'J
PIPELINE TRANSPORT
OF SHREDDED SOLID WASTE
An Open-File Report SW-36c. of
U.S. ENVIRONMENTAL PROTECTION AGENCY
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PIPELINE TRANSPORT OF SHREDDED SOLID WASTE
Final Report
This open-file report (SW-36c.of) was written for
the Federal solid waste management program by
The Western Company, Research Division, Richardson, Texas
under Contract No. CPE 70-132
U.S. ENVIRONMENTAL PROTECTION AGENCY
1971
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ABSTRACT
t
A brief summary is made of past and current studies on the pipeline
transportation of solid waste. A plan is made for a proposed program to augment
existing knowledge on this means of transport. The testing facility necessary
to perform this plan is described and equipment layout sketches and material
lists are provided. An economic analysis of a truck transfer system is presented
and requirements for the economic analysis of a pipeline transport system are
indicated.
This report was submitted in fulfillment of contract CPE-70-132 between
the U.S. Department of Health, Education and Welfare, Bureau of Solid Waste
Management and The Western Company.
iii
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TABLE OF CONTENTS
Page
SECTION I CONCLUSIONS 1
Recommendations 2
SECTION II INTRODUCTION 3
Background 4
Slurry Transport 4
Capsule Transport 5
Size Reduction 6
Solid Waste Composition 7
Limitations 8
Polymer Use 9
Purpose 10
Scope 10
Program Description and Approach 10
SECTION III DISCUSSION AND TECHNICAL CONSIDERATIONS 14
Technical Approach 14
Test Plan Logic 14
Test Program Requirements 16
Sizing 17
Injection 17
Dewatering 18
Transport Testing 18
Facilities Requirements 20
Economic Considerations 24
SECTION IV REFERENCES 28
APPENDIX A POLYMER ADDITIVES 31
APPENDIX B TEST PROGRAM 32
APPENDIX C TEST FACILITY DRAWINGS 41
APPENDIX D TRUCK TRANSFER ECONOMIC ANALYSIS 47
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SECTION 1
CONCLUSIONS
The literature search revealed some prior work has been accomplished
verifying that solid waste can be transported in a slurry form thr.mgh pipelines
just as many other materials have been over the past 30 years. There are
accessory operations which are required by a slurry transport system which
have not been perfected for a solid waste system. The grinding of solid waste,
while possible, is not as efficient or predictable as desired. The state-of-the-art
of introducing the wastes into the pipeline has not been perfected. Dewatering
units have been used for many materials but never for solid waste slurries.
Although solid waste research programs are now in progress using some methods
of slurry dewatering, the results are as yet unpublished. Finally, while all
of the unit operations associated with slurry transport have been used on other
products, they have yet to be all put together in a single solid waste slurry
transport system. The program plan outlined in this study will put it all
together.
Capsule transport to date has been done only on a laboratory scale.
Evaluation of the laboratory scale capsule transport shows some potential
benefits over slurry transport.
To be economically feasible, any pipe transport system must compete
with the current method of transport to the disposal site. Pipelines represent
an alternative transport mechanism which can be most readily integrated into a
transfer station operation. Typical cost of a transfer station with large
compacter truck haul to the disposal site is $.09 per ton mile of trash handled
on a round trip mileage basis.
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RECOMMENDATIONS
To increase the available information on solid waste handling, it is
recommended that the program plan outlined in this study be undertaken at the
earliest opportunity. It is further recommended that the unit operations
necessary for the slurry transport be used in their present state of development,
rather than attempt to optimize their operation during this study. If the results
of this program show economic or other tangible benefits, work should be
undertaken to optimize the various unit operations used in the pipe transport
of solid waste and a complete transport system demonstrated on the municipal
level.
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SECTION 2
INTRODUCTION
The solid waste problem has been characterized as a health problem which
1
needs an engineering solution. It has been estimated that 75 percent of the
cost of disposing of solid waste is in the collection and transportation to a
disposal site. Some $ 3 billion are spent annually in the United States to
collect and dispose of solid refuse. The collection and disposal practices in
2
common usage are but little improved over those of a quarter century ago.
The trend toward concentration of people plus the increase in poundage of
refuse per person is compounding the problem. The cost and the air pollution
problems which are currently inherent with incineration has resulted in most
cities turning to the only acceptable alternative technique—sanitary landfill.
However, in many areas there are no satisfactory landfill sites within a
reasonable distance. The long haul distances plus the hazards and restrictions
imposed upon refuse trucks moving through suburban cities creates a major
problem, particularly for large metropolitan areas.
An engineering solution for one facet of the solid waste collection and
disposal would be the use of a pipeline to transport solid wastes the long
distances from collection area to disposal site. Traditionally,
pipelining has many advantages over truck transport, such as reduced
transportation costs, less recurring capital costs, less labor costs, etc.
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Background
Presently, there are no programs ongoing which study the complete pressure
system of pipe transport of solid wastes in other than a theoretical manner.
The Foster-Miller Associates household grinder contract (CPE-70-115) is, in
essence, experimentally studying a complete pipe transport system in connection
with nonpressure flow in sewer pipelines. There are projects completed or in
progress which are examining unit operations required by a pipe transport
system. For example, size reduction of solid waste has been done at Madison,
Wisconsin, for direct landfill. Size reduction has been done at Gainesville,
Florida, for composting solid waste and also at New York City and other towns
to aid in incineration of the waste.
Zandi, at the University of Pennsylvania, has studied the hydrodynamics of
various concentrations of solid waste slurries and has pumped solid waste
slurries through three size of pilot pipelines. Stanford Research Institute is
doing an examination of hydraulic pipe transport of solid waste in slurry,
capsules, and slugs.^ To date all of their work has been entirely theoretical
with pilot pipelines to be constructed later. No other programs which dealt with
the actual hydraulic transport of solid waste was found.
