EPA-600/2-78-014
February 1978
Environmental Protection Technology Series
PILOT INVESTIGATIONS OF SECONDARY SLUDGE
DEWATERING ALTERNATIVES
Industrial Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ENVIRONMENTAL PROTECTION TECH-
NOLOGY series. This series describes research performed to develop and dem-
onstrate instrumentation, equipment, and methodology to repair or prevent en-
vironmental degradation from point and non-point sources of pollution. This work
provides the new or improved technology required for the control and treatment
of pollution sources to meet environmental quality standards.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/2-78-014
February 1978
PILOT INVESTIGATION OF SECONDARY SLUDGE
DEWATERING ALTERNATIVES
by
Reid A. Miner
Duane W. Marshall
National Council of the Paper Industry
for Air and Stream Improvement, Inc.
Central-Lake States Regional Center
Kalamazoo, Michigan 49008
Isaiah Gellman
National Council of the Paper Industry
for Air and Stream Improvement, Inc.
New York, New York 10016
Grant No. R-804019-01-0
Project Officer
Victor J. Dallons
Industrial Pollution Control Division
Food and Wood Products Branch
Corvallis, Oregon 97330
INDUSTRIAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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DISCLAIMER
This report has been reviewed by the Industrial Environ-
mental Research Laboratory, U.S. Environmental Protection
Agency, and approved for publication. Approval does not signify
that the contents necessarily reflect the views and policies of
the U.S. Environmental Protection Agency, nor does mention of
trade names or commercial products constitute endorsement or
recommendation for use.
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FOREWORD
When energy and material resources are extracted, processed, converted,
and used, the related pollutional impacts on our environment and even on
our health often require that new and increasingly more efficient pollution
control methods be used. The Industrial Environmental Research Laboratory -
Cincinnati (lERL-Ci) assists in developing and demonstrating new and
improved methodologies that will meet these needs both efficiently and
economically.
This report concerns evaluating and comparing various sludge dewatering
devices for use on biological sludges produced in the treatment of pulp
and paper mill wastes. The information and comparisons developed should be
useful to designers of pulp and paper waste and treatment systems to evaluate
which sludge dewatering technology and which ultimate disposal scheme will
be most applicable to the site in question. For further information about
this report contact the Food and Wood Products Branch of the Industrial
Pollution Control Division.
David G. Stephan
Director
Industrial Environmental Research Laboratory
Cincinnati
1X1
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ABSTRACT
A pilot investigation of biological sludge thickening and
dewatering alternatives, including pressure filtration, precoat
vacuum filtration, filter belt pressing, capillary suction
dewatering, gravity filtration, centrifugation, and ultrafiltra-
tion has been conducted on waste activated sludge resulting from
the treatment of waste water from an integrated bleached kraft-
fine paper mill. Based upon a criterion of attainable cake con-
sistency, three levels of performance are indicated: (1) pres-
sure filtration and precoat vacuum filtration generating the
driest cakes, (2) filter belt pressing yielding intermediate
cake consistencies, and (3) gravity filtration, centrifugation,
and ultrafiltration resulting in relatively low cake consisten-
cies. In general, performance has been found to be severely
affected by changes in feed sludge consistency, the amount of
sludge conditioning, and the sludge's specific resistance to
filtration. The type and amount of sludge conditioning required
has been shown to be extremely variable, depending upon the
dewatering technique being employed, the level of performance
being expected of it, and the consistency and nature of the
sludge being dewatered.
IV
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CONTENTS
Foreword iii
Abstract iv
Figures vi
Tables viii
Acknowledgment x
1. Introduction 1
2. Conclusions 3
3. Recommendations 5
4. General Description 6
5. Pressure Filtration Investigation 8
6. Precoat Vacuum Filtration Investigation 11
7. Tait-Andritz Sludge Dewatering Machine (SDM)
Filter Belt Press Investigation 37
8. Permutit Dual Cell Gravity Filter-Multiple Roll
Press Investigation. 44
9. Capillary Suction Sludge Dewatering Device
Investigation 52
10. Sharpies P3000-BD Horizontal Bowl Centrifuge
Investigation 63
11. Ultrafilter Investigation 69
12. Discussion of Alternatives 79
13. Other Pulp and Paper Industry Experience. ..... .83
References 89
Appendices
A. Pilot equipment performance data 90
B. Performance levels used to calculate equipment
requirements ....108
C. Manufacturers of pressure filters 112
D. Manufactures of precoat vacuum filters 113
E. Manufacturers of filter belt presses 114
v
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FIGURES
Number Page
1 Variability of biological sludge dewaterability 7
2 Netzsch pressure filter 10
3 Typical pressure filtration cycle 12
4 Relationship between bulk cake consistency and
accumulated solids mass 14
5 Diatomaceous earth slurry filtration rates through
unused and used, nonprecoated media 20
6 Rotating knife doctor blade assembly 23
7 Precoat vacuum filter solids loading rates 26
8 Loading rates attained on high specific resistance
(SR) sludges. . '. 27
9 Precoat Vacuum Filter cake consistency 29
10 Effect of vacuum upon Precoat Vacuum Filter cake
consistencies 30
11 Tait-Andritz SDM 38
12 Tait-Andritz SDM cake consistencies 42
13 Permutit DCG-MRP 45
14 MRP cake consistencies 50
15 Schematic of Squeegee 53
16 Squeegee belt speed requirements 56
17 Squeegee cake consistencies at 0.6-1.7 t/linear inch
of roller pressure (1-3 N/cm) 57
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FIGURES
(continued)
Number Page
18 Squeegee cake consistencies at 3.9-4.5 ft/linear inch
of roller pressure (6.8-7.8 N/cm) 58
19 Squeegee cake consistencies at 6.1-7.3 #/linear inch
of roller pressure (11-13 N/cm) 59
20 Squeegee solids recovery. . 60
21 Centrifuge performance at 90 percent solids recovery. . 66
22 Effect of pond setting on solids recovery and cake
consistency 68
23 Typical ultrafiltration flux curve 71
24 Effect of backflushing for flux maintenance 72
25 Ultrafiltration steady state flux rates as functions
of feed consistency and fluid velocity 74
26 Pressure drop through the membrane module during six
tube operation 75
VI1
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TABLES
Number Page
1 Biological Sludge Dewatering Alternatives Studied. ... 7
2 Pressure Filtration Process Variables 9
3 Characteristics of Pressure Filter Media 9
4 Pressure Filter Performance Summary 15
5 Effects of Operating Pressure upon Pressure Filtration .16
6 Correction of Cake Consistencies for Admix Content . . .17
7 Alternative Conditioning Techniques Evaluated for
Pressure Filtration 18
8 Precoat Vacuum Filtration Process Variables 24
9 Evaluation of Alternative Precoat Materials 32
10 Flyash - Diatomaceous Earth Size Distribution Compar-
ison 33
11 Flyash Particle Size 34
12 Combustible Matter Content of Flyash Samples 34
13 Utilization of Polymer Conditioning in Precoat Vacuum
Filtration 36
14 Tait-Andritz SDM Operating Variables 39
15 Tait-Andritz Sludge Dewatering Machine (SDM) 40
16 Dual Cell Gravity Filter (DCG) and Multiple Roll
Press (MRP) Process Varabiles 46
ly DCG 100 Performance Summary 48
18 Squeegee Process Variables 54
19 Sharpies BD Decanter Centrifuge Process Variables. . . .63
viii
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TABLES
(continued)
Number Page
20 Characterization of Centrifuge Feed 65
21 Ultrafiltration Process Variables 69
22 Membrane Area Requirements for 2000 Pounds (908 KG)
Sludge Solids Per Day 76
23 Proposed Membrane Configuration to Thicken 1 TPD
of Sludge Solids 78
24 Equipment Requirements for 10 TPD of Waste Activated
Solids Based on Pilot Study Findings 80
25 Pulp and Paper Industry Filter Belt Press Experience . .84
26 Pulp and Paper Industry Pressure Filter Experience . . .87
A-l Precoat Vacuum Filter Data 90
A-2 Dual Cell Gravity Filter (DCG) - Multiple Roll
Press (MRP) Data 94
A-3 Sharpies BD-3000 Centrifuge Data 96
A-4 Tait-Andritz SDM Data 99
A-5 Squeegee Data 101
A-6 Pressure Filter Data 104
IX
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ACKNOWLEDGMENTS
The authors gratefully acknowledge the contributions of the
following individuals and organizations in the conduct of this
study.
P.H. Glatfelter Company
Packaging Corporation of
America
Johns-Manvilie Company
P-K Associates-
Permutit Company
Sharpies Division of Pennwalt
Corporation
Tait-Andritz Corporation
Mr. Phillip Hershey
Dr. Neal Carter
Mr. Larry Metzger
Dr. Robert Olsen
Mr. Dean Hoover
Mr. Bill Higgs
Mr. Bob Foti
Mr. Roger Smithe
Mr. G.R. Bell
Mr. Alan Wirsig
Mr. Peter Kaye
Mr. Doug McCord
Mr. James Walzer
Mr. Bill Coon
Mr. Dick Moll
Mr. John McKenna
Mr. Charles Hetrick
Mr. Jack Malcomson
Dr. John Leppitsch
Dr. Joseph Bauer
In addition, the efforts of National Council for Air and
Stream Improvement technical assistants Rick Hartman, Jane Mc-
Clary, Dana Marks, Jeff Marks, Dirk Swinehart, Paul Turpin, and
Tom Wistar are gratefully acknowledged.
The contributions of Mr. Russell 0. Blosser, Assistant
Technical Director of the National Council for Air and Stream
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Improvement, and the secretarial assistance of Ms. E. Kavelman
and Ms. C. Clark are especially appreciated.
Finally, the support of this study by the Research and
Development Office of the United States Environmental Protection
Agency, and the assistance provided by the Project Officer,
Mr. V. Dallons, is gratefully acknowledged.
XI
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SECTION 1
INTRODUCTION
The process of wastewater treatment is primarily one of
concentrating or converting potential pollutants into dilute
slurries of solids, commonly called sludge, which require dis-
posal. Because the costs of disposing of these solids are often
strongly dependent upon the amount of water associated with them,
most sludge handling systems include a dewatering stage. Due to
the nature of the solids involved, sludges vary widely in their
responsiveness to dewatering, with biological sludge being among
the most difficult to dewater.
The most common method for dewatering biological solids in
the pulp and paper industry has been in combination with primary
solids on vacuum filters or centrifuges (1). This technique has
been generally successful due to (a) the fibrous nature of much
of the industry's primary sludge and (b) the existance of favor-
able ratios of primary-to-secondary solids, normally 5:1 to 3:1.
However, there are a growing number of mills finding it advanta-
geous or necessary to dewater sludges composed primarily or
entirely of biological solids.
For instance, the sulfite and NSSC segments of the industry
are characterized by high BOD generation rates relative to sus-
pended solids losses resulting in primary-to-secondary sludge
ratios of from 1:1 to 1:3. Recycled paperboard mills are able,
in many instances, to reuse primary solids in the production
process making them unavailable for admixing with secondary
sludge. Even in those segments of the industry where the pri-
mary sludges have been typically fibrous in nature and. the
ratios of primary-to-secondary solids have been favorable, inten-
sified efforts at minimizing fiber losses have resulted in dimin-
ished quantities of increasingly difficult-to-dewater primary
sludge being available for admixing. Other mills are considering
separate dewatering of primary and secondary sludges to preserve
the superior dewaterability of their primary sludge, or protect
by-product opportunities for either of the sludges. The sludges
resulting from these sludge handling and dewatering practices
have generally not been amenable to conventional vacuum filtra-
tion, decanter centrifugation, or V-pressing. Concurrent with
the generation of more difficultly dewatered sludges, many mills
are beginning to utilize final disposal methods that favor the
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the generation of cakes with consistencies beyond the capabili-
ties of applicable conventional dewatering technologies.
In general then, the industry's final disposal requirements,
and changing sludge characteristics clearly indicate the need
for dewatering technologies with capabilities beyond those nor-
mally associated with vacuum filtration, decanter centrifugation,
and V-pressing.
This report describes the findings of a field investigation
in which eight pilot dewatering devices were operated on biolog-
ical sludge from the activated sludge process.
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SECTION 2
CONCLUSIONS
All of the units investigated were capable of dewatering
this mill's waste activated sludge.
The pressure filter and precoat vacuum filter generated the
driest cakes (25 to 40 percent solids) making them likely alter-
natives where incineration, or dry cake for landfilling or haul-
ing are involved in final disposal. The possible effects of
handling and disposing of the nonsludge fraction of these cakes
require consideration.
Pressure filter performance on the sludge studied was not
enhanced by higher operating pressures (13 atmospheres v. 7 at-
mospheres) . Additional industry experience suggests lower oper-
ating pressures to be adequate for other types of sludges as
well.
The filter belt presses generated cake consistencies
approaching 20 percent solids. Relatively low power and main-
tenance costs are likely to be associated with these units. The
filter belt presses generated the driest cakes of the units not
utilizing inorganic conditioning, suggesting them as a likely
alternative where inorganic contamination of the sludge is not
desired.
The gravity filter and centrifuge generated cakes at 8 to
10 percent maximum consistency, indicating probable applications
in prethickening for pressure filtration, digestion or heat
treatment, or where land disposal of semi-fluid sludge is envi-
sioned. The gravity filter offers very low power costs while
the centrifuge offers no sludge conditioning costs.
The ultrafilter was capable of thickening sludge to 7 per-
cent consistency. However, the high power costs associated with
overcoming the pressure drop through the system suggest that a
different membrane configuration would be required to make the
process feasible.
There were several units that consistantly operated at
solids recoveries of 99 percent or better suggesting their
applicability where the liquid fraction solids levels had to be
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low. These units were the pressure filter, the precoat vacuum
filter, the gravity filter and the ultrafilter.
Artificially increasing the specific resistance of the
unconditioned sludge from a range of 50 to 200 x 107 sec2/gm to
a range of 150 to 400 x 107 sec^/gm had a substantial detri-
mental impact on the performance of those units which could
handle the degraded sludge. Caution is, therefore, indicated
in applying the data in this study directly to other sludges,
particularly where knowledge of the specific resistance of the
sludge in question is lacking.
Most of the units indicated a sensitivity to feed concentra-
tion and achieved or indicated significantly superior perfor-
mance at sludge feed consistencies of 2 percent solids as com-
pared to 1 percent solids.
Additional pulp and paper industry experience has shown
both pressure filtration and filter belt pressing to be applica-
ble to primary, secondary, and combined sludge dewatering. Per-
formance levels are determined by the equipment configuration,
the nature of the solids, the type and amount of sludge condi-
tioning, and the feed consistency.
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SECTION 3
RECOMMENDATIONS
This study has given rise to a number of issues related to,
but not within the scope of, this investigation.
1. Documentation of the capabilities of these technol-
ogies on other pulp and paper industry sludges should
be continued as more pilot and full scale data is
generated throughout the industry.
2. As full scale pulp and paper industry experience
on these technologies becomes increasingly avail-
able/ an ongoing effort is warranted to (a) deter-
mine the reliability of manufacturer's performance
estimates and (b) identify any chronic process
limitations or maintenance problems that arise.
3. The information available on the capabilities of
sludge dewatering technology requires delineation
of an analysis framework conducive to the develop-
ment of some optimal strategy for achieving speci-
fied ultimate disposal objectives at individual
locations. Implicit in doing so is the availabil-
ity of cost information adequate for comparisons.
4. Because the nature of the filtration media has been
found in several instances to be a crucial variable
in assuring acceptable performance, the need exists
for a rational method of media selection based upon
an understanding of the properties of the sludge-
media interface.
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SECTION 4
GENERAL DESCRIPTION
Recognizing the need for additional dewatering alternatives,
especially for biological sludges, and realizing the importance
of unbiased performance data in the selection of dewatering equip-
ment, the National Council, with the cooperation of the Environmental
Protection Agency, Cincinnati, Ohio, and P. H. Glatfelter Company in
Spring Grove, Pennsylvania, and Packaging Corporation of America
in Filer City, Michigan, conducted a study of the eight different
emerging or novel dewatering alternatives listed in Table 1. All
units except the ultrafilter were tested at P. H. Glatfelter Company,
a bleached kraft mill producing 600 tons of fine papers per day.
The sludge utilized was secondary clarifier underflow generated in
the mill's contact stabilization activated sludge system. The sludge
was characterized by consistencies of 0.5 to 1.5 percent solids,
ash contents of 35 to 45 percent, a mixed liquor SVI (sludge volume
index) of 100 to 200, and a specific resistance to filtration (2)
(3) ranging from 50 to 200 x 107 sec2/gm. The variability in the
secondary sludge's resistance to dewatering is demonstrated in Figure 1
Because the specific resistance of the sludge was relatively low for
biological sludge in general, efforts were made, when possible, to
also test the equipment with sludge that had been physically degraded
by either aging or pumping through a centrifugal pump. Sludges thus
treated typically had a specific resistance of 200 to 1000 x 10?
sec^/gm suggesting that centrifugal pumping and sludge aging might
contribute to decreased sludge dewaterability at other mills as well.
Because of the variability in sludge characteristics from mill to
mill, the data generated in this study are not necessarily directly
applicable to sludges at other locations, particularly where a know-
ledge of the specific resistance of the sludge in question is lacking.
Furthermore, the documented variability at an individual location
suggests the importance of collecting sludge dewaterability data
over a period longer than, but inclusive of, any pilot study under-
taken.
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TABLE 1. BIOLOGICAL SLUDGE DEWATERING ALTERNATIVES STUDIED
Technology
Pressure filter
Precoat vacuum filter
Filter belt press
Filter belt press
Capillary filter belt press
Biological sludge deanter
centrifuge
Gravity filter
Ultrafilter
Manufacturer
Netzsch
Dorr-Oliver, pilot unit obtained
through Johns-Manville Corp.
Pernmtit
Tait-Andritz
Prototype built by Westinghouse
under EPA contract
Sharpies
Permutit
Westinghouse modules utilized,
assembled by the National
Council
Date
Figure 1. Variability of biological sludge
dewaterability.
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SECTION 5
PRESSURE FILTRATION INVESTIGATION
PROCESS DESCRIPTION
Pressure filtration is a batch dewatering process using a
series of filter media-lined chambers formed by adjoining
recessed plates. Sludge is forced into the chambers under pres-
sure, the liquid passing through the filter media into collec-
tion troughs in the plates and away from the chambers. The
solids meanwhile accumulate in the chambers until additional
solids are entering at a very low rate. At this point the
plates are separated and the cakes of accumulated solids are
discharged. These filters can be operated in a precoat mode
utilizing diatomaceous earth or flyash (or other suitable mater-
ials) to provide a layer of solids between the sludge solids and
the filter media, to provide protection for the filter media and
promote clean cake discharge. The operating variables for the
pressure filtration process are listed in Table 2.
DESCRIPTION OF PILOT UNIT
The pressure filter used in this study was a three-chamber
Netzsch filter with a capacity of 0.87 gallons (3.3 liters).
The cakes generated on this unit were 10 in. (25.4 cm) square
and 1 in. 42.54 cm) thick. The three chambers offered a total
of 2.94 ft2 (0.27 m2) of filter area. The operating pressure
was variable from 0 to 200 atmospheres (0 to 200 bar) and was
maintained with a progressing cavity sludge pump in conjunction
with an air compressor and pressurized feed tank as shown in
Figure 2. The three different filter media that were used are
described in Table 3.
OPERATION OF THE PILOT NETZSCH PRESSURE FILTER
In those cases when a diatomaceous earth precoat was
required, it was applied at 0.13 Ib of diatomaceous earth per
ft2 filter area (0.63 kg/m2). This amount was determined
through a procedure involving visual examination of the depos-
ited precoat. A diatomaceous earth slurry at about 1 percent
concentration was introduced to the unit between the pressure
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TABLE 2. PRESSURE FILTRATION PROCESS VARIABLES
Independent variables
1. Chamber dimensions and characteristics
2. Media characteristics
3. Precoat utilization
4. Precoat characteristics
5. Operating pressure
6. Cycle time
7. Sludge consistency
8. Sludge conditioning
9. Nature of the sludge solids
Dependent variables
1. Cake consistency
2. Loading rate
3. Solids recovery
TABLE 3. CHARACTERISTICS OF PRESSURE FILTER MEDIA
Media A - monofilament
4:1 satin weave
56 threads/inch x 56 threads/inch
interthread opening - 0.37 mm x 0.29 mm
Media B - monofilament
4:1 satin weave
46 threads/inch x 46 threads/inch
interthread opening - threads tightly packed
Media C - multifilament
3:2 satin weave
150 threads/inch x 35 threads/inch
interthread opening - threads tightly packed
9
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AIR COMPRESSOR
SLUDGE PUMP
PRESSURIZED FEED TANK
FILTER CHAMBERS
v
A
FILTRATE
RELIEF VALVE
AND INJECTION POINT
FOR PRECOAT SLURRY
Figure 2. Netzsch pressure filter
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tank and the filter chambers at 0.5 to 1 gpm/ft^ of area
(20-40 1/min/m2). The resulting filtrate was recirculated to
the diatomaceous earth slurry feed vessel until the vessel con-
tents were clear. This flow rate was found necessary to achieve
even distribution of the diatomaceous earth. A somewhat lower
rate would be suitable for less easily filterable precoat mater-
ials. After the diatomaceous earth slurry feed tank contents
were clear, it was found necessary to pump air through the
chambers until the majority of the water had been removed from
the deposited precoat. This prevented the precoat from sliding
to the bottom of the chambers prior to sludge's being introduced.
Test runs were preceded by adjusting the pressure regula-
tors to the desired operating pressure. The test was initiated
by turning on the feed pump and air compressor causing sludge to
be forced into the filtration chambers. Stopwatch timing of the
run was started when the first drop of filtrate was collected.
