EPA-600/2-76-186
October 1976
Environmental Protection Technology Si ies
DEMONSTRATION OF AERATION
SYSTEMS FOR POULTRY WASTES
Office of Research and Development
U.S. Environmental Protection Agency
Athens, Georgia 30601
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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:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
This report has been assigned to the ENVIRONMENTAL PROTECTION
TECHNOLOGY series. This series describes research performed to 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.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/2-76-186
October 1976
DEMONSTRATION OF AERATION SYSTEMS
FOR POULTRY WASTES
by
J. H. Martin
R. C. Loehr
Cornell University
Ithaca, New York 14853
Project Number S800863
Project Officer
Lee A. Mulkey
Technology Development and Applications Branch
Environmental Research Laboratory
Athens, Georgia 30601
ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
ATHENS, GEORGIA 30601
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DISCLAIMER
This report has been reviewed by the Athens Environmental Research
Laboratory, US Environmental Protection Agency, and approved for
publication. Approval does not signify that the contents necessarily
reflect the views and policies of the US Environmental Protection Agency,
nor does mention of trade names or commercial products constitute
endorsement or recommendation for use.
11
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ABSTRACT
A full scale study demonstrated the potential of aeration systems to
reduce the water and air pollution potential of poultry wastes under
commercial conditions. The performance of two oxidation ditches, each
receiving the wastes from approximately 4000 laying hens, was monitored
and evaluated.
The relationships between two design and operational variables and
system performance were examined. The variables were level of oxygen
supply and solids retention time. It was observed that an oxygen input
equivalent to the exerted carbonaceous oxygen demand provided a high
degree of odor control. Increase in oxygen supply to also satisfy the
exerted nitrogenous oxygen demand resulted in nitrification which terminated
ammonia desorption. Subsequent nitrogen losses were the result of de-
nitrification relationships between removals of total solids, volatile
solids, COD, and organic nitrogen in aerated poultry wastes were
developed.
Two major problem areas were identified and examined. The first was
the removal and concentration of residual solids to maximize oxygen
transfer efficiency and minimize the volume of material requiring
ultimate disposal. The second was sedimentation of solids in the oxida-
tion ditch channel which reduced and in several instances stopped mixed
liquor circulation.
The economics in terms of capital and operating costs of these systems
were evaluated. Results indicated that the total cost of aeration would
have increased egg production costs by a maximum of 4.9 percent in 1973.
This report was submitted in fulfillment of Project Number S800863 by
Cornell University for Manorcrest Farms under the sponsorship of the
Environmental Protection Agency. Work was completed December 1975.
iii
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CONTENTS
Page
Abstract iii
List of Figures vħ
List of Tables ix
Acknowledgements xii
Sections
I Conclusions 1
II Project Need and Objectives 3
III Theoretical Considerations 7
IV Investigative Facilities, System 27
Design and Construction
V Methods and Materials 47
VI System Performance Results 56
VII Discussion of Experimental Results 113
VIII References 138
IX Appendices 146
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LIST OF FIGURES
No. Page
1 Removal characteristics of total COD and suspended
solids - semi-logarithmic plot (11) 9
2 Relationship between a and mixed liquor total solids
concentration in aerated poultry wastes (37) 25
3 Aeration requirements in relation to mixed liquor
total solids and CL (37) 26
4 Location and site plan of Manorcrest Farm No. 2 28
5 Plan view, Building No. 1, before modification 29
6 Cross section, A-A', Building No. 1 30
7 Floor plan and analytical laboratory in the Cornell
Agricultural Waste Management Laboratory 33
8 Plan view of oxidation ditches and settling tanks 35
9 Location of velocity measurements, plan view 49
10 Location of velocity measurements, cross section 49
11 Comparison of oxygen transfer characteristics,
Thrive Centers cage rotors 63
12 Observed relationships between SRT and removal of
total and volatile solids 68
13 Observed relationships between SRT and removal of
organic nitrogen and COD 68
14 Nitrogen transformations during the start-up period,
Ditch II 74
15 Reoccurrrence of nitrite accumulation in Ditch II 76
16 Dissolved oxygen concentrations in Ditch I at the
oxygen transfer capacity of 351 gms 02/1000 bird-hours 77
17 Mixed liquor concentrations of total and free ammonia
plus pH at the oxygen transfer capacity of 351 gms 0?/
1000 bird-hours 79
vi
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LIST OF FIGURES continued
No. Page
18 Mixed liquor concentrations of total and free
ammonia plus pH at the oxygen transfer capacity
of 520 gms 02/1000 bird-hours 82
19 Dissolved oxygen concentrations in Ditch I at the
oxygen transfer capacity of 520 gms 0?/1000 bird-
hours 83
20 Dissolved oxygen concentrations in Ditch II at the
oxygen transfer capacity of 815 gms 0?/1000 bird-
hours 84
21 Dissolved oxygen concentrations in Ditch II at the
oxygen transfer capacity of 790 gms Op/1000 bird-
hours 84
22 Comparison of mixed liquor and settling tank
overflow total solids concentrations at MLTS
concentration below 12,000 mg/£ 87
23 Comparison of mixed liquor and settling tank
overflow total solids concentrations at MLTS
concentration above 18,000 mg/a 87
24 Typical results from a batch settling test,
aerated poultry wastes 88
25 Zone settling velocity versus total solids con-
centration in aerated poultry wastes 89
26 Sludge volume index versus total"solids concen-
tration in aerated poultry wastes 91
27 Vertical section through a basic single deck, 18
inch Sweco Vibrating Screen Separator 93
28 Illustration of average material travel on the
screen 93
29 Assembly diagram of a Thrive Centers cage rotor 97
30 Sediment profile in Oxidation Ditch II, 1973-74 100
31 Sediment profile in Oxidation Ditch I, 1973-74 100
Vll
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LIST OF FIGURES continued
No. Page
32 Sediment profile in Oxidation Ditch I, 1974-75 102
33 Sediment profile in Oxidation Ditch II, 1974-75 102
34 Cross section of a Hart Cup 105
35 Observed relationship between SRT and removal of
total solids in aerated poultry wastes 115
36 Observed relationship between SRT and removal of
volatile solids in aerated poultry wastes 115
37 Observed relationship between SRT and removal of
COD in aerated poultry wastes 116
38 Observed relationship between SRT and removal of
organic nitrogen in aerated poultry wastes 116
via
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LIST OF TABLES
TABLE TITLE PAGE
1 Egg Production Flock Number and Size Changes, U.S. 4
2 Observed Total and Volatile Solids Destruction,
Percent, as Related to Poultry Waste Stabilization
Time 10
3 TKN Concentration, Percentage of Total Solids in
Animal Wastes 11
4 Nitrogen Losses from Aerated Poultry Wastes
Attributed to Denitrification 14
5 Assumed Fresh Poultry Manure Characteristics 36
6 Kinetic Coefficients and e m Used for Project Oxida-
tion Ditch Design c 39
7 Expected Treatment Efficiencies of Aerobic Poultry
Wastes Stabilization at a 20 Day SRT 39
8 Design Estimates of Oxygen Requirements 40
9 Design Values for Sludge Storage Time 42
10 Oxygenation Capacity for the Thrive Center Cage Rotor 45
11 An Outline of the Manorcrest Demonstration Activities 56
12 Summary of Initial Operating Conditions, September,
1973 57
13 Changes in Operating Conditions 58
14 Results of Oxygen Transfer Measurements - Ditch I 60
15 Results of Velocity Measurements - Ditch I 61
16 Results of Oxygen Transfer Measurements - Ditch II 62
17 Results of Velocity Measurements - Ditch II 62
18 Raw Manure Characteristics, Manorcrest Farms 65
19 Comparison of COD Removed with Oxygen Supply 70
ix
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LIST OF TABLES continued
TABLE TITLE PAGE
20 Dissolved Oxygen Concentrations 71
21 Observed Removal of Soluble COD 72
22 Relationships Between Oxygen Transferred and
Removal Efficiencies of Organic and Total Nitrogen 78
23 Change in Mass of Ammonia Nitrogen in Ditch I at
351 gms 02 Transferred/1000 Bird-hours 80
24 Results of Centrifuge Test 90
25 Relationship Between Lead Angle and Performance
200 Mesh Screen, 0.074 mm 94
26 Results of Single and Two Stage Screening Trials 95
27 Comparison of Initial Ditch Velocities at Volumes
of 68,877 t and 105,980 i. 101
28 Sediment Characteristics 101
29 Initial and Annual Capital Costs, Manorcrest Project
Aeration Systems Components 108
30 Total and Annual Capital Costs for the Manorcrest
Aeration System 109
31 Energy Costs for Aeration in Relation to the Level
of Oxygen Transfer 110
32 Operating Costs for Manorcrest Aeration Systems per
1000 Hens per Year 111
33 Cost Summary of Aeration of Poultry Wastes, Manorcrest
Farms 1i2
34 Comparison of the Physical Details of Manorcrest
Ditch II and an Oxidation Ditch Discussed by
Windt et al. 128
35 New York State Egg Production Costs 132
x
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LIST OF TABLES continued
TABLE TITLE PAGE
36 Comparison of Capital Costs per 1000 Birds,
Manorcrest Farms and Houghton's Poultry Farm 134
37 Effect of Power Costs for Aerobic Stabilization on
Egg Production Costs 136
38 Effect of Total Costs for Aerobic Stabilization on
Egg Production Costs 136
XI
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ACKNOWLEDGEMENTS
This research was supported by the Environmental Protection Agency under
project number S800863; Manorcrest Farms, Camillus, New York; and the
College of Agriculture and Life Sciences, Cornell University. The
guidance of Mr. Lee Mulkey, Environmental Protection Agency, Athens,
Georgia who served as the project officer is gratefully acknowledged.
