Figure 7.

Manguscrubber peeler - with roll removed to show coupling and water jets


TABLE 6

COMPARISON OF PEEL LOSS DATA

WET CAUSTIC ~ PSI DRY CAUSTIC - WPSI
Season % of Raw Potato Season % of Raw Potato
Winter 3-24 to 3-31 2-16 to 3-31
Avg 19.53 19.69
s 3.31 1.71
n 45 148
Spring 4-22 to 6-30 4-6 to 6-19
Avg 21.00 20.81
s 2.31 1.97
n 86 191
Fall 9-1 to 11-31 9-2 to 12-2
Avg 18.05 16.26
s 3.11 1.00
n 367 239
Winter 12-2- to 12-14 12-2 to 12-30
Avg 23.63 17.23
s 4.42 1.32
A 60 26
Late Winter & Spring Avg* | 20.50 20.32
Fall Early Winter Avg* 18.83 16.36
All Seasons Avg* 19.22 18.58

s Standerd Deviation - see glossary
n Number of samples - see glossary

* Weighted averages throughout

32



82

TABLE 4

‘WASTE ANALYSES.
WET- CAUSTIC ~ PSI

SEASON FLOW BOD COD ss# TS. ws KN OAK SETT SLDS
SP GR
Gal/ton Lbs/Ton mi/L
Avo «IT 646 98,0 15372 1.47 32.8 12,3 251 1,000
+ 76 974 m7 W788 1.76 26.1 08 54 1,002
a 4 4 4 4 4 4 3 4 4 4 4
£, Main Clarifier Ava «2591907147968 15Z_ M880 2.300 16 78 0,999
Influent 517 28.2 8 2.8 37 2B 0.44 8,88 (08 u 0.001
n 3 4 4 4 4 4 3 4 4 4 4
F, Main Clorifier Ce 72 1,90 22.8 74 51 0.998
Effluent s 47 206 32 a9 8 9 0.57 3.200 23 7 0,001
a) 4 4 4 4 4 2 4 4 4 4
REMOVAL (%) —- 4 8 92.8 40 35 95 552 1B 35 =
G.Mud Clarifier Ava (1315 3.9010 13.5017 98 0,200.60 5 25 0.998
influent + M7 287 0.8 862.69 400 0.2 05 13 0.001
n 4 3 3 2 3 3 2 1 3 3 3 4
HH. Mud Clorlfler Avg 587188 HT 38 01S 030.3 1.2 0,997
Effluent 5 29 029 1d 0.27 2.7 3.3 (0,07 0 0.7 0.001
n 4 3 2 3 3 2 1 3 3 4
REMOVAL (%) =~ 68 | 35 4 0.0 (0 40 = 5 =
SPRING
B. Hydro Bruther-pesler Avg 1224. 501114 90,8 14298 77 1,50 82.00 11,9 294 0.999
s 1033 23.8 73 537 8.4059 39 65 20.808 150 0.001
n 8 7 8 8 8 8 6 ry 8 8 8 8
E, Main Clorlfer Avo 379h 9h.) 721386 10158545 42.0108 8 0.998
lofluent s 827.450 3640 57 36 W16 1.29 5.667 24 0,001
a 8 7 8 8 8 7 8 8 2 8 8 8
F, Main Clarifier Avg (9777 65,1 1389 15K OH 3.00 3.08 40.5 9,0 7.0 0,998
Effluent + 87) 19.938 7.50 40.3 30 1,04 097495 2.2 u 0.001
n 8 7 8 7 7 8 4 8 2 8 8 8
REMOVAL (%) = 8 71 26 a Eo 9 a


The balances for six (6) days at WPSI were determined by accounting

for (1) all the dry solids and water entering the plant in the form

of raw material, chemicals, and water, and (2) the dry solids and water
in the finished products and wastes. Table 10 presents the difference
between the material leaving the plant as a percentage of the material
entering the plant. The balances for WPSI were good with a mean of
95.3 percent for dry solids and 107.3 percent for water. These percen-
tages are reasonable considering the difficulty encountered in obtaining
representative samples from.such a large volume operation.

Table 10, PLANT MASS BALANCES

WET CAUSTIC - PSI IR-DRY CAUSTIC - WPS!

Solids Solids Water

Day Pay Selick Dey Solids “a
1 85.4 94.3 95.4
2 88.4 88.7 110.1
3 112.1 88.3 107.4
4 86.1 100.0 106.3
5 94.8 103.3 110.5
6 91.4 97.5 114.3
Avg | 93.1 95.3 107.3
s 10.0 6.1 6.5

s Standard Deviation = see glossary

Solids balances were calculated for six (6) days at PSI by accounting
for all the solids entering and leaving the plant in the form of raw
material, chemicals, finished product, and waste products. Only the
solids balance could be obtained from PSI because the plant fresh water
was not metered. The dry solids recovery for PSI was determined in the
same manner as for WPSI. The solids leaving the plant were expressed
as a percentage of the solids entering the plant. The solids balance
for PSI was also quite good (93.1 percent) considering the problems
encountered in sampling.

WASTEWATER CHARACTERISTICS

Biochemical Oxygen Demand

The PSI plant main clarifier influent BOD values of 90.7, 94.1, 58.4
pounds per ton of raw potatoes processed for the winter, spring, and
fall seasons, respectively, were considerably larger than the correspon-
ding values of 35.1, 25.9, 38.4 pounds per ton at the WPSI plant.

37


PROCESS = WASTES = SCS POS

PRODUCT Liquid to Aerated Lagoon —>

to Stabilization Lagoon >

Recirculated R
Water From FLUMING MUD, SOLIDS, WATER
Processing

CAUSTIC REELS.

Solids to Landfill
RETENSION BELT

SOLIDS, WATER

SOLIDS, WATER Large Potato Solids to Cattle

4

Vacuum Filtration

SOLIDS, WATER

SOLIDS, WATER
SOLIDS, WATER

SOLIDS, WATER

WASTE
To Cattle Feed
WASTE

Solids to Cattle Feed
or Landfill

COOLING

GRADING

PACKAGING
CLEANING

FINISHED
PRODUCT

FIGURE | -— FLOW DIAGRAM OF POTATO SERVICE, INC. (PSI)
WET CAUSTIC METHOD OF PEELING

* uvoro BRUSHER WASHER PEELER


TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)

1, REPORT NO, 2. 3. RECIPIENT'S ACCESSIONNO.
EPA-660/2-74-088
4. TITLE AND SUBTITLE Is. REPORT DATE
. . . 19 i
Infrared Dry Caustic Vs. Wet Caustic Peeling of duly 1975 (issue date)
White Potatoes
7, AUTHOR(S) |8. PERFORMING ORGANIZATION REPORT NO.

Otis Sproul, John Vennes, Wayne Knudson, Joseph W. Cyr|

9. PERFORMING ORG ANIZATION NAME AND ADDRESS 10. PROGRAM ELEMENT NO.
Western Potato Service, Inc. 1BB037
P.O. Box 518 11, CONTRACT/GRANT NO.
Grand Forks, ND 58201
12060 EIG
12, SPONSORING AGENCY NAME AND ADORESS 13, TYPE OF REPORT AND PERIOD COVERED
Environmental Protection Agency Final
Pacific NW Environmental Research Laboratory 14, SPONSORING AGENCY CODE

National Environmental Research Center
Corvallis, Oregon 97330

75, SUPPLEMENTARY NOTES

“the intrared dry caustic peeling system has been evaluated through plant scale compa-
risons with the conventional wet caustic system. The following significant differen-

ces were noted when the dry peel system was compared to the wet process:

(a) decreased peel loss by 13.1 percent.

(b) decreased caustic consumption by 26 percent.

(c) decreased wastewater from peeling by 73 percent.

(d) decreased BOD; in the peeler wastewater by 78 percent.

(e) decreased suspended solids in the peeler wastewater by 77 percent.

(f) decreased alkalinity in the peeler wastewater by 61 percent.

(g) increased operating costs of peeling by 39 percent but decreased total annual
cost of peeling and primary treatment through lower peel loss by 10 percent.

(h) decreased total plant raw waste load: water use by 18 percent, BOD; by 47
percent, and suspended solids by 57 percent.

No significant differences were noted in the efficiency of primary sedimentation of
the raw wastes nor in the mud clarifier results. Primary sludges and their de-
watering characteristics were found to be similar.

7. KEY WORDS AND DOCUMENT ANALYSIS

ja. DESCRIPTORS lb. IDENTIFIERS/OPEN ENDED TERMS |c. COSATI Field/Group
Process Engineering, Food Technology, Potato peeling, North
Waste Management, Environmental Dakota, Maine, Manage- 13/13B
Engineering ment of Potato Process-

ing Wastes

18. DISTRIBUTION STATEMENT 19, SECURITY CLASS (This Report) 21. NO. on

Release Unlimited 20. SECURITY CLASS (This page) 22. PRICE

EPA Form 2220-1 (8-73) s U.S. GOVERNMENT PRINTING OFFICE: 1975~698-963 17 REGION 10


Table 14. SLUDGE CHARACTERISTICS FROM CLARIFIERS

WET CAUSTIC = PSI IR-DRY CAUSTIC - WPSI
Total Total | Fotal Total Total ~ Total | Total Total
Season | Solids Solids | Solids Solids Solids Solids [Solids Solids
Ths/ton % ~~ | Ibs/ton  % Ths/ton % ~~ |Ths/ton  %
WINTER] Main Clarifier | Mud Clarifier Main Clarifier | Mud Clarifier
Avg 23 2.7 4.3 26 32.9 6.9 [19.7 19.6
st Loe 0.14 4.0 7.9 2.4 8.0 5.5
n 1 1 2 2 15 16 7 7
SPRING
Avg 53 6.6 113.6 21 32.7. 9.30 fron --
s - m-- [11.2 21 13.7, 2.9 Jone _—
n T 1 5 5 7 18 <= --
FALL
Avg 34 3.9 4.3 30 34.1 7.9 [19.7 29
s 15 1.5 1.66 26 15.7 2.1 14,1 16
n 12 i 11.0 11.0 18 19 15.0 16
AVGS| 35 4.0 [6.9 27 33.3 8.1 [19.7 26

a Standard Deviation
b Number of Samples
c Weighted average

The filtration results of WPSI are nearly those which Grames and
Kueneman (7) indicated as expected for a wet caustic peeled potato
primary sludge. At theiWPSI plant the total solids content of the
filter cake was about 13 percent and the recovery of total solids in
the cake was about 40.3 pounds per ton of potatoes. The results
showed a significant difference between plants during the winter and
fall and between seasons at PSI but not at WPSI. The filter loading
was 4.6 pounds of dry solids per square foot per hour for WPSI.

47


were insufficient for a comparison between plants during the spring.

The higher overflow rate of 755 gpd/ft2 at PSI may have promoted better
settling of the flocculent material in the effluent than the lower
overflow rate of 298 gpd/ft2 at WPSI.

Suspended Solids Removal

The effluent suspended solids data at the PSI plant have been computed
from the total solids data. The computation was made using a ratio

of 0.186 for the main clarifier effluent and 0.458 for the mud clarifier
effluent. These ratios were developed from the WPSI data. As indicated
earlier, this procedure was necessary because the original suspended
solids data at PSI were determined incorrectly.

The suspended solids removals in the main clarifiers at each of the
plants were between 70 and 85 percent for each of the seasons. The
difference in these percent removals was significant at the 0.05 level
during the fall season between plants and between seasons at WPSI,

but not during the spring and winter nor between seasons at PSI. The
PSI main clarifier effluent averaged 16.9 pounds of suspended solids
per ton of potatoes processed versus 8.8 pounds per ton at WPSI. The
results showed a significant difference at the 0.05 level between plants
during the winter and spring season, but not during the fall seasons;
there was also a significant difference at the same level between seasons
at PSI but not at WPSI. The amount of suspended solids in the effluent
after primary clarification was significantly less when the dry caustic
peeling system was used. These solids would require a larger secondary
treatment system and would represent some loss of revenue if the primary
sludge solids were being sold. The mud clarifier at PSI removed 63.3
percent of the influent suspended solids versus 76.3 percent at WPSI.
The PSI mud clarifier effluent had 4.37 pounds per ton of suspended
solids in the effluent, while the WPSI effluent contained 3.82 pounds
per ton. The percent removals were not significant at the 0.05 level
between seasons at the individual plants nor during the winter season
between plants, but were significant during the fall season. Spring
could not be compared because of no results at WPSI.

Nitrogen And Phosphate Removal

The total Kjeldah] nitrogen and total phosphate removals in the main
clarifier at PSI exceeded those at WPSI. The Kjeldahl nitrogen removal
by primary clarification over the three seasons was 36.8 percent and
14.1 percent at PSI and WPSI, respectively, while the phsophate removal
was 38.6 percent and 29.2 percent. The lower removals at WPSI may be
attributed, in part, to the lower main clarifier influent nitrogen

and phosphate values. The influent Kjeldahl nitrogen (as N per ton)
at PSI was 4.3 pounds versus 1.5 pounds at WPSI. The corresponding
phosphate values (as P0q) were 4.5 pounds and 2.2 pounds per ton at
PSI and WPSI, respectively. The higher influent values at PSI, even
though higher percent removals were obtained, resulted in higher concen-
trations in the effluent. These figures all are from winter-spring
results because determinations were not made during the fall at PSI.

