:- H
FEDERAL WATER POLLUTION CONTROL ADMINISTRATION
NORTHWEST REGION, PACIFIC NORTHWEST WATER LABORATORY
POTATO WASTE TREATMENT
PROCEEDINGS OF A SYMPOSIUM
March 8, 1968
SPONSORED BY:
FEDERAL WATER POLLUTION CONTROL ADMINISTRATION
and
UNIVERSITY OF IDAHO, MOSCOW, IDAHO
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POTATO WASTE TREATMENT
Proceedings of a Symposium
jointly sponsored by
University of Idaho
and
Federal Water Pollution Control Administration
Pacific Northwest Water Laboratory
March 8, 1968
U. S. DEPARTMENT OF THE INTERIOR
Federal Water Pollution Control Administration
Northwest Region
Pacific Northwest Water Laboratory
Corvallis, Oregon
July 1968
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CONTENTS
Perspectives and Problems in Treatment of Potato
Processing Wastes - J. R. Boydston 1
Mechanisms of Anaerobic Waste Treatment -
G. L. Dugan and W. J. Oswald 5
Recent Developments in Anaerobic Waste Treatment -
D. A. Carlson 19
Pilot Plant Studies on Secondary Treatment of
Potato Processing Wastes - K. A. Dostal 27
Other Treatment Methods for Potato Wastes -
J. W. Filbert 43
Spray Irrigation Treatment - F. C. Haas 55
Potato Waste Treatment Research Need -
H. S. Smith 61
Future Growth of the Potato Processing Industries -
Ray W. Kueneman 73
General Discussion 81
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FOREWORD
Processing of potatoes has grown markedly during the
past fifteen years, especially in the Western States.
Unfortunately, waste production has increased as rapidly
as the processing. Several of the nation's largest fishkills
have resulted, in part, from this increasing wasteload.
Research is being done on treatment of potato processing
wastes by various interested parties. It is for this reason
that this symposium was scheduled so that existing knowledge
could be shared and the gaps identified so that future re-
search and demonstration efforts will be properly channeled.
JAMES R. BOYDSTON, Chief
Treatment and Control
Research Program
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PERSPECTIVES AND PROBLEMS IN TREATMENT OF
POTATO PROCESSING WASTES
by
James R. Boydston
The Federal Water Pollution Control Administration is pleased
to join with the University of Idaho today in sponsoring this
symposium on the status of waste treatment technology in the
potato processing industry. May I welcome you to this important
session and offer my agency's keen interest in the combined
expertise you can bring to bear on a major pollution problem we
face: water pollution from the discharge of inadequately treated
potato wastes.
I'd like to begin this session with a few brief comments on
FWPCA's interest in this symposium and to set the stage for the
important papers on the agenda before us.
To put our problem in broad perspective, I'm sure I need
not emphasize to Idahoans that potatoes are about the most
important vegetable crop grown in the United States -- after
all, a quarter of the nation's potato crop is grown right here
in Idaho. That's a pretty significant percentage when we consider
that the total average annual potato production in this country
is about 300 million hundred weight, or 15 million tons.
For our purpose today, however, an even more significant
statistic is that the wastes produced in processing a ton of
these potatoes is equivalent in organic strength to the wastes of
a population of 300 to 500. In other words, the average daily
national potato production can create an untreated waste load
equivalent to 6 to 8 million people, and in Idaho alone a popu-
lation equivalent of about 2 million. If discharged untreated,
or inadequately treated, to our freshwater streams, these wastes
create serious pollution problems.
Chief, Treatment and Control Research, Pacific Northwest Water
Laboratory, Federal Water Pollution Control Administration,
Corvallis, Oregon.
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Since that significant percentage of the national potato
crop is grown right here in Idaho, it is not surprising that
many of the pollution problems from this source also occur here.
For example, Milner Reservoir has had the dubious honor of four
of the nation's largest fishkills since 1960—due principally to
the combined effect of inadequately treated potato wastes and the
curtailment of streamflow at the dam. Other examples occur to
you, I know. The severe pollution in the Snake Basin has resulted
in stringent State and Federal requirements for treatment of those
wastes -- and technology has barely kept abreast of the need.
Water quality standards—which were adopted last year in compliance
with the Water Quality Act of 1965 — require that all wastes
receive the highest and best degree of treatment, consistent with
the goal of maintaining or restoring water quality to make it
suitable for the wide variety of uses the public demands.
It doesn't take a crystal ball to project population growth
and industrial production to see that even secondary waste treat-
ment may not be adequate to preserve minimum water quality. Future
demands for water for recreation, irrigation, municipal and indus-
trial supply, propagation of fish and wildlife, and other uses will
exceed the limited supply of water, unless it is kept clean and
usable. There is little we can do to increase the natural supply
of water; so we must reuse our limited supplies many times along
the streams' course to the ocean. This water reuse will be im-
possible without adequate waste treatment. And the definition of
"adequate" will mean higher and higher levels of treatment as
our economy grows and our demands for clean water increase.
In this context, the purpose of our meetings here assumes
great importance to the State of Idaho and the potato .processing
industry. For while the State Department of Health and the FWPCA
require the maintenance and restoration of water quality, it will
be in the public's best interests to achieve that goal in the most
economical and efficient manner. Not only is the degree of treat-
ment an important consideration, therefore, but we must continually
seek more efficient and less costly means of providing that treat-
ment. These are the areas of research we hope to define today,
as we learn more of the present state of the art in potato waste
treatment.
Before I turn the meeting over to the other speakers for the
technical presentations, may I offer a few words on FWPCA1s interest
in this field and the ways we hope to assist in solving these
problems. Congress has directed the FWPCA to spearhead an expanded
program of pollution control research. This national research
program has been divided among several research laboratories, each
assigned responsibilities for specified areas of research. The
Pacific Northwest Water Laboratory in Corvailis is designated as
the national center for research into new or improved methods for
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treatment of wastes from the potato processing industry. (Other
national research programs centered in Corvallis include eutrophi-
cation, disposal of wastes to marine waters, pulp and paper waste
treatment, and thermal pollution from the power industry.) In
potato waste treatment research, the funds to initiate the program
have been curtailed in this national budget-cutting year; but it
has been possible to undertake cooperative studies at the J. R.
Simplot Company plant at Bur ley, Idaho.
In addition, the Clean Waters Restoration Act of 1966 made
grant moneys available, for the first time, directly to industry
for research to demonstrate new or improved methods of waste
treatment which will have industry-wide applications. One of the
first grants awarded was $483,000 to the R. T. French Company to
demonstrate the use of surface aerated ponds in the combined treat-
ment of wastes from potato processing. Construction of this full-
scale facility is expected to begin shortly at the Shelley, Idaho
plant. Upon completion, the company will determine plant efficiencies
and investigate operational methods to obtain optimum treatment.
Total project costs for this venture will exceed $700,000.
FWPCA grants are also available for university research into
new treatment methods. We recognize that industry and university
talents provide excellent capabilities for research into the pollu-
tion problems we have found. Consequently, we have adopted a policy
of promoting extramural research. In fact, it is expected that the
inhouse research by FWPCA may be the smaller part of the total
Federal dollars expended on water pollution control research as a
whole.
With this brief background on my agency's interests in these
discussions today, may I close by reaffirming our interest in a
cooperative approach to the development of potato waste treatment
technology. We will continue to look to the industry and the
universities for expertise in solving pollution problems. We
welcome this opportunity for a direct and formal exchange of current
knowledge and the chance to discuss future needs together.
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MECHANISMS OF ANAEROBIC WASTE TREATMENT
by
Gordon L. Dugan and William J. Oswald
"Anaerobic" as the name implies from its Greek root origin,
literally means "life without air." Such life in ponds will be
the major subject of this paper, but in a discussion of anaerobic
mechanisms in waste treatment, it is advantageous also to explore
the aerobic or "air-life" mechanisms, since the two groups are
interrelated in almost all of the steps involved in waste treat-
ment processes.
With regard to an aquatic environment, the zone containing
dissolved oxygen is called the aerobic zone. Dissolved oxygen
is utilized by most organisms ranging from bacteria to fish. In
most natural waters dissolved oxygen in equilibrium with the
atmosphere has a concentration of from 8 to 9 mg/1. Many factors
such as temperature of the water, oxygen consuming or producing
organisms, and turbulence of the water, affect the dissolved oxygen
content which in general may range from less than 1 milligram per
liter (mg/1) to 4 above saturation. The saturation point increases
with decrease in temperature. Free oxygen produced from algal
growth can bring about a condition known as supersaturation in
which the dissolved oxygen content of the water may exceed satura-
tion assuming a value equivalent to equilibrium with atmospheres
having more than 2YL oxygen. Supersaturation generally occurs
during warm sunny days when algal growth is at a maximum. The dis-
solved oxygen concentration will tend to decrease to saturation or
less at night when, due to a lack of light, there is no photosynthesis,
Graduate student in Environmental Health Sciences, University of
California, Berkeley.
2Professor of Sanitary Engineering and Public Health, University
of California, Berkeley.
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Waters in which no detectable dissolved oxygen is present are
classified as anaerobic or "septic". Organisms which live under
this condition must obtain their energy from chemical reactions
which lead to production of alcohol, acid and methane. Some of the
various types of anaerobic waste treatment processes presently
being used are carried out in the well known municipal and industrial
digestion tanks, anaerobic and facultative ponds, Imhoff tanks, and
septic tanks. There are many variations and combinations of these
basic systems, but essentially the basic principles are the same
for all. These processes of fermentation will be discussed in
greater detail later in this paper in conjunction with the major
topic of pond design.
The facultative stabilization pond is emphasized in this
presentation because this is the most versatile type of pond avail-
able at present and because interest in this type of waste treat-
ment facility is on the increase. The comparative position of the
facultative pond with respect to the aerobic and anaerobic pond is
of interest. In Figure 1 are illustrated the three basic types of
ponds, viz. aerobic, anaerobic, and facultative. Although ponds
are often designated by various names, such as lagoons, oxidation
ponds, stabilization ponds, and waste conversion ponds, in this
discussion, the classification given in Figure 1 will be used.
This classification, suggested by Oswald at the Manhattan Conference
in 1960 is as follows: Those ponds in which only the reactions
above the point where dissolved oxygen becomes zero (termed the
oxypause) occur, which provide aerobic oxidation and photosynthetic
oxygenation, should be classified as aerobic ponds. Ponds in
which the anaerobic reactions below the oxypause line are the pre-
dominant ones, are called anaerobic ponds. Ponds in which an
aerobic zone exists in the surface strata and an anaerobic zone
exists in the lower strata are termed facultative ponds.
Although it is appreciated that a multitude of interdependent
complex chemical, physical, and biological reactions occur both
simultaneously and in sequence in the stabilization of organic
waste, only typical overall carbohydrate reactions will be considered
in this paper. In the following simplified reactions, carbohydrate
is typified by the simplified formula
(CH20)x
By referring to Figure 1 it can be seen that in aerobic oxida-
tion carbohydrate and oxygen combine to yield carbon dioxide, water
and energy.
(CH20)X + 02 » C02 + H20 + energy
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FIGURE I. SCHEMATIC CROSS SECTION OF A STABILIZATION POND
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In the photosynthetic reaction algae use carbon dioxide, water,
and solar energy to form algae cells and free oxygen as indicated
by the equation:
C02 + 2H20 Solar Energy (QR^ ^ + ^ + ^
Oxygen released photosynthetically is, in turn, utilized by the
bacteria in completing the symbiotic semi-cycle. The algal cells
may be removed by harvesting (mechanical, centrifugation, or chem-
ical flocculation), discharged in the effluent, or allowed to
settle into the anaerobic zone as happens in a facultative pond.
Broadly speaking, decomposition takes place as two phases in
the anaerobic zone. The two phases are the "acid" phase and the
"gas" phase. In the "acid" phase settled sludge is broken down
to organic volatile acids and energy, and in the "gas" or "methane"
phase, the organic volatile acids are converted to carbon dioxide
(C02), methane (CH4), hydrogen (H2>, nitrogen (N2), and minor
amounts of other gases.
The general reactions occurring in an anaerobic pond or in
the anaerobic portion of a facultative pond are also depicted in
Figure 1. The reactions are essentially the same as those occurring
in a conventional digester, except with respect to gas composition.
In a digestion tank the composition of the gases is approximately
607. CH4, 30% C02, 57o H2, and 5% inert gas (eg. N2) . In an anaerobic
pond, the composition is generally 60% Cfy, less than 57= C02> 5-107o
H2, and 20 to 3070 N2. The reason for the high nitrogen content
in the gases discharged from facultative ponds is not fully under-
stood.
In Table 1 is presented a summary of the major reactive phases
that occur in a facultative pond. It should be noted that the
optimum growth conditions for the several phases differ greatly.
Therefore, compromises are necessary. The aerobic phases are more
closely compatibile than the anaerobic phases. The acid formers
can reach their maximum activity in 10 to 20 days, whereas it takes
from 40 to 50 days for the methane formers to do so. Another dis-
crepancy is that the optimum pH range of the volatile organic acid
formers is from 4.5 to 7.5, whereas the optimum pH range for methane
formers is from 6.8 to 7.2, Therefore, if the acid formation is
allowed to proceed too rapidly, the pH level will drop to a point
at which the slower growing methane formers would be inhibited.
Should this happen, the acid formers will predominate, and as a
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TABLE I
SUMMARY OF THE MAJOR REACTIVE PHASES IN WASTE DISPOSAL PONDS
Phase
Aerobic
Oxidation
Photo-
synthetic
Oxygenatior
Acid
Formation
Methane
Fermentatic
Characteristics
Organisms
Aerobes
Algae
Facultative
Heterotrophs
Methane
n Producers
Substrate
Carbohy-
drates,
proteins
CO 2
NH3
Carbohy-
drates,
Proteins,
Fats
Organic
Acids
Products
C02 +
NH3
Oxygen
Algae
Organic
acids
CH4, C02,
H2
Time
Req'd
(days)*
5-10
10-20
10-20
40-50
bdors
Pro-
duced
None
None
H2S
H2S
Environmental Factors
Temp.
<°C)
0-40
4-40
0-50
6-50
Oxygen
Required
Required
Under Cer-
tain Con-
ditions
Required
Under Cer-
tain Con-
ditions
Not
Required
PH
7.0-9.0
6.5-10.5
4.5-7.5
6.8-7.2
Light
Not
Req'd
Req'd
Not
Req'd
Not
Req'd
Toxic
Compounds
Cr-H-+
NH3+
Ca-H-
C12
Cr-H-l-
Cr+++
02.