Most sincerely appreciated are:
- The contributions of Mr. and Mrs. Earl Hudson and the personnel of
Manorcrest Farms,
- The technical assistance of Lorraine Marnell and Charles Barton,
- The help of R.J. Krizek and J.F. Gerling in preparation of the figures,
- The patience and skill of Sue Giamichael in typing the report.
xii
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SECTION I
CONCLUSIONS
1. Properly designed aeration systems for poultry wastes will provide
excellent control of odors as well as removal of COD, total and
volatile solids, and nitrogen.
2. The process can be utilized to meet individual waste management
objectives such as odor control, odor control and nitrogen removal
via nitrification-denitrification, or odor control and possibly
nitrogen conservation.
3. Odor control can be achieved by satisfying the exerted carbonaceous
oxygen demand. The quantity of oxygen transferred to achieve odor
control was 351 gms 0? per 1000 bird-hours.
4. Removal of total and volatile solids and COD, increase with solids
retention time (SRT).
5. Removal of soluble COD exceeded 85 percent at SRT's of 10 days
or longer.
6. The potential for nitrogen removal is controlled by the ammonifi-
cation of organic nitrogen which is also a function of SRT.
7. Losses of nitrogen will occur via ammonia desorption or nitrifi-
cation-denitrification in oxidation ditches. The removal mechanism
is dependent on the level of oxygen supply. Observed losses ranged
from 48.8 to 63.3 percent of nitrogen loading.
8. Complete oxidation of ammonia with simultaneous denitrification
occurred at the oxygen transfer level of 520 gms Op per 1000 bird-
hours. This slightly exceeded the calculated, exerted carbonaceous
and nitrogenous oxygen demand.
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9. The potential for nitrogen conservation by storage in the tİv-:N
form is unclear but oxygen requirements are high. Favorable con-
ditions for denitrification make the practicality of this approach
questionable.
10. Control of mixed liquor total solids concentrations is desirable
to optimize system performance. No conclusions could be drawn as
to the best method of liquid-solid separation with aerated poultry
wastes. Both gravitational settling and centrifugation appear to
have potential, but additional study is necessary.
11. Sediment accumulations in oxidation ditches due to improper physical
design can result in process failure. Improved hydraulic design
can help overcome this problem.
12. The use of aeration systems for poultry wastes will increase egg
production costs. Energy cost for odor control was $0.0033 per
dozen eggs which represents a 0.8 percent increase in 1973 New York
egg production costs. Total cost was $0.0167 per dozen eggs or 3.8
percent increase in production costs. Although these costs appear
reasonable, further opportunities for reduction exist.
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SECTION II
PROJECT NEED AND OBJECTIVES
PROJECT NEED
Significant changes in the efficiency of commercial egg production have
occurred in the past 20 years. The result is an increasingly intensive
industry with fewer commercial egg farms and higher numbers of laying
hens per farm. Data for the years 1964 and 1969 (Table 1) show this
trend. Today (1975), the minimum size of an economically viable unit
is about 30,000 birds if egg production is the only source of income.
Larger operations are the rule rather than the exception with the
largest farms containing 300,000 to 500,000 hens. The gains in efficiency
in egg production have been accompanied by serious problems in the area
of waste management. The satisfactory disposal of poultry wastes is
necessary for both environmental protection and successful egg production.
Perhaps the most important factor in the development of commercial egg
production as it exists today was the change from the floor to the cage
management system. As the name implies, the floor system consisted of
hens unconstrained on the floor of pens. Sawdust, straw or some similar
material was placed on the pen floor, and the accumulated manure mixed
with this material. The result, termed litter, provided a medium for
stabilization through drying and a degree of biological activity. It
also provided a storage mechanism for periods of up to 12 months.
The floor or litter system had two disadvantages which resulted in the
conversion to the cage management system. One, the cage system allowed
an increase in bird density which lowered capital costs per hen. The
minimum floor area per bird in a floor system was about 0.19 square
meters (2 square feet). At higher densities, the litter could not be
kept dry. Dirty eggs and disease problems resulted. Conversion to the
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Table 1. EGG PRODUCTION FLOCK NUMBER
AND SIZE CHANGES, U.S. (1)
1964
Chickens on hand, 4 months old and over
Under 100
100 - 3,199
3,200 - 9,999
10,000 and over
Number of
farms (1,000)
896.2
300.9
12.9
5.8
Percent of
farms
73.7
24.7
1.1
0.5
Percent of
birds
7.3
30.7
21.0
41.0
1969
Chickens on hand, 3 months old and over
Number of
farms (1,000)
337.7
115.1
9.2
8.9
Percent of
farms
71.7
24.4
2.0
1.9
Percent of
birds
2.7
10.8
14.9
71.6
1,215.8
100.0
100.0
470.9
100.0
100.0
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cage system reduced floor area per bird to about 0.04 square meters
(0.45 square feet).
The second disadvantage of the floor system was its high labor require-
ment. The cage system permitted the mechanization of feeding, egg
collection, and manure handling, thus reducing manual labor requirements.
With the floor system, one man could care for approximately 5,000 birds.
Today, with cages, one man can handle from 35,000 to 50,000 hens.
The adoption of new management techniques resulted in changes in both
physical waste characteristics and the nature of poultry farms. With
the increase in bird density, the natural drying and stabilization which
was a characteristic of the floor system no longer occurred. The raw
waste which has a moisture content of about 75 percent wet basis, was
collected in pits beneath the cages. Due to the semi-solid nature of
the waste, liquid manure handling techniques were possible. Additional
water was normally added either directly or via water spillage to create
a pumpable slurry. Liquid manure systems were attractive because the
physical labor associated with manure handling was reduced.
The shift to liquid manure storage and handling techniques created an
ideal environment for uncontrolled, anaerobic microbial activity. Such
activity results in objectionable odors which are exhausted through ven-
tilation fans and are dispersed when the wastes are disposed of on the
land. The odors consist of malodorous mercaptans, amines, volatile
acids, and sulfides. Odor problems related to poultry farms have
resulted in legal and administrative actions by a number of state environ-
mental agencies.
The trend towards intensification in the egg industry has been accom-
panied by specialization. Many farms, especially the larger operations,
purchase some or all the feed required. Therefore, land for the production
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of feed is not necessarily a part of these farms. In many instances
purchase of feed may present economic advantages. The result can be
heavy waste loadings on small areas which intensifies the potential for
water pollution. Of particular concern is the loss of nitrogen to both
surface and groundwaters. Numerous studies (2,3,4) have shown that
nitrogen is the limiting parameter in the disposal of animal wastes to
the land.
Aerobic biological treatment processes have the potential to eliminate
odor problems associated with poultry wastes (5,6), provide an innocuous
method for nitrogen removal when required, and provide waste stabiliza-
tion through the removal of readily biodegradable organic compounds.
Experiences with oxidation ditches have indicated they are an aerobic
treatment process that can accomplish these benefits and be a feasible
treatment unit for poultry wastes.
OBJECTIVES
Although laboratory and pilot plant investigations have provided a great
deal of information about the application of aerobic biological processes
to poultry wastes, the feasibility under full scale commercial conditions
has been unclear. The objective of this project was to establish an
aerobic biological treatment system on a commercial poultry farm in
order to:
1) Demonstrate and evaluate the potential of aerobic treatment
to reduce the air and water pollution potential of poultry
wastes under commercial conditions.
2) Identify problem areas in the design and operation of these
systems and evaluate possible solutions to these problems.
3) Evaluate the economic impact of aerobic treatment of poultry
wastes.
4) Develop operating procedures which will serve as guidelines
for commercial applications.
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SECTION III
THEORETICAL CONSIDERATIONS
INTRODUCTION
The use of aerobic biological processes for the stabilization of animal
wastes such as poultry manure has been preceded by their application to
domestic and industrial wastes. However, the process fundamentals are
independent of the type of waste undergoing treatment. Therefore, basic
information derived from domestic and industrial waste treatment studies
can be applied in the biological treatment of animal wastes. However,
for the rational use of fundamental concepts developed from domestic
and industrial wastewater treatment, differences in treatment objectives
and waste characteristics should be recognized.
Normally, domestic and industrial wastewaters are discharged to surface
waters. This requires high levels of removal of both oxygen demanding
and nutrient compounds. In contrast, the effluent guidelines for the
feedlot industry (7) state that animal wastes should not be discharged
to watercourses. This is in keeping with the historic practice of
returning animal manures to the land. The use of the land for ultimate
disposal changes the treatment objectives. In light of the waste
stabilization capacity of soils, emphasis in animal waste treatment is
on the removal of the oxygen demanding and nutrient fractions which are
susceptible to movement to both surface and groundwaters. Achievement
of these objectives will provide the necessary control of odors.
The characteristics of animal wastes subjected to biological treatment
differ significantly from conventional municipal and industrial wastes.
Animal wastes have both greater oxygen demand and higher solids concen-
trations. Removal of settleable solids prior to treatment is not necessary,
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High solids loadings are a characteristic of aerobic treatment units for
animal wastes. Since these units are normally operated at relatively
long solids retention times (SRT's), the process is comparable to combined
activated sludge and aerobic digestion.
