EPA-670/2-74-G04
February 1974
Environmental Protection Technology Series
Optimization and Design
of an Oil Activated Sludge
Concentration Process
Office of Research and Development
U.S. Environmental Protection Agency
Washington, D.C. 20460
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Research reports of the Office of Research and
Monitoring, Environmental Protection Agency, have
been grouped into five series. These five broad
categories were established to- facilitate further
development and application^ of environmental
technology. Elimination of traditional grouping
was consciously planned to foster technology
transfer and a maximum interface in related
fields. The five series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
fl. Environmental Monitoring
5. Socideconomic Environmental Studies
This report has been assigned to the ENVIRONMENTAL
PROTECTION TECHNOLOGY series. This series
describes research performed to develop and
demonstrate instrumentation, equipment and
methodology to repair or prevent environmental
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.
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EPA-670/2-74-004
February 1974
OPTIMIZATION AND DESIGN OF AN OIL
ACTIVATED SLUDGE CONCENTRATION PROCESS
By
T. M. Rosenblatt
Project 17070 HDA
Program Element 1BB043
Project Officer
J. E. Smith, Jr.
U.S. Environmental Protection Agency
National Environmental Research Center
Cincinnati, Ohio 45268
Prepared for
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 - Price $1.40
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EPA Review Notice
This report has been reviewed by the Environmental Protection
Agency and approved for publication. Approval does not signify that the
contents necessarily reflect the views and policies of the Environmental
Protection Agency, nor does mention of trade names or commercial products
constitute endorsement or recommendation for use.
ii
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ABSTRACT
This report describes laboratory and pilot plant studies and
cost calculations for a new process for the disposal of sewage sludge.
The process consists of an oil assisted gravity separation of the
majority of the water, with heating, followed by multiple effect evapora-
tion to dryness in an oil slurry and incineration of the dry solids.
In the gravity separation, secondary sludges were concentrated
from about 0.5% up to 5-10% solids. Solids capture was >_ 98% with high
shear oil-sludge contacting. However, solubilized organic carbon losses
were observed in the separated water from the oil concentration, and in
the distillate from the evaporators. These losses were primarily tem-
perature dependent and ranged up to about 25% of the organic content
of the feed. The agreement of performance between laboratory and pilot
plant results was good, indicating no scale-up problems. The process
economics show an advantage of $13-32 a ton compared to the best known
commercial technology, for a 189 ton/day plant processing a 50/50 mixture
of primary + activated sludges to ash. The total costs for the process
are estimated at $21-39/ton of dry solids for the 189 ton/day plant. These
cost estimates include an economic penalty for a 25% recycle of solubilized
secondary sludge. A lower temperature gravity separation step would
greatly reduce the total solubilization loss and could yield a net economic
improvement of $l-12/ton of dry solids, depending on plant size and sludge
type. Other possible cost reductions in the thickening and settling steps
have been identified which could amount to $1-5/ton dry solids.
This report was prepared by Esso Research and Engineering
Company in fulfillment of Contract No. 68-01-0095, under the sponsorship
of the Office of Research and Monitoring, Environmental Protection Agency.
iii
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TABLE OF CONTENTS
Pag
1. CONCLUSIONS 1
2. RECOMMENDATIONS 3
i
2.1 Confirm Projected Improvements
in Present Process 3
2.2 Increase Concentration Factor and/or
Increase Rate of Concentration 3
2.3 Establish Firmer Basis for Range of
Process Response for Different Sludges 4
3. INTRODUCTION 5
4. PHASE 1: LABORATORY PROCESS
DEVELOPMENT AND OPTIMIZATION STUDY 9..
4.1 Experimental Program and Procedure "'9
4.2 Analysis of Sludges and Plant Streams 12
4.3 Why Does the Esso Oil
Concentration Process Work? 14
4.4 Results of Process Study 16
5. PHASE 2: PILOT PLANT SCALE UP 51
5.1 Description of Pilot Plant Operation 51
5.2 Pilot Plant Scale-Up Correlates
Well With Laboratory Results 52
5.3 Analysis of Raffinates 57
6. PHASE 3: DETERMINATION OF HEAT TRANSFER PROPERTIES 61
6.1 Basis for Carver-Greenfield Test Program 61
6.2 Evaluation of Heat Transfer Coefficients
in Carver-Greenfield Pilot Plant 63
6.3 Distillate TC Losses for
Pilot Plant Batches 68
6.4 Composition of Product Streams for Evaporator 71
6.5 Reduced Concentration Temperature
for Esso Process is Indicated 72
7. PHASE 4: PROCESS TRADE OFF
STUDIES AND COST ANALYSIS 75
7.1 Process Flow Plan for Commercial Plant 75
7.2 Basis for Process Design and Analysis 77
7.3 Procedure Used for Cost Estimates 82
7.4 Cost Estimates - Present Data Basis 84
7.5 Cost Estimates - Projected Data Basis 93
7.6 No Incentive for Sludge
Prethickening to >1.5% 101
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TABLE OF CONTENTS (Cont'd)
7.7 Four Effect Evaporator System
Reduces Fuel Costs 101
7.8 Thickener Costs May Be Greatly Reduced
or Eliminated With Other Sludges 102
7.9 Process Costs Expected to Be
Lower for Other Sludges 103
7.10 Esso Carver Greenfield Process Costs Considerably
Lower Than Current Commercial Processes 104
8. ACKNOWLEDGEMENTS 107
9. REFERENCES . . 109
10. APPENDICES
GLOSSARY OF ABBREVIATIONS
BOD,- ~ Biological Oxygen Demand, as determined in a 5-day test
J ^ "" "
HLB = _Hydrophilie/Lipophilic Balance, characteristic of a
surface-active material.
HO = Heating Oil
LOPS = Lew-Odor Paraffin J5olvent (brand name)
MGD - Thousands of gallons per J)ay
TC - Total Carbon, as determined on an aqueous sample by
ASTM test D-2579-69 (APHA-138A).
TOC = Total ^)rganic JSarbon, same procedure.
TEI = Total JErected and Jnstalled cost (Esso Engineering estimates).
All costs are as of March 1972, unless otherwise noted.
U = Overall heat transfer coefficient
v
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LIST OF TABLES
No. Page
1 EXPERIMENTAL VARIABLES TESTED IN
LABORATORY PROGRAM 10
2 ANALYSIS OF SLUDGE SOLIDS (1) 13
3 OIL SOLUBLE CONTENT OF SLUDGES. . 12
4 DESCRIPTION OF PLANTS PROVIDING SLUDGE SAMPLES 14
5 EFFECT OF SLUDGE STORAGE TEMPERATURE
AND TIME ON CONCENTRATION RESPONSE 17
6 CONCENTRATION FACTOR VS RAFFINATE VOLUME 18
7 CENTRIFUGAL PUMP IS SATISFACTORY MIXER 22
8 MIXING SHEAR RATE CONTROLS SOLIDS CAPTURE ....... 23
9 OIL CONCENTRATION PROCESS WORKS FOR
DIFFERENT TYPE SLUDGES. 24
10 FINAL SOLIDS CONCENTRATION VS % SOLIDS IN FEED 26
11 COMPARISON OF OILS FOR CONCENTRATION 28
12 SURFACTANTS TESTED WITH SLUDGE 30
13 ACIDIFYING SLUDGE INCREASES CONCENTRATION FACTOR. ... 31
14 TC IN RAFFINATE NOT DUE TO OIL 38
15 OIL REDUCES TC LOSS 38
16 EFFECT OF OIL ON TC LOSS IN RAFFINATE 40
17 TC LOSS REDUCED WITH SLUDGE AT pH 3 41
18 TC LOSSES IN RAFFINATE DEPENDENT UPON SLUDGE BATCH. . . 42
19 VARIABILITY IN FINAL SOLIDS CONCENTRATION . . , 43
20 EFFECT OF STAGED TEMPERATURE SETTLING
ON SOLIDS CONCENTRATION 45
21 EFFECT OF OIL RECYCLE ON EXTRACTION 47
22 SLUDGE CONCENTRATION WITHOUT OIL 49
23 PILOT PLANT TEST PROGRAM. 52
24 SUMMARY OF OPERTING DATA FOR PILOT PLANT RUNS 53
25 COMPARISON OF CONCENTRATION SOLIDS CONTENTS
OF PILOT PLANT & LABORATORY RUNS 54
26 RAFFINATE ANALYSES - PILOT PLANT RUNS 60
27 CARVER GREENFIELD HEAT TRANSFER TEST RESULTS 66
vi
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LIST OF TABLES (Cont'd)
No. Page
28 SOLIDS RECYCLE IMPROVES U VALUE 68
29 ANALYSIS OF DISTILLATES FROM
CARVER-GREENFIELD HEAT TRANSFER TESTS 69
30 TOTAL CARBON LOSSES IN CARVER-GREENFIELD
EVAPORATION 70
31 TOTAL CARBON LOSSES IN
DRYING STAGE DISTILLATE 70
32 COST FACTORS AND INDICES USED IN ESTIMATES 78
33 SECONDARY SLUDGE SETTLING CURVES 80
34 COSTS FOR ESSO PROCESS COMPONENT 84
35 INVESTMENT BREAKDOWN FOR ESSO PROCESS COMPONENT 85
36 COSTS FOR CARVER GREENFIELD PROCESS COMPONENT 86
37 COSTS FOR COMBINED ESSO CARVER-GREENFIELD
PROCESS; SECONDARY SLUDGE ONLY 89
38 COST COMPARISON OF ONE VS THREE SHIFT OPERATION 90
39 COSTS FOR THICKENING PRIMARY SLUDGE 93
40 TOTAL TREATMENT COSTS FOR 50/50
PRIMARY + SECONDARY SLUDGE 93
41 COMPARISON OF PROCESS RESULTS FOR
105°F AND 175°F OIL SLUDGE SETTLING 94
42 PROJECTED COST SAVINGS FOR 105°F SETTLING
ESSO CONCENTRATION PROCESS COMPONENT 95
43 TREATMENT COSTS FOR CARVER
GREENFIELD PROCESS COMPONENT 96
44 TOTAL TREATMENT COSTS FOR 50/50 PRIMARY + SECONDARY
SLUDGE PROJECTED DATA BASIS. 96
45 SAVINGS EXPECTED FOR LOW TEMPERATURE SETTLING
COMBINED ESSO-CARVER GREENFIELD PROCESS 98
46 INCENTIVES FOR 4 EFFECT EVAPORATION
SYSTEM - PROJECTED DATA BASIS 98
47 POTENTIAL COST SAVINGS FOR
REDUCED SLUDGE THICKENER AREA (1) 99
48 TREATMENT COSTS OF CURRENT COMMERCIAL PROCESS 102
49 COST ADVANTAGE OF ESSO CARVER GREENFIELD
PROCESS OVER CURRENT COMMERCIAL PROCESS 103
vii
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LIST OF TABLES (Cont'd)
No. Page,
50 COSTS OF CURRENT COMMERCIAL PROCESS 104
51 COST ADVANTAGE OF ESSO GREENFIELD
PROCESS OVER CURRENT COMMERCIAL PROCESS 105
viii
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LIST OF FIGURES
No.
1 CONCENTRATION FACTOR VS. SETTLING TIME
80 °C SETTLING HIGH SHEAR MIXING 19
2 CONCENTRATION FACTOR VS. SETTLING
TEMPERATURE (HIGH SHEAR MIXING) 20
3 CONCENTRATION FACTOR VS. % FEED
SOLIDS 20 HOURS AT 175°F 25
4 FEED CARBON IN RAFFINATE INCREASES
WITH SETTLING TIME 34
5 TC LOSSES IN RAFFINATE VS SETTLING TEMPERATURE - 35
6 EFFECT OF FEED SOLIDS CONTENT ON
TOTAL CARBON LOSSES 36
7 EFFECT OF FEED SOLIDS CONTENT ON TC LOSS 37
8 TOTAL CARBON LOSSES IN RAFFINATE -
PILOT PLANT RUNS 56
9 PILOT PLANT TOTAL CARBON LOSSES
CONSISTENT WITH LABORATORY DATA 58
10 BOD5 VS TOG 59
11 SCHEMATIC FLOW PLAN OF CARVER GREENFIELD PROCESS .... 64
12 SCHEMATIC FLOW PLAN OF ESSO-CARVER
GREENFIELD PROCESS 76
13 TOTAL INVESTMENT (TIE) FOR ESSO AND CARVER
GREENFIELD PROCESS COMPONENTS - PRESENT DATA BASIS ... 87
14 TREATMENT COSTS OF ESSO AND CARVER GREENFIELD
PROCESS COMPONENTS-PRESENT DATA BASIS 88
15 EFFECT OF % SOLIDS IN CONCENTRATE ON OPERATING COST OF
CARVER GREENFIELD PROCESS (3 EFFECT EVAPORATOR) 92
16 TREATMENT COSTS OF ESSO AND CARVER
GREENFIELD PROCESS COMPONENTS-PROJECTED BASTS 97
ix
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1. CONCLUSIONS
The effectiveness of the Esso oil concentration process for
concentrating secondary sludges, and mixed primary plus secondary sludges,
has been demonstrated by both laboratory and pilot plant tests. Sludge
concentrations of up to about 9% solids have been attained, including
corrections for solubilized sludge solids and for the oil soluble com-
ponent of the feed sludge (12% solids on uncorrected basis).
Cost estimates show a considerable advantage over the best
comparable commercial technology (gravity thickening of primary, air
flotation thickening of secondary, vacuum filtration, incineration).
This advantage is from 13 to 31 $/ton dry solids for a 189 ton solids
(primary plus secondary) per day plant. The cost advantage is larger
for smaller plants.
Treatment costs for the Esso-Carver Greenfield process (including
depreciation) are estimated at 21 - 39 $/ton dry solids for the 189 ton/day
plant treating primary plus secondary solids. These cost are based on
waste secondary sludge feed at 0.5% solids, with the higher numbers cor-
responding to a sludge very difficult to process. The economics include
a debit for the cost of BOD recycle for any solubilized solids.
The Esso concentration step couples very well with the Carver
Greenfield evaporative drying process; the oil used for the concentration
provides the oil required in the evaporation to maintain fluidity and
high heat transfer. The oil soluble component of the feed sludge serves
as a partial replacement for the oil burned with the dry sludge solids
in the incineration step.
An extensive laboratory study was first made in order to identify
the factors controlling the concentration process and in order to
optimize the process response. The degree of concentration obtained
for a given sludge was primarily a function of the time and temperature
of settling after the contacting of the oil plus the sludge; concentration
increased with increasing time and temperature over the range covered,
which was up to 90°C and up to 70 hours. Solids content after concentra-
tion was increased about 20% by adjusting the pH of the sludge feed from
the initial near neutral pH to 3.0.
Little or no effect of oil type, oil/sludge ratio, and initial
sludge solids content on final concentration was found. Use of sur-
factants, covering a wide range of HLB* values and chemical type, produced
only a slight increase (if any) in solids concentration.
* See Glossary, following Table of Contents
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High mixing intensity as measured by shear rate and exemplified
by a centrifugal pump, was found necessary to obtain >_ 98% capture or
the feed solids over the full range of feed solids contents tested. With
relatively low shear mixing, such as produced by a turbine impeller, the
solids captures were as low as 60%. A centrifugal pump is therefore a
practical, low cost mixer for use in scale-up if needed.
Solubilization of some of the organic matter from the sludge
solids has been observed to increase with the temperature and time of
the oil-sludge thickening step. Some of the decomposed material also
distills over into the drying stage of the evaporator. The economics
in this report include a penalty for 25% BOD recycle, although reduction
to 10% is believed possible with lower temperature settling.
Further possible net economic improvments to the proposed process
totalling from 1 to $12/ton dry solids have been identified by use of a
lower settling temperature.
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2. RECOMMENDATIONS
Based on the experimental data available from a laboratory
process study and the Carver Greenfield heat transfer tests, plus the
results of a process and cost analysis, the route to a considerable
reduction in the cost of the Esso Carver Greenfield process can be
clearly predicted and the savings projected. In addition, several areas
requiring further work to either explore potentially promising leads or
better define the process response for different sludges have been
identified. This will enable further pilot plant work to be done on the
most favorable process system. Finally, evaluation of the Esso process
component in a continuous pilot plant, with several different sludges is
considered
To carry out the work needed to meet the objectives indicated
above a program is recommended with the following specific objectives:
2.1 Confirm Projected Improvements
in Present Process
Reduce total TC loss in both concentration and evaporation
steps, and increase overall heat transfer coefficient (U)
value for evaporation, by operating the concentration step
at a lower temperature.
Reduce design area of oil-sludge settlers 50%, by confirming
less conservative factor for scale-up to commercial sized
plants.
Reduce design area of sludge thickeners by obtaining firmer
scale-up data than obtained from the static 1 liter batch
settling tests.
2.2 Increase Concentration Factor and/or
Increase Rate of Concentration
Evaluate effectiveness of polyelectrolytes and new additives.
Determine relationship between mixing intensity (shear rate)
and time) with concentration factor and concentration rate.
Explore potential of combined oil extraction-air flotation
system.
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2.3 Establish Firmer Basis for Range of
Process Response for Different Sludges
Only 3 different sludges were tested and at least one is
believed to be a very "difficult" material to concentrate. A considerably
wider range of sludge samples is therefore required for a better measure
of the variation in process response.
There is good reason to believe that 1) sludges from some plants
will concentrate to higher solids contents than attained in this current
program, 2) most sludges will concentrate to the higher levels attained
in our study.
The operation of a continuous unit on site is the only practical
way to be sure of the satisfactory scale-up of the mixing and settling
steps. Successful operation of a continuous prototype unit at plant
sites will hopefully also serve as a confirmation of a novel process
concept to careful and conservative plant management.
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3. INTRODUCTION
The handling and disposal of sludge from sewage plants has
often been called the most troublesome aspect of the entire treatment
process (1, 2). The volume of sludge requiring disposal is enormous,
as can be inferred from the estimate that the average daily production
of sludge is about 0.2 tons per 1000 people on a dry basis (9). Not
only is sludge disposal a major problem now, but it is a growing
one; within the next 15 years the volume of sludge will increase by an
estimated 60-70% (10). Finally, disposal is a very costly operation,
representing up to 50% of the total capital and operating costs of the
treatment plant (2).
Because of the technical and economic importance of the problem,
our country and other industrialized countries have become increasingly
aware of the need for development of more efficient and lower cost pro-
cesses to accomplish this disposal operation. With the rapidly growing
awareness and concern for environmental protection, however, all new
approaches must be geared to the objective of disposal without causing
damage to the environment. As stated by the Chicago Metropolitan
Sanitary District (1), the ultimate goal of any solution must include
the following elements:
Low cost
o Not produce air, water or land pollution.
Make beneficial use of the sludge constituents.
Solve the problem in perpetuity.
There is no lack of commercial processes for treatment and
disposal of sludge with the most widely used listed below:
Thickening - initial volume reduction
- Gravity settling
- Centrifugation
- Air Flotation
Stabilization - mass reduction
- Anaerobic digestion
- Aerobic digestion
- Wet air oxidation
- Heat treatment
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Dewaterlng - further volume reduction
- Vacuum filtration
- Pressure filtration
- Centrifugation
Chemical conditioning usually used for dewatering processes
Ultimate Disposal
- Dumping at sea
- Soil conditioning and/or fertilization
- Land fill
Incineration
Any of the treatment processes can be combined with any of the
disposal methods. Each individual process and process combination has
technical and/or economic problems and drawbacks. In the opinion of
many, incineration Is the only practical long term solution for sludge
disposal for large and growing urban areas (11, 54). This view tends to
gain credence in light of a) the increasing questioning of and restrictions
on dumping at sea, b) the rapid decrease in available acreage for land
fill, and c) the limited practical outlets for use of sludge as soil con-
dition/ fertilizer (1,2,9,10,11).
All treatment + disposal processes have one technical problem
in common: the necessity of handling the very dilute sludges produced
by the sewage plant. Primary sludges from the sedimentation tanks
normally have a concentration of 2.5-5% with activated sludges 0.5-1.0%;
these concentrations represent water/solids ratios of 200/1-20/1.
Irrespective of the combination selected for treatment and disposal,
there is a large economic incentive for dewatering of the sludges prior
to processing, in order to reduce the volume that,must be processed
and/or to minimize the quantity of water to be removed during processing
(2,4,9).
In considering sludge disposal a distinction must be made
between primary + secondary sludges and digested sludges. Digested
sludges, at least partially stabilized in regard to further decomposition,
may be amenable to disposal techniques such as land fill and dumping at
sea, which are not open to the raw or unstabilized primary + secondary
sludges. Development of an improved process for disposal of the primary +
secondary sludges is of prime concern for two reasons: the disposal pro-
blem is greater because of more limited disposal options, and an
economically attractive process could eliminate the need for treatment
by digestion.
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Secondary sludges either from activated or trickling filter
processes are the most difficult to concentrate prior to subsequent
treatment steps. Current commercial concentration processes can be
classified as "thickening" or "dewatering" according to the fluidity
of the product (2);
Thickening Dewatering
Gravity Vacuum Filtration
Air Flotation Centrifugation
Centrifugatipn . Pressure Filtration
These processes are normally used to concentrate separately either primary
or secondary sludges, or mixed primary + secondary sludges. All of these
processes have limitations in the solids concentrations attainable and/or
the cost. Assuming that incineration will in the future be the preferred
disposal method, there is an incentive for the development of a new, lower
cost process for the total, combined dewatering + disposal process.
Esso proposed a new process to accomplish the stated objective;
this process consists of combining a novel Esso sludge dewatering technique,
based on an oil activated concentration step, with the commercial Carver
Greenfield multiple effect evaporative sludge drying systenr. The Esso
process component concentrates the sludge feed to a specified level; the
Carver Greenfield process component completes the dewatering and produces
a dry feed suitable for incineration in a conventional incinerator-boiler.
The energy recovered from the burning of the sludge is reused in the
evaporation step to provide maximum energy efficiency. The Carver Green-
field evaporation system is based upon use of a water insoluble oil as a
fluidizing carrier for the sludge solids; this maintains high heat transfer
rates even at very low water contents and prevents fouling of the heat
exchange surface. The oil required for the Esso concentration provides
the oil required for the Carver Greenfield evaporation step; the separate
concentration and evaporation steps therefore dovetail extremely well
into an overall integrated process. A patent application has been filed
on the Esso process based on work done before the contract; the Carver-
Greenfield process is patented.
Preliminary cost estimates for the proposed Esso Carver Green-
field process were very attractive, with total operating costs/ton sludge
solids of 5$40 for plant sizes of >_20 tons/day. The present contract
was undertaken in order to a) make a detailed variable study in order
to optimize the dewatering process, b) to develop the process costs for
a range of operating conditions and options on the basis of the experi-
mental data obtained in the study.
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The contract was carried out as a four part program:
Phase 1: Laboratory Process Development and Optimization.
Phase 2: Pilot Plant Scale-up
Phase 3: Heat Transfer Studies at Carver Greenfield
Phase 4: Process Trade Off and Cost Analysis
In the first two phases, concerned with the study of the controlling
process parameters, the process responses evaluated were the solids
concentrations achieved, the degree of capture of the feed solids ana
the quality of the water phase (defined as the "raffinate") separated
during concentration. These latter two factors were important in
determining the recycle load generated by the process. Recycle load is
an important consideration, since one of the projected advantages for the
Esso Carver Greenfield process over several current processes (heat treat-
ment, wet oxidation, centrifugation) was low recycle.
The initial theoretical basis for the Esso process was the
selective "wetting" of the lipophilic sites on the sludge solids by an
oil with properly matched properties, followed by "flotation" of the
oil droplets with attached sludge solids to form a concentrate phase.
One component of the laboratory process study was to attempt to confirm
this hypothesis and to follow technical implications derived from the
initial model.
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4. PHASE 1: LABORATORY PROCESS DEVELOPMENT
AND OPTIMIZATION STUDY
The objectives of the laboratory program were to a) evaluate
the effects of the variables considered to be potentially important for
the oil concentration process, b) establish the operating conditions
required to "optimize" the process in terms of the different performance
criteria set up and, c) develop a range of process alternatives (derived
from a and b)^ required for the final prototype commercial designs and
the overall process cost analysis.
4.1 Experimental Program and Procedure
4.1.1 Variables Tested
Over the course of the laboratory program an extensive list
of variables was evaluated; the variables and the range tested for each
are summarized in Table 1. The variations in response of the different
sludge batches of the same type from the same plant, and the limited
"shelf life" of the batches can, in a practical sense, be considered
implicit variables; problems associated with these two factors imposed
severe restrictions at times oh the design of .the test program.
In the discussions below on the effects of specific variables,
the order presented does not necessarily reflect the chronological order
in which the work was actually done, nor the relative importance of each
variable. Because of the batch/batch variability, individual experimental
results are identified by batch for convenience. In many cases a specific
experiment will appear in more than one summary (or tabulation) for
convenience in making comparisons where the data are pertinent to more than
one variable parameter.
4.1.2 Experimental Procedure
The sludge sampling, transport and storage procedure, as well
as the description of the test procedure, are described in detail in
Appendix A-l; a condensation of this procedure follows:
Sludge was kept stored in refigerator at 40°F except when
removed to obtain material for the day's tests.
« A measured quantity of sludge, adjusted to the required
temperature and pH was charged to the mixing unit with a
measured quantity of oil preheated to the required temperature.
After mixing for the specified time, where batch mixing
with a turbine agitator or Waring Blender was used, the
combined oil-sludge was transferred for settling to
calibrated 250 or 500 cc straight sided glass settlers
9
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TABLE 1
EXPERIMENTAL VARIABLES TESTED IN LABORATORY PROGRAM
Variable
o
i
Sludge Type
activated
- trickling filter
- primary + activated
- digested
Sludge Properties
initial suspended solids content
- initial pH
- initial temperature
Mixing Intensity (Shear Rate)
and Time
Oil Type
Oil/Sludge Ratio for Extraction
Concentration (Settling) Temperature
After Mixing
Use of Surfactants
Effect of Impurities in Recycle Oil
Range Tested
2 different plants, total of 13 different batches,
1 plant, total of 2 different batches.
2 plants, total of 3 different batches.
1 plant, 1 batch
0.5 - 4.6%
3.0 to 6.5-7 (as received)
8-50°C (46-120°F)
hand mixing, turbine impeller, centrifugal pump,
Waring Blender
6 oils
0.1 - 0.8 (volume basis)
25 - 90°C (75 - 194°F)
HLB of 1-10, 100-100,000 ppm based on solids,
several chemicals types.
Recycle oil from commercial plant, simulated
recycle subjected to "degradation" for varying times.
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and stored in constant temperature ovens. For pump mixing,
the oil + sludge was premixed in a stirred vessel and fed
thru the pump at a controlled rate into the settlers.
The water raffinate-oil sludge interface level was periodicallj
measured and the degree of concentration calculated (see
below for procedure used). Alternatively, the water
raffinate phase was withdrawn and weighed.
Samples for Total Carbon (TC) analysis were submitted
"as is" from raffinates without visible settled solids
(from pump and Waring Blender runs); samples containing
settled solids, from feed sludge or where turbine mixing
was used, were first centrifuged.
4.1.3 Parameters Measured in Laboratory Tests
Very early in the program it became clear that three different
factors had to be measured to adequately describe the test results:
!
Increase in sludge concentration vs. settling time:
calculated from the initial weight of sludge, and
the weight of water raffinate phase separated
/v^^i-r-an va^n-r - % Solids in Concentrate (Water Phase Basis) _
Concentration factor =, .;;r-rr::-t =
% Solids in Feed Sludge
fi
Initial Sludge Volume
Initial Sludge Volume - Raffinate Volume
Solids "capture" in oil-sludge phase: determined by
filtering the raffinate phase and weighing the^solids.
Decomposition/solubilization of sludge solids: calculated
from total organic carbon and/or total carbon analysis of
initial sludge solids, and of the water raffinate phase.
4.1.4 Basis for Selection of Sludge Sources
The contract specifies that the test sludges include two different
activated sludges, one trickling filter,secondary sludge, and one mixed
primary and secondary sludge. The most important considerations were
that the plants should be representative of the important secondary
treatment plants in the country and adequately convenient to the lab-
oratory. Based on a review of the sewage plants in the New Jersey area
with secondary treatment, Bergen County, N.J. and Wards Island, NYC
were selected as activated sludge sources and Trenton, N.J. as trickling
filter source. General information on these sources is summarized below.
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4.2 Analysis .of Sludges and Plant Streams
4.2.1 Waste Sludges from Sewage Plants
Chemical analyses and respiration rates obtained on the early
samples taken from the plants are presented in Appendix A-2 and analysis
of the dry sludge solids filtered from the waste sludges in Table 2 (page
Results obtained for the dry sludge solids and the oil fraction
are in line with data reported in the literature (7, 29).
Data on the hexane extractable component of the total sludge
feed (defined in the rest of this report as "oil") are shown in Table 3.
TABLE 3
HEXANE-SOLUBLE CONTENT OF SLUDGES
Sludge Batch (1)
Bergen County
Bergen County
Wards Island
Bergen County
Type
activated
activated
activated
primary +
activated
Oil Solubles
Wt. %
9.5
16.7
8.2
6.2
Average 10.2
(1) Sludges used for Phase 3 program,
in order processed.
This oil component, which averaged 10% for the 4 batches tested, is an
important factor in calculating the overall heat balance for the system
and is required to calculate the effective solids concentration going
into the Carver-Greenfield evaporation step] since the oil component of
the feed will dissolve in the process oil used for the concentration
step, the initial solids content must be reduced in calculating a) the
true solids concentration achieved and b) the solids load for incineration.
4.2.2 Plant Treatment Data
Analytical results obtained from the plant laboratories for
the various plant streams are assembled in Appendix A-3 4 5.
- 12 -
-------
TABLE 2
ANALYSIS OF SLUDGE SOLIDS DRIED
Batch Type Sludge
Bergen
Wards
County
A Activated
B
C
D
E
F
G
J
D Primary + Activated
E
I
D Digested
Island
A Activated
B '
D
Trenton
Bergen
Wt. %
1 10
1-10
A Trickling Filter
B
County I - Qualitative Analysis
1 ' ' .... - /
Al
Ca, Cr, Fe, P
% Volatile
at 1000°F
63.0
63.1
64.6
68.8
66.3
68.6
66.0
65.1
63.3
71.4
55.3
70.1
69.6
68.7 '
4 A V
39.3(2)
50.1
of Ash (after
.1-1
<.l
AT 102°C (1)
Elemental Analysis
C
29.7
32.8
33.0
34.2
34.8
34.1
37.5
34.0
31.0
37.9
31.9
, 36.7
38.9
1
20.9,
27.6
volatiles
Ba, Sr, Mn
B, Pb, Sn,
H
4.7
4.6
5.2
4.9
5.3
5.1
5.6
4.8
4.6
5.5
4.7
5.2
5.8
3.3
4.1
removed)
» Mg, Zn,
Mo, V, Cu
N P205
5.3
6.1
6.5
5.9
6.0 3.1
6.0
6.3
3.4
4.3
4.9 1.6
4.7
6.6
5.2
2.7
2.5
Ti
, Ag
(1) All analyses by Analytical and Information Division of Esso Research
(2) Low values due to high rust content in sample.
- 13 -
-------
TABLE 4
DESCRIPTION OF PLANTS PROVIDING SLUDGE SAMPLES
Design Capacity Population
Plant Type MGD Type Feed Served (Approx.)
TT j T -i j «v Activated ... Sanitary
Wards Island, NY sludge 220 + industriai 750,000
Bergen County, NJ " 50 " 250,000
Trenton, NJ "filter8 20 " 15°'0°°
4.3 Why Does the Esso Oil
Concentration Process Work?
A very brief review of the background used to initially develop
the concept for the process, as well as the more recent modifications
required by the actual test data, should provide a useful background for
the experimental program.
The chemical and physical properties of activated sludge have
been extensively described in the literature, (3, 12-16). Considerably
simplified, the sludge solids can be considered as highly hydrated bacteria,
bacterial fragments, and slimes produced by the bacteria, in a fine
particle size, floe-type structure. These solids possess a very high sur-
face area* with a large fraction of hydrophilic (hydrogen bonding) surface
sites. The particle surfaces tend to acquire a negative electric charge.
Ionized solubles and water will be attracted to and held to the surface
of the particles by both of these sludge surface characteristics. The
net result is a system of sludge solids with a strong affinity for water,
a low effective specific gravity, and with a tendency to remain dispersed
due to electrostatic repulsion (zeta potential). Chemically, the solids
consist of a complex mixture of polysaccharides, proteins, amino acids,
sugars, carbohydrates and high molecular weight polymers.
In our initial concept for the concentration of sludge solids by
use of oil, the lipophilic sites on the solids were assumed to be wet by
the oil, so that the solids transferred to the interface with the oil
droplets; according to this concept, "free" water is expelled as a "raffinate
phase", with mainly "bound" or hydration water remaining with the solids
in the concentrate phase. The concentration process could be considered
as analogous to solvent extraction, with oil the "solvent" and solids the
material being "extracted" from the aqueous phase. On a more theoretical
level, two unrelated steps were assumed to be involved;
- 14 -
-------
1. Since the solids are collected by the oil, it is evident
that the hydrocarbon has a contact angle less than that for complete
non-wetting. Due to the omnipresent, non-selective London forces that
exist among all molecules regardless of type, this is not 180° but only
about 110°. Evidently, the lysed bacteria retain some waxy coating or
other lipophilic spots which lower this to below 90°, so that the cosine
of this angle has a positive value. This causes the finely divided solid
to serve as an emulsifier and separate the oil into drops whose diameter
is that of the solid particle divided by the cosine of the contact
angle (50).
2. Since this cosine is not very large, the drops will be large
and the emulsion of poor stability. However, solids-stabilized emulsions
do not fail by coalescing, as the solids coating prevents oil/oil contact;
the result is failure by creaming (17). This brings all the oil, all
the solids and a minor amount of water into a layer which can be skimmed.
The above concept was put in considerable doubt after finding
that the oil concentrate phase was actually an oil in water (o/w) emulsion.
This fact was established experimentally by electrical measurements, showing
that the specific resistance of the oil-sludge concentrate phase was equal
to that of the sludge alone.
Based on literature correlations for o/w emulsion properties,
the Hydrophylic-Lipophylic Balance (HLB) of the sludge system was estimated
to be 12-14 and the Cohesive Energy Ratio (CER) 0.3-0.6 (18). Applying
the calculation method of group contributions (18) on the assumption of a
predominately cellulose structure gave values of 14 and '0.43 respectively,
in excellent agreement with the estimate.
In the model of the system, the sludge solids were assumed to
be attached to the rising oil droplets by simple contact adhesion; good
mixing was assumed necessary both to insure contacting and capture of all
the sludge solids by the oil, and to provide the needed energy for adherance.
As an extension of this hypothesis, the lipophilic character of the solids
should be enhanced by proper choice of the specific oil used and by adding
an appropriate surfactant. As will be discussed in later sections, however,
experiments along the lines of this hypothesi3 failed to produce the
expected results, casting doubt on the basic concept.
