EPA-660/2-74-092
DECEMBER 1974
Environmental Protection Technology Seriej
Dry Caustic Peeling of Clingstone
Peaches on a Commercial Scale
National Environmental Research Center
Office of Research and Development
U.S. Environmental Protection Agency
Corvallis, Oregon 97330
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development,
U.S. Environmental Protection Agency, have been grouped into
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
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
This report has been assigned to the ENVIRONMENTAL PROTECTION
TECHNOLOGY STUDIES 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.
This report has been reviewed by the Office of Research and
Development, EPA, 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.
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EPA-660/2-74-092
December 1974
DRY CAUSTIC PEELING OF CLINGSTONE PEACHES
ON A COMMERCIAL SCALE
By
Herbert E. Stone
Giant NO. 12060 hFY
Program Element 1BB037
ROAP/TASK No. 21 BAB/025
Project Officer
Harold W. Thompson
Pacific Northwest Environmental Research Laboratory
National Environmental Research Center
Corvallis, Oregon 97330
NATIONAL ENVIRONMENTAL RESEARCH CENTER
OFFICE OF RESEARCH & DEVELOPMENT
U. S. ENVIRONMENTAL PROTECTION AGENCY
CORVALLIS, OREGON 97330
lor sale by the Superintendent of Documents, VS. Government Pnnti
Wellington. IJ.C". _'04()2 - Stix-k No. >>(3!-00991
ting Qihce
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ABSTRACT
Del Monte Corporation, In cooperation with the Environmental
Protection Agency tinder Grant Project No. 12060 HEY, designed and
constructed a commercial size unit rated at 10-12 tons per hour
capacity to demonstrate the feasibility for using the dry caustic
peeling process to remove chemically softened peach peel from
pitted peach halves and to collect and retain the peel residue as
a solid material. This process gently wipes off major portions
of peel lay means of a series of rotating soft rubber discs mounted
in equipment specifically designed and constructed for this pur-
pose. A series of fresh water sprays, applying a minimum amount
of water, remove residual peel remaining after the wiping action.
The dry caustic process is compared with the most common commer-
cial peeling process for cling peaches where a dilute caustic
solution is used to soften the peel, followed by large quantities
of fresh, potable water applied under high pressure to dislodge
and remove peel and caustic residues. The effluent from this
operation contains relatively high amounts of dissolved and un-
dissolved organic materials which do not lend themselves to
mechanical removal.
The project data indicate that BOD, in the effluent from the peel-
ing operation can be reduced by almost 6o£. This represents ap-
proximately a 15# reduction of BOIXj in the final plant effluent
from all sources of organic waste in a typical peach plant using
a conventional peeling process. The data also Indicate that the
dry caustic process can achieve a £ reduction in fresh water
requirements for the peeling operation. This represents approx-
imately a 10% reduction in total fresh water usage in a typical
peach plant.
Economic benefits associated with this process are somewhat offset
by increases in solid waste handling and disposal costs as well as
slightly reduced case yields for the finished product.
This report was submitted in fulfillment of Grant No. 12060 HFY by
Del Monte Corporation under partial sponsorship of the Environmental
Protection Agency. Work was completed as of October 1973.
ii
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CONTENTS
Sections
Page
CONCLUSIONS
II
RECOMMENDATIONS
III
INTRODUCTION
IV
EQUIPMENT
ANALYTICAL PROGRAM
14
VI
RESULTS
19
VII
DISCUSSION
20
VIII
REFERENCES
24
IX
APPENDICES
25
ill
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FIGURES
No.
Page
1. SCHEMATIC - CONVENTIONAL LIQUID
CAUSTIC PEELER
2. SCHEMATIC - DRY CAUSTIC PEELER 9
3. FLANGE DISC DETAIL 10
4. STUB DISC DETAIL 11
5. SCHEMATIC DIAGRAM OF SAMPLING 15
POINTS
iv
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ACKNOWLKDGEMENTS
Del Monte Corporation acknowledges the 1970 pilot plant evaluations
of dry caustic peeling of tree fruits conducted by the National
Canners Association, Berkeley Laboratory, in cooperation with the
Western Utilization Research Laboratory of USDA in Albany, Cali-
fornia. Their early efforts and subsequent consultation contri-
buted substantially to this demonstration project.
We are further indebted to Mr. Kenneth A. Dostal and Mr. Harold
W. Thompson in the Pacific Northwest Environmental Research Lab-
oratory of the Environmental Protection Agency for their guidance
and numerous helpful suggestions in all phases of the project.
The following members of the Del Monte Corporation made signifi-
cant contributions to the design, development and evaluation of
this project:
Scientific Research Department
Herbert £. Stone Richard J. Maass
Wayne W. Thornburg Robert B. Devore
Raymond M. Jadarola Jo Ruth Wright
Jack G. Allen Paul Reiche, Jr.
Andrew T. Halton Demetrios Papakonstantino
Production Management
William L. Hole Walter C. Bergstrom
Robert E. Crawford Edward E. Garcia
Fred H. Laudenslager Robert M. Jorgensen
Gene R. Zolezzi Richard W. Fish
Engineering Department
Charles D. Wintermantel Jack B. Schumate
Robert E. McLees Favio Franceschi
Warren C. Hageman Dr. Charles F. Niven, Jr.
Grant Director Project Director
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SECTION I
CONCLUSIONS
1 The gentle abrasion of rapidly rotating flexible rubber discs
can remove softened peels on clingstone peaches and yield a
canning peach of satisfactory quality.
2 Based upon pounds of BOD per ton of peaches, approximately a
60% reduction of the organic load in the plant's peeler efflu-
ent can be realized with the utilization of the dry caustic
procedure for removal of peach peel and segregation of the
peel as a solid waste. In this project, the conventional
peeler was determined to contribute 20-30$ of the organic
load in the final plant effluent. Using the dry caustic
procedure, data from the demonstration project indicate the
organic load from the peeler operation can be decreased to
a level of 12-20% of the organic load in the final plant
effluent.
3 The action of rotating rubber discs removes major portions of
softened peel and allows for a 90% reduction in fresh water
requirements normally associated with the conventional peeling
of peaches for canning. This volume can represent 10% of the
total fresh water utilized in some peach canneries.
4 Dry caustic peeling of cling peaches reduces plant operating
expenditures for water requirements and capital investments,
operating and maintenance costs of their waste treatment fa-
cilities. However, the process increases the costs of hand-
ling and disposing of solid waste.
5 The dry caustic peeling process results in a 0.9% higher peel
loss than the conventional process.
6 Further work is necessary to establish the full commercial
potential of the dry caustic peeling process for clingstone
peaches.
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SECTION n
RECOMMENDATIONS
Continue the demonstration project and modify the peeled peach
distribution system to allow for increased production rates,
and to further evaluate the full commercial potential of the
dry peeling process.
Evaluate the peeling efficiency of the dry caustic equipment
using lower hydroxide concentrations as a means for reducing
peel losses.
Install a peach-half-turnover slide to assure inverting the
peach half into a cup-up position as it moves onto the rotat-
ing rubber discs.
Install a short flat inclined plate after the last set of
rubber rollers in order to minimize peel solids carry over
into the rinse vater section.
Design full scale commercial units to allow for a straight
thru flow of this delicate fruit and minimize excessive
abrasion.
Design commercial units which provide for optimum accessibility
of all equipment surfaces and allow for proper sanitation and
associated cleaning requirements.
7 Install automatic lubrication systems on ftii moving parts.
8 Evaluate the potential of the peel residue for by-product
utilization.
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SECTION III
INTRODUCTION
Clingstone peaches are a major crop with an annual production
exceeding 30 million cases during a relatively short period of
two to three months. Being a seasonal fruit and subject to
natural degradation, if left unprocessed, it cannot be stored
for any length of time.
The most common commercial peeling procedure for cling peaches
utilizes a dilute (1-3$) sodium hydroxide (caustic) solution to
soften the peel, followed by large quantities of potable water
applied under high pressure to dislodge and remove peel and
caustic residues. Effluent from this operation normally contains
20-30% of dissolved and undissolved organic materials. Their
relatively high levels of solids do not lend themselves to
mechanical removal and consequently comprise a portion of the
liquid effluent from the plant.
Disposal of liquid waste with the resultant organic and hydraulic
loads, which may be imposed on waste treatment systems, has fre-
quently been a serious concern to management in the food process-
ing industry. In response to this concern, the Industry has com-
pleted numerous research projects whose prime goals have included
seeking means for reducing: 1) the generation of oxygen demand-
ing substances which are a natural component of the food; and
2) the use of fresh water in plant processing areas where product
quality and sanitation requirements would not be adversely af-
fected.
One such project was carried out during 1970 under Environmental
Protection Agency (EPA) Research and Development Grant No. 12060
PQE, entitled "Dry Caustic Peeling of Tree Fruit for Liquid Waste
Reductions" (Reference l). Under this project, the National Can-
ners Association (NCA), Western Research Laboratory, in Berkeley,
California with the assistance of the Western Utilization Research
Laboratory of USDA in Albany, California demonstrated the feasi-
bility for mechanically removing caustic softened peel from tree
fruits, including pears and apricots. The softened peel was
separated from the liquid waste stream and the small amounts of
residual peel and chemical residue were flushed off the fruit
using significantly reduced volumes of fresh water.
On the basis of these pilot scale studies, the Del Monte Corpora-
tion proposed to EPA to design, construct and permanently install
equipment which would commercially demonstrate the principles
developed in the pilot project. Following a series of discussions
concerning the parameters to be investigated to assure that the
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proposed evaluation and analytical program would develop and accu-
rately reflect the commercial feasibility and potential advantages
of the new peeling method, EPA Research and Development Grant No.
12050 JffY was awarded on April 1, 1971 as a partial support for
implementing the project.
Del Monte Corporation, Plant No. 3, located in San Jose, Californ-
ia, was selected as the site for the demonstration. Factors which
contributed to this decision were:
The Plant is a major production unit for cling peaches
and fruit cocktail.
Liquid effluent from the cannery flows into a municipal
water pollution control plant which has had occasional
difficulties in meeting local water quality standards.
Some of the treatment plant problems have been attrib-
uted to the food processing plants in the area, parti-
cularly during the summer months. It was hoped that a
successful commercial feasibility demonstration would
result in reduced organic and hydraulic loads from the
cannery and would relieve some of the strain on this
secondary treatment system.
Proximity of the Plant to the Del Monte Research Cen-
ter in Walnut Creek, the California Division Operations
Office in Berkeley, and the Del Monte Corporate Office
in San Francisco. Thus, research, operating and cor-
porate management personnel were within easy access to
the project for necessary observation and supervision*
The Del Monte Research Center is a state certified, non-
commercial laboratory with complete facilities readily
available for the desired comprehensive analytical pro-
gram. The analytical program is detailed below and
results are in appended tables.
Equipment designed by Del Monte Corporation engineers was con-
structed by mechanics and machinists in a company-owned machine
shop, located in Berkeley, California, and on the site by plant
personnel. Limited details of the design and installation are
included in this report. Complete design and material specifi-
cations are available from EPA.
