air Flotation Thickening—Several different sets of tests were completed
using the air flotation thickener for the Al and Fe-primary sludges and also
the conventional primary sludge. To have a basis for comparing thickening
characteristics, we used conventional primary sludge and Fe-primary sludge
in the first set of tests. These sludges were produced by the duplicate
physical-chemical units shown in Figure 1. The conventional sludge was
205
-------
generated by settling the sewage in the clarifier without the aid of chemicals,
The Fe-primary sludge was generated by adding 27 mg/1 Fe+3 (M/p = 2.0) and
0.5 mg/1 anionic polymer to the sewage. Phosphorus and suspended solids
removal are shown below:
j> P Removal $> SS Removal
Ho chemical 13 52
High Fe 87 72
The lower phosphorus and suspended solids removal obtained with the unit
receiving no chemical would be expected to produce a sludge less mineralized
and containing a far lower proportion of fine solids than the sludge from the
Fe-dosed unit.
Experimental conditions and results of the flotation tests are presented
in Table 6. Conventional sludge was fed into the unit at an average of
205 kg/m^day (Ul Ib/ft2-day) solids loading rate. The sludge readily
floated to an average of 7 percent solids with no chemical conditioning.
The solids capture was 90 percent or greater. The Fe-primary sludge fed in
^ o
at approximately the same rate, 180 kg/m -day (36 Ib/ft -day), gave much
poorer results. It required anionic polymer conditioning to achieve an
average of 3.2 percent final solids. Solids capture ranged from 60 to 83
percent.
The poor flotation characteristics of the Fe-primary sludge is attri-
buted to two factors: the presence of the ferric hydroxide and phosphate,
and the high proportion of fine particles in the sludge.
206
-------
Another set of experiments was carried out to determine the effect of
important variables or factors on the solids content to which the sludge
could be thickened and on the solids loss to the underflow. The factors
selected were metal to phosphorus ratio, dose of polymeric conditioner to
the sludge, and feed rate of sludge to the thickener. Each variable was
investigated at two levels. The minimum number of experiments for evaluating
these three variables or factors at two levels was eight (a 2^ factorial
experiment). Enough sludge for the eight experiments could be collected in
two days, but only four experiments could be run in one day. Since sludge
properties can change if sludge is stored even for one day, a blocked
factorial experiment was designed with the day of testing as the blocking
factor. Numerous statistical texts, e.g., Davies et al (7) explain the
principles of factorial experimental design, including techniques for
blocking out the effects of certain factors (i.e., variables).
The experimental design is shown in Tables 7 and 8: Table 7 shows the
levels of the factors investigated, and Table 8 shows the design matrix of
the experiment. The four Block 1 tests were run on the first day following
collection of sludge and Block 2 tests were run on the second day. The
blocking factor was confounded with (confused with) the M x P x L interaction
(s'ee footnote to Table 9 for explanation of an interaction). The M x P x L
interaction can no longer be calculated, but, assuming that effects of
factors are linear, other effects are unaffected.
207
-------
Phosphorus removals were checked during the periods when sludges were
being collected for the factorial experiments and the following results
were obtained:
j> P Removal
Al Fe
Low level (M/P = 1.2) h2 57
High level (M/P = 2.0) U5 6?
Phosphorus removals were poor when the units were producing Al-primary
sludge, because some very light fLoc escaped capture in the clarifier.
Despite losses of solids, the sludge did not appear unusual and did not
gravity- thicken to a higher than usual solids content. Removal of
phosphorus was better when the units were producing Fe-primary sludges.
Better removal tends to produce a more mineralized sludge with more fine
particles, which may account in part for the poorer results (see below)
obtained with Fe-primary sludge.
An independent estimate of the experimental error in measuring the
response, "solids content of the sludge," and "solids loss into the under-
flow," was obtained by making four successive runs on Fe-primary sludge at
constant operating conditions . The standard deviations of the response
' \
were determined and the 95 percent confidence interval of an "effect" in
a 2~ factorial experiment were calculated:
/
Solids Content ($j Solids Loss
Standard deviation 0.2k 2.9 .
95$ confidence interval + 0.5k + 6.7
208
-------
The 95$ confidence interval for solids loss is excessively large. It means
that the experiment cannot establish with reasonable certainty effects of
variables on solids loss unless they differ from the average by 6.7 percent.
Although the effect of variables on both solids content of the sludge and
the solids loss into the underflow were determined in the experiments, the
effects of the various factors on solids loss were not reliable and are not
reported in detail. Average solids loss for the eight tests making up the
factorial experiment was 13.0 percent for the Al-primary sludge and 8.1
percent for the Fe-primary sludge.
The effect of variables on the solids content of the sludge calculated
from the experimental results of the factorial experiments are presented in
Table 9. Effects in the table marked with an asterisk were significant.
The effects of the main factors—mineral dose, polymer dose, and solids
loading—were all significant. Although the magnitude of their effects differ,
they each affected sludge solids content in the same direction. The average
solids content was higher for the Al-primary sludges than for the Fe-primary
sludges. No significance should be given to this observation because the
sludges were collected at different times.
The results of the experiments at the high solids loading are presented
graphically in Figure 6. The data points have been calculated from the
averages and significant effects shown in Table 9. For both the Al-primary
and Fe-prinary sludges, increased metal to phosphorus ratio reduced the solids
content of the sludge. Polymer dose increased solids content for both types
of sludge.
209
-------
SUMMARY AND ItLC'J^LJNDATICNS
The experiments demonstrate that Al-primary and Fe-prima.ry sludges •; ,
not gravity thicken as well as conventional primary sludges. Al and Fe™
primary sludges produced from wastewater at Lebanon, Ohio, gravity thicken
to about 4-5 percent solids. Bench-scale experiments have shown that rates
can be greatly improved by dilution with effluent or polymer conditioning or
both. Demonstration that dilution and/V-r polymer conditioning improves
thickening in continuously operated equipment is needed.
Air flotation is a satisfactory means for thickening Al and Fe-primary
sludges. Performance is not as good as with conventional primary sludge but
solids content of 5-8 percent can be achieved, with solids recovery in excess
of 90 percent. Anionic polymer doses of 4-8 Ib/ton dry solids improves
performance. Poorer results are obtained at higher doses of metal to the
wastewater.
Only a limited number of polymeric flocculants were examined in this
study. There is good likelihood that a more comprehensive screening would
uncover polymers which produce higher solids content sludges at higher
thickening rates.
Preliminary filtration experiments carried out at Lebanon have shown
that filtration of Al and Fe-primary sludges can be carried out at reasonable
rates, provided the sludge solids content is k percent or above. This solids
content can be achieved by gravity or flotation thickening. Consequently,
this investigation has demonstrated that Al and Fe-primary sludges can be
thickened to concentrations that make subsequent dewatering steps practicable.
210
-------
Thickening rates are sufficiently high so that capital costs for equipment
will not be excessive. When polymeric conditioning was needed, dose levels
were not excessive so chemical costs would "be reasonable.
211
-------
ACKNOWLEDGEMENTS
The assistance 01' J, T» Burden and 0. L. Grant in carrying out these
investigations is gratef-ally acknowledged.
212
-------
LITERATURE CITED
1. Black and Veatch, "Process Design Manual for Phosphorus Removal," EPA
Technology Transfer Program (Oct. 19T1).
2. Adrian, D. D., and Smith, J. E., Jr., "Dewatering Physical-Chemical Sludges,"
Vanderbilt Symposium on Applications of New Concepts of Physical-Chemical
Wastewater Treatment, Sept. 18-22, 1972. Pub. Pergamon Press, Inc.
3. Burns, D. E., and Shell, G. L., "Physical-Chemical Treatment of Wastewater
Using Powdered Carbon," pub. U.S. EPA, EPA-R2-73-2614- (Aug. 1973).
k. Van Fleet, G. L., Barr, J. R., and Harris, A. J., "Treatment and Disposal
of Chemical Phosphate Sludges in Ontario," presented at Water Pollution
Control Federation Meeting, Atlanta, Ga. (Oct. 1972).
5. Dick, Richard I., "Thickening," in "Advances in Water Quality Improvement-
Physical and Chemical Processes," edited by E. F. Gloyna and W. W. Eckenfelder,
Jr., Univ. of Texas Press, pp. §58-369 (1970).
6. Torpey, W. N., "Concentration of Combined Prinary and Activated Sludges in
Separate Thickening Tanks," Jour. San. Eng. Div., ASCE, 8o(l), 1-17 (195*0.
7. Davies, 0. L., Edit., "The Design and Analysis of Industrial Experiments,"
2nd edition, Hatner Publishing Co., N. Y. (1967).
213
-------
TABLE 1
EFFECT OF DILUTION ON GRAVITY THICKENING
OF HIGH Al A5D Fe PREIARY SLUDGES
(NO POLiMEh COirorriOITIlI
T£?°
High
Alum
High
Alum
High
Alum
High
Alum
High
Alum
High
High
High
FeCl
High
TeCl
Initial
Solid? >
, .
1.7
1.2
0.9
1.5
0.8
1.2
1.2
1.2
0.9
i ' i 1 ' : '• .' I
^ With L.r;. ;,,_
Nor-
None
1:1
1:1
1:1
None
None
1:1
1:1
r: :" --ul-'^o ? i! i'dc
Ihy ,'L.- -da-'
3.U
20.0
38.0
54.0
< 0.4
0..
1.5
3.0
Thichoned Li oil ox"
Ax, Caiculateu
Solids Loadj'.irt
< 2.0
3A
4.0
5.0
5.0
< 2.0
3-0
*.»
4.0
214
-------
TABLE 2
GRAVITY THICKENING OF HIGH DOSE
ALUM PRIMARY SLUDGE
(ANIONIC POLYMER ADDED FOR SLUDGE CONDITIONING)
Sludge
Type
High
Alum
High
Alum
High
Alum
High
Alum
High
Alum
High
Alum
tnitial
Solids %
1.8
1.2
1-3
1.7
0.8
0.9
Dilution
With
Effluent
None
None
None
None
1:1
1:1
Chemical
Conditioning
Ib Polymer/Ton
6.0
6.0
6.0
k.o
k.o
6.0
Calculated Solids
Loading
Xb/ft2-day
90
21
95
60
139
367
Thickened Solids %
At Calculated
Solids Loading
5.0
U.O
5.0
*.o
i*.o
3.0
215
-------
TABLE 3
GRAVITY THICKENING OF HIGH DOSE
IRON PRIMARY SLUDG2
(ANIONIC I'OLYJtR ADDED FOR SLUDGE CONDITIONING)
1 "*• . 1 (- • f\
i-c^
•'
H'.gh
FtiCl ,
Rich
PeCl3
High
High
High
High
PeCl3
Irritia'
-3 olid r •
1 . j
1.2
1.2
1.3
0.9
1.2
0.9
r"r. , -.",'., -~. '.,'•, '
.'t :..';•":
Kone
N;.;i a
None
1:1
1:1
1:1
Chemj r.al
{'"Ti'l" tJ onir ;
UO
3.0
8.0
2.0
8.0
2.0
1.8
Calculated Sc-lids
17.0
21.0
70.0
58.0
150.0
93-0
260.0
Thickened Solids >
/\t Calculated
Solids Loading
4.0
4.0
4.0
4.0
3.0
5.0
3-5
216
-------
TABLE k
GRAVITY THICKENING OF LOW DOSE Al AND Fe-
PRIMARY SLUDGES:
ANIONIC POLYMER ADDED FOR SLUDGE CONDITIONING
Sludge Initial
Type Solids ^
Low /\ fy"k
0.90
Alum
Low . 2-
.1 -•• • ^-2
Alum
Alum *
LOW « ~*f*
. i 1.30
Alum J
Low . p
Fe *"*
Low - «
Fe
Low
Fe •'•"^
-Low , ,.
Fe •L°
Chemical
Dilution Conditioning Calculated Solids Thickened Solids $
With Ib Polymer/ Loading At Calculated
Effluent Ton D.S. Ib/ft2-day Solids Loading
...... Al-Primary Sludge .
1:1 1.0
1:1 6.0
1:1 2.0
None 7.0
None 2.0
None 5.0
1:1 U.O
1:1 U.O
70
100
135
21
103
43
135
450
5.0
5.0
5.0
4.0
4.0
4.0
5.0
5-0
217
-------
TABLE 3
SUMMARY OF EFFECT OF VARIABLES ON THICKENING RATE
AND SOLIDS CONTENT OF Al AND Fe-PRIMARY SLUDGES
Sludge
Type
High Al
High Al
High Fe
High Fe
High Al
High Al
High Fe
High Fe
Low Al
Low Al
Low Fe
Low Fe
Polymer
Addition
No
No
No
No
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Dilution
No
Yes
No
Yes
No
Yes
No
Yes
No
Yes
No
Yes
Solids Flux
(Ib/ft2/day)
< 0.4-3A
20-60
< Q.h
1.5-3
20-90
llfO-370
17-70
90-260
21
70-135
1*0-100
135-^50
% Solids of
Thickened Sludge
< 2-3. ^
*-5
< 2-3
h-k.5
*-5
3-^
^
3-5
U
5
k
5
Ib/ft2-day x U.9 = kg/m -day
218
-------
TABLE 6
AIR FLOTATION THICKENING - CONVENTIONAL PRIMARY -
IRON PRIMARY SLUDGE
Sludge
Type
Conventional
Primary
Range
Average
*FeCl_ Primary
Range
Average
Solids
Loading Rate
Ib/ft-day
34-48
41
34-48
36
Initial
Solids %
0.8-1.5
1.0
0.7-1.3
0.95
Final
Solids $
5.1-8.7
7.4
2.8-3.5
3.2
Polymer Dose **
Ib/Ton Dry Solids
0
3-6
Solids
Capture $
>90
60-83
* High Dose of Fed - 27 ing Fe/1 to Sewage
Fe+3/P Molar Ratio =2.0
** American Cyanamid 837-A
219
-------
TABLE 7
LEVEL OF FACTORS INVESTIGATED IK
FACTORIAL EXPERIMENT: Al AND Fe-PRIMARY SLUDGE
Level of Variable
- (Low)
+ (High)
(Ib/Poly/Ton Solids)
Poly Dose
1.5
8
Mineral Addition
M+3/P Molar Ratio
1.2
2.0
(Ib/ft^ -day)
Solids Loading Rate
to Air Flotation Unit
2k
96
220
-------
TABLE 8
DESIGN MATRIX OF AIR FLOTATION EXPERIMENT
WITH Al-PRIMARY AND Fe-PRIMARY SLUDGSS
Level of Variables * M x P x L
Test Metal Polymer Loading Interaction
1
2 + +
3 - + - +
k + +
5 . . + +
6 •«• - +
7 . + +
8 + + + +
Block
1
2
2
1
2
1
1
2
* (-) indicates lov level, (+) indicates high level
221
-------
TABLE 9
EFFECT OF FACTORS AND THEIR INTERACTIONS ON % SLUDGE SOLIDS
- AIR FLOTATION OF Al PRIMARY SLUDGE AND Fe PRIMARY SLUDGE
Average of 8 tests
Mineral dose (M)
Polymer dose (p)
Solids loading (L)
M x P2
M x L
P x L
M x P x L (Block Effect)^
1» Sludge
Al
(6.2)
- 0.7 *
0.8 *
1.4 *
- 0.2
- 0.7 *
0.7 *
0.1
Solids-1
Fe
(5.2)
- 1.6 *
0.8 *
0.6 *
0.2
- 0.5
0.3
- o.h
The average of the results at the low level of the factor or interaction
subtracted from the average of the results at the high level.
2
M x P is a two-factor interaction. M x P = -0.2 means that the effect of
P is 0.2 less at the high level of M than at the low level of M.
3
M x P x L is a three-factor interaction. M x P x L = 0.1 would ordinarily
indicate that the M x P interaction is 0.1 more at the high level of P than
at the low level. In this experiment M x P x L is "confounded" (or confused)
with the block effect so neither can be determined.
* Effects marked with an asterisk are significant.
222
-------
TABLE 10
'EFFECT OF VARIABLES ON $ SLUDGE SOLIDS AND
SOLIDS LOSS - AIR FLOTATION OF Fe PRIMARY SLUDGE
Average of 8 tests
Mineral Dose (M)
Polymer Dose (P)
Solids Loading (L)
M x P
M x L
P x L
M x P x L (Block Effect)
$ Sludge Solids *
(5.2)
- 1.6
0.8
0.6
0.2
- 0.5
0.3
- O.lf
% Solids Loss *
(8.1)
1.3
- 6.2
- 2.7
- 2.2
- 6.8
0.8
3.8
* The average of results at the lovr level of the variable subtracted from the
average of results at the high level.
223
-------
RAW
SEWAGE
AIR
M8X
MINERALS
ADDED
AIR MIX
SEWAGE
FEED
5GPM
COAGULATED
SEWAGE
EFFLUENT
i
COAGULATION
TANK
ro
ro
SEWAGE
DISPENSING
TANK
TO IDENTICAL
SYSTEM
PRIMARY
SETTLING
TANK
SLUDGE
SLUDGE
HOLDING
TANK
FIGURE 1
DUPLICATE PHYSICAL-CHEMICAL TREATMENT UNITS
-------
HEIGHT
OF
INTERFACE
t\>
ro
en
TIME (MINUTES)
FIGURE 2
STANDARD SETTLING CURVE
-------
SETTLING
VELOCITY
(ft/hr)
INi
CTi
% SOLIDS
FIGURE 3
SETTLING VELOCITY
-------
ro
ro
CALCULATED
FLUX
(Ib/ft2-day)
FLUX CURVE
OPERATING
LINE
% SOLIDS
FIGURE 4
FLUX CURVE
-------
THICKENED
SLUDGE
SCRAPED
IN3
t\D
CO
SLUDGE
HOLDING
TANK
'
\.
o
0 0
o
o
o o
o
O 0
o°o
°o (
0 <
1
n
L
3
3
i
j
[
A
1
1
INRFRFI nw
TO DRAIN
. /
t
I I /R
i I
PRESSU
TANK
— 09
POLYMER
FEED
UR SUPPLY
tin Owi r t— 1
ESH WATER
RE
FIGURE 5
DISSOLVED AIR FLOTATION THICKENER
-------
INS
ro
vo
uT 10
9
_i
o
8
LU
O
O
=3
_i
to
u
X
18 Ib. polymer/ton
>1.5 Ib. polymer/ton
1.2 2.0
AI/P RATIO
5T 1°
O
_l
O
to
£ 8
LU
o
o
to
0 6
LU
z
LU
• 8 Ib. polymer/ton
• 1.5 Ib. polymer/ton
1.2 2.0
FE/P RATIO
FIG. 6: EFFECT OF METAL/PHOSPORUS ATOMIC RATIO
AND POLYMER DOSE ON THICKENED SLUDGE
SOLIDS
-------
RAW
SEWAGE
AIR
MIX
MINERALS
ADDED
AIR MIX
ro
oo
1
.•••
• 0
V0'
1
&C\tl A f*C
SEWAGE
FEED
5r^DM
varM
CO/
SEWAGE
DISPENSING
TANK
COAGULATED
SEWAGE
EFFLUENT
TANK
TO IDENTICAL
SYSTEM
PRIMARY
SETTLING
TANK
SLUDGE
SLUDGE
HOLDING
TANK
FIGURE 1
DUPLICATE PHYSICAL-CHEMICAL TREATMENT UNITS
-------
HEIGHT
OF
INTERFACE
ro
oo
TIME (MINUTES)
FIGURE 2
STANDARD SETTLING CURVE
-------
ro
OJ
SETTLING
VELOCITY
(ft/hr)
% SOLIDS
FIGURE 3
SETTLING VELOCITY
-------
ro
GJ
oo
CALCULATED
FLUX
(Ib/ft2-day)
FLUX CURVE
OPERATING
LINE
% SOLIDS
FIGURE 4
FLUX CURVE
-------
THICKENED
SLUDGE
SCRAPED
SLUDGE
HOLDING
TANK
GO
Ill
0 °
o
0 0
0
o
o o
o
o o
o
o o
° 0
L
I
JNC
TO
>ERFLO\
DRAIN
t
1
PR
POLYMER
FEED
AIR SUPPLY
FRESH WATER
TANK
FIGURE 5
DISSOLVED AIR FLOTATION THICKENER
-------
ro
CO
en
sr 10
Q
_j
O
to
K 8
LU
O
O
5 4
18 Ib. polymer/ton
> 1.5 Ib. polymer/ton
1.2 2.0
AI/P RATIO
-------
236
-------
SLUDGE INCINERATORS IN USE TODAY THAT MEET
THE REQUIREMENTS OF STATE AND FEDERAL REGULATIONS*
Presented At
THE PRETREATMENT AND ULTIMATE DISPOSAL
OF WASTEWATER SOLIDS RESEARCH SYMPOSIUM
May I state here at the offset that the topic of my paper will
not be as listed in your program. When first contacted with regard to this
symposium, it was requested that I address my remarks to the different types
of sludge incinerators in operation today that meet the requirements of State
and Federal regulations and suggest proposals for the future. My paper has
been prepared around this topic.
The fact that I do not profess to be a design engineer is perhaps
reason enough not to address my remarks to the topic listed in the bulletin.
My experience is that of supervision of construction. Trying to assure the
client that the manufacturer's fabrication of a sludge incinerator will per-
form in accord with the designer's intent and will meet State and Federal
regulations on such units. General remarks made herein are observations of
field experience.
The actual destruction of sludge cake is not the real problem con-
fronting us today. It is the conditioning of the sludge to place it in suitable
form for presentation into the furnace and then the disposal of the residue of
incineration—the ash and gases. While sludge conditioning is properly called
a problem of incineration, it is separated in that it does take place prior to
the presentation of the sludge into the furnace. On the other hand, the ash
and gases formed as a direct result of the incineration do become part of the
process of incineration.
237
* R. L. Kaercher, Havens and Emerson Ltd.
-------
Before going on, perhaps it would be well to identify State and
Federal regulations. Proposed Federal rules on standards of performance as
related to the Clean Air Act were issued in the Federal Register of June 11,
1973. The adopted rules were issued in the Federal Register of March 8, 1974.
These rules, as one might expect, deal with stack emissions. The proposed
rules of 1973 had as a basic criteria that stack emissions shall not contain
particulate matter in excess of 0.031 grains per dry standard cubic foot and
shall not exhibit 10 percent opacity or greater, except for two minutes in
any one hour. Water vapor was recognized as not being a cause for failure
of the regulations. In this regulation, a detailed test procedure was
established for determining compliance with the regulations.
The State of New Jersey has classified sludge incinerators as
Special Incinerators. As such, standards effective August 15, 1968, limit
emission to not more than 0.1 grains of particles including ash per cubic
foot of dry flue gas at standard conditions corrected to 12% carbon dioxide
by volume excluding the contribution of auxiliary fuel. Smoke emissions
limit has been established as to be not darker than No. 1 of the Ringelmann
Smoke Chart. For new fires, such emission shall not be darker than No. 2
of the Ringelmann Chart for a period of three consecutive minutes.
With regard to ash, the State of New Jersey prohibits the emission
of particles of unburned waste or ash which are individually large enough to
be visible while suspended in the atmosphere.
The State does require a stack test, however, the method of per-
formance is left to the descretion of the Department. Let me say here that
any reference herein to the State of New Jersey is brought about by the fact
that we are meeting today in this state. Regulations of any other state
could be used in comparison.
238
-2-
-------
There are six types of sludge incinerators in use in this country.
The oldest and most popular is the Multiple Hearth. Flash Drying, Wet
Oxidation, Fluidized Bed, and while perhaps not a pedigree sludge incinerator,
the mixing of conditioned sludge cake with solid refuse and incinerating in
a refuse incinerator. The last type on my list is the spray drying of sludge
using waste heat from a refuse incinerator and burning the dried sludge in
the incinerator.
The basic purpose of sludge incineration is to reduce the volume
of sewage sludge to a minimum leaving a residue of inorganic, sterile ash.
This must now be accomplished in conformance with ever increasing tighter
regulations.
Disposal of the ash residue from any sludge incinerator is less of
a problem than handling of the gases created. There are, however, problems to
be concerned with. Hydraulic disposal of the ash to lagoons for settling is
an accepted practice for handling of the ash from the multiple hearth, flash
dryer or wet oxidation units. Ultimately, such lagoons must be excavated.
Disposal sites must be available. Today this is perhaps not a problem but in
years to come, this will be at least an economic problem as haul distances
are increased. Consideration must also be given the characteristics of any
ash cooling waters returned to the plant flow stream. This is especially
important in the Fluidized Bed unit where all ash washing and degritting wash
waters are returned to the plant flow stream. Inefficient capture of solids
will put an extra solids loading on the plant system. Proper consideration
must be given to the materials of construction used in the hydraulic piping
system. Abrasive action of the ash requires special pumping equipment and
special alloys in the fittings of the piping system.
Over the years, two types of emission controls have been developed,
the dry type illustrated by cyclones, electrostatic precipatators and the bag
239
-3-
-------
filters . The wet type of impingement baffles and venturi scrubbers. Venturi
scrubbers might be further defined as medium energy or high energy. High
energy scrubbers usually having a pressure drop of 36 inches or more are more
adaptable to refuse incinerators.
The wet scrubber has achieved greater success and efficiency and
thus more acceptance than the dry. A review of stack emission tests performed
prior to adoption of the new E.P.A. standards on modern sludge incinerators
shows that today's standards can be met. Results of 28 separate stack tests
from 21 existing sludge incinerators equipped with air pollution control facili-
ties averaged particulate emissions of 0.027 gr/scf.
Emission tests reported on five plants studied in the E.P.A. report
of "Sewage Sludge Incineration", Report No. EPA-R2-72-040, August, 1972 indicated
that three of the five plants could meet the standards with existing equipment
and the other two could be within the proposed limitations with relatively minor
modifications.
It can be stated with assurance that properly designed sludge incin-
erators can meet the rigorous standards for particulate emissions.
Remember the bird cage on the stack to collect black birds —
Odor, while not mentioned above as part of Federal or State regu-
lations, obviously must be controlled. The State of New Jersey stipulates that
a special incinerator shall not be constructed or used which will result in odors
being detectable by sense of smell in any area of human use or occupancy. Odor
is controlled by subjecting gas flow to temperatures of 1300-1400 F. before
emission from the units. This has not been a problem with any of the incinerator
types mentioned here, except wet oxidation. The off gas from the separator is
quite odorous with a high organic content. An after burner would definitely be
240
-4-
-------
required. The decant tank must be covered with proper treatment of off gases
from such tanks provided. While this process provides more of a problem of
odor control than others, it too can be handled.
We have all noted the clamor of the environmentalist over the past
five or ten years who would have all the pollution ills of the country cleaned
up overnight. Unfortunately, this is not possible. Usually the individual
crying for such change has no feel for the problem as it really exists. Designs
for sludge incinerators are not completed overnight. It is not unusual for an
incinerator to be placed into actual operation three or four years after the
initial authorization for design was given to the Engineer.
The Federal regulation stipulates that the standards of performance
apply to sources, the construction of which was commenced after June 11, 1973.
We have one plant for which the bids for construction were received on June 15,
1973. The design of this plant was accomplished much earlier under the regu-
lation then in effect. Consideration should be given to installations such as
this in evaluating the stack emission test results should they not meet the
present requirements. The Federal regulations do at least stipulate that the
standards will be applied to an established calendar date of construction start.
One incinerator stack emission standard was changed by a regulatory agency after
construction was started. This agency went further in that they did, in effect,
dictate the type of equipment to be used for controlling stack emission. Even
though the owner expended thousands of dollars to provide the equipment, the
emission test failed to meet standards by a large margin. Fortunately, this is
the only instance I can draw upon of such abuse of regulatory authority in this
field. It does point up the dangers of individual interpretation of existing
regulations.
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Another procedure which must be given consideration in the construction
of complete new wastewater treatment facilities, is the availability of proper
sludge for incineration. Perhaps we have all experienced the wastewater treat-
ment plant having been completed but not having the interceptor lines connected
to provide flow or house connections be made so leisurely that flow was insuf-
ficient to produce adequate amounts of sludge to maintain incinerator operation
for periods long enough to actually test at full load.
As each incinerator with its attendant emission control units is placed
into operation, some new operating condition or design feature will be brought
to the surface to be applied to the next unit. What will we have tomorrow—we
are apparently experiencing a different sludge which will require new conditioning
processes.
The impingement scrubber can work fine if proper alloys are used in the
baffles, and velocities, temperatures and water quality are all controlled.
Venturi scrubbers also do a proper job, again if it is recognized that the high
velocity creates wear on the material. Proper amount of make-up water must be
used to limit recirculation of ash laden cooling waters.
Reference has been made to the environmentalist who would clean up the
air overnight. The cost for clean air should be closely examined before demanding
compliance. High energy venturi scrubbers do perform very well. However, there
is an accompanying cost of electrical power in using this unit due to the larger
horsepower motors required. Is it worth the expenditure of electrical power to
remove that additional grain from the stack emission?
Odor control has not proven to be a major problem. A few years back,
the concensus of opinion seemed to favor the installation of after burners in the
line to provide for temperature control of odors. On multiple hearth installations,
it has been found that such burners are not required.
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The presence of uncombined water or the white plume is recognized
by many as not being a pollutant of the atmospheie, and indeed it is not.
However, consideration must be given to this matter in evaluating the location
of the sludge incinerator. Should the site be one subjected to conditions of
atmospheric inversions, these plumes can raise havoc with traffic flow on
adjacent highways. There is at least one plant site where an interstate high-
way was constructed within a few hundred feet of the existing plant. Under
proper or perhaps improper atmospheric conditions, this highway is "fogged"
out when the incinerator is operating.
It is perhaps too early to evaluate the effectiveness of the test
methods established in the Federal Register, at least from my personal exper-
ience. Our office has only recently completed the first testing of an incin-
erator stack emission under these regulations and as yet, the results are not
available. We do have four additional incinerators scheduled to be tested this
year. Therefore, we do expect to have the proper experience to permit evaluation
of the procedures on the basis of actual field installations in the very near
future.
While six types of sludge incinerators and two basic types of scrubbers
are available, experience has shown that the use of the multiple hearth furnace
and a wet scrubber is providing the most practial answer to sludge incineration
today. What will we have tomorrow? We are apparently experiencing a sludge
having changing characteristics requiring new treatment processes in our waste-
water plants. As we have increasingly restrictive regulations governing all
actions, perhaps we need incinerator types not available today. It was a Buck
Rogers fantasy to fly rockets only 40 years ago. Perhaps the new method will be
to launch sludge ladened rockets to the sun's vicinity for complete destruction—
odors and all.
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It was mentioned a bit earlier that dangers do exist in the
individual interpretation of regulations. Federal government control is
divided into ten regions covering all states and lands under control of the
United States Government. This, in effect, permits ten separate interpre-
tations of the Federal regulations. There must be provisions made for some
latitude in the enforcement of the rules. Otherwise, the same restrictive
emission standards would be imposed for Guam as for New York City.
On the State level, somewhat the same condition does exist. Stack
tests' methods are to be "as approved by the Department". Construction
standards require new units to be of the multiple chamber type or of a type
"approved by the Department". In this instance, a strict interpretation of
the regulations would require the same incinerator design for Buena, in the
openness of South Jersey, as would be required for Paterson. Most have
observed the turnover of personnel in State, and where it is more in evidence,
in Federal regulatory agencies. Replacement has not always been with personnel
having"the expertise necessary to properly review the submittal of an incin-
erator design.
For many years, the Engineer's designs have been restrained from
most effective performance due to the lack of operators with the proper know-
how or initiative to operate an incinerator. This problem is being overcome
by operators and superintendents gaining on-the-job experience which they are
now beginning to put to good use. Engineers have also gained design experience
and further understanding of the problems of sludge incineration which is being
passed onto the industry with each new unit being constructed. Is it not time,
therefore, to research the problem of administration and enforcement of the
standards? This would perhaps permit an intelligent understanding and agreement
on what end results are really required and how fast they should be achieved.
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Economic Considerations for Planning
Sewage Sludge Disposal Systems'1'
by
Donn A. Derr
Victor Kasper, Jr.
Michael Gould
Emi 1 J . Genetel li
Introduction
Muni ciapli ties and other units of government have been devoting more
and more of their scarce resources — tax revenues and manpower — to waste
management. Much of this real location of tax revenue has been brought
about in order to conform to Federal, state and local legislation attempt-
ing to maintain or increase the level of environmental quality.
Until recent years, decision-making bodies (private and public) have
been able to avoid the total cost of waste disposal by passing part of the
cost onto a second party through the use of common property goods like
water and air. This is more commonly known as an externality or market
failure. That is, the user of a resource or product does not pay for its
"total" cost. In many instances, it is very difficult to compute "total"
cost because of non-monetary costs which lack adequate units of measurement
for lost social value.
Also, many of these wastes are becoming a competitive source of raw
materials as they become more plentiful and virgin materials more scarce
'"Presented at the Symposium on Pretreatment and Ultimate Disposal of Waste-
water Solids, Rutgers University, New Brunswick, N. J., May 21-22,
''Associate Professor and Research Associate, respectively, Department of
Agricultural Economics and Marketing; and Graduate Student and Professor,
respectively, Department of Environmental Science, Cook College, Rutgers
University, New Brunswick, N. J.
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and expensive. The wastes have essentially become "misplaced resources."
Through recycling and other means of recovery, the cost of waste management
and the reliance on virgin materials is reduced.
This paper suggests procedures for the estimation and evaluation of
costs for alternative (waste) sewage sludge disposal systems. First, the
basic components or modes of these systems are identified, then the flow of
activity, the components of cost, and, finally, the interpretation of results.
Basic Components
The basic components or modes for sewage sludge disposal are identi-
fied as: (1) transport, (2) dewatering, (3) storage, and (k) site disposal.
Within each of these four basic components are several possible options or
alternatives. For example, the transport mode can include: (1) tank truck,
(2) dump truck, (3) pipeline, (4) barge, and (5) rail.
In the various systems discussed in this paper, a dewater/no dewater
option is incorporated. This option is provided at one of two locations:
the point of origin (treatment plant), and just before disposal. Dewatering
can reduce transport costs and storage facilities; and for certain disposal
methods, it is necessary for proper operation.
The storage option provides flexibility for varying weather conditions,
equipment breakdown and work distribution.
Basic disposal methods include: (1) incineration, (2) landfill, (3)
ocean disposal, and (4) land disposal. For purposes of discussion, sludge
solids concentration will be confined to two levels — 5 and 30 percent.
Transportation Mode
The transport component can be of three possible types: (1) land
modes, (2) water modes, or (3) a combination. For land transport: (1)
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tank truck, (2) dump truck, (3) rail, and (^) pipeline are possible. The
selected method will depend in large part on the distance from treatment
plant to disposal site, the concentration of solids, and the annual volume
of sewage sludge. For example, a tank truck would be needed for 5 percent
solids and a dump truck for 30 percent solids.
The truck transport generally has a lower initial investment cost but
will have higher operating costs relative to rail or pipeline transport
^
for most levels of design volume. A rail transport system involves the
construction of a rail spur and car fees. Pipeline requires a heavy invest-
ment in right-of-way, construction, and restoration (landscaping) costs.
Water transport of sewage sludge can be by either barge or pipeline
outfall. Again, costs for barge and pipeline are analogous to rail and
land pipeline costs, respectively.
Dewateri nq Mode
A dewatering option is provided for technical and economic reasons.
By dewatering, additional equipment can be considered, like dump trucks,
and incineration. Also, since large quantities of water are removed, the
volume of sludge is reduced, and, subsequently, costs.
