WATER POLLUTION CONTROL RESEARCH SERIES • ORD-2
Disposal of Wastes
from
Water Treatment Plants
.S. DEPARTMENT OF THE INTERIOR • FEDERAL WATER POLLUTION CONTROL ADMINISTRATION
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WATER POLLUTION CONTROL RESEARCH SERIES
The Wafer Pollution Control Research Reports describe
the results artel progress in the control and abatement
of pollution of our Nation's Waters. They provide a
central source of information on the research, develop-
ment and demonstration activities of the Federal Water
Pollution Control Administration, Department of the
Interior, through in-house research and grants and
contracts with Federal, State, and local agencies,
research institutions, and industrial organizations.
Triplicate tear-out abstract cards are placed inside
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Space is provided on the card for the user's accession
number and for additional keywords. The abstracts
utilize the WRSIC system.
Water Pollution Control Research Reports will be
distributed to requesters as supplies permit. Re-
quests should be sent to the publications Office.
Dept. of the Interior, Federal Water Pollution
Control Administration, Washington, D, C. 20242
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DISPOSAL OF WASTES
FROM
WATER TREATMENT PLANTS
FEDERAL WATER POLLUTION CONTROL ADMINISTRATION
DEPARTMENT OF THE INTERIOR
by
American Water Works Association
Research Foundation
2 Park Avenue, New York, N. Y. 10016
Program No. 12120 ERC
Project No. WP 1535-01-69
August 1969
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FWPCA Review Notice
This report has been reviewed by the Federal
Water Pollution Control Administration and
approved for publication. Approval does not
signify that the contents necessarily reflect
the views and policies of the Federal Water
Pollution Control Administration.
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Disposal of Wastes from Water Treatment- Plants
ABSTRACT
This report is an intensive study of the disposal of wastes from water treatment
plants. The wastes include filter washwater; sludge resulting from coagulation,
softening, iron and manganese removal processes; diatomaceous earth filtration;
and ion exchange brines. The control of pollution from these wastes is a high
priority problem for the water utility industry.
A series of four status reports describe in detail what is known of the research,
engineering, plant operation, and regulatory aspects of the problem. A special
report reviews current technology and analyzes costs of disposal methods, based
on data collected from fifteen operating plants. A conference was organized to
provide expert evaluation of each report and to extend the data available.
Final reports were prepared by committees of conference participants to identify
future needs for information in each aspect of the waste disposal problem. These
reports recommend substantially expanded programs of research and demonstration,
They include extensive lists of specific problems which must be investigated to
develop effective and economical technology.
Committee reports also recommend establishment of a central service to promote
the planning of research and development, and to implement effective programs
of new or improved technology. The service would collect, coordinate, and
disseminate data on all aspects of water treatment plant waste disposal problems.
This report was submitted in fulfillment of Research Grant 12120 ERC (formerly
WP 1535-01-69) between the Federal Water Pollution Control Administration and
the American Water Works Association Research Foundation.
KEY WORDS
Waste Disposal Operation Maintenance
Waste Treatment Cost Analysis
Water Treatment Regulation
Sludge Treatment Surveys
Ultimate Disposal Utilities - Water Works
Hi
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CREDIT FOR ILLUSTRATIONS
P. W. Doe and F. C. Menzenhauer, Havens and Emerson:
Photographs pp. 6, 34, 38, 52, 80,
D. D. Adrian and J. H. Neblker, Consultants:
Photographs and drawings illustrating Report on Current
Technology and Costs, pp. 133-238.
The mention of products or manufacturers in this re-
port does not imply endorsement by the Federal Water
Pollution Control Administration, U. S. Department
of the Interior.
IV
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FOREWORD
The disposal of wastes from water treatment plants is not a new problem.
The majority of plants dispose of solids removed during the treatment process
by returning them to surface waters. Under recently enacted federal and
state legislation, however, these wastes are generally considered pollutants -
as are the wastes from any industry.
The water utility industry must now take action to solve its problem of
waste disposal. The number of U.S. water treatment plants producing sludges
from coagulation processes is reported by Russelmann (1968) to be about 3,600.
The quantity of solids resulting from municipal water coagulation processes is
estimated by Hudson (1968) to total about 1,000,000 tons per year.
These wastes are highly variable in composition, containing the con-
centrated materials removed from raw water and the chemicals added in the
treatment process. The wastes are produced continuously, but are discharged
intermittently. Since the wastes from each plant are different, no specific
treatment process will yield the same results. In fact, while a variety of
alternative treatment methods are available, there may be only one or two
methods applicable to a specific location.
Experience in the disposal of these wastes has been very limited. The
American Water Works Association Research Foundation has undertaken to
survey the present state of knowledge on this problem, and to identify
additional information needed.
The present report includes a series of four status reports covering
research, engineering, plant operation, and regulatory aspects of the problem.
A special report provides information on current technology and costs. A
two-day conference was organized to critically review, evaluate, and
enlarge upon the prepared reports. The series of four reports on future needs
were prepared by committees of conference participants. These reports
identify specific research and development studies required to support an
action program.
The purpose of the report on disposal of wastes from water treatment
plants is to provide current information on the nature of the water treatment
plant waste disposal problem, and to assist water utilities in solving the
problem. The report describes technology presently available, defines new
approaches to the problem, and suggests future directions for the coordination
and dissemination of information.
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This project- was supported, in part, by a research grant awarded to
the AWWA Research Foundation by the Federal Water Pollution Control
Administration, U.S. Department of the Interior. Grant Project Officer
was William J. Lacy, Chief, Industrial Pollution Control Branch, Division
of Applied Science and Technology.
The AWWA Research Foundation is a non-profit corporation organized
to promote basic and applied research activities in the water utility field.
The Research Foundation serves to initiate and coordinate research in the
technology, operation, and management of water supply systems.
A Project Advisory Committee assisted the Research Foundation in the
development of this report. Members of the Committee were:
James C. Lamb, III
Robert B. Dean
Richard I. Dick
John W. Krasauskas
Walter K. Neubauer
Donald P. Proudfit
Lee Streicher
Edwin C. Weber
Engineering consultants were employed by the Research Foundation to
prepare the report on current technology and costs. Their report includes
data collected by visits to fifteen water treatment plants, selected to provide
examples of various disposal methods, and also includes model studies. The
consultants were:
Donald D. Adrian
John H. Nebiker
The AWWA Research Foundation staff for the project on Disposal of Wastes
from Water Treatment Plants was:
Harry A. Faber, Research Director
Kitty C. Klomp, Administrative Assistant
VI
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CONTENTS
Page
ABSTRACT iii
FOREWORD v
Section 1. REPORT ON WHAT IS KNOWN
Introductory Statement - By H. A. Faber 1
STATUS REPORT ON RESEARCH
By R. I. Dick and R. B. Dean 5
Discussion of Report 15
STATUS REPORT ON ENGINEERING
By W. K. Neubauer and D. P. Proudfit 28
Discussion of Report 64
STATUS REPORT ON PLANT OPERATION
By J. W. Krasauskas and Lee Streicher 75
Discussion of Report . <• * 93
STATUS REPORT ON REGULATORY ASPECTS
By E. C. Weber 106
Discussion of Report 122
VII
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CONTENTS
Page
Section 2. REPORT ON CURRENT TECHNOLOGY AND COSTS
By D. D. Adrian and J. H. Nebiker 133
Review of Technology 136
Cost Analysis 150
Plant Visitations 153
Model Studies 230
Discussion of Report 239
Section 3. REPORT ON WHAT IS NEEDED
Conference Report on Research Needs 247
Conference Report on Engineering Needs 251
Conference Report on Plant Operation Needs 255
Conference Report on Regulatory Needs 258
Concluding Statement - By J. C. Lamb/ III 261
Section 4. DIRECTORY OF CONFERENCE PARTICIPANTS 265
Section 5. REFERENCE BIBLIOGRAPHY 267
Section 6. SUBJECT INDEX 281
VIII
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TABLES
Page
1. Coagulant Sludge Characteristics 31
2. Analysis - Waste Brine From Ion Exchange Softener 45
3. Iron and Managanese Sludge Treatment 47
4. Microstrainer Sludge Treatment 49
5. Sludge Lagoon Capacity Requirements 54
6. Recalcining Plants 57
7. Waste Brine - Cation Exchange Softening 89
FIGURES
1. Sludge Freezing 6
2. Sludge Thickening 34
3. Sludge Pressing 38
4. Typical Sludge Freezing Unit 40
5. Sludge Lagoon 52
6. Sludge Disposal Processes 74
7. Sludge Dewatering 80
8. Recovery of Lime for Reuse 144
9. Austin/ Texas, Flow Diagram 152
10. Austin, Texas, Treatment and Disposal 154
IX
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Page
11, Boca Raton, Florida, Flow Diagram 158
12. Boca Rafon, Florida, Treatment Facilities 160
13. Dayton, Ohio, Flow Diagram 164
14. Goleta County, California, Flow Diagram 172
15. Lansing, Michigan, Flow Diagram 176
16. Lansing and Miami Recalcination Facilities 180
17. Lompoc, California, Flow Diagram 184
18. Los Gatos, California, Flow Diagram 188
19. Los Gatos, California, Drying Alum Sludge 190
20. Miami, Florida, Flow Diagram 192
21. Miami, Florida, Lime Sludge Recalcining 194
22. Minot, North Dakota, Flow Diagram 200
23. New Britain, Connecticut, Flow Diagram 206
24. Point Pleasant Beach, New Jersey, Flow Diagram 210
25. San Francisco, California, Flow Diagram 214
26. San Francisco, California. Washwater Recovery 216
27. San Francisco, California, Drying Alum Sludge 218
28. Sommerville, New Jersey, Flow Diagram 220
29. South Orange, New Jersey, Flow Diagram 224
30. Willingboro, New Jersey, Flow Diagram 226
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Section 1
REPORT ON WHAT IS KNOWN
CONFERENCE INTRODUCTORY STATEMENT
Harry A. Faber
Wastes from water treatment plants are, today, recognized
as an industry-wide pollution problem. The solution of this problem
is not simple. It involves research, engineering, plant operation,
and regulatory aspects.
The AWWA Research Foundation considers this a problem of
high priority. It has undertaken to prepare a comprehensive state-
of-the-art report to determine what is known and what is needed.
The report will be designed to assist the water utility industry in
developing effective and economical control measures.
This Conference has been organized to provide an expert
overview of a series of status reports. The participants have been
selected: (1) to critically review the reports, (2) to extend the
data available, (3) to advise concerning future needs.
Background
The problem of water treatment plant waste disposal is not
new, and has been studied before. Thirty years ago, in 1937 and
1938, research was conducted at the Chicago Experimental Filter
Plant. The detailed report prepared by Herbert Hudson evaluated
the quantity, characteristics, thickening, and dewatering of sludge.
Unfortunately, this report was not published.
In 1946, the American Water Works Association appointed
a committee to study and report on the disposal of wastes from water
purification and softening plants. The 8-man committee included
three individuals who are attending this Conference: W.W. Aultman,
chairman; and A.P. Black and K.E. Shull, members of the committee.
That committee published six reports, the first in 1947 and the last
in 1953. These reports constituted a comprehensive review of the
state-of-the-art about 20 years ago.
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Conference Introductory Statement
The 1953 report of the committee noted that more than 96
percent of 1,530 reporting plants discharged sludge to streams or
lakes without treatment, and 3 percent discharged sludge to drying
beds. About experimental work done in water treatment plants with
vacuum or pressure filters for dewatering sludge, the report stated
that none of the respondents (to a questionnaire) knew of any such
experiments. The last report of the committee includes the state-
ment:
"At present very few water purification plants are act-
ually prohibited from discharging filter washings and sludge from
basins into streams or lakes, but there is a definite trend toward
enactment of federal and state laws to prevent the pollution of
these waters. In the future the disposal of such wastes is like-
ly to be a matter of increasing concern to designers and operators
of water purification plants."
It is evident that the future, anticipated in that state-
ment, has now arrived. For example, a Staff Report of the Ohio
River Valley Water Sanitation Commission, in April 1968, pointed
out:
"Within the past year or two, all of the six states on
the Ohio River have established policies that eventually will lead
to the control of water plant wastes, not only on the Ohio River
but on tributary streams as well. Implementation of these policies,
in fact, has already resulted in the construction of a number of
control facilities on tributary streams in five of the states."
Three individuals participating in this Conference are
from ORSANCO states: G.H. Eagle, Ohio; Edgar Henry, West Virginia;
and H.B. Russelmann, New York.
The changing situation is also evidenced by the recent
publication of several important technical reports. The authors
of three such publications are at this Conference:
P.W. Doe, in 1966-67, published on extensive report
titled "The Disposal of Wastes from Water Treatment
Plants," in the Journal of the British Waterworks
Association.
Donald D. Proudfit, in June 1968, published a paper
titled "Selection of Disposal Methods for Water
Treatment Plant Wastes," in the AWWA Journal.
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Conference Introductory Statement
Walter K. Neubauer, in July 1968, published a paper
titled "Waste Alum Sludge Treatment," in the AWWA
Journal.
Conduct of the Conference
Jerome Weisner, while President Kennedy's science advisor,
defined the word research; "to look again - we didn't find anything
the first time," In this Conference., we will "look again" at the
problem of water treatment plant waste disposal: not because "we
didn't find anything the first time," but because the earlier
studies need to be brought up to date and expanded.
The major work on this new study of the problem has, to
date, been done by an Advisory Committee. The Committee held a
planning meeting in August, 1968, to assist the Research Foundation
in organizing the report and in developing plans for this Conference.
The invaluable services of this Committee are recognized.
It has really served as a working committee rather than as an advi-
sory committee. Each individual member of the Committee made im-
portant contributions to the project by preparing, under a short
deadline, the status reports sent in advance of the Conference.
The AWWA Research Foundation has also been assisted by a
team of consultants responsible for a study of current technology
and costs. The consultants selected operating plants illustrating
varied water treatment and waste disposal methods, collected engi-
neering and operating data, and prepared the report. They also
compiled thejbasic reference bibliography.
Now we have come to the review stage. The Advisory Com-
mittee members and the consultants are meeting at this Conference
with a small group of invited participants. Each individual has
been selected because of his special competency in one or more
aspects of the waste disposal problem. Together, their contribu-
tions will evaluate, critically review, and enlarge available data.
The first day of the Conference is devoted to the pre-
sentation and discussion of status reports. The Advisory Committee
members responsible for the preparation of a report will guide the
discussion. All conferees are invited to raise questions, report
experience, and suggest additional items for inclusion in the final
report.
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Conference Introductory Statement
The morning of the second day of the Conference will be
devoted to meetings of four small committees, assigned to prepare
summary reports on future needs. The afternoon session of the
second day provides for the presentation and open discussion of
each committee report. This will be the final opportunity for
additional questions, comments and recommendations.
I welcome you to the Conference on Disposal of Wastes
from Water Treatment Plants. Your presence is evidence of your
interest in solving this problem.
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Status Report on Research
STATUS REPORT ON RESEARCH
Richard I. Dick and Robert B. Dean
The limited research efforts in the past on handling and dis-
posal of wastes from water treatment plants have been consistent
with the attention given to the sludge disposal generally, but are
not in proportion with the present magnitude of the problem. Some
of the exceptions to this general lack of research on disposal of
wastes from water treatment plants are noted in this section.
REVIEWS OF RESEARCH
Several review papers on waste disposal from water treatment
plants have appeared, and their contents are not repeated here.
Summaries of research results were included in AWWA committee re-
ports on water treatment plant wastes (Aultmann, 1947; Haney,
1947; Hall, 1947; Black, 1949; Haney, 1949; and Dean, 1953).
Additional reviews have been published by Mace (1953), Wertz (1964),
and Aultmann (1966). Results of British research relating to dis-
posal of wastes from water treatment plants have been reviewed in
Civil Engineering (Anon., 1949) and more recently by Young (1968).
Results of research on characterization of water treatment
plant wastes have been summarized recently by Russelmann (1968).
Gauntlett (1963) prepared a comprehensive review of literature re-
lating to settling, compaction and dewatering of water treatment
sludges. An extensive review of water treatment plant sludge dis-
posal practices including research accomplishments and needs has
been presented by Doe (1967).
Reports on Research
Investigations of the chemical and physical characteristics of
alum sludges and filter backwash wastes have been reported by Gates
and McDermott (1966 and 1968) and by Neubauer (1966 and 1968). The
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SLUDGE FREEZING
x 1OO
Unfrozen Sludge
x 100
Frozen Sludge
Photomicrographs - Alum Sludge
Sludge Solids - From Freezing, Thawing, and Drying Processes
- Coin on the left is a dime
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Status Report on Research
volatile solids content of the sludges examined varied from about
20 to 35 percent. Almquist (1946) reported that the average 5 day
BOD of sludge from 13 Connecticut filtration plants was 337 mg/1.
The average solids concentration of the sludges was 1.3 percent.
Both Neubauer and Gates and McDermott reported that alum
sludge was non-Newtonian. Babbitt and Caldwell (1939) summarized
earlier data by Gregory which indicated water treatment plant sludges
to be plastic in their rheological behavior. Some recent studies by
Lagvankar and Gemmell (1968) and Hannah e_t al. (1967) have given
information about the basic physical properties of the floe particles
which comprise sludge and on how conditions in flocculators affect
these properties.
Much of the reported research on water treatment plant sludges
has had as its goal the alteration of the physical properties to
facilitate removal of water. Extensive basic studies on condition-
ing and dewatering of alum sludges have been report by Gauntlett
(1964 and 1965) .
Freezing. Palin (1954) reported on experiments conducted by
Clements and his colleagues on improving the dewatering character-
istics of alum sludges by freezing. After freezing and thawing, a
2 percent alum sludge settled by gravity to 20.2 percent and could
be filtered to a concentration of 33.9 percent solids by weight.
Doe et al. (1965) reported that freezing could be most economically
accomplished in a batch process involving a 90 minute freezing period
and a 45 minute thaw period. The slow freezing period was essential
but no advantage was realized by further reduction of temperatures
after freezing had occurred.
Bishop and Fulton (1968) recently noted that freezing processes
are economically unattractive except in northern climates where
nature can provide freezing conditions free of charge. Natural
freezing has been used sucessfully at Copenhagen to dewater aluin in
sludge lagoons (Christensen, 1968). After two years of sludge ap-
plication to a depth of 1.4m per year, the amount of remaining
dried sludge had a thickness of 4 cm.
Heat. Palin (1954) investigated the possibility of condition-
ing alum sludges by heat treatment. Considerable improvement in
sludge dewaterability was realized at temperatures and pressures
below those of the normal Porteous process.
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Status Report on Research
Acidification. Webster (1966) found that use of sulfuric acid
to lower pH improved performance of gravity thickners because of
the effect of pH of floe particles.
Polyelectrolytes. Doe (1967) reported on his experiments which
indicated that while polyelectrolytes could improve the specific
resistance and the compressibility index of alum sludge, both bene-
ficial effects could not be achieved simultaneously. Gates and
McDermott (1968) reported that filtration characteristics could be
improved by application of certain polyelectrolytes. Neubauer (1968)
found polyelectrolytes to be ineffective but the addition of lime
improved the filterability of one alum sludge. Sankey (1967) found
that vacuum filtration of alum sludge was not possible without chem-
ical conditioning. Two percent by weight of hydrated lime was used
in his experimental work.
Thickening. The need to reduce the moisture content of sludges
in order to reduce the cost of sludge treatment and disposal prac-
tices has prompted research on thickening of waste sludges. Roberts
and Roddy (I960) noted that the practicality of recovery of alum from
clarification sludges is limited by the thickening characteristics
of the sludge, and reported on laboratory and pilot plant experiments
involving sedimentation of alum sludges. Doe ejt al. (1965) indi-
cated that thickening was necessary to assure economical performance
of the process for conditioning sludge by freezing. Alum sludge was
concentrated from 0.5 to 1.9 percent solids in a gravity thickener.
Basic information on the settling characteristics of the calcium
carbonate slurries is available from literature on thickening re-
search - as for example, that by Comings e_t al. (1954). Gates and
McDermott (1968) and Neubauer (1966) presented information on set-
tling behavior of alum sludges and filter backwash wastes from various
water treatment plants. Flotation characteristics of alum floe were
reported by Katz and Wullschleger (1957).
Sludge Dewatering
Filtration. To accomplish volume reduction beyond that possible
by thickening, sludge dewatering techniques have been explored.
Vacuum filtration of alum sludges has been investigated by Gates and
McDermott (1968) and Neubauer (1968) . Gates and McDermott found the
specific resistance of alum sludge to be 0.1 x 1010 to 0.44 x IQlO
sec^/g. In Buchner funnel tests, Neubauer found that a diatomaceous
earth precoat was necessary to produce a cake with 20 percent solids.
A 99 percent solids capture was realized.
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Status Report on Research
Experimental work on dewatering of alum sludges by wedge wire
filters, vacuum filtration, and filter pressing were conducted by
Sankey (1967). It is estimated that capital costs would be lowest
for vacuum filters and that operational costs would be lowest for
wedge wire filtration. However, filter presses were the method of
choice because they gave the lowest annual cost.
Gentrifugation. Gentrifugation of alum sludge was evaluated
by Neubauer (1968), but was not pursued in detail because only 6 to
12 percent cake solids could be achieved. Webster (1966) reported
that alum sludge could be dewatered to over 18 percent solids by
use of a filter press. Sparham (1965) reported on use of wedge
wire filters for dewatering sludge bases on pilot plant studies.
Sand Beds. Neubauer (1968) found that alum sludges could be
dewatered on sand drying beds to 20 percent solids concentration
within 100 hrs. with 97 percent solids capture. Loading rate was
0.8 Ibs/sq ft. Neubauer considered sand drying beds to be more
economical than vacuum filtration or other methods for dewatering
alum sludges.
Lagoons. Experience with lagooning of softening sludge was
summarized by Howson (1961). He concluded that most lime sludges
will air dry in properly designed lagoons with supernatant removal
facilities to about 50 percent moisture. Neubauer (1968) concluded
that deep lagoons were incapable of dewatering alum sludge to the
extent that it could be disposed by landfill.
Reclamation of Chemicals. Reclamation of chemicals from waste
sludges for reuse has been investigated as a means of minimizing
disposal costs. Proudfit (1968) reviewed results of studies which
showed it possible to reduce the volume of sludge requiring disposal
of a St. Paul, Minnesota softening plant by 83 percent by recalcin-
ation. Proudfit also described plans to regenerate alum and recal-
cine lime at the Minneapolis, Minnesota plant.
Palin (1954) investigated recovery of alum for reuse by use of
concentrated sulphuric acid and concluded that cost of the process
would be attractive because of the reduction in the sludge disposal
problem. Chlorine was used in the reclamation process to combat
the difficulty due to release of color colloids during the recovery
process. Additional experimental work relating to alum recovery
has been reported by Webster (1966).
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10 Status Report on Research
Acidification. Ghojnacki (1967) reported on reclamation of
coagulants from clarification sludges. When coagulation was ac-
complished with a mixture of ferric and aluminum salts, 5 percent
sulfuric acid was the most effective regenerant. The highest
purity of recovered coagulants was obtained when 50 to 75 percent
of the stoichiometric acid requirement was used.
Recalcination. Basic technology relating to recalcination of
lime softening sludges has advanced well beyond the basic research
phase and has been demonstrated in full-scale installations such
as at Miami (Black et al., 1951). Albertson and Guidi (1967) have
described removal of magnesium precipitates from softening sludges
prior to recalcination by means of centrifugation. Krause (1957)
reported 40 to 65 percent reduction in magnesium by centrifugation
at the Lansing, Michigan recalcining installation.
Use of Alum Sludge. Possibilities for reclamation of alum
sludge for use in industrial processes was considered by Palin (1954).
Its physical properties and high proportion of impurities rendered
alum sludge impractical as in adsorbent. He reported on a successful
use of sludge in a refractory industry for purposes of altering the
rheological behavior of slip and to serve as a source of aluminum for
manufacture of refractories. Palin also considered the possibility
of using alum sludges from waters in contact with vegatative products
as a source of "humic acid" as did Stockwell (1939). Use of de-
watered softening sludge for street base stabilization at Boca Raton,
Florida was reported by Hager (1965).
Palin (1954) considered the greatest potential use of alum
sludge to be as a rubber filler. In this case, the humic acid would
serve as an extender and the alumina as a filler in vulcanization.
Other possibilities considered by Palin were use of alum sludges as
wetting agents for insecticides, binders for briquettes, and for
medicinal uses.
Land Disposal of Sludge. Dean (1968) emphasized the need for
considering the chemical nature of wastes prior to their ultimate
disposal to assure that they are returned to a sector of the en-
vironment with which they are compatible. Sankey (1967) considered
land disposal of dewatered alum sludge to be the most satisfactory
method of final disposal. Application of sludge at a rate of one
inch per year had no effect on normal vegetation. Sankey proposed
that a program involving stripping of top soil, spreading of dried
cake, and reselling, would be most satisfactory.
Dean (1968) reported that small quantities of aluminum hydroxide
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Status Report on Research
clog soil and make it unfit for agriculture. Doe (1958) found that
spreading of alum sludge on the land sealed the soil and killed
vegetation but that plants were able to grow in the soil after winter
freezing had destroyed the colloidal structure of the sludge. Land
application of alum sludge dewatered by freezing has been reported
by Doe et al. (1965) to be a satisfactory means of disposal. Vegeta-
tion grows on the dewatered solids.
Smith (1948), who reviewed sludge disposal practices from New
England water treatment plants, indicated no account of interference
of water treatment plant sludges, other than softening sludges, with
sewage treatment.
Ultimate Disposal. Residues produced by advanced treatment of
wastes create ultimate disposal similar to those at water treatment
plants. The nature of residues produced in advanced treatment of
wastes has been reviewed by Dean (1968). Much of the recent research
relating to these residues has been summarized in a recent report of
the Advanced Waste Treatment Branch of the FWPCA, (Federal Water Pol-
lution Control Administration, 1968), and work at the South Tahoe
Public Utility District has been summarized by Slechta and Gulp
(1967). From their pilot plant studies, Slechta and Gulp concluded
that alkaline methods of alum recovery were not economically feasible,
and that alum recovery by the acid method was feasible if alum was
used for clarification but not if alum was used for phosphate removal.
Lime used for phosphate removal could be economically reclaimed.
Mulbarger et al. (1968a) have described studies on improvement
in the dewatering characteristic of sludge produced by lime clari-
fication of waste water treatment plant effluents. In related stud-
ies, Mulbarger et al. (1968b) investigated thickening, dewatering,
and recalcination of lime sludges from a laboratory batch waste ef-
fluent treatment system. The chemical quality of the effluent was
found to have a significant effect on the characteristics of the
sludge produced. It was necessary to waste some reclaimed sludge to
avoid the accumulation of inert material.
CURRENT RESEARCH
Doe's report (1967) includes a tabulation of 17 research pro-
jects being conducted throughout the world relating to water treat-
ment plant sludges.
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12 Status Report on Research
Aluminum Phosphate Sludges. Dr. J.B. Farrell heads an FWFCA
in-house program on the recovery of soluble alumlnates from aluminum
hydroxide-aluminum phosphate sludges derived from the treatment of
wastewater with aluminum salts. In this work separation of phosphate
from aluminum is of first importance and so attention has been given
to the basic process with concurrent precipitation of the phosphate
as a calcium (aluminum ?) phosphate. Description of the work has
recently been published by J.B. Farrell, B.V. Salotto, R.B. Dean,
and W.E. Tolliver in the Chemical Engineering Progress Symposium
Series No. 90, Volume 64, pages 223-239, 1968.
Another FWPCA in-house project, also under the direction of
Dr. Farrell, is a study of the freezing of these same aluminum
phosphate sludges as an aid to dex^atering. Some of this work is
being carried out in the laboratory in a deep-freeze cabinet and the
field activities will be carried out at Ely, Minnesota. Again, the
emphasis is on sludges containing phosphates as well as aluminum but
recovery of aluminate is not being stressed.
Under FWPCA Contract 14-12-154, Johns-Manvilie is investigating
the use of a moving bed filter for concentrating aluminum phosphate
sludges derived from secondary effluents. This filter does a good
job of clarifying fluffy floes including aluminum hydroxide and ac-
tivated sludge. Further dewatering of the filter backwash is ef-
fectively accomplished on precoat vacuum filters. Further infor-
mation on this project can be obtained from Dick Bell at Johns-
Manville, P.O. Box 159, Manville, New Jersey 08835.
Monsanto Research, under FWPCA Contract 14-12-199, is studying
the market for phosphates recovered from waste treatment sludges.
There may be some application to lime sludges from water treatment
plants. Lime recovery is also being practiced at South Lake Tahoe
under FWPCA Grant WPRD 52-01, again on secondary plant effluents.
Robert Dean serves as technical backup on this project.
Freezing. The City of Milwaukee is studying sludge freezing
under FWPCA Grant WPRD 71-01-68. While this applies to activated
sludge, much of the work involving refrigeration economics will apply
equally well to the freezing of alum sludges. Dr. Farrell is the
coordinator.
Mathematical Models. Two FWPCA contracts relating to sludge
disposal concern mathematical models. Contract 14-12-194 to Rex
Chainbelt deals with the mathematics of clarifiers, and 14-12-416
to General American Transporation Research Corporation deals with
the mathematics of coagulation and sedimentation. In each case the
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Status Report on Research
objective is to set up a computer program that will apply to the de-
sign of equipment. Robert Smith is project officer for both contracts.
Pipeline. Pipeline transport of sludge is being studied by the
Rand Corporation of Cleveland under FWPCA Contract 14-12-30 and by
Bechtel Corporation under 14-12-156. Mr. Harold Bernard is in charge
and Dr. Farrell is technical backup. The Rand contract involves con-
structing a pipeline in Morgantown, West Virginia, to handle sewage
plant sludges. Bechtel is studying the transport of sewage plant
sludges, dredging spoil, water plant residues, and other wastes at
the Cadiz test facilities which were built to study the transport of
coal in pipelines.
Treatment and ultimate disposal of calcium carbonate, aluminum
hydroxide, and ferric hydroxide sludges produced from pilot plant
treatment of effluent from the District of Columbia Waste Treatment
Plant is currently under study. Sludge thickening, dewatering, and
reclamation processes are being evaluated.
University Research. Centrifugation of water treatment plant
sludges is being studied at the University of Cincinnati. The effect
of chemical additives on dewatering characteristics of sludge from
the Cincinnati water plant is being investigated.
Studies at the University of Massachusetts in the area of water
treatment plant sludges relate to the dewatering characteristics of
sludges in lagoons. Factors influencing dewatering and drying rates
are being evaluated to assist in design of land disposal systems.
At the University of Illinois, studies are underway on the
thickening and vacuum filtration of alum sludges. The basic mech-
anisms involved in thickening of softening sludges are also being
studied.
State Data. A study of the criteria for design and operation
of facilities for water pollution control from softening plants is
being conducted by Burgess and Niple for the Ohio Department of
Public Health. Information is being gathered on treatment processes,
and ultimate disposal techniques relating to softening sludges.
The Illinois Section of the AWWA through its Water Resources
Quality Control Committee has undertaken a study of the effect, if
any, of wastes generated by water treatment plant on potential or
existing water supply sources as well as other legitimate users of
water. Existing methods of water treatment plant waste disposal
are being assessed, the quantities of waste generated in water
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14 Status Report on Research
treatment are being studied, and information is being collected on
the chemical, physical, and biological characteristics of the wastes.
Municipalities. A research program is underway at the Shore-
mont Water Treatment Plant at Rochester, New York, on use of natural
freezing to alter the physical nature of alum sludge.
The City of Dayton, Ohio is conducting research in conjunction
with their lime reclamation plant. Work is underway on techniques
for reducing magnesium content of the recalcined lime and to develop
a process for economic recovery of magnesium.
The City of Atlanta Department of. Water Works is conducting
extensive experimental work on reduction of moisture of alum sludge.
Vacuum filtration, air flotation, centrifugation, and pressure fil-
tration have been evaluated. Of these techniques, the filter press,
using lime as a filter aid, has found to be the most successful and
resulted in 99.9 percent recovery and 30 percent cake solids. Lime
solutions are capable of dissolving some aluminum hydroxide as
metastable calcium aluminate, and the possibility of recycle of
filtrate to take advantage of its aluminum content in the coagulation
process is being considered.
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Discussion of Status Report on Research 15
DISCUSSION OF STATUS REPORT ON RESEARCH
MR. DICK; Presumably, the reason that more research has
not been done on this problem is that the disposal of water treat-
ment plant wastes has not been considered to be a pressing problem
in the past. Today it is clearly a significant problem, and we are
going to need much more research in this area in the future. I
think it is important to point out that recent studies in advanced
waste treatment technology have revealed similar problems.
Studies of water treatment plant waste disposal sponsored
by New York State - those by Neubauer, and by Gates and McDermott -
are recent exceptions to the usual lack of information on the basic
chemical, physical, and biological properties of these wastes.
They found that alum sludges were non-Newtonian, as have previous
workers. Some early work by Gregory indicated water treatment
plant sludges in general to be plastic in nature. Other evidence
would suggest that they are probably thixotropic.
Other basic work in this area recently has dealt more
with water treatment than with waste disposal, but it might provide
information on the basic physical characteristics of the sludges.
I refer to work by Gemmell, Hannah, and Hudson, on factors influ-
encing the specific gravity and physical properties of floe produced
in water treatment processes.
One of the physical properties about which we know very
little is the settling and thickening characteristics of suspensions
produced in waste treatment plants. With softening sludges there is
not the great problem that there is with alum sludges and some'in-
formation is available from basic, studies of carbonate suspensions.
Alum sludge thickening is a far greater problem. The
feasibility of many of the alum treatment and disposal methods is
limited by the fact that these sludges cannot be concentrated to
high consistencies prior to disposal. Yet we know little about
their thickening characteristics. Again, recent exceptions are the
work by Neubauer and Gates and McDermott.
These same physical properties which prevent adequate
thickening of sludges interfere with effective dewatering as well,
and this has led to work on conditioning of sludges to alter their
physical properties.
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16 Discussion of Status Report on Research
Freezing has been reported drastically to alter the phy-
sical nature of alum sludges. Indeed, these sludges have been re-
ported to settle by gravity to 20 percent solids following freezing.
Doe and his coworkers have recommended batch processes for freezing
and emphasized the need for slow freezing. Recently, Bishop and
Fulton have concluded that freezing was not economically attractive
unless it could be done with natural cold. Work of of this type is
being done in Copenhagen with dewatering of alum sludges by natural
freezing.
Successful alteration of physical properties by heat
treatment has been reported. The temperature and pressure conditions
required are less drastic than those used in the Porteous process
of conditioning waste treatment plant sludges.
A variety of results has been reported recently on con-
ditioning of sludge with polyelectrolytes. Factors contributing to
the inconsistencies in the reported results are: differences in the
various polyelectrolytes, the reluctance of manufacturers to tell
what their products are, and unknowns regarding the handling and mix-
ing of polyelectrolytes.
Various means of dewatering sludges have been investigated.
Many of the investigations have been conducted in Great Britain.
Vacuum filtration generally has not been successful with alum sludges
without ample conditioning or use or precoat filters. Filter presses
have been favored in some British work, where various types of de-
watering equipment were compared.
Neubauer reported that centrifugation of alum sludges was
not attractive. Centrifugation, of course, is common with lime
sludges. Neubauer recommended sand filters over all other types of
dewatering devices for alum sludges. This was when the goal was to
dispose of the sludge in land fill.
Little basic research has been done on lagooning. It seems
like a simple enough process but the results reported in the litera-
ture are very divergent, and it would seem that this is an area in
which basic research is needed.
The effects of the ultimate disposal of water treatment
plant wastes on the environment needs to be considered. What is the
effect of the disposal of wastes, from water treatment plants on the
water environment? How about the land environment? For the most
part, our efforts seem to have been to condition and treat the sludge
so that we could fill holes with it, and little attention has been
given to living in harmony with the environment.
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Discussion of Status Report on Research 17
There are numerous nebulous references In the literature
to the fact that sludges are beneficial in wastewater treatment
plant operation, that they somehow improve the quality of water re-
ceiving streams, and that they are beneficial in agriculture. How-
ever, little documented work has been done in this area. We really
don't know much about their effect on land nor on water.
An exception to this lack of work in the ultimate dis-
posal of sludges is in the area of sludge reclamation or the re-
covery of chemicals from sludges. Recalcination of lime sludges
lias become well known and is perhaps beyond the basic research
stage. Reclamation of alum is being done, but it's an area that is
also undergoing research at present. Work at Lake Tahoe indicated
that alkaline methods of alum recovery were not usable whereas the
acid method was.
A list of some of the current efforts on research aspects
of the problem of disposal of wastes from water treatment plants
will include the following:
In Illinois, a committee of the AWWA Illinois Section is
surveying the characteristics of sludges produced and the treatment
methods being used, and the effects on the environment of these
disposal practices.
In Ohio, studies supported by the state deal with the
treatment and ultimate disposal of softening sludges. At the Un-
iversity of Cincinnati work is underway on centrifugation of sludges
from the Cincinnati Water Treatment Plant, using various chemical
additives.
Work on the lagooning of sludges is underway at the Un-
iversity of Massachusetts. They are studying the rates of drainage
and drying of sludges.
At the University of Illinois we are doing work on thick-
ening of sludges from water treatment plants and some work on vacuum
filtration of the sludges.
The effect of freezing by natural conditions is being in-
vestigated at the Shoremont plant at Rochester.
A study at Dayton is directed to the removal of magnesium
in lime sludges by recalcining, and they are exploring possibilities
for reclamation of magnesium.
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18 Discussion of Status Report on Research
At Atlanta work has been conducted on dewatering of
sludges, with the conclusion that filter pressing is an attractive
means of dewatering sludges.
As I indicated, much of the present work in this area
is in the related area of advanced waste treatment. Mr. Dean is
especially qualified to review these projects.
MR. DEAN; Research underway in the advanced waste treat-
ment program relates to the removal of phosphorus, principally as
the simple ortho-phosphate. Not very much condensed phosphate re-
mains after adequate secondary biological treatment.
When alum is used for precipitation in tertiary treatment,
it is used to bring down the phosphate, not just to clarify. To
take out phosphates, you use a lot more alum than you do for clari-
fying. The resulting sludges are quite different, and yet they
have facets in common, and I hope that we can learn a little from
this use of alum.
We are doing some work on freezing. We find that freez-
ing does make sludges settle better, but we have not found the dra-
matic effects that Doe reports. If we freeze a sludge, it may set-
tle twice as fast as it did before freezing. But Doe report a
tremendous difference between a "jelly" that would never dewater
and "coffeegrounds", as he describes it, after freezing.
We have been looking quite seriously at the rates of
freezing in cold climates, and it is obvious that if you want to
freeze a lot of water, the way you do it is in thin layers. By
putting down a layer of one or two inches of water each night in
cold weather, you can freeze up several feet of water with no trou-
ble at all. In central Alaska, the most freezing in a filled la-
goon would be a four foot depth. By putting down two inches a
night all winter for six months, the theoretical feet of ice xrould
be so great that you would have trouble thawing it all out again
during the summer.
The experience in Copenhagen, Denmark, has been that even
mild frost will freeze sludge. We think of Copenhagen as being far
north, yet only about half of the year does it have enough frost to
make good skating on ponds. However, the City of Copenhagen very
successfully freezes its sludges. Every little frost drops the
sludge out as a sand. Then the water is decanted, and another thin
layer of sludge is applied. The ponds are not operated in depth.
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Discussion of Status Report on Research 19
One further comment on the volatile content of the sludge.
The "combustible matter" is not all organic. Aluminum hydroxide is
extremely difficult to dehydrate, it does not dehydrate completely
at 105 degrees C, and the rest of the dehydration takes place after
it is put in the furnace. Most of the volatile content of these
sludges is just plain water of hydration.
MR. DOE: In view of Mr. Dean's statement, I would like
to comment on the effect of freezing sludge. I think one important
point we must recognize today is that all sludges are different. It
certainly is incorrect to say we can treat all sludges by a specific
process and obtain similar results.
The particular sludge reported upon in one of my papers
was from an upland catchment area in England. This was an alum
sludge which showed a spectacular change after freezing.
I have recently tried freezing on two different sludges
from plant in the U.S. These were frozen in the laboratory, and we
got similar results. These samples had more suspended solids, wheth-
er due to the river turbidity or to the activated carbon used, I
don't know. I am now quite willing'to believe that not all sludges
will freeze with such spectacular results as the upland catchment
sludge on which I first experimented. But this is an effective pro-
cess even although it may well be not very economical.
May I comment on the research report in another respect.
I feel that this reports a series of isolated but nevertheless im-
portant incidents. Unfortunately, at the present moment, there is
no central service to disseminate all this information. And, second,
there is no coordinated program at all. Each investigation is an
"ad hoc" project. This situation exists in all the countries that
we are talking about.
Personally, I feel that we now have plenty of tools for
the treatment of these wastes: vacuum filtration, freezing, press-
ing, and so on. I like pressing very much, and I hope this process
will be discussed later.
I do think it is important that a continuing program be
organized. In particular, I hope that a clearing house is created,
preferably through the AWWA Research Foundation, to collect and dis-
seminate new information.
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20 Discussion of Status Report on Research
MR. TCHQBANOGLOUS: I have two specific comments and a
general comment dealing with the characteristics of sludges pro-
duced of water treatment plants.
First, attention should be directed towards defining
the thixotropic properties of these suspensions as related to their
dewatering. It is important that the relationship between the min-
eral and organic composition of the sludge and the property of
thixotrophy be defined.
The second specific comment deals with the use of polymers.
At present, the process of polymer selection can best be described
as random. Characteristically, a number of polymers from various
manufacturers are tried until one is found that seems to work. What
is needed, however, is an ability to first define the properties of
the suspensions and then to design or select a polymer that will
produce the desired results. Based on conversations with polymer
chemists it appears feasible to think in terms of specfically de-
signed polymers.
As a general comment I would like to state that, after re-
viewing the literature on this subject as well as the conference
status reports, it is painfully apparent that more systematic ap-
proach to the study of the disposal of sludge from water treatment
plants is required. For example, although much data may be found
in the literature on this subject it is of little value since it
cannot be cross-correlated: in almost all cases the characteristics
of the sludges were not defined. What in needed is for research
workers to establish priorities in delineating the problem, so that
we may begin to systematically gather meaningful data which can be
used to optimize the design and operation of sludge disposal fac-
ilities ,
MR. DICK; I would amplify the comment on the discontinuity
in our approach to this problem and the need of a clearing house.
Note that on the first page of the status report on research we re-
ferenced a number of previous reviews of this type which were made
and essentially lost. This is an unfortunate thing.
We have been talking about thixotropy, and perhaps a def-
inition is in order. The structure of thixotropic materials breaks
down with time when they are sheared. For example, a lagoon filled
with alum sludge may look as though you would walk across it. If a
drag line is dropped into the sludge, the material changes into a
thin "soup". That is thixotropy. We don't know very much about
this property with regard to alum sludges.
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Discussion of Status Report on Research 21
MR. SHULL: First) I can confirm the comments on sludge
freezing made by Mr. Doe. On a laboratory scale we tried freezing
three different types of sludge: One of these was a straight alum
sludge, another was an alum sludge developed from water containing
high turbidity, and the third was an alum sludge containing acti-
vated carbon. On thawing, each of these sludges produced the
"coffee grounds" form. The material filtered rapidly and the fil-
trate was clear.
I want to mention the use of polymers. in treating fil-
ter backwash water, the addition of alum will sometimes improve
settling of the solids. Other times a polymer is needed. Apparent-
ly the best chemical to use is related to the zeta potential of the
floe particles. When the potential is positive, an anionic polymer
works best; when negative, either alum or a cationic polymer works
best. Thus, in plant operation we have to vary the chemicals used
from time to time as determined by jar tests and zeta potential de-
terminations .
Finally, I want to say a few words about recent research
carried out at one of our plants by representatives of the Sharpies
Division of Penrwalt Corp. This study, which ran from July 1, 1968,
until November 19, 1968, involved the use of several types of cen-
trifuges and it attempted to show the effect of centrifuging on
sludge dewatering. The sludge contained alum and activated carbon.
A preliminary report just submitted by Pennwalt shows the
following: Changes in raw water turbidity ( and accompanying changes
in pH) are reflected quite directly in the compaction characteristics
of the solids both in the sludge clarifier and in the centrifuge
cake. The clarifier is a Walker Process Clariflow, in which the
sludge is removed continuously.
Centrifuge feed concentrations through the summer ranged
from 0.2% to over 4% (by weight) suspended solids. Cake concentra-
tions up to 18% were obtained, although 15% xras a more normal limit
for high feed concentrations. At lower feed concentrations, the
concentration ratio between centrifuge cake and clarifier sludge
was approximately 10:1 for reasonable centrifuge time cycles.
After several modifications to the centrifuge, recovery
of sludge solids exceeded 95% with almost clear effluent obtaining
much of the time. On all but two days (with usual turbidity con-
ditions) centrifuge cakes met the "inversion" tests (viz., cake
would not flow out of an inverted jar).
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22 Discussion of Status Report on Research
Two 50-hour continuous pumping tests as well as other
operating data showed the sludge rates required from the clarifier
for different values of raw water turbidity and the resulting feed
concentrations. It appears that a centrifuge operating at 45 - 50
GEM should handle the clarifier sludge in most cases.
Under some conditions of low solids concentration, capac-
ities up to 507o higher and occasionally to 100% higher might be
needed for relatively brief periods. One 48" X 30" Tornado-Matic
unit operating at 1300 G should meet the usual conditions.
Filter backwash samples collected over several washing
cycles, twice during the summer, indicated a probable average back-
wash loading of 200 - 250 ppm suspended solids. Assuming the pro-
bable worst conditions for filter operation (backwashing every 10
hours), and a sludge which would settle in an auxiliary clarifier
with alum addition to sometimes over 17» concentration, an additional
48" X 30" Tornado-Matic would be required to dewater the underflow
sludge from the auxiliary clarifier, unless it were considered fea-
sible to return this auxiliary flow to the head of the plant.
Some study was made of the effect of polymers on sludge
dewatering by centrifugation. Most of the time the sludge was cen-
trifuged without the use of conditioners. A solids recovery of 95
percent was obtained without conditioning. There was some improve-
ment using a cationic polyelectrolyte, but not a great deal.
MR. DICK: Your comments show that it has been possible
to rationally select a polymer on the basis of physical behavior -
namely, zeta potential. You mentioned pH and other characteristics
which influence compaction. These are reasonable influences, but
they have not yet been explored.
MR. TCHOBANOGLOUS; We have tried process control through
zeta potential measurement, and find a great variability amongst
various polymers. There may be one polymer which reduces the po-
tential with a 1 ppm dose, and another which requires a 30 ppm dose
to get the same reduction in potential. We have found the best
operational results occur when a slight negative potential exists.
MR. SHULL: These findings correspond with ours. In one
particular case, where the zeta potential was slightly positive, an
anionic aid (Rohm & Haas Primafloc A-10) did an outstanding job.
Four milligrams per liter was the required dose. On the other hand,
about 12 mg/1 of another anionic aid would have been required.
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Discussion of Status Report on Research £3
When the zeta potential went on the negative side neither
anionic aid was affective. In this instance, however, Primafloc
C-7 (a cationic aid) did a tremendous job. So did alum. Actually,
alum and C-7 were about equally effective.
Once again, when the zeta potential changed to positive,
neither alum nor C-7 were effective and we had to change to the
anionic aid.
MR. DICK; We have tried the use of various polymers for
treating wastewater sludges. The results have been utterly frus-
trating.
MR. ADRIAN; We have done some work on freezing an alum
sludge having a considerable content of activated carbon. In one
test, the intrinsic permeability of the sludge decreased by a factor
of 50 to 55; that is, from a value of 10.7 x 10^ before freezing
to a value of 0.17 x 10^ per cm2 after freezing. These solids,
after freezing, exhibited the characteristic "coffee grounds" form.
It was noted that the duration of freezing seemed to have
some effect. If the sludge was thawed immediately upon appearing
frozen, then the change was of the order of 20 to 25 fold as meas-
ured by the intrinsic permeability.
MR. DICK; Mr. Neubauer, Do you care to comment on your
experiences with centrifugation as opposed to those in Philadelphia.
I think they are opposed, aren't they?