Detergents
*Time required to develop a stable population
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result the pH level will continue to decrease. Unless the situ-
ation is corrected, a condition will arise in which the system is
said to be "stuck" or "sick". The term applies both to digesters
and to ponds. Volatile organic acids have a very foul odor and
along with hydrogen sulfide (rotten egg odor) are responsible for
moat of the odor nuisances of ponds. The parameters used to
monitor the condition of the anaerobic phase generally are pH,
gas production, volatile acid content, and alkalinity.
Operationally, in the interest of time and efficiency in
Initiating ponds, it is recommended that digesters, facultative
ponds, and anaerobic ponds be seeded with a well-digested sludge,
preferably from the same type installation as the one being initiated.
It is also recommended that aerobic ponds and facultative ponds be
seeded with an algae culture. The amount of seed to use depends on
availability and the economics of transporting the seed, but if
odorous conditions seem likely to cause public concern, however,
the greater the quantity of seed, the greater will be the chance
of successfully starting the system in a shorter period time with
less odor.
Once an acid-gas balance is established, anaerobic decompo-
sition proceeds normally and organic material introduced to a
digester is broken down to gases and stabilized sludge. The
digester acid-gas balance can be upset by excessive organic load-
ing, shock loading, and toxic compounds. In the case of methane
forming bacteria, oxygen is very detrimental. To maintain anaero-
bic conditions, the pond must be deep enough and sufficiently
short in the direction of the prevailing wind so that wave action
will not result in overturn and conveyance of dissolved oxygen
into the anaerobic sludge. The thermocline, above which a strata
of warmer bouyant oxygenated water is located, helps to protect
the pond from having vertical circulation. Another method which
has been used to keep dissolved oxygen from the sludge, is to re-
duce the surface area of the sludge deposits. In Figure 2 are
illustrated three methods which have been successfully used. In
the first method (2A) the bottom of the pond is in the shape of
an inverted funnel. In the second (2B), the bottom is shaped as
an inverted cone. In the third (2C), an enclosure structure is
constructed on the pond bottom.
The importance of temperature should not be overlooked in
anaerobic waste treatment. Its importance is indicated by the
shape of the curve in Figure 3. Based on the information shown,
10
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_V7_
28
DIGESTION ZONE
2C
rIGURE 2. SLUDGE PROTECTION METHODS
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1 ( 1 1 1
CONSTANT LOAD ABOUT 425 Ibs per ocre day
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8 12 16 20
WATER TEMPERATURE ,°C
FIGURE 3. EFFECT OF WATER TEMPERATURE ON GAS PRODUCTION
24
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the minimum functional operating temperature for a significant
fermentation appears to be 15°C (59°F). Gas production is
negligible and waste stabilization is greatly reduced at temper-
atures less than 12°C. In order to take advantage of enhanced
gas production with increased temperature, most modern municipal
digesters are heated to temperatures ranging from 29°C (85°F) to
43°C (110°F), with the average around 35°C (95°F). Gas usually
is collected in the digester plenum and is burned to heat the
digester, adjacent buildings, and other structures. Any excess
is burned as an open flame. Because the temperature in ponds
declines with depth if the depth of the unheated pond is too
great, the sludge temperature will remain too low for effective
waste stabilization to take place. Experience indicates that 14
feet is the approximate maximum functional depth for an unheated
pond for most climatic conditions.
Typical digester loading is measured in terms of pounds of
volatile solids per cubic foot of digester volume per day (Ibs
vs/cf-day); whereas, a pond loading generally is measured in
pounds of 5-day biochemical oxygen demand per acre of surface
area per day (lbs-BOD5/ac-day). Digesters usually are operated
within the range of 0.08 to 0.1 Ibs vs/cf-day. Aerobic ponds
can be loaded as high as 200 Ibs BOD5/ac-day. Facultative ponds
generally are loaded at 20 to 50 lbs-BOD5/ac-day. However, once
they are operating properly, they may be loaded as high as 150
Ibs BOD5/ac-day. With established methane fermentation, anaerobic
ponds have been maintained satisfactorily at 1000 Ibs BOD5/ac-day.
Pond loading also is expressed in terms of number of people
per acre per day. The rule of thumb conversion figure for changing
per capita to BODr is that one person produces approximately 0.2
Ib BOD5/ day. The five-day BOD (BOD5) is considered to be
approximately 2/3 that of the ultimate BOD. The ultimate BOD
refers to the amount of oxygen needed to completely stabilize a
given sample of organic matter. The ultimate BOD test is usually
considered complete after an incubation period of 20 days. The
effect of applied BOD loading on gas production is illustrated in
Figure 4. Maximum gas production efficiency as indicated by ft
of gas per Ib of BOD in the facultative-anaerobic pond at Woodland,
California, apparently occurred when the loading was about 25 Ib
BOD5/ac-day.
The detention time for a digester is approximately 30 days;
for an aerobic pond, 3 days; for a facultative pond, 90 days; and
13
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200
300
400
500
APPLIED BOD LOADING, LB/A/D
FIGURE 4. GAS PRODUCTION AS A FUNCTION OF
APPLIED BOD LOADING
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for anaerobic ponds, 8-10 days. The efficiency of BOD5 removal in
an aerobic pond is approximately 80%; in a facultative pond, 85
to 9570; and in an anaerobic pond, about 70%. Efficiencies of
digesters usually are not calculated since the influent solids con-
tain about 75% volatile solids/total solids (70 VS/TS), and these
are considered stabilized at 50% VS/TS. Digesters are designed
to receive only the settled solids from waste water, the remaining
liquid portion being discharged or subjected to further treatment;
whereas, ponds are designed to receive waste water with or without
the settled solids removed.
The position of the oxypause to some extent influences the
classification assigned to various ponds. In Figure 5 is shown
a curve based on the performance of several ponds in which the
depth of the oxypause is plotted as a function of the average BOD5
loading. The plot pertains to autumn conditions. In the summer
the curve moves to the right, and in the winter it moves to the
left. With use of the information in Figure 5, a designer may
estimate the depth at which the oxypause will occur and the waste
water treatment operator may estimate the loading required to keep
the oxypause in a desired position.
Digesters in many cases have been operated for a number of
years with very little trouble if they are designed, maintained,
and operated properly. Ponds also have been successful in pro-
portion to the correctness of design and to the degree of operation
and maintenance applied. One common source of trouble related to
design has been the use of ponds of approximately three feet in
depth. Such ponds usually are loaded at low rates so that aerobic
conditions initially will prevail. A result of this design is
extensive growth of algae. A secondary effect is that unless the
algae cells are removed in some way, their concentration becomes
so great that light penetration becomes limited and their oxygen
production is inhibited. When the concentration of algae becomes
excessive, algal cells agglomerate and settle to the pond bottom
where together with settled organic wastes they form a sludge
blanket. Under these circumstances, anaerobic conditions develop
and volatile organic acid formation occurs. If the pond depth is
too small, methane formers are frequently inhibited as a result of
any mixing such as wind action which may bring dissolved oxygen into
contact with the settled sludge. Oxygen is lethal to methane
bacteria and under such conditions, volatile organic acid formation
continues unabated but methane conversion stops; hence, extremely
foul odors result. As stated previously, if such conditions are
15
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FALL CONDITIONS
ESPARTO H (After Kepple (6)1
WOODLAND PILOT
STOCKTON
Based on Chironomus Incidence
ESPARTO I (6)
RICHMOND PILOT
-ASHQUALON (After Berend(4)J.
THEORETICAL
POINT
I
<^ /- THEORE
*""•»-.„. / poir
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50 100 150 200
AVERAGE BOD LOAD, Ibs per cere-day
250
FIGURE 5. OXYPAUSE DEPTH AS A FUNCTION OF
THE AVERAGE BOD LOAD
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to preclude, it is imperative that some of the algae be removed
continuously or that the pond contents be mixed periodically to
prevent settling in which case the algae are removed with the
effluent. To eliminate the foul odors so often characteristic
of shallow ponds, it usually is necessary to deepen the pond if
it is possible to do so to protect the sludge or to install
mechanical aerators to keep the entire pond contents aerobic.
The difficulties coming from shallowness can be avoided by
keeping the minimum operating depth of a facultative pond at
six to seven feet. On the other hand, the maximum liquid depth
of an aerobic pond in which algal growth and removal is to be
practiced should be about 12 inches.
Anaerobic ponds have a great waste disposal potential since
they can be loaded at many times the rate normally used for con-
ventional facultative ponds. The greatest drawback of high load-
ing of anaerobic ponds at present is the risk of excessive odor
production. Odors have been controlled in some cases by pumping
liquid from an aerobic pond or aerobic portion of the pond to
the surface of the anaerobic pond. The aerobic pond effluent
usually is warmer than the water in the anaerobic pond, and thus
tends to remain on the upper surface. The sulfide gases are
oxidized in this layer, and odors from the volatile organic acids
are decreased in magnitude. Purple sulfur bacteria growing on
the surface of an anaerobic pond apparently tend in some cases
to act as deodorizing agents, in that they oxidize reduced sul-
fur compounds to inorganic sulfur.
In conclusion it should be emphasized that anaerobic ponds
have a great potential, but at present there is not enough infor-
mation available to permit the development of a design safe from
odor nuisance. Additional research should be conducted to determine
the type of organic waste which can be successfully treated in
anaerobic ponds. Work should also be carried out in order to
establish design criteria and operating parameters with the
objective of obtaining relatively trouble-free anaerobic operation.
If the location of the pond is such that odors would be objection-
able, it is recommended that surface aeration must be applied in
amounts necessary to preclude odor or as an alternative the
additional use of land for a well-designed and operated faculta-
tive pond should be considered.
17
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RECENT DEVELOPMENTS IN ANAEROBIC WASTE TREATMENT
by
D. A. Carlson
Although the conventional digester for solids stabilization
has been in use in sewage treatment systems for many years, the
use of anaerobic systems in waste treatment has, until recently,
been a second stage operation following primary and secondary
treatment under aerobic conditions. Anaerobic systems for direct
in-line operation with waste waters were thought to be inefficient
odor producing schemes which would not provide satisfactory BOD
removal or reasonable effluent quality. However the anaerobic
cultures can provide very satisfactory direct treatment under
proper environmental conditions. In fact anaerobic treatment
offers some very definite advantages over aerobic biological sys-
tems in that (a) the process is not restricted by the cost or
rate of pumping oxygen into the stabilization system, (b) much of
the energy of the incoming wastes is conserved in useful form in
the production of methane gas, and (c) the problem of disposal of
excess biological solids is significantly less than in aerobic
systems since solids production in the anaerobic stabilization
process is an order of magnitude less than that in conventional
aerobic treatments such as the activated sludge process.
Feasible anaerobic treatment of wastes relatively dilute as
compared with primary sludge involves the necessity of increasing
the organism-substrate contact time without providing for detention
of the carriage water over inordinately long time periods. For
example, the conventional digester provided satisfactory stabiliza-
tion over periods of months whereas feasible direct treatment of
wastes streams requires detention times in the order of a day. The
necessary mechanism is the utilization of much higher concentrations
of very active anaerobic biota.
Professor, University of Washington, Seattle, Washington
19
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The basic problem to the anaerobic organism is that of energy
available to the cell in the organic compounds present in the
incoming waste stream. The aerobic bacteria can utilize oxygen as
the hydrogen acceptor in aerobic treatment and thereby realize
the release of much of the energy in the compound. For example:
glucose + oxygen v carbon dioxide + water + energy
bacterial
metabolic
activity
C6H12°6 + 602 > 6C02 + 6H2° + 686 kilocalories/mole
The anaerobic bacteria must provide for oxidation-reduction in
the compounds in the waste so that
3C(>2 + 47.6 kilocalories/mole
bacterial
metabolic
activity
The methane produced represents stored energy and burns with the
evolution of 212.8 kcal/mole. The three moles of methane contain
638 kcal or 93 percent of the energy released during aerobic
oxidation of the mole of glucose. In other words, to provide the
necessary energy to sustain normal metabolic activity the anaerobic
bacteria must stabilize £7^5 or 1^.4 times as much glucose as the
aerobic bacteria to have the same amount of energy released.
Looking at the ATP production from glucose, the aerobic bacteria
can extract 38 moles ATP per mole of glucose while the anaerobic
bacteria can develop only 2 moles of ATP per mole of glucose.
Organisms, like other living systems, have the twin purposes
of using food for energy and for synthesis of new cellular material.
Substrate can be shown as being divided into fiS the fraction of
substrate going to cell mass synthesis, f2S the fraction of
20
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fls
substrate, S^-^"^ bacterial activity
\
(organic wastes.
f2S
>-cell synthesis
> energy production
-->. non degradable fraction
f3S
Figure 1. The Stabilization of Substrates in Waste Treatment
substrate used in energy production, and f3S the non degradable or
biologically resistant fraction which accumulates. Then f}S +
f2S + f^S = S or fj_ + £2 + £3 = 1. If, under anaerobic conditions,
the amount of substrate used for energy production must be over
14 times greater than the substrate fraction used for energy pro-
duction under aerobic conditions, then the amount of substrate
available for anaerobic cell synthesis must be only 7 percent of
that available to the aerobic bacterial cell. Therefore the pro-
duction of anaerobic cell mass must be about an order of magnitude
less than the production of aerobic cells using the same substrate.
The disposal of excess solids is thereby significantly reduced in
anaerobic systems. (Values for f^ in fiS (Figure 1) in cell
synthesis can be expected to be about 0.3 to 0.8 for aerobic systems
and 0.02 to 0.10 for anaerobic systems.)
The Anaerobic Contact Process
Hot process waters are often an enigma for design engineers
in the construction of waste treatment facilities. Anaerobic waste
treatment systems, however, operate better at temperatures sig-
nificantly higher than normal stream temperatures. When, in addition,
the waste organics solids concentrations are in the range of a few
percent rather than tenths of a percent of the weight of the total
waste then processes such as the anaerobic contact process should
be considered as suitable treatment methods for the stabilization
of potato wastes. (Organic solids concentrations as low as 1000/
mg/1 have been treated feasibly by the anaerobic contact process
(1,2).)
