an Industrial Waste Guide to the
Potato
Chip
Industry
U. S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE
Public Health Service
-------
DfMltcatioii
This guide is dedicated in memory of i)r. Howard I). Brown, former Research
Coordinator of the Potato Chip Institute International, who stimulated interest and
inspired much of the work leading to development of this report.
Dr. Brown brought to this project an extensi\e educational background of under-
graduate and doctoral studies at Michigan State. Wisconsin, and Chicago, and a lifetime
of service at other universities. Prior to his assoc iation v\ ith the Institute, he was 5
years with the liniversity of Illinois and the Kxpctiment Station. 10 years associate
professor at Purdue and associate of the Experiment Station. 28 years professor at
Ohio State and the Agricultural Experiment Station, and the past 2 years as professor
emeritus, Ohio State. He had broad experience in food technology including soil
fertility, effects of nutrient levels on the vitamin content keeping qualities of processed
foods, processing and handling frozen foods, vegetable science, and potato chipping.
Dr. Brown was a man of foresight and ideal*,"and a devoted scientist. Me visual-
ized this guide as a much needed aid to the industry. This dedication recognizes his
untiring eff orts toward the production of a practical and technical report as represented
by this document.
-------
an Industrial Waste Guide to the
Potato
Chip
Industry
Prepared by the
Committee on Potato Chip Wastes of the
Potato Chip Institute International
in cooperation with the
National Technical Task Committee
on Industrial Wastes
u s. V
U.S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE
Public Health Service
Division of Water Supply and Pollution Control
Washington 25, D.C.
-------
Other publications in the Industrial Waste Guide Series
PHS Pub. No. 691: Cane Sugar Industry
PHS Pub. No. 677: Cotton Textile Industry
PHS Pub. No. 509: Commercial Laundering Industry
PHS Pub. No. 438: Wool Processing Industry
PHS Pub. No. 386: Meat Industry
PHS Pub. No. 298: Milk Processing Industry
Public Health Service Publication No. 756
Reprinted 1961
For sale by I be Superintendent of Documenu, U.S. Government Printing Office, Washington 25, D.C. • Price 20 cent«
-------
TABLE OF CONTENTS
Fag*
FOREWORD v
INTRODUCTION 1
DESCRIPTION OF PROCESS 2
RAW MATERIALS AND PRODUCTS 2
SOURCES AND VOLUME OF WASTES 3
COMPOSITION OF WASTES 4
POLLUTION EFFECTS 6
SUGGESTIONS FOR EFFECTIVE WASTE PREVENTION
OR REDUCTION 6
WASTE TREATMENT AND DISPOSAL 7
SUMMARY 11
BIBLIOGRAPHY 12
-------
A modern potato chip plant.
iv
-------
Foreword
The Potato Chip Industry is anxious to cooperate with other industries and gov-
ernmental agencies to effect the reduction or elimination of objectionable wastes so
that they will not contaminate or otherwise render the water supply of our Nation
objectionable.
The wastes produced by the potato chipping industry, unless mixed with sanitary
sewage, are seldom, if ever, contaminated with pathogenic organisms which affect
public health. The problem is, therefore, one of the elimination of wastes from
streams so that the animal and plant life therein may flourish, thus producing a greater
abundance of aquatic food and at the same time furnish recreation for fishermen, and
aesthetic waterways and otherwise increase the utility of our water resources for bene-
ficial uses. To further conserve resources, the possibility for the economical utiliza-
tion of the wastes is also explored.
This "Industrial Waste Guide to the Potato Chip Industry" is intended primarily to
aid management and operators of the industry to reduce, utilize, and suitably dispose
of processing wastes. It will also be helpful in acquainting consultants and regulatory
personnel with the nature and source of the potato chipping wastes and the progress
that has been made in the treatment of such wastes.
Members of the Committee on Potato Chip Wastes that helped to prepare this guide
are located in nearly every geographical section of the country, thus problems peculiar
to climate have been considered. The committee was also selected because of special
experience in waste disposal and utilization. Some of the suggestions contained herein
should, therefore, be useful to nearly every chipper regardless of geographical or
urban locations.