The remainder of the- test consisted of recording the
volume of filtrate collected and the pressure attained as a
function of time. A typical time/volume/pressure relationship
is shown in Figure 3. Although in some circumstances the high
initial rate of increase in pressure would indicate media blind-
ing, in the study the fact that cake consistencies and cycle
times were reasonable suggests that the high initial rate of
increase in pressure is a result of an oversized feed pump in
relation to the total chamber volume. Work by Martin and Havden
(4) suggests that the performance levels achieved with a rapid
pressure increase are comparable to those attained under condi-
tions of gradually increasing pressure.
After the prescribed length of cycle time, the pressure was
relieved, the plates were separated and the cakes removed. The
middle cake was weighed and three samples were taken from it:
one from the upper and one from the lower right corners and one
from halfway between the center of the cake and the middle of
the right edge. The effective bulk cake consistency was defined
as the average of these three to minimize the impact of consis-
tency variation throughout the cake. Samples were also taken of
the conditioned and unconditioned feed and the filtrate. Spe-
cific resistance determinations on the conditioned and uncondi-
tioned sludges allowed judgments as to the nature of the uncon-
ditioned solids and the effectiveness of the conditioning util-
ized. To aid in the assessment of the potential advantages of
precoat utilization, the ease of cake discharge and media clean-
ing were noted.
RESULTS OF PRESSURE FILTRATION TESTS
Loading Rates
The rate at which the filter could handle solids depended
upon the required cake consistency, the feed concentration, the
11
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8
0)
ฃ
5
CO
c
- 3
0)
1 2
0)
ฃ 1
25
100
50 75
Time min.
Fiaure 3. Typical pressure filtration cycle.
125
40
30
Q)
S"
20 CL
10
C
3
o>
(D
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(0
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nature of the solids, and the type and amount of conditioning.
Loading rates are related to cake consistencies through the
cycle time and solids accumulation. Figure 4 shows that the bulk
cake consistency increases with the total weight of solids depos-
ited in the filter. The desired cake consistency is then
achieved when sufficient cake solids are accumulated. The
quantity of solids deposited at any particular time is calcu-
lated from the total flow and feed concentration. The total
solids deposited per filter area divided by the cycle time is
the pilot loading rate. However, because of the fact that areas
around the feed ports are of lower cake consistency than the
rest of the filter surface and because these areas represent a
much larger proportion of the filtration surface in pilot than
in full scale units, using the calculated pilot loading rates
will result in values much lower than commonly encountered in
full scale. On this particular pilot unit, the problem is fur-
ther aggravated by a media-anchoring plate which obstructs a
significant portion of.the filtration area in the first of the
three chambers. Because of the difficulties encountered in
determining meaningful pilot loading rates, the values in
Table 4 are the loading rates calculated at the effective cake
consistency (defined in the previous section). These effective
loading rates are determined by calculating the weight of solids
that would be present in the filled press if the cakes were of
uniform consistency using the following equation
T_a/q. _ .. _ Press Volume x Cake Density
Loading Rate = =r r = . *-
* Press Area x Cycle Time
where the cake density is based upon the effective cake consis-
tency as presented in Reference 5. As shown in Table 4, other
things being equal, lower loading rates are required to obtain
higher cake consistencies. The table also illustrates that the
benefits associated with prethickening of pressure filter feed
are substantial, allowing reductions in sludge conditioning
costs, shorter cycle times, or higher cake consistencies. Physi-
cally degraded solids required significantly lower loading rates
or more conditioning to achieve cake consistencies comparable to
fresh waste activated sludge filter cakes.
Seven separate sets of runs were conducted at different
times in the pilot program to document the magnitude of the
advantages associated with higher operating pressures. The
results, summarized in Table 5, provide little basis for using
13.5 atmospheres of pressure in the filtration of this sludge.
Acceptable capacities were maintained in the operating pressure
range of 6 to 8 atmospheres. One issue not addressed in this
study was the effect of chamber depth upon loading rate and
optimum operating pressure.
13
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co 40
TJ
O
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a* 36
o
ง 32
CO
O 28
O
<]>
3 24
03
20
200
.44
350
.77
500
1.10
650
1.43
800
1.76
950
2.04
1100 grams
2.42 pounds
Total Weight of Deposited Solids
Figure 4. Relationship between bulk cake consistency
and accumulated solids mass.
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TABLE 4. PRESSURE FILTER PERFORMANCE' SUMMARY
FRESH WASTE ACTIVATED SLUDGE
Feed
consistency
% solids
0.7-1.00
0.7-1.00
1.1-1.35
1.1-1.35
1.6-1.70
1.6-1.70
1.0-2.00
Bulk cake
consistency
% solids
26-32
32-38
26-32
32-38
26-32
32-38
38-40
Cycle time
requirement
hr
1.00-1.50
2.00-3.50
0.75-1.00
1.00-2.00
0.50
0.50-0.75
3.00-3.50
Conditioning
requirement
25-30% lime & 7-8% FeCl3
35-40% lime & 8-10% FeCl3
25-30% lime & 7-8% FeCl3
25-30% lime & 7-8% FeCl3
25% lime & 7% FeCl3
25% lime & 7% FeCl3
25-30% lime & 7% FeCl3
Loading rate*
#/ft2/hr
1" cake
0.81-0.54
0.49-0.28
1.08-0.81
0.97-0.49
1.62
1.94-1.29
0.37-0.32
#/gal/hr
2.72-1.82
1.64-0.94
3.63-2.72
3.28-1.64
5.44
6.56-4.37
1.25-1.07
H
Ul
AGED OR HIGHLY SHEARED WASTE ACTIVATED SLUDGE
0.6-0.90 ;
1.0-1.30 ;
1.0-1.30
1.4-1.60
1.4-1.60
1.0-2.00
2.1-2.70
2.1-2.70
11.2**
11.2**
26-32
26-32
32-38
26-32
32-38
38-40
2.00-3.
0.75-1.
1.00-2.
0.75-1.
1.00-2.
3.00-3.
26-32 0.50-0.
32-38 1.00-1.
26-32 0.25-0.
32-38
0.50-0.
50
00
00
00
00
50
75
50
50
75
I
|35-45%
35-40%
35-40%
!25-30%
J25-30%
135-40%
|15-20%
'15-20%
lime &
lime &
lime &
lime &
lime &
lime &
lime &
lime &
J30% lime & 7%
i 30% lime & 7%
8-10% FeCl3
7-8% FeCl3
0
1
7-8% FeCl3 0
6-7% FeCl3 | 1
6-7% FeCl3
7% FeCl3
0
0
4-6% FeCl3 , 1
4-6% FeCl3 i 0
FeCl3 : 3
FeCl3 | 1
.41-0.
.08-0.
.97-0.
.08-0.
.97-0.
.37-0.
. 621 .
.97-0.
.24-1.
.94-1.
23
81
49
81
49
32
08
65
62
1
3
3
3
3
1
5
3
10
29 6
.39-0.78
.65-2.74
.28-1.66
.65-2.74
.28-1.66
.25-1.08
.47-3.65
.28-2.20
.95-5.47
.56-4.36
*Based upon cake densities of 68, 70 and 72 pounds per wet cubic foot for cakes of
30, 35, and 39 percent solids respectively (Reference 5)
**0nly one test run attempted with centrifugally thickened, sheared, waste activated
sludge
-------
TABLE 5. EFFECTS OF OPERATING PRESSURE UPON PRESSURE FILTRATION
Data
set
1
1
Date
9/4
9/4
pres-
sure
atm.
or
bar
5.1
7.5
1 ; 9/4 i 13.5
2 9/5 5.1
2 9/5
7.5
2 9/5 13.5
3 9/8 j 7.5
3 9/8 ! 13.5
4 ; 9/22
4 i 9/22
4 ! 9/22
5 ! 9/23
5 ; 9/23
5
6
6
7
7
9/23
9/24
9/24
10/1
10/1
6.8
10.6
13.5
6.8
10.5
13.5
6.8
13.5
6.8
13.5
Cycle
time
hr
2.0
2.0
2.0
2.0
2.0
2.0
1.0
1.0
2.0
2.0
2.0
2.0
2.0
2.0
1.2
3.3
1.6
3.3
% Lime
/% FeCla
conditioning
16/4
11/3
15/4
29/7
25/6
26/6
'35/8
34/8
24/6
24/6
29/7
20/5
20/5
20/5
38/10
32/8
32/8
31/8
Bulk
Cake
consistency
% solids
22.7
Weight of
accumulated
solids
gm
277
24.4 i 320
20.5
33.0
35.5
35.7
32.2
30.6
23.3
23.3
24.4
23.9
23.6
22.5
34.7
39.3
30.4
32.2
257
675
685
595
587
Time to
collect
200 grams
of solids
min
60.0
32.0
70.0
7.0
6.0
8.0
3.1
540 5.5
318
339
309
318
378
347
710
797
630
541
38.0
44.0
22.0
34.0
24.0
28.0
7.0
8.0
6.6
16.3
-------
Cake Consistencies
The higher cake consistencies shown in Table 4 were associ-
ated with (a) fresh waste activated solids, (b) large dosages
of sludge conditioning, (c) thick feed, and (d) long cycle times.
When adjusted for admix content (by using the difference between
the consistencies of unconditioned and subsequently conditioned
feed) the effective bulk cake consistencies in Table 4 are
reduced to the corrected values shown in Table 6.
TABLE 6. CORRECTION OF CAKE CONSISTENCIES
FOR ADMIX CONTENT
Bulk Cake
consistency
% solids
26-32
26-32
26-32
32-38
32-38
32-38
38-40
38-40
% Lime
15-20
25-30
36-40
15-20
25-30
35-40
25-30
35-40
Corrected cake
consistency
% solids
22-31
20-29
17-26
27-38
25-34
22-31
30-37
27-32
Solids Recovery
If two conditions were satisfied, the solids recoveries
attained on the pressure filter remained in excess of 97 percent,
usually being equal to or greater than 99 percent. First, the
correct media was required. Media C performed best in this
regard. Second, the sludge had to be properly conditioned.
When these conditions were satisfied, solids recoveries were
always in excess of 97 percent, even when filtration rates were
unacceptably low. This suggests that the conditioning require-
ments for acceptable recoveries are less than those for adequate
loading rates. Thus, solids recovery is assured when acceptable
throughputs are maintained.
Conditioning
One aspect of the pressure filter pilot study was the
evaluation of alternative conditioning techniques, the results
of which are shown in Table 7. Based upon this conditioning
evaluation, which showed lime and ferric chloride to be the type
of conditioning which gave the most consistant results, it was
decided to conduct the study of other operating variables using
17
-------
TABLE 7. ALTERNATIVE CONDITIONING TECHNIQUES EVALUATED FOR PRESSURE FILTRATION
Conditioning
Results
H
00
1. Lime + ferric chloride
2. Lime
3. Lime + Betz 1260
4. Lime + Percol 725
5. Flyash
6. Flyash 4- lime + ferric chloride
7. Flyash + Herculoc 812.3
8. Flyash -I- Percol 140
9. Betz 1260
10. Hercufloc 812.3
11. Percol 722
12. Percol 140
13. Diatomaceous earth admix + Hercufloc
812.3
14. Lime mud (CaCOs)
15. Lime mud (CaCO3> + Percol 140
16. Repulped broke (reslurried paper)
17. Bark fines (85% by weight between
20 and 100 mesh)
Consistantly acceptable results*
Unsuccessful at 1/3:lime/sludge
Unsuccessful at 2/3:lime/sludge
Unsuccessful at 2/3:lime/sludge
Unsuccessful at 2/l:flyash/sludge
No improvement over lime + ferric
chloride
Unsuccessful at l/l:flyash/sludge
Unsuccessful at l/l:flyash/sludge
Unsuccessful
Unsuccessful
Unsuccessful
Unsuccessful
Successful at 3/l:sludge/diatoma-
ceous earth
Unsuccessful at I/3:mud/sludge
Unsuccessful
Successful at 1/1:sludge/broke
Unsuccessful at 1/3rbark/sludge
successful runs were those resulting in the formation of removable cakes in
cycle times comparable to those shown in Table 4.
-------
line and ferric chloride for conditioning. As shown in Table 4,
the amount of lime and ferric chloride required is higher for
(a) degraded sludge solids, (b) higher cake consistencies,
(c) shorter cycle times, and (d) less concentrated feed.
Utilization of Precoat
Another aspect of the pressure filtration study was the
investigation of the advantages associated with precoat utiliza-
tion. Based upon the cake discharge and media cleanup character-
istics, it was shown that (a) precoat provided insurance that the
media would be protected and (b) cake discharge would be accept-
able even when the filtration characteristics of the sludge re-
sulted in wet, structurally weak cakes. The advantages associ-
ated with the utilization of precoat when dry, tough cakes were
produced were much more difficult to document than when wet cakes
were generated.
To document the advantages of using precoat, two identical
sets of filter cloth'"B" were obtained for the press. One was
utilized for a total of 29 operating hours without precoat, the
other was not used for sludge dewatering. Periodically both
sets of media were used to filter diatomaceous earth slurries.
The easily filtered diatomaceous earth slurries allowed the
identification of any significant blinding in the used media.
For approximately 20 of the 29 operating hours, the used media
were shower cleaned between runs, while no between run cleaning
occurred during the last 9 hours of operation. Although the
media used without precoat was visibly soiled with sludge solids,
the diatomaceous earth filtration rates were not significantly
different for the used and unused media, as shown in Figure 5.
The length of time over which the precoat utilization study was
conducted was probably insufficient to identify any long-term
blinding tendencies that would be minimized through precoat
utilization. However, the results of this study suggest that
precoat may not be a universal requirement for the pressure fil-
tration of waste treatment sludges.
Another aspect of the precoat utilization study was the
evaluation of alternative precoat materials, specifically flyash
and lime mud. Within the previously mentioned constraints upon
determining long-term blinding problems, the flyash performed
satisfactorily, distributing evenly, allowing high filtration
rates, providing clean cake discharge and facilitating media
cleanup. Lime mud (CaCO^) also satisfactorily protected the
media from sludge solids but it was not determined whether or
not filtration rates were reduced from diatomaceous earth levels
(as was to be the case in precoat vacuum filtration).
19
-------
September 25
10
25
ฑ: 20
E 15
4>
E 10
October 3
co 25
= 20
c
" 15
I 10
ฎ * unused media
.O ^ 20-hour media
0123
Time in min.
O
ฎ
unused media
o
2 9 -hour media
0123
Time in min.
Figure 5. Diatomaceous earth slurry filtration
rates through unused and used, nonprecoated media,
20
-------
Overall Performance of the Pressure Filter
The pressure filter was capable of operating at a variety
of performance levels. Table 4 demonstrates the interrelation-
ship between the various process and sludge variables. The
optimum set of operating conditions could vary greatly depending
upon final disposal requirements and other individual circum-
stances. Cake consistencies of from 26 to 40 percent solids
were attainable at conditioning requirements of 15 to 45 percent
lime supplemented with 4 to 10 percent ferric chloride over
cycle times of 15 minutes to 3.5 hours. The most important
operating variables were found to be the feed concentration,
the degree of conditioning and the nature of the solids. Oper-
ating pressures of from 5.1 to 13.5 atmospheres gave comparable
results. The issue of the need for precoat remained unresolved,
the data suggesting that the use of precoat may not be a univer-
sal requirement.
21
-------
SECTION 6
PRECOAT VACUUM FILTRATION INVESTIGATION
PROCESS DESCRIPTION
Vacuum filtration is presently a commonly employed dewater-
ing technique used for both primary and combined sludges. How-
ever, the application of rotary vacuum filtration to biological
or other difficult-to-filter sludges has been limited chiefly
by the inability to remove very thin sludge cakes from filter
media in a manner which minimizes the potential for media blind-
ing. The utilization of a filter precoat makes the removal of
very thin cakes possible while renewing the filtering surface to
a nonblinded condition. To accomplish this/ the deposited
sludge solids are removed from the filtration surface together
with a thin layer of the precoat material. The advent of the
rotating knife-doctoring assembly shown in Figure 6 has in many
instances made it possible to reduce precoat consumption below
the levels attainable with fixed knife-doctoring systems. The
rotary precoat vacuum filtration process differs from conven-
tional vacuum filtration in that (a) the filtration surface is a
precoat material, and (b) the doctor blade assembly, be it fixed
or rotating, advances toward the drum surface. The variables of
importance to precoat vacuum filtration are shown in Table 8.
DESCRIPTION OF PILOT EQUIPMENT
The pilot rotary precoat vacuum filter provided by Johns
Manville Corporation for use in this study, was a 36-in. (91 cm)
diameter by 6-in. (15.2 cm) wide Dorr Oliver drum vacuum filter
offering from 3.62 ft2 to 5.85 ft2 (0.34 to 0.54 m2) of filter-
ing surface, depending upon the width of the precoat face being
doctored. The doctoring mechanism was of the rotating knife
variety depicted in Figure 6.
OPERATION OF THE FILTER
Precoat was applied in a slurry at roughly 5 to 7 percent
solids, at maximum vacuum (10 to 20 in. [250 to 500 mm] Hg,
depending upon the precoat type), at 10 to 25 percent drum sub-
mergence, and at a drum speed of 1 to 2 RPM.
22
-------
ROTATING KNIFE ASSEMBLY
SLUDGE CAKE
Figure 6. Rotating knife doctor blade assembly.
(SLUDGE CAKE THICKNESS AND CUT DEPTH EXAGGERATED)
23
-------
TABLE 8. PRECOAT VACUUM FILTRATION PROCESS VARIABLES
Independent variables
1. Precoat characteristics
2. Type of doctoring assembly
3. Rotational speed of rotating knife doctoring
assembly when utilized
4. Rate of knife advance (precoat consumption)
5. Drum speed
6. Drum submergence
7. Vacuum intensity
8. Feed consistency
9. Sludge conditioning
10. Nature of sludge solids
Dependent variables
1. Loading rate
2. Cake solids
3. Solids recovery
Once the precoat had been applied, sludge was introduced
into the vat to seal the precoat surface, providing sufficient
vacuum to assure precoat adherance to the filter face. After
the precoat surface had been sealed, the precoat was allowed to
stabilize for 30 minutes to 1 hour assuring that any precoat
shrinkage occurred before the test runs were conducted. This
stabilization was accomplished by operating the filter at maxi-
mum vacuum and a knife advance of 1 mil (25.4 microns) per drum
revolution. After the precoat was stabilized, the vat level and
drum speed were adjusted to desired values, and the process of
optimizing precoat consumption was begun.
An initial knife advance of from 1 to 2 mils (25.4 to 50.8
microns) per revolution was selected based upon the results
obtained during previous runs. Initially, 1 hour of complete
cake removal and uninhibited filtration rates were used as the
criteria for an adequate knife advance rate, but as the operat-
ing personnel became familiar with the unit, and as the appro-
priate advance rates became more evident, 30 minutes were felt
to be sufficient indication. Knife advance rates were reduced
until unacceptable cake removal was encountered indicating that
the next highest rate was optimum. Once the optimum knife
advance was found, samples were taken of the sludge in the fil-
ter vat, the cake being generated, and occasionally the filtrate.
In addition, the filtrate rate was measured, generally over a
period of 3 to 10 minutes, to minimize the possible influence of
24
-------
individual precoat laminations, which have been identified as
offering greater resistance to flow than the bulk precoat mater-
ial (6). In conjunction with each filtrate rate, the effective
width of the filter face (the width being doctored) was mea-
sured. A specific resistance test was conducted on each vat
sample to permit identification of changes in sludge dewater-
ability.
PRECOAT VACUUM FILTER RESULTS
Solids Loading Rates
The maintenance of acceptable solids loading rates was
found to require (a) a rate of knife advance suitable for main-
taining a filtering surface free of sludge solids and (b) the
utilization of a precoat with suitable water permeability. The
recommendation of the precoat suppliers, based upon their pre-
vious experience and precoat filter leaf tests conducted at the
site, was Hyflo* diatomacous earth.
The solids loading rates attainable with the vacuum filter
with a diatomaceous earth precoat were found to be influenced by
(a) the specific resistance of the feed, (b) the concentration
of the feed, (c) the drum speed, and (d) the degree of drum sub-
mergence. Figure 7 demonstrates the effect of feed consistency,
drum speed, and submergence upon solids loading rates achieved
on sludges with specific resistances of less than 200 x 107
sec2/gm. The effect of feed consistency upon solids loading
rate was quite pronounced, resulting in 80 to 300 percent
increases in loading rates when feed consistencies were
increased from 0.8 percent to 2.0 percent solids. For sludges
with a specific resistance below 200 x 10' sec2/gm, variations
in specific resistance did not usually result in significant
variations in loading rate. However, upon those occasions when
the specific resistance of the sludge exceeded 200 x 10' sec2/gm,
severe reductions in loading rates were noted. Although the
data are sparce for sludges with specific resistances greater
than 200 x 107 sec2/gm, it is nonetheless clear that the loading
rates shown in Figure 8 fall significantly below their lower
specific resistance counter parts.
Two separate attempts were made to determine the effect of
vacuum intensity on solids loading rates. In one case, the
highest solids loading rate achieved was at a vacuum of 10 in.
(250 mm) of Mercury while in the second instance, the lowest
loading rate was associated with the same vacuum. Thorough
examination of the two sets of data has not provided an explana-
tion for this apparent contradiction.
* Product of Johns-Manvilie Corporation
25
-------
ro
CT\
2.5-
2.0-J
O)
C 1.51
ID
(0
o
1.0-
o
0)
0.5
1 RPM, 33% SUB.
1 RPM
-12.5
I
1.0
RPM, 25% SUB.
RPM, 40% SUB.
5 RPM, 33% SUB.
5 RPM, 25% SUB.
a
O
h7.5 0>
Q.
5'
(Q
-5.0 IQ
3
*>ป
IT
-i
-2.5
1.5
2.0
2.5
Feed Consistency % solids
Figure 7. Precoat vacuum filter solids loadincr rates
-------
N)
2.0-
D)
ฃ ,.OH
T3
OJ
O
(0
o
CO
1 RPM, 25% SUB
SR > 200 x 10
7
67 RPM, 40% SUB,
.5 RPM, 40% SUB.