45


Table 16. COMPARISON OF CAPITAL COSTS OF PEELING SYSTEMS

DRY CAUSTIC WET CAUSTIC

(3'Tines) (4 Tines)
Purchased equipment cost (E) $236900.00 $128300.00
Purchased equipment labor cost (E,) 38100.00 20500.00
Plumbing materials (FyMp) 12000.00 14400.00
Plumber's rate (fy) 16.00 3.00
Plumbing man hours (ML) 1270 1440
Electrical materials (feMe) 13376.00 16100.00
Electrician's rate (fy) ‘ 12.00 3.00
Electrician man hours me) 244 300
Engineering rate (fen) 6.60 6.60
Engineering man hours (Hep) 1140 523
Unit cost per drawing (fy) 168 168
Number of drawings (d) 7 7
Total capital investment (c,) $332,324 $188,980

NOTE: Contractor's fee and contingency (fe) This factor included in
other factors, since this is a completed project.

51


Diminished infrared treatment resulted in a need for increased caustic
treatment. This harsh caustic treatment caused the Shufflo infrared
feeders to become loaded with peeler solids causing build-up and sticking.
The "cure"---a water spray over the Shufflos---further diminished

the infrared effect because of the resulting temperature drop.

Proper caustic treatment and retention belt timing allow the treated
tubers to cross the Shufflos with their skins essentially intact without
the use of water sprays. Also the Magnuson peeling equipment should

be set up to maintain a load occupying approximately 1/3 of the space
within the-Magnuscrubber peelers. Small loads allow the tubers to

pass through with too little actual contact with the abrasive rolls.

OPERATION AND MAINTENANCE COSTS - PRIMARY TREATMENT SYSTEMS

Table 21 shows the operating and maintenance costs of the primary
treatment system. The actual per ton costs for the dry caustic
were $0.77 higher than the wet caustic, and the potential costs were
$0.05 higher per ton.

Table 21. OPERATION AND MAINTENANCE COSTS - PRIMARY TREATMENT SYSTEMS

WET CAUSTIC ~ PSI IR-DRY CAUSTIC-WPS!

Actual/ton | Potential/ton |Actual/ton |Potential/ton
Power/ton $.054 same $.059 same
Labor 3 men at $19/day/man .073 $.059 139 $.099
Maintenance/ton +130 V7 2136 122
Total/ton $.257 $.230 $.334 | $.280

TOTAL OPERATION AND MAINTENANCE COSTS
1

Table 22 shows an evaluation of the overall operation and maintenance
costs. The actual costs for the IR-dry caustic were $0.344 per ton
higher than for the wet caustic, but only 0.113 per ton higher on a
potencial production basis.

Table 22. TOTAL OPERATION AND MAINTENANCE COSTS

WET CAUSTIC ~ PSI IR-DRY_CAUSTIC-WPS!
Actual/ton |Potential/ton|Actual/ton Potential/ton
Table 20 - Peeling costs/ton}| $1,532 $1.490 | $1.799 | $1.603
Table 21 - Primary costs/ton 257 -230 2334 ~280
Total net operating cost/ton | $1,789 $1.720 | $2.133 | $1,833
$5



solids is a function of the hydraulic and solids loadings. The hydraulic
loading data are presented in Table 13. The data show that the overflow
rates in the main clarifiers were not significantly different during
winter and spring months; however, the 221 gallons per day per square
foot (gpd/ft¢) at PSI during the fall was significantly lower at the
0.05 level than the 412 gpd/ft@ at WPSI. There was also a significant
difference at the same level between seasons at each of the plants.

Excessive detention times in primary clarifiers with readily fermentable
wastes such as potato solidsare undesirable. The suspended solids,

if retained for excessive periods, will be fermented by anaerobic
bacteria. This fermentation may result in a sludge that floats due

to gasification in the sludge zone. The sludge may be altered so it
will not dewater well and the BOD in the clarifier overflow may be
increased as a result of the solubilization of the sludge during the
anaerobic fermentation. Since the equipment was designed for acid
conditions, practically no maintenance problems were caused by the acid
resulting from excessive detention times. Table 13 shows that the
average detention time at PSI during the fal] months was 12.9 hours,
compared to 4.7 hours during the winter and 6.4 hours during the
spring. These high detention times permitted excessive fermentation

of the sludge. The weighted average pH of the main clarifier effluent
at PSI was 8.3 versus the average of 7.7 at WPSI. The results showed
no significant difference (at the 0.05 level) between either plants or
seasons at the individual plants. The higher pH at PSI, even though
more acid production occurred, was caused by the much higher initial
alkalinity present in its waste than in that at WPSI. This additional
buffering prevented the pH from dropping to lower levels in the effluent.

BOD Removal

The BOD removal by primary clarification at each plant was nearly the
same, averaging 33.5 and 31.7 percent for the year at PSI and WPSI,
respectively. There was no significant difference at the 0.05 level
between seasons at each plant nor between plants during the winter

and spring; however, there was a significant difference at this level

in the fall, the result of a low main clarifier influent at PSI.

The difference in the peeling method between the two plants did not,
therefore, appear to affect the efficiency of BOD removal through primary
clarification. It should be noted that the PSI plant had a higher

BOD in the main clarifier effluent, 46.0 pounds per ton averaged over
the three seasons, versus the corresponding 23.1 pounds per ton at
WPSI. The results were significantly different at the 0.05 level
between seasons at the individual plants and between plants during the
winter and spring but not during the fall. This represents 22.9 pounds
per ton more BOD from the wet caustic peeling process for treatment

by the secondary treatment system. This 99 percent increase in the _
BOD to be treated in the secondary system is a conservative figure since
the sludge bypass did at times increase the plant effluent BOD level

at WPSI.

43


SECTION III
DESCRIPTION OF PEELING SYSTEMS

Good peel removal is a pre-requisite to maintaining defects at the
level required by U. S. Grade Standards. Peeling may be accomplished
by several methods - caustic treatment to soften the skin and immediate
underlying tissue followed by skin removal by brushes; steam treatment
followed by skin removal; and abrasive treatment. Although steam
peeling will give a lower peel loss in the fall, caustic is preferable
in the winter and spring. In theory, the caustic treatment should

be kept to a minimum consistent with the required peeling (determined
by minor defect count). Peeling should never be used. as a method

of removal of major defects. Theoretically, potatoes could be heated
in water until the skins could be removed. However, this would result
in a very high peel loss as much of the potato immediately under the
skin would be lost. Thus a caustic treatment to soften a minimum
amount of potato along with softening the skin is required to give
optimum results. In fact, it is this reasoning that led to the trial
use of the infrared treatment. By increasing the temperatures of the
skin and caustic, the softening would take place sooner and less of
the potato immediately under the skin would be lost.

CONVENTIONAL WET CAUSTIC---POTATO SERVICE, INC.

The PSI processing plant described herein is an example of a conventional
wet-caustic peel system.

Potatoes reach the peel line via a water flume from storage (no raw
potato washer is included in this line as at WPSI). Each peel line
has a storage hopper for continuous and uniform feed of potatoes to
the remainder of the peel line.

The four peel lines utilize a common large caustic storage tank. Each
peel line consists of four ferris-wheel type caustic-reels each equipped
with its own vari-speed drive, temperature controllers, black-iron
circulation tank and pump and overflows to return excess caustic to

the circulation tank. Following the reels, each line has its own
rubber-belt retention-conveyor on which the caustic-dipped tubers are
held for several minutes. As the tubers leave the retention belts,
they are dropped onto a hydro-brusher-washer peeler which consists of
cylindrical brushes into which water spray nozzles direct wash water
over the moving tubers (see Figure 3).

Water usage is 5 gpm per nozzle (there are 80 nozzles divided among
six headers with a total water usage of 400 gpm). Each of these are
rated at 10 tons of unpeeled potatoes per hour. Potatoes emerging
from the hydro-brusher-washer peeler are dropped onto an evenflow surge
tank from which they are transferred to the trim table. Variables on

15


The above effects appeared to peak during the late winter and spring
when the degree of peeling required was at the maximum. In the fall,
the Magnuscrubber peelers and Magnuwasher peelers were reset to carry
more load---1/3 to 1/2 full. Once this was accomplished and the caustic
treatment cut back to the point at which the potatoes were reaching
the Shufflos essentially intact, the need for water sprays over the
Shufflos was essentially eliminated. With these conditions and with
caustic concentration at 9.5 to 10.5 percent, caustic temperature at
190°F, and caustic immersion time at 2 to 2-1/4 minutes, the retention
belt set for approximately 2 minutes residence time, and the infrared
burners set for 1-1/2 minutes, peel losses as low as 15.0 percent were
obtained.

The peel loss results during the last week in November and the first
two weeks of December are not included due to a breakdown of one scrubber
which necessitated extremely heavy loading of the other two peel lines.

Using the peel losses for fall and early winter (9-2 to 12-30) when the
IR-dry caustic system was operating most successfully and there was a
significant difference at the 0.05 level, the peel loss was 2.5 percent
less than the wet system which calculates to a 13.1 percent decrease

in peel loss when compared to the wet caustic system. There was a
statistical difference at the 0.05 level between the four periods at
each of the plants, and between plants during the fall and early winter
but not during late winter and spring.

COMPARISON OF CAUSTIC USAGE

The caustic consumption data is presented in Table 7 below. It may
be noted that weighted averages were consistently lower at WPSI.

Standard deviations are not shown due to the effect of the caustic
make-up tank. Once this tank was charged, it required an indeterminate
number of hours before recharging was necessary. Thus the daily usage
did not necessarily reflect actual usage, but merely the amount of

50 percent caustic added to the caustic peeling solution. However,
over a period of one or several weeks, this did represent very nearly
the actual usage ("n" indicates the actual number of "daily caustic
usages” represented).

The WPSI caustic consumption was only 73.8 percent of the PSI results,
indicating a significant reduction in caustic usage by the dry caustic
method. The IR-dry caustic peeling system decreased caustic usage

by an average of 0.262 lbs per 100 Ibs peeled and thus would decrease
the costs of peeling by $0.42 per ton of potatoes.

33


STANDARD DEVIATION (s) - The square root of the variance which describes
the variability within the sampling data on the basis of the deviation
of individual sample values from the mean.

s E(x-R)2

n-1

SUSPENDED SOLIDS (ss) - The quantity of material deposited on a filter
when a liquid is drawn through a Gooch crucible.

TATER MEAL - Dried potato waste.

TOTAL KJELDAHL NITROGEN (TKN) - The sum of free ammonia nitrogen and
organic nitrogen in a sample.

TOTAL PHOSPHATE (TP0q) - All phosphate present in a sample
TOTAL SOLIDS (TS) ~ All solids ina liquid, both suspended and dissolved.

TOTAL VOLATILE SOLIDS (TVS) The quantity of residue lost after the
ignition of total solids.

TURBIDITY - An expression of the optical property of a sample which
causes light to be scattered and absorbed rather than transmitted
in straight lines through the sample.

VOLATILE SUSPENDED SOLIDS (VSS) - The quantity of suspended solids
lost after the ignition of total suspended solids.

WEIR - A flow measuring device consisting of a barrier across an open

channel, causing the liquid to flow over its crest. The height of
the liquid above the crest varies with the volume of liquid flow.

64


CONTENTS

Sections Page

I Conclusions 1

II Introduction 3

III Description of Peeling Systems 15

Iv Description of Pretreatment and Primary Treatment 18
Systems

Vv Analyses and Sampling Procedures 21

VI Results and Discussion 26

VII Infrared Dry Caustic Sludge for Animal Feed 49

VIII Capital and Operating Costs for Peeling and Primary Treatment 50
Systems

IX Effect of Peeling System on Cost of Primary and Secondary 57
Systems

x References 62

XI Glossary 63

iii


SECTION VI
RESULTS AND DISCUSSION

The analytical data from the two plants will be presented by separating
the results into winter, spring, and fall sections. The winter data
are for February, March, and December, 1971; the spring data for April,
May and June, 1971, and the fall data are for September, October and
November, 1971. The potatoes used for the late winter (February and
March) and spring data were from the 1970 growing season, while the
fall and early winter (December) 1971 data were from the 1971 growing
season. This separation of data has been made since there may be a
difference in the waste characteristics, especially from the peeling
process, since a deeper peel of the potato is usually necessary on
those held longer in storage. Also the early and late winter data
have been grouped due to the small number of sample sets for these

two periods from PSI.

Although the design tonnage for the PSI plant is 1000 tons of raw pota-
toes per day it only processed 810 tons per day during this evaluation.
Comparable tonnages for WPSI are 600 and 425, respectively. There

was a significant difference in the average quantity of potatoes pro-
cessed between seasons at the WPSI plant; however, this was not so

at the PSI plant. This contrast was probably due to the fact that

the PSI plant had been in operation for more years and thus had more
experienced help than the WPSI plant.

A summary of some of the data collected during this evaluation at
the PSI and WPSI plants is shown in Tables 4 and 5, respectively.

A copy of all the raw data is available upon request from the Waste
Treatment Research Program, Pacific Northwest Environmental Research
Laboratory, Corvallis, Oregon.

The main clarifier influent is made up of the waste loads from the
peel system and all following operations within the plant except for
the potato flumes used to convey the potatoes from storage to the peel
lines. The waste characteristics of these other processes can be ob-
tained by substracting the peel system data from the main clarifier
influent data. The data for the mud clarifier influentare for water
used to flume the potatoes from storage to the unpeeled potato washer
located before the peel lines.

The main clarifier influent at both PSI and WPSI passed through 4 mesh

screens in advance of the sampling point. In correlating certain data,
such as suspended solids entering the main clarifier with that leaving

26


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SEE LUBRICATION ANO $ERVICG INSTRUCTIONS FOR MANTENANGE
OF WOTORS, GEAR REDUCTION UNITS ANO OTHER REQUIREMENTS.

Figure 8.