The use of high concentrations of mixed liquor solids allows,
with mixing and recycle, intimate contact of waste organics and
viable organisms. Whereas in the conventional digester, there is
21
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concern over the fraction of volatile suspended solids that is
actually viable cell mass, there is, in a rapid recycle of high
organism concentrations, the opportunity to maintain highly
viable volatile solids as compared to the conventional digester.
The anaerobic contact process is quite similar to an anaerobic
activated sludge system. This contact process is used by the
Wilson and Company plant at Albert Lea, Minnesota (1). The system
consists of collection of the incoming waste stream in a wet
well. From the wet well waste waters are heated and sent on to
the digester units. An equalizing tank was provided in tandem
with the wet well so that flow peaks could be spread over the
24 hour day.
In the digester the incoming warm wastes (about 90°F) are
mixed with recycled solids to give a mixed liquor suspended
solids concentration of 7000-12000 mg/1. Under these conditions
12 to 13 hours detention time is sufficient to give 90% BOD
removal and 90% suspended solids removal. Thus with BOD loadings
of about 0.15 Ibs/cu ft digester/day the digesters removed 1000
to 1450 mg/1 of BOD.
As described above the anaerobic contact process stabilizes
wastes with the production of gases such as methane and carbon
dioxide and some growth of new biological cells. The methane can
be used to provide energy to the process in the form of heat by
combustion. The cellular growth is essential to maintaining
viability of the working biological culture.
One of the necessary considerations in an anaerobic system
is the separation of the produced gases from the biomass. Often
the gases formed remain as small bubbles enmeshed in the anaerobic
sludge so that extrication of these bubbles can be a problem.
Shear stress or vacuum pressures can be applied to the stream
leaving the digester so that gaseous products can be induced to
leave the biomass.
22
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Following the degasifiers, the sludge is shunted to gravity
separators where the sludge can be settled and returned to the
digesters and supernatant can be routed to oxidation ponds for
final polishing prior to disposal in the receiving waters.
The Anaerobic Filter
While the anaerobic contact process has been used at ambient
temperatures, in the treatment of cooler wastes by anaerobic cul-
tures, the anaerobic filter offers promise as a means of stabilizing
potato wastes. Recent studies by Young and McCarty (3) and Webster
and Carlson (4) indicate the feasibility of removing the COD of
waste streams by anaerobic filters.
The anaerobic filter is an upflow rock filter wherein wastes
are introduced at the base of a rock support system for an anaerobic
culture. The culture did not attach to the stones alone but grew
as discrete particles in the interstitial spaces. Since the flow
is upward through the water covered rocks these sludge particles
are suspended in the rock-water system as the water and gas bubbles
travel upward out of the system. The solids retention time is in
the order of hundreds of days; that is the solids are retained in
the system for long periods of time with gradual accumulation of
solids to the point where solids removal could be necessary. The
filter can be operated at ambient temperatures of about 25°C to
obtain COD removals of 687a at 4.5 hour detention time up to over
9070 COD removal at detention times of 18 hours and greater for
influent COD's of 1500 mg/1 of volatile acids waste. With protein-
carbohydrate synthetic wastes COD removals of 63, 84, and 97%
were obtained with detention times of 4.5, 9 and 18 hours and
influent COD's of 1500 mg/1 (3).
Other studies with pulp mill sulfite waste liquors at 110°F
and about 4 days retention time produced up to 90% BOD reductions
for an initial BOD5 of 30,000 mg/1 (4). Recycle rates of 8:1
were used in 30 inch long, 6 inch diameter filters containing lime-
stone rock media. COD reductions were about 257=. At a recycle
rate of 2:1 BOD reduction was 507o. The gas generation was very
high in these columns. At 110°F the gas produced created so much
agitation in moving up the filter that it was difficult to maintain
the culture in the column. Even at ambient room temperature the
gas production rate was 0.5 liter per hour in this filter containing
9.6 liters of liquor.
23
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In the initial stages of stabilization relatively high con-
centrations of sulfur dioxide were produced along with dimethyl
mercaptan. But after the acclimation period the sulfur dioxide
production diminished and hydrogen sulfide and methane became
large fractions of the gas produced. In this more stable phase
of activity the pH stayed in the range of 6.5 to 7.
Two basic cultures developed in the filter during the stabili-
zation period. During production of S02> a black culture was
dominant in the rock interstices while at the foam level at the
top of the column a white culture was in evidence. As the sulfur
dioxide concentration diminished the white colony moved further
down into the interstices between the limestone rocks. Photo-
micrographs showed long bacterial rods as the dominant fraction of
the black cultures. The white culture appeared as a mixture of
larger yeastlike organisms interspersed with the bacterial cells.
Under stable stabilization activity the white culture penetrated
throughout the filter.
This study indicated that soluble wastes such as sulfite
waste liquors are amenable to treatment on anaerobic filters. The
effective filter length seems to about two to three feet of rock
support system.
Since the anaerobic filter will lend itself to soluble or
colloidal wastes, the potato wastes should be treatable on the
anaerobic filter. These rock filters should provide a relatively
simple treatment system for blodegradation of potato waste streams
and deserve further laboratory and pilot plant research to deter-
mine the feasibility of application to field installations. The
prospects of a relatively simple process with adequate gas strip-
ping and odor control may be quite attractive to industry.
Odor Control
The anaerobic processes have the problem of producing odors
which could be objectionable to persons living in the vicinity of
the treatment facility. Recent studies on soil filters, however,
indicate that the soil can selectively remove the polar gases from
exhaust gas streams while allowing methane to pass through the soil
filter with little or no loss. The soil filter provides complete
removal of hydrogen sulfide within less than a foot of soil depth.
Current studies indicate that the soil removal capacity is a
function of the bacterial population, the. physiochemical properties
of the soil, and the oxygen and moisture content of the system (5,6)
24
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Soil capacity for removal of hydrogen sulfide is enhanced
by gas concentration, the presence of oxygen and the leaching of
sulfates by flow through moisture. Soil capacities for hydrogen
sulfide removal in bath feed systems have been shown experimentally
for forest humus soils to be from 0.04 pound of H2S per cubic foot
of soil at an H2S concentration of 1000 mg/1 to 2.45 pounds of
H2S per cubic foot of soil at an H2S concentration of 100,000 mg/1
(7). On a flow through basis at a rate of 10% H2S in an air flow
of 2540 ml/min/ft^ soil column, Lynden loam soil capacity has been
shown to be 0.3 Ib of H2S per square foot of soil 6 inches deep (5).
In addition the soil sulfidation capacity can be rejuvenated at
least 5 times so that total soil capacity is 1.5 Ib H2S per square
foot of 6 inches deep soil or 3 Ib H2S per cubic foot of soil.
Capacity of the soil was reached when the exhaust ^S concentra-
tion reached 57o of the incoming H2S concentration.
Pumping stations on Mercer Island, Washington, previously
plagued by odor problems, have been operating for over 5 years
using soil filters as the odor control mechanisms. The soil
filter appears to be a useful means of removing odors from gas
streams.
Summary
The anaerobic contact process and the anaerobic filter offer
promise as prospective treatment facilities for stabilization of
wastes from potato processing. These treatment methods deserve
further research in on-line operation in potato processing plants.
Degasifiers and odor control systems should be portions of the
research receiving special attention so that laboratory and pilot
studies can be adapted to satisfactory field installations.
25
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REFERENCES
1. Steffin, A. J. and Bedker, M., "Operation of Full Scale Anaerobic
contact Treatment Plant for Meat Packing Wastes," Proc. of the
16th Purdue Ind. Wastes Conf.. pp. 423-437, (1961).
2. Underkafler, L. A. and Rickey, R. J., Industrial Fermentations,
Vol. II, Chap. 14, Buswell, A. M., "Fermentations in Waste
Treatments," Chemical Publ. Co., (1954).
3. Young, J. C. and McCarty, P. L., "The Anaerobic Filter for
Waste Treatment," Proc. of the Purdue Ind. Waste Conf.,
(May, 1967).
4. Webster, G. and Carlson, D. A., Current Laboratory Studies at
the University of Washington, Seattle (1968).
5. Gumerman, R. C., Typewritten Ph.D. Thesis, University of
Washington, Seattle, (June, 1968).
6. Carlson, D. A. and Gumerman, R. C., "Methyl Mercaptan Removal
by Soil Filtration," Paper presented at the Annual Meeting of
the Pacific Northwest International Section, Air Pollution
Control Association, in Vancouver, B. C., (November, 1965)
7. Hung, M., Typewritten M.S. Thesis, University of Washington,
Seattle, (June, 1968).
8. Hemens, J., Muring, P. G. J. and Stander, G. J., "Full Scale
Anaerobic Digestion of Effluents from the Production of Maize
Starch." Water and Waste Treatment, (May, June, 1963).
26
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PILOT PLANT STUDIES ON SECONDARY TREATMENT OF POTATO
PROCESSING WASTES
by
Kenneth A. Dostal
As most of you present today know, potato processing in Idaho
has had a rapid expansion during the past 15 years. The $23,000,000
payroll and $52,000,000 plant investment by the 11 members of the
Potato Processors of Idaho Association in 1965-66 represent growth
of more than 10 times that of comparable 1950 figures (1). Un-
fortunately, waste production has also kept pace with this expansion.
The Idaho State Health Department has worked, and is working,
closely with the Processors in the development of effective waste
treatment methods. As a result of past cooperative efforts, all
major potato processing plants presently discharging into the Snake
River or its tributaries now provide primary treatment of their
waste stream. But even with primary treatment, these waste com-
bined with others have resulted in fishkills and other pollutional
problems during periods of low flow in the Snake River. The
Processors are now faced with the problem of providing secondary
treatment of their wastes.
In 1964, the consulting firm of Cornell, Rowland, Hayes &
Merryfield was retained by the Engineering Committee of the Potato
Processors of Idaho Association to assist in the design and opera-
tion of pilot plant facilities. These facilities were used to check
the feasibility of several secondary treatment systems. During 1965
and 1966, the pilot plants located at the J. R. Simplot Co.'s waste
treatment plant in Burley, Idaho, were operated and enough data
gathered to allow establishment of design criteria for trickling
filter, activated sludge and conventional stabilization ponds. One
of the conclusions from this work was: "Additional study should be
given anaerobic ponds and flow-through aeration basins to more
closely determine the capabilities of these systems in secondary
treatment of potato process water." (2)
Acting Chief, Food Wastes Research, Pacific Northwest Water
Laboratory, Corvallis, Oregon
27
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In July 1966, the Northwest Regional Office of the Federal
Water Pollution Control Administration (FWPCA) received a request
for technical assistance from the Idaho State Health Department.
The request was for assistance to the Engineering Committee to aid
in data collection and analysis for the development of design
criteria for anaerobic ponds and surface-aerated aeration basins.
The Technical Projects Branch of the FWPCA located in the Pacific
Northwest Water Laboratory in Corvallis, Oregon, was assigned
responsibility for the study since this was a logical extension of
a previously authorized study on aerated lagoon treatment of food
processing wastes. A memorandum of understanding was drawn up and
signed by the three participating groups: Potato Processors of
Idaho, Idaho State Health Department, and Technical Projects, FWPCA.
The objective of the study was the completion of pilot plant
studies of secondary treatment of potato processing wastes.
Specifically, the two methods of treatment to be investigated were
an anaerobic lagoon followed in series by a surface-aerated,
aerobic lagoon and secondly, a surface-aerated aerobic lagoon.
Federal authorization for this type of study comes from the
Federal Water Pollution Control Act, as amended. Section 5(b) of
the Act provides that the FWPCA may, "... upon request of any State
water pollution control agency, conduct investigations ... con-
cerning any specific problem of water pollution confronting any
... industrial plant, with a view to recommending a solution of
such problem."
Description of Processing Plants
The Simplot Burley Processing Company processes about 75,000
tons of potatoes per year. It is a highly automated processing
plant and produces instant mashed potatoes and related specialties.
The potatoes are washed, lye peeled, cut, automatically sorted for
flakes or granules, dehydrated, and packed for shipment. Water use
is about 1.2 mgd.
The J. R. Simplot Heyburn plant is one of the largest potato
processing plants in the world. It processes approximately 180,000
tons per year. Products include french fries, potato specialties,
and potato starch. Here, too, the potatoes are washed and lye
peeled; then trimmed, blanched, processed, and packed. Water use
totals about 5.0 mgd.
28
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Table 1 presents average figures for waste production per ton
of potatoes processed as measured during the 1966-67 processing
season. These figures are based on the combined waste and total
potato production at both plants, but they do not include fat re-
covered or solids screened out for cattle feed.
Table 1
Waste Production per Ton of Raw Potatoes
Parameter
BOD5 92 Ibs.
CODS 208 Ibs.
TVS (Total Volatile Solids) 165 Ibs.
SS (Suspended Solids) 106 Ibs.
SVS (Suspended Volatile Solids) 105 Ibs.
Process Water 4,170 gal.
About 4200 gallons of water were used per ton of potatoes
processed. The raw waste from the plant contained 92 pounds of
five-day Biochemical Oxygen Demand (BOD), 208 pounds of Chemical
Oxygen Demand (COD), and 106 pounds of suspended solids per ton.
It should be mentioned that these values were higher than those
measured during previous processing seasons.
Waste Treatment Plant
Waste streams from both potato processing plants are piped
to a primary waste treatment plant. They first enter a receiving
tank and are passed through two 5-foot diameter, 10-foot long rotary
drum screens. All solids retained on the +20 mesh screens are stored
in bins.
The remaining waste water then enters a 100-foot diameter
clarifier with an overflow rate of about 800 gallons per day per
square foot. Additional solids settle out in the clarifier and
the overflow passes through a Parshall flume and is discharged to
the Snake River.
29
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The solids collected from the clarifier are pumped through
a centrifuge. Resulting sludge is stored in bins and the centrate
is either returned to the clarifier or discharged to the river.
The screenings and the sludge from the centrifuge are trucked
to a cattle feed-lot operation for use as part of the animals' diet.
During the last (1966-67) processing season, the primary
clarifier effluent had the characteristics shown in Table 2. The
pH ranged from 7.1 to 11.6 with a median of 10.4. Temperature,
which is quite important when designing any biological treatment
process, averaged 74° Fahrenheit. Standard Methods COD ranged
from 2500-6000 and averaged 3400 mg/1. The five-day BOD averaged
1680 mg/1 and the suspended solids averaged 740 mg/1.