Slurry Transport
Slurry transport of solid material through pipes is a handling process
used many years by various industries. The flow of slurries in pipes, however,
cannot be qualified by density and viscosity as can pure fluids. Because of the
interaction between fluid and solid and the properties of the solid and fluid,
each system must be treated individually. The solids-carrying pipelines now in
use have been designed and modified by the use of empirical formulas and
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large-scale tests losing the specific solid being transported. For example,
Condolios, through such testing, limits the particle size to no more than
one-half the transport pipe diameter.
A recent program has been completed in which development of eapirical
data was made on the slurry transport of ground solid wastes. Zandi and Hayden
have demonstrated that solid wastes, sufficiently ground and pulped can be
transported through a pipe. Formulas were developed which will allow
calculation of pressure losses from a knowledge of pipe diameter, mean velocity,
and solids concentration. It was further demonstrated that a solid waste slurry
behaves, from a pressure loss standpoint, identically with a slurry formed
from only the paper portion of the solid waste.
Hayden observed pressure losses of approximately 500 psi per mile when
transporting a 10 percent solid waste slurry at 3.7 feet per second through a
6-inch pipe.
Capsule Transport
Hydraulic capsule transport of solids can be used when the solid cannot
stand contamination from the carrier fluid or when the separation of the solid
from the carrier is difficult or expensive. Experimental work to date on capsule
transport has been on a laboratory scale only.
Ellis investigated both single spherical and single cylindrical capsule
transport in a 1 1/4-inch diameter pipe.^ He found that the velocity of the
capsule varied from 1.05 to 1.5 times the average water velocity which ranged
from 0.20 to 12.15 feet per second. The velocity ratio increases with increasing
length/diameter ratio of the capsules. Trebling the L/d ratio increased the
velocity ratio about 3 percent. The presence of the capsule appeared to delay
the onset of turbulence in the annulus between the capsule and the wall to a
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much higher value of Reynolds number than would hold in unobstructed fluid flow.
This indicates a reduction in normal head losses as a result of the capsule
being transported.
Evaluation of the small scale tests indicated favorable possibilities in
the use of hydraulic capsule transports assuming scale up to commercial
quantities is possible. Among the benefits indicated are:
lower power requirements
minimum expense in separating the capsule
from the carrier fluid.
Information on the technical feasibility or cost of forming the capsules
from solid waste was not found in the literature.
Size Reduction
The size reduction of solid waste presents an unusual problem. The
unlimited variety in the composition of solid waste with regard to density, size,
shape, and composition of the components increases the difficulty in selecting
and sizing the necessary equipment.
Size reduction is a grinding and crushing operation. Crushing denotes
size reduction by the application of compression stresses which in turn cause
tensile and shear stresses to break the particle. Grinding is size reduction due
to abrasive or attrition forces.
The common hammermill combines both these forces in its operation. Sanders
reports satisfactory size reduction and homogenizing of solid waste when passed
p
through a hammermill. He indicates a grate size (1.5-inch) but does not state
the resulting particle size or range of particle sizes.
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Wixson reports the reduction of urban solid wastes is generally feasible
Q
by use of the hammermill. Here again the grate size is given (3/4-inch) but no
resultant particle size range.
Zandi and Hayden report that the haimnermill is capable of premizing solid
wastes but requires considerable maintenance. They further stated that, while
sufficient size reduction for pipe transport is possible, a more efficient
system must be developed for an actual industrial application. However, in their
solid waste transport study, a two-stage reduction, a combination of a Wascon
pulper and a Dorr-Oliver Gorator, was used.
The city of Madison, Wisconsin, started a solid waste reduction study using
a horizontal mill (a Gondard) but ended the study using a vertical mill made by
Tollemache.10 This study related to direct landfill and did not report the
particle size range resulting from the reduction.
Solid Waste Composition
The physical and chemical characteristics of the waste material, as
determined by its composition, has a significant impact on the handling of solid
wastes. The as-collected household and commercial refuse is composed of varying
amounts of each general group of the various waste categories. Table 1 indicates
the primary components of each refuse group.
The actual percentage of any caregory from a specific location on any given
day is dependent on the geographic location, season of the year, day of the
week, the economic status of the collection area, and many other variables.
Niessen and Chansky in their study have defined the nature of solid waste
and projected the quantity and composition through the year 2000.H They predict
an increase in the total solid waste load by a factor of 2.7 by the year 2000
with the ratio of paper and plastics increasing and food wastes and yard wastes
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decreasing. Table 2 lists the solid waste composition range in a number of U.S.
cities.
From the wide range in composition of the various categories, the
difficulty in obtaining a uniform solid waste from an as-collected municipal
source can be easily understood. Therefore, a synthetic or manufactured solid
waste will be required, for uniform or equivalent products during pipe transport
tests. The manufactured solid waste composition could be expected to conform
to the average shown in Table 2.
Limitations
To date, no previous work has been found which demonstrates equipment or
methods to introduce presized solid waste particles into a slurry transport line
on a regular and continuous basis. Nothing is reported yet on the largest solid
waste particle size which can be made into a pumpable slurry. Zandi and Hayden
reduced the solid waste to a pulp, evidently uniformly approaching the size of
the paper fibers. No method has been demonstrated which will introduce the
presized solid waste into a pipeline running full.
Wixson's study pumped the solid waste slurry from a main reservoir and
returned the slurry to the same reservoir for further cycling. Zandi and Hayden
also recirculated the slurry from a mixing tank.
The slurry transport pipe system has also been neglected at the discharge
end. The dewatering method or degree of dewatering has not been demonstrated,
nor has the disposition of the carrier fluid been specified. The handling of the
dewatered slurry should be possible in conventional equipment. Metcalf and
Eddy, under subcontract to the Environmental Protection Agency Contract with
Foster-Miller Associates have performed bench-scale studies of the vacuum
filtration of solid waste slurries. Indications are that this method is quite
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successful. Screw press dewatering of pulped refuse is also being practiced
in New Haven, Connecticut, as a part of EPA Contract PH-86-67-167 "Solid
Waste Research in the Application of On Site Refuse Storage, Colle -tion and
Reduction Systems for High-Rise Residential Structures... The results of these
efforts have not yet been published.