The following is the committee personnel: H. D. Brown, Research Coordinator,
Potato Chip Institute International; Gil DuVernay, Food Technologist, The Frito Co.,
Nicolay-Dancey Division; R. D. Foster, Chief Engineer, Red Dot Foods, Madison,
Wis.; Barney Hilton, Food Technologist, H. W. Lay & Co., Atlanta, Ga.; Cliff Marshall,
Engineer, Nalley's Inc., Tacoma, Wash.; Ralph Porges, In Charge, Waste Treatment
Studies, Field Operations, Water Supply and Pollution Control, Robert A. Taft Sanitary
Engineering Center, Cincinnati, Ohio; and Paul A. Xander, Director of Research and
Development, Wise Potato Chip Co., Berwick, Pa.
Material for the guide was obtained in large part from publications prepared by
the Waste Treatment Studies Unit of the Robert A. Taft Sanitary Engineering Center,
Public Health Service, Cincinnati, Ohio.
The guide was reviewed by the Potato Chip Institute International through inter-
ested supporting activities of Harvey F. Noss, Executive Vice President. It was
submitted to the Public Health Service by the industry representatives on the National
Technical Task Committee on Industrial Wastes.
The National Technical Task Committee on Industrial Wastes is composed of
representatives from the Nation's leading industries concerned with solving difficult
industrial waste problems. Its objective is to perform certain technical tasks pertain-
ing to industrial wastes in cooperation with the Public Health Service and others con-
cerned with improving the quality of the Nation's water resources. Preparation of
the guide was one of the tasks assumed by the Potato Chip Industry in carrying out
this objective.
This is the seventh of a series of Industrial Waste Guides prepared by the National
Technical Task Committee in cooperation with the Public Health Service.
-------
Introduction
This publication includes suggestions and procedures
which chippers can employ to economically reduce or
eliminate the wastes from their operations which may
ultimately reach fresh water streams either through
their own waste disposal and utilization facilities or
through those owned and operated by governmental
agencies.
In facilities wholly operated by chippers, these
procedures may be as simple as disposing of the
untreated wastes on agricultural lands where they also
serve the dual purpose of raw product conservation
and soil enrichment; not to mention the possible value
for crop irrigation. If spray irrigation is utilized the
publication includes details for separating the solids
which may clog irrigation nozzles.
Finally, directions are given for the removal and, in
some cases, the utilization of soluble solids.
The procedures utilized for the separation of soluble
and insoluble wastes from the liquids can in most in-
stances be employed to reduce the B.O.D. (biochemical
oxygen demand) of wastes which are disposed of
through local municipal waste disposal systems. By
calculating the costs involved, chippers, regardless of
location, can determine whether to eliminate a part,
or most of the BOD before allowing it to enter the
municipal system.
Because of economics involved, considerable atten-
tion is directed to the use of various irrigation systems
and stabilization ponds even though most chippers
cannot currently employ such systems.
Costs and sewage plans have not been included in
this guide because of the great variations involved.
The Research Department of the Potato Chip Institute
International does, however, have a limited amount of
cost figures which will be supplied on request. No two
chippers will have identical problems. It is obvious,
therefore, that this guide should be construed as an aid
and not as the whole and final answer to waste dis-
posal problems.
Insofar as possible the guide includes factors which
cause deviations from normal waste loads and sug-
gestions for meeting these deviations.
It is probable that newer and better methods of waste
disposal will be discovered in the foreseeable future.
When such improved procedures are available in suffi-
cient number it is the thought of this committee that
a revised guide will be published.
Figure I.—Processing potato chips in a plant in Ohio.
-------
Description of Process
The processing of potatoes to potato chips involves
essentially the slicing of peeled potatoes, washing the
slices in cool water, and rinsing, partially drying,
and frying them in fat or oil (fig. 1).
Potatoes are generally received for storage at the
chipping plant in 100-lb. sacks or in large wooden con-
tainers. The potatoes are fed to a peeler where high-
speed, abrasive, rotating discs remove the skin. The
Figure 2.—Flow diagram.
SEWER
PEELER
TRIMMING BELT
SALT
SLICER
WASHER
STORAGE
PACKAGER
2nd RINSE
COOKER
peeled potatoes are washed, trimmed, and then sliced,
15 to 20 slices per inch. The slices are washed, gen-
erally in a tank or trough of water, and twice rinsed to
remove the starch to prevent matting or sticking of
the chips. After partial drying, the slices are fried in
deep-fat cookers. The chips are then salted and pack-
aged (fig. 2).