Microscopic examination of several oil sludge concentrates showed
no evidence of any solids adhering to the surface or even trapped within oil
droplets; the smaller oil droplets or larger drops and globules formed by
coalescence were suspended in the aqueous sludge, but untouched by any
solids. Unless we assume that the solids separated from the oil droplets
almost immediately after mixing, the physical adherance theory does not
appear to be valid.
15 -
-------
The current hypothesis is that the rising oil droplets are
ped by the interconnected, web-like floe structure of sludge solids and
actually float them "en-masse". An analogy would be a blanket being ±oa
by a number of balloons. An alternative possibility is that the
droplets become trapped within floe masses. In either case, the
solids particles do not physically adhere to the oil droplets.
4.4 Results of Process Study
4.4.1 Short Term Storage of Fresh
Sludge Hot Detrimental
Storage characteristics are of little importance in any commercial
process, but initially were of considerable concern since the laboratory is
removed from the plant sites. ,A further refinement of this problem was the
uncertainty about the need to refrigerate samples during transfer from
plant to laboratory or pilot plant; total transfer time was in the range
of 2-4 hours. Long shelf life (up to 1 week) was naturally hoped for
in order to be able to minimize the frequency of procuring new batches.
Tests carried out at the start of the program (see Table 5)
did not show any apparent effect in terms of response to the oil concentra-
tion process for 3-7 day storage at 40CF or 1-2 day storage at ambient
temperature ( 80°F). Samples stored for 7 days showed a definite change
in response, with the solids capture for mild agitation sharply lower.
These results have been confirmed by more recent data with high shear
agitation (Table 6). On the basis of the above, storage life at 40°F
for laboratory work was set at 6 days maximum, with 5 days preferred, and
2 days at ambient for subsequent pilot plant work.
4.4.2 Solids Concentration Increases
With Increasing Settling Time
Immediately after the mixing of the sludge and oil, a water
raffinate phase starts to separate out of the oil-sludge mixture. The
phase interface is well-defined and stable, provided the proper processing
requirements of oil/sludge ratio and mixing intensity are met (these
points are discussed in detail in the section below). After the initial
very rapid breakout of the two phases, the rate of further separation of
water decreases rapidly with time. The extent of solids concentration
achieved as a function of the volume of water separated l(*affinate) has
been previously defined as: .-
-n ^ % solids in concentrate (ex oil)
Concentration Factors % solids in feed sludge =
Initial Sludge Volume
Initial Sludge Volume - Raffinate Volume
- 16 -
-------
TABLE 5
EFFECT OF SLUDGE STORAGE TEMPERATURE
AND TIME ON CONCENTRATION RESPONSE
Sludge.. Batch
Bergen County "A1
,,(3)
,,B,,C3)
Concentration Factor (2^
Date of
Storage Temp °F Test
40 8/10/71 (1)
8/11/71
8/17/71
40 8/12/71
8/13/71
8/16/71
80 8/18/71^
8/19/71
8/20/71
40 8/20/71
8/23/71
40 2/24/72 (1)
2/29/72
40 3/6/72 (1)
3/9/72
For
1 Hr
1.7
1.6
1.7
2.5
2.9
2.9
3.3
3.5
3.3
1.4
1.5
Settling Times of
5 Hr 16/20 Hr
2.4
2.7
3.0
4.6
4.6
5.5
7.1
7.1
6.6
2.8
3.1
7.7 10.6
7.9 10.0
7.5 10.9
7.5 11.4
(1) Date sampled from plant.
(2) Values shown are averages of 2 tests on same day; test conditions were '
constant for comparisons within a sludge batch; test conditions were not
the same for different batches.
(3) Low shear agitation.
(4) High shear agitation. '
- 17 -
-------
As concentration proceeds, the importance of each fixed increment of
raffinate volume becomes greater, as shown below:
TABLE 6
CONCENTRATION FACTOR VS RAFFINATE VOLUME
Raffinate Volume
% of Initial Sludge Concentration Factor
20 1.25
40 1.67
60 2.50
80 5.00
90 10.00
i
Typical curves for concentration factor vs. settling time are
shown in Figure 1; all runs were made under the same set of conditions
(mixing, settling temperature, oil-type, etc). The linear relationship,
using the semi-log type correlation, held up to about 20 hours settling
for almost all test runs made, and in some runs even up to about 70 hours.
The increase in concentration factor per unit settling time decreases
rapidly for all runs. Detailed test data for different sludges, settling
temperatures, feed solids contents are tabulated in Appendices A-6 and A-7.
The data presented in the curves illustrate several additional
points:
The slope of the settling curve (rate of increase in con-
centration factor per unit time) increases with decreasing
initial sludge solids content.
For the same initial solids content, activated sludge and mixed
primary + activated show the same concentration characteristics.
Test reproducibility is good, with the difference between
duplicates <_ 10%; this can be seen from the curves, where the
different symbols represent duplicate batches.
4.4.3 Concentration Factor Increases
With Increasing Settling Temperature
As would be expected in any separations process, temperature has
a very considerable effect. For all sludges, concentration factor increased
with increasing settling temperature over the range tested, which was
25°C - 95°C (see Appendix A-8, for complete summary); typical data are
shown in Figure 2.
- 18 -
-------
FIGURE I
CONCENTRATION FACTOR VS. SETTLING TIME
80°C SETTLING HIGH SHEAR MIXING
in
o
o
o
oo
I '
fig
2 4
UJ
O
T
~\ 1 1T
I I I I I I I
15
14
13
12
II
o
i
o
10 5
' 3
o
TO
6
5
I I I I I I
1 1 I i i
1.0
10
SETTLING TIME - HRS.
-------
CO
cc
o
CN
FIGURE 2
CONCENTRATION FACTOR VS. SETTLING
TEMPERATURE (HIGH SHEAR MIXING)
10
0.5-0.70$
Susp. Sol ids
u_
o
o
o
o
1.9-3.0$
Susp. Sol ids
I
30
40 50 60
SETTLING TEMPERATURE °C
70
,80
- 20 -
-------
The effect of temperature is inversely related to initial sludge
solids content. For initial solids contents of 0.5-0.7%, concentration
factor increases by 40-90% over the range of 45°C-80°C, vs. 10-40%
Increase for initial solids content of 1.7-3% for the same temperature
span.
j
Concentration Factor Ratio
% Solids in Feed Sludge 80°C/40-50°C (1)
0.5-0.7 1.54
1.7-3.0 1.19
(1) Difference significant at 97% confidence level.
j
Limited data for the range 80-95°C indicate relatively little
further increase in concentration factor; the average increase was about
6% for initial feed solids contents of 1-2%.
The concentration process can be considered as a combination of
"bulk flotation" of the sludge floe by the oil, sedimentation of the oil
droplets, and coalescence of the settled oil droplets. Increasing tempera-
ture should therefore increase the rate of "flotation" by increasing the
density difference between the oil and water phases, and the rate of
sedimentation by reducing the viscosity of the continuous water phase. As
shown below, the temperature effect on both density difference and water
viscosity is substantial..
Water
Viscosity £Specific Gravities A Sp.
Temperature..°C Centipoises Water #4 Heating Oil Gravity
25 0.894 .997 .884 .113
40 0.656 .992 .870
80 0.357 .972 .824
95 0.299 .962 .819 -143
Settling temperature is one of the important trade-off factors
considered in the final process and cost analysis phase of this project.
While increasing.temperature does increase solids concentration, balancing
factors are the added cost for the large quantity of extra heat required
and the adverse effect on sludge solubilization/decomposition.
- 21 -
-------
4.4.4 Centrifugal Pump is Satisfactory
and Practical High Shear Mixer
Based upon early test (Appendix A-9) data, only a very high
shear mixer, the Waring Blender, was suitable for extraction of low
(<0.7%) suspended solids content sludges. Even for settled sludges,
the solids capture for the Waring Blender was better than for the mi s
type turbine. Since a Waring Blender cannot be scaled up to commerc
size, a variety of other practical mixer types, capable of generati g
high shear and of scale up to the large commercial size required, we
considered. An additional factor was to find a mixer which could aiso
be used in the pilot plant operation.
A standard centrifugal pump was found to be very effective;
solids capture and concentrations equal to the Waring Blender and
superior to the turbine were achieved, as summarized in Table 7 below
and detailed in Appendix A-10 and A-ll.
TABLE 7
CENTRIFUGAL PUMP IS SATISFACTORY MIXER
Type Sludge
Activated
Primary and
Activated
% Solids
in Feed
1.0
1.8
1.9
Type Mixing
turbine
centrifugal pump
turbine
centrifugal pump
turbine
Waring Blender
centrifugal pump
Concentration Factor % Solids
1 Hour 20 Hours Capture
3.2
1.6
2.8
2.1
2.9
2.8
8.3
3.2
4.8
3.8
4.4
4.5
98
95
98
95
98
98
The specific pump used in the laboratory program was a 1/20 HP,
6000 RPM, single stage, open impeller, Eastern Industries Company pump.
A centrifugal pump can be used on a commercial scale, either
conventionally or with reverse flow feed for greater mixing efficiency
if required.
From a limited amount of testing, excessive mixing in the pump
appears detrimental to achieving maximum concentration. 'Increased mixing
was produced by use of a second mixing pass through the pump. The residence
time (mixing time) in the pump was *-0.3 seconds per pass. This result
is directionally consistent with the data for the Waring Blender, where
concentration factor was related to mixing time.
- 22 -
-------
% Solids
in Feed
1.0
1.
Number of Passes
through Pump
1
2
1
2
Number of
Test Runs
2
2
1
1
% Solids in Concentrate
After Settling
1 Hour
3.5
3.3
3.1
3.4
22 Hours
9.0
5.6
5.4
4.5
The relationship between mixing intensity and solids capture
can be put on a more quantitative basis by defining mixing in terms of
shear rate:
-1 Impeller tip speed, cm/sec
'' - - - - - - " ' ~
- - - - - ---- - - - - ____________ ___________ -
Clearance between impeller tip and mixing chamber wall-cm
For all sludges tested solids capture increases with increase in shear
rate; the sensitivity 6f the solids capture to shear rate decreased with
increasing sludge solids content, as is summarized below:
TABLE 8
MIXING SHEAR RATE CONTROLS SOLIDS CAPTURE
Type Sludge
Activated
Activated
Type Agitation
Turbine
Turbine
Turbine
Turbine
Centrifugal pump
Waring Blender
% Solids
in Feed
0.5
0.8
1.5
2.3
X).5
>0.5
Shear Rate
75
130
130
130
73,000
210,000
Solids Capture - %
80-90
95
98
98+
98+
The mixing intensity for the turbine agitator - baffled vessel
system would be considered vigorous for a batch mixing system, but is low
compared to either the pump or blender. Some intermediate shear rate
between the batch turbine and centrifugal pump probably will be adequate
to insure high solids capture, but remains to be defined.
- 23 -
-------
4.4.5 Satisfactory Solids Concentration
Achieved for Different Type Sludges
Activated, mixed primary + activated, and digested sludges from
the Bergen County plant were all successfully concentrated with high
solids capture using high shear mixing (see Appendix A-ll). Results or
20 hour settling at 80°C with a Waring Blender are summarized below for
comparison, with the final solids content adjusted for average % oil
solubles in the feed sludge and for average TC losses in the raffinates:
TABLE 9
OIL CONCENTRATION PROCESS WORKS FOR DIFFERENT TYPE SLUDGES
Type Sludge
Activated
Primary + Activated
Digested
% Solids
in Feed
2.3
2.7
2 . 8
% Solids in
Concentrate
8.5
9.6
6.9
While the digested sludge was not included in the original
program, a very limited amount of work was considered desirable to
demonstrate the suitability of the Esso process for the full range--of
sludge types produced in sewage plants.
4.4.6 Final Solids Concentration Not Affected
by Initial Feed Solids Content
As noted above, for a given sludge type and source the concentra-
tion factor (a measure of the rate of separation of water phase) is
inversely related to the initial feed solids content: concentration factor
decreases with increasing feed solids content; this is shown in Figure 3,
for all test data at 80°C. The final solids concentrations achieved,
however, appear to be independent of initial feed solids content, using
the data from Figure 3 and Appendix A-12; the ranges of final solids
contents for different feed solids contents are summarized in Table 10:
- 24 -
-------
18
16
14
12
g
b
10
o
FIGURE 3
CONCENTRATION FACTOR VS. %
FEED SOLIDS 20 HOURS AT I75°F
Notes:
Points represent different sludge batches"
All sludge types included
Curves are visually drawn to
represent data band.
1
1
0.5
1.0 1.5 2.0
; SUSPENDED SOLIDS IN SLUDGE FEED
2.5
- 25 -
-------
TABLE 10
FINAL SOLIDS CONCENTRATION VS % SOLIDS IN FEED
% Solids
in Feed
0.5
1.0
1.5
2.0
2.5
Concent ration
Factor
12-20
6.5-11.5
4-8
2.8-5.9
2.2-4.7
% Solids in
Concentrate
6-10
6.5-11.5
6-12
5.6-11.6
5.5-11.7
This conclusion is based on the generalized curve and is
supported by the results for individual sludge batches tested over a
range of feed solids contents; data for one batch, Bergen County activated
sludge LF-"J", settled at 80°C, are summarized below:
I Solids
in Feed
0.70
0.75
1.0
1.5
3.0
% Solids in Concentrate
5 Hrs 20 Hrs
7.8
8.0
7.7
7.8
7.7
10.0
9.6
10.5
10.3
10.3
This lack of effect of feed solids content on final solids con-
centration is an important factor in the overall process analysis and
cost estimation. The trade off factors will be limited to the Esso oil
concentration process components, since the solids content to the Carver
Greenfield process will be constant.
4.4.7 Oil/Sludge Ratio for Concentration Step
Since the oil concentration process is coupled directly with the
Carver Greenfield process, the oil/solids requirement for the Carver
Greenfield process can be considered as a potentially limiting factor; the
minimum oil/solids weight ratio for the Carver Greenfield process is about
10/1, with a preferred range of 10/1-15/1. Use of a lower oil/solids ratio
for the Esso concentration step presents no problem (oil can be added
before the evaporation), but a higher ratio would be undesirable; the
Carver Greenfield requirements therefore set the preferred range for the
Esso concentration step.
- 26 -
-------
As shown in Appendix A-13, the oil/sludge (0/S) ratio required
to provide the preferred oil/solids ratio is a functinn of the initial
feed solids content of the sludge; this varies from a ratio of about 0.06
for 0.5% initial feed solids content to about 0.25 for 2.0% feed solids
content, on a volume basis.
For evaluating the effect of oil/sludge ratio on the concentra-
tion step itself, a range of 0.1-0.6 was used for most of the testing.
Considering only the effect of oil/sludge ratio on concentration factor,
the optimum response was obtained at 0/S values of 0.1-0.2 for nine out
of the ten batches evaluated (Appendix A-14). On average, the concentration
factor descreased with increasing oil/sludge ratio:
Oil/Sludge Concentration Factor
Ratio 1 Hour 20 Hour
.1 2.8 5.0
.2 2.5 4.6
' ?1 .4 2.2 4.4
With an oil/sludge ratio of 0.1, however, the interface between
the oil + sludge concentrate phase and the water raffinate phase was less
sharp and less stable than at higher ratios. Slight movement of the set-
tler caused sludge solids to disengage from the concentrate phase.and set-
tle in the raffinate. From practical considerations of interface stability
and requirements for the Carver Greenfield process, thus, an oil/sludge
ratio of 0.2 appears to represent the best choice; this value was therefore
used in the design basis for a commercial plant in Phase 4.
The majority of the tests in the laboratory program were made
within an oil/sludge ra.tio of 0.2, and almost all with the 0/S ratio
0.2-0.4. The effect of 0/S ratio on any of the results for the other
variables was therefore very small, if any.
4.4.8 #4 Heating Oil Preferred Oil
for Sludge Concentration Step
A wide variety of candidate hydrocarbon oils are available
for the extraction process. The oils have different physical properties
(density, boiling point, viscosity) and chemical composition (paraffin/
aromatic content). The oils selected for the screening study and their
properties plus approximate cost, are summarized in Appendix A-15.
Essentially all of the comparisons of oils involved #4 and #2
Heating Oils, #1 Varsol and LOPS; these comparisons, which were carried
out for different sludges and % feed solids contents, as well as different
mixing systems, are tabulated in Appendix A-16. While differences of up
to about 15% where found between oils for individual runs, there were no
apparent consistent differences. On average, #4 Heating Oil was as good
- 27 -
-------
as any of the other oils in terms of concentration factors obtained. Of
the four oils most completely evaluated, #4 Heating Oil, #1 Varsol and
LOPS appeared about equal in performance; concentration factors with #2
Heating oil were slightly inferior.
The performance of #4 Heating Oil was at least as good as the
other candidate oils for the sludge concentration and has the lowest
cost; this oil was therefore used for the bulk of the process studies.
TABLE 11
COMPARISON OF OILS FDR CONCENTRATION
Oils Compared
#4 Heating Oil
#1 vVarsol
#4 Heating Oil
LOPS
LOPS
#2 Heating Oil
#4 Heating Oil
#2 Heating Oil
No. Tests in
Comparison
7
3
2
Ave. Concentration Factor
(20 Hour Settling)
3.8
3.7
3.1
3.0
4.0
3.5
3.1
The initial "model" for the oil concentration process involved
the following sequence:
a) The lipophilic sites on the sludge.solids were supposed
to be "wet" by the oil.
b) Followed by "flotation" of oil droplets with sludge solids
adhering to the droplet surface.
c) The oil droplets with adhering solids then formed a con-
centrate phase. Proper selection of the oil, on the basis
of matching the oil properties to the sludge solids surface
using three dimensional solubility parameters was considered
essential for maximizing solids concentration. The wide
range of oil types tested in this study was based on the
logic of the initial model.
- 28 -
-------
Subsequent microscopic examination of the oil sludge concentrate
showed that the model above was not valid, that the sludge solids did not
adhere to the surface of the oil droplets due to any "wetting" phenomena.
The chemical composition of the oil and its derived interfacial properties
should have no effect on the concentration and this is what the tests
actually showed.
The revised "flotation" model, however, implies that at least
the rate of concentration, if not the final concentration achieved, should
be a function of the oil density; rise velocity of a given size oil droplet
is proportional to the density difference between the oil and the bulk
phase fluid (water). The lack of any apparent oil effect even on the
rate of concentration can be due to two factors:
Sludge solids show a dominant effect so that the "flotation"
* rate is controlled by the rate of "escape" of the free water
S through the interlocking floe structure of the sludge solids.
Oil droplet size interacts with density, so that the effect
of lower oil density is offset by the formation of smaller
droplet size.
4.4.9 Surfactants Have Little
Effect on Concentration Factor
/
The initial concept of the oil concentration process assumed that
oil adhered to the lipopohilic sites on the sludge solids, to effect trans-
fer to the concentrate phase. Use of surfactants was considered an attractive
possibility for increasing solids concentration by increasing the "wet^
tability" of the sludge solids by the oil. A wide range of surfactants, in
regard to HLB and chemical type, as summarized in Table 12, were therefore
screened for effectiveness (19). The surfactants were tested at two stages
of the concentration process; during the initial concentration step, (when
the sludge was mixed with the oil) and after the standard concentration had
been completed.5 The surfactants tested were all oil soluble and added to
the system by dissolving in the oil before mixing with the sludge or oil-
sludge concentrate.
In the initial exploratory screening test, emulsification of the
oil with water was found with surfactants having HLB >_ 7.8 thus reducing
the actual concentration obtained; an increase in solids concentration was
found with a surfactant of the same chemical type, but with an HLB = 3.6.
Based on this lead, a more intensive evaluation was carried out using
surfactants with HLB values _< 3.6 in order to minimize the undesirable
emulsification; these surfactants are strongly liphophilic in character.
Several duplicate tests were carried out using different batches of fresh
sludge and at both 25°C and 80°C; improvements in concentration factors
for any given test were relatively small (_< 10%) and not consistent from
test to test (see Appendix A-17 for representative data).
- 29 -
-------
TABLE 12
SURFACTANTS TESTED WITH SLUDGE
Surfactant (1)
Triton X-15
Triton X-35
Triton X-35
Atmos 300
Type
Nonionic
Nonionic
Nonionic
Nonionic
HLB Value
3.6
7.8
12.4
2.8
Span 85
Oleic Acid
Armoflo 49
(Armeen T)
Nonionic
Anionic
Cat ionic
1.8
1.0
Paranox 24
Anionic
Chemical Description _
Octyl phenoxy polyethoxy
ethanol.
Octyl phenoxy polyethoxy
ethanol.
Octyl phenoxy polyethoxy
ethanol.
(*
Mono and diglyceride of fatty
acids.
Sorbitan Trloleate
Representative of the acids in
commercial Tall Oil Fatty Acid
Primary aliphatic amine
Calcium sulfonate; MW of ~900
SURFACTANTS TESTED WITH OIL-SLUDGE CONCENTRATE
Surfactant
(1)
Type
HLB Value
Chemical Description
Tween 81
Span 60
Span 40
Span 20
(2)
ECA 4360 *
(2)
Paranox 30
(2)
F-0525V
non ionic
non ionic
non ionic
non ionic
cat ionic
anionic
non ionic
10.0 Bolyoxyethylene sorbitan monooleate
4.7 Sorbitan monostearate
6.7 Sorbitan monopalmitate
8.6 Sorbitan monolaurate
Detergent cleaner type
Barium sulfonate
Demulsifier, amine type
(1) Trade names for commercial products.
(2) Proprietary and/or experimental products.
- 30 -
-------
Comparable results were obtained when evaluating the surfactants
on the oil sludge concentrate, rather than the fresh sludge as discussed
above; one additive, an experimental Enjay Chemical Co. demulsifier, F-025,
produced a 10% additional increase in concentration, with no effect found
for any of the others evaluated.
Considering the combined data for the different tests, the
improvement in concentration that could be expected with any of the sur-
factants tested is no more than 10% and probably less. The first test
series (fresh sludge) was conducted at a very high surfactant dosage. In
the second series, the oil sludge concentrate dosage was varied from
50-10,000 ppm based on sludge solids; for the one additive with any beneficial
effect, a dosage of 'X/IOOO ppm was required for maximum effect. At this
dosage the cost/ton sludge was estimated at ^$7 for the additive, assuming
a "once-thru" basis (no reuse). Further work would be required to a) firmly
establish the reuse factor for oil soluble additives and b) to evaluate
other additives in the same structural type series which may be more
effective. Unless considerably greater improvements in concentration
factor than those found to-date were consistently obtained, or a large
reuse factor confirmed, the economic incentive for surfactant (additive)
usage appears to be small.
4.4.10 Lowering Sludge pH Increases
Solids Concentration
The sludge solids carry a negative surface charge which produces
a repulsive force between particles; this repulsive force is believed to
contribute to the poor settling and compaction characteristics of secondary
sludge. The surface charge can be neutralized by lowering the pH from
the initial 6.5-7.0 to the isoelectric point, which is reported in the
literature as occuring at pH 2-3 (16). Adjustment of sludge pH was there-
fore evaluated as a means of increasing solids concentration. Another
reason for acidification is to "shrink" the proteinaceous solids by
reducing the degree of hydration.
pH adjustment was tested at two levels, pH 4.0 initially and
than at pH 3.0; test data are tabulated in Appendix A-18 for pH 4 and
Appendix A-19 for pH 3, and summarized below in Table 13:
TABLE 13
ACIDIFYING SLUDGE INCREASES CONCENTRATION FACTQR
Sludge pH Relative Concentration Factors (80°C)
1 Hour Settling 20 Hour Settling
Unadjusted (6.5-7) 1.00 1.00
4.0 1.20 1.10
3.0 1-33 1-15
- 31 -
-------
Solids concentration, as measured by average concentraction factor,
increased with decreasing sludge pH over the range tested. The effect of pH
appeared to be greatest at the beginning of the settling step, but was still
substantial after 21 hours at the termination of the test. Based on the
three batches tested, solids content can be increased by 15% after
20 hours settling at 80°C and pH 3, compared to the unadjusted sludge.
As discussed in the sections on Total Carbon losses in the
raffinate, pH adjustment has the added benefit of reducing TC losses.
From the practical standpoint of commercial operation, these benefits
must be balanced against the costs of pH adjustment: chemicals, added
storage and mixing equipment, corrosion resistant settlers. This process
option has been included in the Phase 4 Process and Cost Analysis.
4.4.11 Factors Controlling Loss of Feed
Solids During Concentration Process
The effect of the oil concentration process on the quality of
the water raffinate, in terms of dissolved solids from the feed sludge,
was monitored by analysis for Total Organic Carbon (TOG) and/or Total
Carbon (TC). The loss of feed solids in the raffinate is important for
establishing a) if the raffinate streams require recycle, b) if so, the
magnitude of the recycle load relative to plant capacity^
Decomposition/solubilization of sludge solids into water
soluble components was found to be dependent upon the variables found
controlling for the concentration process: settling .time and temperature,
initial pH, the particular batch of sludge processed. The loss of
solubilized solids into the raffinate was also dependent upon the solids
content of the feed sludge.
Losses in the raffinates were calculated from a) the TC analysis
of the raffinates, centrifuged to remove suspended solids, b) the volumes
(weights) of the raffinate, c) the weight of suspended solids in the feed,
and d) the TC of the solids. The BOD recycle load to the plant can then
be estimated from the correlations established between TC and TOC, .and
between TOC and BOD5.
4.4.12 TC Losses Increase with Increasing
Settling Time and Temperature
The Esso oil concentration process requires a settling step at
temperatures ranging up to **80°C for times up to »-24 hours. Some thermal
decomposition of the sludge solids was therefore expected. That heat
treatment at high temperature can result in large losses has been well
documented in the literature for known commercial processes (30-33);
BOD levels in the recycle stream can be as high as 5000 mg/lit.
- 32 -
-------
As expected for a thermal process, the TC losses with the Esso
oil concentration process increase with increasing settling time and
settling temperature; the effects for representative runs for several
different sludges are shown in Figures 4 and 5 respectively; complete test
data are tabulated in Appendices A-20 and A-21. The rate of TC loss with
time rapidly decreases for settling times above about 2 hours. Over the
temperature range tested, the rate of TC loss into the raffinate appears to
increase linearly with temperature up to 60°C and then taper off.
4.4.13 Losses Decrease With
Increasing Feed Solids Content
As shown in Figures 6 and 7, for 2 hour and 20 hour settling at
80°C, respectively, raffinate losses were inversely proportional to
initial feed solids content; similar results were obtained for lower
temperatures as well. The large scatter of the data points around the
regression line is believed to be primarily due to the variability in TC
losses for the different batches tested. Further work with a few batches
at many dilutions would be required to develop a more quantitative correla-
tion curve.
The inverse effect of feed solids content can be explained by
the reduction in concentration factor (and corresponding reduction in
raffinate volume) with increasing feed solids content, rather than a
reduction in rate of solubilization itself.
As previously shown, final solids content after concentration
was not effected by initial feed solids content. Since TC losses are
inversely related to feed solids content, there is a definite incentive
to operate at maximum solids content consistent with overall process
economics, considering costs for thickening and heat balance.
4.4.14. Total Carbon Increase in Raffinate
not Due to Presence of Oil
One possible source for at least part of the TC in the raffinate
was initially considered to be-the oil itself; since oil solubilities in
water are low, dispersion of oil into very fine droplets due to the high
shear mixing seemed possible. Tests with two oils, #4 Heating Oil and
#1 Varsol, mixed with the filtered supernate from the sludge showed only
small increase in TC after 20 hrs at 80°C compared with normal sludge
tests:
- 33 -
-------
FIGURE 4
FEED CARBON IN RAFF^NATE
INCREASES WITH SETTLING TIME
24
22
20
18
t 16
- 14
1 T
OL
<
O
Q
UJ
UU
u_
o
fe*.
12
10
8-
WI-D - 0.49$ Solids
A 1.75$ Sol ids
O LF-K - 2.2$ Sol ids
o-
I I I I
J L
J L
8 10
12 14
16
SETTLING TIME - HRS. AT 80°C
18 20
22
- 34 -
-------
FIGURE 5
TC LOSSES IN RAFF I NATE VS SETTLING TEMPERATURE
18/22 Mrs of Settling
A LF-D - 0.8$ Solids O LF-I - 0.52$ Solids
A 2.3$ Solids 2.1$ Solids
0 WI-D - 0.49$ Solids
1
26
24
22
20
LU
j
<
il 18
i ,
ML
<
^ 16
"Z.
< 14
o
2
U! 12
_j
£ 10
o
vt g
6
4
2
0
1 1.8$ Solids
1 1 1 1
1
.^
v<-> i
/ T
/ i
/ ^H
/ ^ 1
/ *^
°/ / 4
yX H
" --- ^"""""" " 4
^^ ^ 1
A ^^^
_ ^ .^ Note:
^^ Curves represent average of
two runs with different init-j
ial feed solids contents ~~
25
40 50
SETTLING TEMP - °C
- 35 -
60
-------
20
FIGURE 6
EFFECT OF FEED SOLIDS CONTENT ON TOTAL CARBON LOSSES
80°C Settling for 2 Hrs
T
T
T
T
16
LU
<
I 14
O WI-A
Q WI-D
WI-B
A LF-D
A LF-I
O LF-F
LF-G
D WI-D
4 LF-K
- 12
CD
cr
<.
o
10
a
LU
LU
u_ 8
o
2
0
% Loss = -2.5 x % Susp. Solids +11.I
Corr. Coeff = .536
D -
.4
.6
.8
.0
.2 1.4 1.6 1.8 2.0 2.2
% SUSPENDED SOLIDS IN FEED
- 36 -
-------
24
FIGURE 7
EFFECT OF FEED SOLIDS CONTENT ON TC LOSS
80°C Settling for 18/22 Hrs
1 | \
22
20
18
UJ
14
DQ
o
Q
LU
|2
I0
Loss = -5.5 x % Susp. Solids + 19.5
Corr. Coeff = 0.689
_
o
D WI-D
WI-B
A LF-D
LF-K
LF-I
O LF-F
A LF-G
.2 .4 .6 .8 1.0 1.2 1.4 1.6 1.8 2.0 2.. 2
% SUSPENDED SOLIDS IN FEED
- 37 -
-------
TABLE 14
1C IN RAFFINATE NOT DUE TO OIL
Increase in TC in
Oil Mixed With Raffinate. ppm
#4 Heating Oil Supernate 43
#1 Varsol Supernate 15
#4 Heating Oil Sludge 1020
#1 Varsol Sludge 860
On the basis of these results the oil itself is not the source of the
TC in the raffinate.
4.4.15 TC Loss in Raffinate
Reduced by Oil
As part of the study on factors controlling TC loss, comparison
runs were made with and without oil, but using the same conditions of
mixing and settling. The percentage of feed solids solubilized was found
to be almost twice as high without oil as with oil, as shown in Table 15 .
for 20 hours settling at 80°C:
TABLE 15
OIL REDUCES TC LOSS
Sludge Batch
Bergen County D
Bergen County G
% Solids
in Feed
0.8
2.3
0.55
Settling
Temp. °C
80
80
80
Average
% Feed C
No Oil
18.4
19.7
48.7
29
Solubilized
With Oil
11.1
i: 12.1
20
15
Explaining these results without considerably more work is not
possible; some form of "shielding" of the sludge solids by the oil is
indicated, possibly from the effects of the mixing. This hypothesis is
apparently supported by the results of one test comparing agitation vs. no
agitation at 25°C, both without oil, with 20 hours settling:
% Feed C
AllEation Solubilized
none 7.3
pump 15.3
- 38 -
-------
The higher solubilization with agitation indicates that cell walls have
been ruptured, releasing water soluble compounds.
4.4.16 No Apparent Effect of Oil Type
Comparison of TC losses for #4 Heating Oil and #1 Varsol show
no consistent effect of oil. As shown in Table 16, the average TC loss
for all tests at 20 hour settling is the sue for bofefe oils, with some
indication of lower TC with #1 Varsol for short settling time. The lack
of an oil effect is also supported by the single tests with #2 Heating Oil
and LOPS.
One possibility remains to be tested in regard to effect of oil
on TC loss: that the "light ends" in the different oils actually used
anesthesize the living bacteria cells, causing leakage of amino acids.
Evaluation of a high boiling, lube oil base, such as Coray 37, would be
required.
4.4.17 Lowering Sludge pH to 3.0 Seduces TC Loss
In addition to increasing concentration factor, reducing pH
also has the desirable effect of reducing TC loss in the raffinate. For t
the three runs evaluated (see Table 17), the TC loss was 13-24% less than
the unadjusted controls, with the average reduction 18%.
The actual reduction obtained in feed solubilized at pH 3 is
somewhat greater than the effect above for raffinate loss. At pH 3 the
concentration factor is increased by 'Vl5%, so the raffinate volume is
correspondingly 4-5% higher than for unadjusted sludge.
4.4.18 Estimate of Recycle Load
vs. TC Loss in Raffinate
In calculating the impact of TC losses in the raffinate the most
important value is the recycle load to the plant, rather than the TC loss
per se. The quantitative translation of TC loss to recycle load depends
upon many factors which are specific to each particular plant. A
preliminary estimate of the recycle load for a given TC loss level can
be made for activated sludge assuming the following:
1. BOD, of plant influent = 200 mg/liter
2. BOD5 of primary effluent = 130 mg/liter
3. Production of waste activated sludge = 655 pounds total
solids per MGD influent
4. % Carbon in waste sludge solids = 35%
5. TC/TOC ratio for the raffinate recycled =1.17
6. BOD5/TOC ratio for the raffinate recycled = 2/1
- 39 -
-------
EFFECT OF OIL ON TC LOSS IN RAFFINATE
o
I
% Suspended
Sludge Batch Solids in .Feed
WI - A 1.5
1.5
B 2.35
1.65
1.65
0.55
LF D 2.3
2.3
2.3
2.3
LF F .95
1.28
WI - D 0.66
1.06
Averages:
-
Settling
Temp . ° C Time-hrs
80 3
20
(1)
80 V ' 1
7
20
20
(1)
25 v ' 1
(1) 2*
80 V ' 1
20
70(1) 18
20
70(1) 21
24
(2)
70/80(2) 1/7
70/80 18/24
#4HO
5.8
9.5
1.9
6.0
11
18.8
1.7
4.3
3.9
10.8
16.7
21.7
3.8
15.8
% Feed C in
in Raffinate
7/1 Varsol #2HO LOPS
3.1 5.6
12.9
2.1
5.0
12
18.8
0.2
0.9
2.7
8.8
16.4
22.2
2.6
15.6
(1) Laboratory runs
(2) Pilot Plant runs
-------
Sludge Batch
Wards island
(W.I. "D")
Bergen County
-------
The first three assumptions were recommended by the EPA. Item
4 was based on analysis of sludge solids tested in this program (see
Table 2), items 5 and 6 on analytical data obtained during the pilot
plant program (Phase 3).
Based on these assumptions, a 10% loss of sludge solids, based
on TC loss in the raffinate would be equivalent to about 3. 7% of the BODs
load to the secondary treatment, or about 2.5% of the BOD influent to the
plant.
