Current Practice
  Potato Processing Waste Treatment

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               CURRENT PRACTICE

             Kristian Guttormsen
              Research Engineer

               Dale A. Carlson
        Professor of Civil Engineering
       Department of Civil Engineering
           University of Washington
          Seattle, Washington  98105
            Grant No. WP-01486-01
                 October 1969

            FWPCA Review Notice

This report has been reviewed by the Federal
Water Pollution Control Administration and
approved for publication.  Approval does not
signify that the contents necessarily reflect
the views and policies of the Federal Water
Pollution Control Administration, nor does
mention of trade names or commercial products
constitute endorsement or recommendation for

     The continued rapid growth of the potato processing industry represents
a corresponding increase in waste water volume.  This paper is a discussion
of potato processing, waste treatment, and current and needed research in
water quality control in this production field,  A brief discription is
given of general characteristics of the potato and the effects and im-
portance of cultural and environmental conditions on potato processing.
General descriptions of the production processes have been included and the
literature has been extensively reviewed to present current and proposed
waste treatment technology.  The most urgent research needs are discussed
together with suggested methods for meeting these needs.  This report was
submitted in fulfillment of Grant Number WP-01486-01 between the Federal
Water Pollution Control Administration and the University of Washington.


SECTION                                                            PAGE

          Abstract                                                 iii
          List of Tables                                            vi
          List of Figures                                          vii
1         Introduction                                               1
2         The Potato Processing Industry - Its Growth
            and Waste Production                                     2
3         The Potato                                                 4
              General Characteristics of the  Potato                  5
              Variations in Types of Potatoes                       6
              Cultural and Environmental Conditions                  7
4         The Processes                                             12
              General Requirements on Raw Potatoes                  12
              Handling and Storage                                  12
              Washing of Potatoes Prior to Processing               14
              The Peeling Process                                   14
              Potato Chips                                          20
              Frozen French Fries and Other Frozen Potato
                Products                                            22
              Dehydrated Diced Potatoes                             25
              Dehydrated Mashed Potatoes - Potato Granules          27
              Potato Flakes                                         27
              Potato Starch                                         31
              Potato Flour                                          35
              Canned Potatoes                                       36
              Pre-Peeled Potatoes                                   38
              Alcohol                                               38
5         Methods for Reducing the Waste Load                      40
              Water Re-use and Conservation                         40
              Counter-Current Flow of Process Water                 42
              Process Control and In-Plant Treatment                42
              Redesign and Modifications of the Process             44
              By-Product Recovery from Potato Waste                 46
              Waste Separation and Combination                      49
6         Current Waste Water Treatment Processes                   50
              Preliminary Treatment                                 50
              Primary Treatment                                     52
              Secondary Treatment                                   55
              Ponds                                                 63
              Spray Irrigation                                      69
              Tertiary Treatment                                    72
7         Disposal of Solids                                        74
8         Current Research and Development Efforts                  79
9         Research Needs                                            80
              Specific Research Needs                               81
              Suggested Approach to the Problem                     85
          Appendix A - Bibliography                                 87
          Appendix B - Research Grants on Potato Processing
                       Wastes                                       97
          Appendix C - Potato Processing Waste Treatment Costs    102


       PRODUCTS                                                       2


III    PROXIMATE ANALYSIS OF WHITE POTATOES                           5

 IV    MINERAL CONTENT OF POTATO ASH                                  6

  V    DESCRIPTION OF VARIETIES                                       8

       1955 TO 1965 ARRANGED IN ORDER OF POPULARITY IN 1965           9

       1956                                                           9


 IX    STARCH PLANT WASTE                                            33

  X    ORGANIC LOAD FROM STARCH PLANTS                               34

 XI    RAW SCREENED FLOUR PROCESSING WASTE                           37







  1     TYPICAL POTATO CHIP PLANT                                    21

  2     TYPICAL FRENCH FRY PLANT                                     26

  3     TYPICAL POTATO GRANULE PLANT                                 28

  4     TYPICAL POTATO FLAKE PLANT                                   30

  5     TYPICAL POTATO STARCH PLANT                                  32

  6     TYPICAL POTATO FLOUR PLANT                                   36

  7     ENGINEERING NEWS  RECORD  INDEX                               104

  8     MECHANICAL SILT REMOVAL  -  CAPITAL COST                       105

  9      PRIMARY TREATMENT CAPITAL  COST                               105

10      SECONDARY TREATMENT CAPITAL COST                             106

11      DISPOSAL BY SPRAY IRRIGATION CAPITAL COST                    106

12      OPERATING AND MAINTENANCE COSTS                              107

13      STABILIZATION POND CAPITAL COST                              107

14     CLARIFIERS CAPITAL COST                                      108


                               SECTION 1


     The potato processing industry in the United States has experienced
tremendous growth during the last decade,  and future projections indicate
that this trend will continue.  Unfortunately, such marketable products
as French fries and potato chips are not  the only products of the industry.
Large quantities of wastes requiring disposal are produced as well.   If
discharged untreated or inadequately treated to our waters, these wastes
may create serious pollution problems. Milner Reservoir on the Snake River
in Idaho has experienced four of the nation's largest fish kills since 1960,
due principally to the combined effects of inadequately treated potato waste
and curtailment of the stream flow at the dam.

     The predicted future growth of the potato processing industry repre-
sents a corresponding increase in waste water volumes.  Since increased
waste discharges to our waters cannot  be tolerated, higher and higher
degrees of waste treatment will be required of the potato processing
industry as well as other industries.  High degrees of waste treatment with
the methods available today represent large economic burdens on the industry.
More efficient and less costly methods for providing such treatment must,
therefore, be developed.

     Industrial wastes often exhibit unique characteristics such as high or
low pH which create unique treatment problems.  Troublesome characteristics  may
be common to several types of industrial waste, and may therefore have been
thoroughly investigated for purposes of waste treatment.  The purpose of
this report is to present waste problems  of the potato processing industry
together with current technology and available information.  Hopefully this
presentation will serve as an introduction to the  field for a larger group
of people involved in waste treatment research and development.  By dis-
cussing the capabilities and limitations  of the current and proposed
technology, this material should be of value  to potato processors and
engineers concerned with potato waste treatment.

     The report contains a brief description  of the general characteristics
of the potato and the effects and importance  of cultural and environmental
conditions.  General descriptions of the different processes involved have
been included also.  The literature has been  extensively reviewed to present
the current and proposed waste treatment technology and pertinent available
information.  Finally, the most urgent research needs have been discussed
and methods have been suggested to meet these needs.

                                SECTION  2


      The total annual potato production in the United States now is
 approximately 15 million tons.   This  represents an increase  of 25 per
 cent  since 1956.  While per capita consumption of  potatoes  in this
 country  has remained at about 110 pounds per year  during the last
 decade,  the fraction consumed as  processed potatoes has increased rapidly.
 In 1956  the annual per capita consumption of processed potatoes was
 23.4  pounds, more  than  twice  that in 1949.   In  1964 consumption
 had increased by almost 54  per  cent  to 36 pounds.   To meet  the demand
 for processed potatoes about 35 per  cent of the total crop  is now used
 for processing.   This is an increase of  147 per cent over the
 tonnage  processed in 1956.   (Talburt and Smith 1967)  (Irish  Potatoes
 1965,  1966).

      The growth  of the industry is expected to continue in  the future.
 Results  of a computer analysis  of the  future increase in frozen potato
 products  are shown in Table I (Kueneman  1968).   In 1965 potatoes repre-
 sented more than 50 per cent of all frozen  vegetables.   Projections for
 1976  indicate  that potatoes will  constitute 75 per cent of the vegetables
 frozen and will  represent about 10 per cent of all frozen foods.
                                 TABLE  I

     Year          Poundage Processed          Per  Capita  Consumption
                    (Million Pounds)                   (Pounds)
                          1660                           8.35
                          1880                           9.38
                          2110                         10.44
                          2360                         11.53
                          2610                         12.64
                          2870                         13.76
                          3130                         14.88
                          3400                         16.00
                          3680                         17.11
                          3920                         18.20
     In a study of the Pacific Northwest by the U. S. Department of the
Interior (1966), a potato production increase of 83 per cent was predicted
during the period from 1965 to 1985.  During the same period the pro-
duction of frozen and dehydrated potato products is expected to increase
by approximately 250 per cent.

     A significant fraction of the potato is rejected as waste during
processing.  The amount wasted depends upon the quality of the potato as
well as the particular type of process, and may vary from as low as
20 per cent to more than 50 per cent.  Cooley et al. (1964) analyzed the
waste streams from various types of processing plants and determined
their population equivalents based on biochemical oxygen demand (BOD).
The results are shown in Table II.

                                TABLE II

                 Flakes (Lye Peeling)              420
                 Chips (No Treatment               171
                 Chips (With Clarifier)              84
                 Flour (No Treatment)              318
                 Flour (With Clarifier)             110
                 Starch                            353
   *Based on 0.17 Ib. of 5 day 20C biochemical oxygen demand (BOD.)
    per population equivalent.

     The average population equivalent of an untreated waste stream
from Table II is 315 per ton of raw potatoes processed.  Thus, the average
daily tonnage of potatoes processed in this country at the present creates
an untreated waste load equivalent to a population of about 5.5 million
people.  Based on projections for frozen and dehydrated potato products,
7.4 million tons of raw potatoes will be used in these two processes
alone in 1977 (Kueneman 1968).  This represents an untreated waste load
equivalent to a population of almost 8 million people.  (In 1966, 56
per cent of all processed potatoes were used for dehydrated and frozen
products.)  The magnitude of waste production from potato processing is
indeed immense.  The fact that the industry is located primarily in
Idaho, Maine, and the Red River Valley of the North concentrates the
problem in three relatively small areas.

                                SECTION 3

                                THE POTATO

 Historical Comments

      The white  potato,  Solatium  tuberosum. has been cultivated in  the
 Andes as far back  as  200 A.D.   Potatoes were a primary source of  food
 for  the Indians  of  Peru; they had even developed methods of dehydration
 to provide  supplies of  food for periods between successive crops when
 fresh potatoes were not available.

      Spanish and English explorers soon recognized the food value of the
 potato, and it became an important source of provisions for their ships.
 The  explorers brought the potato back to their native countries.  Records
 have shown  that  a hospital in Seville, Spain, bought potatoes as  early as
 1573.  The  potato was introduced to the other European countries, but was
 used as food only on a  limited  scale.  In the early years it probably was
 regarded a  luxury,  and  later was reputed to cause a number of diseases,
 including leprosy.  Nevertheless, the potato soon was cultivated extensively.

      Although wild  ground nuts  were used by Indians in the area of the
 United States, the  white potato was first introduced to this country in
 1621,  where, as  in  Europe, it became a major source of food.

      Today, the  potato  is grown in almost every important agricultural
 country in  the world, and in many countries is still a major contributor
 to the average man's diet.  In  the United States potatoes comprise 7% of
 the  1488 pounds  of  food consumed per capita annually (Mercker 1965).

 Development of the  Crop Potato

     During the  early cultivation of the potato by the Peruvian Indians
 no conscious efforts were made  to develop varieties with specific
 characteristics.  Natural cross-pollination resulted in new varieties
 which may have  attracted  attention and were  thus  replanted.   In this way a
 number of varieties occurred.

     After  the potato was introduced to Europe and North America, a number
 of varieties of varying popularity were cultivated.  At that time potatoes
 usually were not grown  to be sold, and quality control was not important.
 The  crop was consumed on the farm where it was grown, with low quality
 varieties used as livestock feed.

     The first great effort to develop varieties with specific characteris-
 tics came in the middle of the 19th Century, when the crops in both North
 America and Europe had been largely destroyed for several reasons.
Although efforts to develop a disease resistant potato failed, a number of
new varieties with high cooking quality resulted, some of which remained
 popular for many years.

     Today potatoes are available for specific purposes and environments.
Varieties with characteristics such as resistance to disease, high solids
 content, low reducing sugar content,  and thick or thin skin have been
developed.   New varieties are derived mainly from cross-pollination.

     Research on hybridization of haploid and diploid species is under
way.  If successful, diploid varieties may become available, and it may
be possible to add additional characteristics to the varieties while
retaining the varietal characteristics.  (Talburt and Smith 1967).
                 General Characteristics of the Potato

Anatomy of the Tuber

     A potato tuber is, morphologically, a modified stem, with its axis
greatly shortened and its lateral members only weakly developed, the
latter forming what are known as the "potato eyes."

     The outer layer, the skin, consists of a corky periderm, the purpose
of which is to resist evaporation losses and attack by fungus.  In the
event that the potato is cut or wounded, a wound periderm is formed which
apparently is more effective in protecting the tissue than the original
layer.  Underlying the periderm is the cortex, a narrow layer of parenchyma
tissue.  Between the cortex and the pith, which forms the central core of
the tuber, is the vascular area.  This accounts for by far the largest
part of the tuber tissue, and is high in starch content.  The vascular
storage parenchyma tissue is divided in two unequal parts by a discontinuous
ring, called the vascular ring, consisting of large polyhedral parenchyma
cells in which small islets of phloem are embedded.  The pith, sometimes
called the "water core", is connected to each of the eyes by lateral
branches.  It consists primarily of large cells, containing less starch
than the cells in the vascular area and the inner part of the cortex.

     The eyes show the relation of the tuber to the stem.  Each eye is a
leaf scar, arranged in a spiral around the tuber, with 13 eyes to each
5 turns of the helix.

Composition of the Potato

     An accurate description of the composition of the potato is not
possible because of the great variety of potatoes, the area of growth,
cultural practices, maturity at harvest, subsequent storage history and
other factors.  Talburt and Smith  (1967) presented the following tables,
based on values given by various reviewers.

                                TABLE III

                            Average Percent     Range Percent
          Water                    77.5           63.2 -  86.9
          Total Solids             22.5           13.1 -  36.8
          Protein                  2.0            0.7 -  4.6
          Fat                      0.1           0.02 -  0.96
            Total                  19.4           13.3 -  30.53
            Crude Fiber            0.6           0.17 -  3.48
                                   1.0           0.44 -  1.9

                                TABLE IV
                     MINERAL CONTENT OF POTATO ASH

                        Average Percent       Range Percent

             K20              56              43.95 - 73.61

             P205             15               6.83 - 27.14

             S03               6               0.44 - 10.69

             MgO               4               1.32 - 13.58

             Ma 0              3               0.07 - 16.93

             CaO              1.5              0.42 - 8.19

             SJXL              1               0.16 - 8.11
     Starch - Starch is, calorically, the most important nutritional
component of the potato.  The starch content, comprising about 65 to 80
percent of the dry weight of the tuber, influences quality parameters
of processed products as well as operational conditions of the processes.

     Starch is present in the raw potato as microscopic granules in cells
of the parenchyma tissue, especially in the vascular area.  It has been
found that starch content is closely correlated to specific gravity, and
an equation has been derived for the percentage starch based upon specific
gravity.  Other factors affecting the starch content are fertilization,
cultural conditions, disease, morphology, and internal distribution.

     Sugars - The sugar content of potatoes may vary from trace amounts
to ten percent of the dry weight of the tuber.  Different potato varieties
have different sugar contents when harvested, but sugars will easily
accumulate after harvesting.  Factors affecting the accumulation of sugars
include variety, storage temperature, maturity when harvested, and different
kinds of treatment during storage.

     Potatoes with a high sugar content taste sweet and have poor texture
after cooking.  Coloration of potato products, such as French fries,
potato chips, and dehydrated potatoes is closely correlated with the
content of reducing sugar in the raw potato.  This results from the non-
enzymatic browning reaction between the aldehyde groups of the reducing
sugars and the free amino groups of the amino acids.  Generally, potatoes
with a reducing content above 2 percent are not considered acceptable
for processing.
                    Variations in Tvpeg_of Potatoes

     As mentioned earlier, a wide variety of potatoes is available.
Throughout Europe, 700 varieties are listed; 300 of these are suitable

for industrial processing (Wiertsema 1968).   The varieties in the United
States also are numerous.  Many of the species are of little or no
importance, and the majority of the crop consists of a dozen varieties.
Also, new varieties are developed continuously while others are being

     Talburt and Smith (1967) presented a general description of the older
varieties which are still popular and the newer varieties which contribute
to most of the present production (Tables V, VI, and VII).

                 Cultural and Environmental Conditions

     The quality of potatoes, as well as the yield, is to a great extent
determined by the cultural and environmental conditions during the growth
period.  Factors of influence include (1) date of planting, (2) soil type,
(3) soil reaction, (4) soil moisture, (5) season, (6) location, (7) mineral
nutrition of the plant,  (8) cultivation and weed control, (9) spray program
for control of insects and diseases, (10) temperature during the growing
season, (11) time and method of vine killing and (12) time of harvest.

     Since different varieties are affected to different degrees by the
above mentioned factors, the choice of variety is of course very important.

Date of Planting

     This factor is related to the specific gravity, or solids content,
of the potato.  Early planting generally means a longer growing season,
resulting in a potato of greater maturity and with higher solids content
at harvest than potatoes from later plantings.

Soil Type

     The soil type in which potatoes are grown also may affect solids
content.  Characteristics of the soil such as water holding capacity,
drainage, aeration, structure, temperature and fertility all may affect
the dry weight of the potato.  Also, they may balance each other in
effect so that no change occurs.  Obviously the possibilities are many.
It has been  stated that  loam soils generally produce the highest specific
gravity tubers.  Probably,  this  is because loam soils have more nearly
optimal moisture, temperature, and structural relationships for potato
production than the lighter or heavier  structured soils.   (Talburt and
Smith 1967).

Soil Reaction

     Little  research has been  reported  on the effect of pH  on potato
production.  Smith  (1937)  found  that potatoes grown under  slightly  acid
conditions had higher specific gravity  than tubers  from neutral or
slightly alkaline soils.

                                                                               TABLE V
                                                                      DESCRIPTION OF VARIETIES
Year Originating Tuber Depth of Skin
Variety Released Agency Maturity1 Shane Eve2 Color

Early Gem


Irish Cobbler



La Rouge
Norgold Russet



Red LaSoda
Red McClure
Red Pontiac

Russet Bur bank
Russet Rural
Russet Sebago


White Rose









. . .


Iowa, Indiana and
Dept. of Agr. 3
Dept. of Agriculture3
Dept. of Agr.3 Idaho &
North Dakota


Dept. of Agriculture3

Dept. of Agriculture3

Louis iana
North Dakota
North Dakota

Michigan and Dept.
of Agriculture3
Virginia and Dept.
of Agriculture3
Dept. of Agr.3

Dept. of Agr.

North Dakota











Long elliptical


Round with
blunt ends



Round, oblong

Oval, flattened
Round, elliptical



















Gravity Disease Resistance











Late blight, scab,
net necrosis
Mild mosaic


Mild mosaic

Mild mosaic, net
Late blight, net

Scab and late
Late blight

Net necrosis

Scab, field resis-










tance to late blight

Round, elliptical

Oval to long



Field resistance to
late blight

                      ^-early; M-medium; L-late.
                       S-shallow; M-medium; D-deep.
                      3U.S. Dept. of Agr.
Talburt and Smith, 1967.

                                                      TABLE  VI

Rutiflet Burbank . . .

Red LaSoda. .......

.... 2
.... 1
.... 6
.... 3

.... 4

. ... 21
.... 5
.... 7

   Inghaa Co.
Yield   Sp. Gr.
 Missaukee Co.
Yield   Sp. Cr.
Preaque Isle Co.
Yield   Sp. Cr.
    Bay Co.
Yield   Sp. Cr.
  Montcalm Co.
Yield   Sp. Gr.
   Delta Co.
Yield   So. Gr.

... 347
. .. 365

,.. 294
,.. 413
. .. 382
, .. 348
, . . 265

, .. 277
, . . 258

, .. 508
... 369












Courtesy of D. R. Islleb.

Soil Moisture

     The effect of soil moisture on yield and solids content of potatoes
is  a fairly complex matter.  In arid regions irrigation is necessary,
while in other areas rainfall may suffice.  The amount of water applied
and the time and schedule of application are important factors.  Tempera-
ture is another important variable.

     Ample soil moisture may result in high yield of potatoes with low
specific gravity.  Uniform soil moisture during the growing season to-
gether with the withholding of irrigation prior to harvest has produced
potatoes with high specific gravity.  Excessive rainfall or irrigation
late in the season results in crops with low specific gravity.

     High moisture content tends to keep the soil temperature cool and
stable, thereby reducing loss by respiration.  High moisture content may
thus prove advantageous in high temperature growing areas.


     Yield and solids content of the same varieties may differ considerably
from season to season in the same area because of differences in soil
moisture, temperature, and other environmental conditions.


     Solids content and reducing sugar content are greatly dependent upon
location, due to differences in environmental conditions.  In Sweden a
study was made on the quality of potatoes grown at different latitudes
(Carlson 1968A).  It was clearly demonstrated that because of the difference
in  temperature and length of growing season, the yield and solids content
were highest and reducing sugar content lowest for potatoes from the
southernmost locations.

Cultivation and Weed Control

     Cultivation methods affect primarily the moisture content of the
soil, and thus will have the effects discussed previously.  Respiration
of water from leaves Of weeds may reduce the moisture content of the soil
rapidly, and destruction of the weeds when they are small may be important
for retaining sufficient moisture in the soil.  A common weed control
chemical is 2, 4 - D, which has been reported to reduce yield as well as
increase it.   Increase in specific gravity has been reported to result
from 2,  4 - D application.  (Talburt and  Smith  1967.)

Mineral Nutrients of the Plants

     Several workers have reported that as the fertility of the soil
increases, the specific gravity of the potato decreases.  Nitrogen may
increase the yield of potatoes but be detrimental to the quality for
processing.  It has been found that starch and solids content decrease

with increasing application of nitrogen.  The application of phosphorous
has provided little or no increase in starch and solids content.   Potassium,
as muriate of potash (KC1), the most widely used form, reduces the solids
content of potatoes when heavily applied.  This is thought to result from
the chloride ion rather than the potassium ion.  The sulphate form of
potash usually gives higher starch and solids content than the equivalent
quantity of the chloride form.  Magnesium often is not present in sufficient
quantities to give a high yield of potatoes, especially in acid soils.
Addition of magnesium have been found to increase the yield as well as the
starch content of the tubers.  (Talburt  and Smith  1967.)

Spray Program for Control of Insects and Diseases

     Spraying to control insects and diseases is necessary in almost all
potato growing areas, to prevent early death of the plant, reduced yield,
and poor quality.  DDT is the most common insecticide used in the United
States.  Because of its excellent control of insects, the plants continue
to grow, and do not die or mature naturally, but are killed by frost or by
mechanical or chemical means.  This results in poorer chemical composition
of the potato for processing.  Specific gravity is lowered and reducing
sugar content increased.

Temperature During Growing Season

     The effect of temperature has been mentioned earlier.   It determines
to a great extent the length of the growing season and thus  the maturity
and specific gravity at harvest.

Time and Method of Vine Killing

     As mentioned earlier, because of Insect control  the  potatoes continue
to grow, and it often is necessary to kill  the vines  by mechanical  or
chemical methods.  When the plant is left  to die  naturally,  food in the
form of sugar is transferred  from the stem to  the tuber,  where it is
converted to starch, resulting in higher specific gravity.   Artificial
vine killing methods give  little opportunity for  transfer of food,  and
thus a lower quality potato results.  Studies have  indicated that slow
vine killing, i.e. by chemical means, provides better quality potatoes.
Late killing appears more  feasible than early  killing.  Other studies
indicate  that variations  in quality during storage  are different for
mechanically killed plants and chemically  killed  plants.   (Gustafson 1968).

Time of Harvest

     Mature  tubers are  superior in quality and yield  to immature  tubers,
and quality  of processed  products is improved  when  mature tubers are used.
Therefore, harvest should  be  as late in the season  as possible without
subjecting  the potatoes  to low  temperatures.   Potatoes used for processing
should not be exposed to  temperatures below 40F.

                                SECTION 4

                              THE PROCESSES

                   General Requirements  on  Raw Potatoes

      High  quality raw potatoes  are  important  to  the  processor.  Potato
 quality affects  not  only the  final  product, but  also the  amount of waste
 produced.   Generally,  potatoes  with high solids  content,  low  reducing
 sugar content,  thin  peel, and of  uniform shape and size are desirable
 for processing.   Cull potatoes  sometimes are  sorted  for starch and flour
 production, but  more often low  quality  potatoes  must be wasted and
 thereby represent a  loss to the processor.

                           Handling  and  Storage

      As mentioned earlier,  potato quality  is  dependent upon cultural
 and environmental conditions.   Handling and storage  of the crop by the
 grower and the processor also affect the quality to  a great extent.  Thus
 efforts to reduce losses and  waste  loads should  include consideration of
 these aspects of quality control.

      Harvesting  is a very important operation.   Bruising  and  other
 mechanical injury to potatoes during harvest  often result in  excessive
 rot during subsequent  storage.  Careful operation and adequate machinery
 obviously  are very important  in maintaining a low level of injury to the
 tubers.  Numerous  types  of  mechanical harvesters have been developed,
 but none has performed satisfactorily under all  conditions.   Improved
 harvesting machinery no  doubt would reduce the losses and waste loads.

      Transportation  of potatoes for processing is another operation where
 improper conditions  during  transit  may  render potatoes undesirable for
 processing.  Proper  temperature is  the  most important consideration.
 During transit potatoes  should  be kept  at  temperatures between 50 and
 75F.   If  potatoes are held at  40F or  below  for several  days, reducing
 sugars will accumulate resulting  in dark color of products such as chips
 and French fries.  An extended  period of temperatures above 75F may
 cause  an increase in certain  types  of storage rot diseases and, in fairly
 air-tight  areas, may result in  blackheart, a  discolored breakdown of the
 tissue at  the center of  the tuber.   (Talburt  and Smith 1967).