Installation of the equipment was completed during the early sum-
mer of 1971. Following a brief test period under normal produc-
tion conditions during which it was found necessary to adjust and
slightly modify a conveyor belt, the experimental peeler began a
three-shift operation on August 19, 1971* The demonstration pro-
ject continued through September 23, the close of the 1971
peach canning season.
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In the conventional peeling method used at this plant, pitted
peaches are turned so that the pit cavity is facing downward
(termed "cup-down") on a LaPorte conveyor (linked metal chain)
immediately prior to entering a long and partitioned tank in
which peeling is accomplished. In the first section, peach
skins are sprayed with a dilute solution of hot sodium hydroxide
(caustic). The fruit is in this section for approximately ten
seconds and is conveyed into the second or steam heated holding
section for another 30 seconds where chemical action on the skins
is completed. In the last section, fruit is carried under a
series of high pressure water sprays where peel and caustic resi-
dues are removed and flushed into floor drains for disposal. As
many as 20 banks of sprays may be used for removing this peel and
caustic residue. In the operation at Del Monte Plant No. 3, only
the final six spray headers apply fresh water. The remaining
sprays are divided into two sets, using recycled rinse water
applied in a counter-current manner.
Control of chemical peeling is achieved by adjustments of the
sodium hydroxide concentration within the range of 1-3$ sodium
hydroxide, temperature of the solution between 212-220OF., and
holding time on the conveyor between 40-60 seconds.
Fallowing the final series of fresh water sprays in the last sec-
tion of the peeler, peach halves are inverted such that the pit
cavity faces up as the fruit is conveyed past a visual inspection
station. Here defects, blemishes, imperfect halves, green fruit
or other lower quality peaches are removed for any necessary trim-
ming, diversion to an alternate product style, or discard.
Peach halves peeled by the experimental dry caustic method were
subjected to the identical sodium hydroxide solution concentration,
temperature and holding period as the conventional method previous-
ly described. However, Immediately prior to rinsing with water,
peach halves were diverted from the LaPorte conveyor belt onto a
cross conveyor rubber belt which allowed distribution over the full
width of the demonstration dry caustic peeling unit where peeling
was achieved by the gentle abrasive action of the rotating rubber
discs against the softened peach skin. The rotating action of the
discs served both to clean the peach halves by removing the soft-
ened peel and caustic residue and to transport them across the top
of the peeler.
From the peeling unit, a short metal slide dropped the peaches
gently into a tank of water from where they were elevated by a
link chain slat conveyor for return to the same inspection belt
described previously.
For purposes of this demonstration and to facilitate general visual
comparisons between fruit peeled by the two methods, the peaches
were slightly separated on the inspection belt. Once past this
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inspection station, "dry" and conventionally peeled peaches were
mixed and, no attempt was made to keep them separated or to dif-
ferentiate in subsequent grading, preparation, canning or process-
ing of the fruit.
The subsequent size grading, preparation, canning and processing
of the cling peaches are not considered a portion of this project
and are not detailed. However, it can be stated that Del Monte
production personnel made frequent evaluations in these latter
areas to assure that the experimental peeling process did not
create any unexpected or adverse problems. None were experienced.
Some reduction in the concentration of sodium hydroxide and/or
holding time of treated fruit can be expected in the dry caustic
peeling method. However, during the initial season, no changes
could be evaluated as 25& of the plant production utilized the
same caustic application and fruit conveying equipment.
The project did substantiate expectations of segregating the peel
from the liquid waste and for achieving a significant reduction in
fresh water requirements for this operation. The cost savings in
fresh water and potential treatment requirements of the organic
matter in the liquid effluent were also evaluated in the project
and are detailed in Section VII, "Discussion". Limitations on
potential changes in plant operating conditions prevented the full
economic evaluation of the process.
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SECTION IV
EQUIPMENT
Commercially sized dry caustic peeling equipment for this de-
monstration project was patterned after the NCA-USDA model de-
scribed in EPA Project 120oO FQE (Reference l). The commer-
cial size unit, designed by Del Monte engineers, was scaled
to handle approximately 10-12 tons per hour of pitted cling
peachesequal to approximately 25% of the plant production
of peaches.
Figures Nos. 1 and 2 on the following pages are schematic re-
presentations of the equipment layout used for conventional
and dry caustic peeling comparisons. Sampling points for the
extensive analytical program associated with this project are
also identified on these figures.
The dry caustic peeling unit consisted of a frame six-feet
wide by ten-feet longmounted on adjustable legs. A series
of 39 stainless steel shafts were positioned across the six-
foot dimension. Specially designed soft rubber discs made
from food grade rubber were mounted on each shaft. A chain
drive from a 7-1/2 H.P. vari-speed U. S. Motor to sprockets
on the end of each shaft provided positive rotation of the
discs. A speed of approximately 325 RPM was determined to be
optimum during the evaluation program.
Discs used in the dry peeler were of two typesj the larger
k-I/k inch diameter size incorporated a flexible flanged edge
which gently removed the softened peel on peaches traveling
in a single layer on the tops of the discs; the smaller 2-3/U
inch diameter stub discs were mounted on specific shafts and
strategically placed to invert peach halves which may have
turned over into a "cup-down" position as a result of the
tumbling action. It was, of course, necessary to expose the
peel portion of the peach to the abrasive action of the discs.
Discs and disc spacer sections were cast as one piece in the
mold, designed by Del Monte. A "key", or projection, into the
center hole was also an integral portion of each disc fitting
into a slot on the shaft and achieving positive drive of the
disc. This contrasted with the previous year's pilot model
which used plastic spacers and depended upon friction to drive
the discs.
Figures No. 3 and k are engineering diagrams of the two types
of discs. Complete details on equipment specification and con-
figuration, dimensions and placement of discs are available from
EPA's Pacific Northwest Environmental Research Laboratory, 200
3. W. 35th Street, Corvallis, Oregon 97330, Attn: Chief, Pood
Waste Research.
7
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PITTED
FRUiT
(cup-down)
-SODIUM
HYDROXIDE
SOLUTION
-VALVE
APPLICATION
SECTION
HOLDING
SECTION
SPRAY
RINSE
SECTION
'''O'M ;,'V V
recifculotion
L
SODIUM HYDROXIDE
PEELER TANK
PUMP
SAMPLER
-SAMPLE BOTTLE
(refrlgerotod)
Figure 1. Schematic-conventional liquid caustic peeler
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FRESH
WATER
METER
DRY PEELER
DISC SECTION
(cup-up)
SODIUM HYDROXIDE
PEELER TANK
PEEL SOLIDS
TO WASTE
HOPPER
TO CUP-UP
SHAKER AND
INSPECTION BELT
RINSE WATER
TO BIOLOGICAL
TREATMENT SYSTEM
^0
TIMER /
^-SAMPLE BOTTLE
(r«fr!g»rot»a)
Figure 2. Schematic-dry caustic peeler
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R. (typical)
^"R.(typical)
1.000 0.
1.005" D.
Material: Black Rubber - 50 Durometer Food Grade
Figure 3. Flange Disc Detail
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1.000" 0.
1.005" D.
^"R. (typical)
Material: Black Rubber -SO Durometer-Food Grade
Figure 4 . Stub Disc Detail
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As noted above, movement of the peach halves was achieved by discs
rotating in the sane direction as the flow of fruit. Duration of
time on the peeler unit was controlled "by adjustment of the height
of the discharge end over the feed end. Over the ten-foot length
of the peeler unit, a 17-18 inch rise from feed to discharge end
was considered optimum for the varieties of peaches process during
the 1971 canning season at Plant No. 3*
Peel and caustic residues fell between the rotating rubber discs
into a conically shaped tank from where they were pumped through
a separate V diameter pipe Into a large collection hopper In the
plant yard and combined with solid residues from other fruit pre-
paration operations (see Figure No. 2). These wastes were hauled
to an approved land disposal site by trucks, which were specially
modified to prevent seepage of liquids draining from the food
reildu,il s
Che softened peel material, as it was removed from the peach
halves, was a viscous slurry, or semi-solid, which could be
pumped by commercially available cement type equipment. In this
project, the primary collection tank beneath the rollers was
drained 2-3 times per hour. Each draining was equivalent to ap-
proximately 60 cubic feet of peach peel slurry.
Three manifolds of fresh water sprays, mounted above the link
chain elevator conveyor, removed peel and caustic residues and
provided the only fresh water rinsing necessary on the "dry"
peeled fruit (see Figure No. 2). Four spray nozzles, each noz-
zle delivering approximately one gallon per minute of fresh water,
were mounted on each manifold and positioned to achieve full cov-
erage of the width of the elevator conveyor. Hater draining from
the fruit became make-up water for the tank into which the fruit
slid following the peeler section. An automatic sensing device
maintained the proper level of water in the tank following the
peeler. Rinse water from this tank was pumped directly to the
biological treatment system which was operated by BCA personnel
as a sub-project of the peeling evaluation.
From the flight elevator, "dry-peeled" peach halves were conveyed
on an overhead "V" trough-shaped rubber belt to a chute where they
were gently lowered onto the link chain conveyor carrying conven-
tionally peeled fruit emerging from the final series of fresh water
sprays. Peach halves peeled by both methods were then conveyed
side-by-side past the inspection station where imperfect halves
were removed as previously described.
12
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The peeling unit itself was scaled to handle 10-12 tons per hour
of fruit. Although several brief runs indicated an l8-24 ton per
hour rate of production was feasible, these could not be main-
tained without extra supervision by plant personnel to Manually
distribute the peeled fruit over the inspection belt.
During the course of the demonstration project, the "y" belt
trough conveyor also became a limiting factor for the volume of
peach halves which could be peeled by the dry caustic method.
As a precautionary measure to allow the plant to use the full
capacity of both conventional peeling units in the event some
unexpected problems occurred, the dry caustic peeler, rinse
unit and associated equipment were "fitted" into available
space. Consequently, the direction of flow for the peach
halves was changed several times. Under normal circumstances,
a straight flow would be preferred and equipment, such as the
"V", trough conveyor, would likely be eliminated.
A sub-project evaluated the potential benefits of biological
treatment of the rinse water from the dry caustic unit. Con-
centrated waste water was piped directly to the treatment sys-
tem and was segregated from all other liquid streams. Briefly,
the concentrated waste water was biologically treated to reduce
the organic content in an existing high-rate polyvinyl chloride
plastic media trickling filter used in previous studies (Refer-
ences 2 & 3).
A full description of the treatment system and a summary of the
analytical results may be found in the "Proceedings Third National
Symposium on Food Processing Wastes11 (EPA Report No. R2-72-018,
November 1972.)
13
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SECTION V
ANALYTICAL PROGRAM
An extensive analytical program designed to evaluate the effective-
ness of the dry caustic peeler in removing peach skins and retain-
ing the solid material as a separate entity was conducted at the
Del Monte Research Center and NCA, Berkeley laboratories. Signi-
ficant characteristics of the waste rinse waters from the "dry"
method were compared with those from the conventional peeling
method, figure 5 is a schematic of sampling points for peach
peel and rinse waters. Table I indicates the sampling schedule
for each parameter investigated at each sampling point.
Sampling Points No. la and Ib are peach rinse water from
the conventional commerical peeler.