With the recognition of these differences, many of the principles which
have been developed in studies of conventional biological waste treat-
ment can be successfully applied to animal waste treatment. This will
provide a more rational approach to the design and operation of animal
waste treatment systems and result in more reliable and efficient operation.
POULTRY MANURE - CHARACTERISTICS AND TRANSFORMATIONS
Raw poultry excreta is a complex substrate containing soluble and parti-
culate inorganics and organics. The organic fraction contains carbona-
ceous and nitrogenous components which vary in their rate of biodegrada-
bility. The non-biodegradable inorganic or fixed solids constitute about
20 to 28 percent by weight of poultry manure total solids (8,9,10).
Phosphorus, calcium, and chlorides are the major components of fixed
solids (10). This is an expected result since both calcium and phosphorus
are fed at levels in excess of the birds physiological needs to insure
adequate uptake. Although the percentage of fixed solids will vary
with feeding practices, 25 percent appears to be a reasonable average
estimate.
Due to the complex nature of the organic fraction, substrate utilization
rates for the various components vary significantly. In a batch study
involving the non-settleable components of a poultry manure suspension,
three distinct COD removal rates over a 20 day period were observed
(Figure 1). The most rapid removal of COD occurred during the first 10
days of treatment. Additional removal results from utilization of the
more slowly biodegradable compounds. Degradation of soluble organic
matter appears more rapid than that of particulate material. The removal
of suspended solids followed a similar pattern, although two rather
than three removal rates were observed (Figure 1).
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1.0
Q 0.6
O
o
O 0.4
BATCH UNIT
40 g/l SETTLED
POULTRY MANURE SUSPENSION
O , c
x 15
CO
§ 'o
O
CO
o 0.8
LJ
O
0.6
CO
ID
CO
1
)
1
4
1 1
8
1 1
12
I 1
16
|
20
AERATION TIME, days
Figure 1. Removal characteristics of total COD and suspended solids -
semi-logarithmic plot 01)
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Table 2. OBSERVED TOTAL AND VOLATILE SOLIDS DESTRUCTION
PERCENT, AS RELATED TO POULTRY WASTE
STABILIZATION TIME
Average Solids Retention Time
Parameter 12 days (12)* 36 days (12) 4.5 mo (6) 6.5 mo (9) 7.5 mo (9)
Total solids
Volatile solids
COD
27
35
26
47
64
51
53
63
63
43
56
60
42
54
"
*Numbers in parentheses indicate data source
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The removal of total and volatile solids and COD with time observed by
various investigators is presented in Table 2. These data were collected
from both pilot and full scale oxidation ditches. The 12 and 36 day
results were collected from a continuous flow system, whereas the other
data were obtained from continuously loaded batch systems. The compar-
ison indicates that little additional removal of solids or COD occurs
when time of treatment is extended beyond 36 days. An important factor
is that approximately 50 percent of the total solids added to the system
remains as residual solids following treatment. This results in a con-
tinuous increase in total solids concentration in a continuously loaded
batch system.
An important characteristic of poultry manure is the concentration of
nitrogen. In comparison to the wastes of other major agricultural species
of domestic animals, poultry excreta contains the highest concentration
of nitrogen (Table 3).
Table 3. TKN CONCENTRATION, PERCENTAGE OF TOTAL SOLIDS
IN ANIMAL WASTES
Beef Dairy Swine Poultry
TKN, % of T.S. 1.9 (13)* 4.9 (14) 3.4 (15) 8.4 (16)
*Numbers in parentheses indicate data source
The nitrogen in poultry manure is in the form of proteins and uric acid.
About 65 to 75 percent of the TKN in fresh poultry wastes is in the form
of uric acid (17). This nitrogen undergoes transformation during waste
storage and stabilization. Both proteins and uric acid can be converted
to ammonia under aerobic and anaerobic conditions. Uric acid results in
11
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urea which in turn is converted to ammonia. These reactions can be com-
bined under the term ammonification and expressed as:
Ammonification .
Organic Nitrogen ğ NH3 + H2<3 _ NH4 + OH" (1)
Ammonification results in an increase in pH due to ionization of NH^OH.
If ammonium concentrations and pH are sufficiently high, ammonia volatili-
zation will occur.
Under aerobic conditions, ammonia nitrogen can be microbially oxidized
to nitrite and nitrate nitrogen. The two groups of microorganisms
primarily responsible for this transformation are Nitrosomonas and Mitro-
bacter. The oxidation of NH. to NO- is a two step process termed nitri-
fication and can be expressed as follows:
. Nitrosomonas
NH + 3/2 0 > m~ + 2H + H0 (2)
Nitrobacter
NO~ + 1/2 o2 > NO" (3)
Nitrification studies have indicated that 50 to 60 percent of the initial
TKN in poultry wastes could readily be nitrified. Therefore, 50 to 60
percent of the initial organic nitrogen was easily converted to ammonia,
since the fresh manure contains only trace amounts of ammonia.
Nitrifying organisms and hence nitrification can occur in natural waters
and soils as well as in waste treatment systems. The process results in
the exertion of a nitrogenous oxygen demand (NOD) which is important in
both natural waters and waste treatment systems. In poultry manure, the
NOD is significant being equal to approximately 25 percent of the chemical
oxygen demand of the waste.
^
Under anaerobic conditions, nitrite and nitrate nitrogen can be reduced
to nitrogen gas (N2) or nitrogen oxides (N20 or NO) by denitrifying
12
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microorganisms. The combined processes of nitrification-denitrification
can result in significant nitrogen removal from aerated poultry wastes.
Some observed nitrogen losses from aerated poultry wastes attributed to
denitrification are presented in Table 4.
PROCESS DESIGN
General
The design criteria for aerobic treatment of animal wastes suggested by
Jones et al. (21) has served as the standard basis of design for these
systems. Both the Midwest Plan Service and the Canada Department of
Agriculture suggest this method of process design (22,23). These design
criteria are empirical based upon studies involving swine and dairy
cattle wastes. System volume is determined using the organic loading
o
rate concept. The recommended loading rate is 0.5 kg BODc/m /day (0.03
3
Ibs BODg/ft /day). The suggested parameter for oxygen requirement is
twice the daily BODg loading assuming that in the stabilization unit, the
aeration system will transfer 80 percent of the amount it will transfer
in tap water.
Although many systems developed from these empirical parameters have
performed satisfactorily, this approach has several disadvantages. It
is difficult to extrapolate between different wastes and environmental
conditions. Reasons for process failures are unclear since the design
and operation of the system is not based on process fundamentals. Possibly
the greatest liability of the empirical approach is its inflexibility.
No opportunity exists to adjust the degree of waste stabilization to
specific requirements. This is especially significant when only a minimal
degree of stabilization is required.
This organic loading rate concept represents an early approach to slurry
type biological treatment system design. A more fundamental approach was
developed from the observation that effluent quality was related to the ratio
of substrate loading (F) per unit time and the mass of microorganisms (M).
13
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Table 4. NITROGEN LOSSES FROM AREATED POULTRY WASTES
ATTRIBUTED TO DENITRIFICATION
System Type
Oxidation Ditch
Oxidation Ditch
Diffused Aeration Basin
Oxidation Ditch
Oxidation Ditch
Dissolved Nitrogen
Oxygen, mg/Ji Loss, %
2-7 36
2-6 66
0-2 50-60
0-6 70-80
* 30-90
Reference
6
9
18
19
20
*Intermittent to continuous aerator operation
14
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As the substrate loading increased, effluent quality deteriorated. Based
upon these observations, the food to microorganism (F/M) ratio was
established as a design parameter for biological treatment processes (24).
Owens et al. (25) have investigated the effects of different F/M ratios
on effluent quality in the aerobic treatment of swine wastes. Their
observations of decreasing effluent quality at increasing F/M ratios con-
curred with results of previous studies.
Although the F/M concept is fundamentally sound, it is difficult to use
due to problems in determining concentrations of active microorganisms.
Traditionally, volatile suspended solids concentrations (VSS) have been
used to estimate active mass. Due to high concentrations of VSS present
in raw poultry manure, this method of estimation has little significance
in poultry wastewaters.
Other design approaches have been developed based upon microbial kinetics
using first order substrate utilization kinetics. These approaches can
be applicable to poultry wastes (11).
Another kinetic approach has used a Monod (26) type equation as the basis
of a treatment model. This approach relates microbial growth to a limit-
ing substrate concentration. Substrate limited growth appears a more
precise description of conditions in biological waste treatment systems
than the first order substrate utilization approach. Practical appli-
cation of this approach (27) utilizes the biological solids retention
time, 9 , as the unifying design parameter in that all system variables
can be related to it. Mathematically, e can be represented as
(4)
(AX_)
k '
where XT = total active microbial mass in
treatment system, mass.
15
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(AX/At)T = total quality of active microbial
mass leaving the system in a unit
of time, mass per time.
As e increases, the effluent concentration of the growth limiting sub-
strate will decrease. The microorganism concentration is a function of
the available substrate concentration and 6 . Excess microorganism pro-
N*
duction is also related to 9 . As e increases, the excess microorganism
production will decrease due to endogenous respiration.
This latter approach is not unlike the F/M approach. When a value for
the microorganism concentration is specified in the F/M approach, a
value for e is specified implicitly but not explicitly. The F/M and e
C \f
design approaches have been compared in a treatability study of an oil
refinery wastewater (28) and found to produce similar designs.