ซ>
.5 RPM, 25% SUB.
<- .5 RPM, 40% SUB.
.5 RPM, 33% SUB,
ซ-.2 RPM, 40% SUB.
1.0 1.25 1.5 1-75
Feed Consistency % solids
Figure 8. Loading rates attained on high specific
resistance (SR) sludaes.
-10
-5.0
0)
O_
E
CO
O
0)
Q.
(O
CO
\
3
M
rr
2.0
-------
Cake Consistencies
The cake consistencies attained with a diatomaceous earth
precoat, after being corrected for precoat content, were found
to be influenced primarily by drum speed, drum submergence and
vacuum intensity. Figure 9 constructed from all data collected
with diatomaceous earth precoats on sludges with a specific
resistance of less than,200 x 10^ sec^/gm and with vacuum
intensities of 20 in. (250 mm) of mercury or greater, demon-
strates that slow drum speeds and low drum submergences contri-
buted to higher cake consistencies. In addition, the ability of
higher vacuums to produce drier cakes was quite pronounced as
shown in Figure 10. The cake consistencies attained on sludges
with a specific resistance greater than 200 x 107 sec2/gm were
generally about 5 percent solids content below those typical of
sludges with a lower specific resistance.
Precoat Vacuum Filter Solids Recoveries
The solids recoveries attained with diatomaceous earth pre-
coats (Hyflo* and Celite 545*) were measured on 11 different
occasions. All 11 values fell between 98 and 100 percent solids
recovery, with 8 of the 11 values being in excess of 99.9 per-
cent. Because the knife advances associated with the use of
Celite 545* were frequently in the 2 to 3 mil/revolution range
(75 to 100 micron/revolution) the acceptable filtrate qualities
and loading rates attained do not necessarily suggest Celite
545* as an acceptable precoat material in this application.
Hyflo* is the grade of diatomaceous earth usually used in this
application. The solids recoveries associated with the use of
flyash precoats were more variable. Of the 7 determinations,
4 were in excess of 99.8, the lowest value of the 7 being 97.3
percent. During one day's testing with flyash precoat, the
filtrate solids levels decreased from 800 to 70 parts per mil-
lion throughout the day suggesting that the precoat was being
penetrated and filled with sludge solids. However, this gradual
plugging did not have a noticeable effect upon solids loading
rates.
Precoat Consumption
The minimum precoat consumption that assured consistantly
acceptable performance was determined to be 1 mil (25.4 microns)
of Hyflo* precoat per drum revolution. At drum speeds greater
than 1 revolution per minute, it was not possible to attain
consistantly good cake removal at any knife advance. This was
presumably caused by having exceeded the capacity of the rotat-
ing knives. This limitation upon drum speed may be counter-
acted by increasing the rotational speed of the doctoring knives.
* Product of Johns-Manvilie Corporation
28
-------
to
V)
w ง 30-
10
S
ซป
+ซ o
CO -
'
c
o ซ
O 5
0 ฐ
CO
O
OK.
r. 2b'
20-
25
30
i
35
Percent Drum Submergence
Figure 9. Precoat Vacuum Filter cake consistency.
40
-------
U)
o
(0
o 2
O ฃ
CO
O
29-
Z= c 28H
O ซ>
O
C a
0) 26-
ซs
25-
24-
23
0.5 RPM
RPM, 25% Submergence
5.0
125
10
250
Figure 10.
15
375
20
500
25 inch** of Hg
625 mm of Hg
Vacuum
Effect of vacuum upon Precoat
Vacuum Filter cake consistencies,
-------
Alternative Precoat Materials
The investigation of precoat vacuum filtration included a
preliminary assessment of the feasibility of utilizing materials
other than diatomaceous earth for precoating. The pilot unit
was operated with both flyash and lime mud (CaC03> precoats at
different times in the test program. Table 9 summarizes the
results of these tests. Flyash provided filtration rates, and
cake consistencies quite comparable to diatomaceous earth.
As Table 10 indicates, the flyash solids particle size used
in this pilot study was substantially larger than that of Celite
545, a relatively coarse grade of diatomaceous earth. In addi-
tion, as shown in Table 11 & 12(7),flyash solids size distribation
and volatile content vary considerably from mill to mill, making
it necessary to evaluate the potential for flyash precoat fil-
tration on a case-by-case basis. Even at a particular mill, the
day-to-day variations in flyash characteristics suggest that
consideration might wisely be given to installation of size
classification equipment to assure a consistent quality of pre-
coat material. Utilization of flyash solids of such a size dis-
tribution that sludge solids freely penetrate the precoat body
will necessitate a knife advance significantly greater than
1 mil (25.4 microns) per revolution to provide a filtering sur-
face with acceptable permeability and may ultimately lead to
media blinding. As shown in Table 9 and discussed in the solids
recovery section, there was some indication that the flyash
precoat body was penetrated by sludge solids in this study but
not to a degree that solids loading rates were noticeably
affected over the three-hour test period.
Lime mud (CaCO3), as utilized in this program, resulted in
reductions in sludge solids loading rates of roughly 50 percent.
The lime mud precoat was prepared by reslurrying lime mud filter
cake from the mill's recovery system to 5 to 10 percent con-
sistency in fresh water. The application of a 1-in. (2.54 cm)
thick lime mud precoat to the pilot filter from slurry prepared
in this manner required 2 hours, suggesting that its filtration
characteristics had been altered in preparation. Later labora-
tory investigations designed to determine the effect of precoat
preparation upon lime mud filtration rates revealed that the
specific resistance to filtration of lime mud from the lime mud
filter vat (in the kraft recovery system), at 4.7 percent con-
sistency and cooled to 104ฐ F (40ฐ C), was roughly one-half of
the specific resistance measured when lime mud filter cake was
reslurried in fresh water at the same temperature and consis-
tency. It is not clear whether this phenomenon is attributable
entirely to the nature of the mother liquor or to a combination
of factors. In any case, the utilization of lime mud in the pre-
coat filtration of waste treatment sludges will require a more
complete understanding of lime mud filtration characteristics.
31
-------
TABLE 9. EVALUATION OF ALTERNATIVE PRECOAT MATERIALS
Test
No.
* 2
2 *
3 2
4 2
5 2
6 2
i 2
8 2
9 2
10 ซ
Precoat
material
D.E.*
Flyash
D.E.
Flyash
D.E.
Flyash
D.E.
Flyash
D.E.
Flyash
Lime mud
D.E.
Lime mud
D.E.
Lime mud
D.E.
Lime mud
D.E.
Lime mud
D.E.
Feed
consistency
% solids
Water
Water
0.97
1.78
1.45
1.70
1.07
1.01
1.03
1.04
Water
Water
1.07
1.02
1.25
0.96
0.94
1.08
1.06
1.46
Drum
speed
RPM
1.00
1.00
0.50
0.50
0.67
0.67
0.67
0.67
0.50
0.50
1.00
1.00
1.00
1.00
0.50
0.50
0.50
0.50
1.00
1.00
%
Drum
submerg-
ence
25
25
25
25
25
25
40
40
40
40
25
25
40
40
40
40
25
25 j
25
25
Vacuum
inches
Hg
10
10
21
21
21
21
21
21
21
21
10
10
21
21
21
21
21
21
21
21
Filtrate
rate
gal/ft2/hr
111.10
2.16**
4.47
5.72
6.48
7.43
8.72
8.40
8.26
8.5
3.20
35.50
9.03
17.73
7.01
11.79
3.39
8.27
4.14
11.68
Solids
loading
rate
#/ft2/hr
-
0.36
0.85
0.78
1.05
0.78
0.71
0.71
0.74
-------
TABLE 10. FLYASH - DIATOMACEOUS EARTH
SIZE DISTRIBUTION COMPARISON
OJ
GJ
Flyash
Size range
(microns)
>250
65-250
40-65
20-40
10-20
<10
% by
weight
12
84
3
1
0.2
<0.01
Celite 545
Size range
(microns)
40-60
20-40
10-20
8-10
6-8
<6
% by
weight
16
31
41
I
3
Hy-Flo
Size range
(microns)
40-60
20-40
10-20
8-10
6-8
4-6
2-4
<2
% by
weight
4.0
11.0
30.0
12.5
13.5
15.0
10.0
4.0
-------
TABLE 11
FLYASH PARTICLE SIZE
Sample no.
20
50
60
80
100
120
150
200
<150
<200
Retained on mesh size (percent of total weight)
0*
4
_
8
11
8
-
13
-
56
-
1 i 2 ; 3
!
i
o ! o
10 :is
5 ! 4
13 : 9
19 ;13
13 J13
_ . _
27 .21
;
13 !22
12
52
5
12
9
4
-
4
2
4
12
23
18
25
10
6
-
5
1
b
0
2
2
4
21
6
-
23
42
6
21
71
3
3
2
0
-
0
0
7
14
14
4
12
14
12
-
15
8
0
1
1
2
3
5
-
17
15 71
9
2
50
5
25
12
5
-
1
0
10
0
19
5
30
18
11
11
6
11
2
59
4
14
8
5
5
3
12
0
14
4
13
13
13
20
23
TABLE 12,
COMBUSTIBLE MATTER CONTENT OF FLYASH SAMPLES
Sample no.
0*
1
2
3
% Combustible
32
39
43
78
4 l 27
5
46
6 54
7 | 25
0
9
9 6
10 9
11 i 47
12
21
* Sample 0 used for precoating
in this study. Other data is
from reference 7.
34
-------
Sludge Conditioning
The application of polymer conditioned sludge to the pre-
coat vacuum filter resulted in approximately 50 percent
increases in solids loading rates and decreases in cake consis-
tencies of 7 to 8 percent solids. The degradation in cake con-
sistencies, shown in Table 13, appeared to be caused by the
thickness of the individual sludge floes as they were deposited
on the precoat. The deposited cake was uneven, consisting of
raised individual floes as opposed to a flat cake, the raised
areas of the cake remaining wet throughout the filter cycle.
Overall Performance of Precoat Vacuum Filtration
The data generated during this pilot investigation sug-
gested that the feasibility of precoat vacuum filtration would
be greatly enhanced at this mill by thickening of the waste
activated sludge from 0.7 to 0.8 percent consistency to 1.5 to
2.0 percent consistency. Depending upon the conditions of oper-
ation, such thickening could be expected to increase solids
loading rates by from 80 to 300 percent. This mill's fresh
waste activated sludge at 1.5 to 2 percent consistency could be
dewatered at 1.5 to 1.75 Ib/ft2/hr (7.33 to 8.55 kg/m2/hr) gen-
erating cakes of 25 to 30 percent consistency after being
corrected for precoat content (26 to 31 percent bulk consis-
tency) . Based upon a knife advance of 1 mil (25.4 microns) per
revolution, diatomaceous earth consumption is calculated to be
about 3 percent of the weight of sludge solids being dewatered.
To achieve these performance levels, the filter would be oper-
ated at a vacuum of 20 to 22 in. (510 to 560 mm) of mercury, a
form time of 48 seconds and a cycle time of 2 minutes.
Mills generating biological sludges with a specific resis-
tance in the 200 x 10? to 1000 x 10? sec2/gm range might realis-
tically expect to attain solids loading rates of roughly 0.5
Ib/ft2/hr (2.4 kg/m2/hr) while generating cakes of 20 to 25
percent consistency after being corrected for precoat content
(22 to 26 percent bulk consistency). Because a knife advance of
1 mil (25.4 microns) per revolution would again likely be
required, the precoat consumption would be approximately 5 to 10
percent of the weight of sludge solids being dewatered.
In all instances, solids recoveries would be expected to
exceed 99 percent.
35
-------
TABLE 13. UTILIZATION OF POLYMER CONDITIONING IN PRECOAT VACUUM FILTRATION
u>
)
Data
set
1 .
1
2 i
2
3 .
3 '
4
4
Conditioning
#polymer/ton
0
5
0
5
0
5
0
5
Feed
Consistency
# solids
1.53 !
2.78
0.94
1.24
1.62 !
1.21
0.94
1.45
Drum
speed
rpm
0.50
0.50
0.50
0.50
0.67
0.67
0.67
0.67
Submergence
25
25
40
40
25
25
40
40
Knife
advance
mil/min
0.5
0.5
0.5
0.5
1.0
1.0
1.0
1.0
Loading
rate
#/ft2/hr
1.13
2.24
0.89
1.73
1.05
1.31
0.93
2.23
Cake
consistency
% solids
31.5
23.1
26.4
18.6
30.6
23.1
25.2
18.5
-------
SECTION 7
TAIT-ANDRITZ SLUDGE DEWATERING MACHINE (SDM)
FILTER BELT PRESS INVESTIGATION
PROCESS DESCRIPTION
The Tait-Andritz SDM filter belt press, shown schematically
in Figure 11, dewaters sludges through a combination of gravity,
pressure and shear forces. A free-draining sludge is applied to
the belt and allowed to undergo gravity drainage over the first
section of the press. The sludge is then met by a second belt,
and conveyed through a wedge section where the two belts gradu-
ally converge. In this section, dewatering is achieved by both
the pressure applied by the belts and by table rolls behind both
top and bottom belts. The two belts converge at the beginning
of the "S" press section where they travel an "S" shaped path
around several rollers, as a result of which the belts are
forced to move at slightly different speeds imparting shear to
the sludge cake. The pressure exerted upon the sludge is con-
trolled through adjusting the tension on the belts. The cake is
discharged by doctor blades on both top and bottom belts. Both
belts are shower cleaned while returning to the head of the
machine. The SDM also can be equipped with a "P" press section
consisting of a series of nips for dewatering fibrous sludges.
The variables of importance to SDM performance are listed in
Table 14 .
DESCRIPTION OF TAIT-ANDRITZ SDM
The unit used in this study was the smallest production
model offered by Tait-Andritz. The belt was 22 in. (56 cm) wide,
the entire unit being about 12 feet (3.7 m) long. Belt tension
was controlled pneumatically, allowable air pressure ranging
from 0 to 3 atmospheres (bars). The two belt materials evalu-
ated were 60- and 30-mesh plain weave polyester fabrics.
OPERATION OF THE TAIT-ANDRITZ SDM
In the conduct of the pilot study the feed rate was first
adjusted to the desired value. It was then necessary to deter-
mine the belt speed and polymer dosage combinations that
37
-------
u>
00
feed
gravity
drainage
application
of pressure
intense
pressure and/or
shear and
cake discharge
cake
cake
Figure 11. Tait-Andritz SDM.
-------
TABLE 14. TAIT ANDRITZ SDM OPERATING VARIABLES
Independent variables
1. Belt characteristics
2. Type of press section ("S" or "P")
3. Belt tension and/or nip pressure
4. Belt speed
5. Feed rate
6- Feed consistency
7. Sludge conditioning
8. Nature of the sludge solids
Dependent variables
1. Cake consistency
2. Solids recovery
produced stable operation as manifested by a nonincreasing
liquid level in the gravity drainage section. After an accepta-
ble set of operating conditions had been established, a 5- to
10-minute stabilization period was allowed before collecting
samples of unconditioned feed, conditioned feed, gravity drain-
age filtrate, press section filtrate, belt shower water and
cake. The flow rates of the two filtrate streams and shower
water stream were measured and the cake generation rate was
documented. The evaluation was then continued by varying belt
speed and belt tension at the feed rate and polymer dosage of
interest, samples and flow rates being taken at each set of
conditions. Then either the polymer dosage and/or the feed rate
were adjusted to different levels.
TAIT-ANDRITZ SDM RESULTS
Capacity
The rate at which the 20-inch (500 mm) unit could dewater
fresh waste activated sludge at 0.8 percent consistency was
determined by the rate at which drainage occurred prior to the
sludge's entering of the press section, and thus was determined
by polymer dosage. The polymer requirements for different feed
rates of fresh waste activated sludge (unconditioned specific
resistance less than 150 x 10 sec/gm) are shown in Table 15.
The table suggests that the sludge had to be conditioned to a
specific resistance of 30 x 10? sec2/gm or less to provide
acceptable throughputs. The belt was run at the slowest speed
possible while maintaining an acceptable (not overflowing)
39
-------
TABLE 15. TAIT-ANDRITZ SLUDGE DEWATERING MACHINE (SDM)
PERFORMANCE SUMMARY ON FRESH WASTE ACTIVATED SLUDGE:
FEED CONSISTENCY OF 0.8 PERCENT SOLIDS
Feed rate
per unit belt
width
g/min/ft (1/min/m)
4.7- 5.6 ( 60- 70)
10.3-11.2 (130-140)
12.5-12.0 (160-170)
18.1-19.4 (220-240)
23.1-31.7 (290-390)
Polymer
requirement
Betz 1260
#/tn (mg/gm)
5-10 (2.5-5)
5-10 (2.5-5)
5-10 (2.5-5)
8-12 (4.0-6)
10-15 (5-7.5)
Belt
ft/min
6.6-8.2
6.6-8.2
8.2-9.8
16.4
18.0-21.3
speed
(cm/min)
(200-250)
(200-250)
(250-300)
(500)
(550-650)
Specific resistance
of conditioned
sludge
x 107 sec2/gm
15-30
15-30
15-30
10-20
<15
-------
liquid level in the gravity drainage and wedge sections. The
maximum belt speed corresponded to the occurrence of solids ex-
trusion at the end of the wedge section due to the cake being
too wet for pressing. Maximum belt speeds were seldom encoun-
tered at low feed rates, 5 to 7 gpm (20 to 25 liters/min),
whereas at the other extreme, 40 gpm (150 liters/min), there was
very little difference between maximum and minimum belt speeds.
Because of the strong dependence of machine capacity upon liquid
drainage rate, it is anticipated that prethickening of sludge
feed would allow substantial improvements in solids handling
capacity. The data were insufficient to allow a determination
of polymer requirements on sludge with an unconditioned specific
resistance in excess of 150 x 107 sec2/gm.
Cake Consistencies
The cake consistencies attained by the SDM were determined
by the belt tension utilized and the nature of the sludge solids.
Figure 12 demonstrates that the highest cake consistencies were
associated with unconditioned fresh sludges, and the lowest with
conditioned, physically degraded (sheared or aged) sludges hav-
ing unconditioned specific resistances in excess of 150 x 10'
sec^/gm. Conditioned fresh waste activated sludge cake consis-
tencies fell between these other two. Belt tensions in excess
of 40 pounds per linear inch were not beneficial. Varying belt
speed within the range of 4.3 to 21 ft/min (130 to 650 cm/min)
did not generally have a significant impact upon cake consis-
tency. There was some indication that belt mesh also impacted
upon cake consistencies, with a 30-mesh belt providing drier
cakes than a 60-mesh belt.
Solids Recoveries
There were three different types of solids lost from the
SDM: those which either (a) passed through the belt in the
drainage sections, (b) overflowed the drainage sections due to
insufficient conditioning and/or belt speed, or (c) washed from
the media in the shower section. The shower water solids were
particularly evident at high belt tensions, accounting for an
average of 54 percent of the unrecovered solids at belt tensions
of 50 pounds per linear inch, and an average of 38 percent of
the unrecovered solids at belt tensions less than 50 pounds per
inch. The SDM solids recoveries were consistantly in excess of
85 percent with 90 percent recovery being representative during
periods of operaiton at likely operating conditions. Insuffi-
cient sludge conditioning resulted in limited capacity before
solids recovery was severely affected.
Conditioning Requirements
As previously demonstrated in Table 15 , conditioning
41
-------
23-
CO
o
"o
0)
<0
O
21-
19
17-
c
* 41=
o 15
CD
O.
13
11
1 1 1 7^: '-V
0 20 40 60
Belt Tension (pounds per linear inch)
Unconditioned Sludge, Specific Resistance <150 x 10 sec /r:n
9> Conditioned Sludge, Unconditioned Specific Resistance
<150 x 107 sec2/gm
O Conditioned Sludge, Unconditioned Specific Resistance
>150 x 107 sec2/gm
Figure 12. Tait-Andritz SDM cake consistencies.
42
-------
requirements were primarily dictated by feed rate. Higher feed
rates required more conditioning.
Overall Performance of the Tait-Andritz SDM
The unit was capable of dewatering up to 45 gpm (165
liters/min) with conditioning requirements of up to 15 pounds
Betz 1260/ton (7.5 mg/gm). A feed rate of 20 to 25 gpm (76 to
95 liters/min) conditioned with 5 to 10 pounds of Betz 1260/ton
(2.5 to 5 mg/gm) was found to be the maximum throughput at which
consistent results were assured. At these conditions, fresh
waste activated sludge was concentrated from a feed consistency
of 0.8 percent solids to a cake consistency of 17 to 20 percent
solids at 90 percent recovery.
43
-------
SECTION 8
PERMUTIT DUAL CELL GRAVITY FILTER MULTIPLE
ROLL PRESS INVESTIGATION
PROCESS DESCRIPTION
The Permutit DCG-MRP is a two-stage moving belt press
dewatering system consisting of a dual cell gravity filter (DCG)
and a multiple roll press (MRP). The DCG, shown schematically
in Figure 13, consists of two parallel, cylindrical, media-
covered chambers, connected by virtue of being covered by the
same piece of media. A well-conditioned sludge is fed to the
first chamber where the initial dewatering occurs, removing a
majority of the free water. As this initial dewatering takes
place, sludge solids are deposited upon the moving media and
transported over the raised interchamber barrier into the
second cell. In this second cell the sludge solids agglomerate
into a flexible "plug" which continuously "rolls" as the drum
rotates. This rolling and kneading action releases additional
water. The plug grows in size until segments of it at the ends
of the cell overflow retaining rims and fall onto a conveyor belt
to be transported to the MRP.
The MRP, also shown in Figure 13, is a twin belt, multiple
roll press containing a series of opposing and alternating
rollers between which the DCG cake passes, releasing additional
water. Both roller pressure and belt speed are variable. The
cake is discharged from the media by doctor blades.
The variables of importance to DCG and MRP operation are
listed In Table 16.