MR. NEUBAUER; No, I would say that they are quite com-
parable. We found that, with lab scale models, the best concentra-
tion we could get was close to 15 percent solids and more like 6
to 12 percent. We just didn't feel that this concentration could
be handled for disposal by landfill. I would like to ask how Mr.
Shull planned to handle sludge at that low a concentration.
MR. SHULL; We haven't gone that far. Ours is a pilot
plant test, but it is definitely beyond the laboratory. In our ex-
perience, the centrifuged cake of 15 percent solids appeared to be
a material which could be hauled
MR. NEUBAUER; We found that a centrifuge cake of 6 to 12
percent solids was a very greasy material. It appeared that haul-
ing this material in a truck would present a lot of problems. We
felt that a reduction to about 20 percent solids was needed before
it could be handled readily.
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24 Discussion of Status Report on Research
Just one other point. On the question of freezing, while
we didn't report on it, we did perform some laboratory tests on the
Monroe County sludge, and obtained very similar results - a "coffee
grounds" type of sludge solids.
MR. BISHOP: We have been working with the Monroe County
Water Authority to develop a method for handling their particular
sludge disposal problem. Since Monroe County lies in upper New York
State and experiences cold winter weather for extended periods of
time, freezing of their sludge appears to be an economical method
for consolidation with resulting disposal of the dried waste as land
fill.
Our first step was to freeze, in the laboratory, a sample
of the sludge from their upflow clarifiers. The sample of sludge
had thickened to about 3.5 percent total solids prior to freezing.
After freezing, the sludge had consolidated to a 17.5 percent total
solids concentration.
The results of these tests encouraged us to construct one
test lagoon which was operated through the winter of 1967-68. This
lagoon was filled to a depth of about 30 inches in January of 1968
with a sludge containing 0.3 percent total solids. The test was
terminated on August 1 with a resulting sludge total solids concen-
tration of 34 percent or about twice the results which were obtained
from the quick-freezing method performed in the laboratory.
In analyzing the cause for this increase, there is a large
increase in holding time, thereby allowing consolidation of the
sludge. The supernatant in the test lagoon contained about 5 mg/1 of
solids. The settled sludge in the bottom of the lagoon contained
about 76 percent combustible material and about 24 percent ash.
After decanting the supernatant liquid from the lagoon, about one
week was required to dry out the sludge to allow ease of handling.
Presently, we have three test lagoons in service which
have been operated through the winter season of 1968-69, Our ap-
proach at this time has concentrated on the disposal of sludge on a
batch basis. The three lagoons were constructed with varying depths
of 2 ft., 3 ft., and 4 ft. From these three test lagoons, we hope
to obtain additional data relating to the effectiveness of varying
lagoons depths. No results are available at this time.
MR. DICK: Will any individual studying freezing explain
the mechanism to me? I think there is no explanation in the liter-
ature. Are there some ideas from the group?
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Discussion of Status Report on Research
MR. DEAN; Really, we don't know. However, slow freezing
will form ice crystals. Water is removed from the sludge. In gen-
eral, the information of ice is inhibited by a colloid. Normally
the ice crystal grows at the expense of the water of hydration of
the colloid around it.
The frost heave in clay soil is similar. Here, water
migrates from the clay into the ice crystal and dehydrates the clay
around it.
I think the same sort of thing happens in freezing alu-
minum hydroxide gel. In freezing, water moves into the ice crystals,
leaving the aluminum hydroxide. When the ice is melted, there is no
great force pulling the water back into the gel.
Now, the effectiveness of freezing decreases as the or-
ganic colloid content increases. If we freeze activated sludge, as
we are doing in Milwakee, then slow freezing must be used. Fast
freezing would not allow the water time to move out of the colloid
into the ice crystal. No spectacular change takes place: the "cof-
fee grounds" form does not result. The sludge, if very carefully
handled, can be dewatered on a screen. If the sludge is pumped any
distance, or run down a flume, most of the effect of freezing will
be lost. What has been described is the extreme case of a sludge
having a very high content of organics. We are now working with
activated sludge containing alum.
The ultimate disposal of alum sludges is something I
should have said more about. Thick layers of alum sludge will clog
the soil, as Mr. Doe has described on the basis of his experience.
We know that if alum is put on the soil and allowed to dry down, it
will inhibit seed sprouting. We have made a little study of organic
sludges containing alum. It doesn't take very much force to break
up this crust. If freezing occurs, there is no trouble with alum.
Getting back to disposal of alum, Mr. Earth, in Cincinnati,
has been studying the addition of alum or sodium aluminate to trick-
ling filters and activated sludge plants. He report that the alumi-
num hydroxide has no effect on the biological operation of the acti-
vated sludge plants, and little effect on the trickling filter plant.
If you waste alum sludge to the sewer at the rate it is produced, our
evidence indicates that there will be no upset of the biological
plant, and there may be some increased phosphate removal.
MR. NEBIKER: What is the effect of alum sludge on sewage
sludge digesters?
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26 Discussion of Status Report on Research
MR. DEAN: The effect of aluminum hydroxide on digesters
has been studied on only a small scale. We have small 15-gal. di-
gesters that appear to operate very well with added alum sludge.
No influence on digesters or on sludge drying was noted when 110
parts of alum equivalent was added to the activated sludge feed to
the digesters.
MR. BACH: It is interesting to note that, in practically
every instance, studies of freezing alum sludge give results similar
to those reported by Mr. Doe. At Minneapolis we have made such
studies and find that, on thawing, water separates readily and leaves
granular solids.
We are not presently using alum as a coagulant except in
our experimental plant. Our interest in research on alum sludge
disposal is as a very practical problem - we have no space available
to dispose of sludge as land fill. We have made some study of cen-
trifuging and some of filter pressing. With each method, we found
it necessary to use about 125 ppm of coagulant aid in order to re-
move 95 percent of the solids. We are very interested in some means
of concentrating the sludge and drying it.
MR. KINMAN; One point has been made, and I think we need
to emphasize it again: the fact that these sludges are different,
even within the same treatment plant, and this may account for some
of the variations in the research results.
Maybe one of our primary needs is to be able to charac-
terize an alum sludge chemically. Some reports do not indicate what
the chemical characteristics of the sludge actually were. I am re-
ferring to changes in the nature of the sludge which result from
variations in the quality of raw water, and of chemical dosage which
affect changes in the composition of the sludge.
MR.., LACY: This comprehensive report would be much more
useful if the authors could point out future research and develop-
ment requirements as the participants see them, no matter how im-
aginative and far out the ideas might be.
Also, I think there should be some elaboration in this re-
port on the possible industrial applications of the lime sludges, for
example. I have no experience on sludge utilization to cite, but
encourage studying this.
-------
Discussion of Status Report on Research 27
MR. BIAGK: I can mention two recent reports on practical
applications of lime softening sludges. One describes the use of
such sludge to remove sulfur dioxide from a hot gas stream (Hawkins
and Malina, 1969). The second describes phosphate removal charac-
teristics of lime softening sludge (Emery and Malina, 1969).
These two references should be added to the excellent
bibliography prepared by the AWWA Research Foundation as a. part of
this report. (Note: These references have been included in the
bibliography.)
MR. DICK; The need for pointing out areas where research
is needed is certainly an important contribution to be made by this
Conference. We hope to do that in our Committee reports.
This concludes discussion of the status report on research.
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28 Engineering Report - Filter Wash-water
STATUS REPORT ON ENGINEERING
Walter K. Neubauer and Donald P. Proudfit
TREATMENT AND REUSE OF FILTER WASHWATER
In the past it has been common practice for washwater wasted
from water purification plants to be discharged directly to the
nearest stream as filters are washed. Recent emphasis on control
of pollution sources and the fact that the water works industry is
the major benefactor of this emphasis, has made direct discharge
of the washv/ater unacceptable in most cases.
Characteristics of Washwater
Filter washwater may contain fine clay particles, hydroxides
of iron and aluminum, iron oxide, activated carbon and other mate-
rials representative of the chemicals used in water treatment. The
wastes will often include debris and chemical precipitates from the
filter media and small portions of the media itself, and they may
include a concentration of strainings of organic debris. Turbid-
ities have been recorded in excess of 2,000 mg/1. Excessive chemi-
cal doses may change the character of the washwater (Dean, 1953,
and Hall, 1947).
Typical 5 day BOD values for alum plant washwater are extreme-
ly low, ranging from 0 to 5 mg/1. COD values have been recorded as
high as 160 mg/1. The pH values are reported to range from 6.9 to
7.8 (Russelmann, 1968).
The solids content will vary during backwash with peaks in
excess of 800 mg/1 (O'Brien and Gere Report, 1966) and average val-
ues ranging up to 400 mg/1 for plants utilizing alum. Average val-
ues are cited as 1500 mg/1 for plants utilizing iron and manganese
removal (Russelmann, 1968). Approximately 1/3 of the total solids
are volatile in most cases. Suspended solids range from 40 to some-
what in excess of 100 mg/1 in alum plants, and up to 1,400 mg/1 for
-------
Engineering Report - Filter Washwater 29
plants utilizing iron and manganese removal. Average values of
suspended solids are reported at approximately 800 ppm (Walton).
Reuse of Washwater
Many chemical coagulation plants reuse filter washwater. Since
the washwater comprises 2 to 57o of plant flow, many plants practice
conservation by recycling filter washwater, thus eliminating the
washwater as a waste stream.
Wichita Falls, Texas, mixes the filtered backwash water with a
lagoon overflow before recycling.
It is sometimes desirable to settle the backwash water before
recycling. Colorado Springs has a 20 mg reservoir converted for
reuse of washwater. At this plant, 97% of the turbidity and 79% of
the total solids are removed in one hour after each backwash (Proud-
fit, 1968). Recirculation of filter backwash waters is practiced in
some plants only during periods of low flow.
Direct Discharge of Washwater
The most common method currently utilized in the disposal of
filter washwater is direct discharge to a watercourse.
In a survey of some 1700 plants, it was shown that 93% of the
plants eventually discharged filter washings into streams or lakes
without treatment (Dean, 1953).
When it is deemed necessary to discharge filter washwater di-
rectly to a watercourse, low flow augmentation can be utilized to
offset the pollutional loading.
Treatment Methods
A small number of plants treat filter washwater before dis-
charging them to stream. The most common methods of treatment in-
clude lagoons and settling basins. In the survey referenced above,
this type of treatment was used in only 2% of all plants surveyed.
Even when lagoons are employed, there are normally no facilities
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30 Engineering Report - Coagulant Sludges
for removal of the sludge that accumulates and this is sometimes
discharged at high water levels (Hall, 1947).
A substantial portion of the suspended solids may be removed
by settling basins or lagoons. When these clarification basins are
large in size, provision should be made for surface withdrawal of
the supernatant and removal of sludge accumulation.
No papers outlining other forms of treatment were found in the
literature searched.
COAGULANT SLUDGES
Sludge Characteristics
The water treatment plant wastes most difficult to treat are
those resulting from chemical coagulation processes. Such sludges
are likely to contain inert materials such as sand or silt, organics
in solution or suspension, microscopic organisms of considerable
variety, and constituents characteristic of the chemicals used in
the process: aluminum or iron salts, polyelectrolytes, lime, soda
ash, caustic soda, etc. (Russelmann, 1968). These constituents
yield a chemical suspension or sludge of extremely high moisture
content (over 98%). This sludge varies in color depending on the
nature of the impurities and remains insoluble in a pH range of nat-
ural water. When discharged to streams of low velocity if may form
sludge banks and, on occasion, has caused unpleasant odors.
Perhaps the most important parameter in discussing wastewater
sludge is the solids content. Reported values for alum sludges
range from 1,000 to 17,000 mg/1 dry solids, with suspended solids
usually accounting for 75 to 90 oercent of the total (Neubauer,
1968; O'Brien and Gere Report, 1966; Russelmann, 1968). The vol-
atile content ranges from 20 to 35 percent of total solids.
The biochemical oxygen demand (BOD) is relatively low, approx-
imating that of secondary sewage effluent. In carrying the BOD
test to its ultimate value it was found that & considerable amount
of BOD was exerted after the initial 5 day period. In one instance,
the 5 day BOD was less than 30 percent of the ultimate demand. Typ-
ical values of 5 day BOD range from 30 to approximately 150 mg/1.
The chemical oxygen demand (COD) is considerably higher. It
-------
TABLE I
COAGULATION SLUDGE CHARACTERISTICS
From: Russelman, 1968
Plant
A
B
C (3)
D'
E
Treatment
Alum
Coagulation &
Sedimentation
Alum
Coagulation,
Clarifier
Alum
Coagulation,
Clarifier
Alum
Coagulation
Clarifier
Diatomite
Filter
BOD Total
(5-day) COD Solids
mg/1 ms/1 pH mg/1
41
72 (1)
144 (2) 540 7.1 1,159
90 2,100 7.1 10,016
108 15,500 6.0 16,830
44 XXX 6.0 XXX
105 340 7.6 7,466
Total
Volatile Suspended
Solids Solids
mg/1 mg/1
571 1,110
3,656 5,105
10,166 19,044
XXX 15,790
275 7,560
Volatile
Suspended
Solids
mg/1
620
2,285
10,722
4,130
260
(1) BOD after 7 days
(2) BOD after 27 days
(3) Activated carbon in sample
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32 Engineering Report - Coagulant Sludges
has been found to range anywhere from 500 to 15,000 rag/1, the high-
er value being due to activated carbon present in the sample.
Table 1 illustrates some typical values of coagulation sludge
characteristics.
The dry unit weight of coagulant sludges ranges from 75 to 95
Ibs/cu.ft. (Krasauskas, 1968). For purposes of disposal by land-
fill it is estimated that a 20 percent solids content is nesessary.
Alum sludge at 20 percent solids was found to have a unit weight of
approximately 73 Ib/cu.ft.
Direct Discharge to Lakes, Streams, etc.
The most common method of disposal of coagulant sludges pre-
sently is by direct discharge to water courses. In a survey of
1,530 filter plants it was revealed that 92.5 percent discharged
sludges directly (Dean, 1953) .
The satisfactory disposal of sludge in streams or rivers is
dependent upon flow for adequate dilution. Controlled discharge at
high flow will help, but of course requires storage facilities.
Filter plants at Bangor and Biddeford, Maine, and Lawrence, Massa-
chusetts pump raw water from large rivers and disposal of sludge
and washwater in these streams with ample dilution is reported to
be a practical and economical method (Smith, F.E., 1948).
The City of Atlanta treats a most difficult water from the
Chattahoochee River by coagulation with alum. The 30,000 Ibs per
day of sludge produced, together with the washwater, are returned
directly to the river below the intake. Because of the polluted
status of the Chattahoochee, the wastes from the water treatment
plant have been regarded as of relatively minor importance. How-
ever, a major research project is now being undertaken by the
Atlanta Water Department for more satisfactory methods of disposal
(Doe, 1966-67).
The list of plants utilizing this method of disposal is almost
endless. The growing emphasis on pollution control is turning what
has been in the past a very economical method of disposal into one
that is completely untenable. For many treatment plants adequate
methods of disposal other than direct discharge simply have not been
available.
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Engineering Report - Coagulant Sludges 33
Concentration of Coagulant Sludges
Of primary concern in disposal of sludges is the reduction of
volume. In the case of coagulant sludges not only is the waste dis-
posal problem reduced, but in many cases the supernatant from such
reduction can by used to supplement the raw water source.
The simplest method of sludge concentration is plain sedimenta-
tion. Some preliminary design criteria for sedimentation of coag-
ulant sludges indicate that a settling basin designed on a one hour
detention time, above four months sludge storage, should suffice
(Hall, 1947). Settling tests on alum sludge indicate that the sludge
could be brought from 0.5 to 1 percent solids through sedimentation
(McWain, 1968; Neubauer, 1968; O'Brien and Gere, 1966). Vertical
flow tanks, by the very nature of their design, are usually de-
sludged periodically as part of the operation of the tanks. On the
other hand, horizontal flow tanks are usually emptied two or three
times a year. Design considerations should include the volume and
thickness of the sludge produced (Doe, 1966-67).
A promising new method of sedimentation titled Lamella Sedi-
mentation has recently been developed at Chalmers University in
Sweden. Its main advantages are that it greatly reduces the volume
of the sedimentation tank and limits the problem of piping during
de-sludging. The process consists of the upward flow of flocculated
water at an angle of some 55 to 60 degrees from the horizontal, be-
tween a series of parallel plates spaced a few inches apart. The
tanks are designed to have a throughput capacity of 3 cubuc meters
per hour per cubic meter of volume, some five times that of conven-
tional sedimentation tanks (Doe, 1966-67). The method is analgous
to that utilized by Neptune Microfloc in the United States (Gulp
et al., 1968).
Sedimentation may be greatly enhanced by thickening x^hereby
the sludge is stirred during the sedimentation process. The sim-
plest and most widely used form of disposal of hydroxide and lime
softening sludges in the United Kingdom involves collection and
thickening by natural sedimentation and holding tanks prior to dis-
posal in lagoons or drying beds (Young, 1968). The effectiveness
of thickening for coagulant sludges is well documented in the lit-
erature.
Detailed design and operating criteria for sedimentation and
thickening are readily available in the literature on sewage treat-
ment and industrial waste disposal.
-------
SLUDGE THICKENING
i
1
6 hrt
THE EFFECT OF SLOW STIRRING
Stocks Plant, Fylde Water Board, England
Left: 30-foot diameter Stirrer
Right: Three Sludge Thickening Tanks
-34-
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Engineering Report - Coagulant Sludge Treatment 35_
TREATMENT OF COAGULANT SLUDGES
Discharge to Sanitary Sewers
An increasingly popular method of disposal of coagulant sludges
is discharge to sewage treatment plants via sanitary sewers. In a
survey of over 1,500 plants Dean found only four that used this meth-
od prior to 1953 (31). A number of large cities, such as Detroit,
Wilmington, and Philadelphia presently discharge to sanitary sewers.
There are no reported difficulties at the waste treatment plants in-
volved caused by the addition of the sludge, with the exception of
some initial problems in the vacuum filtration process at Detroit
(Krasauskas, 1968). Some chalk sludges have been found capable of
neutralizing acid wastes and actually provide a benefit to the sew-
age treatment plants (Anon., Civil Eng., 1949).
Depending on their nature, specific sludges may actually work
as coagulant aids in the treatment of sewage. An example of this
would be the use of sludges containing lime as coagulant aids for
vacuum filtration.
A flow velocity of 2.5 fps is used to prevent settling of these
coagulant sludges in Detroit sewers. The possibility of the sludge
silting in the sewer must always be considered (Smith, 1948; Doe,
1966-67; Krasauskas, 1968).
Another major problem in the discharge of coagulant sludges to
sanitary sewers is the possible slug load on the sewage treatment
plant. Most sedimentation basins in water treatment plants are
cleaned by completely unwatering and the sludge is pumped to the
sewer as a slug.
Evaluation of the following considerations before discharge of
a coagulant sludge to a municipal treatment plant is recommended
(Smith, 1948):
1. Waste damage to sewer system.
2. Amenability of the waste to existing treatment processes.
3. Hydraulic capacity of sewage treatment facilities.
4. Strength of the waste in relation to interfere with the
treatment processes.
5. The effect of waste on the final plant effluent.
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36 Engineering Report - Coagulant Sludge Treatment
The following recommendations have also been made (Doe, 1966-
67):
1. Cross connections must be precluded, possibly by a water
break, to insure that if the sewer backs up the raw sew-
age passes elsewhere.
2. Sludge should be discharged as an average flow over 24
hour period, not as a slug flow.
3. Fears have been expressed that an alum sludge would choke
the bacteria in trickling filters; the activated sludge
process, however, does not seem to have such drawbacks.
Use of Lagoons
The most common treatment method presently utilized at water
treatment plants for handling coagulant sludges is lagooning. In
areas where ample land is available, lagooning can be quite eco-
nomical. It enables the utilization of natural temperatures (both
drying and freezing) to aid in the dewatering of the sludge.
The major problem in many lagoons is that the sludge is not
sufficiently concentrated so that it can be removed from the lagoon
to land fill. Typical solids contents obtained by lagooning coag-
ulant sludges range from 1 percent to as high as 10 percent. The
detailed study of lagoons at the Monroe County Water Authority
Shoremont Plant, in New York state, indicated that after three years
of lagooning, the highest solids concentrations found anywhere in
the lagoon was about 10 percent (McWain, 1968; Neubauer, 1968;
O'Brien and Gere Report, 1966).
Lagoons may also be provided with underdrain systems. The
British Water Research Association is proceeding to investigate
such artificial drainage in lagoons (Doe, 1966-67).
Drying Beds
Sand drying beds are used extensively for the dewatering of
sewage sludges. These beds usually consist of 6 to 12 inches of
sand ranging in size up to 0.5 mm. The underdrain system includes
graded gravel, varying in depth from 6 to 12 inches, and 6 to 8 inch
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Engineering Report - Coagulant Sludge Treatment 37
drain pipes to convey the filtrate from the beds. A number of pa-
ameters affect the ability of the drying beds to dex^ater the sludge.
These include air temperature and humidity, wind currents and vis-
cosity of the sludge.
A Colorado Springs Plant is designed to treat basin sludge
with drying beds. Sludge from the recovery basin will be discharged
to drying beds and it is expected that only a. small amount of clear
filtrate will be discharged from the beds to the stream. After
natural drying, sludge will be landfilled (Proudfit, 1968).
Bench scale tests performed on alum sludge indicate that a
solids content of 20 percent can be obtained in 70 to 100 hours
with 97 percent suspended solids removed from the filtrate. These
tests indicate that a final filtrate containing suspended solids in
the range of 200 to 450 mg/1 could be expected, dependent on the
sand size and the time required to reach the required solids con-
tent. A 1.0 mm sand was found too coarse to yield the necessary
filtrate quality.
Another form of drying beds, termed wedge wire filtration,
has been reported (Sankey, 1967). This utilizes mesh sizes ranging
from 0.125 to 0.25 millimeters. An optimum depth for a 2 percent
solids sludge is given at 6 to 12 inches. Beds must be covered for
the first 7 to 10 days, and then can be left open for a 21 day drain-
ing and drying period. It is also possible to layer new sludge over
the old. Beds should be designed in pairs with a traveling cover.
Vacuum filtration
The vacuum filter has long been a popular method for dewatering
sludges in the waste treatment and chemical process industries. Its
application to coagulant sludges has, however, met with limited suc-
cess. The Opel Car Works in West Germany has been listed (Doe,
1966-67) as making the only successful application of vacuum filters
to alum sludges. The success is attributed to the tremendous amount
of calcium carbide, readily converted to lime, available as a by
product of the car works. Cake thickness varied from 2 to 20 milli-
meters and solids content ranged from 20 to 40 percent.
While vacuum filters are often used with lime sludges, a pre-
coat is required with hydroxide sludges (Young, 1968). This was
borne out in numerous bench scale tests where a pre-coat was re-
quired at 2 percent solids content, giving filter loadings of 5.6
-------
SLUDGE PRESSING
Pilot Scale
Sludge Pressing
Equipment
(New Jersey)
Full Size
Sludge Press
Industrial Use
(USA)
-38-
-------
Engineering Report - Coagulant Sludge Treatment 39
gph per sq.ft. with a pre-coat of 1 pound per 10 gallons. Cake
solids approximated 15%.
Tests of a rotary vacuum pre-coat filter at the Albany treat-
ment plant by Johns-Mansville indicated successful dewatering of
1.25% solids content sludge to 32% cake.
In an unique application of an industrial waste, H. R. Peters
of the Atlanta Waterworks reports that a. combination of coagulant
aids, alum sludge and a paper pulp filler yielded a loading rate
of 5 Ibs. per hr. per sq.ft. on a rotary vacuum filter.
Pressure Filtration
Pressure filters are used extensively in the chemical process
industries for dewatering sludges. They have been utilized in Eng-
land in the treatment of waste coagulant sludges, but their use in
treatment of these sludges in the U.S. has not been extensive.
Pressure filters are utilized with dewatering of alum sludges
at the Arnfield Water Works. A 1.8% raw sludge, after conditioning
with lime, is pressed to get a cake thickness of 25% solids. Press-
ing time is normally eight hours (Doe, 1966-67).
The Daer Water Works reports 18.37, solids in an alum sludge
after 24 hours of pressing. Addition of a lime slurry to the sludge
reduced the required pressing time to 6 hours (126). A number of
other reports indicated success with pressure filtration of chemi-
cally pretreated alum sludge (Webster, 1966; Sankey, 1967; Young,
1968; Doe, 1958).
Gentrifugation
The success of centrifugation in dewatering lime softening
sludges has been demonstrated in many installations throughout the
world, due to the relatively high ratio of solids weight to liquid
weight. However, in the case of coagulant sludges, this ratio is
very low.
A number of investigations have been conducted on the use of
centrifuges for dewatering coagulant sludges and several full-scale
installations have been built. At present, however, the process
has been found to be unacceptable for this purpose.
-------
SLUDGE FREEZING
>v
Sketch - Typical Alum Sludge Freezing Unit
To thaw, flow of refrigerant (ammonia)Js reversed
Doe, P.W., Report
British Waterworks Association
Used by permission
-40-
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Engineering Report - Coagulant Sludge Treatment 41
Doe, in 1966-67, published an review of water works waste dis-
posal practices throughout the world. He found no successful ex-
amples of dewatering of alum sludge by centrifuging. Lab scale
tests experienced difficulty in obtaining greater than 12% dry sol-
ids by this process although Peters, in 1968, reported getting 25-
30% dry solids from recent experiments conducted at the Chattahoo-
chie Water Treatment Plant, The latter results may be affected by
the relatively high turbidity of the incoming raw water plus the
addition' of lime (along with alum), resulting in a sludge with ap-
proximately 5% dry weight of solids.
Freezing
Dewatering of sewage sludge by freezing was first studied and
reported on by Clements, in 1950. Consideration of application of
this method to alum sludge was given by Palin, in 1954, and again
by Doe, in 1958. These early experiments on this process indicated
that the freezing of a coagulant sludge would produce a physical
change in the solids which is quite dramatic. The gelatinous con-
sistency is dissipated and sludge particles become of a finite
size, similar to grains of sand. Saturation with water does not
produce any marked dissolution of the particles.
Based on this early experimentation, the Fylde Water Board in
Blackpool, England, through Frank Law, Engineer for the Board, con-
structed a full-scale plant at the Stocks Waterworks for the freez-
ing of alum sludge. This plant has operated successfully since
1961, and a second plant at Fishmoor has operated successfully
since 1964. The design, construction and operation of these plants
have been reported upon quite fully by Doe.
In Scotland, the Daer Water Works is in the process of con-
structing a sludge freezing and alum recovery plant for its water
works. This plant was expected to be in operation in 1968. The
basis for this process has been discussed (Webster, 1966) and fur-
ther reported upon (Young, 1968). Other plants reported to be con-
structing facilities for the mechanical freezing of sludge are at
Tokyo, Japan and Lippstadt, W. Germany (Doe, 1966-67).
In those climates where frost occurs frequently during the
winter months, natural freezing of alum sludge is a distinct pos-
sibility. The only full-scale natural freezing operation concern-
ing alum sludge is being practiced at the Senders«5 Treatment Plant
of the City of Copenhagen, Denmark. This process has operated very
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4_2 Engineering Report - Coagulant Sludge Treatment
successfully since 1963 (Doe, 1966-67; Christensen, 1968). The
freezing of the sludge takes place in lagoons with an effective
height of one meter and having a drained gravel bottom. As a re-
sult of the freezing and thawing cycles, and drainage through the
gravel, the sludge reduction is dramatic. The amount of sludge
remaining after 2 years of operation consisted of a layer about 4
centimeters deep.
Experiments in natural freezing have also been conducted in
the United States at the Shoremont Plant of the Monroe County Water
Authority in Rochester, New York. Reports have indicated that nat-
ural freezing of the alum sludge from Shoremont in lagoons does
produce a very marked reduction of sludge solids. Freezing also
results in a change in the character of the solids which should per-
mit of easy disposal (McTighe, 1968; Bishop, 1968).
Heat and Pressure
Very little is known about the treatment of coagulant sludges
by heat, i.e., high temperatures applied to the sludge under pres-
sure. Palin (1954) reported on experiments utilizing the Porteous
process for dewatering sewage sludge. These experiments showed
that coagulant sludge volumes were substantially reduced by ap-
plication of heat and pressure at levels below that utilized by the
Porteous process. Doe (1958) felt that heat treatment or "boiling
the sludge under pressure" would be effective in destroying the ge-
latinous nature of alum sludge.
Chemical Recovery of Alum
Although it has been reported that attempts were made in the
early 1900's to reclaim alum from water treatment plant sludge,
the first definitive investigations seemed to have been made by
Eidsness of Black Laboratories, Inc. for the City of Orlando,
Florida (1952) . Later studies were made by Palin (1954) and Vahidi
(1960).
The first engineering investigation leading to full scale op-
eration of a recovery plant was undertaken by Roberts and Roddy
(1960) for the water treatment plant at Tampa in the late 1950's.
Based on these experiments, a portion of the Tampa treatment plant
was converted to recovery aluminum sulfate from the aluminum hydroxide
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Engineering Report - Coagulant Sludge Treatment 43
sludge by the addition of sulfuric acid. The full scale plant op-
erated for a short time and then the process was abandoned, accord-
ing to Doe (1966-67), because of the rapidly changing water quality
and the fact that at times softening was required, resulting in no
production of hydroxide sludge. In addition, the high color residual
could not be eliminated except by high doses of chlorine, and the
entire process required constant and skilled supervision.
At the Daer Water Treatment Works near Hamilton, Scotland, an
ambitious pilot plant program reported by Webster (1966) and com-
mented on by Doe looks to a combination of the mechanical freezing
of sludge with subsequent recovery of alum by treatment with sulfuric
acid. One of the important aspects of the pilot plant study has been
to be certain that there is no build-up of color or iron over a per-
iod of time. This .problem has been experienced in other attempts at
alum recovery. The full scale plant at Daer was expected to go into
operation in 1968.
DIATOMETE FILTER SLUDGES
Description of Sludge
The nature of the diatomaceous earth process is such that the
amount of filter aid is -usually twice that of the impurities removed
from the water. This means that the filter cake, which is removed
from the filter element and disposed of periodically, has charac-
teristics similar to the diatomaceous earth itself. This material
is the fossil skeletons of microscopic water plants and is composed
almost entirely of pure silica. It has a dry density of about ten
pounds per cubic foot and the specific gravity is approximately
2.0.
Direct Disposal
As in most other types of waste from water treatment plants,
the filter cake which is removed in diatomaceous earth filtration
has, in most cases, been discharged directly to a water course.
Because of the relatively high ratio of the solids weight to the
liquid weight, settlement takes place relatively rapidly. In deep,
quiet waters, the wastes settle out quickly and the nuisance is of
a minor nature. In shallow, swift moving bodies of water, the
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44 Engineering Report - Coagulant Sludge Treatment
waste can be carried considerable distances and deposited in areas
where it can become a nuisance.
Treatment
The only method of treatment of diatomaceous earth sludges in
common use today is lagooning. As noted earlier, the ratio of sol-
ids weight to liquid weight promotes fairly rapid settlement of the
solids in the sludge. Although no specific date are available,
observations indicate that a detention time of 2 to 4 hours is ad-
equate to settle out a majority of the solid particles. This re-
latively short detention time permits construction of small lagoons
and the method is thus an economical one.
An installation which has been very successful is at Massena,
New York, where a small lagoon treats the waste from a 5 mgd dia-
tomite filtration plant prior to discharge of the supernatant to
and old canal. Another plant in Newark, New York, utilizes a small
detention basin with equal success prior to discharge of the waste
effluent into a very small stream.
BRINE WASTES
Description of Wastes
Brine wastes are principally those resulting from regeneration
of ion exchange softening units utilizing sodium zeolite as the
resin. These wastes constitute from 3 to 10% of the treated water
volume (Haney, 1947; Haney, 1949) and contain substantial quantities
of the chlorides of calcium and magnesium with small amounts of var-
ious compounds of iron and manganese. Haney in 1949 reported the
analysis of a waste brine shown in Table 2.
Russelmann (1968) described the waste effluent of an ion ex-
change softener near Albany, New York, as containing over 20,000
mg/1 of total solids and almost 12,000 mg/1 of chlorides. Very lit-
tle suspended solids are present in waste brines.
The most troublesome component of the waste is the chloride
ion derived from the salt used for regeneration. Chlorides cannot
be removed by any reasonably economical method.
-------
Engineering Report - Brine Wastes 45
TABLE 2
ANALYSIS - WASTE BRINE FROM ION EXCHANGE SOFTENER
Item mg/1
Calcium 1,720
Magnesium 600
Sodium and Potassium 3,325
Sulfate 328
Chloride 9,600
Total Dissolved Solids 15,656
Total Hardness 7,762
Direct Disposal
Direct disposal to streams, lakes and other bodies of
water has been practiced to a large extent by many water works
operating ion exchange softening units. If the dilution is suffi-
cient to very quickly reduce the concentration of chlorides below
an acceptable level, this method may be tolerated. However, if
dilution is not adequate, excessively high concentrations of chlo-
rides can create not only a nuisance but problems of a toxic nature,
affecting aquatic and fish life and livestock (Haney, 1947; Haney,
1949; Russelmann, 1968).
The U.S. Public Health Service has set a limit of 250 mg/1
of chlorides for potable water. However, lesser concentrations can
be harmful to certain life forms. The Federal Water Pollution Con-
trol Administration has indicated the hazards of excessive salts,
particularly sodium, to irrigation waters.
Sewage Treatment Plant
In some cases, brine wastes have been discharged to a sanitary
sewer system and ultimately treated in a sewage treatment plant
through dilution. However, if the concentration is high, these wastes
may cause corrosion of equipment as they pass through the plant and
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46 Engineering Report - Brine Wastes
piping system. If such wastes reach the treatment plant as a slug,
they can cause an upset of biological balance of the plant.
Lagoons
Lagoons or evaporation ponds have been used with mixed success,
according to reports by Haney (1947, 1949). Because of the lowering
of the vapor pressure of the water by the dissolved salts, evapora-
tion from lagoons may be substantially less than for fresh water in
a particular area. Haney notes, that, as evaporation does occur,
the concentration of dissolved salts is increased with further low-
ering of the vapor pressure and retardation of evaporation. Even
if evaporation is successful, there remains a problem of disposing
of the residual salts.
If the soil is porous, brine seepage from a lagoon may result
in mineralization of nearby surface streams or ground water. Many
instances of pollution of this nature have been reported. The use
of a lagoon for temporary storage and then subsequent release to a
watercourse has also been reported. This type of operation is suit-
able where an adequate watercourse is available at certain periods
of the year. A method such as this requires careful control of dis-
charges to avoid undue contamination of the receiving stream.
Brine Disposal Wells
In certain geological formations, the use of deep wells for the
disposal of brine waste has proven satisfactory. This has been par-
ticularly true in the oil fields where large quantities of brine
have been disposed of in wells from 400 to 5,000 feet in depth.
However, Haney points out that the danger of contamination of aquifers
supplying potable water supplies is great. Care must be taken to in-
vestigate the geological formation into which the brine will flow and
extensive testing must be undertaken from time to time to determine
the effects of the brine flow on adjacent water supplies. Care must
also be taken that the formation into which the brine is disposed
does not become plugged with the products of corrosion. Prevention
or removal of these products and suspended matter in the brine be-
fore injection into the well is essential.
-------
Engineering Report - Iron and Manganese Sludges
J£L
TABLE 3
IRON AND MANAGANESE SLUDGE TREATMENT
Process
Oxidation with
or without
chemical assist.
Slow sand fil-
tration.
Coagulation
and clarifi-
cation. Rap-
id sand fil-
tration.
Oxidation with
chemicals.
Pressure or
gravity fil-
tration.
Aeration with
pH adjustment.
With or with-
out chemicals.
Detention.
Pressure or
gravity fil-
tration.
Manganese zeo-
lite.
Sludge Form Sludge Disposal
Ion-exchange
Retained on
filter media
Clarifier
sludge;
retained on
filter media
Retained on
filter media
Retained on
filter media
Precipita-
tion on fil-
ter,
generally
anthracite
Insignifi-
cant, pre-
dominately
and regener-
ant brines
Physical-mechanical
removal from filter
media, hauled to
disposal site.
Removed with clari-
fier and/or filter
backwash sludge
Removed with fil-
ter backwash
sludge
Removed with fil-
ter backwash
sludge
Removed with back-
wash sludge. Re-
gener ant brines
removed with rinse
water
Removed with rinse
water
Comments
Primarily used
in older plants.
Considered ulti-
mate disposal;
no further study
needed
Usually combined
with coagulation
and/or softening
sludges. Addi-
tional disposal
study needed.
Disposal problem
same as for other
filter backwash
sludge
Disposal problem
same as for other
filter backwash
sludge
Additional study
needed on effects
of brines on re-
ceiving vehicle
Additional study
needed on effect
of brines on re-
ceiving vehicle
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48 Engineering Report - Iron and Manganese Sludges
IRON AND MANGANESE SLUDGES
Processes for removal of iron and manganese from water are cat-
egorized in Table 3. Variations of each process are in use but dis-
posal of any sludges would be the same as listed for the basic pro-
cess category. With the exception of regenerant sludges as refer-
enced under the manganese zeolite and ion-exchange processes, no
sludge disposal data were found in the available literature.
MICROSTRAINER SLUDGES
Microstrainer sludges consist primarily of algal growths and
larger particles of turbidity. The sludges produced by microstain-
ers are not considered a waste disposal problem by some authorities;
however, this is moot and depends on circumstances in a given in-
stallation. The Recommended Standards for Water Works (10-State
Standards) (146) requires that provisions be made for the proper
disposal of washwater. Table 4 summarizes available data on a num-
ber of microstrainer installations.
Additional investigation of the installations listed in Tables
3 and 4, such as definitive information on raw water characteristics,
special provisions, amount of waste, and its characteristics would
be helpful.
PRESEDIMENTATION WITHOUT TREATMENT
Description of specific installations and factual data on con-
trolled tests or nature of presedimentation sludges are not found
in available literature. In general, the literature expresses only
the author's opinion regarding the degree of pollution to the re-
ceiving stream. It is the apparent consensus that pollution is not
produced if sufficient dilution of the sludge is obtained in the
receiving stream. By controlling the time and amount of sludge
discharged to the stream, it is contended proper dilution can be
effected. The implied criterion to judge pollutional effect is the
formation of sludge banks in the receiving stream. The more recent
literature implies that states increasingly classify presedimenta-
tion sludges as sources of water pollution along with other types
of sludges, and that better methods of disposal must be found.
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Engineering Report - Microstrainer Sludges
49
TABLE 4
MICROSTRA1NER SLUDGE TREATMENT
Installation
Fontana System
San Gabriel
Water Co.
Raw Water
Lytle Creek
0-3 ppm
turbidity
Special Provisions Sludge Disposal
Bypass screems when
turbidity is great-
er than 25 ppm.
Treat screens with
hypochlorite and
ultraviolet radia-
tion
1.6% waste water
no information
on disposal
Kenosha, Wise.
Lake Michigan Treat screens with 4.170 washwater
5-15 ppm
turbidity
hypochlorite ea 6
wks, oxidizing
agent ea 4 mo. to
remove iron bacte-
ria
pumped, 2.77o
wasted - return-
ed to Lake Mich-
igan
Denver, Colo.
Colorado Springs,
Colo.
Boulder, Colo.
Surface-Mar-
ston Lake. 3-5
ppm avg. tur-
bidity
Snow melt,
less than 3
JTU turbidity
Snow melt
Add Cl2 to waste.
Treat screens with
hypochlorite
Microstrainers used
only for peak loads
1% waste, return-
ed to Lake Mich-
igan
Returned to Monu-
ment Creek down-
stream from plant
To sludge ponds,
then drained off
to Boulder Creek
Baker Metro,
Colo.
Palisade, Colo.
Glenwood Springs,
Colo.
To sewage treat-
ment plant
To irrigation
ditch and used
for irrigation
Returned to No
Name Creek
-------
50
Engineering Report - Microstrainer Sludges
TABLE 4 (Contd)
Installation
Loveland, Colo.
Estes Park,
Colo.
Grand Junction,
Colo.
Durango, Colo.
Golden, Colo.
Ft. Collins,
Colo.
Greeley, Colo.
Fort Collins-
Love land W.D.,
Colo.
Little Thompson
Valley W.D.,
Colo.
Evergreen, Colo.
Danvers, Mass.
Raw Water
Middleton Pond
4.0 ppm avg-
turbidity
Special Provisions Sludge Disposal
Returned to river
To sludge pond,
supernatant drain-
ed off to sewage
treatment plant
To irrigation
ditch
To washwater pond
and water reclaim-
ed
Returned to Clear
Creek
3 units; third No data
unit for reclaim-
ing waste water
from others
Returned to Boyd
Lake
To irrigation
ditch
Returned to Dry
Creek
Returned to Bear
Creek
1% to 57= net
waste water. No
information on
disposal
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Engineering Report - Microstrainer Sludges
51
TABLE 4 (Contnd)
Installation
Belleville,
Ontario
Haweswater,
Great Britain
Turret Water
scheme of the
Loch Turret
Water Board
Raw Water
Lake Ontario
Special Provisions Sludge Disposal
Low turbidity
Low turbidity
Treat screens with
sodium hypochlo-
rite and ultra-
violet radiation
Pilot plant
1.57= to 2.7% net
waste water
No information on
waste water.
Reference does
not consider this
washwater as a
sludge disposal
problem
Returned to Turret
Burn. Reference
considers waste
water beneficial
to animal life
-------
SLUDGE LAGOON
City of Minneapolis, Minn.
Water Department
-52-
-------
Engineering Report - Lime Sludges . 53
Research regarding the characteristics, magnitude and disposal
methods for presedimentation sludge is indicated.
LIME SLUDGES
Discharge to Surface Waters
Presently, most lime sludges are disposed of in the nearest
watercourse as the most expedient and least expensive method, and
because there has not existed legislation or other prohibition
against such disposal. With recent state and federal legislation,
the emphasis on pollution abatement is directed primarily to those
areas where nuisances are created in the receiving waters. It can
be expected that greater pressures will be exerted in the future by
legislative authority as problems increase and public opinion re-
quires action.
Lagooning
1. Continuous - fill Lagooning. This disposal means is suit-
able where large areas of land are available within reasonable dis-
tance of the treatment plant site. The words "suitable", "large
areas", and "reasonable" can be defined only after studying of each
treatment plant situation, and making engineering, economic, and
esthetic evaluation for alternative methods of disposal.
In instances where the sludge must settle through ponded water,
a consolidation of only 40 percent maximum by weight of dry solids
can be expected. In several instances, a consolidation of only 20
to 30 percent was reported. In lagoons where the supernatant is
allowed to flow off the site without ponding, an upper limit of 50
percent dry solids has been obtained. In either case, the effluent
usually can be reclaimed if desired, as was done at Lompoc, Califor-
nia (Scolari, 1968).
Mace (1953) reports that odor problems with lime sludge lagoons
are rare, and are temporary and insignificant when they do occur.
Generally odors are from plankton or algae growths.
When the lagoons are completely filled with lime sludge, the
next problem is how to reclaim the large lagoon area. Low land
-------
_54 Engineering Report - Lime Sludges
TABLE 5
SLUDGE LAGOON CAPACITY REQUIREMENTS
City
Cedar Rapids , Iowa
Columbus , Ohio
Sandusky, Ohio
Lansing, Michigan
Hinsdale, Illinois
Acre-Feet of
Sludge/yr/mgd/lOOppm
Hardness Removed
0.62
0.52
0.66
0.65
0.45
Assume
Moisture 7,
50
50
50
50
50
around the Miami, Florida, water treatment plant was filled with
sludge and subsequently covered with 1 to 2 inches of soil and
sown with grass (Dittoe discssn. 1933). Dean (1953) states that
fills have been made by continuously applying sludge without pre-
drying in some cases, but cautions that heavy loads should not be
applied for several years.
Rules of thumb for determining the storage capacity of lagoons
have been used in the past, in some cases based on scant information.
Lagoon requirements at several locations have been reported by Howson
(1961) as indicated in Table 5.
The 10-State Standards (1968) recommend a minimum lagoon depth
of 4 to 5 feet, a capacity of 3 to 5 years solids storage, with
multiple cells and adjustable decanting devices. Criteria for de-
sign of sludge drying beds are:
1. Minimum of one year's total storage at a depth of 12 inches
2. Multiple beds
3. Two ppm of sludge for each 1 ppm of hardness removed
4. Assume accumulated sludge will air dry to 75 percent moisture
5. Sludge density will be 120 pounds per cubic foot.
-------
Engineering Report - Lime Sludges 55
Aultman (1947) reported that Hoover estimated lagoon capacity
to be 0.00211 acre-feet for each million gallons of water softened.
The sludges from different treatment plants vary widely in settle-
ability, specific gravity, amount of consolidation, and other
characteristics. Nelson (1957) pointed out that sludge character-
istics and settleability cannot be predicted with any measure of
accuracy. Because of the unpredictable nature of water plant sludges,
application of rules of thumb can result in inadequate lagoon cap-
acity.
Additional engineering studies of continuous fill lagooning
should be made to determine: (1) Better guidelines for sizing la-
goons; (2) Ultimate uses of lagoon sites after filling; (3) Costs
of construction, operation, and maintenance.
Fill and Dry Lagooning. This disposal requires that a land-
fill site be available within economic hauling distance of the
lagoon. Usually, two or three lagoons are necessary for alternate
filling, drying, and subsequent removal of the dried sludge. La-
goons are sized depending upon sludge production rates, character-
istics of the sludge, average air temperature, etc. Except as
cited in the Ten-State Standards for continuous fill lagoons, spe-
cific design criteria for sizing fill and dry lagoons are not
found in the literature. However, Howson (1961) and Savage (1954)
do state that lagoons should be of such dimension that dried sludge
can be removed readily by dragline or other conventional equipment.
Additional engineering studies of fill and dry lagooning
should be made to develop the same information desired for contin-
uous fill lagooning.
Recovery of Lime by Recalcination
The literature discusses existing lime recalcining plants
individually rather than on a comparative basis. Regardless of
the type of recalcining equipment utilized, each process comprises
the same steps as follows:
a. Sludge thickening and or blending. In some cases, re-
carbonation is utlized in this step.
b. Dewatering by centrifuge or vacuum filter.
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56 Engineering Report - Lime Sludges
c. Flash drying of dewatered sludge by use of off-gases.
d. Recalcining of high temperature; i.e., converting
calcium carbonate to calcium oxide.
e. Product cooling, where required.
Types of recalcining plants. The two predominant types of re-
calciners in present use are the rotary kiln and the fluidized bed
reactor. As indicated by recent installations, fluidized bed reactor
plants appear to be gaining favor. It is contended that the latter
system: (1) operates more economically; (2) produces less dust;
(3) produces a harder CaO product, less susceptible to airslaking;
(4) requires less installation space; and (5) is capable of faster
start-up and shutdown.
Other types are variations of multiple hearth furnaces as the
plant at Lake Tahoe, Nevada (Moyer, 1968); flash drying furnaces,
as plant at Salina, Kansas, and Pontiac, Michigan (Swab, 1948);
and at Marshalltown, Iowa (Pedersen, 1944)).
Existing recalcining plants. Table 6 summarizes available
data on existing recalcining plants or plants under construction.
Sludge Characteristics. Sludge from the water treatment and
softening process consists primarily of calcium carbonate with hy-
droxide precipitates of coagulants. It may also contain hydrox-
ides of dissolved iron, manganese, aluminum, and magnesium as well
as silicates, clay or silt particles and organic matter.
As excess of hydroxide precipitates in the sludge will soon
render the recovered lime useless due to their build-up during
recycling through the water plant. These precipitates must be
removed prior to recalcination. The separation can best be ac-
complished by centrifuging, either by separate classification or
as the sludge is dewatered. Recarbonation of the sludge prior to
centrifugation will return the insoluble magnesium hydroxide to
the soluble magnesium bicarbonate. The magnesium is subsequently
removed with the centrate which must be wastes.