The design equations for most approaches have been developed based on
studies involving liquid wastes. Although the equations are fundamental
to all biological systems, detailed application to a waste such as poultry
excreta is difficult. One factor is the high solids concentration of
the poultry waste. Whereas the influent solids concentrations of municipal
and certain industrial wastes are small in comparison to concentrations
in the treatment system, the reverse can be true with poultry and other
animal wastes. This complicates determination of kinetic coefficients
which depend on measurement of volatile suspended solids to estimate
cell mass.
A second problem is introduced due to the complex nature of the waste.
Due to the composition of these wastes, the single substrate hypothesis
is not directly applicable. In waste treatment, it is normally assumed
that the limitation of total biodegradable material controls microorganism
population. Due to the limitations of the BOD determination, COD is
commonly used to estimate biodegradable compounds. However, the COD test
measures both biodegradable and non-degradable compounds which are subject
to chemical oxidation. Therefore, it is necessary to estimate the
16
-------
biodegradable portion of COD. This approach was used (29) to model the
aerobic treatment of swine wastes. However, the biodegradable fraction
is a function of time of treatment due to the different substrate utili-
zation rates for different fractions of the organic matter. Therefore,
estimation of the biodegradable fraction is a function of the time of
treatment and vice versa.
Although there are inherent difficulties in the detailed application of
substrate limited approach (27) to the aerobic treatment of poultry and
other animal wastes, it provides a rational basis for relating treatment
efficiency to 6 . In this context, treatment efficiency expressed as
c*
removal of COD, total and volatile solids, and/or degradation of organic
nitrogen can be related to and controlled by manipulation of e . Changes
in both COD and organic nitrogen removal have been related to e in
\Ğ
aerobically treated poultry wastes (16).
Determination of e as defined in Equation (4) requires measurement of
\f
active biomass. However, assuming complete mixing resulting in the
uniform distribution of microorganisms, the solids retention time (SRT)
of the solids can be used to estimate e . SRT is the theoretical time
that solids are retained in the treatment system and can be expressed as
/5\
* '
wt of solids in the system _
wt of solids leaving the system/time
6 is a function of the active biomass in a system while SRT can be
c
determined by measuring other forms of solids such as volatile, suspended,
total suspended, or total solids. If the system is completely mixed,
SRT is a reasonable estimate of ec and is the key factor in the utili-
zation of this approach. The unifying parameter, SRT, can be estimated
by utilizing an easily determined parameter, solids concentration.
Both biochemical oxygen demand (BOD) and chemical oxygen demand (COD)
tests are methods which provide an indirect measure of available substrate
in terms of the oxygen equivalent of organic matter. An advantage of
17
-------
the BOD determination is that unlike the COD test it includes only
organic matter susceptible to biological degradation. However, the BOD
test is dependent on both the time period and initial seed. It may or
may not include nitrogenous oxygen demand (NOD) depending on the presence
or absence of nitrifying microorganisms. This presents difficulties in
comparing the results from raw and treated waste samples.
The COD test is an alternative. Although this approach includes organic
matter not susceptible to biological degradation, it does not include
the NOD of ammonia nitrogen. If nitrites are present, they will be
chemically oxidized to nitrates. Correction for this factor is simple
requiring only concurrent determination of the nitrite concentration in
the sample.
Neither test is ideal but in a situation where change across a treatment
system is being measured, COD appears to have an advantage. By assuming
that a change in COD is due completely to biodegradation, concern with
the non-biodegradable fraction of COD is eliminated. Theoretically,
the change in COD can be considered equal to the change in BOD.
Another advantage of the COD test is the relatively short analysis time
required in comparison to BOD determinations. Results of COD analyses
are available in less than three hours, whereas the BOD test requires
a minimum of five days. For these reasons, further discussion will
focus on COD rather than BOD.
CHEMICAL OXYGEN DEMAND
The requirement for removal of COD in the aerobic treatment of poultry
manure is a function of the place of ultimate disposal, the land or
surface waters. As noted earlier, the land is the most logical site
for ultimate disposal of these wastes. In this context, the significance
of COD removal is changed. The land has the ability to stabilize the
organic carbon in poultry wastes at application rates of dry solids up
18
-------
to 101 metric tons/ha/yr (45 tons/ac/yr) (2). Loading rates of this
magnitude were shown to be excessive in terms of nitrogen. Therefore,
at acceptable application rates of nitrogen, high levels of COD removal
do not appear necessary.
The importance of COD removal in the aerobic treatment of poultry wastes
lies in two areas: odor control and removal of soluble organics which
are subject to transport in surface runoff. To provide odor control,
the exerted COD must be satisfied aerobically. Otherwise, the biologi-
cally available COD will be utilized as substrate by anaerobic organisms
with the production of malodors. The soluble COD fraction is the most
readily available substrate (11) in poultry wastes. Therefore, the
oxygen required for odor control will also reduce the soluble organics
in the effluent.
The COD of fresh poultry excreta includes both biodegradable and non-
biodegradable compounds. In addition, the test does not distinguish
between rapidly and slowly biodegradable compounds. However, oxygen
requirements can be related to COD removal, i.e., exerted oxygen demand.
The following general equation describes the rate of oxygen utilization
for the oxidation of carbonaceous matter:
H!= rate of oxy9en utilization
41- = rate of substrate utilization
dt
Y = coefficient to convert substrate
units to oxygen units
b = microbial decay coefficient
c = coefficient to convert cell mass
to oxygen units
X = microbial cell concentration
19
-------
Since both terms, substrate utilization and endogenous respiration, are
manifested as COD removed, Equation 6 can be rewritten as:
do _ dCCOD] m
dt " dt ' Uj
COD removal in aerated poultry wastes is a function of time of treatment,
i.e., SRT (11,16). The required degree of stabilization, hence COD
removal, can vary for individual situations. This variation is related
to possible storage of effluent and possible odor problems during final
disposal. Another factor is the potential for surface runoff. By the
control of SRT, COD removal can be matched with overall waste management
objectives and is a rational approach to estimate carbonaceous oxygen
requirements.
NITROGEN
The objective of nitrogen management in aeration of poultry wastes is
a function of the overall farm operation. As previously discussed, a
poultry farm may or may not engage in crop production. Where crop
production is involved, nitrogen conservation, to the extent that the
nitrogen can be recycled through a crop, is a logical objective. Con-
versely, nitrogen removal can be necessary when productive land for
ultimate disposal is limited.
The best approach for nitrogen conservation in aeration systems will
depend on the quantity of available land and on the nitrogen management
objectives of the poultry operation. A number of possible approaches
exist. One involves nitrification which was described earlier.
Although several groups of microorganisms are capable of nitrification,
two groups of autotrophs, Ni trospmonas and Nitrobacter. are of primary
importance in wastewaters. The first step of the process releases
hydrogen ions with a resultant depression in pH.
Nitrification is an aerobic process requiring oxygen above that supplied
to satisfy exerted carbonaceous demand. Therefore, Equation 7, which
20
-------
described the relationship between rate of oxygen utilization and COD
removal, must be modified as follows:
-+3 ,,.
dt . dt + 3.43 g^-+ 1.14 - g^ (8)
where d[NH*] d[N02]
- dt~ and dt are resPectively, the rates of oxidation
of ammonia to nitrite and nitrite to nitrate.
Thus, one approach to achieve high nitrogen conservation is to obtain a
high level of nitrification. This can be accomplished by providing
sufficient oxygen for the aerobic system, adequate mixing, and a sufficient
SRT. However, even with complete nitrification, total nitrogen conser-
vation may not result since denitrification can occur. A number of
facultative microorganisms will utilize nitrites and nitrates as terminal
electron acceptors in place of molecular oxygen under anaerobic conditions.
Although the actual reactions are complex, they can be summarized as
follows:
2 NO" + 10 H* - > N2 t + 4 H20 + 2 OH" (9)
2 N02 + 6 H+ - : - ğ N2 + + 2 H20 + 2 OH" ^10^
The production of nitrogen oxides, N20 and/or NO, is possible. Analysis
of gases from denitrification of aerated poultry wastewater indicated
that N2 is the major end product (30).
Although nitrifying organisms are autotrophic, denitrifiers are hetero-
trophic and require a source of organic carbon. In well stabilized
effluents, addition of a source of organic carbon such as methanol is
normally required. However, there is ample oxidizable organic carbon
in poultry wastes and it does not appear that organic carbon will be
the limiting substrate for denitrification in poultry wastewaters.
Another alternative to accomplish nitrogen conservation is to prevent
nitrification and thus avoid subsequent denitrification and nitrogen loss.
21
-------
A number of methods exist. One would be to exclude nitrifying organisms
from the aeration system. Although these organisms are not present in
fresh poultry wastes (30), they are widely distributed in the soil and
can be easily introduced into aerobic treatment systems. Therefore,
such exclusion would be impractical under commercial conditions.
A second method would be to reduce the system e m for nitrifying
V*
organisms. This is theoretically possible because both Nitrosomonas
ancl Nitrobacter have slow growth rates in comparison to heterotrophic
organisms associated with waste stabilization. A e of less than three
c
days at 20°C would be required (31). At this and shorter SRT values,
waste stabilization would be minimal and the effectiveness of aerobic
stabilization diminished.