Polymer Use
Current oil field technology uses polymers as additives to water to
improve the solid carrying capacity and as a friction reducer. The oil field use
requires the suspending of sand, glass beads, aluminum shot, ground walnut
shells, and other materials in very high concentration. This suspended material
must be moved in large volume through small pipe requiring high pump horsepower.
The polymers used, in addition to their suspension qualities, reduce the
boundary layer turbulence thereby lowering the friction loss in moving through
the pipe. It is believed that similar polymers may act as a suspension aid and
a friction reducer in the slurry transport of solid waste. The polymers for this
application can be found in the general class of polyelectrolytes used in water
and sewage treatment and paper manufacturing as coagulants or coagulant aids.
Appendix A lists manufacturers and products which have been used or considered as
friction reducing materials and suspension aids.
The following criteria should be used in determining the best polymer
additive for use in the waste slurry transport.
friction reduction capability
Solubility in water
high molecular weight
shear stability in flow systems
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storage life
toxicity to biological systems
resistance to biological attack
chemical stability under repeated use
availability from commercial sources
cos t.
Purpose
The purpose of this program is to advance the knowledge and technology
toward better methods of solid waste management. The total program will result
in the generation and collection of data to show to what extent pipelining of
solid waste is a practical and economic process. The program will also result in
design data necessary to construct a demonstration project in the slurry
pipelining of solid waste.
Scope
The scope of this phase of the program is limited to the investigation and
evaluation of the state-of-the-art of slurry transport of solid waste and the
development of a test plan to acquire the data necessary to design and demonstrate
a complete operational pipeline slurry transport system for solid waste. The
system under investigation is to involve the transport of solid waste from the
collection area to the point of disposal.
Program Description and Approach
To meet the purpose and scope of the program, the work was divided into four
areas. The first area of investigation was the review of all work completed and
ongoing studies. This was done to take advantage of the available information, to
learn of needed areas of investigation, and to prevent duplication of effort.
The second work area was a detailed plan on the number, kind, and variation of tests
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which would be conducted. The test plan took into account the variables which
would exist in each test, for example, amount of polymer, solids concentration,
flow velocity, size of solids, data to be taken, etc. The third area of work
consisted of the designing of a pilot system which could provide a maximum of
needed data with a minimum of equipment cost for the several types of tests to be
performed. Economy and ease of operation were considered second only to the
capability of providing acceptable data. The last work area was an economic
analysis of a typical refuse truck transfer transportation system for comparison
later to the transportation costs developed for a typical pipeline transportation
system.
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TABLE 1
REFUSE DESCRIPTION
Category
Description
Glass
Metal
Paper
Plastics
Leather, Rubber
Textiles
Wood
Food Wastes
Mis cellaneous
Yard Wastes
Bottles (primarily)
Cans, wires, and foil
Various types, some with fillers
Polyvinyl Chloride, Polyethylene,
Styrene, etc., as found in packaging,
housewares, furniture, toys, and
nonwoven synthetics
Shoes, tires, toys, etc.
Cellulosic, protein, woven synthetics
Wooden packaging, furniture, logs,
twigs
Garbage
Inorganic ash, stones, dust
Grass, brush, shrub trimmings
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TABLE 2
RANGE IN COMPOSITION OF RESIDENTIAL
SOLID WASTES IN 21 U.S. CITIES*
Category Percent Composition by Ne , Weight
Low High Average
Glass and Ceramics
Metals
Paper Products
Plastics, Rubber, and
Leather
Textiles
Wood
Food Waste
Rock Dirt, Ash, etc.
Garden Waste
3.7
6.6
13.0
1.6
1.4
0.4
0.8
0.2
0.3
23.2
14.5
62.0
5.8
7.8
7.5
36.0
12.5
33.3
9.0
9.1
43.8
3.0
2.7
2.5
18.2
3.7
7.9
*
Unpublished data, Division of Technical Operation, Bureau of Solid Waste
Management. Values were determined from data taken at 21 cities in
continental United States between 1966 and 1969.
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SECTION 3
DISCUSSION AND TECHNICAL CONSIDERATIONS
Technical Approach
Test Plan Logic
Before any flow tests can be made, certain basic data must be collected,
and operating procedures established. Results, in terms of particle size
ranges must be obtained from the various screen plate openings on the size
reduction units. Injection techniques must be developed which will result in a
uniform slurry in the pipe and a consistent injection of capsules. The test
facility must then be calibrated by transporting a solid waste slurry,
measuring the results, and comparing the results to previous work by others.
Figure 1, from Zandi and Hayden, shows the pressure losses observed as a
result of solid waste concentration and velocity changes. It appears from the
graph that pressure losses of all solid waste slurries of seven percent
concentration and above are independent of the velocity. However, examination
of the curve for the six percent slurry shows its pressure losses to be
velocity dependent for the low velocities of two to five feet per second. At
velocities above six feet per second, the pressure losses are approximately
parallel to the pressure loss line for water. The referenced paper did not
report any velocities greater than shown on the graph because the upper limit
of pump capacity had been reached. If it can be assumed that the slurries
higher than six percent concentration will behave similarly to the six
percent slurry it will only be necessary to increase the velocity of each
concentration until the curve breaks upward.
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0.30
0.10
V V
o o
Y Y Y Y YY
O D OO DO D
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m */*
•• • • O/
J/
° /
o J+
CO
to
o
o
uj -010
X
C
—
-
-
>.l
'. /
* V/ATER y *
SOLID V/ASTE /
(PERCENT) / *
J
v 10 y
: : /
• 6 /
• 4
o 2
1 I 1 ! ! 1 1 I 1 I 1 1 1 1 1 I 1 f I 1
1.0 10 30
VELOCITY (ft./sec.)
Figure 1. Concentration Effect, 6 inch Pipe from Zandi, I and J. Hayden.
(Reference 6).
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Capability and capacity tests must be run on the dewatering device, not
for the purpose of optimizing the dewatering, but to define quantitatively what
dewatering results are being accomplished. The accumulation of such basic data
will provide insights into the transport tests and permit the most efficient
performance of those tests.