Magnuwasher peeler, pictorial drawing


SECTION IV

DESCRIPTION OF PRETREATMENT
AND PRIMARY TREATMENT SYSTEMS

POTATO SERVICE, INC.

Pretreatment of liquid wastes at PSI consisted of sliver and nubbin
removal by Shufflos and grader screens, respectively, and of screening
white waste through two 4 mesh screens in advance of the primary clari-
fier. Waste fat removal is accomplished through flume baffles which
allow the liquid waste to flow underneath them but retain the floating
fat which is cleaned out manually. Finished product wastes were removed
as solids rather than allowing them to enter the waste stream.

Primary treatment of wastewater is accomplished by utilizing two cla-
rifiers; a 60-foot diameter process water clarifier (main clarifier)
and a 24-foot diameter fluming water clarifier (mud clarifier).

The process water passes through two 4 mesh shaker screens (process
water does not include fluming water) prior to entering the main clari-
fier, 60 feet in diameter with a 9 foot side wall depth and an appro-
ximate volume of 225,000 gallons. This clarifier is equipped with a
surface skimming device to remove floating solids, such as frying shor-
tening, and a pair of rake arms on the bottom of the tank. These arms
move the settleable solids on the conical bottom surface to the center
of the clarifier where they are drawn off for dewatering on a continuous
belt vacuum filter. The filtrate is discharged into the primary cla-
rifier effluent prior to discharge into lagoons.

WESTERN POTATO SERVICE, INC.

Pretreatment of waste from WPSI consists of three separate operations:
peel solids (peel taken off the potato by the Magnuscrubber peeler)
removal, white waste (trim waste, unusable potatoes, etc.) removal,
and finished product waste (french fries) removal. The peeler solids
are conveyed from the Magnuscrubber peeler to a small pumping pit from
which they are pumped by a concrete pump to a waste hopper for ultimate
disposal by truck to land fill. Removal of white waste is accomplished
by passing the waste stream through a 4 mesh link belt vibrating screen.
These solids are collected in a waste hopper for trucking to cattle
feeders; the remaining wastewater is pumped to primary treatment.

The third operation, finished product removal, is "dry handled" for
ultimate trucking off for cattle feed.

18


they are hydro pumped to Gilkie shakers to feed the cutters from

which they are flumed onto Shufflos (sliver removal) and then onto

key graders (nubbin and short piece removal), then flumed to the
blanchers. From the blanchers, they are dropped into dip tanks
(treatment with dextrose and disodium dihydrogen pyro-phosphate) ;

and after dewatering, to the fryers; then to defatting screens and onto
air cooling belts and into the freezer tunnels.

At WPSI, the potatoes are flumed from storage, passed through a hydro-
brusher-washer and then to an evenflow hopper from which they are

fed into caustic reels, over retention belts, and then onto the Magnu-
shufflo Infrared units (for increased time and temperature treatment).
The potatoes are then fed into the Magnuscrubber-peeler units where
most of the peel is removed as a thick sludge. The potatoes are
discharged from the Magnuscrubber-peelers into the Magnubrusher-peelers
(see Figures 8 and 9) for complete peel removal and washing. They

are then screw lifted to a shaker feeder to grading screens where

they are sized, then trimmed and screw lifted to the surge tank for
evenflow over a Gilkie shaker to the cutters, over Shufflos, then over
nubbin graders to flumes feeding the hydro-pumps which feed the blanchers.
Upon discharge from the blanchers, they are fed into a dip tank, then
are either hydro-pumped or belt removed to dewatering screens which
feed into the fryers, then over defatting screens, over air cooling
belts and into the freezers.

14


the Magnuwasher peeler, it may be noted that the values may be less
entering the clarifier than they are leaving the Magnuwasher peeler.

This has been caused by solids removal at the screen and/or additions

of water with lower solids content. In cases where the values entering
the clarifier are higher than those leaving the washer, the other parts
of the plant have contributed a large load of solids which passed through
the 4 mesh screen.

A perusal of the Magnuwasher peeler data at WPSI for the three seasons
shows that each of the various waste characteristics were lower for the
spring season than for the fall and winter seasons. This was caused

in major part by the decreased by-passing of the Magnuscrubber peeler
waste solids to the Magnuwasher peeler wastewater line during the spring
months. Discharge of this material to this line occurred on certain
sampling days because of peeler solids handling equipment breakdown
and/or increased plant production in the fall and winter resulting

in increased peeler scrubber solids at a rate which exceeded the capa-
city of the solids handling equipment. Therefore, bypassing of the
solids on some of these days to the washer wastewater line was inevitable.

The data have been analyzed for significant differences with a two way
variance test and by a t test. (These results will be presented at
appropriate points in the discussion.)

PEEL LOSS

The data for comparison of the peel loss are presented in Table 6.

It has been expected that the IR-dry caustic system would lessen the peel
loss, and this proved to be true to a degree during the fall and early
winter, but not so in the late winter and spring. The following factors
were thought to be the cause of the low differential between the plants
during the late winter and spring:

1. Water spray use over Shufflos---whenever the caustic treatment
became too harsh, some of the affected potato tissue would build up
on the Shufflos. One remedy for this was to continually wash the Shuf-
flos with a water spray. This treatment would, of course, lower the
tuber temperature which in turn resulted in less efficient treatment
by the infrared necessitating more caustic treatment to effect the
desired result. This difficulty was not discovered and corrected
until early fall.

2. Infrared units too small for load.
3. Operation of the Magnuscrubber peeler and Magnuwasher peeler
with insufficient load to operate efficiently---with low loads, the

potatoes tended to spend more time bouncing than in contact with the
rolls.

27


ROTARY ROLL cAEANER

ae Co

notany Reve cm
poems ATO Bat
ROARS ON Eee we ore erate
val a

os i
ey u

LETT Th
TITLE LI

wate
LITT TT TI

oes

LIT

eee ee
a SEY RCA
Ieee

rary
ree

Mont AS our + son - sobs
covery feng

Figure 5. Pictorial drawing of model D-14 Shufflo infrared unit


Table 18.

PEELER EQUIPMENT

WET CAUSTIC-PSI

IR_DRY_CAUSTIC-WPSI

Caustic make-up tanks

Caustic reels with
circulation tanks

Retention belts
Magnuson shufflos
Magnuson Infrared units
Magnuscrubber peelers
Magnuwasher peelers

Hydro-brusher-washer-
peeler

Peeler solids pump

1
4

PoOooOCOF

1
3

OCW WwW ww

Table 19.

PRIMARY TREATMENT EQUIPMENT

WET_CAUSTIC-PSI

IR_DRY_CAUSTIC-WPSI

Peeler solids storage
hopper

Waste shaker screen
Primary clarifier
Vacuum filter

Filter cake storage
hopper

Mud clarifier

0

1

~o oo

53



SECTION I
CONCLUSIONS

Peel loss (using fall and early winter results when the system operated
most successfully), as shown in Table 1, decreased by 13.1 percent;
caustic usage decreased by 26 percent; peeling water usage decreased
by 73 percent; 5-day biochemical oxygen demand (BOD) decreased by

78 percent; suspended solids decreased by 77 percent; alkalinity de-
creased by 61 percent; and capital and operating costs increased by

39 percent but decreased total annual costs through lower peel losses
by 10 percent>

Table 1. COMPARISON OF PEELING SYSTEMS

Items Compared Wet Caustic | IR-Dry Caustic

Peel Loss (%)

Late Winter & Spring 20.50 20.32

Fall & Early Winter 18.83 16.36

All Seasons 19,22 18.58
Caustic Usage (Ibs/100 Ibs) (Ibs/ton)

All Seasons 1.020 20.4 | .753 15.1
Wastewater Characteristics

Volume (gal/ton) 1302 346

BODs (|bs/ton) 64 19

Suspended Solids (Ibs/ton) 103 29

Alkalinity (Ibs/ton) 28 10
Capital and Operating Costs $/ton 1.869 2.593
Credit for Reduced Peel Costs $/ton -.91
Overall Capital and Operating Costs 1.869 1.683

$/ton

Capital cost was $47,245 for each conventional wet caustic Tine rated
at 20,000 pounds per hour and $110,775 per infrared dry caustic line
(same rating). Capital costs for primary treatment at Western Potato
Service, Inc. (WPSI) (3 peel lines) was $165,304 and at Potato Service,
Inc. (PSI) (4 peel tines) $212,100. Total annual cost of peeling

and primary treatment per ton processed was $2.126 at PSI and $2.017
at WPSI based on actual production. At potential production, these
figures would be $1.993 and $1.537, respectively.


2

WEIGHT - VOLUME MEASUREMENT SAMPLING POINTS /SAMPLE PROPORTION TO FLOW OR WEIOHT:
we.

1) FLUME ai recut Souies. consrant we
8 Flow werer ¢ runswey 1 Brag
3 Flow Maren re) +) sanouv wasuse reecie] MOPoE MON TO MLOW
rtow Merea (compound perecror) 5) caustic’ mraxe (30%)
Sy raven" weiane" (ner) ©) Screen Solos / consTa
3) NRLUEntte ILE FILTRATE. seunoc Da CLaRIZIER INPLUENT Coe <0}7 Proronr 101
Dine IN _ELARIFIER EFFLUENT (60}/ CONSTANT VOLUME: AUTOMATIC. SAMP
ME CONSTANT VOLUME PUMPING ©) Muo cLamirien mruueNr Ces) / oRoPont rie SAMPLER
WW TANK. LEVEL 1) MUD CLARIFIER EFELUENT\2=)/ PROPORTION TO FLOW
ID mane, conve yon seaue Mvp EtAanrien Stvoae’7 cosran voLuie

yup
HIGHT CNO FILTRATION ) 10 MAIN CLANIFIER. SLUDGE / CONSTANT, VOLUME
AVERAGE 50. GPN. WATER TO PEELER S0U108 © vacua CANE) CONSTANT VOU
SNMTER to PU

Ma vacua "PILTER FILTRATE / CONSTANT WOLUME
9) RAW MAT! HAL

SYMBOLS:
X} VALVE FOR DIVERTING FLOW
=) DIRECTION OF FLOW

‘Te forvevce| [wisn]

aw
STORAGE —=—@O— ww!

‘aioe

PEELED
WASHER

1 _t
“ea” | FEBRP] [oscrizee) | eceece|“[ nonce]
= | El Peta ; ir

+69 =
teeter
INCOMING a a ns ~
Ce inreR name cy
epseseence rmagr mvt
ruume poren, LD
5 FRY ¢ PACK
MARE-UP waste (OOM FLUNE
[rae |_Fuvme —-—l
pues | pir rm
ae T viene ¢ FLAKE MER
- ant FLOMe al
(4 Mes ab. | offitne semen HOPPER
MYOROCOOLER
u scREEN A
TF 60 = “Titer
HOPPER
LAND Fa

Figure 12. Sampling points and instrumentation (WPSI)



TABLE 25
TREATMENT SYSTEM PARAMETERS

09

Primary Clorifier | ‘Vocuum Filter Asrutton Seieniey edie Filter || Aerobie Digester
influent Effivent Size Bosin Equipment : Bosin | Equipment
2% : se 2
; ei l$f [a] Hi) ELE [dere |
si glee 3 gaceda (E38 alfad el teld [edeehie bale
roy 8 3 sale j a ¥ 5 al; 3 | é SESE S13
82 2|f8 & SHSUGE |r | 28 alia [ais] [Seach bile
Wet 1.573 1,575
Coustie 300 4 16875 2 125 2
18.8% ‘36100 24400 gis) x 525] « 13.35) x | % [7.83]) 398 | x |.168] x 75} «PIS,
Peat ox us 125 9 1% 75.1% |r0
Loss 95650 46600
I-Dy 1,100 1,100
Couttie 200 2 [3538 2 90 '
16.3% 18150 12300 axa [12] [104 270) x [220] x | 92 7.00) s92 | x J.00s) x aorsise] « Js
Peal no 125 9 “4 50 109
lon 40800 24200 |
\
|



10.

i.

SECTION X
REFERENCES

Graham, R. P. , Huxsoll, C. C., Hart, Mr. R., Weaver, M. L. and
Organ Jr., A. I. "Dry Caustic Peeling of Potatoes", Western
Utilization and Development Division, Agricultural Research Center,
U.S.D.A., Albany, California. Food Tech., 23:61. 1969.

Willard, M. "Pilot Plant Study of the USDA-Magnuson Infra-Red

Peeling Process." Paper presented at 19th National Potato Utiliza-
tion Conference, Big Rapids, Michigan. July 1969.

Standard Methods for the Examination of Water and Wastewater
Edition. Boyd Printing Co., Inc., Albany, New York. 1965.

Technicon Instruments Corporation. Industrial Methods Bulletins
No. 26-69W, 30-69A, 3-68W. Tarrytown, New York. 1969.

Volk, William. Applied Statistics for Engineers, second edition.
McGraw-Hill, New Yorke 354 p. 1969.

EPA Manual - Analytical Methods

12th

Grames, L. W., and Kueneman, R. W. "Primary Treatment of Potato
Processing Wastes with Byproduct Feed Recovery", Journal Water
Pollution Control Federation, 41(7):1358-1367. 1969.

Peters, M. S., and Timmerhaus, K. D. Plant Design and Economics
for Chemical Engineers, McGraw-Hill, New York, 850 p. 1968.

Envirotech Corporation, 1823 East Superior St., Duluth, Minnesota
by letter dated February 26, 1974 and revision of March 18, 1974.

Greeley, S. A. "The Development of the Activated Sludge Method
of Sewage Treatment", Sew. Wastes J., 17:1137. 1945.

Metcalf and Eddy, Inc. Wastewater Engineering, McGraw-Hill,
New York. 1972.

