WATER POLLUTION CONTROL RESEARCH SERIES
12060—07/69
Secondary Treatment of
Potato Processing Wastes
MENTAL PROTECTION AGENCY • WATER QUALITY OFFICE
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WATER POLLUTION CONTROL RESEARCH SERIES
The Water Pollution Control Research Series describes the
results and progress in the control and abatement of pollu-
tion of our Nation's waters. They provide a central source
of information on the research, development, and demon-
stration activities of the Water Quality Office, Environ-
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Inquiries pertaining to the Water Pollution Control Research
Reports should be directed to the Head, Project Reports
System, Office of Research and Development, Water Quality
Office, Environmental Protection Agency, Washington, B.C. 20242.
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SECONDARY TREATMENT OF POTATO
PROCESSING WASTES
Prepared by
Kenneth A. Dostal
Pacific Northwest Water Laboratory
200 Southwest 35th Street
Corvallis, Oregon 97330
for the
WATER QUALITY OFFICE
ENVIRONMENTAL PROTECTION AGENCY
Project #12060 07/69
July 1969
For sale by the Superintendent of Documents, U.S. Goyernment Printing Office
Washington, D.C., 20402 - Price 65 cents
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CONTENTS
INTRODUCTION
Problem 1
Authority 7
Objective 8
SUMMARY 9
DESCRIPTION OF PROCESSING PLANTS 11
PRIMARY WASTE TREATMENT PLANT
Description 15
Efficiency 17
PILOT PLANTS
Description 21
Operation 22
Results 25
DISCUSSION 39
REFERENCES 59
APPENDIX 61
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LIST OF TABLES
No. Page
1 Potato Production and Processing in Idaho 5
2 Waste Production per Ton of Potatoes Processed .... 12
3 Operational Characteristics of Primary Clarifier ... 18
4 Pilot Plant Feed Rates 26
5 Data Summary, 9-20-66 Through 12-23-66 27
6 Data Summary for Anaerobic Pond II 30
7 Loadings and Reductions for Anaerobic Pond II 31
8 Data Summary for Aerobic Pond I 33
9 Data Summary for Aerobic Pond III 35
10 Loadings and Reductions for Pond III 37
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LIST OF FIGURES
No. Page
1 Trends in Potato Production 2
2 Frozen Potato Products Processed 3
3 Flow Diagram of Primary Treatment Plant 16
4 Flow Diagram of Pilot Plants 23
5 Influence of Detention Time on BOD of Effluent VSS ... 42
6 Predicted Influence of Detention Time on Effluent
BOD & VSS 45
7 Influence of Time & Temperature on Calculated
Effluent BOD 48
8 Comparison of Treatability of Primary Effluent vs.
Anaerobic Effluent 52
9 Influence of Detention Time in Anaerobic Pond II &
Aerobic Pond III on Soluble & Total Effluent BOD
from Pond III 53
10 Influence of Detention Time on Pond III Effluent VSS . . 55
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ABBREVIATIONS
BOD 5-day, 20°C biochemical oxygen demand, mg/1
BODS Soluble BOD, mg/1
COD Standard Methods chemical oxygen demand, mg/1
CODS Soluble COD, mg/1
CODjvi National Canners Association's modified COD, mg/1
SS Suspended solids, mg/1
TS Total solids, mg/1
VSS Volatile suspended solids, mg/1
TVS Total volatile solids, mg/1
NH3-N Ammonia nitrogen, mg/1 as N
TKN Total Kjeldahl nitrogen, mg/1 as N
TP04 Total phosphate, mg/1 as P
Alk Total alkalinity, mg/1 as CaCOa
TOC Total organic carbon, mg/1
DOC Dissolved organic carbon, mg/1
DO Dissolved oxygen, mg/1
gpm Gallons per minute
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ACKNOWLEDGMENT
The assistance of the Idaho State Health Department, the
J. R. Simplot Company, and the consulting firm of Cornell,
Howl and, Hayes & Merryfield in this study is gratefully
acknowledged.
In addition, appreciation is expressed to the Wayne
Wiscomb Company and The Eimco Corporation for supplying
surface aerators used in this study.
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INTRODUCTION
Problem
Annual production of potatoes in the United States has
increased from 195 million hundred weight (cwt.) in 1951 to
over 300 million cwt. in 1966^ ' as shown in Figure 1. The
western states of Idaho, Washington, California, and Oregon
have accounted for most of this increase, at least during the
past 10 years. From 1958 through 1966 these four states had
an increased production of 63 million cwt. (from 75 to 138),
whereas the total production for the United States increased
only 40 million cwt. (from 267 to 307).
These increases in potato production reflected the increased
processing of specialty items such as frozen french fries, hash
browns, and others. Figure 2 presents the 1955-1965 growth and
projects for the next 10 years the quantity of potatoes to be
processed into frozen products. This information was a result
(2)
of a computer analysis by DuPontv . From 1955 through 1966 the
quantity of frozen potato products increased from 129 million
to 1460 million pounds. This analysis predicted that 3926 million
pounds would be processed in 1976, an increase of 170 percent, as
related to an expected population increase of only 9 percent.
The potato growers and processors in Idaho have participated
in this growth. Eleven members of the Potato Processors of Idaho
Association had a $23,235,457 payroll and $52,085,335 plant
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300--
h-
o
(D
o
O
250--
200--
g,504-
cr
Q_
IOO--
50--
0
1950
1 I T
UNITED STATES
IDAHO, WASHINGTON,
CALIFORNIA 8, OREGON /
/\
/ \
/ \/
4-
1955
I960
YEAR
1965
1970
Figure I. TRENDS IN POTATO PRODUCTION
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40
CO
Q
£
CO
O
35--
3O-
CO 254-
U
Q
O
CT
Q_
I
u
N 10+
O
cr
5--
0
1955
I960
DUPONT S _,
PROJECTION^7
1965
YEAR
1970
1975
Figure 2.- FROZEN POTATO PRODUCTS PROCESSED
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4
investment during tne 1965-66 processing seasonv°;. This repre-
sents more than a tenfold growth over comparable figures in 1950.
Although the quantity of potatoes produced in Idaho increased
only 39 percent in the 10-year period, 1950 to 1960, the amount
processed for food products increased almost tenfold as shown in
Table 1. In the two-year period, 1958 to 1960, the potatoes
processed for food products more than doubled. Since 1960, more
than 50 percent of the potatoes produced in Idaho have passed
through processing plants. Waste production has, unfortunately,,
grown accordingly.
Since potato wastes have become one of the State's major
water pollution sources, the Idaho State Health Department has
been, and is, working closely with the potato processors in the
development of effective waste treatment methods. As a result of
these cooperative efforts, all major potato processing plants
presently (1968) discharging into the Snake River or its tributaries
now provide primary treatment of their waste streams. Even with
primary treatment, these wastes in combination with others, have
resulted in fish kills and other pollutional problems during
periods of low flow in receiving streams.
(4)
The processing industries have been directedv ' by the Idaho
State Health Department to provide secondary treatment of their
wastes. The timetable calls for operating waste treatment plants
between the dates of July 1969 and July 1973, depending upon
plant location on the Snake River and other factors.