DESCRIPTION OF DUAL CELL GRAVITY FILTER AND MULTIPLE ROLL
PRESS PILOT UNIT
Dual Cell Gravity Filter (DCG)
The unit used in this study was the smallest production
model of the DCG, the DCG 100. The two cells each measured 20.5
in. (52 cm) in diameter by 23.5 in. (60 cm) long and were 27 in.
(69 cm) from center to center. Two different media were
44
-------
DUAL CELL GRAVITY FILTER (DCG)
DIRECTION OF ROTATION
CONDITIONED FEED
DCG CAKE
SECOND CELL FILTRATE
FIRST CELL FITLRATE
MULTIPLE ROLL PRESS (MRP)
DCG CAKE
MRP CAKE
Figure 13. Permutit DCG-MRP
45
-------
TABLE 16 . DUAL CELL GRAVITY FILTER (DCG) AND
MULTIPLE ROLL PRESS (MRP) PROCESS VARIABLES
Dual Cell Gravity Filter (DCG)
Independent variables
1. Screen characteristics
2. Screen speed
3. Feed rate
4. Feed consistency
5. Nature of the feed solids
6. Sludge conditioning
Dependent variables
1. Cake consistency
2. Solids recovery
Multiple Roll Press (MRP)
Independent variables
1. Belt characteristics
2. Belt speed
3. Roller pressure
4. Feed rate
5. Feed consistency
6. Nature of the feed solids
7. Sludge conditioning
Dependent variables
1. Cake consistency
2. Solids recovery
available, one being 100 mesh, the other 40 mesh. The unit was
equipped with variable speed belt drive. The filter media was
washed continuously by showers located above the first cell.
Multiple Roll Press (MRP)
The MRP unit tested was a production unit normally capable
of dewatering the output from three DCG's 100 units. The belts
were 36 in. (91 cm) wide and the unit measured 5 feet (1.5 m)
from the feed point to the doctor blades. The belts first
passed through a series of rollers designed to apply a gradually
46
-------
increasing pressure to the sludge cake. This first set of rol-
lers was mounted together, the upstream end of the set being
fixed at a pivot point and the downstream end floating at an
adjustable pressure. The belt then traveled a serpentine route
through three sets of alternating offset rollers, then between
a pair of opposing rollers. The pressures applied to all sets
of offset and opposing rollers were adjustable. Cake removal
was accomplished with doctor blades on both top and bottom belts.
Belt showers were applied to both belts during their return to
the front end of the machine. The MRP belts were laminations of
100-mesh surface media and coarser support material held toge-
ther with several ribs of bonding material running parallel to
the direction of belt travel.
OPERATION OF THE DUAL CELL GRAVITY FILTER (DCG) AND MULTIPLE
ROLL PRESS (MRP)
Test runs were initiated by adjusting feed rate, condition-
ing levels, DCG belt speed, MRP belt speed, and the MRP roller
pressure profile to the desired values. The DCG was then
observed for approximately 5 minutes to determine whether the
set of operating conditions was a stable set. On occasions when
the sludge conditioning levels were insufficient for the feed
rate being applied, the first DCG cell liquid level would rise
and, when given the opportunity, overflow from the cell. If it
was clear that this was about to occur, the set of circumstances
was recorded and the conditioning was increased until sufficient
to permit free drainage. Due to the, relative capacities of the
DCG and MRP, the latter was never fully loaded. After a deter-
mination that the operating conditions were acceptable, samples
were collected of unconditioned feed, conditioned feed, DCG fil-
trate, DCG cake, MRP filtrate and MRP cake. The flow rates
of the DCG feed, DCG filtrate and MRP filtrate were recorded.
Specific resistance tests were conducted on all unconditioned
and conditioned feed samples to detect changes in the nature of
the solids and to assess the effectiveness of the applied sludge
conditioning.
DUAL CELL GRAVITY FILTER (DCG) AND MULTIPLE ROLL PRESS (MRP)
TEST RESULTS
Loading Rates
Capacities were determined by the rate at which drainage
occurred in the first DCG cell, which reflected the amount of
conditioning agent utilized. Table 17 shows the amount of con-
ditioner required to dewater various feed rates of fresh waste
activated sludge (unconditioned specific resistance of 30 to 250
x 10' sec^/gm) and degraded waste activated sludge (uncondi-
tioned specific resistance of 110 to 350 x 10' sec^/gm). Higher
47
-------
TABLE 17. DCG 100 PERFORMANCE SUMMARY
Polymer requirement Conditioned specific
Feed rate Betz 1260 resistance required
gpm (1/min) #/hr (kg/hr) #/tn (mg/gm) x 107 secygm
FRESH WASTE ACTIVATED SLUDGE AT 0.8 PERCENT CONSISTENCY
5 (19) 20 (9) 5 (2.5) 30-40
10 (38) 40 (18) 5-10 (2.5-5) 20-40
ฃ 15 (57) 60 (27) 5-10 (2.5-5) 10-40
HIGHLY SHEARED OR AGED WASTE ACTIVATED SLUDGE AT 0.8 PERCENT CONSISTENCY
5 (19) 20 (9) 5 (2.5) 30-40
10 (38) 40 (18) 8-10 (4-5) 20-40
15 (57) 60 (27) 10-15 (5-7.5) 10-20
18 (68) 72 (33) 20 (10) 5
-------
feed rates required larger polymer dosages. Table 16 also indi-
cates that the difference between dewatering fresh and degraded
sludge solids was the amount of conditioning required to bring
them into the range of specific resistance necessary for hand-
ling a given feed rate. Degraded sludges required more condi-
tioning than fresh sludges, especially at higher feed rates.
Although the most important factor in maintaining accept-
able loading rates was the level of conditioning utilized, DCG
belt speed was also a factor. In one instance where the sludge
was not quite sufficiently conditioned, an increase in belt
speed of from 57 to 70 in./min (145 to 180 cm/min) was necessary
to prevent the first cell from overflowing. It is likely that
the same effect could have been attained by slightly decreasing
the feed rate or increasing the amount of conditioning. One set
of tests conducted with a thickened feed at 1.2 percent consis-
tency (as opposed to an unthickened consistency of 0.8 percent)
did not demonstrate any significant improvements in performance
attributable to the increase of 0.4 percent in feed concentration.
No significant increase .in capacity was associated with the use
of a 40-mesh over a 100-mesh media fabric.
The relative differences in capacity between the DCG and
MRP did not allow a determination of the loading rate limita-
tions of the MRP. However, based upon observation of the amount
of unused belt at the discharge end of the MRP, it was estimated
that the unit could dewater the output from three Dual Cell
Gravity filters.
Consistencies of Dual Cell Gravity Filter (DCG) Cakes
The most striking aspect of the cake consistencies attained
on the DCG was their uniformity. Thirty-six of the forty-six
cakes generated on polymer conditioned sludges had consistencies
of 7.8 to 9.8 percent solids. The total range of cake consis-
tencies was 6.8 to 9.8 percent solids. Variations in condition-
ing, specific resistance, belt speed, belt mesh and feed consis-
tency did not have a significant impact upon DCG cake consis-
tencies.
Consistency of Multiple Roll Press (MRP) Cakes
The cake consistencies attained by the MRP were determined
by the roller pressure at the final nip which was the highest
pressure applied. Figure 14 demonstrates this effect as well as
the extent of the loss of consistency attributable to high belt
speeds. Analysis of the data revealed that the scatter in cake
consistency at a constant final nip pressure was not due to
differences in the total pressure applied by the other rollers.
The MRP was not loaded heavily enough in this study to encounter
solids extrusion problems attributable to excessive initial
pressures at the first MRP rollers.
49
-------
in
o
U)
TJ
"5
if)
18-
17H
o
c
O 16
(A
O
14-
CO
O
QL 13
QC
12-
35
61.6
50
88.0
168 in/min Belt Speed
396 in/min Belt Speed
65
1144
80
140.8
Final Roll Pressure
I
95 Ib/in
1672 N/cm
Figure 14. MRP cake consistencies,
-------
Solids Recoveries Attained by the Dual Cell Gravity Filter (DCG)
The lowest solids recovery attained by the DCG when operat-
ing under stable (no overflow) conditions was 97.2 percent.
Twenty-five of the thirty-five recorded values for DCG solids
recovery were 99 percent or higher. In essence, the condition-
ing requirements for maintaining acceptable throughputs were
such that solids recoveries were always high. The solids recov-
eries associated with the use of the 40-mesh DCG screen were not
significantly different from those attained with the 100-mesh
screen.
Solids Recoveries Attained by the Multiple Roll Press
The belts utilized on the MRP were laminated and bonded
together with plastic ribs. Because these ribs were slightly
raised from the media surface, difficulties were encountered in
accomplishing complete cake discharge. The solids not removed
by the doctor blades ultimately contributed to the solids in the
filtrate causing decreased solids recovery. In spite of this
difficulty, 31 of the 41 'tests for MRP solids capture showed
values exceeding 90 percent, with 21 of the 41 exceeding 95 per-
cent.
Conditioning Requirements
As was shown in the discussion of DCG capacity, the condi-
tioning requirements were related to the feed rate and the
nature of the solids, higher feed rates and less filterable
sludges requiring more conditioning. In all instances, condi-
tioning was necessary to promote drainage rather than to capture
solids. In addition, all cakes generated by the DCG were suffi-
ciently conditioned to render them pressable in the MRP.
Overall Dual Cell Gravity Filter (DCG) and Multiple Roll Press
(MRP) Performance
The DCG was capable of dewatering up to about 20 gpm of
waste activated sludge at 0.8 percent consistency, generating
cakes at 9 percent consistency, and requiring sludge condition-
ing at from 5 to 20 Ib of polymer/ton of sludge solids depending
upon the feed rate and the nature of the solids. DCG solids
recoveries were generally in excess of 99 percent. The MRP,
operating with a great deal of excess capacity, dewatered the
DCG cake from 9 percent to a cake consistency of 16 percent,
attaining solids recoveries generally in excess of 90 percent.
51
-------
SECTION 9
CAPILLARY SUCTION SLUDGE DEWATERING DEVICE INVESTIGATION
PROCESS DESCRIPTION
Biological and other difficultto-dewater sludges require
partial dewatering prior to being pressed. This is usually
accomplished through gravity or vacuum assisted drainage. In
the case of most filter belt presses, a relatively free-draining
and therefore, well-conditioned sludge is required to provide
acceptable throughputs. As an alternative to gravity drainage,
the capillary suction sludge dewatering device, the Squeegee*,
shown schematically in Figure 15, utilizes capillary suction to
provide a cake suitable for pressing, potentially allowing a
reduction in the amount of conditioning required. The other
unique feature of this unit is the cake discharge mechanism.
Whereas other filter belt presses utilize doctor blades to
remove the sludge cake from the filter belt, the Squeegee trans-
fers the cake to a combination pressure and pickup roll which
is in turn doctored. The main components of the system are
(a) a continuous, traveling screen to support the sludge above
the capillary belt, (b) a porous belt which provides dewatering
through the screen by capillary suction, (c) a combination pres-
sure pickup roll which provides additional water removal and
removes the resulting cake from the screen, (d) a doctor blade
which scrapes the cake from the pickup roll, and (e) a set of
opposing rollers to force water from the porous belt on its
return trip to the head of the machine. The variables of conse-
quence to Squeegee performance are listed in Table 18.
SQUEEGEE PILOT UNIT DESCRIPTION
The capillary suction belt press used in this study was a
prototype Squeegee unit designed and built by Westinghouse Cor-
poration under EPA contract (8). The belt measured 51.5 in.
(130 cm) from the front lip of the feed tray to the center line
of the pickup roller and was 11.8 in. (30 cm) wide. The pickup
roller was 9 in. (23 cm) in diameter. The force exerted
through the pickup roll was applied by a set of springs and
adjusted by varying the spring lengths. Conditioning chemicals
were injected into the feed line between the sludge pump and the
* Designed and built by Westinghouse Corporation
52
-------
SLUDGE FEED
Cn
U)
SLUDGE COMPRESSION ROLLER
CAPILLARY DEWATERING SECTION
BELT DIRECTION
I i I i i i if-i^i I I
SLUDGE CAKE
SCREEN WASH
SCREEN BELT
Figure 15. Schematic of Squeegee.
-------
TABLE 18. SQUEEGEE PROCESS VARIABLES
Independent variables
1. Belt and screen characteristics
2. Belt speed
3. Feed position
4. Pickup roll diameter
5. Pickup roll pressure
6. Feed rate
7. Feed consistency
8. Sludge conditioning
9. Nature of the sludge solids
Dependent variables
1. Cake consistency
2. Solids recovery
head box of the machine, mixing being provided by turbulence in
the feed line.
Screen showers were utilized to wash entrapped solids from
the 80-mesh, plain weave screen.
OPERATION OF THE SQUEEGEE
The test runs were initiated by adjusting feed rate, con-
ditioning rate, pickup roll pressure and belt speed to the
desired values. The machine was then allowed to stabilize for
5 to 15 minutes, depending upon conditions, before samples were
taken. The samples collected were unconditioned feed, condi-
tioned feed, cake samples from several points along the belt,
final cake, and filtrate. Flow rates of feed, filtrate and, on
occasion, screen shower water were determined. All uncondi-
tioned and conditioned feed samples underwent specific resis-
tance determinations to monitor changes in sludge dewaterability
and to assess the effectiveness of the conditioning being ap-
plied.
SQUEEGEE RESULTS
Squeegee Capacity
The single most important factor in attaining acceptable
performance from the Squeegee was the maintenance of complete
54
-------
cake removal by the pickup roll. Any operating conditions
which caused incomplete removal quickly resulted in severe
degradation of filtrate quality and screen blinding. These
incidents tended to be related to excursions from certain ranges
of belt speeds. The range of acceptable belt speeds varied
with the feed rate, as indicated in Figure 16. As demonstrated
in the Figure, unacceptable performance was associated with
(a) excessive belt loadings at low belt speeds causing poor
cake removal, (b) excessive belt speeds, causing poor cake re-
moval, and (c) excessive belt speeds causing incomplete belt
coverage at low feed rates. The fact that allowable belt speeds
were more closely related to hydraulic than solids feed rates
suggests that the unit was hydraulically limited, and might
benefit from sludge prethickening. Figures 17 through 20 show
that maintaining stable cake consistencies and/or solids recov-
eries while dewatering conditioned fresh waste activated sludge
required a belt speed of less than about 3.4 in./sec (8.5 cm/
sec) . This being the maximum belt speed, Figure 16 indicates a
maximum feed rate to be 2.6 gpm of adequately conditioned sludge
per foot of belt width (32 liters/min/m). The maximum feed rate
possible with unconditioned fresh waste activated sludge (speci-
fic resistance between 35 and 100 x 107 sec2/gm) was found to be
1.3 gpm/ft of belt width (16 liters/min/m of belt width).
In general, to assure acceptable performance, the Squeegee
required a ferric chloride conditioned sludge with a conditioned
specific resistance of less than 30 x 107 sec2/gm. Sludges
which had been intentionally physically degraded by subjecting
them to severe shear in a centrifugal pump did not readily con-
dition to 30 x 107 sec^/gm and as a result, could only be
handled at rates less than 2.6 gpm/ft of belt width (32 liters/
min/m). The amount of ferric chloride required to compensate
for the physical degradation and permit loading rates comparable
to fresh sludge was not determined.
In general, the capacity of the machine could be increased
either by widening the belt, lengthening the belt (consistent
with belt speed limitations) or both.
Cake Consistencies
The cake consistencies attained by the Squeegee on fresh
conditioned sludge were found to be functions of the roll pres-
sure and belt speed. Figures 17 through 19 constructed from all
data generated with fresh, adequately ferric chloride condi-
tioned, waste activated sludge (conditioned to a specific resis-
tance of less than 30 x 107 sec2/gm) demonstrate that consistent
cake quality was attained at belt speeds of less than 3.0 to 3.5
in./sec (7.6 to 8.9 cm/sec). Unconditioned or poorly condi-
tioned sludges (conditioned specific resistance of greater than
30 x 10' secVgm) produced cakes at consistencies 3 to 5 percent
lower than those generated from well conditioned sludges.
55
-------
5-
i
Ul
CD
cc
~o
o
o>
3-
c 2-
E
a
O)
H
Acceptable Belt Speed
O Unacceptable Belt Speed
I I I I I I I I l I l
Mil
Removal Caused
by Excessive Belt Loading
Poor Cake
Removal Caused
Excessive Belt
Speed
Incomplete Belt Coverage
0
5
10.7
10
25.4
15
38.1
Belt Speed
-60
-50 3
5"
-40 ^
-30
-20 -
Q.
-10
in/sec
cm/sec
Figure 16. Squeegee belt speed requirements.
-------
U1
-------
Ui
oo
o
(A
c
o
o
-------
vo
(0
TJ
"5
CO
-------
a\
o
100-
90-
> SO-
Si)
8 70H
60-
"5
CA) 50-
40-
Ve ry Low
Consistency
5
12.7
Belt Speed
10
25.4
15 in/sec
38.1 cm/sec
.56-1.68 tf/Linear Inch (1-3 N/cm)
6.1-7.3 I/Linear Inch (10.8-12.8 N/cm)
Greater Than 33 gm Sludge solids/m2
3.92-4.48 I/Linear inch (6.8-7.8 N/cm) O 6.1-7.3 #/Linear inch (10.-8-12.8 N/cm)
Less T.han 33 gm Sludge solids/m2
Figure 20. Squeegee solids recovery.
-------
Solids Recovery
Solids recovery on sludges conditioned to a specific resis-
tance of 30 x 107 sec2/gm or less was generally maintained above
90 percent. On fresh waste activated sludge, this degree of
conditioning was attained with additions of 4 to 7 percent fer-
ric chloride. At high belt speeds and high roll pressures, cake
removal became imparied resulting in reduced capture effici-
encies, the onset of these difficulties occurring at lower belt
speeds when belt loadings exceeded 33 gm of sludge solids per
square meter as shown in Figure 20.
Conditioning Requirements
Because the cake removal properties were very closely
related to the type and amount of sludge conditioning, these
were possibly the most crucial controllable variables investi-
gated. Attempts were made at dewatering unconditioned sludges
and those sludges conditioned with either Betz 1260 (a cationic
polyelectrolyte used successfully on the other filter belt
presses), Percol 140 (a cationic polyelectrolyte), Hercufloc 859
(a cationic polyelectrolyte), and ferric chloride. Quite simply,
ferric chloride was the only conditioning chemical applied which
resulted in consistent performance at reasonable hydraulic load-
ings (greater than 25 Iiters/m2). Dewatering without sludge
conditioning was only possible at very low loadings and machine
capacities, 1.3 gpm/ft of belt width (16 liters/min/m) being the
maximum feed rate attainable. Polymer conditioning produced
large, discrete floe that were impossible to distribute evenly
across media. The tops of these floe remained wet virtually
regardless of belt speed, making complete cake removal very
difficult. Ferric chloride was the only conditioning technique
evaluated that promoted rapid drainage while allowing the for-
mation of a thin, even layer of sludge solids upon the screen
which could be consistantly removed by the pickup roll. Ferric
chloride was required at 4 to 7 percent of sludge solids for
feed rates of 1.3 to 3.2 gpm/ft of belt width (16 to 40 liters/
min/m) and 7 to 10 percent for feed rates between 3.2 to 5.2 gpm/
ft of belt width (40 and 65 liters/min/m). However, above 2.5
gpm/ft poor cake removal or decreased cake consistencies were
often encountered.
Squeegee Overall Performance
The unit used in this study was capable of dewatering
2.6 gpm/ft of belt width (32 liters/min/m) of fresh waste acti-
vated sludge from a feed consistency of 0.6 to 1 percent to a
cake consistency of 14 to 17 percent solids. The data provided
indicates that at feed consistencies of 0.6 to 1 percent the
unit was hydraulically limited, suggesting sludge prethickening
as one alternative for increasing machine capacity. Ferric
chloride conditioning was required at 4 to 7 percent of sludge
61
-------
solids to promote rapid drainage and assure good cake discharge
characteristics. Solids recovery was typically in excess of
90 percent. The fact that cake discharge was of such overriding
importance to the operation suggests that improvements in media
characteristics would be a possible means of substantially
improving the unit's performance.
62
-------
SECTION 10
SHARPLES P3000-BD HORIZONTAL BOWL DECANTER CENTRIFUGE
INVESTIGATION
PROCESS DESCRIPTION
Decanter centrifuges are commonly utilized in primary
sludge dewatering applications in the pulp and paper industry.
However, conventional decanter centrifuges have seldom been em-
ployed for biological sludge thickening due to the high sludge
conditioning requirements to attain acceptable solids recover-
ies. The Sharpies Biological Decanter (BD) series utilizes a
proprietary scroll design to minimize conditioning requirements
while maintaining satisfactory recoveries. The variables of
importance to the performance of the Biological Decanters (BD),
listed in Table 19, are the same as those that apply to conven-
tional decanter centrifugation.
TABLE 19. SHARPLES BD DECANTER CENTRIFUGE
PROCESS VARIABLES
Independent variables
1. Bowl and scroll size and configuration
2. Bowl speed
3. Pond depth
4. Scroll differential
5. Feed rate
6. Feed consistency
7. Sludge conditioning
8. Nature of the sludge solids
Dependent variables
1. Cake consistency
2. Solids recovery
63
-------
DESCRIPTION OF TEST UNIT
The P3000-BD is one of the smaller production models
offered by Sharpies. The bowl is 14 in. (35 cm) in diameter and
30 in. (76 cm) long. The unit used in this study was operable
at either 3250 or 2000 rpm resulting in centrifugal forces at
the bowl wall of 2100 and 800 G's (times the force of gravity)
respectively. The range of pond settings utilized was 8 to
8-3/8, and the scroll differential was varied from 2 to 20 rpm.
When polymer conditioning was utilized, it was introduced in the
feed zone of the bowl as is common with other types of decanter
centrifuges.