62


SECTION XI
GLOSSARY

ALKALINITY (ALK) - The capacity of a solution to accept protons usually
ag the result of the presence of bicarbonate, carbonate and/or hydro-
xide ions.

BIOCHEMICAL OXYGEN DEMAND (BOD) - A measure of the oxygen necessary
to complete the aerobic decomposition of the decomposable organic
material in a liquid by bacteria. The standard BOD is five days at
20 degrees C.

CHEMICAL OXYGEN DEMAND (COD) - A measure of the oxygen equivalent of
the organic matter in a sample which is subjected to oxidation by a
strong chemical oxidant.

CLARIFIER - A basin or tank in which a ‘portion of the material suspended
in a wastewater is settled.

COMPOSITE SAMPLE A portion of waste compounded at regular time
intervals with the volume taken varying with the waste stream flow.

EFFLUENT - Liquid flowing from an area, basin, tank, or treatment plant.
INFLUENT - Liquid flowing into an area, basin, tank, or treatment plant.
MEAN (X) - The arithmetic average of the individual sample values.

n - The number of samples or occurrences in given group or population.

pH - The negative logarithm of the hydrogen ion concentration. It
indicates the intensity of the acid or alkaline condition of a solution.

PRIMARY TREATMENT - A wastewater treatment process that utilizes
sedimentation and/or flotation to remove a portion of the settleable
or flotable solids and thus remove some of the BOD, of the wastewater.

RANGE (R) - The absolute difference between the highest and the lowest
values in a group of values.

SETTLEABLE SOLIDS - Suspended solids which will settle out of a liquid
waste in a given period of time.

SLUDGE - The accumulated settled solids from wastewater in clarifiers
or basins and having the consistency of a semi-liquid mass.

63


SECTION V
SAMPLING AND ANALYSES

Samples were collected at PSI from the cutter deck effluent; caustic
reel dump; hydro-brusher-washer peelers; caustic reel intake; raw
effluent prior to screening; screened solids; main clarifier influent,
effluent and sludge; mud clarifier influent, effluent and sludge; filter
filtrate and sludge; potable water and raw material. Specific analyses
for each sampling point are listed in Table 2. See Figure 11 for sam-
pling and instrumentation at PSI.

Samples were collected at WPSI from the Magnuscrubber peeler; caustic-
peel dump; Magnubrusher peelers; caustic reel intake; screened solids;
main clarifier influent, effluent and sludge; filter filtrate and
sludge; potable water and raw material. See Figure 12 for sampling
points and instrumentation at WPSI.

Twenty-four hour composited samples were collected and analyzed appro-
ximately once a week at PSI and twice weekly at WPSI (see Table 3).

Table 3. SEASONS, DATES, AND NUMBER OF SAMPLE SETS

SEASON DATES NO. DATES No.
WET CAUSTIC - PSI IR-DRY CAUSTIC - WPSI

Winter 03-24-71 to 03-31-71 2 02-09-71 to 04-01-71 14

Spring 04-22-71 to 06-30-71 8 04-06-71 to 06-19-71 19

Fall 09-06-71 to 11-31-71 12 09-02-71 to 12-02-71 21

Winter 12-02-71 to 12-14-71 2 12-02-71 to 12-30-71 7

All samples were collected on the hour with liquid samples being taken
proportional to flow and solid samples collected on the hour in prede-
termined quantities. The samples were analyzed in accordance with
Table 2.

Valid datawere not obtained for every sampling day due to experimental ,
sampling and analysis error, frozen sampling lines, and plant shutdowns.

21


TABLES

NUMBER

1. Comparison of Peeling Systems

2. Sampling Point Designation and Analyses Performed
at WPSI and PSI

3. Seasons, Dates, and Number of Sample Sets

4, Waste Analyses (Wet-Caustic-PS1)

5. Waste Analyses (IR-Dry-Caustic-WPSI)

6. Comparison of Peel Loss Data

7. Comparison of Caustic Usage

8. Peeler Solids Data (Dry Caustic-WPSI)

9. Screenings Data

10. Plant Mass Balances

11. Main Clarifier BOD:N:P Ratios

12. Mud Clarifier BOD:N:P Ratios

13. Primary Clarifier Overflow Rates and Detention Times
14. Sludge Characteristics from Clarifiers

15. Vacuum Filter Cake '

16. Comparison of Capital Costs of Peeling Systems

17. Comparison of Capital Costs of Primary Treatment
Systems

18. Peeler Equipment

21
28
30
32
34
35
36
37
4
42
44
47
48
51

53


FIGURES

NUMBER

1.

10.
11.
12.

Flow Diagram for (PSI) Wet Caustic Peeling Method
Flow Diagram for (WPSI) Dry Caustic Peeling Method
Hydro-Brusher-Washer Peeler

Model D-14 Shufflo Infrared Unit

Pictorial Drawing of Model D-14 Shufflo Infrared
Unit

Magnuscrubber Peeler

Magnuscrubber Peeler - With Roll Removed To Show
Coupling and Water Jets

Magnuwasher Peeler, Pictorial Drawing

Magnuwasher Peeler With Two Rolls Removed To Show
Auger and Water Jets

EIMCO Continuous Filter at WPSI
Sampling Points and Instrumentation (PSI)

Sampling Points and Instrumentation (WPSI)

iv

PAGE

on nan

10
in

12
13

20
23
24


OL

an
eaetey

hyp

ou min wreven
ronson ( Cua

sania

Figure 6.

Magnuscrubber peeler



ACKNOWLEDGMENTS

This project was financed in part by the Office of Research and Deve-
lopment, U. S. Environmental Protection Agency under Project 12060 EIG,
and by Western Potato Service, Inc.(WPSI), Grand Forks, North Dakota
and Potato Service, Inc. (PSI), Presque Isle, Maine where the studies
were carried out. The support and help provided by Mr. Kenneth A.
Dostal, the Grant Project Officer,are acknowledged with sincere thanks.
The assistance of Pradeep Safaya, Environmental Control Manager at
WPSI, with the statistical evaluations and the stenographic labors

of Suzette Olmsteadare also acknowledged with sincere thanks.

vii


the peel lines are caustic dip time (1/2 to 6 minutes), caustic con-
centration (7 to 25 percent), caustic temperature (130°F to 210°F),
and retention belt time (1 to 8 minutes).

INFRARED DRY CAUSTIC---WESTERN POTATO SERVICE, INC.

Potatoes reach the peel line via a water flume from storage, two basket
elevators, then a washer consisting of brush rolls and water sprays,
and finally a storage hopper to control flow to the peel lines.

The three peel lines utilize one large black-iron caustic storage tank
where caustic (50 percent NaOH) is dituted to the desired concentration
of 10 to 20 percent. Each line consists of a ferris-wheel type caustic
reel, each equipped with its own vari-speed drive, temperature controller,
black-iron circulation tank and pump and overflow to return excess
caustic to the storage tank. Following the reels, each line has its
own cleat-type retention conveyor on which the caustic-dipped tubers
are held for various times (controlled through sprocket changes) ranging
from 1-1/2 to 8 minutes. As the tubers leave the retention belts,

they are aligned in rows on the Model D-14 Shufflo infrared units

(see Figures 4 and 5), which are equipped with 60 inch long roller-
conveyors that rotate the tubers as they are conveyed beneath the gas
fired infrared source. To provide the infrared irradiation, seven
porous ceramic heads per assembly row (total of 14 rows present) are
used. These burners provide a temperature of approximately 1650°F

on the ceramic surface with an output of approximately 50 percent in-
frared radiation. The IR section is not necessary insofar as keeping
the peel waste sludge out of the waste system, but does contribute

to a lower peel loss by increasing the temperature of the tuber-caustic
interface to provide increased reaction over shorter contact time with
less penetration.

From the Shufflo infrared units, the tubers drop onto the infrared units
and then into the Magnuscrubber peeler units which allow controlled
scrubbing for minimum waste. The tubers are moved through the scrubber
at a uniform rate by an auger with speed adjustable (700-920 rpm) for
controlling exposure time. Sixteen stud-rubber rolls are arranged

in a circular cage around the auger and rotate at a common fixed speed.
A residue wiper-conveyor inside the drum discharges the peel residue
out of the waste chute. A minimum amount of water is added to prevent
the peel residue from building up inside the scrubber---this is dis-
charged with the peel residue.

From the scrubber, the tubers are fed into the Magnubrusher peeler

(see Figures 6 and 7), and are continuously augered through the brusher
at a uniform rate (see Figures 8 and 9). This rate may be adjusted

to control and minimize exposure time as it is only necessary to wash
off any treated tissue and caustic. Twenty-three abrading rolls, each
with coated surfaces of preselected grit size, are arranged in a cir-
cular cage around the auger. The roll cage rotates at a fixed speed

16


660/2-74-088
June 1975

Environmental Protection Technology Series



The average Magnubrusher peeler suspended solids in the wash water at
WPSI was only 22.9 pounds per ton for the three seasons but was 101.2
pounds per ton for the hydro brusher washer peeler at PSI. This differ-
ence of 78.3 pounds per ton accounted for most of the difference in the
main clarifier influent suspended solids between the two plants. As
discussed earlier, the Magnubrusher peeler suspended solids of only
11.6 pounds per ton at WPSI in the Spring were significantly smaller
than the winter and fall figures of 24.6 and 32.8, respectively. This
was caused in part by changes in the plant production rate. Increased
production during the fall and early winter overtaxed the peeler's
solids handling capacity, causing equipment breakdown at WPSI, and

thus requiring that part of these solids be discharged to the Magnu-
brusher peeler wastewater line. There was a significant difference

at the 0.05 level between seasons at WPSI and during the spring and fall
seasons at the two plants. However, no significant difference at the
0.05 level occurred during the winter season nor between seasons at PSI.

The mud clarifier influent suspended solids to total solids ratio at
WPSI was 0.737, and the suspended solids at PSI were calculated using
this ratio. Clarifier influent suspended solids differed significantly
at the 0.05 level between plants during, the three seasons and within
PSI (but not WPSI) by seasons.

Total And Total Volatile, Volatile Suspended, And Settleable Solids

The remaining solids data show that the peeler solids (except the fall
and winter settleable solids) from the dry caustic peeling process at
WPSI were less than from the wet caustic process at PSI. The settleable
solids at PSI of 250 and 272 ml/liter for the winter and fall were lower
than the 451 and 531 ml/liter at WPSI. This was caused by the occa-
sional bypassing of some of the peeler scrubber waste solids to the
washer wastewater line during the fall and winter months. The difference
between plants also is magnified somewhat since the settleable solids
measurement is a sludge per unit volume of sludge and water. The lower
volume of water used at WPSI in the washers gives an exaggerated esti-
mate of the differences between the two peeling processes.

Peeling Water Use

The water use for the hydro-brusher-washer peelers at PSI was three and
one-half times the use by Magnubrusher peelers at WPSI. The difference
by weighted average was 955 gallons per ton of raw potatoes processed.
The water usage per ton of potatoes reflects the tonnage of potatoes
processed. That is, when the plant is started, all plant valves inclu-
ding peeler water valves are turned on and generally left on throughout
the day. Therefore, during those seasons such as winter when more po-
tatoes are processed than at other seasons, the water volume used per

39


SECTION IT
INTRODUCTION

The increased demand for processed potatoes in the form of dehydrated
or frozen products has occurred concomitantly with an increased demand
for treatment of the processing wastes. Responsibility for treatment
of the wastes produced has become the obligation of the industry or,
in some cases, the industry and the municipality.

Although biologic decomposition and stabilization of the conventional
caustic peel effluent can be accomplished by several well-established
practices, a system of peeling which yields wastes of lower concentra-
tion and less liquid volume has obvious advantages. Additionally,
since potato wastes are acceptable as feeds for livestock, the system
devised should allow maximum recovery of these utilizable solids.

Development of an infrared (IR) dry caustic peeling method characterized
by techniques which allow separation of peel solids from the plant
liquid streams along with reduced consumption of water should present
the industry with an acceptable alternative to their present system

of peeling. However, the acceptance of any new system will depend

upon the overall economics.

The development of the IR-dry caustic peel methods by the U. S. Depart-
ment of Agriculture (USDA) on a pilot plant basis provided the stimulus
for investigation of the method on a full scale basis (1). PSI of
Presque Isle, Maine and WPSI(redesigned to utilize the IR-dry caustic
system) of Grand Forks, North Dakota received support from the EPA

to demonstrate the feasibility of the IR-dry caustic method. Both of
these plants are subsidiaries of JS Industries, now renamed American
Kitchen Foods.

The installation of three IR-dry caustic peeling lines at WPSI along
with the primary treatment system was to be contrasted with the con-
ventional wet caustic peeling plant at PSI, also equipped with primary
treatment facilities. ;

The grant objectives were to:

1. Determine total capital expenditures and operational costs
of the dry caustic process and the conventional caustic
process.

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

3. Determine total water consumption, power requirements, and
maintenance costs of the two systems.


The overall plant raw waste BOD for PSI was 62.8 pounds per ton; at
WPSI, 33.5 pounds per ton. The primary clarifier BOD removal was

33.5 percent for PSI vs 31.7 percent for WPSI. Primary sludge in pounds
of total solids per ton of raw potatoes was 34.6 for PSI vs 33.3 for
WPSI. The primary clarifier effluent at PSI contained 46.0 pounds of
BOD and 16.9 pounds of suspended solids per ton vs 23.1 and 8.80
pounds, respectively, at WPSI.