Table 2
Characteristics of Primary Clarifier Effluent
Parameter Range Mean
PH
Temp. °F
CODS, mg/1
BOD5, mg/1
SS, mg/1
7.1-11.6
63-79
2520-6000
1180-2080
90-3190
„
74
3400
1680
740
Pilot Plants
The pilot plant facility of the Potato Processors is located
at the primary waste treatment plant in Bur ley, Idaho. Three
sealed earthen ponds with ancillary pumps and piping make up the
facility. Each pond is 40 feet square at the water surface and
about 10 feet deep in the center. With side slopes of 3 to 1,
each pond has a capacity of about 50,000 gallons.
The flow diagram of. the pilot plant facilities is shown on
Figure 1. Operation of the three pilot lagoons can be broken down
into three periods. From September through December 1966, ponds
II and III were operated as covered anaerobic units while awaiting
30
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i
Pond I
O
10 hp
Aerator
Sampling
Points
,
1 1
1
Pond
f
II
^
Covered
O
i
Pond
r
\-
5
Aer
Sump
To
River
Figure 1
FLOW DIAGRAM OF PILOT PLANTS
-------
delivery of two surface aerators. From January 1967, to the end
of processing last spring, ponds II and III were used in series.
Pond II continued as a covered anaerobic pond and pond III was an
aerobic cell containing a 5 hp floating surface aerator. During
the current (1967-68) processing season all three ponds are being
used. Ponds II and III are being operated the same as last spring.
Pond I contains a 10 hp surface surface aerator and is receiving
clarifier overflow. Thus far this season, pond I has been fed
at one-half the rate of pond II so that the detention time in pond
I will be equal to the sum of the detention times in ponds II and
III. By varying the hydraulic and organic loads on these two
systems it is hoped that sufficient data will be accumulated to
design an economic system.
Last season eight-hour composite samples were taken of the
clarifier influent and overflow, and grab samples of the pond
effluents. This processing season all samples are eight-hour com-
posites. The samples are split and then shipped by bus in iced
containers to the Idaho State Health Department laboratory and to
the laboratory in Corvallis.
Most of the analyses are performed according to the 12th
edition of Standard Methods. The tests included: pH, temperature,
alkalinity, SS, VSS, TS, TVS, D.O., CODS, National Canner's
Association modified 00%, 8005, Total Organic Carbon (TOG),
Soluble Organic Carbon (SOC), volatile acids, total and ortho
phosphate, nitrite, nitrate, ammonia, and total Kjeldahl nitrogen.
Results
During the first period of operation when both ponds were
operated as parallel anaerobic ponds they were fed at rates which
resulted in theoretical detention times of 20 and 4 days for ponds
II and III, respectively. The contents of neither pond was mixed
and judging by the data obtained both ponds experienced detention
times well below theoretical. Table 3 presents a brief summary of
some of the data collected during this period of operation. As
shown, both the pH and temperatures measured in the effluents were
very similar. The five day BOD was reduced from 1490 mg/1 to 1160
mg/1 or 22 percent by pond II, Across pond III the BOD reduction
averaged 17 percent. Standard Methods COD reduction by both ponds
averaged about 6 percent higher than the BOD reductions shown here.
NCA COD reduction was markedly higher; 76 percent for pond II and
32
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71 percent for pond III. Although organic reductions as measured
by CODS and BOD were low, the CODn, test shows that the molecular
structure of some of the organics was being altered. Suspended
solids were reduced by 62 percent in pond II -and 56 percent in
pond III. Since greater than 95 percent of the suspended solids
entering the ponds was volatile, much of the CODS, and BOD re-
ductions shown here could be attributed to SS sedimentation within
the ponds. This was demonstrated in earlier work; when the temper-
atures were cold, good removals were measured, but as the sludge
temperature started to rise in the spring, increased biological
breakdown of the sludge resulted in an effluent worse than the
influent in many cases.
Table 3
Summary of Anaerobic Pond Operation
Parameter
pH range
Temp, range, °F
BOD5, mg/1
CODm, mg/1
SS, mg/1
Influent
to ponds
10.3-11.8
65-77
1490
2380
950
Pond II (a)
Effluent
6.3-7.0
60-68
1160 (22) (c)
570 (76)
360 (62)
Pond Ill(b)
Effluent
5.8-7.1
61-69
1240 (17)
700 (71)
420 (56)
(a) Pond II - detention time = 20 days
(b) Pond III - detention time = 4 days
(c) Percent reduction
The second period of operation when anaerobic pond II was
followed by aerobic pond III has been covered by a progress report,
copies of which are available. Today I'll briefly summarize some
of the high points. As a result of work which had been done earlier
on the anaerobic ponds a pump was installed on anaerobic pond II to
mix the contents. When this study period was stopped, no sludge
layer was found on the bottom--it operated as a complete-mixed pond.
During this period, the two ponds in series were operated at
three different hydraulic loadings as shown in Table 4. Initially
both ponds were fed at a rate of 4 gpm which resulted in detention
times of 8.8 days each or 17.5 for the two ponds in series. The
33
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rate was then increased to give a detention time of 5 days in
each pond and finally 2.4 days each. Average temperatures in the
anaerobic pond ranged from 62 to 71°F at these three hydraulic
loadings and from 42 to 53°F at the aerobic pond. Daily temper-
atures were as low as 32°F in the aerobic pond with some ice forma-
tion around the edges.
Table 4
Pilot Plant Feed Rates
Anaerobic Pond II Aerobic Pond III
Date-1967 gpm days gpm days
2-23 to 3-20
3-20 to 4-23
4-30 to 5-27
4.0
7.0
15.0
8.8
5.0
2.4
4.0
7.0
15.0
8.8
5.0
2.4
No attempt was made to hold the volatile acids or the ratio
of volatile acids to alkalinity below any set values in the
anaerobic lagoon. The volatile acids concentration ranged from
600 to 3500 mg/1 and the ratio ranged from 0.5 to 3.5. It has
been reported (3) that a volatile acids: alkalinity ratio above 0.8
is inhibitory to methane production in anaerobic digestion. The
aim in this study was not complete digestion of the wastes, but
hopefully an alternation of the organic material to forms which
might be more rapidly treated aerobically.
Table 5 presents a summary of the organic loadings and the SS,
COD, and BOD reductions for the three different levels of hydraulic
loading. At the first level both ponds had a detention time of
8.8 days and a BOD loading of about 10 lbs/day/1000 cu. ft. The
anaerobic pond reduced the suspended solids by 82 percent, COD by
33 percent, and BOD by an average of 25 percent. The aerobic
pond, which was fed the effluent from the anaerobic pond, reduced
the incoming COD by 49 percent and the BOD by 88 percent. Due to
the buildup in microorganisms, the suspended solids increased by
230 percent upon passage through the aerobic lagoon. The overall
reductions shown are the averages obtained across the primary
clarifier plus the anaerobic pond plus the aerobic pond. Although
the suspended solids were only reduced 74 percent, the BOD was
reduced by 95 percent. Again, it should be pointed out that both
the anaerobic and aerobic ponds were complete-mixed units and these
reductions are based on the effluents with all solids remaining.
34
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Table 5
BOD Loadings and Pilot Plant Efficiencies
Anaerobic pond
Aerobic pond
Overall
Anaerobic pond
Aerobic pond
Overall
Anaerobic pond
Aerobic pond
Overall
Detention
Time
Days
8.8
8.8
5
5
2.4
2.4
BOD
Loading
Ibs/day
1000 ft3
11
8
22
20
46
40
Reduction - %
SS
82
-230
74
35
-75
66
52
-226
51
CODs
33
49
73
15
58
82
15
28
68
BOD
25
88
95
12
87
94
13
64
81
After reducing the detention times to 5 days in each pond,
the BOD loading doubled to about 20 Ibs/day/1000 cu. ft. on each
pond. Reductions by the anaerobic pond dropped to slightly less
than one-half the values measured at the lower loading. The sus-
pended solids increase in the aerobic pond was less, 75 percent
compared to 230 percent, whereas the BOD reduction was the same
and the COD reduction slightly higher. Overall reduction was 8
percent lower for suspended solids, 9 percent higher for COD, and
similar for BOD.
Increasing the hydraulic loading from 7 to 15 gpm reduced the
detention time from 5.0 to 2.4 days. The BOD loading on the anaerobic
pond averaged 46 lbs/day/1000 cu. ft. and on the aerobic pond 40.
Suspended solids reduction in the anaerobic pond increased, but
this was due to the fact that the influent had a higher suspended
solids concentration. Both the COD and BOD reductions remained the
same. Through the aerobic pond, both the COD and BOD reduction
fell off significantly; COD from 58 to 28 percent and BOD from 87
to 64 percent. Total reductions across the clarifier plus both
ponds were lower for all three parameters.
35
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As mentioned earlier, this processing season all three ponds
are being utilized. The anaerobic pond and the aerobic pond in
series are being run at about the same loadings as last year. The
third pond with a 10 hp aerator is being operated in parallel with
a detention time equal to the sum of the detention times in the
anaerobic pond and aerobic pond. These two systems will be oper-
ated until the end of processing this spring.
Thus far, the two ponds in series have been functioning similar
to last year. The parallel aerobic pond has reduced the BOD to the
same levels as the two ponds in series. This is shown in Figure 2.
The horizontal scale is the total BOD in the effluent, including
all SS. The left-hand scale is the detention time in aerobic pond
III. This pond receives the effluent from the anaerobic pond, so
the total detention time through both ponds would be twice the values
shown here or the same scale as shown for the parallel aerobic pond
on the right-hand side.
The circles represent averages from last year for the two
ponds in series. Squares are averages from this year's data for
the two ponds in series. The triangles represent the data collected
this year on the all aerobic system, pond I. If these points can
all be adequately described by a single curve, and this appears
to be the case, then the anaerobic pond is accomplishing as much as
would be accomplished by an added increase in detention time in an
aerobic system such as pond I.
This figure ignores several things such as varying influent
strength and different average operating temperatures but it is
useful. Even though the BOD reduction across the anaerobic pond
at any given detention time is not equivalent to the reduction
that could be obtained, across an aerobic system with the same de-
tention period, there are evidently changes in the waste character-
istics upon passage through the anaerobic pond which makes the
effluent more treatable aerobically.
Preliminary Cost Estimate
The data collected thus far was used to make some rough cost
estimates to see if a combination anaerobic-aerobic system might
result in lower total annual charges than an all aerobic system.
The following assumptions and prices were used to develop the cost
estimates.
36
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CO
>v
&
10
O Pond III 1966-67
Q Pond III 1967-68
Pond I 1967-68
12
a
o
•H
4J
c
"U
c
o
p.)
•r-l
H
e
o
O
o<
I
100
Figure 2
200 300 400 500 600
Total Effluent BOD - mg/1
INFLUENCE OF DETENTION TIME ON EFFLUENT BOD
700
800
-------
1. BOD of clarifier influent = 2700 mg/1.
2. BOD of clarifier effluent = 1700 mg/1. (Thirty-seven
percent reduction by clarifier.)
3. Overall BODs reduction = 90% (effluent BOD = 270 mg/1).
4. Aerators installed at $500/HP (amortized across 10 years
at 6 percent).
5. Cost of aerator maintenance at 27o/year of installed cost.
6. Aerators add 2 Ibs 02/HP-hr.
7. Oxygen requirements of waste =1.2 Ibs/lb BOD applied.
8. Power costs $0.01/KW-hr.
9. Total land costs based on $1000/acre of lagoon surface
(yearly cost of 6%).
10. Aerobic ponds installed (lined) at $10,000/acre (10
years - 6%).
11. Anaerobic ponds installed (lined, covered, and mixed) at
$16,000/acre (10 years - 6%).
12. Waste plant operates 300 days/year, 24 hours/day.
A series of annual charges were calculated using these assump-
tions for various combinations of anaerobic-aerobic loadings to
achieve the effluent BODj concentration of 270 mg/1. Other costs
were assumed to remain relatively constant for a given size plant
regardless of type of treatment used. On Figure 3 is shown the
annual charges in $l,000/yr/mgd treated. Any combination of anaerobic
reduction and aerobic reduction, shown directly opposite will reduce
the BOD from 1700 to 270 mg/1. Arriving at the desired endpoint by
aerobic ponds only (84% reduction) results in a cost of about
$48,000/year per mgd treated, whereas, anaerobic ponds removing
35% of its influent BOD followed by aerobic ponds reducing it to
270 mg/1 results in a cost of about $39,000. The important point
from this preliminary analysis is that a combination anaerobic-
aerobic system appears at this time to result in an overall cost
lower than either of them separately. This is true despite the
relatively poor BOD removals obtained by the anaerobic pond and the
higher installed cost of anaerobic ponds.
Discussion
The pilot plant study on secondary treatment of potato processing
wastes is being continued during the 1967-68 processing season.
Due to the late arrival of the 5 hp aerator the anaerobic-aerobic
lagoons in series were only operated about one-half of the 1966-67
season. The 10 hp aerator for the third lagoon did not arrive
until the end of last processing season.
38
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O
o
O
\
T3
60
00
M
.8
O
g
C
82.5
Reduction in aerobic pond - %
80 77.5 72.5 68
10 20 30 40 50
Reduction in anaerobic pond - °/0
60.5
60
70
Figure 3
PRELIMINARY ESTIMATE OF ANNUAL CHARGES
-------
Based on the data collected thus far, a 8005 reduction of at
least 90 percent is feasible with primary clarification followed
by anaerobic and aerobic ponds in series. Preliminary findings
indicate that loading rates in the range of 10 to 20 pounds of
BOD5 per 1000 cu. ft./day can be applied to the lagoons to achieve
the desired removals. The BOD5 removal varied from 12 to 25 per-
cent across the anaerobic pond and from 87 to 88 percent across
the aerated pond at these loading rates. Efficiencies across the
anaerobic-aerobic ponds in series ranged from 88 to 91 percent BOD
removal. Coupled with an average of 40 percent removal by the
primary plant, this results in a total BOD removal in excess of
90 percent.
Based on last season's data, the combination of high BOD
removals with substantial increases in suspended solids across
the aerobic lagoon indicate that inorganic nutrient levels were
not limiting to growth of required organisms to accomplish treat-
ment. As a result of this solids increase, the overall suspended
solids reduction was relatively poor—ranging from 50 to 75 percent.
In order to increase the suspended solids reduction to 90 percent
or higher, secondary clarification will be needed. This should
also increase overall BOD removals.