OPERATION OF THE P3000-BD
In preparation for a series of test runs a bowl rpm and
pond depth were selected and applied. The testing was then
conducted by utilizing the desired combinations of feed rate,
scroll differential, and, when applicable, polymer dosage. A
stabilization period of 10 minutes was included prior to col-
lecting samples of conditioned feed, unconditioned feed, cen-
trate, and cake. In conjunction with sample collection the
centrate flow rate was measured. Specific resistance and SVI
(Sludge Volume Index) tests were conducted on conditioned and
unconditioned feed samples to monitor the sludge settleability
and dewaterability and to assess the effectiveness of sludge
conditioning. The Sludge Volume Index test was included in the
characterization of centrifuge feed because of the centrifuge's
anticipated dependence upon solids settleability.
P3000-BD TEST RESULTS
Capacity
The pilot unit dewatered from 20 to 60 gpm (75 to 225 li-
ters/min) of feed. The only available pump capable of providing
such rates was a centrifugal pump, so that all data generated by
the P3000-BD was on "sheared" sludge with a specific resistance
ranging from about 100 x 107 to 700 x 107 secVgm with typical
values falling between 100 x 107 and 300 x 107 sec2/gm. Over
the same period the fresh, "unsheared" sludge specific resis-
tance typically ranged from 50 to 150 x 107 sec2/gm. During
the course of the tests, however, the sheared and fresh sludge
SVT's remained roughly equivalent, ranging between 100 and 200.
Other than the large differences between conditioned and uncon-
ditioned sludges indicated in Table 20 and Figure 21, no depen-
dence of centrifuge performance upon sludge specific resistance
was observed. At least partially because the sludge volume
index testing was applied to clarifier underflow rather than
less concentrated mixed liquor, the sludge volume index test was
64
-------
TABLE 20 . CHARACTERIZATION OF CENTRIFUGE FEED
Feed
Sludge Volume
Index*
average/(range)
Specific resistance
x 107 sec2/sec
average/(range)
Fresh waste
activated sludge
"Sheared" waste
activated sludge
"Sheared" waste
activated sludge
conditioned with
3 to 5# polymer/
ton of solids
- /(100-200)
135/U09-217)
126/(78-169)
112/57-163)
191/(90-722)
74/(29-132)
* Sludge consistencies of 0.6 to 0.8 percent suspended solids
not sensitive to changes in the dewaterability of the centrifuge
feed. The SVI test itself becomes insensitive as consistencies
approach 1 percent solids, especially on slow settling sludges.
Figure 21 shows the cake consistencies associated with various
feed rates at scroll differentials and pond settings yielding
90 percent solids recovery. As demonstrated by the figure,
attaining 90 percent recovery at the higher feed rates resulted
in lower cake consistencies. The detrimental impact of higher
feed rates upon cake consistency were minimized by the applica-
tion of polymer conditioning and by using higher rotational
speeds. An 8-1/4 pond setting was found to be satisfactory for
the range of feed rates encountered.
Cake Consistencies
The cake consistencies achieved by the P3000-BD were deter-
mined by the scroll differential and G-force. Because lower
scroll differentials were required to maintain 90 percent recov-
ery at lower feed rates, the cake consistencies attained at the
lower feed rates were higher. Polymer utilization and higher
G-forces probably resulted in drier cakes because these prac-
tices released additional water from the cakes and/or because
lower scroll differentials were required compared to uncondi-
tioned sludges and lower G's to maintain 90 percent solids
recovery
. An optimum pond settling was chosen by trading off cake
consistency and solids capture. A pond setting of 8-3/8 was
found to be detrimental to cake consistencies while not
65
-------
12-
= 8
- O
O O 9
M 0>
OC
Ch
0)
u
O
CO
*8
(0
3-
Note: Sludge feed consistency is 0.6 to 0.8 percent solids
2100-G
Unconditioned
2100-G
3-5 #/tn polymer
800-G
3-5 #/tn polymer
800-G
Unconditioned
1
20
75
25
93.7
I
30
112.5
I
35
131.3
40
150
i
45
168.8
I
50
187.5
l/min
Figure 21.
Feed Rate
Centrifuge performance at 90 percent solids recovery.
-------
resulting in substantially higher recoveries. On the other
hand, a pond setting of 8 did not provide acceptable solids
recovery, 8-1/4 proving to be the best compromise, as shown in
Figure 22.
Solids Recoveries
Solids recoveries were maintained in excess of 90 percent
by varying scroll differential. Those runs utilizing no condi-
tioning, higher feed rates and lower centrifugal forces
required higher differentials to achieve 90 percent recovery
which resulted in lower cake solids. Pond settings in excess of
8-1/4 resulted in decreased cake consistencies without substan-
tial increases in solids recoveries while those below 8-1/4 did
not provide adequate recoveries.
Benefits of Sludge Conditioning
As shown in Figure 21, polymer conditioning at 3 to 5
pounds of Betz 1260 or Hercufloc 844 per ton of sludge solids
(1.5 to 2.5 mg/gm) proved to be beneficial to P3000 BD perfor-
mance , especially at higher feed rates and lower centrifugal
forces. However, when the unit was dewatering 20 to 25 gpm
(75 to 90 liters/min) at 2100-G, polymer conditioning did not
result in substantially improved performance.
Overall P3000-BD Performance.
At 2100-G1s of centrifugal force and a pond setting of 8.25,
the P3000-BD proved to be capable of thickening the "sheared",
waste activated sludge from 0.8 percent consistency to 8 to 10
percent consistency. No conditioning was required to dewater
20 to 25 gpm (75 to 90 liters/min). The application of 3 to 5
pounds of Betz 1260 or Hercufloc 844 per ton of sludge solids
(1.5 to 2.5 mg/gm) was advantageous in dewatering 25 to 40 gpm
(90 to 150 liters/min).
67
-------
11
10
*>
o ^
0)
5-
o
3
8
2100-G
12-15 Differential
25-30 GPM of unconditioned
sludge at 0.8%
solids
8V4
Pond Setting
95
93
91 ซ
O
O
0)
o
89
87
85 O
O
83
81
L79
83/.
Figure 22. Effect of pond setting on solids
recovery and cake consistency.
68
-------
SECTION 11
ULTRAFILTER INVESTIGATION
PROCESS DESCRIPTION
Ultrafiltration is a membrane-based, separation technology.
By selecting a membrane with the desired properties, and main-
taining an appropriate pressure against the membrane, a separa-
tion of suspended, colloidal, or dissolved material can be
accomplished. -Because the separation is taking place at the
membrane and there is a net movement of fluid to the membrane,
there is a buildup of retained species at the membrane. The
depth of this buildup, anticipated to be of major importance in
sludge thickening applications, can be reduced by maintaining
turbulence at the membrane surface. The variables of importance
to the ultrafiltration of solids-laden feed streams are listed
in Table 21.
TABLE 21. ULTRAFILTRATION PROCESS VARIABLES
Independent variables
1. Membrane characteristics
2. Membrane configuration
3. Feed rate
4. Feed consistency
5. Feed temperature
6. Operating pressure
7. Flux maintenance technique
Dependent variables
1. Flux rate
2. Solids retention
3. Pressure drop per unit membrane area
4. Concentrate consistency
69
-------
DESCRIPTION OF ULTRAFILTER PILOT UNIT
The ultrafiltration unit was assembled by the National Coun-
cil for Air and Stream Improvement for this study. A Westing-
house D170, 19-tube membrane module containing 9.5 ft^ (0.91 m^)
of membrane area was selected for sludge concentration. The
module contained 18 one-half inch diameter membrane tubes in
series, supported upon a porous epoxy/sand material. By rota-
ting the end caps in relation to the module, the unit could oper-
ate with as few as six tubes. Six tube operation was the mode
of operation favored for this study due to pressure drop con-
siderations.
The module was fed by a 10 gpm (37.8 liters/min) progress-
ing cavity pump. When concentrating dilute sludge, the unit was
operated on a once-through basis. To provide a constant supply
of concentrated feed, the inlet of the feed pump was fitted with
a 15-gallon (60 liter) feed tank into which both ultrafiltration
concentrate and permeate could be recycled. Line pressure was
measured at both the inlet and outlet of the module and was con-
trolled with a throttle valve following the outlet pressure
gauge. The average operating pressure was defined as the aver-
age of the inlet and outlet pressures.
OPERATION OF THE UNIT
A variety of techniques was evaluated to clean the mem-
branes and thus maintain high flux rates. One of these was an
automated backflush system designed to pump permeate back
through the membrane, loosening deposited solids and restoring
flux rates. The backflushing comprised from 5 to 25 percent of
the total cycle time. Figure 23 is a typical flux curve gener-
ated in this study. The automated backflush system was in-
tended to backflush the membrane as soon as the flux began to
level off. By cycling the flux through only the first part of
the flux curve, a higher average flux rate was anticipated. How-
ever, as Figure 24 demonstrates, by the time the backflushed
volume had been recollected, the flux levels had dropped approx-
imately to the levels attained before the backflush had been
started. As a result, the backflushing technique did not result
in higher overall flux rates. Since short cycle flux mainten-
ance techniques had proven generally unsuccessful, efforts were
concentrated upon finding a membrane-cleaning technique that
could be applied once every 4 to 8 hours to restore flux rates
to original levels. The methods tested were high velocity water
feed, 5-minute backflushing, 1/2 percent Biz solution washing,
sponge ball flushing of the system and combinations of these
methods. Of the techniques investigated, flushing the tubular
membrane system out a dozen times with a slightly oversized
sponge ball was the only method capable of consistantly restor-
ing flux levels to those attained on clean membranes.
70
-------
140-
-5.5
12O-
CD
T3
1OO-
-4.5 TJ
C
X
(D
O)
_ 8OM
X
LL 6O-
-as
-2.5
10
oT
0)
40-
20 40 6O 8O 1OO 12O
Time in min.
Figure 23. Typical ultrafiltration flux curve.
1.5
-------
-0
(0
6OOO
1.6
-------
After cleaning the membranes in this manner, feed was intro-
duced at the desired rate and the average pressure in the module
was adjusted. The permeate rate and temperature were measured
throughout the first 5 to 10 minutes of each run. Thereafter,
flux rates and permeate temperatures were measured every 30
minutes until flux remained reasonably constant for two or
three consecutive readings. This constant flux rate, attained
after 90 minutes in Figure 23, was defined as the steady state
flux. Runs were usually terminated after the steady state flux
had been determined.
Samples were taken of the feed as often as was necessary to
monitor the sludge consistency, and an occasional permeate or
concentrate sample was analyzed for suspended solids. When feed
consistencies higher than the levels attained by gravity set-
tling were required, the sludge concentration was increased by
recirculating concentrate into the feed tank until the desired
concentration was achieved and the run could be initiated. To
maintain a constant feed consistency throughout these runs, both
concentrate and permeate were recycled for the duration of the
run, allowing continuous loading of a concentrated feed.
RESULTS OF ULTRAFILTRATION STUDY
Steady State Flux Rates
As illustrated by Figure 25, steady state flux rates were
found to be strongly dependent upon the average fluid velocity
in tubes {calculated by dividing the volumetric feed rate by
the cross sectional area of the membrane tube) and less strongly
dependent upon feed concentration.
The data in Figure 25 were generated at average operating
pressures of from 25 to 75 psi (17-52N/cm2). These variations
in average operating pressure did not significantly affect the
flux rates attained in the range of pressures investigated.
The maximum feed rate was limited by the pressure drop
through the tubes. As shown in Figure 26, the pressure drop
was a function of feed rate and feed consistency, higher consis-
tencies and feed rates resulting in larger pressure drops.
Table 22 translates the flux rates shown in Figure 25 into
area requirements to accomplish various degrees of thickening
at different average feed velocities. As shown, the advantage
associated with thickening a feed of 2 percent consistency as
opposed to 1 percent consistency is quite substantial, result-
ing in a reduction in required membrane area of roughly 50
percent.
73
-------
15O
125-
75
(D
O>
50
X
ฃ3
u.
25
Ln/se
O.5 1.O 1.5 2.O 2.5 3.0 3.5 4.O 4.5 5.O
Feed Consistency (% Solids)
5.5
4
ZJ
c
X
3 3
3
u
^v.
3
ra
^x
Q.
CD
6.O
Figure 25. Ultrafiltration steady state flux rates as functions
of feed consistency and fluid velocitv.
-------
tn
o
CO
CO
0)
60-
50-
a" 40"
2w
Q3 30H
a>
20-
10-
0-
O-4.0 to 6.0% Solids
I I
20 40
50.75 101.5
\
60
I
80
I
100
I
120
I
140
152.4 203.2 253.9 304.7 355.5
Feed Velocity
r50
-40
-30
-20
-10
(0
(0
c
3
I
O
160 IN/SEC
406.3 CM/SEC
Figure 26. Pressure drop through the membrane module
during six tube operation.
-------
TABLE 22 . MEMBRANE AREA REQUIREMENTS FOR
2000 POUNDS (908 KG) SLUDGE SOLIDS PER DAY
Average feed velocity of 129-155 in/sec (328-394 cm/sec)
Thickening
From 1% to 2%
From 2% to 3%
From 3% to 4%
From 4% to 5%
From 5% to 6%
Flux
gal/ft2/day
105
80
60
40
25
m /m /day
4.3
3.3
2.4
1.6
1.0
Area
ft2
114
50
33
30
32
m2
Ll.O
4.6
3.1
2.8
3.0
Total area
ft2
114
164
197
227
257
2
m
11
15
18
21
24
Average feed velocity of 78-103 in/sec (197-262 cm/sec)
Thickening
From 1% to 2%
From 2% to 3%
From 3% to 4%
From 4% to 5%
From 5% to 6%
Flux
gal/ft2/day
32
22
18
15
13
3 2
m /m /day
1.30
0.90
0.73
0.61
0.53
Area
ft2
375
182
111
80
61
m2
35.0
L7.0
LO.O
7.4
5.7
Total area
ft2
375
557
668
748
809
2
m
35
52
62
70
75
Average feed velocity of 16-51 in/sec (40-130 cm/sec)
Thickening
From 1% to 2%
From 2% to 3%
From 3% to 4%
From 4% to 5%
From 5% to 6%
Flux
gal/ft2/day
10
8
8
7
7
3, 2 ,,
m /m /day
0.41
0.33
0.33
0.29
0.29
Area
ft2
L199
500
250
171
114
2
m
111
47
23
16
11
Total area
ft2
L199
1699
1949
2120
2234
2
m
111
158
181
197
208
76
-------
Table 23 demonstrates one possible module configuration to
thicken sludge from 1 to 6 percent consistency. Flow velocities
of about 140 in./sec (360 cm/sec) are assured by maintaining
feed rates of 7 gpm (26.5 liters/min) per module. Pressure drop
constraints would likely require a booster pump for every three
stages over the initial stages and as much as one booster pump
per stage toward the end of the thickening sequence. Lower feed
velocities would allow less frequent interstage pumping but
would also require much more membrane area as shown in Table 21.
Sludge feed temperatures varied from 68ฐ to 95ฐF (20ฐ to
35ฐC). Over that range of temperatures fresh water flux rates
increased by 20 to 40 percent. Although a similar relationship
was anticipated in regard to sludge flux rates, the data did not
permit its identification.
Concentrate Consistencies
Using the ultraf-ilter, it was possible to thicken waste
activated sludge to 7 percent solids by recirculating concen-
trate. However, as the feed consistency approached 5 percent,
the pressure drop through the module became 25 to 75 psi (17 to
52 N/cm2) depending upon the feed rate. Thickening this waste
activated sludge to beyond 7 percent solids will require a mem-
brane configuration with less pressure drop per unit membrane
area.
Overall Ultrafilter Performance
The utlrafilter was capable of concentrating waste acti-
vated sludge from 1 to 7 percent consistency. The membrane area
required depended upon feed velocity. The minimum estimated
membrane area required per ton of solids per day to concentrate
from 1 percent to 6 percent consistency was calculated to be
about 260 ft2 (24.2 m2). One penalty encountered at high feed
velocities and associated high flux rates was a very large
pressure drop through each module. This suggests a potential
requirement for one booster pump for each two or three module
stages. Sponge flushing was found to be an effective means for
restoring flux rates to levels attained with unused membranes.
77
-------
TABLE 23. PROPOSED MEMBRANE CONFIGURATION
TO THICKEN 1 TPD OF SLUDGE SOLIDS
Feed Velocity of 120-155 in./sec (328-394 cm/sec)
Which is Equivalent to 7 gpm per module (26.5 1/min per module)
Stage
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
# Modules
(27 modules
254 ft2)
0
3
2
2
2
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
Feed
rate
gpm
0
16.65
14.38
12.86
11.37
9.99
9.34
8.71
8.12
7.55
7.02
6.52
6.02
5.55
5.11
4.70
4.33
4.00
3.71
3.46
3.26
3.08
2.92
Recirculation
rate , gpm
0
0
0
0
0
0
0
0
0
0
0
0
0
1.45
1.89
2.30
2.67
3.00
3.29
3.54
3.74
3.92
4.08
-^ ^
Flux
0
115
115
113
105
100
97
90
87
82
77
76
72
67
63
57
50
45
39
31
27
24
22
Concentrate
consistency
% solids
1.0
1.2
1.3
1.5
1.7
1.8
1.9
2.1
2.2
2.4
2.6
2.8
3.0
3.3
3.5
3.9
4.2
4.5
4.8
5.1
5.4
5.7
6.0
78
-------
SECTION 12
DISCUSSION OF ALTERNATIVES
EQUIPMENT REQUIREMENTS
The equipment, conditioning/ and power required to dewater
10 tpd of this mill's waste activated solids on the different
dewatering technolgies investigated are shown in Table 24.
Except for the centrifuge sizing calculations, which were done
by Sharpies Division of Pennwalt Corproation based upon this
pilot study, the estimates of required capacity, sludge condi-
tioning and cake consistency were made by Council staff based
upon results of this study. The power requirements shown in
the table are primarily based upon information provided by the
equipment manufacturers. Those estimates made by Council staff
without manufacturer consultation were those for the Squeegee,
centrifuge and ultrafilter. The performance levels used to
assemble Table 24 can be found in Appendix B.
FINAL SLUDGE DISPOSAL CONSIDERATIONS IN DEWATERING PROCESS
SELECTION
The different dewatering technolgies investigated in this
study generate cakes with varying characteristics which suggest
different final disposal alternatives. The pressure filter and
precoat vacuum filter are the probable alternatives if sludge
incineration or long distance hauling are required. The desira-
bility of subjecting an incinerator to the associated levels of
ferric chloride, lime, or diatomaceous earth would require con-
sideration, as would the quantities of residual ash generated in
each case. The drier bulk cake consistencies and tougher cakes
attained on the pressure filter might suggest its applicability
in those landfill applications requiring a high degree of fill
stability. However, without having determined the consolidation
characteristics of the pressure filter and precoat vacuum filter
cakes, an accurate assessment of their relative stability was
not possible.
If final disposal requirements favor "truckable" cakes free
of precoat or inorganic conditioning, the filter belt presses
are probably the best suited dewatering alternatives.
79
-------
TABLE 24.
EQUIPMENT REQUIREMENTS FOR 10 TPD OF WASTE ACTIVATED SOLIDS
BASED ON PILOT STUDY FINDINGS
Dewatering option
Pressure filter,
1% feed
Pressure filter,
2% feed
Precoat vacuum
filter, 1% feed
Precoat vacuum
filter, 2% feed
Squeegee, 1% feed
DCG-MRP, 1% feed
Tait-Andritz ADM,
1% feed
BD Centrifuge,
1% feed
DCG, 1% feed
Ultrafilter, 1%
feed
Ultrafilter, 2%
feed
Equipment required
1 5- by 5-ft press
with 80 plates
1 5- by 5-ft press
with 90 plates
2 500-ft^ filters
1 500-ft^ filter
75 ft of belt width
7 DCG-200's, 4 MRP's
2 80-inch SDM1 s
2 P5400 BD's
7 DCG-200's
270 modules with
2540 ft^ of membrane
160 modules with
1500 ft^ of membrane
Cake sol-
ids bulk/
corrected
32-3S/
22-28
38-40/
30-33
26-31/
25-30
26-31/
25-30
15-17
15-17
17-20
8-10
8-10
6
6
Conditioning
required
750# lime/ton
180# FeClVton
54 0# lime/ton
140# FeClVton
100# Diatomaceous earth/
ton
50 # Diatomaceous earth/
ton
100# FeCl3/ton
5 -10* Betz 1260 or
equivalent/ ton
8# Betz 1260 or equiva-
lent required/ton
0
5 -10# Betz 1260 or
equivalent required/ton
0
0
Oper-
ating
horse-
power
20*
20*
132
66
60
12
10
120
4
300
250
00
o
*Average throughout cycle
-------
The DCG, the BD series centrifuge/ and the ultrafilter
appear best suited in thickening applications. Such thickening
might be advantageous ahead of pressure filtration, digestion,
or heat treatment or in situations where land application of
semi-fluid sludge is the favored disposal alternative.
OPERATING COST CONSIDERATIONS
The various dewatering alternatives each have characteris-
tic operating costs associated with them. Those aspects of each
process which are likely to represent a major contribution to
these operating costs are discussed below.
Pressure Filtration
Conditioning requirements represent the majority of the
operating costs associated with this alternative. Historically,
the process has also been relatively labor intensive, but many
recent installations have been automated to a large degree.
Power costs are less of an issue than with some of the other
units evaluated in this study. The sludge conditioning chemical
storage and handling facilities required for pressure filtration
are probably the most elaborate of those associated with the
dewatering alternatives evaluated herein. A list of pressure
filter manufacturers can be found in Appendix C.
Precoat Vacuum Filtration
Precoat consumption is a crucial variable in determining
the relative economies by this technology. The fact that diato-
maceous earth costs can vary by plus or minus 10 percent from
the west to the east coast of the United States may affect the
operating costs associated with this process. Power requirements
for vacuum filtration are among the highest of those estimated
for the units in this study. The amount of operator attention
required by this process is anticipated to be somewhat more than
that associated with conventional vacuum filtration due to the
necessity of precoating about once daily. The operation and
maintenance of precoat storage and handling facilities also add
a degree of complexity beyond conventional vacuum filtration.