Three methods are in current use today: (1) sand beds, (2) centrifuge,
and (3) vacuum filters. Sand beds have low initial costs but operating
costs are high because of maintenance such as the removal of dried sludge
and operating difficulties caused by heavy rainfall and freezing conditions.(1)
Centrifuges are affected much less by varying weather conditions and
have lower operating costs. However, the initial investment will generally
be higher. Centrifuges are plagued by the fines that do not settle out
well when returned to the treatment system. This problem can be overcome
with greater bowl speed, retention time, and chemical treatment. (2) Vacuum
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filters generally operate with less trouble, particularly with chemical-
treated sludges. (3)
Storage Mode
Storage of sewage sludge can occur primarily at the sewage plant or
the disposal site, or both. Storage permits flexibility in terms of
equipment usage, work loads, and weather variability. It also reduces
environmental impact. With storage capacity, sludge can be disposed at
a rate in keeping with the rate of soil capacity.
Disposal Methods
Disposal methods include: (1) incineration, (2) land disposal, (3)
landfill, and (^) ocean disposal. Each have advantages and disadvantages.
For example, incineration requires dewatering, air pollution control devices,
residue disposal, and relatively little land use. Land disposal obviously
requires extensive land area but permits utilization of the nutrients
contained in the sludge and may be less of a problem to the ground water
than landfi11.
Disposal at a landfill site after considering all disposal costs is
probably cheaper than land disposal. However, there is the problem of
leachates, possible contamination of ground water, aesthetics and the future
availability of landfill sites.
Ocean disposal costs will be affected by the location of the sewage
treatment plant. Two transport modes may be required — land and water.
Also, the effect on marine life and recreational facilities, as well as
varying legislative policies makes this method somewhat uncertain.
It is also possible to use more than one disposal mode in order to
minimize costs and/or the impact on the environment. For example, it may
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be possible to use ocean outfall to certain limits and then apply the
balance through land disposal with nutrient recovery. This can be handled
through an optimization technique (cost minimization) similar to linear
programming. This will be discussed in a later section.
Flow of Activity
The flow of sludge or the combined modes of activity of various
alternative combinations are portrayed in Figures 1 through k. Figure 1
illustrates the combined activities for incineration, Figure 2 for land
disposal, Figure 3 for landfill, and Figure 4 for ocean disposal.
The flow charts are divided into three segments with each segment
representing modes of activity at a given location. The three segments
include: (1) the origin (sewage treatment plant site), (2) the transport
mode, and (3) destination (disposal site). This three-way grouping is
made to indicate the possible location of modes. For example, in Figure 1
(incineration), dewatering plus storage facilities could be located at the
sewage treatment plant. Also, storage and dewatering could be located
at the disposal or incineration site, depending upon the availability of
land area. The origin and destination are then connected by the transport
mode. The location of dewatering and storage facilities can, and probably
will, affect costs because sludge would be transported at 30 percent solids
if dewatered at the sewage plant, and at 5 percent solids if dewatered at
the incineration site. More equipment and time would be required for 5
percent solids.
The flow of activity in Figure 2 indicates that sludge can be dis-
posed with or without dewatering by land disposal. The equipment used for
the disposal activity, however, will depend on whether the dewatering option
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cn
O
TRANSPORT OPTION
Transport
30%
Solids
Transport
5%
Solids
FIGURE 1
FLOW CHART OF ACTIVITY FOP INCINERATION DISPOSAL OF SLUDGE
-------
ORIGIN
ro
en
FLOW CHART OF ACTIVITY FOR DISPOSAL OF SEWAGE SLUDGE'BY LAND DISPERSAL
-------
ro
en
ro
Sewage
Plant
ORIGIN
I
(TRANSPORT OPTION
5%
Transport
@5% Solids
DESTINATION
30°/
Dewatering
FIGURE 3
FLOW CHART OF ACTIVITY FOR DISPOSAL OF SEWAGE SLUDGE BY LANDFILL
-------
ORIGIN
TRANSPORT OPTION
DESTINATION
ro
on
CO
FLOW CHART OF ACTIVITY FOR DISPOSAL OF SEWAGE SLUDGE BY OCEAN DUMPING
-------
was selected. Here, again, dewatering can occur either prior to or following
transport. In addition, if the disposal destination is adjacent to the
sewage treatment plant, one alternative is for sludge to be loaded directly
into the land disposal equipment.
Land disposal offers the greatest opportunity for recycling of sludge
into the soil using a crop like Bermuda grass for nutrient removal.
Disposal through landfill is quite similar to the activities dis-
cussed under land disposal.
The flow of activity for ocean disposal is presented in Figure k.
Ocean disposal can be used to dispose dewatered or nondewatered sludge.
Two forms of transportation may be necessary. If the sewage plant is
located adjacent to a water transport facility, only an ocean transport
capability will be required. On the other hand, if the sewage treatment
plant is located a distance from the coast, land transport is required in
addition to the ocean transport. Dewatering can take place either before
or after land transport. Also, ocean transport can be implemented by barge
and by pipeline (outfall).
Estimation and Components of Sewage Sludge Costs
In most cases of computer modelling and resource allocation, the ob-
jective function is to maximize profit or minimize costs. Here, the basic
objective is to minimize the cost of sewage sludge disposal, taking into
account environmental constraints which may be dictated by law or public
welfare considerations.
Costs can be placed into three categories: (1) capital investment,
(2) operating or variable costs, and (3) fixed costs. Capital investments
are those costs or outlays required before the first unit of sewage can
be disposed. Included are such costs as engineering and planning fees,
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buildings, equipment, land, cost of initial financing and certain personnel
costs, like administration.
Variable costs include hourly labor, electricity, chemicals, petroleum
products, and repairs and servicing. These costs vary directly with the
quantity of product being processed. Fixed costs include those expendi-
tures that are incurred independent of the volume of processing, like
insurance, reserves for replacement, administration, interest and taxes.
Initial capital investment in machinery, buildings and structures pro-
rated over its physical life and reflected in the reserves for replacement
is much of fixed cost. In essence, initial capital investment cost indi-
cates the amount of funds required to start an operation. The design
capacity associated with the initial capital investment results in a speci-
fic annual cost made up of fixed and variable costs. On a per unit basis,
fixed costs will vary depending upon how close to optimum capacity the
system is operated while per unit variable costs will remain relatively
constant. Figure 5 indicates the typical relationship of total cost per
unit as the system is operated closer to optimum design capacity. The
total cost per unit drops rapidly at first and then approaches a minimum
when it reaches design capacity.
Figure 5.-Total Cost per Unit as Volume of Sludge
Disposed Approaches Optimum Design Capacity
Total
cost
per
unit
Optimum
design capacity
Vo 1 ume
of sludge disposed
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A relationship similar to that presented in Figure 5 may exist for
total unit cost and design capacity. In many processes, the incremental
capital investment per unit declines as design capacity is increased. In
other words, the overall investment per unit of capacity decreases for
systems with larger design capacities. This has been referred to as
"economies of size". This concept should not be confused with the rela-
tionship between total cost per unit and sludge disposal operating at less
than design capacity as described by Figure 5.
Figure 6 is a representation of the relationship between total cost
per unit and design capacity illustrating the concept of economies of
size. Point A represents a system such as that presented in Figure 5
operating at optimum design capacity.
Figure 6.-Total Cost per Unit as Design Capacity is
Increased - An Example of "Economies of Size"
Total
cost
per
unit
Design Capacity
Evaluation
To evaluate the alternative methods of sludge disposal, in addition
to investment and cost data, consideration must be given to budgetary con-
straints, environmental impact and risk associated with each alternative.
Which method a community can select is limited by the funding available
and its potential revenue over time. The selection can also be affected
by legislation restricting the environmental impact. Finally, the potential
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risk (probability of making a wrong decision) associated with changes in
factor-price relationships, technology, growth rate, revenue, environmental
legislation, and loading capacity of the soil, must also be considered.
1. Budgetary Constraints
After estimating the required investment, and, subsequently, costs,
a decision-making unit must determine the amount of present and future
resources which must be allocated to sludge disposal. The investment and
cost estimates can then be compared to available resources. This cash-
flow analysis would eliminate alternatives outside the decision-making
unit's budgetary constraint. Table 1 indicates a general cash flow
situation over the operating life of a particular system. The cash out-
flow of each year is compared to the available resources allocated to
sludge disposal. The cash outflows of alternative systems designed for
the community's needs could then be compared to the resources available
for allocation to sludge disposal. The cash outflow of alternative systems
which were equal to or less than the available resources would lie within
the planning unit's budgetary constraint.
It must be noted that 0. (Table 1) represents net cash outflow for
each period, t. Revenue has been subtracted from gross cash outflow.
This revenue could result from the sale of a possible product produced
from the disposal activity. As a varient of the land disposal technique,
sludge could be heated, dried, and sold as a soil conditioner. This method
has been tried and has met with limited success. The main obstacle is
market development costs. Another possibility of off-setting sludge dis-
posal costs is the recovery of heat from incineration for plant heating.
In any case, potential revenue from possible sales should be considered a
cost offset. As the price of fertilizer increases the sale of sludge as
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Table 1.-Example of a Cash-Flow Comparison of a Sludge Disposal
System Given Resource Constraint
Expected Resources Allocated
Cash Outflow to Sludge Disposal
0. R.
0, R,
°2 R2
°T RT
R = f (tax revenue, credit, state, and Federal aid)
T = operating life of the system
0 = variable costs + fixed costs - depreciation + equipment
replacement outlays - revenue from sales.
a soil conditioner may increase in importance as a source of revenue
for off-setting sludge disposal costs.
Alternatives within the planning unit's budgetary constraint could
then be evaluated with respect to the present worth of the cash outflow
over time. The alternatives with a smaller present worth of total costs
could then be further evaluated. The following formula could be used for
thi s purpose:
T Ct
PW =' V=, T^>1
where:
PW = present worth of total cost of the system
I = initial capital investment
C = variable cost + fixed cost - revenue deprecia-
tion - interest charge
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r = discount rate
T = life of disposal system
The discount rate can be estimated by the rate of return the planning
unit could have received by investing each C. in alternative investments.
Ct
The discounted costs in time period t, - -, is interpreted as the present
(i+r-r
worth of a payment. C , made in period t. The higher the discount rate,
the lower the value of these future operating costs. Thus, a capital
intensive alternative which has a large initial capital investment but
relatively low operating costs will more likely be selected when the dis-
count rate is high. On the other hand, a labor intensive alternative
with a lower initial capital investment and a higher operating cost will
more likely be selected when the discount rate is low.
r ct
The present worth of the discounted cash outflows,/ - s— r — , can be
interpreted as the amount of capital which would have been invested at
the going rate of interest so that the periodic expenditures are met.
2. Environmental Impact
The impact of the disposal method on the environment is difficult to
measure. Assumptions must be made in order to estimate how environmental
effects will influence the selection of a disposal method or methods. En
vironmental constraints can be placed in the planner's selection process
in two ways: (1) the planner can be given restrictions on how the environ
ment can be affected from members of the political entity for which they
are planning, and (2) legislation may set limits in terms of rates of
disposal, available disposal sites, or types of equipment which can be
used. For the following discussion, it is assumed that a given level or
constraint is provided.
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Figure 7 illustrates the problem of selecting a sludge disposal system
under an environmental constraint. A planning unit must provide for the
disposal of V, volume of sludge. Under no constraints it would select
the system which had the least cost at a design capacity of V,. In the
hypothetical example illustrated by Figure 7, the no constraint selection
would be system IV. This system provides a disposal capacity of V, at
a cost per unit of CQ.
Now consider the case where an environmental constraint is placed
on the planning unit by legislation. The hypothetical law limits the
volume which can be disposed by system IV to V . This volume, V , becomes
an environmental constraint.
Figure 7.-Hypothetical Cost per Dry Ton for Four Alternative Sludge Disposal
Systems Illustrating Different Levels of Economies of Size
and Environmental Constraints
System I
System I I
System I I I
System IV
* Vc ~- V2
Design Capacity
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Given this constraint, the question arises as to what is the next
best alternative. A number of alternatives are possible. One alternative
is to select system III which has the next lowest cost per unit at design
volume V,. A second alternative would be to select a two-system approach
such as disposing of volume V by system IV and volume V, - V by system
II, where system II has the least cost at a design capacity at volume V, - V ,
There is a large number of multi-system approaches which can be considered.
The question is which approach has the least total cost per unit for a
design capacity V,. A method which can be used to determine the least cost
alternative(s) is the recursive programming approach. The environmental
constraints and cost functions as illustrated in Figure 7 would be inputs
into the program. The program is then used to search both individual and
multi-system alternatives within these constraints and cost functions to
arrive at a solution which approximates the least cost alternative.
The question of what should be the environmental constraints is a
question yet to be determined. Once determined, however, the constraints
can be evaluated in terms of their effects on decision-making by the pro-
cedure suggested above.
3. Risk
The element of risk can be an important factor in evaluating the
feasibility of alternative methods. Relative factor prices, technology,
legislation, and available resources may change. All of these can affect
the criteria for selection of sludge disposal methods.
To take these factors into consideration, the importance and proba-
bility of each source of uncertainty could be estimated. The minimum
cost alternatives could be estimated for a variety of factor-price relation-
ships, technology, legislation, and resource constraints. This is a form
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of sensitivity analysis. The factors which produced radically different
costs for alternatives could then be evaluated in terms of their probability
of occurrence. The minimum cost alternative could then be selected using
the expected value of these sensitive factors.
The procedure of estimating the probability of possible changes would
be a key factor in determining the minimum cost alternative. These estimates
would rely heavily on the judgement of the planners, historical information
and life span of the project.
The life span of the system is particularly important. Systems with
longer operating lives are more risky in the sense that factors are more
likely to change as the length of time considered increases. In evaluating
two systems, the expected value of a sensitive factor for a long-lived
system could be different from a system which was relatively short-lived.
Another risk which could be considered is that of the use of inaccurate
estimates of population growth over time. Inaccuracies in these estimates
could result in not considering systems which would otherwise have been
selected as least cost alternatives. The weighted expected value approach
could be used under these circumstances.
A simplified example of how these factors could be incorporated is
illustrated in Table 2.
The decision-making unit has determined the probability of wage rates,
W., to be, P., during the operating life of a particular system. The
expected value of wages is then I P.W.. This value provides a means of
estimating the cost of a disposal system while taking into consideration
the possible instability of a factor to which per unit cost is particularly
sensitive. Other factors can be evaluated in a similar manner.
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Table 2.-Determination of the Expected Value of Wages for a Hypothesized
Disposal System
Wage Probability of
rate each wage
Wl Pl P1W1
w2 P2 P2w2
W3 P3 P3W3
Expected wage I P.W.
where:
Pl + P2 + P3 = ]
P. = probability of Wi i = 1, 2, 3
Hypothesized Solutions
Given the components or activities described in this paper, estimates
of costs were obtained from past literature, and previous research of
the authors, and are presented in Table 3. These are estimates of total
costs. The conditions under which each cost was estimated differed in
such areas as design volume, distance transported, soil absorption
capacity, etc. However, they provide the basis for a hypothesized solution
to the selection of a sludge disposal system.
The least expensive solution based on Table 3 would be for a sewage
treatment plant located at barge-docking facilities to barge sludge at
5% solids for a distance less than 30 miles and dispose the sludge in
the ocean. This solution does not provide for storage facilities.
The most expensive alternative is for sludge to be transported over
land by tank truck for 17 miles or more, stored at 5 percent solids con-
centration, and disposed by land disposal.
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Table 3»-Typica1 Estimated Total Costs per Dry Ton for Component
Activities, 1974
Methods Cost per Dry
($)
1. Dewatering
A. Vacuum filter 31.00
B. Centrifuge 26.00
C. Sand beds 30.00
2. Land Transport 5%
A. Tank truck 3.02/mile
B. Railroad .25/mile
C. Pipeline 1.55/mile
3. Land Transport 30 %
A. Dump truck ,65/mile
B. Railroad .25/mile
4. Ocean Transport 5%
A. Barge .20/mile
B. Outfall .60/mile
5. Ocean Transport 30%
A. Barge .03/mile
6. Storage
A. 30% 2.30
B. 5% 14.00
7. Disposal 5%
A. Ocean disposal
B. Landfill 3-00
C. Land disposal 20.00
8. Disposal 30%
A. Ocean disposal
B. Landfill 3.00
C. Land disposal 10.00
D. Incineration 12.00
\J Cost has been adjusted for inflation at $6 per year.
Source: Burd, R.S., A Study in Sludge Handling and Disposal, U.S.
Department of the Interior, Publ. pp. 179-514, Washington,
D.C., May, 1968.
(cont. next page)
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Thus, the cost of alternatives presented by Table 3 ranges between
$6 per dry ton for barging and $85 per dry ton for land disposal.
Given the costs in Table 3, however, all that can be determined is
that current costs of sludge disposal can range between these values.
Little or no comparison of systems can be made without additional informa-
tion. The information required for further evaluation is the total investment,
the variable and fixed costs for the relevant range of design capacities,
the budgetary constraints of the decision-making unit, the institutional
and/or environmental constraints, and the possibility of change in unstable
factors for which costs are particularly sensitive. Once this information
has been estimated, the array of alternative systems can be adequately
Source: (Table 3> cont.)
Bauer, W.J., "Modes of Transporting and Applying Sludge", paper pre-
sented at the Land Disposal of Municipal Effluents and Sludge Conference
held at Rutgers University, New Brunswick, New Jersey, March 1973.
Oiurk, P.P., "Economic Aspects of Incineration Versus Incineration
Drying in "Sludge Concentration and Incineration", Continued Education
Series, No. 113, University of Michigan, Ann Arbor, 1964.
Land Reclamation Project, U.S. Dept. of H.E.W., prepared by Harza
Engineering, Chicago, Illinois (1968).
Albertson, O.E., "Low-Cost Combustion of Sewage Sludges", Proceedings
of the 9th Great Plains Sewage Works Design Conference (1965).
Adler, Cyrus, "Ocean Dumping - Pollution or Fertilization", Water and
Wastes Engineering, Vol. 8, No. 4, April 1971.
Holmes, Billy P., Robert M. Clark, "Selecting Solid Waste Disposal
Facilities", Journal of the Sanitary Engineering Division - Proceedings
of the American Society of Civil Engineers, August, 1971. (c) American
Society of Civil Engineers, New York.
Kasper, Victor Jr., Michael I. Gould, Donn A. Derr, and Emi1 J. Genetelli,
"Procedure for Estimating the Cost and Investment Required for Sludge Re-
cycling through Land Disposal", Unpublished Report of Department of Agri-
cultural Economics and Marketing and Department of Environmental Sciences,
Rutgers University, New Brunswick, New Jersey, August, 1973.
265
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considered by the decision-making unit for selection of the least cost alterna-
tive necessary to meet a region's sludge disposal needs.
Alternative sludge disposal systems must be evaluated under comparable
design conditions and with consideration of budgetary constraints on en-
vironmental impact and risk. To make decisions on the partial information
such as that in Table 3, increases the possibility that sub-optional or
less efficient solutions will be selected.
References
(1) American Society of Civil Engineers, Sewage Treatment Plant Design,
1959.
(2) White, W.F., and J.E. Burnes, "Continuous Centrifugal Treatment of
Sewage Sludge", Water and Sewage Works, Volume 109, No. 10, October,
1962, pp. 38it-386.
(3) Burd, R.S.. A Study of Sludge Handling and Disposal. U.S. Dept. of
Interior, Publ. PB-179-51^, Washington, D.C., May 1968.
266
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Future Problems in
Sludge Production and Handling Systems
Joseph V. Hunter
The salts of iron (ic) or aluminum, or calcium hydroxide
(lime) can be employed in waste water treatment in two major
capacities. Firstly, they can be employed as coagulants for
the removal of particulate materials, and as such can be used
for secondary effluent upgrading or on waste water itself as part
of a complete physio-chemical treatment process.
Secondly, they can be employed as precipitants (or adsorbents)
in phosphate removal processes, and as such may also be employed
for concurrent particulate matter removal. In addition, alum can
also be added directly to activated sludge tanks to achieve
phosphate removal. Wherever employed, the inorganic compounds
formed by their reactions will be found in the sludge, and it is
the purpose of this paper to indicate what modifications and
problems in present sludge treatment and handling processes might
be expected from their employment.
Sludge Composition
As the composition of the sludges will depend on the nature
of the coagulant or precipitant, its dosage, the extent of phosphate
removal and the waste water composition, particularly the concen-
tration and value of the particulates, generalizations on the
267
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composition of such sludges are difficult to make. However, a
knowledge of these factors and of the nature of the reactions
involved does enable certain predictions as to what would be the
expected composition of the sludge.
1. Alum Precipitation:
Alum (aluminum sulfate hydrate) can be used to precipitate
phosphorous as follows: A12(SO^) + 2 Na^PO/^ = 2 AlPO^ j- +
3Na2SOi|,. At the same time, alum will be reacting with the
waste water alkalinity as follows:
Al2(SOi4,)3 + Ca(HC03)2 = 2Al(OH)3l + 3CaSO^ + 6C02 .
In theory, one mole of aluminum should precipitate one mole
of phosphorous, or, on a weight basis, 0.8? parts of aluminum
should precipitate one part of phosphorous. As alum contains
about 9% aluminum, 9.7 parts of alum would be required to
precipitate one part of phosphorous or 3.1 parts of phosphate (1).
Due to the reaction with alkalinity and possible reactions with
the organic constituents, the actual dosage required to preci-
pitate one part of phosphorous or 3.1 parts of phosphate would
be about 2 parts of aluminum or 22.2 parts of alum. Dosages,
therefore, in the range of 22.2 mg/1 alum per 3.1 mg/1 phosphate
will give about a 95% phosphate reduction.
If the suspended solids removed, the % volatiles in the
suspended solids, the phosphate concentration, and the alum
dosage are known, it should be possible to predict the sludge
composition. For example, an average dosage of 8? mg/1 alum
was employed to coagulate a trickling filter effluent containing
48 mg/1 suspended solids. The alum dosage reported could precipitate
268
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3.9 mg/1 of phosphorous, or form 15 mg/1 of aluminum phosphate.
If the aluminum required to react with the phosphate is
subtracted from the alum dosage, the remainder represents the
amount of aluminum that precipitates as the hydroxide. If the
trickling filter effluent solids are 70$ volatile then the
following composition would be predicted:
particulate organics ^3 mg/1
particulate inorganics 5 mg/1
aluminum phosphate 15 mg/1
aluminum hydroxide 12 mg/1
If, on ignition, the aluminum hydroxide forms aluminum oxide
(Al2C>3), then the volatile solids of this sludge would be 63%,
which agrees with the reported value of 60f0 (2). In this case
it was not necessary to know the phosphate concentration, as it
was unquestionably above 12 mg/1.
2. Iron Precipitation
The reactions of iron salts in water are quite similar to
those of alum. If ferric chloride is used as a precipitant, then
the phosphorous precipitation reaction would be an analogous
calculation procedure which can be employed to determine sludge
composition. In a study on waste water composition, 70 mg/1
(anhydrous) ferric sulfate was used to coagulate Highland Park,
N.J. domestic wastewater (4). The volatile suspended solids
were 125 mg/1 and the nonvolatile solids 21 mg/1. This dosage
of iron would form 10.7 mg/1 FePO^, and the remainder would
form Jj-1.5 mg/1 Fe(OH)o. Assuming complete suspended solids
precipitation, and that on ignition the Fe(OH)o would form
F6203, the calculated volatile solids of a dry sludge would be
68fo. This again agrees quite well with the observed value of 70%
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Chemical coagulation, however, can do more than simply remove
suspended solids. In the domestic waste water study noted above,
about one-fourth of the soluble COD was removed along with the
particulates, and detailed sludge analysis indicates that the
additional organics removed by chemical coagulation (i.e., over
that of physical separation) were not analogous to the usual
particulate constituents, confirming to some extent their
different mechanisms.
3. Lime Precipitation
Due to the many reactions involved, lime precipitation
is a far more complex process than alum or ferric chloride
precipitation. In addition to the effluent organic and inorganic
particulates, the precipitation reactions will add the following
constituents:
a. Hydroxyapatite
This is the phosphorous removal precipitate, and is
formed as follows:
5Ca(OH)2 + HPOj+ = Ca5OH(PO|4,)3-i'+ 3H20 + 60H~
b. Calcium Carbonate
Calcium carbonate is generated in two ways through lime
addition. The first is through reaction with the alkalinity
(the lime softening reaction)
Ca(OH)2 + Ca(HC03)2 = 2CaC03i + 2H20.
The second is through reaction with carbon dioxide
Ca(OH)2 + C02 = CaCOol+ H20.
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c. Magnesium Hydroxide
If the pH is sufficiently high (i.e.,—11), the magnesium
in solution will also be precipitated as follows*
MgSOij. + Ca(OH)2 = M2(OH)2 J> + CaSO^.
In addition to these materials we may also find insoluble
impurities in the lime itself.
Unlike precipitation with iron and aluminum salts,
phosphate reduction employing calcium hydroxide is mainly a
function of the pH to which the system is raised by the lime
addition. Thus, the dosage of lime required is more a function
of the wastewater alkalinity than the phosphate concentration.
Thus, if the pH of the system is raised to about 11, then
phosphate reductions of over ^Q% can be achieved (3).
Despite the complexity of the sludge formed it has been
possible to predict the sludge composition (5). This was done
on the basis of wastewater suspended solids removed, the
phosphorous removed as CatOH(PO^)o, that all magnesium was
precipitated as Mg(OH)2 and that calcium carbonate precipi-
tation could be calculated by employing a mass balance around
the calcium ion as follows (as equivalents)*
CaCOo pptated = Ca(in) + Ca (dose) - Ca (out) - Ca (apatite).
On this basis, the following results were obtained:
Constituent Observed Calculated
Organic 28.9 24.4
Hydroxy apatite 5,9 4.8
Magnesium hydroxide 6.7 3.9
Calcium carbonate 52.1 60.6
Balance 6.4 6.0
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Considering the complexity of the system, these results show
reasonably good agreement, and thus lime sludge composition
can also be predicted with reasonable accuracy.
Sludge Production
Using the same type of computations employed to calculate the
sludge composition, it should be also possible to predict the dry
weight of sludge produced. The Highland Park, N.J. data mentioned
in the previous section represented results on a daily average basis
(flow composited over an extended period. The sludge produced was
198 mg/1, which is equivalent to 1.7 lbs/1000 gallons. This was,
however, for a phosphate removal of b mg/1 phosphate-P. As the
wastewater probably contained about 8 mg/1 phosphate-P, the sludge
concentration for complete phosphate removal would have been about
250 mg/1 (doubling the hydroxyapatite value of 10.7 and the aluminum
hydroxide value of 4-1.5) equivalent to 2.1 Ibs./lOOO gallons. As
the average flow over this period was 1.7 mgd, then the daily sludge
production for about 50$ phosphate reduction would have been 2890 Ibs.,
and for essentially complete phosphate reduction it would have been
about 3570 Ibs.
These values are not out of line with those to be expected of
such sludges ( ). For example, alum processes tend to produce
2-2.5 Ibs. of dry solids/1000 gals, of wastewater treated, ferric
chloride processes 2.5-3 Ibs./lOOO gals., and lime processes 6-13
Ibs./lOOO gals.
Sludge Water Holding Capacities
Although the dry weight quantities of sludges produced by alum,
ferric chloride or lime coagulation or precipitation may be predicted
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with some degree of reliability, the water holding capacities of
the sludges have essentially been determined by empirical study
rather than from basic considerations. In general, alum and iron
sludges have the greatest water holding capacity, and lime sludges
least (6). Typical ranges aret
Sludge Type
Activated Alum Ferric Chloride Lime
Thickened Solids, % 2-4 2-4 3-4 10-15
Dewatered Solids, % 15-20 12-18 12-20 25-50
Although lime sludges thicken and dewater better than alum or ferric
chloride sludges, more lime sludge is produced on a dry solids basis
Thus we have a somewhat self-compensating effect, and the result is
that the wet volumes of sludges produced may not be too different (6),
and the following results might be expectedj
Type of Sludge
Alum Ferric Chloride Lime
Ibs. wet sludge
per 1000 gallons 11-21 12-25 12-26
wastewater treated
Needless to say, such generalizations are always hazardous. Local
conditions, the nature of the wastewater or plant effluents
treated, the purpose of the chemical treatment all influence the
values noted, but they do represent typical results if such can be
said to exist.
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Sludge Digestion
Although chemical precipitation or coagulation unques-
tionably increases the dry weight of sludge, the dewatering
characteristics of the sludges are such that there are not
particularly large increases in the volumes of sludges produced.
For example, there have been reports that the use of alum (?)
or lime (8) did not increase the volumes of sludge produced in
the treatment process. In such cases, additional digestor capacity
would not be required from a strictly volumetric loading standpoint.
However, if larger sludge volumes are produced, this would decrease
the digestor retention time and thus could adversely influence
digestion unless digestor capacity was increased.
It is also possible that the presence of the reaction products
of the chemical precipitants or coagulants could interfere in the
digestion process itself. Although aluminum precipitated phosphate
has been reported to give no interference in sludge digestion (7» 9),
the addition of 15^9 mg/1 aluminum (as the hydroxide) to a sludge
containing 1.8$ solids gave a 15% decrease in gas production over
a 37 day period (10). It was concluded that as little as 100 mg/1
aluminum (as the hydroxide) could adversely affect sludge digestion.
Lime coagulation sludge also indicated an adverse effect on
digestion processes (5). Using a lime sludge containing 50-55$
inorganic constituents, it was observed that both volatile matter
destruction and gas production were adversely affected. For example,
after 15 days, volatile matter reductions in the lime sludges were
about 35$i while volatile matter reductions in the control sludge
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were about $Q%. The volume of methane produced per part of
volatile matter destroyed were essentially the same; but the gas
produced by the lime sludge digestion contained considerably less
carbon dioxide, due to its interaction with the alkaline sludge
constituents. Whether this was due to a limitation on the rate
or the extent of digestion is not clear, but the authors suggest
that it may be rate considerations. If so, this could possibly
be compensated for through increased retention time. Even with
relatively poor digestion, the sludge was not too objectionable
dueto its high alkalinity (eg., low free hydrogen sulfide levels,
etc.). However, as there are problems of stratification due to
the denser calcium carbonates, and as the lime sludge itself is
relatively stable and can be disposed of advantageously employing
other technologies, the digestion of such high inorganic contents
lime sludges is questionable.
As a considerable part of the interest in the use of alum,
ferric chloride or lime lies in their use as phosphate precipitants,
one of the major concerns must be whether or not sludge digestion
causes phosphate resolubilization. Studies have indicated no phos-
phate release from the digestion of alum precipitated sludges (11);
nor is this surprising as there is no obvious resolutilization
mechanism. However, it was also reported that no solubilization
of phosphate occured when iron precipitated sludges were digested
(11). This is somewhat surprising as phosphate recycling in
stratified lakes has long been explained by the reduction of ferric
phosphate to a more soluble ferrous phosphate under anerobic conditions,
Lime precipiation is carried out at pH values above 11, but
275
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during digestion the production of carbon dioxide and volatile
acids will reduce this to about 7.7 (5). Theoretically, this
should release substantial quantities of the precipitated ortho
phosphate, but the digestion study previously described indicated
that only about 1.57° of the phosphate was resolubilized. However,
the reduction of pH did solubilize essentially all the magnesium
hydroxide in the lime precipitated sludge.
Precipitant or Coagulant Regeneration
Whenever chemically coagulated or precipitated sludges are
discussed, the question of coagulant or precipitant regeneration
inevitably arises. This is due to the cost of these materials,
the problems they do or may cause during treatment and disposal,
as well as the greater quantities of sludges produced for disposal.
At present, iron is not in extensive use and substantial work
has not been done in studying its regeneration, although processes
may be applicable Lime and alum regeneration, however, have been
extensively studied, and the discussion will be limited to these two.
1. Lime Regeneration
Lime sludge contains coagulated or precipitated organic
materials, calcium carbonate, calcium hydroxyphosphate (hydroxy-
apatite), magnesium hydroxide, and other insoluble inorganic
constituents (silica, clays, etc.). Regeneration procedures
usually involve dewatering to 50-55% solids then recalcifying at
1800°F. What occurs here is the loss of organics by combustion,
the conversion of calcium carbonate to calcium oxide, and the
conversion of magnesium hydroxide to magnesium oxide. The
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miscellaneous inorganics and the hydroxy apatite remain relatively
unaffected.
This mixture can then be rehydrated and agin used as a
precipitant. However, it does contain both inorganics and hydroxy
apatite. As the lime is recycled, these could build up and cause
problems. Although calcium hydroxide is considerably more soluble
than the other constituents, the lime is fed as a slurrey and thus
this property of calcium hydroxide is not usually employed at present.
Gulp and Gulp (3) have described a possible way out of this
difficulty. The calcium carbonate sludge is denser than the phosphate
sludge, and they propose a series of two centrifuges; the first to
remove the carbonate (and some organic and magnesium hydroxide).
The second to remove the phosphate sludge and the remainder of the
organics and magnesium hydroxide. The first is recalcined and
returned to the process as a lime slurry. The second is incin-
erated and then processed for disposal. However, there still are
reservations about the build up of inert, insoluble inorganics in
return hydrated re calcined lime sludges (11).
2. Alum Sludges
Aluminum sludges are simpler, containing only sluminum
hydroxide, aluminum phosphate, and the wastewater or effluent
particulates removed during coagulation or precipitation. As
aluminum is amphoteric »- two regeneration processes can be employed!
a. Alkaline regeneration
At a pH of 11.9» the precipitated aluminum hydroxide will
dissolve to form soluble aluminate as follows:
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+ NaOH = NaA102 + 3H20.
At the same pH, aluminum phosphate will also dissolve as followsi
AlPOij, + Jf-NaOH = NaA102 + 2H20 + ^PO^.
Thus the phosphate will go into solution as well as the aluminum.
Fortunately, the phosphate can be precipitated with calcium
chloride as followsi
2Na3PO^ + 3CaCl2 = Ca3(PO^)2 + 6NaCl.
At pH values above 12, about 90-95$ of the aluminum can be
recovered, and be substantially freed of its phosphate contents.
As many organic materials are anionic and are insoluble in
neutral or acid pH ranges but soluble in alkaline pH ranges
(eg., stearic acid), alkaline regeneration will dissolve or
solubilize some of the sludge organics. The remainder of the
sludge particulates remain in the alkaline suspension which
in turn must be treated and disposed.
Alkaline regeneration thus produces the highly alkaline
sodium aluminate. The optimum pH for aluminum precipitation/
coagulation is below 7 however, and thus it is not too sur-
prising that sodium aluminate has been reported to be a poor
coagulant or precipitant (3). It has also been noted that
such regeneration is more costly than the original alum, but
this must be weighed against the lesser sludge produced for
disposal.
b. Acid regeneration
When the pH of an alum sludge is reduced to 2.5-3»
approximately all the aluminum will go into solution as follows:
278
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2A1(OH)3 + 3H2SOij, = A12(30^)3 + 6H20
2A1PO^ + 3H2SOij, + A12(30^)3 -I- 2H3P04
Unfortunatelyt in &n acid media it is not possible to remove the
phosphate by precipiation with calcium chloride. Thus, acid
regeneration of alum, although it produces an acceptable
precipitant or coagulant and is economically advantageous
(less costly than alum) (3), cannot be employed for phosphate
removal systems. It may be possible to remove the solubilized
phosphate by ion exchange (3), but this considerably lessens
the economic advantages of the acid regeneration process, and
must result in ion exchange regenerants for disposal as well.
As in the previous regeneration system, inorganic and organic
particulates will remain in a acidic sludge for dispoal or
treatment, but in this case little solubilization of organics
is to expected.
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SUMMARY
The use of alum, ferric chloride or lime as coagulants or
precipitants unquestionably increases the total dry weight of the
sludges produced. Due to the better dewatering characteristics of
certain of these sludges (i.e., lime sludge), the volumes of the
sludges produced may not be larger than those produced before the
introduction of the coagulation or precipitation processes.