     Potatoes are shipped in bulk or  containers by truck  or by rail, and
 generally  it is necessary to use  trucks and railroad  cars specifically
 designed for potato  transport.  Temperature must be kept  constant
 throughout the car,  and  since outside temperatures may  fluctuate  con-
 siderably, good  ventilation must  be provided.
     A railroad car for bulk transportation of about 90 tons of potatoes
is being developed by ACF Industries (Curry 1968).  Tests with outside
temperatures ranging from 9 to 130F showed that the temperature could
be maintained at 60F throughout the car.

     Loading of trucks and cars must be done with care to prevent mechan-
ical injury.  Low outside temperatures during loading may create problems
unless the temperature control in the car performs adequately.

     Storage is necessary to provide a constant supply of tubers to the
processing lines during the operating season.  In storage, potato quality
may be changed drastically unless adequate conditions are maintained.
The major problems associated with storage are sprout growth, reducing
sugar accumulation, and rotting.  Reduction in starch content,  specific
gravity and weight also may take place.

     Sprouting occurs at temperatures of 50F and above following a rest
period of several months after harvest.  At lower temperatures  little  or
no sprouting will take place, but reducing sugars will accumulate in the

     One approach to maintaining high quality potatoes is to treat the
crop with a sprout inhibitor in the field or in storage and then to keep
the storage temperature at 50 to 60F.  A variety of sprout inhibitors
have been used.  Maleic hydrazide sprayed on the plants in the field has
given good results.  Other chemicals used are tetrachloronitrobenzene,
nonanol, and CIPC, all with various degrees of success.  The storage
temperature and especially the storage time appear to be very important.

     Gamma irradiation of potatoes at dosages of 10,000 to 15,000 REP  has
been found to inhibit sprouting completely for at least one year when the
storage temperature is kept at 50F.
     Reconditioning of potatoes stored at low temperatures over a period
of time by subsequent storage at higher temperatures for a similar length
of time has the effect of reducing the sugar content.  Potatoes stored
at 40F for six weeks and then removed to 70F for six weeks had sugar
contents similar to the content prior to storage.  Potatoes stored at
lower temperatures had higher sugar content after reconditioning.
     To prevent large losses by rotting, low quality potatoes should be
sorted out before the crop is placed in storage.  Mechanically injured
potatoes are especially susceptible to certain rot diseases and should be
removed prior to storage to avoid rotting of a large portion of the load.

     In summary, handling and storage of the raw potatoes prior to pro-
cessing are major factors in maintaining high quality potatoes and re-
ducing losses and waste loads during processing.  Careless handling and
storage may well destroy efforts to reduce and treat the waste from the
process line.

                Washing of Potatoes Prior to Processing

     Raw potatoes must be washed thoroughly to remove sand and dirt
prior to the actual processing steps.  Sand and dirt carried over into
the peeling operation can damage or greatly reduce the service life of
the peeling equipment.

     Often the incoming potatoes are washed in the water used for trans-
port from the storage or receiving area into the plant.  Fluming is an
economical and effective method of transporting potatoes which results
in a minimum of bruising damage.  Sand and gravel are removed in stone
traps in which these heavier solids settle out while the potatoes pass
on.  Tubers transported into the plant by other means or washed inade-
quately in the flume are passed through washers.  A number of different
types of washers are employed.  Barrel-type washers are quite common.
Potatoes are tumbled and rubbed against each other and against the sides
of the barrel while immersed or sprayed with water.  Other types use
rubber brushes, rolls or paddles to loosen the adhering dirt.  Following
the washing operation the potatoes are allowed to drain for a short
period while being carried to the next step which is usually a short
inspection belt where trash and rotten potatoes are removed.

     Water consumption for fluming and washing varies considerably from
plant to plant.  Wolters (1965) has reported flow rates to vary from
1300 to 2100 gallons per ton of potatoes.  Of this volume, 2/3 is used
for fluming and 1/3 for washing.  Adler (1965) states that 1000 to 1800
gallons of water are used to wash one ton of potatoes.  A study on the
waste waters from five potato starch plants in Idaho, shows a range of
flume water flow rates from 600 to 2700 gallons per ton of raw potatoes
(Ambrose and Reiser 1954).  The volumes reported above are based on no
recirculation of the flume and wash water.  Today recirculation systems
are used to some extent, and the fresh water input may be reduced
significantly compared to a "straight-through" system.

     Depending upon the amount of dirt on the incoming potatoes, the
waste water will contain from 100 to 400 Ibs of solids per ton of potatoes,
Organic degradeable substances are predominately in dissolved or finely
dispersed form, and amount to from 2 to 6 Ibs of BOD,, per ton of potatoes
(Wolters 1965).  In a potato starch waste study, an average of 0.4 Ibs of
BOD5 per ton of potatoes was reported (Ambrose and Reiser 1954).  This
value naturally depends to a great extent on the quality of the raw
potatoes.   Wolters (1965) states that with a recirculation system the
organic matter discharged from the fluming and washing operation will be
from 30 to 50 percent less than with a "straight-through" system.
                          The Peeling Process

     Peeling of potatoes contributes the major portion of the organic
load in potato processing waste.  The operation determines to a great
extent the yield of final product and the labor cost for subsequent trim-
ing and inspection.

     Many factors must be considered when choosing the peeling method and
establishing the tolerable peeling losses.  Peeling requirements vary from
process to process and from plant to plant.   Production of potato chips,
for example, requires less complete peel removal than production of French
fries.  Thus, disregarding potato quality, peeling losses will be less in
chip factories than in French fry factories.

     Potato quality is an important consideration, however.  Deep eyes
and thick peel result in high peeling losses if a high degree of peel
removal is required.  Other variables which affect peeling efficiency are
age of the crop, size and shape of the tuber.  With small potatoes,
peeling losses are generally high because the surface area per unit
weight is large.

     Three different peeling methods are used extensively today.  These
are abrasion peeling, steam peeling and lye peeling.  No one of the
methods will satisfy the requirements of every type of plant.  All three
methods may be operated either as a batch process or as a continuous
process.  Small plants generally favor batch type operation due to greater
flexibility.  In such plants peeling losses and labor costs for trimming
are usually quite high.  Large plants use continuous peelers.  These are
much more efficient than batch-type peelers, but the capital cost is high
(Talburt and Smith 1967) .

Abrasion Peeling

     Abrasion peelers have abrasive discs or rolls which remove peel by
uniform contact with the surface of the potatoes.  Peelings and potato
tissue are removed from  the abrasive surfaces by water sprays which  also
reduce the tendency of potatoes to darken through enzymatic action.  The
potatoes must be spun and rotated so that all surfaces are equally exposed
to the abrasive surfaces.  Thus it is important that  tubers subjected to
abrasion peeling are round.  Digger cuts may cause the tuber  to slide on
the flat surface thus losing excessive  tissue on one  side.  Uniformly
sized potatoes will result in more evenly peeled potatoes when  using this
peeling method.  Tubers with deep eyes  are  not  suitable  for abrasion
peeling because excessive trimming will be  required  (Talburt  and  Smith

     Abrasion peeling is used especially  in potato chip  plants  where
complete removal of  the  skin is not essential.  Sijbring (1968A)  said
peeling losses  of  from  4 to 8 percent are not unusual in chip production.
Smith  (1964) made  a  survey of chip operations in  the  United States and
found peeling losses ranging from 0  to  25 percent.  Abrasion  peeling has
been used in the production of pre-peeled potatoes, since  the heat ring,
which results from high  temperature exposure, does not occur  with this
method.  High peeling  losses, possibly  as high  as  25  to  30 percent,  may
be necessary to produce  a satisfactory  product, however.

      The characteristics of  the  peeling waste vary with  potato quality
and peeling  requirements.  Gray  and Ludwig  (1943)  reported the following
peeling waste quality in a dehydration  plant:

     Flow -  600 gal/ton

     BOD.   20 Ib/ton

     Suspended solids - 90 Ib/ton

     Settleable solids = 15 cu. ft/ton  (2 hr settling)

The organic  content appears to be directly proportional to the percent
peeling loss, and therefore would be minimized by feeding optimum
quality potatoes.  Up to 90 percent of  the settleable solids appear to
consist of coarse potato matter, the rest being fine starch particles.

Steam Peeling

     Steam peeling yields thoroughly clean potatoes.  The entire surface
of the tuber is treated, and size and shape are not important factors as
in abrasion peeling.  The potatoes are  subjected to high pressure steam
for a short period of time in a pressure vessel.  Pressures generally
vary from 3 to 8 atmospheres and the exposure time is between 30 and
90 seconds.  While the potatoes are under pressure the surface tissue is
hydrated and cooked so that the peel is softened and loosened from the
underlying tissue.  After the tubers are discharged from the pressure
vessel, the softened tissue is removed by brushes and water sprays similar
to the ones used for prewashing.  An increase in exposure time causes
larger peeling losses and lower trimming requirements (Talburt and Smith

     Because the gelation point of potato starch is surpassed in steam
peeling, there will always be a heat ring.  This heat ring is not always
objectionable, as, for example, in the  production of French fries where
it is not noticeable in the finished product.  Steam peeling of pre-peeled
potatoes may result in enzymatic darkening under the heat ring.  The ring
may harden during storage, seriously affecting the quality of the product
(Talburt and Smith 1967).

     One disadvantage with steam peeling is the difficulty with which skin
in the eyes is removed during trimming, particularly when the tubers start
showing sprouts (Sijbring 1968B).

     The waste water characteristics from this operation will vary with
potato quality and peeling requirements.  Cooley et al.  (1964)  reported
the following characteristics from a potato flour plant peeling waste:

     Flow =625 gal/ton

     COD =52.2 Ib/ton - 10,000 ppm

     BOD =32.6 Ib/ton - 6,750 ppm

     Total solids =53.2 Ib/ton - 10,200 ppm

     Volatile solids = 46.8 Ib/ton - 9,000 ppm

     Suspended solids =26.8 Ib/ton - 5,150 ppm

     pH = 5.3

     The peelings and solids usually are removed by screens before the
waste water is treated.   These screenings are simply cooked potato
tissue and can be used for cattle feed without additional treatment
except for possibly some drying or mixing with other feed materials.
Because of the relatively high temperature of the waste water,  a con-
siderable amount of starch dissolves and cannot be removed by plain

Lye Peeling

     Lye peeling appears to be the most popular peeling method used in
the United States today.  The combined effect of chemical attack and
thermal shock softens and loosens the skin, blemishes and eyes so that
they can be removed by brushes and water sprays.  Lye concentration,
temperature and immersion time are the variables controlling this peeling
method.  Two general procedures are in use.  One method uses lye temper-
atures from 190 to 220F, well above the gelation point for potato
starch.  Immersion times from 2 to 6 minutes are required in lye concen-
trations of 15 to 25 percent.  The other method is operated at temper-
atures from 120 to 160F to avoid the formation of a heat ring.  Longer
immersion times generally are required.  At temperatures below 140F
minimum immersion times are obtained at lye concentrations between 15
and 20 percent (Talburt and Smith 1967).  Lye usage is less at lower
lye concentrations.  Sijbring (1968B) reports a usage of 15 kg of lye
per ton of potatoes peeled at a lye concentration of 20 percent, while
at concentrations of 10 to 13 percent the lye usage is 7 to 8 kg per

     If a heat ring remains on the peeled potatoes  this can be removed
by immersing the tubers in a second lye bath at lower temperature.  It
has been found that a bath at 120F with a lye concentration of 15 to 20
percent effectively removes the heat ring caused by high temperature
treatment (Harrington 1957).

     Preheating of the potatoes in water before the lye bath minimizes
the cooling effect of the tubers  on the solution, helps to maintain a
constant temperature, and increases the capacity of the peeler.  A
wetting agent or detergent has been found to improve peeling efficiency.
(Lankier and Morgan 1944) (Sijbring 1968B)

     If sludge formed in  the peeler by the chemical action of lye on  the
potato tissue is removed by screening or settling,  the service life of
the lye solution can be extended  markedly.

     The peel, after having been  softened and loosened in  the lye bath,
is removed by brushes and water sprays as in steam  peeling.  Sometimes
a short period of time  is allowed for  the lye  to work on  the potato  tissue
before removing  the peel.   The tubers  then must be  thoroughly washed  to
remove any lye and lye-affected surface which will  harden and  cause a
yellowing of  the surface.

     Lye peeling waste water is the most troublesome potato waste.
Because of  the lye, the waste water pH is very high, usually between
11 and 12.  Most of the solids are colloidal, and the organic content
is generally higher than for the other peeling methods.  The temperature,
usually from 50 to 55eC, results in a high dissolved starch content.
Furthermore, the waste water has a tendency to foam.  Cooley et al.
(1964) reported the following waste water characteristics from a lye
peeling installation in a potato flake plant:

     Flow  715 gal/ton

     COD =65.7 Ibs/ton - 11,000 ppm
     BOD -  40.0 Ibs/ton - 6,730 ppm

     Total  solids = 118.7 Ibs/ton = 20,000 ppm

     Volatile solids - 56.4 Ibs/ton  9,500 ppm

     Suspended solids =49.7 Ibs/ton = 8,350 ppm
     pH -12.6

     Because this peel is extremely caustic, the pH must be lowered
before the  solids can be used for cattle feed.  This is accomplished
through microbiological action.  In a primary sedimentation tank, for
example, the pH of the settled solids can be lowered by controlling
solids detention time in the tank so that the primary sludge can be
fed directly to cattle after dewatering.

Evaluation  of the Peeling Methods

     As mentioned earlier no one peeling method will satisfy the
requirements for every type of plant.  In choosing the peeling method
the processor must try to achieve the proper balance between peeling and
trimming losses and raw material costs for most efficient operation.
Some larger plants may install more than one type of peeler.  Early in
the season, when the potatoes are easy to peel, steam peeling may be
advantageous.  Later, when potatoes become difficult to peel, lye
peeling may be more economical.

     The waste production should be considered carefully because it may
seriously affect the economic feasibility of a particular peeling

     Abrasion peeling wastes do not have the high content of dissolved
starch and  fine and colloidal solids associated with wastes from lye and
steam peeling installations, and thus can be treated to a higher degree
by sedimentation.  The amount of solids which must be removed from
abrasion peeling waste is large, however, since the peeling losses
generally are high.

     In comparing lye and steam peeling wastes, the biggest difference is
the pH of the two wastes.  While steam peeling wastes usually are near

neutral, lye peeling wastes have pH values from 11 to 12.  This high pH
may cause problems in receiving waters as well as in biological treatment.
Furthermore, the organic content of lye peeling waste is generally higher
than that of steam peeling waste.  A study carried out in the Netherlands
on tubers from the same lot clearly shows this (Sijbring 1968B).

                                                Peeling Method

Peeling loss, percent
Average weight of tubers, grams
Pollution, pop. equivalent/ ton/day
Water consumption, m /ton
     The study was carried out at a plant processing French fries.  Thus
the peeling requirements were quite high.  The population equivalent was
based on a BOD of 54 grams discharged per capita per day after one hour
settling of the waste water.

     Another study analyzed the combined waste stream from a potato flake
plant in North Dakota prior to and after converting from lye to steam
peeling (Olson et al. 1965):
       Total Suspended Solids

       Volatile Suspended Solids

       Fixed Suspended Solids
       Sample date


1297 mg/1

1107 mg/1

 190 mg/1

1265 mg/1



297 mg/1

201 mg/1

 96 mg/1

701 mg/1

      Oxygen demand as well  as pH  and solids  content were  substantially
 reduced.  Similar differences in  waste  quality have been  reported by
 Talburt and Smith (1967) .

                              Potato Chips

     The processing of potatoes to potato chips involves essentially
 the slicing of peeled potatoes, washing the slices in cool water,
 rinsing, partially drying, and frying them in fat or oil.  White skinned
 potatoes with high specific gravity and low reducing sugar content are
 desirable  for high quality chips.  A flow sheet of the process is shown
 in Figure  1.

     After conventional prewashing, the potatoes are peeled, usually by
 the abrasive method, washed and inspected and trimmed prior to slicing.
 Losses vary over a wide range.  A survey of more than 50 plants in the
 U.S. showed that peeling and trimming losses for old potatoes varied
 from 2 to  20 percent and for new potatoes from  0.3  to  13 percent.
 Another survey showed the losses ranging from  0.5  to 25  percent
 and from 0 to 8 percent for old and new potatoes, respectively.  Trimming
 losses alone may vary from negligible amounts to 10 percent (Smith 1964,
 1966).  The quality of waste water from the peeling operation has been
 discussed  earlier.  Trimming contributes primarily to the amount of
 solid waste.

     Slicing yields from 15 to 20 slices per inch.  Considerable amounts
 of starch  are released in the operation and must be washed off to avoid
 matting and sticking of the chips during frying (Potato  Chip Industry
 1960).  Most of the starch and slivers are removed in a washer with cool,
 fresh water.  The combined waste water from slicing and washing has been
 reported to have the following characteristics (Cooley et al. 1964):

     Flow  = 1140 gal/ton raw potatoes

     COD - 75.5 Ib/ton

     BOD =21.9 Ib/ton

     Total solids = 118.5 Ib/ton

     Volatile solids = 63.6 Ib/ton

     Suspended solids - 53.8 Ib/ton

     pH -  7.4

Losses during slicing and washing amounts to 0.05 to 1.0 percent of the
raw potatoes (Talburt and Smith 1967).  After washing,  the chips are
rinsed in  one or two water baths to further remove starch.  The waste
from these steps is negligible both in volume and organic content.  Drying
of the chips prior to frying reduces the frying time and thus increases
the capacity of the kettle.  This is accomplished by a variety of methods
including  compressed air and perforated revolving drums.  The chips also
may be treated by hot water or chemicals prior to frying to prevent
darkening.   Chemicals used include sodium bisulfite, hydrochloric acid,
phosphoric acid and citric acid.


                                                                                        PRODUCT      CONVBYOR
                                                                                          MAKE-UP WATBR

                                                                                       ^ WATK  WUATBR
                                                              TYPICAL. POTATO  CHIP PLANT

      Most  plants  now use continuous  friers.   Frying oil  is  circulated
 constantly through  the kettle,  and  through  a strainer  so that  small
 bits  of  chips  and suspended particles  may be removed.  Because of  the
 cost  of  frying oil,  recirculation is essential,  and the  oil must be
 handled  carefully to prevent spoilage  by overheating or  oxidation.
 The temperature of  the frying oil varies at the  heat source, where the
 chips enter,  from 350 to 375F and  at the  finishing end of the kettle
 from  320  to  345F.   The temperature is altered  to  fit the  raw material
 and the  conditions  prevailing at the time.
     After  frying  the  chips are passed over  a shaker screen  to remove
 free oil, then salted  or  flavored, and finally cooled and  inspected
 before  packaging.

     Cooley et al.  (1964) presented the following figures  for the
 combined waste from a  potato chips plant:

     BOD  - 29.2 Ibs/ton  potatoes

     COD =78.4 Ibs/ton potatoes

     Volatile Solids = 68 Ibs/ton potatoes
     Fixed  Solids = 115 Ibs/ton potatoes

     Suspended Solids =59.8 Ibs/ton potatoes

     pH = 7.4

 A survey by Forges  and Towne (1959) on four  chip plants showed an average
 of 50 Ibs of BOD  and 66 Ibs of suspended solids discharged per ton of
 potatoes processed.  The average waste flow was 3980 gallons per ton.

     New methods for frying chips are being developed.  The microwave oven
 has been used to dry chips partially fried in oil.  It was found that
 potatoes of high reducing sugar content could be processed to acceptable
 colored chips in this way while complete oil frying produced dark colored

     A vacuum frier for chips has been developed at Wageningen, the
Netherlands.  This  frier enables the processor to fry the chips at lower
 temperatures, thus  improving the color of the chips.  The vacuum frier
has been tested on  a large scale basis with good results (Sijbring 1968C).

          Frozen French Fries and Other Frozen Potato Products

     Of the 1966 crop,  32 percent of the potatoes processed were used
for frozen French fries.   Including other frozen potato products the
figure  amounted to  37 percent.   (Irish Potatoes 1967)  The grade and
quality of potatoes processed into frozen products vary over a wide range.
For French fry production large potatoes of high specific gravity and
low reducing sugar content are most desirable.   Large potatoes result in

lower peeling losses and larger yield of long French fry cuts.   High
specific gravity insures higher yield per ton of potatoes processed
and low reducing sugar content improves the color of the finished

     After prewashing, the potatoes are peeled by the steam or  lye
method.  The peeling requirements on potatoes for French fry processing
are high, and the abrasion peeling would result in excessive losses.
Peeling and trimming losses vary with potato quality and range  from
15 to 40 percent (Talburt and Smith 1967).  On the trimming belt low
quality potatoes are diverted from the process line and small tubers
may be removed for processing into co-products like potato patties,
hash brown or mashed potatoes.

     The strip cutter produces, besides French fry cuts, slices and
nubbins which must be removed.  This is usually accomplished by shaker
screens or rotating reels having slots through which the smaller pieces
pass.  These pieces may then be diverted to the co-product processing
lines.  The removal of slivers and nubbins may amount to an additional
loss of 10 percent, reducing the overall yield of raw French fry cuts to
within the range of 50 to 75 percent of the tonnage of potatoes processed.

     After cutting and sorting, the strips usually are water blanched.
Advantages of blanching include (a) more uniform color of the finished
product, (b) reduction of fat absorption through gelatinization of the
surface layer of starch, (c) reduced frying time because the potato
is partially cooked by blanching, and (d) improved texture of the final
product (Talburt and Smith 1967).

     Because the blanching water is relatively warm, its leaching effect
may result in a high dissolved starch content in the waste water.

     Surface moisture from the blanching step is removed by hot air
prior to frying.  This reduces the frying time and improves the texture
of the strips.

     The French fry cuts are carried through the frier by a conveyor.
The temperature of the frying fat usually is maintained within the range
from 350 to 375F.  Frying time is adjusted to meet the requirements of
the consumers.  Institutions usually finish frying in deep fat to develop
color and crispness and thus desire a minimum of frying by the processor.
French fries for the home consumer are fried more completely so that
subsequent deep fat frying is unnecessary.

     After frying, the free fat is removed on a shaker screen and by hot
air streams.  The fries then are frozen and packaged.

     Table VIII gives the waste water characteristics from a French fry
plant in Maine (Sproul 1965).  This plant used the lye peeling method.
The spray washer, which removes the loosened skin, contributes the bulk
of the pollution load.  Of the 22 Ibs of BOD per ton of potatoes
processed, 20 Ibs came from the lye peeler.  The table shows also  that

                                                       TABLE VIII
                                            (All results in mg/L except pH)
Spray Washer
& blanching
Plant Composite
as N

              Notes:  Raw potatoes  processed  -  8.8  tons/hour

                      Plant BOD               -  22#/ton potatoes

                      Plant suspended  solids  -  25#/ton potatoes

                      Water use               -  2310 gal/ton potatoes

                      Data from  Sproul (1965)

the by-products contribute a minor part of the waste.   This would of
course depend upon the number and kinds of by-products and upon the
fraction of the potatoes diverted to the by-product line.   Figure 2 is
a flow diagram of the French fry process.

                       Dehydrated Diced Potatoes

     Dehydrated potato dice are becoming increasingly important in
today's food industry.  The major part of the production is used in
processed foods, primarily canned meats.

     Potatoes with white flesh color and low reducing sugar content are
desirable for dice production.  Exposure of peeled potatoes to the
atmosphere results in increased darkening of the finished product.  This
is overcome by using water sprays and dips and by preventing undue delays
along the process line.

     After washing and preliminary inspection to remove tubers showing
"light greening", rot, mechanical injury and other defects, the potatoes
are peeled by the steam or lye method.  Minimum losses amount to about
10 percent.

     The use of electronic sorting machines for removing blemishes and
discolored dried dice has reduced the amount of inspection required at
the trim table.  One important factor during trimming is minimizing the
exposure time.  The surfaces therefore should be kept wet by water sprays
along the trim table.   (Talburt and Smith 1967)

     The tubers are cut into different size pieces.  Losses in cutting
appear to be directly related to the degree of subdivision.  Simon et al.
(1953) report a range of cutting and washing losses from 9 percent for
the larger pieces to 14 percent for the smaller pieces.

     After cutting and washing, the dice are blanched with water or steam
at 200 to 212F.  Blanching results in better and more even surface
color and also reduces microbiological contamination.  A small solids loss,
up to 1.5 percent, is associated with the blanching operations.

     Following blanching a carefully applied rinsing spray removes surface
gelatinized starch to prevent sticking during dehydration.

     Sulfite usually is applied at  this point as a spray solution of
sodium sulfite, sodium bisulfite or sodium metabisulfite.  Sulfiting
protects the product from non-enzymatic browning and scorching during
dehydration and increases the storage life of  the product  under  adverse
temperature conditions.

     Calcium chloride often  is added concurrently with sodium bisulfite  or
sodium metabisulfite.   This  has the effect of  firming the  dice and  preventing
sloughing.  Sodium sulfite and calcium  chloride should not be  added
concurrently since a precipitate is formed.

                                j     L
                                                                             TRMMNMQ      CUTTER
                                                                   FRYING    DE-\MATEmiMO   BL.AIMCHHMO
                                                                            <=> MAKE-UP \AMVTER

                                                                            . WASTE \MATER
                                                   TYPICAL FRENCH FRY PLANT

     Modern continuous belt dehydrators dry the product to the desired
moisture content in 6 to 8 hours.  Since storage life has been found
to be closely related to moisture content, it is important to dry the
product to as low moisture content as is economically feasible.  Piece
size greatly affects the drying rate.  The thicker the pieces, the
slower the rate of drying.