Raw Materials and Products
The potato is the most important item in the science
and art of chipping. It must produce a chip with eye
appeal and have a solids content that assures a profit-
able enterprise. High sugar content and nitrogenous
portions of the potato combine during cooking to cause
the undesirable dark chip, a condition which is con-
trolled by selection of potato variety, growing condi-
tions and proper storage.
For economical processing, the potato should have
a high density which can be determined by analysis or
estimated from the specific gravity. Since specific
gravity can be more easily assayed and is indicative
of production volume, the potatoes are usually received
at the plant with their specific gravity recorded. The
Department of Agriculture states (5) that the correla-
tion between specific gravity and dry matter has usually
been found to be very high with correlation coefficients
varying from 0.85 to 0.95. It indicates that the follow-
ing formula developed by Von Scheele, Svensson, and
Rasmussen seemed to approach analytical results:
Percentage dry matter = 211.04 X specific gravity —
207.709 (1).
However, analytical results provide the best data.
The starch content may be likewise estimated from
the specific gravity, by the formula given by Von
Scheele et al. (5)
Percentage s t a r c h = 199.07 X specific gravity —
201.172 (11)
The estimated solids and starch content of potatoes
at the given specific gravities is found in table 1(1).
Potatoes may be assumed to contain about 20 percent
solid matter and 80 percent water; the starch content
ranges from 65 to 75 percent of the dry weight (12).
WATER
2
-------
Table 1.—Calculated solids and starch content at various
specific gravities (Von Scheele et al.) (5)
Specific gravity
Solids
Starch
Starch in
solids
Percent
Percent
Percent
1.06
15. 99
10. 16
63. 3
1.07
18. 10
12. 15
67. 2
1.08
20. 21
14. 15
70. 0
1.09
22. 32
16. 14
72. 3
1.10
24. 44
18. 14
74. 2
Other information indicates that the solid matter may
average as high as 25 percent (10). The variety of
potato influences these values although the former fig-
ure might prove a more realistic average. The varieties
best for chipping include Russet Rural, Russet Bur-
bank, Smooth Rural, Irish Cobbler, Kennebec, Sebago,
Katahdin, Delus, Merrimack and Saco (1) (9) (13).
The next important raw material is the cooking oil,
almost always a high-grade vegetable product. The
least significant ingredient is salt.
Chip production will vary with solids content of the
potato. From 1,000 pounds of the so-called standard
potato (20 percent dry solids), chip production will ap-
proximate 250 pounds with an average moisture content
of 2*4 percent. The finished chip also contains about
40 percent absorbed oil. With potatoes having greater
than 20 percent dry solids, chip yields will generally
increase.
Source and Volume of Wastes
The primary sources of wastes are shown in figure 2. tary sewage.
Wastes are derived from the peeling, trimming, slicing, Table II presents plant data on waste flows based
and rinse operations. Other wastes accrue from clean- upon a unit production of 1,000 pounds of potatoes,
up, small amounts of waste oil, and occasionally sani-
Table II.—Plant operation and wastes discharged -per 1,000 lbs. of potatoes processed (11)
Plant
Month
Employ-
ees (num-
ber)
Potato
chips*
(pounds)
Waste
flow (gal-
lons)
B.O.D.
Suspended solids
p.p.m.
lbs.
p.p.m.
lbs.
A
Julv
0. 9
1. 3
1. 0
2. 3
240
260
240
255
2, 480
2, 020
2,000
1,450
730
1, 560
1,850
1,200
15.0
26. 2
30. 8
**14. 5
820
2, 140
2, 190
1, 700
24 3
35.9
36.4
**20. 4
B
December
C
October
D
December
Average ... -
1. 4
250
1, 990
•Average weight of oil on finished chip is 40%.
"Much solid material was removed manually and did not reach the sewer.
620218—61 2
3
-------
Composition of Wastes
Waste from a potato chip plant varies with the season
as it influences the types of potatoes used and with the
method of processing. The greater the solid content
of the potato, the greater the oxygen-demanding prop-
erties the gross waste material will have. For example,
the following hypothetical condition is presented:
Specific pravity
Solids
B.O.D. p.p.m.*
(porcent)
(whole potato)
1.06
15. 99
72, 400
1.07
18. 10
82, 000
1.08
20. 21
91, GOO
1.09
22. 32
101, 100
1.10
24. 44
110, 700
•Based on 0.453 pound B.O.D. per pound dry potato solids.