At PSI, the total solids content of the filter cake averaged 12.6
percent and a recovery of total solids in the cake of 12.7 pounds per
ton; at WPSI, 39.3 percent and 40.3 pounds per ton, respectively.
Filter loadings were 0.75 of total solids per square foot per hour
at PSI and 4.6 pounds at WPSI.

There were no expectations that the dry caustic peel system would
have any effect on the finished product and none was observed. It
would be extremely unlikely that a change in peeling procedures would
affect the finished product since peeling variables are altered as
required to keep the finished product in grade.


Table 17. COMPARISON OF CAPITAL COSTS OF PRIMARY TREATMENT SYSTEMS

IR DRY CAUSTIC WET CAUSTIC
WPST PSI
(3 lines) (4 lines)

Purchased equipment cost (E) $113100.00 $156800.00
Purchased equipment labor cost (E,) 18200.00 25100.00
Plumbing materials (fpMp) 8200.00 8200.00
Plumber's rate (fyp) 6.00 3.00
Plumbing man hours (ML) 1160 1300
Electrical Materials (f Me) 11500.00 12300.00
Electrician's rate (fye) 12.00 3.00
Electrician man hours (My) 245 250
Engineering rate (fen) 6.60 6.60
Engineering man hours (Hen) 540 640
Unit cost per drawing (fq) 168.00 168.00
Number of drawings (d) 5 5
Total capital investment (Cy) $165,304 $212,114

NOTE: Contractor's fee and contingency (f,) This factor included in
other factors since this is a compl Sted project.

52


Table 8. PEELER SOLIDS DATA---DRY CAUSTIC - WPSI

SEASON Ory Solids | TS | |TVS| AIK |TPO4g [TKN |pH p. Gr.
percent pounds/ton
WINTER
Avg 9.8 53]35 | 9.6] 0.2 | 0.5 [12.6 | 1.004
s 1.1 30}19 | 5.0] 0.1 0.2 | 0.3 | 0.009
a 16 16 [16 19 13 13 19 16
SPRING
Avg 9.4 81157 114 0.4 | 0.9 112.6 } 1.022
s 1.1 17] 11] 4.0] 0.1 0.2 | 0.2 | 0.025
A 18 18 | 18 415 8 6 16 18
FALL
Avg 8.6 41/28/11 0.2 | 0.6 [12.4 | 1.000
s 2.3 22: | 14 16 0.1 0.3 | 0.2 | 0.025
n 12 12 [12 {12 12 u 12 12
ALL SEASONS
Avg* 9.3 61 {42 111 25 +62 112.6 | 1.010

s Standard Deviation - see glossary
n Number of samples - see glossary
* Weighted average

Occassionally, a whole potato entered the peeler solids line and plugged
the pump. This necessitated reversal of the pump flow to dislodge the
potato. Future installations should consider the addition of a food
chopper prior to the pump to grind whole potatoes to a pumpable consis-
tency thereby reducing pump maintenance problems.

SCREEN SOLIDS CHARACTERISTICS

The data for the sludge from the vibrating 4 mesh screens located in
advance of the main clarifier are shown in Table 9. The total solids
averaged over the year was 15.7 pounds per ton at PSI and 33.0 pounds
per ton at WPSI. This difference was significant at the 0.05 level

for all three seasons between plants as well as at WPSI between seasons.
However, there was no significant difference between seasons at PSI

at this same level.

35


€@

- _
NOTES —
4 PROPOSED MSTALLATION OF STRUMENTATION
Roar

Eee
= oan fener | 1 Be ee

~ ©) Muo CLANIFIER 70 WO.
— KC DUMPED TO MUD CLARIFIER
iw peur 3, Bites FROM VACUUM FILTER
ee ‘PLES TO BE RUN OW TWO £4 HOUR COMPOSITE YW
MPLING POINTS = FLOW MEASURENE)
- 2 sogekn corte DECK EFFLUENT. wares ‘0 ah BRUSHER WASHERS
PUMP LUENT WATER FROM

iS BRUSHER
iS a Se on ok EFFLUENT TO SCREEN - CLARIFIER MHLUENT + SCREEN
chen IER EFFLUENT * FILTER CAKE = MUD Ci

? caper
Ce ee ee a eaten che A AP aces
er

apes
Pas

TER
N) CAUSTIC PEEL DUMP

p@amesu)

Se em ate

Ls CLAMFER CFLUEMT

Figure 11. Sampling points and instrumentation (PSI)


ton goes down. This occurred during the winter season, reflected in
the data by the smaller values of 1117 gallons per ton at PSI and 272
gallons per ton at WPSI (see Tables 4 and 5). The results showed a
significant difference between plants for all three seasons, as well
as between seasons at WPSI (but not at PSI).

Main Plant And Fluming Use

The yearly average main clarifier influent was 2672 gallons per ton

at PSI and 2192 gallons per ton at WPSI. At WPSI, where the fresh
water was metered into the plant, a total of 2593 gallons per ton-

were used. Thus, 401 gallons were lost in boiler usage, condenser
usage, and evaporation. By estimation, PSI's equivalent losses should
be about 490 gallons, making a total usage of approximately 3162 gallons
and a difference between plants of 568 gallons (less than the 955 gallons
per ton decrease in the peeling systems usage). These differences
between total plant use and between peeler washer use---955 gallons

per ton vs 568, respectively-~--are probably due to blanching and leaching
procedures to remove excess sugar. Whenever high sugar raw material

is encountered, increasing the overflow from the blanchers to leach

out the necessary amount of sugar is necessary in order to produce
material within the acceptable color range.

The yearly average fluming water use was 665 gallons per ton at PSI
but only 265 gallons at WPSI. This difference, while significant, is
not related to the peeling methods but simply to the efficiency of the
two fluming systems.

Nitrogen and Phosphate

The total Kjeldahl nitrogen for the main clarifier influent at PSI

for the two seasons (when tests were taken) averaged 4.30 pounds as
elemental N per ton of potatoes processed versus 1.53 pounds per ton

at WPSI. The results were significantly different at the 0.05 level
during the winter and spring seasons between plants and between seasons
at PSI but not at WPSI. This difference was not caused by the difference
in the peeling systems since the hydro-brusher-washer peeler waste at
PSI for the three seasons averaged 1.00 pound of total nitrogen per ton
of potatoes while the corresponding value at WPSI was 0.72 pounds.

Differences were noted in the peeling system liquid effluent total
phosphate of the two plants. The PSI hydro-brusher-washer peeler wastes
averaged 1.28 pounds of P04 per ton processed for the three seasons
while the WPSI pliant had only 0.18 pounds per ton in its Magnubrusher
peeler wastes. The results were significantly different at the 0.05
level during the winter and spring seasons between plants and also
between seasons at WPSI (but not at PSI). The weighted average for

40


2

SAMPLING POINT DESIGNATION AND ANALYSES PERFORMED AT WPS! AND PSI

TABLE 2

Letter Coda z
g 5
an = 2 ~t al») = a = 4
ES; 2 | 3) '1s/ Zi 9/8} 4) al Slee) 2] le
Ss; Ss] Fle al} 2 8
Sampling Point Fig.6 |Fig. 7 Fy? a < a
Cutter Deck Effluent - A X{ X{XtX} xX} X| XI XI xX} xX} xt xt x!
Peeler Solids A = X| x1 x X{ Xi Xi Xt Xx
Ceustic Peel Dump B N. Xi xX] Xt xX} Xt X] XIX] Xt Xt xX} Xt Xx!
Viashers Cc B_ Xi X| xX} XI xX] xX} xX] Xt xl x! x} xt x
| Coustic Reel Intake D fe) xX X|
Raw EHluant before Screening - Cc X{ X| Xt xX} XIX] xX] xX} Xt x} xy xt x
Screen Solids E D Xx X|_x x
Main Clarifier Influent F E X{ X| Xi xX] x1 X1 Xi xX] Xi xt x} x] x
Main Clerifier Effluent G F Xi X] xX} Xj xX} x} XI Xt xX} xX} xX} xX} Xt x
Mud Clarifier Influont H G X|_ XIX xX} X) xX} Xt XTX) XT XT XI Xx
Iéud Clarificr Effluent { H Xi X} Xi] xX} Xi Xi Xt xt xt x} xt x) x
TAud Pums Sludge J ! Xx X{Xi_ xX] Xx]
asin Clarifier Sludge K J x X{_ Xi XxX} Xt Xx}
Filter Filtrate N K X X{_X} X} X} Xx X}_ |
rilter Sludge L L xX| xX} x x|_x X|_X
Potable Water M M Xi_x'xX| X] X| XI XI Xt Xt Xt XT XxX] xX
Water to Flume - P
Raw Material Q Q Xx

Twenty-four hour samples composited on flow basis twice weekly at WPSI and weekly at PSI at all locations.



The waste activated sludge would be processed by aerobic digestion.

The sludge produced each day would be approximately 20 percent of

the BOD remaining after the primary clarification or 4880 pounds per
day and 2460 pounds per day, respectively (9). At 0.7 percent solids
in the underflow sludge and with a 15 day detention time in the digester,
the volumes to be handled are 168,000 cubic feet for the wet caustic
and 85,000 cubic feet for the IR-dry caustic system. Using a 19 foot
depth, the digesters required would be 125 feet by 75 feet and 90 feet
by 50 feet, respectively. The effluent from the digesters would

be returned to the primary clarifier for processing with the main plant
effluent. The aeration requirements based on 40 percent bacterial

cell destruction and 2 pounds of oxygen per pound of cells destroyed
are 3910 pounds per day of oxygen for the wet caustic and 1960 pounds
per day for the dry caustic (11). These requirements would be met
with 100 horsepower for the wet caustic and 50 horsepower for the

dry caustic (11). Table 25 shows the waste treatment equipment re-
quired for both the wet and dry peel systems.

Table 26 shows the differential costs between the waste treatment
systems as related to the reduced requirements of the IR-dry caustic
system. Plumbing and electrical supplies and labor have not been
included (except the electrical for the aerators) since the remaining
equipment installation and costs would be practically the same for
each system.

59


19,
20.
2.

22.
23.
24.
25.
26.

TABLES

Primary Treatment Equipment
Operation and Maintenance Costs - Peeling

Operation and Maintenance Costs - Primary Treatment
Systems .

Total Operation and Maintenance Costs

Total Annual Costs - Peeling and Primary Treatment
Design Criteria

Treatment System Parameters

Effect of Peeling System on Cost of Primary and
Secondary System

vi

53
54
55

55
56
58
60
61


eee

‘ reer hetery)
MSNA AAD MWA NCAN Aynsley

Figure 9. Magnuwasher peeler with two rolls removed to show auger and water jets


SECTION VIII

CAPITAL AND OPERATING COSTS FOR PEELING
AND PRIMARY TREATMENT SYSTEMS

CAPITAL COSTS
The capital costs have been grouped to fit into the categories of the
unit cost estimate formula of Peters and Timmerhaus (8). Their equa-
tion is:

=| f,
CyrEtEL + (FpMp + Fst) + (FoMe + Felt.) + fenton + fyd(14"F)
where Cy, = new capital investment  M_, = electrician man hours

— = purchased equipment cost fen = engineer rate

E, = purchased equipment Hen engineering man hours
installation labor cost

fpMp = plumbing materials fq = unit cost per drawing

typ = plumbers rate d = number of drawings

ML = plumbing man hours ff = contractor's fee and contingency
P This factor was not included.

FM, = electrical materials since it would be included in

the other factors on a completed
fyy = electrician rate project

Table 16 shows the costs for these factors with the total capital
investment of $332,324 for three lines of the IR-dry caustic system
and $188,980 for four lines of the wet caustic system. Table 17 shows
the cost for each of the factors with a total capital investment of
$212,114 for the PSI primary treatment system and $165,304 for the
WPSI primary treatment system. Buildings and yards have not been
included since those cost factors are common to both systems and

this essentially is a comparison of the two peeling systems.

Purchased equipment includes the items for each peeler system listed
in Table 18 and items in Table 19 for each primary treatment system.

50


SECTION IX

EFFECT OF PEELING SYSTEM ON COST
OF PRIMARY AND SECONDARY SYSTEMS

This section presents an analysis of the effect of a dry lye peeling
system on the costs for wastewater treatment.

For these purposes, both plant capacities have been set at 500 tons
and the actual percent peel losses of fall and early winter are used
for both plants. Since the difference in water usage for peeling
between the plants (995 gal/ton) was not reflected in the overall
plant water use figures Giez vs 2593 gal/ton or 570 gal/ton), the
total plant effluent at PSI has been increased to remedy this as
shown in Table 24. The additional water use in the remainder of the
WPSI plant (730 gal/ton) is probably due to the need for increased
leaching at WPSI, resulting in more water use as mentioned before.
The wet caustic water use has been increased to allow a comparison
assuming that potatoes of the same characteristics are being processed
at each plant. This table also includes other design criteria from
Tables 4, 5 and 6, as well as from other sources as cited below.

Assuming an overflow rate of 600 gallons per day per square foot (7),
the areas of the primary clarifier are 2625 square feet for the wet
caustic system and 1833 for the IR-dry caustic system. These figures
designate primary clarifiers with diameters of 57.8 feet and 48.3
feet, respectively. Using a retention time of 3 hours (9) for each
system, the clarifier volumes are 26,320 and 18,380 cubic feet,
respectively. Using these areas and volumes, the sidewall depth
will be about 10 feet in each clarifier. The clarifiers should be
equipped with skimmer, weirs, baffles, and a thickening compartment
for the biodegradable solids.

The required vacuum filter for filtration of the four to five percent
clarifier underflow solids should be equipped with a removable belt,
wash sprays, vacuum pump, filtrate pump, and receiver. The required
vacuum filter was a 6' X 10' filter for the wet caustic plant and a
6' X 8' filter for the IR-dry caustic plant(9).