Sampling Points No. 2a and 2b are peach rinse water from
the experimental dry caustic peeler.
Sampling Point No. 3 is peach peel slurry from the exper-
imental dry caustic unit.
Sampling Point No. U is influent to the trickling filter
plus some recycle treated rinse water.
Sampling Point No. 5 is final effluent from the trickling
filter.
As indicated in the sampling schedule, rinse water characteristics
for Points 1 and 2 were determined on both 2U-hour composite sam-
ples collected 5 days per week during four consecutive weeks of
the project period, and on a series of hourly grab samples collected
on two operating days per week during the four week (total 21 days)
sampling period. Insofar as possible, this schedule was adjusted
to allow for initiation and completion of all laboratory analyses
during the normal work week.
Automatic sampling devices were installed on the continuously
flowing rinse water discharge lines from both peelers. These
samplers were activated by electric timers which opened a valve
allowing air to "push" a measured quantity of rinse water from
sampling Points la and 2a through plastic tubing into large
individual plastic bottles inside a conventional household style
refrigerator, located adjacent to the dry caustic peeling unit.
14
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PEELER DISC
SECTION
SPRAY RINSE SECTION
RINSE TANK
t_n
OVERFLOW
TO SEWER
DRY CAUSTIC PEELER
TRICKLING
FILTER
HATER 1
L SUMP ^
ELER
>i
4=
1
I
r
^
PUMP
^x FLOW METER
WASTE WATER
STREAM
CONVENTIONAL LIQUID CAUSTIC
PEELER
IDENTIFICATION OF SAMPLING POINTS:
I. RirtM wattr from conventional commercial peeler
2. Rinse water from experimental dry caustic peeler
3. Peel slurry from experimental dry caustic peeler
4. Influent to trickling filter
5. Final effluent discharged to municipal sewer
Figure 5. Schematic diagram of sampling points
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TABLE I - ANALYTICAL PROGRAM
Analyses Sampling Points
BODS (Total)
BODS (Soluble)
COD (Total)
COD (Soluble)
Total Solids
Suspended Solids
Volatile Suspended Solids
Kieldahl Nitrogen
Nitrite - Nitrogen
Nitrate - Nitrogen
Total - Phosphate
Opfjio - Phoj^phate
Alkalinity (Total)
pH
Dissolved Oxygen
Temperature (°C)
la
24C
24C
24C
24C
24C
24C
24C
G
G
Ib
G
G
G
G
2a
24C
24C
24C
24C
24C
24C
24C
24C
24C
24C
24C
G
G
G
2b
G
G
G
G
3
8C
G
4
8C
8C
8C
8C
8C
G
5
24C
24C
24C
24C
24C
24C
24C
24C
24C
G
G
G
Footnotes:
24C refers to a composite sample drawn once per hour over a 24 hour
period.
8C refers to a composite sample drawn once per hour over an 8 hour
period.
G refers to a random grab sample collected once during an operating
day for specified sample stations except stations Ib & 2b. For
stations Ib & 2b, grab samples are collected hourly throughout an
8 hour operating shift with the indicated analyses completed on
each grab sample.
16
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An eight-ounce sample, drawn once per hour was the quantity and
frequency of sub-sample selected for each composite at Points
la and 2a. The reasonably uniform volume of irater used in this
operation, and the similarly uniform flow of peaches did not re-
quire more frequent sampling or necessitate attempts to catch
subtle variations. Approximately 2-1/2 gallons of composite
sample were collected daily from each line. The composite bot-
tle was shaken thoroughly before transferring approximately
one gallon of each sample to another clean plastic bottle for
transport to the Del Monte laboratory. The larger composite
sample "bottles were then drained, rinsed several tines with
fresh water, drained again and returned to the refrigerator
for collection of the next 2U-hour composite sample. A total
of 21 composite samples each were collected from Points la and
2a.
Samples lb and 2b represent a series of hourly grab samples of
rinse water which were taken from both the conventional and
experimental lines during two 8-hour day shift periods each
week. On these days, one quart grab samples were collected in
plastic bottles over the eight hour schedule by Research Center
personnel manually draining small pipes, located at the same
point in the liquid discharge line as the automatic samplers
described above. Immediately after collection, the grab sample
was placed in the same refrigerator as the composite sample un-
til transport to the Research Center laboratory the following
morning. A total of eight grab samples each were collected
from Points lb and 2b on each of eight separate days.
Composite samples from Point Ho. 3 for analysis of peel char-
acteristics were made by combining hourly collections of a
uniform quantity of peel slurry into a single one gallon con-
tainer. This container was held inside the refrigerator un-
til transfer to the Del Monte laboratory the following morning,
along with composite and hourly samples of rinse water. A
total of 21 composite samples of peel were collected. There
is no comparable solid waste sample from the conventional
peeling unit, as in the latter instance, all peel is flushed
into the liquid stream from where it cannot be physically
separated.
With the exceptions noted below, all analytical procedures used
by the Del Monte laboratory were in accordance with those listed
in "Methods for Chemical Analysis of Water and Wastes - 1971
Edition" as prepared by the Water Quality Office of EPA. The
BOD procedure outlined in Standard Methods for the Examination
of Water and Wastevater - 13th Edition was followed. ~
17
-------
The single exception to the standard methods of analysis was
necessitated by interference of natural pectin in the fruit
with conventional methods for separating soluble and sus-
pended or colloidal fractions of natter in the wastewater
samples. A series of experiments at the Del Monte laboratory
developed the following procedure for pretreatment of the
samples, prior to determining soluble BOD and soluble COD:
Filter wastewater samples through diatomaceous
earth, followed by filtration through Whatman
No. k2 filter paper and ultimately centrifug-
ing at 2,000 RPM for 20 minutes. The resultant
supernatant is reasonably clear and considered
suitable for soluble BOD and soluble COD deter-
minations by standard methods.
Peel loss on the fruit for both "dry" and conventional peel-
ing methods was determined by comparing weights for a random
selection of 100 peach halves, before exposure to the sodium
hydroxide solution, and another 100 randomly selected halves
after peeling and rinsing. Peach halves from each peeling
method were weighed by trained plant personnel, approximately
every half hour throughout the operating day during the dur-
ation of the demonstration project. A total of 6ll observa-
tions were made on the conventional peeler and an additional
591 observations on the demonstration dry caustic peeler.
18
-------
SECTION VI
RESULTS
The results of the demonstration project are summarized in a ser-
ies of tables appended to this report.
Table I is the Analytical Program for this project and appears in
Section V, p. 16.
Table II, appended, is a comparative tabulation of fresh water
usage for each peeling method (p. 26).
Table III is a compilation of analytical data for 2Vhour compos-
ite samples of rinse water from the dry caustic cling peach peel-
ing process (p. 27).
Table IV is a compilation of analytical data for 24-hour compos-
ite samples of rinse water from the conventional cling peach peel-
ing process(p. 28).
Tables V and VI are a series of sub-tables detailing analytical
data for hourly grab samples of rinse water on selected dates from
each peeling process(P 29).
Table VII tabulates analytical data for 3-hour composites of the
peel solids and caustic residue separated and collected from the
dry peeling process (p- 37).
Table VIII is a tabulation of concentrations and the related mass
emission level for selected parameters in the 2^-hour composite
samples from the dry caustic peeling process (p* 38).
Table IX is comparable to Table VIII parameters and tabulates the
same data for 2U-hour composite samples from the conventional
peeling process (p. 39).
Table X is a summary comparison of selected rinse water character-
istics from both peeling processes showing the range, average,
median and standard deviation for each of the characteristics
listed (P. 40).
Table XI compares peel losses for the conventional and dry caustic
processes (p. 41).
19
-------
SECTION VII
DISCUSSION
EPA Project No. 12060 HFY demonstrated that the gentle abrasion of
rapidly rotating flexible rubber discs can remove major portions
of softened peels and caustic residues on the surface of clingstone
peaches and yield a product of satisfactory quality for canning.
Limitations on several aspects of the demonstration equipment indi-
cate that modifications were necessary and additional work desir-
able to establish the full commercial potential for this method.
Some of these modifications are indicated in the discussion below.
Del Monte's Plant No. 3 has two completely separate, but identical,
conventional peach peelers. During this project, one peeler,
designated as a "control", allowed evaluation of conventional
rinse water characteristics, water volume measurements and peel
loss determinations. Rinse water discharged from this peeler was
mixed with liquid waste streams from other areas in the Plant.
One-half of the Plant* s second peeler was used for the demonstra-
tion project. Only those peaches and rinse waters associated with
the experimental unit are included in the data and discussion
which follow and compared to the control unit. Rinse water from
the dry caustic peeling unit was kept separate from all other
liquid waste streams and served as the influent to the trickling
filter described previously.
The commerically sized demonstration unit was designed to peel 10-
12 tons of cling peaches per hour, equivalent to approximately 2
tons per foot of width. Brief test runs indicated that production
rates of 18-24 tons per hour (3-4 tons per foot of width) were
feasible in the peeling unit. At higher peach flow rates, a number
of halves were observed to traverse significant lengths of the
peeler in a cup-down position, indicating that a greater number and
perhaps different positioning of stub rollers may be necessary.
Tine did not permit an investigation of alternate roller alignments
during the 1971 canning season.
Substantial reductions were realized in the fresh water require-
ments normally used during this phase of the preparation of cling-
stone peaches for canning. Table II is a comparative tabulation
of the gallons per day of fresh rinse water used for each peeling
method. The conventional peeler, preparing peaches at the rate of
approximately 25 tons per hour, used a seasonal average of 254
gallons per minute, or a total of approximately 370,000 gallons
per day. This is equivalent to approximately 850 gallons fresh
water per ton of cling peaches. In terms of fresh water usage in
the plant, this can represent up to 10$ of its total fresh water
requirement s.
20
-------
Table II shows that the dry caustic unit, preparing peaches at the
rate of 10-12 tons per hour, vised a seasonal average of 13 gallons
per minute or approximately 19,500 gallons per day. This is equi-
valent to approximately 90 gallons of fresh water per ton of cling
peaches or slightly more than 1.0% of the fresh -water required for
the conventional process. Expressed in other terms, this volume
would represent approximately 1$ of the total fresh water usage in
the plant.
Cost savings for fresh water usage using the dry caustic peeler
would be in the range of $. 19 per ton of fruit (assuming a cost of
$.25/1000 gallons for fresh water).
The project further demonstrated that the softened peel can be
segregated from the liquid waste stream and handled as a solid
waste fraction of the residues hauled from the plant. Calcula-
tions based upon the analytical data comparing "dry caustic"
versus conventional methods indicate that for this step in the
preparation of cling peaches for canning, a reduction of almost
6O% of the BOD load in the liquid waste stream (2.7 Ibs. vs. 6.7
Ibs. per ton peaches) and 63% of the suspended solids in the waste
stream (1.9 Ibs* vs. 5*1 Ibs. per ton peaches) was achieved. The
reductions in volume of waste water, BOD and suspended solids
would result in a direct reduction in the user charges of a muni-
cipal waste water treatment facility as shown below.