Waste handling practices are also important. If
solid materials such as peelings and small pieces of
potatoes are removed for disposal other than sewage,
the waste load will be reduced.
Table II contains data from several plants showing
B.O.D. and suspended solids. Plant A (table II) at
the time of study was handling during the summer
(July) a potato with low solids and thin peel; it will
be noted that the pounds of B.O.D. per unit potato was
low. Plant D was removing solid material from the
waste flow, with a corresponding reduction in the
strength of the waste discharged. Plants B and C were
studied in the fall (October and December) and the
waste values were in close agreement with a much
higher B.O.D. per 1,000 pounds of potatoes.
The process was evaluated on a dry-solids basis and
an estimated waste calculated from the solids dis-
charged compared with the actual waste collected in
the sewer. The results of this evaluation are shown
in table III. The data presented are based on 1,000
pounds of potatoes. Column 1 shows the dry weight
of 1,000 pounds of potatoes; column 2, the pounds of
chips produced.
The B.O.D. of a potato was determined in the labo-
ratory (11). Two individual runs were made with
the following results:
Raw potato
Solids
(percent)
n.o.D.
p.p.m.
Pounds
B.O.D./lbs.
Solids
A
18. 57
18. 70
84, 000
85, 000
0. 452
. 455
B
Average
18. 64
84, 500
. 453
Since chips will average about 2^4 percent moisture,
the dry weight is presented in column 3. The average
oil content of the chip is 40 percent, so the oil weight
shown in column 4 was subtracted from the net dry
weight of the chip in column 3 to show the dry potato
solids ultimately sold (column 5). The difference be-
tween the dry weight of the potatoes (column 1) and
the dry solids produced (column 5) represents the
pounds of dry solids lost (column 6). It will be ob-
served at the bottom of table III for each pound of
dry solids, a B.O.D. of 0.453 pounds will be exerted.
Based on the pounds of dry potato solids lost (column
6), the pounds B.O.D. discharged can be determined,
Table III.—Solids balance and B.O.D. relationship per 1,000 pounds potatoes (11)
« Dry-solids variation probably due to seasonal variation,
b 2li% moisture.
• Ohtp contains 40% oil.
Dry weight •
(1)
Chips
produced b
(2)
Dry weight
(3)
Oil in chip •
(4)
Dry solids
produced
(3)-(4)
(5)
Solids lost
-------
as indicated in coimn 7. Column 8 gives the B.O.D.
obtained from the sewage analysis divided by the num-
ber of thousands of pounds of potatoes used. Com-
parison of the results of determining the waste load by
the two independent methods (columns 7 and 8), is
extremely good. Deleting results for plant D because
of manual removal of much of the solids, adjusting for
the remaining data, and then averaging columns 7 and
8, the calculated average B.O.D. based on solids lost is
25.4 pounds while that obtained from the waste in the
sewer is 25.0 pounds.
Suspended solids will average about 32 pounds for
each 1,000 pounds potatoes processed. Based on a
suspended solids population equivalent of 0.20 pounds,
this amounts to the suspended matter discharged by
165 people.
A representative condition, the average in table III,
that might well be used for a general case would start
with potatoes having 20 percent, or 200 pounds solids
per 1,000 pounds potatoes. Dry solids produced would
equal 143 pounds, indicating 56 pounds of solids lost.
The B.O.D. of the solids lost would be 25.4 pounds
and should represent the amount found in the sewer.
Since the B.O.D. normal to sewage waste from one per-
son is 0.167 pound per day the population equivalent,
based on B.O.D. for each 1,000 pounds of potatoes
processed with the above characteristics, would be
about 150.
The above method of estimation will provide a quick
means of evaluating wastes from a potato chipping
plant. For example, assuming that a plant processing
20,000 pounds of potatoes with a solids content of 22
percent, the dry solids handled will amount to 4,400
pounds. Assuming a chip production of 26 percent of
the raw potato, the chip poundage produced would be
5,200 or a dry weight of 5,120 pounds. The oil content
may be estimated at 40 percent of the gross weight of
chips or 2,080 pounds. The dry solids produced would
amount to 3,040 pounds. In this example, the dry
solids discharged to sewerage would be 1,360 pounds.