4.4.19 TC Losses in Raffinate
Dependent Upon Sludge Batch
Review of all data on TC losses clearly shows the large variability
between batches for a constant set of test conditions. As summarized in
Table 18, TC losses for 20 hours at 80°C, with feed solids content of
1.5%, varied from 6.5-24% for the different types of sludge; the range
for one type of sludge, Bergen County activated, was 10-24%.
TABLE 18
TC LOSSES IN RAFFINATE DEPENDENT UPON SLUDGE BATCH
% Feed C in
Sludge Batch Raffinate (1)
Bergen County D 10
F 16
G 23
I 24
K 17
Wards Island A 11
B 15
D 16
Trenton B 6.5
(1) All values adjusted to 20 hrs at 80°C,
1.5% solids in feed sludge.
- 42 -
-------
At this time no information is available which provides an
explanation for the variability shown above. Since the test conditions
were, to the best of our knowledge, closely controlled the variability is
assumed to reflect differences in chemical composition and physical
structure. \
4.4.20 Batch/Batch and Plant/Plant Variability
in Solids Concentration Achieved
Using the data available from the laboratory program, some
preliminary indication of variability in response to the concentration
process can be obtained; the differences of interest are batch/batch for
a given sludge type and source (plant) and plant/plant. This comparison
is summarized below, using results obtained with high shear mixing only,
and for 20/22 hours settling at 80°C:
TABLE 19
VARIABILITY IN FINAL SOLIDS CONCENTRATION
Number
of Batches Raage of % Range of % Solids
Sludge Source Type Compared Solids in Feed ta. Concentration (1)
Bergen County activated 5 0.5-2.1 7.5-10
Bergen County primary + 2 1.7-3.5 6-12
activated
Wards Island activated 3 0.5-1.8 6-8
primary +1 2.1 11
activated
Trenton trickling 1 1.2 7
filter
(1) Hot corrected for % oil in sludge or TC losses in raffinate.
i
The variability between batches of the same sludge type and source,
as well as between plants for the same sludge type, is considerable. This
variability is believed primarily due to intrinsic differences, rather than
experimental error or test reproducibility. The large differences in sludge
thickening properties support the assumption of intrinsic differences in
the sludge batches and the variable response to the oil concentration
process. The differences between the two batches of Bergen County
primary + secondary may reflect sampling problems as well as inherent
variability.
- 43 -
-------
Several batches, from each of many more plants, would have to
be evaluated for response to the concentration process to establish the
expected range of variability of the process in general commercial usage.
4.4.21 Staged Settling Offers Advantages
Previous data on TC loss vs. settling temperature: have clearly
established that TC loss increases rapidly with temperature. Since the
concentration factor also decreased with decreasing temperature, however,
use of low temperature settling might not prove to be economically practical.
A staged settling process, where most of the water is removed in the first
stage(s) at low temperature, with final cpacenfcraticm at high temperature,
was considered a promising approach; the hope was to- reduce TC loss without
sacrificing solids concentration. The other important advantage of a
temperature staged extraction process is the large savings in heat require-
ment, since less than 1/2 the initial water in the feed sludge will remain
for heating to 80°C.
In the actual laboratory tests, the first stage settling was
carried out for 5-1/2 hours at 40°C, and second stage at 80°C for an
additional 15 hours. The TC loss was 15% lower for the one test run by
staging (see Table 17). As shown in Table 20, the final solids concentra-
tion achieved by staging was about the same as the straight 80°C reference
run at high feed solids content, and considerably lower than the reference
at the low feed solids. The difference in response is believed due to the
reduced effect of temperature on concentration factor with increasing
feed solids content; this directional effect has been previously noted
in the laboratory variable study program for constant temperature settling.
The general effectiveness of the temperature staged settling
has been qualitatively confirmed in the pilot plant program, (discussed
in the section on Phase 3) since these tests were actually run on a staged
basis. The feed sludge was at ambient temperature at the start of the run
and required several hours (3>-4) to reach final settling temperature in the
jacketed settler; water raffiaate was removed periodically during the run,
including this warmup period. While direct, controlled comparisons, such
as the above laboratory tests, were not made, the solids concentrations
achieved were equal to the values for the isothermal laboratory runs with
the same sludge or sludge type; TC losses were nt>t consistently lower, how-
ever. Taken together with the laboratory tests, the pilot plant results
appear to confirm the feasibility of the temperature-staged settling.
The possibility of utilizing the staged concept for pH adjust-
ment, in order to obtain higher solids concentration at pH 3, was also
evaluated on a preliminary basis. The oil sludge concentrate obtained
from pH ^.5 sludge after "regular" 24 hour settling was adjusted to pH 4
and to 2, then settled for an additional 16 hours. Without pH adjustment,
no further increase in concentration was obtained; with pH adjustment,
appreciable increases in concentrations were obtained as shown below (on
page 46).
- 44 -
-------
TABLE 20
EFFECT OF STAGED TEMPERATURE SETTLING
ON SOLIDS CONCENTRATION
Susp. Solids
in Feed
0.5
2.2
Bergen County "K" Activated
Settling
Temp., °C
40
80
40-80 (1)
40
80
40-80 (1)
Settling %
Time, Hr,s.
2
21
2
21
2
21
2
21
2
21
2
21
Sludge
(2)
Solids in Concentrate v
pH ~6.5(3) pH 3.0
3.9 4.2
6.5 6.8
5.9
9.2
4.5
7.4
5.3
8.2
6.6
9.7
4.8 5.7
9.9 12.2
(1) Settling temperature increased to 808C after 5 hrs,
(2) Not corrected for TC losses.
(3) Sludge as received.
- 45 -
-------
Increase in Solids Concentration, %
Sludge pH Test 1 Test 2
' 6.4 0 0
4.0 11
2.0 22 27
Since stainless steel equipment is required for operation below pH 5.5,
staging can be used to minimize costs: with staged settling only the
final concentration stage will require corrosion resistant equipment.
4.4.22 Oil Recycle Not Detrimental
to Concentration Step
One of the major concerns early in the program was the effect
of oil recycle on the efficiency of the extraction process; specifically,
would surface active compounds, formed by thermal degradation, build up
in the oil and gradually reduce the concentration factor obtained. Three
separate tests were carried out in connection with this problem, evaluating
a) recycle oil from the Hershey, Pa. plant using the Carver-Greenfield
process to dry mixed primary + secondary sludge, b) recycle oil from the
Carver Greenfield pilot plant test (Phase 3) , c) simulated recycle oil
prepared in the laboratory.
The recycle oil from Hershey, which had been through an undefined
number of cycles, contained several percent of calcium stearates, plus an
appreciable amount of fatty acids and nitrogen containing compounds
(see Appendix A-22). This oil from the Hershey operation is Cdray 37, an un-
refined lube oil base stock. The oil from Carver Greenfield, which was
processed once through the entire concentration-evaporation cycle,"was
#4 Heating Oil. Laboratory simulation tests were carried out by refluxing
sludge with the recycle oil from Carver Greenfield for several hours,
then centrifuging to recover the oil; this .procedure was repeated on a
portion of the oil for greater severity.
The effects of oil recycle, using the oils described above,
were evaluated for several different batches of Bergen County activated
sludge, and of several different feed solids Contents. Test data, tabulated
in Table 21 and summarized below, show essentially no difference between
fresh vs. recycle oil:
Concentration Factors (18/20 hrs at 80°C)
Type Oil . 1 Hr Settling 20 Hr Settling
Fresh oil 5.6 8.9
Recycle oil 5.6 8.7
Based on the data from these seven tests, there is no reason for concern
about adverse effects with recycle oil.
- 46 -
-------
TABLE 21
EFFECT OF OIL RECYCLE ON EXTRACTION
Bergen County - Activated Sludge
% Susp.
,,v Solids in
_ (O )
Eestv ' Feeds
1 0.84
2.3
2 1.72
3 0.75
1.5
3.0
4 1.0
5 0.50
6 2.2
Type Oil
Fresh Co ray 37
recycle "
Fresh f . #4 H.O.
1 recycle^
Fresh , . "
1 recycle "
Fresh "
1 recycle * ' "
i
Fresh
1 recycleu;
Fresh ''
multiple recycles
Fresh "
multiple recycles
Fresh *'
multiple recycles
Average fresh
Average recycle
% Solids
0.8/1.5 hrs
2.7
3.1
4.1
3.6
4.2
4.1
5.4
5.3
5.3
4.9
<
5.6
5.6
u a. J-iig
in Concentrate
5.5 hrs 18/20 hrs
6.3
6.6
7.9
6.6
9.2
8.5
10.3
9.3
10.1
10.0
8-°m 8-9m
8.2( 9.4(
6.6 8.2
7.6 9.0
8.1 9.9
8.4 10.2
8.9
8.7
(1) Uncorrected for TC losses in raffinate.
(2) Processed once thru Carver Greenfield concentration step.
(3) Oil from (2) refluxed for 2 hours with sludge, then centrifuged.
(4) Average of 2 runs.
(5) Oil-sludge from (3) refluxed for 4' hrs, then centrifuged.
(6) Test 1 batch LF-"D", Tests 2-5 batch LF-"J", test 6 batch LF-"K".
- 47
-------
4.4.23 Concentration of Sludge Without Oil
Control runs without oil, but employing the standard agitation
used for the oil process, have been made for most sludge batches processed
in the laboratory. For most of the batches the sludge solids were con-
centrated by "floating" to the top of the settling vessel. As shown in
the data summary in Table 22, however, there is no apparent pattern or
consistency to the occurrence of this "no-oil" type concentration in
terms of initial solids content, type of agitation, or settling temperature.
This lack of consistency in response (settling or floating) occurred with
different batches from the same sludge source.
In the cases where the solids floated, gas bubbles at the bot-
tom and mixed in with the sludge concentrate phase were observed. The
solids did not float unless agitated first. The interface between the
concentrated sludge and the relatively clear liquid was much less stable
than when the oil concentration process was used; even slight disturbance
of the settler caused some of the solids in the "float" layer to detach
and settle out in the raffinate.
As discussed in the section on TC losses in the raffinate, the
losses were more than twice as h&gh for the control runs without oil as
with the oil present; this relative difference occurred at both 25°C and
80°C.
(
Considering the unpredictability of the concentration achieved
without oil, the higher TC losses incurred, and the unstable interface,
there was no apparent incentive to consider this approach further.
- 48 -
-------
TABLE 22
SLUDGE CONCENTRATION WITHOUT OIL
Sludge % Susp. Storage (2>
Batch (1) Type Solids Time, Days
L.F.-"B" activated 0.9 6
1.7 6
L.F.-"E" " 1.0 1
i7.I.-"B" " 0.55 - 6
H.I.-"D" primary + 2.1 10
secondary
W.I.-"D" activated 0.6 1
5
30
5
20
2
2
1
1
Agitation
sec W.
Blender
sec propeller
sec W.
Blender
sec turbine
x thru
x thru
x thru
x thru
"
pump
pump
pump
pump
Type Sludge Response
solids
' n
it
n
11
"
solids
solids
split ;
s
settled
n
,.
n
ii
ii
floated
settled
mostly settled
Settling
Temp.
22°C
"
25
°C
Comment
comparable settling
to no agitation
slower settling
" than no agitation
"
25
80
25
60
c
°C(3)
°C
°C
slower settling
no agitation
comparable cone.
oil extraction
thai
to
same floated
L.F.-"G" activated 0.4 15
1.8
L.F.-"H" secondary 0.53 12
L.F. "I" activated 1/2
n ti
tt n
L.F. "I" primary +
secondary "
ii ti
enton B Trickle Filter 1
1
1
1
1
1
x thru
11
x thru
11
x thru
"
"
x thru
n
x thru
pump
pump
pump
pump
pump
solids
solids
solids
tt
»
11
H
tt
II
solids
11
settled
floated
floated
ti
"
ti
ii
n
it
settled
split
25
It
25
60
50
80
25
50
80
25
60
°C
°C
°C
°C
c
°c
°C(2)
°C(2)
°C
°C
very little con-
concentration; C.
1.2 in 22 hrs.
F=
(1) L.F. = Bergen County, W.I. = Wards Island.
(2) At 40°F in refrigerator.
(3) Separation started immediately after mixing and before sample heated up; so same result can
be assumed at 25°C.
-------
5- PHASE 2; PILOT PLANT SCALE UP
After completion of the laboratory process and optimization
studies, a pilot plant program was then carried out, with two broad
objectives:
Produce the oil-sludge concentrates required for the
heat transfer studies of Carver-Greenfield.
Confirm the small scale laboratory results and determine
if there were any unexpected scale-up problems.
The program was set up on the basis of a total of seven runs.
These runs were selected to study a) a range of sludge sources and types,
and b) oil types considered necessary for the heat transfer program. Oil
viscosity was considered to be an important consideration by Carver-
Greenfield; therefore, #4 heating oil and #1 Varsol were selected to
provide a wide practical range for comparison.
The process parameters of concern for the pilot plant program,
in terms of scale up from the 400 cc laboratory scale to the 200 gallon
pilot plant scale, were a) concentration factor achieved, b) total carbon
losses in the raffinate, c) suitability of the centrifugal pump for mixing
of the oil and sludge.
*
5.1 Description of Pilot Plant Operation
The design basis for the pilot plant was patterned very closely
on the laboratory operation: batch premixing of the, oil and sludge, process
mixing with a centrifugal pump to impart high shear contacting, and finallv
batch settling to produce the oil sludge concentrate. Detailed operating
procedures and description of the equipment are given in Appendix B-l.
Setting up and operating a continuous pilot plant for all steps, while
desirable from a process demonstration aspect and to provide additional
data for detailed design of a commercial plant, was beyond the scope of
the current project in terms of manpower and cost.
Mechanically the system worked well, with only two problems
developing at the end of the program:
Plugging of the sludge transfer pump and/or the sludge
tanks discharge line. This problem was caused by the
fibrous solids in the mixed primary and secondary sludge
and will not be encountered in commercial-size operation,
employing larger pumps and lines and a solids grinder
{comminuter) ahead of the concentration process.
- 51 -
-------
Excessive compaction of sludge solids after batch settling
in the sludge storage tank; channeling developed in the
compacted solids, which resulted in high supernant and
low solids content in the sludge removed for a run. This
would not occur in a commercial thickener with continuous
flow. -'
For all runs, sludge at ambient temperature ( 65-75° F) was mixed
with 250°F oil and pumped by a centrifugal pump "mixer" to the jacketed
batch settler; the jacket temperature was set at 175°F for the initial
runs and 185°F for the later runs. Final concentrate temperatures under
these conditions were 158°-165°F; higher jacket temperatures were not
used to avoid excessive overheating of the material along the settler
wall. Since the heat transfer surface/batch volume ratio was low due'
to settler configuration, 2-4 hours were required for the average batch
temperature to reach steady state value.
The test program, in terms of sludge and oil types selected,
and initial feed solids contents actually processed are summarised below:
TABLE 23
PILOT PLANT TEST PROGRAM
Sludge Feed % Suspended
Run No. Source Type Oil Solids in Feed
1 Bergen County Activated #4 Heating Oil 0.9
2 " " " #1 Varsol 1.3
3 " " " #4 Heating Oil 1.8 >
4 Wards Island " " " " > Q.6
5 " " " #1 Varsol 1.1
6 Bergen County Mixed Primary #4 Heating Oil i.7
+ Activated u
7 Trenton Trickle Filter " " " 1.6
Results of the pilot plant program, in terms of concentration
factors achieved and total carbon losses in the raffinate, are summarized
in Table 24 and discussed in detail in the sections below.
5.2 Pilot Plant Scale-Up Correlates
Well With Laboratory Results
5.2.1 Solids Content After Concentration
One of the objectives of the pilot plant operation was to determine
the effect of scale-up, if any, on concentration factor. Comparison of
pilot plant and laboratory results shows satisfactory agreement on concentra-
tions achieved, with the pilot plant solids contents at least equal to the
- 52 -
-------
TABLE 24
SUMMARY OF OPERATING DATA TOR PILOT PLANT RUNS
Sludge % Feed Oil Hrs.
Run Sludge Source Batch Type Solids Used Settling
1 Bergen County F Activated 0.95 #4 HO 1
18
2 Bergen County F Activated 1.28 #1 Varsol 1
2
20
3 Bergen County G Activated _ 1.82 #4 HO 1
3
20
i
u, 4 Wards Island D Activated 0.66 #4 HO 1
w 2
1 4
21
5 Wards Island D Activated 1.06 #1 Varsol 1
4
7
24
6 Bergen County I Activated 1>68 #4 H° X
4
21
27
7 Trenton B Trickling 1.63 #4 HO 1
Filter 2
3
16
22
Settling
Temp." CM-)
50
70
50
66
70
40
70
70
60
70
70
68
60
60
67
72
62
65
74
74
55
55
61
80
80
Concentration
Factor
1.0
7.8
1.0
2.7
5.6
1.0
1.6
4.8
3.9
4.7
5.5
10.4
1.1
3.6
4.7
6.8
2.4
3.0
4.7
5.0
1.1
1.2
3.5
4.3
TC Loss In
Raffinate-% (2)
HAMHH^BaMt^^HflBMaflH^^MB^VMVBVHB
16.7
0.2
11.7
16.4
0.3
8.7
21.0
8.9
11.3
21.7
0.4
8.8
11.8
15.1
5.0
8.1
14.1
15.0
0.15
0.36
5.9
6.5
(1) Temperature of water raffinate at time of sampling.
(2) % of TC in feed solids.
-------
corresponding laboratory values; for the seven runs, the average solid,
content of the sludge concentrate, not corrected for oil solubles, or
losses, was ^7.6% for the pilot plant vs. -W.3% for the laboratory (see
Table 25).
TABLE 25
COMPARISON OF CONCENTRATE SOLIDS CONTENTS
OF PILOT PLANT & LABORATORY RUNS
Run No.
1
2
3
4
5
Feed Sludge
Type
Source
Activated Bergen County
Activated Bergen County
Activated Bergen County
Activated Wards Is.
Activated Wards Is.
Primary + _ _
A ,- 1 j Bergen County
Activated
Trickling _
_,., ° Trenton
Filter
0-95
1.28
1.82
0.66
1.06
1.68
1.63
Settled Oil Sludge
Uncorrected Solids
Content - %
(1)
Pilot Plant
6.7
7.7
8.7
6.8
7.9
8.8
Lab (2)
7(3)
7.5<3>
8<3>
7(4)
7(4)
8(4)
6.9
6.5
(4)
(1) 18/22 hrs settling,no corrections for solubilized sludge
solids or oil soluble fraction.
(2) Interpolated to match pilot plant conditions.
(3) Composite average of all Bergen County batches.
(4) Results on same batch as processed in pilot plant.
The satisfactory agreement between the solids concentrations
obtained in the pilot plant and the equivalent laboratory runs at least
directionally confirms the effectiveness of the staged settling technique.
In the laboratory test of this technique the oil-sludge mixture was first
settled for 5 hours at 40°C (105°F) to remove 50-60% of the water, followed
by 15 hours at 80°C (175°F), The pilot plant runs were actually a modified
form of staged settling, since the oil sludge mixture after contacting was
only about 90°F and required 3-4 hours in the jacketed settler to reach
the desired temperature.
- 54 -
-------
In terms of further scale-up of the concentration (settling)
step to plant scale, which involves the rate of separation of the oil +
sludge arid the water raffinate phases, the above results are encouraging.
The initial liquid depths at the start of the concentration step were
0.501 & 0.65' in the laboratory tests vs. 1.75' in the pilot plant runs.
The relative rate of separation of the oil sludge concentrate phase, which
controls the design of the settler, apparently was not effected by the
3.5/1 increase in liquid depth. The liquid depth of 1.75* for the oil-
sludge mixture at the start of the settling step was used for the design
of plant size settlers, recognizing that this represented a very conservative
design basis. A further substantial increase in initial liquid depth
(to 3-4') without adversely effecting settling rate could reasonably be
assumed on the basis of the scale-up results, but cannot be used with con-
fidence until actual experimental verification is obtained. As will be
discussed further in Phase 4, confirmation of an increased scale-up
factor would permit a substantial reduction in settler cost.
5.2.2 Centrifugal Pump Satisfactory Mixer
The degree of solids capture with a centrifugal pump was
excellent in the laboratory, with no reduction in effectiveness at low
sludge suspended solids contents. Since scale up of mixing effects with
a centrifugal pump is not well defined, one of the objectives of the
pilot plant program was to confirm the laboratory results showing high
solids capture. Quantitative analysis of the 3 runs confirmed this
observation:
% Suspended Solids
Run Solids in Feed Capture %
3 1.82 97.3
4 0.66 98.3
5 1.06 97.2
These values for solids capture are, if anything, too low; a small portion
of the feed solids was not contacted by the oil in the mixing step, but
was trapped in the lines during the sludge transfer step and charged
directly to the settler.
The contacting time in the centrifugal pump mixer was adjusted to
match that used in the laboratory runs. The agreement between laboratory
and pilot plant concentration factors and solids capture indicates that
satisfactory scale-up of mixing intensity was obtained.
5.2.3 Total Carbon (TC) Losses Are
Consistent with Laboratory Data
TC losses in the raffinates vs. settling time are shown in
Figure 8 for all runs; the curves have the characteristic shape found for
the laboratory studies on TC loss, and are grouped within a fairly close
range for similar type sludges.
- 55 -
-------
FIGURE 8
TOTAL CARBON LOSSES IN RAFF I NATE - PILOT PLANT RUNS
Bergen County runs
Wards Island runs
O Trenton
10 12 14 16
i
HOURS SETTLING
18 20 22 24 26
- 56 -
-------
Losses for 18/21 hours settling were in the range of 15-22% for
the Bergen County and Wards Island activated sludge vs. 6.5% for the
Trenton trickling filter sludge. Without prior and more extensive data
on trickling filter sludge, we can only assume either that a) the rate of
solubilization/decomposition for this type is markedly different from
activated sludge or b) this low value reflects the large batch/batch
variability noted in the laboratory program for TC losses in the raffinate.
As shown in Figure 9, the TC losses for the pilot plant runs
are consistent with these values obtained in the laboratory program. Con-
sidering the range of values found for TC losses for different sludge
batches, the pilot plant results can be considered as confirming the
laboratory results. Since TC losses are a function primarily of kinetic
parameters (temperature, time) not involving scale-up factors, good
agreement between laboratory and pilot plant was expected.
The agreement between laboratory and pilot plant for mixing,
concentration factor and TC loss discussed above is important for two
reasons: confidence is. established in the feasibility of increasing
the scale-up factor to commercial size, and results of any laboratory
studies can be extrapolated to commercial scale as required for the process
trade-off studies in Phase 4.
,,5.3 Analysis of Raffinates
;;- \
5.3.1 Soluble Orgariics in
Raffinate are Biodegradable
One of the concerns about the TOC in the raffinate was the BOD
equivalent, which is important in calculating recycle load and effect on the
overall treatment plant. As shown in Figure 10, the BOD5/TOC correlation
factor for two pilot plant runs ranges from 1.67-2.47/1 over the range tested
(TOC range 60-1620 ppm) ; this is consistent with the literature correlation
for BOD vs TOC in effluent streams from conventional processes at the lower
TC levels (6). The recycled organics from the Esso process will therefore
be normally biodegradable in a secondary treatment plant.
In the initial evaluations of raffinate losses, both laboratory and
pilot plant, TOC analysis was obtained in addition to TC. A consistent
correlation between TC and TOC of about 1.1-1.25 was found with an average
of 1.16 so the dual analysis system was dropped and only TC analysis
obtained. All raffinate losses are therefore calculated on the basis of
TC; where conversion to BOD5 equivalent is needed, a TC/TOC factor of 1.16
was used, along with a BOD/TOC5 factor of 2.0. The limited data on BOD/TOC
ratio show a fairly wide variation for the TOC range evaluated; further
comparisons at the high TOC level would be required to establish a more
precise correlation.
- 57 -
-------
26
24
22
20
18
u_
<
a:
g I4
CO
ce
o
UJ
LU
U_
d 10
FIGURE 9
PILOT PLANT TOTAL CARBON LOSSES
CONSISTENT WITH LABORATORY DATA
18/22 HOURS SETTLING
T
T
T
Notes:
Data points:
Band curves:
pi lot plant runs
range for laboratory runs (from Figure 7)
0 .4 .6 .8 1.0 1.2 1.4 1.6 1.8 2.0 2.2
SOLIDS IN SLUDGE FEED
- 58 -
-------
FIGURE 10
4000
3500
3000
2500
Q_
2000
in
Q
1500
1000
500
0
BOD5 VS TOG
RAFF I NATE FROM PILOT PLANT RUNS I & 3
I'll I
,
Literature
Correlation
j i I i
02468 1000 12 14 16 18 2000
TOTAL ORGANIC CARBON (TOO - PPM
- 59 -
-------
5.3.2 Nitrogen and Phosphorous
To obtain some indication of the effect of the oil concentration
process on N and P in the sludge solids, initial sludge supernatants and
the raffinates were analyzed for NIty and NC>3 nitrogen and for phosphorus.
The available results detailed in Table 26 show a 400-500% increase in
ammonium N, almost a 50% reduction in nitrate N, and about a 50% increase
in phosphorus. The large increase in ammoniacal N is assumed to reflect
the solubilization/decomposition of the proteins and amino compounds in
the sludge solids. The decrease in nitrate suggests some form of denitri-
fication. Further interpretation and explanation of these analyses is
beyond the scope of this project, however.
TABLE 26
RAFFINATE ANALYSES - PILOT PLANT RUNS
Sludge Type Feed Supernate - ppm Raf fin ate - ppm
Run No. and Source NH4-N N03-N P205 NH4-N NOsN P20
1 Bergen County 29 30 38 133 12 60
Activated
3
4 Wards Island 42 42 42 210 20 60
Activated
5 " 190 24 82
- 60 -
-------
6. PHASE 3: DETERMINATION OF HEAT
TRANSFER PROPERTIES
6.1 Basis for Carver-Greenfield Test Program
What is referred to as the "Carver-Greenfield" component of the
total process includes the following principal elements:
A multiple effect evaporator system to remove essentially
all of the water from the oil-sludge concentration produced
in the Eseo concentration.
Solid bowl centrifuge to separate most of the oil from the
dried sludge solids, for recycle to the sludge concentration
step.
Solvent stripping of the solids to remove additional oil
in excess of that required for heat balance.
Incineration of the sludge solids and remaining oil required
to a) reduce the solids to inorganic ash which permits dis-
posal with minimum pollution problems, b) generate the heat
needed for the evaporation step.
The investment cost of the multiple effect evaporator system depends
upon the number of effects required and the size of each effect. The number
of effects is determined primarily by heat balance considerations, i.e. the
pounds of steam required to evaporate a pound of water in the feed stream
vs. the pounds of steam generated by the incineration of the sludge solids and
associated oil. By increasing the number of effects the heat balance becomes
more favorable. As a generalization, an evaporation system is designed to
optimize this balance between investment (number of effects and size of
boiler to produce the steam) vs. cost of added fuel oil. The incinerator-
boiler cost is primarily a function of the total quantity of steam generated,
which in turn is dependent upon the evaporation load (total pounds of water
to be evaporated) and the number of effects (which fixes pounds of steam
required to evaporate one pound of water).
The size of each evaporator is determined by the total evaporation
load and by the rate at which heat can be transferred from the condensing
steam to the evaporating process stream. This overall heat transfer rate,
in turn, is controlled by a) the operating temperature differential between
heat source and heat sink and b) the overall heat transfer coefficient (U).
The temperature differential for each effect is, in part, dependent on the
design of the evaporator system, but generally must be held within fairly
narrow limits by both operating and economic design requirements. For a
given temperature differential, then, the controlling factor becomes the
overall heat transfer coefficient which is determined primarily by the
nature of the process stream being evaporated.
- 61 -
-------
Streams that are fluid, with low viscosities, normally have much
less resistance to heat flow than viscous fluids for the same flow rate
through the evaporators. The viscosity and associated flow properties are
very much dependent upon the physical-chemical characteristics of the pro-
cess stream. As the oil sludge mixture is concentrated in the first and
second effects, the viscosity increases and the overall heat transfer coejucxe
can therefore decrease. The specific type and source of sludge, as well as
the oil used as the fluidizing -medium in the evaporation, also can effect
the overall heat transfer coefficient.
In a conventional evaporation system, where the process stream
consists of an aqueous phase only, complete drying of the sludge solids
would be almost physically impossible. At a point well before dryness the
straight sludge concentrate would be too viscous to be circulated for further
evaporation; in addition, considerable scaling of the heat transfer surface
would occur due to solids deposition, drastically lowering the U value. The
Carver-Greenfield process minimizes the increase in viscosity and the extent
of scaling by utilizing a water insoluble oil as a fluidizing carrier for
the sludge solids. Thus, though water is being completely removed the
process stream is still kept fluid, even in the last effect (drying stage),
and heat transfer rates are kept high. This is the key to the success
of the patented, commercially demonstrated, Carver-Greenfield evaporation
process (51).
Since the investment cost of the Carver-Greenfield process is a
large fraction of the total cost, it must be estimated as accurately as
possible within the limits of the project. The specific objectives of the
test program carried out by the Carver-Greenfield Co. were therefore set as
follows:
Determine the overall heat transfer coefficients for the
oil sludge concentrates from the Esso concentration process,
as a function of sludge type and source, feed solids concen-
tration, oil type*
Evaluate the de-oiling characteristics of the solids after
the drying stage, to be able to predict the oil recovery for
different sludge types and oils used.
Determine the organic contaminant levels of the distillate
fractions as a function of process conditions (both Esso and
Carver-Greenfield process components).
Provide the necessary data for and assist Esso in the cost
optimization of the Carver-Greenfield evaporation process,
and in the preparation of a prototype design for a plant.
- 62 -
-------
6.2 Evaluation of Heat Transfer Coefficients
in Carver-Greenfield Filot Plant
The seven oil-sludge concentrates prepared by Esso (see Phase 3,
Pilot Plant Program) were evaluated according to the program above in the
Carver-Greenfield pilot plant, located in Hanover, N.J. For the tests,
the oil-sludge concentrates were remixed in a batch feed tank, then fed
to a single effect recirculating evaporator; the partially concentrated
effluent was collected and recycled thru the evaporator as required to simulate
operation in a multiple effect system. Vacuum and steam temperatures were
adjusted as required for simulation of the particular effect being tested.
A schematic flow diagram of the Carver Greenfield pilot plant is shown in
Figure 11.
The heat transfer resistance of a test oil-sludge process stream
in the evaporator is defined by means of the following equation:
W H
n = 9 = . s s
A(T -T) A(T -T)
s s
where q = rate of heat transfer in Btu/hr
2
A = area of heating surface ft
U = overall heat transfer coefficient for the system
= to the reciprocal of the overall system heat transfer
resistance BTU/hr-ft2-°F
T = condensation temperature of the steam °F
s
T = boiling temperature of the oil-sludge mixture °F
W = mass of steam condensate Ibs/hr
s
H = heat of vaporization of steam Btu/lb
S
Thus U, the overall heat transfer coefficient (equal to the reciprocal of
the overall heat transfer resistance) can be obtained by the experimental
measurement of the steam condensate rate and temperature, and boiling sludge-
oil mixture temperature during steady state operation. (The latent heat of
vaporization and the evaporator heat transfer area are known fixed quantities.)
This type of test procedure, for determining U value, deoiling
characteristics, distillate quality, etc. has been used routinely by Carver-
Greenfield to get data for the design basis for commercial plants.
- 63 -
-------
FIGURE 11
Pyrometer Switch Points
(Tl-l)
(TI-2)
(TI-3)
(TI-4)
(TI-5)
(TI-6)
(TI-7)
(TI-8)
(TI-9)
TI-IO)
Tl-ll)
TI-12)
Product Temp.
Vapor Temp.
Steam In
Steam Out
Cold H20 In
Cold H2<3 Out
Steam Top of Tower
Centrifuge Feed Tank
Spare
Recirculation Line
Feed
Vent Line
-------
6.2.1 High Viscosity Reduces Heat Transfer
Coefficients In Initial Tests
Carver-Greenfield has carried out pilot plant testing of mixed
primary and secondary sludges taken directly from two sewage plants: Hershey,
Pa. and Bergen County, N.J.; in the test work on these plant samples the
sludges were not preconcentrated further or otherwise treated, but mixed
with the oil just before processing in the Carver-Greenfield evaporator.
The Bergen County plant is the one which provided most of the sludge samples
for the Esso program. These results provide a basis for comparison with
the data for the Esso oil-sludge concentrates.
In the initial tests to simulate the first stage evaporation,
the TJ values obtained with the viscous Esso oil-sludge concentrates were
considerably lower than expected, in the range of 9-50 BTH/hr/ft2/°F vs.
VL20 for the directly processed sludges. The Carver-Greenfield test data
are summarized in Table 27, with complete test data in Appendices C-l and
C-2.
The U values varied considerably, with no apparent effect of sludge
type, sludge source, percent solids in the feed, or oil/sludge ratio. For
the single test with #1 Varsol as the oil, the U values obtained were higher
than -for any of the tests with #4 heating oil by ^20%; further tests would
be needed^£0 confirm this difference, which could be an important factor
in minimizing evaporator costs.
Because of the high viscosity, a simulation of three evaporation
effects could not be made. Instead, the first stage concentrate was used
as feed for the third stage (drying stage). U values for the Esso batches
in the drying stage were lower than for the untreated sludge runs, but the
differences were considerably less than found in the first stage (see
Appendix C-2 for summary of drying stage data).
Carver-Greenfield's opinion was that the very hjlgh viscosities
developed by the Esso samples during concentration were the major cause
of the difference. This high viscosity drastically reduced the recirculation
rate for the evaporator (estimated at 1/5 normal), due to the capacity limita-
tions of the specific equipment in the Carver-Greenfield pilot plant. At
these low recirculation rates the film resistance to heat transfer is drastically
increased relative to normal flow. In addition, all of the transfer sur-
face may not be utilized with high viscosity. The fluid being processed
probably is not uniformity distributed over all the heat excharger tubes
in the desired thin film, but rather as thick films over some of the tubes
only.
Carver-Greenfield was able to confirm the effect of flow rate in
one test (which could not be duplicated) using chemical treatment to reduce
viscosity. When recirculation rate was increased from an estimated 1 gpm
to an estimated 3 gpm, the U value increased from VLO to ^50. The U value
projected for the noacmal pilot plant recirculation rate was estimated at
75.
- 65 -
-------
TABLE 27
CARVER GREENFIELD HEAT TRANSFER TEST RESULTS
Run No. Sludge Type and Source
1 Bergen County Activated
3 Bergen County Activated
4 Wards Island Activated
5 Wards Island Activated
6 Bergen County Prim. + Act.
7 Trenton Trickle Filter
Hershey, Pa Primary.+ Trickle Filter
Bergen County, N.J., Activated
Overall Heat Transfer Coefficient (U)
Oil Used
#4 Heating Oil
#4 Heating Oil
#4 Heating Oil
#1 Varsol
#4 Heating Oil
#4 Heating Oil
Coray 37 (1)
#2 Heating Oil (1)
1st Stage
22-49
23-32
9-38
41-60
19-82
8-33
93-122
75-186
Drying Stage
54-58
33-45
75-97
50-110
93-132
93-130
(1) Oil added just before evaporation; no prior processing.