Also, when tastes, odors, or color occur in the water, the
centrate must usually be wasted. Where build-up of minor constituents
-------
ui
•-j
i
TABLE 6
RECALCINING PLANTS
Rated
Capacity
Approximate Product
Construction Output
Location
Marshalltown,
Iowa
Pontiac ,
Michigan
Miami,
Florida
Lansing,
Michigan
Salina,
Kansas
Dayton,
Ohio
San Diego,
California
S. D. Warren
Company (3)
Merida,
Yucatan
Ann Arbor,
Michigan
Lake Tahoe,
Nevada(5)
St. Paul,
Minnesota(M
Date
_
-
191*8
195U
1957
I960
1961
1963
1965
1968
1968
1969
(Tons /Day)
it. 2
-
80
30
-
150
25
70
UO
2k
10.8
50
Type of
Type of
Dewatering Recalciner
Equipment ( 1 )
c
c
C
C
c
c
c
VF
C
c
c
c
(2)
FC
FC
RK
FB
FC
RK
RK
FB
RK
FB
MH
FB
Heat
Requirement
Water
Lime Plant
Plant Rated Lime
(Mil Btu/Ton COg Cost Capacity Fed
Output )
9.66
-
8.5
8.0
-
9-0
9-0
7.2
-
-
7-0
8.2
Recovered $ (mgd) (lb/mg)
3.5
2Ul,000 10 2,200
Yes 856,000 180 1,800
20 2,200
_
Yes 1,500,000 96 2,lUO
531* ,000
_
Yes 2k
_
Yes - 7-5
Yes 1,750,000 120(6) 990
Sludge/
Lime
Ratio
-
2.50
2.20
2.27
-
S.k"7
-
-
-
-
-
2.1*0
(1) C - Centrifuge; VF - Vacuum Filter
(2) RK - Rotary Kiln; FB - Fluidized Bed; FC - Flash Calcination; MH - Multiple Hearth
(3) Paper mill owned by Scott Paper Company
(k) Now under construction
(5) Activated sludge disposal plant
(6) Lime recalcining plant designed to accommodate future water treatment plant capacity of 170 mgd.
-------
58 Engineering Report - Lime Sludges
is not detrimental, or where tastes, odors and color are not present,
the centrate can be returned to the water treatment plant for re-
processing.
The effect of silt and clay particles in the sludge has not
been fully investigated or reported in the literature. However, the
recalcined product may take on the characteristics of cement rather
than lime if the amount of particulate matter is sufficient.
It is reported by Aultman.(1939) that, in extreme cases, it
could be necessary to remove the silt and clay in a pre-sedimentation
basin before application of softening chemicals. For existing
plants where recalcining of lime is being considered, this factor
may be insurmountable due to plant layout.
Sludge Conditioning. Conditioning of softening sludges may
involve thickening, blending of sludges from several clarifiers,
recarbonation for magnesium removal, or combinations of the three
functions. Thickening to reduce the amount of water processed may
be undesirable where magnesium removal is required. Removal ef-
ficiency is reduced as the solids content of the sludge increases.
Consequently there are limitations to the amount of thickening per-
mitted. Where recarbonation is contemplated, pilot plant tests are
recommended by Nelson (1957). Where several clarifiers or basins
are used, all sludges should be blended.
Sludge Dewatering. Dewatering of softening sludges is accomp-
lished by means of vacuum filters or centrifuges. Aultman (1939)
reports that vacuum filters commonly produce sludge of 45 to 50 per-
cent dry solids by weight. Sowden (1941) reports sludge of 62
percent dry solids, and Dloughy (1968) reports 75 percent.
As reported by Nelson (1944), centrifuges regularly produce
sludges of 60 to 65 percent dry solids, and higher solids content
in some instances. As shown in Table 6, use of centrifuges pre-
dominates. This is attributed to their smaller space requirement,
higher solids concentration, and their dual capability of magnesium
classification and dewatering.
Flash Drying. Flash drying of the sludge is accomplished fol-
lowing iewatering by injecting the sludge into the s-tream of hot off-
gases from the recalciner. The dried sludge is subsequently removed
in a cyclone separator and the stack gas is scrubbed of particulate
matter before being discharged to the atmosphere.
-------
Engineering Report - Lime Sludges
Recalcination. Dried sludge is fed to rotary kilns by means
of screw conveyors or similar devices at the upper end of the
sloping, rotating kiln. The kiln operates at a temperature of ap-
proximately 2,OOQOF. The product may be in a powdered form of
irregular pebbles.
Calcium carbonate sludge is fed by an air conveyor system to
the fluidized bed reactor where it is instantly transformed to cal-
cium oxide. The calcium oxide adheres to previously calcined and
crushed "seed" pellets which are also fed into the calciner.
Pellet growth is promoted by the addition of soda ash to the
dewatered sludge prior to flash drying. The soda ash fuses at the
calcining temperature of 1,600°F forming a molten nucleus to which
the calcium oxide particles and seed pellets adhere. The pellets
grow in this manner to a size which can no longer be suspended by
the fluidizing velocity of the gases in the calciner, and at that
point are discharged from the reactor.
Carbon Dioxide. The stack gases contain 15 to 27 percent CC>2
depending upon the amount of excess air used in fuel combustion.
The bulk of the C02 contained in the stack gases is liberated from
calcium carbonate as it is reduced to calcium oxide.
The C02 in the stack gas can be used to recarbonate the softened
water and/or the sludge before dewatering. Sheen and Lammers (1944)
suggests that the C0£ may be recovered and marketed as "dry ice".
Liquid CC>2 recovery may also be economically feasible as this process
requires less energy than does the manufacture of dry ice.
Additional Study and Research. Recalcining plants are purport-
edly feasible only above 20 ton per day product capacity for flu-
idized bed reactors and 50 ton per day for rotary kilns. Develop-
ment by manufacturers of economically packaged units for water
treatment plants producing sludge in lesser amounts is indicated.
Also indicated are additional studies of methods for obtaining
higher efficiencies. Finally, economical liquid C02 recovery
should be investigated as a means to reduce costs where sale of the
C02 is practicable.
Discharge to Sewage Treatment Plants
The discharge of waste lime sludges to sewage treatment plants
-------
60 Engineering Report - Lime Sludges
has been considered and used at Daytona Beach, Florida (Russell,
1955) . The plant employing the "Daytona Beach Process" was con-
structed in April, 1949, after pilot plant studies. The addition
of 15,700 pounds of sludge (dry solids weight basis) to the sew-
age treatment plant designed for 70,000 people removed 45 percent
of the BOD and 75 percent of the suspended solids. Sewage sludge
and waste lime sludge were removed from the upflow clarifier and
dewatered by vacuum filter.
On the strength of the successful application of this process
at Daytona Beach, Florida, a similar plant was constructed at Ocala,
Florida. In view of the successful reports at Daytona Beach, it is
curious that in 1961 the disposal of lime sludge at Ocala was re-
ported as a problem, and a new sewage treatment plant was constructed
to replace the plant constructed in 1949.
Garland (1969) reports the process was abandoned at Ocala be-
cause: (1) the state regulatory agency now requires secondary treat-
ment, and (2) the plant was poorly maintained, and would have re-
quired replacement of much of the mechanical equipment which was not
considered justifiable.
A similar project is in the planning stages for the City of
Dallas, Texas by Black and Veatch (1968). Spent lime from the City's
Bachman Creek Water Treatment Plant will be used to treat overflows
from the sanitary sewer system. The interceptor sewer receives in-
filtration which causes flows exceeding its capacity. A point of
diversion of flocculation and sedimentation facilities is planned,
permitting diversion and treatment of all flows above the capacity
of the sewer.
The project has received an offer from the Federal Water Pollu-
tion Control Administration for a supporting research and develop-
ment grant. It is anticipated that the plant efficiency will exceed
that of plain sedimentation.
Disposal as Agricultural Lime
Dloughy (1968) and Fleming (1957) cite instances where water
softening plant sludge has been air-dried in lagoons and offered
to local farmers. These plants were relatively small in capacity
An increased need for agricultural lime, particularly in conjunc-
tion with nitrogen fertiliziers, has been cited." However, local
needs and marketability will determine its success. This method
is probably not applicable to medium or large sized plants.
-------
Engineering Report - Lime Sludges 61
Mechanical Dewatering and Disposal of Cake in Landfill
This method of disposal has been suggested in the literature,
but no actual American installations are known. Young (1968) de-
scribes the Pitford, United Kingdom, plant. Unpublished research
bases on the St. Paul, Minnesota project indicated that sludges can
be dewatered by either vacuum filtration or centrifugation. A dry
solids content by weight of 60 percent and higher can be obtained
from centrifugation as contrasted to about 50 percent maximum from
vacuum filtration in most installations. Dloughy (1968) states
that 75 percent dry solids has been obtained at Boca Raton, Florida.
Freshly dewatered sludge is difficult to handle and haul as it
is extremely sticky. In transit, water may tend to separate fur-
ther from the sludge and, unless the truck is watertight, a nuisance
may be created along the hauling route. The main problem is in re-
moving the sticky sludge from the vehicle. One suggested mean is
to line the truck bed with polyethylene film or other liner and dump
the liner with the sludge. Italiano (1968) attempted this method
of disposal but abandoned it because of handling difficulties.
Reliable cost data are not available except those developed in
the St. Paul study, and these indicate that hauling is considerably
more expensive than pumping the sludge at a higher water content.
A review of additional treatment plant experiences would be
helpful in assessment of this disposal method.
Modification or Selection of Treatment Process
In order to simplify sludge disposal problems, Doe (1966-67)
proposed modification or changing water treatment processes. He
cites the Broughton Treatment Plant of the Fylde Water Board,
England, as an example. The design of this treatment plant was
revised to incorporate contact reactors in lieu of conventional
equipment. This is the "Contact Reactor Process11 in Europe and
the Permutit "Spiractor Process" in the United States.
The "reactor" is a cone-shaped, bottom apex, vertical tank.
The raw water and chemicals enter the tank tangentially at the apex,
flow spirally upward, and discharge over a weir near the top. The
raw water and chemicals mix with a sand catalyst admitted at the top
of the tank, and the mixture suspension is maintained by the upward
spiraling flow of the water.
-------
62 Engineering Report - Treatment Process Modifications
The calcium carbonate plates out on the sand catalyst or nuclei,
forming small hard pellets which grow in size until the vertical
flow of water can no longer maintain suspension. The pellets drop
to the apex of the tank and are periodically discharged to a sump for
dewatering. It is contended the pelletized sludge will contain only
5 to 10 percent water by weight.
Although the pellet form is attractive from the standpoint of
sludge handling, the process is reported to have several limitations
in application. These are:
1. Minimum water temperature is 55°F
2. Magnesium content in raw water should not exceed 85 ppm
(as CaC03)
3. Turbidity should not exceed 10 ppm
4. Tri-sodium phosphate must be added to retard and control
plating action of calcium carbonate on the sand nuclei
5. In cold climates the reactors must be enclosed in heated
structures, thereby adding to the cost of installation.
Excessive magnesium will form magnesium hydroxide which will
not plate out on the catalyst. Instead, it will remain.in the water
and will quickly clog filters. The process will not remove exces-
sive suspended solids, which will remain in the water unless removed
on the filters.
Doe (1966-67) cited an instance where a choice of raw water
source was made largely to reduce the waste sludge. In the case
cited, the softer of two waters was selected to reduce the amount
of sludge requiring disposal.
Burd (1968) reported that San Diego, California no longer sof-
tens its water and lime recovery is no longer practiced.
DEFICIENCIES IN ENGINEERING
The major deficiency that exists in the design of adequate
-------
Engineering Report - Deficiencies in Engineering 63
facilities for the disposal of wastes from water treatment plants
is the lack of full scale operating facilities from which design
parameters for successful installations can be established.
With few exceptions, most of the work done to date has been
in laboratory investigations and pilot plant studies. While these
are necessary as an initial step, proper engineering design cannot
proceed without the benefit of operating data on full scale instal-
lations .
Of particular concern are those facilities which might be
utilized in the disposal of coagulants sludges. The majority of
large plants utilize coagulations, sedimentation and filtration
processes for water purification. Coagulant sludges are produced in
the largest quantities, and also are the most difficult of the
sludges to treat.
Cost Data on Engineering
Very little cost data is available today because of the lack
of full scale plant operations for the disposal of sludges. The
one exception to this would be in the area of lime-softening sludges
where numerous full scale operations have produced rather good cost
data.
In the case of diatomaceous earth sludges, microscreening sludges,
manganese sludges and brines, there are so few installations which
practice sludge disposal on a major scale that costs are not normally
available.
In the disposal of coagulant sludges, a few costs have been
developed, mostly from plants in England where several full scale
facilities have been erected. These costs are for specific instal-
lations and have been difficult to translate into American dollars.
Another factor which makes it difficult to establish cost guide-
lines is the varying circumstances which substantially affect the
cost of the process. A basic unit cost should be established. Modi-
fications of costs would then be made for any particular circumstance.
(Note that a report on current technology and costs for 15 waste
treatment plants in the U.S. is included in this report.)
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64 Discussion of Status Report on Engineering
DISCUSSION OF STATUS REPORT ON ENGINEERING
MR. NEUBAUER: Discussion of the status report on research
has made very evident the overlapping interests between research and
engineering aspects of this waste disposal problem. I am sure sim-
ilar interests will be evident in the report on plant operation
aspects.
With regard to engineering aspects of the problem, our
discussion should relate especially to identifying gap areas in
which information is inadequate. A great deal of information
remains to be filled in to make the engineering details complete.
In the case of filter washwater, for example, its reuse
at some plants is more for economy than it is to provide waste
treatment. Little study has been done in this area, and more is
needed.
The most information is available on coagulant sludges.
Substantially more needs to be known about the coagulant sludges,
starting with their properties.
The concentration of sludges is important. Just the
difference between half of one percent and one percent dry solids
content means a reduction of 50 percent in volume. Better methods
of concentration of coagulant sludges can make the process of de-
watering and disposal more economical. They will result in hand-
ling fewer solids, with less volume. As to the treatment of
coagulant sludges, there are many possibilities.
We find even less information available concerning
diatomaceous earth sludges. Our report includes a few references,
and I am hopeful there will be more reported in the discussion.
Brine wastes are almost impossible to treat, and must
be disposed of in a manner which will render them innocuous.
The salts cannot readily be removed from the waste. Disposal
methods used to date include evaporation, brine injection wells
and direct discharge to surface waters. The use of ion ex-
change softeners is widespread throughout the country, and brine
wastes are becoming a critical problem.
-------
Discussion of Status Report on Engineering 65
Finally, I wish to refer to Mr. Peter Doe's fine comments,
in his most recent paper. He urges that the agency responsible for
determining the type of water treatment process should give serious
consideration to the type of wastes that will be generated, and
to the disposal of the wastes. In many cases there may be no choice.
But, in others, there are means by which the process can be varied
to make the waste more easily handled. I believe this consideration
is generally overlooked today, but recommend that it should be more
generally emphasized.
MR. PROUDFIT: In preparing our status report on engi-
neering, my part covered pre-sedimentation, iron, maganese,
micros trainer, and lime softening sludges. Additional comment on
several of these items is justified.
Micros trainer sludges are constituents strained from
water, and generally returned to the water source. There is very
little information available in the U.S. on micros trainer sludges.
In Colorado, many microstrainers have been installed and
are considered as a water treatment process. These units are
simply strainers which remove some organisms and turbidity; these
are returned to the raw water source, except in some instances
where strainings and wash water have been used for irrigation.
Microstrainers are used at Kenosha, Wis, to strain algae from Lake
Michigan water.
I believe microstrainers have a place in pre-treatment but
should not be considered as complete treatment. The return of
microstrainer sludge containing large concentrations of algae to
the raw water will increase algal populations and compound the
original straining problem. This problem could be acute where the
raw water source is a limited impoundment.
Pre-sedimentation basin sludge is in the category of
microstrainer sludges. My area of familiarity is primarily the
Missouri River, where water treatment plants settle out sand and
silt and return it directly to the stream. There is very little
design or engineering information available on pre-sedimentation
basins. In general, they are designed on an empirical basis to
perform over a wide range of turbidity loadings. It can be argued
that pre-sedimentation basins, if used without chemical coagulatioia,
do not contribute any additional stream pollution. Additional
research should be done on these basins.
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66 Discussion of Status Report on Engineering
The treatment of lime sludges has already been discussed.
One of the important aspects of lime sludge recalcination is the
need for more research and information on small plants. It is my
experience that lime recalcining may be uneconomical in small water
softening plants.
MR. HARTUNG; I don't believe that Mr. Proudfit intended
to minimize the problem of iron and manganese waste disposal.
There are a large number of iron and manganese removal plants which
remove only iron and manganese after aeration or oxidation with
potassium permanganate. The disposal of these sludges constitutes
a tremendous problem because of the discoloration they cause
when disposed of on the ground, and because they kill vegetation.
I think this waste also should be considered as one of our major
problems.
MR. PROUDFIT; I did not intend to minimize the specific
problem you have discussed. Your comments are correct. I re-
ferred only to the removal of small quantities of iron and
manganese with other products of sedimentation, and not to pro-
cesses primarily for iron and manganese removal.
MR. TCHOBANOGLOUS: In terms of both engineering and
operation, attention should be given to the problem of developing
methods for estimating the sludge quantities and characteristics,
especially reliable methods that can be used in the field.
MR. NEUBAUER; That problem was one of the first con-
sidered by the AWWA research committee on sludge disposal. We
have not yet developed standard methods of analysis by which
quantity and quality characteristics could be determined in plants
throughout the country.
I wish to call attention to several significant items
not included in our status report. These are summarized from reports
prepared by Gauntlett for the British Water Research Association,
and included in the reference bibliography.
Gauntlett noted that a small particle size and high
gelationous metal hydroxide content in the sludge tend to give
low settling rate, large settled volume and low permeability to
water. He also reports that alum clarification sludges are not
significantly improved (as regards settled volume and permea-
bility) by chemical means.
-------
Discussion of Status Report on Engineering 62.
He concluded that alum sludges can be drained since a
significant proportion of the water is physically and not chem-
ically bound. He recommended that the beds should be designed
to provide maximum drainage rate without floe breakthrough; to
permit a. shallow sludge depth and to provide protection from
rain until drainage is complete.
MR. MEBIKER; In our plant visits, we encountered wide
fluctuations in the amount of sludge discharged from sedimentation
basins. This is less so in sewage treatment. In sewage treatment,
there is emphasis on minimizing the amount of sludge, because it
is recognized the sludge must be disposed of. In water treat-
ment, where sludge is generally discharged to surface waters no
attempt is made to minimize quantities.
This is an area of research and engineering study that
should be emphasized; the removal of sludge from clarifiers to
minimize the quantity of the sludge. If this need was emphasized in
plant design and operation, the sludge disposal problem would be
substantially reduced.
For example, the solids content of sludge recorded
at Moline, Illinois,is 1.0 percent. Ann Arbor reports solids of
25 percent. Similarly, the figures for tons of solids removed
per million gallons exihibit tremendous variation. I believe
this is due to the fact that operators have not emphasized
maximizing the solids content. In sewage plant operation,
equipment, manufacturers and the operators are concerned both
with the overflow rate and the underflow rate. This is not
the case in water treatment.
I would say the variation in the water softening
sludge and the alum sludge is about the same, with differences
several magnitudes of between minimum and maximum.
MR. RUSSELMANN; In New York State, there are three
microscreen installations. Although they discharge only what has
been removed from the waters, the effect of the waste upon re-
ceiving waters is variables - depending upon the receiving
waters, the amount of waste, and the manner of disposal. These
installations take waters from lakes and returns the wastes to the
lake or to an entirely different stream which may have a very low
flow. The wastes cause undesirable conditions because of the
concentrated loadings of organic materials. Where the wash-
water is returned to a cove in the same lake from which the
water is taken, excessive fertilization takes place and creates
algae problems.
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68 Discussion of Status Report on Engineering
We should bear in mind that handling wastes from water
treatment should be part of the entire design of the water treat-
ment plant. Waste disposal is an engineering project from the
very beginning to the very end. Unless we do this, even though we
may not contravene standards for receiving waters, we may degrade
the quality of that resource as a source of water supply or for
other uses.
MR. TCHOBANOGLOUS: On reading all these status reports
and looking at the various proposed regulations, I am almost con-
vinced that the disposal of waste solids may eventually become the
limiting or controlling factor in the design of water treatment
plants.
MR. RUSSELMAMt It becomes increasingly obvious that
the selection of any water treatment project for communities must
be determined in considerable part by the methods for waste dis-
posal and the location of the plant.
MR. DICK: I am pleased to hear the comments regarding the
need for incorporating waste disposal considerations into the over-
all design. Our present water treatment practices stem from opti-
mization of the various unit operations and processes that go into
normal treatment - with total disregard for wastes. As the report
on current technology suggests, when we put in waste disposal the
economics will shift. The entire scheme of water treatment could
conceivably change as a result.
For example, depending on the treatability of clarifi-
cation sludges and backwash sludges, it might be desirable to
minimize clarification process and maximize removal on the filters,
or vice versa. We might want to emphasize plain sedimentation,
where applicable, if this gives the better sludge for treatment.
Perhaps radical changes in our approach to water treat-
ment technology are indicated when waste problems are considered.
We should not attempt to solve only those problems that have been
created by present practices. Instead, we should look to the
source of the problems and, if preferable, change the treatment
scheme.
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Discussion of Status Report on Engineering 69
MR. DOE; May I amplify those remarks by referring to
the Fylde "Water Board softening plant in England which, about ten
years ago, provided a perfect illustration of this. The plant is
designed to treat an underground water of some 250 mg/1 calcium
carbonate hardness, and about half the amount of magnesium.
The problem from the very start was waste disposal. We
thought initially of a straight lime precipitation process, but
we were well aware of the difficulty of disposing of this particular
waste material. We then considered ion exchange process but we met
the same problem of waste disposal. The plant location was about
20 miles away from the sea, and we actually investigated the route
for a nine-inch diameter pipeline to carry the waste to the sea.
The third alternative considered was to produce a
neutral effluent by mixing the two wastes together. Again we
had the same problem of disposing of the effluent. The plant as
eventually designed was our original conception of precipitation
with hydrated lime.
When this plant was actually under construction, we
learned of the contact reactor process, in the status report on
engineering. The entire design of the plant was changed with,
I think, great courage on the part of the chief Engineer, Mr.
F. Law; and great loss of hair on my part as I was in charge of
the plant construction. We installed a contact reactor plant.
The practical result is that we make a maximum of 30 tons of
pellets per day and we sell these. We made about $2,000 profit
last year.
We have not found evidence of the limiting factors
affecting the contact reactor process referred to in the
engineering report. In our particular case, we found that
minimum water temperature had little effect as long, of course,
as it did not go down to 32 degrees Fahrenheit. We operated
at temperatures somewhere between 40 degrees and 60 degrees
Fahrenheit, mainly of course, because we treated underground
water. And we didn't find operating problems at this low
temperature.
We had been told that it was necessary to operate under
a pressure of two atmospheres, but when we tried the process at
atmospheric pressure it still worked exactly the same. We then
designed three additional reactors without covers of any time.
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70 Discussion of Status Report on Engineering
Two of these were made of concrete and the third of steel; they
all worked perfectly well. We didn't find the magnesium content to
be a limiting factor; in this water, the ratio was about two calcium
to one magnesium. A paper is being written by the chemist of the
Fylde Water Board, Mr. M. A. Hilson, and when it becomes available
I will try and arrange for him to bring it to the attention of
the AWWA.
Finally, as far as Calgon is concerned, or the trisodium
phosphate referred to here, some form of phosphate control apparently
is necessary to prevent after-precipitation. This did cause us a
little trouble because the reaction continues beyond the reactors.
Precipitation occurs in the sedimentation tanks and could reach the
filters. The reaction must be stopped. Perhaps Dr. Black will
comment on this chemical problem.
One final point. The bottom of our reactors is not in
the form of an apex. Our tanks end with a cylindrical portion
something in the order of three and one-half feet in diameter.
There appears to be a minor disadvantage which is
inherent in this process. The large beads, as has been stated,
cannot drop right to the bottom of the reactor, because of
increasing velocity due to the tapering shape of the reactor.
They are suspended perhaps ten to 15 feet above the bottom. It
is at that level that the beads must be removed.
The problem is this: The process should be controlled
to form the fine beads, because they have the greatest surface
area for a given weight. Fine beads are the ones on which the
plating is done. But the big beads come down and mix with the
small ones, and in debeading the small ones are removed as well
as the large ones. When this problem has been overcome, the
contact reactor process will be improved.
MR. BLACK; I think you will probably find that you
are selectively softening that water and removing only the
calcium hardness. The process of selective softening is
applicable only to waters very low in magnesium, and from which
no magnesium will be removed in the softening process. Almost
all of our Florida waters are of that type. This treatment is
discussed in a paper now in press in the Journal of AWWA.
These waters are also warm - which, of course, promotes the
softening reaction.
-------
Discussion of Status Report on Engineering 7l_
Several such plants are successfully operating in
Florida. One of our major cities has just converted an ion
exchange, sea water regeneration, plant to this new process
employing selective lime softening.
I shall report to the Conference Committee on Research
Needs that the problem of disposal sludge resulting from softening
of high magnesium waters has recently been solved in one American
city. The solution involves:
"A process whereby all calcium values are recovered as
high quality quicklime; all magnesium values as very pure Mg C03,
Mg (OH)2 or both; all sludge water is recycled and recovered; and
all liquid and solid wastes eliminated. This is accomplished in
one installation serving two major softening plants,one 100 mgd
and one 50 mgd, separated by a distance of approximately four
miles."
MR. PROUDFIT; The remarks by Mr. Doe are very interesting.
I think the contact reactor reference in the report emphasizes the
dangers of generalization. This information is primarily from the
manufacturer of these units. 1 have no firsthand knowledge of them.
MR, NEUBAUERi I would like to know from Mr. Doe, since
he said this waste is being sold at a profit, just what use is
being made of it?
MR. DOE: At the present moment, the British Government
gives a subsidy to farmers for certain types of fertilizer. The
word "fertilizer" is here used in a very loose sense. Anything
which will give benefit to the land may generally be called
fertilizer. Fo pH correction of the clays in this area, the
pellets are spread on the land by the farmer. Large dumps must
be provided to store the pellets, so that they are available
for spreading on land at the times that they are required.
These pellets are very attractive to chickens and birds.
MR. DEAN: I emphasize what was said about looking at
the disposal of the sludge. Let's take the specific example,
water softening. Lime softening or ion exchange processes can be
ocean, brine softening, by which I mean ion exchange with brine
regeneration, is impractical.
The salt content in many of our waters, is already too
high, and there isn't an-economical way of getting rid of brine.
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72 Discussion of Status Report on Engineering
So this fact can change the process, and it has very definitely
influenced the decision as to whether or not to use ion exchange or
lime softening.
MR. DICK: I think this discussion emphasizes the need for
keeping the whole picture in perspective. For instance, it would
be very unfortunate if we create an impression that lime sludges are
a problem and, as a result, ion exchange softening seems more
acceptable. Actually, ion exchange is not an acceptable treatment
except on a seacoast.
MR. AULTMAN: We must, indeed, look at the overall
problem. As Mr. Doe indicates, going to the pellet type of sludge,
there was no problem with disposal in that particular area. But
in an area where there is alkaline soil, there may be just as great
a problem with disposal of the pellets as would exist with normal
lime sludge. There is no one answer to the problem.
MR. FAHY; I might comment on experiments with the use
of lime softening sludge as a soil conditioner. The City of
Grand Forks, North Dakota, attempted to use the sludge in order to
stabilize the soil in certain alleys, Initially, sludge application
in the first several blocks was highly successful. The sludge was
spread in the alleys, rototilled in, and no traffic was allowed
while the sludge settled.
However, later in the fall when more sludge was spread,
quite an extended period of rainfall occured. It was then nec-
cessary to block those alleys off for several weeks. The soil
became veritable a quagmire. There is much need for study in
using lime sludge for soil stabilization.
Grand Forks proved that soil stabilization could be
done successfully when there was an extended period of warm weath-
er. This is not an approach to use if there is a chance of an
extended period of rainfall shortly after the sludge is applied.
MR.ADRIAN^ Lompoc, California, had an interesting
experience in trying to find a use for sludge. The Los Angeles
Times published an article on the availability of Lompoc's lime
softening sludge - free of charge, if anyone wanted to take it,
A manufacturer considered the use of sludge as a paint
additive, but found other material was commercially available at
a cost lower than that of transporting sludge. -Other inquiries
were received, but no good use for sludge was developed.
-------
Biscussion of Status Report on Engineering 73
MR. PRQUDFIT: On the subject of various uses of lime
sludge, I would like to add a few comments. We have done research
and had discussions regarding various methods of disposal.
In one instance, a contractor thought he could reclaim
and dry lagooned lime sludge and use it as filler in asphaltic
concrete for paving. He learned that handling and drying the
sludge was more costly than commercial filler, such as cement
or other inorganic material.
In another area, it was concluded that lime sludge
could be spread in cattle feed lots to prevent or alleviate hoof
and mouth disease. Whether or not this application would be
effective, feed lots are limited. This use could not accommodate
disposal of large continous volumes of sludge.
I believe one of the most important applications for
lime sludge may be in sewage treatment plants which must remove
phoshates. This will be a beneficial use, and should not increase
the final sludge disposal problem.
Land disposal appears attractive, but land costs are
increasing. In many instances, when water treatment plants are
located in highly populated areas, land for sludge disposal is not
within economic reach - either because of cost or distance.
Engineers should recognize that a water treatment plant
design must now include positive means for disposal of sludge. At
the same time, engineers should consider economy as a basic con-
sideration in the selection and design of disposal methods.
This concludes discussion of the status report on engi-
neering.
-------
SLUDGE DISPOSAL PROCESSES
f Origin ol )
i the Sludge |
! Thickening
the Sludge
I Processing
the Sludge
Final
Disposal
Sedimen- Filter
talion Tank Washwater
t f
f
Sludge From
Washwato
Recovery
Combined
Washwater
and Clarifier
Sludge
1 1
Holding
Tank
1
Wedge -Wire
Thicken ng
Bypass
Stirred /
Conditioned
Thckening
1
Bypass
T
Acid Dosing
and Sludge
Separation
Holding Tank
or S los
<\
t *
Drying Beds Filter Vacuum
or Lagoons Presses Filters
\ 1
i '
'
f
Centriiuges
.
nterim Cake
Storage
'
Dumping or
Spreading
Bypas
Incineration
J
f 1
Pipe to Sea
o, Estuary Free21n8
, ,
s Dump
1
Sale of Lime
-Softening
Cake
Alternative Successive Stages in Sludge Disposal
Young, E.F. J.AWWA, 60:717 (1968)
Used by permission
-74-
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Status Report on Plant Operation 75
STATUS REPORT ON PLANT OPERATION
J. W. Krasauskas and Lee Streicher
The disposal of water treatment plant wastes has, up to the
present, posed no real problems of plant operation - because the
majority of water treatment plants in the United States discharge
these wastes to surface waters. In most instances, plant managers
have not considered discharge of these wastes to surface streams
as pollution.
Recent actions have been taken by the Federal Water Pollu-
tion Control Administration to implement the Water Quality Act of
1965, and stricter State regulations have been developed which ap-
ply to the discharge of such wastes to surface streams. Thus,
water production officials are required to critically review their
current methods of disposal, and to actively seek practical solu-
tions. The majority of water treatment plants in the U.S. do not
have the capability of conducting applied research, but must de-
pend upon governmental agencies, equipment manufacturers, consult-
ing engineers, and the larger water treatment plants to supply
practical answers to this vexing problem.
Types of Water Treatment Sludge
It has been estimated that water treatment plant alum coag-
ulant sludge production in the U.S. amounts to over one million
tons annually. Since the majority of water plants in the U.S. use
alum as the prime coagulant, the disposal of this type of sludge
should receive primary consideration. Other sludges which must be
considered from the use of coagulants such as, sodium aluminate,
potassium aluminum sulfate, ferric sulfate, ferric chloride, cop-
peras, chlorinated copperas, and sometimes lime.
Another consideration is the increasing use of coagulant aids
such as, bentonite clays, activated silica, and various polyelec-
trolytes. Other miscellaneous chemicals contributing to sludge
volume or influencing sludge composition are: copper sulfate used
for plankton control; activated carbon for taste and odor control;
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76 Status Report on Plant Operation
and potassium permanganate for color, iron and manganese removal.
The other types of plant waste discharges which must be con-
sidered are the calcium carbonate sludges and brines resulting from
water softening processes.
DISPOSAL OF ALUM SLUDGE
An Alum sludge consists of aluminum hydroxide plus loam and
clay particles, color colloids, microorganisms including plankton,
and other organic and inorganic matter removed from the water being
treated. The sludge is usually bulky, and gelatinous in consistency.
It has a high moisture and a low solids content. It varies in color
from a light yellow to a black depending upon the character of the
source water and the chemicals used for treatment.
Plant operations for disposal of alum and other coagulant wastes
may include:
1. Direct discharge to surface waters
2. Lagooning
3. Discharge to sanitary sewers
4. Freezing
5. Centrifuging
6. Vacuum filtration
7. Sand bed and wedge wire drying
8. Filter pressing
9. Barging to sea
10. Pipeline transport
11. Alum recovery
The discharge of water treatment plant wastes directly to sur-
face waters is, obviously, the most economical method of disposal.
This method is becoming impractical in many locations. Almost all
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Status Report on Plant Operation _^__^ ^^ 77
states now have pollution control laws or regulations to limit such
discharges. State and interstate regulatory agencies increasingly
require the installation of waste control facilities.
Operation of Lagoons
Lagoons for disposal of waste sludge require suitable land
areas. As has already been pointed out in the engineering report,
these are not generally available adjacent to large urban water
treatment plants. In the case of rural water treatment plants,
where cheap land is available, lagoon disposal is simple and eco-
nomical.
While operational costs of lagoons are low, factors such as
climate, intermittent or continuous input, percentage of sludge
solids, and the availability of one or more alternating lagoons,
will have a bearing on the land area required. Generally, at least
two lagoons are needed. They can serve as settling basins or as
thickeners preceding some other process.
Problems exist with insect breeding. Lagoons serve as at-
tractive nuisances to children in inhabited areas, x
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78 Status Report on Plant Operation
Discharge of Wastes to Sanitary Sewers
A disposal method which deserves more study is the discharge
of wastes to the sanitary sewer. Four large U.S. cities discharge
sludges and washwater to sanitary sewers; Detroit, Michigan;
Philadelphia, Pennsylvania; Wilmington, Delaware; and Washington,
D.C. Primary wastewater treatment plants in these cities have not
experienced treatment difficulties from these discharges.
In one city, where the sedimentation basin wastes were re-
leased as a slug, difficulties with vacuum filtration were experi-
enced. When the waste discharges were spaced over several days,
the difficulties ceased. Continuous removal and discharge of sludge
reduces the possibility of interference with the wastewater plant
processes.
Settling basin sludges and waste water can be discharged into
sanitary sewers if large fast flowing sewers are available and prima-
ary settling is a part of the waste treatment plant process. In one
large city, a 100 gpm pilot activated sludge plant has received a
proportionate share of the water plant sludge discharged to the pri-
mary plant without experiencing any difficulty in handling the com-
bined wastes.
Waste Treatmentby Freezing
In the United Kingdom, a freezing process for treatment of alum
sludge has been sucessfully operated. Pre-thickening, to reduce the
volume and thereby the cost, is a primary step, in the process,
water of hydration is removed from the gelatinous aluminum hydroxide,
changing the character of the sludge to small granular particles
which settle rapidly, and the final volume to one-sixth of the orig-
inal volume.
Although the original freezing process for sewage sludge was
developed in 1950, use of this method for treatment of water plant
sludge was first initiated in England in 1963. Capital costs for
construction in England generally approximate $17,000 per 1,000 gal-
lons of sludge frozen per day. Power costs in England vary between
180 KWH and 230 KWH per 1,000 gallons of sludge frozen, depending
upon the ambient temperature of the sludge.
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Status Report on Plant Operation 79
Waste Treatment by Centrifuging
Wastewater treatment plants have used centrifuges for dewater-
ing primary and activated sludges with some degree of success, but
their use in water treatment plants has been very limited. It has
recently been shown that alum sludge, removed continuously from a
conventional sedimentation basin (1.0 to 1.5 percent total solids)
can be concentrated in a centrifuge (to about 17 to 18 percent sol-
ids) . A solids concentration of at least 18 to 20 percent is con-
sidered necessary if the material is to be handled with mechanical
equipment and hauled to a disposal site.
Advantages of the centrifuge method are the low space require-
ments, complete process automation, and ability to handle either
dilute or thickened sludges. Disadvantages are relatively high
maintenance costs and scarcity of disposal sites for the dewatered
sludge.
Waste Treatment by Vacuum Filtration
Vacuum filtration equipment is extensively used for dewatering
wastewater treatment plant sludges, but its application to water
treatment plant sludges has been limited. This method utilizes a
cylindrical drum covered with a porous fabric made of metal mesh,
steel coils, wool, cotton, nylon, saran, or one of the newer syn-
thetic fiber cloths as filtering media.
To obtain optimum results with this method it is necessary to
chemically condition the sludge with polyelectrolyte, diatomaceous
earth, or lime, to prevent clogging of the filter cloth and to im-
prove the dewatering qualities of the sludge.
The advantage of this process is that a product suitable for
direct disposal on land may be produced.
The disadvantages are that vacuum filters are unable to filter
dilute sludges, such as those obtained from basins having contin-
uous sludge removal devices. A disposal site for the dried sludge
is still needed. Vacuum filters are particularly applicable to
large treatment plants producing substantial quantities of sludge.
-------
SLUDGE DEWATER1NG
Samples of Alum Sludge from Various Dewatering Processes
1 . Raw Sludge
2. Settled for 4 days
3. Treated in Centrifuge
4. Frozen & Thawed
5. Dried Solids
6. Sludge Cake after Pressing
-80-
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Status Report on Plant Operation 31
Waste Treatment by Sand Bed and Wedge Wire Drying
Sand drying beds are probably the method of choice in rural
areas where land is readily available and relatively cheap. How-
ever, since large land areas are generally required and sand is
expensive, cost is a factor not to be ignored. The sand beds may
be open or covered.
Disadvantages of this method are the poor dewatering of sludge
in cold or rainy climates, high labor costs for collection of dried
sludge and hauling to disposal site, and the long time needed to
adequately dewater the sludge. Mechanical devices can be used to
expedite the collection of dried sludge but their use results in
loss of sand and causes increased operation costs because new sand
must be purchased for replacement.
It is reported that in England, where large land areas are
available, the cheapest method of drying water plant sludge has been
in lagoons and on sand drying beds. A modification of sand drying
was developed using wedge wire as the filter media. Wedge wire re-
quired an initially high capital outlay, although maintenance costs
were low. In England, this method was rejected in favor of the
filter press.
Waste Treatment by Filter Pressing
The filter press has not been used extensively in the United
States for dewatering of alum sludges. However, pilot studies have
been conducted recently in several large U.S. water and waste treat-
ment plants with reported success. One water treatment plant in
Great Britain has pressed sludge containing 1.5 to 2.0 percent sol-
ids and obtained a wet cake containing 15 to 20 percent solids.
The original objections to the use of this method have been
the short life of filter cloths and lack of automation. However,
the use of snythetic fibers has increased cloth life, and recent
modifications have provided complete automation for the feeding and
pressing cycle. Short shutdowns required for cake removal.
Disadvantages of this process are reported to be initial high
costs for equipment, relatively high maintenance and operation costs,
operation not completely automatic, and after discharge of cake the
filter cloth must be inspected to prevent operating difficulties.
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82 Status Report on Plant Operation
Barging To Sea
Barging water plant sludge to sea may be advantageous where
the plant is located on a river, close to the sea. To reduce costs
the sludge should be thickened before hauling to the disposal site
which may be 400-500 miles, round trip. This disposal method should
be closely evaluated with other disposal methods for cost, flexi-
bility of operation, and ease of handling.
Pipeline Transport
Pipeline transportation of sludges for long distances to la-
goons or to the ocean for disposal is simple and relatively inex-
pensive. Asbestos cement pipe of 4 to 6 inches in diameter is
adequate and can be constructed at low cost.
Advantages are relatively low original cost, low maintenance
costs, flexibility in handling plant sludge loads, and combining
sludge from more than one operation.
Alum Recovery
Recovery of alum from alum sludge through treatment by sulfuric
acid results in reduction in sludge volume to less than 10 percent
of the original volume, and concentrates the sludge to 20 percent
solids by weight. In recent pilot plant tests, during which a fil-
ter press was used to dewater the acidified alum sludge, alum re-
coveries of 80 to 93 percent were attained and the residual cake
contained 40 to 55 percent solids.
Disadvantages of alum recovery from sludge are the high cost
of sulfuric acid in certain areas, need for increased alum dosage
when the recovered alum is reused, concentration of undesirable
chemicals, and operating costs of the treatment process. When com-
paring costs of recovered alum with that of purchased alum due
credit must be given to capital investment, interest, and depre-
ciation as well as the cost of acid used for recovery.
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Status Report on Plant Operation 83
DISPOSAL OF FILTER WASHWATER
Filter washwater can be lagooned, and the settled water pumped
back to the plant intake or discharged to a sanitary sewer. In
some plants, washwater has been pumped back to the rapid mix unit
without settling, but this practice has been reported to adversely
affect coagulation. Where washwater is lagooned, the clear super-
natant may be drained off and the sludge dewatered.
Some plants have installed small auxiliary water treatment units
specifically for treatment and recovery of their filter washwater.
The capacity of these units is about 2 to 3 percent of the capacity
of the main plant, and the treatment process is similar to that used
in the main plant. That is, alum (with or without a polyelectrolyte
coagulation aid) is flash mixed with the dirty washwater. Passage
through a conventional mixing and settling basin follows.
The clarified washwater flows by gravity to the main plant fil-
ter influent channel where it is mixed with the clarified water from
the main plant settling basins. This method of washwater recovery
has been found to be efficient and economical, and the amount of
washwater used in filter operation has been reduced to less than one
percent.
DISPOSAL OF SLUDGE FROM SOFTENING PLANTS
Methods for disposal of softening plant sludges have, in gen-
eral, been similar to those used for disposal of alum or iron sludges
from coagulation treatment processes. Discharge to surface waters
(where dilution permitted), and lagconing, have been by far the most
common practices for such waste disposal. In some instances disposal
into sewer systems has been allowed. A few plants have installed
facilities for lime reclamation.
The major constituent in the sludge produced at lime or lime-
soda softening plants is calcium carbonate, which generally falls
within the range of 85 to 95 percent of the dry weight of the solids
in the sludge. Other constituents which may be present include:
magnesium hydroxide, the hydroxides of iron and/or aluminum, in-
soluble inorganic matter such as clay, silt, or sand, and organic
matter such as algae or other plankton removed from the water being
treated.
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84 Status Report on Plant Operation
The quantities of calcium carbonate produced during lime treat-
ment are quite substantial, as one pound of pure quicklime (calcium
oxide) when added to water will react with the calcium bicarbonate
in the water to precipitate 3.57 pounds of calcium carbonate. As
commercial quicklime usually contains only 85 to 95 percent calcium
oxide, and as the lime also reacts with some of the magnesium,
iron, and aluminum that may be present, the amount of sludge produced
during lime treatment is generally assumed to be about 2.5 pounds,
dry basis, for each pound of quicklime added.
The use of lime and soda ash together, in proper proportion and
dosage for the water being treated, can effect the removal of prac-
tically all the magnesium and most of the calcium from the water to
leave a residual hardness of only about 25 parts per million.
Softening Sludge Characteristics
The physical characteristics and wet volume of the sludge pro-
duced during lime or lime-soda treatment may vary very widely, de-
pending upon the ratio of calcium carbonate to magnesium hydroxide
in the sludge, whether or not alum or another coagulant (with or
without a coagulant aid) was used, and the nature and amount of
foreign material (inorganic or organic) that may be present in the
water being treated. The calcium carbonate particle sizes are
quite small, usually falling between 5 and 15 microns. Solids in
sludge collected in the settling basins of lime and lime-soda sof-
tening plants have been reported to range from 2 to 33 percent.
Similarly, the volume of sludge discharged from such plants has
ranged from 0.3 to 6 percent of the water softened.
Most of the large softening plants have been built adjacent to
their source of supply of raw water, usually a large river, and it
has been very simple and economical to discharge their waste sludge
to a point downstream from the plant intake. As this sludge con-
sists mainly of inorganic matter which has no oxygen demand and
contributes essentially no disagreeable tastes or odors to the water,
its primary nuisance qualities have been the production of turbidity
and the formation of sludge banks. Nevertheless, more and more
States are classifying such sludge disposal as water pollution and
are enacting legislation regulating or prohibition this practice.
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Status Report on Plant Operation 85
Lagoon Treatment of Softening Sludge
Discharge into impoundment basins or lagoons has also been a
relatively simple and inexpensive method for disposal of softening
plant sludge. Where sufficient land is available at low cost, this
practice can offer a long term solution to the sludge disposal pro-
blem. Unfortunately, with continued urban development and popula-
tion growth, land for sludge lagoons becomes increasingly difficult
to find; at the same time, the volume of sludge produced is in-
creased, due to the need for more and larger plants to provide the
water for urban communities.
The lagoon capacity required for disposal of the sludge is de-
pendent upon the physical characteristics of the material and the
extent to which it is dewatered during impoundment. Where the sludge
has been dewatered to about 50 percent moisture content, the lagoon
capacity requirement has been reported as about 0.5 acre-foot/year/
mgd/100 ppm hardness removed. Lagoon depths usually vary from 3 feet
to 10 feet ore more, but may be much deeper where a canyon or gully
can be dammed to form a suitable impoundment area, or where worked-
out gravel pits are available.
Successful operation of sludge lagoons requires that they be
divided into several independent ponds or pools so that each section
in turn may be permitted to dry while the others remain in use.
Generally, the supernatant from the sludge ponds is decanted and
diverted into a natural watercourse or pond, or is permitted to per-
colate into the underground. As the decantate is of essentially the
same quality as the water being treated at the plant (except that it
is softer and usually lower in bacterial population) its addition to
the surface or underground water should not prove objectionable.
The dry sludge, when accumulated in sufficient quantity in the
dewatered section, may be hauled away to a more remote disposal area,
may be used in landfill operations or for soil conditioning, may
prove useful as a neutralizing agent for acid wastes produced in
some industrial processes or, if it is sufficiently pure calcium
carbonate, may even serve as an inert filler in some industrial pro-
ducts or as a pigment in inexpensive whitewash coatings.
In the operation of sludge lagoons, measures are usually re-
quired to protect the public from potential nuisance or hazard.
As the ponds may be an attraction to children and animals (and even
to adults if someone has planted fish in the ponds or if ducks land
there), it is usually necessary to enclose them with an adequate
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£!6 Status Report on Plant Operation
fence. Mosquito and fly abatement measures may be required. If
organic matter is present in sufficient quantity to cause odors upon
decomposition these must also be controlled, and periodically it may
be necessary to cut down or otherwise restrain the growth of pond
weeds and grasses.
Sewer Discharge of Softening Sludge
Disposal of softening sludge to a sanitary sewer is used only
in a relatively small percentage of water softening plants. Calcium
carbonate sludge may be sufficiently dense to settle and plug the"
sewer lines unless adequate dilution water and high velocities are
maintained to keep it moving freely.
Softening plant sludge is also reported to have caused pro-
blems in the operation of sludge digestion units in sewage treatment
plants, possibly due to a mixture containing a disproportionately
high percentage of sludge over a period of time with consequent in-
hibition of biological activity.
Reclaiming Lime from Softening Sludge
As regulations to control stream pollution become more stringent,
the practice of reclaiming lime from softening plant sludge may be-
come more widely accepted. Theoretically, it would be possible to
recover from pure calcium carbonate sludge twice as much quicklime
as had been used in the water treatment process to produce that sludge.
Thus, a plant practicing lime reclamation would produce suf-
ficient lime to meet all of its needs and have a surplus to sell to
other users. Actually, impurities in the sludge and less than 100-
percent efficiencies in the reclamation process reduce the amount
of lime recovered. Nonetheless, it can produce substantially more
than is used for softening the water.
The reclamation of lime from softening plant sludge has been
slow because most plants used the simple and inexpensive methods of
lagooning or discharging sludge into a nearby watercourse. Addi-
tionally, the adaption has been retarded by: (1) constantly changing
quality of the river water being treated, with resultant variations
in sludge quality and complications in the calcining process; (2)
the difficulties occasioned by the accumulation of magnesium in the
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Status Report on Plant Operation 87
reclaimed lime; (3) lack of fully satisfactory calcining equipment,
especially for small plant installations; and (4) the reluctance of
small communities to adopt a procedure which had not been completely
proven and widely accepted.