The pounds of B.O.D. wasted would be 616 pounds or
equivalent to a population of 3,700.
A previous study of potato chip processing wastes
(10) indicated a population equivalent (B.O.D.) of
65 per 1,000 pounds of potatoes. This estimate is low
when compared to the present value of 150 P.E. per
1,000 pounds. However, that study was made on a
batch process and some solid materials such as sprouts
and possibly peelings were disposed of to a dump. The
report (10) stated that the data was limited to a single
plant and might not give accurate indications of waste
loadings for application to other plants.
Several reports of wastes from potato dehydration
processes appear to be of interest since these wastes
may compare grossly to the wastes from chipping
plants. Gray and Ludwig (7) show dehydration wastes
to contain 40 pounds of B.O.D. per ton of potatoes
processed, amounting to 120 population equivalents per
1,000 pounds. Jones (8) reports 12,000 population
equivalents for 40 tons of potatoes, or 150 P.E. per
1,000 pounds; a check with the present study. De-
Martini, Moore, and Terhoven (6) reported on two
separate dehydrating plants. One plant discharged 3.28
pounds of B.O.D. per 100 pounds of potatoes, or 198
P.E. per 1,000 pounds. The other plant showed 4.57
pounds per 100 pounds or 274 P.E. per 1,000 pounds
of potatoes.
The variation in these data probably results from the
types and maturity of potatoes used and the processing
methods employed. A smooth potato with thin skin
produced less waste than that from a rough potato with
thick skin. Evaluation of the wastes from these proc-
esses on the basis of dry solids lost to sewerage would
bring these studies to a common basis and might indi-
cate a closer correlation.
5
-------
Pollution Effects
The discharge of untreated potato chip wastes has
several undesirable effects upon the receiving water-
course. Floating solids create a visual nuisance while
decomposable organic sludges drain available dissolved
oxygen from the flowing waters. The high turbidity
interferes with light penetration thereby reducing
normal algal life. The organic matter in the wastes
may undergo rapid decomposition utilizing oxygen
that may be reduced to low levels in the stream. The
solids coat the stream bottom breaking the normal
food chains for stream biota. Fish habitat may be
destroyed, or at least damaged. The sum total effect
may be the creation of a stream not available for maxi-
mum beneficial use.
Suggestions for Effective Waste Prevention or Reduction
The volume of water used is a matter of importance
both from the standpoint of cost of the water and of
waste disposal. Generally, a reduction in volume de-
creases sewage disposal costs. Some attempts have
been made to reuse water, particularly that clearer
portion of the rinse waters. Filtering (centrifuging
better) of the water prior to reuse has not proven
practicable as the starch particles rapidly clog most
filter media. Application of the counter-current prin-
ciple appears promising especially since the initial
machines and peelers and the first potato wash before
peeling do not require high quality water. Consid-
erable water could be saved by pumping the final rinse
waters to the wash tank and using the wash tank over-
flow to feed the peeler and then discharging it to
sewerage. No filtering or water conditioning would
seem to be necessary.
The method of housekeeping also influences the waste
load. Where peelings, and solid wastes are removed
manually for dry disposal, the waste load is reduced
appreciably. At one plant the B.O.D. of the waste was
reduced to nearly 50 percent of that estimated from
the solids balance. Other plant operators, mostly in
large cities, feel that disposal to sewerage facilitates the
handling of waste solids.
Starch could be setded from the waste stream by
proper sedimentation units. Development of by-prod-
uct use of this starch is a distinct possibility, but at
present the cost to remove the starch is too high for
value returned.
Soluble solids removal
One of the methods for the removal of soluble
solids; i.e., sugars, amino acids, and minerals, is their
conversion into algal masses in stabilization ponds.
A method for removing amino acids and the purifica-
tion of the same has been patented by Xander et al.
(14).
Grease
A grease trap is useful in separating grease (from
other wastes) which arises during machinery cleaning
operations.
Feed value of recovered solids
Solids recovered have a feeding value for dairy cows
approximately one-third that of alfalfa (2). Dairy
cows utilize the raw as well as cooked product but the
wastes must be cooked when fed to hogs to achieve
maximum nutritional value.
The wastes can also be dehydrated and fed as sup-
plements to other foods. A typical analysis of the dried
product is as follows: Moisture 10 percent, carbohy-
drates 68 percent, protein 9.5 percent, minerals 4.0
percent, fiber 7 percent, and fat 1.5 percent.