A volatile acids: alkalinity ratio above 0.8 did not seem
to affect the removals in the anaerobic pond. Short detention
times and fluctuating loading conditions contributed to the inhibi-
tion of methane production. The purpose of the anaerobic cell
was to carry out the first stage of anaerobic fermentation and
hydrolize some of the more complex organics to simpler forms more
amenable to aeration. The effectiveness of this cell cannot be
evaluated until all the results from the parallel aerobic lagoon
study are obtained. Mixing the contents and covering the anaerobic
pond with styrofoam did, however, increase its effectiveness by
holding the temperature drop to a minimum and preventing sludge
deposits from accumulating in the pond.
Foaming in the aerated cell has been an intermittent problem.
At the small scale of the pilot lagoons it is not a major nuisance,
but a full-scale lagoon may require some means of preventing foaming.
The cost analysis presented is based on rough assumptions and
the annual charges derived from it are subject to gross adjustment.
The figures do, however, provide an idea of the relative weight to
be applied to removals in the anaerobic or aerated cells.
40
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This processing season should provide the necessary pilot
plant data for formulation of design parameters for lagooning
potato wastes.
Preliminary conclusions drawn from the information gathered
during this period include:
1. The BOD5 in potato wastes can be reduced by greater than
90 percent by primary clarification plus anaerobic-aerobic lagoons
in series.
2. Mixing of the contents of the anaerobic lagoon appears
necessary for proper operation of the anaerobic-aerobic system.
3. Covering the anaerobic lagoon will reduce the temperature
drop and help control odors.
4. Secondary clarification for removal of suspended solids
will be required following an aerobic lagoon.
5. Foaming may cause operation difficulties in full-scale
aerobic lagoons, but can be controlled by proper design.
6. Preliminary cost estimates show that a combination of
anaerobic-aerobic lagoons may result in a lower cost than either
anaerobic or aerobic treatment separately.
41
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REFERENCES
1. "Idaho Image", Idaho State Department of Commerce and Develop-
ment, Boise, Idaho. July 1967.
2. "An Engineering Report on Pilot Plant Studies, Secondary Treat-
ment of Potato Process Water". Cornell, Rowland, Hayes, and
Merryfield, Boise, Idaho. September 1966.
3. "Anaerobic Sludge Digestion", Journal Water Pollution
Federation, p. 1684, October 1966.
42
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OTHER TREATMENT METHODS FOR POTATO WASTES
by
John W. Filbert1
The potato processing industry in the Pacific Northwest has
for several years been gathering and developing information for
use in the design of effluent treatment processes. During these
years, we have learned much about potato process effluents and
their treatability by most conventional and some unconventional
means. No panacea has been found from the standpoints of cost,
end-product, odor, noise, etc. It would be a tragic mistake to
now discontinue the search for better processes and process modi-
fications; however, it appears that in some cases time has run
out and current knowledge and technology must be applied to solve
severe pollution problems.
This paper considers knowledge currently available or being
developed which is applicable to the design of activated sludge
and biological filtration processes. The tube settler technique
for removal of suspended solids from effluent flows is also dis-
cussed.
Activated Sludge
The homogenous activated sludge process in its various forms
has probably received as much study regarding its applicability
to the treatment of potato process effluents as any other biologi-
cal process. This process has been widly applied to a great
variety of wastes with success. The general conclusion of these
studies has been that the activated sludge process is capable of
producing a high quality effluent.
The author is an Industrial Effluent Specialist for Cornell,
Rowland, Hayes & Merryfield, Engineers and Planners, Corvallis,
Oregon.
43
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It is logical that this process was the first selected by the
U. S. Department of Interior for research on and development of
processes applicable to the secondary treatment of potato process
effluents. The activated sludge research and development plant
currently under design for the R. T. French Company of Shelley,
Idaho will demonstrate the full-scale performance of the activated
sludge process; locate deficiencies and, we hope, remedy these
deficiencies; develop more complete design criteria; and establish
capital and operating cost data.
Figure 1 is a preliminary perspective view of the R. T. French
system. Table 1 lists the pertinent criteria used in the design
of the biological treatment facilities. The proposed system is
being designed to accommodate an average daily flow of 1.25 mgd,
including both lye peel process water and silt water flows.
The 16-foot deep aeration basins will be of earthen construction
with interior embankment slopes of two horizontal to one vertical.
The basins will be lined with plastic or rubber sheet because of
local soil conditions and anticipated erosion. Influent may be
discharged to either one or both basins through submerged header
systems. Recycled sludge will be returned to the basins through
separate lines. Effluent will be removed through outlet boxes
along one side of each basin. Inlet and outlet arrangements are
being designed to assist in making the aeration basin contents
as homogeneous as possible. Floating mechanical surface aerators
will be used to enable repositioning of the oxygen supply and mixing
sources as required to meet operational and testing needs.
The secondary clarifier will be of conventional design. The
sludge removal mechanism will be a multiple-port hydraulic device
to enable rapid sludge removal and operation at high recirculation
rates.
An aerobic digester will be used to further stabilize the
waste activated sludge prior to its disposal to a mechanical
clarifier-thickener, along with the plant eilt water. The digester
will have a concrete ring wall to 4 feet below the water surface.
The earthen slope from the bottom of the ring wall will terminate
at the 12-foot water depth. A self-cleaning tube settler will be
used to concentrate the waste activated sludge within the aerobic
digester, reducing the required digester volume five times.
44
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SOLIDS HANDLING SYSTEM
CONTROL 6UIIDING
:£ £S -Z_
FIGURE 1
R.T. FRENCH COMPANY
SHELLY, IDAHO
PERSPECTIVE VIEW
PROPOSED TREATMENT SYSTEM
CORNELL, HOWIAND, HAYES 4 MERRYFIOO
•CATTUK COAVM.U* 9OM.
-------
Table 1
R. T. French Company
Shelley, Idaho
General Design Criteria
Proposed Activated Sludge System
Item
Criteria
Aeration Basins
Basin No. 1 detention time
Basin No. 2 detention time
Total detention time in parallel
BOD Loading (Ibs/lb. mlvss*)
Basins 1 and 2 at 4,000 mg/1 miss
Basin 1 only at 2,000 mg/1 miss
Equipment
Clarifier
Surface overflow rate (gal./ft./day)
Detention time
Max. recirculation ratio
Mechanism type
Aerobic Digester
Solids content
Thickening equipment
Tube settler overflow rate (gal./ft.^/min.)
Aeration device
Total solids age**
24 hrs.
48 hrs.
72 hrs.
0.13
0.80
Floating -•
pump type
mechanical
surface
aerators
650
1.17 hr.
0.7
Multiple port
hydraulic
suction
2%
Tube settlers
0.50
Mechanical
15-25 days
*
**
Mixed liquor volatile suspended solids
Includes sludge age in aeration basins
46
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Digested or undigested waste activated sludge will be pumped
to the mechanical silt water system. The waste sludge will be
settled, thickened, and hauled to the disposal with the silt.
Clarified liquid from the silt water system will be discharged to
the aeration basin influent.
The treatment facilities are scheduled for start-up in Septem-
ber, 1968. Data will be collected throughout the 1968-69 campaign.
The data collected is to be analyzed and placed in the final
report form prior to 31 December 1969. It is anticipated that the
most difficult problems to be encountered during the research and
development program will be related to cold weather and solids
dewatering and disposal.
Biological Filtration
Biological filters are classified according to the applied
hydraulic and organic loadings. On this basis there are three
general classifications: low-rate filters, high-rate filters, and
super-rate filters. In general, as organic loadings are increased
on biological filters, the BOD removal efficiency decreases.
Low-rate and high-rate filters generally use rock media, while
a prefabricated plastic, tile, or wood media with controlled con-
figuration is generally used in the construction of super-rate
filters. Because of the extremely large volume of filter media
needed and consequent cost of the media and support structure
required, low-rate and high-rate filters have not found much accep-
tance in the treatment of high-strength, high-volume industrial
wastes. Approximately 20 cubic feet of rock media per pound per
day of BOD applied is required in the high-rate filter system.
The super-rate filter is capable of assimilating much more
organic matter per unit volume of media than is a conventional
rock-filled, high-rate filter. This greater capacity is due in
part to the greater surface area per unit of filter volume. In
addition, the high-rate filter process often employes recirculation
of the underflow from the secondary clarification system. This
tends to maintain a high biological solids content within the
liquid flow through the filter and the clarification system which
follows. As a result, the high-rate filter system is somewhat re-
lated to the activated sludge process. Design of a super rate
biological filtration system must be based on knowledge of both
activated sludge and biological filtration processes, and with the
realization that, at present, treatment efficiency cannot be
accurately predicted without prior pilot plant study.
47
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Pilot plant data using the Dow Surfpac media on lye peel
process effluent(l) indicates that it is possible to remove approx-
imately 300 pounds of BOD5 per day per 1,000 cubic feet of media
volume at BODs loadings of between 400 and 1,000 pounds per 1,000
cubic feet of media. The BOD 5 removal indicated includes that
obtained in secondary clarification. Efficiencies experienced in
the treatment of food processing effluents have generally been
greater than those experienced on other substrates. No valid
relationship was established between percent BOD removal through
the filter and recycle rate during the subject pilot plant study.
Chipperfield (2) reports that above a minimum hydraulic loading,
which he refers to as the "minimum wetting rate," BOD removal is
not enhanced but is actually decreased somewhat. Germain(3)
has theorized that when treating domestic wastes the BOD removal
efficiency is not increased with increased recirculation rates
since the detention time within the filter on each pass is pro-
portionally lower with the number of passes. Disagreement still
exists on the role of recirculation in BOD removal efficiency and
systems designed should provide substantial flexibility in recircu-
lation capability for this reason. Recirculation should be sufficient
to reduce the pH of lye peel effluents below 8.5 prior to discharge
onto the filter.
Presently, there are numerous manufacturers of prefabricated
super-rate filter media. To this author's knowledge, no good
comparisons of the various materials available have been made to
date. Any comparison should include BOD removal efficiency, depth
to which media is self-supporting, estimated service life of the
media, the cost of providing bottom and side structural support
and housing, and the cost of the media itself. The cost of plastic
media is currently estimated at approximately $2 per cubic foot,
while redwood media is available at approximately $0.70 per cubic
foot.
Some of the general advantages and disadvantages of super-rate
filter systems when compared to homogeneous activated sludge systems
in the treatment of potato process effluents are as follows:
Advantages
1. Lower temperature loss through the process.
2. Lower power costs.
3. Lower total operating costs.
4. Reduced waste biological solids separation and handling
problems.
48
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Disadvantages
1. Lower organic removal efficiency.
2. Less absorption of shock loads.
3. Greater probability of problems related to nutrient
deficiency and pH variations.
4. Greater risk of odor production.
Tube Settlers
The removal of suspended matter from liquid flow is an integral
part of most effluent treatment systems. Numerous primary clarifiers
of conventional design presently serve the potato processing
industry. Secondary clarifiers of conventional design are in the
planning stage.
The conventional clarifier is either rectangular or circular
and generally has a side-water-depth of 6 to 12 feet. The clarifier
basin is usually continuously cleaned of settled solids by mechanical
means. Loadings to primary clarifiers are usually from 800 to 1,000
gallons per square foot of surface area per day (0.555 to 0.695 gpm
per square foot). Loadings to secondary clarifiers will be from
500 to 800 gallons per square foot of surface area per day (0.347
to 0.555 gpm per square foot).
Recently there has been developed what may well prove to be
the most significant advance in the modern history of sedimenta-
tion. The recent development of tube settlers is a practical appli-
cation of the tray sedimentation theory presented by Hazen(4) over
60 years ago.
Figure 2 shows the self-cleaning tube settler pack as developed
and marketed by Neptune-MicroFLOC Corporation. Alternate rows of
tubes having 60-degree slopes from horizontal are sloped in opposite
directions to provide the structural rigidity of the poly-vinyl-
chloride (PVC) tube pack shown. The individual tubes in the tube
pack shown are approximately 39 inches long and 2 inches square.
The tube packs are placed side-by-side to provide the required
settling area.
Each tube within a tube settler acts as an individual settling
basin. A single tube 39 inches long, 2 inches square, and inclined
at a 60-degree angle with the horizontal will theoretically have
49
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FLOW
FIGURE 2
R.T. FRENCH COMPANY SHELLY, IDAHO
SELF-CLEANING TUBE
SETTLER PACK
CORNELL. HOWIAND, HAYES t MEiBYFIELD
Engin«*n and Planners
UATTIE COIVAUIS tQlif PtMTUtM*
-------
the same removal efficiency as will each 2-inch wide segment of
a rectangular clarifier having a 78-foot length and an 8-foot
depth. Since a tube pack contains several layers of tubes, the
theoretical capacity per unit of area is extremely high. In
practice it appears that the self-cleaning tubes can be operated
at rates of 2.0 to 2,5 gpm per square foot of top surface area
when used for secondary clarification of liquids containing 3,000
mg/1 of suspended solids. This rate is over 400 percent of that
generally used in the design of conventional secondary clarifi-
cation systems.
Solids which settle from the liquid being clarified slide
down the lower surface of the tube and out of the settling zone.
The solids which fall from the tubes must be removed by hydraulic
or mechanical means.
The self-cleaning tube packs can be placed in existing or
new clarification basins, when specially designed outlets are
used, or may be installed in reaction vessels such as aeration
basins. When installed near the surface of a clarifier, the
solids falling from the tubes can be removed by the standard
solids removal mechanisms. When installed in an aeration basin,
the solids are generally removed from beneath the tubes by liquid
currents.
The tube settlers are now being marketed for use in water
and wastewater treatment. Only limited operational data is now
available. As previously mentioned, expectations are that self-
cleaning tube settlers will be used in concentrating waste
activated sludge at the R. T. French secondary effluent treatment
facilities. A pilot unit is also now being installed to serve as
a secondary clarification device in the joint Idaho Potato Processors
Association, Federal Water Pollution Control Administration, pilot
anaerobic-aerobic studies at Burley, Idaho. Full-scale applica-
tion of tube settlers should be preceded by pilot plant studies or
at least a review of operating results obtained in similar applica-
tions. Caution should be used if the waste contains large solids,
stringy material, and substantial concentrations of grease.
Summary
A full-scale activated sludge system being designed to treat
potato process effluent has been discussed. This system, to be
financed by the U. S. Department of Interior and the R. T. French
51
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Company of Shelley, Idaho as a research and development project,
will answer many remaining theoretical and practical questions
regarding activated sludge in this application. Super rate
biological filtration is a second aerobic treatment process which
should be considered when selecting a system to meet current pollu-
tion abatement needs. The tube settler, a new application of basic
sedimentation theory, could and should be considered for use in
primary and secondary treatment systems.