-------
The viscosity of the Esso concentrates is apparently much higher than
the untreated sludges at the same solids concentrations. The explanation for
this difference is not presently known, but is believed to be related to the
solubilization/decomposition of the sludge solids prior to evaporation (see below).
A series of tests were made in an effort to reduce viscosity by
"demulsifying" the system, using pH adjustment and chemical treatment;
none of the treatments tried was successful. An alternative approach,
described below, was successfully developed by Carver-Greenfield.
Since the viscosity of the Varsol is considerably lower than #4
heating oil, it seemed reasonable to assume that the viscosity of an oil-
sludge concentrate prepared with Varsol would be lower than with #4 heating
oil. The viscosity data for comparable oil sludge concentrates using a
Bropkfield viscometer did not show this effect, however; since the con-
centrates are o/w emulsions, the viscosity of the continuous aqueous sludge
phase appears controlling.
Average Viscosity
Oil in Concentrate (Brookfield) of Concentrate
#4 Heating Oil 380 cp
#1 Varsol 430 cp
Varsol, which has a relatively low boiling point (319-380°F),
steam distills readily during the evaporation. The added turbulence due
to the boiling oil may explain the higher U value compared to #4 heating
oil; recent data from Carver-Greenfield with another type of sludge and a
low boiling oil tends to confirm this hypothesis.
6.2.2 U Value Markedly Improved
by Solids Recycle
Carver-Greenfield previously found that concentrate viscosity
increased up to ^25% solids, then markedly decreased. This effect was
successfully utilized to get around the viscosity-flow rate problem; centri-
fuged dry solids were added back to the feed sludge to produce 30% solids
concentration, at which point the viscosity dropped appreciably. With this
technique Carver-Greenfield reported close to normal recirculation rates,
and a D value more than twice as high as previous results in the first
test of the technique (run 7). A repeat test of the solids recycle
technique, using the last batch of oil sludge concentrate from the Esso
pilot plant program, was therefore made with the objective of confirming
the higher U value for plant design (run 6); test results are shown in
Table 28 below:
- 67 -
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TABLE 28
SOLIDS RECYCLE IMPROVES U VALUE
Overall U Value for 1st Stage _
Run No. No Solids Recycle Recycle to 30% Solids
6 19-52 42-66(1)
7 8-33 32-75
(1) Decomposed .during long storage between tests.
Results of this final test (run 6) confirmed the effectiveness
of the solids recycle, even though the improvement was not as great as the
initial test. While the viscosity was reduced as expected, an improvement
in U value of only -v30% was obtained. Carver-Greenfield reported that the
batch had "decomposed" during the long storage time (about 8 weeks) between
the preparation of the oil-sludge concentrate and the heat transfer test;
this decomposition could have changed the characteristics of the system
sufficiently to effect the heat transfer; for example, poor dispersion
of the sludge solids, or greater adheranee of solids to the heat exchange
surface would adversely effect the U value.
For the design of the evaporator system Carver-Greenfield used
a U value of 60 BTU/hr/ft2/°F; this was based on the last two test results
and provides a reasonable basis for plant design, considering all factors.
This U value of 60, which was attained only with solids recycle to reduce
viscosity, is about 1/2 the value Carver-Greenfield obtained for sludges
from the Hershey, Pa. and Bergen County, N.J. sewage plants. These sludges
were not treated prior to the evaporation test, and therefore were not subject
to thermal decomposition-solubilization of the solids prior to the heat
transfer studies.
Solids recycle is considered completely practical for commercial
operation by Carver-Greenfield, with an estimated small effect on overall
economics. This technique of solids recycle was therefore used in their
plant design studies based on the actual experimental data obtained.
6.3 Distillate TC Losses for
Pilot Plant Batches
Distillate"samples from >all Carver-Greenfield runs were .analyzed
for nitrogen (as NIty) and/or total carbon (TC),,with available data sum-
marized in Table 29. The Carver-Greenfield tests were carried out as a
two stage evaporation process due te>"the operational problems in their
- 68 -
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pilot plant caused by high viscosity or solids recycle; about 2/3 of
the initial water was evaporated in the first stage to simulate the
first 2 stages of a 3 stage commercial unit, with the final 1/3 of the
water removed in the drying stage.
TABLE 29
ANALYSIS OF DISTILLATES FBOM CARVER-GKEENFIELD HEAT TRANSFER TESTS
Esso
Run
1
3
4
5
6
7
Distillate
Stage (1)
1st
Drying
1st
Drying
1st
Drying
1st
Drying
1st
Drying
1st >
Drying
ppm as
-JEIL
8.9
7.0
9.1
7.0
9.4
9.2
6.7
9.2
5.5
8.7
M A
NH4-N
160
2400
330
2000
420
3190
Total C
265
6800
480
5200
670
8950
460
190
13000
185
TC/N
1.65
2.84
1.45
2.60
1.60
2.81
Odor
Slight NH3
Petroleum, putrid
Petroleum, putrid
Petroleum, putrid
Petroleum, putrid
Petroleum, putrid
Petroleum, putrid
^.
(1) Volume of 1st stage distillate stage
stage
Both nitrogen and TC losses in the combined distillates were sub-
stantial, with the TC loss averaging 10% of the feed solids on a carbon
basis; of this total, an average of 90% is contributed by the drying stage
distillate, as shown below:
- 69 -
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TABLE 30
THTAT, TARPON T,ns$F,s TN rAPVRH-CumMPIELD EVAPORATION
Esso
Run
1
3
4
6
#H20/#Solids
in Feed
13.8
10.5
13.7
10.9
Wt. %
in Feed
34
34
38
37
Carbon
Solids
.8
.1
.9
.9
Average PPM
Total Carbon
in Distillate (1)
2450
2100
3420
4560
Average
Total TC Loss - %(2)
in Total
Distillate
9.6
6.5
12.1
13.0
10.3
in Drying
Stage
8.8
.4
10.7
12.6
9.3
(1) Data from Table 29, with ratio of 1st stage/drying stage
volumes 2/1.
(2) Based on total carbon in sludge before oil concentration.
These losses in the drying stage distillate were unexpected,
being ^4x greater than the values found for the distillates from the
Hershey, Pa. sewage plant, where mixed primary + secondary sludge are
dried in a three effect Carver-Greenfield evaporator system.
TABLE 31
TOTAL CARBON LOSSES IN
DRYING STAGE DISTILLATE
Distillate Fraction
1st + 2nd Stage
Drying Stage
Average TC Content - PPM
175° F Settling
Esso Pilot Plant
410
8500
No Pretreatment
Hershey Plant
520
2180
% of Feed Solids
in Distillate (1)
Esso Pilot
Plant
1
9
Hershey
Plant
1
2
(1) Total Carbon basis.
While the distillates have not been analyzed to identify specific
compounds, several general observations can be made:
The high pH and ammonia odor of the first stage distillates
indicates free NH3 and or low molecular weight amines,
The neutral-slightly acidic pH of the drying sfcage distillates,
plus the high nitrogen content, suggests the presence of ammonium
salts of volatile fatty acids.
- 70 -
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The decomposition of sludge solids and/or solubilixed water
soluble compounds (formed during the settling) appears very
temperature sensitive. Only a minor portion of the total
distillate loss (3-17%) occurred in the first stage evaporator
at 130-160 F, with the major loss in the drying stage at
240-250°F.
A precise explanation for the high distillate losses relative to
the Hershey plant data cannot he given at this time. Since the Hershey
sludge was not treated prior to evaporation, a reasonable explanation,
consistent: with all the available data, is that the high temperature set-
tlta| ff*P WJ84 & #N £W £Wfg 4f j?pJ?°n$W?;te; either the water soluble
comppwjds fe>j#|ed during *?£*;##£ §f£ *elatiifej.y low in molecular weight and
therefore steam distill, -or these compounds are unstable at the 250° F tem-
perature in the drying stage and degrade further into compounds which do
distill. The Hershey data demonstrate that high distillate losses are not
inherent in the evaporation process per se. The effect of the time delay
between the Esso concentration runs and the Carver-Greenfield heat
transfer tests cannot be evaluated.
6.4
6.4.1 Analysis of Dry Solids
i
The dried sludge solids, with most of the oil removed in the
centrifuge, were analyzed for residual oil and water; these solids were also
deoiled by solvent extraction and the oil free residues analyzed for ash,
carbon, hydrogen and nitrogen,- and the heats of combustion were determined
for use in heat balance calculations. Results are summarized below, with
the detailed analytical data tabulated for the centrifuged and the deoiled
solids presented in Appendix C-4:
» Residual oil in centrifuged solids : 40-47%, which is equivalent
to 0.7-0.9#oil/# sludge solids. According to Carver-Greenfield
these values are to line with their results on other sludges
processed.
Residual water in centrifuged solids: 0.9^2.8%, with an average
of 1.6%. Again, Carver-Greenfield reports that those values
are consistent with results from other sludges.
Ash content of deoiled centrifuged solids: 40-47% vs.
30-37% for the deoiled, initial feed solids (see Table 2).
C,H,N content of deoiled centrifuged solids: 25-38%, 3.8-5.5%,
4.0-4.9%, respectively for the three elements.
The significantly higher ash values for the final solids, and
the correspondingly lower C,H,N values, reflect the TC & TOC losses in
the raffinates and distillates during processing.
- 71 -
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Heat of combustion (heating value): net heating values of
4,570 BTU/# and 4,850 BTU/# were obtained for the oil free
centrifuged solids from Bergen County and Wards Island
activated sludges. The average of 4,680 BTU/# was used tor
the heat balance calculations for the Carver-Greenfield
process; this value is M.6% lower than calculated for the
feed sludge, and reflects the reduction of combustible
(volatile) components due to TC losses.
The centrifuged dry solids from the Easo concentrates were odorless,
dark brown, crumbly solids; these solids had an appearance and physical feel
very similar to Michigan peat moss.
6.4.2 Analyses of Recycle Oil
Oil recovered from the centrifuging step was evaluated for water,
sludge solids not removed in the centrifuge, and viscosity. Test data are
tabulated in Appendix C-5 and can be summarized as follows:
Water content: 0.1%
% non fat sludge solids: 1.9-2.7%
Viscosity: 116 Sayhplt seconds (100°F) vs. 73 for fresh oil.
The residual solids level in the centrifuge oil is normal for the
Carver-Greenfield process. According to Carver-Greenfield the solids le-yel
in the recycle oil will not build up beyond this value, since an equilibrium
condition is rapidly established.
The viscosity increase in the recycle oil is probably attribut-
able to the solids content. No pumping or fluid flow problems have
developed in any of the commercial Carver-Greenfield plants; based on
this experience, no problems would be expected for a plant operating the
Esso-Carver Greenfield process, either.
6.5 Reduced Concentration Temperature
for Esso Process is Indicated
Comparing the results of the heated Esso sludges and the untreated
sludges, a major reduction in the severity of heat treatment, as measured by
TC loss in the raffinate, should significantly improve the heat transfer
properties of the Esso oil sludge concentrates. One way to accomplish this
would be to eliminate the 175°F settling stage and operate at 105°F. The
reduced settling temperature would cut TC loss in the raffinate from VL5%
to ^7% and should similarly reduce the distillate TC loss from M.0% to
v/3%. *
- 72 -
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The net expected effect of the lower temperature operation is
an Increase in the U value of up to 100%, to a value closely approaching
that for sludges not processed thru the Esso oil concentration step.
Operation at a lower settling temperature would have other effects
on the overall process, the most important ones being reduced heating
requirements for the oil sludge concentration step and a decrease in the
final solids concentration. Detailed evaluation of this process
alternative has been made as part of the Phase 4 program.
- 73 -
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7. PHASE 4: PROCESS TRADE OFF STUDIES
AND COST ANALYSIS
7.1 Process Flow Plan for Commercial Plant
In order to simplify the task of cost estimation and process
optimization, the overall process was divided into sections or modules,
for separate detailed analysis. The primary modules considered were:
« Waste sludge thickening.
Oil-sludge mixing and concentration (settling).
Multiple effect evaporation of oil sludge concentration.
Incineration of the dry solids.
The first two represent the "Esso Preeess", and the last two the "Carver-
Greenfield Process". The detailed cost estimation, equipment sizing, etc.
for the Carver Greenfield steps were made by the Carver Greenfield Corp.;
modifications were made as required by Esso for integration with the Esso
modules and to evaluate several of the process alternatives considered.
A further simplification in the overall process and cost analysis
was to design the Esso process modules for secondary sludge alone. The
design basis for the Carver Greenfield process has been set up with wide
enough limits to permit inclusion of primary solids at a later date by
merely adjusting the total water and solids load. Since dewatering of
secondary sludges to a concentration suitable for feeding to the Carver
Greenfield process is much more difficult than primary sludges, the
final integrated system will require processing of the secondary sludge
alone thru the Esso concentration process, then mixing with conventionally
thickened primary sludge for evaporation and incineration.
A listing of the actual individual steps in the overall process
and their interrelation will provide a useful introduction for the design
basis and the specific assumptions used in the process studies and^cost
estimates. The process flow plan used for the basic design is shown in
Figure 12 and consists of the following steps:
Prethickening of waste secondary sludge from 0.5% to 1.5% in
a conventional thickener.
. Preheating the thickened sludge to 105°F by direct contact
in the barometric condenser of the 3rd effect of the Carver-
Greenfield evaporator system.
. Mixing the preheated sludge with hot recycle oil from the
Carder-Greenfield process in a high shear, in-line mixer.
. Settling of the oil-sludge mixture in three separate stages.
- 75 -
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FIGURE 12
SCHEMATIC FLOW PLAN OF ESSO-CARVER GREENFIELD PROCESS
Present Secondary Treatment Plant
r
Primary
Ff f lnen+ _
f
1
Effluent
' Sludgff Ararat Ion * Fin^|
1 j-lud9° Thickener
L return sludge - 1 1 Unthickened f
_J Sludge
Condenser-
Sludge Heater
High Shear Mixer
±i |
* STu'cJge-
-
Lunnp-p^J ,
Heated as
Settlers Required
II1 t ' f '
si aye
' ' r f
Water Raff mate
Multiple Effect
Fvaporator
I ~J\
1 ^ > -.Steam
1 '
1 XT ».
\*r i Incinerator
r^ I
^_ 1 Ash
t >
^V^ Centrifuge Deotled
f i^1 r~~ Solids
» 1 l~H r
f Sol ids Conveyer
Recyc 1 e
Oil
Thickened Primary Sludge
(Optional)
Esso Process
Commercial Carver-Greenfield Plant
-------
1st stage, which is characterized by rapid separation of
phases, in a horizontal drum with 1 hr. residence time.
»n n » c°Yered slud§e thickener, but without the
picket-fence agitator, in which the oil-sludge concentrate
is taken off as a "float" phase.
- The effluent from the 2nd stage is then heated to 175 °F
for the 3rd and final stage; this 3rd stage settler is the
same type as the second stage unit.
- Water raffinates from the 3 settling stages, containing
solubilized feed solids, are recycled to the inlet of the
secondary treatment plant.
The final oil-sludge concentrate from the final settling stage
is then fed to the Carver-Greenfield multiple effect evaporator
system (3 or 4 effects, reverse flow). Primary sludge is mixed
with the concentrate before the evaporation step, where mixed
sludge is processed to dryness.
0 After the final drying stage, the dry solids are separated
from the oil in a Bird solid bowl centrifuge; the oil is
recycled to the Esso concentration step and the solids
deoiled by solvent stripping to the extent required for heat
balance.
The deoiled solids are then burned in an incinerator with the
heat energy used to generate steam for the multiple effect
evaporator system.
As the final step in the process, the ash from the incinerator
is removed for disposal; the quantity of ash will be ~30-35%
by weight of the input secondary sludge solids to the concentra-
tion process. The actual volume of ash is <0.1% of the waste
sludge volume, with 0.5% solids content assumed.
7.2 Basis for Process Design and Analysis
Brief descriptions of the design basis used for sizing the major
units in each step of the Esso concentration process are given below. The
process design, heat balance and cost data for the complete, installed
Carver-Greenfield process were provided by Carver-Greenfield for 9 dif-
ferent cases (see Appendices D-6, 7 and 8). These cases covered the range
of plant sizes and concentrate feed solids contents selected for the pro-
cess analysis, as well as evaluating the effect of increasing U value on
plant cost; the cost data for all other cases required to complete the
study were computed using the basic design and cost data provided by
Carver Greenfield.
- 77 -
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Equipment cost data were obtained from the open literature, up-
dated using appropriate inflation indices. Factors for estimating capital
costs (amortization and interest), maintanence, insurance, total labor
rate (direct operating, overhead, supervision, etc.), engineering fee and
contingency factor were obtained from the literature and discussion
with knowledgeable persons in the field. The various factors and cost
basis used in the estimating are summarized in Table 32, as of March, 1972,.
Equipment sizing was based on 100% of design capacity in all
cases, and on 365 days/year operation.
TABLE 32
COST FACTORS AND INDICES USED IN ESTIMATES
Inflation Factors for Equipment: US Dept. of Commerce Composite Index,
= Sewage Treatment Plant Construction
Cost Index (41, 44).
Amortization Rate: 25 year straight line.
Interest Rate: 5% (Feb. 1972 rate on AAA Bonds).
Engineering Cost: See Appendix D-l for variable rates (37).
Contingency Factor: 10% of installed equipment cost.
Maintanence labor + materials: 5% of total erected + installed
(TED* cost (34, 35, 38).
Insurance: 1% of total installed cost (34, 35).
Labor Rate: Direct Operating: $3.90/hr (43)
Indirect Operating: $0.60/hr (37)
Plant Overhead: 30% of Direct + Indirect labor =
$l,.35/hr (37).
Electricity: $0.01/KWH (37, 39).
Fuel (#4 Heating Oil): $0.016/lb. (from Humble Oil & Refining Co.).
^
* Installed equipment + engineering cost + contingency = TEI cost,
- 78 -
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7.2.1 Selection of Plant Sizes
! i ' 111 I in . ^,^^_m**m ,)
The range of plant sizes chosen for any process and cost analysis
must be somewhat arbitrary, but also must be broad enough to cover the
likely range of both interest and practicality. For this study, plants
with raw influent flows of 12.5-250 MGD were selected; these plants are
the size estimated to serve populations of about 100,000 td 2,000,000 people.
The waste secondary sludge was fixed at 1.8% of the plant influent
volume, with a suspended solids content of 0.50%; these values correspond
to secondary sludge solid feed rates of 4.72-94.5 tons/day.
The population equivalents to influent flow and the waste
secondary sludge/plant influent ratio were based on literature references
(4, 21) and were intended primarily as guides to plant size. All detailed
cost calculations and equipment sizing was made on the basis of sludge
solids feed rates, however.
For calculating plant sizes for mixed primary-secondary sludges,
a 50-50 weight ratio was selected (48).
7.2.2 Prethickening of Waste Secondary Sludge
[.
A total of 14 batches of secondary sludge have been processed
from 3 different plants; 9 from .Bergen County, 4 from Wards Island and one
Trenton. Settling characteristics of all batches were measured by the
standard 1 liter batch test. The settling rates varied appreciably for
different batches from the same plant, as show in Table 33, listing
the data for the slowest and fatest batches from Bergen County and Wards
Island. The Trenton, N.J. trickling filter sludge fell within these ranges.
Design of the thickener, in terms of surface area required, was
calculated by the Kynch method, using the procedure of Talmadge and Fitch
(27). The actual initial suspended solids contents of the sludge batches
as obtained from the plants was 0.5-0.6%; in all cases the thickener design
was based on an underflow concentration of 1.5%, which was the maximum
attainable for the slowest settling batches.
7.2.3 Heating of Thickened Sludge
Prior to Oil Contacting
Heating of the sludge was carried out using the sludge as the
condensing (cold) fluid in the barometric leg of the 3rd effect evaporator.
Including the heat input from the hot recycle oil, the total
heat available for preheating the sludge is adequate even for winter
conditions (40°F minimum sludge temperature); preheating of the oil sludge
mixture to 115°F at the inlet of the 1st concentration (settling) stage
was assumed. This heat balance was one of the considerations used for
selection of the prethickening step to 1.5% solids.
- 79 -
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TABLE 33
SECONDARY SLUDGE SETTLING CURVES
Ambient Temperature (20-25°C)
Initial Suspended Solids = 0.5 - 0,6%
Settling Relative Sludge Volume (V/Vo) (1) .
Time Hrs Bergen County (2) Wards Island (3)
0 1.0 1.0
1 .27-.77 .55-.88
2 .215-.56 .36-.75
3 .195-.38 .32-.65
4 .188-.31 .30-.52
6 .173-.27 .292-. 48
8 .168-.258 .289-.465
10 .166-.248 .285-.455
12 .164-.243 .283-.450
24 .155-.240 . .275-.445
(1) Range of data for individual batches tested.
(2) 9 batches.
(3) 4 batches.
7.2.4 Oil-Sludge Mixing
Use of an in-line mixer, which is basically a turbine agitator
with close clearance to the mixing chamber wall to provide high shear rates,
was assumed. The costs for in-line mixers are comparable to those for centri-
fugal pumps actually used in the experimental program, so choice of the
specific mixing system will have no effect on the cost estimate.
7.2.5 First Stage Settler
This was designed on the basis of a conventional, horizontal drum
type oil-water separator, with 4 horizontal baffles to increase effective
settling area; the rapid initial rate of settling permits use of this low
cost unit for the first stage only. >.
- 80 -
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7.2.6 Second and Third Stage Settlers
These were designed as "inverse thickeners", with the conventional
rake agitator replaced by a top skimmer, similar to that used in an air
flotation unit. The actual sizing was based on use of the Kynch method,
since the settling curves for oil-sludge are very similar to waste sludge
and the controlling mechanism was also judged very similar; literature
references support use of this approach (49).
The oil-sludge concentrate from the second stage settler must
be preheated to 175°F before the final settling stage. In the process
design this preheating was based on heat exchange in a conventional shell
and tube exchanger, using 100# steam as the heating fluid, with the steam
generated in a self contained, "package" boiler unit.
7.2.7 Process Oil and Oil-Sludge
Concentrate Storage
An oil inventory equivalent to 36 hours operation of the Esso
concentration process was assumed, with the cost capitalized. Oil storage
capacity equivalent to the oil inventory was included in the overall design.
To provide surge capacity for both the Esso concentration process
and the Carver-Greenfield process, a storage tank for oil sludge concentrate,
with 24 hour capacity, was provided for in the design.
7.2.8 Carver Greenfield Process
The design and plant cost estimation for the Carver-Greenfield
process, including both the evaporation and incineration steps, was made
by Carver Greenfield. Their cost estimates are for installed plants,
with all equipment, installation, engineering and contingency included.
The incinerator cost, which represents a large component of the total
investment was based on the average of quotes from two different suppliers
of commercial units, and also includes engineering plus contingency.
Costs were calculated on two bases: 1) using the experimentally
determined U values found with the Esso pilot plant batches concentrated
at 175°F, 2) using a U value 2x larger, equivalent to values obtained for
sewage sludges without prior treatment, and which we assumed would also be
obtained with Esso sludges concentrated at 105°F. In the first case 3
etfect evaporation was assumed; in the second high U case, costs were
calculated for 3 and also for 4 effects for those situations where 4
effects are practical - namely £ 6% solids in the feed and plant sizes
sizes >
-------
were made for the maximum, minimum and average concentration factors found
experimentally for the particular sludge feed suspended solids content
and settling temperature-time cycle selected as the base conditions.
These conditions were selected as follows:
- % suspended solids in feed: 1.5%
- laboratory settling conditions: 5 hrs. at 105°F
15 hrs. at 175°F
For these settling conditions, the values for concentration factors taken
from the experimentally derived curve were 8, 6, 4 (see Figure 3). This
curve summarizes all of the experimental data, including pilot plant ^
results, of concentration factor vs. % feed solids for 20 hours at 175 F;
the most recent test data showed that essentially the same results were
obtained for the 5 hr. at 105°F - 15 hrs. at 175°F cycle. To convert the
initial feed solids concentration to final solids in the concentrate, the
concentration factors must be corrected for the following:
- Weight loss due to Total Carbon (TC) losses in the raffinates
= 15% of initial weight. This value is based on the average
TC loss found experimentally for the settling conditions
above, and assuming that the total loss of solids weight
equals the loss of TC.
- Oil solubles in the feed sludge solids" = 10% of initial
weight. This value represents the average oil soluble
content of 4 sludge batches; the correction must be made
since any oil soluble fraction present in the sludge solids
will remain in the oil even after evaporation of the water
in the Carver Greenfield process.
Using the concentration factors specified above and the two
correction factors for TC loss and oil solubles in the sludge, the solids
contents after the Esso concentration are 4.5, 6.0 and 9.0% respectively.
7.3 Procedure Used for Cost Estimates
*
As noted above, the Esso process involves two primary and essentially
independent steps - prethickening of the sludge and oil concentration. The
widely varying thickening rates of the waste sludge mean a wide range of
thickener surface area requirements (loadings of 2.5 -10.4 lbs/day/ft2), and
therefore thickener costs.
Similarly, for a fixed feed solids content to the oil concentra-
tion step, (1.5%) a wide range of final solids concentrations will be
attained. Based on the actual experimental data obtained in the program
to-date, this concentrate solids content, which is the feed to the Carver
Greenfield process, can vary from 4.5-9.0% (equivalent to concentration
factors of 4-8).
- 82 -
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A relationship between settling rate of the waste sludge and the
concentration factor attained in the oil-extraction process has not been
found for batches from a particular plant. However, comparing the two plants
tested in the program, Bergen County and Wards Island, the available data
clearly show that:
Settling rates of waste sludges (for thickening) from Bergen
County are higher than from Wards Island.
Concentration factors of batches from Bergen County are also
higher than from Wards Island.
For purposes of broad cost analysis, then, the fastest settling sludge
batches can be associated with those batches giving the highest concentra-
tion factors and vica versa. The cost analysis for the Esso process was
therefore set up for three sets of process combinations to permit coverage
of the full range of practical possibilities:
Fastest thickening + highest concentration factor
( 9.0% solids)
Medium thickening + medium concentration factor
(6.0% solids)
Slowest thickening + lowest concentration factor
(4.5% solids)
The final cost composite for the combined Esso-Carver Greenfield
process is straight forward, since the C-G process is calculated separately
on the basisi of 4.5, 6.0 and 9.0% solids in the feed to the evaporators.
Two types of cost estimates were made: a) processing only
secondary sludge, such as might be the situation with a contact stabilization
plant, or if some alternate process were available for primary sludge, b)
processing only secondary sludge thru the Esso process, and combining the
concentrate with primary sludge for the Carver Greenfield evaporation and
incineration steps.
For secondary sludge alone, the size of both processes is fixed
only by the initial feed solids load; combined total cost data for the
Esso-Carver Greenfield processes is therefore appropriate. For mixed
primary + secondary, the solids load for the Carver Greenfield process will
be greater than for the Esso process, with the factor dependent upon the
weight ratio of primary/secondary. Separate cost curves for the Esso process
and for the Carver Greenfield process were set up to permit selection of
the components for the assumed 50/50 weight ratio and also for differing
ratios as required.
- 83 -
-------
All cost estimates were prepared on the basis of two sets of
process responses:
Present Data Basis - using the experimental data actually
obtained for the concentration and evaporation steps in
Phases 1-3.
Projected Data Basis - using the results expected from
modified operating conditions.
7.4 Cost Estimates - Present Data Basis
7.4.1 Esso Oil Concentration Process Component,
Capital costs for the Esso process components covering the
range of plant sizes, waste sludge settling rates, and concentration
factors discussed above are summarized in Appendix ..D-1?. Costs for the
individual steps of sludge thickening, oil-sludge tttixirig, oil-sludge
heating before 3rd stage settling, oil-sludge 'settling, concentrate surge
tank, process oil storage, and process pumps are included.
Total investment for the Esso process, and the detailed summary
of the individual components of the treatment costs, are given in Table D-3
and summarized below:
TABLE 34
COSTS FOR ESSO PROCESS COMPONENT. (1972)
Total Capital and Operating
Total Investment. $MM Costs $/Ton Sludge
Tons Sludge/Day Low High Low High
4.72 .32 .38 48 54
14.12 .55 .69 27 32
94.5 2.0 2.8 18 22
Low = fastest thickening, highest concentration.
High = slowest thickening, lowest concentration.
The major fraction of the total investment, and therefore of the
operating cost as well, is tied up in sludge thickeners and oil-sludge
settlers:
- 84 -
-------
TABLE 35
INVESTMENT BREAKDOWN FOR ESSO PROCESS COMPONENT
% of Total Investment
Sludge
Thickening
Average
24
24
26 '-'-
Oil Sludge
Concentration
Average
39
41
44
Combined
63
65
70
Tons Sludge/Day
4.72
14.16
94.5
Low = fastest thickening
High = slowest thickening
, . ' ' ";i u. '. .<~c
Since thickeners and settlers represent such a large component
of investment amd total operating cost, there is considerable incentive
to reduce the size (surface area requirements) of these units. As will
be discussed later in greater detail, there are several possible approaches
to significantly reducing equipment size and correspondingly improving
process economics.
7.4.2 Carver-Greenfield Process Component
The consolidated total investment and total operating costs
for the Carver Greenfield process are tabulated in Appendix D-4. Three
different sets of process conditions and/or equipment design bases were
evaluated and costs calculated:
1. Experimentally determined overall heat transfer coefficient
(U value = 60 BTU/hr/ft2/°F), experimentally determined
average Total Carbon (TC) losses in raffinate aAd distillate,
(15% TC in raffinate, 10% in distillate), 3 effect evaporator
system. This set of process conditions will be referred to
as the "Present Data Basis".
2. U value of 120, reduced Total Carbon loss (7% in raffinate,
3% in distillate), 3 effect evaporator system. The U value
and TC losses are the projected values considered attainable
with low temperature settling in the Esso concentration
process. These assumed conditions represent the "Projected
Data Basis".
3. Same as 2, but with 4 effect evaporator system in place of
3 effect. According to Carver-Greenfield, use of a 4 effect
evaporator is limited practically to ^6% maximum feed solids
content and VL4 tons/day minimum sludge solids rate.
- 85 -
-------
Total capital and total operating costs for the Carver
Greenfield process, using the present data (experimental) basis, show a
large cost reduction with increasing plant size and increasing feed solids
content.
TABLE 36
COSTS FOR CARVER GREENFIELD PROCESS COMPONENT
Total
Plant Size % Solids Investment Total Capital and Operating
Tons Sludge/Day in Feed $MM Cost $/Ton Sludge
4.72 4.5 .62 84
9.0 .56 73
14.16 4.5 .88 40
9.0 .64 26
94.5 4.5 3.8 27
9.0 2.4 12
The unusually large effect of increasing solids content fot the 94.5
tons/day plant size is mainly due to reduction in the number of individual
evaporator trains required (from 4 to 2), as well as a reduction in man-
power (from 3 to 2 men/shift) and the size of the incinerator-boiler:
the cost of the incinerator-boiler is largely dependent upon the steam load.
7.4.3 Combined Esso Carver Greenfield
Process Secondary Sludge
The individual investment and operating costs for the Esso and
Carver-Greenfield process components are shown in Figures 13 and 14 based
on the present experimental data. These cost estimates are based on con-
tinuous (3 shift) operation for all size plants. For the limiting com-
bination of process conditions for the Esso concentration process, the
total investment, total operating costs, and operating cost breakdown are
summarized below:
- 86 -
-------
oo
I
6
5
4
te
o
o
UJ
UJ
en
UJ
1.0
.9
.8
.7
.6
.5
.4
.3
.2
FIGURE IS./
TOTAL INVESTMENT (TI.E) FOR ESSO ..AND CARVER GREENFIELD
PROCESS COMPONENTS - PRESENT DATA BASIS
O Esso Process - Fast thickening - max. concentration
O Esso Process - Slow thickening - min. concentration
Q Carver-Greenfield Process - 4.5% solids
"Carver-Greenfield Process - 9.0% solids
10
PLANT SIZE - TONS SLUDGE/DAY
100
-------
60
50
40
30
20
FIGURE 14
TREATMENT COSTS OF ESSO AND CARVER GREENFIELD
PROCESS COMPONENTS-PRESENT DATA BASIS
Esso Process
CD
Q
CO
QO
O
o
_l
<
100
Carver-Greenfield
Process
10
j i i
1.0
10
PLANT SIZE - TONS/DAY SLUDGE SOLIDS
100
200
-------
TABLE 37
COSTS FOR COMBINED ESSO-CARVER GREENFIELD
PROCESS; SECONDARY SLUDGE ONLY
Total Cost Breakdown - %
Based on
Plant Size Process Investment Total Power TC
Tons/Day Conditions $MM Cost. $/Ton Investment Labor +Fuel Loss
4.72 Max. .88 121 55 37 4.1 3.6
Mm. 1.0 138 55 32 9.8 3.2
14.16 Max. 1.2 54 56 27 8.3 8
Min. 1.6 73 55 21 18 6
94.5 Max. 4.4 29 57 15 13 15
Min. 6.6 49 52 12 27 9
Max - fastest sludge thickening, highest concentration factor,
9% solids to evaporator
Min - slowest sludge thickening, lowest concentration factor,
4.5% solids to evaporator.
The effect of size on investment deviates from the normal for t\ e
Carver Greenfield process at the small-size end of the curve; the difference
between the 4.7 T/D and 14.2 T/D plants is small, particularly for the 9%
solids case. According to Carver Greenfield, the costs of the instrumenta-
tion, controls, auxiliaries and engineering remain essentially the same
for the two size plants; as well as the actual cost differential for the
incinerator-boiler.
Investment based costs are >50% of the total for all size plants,
with labor based costs the next most important category. The inverse
relationship between power + fuel, and TC loss vs. plant size reflects
the fact that these items are only slightly dependent upon size.
7.4.4 Costs to Recycle Total-Carbon Losses
Total Carbon losses for the present data basis were assumed to
be 25% of the feed sludge, for both the oil concentration and evaporation
steps. The process was debited with a recycle "cost" of $4.37/ton, cal-
culated from the BOD equivalent of the TC recycled and the influent
charge for BOD to the Chicago municipal sewage system (47); this is
equivalent to $1.75/10% TC loss. Similar debiting of the operating cost
for recycle loads associated with any process is required for valid
comparisons of different competitive processes.
7.4.5 One Shift vs. Three Shift Operation
For the smallest size plants the labor costs component is
relatively the highest. Operation of the plant on a one shift basis
can under certain conditions, result in a significant cost reduction.
- 89 -
-------
For one shift operation the plant must be sized 3x larger than for
continuous operation; reduced labor costs must then be balanced against
increased capital based costs.