A third and possibly the most practical approach is to limit oxygen
availability. Nitrifying bacteria cannot compete with heterotrophic
organisms for oxygen. Therefore, limiting oxygen input to that required
to satisfy the exerted carbonaceous oxygen demand will prevent nitrifi-
cation. Nitrogen losses can still occur via ammonia stripping. Predic-
tion of these losses is possible although difficult due to the variables
involved such as ammonia concentration, pH, temperature, and degree of
turbulence.
Biological nitrification-denitrification is a feasible approach for
nitrogen control with poultry wastes (4,11,30). This approach is
attractive due to its compatibility with aerobic treatment for odor
control. The only difference is that conditions to control nitrification
and denitrification also are provided.
OXYGEN TRANSFER
In an aerobic system, the oxygen transferred should be equal or greater
than the biological oxygen requirements of the system. The oxygenation
capacity of aeration equipment is normally determined in tap water at a
22
-------
zero dissolved oxygen concentration. However, equipment oxygenation
capacity can vary under process conditions.
Oxygenation under process conditions can be described as:
N = aKLa(0Cs-CL) (W) (10~6) (11)
where N = oxygenation capacity, pound-time'1
KLa = overall gas transfer coefficient, time
a = the ratio of KLa in wastewater to KLa in tap water
Cs = oxygen saturation concentration, mass/volume
3 = the ratio of C in wastewater to C_ in tap water
o S
C. = the equilibrium dissolved oxygen concentration,
mass/volume
W = weight of liquid under aeration, pounds
The values of K,a and W are functions of the aeration unit and system
volume, and are constant for a given operating condition. C is an
independent variable related to liquid temperature and atmospheric
pressure. Both a and B are dependent variables. Although a is a
function of many factors, it appears that it is primarily related to
mixed liquor characteristics as is e (32). C. is a function of the
relationship between the quantity of oxygen supply and demand. The
quantity of oxygen transferred is directly related to a. Thus factors
that affect a directly affect the oxygen transferred under process
conditions.
Constituents of the mixed liquor under aeration can affect the quantity
of oxygen that is transferred. Small quantities of surface active
agents can cause significant reductions in a values (33-35). Downing (34)
found that suspended solids in the range of 1,000 to 6,000 mg/£ have had
little effect on oxygen transfer. However, a was reported reduced to
0.2 in a sludge with a total solids concentration of 10,000 mg/£ (36).
Alpha values in aerated poultry wastes have been shown to be related to
mixed liquor total solids concentrations (6,37). The results indicated
23
-------
that a has the value of 1.0 at mixed liquor total solids concentrations
less than 20,000 mg/£. As total solids concentrations increase beyond
that point, a values decrease to 0.4 at 55,000 mg/£. This relationship
between a and mixed liquor total solids concentration is presented in
Figure 2.
The oxygenation capacity is also a function of B (Equation 11). An
empirical relationship describing the effect of salinity on C has
been developed (38) and may be used with reasonable accuracy for deter-
mination of 6 in wastewater (39). Beta values in the range of 0.9 to
1.0 have been reported in studies involving domestic wastewaters (40-42).
In aerated poultry manure slurries, e appeared independent of total
solids concentrations (42). Beta values approached unity for total
solids concentrations up to 30,000 mg/£.
The value of C, is important in that as N increases above that necessary
to provide a minimum dissolved oxygen concentration, C, will increase.
The result will be the decrease of the oxygen deficit, C -c, . This in
turn will reduce the oxygen transfer efficiency of the aerator and
increase operating costs. In an aeration system, C, need be no more
than that necessary for odor control, generally no more than 0.5 to
1.0 mg/£, or for nitrification, generally about 2.0 mg/a.
The combined effects of a expressed as total solids concentration and
C. on required tap wateraeration capacity for poultry wastewater is
shown in Figure 3. The consequence of increasing oxygenation capacity
is translated into higher capital and operating costs.
f
The relationships of SRT to degree of waste stabilization, and mixed
liquor total solids concentration to oxygen transfer described previously,
form a rational basis for the design and operation of aeration systems
for poultry wastes. These concepts were employed in the design of the
Manorcrest oxidation ditches and will be used in discussing and inter-
preting the results of this study.
24
-------
to
01
UJ
1.4
1.2
^^fc^.
""*ğ*
tr
£ 1.0
o_j -8
.6
i .4
1
J 2
t
(
^^MMVk
(^^
*^>\
" "" *i.Ss
- ^J
1 1 1
3 2349
TOTAL SOLIDS-PERCENT
Figure 2. Relationship between a and mixed liquor total solids
concentration in aerated poultry wastes (37)
-------
1C
2oo:
I-. .UJ
CL
z<
^CD1"?
£i_0 I
£^5 ^
0^5 Q
co...u. 9E
Q^w 5
CLQI- =
6
5
4
3
2
I
0
DISSOLVED
OXYGEN-mg/l
3
RECOMMENDED
OPERATING
RANGE
Mil I
TEMPERATURE Ğ 20°C
I
I
I
.5 I 1.5 20 25 30 3.5 40 4.5
TOTAL SOLIDS CONCENTRATION (%)
Figure 3. Aeration requirements in relation to mixed
liquor total solids and C, (37)
-------
SECTION IV
INVESTIGATIVE FACILITIES, SYSTEM DESIGN AND CONSTRUCTION
INVESTIGATIVE FACILITIES
This study was conducted at Manorcrest Farms No. 2 which is located in
Camillus, New York, less than 10 miles west of the city of Syracuse.
This area (1975) is located in the outer fringe of the suburban Syracuse
area. Details of the area are presented in Figure 4.
Manorcrest Farms are owned and operated as a family partnership. The
farming activities consist of dairy and poultry enterprises accompanied
by crop production to provide animal feed. The main farm is the site of
the dairy operation. Farm No. 2 is the location of two-thirds of the
poultry enterprise with cropping activities occurring on both farms.
The poultry operation is managed by Mr. Earl Hudson, one of the partners
in Manorcrest Farms. He also served as grant director of this project.
This enterprise is an integrated operation. Home grown grains are used
in the manufacture of the poultry feed. The eggs produced are processed
and packaged by Manorcrest Farms. The major portion of the egg production
is sold at the wholesale level to retail food stores and institutions.
The remainder is sold at a retail outlet on the farm.
Building No. 1 (Figure 4) was the site of the demonstration activities.
The building is a single story poultry house with a capacity of 8,000
birds contained in four rows of stair-step cages. Figures 5 and 6 are
a plan and cross-section of this building. Prior to the installation of
the aeration systems, manure accumulated in 73 cm (29 in) deep pits and
was removed semi-annually. Anaerobic conditions prevailed in these col-
lection pits resulting in the production of malodors. These odors were
discharged through ventilation fans and during manure spreading resulted
in neighbor complaints. In addition, a fly problem existed during the
warm months of the year.
27
-------
RT. 5
TO CAMILLUS
BUILDING
NO. 2
BUILDING
NO. I
I
DISPOSAL AREA
(CORNFIELDS)
SITE PLAN
RT5
3m[ CAMILLUS
MANORCREST
FARM NO. 2
MAIN
FARM
SYRACUSE
LOCATION
Figure 4. Location and site plan of Manorcrest Farm No. 2
28
-------
-5
ft)
to
en
*
~o
EU
<
£
CO
c
Q.
3*
154'-0"
ħ
MANURE COLLECTION a STORAGE PITS ^^
)\
/ \
i
cr
n>
-h
O
CD
Q.
-h
O
QJ
rt-
-------
u
t]
<
* 0 n" >
* Jc. *
;..-4 . p.,- ..
4 Q°" 1.
* y £. '
44'
*
^ Q°" *
^ y t ^
n"
* QĞ" k
< 9
-------
The other building, Building No. 2, is a two-story, high-rise poultry
house with a capacity of 11,000 birds. The birds are located on the
second floor. The first floor serves as a manure collection and storage
area. Ventilation air is circulated over the wastes to promote drying.
This building was not directly involved in the study except as a control
to compare conditions and manpower associated with other poultry production
and waste management situations.
Mr. Earl Hudson was responsible for the supervision of the construction
activities in converting the existing waste management facilities in
\
Building No. 1 to the aeration systems. In keeping with the concept of
demonstration under commercial conditions, he was also responsible for
the operation of both oxidation ditches including maintenance and ultimate
disposal functions. General operating procedures were provided by Cornell
University personnel.
Personnel from the Agricultural Waste Management Program, New York State
College of Agriculture and Life Sciences at Cornell University acted as
consultants to the project. Their responsibilities included systems
design, provision of guidelines for operation, and evaluation of performance
including identification of problem areas. Cornell personnel collected
and analyzed the data necessary for performance evaluation.
Also participating in the project were Professor Charles E. Ostrander,
Extension Specialist in Poultry Science, Cornell University and Mr. Antonio
Aja, Cooperative Extension Agent, Onondaga County, New York. These indi-
viduals assisted in the transfer of the project results to the poultry
industry.
The oxidation ditches at Manorcrest were monitored for an 18 month period
in order to collect necessary data to evaluate their performance. Cornell
personnel visited the demonstration site at least twice a week to observe
the systems, to make adjustments in operating procedures when necessary,
and to obtain samples.
31
-------
The Agricultural Waste Management Laboratory (AWML) at Cornell University
served as a support facility for this investigation. The laboratory was
constructed with funds from EPA Project 14040 DDG and contains a wet
chemical laboratory, pilot plant process equipment, and animal housing
facilities. Figure 7 is a floor plan of the Laboratory and illustrates
the area used for sample analysis. Cornell personnel associated with
the project were located at the AWML. Analyses of Manorcrest samples as
well as supplemental studies were conducted in this facility.