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Table 1
POTATO PRODUCTION AND PROCESSING IN IDAHO
Quantity of Potatoes - tons
Year
1946
1950
1956
1958
1960
Produced
1,388,400
1,525,800
1,655,200
2,041,900
2,120,000
Used in
Starch
153,450
240,700
163,700
344,900
77,500
Used in
Food
Products
143,800
101,250
324,250
483,500
1 ,005,000
Percent
of Crop
Processed
21.4
22.4
29.5
40.6
51.1
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6
In 1964, the consulting firm of Cornell, Howland, Hayes &
Merryfield (CH2M) was retained by the Engineering Committee of
the Potato Processors of Idaho Association to assist in the
design and operation of pilot plant facilities. The pilot plants
were used to check the applicability of several secondary waste
treatment processes to potato processing wastes. As a result of
(c\
this workv , design criteria were established for secondary
treatment by activated sludge, trickling filter, and conventional
stabilization ponds. One of the conclusions from this work was:
"Additional study should be given anaerobic ponds and flow-through
aeration basins to more closely determine the capabilities of
these systems in secondary treatment of potato process water."
This, coupled with the fact that both trickling filter and
activated sludge treatment plants have high capital and operating
costs, prompted the initiation of the study reported herein.
In addition to work reported by CF^M, Atkins and Sproul^ '
have reported on laboratory-scale pilot plant studies using both
completely mixed activated sludge and contact stabilization to
treat potato processing wastes. The completely mixed activated
sludge pilot plant reduced the BOD by greater than 90 percent
without pH adjustment (lye-peel waste) or addition of inorganic
nutrients. Also included in this report were the results of
extensive in-plant changes in water use (conservation, recirculation,
and by-product recovery). Water use was reduced from 2520 to
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7
2310 gallons per ton of potatoes. The plant effluent BOD was
reduced by over 50 percent from 52 to 22 pounds per ton of
potatoes and the suspended solids discharged were lowered from
37 to 25 pounds per ton.
At the 18th National Potato Utilization Conference held at
Corvallis, Oregon, in July 1968, Mr. Robert P. Graham of the
Western Regional Research Laboratory, U. S. Department of
Agriculture, Albany, California, reported on a semi-dry method
of caustic peeling of potatoes. The work used a 500 pound per
hour pilot plant and most of the potential variables were investi-
gated. Should this method prove to be economical, it could reduce
the present BOD and SS effluent loads by 50 to 75 percent.
Additional work on a larger scale is underway to evaluate the
overall economics of this method.
Authority
Federal authorization for this type of cooperative study
with both industry and State comes from the Federal Water
Pollution Control Act, as amended. Section 5(b) of the Act
provides that the Federal Water Pollution Control Administration
(FWPCA) may, "upon request of any State water pollution control
agency conduct investigations concerning any specific
problem of water pollution confronting any... industrial plant,
with a view of recommending a solution of such problem."
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8
In July 1966, a request to the regional office of the FWPCA
was received from the Idaho State Health Department for technical
assistance in the development of secondary treatment methods for
potato processing wastes. A memorandum of understanding authoriz-
ing the study and delineating responsibilities was signed by the
three participants: Potato Processors of Idaho, Idaho State
Health Department, and FWPCA
Objective
The objective of this study was to bring to conclusion
pilot plant studies started in 1965 on feasible methods of
secondary treatment of potato processing wastes. Investigation
of two methods of secondary treatment was requested:
(1) An anaerobic lagoon followed in series by a
surface-aerated aerobic lagoon, and
(2) A surface-aerated aerobic lagoon.
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SUMMARY
This report presents the results obtained from three pilot
lagoons which were used to treat potato wastes during the period
October 1966 through June 1968.
One of the lagoons received primary clarifier effluent and
was operated as a surface-aerated, aerobic unit. A second pond
also received clarifier effluent but was operated as a completely-
mixed, covered anaerobic unit. The effluent from the anaerobic
unit was pumped into a third pond which contained a surface
aerator. Hydraulic and organic loadings were varied to yield a
spectrum of results.
Conclusions drawn from the data collected during this study
are:
1. Both systems are economically feasible; the choice would
depend upon local costs and conditions.
2. The BOD in these potato wastes could be reduced 90
percent or more by primary clarification plus subsequent treat-
ment in either an aerobic lagoon or anaerobic-aerobic lagoons in
series.
3. BOD reduction across the ponds can be adequately described
using available mathematical models with necessary constants
derived from this study.
4. No chemical additions were necessary for either pH
control or inorganic nutrient adjustment.
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10
5. Covering the anaerobic lagoon surface with insulating
material will reduce the weather-induced temperature drop and
help control odors. Such covering will usually be required
for odor control.
5. Secondary clarification for removal of suspended solids
should be employed following either an aerobic lagoon or an
anaerobic-aerobic lagoon system.
7. Foaming may cause operational difficulties in full-scale
aerobic lagoons, but can be controlled by proper design.
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DESCRIPTION OF PROCESSING PLANTS
The pilot plant facility of the Processors Association is
located at the site of the J. R. Simplot Company's primary
waste treatment plant in Burley; Idaho. About 300,000 tons of
potatoes per year are processed by three J. R. Simplot Company
processing plants in the immediate vicinity.
One of these, the Burley Processing Company, processes
about 28 percent of the total. It is a highly automated plant
and produces instant mashed potatoes and related specialties.
The potatoes are washed, lye-peeled, cut, automatically sorted
for flakes or granules, dehydrated, and packed for shipment.
The Heyburn Plant, one of the world's largest in this
field, processes about 59 percent of the total, or 180,000 tons
of potatoes per year. Products include french fries and potato
specialties. Here, too, the potatoes are washed and lye-peeled;
then trimmed, blanched, processed, and packed. The remaining
13 percent of the Simplot Company's total potato tonnage at
Burley is processed in a starch plant.
During the 1966-67 processing season, these three plants
used an average of 4,170 gallons of water per ton of potatoes
processed. As shown in Table 2, an average of 90 pounds of BOD
and 110 pounds of suspended solids (SS) was added to the waste
stream per ton of potatoes processed. Three and one-half pounds
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12
Table 2
WASTE PRODUCTION PER TON OF POTATOES PROCESSED
Parameter Quantity*
Process water 4200 gal.
BOD 90 Ibs.
COD 210 Ibs.
SS 110 Ibs.
TP04 0.6 Ib.
Total nitrogen as N 3.5 Ibs.
*After screening
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13
of total nitrogen and 0.6 pound of total phosphate were also
contributed per ton of potatoes. These figures do not include
fat recovered or solids screened out for cattle feed; they were
derived from the flows and concentrations measured entering the
primary clarifier.
Both the SS and BOD values shown on Table 2 are higher than
experienced during previous seasons. Average values for the
potato processing industry are about 4200 gallons, 60 pounds of
SS, and 50 pounds of BOD per ton processed. As mentioned
earlier, these values can all be reduced by about 50 percent
through extensive in-plant changes.