Table X summarizes analytical data for selected characteristics
of rinse water from both peeling methods. As had been anticipated,
the rinse water from the dry caustic process contained substanti-
ally higher concentrations (mg/l) of organic matter. However,
when related to the total liquid waste and expressed in terms of
pounds of waste per ton of peaches processed, the dry caustic
method was determined to reduce the pounds of organic matter that
would otherwise be present in the liquid effluent from the plant.
Briefly summarized, these are calculated on the basis of Ibs. per
ton of peaches to be a 60% reduction in BODt, a 63% reduction in
suspended solids, and a 70% reduction in total solids.
Slightly lower pH levels for 2^-hour composite samples of rinse
water from the "dry" peeler also indicate removal of caustic
residue in the solid peel slurry. Table VII data shows a pH
range of 9.0 to 10.6.
Peaches peeled by the "dry" process exhibit slightly greater than
average weight losses over those from the conventional peeling
method. Table XT is a summation of weekly and seasonal averages.
The seasonal average indicates a 7* b% weight loss for the dry
peeling method versus a 6. k% weight loss for peaches peeled by the
conventional method.
It is believed that some causes for the higher loss in the dry
caustic method can be reduced.
21
-------
Specifically, the concentration of sodium hydroxide
solution may be higher than necessary for the dry
caustic peeling method resulting in greater soften-
ing of the peel and sub- dermal layers than would be
required by full commercial development of the pro-
cess. As noted previously, the sodium hydroxide
solution concentration could not be decreased during
this project as 25$ of the Plant's non-experimental
peach production used the same spray section. Any
significant reduction in sodium hydroxide concentra-
tion would likely have resulted in an unsatisfactory
canning peach on the conventional portion of the line.
Another possible factor contributing to the somewhat
greater peel loss observed for the dry peeled peaches
is the additional handling which these halves received.
The action of the diversion bar shearing fruit across
the LaBorte conveyor onto the cross conveyor to the
dry peeling unit could also scrape some flesh from
the center of the peach. Commercial units with a
straight flow of fruit would preferably not have this
diversion and its consequent abrasion action.
Although the scale of the demonstration project did not allow for
a full determination of the economic impact of the dry caustic
peeler, the data does allow for a theoretical calculation and
indicates the use of the dry peeler can be more costly to the
canner when a.Ti economic advantages and disadvantages of the pro-
cess are considered. The rates used in the calculations below
represent costs in the city of San Jose, California during 1971.
In determining the potential benefits to the canner using the dry
caustic peeling process, appropriate substitutions must be made
for waste water treatment charges, solid residue disposal and
possibly reduced peel loss as the result of modifications in the
peeling unit or process line where abnormal abrasion could be
occurring.
In terms of potential sewer service charges in San Jose
1971, the dry caustic process would provide a cost savings to
the canner:
Conventional Peeling System
8^0 gallons x 4.60 = & .510/ton
6.7 Ibs. BOD x $.0045 * ? .030/ton
5.1 Ibs. SS x .00^5
.023/ton
$ .563/ton
ELus fresh water .210
Total $ .773/ton
22
-------
Dry Caustic Peeling System
90 gallons x $.60 = $ .051*
2.7 Ibs. BOD x $.001*5 = .012
1.9 Ibs. SS x .00^5 = .008
$ .
Plus water = .023
Total $ .097/ton
2. In terms of handling solid residues generated by the peeling
process, the additional cost to the canner would be:
Conventional System
No Cost
Dry Caustic Peeling System
5.55 cu. yds. per hour equivalent to
0.1)63 cu. yds. per ton peaches.
@ $3.90/cu. yd* = $L.8l/ton peaches
3. In terms of peel loss, the additional cost to the canner would
be:
1971 cost of product = $ 79.00/ton
Peel Loss (Table XI )
Conventional System
Dry Caustic Process 7*35%
$ 79-00 x 0.9# = $ .TU/ton peaches
23
-------
SECTION VIII
REFERENCES
1. National Canners Association, Berkeley Laboratory. Dry
Caustic Peeling of Tree Fruit to Reduce Liquid Waste
Volumes and Strength. Report on EPA Project No, 12060 FQE,
December, 1970.
2. National Canners Association, Berkeley Laboratory Waste
Reduction in Food Canning Operations. Report to the Water
Quality Office on EPA Project No. 12060, August 19700
3. National Canners Association, Berkeley Laboratory. Trickling
Filter Treatment of Fruit Processing Waste Waters. Report to
the Water Quality Office on EPA Project 12969 EAE, September
1971.
4. Chipperfield, P.N.J. Performance of Plastic Filter Media in
Industrial and Domestic Waste Treatment. JWPCF. 39:1860-
1874, 1967.
5. Jeris, J0SP A Rapid COD Test. Water and Waste Engineering.
4(5):89-91, 1967.
24
-------
SECTION IX
APPENDICES
Page
A-1 TABLES II-XI INCLUSIVE 26
A-II SUPPLH-EHT REPORT - 1972 OPERATING SEASON 42
A-III SUPPLEMENT REPORT - 1973 OPERATING SEASON 59
25
-------
TABLE II
PEELING OPERATION - RINSE WATER USE
Volume Rinse Water
Dry Caustic Peeler
Pate
8/19/71
8/23/71
8/24/71
8/25/71
8/26/71
8/27/71
8/30/71
8/31/71
9/2/71
9/3/71
9/7/71
9/8/71
9/9/71
9/10/71
9/11/71
9/13/71
9/14/71
9/15/71
9/16/71
9/17/71
9/20/71
9/21/71
9/22/71
Gal. /Day
12, 070
16,090
15,540
16,600
18, 110
14,040
20,940
20, 710
19,190
19,190
21,150
20,850
19, 280
24, 280
22,740
18, 825
18, 825
22,100
22,000
21,560
23, 070
22,150
17,560
Gal. /Ton
56
75
72
77
84
65
97
96
89
89
98
97
89
112
105
87
87
102
102
100
107
103
81
Volume Rinse Water -
Conventional Peeler
Gal. /Day
389, 100
378, 700
375, 300
370,000
394,400
373,400
374,900
348,000
368,900
368,900
381, 700
377, 100
367,000
380, 200
342, 800
348,000
344,100
360,300
363,600
361,500
355, 800
331,700
Gal. /Ton
901
877
869
856
913
864
868
806
854
854
884
873
850
880
794
806
797
834
842
837
824
768
Average gallons per 24-hour day:
"Dry Caustic" Peeling
Conventional Peeling
Average gallons per minute;
"Dry Caustic" Peeling ,
Conventional Peeling
Average gallons per ton fruit:
" Dry Caustic" Peeling (S> 216 tons per day .
Conventional Peeling @> 432 tons per day
19,430
366,150
13
254
90
850
26
-------
ANAMTICAL DATA - 2U-HOUR COMPOSITE SAMPLES
Sample
Date
8/19/71
8/23/71
8/2U/71
8/25/71
8/26/71
8/27/71
8/30/71
8/31/71
9/2/71
9/3/71
9/7/71
9/8/71
9/9/71
9/10/71
9/11/71
9/13/71
9/1U/71
9/15/71
9/16/71
9/20/71
9/21/71
Average:
COD
mg/1
1+785
7290
8015
9895
8030
31+35
11,305
51+10
5350
3725
3200
-_
1+300
1+325
1+095
2965
51+90
2670
1+820
5910
6965
5600
BOD5
mg/1
2190
3820
5770
6170
3860
2890
8655
21+05
2365
.-
21+85
2375
2720
-_
1+51+5
2150
1+000
35^0
3750
0.1+6
0.52
0.72
0.62
0.1+8
0.81+
0.77
0.65
0.71+
0.58
0.55
0.66
0.83
0.81
0.83
0.51
0.66
CRY CAUSTIC PEELING PROCESS - CLING PEACH RINSE WATER
Total
Solids
mg/1
53^5
7010
81+65
7825
6800
1+205
7160
1+320
5180
3930
1+290
1+1+70
1+085
3990
3895
-
--
--
Suspended
Solids
mg/1
1650
2925
3550
3630
1630
2860
21+50
2170
1150
2200
2300
2300
1650
2310
2670
2850
2700
2750
Volatile
Suspended
Solids
mg/1 %
._
__
-_
3V70 95.6
__
2630 91.2
._
__
._
--
.-
__
2170 93.9
251+0 95.1
2590 95.9
._
Total
N
mg/1
110.7
122.6
156.9
108.6
--
119.8
86.2
--
108.6
92.5
--
118.1+
110.1+
116.5
106.5
117.0
Nitrite
N
mg/1
< 0.02
--
< 0.02
--
< 0.02
--
--
< 0.02
_ _
0.2
< 0.02
Nitrate
N
mg/1
--
2.8
--
--
--
--
0.2
< 0.1
--
0.2
1.0
--
0.8
< 0.1
Total Ortho Alkalinity
P P CaCO,
mg/1 mg/1 mg/1
0.8
21+30
2680 9!+. 5 113-5 < 0.02
0.7
7.9
10.0
15.1+
10.1
5.0
2.3
1+.9 2.2
3.6 1.6
2.8 0.3
12.0
5.2 3.2
6.7 3.0
7.0 1.6
1+70
615
1+50
520
370
595
1+80
605
1+75
620
5l+0
1+.56
^.55
1+.90
5.35
i+.9»+
1+.89
5.10
5.85
U.73
1+.70
1+.88
1+.78
515
-------
TABLE IV
ANALYTICAL DATA - 2k HOUR COMPOSITE SAMPLES
CONVENTIONAL PEELING PROCESS - CLING PEACH RINSE WATER
Sample
Date
8/19/71
8/23/71
8/214/71
8/25/71
8/26/71
8/27/71
8/30/71
8/31/71
9/2/71
9/3/71
9/7/71
9/8/71
9/9/71
9/10/71
9/11/71
9/13/71
9/1U/71
9/15/71
9/16/71
9/20/71
9/21/71
COD
mg/1
1680
1305
ll*l*5
2030
111*5
ll*15
1180
1335
1295
1650
2060
1170
1820
3275
1135
905
1100
1>*35
BOD
&JL>5
mg/1
860
790
930
860
795
1025
990
1080
1255
835
Average 1520
830
705
1080
91*0
BOD/COD
0.51
o.6l
0.6U
0.1*2
0.69
0.72
0.76
0.65
0.61
0.71
0.63
0.73
0.78
0.75
0.65
Total
Solids
mg/1
2725
2165
2600
2525
2000
1910
2275
2225
2160
2680
3125
2100
25MD
^135
__
-_
Suspended
Solids
mg/1
675
1^50
1250
1020
525
570
1350
1+25
250
800
--
750
200
13^0
700
300
710
1000
Volatile
Suspended
Solids
mg/1 1°
--
o/kQ 92.2
U90 90.7
_.
_-
--
_.
--
__
1260 9^.0
6itO 91.1
_-
620 87.3
Total
N
mg/1
36A
25.2
35.7
39-9
35.0
32.2
1*7.6
29.1*
56.0
31.9
29.1
22.1*
35.7
Nitrite
N
--
< 0.02
< 0.02
< 0.02
< 0.02
< 0.02
< 0.02
< 0.02
Nitrate
N
0.2
0.3
0.3
0.2
0.5
0.1
< 0.1
Total Ortho Alkalinity
P P CaCO^
mg/1 mg/1
6.5
9.2
1.9 0.7
3.6 -
1.0
1.8
1.6
0.7
i.o
0.2
2.6 0.6
1.7
1.