For the Carver-Greenfield plant, processing 4.7 tons/day, there
is a considerable cost advantage for one shift vs. 3 shift operation at
the highest level of solids in the concentrate; there was no advantage
for one shift operation at the lowest solids level, however. For the
Esso process component, one shift operation was more costly than three
shift:
TABLE 38
COST COMPARISON OF ONE VS
THREE SHIFT OPERATION
, .Plant Thruput: 4.7 Tons/Day Sludge Solids
Total Costs, $/Ton
% Solids in Number Esso Process Carver Greenfield
Concentrate j>hifts Component Process Component
4.5 1 63.5 84.8
3 53.9 84.2
9.0 1 52.1 58.5
3 48.1 73.1
The difference in response for the Esso and Carver Greenfield
components is due to the differences in the equipment vs size cost
relationship (see Figure 13). For the smallest size Carver Greenfield
plant there appears to be a definite cost advantage for one shift opera-
tion except at the lowest solids content (most unfavorable process
response).
One shift operation of the evaporation-incineration process
is actually practiced at the Hershey, Pa. sewage treatment plant; no
operating difficulties associated with one shift operation have been
reported.
7.4.6 Combined Esso-Carver Greenfield Process
The majority of treatment plants require disposal of primary
as well as secondary sludges. As noted above the design basis for these
plants was set up on the assumption of processing only the secondary
sludge thru the Esso concentration process, then adding the primary
sludge for the Carver Greenfield process. In this way the capital
investment and operating costs required for the Esso process is minimized
and TC loss from processing of primary sludge avoided.
- 90 -
-------
The actual plant size required, as well as the final invest-
ment and operating cost, will depend on two factors for any given plant:
ratio of primary/secondary sludge solids and the concentration of the
primary sludge; this latter factor in turn will depend upon the operation
of the specific plant (type solids, operation of primary sedimentation
unit) and whether or not a sludge thickener is available.
The EPA recommended a value of 50/50 for the primary /secondary
sludge ratio. Based on a literature survey + personal references, the
following values for primary sludge solids contents were assumed:
no thickener: 4-8%
thickener : 8-10%
Combining these solids contents with the range of solids
from the Esso process for secondary sludge, (4.5-9.0%) the following
design basis would be obtained, assuming 15% oil solubles in the primary
sludge:
Maximum Range of
% Solids in % Solids in Combined
Primary Sludge Feed to Carver-Greenfield
4-8 4.0-7.9
8-10 5.7-8.8
Using the 50/50 sludge ratio, total costs were calculated for
a solids range from the Esso process (concentrated secondary sludge) of
4.5-9.0%, and a combined feed to the Carver Greenfield process of 4.0-
8.8%. Costs for the Carver Greenfield process component were taken from
the curves in Figure 15, and for the Esso component from Figure 14. Since
the final mixed sludge contains only 50% activated, the cost for the Esso
process component was multiplied by 0.5 in calculating its contribution
to the total process cost.
For a new plant, or one without a thickener, the cost of primary
sludge thickening must be added to the costs of the Esso and the Carver-
Greenfield components to get the total process cost. The following costs
for thickening primary to 8% (37, 48) were used for this purpose:
- 91 -
-------
FIGURE 15
EFFECT OF % SOLIDS IN CONCENTRATE ON
COST OF CARVER GREENFIELD PROCESS (3 EFFECT EVAPORATOR),
LU
en
-------
TABLE 39
COSTS FOR THICKENING PRIMARY SLUDGE
Sludge Load
Tons/Day (1)
4.7.7 *
,14.2
47.2
94.5
Thickening to 8%
.Cost - $/Ton (2)
3.60
1.90
1.10
.80
(1) Primary
(2) Primary + secondary (total sludge basis).
Total costs for the combined Esso-Carver Greenfield process,
including the cost of thickening primary sludge, are summarized in
Table 40 below:
TABLE 40X.
TOTAL COSTS"FOR 50/50
PRIMARY+ SECONDARY SLUDGE
<.- ,»'''' jf
ff s
Present Data Basis
Plant Size
Sludge Load
Tons/Day
9.4
28.3
94.5
189 .
f*
Total
'-*'
Esso
24-27
/ 14-16 **
9.6-12
8 . 8-11
Cost Range t
Carver
Greenfield
34-53
18-36
12.5-30
10.7-28
$/Ton
Total
Process
62-80
34-52
23-42
21-39
The values for the Carver Greenfield component of the largest size plant
were obtained by extrapolation of the curves, and many therefore contain
an added "uncertainty factor" estimated at + $l/ton.
7.5 Cost Estimates - Projected Data Basis
V1.*'
Review of the cost components of the overall process, based
on the present experimental and design basis point up several areas
where large cost savings could be achieved:
f
Reduction in Total Carbon losses.
Increase in overall heat transfer coefficient (U).
- 93 -
-------
Reduction In fuel costs required to heat oil-sludge con-
centrate to final stage temperature of 175°F.
Reduction in size (surface area) of oil sludge settlers
for concentration step.
The first two items, TC loss and U value, are believed to be
closely connected; TC losses are an indication of the decomposition/solu-
bilization of sludge solids, believed to be responsible for the the low U
values compared to sludges not heat treated prior to evaporation.
7.5.1 Lower Oil Sludge Concentration Temperature
Expected to Reduce Costs Appreciably
The primary objectives for the use of a lower temperature for
the oil sludge concentration step are a) reducing the TC losses in the
concentration and evaporation steps and b) increasing the U value for
evaporation. Use of a constant settling temperature of 105°F was considered
the most reasonable choice on the basis of balancing both TC loss and the
concentration factor: while total TC losses will be reduced by an estimated
60% compared to the base case of 175°F, concentration factor will be
reduced by 10-25% at the same time, as summarized below in Table 41:
TABLE 41
COMPARISON OF PROCESS RESULTS FOR
105°F AND 175°F OIL SLUDGE SETTLING
Concentration Final Solids
Factors TC Losses Content - %
Settling Conditions Max Min Raffinate Distillate Max Min
5 hrs 105°F, 15 hrs 175°F 8 4 15 10 9.0 4.5
20 hrs 105°F 5.4 3.3 7 4 6.7 4.1
Final solids contents are based on 1.5% solids in feed sludge, 10% oil
solubles in sludge, and TC losses in the raffinate as shown. Lower final
solids contents will increase the cost of the Carver Greenfield process, in
most cases.
Reducing settling temperature from 175°F to 105°F will have the
following overall and specific effects on heat and material balances:
Eliminate the need for heating the feed to the 3rd con-
centration stage to 175°F (reduce both fuel and equipment
costs).
- 94 -
-------
Reduce TC recycle loss (reduce cost).
Eliminate the "superheat" in the concentrate feed to the
evaporator (increase fuel costs).
Increase weight of sludge solids to the incinerator, due
to lower TC losses (reduce fuel costs).
Reduce the solids content in the oil-sludge concentrate
feed to the Carver-Greenfield evaporation step (effect
on costs variable, depending upon specific plant size and
feed concentration).
Combining all of the cost factors listed above, the net result
is a considerable reduction in costs for the Esso process component, as
shown in detail in Appendix D-7 and summarized in Table 42 below:
TABLE 42
PROJECTED COST SAVINGS FOR 105°F SETTLING:
ESSO CONCENTRATION PROCESS COMPONENT
Sludge Load Concentration Savings vs 175°F Revised
Tons/Day Factor Settling - $/Ton Costs $/Ton
4.7 Max 8.4 39.7
Min 9.5 44.4
14.2 Max 7.3 20.1
Min 8.4 23.7
94.5 Max 6.4 11.1
Min 7.5 14.3
Using the solids contents for the primary sludges as detailed
previously, the solids contents for the combined primary + secondary
sludges to Carver Greenfield process will range from 3.8-7.6%. The costs
for these solids contents were obtained from the data in Figure 15 and
are summarized below:
_ 95 _
-------
TABLE 43
COSTS FOR CARVER
GREENFIELD PROCESS COMPONENT
PROJECTED DATA BASIS
Sludge Load % Solids Cost
Ton/Day in Feed $/Ton
4.7 3.8 83
7.6' 74
14.2 3.8 41.2
7.6 < 27.6
t
94.5 3.8 24.1
7.6 11.5
The savings for the Carver-Greenfield process by operating
under the projected data basis conditions'can be estimated by comparing
the operating costs for maximum and minimum feed concentrations for the
two cost bases; these savings are tabulated below:
TABLE 44 '.. ' \
COST SAVINGS FOR CARVER GREENFIELD PROCESS
PROJECTED DATA BASIS '
8
"" *
Savings in Cbsts - $/Ton '.
Plant Size for % Solids in Feed of
Tons Sludge/Day Minimum (3.8%) Maximum (7.6%)
9.4 , 6 / 3
28.3 ,., 5 Xl
94.5 4 0.5
189 2 0.5
These values include the negative effect of operating at lower % solids
contents compared to the original "present data" basis. The difference
in solids contents at the maximum level is large (8.8 vs 7.6%) so the
absolute magnitude of the net savings is relatively small.
Combining the projected costs for the two individual process
components, costs for the projected data basis are shown in Figure 16 and
tabulated below; thickening of primary sludge is included:
- 96 -
-------
FIGURE 16
TREATMENT COSTS OF ESSO AND CARVER
GREENFIELD PROCESS COMPONENTS-PROJECTED BASIS
50
40 L.
30
20
15
^»
>
100 -
Esso Process
1 I
CD
Q
CO
01
8
50
30
20
10
Carver-Greenfield
Process
200
PLANT SIZE - TONS/DAY SLUDGE SOLIDS
-------
TABLE 45
TOTAL COSTS FOR 50/50 PRIMARY-+ SECONDARY SLUDGE
PROJECTED DATA BASIS
Plant Size
Sludge Loads Treatment Cost Range, $/Ton
Tons/Day
9.4
28.3
94.5
189
Comparing the costs for the original "present data" basis with
the "projected data" basis, average savings of around $6/ton are expected
for the combined Esso Carver Greenfield process:
TABLE 46
SAVINGS EXPECTED FOR LOW TEMPERATURE SETTLING,
COMBINED ESSO-CARVER GREENFIELD PROCESS
Esso
20-23
10-12
6.5-8.5
5.6-7
Carver Greenfield
37-51
19-32
12-25
10.2-22
Total Process
61-74
31-44
20-34
17-29
Plant Size
Sludge Load
Tons /Day
9.4
28.3
94.5
189
Cost Savings
$/Ton
1-6
3-8
3-8
4-10
Further cost reductions are also realistically possible, as
discussed in subsequent sections.
7.5.2 50% Reduction in Oil-Sludge
Settler Size Worth ^$2/Ton
The oil sludge settlers for the 2nd and 3rd stages of the Esso
concentration process were designed on the basis of the liquid depths
measured in the pilot plant runs.
Reduction in the calculated size (surface area) of the oil-
sludge settlers by 50% requires the use of a scale-up factor only 2x
greater than the factor actually used. Scale-up from laboratory to pilot
- 98 -
-------
plant indicates that the factor actually used was very conservative, and
that an increased factor would be a reasonable extrapolation. Cost savings
calculated for a 50% reduction in 2nd and 3rd stage steelers only are
detailed in Appendix D-10 and summarized below:
TABLE 47
POSSIBLE SAVINGS IN SETTLER SIZE
Secondary Sludge Cost Savings for 50%
Load, Tons/Day Area Reduction-
4-7 2.3
14.2 1>9
94-5 1.6
This savings of ^$2/ton can be added to the savings already
projected for the 105°F settling, and increase the total cost reductions
for all projected modification to $7-16/ton.
7.5.3 Alternative Process Modifications
Use of unthickened waste sludge, and adjusting sludge pH to
3.0 for the oil concentration step were two process alternatives that
initially appeared attractive. These alternatives were considered in
the cost analysis but both were found to be unacceptable, as detailed
below.
7.5.3.1 Unthickened Sludge for
Concentration Step
Use of waste sludge directly at 4X.J5% suspended solids content
for the oil-concentration step would eliminate the considerable cost of
the sludge prethickener. Other costs would be increased, however, due to
the following factors:
Added heating requirements to raise the sludge temperature
to concentration temperature of 105°F.
Added heating requirements to heat the oil-sludge mixture
to 175°F for the final concentration stage.
Increased settler size (surface area) due to the larger
volumes of oil-sludge feed to each concentration stage.
The combined effect of these factors is a very large increase
in costs compared to the use of a sludge thickener; specifics are sum-
marized below:
- 99 -
-------
In winter, costs to preheat the sludge to the extraction
temperature of 105°F were calculated at $19.7/ton sludge,
exclusive of the steam generation boiler; for prethickened
sludge no added heat input is required.
Increased fuel costs to heat the larger volume of oil
sludge to 175°F from 105°F, for the 3rd stage of the con-
centration, is calculated at about $2/ton.
Total combined thickener 4- settler size (surface area) is
greater for unthickened sludge than prethickened, even for
the case of the slow settling waste sludge; use of prethickened
sludge retains this advantage even if the projected 50%
reduction in oil sludge settler requirements is assumed, as
shown below:
Total Thickener + Settler Area - ft2
Type Sludge to
Esso Process Present Design Basis 50% Reduction
Unthickened (0.5%) 2900 1450
Prethickened (1.5%) 1470 1135
7.5.3.2 Adjustment of Sludge pH to 3.0
Reducing the pH for extraction increased the concentration factor
about 15-20%, and reduced TC losses in the raffinate by approximately the
same amount. Depending upon the size of the plant and the solids content
after concentration, savings fo up to ^$7/ton could be expected for
secondary sludge.
On the debit side, however, this must include the cost of chemicals
to acidify and to reneutralize, the cost of the chemical feeding and mixing
equipment, and the cost of stainless steel for the 3rd stage settler and
associated equipment. pH adjustment actually requires 3 separate steps:
1) oil-sludge adjustment from 5.5-6 to 3.0 before the final concentration
step, 2) the adjustment of the aqueous raffinate back to a pH of ^6, and
3) adjustment of the final concentration back to ^6 prior to the Carver-
Greenfield evaporation.
Sulfuric acid can be used for acidification; reneutralization
requires the use of ammonium hydroxoxide (or ammonia) rather than lower
cost caustic, in order to avoid a high sodium content in the feed to the
incinerator. Chemicals + equipment for the pH adjustments are estimated
at $12-19/ton for the different size plants. These costs alone are con-
siderably greater than the calculated savings for pH 3 operation, even
without considering the large added cost for a stainless steel 3rd stage
settler.
- 100 -
-------
7.6 No Incentive for Sludge
Prethickening to >1.5%
For a given sludge batch, increasing the solids content above
1.5%_by further prethickening will not increase the final solids content
attainable by the Esso concentration process; therefore, there will be
not cost savings in the evaporation step.
There is no. effect of higher solids on the heat balance, assuming
use of the 105°F settling temperature. With 175°F settling, costs to
heat the 3rd stage feed from 105°F-175°F will be somewhat lower due to
the reduced volume of the oil-sludge mixture.
Pumping costs will be slightly lower with increased feed solids
content, due to the reduced volumes of oil + sludge processes. TC losses
will also be lower, since the raffinate volume will be reduced.
As noted above, the benefits of increased feed solids content
are all minor, and will certainly be less than the increased costs for
larger sludge thickeners.
7.7 Four Effect Evaporator System
Reduces Fuel Costs
For the lower range of solids contents in the concentrates to
the evaporation step, considerable fuel economy can be obtained using
a 4 effect evaporator in place of a 3 effect system. As noted above,
Carver-Greenfield normally restricts the use of 4 effect systems to
<_ 6% solids content and solids loads >y5 tons/day.
Using the Carver Greenfield design data for 4.5% and 6.0%
solids (Appendix D-3), the potential savings (primarily in fuel), are
about $5/ton as shown below for the projected data basis:
- 101 -
-------
TABLE 48
INCENTIVES FOR 4 EFFECT EVAPORATION
SYSTEM - PROJECTED DATA BASIS
Sludge Load
Tons /Day
14.2
94.5
% Solids
in Feed
4.5
6.0
4.5
6.0
of
Effects
3
4
3
4
3
4
3
4
Total
Investment
$MM
.835
.822
. 716
2.8
2.61 :'
2.10 :
Total
Costs,
$/Ton
38
33
32
27
>' 20
Z-15' :
.),- ', '- ^ .,":
',' 16 .
Fuel
Costs
$/Ton
4.45
(.16)*
2.20
, (3.04)*
4.45
(.16)*
2.20
(3.04)*
*( ) Fuel equivalent of surplus heat generated.
The reduced fuel costs for solids contents of ^4.5%,.where the 4 effect
system is essentially in thermal balance, represent real operating savings
for all plants. Where surplus heat is generated, at solids contents
>^4.5%, some requirement for the steam for either heating or power must
exist in order to credit the total reduced fuel"cost as a "real" saving.
The situation for each plant will have to be considered on an individual
basis in order to establish the specific incentive. If a need for the
surplus steam does not exist, a condenser system will have to be installed.
7.8 Thickener Costs May Be Greatly Reduced
or Eliminated With Other Sludges
Based on a recent survey of plants by the EPA's Advanced Waste
Treatment Research Lab (48), the typical waste activated sludge solids
concentration was between 0.50 and 1.40% with a mean value of 1.0% solids.
The cost estimate for the Esso process component was based on
a waste sludge concentration of 0.5% being thickened to 1.5%; therefore,
for some sludges the thickener size requirements may be greatly reduced
and in some cases even eliminated. The value of 1.5% solids after
thickening was based primarily on heat balance considerations for the
most severe conditions of mid winter operation.
At 1.5% solids and an oil/sludge ratio of 0.2 the oil-sludge
concentrate can be heated to the required settling temperature in the
barometric leg of the 3rd evaporation stage without additional heat
input. Plants in warmer climates, where sludge temperatures as low as
40°F are not encountered, can operate at sludge concentrations below
1.5%; therefore thickener size requirements will be lower, even for
0.5% waste sludge feed, and particularly lower for waste sludges With
solids contents above 0.5%.
- 102 -
-------
The exact cost savings for reduced thickener size will depend
upon the plant size, heat balalnce requirements, and sludge, properties.
Reductions in thickener area requirements of 25-100% for operation in
warm climates and/or with waste sludges of high solids content appear
likely for many plant locations. Cost savings of $0.3-8.6/ton sludge
can be projected for these situations:
TABLE 49
POTENTIAL COST SAVINGS FOR
TfflGKENER AREA (1)
Plant Size
Tons /Day
Sludge
4.72
14.16
94.5
Thickening
Rate
Fast
Slow
Fast
Slow
Fast
Slow
Cost Savings
For Area
25% (2)
1.1
2.1
0.6
1.0
0.3
0.9
, $/Ton Sludge
Reduction of
100% (2)
4.5
8.6
2.3
4.1
1.1
3.7
(1) Costs for secondary sludge only.
(2) Based on requirements for sludges tested.
7.9 Process Costs Expected to Be
Lower for Other Sludges
As fully discussed in the section above, the total operating
and investment costs are very sensitive to the process responses of the
particular sludge batch processed; the specific responses of most concern
are rate of thickening of waste sludge, and the final solids content
achieved after the oil concentration step. Process economics were based
on the range of responses for only three different sludge sources tested
in one particular geographic area.
Most of the sludges tested can be characterized by slow thickening
rates and low solids contents achieved by thickening; this is particularly
the case for the Wards Island activated sludge. Other sludges in dif-
ferent parts of the country can be thickened to considerably higher
solids contents than the samples used in this program (48). On average,
the solids content after the oil concentration process was considerably
higher .for the sludges that thickened most rapidly (Bergen County) than
for the slow thickening sludges, Wards Island. Sludges that thicken more
rapidly and to higher solids content than Bergen County should therefore
also produce higher solids concentrates from the Esso oil process.
- 103 -
-------
The Wards Island sludges are recognized as being very difficult
to dewater and so probably represent the high cost end of the spectrum
for all plants. Costs for the Bergen County sludges are therefore
probably more normal and representative of an "average" sludge, and should
be used as the basis for comparative analysis with competetive processes.
7.10 Esso Carver Greenfield Process Costs Considerably
Lower Than Current Commercial Processes
To better define the incentives for the new Esso Carver Greenfield
process, a comparison was made with a process, proposed by the EPA for
this purpose (48), which consists of the following sequence of steps:
Primary sludge with 5% solids thickening to 8%.
Waste activated sludge at 0.6% solids thickened to 4.5%
by air flotation.
Vacuum filtration of mixed thickened primary plus activated
sludges, containing 5.7% solids, to a final solids content
of 25%.
Incineration of filter cake in a multiple hearth incinerator.
The operating cost breakdown for the process is tabulated in
Table 50 below on the basis of the data provided by the EPA (48); the
individual investment components, labor costs , maintanence, capital costs,
etc. were derived from reference (37).
TABLE 50
' , "*" ~. ._' ? . ....
COSTS OF CURRENT COMMERCIAL PROCESS
Cost Effects of Plant Size
(C/1000 gal.)
1 MGD - 10 MGD - 100 MGD
Process Component .86/Day (1) 8 .6/Day 86/Day
Primary Sludge Thickening 1^466 0.218 0.076
Air Flotation, Activated Sludge(2) 2.276 1.005 0.753
Holding Tanks 1.005 6.263 0.097
Vacuum Filtration 8.389 5.147 3.698
Multiple Hearth Incineration 13.534 5.023 1.160
Totals, c/1000 gal 25.665 11.393 5.6807
4/Ton (3) 297.4 132.0 65.9
(1) 816.8 pounds of primary + 909.3 pounds
of activated sludge/10^ gallons.
(2) Includes chemicals cost of $l-2/ton.
(3) Mixed primary + activated sludge.
- 104 -
-------
Commercial
130
92
64
52
Present Data
62-80
34-52
23-42
21-39
Projected
61-74
31-44
20-34
17-29
^
Comparing the costs for the representative present commercial
process and for the Esso Carver Greenfield (ESSO-CG) process, the Esso-CG
process has a considerable advantage even on the present data basis.
The advantage is increased considerably on the projected basis.
TABLE 51
COST ADVANTAGE OF ESSO CARVER GREENFIELD
PROCESS OVER CURRENT COMMERCIAL PROCESS
Plant Size ' ' Cost, $/Ton Esso .C-G
Tons/Day Sludge
9.4
28.3
94.5
189
The advantage for the Esso C-G process becomes even more
striking when the following factors not included in the above costs
are considered:
The upper limit for the cost range includes the effects of
the poorest process response and use of unthickened primary
sludge. The costs for thicker sludges will therefore range
from the lower limit shown to about the midpoint of the
total range.
No credit was taken for anticipated cost reductions from
reduced thickener and settler area requirements, which
could total $l-5/ton of final mixed primary + activated
sludge.
Considering all factors, the cost advantage of the Esso C-G
process, for the above plant size range, is calculated to be "913-
68/ton on a present data basis and + $24-74/ton on a projected basis
the advantage for the Esso-Carver Greenfield process, on a percentage
basis, actually increases with increasing plant size.
- 105 -
-------
8. ACKNOWLEDGEMENTS
The support given this project by the Robert Taft Water
Research Center of the Environmental Protection Agency is acknowledged
with sincere thanks. We particularly wish to thank Dr. James E. Smith,
the Project Officer for this contract, for his interest, assistance and
guidance during the period of this research.
Thanks are also offered to Mr. Alan Beerbower of Esso Research
for his considerable advice and assistance in the development of the
technical concepts on which the process is based.
Finally, we are most appreciative of the cooperation and assistance
of the supervisory and operating personnel of the treatment plants that
supplied the sludges for the program: (a) North Bergen County Sewage
Authority, Little Ferry, New Jersey, (b) City of New York, Department of
Water Resources, Wards Isladd, New York, (c) City of Trenton, Department
of Public Works, Trenton, New Jersey.
- 107 -
-------
9. REFERENCES
1. Dalton, F. E. et al "Land Reclamation-* A Complete Solution of the Sludge
and Solids Disposal Problem", JWPCF 40,5 Part 1, 789-800 (May 1968).
2. Burd, R. S., "A Study of Sludge Handling and Disposal", Water Pollution
Control Research Series Publication WP-20-4 (1968).
3. "Sludge Dewatering", WPCF Manual of Practice NO. 20 (1969).
4. Smith, J. E. ,,"Wastewater Solids Process Technology for Environmental
Quality Improvement", presented at the Filtration Society Meeting on
Application of Filtration Technology in Municipal and Industrial Water
and Waste water Treatment, Univ. of Houston, Dec. 4, 1970.
5. "Operation of Wastewater Treatment Plant", WPCF Manual of Practice No. 11,
(1970).
6. Eckenfelder, Jr. ,.W. W., "Waste Composition - Estimating the Organic
Content", Manual of Treatment Processes Volume 1, Environmental Science
Services Corporation.
7. "Utilization of Municipal Wastewater Sludge", WPCF Manual of Practice
No. 2, 9-11 (19551).
8. "Standard Methods for the Examination of Water and Wastewater", Thirteenth
Edition (1972).
9. Sparr, A. E., "Sludge Handling", Journal WPCF 40, No. 8, Part 1, 1434-42
(Aug. 1968).
10. McCarty, P. L. , "Sludge Concentration-Needs, Acpomplishments, and Fugure
Goals", JWPCF 38, No. 4, 493-507 (April 1966).
11. Mar, B. W., "Sludge Disposal Alternatives-Socio-Economic Considerations",
JWPCF 41, 4 547-52, (April 1969).
12. Dean, R. B., "Colloids Complicate Treatment Processes" Environmental
Science and Technology 3, 9, 820-24, (Sept. 1969).
13. Busch, P. L., and Stumm, W., "Chemical Interactions in the Aggregation of
Bacteria Bioflocculation in Waste Treatment", Environmental Science and
Technology, 2, 1, 49-53 (Jan. 1968).
14. Dean, R. B., "An Electron Microscope Study of Colloids in Waste Water",
Environmental Science and Technology 1, 2, 147-50 (Feb. 1967).
15. Heukelekian, H. and Weisberg, E., "Bound Water and Activated Sludge
Bulking", Sewage and Industrial Wastes, 28, 4, (April 1956).
16. Forster, C. F. , "Activated Sludge Surfaces in Relation to the Sludge
Volume Index", Water Research 5, 10, 861-69, (Oct. 1971).
- 109 -
-------
17. Lissant, K. J. , "Geometry of Emulsions", J. Soc. Cosmetic Chemists,
21, 141-154 (Mar. 1970).
18. Beerbower, A. and Hill, M. W. , "Application of the Cohesive Energy
Ratio (CER) Concept to Anionic Emulsions-', McCutcheon's Detergents and
Emulsifiers Annual - 1972.
19. "HLB Index of Materials", McCutcheon's Detergents and Emulsifiers
Annual - 1971, 209-21.
20. Sherman, P., "Rheolpgy of Emulsions", Emulsion Science (1968), Chapter 4.
21. Michel, R. L. , et al, "Operation and Maintenance of Municipal Waste
Treatment Plants", JWPCF 41, 3 Part 1, 335-354 (March 1969).
22. "Municipal Waste Facilities in the United State - Statistical Summary
1968 Inventory", USDI Federal Water Quality Administration.
23. "City of Trenton-Sewage Treatment Plant", Dept. of Public Works, City
of Trenton, N. J.
24. "Summary of Plant Operations - 1970", EPA City of New York, Department
of Water Resources.
25. Fitch, B. , "Batch Tests Predict Thickener Performance", Chemical
Engineering, 83-88, August 23, 1971.
26. Sparr, A. E. , and Grippi, V., "Gravity Thickeners for Activated Sludge"
JWPCF 41, 11 Part 1, 1886-1904 (Nov. 1969).
27. Talmage, W. P., and Fitch, B. , "Determining Thickener Unit Areas",
IEC Engin. Design and Process Devel. , 47, 1, 38-41 (Jan. 1955).
28. Malina, J. F. , and Difilippo, J. , "Treatment of Supernates and Liquids
Associated with Sludge Treatment", Water and Sewage Works - Reference
Number - 1971, R-30-38.
29. Carves, B. A., "Characterization of Wastewater Solids", pg. 30 j presented
at 44th Annual Conference of WPCF, San Francisco, Calif., Oct 3-8, 1971.
30. Teletzke, G. H. , "Thermal Conditioning of Sewage Sludge", pg. 9; presented
at 44th Annual Conference of WPCF, San Francisco, Calif., Oct 3tf8, 1971.
31. Everett, J. G. , "Dewatering of Wastewater Sludge by Heat Treatment", JWPCF
44, 1, 92-100 (Jan. 1972).
32. Harrison, J. and Bungay, H. , "Heat Syneresis of Sewage Sludges - Part 1",
Water and Sewage Works, 217-20, (May 1968).
33. Brooks, R. B. , "Heat Treatment of Sewage Sludges", Water Pollution Control,
69, 221-30, (1970).
- 110 -
-------
34. Peters, lUs,, and Timmerhaus, K. D., "Plant Design for Chemical Engineers",
2nd edition 1968.
35. Popper, H. , "Modern Cost-Engineering Techniques", McGraw Hill, 1970. '
36. Smith, R. , "Cost of Conventional and Advanced Treatment of Wastewaters",
EPA, Advanced Waste Treatment Branch, Cincinnati, Ohio, July 1968.
37. Patterson, W. L. , and Banker, R. F., "Estimating Costs and Manpower
Requirements for Conventional Wastewater Treatment Facilities", for the
Office of Research and Monitoring, EPA, Contract No. 14-12-162, Oct. 1971.
38. Ciprios, G. et al., "Studies for the Purification of Isopropyl Alcohol-
Part II", for USDI, Fish and Wild Life Service, Bureau of Commercial
Fisheries, Contract No. 14-17-0007-976, Dec. 1969.
39. "Appraisal of Granular Carbon Contacting - Phase II, Economic Effect of
Design Variables", for EPA, Advanced Waste Treatment Research Lab, Robert
A. Taft Water Research Center, Contract No. 14-12-105, May 1969.
40. Chapman, F. S., and Holland, F. A., "New Cost Data for Centrifugal Pumps",
Chemical Engineering, 200-3, July 18, 1966.
41. "Sewage treatment Plant Construction Cost Index", from EPA, Advanced Waste
Treatment Research Laboratory, Cincinnati, Ohio.
42. Smith, R., and McMichael, W. F., "Cost and Performance Estimates for
Tertiary Wastewater Treating Processes", USDI, FWPCA, Advanced Waste
Treatment Research Laboratory, Cincinnati, Ohio June 1969.
43. "Employment and Earnings", 18, 8 103, (Feb. 1972).
44. U.S. Department, of Commerce. Composite Index Survey of Current Business,
U.S. Department of Commerce, Office of Business Economics.
45. Section 10, "Heat Transmission" from Perry's Chemical Engineering Handbook,
4th edition, 1963.
46. Adamson, A. W., "Physical Chemistry of Surfaces", J. Wiley and
Sons 1963.
47. Anderson, N.'.E. and Sosewitz, "Chicago Industrial Waste Surcharge
Ordinance", JWPCF 43, 8, 1591-3 (Aug. 1971).
48. Smith, J. E., EPA, Advanced Waste Treatment Research Lab.,
Cincinnati, Ohio, Personal Communications.
- Ill -
-------
49. Vrablik, E. R., "Methods Used for the Design and Selection of
Dissolved Air Flotation Units" presented at California Section
Meeting of the Sewage and Industrial Waste Association, Stockton
California, April 23, 1958.
50. Prince, L. M., "A Theory of Aqueous Emulsions II. Mechanism of
Film Curvature at the Oil/Water Interface", J. Coll. Interface
Sci. 29, 216-221 (1969).
51. U.S. patents: 3,223,575, 3,251,398, 3,304,991, "Apparatus and
Processes for Dehydrating Waste Solids Concentrates" assigned to
Carver-Greenfield Corp. 7
52. Sptelman, L. A., and Goven, S. L., "Progress In Induced Coalescence
and a New Theoretical Framework for Coalescence by Porous Media",
IEC 62, 10, 10-24 (Oct. 1970). ]
53. Roy F. Weston, Inc., "Process Design Manual for Upgrading Exisiting
Wastewater Treatment Plants", for EPA Technology Transfer, Oct. 1971.
54. Anderson, R. V., "Sludge Incineration - the Argument For", Water
and Pollution Control (Canada) 105, 7, 21, (1967). "a
,' . :'" i ;''
55. Eller, J. M., "Characterization of Wastewater Solids", JWPCF 44,
8, 1498-1517 (Aug. 1972). , V'
- 112 -
-------
10. APPENDICES
A. Laboratory Process Development and Optimization Study
A-l Sample Processing, Equipment, Test Procedures
A-2 Analyses of Activated Sludge From Bergen County,
(Little Ferry, N.J.) Sewage Plant
A-3 Characteristics of Little Ferry, N.J. Plant Streams
A-4 Wards Island Sewage Plant
A-5 Trenton, N.J. Sewage Plant
A-6 Laboratory Concentration of Secondary Sludges
A-7 Laboratory Concentration of Mixed Primary &
Secondary Sludges
A-8 Effect of Settling Temperature on Concentration Factor
A-9 Turbine Agitator Not Effective for Consistently
High Solids Capture
A-10 Centrifugal Pump Effective Mixer; Bergen County
Sludges - Batch "E11
A-11 Oil Concentration Process Works For Different Type
Sludges: Bergen County Batch "D"
A-12 Effect of Solids Content of Feed On Final Solids
Concentration, 80°C Settling
A-13 Effect of Initial Feed Solids Content And Oil/Sludge
Ratio On Final Oil/Sludge Ratio
A-14 Effect Of Oil Sludge Ratio On Concentration Factor
A-15 Properties Of Potential Oils For Sludge Dewatering
A-16 Comparison Of Oils For Concentration Process
A-17 Effect Of Surfactants - Wards Island Batch A
A-18 Effect Of Sludge pH On Concentration (pH 4)
A-19 Effect Of Initial Sludge pH On Concentration (pH 3)
A-20 TC Losses In Raffinate
A-21 TC Losses In Raffinate (Mixing Effects)
A-22 Analysis Of Coray 37 Recycle Oil Form Hershey, Pa.
B. Pilot Plant Operating Procedure
B-l Pilot Plant Operating Procedure
B-2 Settling For Separation Of Water Raffinate
C. Determination Of Heat Transfer Properties
C-l 1st Stage Concentration
C-2 Drying Stage Concentration
C-3 Solids Added To Reduce Viscosity
C-4 Analysis Of Dried Sludge Solids From Centrifuge
C-5 Analysis Of Recycle Oil
C-6 Test Data From Carver Greenfield Corporation
-------
D. Process Trade-Off Studies and Cost Analysis
D-l Engineering, Legal and Administrative Costs
vs. Plant Investment
D-2 Capital Costs for Esso Oil Concentration Process
Sludge Prethickening - Final Settling at 175°F
D-3 Cost Estimate for Esso Oil Concentration Process
Sludge Prethickening - Final Settling at 175°F
D-4 Cost of Sludge Thickeners and Oil-Sludge Settlers
D-5 Installed Cost of Oil Sludge Settlers
D-6 Cost Estimate for Carver Greenfield Process
D-7 Fuel And Power Requirements For Carver Greenfield
Evaporation Process
D-8 Preliminary Heat and Material Balances For
The Carver Greenfield Dehydration Process
D-9 Projected Cost Savings For Low Temperature Settling
D-10 Cost Savings For 50% Reduction In Area Of
Oil Sludge Concentrations
D-ll 9% Solids In Feed 4.72 Tons/Day Sludge Solids
-------
TABLE A-l
A. Sample Processing (Sampling. Transport. Storage)
The sludge was taken from the most appropriate sampling point
at the sewage treatment plant with an open pail and poured
into clean 2 and 5 gallon polyethylene wide mouth containers
with bottom spigot valve.