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PRIMARY WASTE TREATMENT PLANT
Description
Waste streams from the three processing plants are piped to
a primary waste treatment plant. They first enter a receiving
tank and then are passed through two five-foot diameter, ten-foot
long rotary drum screens as shown in Figure 3. All solids retained
on the +20 mesh screens are removed and stored in bins.
The screened waste water then enters a 100-foot diameter
clarifier which operates with an average overflow rate of about
800 gallons per day per square foot. Most of the settleable
solids are removed and the effluent passes through a Parshall
flume prior to discharge to the Snake River.
Solids collected in the clarifier are pumped through a
centrifuge for thickening. The thickened sludge is also stored
in bins and the supernatant is either returned to the clarifier
influent or discharged to the river. During the study reported
herein the centrifuge was overloaded which reduced its efficiency
and resulted in less than optimum operation of the clarifier
when the supernatant was added to the influent.
Both the screenings and the sludge from the centrifuge are
trucked to a cattle feed-lot operation for use as part of the
animals' diet.
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SCREENED
SOLIDS
BIN
SLUDGE
BIN
I
RAW
SCREEN
WASTE
SCREEN
---I
_ J
CENTRIFUGE
CENTRATE
I
I SLUDGE
«TO
SNAKE
RIVER
PARSHALL
FLUME
EFFLUENT
PRIMARY
CLARIFIER
Figure 3.-FLOW DIAGRAM OF PRIMARY
TREATMENT PLANT
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Efficiency
The efficiency of the primary clarifier at the J. R. Simplot
Company's waste treatment plant is indicated by the data shown in
Table 3. All data collected on the clarifier influent and the
clarifier effluent during both processing seasons are included.
The pH of the clarifier-influent ranged from 10.6 to 12.1
with a median of 11.3; for the clarifier effluent it ranged from
7-1 to 11.6 with a median value of 10.4 Temperature of the waste
dropped an average of 4°F across the primary clarifier. In the
effluent it ranged from 63 to 79°F and averaged 74°F.
BOD removal by the primary clarifier averaged 41 percent.
The concentration in the clarifier effluent ranged from 650 to
2570 mg/1 and averaged 1600 with a standard deviation of ±24
percent.
Average COD was reduced from 5390 to 2960 mg/1, 45 percent,
by the primary clarifier. The clarifier influent contained an
average of 2320 mg/1 of suspended solids with a range of 280 to
5900 mg/1. Suspended solids in the effluent varied from 80 to
3190 and averaged 620 mg/1 for an average reduction of 73 percent.
Both the total Kjeldahl nitrogen and total phosphates were
reduced by 21 percent upon passage through the primary clarifier.
The effluent contained an average of 84 mg/1 of total Kjeldahl
nitrogen as N which resulted in a BOD to nitrogen ratio of 19:1.
On individual samples this ratio ranged from 7:1 to 33:1. Total
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Table 3
OPERATIONAL CHARACTERISTICS OF PRIMARY CLARIFIER
pH
Temp.
°F
BOD
COD
SS
TKN
TP04
Range
Median
Range
Median
Std. Deviation
Range
Mean
Std. Deviation
Range
Mean
Std. Deviation
Range
Mean
Std. Deviation
Range
Mean
Std. Deviation
Range
Mean
Std. Deviation
Clarifier
Influent
10.6-12.1
11.3
68-82
78
±3
1220-5150
2730
±790
3120-9860
5390
±1520
280-5900
2320
±1150
73-225
107
±28
7.2-45.1
18.0
±6.9
Clarifier
Effluent
7.1-11.6
10.4
63-79
74
±3
650-2570
1600
±390
1440-6000
2960
±750
80-3190
620
±490
38-175
84
±25
6.0-37.2
14.2
±6.1
Removal
%
__
41
45
73
21
21
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phosphates in the effluent averaged 14.2 mg/1 as P. The average
of individual BOD:P ratios, which ranged from 48:1 to 285:1, was
130:1.
Effluent from the primary clarifier contained an average of
6.9 mg/1 of ammonia nitrogen as N with a range of 3.4 to 16.9 mg/1.
An average concentration of 1.8 mg/1 was measured for orthophosphates
as P with a range of 0.2 to 5.8 mg/1.
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PILOT PLANTS
Description
The pilot plant facility of the Potato Processors of Idaho
Association was located at the primary waste treatment plant
of J. R. Simplot Company in Burley, Idaho. Three earthen ponds
sealed with concrete applied as gunite were utilized. Each
pond was 40 feet square at the water surface and approximately
10 feet deep. During the 1966-67 processing season each pond
had a capacity of 51,000 gallons. Prior to the 1967-68 season
overflow weirs were installed in place of the overflow pipes;
this reduced the depth and thus the volume of each pond to
about 45,000 gallons. The influent to, and the effluent from,
the ponds were added and withdrawn, respectively, near the water
surface on opposite sides of the ponds.
When the ponds were operated as anaerobic units they were
covered with three-inch thick styrofoam blocks to help retard
heat loss and control odors.
Two surface aerators were used during most of the study
period, a 5 hp floating Wells* aerator and a 10 hp fixed Eimco*
aerator.
*Mention of specific proprietary equipment is for information
purposes only and does not constitute endorsement by the
Federal Water Pollution Control Administration and the U. S.
Department of the Interior.
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Operation
Ponds II and III were started September 19, 1966, as
covered anaerobic units while awaiting the arrival of previously
ordered surface aerators. They were operated as parallel
anaerobic units until the processing and waste treatment plants
were shut down for the holidays on December 23, 1966.
Initially both ponds were filled two-thirds with tap water
and one-third with primary clarifier effluent. They were seeded
initially with activated sludge and later with sludge from another
(5}
anaerobic lagoon. As suggested in an earlier study^1 ', the
.flow-through rates were set and maintained at 1.8 and 8.8 gpm
for ponds II and III, respectively. This resulted in theoretical
detention times of 20 and 4 days, respectively.
In mid-January 1967, after arrival of the 5 hp surface
aerator, pond III was converted from a covered, anaerobic unit
to a surface-aerated unit. It was placed in series with anaerobic
pond II. At that time a recirculation pump was installed on
anaerobic pond II to keep the contents completely mixed. Reasons
for this will be discussed later. The two ponds were operated
at various hydraulic and organic loadings until the end of
processing on May 27, 1967.
During the 1967-68 processing season all three ponds were
used. As shown in Figure 4, pond I contained a 10 hp surface
aerator and ponds II and III were operated as during the last
half of the previous processing season.
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PUMP
POND I
£>
IOHI
AERATOR
SUMP
TO RIVER
PONDH
COVERED
ANAEROBC
1
POND HI
5HP^
AERATOR
Figure 4.-FLOW DIAGRAM OF PILOT PLANT
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24
Samples were collected from the clarifier influent, clarifier
effluent, pond I effluent (when in operation), pond II effluent
and pond III effluent. Throughout the study, eight-hourly grab
samples of both the clarifier influent and effluent were
collected and composited with time. This method was used rather
than compositing according to flow, since variations in flow
through the clarifier were usually less than +10 percent of
the average based on individual readings.
During the first processing season the effluent samples from
ponds II and III were individual grab samples. In the second
season of operation, all three pond effluents were sampled
hourly for eight hours and composited the same as the clarifier
influent and effluent.