The aeration basin influent with a 32.5 percent BOD reduction (average
of both PSI and WPSI) across the primary clarifiers is 24,400 pounds
for the wet system and 12,300 pounds for the dry system. Using
Greeley's (10) recommendation of 30 pounds of BOD per day per 1000
cubic feet, the aeration basins would be 813,000 cubic feet and
410,000 cubic feet, respectively. These volumes are 6.08 and 3.06
million gallons and include an allowance of 20 percent of the flow

57


0€

IR = DRY ~ CAUSTIC - WPS!

TABLE 5

WASTE ANALYSES

SEASON FLOW BOD COD ss vss 1S TVS TKN «TRO ALK SETT SLOS TURB
SP GR
Gal/Ton LbyTon mAs
WINTER
C.Mognuwasher-peeler Avg «272, 18,2 35 2B 4 29 0.49 0,20 5.811158 +002
s 8.0 101 99 15 18 13 0.21 0.07 = 3.570.426 003
ao WW 1B 18 20 16 16 12 12 18 19 a 2
F. Main Clatrfler Ava 1716 35,1 68 37 al 53 136-2670 14.30 (10.738 0.999
Influent s 366 B56 2) n 7 Ty 0.97 (113 3.0508 0.002
a 2 BO 20 16 16 10 9 1” 19 a ai
G.Main Clorifler Avg «(1815 3,8 47 6 45.0 26 1,2 «179M 7.9212 560 (0.998
Effluent s 5 639 ON 1.8 10.8 868.7 = 0.47054 1,75 TS 194 9.002
na w 13 20 16 16 W 18 9 a wv a
REMOVAL (%) 33.6 45 = 80.5 | Bd 44 51 15.4 2 30.9 =~ 6 =
H. Mud Clorlfler Avg 2800-51) 121777 12 0.7 0,94 2.8 10.8 37.71 1,000
tofluent s 2 9,60 64 10,0514 98 0.13 0.310 2.00.6 14.8 0,002
o Bb 9 9 1o 14 10 10 9 9 3 13 3 15
1, Mud Clorifler Avg 274 4,72 8.34.21 8,7 u 7.2 0.18 0.26 1.995 32 1900 (0,999
Effluent s 23 3.61 4,0 © 2,26 4,1 7.0 5.0 0,10 0.23 1.8 1600 6 527 (0,008
ao 1 9 a 2 4 10 10 8 9 13 3 13 12 1
REMOVAL (%) 22 33 71.8 52 50 39 0 25 32 oe 28 =
SPRING
C.Mognuwarher-pesler = Avg «9927.38 1S NG 2 12 1,93 013 4.33110 95.3, 1,001
5 % 233 N 7.39 9.0 5.5 19 0,051.44 0,594.8 0.008
an WwW oO WW 7 18 9 6 9 16 7 16 19
F. Main Clarifier Avg = 2613 25.9 3539.3 30 40 1.52 1,58 18,0 10,5 1,000
Inflvent s 3 7.12 94 (1704 6 0.21.58 4.22 05 4 0.008
nw OW 2 178 WW 6 16 18 v7 WV
G.Matn Clartfier Avg 2536 17,828 10,07 7 1.480 105 7,651 653 1,000
Effluent 2 5H 3,96 9.2 45 OT 9 0.27 0,56 3.86 1.87 19 0.002
o Ww 10 98 1% (18 18 ry ‘6 v7 18 v7 16 w
REMOVAL (%) = Bw 70.2 7 2 34 6.0 94,2 35,5 7 -



Le

H. Mud Clarifier Ava 35668 73 5.6 W2 8.2 > 13 97 7.008
Influent s _ = — —= — — — — — —
a 1 1 1 1 1 1 aed T a] _ T
1. Mud Clarifier Avo 3514.3 64 19 69 A me _ a8 867.5 8501.01
Effluent s on - = —_ — a “ - -- =
n 1 1 v 1 1 — — 1 1 1 1 1
REMOVAL (%) ~~ 32 _ 12 66 a 46 — _ 46 _ 80 _
FALL
‘C. Mognuwasher-peeler Avg 378. 14,90 8 38 52 38 67 0.20 7.2 WS 531 1,001
s 0 = 9.52 24 7 42 24 +26 0.06 3.64 0.3 252 0,008
n 7 9 8 18 18 18 WS 1 W at Ww 18
F. Main Clarifier Avg 2294 38,4 64 34 7 59 1.64 2.21 14.3 10.0 36 0.998
{oflvent s 625 13.1 a 12 2B 29 0.41 0.75 3.35 Mw 55 0.002
a 19 WU 21 7 2 a 7 1 7 a 2 a
G.Main Clarifier Avg 26240 26.30 43 7.5 49.4 32 1.33 1.63 9.72 77 4,2 428 0.999
Effluent 3. 1220 7.51 14 3.3 9.63 10 0.23 0.37 2.5) 14 6.4 er 0.001
. a 12 20 18 20 a 1% WV 7 a a a 2
REMOVAL (%) ad 3 78 31 4% 16.2 26.7 30.8 _ 88 _ bid
1H. Mud Clarifier Ava 255 8.4 W.0 0 9.3 a 8.6 0.19 0.18 3.2 10.7 53.8 1,003
Influent s 142 47 431 5.4 8.6 3.8 0.08 OT V3 15 21.6 0.023
n a 2 5 2 2 2 7 18 2 a Ww 2
1, Mud Clarifier Ave 248 5.9 3.58 2.3 95 5. 0.14 On 2.0 97 20 1380 0.999
Effluent s 153 3.7 2.42 Ve 59 29 0.07 0.09 1.0 1.8 25 6 0.003
n 20 20 9 20 20 2a 18 18 2 20 Ww 20 20
REMOVAL (%) — 46 30 85 75 55 a 50 50 38 — 6 wae

Note: — The letters, preceding the sompling points above, Indicate the “letter code" for those points (See Table 2).

4. Standard deviation - see Glossary
1. Number os Samples ~ see Glossary


pH and Alkalinity Reduction

The pH in and out of the clarifiers at each plant was about the same,
though slightly higher at PSI, even though the alkalinity out of the
primary clarifier was much higher at PSI. This was especially noted
during the winter and spring months when an average of 17.5 pounds

per ton of alkalinity was discharged at PSI but only 10.0 pounds per

ton at WPSI. Each primary clarifier, during the spring months at

PSI, reduced the alkalinity in the influent by producing organic acids
in the sludge zone which leached into the overlying water and neutralized
part of the alkalinity.

Clarifier Sludge Characteristics

Table 14 shows the solids data in the sludge underflows from the clari-
fiers. The difference for the percent total solids in main clarifier
sludge was not significant at the 0.05 level. Grames and Kueneman (7)
have reported that primary sludges from wet caustic peeling systems
should be about 5 percent dry solids. The high percent dry solids

in the main clarifier sludge at WPSI has resulted from the diminished
amount of the peeler washer solids in the sludge. These high dry
solids in the sludge are a desirable result of the dry caustic peeling
process.

The total solids of 19.7 pounds per ton for the IR-dry caustic mud
clarifier sludge was significantly higher (0.05 level) than the 6.9
pounds per ton for the wet caustic at PSI during the winter and fall
seasons. The results were significantly different at the 0.05 level
between seasons at PSI but not at WPSI. The percent total solids

in the sludges were not significantly different at the 0.05 level either
during the winter or fall seasons between plants or within plants by
seasons.

Vacuum Filtration of Process Clarifier Sludge

Table 15 shows the data for the filter cake at PSI and WPSI. The data
for PSI reflect the poor operational characteristics of the primary
clarifier. The dry solids in the filter cake averaged 10.4 percent
with a filter production rate of less than one pound per square foot
per hour. Grames and Kueneman (7) have stated that vacuum filtration
of potato sludge solids at pH 6 or less will be very poor unless the
sludge is conditioned with chemicals. The pH values of the sludge

in this case at PSI were 6.1, 5.1 and 4.8 for the winter, spring and
fall months. Excessive fermentation of the sludge in the primary clari-
fier reduced the pH to these low values. It would be expected that much
higher filter production rates could have been achieved if conditioning
chemicals had been used.

46


Primary treatment of the wastewater is accomplished by utilizing two
clarifiers: a 60 foot diameter process wastewater clarifier (main
clarifier) and a 24 foot fluming water clarifier (mud clarifier).

The process water passes through a 4 mesh vibrating screen (process
water not including fluming water) prior to entering the main clarifier,
60 feet in diameter with a 9 foot sidewall depth and having an appro-
ximate volume of 225,000 gallons. This clarifier is equipped with a
surface skimming device to remove floating solids, such a frying fat,
and a pair of rake arms on the bottom of the tank. These arms move the
settleable solids on the conical bottom surface to the center of the
clarifier where they are thickened and drawn off for dewatering on

a continuous belt vacuum filter (see Figure 10). The effluent from
the main clarifier can be sent either directly to the city sewer or

to secondary treatment consisting of a five million gallon aerated
activated sludge basin and a 100 foot diameter secondary clarifier.
Following the secondary process, the waste can again be directed to
the city sewer or to a tertiary plant where flocculating chemicals

are added prior to filtration through sand filters. At this point the
water can be wasted to the city sewer or chlorinated and pumped back

to the processing plant for reuse in various areas.

The fluming wastewater flows to the mud clarifier, 24 feet in diameter
with a sidewall depth of 8 feet. The mud clarifier is provided with

a set of rake arms, similar to those mentioned above, but has no sur-
face skimmer. The “mud sludge" accumulated in the bottom of the clari-
fier is pumped to a hopper for trucking to land fill. The clarifier
overflow is pumped to the secondary process.

The sludge collected from the process clarifier (main primary clarifier)
is pumped to an 8' X 10' continuous vacuum belt filter for dewatering.
The filter "cake" thus obtained is either fed to cattle or used as land
fill. The filtrate is returned to the center well of the main clari-
fier.

19


SECTION VII
INFRARED DRY CAUSTIC SLUDGE FOR ANIMAL FEED

Since this work was started, J & R Simplot Co. have made feeding
studies of dry caustic peel sludge and have been chopping the
"screenings" into the peeler solids, holding the resulting mixture
in silos for approximately 24 hours, then feeding the nearly neutral
silage to cattle.

Also, the Washington Agricultural Experiment Station at Pullman, Wa-
shington has issued its bulletin number 757, entitled "Nutritive

Value of Potato Slurry for Steers." Those authors compare feeding
studies in which as much as 30 percent of the dry solids have originated
from potato peeler solids.

During the spring of 1973, Pillsbury Co. erected and equipped a plant
in Grand Forks, North Dakota for drying potato plant wastes. At this
writing, only trial runs have been made. However, the company has
found that moisture content is the only problem with the waste from the
dry caustic system and the sludge from the main clarifier. Sixteen
percent solids or better is necessary in order to effect economy in
the drying operation. Presently, the solids are low in both the filter
cake as well as the peeler solids, and efforts are being directed to
increase these levels.

Twenty percent solids primary clarifier sludge is valued at eight to

ten dollars per ton on a feed grain basis. This is about 10 percent
of the market value of feed grain.

49


Table 24, DESIGN CRITERIA

Design Criteria Wet Caustic | IR-Dry Caustic
Production-pounds of raw/day 1,000,000 | 1,000,000
Peel Loss - percent 18.8 16.3
Peeler System Effluent -gallons/ton 1,300 346
Total Plant Effluent-gallons/ton 2,670 2,190
Total Plant Effluent to reflect peeler system 3,150 2,200

difference gal/ton
Primary Clarifier BOD Reduction-% (33.2) (31.7)
BOD Reduction for this section 32.5 32.5
Primary Clarifier Capacity-gal/day/sq.ft. (6)* 600 600
Vacuum Filter Capacity~clarifier underflow (8)* 4-5% 4-5%
Aeration Basin Capacity~#BO D/1000 cu.ft. (9)* 30 30
Pounds Oxygen per pound of BOD Removed (8)* 1.25 1.25
Aerators #O2/HP/hr (8)* 2.2 2.2
Secondary Clarifier Capacity gal/day/sq. ft.(8)* 250 250
Granular Media Filters gal/sq.ft./min. (8)* 2 2
Detention Time for Activated Sludge Digestion(8)* 15 15

*See Indicated Reference

for sludge recycle volume. The retention times with the recycle volume
are 3.35 days for the wet system and 2.30 days for the dry. The F/M
(food to micro-organism) average ratio is 0.04 using pounds of BOD
removed and mixed liquor volatile suspended solid ranges found at the
WPSI aeration basin during the current years (fall and winter 1974).

The aeration required---based on 80 percent BOD reduction of BOD,
2.2 pounds oxygen transferred per HP hour (9), 1.25 pounds 09 per
pound of BOD, and influents of 24,400 pounds of BOD per day for the
wet system and 12,300 pounds for the dry system---is 462 HP and 233
HP, respectively. This could be supplied by 4-125 HP aerators for
the wet system and 2-125 HP for the dry system.

The secondary clarifiers, based on an overflow rate of 250 gallons

per day per square foot (7), are 7260 and 5320 square feet, respectively.
These areas require 96.1 and 82.3 foot diameter clarifiers. The
clarifiers should be of suction type, of steel shell construction,

with adjustable weirs, and with baffles.

The granular media filters, with an 80 percent reuse of the total
plant effluent and 2 gallons per square foot per minute (9), would
require 398 and 321 square feet of filter area, respectively. Two
16 foot and two 14 foot coal and sand media filters are required.
These filters would reduce the suspended solids in the filtered
effluent to the 5 to 10 ppm range (9).