The City of Miami, Florida, put an 80-ton per day rotary kiln
lime recovery installation into service in 1949. The process in-
cludes thickening of the calcium carbonate sludge to 20 to 30 per-
cent solids, dewatering by centrifuge to about 67 percent solids,
followed by calcination at a temperature of 2,000 to 2,200op in an
oil-fired rotary kiln. Original operating difficulties were all
overcome, and satisfactory and economical operation of the lime
recovery plant is reported. Excess lime produced was shipped to
Tampa and Gainesville, Florida.
Recovery of lime from softening plant sludge has been practiced
in Lansing, Michigan, since 1957, The process used includes recar-
bonation (to improve the settling rate and aid in separation of mag-
nesium hydroxide from calcium carbonate), dewatering by centrifuge,
and calcining in a fluidized bed furnace. Production was about 25
tons per day.
Dayton, Ohio, has also been reclaiming lime, but from a larger
plant rated at 150-tons per day capacity. Here the sludge is re-
carbonated, dewatered by centrifuge, and burned at 2,000°F in a
rotary kiln to produce a high quality pebble lime (91 to 92% avail-
able CaO). Excess lime produced is sold to nearby communities.
San Diego, California, recovered lime in a 25-ton per day plant
until the process was abandoned because softening of the water was
discontinued. The calcium carbonate sludge was dewatered by cen-
trifuge and then calcined in a gas-fired rotary kiln at 2,000°F.
Enough lime was produced at the one recovery plant to provide for
the needs of three water treatment plants in the city.
Because pollution control regulations will sharply curtail the
practice of discharging softening plant sludge to surface waters,
lagooning will probably remain for the near future the simplest and
least expensive way of disposing of such sludge.
The reclamation of lime from calcium carbonate sludge will
gain much wider acceptance as improved recovery systems are avail-
able, and as markets for excess lime are developed. The increasing
cost of land, and its decreasing availability will also lead to
that development.
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88 Status Report on Plant Operation
DISPOSAL OF BRINES FROM SOFTENING PLANTS
Cation-exchange softening materials, as well as equipment and
procedures for their efficient use, have been greatly improved in
the past 20 years. However, no significant advancements appear to
have been made in methods for disposal of the spent brines from
such softening operations. Perhaps this is due to the fact that
the greatest increase in cation-exchange softening has occurred in
the use of small units designed for industrial, commercial, or res-
idential use.
From small units, the spent brine and rinse water are almost
always discharged directly into the local sewer system. Although
collectively the quantities of waste brine so discharged are very
substantial, individually the discharges are relatively small and
widely scattered, so no more practicable solution to the disposal
of the brine from these units could be offered.
Disposal of brines from water treatment plants utilizing
cation-exchange softening still follows the long-established pat-
terns of:
1. Dilution (controlled or uncontrolled)
a. Directly to stream
b. To stream via sewer system
2. Discharge to ocean
a. Directly
b. Via sewer system
3. Discharge into wells
4. Evaporation
The chemical composition of waste brines from softening plants
may vary over a wide range, with total dissolved solids concentra-
tions approximating 15,000 to 35,000 ppm. Major constituents are
sodium, calcium, and magnesium chlorides. A representative range
of the major constituents in softening plant brines is shown in
Table 6.
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Status Report on Plant Operation 89
TABLE 6
Waste Brine From
Cation-Exchange Softening Plant
Major Constituent Concentration (ppm)
Calcium (Ca) 3,000 - 6,000
Magnesium (Mg) 1,000 - 2,000
Sodium (Na) 2,000 - 5,000
Chloride (S04) 9,000 - 22,000
The quantities of brine and rinse water used for regeneration
of softening units may vary over a wide range. The total waste
water generally varies from less than too percent to about five
percent of the amount of x^ater treated, although values as high as
10 percent have been reported.
Due to their salinity, regenerant brines cannot be permitted
to come in contact with growing plants; nor can they be discharged
underground at any point where they might possibly percolate into
an underground fresh water aquifer.
Discharge of these brines directly into a river or other
watercourse has been permitted where flows are sufficient to af-
ford the dilution necessary to protect the quality of the water for
downstream users and for aquatic life. Where normal stream flows
are insufficient to meet unregulated dilution requirements, con-
trolled discharge of waste brines may be permitted. This entails
the use of a holding reservoir for collection of intermittent high-
rate brine discharges, and subsequent releases of the stored brine
at regulated rates to correspond with the dilution capability of
the stream flow. If the receiving stream is subject to extended
periods of low flow, relatively large and expensive holding reser-
voirs may be needed for this method of disposal.
Discharge of brines into sewers which ultimately deliver the
wastes into a flowing stream may be subject to the same controls as
prescribed for direct discharge into the stream itself. If sewage
reclamation is practiced and the reclaimed water is returned under-
ground for groundwater replenishment, even greater limitations are
set on discharge of brines into the sewer system.
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90 Status Report on Plant Operation
For those softening plants favorably located close enough to
the coastline to permit direct discharge into the ocean, or via a
sewer system directly to the ocean, the problem of brine disposal
is greatly simplified. Furthermore, if the softening plant can be
located close enough to the ocean to use sea water instead of pur-
chased salt for regeneration, substantial savings in the costs of
plant operation may be effected.
Apparently, only relatively few softening plants use brine
disposal wells to dispose of waste brine. These wells must be lo-
cated in an area where there is no possibility of brine intrusion
into the groundwater supply and where the underground formation is
porous enough to disperse and store the brine received.
The brine must be essentially free of suspended matter to
preclude plugging of the well, and also free of any soluble con-
stituents which might form precipitates upon oxidation or upon
reaction with other mineral matter in the subsoil formation and
thereby cause plugging. Any need for treatment of the brine be-
fore disposal would add to what could already be a relatively high
cost of the injection well itself.
Storage of brine in unlined impoundment basins is not accept-
able in many locations due to the danger of infiltration of the
brine into the underground water supply or into a nearby stream.
If evaporation is considered as a means of brine disposal, proper1}
sealed or lined pits must be developed to avoid seepage from the
storage area.
A vital consideration in the design of these basins is whether
the rate of evaporation exceeds the precipitation in the area,
particularly in view of the fact that the rate of evaporation of a
brine decreases as evaporation progresses and the concentration of
the residual liquid rises. The problem of disposal of the pre-
cipitated salt also may be a difficult one to solve, even though
evaporation may be feasible. Evaporation, therefore, may be one of
the less practicable methods of softening plant brine disposal.
Precipitation of the calcium as a high quality calcium car-
bonate and of the magnesium as relatively pure magnesium hydroxide
is possible if the concentrated portion of the spent regenerant
brine is collected separately from the rinse water which follows it
during the regeneration process. This would, at the same time,
leave a substantial portion of recovered sodium chloride brine for
reuse. Equipment, chemicals, and process control would be required
for such an operation, and it is questionable whether this procedure
could be economically justified.
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Status Report on Plant Operation 91
It appears, then, that discharge to the ocean, either directly
or via the local sewer system, is the best method for disposal of
water treatment plant brines where the geographical location permits.
Controlled or uncontrolled dilution by way of discharge into a near-
by watercourse is used in inland areas when stream flows are adequate
for the purpose. Discharge into injection wells or evaporation in
seepage-free impoundment basins may be the only recourse where neither
of the preferable methods of waste brine disposal is feasible.
PLANT OPERATION REQUIREMENTS
Improved techniques needed to solve the problem of waste disposal
from water treatment plants are suggested below:
To reduce the volume of sludge, improved methods of solids
concentration should be actively researched and practical applica-
tions developed.
Improved dewatering techniques for water plant sludge should
be developed. Wastewater sludge dewatering methods should be con-
sidered for possible adoption to water plant wastes, and research
conducted on newer methods.
Research is needed to develop new chemicals, and extend the use
of present chemicals, to condition sludge for more effective de-
watering.
Continued study should be made of reclaiming by-products of
sludge such as alum, lime, or other chemicals, and to make sludge
more suitable for soil conditioning or other practical uses.
Economic evaluation of current methods of sludge disposal is
needed.
More detailed study of heat, freezing, pressure cooking, and
other physical means for altering sludge structure is desirable.
This could reduce the bulk and improving handling characteristics
of sludge, and result in lower disposal costs.
Develop improved means of sludge transfer which will improve
upon present methods of mechanical handling.
Mechanical dewatering methods should be compared on the basis
of efficiency, cost and final product.
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92 Status Report on Plant Operation
Development of laboratory methods of sludge processing which
will simulate actual plant conditions.
Finally, there is an outstanding need for a continuing survey
of current plant operations, research, and demonstrations. The in-
formation developed should be coordinated and widely distributed.
*
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Plant Operation - Report Discussion 93
DISCUSSION OF STATUS REPORT ON PLANT OPERATION
MR. KRASAUSKAS: The item which impressed me most in
each status report was that it has not been possible to develop
cost figures applicable to the operation of plants for the dis-
posal of water treatment wastes. Each plant has differerent pro-
blems.
The availability of land appears to be an especially
important problem. Where lagoons would be applicable to one
installation, they might not be in another. In Washington D.C.,
our plant is located just below Spring Valley, which is one of
the most exclusive residential areas. Land isn't available
and lagooning cannot be considered.
The most significant operating problem stems from the
fact that no matter which process is used, the end product must
be disposed of, whether it contains 20 percent solids, 30 per-
cent solids, or 50 percent solids. Since water treatment plant
wastes cannot be destroyed, they must be placed ultimately on
land of sufficient size to handle the waste. The Washington
B.C., water treatment plants have a maximum capacity of about
270 mgd, and produce approximately 45 tons of sludge to dispose
of each day. We can drive in any direction up to 50 miles from
the city of Washington without finding cheap land.
One alternative is possibly alum reclamation, because
we have about 16,000 tons of sludge on a dry basis, of which
5,000 tons is alum.
If 70 percent recovery of alum is possible, we can re-
duce the total tonnage to be disposed of. Even then, we must con-
sider where to haul it, and what the cost will be.
Hence, even though possible methods of disposal are iden-
tified in our reports, we have not really solved the problem. If
we could incinerate our sludge like wastewater sludge, so that the
end product is ash, our problem would greatly reduce in scope.
But water plant sludge, being inert, is not amenable to incin-
eration. As a plant operating problem, considering ultimate
disposal, we don't really know the answer.
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94 Plant Operation - Report Discussion
MR. STREICHER: I shall report on our own operating ex-
perience and on of the research and investigations that we have
conducted.
We have had experience in washwater recovery. In fact,
we have built, at each of our two 400 mgd plants, special washwater
reclamation units. Each plant has two units which together have a
rated capacity of about 12 mgd. We handle filter washwater as if
it were a turbid water coming into the plant. The washwater is
treated with alum, flocculated, settled, by gravity, and the clari-
fied water flows back and mixes with the water from the main plant
settling basins,thereby becoming a part of our process water. We
have left for disposal from the washwater reclamation units only
a small increment of alum sludge which we dispose of by lagooning,
in the same manner as the sludge from the main plant settling ba-
sins .
In the early years of plant operation, we used lime and
accumulated considerable lime sludge in our impoundment basins,
located about a mile and a half from the plant. The surface water
was decanted and flowed into a flood control reservoir which was
also used for recreational purposes. It settled and consolidated
to about 50 percent solids. Since we had the impoundment area
divided into four sections, each section was permitted to dry alter-
nately. Incidentally, this sludge was about 93 percent calcium
carbonate.
In about 1949-50, we sold most of our lime sludge to a
manufacturing concern in Los Angeles for use in neutralizing an
acid waste which was disposed of into the sewer system.
With reference to odors, we had none from lime sludge.
The sludge we have today, (mainly organic and inorganic matter
from our main plant settling basins without coagulant, and the
alum sludge from the washwater reclamation unit) has some odor
at times as it is dumped into the lagoon. But once the sludge is
covered by water, there is no noticeable odor.
We have also had experience in brine disposal. We have
the largest ion exchange softening plant in the world, producing
5 mgd of brine for disposal. As was mentioned earlier today, dis-
posal of brine is a real problem unless you are fortunately sit-
uated. In our case, we discharge the waste brine into our waste"
water disposal line which joins with the Los Angeles County sani-
tation system, about 22 miles from the plant. By that means, we
dispose of it to the ocean.
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Plant Operation - Report Discussion 95
When an ion exchange softening plant is far from the ocean,
the only means of brine disposal may be discharge into deep wells or
into evaporation ponds, provided that this can be done without con-
taminating the underground supply. In our location, we are not per-
mitted under any circumstances to discharge brine anywhere except to
the ocean.
We haven't had any significant experience with alum sludge
other than that produced in the washwater reclamation units, a very
small operation representing about three-quarters of one percent of
the main plant flow. However, we will be faced with the problem, of
alum sludge handling and disposal from a new plant now in the early
stages of construction and scheduled to be completed in 1971.
In the new plant area we are not as fortunately situated
with regard to lagooning ponds, as in our existing plants. True,
there are some gravel pits about 12 or 14 miles distant from that
plant site. It would be expensive to construct a sludge line for
that distance but, in addition, the gravel pits themselves are
valued at 1 million to 5 million dollars each.
We are hoping to work out an agreement with the city of
Los Angeles Bureau of Sanitation to accept sludge from the new
plant in their sewer system for ultimate delivery to their sew-
age treatment plant. If we are not successful in this, we have
two other courses left.
We started out by considering about seven different
plans for sludge disposal, and reduced then down to three. The
first choice is disposal to the sewer system as I have just des-
cribed. The second choice will be either disposal to a gravel
pit or the operation of an alum reclamation plant.
To evaluate alum r-eclamation, we visited a few plants in
Japan where that is being practiced. Interestingly enough, water
treatment plants in Japan have been forced by their pollution con-
trol agencies to discontinue discharging alum sludge into streams.
A number of plants are operated for alum reclamation,but do not
recover alum all the time. In fact, more than half the time -
when the flow is sufficient in the streams - the old practice is
used of discharging the alum sludge directly into the surface waters.
Apparently this practice is permissi.ble during very high stream flows.
Obviously, the discharge of sludge is considerably cheaper than alum
reclamation.
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96 Plant Operation _- Report Discussion
I might mention that as a part of alum reclamation they
are using vacuum filters, and are not particularly happy with the
drying they accomplish. The solids content of the filter cake is
about 28 or 30 percent. The cake is very sticky and rather hard
to handle.
Sludge cake is presently dumped into a ravine which is
filling rapidly. I don't know what they are going to do when the
ravine is filled with alum sludge.
We ran some tests of our own on the recovery of alum from
sludge, not being satisfied with 59 or 60 percent alum recovery,
nor with 28 to 30 percent solids in the alum cake. In Japan, the
acid treated sludge is put into a settling basin, permitted it to
settle out, and the alum is decanted for recovery. To the residue,
which contains a mixture of insoluble material and alum, lime is
added and the mixture is filtered.
In our pilot plant tests, we treated the residue with acid
and filtered the mixture at a pH of 1.5 to 2.5. The filtrate is
clear and of good quality.
Because of the poor experience reported with vacuum fil-
ters, we made studies with a small filter press. With this, we were
able to obtain a cake of 40 to 45 percent solids, and in one run
over 50 percent solids. This cake is quite dry. With filtration of
an acid residue, and using a filter press, we were able to attain
recoveries of alum from 80 up to 93 percent and produce a very dry
cake at the same time.
MR. KRASAUSKAS: The cost of sulfuric acid is now very
high, about $27 a ton in our area and expected to increase. At
present, we purchase a grade 2 alum which has about ten percent
impurities; it's very similar to alum we used to manufacture. We
manufactured alum from 1928 until 1964 in Washington B.C.; approx-
imately 5,000 tons a year.
If we purchased sulfuric acid to manufacture alum today,
we would be meeting the price of the alum that we buy. In fact,
it might even cost us more to recover alum than we originally
paid for it.
MR. DEAN; It might be possible to dissolve the precip-
itate with less hydrochloric acid than three mols. In England, one
mol basie, aluminum chloride is used for sludge conditioning.
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Operation - Report Discussion
According to the literature, if alum is not exhausted as a precip-
itant, it should be possible to recover a soluble aluminum chloride
with only one mole of hydrochloric acid. Three moles of sulfuric
acid would probably be needed.
There could be a cost saving, plus the fact that you would
put less sulphate into your water, which is also a consideration.
This might be a research possibility.
MR. STREICHER: In our pilot tests, we found that when
the ratio of aluminum hydroxide to other suspended matter was
high, considerably less than stoichiometric amounts of sulfuric acid
were required to get almost complete alum recovery. As the other
insoluble matter increased in proportion to the aluminum hydrox-
ide, more and more sulfuric acid was required. If the ratio of
other insolubles was high, compared to aluminum hydroxide, it
took more than stoichiometric amounts and the alum recovery was
reduced. So it depends on the ratio of aluminum hydroxide to other
suspended matter, according to our tests, just how much alum can
be recovered.
MR.KRASAUSKAS: There is another benefit in the recovery
of alum. The volume of the sludge is reduced to approximately one-
sixth of the original volume. Do you find this to be true?
MR. STREICHER; Yes, but the recovery of alum would be much
more attractive if the disposal problem disappeared entirely. When
you have any residue left to dispose of, a treatment process loses
some it its attractiveness.
MR. KEASAUSKAS: This is the trouble with all methods of
sludge treatment. ¥e still have an end product which must be dis-
posed of.
MR. LAMB: I'd like to ask a question of the plant oper-
ating people present. The next topic which we will discuss is regu-
latory aspects. It would be interesting, I think, to know the atti-
tudes and philosophy of operating people toward the whole question
of waste disposal from water treatment plants. What do you think
is the general attitude of operating and management officials in the
water works industry concerning this problem?
MR. STREICHER: I think that they would rather be able to
just shrug it off, but obviously it isnt't possible now. In the
present day 1 think we are going to be guided by the regulations
more than anything else.
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98 Plant Operation - Report Discussion
We have enough room for disposal for the next 50 or 100
years, so we are not concerned at this time. What would happen if
we could not dispose of sludge on our own land, I don't know.
MR. KMSAUSKAS: To comment further on Mr. Lamb's question:
the water treatment sludge presently discharged to the Potomac River
in Washington is equivalent to about six-tenths of one percent of
the load of silt which is carried by that river.
In the past, we have considered that the return of solids
removed from the river do not add pollution. We do recognize that
we will have to conform to pollution control requirements.
MR. WEBER: The net effect of returning removed impurities
to a lesser quantity of water must degrade the quality of water.
MR. WEBBER: The City of Toledo is under proscription from
two pollution agencies to cease discharge of wastes to the river.
MR. SHULL: It is the philosophy of our management that
we have a moral obligation to get rid of settling basin sludge and
filter washwater. I realize that a little nudging from the State
regulatory agencies perhaps has had some bearing on this. Since
we have always been very much concerned about what other people put
in the stream above us, so we now feel obligated to do something for
water users below our plants. We are doing everything possible to
provide for adequate waste disposal.
MR. HENRY: Deep well disposal has been mentioned several
times. Can anyone report on the use of deep wells for disposal
of regenerant salt brines?
MR. STRETCHER: I am not familiar with that operation,
but it is mentioned in the literature. I believe there are ex-
amples of this practice in Kansas, where brine taken from salt wells
is used for regeneration. The waste brine is then reinjected into
other wells. This can be done only where aquifers can be definitely
isolated from each other.
MR. DEAN: We are beginning to worry about the disposal
of brines put down into wells. If the pressure of recharge is
higher than the normal pressure, there is a very real danger of
breakthroughs, thus getting salt into good aquifers.
This has happened at a number of places in Texas, not
documented. It might be done safely in some geology situations.
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Plant Operation - Report Discussion 99
But it's not the general answer. It's a special case like discharg-
ing in the ocean is a special case.
MR. KRASAUSKAS: Disposed of waste sludge into the sani-
tary sewer has been mentioned as a preferred method. We considered
that method in Washington.
However, our Department of Sanitary Engineering already
has such a serious problem disposing of wastewater sludge that they
are not interested in adding the sludge from our water treatment plant,
'We must find some other method of disposal.
Our Department of Sanitary Engineering is considering barg-
ing sludge to sea, which would involve a distance of about 200 miles.
They still haven't decided. If they do select that method, then it
will be possible to dispose of our sludge in this manner.
MR. STREIGHER: That's a long way to move sludge.
MR. KRASAUSKAS: Yes, but we simply have no land near-
by to dispose of a large volume of sludge. We have a real pro-
blem.
MR. ADRIAN: Lompoc, California reclaimed the decant from
their dewatering and drying beds. The decant had been added to the
sewer when the beds were first installed and had problems with sol-
ids building up in the sewer line.
Apparently, solids built up would discharge suddenly, then
would be received as a slug at the sewage treatment plant. The pro-
blem was solved by reclaiming the decant water and having no dis-
charge into the sewer. There may be a problem, adding water treat-
ment waste to the sewer, wherever the flow rate is low,
MR. STREICHER: I can report that, some years ago, the City
of Los Angeles put in a test plant to study the treatment of sewage
with alum. As I recall, an excess of some 50 ppm of alum, above
the coagulant dosage, was added. The effluent from this plant dis-
•charged to a sewer line and caused clogging of that line.
Apparently, when the excess alum combined with the greases
in the fresh sewage, a thick deposit was formed and the clogging
problem was serious. That experience made the City reluctant to ac-
cept our sludge.
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IQQ Plant Operation - Report Discussion
We told then that we could not afford to overtreat water
with alum, and planned to have no unreacted alum left in the sludge
at the time it was discharged. Additionally, we would pay for added
capacity of the sewer system to provide a larger line.
The Los Angeles Bureau of Sanitation laboratories tested
tha alum sludge from our washwater reclamation unit, also sludge
samples from the Livermore Plant on the South Bay Aqueduct. We will
be treating the same type of water at our new Balboa plant. Their
tests indicate that the sludge should not give tnem problems in
sewers or in the sewerage treatment plant, except for increasing the
bulk of sludge to be digested.
MR. JOHNSON: In the reclamation of your filter washwater,
you mentioned that you coagulate the water and let it settle?
MR. STREICHER: Yes, we treat it just as if it were raw
water.
MR. JOHNSON: Have you ever tried recycling the washwater
back through the plant without this treatment.
MR. STREICHER: Yes. That's the way we started to reuse
the water, but it caused problems in the settling basins and filters.
In the original 100 MGD plant we had no washwater reclamation unit,
and we recycled the washwater from the filters back to the plant
influent channel.
In the early years, we used lime treatment and no problems
were encountered. Then we abandoned lime treatment and, in fact,
coagulation entirely (because our plant influent water is usually
so good that we don't have to use any coagulation). We then found
that as a result of returning untreated filter washwater, our clari-
fied water contained about four times as much turbidity as the raw
water.
It was necessary to use intermittent alum treatment of
all of the water in the plant, just to remove this returned sus-
pended matter from the washwater. This is the reason we installed
a special washwater reclamation unit. We reduced our washwater
from about two and one-half percent to three-quarters of one percent.
We are continuously treating only this three-quarters of one per-
cent with alum, rather than intermittently treating 102.5 percent.
This is much cheaper, and more efficient procedure.
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Plant Operation - Report Discussion iQj.
MR. TCHOEANOGLOUS: What effect would improved plant oper-
ations have on the total waste disposal problem, in your estimation?
MR. STRETCHER: There is always room for improvement in
plant operation. For example, by washwater reclamation, we never
have washwater going to waste. Additionally, we have reduce the
amount of chemical treatment required, have produced a better water,
and reduced the amount of sludge.
MR. TGHOBANQGLOUS: Although there are large cities that
can afford the manpower required to look into these matters there
are many small cities that barely have enough personnel and facili-
ties. I was wondering if anyone has looked into the effect of im-
proved plant operations.
MR. HARTUNG: I don't understand the question with regard
to improved plant operations. Certainly if you are more efficient
in the operation of your plant, you will reduce operating costs.
But in the last analysis you must dispose of any solids taken out
of the water, efficiently or inefficiently. If you are efficient
in handling it, then obviously you are going to reduce operating
costs, but the problem of how to dispose of the sludge remains the
same.
The preparation for disposal and the disposal of solids,
which have been withdrawn from a clarifier, is the same kind of pro-
blem whether the solids are withdrawn at 0.1% solids or if with-
drawn after concentration to about 10% solids. The cost of hand-
ling and preparation for disposal are different, but the amount of
solids for disposal and what to do with these solids is the same
in either case.
MR. ADRIAN: I'd like to comment on another aspect of ef-
ficiency with regard to plant operation. The City of Minot has a
serious water shortage during the summer. The plant is operated very
well, but the washwater was not reclaimed, and is discharged to a
nearby stream. Apparently this was an oversight in plant design,
that no attempt was made to recover this water which would be help-
ful in aleviating the summer shortage.
MR. PROUDFIT: Just in defense of the engineers I'd like to
comment that there are many well designed plants that are not pro-
perly operated.
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102 Plant Operation - Report Discussion
MR. NEBIKER: Since washwater already has chemicals added,
for pH adjustment, etc,, the reclamation of this water will not only
save water but save on chemicals also.
Regarding the problem of land disposal of sludge. The dis-
posal of a solid sludge is not as difficult as frequently thought.
Many studies have been made to locate sanitary landfill sites. A
survey in Boston showed that about eight percent of this strictly
urban land was not used, predominantly because of the new highways,
Cloverleafs could serve as sites for solid waste disposal. I think
that in many cities one can find small sites for disposal solid
sludge.
The cities of Chicago and Cleveland are studying the
pumping of sewage sludge considerable distances for land disposal.
It would appear that this method is practical for many communities
that have a shortage of available land nearby.
After land has been filled, it can still be used. Re-
moval of the dewatered sludge may be required, but this temporary
solution for disposal may be more reasonable in cost than other
methods. Land dewatering will reduce the volume of sludge to be
rehandled.
MR., HARTUNG: With regard to the return of washwater to
the plant influent: Most of us who have tried the recovery of wash-
water, by returning it to the incoming flow into the plant, have had
about the same kind of experience. We find that the return of wash-
water often places a load on the plant out of proportion to the value
of the water saved, unless the water is treated before it i-s returned.
In analyzing who this is so, we have concluded it is because of the
way washwater is handled prior to recovery.
As the backwash water falls into the washwater troughs and
then flows through a sewer, the floe and coagulated material which
it contains is pulverized and broken. It is then almost impossible
to resettle the washwater in a settling basin, or to re-coagulate
it with the same amount of coagulant being used in the plant for the
raw water being processed.
My company has one plant in which the filter unit is lo-
cated within the settling basin. When we backwash the filter, the
water merely rises up out of the filter unit and then flows back
into the settling portion of the basin. That water is readily
reusable and refilterable. In an adjacent plant, treating almost
the same type of water, the washwater spills into wash troughs,
flows through a sewer, and is not usable.
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Plant Operation - Report Discussion 103
MR. DOE: I have comments on several items in the status
report on plant operation.
As sources of applied research on the sludge disposal
problem, the report suggests: "governmental agencies, equipment
manufacturers, and the larger water treatment plants." I believe.
the greatest future contribution will be in the form of feasibility
reports prepared by consultants, and of research conducted in uni-
versities. Some good reports of this type have been prepared in
New York State.
The status report lists eleven methods of sludge disposal.
We should be careful not to give laymen the impression that "any
method is excellent; which one shall we choose?" In fact, there
may be only one or two methods applicable to a specific location.
On the question of sludge pressing the report refers to
limited possibilities for automation of this treatment process.
There are presses on the market in which the entire operation is
completely automatic. My own firm has been operating a completely
automatic pilot press this summer. This operation will put pressing
in a rather better light. Maintenance is generally rather low on
these presses.
MR. STREICHER: In one plant I visited in Japan they have
filter presses designed for automatic discharge of sludge cake.
Because of the nature of the material, they still have a man stand-
ing by with a scraper to remove sludge solids that don't come off
freely. I understand that the better filter presses are almost
completely self-cleaning.
MR. DOE; Especially the pre-coat ones.
MR. KRASAUSKAS.: How are these, presses arranged to take
the creases out of the cloth automatically?
MR. DOE; We do not have the problem of creases in the
cloth, with the filter press we are studying. In certain presses
I have seen in England, it is necessary to rearrange the cloths
and take the creases out.
There is a new type of press in which the cloth is caulked
into a groove around the circular plate, and there is an additional
rubber "0" ring going all the way around as a sealer. There is no
leakage whatever of sludge. Unfortunately, these presses are not
yet in operation on an alum sludge, but it is anticipated that there
will be one soon.
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104 Plant Operation - Report Discussion
MR. PETERS; As for the filter press being fully automated,
it is our desire to have a remote-manual system to maintain quality
control. The batch-mix may need adjusting, due to variation in sol-
ids content, to insure a firm cake from the filter press.
The filter cloth must be inspected for pinholes and wear,
but according to consultants, the cloth should last for several
thousand hours of operation. This information is based on pilot
plant studies and not on full plant operation.
A question to Mr. Streicher. If it is acceptable in Los
Angeles to discharge water plant sludge to a sewer, what type of
treatment will be provided at the sewage plant?
MR. STREICHER: The sludge will go to the Hyperion ac-
tivated sludge plant. 1'his plant is in the early stages of con-
struction, and will not be in operation for over two years.
If the water plant sludge is accepted, it will add a
relatively small increment to the total load of sewage solids han-
led at the sewage plant. The -final effluent from the plant will
be discharged to the ocean.
MR. PETERS; By discharging water treatment sludge sol-
ids to sewers, we place the burden of disposal on the sewage
treatment plant. Atlanta's sewage treatment plant is overloaded
at the present time and passing approximately 50 percent raw sewage
into the river.
From laboratory tests, we have found that river pollution
is greater during high flows than during low flows. This is mainly
due to the sewage plants bypassing their flow to the river during
times storm waters enter the sewage systems.
MR. KRASAUSKAS; This is an important point. The only
time we have real pollution in our Potomac River water intake is
when we have runoff. Normally, the raw water has an mpn of about
50, which is extremely good water. At the time of a heavy runoff,
the mpn increases to 250,000 or higher.
To answer the question of the effect of sludge on sewage
plant operation, I visited Detroit. Dr. Shannon, is in charge of
both the water plant and the sewage plant. That city discharges
water treatment sludge to the sewer, maintaining a velocity of flow
of about two and one half feet per second. There is no deposition
of solids in the sewer.
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Plant Operation - Report Discussion. 105
When sludge solids were released from the clarifiers as
a slug, the small county sewage treatment plant receiving it had
trouble with vacuum filtration. When sludge was discharged over a
period of about a week, there were no problems with vacuum filtra-
tion.
Detroit also has a pilot activated sludge plant, treating
100 gallons per minute. I was advised that a proportional discharge
of alum sludge into the activated sludge treatment had no plant
deleterious effect.
MR. RUSSELMANN: It is important to consider that in pro-
per water treatment operation there is an accounting for water
quality, from the raw water to the delivered water. Any discussion
of plant operating practice should encourage an accounting for the
wastewater, so that water treatment operations apply the complete
management concept or accountability.
There are many water treatment plants that do not have
adequate facilities for waste disposal. They should immediately be
encouraged to provide operating reports, observations, and measure-
ments of wastes, just as they do now for operating data on producing
finished water. Such observations and measurements should also be
made of land or water receiving areas. Useful data will then be
available when the time comes to provide waste trea-tment or disposal.
This concludes discussion of the status report on plant
operation.
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Status Report on Regulatory Aspects
STATUS REPORT ON REGULATORY ASPECTS
Edwin C. Weber
A status report on the disposal of wastes from water treatment
plants, in order to be complete, must include information on regu-
latory aspects of the problem. To obtain this information, the AWWA
Research Foundation made a survey of regulatory agencies by means of
a questionnaire sent in December 1968.
Summary Report
A period of 15 years has elapsed since Dean, in 1953, reported
on the status of federal and state laws prohibiting the discharge
of water treatment plant wastes into surface waters.
At that time, Dean pointed to a definite trend toward the en-
actment of these laws. He also stated: "In the future the disposal
of such wastes is likely to be a matter of increasing concern to
designers and operators of water purification plants."
The 1968 survey by the Research Foundation shows that, since
Dean's report, a dramatic change has indeed taken place in the en-
actment of laws. The technical literature, in recent years, also
demonstrates increasing concern by designers and operators with
problems of water treatment plant waste disposal.
The Federal Water Quality Act of 1965, requiring states to set
standards for interstate waters in order to enhance water quality,
has given states the authority to order the treatment of water
plant wastes before discharge to surface waters.
Dean, in 1953, reported that 19 states did not consider the
discharge of filter washwater or sedimentation basin sludge to sur-
face waters constituted a violation of their pollution laws or re-
gulations. Only 5 states did consider the discharge of these wastes
to be a violation. The remaining 24 states controlled discharge of
the wastes as needed, but did not have specific laws or regulations.
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Status Report on Regulatory Aspects 1Q7
Responses to the 1968 AWWA Research Foundation survey indicate
how completely the regulatory situation has changed. Instead of
only 5 states having laws or regulations to control the discharge
of these wastes, there are 5 states reporting they do not now have
laws.
SURVEY OF REGULATORY AGENCIES
The Research Foundation questionnaire was sent to the 50 states,
the District of Columbia, Quam, Puerto Rico, and the Virgin Islands.
The questionnaire was also sent to eight interstate agencies.
Response to the questionnaire was excellent. Replies were re-
ceived from 49 states, the District of Columbia, Quam, Puerto Rico,
Virgin Islands, and six interstate agencies. The one state not
replying was Nevada.
The survey form included ten brief questions requiring "yes"
or "no" answers. The form first provided a definition, and there-
after each question referred to "these wastes."
DEFINITION: Wastes from water treatment plants
include those resulting from filter backwash;
coagulation, softening, iron and manganese re-
moval processes; diatomaceous earth filtration;
and ion exchange brines.
The ten questions in the survey form related to Regulatory
Information (5 questions); Statistical Information (3 questions);
and Research Information (2 questions). Respondents were requested
to supply special comments and to elaborate on their replies where
appropriate.
SUMMARY OF REPLIES
A summary of questionnaire replies, and of special comments
made by respondents, is provided on the following pages.
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108 Status Report on Regulatory Aspects
SUMMARY OF QUESTIONNAIRE REPLIES
REGULATORY INFORMATION
Question 1
"This Agency considers discharge of these wastes to surface
waters a violation of pollution control laws or regulations."
Reply Yes; 43 States, Virgin Islands, 6 Interstate Agencies
Reply No ; Alaska, New Mexico, Tennessee, Wyoming
No Reply : Florida, Montana, South Carolina
Question 1 - Comments
Alabama. "Such discharges could be a violation of pollution con-
trol laws if they result in contravention of water quality standards."
Arizona. "Depending on type of waste and size of receiving
stream."
Delaware. "Depends on the stream."
Kansas. "Only lime-soda softening sludge, and ion exchange
brines are now a problem. Wastes from filter backwash, coagulation,
and iron and manganese are presently considered to be problems."
Kentucky. "Depending on volume in relation to stream flow."
Minnesota. "There is no violation per se unless the waste is
discharged without a permit and violates the standards of water
quality and purity for the receiving waters."
Missouri. "Depends on location. Must comply with Water Quality
Stream Standards."
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Status Report on Regulatory Aspects 109
Montana. "Montana has two lime-soda softening plants. The
wastes have not been of sufficient quantity to create a problem,
since the discharges are to Yellowstone River where the river is
already turbid."
New York. "We do not presently take any action against existing
waste discharges unless there is a contravention of stream standards.
This is in accordance with our Public Health Law. We do require
plans and construction of waste disposal facilities for the waste
effluents from new or expanded facilities."
Question 2
"This Agency has laws or regulations requiring control or treat-
ment of these wastes before discharge to surface waters."
Reply Yes: 42 States, 3 Interstate Agencies
Reply No : Alaska, Arizona, Hawaii, Nebraska, Wyoming
No Reply : Florida, Montana, South Carolina
Due s tion 2 - Comments
Alabama. "Alabama's pollution control law provides authority
to control all pollution-causing wastes without reference to specific
sources."
Alaska. "Because there are just four communities in Alaska with
metropolitan populations of 10,000 or more and water supply comes
from ground water sources, the State Agency has not considered it
urgent to control the disposal of wastes from water treatment plants."
Delaware. "Controls all pollution."
Maryland. "Regulation 4.4 lists the requirements that the waste
water must meet prior to discharge to waters of the State. Section
1.31 of Regulation 4.8 states that the waters of the State shall at
all times be free from substances attributable to sewage, industrial
waste, or other waste that will settle to form sludge deposits that
are unsightly, putrescent or ordorous to such degree as to create a
nuisance, or that interfere directly or indirectly with water uses."
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110 Status Report on Regulatory Aspects
Massachusetts. "The Massachusetts Clean Waters Act gives the
Division of Water Pollution Control authority to require treatment
of all wastes."
Minnesota. "Regulations of water quality and purity for the
surface waters of the state have been adopted under the Minnesota
Pollution Control Act, Chapters 115 and 116."
Nebraska. "We are now requiring retention or treatment of
water and swimming pool filter wash and settling basin discharges."
New Hampshire. "Control by virtue of Surface water classifica-
tion and discharge permit system."
Oklahoma. "State Health Laws requires that plans and specifica-
tions be submitted for a permit prior to construction. Also Water
Quality Standards prohibits the discharge of wastes causing sludge
deposits, turbidity, color or floating debris in surface water."
South Carolina. "Have not had to be concerned with this pro-
blem. Most of water treatment plants are small and the water takes
low coagulant doses."
Tennessee. "Do not have separate specific regulations on water
treatment plants."
Delaware River Basin Commission. "Wastes from water treatment
plants are considered to be industrial wastes. Discharge of such
wastes to Basin streams must meet all appropriate requirements of
the Commission's Water Quality Regulations."
New England Interstate Water Pollution Control Commission. "In-
dividual states have rules and regulations and/or laws regarding
control."
Orsanco. "With regard to the discharge of water purification
plant wastewater to the Ohio River, the State pollution control
agencies will establish treatment requirements in conformance to
the following policy:
1. "Installation of waste-control facilities will be
required as a part of the initial construction of
new water purification plants;
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Status Report on Regulatory Aspects 111
2. "Installation of waste-control facilities will be
required at existing water purification plants
whenever substantial improvements or enlargements
are made at these plants;
3. "Installation of waste-control facilities will be
required at existing water purification plants when
the discharge of untreated waste results in obvious
pollution or in quality levels that do not meet
established criteria. In these cases time schedules
for the installation of waste-control facilties
shall be established in conformance with the State's
plan of implementation."
Question 3
"This Agency plans future laws or regulations for control or
treatment of these wastes before discharge to surface waters."
Reply Yes; Alaska, Arizona, Nebraska, Oregon, Tennessee,
Virginia, Washington, West Virginia, District
of Columbia, Virgin Islands, one Interstate
Agency
Reply No ; 36 States
No Reply ; 6 States
Question 3 - Comments
Alaska. "As population grows and as implementation of water
quality standards begin some form of regulation will be desirable."
Maryland. "The Department of Water Resources is of the opinion
that the provisions of Regulation 4.4 and of Section 1.31 of Regula-
tion 4.8 are adequate to control the waste discharges from water
treatment plants to waters of the State. However, the Department
is prepared to recommend additional law and regulation, should the
results of research and study indicate this to be desirable."
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112 Status Report on Regulatory Aspects
Question 4
"This Agency has encountered pollution problems attributed to
the discharge of these wastes to surface waters."
Reply Yes; 28 States, 2 Interstate Agencies
Reply No ; Alabama, Alaska, Arizona, Arkansas, Colorado,
Georgia, Hawaii, Iowa, Nebraska, Nevada, New
Hampshire, New Mexico, Oregon, South Carolina,
Texas, Vermont, Virginia, Washington, Wyoming
No Reply ; Delaware, Florida, Montana
Question 4 - Comments
Idaho. "Has 10 small water treatment plants in the State which
discharge backwash water without removing settleable material which
is considered a violation of regulations. All plants have been
notified to take whatever action is necessary to remove the settlea-
ble solids from the backwash water. We have not taken any legal
action."
Illinois. "Adequate waste treatment is obtained."
Indiana. "Four plants discharging lime sludges to surface waters
causing sludge banks. Required correction and discharge was abated."
Louisiana. "Siltation in lake, sludge banks in small streams."
Maine. "Sediment from backwash left noticeable deposits on
channel beds, as a result, new construction precaution against this
and other items were taken. Statue requires permit for new discharges."
Massachusetts. "Filter backwash and sludges discharged to river."
North Carolina. "Fort Bragg, North Carolina - Sludge from water
plant sedimentation basin discharged to Lower Little River during
period of low flow, resulting in small fish kill. Since the plant
is owned and operated by a Federal Agency, the matter was investigated
and referred to the Federal Water Pollution Control Administration for
investigation and corrective action."
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Status Report on Regulatory Aspects 113
Oklahoma. "Downstream property owners complain of increases in
turbidity and sludge deposits."
Tennessee. "Many new problems are being found each year on
small streams and recreational waters. The City of Johnson City
discharged waste from water treatment plant into a small mountain
rainbow trout stream and killed the trout. Have also had problems
with West Wilson Utility District's water treatment plant discharge
of wastes from the coagulation basin and backwash of the filters
into a recreational embayment on Old Hickory Lake."
Utah. "Salt Lake City Water Works Department's City Creek and
Big Cottonwood water treatment plants discharge wastes to streams."
Question 5
"This Agency has taken official or unofficial action to discon-
tinue the discharge of these wastes to surface waters."
Reply Yes: 32 States, 2 Interstate Agencies
Reply No : Alabama, Alaska, Arizona, Colorado, Delaware,
Hawaii, Mississippi, Nebraska, New Hampshire,
New Mexico, North Carolina, Texas, Virginia,
Washington, Wyoming; 4 Interstate Agencies
No Reply : Florida, Montana, South Carolina
Question 5 - Comments
Illinois. "Demanded corrective action."
Indiana. "New water plants or major construction for existing
plants are required to provide plans for acceptable waste disposal
before the project is approved by the Board of Health. This is not
in the true sense of the word, discontinuing the discharge of wastes
to surface waters."
Iowa. "Motion for discontinuance of softening sludge discharges'."
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114 Status Report on Regulatory Aspects
Kansas. "Lime-soda softening sludge is a serious problem. A
section of one of our major rivers was ruined by softening sludge."
Louisiana. "Issued orders to offenders to correct situation."
Massachusetts. "The Division of Water Pollution Control has
placed several municipalities on 'Implementation Schedules' to
provide adequate treatment before discharge,"
Maryland. "The Department of Water Resources has contacted
officials of the following water treatment plants and requested
that information be provided to the Department regarding any plans
that they may have for avoiding recurrence of the objectionable
conditions caused by the discharge of waste sludges from the water
treatment plants' to State waters:
a. "Anne Arundel County Department of Public Works -
regarding the Pines Water Treatment Plant dis-
charge of iron sludge to Chase Creek, a tributary
of Severn River."
b. "City of Bowie - regarding the Bowie-Belair Water
Treatment Plant discharge of iron and filter back-
wash sludge to a small tributary of the Patuxent
River."
c. "Washington Suburban Sanitary Commission - regarding
the Patuxent Filtration Plant discharge of filter
backwash and alum settlement to Walker Branch, a
tributary of the Patuxent River."
Michigan. "Generally, a. minimum restriction is placed on
quantity of suspended solids in the discharge."
New Jersey. "As an objective of the Potable Water Program,
pressure is being brought against all water purveyors to install
corrective treatment methods where applicable. This will be fol-
lowed up with formal orders to insure compliance."
Ohio. "It is planned to continue to place more plants under
permit by requiring a permit where stream water quality and minimum
conditions criteria are not met, where new plants are constructed,
or old plants altered, and where disposal facilities are now ex-
isting."
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Status Report on Regulatory Aspects 115
Oklahoma. "Construction of holding and settling lagoons or
pumps installed for returning water to treatment plants. New plants
required to install proper control."
Oregon. "There are 50 domestic water treatment plants located
in Oregon. Eight of these 50 plants are impounding the wastewater
before discharge of the partially clarified water to nearby stream."
"Oregon operates under a system of Board of Health Review of
proposed work construction. Approval is required before construc-
tion begins. When new construction is planned, provisions are
required for wastewater treatment which usually amounts to holding
the water until most of the settleable solids are removed."
"All water treatment plants that chemically alter the water
and discharge wastewater back to the stream will eventually require
a discharge permit."
Pennsylvania. "The Sanitary Water Board requires the submission
of an industrial waste application for the treatment of such wastes
at all modifications of existing plants and at all new water treat-
ment plants in addition to taking enforcement action at existing
discharges where pollution exists."
South Dakota. "Cities discharging water treatment plant wastes
have been or are being notified that continued discharges will not
be permitted."
Tennessee. "Correction was made at Johnson City by constructing
a lagoon and supernatant discharged to the stream at a controlled
rate. At West Wilson Utility Control Board, issued Order for cor-
rection and outfall was extended 200 feet from shore."
Utah. "Salt Lake City Water Department was requested and did
provide the necessary corrective measures."
Delaware River Basin Commission. "The Commission, under Section
3.8 and Article 11 of its Compact must approve all projects involving
water treatment plants before they can be constructed."
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116 Status Report on Regulatory Aspects
STATISTICAL INFORMATION
Question 6
"This Agency has available reports on data on the quantities
and characteristics of these wastes."
Reply Yes: Connecticut, Idaho, Kentucky, New York, Texas
ORSANCO
Reply No ; 43 States, Virgin Islands, 5 Interstate Agencies
No Reply ; Florida, Montana
Question 6 - Comments
Idaho. "Has information on quantity and characteristics of most
backwash water; but has not compiled these results in any type of
report."
Maryland. "The Department of Water Resources has not attempted
to collect reports or data from all the water treatment plants in
Maryland."
Minnesota. "Regulations of the Agency require that all inter-
state wastewater dischargers submit operational reports to the Agency.
This information has not been compiled."
Oklahoma. "Quantities of solids and liquid are estimated by
design engineers with extra storage capacity to allow for drying
and cleaning."
Interstate Sanitary Commission. "Discharges of wastes from
water treatment plants are rare as all Interstate Sanitary Commission
waters are tidal (no potable water)."
Question 7
"This Agency can identify water treatment plants having facil-
ities for control on treatment of these wastes."
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Status Report on Regulatory Aspects 117
Reply Yes; 29 States, Puerto Rico, Virgin Islands, 2 Inter-
state Agencies
Reply No ; Alabama, Alaska, Arkansas, Colorado, Hawaii,
Idaho, Iowa, Kentucky, Louisiana, Michigan,
Minnesota, Mississippi, Nebraska, New Mexico,
North Carolina, South Carolina, Washington;
District of Columbia; Guam; 4 Interstate Agencies
No Reply : California, Florida, Maine, Nevada
Question 7 - Comments
Idaho. "At the present time, plants have not installed facil-
ities for the control of these facilities."
Indiana. "Have knowledge of the plants and disposal methods
used by some plants; a listing is not maintained."
Kansas. "Do not believe a satisfactory method of disposing of
lime softening sludge has been developed. We have many sludge la-
goons that are preventing serious pollution but they are very dif-
ficult to operate and design criteria is not well established."
Submitted listing of 20 towns having facilities for either lagooning
or hauling softening sludge."
Massachusetts. "Billerica Water Treatment Plant, Billerica,
Massachusetts."
North Dakota. "Indicated twelve water plants treating wastes."
Ohio. "Listed 52 water plants notified or placed under permit
for waste sludge disposal and listed 35 water plants having lime
softening process sludge disposal facilities.
Oklahoma. "Listed six plants having treatment."
Pennsylvania. "Listed 45 water treatment plants having sanitary
Water Board Permits for Wastewater Treatment Facilities."
South Dakota. "Listed six water treatment plants."
Utah. "Listed eleven water treatment plants providing control
of wastes discharges.'1
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118 Status Report on Regulatory Aspects
Vermont, "Tri-Town Water District plant discharges filter
backwash water to a lagoon for sediment prior to discharge into
Lake Champlain. There are ten municipally owned water plants in
Vermont."
Virginia. "Surveyed 148 plants; only seven provided any form
of waste treatment other than discharge to the nearest available
water course."
Question 8
"This Agency can identify water treatment plants discharging
these wastes to sewage systems."