&
The Manorcrest demonstration site was visited by numerous individuals
during the course of the study. Visitors included representatives of
the U.S. Environmental Protection Agency, the New York State Environmental
Facilities Corporation, consulting engineers, and agriculturalists. In-
cluded in this latter group were members of the Cooperative Extension
County Executive Committee of Onondaga County, New York, as well as
several egg producers. The site was also inspected by foreign researchers
and graduate students in the Agricultural Waste Management Program, Cornell
University. In addition, the Manorcrest study was the subject of an
article in the June 1974 issue of the "American Agriculturalist" which
is a popular farm magazine. These activities were in keeping with the
objective of the demonstration of aeration systems for poultry wastes.
A portion of the results of this investigation was presented at the
International Symposium on Livestock Wastes - 1975 at the University of
Illinois, Urbana - Champaign. The paper "An Evaluation of Aeration Systems
for Poultry Hastes Under Commercial Conditions" was published in the
proceedings of that conference. A second paper, "The Oxidation Ditch -
Problems and Reasons" discussing the problem areas identified in this
study will be presented at the American Society of Agricultural Engineers
1976 Summer Meeting at Lincoln, Nebraska. The results of this study have
also been utilized by other members of the Cornell Agricultural Waste
Management Program in the preparation of scientific papers, reports,
and theses.
32
-------
LABORATORY
PILOT PLANT
PROCESS EQUIPMENT
POULTRY
HOUSING AND
WASTE
MANAGEMENT
WASTE STORAGE
FLOOR PLAN
ANALYTICAL LABORATORY
Figure 7. Floor plan and analytical laboratory in the Cornell
Agricultural Waste Management Laboratory
.;
-------
SYSTEM DESIGN
General
In the design of the aeration systems for this study, it was recognized
that a comprehensive animal waste management system has three components.
1) stabilization
2) solids management
3) ultimate disposal
A number of aerated systems including an oxidation ditch and an aerated
lagoon were considered as possible alternatives. An oxidation ditch
inside the poultry buildings appeared to be the most logical alternative
for the following reasons:
1) ease of incorporation in confinement housing
2) cold weather operational problems are eliminated
3) uniform loading directly from birds
4) equipment to move raw waste to the aerated unit is not
required
In addition, it was possible to easily convert the existing manure
collection pits to oxidation ditches.
The four existing collection pits, Figures 5 and 6, were converted into
two oxidation ditches as shown in Figure 8. The only construction
required was the connection of each pair of ditches with semi-circular
channels at each end. Each ditch served approximately four thousand
birds.
For design purposes, it was assumed that total solids production would be
40 gms/bird-days. This value is comparable to the value of 37 gms/bird-day
reported elsewhere (16) and was conservative. Maximum total solids
destruction was assumed to be 50 percent (Table 2). Other waste charac-
teristics which were assumed are presented in Table 5 and are based upon
reported characteristics (16).
34
-------
en
SETTLING
a STORAGE
TANKS
IfT] PROPELLER
OVERFLOW
DITCH No.1
RECYCLE
BRUSH AERATOR
DITCH No. 2
THRIVE CENTERS
No. H-805 CAGE ROTOR
Figure 8. Plan view of oxidation ditches and settling tanks
-------
Table 5. ASSUMED FRESH POULTRY MANURE CHARACTERISTICS
Parameter Gms/bird-day
Volatile solids 29.7
Fixed solids 10.3
TKN 3.4
COD 31.1
BODC 8.1
Stabilization
Two different modes of oxidation ditch operation were considered:
1) continuously loaded, batch
2) steady-state with a constant SRT
The continuously loaded, batch method of operation has the advantage of
combining stabilization and storage. This is probably the most common
method of agricultural oxidation ditch management. With this approach
the ditch would be emptied periodically, refilled with tap water, and
the system restarted. Based upon a maximum mixed liquor total solids
*
concentration of 50,000 mg/£, maximum storage time for each ditch was
calculated to be 73 days. The average SRT would be 26.5 days. If the
total solids production rate were 30 gm T.S./bird-day, which also has
been reported (10), the storage time would be 97 days.
The batch method of operation has advantages in simplicity of operation
and combination of storage with treatment. However, there are several
disadvantages. The primary liability is a low oxygenation efficiency at
the high total solids concentrations that ultimately result with a batch
system. An a value of 0.5 at a mixed liquor total solids concentration
of 50,000 mg/£ has been reported (37). To maintain aerobic conditions,
the required oxygenation capacity would be approximately twice the oxygen
demand. This would result in increased capital and operating costs.
36
-------
Other possible disadvantages to the batch mode of operation are:
1) potential of recurring "start-up" problems such
as foaming and an initial imbalance in the food
to microorganism ratio.
2) high, short term water requirements to refill the system.
3) additional energy requirements for mixing due to
increasing viscosity at higher total solids concentrations.
It was possible that pumping and not oxygenation capacity would be the
limiting criteria in sizing required aeration equipment for such a mode.
An alternative to the batch approach is a steady-state process with control
of mixed liquor total solids concentrations via continual residual solids
removal. This would allow maintenance of total solids concentrations of
less than 20,000 mg/£, thereby maximizing oxygenation efficiency. With
this type of system, SRT would be a design and operating parameter.
This would allow flexibility in matching degree of stabilization with
overall waste management objectives.
Due to the potential advantages of maximizing oxygenation efficiency, the
Manorcrest oxidation ditches were designed to operate at low mixed liquor
total solids concentrations, and SRT was used as a basic design parameter.
The selection of the design SRT was based upon the objective of providing
conditions which would permit nitrification. Since both Nitrosomonas and
Nitrobacter are known to have slower growth rates than the heterotrophic
organisms utilizing carbonaceous materials, calculation of the minimum
system SRT (e m) was based on nitrification. Information about Building
(_
No. 1 indicated that the average minimum temperature should not be below
10°C. Therefore, the value of 10°C was assumed as the minimum mixed
liquor temperature.
The kinetic coefficients for nitrification at 20°C (44) were used to
calculate e m. A modified form of the van't Hoff-Arehenius relationship,
37
-------
Equation 12, was assumed adequate to correct the 20°C value of the maximum
rate of substrate utilization per unit weight of microorganisms, K, to
10°C. The corrected K in turn was used to determine e m at 10°C.
\*
(VT,)
KT = KT . 6 Z ] (12)
'2 'l
where e = 1.106
T = temperature °K
The e value of 1.106 is that reported (44) for nitrification in the
temperature range of 5 - 20°C. e m was calculated by using Equation 13 (27),
9cm = (YK-b)"1 (13)
The kinetic coefficients and 0 m at 20°C and the calculated e m at 10°C
m
are noted in Table 6. The calculated 6 values of 2.1 and 2.9 days for
\f
ammonia and nitrite oxidation at 20°C compare favorably with the two day
8 m for nitrification of poultry wastes reported elsewhere (4).
Based upon these calculations, a design SRT of 20 days was chosen to
provide a safety factor of two for nitrification during winter operations.
In order to simplify the design and prediction of parameter removals, it
was assumed that SRT would be constant throughout the year. The expected
performance at this design SRT was estimated from relationships of parameter
removal and SRT that occurred in other poultry waste stabilization studies
(12). The expected performance is presented in Table 7.
The anticipated solids destruction and resultant solids concentration
were used to calculate the required volume for each ditch. A volume of
105,980 £ (28,000 gal) was calculated to have an equilibrium total solids
concentration of 19,777 mg/a at a 20 day SRT. This value is slightly
below the 20,000 mg/£ which is the upper limit for best oxygenation
efficiency. This volume resulted in a depth of 50.8 cm (20 in) in each
Manorcrest ditch with a freeboard of 20.8 cm (8 in).
38
-------
Table 6. KINETIC COEFFICIENTS AND ecm FOR BIOLOGICAL NITRIFICATION
USED FOR PROJECT OXIDATION DITCH DESIGN
Process
NH4-N
Oxidation
N02-N
Oxidation
Y, mg/mg N
0.29
0.29
0.084
0.084
b, days"
0
0.05
0.05
0.05
0.05
K, mg N/mg-day
1.8
0.7
4.7
11.7
T°C
20
10
20
10
ecm, days
2.1
6.5
2.9
10.7
Table 7. EXPECTED TREATMENT EFFICIENCIES OF AEROBIC
POULTRY WASTES STABILIZATION AT A 20 DAY SRT
Parameter % Removal
Total Solids 33
Volatile Solids 46
COD 36
Organic Nitrogen 62
39
-------
3
The design volume was compared to the parameter of 0.5 kg BODr/m -day
(0.03 Ibs BODj-ft -day) suggested as adequate for oxidation ditch design (21).
A BOD,-/T.S. ratio of 0.20 for poultry manure was assumed (Table 5). The
o
design volume of 105,989 £ (106 m ) had an expected volumetric loading
3
rate of 0.3 kg BOD5/m -day. Thus adequate performance was expected.
Oxygen requirements to satisfy carbonaceous and nitrogenous oxygen demand
were determined utilizing Equation 8. It was assumed that one unit mass
of COD removed represented one unit mass of carbonaceous oxygen demand
that was satisfied. Based upon the assumed waste characteristics presented
in Table 5 and the anticipated removals, Table 7, the daily COD removal
for each ditch was calculated to be 44.78 kg/day and therefore the oxygen
requirement for carbonaceous oxygen demand was assumed to be 44.78 kg/day.