Inasmuch as a sanitary engineer was stationed onsite during
the first year of operation, most of the analyses were performed
onsite. Once per week a set of samples was split three ways
with one portion shipped in iced containers to the Idaho State
Health Department, one to FWPCA's Pacific Northwest Water
Laboratory in Corvallis, Oregon, and one retained for onsite
analyses. During the second year of pilot plant operation, most
of the analyses were performed by the Laboratory in Corvallis.
Onsite determinations were limited to pH, temperature, dissolved
oxygen, total alkalinity, and some settleable solids.
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Analyses were performed according to Standard Methods' ^
with the following exceptions: volatile acids'8', National
(Q\
Canners Association's^ ' modified chemical oxygen demand (CODm),
nitrate nitrogen'10', Kjeldahl nitrogen^11^, total and ortho-
phosphate^ ', and total and dissolved organic carbon^13'. In
addition to the regular BOD and COD analyses, during the second
season most of the samples were centrifuged, with these analyses
repeated on the centrates. Other analyses performed on most of
the samples included: total solids, total volatile solids,
suspended solids, volatile suspended solids, nitrate nitrogen,
and ammonia nitrogen.
Table 4 presents the feed rates and theoretical detention
times for the main periods of operation of the three ponds. As
mentioned earlier, both ponds II and III were operated as
incomplete-mix, covered anaerobic units during the September 20
to December 23, 1966, period. From January 2, 1967, on, pond III
contained a 5 hp aerator and was operated in series with pond II.
Both ponds I and II were fed primary clarifier effluent.
Results
Anaerobic Pond - (unmixed)
A summary of the data collected during the September 20 to
December 23, 1966, period when both ponds II and III were operated
as covered anaerobic units is presented in Table 5. Pond II was
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Table 4
PILOT PLANT FEED RATES
No.
1
2
3
4
5
6
7
8
9
Pond I
(* \ (b}
Date QU; t(b>
9/20-12/23/66
1/02-01/19/67
2/23-03/20/67
3/29-04/23/67
4/30-05/27/67
9/26-12/19/67 4.0 7.0
1/02-02/29/68 7.5 4.2
3/01-04/02/68 7.5 4.2
4/03-06/15/68 3.0 10.4
Pond
Q
1.8
1.2
4.0
7.0
15.0
8.0
15.0
10.0
6.0
II
t
20
30
8.8
5.0
2.4
3.9
2.1
3.1
5.2
Pond
Q
8.8
4.0
7.0
15.0
8.0
15.0
10.0
6.0
II
t
4
8.8
5.0
2.4
3.9
2.1
3.1
5.2
a) Flow through rate - gpm
b) Theoretical detention time - days
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27
Table 5
DATA SUMMARY, 9-20-66 THROUGH 12-23-66
Average Concentration'5'
Reduction
Parameter Effluent Effluent Effluent Pond IIPond III
°
pH range
Clarifier
Effluent
1490
3130
2380
4010
2210
950
860
870
: 65-77
10.3-11.8
Pond II
Effluent
1160
2160
570
2600
1200
360
170
1010
60-68
6.3-7.0
Pond III
Effluent
1240
2500
700
2880
1430
420
320
1010
61-69
5.8-7.1
BOD 1490 1160 1240 22 17
CODS 3130 2160 2500 31 20
CODm 2380 570 700 76 71
TS 4010 2600 2880 35 28
TVS 2210 1200 1430 46 35
SS 950 360 420 62 56
VSS 860 170 320 80 63
Alk.
(a) mg/1 unless noted otherwise
(b) Both ponds anaerobic, detention times
pond 11-20 days
pond III - 4 days
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28
fed at a rate of 1.8 gpm which resulted in a theoretical detention
period of 20 days and pond III at 8.8 gpm had 4 days. The contents
of neither pond were mixed and, judging by the data, short-
circuiting occurred in pond II and possibly in pond III. The
effluents from both ponds were nearly identical in total alkalinity,
pH, and temperature. Had the actual detention time of pond II
approached 20 days, the temperature drop should have been more than
that observed.
Organic reductions in both ponds were rather low, 22 percent
BOD and 31 percent COD for pond II, and 17 and 20 percent,
respectively, for pond III. With a BOD loading of 4.7 Ibs/day/
1000 cu. ft. on pond II, expected reductions would be higher than
those observed. A possible reason, other than shortcircuiting,
is that it was not operated long enough to properly establish the
second stage of anaerobic decomposition-methane formation. The
fact that both ponds showed +70 percent reductions in CODm reveals
that changes in molecular structure were taking place.. Sedimenta-
tion of suspended solids probably accounted for much of the
measured reductions in both BOD and COD.
Pond II reduced the suspended solids by 62 percent or 590
mg/1 and pond III reduced them by 56 percent or 530 mg/1. The
primary clarifier lowered the BOD by 66 mg/1 for every 100 mg/1
of suspended solids that were removed. If this ratio is assumed
for the solids removed by the anaerobic ponds, then the BOD
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29
should have been lowered by 390 mg/1 across pond II and 350 mg/1
across pond III. Measured reductions were 330 and 250 mg/1,
respectively.
Anaerobic Pond II - (complete mix)
A summary of the data collected on anaerobic pond II when
it was operated as a completely mixed unit is shown in Table 6.
The run numbers refer to the listings shown in Table 4. Clarifier
overflow was fed to pond II at rates of 1.2 to 15 gpm. These
rates resulted in detention times of 30 to 2.1 days as shown
in Table 7, which also presents the loadings and average
reductions in COD and BOD. Pond loadings varied from 3 to 46
pounds BOD per 1000 cubic feet of volume with a resultant range
in BOD reduction of 3 to 50 percent. Reduction in COD ranged
from 5 to 47 percent.
Ammonia nitrogen concentration in the effluent averaged 33
mg/1 as N and total Kjeldahl nitrogen averaged 80 mg/1. The
former had a range of 13 to 88 mg/1 and the latter 41 to 119 mg/1.
The primary clarifier effluent had an average total Kjeldahl
nitrogen concentration of 84 mg/1 (Table 3) but this average
included the time period when the anaerobic pond operated as an
incompletely-mixed unit. This, coupled with the fact that no
sludge was found on the bottom during operation or upon termination
of the study, indicates that the contents were mixed thoroughly.
-------
CO
o
Table 6
DATA SUMMARY FOR ANAEROBIC POND II
Run
No.
2
3
4
5
6
7
8
9
Fl ow
gpm
1.2
4
7
15
4
15
10
6
Temp.
°F
54
61
68
71
62
63
62
68
COD
In
3110
3950
3280
3400
2190
2210
2280
2390
Out
1640
2510
2930
2880
1570
1770
2170
2000
SS
In
360
530
400
610
460
560
470
350
Out
470
310
420
380
440
400
400
470
VSS
In
360
490
360
540
430
500
440
330
Out
260
280
360
300
350
370
360
460
BOD
In
1550
1460
1770
1690
1470
1500
1690
1610
Out
780
1180
1600
1520
1240
1460
1610
1410
BOD5
In Out
1180 1060
1360 1350
1510 1470
1440 1410
-------
31
Table 7
LOADINGS AND REDUCTIONS FOR ANAEROBIC POND II
Run
No.