The capsules for this test will be made of polyethylene bags, 5 inches in
diameter, filled with ground solid waste, compacted to the fill density listed
in the test program, and heat sealed. The capsule length/diameter ratio should
not exceed 3/1 due to the dimensions of the available rotary valve used for
insertion.
The transport tests, both slurry and capsule, will result in the
establishment of transport rates, power requirements and losses. Once the
optimum transport conditions have been established, fluid reuse tests will be
made, which should show savings possible through reuse of the carrier fluid.
Again, in establishing optimum conditions, the slurry solids concentration will
be increased to find the highest concentration which can be transported.
Optimum conditions in this instance means the highest transport rate with the
least power requirement and losses.
Test Program
The test program is outlined in Appendix B. The methods and sequence of
performing the tests are discussed. A detailed test plan gives specifics on the
test variables to be examined.
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Sizing
The first information needed prior to the injection tests is a particle
size range resulting from the use of various size screen plates or grate bars
in the grinders. It is not intended to optimize the grinding or grinders.
Here again, knowledge is needed to define the operating conditions during the
transport tests.
Three tests will be performed with each grate size; 1-inch, 2-inch, and
3-inch openings. The output will be classified on Tyler Standard screens, 2 to 1
opening ratio, 14 mesh to 3-inch opening, (7 screens). The results will be
reported by percentage passing through each screen. A solid waste particle size
classifier is being developed in-house by the EPA in Cincinnati. It is a
potential candidate for performing this aspect of the testing.
Injection
Two general methods to inject solids into a pipeline are: pump installations
using sludge or solids handling pumps, and pump installation using clear water
pumps. To determine the best injection technique, both methods will be used. The
criteria for the best injection system will be that system which can produce a
uniform slurry concentration using the least amount of work added to the system.
The measurements required will be: work required to inject solids (kilowatthours,
foot-pounds, horsepower, etc.), the resulting slurry concentration, and the rate
of slurry generation in gallons per minute, pounds per minute, etc.
The solids handling pump will take suction from the bottom of a reservoir
into which a measured rate of water and ground solid waste is being inserted.
Three tests each using different particle distributions and nine solids insertion
rates will be performed.
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The clear water pump will take suction from a reservoir with the solids
introduced into the pump discharge through an eductor. In each type solid
introduction, three tests each will be made using three different maximum
particle sizes and six solids insertion rates.
It will be necessary to determine the head losses obtained transporting
slurry in the test facility being constructed for this program. These head
losses when compared with previous work done by others, will provide a baseline
for calculating improvements or efficiencies resulting from this new work. The
head loss determination will be accomplished while holding the solid
concentration constant at 4, 6, and 8 percent, using one injection technique,
the best grinder grate size, and flow velocities from 2 to 12 feet per second.
Measurements during the test will include screen analysis of solid waste, input
of water and solid waste, flow rate of slurry, and resulting pressure and
pressure losses.
The capacity of the dewatering equipment will be measured by varying the
slurry feed to the unit and measuring the slurry concentration, quantity of
water removed, and water content of the dewatered slurry. If there is a vacuum
capability on the dewatering unit, it will be varied and appropriate
measurements made.
Transport Testing
The following parameters need to be considered when performing the slurry
transport tests: velocity, particle size, slurry concentration, polymer used,
and polymer concentration. The test range of each of these variables should be:
Velocity - 1.0 to 14 feet per second
Maximum particle size - dependent on information in baseline tests
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Slurry concentration - 2 to 10 percent
Polymer - Polyacrylamide or acrylate/acrylamide copolymer
Polymer concentration - 10 to 100 ppm
The flow velocity will be measured. The particle sizes will ba determined
by screen analysis. The slurry concentration will be determined by measuring
water and solid waste input and confirmed by analysis. The polymer concentration
will be calculated from application rates. The pressure losses will be
measured.
The test items to be considered during capsule transport without polymer
are: capsule weight and shape, fluid velocity and capsule insertion rate. Tests
to be run are:
1. Three capsule configurations
2. Fluid velocities
3. Three capsule fill densities
4. Three capsule spacings
Measurements will be made of head loss and capsule velocity. Transport
rates will be calculated and capsule damage will be noted.
The following test items are to be considered during the gravity slurry
transport tests. These tests are to be conducted with the pipe running half
full?
Velocity 1 to 4 ft/sec
Solids concentration 1 to 9 percent
Measurements will be made of the fluid velocity, transport rates, and
slope required to obtain the required velocity. Visual observations will be
made of saltation tendencies of the slurry.
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The gravity slurry transport with polymer will consider the same
items, and make the same measurements with the following additions?
Two polymers will be used
Three polymer concentrations will be used
Carrier fluid reuse tests will be conducted for:
1. Slurry - the fluid will be recovered and recycled a minimum
of 10 times. Polymer degradation will be measured on a viscometer and
bacterial accumulation will be determined by a plate count after each
cycle.
2. Capsule - the fluid will be recovered and recycled a minimum
of 10 times. Measurement of polymer degradation and bacterial accumulation
will be determined as in the slurry fluid reuse tests.
In determining the most efficient flow velocity, particle size, polymer,
and polymer concentration, tests will be run with increasing slurry solids
concentration measuring the flow rate and head loss. Figure 2 is a flow
chart of the test plan.
Facilities Requirements
The test facility drawings and equipment list are presented in Appendix C.
Schematic layout drawings are presented of the three major tests. An Isometric
of the general equipment layout is included.
The pilot transport facility was designed for maximum flexibility in test
setups. The grinder, storage tanks, pump, test pipe section and dewatering
device will all be permanently located with test changes made by changing
elevator location, removing a spool from the pipeline for rotary valve or
eductor insertion, etc.