A list of rotary precoat filter manufacturers is included in
Appendix D.
Filter Belt Presses
Sludge conditioning costs are the most significant operat-
ing costs associated with these units. Power and supervisory
costs are anticipated to be among the lowest of those estimated
in the study. Maintenance costs, although not well documented,
are generally expected to be relatively low. The DCG-MRP system
suffers a relatively poor economy of scale due to the modular
81
-------
nature of the equipment. A list of filter belt press manufac-
turers is included in Appendix E.
BD Centrifuge
The power costs anticipated for BD centrifugation, are
among the highest of those estimated and are likely to be the
major contributor to operating costs. Although primary sludge
abrasivity has resulted in excessive centrifuge maintenance
costs in some segments of the paper industry, the relatively
nonabrasive nature of biological solids coupled with recent
advances in hard surfacing technology indicate that the mainten-
ance costs for BD centrifugation in this application will be
substantially less than those commonly associated with primary
sludge dewatering. Likely supervisory requirements are felt to
be among the lowest of those encountered in this study.
Ultrafilter
The application of this alternative will require a membrane
configuration which offers far less pressure drop per unit mem-
brane area, resulting in lower power requirements for pumping.
Membrane technology in general suffers a relatively poor economy
of scale due to the modular nature of the membrane area offered
by manufacturers.
SOLIDS RECOVERY CONSIDERATIONS
In those instances where the need for very high solids
recoveries is indicated, the alternatives which suggest them-
selves are precoat vacuum filtration, pressure filtration,
ultrafiltration, and DCG filtration.
82
-------
SECTION 13
OTHER PULP AND PAPER INDUSTRY EXPERIENCE
Since the inception of this study, several pulp and paper
mills, in the process of selecting sludge handling and disposal
systems, have generated data on several of these dewatering
technologies. Recognizing the importance of a broad data base
in the selection of dewatering equipment, it is appropriate to
present and discuss the data that many of these mills have made
available to the NCASI.
FILTER BELT PRESSING
The pulp and paper industry has recently generated substan-
tial amounts of pilot data and some full scale data on filter
belt presses. The data that have been made available to the
National Council, shown in Table 25, allow the formulation of
several generalizations concerning their performance.
First, because the units are usually hydraulically limited,
the most striking process compromise is between capacity, feed
consistency and conditioning requirements. This suggests the
desirability of prethickening sludge to minimize conditioning
costs or maximize capacity. In general, these units have been
applied to sludges that are very difficult to filter or centri-
fuge. Because of this, it is difficult to predict how they
would compare with the conventional dewatering techniques on
more typically fibrous primary sludge. There is some experience
to suggest that filter belt presses require more sludge condi-
tioning to provide economical throughput than is normally
required in conventional vacuum filtration or decanter centri-
fugation where such technologies are applicable. The power
requirements and cake consistencies associated with the filter
belt presses, in most instances, represent significant advan-
tages over centrifugation or vacuum filtration. The cake con-
sistencies attained by these units on fibrous sludges are com-
parable to those associated with V-pressing. In general, the
pilot data have shown filter belt presses to be capable of
dewatering 10 to 25 gpm of primary sludge per foot of belt width,
conditioned with 0 to 5 pounds of polymer per ton and generating
cakes with consistencies of 30 to 40 percent solids.
These units have typically dewatered 5 to 10 gpm of
83
-------
TABLE 25. PULP AND PAPER INDUSTRY FILTER BELT PRESS EXPERIENCE
r-ป
r-l
H
ฃ
A*
Production
pulping/paper
Kraft/fine
A JKraft/fine
B
B
C
D
E
F*
G*
G*
H*
H*
H*
IT*
Sulfite/
Sulfite/
Belt press
type
20-inch Tait-
Andritz, S-press
80-inch Tait-
Andritz, P-press
20-inch Tait-
Andritz, S-press
20-inch Tait-
Andritz, P-press
/Tissue Two -76"xl6l"
Smith & Loveless
Kraft/linerboard
/paperboard
NSSC/NSSC board
Kraft/kraft
/Coated groundwood
Two 2 -meter
Dravo DJ sinus
Two 1-meter
Dravo DJ sinus
20-inch Tait-
Andritz, S-press
20-inch Tait-
Andritz, P-press
20-inch Tait-
Andritz, P-press
Kraf t/linerboard ! 20-inch Tait-
Andritz, P-press
Kraft/linerboard 20-inch Tait-
.Andritz, P-press
Kraft/linerboard
20-inch Tait-
Andritz, S-press
Kraft/linerborad 24-inch Passe-
vant vacupress
Sludge feed
%
Primary
100
166
166
160
160
6
6
6
166
160
166
75
0
160
%
Secondary
0
6
0
0
0
166
166
160
0
0
6
25
160
0
%
Solids
5.0
5.6
2.0
2.0
3.5
4.5
1.0
2.6
7.6
4.6
3.0
4 .5
2.0
3.0
Feed
rate
gpm
(I/HI)
per
unit
35
(130)
126
(450)
76
(260)
70
(260)
12
(45)
25
(95)
17
(65)
15
(55)
56
(190)
15
(55)
16
(60)
16
(60)
16
(60)
26
(75)
Conditioning
Type
Betz 1260
Betz 1260
_
*
Polyelectro-
lyte
Polyelectro-
lyte
Polyelectro-
lyte
Polyelectro-
lyte
Polyelectro-
lyte
Polyelectro-
lyte + alum
Polyelectro-
lyte
Polyelectro-
ly_te + alum
Polyelectro-
lyte
Amount
#/tn
(mq/qm)
3.0
(1.5)
2.0
(1.0)
0
0
36.6
(15.0)
56.6
(15.0)
26.6
(10.0)
20.0
(10.0)
6
4.0
(2.0)
2-(-250
(1+125!
10,0
(5.0)
10+166
(5+50)
2.5
(1.25)
Cake
solids
%
35
36
22
36
16
12
19
12
36
33
25
Z4
17
19
Solids
recov-
ery
%
95
95
99
99
99
98
99
98
98
99
98
98
95
95
Comments
Ray cells + fiber
fines
Ray cells + fiber
fines
Fiber fines
Appreciable quantity
of fiber in sludge
00
* Pilot data
(continued)
-------
TABLE 25 (continued)
r-4
H
r
I*
J*
J*
K*
L*
L*
SF
N*
0*
P*
P*
U*
U*
R*
H*
Production
pulping/paper
/fine
Deinking/fine
Deinking/f ine
Kraft/fine
Kraft/fine
Kraft/fine
Kraft/fine
Kraft/fine
Sulfite /special ties
/fine
Groundwood/special -
ties
Groundwood/special-
ties
Groundwood/special -
ties
Kraft/linerboard
Kraft/linerboard
Belt press
type
20-inch Tait-
Andritz, S-press
20-inch Tait-
Andritz, S-press
20-inch Tait-
Andritz, S-press
20-inch Tait-
Andritz, S-press
20-inch Tait-
Andritz, S-press
20-inch Tait-
Andritz, S-press
20-inch Tait-
Andritz, P-press
20-inch Tait-
Andritz, P-press
20-inch Tait-
Andritz, P-press
20-inch Tait-
Andritz, P-press
20-inch Tait-
Andritz, S-press
20-inch Tait-
Andritz, P-press
20-inch Tait-
Andritz, P-press
20-inch Tait-
Andritz, S-press
0.5-meter Carter
press
Sludge feed
%
Primary
100
90
0
100
100
85
100
0
100
80
80
% Secon-
dary
0
10
160
0
0
15
0
100
0
20
20
see
con' lent
0
100
100
0
0
0
%
Solids
2.0
14.0
2.5
4.0
2.5
2.0
3.0
4.0
3.0
3.0
3.0
1.5
5.0
2.0
2 .0
Feed
rate
qpm
(1/m)
per
unit
30
(115)
5
(20)
1
(4)
9
(35)
20
(75)
10
(40)
30
'(115)
5
(20)
40
(150)
30
(115)
30
(115)
20
(75)
7 '
(25)
15
(55)
40
(150)
Condi tioninq
Type
~
Polyelectro-
lyte
Polyelectro-
lyte
"
Polyelectro-
lyte
Polyelectro-
lyte
Betz 1260
Betz 1260
Polyelectro-
lyte
Hercufloc 859
Hercufloc 859
Polyelectro-
lyte
Polyelectro-
lyte
Betz 1260
Polyelectro-
lyte
Amount
#/tn
mq/qm)
0
'1.5
(0.75)
6.0
(3.0)
0
1.0
(0.5)
2.5
(1.25)
5.0
(2.5)
18.0
(9.0)
4.0
(2.0)
1.0
(0.5)
1.0
(0.5)
5.0
(2.5)
7.0
(3.5)
10.0
(5.0)
10.0
(5.0)
Cake
solids
*
25
34
10
30
30
22
40
14
35
35
20
35
30
25
30
Solids
recov-
ery
'i
91
99
99
93
99
99
98
98
99
98
98
97
80
97
99
Comments
Anaerobic alum coagu-
lated ASB solids
Lagoon bottom solids
Alum filter plant
sludqe
Occasionally anaerobic
Occasionally anaerobic
CO
U1
* Pilot data
-------
biological sludge per foot of belt width, conditioned with 10 to
20 pounds of polymer per ton, and attained cake consistencies of
12 to 19 percent solids. Performance levels on combined sludges
have fallen between those associated with primary sludges and
biological sludges.
Because of the limited amount of full scale operating exper-
ience with filter belt presses in this country, the operating
problems encountered to date are largely associated with startup
and refinement of machinery. The more common difficulties
include bearing failures, belt tracking problems and occasional
belt tearing. Depending upon the unit configuration, utilizat-
tion of high belt tensions or nip pressures may suggest inclu-
sion of a screening device to remove large pieces of debris
from the feed. The limited amount of comparative pilot and full
scale data show generally good agreement between manufacturer's
performance estimates based upon pilot work at mill sites and
full scale performance.
As of July 1976, at least 12 mills in the United States had
purchased filter belt presses.
Appendix E includes those manufacturers of moving belt
presses identified by the National Council.
PRESSURE FILTRATION
Of the emerging technologies evaluated in this study, pres-
sure filtration was initially the most commonly applied alterna-
tive. As a result, full scale as well as pilot data are avail-
able. The pilot and full scale pressure filter data provided to
the National Council are shown in Table 26. In general, the
great variation in reported loading rates can be attributed to
variations in feed consistencies, the amount of admix utilized,
and the nature of the sludge solids. The mills having evaluated
both 100 and 200 psi units have generally selected lower pres-
sure units, citing a loss of less than 5 percent cake consistency
in exchange for greatly reduced capital costs. However, the
exceptions to this generalization provide evidence that the opti-
mum operating pressure may in fact vary from sludge to sludge.
A universal necessity for precoat utilization has not been sup-
ported by industry experience. Several mills having operated
pressure filters continuously for anywhere from several months
to three years report acceptable performance without precoat
utilization. These mills apply thorough, periodic media clean-
ing (weekly to monthly). However, as was the case with optimum
operating pressure, it is likely that the relative advantages of
precoat utilization will depend upon the nature of the solids
being dewatered and the type of filter press involved.
Industry experience has shown that startup problems with
86
-------
TABLE 26. PULP AND PAPER INDUSTRY PRESSURE FILTER EXPERIENCE
f t
lt
H
E
A
A*
B
(.'
D
K
F
G*
H*
I*
Production
pulp/paper
Kraft/fine
Kraft/fine
Kraft/kraft
Kraft/fine
Kraft/linerboard
Thermoraechanical/
Kraft/fine
Groundwood, kraft/
newsprint
/paperboard
Kraft/fine
Manufact-
urer
Passevant
Passevant
Passevant
Netzsch
Passevant
Edwards-
Jones
Shriver-
Johnson
Edwards-
Jones
Passevant
Edwards-
Jones
Size of
unit (s)
100, 52-inch
chambers
100, 52-inch
chambers
75, 62-inch
chambers
315, 47x47-
inch chambers
64, 62-inch
chambers
68, 48x48-
inch chambers
146, 48x72-
inch chambers
103, 48x72-
inch chambers
120, 62-inch
chambers
250, 60-inch
plates
%
Sec-
ondary
solids
0
20
10
0
100
50
20
15
100
20
Feed
consis-
tency
% solids
4.0
4.0
2.5
11.0
2.5
4 .0
2.0
2.0
8.0
Conditioning
requirements
7% lime
15% lime + diato-
maceous earth pre-
coat
3.5# polymer/ton +
coke breeze pre-
coat
1.5 # polymer/ton
2# flyash/tf sludge
+ flyash precoat
10% alum
7% lime+1-1/2%
Fed 3
T% alum
0.5 Ib lime/lb
sludge + 6% FeCl3
+ cement dust preco
lime + FeCl3
Total solids
dewatered
lb/hr/ft2
(kg/hr/m2)
2.8
(14.0)
3.6
(18.0)
0.6
(3.0)
1.3
(6.0)
3.1
(15.0)
0.3
(1.5)
1 .2
(6.0)
1.4
(7.0)
0.4
(2.0)
?tl
2.5
(12.0)
%
Cake
solids
35
35
35
50
50
30
37
38
38
43
Comments
Includes 25ฐ alum
color removal solids
and 25% silica
00
*Pilot data
-------
pressure filters can be substantial. Among the more common dif-
ficulties encountered are (a) plate warping or breakage (most
commonly associated with plastic plates), (b) media tearing,
(c) media blinding, (d) poor sludge and/or precoat distribution
within the chambers, and (e) malfunctions with timing and plate
shifting devices. In most instances these problems have been
resolved, some, however, only after months (in one instance over
a year) of more or less trial and error trouble shooting. It is
yet too early to accurately estimate the amount of operator
attention that these units will require once startup difficulties
have been dealt with successfully. Although the data is sparce,
the industry experience presently available suggests that pilot
data can, with experienced interpretation, provide a reasonably
accurate estimate of full scale capacity requirements. However,
the sensitivities (reported by several mills and confirmed in
this study) of pressure filtration to day-to-day variations in
feed consistency and the nature of the sludge solids suggest the
application of conservative estimates in filter press sizing.
This is especially true since presses purchased with room for
additional plates can accomodate an increase in capacity at a
relatively low cost compared to the purchase of additional
presses.
As of July 1976, at least 11 mills in the United States had
purchased pressure filters for sludge dewatering.
The manufacturers of the pressure filters that have been
applied to pulp and paper industry sludges are listed in
Appendix C.
88
-------
REFERENCES
1. Miner, R.A., D.W. Marshall, and I. Gellman. Sludge Dewater-
ing Practice in the Pulp and Paper Industry. NCASI Technical
Bulletin No. 286. NCASI, New York, New York, June 1976.
2. Eckenfelder, W. Wesley. Industrial Water Pollution Control.
McGraw-Hill Book Company, 1966. p. 236.
3. Process Design Manual for Sludge Treatment and Disposal.
U.S. Environmental Protection Agency Technology Transfer
Series, EPA 625/1-74-006, U.S. Environmental Protection
Agency, 1974. pp. 7-2 through 7-11.
4. Martin, James., and Phillip L. Hayden. Pressure Filtration
of Waste Industrial Sludges, Modeling, Design, and Opera-
tional Parameters. Presented at the 31st Annual Purdue
Industrial Waste Conference, May 1976.
5. Adams, Carl E. , and W. Wesley Eckenfelder, ed. Process
Design Techniques for Industrial Waste Treatment. Enviro
Press, Nashville, Tennessee and Austin, Texas, 1974. p. 170.
6. Smith, Gordon R.S. How to Use Rotary, Vacuum, Precoat Fil-
ters. Chemical Engineering, 83 (4):84, February 16, 1976.
7. Carpenter, W.L., and I. Gellman. Evaluation of Fly Ash as a
Filter Aid for Precoat Vacuum Filtration of Papermill
Sludges. NCASI Technical Bulletin No. 158. NCASI, New York,
New York, July 1962.
8. Lippert, R.E., and M.C. Skriba. Evaluation and Demonstration
of the Capillary Suction Dewatering Device. Environmental
Protection Agency Technology Series, EPA-670/2-74-017.
Environmental Protection Agency, Cincinnati, Ohio, 1974.
89
-------
APPENDIX A
PILOT EQUIPMENT PERFORMANCE DATA
TABLE A-l. PRECOAT VACUUM FILTER DATA
Drum
speed
RPM
1.0
0.5
1.0
1.0
2.0
0.5
2.0
0.5
1.0
1.5
0.5
0.5
1.0
1.0
Drum
submer-
gence
%
25
25
25
40
40
40
25
25
25
25
25
40
40
25
Vacuum
." Hg
23
23
23
23
'23
23
23
23
23
23
23
23
23
23
Knife
advance
mil/min
2.00
1.00
2.00
2.00
4.00
0.75
3.00
1.00
2.00
3.00
1.00
0.75
2.00
3.00
Feed
consis-
tency
% solids
0.96
0.96
0.62
0.62
0.62
1.40
1.40
1.40
0.78
1.40
1.40
1.40
1.40
1. 30
Bulk cake
consistency
% solids
32.7
32.3
31.2
26.9
24.6
29.1
33.6
27.7
28.9
30.0
25.8
23.4
31.8
Solids
loading
rate
Ib/ft2/hr
0.42
0.41
0.75
0.89
0.72
1.19
0.17
0.71
0.69
1.69
0.73
1.46
2.09
0.69
Sludge
specific
resistance
X10 sec2/gm
168
168
104
104
104
104
104
104
85
85
85
85
85
490
Diatomaceous
earth content
in cake - % of
solids in cake
32
20
21
18
36
6
64
12
22
15
12
5
9
30
ID
O
(continued)
-------
TABLE A-l (continued)
Drum
speed
RPM
0.5
0.5
0.2
0.5
1.0
1.5
0.5
0.5
1.0
1.0
0.5
1.0
0.5
0.5
Drum
submer-
gence
0
25
40
40
33
25
25
25
33
33
25
25
40
40
33
Vacuum
" Hg
23
23
23
23
23
23
23
23
23
23
23
23
23
23
Knife
advance
mil/min
1.50
2.00
0.75
1.00
2.00
5.00
1.00
1.00
2.50
3.00
0.50
2.00
0.50
0.50
Feed
consis-
tency
% solids
1.50
1.60
1.60
1.60
0.61
0.61
0.57
0.57
0.57
0.30
0.42
0.71
0.81
0.81
Bulk cake
consistency
% solids
32.3
20.1
24. 3
29.3
32.0
32.6
32.3
32.1
37.4
32.3
31.9
26.7
27.2
29.8
Solids
loading
rate
Ib/ft2/hr
0.42
0.60
0.36
0.55
0.66
0.81
0.38
0.33
0.60
0.48
0. 34
1.40
0.96
0.82
Sludge
specific
resistance
X107 sec2/gm
490
790
790
790
84
85
86
86
79
72
72
72
40
40
Diatomaceous
earth content
in cake - % of
solids in cake
26
25
17
15
23
38
21
23
29
38
13
12
5
6
(continued)
-------
TABLE A-l (continued)
Drum
speed
RPM
1.00
1.00
0.50
0.50
1.00
0.50
0.50
0.50
0.50
0.67
0.50
0.50
0.67
0.50
1.00
1.00
0.50
Drum
submer-
gence
%
33
25
25
40
40
33
33
33
33
25
25
40
40
25
25
40
40
Vacuum
" Hg
23
23
23
23
23
22
15
10
7.5
22
22
22
23
18
18
18
18
Knife
advance
mil/min
1.0
1.0
0.5
0.5
1.0
0.5
0.5
0.5
0.5
2.0
0.5
1.0
1.0
0.5
2.0
2.0
0.5
Feed
consis-
tency
% solids
2.27
1.51
1.18
0.87
1.11
1.80
2.10
1.80
2.00
1.53
1.60
1.32
1.43
1.66
1.14
0.61
0.75
Bulk cake
consistency
% solids
23.3
32.6
33.2
29.7
22.8
29.3
27.3
26.1
24.6
36.2
33.1
28.0
26.8
33.1
33.4
34.1
29.4
Solids
loading
rate
Ib/ft2/hr
2.82
1.35
0.55
0.62
1.27
1.25
1.04
1.02
1.42
0.57
0.55
0.65
0.89
1.06
0.86
0.61
Sludge
specific
resistance
X107 sec^/gm
181.0
71.5
76.5
85.4
82.5
94.3
78.6
106.7
157.0
185.0
205.0
224.0
238.0
179.0
90.0
94.0
105.0
Diatomaceous
earth content
in cake - % of
solids in cake
3
7
8
7
7
4
5
5
3
26
15
13
5
16
19
8
vo
ro
(continued)
-------
TABLE A-l (continued)
Drum
speed
RPM
1.00
1.00
0.50
0.50
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
0.13
1.00
0.50
Drum
submer-
gence
%
33
25
25
40
40
40
25
25
25
25
25
25
40
40
40
Vacuum
" Hg
23.0
24.0
24.0
24.0
24.0
24.0
7.50
10.0
15.0
24.0
23.0
23.0
23-0
23-0
23.0
Knife
advance
mil/min
0.75
1.50
0.75
1.00
1.00
1.50
1.50
1.50
1.50
1.50
1.00
0.50
0.50
1.00
0.50
Feed
consis-
tency
% solids
0.81
0.85
0.95
1.14
1.11
1.00
1.50
1.64
1.60
1.46
1.89
2.20
2.53
1.47
1.99
Bulk cake
consistency
% solids
32.0
26.2
22.3
25.8
24.2
25.6
26.5
28.8
28.0
27.2
28.0
21.1
23.0
Solids
loading
rate
Ib/ft2/hr
1.22
0.85
0.56
1.12
1.35
1.05
1.36
1.78
1.68
1.57
2.12
1.45
0.76
2.00
1.78
Sludge
specific
resistance
X10^ sec^/gm
40
140
111
70
82
126
90
90
139
120
92
146
201
132
137
Diatomaceous
earth content
in cake - % of
solids in cake
6
15
12
8
7
12
10
8
8
9
4
3
6
5
3
vo
to
-------
TABLE A-2 (Part I) .
vo
DUAL- CELL GRAVITY FILTER (DCG) - MULTIPLE ROLL PRESS (MRP) DATA
(Fresh Waste Activated Sludge)
net:
belt
.speed
in/mtn
115
135
57
US
1)5
57
135
135
57
135
57
135
57
135
m
135
135
115
135
135
135
135
135
135
135
135
135
135
135
135
PCC; Peed
belt rons .
mesh % sol ids
100 0.9
100 0.9
100 0.9
100 0.9
100 1.0
100 1.0
100 1.0
1 00 0.7
100 0.7
100 0.8
100 0.9
100 1.0
100 1.0
100 1.0
1 00 1.1
40 0.8
40 0 . 8
40 0.8
40 0.8
40 0.8
40 0.8
40 0.8
40 O.H
40 0.8
40 0.8
40 0.8
40 0.8
40 0.8
40 0.8
40 0.8
Condi t inning
type
Betz 1260
Betz 1260
Bi-tz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 126Q
Betz 1260
Fed 3
Fed 3
Betz 1260
Bet* 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Hetz 1260
Betz 1260
Betz 1260
Betz 1260
* V,
OC O TJ
"* t* r~
c c
O 1 tf
4J 4-ป !L
H C y
"c c 1
U 15 *
65.0
10.6
10.6
5.6
20.0
20.0
11.0
13.5
13.5
6.1
5.4
21.0
20.0
5.0
4.5
13.0
1 3.0
13.0
13.0
13.0
13.0
13.0
13.0
33.0
12.5
12.5
12.5
12.5
3.1
3.1
ฃ a
o> '- * "*-
C c org
F c* C ^
if JlJ
M-ป CL C3 C>
U. V. ^ IT,
ซg ~y "*r*~
1 I ฃH
(j i 1ป X
2.5
1.5
80.0
6.K
6.5
7.2
10. 1'
13.5
27.7
40. 1
2.5
7.2
13.1
11.4
7.0
2.0
15.6
1Z e
s *- ซ
C il ~-
t, JCN
*J C, M 'ซ*
- C- C1 -
u y *j r.