2
3
4
5
6
7
8
9
D.T.
days
30
8.8
5.1
2.4
7.8
2.1
3.1
5.2
Ibs BOD/day/
1000 cu.ft.
3.3
11
22
46
12
45
34
19
BOD Red.
%
50
19
10
10
16
3
5
12
COD Red
%
47
36
11
15
28
20
5
16
-------
32
Effluent from the clarifier contained an average of 14.2 mg/1
of total phosphates as phosphorus while the effluent from pond II
averaged 14.5 mg/1 with a range of 7.8 to 20.3 mg/1. Ortho-
phosphate in the effluent ranged from 2.1 to 7.7 mg/1 and averaged
4.6 mg/1.
The ratio of BOD to total Kjeldahl nitrogen in the effluent
averaged 18 to 1 as compared to 19 to 1 for the effluent from the
primary clarifier. It had a range of 8:1 to 28:1. The overall
range was slightly reduced from that observed for the clarifier
effluent, 7 to 33:1.
In the clarifier effluent the ratio of BOD to total phosphates
as P was 130:1 with a range of 48 to 285:1. This was also reduced
upon passage through the anaerobic lagoon as it ranged from 67 to
173:1 and averaged 107:1 in the lagoon effluent.
Aerobic Pond I
A summary of some of the data collected for aerobic pond I
containing the 10 hp surface aerator is shown in Table 8 along
with BOD loadings and both BOD and COD reductions. Three levels
of hydraulic loading were fed to the pond: 3, 4, and 7.5 gpm,
resulting in theoretical detention times of 10.4, 7.8, and 4.2
days, respectively. Although the average temperatures of the
lagoon contents were 44 and 47°F, daily temperatures as low as
32°F were measured.
-------
Table 8
DATA SUMMARY FOR AEROBIC POND I
Run
No.
6
7-8
9
D.T. Temp.
gpm days °F
4 7.8 44
7.5 4.2 44
3 10.4 47
Run Ibs BOD/
No. acre/day
6 1840
7-8 3870
9 1660
COD
In Out
2210 860
2160 1480
2390 1190
LOADINGS
Ibs BOD/day/
1000 cu. ft.
11.3
23.7
10.2
SS
In Out
490 630
470 700
310 650
Ibs BOD/day/
Ib. MLVSS
0.32
0.62
0.26
In
440
420
280
COD
Red
%
61
31
50
VSS
Out
560
610
620
BOD
Red.
%
81
55
82
BOD
In Out
1410 270
1580 710
1700 310
BODS
Red.
%
93
76
95
BODS
In Out
1060 70
1440 340
1440 75
oo
CO
-------
34
BOD loadings on the pond are shown as Ibs/acre/day, Ibs/day/
1000 cu.ft., and Ibs/day/lb MLVSS. In run number 6 the loading was
1840 Ibs/acre/day or 11.3 Ibs BOD/day/1000 cu.ft. and this
resulted in a COD reduction of 61 percent, total BOD reduction of
81 percent, and soluble BODS reduction of 93 percent. It should be
emphasized that the measured effluent BOD of 270 mg/1 contained all
the suspended solids (630 mg/1) since the lagoon was completely
mixed and no secondary settling facilities were in use. When the
load was increased to 3870 Ibs BOD/acre/day the reductions fell
off: 31 percent for COD, 55 percent for total BOD, and 76 percent
for soluble BOD.
The last run, number 9, at 3 gpm produced an effluent with a
total BOD of 310 mg/1 and a soluble BODS of 75 mg/1 for reductions
of 82 and 95 percent, respectively.
Aerobic Pond III
Table 9 presents a summary of some of the data collected on
aerobic pond III which contained the 5 hp surface aerator. Effluent
from anaerobic pond II was fed to this pond at varying rates of
4 to 15 gpm during the two processing seasons. These rates
resulted in theoretical detention times ranging from 2.1 to 8.3
days. The approximate average temperatures of the lagoon contents
ranged from 39 to 56°F as shown in Table 9. Individual daily
temperatures ranged from 32 to over 60°F.
With the exception of run number 7, the dissolved oxygen
content of the lagoon exceeded 1.5 mg/1. Several readings
-------
Table 9
DATA SUMMARY FOR AEROBIC POND III
Run
No.
3
4
5
6
7
8
9
Q
gjpm
4
7
15
8
15
10
6
D.T.
days
8.8
5.1
2.4
3.9
2.1
3.1
5.2
Temp.
°F
39
44
56
44
43
43
50
COD
In
2380
2930
2910
1540
1770
2170
2150
Out
1400
1250
2160
860
1600
1300
1100
SS
In
250
490
260
410
400
470
410
Out
730
820
860
580
810
890
510
VSS
In
240
420
210
360
360
410
340
Out
630
790
710
510
650
790
500
BOD
In
1150
1600
1510
1150
1460
1670
1480
Out
180
270
640
380
730
550
370
BOD
In
980
1350
1470
1440
<;
Out
80
485
190
110
GJ
en
-------
36
during run 7 were less than 0.5 mg/1 which may have hindered
the rate of organic reduction. During that run the average
loading on the pond was 260 pounds BOD/day with some loads
exceeding 300 pounds.
The average loadings during the seven runs, along with
percentage reductions in BOD and COD, are shown in Table 10.
In pounds of BOD per acre per day the loading varied from 1500
to 7400 or from 8 to 40 lbs/day/1000 cu.ft. The COD average
reduction ranged from 10 to 57 percent and BOD reduction
ranged from 50 to 84 percent. During the last four runs, when
soluble BODS was routinely measured, its reduction averaged
19 percent higher than the reduction in total BOD.
-------
Table 10
LOADINGS AND REDUCTIONS FOR POND III
BQD Loadings
Run
No.
3
4
5
6
7
8
9
Ibs/acre/
day
1500
3660
7400
3000
7150
5460
2900
Ibs/day/
1000 01. ft.
8
20
40
18
44
33
18
Ibs/day/
Ib MLVSS
0.21
0.40
0.88
0.58
0.96
0.68
0.57
Reductions-%
COD
41
57
26
44
10
40
49
BOD
84
83
58
67
50
67
75
BODc;
92
64
87
92
CO
-------
DISCUSSION
To gain as much information as possible from the data
generated during the two processing seasons, several avail-
able mathematical relationships were reviewed in an attempt
to descri.be the kinetics of both the anaerobic and the aerobic
ponds. In 1942 Monod^ ' expressed the relationship existing
between bacterial growth rate and the concentrations of a growth
limiting nutrient as follows:
dF = k M s
dt = Ks + s (1)
where: dF _ rate of waste utilization per unit volume of reactor,
dt mass/volume-time
s = soluble waste concentration in the reactor, mass/
volume
M = microorganism concentration, mass/volume
k = maximum rate of waste utilization per unit
weight of microorganism at high waste
concentration, time-1
Ks = half velocity constant equal to the waste concen-
tration when -rr is equal to 1/2 of the maximum
rate, (-rr)max., mass/volume
According to this equation, at high waste concentrations the
waste utilization rate approaches a maximum value which is
essentially independent of waste concentration and, at low waste
concentration, the rate is proportional to the waste concentration.