These sludges contain higher inorganic contents, and their
composition is fairly predictable from a knowledge of the reactions
involved and the amounts of particulates and phosphate removed.
The presence of these precipitants or coagulants may adversely
affect anaerobic digestion, but as there are many other aludge
treatment and disposal methods applicable, this may not be too
significant a disadvantage.
Both lime sludges and alum sludge can be reprocessed to recover
the precipitants. Lime carbonate sludges may be segregated from
the phosphate sludges, recalcined hydrated, and returned to the
process, Alum sludge may be recovered using acid or alkaline
processes, but the acid process while economically feasible and
producing a satisfactory coagulant, cannot be used for phosphate
removal systems. Alkaline regeneration can be employed for phosphate
removal systems but seems to result in a poorer coagulant.
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REFERENCES
(1) "Chemical Treatment of Waste Water," Industrial Chemical
Division, Allied Chemical, Morristown, N.J.
(2) G.R. Bell, Johns Manville Corp., Denver, Colo, personal
communication.
(3) Gulp, R.L. and Gulp, G.L., "Advanced Waste Water Treatment,"
Van Nostrand Reinho.ld, New York, N.Y. , 1971.
(4) Hunter, J.V. , Dcotoral Thesis, Rutgers University, New
Brunswick, N.J. (1962).
(5) Parker, D.S., Zadick, F.J. and Train, K.E. , EPA-R2-13-250,
July 1973 » Office of Research and Development, U. S.
Environmental Protection Agency, Washington, D.C.
(6) Zaferatos, J. , Environtech, Eimco BSP, Brisbane, Calif.,
personal communication.
(7) Mulbarger, M.C. and Shifflet, D.G., Chemical Eng. Progr.
Symp., Ser. 67, 107 (1971).
(8) Stukenberg, J. , Jour. Water Pollu. Contr. Fed., 43, 1791 (1971).
(9) Grigoropoulos, S.G., et al, Jour. Water Pollu. Contr. Fed.,
, 2366 (197^).
(10) Hsu, D.Y. and Piper, W.O., Jour. Water Pollu. Contr. Fed.,
, 681 (1973).
(11) Jenkins, D. , ejt al, Water Res. (G.B.), j>, 369 (1971).
281
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282
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ERA'S POSITION ON OCEAN DISPOSAL IN THE NEW YORK BIGHT
Richard T. Dewling, Richard D. Spear, Peter W. Anderson and Randy J. Braun
Ocean disposal in the New York Bight is a significant environ-
mental issue, particularly when one realizes that on a national basis
more than 70 percent of all municipal sludge dumping occurs in the
New York Bight. Similarly, industrial waste dumping represents more
than 60 percent of the national problem.
EPA's responsibility for managing and monitoring ocean disposal
activities only began in April 1973, the effective date of the Marine
Protection, Research, and Sanctuaries Act. Our actions, however,
considering this short time period, have been significant in the
New York Bight and have resulted in reducing the environmental impact
associated with this practice. Highlights of our actions and progress
during the past 15 months are as follows:
...Eight (8)
denied.
industrial applications/permits have been
.Forty-seven (47) previous dumpers have been forced
to choose other environmentally acceptable alternatives,
thus phasing out ocean disposal. An additional twelve
(12) industries will be phased out by June 1975-
.Industrial wastes, previously dumped at the 12-mile sewage
sludge site, are now all being transported off of the con-
tinental shelf and disposed of at the 106-mile site.
.Digester cleanout from sewage treatment plants, which
contains a high percentage of floatables, must now be
disposed of off the continental shelf. Previously,
this material was dumped twelve (12) miles from our
shore.
.No new industrial or municipal dumpers, other than those
using this method of ultimate disposal prior to the pas-
sage of the Ocean Dumping Bill, have been approved for
using any of the sites in the New York Bight.
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....All dumpers are now required to provide EPA with a
detailed chemical and biological analysis of the
waste materials being discharged into the ocean.
No such requirement existed prior to April 1973-
....With the cooperation of the U. S. Coast Guard,
which is responsible for "police type" monitoring
of vessels using the disposal sites, EPA has init-
iated a vigorous enforcement program. Violations
of permit conditions, including "failure to notify",
premature dumping, and non-segregation of municipal
and industrial wastes, have been discovered and legal
action initiated.
....Municipalities in the metropolitan area have been
notified of our intention to move the present sewage
sludge dumping ground in 1976, or earlier, if our
monitoring programs indicate an environmental threat.
EPA's long-range goal is to completely phase out ocean
disposal of municipal sludge by 1981.
Present Problems Real or Imaginary??
The furor created in the press has undoubtedly caused concern
among the citizens of the metropolitan area, and naturally, with the
regulatory agencies, namely, the state, county and local health de-
partments, and the United States Environmental Protection Agency.
Information presented in the media, in our opinion, lacks the tech-
nical support needed to draw the types of conclusions that have been
reported namely, that there is a massive uprooting and movement
of the sludge mass from the present 12-mile disposal site to the
shore of Long Island.
Rather than try to attack the technical validity of the statements
made by others, we would prefer to have you examine the problem as a
whole, thus hopefully recognizing the complexities of resolving this
problem in an environmentally acceptable manner.
At the present time, 5-6 million cubic yards per year of munici-
pal sludge (see Table I) are being disposed of within the New York
Bight. Ocean disposal of municipal sewage sludge in the New York
Bight was initiated by the Passaic Valley Sewerage Commissioners.
The dumping of this material at sea was permitted by the United States
Army Corps of Engineers under the Captain of the Port proviso of the
Rivers and Harbors Act of 1888. By 1977, the date by which municipal-
ities are required to provide secondary treatment, in accordance with
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TABLE I
OCEAN DUMPING IN THE NEW YORK BIGHT
70% OF ALL MUNICIPAL SLUDGE DUMPING IN U. S.
60% from NYC
1973 - 5,590,1^ cu. yds. 1% Nassau & Westchester
33% New Jersey
60% OF ALL INDUSTRIAL WASTES DUMPED IN U. S.
Al1ied Chemical
American Cyanamid
Chevron
E. I. duPont
Hess Oil
Modern Trans. Co.
NL Industries
1973 TOTAL
Vo 1 ume
(yd3)
1 68,128
mid 151,371
40,677
291,528
8,959
Co. 99,537
3,135,9^7
1 3,796,1^7
Vol ume
(gal)
13,795,992
30,652,640
8,237,18*1
59.03M82
1,814,172
20,156,250
635,029,200
768,719,920
DREDGE SPOIL FY'73 - 11,818,250 cu. yds.
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the mandates in the 1972 Amendments to the Federal Water Pollution
Control Act, it is anticipated that the sludge volume generated will
increase significantly. By 1980, it is expected to reach 18 million
cubic yards per year. How do we handle this large volume of sludge
in an environmentally acceptable manner? The alternatives available
to us are as follows:
(1) Disposal in a regional incinerator or incinerators,
located at a site where air quality impact would be
minimal. Offshore sites merit serious consideration.
Power generation and the burning of other solid wastes
along with sludge should be considered in order to en-
hance the economic feasibility of this type project.
(2) Controlled disposal to the marine environment. Other
sites and disposal techniques are presently being in-
vestigated by EPA and NOAA. More than $7,000,000 of
Federal funds are being expended to study the acute
environmental stresses associated with this practice,
as well as determining the long-term effects which
includes measuring the impact on marine organisms and
the food web.
(3) Disposal at remote landfill sites. If this alternative
is considered feasible, pretreatment techniques such as
sludge dewatering and leachate treatment will be required.
Let's dwell on this alternative for a moment. It is our opinion
that the technical solution to resolving this complex environmental
problem of ocean disposal is here today, i.e., sludge could be pumped
or shipped to the strip mines in Pennsylvania or to open land areas in
New York State. One of the problems with this alternative, assuming
that the environmental consequences associated with this type of oper-
ation could be resolved and they can is overriding the political
and social constraints associated with the various governmental agencies.
In other words, the people in Pennsylvania, or for that matter upstate
New York, do not want the waste products from people outside of their
geographical, social, or political boundaries. Thus, one is forced to
resolve his environmental problems in his own "back yard". It is in-
teresting to note that the City of Chicago has just won the 1971* Amer-
ican Civil Engineering Award for its project involving the transportation
of sludge to a land site 200 miles south of the City. Chicago purchased
11,000 acres and reportedly has satisfactorily solved their sludge
disposal problem in this way.
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(4) Disposal as a soil conditioner or fertilizer. Several
years ago, EPA, recognizing that this was a viable
alternative, provided $200,000 to Ocean County, New
Jersey, to demonstrate the feasibility of land recycl-
ing on the sandy soils of the Pine Barrens. The results
of this study will be available by June of next year.
Pre-treatment Prerequisite to Disposal
It must be recognized that for sewage sludge to be disposed
of by any of the above-mentioned alternatives, it must be properly
pretreated to meet EPA requirements for heavy metals and toxic com-
ponents, as mandated in the 1972 FWPCA Amendments. All land disposal
alternatives must consider the potential pollution problems of ground-
waters in the disposal areas. In addition to requiring sophisticated
techniques to meet stringent air quality standards, sludge incineration
will still produce an ash 0.35 million cubic yards per year by
1980 that must be handled. Thus, without further study of these
alternatives, it is impossible to predict whether any of these approaches,
as applied to resolving the problem in this metropolitan area, are more
or less damaging to the environment than the present practice of ocean
disposal. It is for this reason, therefore, that EPA funded a two year,
$200,000 study with the Interstate Sanitation Commission to look at these
and other alternatives and to recommend, by June 1976, the soundest and
most environmentally acceptable alternative to resolving this problem.
Phase Out Ocean Disposal by 1981
Our approach to assessing and managing the present practice in
the New York Bight has been at two levels short-term and long-
term. With regard to the latter, we have developed and implemented
a plan with an ultimate goal of phasing out ocean disposal by
1981 which is technically feasible, environmentally sound, and
one that, hopefully, has not been influenced by media-induced hysteria
and emotionalism. Figure I highlights this plan.
287
-------
FIGURE I
LONG RANGE PLAN FOR PHASE OUT
1970 N. Y. BIGHT STUDY - U. S. CORPS OF ENGINEERS:
SANDY HOOK LABORATORY
1971 EPA CONDITIONS CONSTRUCTION GRANTS
JUNE 1972 EPA OCEAN COUNTY STUDY: $200,000, 3 YRS;
LAND RECYCLING
APRIL 1973 OCEAN DUMPING BILL EFFECTIVE - EPA PERMIT
PROGRAM STARTED
DECEMBER 1973 EPA SEGREGATES WASTES AT DUMP SITES
APRIL 197^ EIGHT (8) INDUSTRIAL PERMITS/APPLICATIONS
DENIED OR WITHDRAWN: FORTY-SEVEN (kj) IN-
DUSTRIAL DUMPERS PHASED OUT: TWELVE (12)
INDUSTRIAL DUMPERS REQUIRED TO PHASE OUT
BY 6/75
APRIL 10, 197^ MUNICIPALITIES NOTIFIED OF MOVING TO ALTERNATE
SITE BY 1976
JUNE 197^ NOAA INITIATES FIELD STUDIES OF ALTERNATE
SITES FOR EIS
JUNE 197^ EPA INITIATES "ENVIRONMENTALLY ACCEPTABLE
ALTERNATIVE" STUDY, $200,000, 2 YRS
1974 NOTIFY CORPS OF ENGINEERS OF SITE CHANGE
FOR "POLLUTED" DREDGE SPOIL
JULY 197*4 EPA AWARDS $5^0,000 TO RAYTHEON FOR ADDITIONAL
EIS STUDIES
288
-------
FIGURE I (Continued)
LONG RANGE PLAN FOR PHASE OUT
1976
EIS ON NEW SITES COMPLETED
CLOSE EXISTING SEWAGE SLUDGE
SITE AND MOVE TO ALTERNAT
SITE
START IMPLEMENTATION OF ALTERNATIVES
AS RECOMMENDED BY EPA STUDY
(SITE SELECTION, EIS, CONSTRUCTION)
•1981
I
IF CONTROLLED OCEAN DUMPING
CONSIDERED MOST SUITABLE
ENVIRONMENTAL ALTERNATIVE
DECISION REQUIRED TO EITHER
KEEP ALTERNATE SITE ACTIVE
OR MOVE OFF SHELF AS PER
PL 92-532
COMPLETE ALTERNATIVES
GOAL: OCEAN DISPOSAL PHASED OUT
289
-------
The short-range solution is somewhat more complex, not from the
technical standpoint, but because it is heavily impacted by emotional
reactions to what has been reported in the press. In that regard, our
studies, which are presented in detail in Appendix A, can be summarized
as follows:
(1) Renewed claims and reports by private scientists that
the sludge mass has uprooted itself and is moving toward
the Long Island shore at an alarming and unprecedented rate
have not been substantiated. In fact, our surveys show con-
tradictory data, not from the standpoint of disclaiming the
findings of private researchers since EPA has also found
"black mayonnaise" one-half mile from shore at random loca-
tions but in technically disagreeing with the conclusions
drawn by these individuals.
(2) Studies on and along the beaches of Long Island, New York
and New Jersey clearly indicate that these waters, based
on Federal and State bacteriological standards, are safe
for contact recreation. The absence of pathogens
disease-causing bacteria in these waters provides
further verification of the excellent quality.
(3) The "black mayonnaise" found at random locations one-half
mile from the beach has been identified as natural decaying
organic material.
(k) Results of cruises, perpendicular to, and through the
dumping grounds, suggest that the problems reported in
the press are related to inland occurrences and not
associated with a massive movement of material from the
disposal site. If, in fact, there was a massive movement
towards shore, one would expect to find a gradual diminu-
tion of pollution levels from the disposal site to the
shore area. (See Appendix A)
(5) The leading edge of the sludge mass, associated with the
sewage sludge disposal site, is still located approximately
5-1/2 to 6 miles from the shore of Long Island, thus negating
the urgency to move the present disposal site before the
scheduled 1976 closure.
(6) A recommendation to immediately move the present sewage
sludge site, without simultaneously moving the dredge
spoil site, which presently influences and impacts the
sludge site, would be shortsighted and environmentally
unwise. To simply move one without the other would not
solve any problems, except satisfy those who personally
feel that the sludge dumping ground is the major cause
of all environmental ills in the New York Bight.
290
-------
(7) A recommendation to immediately move the present
disposal sites sewage sludge and dredge spoil
founded on emotionalism rather than technical data,
could prove environmentally disastrous.
EPA is pledged to protecting the environment. That is our role
as professionals, citizens, and as representatives of this Agency.
We will not permit the deterioration of water quality along the beaches
of Long Island or New Jersey, and most certainly will not permit jeop-
ardizing the health, welfare, and well being of individuals using these
waters. It must be recognized that moving of the dumping grounds
sewage sludge and dredge spoil at this time, without the availabil-
ity of environmental background data needed to demonstrate that a new
site is suitable or environmentally acceptable, would simply translocate
the present problem.
Our Agency with NOAA is moving as quickly as possible towards a
better solution of the sludge disposal problem. We are not about to
abdicate our responsibilities as individuals, or as an Agency, to such
an extent that our position and/or recommendations might cause greater
damage to the environment and possibly result in irreparable harm.
291
-------
APPENDIX A
EPA MONITORING PROGRAM OF SLUDGE/DREDGE
SPOIL DUMPING SITES
A comprehensive sampling program was initiated by the EPA,
Region II in April 1974 to monitor the quality of water and bottom
sediments in the apex of the New York Bight and along the beaches
of Long Island and New Jersey. Sites sampled in the program are
illustrated in Figure 0 and information as to their location is
given in Table 0. This monitoring program is segmented into three
phases as shown below:
Type I Surf Zone Biweekly
Type II Near Shore Monthly
Type III Transect Monthly
Type I samples are collected in the surf zone at selected sites along
the Long Island and New Jersey coastlines. Type II are collected by
boat approximately 100 yards from shore and in water about 15-20 feet
deep. Similarly, Type III samples are collected by boat in three
transects, each running from the 12-mile sewage sludge dump site, one
to the Long Island beaches, a second to the New Jersey beaches, and a
third to the New York Harbor entrance. Water-quality data, including
sediment characterization, collected at these sampling sites from April
to early July 197** are summarized in Tables 1-12 and selected parameters
are illustrated in Figures 1-12.
Long island Surf Zone and Near Shore
Data from the samples collected in the surf zone and near shore
(Figs. 1-2) indicate low total and fecal coliform densities. The levels
of fecal coliform at all sampling stations are significantly below the
geometric mean density standards for primary and secondary contact re-
creation waters under New York's Class SB standard of 200 organisms/100 ml
The effect of poorer quality runoff from New York Harbor and through East
Rockaway inlet is evident from elevated values observed at LC101 and
LC106, respectively. It is important to note that attempts to isolate
Salmonella (enteric pathogens) at four sampling stations were unsuccessful
Data on coliform densities, total organic carbon content, and heavy
metals in bottom sediments are illustrated in Figures 3 and 3a for near
shore sampling stations. Highest values are again found at stations
LIC01 and LIC06, reflecting the influence of New York Harbor and East
Rockaway inlet. Comparison of data presented in these two graphs (Figs.
3 and 3a) with similar data collected in the vicinity of the sewage dump
site (Figs. 5 and 5a) indicate wide variations in quality. For example,
292
-------
the highest geometric mean fecal coliform recorded at Long Island
near shore sampling stations was 400/lOOg, while that near the dump
site was 962/lOOg. Similarly, along the Long Island near shore the
highest mean total organics observed was 2.6 percent and that for
metals was 13^ mg/kg, while those near the dump site were 4.6 percent
and 426 mg/kg, respectively. (Note about 80 mg/kg in the metals value
reflect the use of absolute values when summing individual metals re-
ported as less than analytical sensitivity.) Salmonella were not
isolated in bottom sediment samples collected at LIC06 even though
high fecal coliform densities were observed.
New York Bight Transects
Water and bottom sediment samples were collected along three
transects, each originating in the vicinity of the sewage sludge
dump site and extending to the Long Island coast, the New Jersey
coast, and the New York Harbor entrance.
Geometric mean fecal coliform densities observed in samples col-
lected from the water column in the Long Island transect (Fig. k)
and New York Harbor transect (Fig. 6) indicate that the New York Class
SB standard of 200/100 ml is not contravened, except at station NYB30
(436 fecal coliform/100 ml). This station is located closest to New
York Harbor and thus, reflects a combination runoff and wastewater
discharges from the Hudson River and Raritan Bay. Even at sampling
stations within the sewage dump site, observed fecal coliform densities
in both surface and bottom water samples were low. A similar review
of bacteriological quality in water column samples collected along the
New Jersey transect (Fig. 8) indicate that the more stringent New Jersey
Class CW-1 standard for primary contact recreation of a geometric mean
of 50 fecal coliform/100 ml is not contravened except by the 61/100 ml
at the near shore station (NYB20).
Review of the data illustrated for mean coliform densities at
bottom sediment sampling stations in the three transects (Figs. 5,7,9)
indicate extreme elevated counts of both total and fecal coliform in
the vicinity of the sewage sludge dump site. Total coliform densities
(geometric means) generally exceed 15,000/lOOg and fecal coliform,
500/lOOg in the vicinity of the dump site. A distance of 5-1/2 to 6
miles of low coliform densities separates the high counts in the vicinity
of the dump site and the slightly elevated values found at near shore
sampling stations. Salmonella were not found at six (6) of the twenty-two
(22) transect sampling stations, even though elevated fecal coliform den-
sities were observed at some of the six sites tested.
293
-------
Results of total organic carbon and heavy metal analyses on
bottom sediments at the transect stations (Figs. 5a,7a,9a) also
show wide variations in quality. Highest mean values are found
in the vicinity of the dump site, with total organic carbon con-
tent generally exceeding four percent and metals exceeding 300mg/kg.
The data illustrated show a "clean water-sediment" zone of about
5-1/2 to 6 miles separating the dump site from the New Jersey and
Long Island bathing beaches. Total organic content are in the main
less than one percent and metals under 100/mg/kg in this "clean
water-sediment" zone.
New Jersey Surf Zone and Near Shore
Results of sampling in the surf zone and near shore (Figs. 10,12)
indicate low total and fecal coliform densities. The level of fecal
coliform at all sampling stations generally are far below the geo-
metric mean density standards for primary contact recreation under
New Jersey's Class CW-1 standard of 50 organisms/100 ml. Elevated
coliform values observed at JC14 (Fig. 10) are related to an ocean
outfall from a local municipal treatment plant.
Data on coliform densities, total organic carbon content, and
heavy metals in bottom sediments are illustrated in Figures 11 and
lla for near shore sampling stations. Comparison of data presented
in these two graphs with similar data collected in the vicinity of
the sewage sludge dump site (Figs. 5,5a) indicate wide variations
in quality. For example, the highest geometric mean fecal coliform
recorded at New Jersey near shore sampling stations was 382/lOOg,
while that near the dump site was 962/lOOg. Likewise, along the New
Jersey near shore the highest mean total organics observed was 1.6
percent and that for metals was 123 mg/kg, while those near the dump
site were 4.6 percent and 426 mg/kg, respectively. Note that while
tested at two sites, Salmonella were not found in the bottom sediments,
Pi scuss ion
Based upon sampling in the surf and near shore waters along the
Long Island and New Jersey beaches, it is evident that water quality
remains excellent with respect to coliform density and is acceptable
for contact recreation. More important, there is no evidence of a
trend towards increased coliform density and thus, no indication of
degradation. The occasional elevated coliform counts noted in Tables
1,2,10 and 12 appear randomly distributed in time and location, and
does not indicate a systematic change or degradation of water quality.
294
-------
Review of data from sampling in the Bight of the water column
and bottom sediments indicate the general locationoof the sludge
mass associated with the sewage sludge and dredge spoil dump site.
A "clean water-sediment" zone of about 5-1/2 to 6 miles separates
athe leading edge of the sludge mass from the New Jersey and Long
Island coasts. Slightly elevated organic carbon content and bac-
terial counts at selected near shore sampling stations can be re-
lated to inland occurrences, such as runoff and wastewater discharges.
Authors: Richard T. Dewling, Director, Surveillance & Analysis Divi-
sion, EPA, Region II, Edison, N. J., Richard D. Spear, Chief, Surveillance
Branch, Surveillance S Analysis Division, EPA, Region II, Edison, N. J.,
Peter W. Anderson, Chief, Ocean Disposal Program, EPA, Region II, Edison,
N. J., and Randy J. Braun, Physical Scientist, Surveillance Branch,
Surveillance & Analysis Division, EPA, Region II, Edison, N. J.
295
-------
Figure 0
296
-------
TABLE 0
STATION LOCATIONS
Loran
Station Latitude Longitude 3H4 (Brown)3H5 (Green)
Visuals
NYB20
NYB21
NYB22
NYB23
NYB24
NYB25
NYB26
NYB27
NYB30
NYB31
NYB32
NYB33
NYB34
NYB35
NYB40
NYB41
NYB42
NYB43
NYB44
NYB45
NYB46
NYB47
40°23'54"
40023'54"
40°23'54"
40°23'54"
40°23'54"
40°23'54"
40°23'54"
40°23'54"
40° 30 '25"
40° 30 '00"
40°29'25"
40°28'36"
40°27'15"
40°26'10"
40°33'36"
4003T39"
40°29'42"
40°27'45"
40°25'54"
40°25'00"
40°22'00"
40°20'00"
73056 '03"
73°53'30"
73°5TOO"
73°49'12"
73°47 ' 30"
73°45'00"
73°43'15"
73°40'32"
73°58'42"
73°57'36"
73°56'00"
73°53'45"
73°50'00"
73°47'12"
73°45'00"
73°45'00"
73°45 '00"
73°45'00"
73°45 '00"
73°45'00"
73°43 '15"
73°43' 15"
4560
4575
4590
4600
4609
4624
4634
4649
3294
3274
3253
3237
3223
3200
3185
3161
South of Fl "5"
South of Fl "3"
South of Fl "1A" WHIS
South of BW Mo (A) WHIS
South of Ambrose Horn
4629
4699
4684
4669
4654
4640
4633
4619
4603
3220
3182
3188
3193
3197
3200
3200
3183
3182
297
-------
86Z
-------
TABLE 1
IND
10
SUMMARY OF BACTERIOLOGICAL DATA (WATER COLUMN) COLLECTED ALONG LONG ISLAND SHORELINE
(Samples
Date
4/11/74
4/23/74
5/7/74
5/22/74
6/5/74
6/19/74
7/2/74
Samples to date
Median
Geometric Mean
Max
Min
LIC01
TC FC
38
10
5
12
8
—
8
6
9
11
38
5
20
7
1
5
3
—
6
6
4
20
1
Station
Collected in Surf Zone)
Identification Number
LIC02
TC FC
11
11
6
3
4
2
12
7
6
6
12
2
6
5
3
2
1
<1
4.1
7
2
6
<1
LIC03
TC FC
7
84
2
3
32
44
5
7
7
12
84
2
7
17
<1
2
11
5
<.!
7
4
17
<1
LIC04
TC FC
1
19
4
9
25
3
4
7
4
5
25
1
1
10
1
6
3
*1
-------
TABLE 1 - Cont.
OJ
o
o
SUMMARY OF BACTERIOLOGICAL DATA (WATER COLUMN) COLLECTED ALONG LONG ISLAND SHORELINE
(Samples Collected in Surf Zone)
Date
4/11/74
4/23/74
5/7/74
5/22/74
6/5/74
6/19/74
7/2/74
Samples to date
Median
Geometric Mean
Max
Min
Station Identification Number
LIC07
TC FC
a a
8 3
«1 <\
15 <1
<1 4
39 4
4 <1
7 7
2 1
39 4
LI COS
TC FC
4
11
1
2
1
18
2
7
2
3
18
1
1
8
<1
1
1
1
-------
LUt
-------
TABLE 2
SUMMARY OF WATER-QUALITY DATA (WATER COLUMN) COLLECTED ALONG THE LONG ISLAND COAST
(by boat approximately 100 yards from beach)
Parameter Date
Total Coliform 05-01-74
(MPN/100 ml) 05-01-74
06-06-74
06-06-74
07-11-74
07-11-74
Fecal Coliform 05-01-74
(MPN/100 ml) 05-01-74
06-06-74
06-06-74
07-11-74
07-11-74
Water Temperature 05-01-74
(°C) 05-01-74
06-06-74
06-06-74
07-11-74
07-11-74
Dissolved Oxygen 05-01-74
(mg/1) 05-01-74
06-06-74
06-06-74
07-11-74
07-11-74
Conductivity 05-01-74
(micromhos) 05-01-74
06-06-74
06-06-74
07-11-74
07-11-74
Salinity 05-01-74
(g/1) 05-01-74
06-06-74
06-06-74
07-11-74
07-11-74
T Top - Approximately 2 ft.
B Bottom - Approximately 2
Top/
Station Identification Number
Bottom LIC01
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
790
2,210
5
2
2
5
330
1,090
< 2
< 2
< 2
< 2
9.4
8.1
16.4
16.2
16.1
16.1
9.4
8.9
8.2
8.4
5.7
5.7
33,000
32,600
35,600
35,600
37,000
37,000
29.6
30.4
27.2
27.2
28.7
28.9
LIC02
23
< 2
4
2
< 2
11
2
< 2
< 2
< 2
< 2
< 2
9.0
8.5
16.8
15.2
15.8
15.7
9.4
9.3
8.4
8.0
6.0
5.9
33,100
33,000
35,900
34,900
36,300
36,800
29.9
30.4
27.2
27.4
28.2
28.8
LIC03
2
< 2
7
5
5
7
< 2
< 2
2
< 2
2
4
9.8
8.7
16.6
16.6
15.4
15.2
10.7
10.5
8.3
7.8
4.8
4.8
33,400
33,200
35,900
35,700
36.400
36,400
29.7
30.4
27.3
27.1
28.5
28.8
from surface
ft. from
sampling sites ranged from 12-22
bottom (Total
ft.)
depth at
LIC04
7
11
7
2
5
5
< 2
< 2
< 2
< 2
2
< 2
9.6
8.2
16.9
16.4
15.2
15.1
9.6
8.9
8.9
7.2
4.5
4.3
34,000
33,100
36,300
36,200
36,300
36,200
30.5
31.0
27.4
27.5
28.6
28.6
LIC06
LIC11
LIC05 LIC06
8 3
17 3
17
17
17
5
< 2 1
< 2
2
5
5
< 2
10.7
9.5
15.8
15.2
16.1
14.8
9.6
9.2
8.3
7.4
5.2
4.3
34,200 34
33,600 34
36,600 36
35,000 35
36,900 36
36,200 36
29.9
30.2
27.3
27.5
28.6
29.0
E. Rockaway
Jones Inlet
,480
,480
8
< 2
7
2
,300
790
< 2
< 2
< 2
< 2
11.5
11.5
15.8
15.6
15.2
15.3
7.8
7.8
8.4
8.0
4.7
4.6
,900
,800
,000
,600
,500
,500
30.0
29.9
28.0
27.6
28.7
28.7
Inlet
LIC07
2
< 2
17
< 2
2
2
2
< 2
4
< 2
< 2
< 2
9.3
8.8
16.3
15.6
14.7
14.3
10.3
10.2
8.4
7.2
4.7
4.3
33,700
33,500
36,400
36,100
36,100
35,900
30.6
30.5
27.9
28.1
28. 7
28.9
LIC08
< 2
< 2
2
5
< 2
2
< 2
< 2
< 2
2
< 2
2
10.1
9.9
16.8
16.7
15.2
14.7
9.6
9.7
9.2
9.3
5.0
4.4
34,500
34,400
36,900
36,700
36,300
35,900
30.6
30.8
28.0
28.0
28.7
28.7
LIC09
< 2
2
5
2
13
17
< 2
< 2
2
2
5
4
9.6
8.4
17.9
17.4
18.3
16.0
9.6
9.0
9.6
9.1
6.9
6.0
34,200
33,400
37,500
37,400
38,600
37,100
30.8
31.1
27.8
28.0
28.5
28.8
LIC11
1,300
8
4
11
7
< 2
109
5
2
4
2
< 2
8.9
7.6
15.7
15.7
16.3
15.5
10.0
9.2
8.6
8.6
6.0
6.0
33,500
32,600
35,800
35,800
37,200
36^900
30.6
30.9
27.7
27.8
28.8
29.0
LIC12
31
< 2
< 2
< 2
< 2
2
< 2
< 2
< 2
< 2
< 2
2
16.2
15.4
16.0
15.5
8.5
9.5
9.5
8.6
6.0
5.8
36,300
35,400
37,300
36,900
27.9
27.4
28.9
29.9
-------
GO <0
0
LONG ISLAND NEARSHORE - SEDIMENTS
TOTAL COLIFO )M (MPN/100 g)
FECAL COLIIFORM (MPN/100 y)
-— 40' ?0
-------
CO
-------
TABLE 3
SUMMARY OF WATER-QUALITY DATA (BOTTOM SEDIMENTS) COLLECTED ALONG THE LONG ISLAND COAST
(Samples collected by boat approximately 100 yds. from beach)
Station Identification Number
Parameter
Total Coliform
(MPN/100 g)
Fecal Coliform
(MPN/100 g)
Salmonella
(qualitative)
Total Organics
(mg/kg)
Cadmium
w (mg/kg)
O
01 Chromium
(mg/kg)
Copper
(mg/kg)
Lead
(mg/kg)
Nickel
(mg/kg)
Mercury
(mg/kg)
Arsenic
(mg/kg)
Date
05-01-74
06-06-74
07-11-74
05-01-74
06-06-74
07-11-74
05-01-74
05-01-74
06-06-74
07-11-74
05-01-74
06-06-74
07-11-74
05-01-74
06-06-74
07-11-74
05-01-74
06-06-74
07-11-74
05-01-74
06-06-74
07-11-74
05-01-74
06-06-74
07-11-74
05-01-74
06-06-74
07-11-74
05-01-74
06-06-74
07-11-74
LIC01
7,900
< 20
50
1,720
< 20
< 20
25,600
2,550
< 3
< 5
5
< 10
< 6
5
< 50
< 50
< 10
< 10
< .5
.16
< .5
.6
LIC02
130
230
50
< 20
20
20
5,450
3,400
12,770
< 3
< 5
20
< 10
< 6
4
< 50
< 50
< 10
< 10
< .5
.12
4.3
.9
LIC03
220
50
50
50
< 20
20
2,510
3,860
2,490
< 3
< 5
20
< 6
4
< 50
< 50
< 10
< 10
< .5
.08
1.3
.7
LIC04
490
13,000
80
50
330
< 20
--
3,850
34,100
5,260
< 3
< 5
40
< 10
24
< 3
80
< 50
< 10
< 10
1.02
.14
16
.6
LIC05
460
110
20
80
< 20
< 20
--
1,770
2,430
1..450
< 5
< 5
4
< 10
< 3
< 3
< 40
< 50
< 10
< 10
0.1
.12
.8
.5
LIC06
2,210
7,000
1,300
630
790
130
Neg.