58


ABSTRACT

The infrared dry caustic peeling system has been evaluated through
plant scale comparisons with the conventional wet caustic system.
The following significant differences were noted when the dry peel
system was compared to the wet process:

(a) decreased peel loss by 13.1 percent.

(b) decreased caustic consumption by 26 percent.

(c) decreased wastewater from peeling by 73 percent.

(d) decreased BOD, in the peeler wastewater by 78 percent.

(e) decreased suspended solids in the peeler wastewater by 77
percent.

(f) decreased alkalinity in the peeler wastewater by 61 percent.

(g) increased operating costs of peeling by 39 percent but de-
creased total annual cost of peeling and primary treatment
through lower peel loss by 10 percent.

(h) decreased total plant raw waste load: water use by 18
percent, BOD, by 47 percent, and suspended solids by 57
percent.

No significant differences were noted in the efficiency of primary
sedimentation of the raw wastes nor in the mud clarifier results.
Primary sludges and their dewatering characteristics were found to be
similar.

This report was submitted in fulfillment of Project 12060 EIG by
Western Potato Service, Inc. of Grand Forks, North Dakota, and Potato
Service, Inc. of Presque Isle, Maine under the partial sponsorship
of the Environmental Protection Agency. Work was completed as of
December 31, 1971.

ii


The weighted average for the year (all three seasons) was 33.5 pounds
at WPSI and 62.8 at PSI - a difference of 29.3 pounds per ton. The
results during the winter and spring seasons between plants were sig-
nificantly different at the 0.05 level as were those between seasons
at each plant. However, there was no significant difference between
the plants during the fall season.

The BOD values for the washer wastewater at WPSI were about one-third
that of the hydro-brusher peeler at PSI. The values at PSI for winter,
spring and fall were 64.6, 50.1, and 78.2 pounds per ton while the
corresponding values at WPSI were 18.2, 7.4 and 14.9 pounds per ton.

The weighted average for the year was 66.2 pounds per ton at PSI and only
14.5 at WPSI - a difference of 52 pounds per ton. The results were
significantly different between plants during the spring and fall sea-
sons and between seasons at WPSI but not during the winter between

plants nor between seasons at PSI (0.05 level). A very marked BOD
reduction was obtained by the IR-dry caustic peeling system over the

wet caustic system. The removal of the peeler solids in the Magnuscrubber
peeler prior to the Magnubrusher peeler effected a significant reduction
jin the BOD reaching the wastewater from the potato peeling operation

as shown by the above mentioned significant difference at 0.05 level
between the plants during the spring and fall. The BOD value of 7.4
pounds per ton in the spring at WPSI was caused partially by decreased
production but largely by better handling of the peeler solids.

The mud clarifier influent from the potato fluming lines had about the
same BOD values at each plant with no significant difference between
plants or between seasons at the plants. The BOD did show some increase
from fall to spring indicating increased leaching of solubles from
stored potatoes which had broken down over the storage season.

Suspended Solids

The suspended solids data at the PSI plant have been computed from the
reported total solids data, using a ratio of 0.639 pounds of suspended
solids per pound of total solids for the main influents, 0.6413 for

the peeler wash water, and 0.1859 for the main clarifier effluent.

These ratios were established from all the usable data for winter,
spring and fall at the WPSI plant because the analytical method for

the suspended solids at the PSI plant was not used correctly. The
analysis of the suspended solids data at PSI must be cautiously reviewed
considering the method used to obtain it.

The main clarifier influent suspended solids of 47.6, 39.3 and 38.5
pounds per ton for the winter, spring and fall seasons at WPSI were
significantly smaller than the 96.8, 133.9 and 71.6 pounds per ton
obtained at the PSI plant, even with the additional screening at PSI
and the bypassing at times of the peeler sludge disposal system at
WPSI. The differences in these data between plants by seasons were
SWS at the 0.05 level and also between seasons at PSI (but not
at .

38


Table 9, SCREENINGS DATA

WET CAUSTIC - PSI IR-DRY CAUSTIC - WPSI
(4 Mesh Screenings) (4 Mesh Screenings)
SEASON Se - TVS | Dry Solis oe LINS Pry el ids
WINTER
Avg 12.7 12.0 16.6 || 28.8 | 27.0 17.6
s 5.87 5.8 1.81 17.20] 17 4,32
n 4 4 4 16.0 | 16 15
SPRING
Avg 14,4 13.4 15.6 35.3 [27.5 18.3
s 5.12 7.7 1.58 8.55] 8.34 1.71
n 7 8 7 15 15 7
FALL
Avg 19.0 17.6 15.1 40.7 {39.7 21.6
s 8.75 8.8 2.61 6.38) 9 1.56
n 12 u u 20.0 {21 20.0
ALL SEASONS
Avg* 15.7 5 14.8 33.0 | 34 19.4

s Standard Deviation - see glossary
n_ Number of samples - see glossary
* Weighted average

This was probably caused by more internal screening at PSI for potato
recovery for specialty products.

PLANT MASS BALANCES

Mass balances were performed on both the WPSI and the PSI plants.

The purpose of the balances was to ascertain the degree of control each
plant had over its raw materials, finished product and waste products.

36


TABLE 26

EFFECT OF PEELING SYSTEM ON COST

OF PRIMARY AND SECONDARY SYSTEM*

WET CAUSTIC IR-DRY CAUSTIC
Primary Clarifier
60' C2T X10" SWD $50,000
50' C2T X10' SWD $42,000
Vacuum Filter
8' X 10’ E-Belt Eimco 40,000
6' X 8'  E-Belt 36,000
Aeration Basin
300' X 145' X 19° 47,000
200' X 110' X 19! 26,000
Aerators
Four 125 HP LS Fixed Eimco 100,000
Electrical supplies and labor 6,000
Two 125 HP LS Fixed Eimco 50,000
Electrical supplies and labor 3,000
Secondary Clarifier
95' C2D 75,000
85' C2D 69,000
Granular Media Filter
Two X 16' Dia. Eimco 70,000
Two X 14! Dia. Eimco 50,000
Activated Sludge Digester Tank
125' X 75' X19 95,000
90' X 50' X19" 40,000
Aerators
Two X 100 HP LX Fixed Eimco 50,000
Electrical supplies & labor 3,000
One &100 HP LS Fixed Eimco 25,000
Electrical supplies & labor 1,500
$536,000 $342,500

* Costs are as ‘of March 1974 for this section

61



PROCESS wast. POSAL

Recirculated
Water From
Processing

MUD, SOLIDS, WATER

Solids to Lan:

To Landfill

Large Potato Solids to Cattle Feed
Liquids to City Lagoon
or Advanced Treatment

VISCOUS, SEMISOLID

SOLIDS, WATER

SOLIDS, WATER

SOLIDS, WATER

SOLIDS, WATER
‘Sludge > Filtration

SOLIDS, WATER

WASTE,
To Cattle Feed
WASTE.

 MAGNUSCRUBBER
 MAGNUWASHER

Solide to Cattle Feed
or Landfill

‘COOLING

CLEANING
FINISHED
PRODUCT,

FIGURE 2, FLOW DIAGRAM OF WESTERN POTATO SERVICE, INC
(WPSI) ORY CAUSTIC METHOD OF PEELING



Table 16, VACUUM FILTER CAKE

WET CAUSTIC - PST TR ORY CAUSTIC - WPSI

Seaton [ioe we TS [TVS [PH bp. Gr. [essn2/nr. * | EE] ts |rvs fark [rPO, [TKN pH] Sp.Grfis/ft.“/iar.

~Ths/ton Tbs. bs7fon Ibs.
WINTER
Avg a9| 9.5/8.5 | 5.1] 1.013] 0.62 314 | 40] 37|1.1]0.4 |0.2 p.5] 1.097] 4.6
s 37| 6.3]5.7 | 0.7] 0.005] 0.25 78 | 9| 9.2.0.6|0.2 0.1 2.7] 0.011) 1.0
n 4) 414 [4/2 4 7) 77 \7 \7 7 b |7 7
SPRING|
Avg 210} 18 | 15 | 4.8) 1.020} 0.99
s 123] 9.5} 8.0) 0.5] 0.021 0.52 No results due to inoperative vacuum filter.
n 7) 717137 7
FALL
Avg 12] 11 | 8.6] 6.1] 1.039] 0.66 390 | 51] 47] 1.9/0.4 |0.4|7.6| 1.046] 4.6
s 47| 4.13.6 | 1.9] 0.033) 0.25 345 | 36) 34]2.910.1 |0.3 6.5] 0.035] 3.3
n 12] 12 fz. [ro {12 12 9| 8} als j2 |2 6 |e 8
Avg** | 144/12 | 11 | 5.6 1.090] 0.75 557 | 46| 42] 1.4.41 [0.21.7] 1.0421 4.6

* Output based on 22 hr. operating day.
3 Standard Deviation - see glossary

n_ Number of samples ~ see glossary

** Weighted Average



Single peel line costs for the two systems-are $110,800 for the IR-
dry caustic system and $47,200 for the wet caustic system. The dif-
ferences are primarily in the cost of Shufflos, infrared units, scrub-
bers, washers, and the waste pump.

Primary treatment costs were $212,100 for PSI and $165,300 for WPSI.
The differential is due to the smaller clarifiers and vacuum filter
but partially offset by the need for a peeler solids storage hopper

at WPSI. Sludge disposal costs have not been included in the study
since this cost is extremely variable, and both plants are disposing
of the waste solids to cattle feed producers willing to do the trucking
in return for the waste.

OPERATING AND MAINTENANCE COST - PEELING

The operating and maintenance costs for both plants are presented in
Table 20. Actual operating costs for PSI and WPSI are based on

810 and 426 tons per day, réspectively, whereas potential operating
costs are respectively based on 1000 and 600 tons per day. The actual
peeling costs for the IR-dry caustic were $0.276 higher than the wet
caustic with potential costs $0.113 per ton higher. Difficulty was
encountered in the IR-dry caustic lines which were overloaded when
running at their designed rate of 20,000 pounds per hour. Although
the lines were designed for this rate, it was learned much later that
90 seconds of infrared treatment were required. The lines were equipped
with only 14 IR burners rather than the 20 burners required for

90 seconds of infrared treatment. The lines operated with only 14
burners during the grant period.

Table 20. OPERATION AND MAINTENANCE COSTS - PEELING

WET. CAUSTIC - PSI IR-DRY_CAUSTIC~WPS1
Actual/ton |Potential/ton| Actual/‘ton | Potential/ton

Caustic at $0.0416 $ .523 same $ .626 same
Water at (0.30/1000 gal.) 269 same 110 same
Power at (0.014/KWH) 127 same .077 same
Gas at (0.85/106BTU) ---- +24 17
Labor $19.79/day/man 147 9 467 198
Maintenance -140 126 467 422
Total $1.523 $1.490 $1.799 $1.603

54


Figure 4. Model D-14 Shufflo infrared unit


EPA-660/2-74-088
JUNE 1975

INFRARED DRY CAUSTIC VS. WET
CAUSTIC PEELING OF WHITE POTATOES

by
Otis Sproul
John Vennes
Wayne Knudson
Joseph W. Cyr

Grant 12060 EIG
Program Element 18B037
ROAP/TASK No. 21 BAB/019

Project Officer

Kenneth Dostal
Pacific Northwest Environmental Research Laboratory
National Environmental Research Center
Corvallis, Oregon 97330

NATIONAL ENVIRONMENTAL RESEARCH CENTER
OFFICE OF RESEARCH AND DEVELOPMENT
U. S. ENVIRONMENTAL PROTECTION AGENCY

CORVALLIS, OREGON 97330

For sale by the Superintendent of Documents, U.S. Government
Printing Office, Washington, D.C. 20402


62

G.Mud Clarifier Avg (7289.68 135 (22 10 84 19 0.998
Influent s MS 7.8889 58915 6.3 18 3 0.001
a 8 8 7 a 8 8 8 8
H, Mod Clarifier Avg 723 233 5.3 496 37 a5 2.8 0.997
Effluent fy at 1.660 4,8 1.61 5.0 2.0 V7 2.2 0.001
no 8 7 8 7 8 8 a 8 8
REMOVAL (%) a 66.6 St 80 —— 85 a
FALL
B. Hydro bruther-peeler Avg = 1425 78.2148 10 160 Ns 10.8 264 1.000
s 0 20,843 246 55 40 0.8 n 001
fn W 10 12 W 12 12 12 v2 12
E, Maln Clorifier Ave 2121 58.4 NS 716 192 157 10.2 72 0.999
Influent s 197 184 047 244 2800-278 1.0 20 0.001
A u n 12 u 12 12 2 12 12
F, Main Clorifier Avg (1790 28,05 9.19 49.4 30 8.2 % 0,998
Effluent + 726 (145 6 6.38 34.3025 1.8 40 002
A 12 i n u nu 12 2 12 12
REMOVAL (%) 7 5 74.2 76 = a
G.Mud Clarifier Avg 810—~C«CS TSS 73.0 68.8 3.0 9.6 3.8
influent ’ a4 193 9.8 4,897 10 1.3 2.8
n 12 9 un 9 u n u u
H. Mud Clerifier Avg 661 157° 3.3 4.08 88 344 9.3 0.9
Effluent ry 192 0,991.8 2425.3 3.3 13 0.4
ry 12 9 n. nv n n n n
REMOVAL (%) - 48.1 56 60.2 58 58 - — 33 -— 85 -

Note: The letters, preceding the sampling points above, indicate the "Iétter code" for those points. (See Table 2),

4. Standard deviations ~ see Glossory
n. Number of somples ~ s00 Glossary


about the auger to mix and turn the product to expose all surfaces
uniformly, while the abrasive rolls rotate to regulate the applied
abrasiveness. A centralized water system, with jets located on the
shaft of the auger, provides a constant water spray to the product and
the abrasive rolls. The desired water flow is 20 gpm at 40 to 60

psi for each 10 ton per hour unit.