-------
40
This equation, along with appropriate materials balance equations,
has been widely used to describe both activated sludge and
anaerobic waste treatment kinetics.
Combining equation (1) with the following empirical equation
describing the net growth of microorganism as a function of time,
£• >(£)-•"< <*>
, . dM microorganism net growth rate per unit volume
dt of digester, mass/volume-time
a = growth yield constant
b = microorganism decay constant, time~^
will give the following equation:
= Ks(l+bt)
5 akt-(l+bt) (3)
where: t = hydraulic detention time, time
It is readily seen that the soluble waste concentration in the
reactor is a function of detention time only once the constants
a, b, k, and Ks are obtained. For a completely-mixed, aerated
lagoon, the soluble waste concentration in the lagoon would be
the same as that in the effluent.
Equation (1) can also be rearranged to show the microorganism
concentration in the reactor as a function of the waste removed
and the detention time as follows:
M - (L-s)(Ks+s)
k s t (4)
where: L = influent waste concentration, mass/volume
-------
41
The microorganism concentration in the effluent will be the
same as in the lagoon for a completely-mixed system.
For aerobic pond I the necessary constants were derived
for use in equations (3) and (4). The soluble BODS and volatile
suspended solids concentrations in the effluent from the pond
were calculated using the following values for the constants:
Ks = 110 mg/1
k =0.64 day'1
a - 0.63
b = 0.06 day'1
The total BOD in the effluent was calculated from:
BOD = s + c M
where: BOD = total effluent BOD, mg/1
s = soluble effluent BODS, mg/1
M = effluent VSS
c = BOD equivalent of the effluent VSS
From data collected on both aerobic ponds the value of "c" was
found to vary with detention time as shown on Figure 5:
- 1.68 - log (t)
c = 2.51 (5)
The following table compares these calculated values with the
observed concentrations.
Run
No.
6
7&8
9
VSS
Meas.
560
610
620
Cal.
560
640
630
BODs
Meas.
70
340
75
Cal.
95
320
70
BOD
Meas.
270
710
310
Cal.
270
590
240
-------
12
10-
CO
Ld
F
z
o
\-
z
u
H
LJ
0
I .
TEMP~ 45 F
c =
o POND I
K PONDU
.68-LOG C t")
2.51
0
0.2
—h-
0.4
4-
0.6
0.8
BOD EQUIVALENT OE EEELUENT
VSSC c )
Figure 5. -INFLUENCE OF DETENTION TIME
ON BOD OF EFFLUENT VSS
-------
43
As shown by the comparisons of both the soluble BODS and the
volatile suspended solids, the equations adequately describe
the kinetics. Differences between the calculated and measured
values of volatile suspended solids and soluble BODS are all
within the accuracy limits of the tests. There is a significant
difference between the calculated and measured total BOD for
the last two sets; 590 versus 710 and 240 versus 310. Some
of this difference can be explained by the data points shown
on Figure 5. These points were calculated from the observed
values as follows:
= BOD - BODs
C VSS (6)
Since there were only three values for pond I (open circles)
they were combined with the data from pond III and a single
curve was estimated for all the data. If a separate curve
had been drawn for pond I to the right of the existing curve,
all three calculated total BOD values would have been within
10 percent of the measured concentrations. Due to the lack
of additional data, a single curve was deemed sufficient for
both ponds.
At this point it should be pointed out that all of the
discussion concerning the values of the constants a, b, k, and
Ks, as well as the relationship shown on Figure 5, refers only
to a limited temperature range. The average lagoon temperatures
-------
44
for the three runs were 44, 44, and 47°F (Table 8); therefore,
it was not possible to determine if the constants as well as
the relationship shown for "c" versus "t" were temperature
dependent. Temperature would affect the curve on Figure 5 but
it is not certain whether it would affect all four of the
constants. Over one-half the points for pond III on Figure 6
were also from runs with an average temperature of about 44°F
(Table 9), so the same comments hold for the pond III kinetics
discussed later.
By using equations (3), (4), (5), and (6) and the values
for the constants shown previously, a set of curves was calcu-
lated to show the influence of contact time on soluble BODS,
total BOD, and volatile suspended solids. These curves, shown
on Figure 6, would be the expected results when a surface-aerated
pond such as pond I was used to treat clarifier effluent contain-
ing a BOD of 1600 mg/1. At a hydraulic detention time of four
days the soluble BODS in the effluent would be about 370 mg/1,
VSS would be 620 mg/1, and the total BOD would be 640 mg/1.
Increasing the detention time to eight days would reduce the
soluble and total BOD to 90 and 290 mg/1, respectively. The
VSS would be about the same, 640 mg/1. With a detention time
of six days or higher, 90 percent BOD reduction (effluent =
160 mg/1) could be obtained by removal from the effluent of a
known amount of VSS. For example, with a detention time of
-------
12 -•
CO
Q
i 10
IJ
:E
h-
Z 8
O
h-
LJ
LJ 6
Q
H
Q
-- I
-- \
4 --
U
CD
O
cr
LJ
TOTAL
BOD
\
\
vss
\
\
\
SOLUBLE
BOD
*
J
45° F
0 200 400 600 800
EFFLUENT BOD8, VSS -MG/ L
Figure 6.-PREDICTED INFLUENCE OF DETENTION
TIME ON EFFLUENT BOD 8 VSS
-------
46
eight days, the required VSS reduction would be:
- 6090
640
(7)
where: E = desired total effluent BOD-160 mg/1 ,
RVSS = required VSS reduction
In the completely-mixed, anaerobic pond II, it was assumed
that the rate of waste utilization or stabilization was a
constant or
or F0-Feff - Kt
where: F0 = total influent BOD, mg/1
Feff = total effluent BOD, mg/1
t = detention time, days
K = constant, days'1
For the various runs the constant K was corrected for temperature
by the fol lowing:
KT = K2o(1.04)T-20 (9)
where: T = temperature, °C
combining equations (8) and (9) and using a value of 35 per day
for K2Q gave:
Feff - F0 - 35t(1.04)T-20 (10)
The table on the following page compares the observed effluent
BOD concentrations with those calculated with this equation.
-------
47
Run
No.
2
3
4
5
6
7
8
9
Measured
780
1180
1600
1520
1240
1460
1610
1410
Effluent BOD
Calculated
780
1200
1590
1600
1230
1440
1600
1430
Difference
0
20
10
80
10
20
10
20
Agreement between the measured and calculated values is very
good considering the accuracy of the BOD test. Only one value
in the difference is greater than two percent of the BOD con-
centration and it is only about five percent, well within the
limits of the test.
Figure 7 presents three curves which show the influence of
detention time on total effluent BOD at three different operat-
ing temperatures with an assumed influent BOD of 1600 mg/1 and
equation (10). With a 10-day detention time the effluent BOD
would be 1360, 1250, and 1170 mg/1 at 10, 20, and 25°C,
respectively. Percentage reductions would equal 15, 22, and 27
percent, respectively. These reductions would increase to 29,
44, and 53 percent at the three temperatures with a detention
time of 20 days.