Reply Yes; Arizona, Connecticut, Delaware, Georgia, Indiana,
Kentucky, Missouri, Montana, New Hampshire,
New Jersey, North Dakota, Ohio, Oklahoma,
Texas, Virginia, Wisconsin, Wyoming; District of
Columbia; Virgin Islands; Interstate Agency
Reply No ; 28 States; 5 Interstate Agencies
No Reply ; California, Florida, Maine, Nevada, South Dakota
Question 8 - Comments
Idaho. "None of the water treatment plants discharge to sewer-
age systems."
Indiana. "Know that certain plants do discharge to the sewers,
a listing is not maintained."
North Dakota. "Indicated nine water plants discharging wastes
to sewer system."
sewer."
Ohio. "Indicated three water plants discharging wastes to
Oklahoma. "Only one - Tecumseh, not a desirable situation."
South Dakota. "For most larger installations, this method has
been found unsatisfactory."
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Status Report on Regulatory Aspects 119
Tennessee. "There are a number of plants that discharge into
municipal systems."
Virginia. "The Town of Berryville and Selma discharge wastes
to municipal sewerage systems."
RESEARCH INFORMATION
Question 9
"This Agency has previously conducted or supported research on
the treatment of these.wastes."
Reply Yes; New York
Reply No : 46 States; Virgin Islands; 6 Interstate Agencies
No Reply : California, Florida, Maine
Question 9 - Comments
New York. "New York State Health Department has completed Re-
search Report No. 14, "Characteristics of and Methodology for
Measuring Water Filtration Plant Wastes" prepared by Cornell University;
and Research Report No. 15, "Waste Alum Sludge Characteristics and
Treatment" by O'Brien and Gere, Consulting Engineers."
Question 10
"This Agency is currently conducting or supporting research on
the treatment of these wastes."
Reply Yes; Ohio, West Virginia
Reply No : 45 States; Virgin Islands; 6 Interstate Agencies
No Reply : California, Florida, Maine
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120 Status Report on Regulatory Aspects
Question 10 - Comments
Maryland. "On November 23, 1966, the Maryland Water Resources
Commission, at its regular meeting, discussed the periodic discharges
by Maryland water treatment plants of filter backwash and of sedi-
mentary deposits from settling basins."
"At this Commission meeting, a motion was unanimously approved
to request the Washington Suburban Sanitary Commission to explore
the possibility of a demonstration project for the purpose of con-
trolling and disposing of filter backwash and the discharge of
sedimentary deposits from settling basins of water treatment plants."
Ohio. "Ohio entered into contract July 1, 1968, with Burgess
and Niple, Ltd., Consulting Engineers, Columbus, Ohio, to study
methods of handling lime softening plant wastes from water plants
under 10 M.G.D. capacity. Five or six plants are being studied.
The report on this study is due on July 1, 1969."
West Virginia. "West Virginia has been studying and requiring
the recycling or reuse of filter washwater when new plants are con-
structed, in order to control sediment to the streams."
ADDITIONAL SURVEY INFORMATION
Kansas reports lime-soda softening sludges and ion exchange
brines to be serious problems. Lagoons to retain these sludges are
difficult to operate, and a satisfactory method to dispose of these
sludges has not been developed. At present, Kansas has 20 munici-
palities using lagoons or hauling sludges to disposal sites.
Tennessee and North Carolina reported fish kills caused by the
discharge of sludge from settling basins during periods of low
stream flow.
Six Interstate Commission Agencies reported that they consider
the discharge of wastes from water treatment plants a violation of
pollution control laws and regulation.
Delaware River Basin Commission, ORSANCO, and Interstate
Sanitary Coroiiission have laws and regulations to control or treat
these wastes before discharge to surface waters. New England Inter-
state Water Commission plans future laws and regulations for control
or treatment of these wastes.
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Status Report on Regulatory Aspects 121
Delaware River Basin Commission, Interstate Sanitary Commission
and ORSANCO have encountered pollution problems attributed to the
discharge of these wastes and have taken action to discontinue the
discharge of these wastes to surface waters.
*
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122 Discussion of Status Report on Regulatory Aspects
DISCUSSION OF STATUS REPORT ON REGULATORY ASPECTS
MR. WEBER; We consider the response to our questionnaire
was excellent. Replies were received from 50 states, and also from
the District of Columbia, Guam, Puerto Rico, the Virgin Islands, and
6 interstate agencies.
I believe the summary of replies to the ten questions con-
stitutes a very good status report on current regulatory aspects of
the water treatment plant waste disposal problem.
When we compare the information obtained in this survey
with that reported in the 1953 survey, it is evident that the states
have recognized the need for control of these wastes, and have pro-
mulgated laws and regulations. Fifteen years ago, 5 states had laws
to control the discharge of these wastes to surface waters - and now,
only 5 states do not have laws.
It is possible that the Federal Water Quality Act of 1965
has significantly affected this change. The Act requires states to
set water quality standards for interstate waters in order to enhance
water quality, and gives states authority to order the treatment of
wastewaters before discharge to surface waters.
Finally, I wish to emphasize that the problem of water
treatment plant waste disposal is a very real problem. Our survey
data demonstrate this point clearly.
Note that:
28 states report they already have encountered pollution
problems from these wastes, and
32 states report they have taken action to discontinue
discharge of these wastes. (Even though no pollution problems were
recognized, the State of Idaho issued an order on all of its ten
water treatment plants.)
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Discussion of Status Report on Regulatory Aspects 123
MR. LAMB; As a member of the AWWA research committee on
disposal of sludge, I looked at the replies to this survey for evi-
dence of research. It is apparent that the states are not doing much.
Only one state reported that it has supported research,
and two states indicate that they are supporting some now. This
is an interesting situation, which does not speak well of our ap-
proach to the problem. The need for research or investigations is
certainly made evident by the responses to question 4, which indi-
cates that 26 states have encountered pollution problems in the
discharge of these wastes.
MR. RUSSELMANN; It is true that New York state is not
presently supporting research on this problem. Two projects were
supported at a time when the State Health Department became concer-
ned with the problem, and money was available. Unfortunately, it
isn't possible now for the State to commit funds for this kind of
activity.
MR. DICK; I remember that a major bond issue in New York
state supports a program of construction grants for pollution control.
It seems there is some disparity in supporting construction of new
plants, but not supporting attempts to develop new means of improving
water quality or to make construction dollars more effective.
MR, RUSSELMAHN: The State's construction grants are for
sewage treatment works, and are not applicable to water treatment
plants.
I would like to repeat my suggestion discussed earlier.
The resource for gathering data and measuring the problem we are deal-
ing with exists in all water treatment plants. We are not doing much
about it. This is an activity which can be done without financial
support.
MR. HARTUNG; Several speakers today have mentioned that
it is advisable to collect data so that we can measure the scope and
the kind of problem with which we are dealing. I agree.
I would also like to say that, in conjunction with that
problem, we need some kind of measure as to when the discharge of
waste into a surface water supply actually is detrimental to that
water supply. It has been emphasized that when waste discharge
affects the raw water quality standards, then there should be abate-
ment. My question is: How can we measure whether or not the disposal
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124 Discussion of Status Report on Regulatory Aspects
of these wastes into a river in any way affects the quality of that
water as measured by the raw water quality standard which has been
set?
An answer by one state to the questionnaire is that they
are requiring abatement or the treatment of washwater wastes before
such are dumped into the river, even when there is no possibility at
all of measuring the effect upon the river. In one instance I know
about, there is no change in turbidity from the discharge of waste-
water. There is no change in BOD, or in appearance, and no sludge
deposits. But yet the state has asked for the treatment of the
wastewater before it's discharged to the river. Perhaps we ought
to be practical in terms of the data we are collecting, in solving
the problem.
When does the disposal of the waste in a body of water
really cause a problem?
MR. COULTER: You have opened a subject on which I have
strong thoughts. Very dramatic changes are taking place in water
pollution control, and the water works industry is directly affected.
I think that we are playing a game called "water quality
standards" in which we are trying to identify impacts on beneficial
uses. We cannot except for some outstanding cases, really trace
the impact back to any particular wastewater discharger and say,
"Here is the polluter causing the damage that we are talking about."
In the State of Maryland, we have very strong feelings
about the quality of water in the Chesapeake Bay and even in the
polluted Potomac River. The Potomac is cleaner than any river that
goes through a town of a million or more, but it still is considered
polluted. We are moving towards the attitude that those waters are
the property of the state. To discharge anything into those waters
is a privilege accorded by the state, and to discharge anything into
them that is not necessary is an abuse of the privilege.
I think that this kind of philosophy will be adopted more
and more. It is important that we think this way in Maryland, be-
cause in the next 25 years the State's increase in population will
be equal to the level of population reached in the first 200 years.
If we are to keep the waters clean for recreational purposes,
if we are to continue to harvest shell fish and eat them raw, if we
are to have the much higher quality of water that people talk about,
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Discussion of Status Report on Regulatory Aspects 125
if we are to make whole stretches of streams into parkland, then
it seems to us that the strategy is to remove every bit of con-
taminant that we '.possibly can from every capturable source of
wastewater.
Mr. Krasauskas reported that during high flows the Potomac
River had bacterial counts up into the hundreds of thousands. During
low flows, the counts are down to around 50.
This illustrates the point that a tremendous amount of
pollution comes from uncontrolled and uncontrollable runoff. If
we are to offset the pollutional aspects of that uncontrolled run-
off, it becomes more and more incumbent on us to clean up all water
that we can capture before it is discharged.
Waste treatment might appear to be a large cost to the
water works industry. It has been pointed out that "the effects of
wastewater might be beneficial," or that "the effect of wastewater
discharge cannot be measured." This is temporizing. The elimina-
tion of waste discharges will have a cost, but it will have a bene-
ficial effect.
For example, in the Patuxent River Basin we have recently
requested several communities to go through the engineering work
and come up with plans and specifications for removal of nitrogen
and phosphorous from their wastewater discharges. We haven't seen
the results of those engineering -reports, but I would guess that
the cost is going to be about 25 cents a thousand gallons to re-
move those contaminants from the wastewater.
I cite this to illustrate the point that tremendous in-
vestments are about to be made in water pollution control. It is
going to become absolutely incumbent upon us to remove impurities
from waste discharges to the maximum extent possible, whether we
can demonstrate whether or not individual instances of removal
are going to have a beneficial effect.
MR. KINMAN: I would like to have individuals representing
states comment on the question, "Do you know of any actual enforce-
ment proceedings taken against a water treatment plant or water
utility to clean up its wastes?
MR. WEBER; Several years ago in Maryland, the City of
Laurel brought a court case against the Washington Suburban Sanitary
Commission for the discharge of wastewater. The Gity lost the case.
At that time, the Commission obtained permission, or an easement, to
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126 Discussion of Status Report on Regulatory Aspects
discharge sludge to Walker Branch and to the Patuxent River.
The State of Maryland brought the matter of water treat-
ment plant waste disposal before its Water Resources Commission.
Mr. McLeod, Chief Engineer of the Washington Suburban Sanitary
Commission, at that time called upon the AWWA for assistance.
MR. EAGLE; About going to court: I think we have tools
equally effective, if not more effective than going to court, in
our respective state water pollution control Boards. In the case
of Ohio, I think we reported in the survey that some 35 water util-
ities were under permits. There are now some 55 under permit or in
the process of being placed under permit. Every one of these
permittees has orders or conditions issued by the Water Pollution
Control Board that they small meet within specified periods of time.
To me, permits, orders, and conditions are official legal
actions. In Ohio we try to stay away from court action, which is
another way to stall. You will find that the Board is much more
effective than the courts.
MR. COULTER; I might say one other word about research.
In Maryland, I have attempted to promote research with the General
Assembly, the Appropriations Committee, and others, and have had no
success whatever.
If our state is any indication of the mood in the state
legislatures at the present time, money for research on the disposal
of these wastes will be very hard to come by. It is pointed out
to me that the Federal Government can support research programs, so
that each one of the 50 states will not have to provide laboratories
and conduct research themselves.
MR LAMB; With respect to research, I believe we should
not fail to point out that there is responsibility for supporting
research at the plant level. If we were speaking about a different
industry today, there would be some question concerning the extent
to which the Federal Government should support research to solve
the industrial problem.
I think that none of us would question that an industry
should support a substantial amount of the investigation relating
to the specific plant which stands to benefit from the research; for
example, to demonstrate that they must or need not do something; if
so, what need be done; and most economical ways for solving indus-
trial waste problems at that plant.
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Discussion of Status Report on Regulatory Aspects 127
If we are to look at the water treatment plant discharge
as an industrial waste, why should the plant not also carry some
of the financial load? I realize that these are practical problems
involved, but repeat that if we were talking about any other in-
dustry, we would be looking to the industry to help. I see no
reason why we shouldn't look to the water works industry in the
same manner.
MR. WEBER; Some states do consider wastes from water
treatment plants to be industrial wastes. Their regulations apply
equally to do any type of industrial waste.
MR. LAMB; Frequently, Federal support of industrial waste
studies is available only for categorical types of investigations
which apply to a rather broad spectrum of some industry, or perhaps
group of industries. There is another type of research, which the
Federal Government and the States usually are not involved in. This
deals with the solution of specific problems at specific plants.
In these instances, the industry usually has to carry substantially
the whole load.
I think that we in the water field will have to view our
situation in somewhat the same light. In research or investigations
which apply to a broad spectrum of the water industry (for example
softening sludges and other categorical wastes), we might look to
the Federal Government or the States for help. To solve the problems
of specific water treatment plants, we should look to the plants
themselves to come up with design parameters for construction of
facilities suitable for treating their wastes.
MR. LACY; I will augment references to Federal support
for research. The Federal Water Pollution Control Administration,
through its Office of Research and Development, can award grant funds
to do exactly what Mr. Lamb pointed out. Under out Industrial Waste
Treatment grant program, we can support projects which have industry-
wide application. These grants can provide up to 70 percent of the
project cost, with a maximum of $1 million.
If a project is limited to solving the problem of a
specific water treatment plant, it is obvious that the plant must
solve its own problem. However, almost every problem does have
some industry-wide application. I suggest that you come to us with
demonstration projects you would like to implement. We will work
out with you the degree of our interest in the project, and its
applicability to the industry.
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128 Discussion of Status Report on Regulatory Aspects
Our support of a project may not be 70 percent, but might
be 50 percent. But we do have funds, and it is to your benefit
to discuss your proposed demonstration projects with us.
MR. LAMB: For purpose of clarification, could you tell
us what the situation is with respect to funds which do not require
as much matching - such as projects for preliminary investigations
not involving demonstration.
For example, do you have grant or contract funds which
would be available for research studies with rather broad implica-
tions?
MR. LACY: In 1968, our funds for. industrial waste treat-
ment grants are a little more than $10 million, and for contracts
about $300,000.
Research grants are our third type of grant. These grants
support studies for basic or applied research preceeding the dem-
onstration phase. These grants do not support the full cost of a
project.
Under our research grant program, we are providing partial
support for the AWWA Research Foundation's study of water treatment
plant waste disposal, and the Foundation is providing the remaining
support.
Let us assume that, following this study, pilot scale
projects are developed which could be conducted at an AWWA member's
laboratory or treatment plant. We would be favorably inclined to
accept the recommendation of the Foundation and its advisory com-
mittee, and fund pilot scale development projects.
From that work, one or two processes might be developed
which would be applicable industry-wide. Then we would welcome
and encourage full scale demonstration of the process or processes
at a specific plant. We invite you to come to us directly or
through the Research Foundation with projects to demonstrate tech-
nology for treating these wastes.
MR. BISHOP; This question is directed to Mr. Doe. Who
supports the Water Research Association in England?
MR. DOE; It is supported in part by means of a levy on
those water undertakings in England who are members, and in part
by Government funds. Some 75 percent of all the water undertakings,
public or private companies, contribute to the Association.
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Discussion of Status Report on Regulatory Aspects 129
Many industrial research associations in Great Britain
are partly supported by the Government and partly by the industry.
Perhaps one-half of a research association's funds represent a
Governmental subsidy.
MR. BISHOP; The cast iron pipe industry of the United
States supports its own research organization. The paper industry
supports its own national council which conducts research on pro-
blems of that industry. Could research support be provided by the
water works industry in this country?
MR. FABER; The AWWA Research Foundation was not organized
on the same basis as the British Water Research Association. The
Water Research Association does provide an excellent example of how
water utilities and Government can together contribute to the cost
of research.
I anticipate that the AWWA Research Foundation will
develop the interest and support of water utilities for specific
projects. As we identify applied research projects that are of wide
interest to water utilities, I believe we can anticipate that sup-
port will be forthcoming from the industry.
MR. AULTMAN; The State of California has, in the past,
not established regulations until a definite problem exists. As a
result of the Federal Water Pollution Control Act, the State's
Water Pollution Control Board has established standards.
I expect that the Board will undoubtedly sponsor investiga-
tions and reports on the problem of water treatment plant waste dis-
posal. The Board has supported and published excellent reports on
other problems.
MR. TECHOBANOGLOUS; The California Water Quality Control
Board has been interested primarily in waste discharges, but is now
beginning to look at water treatment discharges. I expect they will
support research in this area. They have supported numerous studies
in the wastewater field, and have published some 20 or 25 reports.
MR. RUSSELMANN: Regulatory agencies should at least fix
some responsibility by requiring existing water treatment plants to
observe the effects of their discharges upon receiving streams.
When a new plant or extension of an existing plant is contemplated,
the agency could require the community or the consulting engineer
to evaluate the impact of wastes on the receiving stream.
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130 Discussion of Status Report on Regulatory Aspects
MR. HENRY; Under the West Virginia water pollution con-
trol law, we do not have to prove pollution to require permits.
Our permit system requires that anyone discharging water - carried
waste into a stream must have a permit.
The last session of our legislature increased the criminal
penalties for violation of the law which formerly was on a three-
part basis: first offense, second offense, and third offense. Now
it is on a one time basis. It costs up to $1,000 for the first offense,
with, a minimum of $100. The cost is $10,000 if we can prove de-
liberate pollution.
We have, so far, been quite lenient with the water industry
in our state. Almost two years ago, we encouraged the water industry
to correct its pollution problems. We agreed to cooperate in the
development of workable solutions. We are now doing this with a com-
mittee of the State AWWA Section.
MR. ADRIAN; Massachusetts has a state-wide fund for sup-
porting research on waste treatment and disposal. This fund amounts
to some $1 million per year. We find that, to date, the agency in
charge has not been very receptive to supporting work on water treat-
ment plant sludge disposal,
MR. STREICHER; The state of California is divided into
nine regions, each of which has a regional water quality control
board. Each regional board sets standards for surface or ground
waters within its jurisdiction, and exercises control over waste
discharges which might affect the quality of the surface or ground
waters.
As waste discharges in basins at higher elevations may
often degrade the quality of the waster moving into a lower basin,
the lower basin users have an opportunity to voice their objections
to such discharges or proposed discharges at regularly scheduled
meetings of the regional water quality control board having juris-
diction.
MR. SHULL; In Pennsylvania no new permits for water
treatment plants will be issued by the State Department of Health
or the Sanitary Water Board unless provisions are made for the dis-
posal of filter washwater and settling basin sludge.
Problems at existing plants are handled as complaints
are received. If a complaint is received from someone downstream,
the particular plant involved is cited and given a specific deadline
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Discussion of Status Report on Regulatory Aspects 131
to construct waste treatment facilities. All new plants must have
waste treatment facilities incorporated in their plans. As I re-
call, the suspended solids discharged are limited to about 25 or
30 ppm.
MR. EAGLE; I believe that Ohio is not quite as arbitrary
as Pennsylvania in this matter of filter washwater. We do require
that adequate provision be made in the design of new or remodeled
plants for taking care of the waste. If the engineer can show to
our satisfaction that the waste discharges will not cause pollution
to the waters of the state, then treatment facilities are not re-
quired.
This concludes discussion of the status report on regula-
tory aspects.
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Section 2
REPORT ON CURRENT TECHNOLOGY AND COSTS
D.D. Adrian and J.H. Nebiker
The AWWA Research Foundation report on the disposal of wastes
from water treatment plants was designed to include studies of
current technology and costs. These studies were made, under a
contract with the Research Foundation, by Messrs. Adrian and Nebiker
of the Department of Civil Engineering, University of Massachusetts,
Amherst, Mass. Their report follows.
INTRODUCTION
The authors of this report have made detailed studies of se-
lected water treatment plant waste disposal practices currently in
operation. The following report included a description of the pro-
cess employed, its efficiency, accomplishments, and costs. The de-
tails are based upon literature reviews, questionnaire returns, and
visitations to 15 operating plants. In addition, model studies x?ere
developed for three types of sludge dewatering.
ACKNOWLEDGEMENT
This report could not have been prepared without the active
cooperation and help of many individuals. The authors have attempt-
ed to recognize those plant operators and superintendents who pro-
vided assistance by including their names in the Appendix on Plant
Visitations. In addition, the assistance of Fred Eidsness and A.P.
Black of Black, Crow and Eidsness; Peter Doe and Fred Menzenhauer
of Havens and Emerson; and Robert Curran of Curran Associates
(Northampton, Mass.) is gratefully acknowledged. The assistance of
members of the AWWA Research Foundation Advisory Committee should
also be given recognition.
-133-
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REPORT ON CURRENT TECHNOLOGY AND COSTS
Contents
REVIEW OF TECHNOLOGY
I. Summary of Conclusions 136
II. Objective of Report 136
III. Methodology 136
IV. Treatment and Reuse of Filter Washwater 137
V. Disposal to Sewers 138
VI. Lagooning of Sludge Solids 140
VII. Sand Bed Drying 140
VIII. Vacuum Filtration 141
IX. Centrifugation 142
X. Recovery and Reuse of Lime 143
XI. Freezing and Miscellaneous Processes 145
XII. Conclusions 146
APPENDIX
Cost Analyses 150
Plant Visitations 153
Aus tin, Texas 153
-134-
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Current Technology and Costs 135
Plant Visitations (continued)
Boca Raton, Florida 157
Dayton, Ohio 165
Goleta, California 171
Lansing, Michigan 177
Lompoc, California 183
Los Gatos, California 189
Miami, Florida 193
Minot, North Dakota 199
New Britain, Connecticut 205
Point Pleasant Beach, New Jersey 211
San Francisco, California 213
Somerville, New Jersey 221
South Orange, New Jersey 223
Willingboro, New Jersey .. .' 225
MODEL STUDIES
Dewatering Alum Sludge by Vacuum Filtration 230
Dewatering Softening Sludge by Vacuum Filtration 234
Dewatering Softening Sludge by Centrifugation 237
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136 Current Technology and Costs
REVIEW OF TECHNOLOGY
I. SUMMARY OF CONCLUSIONS
Neither the disposal of filter washwater nor softening brines
appears to be a major engineering problem. Coagulation sludges,
particularly those resulting from alum treatment, are not presently
dewatered by mechanical means in the United States. Where space is
available, drying on sand beds is a feasible method for dewatering
alum sludges in the few examples found that are in use today.
Pressure filtration of alum sludge is technologically feasible,
but is not yet in use in the U.S. and costs are unknown. Freezing
and thawing substantially alters favorably the dewatering and set-
tling characteristics of alum sludge, but cost considerations suggest
that only natural outdoor freezing in lagoons or drying beds will be
economically attractive. In some instances, the disposal of alum
sludge to the sewer is not considered a problem, either because of
undesired sedimentation in the sewer or deleterious effects on the
sewage treatment process.
Lime softening sludges are capable of dewatering by land meth-
ods or, in certain instances, by centrifugation or vacuum filtration.
They can generally not be disposed of to the sewer owing to problems
o£ sedimentation, both in sewers and in digesters. Recalcination of
lime softening sludge can be of significant economic benefit, but
the process is limited to date to sludges from larger plants, treat-
ing water low both in turbidity and magnesium.
II. OBJECTIVE OF REPORT
This report seeks to provide detailed information on various
water treatment waste disposal practices, including descriptions of
these processes; data on process efficiency; evaluation of process
accomplishments; and analyses of capital, operating, and maintenance
charges. Visits by the authors to a number of treatment plant were
made to directly ascertain the information.
III. METHODOLOGY
Initially, there was little information available to identify
operating plants which could provide good examples of current technology.
-------
Current Technology and Costs 137
A straight-forward approach was used to obtain and evaluate infor-
mation:
1. Review of the literature to ascertain the various disposal
methods used in this or other countries.
2. Contact with state regulatory agencies to locate plants
with disposal methods which met with their water quality
standards.
3. Preparation of a questionnaire to aid evaluation of per-
formance by the various methods during plant visitations.
4. Selected plant visitations.
5. Compilation of data, including cost analyses.
6, Preparation of a preliminary report, which was submitted
to the Foundation's Advisory Committee for comment.
7. Preparation of this report, including comments received
from the Advisory Committee and plant officials.
IV. TREATMENT AND REUSE OF FILTER WASHWATER
An increasing number of state regulatory agencies now identify
the discharge of untreated filter washwater as a violation of their
stream pollution regulations.
Boca Raton, Florida, practiced re-cycling of their washwater
with apparently a slight profit. A washwater recovery basin served
to reduce the impact of the large washwater flows on the upflow-
clarifiers, and to some extent clarify the washw,ater, though this
was unintentional. Since this was a lime softening plant for ground-
water there were no difficulties with algae re-cycle and buildup.
Similar situations were found at Lansing, Michigan, and Miami, Flor-
ida, but recovery basins were not needed due to the larger cap-
acities of the plants and the numbers of filters.
The Rinconada Water Treatment Plant in Los Gatos, California,
and the Sunol, California, plant utilized washwater recovery basins,
with periodic washwater sludge removal. Both plants were designed
for alum treatment of surface water, and no problems were noted.
It should be emphasized, however, that the value of water in this
area is high, and thus incentive for recovery is greater than in
water rich areas.
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]_38 Current Technology and Costs
Willingboro, New Jersey, and New Britain-, Connecticut, treat-
ment plants sent their washwaters to sludge thickening lagoons, and
the decants from these were sent to a stream and to the reservoir,
respectively. Both plants used alum for coagulation. It is ques-
tionable whether this method is sound, for the quality of the de-
cant is not clearly superior to the quality of the washwater, and
the addition of washwater to the sludge merely aggravates the sludge
problem.
Overall, it would appear that washwater recovery is economically
feasible for water-scarce regions, or in instances where ground water
is softened, for the washwater will not create an algal buildup pro-
blem, and the recovered water has the added value of being, in fact,
softened water.
V. DISPOSAL TO SEWERS
An example of diatomaceous earth filtration backwash water dis-
posal to the sewer was found at Point Pleasant Beach, New Jersey.
Since surges of washwater could not be handled by the sewer, a hold-
ing tank was used to distribute the flow over longer time intervals.
Neither deposition in the sewer nor adverse effects on the primary
sewage treatment plant were noted.
Washbrine from a zeolite water softening plant was disposed of
to the sewer at South Orange, New Jersey. The capacity of this water
treatment plant was far smaller than the capacity of the regional
sewage treatment plant to which the brine flowed. In most instances
it is doubtful that brine could or should be disposed of to the
sewer unless, as here, significant dilution took place.
Disposal of alum sludges to the sewer has not been found to
cause deposition problems. However, the same cannot be said of lime
sludges. And whereas the addition of alum sludge to the sewage treat-
ment processes may cause little problem beyond that of creating
greater sewage sludge volumes, lime sludges would cause, in addition,
sedimentation problems in the digesters.
Disposal of water treatment wastes to the sewer must be consid-
ered an intermediate step, placing final disposal into the hands of
the sewage treatment plant operator. If the plant is large compared
to the water treatment plant, a satisfactory solution is available
(with the possible exception of lime sludges). Costs can be based
on the charge structure set for inclusion of other industrial wastes
into the sewerage system. If the sewage is discharged into the
ocean, larger volumes of brine may be accepted.
-------
Current Technology and Costs 139
VI. IAGOONING OF SLUDGE SOLIDS
Lagooning remains the most popular and acceptable method of dis-
posal of water treatment sludges. Yet lagooning is in fact fre-
quently not so much a disposal method as one for dewatering, thick-
ening, and temporary storage.
One should clearly differentiate between lagoons and drying
beds: lagoons are generally built solely by enclosure of a land
surface by dikes, or by excavation. Drainage is not maximized by
underdrains or by surfacing with sand. Sludge is added continuously
or intermittently until the lagoon is filled, whereupon the lagoon
is abandoned or cleaned. Sand beds are described in Section VII.
Lagoons may be equipped with flashboards or the like to enable
the operator to decant. This is particularly desirable if filter
washwater is also sent to the lagoon. As previously mentioned in
Section IV, this procedure is not desirable.
Overall, lagooning must be considered a very inefficient pro-
cess; nonetheless, where land is cheap it is difficult to justify
any other disposal method. Where land is more expensive and sites
for new lagoons cannot be found, the old lagoons can, of course, be
cleaned or the dikes raised.
It is technically incorrect to state that sites for new lagoons
cannot be found. What is meant is that sites cannot be found in the
immediate area or that the sites are too costly. More distant sites
could be found, and they would probably be cheaper. The problem is
to transport the sludge to the more distant site, usually achieved
by pumping. Lansing, Michigan, formerly pumped its lime sludge
7,000 feet to a lagoon until a recalcination plant was built.
Some specifics might be mentioned about the character and dis-
posal of lagooned sludges. Alum sludge will gradually consolidate
sufficiently to provide a 10 or 157, solids content. Water removal
is by decantation or by evaporation, with some drainage. Evapora-
tion may provide a hard crust, but the remaining depth is thixotropic,
capable of turning into a viscous liquid upon agitation with near
zero shear resistance under static load. Removal can be accomplished
by dragline or clamshell, dumping the sludge on the banks to air dry
previous to later removal. Willingboro, New Jersey, removes shallow
layers of lagooned and thickened sludge by front-end loader to a
specially prepared drying lagoon, where drying will yield a crumbly
cake. This lagoon has a sanded surface to aid in draining rainwater.
-------
140 Current Technology and Costs
New Britain, Connecticut, contracts out to have the thickened
alum sludge removed and spread on the roadsides. On the other hand
Somerville, New Jersey, lagoons at very shallow depths, allowing
the sludge to air dry sufficiently to allow walking.
Mention might also be made of the effect of freezing and thaw-
ing by weather. Although such cases have not been seen by the au-
thors, it is known, for example, that thin layers of sludge when
frozen in winter and later thawed will dramatically increase in
drainage and settling rates, producing fine granules of material.
Sludges from water softening plants (lime sludge) are more
easily dewatered in lagoons. The higher specific gravity of the
particles aids consolidation, and solids contents of 50% can be
attained. Where lime sludges are dumped in flooded quarries or in
excavations with water, perhaps only 2570 solids can be expected.
The latter case occurs at Miami (Hialeah) requiring sludge removal
by scraper and tugger hoist. Another Miami plant (Orr) utilizes a
lagoon excavated out of limestone for which the contractor paid
4c/cu.yd. Generally, lime sludges are considered poor fill, and
final disposal after lagooning is a problem.
Sludges from an iron removal treatment plant in Amesbury,
Massachusetts, suggested that this type of sludge in lagoons de-
waters somewhat better than an alum sludge, but not as well as a
lime sludge.
Costs for lagooning will thus be highest for alum sludges.
This report deduces that costs are highly variable, ranging up to
$40/ton of solids. Land costs do not appear to be as important a
factor on the total overall costs as may be initially expected.
This is because the initial capital outlay for the land can be re-
covered at 1007o salvage value if the lagoon is cleaned.
VII. SAND BED DRYING
Sand beds for drying water treatment sludges are basically
identical to those employed in sewage treatment: a prepared under-
drained sand surface. Operation may include decantaion, but basic-
ally water is removed by drainage and air drying, preferably with
sufficiently shallow sludge depths to allow cracking of the sludge
down to the sand-sludge interface, thus accelerating drying and
yielding solid cakes.
-------
Current Technology and Costs
The practice of decantation allowed Lompoc, California, to add
backwash water to the lime sludge on the drying beds. Here, however,
deep cracking of sludge cake to the sand-sludge interface was probably
not attained, because the beds were filled to a depth of 5 feet. After
four months the sludge was sufficiently dewatered (about 507o solids)
to be removed by front end loader.
The Los Gatos, California, Rinconada plant charged drying beds
with alum sludge. Decantation was provided for, but operating pro-
cedures have not yet been standardized. Sunol, California, also
dries alum sludge on sand beds along with sludge from the washwater
recovery basins. Filling depths are limited to two feet to allow
cracking down to the bottom. The solids content of the dried sludge
was a least 25%, and sludge removal could be done by front end loader.
The cases cited are obviously located in dry climates, and the
costs (Lompoc - $5.05/ton; Sunol - $58.50/ton) reveal little. Part
of the difference in the costs is due to the greater tonnage of lime
sludge produced by softening; also, it is easier to dewater. Wheth-
er or not drying beds are superior from an economic viewpoint to
lagoons is not clear. However, it appears logical that drying beds
could be superior where land costs are high. The addition of under-
drains and a sand surface will not greatly add to the overall costs,
and drainage should be accelerated.
VIII. VACUUM FILTRATION
Vacuum filtration of lime sludges has been practiced at various
plants over the last few years. Some successes and some failures
have been noted. Explanations for this need extend no further than
to note that belt filters have worked successfully, but coil filters
have been plagued with incrustation of the coils. The two success-
ful installations visited, Boca Raton, Florida,-and Minot, North
Dakota, were both of Eimco manufacture. Both received thickened
lime sludge at about 30% solids, and yielded'a crumbly cake at ap-
proximately 657o solids, sufficiently dry to be used as landfill.
Operating problems were reported minimal, and Boca Raton found a
cloth belt lasted 6-9 months.
Total cost for sludge disposal at Minot calculated to be $7.29/
ton of dry solids; Boca Raton, $16.00. The difference in costs
can be attributed to the quantities of sludge produced: Minot fil-
ters approximately twice as much dry cake solids.
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142 Current Technology and Costs
Vacuum filtration of alum sludge has been attempted in the Unit-
ed States by Johns-Manville. Since the dilute sludge (here 1.25%
solids) readily penetrated the filter media, a pre-coat vacuum filter
using diatomaceous earth (Celite, etc.) was needed. Costs for vacuum
filtration by this method were projected by Johns-Manville to be
$3.96/1,000 gals, ($76.00/ton of dry solids).
In order that cost estimates for vacuum filtration of both lime
and alum sludges could be compared between themselves and with other
processes, model studies were initiated (see appendix). For lime
softening sludge, a figure of $12.35/ton was determined, including
disposal charges of $6.15/ton. Vacuum filtration of alum sludge
using a precoat was found to cost $177.00/ton and upward, of which
$20/ton was for trucking and disposal charges.
The great differences in costs for vacuum filtration of lime
and alum sludges must be borne in mind when vacuum filtration is
contemplated for other sludges of intermediate character, such as
iron removal sludge. One factor cannot be sufficiently stressed:
lime sludges at Boca Raton and at Minot were low in magnesium hy-
droxide which adversely affects the settleability, compactability, and
filterability of a sludge. Thus in the cases studied good results
were obtained, but lime sludges with greater concentrations of
magnesium could behave more closely to alum sludges, with attendant
higher dewatering costs.
In sum, vacuum filtration of alum sludge appears economically
questionable, and possibly technologically unfeasible. Some thick-
ened lime sludges, low in magnesium, can be vacuum filtered without
problems. But correspondingly, when low in magnesium, the sludge
is amenable to lagooning, centrifugation, and possibly recalcination.
IX. CENTRIFUGATION
Only lime softening sludges were found to be centrifuged, at
treatment plants in Miami, Florida (Hialeah); Dayton, Ohio; Lan-
sing, Michigan; and Austin, Texas. The first three plants are re-
calcination plants. All four used the 40" x 60" Bird continuous
feed, helical conveyor centrifuge. The first installed was at
Miami in 1948, and apparently because of its successful operation,
the others followed suit. The choice of centrifuges for the re-
calcination plants is based on the ability of the centrifuge to
selectively throw magnesium hydroxide out into the centrate, pro-
viding a purer sludge cake for recalcining.
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Current Technology and Costs
143
A summary of these installations regarding pertinent data
follows:
Austin, Texas
Dayton, Ohio
Lansing, Michigan
Miami, Florida
Ave.
flow (mgd)
30
61.2
23
81
Number of
Centrifuges
1
3
1
2
Feed
% Solids
1.
15-25
20
40
Centrate
% Solids
0.5
5.5
3
5-10
The cakes in each case were of toothpaste consistency (60-707=
solids). Moyno pumps readily handle this consistency.
Costs for dewatering be centrifugation are available only for
Austin (about $25.00/ton, including $8.70/ton for transport and dis-
posal). Thickening was not done. A model study (see appendix)
utilizing thickening prior to centrifugation revealed a total cost
of $11.40/ton, which includes $6.15/ton for trucking and disposal
charges. This cost compares favorably to that predicted by a
model study for vacuum filtration of a lime sludge.
Operating problems for the centrifuges are certainly minimal.
There are some vibration problems, and in Dayton there is some hea-
vy wear on the helix. However, all cases visited had sludges with
low magnesium contents. More impure sludges could be difficult to
centrifuge.
X, RECOVERY AND REUSE OF LIME
Two different processes are being used to recalcinate lime sof-
tening sludges today:
The rotary kiln illustrated is used at Miami, Florida, and at
Dayton, Ohio. Both installations were designed by Black, Crow and
Eidsness. This firm also designed a rotary kiln for San Diego,
which operated successfully until San Diego ceased softening water.
The "Fluo-solids' reactor is a vertical kiln illustrated man-
ufactured by Dorr-Oliver, and operating at Lansing, Michigan. It
is claimed that this installation is better adapted to smaller plants
than is the rotary kiln. Certainly the latter requires a larger land
area, and being less compact, dissipates more "heat.
-------
RECOVERY OF LIME FOR REUSE
Rotary Kiln and Vertical Kiln Processes
Backet
Elevator
IAAAAVVAAAAAAAAA A*J
Product Screw \
Lime
Storage
Bin
Product
Lime Sludge Calcining
Rotary Kiln Flow Sheet
I R»octo<_ _Ai
Lime Sludge Calcining
Fluosolids Flow Sheet
-144-
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Current Technology and Costs 145
Proper recalcination places a premium on the purity of lime
sludge produced. Split treatment is required to minimize magnesium
impurities to less than 107o, and successive sludge thickening de-
watering operations must emphasize reduction to a minimum of the
magnesium. It would appear, however, that only certain ground waters
are suitable for producing a sludge by excess lime treatment with
minimal impurities. Hence recalcination is limited by existing tech-
nology to a few instances.
Miami and Dayton plants show profits from their recalcination.
In both instances they produce more lime than needed in treatment.
The profitability of their operations is sharply dependent on the
value placed on these excess quantities. Lansing did not show a
profit, but it is a smaller plant, and cannot produce sufficient
lime for its own purposes, let alone for sales. This is not a fault
of the vertical kiln, but rather a result of the design of the third
stage sedimentation basins. Removal of sludge is intermittent, and
the sludge cannot be stored; hence it is discharged to a distant
lagoon.
Considering the cost of lime sludge disposal, all recalcination
plants visiting would show a large profit. With this in mind, perhaps
greater attempts at recalcination are needed, even at smaller plants.
The question of raw water quality remains, and is certainly a key
factor in deciding the efficacy of recalcination.
XI. FREEZING AND MISCELLANEOUS PROCESSES
Freezing; The freezing and thawing of alum sludge has been proven
to significantly increase rates of settling and filtration by con-
version of a hydrogel into a suspension of granular solids. A
batch process has been developed in England and Japan, but, according
to the latest information, power costs and maintenance costs on the
freezing tanks are prohibitive.
Pressure Filtration; The trend in England is to this process. Both
the Atlanta, Georgia, and Passaic Valley, New Jersey, water utilities
are considering this method. A large body feed (usually of lime) is
required for the pressure filtration of alum sludge. This is batch
process, but operating costs are said to be lower than previously
assumed because of new developments with rubber gaskets and filter
cloths. The waterworks mentioned above have had their sludges tested
by Beloit-Passavant. The sludge cakes were dense (65% solids) and
suitable for landfill.
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146 , Current Technology and Costs
Thickening; Thickening of lime sludge was employed at Minot, North
Dakota; Dayton, Ohio; Lansing, Michigan; Boca Raton, Florida;
and Miami, Florida. Solids contents of up to 35% were produced. No
clearcut design bases were noted. Miami used their thickeners pri-
marily for equilization of the sludge flows. Both Minot and Boca
Raton operated their thickeners intermittently, which then allowed
solely day-time operation of the vacuum filters. Lansing had a steel
4-tray thickener, whereas the others were all of the circular, con-
crete, sloping floor design. Boca Raton had an interesting torque
control on their scraper mechanism.
Thickening of alum sludge is being considered at Atlanta, Geo-
rgia. Possibly a 5% solids content can be obtained with the aid of
chemical conditioning.
Alum Recovery: The recovery and reuse of alum by treatment of alum
sludge with sulfuric acid is being tested by Minneapolis. St. Peter-
sburg, Florida, has pilot-plant tested this method several years ago.
Apparently costs were excessive. Alum recovery is still in the ex-
perimental stage.
XII. CONCLUSIONS
1. Filter washwater is increasingly considered a pollutant,
and action is being taken by state regulatory agencies to require
its treatment prior to discharge to surface waters. Washwater
recovery can be accomplished by direct recycle to the flocculation
basins, or to the reservoir. There is some concern over algae
buildup, however, and thus recycling may be best suited for soft-
ening of ground waters. Water-scarce areas find washwater recla-
mation practical if the washwater is first clarified by sedimen-
tation.
2. Disposal of alum sludges to the sewer appears to be a prac-
ticable solution, recognizing that the capacity of the sewage
treatment plant must be adequate and acknowledging that the sew-
age treatment plant inherits the problem of ultimate disposal.
No deleterious effects of the alum sludge on the sewage treatment
processes are known. Lime sludges are not recommended for in-
clusion in the sewage due to problems of deposition in the sewers
and in the digesters.
3. Lagooning is presently the most widespread process for
-------
Current Technology and Costs ^^^^^ 147
dewatering and disposing of sludges. Washwater should be sep-
arately handled. At present there are few alternatives to la-
gooning, and efforts to improve this process, such as by under-
draining and by operation as sand drying beds, should be more
widely attempted. Natural freezing and thawing may improve per-
formance greatly, and this encourages the filling of lagoons to
very shallow depths.
4. Vacuum filtration or centrifugation of lime softening
sludges is entirely feasible for sludges with low magnesium
content. The two methods are comparable in cost, but the cen-
trifuge is capable of passing non-calcium impurities out with
the centrate, desired for recalcination.
5. Recalcination is presently limited to softening plants
treating ground water low in magnesium. Either of the two pro-
cesses, the vertical kiln or the rotary kiln, is sound, but
only applicable to large treatment plants. Profits from recal-
cination are marginal from a business standpoint, but consid-
ering the reduction or elimination of the sludge problem, it is
clear that recalcination is saving the taxpayer a great deal of
money.
6. Both vacuum and pressure filtration of alum sludge have
been attempted on a pilot scale. While both processes may be
technically feasible, cost data are lacking, and definite con-
clusions as to the economic feasibility cannot be made at this
time.
7. Thickening of lime softening sludges is entirely practical,
although perhaps unnecessary where centrifugation follows.
Thickened lime sludges readily clog piping. The thickening of
alum sludge is of great potential benefit.
8. Freezing and thawing of alum sludge by mechanical means has
been practiced in England and Japan. Although dewatering and
settling characteristics are greatly enhanced, questions about
the economic feasibility of this method remain. Recovery and
reuse of alum has not evolved beyond the experimental stage.
9. Disposal of diatomaceous earth washwater can be accomplished
by discharge to the sewer, or by direct vacuum filtration, as
practiced at Goleta, California.
10. Brine disposal to the sewer is satisfactory, provided suf-
ficient dilution occurs at the treatment plant.
11. Costs for disposal of water treatment sludges were found to
be as shown in the following Table.
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148
Current Technology and Costs
TABLE
Costs for Disposal of Water Treatment Sludges
Location
Sludge Type Processes
Total Disposal Cost
Austin, Texas
Boca Raton, Florida
Dayton, Ohio
Goleta, California
Lansing, Michigan
Lompoc, California
Miami, Florida
Minot, North Dakota
New Britain, Conn.
Somerville, N.J.
Sunol, California
Willingboro,N.J.
Model Studies
Lime
Lime
Lime
D. Earth
Lime
Lime & D.E.
Lime
Lime
Alum
Alum
Alum
Alum
Alum
Lime
Lime
C
T&VF
TC&R
VF
TC&R
S
TC&R
T&VF
L
L
S
L
T&VF
T&VF
T&C
$/mg
25.10
16.00
2.20*
14.10
2.00
24.20
6 . 95*
21.80
3.30
0.09
1.18
4.90
36.90
12.35
11.40
$/ton $/ton
dry solids lime
25.10
16.00
1.50* 0.79*
126.60
6.15 2.60
4.89
10.55* 5.08*
7.29
39.00
2.00
56.60
33.50
177.00
12.35
11.40
Process Symbol:
C= Centrifuge/ L= Lagooning/_R= Recalcination/ S= Sand Beds/
T= Thickening/ VF= Vacuum Filtration.
*Profit from recalcined lime.
-------
Current Technology and Costs __^ 149
12. Sludge disposal will generally add about 570 to the total
cost of treating water; however, all conclusions as to costs
are subject to many conditions and limitations. It is felt
that each sludge disposal problem is unique.
13. As new installations to dispose of sludge are built, ef-
forts to ascertain their construction and operating costs should
be made. Particular emphasis is needed to determine the solids
quantities through rigorous measurement procedures.
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150 Current Technology and Costs
APPENDIX
Cost Analyses
The cost analyses provided in the appendix follow standard
engineering-economic evaluation procedures. However, some clarifi-
cation of the procedures used may be helpful.
Of primary interest to waterworks engineers is the cost for
sludge disposal per unit volume of water treated. This was done
here, and expressed in units of dollars per million gallons of water
treated. This presupposes a cost calculated on the basis of actual
operating expenses and capital recovery, summed together.
Also of special interest to those specializing in ultimate dis-
posal is the sludge disposal cost per ton of dry solids. This, too,
was done here, again including both actual operating expenses and
capital recovery. In the few instances where recalcination was prac-
ticed, costs (or profit) were also calculated on the basis of dollars
per ton of lime produced (90% pure CaO).
The form of ownership of the water utility creates some dif-
ficulty in the analyses, for public ownership can have available free
land, lower interest rates, and freedom from taxation. The basic
calculations used in this report include the cost of land, interest
at 6%, with no taxes; which is to represent conditions for public
operation.
Calculations for taxes and insurance, and interest on land costs
are included in parentheses, and represent a private operation.
Higher interest rates could have been allowed for here. One notes
numbers in parentheses under "Disposal Costs/Unit" for each plant.
These numbers include the costs for private operation mentioned above.
Emphasis must be placed on the method for land cost calculations,
The purchase price for land need not be recovered, since land is con-
sidered a fixed asset (non-depreciable). Therefore only the interest
on the purchase price is involved. Any cost for returning the land
to the original purchase condition was deducted from salvage value of
equipment and buildings.
-------
Current Technology and Costs 151
Capital recovery of equipment and buildings followed a 670 in-
terest rate, generally over a 25-year period, with 257= salvage
value at the end of the 25 years. Taxes and insurance were assumed
to amount annually to 2% of the capital cost (including the cost of
land).
The accuracy of certain figures in this report will undoubtedly
be questioned by some. The authors have used actual data supplied
by plant superintendants and operators, when such data was considered
by the authors to be accurate and representative of average operating
conditions. Much data was unfortunately not available, and had to be
estimated by the authors. It is felt that uncertainties in the es-
timates tended to balance out. Noticeable exceptions occur in the
calculations for costs/ton of dry solids. Most treatment plants had
no information on the quantities of solids produced, and thus costs/
ton cannot be completely reliable.
-------
AUSTIN, TEXAS
Nlorfhwesf Plant- - Flow Diagram
Reservoir
Clear \ Distribution
Well
AUSTIN, TEXAS
Northwest Plant
-152-
-------
PLANT VISITATIONS
AUSTIN, TEXAS
Treatment- by CentTtfugafrion
Population: 186,545 (1960)
Ownership: Municipal
Superintendent: Curtis E. Johnson
Water Source: Reservoir
Flow: ave. 30 mgd
peak 80 mgd
cap. 120 mgd
Influent Quality :
Total hardness
Carbonate hardness
Magnesium
Turbidity
pH
165 mg/1 as CaCC>3
133 mg/1 as CaCO,,
14 mg/1
10 - 60
Method of Treatment:
Flocculation and sedimentation.