     Following drying the potato dice are screened to remove small
pieces and bring the product within size specification limits.  Sorting
to remove discolored pieces is done either manually or by electronic
sorters.  Finally the dice are packaged in cans or bags.

              Dehydrated Mashed Potatoes - Potato Granules

     Potato granules are dehydrated single cells or aggregates of cells
of the potato tuber dried to about 6 to 7 percent moisture content.  They
can easily be made into mashed potatoes by mixing with hot or boiling
liquid.  Because of the increasing popularity of convenience foods,
potato granule production has grown steadily since about 1950.

     Since coloration of the finished product is a problem, potatoes of
low reducing sugar content are desirable.  Also the low reducing sugar
content minimizes scorching during drying.

     A flow diagram of  the "add-back" process, which is used in the United
States, is shown in Figure 3.  After peeling and trimming, the potatoes
are sliced to obtain more uniform cooking.  The slices are cooked in
steam at atmospheric pressure for about 30 to 40 minutes.  Cooking usually
is a continuous process where the slices are carried on a moving belt.
After cooking is completed, the  slices are mixed with  the dry add-back
granules and mashed to  produce a moist mix.  This mix  is cooled and con-
ditioned by holding for about one hour before further  mixing and dried to
about 12 to 13 percent  moisture  content.  The powder then is screened,
and granules coarser than 60 to  80 mesh are returned as add-back together
with some of the finer  powder.   Very coarse material,  retained on a 16-mesh
screen, is removed from the process since it does not  absorb moisture from
the cooked slices rapidly enough to be helpful.  About 12 to 15 percent
of the material is removed for final drying to about 6 percent moisture
content and packaged  (Talburt and Smith 1967).

     Two very important factors  in the process are  (1) minimum cell
rupture, and (2) satisfactory granulation.  Cell rupture releases excessive
amounts of starch, resulting in  a sticky or pasty product.  Unsatisfactory
granulation results in  a lumpy and grainy finished  product.

                             Potato  Flakes

     Potato flakes are  a  form of dehydrated mashed  potatoes which  have
been dried on a steam-heated roll as a thin sheet  and  then broken into
small pieces for packaging.  Potatoes  for  flake  processing should have


                                                         TYPICAL. POTATO   ORANULE  PLANT

the same characteristics as those for potato granule processing.  It is
important in this process, also, to keep cell rupture to a minimum.

     A flow diagram of the process is shown in Figure 4.  After pre-
washing, the potatoes are lye- or steam-peeled.  Losses and waste water
from these operations have been described earlier.  Following trimming
the tubers are sliced into 0.25 - 0.50 in. slices and washed prior to
precooking in water at 160 to 170F for about 20 minutes (Cooley et al.,
1964).  The water used for precooking may be treated with certain
additives, such as sodium acid pyrophosphate, to prevent graying of the
potatoes.  Fresh make-up water is added, and the overflow stream is high
in solids but low in volume.  The potatoes are then cooled in fresh water
for about 20 minutes.  The purpose of the precook and cooling is to
improve the texture of the finished product.  Cooley et al. (1964) have
reported the following characteristics for the combined waste from the
slicer, washer, precooker and cooler:

     Flow - 1540 gal/ton potatoes
     COD =56.2 Ibs/ton potatoes

     BOD =38.4 Ibs/ton potatoes

     Total solids - 125.6 Ibs/ton potatoes

     Volatile solids * 53.3 Ibs/ton potatoes

     Suspended solids =16.4 Ibs/ton potatoes
     pH - 5.2

     Using steam at atmospheric pressure the cooled potatoes are given  a
final cook in a continuous cooker until they are just soft enough  for
ricing.  This requires about 30 minutes for potatoes of high starch and
solids content and about 40 minutes for varieties of lower solids content.
The only waste stream from the cooker is the steam which condenses on
the potatoes and drains off.  This waste water is high  in solids but
very low in volume.

     After cooking, the potatoes are riced or mashed and the mash  is then
dried on a single drum drier.  The dried product is in  the form of a sheet
a few thousandths of an inch thick.  The sheet is broken into flakes of
convenient size for packaging.  Olson et al. (1965) analyzed the combined
waste from 3 different flake plants and reported the following  values:
Total solids
Volatile solids
Fixed solids
Total suspended solids
Total volatile solids
Total fixed solids
5-day BOD

Plant A
Steam Peeling
Plant B
Lye Peeling
Plant C
Lye Peeling

[=> MAKE-UP  WA-
                            TYPICAL POTATO FLAKE  PLANT
                                         no. 4

                             Potato Starch

     Potato starch is a superior product for most of the applications for
which starch is used.  Because of its high phosphorous content it has
much greater swelling capacity than either tapioca or corn starch.  Two
factors which prevent the industry from capitalizing on these advantages
are the unstable supply of raw potatoes and the price paid for starch.
Since the raw material for starch manufacture is primarily cull and
surplus potatoes, starch production is closely tied to fluctuations in the
potato industry, and adequate supplies of low-priced potatoes are often
not available during short crop years.  (Douglass 1965) (Harp 1965)  The
principal use of potato starch is for paper sizing and coating.  Another
important application is textile sizing, and it is used also in the
baking industry, in fine laundering, as a thickening agent, and in adhesives,

     The bulk of the starch plants in the United States is located in
Maine and Idaho.  Figure 5 shows a flow diagram of a typical Idaho starch
plant.  After fluming and washing the potatoes are fed to a grinder or
hammer mill and disintegrated to a slurry which is passed over a screen
to separate the freed starch from the pulp.  The pulp is passed to a
second grinder and screened for further recovery of starch.  The starch
slurry which passed through the screens is fed to a continuous centrifuge
to remove the protein water which contains solubles extracted from the
potato.  Process water is added to the starch, and the slurry is passed
over another screen for further removal of pulp.  Settling vats in series
are used to remove remaining fine fibers.  The pure starch settles to the
bottom while a layer of impurities, known as "brown starch," forms at the
top.  The brown starch is removed to the starch table consisting of a
number of settling troughs for final removal of white starch.  The white
starch from the settling tanks and the starch table is dried by filtration
or centrifugation to a moisture content of about 40 percent.  Drying  is
completed in a series of cyclone driers by contact with hot air.  The
starch which now has a moisture content of 17-18 percent is screened  and
then packaged.  (Ambrose and Reiser 1954)  (Talburt and Smith 1967)

     Ambrose and Reiser (1954) made a survey of 5 starch plants in Idaho
and found the average values for the waste streams, as shown in Table IX.
The protein water and the pulp accounts for about 95 percent of total
organic load.  If the pulp is retained and not wasted, the organic load
is significantly reduced, as shown in Table X.  The population equivalent
values are based on 0.167 pounds of 5-day BOD per capita per day.

                               PLUMB f     WASHBR
                                                                           OBR       CRBBM

                                                                           STARCH  TABLE
                                                                                                c=C> MAKE-UP WATER

                                                                                                * WASTE  WATER
                                                                        TYPICAL POTATO STARCH  PLANT

                                          TABLE IX
                             STARCH PLANT WASTE CHARACTERISTICS

Flume Water
Protein Water
First Starch Wash Water
Second Starch Wash Water
Brown Starch Water
Starch Water
Pulp (Dry basis)
Flow Rate
Gal /ton



Solids Content
% wt.



Protein in
Solids, wt%


(a)   No recirculation
(b)   An average of 55.5 Ibs of pulp (on dry basis) were produced per ton
     of potatoes processed.

            TABLE X

Potatoes processed, tons /day
5-day BOD, Ibs/ton
BOD population equivalent /ton
BOD population equivalent of plant
5-day BOD, Ibs/ton
BOD population equivalent/ton
BOD population equivalent of plant



     Potato pulp has proven to be a valuable feed for livestock when
mixed with other Ingredients and thus represents a valuable by-product.
(Dickey et al. 1965)

     The protein water is difficult to treat because of the high content
of soluble organic matter.
                              Potato Flour

     Potato flour is the oldest commercial processed potato product.
Although widely used in the baking industry, production growth rates have
not kept pace with most other potato products.

     The potato flour process is based on the efficient dehydration of
peeled cooked potatoes on a drum drier and is quite similar to the potato
flake process.  The main difference is the cooking step which generally
is one continuous cook in steam at atmospheric pressure rather than the
precook, cooling and final cook in the flake process.

     Raw material for potato flour consists primarily of very large
potatoes, small potatoes and potatoes having surface defects.

     A flow diagram of the process is shown in Figure 6.  After the pre-
wash the potatoes are peeled, usually with steam.  Trimming requirements
are not as high as for most potato products due to the "scalping" action
of the applicator rolls on the drum drier.  Rot, green end and other
discolorations must be trimmed off, however.

     The "flaking" operation requires well cooked potatoes.  A cooking
time of 45 to 60 minutes with steam at atmospheric pressure usually is
adequate.  (Talburt and Smith 1967)  The tubers are conveyed directly
from the cooker to the dryer, where 4 to 5 applicator rolls along one
side of the drum contribute a thin layer of potato mash.  The mash  is
rapidly dried and scraped off the drum at the opposite side by a doctor

     The dried sheets are passed to the milling system where they are
comminuted by a beater or hammer mill and then screened to separate
granular and fine flour.  The moisture content of the final product is
generally from 7 to 9 percent.

     The waste water from the peeling operation accounts for the major
part of the organic load.  Another source of organic waste is the drum
drier, where peel fragments and other solids tend to accumulate.  The
waste water characteristics show much variation from plant to plant as
is the case with all potato processing.  The  values in Table XI have been
reported by Cooley et al. (1964) and Olson  et al.  (1965):

                                    o   o

                                                                         TYPICAL  POTATO  FLOUR  PLANT
                                                                                          FIO. B

                                TABLE  XI

                                 Cooley et al.  (1964)    Olson et al.  (1965)

PH                                       4.2                     6.9
Total Solids*                           11792                  7493

Volatile Solids                         10614                  5572

Fixed Solids                             1178                  1921

Total Suspended Solids                   6862                  4398
Volatile Suspended Solids                6480                  3019
Fixed Suspended Solids                    382                  1379

5-day BOD                                7420                  3314

COD                                     12582                  8314
    *mg/l except for pH

                            Canned Potatoes

     The production of canned potatoes has increased steadily during the
postwar years as a result of the increasing demand for convenience foods.
Potatoes are canned in several different forms, but whole potatoes account
for the major part of the production.

     Potatoes used for canning are primarily the smaller sizes not suitable
for fresh market.  An important requirement of canning potatoes is that
they should not slough or disintegrate during processing.  Potatoes of
high specific gravity are most likely to slough.  Sloughing usually can be
prevented in specific gravity lots of 1.075 to 1.095 by adding calcium
chloride.   (Talburt and Smith 1967)

     After  conventional prewashing the potatoes are peeled.  Lye, steam,
and abrasion peeling as well as combinations of these are used in the
canning process.  Abrasion peelers sometimes are used rather than lye or
steam peelers to give the potatoes a smoother surface.  Because the heat
ring may present a problem, low rather than high temperature lye-peeling
appears to  be more suitable for canning.

     Since  canned potatoes are a low cost product, only a minimum of
trimming is allowed.  Some processors prefer to sort out the potatoes
which need  trimming and send them through the peeler a second time.
(Talburt and Smith 1967)

     If the potatoes have not been size graded previously, this is done
following  the trim table inspection.  Larger size tubers are usually not
canned whole but cut to make diced, sliced, shoe string or julienne

     The whole and cut potatoes are  then filled in cans, and boiling
water or brine containing 1.5  to  3.0 percent salt is added.  A salt
tablet is used with boiling water.  The salt, calcium chloride, has
a firming effect on the product.

     The cans are closed at a  temperature of 160F or above and then
processed at 240 to 250F for about 25 to 50 minutes depending upon
the  can size.  Following processing the cans are water-cooled promptly
to about 100F.
                          Pre-Peeled Potatoes
     As a result of the demand for convenience foods and the high cost
of hand labor, prepeeled potatoes are becoming increasingly popular.
Restaurant operators generally find it more economical to purchase
pre-peeled potatoes than to invest in labor for hand peeling or in
peeling machinery.  Pre-peeled potatoes also have gained popularity in
the household.

     Potatoes are pre-peeled for sale as whole potatoes as well as for
French-fry cuts, chips, hash browns and others.  The selection of raw
material is to a great extent dependent on the final product and the
same factors discussed earlier must be considered.

     The pre-peeling processes do not differ significantly from the pro-
cesses discussed earlier, and the waste streams are consequently similar.
Peeling methods which involve temperatures above 160F, the gelation
point of potato starch, generally are not feasible in pre-peeling
processes.  Abrasion and low-temperature lye peeling are therefore the
most popular peeling methods in use.  Trimming and cutting requirements
do not differ from what has been described previously.

     Discoloration of pre-peeled potatoes takes two forms.  The first
type is the enzymatic formation of melanin, a dark pigment.  The second
type is the non-enzymatic "after-cooking darkening".  Black-spot or
black-heart may also occur.  Microbial spoilage furthermore limits the
shelf-life of pre-peeled potatoes.

     To prevent discoloration, addition of chemicals is helpful.  The
most common additive is sulphur dioxide.  Garrick (1968) reports that
50 ppm of S0? delays browning of peeled potatoes up to 2 days at 20C
and up to 14 days at 4C.  Microbial deterioration may be controlled
for 10 to 14 days by keeping the peeled potatoes under refrigeration.
(Talburt and Smith 1967)

     Alcohol production from potatoes in the United States is small
compared with the volume produced from grain.  In Europe potato alcohol
production is important.

     In fermentation plants,  the potatoes are washed, steamed at
about 135-140C and cooled to 62-65C.   The starch is hydrolyzed by
barley malt or by a mold amylolytic enzyme preparation.  The resulting
mash, of 17-20% dry matter, is subjected to alcohol fermentation for 2-3
days.  The residue after distillation (120-140 kg/100 kg potatoes, of
4.5% dry matter) is a valuable feed for cattle.  Waste water from
distilleries has been reported to have a 5-day BOD of about 530 mg/1
(Szebiotko 1965).  Joint production of starch and alcohol is carried
out in Poland, Russia, and Czechoslovakia.   The pulp and protein water
from the starch production is used for alcohol fermentation, and the
distillery residue is fed directly to livestock.  This allows for
disposal of all wastes.  (Szebiotko 1965).

                                SECTION 5


     The Importance of in-plant efforts to reduce the total waste load
can hardly be overemphasized.  In many cases the reduced losses, improved
product recovery, and reduced water usage have more than offset the cost
of the treatment facilities.

                     Water Re-use and Conservation

     The capital and operational costs of waste treatment facilities are
closely related to the volume of waste that has to be treated.   Reduced
waste volumes will significantly reduce the size of the treatment units
and hence the overall cost of treatment.  Excessive use of water where
it is not strictly necessary often occurs in processing plants.   The
processor, therefore, should examine every point of water use within
the plant to determine where water may be conserved or re-used.

     There are several areas in the day-to-day operation where water is
wasted unnecessarily into the waste stream from the processing plant.
The following corrective steps have been suggested by the National Canners

     1.  All water hoses should have automatic shut-off valves  to prevent
         wastage of water when hoses are not in use.  A running hose can
         discharge up to 300-400 gallons of water per hour.

     2.  Use low-volume, high-pressure nozzles rather than low-pressure
         sprays  for clean-up.

     3.  Avoid unnecessary water overflow from equipment,  especially when
         not in  use.   Automatic fresh  water make-up valves should be

     4.  Avoid using water to  flume the product or solid waste where the
         material  can be moved effectively by dry conveyors.

     5.  Avoid using water in  excess of amount  needed  to accomplish  the
         job,  e.g.,  reduce cooling water flow to the minimum  needed  to
         accomplish  the  necessary  product  cooling.

     6.  Divert  rain water run-off from buildings away from the  factory
         and do  not  allow it to collect inadvertently  in the  waste
         disposal  system.

     7.   Certain water used in the plant which  is not  re-used and which
        meets the  purity requirements of  the State  may  be discharged
         directly  into streams without prior  treatment through a waste
         disposal  system.   In  some cases this may amount to over 50  percent
        of  the  total  water used.

     Reduced water usage  may result  not  only  in  reduced waste volumes.
In a vegetable processing plant  it was  found  that the  heat  loss  in  the
plant was reduced significantly  as  a  consequence  of  reduced water use.
(Weckel 1969)

     Re-use of process water reduces  the  waste load  as well as the  water
usage.  In England,  biologically treated  effluents sometimes  must be
partially re-used because of limited  water supply and  restrictive water
quality criteria.  This practice will undoubtedly become more common in
the future.  (Gallop 1965)

     A large percentage of the process water  does not  require biological
treatment before re-use.  Flume  and wash  water are low in BOD and dis-
solved solids, and may be reused, in  most cases,  following  treatment by
settling.  Water for recirculation must not be allowed to undergo
anaerobic decomposition since, besides being  corrosive and  odorous, it
may affect the quality of the final product.   Thus,  the detention  time
in the settling tanks should not be excessive, and chlorine should  be
added to prevent putrefaction.  Welters (1965) suggested that detention
times of about one hour are sufficient, while Dickinson (1965)  claimed
two hours of quiescent settling are required  to clarify potato  wash water.
The constant velocity channel, or grit chamber, designed for water  velocities
of one foot per second, is a suitable device  for removing sand  and
inorganic solids.  Mechanical screening should be used to remove larger
organic debris.  In two of the largest starch plants in southern Germany,
90 percent of the flume and wash water is re-used after treatment  in
sedimentation tanks with continuous sludge removal.   The contaminated water
discharged from the system is replenished by  fresh water.   A dosage of
19 mg of chlorine is added per gallon of  wash water.  Chlorination  requires
close attention, however, since chlorine  promotes the formation of  the
dark pigment, melanin.  (Adler 1965)

     Bacterial growth can be controlled by environmental factors.   Acidi-
fication of such water with citric acid or other edible acids to pH 3-4
has been found to reduce greatly the growth rate of bacteria.  Equally
effective may be reduction of the water temperature.  (Rose 1965)   Such
precautions permit recirculation of the water until build-up of physical
or chemical components preclude further use.   Recirculation may reduce  the
organic load from the fluming and washing operation by 30 to 50 percent.
(Wolters 1965)

     An example of efficient re-use of cooling water and process water in
a potato granule plant has been described by Berry  (1967).   Fresh water
is pumped  from a well for use in 3 separate systems:  (1) sanitary-potable
water system,  (2) equipment cooling - potato fluming and washing system,
and  (3) process water system.  Waste water from  the first system is not
reused and is discharged  to a sanitary septic tank with a  tile drain field.
The equipment cooling water is pumped under high pressure  into a rotary
drum washer  for  removing dirt from the potatoes.  The water  from the drum
washer then  is used for  transporting the  potatoes by  flume to the  process
operations.  The  flume water is passed through a 20 mesh vibrating screen
and piped  to a settling  pond for silt removal prior to disposal by spray

 irrigation.   Process  water,  after  having been used  for steam  generation,
 cooling,  and plant clean-up, is  passed  through  a  40 mesh  stationary
 screen to remove  solid waste and peel which  is  used as cattle feed.
 The screened water is piped  to the spray irrigation system  for final

      Others  reporting on  the effects and importance of re-use of process
 water include Ambrose and Reiser (1954), Atkins and Sproul  (1964) ,
 Eckenfelder  (1969), Gallop (1968),  Kueneman  (1965), and Mercer (1969).

      Re-use  of a  large percentage  of the process  water will be necessary
 in  the future as  water and waste problems become  much more  important
 factors in the survival and  growth  of food processing plants.   Gallop  (1965)
 indicated that industry could manage with 10-15 percent of  the present
 usage of  water for processing without loss of product quality.  One of the
 largest Idaho plants  has  reduced the water usage  to 200-400 gallons per
 ton of potatoes by considerable  recirculation, and  it is  expected that
 this amount  can be reduced by about 75  percent  within a few years.
 (Kueneman 1965)
                 Counter-Current Flow of Process Water

     Another method for water conservation and waste concentration is
counter-current flow of product and process water.  In this system, water
from the last product fluming or washing operation, instead of being
wasted, is collected and passed back in a counter-current manner to be
used in preceding washing and fluming operations.  The overall effect is
that the product is moved forward after each washing or fluming operation
 water which  is  cleaner  than that  used  in the preceding operations.
A recent development for final purification of starch employs this
principle.  The starch milk is pumped into the first of several solid-
liquid cyclones while clean water is pumped into the last cyclone, and the
two work their way counter-currently through the batteries.  The water
emerges from the first unit carrying all the soluble impurities which
had been in the starch milk while the purified starch emerges from the
last unit ready for filtration and drying.  (Douglass 1965)  In any
process line with successive washes and rinses, counter-current flow
should be considered if water conservation by recirculation is unfeasible.
                 Process Control and In-Plant Treatment

     Proper operation of the process equipment can reduce the waste load
as well as the loss of product.  It is therefore important that the
different process steps are adjusted according to the operational
variables so as to reduce the waste volume and/or amount of contaminants
to a minimum under the prevailing conditions.  This may involve reduced
solids losses allowed in operations such as peeling, cutting, and screening.
Reduction of water usage should of course be considered.  In many cases
such adjustments may require an evaluation of treatment cost versus
trimming cost or product quality.  Previous records are helpful in such

situations.  Examples of steps that may be taken to reduce peeling losses
include better control of the caustic concentration in lye peeling and
use of higher pressure water sprays in washing facilities.  (Talburt and
Smith 1967)  Maintenance of the process equipment is another important
factor.  Efforts to reduce the volume or strength of a waste stream are
easily offset by the effects of inadequate equipment.

     Good house-keeping and in-plant treatment, such as screening, can
result in significant waste load reductions.   Potato peel and pulp
contain 0.1 mg of BOD per mg of dry solids.  (Carlson, 1967)  Therefore,
in-plant efforts to separate potato solids from the waste water as early
as possible, or keeping the solids out of the liquid waste altogether,
will markedly reduce the dissolved organic content of the waste stream.
When potato solids are left in contact with water over a period of time,
considerable leaching of organic materials take place.  The following table
shows the influence of contact time on soluble BOD.  (Sproul, 1968)
                               TABLE XII
                     FROM SLICED POTATOES IN WATER
Mixing Time
Dissolved BOD
In this experiment Maine Russet potatoes were cut into 1/4-inch cubes
and 150 grams were added to 1.5 liters of distilled water.  The starch
liberated during cutting vas added also, which accounts for most of the
BOD after 2 minutes of mixing.  After 30 minutes the dissolved BOD
had increased by 50 percent with respect to the 2 minute concentration,
and additional mixing would have increased the BOD even more, since 10
percent of the dry weight would give about 2.6 grams of available BOD.
Only 0.45 grams were measured after 30 minutes.  Potato pieces with larger
surface area, such as flakes or granules, would leach considerably larger
amounts of organic material per unit weight, since the leaching rate is
proportional to the surface area exposed.  The temperature of the water
also influences leaching.  Warm water will extract more organics than
will cold water.

     Unnecessary spills must be avoided, since spills increase waste loads
as well as product losses.  Automatic controls may be used to reduce spills,
and sumps substituted for floor drains will prevent  the spilled material

 from entering,  the waste water.  Useable materials may be recovered in
 this manner.   (Black and Forges  1965)  Spills during  the packing operation
 represent a direct loss of  finished product as well as solid waste which
 often  is washed away to the plant waste stream.  Wreckel (1969) found a
 loss of 1 percent of finished product in the filling  operation in a pea
 cannery.  Similar losses in a plant processing corn were estimated to be
 3 percent.

     Very few of the persons working on the process line understand the
 magnitude of the waste problem and what contributes to it.  Efforts to
 explain how they, through better house-keeping and consideration, can
 reduce this problem, seem well worthwhile.
               Redesign and Modifications of the Process

     Numerous possibilities exist for redesign and modifications of the
process to reduce the waste load.  New and improved equipment and methods
are being developed, but for economical reasons the processor cannot
always take full advantage of the improvements.

     Much attention should be given to improving the peeling process,
which contributes the major part of the waste load in potato processing.
Change of peeling method can reduce the waste load considerably.
Conversion from caustic to steam peeling at the Borden's Food Company
processing plant at Grafton, North Dakota, resulted in a BOD reduction
of the combined plant waste of almost 47 percent.  The total suspended
solids concentration was reduced by 79 percent and the volatile suspended
solids by 83 percent.  Fixed solids were reduced by almost 50 percent.
(Olson et al. 1965)

     Presently, two newly developed "dry" peelers are being tested.  These
peelers were developed independently by the Western Research Laboratories,
USDA, at Albany, California, and by the Institute for Storage and Pro-
cessing of Agricultural Produce, IBVL, at Wageningen, the Netherlands.