52
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REFERENCES
1. Cornell, Rowland, Hayes & Merryfie Id, Engineers and Planners,
"An Engineering Report on Pilot Plant Studies, Secondary
Treatment of Potato Process Water," for the Potato Processors
of Idaho Association, September, 1966.
2. Chipperfield, P. N. J., "Preformance of Plastic Filter Media
in Industrial and Domestic Waste Treatment," Journal of the
Water Pollution Control Federation, 39:11, 1860-1874,~~(1967) .
3. Germain, J. E., "Economic Treatment of Domestic Waste by
Plastic - Medium Trickling Filters," Journal of the Water
Pollution Control Federation, 38:2, 192-203,(1966).
4. Hazen, A., "On Sedimentation," Transactions of the American
Society of Civil Engineers, 53, page 45, (1904).
53
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SPRAY IRRIGATION TREATMENT
by
Frank C. Haas
The American Potato Washington plant is located about 6
miles southeast of the town of Moses Lake and started operation
in the fall of 1965.
Recognizing that disposal of waste water was a major problem
in operating a potato processing plant, American Potato started
a feasibility study upon which a decision could be made regard-
ing the location of a plant in Washington state. From past
experience in Idaho, it was known that the disposal of waste
water must be given primary consideration in both the design and
location of a processing plant.
Due to the cost and complexity of a primary and secondary
waste treatment facility, it was decided that spray irrigation
would be less costly than conventional treatment. A literature
search revealed that numerous companies were using spray fields
for disposal water and several of these were visited to determine
how these spray fields were designed and operated.
Description of the Plant Waste Systems
There are three main sources of waste water from the plant:
1) the sanitary sewer which discharges into a septic tank and then
into an underground drain field, 2) potato fluming and washing
water which is low in COD (600 to 1200 ppm), and 3) process waters
which have been in contact with peeled potatoes and these waters
have a high COD content (2000 to 3000 ppm). The wash and flume
American Potato Company
55
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water is screened in the plant over 20-mesh Linkbelt vibrating
screens to remove vines, small pieces of potato, and trash. The
screened water is then pumped to one of two settling basins of
18,000 cubic feet capacity in which most of the silt and dirt
settles out. Settling time in this basin is several hours or
more and the water overflows into a concrete sump. Water from
our fresh pack fluming and washing operation also discharges into
the same settling basin.
The process water before it is pumped out of the plant is
screened on a Dorr-Oliver DSM 40-mesh screen to remove peel and
small chips. This water is then pumped to the same sump as the
washing and fluming water.
The concrete sump is equipped with two 700 gpm 100 psig
head vertical pumps which discharge into the main buried spray
field header and then to the laterals and sprays. Pump operation
is controlled by means of level controls in the sump so that one
or both pumps are continuously operating.
Spray Field
The spray field is approximately 120 acres and is about
3000 feet long and 2200 feet wide. This width varies because of
the irregular shape of the land. An 8" buried line runs the length
of the field and has 52 rizers to which the 3" laterals are con-
nected. These laterals are above grade and are each 40' long.
Each rizer is equipped with one sprinkler nozzle. Nozzles have
3/16" openings except for the end nozzle on each lateral which has
a 11/32" opening. Since small pieces of peel and potato are
present in the waste water, these collect in the ends of the
laterals and are discharged through the larger end nozzles. It
has been found that when using the smaller size nozzles at the
end of the laterals, the nozzles plugged frequently.
The total waste flow rate to the spray field is about 840 gpm,
or about 1.2 x 106 gallons/day. This includes primary washing and
fluming water as well as process water. This is equivalent to
0.35" of precipitation per day or an annual precipitation of 100"
per year. The temperature of the spray water is 90 to 100°F.
Well water temperature is 69 to 70°F.
56
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Normally, five laterals are in operation at one time and
operate continuously for 24 hours, after which the next five
laterals are used. The movement of laterals and sprinkling
area thus progresses down the length of the field until the end
of the field is reached, at which time the laterals are brought
back to the head end of the field and the sprinkling process is
repeated. The average precipitation is any one 24-hour period
for a given area is about 3.5". Therefore, it takes about 10
days to make a complete rotation of the field. During the summer
months while the plant is down and plant water usage is low,
water is obtained from an irrigation ditch so that the cover crop
does not die out due to lack of water. This water flows via
ditches to the spray field sump and is also sprayed onto the field.
We are putting 5 to 6 million pounds of organic solids on the
field per season.
Winter Operation and Problems
The end nozzles on each lateral are changed for water oper-
ation from 11/32" to 1/2". This increases the velocity in the
last section of lateral and reduces the possibility of freezing.
Although this change of nozzle size reduces freezing problems,
it increases the water flow rate so that the area covered by the
end nozzle tends to pond. Of course, if a nozzle plugs, the line
freezes, and if the end nozzle freezes, the last 40' section of
lateral will also freeze in time since there would be no water
flow through this section. If a lateral freezes, the pipe
ruptures or the sections are forced apart at the joints.
If tall weeds or grass are near the laterals, they may collect
enough ice to completely cover a section of lateral. If so, it
is necessary to chip and break the ice away to move the lateral.
Ground Cover
The ground cover is a mixture of grasses and alfalfa, which
is cut, cured, and baled. This is done twice per year, but should
probably be done more often--4 or 5 times a year. Gerber's in
Minnesota has found that "quack" grass is a very good crop for
spray fields. Grazing of livestock has not been tried since
stock will compact the ground. They also rub against the nozzles
and rizers and break them off.
57
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Land
The spray field is not completely flat, but rather sloping
and rolling so the field was contoured at 4' intervals to reduce
run off and prevent the forming of large ponded areas. The sur-
face soil is loam with 2 to 4' of top soil followed by a broken
layer of caliche and gravel about I1 thick with sand below this.
Six or seven feet beneath the surface, the subsurface is compacted
clay mixed with sand. At one location, a perched water table
was found 6 or 7' below the surface. We have not investigated
the subsurface conditions since the preliminary survey, and do not
know if this perched water table has increased in size or if it
has moved closer to the surface. At the start of this season,
the field was subsoiled and we have found this has greatly in-
creased the percolation rate. At this time, it is believed that
this should be done at least once a year before the start of each
processing season.
Costs
The initial capital investment for the spray field, sump,
pumps, and silt settling basin was about $30,000 without the land.
The total operating costs for the spray field are $40,0007
year. This includes three laborers who are assigned full time to
the spray field, plus supervision and maintenance costs.
Both the initial cost and operating cost of a spray field
are considerably cheaper than any other complete treatment if
sufficient area is available at a reasonable cost. In addition,
the problems associated with spray fields are simpler and easier
to correct than those associated with a conventional primary and
secondary treatment system.
Odors
The spray field has been relatively odor-free, since most of
the bacterial action is aerobic. However, when ponding occurs
and the bacterial action is anaerobic, the odor increases.
The silt settling pond is also relatively odor-free while in
operation, but the silt and dirt must be removed every 3 to 6 weeks.
It is during these times that there is a real odor problem, but
fortunately, it is of short duration.
58
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Test Spray Field
We have installed a small spray field at our Blackfoot plant
to study the feasibility of spray field disposal in Idaho. This
was put in operation the first of February this year, so we do
not have any very cold weather experience with this system.
However, we have sprayed at temperatures of 5 to 10° above zero
and have found the sprays operate satisfactorily at these temper-
atures. The ice formed a layer 3 to 5" thick on the spray field,
but as the ice melted, we had very little runoff or ponding. We
are presently applying water at a rate of 1/4 to 1/2" per day and
the ground is absorbing this water rate very well except for a
strip about 6* wide that is completely bare—no grass or alfalfa.
In this bare area, the water tends to pond.
59
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POTATO WASTE TREATMENT
RESEARCH NEEDS
by
H. S. Smith
I What is research?
A. Basic. Discovery of hitherto unknown facts and their
interpretation to explain mechanisms or observed events.
B. Applied.
1. Organization and incorporation of products of basic
research into a useful system; after first time becomes development
and re finement.
C. Research, development and consulting often confused.
1. Large amount of research covers ground already
researched.
a. Lack of familiarity of researcher with prior work.
b. Inability or unwillingness to recognize basic
facts and the universality of their application regardless of
superficial concepts and terminology of different disciplines or
fields of application.
2. Much of what is termed research should be the job
of competent development engineer or designer who know field and
can relate already available knowledge to problem at hand.
Dean, University of Idaho
61
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II Kinds of information needed to solve industrial waste treat-
ment problem.
A. With respect to specific problem.
1. Define and minimize problem.
2. Treatment objectives; how much treatment is needed?
3. "Fill-in" information needed to apply existing
technology.
4. Develop new technology when existing technology is
inadequate.
5. Optimization of treatment system.
B. With respect to general problem.
1. Improved understanding of treatment process mechanisms.
2. Prediction models for various unit operations and
processes.
3. Continuing search for new and better processes.
C. Assembly and organization of information into form appli-
cable to problem may - or may not - involve research.
Ill Source and character water borne potato processing wastes
(Maxson)
A. Washing
1. Largely inorganic clay and silt.
2. Low water use if recirculated: 0.02 gal/pound.
3. Little oxygen demand
B. Peeling
1. Steam
2. Lye
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3. Low water use: 0.08 gal/pound
4. High oxygen demand: 6000 mg/1 COD
5. High pH and cation concentration if lye process used.
C. Trimming
1. Low water use: 0.02 gal/pound
2. Low oxygen demand: 193 mg/1 COD
D. Slicing
1. High water use: 0.43 gal/pound
2. Medium oxygen demand: 845 mg/1 COD
E. Blanching
1. High water use: 0.55 gal/pound
2. High oxygen demand: 7300 mg/1 COD
F. Final processing with corresponding minor waste.
G. Overall average and characteristics
1. Water: 2.00 gal/pound processed
2. Oxygen demand: 6000 mg/1 COD
3. 507= COD removable by plain sedimentation.
4. After settling.
a. 1.6% (17,000 mg/1) dissolved solids.
b. Dissolved solids 38% (6500 mg/1) nitrogeneous
compounds; about 1000 mg/1 nitrogen on basis of protein.
c. BOD/N ratio on order of 3:1; plenty of nitrogen
_if in available form.
d. Trace nutrients probably satisfactory for biological
synthesis.
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IV Existing applicable technology
A. Preliminary treatment
1. Wash water silt removal by sedimentation.
2. Main waste screening
B. Primary treatment
1. Plain sedimentation.
2. Flocculation and sedimentation.
a. Without chemicals
b. With chemicals
3. Centrifugation.
C. Secondary treatment
1. Biological
a. Aerobic
b. Anaerobic
2. Land methods; irrigation
3. Chemical for selective component removal and recovery,
a. Protein coagulation and filtration.
b. Ion exchange for amino acid recovery.
D. Tertiary treatment
1. Adsorption
2. Foam fractionation
3. Ion exchange
4. Filtration
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E. Utilization or disposal of recovered solids
1. Sources
a. Preliminary treatment; peels, trimmings
b. Primary treatment; primary sludge
c. Secondary treatment; excess cellular and biologically
inert solids from biological treatment.
2. Use for by products; cattle feed base
3. Further disposal
a. Biological; sludge digestion
b. Physical; dewater, incinerate, landfill, etc.
V Information needed to approach specific problem
A. Define and minimize problem
1. Cited volumes and COD concentrations are typical
"as is" values.
2. Can production process be controlled to minimize the
volume of waste and/or the amount of contaminants?
a. All process performance a function of time;
time a function of treatment unit size and flow rate (t = —); reduce
volume of waste and reduce unit size for given time; reduce cost.
b. Reduce contaminant quantity; reduce load on
secondary and tertiary system; reduce capital and operating cost.
c. Even if contaminant amount cannot be decreased
reduction in waste volume and corresponding concentration of con-
taminant usually results in higher rate of contaminant removal per
unit volume of treatment facility; can lead to economical stage
treatment when high quality effluent required.
3. Waste that can be prevented at source does not require
treatment! Research begins within the processing plant.
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B. How much treatment is needed?
1. Receiving stream capacity to assimilate some mass
of contaminant implied by water quality standards.
2. How much assimilative capacity available to a given
industry?
3. Unless answer clear research is needed to determine
level to which industry must treat.
a. No use to fly an SST when an F-27 will do the
job.
b. Probably involve more political than technological
decisions. Who gets first call on the stream capacity?
C. What "fill in" information is needed to apply existing
technology.
1. Sedimentation - preliminary and primary. Principles
well understood but need data to apply.
a. Settling velocities of particles in non-floccu-
lent regime - silt removal. Need this for rational design.
b. Settling characteristics of particles in floccu-
lent regime - primary treatment. Can't really design without this.
2. What are effects of preflocculation? Can primary
efficiency be significantly improved?
a. Plain flocculation without chemicals.
b. Flocculation with chemical coagulants.
3. Biological secondary treatment
a. General questions
(1) Is nutrient balance O.K.?
(2) Is nitrogen present in a useable form?
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(3) Are there inhibiting components?
(4) What is the BOD rate constant compared
with other wastes?
b. Aerobic treatment; available models
(1) What are the rate constants for BOD removal?
(a) Log growth
(b) Declining growth
(2) What are the oxygen uptake rate constants?
(a) For BOD
(b) For active fraction of biological
sludge mass-cell respiration.
(3) What are the active mass growth rate
constants?
(a) Synthesis
(b) Auto-oxidation
(4) What are the settling characteristics of
the mixed liquor solids?
c. Anaerobic treatment; empirical basis
(1) Heat inventory
(2) Notion of "balance condition".
(3) Volumetric and/or organic loading at which
balance between volatile acid and methane production is achieved
for continuous operation- with and without sludge return.
(4) Volatile acid concentration at balance
condition - for operation control
(5) Cation concentration at balance condition -
for operation control.
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(6) What is the concentration of active
anaerobic biological mass that exists at balance condition result-
ing from given loading?
(7) What is the effluent quality corresponding
to any given balance condition?
d. Combined anaerobic-aerobic systems. General
questions related to quality of anaerobic effluent resulting from
any given balance condition. Same questions must be answered for
the aerobic stage as in the case of single stage aerobic treatment.
e. Liquid-solids separation of biological reactor
effluent.