2,570
18,300
2,890
< 5
< 5
< 3
< 10
3
4
< 40
< 50
< 10
< 10
0.5
.07
.9
< .5
LIC07
70
80
20
< 20
< 20
< 20
--
3,300
1,810
1,980
< 5
< 5
4
< 10
3
< 3
< 40
< 50
< 10
< 10
< 0.1
.08
1.8
.6
LIC08
230
20
230
< 20
< 20
< 20
--
10,600
4,900
3,340
< 5
< 5
12
10
15
4
< 40
< 50
< 10
15
< 0.1
.21
2.4
< .5
LIC09 LIC10
230
80
230
< 20
< 20
< 20
--
5,620
3,090
3,340
< 3
< 5
< 4
< 10
< 6
3
< 50
< 50
< 10
< 10
< .5
.52
0.7
.6
LIC11
230
< 20
< 20
< 20
< 20
< 20
--
1,240
1,280
1,450
< 5
< 5
< 3
< 10
< 3
3
< 40
< 50
< 10
< 10
< 0.1
.oi
.4
< .5
LIC12
110
20
20
20
< 20
< 20
--
3,000
1,840
2,990
< 5
< 5
5
< 10
< 3
3
< 40
< 50
< 10
< 10
6J-1
.21
1.2
.6
Neg. - Sought but not detected
-------
OJ
O
01
LIC-2
FECAL COLIFORM (MPN/100ml)
TOTAL COLIFORM (MPN/ioomi)
NEW JERSEY
D122
TOP
BOTTOM
LONG ISLAND TRANSECT-WATER
1 STANDARD
200 160 120 80 40
20 40 60
STANDARD // I
80 100 120 140 ' 2/i)00 2400
ASBURY/
PARK
-------
TABLE 4
SUMMARY OF WATER-QUALITY DATA (WATER COLUMN) COLLECTED ALONG LONG ISLAND TRANSECT
GO
o
Parameter
Total Coliform
(MPN/100 ml)
Fecal Coliform
(MPN/100 ml)
Water Temperature
(°C)
Dissolved Oxygen
(mg/1)
Conductivity
(microrahos)
Salinity
(g/D
Date
04-17-74
04-17-74
05-14-74
05-14-74
07-09-74
07-09-74
04-17-74
04-17-74
05-14-74
05-14-74
07-09-74
07-09-74
04-17-74
04-17-74
05-14-74
05-14-74
07-09-74
07-09-74
04-17-74
04-17-74
05-14-74
05-14-74
07-09-74
07-09-74
04-17-74
04-17-74
05-14-74
05-14-74
07-09-74
07-09-74
04-17-74
04-17-74
05-14-74
05-14-74
07-09-74
07-09-74
Top/
Bottom
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
Station Identification Number
NYB40
13+
109+
330
2
13
< 2
< 2+
5+
27
< 2
< 2
< 2
12.5
10.0
19.4
14.2
7.2
5.0
32,400
34,300
38,500
35,800
28.2
28.8
NYB41
2+
700+
3,480
1,300
8
< 2
< 2+
13+
700
13
< 2
< 2
12.1
11.0
19.5
13.2
7.4
3.5
32,300
34,400
37,100
34,600
27.8
29.6
26.6
28.6
T Top - Approximately 2 ft. below surface
B Bottom - Approximately 2 ft. above bottom
NYB42
< 2+
230+
79
278
23
< 2
< 2+
8+
11
2
5
< 2
12.1
11.7
20.1
13.9
5.6
5.4
33,400
34,300
37,500
34,800
27.9
28.8
26.5
28.7
* Samples
+ Samples
NYB43
5
79
49
< 2
< 2
5
8
< 2
12.2
11.8
19.9
13.5
5.9
4.0
33,200
34,400
36,100
34,500
27.7
29.1
25.7
28.3
Collected
Collected
NYB44
11
14
79
< 2
< 2
5
2
< 2
11.7
11.7
20.7
14.8
3.7
3.4
34,100
34,700
36,500
35,700
28.8
29.5
25.5
29.0
04-18-74
04-24-74
NYB45
5,420*
49*
8
49
8
< 2
1,300*
< 2*
5
< 2
< 2
< 2
7.7*
6.7*
11.7
11.6
21.0
15.1
11.0*
9.2*
2.7
2.3
30,700*
31,400*
34,200
34,800
37,200
36,000
28.5*
30.3*
29.1
29.6
26.2
28.8
NYB46
2,210
8
< 2$
79$
< 2*
490#
49
2
< 2$
5$
< 2#
11#
6.9
7.0
14.1$
--$
17. 5#
10. 9#
7.3
8.6
9.7$
7.6$
9.0#
6.2#
29,300
31,000
35,200$
--$
37,500*
34 , 700#
27.8
29.7
28.2$
--$
28. 3#
28. 5#
NYB47
420
7
< 2$
17$
< 2#
8#
49
< 2
< 2$
< 2$
< 2#
< 2#
6.8
6.5
13. 9$
--$
17. 3#
12. 1#
10.9
10.0
10.3$
7.6$
8.8#
4.7#
28,600
30,600
34,700$
--$
37,800*
33,000#
27.0
29.0
27.7$
--$
28. 4#
28. 1#
$ Samples Collected 05-21-74
# Samples Collected 06-14-74
-------
8 =
LIC -Z
FECAL COLIFORM (MPN/IOOg)
TOTAL COLIFORM (MPN/IOOg)
) TRANSECT-SEDIHEMTS
-------
si
^D IS
(si
a
LIC-5 '.
LIC-4 LIC-7 LIC-8 ' LIC-9 LIC'IO ".
i I
LIC-12
LIC-3
NICS (PERCENT)
METALS (Rig/kg)
Cd, \Ct. Cu. Pb, Mi, Hg, As
LONG ISLAND TRANSECT-SEDIMENTS
70 elo B.O 4d so 20 10
400 600 000 700 100 900
-------
TABLE 5
GO
o
SUMMARY OF WATER-QUALITY DATA (BOTTOM SEDIMENTS) COLLECTED ALONG LONG ISLAND TRANSECT
Station Identification Number
Parameter
Total Coliform
(MPN/100 g)
Fecal Coliform
(MPN/100 g)
Salmonella
(qualitative)
Total Organics
(mg/kg)
Cadmium
(mg/kg)
Chromium
(mg/kg)
Copper
(mg/kg)
Lead
(mg/kg)
Nickel
(mg/kg)
Mercury
(mg/kg)
Arsenic
(mg/kg)
Date
04-17-74
05-14-74
07-09-74
04-17-74
05-14-74
07-09-74
05-14-74
07-09-74
04-17-74
05-14-74
07-09-74
04-17-74
05-14-74
07-09-74
04-17-74
05-14-74
07-09-74
04-17-74
05-14-74
07-09-74
04-17-74
05-14-74
07-09-74
04-17-74
05-14-74
07-09-74
04-17-74
05-14-74
07-09-74
04-17-74
05-14-74
07-09-74
NYB40
330+
490
110
< 20+
50
< 20
::
17,500+
5,890
8,370
< 5+
< 5
13+
12
4+
5
< 40+
< 50
< 10+
< 10
.2+
.42
6.3+
2.4
NYB41
270+
230
130
40+
< 20
< 20
::
7,320+
16,100
14,700
< 5+
< 5
9+
< 10
4+
< 3
< 40+
< 50
< 10+
< 10
< .2+
.06
5.2+
5.2
NYB42
2,780
< 20
20
<{ 20
:;
15,000
10,700
< 2
< 5
12
19
9
8
< 50
< 50
7
< 10
.2
.09
17.8
26.0
NYB43
2,300
20
50
20
--
28,800
27,600
2
< 5
54
71
42
51
82
60
11
15
.8
.65
7.8
4.8
NYB44
1,300
4,900
170
790
Neg.
21,400
29,600
< 2
9
30
146
38
156
50
370
9
27
.7
2.4
6.3
3.6
NYB45
34,800*
17,500
10,900
790*
230
4,900
Neg.
48,700*
75,500
4,660
9*
2
< 5
115*
48
12
133*
97
8
208*
130
< 50
17*
12
< 10
1.8*
1.1
1.35
3.7*
4.2
.8
NYB46
2,300
7,900$
22,100*
50
230$
940*
~ ~
7,560
76,600$
13,700*
< 3
< 3#
9
10#
5
10#
< 40
< 50*
6
< 10*
5.0
.16*
5.6
21#
NYB47
490
130$
70#
20
< 20$
20#
:;
7,630
6,840$
6,770*
< 3
< 3#
8
8*
4
19*
< 40
< 50#
5
< 10#
1.4
1.0$
< .u
3.0
2.2#
* Samples Collected 04-18-74
+ Samples Collected 04-24-74
$ Samples Collected 05-21-74
# Samples Collected 06-14-74
Neg. - Sought but not detected
-------
CO 10
—' C
NEW YORK HARBOR TRANSECT-WATER
TOTAL COLIFORM (MPN/100ml)
LL.
1
FECAL COLIFORM (MPN/100ml)
I TOP
I BOTTOM
In. .
NEW JERSEY
2000
1500
1000
200
160
120
80
40
0
600
400
200
160
•120
60
•40
0
ASBUBY /
PARK
-------
TABLE 6
SUMMARY OF WATER-QUALITY DATA (WATER COLUMN) COLLECTED ALONG N.Y. HARBOR TRANSECT
CO
ro
Parameter
Total Col i form
(MPN/100 ml)
Fecal Coliform
(MPN/100 ml)
Water Temperature
(°C)
Dissolved Oxygen
(mg/1)
Conductivity
(micromhos)
Salinity
(g/1)
Date
04-17-74
04-17-74
05-21-74
05-21-74
07-09-74
07-09-74
04-17-74
04-17-74
05-21-74
05-21-74
07-09-74
07-09-74
04-17-74
04-17-74
05-21-74
05-21-74
07-09-74
07-09-74
04-17-74
04-17-74
05-21-74
05-21-74
07-09-74
07-09-74
04-17-74
04-17-74
05-21-74
05-21-74
07-09-74
07-09-74
04-17-74
04-17-74
05-21-74
05-21-74
07-09-74
07-09-74
Top/
Bottom
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
NYB30
3,480
330
330
70
3,480*
2,210*
490
109
130
5
1,300*
790*
7.5
6.4
11.9
10.2
18.6*
16.7*
9.8
7.2
9.0
7.3
7.2*
7.0*
19,200
27,400
34,600
34,300
29,600*
33,100*
17.0
26.2
29.1
29.8
21.0*
24.8*
NYB31
172
17
--
--
--
--
109
< 2
--
--
--
--
12.3
9.6
--
--
--
--
9.4
9.4
--
--
34,900
34,000
--
--
--
29.3
30.2
--
--
Station Identi:
NYB32
2,400
23
109
33
230
5
790
23
23
17
23
2
7.1
5.8
12.7
10.8
21.3
14.0
10.9
9.3
9.6
8.2
--
--
23,400
32,000
34,700
34,700
33,300
35^200
21.4
31.7
28.2
30.3
22.9
28.5
fication Number
NYB33
3,480
22
< 2
13
330
8
1,090
< 2
< 2
< 2
79
5
7.2
5.9
12.8
9.5
19.4
13.0
8.5
9.3
8.7
6.3
--
--
24,300
32,000
35,000
34,000
35,500
34,600
22.4
31.6
28.6
30.2
25.5
28.7
NYB34
1,300
< 2
< 2
2
79
8
230
< 2
< 2
2
8
2
7.9
6.5
13.0
--
19.6
10.9
10.0
9.1
9.9
6.7
--
--
23,100
30,100
35,400
--
36,300
33^100
20.7
29.1
29.0
--
25.8
28.9
NYB35
130
2
< 2
17
11+
2+
9
< 2
< 2
2
2+
< 2+
8.0
71
.4
14.2
--
17.6+
18.2+
11.9
9.5
9.5
6.5
9.5+
8.0+
26,300
30,200
36,400
--
37,100+
30,600+
24.0
28.4
29.5
--
27.8+
28.8+
Top - Approximately 2 ft. below surface
Bottom - Approximately 2 ft. above bottom
Samples Collected 06-11-74
Samples Collected 06-14-74
-------
CO
-------
GO 1C
—I C
NEW YORK HARBOR TRANSECT-SEDIMENTS
ORGANICS (PERCENT) •• _
.. ill.
METALS (mg/kg)
Cd, Cr, Cu, Pb, Ni, Hg, As
so
40
30
20
10
0
700
600
500
400
300
ASBURY/
PARK
-------
TABLE 7
SUMMARY OF WATER-QUALITY DATA (BOTTOM SEDIMENTS) COLLECTED ALONG N.Y. HARBOR TRANSECT
Station Identification Number
00
01
Parameter
Total Coliform
(MPN/100 g)
Fecal Coliform
(MPN/100 g)
Salmonella
Iqualitative)
Total Organics
(rag/kg)
Cadmium
(mg/kg)
Chromium
(mg/kg)
Copper
(mg/kg)
Lead
(mg/kg)
Nickel
(mg/kg)
Mercury
(mg/kg)
Arsenic
(mg/kg)
* Samples Collected
+ Samples Collected
Date
04-17-74
05-21-74
07-09-74
04-17-74
05-21-74
07-09-74
04-17-74
06-11-74
04-17-74
05-21-74
07-09-74
04-17-74
05-21-74
07-09-74
04-17-74
05-21-74
07-09-74
04-17-74
05-21-74
07-09-74
04-17-74
05-21-74
07-09-74
04-17-74
05-21-74
07-09-74
04-17-74
05-21-74
07-09-74
04-17-74
05-21-74
07-09-74
06-11-74
06-14-74
NYB30
2,300
1,410
7,900*
230
80
460*
Neg.
3,490
4,630
6,530*
< 2
< 3*
3
4*
< 6
< 6*
< 50
< 50*
< 7
10*
.2
< .1*
1.4
3.6*
NYB31
1,720
170
--
6,660
< 2
7
< 6
< 50
< 7
.5
1.8
Neg.
NYB32
1,300
230
490
130
20
110
--
2,580
3,080
1,290
< 2
< 5
3
< 10
< 6
3
< 50
< 50
< 7
24
< .2
.06
1.6
.8
- Sought but not
NYB33
790
1,410
790
130
110
20
--
7,190
6,260
5,380
< 2
< 5
9
11
8
7
< 50
< 50
< 7
< 10
1.1
.21
4.9
1.8
detected
NYB34
1,300
490
230
20
50
50
Neg.
27,700
11,500
11,400
< 2
< 5
9
17
42
13
50
< 50
8
13
2.1
1.0
.31
4.5
2.4
NYB35
2,300
1,720
1,300+
50
20
20+
Neg.
60,900
32,500
38,200+
3
6+
74
19+
82
140+
134
250+
17
20+
4.4
1.7+
2.4
12+
-------
9ie
Dl
I STANDARD
o m
^ -<
3 v>
•D m
z o
-------
TABLE 8
SUMMARY OF WATER-QUALITY DATA (WATER COLUMN) COLLECTED ALONG NEW JERSEY TRANSECT
CO
-J
Parameter
Total Coliform
(MPN/100 ml)
Fecal Coliform
(MPN/100 ml)
Water Temperature
(°C)
Dissolved Oxygen
(mg/1)
Conductivity
(micromhos)
Salinity
(g/D
Date
04-18-74
04-18-74
05-16-74
05-16-74
06-14-74
06-14-74
04-18-74
04-18-74
05-16-74
05-16-74
06-14-74
06-14-74
04-18-74
04-18-74
05-16-74
05-16-74
06-14-74
06-14-74
04-18-74
04-18-74
05-16-74
05-16-74
06-14-74
06-14-74
04-18-74
04-18-74
05-16-74
05-16-74
06-14-74
06-14-74
04-18-74
04-18-74
05-16-74
05-16-74
06-14-74
06-14-74
Top/
Bottom
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
NYB20
460
5
2,400
27
5
13
230
< 2
490
2
< 2
8
7.9
5.9
14.1
9.3
18.2
12.2
8.7
4.5
11.0
7.4
9.8
9.2
24,700
31,800
25,900
32,800
34,000
33,600
22.4
31.4
20.2
29.4
' 24.8
28.2
NYB21
17
< 2
33
2
79
22
5
< 2
7
< 2
< 2
5
7.6
6.1
9.9
8.7
17.9
9.2
7.3
8.2
7.6
8.9
10.4
4.5
30,100
31,300
33,300
33,200
33,100
31,800
28.2
30.9
29.8
30.4
24.5
28.3
T Top - Approximately 2 ft. below surface
B Bottom - Approximately 2 ft. above bottom
Station
NYB22
70
13
22
2
79
141
< 2
7
< 2
5
14
7.8
7.8
9.9
9.3
18.1
9.4
7.6
9.1
9.2
8.3
11.4
7.5 -.
29,900
29,900
34,100
33,900
34,000
31,700
27.7
27.8
30.3
30.8
25.1
28.4
* Samples
+ Samples
$ Samples
Identification Number
NYB23
79
< 2
< 2
7
49
130
5
< 2
< 2
2
2
33
7.8
7.1
10.2
9.7
17.7
8.1
6.4
6,4
9.0
8.1
11.2
5.0
31,000
31,800
34,200
34,100
34,500
31,100
29.0
30.3
30.3
30.6
25.6
28.9
Collected
Collected
Collected
NYB24
46
2
2
< 2
11
11
5
< 2
< 2
< 2
5
< 2
7.8
6.9
10.8
10.1
17.5
7.3
11.2
9.2
9.8
9.0
10.0
10.0
30,400
31,500
34,500
34,300
36,600
30,700
28.4
30.2
30.0
30.4
27.3
29.4
04-17-74
05-14-74
05-21-74
NYB25
3,480
9
< 2+
14+
230
130
175
2
< 2+
2+
22
79
7.8
7.1
11.7+
11.5+
17.1
10.6
12.0
7.2
4.5+
2.7+
9.3
6.6
30,500
31,200
34,800+
34,900+
31,200
32,600
28.4
29.8
29.8+
29.8+
28.1
28.6
NYB26
79*
490*
< 2
2
17
13
2*
2*
< 2
< 2
2
2
7.2*
6.9*
11.6
10.7
16.9
11.4
8.0*
9.5*
8.7
8.0
9.2
9.1
27,300*
30,100*
34,900
34,600
37,100
33,200
25.5*
28.6*
29.7
30.3
28.2
28.4
NYB27
8
1,720
< 2$
< 2$
< 2
22
2
33
< 2$
< 2$
< 2
7
7.9
7.2
14.1$
--$
17.9
9.8
8.8
9.1
9.2$
6.7$
10.0
5.2
29,100
30,700
36,900$
--$
37,300
32,000
26.7
29.2
29.6$
--$
27.9
28.5
-------
OJ <0
—i C
oo r
NEW JERSEY TRANSECT-SEDMENTS
TOTAL COLIFORM(MPN/100g)
^r^
r>—J i
FECAL COLIFORM(MPN/100g)
_1U
NEW JERSEY
-------
GO
m
o
o
NEW JERSEY
NEW JERSEY TRANSECT-SEDIMENTS • TOTAL ORGANICS(PERCENT)
METALS (mg/kg)
Cd, Cr, Cu, Pb. Ni, Hg, A$
so
40
3 0
20
10
0
600
500
400
300
200
100
0
-------
TABLE 9
SUMMARY OF WATER-QUALITY DATA (BOTTOM SEDIMENTS) COLLECTED ALONG NEW JERSEY TRANSECT
Station Identification Number
Parameter
Total Coliform
(MPN/100 g)
Fecal Coliform
(MPN/100 g)
Salmonella
(qualitative)
Total Organics
(mg/kg)
Cadmium
(mg/kg)
Chromium
(mg/kg)
Copper
(mg/kg)
Lead
(mg/kg)
Nickel
(mg/kg)
Mercury
(mg/kg)
Arsenic
(mg/kg)
Date
04-18-74
05-16-74
06-14-74
04-18-74
05-16-74
06-14-74
04-18-74
04-18-74
05-16-74
06-14-75
04-18-74
05-16-74
06-14-74
04-18-74
05-16-74
06-14-74
04-18-74
05-16-74
06-14-74
04-18-74
05-16-74
06-14-74
04-18-74
05-16-74
06-14-74
04-18-74
05-16-74
06-14-74
04-18-74
05-16-74
06-14-74
NYB20
2,300
230
230
330
20
< 20
—
1,640
2,840
3,330
< 2
< 3
< 3
5
< 6
< 6
< 50
< 50
< 7
< 10
< .2
.1
2.8
4.1
NYB21
130
490
490
< 20
20
20
--
31,500
24,000
24,000
< 2
< 3
33
40
34
34
< 50
58
10
14
.7
.7
4.7
4.7
NYB22
490
1,090
1,720
110
230
330
--
13,200
12,300
18,600
< 3
< 2
< 3
38
19
31
47
35
30
58
< 50
52
12
13
13
3.8
.4
.35
3.6
3.4
2.6
NYB23
20
220
230
< 20
< 20
50
--
72,600
27,900
3
< 3
87
59
100
68
126
118
24
25
4.0
1.0
12.8
14
NYB24
790
1,300
1,300
< 20
50
20
--
96,700
73,800
38,900
13
< 3
240
41
260
37
302
70
39
21
8.7
.75
2.4
11
NYB25
7,900
7,000+
34,800
80
490+
7,900
--
7,030
13,000+
13,400
< 3
< 3
10
10
5
10
< 40
< 50
< 10
< 10
2.9
< .1
5.0
13
NYB26
92,000*
1,410
54,200
490*
50
3,300
--
5,670*
4,850
7,740
< 3*
< 3
9*
8
5*
6
< 40*
< 50
5*
< 10
2.2*
< .1
3.0*
NYB27
24,000
7,900$
1,300
490
130$
50
Neg.
7,670
11,300$
11,600
< 2$
< 3
10$
14
7$
9
< 50$
< 50
< 7$
< 10
.3$
< .1
3.7$
3.3
* Samples Collected 04-17-74
+ Samples Collected 05-14-74
$ Samples Collected 05-21-74
Neg. - Sought but not detected
-------
FECAL COLIFORM <¥PK/100»I>
STANDARD
TOTAL COLIFORM (MPM/lttaO
I TOP
1 BOTTOM
NEW JERSEY NEARSHORE-WATER
HI 120 lit 10 H 10 21 I 50 Ml HI 211
ATLANTIC OCEAN
39*50'
Figure 10
321
-------
TABLE 10
SUMMARY OF WATER-QUALITY DATA (WATER COLUMN) COLLECTED ALONG THE NEW JERSEY COAST
(by boat approximately 100 yards from beach)
Parameter
Total Coliform
(MPN/100 ml)
Fecal Coliform
(MPN/100 ml)
Water Temperature
(°C)
CO
ro
ro
Dissolved Oxygen
(mg/D
Conductivity
(micromhos)
Salinity
(g/1)
Date
04-06-74
04-06-74
04-30-74
04-30-74
07-10-74
07-10-74
04-06-74
04-06-74
04-30-74
04-30-74
07-10-74
07-10-74
04-06-74
04-06-74
04-30-74
04-30-74
07-10-74
07-10-74
04-06-74
04-06-74
04-30-74
04-30-74
07-10-74
07-10-74
04-06-74
04-06-74
04-30-74
04-30-74
07-10-74
07-10-74
04-06-74
04-06-74
04-30-74
04-30-74
07-10-74
07-10-74
Top/
Botiom
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
T
B
Station Identification Number
JC01
141
330
130
94
230
13
14
17
17
11
5
5
16.1
16.4
14.4
10.0
21.9
19.6
7.0
7.0
12.4
11.1
10.0
7.6
29,500
29,200
29,400
30,400
34,100
36,100
22.3
21.9
23.3
26.7
23.0
25.7
JC02
70
79
120
221
23
33
13
23
9
46
2
5
15.7
15.8
11.1
8.7
21.6
21.1
7.7
8.2
12.9
10.2
9.4
9.1
31,600
31,700
29,700
31,600
35,900
36,400
24.2
24.3
25.2
28.8
24.5
27.4
JC03
23
33
49
33
23
2
2
5
8
4
8
< 2
16. '9
16.9
10.5
10.5
21.8
20.1
7.6
8.3
12.0
11.6
10.2
7.2
32,000
32,000
30,000
30,200
36,600
36,800
24.1
24.1
25.9
26.3
24.9
26.0
JC05
13
79
23
49
2
7
< 2
5
2
13
< 2
< 2
16.6
16.8
11.1
8.8
21.4
17.6
7.8
8.7
12.0
10.5
10.5
4.2
32,700
32,100
29,700
31,700
38,600
37,300
24.7
24.2
25.4
28.8
26.6
27.2
JC08
11
17
70
490
2
11
2
2
8
5
< 2
2
16.3
16.5
9.7
8.3
21.2
16.7
8.2
9.3
11.3
11.2
8.5
3.5
33,000
32,600
31,200
32,800
37,500
36,800
25.2
24.7
27.7
30.5
25.9
27.8
JC11
9
8
33
172
> 24,000
790
2
< 2
2
2
> 24,000
230
14.9
15.6
9.7
8.5
21.7
15.7
7.0
8.4
11.3
9.0
'- 9.2
2.5
33,600
33,800
30,400
30,500
38,300
36,500
26.4
26.1
27.0
27.6
26.2
28.4
JC14
22
14
490
3,480
9,200
1,300
5
< 2
130
2,400
3,480
490
14.8
15.1
8.4
8.5
22.3
18.1
8.2
9.5
11.3
9.2
10.2
4.6
33,400
33,900
30,800
32,600
38,200
38,300
26.1
26.4
26.8
30.0
25.9
28.0
JC21
17
34
330
49
79
700
2
5
49
14
33
23
]5.1
15.3
10.0
9.3
20.7
17.8
9.3
9.0
10.8
11.2
8.6
7.4
33,400
33,400
31,700
32,100
39,100
38,100
26.1
25.8
27.9
28.8
27.6
28.2
JC24 JC27
22 2
49 2
1,300 278
172 330
172 33
130 8
2 < 2
5 < 2
109 49
49 34
130 11
79 2
14.7 15.5
15.3 15.5
9.5 9.8
8.2 8.6
21.0 21.6
18.8 18.2
7.0 8.3
8.2 8.4
10.1 9.5
10.5 6.5
7.9 8.6
6.3 5.6
33,400 33,700
33,200 33,700
32,500 33,100
32,900 33,400
39,300 39,800
38,500 381200
26.3 26.4
25.7 26.0
29.5 29.1
30.5 30.4
27.3 27.6
28.1 28.1
1 Top - Approximately 2 ft. from surface
B Bottom - Approximately 2 ft.
from bottom
-------
TOTAL COLIFORM (MPN/IOOj)
NEW JERSEY NEARSHO RE-SEDIMENTS
Figure 11
323
-------
METALS (»j/k|)
M. Cl. Ci. n. Hi. H|. As
ORE-SEDIMENTS
Figure lla
324
-------
en
TABLE 11
SUMMARY OF WATER-QUALITY DATA (BOTTOM SEDIMENTS) COLLECTED ALONG THE NEW JERSEY COAST
(by boat approximately 100 yards from beach)
Station Identification Number
Parameter
Total Coliform
(MPN/100 g)
Fecal Coliform
(MPN/100 g)
Salmonella
(qualitative)
Total Organics
(mg/kg)
Cadmium
(mg/kg)
Chromium
(mg/kg)
Copper
(mg/kg)
Lead
(mg/kg)
Nickel
(mg/kg)
Mercury
(mg/kg)
Arsenic
(mg/kg)
Date
04-06-74
04-30-74
07-10-74
04-06-74
04-30-74
07-10-74
04-06-74
04-30-74
04-06-74
04-30-74
07-10-74
04-06-74
04-30-74
07-10-74
04-06-74
04-30-74
07-10-74
04-06-74
04-30-74
07-10-74
04-06-74
04-30-74
07-10-74
04-06-74
04-30-74
07-10-74
04-06-74
04-30-74
07-10-74
04-06-74
04-30-74
07-10-74
JC01
1,720
110
80
230
40
< 2
~-
11,000
8,010
7,460
< 5
< 5
9
14
3
5
40
< 50
< 10
< 10
0.1
.42
4.7
1.9
JC02
17,200
2,780
130
1,300
110
< 2
__
17,700
8,610
6,350
< 3
< 5
< 5
43
15
16
14
3
< 3
< 50
< 40
< 50
< 10
< 10
< 10
0.26
< 0.1
.17
11
2.9
2.1
JC03
130
1,300
130
< 20
40
20
--
7,130
5,930
6,440
< 3
< 5
18
12
< 6
< 3
< 50
< 50
< 10
< 10
< 0.1
.95
2.1
1.4
JC05
230
490
20
< 20
20
< 2
Neg.
8,500
8,750
7,400
< 5
< 5
13
9
4
3
< 40
< 50
< 10
< 10
0.2
.17
4.3
1.7
JC08
130
1,720
80
20
40
< 2
--
15,300
16,900
11,120
< 3
< 5
28
30
< 6
16
< 50
< 50
< 10
10
0.32
.08
4.9
3.0
JC11
50
22,100
3,300
< 20
2,300
790
Neg.
15,800
14,900
16,340
< 5
< 5
27
29
4
5
< 40
< 50
< 10
< 10
< 0.1
.08
9.2
3.6
JC14
790
4,900
490
110
2,300
220
--
18,900
12,600
9,880
< 3
. < 5
26
27
< 6
< 3
< 50
< 50
< 10
10
0.10
.06
12
2.6
JC21
3,300
1,720
3,300
330
230
330
--
13,300
10,900
9,460
< 3
< 5
< 5
27
16
13
< 6
7
< 3
< 50
< 40
< 50
< 10
< 10
< 10
< 0.1
0.8
.07
3.7
5.0
2.7
JC24
1,300
2,210
790
50
50
330
--
11,300
9,500
11,020
< 3
< 5
17
16
< 6
7
< 50
< 50
< 10
< 10
< 0.1
1.16
3.0
4.7
JC27
230
50
230
< 20
< 20
< 2
14,200
28,400
9,680
< 3
< 5
< 5
6
51
18
< 6
65
4
< 50
< 40
< 50
< 10
34
< 10
< 0.1
0.1
1.25
3.8
2.1
2.8
Neg. - Sought but not detected
-------
39"50'
Figure 12
326
-------
TABLE 12
SUMMARY OF BACTERIOLOGICAL DATA (WATER COLUMN
} COLLECTED ALONS NEW JERSEY' SHORELINE
(Samples Collected in Surf
Date
Zone)
Station Identification Number
JC01A
4/8/74
4/22/74
5/6/74
5/20/74
6/3/74
INi
6/18/74
7/1/74
Samples to date
Geometric Mean
Max
Min
TC
12
—
10
44
41
84
6
6
22
84
6
FC
1
—
2
6
13
3
*
6
3
13
JC02
TC
4
48
14
64
15
44
7
7
19
64
4
FC
1
19
<1
4
5
<]
7
2
19
JC03
TC
10
4
8
36
28
3
6
10
36
3
FC
1
2
5
6
2
—
5
3
6
1
JC05
TC
12
12
8
31
34
11
1
7
10
34
1
FC
-------
SUMMARY OF BACTERIOLOGICAL DATA (HATER COLUMN) COLLECTED ALONG NEK JERSEY SHORELINE
CO
ro
00
(Samples Collected in Surf
Date
4/8/74
4/22/74
5/C/74
5/20/74
6/3/74
6/18/74
7/1/74
Samples to date
Geometric Mean
Max
Min
Zone)
Station Identification Number
JC11
TC FC
6
7
176
12
10
18
5
7
13
176
5
1
<1
47
5
1
3
«
7
3
47
JC14
TC FC
18
3
23
500
17
64
96
7
35
500
3
9
1
5
13
6
8
3
7
5
13
1
JC21
TC FC
—
9
31
9
14
23
2
6
11
31
2
—
•Cl
5
1
3
3
Cl
6
2
5
JC24
TC FC
4
2
3
2
16
168
5
7
7
168
2
2
1
1
1
3
17
«
7
2
17
JC27
TC FC
8
<1
4
2
10
19
28
7
6
28
4
<1
1
2
2
16
1
7
2
16
TC = Total Col 1 form (MF/100 ml)
FC = Fecal Coliform (MF/100 ml)
< = Less than
-------
SUHiiARY OF BACTERIOLOGICAL DATA (HATER COLUMN) COLLECTED ALOH3 NEW JERSEY SHORELINE
CO
(Samples Collected in Surf
Date
4/8/74
4/22/74
5/6/74
5/20/74
6/3/74
6/18/74
7/1/74
Samples to date
Geometric Mean
Max
Min
Zone)
Station Identification Number
JC30
TC FC
42 41
1 1
2 4.1
*1 <1
8 <1
2 <1
2 4.1
7 7
2 4.1
8 1
JC33
TC FC
6
1
2
<1
60
112
28
7
8
112
2
41
*1
*1
8
17
1
7
2
17
JC37
TC FC
94
10
15
8
82
148
35
7
34
148
8
46
3
6
2
13
32
2
7
8
46
2
JC41
TC FC
—
—
6
7
420
4
1
5
9
420
1
—
—
1
7
71
*1
*
5
3
71
JC44
TC FC
—
—
10
<1
12
5
1
5
4
12
—
—
2
4,1
4
1
*
5
2
4
TC = Total Coliform (MF/100 ml)
FC = Fecal Coliform (MF/100 ml>
< = Less than
-------
TABLE 12 - Cont.
OJ
OJ
o
SUMMARY OF BACTERIOLOGICAL DATA (WATER COLUMN) COLLECTED ALONG NEW JERSEY SHORELINE
(Samples Collected
Date
4/8/74
4/22/74
5/6/74
5/20/74
6/3/74
6/18/74
7/1/74
Samples to date
Geometric Mean
Max
Min
in Surf Zone)
Station Identification Number
JC47A
TC FC
—
—
1 1
«1 «1
3 2
2 ^1
1 <.!
5 5
1 1
3 2
^•1 <\
JC49
TC
no
56
2
1
6
2
6
7
7
no
1
FC
9
1
1
«1
1
<1
<]
7
1
9
^|
JC53
TC FC
6 2
4 <1
8 2
!
7 7
4 1
8 2
<1 ^1
JC55
TC
*2
*1
23
1
11
2
1
7
3
23
<1
FC
<1
<1
<1
1
1
*1
<]
7
<1
1
<.!
TC = Total Collform (MF/100 ml)
FC = Fecal Col 1 form (MF/100 ml)
< = Less than
-------
DISPOSAL OF SEWAGE SLUDGE TO SEA;
UNITED KINGDOM EXPERIENCE AND PRACTICE
by
J. E. PORTMANN
MINISTRY OF AGRICULTURE, FISHERIES AND FOOD
FISHERIES LABORATORY
BURNHAM-ON-CROUCH, ESSEX
Introduction
The disposal of sewage sludge to sea off the coasts of the United Kingdom
is not a recent development. At least three large cities, London, Manchester
and Glasgow, have used this method of sludge disposal for over fifty years.
The scale of their operations has however increased considerably in recent
years; in addition, many more local authorities are turning to the marine
environment as a means of disposal for their sewage sludge. In 1971 Wood(1)
stated that, in addition to London, Manchester and Glasgow, at least twelve
other authorities disposed of sewage sludge to sea and the total quantity so dis-
posed then amounted to 6947 x 103 wet tons per year. At the present time
(May 1974) the number of other authorities dumping sewage sludge has risen to
twenty-two and the total quantity to 8054 x 103 wet tons per year. The distribu-
tion in geographical terms is given in Table 1 (see Figure 1).
The reason for the upsurge in marine disposal of sewage sludge is twofold.
Firstly, experience to date shows little accumulation of sewage sludge solids in
any of the three main dumping areas (the Thames estuary, Liverpool Bay, and
the outer Clyde estuary) and comparatively little effect on the benthic fauna and
commercial fisheries in the areas of disposal. As a result the regulatory
authorities continue to be favourably disposed towards sewage sludge disposal
at sea and have allowed the increase in quantities.
The greater quantities dumped at sea arise primarily from increased
pressure, from a variety of sources, against sludge disposal on land. First,
transport costs have increased enormously, which renders land transport
unattractive on economic grounds. Secondly, the Ministry of Agriculture,
Fisheries and Food (MAFF) Agriculture Division has recently pressed strongly
against the spreading of sewage sludges on land, because in the United Kingdom,
in common with much of northern Europe, most sewage works treat a mixture of
domestic and industrial wastes. This leads to the inclusion of appreciable quan-
tities of metals in the resultant sludges, which may adversely affect the growth
of certain crops and possibly lead to higher levels of these metals in foodstuffs
grown on treated soils. These problems do not of course apply to sludges from
rural communities.
Furthermore, regulatory authorities are reluctant to allow the solids
removed in the course of sewage treatment to be discharged to rivers, and
some authorities have recently exercised their powers in respect of drainage
from several land-fill sites. Their objection against certain land-fill sites has
been coupled with the saturation of several other major land-fill areas and a
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general shortage of alternative new sites. No place in the United Kingdom is
more than about 70 miles from the sea, and it is perhaps not surprising that
very many authorities have begun looking towards the sea as a means of solving
their problems of sewage sludge disposal. Often sea disposal has an additional
economic bonus in that cheap water transport down navigable rivers or estuaries
can be used, and the more expensive road journeys can be reduced.
At present over 25% of the sludge produced for sewage treatment in the
United Kingdom is discharged to sea, both from vessels and from long sea out-
falls, and this quantity is likely to increase.
Policy and practice
The United Kingdom is a signatory to both the Oslo and London Dumping
Conventions, and legislation which will allow ratification of these Conventions
is currently passing through Parliament. The absence of formal controls does
not however mean that UK dumping practice in either deep or shallow waters is,
or has been, haphazard. For at least eight years control of disposal of mate-
rials to sea from the United Kingdom has been carried out under a voluntary
scheme. At first this was operated by the then Board of Trade in consultation
with the Fisheries Department of MAFF, but for the last five years or so MAFF
has administrated the scheme in consultation with other interested parties such
as the Department of Trade and Industry and the Department of the Environment.
Under this scheme any party wishing to dump waste at sea must apply for
a licence and supply details of the waste. The details to be provided, usually on
a standard application form, include mode of arising of the waste, its quantity
and composition, and the proposed method and site of disposal. The administra-
tive and scientific aspects of the scheme have been improved progressively and
although in the past local authorities, and hence most sewage sludges, were not
included in the scheme they are now.