     The peeler developed by the Western Research Laboratories is based
on the application of infra-red radiation to caustic treated potatoes
followed by abrasion treatment to remove the peel.  The use of water to
remove the peel, as in conventional caustic or steam peeling, is eliminated,
and the peeling waste can be removed from the process as a concentrated

     A pilot plant operation of the process by the Potato Processors of
Idaho Association has been described by Willard (1969).  Potatoes were
removed continuously and randomly from the flow to a conventional caustic
peeling line and transported by conveyor to a small conventional ferris-
wheel type caustic peeler.  A woven wire mesh conveyor fitted with cleats
transported the potatoes from the caustic peeler to the infra-red treatment
unit.  The holding time on the conveyor allowed the caustic solution to
penetrate to the desired depth.  The infra-red treatment unit consisted
of a feeder, used  to align  the  potatoes  in rows and deliver  them

to a 48 inch roller conveyor, 10 feet long, which conveyed and turned the
potatoes beneath the infra-red source.  To provide infra-red radiation
8 rows of 6 porous ceramic burners were used, each rated at 20,000 BTU
per hour, operating on natural gas.  The burners provided a temperature
of 1650F with an output of approximately 50 percent infra-red radiation.
Following the infra-red treatment the softened skin was removed in a
scrubber.  The scrubber contains twenty-three 3 inch diameter soft stud
rubber rolls, 6 feet long, rotating in planetary action at adjustable
speeds from 700 to 920 r.p.m. in a continuously rotating cylindrical
cage.  An adjustable speed inner screw conveyor controls the residence
time in the scrubber.  The peel removed by this vigorous action is thrown
by centrifugal force and collected on the inner surface of a drum sup-
ported to rotate about the rolls.  A drag conveyor installed in the drum
continuously wipes the residue to one point for collection.  After the
scrubber the potatoes were given a final brush washing.  This unit is
similar to the scrubber except that the stud rubber rolls have been
replaced by polypropylene cylinder brushes.
     The test conditions used to obtain a "normal" peel were:

     Feed rate - 5500 Ibs of raw potatoes per hour.
     Caustic treatment - 12.3% concentration, 0.8 minutes contact time,
         185F, holding belt time 9 minutes.
     Infra-red treatment - 48 burners operating at 20,000 BTU's per
         hour, effective treatment time 1.2 minutes.
     Scrubber - 1.32 minutes treatment time with rolls operating at
         772 r.p.m.
     Brusher - 1.23 minutes residence time with rolls operating at
         778 r.p.m., water rate about 4.6 g.p.m.

The process was frequently compared with the conventional caustic peeling
line.  Trim loss was taken as an indication of the effectiveness of peel
removal.  Following are the results of two tests when the peel removal
on the two lines were approximately equal, as indicated by the identical
trim losses.

                              Conventional   Pilot   Conventional
                                  Line        Line       Line
       Trim Loss       5.0%       5.0%        2.5%       2.5%

       Peel Loss      12.9%      20.4%       13.1%      22.7%

       Caustic Use*    0.18       0.63        0.18       0.63

           *Lbs of NaOH used per cwt. of raw potatoes peeled.

These results indicate a substantial reduction in peeling losses and
caustic usage with the infra-red peeler when compared to the conventional
caustic peeler.

      Three  separate waste materials were produced in  the infra-red process.
 These were  debris brushed from  the conveyor rollers in the radiation unit,
 the  scrubber sludge,  and the concentrated washer effluent.  The scrubber
 sludge was  a heavy viscous paste with a solids content of about 23 percent.
Pump tests demonstrated that the sludge could  be  pumped,  even
 at the original solids content.  When combined with the brush washer
 effluent  the solids content was reduced to about 12 to 14 percent, and this
 greatly reduced the handling problem.

      Successful operation of the infra-red peeling process would reduce
 the  total waste load  significantly.  An estimate of the reduction in
 waste load  to a secondary treatment system using both conventional and
 infra-red peeling for two hypothetical operations is shown in Table XIII.
 From this table it appears that, based on solids content, infra-red  peeling
 can reduce the waste load  by 70 percent in a  French  fry  plant.   Similarly,
 in a granule plant  the waste load  is reduced  by  50 percent.

      The  peeler developed in the Netherlands  is quite similar to the
 infra-red peeler.  The main difference is that no infra-red radiation is
 used.  The  potatoes,  after treatment by lye or steam are conveyed directly
 into a brushing machine for peel removal.  Sijbring (1968B) has reported
 operational results on the brush peeler.  Two steam peeling lines were
 operated  in parallel, one using a conventional washer for peel removal,
 the  other using the brushing unit.  The results are shown in Table XIV.
 Indications are that, with proper adjustment, water usage for brushing
 unit could  be reduced to 1 m^ per ton of potatoes.

                               TABLE XIV
                                                   Peel Removal by
                                                 Washing    Brushing
    Water consumption, m /ton                      21.7       12.1

    Pollution, pop. equiv./ton/day                190         48

    Peel Loss, percent                             17.3       19.0
    Solids removable by sedimentation, m /ton       0.890      0.130
                 By-Product Recovery from Potato Waste

     Any reduction of the amount of solids entering the waste stream will
aid in the alleviation of the waste problem.  Utilization of the recovered
solids in a manner that results in income will reduce the total cost of
waste treatment and eventually reduce the cost of the final product.

                                              TABLE XIII
                              EFFECT OF PEELING METHOD ON WASTE DISPOSAL
            Type of Plant
          Method of Peeling
 Input, Ibs/hr
 Peel Loss,  percent
 Peel Loss,  Ibs/hr
 Peeled Potatoes, Ibs/hr
 Peel Waste  Solids, Ibs/hr
 Non-Peel Waste Solids,  Ibs/hr
 Total Plant Waste Solids, Ibs/hr
 Primary Waste Recovery, Ibs/hr
 Total Waste Solids Recovery,  Ibs/hr
 Waste Solids  to Secondary,  Ibs/hr
French Fry Manufacturer
Granule Manufacturer
Lye Peel
18 (a)
326 (c)
543 (e)
13 (a)
326 (c)
163 (e)
Steam Peel
10 (b)
400 (d)
400 (e)
10 (b)
18 ,000
400 (d)
200 (e)
      (a)  Estimated year-round average, based on pilot plant observations.
      (b)  Recovery using  IR peeling assumed equal until further data available.
      (c)  Assuming 70 percent total plant loss is peeling loss.
      (d)  Assuming 50 percent total plant loss is peeling loss.
      (e)  Assuming 50 percent solids recovery in primary clarifier.
(From Willard 1969)

     All  potato  processing plants probably use screens  to remove large
 solids before  further  treatment  or disposal of their waste water.  The
 degree of removal varies  from plant to plant, as do the methods for
 handling  the solids  after removal.  In some plants the  solids are disposed
 of by one of several conventional solid waste disposal methods, while
 in others the  solids are  merely  ground to a fine slurry for return to the
 waste streams.   More and  more attention is being directed, however, towards
 producing salable by-products from the recovered solids.  The feasibility
 of by-product  recovery depends to a great extent on the size of the plant
 and  the amount of solids  recovered.

     The  part  of the potato which is wasted generally has about the same
 high food value  as the part which is processed.  Shaw (1965) has proposed
 utilization of solid waste like  pulp and particulate materials for a
 number of snack  items.  Solid waste has been used extensively as feed for
 livestock.  Depending upon the moisture content, the waste may be dried
 or mixed  with  other  feedstuffs or fed directly.  Experiments have shown
 that the  nutritional value of dried potato pulp is equivalent to corn
 when fed  to beef cattle.  (Harp  1965) (Dickey et al. 1965)

     Potatoes  are a  high  energy  carbohydrate feed with a low protein to
 carbohydrate ratio,  generally on the order of 1:10 to 1:12.  Thus,
 excessive use  of potatoes for cattle feed results in over-fattening of
 the  animals and  unnecessary wastage of carbohydrate.  In Poland, Janicki
 et al. (1965)  have tried  to overcome this problem by growing yeast on
 a potato  medium  to produce a  feed material richer in protein.  The result-
 ing  product can  be fed to the animals directly or in dehydrated form.

     A symbiotic yeast process has been developed and patented by the
 Swedish Sugar  Corporation.  (Wramstedt 1968)  Process water is screened
 and  passed through a desludger,  and the supernatant, containing about
 2 percent solids, is used to  make a growth medium for the yeast, Torula.
 The  finished product can be used as a feed additive or for human con-
 sumption.  Pilot plant results have been very promising.  Not only is a
valuable by-product  produced, but the BOD of the process water is reduced
by 80 to  90 percent.

     The protein water, or fruit water, from starch plants is difficult
 to treat because of  the high  concentration of dissolved organics.   Recovery
of proteins from this waste stream would result not only in BOD reduction
but also in yield of a valuable by-product.

     Protein may be  precipitated from the waste stream either by heating
or by acidification.  At  temperatures above 80C the protein coagulates
and settles out.   At low pH values precipitation takes place as well.
Theoretically,  the pH should be adjusted to the iso-electric point, pH 4.7.
Experiments at the University of Idaho showed that most efficient pre-
cipitation took place at pH 3.2.   No coagulation took place above pH 5.8.
 (Jackson 1962)   Heat treatment yields a more easily filterable deposit
than chemical  treatment but is more expensive.   Acidification, on the
other hand, preserves the valuable ascorbic acid present in the waste,
gives a more desirable product on drying,  and inhibits foaming during

processing.  Ascorbic acid and remaining protein can be recovered by
acid and basic ion exchange, respectively.   Protein water treated by
coagulation and ion exchange has been found to contain less than 2
percent of the solids originally present, and would not present any
pollution problem.  (Jackson 1962)  Presently, work is underway to
develop methods for extensive recovery of by-products from starch waste
at the Eastern Utilization Research and Development Division of the
USDA.  (Heisler et al. 1969)  The proposed treatment process would
consist of five steps:  (1) concentration of dilute waste by reverse
osmosis; (2) precipitation and recovery of protein by steam injection
or other suitable method; (3) separation and recovery of potassium
and other inorganic cations by ion exchange; (4) separation and
recovery of amino compounds by ion exchange; and (5) recovery of organic
acids and phosphates by ion exchange.  Promising results have been
ob tained.

     Deproteinized process water also can be used for yeast production
or alcohol fermentation, and it is more suitable for disposal by spray
irrigation than protein-rich water, since the protein tends to clog
the pores of the soil.

     The fuel value of potato wastes has been investigated by Hindin and
Dunstan (1965).  They considered anaerobic digestion and combustion and
concluded that because of the capital investments for construction of
such facilities, the use of potato solids as fuel does not appear feasible
at this time.  In the future, however, incineration and combustion units
may bring financial return.
                    Waste Separation and Combination

     Waste streams from different process steps in many cases should not
be combined.  Large savings in treatment costs may result from keeping
dilute and concentrated waste streams separate.  Dilute waste water can
often be re-used or disposed of after little or no treatment.  Also, since
the size of treatment units generally is determined by the waste volume
rather than the strength, concentrated wastes will require smaller treat-
ment units at lower capital investments.  Waste streams with extreme pH
values should be carefully considered because of their effect on biological
treatment.  The combination of acid and basic waste streams may result in
neutralization, and if possible, cooperation between adjacent industries
may be very beneficial.

                                 SECTION 6


                          Preliminary  Treatment

 Wash Water  Silt  Removal

      Removal of  silt  and  sand  resulting from washing  the raw potatoes
 is  important for several  reasons.   If the wash  water  is to be reused, the
 presence  of sand and  grit can  seriously damage  pumps  and other equipment
 through which the water might  pass.   The presence of  such inorganic
 solids in primary sludges is undesirable, since they  are not biodegradeable
 Where sludges are treated by anaerobic  digestion, for example, inorganic
 solids can  increase the total  volume  of solids  significantly since con-
 siderable dirt may be present  on raw  potatoes.   If sand and silt are not
 removed prior to disposal by spray  irrigation,  clogging of pipes and
 nozzles is  likely to  occur.

      Stones  and  gravel in flume water often are removed by sand traps.
 These are sections of increased depth in the flume where particles of
 high specific gravity settle out.   The  potatoes  are kept from settling
 by  agitating the water with compressed  air or by other means.  Stones also
 may be caught on riggles,  while  the potatoes are carried on by rapidly
 flowing water.   (Talburt  and Smith  1967)  Regular grit chambers or constant
 velocity  channels  may also be  used.  Flow velocities  of about one foot
 per second will  allow the  heavy inorganic solids to settle out, while
 the lighter  organic matter is  carried on.  (Dickinson 1965)

      Silt- laden  wash  water sometimes  is treated separately in
 shallow settling  ponds.  Usually, the settled solids do not contain enough
 organic matter to  cause serious odor problems,  and can be removed
 mechanically  during an off period, when  the pond can be drained.   (Haas
 1968) (Talburt and Smith  1967)  The organic content of the effluent
 from silt ponds is generally low (BOD of 200-300 mg/1) compared with
 overflow  from other treatment processes.  However, as secondary treatment
 plants are installed,  the silt pond effluent may contain higher BOD
 concentrations than the secondary effluent.   Additional treatment of the
 silt  pond effluents will then probably be required.    (Dostal 1968A)

     A variety of  grit removal and separation equipment is  available from
waste treatment equipment manufacturers.  One type of degritter is
 essentially a centrifuge with no moving parts.   This unit  is  very compact
 and  requires  a minimum of space.  Another type combines grit  removal,
 sedimentation, and surface skimming in a circular tank having an  aerated
 grit  chamber  in the middle.  Primary sludge and grit are discharged
separately.   Aerated grit chambers might prove beneficial when the water
 is  to be reused.

     Disposal of  sand  and silt presents no  problems  since  the material
is almost completely inert.

Main Waste Screening

     Screening is an effective and extensively used method for removing
larger solids and floating debris.  Three types of screens are in use:
fixed or stationary, rotary, and vibratory screens.

     The simplest type of stationary screen consists of a number of bars
evenly spaced across the waste channel.  The bars usually are installed at
an angle so that material retained on the screen tends to "ride up" on
the bars and thus not restrict the flow of water through the screen.  The
simplest type of bar screen is cleaned by periodically raking off the
accumulated material manually.  A variety of automatically cleaned bar
screens are available also.  The cleaning mechanism consists of a set of
rakes on a motor driven endless chain.  Cleaning may be continuous or
programmed to follow an operation schedule.  More sophisticated control
and reduced power cost are obtained by having the raking mechanism start
when the head loss across the screen reaches some predetermined value.
Cleaning by rakes limits the bar spacing to a minimum of 1/2 inch, although
3/4 inch is much more common.  Bar spacing down to 1/2 inch is possible
when the screen is cleaned by brushes.

     Removal of solids smaller than those retained on number 7 mesh is
not practical with fixed screens.  Mesh screens with openings of such
size plug easily.  Nevertheless, fixed screens, and especially bar screens,
hare proven helpful in affecting further treatment by removing large solids.
This is necessary to protect pumps and finer screens located downstream.
(Ballance 1965)

     Rotary screens also are used to a large extent, and a variety of
types are available.  The most common  type is the drum screen which con-
sists of a revolving mesh drum where waste water is fed into the middle of
the drum, and solids are retained on the peripheral mesh as the water
flows outward.  The solids  are removed by high-pressure water jets directed
against the outside of the  mesh at the top of the drum.  The solids fall
into a trough and are removed hydraulically.  The smallest practical
opening for screening waste water is about 120 mesh, but more commonly
mesh sizes 20 and 40 are used.   (Ballance 1965)

     Another type of rotary screen is  the disc screen which is a perforated
plate or wire mesh disc set at right angles to the waste stream.  The
retained solids are removed at the top of the disc by brushes or water
jets.  Mesh sizes smaller  than 20 are  impractical because of  the large
diameter disc necessary to  provide enough openings  for water passage.

     A common disadvantage  of rotary screens  is  the high moisture content
of  the screenings.  When water jets are used  to  remove  the retained
materials, the moisture content  of the screenings may be  as high as 99
percent.   (Ballance 1965)

     Vibratory screens may  have  reciprocating, orbital  or rocking motion,
or  a combination of these.  The waste  water is  fed onto the horizontal
surface of the screen, and  the water passes through while the retained

solids are bounced across the screen to a discharge point.  Vibratory
screens finer than mesh 40 are uncommon in waste treatment.  The main
advantage of this type of screen is the relatively dry screenings
produced.  The moisture content is usually about 80 percent.

     Removal efficiencies by screening will naturally vary greatly with
the type and number of screens employed and the bar spacing or mesh
sizes of the screens.  Ballance (1965) stated  that  the solids  removal by
a 20 mesh screen should not be expected to exceed 35 percent.

     The Engineering Committee of the Idaho Potato Processors Association
made a thorough investigation of the standard methods of preliminary  treat-
ment of potato wastes.  They concluded that self-cleaning rotary or
vibratory screens were effective in removing larger solids which may
cause plugging of pipes and pumps.  To prevent plugging and extremely
wet screenings it was recommended that the minimum screen opening should
be 20 mesh.  If the screen was to be followed by clarification, it was
felt that it would be better to use larger openings - from 6 mesh to
1/2 inch.  Such screens would reduce the BOD by 10 to 15 percent and
the suspended solids by about 25 percent.  (Grames and Kueneman 1968)

     Talburt and Smith (1967) have summarized waste characteristics from
several operations prior to and after screening.  Their data indicate
the following removal efficiencies:
Description of Waste Stream
Chip Plant Waste
French Fries and
Starch Waste
Caustic Peeling Waste
Screenine Removal Efficiency. %





                           Primary Treatment

     Although secondary treatment will be required by many authorities in
the near future, primary treatment will become no less important.  Secondary
treatment is more expensive, and the maximum degree of primary treatment
should be obtained to reduce the load on the secondary system.  Primary
treatment is used extensively with good results, but much can be done to
improve its performance.

Plain Sedimentation

     Because of the high concentration of settleable suspended solids in
potato wastes, sedimentation has been an effective treatment method.
Treatment facilities range from simple settling ponds to rather sophisticated
clarifiers specifically designed for potato waste.

     Settling ponds provide good removal of suspended solids  until they
become filled with solids and must be drained and dredged.  Dredging
is an expensive and odorous operation which makes the use of  clarifiers
seem more desirable.

     Conventional clarifiers are either rectangular or circular.   The
circular type is available from a number of equipment manufacturers and
is the most common.  Many workers have presented design recommendations
and expected removal efficiencies.

     Talburt and Smith (1967) report that most clarifiers are designed
for an overflow rate of 800 to 1000 gallons per day per square foot of
surface area and a depth of 10 to 12 feet.  Most of the settleable solids
will be removed from the effluent, and COD removals of 50 to  70 percent
may be expected if the plant effluent has been properly screened.
Filbert (1968) recommends similar design parameters.  Pilot plant studies
by the Engineering Committee of the Idaho Processors Association indicated
that detention times of 2 to 4 hours with overflow rates of 800 gal/day/sq ft
would give BOD removals of 50 percent.  (Kueneman 1965)  A deep sludge
blanket gave the highest solids concentration in the underflow.  With
caustic peel waste, the underflow would be about 3.5 percent solids, and
by additional conditioning and lowering of the pH, the solids content
could be 5.0 to 8.0 percent.  With steam peeling waste the underflow
could be expected  to contain 5.0 to 6.0 percent solids.

     The results from further pilot plant studies and experience from
early clarifier installations have been reported by Grames and Kueneman
(1968).  The maximum desirable overflow rate was found to be 600 gal/day/sq ft
with detention times of 2 1/2 to 3 hours.  A deep clarifier with a deep
feed well gave best settling of  the fluffy potato solids.  Side water
depths of 9 to 12  feet were used successfully, and better solids removal
was obtained when  the feed well was provided with anti-turbulence baffles
near the lower lip.  Rake mechanisms with sludge-thickening pickets
provided a combined clarifier and  thickener and produced an underflow  of
maximum solids concentration.  This is  important for  proper sludge

     Corrosion protection was found to  be another very important consid-
eration.  Bacterial decomposition  of  the settled sludge will lower  the
pH, and sometimes  it is  impossible to prevent  the pH  from dropping  to
4 or even  3,  a problem especially  for plants using  steam peeling, and
sometimes with wastes from  caustic peel plants.  Two  or  three heavy  coats
of epoxy-tar  paint were  found effective in  protecting both steel and
concrete structures submerged in the  clarifier.

     Many  investigators  have reported on  the actual  performance  of  primary
clarifiers.   Kueneman  (1965) reported suspended  solids and BOD reductions
of 93  and  70  percent, respectively in an  Idaho plant  with steam  peeling.
A plant with  lye  peeling was reported to  obtain  66  percent COD removal.
Pailthorp  and Filbert  (1965) reported 58  percent removal of  suspended
solids  and  44 percent removal of BOD  in another  lye peeling  plant.   Olsen
et al.  (1965)  studied  the  performance of  a clarifier treating waste from

 a  chip  plant  in North Dakota.   Suspended solids removal was 92 percent
 and  BOD removal was  63  percent.  Primary clarification of potato  flour
 processing waste  gave 83 percent suspended solids removal and 51  percent
 BOD  removal.  Wastes from  the J. R. Simplot Company's plants at Heyburn
 and  Burley, Idaho, are  treated  in a 100 ft diameter clarifier with an
 overflow rate of  about  800  gal/day/sq ft.  Dostal (1968B)reported 37
 percent BOD reduction for  this  unit.  Both plants are using lye peeling.
 Performance data  from Simplot's plant at Caldwell, Idaho, has been
 presented by Grames and Kueneman (1968).  The primary treatment plant
 consists of grease removal  facilities,  three rotary screens with 4-mesh
 cloth,  and a clarifier  100  ft.  in diameter with 12 ft. side water depth.
 Based on the reported flow  rate the overflow rate is about 730 gal/day/sq ft.
 Average removal efficiencies for the 1967-68 operating season were:
 COD  - 62.2%; suspended  solids - 93.5%; and settleable solids - 95.2%.

 Flocculation and  Sedimentation

     Little has been reported on flocculation of potato wastes prior to
 sedimentation.  Flocculation has been found to increase the removal
 efficiency of clarifiers markedly when  treating domestic waste as well as
 industrial waste.

     Mechanical flocculation is accomplished by gently stirring the
 waste with rotating paddles, thus causing the finely divided particles
 to coalesce into  larger floes with improved settling characteristics.
 Floes so produced are easily broken up by too rapid stirring, and the
 most efficient peripheral speed of the flocculator has been reported to
 be 1.4  ft/sec (Klein 1966).  Hurley and Lester (1949) obtained 20
 percent  increase  in clarifier removal efficiency by mechanical flocculation
 prior to sedimentation.   It has been indicated that return of some of
 the settled sludge may be beneficial in some cases (Klein 1966).

     Chemical flocculation or coagulation is used more extensively in
waste treatment.  The addition of certain chemicals to the waste followed
by gentle stirring, results in the formation of an insoluble flocculent
precipitate, which adsorbs and carries down suspended and colloidal
matter.   Chemicals commonly used include lime, aluminum sulphate,
copperas, and various ferric salts.   The cost of the chemicals makes this
method considerably more expensive than mechanical flocculation, but
higher removal efficiencies are obtained.

     In potato processing, coagulation is  used to recover protein from
the fruit water  of  the starch process, as discussed earlier.  Heating
of the protein water is  also used to coagulate and precipitate protein.

     Flocculation prior to sedimentation deserves more attention as a
treatment method for potato wastes than it has received thus far.
Experiments with oxidized lignite and other coagulants have been performed
in North Dakota with some success (Fossum 1965).


     Flotation is another solids removal method which has not been used
to any extent in potato waste treatment.

     The waste or a portion of the clarified effluent is pressurized to
40 to 60 psi in the presence of sufficient air to approach saturation.
When this air-liquid mixture is released at atmospheric pressure, minute
air bubbles are released from solution.  The rising bubbles adhere to
or are trapped by the suspended solids and sludge floes and float them
to the surface where they are skimmed off.

     The process is used by a potato processing plant in Presque Isle,
Maine, and the removal efficiency of settleable solids has been reported
to be as high as 86%.  However, since the calculations are based on a
volume per unit volume measurement (ml/1) it is difficult to compare this
result with removal efficiencies based on weight per unit volume measure-
ments.  (mg/1) (Ballance 1965)

     A pilot plant study was carried out by the Potato Products Waste
Disposal Executive Committee for the Red River Valley area of North Dakota
and Minnesota.  The flotation unit was a standard Permutit colloidair
unit with a capacity of 80 gallons per minute.  Reductions in suspended
solids of from 86 to 94 percent and BOD of from 66 to 75 percent were
obtained.  Lye peeling wastes were used.  (Francis 1962)

     The primary treatment investigations in Idaho considered flotation
as a possible method, but it was concluded that because of the expense
and operational results obtained this method was not feasible.   (Grames
and Kueneman 1968)


     Dickinson (1965) pointed out the advantages of  treating potato waste,
particularly flume and wash water, by Centrifugation.  A centrifuge
conserves space and delivers the solids  in a relatively dry state.
Furthermore, any risk of anaerobic decomposition in  settling tanks is

     The investigation carried  out in Idaho did not  find Centrifugation a
feasible replacement for conventional clarification.   (Grames and Kueneman
                           Secondary Treatment

      Secondary treatment  at  the  present is  not  being used  to any extent
 by the  potato  processing  industry.   Stricter water quality criteria in the
 future  will, however,  require  higher degrees of treatment.  Thus, the
 Idaho Department  of  Health has asked that processors now using primary
 treatment plants  be  prepared to  supplement  these with secondary treatment
 in the  future.  (Cornell, Howland,  Hayes and Merryfield 1966)

Biological Treatment

     Since biological treatment depends on the activity of microorganisms,
such treatment can be effective only when the environmental conditions
are favorable to growth.  Potato processing wastes
do not always provide a suitable environment for microorganisms.  Most
organisms are sensitive to extreme pH values, and wastes from a lye-peeling
plant thus may present problems.  Potato wastes also are generally
deficient  in two essential nutrients, nitrogen and phosphorous.  These
factors must be considered carefully in the design of any biological
treatment facility.

Activated Sludge

     No reports on large scale installations of activated sludge treatment
of potato wastes could be found in the technical literature, but several
workers have reported on pilot plant studies.

     Anderson (1961) has reported on  early activated sludge  treatment of wastes
from a plant using lye peeling.  The system, which provided for about 4
days aeration time, settling, and sludge return, could not remove more
than 50 to 60 percent COD without nutrient addition.   Batch treatment by
aeration and settling with detention times of 2 and 4 days gave COD
reductions of 49 and 82 percent, respectively, when pH was adjusted to
7.0 and nutrients were added.  The conclusions from the study were that
pH adjustment of lye peel wastes prior to activated sludge treatment is
not necessary, but addition of nitrogen and phosphorous will increase the
treatment efficiency.