Chemicals Added:
Lime
Copperas
90 mg/1
5 mg/1
Description of Disposal Process
Sludge is removed at 5-10% solids from the primary settling
tanks equipped with scrapers. The sludge from the secondary
units, representing 30-35% of all sludge produced, is recycled.
The primary sludge is sent to a 40" x 60" centrifuge, leaving at
55-60% solids. Centrate contains less than 0.5%-solids, and is
returned to the lake. Cake (paste) is pumped by Moyno pump to a
-153-
-------
AUSTIN, TEXAS
Center: Centrifuge for
Dewatering Lime Sludge
Left: Hopper for Cake Storage
Truck for Hauling
Centrifuged Sludge Cake
Final Sludge Disposal Area
-154-
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Current Technology and Costs 155
storage hopper (14* x 35* x 15' deep) equipped with 4 draw-off
points. 24 hours storage at capacity operation is provided.
Sludge is hauled by trailer truck about 12 miles to a
200' x 200' disposal area near a creek bottom.
COST OF SLUDGE DISPOSAL
Construction
The following items were installed in 1963:
Centrifuge $30,000
Motor and switchgear 4,000
Pump 600
34,600
Installation 5,000
$39,600
The hopper was fabricated locally of steel. An estimated
cost would be $20,000. A total replacement value of $80,000
would be expected today. (Note that the centrifuge is located
outdoors). Set a salvage value of 257» after 25 years.
Land
2
Land required at the plant is about 5,000 ft . A value of
$20,000/acre may be set, or $2,500. The disposal site has a few
years of life expectancy at best. Over a 25-period, with a 10 ft.
final depth, about 20 acres will be required. This could cost
$40,000.
Operation
Labor and supervision costs are considered negligible;
however, a probable figure of $2,000/year could be assumed.
Maintenance, power and supply costs were $7,360 in the last year
(August 1, 1966 - July 31, 1967). This appears to be far too low.
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156 Current Technology and Costs
Maintenance alone will run about $5,000/year. A figure of $10,000
is used here.
Trucking
Records state trucking costs are $9,600/year.
Annual Costs
Capital recovery ($60,000 @ 6% for 25 years) $ 4,700
Operation 12,000
Trucking 9,600
(Interest on salvage)($20,000 @ 6%) 1,200
(Interest on land)($42,500 @ 6%) (2,550)
(Taxes and Insurance) ($122,500 @ 2%) (2,430)
Total $ 27,600/yr.($31,580)
Cost / Unit
Cost/mg
$27,600/1,100 rag = $25.10/mg ($28.70)
Cost/ton of sludge solids
It is said that one ton of dry solids originates from one
mg of water treated, or
$25.10/ton ($28.70)
Discussion of Cost
Approximately one third of the costs is for trucking, and about
the same can be said for operating expenses. The remainder of the
costs are items for which Austin does not pay, as financing was out
of current revenues.
-------
Current Technology and Costs
157
BOCA RATON, FLORIDA
Thickening and Vacuum Filtration
Population: 30,000 permanent, 10,000 temporary, plus 5000 students
Superintendent: Augustave P. Hager
Ownership: Municipal
Water Source: Wells
Flows: Ave. (1968) 7.61 mgd
Cap. 23 mgd
Influent Quality:
Effluent Quality:
Total solids
Iron
Total hardness
Temporary hardness
Magnesium
Alkalinity
pH
Total hardness
Temporary hardness
Alkalinity
pH
312 mg/1
0.5-1.5 mg/1
210-250 mg/1 as CaCO,.
192 mg/1 as CaCO J
6 mg/1 3
190 mg/1 as CaCO
7.3 3
68 mg/1 as
26-28 mg/1 as
26 mg/1 as CaC03
9.5
Method of Treatment:
Chemicals Added:
Coagulation, clarification, and rapid sand
filtration; with pre-chlorination.
Lime
Chlorine
Sodium silicate
120-130 mg/1
6.5 mg/1
5.7 mg/1
-------
BOCA RATON, FLORIDA
Flow Diagram
Wells
Distribution
Drainage
Canol a
Truck
Truck -*•
O Vacuum
Filter
Truck
BOCA RATON, FLORIDA
-158-
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Current Technology and Costs 159
Description of Sludge Disposal Process
Sludge is removed continuously from the upflow clarifiers at
a l-47<, solids content and sent to a 25' thickener. The sludge is
taken during the day and thus several feet of dense sludge accu-
mulate. To prevent damage to the scraper blades, provision was
made to raise and lower them. If the operator sets the blades too
deep into the sludge, a torque control will stop the drive unit.
Thickened sludge (28-32% solids) is pumped up to the vacuum
filter building. Rotary pumps are used for this purpose. The
sludge is then filtered on a 6' diameter rotary belt cloth filter.
Cake is discharged to a waiting 2% ton dump truck below. With a
65-70% solids content, the cake if friable and ready for direct use
for highway construction as a road stabilizer. No revenue is de-
rived. The 6-mile round trip is driven by the plant personnel.
The backwash recovery basin receives thickener overflow, and
vacuum filtrate in addition to backwash waste. It is a gunnited
approximately 65' x 115' x 12' deep basin equipped with pumps to
recirculate the entire flow. Past operation has been to recir-
culate only the clearer water, flushing and pumping the deposited
solids into a nearby drainage canal. A reserve unlined lagoon
measuring approximately 30' x 30' x 12' deep serves to store sludge
during holiday weekends and repairs to the thickener or vacuum
filter. It is cleaned by dragline 1 - 2/ year, and the sludge is
trucked away and dumped.
COST OF SLUDGE DISPOSAL
Construction
The disposal facilities were built in 1964-1965. An approx-
imate breakdown of costs is as follows:
Thickener $10,000
Vacuum filter 35,000
Building and miscellaneous 35,000
Total $80,000
-------
BOCA RATON, FLORIDA
. •'
Lime Sludge Thickener and Vacuum Filter Building
1
Recovery Basin for
Thickener Overflow, Vacuum Filtrate, and Filter Washwater
-160-
-------
Current Technology and Costs 161
The reserve lagoon does not have a direct cost attached, as it was
part of a larger abandoned lagoon on which the present facilities
are located. Salvage is figured at 257<>.
Land
About % acre of land is used, with a true value (1968) of
about $9,000. The land is municipally owned.
Labor and Supervision
Vacuum filter operation of 4 hours per day costs about
$18,000/year. Another 2 hours is spent on maintenance of the
system ($9,000/year). Supervision is estimated at $4,000.
Power
Only a crude estimate may be made. Rated horsepower of the
motors driving the vacuum pump, rotary pumps, etc. totaled some
50 hp. Operation of these 4 hours/day at 1.5C/KWH would cost
approximately $1,400. There is no heating needed.
Maintenance
Two filter belts a year @ $80 apiece are needed. Practically
all repairs are charged under labor. A total figure for mainte-
nance is listed here as possibly $2,500.
Trucking
The truck was bought for about $4,500 in 1965. It is main-
tained by the Public Works Department and is used for purposes
other than sludge disposal. Probably the best estimate is 20c/mile,
3 loads/day, 12 miles/load - or $2,600/year.
-------
Current Technology and Cc
Cleaning of Lagoon
It takes 6-8 hours to clean. The dragline costs $20/hour.
Probable cost: $500/cleaning or $1,000/year.
Total Disposal Costs
Capital recovery ($80,000-20,000 @ 6% for 25 years) $ 4,690
Annual costs 38,500
(Interest on land) ($9,000 @ 6%) (540)
(Taxes and Insurance) (2% of $89,000) (1,780)
Interest on Salvage ($20,000 @ 670) 1,200
Total $ 44,390/year ($46,710)
Disposal Cost /Unit
Cost / mg of water treated:
$44,390/7.61-365 = $16.00/mg ($16.80)
Cost / ton of dry solids:
The amount of sludge produced was said to be 1 ton of
solids per mg. This checks out, yielding a. cost of $ 16.00/ton.
($16.80)
Discussion of Cost
The costs are about 70% due to labor and supervision. Since
the construction costs are recent, little change would result in
updating prices. Land costs, taxes and insurance in the case of
a private utility would add about 6% to the costs. Note that the
sludge is low in magnesium hydroxide, and thus easy to filter.
-------
Current technology and Costs 163
Washwater Recovery
The washwater recovery basin was constructed at a cost of
$20,000 in 1964-65. Operating costs etc. are probably less than
$l,000/year. The total backwash flow is 30 mg/year. Salvage
value of the basin is assumed zero.
Capital recovery ($20,000 @ 6% for 25 years) $1,560
Annual costs 1,000
(Interest on land) ($9,000 @ 6%) (540)
(Taxes and Insurance) (2% of $29,000) (580)
$2,560/yr.($3,680)
This is calculated to be $2,560/30 mg = $85.00/mg ($120).
Boca Raton produces water at $200/mg, and thus a savings through
recycle is likely because a significant percentage of water supply
costs is due to the chemicals added and to well development and
operation.
-------
DAYTON, OHIO
Ottawa Street Plant - Flow Diagram
Recorbonotor
Wells
Logoon
Thickener
Sludge from Miami River
Sludge
Trantment Plnnt
Distribution
^ Woshwoter
Storage
Storage
L-,
Kiln
Nojurol Gas
- Truck
Centrafe
Overflow _
Storage
Lagoon
Truck to
Recarbonator
to atmosphere
i
Sludge
Expansion ,,, ...
Chamber Centrifuge
Cake
DAYTON, OHIO
Ottawa St. Plant
-164-
-------
Current Technology and Costs
165
DAYTON, OHIO
Recalcination
Population: 262,332 (1960)
Superintendent: Robert Stout
Ownership: Municipal
Water Source: Wells
Flows: Miami Plant
Ottawa Plant
ave. (1967) 7.6 mgd
cap. 24 mgd
ave. (1967) 53.6 mgd
cap. 96 mgd
Influent Quality:
Total hardness
Carbonate hardness
Magnesium
Iron
Total solids
PH
365 mg/1 as CaC03
263 mg/1 as CaC03
34 mg/1
0.15 mg/1
463 mg/1
7.6
Effluent Quality:
Total hardness 108
Carbonate hardness 34
Magnesium 10
Iron 0
Total solids 242
pH 9.0
mg/1 as CaCOs
mg/1 as CaC03
mg/1
mg/1
Method of Treatment:
Split treatment (water softening), in-
cluding coagulation, sedimentation, and
rapid sand filtration; with pre-chlorin-
ation.
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166 Current Technology and Costs
Chemicals Added: Lime 227 mg/1
Soda ash 23.9 mg/1
Sodium silicate 0.36 mg/1
Chlorine 0.87 mg/1
Method of Sludge Disposal;
The sludge from the primary basins at both plants is brought
to a carbonation basin at the Ottawa plant. The solids content is
from 2 - 4%. It is then thickened to between 15 and 25% solids,
and stored in a holding tank equipped with an agitator to keep the
sludge in suspension. Flue gas from the kiln is used for carbon-
ation, the purpose of which is to reduce the magnesium content of
the sludge solids from 7% to 4% (as MgO) , the difference resulting
from the conversion of magnesium hydroxide to a dissolved magnesium
carbonate which passes out in the overflow from the thickener to a
lagoon.
Sludge from the storage tank is sprayed into the expansion
chamber of the kiln exhaust system, in part to scrub and cool the
gases, and in part to heat the sludge (up to 50 C) and create
better liquid-solids separation in the centrifuges which follow.
The solids content increases by centrifugation to about 60% solids,
and the magnesium content decreases to 2%. Centrate is passed to
a lagoon, or at times back to the sludge carbonation basin.
The cake, of toothpaste consistency, is pumped by a Moyno pump
into the rotary kiln, and leaves the kiln as better than 90% pure
CaO. A screw conveyor and bucket elevator transport the lime to
two storage bins. Lime is trucked to the Miami plant, or is sold.
Each water treatment plant has a washwater recovery lagoon.
In addition, the recalcination plant has a nearby lagoon for the
centrate. Further away (800 yards) lies a ten-acre lagoon which
receives the thickener overflow. Until 1957, when the recalcin-
ation plant was built, this lagoon was used for the disposal of all
Ottawa plant sludge. The accumulated sludge from this lagoon later
supplemented the sludge production of the Ottawa plant, for there
is a significant reserve in recalcination capacity. Present aver-
age production of lime is about 100 tons/day; the capacity is 150
tons/day. The accumulated sludge was exhausted in 1962. A dredge
is available to remove further accumulations due to the thickener
overflow and emergency bypassing.
-------
Current Technology and Costs \(,j
A more complete description of the recalcination plant is
available in the literature. For the purposes here intended, the
following data is important:
Thickener: 130 feet in diameter, with continuous removal.
Depth of 8 to 15 feet. Volume - 1 mg.
Centrifuges: Three. 40" diameter, 60" long. Two in con-
tinuous operation suffice for present production.
Kiln: 265 feet long, 9% feet in diameter.
A very approximate solids and total flow balance may be made:
Solids Balance (ave. daily)
Flow Rate Solids Content Solids Rate
(%) (tons)
Thickener Influent 1,000,000 gals (+ 130,000) 4.0 (4.1) 167 (+27)
Overflow 920,000 gals 0.1 5
Underflow 210,000 gals 21.6 189
Centrifuge Feed " " "
Centrate 145,000 gals 5.0 30
Cake 65,000 gals (271 tons) 59. 159
Kiln Input 271 tons " 55 "
Output 89 tons CaO(= ^CaCO-j) 89
The actual average total of lime produced is 88 tons/day. Note
that about 90% of the centrate is returned to the carbonationjmsin
and thence to the thickener. A sludge density of 62.4 Ibs/ft was
used in the calculations, which creates a slight error in the flow
rate.
COST OF SLUDGE DISPOSAL
Construction
The initial cost for the recalcination plant was $1,500,000
(1956-57). An additional lime storage tank costing $85,000 has
-------
168 Current Technology and Costs
since been added. A 1968 total replacement cost would be about
$2,500,000. There should be a salvage value of perhaps 25% at the
end of 25 years.
Land
About 3 acres of land are used for the lime recovery operation,
plus an additional 10 acres for lagoons. At $6,000/acre, this
yields a purchase price of $78,000.
Operation
The best information here is from the 1967 records.
Operation (14 men) $130,533
Supervision 19,155
Fuel and power 184,440
(gas is $0.52/1,000 cu.ft.)
Materials and supplies .... $ 25,469
(and Maintenance)
However, it must be noted that these costs are based on less
than capacity operation. If operation were to take place at cap-
acity (150 tons/day) for 907o of the year, the year's production
would be 49,400 tons, and not 32,604 tons as in 1967. Since fuel
and power costs are approximately directly proportional to the
quantity of lime produced, a figure of $279,000/year should be
used. The total gross operating cost would then oe $454,000. From
this should be subtracted the value of the CC^ delivered to the
water treatment plant. Dayton assumes a value of $24,000 for the
co2.
Value of Lime
Prior to the building of the lime recovery plant (1957),
Dayton paid $18.60/ton delivered. The plant has depressed prices
in the area, as Dayton sells about 207o of its production to nearby
treatment plants. Commercial prices are at present $16.00/ton,
and it is felt that if.Dayton were to buy its lime supply, a price
of at least $20.00/ton would be charged. Dayton sells lime to
-------
Current Technology and Costs 169
itself for $12.00/ton, and to communities for $10.50/ton plus
freight. This low price is provided because of the uncertainty of
supply quantity. Higher prices could be set, but Dayton believes
a price of $12.00 is necessary to maintain a strong competitive
position. A compromise between $16.00 and $12.00 is used here.
Annual Costs
Capital recovery ($1,750,000 @ 6% for 25 yrs.) $137,000
Interest on salvage ($750,000 @ 6%) 45,000
(Interest on land) ($78,000 @ 6%) (4,700)
Operation, etc. 454,000
(Taxes and Insurance) (2% of $2,578,000) (51,600)
Sub-Total $636,000 (692,300)
Less value of lime (49,000 tons @ $14.00) 686,000
Less value of C02 24,000
Gross Profit $ 74,000/yr. (17 ,700)
Profit / Unit
Profit/mg of water treated:
$74,000 / 61.2 • 49,400 • 365 = $2.20/mg ($0.52)
32,600
Profit/ton of lime produced:
$74,000/49,400 = $1.50/ton ($0.36)
Profit/ton of sludge solids:
$1.50/ 1^7 = $0.79/ton ($0.19)
88
Discussion of Profit
The profit from lime recovery as a per cent of investment is
-------
170 Current Technology and Costs
37o, and about %% if allowance is made for property taxes and insur-
ance. This is low. If the operation were entirely private, a loss
would occur because of higher interest rates. Thus it appears that
lime recalcination of water softening sludge, as an independent and
private operation, is questionable.
Yet it should be noted that a profit is shown, as opposed to .a
deficit for all other disposal methods. This should be taken into
account. Also, one must note the possibility of wide ranges in
market price of lime and its effect on net profitability. A sale
price of $15.50/ton would double the profit attained from sales of
$14.00/ton.
Dayton figures their costs at $12.46/ton (before sales of
lime), but this is from an originally much lower capital cost, with
no taxes or land costs included in the annual expenses. On the
other hand, their present operation is only running at 2/3 capacity.
Bonding was at 3%70.
-------
Current Technology and Costs 171
GOLETA, CALIFORNIA
Vacuum Filtration
Superintendent: Temple A. Tucker
Ownership: Goleta County Water District
Water Source: Lake Cachuma
Flow: ave. (1967) 2.6 mgd
cap. 6.7 mgd
Influent Quality: (Lake Cachuma 1966)
Calcium 74 mg/1
Magnesium 31 mg/1
Sodium and Potassium 56 mg/1
Bicarbonate 196 mg/1
Sulphate 225 mg/1
Chloride 27 mg/1
Iron 0.72 mg/1
Nitrate 0.20 mg/1
Hardness 312 mg/1 as CaCC>3
Turbidity 4.0 mg/1
Method of Treatment: Diatomaceous earth filtration of the raw
water without pretreatment; activated
carbon filtration followed by chlorination.
Chemicals Added: Chlorination prior to Tecolote Tunnel
Sodium bisulfite at the plant
Post chlorination
-------
GOLETA COUNTY WATER DISTRICT, CALIFORNIA
La Vista Plant - Flow Diagram
Agitated
Lake Cochuma Alum—*- S|urry
Tank
ring J
3ter J
1
'
o Several
eatment
s Tecolote
; Tunnel
Diatorr
^ Fn
Filtra
Backwash
Water
aceous
th
ion
Water f
Plants Diatomaceous — '
Earth
Vacuum
Filters
1
Sludge Cake
Trucked to
Landfill
Carbon
Filters
— *- Filtrate to
— Chlorine
V well
^ — •
\
Backwash to Creek
• Distribution
GOLETA COUNTY WATER DISTRICT
CALIFORNIA
La Vista Plant
-172-
-------
Current Technology and Costs
173
Description of Sludge Disposal Process
Having no clarification process, all of the solids to be dis-
posed of come from backwashing the diatomaceous earth filters or
the activated carbon beds. The activated carbon beds are backwashed
at 6-week intervals to remove a small carry-over of diatomaceous
earth with the backwash discharged to a creek. The diatomaceous
earth filters are backwashed every 48 hours. Each backwash contains
about 850 Ib of precoat and body feed, in addition to about 70 Ib
of the removed suspended solids. Annual sludge production would be
85 tons. Part of the suspended solids consists of colloidal sulphur
particles which are removed by filtration. The backwash is passed
to an agitated slurry tank, then it is vacuum filtered.
Two Komline-Sanderson drum vacuum filters are used. Each has
a 36-inch drum diameter and a length of 36 inches. The vacuum
fluctuates between 7-10 inches Hg during operation. There is no
provision for chemical conditioning of the sludge prior to vacuum
filtration, although about 6 Ib of alum is added by hand to the agi-
tated slurry tank. The filter cake is discharged to a bin which can
be wheeled to a truck for hauling to the landfill disposal site
about 1.5 miles away. Filtrate is discharged directly to a nearby
creek.
COST OF SLUDGE DISPOSAL
The cost of vacuum filtering was reported to be $2.00 per
million gallons of water treated (1967). Included in the cost was
power, washwater, alum conditioner, labor and replacement costs.
With an average flowrate of 2.5 mgd, the above cost would be $1,825
pe r annum.
Construction Costs
2
No cost figures were available, but assuming 2,000 ft^ was
allocated to sludge handling and a unit cost of $15 per ft , the
capital cost would be $30,000. Annual cost at 6% for 25 years as-
suming 25% salvage value would be $2,210.
-------
174 Current Technology and_Cpsts
Truck
Assuming an initial value of $6,000, an economic life of 6
years and a salvage value of $1,500, the annual cost would be $1,005,
However, the truck has other uses at the plant, so half may be
charged to other purposes, leaving an annual cost of $502. Mainte-
nance, operation, insurance, licensing are calculated at $.20 per
mile. One trip per week yields an annual charge of $31. Total an-
nual trucking cost would be $533.
Land
The land requirements were small, consisting of the land area
covered by the building and driveway. Assuming a land cost of
$15,000 per acre and 0.10 acre for the sludge handling facilities,
1007o salvage value results in an annual charge of $1,500 x 67, = $90.
Vacuum Filters
The cost of each 3-ft. x 3-ft. vacuum filter is estimated as
$12,800 -f 37,200 (sq.ft./lOO) , or $23,360 for an EM index of 812.
Using an ENR index of 1,200 yields a cost of $34,500. The total
annual cost at 670 assuming a 20 year life and no salvage value
would be 2 x 34,500 x 0.08718 = 6,200.
Total Disposal Costs
(Interest on Land) (670 of 1,500) $ (90)
Power, wash water, alum, 1,825
labor and maintenance
Building 2,210
Truck 533
(Taxes and Insurance)(2% of $99,000) (1,980)
Vacuum Filters 6,200
Total $ 10,768 ($12,838)
-------
Current Technology and Costs 175
Disposal Cost / Unit
Cost per mg of water treated:
$10,768/365-2.5 = $11.80/mg ($14.10)
Cost per ton of dry solids:
$10,/768/85/ton = $126.60/ton ($151.10)
Discussion of Cost
The cost of supervision may have been omitted from the above
costs. Naturally, if it was not included in the plant's cost
allocation to sludge handling, the above figures would be propor-
tionately low.
The high proportion of diatomaceous earth in the slurry fed
to the vacuum filters accounted for most of the weight of the sol-
ids. Filtrate recovery has not practiced due to the absence of
chemical coagulation. It would have had a minor influence on the
costs. A private system would have been about 20?0 more expensive.
-------
LANSING, MICHIGAN
Flow Diagram
Chlorlrw
I Soda Ash
Dlitrlbu-
LANSING, MICHIGAN
-176-
-------
Current- Technology and Costs
177
LANSING, MICHIGAN
Recalcination
Population: 107,807 (1960)
Operator: Fred Krause
Ownership: Municipal (Board of Water and Light)
Water Source: Wells
Flows: ave. (1968) 23 mgd
cap. 40 mgd
Influent Quality:
Total hardness
Carbonate hardness
Magnesium hardness
Total solids
PH
390 mg/1 as
310 mg/1 as CaC03
140 mg/1 as CaC03
550-600 mg/1
7.1
Effluent Quality:
Total hardness
Carbonate hardness
Magnesium hardness
Total solids
PH
85 mg/1 as CaC03
35 mg/1 as CaCQ%
40 mg/1 as CaC03
210 mg/1
10.3
Method of Treatment:
Split treatment (water softening), including
coagulation, sedimentation, and rapid sand
filtration; with second-stage chlorination.
Three stage settling is used.
Chemicals Added:
Lime 250 mg/1
Soda ash 22.8 mg/1
Chlorine
Glassy polyphosphate 0.06 mg/1
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178 Current Technology and Costs
Method of Sludge Disposal
Sludge to be recalcined is removed from the 1st stage sedimen-
tation basin. This represents about 85% of all sludge produced.
The 2nd stage basin sludge is recycled, whereas the sludge from the
final basin is sent annually to a lagoon.
The sludge in the 1st stage basin is removed continuously by
scrapers. It contains 86-887o calcium carbonate at a solids content
of 12-187., and is sent to the gas scrubber of the recalcination
plant. Here the exhaust gases are cleaned, the sludge pH dropped
(setting magnesium into solution), and the sludge temperature raised
to 130°F (to increase efficiency of thickening and centrifugation).
A 4-tray 30-ft. diameter thickener is used to concentrate the
sludge to 207o solids. Then follows centrifugation (40" x 60"). The
cake is sticky (607» solids), and requires the addition of dried
sludge to create a sufficiently lumpy material which can be sent to
the waste gas stream and dried. This dried sludge is removed in a
cyclone and part is sent to a storage hopper and part back to be
mixed with the centrifuge cake. The majority is blown into the re-
actor.
Recalcination is accomplished by driving off CC^ from the CaC03,
which is done here with heat from the burning of fuel oil. The ver-
tical reactor is fired near the bottom. Dry sludge enters near the
bottom and rises with the gas stream. As agglomeration'develops,
the pellets formed drop. The lime is removed at the bottom and sent
by bucket elevator to the lime storage bin. Some dusty lime is re-
circulated, and soda ash (0 - %7») is added to aid agglomeration.
One lagoon of 16.5 acres serves to receive sludge from the final
sedimentation basin, the thickener over-flow, and the centrate. It
is located along the river, 7,000 feet away. The pipeline and pumps
were installed at the time of original construction of the water
treatment plant (1939).
The system described is the "Fluo-Solids Calciner" built by the
Dorr-Oliver Company. Advantages of low fuel requirements are claimed.
The reactor, centrifuge, etc. (except the thickener) are located in
one compact building (see photo).
A very approximate average flow and solids balance follows:
-------
Current Technology and Costs
179
Solids Balance (ave.daily)
Thickener
Influent
Overflow
Underflow
Centrifuge Feed
Centrate
Cake
Reactor
Input
Output
Flow Rate
Solids Content
100,000 gals 12.
30,600 gals 0.9
59,400 gals 20
43,400 gals 3
16,000 gals (68 tons) 65
44 tons
25 tons
100.
CaO =
100
Solids Rate
(tons)
50
1
49
5
44
44
25
o
A sludge density of 62.4 Ibs/ft was used in the calculations.
This leads to a slight error in the balance. More correctly, for
instance, a figure of 68 Ibs/ft should be used at a 157o solids
content.
COST OF RECALCULATION
Capital Costs-
The existing plant was built in 1954 at a cost of $420,000,
financed from revenues. It is claimed that $80,000 of equipment
was unnecessary. However, the lagoon was built in 1939, along
with the pipeline and pumps. Hence a figure of $.1,000,000 as 1968
replacement value could be used. Salvage value after 25 years is
figured at 25%.
Land Costs
The recalcination plant and thickener use little land (<1 acre),
Assume $40,000, which will also allow for the la-goon.
-------
MIAMI, FLORIDA
Hialeah Plant
Lime Storage Silo
LANSING, MICHIGAN
Recalcination Building
Sludge Thickener in
Left Background
-180-
-------
Current Technology and Costs
Operation
The plant is running at 2/3 capacity; that is, 1967 production
was 7,500 tons of lime, or 20.5 tons/day. Plant capacity is 31.5
tons/day and shutdowns are infrequent. Were sufficient sludge
available, a 90% utilization should be obtainable (10,400 tons/year)
As of now this figure is reached only occasionally over a one or
two month period.
It takes 60-65 gallons of modified #6 oil per ton of lime.
This oil sells at 8.3£/gal, with a resulting annual fuel cost of
$57,300.
Only one man is required per shift, necessitating a staff of
five. Their wages could be $10,000/year/man, or $50,000/year. An
additional 107o should be charged for supervision.
Maintenance would be about $15,000/year; power at $37,000/year.
(These figures are based on 1960-1962 data for 5,000 tons/year pro-
duction). Similarly, supplies would cost perhaps $8,000 per annum.
Value of Lime
Only 85% of the lime needs of the water treatment plant are met
by the lime production from the recalcination plant. The remainder
is purchased at $17.50/ton.
Total Costs
Capital recovery ($1,000,000-$250,000 @ 6% for 25 yrs.) $58,600
Interest ($250,000 @ 6%) 15,000
Operation 172,300
(Taxes and Insurance) ($1,040,000 @ 2%) (20,080)
(Interest on Land) ($40,000 Q 6%) (2,400)
Sub-Total $245,900/year
Less sale of lime (10,400 tons @ $17.50/ton) 182,000
Gross loss $ 63,900/year
($86,400)
-------
182 Current Technology and Costs
Cost / Unit
Cost / rag of water treated:
Sufficient sludge is not produced to allow for a 90% utili-
zation of calcination capacity. A raw influent flow of
10,400 . 23 = 32 mg would be required.
7,500
$ 63,900/32 = $2.00/mg ($2.70)
Cost / ton of lime produced:
$ 63,900/10,400 = $6.15/ton ($8.30)
Cost / ton of sludge solids:
Two tons of solids yield approximately one ton of lime.
Approximately 85% of the sludge is used for recalcination.
$ 63,900/20,800/0.85 = $2.60/ton ($3.50)
Discussion of Cost
According to the assumptions used, the value of the lime pro-
duced is approximately equal to the cost of recalcination. However,
this does not take into account the fact that the sludge disposal
problem is eliminated, a large saving in itself. It should also be
noted that a slight change in the estimated costs can sharply in-
crease or decrease the cost for recalcination per unit.
Figures supplied by Lansing are as follows:
1960-61 61-62 62-63 63-64 64-65 65-66
Production cost $ 17.72/ton 17.52 --- 16.69 16.76 16.73
A slight profit is seen here, but again the savings from eliminating
the sludge disposal problem are not included. The original construc-
tion had the benefit of no financing or land charges.
-------
183
Current Technology and Costs
LOMPOC, CALIFORNIA
Lime-Soda Softening and Diatomaceous Earth Filtration
Superintendent: Dale E. Batchelor
Ownership: Municipal
Water Source: Wells
Flows: ave. 4.1 ragd
cap. 7.0 mgd
Influent Quality:
Ca MS Fe Mn Cl_ SO/, TDS Turb.
159 69 1.83 0.57 99 400 1,158 0.65
T Hardness(CaC03)
684
Effluent Quality:
Ca MG Fe
29 18 0
MS £1 S04 CJL2 TDS Turb. T Hard.(CaCO^)
0 100 390 0.39 835 0.21 147
Method of Treatment:
Chemicals Added:
(July 1968)
Pre-chlorination, coagulation, sedimentation,
recarbonation, diatomaceous earth filtration;
post chlorination.
Lime
Soda Ash
Nalco 671
Chlorine
Diatomaceous Earth
376 mg/1
295 mg/1
0.251 mg/1
2.3 mg/1
10.31 mg/1
Sludge Production:
Softening sludge
Diatomaceous earth
backwash
120,000 gals/day @ 47. solids
2,600 gals/day
-------
LOMPOC, CALIFORNIA
Flow Diagram
OPEN BEOS FOR DRYING OF WASTE DIATOMITE
AMD SLUDGE FROM SOFTENING PROCESS
CLEAR WELL
STORAGE TANK
CHLORINATION AND POST-PHOSPHATE
^OIATOMACEOUS EARTH FILTER
/ AID DELIVERY
' \ ^_
V X - DIATOMITE FUTURE '
^- FACILITY I
J^ FILTERS ^ FILTERS j
I
1
BOOSTER | FUTURE
PUMPS | ADDITION
1
I !
i i_
CAR80N •<-
A
T
CL ARIDER
SLOW 4
r
— DIOXIDE
.4
T
CLARIFIER
J
T MIX
±
T LIME — CHEMICAL BUILDING
1 OtLWtHI FEED OND RAp|D
* M\X CHEMICALS
I ALSO PRECHLORINATION
T LAB. OFFICE
1
FUTURE
ADDITION
J
— SODA ASH . PHOSPHATE ,
ALUMINATE , AND
CHLORINE DELIVERY
1 t
| f MUN
"^ TO 1 INCOMING
1 DISTRIBUTION » WELL KOEBIG
^ SYSTEM J WATER ENGIN
PLANT
INITIAL
EVENTUAL
7,000
14 ,000
000
ooo
CAPACITY
GALLONS
GALLONS
PER
PER
DAY
DAY
PLANT CAPABILITY ' •
TYPE
WATER
RAW
TREATED
(AVERAGE)
TOTAL HARDNESS , CiC05
PARTS PER
MILLION
750
ISO
GRAINS PER
GALLON
4 4
88
NOTE: DELIVERED WATER HftRONESS IS ADJUSTABLE.
CITY OF LOMPOC , CALIFORNIA
MUNICIPAL WATER TREATMENT PLANT
DECEMBER 19 , 1963
ENGINEERING - ARCHITECTURE
FRED J EARLY CO , ,NC
GENERAL CONTriACTOR
-184-
-------
Current Technology and Costs 185
Description of Sludge Disposal Process
The sludge from the softening units is pumped to the dewatering
and drying beds. However, about 207= of the sludge from the bottom
of the clarifier is pumped back to the flash mixer. The recirculated
sludge stabilizes the softening process and saves some chemical
costs. Also, the wash water is pumped directly to the beds.
The dewatering and drying beds are filled with sludge, then
they are decanted with the decant returned to the plant influent.
Each of the 8 beds measures 140 ft. x 140 ft. on the bottom, and
160 ft. x 160 ft. at the top. The berm separating the beds is about
10 ft. wide. A total of 6 acres is now devoted to the sludge de-
watering and drying beds. When the bed is filled with 4 to 5 ft. of
sludge, it is left to drain and dry. In about 4 months the sludge
has dried to a 50% solids content. It is then removed with front
end loaders and placed in trucks for transport to a landfill dispos-
al site about 2 miles away.
The beds were constructed with sand bottoms and a special 15 ft.
diameter core in the center of the bed was dug about 15 ft. deep,
then refilled with sand. Its purpose was to aid dewatering by inter-
secting a permeable natural sand layer at the 15 ft depth.
Softening sludge production is 365 x 120,000 gals/day x 0.04 lb/
sludge x 8.34 = 14,600,000 Ib/yr. = 7,300 tons/yr. In addition, per-
haps 100 tons/yr. of backwash solids are added to the beds.
COST OF SLUDGE DISPOSAL
Land
Land costs are estimated at $10,000 per acre near the plant,
yielding a land value of $60,000. Preparation of the dewatering and
drying beds was assumed to cost $5,000 per acre, or a total of
$30,000.
Sludge Removal
Sludge removal and transport to the fill site is estimated to
cost $20,650.
-------
186 Current Technology and Costs
Labor_and Supervision
Perhaps 107.. of the plant's labor and supervision time is devot-
ed to the dewatering and drying beds, yielding a cost of $7,725.
Maintenance and Operation
Power for sludge pumping is estimated at $1,000 per annum.
Maintenance is estimated to cost $1,000 per year.
Total Disposal Costs
(Taxes)(2% of $60,000) $ (1,200)
(Interest on Land)(6% of $60,000) (3,600)
Land Preparation ($30,000 @ 6%, 30 years) 2,180
Sludge Removal 20,650
Labor and Supervision 7,725
Maintenance and Operation 2,000
Total $ 36,155 ($37,355)
Disposal Cost /Unit
Cost per mg of water treated:
$36,155/365-4.1 = $24.20/mg ($25.00/mg)
Cost per ton of solids:
$36,155/7,400/ton = $4.89/ton ($5.05/ton)
Discussion of Costs
The sludge removal and disposal cost of $20,650 appears to be
a reasonable estimate based upon extensive documentation from prior
years' costs.
-------
Current Technology and Costs 187_
No allowance was made for the value of the decant which was
reclaimed. However, based on the cost of pumping an equivalent
volume of water from the well field, the decant had a value of
about $5,000 per year.
The land cost was taken as a high value of $10,000 per acre.
However, each $1,000 per acre increase in land costs would only
increase the sludge handling cost by 1.570.
-------
LOS GATOS, CALIFORNIA
RinconadcrTreatment- Plant - Flow Diagram
Influent
Alum
Distribution
Decant to
Creek
Solids Trucked
to Landfill
SANTA CLARA COUNTY
CALIFORNIA
Rinconada Water Treatment Plant
-188-
-------
Current Technology and Costs 189
LOS GATOS, CALIFORNIA
RINCONADA WATER TREATMENT PLANT
Alum Sludge to Drying Beds
Ownership: Santa Clara County Flood Control and Water Conservation
District
Flows: ave. 10 mgd
cap. 40 mgd
Influent Quality: (Composite October 1968)
Ca Mg Na K Fe HC03 Cl S0_4 F B IDS
18.8 10.4 32 2.9 1.05 66 56 35 0.2 0.26 "268 mg/1
Turbidity 52
Total Hardness (CaC03> 88
Method of Treatment: Flash mixing, flocculation, sedimentation,
rapid sand filtration, chlorination.
Chemicals Added: Alum 16-20 mg/1
Chlorine
Description of Sludge Disposal Process
Wash water recovery is practiced by discharging the wash water
to two 700,000 gallon capacity recovery basins. The sludge may be
flushed to the drying beds. It is estimated that the wash water
recovery basin will be cleaned once every six months. As the plant
is new, it has been cleaned only once.
The sludge from the sedimentation basins may be discharged to
any of a set of 10 drying cells measuring 21 ft. x 100 ft. x 3% ft.
-------
LOS GATOS, CALIFORNIA
Drying Alum Sludge
Alum Sludge Dewatering and Drying Beds
Crack Development in Drying Alum Sludge
-190-
-------
Current Technology and Costs 191
deep, or to either of two other drying beds measuring approximately
80 ft. x 600 ft. All the drying beds are underdrained.
The drying beds may be decanted with the decant discharged to
a creek.
Cost of Sludge Disposal
The plant is new, and sludge disposal costs are not yet avail-
able.
-------
MIAMI, FLORIDA
Hlaleah Plant - Flow Diagram
Wells j~MixerJ
Wells | mixer I*
Upfiow
Clarifier
. Fluoride
Washwater
Washwoter
Floe
inn
Sedimentation
Basin
Make-up Sludge
Washwoter
_ f.1§5I?D'_ fi*!^.
H1ALEAH PLANT
. Fluoride
U
Bockwosh
Overflow
Sludge
Distribution
Thickener
8 Storage
.2
I
T
Lagoon
J
Lime
1 — ' — 1 Kiln
c
z>
bTora" L _^^ Cake /
X / i— —~ — \
1 j. Fuel Oil Centrifuge
Cenrrote
MIAMS, FLORIDA
-192-
-------
Current Technology and Costs
193
MIAMI, FLORIDA
Recalcination
Population: Three treatment plants serve 730,000 (1965)
Superintendent of Lime Recovery: Guy C. Collins
Ownership: Municipal
Sources: Wells
Flows: Hialeah Plant
Preston Plant
ave. (1958) 36 mgd
cap. 60 mgd
ave. (1968) 45 mgd
cap. 60 mgd
Influent Quality:
Total hardness 236
Carbonate hardness 224
Magnesium 6.4
Total solids 330
Iron 1.1
pH 7.3
mg/1 as CaC03
mg/1 as CaC03
mg/1
mg/1
mg/1
Effluent Quality:
Total hardness 75
Carbonate hardness 40
Magnesium -5.5
Total solids 185
Iron 0
pH 9.0
mg/1 as CaC03
mg/1 as CaC03
mg/1
mg/1
Method of Treatment:
Coagulation, sedimentation (Hialeah), or
upflow clarification (Preston), and rapid
sand filtration; with pre-chlorination and
fluoridation.
-------
MIAMI, FLORIDA
Hialeah Plant
Centrifuge for Dewatering Lime Sludge
-194-
-------
Current Technology and Costs _^_^_ Ig5
Chemicals Added: Lime 150-160 mg/1
Sodium silicate 2 mg/1
Chlorine
Fluoride 1 mg/1
Method of Sludge Disposal
The Hialeah and Preston plants are adjacent to one another.
Recalcination is done at the Hialeah plant and receives sludge from
both. Sludge from Preston is removed continuously over to one of
three thickeners at Hialeah, where it joins the intermittent (5 min.
on, 5 min. off) flow of sludge from the Hialeah sedimentation basins.
The large thickener (90 ft. diameter) serves partially as a
storage unit, whereas the other two, each 32 ft. in diameter, are
operated continuously. The sludge enters at a high solids content
(up to 307o) and leaves at about 40%. Overflow is returned to the
head of the plant.
The sludge is then sent to two centrifuges (40" x 60") and
brought to a toothpaste consistency of 657» solids. The centrate,
containing about 57, solids, is sent to a lagoon, where by-pass
and excess sludge is also sent.
A screw conveyor carries the sludge cake into the 7.5 ft. di-
ameter, 230 ft. long rotary kiln. There are three lime storage
silos from which lime is drawn to supply both treatment plants
(Hialeah and Preston) plus a portion of a third plant. Each pound
of lime added in treatment yields 1.35 pounds of lime by recalcin-
ation.
The lagoon previously described covers 20 acres. Sludge is
withdrawn from here at times by a scraper and tugger hoist and
trucked to the plant to provide make-up material for the recalcin-
ation plant. This lagoon has accumulations from times previous to
the construction of the plant (1936-1949).
The recalcination plant is shut down about 20 days each year,
or about 5% of the time. Capacity of the plant is 97 tons/day,
although the initial rating was 80 tons/day. A flow and solids
balance sheet might look like this:
-------
196
Current Technology and Costs
Flow and Solids Balance (ave. daily)
Thickener
Centrifuge
Kiln
Influent*
Overflow
Underflow
Feed
Centrate
Cake
Input
Output
Flow Rate
320,000 gals
230,000 gals
90,000 gals
Solids Content
12.
1.
40.
39,000 gals 7.5
51,000 gals (213 tons) 65
213 tons
77 tons CaO
100
CaCO.
Solids Rate
(tons)
160
10
150
12
138
77
^includes an average of 11-12% make-up sludge. Note
also that a sludge density of 62.4 Ibs/ft was used
throughout the table.
COST OF SLUDGE DISPOSAL
Construction Costs
The original construction cost for the plant was $792,000 in
1948. Since then additions have brought this figure to approximately
$1,200,000. A silo was added in 1964 at a cost of $100,000, and the
large thickener at a cost of about $150,000 in 1965. The Handy-Whit-
man Water Works Cost Index suggests a present day replacement value
of $2,200,000. Miami depreciates at 1%2,/year (straight-line). This
is unrealistic, and a more likely salvage value at the end of 25
years is $550,000 (25%). This should include sufficient allowance
for lagoon construction costs (originally a pond).
Land Costs
The plant uses about 3 acres, valued at $15,000/acre. The la-
goon covers 20 acres, but could be smaller for a new design. Its
value may be set at $100,000.
-------
Current Technology and Costs _197
Operating Costs
Projections based on past years indicate $250,000/year for a
production of 32,000 tons/year, representing 907o of capacity pro-
duction.
Value of Lime
Additional lime needed for the third treatment plant costs
$2l.l3/ton delivered.
Annual Costs
Capital recovery ($1,650,000 @ 6% for 25 years) $129,000
Operation 250,000
Interest on salvage ($550,000 @ 6%) 33,000
(Interest on land) ($145,000 @ 6%) (8,700)
(Taxes and Insurance) (2% of $2,345,000) (46,900)
Sub-Total 412,000/yr.($467,600)
Less value of lime (32,000 tons @ $21.13/ton) 676,000
Gross Profit $264,000/yr.($208,400)
Profit / Unit
Profit/mg of water treated:
Sludge is in fact "mined" from the lagoon, and as a result
the lime produced beyond 25,000 tons/year comes from past
accumulations and flows. A production of 32,000 tons/year
represents a flow of 38,000 ing.
$264,000/38,000 = $6.95/mg ($5.50)
Profit/ton of lime produced:
$264,000/25,000 = $10.55/ton ($8.35)
-------
198 t p Current Technology and Costs
Profit/ton of sludge solids
$10. 55/ - = $5.08/ton ($4.00)
Discussion of Profit
The profits indicated are about 11.2% (8.97.) of the total in-
vestment, which is attractive. Lime prices in the region appear
stable, and it seems that lime recovery in this instance is to be
recommended. Miami has calculated their profits to be running at
$300,000/year. The calculations here show lower profits, chiefly
due to the differences in interest rates (6% vs. 2.87o) and, of
course, capital costs.
-------
Current Technology and Costs 199
Ml NOT, NORTH DAKOTA
Vacuum Filtration of Lime Softening Sludge
Population: Minot 35,000: Air Force Base 15,000
Superintendent: Glenn Berg
Ownership: Municipal
Water Source: Mouse River and 13 wells. The river supplies about
half the water and the wells the other half.
Flow: Plant capacity 18. mgd
Summertime water availability limits the production to
10 mgd, winter production is 3.5 mgd
Influent Quality:
Total hardness for combined flow from wells varies from
250-450 mg/1 as CaCC^.
Total hardness for the river is low during spring runoff
and reaches 480 mg/1 as CaCO., during low flows.
Typical Analyses of wells (as CaCC^):
Hardness Ca Mg Na+K HC03 Cl S04 Fe as Fe
Well No.l 166 93 73 395 440 1.08 17 1.0
Well No.2 315 188 127 539 577 175 100 2.0
Well No.3 347 233 114 1,029 806 423 149 3.0
Effluent Quality: Total hardness 84 mg/1 as CaC03
Calcium hardness 39 mg/1 as
Method of Treatment: Well water receives aeration, sodium
aluminate addition, lime softening,
-------
MINOT, NORTH DAKOTA
Flow Diagram
Mouse River
Row Water
Distribution
Chlorine
Backwash Water
to Mouse River
•MINOT, NORTH DAKOTA
Water Treatment Plant
-200-
-------
Current Technology and Costs 201
Method of Treatment: clarification, recarbonation, rapid
(continued) sand filtration and chlorination.
River water receives aeration, pre-
chlorination, sedimentation, sodium
aluminate addition, lime softening,
clarification, recarbonation, rapid
sand filtration and chlorination,
The river and well waters are mixed
at the sodium aluminate addition step.
Chemicals Added: Chlorine
Sodium aluminate
Lime 426 mg/1
Polyphosphate
Description of Sludge Disposal Process
Sludge from filter backwash water is discharged directly to the
Mouse River. Approximately 3 tons of dry solids are produced per
million gallons of water treated. The sludge from the upflow Walker
Process clarification unit is discharged to a sludge thickener lo-
cated in a separate building housing the vacuum filters. From the
thickener the sludge goes to two EIMCO vacuum filters, one 8-ft.
diameter by 10-ft. long, and the other 8-ft. diameter by 8-ft. long.
The vacuum filters are equipped with Eimcobelt filter cloths.
The two filters operate three days/week in the winter, and more
often in the summer. They each average 18 hours of operation for
each 70 hours of plant operation. Filtrate is returned to the clar-
ifier.
The sludge cake, having approximately 44% solids, is moved by
conveyor belt from the vacuum filters to discharge to one of three
hoppers. The hoppers can be emptied into a dump truck for transport
to the landfill disposal site on the plant grounds. At the landfill
site the sludge is dumped over the edge of an embankment of sludge
cake. Spreading several inches of gravel on the surface of the fill
provides sufficient traction for the truck. No problem of embank-
ment settlement has been noted.
Special modifications consisting of the installation of rubber
seals in the dump truck box were necessary to minimize sludge leak-
age during transport. Prior experience in hauling sludge cake to
the town dump had shown vehicles could easily become stuck in any
-------
202 Current Technology and Costs
sludge spilled on the ground.
Total sludge production was estimated to be three tons of dry
solids per million gallons. Annual production based on an average
flow of 5 mgd would be 5 mgd • 3 _T • 365 day = 5,470 tons/yr.
mg yr
COST OF SLUDGE DISPOSAL
Land
It is estimated that 5 acres of the land is devoted to sludge
handling purposes, including the disposal site. The unit cost is
estimated as $1,000 per acre, resulting in a land value of $5,000.
Full salvage is assumed.
Building
A 70-ft, by 40-ft. two-story building which houses the thick-
ener and vacuum filters cost $184,700 in 1962. However, this fig-
ure included the sludge thickener and the 10-ft. by 10-ft. vacuum
filter. Deducting $37,000, the estimated 1962 cost of the vacuum
filter leaves a building and thickener cost of $147,700. An eco-
nomic life of 30 years with a 25% salvage value is assumed.