0.1
0.5
1*30
Uio
1*70
1*10
1+05
375
1*05
1*10
1*60
1*90
1*80
__
__
_-
8.91
7.62
5.70
6.85
6.51
7.11
6.92
6.80
8.32
6.1*0
6,59
6.21
6.20
6.70
6.00
2510
725
790 91.1
35.1 < 0.02
0.3
2.9 0.6
-------
TABLE V-l
ANALYTICAL DATA - HOURLY GRAB SAMPLES
DRY CAUSTIC PEELING PROCESS - CLING PEACH RINSE WATER
Sample
8/25/71- 8 AM
8/25/71- 9AM
8/25/71-10 AM
8/25/71-H AM
8/25/71 -12 N
fa/ 25/71 - 1 PM
8/25/71- 2 PM
8/25/71- 3 PM
COD BODS
mg/1 mg/1
10, 600 7, 760
12, 960 8, 655
13,670 8,300
--
10, 500 5, 970
11,950 6,470
14, 220 7, 325
12, 950 6, 965
Total
Solids
BOD/COD rns/1
0. 73
0. 67
0.61
0. 57
0.54
0. 52
0.54
Suspended
Solids
mg/1
1,185
1,550
2,450
--
1,975
2,350
2,650
2,550
Alkalinity
CaC03
mg/1
825
960
1,000
--
770
800
980
865
Avg. of 8/25/71
Hourly Grab
Samples
12,400 7,350
0.60
2, 100
885
6.30
8.46
8.90
8.19
6.58
8.80
8.36
8/ 27/71- 8 AM
h/ 27/71- 9 AM
8/27/71-10 AM
8/27/71-11 AM
8/27/71-12 N
8/27/71- 1 PM
8/ 27/71- 2 PM
8/27/71- 3 PM
Avg. of 8/27/71
Hourly Grab
10, 380
10, 975
10, 345
11,040
9,975
10,015
9,510
8,300
5,250
6,735
6,455
6,555
6,060
6,160
5,565
4,870
0.51
0.61
0.62
0.59
0.61
0.62
0.59
0.59
.-
10,565
12,010
10,856
10, 770
9,990
8,925
__
1,725
--
1,700
1,450
785
890
810
920
905
890
825
715
8.89
9.09
6.68
6.56
8.79
8.27
6.80
8.84
Samples
10, 070 5, 955
0.60
10,520
1,625
845
29
-------
TABLE V-2
ANALYTICAL DATA-HOURLY GRAB SAMPLES
DRY CAUSTIC PEELING PROCESS - CLING PEACH RINSE
Sample
9/2/71 - 8 AM
9/2/71 - 9AM
9/2/71 -10AM
9/2/71 -11 AM
9/2/71 -12 N
9/2/71 - 1 PM
9/2/71 - 2PM
9/2/71 - 3 PM
Avg. 9/2/71
Hourly Grab
Samples
9/7/71 - 8 AM
9/7/71 - 9 AM
9/7/71 -10 AM
9/7/71 -11 AM
9/7/71 -12 N
9/7/71 - 1 PM
9/7/71 - 2 PM
9/7/71 - 3 PM
Avg. of 9/7/71
Hourly Grab
Samples
COD
jng/1
8,905
6,030
4,960
3,175
6,800
10, 535
7,490
10,205
7,265
9,065
9,110
4,935
7,165
9,080
5,410
6.675
7,505
7,370
Total
BODs Solids
mg/1 BOD/COD mg/1
9, 600
6, 645
__
__
--
--
8, 125
4,515 0.50
4,315 0.47
2,980 0.60
4,265 0.60
4, 970 0. 55
2. 168 0. 40
4, 415 . 0. 66
3,705 0.49
3,915 0.55
Suspended
Solids
mg/1
..
785
800
1,250
1,150
1,000
1,600
950
600
800
~
350
860
WATER
Alkalinity
CaCOs
mg/1
705
550
520
695
660
885
710
855
700
845
810
490
630
950
495
580
625
680
.£"
9. 15
8.90
9.00
9.30
9.20
9.35
9.10
9.25
7.24
8.63
6.85
6.88
9.61
6.40
6.58
6.15
30
-------
TABLE V-3
ANALYTICAL DATA - HOURLY GRAB SAMPLES
DRY CAUSTIC PEELING PROCESS - CLING PEACH RINSE WATER
Sample
9/9/71 - 8 AM
9/9/71 - 9 AM
9/9/71 -10AM
9/9/71 -11 AM
9/9/71 -12 N
9/9/71 - 1 PM
9/9/71 - 2 PM
9/9/71 - 3 PM
Avg. of 9/9/71
Hourly Grab
Samples
COD
mg/1
9,915
8,240
10, 870
5,530
--
8,000
5,575
4,815
7,565
BODS
mg/1
4,675
3,980
5,110
2,930
4,180
2,505
2,070
3,635
Total Suspended
Solids Solids
BOD/COD ma/1 mg/1
0.47
0.48
0.47
0. 53
0. 52
0.45
0.43
0.50
Alkalinity
CaC03
mg/1
710
570
535
520
650
580
475
575
pH
9.03
9.02
8.98
9.00
8.88
9.07
8.85
9/10/71- 8 AM
9/10/71- 9AM
9/10/71-10 AM
9/10/71-11 AM
9/10/71 -12 N
9/10/71- 1 PM
9/10/71- 2PM
9/10/71- 3 PM
7,285
9, 180
9,180
9,835
5,100
11, 140
7,915
11,075
3,800
4,355
4,220
4,220
2,630
5,345
3,960
4,950
0.52
0.47
0.46
0.43
0.52
0.48
0.50
0.45
Avg. of 9/10/71
Hourly Grab
Samples
8.73
8. 55
8.29
8.70
8.98
8.62
8.58
8.82
8,840 4, 185 0.50
31
-------
TABLE V-4
ANALYTICAL DATA - HOURLY GRAB SAMPLES
DRY CAUSTIC PEELING PROCESS - CLING PEACH RINSE WATER
Sample
9/16/71 - 8 AM
9/16/71 - 9 AM
9/16/71 -10 AM
9/16/71 -11 AM
9/16/71 -12N
9/16/71 - 1 PM
9/16/71 - 2 PM
9/16/71 - 3 PM
Avg. of 9/16/71
Hourly Grab
Samples
9/21/71 - 8 AM
9/21/71 - 9 AM
9/21/71 -10 AM
9/21/71 -11 AM
9/21/71 -12 N
9/21/71 - 1 PM
9/21/71 - 2 PM
9/21/71 - 3 PM
COD
mg/1
8,020
5,810
7,895
5,770
8,320
8,530
10, 5O6
7, 110
7,745
9,905
10, 670
7, 130
9,205
9,410
9, 190
10, 285
13,515
BODs
mg/1
5,570
4,010
4,975
3,880
4,875
4,340
5,375
3,940
4,620
5,095
5,850
4,060
5,395
4,855
4,000
5,455
6,885
Total Suspended
Solids Solids
BOD/COD mg/1 mg/1
0.69 2,650
0.69
0.63 2,050
0.67
0. 59 1, 850
0.51
0.51 -- 2,550
0. 55
0. 60 2, 275
0.51
0. 55
0. 57
0. 59
0. 52
0. 44
0. 53
0.51
Alkalinity
CaCOa
mg/1
715
550
730
540
725
750
680
670
670
~
~
pH
8.50
8.70
8.65
8.65
9.20
9.05
9.40
9.20
-.
__
..
__
-_
__
-_
Avg. of 9/21/71
Hourly Grab
Samples 9,925
5,200
0.55
32
-------
TABLE Vl-1
ANALYTICAL DATA - HOURLY GRAB SAMPLES
CONVENTIONAL PEELING PROCESS - CLING PEACH RINSE WATER
Sample
8/25/71 - SAM
8/25/71 - 9 AM
8/25/71 -10 AM
8/25/71 -11 AM
8/25/71 -12 N
8/25/71 - 1 PM
8/25/71 - 2 PM
8/25/71 - 3 PM
COD BODS
mg/1 mg/1
1, 880 1, 050
2, 045 1, 175
1, 870 1, 175
1, 210 665
1, 530 760
2, 265 1, 135
2,155 1,055
Total
Solids
BOD/COD mg/1
0. 56
0. 57
0.63
0. 55
0.50
0.50
0.49
Suspended
Solids
mg/1
1,450
780
775
540
1,615
1,850
2,025
Alkalinity
CaCO3
mg/l
465
465
465
390
530
500
495
Avg. of 8/25/71
Hourly Grab
Samples
1,850 1,000
0.55
1,290
475
9.65
9.65
9.61
9.45
9.78
9.70
9.68
8/27/71 - 8AM
8/27/71 - 9 AM
8/27/71 -10 AM
8/27/71 -11 AM
8/27/71 -12 N
8/27/71 - 1 PM
8/27/71 - 2 PM
8/27/71 - 3 PM
2,170
2,150
2,880
2,455
1,635
2,350
1,970
1, 165
1,200
1,175
1,680
1,290
920
1,290
1,060
535
0.55
0.55
0.58
0.53
0.56
0.55
0.54
0.46
3,725
3,230
2,440
3,200
2,730
-_
725
__
600
700
--
445
470
__
530
445
520
485
385
9.61
9.73
9.87
9.88
9.71
9.89
9.75
9.53
Avg. of 8/27/71
Hourly Grab
Samples 2,100 1,145 0.55
3,065
675
470
33
-------
TABLE VI-2
ANALYTICAL DATA - HOURLY C RAB SAMPLES
CONVENTIAL PEELING PROCESS - CLING
Sample
9/2/71- 3AM
9/2/71. 9AM
9/2/71. 10 AM
9/2/71-11 AM
9/2/71- 12 N
9/2/71- 1 PM
9/2/71- 2 PM
9/2/71- 3 PM
Avg. of 9/2/71
Hourly Grab
Samples
COD BODs
mg/1 mg/1 BOD/COD
2, 275
2,855
2, 500
3, 175
1, 115
2,330
2,380
2, 160
2,350
Total
Solids
mg/1
3,270
3,850
--
--
--
--
3,560
PEACH RINSE WATER
Suspended
Solids
mg/1
~
550
615
585
Alkalinity
CaC03
mg/1
530
555
545
425
405
485
530
490
495
10.1
10.1
10.1
9.70
9.65
9.85
9.75
9.95
9/7/71- 8 AM
9/7/71- 9 AM
9/7/71- 10 AM
9/7/71- 11AM
9/7/71- 12 N
9/7/71- 1 PM
9/7/71- 2 PM
9/7/71- 3 PM
Avg. of 9/7/71
Hourly Grab
Samples
2,625
2,760
2,670
3,550
3,470
2,450
2, 120
2,285
2,740
1,300
1,310
1,080
1,480
1,315
920
700
1,265
1,170
0.50
0.47
0.40
0.42
0.38
0.38
0.33
0.55
0.45
1,150
1,350
500
750
500
~
580
590
525
640
595
480
450
505
9.85
9.91
9.83
10.01
10.88
9.80
9.70
9.70
850
545
34
-------
TABLE VI-3
ANALYTICAL DATA - HOURLY CRAB SAMPLES
CONVENTIONAL PEELING PROCESS - CLING PEACH RINSE WATER
Sample
9/9/71 -
9/9/71 -
9/9/71 -
9/9/71 -
9/9/71 -
9/9/71 -
9/9/71 -
9/9/71 -
8
9
.0
11
12
1
2
3
AM
AM
AM
AM
N
PM
PM
PM
COD
mg/1
4,
5,
-
1,
4,
3,
3,
420
195
325*
050
920
365
Total
BODs Solids
mg/1 BOD/COD mg/1
2
3
1
1
1
..