-------
28--
CO
^ 244
Q
I
LJ
i»
O
h-
Z
LJ
Ld
Q
6--
12--
Q
Z
o
CL
O 8
OQ
O
cr
LU
< 4
0
0
IOC
25
4-
400 800 1200 1600
TOTAL EFFLUENT BOD-MG/L.
Figure 7.
INFLUENCE OF TIME a TEMPERATURE
ON CALCULATED EFFLUENT BOD
-------
49
No attempt was made to formulate the change in suspended
solids upon passage through the anaerobic lagoon. It was shown
earlier that the volatile suspended solids in the effluent
from pond I depended upon time and the amount of BOD removed.
Therefore, the solids concentrations in anaerobic pond II
effluent were not needed inasmuch as the same kinetic relation-
ships were used for both aerobic ponds I and III.
For aerobic pond III which received the effluent from
anaerobic pond II, the constants required in equations (3)
and (4) were assigned the following values:
Ks = 140 mg/1
k = 1.1 day'1
a = 0.63
b = 0.06 day1
The same values of "a" and "b" were used for pond III as were
used for aerobic pond I. As mentioned earlier, the relation-
ship shown for "c" on Figure 5 and by equation (5) was used
for both aerobic ponds I and III. The following table compares
the observed values of soluble BODS, total BOD, and volatile
suspended solids with those calculated using the various equations.
As shown in the table, the calculated values of volatile
suspended solids are within 10 percent of the measured values
except for runs 3, 7, and 9. Agreement on soluble BODS in the
-------
50
Run
No.
3
4
5
6
7
8
9
VSS
Meas.
630
790
710
510
650
790
500
Cal.
450
730
660
520
550
800
670
BOD
Meas.
80
485
190
no
s
Cal.
47
82
310
120
480
170
80
BOD
Meas.
180
270
640
380
730
550
370
Cal.
180
360
650
360
780
550
340
effluent as well as total BOD is very good inasmuch as only one
calculated value is more than 50 mg/1 from the observed concen-
tration. Soluble BODS was not measured during the first three
runs shown in this table.
In view of the fact that no corrections were made for
operating temperatures and that several times during various
runs the aerator was turned off for repairs, overall agreement
of the measured values with those obtained from the kinetic
relationships is very good.
Although there was some difference in the value of "Ks"
for the two aerobic ponds, 110 for pond I versus 140 for pond III,
the primary difference was in the value of "k,", the maximum
rate of waste utilization per unit weight of microorganisms at
high waste concentrations. For pond I a value 0.64 per day
-------
51
was used as compared to a value of 1.1 for pond III, 56 percent
higher. Although the anaerobic pond did not remove many organics
as measured by BOD, it very probably altered the molecular
structure of many of the more complex organic materials which
made them more treatable aerobically. The influence of the
different values of "k" and "Ks" on the soluble BODS in the
effluent is shown on Figure 8. It was assumed both ponds
received the same BOD concentrations in the feed so that a
direct comparison of effluents could be made. At detention
times of six days or less the soluble effluent BODS in pond I
effluent would be more than double that in the effluent from
pond III. A four-day detention time would result in a soluble
effluent BODS of 370 mg/1 for pond I and 110 mg/1 for pond III.
The kinetic relationships developed for anaerobic pond II
and aerobic pond III can be combined to calculate a series of
curves similar to those presented in Figure 6 for pond I. On
Figure 9 is shown the influence of contact time in both the
anaerobic and aerobic cells on the total BOD in the effluent
from the aerobic unit. Also shown is the soluble BODS in the
aerobic pond effluent but this is independent of the detention
time in the anaerobic unit since it does not depend upon the
BOD concentration in the aerobic pond influent. An average
operating temperature of 63°F (K = 32 per day) was assumed for
the anaerobic pond and 45°F for the aerobic pond.
-------
0
s(1+bt)
AEROBIC POND
= 0.64
Ks= NO
'AEROBIC POND IE
k= I.I
Ks= 140
4-
0 200 400 600 800
SOLUBLE EFFLUENT BOD-MG/L
Figure 8. COMPARISON OF TREATABILITY OF
PRIMARY EFFLUENT vs. ANAEROBIC
EFFLUENT
-------
2--
Q
i
U
10-
Z 8 +
O
I-
LJ
Q
Q
Z 44-
O
CL
y
m
O 2
cr
Ld
0
\
ANAEROBIC POND H
DETENTION TIME
POND IT 63 F
POND IE 45° F
\
SOLUBLE T>~-^
200 400 600 800
EFFLUENT BOD-MG/L
Figure 9.
INFLUENCE OF DETENTION TIME
IN ANAEROBIC POND E a AEROBIC
POND IE ON SOLUBLE 8 TOTAL
EFFLUENT BOD FROM POND
-------
54
For any specific concentration of BOD in the final effluent,
a comparison of Figures 6 and 9 shows that when just detention
time is considered, aerobic pond I will result in a lower total
BOD than the sum of the detention times in ponds II and III.
This is only true when secondary clarification is not considered.
The soluble BODS in the effluent from pond III is markedly lower
than it is in the effluent from pond I so, if secondary clari-
fication is employed, a better effluent could be obtained from
the anaerobic-aerobic combination than from the straight aerobic
unit.
The quantity of volatile suspended solids in the effluent
from pond III could differ markedly from pond I, depending
mainly upon the detention time in the anaerobic lagoon as shown
on Figure 10. With a four-day detention period in the aerobic
pond an increase in detention time in the preceding anaerobic
pond from 8 to 16 days would result in a reduction in volatile
suspended solids in the aerobic pond effluent from 630 to 500
mg/1. The combination of 28 days'detention time in the anaerobic
pond and 4 days in the aerobic pond would produce an effluent with
an estimated volatile suspended solids concentration of 330 mg/1
or nearly one-half the value of that obtained with only 8 days
detention time in the anaerobic pond.
Mixing of the anaerobic pond in an anaerobic-aerobic system
may not be required in a full-scale installation, depending
-------
(/>
'2 +
Q
I
LJ I0
Q 8 +
z
LU
LU „
Q 64-
N
Q
Z
o
Q_
4--
g
CD
O 2-H
o:
LU
o
28 16 8 days
ANAEROBIC POND I DETENTION
TIME
200 400 600
EFFLUENT VSS-MG/L.
800
Figure 10.-INFLUENCE OF DETENTION TIME
ON POND IE EFFLUENT VSS
-------
56
upon its operational flexibility. An unmixed anaerobic lagoon
will remove suspended solids which will accumulate during the
cold winter months, unless the lagoon is insulated or its
contents heated. Then, as the temperatures increase in the
spring, the rate of biological decomposition of the sludge
will increase and may result in the effluent from the anaerobic
pond containing more BOD than its influent. This was demonstrated
(5}
during earlier^ ' pilot plant studies. As a result, the BOD
load applied to an aerobic lagoon in series with the anaerobic
unit would vary markedly with the climate. This potential
increase in load would have to be considered in the design by
the use of additional aerators or the use of some two-speed
aerators.