The filled sludge containers were packed in crushed ice for
transport back to the GRL laboratory at Linden, New Jersey.
Sludge was stored in a 40°F refirgerator after it was received
in the laboratory, except for the short times required to remove
material for analyses or experiments.
Sludge samples for analyses as for testing were taken from
the containers via the spigots after thorough mixing with a
turbine agitator.
To increase suspended solids content of the initial sludge
sample as received, the contents of the container were allowed
to settle to the desired degree and the supernate removed by
careful siphoning.
To determine suspended solids content duplicate lOOcc samples
were filtered thru Whatman #40 paper and dried to constant
weight in accordance with the method given in "Standard Methods
f or' the '^Examination of Water and Waste Water" (13th edition).
B. Equipment
The oils used for the concentration step were heated to the
desired temperature in 2 liter stainless steel pots, using
resin kettle type heating mantles. Temperature control was
provided by a West "Gardsman" controller, with the control thermo-
couple placed 1/4 of the distance up from the bottom of the
pot in the outside surface (in contact with the heating mantle).
The oil in the pot was agitated by means of a controlled nitrogen
purge. Oil removal was made via a bottom drain line fitted with
a needle valve.
Sludge temperature was adjusted to the desired level by immersion
in a standard constant temperature water bath.
When using a propeller or turbine agitator, the mixing vessel
was a 400cc plastic beater with two 1/4" steel baffles.
Mixing by pump was carried out by premixing the sludge + oil
in an agitated lOOOcc resin kettle (with the bottom drain
connected to the pump) for 10 seconds; the purpose of the
premixing step was to insure a uniform oil/sludge ratio in the
pump feed.
-------
- for the laboratory program a single stage, open impeller Eastman
Industries Co. pump was used; the pump was rated 6000 RPM,
1/20 HP.
-%flow rate thru the pump was set at 10-15 seconds by use of
'needle valve on the 1/4" outlet line, set at 1/4" turn
open for all runs.
Settling of the oil-sludge mixture was carried out in either
250cc or SOOcc straight sided dropping funnels with teflon
plug stop codes; these settlers, all had volume markings and
were individually precaldrated.
The settlers were held for the required time at the required
temperature in constant temperature ovens of the recirculating,
forced air type.
C. Test Procedures
Sludge and oil at the specified temperature were normally
measured by volume in calibrated graduates, with the accuracy
periodically checked by weight.
The measured quantities of sludge and oil were added to the
mixing vessel, then agitated for the required time using a
stop watch.
Immediately after mixing the mixture was charged to the settling
vessel and placed into the constant temperature oven.
The volumes of the separated oil-sludge and water raffinate
phases were measured at the predetermined time intervals. The
volume of any solids (sediment) which was not "captured"
by the oil was also noted and the quantity of solids calculated
from predetermined factors.
- raffinate volumes were converted to density by applying the
appropriate temperature correction in order to calculate
concentration factor.
- in many cases the raffinates were separated off periodically
and weighed directly; this procedure was used for many of
the runs involving TG determinations, and as a periodic
check on the accuracy of the volumetric method.
-------
A-2
TABLE A-2
ANALYSES
OF ACTIVATED
FROM SEWAGE PLANTS
Test
Suspended Solids, ppm
Volatile Solids
as % of Suspended
Kjeldahl N, ppm
NH4 N, ppm
N03N, ppm
Total P2°5» PPm
Ortho P2C>5, ppm
Acidity, ppm as
CaC03
Alkalinity, ppm as
CaCOs
(2)
Total organic C, ppm
(2)
Total C, ppm\
Respiration rate,
ppm/02/min(4)
COD, ppm
L.F.-"B"
8/18/71 (3)
4600
64.1
500
90
<2
11.7
<1
445
415
29, 38, 37
45, 63, 56
L.F.-"C"
9/7/71 (3)
4100
64.6
200
28
5
22.7
12
450
47
99
SLUDGES
(D
L.F.-"D" WI-"A" WI-"B"
9/20/71 (3) 10/4/71 (3]
8200 6800 16,500
68.8 70.1 69.6
350 1,200
37 9 120
1 14 23
24.1 11.5 5.5
30 83
144 230
51 36
61 9
2.15 ' 1.24 5.1
9600 2700 7,500
(1) Analyses by ERE analytical laboratory (AID).
(2) Run on Supernate; all other samples on total sludge.
(3) Date Sampled.
(4) LF - Bergen County, N.J. ; WI «- Wards Island, N.Y.
-------
TABLE A-3
CHARACTERISTICS OF LITTLE FERRY. N.J. PLANT STREAMS
Plant Data
(1)
Primary Treatment:
Date
Raw Sewage BODcj
SS
Effluent
SS
GOD
Alkalinity
pH
Secondary Treatment:
(Activated Sludge)
Date
Mixed Liquor Effluent
COD
SS
Alkalinity
Stabilizer tank position
Stabilizer tank COD
SS
PH
Alkalinity
8/10
198
138
8/10
8/11
97
360
6,6
8/11
8/18
140
384
8/25
112
364
U)
8/18
8/25
Inlet
105
5350
7.0
700
19.7
Outlet
96
5070
6.9
660
13,5
-
Inlet
5250
7.1
500
2080
340
Outlet
5360
7.1
420
Inlet
5480
5240
1220
1080
Outlet
5040
4490
1340
1380
Inlet Outlet
3760 3720
(1) Analyses as reported by plant laboratory; all values mg/liter - ppm.
-------
A-4-
TABLE A-4
WARDS ISLAND SEWAGE PLANT
AUG. 1971 PLANT ANALYSIS SUMMARY
Raw Sewage Max Min Average
- BOD Total Steam 159 50 97
- BOD Filtrate only 52 17 27
Primary Effluent
- BOD Total 97 28 64
- BOD Filtrate 40 16 29
Return Sludge (Battery B, Step Aeration)
- Suspended Solids 6200 1700 4100
- % Volatiles in SS 80.2 72.0 75.2
Final Effluent
(2)
- Total Plant ' ,,
Suspended Solids 40 19 «
BOD Total 28 M «
BOD Filtrate 14 ,
- attery B u
Suspended Solids » ' ?
BOD Total o 1 4
BOD Filtrate 8
1) Source of sample for extraction tests.
2) Secondary treatment: ,,2/3 activated aeration, 1/3 step aeration on flow
basis.
-------
TABLE A-5
TRENTON. N. J. SEWAGE PLANT
JULY-AUG. 1971 PLANT ANALYSIS SUMMARY
July Augus t
Max Min Average Max Min Average
Raw Sewage
BOD 208 140 162 192 112 159
SS 524 186 350 602 272 382
(2)
Plant Effluent^ '
BOD 55 38 48 52 23 39
SS 194 70 112 60 148 101
(1) All values ppm.
(2) From secondary treatment.
-------
TABLE A-6
Sludge Source
Wards Island
"D" (3)
Bergen County
LABORATORY CONCENTRATION OF SECONDARY SLUDGES
(All
% Suspended
Solids in Feed
0.49
1,7
0.52
2.1
runs with #4 Heating Oil, mixed
Oil/Sludge Settling
Ratio Tamperature°C
0.2 50
0.2 80
0.2 50
\
0.2 80
0.2 40
0.2 60
0.2 80
0.2 40
60
80
by 1 pass
Settling
Titne-hrs
1
5
20
1
5
20
I
5
20
1
5
20
2
4
18
2
4 .
18
2
4
18
2
4
18
2
4
18
2
4
18
thru pump)
% Solids in Concentrate
Uncorrected(l)
2.7
3.7
4.5
3.3
7.1
7.8
2.3
3.8
6.1
3.1
4.6
6.7
4.9
5.7
7.7
4.2-
5.2
6.9
6.1
9.5
9.5
2.9
3.6
5.4
3.4
4.2
7.5
4.4
5.5
7.1
-------
(Continued)
Sludge Source
Trenton
"B" ( )
% Suspended Oil/Sludge Settling Settling
Solids in Teed Ratio Temperature Time-hrs
1.24
Solids in Concentrate
UncoTrected(l)
0.1
0.2
0.2
0.4
80
60
80
80
1
2.5
17
1
2.5
17
1
2.5
17
1
2.5
1.7
4.7
6.1
6.1
3.0
4.6
5.1
4.0
6.8
6.8
3.8
5.1
7.7
T
VJ
(1) Calculated from feed solids x concentration factor; value reported previously.
(2) Activated.
(3) Trickle Filter.
-------
A-8
TABLE A-7
LABORATORY CONCENTRATION OF
MIXED PRIMARY & SECONDARY SLUDGES
Sludge Source
Wards Island
"Tk»
% Suspended
Solids in
Feed
2.1
Oil/Sludge
Ratio
Bergen County
(L.F.)-'T'
1.7
3.5
.25
.25
.25
Settling
Temperature
50
80
80
70e
50
80
50
80
% Solids
in Concentrate
Time-hrs Uncorrected
1
5
20
1
5
20
1
5
20
1
7
20
1
7
20
1
7
20
1
7
20
1
7
20
(1)
2.9
4.2
5.5
3.6
7.2
11
3.7
8.4
13
3.7
5.2
5.2
3.7
5.9
7.1
4.0
6.6
7.1
3.5
4.7
6.6
3.9
6.0
7.1
(1) Calculated from feed solids x concentration factor;
value reported previously.
-------
TABLE A-8
EFFECT OF SETTLING TEMPERATURE ON CONCENTRATION FACTOR
Sludge Batch
Secondary Sludges
Bergen County A
Bergen County B
Bergen County E
Bergen County I
Bergen County J
Bergen County K
Wards Island D
Trenton B
Primary +
Activated Sludges
Bergen County I
Wards Island D
% Solids
in Feed
0.86
2.3
0.89
0.89
1.7
1.0
1.8
0.52
2.1
0.7
3.0
0.5
2.2
0.59
1.75
1.2
3.5
2.1
Concentration Factor
Oil
#4 HO
#1 Varsol
#4 HO
#1 Varsol
#2 HO
LOPS
#2 HO
LOPS
#4 HO
#4 HO
#4 HO
#4 HO
#4 HO
#4 HO
#4 HO
#4 HO
#4 HO
#4 HO
#4 HO
#4 HO
Agitation Type 25°C 40°C 45°C
1 hr 17/21 1 hr 17/21 1 hr 17/21
hand 2.0 3.1
hand 2.0 2.8
Waring Blender 1.4 2.1
Waring Blender 1.6 2.8
Waring Blender 1.6 2.5 1.6 3.8
propeller 1.8 2.6 1.8 3.3
Waring Blender 1.7 2.5 1.8 4.2
propeller 1.9 2.7 2.0 4.1
Waring Blender 1.6 2.3 1.7 3.3
propeller 1.6 2.3 1.8 3.3
pump
pump
pump 8.1 13.3
pump 1.4 2.6
pump 4.3 8.5
pump 1.2 2.2
pump 6.4 12.9
pump 2.0 4.0
pump
pump
pump
pump
pump 1.4 2.7
50° C 60
1 hr 17/21 1 hr
2.7
2.3
1.6'
2.0
2.2
2.0
2.2
2.2
1.9
1.8
9.5
1.6
4.0
1.2~
11.8
3.0
5.5 9.2
1.3 3.5
2.9
1.1 2.1
°C
17/21
5.0
5.0
3.0
3.3
4.5
3.3
5.0
4.5
3.3
3.3
14.9
3.4
9.8
2.4
18.4
4.4
4.1
80° C 95° C
1 hr 17/21 1 hr 17/21
I
3.1 6.8 3.2 1.0
2.0 3.5 2.2 3.6
11.8 18.3
2.1 3.7
5.8 16.0
1.4 3.0
6.8 15.9
1.8 3.8
3.2 5.5
1.2 2.1
1.9 5.2
-------
Activated
sludpe Batch
""
Bergen County "C
""
Bergen County "D
""
Wards Island "B
Suspended
Solids
0.40
0.74
0.74
0.74
1.2
1.2
2.1
2.1
.82
.82
.82
2.3
0.55
0.55
1.65
1.65
1.65
Agitator Type
Turbine - 350 RPM
Turbine - 350 RPM
Waring Blender
Turbine - 500 RPM
Turbine - 500 RPM
Turbine - 350 RPM
Waring Blender
Turbine - 350 RPM
Turbine - 350 RPM
Waring Blender
Mixing Time
Seconds
30
20
5
20
20
20
2
20
60
2
Oil
#4 HO
#4 HO
#4 HO
LOPS
#4 HO
#4 Varsol
#4 HO
#4 Varsol
#4 HO
#4 HO
#4 HO
#4 HO
#4 HO
#4 HO
#4 HO
#4 HO
#4 HO
0.
0.
0.
1
3
1
3
/
F
0.2
0.2
0.2
0.2
0
0
0
0
0
.2
.2
.2
.2
.2
Solids
Capture -
75
75
93
75
95
92
98
95
< 75
« 99
90
97
< 50
99
91
94
99
-------
TABLE A-M
Axe. Days fil Type Sludgg
0 activated
n
ti
it
mixed
primary +
activated
»
4 activated
*
H
mixed
primary +
activated
5 activated
t Susp.
Solids Oil
1-0 *4 BO
1.8 "
1.0 »
n n
1.9 '
n n
" tl Varsol
" *4 HO
1.0 "
II II
1.8 "
-
1.9 "
1.0 "
M n
" #1 Varsol
1.8 #4 HO
tl It
It * II
11 LOPS
11 #4 HO
it n
raNTBTMTP-AT P
Oil/Sludge
Ratio
0.2
it
it
ii
0.4
0.2
ir
it
ii
0.1
0.2
0.4
0.2
0.1
0.2 ,
0.4
0.2
"
M
"
"
n
ti
5 aec./ 680
DM? 'EFFECTIVE mm BERtEH d
AKltation ,
20 86C./500 in turbine*
" * i ( 1)
n
2 passes through BMP
(3) Solids not as firmly held in oil layer as for higher oil/sludge, ratios.
(4) Days stored at 40"F after sampling from plant.
-------
TABLE A-II
Sludge
Age. DaysU)
Type
activated
digested
activated
primary +
activated
activated
it
primary +
activated
activated
Feed
% Susp.
Solids
.82
tt*
2.3
.82
2.3
2.8
2.3
||
II
2.7
it
ii
4.5
2.3
2.3
4.5
.82
2.3
OIL CONCENTRATION FROCKS
Oil/Sludge
Oil
#4 H)
#1 Varsol
#4 HO
#1 Varsol
#1 Varsol
#4 HO
#4 HO
II
tt
#1 Varsol
ti
tt
#4 BO
It
II
#4 BO
it
#1 Varsol
#4 K)
tl
tl
#4 BO
II
It
#4 m
' tl
tt
Ratio
.2
H
it
n
it.
ti
.1
it
.3
.3
.3
.1
.2
tt
ii
.1
.2
.2
.2
.2
.4
.2
.2
.2
.2
.2
.2
WORKS FOR DIFFERENT TYPE SLUDGES: BERGEN COMITY BATCH "D"
Batch
Agitation , Size, cc
5 sec.
20 sec
20 sec
2 sec.
5 sec.
20 sec
2 sec.
5 sec.
10 sec
20 sec
50 sec
5 sec.
20 sec
20 sec
20 aec
5 sec.
20 sec
W. Blender
ii.
ii
"
./5QO "RPM turbine
n
,/SOORIM turbine
W. Blender
W. Blender
./500 RIM turbine
W. Blender
W. Blender
./500 -RPM turbine
./500 RIM turbine
./500 RIM . "
H. Blender
it
tt
ti
./500 RIM turbine
ii
./SOO RIM, 1 turbine
" 2 turbines
" 1 turbine
./SOO RPM turbine
.W. Blender
./SOO RIM turbine
MBb^B*>VB^^
200
It
II
If
It
It
II
II
If
tl
II
It
f'l
tt
tl
II
II
tt
II
It
II
500
750
450
200
ii
ii
Settling
Temp. °C
80
25
25
80
tt
II
fi-
ll
It
If
ft
ft
II
II
If
II
II
fl
fl
II
II
fl
t|
tl
25
80
it
Concentration Factor after Settling (*)
1 hi.
6.7
2.3
2.9
2.6
4.0
2.6
1.2
1.6
1.3
1.3
1.3
1.6
1.3
1.3
1.2
2.5
2.7
2.7
1.4
1.2
1.3
1.5
1.4
1.2
2.8
2.5
2.0
2 hrs.
7.4
3.6
3.3
3.1
4.0
2.6
1.8
1.8
1.5
1.6
1.6
1.8
1.6
1.6
1.6
3.1
3.3
3.3
1.7
1.3
1.6
1.8
1.7
1.3
2.9
3
2
2
I
1
1
1
1
1
1
2.
1.
1.
3.
3.
2.
hrs
.1
.0
.6
.7
.7
.9
.9
.9
.8
,0
9
4
3
2
3
. 4 hrs. 19/Z2 hrs. 72 hrs.
10.0 10.0 10.0
4.5 5.7 5.7
3.6 4.5 4.5
3.1 4.4 5.0
5.0
3.3
2.1
2.2
1.8
2.5
2.4
2.9
2.9
2.7
2.9
3.3 4.4
3.6 5.0
3.6 4.8
1.9 2.5
1.7 2.2
1.8 2.4
3.3
2.0
3.3 (3.5) 3.6
3.4 (4.4) 4.6
2.6 (3.2) 3.6
Approx.
Solids
Capture, %
99
65
92
94
98
99
90
99
97
(I) Data not corrected lot TO losses in raffinate and oil content of feed sludges; the
estimated correction factors for these items are 0.85 +0.90, respectively.
-------
TABLE A-12
EFFECT OF SOLIDS CONTENT OF FEED ON
FINAL SOLIDS CONCENTRATION 80°C SETTLING
Sludge
Batch(l)
LF-D
LF-E
LF-E
LF-D
LF-K
LF-J
WI-B
WI-D
Sludge
Type
activated
activated
primary +
activated
activated
activated
activated
activated
% Suspended
Solids in Feed
0.82
2.3
1.0
1.8
*s. -
1.9*-.
2.7
4.5
0.52 -\
0.96 -
2.1
0.70- re
0.75 : :.:
i.o
1.5
3.0
3.0
0.55
1.6
2.3
0.59
1.75
Type Concentration
Mixing 1 Hr 2 Hr
Waring Blender 6.7
2.6
pump 3.3
2.8
Waring Blender 2.9
2.5
1.2
pump - 11.8
; ; 6.4
: 3.0
pump - 6.0
- .. ,--:,::-xL - '' : 6.7 :. " *:,,
' ".. I.'',' "''' 5V4
~;' ~5'--'-: ' 3.5
1.45
1.40
Waring Blender 4. "5
.. :: ,.,-.... ;', 1.9;. ; :.-
pump 6.8
1.8
Fact or (2)
20 Hr
10
4.5
8.0
4.8
4.4
4.5
2.1
18.4
10.4
4.4
15.0
12.8
10.5
6.9
3.4
3.6
8.2
3.5
2.0
15.9
3.9
% Solids in Concentrate
1 Hr
5.5
5.7
3.3
5.0
5.5
6.8
5.4
2 Hr
4.2
5.0
5.4
5.3
4.4
4.2
2.5
3.0
3.0
3.3
3.1
5.9
6.3
6.6
20 Hr
8.2
8.6
8.0
8.6
8.3
10.8
9.5
9.2
10.3
9.7
10.5
9.6
10.0
10,
10.
10.
4.6
5.2
4.6
7.8
6.9
(1) LF = Bergen County, WI = Wards Island
(2) All runs wth oil/sludge ratio = 0.2, 80°C settling temperature, #4 Heating Oil.
-------
TABLE A-13
EFFECT OF INITIAL FEED SOLIDS CONTENT AND
OIL/SLUDGE RATIO ON FINAL OIL/SLUDGE RATIO
% Suspended Solids
in
Total
0.50
1.0
1.5
2.0
Feed Sludge
Basis (1)
0.45
0.90
1.35
1.80
Oil/Sludge
Ratio
for Concentration
Vol. Wt. (2)
0.05
0.1
0.2
0.3
0.1
0.2
0.3
0.1
0.2
0.3
0.1
0.2
0.3
.04
.08
.16
.24
.08
.16
.24
.08
.16
.24
.08
.16
.24
Oil/Solids
Uncorrected
8.9
17.8
35.6
71.2
8.9
17.8
26.7
6.0
11.9
17.9
4.5
8.9
13.4
Weight Ratio (#/#)
Corrected (3)
10.5
21.0
42.0
65.0
10.5
21.0
32.5
7.0
14.0
21.0
5.2
10.5
16.2
(1) Assume 10% oil solubles in sludge.
(2) Assume oil specific gravity of 0.8.
(3) For 15% TC loss during concentration step.
-------
TABLE A-14
Sludge
Batch
WI-B
Sludge
Type
activated
LF-D
LF-E
primary +
activated
activated
activated
EFFECT
% Solids
in Feed
0.55
1.65
1.65
2.35
2.35
2.7
1.9
1.9
OF OIL SLUDGE RATIO ON CONCENTRATION FACTOR
Settling
Oil Used Temperature Type Mixing
#1 Varsol 80 Waring Blender
#4 H.O..
#4 H.O.
#1 Varsol
#4 H.O.
#1 Varsol
. ^ - ,- ^ "l-,. »<* 'J
#4 H.O. 80
#4 H.O. 80 pump
#4 H.O.
Oil/Sludge
Ratio
.1
.2
.4
.1
.2
.4
.1
.2
.4
.1
.4
.1
.2
.4
.1
.2
.1
.2
.1
.2
.4
.1
.2
.4
Concentration
Factor
1 Hr 20 Hr
4.5
2.9
2.8
6.4
4.5
4.2
2.0
2.1
1.8
1.7
1.6
1.3
1.3
1.0
1.2
1.1
2.4
2.6
2.4
2.8
2.2
2.3
2.9
2.8
8.1
6.7
6.0
11.2
8.1
8.1
2.9
3.3
3.3
472
3.7
1.7
2.0
1.7
2.3
2.0
4.0
4.5
5.1(1)
4.5
3.8
5.2(1)
4.8
4.5
Ul
-------
LF-J
activated
Trenton trickle
B filter
3.0 #4 H.O. 80
1.24 #4 H.O. 80
Average Values (2)
pump
pump
,2
.33
.1
.2
.a
Concentration
Oil/Sludge Ratio
.1
.2
.3
1 HR
2.8
2.5
2.2
1.4
1.5
3.5
3.2
3.1
Factor
20 HR
5.0
4.6
4.4
3.4
3.1
4.9(1)
5.5
6.2
(1) Oil + sludge-water interface less stable than at higher o/s ratios.
(2) Based on direct comparisons only.
-------
TABLE A-15
PROPERTIES OF POTENTIAL OILS FOR SLUDGE
Composition, Vol. %
Oil
#2 Heating Oil
#4 Heating Oil
Varsol #1
Varsol #4
LOPS(2)
ISOPAR M
CORAY 37
Specific
Gravity 60° F
.87
.884
.789
792
.796
.782
.901
Paraffins Napthenes
OQ *>/\ » *
Jo ju
46.1 39.8
54.5 31.5
54.3 43.3
79.9 19.7
69.5
Aromatics
Total Cgt Olefins
32
14.0 13.0 0.1
13.8 13.8 0.2
2.4
0.3 0.3 0.1
30.5
DEWATERING
Distillation,
°F
IBP
335
342
319
363
383
405
50%
499
577
342
373
426
434.
Dry
648
860
380
402
474
484
Flash
Point, °F
158
200
105
140
152
172
310
Viscosity
2.3cs at 100° F
50SSU at 100° F
.92cp at 25°C
1.15cp at 250° C
1.2cs at 100° F
2.43cp at 25°C
80SSD at 100 °F
Approximate
Cost, $/Ral
.115
.110
.19
.20
.20
.31
.19
J
VI
(1) Napthenes + Olefins.
(2) Low Odor Paraffin Solvent (Product of Enjay Chemical Co.)
-------
TABLE A-16
COMPARISON 'OF OILS FOR CONCENTRATION PROCESS
Sludge
Batch
W. I-A
W.I-B
LF-D
LF-E
LF-A
% Solids Oil/Sludge Settling Type
in Feed Ratio Temperature Mixing
1.5 0.4 80 Turbine
0.55 0.2 80 Waring
Blender
1.65i 0.2
1.65 0.6
2.33 0.2 "
0.82 0.2
2.3 0.2
1.88 0.2 " "
2.3 0.2 60
Oil Used
#4 H.oa*
LOPS
#4 H.O.
#1 Varsol
#4 H.O.
#1 Varsol
14 H.O.
#1 Varsol
#2 H.O.
#4 H.O.
#1 Varsol
#4 H.O.
Coray 37
#4 H.O.
Coray 37
#1 Varsol
#4 H.O.
#1 Varsol
LOPS
#4 H.O.
#1 Varsol
Concentration
1 Hr
1.6
1.5
4.5
2.9
2.1
1.7
1.4
1.4
1.3
1.3
1.1
5.8
3.8
2.5
1.5
2.6
1.5
1.3
1.4
1.7
2.0
Factor
20 Hr
2.3
2.1
8.1
6.7
3.3
4.0
3.0
3.0
2.7
2.0
2.0
8.2
8.2
4.2
2.7
4.6
2.8
2.3
2.6
2.9
3.3
I
00
-------
LF-B
0.9
1.7
0.2
0.2
60
Propeller
#2 H.O.
LOPS
#4 H.O.
#2 H.(D.
LOPS
2.2
2.3
1.5
1.2
1.9
4.2
3.8
4.0
3.5
4.2
Averages :
Oil
#4 H.O.
#1 Varsol
#4 H.O.
LOPS
#2 H.O.
LOPS
12
H.O.
Ntnber of Tests in
Direct Comparison
3
2
Concentration Factor
1 Hr
2.1
1.9
1.5
1.6
1.7
2.1
1.5
1.3
20
3.8
3.7
3.1
3.0
3.8
4.0
3.5
3.1
-------
A-20
TABLE A-17
EFFECT OF SURFACTANTS - WARDS ISLAND BATCH A
Oil: #4-Heating Oil. Oil/Sludge Ratio i- 12 Suspended Solids in Feed: 1.5%
i
Settling Temperature: 25"C for 1-5 hrs, Then 80°C for 5-22 hrs.
Mixing: 60 seconds, 350 RPM Turbine
Concentration Factors
(2)
Surf act ant v '
None
1% Triton X-15
5% Triton X-15
1% Tallene
1% Armeen T
1% Span 85
2% Armoflo 49(3)
1% Atmos 300
1% Paranox 24
1% Oleic Acid
1
1.2
1.2
1.3
1-3
1.3
1.2
1.3
1.2
1.1
1.2
Hr.
- 10
- Trace
- 1
^
- Tr.
- Tr.
- Tr.
- Tr.
- Tr.
- 5
5 Hrs.
1.5
1.5
1.5
1.6
1.5
1.4
1.6
1.5
1.5
1.6
22 Hrs.
3.1
13
13
3.1
3.4
3.1
3.1
3.1
3.3
3.1
(1) First number - concentration factor, 2nd value = cc
sediment; 10 cc * 5% of feed solids.
(2) Surfactant dosage based on oil; 1% dosage in oil -
0.1#" Surfactant/1.0* Sludge Solids.
(3) 1% active amine.
-------
TABLE A-18
EFFECT OF SLUDGE
JjH ON CONCENTRATION (pH 4*
Concentration Factor (3)
Sludge (1)
L.F.-B
L.F.-C
W.I. -A
W.I. -A
W.I. -A
W.I.^A
% Susp
Solids Oil
1.7 #4 HO
#1 Varsol
2.1 #4 HO
#4 HO
LOPS +
Varsol'
1.5 #4 HO
LOPS
1.5 #4 HO
#4 Varsol
1.5 #4 HO
#4 Varsol
1.5 #4HO
" J-i ;-'." ."
Average
pH 6.5 - 7(4)
1 hr. 16/20 hrs.
1.6 3.6
1.5 2.9
1.9(8) 6.0
2.0
2.1
1.6 .2.3
1.5 2.1
2.6(17)
3.0(37)
2.3(30)
2.3(5)
1.9(10) 3.7
2.0(18) " 3.6
pH 4.0
1 hr. 16/20 hrs.
2.2 3.8
1.8 2.9
3.0(10) 6.0
2.3
2.5
1.9 3.7
1.9 3.3
2.6(3)
4.0(22)
2.3(10)
2.3(10)
1.6(5) 3.3
2.4(10) 3.9
(1) L.F. » Bergen County, W.I. = Wards Island.
(2) Averaged results for 1/2 factorial.
(3) Number in parenthesis cc sediment for 150 cc feed; 10 cc sediment
solids; where no sediment shown, value <1 cc.
(4) pH of sludge before acidification.
7% of initial feed
Ni
-------
TABLE A-19
EFFECT OF INITIAL SLUDGE pH ON CONCENTRATION (pH 3)
#4 Heating Oil, pump mixing, 0.2 Oil/Sludge ratio
- Solids in Concentrate
Sludge % Suspended
Batch Solids in Feed
Wards 0.49
Island - D
0.49(1)
v
1.7
Bergen 2.2
County - K
Settling
Temp. °C.
80
80
80
40
40
80(2)
Settling
Time-hrs
1
5
21
1
5
21
1
5
21
1
5
21
Improvement with
Ave.
pH 3/pH
% Solids in
pH 6.7
3,3
7.2
7.8
3.6
7.8
8
3.1
4.9
6.7
3.9
6.4
9.9
pH 3 sludge vs
6.7: 1 Hr. 1
5 Hr. 1
21 Hr. 1
Concentrate
pH 3.0
5.6
9.6
9.6
4.4
8.2
8.2
4.0
7.4
7-7
4.1
7.3
12.2
pH 6.7
.33
.25
.15
Ratio
pH 3.0/6.7
1.7
1.33
-: 1.23
1.23
1.05
1.0
1.29
1.50
1.15
1.06
1.14
1.23
I
(1) Repeat run next day.
(2) Settling temperature raised to 80°C after 5 hours.
-------
A-23
TABLE A-20
Susp.
Solids
0.49
1.75
TC LOSSES IN RAFFINATE
Activated Sludge
Special
Conditions
pH 3.0
H20 removal
after 2 , 6 hrs
pH 3.0
H20 removal
at 4 hrs.
H20 removal
after 5 hrs
(3)
Settling
Temp . Time
*C Hrs.
50 2
6
20
80 2
6
20
80 2
6
20
80 2
6
20
50 2
6
20
80 2
5
19
80 2
20
50 2
5
19
Total(2>
Carbon
PPM
78
142
240
174
340
570
306
325
310
226
1140
2310
126
370
1230
813
1035
1200
545
2390
285
650
2600
Feed C in
Raffinate-%
1.3
5.1
9.0
6.5
15.0
20.5
14.2
17.5
15.7
9.7
12.1
15.5
0.4
3.0
11.8
7.0
9.9
13.4
5.3
10.1
1.4
5.1
12.4
(1) In sludge feed.
(2) In raffinate.
(3) All runs with pump mixing, #4 H.O., oil/sludge ratio
(4) Based on total carbon in sludge solids.
0.2
-------
TABLE A-20 (Continued)
LF-I Activated Sludge (
TC LOSSES
!3)
IN RAFFINATE
Settling
% Susp.
Solids
0.52
2.1
1
1
1
Temp.
°C
40
60
80
40
60
80
Time
Hrs.
2
18
2
18
2
18
2
18
2
18
2
18
PPM
Total
Carbon
340
390
570
630
440
578
550
1500
1250
1265
1470
2022
Feed C in
Raffinate - %
10.1
13.1
12.0
26.2
16.2
24.1
1.8
8.5
6.1
17.8
10.2
19.2
-------
A-25
TABLE A-20 (Continued)
LF-K Activated Sludge
(3)
% Susp.
Solids
2.2
Special Conditions
staged temperature
settling
pH adjusted to 3.0
staged temperature
settling
Settling
Temp.
°C
40
40
80
80
40
40
80
80
40
80
Time
Hrs.
1.7
5.8
7.8
21
2
5.5
7.5
20.5
1.8
5.8
21
1.8
5.8
21
Feed C in
Raffinate -
4.8
6.4
8.3
11.5
4.8
5.7
7.0
9.7
4.9
6.3
8.0
8.1
11.5
13.9
-------
A-26
TABLE A-21
TC LOSSES IN BATffTMATI?
LF-G Activated Sludge (No Oil Controls)
% Solids
in Feed
_0il Mixing
PPM
Temp. Time Total % Feed C % Feed C
°C Hrs. Carbon in Raffinate Solubilized
0.55 none Waring Blender 80
0.36 none pump
1.82 none no agitation
1.82
none pump
25
25
25
1
2.8
21
1
3
21
1
3
21
1
3
21
410
730
950
52
135
220
255
285
535
310
400
910
17.4
34.7
48.7
3.3
10.0
16.6
(1)
(1)
22
40
52
4.2
11.4
18.0
4.3
4.7
8.0
5.2
6.7
15.2
(1) Solids did not separate to give raffinate phase.
Wards Island B - Activated Sludge
Settling
% Susp.
Solids
0.55
1.65
2.35
Oil
#4 H.O.
#1 Varsol
#4 H.O.
#1 Varsol
#4 H.O.
#1 Varsol
#1 Varsol
Mixing
Waring Blender
Waring Blender
Waring Blender
Temp.
°C
80
80
80
80
Time
Hrs.
20
20
7
20
7
20
1
1
20
PPM
Total
Carbon
410
480
730
1090
640
1430
920
1010
2180
% Feed C
in Raffinate
18.5
18.5
6
11
5
12
1.9
2.1
15.5
Wards Island A - Activated Sludge
1.5
#4 H.O.
#2 H.O.
#1 Varsol
#4 Varsol
#4 H.O.
LOPS
turbine
turbine
turbine
turbine
turbine
turbine
80
80
80
80
80
80
3
3
3
3
20
20
480
460
260
260
710
1180
5.8
5.6
3.1
3.1
9.5
12.9
-------
A-27
TABLE A-21 (Continued)
9 LF-D Activated Sludge
Settling
% Susp.
Solids
0.80
2.3
none'1'
none'1'
.80
.80
2.3
2.3
2.3
2.3
Oil
none
none
/MHO
#1
Varsol
#1
Varsol
#4HO
#4HO
#1
Varsol
#4HO
#1
Varsol
Mixing
Waring Blender
turbine
turbine
Waring Blender
Waring Blender
Waring Blender
Waring Blender
turbine
turbine
Waring Blender
Temp.