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The grinder, a hammermill, will be equipped with a suitable hopper and
three grates with 1- to 3-inch openings. The elevators can be screw, bucket
or pneumatic of the capacity noted on the equipment list. The stora ,e tanks
should be mild steel, painted or galvanized corrugated iron construction. The
ground waste storage bin must not necessarily be shaped exactly as shown on
the isometric general layout drawing (figure C-4). The ground refuse by its
nature is very reluctant to flow and is highly susceptible to bridging in a
holding tank. In general, constrictions in movement must be avoided with this
material. The slurry mix tank will require motor driven agitation to achieve
complete mixing. The legs should support the tanks high enough to allow working
under the cone, if necessary, to change piping or other hookups. The pump will
be capable of handling solids up to three inches in diameter and variable in
pumping rate by changing the motor speed. A gasoline driven trash handling
centrifugal pump will probably be best suited for this temporary application.
The magnetic flow meter is used because of no internal obstructions. The test
pipe section requires six inch cast iron or epoxy lined steel pipe. When the
solids are being inserted in the pressure side of the pump via the eductor, the
solids from the ground storage tank will be discharged directly from the metering
feeder into the eductor hopper. When capsules are being inserted in the
pressure side of the pump, a slat conveyor will move the capsules to the rotary
valve. The Geneva drives of the conveyor and rotary valve will be synchronized
so that the conveyor will drop a capsule during the valve rest cycle. The
pressure measurements will be made by pressure transducers located at the
pressure tap locations noted on the schematic drawings. The pressure will be
transmitted through an oil filled chamber from the flush mounted diaphragm to
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the transducer. The pressure differential will be determined electronically and
displayed on a direct readout recorder.
The dewatering unit will have the capacity indicated on the equipment
list and will be a revolving or vibrating screen with or without vacuum
assistance, a dewatering screw and press or some other suitable type of water
removal process. There will be a capability of returning the removed water to
the slurry tank for subsequent carrier reuse tests.
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Economic Considerations
Any evaluation effort dealing with an operational problem, such as solid
waste management, lacks meaning and relevance without the parallel development
of a standard of comparison. In addition, past and current programs have not,
for the most part, evaluated pipeline systems that are truly representative
models of anticipated operating conditions. The technical evaluation cannot be
divorced from economic evaluation of the system, including a comparison with
other available alternatives.
The proposed program will result in data identifying the operating
characteristics of a pipeline system model that will be representative of
anticipated full-scale operating conditions and practice. This basic data can
be used to provide a realistic evaluation of a pipeline system compared to
other transport alternatives, and as a standard of comparison for the evaluation
of potential improvements to pipeline operations such as polymer and capsules.
As a result, the data will permit a realistic appraisal of both investment
cost and recurring operating cost for both the basic pipeline concept and the
specific potential improvements to be investigated.
The program proposed is primarily addressed to the utilization of
pipelines as an alternative in the solid waste transfer station operation. Due
to the large geographic variation in operating conditions and results it is
felt to be most productive to analyze carefully a specific application.
From the standpoint of comparability and ease of potential early implementation,
the transfer operation is well suited to the pipeline application. Within that
operation, the long haul truck transport mechanism is the current practice and •
the appropriate standard of comparison for a pipeline.
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Figure 3 portrays a comparison of the two alternative systems in terms
of their functional components. To be valid, the economic evaluation must
compare equivalent systems and these components identify the basis of such a
couparison. It is assumed that the equivalent systems identified in the figure
have no influence on the operating characteristics of units outside either
system. With this assumption, for example, collection schedules and resulting
input to the systems are fixed. Investment (and resulting operating costs)
for this fixed handling capability is the variable of comparison between these
systems .
Appendix D outlines the operating characteristics and economics of an
operational and typical truck transfer system. It is intended that a pipeline
system operation, based on the results of the proposed testing, will be
compared to the key performance measures developed in the Appendix.
Specifically, the Appendix indicates that the pipeline must process
a given quantity at less than $2.83 per ton or about $.09 per ton mile for a
33 mile round trip to justify as an alternative to truck transport. These
operating costs are also shown to be within the ranges established through
previous analysis. ^» ^' ^» ^ It is also useful to more directly identify
these costs with functional components such as station operations and transport
operations. In this way, a clearer picture of the less competitive aspects and
sensitivities of each system can be given.
The equivalent systems identified in Figure 3 relate only to the direct
costs associated with each system. Overhead costs are not considered. It is
assumed that these are fixed relative to any transport alternative and need not
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be included. Some differences other than direct cost must also be taken into
account, however. Most important of these are the differences in the impact
of each system on the environment. Noise, odor, litter, traffic congestion,
and .other nuisance costs associated with truck transport which are reduced
or eliminated with a pipeline must be taken into account. Many of these are
effectively intangibles. However, methods for approximating their value have
been attempted and should be utilized.1"
While the operating measures of cost per ton and cost per ton mile
are useful and common tools in the economic comparison of alternatives, they
fail to take into account a fundamental difference in the nature of the
alternatives.
Pipeline transport represents a high initial investment relative to
truck transport in anticipation of lower operating costs. The truck system
represents smaller incremental, but more frequent investment requirements.
Operating measures such as cost per ton do not take funds flow or the timing
of cash outlays into account. To recognize these differences, the system must
be ultimately compared on the basis of the discounted or present value of the
cash flows they require. The discount rate employed in this analysis should
represent the cost of capital to the cognizant operating unit. It is anticipated
that a rate of about 8-10 percent would be appropriate. However, the analysis
should be conducted over a range large enough to reflect changing financial
conditions and identify the limits of economic justification of each system.
26
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SECTION 4
REFERENCES
Literature Cited
1. Black, R.J., and L. Weaver. Action on the solid wastes problem. Journal
of Sanitary Engineering Division, Proc. ASCE: 91-95, Dec. 1967.
2. Ludwig, H.F., and R.M. Black. Report on the solid wastes problem.
Journal of Sanitary Engineering Division, Proc. ASCE: 355-370,
Apr. 1967.
3. Zandi, I., and J. Hayden. Collection of municipal solid wastes in
pipelines. Preprint No. 640. ASCE National Meeting of Transportation,
San Diego, Calif., Feb. 19-23, 1968.
4. Personal Communication. R.A. Boettcher, Stanford Research Institute, to
R.M. Clarke, The Western Company, Oct. 13, 1970.
5. Condolios, E., and E.E. Chapus. Operating solids pipelines.
Chemical Engineering; 145, July 22, 1963.