     Atkins and Sproul (1964) studied the feasibility of treating the
combined wastes from a processing plant using lye peeling by the complete
mix activated sludge process.  The plant produced several types of French
fried products as well as prepeeled uncooked potatoes.

     Straight potato processing waste as well as waste adjusted to pH 8
were treated in bench scale units.  Treatment of the pH adjusted waste
at a detention time of 8 hours and mixed liquor suspended solids (MLSS)
concentration of 4000 mg/1 gave BOD removals ranging from 85 to 99 percent.
Most of the time the efficiency was above 97 percent.  Suspended solids
removal was approximately 90 percent.  The organic loading varied from
234 to 413 Ib BOD/1000 cu ft/day.  The straight potato waste (no pH
adjustment) was treated at detention times of 6 and 12 hours at a MLSS con-
centration of 4000 mg/1.  With organic loadings from 191 to 358 Ib BOD/100 cu
ft/day and 6 hours detention time, BOD removals from 96 to 99 percent were
obtained.  The COD removals ranged from 71 to 94 percent.  The suspended
solids concentration was generally reduced by more than 90 percent.  For the
12 hour detention time, organic loading ranged from 65 to 276 Ib BOD/1000 cu
ft/day.  No improvements in removal efficiency over the runs at 6 hours
detention time were observed.  It was concluded that pH adjustment of
potato wastes prior to activated sludge treatment is unnecessary, since

the production of carbon dioxide with subsequent formation of  carbonic
acid is sufficient to offset the high alkalinity and thus  reduce  the pH
of the mixed activated sludge to a tolerable level.   The unadjusted
influent waste had a pH of 11.5, while the effluent  pH had been reduced
to about 9.0.

     Based on the results reported above,  Sproul (1965) recommended the
following design criteria:

     Organic loading:  200-400 Ib BOD/1000 cu ft/day

     Mixed liquor suspended solids concentration:  3000-4000 mg/1

     Detention time:  8 hours
     No pH adjustment is necessary

     Cornell, Rowland, Hayes and Merryfield, Consulting Engineers, (1966)
have reported results of a pilot plant study for the Potato Processors
of Idaho Association.  It was found that the complete mix activated
sludge system performed best at loadings below 150 Ib BOD/1000 cu ft/day.
At a temperature of 60F BOD removals above 90 percent were obtained.  At
lower temperatures the treatment was less efficient.  This is in agreement
with Eckenfelder (1966) who has presented an equation by which a temperature
correction factor can be estimated.  Foaming was a problem with loadings
in excess of 150 Ibs BOD/1000 cu ft/day.  When  operating at this loading,
excess sludge production is high.  About one pound of biological solids
will be produced per pound of BOD removed.  Because it is difficult to
concentrate activated sludge in a clarifier beyond one percent, a large
volume of excess sludge would result, and present another disposal problem.
Treatment of one million gallons of waste with a BOD concentration of
2000 mg/1 would result in approximately 180,000 gallons of 1 percent
solids excess sludge.  This sludge can be concentrated to about 4 percent
solids in a flotation type thickener and, after chemical conditioning,
further concentrated to about 18 percent solids by centrifugation or
vacuum filtration.  This would reduce the volume of excess sludge to
10,000 gallons.  It was further pointed out in  the report that nutrient
addition and chlorination would probably be necessary  in a full scale
activated sludge plant.

     Bench scale studies on completely mixed continuous flow activated
sludge systems for French fry processing waste  and French fry waste in
combination with starch processing waste has been made by the Edward
C. Jordan Company, Engineers and Planners, Maine.   (Hunter 1969)  With
a mixed liquor concentration of  3000 mg/1 and a detention time of  7 hours,
BOD removals of 90 percent were obtained.  The  growth  rate constant,  K  ,
was found to be 0.000425.  A limited sludge production study indicated
a range of from 0.65 to 1.0 Ibs of volatile solids produced per  Ib of
BOD removed.  The lower figure was found  for the French fry waste, while
the higher value was for  the combination of French  fry and starch wastes.
The waste from the French fry plant, which used  steam peeling, had been
 settled for removal of suspended solids and about 40 percent of the BOD.

      Buzzel et al (1964)  studied the treatment  of  protein water  from
 a potato starch plant by  the complete mix activated  sludge  process.
 It was  found that protein water contains  sufficient  nitrogen  and
 phosphorous for biological treatment.  The data collected indicated
 that whenever the loading intensity was less  than  80 Ibs of BOD/day/
 1000 Ibs of suspended solids/hour of aeration,  the BOD removal would
 exceed  90 percent.   The loading in terms  of BOD/1000 cu ft  of aeration
 capacity/day would be 420.   At higher loadings  the removal  efficiency
 decreased rapidly.   Foaming was a problem and was  found to  increase
 with decreased detention  time.

      Weaver et  al.  (1953) have  reported high  removal  of COD from protein
 water.   The waste was  aerated vigorously  at 30C with  12 hours detention
 time.  With an  initial COD  of 4050  mg/L the removal  efficiency was 79

      At  the time  this  report was  prepared a full-scale complete mix
 activated sludge  plant was  started  up at  the  Pillsbury Company's processing
 plant at Grafton, North Dakota.   (Michaelson  1969)   The design loading
 was  400  Ibs  BOD/1000 cu ft/day with  a detention time of 5 hours.  A
 sludge thickener  designed for a  solids  loading of  8  Ibs/sq ft/day was
 included.   The  effluent from the  treatment facilities, which was expected
 to have  a BOD concentration of  200-400 mg/L, was to be discharged to
 the  Grand Forks municipal sewer  for  final lagoon treatment before discharge
 into  the Red River of  the North.

      Atkins  and Sproul  (1964) also  investigated the possibility of using
 the  contact  stabilization process.  With a contact time of one hour and
 reaeration  time of 6 to 8 hours,  80 percent of the BOD was removed.  The
 results were obtained  in a batch  unit at a mixed liquor suspended solids
 concentration of 4000 mg/L and with  the pH of the waste adjusted to 8.0.

      Based on these experiments Sproul  (1965)  presented the following
 tentative design recommendations:

      Contact time = 60 min.

      Reaeration time = 6-8 hours
     Mixed liquor suspended solids =  3000-4000 mg/L

      Some pH adjustment by acid may be necessary, but wastes with pH
values of 9.0 to 9.5 could probably be handled successfully.

     The pilot plant study by Cornell, Howland,  Hayes and Merryfield
 (1966) also included contact stabilization.  It  was found that the
process was capable of about 60 percent BOD removal at loadings  up to
480 Ibs BOD/1000  cu ft/day, when  operated at  a contact  time
of one hour and a reaeration time of 10 hours.  Reducing the reaeration
time  to 6 hours caused a decrease in removal efficiency to about 50
percent.   The results were obtained at a temperature  of 70F.   Foaming
in the contact basin was a problem.  It was stated that nutrient addition
probably would be required in a full scale plant.  Excess biological

solids produced by contact stabilization treatment amounted to about
1.3 pounds per pound of BOD removed, and possessed the same characteristics
as sludge produced in the complete mix process.

     Kintzel (1964) has reported on laboratory treatment of potato starch
waste water by contact stabilization.  Seventy percent BOD removal was
obtained after a contact time of 5 minutes.  The removal increased to 90
percent after 30 minutes.  The whole process had a combined detention
time of 2.5 hours.

     Pasveer (1965) has found the oxidation ditch effective for treating
domestic waste as well as industrial wastes.  The oxidation ditch is a
modification of the activated sludge process, similar to the extended
aeration process.  The ditch is simple to construct, and the most common
form is a ring-shaped circuit or ditch.  Aeration and circulation in the
ditch are provided by one or more partially submerged rotors.  The ditch
can be loaded at up to 34 Ibs BOD/1000 cu ft/day and still provide
essentially complete oxidation of the waste.

Biological Filtration

     A considerable amount of pilot plant work has been done on the
application of trickling filters for secondary treatment of potato
wastes.  The most recent investigations have employed artificial filter
media, which have proven superior to the stone media used earlier.

     Buzzel et al. (1964) studied the treatment of protein water by
standard and high rate biological filters using rock media.  The standard
filter gave BOD reductions of 90 percent and above at loadings up to 1300
Ibs BOD/acre ft/day (30 Ibs BOD/1000 cu ft/day).  The hydraulic loading
rate was rather low because of the high BOD of the protein water.  Large
reductions in acidity were obtained at all loadings.  The effluent
alkalinity was reduced over the influent but generally increased in
response to the organic loading to values on the order of 200 to 300 mg/1.
The pH of the effluent was generally between 7 and 8.

     With the high rate filter, BOD reductions of 90 percent and above
were obtained at organic loadings up to 3000 Ibs BOD/acre ft/day (69 Ibs
BOD/1000 cu ft/day).  The recirculation rate was 10.  At higher loadings
the filter became clogged with sloughed biological solids.  Since the
filter media consisted of rather small rocks, of 3/4 inch diameter, it
was felt that the practical upper limit of organic loading was not
reached in the study.  A full scale filter with larger rocks, and thus
larger interstices, would permit the passage of a greater amount of
sloughed material without clogging.

     Pailthorp and Filbert  (1965) reported  results  of  a pilot plant
study for the Potato Processors of  Idaho.  The pilot unit used  a
synthetic media, Surfpac, which is  a polystyrene plastic media made by
the Dow Chemical Company.  The unit was classified as a super-rate
filter, and was operated with a recycle ratio of 6.  At an  organic  loading
of 132 Ibs  BOD/1000 cu  ft/day the  BOD reductions were  71 percent with

no settling and  85 percent with settling.  No nutrients were added to
the waste before treatment.  The  influent pH was about 9.0.

     Cornell, Howland, Hayes and  Merryfield (1966) have reported on
further studies  with  the  same  pilot plant.  It was found that the Surfpac
unit operated most satisfactorily at a BOD loading of about 400 lbs/1000
cu ft/day; the filter appeared capable of removing 300 Ibs.  Although
the recycle ratio was varied during the course of the study, no valid
relationship could be established between percent BOD removal and recycle
rate.  It was recommended that full scale installations be designed for
a minimum recycle ratio of 3 with provisions to permit increasing the
ratio  to 7.  Addition of nutrients was found to be advantageous.  It
was not found necessary to adjust the pH of lye peel process water.
Treatment of steam peel wastes may require addition of an alkaline
substance when the loading exceeds 400 Ibs BOD/1000 cu ft/day, to prevent
the pH of the system  from dropping below 6.3 to 6.5.  Excess solids
production was found  to be on  the order of 0.6 to 0.8 Ibs per pound of
BOD removed when operating at  loadings around 400 Ibs BOD/1000 cu ft/day.
This sludge could be  concentrated to about 3 percent solids by gravity
and further concentrated by flotation.  One million gallons of waste with
a BOD  of 2000 mg/1 would yield 5000 gallons of 18 percent solids excess
sludge.  It was  further stated that chlorination of the effluent would
most likely be required to meet state requirements on coliform counts.

     Mercer et al. (1964) used a  Surfpac pilot plant for secondary
treatment of peach and pear canning waste.  The influent and effluent
samples were settled  for 15 minutes to simulate primary and secondary
clarification.   The raw waste  had a pH of 10.5, and the effluent pH was
6.2.   The results of  the study is presented in the following table:

                               TABLE XV

              2         "~   -~                     -
  Flow, gpm/ft        BOD, mg/1        BOD, Ibs/1000ft /day    Percent

   Raw  Recycle  Influent  Effluent    Loading  Removal    BOD Removal
    Nutrients added (20 Ibs diammonium phosphate per 24 hours)

     Norman et al. (1965) compared the use of the activated sludge process
and the plastic media trickling filter as roughing treatment for beet
sugar waste.  Overloading the activated sludge unit to obtain only 50

percent BOD removal caused the formation of bulking sludge,  and it was
concluded that this process was not feasible for such treatment.   The
trickling filter gave BOD removals of between 33 and 50 percent on once
through passes at loadings of 400 to 230 Ibs BOD/1000 cu ft/day.

     Sak (1967) has reported operating results from full scale installations
as well as pilot plants employing Surfpac media to treat a variety of
industrial wastes.

     Hatfield et al. (1956) treated corn processing waste by super rate
biofiltration in a two stage filter system.  An artificial filter media,
"Aero Block," consisting of clay blocks with vertical openings of 1 inch
diameter and made by the Red Wing Sewer Pipe Corporation was used in the
filter.  The BOD of the waste ranged from 500 to 2000 mg/l with an average
of about 900 mg/l.  The pH of the waste, which was predominately acid,  was
adjusted to between 6.5 and 8.5 with soda ash.  Nitrogen and phosphorous
were added to the waste prior to treatment to give ratios to BOD of 1 to
20 and 1 to 75, respectively.  At BOD loadings up to 150 lbs/1000 cu ft/day
and a recycle ratio of 10, BOD removals above 94 percent were obtained.
Similar removals were obtained with BOD loads up to 110 lbs/1000 cu ft/day
when the recycle ratio was 5.

The Anaerobic Filter

     The anaerobic filter offers promise as a prospective treatment
facility for certain potato processing wastes.  While conventional
anaerobic digestion is limited to wastes of high strength and solids
content at relatively high temperatures, the anaerobic filter has performed
well at nominal temperatures with relatively dilute, soluble wastes.

     The anaerobic filter, which is similar to  the aerobic trickling filter
in appearance, has upward flow so that  the rock media is  completely sub-
merged.  The anaerobic organisms are attached to the stones as well as
suspended as discrete particles in  the  interstitial spaces.  High solids
retention time  (SRT), which is an important operational parameter in
anaerobic treatment, is  easily obtained in the  anaerobic  filter, and is
on the order of hundreds of days  (Carlson  1968B). A gradual accumulation
of solids may  take place to  the point where solids wasting may be

     Recent studies have indicated  the  feasibility of  the anaerobic filter.
Young  and McCarty  (1968) obtained BOD removals  ranging  from 60 to 99
percent when  treating either  simple volatile  acids or  complex protein  -
carbohydrate wastes.  The BOD concentration of  the wastes ranged from
500 to 8000 mg/l,  and the  filter was  loaded up  to  150  Ibs BOD/1000 cu  ft/day
at a temperature  of  25C.  The treatment efficiency was  found to be
inversely proportional  to  the hydraulic detention  time, which was varied
from 4.5  to 72 hours.   The  filter  could be operated  from several months to
years without  requiring solids wasting, and the effluent  suspended solids
concentration  was  sufficiently low  so  that subsequent  settling was  not
required.  Shock  loadings  did not  appear to have adverse effects,  as the
filter recovered  very rapidly.   Some  possible limitations mentioned were:

 (a)  The filter is  best suited for treating completely  soluble wastes,
 (b)  a significant  fraction of carbohydrates in the waste  may require
 solids wasting,  and (c)  hydrogen sulfide  produced  from sulfate  reduction
 may  cause odor nuisances,  corrosion problems,  and  may  be  toxic  to
 anaerobic treatment.

      Caudill (1968) studied the treatment of dilute  wastes  by the  anaerobic
 filter.  Soluble,  synthetic sewage with a COD of  300 mg/1 was treated  at
 26 and 37C, and removal efficiencies  of  67 and 80 percent  were obtained,
 respectively.   Potato starch waste with a COD of  300 mg/1 was treated  at
 37C.   Removal efficiencies of 76 percent was  obtained with this waste.
 The  theoretical hydraulic detention time  for these wastes was 1.64 days
 and  the loading was 5.1 Ibs COD/1000 cu ft/day.   Treatment  of a more
 concentrated starch waste (COD of 1000 mg/1) gave  COD  reductions of 78
 percent at 30C.  It was found that most  of the COD  removal took place in
 the  first 10 inches of the 6 inch diameter column  used in the study.
 Also,  most of  the  microorganisms were  found suspended  in  the liquid
 rather than attached to the rock media.

      Webster and Carlson (1968) used the  anaerobic filter for treatment
 of pulp mill sulfite waste liquors. The  temperature was  held at 110F
 and  the initial BOD was  about 30,000 mg/1.   At detention  times  of  about
 4 days and recycle rates of 8:1, BOD reductions up to  90  percent were
 obtained.   The COD removal was about 25 percent.   High gas  production
 was  experienced.  The gas  consisted mainly of  methane  and hydrogen sulfide.
 Odor control by soil columns was suggested.

     Extensive pilot  plant  studies  for the Potato  Processors of  Idaho
 Association  on  the  application  of  anaerobic  filters  to  potato processing
 waste  were completed  recently by Cornell, Rowland, Hayes  and Merryfield
 (1969).  Two 5-foot diameter  filter  units were tested,  one with  a  4-foot
 rock media depth and  the other with  an 8-foot depth.    The pilot  plant
 feed consisted of primary  treated  process water from the  J.  R.  Simplot
 Company's Heyburn and Burley plants.  This is a combined waste from lye
 peeling operations, potato  processing,  and potato  starch  production.  The
 pH of  the primary treated waste varied with  the operation of the clarifier
 from about 7.5 to about 11.0 with  a median value of  10.2.   Average
 organic removals of almost  70 percent were obtained at  loadings of 100 Ibs
 COD/1000 cu  ft/day.  This corresponds to a BOD loading  of 57 lbs/1000 cu
 ft/day, according to  the average COD/BOD ratio determined.  Average total
 suspended solids removal at this loading was about 60 percent.   Almost
 identical treatment efficiencies were obtained in both  filters.   The
 average temperature of the  filter  influent was 25C,  while  the effluent
was  at  a slightly lower temperature.  It was estimated  that  a full-scale
 installation would operate  at approximately  20C.   Only occasional
 additions of alkalinity in  the form  of sodium bicarbonate were necessary
 to adjust the pH in the feed to  the  filters.  It was  expected that
 alkalinity addition would not be required when operating  the filter under
 stable  conditions on potato processing waste, including wet  lye peeler
discharge.  The  gas produced in  the  filter had a methane content of more
 than 70 percent.  This gas  is combustible, and, in a full-scale plant,
 could be used for energy production.

     The organic removal efficiencies of both filters were found to
increase over the test period without regard to loading,  temperature,
or detention time, indicating that the anaerobic bacteria were continuing
to build and becoming further acclimated as the test progressed.  It
was expected that the acclimation period, from start-up until efficient
operation is experienced might take two to three weeks.  During start-up,
alkalinity should be added to act as a buffer against pH drop from volatile
acids production, and fresh anaerobic seed should be added to provide the
system with methane bacteria.  The effluent from an anaerobic filter
should be passed through a short-term, flow-through aeration basin to
provide additional organic removal and render the effluent suitable for
discharge to a receiving stream.  With primary treatment, this system
appears capable of 90 percent BOD removal.


     Pond treatment of domestic sewage as well as industrial wastes is
common around the world, and there are several reports of application of
this treatment method to potato processing wastes on a pilot plant basis
and in full scale ponds.  Ponds are often designated by various names,
such as lagoons, oxidation ponds, stabilization ponds, and waste conversion
ponds.  Dugan and Oswald (1968) classified the different types of ponds
as follows:

     Aerobic ponds - 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.
     Facultative ponds - Ponds in which  an aerobic zone exists  in the
                     surface strata and  an anaerobic zone exists in
                     the lower strata.
     Anaerobic ponds - Ponds in which  the anaerobic  reactions below
                     the oxypause are  the predominant  ones.

     The aerated  lagoon is a fourth  type, where oxygen is supplied by
diffused or mechanical aeration systems, which also  cause sufficient mixing
to induce a significant amount of surface aeration.

Aerobic and Facultative Ponds

     Aerobic and  facultative ponds depend upon  the  photosynthetic  capa-
bilities of algae  to provide  the oxygen required  to  satisfy  the BOD
applied.  Some  surface  aeration  from wind action  also  occurs.   Since
sunlight is essential  for  algae,  the depth  of the ponds  is limited.  In
aerobic ponds  the waste material  is  stabilized wholly  through  aerobic
oxidation.  The depth  is  therefore  limited  to that  through which  sunlight
will penetrate.   For most  wastes  this  will  not  exceed  18 inches.   (Eckenfelder
1966)  Extremely  large  surface  areas are therefore  required.  Most existing
ponds are facultative.  In facultative ponds, settled solids undergo
anaerobic decomposition in the  bottom layers, while aerobic  oxidation

 takes place in the upper layers.  Serious odor problems will not develop
 if  adequate depth is maintained and an upper aerobic environment is
 predominant.  The depth of  facultative ponds is seldom greater than
 5 feet.

     Since both aerobic and facultative ponds are highly dependent upon
 algal photosynthesis, the environmental factors affecting the growth
 rate of algae must be considered carefully in pond design.  Gloyna (1968)
 has presented design criteria for the various classifications of ponds.

     Cornell, Rowland, Hayes and Merryfield (1966) carried out studies
 on  3 foot deep pilot size ponds.  It was found that the BOD loading to
 the ponds should be kept well below 80 Ibs per acre per day.  This is
 within the conventional loading range and it was concluded that aerobic
 ponds for potato waste be designed according to the criteria used for
 domestic sewage ponds.

     Forges (1963) made a survey of industrial waste ponds in the United
 States in 1962.  He reported three ponds treating potato processing
 waste.  The median loading to these ponds was 111 Ibs BOD/acre/day, and
 the median detention time was 105 days.  The ponds had an average depth
 of 5 feet.  No BOD removal efficiencies were reported, but one of the
 installations was reported effective while another caused odor nuisances.

     Possum et al. (1964) presented data collected over a 40-month period
 on the operating characteristics of two ponds for the municipalities of
 Park River and Grafton in northern North Dakota.  Both ponds had been
 heavily overloaded by potato processing wastes during the processing
 season.  The ponds were ice covered during the winter and acted merely as
 storage ponds during this period.  The accumulated organic load had to
 be stabilized during the summer months.  It was found that potato pro-
 cessing wastes combined with domestic sewage digest readily in these
 ponds, when the organic loading from potato wastes was 15 times or more
 the organic loading from domestic sewage.  Digestion may be aerobic or
 anaerobic.  Anaerobic digestion in these shallow ponds caused severe
 odors.  During summer conditions, potato waste and domestic sewage could
 be applied at rates well above the conventional design loading for
 northern climates of 20 Ibs BOD/acre/day.  Although no specific loading
 recommendations could be made from the study because of the "diametrically
 opposed" operating season for the processing plant and the pond, it was
 indicated that loadings on the order of 50 to 60 Ibs BOD/acre/day might be
 possible.   The ponds remained aerobic until the BOD in the ponds exceeded
 200 mg/1.   Once anaerobic conditions were established, the ponds did  not
 convert back to aerobic operation until the BOD fell below 100 mg/1.

     One reason for the extended anaerobic period was found to be the
wave damping effect of potato organics, reducing surface reaeration.
Although the ponds have been subject to serious complaints because of the
 odors produced, they carried loadings far above what might have been
 expected possible, and certainly much higher than their design loading.

     Olson et al.  (1965)  have commented  further on the over  loading of
the Grafton ponds.   The increased loading of  the ponds presented  the
problem of growth  of the  purple sulphur  bacterium, Chromatium.  Due to
the extended anaerobic period, the Chromatium was  selected  out by the
pond.  This photosynthetic organism utilizes  the hydrogen sulfide
released from anaerobic decomposition in the  pond.  It was observed that
BOD removal from the pond was about the  same  during the growth  of the
sulphur bacteria as during the later period of algal growth, but  the
purple color from the photosynthetic pigments of the bacterium  gives
the lagoon a purple color.  The pigmentation  and anaerobic nature of
the Chromatium prevent the growth of algae.  It thus seems that the
growth of purple sulphur bacteria could  be a  good indicator  of  an over-
loaded pond.

     Voege and Stanley (1963) have reported on the use of industrial
waste stabilization ponds in Canada.  A cannery in Vancouver, B.C.,
processing peas and beans, used 4 ponds  in series, with depths  varying
from 2 to 5 feet.   The influent was passed over a 20-step aeration
deck along with recycled effluent.  The temperature of the waste  varied
between 57 and 72F, and the pH was controlled between 6.5 and  8  by
adding lime at the aeration deck.  Assuming no substantial removal on
the aeration deck, the BOD loading was about  1400 Ibs/acre/day  and the
removal efficiency about 87 percent.  The effluent had a bright green
color and a BOD of about 100 mgA  It was finally discharged to  spray
irrigation fields.

Anaerobic Ponds

     Although anaerobic ponds have been used  quite extensively for
treatment of food processing waste, they have not been used with much
success by the potato processors.  Forges  (1963) reported that, in 1962,
3 anaerobic ponds were used in the United  States for treatment of
potato wastes.  No information was given on the efficiency of these
ponds, but it was reported that odor nuisances were associated with one
of them.

     Other industrial wastes have been  treated successfully with anaerobic
ponds.  Howe and Miller  (1963) used an  anaerobic pond  to  treat wastes
from a chemical and fermentation  products  plant.  With a  BOD loading of
2.6  lbs/1000 cu ft/day a removal  efficiency of 60 percent was obtained
at a temperature of 5C.  At a temperature of  15C  the removal efficiency
increased  to 78 percent.  To obtain this efficiency it was necessary to
adjust the pH  to 6.8  to  7.2.  Nitrate was  added  to prevent  formation of
hydrogen sulfide.
     Mclntosh  and McGeorge  (1964) had some success with a full scale
anaerobic  pond receiving corn processing waste.   The  pond was  loaded at
about  40 Ibs BOD/1000 cu ft/day with sludge  recirculation from the  end
to the inlet of the pond.  After  about  40  percent of  the  surface area  of  the
pond was covered with a  Styrofoam raft, the  BOD  removal was  found to
increase  from  32 percent to  40 percent. The pond influent  was at a
temperature of 91  to  114F,  and  this high  temperature undoubtedly improved

 the performance  of  the  system.   Nitrate was  added  for  odor control,  and
 the pH was  adjusted to  between  9 and  11 with caustic soda.