6
-------
Waste Treatment and Disposal
Potato wastes unless mixed with sanitary sewage are
seldom, if ever, contaminated with pathogenic organ-
isms which affect public health. Furthermore, they
afford valuable organic materials as well as some min-
erals which if applied to farm lands may ultimately
lead to increased yields. The use of the liquid wastes
for irrigation may also offer certain economies when
the plant is located in a farm area.
Flood, furrow and ditch irrigation
In a limited number of cases, i.e. where chipping
plants are located within 1 to 3 miles of available farm
land the combined liquid and solid wastes (do not in-
clude sanitary sewage) can be spread by flood, furrow
or ditch techniques to land which may be set aside spe-
Sp
The liquid portion of settled effluents can also be
spray irrigated on land without any trouble from nozzle
clogging (see fig. 4). No attempt has been made to
comminute the solids so that they can also be sprayed
onto the land as in the case in the canning industry (4).
It is possible to employ overhead irrigation even
during the coldest of winters with precautions taken
to prevent freezing of equipment. The warm wastes
will keep the ground from freezing, except around the
periphery (3).
Settling basins
The separation of the liquid from the solids (mostly
starch) requires settling basins of one type or another.
Figure 3.—Ridge and fur-
...
row irrigation.
cifically for this purpose, or with additional planning,
the wastes may be used for irrigation during the
cropping season (4). Timbered land will absorb mois-
ture more quickly than cropped or fallow lands. West-
ern sands and gravel, especially in arid sections, have a
great capacity for moisture.
Irrespective of the procedure employed it is essential
that moisture and wastes shall not be allowed to stand
stagnate for more than 24 hours (4). If this simple
precaution is observed there will be no trouble from
odors or undesirable insect infestations. This perhaps
is the cheapest method of waste disposal (see fig. 3).
i '
* JS£ *
Settling basins may be employed for holding the
effluent from the chip plant. A holding period of one
hour is sufficient for the removal of most of the starch
and large solids (approximately 50 percent of the total
B.O.D.). If held for as much as 3 hours a B.O.D. re-
moval of 60 percent has been reported. Table IV shows
the reduction effected in a trial run made to supply
data for this guide. For details of equipment required
consult the research division of the P.C.I.I.
A basin of this type may be constructed of concrete
with manholes on top for cleaning. Periodic cleaning
of small basins may be accomplished by pumping the
7
-------
Figure 4.—Spray irrigation on nlfnlfu stubble. Wastes containing 220 p.p.m. solids, from settling basin ure effec-
tively disposed of by this system.
sludge from it, similar to the cleaning of a septic tank,
and the solids then hauled to a field or some other
dumping area. This will reduce the load going to
the municipal sewage plant.
Tablb IV.—Sa7>iple B.O.D. reductions effected by screening
and nettling
To vibnit-
ing screen
To settling
basin
Prom set-
tling lmsin
after 3 hours
pH
5.33
1, 700
5,910
270
5. 74
1, 280
3, 350
26
5. 82
650
226
Trace
B.O.D., p.p.m -
Suspended solids, p.p.m
Settleable solids, ml/L
Another method which has been used in the past is
a system which operates similar to a plain settling
basin but has automatic equipment for pumping out
the sludge either to tanks or to a tank wagon. This
is rather a costly method, but improvements have been
made to make it more efficient.
Another method which could be considered is use
of a settling tank, passing the effluent through a
series of underground weepers similar to the drain tile
installations attached to domestic septic tanks. It may
be necessary to direct the effluent periodically from one
group of weepers to another. The needed drainage re-
quires a considerable amount of land space. Another
point that must be considered in using this type of
installation is the absorption characteristics of the soil.
The absorption test of the soil will determine the area
that will be needed to absorb the effluent from the
settling tanks. One advantage of this method over a
lagoon is that there are no odors.
Lagoons
In some areas lagoons may be used, providing
the location of the lagoon does not result in an
odor nuisance. Two lagoons should be used and when
one becomes filled with residue, the effluent from the
plant can be diverted into the second lagoon. When
the first lagoon dries up a bulldozer may be used to
remove the solids lhat have accumulated. If the odor
from such a lagoon creates a nuisance, chemicals (usu-
ally certain soluble nitrogenous compounds) may be
used to curtail it.