The anticipated nitrogenous oxygen demand was an additional 38.20 kg 0?/day.
The anticipated oxygen requirements for the two levels of treatment, odor
control and odor control plus nitrification, per 1000 bird-hrs, were:
Table 8. DESIGN ESTIMATES OF OXYGEN REQUIREMENTS
Degree of Treatment Gms O^/IOOO
bird-hr
Odor control 470
Odor control &
Nitrification 860
The value of 860 gms 0^/1000 bird-hrs compared favorably with the oxygen
requirement of 940 gms Op/1000 bird-hrs determined from oxygen uptake
rate measurements reported by Baker et al. (37), for an oxidation ditch
treating poultry manure. The design value of 860 gms 0^/1000 bird-hrs
is conservative when compared to the 2 x BODj- value of 670 gms 02/1000
bird-hrs that has been suggested (21).
40
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Solids Management
In order to maintain an equilibrium mixed liquor total solids concentra-
tion and SRT, removal of solids was required. The following options
were considered:
1) creation of a continuous flow system by water addition
2) liquid-solids separation via gravitational settling
The first option was not considered practical due to the volume of effluent
involved. To maintain a 20 day SRT, 5299 £ (1400 gal) of mixed liquor
would have to be removed from each ditch daily. This would require the
handling of 484 £ (128 gal) of wastewater per bird per year. A 1,290,667 a
(340,995 gal) lagoon would be required to provide three months storage
of mixed liquor discharged for both oxidation ditches with this option.
Limited experience at the AWML indicated that liquid-solids separation via
gravitational settling could be a feasible method of controlling mixed
liquor total solids concentrations. However, detailed knowledge of
aerated poultry waste settling characteristics was not available. An
apparently conservative value of 50 percent solids removal via settling
was assumed for design purposes. Based on expected biological removal
of total solids, (Table 7), it was calculated that daily removal of 107 kg
dry weight of total solids was necessary to maintain the desired equili-
brium conditions. The required daily flow through the settling basin
for each ditch was calculated to be 10,720 £/day (2832 gal/day).
The design of the settling basins was based upon a number of factors.
First, it appeared desirable to combine settling with sludge thickening
and storage to simplify operation. Therefore, volume as well as surface
area was an important design consideration. Limitation of funds in part
constrained the maximum tankage volume that could be obtained. The lowest
cost option in terms of cost per unit volume was 2500 gallons (9462 i)
precast concrete tanks. The design specified four tanks per oxidation
2 2
ditch. The four tanks for each ditch had a surface area of 5m (54 ft ).
41
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The arrows in Figure 8, indicate the direction of flow through the.tanks.
The method of operation was to withdraw clarified liquid from the last
tank and reintroduce it into the ditch. This created an overflow of
mixed liquor through a standpipe into the first settling tank.
Based upon required mixed liquor flow and settling tank volume, the design
hydraulic detention time was 3.5 days. The calculated overflow rate was
2163 £/day/m2 (53 gal./day/ft2). An overflow rate of 48,975 £/day/m2
P
(1200 gal./day/ft ) for poorly settling activated sludge has been suggested
as adequate (24). Therefore, it appeared that sufficient settling capacity
was available with flexibility for increasing overflow rates if necessary.
The amount of storage time provided, and the volume of material requiring
ultimate disposal, was a function of the degree of sludge thickening.
Anticipated values for sludge volume on a daily basis and storage time
are given in Table 9.
Table 9. DESIGN VALUES FOR SLUDGE STORAGE TIME
Sludge Concentration Volume of Sludge Storage Time
(mg/£) per day (A) (days)
40,000
50,000
60,000
70,000
2684
2150
1785
1532
14.1
17.6
21.2
24.7
Ultimate Disposal
The 60.7 ha (150 acres) of crop land located adjacent to the poultry
houses (Figure 4) has served as the site of ultimate disposal for the
wastes produced on this farm. The available land is used for continuous
42
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corn production. The corn crop is harvested as grain which is field
shelled. Production averages 63 kg/ha (100 bu/acre).
The ability of the available land to accept the wastes produced by the
19,000 birds located on this farm was estimated as part of the overall
project design. The objective was to determine the level of stabiliza-
tion which would be required to prevent adverse environmental impact
from ultimate disposal of these wastes. Both total solids and nitrogen
loadings were considered. Based upon the assumed waste production values
(Table 5), the yearly total solids production was calculated to be
277,400 kg (611,013 Ibs). This would result in an application rate of
4570 kg/ha/yr (4073 Ibs/acre/yr). This value is substantially below
the level of 101 metric tons/ha/yr (45 tons/acre/yr) which has been demon-
strated to be acceptable (2).
The total nitrogen production per year was calculated to be 23,371 kg/yr
(51,478 Ibs/yr). This would result in an application rate of 385 kg
N/ha/yr (343 Ibs N/acre/yr). At the maximum recommended application rate
for corn of 224 kg N/ha/yr (4), it was calculated that 42 percent of the
nitrogen excreted by the birds on this farm should be removed prior to
land application to avoid potential nitrogen problems.
The consideration of some nitrogen loss by denitrification and hence the
inclusion of nitrification as a process design objective was based upon
this fact. It was assumed that denitrification would occur during settling
and sludge storage and perhaps also in the ditches.
CONSTRUCTION
The four existing collection pits (Figures 5 and 6), were converted to
two oxidation ditches by the removal of the end walls in each pit
followed by construction of four semicircular channels. The result was
the formation of two elongated loops. The outer perimeter of each semi-
circular channel was formed with precast concrete silo staves. The inner
43
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surface of the outer perimeter was plastered wi,th mortar to seal the
joints between the staves. A concrete floor was poured in each semi-
circular channel.
The connecting channels extended beyond the ends of the cage rows into
the service alleys. To permit movement of feed and egg carts as well
as personnel, it was necessary to cover the semicircular channels.
Pressure treated wood was used for beams and joists. Exterior grade
plywood was used as flooring.
Four interconnected 9462 s, (2500 gal) precast concrete tanks provided
settling and sludge storage facilities for each oxidation ditch. The
tanks were located outside the poultry house (Figure 8). The tanks
were interconnected and connected to the oxidation ditches with 20 cm
(8 in) bituminous fiber pipe. Influent pipes to each tank were baffled
to minimize turbulence. Influent and effluent lines were alternated
to minimize short circuiting of flow.
EQUIPMENT SELECTION
Two different types of surface aeration equipment were employed, one
in each oxidation ditch, to evaluate alternatives for aeration of oxida-
tion ditches. One was a cage rotor which functioned as both an aeration
and mixing device. The second aeration unit was a brush type rotor.
Design of the latter aerator was based on oxygenation and appeared to
require a supplemental mixing unit. A submerged industrial propeller
was used to provide supplemental mixing. Equipment placement is shown
in Figure 8.
Although several commercial cage rotors were available, a Thrive Centers, Inc.
unit was selected. This choice was based in part on availability of
operating characteristics as well as familiarity with a similar cage
rotor at the AWML. The channel width of 2.3 m (7.7 ft) limited the
maximum length of a single cage rotor to 1.68 m (5.5 ft). The rotor,
44
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model H-805, had a diameter of 70 cm (27.5 in) and was driven by a 3.7 kw
(5 hp) motor at a speed of 100 rev/min. The maximum recommended immersion
depth for this unit is 15.2 cm (6 in.).
The oxygenation characteristics of the Thrive unit were not available
from the manufacturer. However, characteristics presented by Jones,
et al. (45) and unpublished test data (46) were available. These studies
involved rotors of the same design at a 15.2 cm (6 in) immersion depth
and resulted in the data in Table 10.
Table 10. OXYGENATION CAPACITY FOR THE THRIVE CENTER CAGE ROTOR
Rotor Length
cm (in)
Oxygenation Capacity
gms 02/m/hr (Ibs 02/ft/hr)
Reference
55.9 (22)
66.0 (26)
114.3 (45)
2150 (1.4)
2383 (1.6)
1974 (1.3)
(46)
(45)
(45)
The results are approximately equal. Therefore, a value of 2150 gms
0?/m/hr was used for design purposes for the expected rotor size. It
was estimated that the 1.68 m rotor would transfer 3612 gms 02/hr. This
amount was greater than the maximum anticipated oxygen demand of 3440
gms 0?/hr thereby providing a small safety factor. The ability of the
1.68 m rotor length to provide adequate mixing was estimated as follows.
A minimum oxidation ditch velocity not less than 0.38 m/sec (1.25 ft/sec)
has been suggested (21) to provide adequate mixing. The pumping capacity
of the Thrive Centers cage rotor was reported (47) to be 29.3 a/sec/m
rotor length (3.4 ft3/sec/ft rotor length). It was calculated that a
1.68 m rotor should provide a velocity of 0.44 m/sec (1.46 ft/sec) and
it appeared that the 1.68 m cage rotor was adequate in both mixing and
oxygenation capacity.
45
-------
The brush type rotor manufactured by Montair, Inc. was of a new design.