6. Zandi, I., and J. Hayden. The flow properties of solid waste slurries.
Paper Jl. Hydrotransport 1, Cranfield, Bedford, England, Sept. 1-4,
1970.
28
-------
7. Ellis, H.S., P.J. Redberger, and L.H. Bolt. Transporting solids by
pipeline capsules and slugs. Industrial and Engineering Chemistry,
55(9): 29-34, 1963.
8. Sanders, T.G. Grinder evaluation and development. Progress Report No.
WP-02-69-26, Open File, Bureau of Solid Waste Management, 1970.
9. Wixon, E.G., J. Huang, and W.L. Sago. Improved concepts for the
processing and tube transport of urban solid wastes. Conference
on solid waste collection systems trends for the 1970s, University
of Houston, Houston, Texas, Mar. 23, 1970.
10. Reinhart, J.J., and G. Rohlich. Solid waste reduction/salvage plant.
Interim Report, Grant No. D01-UI-00004, U.S. Department of Health,
Education & Welfare, Dec. 31, 1967.
11. Niessen, W.R., and S.H. Chansky. In Proceedings of 1970 National
Incinerator Conference, Cincinnati, Ohio, May 17-20, 1970.
12. Comprehensive studies of solid waste management, Research Grant
EC-00260, University of California, 1970.
13. California integrated solid waste management project systems study in
the Fresno area. Report No. 3413, Agreement No. 15100, 2v.,
Aerojet-General Corp. with Engineering Science, Inc. for California
Dept. of Public Health, Mar. 1968.
29
-------
14. Marks, D.H., and J.C. Liebman. Mathematical analysis of solid waste
collection. Final Report (SW-5rg) on BSWM Grant EC-00309, 1970.
15. Jones and Henry Engineers Limited. Proposals for a refuse disposal
system. Report (SW-7d) on BSWM Grant No. D01-UI-00068, Oakland
County, Michigan, 1970.
16. California waste management study. Report No. 3056, Von Karman Center,
Aerojet-General, Aug. 1965.
30
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APPENDIX A
POLYMER ADDITIVES
Product
Percol 139
Percol 155
Percol 351
RC 301
RC 322
Polyfloc 1100
FR-X
WCL 727
WCL 755
WT 3000
D2-52
Separan AP 30
Separan AP 273
CMC-7H
FR 4
NGL 3958
Polyox WSR 301
Polyox Coagulant
Polyox FRA
Probable Composition
Polyacrylamide
Polyacrylamide
Polyacrylamide
Polyacrylamide
Polyacrylamide
Copolymer Aerylate/
Acrylamide
Polyacrylamide
Polyacrylamide
Polyacrylamide
Polyacrylamide
Copolymer (Acrylamide)
Polyacrylamide
Polyacrylamide
Cellulose Copolymer
Copolymer (Acrylate/
Acrylamide)
P o ly ac ry lami de
Polyethylene Oxide
Polyethylene Oxide
Polyethylene Oxide
Manufacturer
Allied Colloids
Allied Colloids
Allied Colloids
American Cyanamid
American Cyanamid
Betz Chemical Co.
Calgon Chemical Co.
Calgon Chemical Co.
Calgon Chemical Co.
Calgon Chamical Co.
Calgon Chemical Co.
Dow Chemical Co.
Dow Chemical Co.
Hercules Corporation
Hercules Corporation
Stein, Hall and Co.
Union Carbide
Union Carbide
Union Carbide
31
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APPENDIX B
TEST PROGRAM
Discussion
The solid waste sizing tests will be performed using the standardized
manufactured solid waste as previously defined. It is imperative that all
refuse be tested for initial moisture content before mixing with the test
fluid. This moisture may account for up to 30 percent by weight of the
refuse. Final slurry concentration determinations will involve drying and
weighing of the residue and these must take into account the initial
moisture. Each hammermill grate size will result in a distribution of solid
waste particle sizes. The material from each grate size will then be used to
perform the injection tests for the particular particle size and the flow tests
requiring that distribution of particle sizes. The capability and capacity tests
of the dewatering equipment will be performed on the exit material from the
flow tests. The dewatered solid waste will be disposed of in a sanitary
landfill adjacent to the test facility. The carrier fluid will be lagooned
nearby for natural oxidation prior to ultimate disposal.
The sizing tests, injection tests, flow tests, and dewatering tests will
then be performed in sequence using each of the remaining grate sizes.
After the base information tests have been performed, an analysis will
determine the best grate size and the best injection technique for
slurry. These will be used for all of the slurry transport tests with polymer.
Gravity transport of the slurry will be performed with the pipe running
half full with the velocity varied by changing the slope of the test line.
32
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The slurry will be blended continuously in the mixing tank and gravity
flowed into the line.
All slurry transport tests will be performed on a once-through basis with
none of the solid waste or carrier fluid being reused. The solid waste will be
disposed of in a nearby sanitary fill and the carrier fluid lagooned for
future disposal.
The capsule transport tests will be performed on a once-through basis for
the carrier fluid with the capsules being reused if there is no contamination
of the capsules from broken containers in transport. The capsules will be
segregated according to size and fill density and stored between tests.
The capsule transport tests without polymer should reveal the difference
caused by either the fill density or the capsule configuration. An analysis
will allow the selection of a capsule size and a fill density to be used
on the tests with polymer.
The capsule transport tests, with polymers, will also be performed with
the carrier fluid discharged to waste. The capsules will be reused if undamaged
or not contaminated from prior transport tests.
The carrier fluid reuse tests will be performed by collecting and
returning the carrier fluid to the mixing tank. It will then be mixed with new
manufactured solid waste and measurements of flows, velocities and losses made
as before.