(1) By gravity-sedimentation
(2) Centrifugation
(3) Floatation
(4) Solids characteristics as they relate
to these unit operations must be ascertained.
f. Ultimate disposal of excess synthesized cellular
material - waste sludge.
(1) For aerobic digestion - same kind of infor-
mation as needed for basic aerobic process.
(2) For anaerobic digestion - same kind of
information is needed for basic anaerobic process.
(3) For physical disposal - whatever characteris-
tics are pertinent.
(a) Solids concentration
(b) Dewatering characteristics
(c) Heat value
(d) Concentration of constituents of
interest.
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4. Other secondary and tertiary treatment possibilities
need same kind of "fill in" information. Can be obtained by persons
well informed to ask proper questions. No new concepts are involved,
only new applications.
D. Is the need for new technology to solve problems unadequately
covered by available Technology?
1. Each previously described unit operation can be con-
tinuously refined by research, but,
2. Do gaps in present technology preclude attack on
problem with confidence?
a. Unit operations described and others similar
afford sufficient tools to proceed now.
b. Must conclude that problem solution need not
wait for new technology to be produced by research.
3. New technology will come in future. Treatment systems
can be modified to incorporate, if feasible.
E. Optimization of treatment system.
1. What combination of unit processes will achieve degree
of treatment most effectively?
a. From standpoint of cost
b. From standpoint of operating dependability
2. How should load be distributed among the unit processes
comprising the system?
3. Economic base for comparison
a. Industry - shorter amortization period and tax
situation favors minimum investment even if higher operating cost.
b. Municipal - longer amortization period and no
tax effect favors higher investment to reduce operating cost.
c. Industry - municipality relationship will affect
basis of economic optimimization.
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4. Must consider available operating skill.
V What are questions of general concern to treatment technology
that might bear on this problem?
A. Better understanding of mechanisms of various unit processes
1. Leads to identification and quantitative understanding
of factors entering into process so can
a. Design and operate closer to real process capa-
bility - reduce the "factor of ignorance" or "shrink the black box".
b. Better prediction of behavior under conditions
different than those for which empirical performance prediction is
based,
2. Such questions include
a. Affect of environmental conditions on process
capability
b. Process limiting factors such as
(1) Nutrient levels
(2) Temperature
(3) PH
(4) Oxygen concentration
(5) Concentration of limiting constituents
(6) Hydraulic rates
c. Actual biological, physical or chemical mechanisms
at work in each unit process.
B. Prediction models needed to replace empirical approaches
1. Reasonably useful models are available for sedimen-
tation, aerobic biological treatment and several tertiary processes.
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2. No useful models yet available for anaerobic biological
process.
3. Need much work on the coefficients and factors needed
to apply models to a wide range of waste conditions.
C. Always need for continuing search for new and better methods
but must face existing need to get on with present solutions using
available techniques. Improve or modify systems when application
of new methodology becomes feasible.
VI So what are research needs?
A. Seems that there is a sufficient kit of tools already
available to make significant attack on potato waste treatment
without having to wait for further generalized basic research!
1. Classical engineering attack will go a long way.
a. Identify problem
b. Assemble necessary information
c. Analyze information
d. Decide
e. Act
2. Gaps in information and insight needed to apply
existing technology for which field scale experience is needed.
a. Demonstration projects operating under field
conditions.
b. Use of available "know how" to interpret operating
experience. "Know how" exists as evidenced by literature; not wide-
spread, may need to be especially recruited.
c. This is more development and consulting than
research, but the researcher must be involved to help interpret.
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3. Better design for process environmental control can
now be done with present understanding even though not fully
quantified. Incorporate control in system to allow operation over
a range; let actual operation determine absolute value;
a. pH
b. Temperature
c. Cell mass concentration
d. Oxygen concentration
e. Recirculation and mixing
f. Etc.
B. Real research needs appear concerned with matters generally
applicable to all industrial waste matters; not unique to potato
wastes.
1. Better prediction models especially for anaerobic
biological treatment and some tertiary processes.
2. More precise values for the model factors
3. Better knowledge of waste character effect on value
of model factors
4. More .quantitative information on effect of water
quality parameters on use of receiving stream.
5. Combination of these and related questions into
systems analysis approach.
6. First time demonstration of unique process combinations.
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FUTURE GROWTH OF THE POTATO PROCESSING INDUSTRIES
by
Ray W. Kueneman
In order to assess the future of the potato processing
industry, I think it is very interesting to go back and review how
this industry has developed. The history of the potato reflects
one of the real contributions the New World has made to every
population growth, practically speaking, in the world.
The potato made its first contact with European civilization
when the Spanish Conquistadors started their invasions into South
America somewhere along in the 1550's. These invaders found quite
an advanced civilization that was led by the Incas who ruled the
continent of South America from Patagonia up into what is now
Mexico.
There was one pertinent factor that was important to the
ability of these people to rule such a vast area. Their military
forces, in all their contacts with the various areas, carried on
their communications by the use of "runners", who were able to
cover vast distances during the day and pass on information to the
next command post or area, where the message could be relayed by
additional runners. Military forces could be dispersed as a result
of this rapid form of communication. Both the runner and the
military forces were able to carry lightweight emergency food
supplies, which consisted largely of potato, a product called
"Chuno". The potatoes were indigenous to the high altiplano of
South America. Farmers harvested their crops, boiled them, and
placed them on reed mats to dry. Since these crops were harvested
in what was their harvest season in the autumn, cold weather was
1
Vice President, Research and Development, J. R. Simplot Company,
Caldwell, Idaho.
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prevalent at night, especially at these high altitudes. The
boiled product would freeze at night and then during the day would
dry. This alternate freezing and drying process led to a product
that could be crumbled into a fine powder and carried in a pouch
by the runner or soldier. By adding water to it, they could re-
constitute it into a form of meal which would sustain them on their
forced marches. This product still persists in South America and
has had a dramatic influence on life there.
The first mention we find of potatoes coming into Europe is
through the records left by the Monk, Hieroymas Cordan, who mentions
that potatoes were placed on Spanish ships returning to Spain, in
ballast, and that they were very useful as a foodstuff. However,
when these potatoes arrived in Spain, the clergymen warned the
populace that these were heathen vegetables not mentioned in the Bible;
and it took a lot of convincing to bring about the use of potatoes
in Europe.
Frenchmen planted them in botanical gardens and regarded them
as a curiousity, and refused to put them on the table. However,
little by little, farmers recognized potatoes as a good food. They
spread to England, then to Ireland, and to much of Europe.
There are a number of interesting points in history where we
find mention of the use of potatoes. Frederick, The Great, promoted
potatoes as a food for his peasants and issued an edict that he would
"cut off the nose of any peasant not raising the required acreage".
The War of the Bavarian Succession in 1778, entitled, "The
Kartoffelkreig," was a war between the Germans and Austrians. The
final battle, which was decisive, was over stores of potatoes located
in farmers' fields.
Antoine Parmentier campaigned for the acceptance of potatoes as
a food in France. He enlisted the aid of Marie Antoinette, who wore
blossoms in her hair; and due to her influence, the court chefs
created court dishes. As a result, the potato began to get greater
acceptance as a food in France. It was calculated at this time that
a single acre of potatoes could support a family of six to eight, and
a cow, for a year. So you can see, it was a very important crop
indeed, and a valuable contribution from the New World.
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Potatoes became a field crop in Ireland some time before 1660
and were popular with the Irish farmers because they protected
against the loss of other foods—they would store well in the ground
and would survive the rains. Lady Montgomery, who had extensive
farms in County Downs, Ireland, in the 1760's provided land for her
people to raise potatoes for food, and flax for clothing. By 1780,
it was reckoned in Ireland that a 280-pound barrel would provide a
week's supply of food for a family, at the rate of five to eight
pounds per head per day, served three times a day. As a result of
this almost enforced diet, our present potato became known as the
Irish potato. This nomenclature, of course, was reinforced by the
great potato blight in 1848, when the crop failed and over half the
Irish population immigrated to the United States.
In 1719, potatoes were introduced into the Colonies at London-
derry, New Hampshire, which was an Irish colony. Some of the farmers
there thought the potatoes were bad, by some, good. By 1740, they
had pretty generally spread through the colonies. Today, potatoes
represent about 20% of all the vegetables in the United States.
We think, in this country, we are very large users of potatoes;
but I would like to give you some figures which probably could be
updated from the information I have, but they are interesting indeed.
In 1963, the world crop of potatoes represented some 262,700,000
metric tons of potatoes, distributed as follows:
Country Metric Tons Growth
U.S.S.R. 69.7 million
Poland 37.8 million
West Germany 25.1 million
East Germany 13.3 million
U.S.A. 12.5 million
Other countries followed along with varying amounts; however, the
first five mentioned were the predominant producers of potatoes in
1963.
It is interesting to examine what Poland was doing with their
potatoes at that time. This was presented in a paper on Waste
Utilization at New Brunswick, Canada. Poland raises about seven
times the U.S.A. production. It consumes as fresh potatoes some
6.5 million metric tons, feeds about 23.3 million metric tons, uses
about 5.4 million metric tons for seed. Industry, as starch and
alcohol, utilizes 3.2 million metric tons. They export about 100,000
metric tons. Storage loss is calculated at about 3.5 million metric
tons.
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I think, with this little background of the past, we can turn
towards the subject I have been asked to speak on, "The Future Growth
of the Potato Processing Industries", This is a symposium on potato
waste treatment, directed towards a cure for an alarm we have in
this industry. We should not forget the real nature of the problem.
I think it is appropriate to discuss the cause as well. The cause
in this case is certainly the potato industry. The future growth
is such a tremendous factor in this field that it must impose a
tremendous sense of urgency for problem solving on all who are work-
ing in this field. I hope to transfer some of this urgency to you.
I have been involved in some phase of the "Potato World" since
about 1940. The requests for talks on the future of potato processing
have been many. I have acceded to some of these requests. Each
time one reviews what has been said in the past, cuts, culls, and
steals a bit, and in general updates what has been prophesied, said,
and guessed at in the past, I am sure this is standard operating
procedure with those who continue to work and to discuss continuing
problems in their field.
In preparing for today, I followed this familiar pattern, I
confess, with a little complacency and a touch of smug satisfaction,
let us say. After all, potato processing has grown into a giant;
and it is nice to see one's predictions come true, and to continue
to be a part of it—and then the bomb fell!
The growth of the industry in the past two decades has been
little short of phenomenal, and various kinds of expertise, good and
bad, informed and otherwise, has been exerted in the past, projecting
the future growth. However, a DuPont computer analysis which appeared
in the December, 1967, issue of "Quick Frozen Foods" is 3 key to the
bomb I referred to above. This projection cannot be ignored because
it imposes some tremendous parameters to the problem we are discussing.
Dan Pichulo of DuPont and "Quick Frozen Foods" magazine pumped
the potato picture into the DuPont computer memory bank, as one of a
series of projects on the frozen food industry. Fortunately, the
frozen food industry, through its association efforts, has had a good
set of records and provided adequate data. Let us look at these
projects now, so the enormity of the future problems will give you
the same sense of urgency that hit me.
This joint study is one of the fortuitous circumstances that
comes along once in awhile where the right kind of statistical data
exists in sufficient quantities to lend itself to this type of analysis,
The industry is new enough and accurate records exist, to1permit this
study to be made with a great deal of reliability, in my estimation.
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DuPONT STUDY—FROZEN POTATOES—1966-1976
(In analyzing some of the points on the DuPont study, we find it is
convenient to look at just frozen potatoes for the period, 1966 to
1976. The data projects the following information.)
1966
1976
$319,657,000 $871,670,000
1,459,633,000 Ibs. 3,926,140,000 Ibs.
7.41 Ibs. per capita 18.2 Ibs. per capita
% Increase
in Value & Poundage
270 (value)
248 (poundage)
146
The population will increase from about 200 million in late 1967 to
218 million by the end of 1977. Thus, we get a 248% poundage in-
crease with a 9% population increase. Frozen potato products must
indeed be popular.
In view of the past growth, these numbers may be on the cautious
side. When one translates them to the problem, the size of the task
is indeed enormous. Are these projections reasonable? If we review
the past, on the figures that were used, I think we can see what I am
talking about.
ARE THEY REASONABLE AS PROJECTIONS? A REVIEW OF THE PAST
Year
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
Million
Pounds
70.7
85.2
128.9
189.7)"
219.8)
269.4)-
371.0)
551.4)
579.1)
761.6)-
861.5)
1,117.8)
1,218.5)
1,459.6)
Almost double
Almost four times
Over 600% net increase in
decade from 1956 to 1966
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Therefore, by past performance, we can accept these DuPont
forecasts as reasonable, in my opinion. An actual summary of the
DuPont projection is as follows:
Year Poundage Processed Per
(Billion) Capita
1967 1.66 8.35
1968 1.88 9.38
1969 2.11 10.44
1970 2.36 11.53
1971 2.61 12.64
1972 2.87 13.76
1973 3.13 14.88
1974 3.40 16.00
1975 3.68 17.11
1976 3.92 18.20
By 1965, potatoes represented more than 50% of all frozen
vegetables. By 1976, it is projected that potatoes will represent
more than all other frozen vegetables by 50%, and will represent
about 10% of all frozen foods.
It is interesting to look at the distribution of frozen potato
products in a typical year; and we can take our Association figures
for 1966 to 1967, as a process year.
DISTRIBUTION OF A TYPICAL PROCESS YEAR
1966-67
Retail French Fries 421,000,000 pounds
Institutional French
Fries 862,000,000 pounds
Other Frozen 176,000,000 pounds
TOTAL 1,459,000,000 pounds
POUNDS PER CAPITA (USDA-1960)
Year Pounds per Capita Processed
1910 198.0
1940 123.0 1.9
1948 104.9
1952 102.0
I960 109.0 34.8
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What do all of these trends show, as far as the problem is con-
cerned? One thing quite simply. We will have more was IE to handle.
Obviously, potatoes cannot be the scapegoat or fall guy in this
picture. All ways of life that contribute to waste will have to
stand and be counted. All segments of society will have to pay their
share, and somewhere in the "accounting scheme", this cost will have
to be reckoned with.
Potato processing, with its relative newness and potential
expansion, and its long operating season, is a convenient tool to
study, to seek efficient and economical solutions to the problems
of all waste in an orderly, progressive manner. I must stress this
lest we inadvertently kill the goose that lays the golden egg.