When the new Dumping Bill receives the Royal Assent and becomes law,
the voluntary scheme will become statutory and no dumping will be permitted
without prior approval. Existing approvals will be given the status of licences
and all new applications approved will receive formal licences.
In most cases, licences will be subject to conditions which will be reviewed
at yearly intervals, and no guarantee of renewal of a licence will be given.
Inspections will be conducted and a licence fee will be charged. Although it is
not intended to make a profit the fee charged will cover all administrative,
investigational and monitoring costs. The charges are unlikely to affect appli-
cations related to sewage sludge, but it is believed that they will deter the
small-scale industrial applicant who in the past may simply have regarded
marine disposal as a cheap and ready means of disposing of his wastes, without
due consideration of alternative methods.
When application is received by MAFF for an approval to dump a waste at
sea some applicants suggest a dumping site, but others leave this open for dis-
cussion with and guidance from MAFF. In either case before a site is approved
many factors have to be taken into account. Some of these are related specifically
to the composition and characteristics of the waste and for the purposes of this
paper are considered later.
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Other important factors are also considered and apply to any waste.
Amongst the first of these are the navigational and operational aspects of the
dumping area. The shipping lanes around the United Kingdom are among the
busiest in the world and it is essential that interference with normal commer-
cial shipping operations, as for example a dumping vessel depositing waste in
the path of oncoming vessels, is avoided. This is an important practical con-
sideration; thus one of the main reasons for the alteration of the agreed site
for disposal of the sewage sludge from London was due to the original site being
the main shipping channel into and out of the Port of London. It is also neces-
sary to ensure that any accumulation of solids does not affect navigational
channels.
There are extensive deposits of sand and gravel around the United Kingdom,
and increasing quantities are being won and used in the construction industry in
England and in continental Europe. These operations must be safeguarded, and
care must be taken to avoid impairing the operation of dredgers and to ensure
that the deposits which are being extracted, or which might be extracted in the
future, are not fouled or contaminated in a way which would render the material
unsuitable for construction purposes.
Interference with amenities must also be considered. With the increasing
use of the sea for various forms of recreation, dumping grounds are sited suf-
ficiently far from land to ensure that no unacceptable discoloration of water or
offensive floating or suspended matter is detectable by the public. This includes
the possibility of material being carried to the coast by wave action or local
current systems, and is especially relevant in areas of high recreation value
which might be threatened by dumping of raw or partially-treated sewage sludge.
Experience has shown that in respect of sewage sludge dumping there is no evi-
dence of increased number of faecal micro-organisms in bathing beach waters,
and this has been confirmed by tracer tests(^); the effects of local coastal dis-
charges from pipelines are far more important in this respect.
In many areas, the most important consideration is the possible effect on
marine resources. The coastal waters around the United Kingdom are extremely
productive and fishing activity is very heavy in many areas. In selecting a suit-
able area for dumping it is essential to ensure that interference with fishing
activity is minimal. Although it is unlikely that sewage sludge will affect the
physical operation of fishing gear by obstructing trawling, potting, etc., it is
aesthetically undesirable that fishing should be carried out in an area of sewage
sludge disposal. Due to the high numbers of faecal micro-organisms present,
sewage sludge should not be dumped on or near exploited molluscan shellfish
beds - in practice this is not a great problem in UK waters but it may be in other
parts of the world.
Generally, the direct acute toxicity of sewage sludges is low, at least to
commercially-sized marine fish or shellfish, but sub-lethal effects may be
important. That part of the ecosystem on which commercial species depend for
food must also be protected. The spawning grounds of species such as herring,
sand eels and rays, whose eggs require a firm substrate on which to adhere and
develop, are especially vulnerable. Such species are threatened not only by the
smothering of deposited eggs but by the permanent or temporary loss of suitable
substrate for subsequent spawnings. Fortunately, the major spawning grounds
around the United Kingdom for such species are well known and can be safeguarded.
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Nursery grounds of flatfish such as soles and plaice may also be harmed by the
dumping of sewage sludge, because they often occur close inshore and near to
large estuaries where many of our major towns are situated. Fortunately,
these too are reasonably well established, following intensive inshore investi-
gations by staff of the Ministry's Fisheries Laboratory at Lowestoft.
It is often stated that the solution to pollution is not simply a question of
dilution. In general, however, marine resources can be protected from the
polluting effects of sewage sludge, provided it is adequately dispersed either
during or after disposal, and provided it does not subsequently reaccumulate
in sludge banks or hollows in the sea bed. Lee and Ramster(3) have reviewed
the various hydrographic techniques which have been used to measure or pre-
dict this in the context of pollution problems in the open sea.
The direction and extent to which a waste is transported after dumping is
largely determined by the residual current flow. This can be measured through
the water column by deploying moored recording current meters and long-term
tracer experiments, often supplemented by a mathematical model, from which
the likely movement of discharged materials can be satisfactorily predicted.
To predict the movement of sewage sludge, the rate of settlement of the
solid particles is often important. Settlement will depend largely upon the
density and particle size and can vary considerably with different sludges, due
to the extent of dewatering and addition of flocculating aids. For example, the
settlement rate of sewage sludge dumped from Manchester in Liverpool Bay was
described as "low"(4), whereas MAFF scientists observing the release of sewage
sludge in the outer Thames estuary reported settlement rates to be "quite rapid".
Dispersal before settlement may be increased by the selection of a deep-water
site with suitable physical oceanographic characteristics. Settlement may, how-
ever, be inhibited by stratification of the water column which may result in the
temporary holding of sludge particles in the layer of discontinuity.
Once the sludge particles approach the sea bed their behaviour and fate is
determined by their size and density, the bottom currents and the nature of the
natural sea bed in the area of deposition. The currents at the sea bed may differ
markedly from those at the surface, both in strength and direction, and the cur-
rents should therefore be measured at representative depths.
An inspection of the sediment types in the proposed dumping area and
expected area of deposition can sometimes provide a general indication of the
bottom currents. This can be achieved directly by divers, and by grab or dredge
techniques, or indirectly by the use of echo sounders or other scanning devices.
Fine sediments usually indicate low currents which would allow settlement,
whereas sands and gravels generally indicate higher currents. These are only
guidelines and several exceptions have been noted; for example, in an area of
china clay waste disposal the natural sea bed was rocks and stones, but current
velocities were low, the china clay settled out rapidly, and was retained in spite
of winter storms(^).
Crickmore and Kiff(6) suggested that sludge particles are more readily
absorbed on smooth mud than on rocks, where agitation associated with ripple
movements discourages the retention of settled particles. The scale of the
dumping operation is also important in this respect, since even strong currents
may not be able to keep an area clear if the rate of deposition exceeds the
carrying-capacity of the current.
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The advent of the use of radioactive tracers has greatly increased the
hydrographers' capacity to predict the transport of sewage sludge solids, both
in the water and on the sea bed. By careful selection of the labelling isotope,
initial dispersal and subsequent movement can be followed for several months.
This technique has been used in connection with the studies made by MAFF and
other scientists in both the Thames estuary (London sludge) and Liverpool Bay
(Manchester sludge).
A final factor which is important in the United Kingdom, because of the
considerable dumping of sludges derived from a heavily industrialized, densely
populated island, is the possible interaction and synergism of toxic materials in
the sewage sludge. The presence of existing discharges and of other dumping
activities within a reasonable distance of the proposed dumping site are always
taken into account.
Once the disposal site has been selected, for a sludge to be dumped in
significant quantity, monitoring operations are instituted before any dumping
takes place and are continued at intervals as necessary after dumping has com-
menced. At the present time the major emphasis is placed upon studies of the
particle size composition of the sediment material, and the chemical composition
of the sediments, animals and fish species, including those of non-commercial
importance. The sediments are examined for their organic content and the pre-
sence of persistent substances such as metals, organochlorine pesticides and
PCBs, where they are known to be present in the sewage sludge. The benthic
animals and fish are also examined for the same persistent materials. Wher-
ever possible, these chemical and physical studies are accompanied by short
ecological surveys using grabs, dredges and Agassiz trawls. In spite of the fact
that benthic populations can change very markedly, both in number and character,
due to natural causes, these studies are considered essential, because they give
indications to community structure and might provide warnings of changes that
the chemist may not detect until later.
Experience
On the whole, British experience with sewage sludge disposal at sea has
been satisfactory and the practice is generally viewed favourably. There have
been a number of minor problems, usually caused by short dumping, e.g. where
the dumping vessel discharged its cargo in the wrong area over a string of crab
pots. However, although most applications are viewed favourably they do not
automatically receive approval and some are refused. In common with the
practice adopted for industrial wastes, each application is carefully considered
on its merits.
The first consideration is the method of disposal, and the selection of a
suitable disposal site in relation to fisheries, amenities and the ultimate fate of
the sewage sludge solids. The general pattern of operation for the major
authorities using sea disposal of the sewage sludge is to use hopper-type vessels,
generally self-propelled but in a few cases of the dumb-barge type. These ves-
sels discharge their cargo rapidly through bottom-opening doors; for instance,
the London sludge vessels can discharge their entire cargo in about 5 minutes.
Usually the vessel discharges under way. Many of the smaller authorities
employ disposal contractors, and in general these operators use small coastal
tankers with pumps discharging the sewage directly into the wake of the vessel.
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It is estimated that the latter procedure provides a minimal initial dilution of
around 1000, in contrast to the hopper-type operation which provides dilution of
around 200-fold(4). It has been shown that subsequent dilution of 10-20-fold
occurs(2) within an hour of disposal but that further dilution and dispersal is
dependent on local tidal and climatic conditions. In general the aim for sewage
sludges is to ensure maximum dispersal so as to avoid local build-up of sludge
particles, de-oxygenation or hyper-nutrification.
Most disposal sites are situated outside the territorial limit of 3 miles but
generally not more than 20 miles off. In no case have complaints been made of
sewage sludges dumped at sea causing nuisance on beaches; however, in one
instance an application to dump sewage sludge at sea was refused because of the
risk that sludge would reach local beaches. This was due to the fact that the
sludge in question had been dewatered and filter-pressed and was in pieces
ranging from small particles up to quite large conglomerates which were either
positively buoyant or only just negatively buoyant and liable to be moved on the
surface by onshore winds. The composition of the sewage sludge is also taken
into account. Both the Oslo and London Dumping Conventions require prohibi-
tion or limitation of the amounts of certain materials which may be dumped, and
some of these may be present in sewage sludges.
The typical range of concentrations of various constituents of sewage
sludges in the UK is given in Tables 2 and 3. The composition of a sewage
sludge varies according to the nature of the crude sewage entering the treatment
works and the degree of treatment. In the UK, raw primary sludge contains
3-8% dry solids, of which up to 20% might be grease; secondary sludge usually
has a lower dry solids content of 1-3%, but also contains less grease and has a
lower oxygen demand. Both primary and secondary sludges are dumped at sea,
and the data in Tables 2 and 3 include both types.
From Table 2 it will be seen that the solids content of these wastes ranged
between 1. 3% and 60% (mean 8.4). Of these solids about 50-80% was organic
matter, the remainder being fine grit, sand and other inorganic material. As
stated earlier, quite a high proportion of the organic matter is grease or oil,
typical contents falling in the range of 10-20% of the total solids. Generally,
the majority of the oil is of mixed vegetable and animal origin, but occasionally
quite high contents of mineral oil are encountered. It was on this count that
applications have been refused, for it was found that the mineral oil content may
exceed 3100 mgAg wet weight; such wastes contravene legislation designed to
control the discharge of oil at sea as required by the IMCO Convention. This
legislation limits the discharge of oil or oily waste of any description, if it con-
tains oil in excess of 100 ppm or if it is discharged at a rate in excess of
60 litres/mile. Most sewage sludges from large cities exceed this level and
special dispensations are usually allowed, but in some cases the oil content is
considered too high. The precise source of the mineral oil cannot always be
traced but repeated sampling suggests it is likely to be of industrial origin. In
this context it is believed that these difficulties arise as a result of the disposal
by motorists of waste engine oil, much of which currently finds its way into the
municipal sewer.
Only comparatively recently has it been realized that associated with the
organic matter in sewage sludges there is an appreciable content of a wide range
of metals and other persistent substances. The presence of these substances
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must be considered, since even if the sludge does not directly affect marine
resources, the quality of benthic animals, fish or shellfish may be so affected
as to render them unfit for human consumption. For example, mercury and
cadmium - both of which, although permitted as trace quantities in other
wastes, are specifically banned under the two Dumping Conventions - have
been found to occur in concentrations of up to 20. 4 mg/kg and 6. 3 mg/kg res-
pectively in UK sludges. Fortunately the normal or average content is much
lower, i.e. 0. 35 mg/kg for mercury and 1.1 mg/kg for cadmium. Other
metals, such as lead, copper and zinc, must be controlled under the London
Convention, and sewage sludges in the United Kingdom can contain considerable
quantities; the maxima so far noted were 2130 mg/kg zinc, 171 mgAg lead
and 526 mg/kg copper, on a wet weight basis.
Investigations are in progress, both in the field and in the laboratory, in
an attempt to determine whether or not all the metals in sewage sludges can
enter the food chain and result in unacceptably high levels in edible fish and
shellfish. From monitoring studies in sewage sludges disposal areas it has
been shown that these substances are present in the sediments and in benthic
organisms and in fish and shellfish which take them as food. In both the Clyde(^)
and Thames (?) estuaries, high values of copper, lead and zinc were found in
areas of high organic content sediments. There was a high degree of correlation
between the zinc and copper and organic matter in the sediments in Liverpool
Bay(lO) but the zincrcopper ratio (9:1) was different from that in the sludge (2:1)
or in harbour dredgings (6:1)(H). There was no clear correlation between the
amounts of these metals in the sediment and in benthic molluscs, which suggests
that the ecological relationships are very complex. Some of the analyses were
carried out on whole animals and it is probable that the reported "tissue" levels
refer, at least in part, to the metal associated with sediments contained in the
gut of the animals. This metal may not be in a form available to the animal.
For some metals, particularly mercury, the evidence for their absorption
is very strong. In both the Thames estuary and Liverpool Bay the mercury con-
tent of fish muscle is as high as that found in an area polluted by a chlor-alkali
discharge (range of means 0.45-0. 55 mg/kg; range of maxima 1. 5-2. 5 mg/kg).
As is indicated in Table 3, sewage sludges also contain persistent organic sub-
stances such as organochlorine pesticides and PCBs. The concentrations found
in sewage sludges from the UK cover a considerable range (e.g. for DDT between
0. 01 mg/kg and 0. 5 mg/kg), whereas for PCB the range was 0.1 mg/kg to
8. 6 mg/kg. From our investigations, the average values for UK sludges appear
to be about 0. 2 mgAg for DDT and 1. 2 mgAg for PCB. The source of these
normal levels is obscure but in all probability is linked with levels in food and
domestic sewage. Where abnormally high values occur they can usually be
ascribed to loss from a specific industrial process; for example, 8. 6 mgAg
PCB found in one sewage sludge was traced to losses of transmission fluids from
railway locomotives(12). Similarly, certain sewage sludges from the Yorkshire
woollen-processing area have been found to contain higher than average amounts
of dieldrin, which was once used as a sheep dip and is still used for
mothproofing(13),
Where urban sewage has a large industrial component, chlorinated solvents
such as carbon tetrachloride and trichlorethylene may be found in sludges at
concentrations of up to 20 mg/1 on a dry weight basisC14).
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Although the metal, organochlorine pesticide or PCB content of sewage
sludge from UK sources does not normally give cause for concern, warnings
have been given to dischargers that continuation of approval in the long term
will be dependent upon significant reductions in the amount of some substances,
such as cadmium, mercury or PCB. Frequently the discharger is unaware of
the composition of his sewage sludge, or that it is exceptional, until discussions
related to sewage composition are started. Usually, however, the principal
source or sources of the pollutant are found and can be controlled.
It is always important to ensure that the requirements related to sludge
quality take into account the input of similar substances from other sources.
For example, in Liverpool Bay dredging spoil contributes a daily load of
3270 kg zinc, and sewage sludge adds a further 650 kg(1). Other sources such
as input from pipelines and rivers may also be important, and aerial input can
be considerable. For example, the annual rates of input of lead and copper
respectively to the North Sea by aerial deposition have been estimated to be
15 000 tons and 13 000 tons respectively!15).
Where large amounts of organic matter and nutrients are dumped or dis-
charged to the sea there is a danger that de -oxygenation or eutrophication might
occur. In the United Kingdom, de-oxygenation has not proved to be a problem in
sewage sludge disposal areas, largely because there are comparatively large
tides which ensure considerable dispersion of the waste, and re-aeration of sea
water. Tidal ranges (in metres) for the east coast of England and Scotland are
shown in diagrammatic form in Figure 2. Clearly the currents associated with
such tides are considerable.
The input of nutrients in sewage sludge is small by comparison with that
from other sources; thus, in the North Sea only 7% of the nitrogen entering the
North Sea can be attributed to sewage discharges of all types, and there is little
evidence of eutrophication problems. It should however be stated that in at least
one north European area (Oslofjord) the occurrence of a bloom of toxic algae and
the incidence of paralytic shellfish poison toxin has been associated with the dis-
charge of sewage effluents. In Liverpool Bay there is an annual bloom of the
colonial flagellate Phaeocystis which can be toxic to young shellfish but this has
not been linked with sewage sludge dumping(16).
The three major sewage sludge disposal operations around the United
Kingdom, namely those from London, Manchester and Glasgow, have been
thoroughly studied and this paper would not be complete without a brief sum-
mary of the findings, most of which have been published (London(^), Manchester(2)
and (1?) andGlasgow(18)).
The sewage sludge from London is dumped in the outer Thames estuary in a
water depth of about 60 ft. In 1967 the area of disposal was altered from the
Black Deep to the Barrow Deep, and both Deeps have been intensively studied
since 1970. These studies have included dye releases, releases of radioactively-
labelled sludge, current measurements and numerous surveys in which samples
of sediment and animals have been collected for examination in the laboratory.
The area is characterized by relatively deep channels separated by sandbanks,
some of which can be exposed on extreme spring tides. The tidal currents in the
present dumping zone are generally of the order of 2 knots but speeds greater than
this have been observed.
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In the first survey, which was conducted in 1970(9), no great accumulation
of organic matter was found in either the old or new dumping zone, although there
was an appreciable number of tomato seeds in the sediments in the Black Deep
disposal zone. The main accumulation of organic matter was found inshore
near the mouth of the Thames estuary. This organic matter was associated with
elevated metal levels but the ratio of the metal was not the same as that in the
sludge. Subsequent investigations using a radioactive tracer technique suggested
that the high organic levels found at the mouth of the estuary were of estuarine
origin rather than from the sewage sludge.
Owing to the fast currents and the high suspended matter load in the water
of the Thames estuary, the numbers of benthic animals, particularly of bivalve
molluscs, was not expected to be high and the surveys confirmed this. The dis-
tribution of bivalve molluscs did not appear to be linked to the sewage sludge
disposal area, although it may be significant that most of the observed species
were deposit feeders. The total numbers of polychaetes present appeared pos-
sibly to be related to the sludge disposal area, at least that of earlier years, but
species diversity was also greatest in the area of greatest numbers.
Sludge from the city of Glasgow in Scotland has also been dumped to sea
for almost seventy years. The current quantity dumped in the outer Clyde estuary
is about 1 million tons per year. The characteristics of the disposal area are
rather different from those in the Thames estuary; the shore is little more than
3 miles away on three sides but the water is deeper, about 300 ft. Current velo-
cities are lower, generally < 0. 5 knots. Releases of seabed drifters(18) have
shown that light material such as sewage sludge would however be spread over
a wide area relatively rapidly.
As might perhaps be expected, in view of the conditions in the disposal area,
there is some evidence of an accumulation of organic matter in the sediments.
However, the concentrations found were not unduly high - the highest being only
8%, i.e. about eight times the lowest observed in the survey area. Similarly,
the levels of metals present in the dumping zone were in excess of those found
further away, and the highest values were coincident with those for organic
matter. Concentrations of up to 208 mgAg of copper, 320 mgAg of lead and
488 mg/kg of zinc were observed in the centre of accumulation. There was some
evidence of a change in species composition which may be associated with the
greater concentration of organic matter in the dumping area, since the change is
from a basically molluscan/echinoderm community to a polychaete community in
the organic-rich zone.
Analyses of mussels from selected sites(^) in the immediate dumping area
and from a control area some distance away suggest that the animals in the dis-
posal area carry a higher heavy metal burden than those outside the dumping
area, although often the differences are not very great.
The conclusions drawn to date from this study are that the sewage sludge is
spread fairly widely after disposal and that although there has been a limited
build-up of organic matter and heavy metals there is little evidence of gross pol-
lution, either in chemical or biological terms.
The area which has been the subject of most intensive study is Liverpool
Bay, where for over seventy years sewage sludge from the Manchester area has
been dumped. The main reason for this intensive study, which began in 1969 and
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the initial stages of which were reported on in 1972(2>17), was the need to pre-
dict what would happen if the existing rate of disposal (around \ million wet tons/
year) was increased by about 10 times. A multi-disciplinary working party was
established and money was made available by the Department of the Environment,
which acted as a coordinating body.
The study included investigations of the hydrography of the area, the com-
position of the sediments, movement of the sludge, the fisheries, the benthic
fauna composition, etc. Toxicity tests were conducted using a variety of marine
species, ranging from algae to shrimps and fish. Current measurements sug-
gested a persistent two-layer structure of the water column, with a bottom
onshore-moving residual current and a variable surface current, with a possible
gyre action in the summer months.
Examination of the sediments in the survey area showed the highest
accumulation of organic matter to be at the mouth of the Mersey, inshore from
the dumping area. There was a strong correlation between the organic content
and the contents of metals such as copper and zinc. The ratio was however dif-
ferent from that in the sewage sludge. There was little evidence of accumulation
of sludge material in the immediate dumping zone.
The tracer experiments confirmed the tentative conclusions from these
findings. The release of sewage sludge labelled with silver-HOm was made
late in September 1970. Subsequent surveys showed a rapid dispersion of the
solids: by mid-October there was a distinct indication of movement towards
the Mersey estuary and extensive dispersion. Further surveys confirmed these
early trends. Up to one month after release no silver-110m could be detected on
the shore but by early February 1971 most of the shore detection sites showed
some silver-HOm present, although only in small amounts. The final stage of
this work was a projection of the distribution likely to take place when increased
quantities are dumped. This showed that for one year's input the highest concen-
tration to be expected was 0. 5% in the sediments at the entrance of the estuary of
the Mersey, but around the actual dumping site it was only 0.1%. The early sur-
veys showed that the area of maximum fall -out would be a band approximately
8 x 30 km, running roughly east-west. On the basis of these surveys it was
estimated that, although the sludge does contribute to the organic loading of the
sediments, the existing rates of disposal contribute less than 10% of the total
organic matter, the remainder coming from the estuary and from other terres-
trial sources. Dispersal during neap tides was less pronounced and it was
recommended that the dumping area be enlarged with vessels dumping along
north-south lanes.
The report recommended that there would be little effect on the fauna,
fisheries and sea bed composition if the quantity of sewage sludge were increased
as proposed. A plan for further surveys was recommended and work is now in
progress. The areas of disposal have been altered in accordance with the
recommendations made in the light of the radio-tracer surveys.
Summary and conclusions
The disposal of sewage sludge by dumping at sea has been conducted from
the United Kingdom for well over seventy years. The quantities of sludge dis-
posed of in this way are steadily increasing, both in volume and with regard to the
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number of sources. Although in some areas limited accumulation of both orga-
nic matter and persistent substances has occurred, the extent to which this has
taken place is small. The main reason for this limited effect is probably to be
found in the adequate dispersion characteristics in relation to the quantities
disposed of in the areas in question.
Disposal by dumping at sea of sewage sludges, and indeed wastes of indus-
trial origin, from the United Kingdom will undoubtedly continue for the
foreseeable future. However, the quantities which can be approved will continue
to be related to the capacity of the area to receive wastes. The quantity can be
estimated from a knowledge of current movements and the polluting characteris-
tics of the waste, e.g. its oxygen demand, and its nutrient, metal and PCB
content. Careful monitoring must of course be conducted to ensure that these
predictions are accurate and that the capacity of the area to receive a waste is
not pushed beyond its limit.
From this it should not be assumed that the sea may be used for the dis-
posal of any waste which proves difficult or expensive to dispose of on land.
Nor should the total capacity of an area to receive wastes be fully utilized.
There must be some reserve of capacity to ensure that other uses of the area
can continue. It is clear, however, that with care the sea can be used for the
disposal of many waste materials and that in some respects it may offer advan-
tages over land disposal, as currently conducted, although as new methods of
treatment recovery or disposal (e.g. by incineration) are developed these may
in turn be adopted in preference to sea disposal. At the present time, however,
sewage sludge is a bulky waste with a high water content which proves difficult
to dispose of on land but which with care can often be safely disposed of to sea.
References
(1) Wood, P. C. , 1973. Disposal of Sludge to Sea, Paper No. 8, In:
Proceedings of "National Symposium on Disposal of Municipal and Indus-
trial Sludges and Solid Trade Wastes", London, 26-27 November.
(2) Department of the Environment, 1972. "Out of Sight Out of Mind"
Report of a Working Party on Sludge Disposal in Liverpool Bay, 1,
HMSO, 36 pp.
(3) Lee, A. J. and Ramster, J. , 1968. The hydrography of the North Sea.
A review of our knowledge in relation to pollution problems. Helgola'nder
wiss. Meeresunters, 17 44-63.
(4) Crickmore, M. J., 1972. Initial behaviour of sludge, pp. 45-54 In: "Out
of Sight Out of Mind" Report of a Working Party on Sludge Disposal in
Liverpool Bay, 2_, HMSO, 485 pp.
(5) Portmann, J. E., 1968. The effect of china clay on the sediments of
St. Austell and Mevagissey Bays. J. mar. biol. Ass. U.K., 50^
577-581.
(6) Crickmore, M. J. and Kiff, P. R., 1972. Bed sediments: particle size,
pp. 273-286 In: "Out of Sight Out of Mind" Report of a Working Party on
Sludge Disposal in Liverpool Bay, 2, HMSO, 485 pp.
(7) Weichart, G., 1972. Chemical and physical investigations on marine
pollution by wastes of a titanium dioxide factory, pp. 186-188 In:
Ruivo, M., ed., "Marine Pollution and Sea Life". London, Fishing News
(Books), 624 pp.
341
-------
(8) Mackay, D. W. , Halcrow, W. and Thornton, I. , 1972. Sludge dumping
in the Firth of Clyde. Mar. Pollut. Bull. 3^ (i) 7-10.
(9) Shelton, R. G. J., 1971. Sludge dumping in the Thames estuary. Mar,
Pollut. Bull. 2^(2) 24-27.
(10) Winter, A. and Barrett, M. J., 1972. Bed sediments: chemical examina-
tion, pp. 289-295 In: "Out of Sight Out of Mind" Report of a Working Party
on Sludge Disposal in Liverpool Bay, 2, HMSO, 485 pp.
(11) O'Sullivan, A. J., 1972. Discharges to Liverpool Bay. Ibid. 9-15
(12) Waddington, J. I., Best, G. A., Dawson, J. P. and Lithgow, T., 1973.
PCBs in the Firth of Clyde. Mar. Pollut. Bull. 4 (2) 26-29.
(13) Croll, B. T., 1969. Organo-chlorine insecticides in water, Parti.
Wat. Treat. Exam. 113 (4) 225-274.
(14) Ainsworth, G., 1972. Composition of sludge, pp. 2-7 In: "Out of Sight
Out of Mind" Report of a Working Party on Sludge Disposal in Liverpool
Bay, 2. HMSO, 485 pp.
(15) ICES, 197-. Report of Working Group for the International Study of Pol-
lution of the North Sea and its Effects on Living Resources and their
Exploitation. ICES Cooperative Research Report Series A (In press).
(16) Spencer, C. P., 1972. Plant nutrient and productivity study, pp. 353-401
In: "Out of Sight Out of Mind" Report of a Working Party on Sludge Dis-
posal in Liverpool Bay, 2_, HMSO, 485 pp.
(17) Department of the Environment, 1972. "Out of Sight Out of Mind" Report
of a Working Party on Sludge Disposal in Liverpool Bay, 2_, HMSO, 485 pp.
(18) Mackay, D. W. and Topping, G., 1970. Preliminary report on the effects
of sludge disposal at sea. Effl. and Wat. Treat. Jnl j5 641-649.
342
-------
Table 1 Quantities of sewage sludge from England
and Wales approved by MAFF for disposal
on continental shelf since 1971
Area
Irish Sea
Bristol Channel
English Channel
North Sea
Total
Thousand tons per annum
2 025 including Glasgow
356
210
5 463
8 054
343
-------
Table 2 Composition of UK sewage sludges dumped at
sea
Component
Solids - total (%)
Solids - volatile (%)
BOD (ppm wet weight)
Nitrogen*
Phosphorus*
Grease/fat*
Range
1.3-60
50.0-80
40 000-290 000
0.1-48
0.3-20
0.1-26
Mean
8.4
66
230 000
12
6.0
8.4
*Given as percentage of dry solids.
344
-------
Table 3 Heavy metal and organochlorine content of UK sewage sludges dumped at sea
GO
-P»
on
Component
Wet weight (mg/kg)
Range
Cadmium
Chromium
Cobalt
Copper
Lead
Manganese
Mercury
Nickel
Zinc
Total organochlorine pesticides
Total PCBs
0.
0.
-
3.
0.
0.
0.
0.
3.
0.
0.
2 -
3 -
6 -
2 -
8 -
01-
3 -
0 -2
01-
1 -
6.3
152
526
171
128
20
92
130
0.50
8.6
Mean
1.1
21
7.5
54
26
35
0.35
9.3
176
0.20
1.2
Dry weight (mgAg)
Range
3.
2.
-
26.
5.
10.
0.
4.
93.
0.
0.
0-
0- 3
0-11
0- 1
0- 1
2-
0- 1
0-48
3-
O _
76
700
955
208
530
85
100
410
9.4
94
Mean
21
433
89
1 004
361
423
7.0
111
3 409
3.0
20
-------
Figure captions
Figure 1 The British Isles, showing the main areas referred to in the text.
Figure 2 North Sea, co-range chart.
346
-------
61
60°
59°
58°
57°
56°
55°
54°
53°
52°
51°
50°
49°
012° 11° 10° 9° 8° 7° 6° 5° 4° 3° 2° 1° 0° 1° 2° 3°
I i i i i i i i i i
t
i i i i
Liverpool
Bay
London j Thames
Bristol
Channel
ENGLISH CHANNEL
I I I I \ r \ Iv I I I I I I
NORTH
SEA
347
-------
10 nO 10
go ^o 2° 3° IS 5° 6° 7° 8° 9° 10'
348
-------
Preliminary Summary
of
Sludge Degradation Studies
in a
Marine Benthic Environment
William P. Muellenhoff*
Research Symposium
Pretreatment and Ultimate
Disposal of Wastewater Solids
Cook College
Rutgers University
May 22, 1974
*Graduate Student, Department of Civil Engineering, Oregon State University
Corvallis, Oregon
*Research Associate, Coastal Pollution Branch, Pacific Northwest Environ-
mental Research Laboratory, Environmental Protection Agency, Corvallis,
Oregon,
349
-------
This paper describes in summary form, the research efforts of the
author in the past two years. Details of each topic, a description of
experiments in progress and analyses of all data will be submitted in
dissertation form as partial fulfillment of the requirements for the
degree of Doctor of Philosophy in the Department of Civil Engineering,
Oregon State University.
350
-------
ABSTRACT
A series of field and laboratory experiments were carried out to
determine degradation rates of organic sludge deposits in a sea floor
environment. In laboratory experiments total carbon concentrations were
found to decrease approximately 70% in 80 days for experiments at 1
atmosphere. The total carbon decreased 30% in 47 days, in elevated
pressure experiments with a Deep Sea Simulator. Oxygen consumption
rates ranged from 3.74 grams-02/m /day to 0.55g-02/m /day depending on
sludge source, type of digestion and time since deposit. Dissolved
oxygen was depleted beyond 1 millimeter in the bed; oxidation-reduction
potential ranged from +150 millivolts at the sludge bed surface to -100
mv at 2 centimeters. Diffusion of hydrogen sulfide into underlying
sediments began at 24 days into the experiments and proceeded at a rate
of 0.09 mm/day. Due to compaction, sludge beds decreased to one-half
their original thickness in 80 days. Approximately 60% of all compaction
occurred in the first day.
Current experiments are being devoted to better definition of
initial carbon losses and documentation of carbon decreases in a 50
centimeter bed. A conceptual mathematical model of dissolved partic-
ulate and gaseous fractions of sludge bed carbon is being formulated in
an effort to better understand the mechanisms and transfer rates of the
sludge bed carbonaceous materials.
351
-------
TABU 01 CON! I NTS
Abstract ?
Introduction 4
Background 5
Laboratory Measurements 7
Simulation Procedures 9
Laboratory Carbon Data 13
Laboratory Oxygen Consumption Rates 21
Other Laboratory Measurements 21
Field Study 23
In-Situ Oxygen Uptake 25
Experiments in Progress 27
Conclusions 29
Appendix 31
Acknowledgements 37
References 3H
35?
-------
INTRODUCTION
Significant amounts of domestic sewage sludges are being released
to coastal waters without an adequate understanding of the impact of
such practices on marine ecosystems (Buelow, 1968; Brown, et. al., 1971;
National Marine Fisheries, 1972). Over 1.3 million metric tons of
sewage sludge are produced annually in coastal regions of the United
States. Due to population increases in these areas, this figure is
expected to exceed 1.9 million metric tons annually by the year 2000
(Council on Environmental Quality, 1970).
Additional disposal requirements will be created by upgrading of
existing domestic treatment facilities to secondary, and primary treatment
of raw sewage discharges. In 1970, more than 3.8 million cubic metres
of sludge were dumped 22 kilometres from the New York Harbor entrance.
By last year, the amount had risen to 4.4 million cubic metres (Dewling,
1974). With further wastewater treatment requirements, the annual disposal
requirements of the New York-New Jersey metropolitan area are expected to
exceed 11.5 million cubic metres (Home, et. al., 1971; Gross, 1969).
Because of the probable future increases in the ocean disposal of
sludges, the need to optimize disposal techniques has become even more
critical. Such an optimization program cannot be developed without a
sound scientific basis. Yet data on the fate and effects of disposed
sludges is lacking. A Smithsonian Institution evaluation of New York
Bight waste disposal studies concluded that research on post-deposition
waste characteristics is preliminary and inconclusive (Buzas, et al.,
1972). The report stressed the need to determine the time required to
stabilize and decrease the extent of benthic deposits on the ocean
floor. Previous descriptions of equilibrium conditions in ocean disposal
zones, have assumed decomposition-rate constants from river deposit data
(Barnett, et al_, 1969).
353
-------
The primary objective of this research was to determine the rate
and extent of organic carbon decreases in a digested domestic sewage
sludge deposited on the sea floor. A set of predictive mathematical
equations was formulated to describe decreases in the organic content of
a sludge deposit as a function of time and depth in the bed. A sludge-
bed model is being developed to describe temporal and spatial exchange
rates between dissolved, participate and gaseous phases of the sludge
bed. Fxperimental observations have provided additional data on compac-
tion rates, losses of volatile fractions during settling through a sea
water column, sulfide diffusion rate into underlying sediments and
sludge oxygen consumption rates.