33
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TEST PLAN
Base Information
Grinder Tests - 9 Tests
1 in. grate size, 3 tests of 20 min. each
2 in. grate size, 3 tests of 20 min. each
3 in. grate size, 3 tests of 20 min. each
Classify outputs on each test - use these outputs in performing injection tests,
Injection Tests - 15 Tests
Through Pump
1 in. grate output
3 percent solids concentration rate
5 percent solids concentration rate
10 percent solids concentration rate
2 in. grate output
2 percent solids concentration rate
6 percent solids concentration rate
8 percent solids concentration rate
3 in. grate output
1 percent solids concentration rate
4 percent solids concentration rate
9 percent solids concentration rate
Eductor Method
1 in. grate output
3 percent solids concentration rate
6 percent solids concentration rate
2 in. grate output
1 percent solids concentration rate
4 percent solids concentration rate
34
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3 in. grate output
2 percent solids concentration rate
5 percent solids concentration rate
Flow Tests - 27 Tests
4 Percent Solids
1 in. grate plate
flow velocity 4 ft/sec
flow velocity 8 ft/sec
flow velocity 12 ft/sec
2 in. grate plate
flow velocity 2 ft/sec
flow velocity 6 ft/sec
flow velocity 10 ft/sec
3 in. grate plate
flow velocity 3 ft/sec
flow velocity 5 ft/sec
flow velocity 9 ft/sec
6 Percent Solids
Same matrix as 4 percent
8 Percent Solids
Same matrix as 4 percent
Transport Tests
Water Slurry with Polymers - 54 Tests
First polymer (Use the same test matrix for the second polymer)
10 ppm polymer concentration
slurry concentration 2 percent
velocity 6 ft/sec
velocity 10 ft/sec
velocity 14 ft/sec
slurry concentration 5 percent
velocity 5 ft/sec
velocity 9 ft/sec
velocity 13 ft/sec
35
-------
slurry concentration 8 percent
velocity 2 ft/sec
velocity 5 ft/sec
velocity 8 ft/sec
50 ppm polymer concentration
slurry concentration 3 percent
velocity 4 ft/sec
velocity 7 ft/sec
belocity 10 ft/sec
slurry concentration 6 percent
velocity 3 ft/sec
velocity 6 ft/sec
velocity 9 ft/sec
slurry concentration 9 percent
velocity 1 ft/sec
velocity 3 ft/sec
velocity 5 ft/sec
100 ppm polymer concentration
slurry concentration 4 percent
fluid velocity 4 ft/sec
fluid velocity 8 ft/sec
fluid velocity 12 ft/sec
slurry concentration 7 percent
fluid velocity 2 ft/sec
fluid velocity 4 ft/sec
fluid velocity 6 ft/sec
slurry concentration 10 percent
fluid velocity 1 ft/sec
fluid velocity 3 ft/sec
fluid velocity 5 ft/sec
36
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Capsule in Water Without Polymer - 81 Tests
Capsule size L/D = 1
Fill density looae fill (10 lb/ft3)
Capsule spacing - close spaced
capsule velocity 1 ft/sec
capsule velocity 2 ft/sec
capsule velocity 3 ft/sec
Capsule spacing - 1/2 capsule length between capsule
capsule velocity 1 ft/sec
capsule velocity 2 ft/sec
capsule velocity 3 ft/sec
Capsule spacing - 50 percent occupied by capsule
capsule velocity 1 ft/sec
capsule velocity 2 ft/sec
capsule velocity 3 ft/sec
Fill density - 50 percent compacted (15 lb/ft3)
Same test matrix as loose fill
Fill density - 100 percent compacted (20 lb/ft3)
Same test matrix as loose fill
Capsule size L/D = 2/1
Same test matrix as L/D = 1
Capsule size L/D = 3/1
same test matrix as L/D = 1
Capsule in Water With Polymer - 54 Tests
First Polymer (Second polymer use same test matrix)
10 ppm polymer concentration
capsule spacing - close
capsule velocity 1 ft/sec
capsule velocity 2 ft/sec
capsule velocity 3 ft/sec
capsule spacing - 50 percent occupied by capsule
capsule velocity 1 ft/sec
capsule velocity 2 ft/sec
capsule velocity 4 ft/sec
37
-------
50 ppm polymer concentration
capsule spacing - close
capsule velocity 1 ft/sec
capsule velocity 2 ft/sec
capsule velocity 3 ft/sec
capsule spacing - 1/2 capsule length between capsule
capsule velocity 1 ft/sec
capsule velocity 2 ft/sec
capsule velocity 4 ft/sec
100 ppm polymer concentration
capsule spacing - 1/2 capsule length between capsule
capsule velocity 1 ft/sec
capsule velocity 2 ft/sec
capsule velocity 4 ft/sec
capsule spacing - 50 percent occupied
capsule velocity 1 ft/sec
capsule velocity 1 ft/sec
capsule velocity 4 ft/sec
Second Polymer - same matrix
Water Slurry Gravity Transport - 12 Tests
Flow velocity 1 ft/sec
solids concentration 2 percent
solids concentration 6 percent
solids concentration 8 percent
Flow velocity 2 ft/sec
solids concentration 1 percent
solids concentration 5 percent
solids concentration 9 percent
Flow velocity 3 ft/sec
solids concentration 2 percent
solids concentration 4 percent
solids concentration 8 percent
38
-------
Flow velocity 4 ft/sec
solids concentration 1 percent
solids concentration 3 percent
solids concentration 7 percent
Water Slurry with Polymer Gravity Transport - 24 Tests
First Polymer (Use the same test matrix for the second polymer)
10 ppm polymer concentration
Flow velocity 1 ft/sec
solids concentration 2 percent
solids concentration 4 percent
Flow velocity 3 ft/sec
solids concentration 2 percent
solids concentration 4 percent
50 ppm polymer concentration
Flow velocity 2 ft/sec
solids concentration 1 percent
solids concentration 5 percent
Flow velocity 4 ft/sec
solids concentration 1 percent
solids concentration 3 percent
100 ppm polymer concentration
Flow velocity 2 ft/sec
solids concentration 5 percent
solids concentration 9 percent
Flow velocity 4 ft/sec
solids concentration 3 percent
solids concentration 7 percent
39
-------
Carrier Fluid Reuse
Slurry w/o polymer
10 cycles of fluid
Slurry with polymer
10 cycles of fluid
1 cone, solid
1 flow velocity
1 particle size
1 cone, solid
1 flow velocity, 1 polymer cone.