°C
80
80
80
80
25
80
25
25
80
80
time
Hrs.
1
22
1
22
1
22
1
22
1
22
1
22
1
22
1
20
1
20
1
22
PPM Feed
Total Feed C in Solubilized
Carbon Raffinate % %
260
540
815
1480
85
43
11
16
95
180
225
305
190
415
53
220
350
1020
325
860
6
16
4
13
mum
mm
2
4
6
9
1
4
0
0
3
10
2
8
.9
.1
A
.6
.5
mum
mm
-
.5
.3
.4
.1
.7
.3
.2
.9
.9
.8
.7
.8
8
18
10
19
3
6
7
11
3
5
0
2
4
13
4
10
.6
.4
.9
.7
.4
.1
.6
.1
.5
.6
.3
.9
.6
.9
.3
.4
(1) Supernate with solids removed by filtration.
-------
A-28
TABLE A-22
ANALYSIS OF CDRAY 37 RECYCLE OIL FftQM HERSHEY. PA.
ESSO RESEARCH AND ENGINEERING COMPANY
ANALYTICAL AND INFORMATION DIVISION P. O. BOX 121. LINDEN. N. J. 07036
J. W. HARRISON
P1RKCTOR
November 17, 1971
Dr. T. M. Rosenblatt
Government Research Laboratory
Building #1
Esso Research Center
Dear Ted:
Attached is a brief interpretation of the IR spectra of the
Coray oil used in your extraction studies. The bulk of the material in
the oil is a soap, probably calcium stearate. The spectra will be kept
on file for future use.
If I can be of further help, please call.
Very trul? yours,
JJE/bam
Attachment
cc: Messrs. R. E. Barnum
R. A. Brown
-------
A-29
TABLE A-22 (Continued)
ATTACHMENT
IR of used oil. Coray used in the reference beam.
- Organic acids (1715 cm )
- Organic esters (1748 cm )
- Soap (intense peak at c. 1570 cm )
- Strong broad band at 1100 cm"1 could be a C-O-C bond; Not
hydroxyl, for 3300 cm~l region only has a relatively weak
peak. Could also be due to inorganics (804", maybe P04*f)
Used oil diluted 10:1 with1 pentane, centrifuged, supernatant decanted
and precipitate washed with pentane.
- Precipitate (as KBr disk)
+ Calcium stearate
>
- Oil after 05 stripped
i
+ Similar to oil before dilution but with much weaker soap
peak.
After calcium stearate had been precipitated with pentane, the oil
still showed a peak at 1570 cm~l. The oil was then shaken with
dilute HC1, pentane added, the organic phase separated and dried, and
the pentane stripped. The IR of the oil showed a strong increase in
the 1715 cm organic acid band and the total elimination of the
1570 cm~l, showing this latter band to be due to a soap. In addition,
the 1100 cm'1 band also disappeared, again suggesting an inorganic
ion as being responsible for this absorption. Some general weak
absorption in the 1600-1700 cm~l now shows (lost in the broad soap
peak before) and this is probably due to some nitrogen-containing
species.
No work was done on the aqueous extract.
JJE/bam
11/17/71
-------
B-l
APPENDIX B
TABLE B-l
PILOT PLANT OPERATING PROCEDURE
SLUDGE TRANSPORT AND STORAGE
The 900-gallon sludge tank, mounted on the rented flatbed truck,
was filled at the sewage plant, returned to the pilot plant and allowed to
settle as required to obtain the desired sludge concentration. After settling,
the supernate was decanted off, the sludge recirculated with the process cen-
trifugal pump to provide mixing, and the volume required for a run pumped up
to the 300-gallon mixing tank. Mixing of the sludge tank contents by recircu-
lation was only partially successful, due to channeling of supernate thru the
settled solids; this presented no serious operating problems, but prevented
the degree of presettling desired for some runs.
FEED SLUDGE SAMPLING
After charging the prescribed run volume to the mixing tank, the
contents were agitated for 1 minute and samples taken from the top and bot-
tom (via dip samples and drainline, respectively) for 7, suspended solids.
Sludge volume was determined from a previously prepared tank calibration.
MIXING OF OIL AND SLUDGE FOR EXTRACTION
The oil to be used for the run was charged to the oil storage sys-
tem and recirculated thru an external steam-heated heat exchanger until the
oil temperature reached 240°F. The oil was then charged to the mix tank,
thru the heat exchanger, at 250°F, with the quantity charged determined from
the oil tank calibration curve.
The oil was charged to the sludge without agitation. After the oil
has been added, the tank contents are thoroughly mixed by agitating for 10
seconds before starting the process (transfer and mixing) pump. The process
pump is a Mar low open impeller centrifugal*, operating at 3460 RPM. Resi-
dence time in the pump was adjusted to~l/3-l/2 seconds, comparable to labo-
ratory operation, by adjusting the pump outlet throttle valve. The discharge
from the pump was fed to the 500 gallon settling tank.
i" 3-5# air pressure was put on the mixing tank during transfer to
maintain feed rate and to blow the lines. After emptying the tank, an addi-
tional 5 gallons of oil were charged and added to the batch in the settler to
clean the lines.
After completing the transfer, the oil and sludge lines were drained,
and the drainings weighed for use in the material balance.
* Same type as lab pump.
-------
B-2
SETTLING FOR SEPARATION OF WATER RAFFINATE
Before transfer the heat transfer fluid in the settler jacket
(Dowtherm A) was adjusted to 180°F and maintained at this temperature during
settling. Settling was continued for 21-26 hours for most runs, with the
settled water phase drained off periodically. The quantity of raffinate was
determined in a calibrated, agitated 40-gallon measuring tank and then
dumped to the sewer. The water collected in the measuring tank was sampled
(with agitation) to obtain a representative sample for analysis for each
sampling period. Raffinate temperature was measured in the measurement tank.
At the completion of the run, as determined by levelling off of
the raffinate volume-settling time curve, the oil sludge concentrate was
drained out of the settler into drums for weighing and storage prior to
shipment to Carver Greenfield. 25 grams of mercuric chloride (HgCl2)
were added as a perservative just prior to removal of the batch from the
settler.
-------
APPENDIX C
CARVER-GREENFIELD
Pilot
Plant
Run No. Sludge Type
1 Bergen County
Activated
2 "
3
4 Wards Island
Activated
5
6 Bergen County
Primary &
Activated
7 Trenton
Trickle
Filter
Hershey, Pa. primary &
secondary (4)
Bergen County, N.J.
Activated (4)
Oil
Used in Esso
Concentration
#4
#1
#4
#4
#1
#4
#4
Heating Oil
Varsol
Heating Oil
Heating Oil
Varsol
Heating Oil
Heating Oil
Coray 37
#2
Heating Oil
%
NFS in
Feed(D
6.5
5.1
4.8
4.3
4.0
7.2
5.0
5.0
1.32
TABLE C-l
HEAT TRANSFER TEST
1st Stage Concentration
Oil/ Oil/
Solids Product Source
Wt. Ratio Tenro.OF.
27/1
8.3/1
13.6/1
46.8/1
9.5/1
11.7/1
13/1
14/1
130
N.A. -
157-160
160-170
120-170
121-128
145-155
120
Temp.°F
150-160
unstable
203-208
180-190
148-152
145-155
170-175
/
140
RESULTS
Vacuum
Circula-
tion
Inches Hg Rate GPM
25
operation
17
17
25.5
26
21.5
26.5
low (3)
with rapid
low
low
low
low
low
Normal
Normal
Exchanger
Overall U Tube
Min. Max. AveW
22
49
Fouling
None
Varsol distillation
23
8.
41
19
8
93
75
32
8 37.5
60
52
33
122
186
None
None
None
None
None 9
1
M
None
None
(1) % Nonfat solids « % feed solids corrected for solvent extractable fraction; % solids in
water phase; Carver-Greenfield analysis.
(2) Design basis, representative of steady state conditions.
(3) Estimated at <2 gpm vs. normal 4.5-5.
(4) Samples directly from plant without prior treatment.
-------
TABLE C-2
CARVER-GREENFIELD HEAT TRANSFER TEST RESULTS
Pilot
Plant
Run No. Sludge Type
1 Bergen County
Activated
2 "
3 "
4 Wards Island
Activated
5 "
6 Bergen County
Primary &
Activated
7 Trenton
Trickle
Filter
Hershey, Pa. priamry &
secondary (4)
Bergen County, N.J.
Activated (4)
Oil %
Used in Esso NFS in
Drying Stage Concentration
Oil/ Heat Circula- Exchanger
Solids Product Source Vacuum tion Overall U Tube
Concentration Feed(D Wt. Ratio Temp.°F Temp.°F Inches Hg Rate GPM Min. Max. Ave^ Fouline
#4 Heating Oil
//I Var<5fi1
ir .1. vct^iauj.
#4 Heating Oil
#4 Heating Oil
#1 Varsol
#4 Heating Oil
#4 Heating Oil
Coray 37
#2 Heating Oil
.
240 ' 280-290 19 4.5 54 58 None
N A "}
240-250 240 18 4.5 33 45 None
229-240 260-280 19 4.5 75 97 None
235-244 262-271 19 .4.5 50 110 None
Not Run ft
i
Not Run
215 258 15 Normal 93 132 None
",;
215 260 15 Normal 93 130 None
>
(1) % Nonfat solids = % feed solids corrected for solvent extractable fraction; % solids
in water phase; Carver-Greenfield analysis.
(2) Design basis, representative of steady state conditions.
(3) Estimated at <2 gpm vs. normal 4.5-5.
(4) Samples directly from plant without prior treatment.
-------
TABLE C-3
DRY RECYCLE SOLIDS ADDED TO
1ST STAGE CONCENTRATION
PILOT PLANT % NFS OIL/SOLIDS
RUN NO IN FEED WT. RATIO
6A (1) 30 11.7/1
7A 30 13/1
DRYING STAGE CONCENTRATION
6A<1>
7A
PRODUCT
TEMP. °F
126
140
225-235
230
HEAT
SOURCE
TEMP. °F
150
160
275
260
VACUUM
INCHES Hg
265
26
19
19
REDUCE VISCOSITY
CIRCULA-
TION
RATE, GPM
LOW
4.5
4.5
4.5
OVERALL U
MIN. MAX. AVE.
42 66
32 75 60
52 72 60
132 210 160
EXCHANGER
xTUBE FOULING
None
None
o
(1) Batch decomposed during 8 week storage before test;
low U values associated with decomposition.
-------
C-4
TABLE C-4
ANALYSIS OF DRIED SLUDGE SOLIDS FROM CENTRIFUGE
"As is" (with oil) basis residual
PILOT PLANT
RUN NO
1
3
4
5
6
TYPE SLUDGE
BERGEN COUNTY ACTIVATED
BERGEN COUNTY ACTIVATED
WARDS ISLAND ACTIVATED
WARDS ISLAND ACTIVATED
BERGEN COUNTY PRIMARY TACT
WEIGHT %
OIL
46.7
47.7
40.7
40.0
44.3
WATER
1.8
1.0
1.8
2.8
0.9
Oil free basis
PILOT PLANT
RUN NO
1
3
4
6
WEIGHT %
ASH
46.7
47.4
39.9
47.3
C
25.8
25.2
29.9
37.9
H
3.8
3.8
4.3
5.5
W
4.6
4.5
4.0
4.9
HEATING VALUE, BTU/f
GROSS NETW
4,856
5,245
4,509
4,853
(1) Gross BTU/# corrected for hydrogen according to procedure
in ASTM D-2382.
-------
C-5
TABLE C-5
ANALYSIS OF RECYCLE OIL
PILOT PLANT WEIGHT % VISCOSITY,
RUN NO. WATER NON FAT SOLIDS SSU (100
1 <0.1 2.7 115.9
3 " 1.9 115.4
4 " 2.2
5 " 2.4
6 " 2.0
7 " 2.2
(1) Eresh oil viscosity = 73.1 SSU (100°F)
-------
C-6
TABLE C-6
TEST DATA FROM
CARVER GREENFIELD CORPORATION
-------
CARVER-GREENFIELD CORPORATION
"Test Data"
Customer:
Date :
Run (customer).! /
Carver-Greenfield f
Raw Feed:
Oil Used Fbr Drying:
RAW FEED:
Oil Present In Raw Feed:
%H20
2Z3
%Solids
3*3&
%0il
&#,£>
Ph
^./
Oil/NFS As Is
J?^V
Oil/NFS As Feed
J7S/
Viscosity
/V^l«3*>/?X
Particle Size
s*//?*?
Remarks
x^/Kf ~ ^-^J^
NFS
%D.esign
STAGE EQUILIBRIUM CONDITION
%H20 %Solids
Oil/NFS
^?7/ /
Product
Temp. °F.
/&>
Vac.
11 Hg.
0
Overall Heat Trans.
Min.
££
Max.
?v
Avg.*
Ci re. Rate
GPM
^0»S
Vise.
//^X
Fouling
SSCwt?
Act.
Evap.
Rate
-
Distillate
Ph
#7
Odor
&,?#s
sV/Sg
COD
-
%0il Vo.
3&*V*£'
NFS
%Design NFS
c?^* STAGE EQUILIBRIUM CONDITION
%Actual. %H20 %Solids
Oil/NFS
Product
Temp'. °F.
£40
Vac.
"Hg.
/9
Heat Source
Temp.°F.
200-270
Overall Heat Trans.
Min.
&4
Max.
*tff
Avg.*
.
Circ.Rate
GPM
4.5
Vise.
££>*!/
Fouling
/Wf
Act.
Evap.
Rate
-
Distillate
Ph
^7
Odor
fZwot
M&S
*l*r/Z.j>
COD
-
%0il VoJ
£e>+v*e
NFS
%Design NFS
STAGE EQUILIBRIUM CONDITION
%Actual %H0%Solids
* Design Average
Oil/NFS
Product
Temp.°F.
Vac.
"Hg.
Heat Source
Temp. °F.
Overall Heat Trans.
Min.
Max.
Avg.*
Circ.Rate
GPM
Vise.
Fouling
Act.
Evap.
Rate
Distillate
Ph
Odor
COD
%0il Vo]
Remarks :
Page
Of
-------
CARVER-GREENFIELD CORPORATION
"Test Data"
Custo~er:
Date :
Run (customer)!
DEHYDRATED
SLURRY
Carver-Greenfield
GRAVITY THICKENED
Oil/Solidsi % H20
Time Period #1 j Time Period #2
% Vol.
Time 1 % Vol.
!
!
Time
Time Period S3
% Vol.
Time
Time Period 14
% Vol.
Time
Tenro.
Maintained
°F.
CENTRIFUGE: Temp..*b*? °F. Type &" G's 30G6 Rate ^ f^^
% Solids
^.«r
%H20
*«f
,0,,
/<£
Fraction Of Oil
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Pool Depth
RECYCLE OIL:
PRESSING SOLIDS:
% Solids
Vol.
wt.
3.7
Fraction Of Oil
"10% '
20%
30%
40%
50%
'60%
70%
80%
90%
100%
HYDROEXTRACTION : Prod, in Temp.
PRODUCT: Prod, out Temp.
F.
Pressure
Blowing Steam Rate
°F. Production Rate
Heat Source Temp.
% Oil % Sol. % H20
Fraction Of Extractent
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Remarks:
Distillate
Fraction Of Extractent
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Page
Of
o
oo
Temp °F.
Rate
% Oil
% H2O
'P.
-------
CARVER-GREENFIELD CORPORATION
Customer:
Present In
Viscosity
^
Date : '/iTfS/72
Raw Feed: ^xx^^^ey /c3cs-si"F7-*&?
Raw Feed : z?2if'*<&&!?e*'f {ZJ'6
Particle Size Remarks
i
i
NFS
%Design NFS 7<0
/j> STAGE EQUILIBRIUM CONDITION
%Actual %H0%Solids
1
Oil/NFS I Product
1 Temp.°F.
I
i
i
Vac.
"Hg.
Heat Source
Temp. °F.
Overall Heat Trans.
Min.
$
Max.
^
Avg.*
Circ.Rate
GPM
Vise.
Fouling
Act.
Evap.
RatS
Distillate
Ph
Odor
COD
%0il Vo
I
NFS
%Design NFS
STAGE EQUILIBRIUM CONDITION
_%Actual %H2O %Solids
Oil/NFS
Product
Temp.°F.
Vac.
"Hg.
Heat 'Source
Temp.°F.
Overall Heat Trans.
Min.
Max.
Avg.*
Circ.Rate
GPM
Vise.
Fouling
Act.
Evap.
Rate
Distillate
Ph
(.£
Odor
jOf-ftf*
3A&«rtz>
S&/SS0
COD
f
%0il Vo
NFS
%Design NFS
STAGE EQUILIBRIUM CONDITION
_%Actual %H2O %Solids
* Design Average
Oil/NFS
Product
Temp.°F.
Vac.
"Hg.
Heat Source
Temp.°F.
Overall Heat Trans.
Min.
Max.
Avg.*
Circ.Rate
GPM
Vise.
Fouling
Act.
Evap.
Rate
Distillate
Ph
Odor
COD
%0il Vo
Remarks:
Page / Of
-------
CARVER-GREENFIELD
Cus tome r:
"Test Data"
Date:
Run (customer)
DEHYDRATED
Carver-Greenfield #
SLURRY
Oil/Solids
% H20
-
GRAVITY THICKENED
Time Period #1
% Vol.
Time
Time Period #2
% Vol.
Time
Time Period 13
% Vol.
Time
Time Period #4
% Vol.
Time
Temo.
t-laintained
°F.
CENTRIFUGE :
_._i'i n
% .Solids
%H20
Temj
MH^^^WMOAVVBH
%0il
3. . °F. Type G's
_^WBHH*M»>_~««^^_
Fraction
10%
20%
Rate
Of Oil
30%
40%
50%
60%
70%
80%
90%
100%
Pool Depth
RECYCLE OIL:
PRESSING SOLIDS:
% Solids
Vol.
Wt.
Fraction Of Oil
10%
20%
30%
40%
50%
. 60%
70%
.,
80%
90%
100%
HYDROEXTRACTION; Prod, in Temp. °F. Pressure
Prod, out Temp. _°F. Production Rate
Blowing Steam Rate
Heat Source Temp.
Distillate
Fraction Of Extractent
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Page
Of
n
I
Temp °F.
Rate
% Oil
% H20
'F.
% Oil % Sol. % H20
Fraction Of Extractent
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Remarks :
-------
CARVER-GREENFIELD CORPORATION
"Test Data"
Customer:
Date:
Run (customer) f
Oil Used For Drying:
RAW FEED:
Carver-Greenfield # &
Raw Feed ;
Oil Present In Raw Feed:
%H20
£7.5
%Solids
e ?/
%0il
39.7
Ph
6-3
Oil/NFS As Is
/3.s .: /
Oil/NFS As Feed
/*.<£ / /
viscosity
Particle Size
^/sT&si^
Remarks
xx^-r- +.f3%
/sS, STAGE EQUILIBRIUM CONDITION
NFS %Design NFS 7-& %Actual %H20 %Solids %0il
I
Oil/NFS Product
Temp.°F.
i
Vac.
"Hg.
/7
Heat Source
Temp. °F.
*****
Overall Heat Trans.
Min.
&
Max. .
J*
Avg.*
Circ.Rate
- GPM
^ &0&0/' //? /&: ^T&l&f^.
, ., ... pa^
je / Of f
-------
CARVER-GREENFIELD CORPORATION
"Test Data"
Cus tome r :
Date:
72
Run (customer)#
DEHYDRATED
SLURRY
Carver-Greenfield #
GRAVITY THICKENED
Oil/Solids
//.*.'/
% H20
TX&C-f
Time Period 11
% Vol.
Time
Time Period #2
% Vol.
Time
Time Period #3
% Vol.
Time
Time Period #4
% Vol.
Time
Temo.
Maintained
°F.
CENTRIFUGE; Temp.
F. Type
G's
% Solids
*9.e
mmMiiiimimmmmmiiimm
%H20
/*
I
s?.e
Fraction Of Oil
10%
20%
-
30%
40%
50%
60%
70%
80%
90%
100%
Rate &<£fp*7 -Pool Depth
RECYCLE OIL:
PRESSING SOLIDS:
% Solids
Vol.
wt.
/.?
Fraction Of Oil
10% '
20%
30%
40%
50%
. 60%
70%
80%
90%
100%
HYDROEXTRACTION; Prod, in Temp.
Prod, out Temp
"F.
Pressure
Blowing Steam Rate
"F. Production Rate
Heat Source Temp.
Distillate
Fraction Of Extractent
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Page
Of
L
IS5
Temp °F.
Rate
% Oil
% H2O
% Oil % Sol. % H20
Fraction Of Extractent
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Remarks :
-------
CARVER-GREENFIELD CORPORATION
"Test Data"
Customer:
Date:
Sun {customer)^ £
Oil Used For Drying:
RAW FEED:
Raw-Feed:
Carver-Greenfield I <3> & /^rs?4.
Particle Size
^&^S?JL4-
Remarks
/«?*& - -*'- %Actual
Vac.
11 Hg.
/?
Heat 'Source
Temp.°F.
**>-«»?
%H'2O %Solids %Oil
* -v
Overall Heat Trans.
Min.
75
Max.
97
Avg.*
Ci re. Rate
GPM
**
Vise.
*»,
Fouling
"+*r
Act.
Evap.
Rate
Distillate
Ph
&*&
Odor
*
COD
'
%0il Vo2
STAGE EQUILIBRIUM CONDITION
* Design Average
NFS
%Design : NFS
%Actual
%H20_
%Solids
Oil/NFS'
-
Product
Temp.'F.
Vac.
"Hg.
Heat Source
Temp.°F.
Overall Heat Trans.
Min.
Max.
Avg.*
Ci re. Rate
GPM
Vise.
Fouling
Act.
Evap.
Rate
Distillate
Ph
Odor
COD
%Oil Vol
Remarks:
Page _/ Of &
-------
"Test Data"
Customer: ^tr-
Date:
Run (customer)#
DEHYDRATED
SLURRY
Carver-Greenfield g
GRAVITY THICKENED
Oil/Solids
/7.V
% H20
~71i?s?(?£-
Time Period 11
% Vol.
Time
Time Period 12
% Vol.
Time
Time Period #3
% Vol.
Time
Time Period 14
% Vol.
Time
Terno.
Maintained
°F.
CENTRIFUGE:
^ °F. Typex^/*3P G's Jbexs Rate
% .Solids
£%0
%H20
/
-------
CARVER-GREENFIELD CORPORATION
"Test Data"
Customer:
Date:
Run (customer)^ ^
Oil Used For Drying:
.RAW FEED:
Carver-Greenfield £
Raw Feed:
Oil Present In Raw Feed:
%H20
72
%Solids
283
%0il
£7./7
Ph
6.7
Oil/NFS As Is
9.S ' t
Oil/NFS As Feed
9.5 '/
Viscosity
40tV
Particle Size
i5/v/7,9ZX.
Remarks
s
/Vie? - 3- 95"%
NFS
%Design NFS
_/** STAGE EQUILIBRIUM CONDITION
%Actual %H0%Solids
Oil/NFS
Product
Temp. °F.
/£0-/40
Vac.
11 Hg.
tt?
Heat Source
Temp.°F.
ste- s£2
Overall Heat Trans.
Min.
^
Max.
tfP
Avg.*
Circ.Rate
GPM
^&tv
Vise.
+?
-------
Customer:
"Test Data"
Date:
Run (customer)!
DEHYDRATED
SLURRY
Carver-Greenfield #
GRAVITY THICKENED
Dil/Solids
£>
-------
CARVER-GREENFIELD CORPORATION
"Test Data"
Cus tome r:
Run (customer)S 7_
Oil Used For Drying:
RAW FEED:
Carver-Greenfield
Raw Feed:
Oil Present In Raw Feed:
%H20
5 a 3
%Solids
3-74
%0il
43.96
Ph
Oil/NFS As Is
//- 7 : /
Oil/NFS As Feed
//.7 ' /
Viscosity
Xf^E'/t-T^X
Particle Size
£fss?/94.4.
Remarks
NFS
_%Design NFS
^ STAGE EQUILIBRIUM CONDITION
%Actual %H20 %Solids
Oil/NFS
-
Product
Temp. °F.
/£/-/<*&
Vac.
"Hg.
e&
Heat Source
Temp.°F.
/^^- /&£~
Overall Heat Trans.
Min.
/?
Max.
#?
Avg.*
o
Ci re. Rate
GPM
^0*'
Vise.
6^/f
Fouling
MbV£"
Act.
Evap.
Rate
Distillate
Ph
Odor
COD
%0il Vo
NFS
%Design NFS
STAGE EQUILIBRIUM CONDITION
%Actual %H0%Solids
Oil/NFS
Product
Temp.°F.
Vac.
"Hg.
Heat 'Source
Temp.°F.
Overall Heat Trans.
Min.
Max.
Avg.*
Circ.Rate
GPM
Vise.
Fouling
Act.
Evap.
Rate
Distillate
Ph
Odor
COD
%Oil Vo
NFS
%Design NFS
STAGE EQUILIBRIUM CONDITION
%Actual %H0%Solids
* Design Average
Oil/NFS
Product
Temp.°F.
Vac.
"Hg.
> Heat Source
Temp. °F.
Overall Heat Trans.
Min.
Max.
Avg.*
Circ. Rate
GPM
Vise.
Fouling
Act.
Evap.
Rate
Distillate
Ph
Odor
COD
%0il Vo
Remarks:
-TOO
Page / Of
-------
CARVER-GREENFIELD CORPORATION
"Test Data"
Customer:
Date :
Run (c us toner)#
Oil Used For Drying:
RAW FEED:
Carver-Greenfield t
Raw Feed:
Oil Present In Raw Feed:
%H20
523
%Solids
3.74-
%0il
43. 9&
Ph
Oil/NFS As Is
//.?'/
Oil/NFS As Feed
//. ?'/
Viscosity
/J/23^*^Z
Particle Size
S**#sU.
Remarks
NFS *£ %Design NFS
£7T STAGE EQUILIBRIUM CONDITION
%Actual %H2O %Solids
Oil/NFS
Product
Temp. °F.
/6/s&
Act.
Evap.
Rate
Distillate
Ph
7.7
Odor
t&a/.
*#3
COD
%0il Vc
NFS
%Design NFS
STAGE EQUILIBRIUM CONDITION
%Actual %H2O _ %Solids _
%0il
I
00
Oil/NFS
Product
Temp.°F.
gfy-<2Z5
Vac.
"Hg.
/e>
Heat Source
Temp.°F.
£73
Overall Heat Trans?*
Min.
&z
Max.
7Z
Avg.*
&&
Circ.Rate
GPM
/.i5
Vise.
460V&/-
Fouling
/*^>/Klf
Act.
Evap.
Rate
Distillate
Ph
£45
Odor
#7Z»t
&£/*
COD
%0il Vo
NFS
%Design NFS
STAGE EQUILIBRIUM CONDITION
_%Actual %H2O %Solids
* Design Average
Oil/NFS '
Product
Temp.°F.
Vac.
11 Hg.
Heat Source
Temp. °F.
Overall Heat Trans.
Min.
Max.
Avg.*
Circ.Rate
GPM
Vise.
Fouling
Act.
Evap.
Rate
Distillate
Ph
Odor
COD
%Oil Vo
Remarks :
Page
Of -3
-------
CARVER-GREENFIELD CORPORATION
"Test Data"
Custoner:
Date:
Run (customer)f
DEHYDRATED
SLURRY
Carver-Greenfield f
GRAVITY THICKENED
Oil/Solids
SV&>r s&£SS/
% H2<3
Time Period 11
% Vol.
Time
Time Period 12
% Vol.
Time
Time Period 13
% Vol.
Time
Time Period §4
% Vol.
Time
. Temp .
raaXn uainSQ
8F.
1
CENTRIFUGE: Temp. f&& °F. Type £f00 G's 3&o<9 Rate gcf/W
% Solids
S4.*
%H20
.9
.on
*<#£
Fraction Of Oil
10%
20%
30%
40%
5Q%
60%
70%
80%
90%
100%
Pool Depth -
RECYCLE OIL:
PRESSING SOLIDS:
% Solids
Vol.
wt.
-------
CARVER-GREENFIELD CORPORATION
"Test D£-a"
Cuszcr.er:
Date:
Run (customer)? ^
Oil L'ssd For Drying:
RAX FEED:
Carver-Greenfield =
Raw Feed:
Oil Present In Raw Feed:
i !
?H20 ; ISolids %0il Ph i Oil/NFS As Is
59.O \ 2.13 3S.3 73 \ /J-V
i ' ;
! Oil/NFS As Feed j Viscosity Particle Size
/3.V
\
Remarks
/$r STAGE EQUILIBRIUM CONDITION
NFS %Design NFS &*<£ %Aci;ual %HsO %Solids %0il
''il/NFS ?rnr'1'ct Vac, He^t Source _ ve
"J"t/"i" : Temp.°F. "Hg. Temp.°F; Mi
/45-/S5 2/-5 /7O-/75 £
\
rail Heat Tran
n . Max . Avg
S3
s- rirf- pat« v- It- i- 1°
.* GPM T Ra
^ .*** M»*
c~ STAGE EQUILIBRIUM CONDITION
NFS %Design NFS %Actual %H50 %Solids %0il
t. Distillate
te' Ph Odor COD %0il Vol.
I
0
3i I/NFS ! Product
Temp.°F.
i
Vac.
"Hg.
Heat Source
Temp.°F.
. -
Overall Heat Trans.
Min.
Max.
Avg.*
Ci re. Rate
GPM
Vise. pouling
i
!
i
Act.
Evap.
Rate
Distillate
Ph
Odor
COD
%0il Vol.
NFS
%Design NFS
STAGE EQUILIBRIUM CONDITION
_%Actual %H2O %Solids
* Design Average
Overall Heat Trans.
Mm. I Max. Avg.*
Ph Odor COD %0il Vol
Remarks:
Page / Of 3
-------
CAHVEH-GREENFIE'LD CORPORATION
"Test £a~a
Customer:
Date:
Run (custc-er) $
Oil Used Fcr Drying:
RAW FEED:
Carver-Greenfield #
Raw Feed:
Oil Present In Raw Feed:
*H2O
&0
%Solids ; %0il
e. 93 \ 38.3
\
Ph j Oil/NFS As Is
i
73 \ /3'/
Oil/NFS As Feed
f^i « j
.. /3:f
Viscosity
4&&vr&iL
Particle Size
z5s
to
Oil/NFS I Product
1 Temp . F .
\- £30
Vac.
"Hg.
/9
Heat Source
Temp. °F.
2GO
Overall Heat Trans.
Min.
/3£
Max.
Vise.
t^a^y/.
Fouling
/v&+/e
Act.
Evap.
Rate
Distillate
Ph
Odor
COD
%0il Vo!
NFS
%Design NFS
STAGE EQUILIBRIUM CONDITION
_%Actual %H2O %Solids
* Design Average
%oir
Oil/NFS
Product
7emD.°F.
Vac.
"Hg.
Heat Source
Temp. °F.
Overall Heat Trans.
Min.
Max.
Avg.*
Circ.Rate
GPM
Vise.
4l^^^^HHMIIIBIBBBHflBBIBHI
Fouling
HHVVWIVIVHIHVVHtH^HBBMVIIII
Act.
Evap.
Rate
HBHHBI^BHHII^H^HIIIHI
Distillate
Ph
^^^^(MVM
Odor
^H^P^B^PW^^
COD
%oii vo:
-^^^^^^H
Remarks:
30% ^
7c>
Page £ Of
-------
CARVER-GREEN t'ltLU
"Test Data"
Customer: <~
Date:
Run (customer)%
DEHYDRATED
Carver-Greenfield #
SLURRY
Oil/Solids
% H20
GRAVITY THICKENED
Time Period #1
% Vol.
Time
Time Period #2
% Vol.
Time
Time Period #3
% Vol.
Time
Time Period #4
% Vol.
Time
Temp.
! \? a ^ Vfc^^-i *\ s\ A
r Mamtaznea
°F.
CENTRIFUGE: Temp, /fc*? °F. Typex5/^^ G's J'
-------
D-l
TABLE D-l
ENGINEERING, LEGAL AttD ADMINISTRATIVE COST VS PLANT INVESTMENT
Total Construction
Cost $MM (1)
.2
.5
1.0
2.0
3.0
4.0
5.0
. Total
HF-^
^*fi*^f
36
70
120
200
270
340
410
i
Engineering Cost (2)
"^^l^s^^^'*^W^T*'"?rr £-.; -V1*. ' ' "I "I*IJ^* "
18
14
12
10
r 9
8.5
8.2
Legal, Fiscal
and Administrative
-J8L
5.2
9.2
14
22
27
31
35
Combined
(3)
2.6
1.8
1.4
1.1
0.9
0.8
0.7
41.2
79.2
134
222
297
371
445
% of
Construction
20.6
15.9
13.4
11.1
9.9
9.3
8.9
(1) Construction rcost * installed cost
(2) Ref. f pg. 55 for complete ' plant
(3) Kef. pg. 57
-------
TABLE D-2
CAPITAL COSTS FOR ESSO OIL CONCENTRATION PROCESS
SLUDGE PRKTHICKBNH1B - FINAL SETTLING AT 175°F
Raw
Influent
MOD
12.5
37.5
250
Secondary
Waste
Sludge
MCD
(1)
.225
.675
4.5
Concentrate Surge
Secondary Waste
Solids Sludge
Ions /day Settling
(2) (3)
4.72 Fastest
Median
Slowest
14.16 Fastest
Median
Slowest
94.5 Fastest
Median
Slowest
Thickened Thickener Design Oil Sludge
Sludge Surface
MOD Area-ft2
(4)
.075 905
2,360
3,780
.225 2,710
7,080
11,350
1.5 18,050
47,300
76,600
Installed Mixer
Cost $MM Costr$MM H.P.
(4a) (5)
.046
.068 .0046 2
.088
.074
.125 .0064 3
.173
.248
.550 .0085 6
.840
Concentration
Factor (6a)
8
6
4
8
6
8
6
4
Oil-Sludge Heating (6)
Exchange Boiler Fuel Costs
Cost-$MM CCa*f$MM $/Ton Solids
3.75
.015 .012 4.50
5.15
3.75
.029 .020 4.50
5.15
3.75
.090 .065 4.50
5.15
Oil-Sludge
Settler
Cost-$MM
(7)
.105
tl
II
.200
II
II
.843
"
ii
Tank
Cost $Mtf
m~
.025
.026
.028
.037
.042
.049
.164
.177
.207
Motor
H.P.
2
2
3
4
5
6
10
11
12
Process Oil
Storage - $MM
Tank Oil
(9) (10)
.0106 .0025
.0230 .0075
.0700 .050
Process Punps
Cost $MM H.P.
.028 18.5
.042 41
.110 193
1) 1.8% of influent.
2) 0,5-.6% suspended solids in waste sludge.
3) Sludge thickened to 1.5%.
4) Calc. from batch setting data and Kynch Method.
4a) Cost data in Appendix D-4.
5) In-line type, high shear.