BACKGROUND
Previous laboratory studies on the stabilization rates of organi-
cally laden river deposits were devoted to the measurement of the oxygen
depletion of water in contact with deposits of specific configuration
for a known period of time (Fair, et. al., 1941). The oxygen consumption
was partly attributed to oxidation of organic matter close to the sludge
bed surface, txposure of reduced anaerobic degradation products,
forced upward during compaction, was also thought to impose a substantial
oxygen demand on bottom waters. Allowance was given for the anaerobic
production of gases (methane and carbon dioxide) which could, upon
accumulation, become sufficently buoyant to erupt through the deposit
causing significant overturn, exposure of reduced sediments and resultant
high oxygen utilization rates in near bottom waters.
Comparison of benthal oxidation rates as measured above with the
anaerobic stabilization rates obtained by running a time series of 5-day
BOD tests on samples from a deposit covered with oxygen depleted water
showed the anaerobic rates to be much higher (Rudolfs, 1938; Mohlman,
193M). The conclusion was that the rate of oxygen consumption by a
354
-------
deposit does not necessarily correlate with the overall stabilization
rate due to different chemical conditions at the surface and deeper in
the deposit. Reduced by-products in the deeper anaerobic regions may
not exert a predictable oxygen demand on the overlying waters.
Kuznetsov (1973) suggested that the amounts of released carbon
dioxide and methane would better relate overall sediment decomposition
rates since these gases are created during mineralization in anaerobic
and aerobic regions. Simultaneous measurement of oxygen consumption in
the overlying waters, calculation of the equivalent C02 produced due to
the aerobic degradation, and subtraction of this from the total C02
produced would provide measure of the C0? associated with anaerobic
degradation.
Previous research on organic deposit stabilization has been primarily
devoted to measuring the effects of such a process on overlying waters.
Such an approach is particularly attractive because low oxygen levels in
these waters can significantly affect both pelagic and benthic biota.
The studies revealed the differences in aerobic and anaerobic breakdown
rates, but an effective procedure to relate this information to the
overall (aerobic and anaerobic) stabilization rate of a river bed or sea
floor deposit has not been developed.
The presence or absence of molecular oxygen as a terminal hydrogen-
ion acceptor is one of many parameters which could control the microbial
conversion of organic matter. Substrate availability, physical stability
of the deposit, varying chemical conditions and bacterial community
succession could each be influential.
The size of the particulate fraction of sewage has also been shown
to influence the biochemical oxidation rate (Balmat, 1957). Laboratory
studies over a period of 5 days showed that aerobic decomposition of
355
-------
relatively large settleable and supracolloidal (1-100 micron) solids may
be limited by a slow hydrolysis rate, whereas colloidal (0.08 to 1.0
micron) and dissolved (<0.08 micron) organic matter is utilized much
more rapidly. Biochemical oxygen demand (BOD) rate constants (K-|)
defined by the following equation were found to range from 0.18 to 0.90
(per day).
ht _ p-K,t (1)
L e '
where L = ultimate biochemical oxygen demand (ppm)
L. = the BOD at time t (ppm)
K, = rate constant (per day)
The rate studies on sewage solids suspended in mineral dilution
water (with a 1% sewage seed) were made at 20°C over a 5 day period with
a Warburg Respirometer.
LABORATORY MEASUREMENTS
Microbial degradation of settled sludge on the sea floor involves
solubilization and subsequent utilization of dissolved organic and
inorganic compounds for the production of energy. In aerobic zones,
organic or reduced inorganic compounds are oxidized to carbon dioxide
and used for cell synthesis, maintenance, motility or active transport.
At sludge bed depths greater than about 1 millimeter, molecular oxygen
is rapidly depleted and degradation proceeds either anaerobically by
anaerobic respiration in the presence of exogenous hydrogen-ion acceptors
(e.g., sulfates and nitrates), or by fermentation where lack of exogenous
acceptors requires their endogenous generation (Schroeder et al., 1966).
As a result of these metabolic processes, the sludge organic carbon
content will continually decrease due to conversion to inorganic products
or gaseous losses. The rate of breakdown, however, will be dependent on
356
-------
the dominant degradation mode at different locations in the bed. Since
carbon is the most abundant element in sewage sludge (Gross, 1970) and
carbonaceous compounds act as food sources for resident bacteria, large
changes in sludge carbon concentrations will occur as decomposition
proceeds. For this reason, organic and inorganic carbon were selected
as principal indicators of the stabilization process.
Initial laboratory experiments have been devoted to the measurement
of sludge sample total carbon (TC) and total inorganic carbon (TIC)
concentrations as a function of time since deposition and depth in the
bed. Organic carbon content was calculated as the difference between
these two measurements. An QIC* Direct Injection Module was used for TC
determination and TIC measurements were made by acidifying samples in
the presence of nitrogen gas and recording the amount of C02 released.
Sludge carbon content was determined on samples from treatment plant
holding tanks just prior to loading on an ocean going barge, after
settling through sea water, subsequent to transfer of the settled solids
to a sea floor simulator and at selected time intervals thereafter (30
and 60 days on initial experiments; in a geometrical time sequence on
those currently in progress). Aliquots of all samples were also analyzed
for total solids, total volatile solids and ash content.
Parameters measured to record the sludge chemical characteristics
included sulfate, phosphate, nitrate, and Kjeldahl nitrogen. Profiles
of oxygen concentration, oxidation-reduction potential and pH in the
experimental apparatus were also made. Microbial observations were made
and photographed at 1400X using phase contrast microscopy.
*0ceanography International Corporation, Mod. 0524B-HR. Mention of
trade names or commercial products does not constitute endorsement or
recommendation for use.
357
-------
SIMULATION PROCEDURES
Initial laboratory experiments were designed to measure approximate
rates of organic carbon conversion and changes in chemical conditions in
the bed. Oxygen utilization rates were also measured to compare with
respirometric recordings made during field studies.
Experiments of 42 and 81 days were carried out with the one-
atmosphere acrylic reactor shown in Figure 1. Sea water was pumped from
a 95 liter (25 gallon) reservoir, through a series of baffles designed
to insure uniform channel flow over the bed, and returned to the reservoir.
Reservoir seawater was continuously replenished (5 day residence time)
from a 3800 litre storage tank. Dissolved oxygen concentration was
maintained at 6-7 mg/1 and flow rate controlled to provide a mean current
of 1.2 cm/sec. Fifty millilitre sludge samples were periodically
withdrawn with a 13 gauge needle through a series of sampling septums
along the reactor sidewall.
Two 47 day experiments at 6.8 atmospheres (100 PSI) and 34 atmos-
pheres (500 PSI) were conducted with the Deep Sea Simulator shown in
Figures 2 and 3. A sludge reactor similar to that described above was
sealed inside the pressure vessel.* Sea water was pumped by an air-
hydraulic pump through the end-cap into the reactor, over the sludge bed
and out into the pressure vessel interior. An exit port in the opposite
end-cap permitted sea water to then return to the reservoir. The pressure
pulse caused by the piston-pump was reduced through the use of an
accumulator at the inlet port. Flow rate and internal pressure were
controlled by regulating line air pressure (pump rate) and exit valve
settings. Although initial experiments were at pressures of less than
35 atmospheres (to simulate continental shelf and inner continental
slope site pressures), the simulator system is designed to operate up to
680 atmospheres (10,000 PSI).
Converted surplus U.S. Navy, MK13, Mod. 2, High Capacity 406m (16-inch)
projectile.
358
-------
AIR
oo
en
_n
PUMP
PRESSURE RELIEF
ACCUMULATOR
SEA0WATER
/
SEDIMENT
/
SLUDGE
SEA WATER RESERVOIR
Fig. i LABORATORY SLUDGE REACTOR-MOD I
(I ATMOSPHERE)
-------
09£
>
33
J
t
:0s?
r-i 1
O
m
m
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c
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i§
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-------
Because of reports that controlled decompression and recompression
rates can minimize adverse effects on bacteria (Zobell, 1970) non-
selective sludge sampling through the pressure vessel eid-cap was
discarded in favor of opening the vessel and removing t;ne reactor.
After samples were selectively taken through the side-wan septums the
reactor was returned to the pressure vessel and slow]y recompressed to
the experimental pressure.
- Dissolved oxygen concentrations in sea w+L&r Overly1ng shallow (2
cm.> sludge beds were measured using a ;ealed glass reactor equipped
with «?.n IBC* dissolved oxygen sensor ^th stl>rer (Figure 4). Aerated
seawater^wS^continuously fed into ^nd removed from the reactor to
provide required nutrients and to maintain a 6-7 mg/1 oxygen concentration.
Air and sea water supplies were periodically stopped and the changes in
the oxygen content of the entrapped water was recorded on a strip chart
recorder. The dissolved oxygen probe was calibrated prior to each set
of measurements by using the Azide Modification of the Winkler Titration
described in Standard Methods (APHA, 1971).
LABORATORY CARBON DATA
Tables 1 through 5 in Appendix list the concentrations of total
carbon, total inorganic carbon, total solids, total volatile solids and
ash content of samples from the three experimental systems previously
described. Total organic carbon is calculated. Due to initial compac-
tion, the solids (and hence carbon) concentrations at a given location
in the bed will increase. To visualize only those changes in carbon
concentration due to other causes, the data are presented in normalized
form as mg-C/gram solid.
In the first experiment, the sludge was not pre-settled in seawater
prior to placement in the sludge-bed reactor, hence a relatively high TC
international Biophysics Corporation, Mod. 501-001
362
-------
-------
GO
CTi
CO
DISSOLVED OXYGEN SENSOR
STRIP CHART RECORDER
Fig. 4 LABORATORY SLUDGE RESPIROMETER
-------
of 329.5 mg-C/g solid. Presettling through a 0.75 metre water column
was carried out for all other experiments resulting in a relatively
large decrease in total carbon content to approximately 120 mg-C/g
solid. Careful assessment of such losses is currently being made by
analysis of both sludge and seawater before and after settling. Parameters
determined include total and dissolved carbon (organic and inorganic),
total and volatile solids, and ash content. An understanding of the
form and exchange of sludge organic matter and carbon after dumping in
sea water is critical to the prediction of concentrations in the waste
upon arrival on the sea floor and subsequent degradation rates.
The data in Tables 1 through 5 indicate that, where sea water
continually moved over the sludge bed, TC concentrations decreased more
rapidly and to a greater extent in surface zones than in the deeper
anaerobic regions. Some reservation is made regarding the value of the
surface carbon in that it may represent the characteristic carbon concen-
tration in the bacterial slime layer. This is substantiated by the fact
that surface carbon concentrations remained higher for surface sludge in
the glass (static) reactor where no slime layers developed.
Figures 5 and 6 (plotted data from Tables 1 and 5) indicate that
decreases in total carbon content of subsurface sludge amounted to 71
and 68%, respectively, for 81 and 68 day experiments. Studies of organic
river deposits showed that in 45 to 60 days 50% of the ultimate oxygen
demand (L) was expended. In 7 to 10 months, this requirement reached
90% of L (Fair e_t a]_, 1941). Because measured initial degradation rates
were high, experiments in progress involve a geometrical sampling pattern
(0, 1/4, 1/2, 1, 2, 4, 8, 16 days etc.) to better document the first
stages of degradation.
A comparison of the differences in initial carbon concentrations
(Figures 5 and 6) and associated slopes of the Total Carbon versus Time
364
-------
co
01
on
I ATM. REACTOR
TEST NO. I
DATA-TABLE I
BOTTOM (2 cm)
SURFACE (siime layer)
20
40
TIME (days)
60
80
Fig. 5 Total Carbon vs. Time
(1 atmosphere reactor)
-------
oo
0}
en
GLASS REACTOR
TEST NO. I
DATA-TABLE 5
BOTTOM (2 cm)
40
TIME (days)
Fig. 6 Total Carbon vs. Time
(laboratory respirometer)
-------
plots at these points suggests that the rate of change of carbon mass is
proportional to the mass present. This might be described by a first
order equation, viz.:
f = -KC (2)
where
C = Total carbon mass per unit volume in deposit at any time t
K = Reaction velocity constant
Using the solution to equation (2) in the form of
K = |ln§ (3)
r Lo
where
C = Initial total carbon mass per unit volume
the reaction velocity constants calculated for each experiment are given
in Table 6. These values can be compared to sludge benthal oxidation
velocity constants measured by Fair, et a!. of 0.007 to 0.010 (per day)
and sludge stabilization rate constants by Rudolfs and Mohlman of 0.010
and 0.012 (per day). Work by McGowan, Frye and Kershaw on English river
muds produced reaction constants of 0.001 to 0.005 (per day) (McGowan,
et aj^, 1913).
Although much more data is required, some insight into the degrada-
tion rates and variation in these rates can be gained from data obtained
to date. There appears to be a decrease in the reaction velocity under
367
-------
Table 6 REACTION VELOCITY PARAMETERS (K)
dC _ vr
dt ' "KC
EXPERIMENT
T
1
EXPERIMENT
II
Flowing
1 Atmosphere Reactor
Surface
0.046
(4l)
0.024
(81)
0.015
2 cm.
0.030
0.015
(81)
0.011
Flowing
Pressure Reactor
Surface
100
0.017
(47)
500
0.016
(47)
2 cm.
PSI
0.006
(47)
PSI
0.007
(47)
Semi - Static
Glass Reactor
Surface
0.013
0.010
(68)
2 cm.
0.020
0.017
(68)
en
00
HOS. in parentheses designate time (days) into the test.
-------
pressure conditions (K = 0.006, 0.007). Jannasch (1971) has shown that
microbial degradation rates of selected organic substrates in the deep
ocean (5000 metres) are 10 to 100 times slower than at 1 atmosphere and
similar temperatures. Paul, et. al. (1971) attributes the decreased
microbial metabolic rates to pressure (and low temperature) inhibition
of cellular acid uptake. (
In tests where the reaction velocity is evaluated at two points in
time, K appears to have decreased implying that a modification to equation
2 must be made to appropriately describe the carbon changes. Fair
points out that the constant K describes the initial availability of the
substrate but does not describe the reduction in this availability with
time. He suggests the inclusion of a retardation factor of the form
— = -( K
— -
dt M + at
where
a = Coefficient of retardation which is dependent on type of
organic matter present and condition of the environment
Whether this equation or one of another form describes carbon
changes in an ocean sludge bed will become apparent by analyses of data
from detailed experiments now in progress.
369
-------
LABORATORY OXYGEN CONSUMPTION RATES
Initial oxygen uptake of a 2.0 cm bed of anaerobically digested
2
sludge* (measured with the apparatus in Figure 4) was 2.72 g-^/m /day.
After 53 days exposure to aerated sea water, this rate had decreased to
9
0.95 g-09/m /day. Anaerobically digested sludge from a New York sewage
2
treatment plant** required 0.72 g-O^/m /day initially, decreasing to
0.55 g-02/m2/day in 20 days.
OTHER LABORATORY MEASUREMENTS
Prior to concentrating on measurements of carbon changes in a
sludge bed, some data on organic nitrogen and phosphorus content of the
bed were also collected (Table 7). In all experiments, there was a
considerable decrease in the total dissolved and suspended organic
nitrate and phosphate content suggesting biochemical conversion and/or
transfer to the sea water (i.e., solubilization and subsequent loss due
to compaction).
Redox-potential (E, ) profiles on the shallow beds showed a typical
change from +150 millivolts at the bed surface to -100 millivolts at 2
cm. deep. Current experiments with a redesigned reactor will permit Eh
profiles to bed depths of 50 cm.
The diffusion of hydrogen sulfide into the sediments beneath the
sludge could easily be seen due to the downward progression of a dark
black zone in which iron-sulfide was formed. The discoloration was
typically detected 20 to 24 days after start of the experiment and
progressed downward at a rate of 0.09 mm/day. At the conclusion of an
84 day experiment the Fe-S band was 7 mm in thickness.
* Corvallis Wastewater Treatment Plant, Corvallis, Oregon
**Nassau County Sewage Treatment Plant, East Rockaway, New York
370
-------
TABLE 7 Laboratory Nutrient Measurements
SLUDGE
NITROGEN
and
PHOSPHORUS
(g. /kg. dry solid)
N
I
T
R
0
G
E
N
V
H
0
s
P
H
0
R
U
S
Total Kjeldahl
NH3 - N
Organic - N
Total
Hydro lyzable
+ Ortho
Organic - P
One atmosphere reactor (NYK)
As
Received
52.10
12.60
39.50
16.40
13.30
3.10
V41
Surf
10.40
0.63
9.77
3.11
2.28
0.83
2 cm.
13.30
0.70
12.60
3.54
2.09
1.45
TQ + 81
Surf
7.84
0.40
7.44
2.61
2.07
0.54
2 cm.
11.50
0.58
10.92
2.98
_
—
Dressure Reactor (NYK)
As
Received
42.00
3.40
38.60
19.40
16.10
3.30
T + 47
0
Surf
10.70
0.33
10.37
4.50
3.20
1.30
2 cm.
17.10
0.44
16.66
6.75
4.64
2.11
Semi-static Reactor (CORV)
As
Received
26.50
3.71
22.79
11.55
9.03
2.52
V46
Surf
13.00
0.49
12.51
4.89
3.73
1.16
2 cm.
9.32
0.3J
8.94
3.79
2.68
1.11
T + 68
0
Surf
13.00
0.46
12.54
4.73
3.42
1.31
2 cm.
7.0!
0.3?
6.6;
2.6^
2.42
0.25
co
•vj
-------
Due to compaction of the settled solids, experimental sludge beds
decreased to approximately 1/2 their original thickness during the 60 to
80 day tests. Initial rates are very high (i.e., 54 to 56% compaction*
within the first 12 hours). At the conclusion of one day, compaction is
typically 60% complete. Thereafter, decreases in bed thickness occur
very slowly at a rate of 1.2mm/day.
Pratt et. al. (1973) gave a description of microbial colonies
formed on the surface layers of sludge during laboratory experiments.
The experiments described in this paper confirmed their observations
that an initial predominance by vibrio-like rods was followed by a
succession of trichome-producing bacteria possibly of the genera Thiothrix
and Beggiatoa (Breed, et. al., 1957). In the pressure experiments,
filamentous bacteria also predominated the surface slime layer, but the
encased granules did not occur in long chains (when observed after a 2
hour decompression from 34 atmospheres). Short segments contained
typically 3 or 4 granules. Zobell et. al., (1950) found that some
barotrophic organisms modify their morphology to accommodate higher
pressures and that changes can be expected in some cases upon decompression.
No dominance of a single species of bacteria occurred deeper in the
sludges at either one atmosphere or under pressure.
FIELD STUDY
A four week field study was devoted to a preliminary assessment of
sludge dispersion and degradation characteristics upon release to
offshore waters. The research site, located in 15 metres of water, was
instrumented with current meters, water quality sensors and station
markers (Figure 7). A baseline survey included areal sampling of sea
water and bottom sediments to establish pre-release carbon, nitrogen,
phosphorus, and volatile matter levels. Anaerobically digested sludge
released near the bottom at the upstream end of the marked site formed a
patchy (0-1 cm. thick) sludge bed 12 metres wide and 60 metres in length.
Compaction is defined as initial minus bed thickness at any time t, divided
by initial minus terminal bed thickness at the experiment conclusion.
372
-------
OJ
•-J
co
SUBSURFACE
FLOATS
Q-15 HYDROPROOUCTS
CURRENT METER
BRAINCON
CURRENT
METERS^*
UNDERSEA
INSTRUMENT
CHAMBER
BENTHIC RESPIROMETERS
ANCHOR
WEIGHTS
SLUDGE
Fig. 7
SEA FLOOR RESEARCH SITE
Freeport, Grand Bahamas
-------
Samples of the bed and near bottom waters were transported ashore for
analysis and preparation for shipment. Heavy seas (estimated significant
wave height of 3.5 metres) and bottom currents (to 0.5 knots) effectively
removed the settled sludge within several days of the release.
All samples taken during the field exercise have not been analyzed
and current meter data has yet to be completely reduced. Pre-release
organic carbon concentrations in near bottom and interstitial waters
ranged from 0.9 to 1.1 mg-C/liter. Samples taken in the plume contained
2.0 to 2.7 mg-C/1 and post release bottom samples (in the bed zone)
contained 3 to 20 mg-C/1. Within 6 days bottom and interstitial water
organic carbon concentrations had returned to approximately 1 mg-C/1.
IN-SITU OXYGEN UPTAKE
Oxygen consumption rates of anaerobically and aerobically digested
sludges were measured using bottom mounted 76 and 50 cm. diameter trans-
parent acrylic hemispheres (Figure 8). The larger dome contained a
temperature/dissolved oxygen probe with magnetic stirrer to insure
adequate sea water flow over the sensor membrane. A 30 metre cable
linked the sensor to a readout meter and strip chart recorder within the
nearby habitat used as living quarters. As required, a submerged pump
replenished the respirometer with oxygen laden seawater. The second
hemisphere used a recirculation pump system to insure movement of seawater
in contact with the sludge bed past an externally mounted oxygen probe
chamber and back into the dome. The probe meter and strip chart recorder
were mounted on the sea floor adjacent to the dome.
The oxygen utilization rate of aerobically digested sludge varied
from an initial rate of 3.74 grams of 02/m2/day to 2.0 g-02/m /day after
65 hours. Anaerobically digested sludge oxygen use was initially 2.51
g-02/m2/day and decreased to 1.68 g-02/m /day in 70 hours. Oxygen
374
-------
col
1
>^^B^^
Fig. 8 Sea Floor Respirometer Measurements
-------
uptake rates for marine sediments in Long Island Sound have been measured
2
at 0.03 g-02/m /day and for sediments near Woods Hole Oceanographic
Institution rates ranged from 0.01 to 0.007 g-09/m2/day (Carey, 1967).
EXPERIMENTS IN PROGRESS
To account for the relatively large losses of carbon in the sludge
bed, the amounts of carbon in the seawater moving over the bed and in
gas emanating from the bed are also being monitored. By centrifuging
(16,300 G's for 1 hour) and filtering (0.45 micron), a distinction is
being made between total, dissolved and particulate carbon concentrations
in the sludge. Such measurements give the added definition required to
quantify solubilization rates, expulsion losses due to bed compaction,
and conversion to dissolved and gaseous end products. A redesigned
reactor allows more detailed sampling of sludge beds to 50 centimetres
(Figure 9). A gas trap has been included and provisions for gas chromat-
ographic analyses (carbon dioxide and methane) have been made. The sea
water flowing over the bed is sealed from the atmosphere, saturated with
carbon-dioxide free air and monitored for changes in carbon concentrations,
Although the forms of carbon in a domestic sludge prior to disposal
can be fairly well specified, the changes in these forms during settling
through sea water and during benthic degradation have yet to be determined
in detail. Experiments in progress have been designed to partly fill
this information gap. In addition, a preliminary (conceptual) sludge
bed carbon model is being developed in an effort to better describe
degradation and exchange mechanisms. The model allows for advective and
diffusive transfer of particulate, dissolved and gaseous fractions of
the sludge carbon between bottom waters, aerobic and anaerobic regions
in the bed, and sediments beneath.
376
-------
GAS SAMPLING SEPTUMS
CO
--J
I
AIR
CARBON
DIOXIDE j\
SCRUBBERS ^
A WATER FROM
.DING TANK
»-
^
V
I
1]
]
n
L
]-=
1 FLOW
? METER
SLUDGE
SAMPL NG ,J"N
SEPTUMS
SEA WATER
=-D
SLUDGE
SEDIMENT
/
r
" " 1
PUMP SEA WATER RESERVOIR
rf
Fig. 9 LABORATORY SLUDGE REACTOR-MOD It
(I ATMOSPHERE)
-------
CONCLUSIONS
Field and preliminary laboratory experiments have provided data on
the decreases in sludge bed carbon concentrations and oxygen consumption
rates. Further experiments are being devoted to better definition of
initial carbon losses and documentation of carbon decreases in deeper
beds. Measured signficant losses of organic carbon upon settling the
sludge through a sea water column are being better documented because of
possible ramifications regarding disposal procedures. A conceptual
mathematical model of sludge bed dissolved, particulate and gaseous
carbon fractions is being formulated in an effort to better understand
the mechanisms and transfer rates for carbonaceous materials in stabil-
izing sea floor sludges.
Decreases in sludge bed total carbon content (grams of carbon per
gram solid) amounted to 71 and 68% respectively for 81 and 68 days
experiments at 1 atmosphere. Sludges subjected to pressures of 6.8 and
34 atmospheres had a carbon content loss of approximately 30% in 47
days. Reaction velocity constants (K) of 0.006 and 0.007 for the pressure
experiments were lower than for experiments at 1 atmosphere where K
ranged from 0.010 to 0.046.
The in-situ oxygen consumption rate of an aerobically digested
2 2
sludge ranged from 3.74 grams 02/m /day to 2.0 g-Op/m /day after 65
hours. For an anaerobically digested sludge the initial rate of 2.51 g-
9
0?/m /day in 70 hours.
Laboratory measurements with anaerobically digested sludges revealed
significantly different oxygen consumption rates depending on the sludge
source. Sludge from a local treatment plant had an initial uptake rate
of 2.72 g-02/m2/day which decreased to 0.95 g-02/m2/day after 53 days.
378
-------
p
Sludge from a New York treatment plant required 0.72 g-00/m /day initially
2
and 0.55 g-02/m /day after 20 days exposure to aerated seawater.
379
-------
APPENDIX
380
-------
Table 1. Carbon and Solids Determinations 1 Atm. Reactor, Test 1
CO
CO
1 ATMOSPHERE REACTOR
TEST 1
(N.Y. STP SLUDGE)
TOTAL CARBON
mg-c/1 sample
mg-c/g solid
TOTAL INORGANIC CARBON
mg-c/1 sample
mg-c/g solid
TOTAL ORGANIC CARBON*
mg-c/1 sample
mg-c/g solid
Calculated
TOTAL SOLIDS
mg/1 sample
mg/g sample
TOTAL VOLATILE SOLIDS
mg/1 sample
mg/g sample
% total solids
ASH (measured)
mg/1 sample
mg/g sample
% total solids
To
ALL DEPTHS
12620
329.5
234.1
6.1
12385.9
323.4
38300
39.8
27600
28.7
72.1
10701
11.1
27.9
TQ + 41 DAYS
SURFACE 2cm
1992 5557
48.0 97.0
115.7 128.5
2.8 2.2
1876.3 5428.5
45.2 94.8
41471 57289
40.9 56.6
9140 17164
9.0 17.0
22.0 30.0
32331 40125
32.0 39.7
78.0 70.0
TQ + 81 DAYS
SURFACE 2cm
2110 5969
46.5 94.0
26.5 96
0.6 1.5
2083.5 5873
45.9 92.5
15418 63490
45.0 62.5
10566 14923
10.5 14.7
23.3 23.5
S4882 48567
33.1 47.8
76.8 76.5
NOTE: T sludge not settled through a sea water column before being placed in reactor (this test only),
-------
Table 2 Carbon and Solids Determinations 1 Atin. Reactor, Test 2
oo
oc
PC
1 ATMOSPHERE REACTOR
TEST 2
(N.Y. STP SLUDGE)
TOTAL CARBON
mg-c/1 sample
mg-c/g solid
TOTAL INORGANIC CARBON
mg-c/1 sample
mg-c/g solid
TOTAL ORGANIC CARBON*
mg-c/g sample
mg-c/g solid
Calculated
TOTAL SOLIDS
mg/1 sample
mg/g sample
TOTAL VOLATILE SOLIDS
mg/1 sample
mg/g sample
% total solids
ASH (measured)
mg/1 sample
mg/g sample
% total solids
To
ALL DEPTHS
9584
113.5
423.7
5.0
9160.3
108.4
84468
83
21980
21.6
26.0
62488
61.4
73.9
To + 42
SURFACE
2903
59.6
72.5
1.5
2830.5
58.1
48729
48.4
10355
10.3
21.3
38383
38.1
78.8
2cm
9440
71.5
186.9
1.4
9253.1
70.1
132072
125
22794
21.7
17.3
109278
103.8
82.7
-------
Table 3 Carbon and Solids Determination, Pressure Vessel, 100PSI
GO
•00
OJ
PRESSURE VESSEL REACTOR
1 OOPS I
/ M v CTn ci i inp r \
(N.Y. STP SLUDGE)
TOTAL CARBON
mg-c/1 sample
mg-c/g solid
TOTAL INORGANIC CARBON
mg-c/1 sample
mg-c/g solid
TOTAL ORGANIC CARBON*
mg-c/1 sample
mg-c/g solid
Calculated
TOTAL SOLIDS
mg/1 sample
mg/g sample
TOTAL VOLATILE SOLIDS
mg/1 sample
mg/g sample
% total solids
ASH (measured)
mg/1 sample
mg/g sample
% total solids
T
O
ALL DEPTHS
8425
126.0
180.5
2.7
8244.5
123.3
66872
66.2
22022
21.8
32.9
44850
44.4
67.1
T +
0
SURFACE
2486
55.4
89.6
2.0
2396.4
53.4
44843
44.2
9988
9.8
22.3
34846
34.3
77.7
47 DAYS
2 cm
9250
96.1
168.6
1.8
9081
94.4
96222
93.5
24829
24.1
25.8
71393
69.4
74.2
-------
Table 4 Carbon and Solids Determinations, Pressure Vessel, 500PSI
CO
00
PRESSURE VESSEL
500PSI
(N.Y. STP SLUDGE)
TOTAL CARBON
mg-c/1 sample
mg-c/g solid
TOTAL INORGANIC CARBON
mg-c/1 sample
mg-c/g solid
TOTAL INORGANIC CARBON*
mg-c/1 sample
mg-c/g solid
Calculated
TOTAL SOLIDS
mg/1 sample
mg/g sample
TOTAL VOLATILE SOLIDS
mg/1 sample
mg/g sample
% total solids
ASH (measured)
mg/1 sample
mg/g sample
?' total solids
To
ALL DEPTHS
10110
119.7
256.3
3.0
9853.7
116.7
84468
83
21980
21.6
26.0
62488
61.4
73.9
T +
0
SURFACE
2580
56.3
63.1
1.4
2516.9
55.0
45789
45.2
8797
8.7
19.2
36992
36.6
80.8
47 DAYS
2cm
10969
83.7
221.2
1 . 69
10747.8
82.0
131047
124. 2
23988
22. 8
18. 3
107061
101.7
81 . 7
-------
Table 5 Carbon and Solids Determinations, Glass Reactor, Test 1
GO
oo
en
SEMI-STATIC GLASS REACTOR
TEST 1
(Corvallis STP Sludge)
TOTAL CARBON
mg-c/1 sample
mg-c/g solid
TOTAL INORGANIC CARBON
mg-c/1 sample
mg-c/g solid
TOTAL ORGANIC CARBON*
mg-c/1 sample
mg-c/g solid
Calculated
TOTAL SOLIDS
mg/1 sample
mg/g sample
TOTAL VOLATILE SOLIDS
mg/1 sample
mg/g sample
% total solids
ASH (measured)
mg/1 sample
mg/g sample
% total solids
To
ALL DEPTHS
11278
169.6
805.7
12.1
10472
157.5
66490
68.7
28868
29.8
43.4
37625
38.9
56.6
TQ + 46 DAYS
SURFACE 2cm
6715 11274
94.7 66.1
N/M N/M
70890 170473
71.2 167.0
20393 31463
20.5 30.8
28.8 18.4
50497 139010
50.7 136.2
71.2 81.6
TQ + 68 DAYS
SURFACE 2cm
4897 10208
84.0 54.5
50.1 204.8
0.8 1.1
4846.9 10003
83.2 53.4
58259 187492
58.9 173.8
14824 31282
15.0 29.0
25.4 16.7
13435 156210
44.0 145.0
74.6 83.3
-------
ACKNOWLEDGEMENTS
I wish to express my appreciation for the many hours of careful
guidance and technical support by my Oregon State University doctoral
committee members, Dr. D. J. Baumgartner, Dr. D. A. Bella, Dr. L. R.
Brown, Dr. S. Corder and Dr. L. I. Gordon. This research would not have
been possible without the award of a 2 year Environmental Protection
Agency research fellowship and the agency's additional provision of
facilities, equipment, and personnel and funding as required. For the
field experiments, the Manned Undersea Science Office of NOAA arranged
for the use of the HydroLab habitat and the Undersea Instrument Chamber.
They also provided financial support and personnel for which I am grateful
Finally, I wish to thank the sewage treatment plant operators in Oregon,
New York and Florida for so patiently responding to my many requests for
sludge.
386
-------
REFERENCES
American Public Health Association. Standard Methods for the Examination
of Water and Wastewater. 13th Edit., APHA, Washington, D.C. (1971).
Balmat, J. L. Biochemical Oxidation of Various Particulate Fractions of
Sewage. Sewage Works, 29, 7, 758 (1957).
Barnett, M. A., R. E. Davis, M. E. Silver and R. R. Warner. The Ecology
and Oceanography of Sewer Outfalls. Scripps Institution of Oceano-
graphy, SIO Ref. No. 70-18 (1969).
Breed, R. S., E. G. D. Murran, and N. R. Smith. Sergey's Manual of
Determinative Bacteriology, The Williams and Wilkins Co., Baltimore
(1957).
Brown, R. B. and E. H. Shenton. Evaluating Waste Disposal at Sea - The
Critical Role of Information Management. Contract PH 86-68-203.
Bureau of Solid Waste Management, EPA (1971).
Buelow, R. W. Ocean Disposal of Waste Materials. In: Ocean Science
and Engineering of the Atlantic Shelf. Trans. Nat. Symposium,
Phil., PA (1968).
Buzas, M. A., J. H. Carpenter, B. H. Ketchum, J. H. McHugh, V. J. Norton,
D. J. O'Connor, J. S. Simon and D. K. Young. Smithsonian Advisory
Committee Report on Studies of the Effects of Waste Disposal in the
New York Bight. Oceanography and Limnology Program, Office of
Environmental Sciences, Smithsonian Institution, Wash. D. C., NTIS
AD-746960 (1972).
Carey, A. G. Jr. Energetics of the Benthos of Long Island Sound Part I,
Oxygen Utilization. Bulletin of the Bingham Oceanographic Collection,
19, Article 2, pp. 136-144, April (1967).
387
-------
Council on Environmental Quality. Ocean Dumping - A National Policy. A
Report to the President. U.S. Govt. Printing Office, Washington,
D.C. (1970).
Dewling, R. T. Statement: Ocean Disposal. Briefing Report, Ocean
Dumping in New York Bight Since 1973. U.S. Environmental Protection
Agency, Region II, Surveillance and Analysis Division, April (1974).
Fair, G. M., E. D. Moore and H. A. Thomas, Jr. The Natural Purification
of River Muds and Pollutional Sediments. Sewage Works J. 13, 2,
270 (1941).
Gross, M. G. New York City - A Major Source of Marine Sediment. Marine
Sciences Research Center Tech. Rept. 6(3), Series No. 2 (1969).
Gross, M G. Preliminary Analyses of Urban Wastes, New York Metropolitan
Region. Marine Sciences Research Center, State University of New
York, Tech. Rpt. No. 5 (1970).
Home, R. A., A. J. Makler and R. C. Rossello. The Marine Disposal of
Sewage Sludge and Dredge Spoils in the Waters of the New York
Bight. Woods Hole Oceanographic Institution Tech. Memo No. 1-71
(1971).
Jannasch, H. W. Microbial Degradation of Organic Matter in the Deep
Sea. Science, 171, 672-675, Feb. 19 (1971).
Kuznetsov, S. I. Decomposition of Organic Matter in Bottom Sediments.
IBP Handbook No. 23, "Techniques for the Assessment of Microbial
Production," p. 24 (1972).
McGowan, G., C. C. Frye and G. B. Kershaw. Results on Stream Observa-
tions, 1909 to 1912. Royal Commission on Sewage Disposal, 8th
Report, Appendix 148 (1913).
388
-------
Mohlman, F. W. Oxygen Demand of Sludge Deposits. Sewage Works Journal,
10, 613 (1938).