C _ 't:
C i 7: c
C 1 1
a i_ tx
48.3
239.9
35.8
a
C
p
t
15
10
10
10
10
10
15
5
5
5
5
5
5
5
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
T.
c
"^ 'f-
-* -^
^ /.
S ซ--
8.7
8.6
8.6
7.5
8.3
8.7
7.5
8.5
8.0
7.2
7.0
f>.H
8.3
h. \
5.3
9.5
9.7
9.3
9.8
9.4
9.0
9.2
8.6
9.5
8.8
9.0
7.7
7.2
I V
r 1
r3
- >
u
C C,
j; ?
c
0 5
C 1-
99.0
98. 1
99.5
99.5
98.5
99.5
100.0
97.2
99.0
99.0
99.0
99.0
97.8
99.0
99.0
c-
T.
~ i
| ฃ
168
168
I6H
|6H
168
168
168
168
IfiS
16H
168
168
16K
I6.'i
168
8/,
J'Jf>
196
168
168
396
168
168
168
168
396
396
168
168
T.
U
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
29
7
7
7
7
29
29
7
MKP ro
lli/l
-o
c
c/i
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
14
1/4
14
14
29
1 '
14
14
14
29
29
14
! pi i
iiif.ir
u
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
^1
I'l
21
^1
r.
L'l
;>i
:>i
:!
ir>
15
'1
SSUJ'l'S
in
v.
tZ
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
29
2<)
29
29
3r>
29
29
29
29
35
35
:ป>
c
35
35
35
3S
35
33
35
35
35
3r>
35
35
35
35
35
52
52
',2
51'
52
87
ซ7
87
52
52
87
87
87
87
87
I
C, IT.
_y T3
i. X
OC
y "-i
3.6
3.5
3.6
2.7
3.2
2.7
3.6
3.5
3.4
3.6
3.4
12.8
12.7
15.1
15.5
16.5
17.0
14.9
15.H
18.3
17.9
15.7
17.5
I6.H
15.7
16.0
15.0
15.5
14.3
14.1
%\
"c i
/. >
c. C
9 i
97.8
98.8
99.3
86.9
92.6
92.6
92.8
81.3
80.8
79.5
95.4
96.2
89.1
92.2
98.4
96.2
96.2
95.1
88.8
89.5
-------
TABLE A-2 (Part II).
DUAL CELL GRAVITY FILTER (DCG) - MULTIPLE ROLL PRESS
(Degraded Waste Activated Sludge)
(MRP) DATA
DCG
belt
speed
In/min
135
135
135
135
135
135
135
135
135
135
135
135
135
135
135
135
135
57
135
135
135
135
135
135
135
57
70
135
DC<;
belt
me sh
100
100
100
100
100
100
100
100
100
100
100
40
40
40
40
40
40
40
40
40
40
40
40
40
40
40
40
40
Feed
cons.
"/. solids
1 .0
0.9
0.9
0.8
0.8
1.0
1 .0
0.9
0.7
0.9
0.8
0.8
1.0
1 .0
1.0
1.0
0.8
0.8
0.7
0.9
0.7
0.8
1.2
1 .2
1.2
1.2
1.2
1.2
Conditioning
type
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
llercufloc 859
Hercufloc 859
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
*** m
00 O T3
C O
O 1 CO
AJ U 0)
H C 00
T3 3 TJ
COS
OS--'
20.0
11 .0
5.5
12.5
6.2
20.0
10.0
22.0
28.6
22.0
18.7
26.4
15.8
18.0
19.8
22.0
19.8
19.8
3.8
11.7
3.8
24.7
16.7
4.2
8.4
8.4
8.4
0
u
O U-. 60
C CJ CJ(N
H a. nj cu
t-i at AJ m
H CO
T3 T3 t-th~
ฃ3 cy u) o
o
->.
4.8
8.7
8.4
19.4
6.6
24.6
7.7
1.1
-..
37.3
->
CU .-, ฃ
C ^ 6C
o -^ o ~-~
H CJ CJ (N
^ a. a QJ
T3 en *j tn
c en
o -a 'Hr~
o a> en o
c tu u r-t
3 *+- i* x
233.8
355.9
*
300.0
181.3
112.7
-ป
ป
139.0
174.4
162.1
-ซ
-*
I
oc
OJ
T3
a
CJ
u.
5
5
5
10
10
10
15
15
15
15
15
15
15
22
20
18
10
10
10
15
15
11
10
10
10
10
10
10
(fl ^o -'
0 C 'E
cj: tc c; o a. '
c_j CJ o &; c
G fr< o i- y --
8.1 99.0 168
8.2 99.0 168
8.3 98.8 168
8.0 99.0 168
7.8 98.9 168
overflow *
6.8 99.0 168
8.0 99.0 168
8.6 99.0 168
8.1 99.0 168
9.2 98.9 168
8.5 99.0 168
overflow ~>
overflow *
7.4 99.0 168
9.6 99.0 168
9.5 98.0 168
8.9 97.5 168
9.8 98.9 168
9.4 99.0 168
7.7 99.0 168
8.9 99.0 168
overflow -ป
168
overflow -*
8.5 99.0 168
75.0 * before
MRP ro 1 pri'.sstirc's
lb/ 1 iiH'iir in
tc
i
u.
7
7
7
7
7
*
7
7
7
7
7
7
*
ป
7
7
7
7
7
7
7
7
->
7
->
7
c
ฃ
LT.
7
7
7
7
7
>
7
7
7
7
7
7
ป
>
7
7
7
7
7
7
7
14
>
14
"ป
14
wer f low
^
^r
7
7
7
7
7
>
7
7
7
7
7
7
>
*
7
7
7
7
7
7
7
21
>
21
->
21
>-
O
uป
7
7
7
7
7
-ป
7
7
7
7
7
7
*
-ป
7
7
7
7
7
7
7
29
-*
29
-ป
29
0]
H
U.
35
35
35
35
35
>
35
35
35
35
52
52
ป'
-*
52
52
52
52
52
52
52
52
->
52
*
52
y,
C
G,
16.8
17.3
16.9
15.8
16.0
16.5
17.0
15.8
*
15.4
*
16.2
*j
y; |
3 >.
'c co
ffi >
o
Cu U
'
98.9
98.2
97.0
96.0
97.6
*
98.1
97.7
99.0
97.8
81 .0
92.8
*
->
93.5
90.1
84.0
83.0
95.3
91.8
95.3
95.7
"*"
93.4
*
93.9
Ln
-------
TABLE A-3. SHARPLES BD-3000 CENTRIFUGE DATA
Centri-
f uqal
force
x gravity
2100
2100
2100
2100
2100
2100
2100
2100
2100
2100
2100
2100
2100
2100
2100
2100
2100
2100
2100
2100
2100
2100
2100
2100
2100
2100
2100
2100
2100
2100
2100
2100
2100
2100
2100
Pond
set-
ting
8.00
8.00
8.00
8.00
8.00
8.00
8.00
8.25
8.25
8.25
8.25
8.25
8.00
8.00
8.00
8.00
8.00
8.00
8.25
8.25
8.25
8.25
8.25
8.25
8.25
6.25
8.25
8.25
8.25
8.25
8.25
8.25
8.25
8.25
8.25
Scroll
differ-
entia 1
RPM
20
15
20
15
10
6
2
20
15
10
6
2
6
8
10
10
12
14
8
8
15
8
20
15
20
8
20
15
15
8
20
20
15
20
8
Feed
rate
GPM
26.5
26.3
26.2
26.4
26.1
26.1
25.9
28.4
23.9
27.2
26.4
25.9
41 .2
39.1
42.1
26.8
27.2
27.0
19.2
26.6
19.6
27.0
19.4
19.1
29.4
19. 3
19.2
19.2
27.4
26.6
19.5
28. 3
27.7
27.6
19.0
Feed
consis-
tency
% solids
0.6G
0.64
0.69
0.75
0.66
0.53
0.70
0.61
0.83
0.69
0.77
0.68
0.66
0.62
0.64
0.64
0.68
0.48
0.74
0.66
0.77
0.83
0.77
0.71
0.75
0.80
0.7i
0.61*
0.89
0.68
0.80
0.67
0.82
0.73
0.69
Solids
recov-
ery
82.6
86.0
72.8
79.2
83.7
86.7
69.2
93.1
89.6
89.0
80.9
69.6
80.8
90.6
81.6
85.4
90.5
91.2
92.6
87.1
92.9
89.9
92.5
90.8
87.8
92.3
87.7
88.1
91.4
89.9
89.5
88. 3
90.0
Cake
consis-
tency
'4 solids
9.8
11.2
11.2
11.2
11.8
11.2
13.5
1.7
9.2
7.7
11.5
13.8
8.6
6.3
4.0
7.5
7.2
6.8
10.9
9.8
8.3
9.8
9.9
10.6
4.6
11.0
9.7
9.8
8.9
10.0
9.4
5.1
7.5
6.8
11.3
Oncondi -
tioned
sludqc
vo 1 ume
index
130
143
128
149
135
138
115
123
114
125
126
141
125
114
136
120
135
134
109
137
121
138
118
130
135
Condi -
t ioned
si tidcie
vol ume
index
Unonndi tioned
s ludqe
speci fie
resistance
xlO7 sec /
-------
TABLE A-3 (continued)
Centri-
fugal
force
x qravity
2100
2100
2100
2100
2100
2100
2100
2100
2100
2100
2100
2100
2100
800
800
800
800
800
800
800
800
800
800
800
800
800
800
800
800
800
800
800
800
800
800
Pond
set-
ting
8.25
8.37
8. 37
8. 37
8. 37
8.37
8. 37
8.37
8. 37
8.37
8. 37
8.37
8.37
8.25
8.25
8.25
8.25
8.25
8.25
8.25
8.25
8.25
8.25
8. 25
8.25
8.25
8.25
8.25
8.25
8.25
8.25
8.25
8.25
8.25
8.25
Scroll
differ-
ential
RPM
15
6
18
12
6
18
12
6
18
12
6
18
12
3
13
8
3
13
8
3
13
8
3
13
8
13
13
13
13
8
8
8
8
8
8
Feed
rate
GPM
28.1
19.3
20.3
20.1
19.3
31.3
19.8
27.3
31.7
31.7
28.7
20.8
31.4
19.0
20.9
20.2
19.2
34.7
20.2
25.6
33.4
31.7
26. 1
20.8
32.5
33.9
63.5
34.6
57. 3
27.3
47.4
57.1
28.6
51.3
27.9
Feed
consis-
tency
% solids
0.82
0.77
0.73
0.69
0.75
0.66
0.74
0.61
0.71
0.76
0.57
0.77
0.80
0.65
O.G7
0.71
0.65
0.72
0.74
0.59
0.62
0.72
0.68
0.69
0.77
0.72
0.69
0.68
0.71
0.75
0.73
0.56
0.69
0.50
0.69
Solids
recov-
ery
%
88.8
89.9
92. 8
92.2
90.5
93.2
92.1
91.1
88.9
93.7
91.4
94.7
39.3
84.7
94.3
93.1
90.9
92.8
89.9
41.2
85.6
90.7
59.7
93.8
92.4
95.4
97.3
96.0
97.4
85.5
98.4
96.9
92.8
96.9
94.7
Cake
consis-
tency
% solids
6.6
10.2
5.9
5.9
10.0
3.1
7.7
6.5
3.0
3.3
4.0
5.5
3.5
10.2
4 .5
6.1
9.7
2.4
6.1
9.9
2.1
3.1
9.6>
4.8
3.1
2.6
1.6
2.4
1 .9
7.5
2.9
1 .5
5.1
1.6
6. 3
Uncondi-
tioned
sludge
volume
index
118
127
140
131
150
130
158
134
127
170
127
127
151
145
138
150
137
131
164
157
134
144
142
127
Condi-
tioned
sludge
volume
index
169
169
153
137
129
124
156
134
155
131
Unconditioned
s 1 udge
specific
resistance
xlO7 sec2/gm
154
133
90
276
171
151
158
159
149
157
142
138
252
105
199
193
116
204
166
229
189
156
171
620
323
337
905
243
722
592
143
143
167
Conditioned
sludge
specific
resistence
xlO7 sec2/gm
59
57
53
70
70
74
94
90
67
70
Conditioning
type
Hercufloc 84<
Hercufloc 84'
Hercufloc 84^
Hercufloc 84'
Hercufloc 84
Hercufloc 84
Hercufloc 84
Hercufloc 84
Hercufloc 84
Hercufloc 84
Condi-
tioning
amount
Ib/tn
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
3.1
3.3
5.6
5.3
7.1
7.3
4.0
3.3
7.6
5.5
(continued)
-------
TABLE A-3 (continued)
Centri-
fugal
force
x gravity
800
800
800
800
800
800
800
800
800
800
800
800
800
800
2100
2100
2100
2100
2100
2100
2100
2100
2100
2100
2100
2100
2100
2100
2100
2100
Pond
set-
ting
8.25
8.25
8.25
8.25
8.25
8.25
8.25
8.25
8.25
8.25
8.25
8.25
8.25
8.25
8.25
8.25
8.25
8.25
8.25
8.25
8.25
8.25
8.25
8.25
8.25
8.25
8.25
8.25
8.25
8.25
Scroll
differ-
ential
RPM
8
8
8
8
8
8
8
8
8
8
8
8
8
8
6
9
15
9
6
9
15
15
15
6
9
8
8
8
8
8
Feed
rate
GPM
51.0
27.7
33.8
32.0
30.2
46.6
31.5
28.3
47.0
48.2
28.3
29.3
46.6
41.2
26.7
43.5
29.9
27.0
39.8
27.2
47.4
29.6
45.9
26.7
42.4
27.0
37.0
27.2
37.5
27.4
Feed
consis-
tency
% solids
0.63
0.72
0.55
0.74
0.64
0.57
0.75
0.70
0.64
0.75
0.67
0.63
0.73
0.61
0.71
0.72
0.74
0.76
0.70
0.75
0.66
0.74
0.76
0.74
0.69
0.68
0.74
0.64
0.62
Solids
recov-
ery
%
96.8
96.1
96.4
94.0
96.4
96.2
98.7
99.2
97.9
97.0
97.7
9B.4
98.9
85.8
87.5
91.0
81.3
67.5
84.7
89.8
89.1
89.1
74.8
82.3
46.9
98.0
85.2
Cake
consis-
tency
% solids
2.0
7.1
2.0
4.0
2.7
2.5
6.4
3.0
2.5
6.2
4.4
2.7
5.8
8.1
3.6
4.0
8,1
5.4
7.4
2.8
3.7
3.0
8.7
4.0
8.9
12.1
8.9
10.3
6.0
Uncondi-
tioned
s 1 udge
volume
index
139
162
140
138
133
130
140
132
154
134
131
134
Condi-
tioned
sludge
volume
index
120
129
149
125
146
78
101
79
115
86
93
91
Unconditioned
sludge
specif ic
resistence
x!07 sec2/qm
269
106
217
124
165
102
109
192
140
124
129
107
Conditioned
s 1 ud ge
specific
resistence
xlO7 sec /gm
78
108
96
107
74
47
57
29
67
41
60
93
67
69
91
61
Conditioning
type
Hercufloc 844
Hercufloc 844
Hercufloc 844
Hercufloc 844
Hercufloc 844
Hercufloc 844
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Condi-
tioning
amount
Ib/tn
8.5
7.4
4.1
3.5
5.1
6.0
4.0
7.1
7.6
8.4
3.1
8.0
3.6
7.3
0
0
0
0
0
0
0
0
0
0
0
3.3
3.3
5.2
6.0
8.6
vo
00
(continued)
-------
TABLE A-4. TAIT-ANDRITZ SDM DATA
Belt
speed
cra/min
137
274
548
274
274
137
274
274
274
548
548
189
189
548
498
498
668
551
650
269
269
668
203
274
668
668
425
425
425
452
132
132
132
312
468
275'
Belt tension
Ib/linear in
40
40
40
60
20
20
40
20
60
60
20
40
40
20
40
40
20
20
20
20
30
30
30
50
50
10
20
40
10
10
30
10
50
50
50
30
Feed
rate
1/min
24
28
2<3
25
24
24
29
27
29
28
28
60
55
59
97
103
105
164
124
74
71
52
67
68
79
69
73
73
74
72
38
36
39
75
74
70
Feed
consis-
tency
% solids
0.95
0.83
0.81
0.81
0.93
0.92
0.87
0.85
0.94
0.90
0.90
0.75
0.77
0.84
0.77
0.84
0.84
0.84
0.78
0.72
0.80
0. 87
0.80
0.75
0.86
0.85
0 .75
0 .78
0.78
0.78
0.57
0.51
0 .91
0 .98
0.73
0.79
Conditioning
type
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Condi-
tioning
amount
0
0
0
0
0
0
8.1
8.6
8.6
8.6
8.6
6.6
4.7
v 0
6.8
10.5
11.2
9.4
11.8
3.2
4.3
4 .2
3.7
3.9
3.4
4.8
6.2
5.9
5.8
6.0
8.7
10.3
3.5
7.2
9 .8
4 .8
Unconditioned
sludge specific
resistance
X10^ sec^/gm
62
60
60
60
63
64
42
40
40
36
40
51
50
50
50
50
50
50
51
80
120
157
150
150
150
150
225
225
225
225
541
550
550
223
200
207
Conditioned
sludge specific
res istance
X107 sec2/gm
62
60
60
60
63
64
23
19
20
23
20
28
24
50
24
22
24
13
11
15
22
20
20
20
20
20
46
24
15
15
50
50
19
20
35
12
Cake
consis-
tency
o solids
22 .5
21 .9
11 .8
20.2
20 .4
19.6
19 .8
17. 7
21.6
18.0
16.6
19.5
20 .9
21 .8
19 .4
18. 3
17.2
16.8
16.2
16.4
18.3
18.8
18.1
19.7
19 .9
15.3
13.7
14 .9
13 .4
13.1
16.4
12.5
17.3
14.7
16 .0
15 .4
Sol ids
recovery
?,
78
40
26
29
59
80
91
85
82
42
72
98
94
27
86
94
90
93
86
99
90
70
90
85
53
83
92
81
94
90
87
93
85
91
76
81
(continued)
-------
TABLE A-4 (continued)
o
o
Belt
speed
cm/mi n
260
493
585
493
425
425
292
292
134
Belt tension
Ib/linear in
50
30
30
30
30
30
30
30
L_ 40
Feed
rate
1/min
68
78
78
74
72
72
70
74
77
Peed
consis-
tency
% solids
1. 16
1 .04
.98
1.05
1.22
1.14
1.18
.81
1.21
Conditioninq
type
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Betz 1260
Condi-
tioninq
amount
6.0
7.4
3.8
6.4
7.7
10.4
10.4
15.1
24.4
Unconditioned
sludqe specific
resistance
X10' sec^/qm
100
330
300
300
249
250
250
257
250
Conditioned
sludqe specific
resistance
X10^ sec /qm
28
31
46
22
31
21
20
37
1
Cake
consis-
tency
" solids
27.2
16.3
17.2
15.4
16.9
16.1
15.6
17.1
23.2
-
Solids
recovery
%
93
90
69
88
77
87
88
78
95
-------
TABLE A-5. SQUEEGEE DATA
Roll pressure
Ib/linear inch
4.2
4.2
4.2
4.2
4.2
4.2
4.2
4.2
1.2
6.7
6. 7
1.2
4.2
4.2
1.2
6.7
6.7
4.2
1.2
6.7
6.7
6.7
6.7
4.2
1.2
1.2
. 6.7
4.2
Belt
speed
cm/sec
8.7
8.7
8.7
8.7
12.7
8.4
16.0
16.0
16.0
8.4
8.4
8.4
12.7
12.7
12.7
8.4
8.4
8.4
8.4
8.4
2.5
2.5
2.5
2.5
8.4
2.5
2.5
Feed
rate
H/min
10.0
6.7
6-7
6.7
8.6
12.6
6.6
12.6
12.6
12.6
5.0
5.0
5.0
10.0
10.0
10.0
10.0
5.0
5.0
5.0
5.0
3.0
3.0
3-0
3.0
10.0
2 . 5
2.5
I
1
^1
0 .
c
0) in
p n
in -H
13 in o
0.7
0.7
0.6
0.7
0.7
0.7
0.7
0.9
0.9
0.9
0.9
0.9
0.9
0.7
0.7
0.7
0.7
0.9
0.9
0.9
0.9
0.9
0.9
0.9
0.9
0.9
0.8
0.8
>^
CJ
c
o in
-u -d
en -H
H -H
Cj in o
^ d in
ra o
DO*1
16.4
15.6
15.6
16.7
14.8
15.1
14.1
15.4
11.8
12.5
16.3
15.1
14.2
16.1
12.4
12.0
15.0
16.6
13.4
12.7
12.5
13-7
14.7
16.4
15.5
12.6
14.7
^
^
in a)
rH O
M CJ
0 0)
in M <*>
96
99
94
91
94
97
' 99
99
96
98
96
98
99
99
98
98
95
61
98
98
CJ
tJ 1-1
(U-rH g
CO CT>
o o cu \
H Q. Of"
4-) U) C O
H /O CU
"O (1) JJ W
c O1 in
O TIf -H '
o d in o
C i-H OJ H
D in n X
240
234
355
74
51
48
u
rH
1-1
H e
T3 U 0^
-------
TABLE A-5 (continued)
o
OJ
Roll pressure
Ib/lincar inch
4.2
1.2
1.2
4. 2
4.2
4.2
4.2
4.2
4.2
4.2
6.7
6.7
6. 7
6.7
6.7
4.2
4.2
4.2
4.2
4.2
4.2
4.2
4.2
4.2
4.2
4.2
4.2
4.2
4.2
t
'
Belt
speed
cni/sec
2.5
2.5
8.4
5.6
3.2
4. 0
12.7
5.6
7.6
15.2
10. 3
10. 3
10. 3
5. 1
5.1
7.6
10.1
7.9
3.3
10. 1
10.1
7. 9
10.1
10. 1
3. 3
3.3
3. 3
10.2
10.1
>,
Feed
rate
2.5
2.5
8.3
4.0
4.0
4.0
8.0
8.0
8.0
12.0
5.0
5.0
4.0
5.0
5.0
7.5
10.0
7.9
3.4
10.0
13.0
7.9
10.0
12. 3
3. 4
5.1
4. 1
5.0
10.0
(j
c.