The processed potato industry has grown because the costs to the
consumer have been kept down to the point where the public can afford
to buy them. Production costs are accurately kept and reckoned with,
to the fourth decimal place; and very often are only the lesser
fraction of the final cost to the ultimate consumer. Sales, distribu-
tion, transportation, etc., all take their toll in the final cost.
This is the way of life today.
One reason we are here is to further our knowledge, attack the
problem, and find feasible, economical solutions on where we stand.
The cost of capital expenditures can easily run 20% or higher of the
total plant investment of a potato processing unit, depending upon
the size of the plant, degree of cleanup required, and other factors.
At this time, this essentially nonproductive cash flow can be a
deterrent and a restrictive factor in the future program of the in-
dustry. I feel that an appreciation of these factors which led to
the growth and progress made to date, has been largely contributed
by our Western group. We must recognize the progress this group has
made in the past and will continue to make. We must appreciate that
no single segment of society can be singled out to contribute at an
accelerated rate, our of proportion to others. Progress must be made
on all fronts. Given an equal shot of time and "fruits of advance,"
I am sure the potato industry will keep pace.
The figures I have presented thus far represent but one segment
of the potato industry, primarily frozen French fries. If we examine
the 1965-66 season, we get an idea of what is happening to the trends
in the total industry.
1965-66 SEASON
Crop 233,283,000 cwt.
Processed (39 1/2%) 92,283,000 cwt.
Fresh and other 141,000,000 cwt.
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WHAT HAS TRANSPIRED IN THE LAST DECADE?
1956 dehydration used 3,200,000 cwt.
1965 dehydration used 20,000,000 cwt. (625% increase)
1956 frozen used 4,300,000 cwt.
1965 frozen used 32,000,000 cwt. (746% increase)
If we convert DuPont's figures of 3.96 billion to hundredweight,
as fresh potatoes, we find we will be using 99 million for frozen in
1977, as compared to 32 million hundredweight in 1965. We will also
use 49.5 million cwt. for dehydration, as compared to 20 million in
1965. Without accounting for any other processed usage, we will
use 148 million cwt. in these two processes alone. If the loss in
processing to be handled runs 25%, as it does generally today, we
will be handling 37.1 million cwt., or 1.85 million tons, or about
40% of the total potatoes we processed in all forms during the 1965-
66 season.
This, gentlemen, is what I meant earlier when I referred to the
bomb.
If we are to use the knowledge and experience we are currently
developing, we must cope with the 25% waste I have referred to. We
must lessen it, convert it to other usable forms for man or animal,
and offset the cost of capital and production to do it.
I have mentioned only two forms of processing and indicated how
they are to grow. These trends point to increases in all other forms
of processing. This useful knowledge must be shared and extrapolated
to other forms of the whole processed food industry, and society as
a whole. My mind refuses to convert these figures to our yardstick,
BOD, population equivalents, or other measuring devices that are in
use now because of the magnitude of the numbers, which to me are
staggering.
The pressure of world increase in population and food requirements
are constantly being studied and deliberated in various world councils.
The problems are not limited to the U.S.A. alone, they are worldwide.
Trends and habits in the United States are being paralleled in every
civilized country in the world; and I suggest to you gentlemen that we
have a worldwide problem.
Thank you!
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GENERAL DISCUSSION
Jackson;
I have sat here today and reflected on how things were about
10 years ago in the potato waste field. I have the distinct
opinion that we've come a long ways, I shudder to think of some
of the things we were talking about then. We had all kinds of
wild ideas and we still need a few today.
Dean Smith mentioned that basic research wasn't so popular
anymore. It's still popular among a great segment of the univer-
sities but it is not so popular among the federal government
supporting agencies. The federal government is now interested in
the solution to problems and the application of knowledge and I
think that future support is going to come heavily from that sector.
It will not necessarily be expended in the university, although if
the university can qualify in engineering applications it will
probably receive support. Dean Smith also mentioned that we should
try chemical flocculatiori. Well, as some of you know, this was one
of the first things tried by the potato association at the R. T.
French plant and it met with some success. We have also been given
a rundown on foam fractionation. My predecessor at this university
15 years ago was interested in coagulating potato protein and he was
using ion exchange to try to recover amino acids.
I would like to suggest that in our discussion here, we look
ahead a little bit. Dean Smith has outlined to us some research
procedures and engineering applications all the way from start to
finish. How about a few "blue sky" ideas. I think it would be
proper to finish the meeting by looking ahead rather than going back
over details.
I'd like to start by pointing this out to you: I think the
biggest waste problem comes from the potato peel itself, the method
of getting the peel off. Other wastes with the big chunks, etc., are
easily removed. The potato peeling is really the main problem. Can
you suggest some other way of peeling the potato or modification of
present peeling methods to minimize the waste?
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Postal;
Research Is being done in this area by ARS in Albany, California,
and they have a pilot plant going there on a semi-dry peeling process.
I know several of the people in the audience have been down to see
this. It processes about 500 pounds per hour and has been operating
intermittently for about the past year.
Jackson:
We are somewhat acquainted with the Albany people. What they
are doing is not what they wanted this university to do when they
were negotiating a contract. Had they gone this way, I'm sure we would
have been glad to go down that road. Anybody else got any exotic ideas
on peeling?
Comment;
The main problem would be that there is too much loss. These
potatoes are peeled deeper than necessary. What do you do with the
caustic and stean?
Jackson;
I'm sure this is true from the standpoint of loss of the potato
itself but how would this alter waste treatment costs when you look
at the process as a whole, including utilization of the peel material.
Could you for instance modify peeling and have a more useful or more
valuable byproduct.
Kueneman;
I'd like to digress for a minute on this peeling. When you have
traveled around through the years as I have, you find a lot of "blue
sky" ideas. During World War II there was a little dehydration plant
that came up with what someone in the war department thought was abso-
lutely the best idea in the world. I went down to take a look at it.
He had gathered up a bunch of old batteries, salvaged the plugs, and
had a controlled dip in a molten pot of lead. Believe me, it peeled
potatoes. There was no question about it, it was fabulous!
We've talked about the research at Albany where after the potato
is dipped under defined conditions of caustic concentration, temper-
ature and time it is exposed to a high heat level under catalytic
burners. Then the material is flaked off before any water is applied
or it is scrubbed or brushed.
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There has been a great deal of work done in considering the
potato as a suitable food for the production of Torula yeast either
for human use directly or as a byproduct for animal feeding. Quite
a bit of work has been done on this in Sweden and other places. Our
friends at the New Brunswick Symposium pointed out that the Polish
people were working on various phases. Of course, we know that every-
body in Scandenavia is producing lots of alcohol. There are some
other organic acids, so this leads to some "blue sky" thinking, and
I think we all need to be doing it.
It's been pointed out that we're taking off too much by conven-
tional systems but it always comes back to the same thing that Dean
Smith pointed out. How long does it take to pay off and what can
you do on utilization of materials?
Jackson;
Certain segments of this research the industry can't do but the
universities can and that was one reason I brought up the peel problem.
But if you were to look at the overall economics now that you have to
do something in waste treatment you might modify procedures somewhat.
Of course, we grew Torula yeast here at this university 18 years ago
and I once approached a starch manufacturer in Southern Idaho with
this. He pointed out the capital investment and said, "Son, if I had
$200,000 I wouldn't be in the potato starch business".
Smith;
Didn't the paper industry find out several years ago that they
could glut the world yeast market in about a month?
Kueneman;
That's right. I talked to some of those people the other day
and they were giving me some of their conversion ratios that they
make this material with.
At the present time we're converting a lot of peel waste into
beef and there's been a lot of debate as to whether that's the most
efficient means of converting the waste to protein.
Smith:
What about greater use of the solids as animal feed. Now I'm
thinking of the biological solids. These are carbon, nitrogen,
phosphorus, calcium sources and usually present a very real problem
of ultimate disposal.
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Filbert:
There was some work done on feeding activated sludge from a
domestic waste treatment plant. They found that cattle, chickens,
and hogs would accept this up to a point. Actually there are quite
a few vitamins available in the activated sludge or waste biological
solids. You can mix about 2 percent of activated sludge with other
feed and have it acceptable to the animals. They don't like it too
well unless you hide it.
I might as well throw in a plug for the Richmond Field Station
(Sanitary Engineering Research Laboratory, University of California)
About two years ago they did some work on using potato waste to
grow algae and it grew algae very well. Studies showed that animals:
chickens, poultry, sheep, and cattle, would accept the algae up to
about 25 percent. Several papers have been written on this work.
Jackson:
If you can get into the food and drug field you know the cost
per unit is a lot higher so this might be one way to go.
This has another factor too. It produces a very high quality
effluent. Once you grow algae and remove the algae you produce a
very high quality effluent.
Jacks«n:
We don't want to go to much "blue sky". How about a few more
specifics. One thing I didn't hear mentioned much today and I would
think this would be an important factor in the kinds of treatments
other than the irrigation that you're talking about and that's the
microbiology. One man mentioned you have to take some time to get
the methane formers growing. Isn't there an easier way of doing it
than relying on chance or are we going to suggest that we embark on
a strong program of studying in this field if we're going to use
anaerobic methods?
Question;
How about if you burn the waste by aspirating the waste water
into a flame such as an oxygen acetylene flame as an example but
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maybe there's a cheaper source of fuel than that? The heat and
steam produced could be used in the plant.
Jackson:
That might be a good way to produce steam but you would have
to produce steam to recover costs. Tom Binford would like to add
to this and tell us about the Dorr-Oliver calcinor I'm sure.
Binford;
It's cheaper to feed it to cattle.
Jackson:
The comment was made back aways that for some reason anaerobic
treatment made aerobic treatment more susceptible. I don't know
what this meant. What I'm leading you up to here is I'm trying to
get some more ideas on the fundamental process involve'd. Why should
anaerobic treatment bring about this effect?
Filbe r t;
This has some reference to K factors, synthesis and oxidation.
Acids and some of the smaller molecules are removed faster in syn-
thesis than some of the other molecules. You actually find that if
you take a waste that contains proteins, carbohydrates and other
materials and add a culture of organisms that some materials will be
utilized faster than others. Basically, it's the size and complexity
of the molecules. We have also found that you generally get better
removals with biological filtration of food processing wastes than
you do with pulp and paper wastes because of the molecular size.
Jackson;
Are you suggesting that anaerobic treatment shortens the
molecule, chops it in half, or makes a different kind of molecule
with different reacting characteristics?
Smith;
He said that the acids that are the intermediate products to
methane formation are just inherently simpler than the starches,
lipids, and proteins you started with.
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Postal;
In regard to the plant at Albert Lea, Minnesota it's fairly
certain that this same process would work on potato wastes. In the
developmental work done at the University of Minnesota a half dozen
industrial wastes were fed to the anaerobic contact process at
different times.
Thus far in our work on aerobic and anaerobic-aerobic lagoons
very little effort has been expended on solids removal from the
effluents. Most lagoons in operation today can obtain good organic
reductions, as high as 80 to 90 percent, if designed and operated
properly. The effluents do contain a large amount of suspended
solids. As a result the capital and direct operating costs have
been about 50 percent of those of more conventional treatment
processes such as activated sludge since there are no sludge handling
and disposal costs. In many locations this practice will have to be
altered. That is, these suspended solids will have to be removed
also. Then we'll be in a new ball park dollarwise and we'll have to
go back and look more closely at some of these other processes such
as the anaerobic contact process.
Binford;
Speaking of basic research there needs to be more research done
on characterizing the original waste. How many or what kind of amino
acids are in there? What kind of protein? Are there any lipids?
You may find entirely different ways of treating these individually.
Jackson;
I'm sure this is a problem. The more one knows about a material
the better off he is.
Paul M;
If you know something about biochemistry, in this matter of
anaerobic versus aerobic digestion, oxygen in a system will tend to
slow down the breakdown of starch to different carbohydrates and so
an anaerobic system will break down the starch much quicker. This
in essence will take it mainly to your organic acids and some more
easily degradable compounds which in turn can be treated. So from
a biochemical standpoint the use of anaerobic digestion would have
a theoretical advantage.
Jackson;
If it works, it must.
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Kueneman;
In answer to the question on what do we know about composition
of the waste we go back to Dean Smith's approach and use what is
available. Eastern Research Laboratory is programming on a computer
28 amino acids found in potatoes. Amino acid studies have been
done on several different potato varieties and much of this information
is available in the literature.
Furgason;
One of the problems we're faced with here is that we're not
talking about a particular material, we're talking about a whole
variety of things depending on the time of year you process, how
long the potatoes have been in storage, how long it has been in the
process stages and so on. So you can't talk about a particular amino
acid concentration or starch concentration, or sugar concentration
and I don't know if even averages make much sense. You just have
to work with what you have. You can't depend on keeping the concen-
trations constant.
Kueneman;
The only constant in this is change.
Jackson;
Are there any last words? Deans always have the last word.
Dean Smith;
One point I had in my outline that I think I skipped over because
the fire whistle blew, is that I would strengthen Ray's remark that
there is a lot of information available on amino acids and so forth.
We are at the point where the demonstration kind of thing that you're
undertaking here in Idaho is likely to pay the most immediate results
on things that can be used. Some of you have got a job to do and it
has to be solved immediately. We're going to keep on working in the
laboratory and we're going to come and ask fog-^research support.
We'll feed the information into the hopper, but it takes a step before
you go out and blanket the country with a treatment process of this
kind or that kind and I believe this is the point where we now are.
More power to you on the kind of thing you're doing on the demonstra-
tion project, as it has been described. I would only hope that you
can bring into these demonstration projects some of what we know
about the mechanisms. Hopefully these curves can be explained by
what's happening inside the individual processes. This is, I think,
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where we are on the matter of application of research. We're here
today to get a job done and keep our enforcement people happy and
the fishermen.
Jackson;
I might conclude on an optimistic note. It was once said when
I used to work in the paper industry that sometime in the future we
would be pulping the wood not for the fiber but for the other half
of the tree which is a wealth of a supply of organic materials, prin-
cipally lignin. I'm sure that our petroleum supply is not going to
last forever, and so I would suggest that at sometime in the future
we might be growing and processing the potato for the peel with the
dehydrated materials as a byproduct.
Fergason;
Once again on behalf of the college of engineering, the FWPCA
and the other participants, I'd certainly like to express my appre-
ciation for the people in the audience, especially to the people
who gave papers and others participating in this Symposium. I hope
you'll go home with some new thoughts in mind and continue the
excellent progress which I think has been made in potato waste
treatment.
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