Vacuum Filters
The 8-ft. by 10-ft. vacuum filter was salvaged from the sewage
treatment plant and converted for use at the water treatment plant
at a cost of $7,200. For purposes of calculating sludge disposal
costs it is preferred to calculate the vacuum filter's 1962 re-
placement value as $33,000. The 1968 cost of the two vaccum filters
would be $70,000 x 1,200/850 = $99,000.
Operation and maintenance is estimated to be $19,250 per year
based on the report WP-20-9 and an average flow of 5 mgd.
-------
Current Technology and Costs ^ 203
Truck
The estimated cost of the truck is $7,500. Due to the modified
box for sludge hauling, it has few other uses. Operation and main-
tenance is estimated as $500 per annum. 25% salvage after six years
is assumed.
Labor
Included in operation and maintenance of the vacuum filter,
Annual Costs
Vacuum Filters ($99,000 @ 6% for 20 years) $ 8,630
(Interest on land) ($5,000 x 6%) (300)
Building (757= of $147,700 @ 6% for 30 years) 8,040
Interest on building salvage (25% of $147,700 @ 6%) . 2,210
Truck (75% of $7,500@ 6% for 6 years) 1,141
Interest on truck salvage (25% of $7,500 @ 6%) 112
Operation and maintenance of truck 500
Operation and maintenance of vacuum filters 19,250
(Taxes and insurance) (2% of $251,700) (5,034)
Total $ 39,883 ($45,217)
Cost / Unit
Cost per million gallons:
$39,883/5-365 = $21.80/mg
$45,217/5-365 = ($24.80/mg)
Cost per ton of dry solids:
$39,883/5,570 ton = $7.29/ton
$45,217/5,470 ton = ($8.26/ton)
-------
204 Current Technology and Costs
Discussion of Cost
The major cost item was the operation and maintenance of the
vacuum filters. Included in the cost were the labor and supervision
charges. The plant superintendent estimated two full-time equiv-
alent men were required for the vacuum filter operation at a wage
cost of $10,400 per annum. Indirect costs would increase this fig-
ure, as would cost of supervision, which may run to $2,000 per year.
Power costs, repairs and special maintenance are thought to be suf-
ficient to bring the operation and maintenance estimate to $19,250.
The large reduction in hardness with the concomitant large
sludge production makes the unit cost per ton quite low. The aver-
age influent turbidity was low due to upstream reservoirs on the
Mouse River and the availability of groundwater to use should the
river water temporarily become turbid. The dewaterability of soft-
ening sludge is high in contrast with an alum sludge. Had the in-
fluent been more turbid, there undoubtedly would have been a sig-
nificant increase in the sludge handling costs.
The cost is relatively independent of changes in land prices.
Had the land price been $10,000 per acre instead of $1,000, the
sludge handling costs would have increased less than 10%.
-------
Current Technology and Costs 205
NEW BRITAIN, CONNECTICUT
Serial Lagoons
Population: 85,000
Superintendent: Fred Sarra
Ownership: Municipal
Water Source: Reservoirs
Flow: ave.(August 1967-1968) 9 mgd
cap. 20 mgd
Influent Quality: Total hardness 17 mg/1 as CaC03
Alkalinity 15 mg/1 as CaC03
Color 12
Turbidity 2-5
pH 6.9
Effluent Quality: Total hardness 37 - 39 mg/1 as CaC03
Alkalinity 17 mg/1 as CaC03
pH 8.7 - 8.8
Method of Treatment: Coagulation, sedimentation, and rapid sand
filtration; with chlorination.
Chemicals Added: Lime 10 mg/1
Alum (aluminum oxide) 10 mg/1
Chlorine
Description of Sludge Disposal Process
Washwater is sent to a concentration lagoon, with an overflow
-------
NEW BRITAIN, CONNECTICUT
Flow Diagram
Reservoirs | milt
Floe.
D-
Lime Alum
Overflow
Sedimentation
Basin
Sludge
Woshwoter
Woshwater
o
Woshwater
Storage
Truck
Overflow
' to Stream
NEW BRITAIN, CONN.
-206-
-------
Current Technology and Costs 207
to a canal leading to one of the reservoirs. Flashboards at another
point can decant to the canal, leaving sludge to be sent by gravity
to a sludge storage lagoon.
Every 4 months, the 4 sedimentation basins are cleaned out by
gravity flow and flushing. A cleaning period of 7-10 days is re-
quired. The sludge flows through the previously emptied washwater
concentration lagoon into the storage lagoon. This storage lagoon
is equipped with flashboards for decantation into a stream.
The concentration lagoon is built out of a hillside, with a.
13 ft. high levee on the downslope side. This elliptical lagoon has
an area of 3/4 acre, with an average depth of 6 ft. Approximately
the same dimensions apply to the storage lagoon, with the exception
of the depth, which is only 4.5 feet.
Cleaning of the storage lagoon by contract is about every 5
years, using a dragline. The sludge is spread on the roadsides of
the large watershed belonging to the system. The lagoons are 30
years old.
COST OF SLUDGE DISPOSAL (ALL 1968 COSTS)
Construction
Figured from construction drawings
Piping $ 19,500
Excavation 18,100
Embankments 36,200
Drainage structures and misc. 10,000
Sub-Total 83,800
+ 25% 20,950
Total $104,750
Land
The 3 acres are worth $9,000,
-------
208 Current Technology and Costs
Operation
Perhaps %/hr/day should be allotted for the daily tour, in
addition to 2 men required to coordinate controls during basin clean-
ings. Estimate $5,000 for all labor and supervision per year, plus
auto costs, etc.
Disposal
A cleaning of the storage lagoon every 5 years costs $7,500, or
$l,500/year.
Total Disposal Costs
Capital recovery ($105,000-25,000 @ 6% for 25 years) $ 6,250
Annual costs 3,000
Interest on salvage ($25,000 @ 67=,) 1*500
(Interest on land) ($9,000 @ 6%) (540)
(Taxes and Insurance) (2% of $114,000) (2,280)
Total $10,750/year ($13,570)
The washwater recovered is negligible, as much of it infiltrates
over the half-mile length of canal. There is a salvage value to the
lagoons, however. This may be estimated to be $25,000,
Disposal Cost / Unit
Cost/mg of water treated:
$10,750/9-365 = $3.30/mg ($4.10)
Cost/ton of dry solids:
The basins when emptied contain 8-10 feet of sludge. The
volume of sludge per year is 3'27,800'9 = 750,000 ft.3, or as-
suming a solids content of 1.5%, the tons/year is 350. Four
feet of sludge at 5% solids accumulated in 5 years calculates
out as 200 tons/year.
$10,750/275 = $39.00/ton ($49.30)
-------
Current Technology and Costs 209
Discussion of Cost
The costs are highly dependent on the initial construction, and
in turn the useful life of the lagoons. Costs for a private system
would be about 25% greater. It should be noted that the concentra-
tion lagoon serves little purpose for sludge disposal, and its cost
should be allocated to backwash disposal.
-------
POINT PLEASANT BEACH, NEW JERSEY
Flow Diagram
Diatomaceous Earth
Calcine Magnesia
Wells
Mixer
Del
Tank
Wash water
Diat.
Earth
Filter
Distribution
Sewer
POINT PLEASANT BEACH, NEW JERSEY
-210-
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Current Technology and Costs
211
POINT PLEASANT BEACH, NEW JERSEY
Disposal to Sewer
Population: 4,500 permanent, 25,000 temporary
Operator: Robert K. Mickle
Ownership: Municipal
Water Source: Wells
Flows: ave. 0.75 mgd
peak 2.0 mgd
Influent Quality:
Total hardness
Alkalinity
Calcium
Iron
pH
26-42 mg/1 as CaC03
24-33 mg/1 as CaC03
10-26 mg/1
1.2-4.0 mg/1
6.48
Method of Treatment:
Flocculation, diatomaceous earth filtration,
and, chlorination.
Chemicals Added:
Calcine magnesia
Chlorine
Description of Disposal Process:
The washwater is collected in a 10,000 gallon holding tank, from
which it is pumped into an 8" sewer. The tank was needed to distri-
bute the flow, as the sewer has a capacity of only 230 gpm. The sew-
age treatment plant, municipally owned, provides only primary treat-
ment. No problems from the washwater have been encountered, and no
charges are levied.
-------
SAN FRANCISCO, CALIFORNIA
Sunol Valley Filtration Plant - Flow Diagram
Calaveras Reservoir
San Antonio Reservoir
Sunol Infiltration
System
Decant to
Creek -•
CakeTrucke
To LandTiT
i
d
Alum (pH Control )
rUimetpH Control)
r — Activated Silica
Flash
Mix
/^
"\_
Rocculating
Chamber
Sludge
Decan4
Drying
Beds
Sludge
1 — Polyelectrolyte
Sedimentation
Basins
| Dual- Media
Filters
Filter
Backwash
Reclamation
San Francisco Water Department
Sunol Vallsy Filt ration plant
Aqueduct
212
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Current Technology and Costs
213
SAN FRANCISCO, CALIFORNIA
SUNOL, VALLEY FILTRATION PLANT
Alum Sludge to Drying Beds
Superintendent: David M. Reeser
Ownership: San Francisco Water Department
Capacity:
The plant balances the load on the Hetch
Hetchy aqueduct serving San Francisco and
neighboring communities. It is therefore
subject to rapid variations in flow. The
range in flowrates has been between 8 to
80 mgd. The design flow was 40 mgd.
Influent Quality:
Turbidity is highly variable, as the plant
draws from surface reservoirs. During
winter rains it may reach 1,500 J.T.U.,
while during the summer dry season turbidi-
ties of 1-2 J.T.U. are common.
Effluent Quality:
Turbidity of 1 J.T.U. is expected.
Method of Treatment:
Flash mixing, flocculation, sedimentation,
dual media filters; post chlorination.
Chemicals Added:
Chlorine
Lime
Activiated sodium silicate
Alum during winter
Polyelectrolyte (Separan MP-10)
During the summer coagulation is not pra-
cticed and the polyelectrolyte is added
immedialtely prior to the filters as a
filter aid. Activated silica is used in
-------
SAN FRANCISCO, CALIFORNIA
Sunol Valley Filtration Plant
Filter Washwater Recovery Basins
Alum Sludge Drying Beds
214
-------
Current Technology and Costs _... 215
Chemicals Added: the winter along with alum. There is
(continued) insufficient alkalinity present and lime
is added to the effluent for pH control.
Description of Sludge Disposal Process
Sludge from the sedimentation basins goes to two drying beds.
The sludge is added continuously during the period when coagulation
is practiced.
Backwash water is reclaimed by discharging it to two holding
basins, allowing the solids to settle and returning the supernatant
to the plant influent. The solids are drawn off intermittently and
are flushed to the drying beds.
The drying beds are constructed to permit decantation of the
supernatant which is discharged to a nearby creek. The floor and
banks of the drying bed are natural earth with no special provision
to encourage seepage.
The filling depth of the drying beds is thought to be critical.
In 1966-1967 the beds were filled with 4 ft. of sludge. After 6
months in the beds (June - December), only the top 2 ft. had cracked
and dried. In 1967-1968 the beds were filled to a depth of 2 ft.
with sludge. After 4 months 200 yd. was removed from one bed and
300 yd.^ was removed from the other. The weight of dry solids is
estimated as 250 tons.
COST OF SLUDGE DISPOSAL
Land
Area of the two drying beds is estimated as 8 acres. The land
has been owned by the San Francisco Water Department for many years.
The disposal site is also on Water Department property. Its area
is estimated as 2 acres. Another acre may be assumed for access
roads. Assuming a land value of $2,000 per acre results in a land
value of $22,000.
Land Preparation
Construction of the drying beds and the connecting sludge lines
-------
SAN FRANCISCO, CALIFORNIA
Sunol Valley Filtration Plant
.
liiWTO-
Drying Alum Sludge
Disposal Site - Dried Alum Sludge
216
-------
Current Technology and Costs ^_ 217
is estimated as $30,000.
Labor and Supervision
During regular operation this may be equivalent to one full-
time man costing $9,000 per year.
Removal Costs
Removal is by outside contract. A front end loader and two
trucks are needed for about one week per year. Cost is estimated
to be $1,500 per annum.
Total Sludge Disposal Costs
Interest on Land ($22,000 @ 6%) $ 1,320
(Taxes) (2% of $22,000 ) (440)
Preparation of Land ($30,000 <§ 6% for 25 yr.) 2,350
Labor and Supervision 9,000
Removal 1,500
Total $ 14,170 ($14,610)
Cost / Unit
Cost per mg treated: (assume 12,000 mg/yr.-)
$14,170/12,000 = $1.18/mg. ($1.22/mg)
Cost per ton of dry solids:
$14,170/250 = $56.60/ton ($58.50/ton)
-------
218 Current Technology and Costs
Discussion of Costs
The labor and supervision cost allocation of $9,000 is thought
high in that there are eight employees at the plant, but the drying
beds require minimal attention during the summer. As this represents
2/3 of the cost, a change will produce a proportionate change in the
cost per unit.
The removal costs would increase greatly if the sludge were
applied in greater debths so that it would dry more slowly.
-------
Current Technology and Costs
219
SOMERVILLE, NEW JERSEY
Lagoons
Superintendent: Jerry Caden
Ownership: Elizabethtown Water Co. Consol., serving 20-30 communities
Water Source: River
Flow: ave. (1967) 90.2 mgd
cap. 170 mgd
Influent Quality:
(September 12, 1968 - 5 samples)
Turbidity 1-30
Total hardness 76-130
Alkalinity 58-77
pH 6.7 - 8.3
Total solids 125-240
mg/1 as CaC03
mg/1 as
mg/1
Method of Treatment:
Flocculation, sedimentation, and rapid sand
filtration; with chlorination.
Chemicals Added:
Alum
Permanganate
Chlorine
Lime
Ammonia
40
0.85
3.3
0.89
0.31
mg/1
mg/1
mg/1
mg/1
mg/1
Description of Sludge Disposal Process
The sedimentation basin is cleaned twice yearly, with the sludge
pumped to a lagoon measuring 400 x 1,200 feet. The lagoon consists
of previously existing roadways on three sides, with a dike as a
fourth side, built about ten years ago by plant personnel. Decant
-------
SOMMERVILLE, NEW JERSEY
Flow Diagram
Floe.
Rivers ^1 Mixer
FL
Carbon Alum
Supernatant
Distribution
Washwaler
SOMERVILLE, NEW JERSEY
220
-------
Current Technology and Costs 221
is removed by overflow pipes. Present depth of sludge is 3% ft.
The lagoon has never been cleaned, and after the total depth of
6 feet is exhausted, cleaning or raising the dike will be necessary.
Backwash water passes directly to the river, as does the lagoon
decant. As a result, the sludge has an opportunity to dry suffi-
ciently to permit walking.
COST OF SLUDGE DISPOSAL
Construction
No cost records were kept, but it may be assumed that present
cost for the construction would be on the order of $10,000.
Land
12 acres are used for the lagoon. This land is worth perhaps
$10,000/acre today, or $120,000. Since estimates for cleaning of the
lagoon are not available, the land is written off at 257.. salvage.
Annual Costs
These are considered very small - perhaps $2,000. The life ex-
pectancy of the lagoon is greater than 20 years with slight changes
to the dike.
Total Disposal Costs
(Based on 1968 throughout)
Capital recovery (6% for 25 years) $ 700 ($7,800)*
Annual Costs 2,000
Interest on Land (6% of $30,000) (1,800)
Taxes and Insurance (2% of $130,000) (2,600)
Total $2,700/year ($14,200)
-------
222 . Current Technology and Costs
Disposal Cost / Unit
Cost/mg of water treated:
$2,800/90.2-365 = $0.09/mg ($0.43)
* A municipal operation provided with free land must recover only
the $10,000 investment. A private operation must, in addition,
recover 75% of the cost of land.
Cost/ton of dry solids:
The basin (350' x 450' x 16') is about half filled when it is
emptied. Assuming the sludge is at 1.5% solids content, the
weight of dry solids produced per year is 1,180 tons. The la-
goon sludge depth of 3.5 feet over 10 years at 3070 solids
yields 1,570 tons. An average is used.
$2,800/1,400 = $2.00/ton ($10.00)
Discussion of Cost
As expected, the major cost for private operation is the price
of land. A municipal plant would have about an 80% lower disposal
cost. Since this plant is privately owned, the costs in paren-
theses are the actual costs although one notes that 6% interest is
too low a rate at the present time.
-------
Current Technology and Costs 223
SOUTH ORANGE, NEW JERSEY
Brine Disposal to Sewer
Population: 17,000
Assistant Superintendent: Gonstantin Stavrou
Ownership: Municipal
Water Source: Wells
Flow: ave. (1967) 1.7 mgd
Influent Quality: Total hardness 210-220 mg/1 as CaC03
Method of Treatment: Ion exchange with post-chlorination
Description of Brine Disposal Process:
The six zeolite softeners are regenerated twice daily with a
saturated salt solution. The waste brine is discharged to the sewer
and thence to a large regional sewage treatment plant. Salt con-
sumption in 1967 was 1211.5 tons.
Cost of Brine Disposal:
No charges are levied.
-------
SOUTH ORANGE, NEW JERSEY
Flow Diagram
Wells
Washbrine to Sewer
Zeolite
Softener
Chlorine
20% ( Bypass
Distribution
Washbrine
Salt
SOUTH ORANGE, NEW JERSEY
-224-
-------
Current Technology and Costs 225
WILLINGBORO, NEW JERSEY
Serial Lagoons
Population: 38,000
Superintendent: Quenton M. Walton
Ownership: Municipal
Water Source: 5 wells, 3 of which require treatment
Flow: ave. consumption - 3.0 mgd (1967)
ave. treatment 2.1 mgd (1967)
Capacity of treatment - 10.0 mgd
Iqfluent Quality: Component of concern is iron - up to 6.0 mg/1
Effluent Quality: Iron - 0.1 mg/1
pH - 7.8
Total hardness - 88 mg/1 as CaCO,
Method of Treatment: Coagulation, sedimentation, and rapid sand
filtration; with pre- and post-chlorination
and fluoridation.
Chemicals Added: Alum 5 mg/1
Chlorine 7.6 mg/1
Lime 31.7 mg/1
Method of Sludge Disposal
Sludge is removed mechanically from the settling basins and is
drained into two thickening lagoons. Each lagoon is a neat exca-
-------
WILLINGBORO, NEW JERSEY
Flow Diagram
Wells
SI
5 U
§3
JL
E
<
i
f
fc| 1 1 Mixer
Fine
Sedimentation
Basin
I
Sand
Filter
l
'
1. .!,
1 s
r V ,
Truck
Sludge
Washwater
Thiekening
Uogoon
Stream
WILLINGBORO, NEW JERSEY
Clear- \ Distribution
well
Washwater
Storage
-226-
-------
Current Technology and Costs 227
vation measuring approximately 75! x 75' x 9' deep. They also
receive the backwash water.
Once daily, usually at night, flashboards are removed, and
supernatant decanted. The decant enters a drainage ditch leading
to a small stream. About three times a year a trash purnp is rented
to pump the thickened sludge into a drying lagoon located 50 feet
away.
This drying lagoon measures 75' x 100', and can contain a depth
of 3 feet. It is built with a gravel base covered by sand. Each
pumping covers a span of one week to allow for maximun drainage.
Approximately every two years the sludge is removed by a front-end
loader dumping into two dump trucks. The dried sludge crumbles
readily and has been used for filling operations about the plant.
COST OF SLUDGE DISPOSAL
Construction
The lagoons were built in 1963 by the plant personnel. Direct
costs, including materials and rental of equipment, totaled about
$2,700. Assuming an indirect cost of 1007o of the direct costs, the
total construction cost estimates to be $5,400.
Land
The half-acre used is valued at $10,000.
Decanting
An allowance of 4 man hours/week may be made ($l,040/year)
Supervision costs would raise this to perhaps $l,300/year.
Pumping
Each pumping requires about two man-weeks ($400) plus the rental
-------
228 Current Technology and Costs
($120), Power costs are negligible. Three pumpings a year cost
$1,560.
Disposal
Each cleaning and disposal is budgeted for $500 - 700. An
annual cost of $500 may be assumed to allow for additional sand.
Total Disposal Costs
Capital recovery (assume 6% for 25 years) $ 420
Annual costs 3,360
(Interest on land) (6% of $10,000) (600)
(Taxes and insurance) (2% of $15,400) (310)
Total $ 3,780/year ($4,690)
Disposal Cost / Unit
Cost / mg of water treated:
$3,780/2.1-365 = $4.90/mg ($6.10)
Cost/ton of dry solids:
The amount of sludge produced is not known. An estimate
may be made as follows;
r\
Area of drying lagoon = 7,500 ftz
x depth = 2 ft
x sludge density = 60
x solids content = 507»
Weight of dry cake solids = 450,000 Ibs = 225 tons
or 113 tons removed/year
$3,780/113 = $33.50/ton ($41.50)
-------
Current Technology and Costs 229
Discussion of Cost
The total costs calculated are not very dependent on the con-
struction costs which are of 1963 vintage; hence the totals of
$4.90/mg and $4.15/ton are valid today. A private system is about
25% more expensive.
-------
230 __ Current Technology and Costs
MODEL STUDIES
Dewatering of Alum Sludges by Vacuum Filtration
Model
Coagulation, sedimentation, and rapid sand filtration for tur-
bidity removal using alum as a primary coagulant, and lime etc. as
aids.
Flow: 10 mgd average
Labor: 10, plus 1 supervisor
Sludge is assumed to be removed continuously from either an up-
flow clarifier or horizontal flow sedimentation basin.
Quantity: 0,5% of influent = 50,000 gpd
Total solids: 1%
Flow Diagram
Sludge »•- Thickener 3»- Vacuum filter s^> Land
Thickener
One thickener was chosen to provide daily batch operation, if
desired. The unit chosen was a conventional circular type. Assuming
24 hrs. detention time, plus 50% excess capacity, the capacity should
be 75,000 gallons. The depth was assumed to be 10 ft. The surface
area is thus 1,000 ft , and the diameter 35 ft. This size unit, in-
cluding pipes valves, fittings, and sludge pump, costs about $29.50/
ft^, or $29,5001). Operation and maintenance costs were set at
$5,200/yr.2)
Vacuum Filter
The sludge is assumed to be at 27» solids, and thus 25,000 gpd.
-------
Current Technology and Costs 231
This is to be dewatered in a 6-hour period. The loading rate was
taken to be 0.4 Ibs of dry solids/ft /hr,^) using a pre-coat of
diatomaceous earth.
Area of Filter = 25,000-0.02-8.33 = 1,600 ft2
6 • 0.4
Cost of filter, building, and equipment^) = $276/ft2, or $458,000.
Three filters would probably be used (14* x 18')
Maintenance was set at 5% of the capital cost:^) $22,,900/yr.
Operation: 1% men @ $10,000/yr ,,.... $15,000/yr.
Supervision: j^-$15,000 $2,250/yr.
10
Power5-*: 6 hrs ' 365 (1.4/KWH) (0.382 HP/S.F.) ' 1,660 ft2 .. $14\720/yr.
1.34 HP/KW
Precoat: From (3), proportioned to sludge flow $17,710/yr.
Sub-Total $72,580/yr.
Trucking
The sludge was taken to be at 25% solids. Weight of sludge:
0.01-50,000-8.33 =8.33 tons/day.
0.25 • 2,000
The annual cost for trucking and disposal could be (at $5.00/ton)
$15,200/yr.
Land
An emergency storage lagoon of 1 acre area, plus 3 acres for the
thickener, vacuum filter building, any necessary roads, etc. is assumed.
At $5,000/acre, land cost = $20,000.
-------
232 Current Technology and Costs
Total of Capital Costs
Construction: $487,500
plus 25% 121,900
$609,400
Salvage value is assumed negligible.
Annual Costs
Capital recovery (6% for 25 years) $ 47,600
Maintenance, operating costs etc 93,000
Taxes and insurance (270 of capital cost) 9,800
Interest on land (6% of $20,000) 1,200
$150,600
Cost/ton of dry solids:
$150,600 = $198.00/ton
760
Cost/mg water:
$41.30/mg (Includes $20/ton T.S. disposal and trucking charge)
Addendum
Assume continuous operation:
Area of filter (20 hours) = 500 ft2
Cost of filter etc.4) 290"1,200 = $348/ft2 or $174,000
1,000
Note: Using (1), $295,000 is calculated.
-------
Current Technology and Costs 233
Maintenance : $8,700
Operation: 4% men @ $10,000/yr. = $45,000
Supervision: 4j| . $15,000 = $ 5,200
13
Power and precoat, trucking: As for 1 shift operation.
The thickener need not have 507o excess capacity. Costs are re-
duced to $20,200 (capital) and $4,000 (operation and maintenance).
Annual costs
Capital recovery $ 19,000
Maintenance, operation etc 110,500
Taxes and insurance 3,900
Interest on land 1,200
$134,600
Cost/ton of dry solids:
$134,600-= $177.00/ton T.S.
760
Cost/mg water: $36.90/mg
(Includes $20/ton T.S. disposal and trucking charge)
-------
234
Current Technology and Costs
MODEL STUDIES
II. Dewatering of Softening Sludge by Vacuum Filtration
Model
Coagulation, clarification, and rapid sand filtration for hard-
ness removal using lime as a primary coagulant, and sodium silicate,
soda ash, etc. as aids.
Flow: 10 mgd average
Labor: 10, plus 1 supervisor
Sludge is assumed to be removed continuously from upflow
clarifiers. The sludge solids produced is assumed to be 2,000 Ibs/
mg. at a solids content of 1%. This represents a flow of 240,000
gals/day.
Flow Diagram
Sludge
Thickener
Vacuum filter
Land
Thickener
The size of thickener necessary should provide 8 hours detention
plus 507,, excess capacity. An average depth of 10 feet is assumed.
The dimensions would then be as follows:
Volume:
Diameter:
Area:
120,000 gals
45 feet
1,600 ft2
From (1), this unit, including accessories (piping etc.), should
cost $38,000. Operation and maintenance costs would be $6,140/yr.^)
-------
Current Technology and Costs
Vacuum Filter
Thickened sludge (30% solids) would be dewatered during an
8-hour day, 7 days/week. The loading rate is assumed to be 40 Ibs
of dry solids/ft^/hr; with an operating time of 6 hrs, the single
vacuum filter should be 6 ft. in diameter and 5 ft. wide. The
area is 94 ft2.
6)
Cost of filter, building, and equipment $67,000
Maintenance @ 57, of capital cost $ 3,350/yr.
Labor: Ik men @ $10,000/yr $15,000/yr.
Supervision: l£ . $15,000 $ 2,250/yr.
10
Power7) : 20 HP @ 1.4$/KWH for 6 hrs/day $ 450/yr.
Sub-Total $21,050/yr.
Trucking
Assume the sludge cake to be 657,, solids, with a specific weight
of 90 Ibs/ft^. Sludge production would be 15.4 tons of wet cake per
day, assuming zero solids loss in thickening and filtration, which
is reasonable if the overflow and filtrate are recycled to the head
of the plant. Due to the higher density, trucking and disposal
charges should be on the order of $4.00/ton, or $4,200/yr.
Land
An emergency storage lagoon of 1 acre, plus 1 acre for the
building and thickener, etc. could cost $10,000.
-------
236 ^ Current Technology and Costs
Salvage and Contingencies
Contingencies, fees, etc. add 25% to the construction costs of
$38,000 + $67,000, for a total capital cost of $131,000. Salvage
is assumed at zero value in 25 years.
Annual Costs
Capital recovery ($131,000 @ 67, for 25 years) .. $ 10,200
Operation, trucking 31,400
Taxes and Insurance (2% of $141,000) 2,800
Interest on land (6% of $10,000) 600
Total $ 45,000
Cost/ton of dry solids:
$45,000/10-365 = $12.35/ton
Cost/mg water:
$12.35/mg (Includes $6.15/ton T.S. trucking and
disposal charges)
-------
Current Technology and Costs 237
MODEL STUDIES
111. Dewatering of Softening Sludge by Centnfugation
Model
This is identical to "II - Dewatering of Softening Sludge by
Vacuum Filtration" except for the substitution of a centrifuge for
the vacuum filter.
Centrifuge
Thickened sludge would be centrifuged from 307o solids to 65%,
6 hours a day, 7 days a week. The flow would be
240,000-1 = 8,000 gals/day,
30
or during the 6 hours, 22.2 gpm. An 18" diameter centrifuge should
suffice °), and cost $15,000 at an ENR-Index of 800. Total cost,
including installation and an ENR-Index of 1,200 would be about
$60,000. The horsepower of the drive is 15.
Operating costs would be:
Maintenance $ 3,000/yr.
Labor 15,000/yr.
Supervision 2,250/yr.
Power 340/yr.
Total $20,590/yr.
Annual Costs
Capital recovery ($98,000 @ 6% for 25 years) $ 7,660
Operation, trucking 30,930
Taxes and Insurance (2% of $108,000) 2,160
Interest on Land (6% of $10,000) 600
Total $41,350
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238 Current Technology and Costs
Cost/ton of dry solids:
$41,350/10-365 = $11.40/ton
Cost/mg water:
$11.40/mg. (Includes $6.15/ton T.S. trucking and
disposal charges)
1) Smith, R., FWPCA Pub. WP-20-9, Preliminary Design and Simulation
of Conventional Wastewater Renovation Systems Using the Digital
Computer, March 1968, Fig. 9. See also Perry's Chemical Engin-
eers Handbook, 4th Ed., p. 19-49.
2) Ibid. p. 44.
3) Long, B.W., Report No. E412-8077, Johns - Manville Research and
Engineering Center, November 15, 1968.
4) Quirk, T.P., "Application of Computerized Analysis to Compar-
ative Costs of Sludge Dewatering by Vacuum Filter and Centri
fuge", Fig. 9. Note: The straight line cost function was re-
placed by a curvilinear relationship. A comparable value from
(1) p. 41 had a considerably higher value than Quirk
380-1200 = $561/S.F. vs. 170-1200 = $204/S.F.
812 1000
5) Filter required of 0.382 HP/S.F. from (3).
6) As (4). Quirk's paper calculates a cost of $62,000; Smith,
$71,000.
7) 20 HP for the unit is assumed.
8) Perry, Chem. Engrs. Handbook, 4th Ed., p. _19-92.
-------
Current Technology and Costs - Report Discussions 239
REPORT ON CURRENT TECHNOLOGY AND COSTS
Discussion of Report
MR. NEBIKER: To open the discussion of this report, I
shall explain some of the methodology used in our investigation.
We determined the location of plants employing different sludge
treatment and disposal methods, and contacted officials to arrange
for inspection visits.
We concentrated on establishing realistic cost data,
this required a great deal of estimation, because operating records
were not complete in most instances. We also attempted to determine
solids balances for those plants which used mechanical processes.
While we have used a fairly high percent interest rate of 6 per cent,
this rate may be unrealistic today.
The cost of land and taxes has been included, we recognize
many water utilities are privately operated and must consider these
items. The cost figures include numbers in parentheses: the pa-
rentheses figures refer to costs of private operation.
We have reported cost figures in dollars per million gal-
lons. This is a general way of expressing a price of water, but
the price divergencies are so great that is is very difficult to
generalize. We also reported costs in dollars per ton of dry solids,
which is comparable to what is done in sewage treatment practice. In
those instances where recalcination was practiced, we. emphasized the
profit or loss in dollars per ton of lime produced.
Comments on specific operating details of plants visited
will be useful.
Two of the treatment plants used lagoons. We found that
there is good reason for operating two lagoons in series. Note in
the Willingboro, New Jersey, flow diagram that the filter washwater
and the alum sludge from the sedimentation tank are discharged to a
thickening lagoon, which is decanted daily. When the sludge has
accumulated to a certain depth in the thickening lagoon, it is pump-
ed by an air lift pump to a drying lagoon. There it is allowed to
-------
240 Current. Technology and Costs - Report Discussions
dry to a very high solids content, 30 per cent and above, which will
hold the weight of a man.
Note in the New Britain, Conn., flow diagram, serial la-
goons which also utilize thickening. Backwash water enters along
with the alum sludge. The first lagoon has a canal at the bottom
which, by manipulation of gates, enables gravity flow movement of
the sludge from the thickening lagoon to the storage lagoon without
pumping.
Several of the installations for lime sludges dewatering
(at Austin, Dayton, Lansing, and Miami) use Bird centrifuges. These
seem to provide a very satisfactory method of concentrating lime
sludge. The rotary kiln used for recalcination of lime sludge in
Miami is a very superior setup, operating fairly close to capacity.
As you will note in our report, we have come to the conclusion that
there is definitely a profit made by the recalcination of sludge
from water softening in Miami. The installation at Dayton also uses
a. rotary kiln, and shows a profit in recalcination of lime sludge.
Note in the Dayton, Ohio, flow diagram the aspects con-
cerned with heating of the sludge. The rotary kiln includes an ex-
pansion chamber and stack for the gases. The expansion chamber is
used to cool and clean the gases by bringing in the thickened sludge
on an impingement device. The temperature of the sludge is increased
and, as a result, the settleability of the particles in the sludge
during centrifugation is increased. These effects illustrate the
value of a well conceived engineering design.
The Dayton plant thickens a non-heated sludge, and the
Lansing plant thickens a heated sludge. Note in the Lansing, Mich-
igan, flow diagram that a Fluo-Solids reactor is used for recalcin-
ation. Heating of the sludge is previous to thickening, so thick-
ening performance is improved. A three-tray thickener is used in
order to conserve the heat during thickening.
The building for the Lansing recalcination operation is
very neat and compact. The illustration shows that all equipment is
enclosed in the building except the thickener, which is on the far
left background.
Note Boca Raton flow diagram. This is a very modern lime
softening plant. A thickener and a vacuum filter are used. The
vacuum filter dewaters lime sludge very well indeed. The thickener
is loaded continuously. Sludge is removed only intermittently;
that is, during the period at which the vacuum filter operates,
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Current Technology and Costs - Report Duscussions 241
which is some six hours a day.
During the night the lime sludge builds up to a depth of
several feet, and compression makes the sludge extremely dense. In
order that the scraper blades do not break, the driving mechanism
has a torque control which will immediately shut off the unit if re-
sistance from the sludge is too great. The blades can be raised and
lowered to remove the top sludge layers first.
The filter cake discharged from the vacuum filter is about
one-half inch thick, about 65 percent solids. The sludge is hauled
out to the highway department, which utilizes it as binder for the
soil on its highways.
MR. ADRIAN; I shall comment on additional plants visited.
The San Francisco Water Department operates, a filter washwater re-
covery plant at its Sunol, Calif., treatment plant. The settled
sludge from this tank is discharged by gravity to the sludge drying
beds which are located at a level some two hundred feet below the
plant.
The sludge drying beds have a "diving board" decant system
at one end which permits the clear supernatent to be decanted con-
tinuously while the sludge is being added to the basin at the opp-
osite end. The decant arrangement involves a vertical half culvert
and a group of baffles which can be selectively lifted to decant at
the correct elevation. The decant is discharged to a nearby creek.
The vertical lift to the plant influent of some two hundred feet
probably influenced the decision not to reclaim the decant.
Sludge from drying beds at the Sunol plant are hauled to
a disposal site. Between three to six hundred cubic yards per year
of solids are cleaned off the beds. Those responsible for cleaning
the beds prefer the solids to be not too dry because of the dust pro-
blem. With a little moisture remaining, the volume to be hauled may
be doubled, but the operators much prefer this form to a dusty cake.
There is some discussion in our report concerning the optimal depth
of sludge application. About Wo feet has been found to be a max-
imum value for good dex-ratering and drying.
Minot, North Dakota, has had several years of experience
with vacuum filtration of lime sludge, using two vacuum filters.
The source of water is from wells and the Mouse River. Turbidity is
low much of the time. At this plant, ten feet or so of sludge cake
has been dumped in the disposal site. There appears to be no dif-
ficulty in compacting the solids in the disposal site so that gravel
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242 Current Technology and Costs - Report Discussions
can be spread over the top, forming a base for a truck roadway used
for future hauling.
At the Rinconada, Calif, water treatment plant dewatering
and drying beds were designed similar to those which are used in con-
ventional sewage treatment operation. The illustration shows a view
of a wash-water recovery basin and the several dewatering and drying
beds in the background. The drying beds are built so that a truck
can be driven between the beds for ease in cleaning. Another illus-
tration show that an interesting structure is formed as the sludge
dries, with the cracks creating greater exposure to the air and in-
creasing the rate of drying.
In sludge drying operations at the Sunol plant, it has been
observed that if the sludge is put into the drying bed to a depth of
three feet or more a great length of time is required for drying. If
the sludge is applied in a lesser depth, the cracks which form pene-
trate to the bottom, enabling the drying to take place in about three
months.
The Lompoc, Calif., employs diatomaceous earth filtration
of well water and disposes of lime softened sludge to drying beds.
This plant has realized quite an economy by reclaiming the decant,
which is cycled back to the plant inlet. It is estimated that a sav-
ings of about $5000 a year are realized by this procedure, estimated
on the basis of the cost to pump an equivalent volume of water from
the well.
MR. AULTMAM: I would like to add certain comments about
the Sunol plant at San Francisco. The first basin there is spec-
ifically a washwater recovery basin, which receives no settled sludge
solids. After settling, the supernatent washwater is pumped back to
the influent of the plant.
Solids are discharged from the sludge settling basins by
gravity. The reason that the decant is not pumped back is partially
because of the elevation but, also, because the water discharged to
the creek is spread a short distance downstream. This decant water
is recovered by existing pumping facilities. The water returns to
the plant in that way. This situation was one of the reasons our
engineers and the City's staff decided on that method of handling.
MR. TCHOBANOGLOUS; After reviewing the cost data in the
report, I wonder if it would be possible to develop costs on some
sort of continuous parametric basis rather than an point estimates?
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Current Technology and Costs - Report Discussions .243
MR. ADRIAN; We have explored this idea. We would like to
be able to make estimates which would show the scale economies. Some
treatment plants reported had small, and some had large flows. There
are very definite scale effects evident in going over such a wide
range. We would like to use something similar to that done in the
Smith report - this is a report put out by Robert Smith of the Federal
Water Pollution Control Administration - on a digital computer simu-
lation of conventional waste water treatment.
MR. NEBIKER; As you may notice, our report includes three
model studies. We came to no definite conclusion because the costs
for lime sludge dewatering by centrifuge or vacuum filter were close.
When more treatment plants are in operation it will be possible to
generate simulation models. The parameter of specific resistance
could apply to the vacuum filter, to the pressure filter, and to the
dewatering lagoon. Another parameter would be settleability, apply-
ing to thickening and lagooning.
MR. TCHOBANOGLOUS; My thought was that, if cost estimates
could be developed for 5 to 10 alternative types, the information
could be broadly disseminated. Then I think the different processes
would receive more attention and more action would be taken.
MR. ADRIAN; Initially, we and members of the Advisory
Committee, were hard pressed to identify one operating plant example
of each type of treatment process. Even today we learned that the
microstrainer process is more widely used than had been thought.
The operation of more plants will give more data, which will result
in better cost information.
MR. DOE; We must compare like with like. The data you
report for the Sunol, California, plant for dried sludge from a la-
goon - if my mathematics is correct - is a sludge of 53 percent
solids. Now, I think that nowhere else in the world could one get the
sludge from a lagoon at 53 percent solids. I think most operators
would be happy to get sludge at 20 percent solids in a lagoon. There
would then be a considerable difference in the figures showing a unit
cost of $56.60 per ton of dry solids for the cost; the unit cost
could be perhaps $120 per ton. Parameters are an excellant idea, but
may result in new problems.
MR. JOHNSON; What can you estimate as the approximate con-
centration of sludge solids from thickeners?
MR. NEBIKER: The only thickeners that we studied were at
water softening plants: Lansing, Miami, Dayton, Boca Raton, Minot,
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244 Current Technology and Costs - Report Discussions
and Austin. The thickened sludge was about 30 percent solids. One
of the great variables is the solids content of sludge discharged
from clarifiers. At the Miami plant the sludge is about 15 percent
solids; at other locations the solids are about five percent.
MR. TGHOBANOGLOUS; Can you report the relation of the
solids content to sludge thickening? For example, is it easier to
thicken a five percent sludge to some given value, or is a ten per-
cent sludge easier thicken?
MR. NEBIKER; What we saw in plant visits are not the
classical types of sewage sludge thickeners with steady underflow
rates. In sewage treatment, the thicker the influent sludge, the
smaller the size of thickener needed.
In operating centrifuges, the thinner the sludge is, the
better the solids capture. Generally, however, operators try to
feed 20 percent solids into the centrifuge because they thereby re-
duce the number of centrifuges in operation. It might be noted that
the centrifuge is ideal in removing magnesium by discharging it out
in the centrate.
The vacuum filter will not throw out the magnesium. Also
I should say that if a lime sludge contains a large porportion of
magnesium, say 10 percent or so, its filterability is very adversely
affected, and it is illogical to utilize a vacuum filter in such a
case. If we consider a ground water is softened by the lime soda
process and it has a low magnesium content, then recalcination is
technically possible. That type of sludge is also suitable for de-
watering on a vacuum filter. On the other hand, if magnesium is
present in large amounts, vacuum filtration or recalcination is ex-
cluded, although centrifugation would be possible.
MR. DEAN; Getting back to the other point brought up
earlier, the variation in solids content. I would refer to the study
by Louis Koenig of treatment costs in small and medium sized water
treatment plants, Jour. AWWA, 59:290 (Mar. 1967). He attributes a
large part of costs to poor engineering. His whole range of costs
was covered, I believe, by a factor of 10 when he tried to reduce it
to parameters. Plant operation was important - the number of oper-
ators, the unneeded capacity available, and other factors. To estab-
lish parametric costs, we should look at the best. Most plants
could do a lot better than they are now doing.
MR. MSBIKER: We have attempted to account for unused cap-
acity, etc., in our cost calculations.
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Current .Technology and Costs - Report Discussions 245
MR. ADRIAN; Additional comment may be desirable concerning
the use of vacuum filters for dewatering a softening sludge. It has
been reported that a few installations did not operate successfully.
One may wonder why vacuum filters work well in certain installations
but not in others. One explanation may be in whether or not the fil-
ter was a coil filter. The installations which did not work well
apparently used a coil filter. In those installations, there was the
problem of deposits forming on the coils; the deposits build up and
gradually force the coils farther apart.
At the Minot, North Dakota,, installation, a polypropylene
belt has been used on an Eimco filter. It seems that the incrusta-
tion problem is more severe with intermittent operation. The belt
replacement might be on the order of a couple hundred dollars every
few years, not an excessive cost.
MR. DICK; We have studied vacuum filtration of sludge from
a surface water treatment plant, which also softens. The plant has
coil filters which have been sitting idle for years because their
operation has been totally unsatisfactory. We have found through la-
boratory leaf tests of fabrics that filtration works very well with
the different media. The source of the difficulty seems to be in the
media selected for the initial installation, although we haven't yet
evaluated possible blinding problems with the fabrics. We don't find
that clogging or incrustation of the coils is the problem at this
plant. The sludge just goes right through the coils, with filtrate
solids as high as seven percent.
MR. KRASAUSKAS; Did you find problems of odor with the
drying lagoons?
MR. ADRIAN; We noticed no odor problem. At the Sunol
plant, odors were not commented upon as a problem.
MR. TCHOBANOGLOUS; To the best of my knowledge, the Rin-
conada plant has had no odor difficulties. The operating personnel
at the Rinconada plant have found that the most successful way to
operate the sludge beds is to place a thin layer of sludge on each
of the beds, and progressively move down the line. This has opti-
mized the drying time and minimized the odor problem. The lack of
an odor problem is also related to the characteristics of the raw
water, which contains few if any organics.
MR. AULTMAN; The water treated in each of these plants
contains practically no organic matter, and there is no indication
of an odor problem. No odor problems were experienced when we were
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246 Current Technology and Costs - Report Discussions
discharging softening sludge from the plant of the Metropolitan
Water District at La Verne. The sludge content will determine the
problem
MR. WEBBER; At Toledo, Ohio, we have two 15 acre lagoons
in about a half mile radius, both 20 feet deep. We have no odor
problem, even though the raw water contains a considerable amount
of organic matter. But we do have a dust problem. The sludge dries
so thoroughly on top that we have to keep it covered with a layer of
water.
MR. ADRIAN: We have brought into the laboratory a number
of samples from the Bellerica, Massachussetts, plant which treats
one of the worst raw waters in the United States. There have not
been odors noted from sludge lagoons at this plant.
We recently brought back several barrels of sludge from
Albany, New York. There was a little odor when we vigorously mixed
this sludge.
MR. JOHNSON; I'd like to direct a question to Mr. Webber.
How deep is the sludge in your lagoons now?
MR. WEBBER; One lagoon is about 20 feet, but during the
last three years has settled back to a depth of about 17 feet. The
other lagoon is kept full right up to the 20 foot mark in order to
reduce wave action on the dikes.
MR. BLACK; You spoke of the need to keep the top covered
with water because of dust problems. Can you tell me the percent of
sludge solids in the bottom of that lagoon?
MR. WEBBER; Yes, a recent analysis at a depth of 12 feet
shows about 47 percent dry solids; and four or five feet below the
surface the solids are about 35 percent. At the surface, solids
are 100 percent.
MR. HARTUNG; This question of sludge odor has come up
several times. I can report one other experience. Sludge odor after
dewatering is not a problem at the St. Louis County plant where we
are treating surface water from the Meramec River. Sludge from the
settling basins is discharged to a lagoon, eight feet deep. We are
in the process of emptying the lagoon with crane and drag line, and
hauling the sludge to a dump about one mile away. There is no odor
problem. This sludge is from a clarification and lime softening
plant, treating a surface water which contains considerable turbidity•,
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Section 3
REPORT ON WHAT IS NEEDED
CONFERENCE REPORT ON RESEARCH NEEDS
Because of the ease with which water treatment plant wastes
could be discharged to streams in the past, the disposal of these
wastes has not commonly been considered a problem warranting re-
search. There is now an urgent need for dealing with wastes from
water treatment plants in a way which does not deteriorate the
quality of the environment.
In order to meet this need, water treatment plants must de-
velop alternative waste treatment techniques without a background
of previous experience in solving the problem. As a result, a
great deal of research is needed to develop efficient and economi-
cal techniques for handling waste from water treatment plants.
Considerable expenditures of time, manpower, and money are
needed for research to learn more about the nature of wastes pro-
duced by water treatment plants, to investigate means of treating
these wastes, to study the alternatives for ultimate disposal of
the residues, and to evaluate future water treatment and waste
management technology as it relates to this problem of waste dis-
posal.
Specific problems in these categories of research needs are
listed below:
A. Nature of Wastes
In order to improve knowledge of the quality and quantity
of wastes produced by water treatment processes, it is recommended
that research be conducted to:
1. Identify the quantities of wastes produced by various water
treatment methods
2. Characterize the physical, biological, and chemical pro-
perties of water treatment plant wastes, particularly those
produced by chemical coagulation
3. Determine the manner in which the properties of raw water
influence the quantity and quality of resulting wastes
-247-
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248 Conference Report on Research Needs
4. Develop meaningful parameters to describe the properties of
wastes and to permit comparisons of wastes from various
plants, particularly in areas of sludge thickening, dewater-
ing, and handling
B. Treatment of Water Plant Wastes
To improve techniques for altering properties of sludges
prior to ultimate disposal, research is need to:
1. Improve techniques for gravity thickening of sludges, par-
ticularly sludges from chemical coagulation processes
2. Develop means for relating laboratory batch sedimentation
results to full scale continuous thickening
3. Evaluate the applicability of flotation processes to the
concentration of water treatment plant sludges
4. Develop diagnostic tests to evaluate the efficacy of various
conditioning agents, particularly in selection of polymers
for sludge conditioning
5. Develop polymers which are specific to conditioning needs
for water treatment sludges
6. Improve understanding of the alteration of physical pro-
perties of sludges by freezing techniques
7. Improve equipment for freezing of sludges, and evaluate
techniques for using natural freezing for sludge condition-
ing
8. Evaluate the role of heat treatment as a means for con-
ditioning of sludges
9. Develop improved methods for dewatering sludge by centrifuges
through improvement in the design and operation of centri-
fugation equipment
10. Develop means for obtaining centrifuge design information
from laboratory study of sludge properties
11. Evaluate suitable media and precoat for vacuum filters, par-
ticularly those applicable to alum sludges
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Conference Report on Research Needs 249
12. Obtain operational and economic data to assess the applica-
bility of pressure filters to dewatering of water treatment
plant sludges
13. Develop models for operation of lagoons to improve their
dewatering ability
14. Improve techniques for solids handling, particularly in the
area of emptying lagoons
15. Evaluate the basic properties of sludges which influence
their behavior on sand drying beds, especially factors in-
fluencing cracking, draining, drying, and the influence of
chemical conditioning agents
16. Develop models for operations of drying beds to optimize
their drying behavior
C. Ultimate Disposal of Wastes
Needed research relating to the return of water treatment
plant residues to the environment includes:
1. Study of the load-bearing characteristics of sludges in
landfills
2. Study of means for improving load-bearing characteristics
of dewatered sludges, possibly by mixing with other waste
materials
3. Study the environmental effects of applying waste sludges
to land, including effects on plants, soil, and ground and
surface waters
4. Evaluate the influence of water treatment plants wastes on
sewerage systems and on waste treatment plants.