6a) Equivalent to 5 hrs at 105°F and 15 hrs at 175°F.
6) Heating from 1Q5°F to 175°F before 3rd stage settling.
7) 3 stage settling; see Appendix D-5 for details.
8) 24 hour holding capacity of oil sludge concentrate for evaporation;
includes agitator; CarverGreenfiedl design requirement.
9) Requirement for 12 hour reserve inventory.
10-) Oil cost at $0.11/gal; 24 hr. process inventory + 12 hr. reserve.
-------
TABLE D-3
COST ESTIMATE FOR ESSO OIL CONCENTRATION PROCESS
SLUDGE PRETHICKENING - FINAL SETTLING AT 175°F
Plant Size Process Operation
Raw Sewage Secondary ' Sludge
Influent Solids Thickening
MGD Tons /Day Rate
12.5 4.72 Fastest
Median
Slowest
37.5 14.12 Fastest
Median
Slowest
250 94.5 Fastest
Median
Slowest
Final
CnllHs
Content
Max.
Median
Min.
Max.
Median
Slowest
Max.
Median
Slowest
Investment - $MM
Installed
.250
.273
.295
.439
.495
.550
1.65
1.96
2.28
TIE .(1)
.322
.351
.380
.552
.623
.694
2.00
2.38
2.76
HP frt-r
$MM/Ton Motors
.0682
.0744 22
.0804
.0389
.0440 49
.0481
.0212
.0252 210
.0292
Capital
13.25
14.45
15.60
7.55
8.55
9.35
4.10
4.90
5.68
Maintanence
9.35
10.20
11.00
5.34
6.03
6.60
2.90
3.45
4.00
Costs - $/Ton Feed Solids
Insurance
1.87
2.05
2.21
1.07
1.21
1.33
.59
.63
.821
Power Fuel
3.75
.67 4.50
5.15
3.75
.50 4.50
5.15
3.75
.32 4.50
5.15
Labor + Total
Overhead TC Loss Total
14.86 4.37 48.12
" 51.10
" " 53.86
4.84 " 27.42
" 30.00
" 32.14
1.49 " 17.5
19.7
" " 21.8
(1) Summation of installed equipment cost, - 10% contingency, engineering + legal + adminstrative (see Table D
(2) Based on Chicago influent BOD charge and recycle factors as detailed in Attachment
(3) Based on 25% total TC recycle; includes both settling and evaporation steps.
(4) 1/2 man/shift for 4.72 and 14.12 T/D plants, i man/shift for 94.5 T/D plant.
for factors).
-------
D-4
TABLE D-4
COST OF SLUDGE THICKENERS AND OIL-SLUDGE SETTLERS
Surface Area
1000 ,ft2
1
2
5
!0
20
40
60
80
100
Construction Costs
Jan 1971 (2)
41
55
91
140
240
430
600
760
920
- $M (1)
Spring
1972 (3)
43
62
102
157
269
482
674
853
1032
(1) Construction cost = installed cost
(2) Ref. 37 pg, 37
(3) Corrected for 12% inflation factor to March 1972,
based on Sewage Treatment Plant Construction Cost
Index, Ref. 41.
-------
TABLE D-5
INSTALLED COST OF OIL SLUDGE SETTLERS
Plant Size 1st Stage 2nd Stage
MGD Thickened Drum Cost Area Installed
Sludge . $MM (1) ', 1000 ft2 Cost-$MM
.075 .0052 . .782 .045
.225 .0134 2.34 .068
1.5 .0450 16.05 .223
'
Roof Total
Cost (2) Installed
.005 .050
.010 .078
.074 .297
3rd Stage '
Area Installed Roof Total
1000 ft2 Cost Cost Installed
1.35 .054 .006 .060
4.05 .091 .017 .108
27.70' .351' .150 .501
-r i ^
Combined
Settler Cost
Installed- $MM
.105
.200
.843
I
(1) Cost data from ref. - for drum settler, corrected for horizontal plates on basis of
cost data from Esso Engineering
(2) Cost data fvom Esso Engineering.
-------
TABLE D-6
COST ESTIMATE TOR CARVER GREENFIELD PROCESS
Plant Size Type X Solids
Raw Influent Sludge Solids Operation Operators in
HCD Tons/Day shifts/day per' shift Concentrate
(1) B>
.225 4.72 1 1 4.5
« 9.0
.225 4.72 3 1 . 4.5
6.0
9.0
4.5
9.0
.675 14.2 3 1 4.5
6».0
9.0
4.5
9.0
4.5
6.0
4.50 94.5 ,3 3 4,5
2 6.0
9.0
4.5
9.0
4.5
6.0
Evaporator Operation
Effects 0 Value
-THT-
3
it
3
ii
4
4
3
ii
ii
3
3
4
4
60(11>
it
60
ii
»
120
120
it
ii
it
120<12)
120
ii
ii
60
n
ii
120
120
1ZO
120
Total Installed & Erected Coat - $MM
Installed IK Sim/Ton/Day
(3)
.870
.630
.605
.575
.550
.572
.539
.870
.767
.630
.823
.590
.810"
.705
3.80
3.18
2.35
2.80
1.85
2.58
2.08
.883
.604
.615
.585
.560
.586
550
.883
.780
.640
.835
.600
.822
.716
3.83
3.21
2.38
2.83
1.87
2.61
2.10
.187-
.136
.130
.125
.119.
.123
.117
.0622
.0552
.0452
.0590
.0425
.0581
.0506
.0406
.0340
.0252
.0300
.0198
.0280
.0222
Capital
(4)
36.4
2&J
25.3
24.3
23.2
23; 9
22.8
12.1
10.7
8.76
11.5
8.26
11.3
9.85
7.90
6.61
4.90
5.48
3.87
5.45
4.32
Malntandice
25.6
18.6
17.8
17.1
16.3
16.9
16.0
8.52
7.56
6.18
8.08
5.82
7.96
6.95
5.56
4.66
3.45
4.12
2.73
3.85
4.32
Coats -
Insurance
(«
5.15
3.74
3.58
3.41
3.28
3.38
3.22
1.72
1.52
1.24
1.63
1.17
1.61
1.40
1.12
0.94
0.70
0.83
0.55
0.77
0.61
$/Ton Teed Solids
Total Labor Power
« »7 3'31
*'*7 2.02
3.32
29.70 2.87
2.84
2.50
2.84
3.31
9.87 2.87
2.02
2.50
2.02
2.54
2.30
4.47 3.30
2.87
2.02
2.97 2.50
2.02
2.25
2.20
(10)
4.45
(2.24)
4.45
2.20
(2.24)
4.45
(2.24)
4.45
2.20
(2.24)
4.45
(2.24)
(.16)
(3.04)
4.45
2.20
(2.24)
4.45
(2.24)
(.16)
(3.04)
Total
8A.78
58.49
84.15
79.58
73.08
80.83
72.42
39.97
33.72
25.83
38.03
24.90
33.12
27.32
26.80
20.25
11.80
20.35
9.90
15.13
10.10
(1-10) See attachment for description of footnote
-------
D-7
FOOTNOTES FOR TABLE D-6
1. Based on waste sludge - 1.8% of influent volume, with suspended
solids content of 0.50%.
2. Process operators specified by Carver Greenfield,
2a. Overall heat transfer coefficient, BTU/hr/ft2/OF.
3. Quotation from Carver Greenfield; complete erected cost, including
boiler; includes 10% contingency.
4. Based on interest and amortization for 25 years, 5% interest rate
on bonds.
5. 5% of total investment.
6. 2% of total investment.
i
7. Operating labor cost - $3.90/hr direct labor cost + 15% for
indirects - $4.50/hr.
8. Taken as 30% of operating labor.
9. Based on electric power cost Of $»010/kwh, and usage at 90% of
installed H.F.
10. Based on fuel oil cost of $.016/#. Where excess energy produced
from incineration, credited at equivalent fuel value; excess
heat denoted by ( ).
11. Value obtained from Carver Greenfield heat transfer studies on
Esso oil sludge concentrates.
12. Value assumed for low temperature settling, with no viscosity
limitation during evaporation.
-------
TABLE D-7
FUEL AND POWER REQUIREMENTS FOR CARVER GREENFIELD
EVAPORATION PROCESS (1)
Plant Size
Tons /Day Sludge
4.72
14.17
94.5
-
Weight %
Water in
Feed
4.5
9.0
4.5
9.0
4.5
6.0
4.5
9.0
4.5
Number of
Effects
3
it
U
ti
4
"
3
"
4
U
Value
60
"
»
it
120
"
60
11
120
Net Heating Total
Value of Horsepower
Sludge Solids Installed
4 110
94
" 31.8
20.0
220.8
" 13.61
4 25.2
" 20.1
148.7
;
Fuel Requirements
#/Day-(2)
1580
(495)
4750
(1490)
552
(2040)
32,100.
(7850)
3860
7
00
(1) Carver-Greenfield data.
(2) ( ) denotes excess energy expressed as fuel equivalent.
-------
D-9
TABLE
PRELIMINARY HEAT AND MATERIAL BALANCES FOR
THE CARVER GREENFIELD DEHYDRATION PROCESS
-------
D-10
DESIGN CRITERIA FOR
THE CARVER-GREENFIELD PROCESS
CUSTOMER
ESSO - EPA
MATERIAL TO BE DRIED
DATE May 8. 1972
PROPOSAL NO. 072-0077-1
REF. NO.
Rate of Feed 10,625
Lbs./Hr. Est. Hrs./Day Operation
24
ANALYSIS - FEED
Percent
Water 90.5
Solids 9.n
Oil in Feed .5
Recycle Oil Rate
Lbs./Hr.
9750
ANALYSIS - DRIED PRODUCT
Percent Lbs./Hr.
4.6 45
.18
89.0
6.4
875
60
Oil used for Fluidizing
Energy Requirements
Effect
team: 4.07 x 106 BTU/Hr.
Total Connected Horsepower
Sludge
Cooling Water: Thickening
Lbs./Hr. @
100
PSIG
199-1/2
Gals./Hr.
Ultimate Use of Solids Burn'as fuel .
Gals./Min.
Total Fuel Value of Solids @ 80% Boiler Efficiency 4.97 x 106 BTU/Hr.
Lbs.
Additional Fuel Required if Solids are for Fuel Value 58 Qacksi/Hr.
Total Fuel if Solids are Recovered
overage
Gals/Hr.
General Material of Construction of Equipment
Approx. Bldg. Space: Lg. 25 Ft., Wd. 30
Manpower Requirements 2J Hrs./Day
Carbon Steel
Ft., Ht. 75 Ft.
.. ,_ , , . , $450,000 Max. boiler cost
Estimated Sales Price (Uninstalled) S41QfQQQ Min. boiler- cost
Est. Install. Cost $200,000
" Stack Emission $10,000
SF-8
1 of 5
-------
D-ll
DESIGN CRITERIA FOR
THE CARVER-GREENFIELD PROCESS
CUSTOMER ESSn - EPA DATE May 8, 1972
MATERIAL TO BE DRIED PROPOSAL NO. 072-0077-2
REF. NO.
Rate of Feed 19.421 Lbs./Hr. Est. Hrs./Day Operation
_24
ANALYSIS - FEED ANALYSIS - DRIED PRODUCT
Percent Lbs./Hr. Pcrcont Lbs./Hr.
Water 4-1/2 18,646 4.2 49
Solids .95-1/2 875 75 875
Oil in Feed 20.8 240
Recycle Oil Rate
Oil used for Fluidizing
Energy Requirements
3 Effect
Steam: 7.78 x 106 BTU/Hr. Lbs./Hr. @ ___ 100 P<;iC
*' Total Connected Horsepower 318
Sludge
Cooling Water: Thickening Gals./Hr. Gals./Min.
Ultimate Use of Solids Burn for fuel
Total Fuel Value of Solids @ 80% Boiler Efficiency 4.97 a! 106 UTU/llr.
Lbs.
Additional Fuel Required if Solids are for Fuel Value 190 X2QaS%/llr.
Total Fuel if Solids are Recovered --- Gals/Hr.
General Material of Construction of Equipment Carbon Steel
Approx. Bldg. Space: Lg._35 Ft., Wd. 30 Ft., Ht .___70__Ft.
Manpower Requirements 24 Hrs./Day
$625,000 Max. boiler cost
Estimated Sales Price (Uninstalled)$565,000 Min. boiler cost
Est. Install. Cost $275,000
Est. Emission Cost $10,000
1 of 5
SF-8
-------
D-12
DESIGN CRITERIA FOR
THE CARVER-GREENFIELD PROCESS
CUSTOMER
ESSO - EPA
DATE
MATERIAL TO BE DRIED
PROPOSAL NO. JJ72-QQ77-3
REF. NO.
Rate of Feed
130,860
Lbs./Hr. Est. Hrs./Day Operation __2JL
ANALYSIS - FKED
Water
Solids
Oil in Feed
Recycle Oil Rate
Percent Lbs./Hr.
95-1/2 125,000 .;
4-1/2 5.860
ANALYSTS - DRIED PRODUCT
Percent Lbs./Hr.
270
3.3
12.^5....
24.2
Utf 5_
Oil used for Fluidizing
Energy Requirements
3 Effect
Steam:
52 x 106
BTU/llr.
Total Connected Horsepower
Sludge
Cooling Water: Thickening
2208
Gals./Hr.
Burn for fuel
Gals./Win
Ultimate Use of Solids
Total Fuel Value of Solids @ 80% Boiler Efficiency
Additional Fuel Required if Solids are for Fuel Value 1340
Total Fuel if Solids are Recovered
UTU/Ilr
Lbs.
Gals/Ur
General Material of Construction of Equipment
Approx. Bldg. Space: Lg. 90 Ft. , Wd.
Manpower Requirements
Carbon Steel:.
Ft., Ht.
95
H'rs./Day
$2,800,000 Max. Boiler cost
Estimated Sales Price (Uninstalled) $2,400,000 Min. Boiler cost
install. $1, 200^000
Est. Emission $40,000
SF-8
1 of 5
-------
D-13
DESIGN CRITERIA FOR
THE CARVER-GKHI-Nni I D PROCESS
CUSTOMER
ESSQ - K
MATERIAL TO BE DRIED
Rate of Feed 68,350
DATE
May 8., 1972
PROPOSAL NO
REF. NO.
Lbs./Hr. Est. Mrs./Day Operation
ANALYSIS - FEED
Percent Lbs./Hr.
ANALYSIS - DRIED PRODUCT
Percent I .bs . /Hr .
Water
Solids
Oil in Feed
Recycle Oil Rate
91
62^500
5,850
585.0.
138
Oil used for Fluidizing
Energy Requirements
3 Effect
Steam: 28.15 x 106
BTU/Hr.
Lbs./Hr.
100
Total Connected Horsepower
Sludge
Cooling Water: Thickening
1361
Ultimate Use of Solids
Gals./Hr.
Burn for fuel
Gals./Min.
Total Fuel Value of fiolicln @ 80't Boiler Kffieicncy 33 x J.Q6 I'.TU/lli .
Lbs. Excess
Additional Fuel Required if Solids are for Fuel Va 1 ue 327
Total Fuel if Solids are Recovered
Gals/Hr.
Par'hrm
Ft., Ht.
General Material of Construction of Equipment
Approx. Bldg. Space: Lg. 30 Ft. , Wd. 90
Manpower Requirements 48 Hrs./Day
$1,800,000 Max. Boiler Cost
Estimated Sales Price (Uninstalled) $1,500,000 Min. "
Est. Install. $700,000
Est. Emission $40,000
1 of 5
SF-8
-------
D-14
CRITL.RIA FOR
THt CARVER-GREENFIELD PROCESS
Oi::,TOMKU
MATKN1AI. 'I'O BI;: UK I Ml)
UATK May _§_,_1_972_..
PROPOSAL NO. 072-0077-5
REF. NO.
Rate of Feed
L42.3_
Lbs./Hr. Est. Hrs./Day Operation 24
ANALYSIS - FEED
Water
Solids
Oil in Feed
Percent Lbs . /ilr.
62QQ
ANALYSIS - DRIED PRODUCT
Percent I.fos./Hr.
94.5
4.5
3.8
15
293
.5
39
Recycle Oi1 Rate
Oil used for Fluidizing
74.5
21.7
as
Energy Requirements
3 Effect
Steam: 2.63 x 103
BTU/Hr.
Lbs./Hr. @
p sic;
Total Connected Horsepower
Heating up of
Cooling Water: sludge
110
Gals./Ilr.
Gals./Mi n.
Ultimate Use of Solids
Burn as fuel
Total Fuel Value of Solids @ 80% Boiler Efficiency 2.06 x 106 BTU/Hr.
Lbs.
Additional Fuel Required if Solids are for Fuel Value 44
Total Fuel if Solids are Recovered
Gals/Hr.
General Material of Construction of Equipment Carbon Steel
Approx. Bldg. Space: Lg. 20 Ft., Wd. 20 Ft., Ht. 75
Manpower Requirements 24 Hrs./Day
Ft.
$615,000 Max. boiler cost
Estimated Sales Price (Uninstalled)$595,000 Min. boiler cost
Est. Install. $195,000
Est. Emission $10,000
SF-8
1 of 5
-------
CUSTOMER
D-15
DESIGN CRITERIA FOR
THE CARVER-GREENFIELD PROCESS
DATE
May B, 1Q?2
MATERIAL TO BE DRIED
PROPOSAL NO. Q73-.nn77-.fi
REF. NO.
Rate of Feed
Lbs./Hr. Est. Hrs./Day Operation
ANALYSIS - FEED
Percent
Water 90,^
Solids 9.0
Oil in Feed j_5_
Recycle Oil Rate
Oil used for Fluidizing
Lbs./Hr.
29^0
293
39
ANALYSIS - DRIED PRODUCT
Percent Lbs./Hr.
86.7
9.0
39
Energy Requirements
3 Effect
Steam: 1.24 x 106
BTU/Hr.
Lbs./Hr. @
100 PSIG
94
Total Connected Horsepower
Heating up of sludge
Gals./Hr.
Cooling Water:
Ultimate Use of Solids
Gals./Min.
Burn as fuel
Total Fuel Value of Solids @ 80% Boiler Efficiency 2. nfi BTU/Hr.
Additional Fuel Required if Solids are for Fuel Value
Total Fuel if Solids are Recovered _ --
Gals/Hr.
Gals/Hr.
Ft.
General Material of Construction of EquipmentCarbon Steel
Approx. Bldg. Space: Lg. 20 Ft., Wd. 20 Ft., Ht. 20
Manpower Requirements 24 Hrs./Day
$560,000 Max. boiler cost
Estimated Sales Price (Uninstalled) S540fQQQ Min. boiler cost
Est. Install. $175,000
'* « - ' Est. Emission $10,000
1 of 5
SF-8
-------
D-16
DESIGN CRITERIA FOR
THE CARVER-GREENFIELD PROCESS
CUSTOMER ESSO DATE May 8, 1972
MATERIAL TO BE DRIED PROPOSAL NO. 072-0077-7
REF. NO.
Rate of Feed ?1 _^An Lbs./Hr. Est. Hrs./Day Operation
ANALYSIS - FEED ANALYSIS - DRIED PRODUCT
Percent Lbs./Hr. Percent Lbs./Hr.
Water 95 20,400 4.4 51
Solids 4.5 960 83.5 96Q
Oil in Feed .5 117 21.1 140
Recycle Oil Rate
Oil used for Fluidizing
Energy Requirements
4 Effect
Steam: 6.475 x 106 BTU/Hr. Lbs./Hr. @ IQQ PSIG
Total Connected Horsepower ^53
Sludge
Cooling Water: Thickening Gals./Hr. Gals./Min.
Ultimate Use of Solids Burn as fuel
Total Fuel Value of Solids @ 80% Boiler Efficiency g.m v i ng BTU/Hr.
Lbs.
Additional Fuel Required if Solids are for Fuel Value 23 iSaJbs/Hr.
Total Fuel if Solids are Recovered ZZII : Gals/Hr.
General Material of Construction of Equipment Carbon Steel
Approx. Bldg. Space: Lg. 44 Ft., Wd. 22 Ft;, Ht. 75 Ft.
Manpower Requirements 24 Hrs./Day
$590,000 Max. boiler cost
Estimated Sales Price (Uninstalled) $530,000 Min. boiler cost
Est. Install. $250,000
Est. Emission $10,000
1 of 5
SF-8
-------
D-17
DESIGN CRITE:RIA i OR
THE CARVI.R OR[.I NF It.I [> PROCl SS
CUSTOMER
ESSO-EPH
MATERIAL TO BE DRIED
TJ-: May 8f 1972
PROPOSAL NO. 072-0077-8
REF. NO.
Rate of Feed.
ANALYSIS - FEED
Lbr,./Hr. , Est. Ilr- /Oay Opr
i on
Water
Solids
Oil in Feed
Recycle Oil Rate
Percent
93.5
6.0
0.5
Lbs./Hr.
15,090
960
117
,; SIS - DRIED PRODUCT
Perc, -'Mr.
4.5
85.2
10.3
51
960
117
Oil used for Fluidizing
Energy Requirements
Steam: 4.91 x 106 . BTU/Hr. ___
4 Effect
Total Connected Horsepower 201
Lbs./IIr.
Cooling Water: Sludge Thickening Gals./Hr.
Ultimate Use of Solids Burn As Fuel
Gals./Min.
Total :Fuel Value of Solids @ 80% Boiler Efficiency 6.15 x 106
Additional Fuel Required if Solids are for Fuel Vaiu<_
Total -Fuel if Solids areRecovered -
Gals/Hr.
General Material of Construction of Equipment Carbon Steel (C.S.)
Approx. Bldg. Space: Lg. 42 Ft., Wd. . 22 Ft. , Ht. 75 Ft,
Manpower 'Requirements 24 Hrs./Day
$520,000 (Max Boiler Cost)
Estimated Sales Price (Uninstalled) $430,000 (Min Boiler Cost)
Estimated Cost Of Install. $220,000
" " " Emmission $ 10,000
SF-8
1 of 5
-------
D-18
DESIGN CRITERIA FOR
THE CARVER-GREENFIELD PROCESS
CUSTOMER
ESSO-EPH
MATERIAL TO BE DRIED
DATE May 8, 1972
PROPOSAL NO. 072-0077-9
REF. NO.
Rate of Feed 139,800
Lbs./Hr. Est. Mrs./Day Operation
24
ANALYSIS - FEED
Water
Solids
Oil in Feed
Recycle Oil Rate
Percent Lbs./Hr.
95.0 132,500
ANALYSIS - DRIED PRODUCT
Percejit Lbs./Hr.
323
4.5
0.5
6,250
758
4.3
83.0
12.7
6,250
923
Oil used -for Fluidizing
Energy Requirements
4Eff.Steam: 42.81 x 106 BTU/Hr.
Lbs./Hr. @
100
PSIG
Total Connected Horsepower
Heating Of
Cooling Water: Sludge
1,487
Gals./Hr.
Gals./Min.
Ultimate Use of Solids Burn as fuel
Total Fuel Value of Solids @ 80% Boiler Efficiency 40.4 x 106 BTU/Hr.
Additional Fuel Required if Solids are for Fuel Value 165 Ib. XSKte/lir.
Total Fuel if Solids are Recovered - Gals/Hr.
General Material of Construction of Equipment Carbon Steel (C.S.)
Approx. Bldg. Space: Lg. 80 Ft. , Wd. 60 Ft., Ht. 75 Ft.
Manpower Requirements 48 Hrs./Day
Estimated Sales Price (Uninstalled)
$2,100,000
$1,650,000
Estim. Install. Cost $610,000
Estim. Stack Emmiss. $ 40,000
SF-8
1 of 5
-------
TABLE D-9
PROJECTED COST SAVINGS FOR LOW TEMPERATURE SETTLING (1)
Plant Size
Tons Sludge/Day
4.72
14.16
94.5
Concentration
Factor
Max.
Min.
Max.
Min.
Max.
Min.
Fuel for Sludge
Heating (3)
-3.75
-5.15
-3.75
-5.15
-3.75
-5.15
Superheat
Equivalent (4)
+ .56
+.90
+.56
+.90
+.56
+.90
TOC Recycle
Charge (5)
-2.53
n
ii
ii
it
n
Investment for
Sludge Heating (6)
-2.7
n
-1.6
II
- .72
ii
Total Esso
Process (7)
-8.4
-9.5
-7.3
-8.4
-6.4
-7.5
(1) For Esso oil concentration process for secondary sludge only.
(2) - = cost decrease for 105°F settling.
+ = cost increase for 105°F settling.
(3) To heat oil sludge concentrate to 3rd stage settler from 105°F to 175°F.
(4) Fuel value of 3rd stage oil sludge concentrate at 175°F flashing to 105°F in 3rd stage evaporator.
(5) Charge for TC recycle or basis of BOD equivalent.
(6) Capital charges for boiler and heat exchanger,required to heat 2nd stage oil sludge concentrate
from 105°F to 175°F.
(7) No change projected for operating manpower.
-------
TABLE D-10
COST SAVINGS FOR 50% REDUCTION IN AREA
OF OIL SLUDGE CONCENTRATORS (SETTLERS)
2nd Stage
Plant Size MGD
Thickened Sludge
.075
.225
1.5
Reduced
Area
1000 ft2
.39
1.17
8.03
Installed Cost $MM
Settler
.036
.052
.138
Roof
.004
.006
.035
Total
.040
.058
.173
Reduced
Area
1000 ft2
.675
2.02
13.85
3rd Stage
- Installed
Settler Roof
.044 .004
.063 .008
.200 .062
Cost
Total
.048
.071
.262
Total
Installed
Settler
Cost
.088
.129
.435
Installed
Cost
Savings
Over
Base Case
.017
.071
.408
Factor
for
TIE (1)
1.28
1.155
1.11
Cost
Savings
TIE
Basis
.022
.090
.50
Cost
Savings
$/Ton (2)
1.6
2.3
1,9
-------
tt-21
TABLE D-ll
CARVER-GREENFIELD CORPORATION
SF-8
8/71
O GREAT MEADOW LANE
HANOVER. NEW JERSEY 07930
(201) BS7.21S2
PRELIMINARY ESTIMATE
FOR
THE CARVER-GREENFIELD DEHYDRATION PROCESS
9% SOLIDS IN FEED
4.72 TONS/DAY SLUDGE SOLIDS
CUSTOMER: ESSO - EPA
PROPOSAL NO.
DATE July 11. 1972
-------
D-22
GENERAL SPECIFICATIONS
FOR
THE CARVER-GREENFIELD PROCESS
CUSTOMER
ESSO - EPA
PROPOSAL MO Q72-OQ77-1
DATE 7/H/72
ITEM
1. Raw Feed Holding Tank
2. Raw Feed Tank Agitator
3. Raw Feed Pump
4. Fluidizing Tank
5. Fluidizing Tank Agitator
6. Fluidizing Pump
7 . Fine Grinder
8 . Feed Tank
9. Feed Tank Agitator
10 . Evaporator Feed Pump
11. Evap. -Concentrating Style
12. Evaporator-Drying Style
13. Circulation Pump(s)
14. Vapor Condenser (Barometric)
15. Vapor Condenser (Surface)
16. Vacuum Pump
L7. Vapor Line Preheater
18. Condensate Pump(s)
L9- Transfer Pump(s)
20. Product Pump
21. Centrifuge (Continuous)
22. Centrifuge (Batch)
23. Solids Bin or Tank
NO.
SUPPLIED
__
1
1
1
1
1
1
1
1
3
1
1
2
1
1
1
MAT'L OF
CONST .
Carbon
Steel
n
Cast
Iron
C.S/
S.S.
Carbon
Steel
n
Cast
Iron
Carbon
Steel
Cast
Iron
Carbon
Steel
Cast
Iron
Cast
Iron
ii
Carbon
Steel
Carbon
Steel
HP
TOTAL
1/2
3
10
1/2
3
2@20
1@15
7-1/2
281
3
25
3
REMARKS
Heated
HfcBteBf
WEJfofr&f'
/ari- speed
12x30
Auto.
Man.
-
SF-8
2 of 5
-------
GENERAL SPEC'S.-(con't.)
CUSTOMER ESSO- EPA
D-23
PROPOSAL NQ.072-0077-1
DATE 7/n/7o
ITEM
24. Recycle Oil Tank
25. Recycle Oil Pump
26. Chutes
27. Cooling Water Tower
28. Cooling Water Pump
29. Condensate System (18)
30. Scalping Oil Tank
31. Coalescer
32. Holding tfank
33. Holding Tank Agitator
34. Bulk Oil Holding Tank ,
35. Oil Pump
36. Operating Panel
37. Controls
38. Piping & Fittings
39. Motor Control Center
40 . Condensate Sump Pump
41. Scalping Tank Discharge Pump
42. Repulping Tank
43. Repulping Tank Agitator
44. Packaged Boiler **
45. Boiler (Solids Handling)
46. Multi -Compartment Hot Well
47. Coarse Grinder
NO.
sriPPT.TFn
1
1
2
1
__
1
1
1
1 set
^^^MMMIOTI^MIIIIIIIB
1 set
1
--
1
__
MAT'L Of
CQNST.
Carbon
Steel
Cast
Iron
Carbon
Steel
\
Cast
Iron
Carbon
Steel
Cast
Iron
Carbon
Steel
C.S/S.S.
^^^^^^^^HMBBWB
Carbon
Steel
Carbon
Steel
HP
TOTAL
1
-«
20
«_
1/2
l^^^^gH^H^UH!^!!^!!!!
30
REMARKS
Heated
tf.B. °p
).B. °F
Heated
I^M^HIH^H
Heated
^^^^^^^^M
SF-8
3 of 5
-------
GENERAL SPEC's.-(con-t.)
CUSTOMER ESSO - EPA
D-24
PROPOSAL NO. 072-0077-1
DATE .7/11/72
ITEM
48. Bar Screen
49. Desolventizer
50. Screw Conveyor
51. Crystallizer Tank
52. Crystallizer Tank Agitator
53. Fine Screen
54. Cyclone Separator solid
55. Boiler Feed Water System
56. Filter
57. PH Controller
58. Silo Holding Bin
59. Boiler Water Softening
60 . Deaerator & Feed Water Pumps
61. Ash System
62. Boiler Stack Emission Devices
63. Process Water Treatment
*Not included in basic guotat
NO.
Supplied
__
1
1
__
1
1
1
1 set
1
1*
.on
MAT'L OB
CONST.
Carbon
Steel
ii
Standard
Carbon
Steel
Standard
n
ii
., (
. ., .
HP
TOTAL
10
3
3
5
2
2@5
2
2
REMARKS
Heated
1 ,
1 1
- . ,
', .- .*
K
. -
,.
J
NOTE:** If solids are to be recovered and heat source to be supplied by C-G.
SF-8
4 of 5
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D-25
Process design is considered commercially acceptable.
The addition of other features as required by various state,
local, and governmental regulations, or by insurance companies
will be considered beyond the scope of this proposal.
Carver-Greenfield Corporations proposa-1 includes supplying
the following:
1. Full process engineering services for equipment supplied
by Carver-Greenfield Corporation, except structural or
architectural engineering.
2. Engineering service liaison during construction of plant
and start-up assistance.
3. Full set of operating instructions.
4. Guarantees of performance as ascertained from our own
pilot plant study.
Normal Supplier Of Major Equipment
Major Equipment Type Supplier
Pumps
Evaporator
Cooling Tower
Centrifuge
n
Motor Control Center
Control Valves
Process Valves
Utility Valves
Piping
Instrument Panel
Pumps
Tanks
Agitators
Boiler-Furnace
Centrifugal
Falling Film
Packaged
Horizontal Bowl
Basket
Modular
Pneumatic
Plug
Globe & Gate
Welded
Hoffman Box
Gear
Vertical
Propeller
Worthington
Mojonnier
Marley
Bird Machine
Fletcher, or Sharpies
Allen-Bradley
MasoneiIan
ACF
Crane
Tube Turn
C-G Subcontract
Blackmer
C-G Subcontract
Mixing Equipment
Babcock & Wilcox, E. Keeler
SF-8
5 of 5
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«
a
-I
1
5
i
o
-sa^... >
CARVER-GREENFIELD CORPORATION
NINE fiMAT MEADOW LANE EAST HANOWB. H.J.
a
K3
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SELECTED WATER
RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
1. Report No.
\e-ession No,
w
4, Title
Optimization and Design of an Oil Activated
Sludge Concentration Process
7. Author* s)
T. M. Rosenblatt, Esso Research & Engineering Company,
Linden, New Jersey
5. Report Date
4 6. August 4, 1972
Si
* 8. Performing Organization
GRtl.lBJB.73
10. Jioject No-.
17070-HDA
11. C;nt,'a'."t-'0j;uit No
68-01-0095
- - -«-- J , 0 -l**3'^1 ' < ut;ReP°« <"'<* Hnal
12. Spe^orifigOrgaaBatwn^ipA,!National Environmental Research Center T * tffiYr&i-)'*nt
15SUPPI«rNou. Cincinnati, Ohio 45268 6/23/716/22/72
Environmental Protection Agency report number EPA.r670/2-74-004,
February 1974.
16. Abstract
Laboratory and pilot plant studies are described for a new Esso-
Carver Greenfield process for the disposal of sewage sludge. An oil-assisted
gravity separation of the majority of the water while heating is followed by multiple
effect evaporation to dryness in an oil slurry, and incineration of the dry solids.
Agreement between laboratory and pilot plant results was good, indicating no
scale-up problems.
In the gravity separation, secondary sludges are concentrated from
about 0.5% up to 5-10% solids. Solids capture of 98% or more is achieved by high
shear oil-sludge contacting. Temperature dependent losses of solubilized organic
carbon up to about 25% of the organic content of the feed are observed in the
separated water from the oil concentration, and in the distillate from the evapora-
tors. The process economics show an advantage of $13-32 a ton compared to the best
known commercial technology: total costs are estimated at $21-39/ton of dry solids
for a 189 ton/day plant processing a 50/50 mixture of primary + activated sludges
to ash. A lower temperature gravity separation step could greatly reduce the
economic penalty for a 25% recycle of solubilized secondary sludge, and yield an
improvement of $l-12/ton of dry solids depending on plant size and sludge type.
Other cost reductions in the thickening and settling steps could amount' to $l-5/ton
diy sullds. '
*"*,>--.-? .,.. . - -.- * ^.^
I7a.
Sludge drying
Sewage disposal
Dewatering
Thickening
Concentrating
Oil slurry
Incineration
Pilot plant
Cost analysis
Comparison
17b. Identifiers
Oil-assisted dewatering, drying secondary sewage sludge.
?o 'X>WRR Field & Group 1302-Civil Engineering; 1309-Industrial Equipment
'if. AVaUa,-!llty
Release Unlimited
19, Security Class.
(Report)
i-iD. Security Clas$. :
'."./ (Page) - #**
2.1. No. of
Pages
22, Pro*
Send To:
WATER RESOURCES SCIENTIFIC INFORMATION CENTER
U.S. DEPARTMENT OF THE INTERIOR
WASHINGTON, OJC. 20240
institution
WRSIC 102 (REV. JUNE XS71)
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