,585
,005
--
630*
,790
,695
,465
0.
0.
0.
0.
0.
58
58
._
._
44
43
44
Suspended Alkalinity
Solids CaCOs
mg/1 mg/1 pH
800 10. 55
880 10. 35
--
10. 73
10. 82
10. 75
10. 60
Avg. Of 9/9/71
Hourly Grab
Samples 4, 190 2, 110
0.50 840
*Not included in average - Apparent plant cleanup sample.
9/10/71- SAM
9/10/71- 9AM
9/10/71-10 AM
9/10/71-11 AM
9/10/71-12 N
9/10/71- 1 PM
9/10/71- 2 PM
9/10/71- 3 PM
3,380
3,100
3,020
3,775
2,095
3,525
2,040
2,240
1,485
1,335
1,350
1,735
930
2, 475*
955
1,095
0.44
0.43
0.45
0.46
0.44
0.70*
0.47
0.49
Avg. of9/10/71
Hourly Grab
Samples
2,900 1,270 0.45
10.35
10.30
10.25
10.45
10.23
10.55
10.00
10.20
*Not included in average - Apparent plant cleanup sample.
35
-------
TABLE VI-4
ANALYTICAL DATA - HOURLY GRAB SAMPLES
CONVENTIONAL PEELING PROCESS - CLING PEACH RINSE WATER
Sample
9/16/71-8 AM
9/16/71- 9AM
9/16/71-10 AM
9/16/71-11 AM
9/16/71-12 N
9/16/71- 1 PM
9/16/71- 2 PM
9/16/71- 3 PM
Avg. of 9/16/71
Hourly Grab
Samples
COD
mg/1
2,060
2,030
785
680
885
1,010
1,935
2,740
1,513
BOD5
mg/1
1, 145
1,185
345
345
400
485
920
1,345
770
Total
Solids
BOD/COD rng/t
0.56
0. 58
0.44
0.48
0.45
0. 48
0.48
0. 49
0.50
Suspended
Solids
mg/1
850
1,050
750
885
Alkalinity
CaCOs
mg/1
490
390
350
335
335
335
405
535
400
9.91
9.68
9.62
9.59
9.69
9.70
10.02
10.31
5/21/71- 8 AM
9/21/71- 9AM
9/21/71-10 AM
9/21/71-11 AM
9/21/71-12 N
9/21/71- 1 PM
9/21/71- 2 PM
9/21/71- 3 PM
Avg. of 9/21/71
Hourly Grab
Samples
2,740
2,080
2,060
2,820
2,095
1,950
1,990
1,285
2,130
1,240
1,015
1,240
1,260
1,095
1,045
970
685
1,070
0.45
0.49
0.60
0.45
0.52
0.72
0.49
0.53
0.55
36
-------
TABLE VH
ANALYTICAL DATA - 8-HOUR-COMPOSITE SAMPLES
DRY CAUSTIC PEELING PROCESS - CLING PEACH PEEL SOLIDS
Sample Date Total Solids (%) pH
8/19/71
S/28/71 7. 1
8/24/71 9.2
8/25/71 7.8
8/26/71 lo.l 10.62
8/27/71 io.2 8.73
8/30/71 8.5 10.50
8/31/71 9.6 10.55
9/2/71 .. 9.85
9/3/71 g.O 9.12
9/7/71 10. S 10.32
9/8/71 10.4 9.00
9/9/71 10.7 9.45
9/10/71 10.5
9/H/71 ll.o 9.50
9/W71 10.9 9>48
9/14/71
9/15/71 7.4
9/16/71
9/20/71 . 11.2
9/21/71 11.0
Average: 9.7
37
-------
TABLE VIII
MASS EMISSION LEVELS - 2k HOUB COMPOSITE SAMPLES
DRY CAUSTIC PEELIMG PROCESS - CLING FEACH RINSE WATER
U>
00
Sample
Date
8/19/71
8/23/71
8/2U/71
8/25/71
8/26/71
8/27/71
8/30/71
8/31/71
9/2/71
9/3/71
9/7/71
9/8/71
9/9/71
9/10/71
9/U./71
9/13/71
9/1U/71
9/15/71
9/16/71
9/20/71
9/21/71
Average
Volume
Hinse Water
g Pd
12,070
16,090
15,5W
16,600
18,110
1U,OUO
20,9^0
20,710
19,190
19,190
21,150
20,850
19,280
24,280
22,7"*0
18,825
18,825
22,100
22,000
23,070
22,150
19,^30
COD
5fiZ!
U785
7290
8015
9895
8030
3U35
11,305
5U10
5350
3725
3200
1*300
U325
>*095
2965
5>*90
2670
1*820
5910
6965
Ibs/ton'
2.2
1*.U
U.8
6.3
5.6
1.9
9-1
M
U.O
2.8
2.6
3-2
1*.0
3.6
2.6
U.O
2.3
l*.l
5.3
6.0
5600
U.2
BOD
HJZ1
2190
3820
5770
6170
3860
2890
8655
21*05
2365
21*85
2375
2720
U5U5
2150
1*000
351*0
3750
Ibs/ton*
1.0
2.3
3-5
U.O
2.7
1.6
7.0
1.8
1.9
i~e
2.2
2.U
3-3
1.8
3."»
3-0
2.7
Total Solids
Sfi/1
53U5
7010
8U65
7825
6800
U205
7160
1*320
5180
3930
U290
UU70
U085
3990
3895
Ibs/ton
2.5
U.2
5.1
5.0
U.8
2.8
5.8
3-5
3.8
2.9
3-5
3-3
3.8
3-5
3-1*
Suspended Solids
atf!
1650
2925
3550
3630
1630
2860
2U50
2170
1150
2200
2300
230O
1650
2310
2670
2850
2700
2750
lbs/ton<
1.0
1.8
2-3
2.5
0.9
2-3
2.0
1.6
0.9
1.8
1.7
2.2
1.5
2.0
2.3
2.U
2.U
2.U
Total Nitrogen
Total
Phosphate
5UOO
3-9
2U30
1-9
110.7
122.6
156.9
108.6
119.8
86.2
108.6
92.5
118. U
110. U
116.5
106.5
117.0
113-5
Ibs/ton*
0.07
0.08
0.10
0.08
0.09
0.06
0.98
0.09
0.10
0.09
0.10
0.09
0.10
0.09
0.006
15. u 0.009
10.1 0.007
5.0
2-3
U.9
U.9
3*6
2.8
12.0
5.2
6.7
7.0
O.OOU
0.002
O.OOU
O.OO5
0.003
0.002
0.010
0.005
O.O06
0.005
* Baaed upon average 216 tons per day.
-------
TABLE IX
MASS EMISSION LEVELS - git HOURS COMPOSITE 3AMPUS
CONVENTIONAL PEELIHG PROCESS - CLIMG PEACH RIHSE WATER
VO
8/19/71
8/23/71
8/2U/71
8/25/71
8/26/71
8/27/71
8/30/71
8/31/71
9/2/71
9/3/71
9/7/71
9/8/71
9/9/71
9/10/71
9/11/71
9/13/71
9AV71
9/15/71
9/16/71
9/20/71
9/21/71
Average
Volume
Rinse Water
g pd
389,100
378,700
375,300
370,000
39!*, 1*00
373,1*00
37U,900
31*8,000
368,900
368,900
381,700
377,100
367,000
380,200
3U8,000
3UU, 100
360,300
361,500
355,800
366,150
COO
seZi
1680
1305
1W*5
2030
11U5
11*15
1180
1335
1295
1650
206o
1170
1820
3275
1135
905
1100
11*35
Ibs/toiv1
12.6
9-5
10.3
15.5
8.3
10.2
7.9
9-5
9-2
12.2
11*. 6
8.6
12.9**
21.7
7.5
6.3
7.7
9-9
BOD
1520
10.8
860
790
930
860
795
1025
990
1080
1255
835
11U5
830
705
1080
9l*O
6.5
5.8
6.6
6.5
5-7
7.0
8.0
8.9
6.1
8.1**
5.5
U.9
7.1*
6.7
Total
mg/1
2725
2165
2600
21*25
2000
1910
2275
2225
2160
2680
3125
2100
251*0
U135
Solids
lb"/ton
ao.5
15.8
18.6
18.5
11*. 1*
13.8
15.3
15.8
15.1*
19-7
22.1
15. 1*
18.0**
27.1*
Suspended Solids
me/1
675
1*50
1250
1020
525
570
1350
1*25
250
800
750
200
13UO
700
300
710
1000
Ibs/ton*
5-1
3-3
8*9
7.8
3-8
U.l
9.1
3-0
1.8
5-9
5-5
1.1***
8.9
U.6
2.1
5.0
6.9
Total Nitrogen
Ibs/tong*
2510
17.9
725
5-1
25.2
35-7
39-9
35-0
32.2
.1*7.6
29.1*
56~0
31.9
29.1
22.1*
35-7
35-0
0.18
0.26
0.30
0.25
0.23
0.3U
0.22
0.37
0.21
0.2O
0.16
0.25
0.25
mg/1
6.5
9.2
1.9
3-6
O.U
1.0
2.6
1.7
5.1*
1.8
1.6
0.7
1.0
2.9
Total
Phosphate
0.01*9
0.067
O.Oll*
0.027
0.003
0.007
0.018
0.012
0.036
0.012
0.011
0.005
0.007
0.021
* Based upon average 1*32 tons per day.
** Based upon average volume rinse water.
-------
TABLE X
SUMMARY COMPARISOH OF SELECTED RINSE WATER CHARACTERISTICS
Characteristics
Water Use
COD
BOD5
Total Solids
Suspended Solida
Total nitrogen
Total Phosphate
Alkalinity
PH
DRY CAUSTIC AHD COHVEHTIOHAL PEELING PROCESSES
Analytical Data
Dry Caustic
Range Avg.
7«*7l7 7*S/l7
13gpo>*
2,670-11,300 5,600
2,150-8,650 3,750
3,900-8,1*50 5, MX)
1,150-3,630 2,1*30
86-157 HO
2.3-15 7
372-619 511*
l*.i*- 5. 8
Median
* j.. i
-
5,350
3,5»*0
l*,l*70
2,310
110
5
520
l».9
St.Dev.