National Marine Fisheries Service. The Effects of Waste Disposal in the
New York Bight Summary Final Report. Mid. At!. Coastal Fisheries
Ctr., Sandy Hook Marine Lab., Highlands, NJ (1972).
Paul, K. L. and R. Y. Morita. Effects of Hydrostatic Pressure and
Temperature on the Uptake and Respiration of Amino Acids by a
Facultatively Psychrophilic Marine Bacterium. J. Bact., 108, No.
2, 835-843, Nov. (1971).
Pratt, S. D., S. B. Saila, A. G. Gaines, Jr., and J. E. Krout. Biological
Effects of Ocean Disposal of Solid Waste. Marine Technical Report
Series No. 9, University of Rhode Island (1973).
Rudolfs, Willem. Stabilization of Sewage Sludge Banks. Industrial and
Engineering Chemistry, 30, 337 (1938).
Schroder, E. D., and A. W. Busch. Mass and Energy Relationships in
Anaerobic Digestion. Journal of the Sanitary Engineering Division,
ASCE, 92, SA1 Paper No. 4655, 85 (1966).
Zobell, C. E. Pressure Effects on Morphology and Life Processes of
Bacteria. High Pressure Effects on Cellular Processes. A. M.
Zimmerman, Ed., Academic Press (1970).
Zobell, C. E., and C. M. Oppenheimer. Some Effects of Hydrostatic
Pressure on the Multiplication and Morphology of Marine Bacteria.
J. Bacteriology 60, 771-781 (1950).
389
-------
390
-------
Bioassay Methods and Impact Evaluation of Ocean Disposal Sites
D. Dorfman Ph.D. Monmouth College, West Long Branch, New Jersey
J.M. McCormick Ph.D. Montclair State College, Upper Montclair,
New Jersey
391
-------
Introduction
The use of ocean waters as final receivers of
effluents and sludges (a liquid containing a certain percentage
of solids) exists because of difficulty with land disposal
due to (1) lack of adequate space for acceptance of large
quantities of effluent and sludge, (2) possible adverse
effects on the water table (eg. heavy metals introduced
from industrial effluents and sludges, and nitrates and
phosphates from both industrial and domestic effluents and
sludges), (3) aesthetics, and (^) high land costs.
Coastal effluent and sludge discharges into
ocean waters will probably expand in the future due to the
effort to provide cleaner inland waters. Because the
coastal concentration of the population is increasing,
the volume of waste, both domestic and industrial, is
increasing. In addition, a number of nuclear-powered
generating plants ar§ planned for the coastal region in
order ts utilise th© large ^uantitieg of water needed for
cooling. The resultant warm-water discharges will Increase
temperatures in marine waters.
The assimilative capacity of the oceans for wastes
is not limitless. Dramatic changes, both biological and
physical, occur ofer undefined areas around effluent
discharges and disposal sites.
392
-------
Ocean disposed effluents and solids, in quantity,
result in Increased nutrients and toxicants, have a biochemical
and chemical oxygen demand, reduce directly or indirectly
the dissolved oxygen, alter salinities, increase turbidity
and temperatures, smother benthic organisms, and probably
cause a number of synergistic and antagonistic reactions of
undetermined consequences.
Nutrients, obtained from domestic and industrial
effluents and sludge, such as nitrogen and phosphorus, serve
as growth factors for algal plant life (Fig. 1), This may
be beneficial if the type plant species and the additional
organisms could be utilized as a food source by animals
higher in the food chain. Chen and Orlob (1972) found
increased numbers of an amphiurid sea star and amphipods
in the vicinity of the San Diego outfall. Population maxima
were found about two miles from the outfall. There may
however be detrimental effects of increased nutrient loads
in concentrated areas. Concentrations of nutrients may
cause a bloom of organisms responsible for red tide. In
addition, since all plants are not utilized by animals,
there is a constant rain of dead, uneaten organisms onto
the sea floor. This may, to an undetermined degree, increase
the rate of eutrophication.
Toxins, including arsenic, cadmium, copper,
cyanide, lead, nickel, mercury, and zinc, may inhibit
or kill certain plants or animals. Toxins which have been
diluted to low levels in the ocean may be accumulated
within some organisms due to their tendency to concentrate
393
-------
certain toxic materials. Filter feeders, such as oysters
and clams, are examples of such organisms (Table 1).
Organisms higher in the food chain that feed on concentrators
of toxins may suffer adverse physiological effects. For
example, mercury discharged from a factory in Minamata,
Japan, was diluted in a bay, but accumulated in edible
fish, which resulted in a number of cases of mercury
poisoning in humans.
The biochemical oxygen demand (B.w»D.) of effluents
and sludge may make water unsuitable for certain animals and,
concomitantly, may be indirectly responsible for introducing
different organisms (eg. anaerobic bacteria and blue-green
algae) to the discharge area. This situation could occur
if the effluent consumed the available dissolred oxygen in
the area about the discharge site. Depletion of dissolved
oxygen to certain levels (eg. below 5*0 mg/1) can make the
environment intolerable for some organisms such as certain
fish species. In an intolerable environment the animals
disappear or are killed. Complete depletion can result in
noxious odors with the destruction of aesthetic values
and elimination of both contact and noncontact recreation
activities. In addition, the new conditions may result in
tha establishment of undesireable organisms (eg. anaerobic
bacteria that produce noxious hydrogen sulfide gas).
394
-------
Salinity changes, due to the introduction of
fresh water, occur In the outfall or dumping areas.
Effluent and sludge are usually warmer and less saline than
seawater and rise to form plumes when introduced through
an outfall pipe. The currents disperse and dilute this
freshwater addition, but for some area above and around
the dispersal point the ocean salinity is reduced.
Marine animals and plants that can tolerate only narrow
salinity changes would disappear, or attempt to avoid
these diluted waters.
Thermal discharges may have adverse impacts on
the marine environment in several ways. Heat affects the
physical properties of water (eg. density, viscosity, and
reduces the solubility of oxygen in water). Heat speeds
the rate of chemical reactions, and of biological reactions.
Increased-temperatures may reduce the number of species in
the community and stimulate excessive populations of
individual species. Increased temperatures may result
in synergistic reactions (eg. increased temperatures may
heighten the toxic effects of some materials). Finally,
sudden temperature changes may have an immediate adverse
effect on fish and other biota. Also, if the dispersal
current carries a thermal plume across an access point
(eg. a bay, or river mouth) movements of migratory species
may be prevented.
395
-------
Increases in turbidity due to sludge dumping
reduces incident light. This results in reduced photosynthetic
activity and concurrently, make less food available for those
animals that feed on the primary producers.
Studies that have been made of specific sludge
dumping grounds indicate that sludge disposal may (Barber
and Krieger, 19?0; Grigg and Kiwala, 1970; National Karihe
Fisheries Service, 1972) or may not (Shelton, 1971;
Davey, 1972) adversely effect marine or estuarine habitats.
The variations' reported are probably due to the difference
in the type of, or the constituents within, sludge disposed;
to the behavior of currents in the disposal site; to the
quantity of disposed materials and the size of the
dispersal site; and to combinations of tr.ase and other
oceanographic factors, including water chemistry. A
number of Interactions can occur that would alter the
toxicity of the effluent or sludge. ?or example, high
phosphate additions might render lead less toxic due to
precipitation (Shelly and Steucek, 1973). Lee (1973) has
indicated that the toxicity of a pollutant may depend
on the form in which the element is found and that may
depend on such factors as the pH and redox potential
of the receiving water.
396
-------
Assay Techniques
Any bioassay or impact evaluation program, when
applied to a particular outfall, should consider each of
the effects previously mentioned.
A number of both laboratory and field procedures
are available today to determine the effects of ocean
disposed materials on plants and animals. However, to
perform bioassays that require the use of marine waters,
some modifications of the standard techniques used for
freshwater bioassays (Standard Methods, 1971) are necessary.
For example, organisms with some degree of salt tolerance
must be employed. In addition, the apparatus utilized in
the performance of laboratory tests should not be
constructed of metals or toxic substances when these parts
would come into contact with salt water. The use of
receiving waters, ie. •natural' waters, for determining
effects of effluents or sludges, while preferred, may pose
problems. Diluting waters of unknown quality may, at different
times, have possible additive, antagonistic, or synergistic
effects on the effluent or sludge to be examined. Further,
utilization of receiving waters may, at any undefined time,
result in acute toxic effects due, not only to the discharged
material, but also to undetermined toxicants in the
diluting assay waters. Since receiving waters may be of
questionable quality, and may be difficult to obtain,
waters of a constant quality with regard to their average
397
-------
dissolved mineral content could be prepared. This would
provide waters with uniform composition, and avoid
background toxic materials. This would result in an assessment
of the toxicity of the effluent as if discharged into a
non-stressed body of water.
Lee (19>?3) indicated that the oxidation state,
solubility, complexation, ionic strength, type and amount
of solids, salt ratios and concentrations, and organic
content of waters cause changes in the environment of a
bioassay that may affect the results of the test. He
indicates that cooperation between chemists and biologists
is necessary in order to produce meaningful results for
bioassays.
Types of Bioassays
Two types of bioassays may be considered;
A. Static bioassays.
A static bioassay is one in which the test organisms
are maintained in vessels containing solutions of various
dilutions of the toxic material. The concentration at vihich
half the organisms remain after a predetermined period
(from minutes to 24-, i|-8, or 96 hours) is known as the
tolerance level median (TLm). This gives an estimate of the
acute toxicity of the material. Sublethal toxicity may be
determined in a similar way except that the effect of the
toxin on some physiological activity, such as respiration,
is determined. The static bioassay is a relatively simple
technique, and may, in some cases, be used in the field.
398
-------
This test has some shortcomings. Some, or all,
of the toxicity of the test solution may be lost during
the assay due to absorption, adsorption or volatilization
of the toxin. In addition, the test organisms may excrete
wastes that change the character of the test water.
B. Flow-through bioassays.
A flow-through bioassay differs from the static
bioassay in that the test solution is allowed to flow into
and out of the vessel containing the test organisms,
maintaining a. constant chemical environment. For this reason,
the flow-through system is the preferred method for longer-
term assays.
The organisms selected for either the static or
flow-through bioassay should be: (1) readily available,
(2) sensitive, to some degree, to the toxin or toxins of
interest, (3) relatively easy to handle and observe, (^) an
organism that is found part or all of the time near the area
affected by the effluent or sludge. It might also be
desireable to use a "standard" organism, such as the brine
shrimp, Artemia salina (Pig. 2), for all ocean outfalls
regardless of location, so that comparisons among outfalls
could be made. It would be advantageous to use more than
one organism, including one or more standards, and one
or mote locals. Temperature and salinity at the time of
capture should be used 33 the test temperature and salinity
when using field organisms to evaluate toxicity. This
reduces the problems associated with longer term
acclimation of the organism, and of possible stresses
399
-------
arising from incomplete acclimation.
Certain animals are not generally considered
as acceptable test organisms because of a considerable
tolerance, relative to other organisms, to adverse conditions.
The mummichog, Fundulus heteroclitis, is such an organism.
However, because of its abundance in certain waters, for
example, Newark Bay, New Jersey, any assay performed with
this water certainly should include this species, since
it is probably the main food source of carnivorous
fishes in the bay.
A number of other invertebrates have been used
as bioassay organisms, including hydrozoans, amphipods,
isopods, shrimp, crabs, clams, oysters, and snails.
Woelke (1972), has detailed a bioassay procedure
using embryos of a commercially valuable marine organism,
the Pacific oyster (Crassostrea gigas). This bioassay
can be applied to marine waters at any time of the year
with more ease and reproducibility than certain other bioassays.
The test determines the number of abnormal 48-hour Pacific
oyster embryos when exposed to a level of stress, or toxicant.
The principle measurement employed has been the percentage
of abnormal larvae found after 48 hours exposure of fertilized
oyster eggs to the variable under consideration. Failure to
develop as normal larvae results in their death, breaking
the life cycle of the oyster at the reproductive stage.
He recommends a laboratory with a flowing seawater system
that is pollution' free.
400
-------
To determine the effects of ocean disposal on
adult clams or oysters, a long-term flow assay could be
performed to determine the effect of disposal waters on
gaping times. This could be accomplished by pasting the
clams or oysters to a basin, attaching one valve to a
kymograph apparatus, and exposing one group of test
organisms to disposal waters and a second to control
waters (either 'natural* or synthetic) (Dorfman,
unpublished data).
Problems with static and flow-system bioassays
include; (1) laboratory conditions that do not wholly
emulate field conditions (eg. the choice of synthetic
seawater or filtered local seawater). Unlike the typical single
stress laboratory test, the natural environment is liable
to create several different stresses simultaneously.
(2) the difficulty in duplicating effluent or sludge
composition, which may vary hourly, or daily (this could
be minimized by performing repeated bioassays, and by using
grab samples of the materials to be disposed. (3) the
virtual impossibility of assaying the effect of the
disposed material on all of the organisms that live for
part of all of their lives in the disposal area. (^) the
questionable extrapolation of data, obtained for one or
more species to other species that may or may not react
in a similar fashion (ie. with the same response).
401
-------
The ideal situation in determining the toxiclty
of an effluent or sludge into a discharge area includes the
determination of its effect on the most susceptible organism
naturally occurring in the area, that is the"weakest link"
in the food chain. Since the response of the weakest organism,
or the most susceptible organism, to the effluent may not
be determined because the weakest organism may not have
been selected as the test organism, an application factor
could be applied to the data suggested by the TLjn, or
from data obtained from sub-ecute responses during
flow-through bioassays. The TI^ as an acceptable number
for allowable dilution is not in itself satisfactory, since
the death of 50 percent of the test organisms is not an
acceptable rate of mortality for anything other than the test
itself. In addition, the TL^ offers no clue as to the
sub-acute or chronic effect of the effluent on the
organism.- Sub-acute effects include (1) reduced fertility,
(2) difficulty in movement, (3) certain physiological
disorders, (^) greater susceptibility of the organism
to disease or predation, (5) the death of the organism after five
or more days of exposure.
Application factors, applied to the obtained
data, would quantify allowable concentrations and dilutions
that would permit the survival of the most susceptible
organism. Mount and Stephan (196?) have suggested a
technique for determining permissable concentrations of
toxicants based upon quantitative experimental data.
402
-------
They proposed the use of a "laboratory fish production
index" (LPPI) as the measure of effect to furnish a first
approximation as to whether an environment is unacceptable
to fish. For this index, exposure data would be obtained
for at least one generation and would reflect effects on
growth, reproduction, spawning behavior, viability of eggs,
and growth of the fry. The maximum acceptable toxicant
concentrations would be established on the basis of
chronic exposure using LFPI as the means of effect.
They indicated that the application factors derived for one
species and one kind of water have not been shown to be
applicable to other species and waters. The duration of
their tests were nine months. Their application factors,
for freshwater minnows, obtained after determining 96
hour TLjQS, ranged from 1/15 to 1A5 of the 96 hour
Sub- lethal tests
A. number of sub-lethal tests can be performed.
Biochemical studies-These include studies on enzyme induction
and Inhibition. They provide information on the nature of
the toxic action. They are useful in predicting side effects
of toxins. The information is not however readily obtained.
Pathological studies-Preparations of tissue and organ sections
from animals exposed to lethal and sub-lethal levels of toxic
substances can give an indication of the site of toxic
action particularly if the damage is severe. The difficulty
lies in the size of the organism being studied. Included in
pathological studies would be hematological changes from
the normal (eg. hematocrits) , and electrophoretic studies
403
-------
of serum and plasma, proteins, which might be indicative
of stressful conditions due to ocean disposal (Pig. 3).
Physiological studies-These studies would determine the
effects of wastes, including thermal discharges, on
osmoregulation, changes in heart and respiration rates, etc,
Growth studies-These studies would Include, with animals,
studies of longer durations (eg. life cycles of fishes
could be examined after exposure to sublethal quantities
of wastes as constant dosages or as slug loads).
Behavior studies-Avoidance studies could be performed
to determine the reactions of organisms to gradients of
pollutants (eg. oxygen gradients, temperature gradients,
heavy metal gradients). In addition, swimming speeds, and
general activity of the organism could .be observed.
Photosynthesis studies-The photosynthetic activity of
planktonlo algae can be studied with mixed, or single
cultures (eg. Massartia rotundatum, Navicula sp.,
Chloromonas sp., Amphora sp.) (Mountford et al,,l973»
unpublished data; Gesamp, 1972) incubated in bottles,
or in the field, using carbon 1^ techniques. These are
tests designed to run for short terms (minutes or hours).
The data generated can be indicative of short-term damaging
effects, and of changing phytoplankton species composition.
Taste tests-The flesh of fish can acquire a taste from
organic compounds in the water, therefore taste tests
can be made to determine the tainting of fish flesh at
concentrations below the lethal level.
404
-------
Other laboratory procedures are available to
assess sublthal or chronic effects. The determination of
hematological characteristics for dertaln species could
be determined as base-line data and periodic examination of
these species inhabiting the disposal area could be made to
determine if subtle changes had occurred. The coughing
response of fish has recently been suggested as a method of
determining unfavorable environments (Newsweek,197^).
Apparently soase fishes have a coughing reflex when
exposed to low concentrations of metals and pesticides.
Field Methods
Field observations, although time consuming and
costly, provide the only direct evidence of the effect of
oceab waste disposal on the local flora and fauna. Field
methods should include base-line data surveys of the general
area of the disposal site. This would include surveys of
both flora and fauna, including benthic organisms. Chemical
features of the surrounding waters would also be examined.
The effect of a particular outfall or sludge
dumping site in the sea can be assessed by field sampling
and determination of the distribution of benthic organisms
(Rei^h, I960; National Marine Fisheries Service, 1972). Many
species may be used as indicators of pollution by their
absence or presence in the area of the disposal site (Table 2)
The variety of organisms, deferred to as species
diversity, has been found to be a useful Indicator of
405
-------
marine pollution (Bechtel and Copeland, 1970; Copeland and Bechtel, 1971;
Norn's, et.al., 1973). In general, the more polluted, highly stressed,
environments are characterized by low species diversity, and cleaner
waters by a greater diversity of species. Field work is an important
means of determining the effects of various point source discharges as
long as they are not in close enough proximity to each other to produce
overlapping effects.
Field observations are not without their problems however. For
example, some fish species are migratory by nature, especially those that
are pelagic. Other species, both plant and animal, have typical seasonal
cycles. Therefore, the presence, or absence, of one or more species may
not be due to ocean disposal effects, but due to the cyclical appearance
or disappearance of that organism.
A multidisciplinary approach appears to be the most satisfactory
one. Determination of the disposal site far enough in advance of its use
to allow adequate base-line data surveys, including chemical, physical, and
biological parameters, should be made. Subsequent field and bioassay
monitoring, on a programed basis, would then be utilized after waste dis-
posal began. In addition, no single test organism can provide the necessary
data to determine the impact evaluation of a disposal site. Extrapolation
of the responses of one species, or of several species, might not include
the response of the most sensitive species if that organism was not included
among the test species. A multidisciplinary approach with constant
406
-------
monitoring would possibly provide enough data to assess the impact on
single species and, more importantly, on the food web. Additional safe-
guards, as promulgated by bioassays and impact evaluation, could then be
made at the effluent and waste disposal sources to reduce possible
toxicants to levels manageable by marine organisms.
407
-------
Literature Cited
Anonymous. 1971. Standard Methods for the Examination of
Water and Wastewater. 13th ed. Am. PUB* Healtn Assoc.
New York. pp. 074.
Barber, H.T., and D. Kneger. 1970. Growth of phytoplankton
in waters from the New York City sludge dumping grounds.
Paper given ar the 33rd annual meeting. A.S.L.O.
Bechtel, T.J., and B.J. Copeland. 1970. Fish species diversity
indices as indicators of pollution in Galveston Bay, Texas,
C->nt. Mar. Sci., Texas Univ., 15, 103,
Copeland, B.J., and T.J. Bechtel. 1971. Species diversity and
water quality in Galveston Bay, Texas. Water, Air, and
Soil Pollution, 1:89-105.
Chen, C.W. and G.T. Orlob. 1972. The accumulation and
significance of sludge near San Diego outfall. J.W.P.C.P.
*1362-1371.
Davey, C.T. 1972. Assessment of the effects of digested sewage
disposal off the mouth of Delaware Bay. Franklin Inst. Hes,
Lab. Tech. Hept. F-C2970.
Dorfman, D. 1973. Serum protein patterns of white perch.
N.Y. Fish and Game J. V.20, No.l. pp. 62-67.
E.P.A. 1972. Pre- conference Report for Water Quality Standards
Setting/Revision Conference New Jersey Atlantic Coastal
Area. U.S. E.P.A. Beg. II Office, New York. pp. 72.
E.P.A. 1973. Interim Sludge Toxlcity Test. U.S. E.P.A.
Unpublished data.
GESAMP. 1972. IMCO/FAO/UNESCO /WHO /WHO/IAEA/UN Joint Group
of Experts on the Scientific Aspects of Marine Pollution
(GESAMP) -He port of the Fourth Session, Geneva, 18-23.
September, 1972.
Grigg, B.W., and H.S. Kiwala. : 970. Some ecological effects
of discharged wastes on marine life. Gal. Fish and Game.
56:U5-55.
Kopfler, F.C., and J. Mayer. 1969. Studies on Trace Metals in
Shellfish. Proc. Gulf and S. Atlantic Shell. Sanit. Res.
Conf. U.S.P.H.S., Environmental Health Series, VI H-9.
408
-------
Lee, G.F. 1973. Review Paper-Chemical aspects of bioassay
techniques for establishing water quality criteria.
Water Research. Pergamon Press. Vol. 7. Great Britain.
pp. 1525-1546.
Meglitsch, P.A. 1972. Invertebrate Zoology. 2nd ed. Oxford
Univ. Press. New York. pp. 834.
Mount, D.I., and C.E. Stephan. 1967. A method for establishing
acceptable toxicant limits for fish-Malathion and the
Butoxyethanol Ester of 2,4-D. Trans. Am. Fish. Soo. 96, 2.
pp. 185-193.
Mountford, K., R.S. Mullen, and R.S. Shippen. 1973. Laboratory
simulation of power plant effects: Response of some
estuarine phytoplankters to time temperature combinations.
Acad. Nat. Scl. Penna. pp 9. Unpublished data.
Newsweek. 1974. Danger, Fish Coughingl May 20. 83:20. p. 100.
New York.
NOAA. Sandy Hook Marine Laboratory. 1972. The Effects of
Waste Disposal in the New York Bight-Final Report to
the U.S. Corps of Engineers, Wash., B.C. National
Marine Fisheries Service (N.O.A.A.). 9 vols.
Norris, D.P., L.E. Birke, Jr., H.T. Cookburn, and D.S. Parker.
1973. Marine waste dlspos
-------
Human oerua
(Koni-Trol)
Uhlte perch
3.00 K
rin rot
Alb.
Uhlte perch
35.75*
J\
Whit* perch
3.75 *
B i c .D.V. a,H A . B . c .D.V.
410
-------
ZONE OF STUNTED GROWTH
MAXIMUM PRODUCTIVITY
ZONE OF TRANSITION
PRODUCTIVITY PATTERN IN AREA OF OCEAN OUTFALL
411
-------
PER CENT OCCURENCE OF DOMINANT ANIMALS SETTLING IN
SEDIMENT BOTTLE COLLECTORS FROM THREE ECOLOGIC AREAS
Species
Polychaetes :
Capitella capitata
Podarke pugettensis
Dorvillea articulata
Armarrdia bioculata
Halosvdna johnsoni
Oligochaetes :
Tubificid
Crustaceans:
Corophium acherusicum
Epinebalia sp.
Number of Bottles Analyzed
Healthy
88
62
52
73
31
2
96
13
48
Semi-Healthy
91
88
79
9
13
7
64
78
67
Polluted
78
59
65
2
2
30
20
63
49
412
-------
TRACE METAL CONCENTRATIONS (ppm)
Type Sample Zinc Copper Cadium Chromium Lead
Oysters 495.0 27.8 1.12 Trace nob
Sediment 61.0 2.1 0.31 2.8 3.7
Water 0.012 0.007 0.01 0.004 0.008
Interium 1500.0 100.0 0.2 — 0.2
Standard
-------
'*v,,
-------
9L17
1
-------
416
-------
EVLUATING THE IMPACT OF SLUDGE
DISCHARGE TO SANTA MONICA BAY. CALIFORNIA
BY
Floyd K. Mitchell*
Municipal wastewater from the City of Los Angeles is treated at
Hyperion Treatment Plant and discharged to Santa Monica Bay through two
separate submarine outfalls. One outfall consists of a 5 mile (8 km)
long, 12 foot (3.66 m) diameter concrete pipeline and two 4,000 feet
(1220 m) long Y diffuser legs through which approximately 335 mgd
(1,270,000 cu m/day) of combined primary and secondary effluent is dis-
charged at a depth of 200 feet (61 m). The other outfall is a 7 mile
(11.3 km) steel pipeline, 22 inches (56 cm) in diameter, through which
about 4.8 mgd (18,150 cu m/day) of combined digested sludge and secondary
effluent are discharged at the head end of a submarine canyon at a depth
of 320 feet (98 m). Both outfalls have been in operation since 1960.
Figure 1 shows the location of these two outfall pipelines in Santa
Monica Bay. As is evident from this figure, Santa Monica Bay is an open
bay and the discharges represent essentially open ocean waste disposal.
The numbered points in Figure 1 are water and sediment sampling and
quality monitoring stations.
A flow diagram of the Hyperion Treatment Plant is presented in
Figure 2. Flow rates (in mgd) are noted in parentheses. The entire
flow of 340 mgd (1,290,000 cu m/day) receives primary treatment and
approximately 100 mgd (378,500 cu m/day) of the primary effluent receives
activated sludge secondary treatment. The raw sludge produced in the
primary treatment amounts to 1.3 mgd (4,920 cu m/day) with an average
total solids content of 6.4 percent. This primary sludge is anaerobically
digested in 18 digesters which provide for a mean detention time of 25 to
30 days. The digested sludge is screened to remove large particulate
matter and then diluted about 3:1 with secondary effluent prior to being
pumped 7 miles (11.3 km) out to sea. The sludge screenings are hauled by
truck to landfill.
The results of quantitative physical and chemical analyses of the two
separate effluents are listed in Table 1. Although the flow of the sludge
* Environmental Specialist, So. Cal. Coastal Water Research Project and
Graduate Student, University of California, Berkeley.
417
-------
-Pi
00
KtA
SANTA MONICA
Figure 1 Hyperion Outfall Locations
-------
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-------
effluent is only 1.4 percent of the five mile effluent flow, the mass
emission rates (MER) from the two outfalls are quite similar for most
of the measured contituents. This comparison establishes the sludge
discharge as a major contributor of waste material to the bay, and
likely a more significant contributor in terms of effects due to the
higher concentrations involved.
Sludge Characteristics
One phase of an assessment of the environment effects of any waste
disposal practice must be a detailed characterization of the waste
material being discharged. The phsical and chemical properties of four
types of Hyperion Treatment Plant sludges are reported in Table 2.
Twenty-six samples of each sludge type were collected and analyzed over
a six week period at the end of 1972. The digestion of the primary
sludge results in significant reductions of total solids, volatile matter,
chemical oxygen demand, and grease without affecting total nitrogen and
total phosphorous concentrations of the sludge. Heavy metals in muni-
cipal sludge is a subject which is of increasing concern, primarily
because of the high concentration usually reported and the general lack
of knowledge and accompanying apprehension regarding the ultimate fate
and effects of these metals in a sludge disposal scheme. Table 3
presents some information on the heavy metals content of three Hyperion
Plant sludges. The metals concentrations are divided into dissolved
and suspended categories and the numbers in parentheses are estimates of
the suspended metals content of the sludges in terms of mg/dry kg. The
digested sludge values represent a combination of the mesophilic and
thermophilic digested sludges metals content. For each of the six metals
and all three sludge types, the metals are predominantly associated with
the sludge particulate matter. It may be of interest to note that the
return activated sludge solids metals content (mg/dry kg) are greater
than the primary sludge solids in every case and greater than the digested
sludge solids for four of the six metals reported.
Although the sludge characteristics reported here are useful in
assessing potential effects of proposed disposal schemes and some
expected effects of existing disposal practices, a knowledge of other
sludge properties is desireable. Some of the more obvious properties
of interest include biodegradability and degradation rates, toxicity,
enrichment potential, metals mobilization potential and rates, and
particle size distributions. It is only with information of this type
along with the traditional physical and chemical composition parameters
normally reported that a scientific assessment of potential and existing
environmental effects of various sludge disposal practices and proposals
can be seriously attempted.
420
-------
Table 1
HYPERION TREATMENT PLANT WASTE DISCHARGES
1973 ANNUAL AVERAGE CONCENTRATIONS AND MASS EMISSION RATES
CONSTITUENT
FIVE MILE EFFLUENT
(335 mgd)
SEVEN MILE EFFLUENT
(4.8 mgd)
Concentration M.E.R. Concentration
mg/1 M Ton/Yr mg/1
SUSPENDED SOLIDS
VOLATILE SUSP. SOLIDS
B.O.D.
C.O.D.
OIL AND GREASE
TOTAL NITROGEN
TOTAL PHOSPHORUS
TOTAL CHLORINATED
HYDROCARBONS
HEAVY METALS
MERCURY
COPPER
NICKEL
ZINC
CADMIUM
LEAD
CHROMIUM
SILVER
81
63
98
205
18
18.4
6.3
.003
.0026
.14
.17
.25
.02
.04
.29
.05
38,100
29,600
46,100
96,500
8,500
8,650
2,970
1.4
1.22
66
80
118
94
18.8
137
23.6
7,400
4,500
-
7,800*
922
540*
145*
.033
.14
13.6
3.6
27
.98
1.57
18.2
.8
M.E.R.
M Ton/Yr
49,300
30,000
-
51 ,900*
6,140
3,600*
965*
.22
.93
90.5
24
180
6.5
10.5
121
5.3
*Estimates, not annual averages
421
-------
Table 2
HYPERION TREATMENT PLANT SLUDGE CHARACTERISTICS*
MEASURED
CHARACTERISTIC
TOTAL Range
SOLIDS, % Mean
Mode
VOLATILE
SOLIDS, %TS Mean
Mode
CHEMICAL Mean
OXYGEN DEMAND Mode
mg/1
TOTAL KJELDAHL Mean
NITROGEN, mg/1 Mode
ORGANIC Mean
NITROGEN, mg/1 Mode
TOTAL Mean
PHOSPHATE, mg/1 Mode
GREASE, mg/1 Mean
Mode
ALKALINITY Mean
mg/1 Mode
PRIMARY
SLUDGE
4.25-8.90
6.40
6.35
80.2
81.0
61,267
47,900
2,066
2,418
1,874
2,320
1,795
2,000
11,080
11,436
1,603
1,420
DIGESTED
Mesophilic
1.15-2.98
2.12
2.36
59.9
61.5
24,195
24,270
2,000
2,113
870
845
1,570
1,596
1,981
2,360
5,524
5,500
SLUDGE
Thermophil
1.67-3.64
2.35
2.47
62.0
62.9
33,420
38,000
1,992
2,028
697
720
1,604
1,665
2,820
2,648
6,190
5,750
RETURN ACTIVATED
1C SLUDGE
0.44-0.89
0.69
0.69
73.1
75.0
7,106
6,820
541
501
512
504
1,148
1,174
400
345
430
440
*Based upon analyses of 26 samples of each type of sludge collected
during the period 11/30/72 to 1/12/73
Analyses by Hyperion laboratory
422
-------
Table 3
HEAVY METAL CONCENTRATIONS IN HYPERION SLUDGES
METAL
CADMIUM
NICKEL
LEAD
ZINC
COPPER
CHROMIUM
METAL
PRIMARY SLUDGE
Dissolved Suspended
.02 2.48
(38.8)
.67 10.83
(169)
8.0**
(125)
1.55 119.5
(1,880)
11.0 52.0
(812)
.09 45.2
(707)
CONCENTRATION, mg/1
DIGESTED SLUDGE
Dissolved Suspended
.02 2.88
(123)
.41 10.1
(427)
2.85**
(324)
.13 72.55
(3,120)
6.0 34.4
(1,460)
.10 51.4
(2,185)
and (mg/dry kg)*
RET. ACT. SLUDGE
Dissolved Suspended
.03 .77
(131)
.38 1.42
(242)
.25 2.25
(384)
.25 12.75
(2,180)
.5 11.5
(1,960)
.07 16.0
(2,730)
* Estimated from mean solids content of sludges (Table 2), not reported
in original data
**Total Content
Analyses by Hyperion Laboratory
423
-------
Physical and Chemical Effects
The most obvious effect of the discharge of sludge to the ocean
is an alteration of the physical and chemical characteristics of the
marine sediments in the vicinity of the discharge site as a result of
the sludge particulate matter settling to the bottom. Sampling and
analysis of Santa Monica Bay and Santa Monica Canyon bottom sediments
for heavy metals and chlorinated hydrocarbons content were conducted
in 1970 and 1971. Sediment sampling stations were as shown in Figures
3 and 4. Some results of the analyses are presented in Figures 5-11.
Figures 5 and 6 show the distribution of lead and copper concen-
trations found in the surface layer of the samples collected. Assuming
a natural background concentration of 8 mg/dry kg for lead and 30 mg/
dry kg for copper (SMC sample, Fig. 7), it is seen that Figure 5 indicates
an enrichment factor for lead varying from 2 to 5 times background levels
over a large portion of the bay area and as high as 31 times background
at station B3, closest to the sludge outfall. Similarly, Figure 6 shows
enrichment factors for copper of 1 to 3 over a wide area and 17 times
background at station B3. The distribution of other metals in the sur-
face sediments is similar to those of lead and copper. The highest
concentrations found (station B3) range from 1/3 to 1/5 of the metals
concentrations reported for the discharged sludge particulates.
Three box core samples (B3, B6 and B8) from the Santa Monica Canyon
were analyzed for metals concentrations with respect to depth. Some
results of these analyses are presented in Figure 7. The plots of
copper, mercury, and lead concentrations versus depth reveal a similarity
between the depth profiles for B6 and B8, and suggests that such profiles
might be used to determine the depth of deposit of significant quantities
of sludge particulates. The relatively constant depth concentrations at
station B3 indicates that this sample was not as deep as the sludge par-
ticulates. Other metals in these cores exhibit similar depth profiles.
Chlorinated hydrocarbons in the surface sediments at the same locations
present a picture similar to that of the metals (Figure 8-11). Total
DDT and total PCB concentrations are higher in the canyon than in the
shallower areas of the bay and are highest by far at locations closest to
the sludge outfall.
Biological Effects
The physical and chemical changes in sediment characteristics
resulting from the deposition of wastewater and sludge particulates on
the ocean bottom would be expected to have a quantitative effect on the
benthic fauna. The most commonly used parameters for assessing the health
of a biological community are total biomass per unit area, species compo-
sition, species diversity, and if possible, organism abnormalities. Data
gathered to date indicates that the discharge of wastewater and sludge
to Santa Monica Bay results in an alteration of the polychaetes, high
proportions of capitellid species are commonly regarded as being indica-
tive of environmental stresses such as reduced salinity, low dissolved
-------
34°00'N
33°50'N
SANTA MONICA BAY
.8C
I.SANTA MO MICA
: BALLONA CREEK
N
Figure 3 Phleger Core Collection Locations Around the Hyperion Outfall System, June 1970.
34°00'N -
33°50'N -
SANTA MONICA BAY
Fiqure 4 Box Core Collection Locations Around The Hyperion Outfall System. July 1971.
425
-------
34°00'N -
33°50'N -
SANTA MONICA BAY
24
118°40-W 118030™
a. Phleger Cores, June 1970.