Stabilization ponds
One rather new development that may be of interest
to a number of chippers who are located within 1 or 2
miles of available farm land, is the use of stabilization
ponds. Ponds have been used throughout the world
for many years to: (1) remove suspended matter; (2)
regulate erratic waste flow patterns; (3) store wastes
for release during high stream flows and to a lesser
extent, store for later irrigation use; and (4) propa-
gate fish with fertilized water. More recently (since
8
-------
Figure 5.—Stabilization pond with a normal loading of 45 pounds H.O.I). (15,500 gal. of 200 p.p.nt. solids) is
stabilized daily by this pond which is 1 acre in size, 6 feet deep (deeper than desirable) and holding 1.9 million
gallons. Overflow is through a wooded area into a nearby stream. An 83 to 93 percent reduction in C.O.D.
has been secured during the summer months by the use of this pond.
1948) it has been recognized that stabilization ponds
may provide a degree of purification comparable to
that achieved by conventional complete treatment
processes.
In stabilization ponds the organic matter is broken
down into simpler compounds by means of bacteria.
The decomposition products, in turn, are utilized by
algae during photosynthesis to produce oxygen and ad-
ditional algal mass. This oxygen then supplies that
necessary for aerobic bacterial decomposition. Photo-
synthesis, and hence oxygen production, depends on
available sunlight. This phenomenon ceases at night
and is reduced by turbid water, an ice cover, or a
cloudy day.
Under normal conditions, sufficient oxygen is pro-
duced during the daytime to supply the demands dur-
ing the night. In addition to sedimentation of the
settleable solids in the pond, suspended and colloidal
solids may be precipitated by the action of soluble salts
which are concentrated by evaporation in summer and
freezing in the winter. The settled material subse-
quently undergoes decomposition.
The load in terms of total organic matter assimilated
in stabilization ponds depends on many factors. Shal-
low (3 feet) ponds are more effective than deeper
ponds. Ponds exposed to wind movements are more
effective than those in sheltered areas. Loadings de-
pend to a great extent on temperature and available
sunlight and hence would vary with different climates.
Loads of 10 to 120 pounds B.O.D. per acre per day
have been recorded. In the only stabilization pond
known to be used exclusively for chip wastes a load of
66 pounds of B.O.D. per acre per day has been effec-
tively utilized during summer months (see fig. 5).
Trickling fillers and chemical coagulation
Trickling filters have been employed for treating can-
ing wastes although the seasonal operation of canneries
makes it difficult to develop effective treatment units.
Year-around operation of potato chip plants should per-
mit more effective operation of trickling filters. Chem-
ical coagulation (rather expensive) has been used for
partial treatment where untreated wastes may overload
small municipal treatment plants. With increasing im-
portance of satisfactory waste disposal, industrial sites
that minimize the waste problem should be selected (see
figures 6 and 7).
Municipal plants
The most used and probably the best method of waste
disposal is that of discharging the sewage into a munic-
9
-------
Figure 6.—Trickling filter.
Figure 7.—Detail of trickling filter construction. The aerobic bacteria living in tile slime coating on the stones
"digests" the organic matter remaining in the wastes coming from the clarifier.
ipal system. In some instances the charges imposed
for municipal handling of wastes are rather high.
In arriving at a cost charge it is well to remember
that approximately 50 percent of the B.O.D. is pro-
duced by solids that can be removed (peels, trimmings
and starch) by shaker screens or basket centrifuges.
Another 25 percent of B.O.D. can be removed by
settling tanks.
Equipment needed for disposal into municipal sew-
ers consists essentially of a food chopper and ade-
quate water to flush the wastes into a larger sewer.
B.O.D. vs. C.O.D.
Biochemical Oxygen Demand (B.O.D.) determina-
tions are difficult to run and require considerable
special equipment. The Potato Chip Institute Inter-
national hopes to establish a correlation between B.O.D.
and more easily determined C.O.D. (Chemical Oxygen
Demand) analyses. A preliminary run of six samples
(without a catalyst) by W. D. Sheets gave an average of
261 p.p.m. (parts per million) B.O.D. as compared to
317 p.p.m. of C.O.D. These data are not sufficient for
practical usage. The use of a silver sulphate catalyst
greatly increased the C.O.D. values.