      Research  efforts on  potato waste  treatment  indicate  that anaerobic
 ponds  can be used advantageously to condition the  waste for  further
 treatment by aerobic means.

      Dostal (1968B)  has reported results  of  pilot  plant studies at Burley,
 Idaho.   Two Styrofoam covered anaerobic ponds were first  operated in
 parallel.   Pond  1,  with a detention time  of  4 days, was loaded at 23 Ibs
 BOD/1000 cu ft/day,  and gave BOD removals of 17  percent.  Pond 2 had
 a  detention time of 20  days and was loaded at 4.6  Ibs  BOD/1000 cu ft/day.
 A  BOD  reduction  of  22 percent was obtained.   Suspended solids reductions
 were  56  and 62 percent  for Pond 1 and  2,  respectively.   The ponds were
 not mixed,  and the  temperature  ranged  from 60 to  70F.

     During the  second  period of operation the ponds were operated in
 series.  The first  pond continued to operate as  an anaerobic pond, and
 a  pump was  installed to mix the contents.  A 5 hp  floating surface
 aerator  was installed in  the second pond  which consequently operated as
 a  mechanically aerated  pond.  The performance of the system under
 different operating "conditions  has been summarized  below.

                    Detention Time,BOD loadingRemoval - %
                          Days       lbs/1000 cuft/day  SS	COD   BOD
Anaerobic pond 8.8
Aerated pond 8.8
Anaerobic pond 5
Aerated pond 5
Anaerobic pond 2.4
Aerated pond 2.4



     These results indicate excellent removals by the combination
anaerobic-aerated ponds.  It should be pointed out that the removal
efficiencies were based on effluents with all solids remaining.

     Continuing studies on the same pilot plant for the Potato Processors
of Idaho Association have been reported by Cornell, Rowland, Hayes and
Merryfield (1966).  The results from the anaerobic ponds were not con-
clusive with respect to design criteria, but valuable information was
obtained.  The ponds appeared to take the waste through the first stage
of anaerobic digestion, breaking down large molecules such as starch
and protein into smaller molecules of organic acids, aldehydes, and

alcohols.  This results in a rather small BOD reduction,  but  yields  an
effluent which is more amenable to aerobic treatment.   Nutrient  addition
did not appear necessary.   It was indicated that it would not be
advisable to design anaerobic ponds at detention times  less  than 4 days
due to the high rate of solids buildup.  A pond with a  4  day  detention
time may possibly be operated for four seasons before cleaning is
necessary, while a pond operating at a one day detention  time probably
would have to be cleaned annually.

     The effluent from one anaerobic pond was treated in  a flow through
aeration basin.  When operated at a loading of 130 Ibs  BOD/1000 cu ft/day
and a detention time of 22 hours, additional BOD removal  of 57.5 percent
was obtained.  Limited data was collected at a detention  time of 11
hours, which showed similar removal efficiency.  Suspended solids in the
effluent were measured in amounts up to 1.2 Ibs per lb  of BOD removed,
and consisted of dispersed bacteria, which could not be settled out  at
normal detention times.  Nutrient addition was not necessary, but foaming
was a problem, and it was recommended that provisions for defoaming agent
addition be included in full scale design.

     Results from continued studies on the Burley pilot plant were
reported recently (Cornell, Rowland, Hayes and Merryfield, 1969).  The
two covered anaerobic ponds were operated in parallel,   one as a straight
flow-through pond, the other as a mixed pond.  The effluent from the
mixed pond was passed through  the aerated pond.  The flow-through pond
obtained BOD removals of about 40 percent at  a loading of approximately
7  Ibs BOD/1000 cu ft/day.  The effluent volatile acids concentration
was much higher  than  the influent because of  incomplete biological
degradation in the pond.  The  continuously mixed pond performed much
better  than the  flow-through pond.  Average organic removal efficiencies
of more  than  70  percent were obtained  at  loadings  of about 8  Ibs BOD/1000
cu ft/day.  The  more  complete  biodegradation  also  resulted in much  lower
volatile acids and suspended solids concentrations  in the effluent.

     The aerated pond was effective in further  reducing  the organic
content of the anaerobic process  effluent.  Organic removals  of almost
40 percent were  obtained at a  loading  of  about  4  Ibs BOD/1000 cu  ft/day.

     It was stated  that alkalinity  in  the influent, such  as  that  derived
from the wet  lye peel process, would be  required  in anaerobic pond
applications.  The  problems  associated with  inefficient  operation
during  start-up  of  the  system, offensive odors  from the  pond  unless
covered,  and  the lack of operational  control  were  emphasized.

     Olson  et al.  (1965)  conducted pilot plant studies on combined
anaerobic -  aerobic treatment.   Two days of  anaerobic  fermentation  gave
solids  and  BOD reductions  of  30  and 22 percent,  respectively.  When the
effluent was  aerated for  4 and 6 days, the combined system yielded  BOD
reductions  of 85 and 90 percent, respectively.   Total  solids reductions
through the system were 52 and 54 percent.   Future work  was  proposed
on a bi-level pond,  where  a suspended air-aqua tube separates the two

 Aerated  Lagoons

      Some  information  on  aerated  lagoons has  already been presented in
 the  review of  the  anaerobic  -  aerated pond systems.  However, these
 aerated  lagoons  are  treating waste which has  already been "conditioned,"
 and  which  appears  to be more amenable  to aerobic  treatment.

      Olson and Vennes  (1963) reported the results of mechanical aeration
 of potato  processing waste and domestic sewage at Park River, North
 Dakota.  A one acre  experimental  aerated lagoon was constructed to
 pretreat the waste prior  to  treatment in primary and secondary facultative
 ponds.   During the first  6 months of operation only domestic sewage was
 treated.   The  average  BOD loading during this period was approximately
 380  Ibs/acre/day with  a detention time of 14 days.  This gave BOD removals
 of 85 percent  or more  even at  temperatures close to 0C.  The average
 pH of the  sewage was 7.8.

      A later operation  using equal volumes of potato waste waters and
 domestic sewage  resulted  in  a waste mixture with a pH of 11.6.  Under this
 loading  the aerated  lagoon pH gradually shifted to 11.3.  Neutralization
 was  not  feasible because  laboratory studies indicated at least 70 ml of
 concentrated sulfuric  acid would  be needed per 100 ml of waste.  While
 BOD  loadings were almost  3000 Ib/acre/day at a 6 day detention time,
 the  decrease of  BOD  removal  efficiency to 25% was attributed to the high
 pH.   It  was evident  that  the aerated lagoon was limited in its ability
 to reduce  the  pH of  the mixed waste, and some form of pH control would
 be required for  this lagoon  to be effective as a pretreatment unit.  It
 was  suggested  that recirculation  from the primary pond might provide the
 necessary  buffering.   In-plant pH control was also suggested.  The use
 of steam peeling rather than lye  peeling will provide a waste with a pH
 more suitable  for biological treatment.

      Olson et  al. (1964)  also have described the results of installing
 an aerator in  one of the  two ponds at Grafton, North Dakota.  These
 ponds are  ice  covered in  the winter, and stabilization of the organic
 matter takes place in the summer.  Anaerobic conditions prevailed
 during a large part of  the stabilization period, and odors have been a
 problem.   Aeration was  found to shorten the anaerobic period considerably,
 and  although insufficient oxygen was supplied for complete stabilization
 of the organic matter,  the purple sulfur bacteria were removed much
 easier and an  active algal population was restored.   It was indicated
 that by keeping  the pond open during the winter months it might be
 possible to maintain the algal population throughout the year.

     Other industrial wastes have been treated successfully in aerated
 lagoons.   Dostal (1968C) reported results from the operation of a lagoon
 treating pea processing waste in Washington.   The pond which had a surface
 area of  1.75 acres, an  average depth of 10 feet, and a volume of about
 5.6 million gallons, provided a detention time of 5.5 days.  Oxygen
was supplied by  four 50 horsepower surface aerators.  The effluent from
 the aeration basin flowed into a smaller polishing pond.  Recirculation
 of settled solids from  the polishing pond back to the aerated pond was

intended, but this practice was never initiated.   According to values
reported the BOD loading to the aerated pond ranged from 3000-4400
Ibs/acre/day (7.0 to 10.3  lbs/1000 cu ft/day).   The influent temperature
ranged from 17C to 30C with a pH range from 6.7 to 8.2.   An average
BOD removal of 76 percent was obtained, while total solids  were reduced
by 20 percent.  Suspended solids were found to increase by  70 percent
through the lagoon.  The polishing pond had little effect  on the degree
of treatment as it   readily   filled with solids.  Bulking sludge was
a problem and was thought to be due to the seasonal operation of the
processing plant.  Improved operation of the lagoon prior  to processing
was expected to better the condition of the sludge.  Recirculation of
settled solids would improve the removal efficiencies of the system.

     Butler and Burns (1968) presented operational data from a lagoon
treating unbleached kraft pulp mill effluent in Pennsylvania.  Two
aeration basins in series, designed for a detention time of 1.5 days
each, were followed by a settling basin with 9 hours detention time.
The design loading was 5 Ibs BOD/1000 cu ft/day.   Three 20 horsepower
surface aerators were installed in each aeration basin, and underflow
from the settling pond was recirculated back to the inlet of the aeration
basin.  Average BOD removal during the first year of operation was 85
percent.  This was obtained with a loading of 4.2 Ibs BOD/1000 cu ft/day
and a detention time of 3.72 days.  The effect of seasonal temperature
fluctuations was reported.  During the summer, fall, and winter, when
the average temperatures were  30C, 25C, and 18C, respectively, the
BOD removals were 88%, 83.7%,  and 81 percent.  Nutrients in  the form of
30% aqua ammonia and 70% phosphoric acid were added to give BOD:N:P
ratios of 240:3:1.  These high ratios made the addition of a defoaming
agent necessary.
                            Spray Irrigation

      Spray irrigation has been used successfully by many processors as
a method of final disposal of waste water from fruit and vegetable
processing.  Successful operation of spray irrigation fields is dependent
on  the  capacity  of  the receiving site to absorb the waste water.  Among
the variables influencing soil receiving capacity are type of soil,
stratification of soil profile, depth to ground water, initial moisture
content, and cover  crop.  Waste water characteristics also are important.

      General design criteria or recommendations cannot be stated  for
spray irrigation because of the variables involved, and most systems
must  be designed with considerable  flexibility.  Results and recommendations
from  some successful applications of spray irrigation will be presented.

      Szebiotko  (1965) reported that agricultural use of the effluents
from  potato starch  plants was  found to  be the most effective and  economical
method  of disposal  in Poland.  It was calculated that one million gallons
of  effluent is  sufficient to irrigate about  3.5 acres of grassland.   The
effluent, which  has a very high  fertilization value,  is  free of  substances
harmful to soil  and plants.  Spray  irrigation was  found most effective

when used on grassland, and  the optimum annual dose was reported to be
from 200 to 500 mm  (8 to 20  inches).  With high doses (800 to 1000 mm
per year) the grass plants disappeared after 2 to 3 years, and nettles,
which  tolerate higher doses  of nitrogen, appeared.

     Adler (1965) reported spray irrigation to be the best and most
economical method for disposal of potato starch processing waste water
in Germany.  One plant was reported to produce from 90 to 130 million
gallons of dilute potato "fruit" water during the 90 days of operation.
The water was sprayed on an  area of 620 acres, which corresponds to a
loading of 145,000 to 210,000 gallons per acre.  A three-year rotation
program was used, so that a  total area of 1860 acres was required.  The
importance of soil characteristics and fertilizer value of the waste

     Successful spray irrigation of effluents from fruit and vegetable
canneries in Britain has been reported by Dickinson (1965).  A small
producer of pre-peeled, packed potatoes sprayed a volume of 14,000
gallons per day on an area of 1 acre.  The effluent had a BOD of 3600 mg/1
a suspended solids concentration of 1300 mg/1, and a pH of 11.8.  A 7-day
rotation program was used, requiring a total land area of 7 acres.

     Rose (1965) presented recommendations regarding application rates and
cover crops.  For different  soil types and drainage conditions the
following application rates were recommended:   (from Maryland Processors'
Report, Vol. 11, No. 12, March 1965)
              Soil Type          Drainage^     Inches per Hour

           Galestown S. L.      Excessive           1.0

           Sassafrass L. S.        Well             0.6

           Matapeake Silt          Well             0.4

           Keyport Silt         Mod. Well           0.3
           Elkton Silt            Poorly            0.2

           Bayboro Silt        Very Poorly          0.2

     Without adequate vegetation excessive soil erosion or surface run-
off will occur.  It has been reported that, without cover crop, the
amount of liquid taken up by the soil will be only 10 to 15 percent of
the amount which can be absorbed by a field with a cover crop.  A cover
crop mixture which has proven to be satisfactory over a wide range of
soils and operating conditions is as follows:
    Ladino  clover - 1 Ib/acre

    Aisike  clover - 4 to 6 Ibs/acre

     Reed canary   - 6 to 8 Ibs/acre

     Haas (1968)  reported on successful spray Irrigation of  potato
processing wastes at Moses Lake,  Washington.   A spray field  of about
120 acres covered with a mixture  of grasses and alfalfa was  used.   The
cover crop was cut, cured, and baled twice per year,  but it  was pointed
out that this probably should be  done more often.   A preliminary survey
showed the soil to be loam with 2 to 4 feet of top soil followed by a
broken layer of caliche and gravel about one foot  thick with sand below.
A compacted clay mixture with sand was found 6 to  7 feet below the
surface.  The water table was, in one place,  found to be 6 to 7 feet
down. The waste  consisted of  fluming water and primary wash water as well
as process water.  Prior to disposal, larger solids were removed on a
20-mesh vibrating screen, and silt was removed in  a settling basin.  The
total flow to the spray field was about 840 gpm.  This corresponds  to
an application rate of 0.35 inches per day or 100  inches per year.   A
ten-day rotation program was used.  The spray field received between
5 and 6 million pounds of organic solids per season.

     Drake and Bieri (1951) reported on spray irrigation of  vegetable
canning wastes at several plants  in Minnesota.  One plant, processing
peas and corn, reported successful disposal of an estimated  16 million
gallons to a 72 acre annually cropped field.   The  waste was  passed
through a 20-mesh rotary screen before being pumped to the spray field.
The soil was a silty loam underlain with clay.

     Another cannery, also processing peas and corn, experimented with
spray irrigation of lagooned waste mixed with fresh waste.  The soil in
this area was a heavy-black loam underlain with clay.  The average
application rate was one half inch per day and the rotation cycle took
8 days.  When the lagooned wastes were sprayed, objectionable odors
occurred.  This was not noticeable when fresh wastes were sprayed.
Similar problems occurred at  another plant employing a storage lagoon
during part of the processing season.  The odors at  this plant did not
appear to be as  serious, probably because of  the more suitable sandy

     Luley (1963) reported results of an unusual application of spray
irrigation for disposal of tomato, peach and  apple processing wastes.
The land area used had a slope varying from 2 to 12  percent.  The soil
was a silty clay mixed with shale, underlain with layers of shale at
1 to 2 feet below the surface, so that very little water infiltrated the
ground.  The waste which was  sprayed on the field trickled slowly over
and through the vegetation on the sloping  terrain, which consisted of
honeysuckle and  reed canary grass, and flowed down to a creek.  It was
found, from average results over one year of  operation, that  the BOD
of the run-off to the river had been reduced  by 97 percent.  To prevent
soil erosion, the steepest slopes had been contour-plowed.  The spray
system provided  at least 2 days rest for  the  ground  between 24-hour  spray
applications.  The land area  used was about 52  acres, and the  average
BOD of the raw waste was 1095 mg/1 or 2196 Ibs/day.   This corresponds  to

 a loading  of  4600  gallons/acre/day.   The  spray  field was  operated
 during  the winter  as well  as during  the summer.   Some  icing of  the  field
 occurred during  the winter, but,  although the BOD reductions were
 somewhat lower,  they were  quite acceptable.

      It should be  emphasized again that the  results presented above are
 valid only under the respective local conditions.  Such results may be
 helpful when  designing  new spray  irrigation  systems, but  local  conditions
 must  be considered carefully,  and flexibility should be provided.

                           Tertiary  Treatment

      As re-use of  treated  waste water becomes more essential, tertiary
 treatment  of  these waters  will become increasingly important.  The
 biological treatment methods, as  presently used,  leave significant
 residues in the  effluents, and several physical and chemical treatment
 methods have  therefore been investigated  as a means for polishing
 effluents before re-use.   These methods include adsorption, foam separation,
 electrodialysis, evaporation, reverse osmosis, coagulation, chemical
 oxidation, and freezing.

      Adsorption -  This process can effectively remove COD-bearing organic
 material.  Activated carbon has been  found to be  the most effective
 adsorbent for many classes of organic substances.  When activated sludge
 effluents are passed through beds of  granular carbon, or when powdered
 carbon  is slurried with the effluent  and subsequently removed, from 70
 to 95 percent of the remaining COD can be removed.  The organics which
 are not removed are believed to be largely colloidal.  Inorganic salts are
 not removed by carbon.

      Foam separation - The foaming tendancy of secondary effluents is
 the basis for this process.  Foam generated by deliberately blowing air
 through the effluent, at an appropriate rate, will contain 85 to 95
 percent of the ABS and up  to 35 percent of the remaining organics.  The
 foam  is collected  and condensed to a  small volume.  Foam separation is
 especially effective in removing dissolved surface active contaminants
 like ABS.  Inorganics are not removed unless they are surface active.

     Electrodialysis - When a difference  in potential is established
 across a solution  of electrolytes, current will flow as a result of ion
migration toward the electrodes of opposite charge.  In electrodialysis,
 cation and anion permeable membranes  are placed in alternate sequence
 across the electric field.  The anion permeable membranes will obstruct
 the movement of cations toward the cathode, while the cation permeable
membranes will obstruct the migration of anions toward the anode.   As a
 result, cells are  formed in alternate sequence in which the water
becomes either more dilute or more concentrated with respect to the
 electrolytes.  Electrodialysis reduces the inorganic ion concentration
 effectively,  with  exception of the ammonium ion.  Some organics are also
 removed, but these will eventually foul the membrane, so that a rather

difficult regeneration process is required.   Power requirements  are
estimated to 6 - 10 kwh/1000 gallons of water treated for a removal of
300 to 500 mg/1 of solids,   Electrodialysis  is already a commercially
proven process.

     Evaporation - Although evaporation or distillation of waste water
effluents does not produce drinkable water,  the process has attractive
possibilities.  The distillate generally contains less than 5-10 mg/1
inorganics and 2-3 mg/1 organic carbon.  However, volatiles such as
ammonia and low boiling organics are not removed.  The effects of many
of the operational variables are not well known, and further work is
required to evaluate the feasibility of the process.

     Reverse osmosis - This process has received less .attention than the
ones above, but nevertheless deserves to be mentioned.  Relatively pure
water has been produced by forcing water through semi-permeable membranes
under a pressure of 750 psi.  The membranes filter out organics, inorganics,
and even bacteria and viruses.  Water with 50 mgA total dissolved solids
and less than 5 mgA organics can be produced.

     Coagulation - Coagulation has already been described in connection
with primary  treatment.  In tertiary treatment coagulation has proven
beneficial as a pretreatment  to  the processes mentioned above.

     Chemical oxidation - Oxidation of organics  to carbon dioxide and
water using chemical oxidants would be a very attractive treatment method.
Short detention times and thus small waste treatment  facilities would
result.  Also, the substances resistant  to bacterial  oxidation would be
removed.  Oxygen, ozone, chlorine, and chlorine  dioxide have been  tried
as oxidation  agents.  Active  oxygen in the form  of  free hydroxyl radicals
is also  a strong oxidant in aqueous systems and will oxidize organic
compounds containing hydrogen and many other  ions  such as  the halogens.
This  radical  can be generated using iron salts and hydrogen peroxide.
When  this method was used to  treat  an  effluent,  refractory organics
were  reduced  by 50  to  70 percent when  the pH  was controlled between
3 and 4.  ABS removals of 98  percent also were achieved.   However,
this method of supplying free hydroxyl radicals  is too  expensive and
further  work  is required to  produce an economical oxidation agent.

      Freezing - Freezing has  received  much attention  as  a  means  of
converting  saline water  to  fresh water.   The  process  also  has been
investigated  for  treating waste  water  effluents.   The ice  crystals
formed under  proper conditions are  relatively pure.   The contaminants
adhere to  the crystals,  and  the  success  of the process depends on
effective washing  of  the crystals.

      Ammonia  as a  problem -  The  ammonium ion is  difficult  to  remove from
the effluent  by the methods  which are  capable of removing  inorganics.
One solution  to this  problem is  to  convert  the ammonia to  nitrate by
microbial nitrification.  This  is  relatively easily achieved in the
activated  sludge  process by extending  the time of aeration or by operating
at higher mixed liquor suspended solids  concentrations.   Ammonia also
can be removed by  air  stripping  at  high  pH.

                               SECTION 7

                           DISPOSAL OF SOLIDS

     Solid waste from potato processing operations include sand and grit,
peelings, trimmings, and potato pulp.  Solids also are one of the end
products of nearly all waste treatment processes.  Effective solid waste
disposal is essential for the waste treatment process to be successful.
Depending upon the method used, solids disposal may result in economic
return or additional treatment cost.

     Complete utilization is the ideal solution to the solids disposal
problem, and fortunately a large fraction of the solid waste from potato
processing is suitable for use as animal fodder and even for processing
into by-products of commercial value.  (Shaw 1965) (Dickey et al. 1963)
However, large amounts of solid waste are disposed of by other methods
for economic as well as practical reasons.  In some areas the demand for
the solid waste products is not sufficient to warrant the capital investment.
Furthermore, pesticide residues and high alkaline content may limit the
 usability of raw solid waste.  Microbiological spoilage of food wastes
presents another problem, since no economical method of preservation has
been discovered.  (Rose 1965)

Disposal to Sewer

     Some processing plants discharge solid wastes as well as liquid
wastes directly to a municipal sewer.  Generally, larger solids are com-
minuted prior to discharge.  From the processor's standpoint this is a
most convenient solids disposal method.  The obvious disadvantage is the
greatly increased waste load to the receiving treatment facility or waterway.
In many instances solid waste discharge would not be permitted or would
be economically unsound because of increased treatment cost.

Land Disposal

     A widely used method for disposal of solids wastes is by land disposal
Strict control is essential to prevent ground water contamination, fly
breeding, and odor nuisances.  An important requirement is that the waste
is covered with a soil layer within 24 hours.  (The Cost of Clean Water
1967)  Primary and secondary sludges have a very high water content and must
generally be dewatered prior to disposal.  The dewatering step can be
omitted by applying the sludge to the land in a thin layer.  Liquid sludges
can easily be pumped and sprayed onto the land.  The same method may be
applied to the solid waste from the processing operations.  This method
provides low cost oxidation of organic matter, providing sufficient low
cost land is available.  In many instances agricultural and forest soils
are improved.  Odors and fly breeding may cause problems.  (The Cost of Clp
Water 1967)                                                                 n


     Composting processes have long been used as a method of converting
putrescible plant residues to more stable organic materials of value as
fertilizers or soil conditioners.  Composting also has had application as

a method of solid waste disposal.   Decomposition of the organic materials
may proceed aerobically or anaerobically,  depending upon the availability
of oxygen.  Anaerobic processes are slow,  and offensive odor production
is difficult to control.  Aerobic  composting is a much more rapid process
and no offensive odors are produced.  The  process may be carried out in
outdoor piles or in high-rate mechanical units.  (Rich 1963)

     Rose (1965) reported results  of experiments on fruit waste composting
by the National Canners Association.  In early experiments it was found
that efficient aerobic composting would proceed in a pile if the water
content of the material was held below 70  percent by mixing with absorbent
materials.  At higher water content slow anaerobic decomposition with
offensive odors was experienced.  Grinding  the solids greatly improved
the rate of the process by exposing more surface area to microbiological
attack.  Fruit acids were found to have an inhibitory effect at pH levels
below 4.5.  By adding lime the acids were  neutralized and the stabilization
period was shortened.  Since composting is a biological process, addition
of urea to the nitrogen deficient waste proved beneficial.  Rich (1963)
states that the initial carbon to nitrogen ratio, C/N, should be from 30
to 35 (by weight) for aerobic composting.   The C/N ratio of the completed
compost will be within the range from 10 to 20.  Further composting
experiments by the NCA compared regular windrows with forced aeration
windrows.  Perforated copper pipes were imbedded in the base of the bins,
which were 9 feet wide and 5 to 6 feet deep, containing about 30 cubic
yards of solids.  The material was mixed with a windrow turner.  Although
the complete results of this experiment were not compiled, all  indications
were that forced aeration increased the composting rate and helped
preventing odorous conditions.  It was found that raw waste could be added
to the bins at rates up to 86 Ibs/cubic yard/day without adversely
affecting the process.  Dried compost together with rice hulls  was used as
the absorbant.   Automated methods  of  handling  the  waste material also were
 investigated.   A two-sectioned  reservoir  was built on the site.  The  first
 section was  used to  hold  the waste as received from the cannery.  A
bucket  elevator was  used  to  convey the solids  to a grinder located  over
 the  second  section.   The  pulpy slurry produced by the grinder  was pumped
 from the  second reservoir to the bins or  windrows  with a  diaphragm  type
 pump.   This  handling method  was found satisfactory.

     Composting of primary sludge requires dewatering of the sludge.
Primary sludge is generally  from 95 to 98 percent water, and unreasonable
amounts of absorbing material would be required to lower the water content
below 70 percent.  Dewatering may be accomplished by air drying, vacuum
filtration, pressure filtration, or centrifugation.   (Ballance  1965)

     Air drying on sludge drying beds is  a method commonly used in
municipal sewage treatment plants.  The sludge  is  applied  to a  bed of sand
and gravel and the water  is  drained off.  Most of  the  removal  takes
place in one day, after which further removal  is primarily by  evaporation.
A major disadvantage with sludge drying beds is  the land  requirement.
Climate is an important factor, and some  drying beds  are  covered with  a
glass building similar  to a  greenhouse.