Wastewater from the unit is transported through a chute to a nearby
flume and then to primary treatment. As shown in Figures 6, 7, 8
and 9, the Magnuscrubber and Magnuwasher are of similar design except
for type and number of rolls, water use, and equipment speed.

A pilot study suggested that the peeling wastes (approximately 75 percent
of the total plant waste load in the wet caustic system) could be removed
from the liquid waste stream (2). In addition, it was also expected
that the peel loss could be reduced by as much as 25 percent.

7


RESEARCH REPORTING SERIES

Research reports of the Office of Research and Development,

U.S. Environmental Protection Agency, have been grouped into
five series. These five broad categories were established to
facilitate further development and application of environmental
technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in
related fields. The five series are:

Environmental Health Effects Research
Environmental Protection Technology
Ecological Research

Environmental Monitoring
Socioeconomic Environmental Studies

OPOn—

This report has been assigned to the ENVIRONMENTAL PROTECTION
TECHNOLOGY STUDIES series. This series describes research
performed vo develop and demonstrate instrumentation, equipment
and methodology to repair or prevent environmental degradation from
point and non-point sources of pollution. This work provides the
new or improved technology required for the control and treatment
of pollution sources to meet environmental quality standards.

EPA REVIEW NOTICE

This report has been reviewed by the Office of Research and
Development, EPA, and approved for publication. Approval does
not signify that the contents necessarily reflect the views and
policies of the Environmental Protection Agency, nor does mention
of trade names or commercial products constitute endorsement or
recommendation for use.


the main clarifier influent total phosphate was 4.50 pounds per ton at
PSI and 2.22 pounds per ton at WPSI. The results were not significantly
different at the 0.05 level during the winter season between the plants
nor between seasons at each of the plants. There was, however, a sig-
nificant difference during the spring between plants.

The weighted average for phosphate as PQ, in the mud clarifier influent
was 0.55 and 0.23 pound per ton at PSI and WPSI, respectively. Results
between seasons at WPSI were significantly different at the 0.05 level.
Sufficient data were not available at either plant for further comparison.
The mud clarifier influent total Kjeldahl nitrogen as N was 0.16 pound
per ton at PSI and 0.22 pound per ton at WPSI. Results were not sig-
nificantly different at the 0.05 level within plants by seasons nor
between plants during the winter or spring; sufficient fall data was

not available for comparison between plants.

BOD:N:P Ratio
The proper BOD:N:P ratio is necessary to maintain a satisfactory bac-

terial population. The best ratio is 100:5:1. Table 11 gives the
main clarifier BOD:N:P ratios.

Table 11. MAIN CLARIFIER BOD:N:P *RATIOS

WET CAUSTIC - PSI IR-DRY CAUSTIC - WPSI

SEASON Influent Effluent Influent Effluent

Winter 100: 3.97:1.06 | 100:3.06:0.79 ||100:3.87:2.48 |100:5.30:2.44

Spring 100: 4.84:1.57_| 100:4.61:1.52 }|100:5.87:2.01 |100:8.03:1.91

Fall = Ny enero 100:4.28:1.88 |100:5.06:2.01

*Weighted averages

No fall results for PSI nor spring results for WPSI are shown because
nitrogen and phosphorus determinations were not made during those periods.
These data indicate that adequate phosphorus will be available for
secondary treatment but that nitrogen may be a limiting nutrient in the
wet caustic waste after primary sedimentation. Supplementation of
nitrogen may be necessary to achieve satisfactory biological treatment

if short term (2 to 4 days) aerated lagoons are used. Longer aeration
periods would allow more biological recycling of nitrogen and could
decrease the amount of supplementation required.

4


Analyses were performed according to Standard Methods (3) for total
solids, total volatile solids, suspended solids, volatile suspended
solids, settleable solids, alkalinity, pH, BOD, and specific gravity.

A Technicon Auto Analyzer was used to determine total Kjeldahl nitrogen,
chemical oxygen demand, and total phosphate (4).

25


Table 7. COMPARISON OF CAUSTIC USAGE

WET CAUSTIC-PSI IR-DRY CAUSTIC - WPSI
SEASON Ibs/100 Ibs Peeled Ibs/100 Ibs Peeled
WINTER

Avg 1.131 1759

n 60 64
SPRING

Avg 1.412 .900

n 54 59
FALL

Avg 643 .608

n 74 63
OVERALLAVERAGE| 1.020 \753

n_ Number of samples - see glossary
* Weighted averages

Caustic peeling conditions at each plant ranged as follows:

PSI WET CAUSTIC WPSI IR-DRY CAUSTIC

Temperature range 170°F to 200°F 145°F to 200°F
Concentration range 7.5 to 23 percent 8.6 to 20 percent
Immersion time range 3 to 7 minutes 1 to 5 minutes

INFRARED DRY CAUSTIC MAGNUSCRUBBER PEEL WASTES

The IR-dry caustic peeler solids data are shown in Table 8. The re-
covery of total solids were 53, 81 and 41 pounds per ton of potatoes
processed during winter, spring and fall respectively.

The increased recovery in the spring was caused by more actual peel loss
due to deeper peeling of the potatoes and also to a diminished bypassing
of the solids to the Magnuwasher peeler wastewater line. The low

dry solids content of the peeler solids---9.8 to 8.6 percent---

was due to the water added to keep the material in a condition that
could be pumped. A dry solid content of 14 to 15 percent might be
expected if the water had not been needed.

34


02

Figure 10.

EIMCO

continuous filter

at WPSI (Produces filter cake from main clarifier sludge).


4. Compare the silt removal systems and primary clarifiers as
to quality and quantity of influent and effluent.

5. Determine whether dry caustic sludge would be accepted or
rejected for subsequent study as animal feed material.

Both PSI (design capacity of 1000 tons per day) and WPSI (design ca-
pacity of 600 tons per day) produce primarily frozen french fries
(for flow diagrams, see Figures ] and 2). There are two types of
french fries---retail and institutional. Retail products are pro-
duced in both straight and crinkle cut in the larger cross section
sizes. Institutional products are also produced in straight and
crinkle cut; however, in three sizes of straights and two of crinkles.
Both plants also produce potato rounds---shredded potato pieces mixed
with potato flakes or starch and condiments, then extruded and fried.
Other products produced occassionally but not on a daily basis are
frozen hash, frozen whole boils, and frozen cottage fries.

PSI has five peel lines (including an automatic steam peeler not used
during the grant period) while WPSI has three. All lines at both plants
are rated at 20,000 pounds of raw stock per hour. The linés at PSI
consist of caustic reels for immersion, retention belts, and hydro-
brusher-washer peelers (see Figure 3). At WPSI, the lines consist

of caustic reels, retention belts, Shufflo-infrared units (see Figures
4 and 5), Magnuscrubber peeler and Magnuwasher peeler, (see Figures

6, 7, 8 and 9).

There are various types of solids generated by the peeling operation

as well as by the waste treatment--- french fry waste, screened solids,
filter sludge, peeler waste solids (from the Magnuscrubber peeler),

and mud sludge. At PSI the french fry waste and a part of the screened
solids and filter sludge are given to a nearby animal food processing
company for the trucking; the mud sludge is hauled off for Jandfill.

At WPSI, the french fry waste and some of the screened waste are given
to farmers for the hauling; any remaining screened solids, filter sludge,
peeler waste solids and mud sludge were trucked to dumping grounds.
Recently a drying plant has been placed in operation and it is planned
that screened waste solids, filter sludge and peeler waste solids will
be taken by this plant.

In-plant treatment systems consist only of effluent screening (4 mesh
screens) before discharge to the primary clarifier. Both plants have
fat traps to remove waste fat before the primary clarifier.

Process steps at each plant are very similar (see Figures 1 and 2).

At PSI, potatoes are flumed from storage to evenflow hoppers from

which they are fed into caustic reels ror caustic treatment), then onto
retention belts (for additional treatment time), then over the hydro-
brusher-washer peelers (to remove the skin) and finally to surge tanks
for controlled flow to the trim tables. Once the potatoes are trimmed,


MAINTENANCE

Maintenance of the IR-dry caustic peel lines was approximately three
times that required for the wet caustic peel lines. The thermocouples
for the infrared burners were the primary source of trouble in these
machines. The infrared conveyors were practically free of breakdowns.

The Magnuscrubbers and Magnuwashers made up the larger portion of
maintenance requirements. The problems centered on the bearings
for the rolls, variable speed units, and trunions. Undoubtedly,
these problems can be corrected in future units.

TOTAL ANNUAL COSTS - PEELING AND PRIMARY TREATMENT

Table 23 shows the actual total annual costs of the peeling and primary
treatment systems for both plants including the reduced peel loss
savings of $0.91 per ton based on a 250-day operating season. As

shown, conventional wet peel and primary treatment costs amount to
$2.126 per ton versus $2.017 for the IR-dry caustic peel and primary
treatment costs. This is a savings of $0.11 per ton of potatoes pro-
cessed. The savings on a potential production basis is $0.456 per ton.
These savings are conservative since operational difficulties with

the infrared equipment necessitated operating conditions which increased
the peel loss.

Table 23. TOTAL ANNUAL COSTS - PEELING AND PRIMARY TREATMENT

WET CAUSTIC -PSI IR-DRY CAUSTIC-WPS1

Actual/ton |Potential/ton |Actual/ton [Potential /ton
Table 20 - Peeling Costs $1,532 |$1.490 $1.799 | $1,603
Table 21 - Primary Costs «257 230 2334 -280
Amortization of Capital
7% interest 10 yr. repayment 337 -273 794 «564
Total 2.126 1.993 2.927 2.447
Less Saving - Reduced Peel Loss 0.91 G.91
Total $2.126 | $1.993 $2.017_| $1,537

*250 operating day season

56


Table 12 gives the mud clarifier BOD:TKN:P ratios.

Table 12. MUD CLARIFIER BOD:N:P *RATIOS

WET CAUSTIC - PSI IR-DRY_CAUSTIC - WPSI
SEASON Influent Effluent Influent Effluent
Winter 100:5.13:5.13 | 100:8.20:5.46 {| 100: -- :2.17 | 100:3.71:1.69
Spring _| 100:1.34:1.86 | 100:8.58:4.29 |] 100:4.29:--- | --------

Fall = 100:5.23:1.65 | 100:5.76:1.39
* Weighted average

The mud clarifier effluent data show that the phosphorus is present in
satisfactory quantities in the effluent from each plant. The nitrogen
level appears satisfactory at PSI, but supplementation might be required
at the WPSI plant.

Alkalinity and pH

The average alkalinity over the three seasons in the main clarifier
influent at PSI was 24.0 pounds per ton, while WPSI had a much Tower
value of 14.9 pounds per ton. Alkalinity for the three seasons averaged
29.2 pounds per ton of potatoes for the hydro-brusher-washer peeler at
PSI versus 5.8 pounds per ton for the Magnubrusher-peeler at WPSI.

Due to a misprint in the method cited in the EPA Manual (6), the analysis
figures from PSI showed the alkalinity as 1/10 of its actual strength.
This has been corrected in the text. This difference between the two
peeler systems resulted because most of the caustic at WPSI was taken
out with the peeler solids and did not gain access to the washer waste-
water. Alkalinity in the peel system wastes at PSI also increased from
25.6 pounds per ton in the fall to 32.3 pounds per ton in the winter
and spring. This is attributed to the increased caustic penetration
required to effectively peel potatoes in storage from the fall season.
The results showed a significant difference between plants during the
winter, spring and fall, as well as between seasons at the individual
plant.

PRIMARY SEDIMENTATION AND SLUDGE FILTRATION

Overflow And Solids Loading Rates

The data for the waste analyses in and out of the primary clarifier
are shown in Tables 4 and 5. The efficiency of removal of suspended

42


Table 13. PRIMARY CLARIFIER OVERFLOW RATES AND DETENTION TIMES

WET CAUSTIC - PSI IR DRY CAUSTIC - WPST
Main Clarifier Mud Clarifier Main Clarifier Mud Clarifier
D

s |. as.dled elsq2hed levtl3 les el88eh.2

8 lsef(eSlseeSsles Sse s | se Es let

& £5 3/55 |Es-lBs iS 2 Bs s/s 8 esr seals 8

BAS) & 2 ears [F SO} 8 20
WINTER

=

Avg } 152 | 336 | 7.1 | 17 720 81 1395 5.1 22 353
s 37 | 126 2.7 4.0 | 247 7 57.4) 1.1 14 284

SPRING
Avg | 210 | 362 | 6.4 |22 | 668 | 45 [373 5.4| 12 | 360

s 57 | 110 | 2.0 115 12 19 35.2] 1.1] -- -—-

n 4 414 3 4 | 1 19 21.0 10 15

FALL
Avg | 137 | 238 112.9 | 26 824 | 77 {412 4.7) 2.1] 253

s 89.2 | 19.0 113.3 27 245 23 39.8/ 0.5 8.6 140
nt 10 10 {12 u 12 (| 21 21 21 2.1 20
s Standard Deviation
n Number of Samples

The weighted average BOD removal in the mud clarifier was 54.1 percent
at PSI versus 25.6 percent at WPSI. The results were not significantly
different at the 0.05 level: by seasons at WPSI nor between plants during
the winter. However, the results were significantly different at the
same Tevel by seasons at PSI and between plants during the fall. Data

44


Figure 3. Hydro-brusher-washer peeler