1 particle size
Capsules w/o polymer
10 cycles of fluid
Capsules with polymer
10 cycles of fluid
Slurry Solids Concentration Limit
Start at solids concentration of 12 percent and increase concentration by
2 percent steps until slurry cannot be pumped.
40
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APPENDIX C
TEST FACILITY DRAWINGS
Page
Figure C-l Schematic Layout of Slurry Pumping Tests 42
Figure C-2 Schematic Layout of Dry Solids Injection Tests 43
Figure C-3 Schematic Layout of Capsule Insertion Tests 44
Figure C-4 Equipment Layout of Slurry Pumping Test 45
Table C-I Equipment List 46
41
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TABLE C-
EQUIPMENT
•1
LIST
Item No.
Description
Capacity, Size, Etc.
1 Hammermill
2 Grinder Feed Hopper
3 Elevator, Grinder to Storage
4 Tank, Ground Waste Storage
5 Rotary Valve
6 Elevator Ground Storage
7 Slurry Storage Tank
8 Slurry Agitator
9 Pump, 6-in.
10 Flow Meter
11 Pressure Transducer
(2 ea)
12 Test Flow Pipe
13 Visual Pipe Sections (2)
14 Solids Separator
15 Dry Solids Eductor
16 Slat Conveyor (Capsule)
17 Rotary Valve
18 Polymer Injection Pump
19 Polymer Mixing and Storage
Tank
20 Water Supply Meter
4 tons/hr of solid waste
4 cubic yards
150 Ibs/min of 10 lbs/ft3
material
2000 cubic feet
750 Ibs/min of 10 lbs/ft3
material
705 Ibs/min of 10 lbs/ft3
material
15,000 gallons
7.5 Hp Lightning
100-2000 gpm vs 150-ft head
6-inch magnetic 100-2000 gpm
0-50. psi
6-in. C.I or steel epoxylined
6-in. cast acrylic
750 Ibs solid/min
6-in. hopper equipped
18-in. wide-Geneva Drive
14-in. x 20-in. blow-through w/6-
in. pipe and Geneva Drive
Duplex piston 250 gph
300 gallons
2 1/2-in. rate indicating
46
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APPENDIX C
TRUCK TRANSFER ECONOMIC ANALYSIS
In 1967, The City of Dallas began definitive planning for the Fair
Oats Solid Waste Transfer Station. The station was designed to service the
northeast quadrant of the City where no disposal sites were available. The
site has frontage along the Southern Pacific Railroad. Both rail and pipeline
movement to ultimate disposal sites were envisioned as potential alternatives
to truck transport from this central depository. Operations began in October
1969 utilizing tractor-trailer transport via a peripheral freeway to a
sanitary landfill operation on the northwest side of Dallas.
The station was completed and placed in operation at a cost of $400,000
including $50,000 for 19.4 acres of land. Receipts consist of garbage and
trash exclusively from three-man crew city collection trucks delivering to the
station's three hoppers. Overall design will permit expansion of the facility to
six hoppers as future thruput requires.
Transfer operations are carried on five days per week by one foreman, four
drivers, one hopper operator, one spotter, one scaleman, and two night
watchmen. Four one-man transfer trucks are currently utilized, each having a 60
cubic yard self-packing trailer. A solid waste density of about 500 pounds per
cubic yard is achieved using these trailers, and each transfer load has
averaged approximately 4.5 collection truck loads. The round trip distance to
the disposal site is slightly under 33 miles.
Table D-l summarizes, quantitatively, the results of the first full year
of operation and identifies certain key comparative operational measures. The
total cost of operation shown is total direct cost and does not include any
allocated overhead or burden. Table D-2 details basic operational data on a
monthly basis.
-------
It is the general feeling of Dallas officials that this data represents a
relatively accurate long term picture of the operation. Some efficiencies and
a reduction in cost are expected with increased operating experience and
growing volume, but those are expected to be partially offset by some inflation
in basic costs, primarily labor.
The cost of $2.83 per ton and $0.09 per ton mile compares favorably with
most previous data available from published studies in other geographic areas
of the United States. This data, which also typically combines station and haul
operations, is highly dependent on local operating conditions, which can vary
dramatically. However, some overall consistency is apparent. Costs developed in
central California range from under $1.00 through $2.60 per ton and from $0.05
to $0.10 per ton mile, while in Maryland they were found to range from $1.50 to
just under $3.00 per ton and from $0.08 to $0.13 per ton mile. Comparable
systems in the suburban Detroit area are found to fall within the same ranges.
Obviously, alternatives to truck transport, which tend not to be as variable
with local operating conditions, must be justified economically on an
installation by installation basis as the available data suggests.
The Fair Oaks truck transfer operation in Dallas was originally justified
on the basis of savings in total rolling stock investment and associated labor
costs. No substantive data is yet available on how well the system measures up
to that objective, but, on the basis of the first year's operation, it is
generally felt that a decrease in total truck investment will be achieved. As
Table D-2 indicates, the transfer ratio has been steadily improved and a ratio of
about 5.0 has probably been achieved on a permanent basis. This ratio alone
has an important impact on rolling stock investment.
48
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TABLE D-l
FAIR OAKS SOLID WASTE TRANSFER OPERATIONS
NOVEMBER 1969 - OCTOBER 1970
SUMMARY
Total transfer truck cost
Direct driver cost
Transfer hauling cost
Direct transfer station operating cost
Total direct cost of operations
Tons transferred
Average tons per working day
Loads received
Loads transferred
Transfer ratio (loads received/loads transferred)
Miles driven in transfer
Manhours employed
Hours of equipment downtime
Average transfer mileage, round trip
Cost per ton
Cost per ton per mile
f\
Truck cost per mi
$ 43,600
24,750
68,350
32,854
$101,204
35,813
138
10,599
2,410
4.4
79,286
20,891
470
32.9
Station Hauling Total
$.92 $1.91 $2.83
.03 ' .06 .09
.55 .55
driver wage of $2.98 per hour.
"Does not include driver cost.
49
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