     Vacuum filtration has been found to be  the most favorable method
 for dewatering primary sludge from potato processing plants.  (Grames and
 Kueneman 1968) (Francis 1962, Red River Valley)  Studies carried out
 by the Engineering Committee of the Potato Processors of Idaho Association
 showed that sludge from plants using steam peeling could be dewatered
 to a solids content of 12 to 16 percent.  The filtrate has a suspended
 solids concentration of 1000 to 1200 mg/1, and most of these solids
 would settle again when the filtrate was returned to the clarifier.
 Dewatering of sludge from plants with caustic peeling at first appeared
 impossible.  The water would not separate from the solids, and the
 gelatinous slurry blinded the filter cloth immediately.  It was found that
 chemical conditioning of the sludge with ferric sulphate and lime re-
 leased the water and flocculated the solids.  The cost of chemicals was
 high, however.  Later it was discovered that ageing of the sludge in the
 clarifier improved the filterability due to bacterial action.  If the
 solids were held too long, the bacteria would decompose the solids and
 filterability was greatly reduced.  Also, reduced clarifier efficiency
 was observed.

     The optimum time of ageing has been found to vary from plant to
 plant.  While 4 to 5 hours may be sufficient in one installation, 24
 hours may be required in another.

     The filtration rate is dependent upon sludge concentration and con-
 ditioning and may vary considerably.  Experience indicates that it is
 safe to size filters on the basis of 5 Ibs of dry solids per square foot
 per hour, although rates as high as 15 Ibs/sq ft/hr have been obtained
 when the sludge characteristics were favorable.  (Grames and Kueneman 1968)

     Pressure filtration is a batch process and does not find much
 application, since it has the major disadvantage of requiring hand labor
 to remove the sludge cake.  (Ballance 1965)

     Continuous centrifugation of primary sludge can be used successfully.
 The solids content of the dewatered sludge is in the range of 16 to 20
 percent.   (Kueneman 1965)  A problem associated with centrifugation is
 removal of the finer solids discharged with the centrate.  The solid
 particles are broken down by the centrifugal force so that they exibit
 poor settling characteristics when returned to the clarifier.  (Grames
 and Kueneman 1968)

 Incineration and Wet-Oxidation

     Incinerators currently are used in municipal treatment plants to
burn solid organic wastes.  (Hindin and Dunstan 1965) (Cost of Clean
Water 1967)  To avoid objectionable odors from the volatile organic
acids,  temperatures of about 1400F must be maintained.  Two basic types
of open-air sludge incinerators are in use.  These are the flash drier-
 incinerator and  the multiple hearth incinerator.

     By incinerating solid waste the fuel value of the solids can be
utilized.   The recovered heat energy may be used to generate steam for

general plant use.  Uindin and Dunstan (1965)  found that screenable
potato waste solids had a fuel value of about  6650 BTU   per pound of
dry solids.  The heat energy obtained from a wet waste depends on the
amount of organic matter present in terms of COD or volatile solids
content and the degree of completion of the combustion.

     In recent years, wet oxidation or pressure burning of industrial
waste as well as municipal waste has been practiced.  The Zimpro process
has been used to oxidize various kinds of sewage sludges and waste pulp
liquors.  The waterborne organic matter is oxidized, under pressure,
with air.  Operational results of the process  have been reported by
Hurwitz et al. (1959).  A sewage sludge containing 5.24 percent total
solids, 3.47 percent volatile solids, and 64400 mg/1 COD was fed to the
reactor at a rate of 229 gallons per hour.  With an average reactor
temperature of 506F and an average pressure of 1200 psi, 7058 BTU
were produced per pound of dry solids when 2.34 Ibs of air were added
per gallon of sludge.  The effluent contained 13700 mg/1 COD, 1.74 percent
total solids, and 0.4 percent volatile solids.  The steam produced was
used to heat the incoming sludge.

     A more recent development is the Dorr-Oliver FS-System.  In this
process a preheated fluidized bed is used to dry and incinerate the wet
organic waste.  Thermal oxidation occurs at a pressure of about 2 psi
and a temperature of 1500 - 1700F.  The process has been found self-
sustaining if the water content of the wet waste does not exceed 65
percent.  If the water content is higher or the waste has a low organic
content, fuel as propane or fuel oil is added directly to the fluidized
bed.  (Hindin and Dunstan 1965)

     It is important to note that dewatering of solid wastes with high
water content is necessary for efficient use of any of the combustion
methods described above.

Anaerobic Digestion

     Anaerobic digestion of solid waste decomposes  the organic liquids
and solids to inorganic matter and organic gases.  Methane is the
principle organic gas formed.

     Hindin and Dunstan  (1963) studied digestion of varying mixtures of
potato waste solids and sewage sludge.  The potato waste solids are
deficient in nitrogen and phosphorous, essential nutrients for bacteria,
and the sewage served as a source of these nutrients.  Also the sludge
provided the mixture with an inocculum of methanogenie microorganisms,
responsible for the methane fermentation process.  Using conventional
rate sewage sludge digestion, satisfactory digester performance was
obtained with a mixture containing equal amounts of potato waste solids
and sewage sludge.  Signs of digester distress were observed when  the
mixture contained 75 percent potato waste solids.   It was recommended
that in actual large  scale operation the digester  feed should not
contain more than 25 percent potato waste solids.   Although  it was  found

 that  the digester destroyed  the solid organic matter efficiently, the
 supernatant had a BOD in excess of 1000 mg/1.  Disposal of this highly
 organic liquid may present problems.

      Much research is needed towards efficient utilization of  the fuel
 value of potato waste solids through anaerobic digestion.  Other areas
 which require further research are supernatant disposal, nutrient
 supplementation, and application of the high rate and contact  digestion

 Animal Feeding

      Utilization of potato pulp and peelings for cattle feed already has
 been  discussed.  Sludge from primary clarification of potato processing
 waste water also has been used successfully for cattle feed.   All the
 sludge recovered from the clarifiers of the J. R. Simplot Company is fed
 to cattle.  The sludge is dewatered to about 14 percent solids content by
 vacuum filtration.  Caustic  peel sludge is stored until the pH falls to
 neutral or below through fermentation.  At the beginning of the feeding
 period, the mixture contains  about 45 percent potato solids (by weight).
 The rest of the feed is mainly chopped hay with some grain.  After 14 days
 the potato solids content is  increased to about 70 percent, and this
 mixture is used for the remainder of the feeding period.  The  potato
 solids have been found to be  at least equivalent to barley in  nutritional
 value, and reports indicate  that there has been an accelerated weight
 gain  of about 1/2 Ib/animal/day after the potato solids were included in
 the diet of the cattle.   At  the present the total weight gain  of the
 Simplot cattle ranges from 2.6 to 4.1 Ibs/animal/day with an average of
 about 3,0 Ibs.  Livestock feeders were long reluctant to use filtered
 sludge.  Since its value was  proven through experience, the filtered
 sludge has been in demand, and many processors are selling the sludge
 along with their screened solids at a price of about $3.00 per ton of
waste at about 14 percent solids content.  This price is sufficient to
 recover capital costs of primary treatment in two to four years.  (Grames
and Kueneman 1968)

                               SECTION  8


     At the present time a considerable amount of research and develop-
mental work is under way on potato processing waste treatment in this
country.  The Pacific Northwest Water Laboratory of the Federal Water
Pollution Control Administration in Corvallis, Oregon, has been assigned
national responsibility for food processing wastes.  In each of the
major food processing areas, such as potato, the waste treatment research
needs will be developed and these needs will be assigned priorities.  The
total problem will be attacked systematically from three directions.
First, the FWPCA will do some in-house research.  Second, research grants,
contracts, and demonstration grants will be awarded to various universities,
industries, and other groups to work on designated problems.  Third, and
not least, work will be done by industries and groups .such as the Potato
Processors of Idaho Association.

     Research grants directly involved with potato processing wastes are
described in Appendix B.  The projects are those given in the Water
Resources Research Catalog (1967, 1968).  These projects cover aspects of
biological waste treatment processes, by-product recovery, in-plant
modifications, chemical process application, peeling processes, odor
control and other process and treatment modifications.  In addition to
the projects described in Appendix B, many smaller projects are conducted
by industry and other institutions.

     Many studies on process waste water disposal  for other related
industries are under way and constitute a large potential source of
research information which may be applicable  to the potato processing
industry.  The concern for environmental quality control is international
and is focused on preventing further deterioration of the environment.
The effects of this growing concern, no doubt, will be to provide  further
stimulus for research and further requirements  for waste water control.

                               SECTION 9

                             RESEARCH NEEDS

     With the existing waste treatment technology any reasonable effluent
quality requirement imposed on the potato processing industry can be met.
In England, where effluent requirements are considerably more restrictive
than in the United States, potato waste treatment facilities capable of
producing effluents with BOD and suspended solids concentrations below
20 mg/1 are in operation.  In one such plant, primary sedimentation is
followed by two stages of biofiltration and activated sludge treatment.
Final polishing on sand filters enables re-use of a large fraction of the
effluent in the processing operations without detrimental effects on the
quality of the final product.  Up to 75 percent of the effluent may be
re-used.  A treatment scheme such as this is of course costly, and cost
is the main treatment problem facing most potato processors.  Capital as
well as operating costs are high, with little or no possibility for
return on the investments.  This is true now for conventional
secondary treatment and will be a continuing problem as  federal and
state requirements on effluent quality become more restrictive, and a
higher degree of treatment becomes necessary.

     Cornell, Rowland, Hayes and Merryfield (1969) have presented average
capital and operating costs for potato waste treatment and compared these
with similar costs for municipal waste treatment presented by Smith (1968)
The costs for primary potato waste treatment were based on facilities
constructed in the Pacific Northwest, while the costs for secondary
treatment were based on engineering estimates from demonstration projects
and from pilot plant systems studied by the Potato Processors of Idaho
Association.  The curves presented are shown in Appendix C.   Because of
the rapid change in construction costs, all figures were adjusted to a
common base of June 1967 by using the Engineering News-Record building
cost index.   The history of the building cost index and a projection of
the index into the future also is shown in Appendix C.

     A survey of many potato processing plants was made in connection
with this report.  Limited treatment cost information was obtained.
Primary treatment was reported to cost from $0.02 to $0.064 per pound of
BOD removed.  In terms of raw product input a treatment cost of $0.50 per
ton of potatoes was given.  A starch plant reported operation and main-
tenance cost of $0.04 per pound of BOD removed.   Protein water was
treated by anaerobic fermentation and diffused aeration and combined with
flume water for sedimentation and disposal to a municipal sewerage system.

     The survey showed that a large percentage of the potato processors
do   not know the cost of treating their own waste.  Capital cost of the
facilities is of course known, but operational cost is not determined.
For efficient operation and control of the waste treatment facilities
and to evaluate the effects of in-plant changes and procedures, cost
information is essential in most cases.  Large sums of money may be
wasted unnecessarily unless consideration is given to cost of treatment
versus the operational variables in the processing plant as well as in
the treatment plant.

     Proper considerations on the part of the processor also will  result
in considerable savings in capital costs.  Efforts to reduce waste
production must start with the operations prior to processing,  i.e.,
harvesting, handling and storage.  The in-plant efforts have been  dis-
cussed earlier.  Finally, good engineering knowledge must be used  in
designing and constructing the waste treatment facilities.

     Although much can be done to reduce the cost of waste treatment
with the knowledge and means available today, the future will bring more
restrictive waste treatment requirements, and we must prepare to meet
these requirements with economically feasible methods.

               Specific Research  and/or Demonstration Needs

     Many possibilities exist for reducing the amount of waste from
potato processing and improving  the waste treatment technology; a great
deal of work has already been done to alleviate the potato waste problem.
However, with  all due respect to previous and present efforts, there
is always room for further improvements.

Harvesting. Handling, and Storage

     Improvements in the operations prior to processing may reduce the
total waste load significantly.

     Harvesting.  Mechanical injury to the tubers during harvesting
greatly increases the chance of  tuber disease and discoloration during
storage.  Rejection of injured tubers during processing increases the
amount of solid waste and represents a direct loss  to  the processor.
Improved mechanical harvesting equipment therefore  should be developed.

     Dirt Removal.  Removal of dirt from the potatoes  in  the field would
reduce the amount of water used  for washing in  the  processing plant.
Although wash  and flume water does not require  a  high  degree of treat-
ment at the present time, secondary treatment will  undoubtedly be re-
quired in the  future.  Therefore, reduction of wash water volume is

     Transportation.   Potato  quality  is  affected  by temperature during
transit, and improvements  in  the environmental  control systems  in rail-
road cars and  trucks would reduce the amount of potatoes  wasted due  to
high reducing  sugar content.

     Storage.  Temperature control is equally  important during  storage.
Research also  is  needed  in  the  field  of  sprout  inhibition and  in  pre-
venting diseases  like  rotting.   Mechanically  injured tubers should be
sorted out before the  crop  is placed  in  storage.

Processing Operations

     In-plant  changes  and modifications  are considered by many to be the
most important for waste reduction and prevention.   In general, processing

 equipment and techniques  need be improved to  reduce  the  amount  of waste
 water produced and the amount of solids  entering  the waste  streams.
 Several possibilities  and practices  have been discussed  earlier.

      Peeling.   The peeling operation, which contributes  from  50 to 75
 percent of the total plant waste load must be improved in order to
 reduce the waste load  significantly.  Very promising results  have been
 obtained with the dry  caustic peeler previously described.  However,
 more work is  required  to  perfect this process.  Handling, disposal and
 utilization of the slurry produced from  the peel  and waste water must be
 investigated.   The economics  of  the  process compared to  other peeling
 methods also  must be demonstrated.

      Other possible methods of peeling with minimal  water usage should
 be investigated.

      Other Processing  Operations.  The rest of the processing operations
 should be considered as well.  Solids losses  and  watet usage  must be
 reduced,  since these increase the waste  load  as well as  the total loss
 from the process.   Improved equipment and  methods for slicing,  blanching,
 cooking,  etc.  should be developed.   In the same respect, firm guide lines
 for good housekeeping  should  be  established,  and  process line personnel
 should be educated in  waste prevention.

      Solids Removal.   A certain  loss of  solids will  always occur.  Pre-
 ferably these  solids should not  be allowed to enter  the waste stream.  If
 they do enter  the  waste water, then as much as possible of these solids
 should be removed  from the waste water immediately in the processing
 plant before considerable  leaching of organics take  place.  Removal may
 be achieved by screening,  filtration, or centrifugation.  In  this respect,
 research  is needed on  suspended  solids particle size in relation to
 screening.  Fragmentation  of  the particles on the screen may  increase the
 apparent  BOD.   A similar phenomenon may  take place in the centrifuge.  The
 solid particles may  be broken  down by the  centrifugal force and thus
 remain in the  centrate.  It has been reported that this indeed happens
 when primary potato  sludge  is  dewatered by centrifugation.  The small
 particles  discharged with  the  centrate have poor  settling characteristics
 and  thus  are not removed easily by sedimentation.

      Re-use of  Process Water.  Re-use of process water has been discussed
 earlier.   Besides  removal  of suspended solids, quality control of the
water  must be  investigated.  Various methods of microbial control should
be evaluated to control deterioration of the recirculated water.  The
 tolerance  limits for different pollutants should be established for
various steps  in the process on a health hazard basis as well as on a
 product quality basis.

      Separation and  Concentration.  As mentioned earlier, separation
of various waste streams may be advantageous for subsequent treatment in
different systems.  Waste concentration also may prove very advantageous,
since  concentrated waste can be treated more efficiently than dilute
waste.  Concentration and separation would be necessary for efficient

by-product recovery in many cases.   Concentration and  separation by
reverse osmosis is one possibility which presently is  being investigated.
The concentrated portion of the waste stream may be subjected to recovery
of various valuable constituents while the separated dilute portion may
be re-used in the processing operations.  The present  research efforts
are directed towards potato starch plant waste.   Feasible application of
this or similar processes to other types of potato waste water should
be investigated.

     By-Product Recovery.  A variety of salable  by-products can be re-
covered from the various waste streams, and considerable research has
been conducted in this field.  Few large scale economically feasible
processes have been developed, however.

     Some of the compounds which may be recovered from potato waste
include amino acids, protein, organic acids, potassium, phosphates and
other inorganic ions.  All these compounds have been recovered by physical
or chemical processes.

     Potato pulp and waste water may also be used as growth media for
yeasts and molds for production of protein and antibiotics.  Promising
results have been obtained with the yeast Torula.

     A number of edible products for human consumption have been proposed
from larger potato solids.  Utilization of potato solids for livestock
feed has  found  wide acceptance.

     In order to take advantage of these possible by-products from
potato wastes, feasible processes and a market must be developed.  The
present efforts on by-product recovery are concentrated mainly on starch
plant waste, since the potato starch industry is a rather marginal industry.
More emphasis should be directed towards recovery of salable products
from other types of potato processing waste.

Waste Treatment

     The  ultimate solution to the waste  treatment problem would be to
produce an effluent which could be completely re-used  in the processing
operations.  Although such a  goal is rather  impractical at  the present
time, the possibility of effluent re-use nevertheless  should be kept
in mind.  In order  to solve the more contemporary problems  facing  the
potato processors,  existing and proposed  technology must be improved
and modified to give more efficient, less  costly waste treatment.  The
most pressing problem at present is secondary treatment, a  requirement
which is  facing most of  the processors  across the nation.   However,
continued efforts  to improve  primary  treatment  methods should not  be
ignored since primary treatment can reduce the  load on the  secondary
treatment facilities significantly.

     Primary Treatment.  Primary  treatment has  been adopted by  a large
part of the potato  processing industry,  and design  criteria have been
established through experience  from  pilot plants and  full  scale operations.

 Methods  for  improving  the  removal  of colloidal and dissolved matter
 should be  improved.

      Flotation.   Solids  removal by flotation has been  tried to some
 extent in  potato  waste treatment.   Promising results have been obtained,
 but  high costs also have been  reported.  Further research on the
 applicability of  the process to potato waste is needed.

      Coagulation.  Some  research has been conducted on chemical coagula-
 tion of  primary treated  potato waste.  Although the results obtained
 did  not  show appreciable improvement in  the overall removal efficiencies,
 work in  this area should be continued.   The large variety of coagulants,
 coagulant-aids, and polyelectrolytes available should be tested at various
 points in  the waste treatment  process and for different types of potato

      Flocculation by pH  Control.   Recent investigations have shown that
 additional removal of solids from  primary effluent can be accomplished
 by holding the effluent  for a  period of  time until the pH is lowered
 by microbiological action.  When the pH was lowered, the solids tended
 to flocculate and settle or float  to the surface.  Up to 50 percent
 additional removal was obtained.   (Gates 1969)  The feasibility of pH
 control  for  additional solids  removal should be further investigated.
 The  effects  of coagulant aids, temperature and density should be established,

      Secondary Treatment.  Potato  processing wastes have been found
 easily degradable by biological treatment processes, and considerable
 progress has been made in  the  application of different processes to
 potato waste treatment.  A significant amount of pilot plant work has
 been done, but operational results and experience from full scale in-
 stallations  are limited.

      Biological Processes.  Research needs for biological treatment pro-
 cesses are not unique to potato processing wastes but apply to most
 industrial wastes.  In general, better prediction models for the different
 processes must be developed.   The values of the model factors, i.e.,
 removal  rate constants,  growth rate constants, etc., and their variations
 with  waste quality parameters, should be determined more precisely.  More
 specifically, the availability of  the essential nutrients, such as
 nitrogen and phosphorous, for adequate treatment should be investigated.
 The  amount of nutrients  in potato waste is generally sufficient for
 effective biological treatment, but the nutrients may not be readily
 available  for cell incorporation.   The effects of conditions or compounds
 directly inhibitory to biological treatment, such as high pH,  antifoaming
 agents and cleaning compounds,  should be studied further.

     Anaerobic Processes.  Promising results have been obtained with the
 anaerobic filter and the anaerobic contact process in potato waste treat-
ment, and work on these processes  should be continued.   Special attention
should be given to start-up characteristics, duration of start-up period,
optimum operating conditions,  and  solids-liquid separation.   Solids
disposal also should be considered.

     Spray Irrigation.   Successful applications of spray irrigation have
been reported.  Research is needed to determine the effect of sodium on
the soil used for spray irrigation, and on proper soil conditions and
operating conditions for maintaining adequate growth and soil drainage.

     Chemical-Physical Processes.   High-rate chemical oxidation processes
have not been found economically feasible at the present.  Further research
on these and other chemical and physical processes should be conducted,
especially with regard to more complete re-use of treated effluents.

     Solids Handling and Disposal.  Conventional primary treatment and
biological secondary treatment produce excessive solids.  Primary sludge
has been used successfully for cattle feed.  The possibility of utilizing
secondary sludge in a similar way should be investigated.  The economics
of other solids disposal methods should be evaluated, since little is
known about the feasibility of secondary sludge for cattle feed, and
since there may not be a market for this product.  Efficient and economical
methods for dewatering dilute sludges should be developed, along with
methods for handling sludge with high solids content.

     Tertiary Treatment Processes.  Although enforcement of tertiary
treatment may be some years in the future, several of the processes
developed for polishing effluents may soon be applicable in potato waste
treatment for extensive effluent re-use and by-product recovery.  The
feasibility of these advanced treatment processes for potato waste should
therefore be investigated.
                   Suggested Approach to the Problem

     Current research in the specific area of potato processing waste
waters involves about two million dollars per year.  This expenditure
includes demonstration grants.  The research thus far has made in-roads
on the pressing problems of applying secondary treatment and more
satisfactory peeling methods to field installations.  Further development
is yet needed on anaerobic and non-conventional treatment.

     Major emphasis needs to be given to reuse, recycle, recovery and
good housekeeping as techniques to reduce waste loads.  Research in
these aspects of process modification may provide mechanisms which will
offset much of the research investment.  The salvage, saving and use of
waste soil, potato material, and process chemicals involved in utilization
of the potato can represent monetary gain to the producer as well as
relieve some of the waste burden on the environment.  The use of pollution
control awareness programs for employees helps spread the appreciation for
waste control and its beneficial aspects throughout the operation and
will, if properly handled, produce significant waste load reductions.

     With proper direction toward evaluation of newer experimental process
control techniques and with a proportional investment in good research
aimed toward applying new and imaginative processes to potato processing
and potato processing wastes, the present dollar research expenditure and
more could be well spent in the future in developing  the production  and
waste control processes toward the continued further  alleviation of  waste
load insults to the environment.  At least 10% of  the total monies spent
on research and development should be reserved for  innovative  laboratory


 research.   Of the remaining monies,  care  should  be  taken  to  avoid  spending
 major fractions  of the  available  research dollars on  construction  and
 maintenance of conventional facilities  which  have already been  investigated
 in some detail.   The  research  supported should be able  to provide  meaning-
 ful results which can be of significant value in solving  the waste control
 problems of the  industry.   Enthusiastic monetary support  is  difficult  to
 sustain when applicable fruitful  results  are  not forthcoming for the projects
 supported.   However,  the problems in potato processing  are real and require
 attention.   With imagination,  persistence, diligence  and  adequate  support,
 competent  researchers can provide the information needed  to  maintain the
 quality of  the environment.

 Environmental  Impact

      The impact  of  the  potato processing  industry on the  total environment
 will  be  an  area  of  vital concern  in  the seventies.   It is not sufficient to
 consider only  the  growth and production of the product and the treatment of
 emanating waste  streams.   Concern must be directed as well to the chemicals,
 materials,  energy  and ecological balances involved in the production
 system and  perhaps  the  most important research will deal with the effect of
 production  on  these balances.  While  the problems are not unique to the
 potato processing  industry they are  part of the  total responsibility of
 mankind in  maintaining  the quality of the environment.

      The loads of salts, pesticides,  and herbicides dumped into the en-
 vironment should be carefully evaluated in terms of their insult capacity
 to  the environment  and  alternative methods should be considered for growing
 and processing where the method used  is not compatible with maintaining
 the quality of the  environment.  Other methods of growing, harvesting and
 processing  should be under study to explore mechanisms for providing greater
 amenability with the use of preservation of resources.  Increases in re-
 ceiving water  temperature resulting  from waste discharges can disrupt bio-
 spheres and create  system imbalances which may have perturbations in other
 industries  and water uses.

      Cultivation and processing of food products encumber the growers and
 processors with  the responsibility for proper management of  the unused and
wasted portions of the materials applied in the process as well as with
 the sale of satisfactory products.  The use of the  environment and its
 growing potential entails with that use the care and preservation of the
 environmental components which make life possible.   Thus conservation of
 energy and material as well as proper use of those  commodities and proper
 stabilization of components returned to the environment are all part of the
 total production process.  Future research should deal effectively with the
 individual processing industry not only as an entity but also as part of the
 total environmental picture.  While every productive consumptive use of
material involves the destruction and wastage of some environmental component,
 it is necessary, for the future, to consider resources in terms of their
highest and best use.

      It  is  incumbent on workers in this field to be cogniant of their
 societal impact  and research may well be  involved with the legal and
 regulatory  aspects  of the process including incentive systems, planning
 and agricultural basin  development.   The  future  for research in potato
 processing  involves technological assessment and improvement.  Future
 research should  expand  also into  the  role of the industry in relationship
 to man's needs and  the  maintenance of a quality  environment.