10
-------
Summary
The potato chipping process consists of peeling, trim-
ming, slicing, washing, rinsing, drying, cooking, and
packaging. Wastes originate primarily from the peel-
ing, trimming, washing, and rinsing operations.
Representative data evolved from a study of several
plants, based on 1,000 pounds of potatoes handled, were
as follows:
Flow in gallons
H.o.n.
Suspended wilds
Lbs.
P.F.
Lbs.
F.
1, 990
25. 4
152
33
105
Waste products vary with types of potatoes and
methods of processing. If preliminary estimates of
plant wastes must be made without a sampling study,
it will be advantageous to evaluate the process based
on dry solids in the potato and dry solids produced.
Excellent correlation was obtained by comparing
pounds of B.O.D. calculated from the weight of solids
lost with the pounds of B.O.D. in the sewer. The aver-
age B.O.D., estimated from solids wasted per 1,000
pounds of potatoes, was 25.4 pounds as compared with
an average B.O.D. of 25.0 pounds in the sewer per
1,000 pounds of potatoes.
A dry solids balance can be computed using the
solids content of the potato and the pounds of chips
produced, and allowing for the oil and moisture con-
tent of the finished chip. The pounds of dry potato
solids lost times the factor 0.453 pounds B.O.D. per
pound dry potato solids results in the pounds B.O.D.
discharged. If all wastes reach sewerage, the above
value will reasonably approach the B.O.D. of the dis-
charged liquor. Should some solids be removed for
manual disposal, the value must be adjusted accord-
ingly.
A counter-current principle of water use would seem
to hold promise for reduction of water consumption
and of waste discharge. Although manual removal
of solids reduces the waste load, the choice between
manual and water-carried disposal is a matter of eco-
nomics and cleanliness, and is one that management
must make.
A residual amount of wastes will require disposal.
Discharge to municipal sewerage, with or without
chemical pre-treatment, is probably the best method.
Other methods that might be considered are flood, fur-
row, and ditch irrigation, lagooning with land applica-
tion or spray irrigation, stabilization ponds, and trick-
ling filters. Industrial plant sites that minimize dis-
posal problems should be selected.
II
-------
Bibliography
1. Anonymous, 1958. Potatoes for Chipping, Potato
Chip Institute International.
2. Atheson, F. W. and Anderson, C. C. 1935. Pota-
toes as a Feed for Dairy Cows, Idaho Agr. Exp.
Sta. Bui. 216.
3. Brown, H. D. 1956. Disposal of Cannery Waste
in Ohio, Canning Trade Jan. 2.
4. Brown, H. D., Hale, Harold H. and Sheets, W, D.
1955. Reprint from Aug. and Sept. Food
Packer.
5. Communication—Heinze, P. H., Leader, Beltsville
Horticultural Crops Unit, Agricultural Market-
ing Service, U.S. Department of Agriculture
(Feb. 1958).
6. DeMartini, F. E., Moore, W. A., and Terhoven,
G. E., "Food Dehydration Wastes," Supplement
No. 191 to the Public Health Reports, 36 pages
(1946).
7. Gray, H. F., and Ludwig, H. F., "Characteristics
and Treatment of Potato Dehydration Wastes".
Sewage Works Journal, 15, 1, 71-77 (January
1943).
8. Jones, E. E-, "Disposal of Waste Waters from the
Preparation of Vegetables for Drying". Journal
of the Society of Chemical Industry, 64, 80-83
(March 1945).
9. "In the Chips" Esso Oilways, 1-5 (January 1958).
10. Porges, R., "Waste Loadings from Potato Chip
Plants". Sewage and Industrial Wastes, 24, 8,
1001-4 (August 1952).
11. Porges, R. and Towne, W. W., "Wastes from the
Potato Chip Industry". Sewage and Industrial
Wastes, 31,1, 53-59 (January 1959).
12. Treadway, R. H., and Coldon, T. C., "The Chemi-
cals We Get from Potatoes". Yearbook of Agri-
culture—Crops in Peace and War, 1950-51,
Pages 190-194.
13. Wright, R. C., Davis, Martha E., and Hendel, C. R.,
"The Making of Potato Chips", Yearbook of
Agriculture—Crops in Peace and War, 1950-51,
Pages 188-189.
14. Xander, Paul A., Nescopeck, and Edward F.
Hoover, 1959. U.S. Patent 2,87.9264.
12
------- |