34°00'N -
SANTA MONICA BAY
ii8°40'w
b. Box Cores, July 1971.
Figure Lead Concentrations (mg/dry kg) in Surface Sediments Around the Hyperion Outfall System.
426
-------
34°00'N -
33°50'N -
SANTA MONICA BAY
31
118040™ 118°30'W
a. Phleger Cores, June 1970.
34°00'N -
33°50'N -
SANTA MONICA BAY
nsoso-w
b. Box Cores, July 1971.
Figure 6 Copper Concentrations (mg/dry kg) in Surface Sediments Around the Hyperion Outfall Syst
em.
427
-------
IUUU
800
1 \J\JU
800
600
400
200
100
80
60
40
3
* 20
c
Q
0
— 10
_ COPPER
83
JS*~*^^*^S' ""^^-^ i
^
^
•^ ^^
V
^\ B6
\
>>
-> \
" \
— • \
- VI V
*"*.. SMC V. • w*"^^ " ^"*^^ • *^*i
1 1 1 1 1 1 1
4OO
200
100
80
40
20
10
8
6
4
2
1
0.8
0.6
0.4
0.2
O.1
~ LEAD
B3
^< _ ~~~^^~ ^
—
" v
X
^v B6
*"V
^•^ *
_^\ \
v \
*v *
~7~ \. ^
— '"\\ x
>^ \
\*^^
• •y_^'.^ SMC
— \
_ *««••»••
•^
_
I I I I 1 I I
g 0 5 10 15 20 25 30 35 40 0 5 10 15 20 25 30 35 4C
H DEPTH (CM) DEPTH (CM)
c
~ IIAJU
UJ
« 800
8
600
400
200
100
(
MANGANESE
—
" *
-------
34°00'N
33°50'N
SANTA MONICA BAY
vp.08
275
•"450
SANTA MONICA
':'• BALLONA CREEK
N
118040^
Figure 8 Total DDT Concentrations (mg/dry kg) in Surface Sediments Around the Hyperion Outfall System
(Phleger Cores, July 1972).
34°00'N -
33°50'N -
SANTA MONICA BAY
118040^
118°30'W
Figure 9 Total DDT Concentrations (mg/dry kg) in Surface Sediments Around the Hyperion Outfall System*
(Box Cores, July 1971).
429
-------
-------
oxygen, or highly organic substrate. The results of a 1972 survey of
the polychaetes is Santa Monica Bay sediment samples are presented in
Figure 12, in which the relative abundance of capitellids is recorded
for each station sampled. High proportions (16% - 58%) of capitellids
were found in the sediments in the vicinity of the two outfalls, and
lower percentages (1% - 7%) were observed in areas further from the
outfalls. An indication of the biological enrichment potential of the
sludge discharge was also revealed by this same study. The station at
the end of the sludge outfall had a polychaete biomass of 69 g/sq m
while the station between the two Y diffusers had a polychaete biomass
of 11 g/sq m.
Although the actual causes of fin erosion diseases in benthic fish
has not yet been determined, there are indications that the disease is
related in some way to the discharge of wastewater solids. Fin erosion
in Dover sole has been observed in catches from 5 out of 25 locations
in Santa Monica Bay sampled in 1971. In each case the incidence of
disease was greater than ten percent, and 4 of 5 locations were within
2 miles (3.2 km) of the sludge discharge. The other location was 7
miles (11.3 km) northwest of the discharge.
In addition to sampling and analyses techniques, visual observation
of the ocean bottom and the marine life there is a valuable technique
for assessing the environmental consequences of ocean discharges. Recent
visual inspection of the ocean bottom using undersea television equipment
in the vicinity of the sludge outfall has provided the following qualita-
tive description of the area. The pipe itself provides a solid substrate
upon which sea anemones grow in extremely high densities. The most abun-
dant large organisms in the vicinity of the outfall are starfish and their
population density is highest in the sediments adjacent to the pipeline.
Sea urchins and Dover sole are commonly seen while other fishes and animals
such as crabs are seen less frequently.
Summary and Conclusions
Quantitative analyses of the two Hyperion discharges to Santa
Monica Bay show that the mass emission rates of the sludge discharge
are similar to those of the combined primary and secondary effluents.
Physical and chemical properties of the ocean sediments in the bay
have been altered by the waste discharges, with the greatest effects
observed in Santa Monica Canyon and closest to the sludge outfall.
Depth profiles of sediment heavy metals concentrations indicate that
the depths of significant quantities of sludge particulates are greater
than 1 foot (30.5 cm) near the sludge outfall and 1 foot or less at
distances greater than 2 miles (3.2 km) down canyon from the sludge
discharge. Biological evidence of environmental stress in the vicinity
431
-------
GO
ro
Fig. 12 Relative Abundance of Capitellids (Percent of Total Polychaete Specimens) in Santa Monica Bay, January - February 1972.
-------
of the discharges has been found, but the areas affected are by no means
biological deserts.
Research concerned with the environmental effects of wastewater and
sludge discharges to the open ocean is continuing on the basis that only
by understanding the consequences fo each alternative disposal practice
can rational decisions be made. The California State Water Quality Control
Board has taken the following position with respect to sludge discharge
to the ocean:
"The discharge of municipal and industrial
waste sludge and sludge digester supernatant
directly to the ocean, or into a waste stream
that discharges to the ocean without further
treatment, shall be prohibited." (2)
The difficulty with such a position is that the sludge continues to
be produced and must be disposed of in one way or another. Due to the
nature of the material, any disposal practice is likely to produce environ-
mental stress in the area of disposal. If the solution to the sludge
disposal problem is constrained to be one which minimizes adverse environ-
mental effects, it would be best to have as many viable alternatives open
for evaluation as possible.
Acknowledgements
Much of the data presented in this paper has been obtained from
the Hyperion Laboratory and certainly almost all of the information has
been aided by the cooperation of Hyperion personnel.
Figure 3-12 are exerpted from reference (1).
References
1. "The Ecology of the SOuthern California Bight: Implications for
Water Quality Management", Southern California Coastal Water Research
Project (SCCWRP) Three Year Report, March 1973.
2. "Water Quality Control Plan for Ocean Waters of California", Calif-
ornia State Water Resources Control Board, Sacramento, California.
Adopted and effective July 6, 1972.
433
-------
A DISCUSSION OF
A NEAR FIELD DISPERSION MODEL
FOR SLUDGE DISCHARGES TO COASTAL WATERS
W. F. Rittall
Coastal Pollution Branch
Pacific Northwest Environmental Research Laboratory
National Environmental Research Center
Environmental Protection Agency
Corvallis, Oregon 97330
April 1974
435
-------
In preparing this document it became apparent that use of a consistent
system of units would present a problem. The computer program
utilizes both metric and English units. Thus, to maintain continuity
the units required as input and displayed in the output are used
here.
436
-------
INTRODUCTION
Barging of waste materials to offshore dumpsites is a disposal
method which is being used in this country for a variety of
wastes that include industrial liquids and sludges, sewage sludge,
and dredge spoils. This practice is controlled, in part, by a
permit system, which for industrial wastes and sewage sludge,
is administered by the Environmental Protection Agency.
Investigators, in examining the effects of past ocean dumping, have
demonstrated ecological alterations from such practices. Periodic
monitoring is, or should be, required for all wastes discharged to
coastal waters to enable undesired changes or effects to be recognized,
and corrective action taken to preclude irreversible ecological
damage.
The Coastal Pollution Branch of EPA's Pacific Northwest Environmental
Research Laboratory sponsored the development of a generalized
mathematical model to aid in the prediction of the physical fate
of waste materials barged to coastal waters. Prediction models
of this type may be useful for both monitoring and permit application
evaluations. Computer simulation techniques provide a detailed
description of the sequence of events that occur after discharge,
enhancing the interpretation of physical mechanisms.
437
-------
The objective of this paper is a demonstration of the application
of this simulation technique for the problem of sewage sludge
discharges. For given inputs, the results are compared for
representative environmental conditions. The depth of penetration
of the waste cloud, the dilution, and the depositional characteristics
of settleable and floating solids are also discussed and related
to pertinent federal regulations governing ocean dumping.
The mathematical model, developed by Dr. R. C. Y. Koh and Y. C.
Chang under an EPA research grant to the Tetra Tech Inc., Pasadena,
CA is contained in an EPA report (1) published in December of 1973
and will be described here only conceptually.
The model is descriptive of three separate methods of discharge
representing instantaneous, pumped, and wake releases. The waste
may be characterized by a liquid and a maximum of eight distinct
solid or particulate phases. Each phase is traced through three
computer linked transport modes as represented in Figure 1. These
transport modes are also shown on the program flow diagram, Figure
2.
The first transport mode is a convective descent, terminated when
the material either encounters the bottom or reaches a position
of buoyant equilibrium within the water column (i.e. vertical
velocity equals zero). In the latter case a dynamic vertical
collapse occurs when a density difference exists between the bulk
waste cloud and the ambient fluid. The final transport mode is
one of passive long term diffusion where the vertical concentration
distribution, area! size, and amount of accumulated solids are
determined.
438
-------
-p.
CO
vo
LONG TERM DIFFUSION
[HOURS]
COLLAPSE CONVECTIVE DESCENT
[MINUTES] [SECONDS]
FLUID
SETTLEABLE SOLIDS
Fig. 1 Basic Transport Modes; Barge Operation 1
-------
READ CONTROL PARAMETERS
AND
AMBIENT CONDITIONS
TEST METHOD OF
DISPOSAL
BARGE OPERATION
1
BARGE OPERATION
2
PUFF
CONVECTION
BARGE OPERATION
3
JET
CONVECTION
WAKE-PLUME
CONVECTION
DYNAMIC
COLLAPSE
UPDATE INPUT
DATA FOR LONG
TERM DIFFUSION
BOTTOM
ENCOUNTER
LONG TERM DIFFUSION
UPDATE INPUT
DATA FOR LONG
TERM DIFFUSION
Fig. 2 Computer Model Flow Diagram
440
-------
PROBLEM DEFINITION
The basic problem examined in the subsequent examples relate directly
to the periodic discharge of sewage sludge to typical coastal waters.
Tables 1 and 2 provide the model input requirements necessary to
characterize the barge and waste. Figure 3 depicts the environmental
conditions for the site. The parameters were chosen from available
field data and represent seasonal differences likely to be encountered
in North temperature coastal climates.
BARGE CHARACTERISTICS
The barge characteristics are representative of typical sludge
barging operations. Many operations, however, may have discharge
times or waste volumes that deviate significantly from these
cited values.
The model does not simulate the interactions of multi-port discharges,
and the situation described in Table 1, where twelve ports are shown
will be treated as a single port where only 1/12 of the total barge
load is examined. These results must be proportionately scaled
when a need to account for the entire waste loading exists.
WASTE CHARACTERISTICS
The waste is a digested municipal sewage sludge characterized by
three separate phases; a liquid, a settleable solid, and a floating
solid. The specific characteristics required by the model are
presented in Table 2.
441
-------
0
15
H
LJ
UJ 30
Z 45
I- 60
Q.
Ul
Q 75
90
UJ
CL
UJ
Q
0
15
45
60
90
20 24 0
SUMMER CONDITIONS
FT/SEC FT/SEC
10 05
FT2/SEC
"-'-Ky.|=2.2xlCr3
^Ky =5x10
»-4
= l.lxlO'3
UA
Ky
°t
20 24
WINTER CONDITIONS
UA Wa
0 10 0 .5
Ky
UA
-Ky = I.I x 10'-
Ky
Fig. 3 Site Environmental Conditions
442
-------
SITE CHARACTERISTICS
The environmental conditions at a proposed disposal site must be
characterized in terms of vertical profiles of density, current,
and coefficients of vertical eddy diffusivity. The coefficients
used in these examples are based on a relationship developed
by Koh and Fan (3) where Ky is inversely proportional to the ambient
density gradient as given by the following equation:
Ky = B/E 1.1
where
2
Ky = coefficient of vertical eddy diffusivity [ft /sec]
E = density gradient expressed as [gms/ft-cc]
B = constant = 1.1 x 10~ [ft-gms/cc-sec]
Table 1
Barge Discharge Characteristics
Input
Term
Barge Width
Barge Speed
Discharge time
Direction of travel*
Barge Length
Angle of Discharge**
Number of Ports
Depth of Ports
Diameter of Ports
Velocity of Discharge
Model Req.
Units
60 ft
5.0 ft/sec
600.0 sec
180°
200 ft
0°
12.0
10.0 ft
1.16 ft
4.227 ft/sec
Metri c
Units
18.29 m
152.40 cm/sec
600.0 sec
180°
60.96 m
0°
12.0
304.8 cm
35.36 cm
128.84 cm/sec
*relative to + X axis
**relative to vertical axis where 0° denotes a vertical downward discharge
443
-------
Table 2
Waste Characteristics
Input Model Req. Metric
Term Unit Units
Bulk Specific Gravity 1.040 gms/cc 1.040 gms/cc
Number of Solid Phases 2 2
Density of settleable solids 1.61 gms/cc 1.61 gms/cc
Cone, (by volume) 4.5% 4.5%
Settling Velocity 0.005 ft/sec 0.1524 cm/sec
Density of floating solids 0.98 gms/cc 0.98 gms/cc
Cone, (by volume) 0.5% 0.5%
Settling velocity 0.05 ft/sec 1.524 cm/sec
DISCUSSION OF MODEL RESULTS
PENETRATION AND DILUTION
The output from the program describing the convective descent and
dilution of the waste materials is usually descriptive of effects
for the un-separated waste components but in some cases reveals
constituent separations caused by settling solids and floatable
particles.
The results for the first two transport modes are presently graphically
in Figures 4, 5, and 6. Figure 4 shows the depth of penetration
and the size of the resulting plume for a single port release of
identical wastes under seasonal differences in the current and
density gradients. The summer conditions result in a thermocline
444
-------
0
V
PORT LOCATION
0
1 2
TIME [SECONDS x I031
WINTER
Fia. 4 Waste Cloud Penetration Durina Convective Descent and Collaose Transoort Modes
-------
ioV
r IMTTT] i i i
I04
2,0'
_l
Q
I02
10'
r i r rTTTi| i i i TT, \±
REMOVAL OF SETTLEABLE
SOLIDS TO BOUND ARY-
SEPARATION
FLOATING
START OF PASSIVE
LONG TERM DIFFUSION
START OF COLLAPSE
O TRANSPORT TRANSITION PT
FLOATABLE SOLIDS
FLUID ONLY
SETTLEABLE SOLIDS
COMBINED WASTE
i i i i i ml nl i I i i i i
10'
I02 10
TIME [SECONDS]
I04
I0a
Fig. 5 Minimum Single Port Dilution for Each Waste
Phase as Functions of Time; Summer Conditions
446
-------
n—i i i i ni| 1—I I I I lll| 1—I I I I lii| 1—I I I I ni| I I I I 11 I-H
REMOVAL OF SETTLEABLE SOLIDS TO BOUNDARY
9
ICT
Q
z:
I0
10'
SEPARATION OF
FLOATING SOLIDS
START OF PASSIVE
LONG TERM DIFFUSION
'START OF COLLAPSE
O TRANSPORT TRANSITION PT
- FLOATABLE SOLIDS
FLUID ONLY
SETTLEABLE SOLIDS
COMBINED WASTE
J i i i i i nl
i i M ill
i i i i i 11 il
J i
10'
I02 I03
TIME [SECONDS]
I04
10=
Fig. 6 Minimum Single Port Dilution for Each Waste
Phase as Functions of Time; Winter Conditions
447
-------
which restricts the penetration of the waste cloud. The winter
conditions, with only a slight density gradient, result in buoyant
equilibrium deep within the water column. If no gradient existed
the wastes would penetrate unhindered to the bottom.
During the descent mode the flux of solids in the descending cloud
is decreasing. This is not apparent in Figure 4 but can be seen in
the tabular data, and in the dilution rates as shown in Figures 5
and 6. The separation, or branching, of the dilution curve results
from the removal of solids from the cloud as particles either sink
or float, or are deposited on a boundary. The rapid dilution of the
floatable phase should not be cause to dismiss these pollutants.
A more detailed examination would reveal that the trend is quickly
reversed when the solids collect and concentrate on the boundary and
become available for further transport by wind and ambient currents.
LONG TERM DIFFUSION
The physical sequence after dynamic collapse is presented in Figures
7 and 8. Here, the vertical position and lateral extent of the waste
cloud are presented at four time steps. The figures depict the
horizontal planes where maximum waste concentrations occur and show
the separation of floating and settleable solids and their
ascent-descent paths to the boundaries. The lateral dimensions
calculated from the computed standard deviations account
for 95 percent of the waste load. These plots showing the spatial
location of the three waste phases over a several hour period
can be used to verify the adequacy of a monitoring operation
or to compare the model predictions against regulations that prescribe
maximum permissible concentrations and mixing volumes. The summer case,
448
-------
0
20
40
a- 60
LU
Q
80
100
0
CL
i
10
1.23 hrs.
1.86 hrs.
3.47 hrs.
j FLUID
SETTLEABLE SOLIDS
FLOATABLES
hrs.
SUMMER CONDITIONS
i i
15
20
25
30
WASTE CLOUD (X) POSITION FOR EACH PHASE RELATIVE
TO MOVING COORDINATE SYSTEM C FT x I03]
Fig. 7 Time Series View of Long Term Diffusional Transport; Summer Conditions
-------
on
o
0
20
i — i
t 40
h-
?-, so
LJ
80
100
' ^^7<£MH£> ' ' '
1 xSKry
\/ 186 hrs 2.88 hrs. 4.56 hrs.
V 54 min. L86 nrs __— __
«-: • ^5 - >-O ' ID t • j
<1 1.25 hrs.
_ (S:::^'.,1;.'1:1/,', ,'i^
vv.
— *^i 2.07 hrs.
V'^iii'i'i'i'i'.'ivi'i^^^lx
^ 3.32 hrs.
— -_. ^
Q FLUID
[3 SETTLEABLE
g FLOATABLES
-------
0
10
20
30
40
50
60
70
80
90
100
110
SUMMER CONDITIONS
I I
0
2O 4.0 6.0 8.0
CONCENTRATION [FT3 x I0~3]
Fig. 9 Vertical Distribution of Relative Wastes Concentrations
During Long Term Diffusional Transport; Floatable Solid
Phase; Summer Conditions
451
-------
I
\-
0-
UJ
Q
0
10
20
30
40
50
60
70
8O
90
100
110
0
WINTER CONDITIONS
_L
.11 .22 .33 44
CONCENTRATION CFT3xlO"3]
Fig. 10 Vertical Distribution of Relative Wastes Concentrations
During Long Term Diffusional Transport; Floatable Solid
Phase; Winter Conditions
452
-------
0
10 -
SUMMER CONDITIONS
, T= 1.53 hrs
1.42
284
427
569
CONCENTRATION C FT3 ]
Fig. 11 Vertical Distribution of Relative Waste Concentrations
During Long Term Diffusional Transport; Settleable Solid
Phase; Summer Conditions
453
-------
WINTER CONDITIONS
.90 1.80 2.71 3.61
CONCENTRATION [FT3:
4.29
Fig. 12 Vertical Distribution of Relative Waste Concentrations
During Long Term Diffusional Transport; Settleable Solid
Phase; Winter Conditions
454
-------
n
h-
LL
i — i
X
1 —
Q.
LU
Q
U
10
20
30
40
50
60
70
80
90
100
1 10
| 1 1 1 1 1 1 1 1 I l
i
~ \
-'^^i^
) — 3 -^ -^
s
s
1
'
T = 47 m\r\.
"! T= 1.08 hrs.
- o.bo nrs.
SUMMER CONDITIONS
0
1042 208.5 3127
CONCENTRATION [FT3]
4169
Fig. 13 Vertical Distribution of Relative Waste Concentrations
During Long Term Diffusion and Transport; Fluid Phase;
Summer Conditions
455
-------
0
10 h
20
30
40
50 h
x 60
o_
UJ
Q 70
80
90
100
110
T = 1.26 hrs.
T = 1.87 hrs.
---- T = 4.56 hrs.
WINTER CONDITIONS
J_
72.7 145.5 218.2
CONCENTRATION [FT3]
290.9
Fig. 14 Vertical Distribution of Relative Waste Concentrations
During Long Term Diffusion and Transport; Fluid Phase;
Winter Conditions
456
-------
Figure 7, shows the fluid phase to remain near the surface; the floatables
to be quickly deposited on the surface, and the settleable solid
phase to be transported several miles from the discharge point. Figure
8, for winter conditions reveals the deeper penetration, the slower
release of floatables and the more rapid deoosition of the settleable
solids. Figures 9-14 reproduced from the computer plots show
separate distributions at the tine when the maximum relative
concentration of each waste has been reduced to prescribed percentages
of the initial maximum at the start of this transport phase. In
these examples the percentages were 99, 75, 50 and 25. It should
be noted that the concentrations vary significantly from graph
to graph while appearing to be similar, due to change of scale.
To relate these relative concentrations, (cubic feet of waste in
a horizontal plane of unit thickness) to actual dilutions, a plot,
such as Figure 5 or the tabular output must be compared at
similar times.
Depositional Characteristics
The incremental accumulation of material on the boundaries is shown
in Figures 15 and 16. These distributions are assumed to be
Gaussian and are presented in terms of the percent deposited where
the distributions are shown relative to the discharge point and
to the maximum amount of deposition that has occurred at the
indicated times. The data points shown on the curves denote the
centroid location on the X axis and the percent deposited for that
curve only. The thickness of the bottom deposit may be estimated
through the use of the following equation:
h = W/2u(ax2 az2 - axz2)1/2(l-P) 1.2
457
-------
100 r
in
oo
CJ
050
LJ
<_>
cr.
LJ
0_
32 min.
s
SUMMER
CONDITIONS
I I I I
J I
I I
-1.84 -9.21 0 9.21 1.84
DISTANCE FROM RELEASE POINT C FT x I03]
2.76
Fig. 15 Distribution of Settled Solids; Summer Conditions
-------
100 r-
vo
§50
o
cr
LU
Q.
55 min.
J L
WINTER
CONDITIONS
-1.84 -9.21 0 9.21 1.84 • 2.76
DISTANCE FROM RELEASE POINT C FT x I03]
J I
Fig. 16 Distribution of Settled Solids; Winter Conditions
-------
where
h = maximum thickness [ft]
2
W = total waste discharge [ft ]
n p
a6 = X variance of deposited solids [ft ]
A 2
a% = 1 variance of deposited solids [ft J
2
°XZ ~ covariance °f deposited solids [ft ]
P = porosity
For the examples presented here the maximum thicknesses calculated
for porosities of 0.5 and 0.8 are presented in Table 3.
The accumulation of solids on the surface must be expressed differently
and, for these examples, the floating solids are presented on a
weight per unit area base. The equation for the maximum concentration
(D) assuming the solids to be normally distributed is:
D = AWps/2lf(ax2 °xz2) ' 1-3
2
D = maximum concentration [gms/m ]
W = accumulated solids [ft ]
p = solid density [gms/cc]
A = constant = 3.02 x 105 [cc/ft-m2]
Figures 17 and 18 are representative of these distributions and
their location relative to the discharge point.
Resuspension of deposited solids was not included in these examples,
but is a capability of the model.
460
-------
L9t?
CO
m
3
00
o _
O CO
o cz
11
dm
O ^0
CO
-------
100 r
en
ro
Q
LJ
H
cn
o
Q.
LJ
Q
I-
2
LU
O
LT
LU
Q-
50
0
4.34 hrs
3.47 hrs.
WINTER
CONDITIONS
j i i
0246 8 10 12
X DISTANCE FROM RELEASE POINT [FT x I03 ]
Fig. 18 Distribution of Accumulated Floating Solids; Winter
Conditions
-------
Table 3
Calculated Maximum Thickness of Deposited
Solids and Maximum Concentration of Floating Solids
Maximum Thickness of Bottom Deposits
Assuming Gaussian Distribution
Season
Season
Time hrs.
Deposited
Thickness* (microns)
p = .5 p = .8
Summer
Winter
4.4
4.3
80
86
11.7
10.9
29.2
27.3
Maximum Areal Concentration of Surface Accumulation
Assuming Gaussian Distribution
Time hrs.
% Accumulated
Concentration*
o
(gms/m )
Summer
Winter
< 1
< 1
.0
.0
99+
99+
5.49
3.79
Calculations based on single port discharge only.
463
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INTERPRETATION OF DATA
The model output has been used to demonstrate the penetration of the
waste cloud, the dilution of each waste phase, the location of
maximum waste concentrations as functions of time and soace and the
area! extent and distributions of the solids on the boundaries.
This information can be related to the Federal Regulations (2)
controlling release zones, mixing volumes and limiting permissible
concentrations.
The release zone is defined as,
"The area swept out by the locus of points constantly 100
metres from the perimeter of the conveyance engaged in
dumping activities, beginning at the first moment in which dumping
is scheduled to occur and ending at the last moment in
which dumping is scheduled to occur."
This zone is interrelated to a mixing zone by the following:
"The mixing zone is the region into which a waste is initially
dumped or otherwise discharged, and into which the waste will
mix to a relatively uniform concentration within four hours
after dumping. It is required that the concentration of
all waste materials or trace contaiminants be at, or below,
the limiting permissible concentrations at the boundaries of
the mixing zone at all times and within the mixing zone four
hours after discharge. The actual configuration of a mixing
zone will depend upon vessel speed, method of disposal, type
of waste, and ocean current and wave conditions. For the
purposes of these regulations a volume equivalent to that of
a mixing zone is the column of water immediately contiguous
to the release zone, beginning at the surface of the water
and ending at the ocean floor, the thermocline or halocline,
if one exists, or 20 metres, whichever is the shortest distance."
464
-------
The limiting permissible concentration is:
"(a) That concentration of a waste material or chemical
constituent in the receiving water which, after reasonable
allowance for initial mixing in the mixing zone, will not
exceed 0.01 of a concentration shown to be toxic to
appropriate sensitive marine organisms in a bioassay
carried out in accordance with approved EPA procedures;
or (b) 0.01 of a concentration of a waste material or
chemical constituent otherwise shown to be detrimental
to the marine environment."
The depth criteria are explicit and for the summer conditions, are
descriptive of a thermocline at 10 metres and for the winter conditions
equal to the 20 metre maximum. The settleable solids present in sewage
sludge penetrate the entire water column and violate by presence,
if not by concentrations, these limits. The relative toxicity of
the various waste phases must be known before their true importance
can be assessed; however, the fluid phase, in these examples, makes
up 95 percent of the waste bulk and while not known to be the more
important will be examined in that context.
The fluid phases, for both summer and winter conditions as shown
in Figures 7 and 8, and 13 and 14, have centroids located above their
respective mixing zone depth limits for the entire 4 hour simulation
period.
When it comes to examining the lateral extent and movement of the
waste for mixing zone compliance, some interpretation is necessary.
The more common interpretation assumes the mixing zone to be fixed
465
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Ol
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O)
-I
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3
CQ
01
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3
a.
o
3
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-------
A similar equation can be used to define the horizontal size of
the mixing volume. This equation is:
S - [(200 + LB + UBTd) x (200 + Wg)]1/2 1.4
where
S = Horizontal release zone [metres]
LB = Barge length [metres]
Ug = Barge Speed [metres/sec]
T, = Discharge time [sec]
Wn = Barge width [metres]
The values necessary for this calculation are provided in Table 1
and predict a size for the mixing zone of 506.5 metres ( 1660 ft).
The computer plots for the size of the waste's fluid phase, Figures
20 and 21, show that the mixing zone size is not approached within
the first three hours after discharge. The time series plots represented
in these figures are for times where the concentration has been reduced
to 99, 75, 50 and 25 percent of the maximum at the beginning of
this transport mode; thus, the size can be evaluated directly and
the dilution found by referring to Figures 5 and 6 with proper
corrections to account for multi-port discharges. Implicit in this
approach is an assumption that the movement of both the mixing
zone and waste phase of interest are identical. However,
when a waste is multi-phased, as in these examples, a more rigorous
evaluation of settleable solids and floatables should be undertaken.
It may be necessary to explore other interpretations of the mixing
zone concept and to include limits for accumulated and deposited
materials on boundaries.
468
-------
n
H
Ll_
t_i
X
H
f\
LL.
LU
Q
U
10
20
30
40
50
60
70
80
90
100
1 10
1 1
-
-
i j / \ i ii
/ / / MIXING VOLUME •->
//' / SIZE
/ ' / /
/ / / '
/ •' / /
//
/
i /
/ /
• /
I /
V ••• i
\ \ \ /
T=37min.\ \ \ /
T = 4
/-
-
~
r
r
v\
7min*C\ \
) "-•• \
^ \\
" \ \
J \ \
J
— \
T=l.08hrs. \
\
\
\
\
\
X
\
T=3.64hrs. \
1
FLUID PHASE ONLY
. i i
0 354
i i i i i I i
708 1062 1416
SIZE [FT]
Fig. 20 Vertical Distribution of Size of Diffusing Waste
Cloud at Selected Times; Summer Conditions
469
-------
i 1 r~7
/
/
!T=l.87hrs.
I
T=4.56hrs.
\
\
\
\
MIXING VOLUME
SIZE
FLUID
\
PHASE ONLY \
)
_L
355
711 1067
SIZE EFT]
1423
Fig. 21 Vertical Distribution of Size of Diffusing Waste
Cloud at Selected Times; Winter Conditions
470
-------
Limiting Permissible Concentrations
The regulations (2) prohibit discharge of several materials such
as mercury and cadmium when present as other than trace contaminants.
For sewage sludge, dredge spoils, and the wastes of industries not
using or producing these constitutents, their presence is termed
a "trace contaminant" and they may be discharged under a special
permit when the limits shown in Table 4 are not exceeded.
Table 4
Maximum Allowable Concentrations
for Mercury and Cadmium (2)
Contaminant Max. Allowable Concentration
Solid Phase Liquid Phase
mg/kg mg/kg
Mercury
Cadmium
0.75
0.60
1.5
3.0
Limiting permissible concentrations are also defined in relation
to bioassay results and mixing zone boundaries. To examine compliance
with the regulations, the model results can be used in the following
manner:
471
-------
The maximum concentration centroid location for the waste phase
of interest defines a "worst case" situation. The vertical concentration
distribution can be used to obtain estimates of the concentration
at a given horizontal boundary. When compliance to the vertical
mixing zone boundaries is sought, the concentration and size of the
diffusing waste cloud can be obtained for a given depth. The distribution
within the cloud for this model is taken to be normally distributed
and thus from the model generated standard deviations, concentrations,
and the known mathematics of the distribution the concentration at
any point can determined. Standard tables (4) are available for
the normal distribution and can be used for such evaluations. The
height of the distribution is defined in terms of the maximum concentration
and the width in terms of the centroid location and the standard
deviation along the appropriate horizontal axis. The relationship
of these parameters is provided in Table 5.
Table 5
Concentration - Standard Deviation
Relationship for a Normally
Distributed Waste (5)
Fraction of Max. Number of Standard
Concentration (a = 0) Deviations from Centroid
J\
1.0 0
0.9 0.459
0.8 0.669
0.7 0.844
0.6 1.010
0.5 1.178
0.4 1.353
0.3 1.551
0.2 1.739
0.1 2.145
0.05 2.458
0.02 2.798
0.01 3.034
472
-------
For the examples presented in Figure 19, where the position of the
maximum waste concentration in the fluid phase was compared to the
mixing zone position, such estimates have been made. However, for
simplicity, the centroid location of the waste cloud was assumed
to be at the center of the mixing zone surface area. The boundaries
of interest are then equal to one half the X, I dimensions of the
release zone and can be calculated from the data provided in Table 1,
The distances obtained can then be expressed in terms of the
calculated standard deviations and used with Table 5 to obtain the
concentration at the boundary. Table 6 has been prepared to show
the results for the two times shown in Figure 19.
Table 6
Calculated Mixing Zone Boundary Concentration
for a Single Port Discharge at
Selected Times (fluid phase only)
Summer Winter
time [hrs]
ay [ft]
a* [ft]
3.65
1073
462
4.56
1127
628
nixing Zone
X Boundary [ft] 1928 1928
Mixing Zona
Z Boundary [ft] 358 358
Max. Concentration 4.6 x 10"5 3.1 x 10~5
X Boundary Cone. 9.1 x 10~7 6.1 x 10"7
Z Boundary Cone. 3.0 x 10"5 2.6 x 10~5
473
-------
From the data presented the boundary value concentrations are shown to
o r
be low with dilutions ranging between 35 x 10 and 1.5 x 10 . These
values are for single port discharges and could be decreased by
as much as three orders of magnitude to adjust for multi-port
discharges and the 0.01 factor applicable to demonstrated toxic
levels. While a procedure exists - as before - its usefulness depends
on the analytical information available as to the toxicant-waste
phase relationships and the possible transformations chemical or
otherwise that occur subsequent to release.
No specific criteria seem to exist, at present, to allow direct
comparisions of model predicted deposited solids to maximum
concentrations allowable on either the surface or the seabed.
SUMMARY AND CONCLUSIONS
A mathematical model capable of simulating the barged release of
sewage sludge to coastal waters was demonstrated. The results were
evaluated in terms of predictive capabilities and applications to the
general problem of permit evaluation, site monitoring surveys,
and compliance with regulatory criteria. This model is predicted
to be of significant value to those with the responsibility to
safeguard the marine environment as there is no other procedure
or model available to the regulatory programs which provides this
degree of analysis (6).
474
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RECOMMENDATIONS
Scientist and engineers specifically involved in ocean dumping
studies, permit evaluation, and field monitoring activities are
urged to use the model to demonstrate for themselves its usefulness
in helping them to meet their specific objectives. The staff of
ti
EPA's Coastal Pollution Branch is willing to provide assistance;
however, before this is done the requirements of the model should
be fully understood. As any simulation is extremely dependent on
the data chosen to describe the system, it is important to acquire
sufficient data to accurately characterize the waste, the barge, and
the environment.
Work is ongoing at many locations to improve the model and to
evaluate it under field conditions. The US Army Corps of Engineers,
Waterways Experiment Station has funded a program to refine
the model and make it more responsive to dredging operations in
estuaries. Use by two non-government contractors working on the
problem of open water spoil disposal is currently in the planning
phase.
It will be found by those who attempt to utilize the model that
existing field and analytical data will not always be sufficient
to meet the input requirements, and some additional work may
be required. The benefits, however, will far exceed the costs. The
model is destined to become an intergral part of the ocean dumping
evaluation process and those undertaking independent research and
refinements are urged to make the results available to prevent
duplication of effort and unnecessary delays in the realization of
the model's true ootential.
475
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REFERENCES
1. Koh, R. C. Y. and Y. C. Chang. " Mathematical Model for
Barged Ocean Disposal of Wastes." EPA Report 660/2-73-029
December 1973.
2. Federal Register - Environmental Protection Agency - Ocean
Dumping - Final Regulations and Criteria. Vol. 38, No. 198,
Part II. Oct. 15, 1973.
3. Koh, R. C. Y. and Fan, L. N. "Further Studies on the Prediction
of Radioactive Debris Distribution Subsequent to a Deep Underwater
Nuclear Explosion." TetraTech, Inc. Tech. Report TC-154, 1969.
4. Anon. National Bureau of Standards Applied Mathematics Series
# 23, US Govt. Printing Office, Washington, D.C. 1953.
5. Anon. "Parametric Analysis of a Deep Water Discharge of a
Warm Water Jet." Argonne National Laboratory Center for
Environmental Studies, Dec. 23, 1970.
6. Johnson, B. H. Investigation of Mathematical Models for the
Physical Fate Prediction of Dredged Material and Guidelines
for Future Research - U.S. Army Corps of Engineers Waterways
Experiment Station. November 1973.
U8. * Proton A*n«
476
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