Elimination of the mixing in the anaerobic lagoon would
be advantageous because it would allow some build-up of solids
within the system. This would have the same effect as recycled
sludge does in an activated sludge or anaerobic contact process.
The loadings on an unmixed anaerobic lagoon in Ibs. BOD/day/lb.
MLVSS might vary markedly due to this retention of solids within
the system. In fact, this could partially explain some of the
reported differences in efficiencies in anaerobic systems when
they are compared according to loadings in Ibs. BOD/day/1000 cu.ft.
Either of the two systems studied will discharge excessive
amounts of suspended solids without a secondary solids removal
-------
57
step. Information concerning the ease of solids removal from
the effluent of ponds I and III was not obtained due to the
lack of manpower and equipment. Data on solids removal from
these effluents at various hydraulic and organic loadings would
be desirable. Some of this information may be forthcoming from
additional studies being conducted during the current (1968-69)
processing season.
During the studies reported herein no attempt was made to
evaluate "<*" or "6", both of which would be needed to design an
aerobic system using surface aerators. By definition, "«" is
the ratio of oxygen transfer rate in the lagoon contents to the
oxygen transfer rate in water, and "6" is the ratio of the oxygen
saturation concentration of the lagoon contents to the oxygen
saturation concentration of water. Both of these parameters
can vary from one day to another at any given plant besides
varying between plants due to differences in processing, etc.
Evaluation of both "<*" and "8" should be made at the plant under
consideration prior to design of required horsepower.
Likewise, no attempt was made to formulate the temperature
drop across either the anaerobic pond or the aerobic units used
in this study. Full-scale lagoons would have an area-to-volume
ratio much different from the ratio for the ponds in this study.
The horsepower per unit volume in a full-scale aerobic unit
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58
would also be different inasmuch as these ponds had excessive
horsepower at some of the organic loadings experienced in this
study.
This study has demonstrated that the organic material
present in potato processing wastes can be reduced by 90
percent or more using either surface-aerated aerobic lagoons
or anaerobic plus surface-aerated aerobic lagoons following
primary clarification. Mathematical formulations have been
presented along with assigned values for the required constants
for both of the systems studied. These formulations, accompanied
by proper inputs on costs of land, equipment, power, labor, etc.,
will allow economic comparisons to be made between the two systems
reported herein as well as with activated sludge and trickling
filter systems.
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REFERENCES
1. Agricultural Statistics. 1966. U. S. Department of
Agriculture, U. S. Government Printing Office,
Washington, D. C., 1966.
2. Anon., "Frozen Potatoes: Computer Projection of Growth
The Next Ten Years," Quick Frozen Foods, p. 31,
December 1967.
3. "Idaho Image," Idaho State Department of Commerce and
Development, Boise, Idaho, July 1967.
4. "Implementation, Enforcement, and Surveillance Plan for
the Rules and Regulations for Standards of Water
Quality for the Interstate Waters of Idaho," Idaho
Department of Health, Boise, Idaho, June 1967.
5. "An Engineering Report on Pilot Plant Studies—Secondary
Treatment of Potato Process Water," Cornell, Howland,
Hayes & Merryfield, Engineers and Planners, Boise,
Idaho, September 1966.
6. Atkins, P. F., Jr. and 0. J. Sproul, "Feasibility of
Biological Treatment of Potato Processing Wastes."
Journal Water Pollution Control Federation, p. 1287,
August 1966.
7. Standard Methods for the Examination of Water and Waste-
water, 12th Edition, 1965, Boyd Printing Co., Inc.
Albany, New York.
8. DiLallo, R. and 0. E. Albertson. "Volatile Acids by
Direct Titration," Journal Water Pollution Control
Federation, p. 356, April 1961.
9. Rose, W. W. and W. A. Mercer. "Chemical Oxygen Demand
as a Test of Strength of Cannery Waste Water."
National Canners Association Research Laboratories,
Berkeley, California, May 16, 1956.
10. Kamphake, L., S. Hannah, and J. Cohen, "Automated Analysis
for Nitrate by Hydrazine Reduction." Water Research I,
205, (1967).
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60
11. Anon, Aminco Reprint No. 104. American Instrument Co.,
Inc., June 1959.
12. Strickland, J. D. H. and T. R. Parsons, "A Manual of
Sea Water Analysis." Bulletin No. 125, 2nd Ed.,
p. 47, Revised Fisheries Research Board of Canada.
13. ASTM D-2579-T, issued 1967. Published by ASTM, 1916
Race Street, Philadelphia, Pennsylvania.
14. Monod, J., Recherches sur la croissance des cultures
bacteriennes. Paris: Hermann and Cie, 1942.
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APPENDIX
Table A-l presents averages and standard deviations
for various ratios generated from the data collected during
the two processing seasons. Thirteen pair of analyses were
used to determine the ratio of BOD to CODm for each of four
sampling points. The averages ranged from 0.47 for aerobic
pond III effluent to 1.80 for anaerobic pond II effluent and
the standard deviation ranged from 21 to 66 percent of the
average. As a result of this variability the CODm test
was discontinued after the first processing season.
COD was a better indicator of BOD than CODm, but even the
BOD to COD ratio showed a large variability. In the aerobic
pond effluents this ratio was as low as 0.10 but this is
common in secondary effluents. Generally, the BODrCOD ratio
will decrease with increasing degree of treatment.
The average TOC to BOD ratio was relatively constant from
one sampling point to another as the overall average ranged
from 0.50 for pond II effluent to 0.67 for pond I effluent.
The standard deviation was high for each location as it ranged
from 25 to 43 percent of the average.
Soluble BODS to soluble CODS ratios were similar to the
BOD to COD ratios.
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Table A-l
cr>
ro
No.*
13
50
25
20
55
35
35
35
Ratio
BOD/CODm
BOD/COD
TOC/BOD
BODS/CODS
VSS/SS
TVS/TS
BOD/P
BOD/N
Clarifier
Influent
0.63 ± 0.22**
0.53 ± 0.13
0.56 ± 0.22
0.66 ± 0.09
0.96 ± 0.04
0.73 ± 0.05
Clarifier
Effluent
0.74 ± 0.20
0.60 ± 0.14
0.59 ± 0.15
0.77 ± 0.18
0.91 ± 0.11
0.62 ± 0.04
130 ± 46
19 ± 6
Pond I
Effluent
-
0.42 ± 0.13
0.67 ± 0.29
0.33 ± 0.14
0.87 ± 0.11
0.51 ± 0.10
Pond II
Effluent
1.80 ± 0.38
0.67 ± 0.23
0.50 ± 0.18
0.94 ± 0.29
0.83 ± 0.17
0.52 ± 0.07
107 ± 26
18 ± 5
Pond III
Effluent
0.47 ± 0.31
0.35 ± 0.16
0.59 ± 0.21
0.34 ± 0.19
0.87 ± 0.11
0.46 ± 0.07
*Pairs of analyses in average
**Mean ± 1 standard deviation
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63
Both the VSS:SS and TVS:TS ratios had averages with small
standard deviations. For any additional data collection,
analyses for just SS and TS (if desired) would suffice.
The BOD:P and BOD:N ratios were discussed in the text of
this report.
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