5. Study the factors influencing the transportation of sludges
by various means
6. Evaluate the ecological effect of ocean disposal of water
treatment plant wastes
7. Study the reclamation and reuse of products from water
treatment plant wastes, particularly clarification and
softening sludges, including the reclamation of lime, alum,
magnesium, and other possible usable products
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250 Conference Report on Research Needs
D. Future Water Treatment and Waste Management Technology
The need for control of water treatment plant wastes requires
reassessment of established water treatment practices, and suggests
the need for research to:
1. Develop comprehensive models of water treatment with a view
to evaluating the effect of process and operational changes
on waste disposal problems
2. Develop new techniques for dewatering and drying water treat-
ment plant sludges to a handleable state
3. Develop new products from sludges and new uses for sludge
4. Study the joint handling, treatment, and disposal of water
treatment plant wastes together with wastewater and solid
wastes
5. Consider optimization of waste managment on a regional basis
through operations research studies
Committee Report by:
R.I. Dick, Chairman
R.B. Dean, Secretary
D.D. Adrian
A.P. Black
R.N. Kinman
K.E. Shull
G. Tchobanoglous
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Conference Report on Engineering Needs 251
CONFERENCE REPORT ON ENGINEERING NEEDS
Engineering needs related to disposal of wastes from water
treatment plant currently revolve primarily around additional re-
search on waste characteristics, existing and new methods of dis-
posal, operating data, and costs. In particular, emphasis must
be given to the need to review total management methods constantly
and to develop the concept of sludge and wastewater disposal as an
integral part of the treatment process. Accordingly, investigation
in the following field is recommended:
A. Basic Engineering Research on Waste Characteristics
1. Concentrations and total quantities of dry solids produced
2. Biological, chemical and physical characteristics of floe,
washwater, and sludge
3. Settlement characteristics
(a) Reaction of coagulants as related to sludge production
(1) Kinetics of reaction
(2) Mixing intensity
(3) Time
(b) Sludge thickening
(1) Mechanical means, e.g. stirring, centrifugation,
filtration, pressing, etc.
(2) Chemical conditioning, e.g. polyelectrolytes
(3) Hindered settlement'
4. Hydraulic characteristics
(a) Torque - establishment of hydraulic equations with re-
spect to pumping, mixing, collecting, etc.
(b) Flow - establishment of equations with respect to hy-
draulics of conveyance
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252 Conference Report on Engineering Needs
B. Applied Engineering Research
1. Measurement methods to determine waste flow rates
2. Solids balance
(a) Sludge concentrations
(b) Methods of measurement and sampling
(1) Rapid methods to determine percent solids by weight
(2) Relationship of turbidities and solids concentra-
tion
3. Hydraulics of sludges
(a) Equipment requirements
(b) Behavior in pipelines at varying velocities and concen-
trations
4. Pre-treatment (conditioning)
5. Dewatering methods, both existing and new
6. Ultimate disposal after dewatering
7. Effects of wastes on sewage treatment processes
8. Reclamation
9. Specific utilization of sludge, e.g., as soil conditioner,
rubber filler, etc.
10. Wastewater reuse techniques
(a) Impact on treatment processes with and without treat-
ment of wastewaters
(b) Treatment processes oriented for wastewater reuse
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Conference Report on Engineering Needs 253
C. Assembly of Plant Operating Experience
1. Operating costs for waste disposal processes
(a) Construction costs of sludge handling and treatment
facilities
(b) Labor, equipment and maintenance costs
2. Service charges for disposal to sewage treatment plants
3. Data gathering relating to sludge
(a) Quantities
(b) Concentrations
(c) Characteristics
4. Water treatment methods used
5. Records of Performance
(a) Variations of sludge flows and characteristics
(b) Effect of variations in raw water influent quality.
D. Development of Design Parameters and Costs
1. Effects of variation in sludge characteristics
2. Demonstration of feasible processes
3. Development of unit costs
Finally, it is recommended that members of the Conference be
invited to submit details to the AWWA Research Foundation of any
specific project with which they are familiar or actually engaged
upon which could yield data of the type referred to above. This
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254 Conference Report on Engineering Needs
exchange of information could provide the means of speedy imple-
mentation of the stated objectives during the period when demon-
stration projects are being set up.
Committee Report by:
W.K. Neubauer, Chairman
D.P. Proudfit, Secretary
W.W. Aultman
S.L. Bishop
P.W. Doe
J.C. Nebiker
W.H. Plautz
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Conference Report on Plant Operation Needs 255
CONFERENCE REPORT ON PLANT OPERATION NEEDS
The group of Conferees directly involved in water treatment
plant operation began with the premise that water treatment plant
wastes can no longer be disposed of by returning them to their
original source - the raw water supply. Our conclusion is that a
serious problem exists in the disposal of these wastes. Accord-
ingly, research is needed to determine improved methods for treat-
ment sludge, and in characterization and classification of sludges
for the following purposes.
First, in reclamation - for reuse by the water utility in its
own water treatment plant, or for the sale of reclaimed chemicals
to other wastewater treatment plants, or industrial plants. The
market and potential demands for the waste sludge should be studied,
as should the sludge characteristics, which make the waste products
salable for water treatment purposes and for other uses, such as in
manufacture of paint, building materials, and paper.
Second, for disposal to ground - as in construction of highway
bases, levees, embankments or fill on sub-marginal land, in such a
manner and in such condition that the value of the land is not de-
stroyed but is enhanced if possible.
Third, for disposal to sanitary sewers, so that the sewage
treatment processes are benefited, or at least not adversely af-
fected, and a combined end product is produced which can be disposed
of in one of the above methods.
Fourth, for disposal to the sea - in such form that the waste
will not adversely affect biological life or recreational use.
Consider New or Modified Treatment Processes
To accomplish these purposes, water treatment processes should
be reexarnined and modified, if necessary, or new processes should
be developed. For example, it may be necessary to separate coagulant
(alum, iron, etc.) sludge from softening (lime, magnesium) sludge.
The calcium carbonate may require separation from magnesium hydroxide.
Conditioners may be added in the process solely to alter the
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256 Conference Report on Plant Operation Needs
character of the sludge. The use of alum (or iron salts) for
coagulation may be abandoned entirely in favor of polyelectrolytes
which will markedly reduce the bulk of sludge produced.
Improvement in the types of membranes now used for reverse
osmosis may permit complete removal of suspended matter from water
and a modest reduction in mineral content, thereby eliminating the
need for coagulation and softening. Softening might be eliminated
and reliance placed fully on detergents for washing purposes, and
addition of additives to prevent sealing, and other adverse indus-
trial reactions.
Precipitation processes should be modified to promote floe
growth, strength, and density for more effective removal.
Methods for handling or moving sludge should be controlled so
that its physical properties-are not adversely affected in trans-
portation to the place of its reuse.
Evaluate Uses and Disposal of Wastes
Much more must be learned about the properties of water treat-
ment plant wastes to determine their suitablity for disposal or for
reuse. This means that test methods for physical and chemical pro-
perties must be defined, and these properties related to methods of
disposal or use of the waste.
For example, it should be determined what chemical constituents
contribute to soil plasticity - or to its mechanical strength.
Which physical and chemical characteristics will promote use of the
waste product for agricultural purposes? What properties will de-
termine its suitability for use in embankments of landfill? What
properties enhance its flow characteristics?
What laboratory tests will permit evaluation of the suitability
of wastes for the above and other uses? Standard methods should be
developed to accomplish this. Possibly a system of classifications
such as the construction engineers use would be adaptable. The
properties measured and used in classification of soils are: maximum
dry weight, cohesion, specific gravity, plasticity, liquid and plas-
tic limits, permeability, resistivity, particle size, organic char-
acteristics, etc.
Modification or conditioning of wastes to make them suitable
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Conference Report on Plant Operation Needs 257
for disposal or reuse may include freezing, heating, filtration
(mixed media, rapid sand, vacuum, pressure, etc.) centrifuging, ad-
mixing.
Addition of silicates or other chemicals to enhance mechanical
strength and suitability for use as fill or structural material.
Determine Economics of Improved Operations
The committee recognizes that the cost of water treatment plant
waste disposal must be borne by the ultimate consumer of the water.
Therefore, waste disposal and conditioning methods must be economi-
cally feasible and justifiable. It would be fruitless to develop
processes which would be rejected because of costs substantially in
excess of the benefits obtained.
It must be recognized, however, that the level of cost justify-
ing sludge disposal methods are not the same for all waste sludge
generating agencies. And what at first inspection might seem un-
feasible, might be found feasible after more or less research has
been done.
In summation, the principal needs are to find effective and
economical means, through research, to dispose of water treatment
plant wastes by direct treatment of sludge, or by eliminating un-
desirable chemicals, such as alum, through changes in water treatment
methods. This need applies both to clarification and softening of
surface and well waters.
An important instrument of research should be a central service
operating to gather, document, and disseminate data on plant opera-
tions that are pertinent to the subject.
Committee Report by:
J.W. Krasauskas, Chairman
Lee Streicher, Secretary
C.M. Bach
H. Hartung
C.E. Johnson
H.R. Peters
J.C. Webber
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258 Conference Report on Regulatory Needs
CONFERENCE REPORT ON REGULATORY NEEDS
General Statement
It is general knowledge in today's society that needs are in-
creasing in all quarters for protection and enhancement of the
quality of our water resources. To this end, all waste water dis-
charges must be carefully controlled to insure attainment of that
goal.
The water works industry has a most critical stake in the qual-
ity of our water resources and clearly should adopt a role of lead-
ership in their protection for all beneficial uses. Accordingly,
the conception, design, construction, maintenance, and operation of
any water supply facility must be considered as inadequate if it
does not incorporate the important principles of water quality man-
agement, including acceptable disposal of waste.
The Committee feels that the water works industry, individually
and collectively, has an obligation to conform with all requirements
for water quality control which are applicable to industrial and
municipal wastes. Furthermore, the Committee feels that attainment
of that goal would be greatly facilitated by regulatory action es-
tablishing clear policies for treatment and disposal of wastes from
water supply facilities.
Sources of Wastes
Wastes from water treatment plants can no longer be discharged
without satisfactory control, including the following:
1. Waste filter washwater, including diatomaceous earth
2. Sludge from settling units, including softening sludges
3. "Red" or "black" wastewater from iron or manganese removal plants
4. Waste brine from ion exchange plants
5. Sanitary wastes
6. Other wastes, including silt during construction
7. Operating practices which may be detrimental to the water resources
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Conference Report on Regulatory Needs 259
The water works industry should assist regulatory agencies and
cooperate in providing information relative to water pollution con-
trol. Specific needs are:
For existing water treatment plants
1. Evaluate practices and potential water pollution problems.
As pollution from municipal and obvious industrial sources
is abated, the tendency will be for official and public
attention to turn to other discharges - including those
from water treatment plants.
2. Consider opportunities and factors affecting inclusion of
sedimentation sludges with municipal or other industrial
wastes.
3. Consider other methods and factors affecting reclamation
of coagulants, water softening chemicals and other chemicals
or substances useful in water treatment processes.
4. Consider opportunities for using softening sludges or other
waste discharges for alleviating natural or man-made water
pollution problems.
5. Consider opportunities for using wastes in land reclamation,
highway construction, and other beneficial uses.
6. Consider factors affecting ultimate disposal of sludges or
other waste residual on soil, or at sea. Consider also the
total effect of waste disposal on the environment.
7. The utility should have operating responsibilities for
monitoring, recording, and reporting waste and receiving
stream characteristics.
For new water treatment plants
Waste management should be an integral consideration in the
design or expansion of water treatment facilities. With
proper weighting, waste management should have direct in-
fluence upon the selection of unit processes and the loca-
tion of the water treatment plant.
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260 Conference Report on Regulatory Needs
Summary Statement
The Committee feels the need for development of substantial
detailed information concerning the technology of treatment and dis-
posal of wastes originating from water treatment practices. This
information is vital for rational regulation of the industry. Be-
cause of the unusual size and complexity of the industry, the Com-
mittee discerns great difficulty in planning efficient and eco-
nomical research and development programs and in dissemination of
information from those programs.
Accordingly, the Committee believes that the AWWA Research
Foundation could render valuable service both to the industry and
to regulatory agencies by assuming active leadership in planning
and coordinating research activities for the nation. Specifically,
the Committee believes that a central clearing house for information
on the disposal of wastes from water treatment plants should be es-
tablished as a function of the AWWA Research Foundation.
Committee Report by:
J.C. Lamb, III, Chairman
E.G. Weber, Secretary
J.B. Coulter
G.H. Eagle
Vern Fahy
Edgar Henry
H.B. Russelmann
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gonference Concluding Statement 261
CONFERENCE CONCLUDING STATEMENT
J. C. Lamb, III
This Conference has summarized, in a series of reports
and discussions, our state of knowledge about the disposal of
wastes from water treatment plants. I would like to review what
has been presented by suggesting that our water utilities are an
industry. As an industry, they have an industrial waste problem.
We may examine this industrial waste problem as we would
that of any other industry. Perhaps, from this viewpoint, we may
discover clues which will assist researchers, engineers, plant
operators, and regulatory agencies who endeavor to solve the pro-
blem.
The first question we ask is always "What is the problem?"
To answer it, we need to know about the characteristics of the waste.
We need to identify the specific constituents, their concentrations,
and the ranges which occur in practice. We need to recognize that,
as in other industries, the character of the waste will not remain
constant.
The data we collect will help to define the problem in
broad terms but, like textbook information, is inadequate for plant
design or regulatory purposes. In many alum coagulation plants or
lime softening plants, while wastes are similar, they are not iden-
tical, and the technology required to solve treatment problems will
not be identical.
This situation makes it evident that there is a limit to
the value of information obtained on the basis of averages. No one
plant, or very few plants, will produce wastes close to the national
average. Our need, then, is for general quality measurements, gen-
eral ranges of concentrations, and specific departures from normal
values.
Our second concern must be with the pollutional effects
of wastes from the water treatment industry. Apparently, very
little study has been made of this subject. We do need to
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262 Conference Concluding Statement
substantiate the fact that there are such problems., and we need to
evaluate them. To do this, we must collect information, coordinate
it, and document the problem.
Having determined that there is a problem, we next look
for solutions. No one solution is ideal to solve a problem, even
for a single industry. Treatment is only one solution and, in a
good industrial waste investigation, may be the last one to examine -
because others provide a more reasonable chance of realizing major
savings.
We should, for example, consider dilution. In certain
situations, good engineering may permit impounding and the discharge
of wastes seasonally or in proportion to stream flow. If such dis-
charge does not contravene legitimate uses of a stream, this be-
comes a rational method for attacking the problem.
Another approach, already noted in one Conference report,
suggests the change of treatment processes, to reduce or eliminate
the waste. Changing from lime softening to ion exchange softening
will radically affect the character of a waste. This may solve the
waste problem but only, perhaps, if the plant wastes can be dis-
charged to the ocean.
Similarly, the use of polyelectrolytes is intriguing.
Coagulation by substances other than alum might mean that the waste
problem could be solved by new technology.
We might even give consideration to profitable reclama-
tion and sale' of a waste by-product. This possibility should be
approached with cautious skepticism, but should not be eliminated.
The next approach is to discharge the water treatment
plant wastes into a municipal wastewater system. There are, ap-
parently, many uncertainties about the harmful effects that could
result. Properly done, it also appears that there could be bene-
ficial effects from this method of disposal.
Finally, we come to discuss the treatment processes.
These are not as simple as they might appear. Some available sewage
treatment processes might apply here. In order to apply them, we
need to know much more about the differences in design parameters
operating conditions, and economics.
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Conference Concluding Statement 263
RESEARCH DIRECTIONS
Obviously, there are many legitimate areas of needed re-
search. Our research should, properly, be divided into two general
areas. The first is concerned with questions of general applicabil-
ity. For example: questions involving the quantities and charac-
teristics of waste, their pollutional effects, and the applicability
of treatment processes for different types of water treatment wastes.
The second area of research is concerned with questions
involved in solving specific problems. In this area, we need to
develop adequate technology and uniform methodology to be used on
individual plants. For example: questions dealing with methods for
properly evaluating the dewaterability of sludges, using different
treatment processes. Uniform methods of this type would provide
tools which engineers, plant operators, and regulatory agencies
could apply to the solution of specific problems.
We are then faced with the question: "Who is to do all
this research?" I think that many different groups must contribute.
For example: research of different types can be done in academic
institutions, federal and regulatory agency laboratories, commercial
laboratories, and by consulting engineers, plant operators, and
equipment manufacturers. All of these have something to contribute.
The next question is then: "Who is to pay for this re-
search?" We find that, for broadly applicable basic and applied
research projects, and demonstration projects having industry-wide
utility, some support may be provided by a federal agency. Regu-
latory groups at the state level should develop more research sup-
port than they have in the past.
I submit that support for much research of this nature
must come from within the water industry. We have learned at this
Conference that a number of utilities already have substantial pro-
jects under way. They are working to solve their own problems.
RESEARCH COORDINATION
We come now to the long-range goal of this Conference.
That is, how knowledge derived from research and investigation is
to be applied to the solution of specific problems of the water
industry.
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264 Conference Concluding Statement
The first step will be taken when the AWWA Research
Foundation publishes its project report on the disposal of wastes
from water treatment plants. This report will summarize in some
detail what we know and what we need to know about the problem.
During our Conference discussions, it has repeatedly
been suggested that a central service - a clearing house - is
needed to provide information on continuing research and demonstra-
tion projects.
The Conference committee reports, prepared to outline
what we need to know, emphasize the need for an information clearing
house. These reports recommend that the AWWA Research Foundation
undertake to collect and disseminate such information.
In this activity, the Foundation would, with an appropriate
advisory committee, assume a role of leadership in planning and co-
ordinating research and demonstration projects. Coordination could
significantly stimulate the rate of progress in solving problems of
waste disposal.
We should recognize another important function which the
Research Foundation could serve. This would be to interpret and
translate research results, which must frequently be put into terms
useful for plant operators.
The concept of a clearing house, and the important functions
it could serve, certainly represent a challenge to the AWWA Research
Foundation. This activity would benefit the entire water industry in
solving its problem of treatment plant waste disposal.
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Section 4
DIRECTORY OF CONFERENCE PARTICIPANTS
ADRIAN, Donald D., Associate Professor of Civil Engineering,
Department of Civil Engineering, School of Engineering,
University of Massachusetts, Amherst, Massachusetts 01002
AULTMAN, William W., James M. Montgomery, Consulting Engineers,
Inc., 535 East East Walnut Street, Pasadena, California 91101
BACH, Clayton M., Superintendent of Treatment, Minneapolis Water
Works, 43rd and Marshall Street, Minneapolis, Minnesota 55421
BISHOP, Stephen L., Project Engineer, Metcalf and Eddy, Consulting
Engineers, 1200 Statler Building, Boston, Massachusetts 02117
BLACK, A.P., Consulting Chemical Engineer, Black, Crow & Eidsness,
Inc., 544 N.E. 10th Avenue, Gainesville, Florida 32601
COULTER, James B., Assistant Commissioner, Environmental Health
Services, 2305 N. Charles Street, Baltimore, Maryland 21218
DEAN, Robert B., Chief, Ultimate Disposal Research Program, FWPCA,
4676 Columbia Parkway, Cincinnati, Ohio 45226
DICK, Richard I., Associate Professor of Sanitary Engineering,
Department of Civil Engineering, University of Illinois, Urbana,
Illinois 61801
DOE, Peter W., Havens and Emerson, Consulting Engineers, 507 Boule-
vard, East Paterson, New Jersey 07407
EAGLE, George H., Chief Sanitary Engineer, State Department of
Health, Columbus, Ohio 43221
FAHY, Vernon, City Manager, Minot, North Dakota 58701
HARTUNG, Herbert 0., Exec. Vice Pres. & Mgr. of Production, St. Louis
County Water Co., 8390 Delmar Blvd., St. Louis, Missouri 63124
HENRY, Edgar N., Chief, Division of Water Resources, Department of
Natural Resources, 1201 Greenbrier Street, East, Charleston,
West Virginia 25301
JOHNSON, Curtis E., Assistant Director, City of Austin, Department
of Water & Wastewater Treatment, Austin, Texas 78767
KINMAN, Riley N., Associate Professor of Sanitary Engineering, College
of Engineering, University of Cincinnati, Cincinnati, Ohio 45221
-265-
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266 Directory of Conference Participants
KRASAUSKAS, John W. , Chief Plant Operations, Corps of Engineers,
Dalecarlia and McMillan Plants, 5900 MacArthur Boulevard, N.W.
Washington, D.C. 20016
LACY, William J. , Chief, Industrial Pollution Control Branch, DAST,
R&D, Federal Water Pollution Control Administration, U.S.
Department of the Interior, Washington, D.C. 20242
LAMB, James C., Ill, Professor of Sanitary Engineering, Department
of Environmental Sciences and Engineering, University of North
Carolina, P.O. Box 630, Chapel Hill, North Carolina 27514
NEBIKER, John H., Assistant Professor of Civil Engineering, Department
of Civil Engineering, School of Engineering, University of
Massachusetts, Amherst, Massachusetts 01002
NEUBAUER, Walter K. , O'Brien and Gere, Consulting Engineers, 1050
West Genesee Street, Syracuse, New York 13204
PETERS, Howard R., Director, Water Purification Plants, Department of
Waterworks, 2532 Bolton Road, N.W., Atlanta, Georgia 30318
PLAUTZ, William H., Consoer, Towsend & Associates, Consulting
Engineers, 360 East Grand Avenue, Chicago, Illinois 60611
PROUDFIT, Donald P., Black & Veatch Consulting Engineers, 1500
Meadow Lake Parkway, Kansas City, Missouri 64114
RUSSELMANN, Heinz B., Department of Health, Division of Pure Waters
84 Holland Avenue, Albany, New York 12208
SHULL, Kenneth E., Vice President, Research, Philadelphia Suburban
Water Co., 762 Lancaster Pike, Bryn Mawr, Pennsylvania 19010
STREICHER, Lee, Water Purification Engineer, Metropolitan Water
District of Southern California, Box A, La Verne, California
91750
TCHOBANOGLOUS, George, Assistant Professor of Civil Engineering,
Stanford University, Stanford, California 94305
WEBBER, Joseph C., Chief Engineer, City of Toledo, Ohio, Division
of Water, Erie and Orange Streets, Toledo, Ohio 43624
WEBER, Edwin C., District Engineer, Department of Water Resources,
State Office Building, Annapolis, Maryland" 21401
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Section 5
REFERENCE BIBLIOGRAPHY
The reference bibliography is arranged alphabetically by authors.
In addition to text references, technical articles and publications
are cited to provide related information on the disposal of wastes.
Adrian, D.D.; Lutin, P.A. & Nebiker, J.H. "Source Control of Water
Treatment Waste Solids." Report No. EVE-7-68-1, Dept. of Civil
Engineering, U. of Mass., Amherst, Mass. (1968).
Albertson, O.E. & Guidi, E.J., Jr. "Advances in the Centrifugal De-
watering of Sludges." Water & Sew. Works, Ref. No. 114, R-133
(1967).
Albrecht, A.E.; Wullschleger, R.E. & Katz, W.J. "In-Situ Measure-
ment of Solids in Final Clarifiers." J. San. Eng. Div., Proc.
ASCE, 92:183 (1966).
Ailing, S.F. "Continuously Regenerated Greensand for Iron and Man-
ganese Removal." J.AWWA, 55:749 (1963).
Almquist, F.O.A. "Problems in Disposal of Sludge and Wash Water
for Connecticut Water Filtration Plants.11 J.NEWWA, 60:344
(1946) .
Alsentzer, H.A. "Ion-Exchange in Water Treatment." J.AWWA, 55:742
(1963).
Anon. "Control of Wastewater Discharge from Water Purification
Plants on the Ohio River." Ohio River Valley Water Sanitation
Commission, (Apr. 1968).
Anon. "Dayton, Ohio Recalcines Water Softening Sludge." Water and
Sew. Works, 107:137 (I960).
Anon. "Denver Tries Micros trainers on its Water." Eng. News Record,
(June 1961). p. 28.
Anon. "Harmful to Fish?" Canadian Pulp Paper Industry, 12: No.5
(1959).
Anon. "Joint Plans Speed Construction." Engineering News-Record,
(Dec. 1965). p. 35.
Anon. "Lime-Profit-Making Foreman," Pit and Quarry, (Aug. 1967).
p. 139.
-267-
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268 Reference Bibliography
Anon. "Lime Recovery from a Water Treatment Plant." Industrial
Chemistry (Br.), 9:229 (1933).
Anon. "Microstraining, Test and Operating Results." Glenfield &
Kennedy, Inc., Brochure No. 4.
Anon. "Microstraining, The Denver Story." Glenfield & Kennedy,
Inc., Brochure.
Anon. "The Disposal of Waste Sludge from Water Works." Civil Eng.,
London, 44:506 (1949).
Anon. "Value of Sludge." Waterworks Eng., 90:759 (1938).
Anon. "Water Quality Criteria." FWPCA, U.S. Dept. Int. (1968).
Anon. "Water Softening at Cambridge." The Surveyor (Br.), 88:61
(1935).
Anon. "Water Treatment Plants in the United States." Water Works
Eng., 96:65 (1943).
Aultman, W.W. "Lime and Lime-Soda Sludge Disposal." J.AWWA,
39:1211 (1947).
Aultman, W.W. "Purification Plant Waste Disposal, Comm. Report."
J.AWWA, 45:1225 (1953).
Aultman, W.W. "Reclamation and Reuse of Lime in Water Softening."
J.AWWA, 31:640 (1939).
Aultman, W.W., et al. "Waste Disposal - Water Treatment Plants,
Joint Discussion." J.AWWA, 58:1102 (1966).
Babbitt, H.E. & Caldwell, D.H. "Laminar Flow of Sludges in Pipes
with Speical Reference to Sewage Sludge." U. of Illinois Eng.
Expt. Sta., Bulletin Series No. 319 (1939).
Bacon, V.W. "Sludge Disposal." Indus. Water Eng., 4:27 (1967).
Balden, A.R. "The Disposal of Solid Wastes." Indus. Water Eng.5
4:25 (Aug. 1967).
Bell, G.R. :'Iron Removal Using Filter Aid and Filters." J.NEWWA }
78:258 (1964).
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Reference Bibliography 269
Berry, A.E. "Removal of Algae by Microstrainers." J.AWWA, 53:1503
(1961).
Besselievre, E.B. "Mechanically Cleaned Sedimentation Basins for
Waterworks." J.NEWWA, 41:52 (1927).
Bishop, S.L. & Fulton, G.P. "Lagooning and Freezing for Disposal
of Water Plant Sludge." Public Works, 99:94 (Jun. 1968).
Black, A.P. "Disposal of Softening Plant Wastes, Committee Report."
J.AWWA, 41:819 (1949).
Black, A.P.; Wertz, C.F. & Henry, C.R. "Recalcing Softening Sludge
at Miami, Florida." Waterworks Eng., (Mar. 1951).
Black & Veatch. "Design Report - Bachman Creek Stromwater Overflow
Treatment Plant - Dallas, Texas," (1968).
Bogren, G.G. "Removal of Iron and Manganese from Ground Waters."
J.NEWWA, 76:70 (1962).
Brennan, R.F. "Daytonna Beach's Dilemna: How to Dispose of Lime
Sludge from its Water Softening Plant." Water Works Eng.,
114:704 (1961).
Bruce A.; Clements, G.S. & Stephenson, R.J. "Recent Research Work
at the Northern Outfall Works of the London County Council."
J. Inst. Sewage Purif., 4:238, (1953). Also, J. Inst. Water
Engrs., 12:409 (1958).
Burd, R.S. "A Study of Sludge Handling and Disposal." FWPCA,
U.S. Dept. Int., Pub. WP-20-4 (May 1968).
Camp, T.R. "The New Water Treatment Plant for Billerica, Mass."
J.NEWWA, 72:47 (1958).
Carter, R.C.; Ludwig, H.F.; Ongerth, H.J.; Harmon,-J.A.; & Woody,
S.H., II. "Behavior and Evaluation of Micros training for a
Supply in California." J.AWWA, 54:606 (1962).
Chase, E.S. & Houser, G.C. "Rockport, Mass. - The Evolution of a
Small Water Works System." J.NEWWA, 56:335, (1942).
Chojnacki, A. "Deposits in Water Treatment Plants." Gaz, Woda
Tech. Sanit., 41:416 (1967); (Chem. Absts., 68, 98541)
(1968).
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270 Reference Bibliography
Christensen, W. Manager of Municipal Water Works, City of Copenhagen.
Personal communication (1968).
Clements, G.S.; Stephenson, R.J. & Regan, C.J. "Sludge Dewatering
by Freezing with Added Chemicals." J. Inst. Sewage Purif.,
4:318 (1950).
Comings, E.W.; Priess, C.E. & DeBord, C. "Continuous Settling and
Thickening." Ind. Eng. Chem., 46:1164 (1954).
Committee Report. 1969. AWWA Comm. on Diatomite Filtration, Sub-
corran. on Filter Aid Backwash Disposal. To be published in
J.AWWA.
Committee Report. "Alum Supply and Use in Water Treatment Plants."
J.AWWA, 52:135 (1960).
Committee Report. "Capacity and Loadings of Suspended Solids Con-
tact Units," J.AWWA, 43:263 (1951).
Crow, W.B. "Techniques and Economics of Calcining Softening Sludges
Calcination Techniques." Joint Discussion, J.AWWA, 52:322
(1960).
Gulp, G.; Hansen, S. & Richardson, G. "High Rate Sedimentation in
Water Treatment Works." J.AWWA, 60:681 (1968).
Dalton, F.E.; Stein, J.E. & Lyman, B.T. "Land Reclamation - A Com-
plete Solution of the Sludge and Solids Disposal Problem."
J.WPCF, 40:789 (1968).
Dean, R.B. "Disposal of Wastes from Filter Plants and Coagulation
Basins." J.AWWA, 45:1226 (1953).
Dean, R.B. "Ultimate Disposal of Waste Water Concentrates to the
Environment." Envir. Sci. andTechnol., 2:1079 (1968).
Dean, R.B. "Waste Disposal from Water and Wastewater Treatment
Processes." Proc. 10th San. Eng. Conf., U. of Illinois,
Urbana, 111. (1968).
"Diatomite Filtration of Water." Johns-Manville Corp., Brochure
(1964).
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Reference Bibliography 271
Dittoe, W.H. "Disposal of Sludge at Water Purification and Softening
Works of the Mahoning Valley Sanitary Dist." J.AWWA, 25:1523
(1933) .
Dloughy, P.E. & Hager, A.P. "Vacuum Filtration Solves Problem of
Water Softening Sludge." Water and Wastes Eng., 5:58 (1968).
Doe, P.W. "A Report on the Disposal of Sludge From Water Treatment
Plants." British Waterworks Assoc., Jubilee Travelling Schol-
arship. (1966-67).
Doe, P.W. "The Treatment and Disposal of Wash Water Sludge." J.
Instn. Water Engrs., 12:409 (1958).
Doe, P.W. ; Benn, D. & Bays, L.R. "Sludge Concentration by Freezing."
Water and Sew. Works, 112:401 (1965).
Doe, P.W.; Benn, D. & Bays, L.R. "The Disposal of Wash Water Sludge
by Freezing." J. Indus. Water Eng,, 6:251 (1965).
Eidsness, F.A. "Sludge Disposal from a Coagulation Water-Treatment
Plant." J. Fla. Eng. Soc., 6:9 (1952).
Eidsness, F.A. & Black, A.P. "Carbonation of Water Softening -
Plant Sludge." J.AWWA, 49:1343 (1957).
Eliassen, R. & Bennett, G.E. "Ultimate Disposal of Contaminants
from Wastewater Reclamation Processes." Presented before the
California Water Pollution Control Association, Long Beach,
California (1967).
Emery & Malina. "Phosphate Removal Characteristics of Lime Softening
Sludge." Center for Research in Water Resources, U. of Texas,
Austin, Texas (1969).
Farr, W. & Crow, W.B. "Daytons New Water Plant Features Functional
Simplicity." Waterworks and Wastes Eng., 2:62 (1965).
Fleming, M. "Lime Sludge Becomes Fertilizer." Am. City, (Apr. 1957)
p. 102.
Frissora, F.V. "High Density Solids Contact in Water and Waste Treat-
ment." Indus. Water Eng., 4:26 (Nov. 1967).
Garland, Chet. Personal communication (1969).
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272 Reference Bibliography
Garnet, M.B. & Rademacher, J.M. "Study of Short Filter Runs with Lake
Michigan Water." J.AWWA, 52:137 (1960).
Gates, C,D. & McDennott, R. "Characteristics of and Methodology for
Measuring Water Filtration Plant Wastes." N.Y. State Dept. of
Health, Research Report No. 14 (1966),
Gates, C.D. & McDermott, R.F. "Characterization and Conditioning
of Water Treatment Plant Sludge." J.AWWA, 60:331 (1968).
Gauntlett, R.B. Waterworks Sludge - I. "A Review of the Literature
Relating to Settling, Compaction and De-watering of Waterworks
Sludge." Water Research Association (British), Technical Pa-
per TP.30 (1963).
Gauntlett, R.B. Waterworks Sludge - II. "Physical Properties and
De-watering Characteristics of Waterworks Sludge." Water Re-
search Association (British), Technical Paper TP. 38 (1964).
Gauntlett, R.B. Waterworks Sludge - III. "An Assesment of the
Role of Polyelectrolytes in the De-Watering of Alum Clari-
fication Sludges, with an Evaluation of Polyelectrolytes of
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Gill. "Fifty-Year Accumulation Dredged from Sedimentation Basin."
Waterworks Eng., 99:850 (1927).
Gordon, C.W. "Calcining Sludge from a Water Softening Plant."
J.AWWA, 36:1176 (1944).
Hager, G. "We Vacuum Filter Lime Softening Sludge," Am, City,
(Jun. 1965). p. 105.
Hall, H.R. "Disposal of Wash Water from Purification Plants."
J.AWWA, 39:1219 (1947).
Haney, P.O. "Brine Disposal from Cation-Exchange Softeners." J.AWWA,
41:829 (1949).
Haney, P.O. "Brine Disposal from Zeolite Softeners" J.AWWA, 39:1215
(1947).
Hannah, S.A.; Cohen, J.M. & Robeck, G.C. "Measurement of Floe Strength
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Reference Bibliography 273
Hartung, H.O. "Calcium Carbonate Stabilization of Lime-Softened
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Sew. Works, 1:91 (1944).
Hartung, H.O. "Treatment Plant Innovations in St. Louis, Mo."
J.AWWA, 50:965 (1958).
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Hawkins & Malina. "The Removal of Sulfur Dioxide from a Hot Gas
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Uniformity Control." J.AWWA, 60:570 (1968).
Hoover, C.P. "Discussion of Reclamation and Re-use of Lime in
Water Softening." J.AWWA, 31:675 (1939).
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Italiano, John. Personal Communication (1968).
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(1968).
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Lawrance, C.W. "Lime-Soda Sludge Recirculation Experiments at
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Section 6
SUBJECT INDEX
ADVANCED WASTE TREATMENT
Research 12-13
CONFERENCE REPORTS
Current Technology and Costs
Cost Analysis 150-151
Discussion of Report 239-246
Model Studies 230-238
Plant Visitations 153-229
Review of Technology 136
What is Known
Engineering 28-73
Plant Operation 75-105
Regulatory Aspects 106-131
Research 1-27
What is Needed
Engineering Needs 251-254
Plant Operation 255-257
Regulatory Needs 258-260
Research Needs 247-250
COST CONSIDERATIONS
Barging to sea 82, 99
Basic evaluation procedures
150-151
Centrifugation 9, 16,
142-143
Concentration 146
COST CONSIDERATIONS (cont.)
Diatomaceous earth filtration 147,
171-175, 183, 211-212
Discharge to sewer 104, 138
211-212, 223
Filter washwater 137-138
157-163, 189-191, 213-219
Freezing 16, 41-42, 145
Land disposal 10-11, 60-61, 73, 102
Lagoons 9, 17, 36, 46, 53-55, 77, 85-86,
139-140, 205-209, 221-222, 225-229
Pipeline transport 13, 61, 82, 95,
102
Plant operation 63, 69, 86-87, 91-92,
93-97, 99-101
Pressure filtration 16, 81, 103-104,
145
Recalcination 9-10, 55-58, 86-87,
143-145, 147
Recovery of alum 9-10, 42-43,
82, 93, 95-96, 146
Sand drying 9, 36-37, 81,
140-141, 183-187, 213-219
Ultimate disposal 11, 16-17
Vacuum filtration 8, 37-39, 58
79, 141-142, 230-233, 234-236
DISPOSAL - ALUM SLUDGE
Characteristics 7, 20, 30-32,
66-67, 247, 251
Direct discharge 29, 32, 35-36
Discharge to sewer 25-26, 32,
35-36, 78
-281-
-------
282
Subject Index
DISPOSAL - ALUM SLUDGE (cent.)
Treatment
Centrifugation 9, 13, 16, 21,
23-24, 39-42, 79
Concentration 8, 13, 15, 33,
64, 67
Freezing 12, 14, 16, 18, 21,
23, 24-25, 41-42, 78
Heating 7, 16
Lagooning 9, 13, 16, 36, 77,
85-86, 139-140, 205,209,
221-222, 225-229, 243,
245-246
Polyelectrolytes 8, 16,
20-23, 248
Pressure filtration 14, 39,
81, 96
Recovery of alum 9-10, 17,
42-43, 82, 95-96
Sand drying 9, 36-37, 81,
14.0-141, 213-219, 230,
233
Vacuum filtration 8-9, 12
13, 16, 37-38, 79,
230-233
Wedge wire filtration 9, 81
Ultimate disposal 10-11, 16,
93, 96, 249
DISPOSAL - DIATOMITE SLUDGE
Characteristics 43
Direct discharge 43-44
Treatment 44, 171-175, 183-187
DISPOSAL - FILTER WASHWATER
DISPOSAL - ION EXCHANGE WASTE
Characteristics 44-45, 64
88-89
Direct discharge 45, 88,
89, 94
Discharge to sewer 88-89
223
Effect on biological
processess 45-46
Treatment
Disposal wells 46, 89,
90, 95, 98-99
Evaporation 88, 90
Lagooning 46, 90
Ocean disposal 88, 90, 91,
95
DISPOSAL - IRON AND MANGANESE SLUDGE
Characteristics 47
Treatment 47-48, 66
Ultimate disposal 47, 66
DISPOSAL - LIME SOFTENING SLUDGE
Characteristics 53, 56, 58
61-62, 84, 87
Direct discharge 53
Discharge to sewer 59-60
Engineering problems 59
61-63
Process selection 61-62, 69-70
Treatment
Characteristics 28-29
Direct discharge 29-32
Reuse 29, 94-95, 101-102, 137-138
189, 191, 213-219
Treatment 29, 94-95, 102, 137-138
213-219, 242
Centrifugation 10, 58
Concentration 58
Diatomaceous earth
filtration 183-187
Flash drying 58
Lagooning 53-55, 85-86,
245-246
Recalcination 56-59, 143-145
-------
Subject Index
283
DISPOSAL - LIME SOFTENING SLUDGE
(cont.)
Treatment
Sand drying 183-187
Vacuum filtration 10, 58,
141-142, 157, 199, 234
Ultimate disposal 60-61,
71-72
DISPOSAL - MICROSTRAINER SLUDGE
Characteristics 48, 65
Direct discharge 65, 67
Treatment 49-51
DISPOSAL - PRE-SEDIMENTATION
SLUDGE
Characteristics 48, 65
Dilution 48
Direct discharge 48
Engineering problems 53, 65
Treatment 65
INFORMATION NEEDS
Data collection 123-124
Engineering 48, 49-55, 50,
54, 67, 78
Plant Operation 91-92
Regulatory 126
Research 15-17
PLANT OPERATING PROBLEMS
Discharge to sewer 86
Lagoons 85-86
Odors 53, 94, 245-246
Pressure filtration 103-104
Recalcination 86-87
PROPERTIES OF SLUDGE
Non-Newtonian 7
PROPERTIES OF SLUDGE (cont.)
Rheological 7
Thixotropic 20
Variability 26
RECOMMENDATIONS
Concluding Statement
Pollutional Effect 261-262
Research Coordination 26S.-264
Research Directions 263
Waste Characteristics 261
Engineering Needs
Applied Engineering Research
252
Basic Engineering Research
251
Design Parameters and Costs
253
Information Exchange 254
Plant Operating Experience
253
Plant Operation Needs
Data Collection and
Dissemination 257
Economics of Improved
Operations 257
New or Modified Treatment
Processes 234, 255-256, 262
Uses and Disposal of Wastes
256-257
Regulatory Needs
Existing Water Treatment
Plants 259
General Statement 258-260
Information Clearing House 260
New Water Treatment Plants 259
Sources of Wastes 258-259
Summary Statement 260
-------
284
Subject Index
RECOMMENDATIONS (cont.)
Research Needs
Future Water Treatment and
Waste Management Technology
250
Nature of Wastes 247-248
Treatment of Wastes 248-249
Ultimate Disposal of Wastes
249
REGULATORY ASPECTS
Conference Report on
Regulatory Needs 258-260
Enforcement proceedings 75,
98, 106, 125-126
Great Britain 71, 128-129
Japan 95
Philosophy 98, 124
State and Inter-state
Regulations 2, 108-119,
120-121, 130-131
Survey, AWWA Committee
1-2, 106
Survey, AWWA Research
Foundation 106-121,
122-124
Water Quality Act of 1965
106
RESEARCH PROBLEMS
Coordination 19, 253, 257-263
Current 11-14, 247-250
Nature of wastes 5-7, 247
New Technology 68, 250
Support 127-128, 263
Treatment of wastes 248,
251-254, 255-257
Ultimate disposal 249-250,
251-252
TRANSPORATION OF SLUDGE
Barging to sea 82, 99
Pipeline 82, 94, 102
Trucking 61, 156
UTILITY OF WASTES
Acid neutralization 10, 27, 94
Additive 10
Alum recovery 9, 93-96
Concrete 73
Fertilizer 11, 25
Industrial processes 10, 26
Landfill 10, 61, 73
Phosphate removal 18
Sewage treatment 27, 60, 73
Soil conditioner 60
-------
BIBLIOGRAPHIC: American Wafer Works Association Research Foundation,
Disposal of Wastes from Water Treatment Plants, FWPCA, Water Pol-
lution Control Research Scries, ORD-2, 1969.
ABSTRACT: This report is on intensive study of the disposal of wastes from
water treatment plants, the wastes include filter wathwater; sludge
resulting from coagulation, softening, iron and manganese removal
processes; diatomoceous earth filtration; and ion exchange brines.
The control of pollution from these wastes is o high priority problem
for the water utility industry.
A series of four status reports describe tn detail what is known of the
research, engineering, plant operation, and regulatory aspects of the
problem. A special report reviews current technology and analyzes
costs of disposal methods, based on doto collected from fifteen oper-
ating plants. A conference was organized to provide expert evalua-
tion of each report and to extend the dolo available.
ACCESSION NO:
KEY WORDS:
Watte Disposal
Waste Treatment
Water Treatment
Sludge Treatment
Ultimate Disposal
BIBLIOGRAPHIC: American Water Works Association Research Foundation,
Disposal of Wastes from Water Treatment Plants, FWPCA, Water Pol-
lution Control Research Series, ORD-2, 1969.
ABSTRACT: This report is on intensive study of the disposal of wastes from
water treatment plants. The wastes include filter woshwoter; sludge
resulting from coagulation, softening, iron and manganese removal
processes; diatomoceous earth filtration; and ton exchange brines.
The control of pollution from these wastes is a high priority problem
for (he water utility industry.
A series of four status reports describe in detail what is known of the
research, engineering, plant operation, and regulatory aspects of the
problem. A special report reviews current technology and analyzes
costs of disposal methods, based on data collected from fifteen oper-
ating plants. A conference was organized lo provide expert evalua-
tion of each report and to extend the data available.
ACCESSION NO:
Waste Disposal
Waste Treatment
Water Treatment
Sludge Treatment
Ultimale Disposal
BIBLIOGRAPHIC: American Water Works Association Research Foundation,
Disposal of Wastes from Wafer Treatment Plants, FWPCA, Water Pol-
lution Control Research Series, ORD-2, 1969.
ABSTRACT: This report is an intensive study of the disposal of wasies from
water treatment plants. The wastes include fitter wasliwoter; sludge
resulting from coagulation, softening, iron and manganese removal
processes; diatomaceous earth filtration; and ion exchange brines.
The control of pollution from these wastes is a high priority problem
for the water utility industry.
A scries of four status reports describe in detail what is known of the
research, engineering, plant operation, and regulatory aspects of the
problem. A special report reviews current technology and analyzes
costs of disposal methods, based on data collected from fifteen oper-
ating plants. A conference wos organized to provide expert evalua-
tion of each report and to extend the data available.
ACCESSION NO:
KEY WORDS:
Waste Disposal
Waste Treatment
Woter Treatment
Sludge Treatment
Ultimate Disposal
-------
Fine! reports were prepared by committee* of conference participants
to identify future needj for information in eoch aspect of the waste
disposal problem. These reports recommend substantially expanded
programs of research and demonstration. They include extensive lists
of specific problems which must be investigated to develop effective
and economical technology.
Committee reports also recommend establishment of a central service
to promote the planning of research and development, and to imple-
ment effective programs of new or improved technology. The service
would collect, coordinate, and disseminate data on a!l aspects of
water treatment plant waste disposal problems.
This report was submitted in fulfillment of Research Grant 12120 ERC
(formerly WP 1535-01-69) between the Federal Water Pollution Controf
Administration and the American Water Works Association Research
Foundation.
Operation
Maintenance
Cost Ana I y si i
Regulation
Surveys
Utilities
Water Works
Fine! reports were prepared by committees of conference participants
to identify future needs for information in each aspect of the waste
disposal problem. These reports recommend substantially expanded
programs of research and demonstration. They include extensive lists
of specific problems which must be investigated to develop effective
and economical technology.
Committee reports also recommend establishment of a central service
to promote the planning of research and development, and to imple-
ment effective programs of new or improved technology. The service
would collect, coordinate, and disseminate data on all aspects of
water treatment plant waste disposal problems.
This report was submitted in fulfillment of Research Grant 12120 ERC
(formerly WP 1535-01-69) between the Federal Water Pollution Control
Administration and the American Water Works Association Research
Foundation.
Operation
Maintenonce
Cost Analysis
Regulation
Surveys
Utilities
Final reports were prepared by committees of conference participants
to identify future needs for information in eoch aspect of the waste
disposal problem. These reports recommend substantially expanded
programs of research and demonstration. They include extensive lists
of specific problems which must be investigated to develop effective
and economical technology.
Committee reports also recommend establishment of a central service
to promote the planning of research and development, and to imple-
ment effective programs of new or improved technology. The service
would collect, coordinate, and disseminate data on all aspects of
water treatment plant waste disposal problems.
This report was submitted in fulfillment of Research Grant 12120 ERC
(formerly WP 1535-01-69) between the Federal Water Pollution Control
Administration and the American Water Works Association Research
Foundation.
Operation
Maintenance
Cost Analysis
Regulation
Surveys
Utilities
Wotcr Works
-------
As the Nation's principal conservation agency, the Department of the
Interior has basic responsibilities for water, fish, wildlife, mineral, land,
park, and recreational resources. Indian and Territorial affairs are other
major concerns of America's "Department of Natural Resources."
The Department works to assure the wisest choice in managing all our
resources so each will make its full contribution to a better United
States-now and in the future.
WATER POLLUTION CONTROL RESEARCH SERIES O ORD-2
------- |