01 (/)
4J T-J
M -H
H *-f
-a in o
0.8
0.8
0.8
0.9
0.9
0.9
0.9
0.9
0. 9
0.9
0.8
0.8
1.0
1.0
1.0
0.4
0.6
0.7
0.7
0.6
0.6
0.6
0.6
0.6
0.6
0.6
O.b
0.6
0.6
>*
u
c
jj tf
10 -H
H ^
Hi in o
A: c in
rrj 0
U O o*
16.0
17.0
16.1
15.7
15.5
15.5
14.6
13.8
13.8
13.7
10.6
10. 1
10.9
11.1
10. 8
14.1
15.9
16. 5
16.8
15.4
14.7
15.5
14. 7
14.6
16. 8
15.9
16.5
12. 1
14.9
>,
tt
in 01
tf >
H O
-I O
o -HC-
O 3
-------
TABLE A-5 (continued)
Roll pressure
Ib/linear inch
4.2
4.2
4.2
4.2
1.2
1.2
.1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
Belt
speed
cm/sec
10.1
10.1
10.1
10.1
38.0
31.7
38.1
Feed
rate
a/min
10.0
10.0
10.0
10.0
19.8
10. 9
7.5
34.6 20.3
6.7
6.7
6.7
21.2
21. R
6.0
6.0
6.0
6.0
G.O
31.8 i 12.2
34.6
50.6
25.4
12.2
12.2
12.2
H
Q
ฃ
OJ CO
P "O
CO -H
i-t rH
"3 CO O
C U)
Q) O
Eu O <*>
0.58
0. 59
0.68
0.65
0.59
0.67
0.65
0.64
0.65
0.73
0.72
0.65
0.76
0.68
0.62
0.65
0.80
>,
o
c
01 in
JJ 13
en -H
H i-l
13.0
13.5
14.3
14.6
14.4
12.9
9.0
12.9
18.8
16.4
12.9
11.6
11.9
13.7
9.6
7.2
6.8
! u
' -H
>i
^
U) CL)
T3 >
H 0
i-l O
O 1'
1/5 'M no
49
96
95
95
82
77
39
84
92
88
69
46
83
55
80
29
O >n
4) -H fi
c u tr>
o 4-J CO
C CP in
0 T5 -HI
U 3 W 0
d 1-1 cj -!
D en nx
o
H
U-l
H 6
CO tP
jOJ GJ Q) ^
d a U
-------
TABLE A-6 (Part I). PRESSURE FILTER DATA
(Fresh Biological Solids)
Feed
consistency
% solids
1.2
1.2
1.4
1.6
0.8
0.9
2.4
0.9
1.2
1.7
0.7
1.6
1.2
0.8
1.0
Cycle
time
hr
2.0
3.0
3.0
3.0
3.0
2.0
2.0
1.0
2.0
2.0
2.0
2.0
2.0
Pressure
atm
12.0
12.0
12.0
7.5
7.5
7.5
7.S
7.5
7.5
5.1
7.5
7.5
7.5
7.5
7.5
Precoat and conditioning
% of sludge solids
DE Pre t 20% lime * 5%
FeC 13
DE Pre + 20% lime * 5%
Fed,
DE Pre + 3.4# Betz
1260/ton run aborted
DE Pre + 3.4# Betz
1260/ton *- 8% lime
run aborted
DE Pre -t- 4.61 Betz
1260/ton
DE Pre + 4.6# Betz
1260/ton + 8* lime +
5% FeCl,
DE Pre + 2# flyash/#
sludge solids
lime mud Pre + . 31#
lime mud solids/ft
sludge solids
lime mud Pre * .75*
lime mud solids/*
sludge solids
DE Pre + 24% lime +5.8%
FeCl3
DE Pre + 22.9% lime +
5.6% FeCl3
DE Pre + 27.4% lime ป-
6.6% FeCl3
DE Pre + 1# broke solids/
# sludcre solids
DE Pre +".30# bark fines/
1 sludge solids
DE Pre + .51 broke
solids/S sludge solids
Unconditioned
specific
resistance
X1Q7 sec2/gm
59
72
84
172
198
191
160
54
22
26
21
160
33
Conditioned
specific
resistance
X1Q7 sec2/qra
17
26
45
52
57
177
95
5
8
8
42
87
16
Bulk cake
consist-
ency - %
solids
45
47
14
35
37
33
35
37
35
27
30
Solids
recovery
%
81
99
98
98
99
99
99
98
99
Weight of
dewatered
sol ids
gm
790
670
410
320
560
170
270
810
470
1100
540
250
330
M
O
(continued)
-------
TABLE A-6 (Part I) (continued)
Feed
consistency
% solids
0.9
1.0
0.9
1.1
0.8
0.7
0.8
1. 3
1.2
1.7
0.9
0.9
Cycle
time
hr
3.0
2.2
1.3
2.0
2.0
2.0
2.0
3.3
1.2
2.4
2.3
2.3
Pressure
atm
7.5
7.5
7.5
7.6
13.5
10.6
6.8
13.5
6.8
6.8
13.5
10.5
Precoat and conditioning
% of sludge solids
20.9% lime + 5.2% FeCl3
20% lime + 5# Betz 1260/
ton
21.3% lime + 6. 3# Betz
1260/ton
18.8% lime + 4.7 Fed,
DE Pre + 29.3% lime -t-
7.3% FeCl3
DE Pre + 24.5% lime -t-
6.1% FeCl3
DE Pre + 24.5% lime +
6.1% FeCl,
PE Pre + 31.9% lime +
7.9% FeCl,
DE Pre- + 38.5% lime +
9.6% FeCl,
DE Pre + 34 . 1% lime +
8.5% FeCl,
33% lime + 8.2% FeCl,
100% lime -t- 25% FeCl3
Unconditioned
specific
resistance
X10'' sec^/gm
50
49
48
53
40
36
52
68
62
77
108
Conditioned
specific
resistance
X10? sec2/qm
15
292
317
33
17
21
26
13
7
10
13
Bulk cake
consist-
ency - %
solids
33
15
30
28
27
29
42
38
39
35
35
Solids
recovery
%
99
98
Weight of
dewatered
solids
gm
510
230
460
390
310
340
800
710
700
520
650
O
cn
-------
TABLE A-6 (Part II). PRESSURE FILTER DATA
(Degraded Biological Solids)
Feed
consistency
% solids
1.2
1.1
1.6
1.4
0.7
1.6
1.3
1.4
1.4
1.6
1.4
1.3
1.3
2.2
0.6
2.7
Cycle
time
hr
3.0
3.0
2.0
2.0
3.0
2.0
2.0
2.0
2.0
2.0
2.0
1.0
1.0
2.0
2.0
1-4
2.8
Pressure
atm
7.5
7.5
7.5
7.5
7.5
7.5
13.5
5.1
5.1
7.5
13.5
13.5
7.5
7.5
7.5
7.5
7.5
Precoat and conditioning
% of sludqe solids
DE Pre + 45% lime +4.5%
Fed 3
DE Pre + 45% lime + 4.5%
FeCl3
DE Pre + 29% lime
DE Pre + 33% lime -1-3.3%
FeCl,
DE Pre + 32% lime + 3.1%
FeCl,
DE PreJ+ 11.5% lime +
2.9% FeCl,
DE Pre + 1573% lime -t-
3.7% FaCl,
DE Pre + 15.9% lime *
3.8% FeCl3
DE Prra + 28.6% lime +
7% reel 3
DE Pre + 25% lime + 6.1%
FeCl,
DE Pro + 26% lime +-6.3%
FeCl,
DE Pre + 34% lime + 8. 3%
FeCl 3
DE Pre + 35% lime -1-8.4%
FeCl 3
DE Pre + 22.5% lime +
5.6% FeCl,
DE Pre + 2274% lime +
5.6% FeCl3
E>E Pre + 15,71 lime +
3.9% FeCl 3
DE Pre + 15% lime + 4%
FeCl3
Unconditioned
specific
resistance
X107 sec2/gm
1060
1060
243
396
185
99
74
73
137
71
68
70
76
78
37
94
94
Conditioned
spcci fie
resistance
X107 sec2/gm
20
14
126
19
63
46
48
23
7
8
9
4
2
8
20
IS
15
Bulk cake
consist-
fine/ - %
solids
41
40
37
40
32
29
23
27
33
37
39
36
35
36
32
37
38
Solids
recovery
I
99
98
92
98
99
99
99
99
99
99
99
99
99
99
99
99
99
Weight of
dowaterod
solids
qm
640
830
420
640
200
320
260
280
680
680
590
540
590
720
250
650
700
o
Cf\ '
(continued)
-------
TABLE A-6 (Part II) (continued)
O
-J
Feed
consistency
4 solids
0.9
1.0
1.0
1.1
0.9
1.4
1.7
0.8
0.9
11.2
Cycle
time
hr
2.0
2.0
2.0
1.6
3.3
1.3
3.5
2.9
3. 1
1.2
Pressure
atm
6.8
10.5
13.5
6.8
13.5
10. 5
$.8
10.5
10. 5
11.0
Prccoat and conditioning
% of sludge solids
DE Pro + 19.9% lime + 5%
Fed 3
DE Pre + 20% lime + 5%
Fed 3
DE Pre + 19.74 lime *
4.9% Fed 3
32.3% lime + 8% FeCl-,
30-8% lime + 7.7% FeCl3
.6# lime mud solids/#
sludge solids + 4#
Percol 140/ton
1# flyash/# sludge solids
+ 4# Percol 140/ton
45-2% lime + 11.2% FeCi3
44.7% lime + 11.1 FeCls
30% lime +7.51 FeCl3
Uncondi tionod
specif i c
resistance
X10^ scc^/gm
393
324
246
Condi tionod
specific
resistance
X107 sec2/gm
24
23
29
198 ' 16
289
214
152
110
96
15
46
40
20
16
Bulk coke
consist-
ency - %
solids
27
28
27
32
37
34
35
41
Solids
rocovo ry
Wc-iqht- of
dewa tcred
yolidc
qm
320
380
350
631
540
510
470
530
880
-------
APPENDIX B
PERFORMANCE LEVELS USED TO CALCULATE EQUIPMENT REQUIREMENTS
ULTRAFILTER
Basis; 10 tpd Waste Activated Solids at 1 Percent Consistency
Average flux rate: 80 gal/ft2/day 2
Equipment requirements: 270 modules (2540 ft )
Conditioning: none
Power requirements: for 1 pump (as utilized in the pilot study)
for every third stage connected HP is about 300 HP
Cake Consistency: 6 percent solids
Solids recovery: 100 percent
Basis; 10 tpd Waste Activated Solids at 2 Percent Consistency
2
Average flux rate: 50 gal/ft /day 2
Equipment requirements: 160 modules (1500 ft )
Conditioning: none
Power requirements: under same circumstances as above connected
HP is about 250 HP
Cake consistency: 6 percent solids
Solids recovery: 100 percent
SHARPLES P3000 BD Centrifuge
Basis; 10 tpd of Waste Activated Solids at 1 Percent Consis-
tency
Loading: 95 gpm/unit
Equipment requirements: 2 P5400-BD centrifuges (20 percent
additional capacity included)
Conditioning: none
Power requirements: 320 connected HP, 120 running HP
Cake consistency: 8 to 10 percent solids
Solids capture: 90 percent
Basis; 10 tpd Waste Activated Solids at 2 Percent Consistency
Insufficient data
108
-------
SQUEEGEE
Basis; 10 tpd Waste Activated Solids at 1 Percent Consistency
Loading: 2.6 gpm/ft of belt width
Equipment requirements: units totaling 75 feet of belt width
(includes 20 percent additional capacity)
Conditioning: 5 percent FeC^
Power requirements: estimated to be approximately 60 connected
HP
Cake consistency: 15 to 17 percent solids
Solids recovery: 90 percent
Basis: 10 tpd Waste Activated Solids at 2 Percent Consistency
Insufficient data
PERMUTIT DCG-MRP
Basis; 10 tpd Waste Activated Solids at 1 Percent Consistency
Loading: 30 gpm/DCG 200 and 1 MRP per 2 DCG 200's
(2 DCG 100's = DCG 200}
Equipment requirements: 7 DCG 200's and 4 MRP's (includes
(20 percent addiitonal capacity).
Conditioning requirements: 5 to 10 pounds Betz 1260/ton
Power requirements: 10 to 12 connected HP
Cake consistency: 15 to 17 percent solids
Solids recovery: 90 percent +
Basis: 10 tpd Waste Activated Solids at 2 Percent Consistency
Insufficient data
PRECOAT VACUUM FILTER
Basis; 10 tpd Waste Activated Solids at 1 Percent Consistency
Loading rate: 1 Ib/ft2/hr (1/2 RPM, 40 percent submergence)
Equipment requirements (allowing 20 percent additional capacity)
two 500-ft2 filters
Precoat consumption: at 5 percent of sludge solids = 1000 lb/
day
Power requirements: 132 connected HP during filtration, an
additional 63 during precoating
Cake consistency: 25 to 30 percent solids
Solids recovery: 99 percent +
109
-------
PRECOAT VACUUM FILTER (cont.)
Basis; 10 tpd Waste Activated Solids at 2 Percent Consistency
Loading rate: 2 Ib/ft2/hr (1/2 RPM, 40 percent submergence)
Equipment requirements: one 500-ft2 filter (includes 20 percent
additional capacity)
Precoat consumption: at 2.5 percent of sludge solids = 500 lb/
day
Power requirements: 66 connected HP during filtration, an
additional 63 connected HP during precoating
Cake consistency: 25-30 percent solids
Solids recovery: 99 percent +
TAIT-ANDRITZ SDM
Basis: 10 tpd Waste Activated Solids at 1 Percent Consistency
Loading rate: 15 gpm/ft of belt width
Equipment requirement (allowing 20 percent additional capacity):
two 80-inch SDM;s
Conditioning requirements: 8 pounds Betz 1260/ton
Power requirements: 10 connected HP
Cake consistency: 17 to 20 percent solids
Solids recovery: 90 percent +
Basis; 10 tpd Waste Activated Solids at 2 Percent Consistency
Insufficient data
NETZSCH PRESSURE FILTER
Basis: 10 tpd Waste Activated Solids at 1 Percent Consistency
Loading rate: 0.30 Ib/ft2/hr with 1-inch thick cake or 1.31
Ib/gal/hr (total solids basis)
Equipment requirements: 1 press containing 80 5- by 5-foot
plates
Conditioning: 35-40 percent lime + 8-10 percent FeCl3
Power requirements: 20 HP average over cycle
Cake consistency: 32-38 percent bulk (22 to 28 percent sludge
solids basis)
Solids recovery: 99 percent
110
-------
NETZSCH PRESSURE FILTER (cont.)
Basis: 10 tpd Waste Activated Solids at 2 Percent Consistency
Loading rate: 0.39 Ib/ft2/hr with 1-inch thick cake or 1.25 lb/
gal/hr (total solids basis)
Equipment requirements: 1 press containing 90 5- by 5-foot
plates (includes 20 percent extra capacity)
Conditioning: 25 to 30 percent lime + 7 percent
Power requirements: 20 HP average over cycle
Cake consistency: 38 to 40 percent
Solids recovery: 99 percent
111
-------
APPENDIX C
MANUFACTURERS OF PRESSURE FILTERS
Edwards-Jones
William R. Perrin
530 King Street East
Toronto, Ontario M5A1M1
Netzsch
P-K Associates
Box 701
Valley Forge, Pennsylvania
Passevant Corporation
Carson Road
Birmingham, Alabama 35201
Shriver-Johnson
T. Shriver and Company, Inc.
808 Hamilton Street
Harrison, New Jersey 07920
Phone: 416-869-1463
Phone: 215-935-9201
19481
Phone: 205-853-6290
Phone: 201-484-2500
112
-------
APPENDIX D
MANUFACTURERS OF PRECOAT VACUUM FILTERS
Ametek, Inc.
76 Thomas Street
East Moline, Illinois 61244
Dorr-Oliver, Inc.
77 Havermeyer Lane
Stamford, Connecticut 06904
Envirotech Corporation
669 West Second South
P.O. Box 300
Salt Lake City, Utah 84110
Komline-Sanderson Engineering Corporation
100 Holland Avenue
Peapack, New Jersey 07977
113
-------
APPENDIX E
MANUFACTURERS OF FILTER BELT PRESSES
Dravo
One Oliver Plaza
Pittsburgh, Pennsylvania
15222
Environmental Machine and Mfg. Company
1151 N.W. 6th Street
Gainesville, Florida 32601
Passevant Corporation
Carson Road
Birmingham, Alabama 32501
Permutit Company, Inc.
8700 North Waukegan Road
Morton Grove, Illinois 60053
Ralph B. Carter Company
6659 North Avondale
Chicago, Illinois 60631
Smith and Loveless Division
Econdyne Corporation
Lenexa, Kansas 66215
Tait-Andritz
Box 1138
Lubbock, Texas
Phone: 412-566-3492
Phone: 904-375-2450
Phone: 205-853-6290
Phone: 312-967-5071
Phone: 312-631-0244
Phone: 913-888-5201
Phone: 806-747-8666
70408
114
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/2-78-014
2.
3. RECIPIENT'S ACCESSIONING.
4. TITLE AND SUBTITLE
Pilot Investigations of Secondary Sludge Dewatering
Alternatives
5. REPORT DATE
February 1978 issuing date
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Reid A. Miner, Duane W. Marshall
Isaiah Gellman*
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
10. PROGRAM ELEMENT NO.
National Council of the Paper Industry for Air and
Stream Improvement, Inc.
Western Michigan University(Central-Lake States Reg.Ctr
Kalamazoo, Michigan 49008
1BBQ37
11. CONTRACT/GRANT NO.
'R-804019-01-0
12. SPONSORING AGENCY NAME AND ADDRESS
Industrial Environmental Research LaboratoryGin. .OH
Office of Research & Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
13. TYPE OF REPORT AND PERIOD COVERED
Final 11/1/75 to 10/31/76
14. SPONSORING AGENCY CODE
EPA/600/12
15. SUPPLEMENTARY NOTES
*Isaiah Gellman is with the National Council of the Paper Industry for Air and
Stream Improvement, Inc, New York, New York 10016
16. ABSTRACT
A pilot investigation of biological sludge thickening and dewatering alternatives,
including pressure filtration, precoat vacuum filtration, filter belt pressing,
capillary suction, dewatering, gravity filtration, centrifugation, and ultra-
filtration has been conducted on waste activated sludge resulting from the treat-
ment of wastewater from an integrated bleached kraft-fine paper mill. Based upon
a criterion of attainable cake consistency, 'three levels of performance are
relatively low cake consistencies. Performance was found to be severely affected
by changes in feed sludge consistency, the amount of sludge conditioning, and
the sludge's specific resistance to filtration. The type and amount of sludge
conditioning required was extremely variable, depending upon the dewatering
technique employed, the level of performance expected of it, and the consistency
and nature of the sludge dewatered.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
Pulp mills, Paper mills, Sludge disposal,
Vacuum filtration, Pressure filters,
Dewatering, Centrifuging
b.IDENTIFIERS/OPEN ENDED TERMS
Sludge dewatering,
Precoat vacuum filtration
Sludge conditioning
c. COSATI Field/Group
50 B
IB. DISTRIBUTION STATEMENT
Release to public
19. SECURITY CLASS (This Report)
UNCLASSIFIED
21. NO. OF PAGES
127
20. SECURITY CLASS (This page)
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (9-73)
115
U. S. GOVERNMENT PRINTING OFFICE: 1 978-757- 1 1*0/6696 Reg i on No . 5- 1 1
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