-
2,3"*0
1,803
1,600
650
17
1*
81
Range
TSgAT
-
910-3,275
700-1,260
1,910-U, 130
200-1,350
22-1*8
0.7-9.2
37U-U88
5.7-8.9
Conventional
^^WfjKj^^
25U gpsi**
1,520
9UO
2,510
725
35
2.9
1*30
Median
-
1,1*15
930
2,525
700
35
1.8
1*10
6.9
St.Dey.
-
5"*2
158
573
365
9
1-9
38
Waste Generation
Dry Caustic Conventional
(per ton) (per ton)
90 gal. 850 gal.
U.2 Ibs. 10.8 Ibs.
2.7 Iba. 6.7 Ibs.
3.9 lb«. 17-9 Ibs.
1.9 Ibs. .5.1 Ibs.
0.09 Ibs. 0.25 Ibs.
0.005 Ibs. 0.021 Ibs.
0.39 Ibs. 3.0 Ibs.
* 12 Tons per Hour Rate.
*» 2k Tons per Hour Rate.
-------
TABLE XI
CONVENTIONAL AND DRY CAUSTIC PROCESS
CLINGSTONE PEACH PEEL LOBS DETERMINATIONS
Test Period
8/18 - 8/25/71
8/26 - 9/2/71
9/3 - 9/10/71
9/n - 9/18/71
9/20 - 9/23/71
Average Seasonal Loss*
Standard Deviation
Peel Loss
Conventional Process Dry
U.8*
5.9
7.6
7.1
8.6
6.1*5**
1.92*
Caustic Process
6.6*
6.2
9.0
7.8
9.9
7.35**
2.30*
* t-test for significant difference 8 t » 1,93 with 82 degrees of
freedom* Differences axe significant at 90% confidence level.
41
-------
APPENDIX A-II
SUPPLEMENT REPORT
1972 OPERATING SEASON
42
-------
CONTENTS
Page
A-II-1 PROJECT PROGRAM 45
A-II-2 EQUIPMENT 46
A-II-3 ANALYTICAL PROGRAM 47
A-II-4 RESULTS 48
A-II-5 DISCUSSION 49
A-II-6 CONCLUSIONS 53
43
-------
TABLES
Page
HI 1972 ANALYTICAL DATA - 2l*-HOUR COMPOSITE SAMPLES
DRY CAUSTIC PEELUJG PROCESS-
CLING PEACH RINSE WATER 54
XIII 1972 ANALYTICAL DATA - 2l*-HOUR COMPOSITE SAMPLES
CONVENTIONAL PEELING PROCESS-
CLING PEACH RINSE WATER 55
XIV SUMMARY COMPARISON OF SELECTED RINSE WATER
CHARACTERISTICS
1972 DRY CAUSTIC AND CONVENTIONAL CLING PEACH
PEELING PROCESSES 56
XV SUMMARY COMPARISON OF 1971 AND 1972 OPERATING
SEASONS
DRY CAUSTIC AND CONVENTIONAL CLING PEACH RINSE
WATER WASTE GENERATION 57
XVI DRY CAUSTIC AND CONVENTIONAL PROCESS
1972 CLING PEACH PEEL LOSS DETERMINATIONS 53
44
-------
A-II-1
PROJECT PROGRAM
A continuation of Environmental Protection Agency Research and
Development Grant Project #12060 HFY, Dry Caustic Peeling of
Clingstone Peaches on a Commercial Scale, was carried out at the
Del Monte Corporation Plant Ho. 3 during the 1972 peach
season. The preceding year evaluations of the equipment had
demonstrated that chemically softened peel could be removed from
clingstone peaches and yield a canning peach of satisfactory
quality. The 1971 data also indicated that further work was
necessary to determine the full commercial potential of the dry
caustic peeling process for clingstone peaches.
45
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A-II-2
BKJIPMEHT
Prior to the 1972 cling peach canning season, Del Monte Corpora-
tion completed several modifications to the equipment previously
described in order to more fully evaluate the commercial potential
of the dry caustic process. Included in the modifications were:
1. Installation of a peach discharge distribution
system onto the conveyor leading past inspec-
tion stations following the dry caustic peeler.
This modification provided for a more equal and
less abrasive distribution of the peeled fruit
over the entire inspection area and permitted a
substantial increase in the tons per hour which
could be processed on a continuing basis.
2. Repositioning of some stub rollers in the peeler
unit to permit nore positive turnover of inverted
peaches.
3. Minor modifications of conveyor guides which
permitted a more equal distribution of the
higher volume of peaches over the full width
of the demonstration peeler.
4. Increasing the number of roller guides on the
V-belt trough conveyor, increasing the belt
speed to l6o feet per minute, and various other
conveyor tracing and transmission changes which
allowed for improved utilization and function-
ing of the system.
5. Provision for applying a lover concentration of
dilute caustic to the peach skins and evaluating
the effect this would have on the peeling process.
46
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A-II-3
AHALYTICAL PROGRAM
The 1972 analytical program was directed primarily toward confirm-
ing vastewater characteristics data developed in the extensive
analytical program conducted during the 1971 demonstration pro-
ject.
Sampling points Ho. la and 2a were the same as identified during
the 1971 project and represented conventional and dry caustic
peeling rinse waters, respectively. Composite samples were col-
lected on the same frequency schedule throughout the operating
day as before. Composite samples were refrigerated and trans-
ported to the Del Monte Research Center for analysis as in 1971*
No grab samples of rinse water were obtained during 1972.
47
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A-II-4
RESUI/PS
Results of the analytical program carried out during 1972 are
sunnarized in a series of tables following this supplement. In
order to avoid confusion, the numbering system used for these
supplement tables is in sequence with the tables pertaining to
the 1971 demonstration project and which are included previously
in the appendix.
Table XII is a compilation of 1972 analytical data for 2^-hour
composite samples of rinse water from the dry caustic cling peach
peeling process.
Table XIII is a compilation of 1972 analytical data for 24-hour
composite samples of rinse water from the conventional cling
peach peeling process.
Table XIV is a summary comparison of selected rinse water charac-
teristics for the 1972 evaluation of dry caustic and conventional
cling peach peeling processes.
Table XV is a summary comparison of 1971 and 1972 operating sea-
sons for selected waste characteristics generated in the peach
rinse water for the dry caustic and conventional cling peach
peeling process.
Table XVI compares peel losses for the conventional and dry caus-
tic processes during the 1972 «*mnfrng season.
48
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A-II-5
DISCUSSION
The 1972 peach canning season using dry caustic peach peeling
equipment developed for EPA Project No. 12o6o HFTf continued to
demonstrate that rapidly rotating rubber disks can remove major
portions of softened peels from cling peaches and that the pro-
cess will yield a product of satisfactory quality for canning.
After incorporating several modifications to the peach handling
and distribution system, the 1972 ««nff*?>e season also demonstrated
that increased tonnages could be processed by the dry caustic
peeler. During the period of July 31, 1972 to August 29, 1972,
inclusive, the peeler was operated whenever possible, with sane
days having operating periods of up to 20.U hours. Although a
number of mechanical problems, identified "below, prevented full-
time usage cf the peeler on all days, an average of l8.2 tons
per hour of peaches were peeled using the dry caustic peeler,
with a range of approximately l6 to 22 tons per hour. This rate
is equivalent to a range of approximately 2.7 to 3.7 tons per
hour per foot of peeler width and an average of 3 tons per hour
per foot of peeler width.
The modifications to the peeler during 1972 allowed for diverting
1005& of the fruit from one of Plant 3'a conventional .peelers to
the dry caustic unit. This also enabled an evaluation of the lye
concentration used for peeling peaches with the dry caustic pro-
cess. In 1971, a portion of the conventional peeler unit pro-
cessed peaches, and a change in lye concentration was not feasi-
ble. In 1972, daily records indicated that a 0.1-0.2JC reduction
in lye concentration was used for the dry caustic unit versus the
adjacent conventional peeler. This represents an approximate 10£
savings in caustic usage and would result in a cost savings of
approximately $0.025 per ton of peaches.
Water usage, for removing peel and caustic residues and for pro-
viding the initial rinse of the peeled fruit, was found to be the
sane as during the 1971 demonstration project. Table XII identi-
fies analytical data for selected characteristics of dry caustic
peeler rinse water. Table XIII lists comparable data for the
same characteristics in the conventional peeler rinse water.
Table XIV compares the data from Tables XII and XIII and, as in
1971, indicates the concentrations (mg/1) for these characteris-
tics were higher in the dry caustic peeler rinse water, but that
the pounds of waste generated per ton of peaches were significant-
ly lower. Table XIV also indicates that in 1972 the pounds of
BOD, suspended solids and total solids generated per ton of
peaches peeled with the dry caustic process were, respectively,
49
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approximately 36^, 85^ and 88^ less than peaches peeled using the
conventional method.
These percentages of waste reduction are somewhat greater than
demonstrated during 1971. Table XV compares 1971 and 1972 data.
Reasons for the greater reductions of waste found in the peach
rinse water during 1972 are only speculative, but could possibly
be attributed, in part, to a reduced lye concentration in the
dry caustic unit and also to a slightly modified and perhaps more
gentle method of handling the fruit, resulting in less abrasion
of the peach.
Tests in 1972 for peel loss on the peaches confirmed 1971 data,
that the conventional process yields approximately l.jjt greater
recovery of fruit weight. This is an economic factor which needs
to be folly considered in management's decision-making process
when evaluating the potential advantages and potential disadvan-
tages of the dry caustic peeling process.
The 1972 canning season did not indicate any significant changes
in the amount of combined peel and caustic residues collected
from the dry caustic unit and hauled from the plant. Therefore,
the quantities and costs identified in Section VII of the primary
report would continue to appear to be valid, with an approximate-
ly $.05 per cubic yard increase in the cost of hauling the solid
residue. A slight decrease in handling costs resulted In a slight1
ly lower cost for 1972 versus 1971
During 1972 a number of minor operating and maintenance problems
were associated with the use of the dry caustic peeler and should
be considered in designs of future units. These included:
1. Disc wear necessitating replacement at a cost
of approximately $700.
2. Some bearing and shaft repair costing approx-
imately $750 during 1972. A number of bearings
burned out and were replaced with bearings with
grease fittings.
3. Plugging of the peach peel slurry waste pump
with pits and large pieces of peach. A small
screen to prevent their entry and a piping
change appeared to correct this problem.
U. Tracking problems with the V-fcelt trough con-
veyor when overloaded with fruit. It should
be recalled that this equipment was not de-
signed for this tonnage of peaches and a wider
belt or straight flow of fruit should elimin-
ate this problem.
50
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A comparison of potential costs between the dry caustic and con-
ventional peeling processes indicated that the conventional method
continues to be favored when all major cost items vere considered.
The following calculations reflect 1972 wastewater treatment costs
in the city of San Jose, California and hauling and operating
costs at the Del Monte plant for disposal of solid residues.