                               APPENDIX A
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Anderson, V.,  1961.   "A Tentative Approach to  the Establishment of Engineering
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Atkins, P. F., and Sproul, 0. J., 1964.  "Feasibility of Biological
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Ballance, R. C., 1965.  "A Review of Primary Treatment Processes,"
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Berry, G., 1967.  "Disposal of Process Waste Water from Potato Processing
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Black. H., and Porges, R., 1965.  "The Role of In-Plant Procedures in
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        and Productivity Council,  N. B., Canada, (1965).

Butler, J. L., and Burns,  0. B., 1968.  "Recent Design and Operating
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Buzzell, J. C., Caron, A-L. J., Ryckman, S.  J., and Sproul, 0. J., 1964.
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Carlson, D. A., 1967.   "Biological Treatment of Potato Wastes," Proceedings
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        Washington,  (April 1967).

Carlson, D.  A., 1968B.   "Recent  Developments  in Anaerobic Waste  Treatment,"
        Proceedings of  a Symposium on Potato  Waste  Treatment.  FWPCA and
        University of Idaho,  (1968).

Carlson, H., 1968A.  "Potato  Chips in Sweden,"  Paper presented at  the
        Utilization Section Meeting,  European Association  for  Potato
        Research, Lund, Sweden,  (1968).

Caudill, H.  Jr., 1968.   "Application  of  the Anaerobic Trickling  Filter to
        Domestic Sewage and Potato Wastes," M.  S. Thesis,  University of
        Washington, Seattle,  (August  1968).

Cooley, A. M., Wahl, E. D., and  Fossum,  G.  0.,  1964.  "Characteristics
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        University, 379-390,  (1964).

Cornell, Rowland, Hayes, and  Merryfield, Engineers  and Planners, 1966.
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        of Potato Process Water," prepared for  the  Potato  Processors of
        Idaho Association, (September 1966).

Cornell, Rowland, Hayes, and Merryfield, Engineers  and Planners, 1969.
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        Process Water," Prepared for the Potato Processors of Idaho
        Association, (July 1969).

Cost of Clean Water, 1967.  Volume III, Industrial Waste Profile No. 6,
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Curry, K. 0.,  1968.  "Developments Leading to Bulk Transportation of
        Potatoes," Proceedings of  the 18th National Potato Utilization
        Conference. Corvallis, Oregon,  (1968).

Dickey, H. C.,  Brugman, H. H., Highlands, M. E., and Plummer, B. E., 1965.
        "The Use of By-Products  from Potato  Starch  and Potato Processing,"
        Proceedings International  Symposium. Utilization and Disposal of
        Potato  Wastes. New Brunswick Research and Productivity Council,
        N. B.,  Canada,  (1965).

Dickinson, D.,  1965.   "Treatment of Effluents from  Potato Processing,"
        Proceedings International  Symposium, Utilization and Disposal of
        Potato  Wastes, New Brunswick Research and Productivity Council,
        N. B.,  Canada,  (1965).

Dostal, K. A.,  1968A.   "The State  of the Art of Potato Waste  Treatment,"
        Proceedings of the 18th  National Potato Utilization Conference.
        Corvallis,  Oregon, (1968).

Dostal, K. A., 1968B.  "Pilot Plant Studies on Secondary Treatment of
        Potato Processing Wastes," Proceedings of a Symposium on Potato
        Waste Treatment, FWPCA and University of Idaho, (1968).

Dostal, K. A., 1968C.  "Progress Report on Aerated Lagoon Treatment of
        Food Processing Wastes," Report No. PR-5 Pacific Northwest Water
        Laboratory, FWPCA, (March 1968).

Douglass, I. B., 1965.  "The Manufacture of Potato Starch," Proceedings
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        Canada, (1965).

Drake, J. A., and Bieri, F. K. , 1951.  "Disposal of Liquid Wastes by the
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Dugan, G. L., and Oswald, W.  J., 1968.  "Mechanisms of Anaerobic Waste
        Treatment," Proceedings of a Symposium on Potato Waste Treatment.
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Eckenfelder, W. W. Jr., 1966.  Industrial Water Pollution Control.
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Eckenfelder, W. W. Jr., 1969.  "Research and Development Needed," Paper
        presented at Conference on the Treatment and Disposal of Wastes
        from Vegetable Processing, New Orleans, (August 1969).

Filbert, J. W., 1968.  "Other Treatment Methods for Potato Wastes,"
        Proceedings of a Symposium on Potato Waste Treatment. FWPCA and
        University of Idaho,  (1968).

Eossum, G. 0., 1965.  "Research Needs in the Treatment of Potato Wastes,
        Highlighting Possible Roles of New Materials, New Types of
        Machinery, and Better Methods of Chemical and Biological Control
        of Treatment Processes.  Panel Discussion."  Proceedings
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        Wastes, New Brunswick Research and Productivity Council, N. B.,
        Canada, (1965).

Possum, G. 0., and Cooley, A. M., 1965.  "Stabilization Ponds Treating
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Francis, R. L., 1962.  Summary of Potato Products Waste Study, Potato
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Gallop, R. A., 1965.  Proceedings International Symposium. Utilization
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Gallop, R. A., 1968.   "The Food Science Department,  University  of
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Garrick, P., 1968.  "The Preservation of Raw Peeled  Potatoes.   Experimental
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        National Potato Utilization Conference.  Corvallis,  Oregon,  (1968).

Gloyna, E. F., 1968.   "Basis for Waste Stabilization Pond Designs,"
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Grames, L. M., and Kueneman, R. W., 1968.  "Primary  Treatment of Potato
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        Federation, Chicago, Illinois, (September 1968).

Gray, H. F., and Ludwig, H. F., 1943.  "Characteristics  and Treatment of
        Potato Dehydration Wastes," Sewage Works Journal. 15. 1, (1943).

Gustafson, N., 1968.   "Production Problems with  Special  Reference to the
        Processing Industry," Paper presented at the Utilization Section
        Meeting, European Association for Potato Research,  Lund, Sweden,

Haas, F. C., 1968.  "Spray Irrigation Treatment." Proceedings of a
        Symposium on Potato Waste Treatment. FWPCA and University of Idaho,

Harp, H., 1965.  "Economics of Alternative Uses  for Potatoes in the
        United States," Proceedings International Symposium. Utilization
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Harrington, W. 0., 1957.  "Removing Cooked Potato Tissue from Peeled
        Potatoes," U. S. Pat. 2,797,165.

Hatfield, R., Strong, E. R., Heinsohn, F., Powell, H., and Stone, T. G.,
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        Trickling Filters," Sewage and Industrial Wastes. 28, 10, 1240-
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Heisler, E. G., Siciliano, J., and Porter, W. L., 1969.   "Progress Report
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        National Potato Utilization Conference,  Big Rapids, Michigan,
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Hindin, E., and Dunstan, G. H., 1963.  "Anaerobic Digestion of Potato
        Processing Wastes," Journal Water Pollution Control Federation.
        35, 4, 486,  (1963).                              '"~~

 Hindin, E., and Dunstan, G. H., 1965.  "Utilization of Potato Wastes for
        Fuel Purposes," Proceedings International Symposium, Utilization
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 Howe,  D. 0., and Miller, A. P., 1963.  "Anaerobic Lagooning, a New
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 Janicki, J., Szebiotko, K., and Stawicki, S., 1965.   "Potatoes and Their
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        Wastes. New Brunswick Research and Productivity Council, N. B.,
        Canada, (1965).

 Kintzel, A., 1964.   "Biosorption in Application to the Treatment of
        Potato Starch Waste Waters," Starke.  12, 59-60, (1960).  Water
        Pollution Abstract No.  832, (1964).

Klein, L.,  1966.   "River Pollution. III.  Control." Butterworths, London,

Kueneman,  R.  W.,  1965.   "Performance of Primary Waste Treatment Plants
        in Northwest U.S.A.," Proceedings International Symposium.
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        and Productivity Council,  N. B.,  Canada, (1965).

Kueneman,  R.  W.,  1968.   "Future Growth of the Potato Processing Industries."
        Proceedings of  a Symposium on Potato  Waste Treatment, FWPCA and
        University of Idaho,  (1968).

Laukler, J. G., and Morgan, 0. M., 1944.  "How Wetting Agent Improves
        the Chemical Peeling Process," Food Industries. 16, (1944).

Luley, H. G., 1963.  "Spray Irrigation of Vegetable and Fruit Processing
        Wastes," Jorunal Water Pollution Control Federation, 35. 1252-
        1261, (1963).

Mclntosh, G. H., and McGeorge, G. G., 1964.  "Year Around Lagoon Operation,"
        Food Processing. 82-86, (1964).

Mercer, W. A., 1969.  "Research and Development Needed," Paper presented
        at Conference on the Treatment and Disposal of Wastes from
        Vegetable Processing, New Orleans, (August 1969).

Mercer, W. A., Rose, W. W., Roseid, S., Katsuyama, A., and Porter, V.,
        1964.  "Trickling Filter Treatment of Liquid Fruit Canning Waste,"
        Progress Report Prepared by Western Research Laboratory, National
        Canners Association, Berkeley, California, (February 1964).

Mercker, A. E., 1965.  "The Production and Utilization of Potatoes in the
        United States of America," Proceedings International Symposium.
        Utilization and Disposal of Potato Wastes. New Brunswick Research
        and Productivity Council, N. B., Canada, (1965).

Michaelson, C. H., 1969.  Personal Communications, (March 1969).

Norman, L. W. et al., 1965.  "Waste Water Treatment Studies at Tracy,
        California," Journal of the American Society of Sugar Beet
        Technologists. 13. 5, (April 1965).

Gates, J. H., 1969.  Personal Communications, (September 1969).

Olson, 0. 0., Van Heuvelen, W., and Vennes, J. W., 1964.  "Aeration of
        Potato Waste," Proceedings of the 19th Industrial Waste Conference.
        Purdue University, (1964).

Olson, 0. 0., Van Heuvelen, W., and Vennes, J. W., 1965.  "Experimental
        Treatment of Potato Wastes in North Dakota, U. S. A.," Proceedings
        International Symposium. Utilization and Disposal of Potato Wastes.
        New Brunswick Research and Productivity Council, N. B., Canada,
        (1965) .

Olson, 0. 0., and Vennes, J. W., 1963.  "Mechanical Aeration of Potato
        Processing and Domestic Sewage."  Park River Study, Federal Water
        Pollution Control Administration, (1963).

Pailthorp, R. E., and Filbert, J. W., 1965.  "Potato Waste Treatment in
        Idaho Pilot Unit Study," Proceedings International Symposium.
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        and Productivity Council, N. B., Canada, (1965).

Pasveer, A., 1965.   "The Use of  the Oxidation Ditch for the Purification
        of Domestic  and Industrial Wastes," Proceedings International
        Symposium. Utilization and Disposal of Potato Wastes. New Brunswick
        Research and Productivity Council, N. B., Canada,  (1965).

Forges, R. , 1963.  "Industrial Waste Stabilization Ponds in the United
        States," Journal Water Pollution Control Federation, 35, 456-468,

Forges, R., and Towne, W. W. , 1959.  "Wastes from the Potato Chip Industry,1
        Sewage and Indus trial Was tes, _31_, 1, (January 1959).

Potato Chip Industry, 1960.  An  Industrial Waste Guide to  the Potato
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Rich, L. G., 1963.   Unit Processes of Sanitary Engineering. John Wiley
        and Sons, New York, (1963).

Rose, W. W., 1965.   "Treatment and Disposal of Potato Wastes," Proceeding^
        International Symposium. Utilization and Disposal of Potato
        Was tes, New  Brunswick Research and Productivity Council, N. B.,
        Canada, (1965).

Sak, J. G., 1967.  "Plastic Biological Oxidation Media for Industrial
        Waste Treatment Needs,"  Paper Presented at the 14th Ontario
        Industrial Waste Conference, Niagara Falls, Canada, (June 1967).

Shaw, R., 1965.  "Potato Specialties from Edible Potato Wastes - A Review,"
        Proceedings  International Symposium. Utilization and Disjposal of
        Potato Wastes, New Brunswick Research and Productivity Council,
        N. B., Canada, (1965).

Sijbring, P.  H., 1968A.  Personal Communications, (September, 1968).

Sijbring, P.  H., 1968B.  "The Peeling of Potatoes for Processing," Paper
        presented at the Utilization Section Meeting, European Association
        for Potato Research, Lund, Sweden, (1968).

Sijbring,  P.  H., 1968C.  "Principles of Vacuum Frying and Results of
        Practice," Proceedings of the 18th National Potato Utilization
        Conference, Corvallis, Oregon,  (1968).

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        "Influence of Piece Size on Production and Quality of Dehydrated
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Smith, 0., 1937.   "Some Factors Affecting Culinary Quality in Potatoes,"
        American Potato Journal.  L4, 221-224,  (1937).

Smith, 0., 1964.   "Recent  Research of Value to the potato Chip Industry,
        Proc.  Prod, and Tech.  Div.  Meetings, Potato Chip Institute
        International,  (1964).

Smith, 0., 1966.  "Report of PC11 Director of Research," Proc.  Prod,  and
        Tech. Div. Meetings. Potato Chip Institute International,  (1966).

Smith, R., 1968.  "Cost of Conventional and Advanced Treatment  of  Waste-
        water," Journal Water Pollution Control Federation.  40. 9, 1546,
        (September 1968).

Sproul, 0. J., 1965.   "Potato Processing Waste Treatment Investigations
        at the University of Maine," Proceedings International  Symposium.
        Utilization and Disposal of Potato Wastes. New Brunswick Research
        and Productivity Council, N. B., Canada, (1965).

Sproul, 0. J., 1968.   "Wastewater Treatment from Potato Processing,"
        Water and Sewage Works.  2., 93,  (February 1968).

Szebiotko, K., 1965.   "Total Utilization of Potatoes Including  the Disposal
        of Industrial Wastes," Proceedings International Symposium.
        Utilization and Disposal of Potato Wastes. New Brunswick Research
        and Productivity Council, N. B., Canada, (1965).

Talburt, W. F., and Smith, 0., 1967.  "Potato Processing." The  AVI
        Publishing Company, Inc., (1967).

U. S. Department of the Interior, 1966.  "Pacific Northwest Economic  Base
        Study for Power Markets.  Agriculture and Food Processing."
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Voege, F. A., and Stanley, D. R., "Industrial Waste Stabilization  Ponds
        in Canada," Journal Water Pollution Control Federation. 35.
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Water Resources Catalog, 1967.  Volume 3, Office of Water Resources
        Research, U.  S. Department of the Interior, Washington D.  C.,
        (December 1967).

Water Resources Catalog, 1968.  Volume 4, Office of Water Resources
        Research, U.  S. Department of the Interior, Washington D.  C.,
        (December 1968).

Weaver, E. A., Heisler, E. G., Porges, R., McClennan, M. S., Treadway,
        R. H., Howerton, W. W., and Cordon, T. C., 1953.  "Aerobic
        Microbiological Treatment of Potato Starch Factory Wastes,"
        Bureau of Agriculture and Industrial Chemistry, Eastern Regional
        Research Laboratory, USDA, Philadelphia,  (February 1953).

Webster, G., and Carlson, D. A., 1968.  Laboratory Studies at the
        University of Washington, Seattle, (1968).

Weckel, K. G., 1969.   "Research and Development Needed," Paper presented
        at Conference on the Treatment and Disposal of Wastes from
        Vegetable Processing, New Orleans, (August 1969).

Wiertsema, P., 1968.  "Special Problems of the Potato Chip Industry in
        Western Europe," Proceedings of the 18th National Potato
        Utilization Conference, Corvallis, Oregon, (1968).

Willard, M., 1969.  "Pilot Plant Study of the USDA-Magnuson Infra-Red
        Peeling Process," Paper presented at the 19th National Potato
        Utilization Conference, Big Rapids, Michigan, (July 1969).

Wolters, N., 1965.  "Abwasserprobleme der Kartoffelverarbeitenden Industrie,"
        Per Kartoffelbau. 11, (1965).

Wramstedt, S., 1968.  Personal Communications.  (September 1968).

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        Treatment," Technical Report No.  87,  Department of Civil
        Engineering, Stanford University,  (March 1968).

                 APPENDIX B

                               APPENDIX B

     The following is a list of research work directly involved with
potato processing wastes, as described in the Water Resources  Research
Catalog (1967, 1968).

     Treatment of Protein Water Waste from the Manufacture  of  Potato
     Starch by Anaerobic Fermentation - Aerobic Stabilization  Process
     W. Van Heuvelen
     North Dakota Department of Health
     State Capitol Building
     Bismark,  North Dakota   58501

     The microbiological treatment of protein water waste from the man-
     ufacture  of  potato starch will be evaluated.   A treatment of
     anaerobic fermentation and aerobic stabilization will  be  used.
     Supporting Agency:   Federal Water Pollution Control  Administration

     Treatment of Alkaline Wastes from Potato Processing
     C. Bruce
     Vahlsing, Inc.
     Easton, Maine   04740

     The objectives of this project are to demonstrate  the  feasibility
     of:  Treating potato processing waste using the activated sludge
     system; combining potato processing waste with sugar beet refining
     waste;  and the feasibility of three in-plant  closed  waste water
     systems in the sugar beet plant.   The project will provide extremely
     valuable  data to both the potato processing and beet sugar industry.
     The aim is also to  determine if a $30 million industrial  complex,
     composed  of  potato  and sugar beet processing  and a residential com-
     munity, can  exist on a small stream,  as  is  proposed, and  have clean
     Supporting Agency:   Federal Water Pollution Control  Administration

     Aerobic Secondary Treatment of Potato Processing Wastes with
     Mechanical Aeration
     W.  M.  Swanson
     R.  T.  French Company
     Drawer  AA
     Shelly, Idaho

     The objective of  this  project  is  to  demonstrate  the  aerobic biological
     treatment  for potato processing wastes,  to  establish design criteria
     and to  develop  construction and operating costs.  The  following
     systems will be studied:   1)  Extended aeration with  sludge return;
     2)  Flow through aeration  with  sludge  return;  3)  Intermittant aeration
     with  intermittant effluent  withdrawal.
     Supporting Agency:   Federal Water  Pollution Control Administration

Operation of Potato Processing Plants to Reduce Waste  and  Stream
M. L. Weaver
U. S. Department of Agriculture
Albany, California

Object:  To help alleviate the growing problem of disposing
of wastes  from plants processing potatoes into food products,
without polluting streams or the air, through the development of new
or modified in-plant operations to reduce the quantity of  wastes
discharged and/or to convert them to a form more readily adaptable
to available methods of waste treatment.
 Plan  of Work:   Investigations will be made to determine the basic
 nature of  the waste material, i.e., amount and kind of both mineral
 and organic solid particles, amount and kinds of soluble materials,
 pH, biochemical oxygen demand, chemical oxygen demand, etc.,
 associated with different types of processed potato food products.
 The most economical and efficient means of removing suspended solids
 from  aqueous plant wastes will be sought.  Also, how to separate the
 mineral matter  from insoluble organic solids.  Possible uses for the
 suspended  organic solids will be explored.  Investigations will be
 made  of ways to reduce the  total quantity of soluble solids to be
 disposed of and to concentrate these for more efficient secondary
 treatment. Special attention will be given to the peeling operation
 in order to reduce the disposable waste.
 Supporting Agency:  U. S. Department of Agriculture

 Pilot Plant Development of  the Ion-Exchange Process for Recovery of
 Amino Compounds from  Potato Starch Factory Effluents
 W. L. Porter
 U. S. Department of Agriculture
 Chesnut Hill
 Philadelphia, Pennsylvania   19118

 Object:  To alleviate the problem of disposal of secondary wastes
 from  potato starch factory  effluents and reduce stream and air
 pollution; to obtain  a cost estimate for the process; and to produce
 crude amino acid mixtures.
 Plan  of Work:   An evaluation will be made by pilot plant scale of
 the methods of  recovery of  free amino acids from potato starch plant
 effluent by ion-exchange treatment.  The investigation will include:
 Effect on  process of  variation in concentration of in-put solids
 from  0.5-3.0% solution; applicability of Dutch process for recovery
 of protein before ion-exchange treatment of effluent liquor; degree
 of clarification required before ion-exchange processing; disposal
 of solutions from regeneration of columns and selection of regenera-
 tion  acid  from  this viewpoint; methods  for stabilizing the amino
 acid  product; and determination of composition, BOD and COD of
 effluent stream before and  after processing.  Cost estimates will
 be provided based on  the data and final process lay-out,  for  a  full-

     scale plant  to  recover nitrogen-containing materials from the  'protein
     water' effluent of a 10  ton per day and a 30  ton per day potato
     starch factory.  A minimum of  500 pounds of dry crude amino acids will
     be delivered representing the  typical product of the process for use
     in utilization studies and market development.
     Supporting Agency:  U. S. Department of Agriculture

     Two  grants have been awarded  recently by  the  Federal Water  Pollution
 Control Administration.

     Western Potato Service,  Inc.,  at Presque Isle, Maine, and Grand
Forks, North Dakota, has been awarded a grant for "Full Scale Demonstration
 and Evaluation of Potato Dry  and Wet Caustic Peeling Processes."  It is
proposed to install three dry caustic peeling lines in the Grand Forks
processing plant.  Conventional wet caustic peeling, existing in the
Presque Isle plant, will be studied as a control.  At both facilities
will be installed equivalent  primary waste treatment equipment for  the
purpose of comparative analysis.

     The project objectives are as  follows:

     1.  To determine total capital expenditures and operational and
         maintenance costs of dry caustic process and the conventional
         caustic process.

     2.  To compare the quantity and quality of the waste generated
         by the two systems.

     3.  To compare the treatment efficiency of silt removal systems
         and final clarifier and primary treatment systems at both
         plant locations.

     4.  To determine whether the dry caustic sludge would be accepted
         or rejected during cattle  feeding operations.

     The City of Grand Forks, North Dakota, was awarded a grant to  study
"Controlled Treatment of Combined Potato Processing - Municipal Wastes
by Anaerobic Fermentation, Aerobic  Stabilization Process."  Project
Objectives:  Demonstrate, develop,  and evaluate joint treatment of potato
processing - municipal wastes by use of stabilization pond pretreatment
methods consisting of (1) anaerobic - aerated combination, (2) anaerobic,
or  (3)  aeration treatment.  Study the effects of the treatment methods
on the stabilization ponds.   Determine any special procedures related to
most efficient operation of the anaerobic and aerated units,  factors
most responsible for waste removal, and development, and control of odors.

               APPENDIX C

                               APPENDIX C
     The cost curves presented in the following figures are taken from a
 report  to  the Potato Processors of Idaho Association by Cornell, Rowland
 Hayes,  and Merryfield  (1969).  The costs for domestic systems were
 presented by Smith  (1968).

     The costs for  primary treatment of potato waste are based on systems
 which have been designed and constructed in the Pacific Northwest.  The
 costs for secondary treatment of potato waste are based on engineering
 estimates which have been made for demonstration projects and preliminary
 estimates based on  pilot plant systems studied by the Potato Processors
 of Idaho Association.  All costs have been adjusted to a common base of
 June 1967 by using  the Engineering News-Record building index.  (See
 Figure  7)  The costs, which include the contractor's overhead and profit
 and engineering, are averages, and should be used only for general
 guidance and comparison.

     Silt Removal.  Figure 8 is a presentation of the capital cost for
 silt removal.  The  costs are based on a mechanically-cleaned clarifier,
 and include solids  pumps, electrical, piping and a building to house pumps
 and electrical gear.  It is assumed that the unit would be adjacent to
 and integral with either primary or secondary treatment units.

     Primary Treatment.  The capital costs for primary treatment are shown
 in Figure 9.  The costs include screen, clarifier, solids pumps, vacuum
 filter, solids bin, flow measurement, and a building to house pumps,
 screen, vacuum filter, and electrical gear.

     Secondary Treatment.  Figure 10 shows the capital costs for secondary
 treatment.  The costs include primary treatment and solids handling
 equipment.  It is assumed that the cost of land for stabilization ponds
 would be $500 per acre, that the cost for construction would be $2000 per
 acre, and that stabilization ponds would be loaded at about 50 pounds of
 BOD per acre per day.

     Irrigation.  The costs for irrigation systems are shown in Figure
 11.  The costs include a pump station, a self-cleaning screen, and a
 solids grinder.  An allowance of $500 per acre of land has been made.  The
 costs do not include primary treatment which would precede irrigation.
An application rate of 1/2-inch per day has been assumed.

     Operation and Maintenance Costs.  The operation and maintenance costs
 for primary and secondary treatment systems are presented in Figure 12.
The costs for potato waste treatment are based on very limited field
 information and are, for the most part,  estimates.  No allowance has been
made for return from sale of the reclaimed solids.

     Stabilization Ponds.  The capital costs for stabilization ponds are
shown in Figure 13.  The costs are based on construction costs for municipal

ponds and do not include allowance for land.

     Clarifiers.  Figure 14 shows the costs for clarifiers.  The costs
include the clarifier mechanism, concrete structure, piping, and foundation
gravel.  Normal excavation for a unit which sits 4 feet into the ground
is included.  No unusual foundation problems are included.

                                        FIO. 7

                                     NEWS RECOUP  COST  INDEX
                                                        CONSTRUCT ION
                                                        COST INDEX

                o.i          o.a         0.3

                       FI_O\A/- MOO

                 DCVIOIM  CAPACITY - MOO



                                   TEM, AE
                            ANAEROBIC CONTACT
      i            a            a



                  FIG. 1O
                   APPL. PIATB
                   DESION  CAPACITY - MOO

                 FID. 11

               DMION CAPACITY - MOD

                 TINO & MAIIMTBNAIMCK

                        FIO. 18
        "1        3   4    B   I    7  ' " ""  

                              FIB. 13

           1     8     3    4     B          7

                  DIAMETER - FEET  1O

               CLARIFIER8   CAPITAL  COBT