1. In terms of potential sewer service charges for
wastewater treatment, use of the dry caustic
process had a somewhat greater potential savings
than calculated for 1971:
Dry Caustic Peeling Process
90 gallons wastewater x i.6o « $.05^
1.5 Ibs. BOD x $.00^5 .007
1.0 Ibs. SS x $.0045 .00^5
,066/ton
Plus fresh water .023
Total $.089/ton
Conventional Peeling System
850 gallons wastewater x $.60 $ .510/ton
10.5 Ibs. BOD x $.OOU5 - .OU7/ton
6.7 Ibs. SS x $.001*5 .030/ton
.587/ton
Plus fresh water ,210
Total $ .773/ton
2. In terms of handling solid residues generated
by the peeling process, the additional cost to
the canner would be:
Conventional System
No Cost
Dry Caustic Peeling System
^63 cu. yds. solid residue per ton peaches
@ $3.65/cu. yd. » $l.b9/ton peaches.
51
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In terms of peel loss, the limited 1972 evalu-
ations indicated about l£ greater peel loss
with the use of the dry caustic peeler. At the
1972 cost for peaches of i75»00/ton, this vould
be an additional cost of $.75 per ton.
52
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A-II-6
CONCLUSIONS
The 1972 peach *«ttHT>g season at Del Monte Plant 3 confirmed that
the use of the dry caustic peeling process can result in a sub-
stantial reduction of waste generated during the preparation of
peaches and subsequently discharged in the liquid effluent from
the plant. The 1972 season also confirmed that there nay be
economic disadvantages to the peach canner and that further work.
is required to evaluate the full coonercial potential of this
process. Some mechanical problems also need correction for full-
scale and continuous operations.
-------
TABLE XII
1972 AHALCTICAL DATA - 2^-HOUR COMPOSITE SAMPLES
Ln
Sample
Date
8/22/72
8/23/72
8/2*/72
8/25/72
8/26/72
8/29/72
8/30/72
Volume
Rinse Water
irpd
19,500
19,500
19,500
19,500
19,500
19,500
19,500
Tons
Processed
3*8
376
*o8
3*5
360
31*
300
DRY CAUSTIC
PEELING PROCESS - CLIRf} PEACH RIWSE WATKR
COD
^t/1
*,920
8,160
3,370
5,690
*,895
3,890
3,*75
Iba./ton
2.3
3.5
1.3
2.7
2.2
2.0
1.9
BOD5
ng/1
3,*20
5,560
2,680
3,620
3,135
2,380
2,0*0
Ibs ./ton
1.6
2.*
1.0
1.7
1.*
1.2
1.1
Suspended Solids
«/l
2,825
2,600
1,375
2,175
1,575
1,575
2,275
Ibs. /ton
1.*
1.1
0.6
1.0
0.7
0.8
1.2
Total
Mg/1
9,680
5,875
*,5*5
7,890
5,965
*,320
*,390
Solids
Ibs. /ton
*.5
2.5
1.8
3.7
2.7
2.2
2.*
*.99
6.*9
*.98
*.53
*.8o
*.*8
*.6o
Average
19,500
350
*,915
2.3
3,260
1.5
2,055 1.0
5,*70
2.8
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IABI£ Xtll
1972 ANALYTICAL DATA - 24-HOUR COMPOSITE SAMPLES
Ui
Sample
Date
8/22/72
8/23/72
8/24/72
8/25/72
8/26/72
8/29/72
8/30/72
Volume
Rinse Water
KPd
370,000
370,000
370,000
370,000
370,000
370,000
370,000
i
Tone
Processed
348
376
408
345
360
314
300
COD
sell
1,920
1,300
1,715
1,465
1,240
1,245
1,650
Iba./ton
17.0
10.7
13.0
13.1
10.6
12.2
17.0
BODS
1,335
910
1,645
1,700
970
840
965
Ibs./ton
u.8
7.5
12.4
15.2
8.3
8.3
9.9
Suspended Solids
ng/1 Ibs./ton
150 1.3
375
530
745
1,365
1,510
515
3.1
4.0
6.7
11.7
14.8
5.3
Total
2,350
2,6OO
2,465
2,365
2,84o
2,960
2,130
Solids
Ibs./ton
20.8
21.4
18.6
21.2
24.4
29.1
21.9
6.84
6.19
6.57
6.12
6.52
6.6l
5.63
Average
370,000
350
1,505 13.4
1,195 10.5
740
6.7
2,530
22.5
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SUMMARY COMPARISON OF SELECTED RINSE WATER CHARACTERISTICS
1972 DRY CAUSTIC AND CCHVENTIONAL CLING PEACH PEELING PROCESSES
ffruyact eristic s
COD
BOD5
^ Suspended Solids
Total Solids
pH
ry Caustic
Waste Generation
3,370-8,160 4,915
2,040-5,560 3,260
1,375-2,825 2,055
4,320-9,680 5,470
4.48-6.49
Range
1,240-1,920 1,505
840-1,700 1,195
150-1,510 74o
2,130-2,960 2,530
5.63-6.84
Dry Caustic
(per ton)
2.3
1.5
1.0
2.8
Conventional
(per ton)
13.4
10.5
6.7
22.5
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TABUS XV
Water Use
COD
uj BOD5
Suspended Solids
Total Solids
STOiftBY OOMEABIftOH OP 1971 AHD 1972 OHBRAHBG SEASONS
CAUSTIC AHD CtUVKNTlQHAL GUMS PEACH RINSE WATER HASTE GENERATION
Dry Caustic
Copventiooal
1971
(per ton)
90 gal.
U.2
2.7
1.9
3.9
1972
(per ton)
90 gal.
2.3 U>.
1.5 lb.
1.0 lb.
2.8 lb.
1971
(per ten)
89> gal.
10.8
6.7
5.1
17.9
1972
(per ton)
850 gal.
13A lb.
10.5 lb.
6.7 lb.
22.5 lb.
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IABLE XVI
00
DRY CAUSTIC AHD CONVENTIONAL PROCESS
1972 CLING PEACH PEEL LOSS DETERMINATIONS
Dry Caustic Process
Test No.
1
2
3
*
5
6
7
8
9
Average
Ibs. Input
7^.6
76.3
77.5
l8l.l
152A
18».7
178.9
188.1
218.5
Ibs. Output
69.3
69.2
72.2
157.2
132.9
170.8
153. U
168.1
207.2
% Recovery
93
91
93
87
87
92
86
89
95
90.3
Conventional Process
Ibs. Input
68.9
72.8
70.9
66.3
150.5
18* .1
185.9
-
70.5
Ibs. Output
6k. k
65.8
67.0
61.9
137.7
168.7
166.6
-
ft.5
^ Recovery
93
90
9^
93
92
92
90
-
92
92.0
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APPENDIX
A-III
SUPPLEMENT REPORT
1973 OPERATING SEASON
59
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A-III-1
PROJECT PROGRAM
Environmental Protection Agency Research and Development Grant
Project No. 120oO HFT, Dry Caustic Peeling of Clingstone Peaches
on a Commercial Scale, was continued at Del Monte Corporation
San Jose Plant No. 3 during the 1973 peach canning season. No
substantive changes in the design of the equipment were nade
following the conclusion of the 1972 peach canning season. How-
ever, in preparation for the 1973 season, approximately $2,600.00
was spent for replacement of worn shafts, rubber peeling discs,
bearings and sprockets.
60
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A-III-2
DISCUSSION
In 1973, the dry caustic peach peeling unit was operated for 35
days, with downtime for mechanical problems totaling 18 hours dur-
ing this period. A season average of 22.k tons per hour of peaches
was peeled with the dry caustic process. This is somewhat jrreater
than the 18.2 tons per hour averaged during 1972 and indicated that
3.5 to k.O tons per foot of peeler width was a feasible design para-
meter.
As in 1972, the dry caustic peeler used an average 0.1$ lower con-
centration of lye for peeling the peaches.
During 1973, peach peel recovery tests continued to confirm that
the conventional peeler will yield a greater percentage of recov-
ered peach weight. In 1973, the conventional process averaged 0.5^
greater recovery of peaches for a limited number of tests.
The 1973 observations confirmed, in general, the 1971 and 1972 data
and re-emphasized that substantial reductions in waste generation
in the rinse water from the peach peeling process were achievable.
1973 observations also confirmed that a full evaluation of the com-
mercial potential for the dry caustic peach peeling process in a
straight line, continuous flow pattern and using properly sized
and engineered equipment is desirable. This is not a criticism of
the demonstration project, as limitations of space, the additional
abrasion which the delicate peaches received going across the
LaPorte conveyor through the peeling unit with the resultant po-
tential peel loss, the exceptional wear on shafts and rubber discs
all contributed unknown factors which were necessarily a part of
the original demonstration project and were unavoidable in the
first commercial demonstration and evaluation of this promising
peeling process.
61
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TECHNICAL REPORT DATA
(I'li-ast- read Instructions on the reverse before completing)
m roni NP.
EPA-660/2-74-092
ANUsuuiITLE
DRY CAUSTIC PEELING OF CLINGSTONE PEACHES
ON A COMMERCIAL SCALE
Herbert E. Stone
b~PFRF~0~RMING ORC MMIZATION NAME AND ADDRESS
Del Monte Corporation
San Francisco, CA
NAME AND ADDRESS
Pacific NW Environmental Research Laboratory
National Environmental Research Center
Corvallis, Oregon 97330
RECIPIENT'S ACCESSION-NO.
REPORT DATE
December 1974
PERFORMING ORGANIZATION CODE
PERFORMING ORGANIZATION REPORT NO.
10. PROGRAM ELEMENT NO.
1BB037
11. CONTRACT/GRANT NO.
12060 HFY
13. TYPE OF REPORT AND PERIOD COVERED
Final report
14. SPONSORING AGENCY CODE
ABSTRACT
This study evaluates the peel removal ability and rinse water characteristics
for the first commercially sized equipment using the principle of rapidly rotating
rubber discs to gently wipe softened peel off Clingstone peaches. The conventional
process utilizes large volumes of fresh water to remove the softened peel and flush
it into the liquid effluent from the plant from where it cannot be easily separated.
The dry caustic unit demonstrates that gentle abrasion can remove the softened
peel, yield a peach suitable for commercial canning and allow for separation and
collection of a major portion of this solid residue; thereby preventing its entry
into the liquid waste stream.
In addition to an approximately 60% reduction in the BOD loading in the
liquid waste stream, an approximately 90% reduction in the fresh water requirement
for this phase of the preparation of Cling peaches is demonstrated. These reduc-
tions in volume of liquid effluent and in the total pounds of organic matter which
must be treated are beneficial to both private and public wastewater treatment
facilities.
A potential increased operating cost to the canner is indicated to be
attributable to slightly increased peel loss and to costs associated with the hand-
ling of solid residues separated and collected from the dry caustic peeler.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
Canneries, peel removal, water pollution
sources, wastewater, peaches, costs.
b.IDENTIFIERS/OPEN ENDED TERMS
Food processing, can-
ning, liquid waste
reductions.
COSATI Field/Group
ON STATLMENT
Release unlimited
19. SECURITY CLASS (ThisReport)
20. SECURITY CLASS (Thtspage)
21. NO. OF PAGES
61
22. PRICE
EPA
Form 2220-1 (9-73;
U. S. GC\ERNC'.EHT PANTING OFFICE: !97:-697- £03/74 REGION
10
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