It differed from conventional brush rotors in two ways. First, round
bars were used in place of flat blades to reduce resistance when creating
turbulence for oxygen transfer. Second, in place of multiple rows of
blades, this unit had only two rows of round bars positioned to form a
double spiral. With this geometry only two bars strike the liquid surface
at a given instant. This reduced the impact load on the aerator power
transmission components. The unit sized to fit the 2.3 m (7.7 ft) Manor-
crest channel width had a rotor length of 2.1 m (6.8 ft). It was driven
by a 1.5 kw (2 hp) gearhead motor. Rotor speed was varied by changing
sprocket sizes. Maximum immersion depth was 15.2 cm (6 in).
The operating characteristics of this unit, i.e., oxygen transfer and
pumping capacity, were not known. However, it appeared that this aerator
had the potential for greater oxygen transfer efficiency expressed as
gms CL per kwhr. Another apparent advantage was the light weight of the
aerator which would facilitate maintenance and repair when necessary.
Since the pumping capacity of this aerator was questionable, supplemental
pumping was provided by a 38.4 cm (15.1 in) industrial propeller driven
by a 2.2 kw (3 hp) variable speed motor. The propeller had a design
pumping capacity of 15,500 £/min (4095 gal/min) at the maximum speed of
350 rpm. It was estimated that the propeller would provide a supplementary
liquid velocity of 0.2 m/sec (0.7 ft/sec) at a 50.8 cm (20 in) liquid
depth. This combination of the brush aerator and propeller was installed
in Ditch I while the cage rotor was used in Ditch II. Two small 0.4 kw
(0.5 hp) helical screw pumps were specified to recycle settling tank
effluent.
46
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SECTION V
METHODS AND MATERIALS
OXYGEN TRANSFER
The oxygen transfer capacity of both aeration units in tap water was
determined at the outset of the evaluation phase of the study. The
tests were conducted between the completion of construction and equip-
ment installation and the initial operation of the ditches as treatment
units. The non-steady state chemical method (39) was used. Sodium
sulfite (Na2S03) in the presence of a catalyst, cobalt chloride (CoCl2),
was used to deplete the dissolved oxygen concentration. The cobalt
chloride was added to achieve a concentration of 0.2 mg/a in the tap
water in each ditch. Both chemicals were dissolved prior to addition.
Manual mixing was employed in an effort to achieve uniform chemical
distribution.
Following the commencement of aeration, the rate of increase of the
dissolved oxygen concentration was measured with YSI model 54 dissolved
oxygen meter. The meter was standardized against saturated distilled
water at a known temperature and atmospheric pressure. Saturated oxygen
concentrations were obtained from Standard Methods (48)- The temperature
of the tap water was measured at the time of these tests.
The oxygen transfer coefficient, KLa, was computed using the following
equation:
dc _
dt ~
where dc _
T£ = change in dissolved oxygen concentration with time
K, a = overall oxygen transfer coefficient, time"
C = oxygen saturation concentration, mass/volume
C. = dissolved oxygen concentration at time t, mass/volume
L
47
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K a was determined from semi -logarithmic plots of the oxygen deficit,
C -Ct, versus time. A least squares exponential regression program was
used to fit a straight line to the experimental data and calculate the
slope of the line, KLa.
The values of C were obtained from Standard Methods (48) and corrected
using local barometric pressure readings obtained from the U.S. Weather
Bureau, Hancock Field, Syracuse, New York. Hancock Field is located
approximately twenty miles from the demonstration site and is at the
same elevation. The following equation was used to calculate the actual
value of C .
C (actual) = [Cq (tabular value)] Local Atmos. Pressure (in Hg.) (15)
-> i> Cy . yc. I n ng .
All K.a values were corrected to 20°C using the following relationship.
KLaT = KLa20oC(e)(T-20) (16)
where K,_aT = yalue Qf at rc
KLa20°C = Va1ue °f KLa at 20°C
e = temperature correction factor, 1.02
Equation 11, (Section III), was used to calculate the mass of oxygen
transferred per unit time.
VELOCITY MEASUREMENTS
The velocity of tap water in each oxidation ditch was measured with a
Gurley model number 622 current meter. This was a direct acting current
meter. Velocity measurements were made at two locations in each ditch
as indicated in Figure 9. To determine the average velocity in each
cross-section, measurements were made at the locations indicated in
Figure 10. The results were averaged vertically and then horizontally
to obtain the average velocity at each location.
48
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AERATION UNIT
X
LOCATION
Jf*
c
LOCATION
FLOW
Figure 9. Location of velocity measurements, plan view
.21
X _
x _ _jc_- .- . x =?-
X
re
-1/4 D
1/4 D
1/4 D
1/4 D
Figure 10. Location of velocity measurements, cross section
49
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Attempts were made to measure ditch velocity under process conditions.
Both the current meter and a subsurface float were used. The cups on
the current meter became fouled with feathers which eliminated this
approach. The subsurface float was also unreliable due to cross-
currents a'nd accumulated sediments. No reliable data were obtained
with respect to velocity under process conditions.
One important aspect of the oxygen transfer studies was to compare the
efficiency of the two aeration systems. This normally is done by
measuring energy consumption and expressing efficiency as mass of oxygen
transferred per unit energy consumed. However, electric motor efficiency
increases as loading approaches the design maximum. For a given motor,
the ratio of power consumed to power produced will be less at lower
than design loadings.
In order to eliminate this variable and thus provide an equal basis for
comparison, the shaft power was determined for each motor under the
various test conditions. This was accomplished by measuring energy
consumption of each motor with commercial type watt-hour meters. These
data were then translated into shaft power using motor performance curves.
Performance curves were obtained from the manufacturers of the motors
supplied with the brush and cage aerators. Performance curves for the
propeller drive, which consisted of a variable speed DC motor and gear
reducer, were not available from the manufacturer. Therefore, dynamometer
tests were performed to develop performance curves. The performance
curves that were used are presented in Figures 1 through 4 of the appendix.
DATA COLLECTION
To perform materials balances and to determine the degree of waste
stabilization, routine sampling of fresh wastes, oxidation ditch mixed
liquor (ODML), and settling tank supernatant returned to the ditches
was conducted through the course of the study." A 24 hour, composite
sample of raw manure was collected weekly from randomly selected groups
50
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of four hens. The raw manure was collected by suspending a tray below
an individual cage. Grab samples of ODML and return supernatant were
taken twice a week. All samples were returned to the AWML and analyzed
on the day of collection.
The raw waste samples were analyzed for the following parameters:
Total manure production per bird-day
Total solids
Volatile solids
Chemical oxygen demend (COD) - total and soluble
Total Kjeldahl nitrogen (TKN)
The mixed liquor and settling tank supernatant were analyzed for the
following:
Total solids
Volatile solids
COD - total and soluble
TKN
Ammonia nitrogen (NH*-N)
Nitrite nitrogen (N02-N)
Nitrate nitrogen (NOg-N)
PH
Temperature
Dissolved oxygen (D.O.) - mixed liquor only
ANALYTICAL METHODS
Total and volatile solids were determined as described in Standard Methods
(48). TKN was determined by a micro-Kjeldahl method (49). Ammonia nitro-
gen was determined using the stream distillation procedure (50). Nitrite-
nitrogen was determined by diazotization (51). Nitrate-nitrogen was
described by a salicylic acid method (50). The rapid method (52) was
used to measure COD. Soluble COD was defined as that portion of the total
COD that would pass through a 0.8 y millipore filter. The presence of
nitrifying organisms, Nitrosomonas and Nitrobacter, was determined using
51
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a procedure for estimation of active nitrifying organism concentrations (53).
Dissolved oxygen concentration and temperature of the mixed liquor were
measured in the ditches at the time of sampling with a YSI, model 54
oxygen meter. Dissolved oxygen concentrations were measured at the
locations indicated in Figure 8 to provide a profile of dissolved oxygen
concentration in relation to distance from the aeration unit. The oxygen
uptake rate was determined by aerating a mixed liquor sample and then
measuring the decrease of dissolved oxygen with time.
Zone settling velocity was determined by measuring the downward movement
of a sample mixed liquor-supernatant interface with time. The tests
were conducted in a 1 £ graduated cylinder. Samples were not stirred.
CALCULATION OF SRT AND TREATMENT EFFICIENCY
The conventional approach to calculation of SRT is based upon the follow-
ing relationship.
_R_ _ wt. of solids in the system ,r\
wt. of solids leaving the system/time ^ '
It is implied in this method of calculation that all of the solids
leaving the system are lost in the effluent, and that they can be
measured. However, in the Manorcrest oxidation ditches, solids were
removed from the system in two ways. One method of removal was by the
intentional settling of mixed liquor. The other was via uncontrollable
sedimentation in the ditches. Although it was possible to measure the
solids lost through the settling tanks, accurate determination of solids
lost via sedimentation was not possible.
The problem of sedimentation required a different approach to the calcu-
lation of SRT. Although suspended solids are commonly used in the cal-
culation of SRT, use of total, volatile, or fixed solids is also valid.
In any given system, constant relationships should exist between these
types of solids. At equilibrium, the fixed solids entering the system
should equal those leaving the system assuming fixed solids generated
52
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or lost during treatment are minimal. This permitted a different
approach to the calculation of SRT. It was possible to accurately deter
mine the quantity of fixed solids entering the system. By assuming the
quantities of fixed solids entering the system were equal to those
leaving the system by any physical means, it was possible to estimate
SRT as follows:
SDT = wt. of fixed solids in the system
wt. of fixed solids entering the system/unit time
This was the approach used to determine SRT in this study. Mixed liquor
fixed solids concentrations were used to determine when equilibrium
conditions were attained.
Equation 18 defines treatment efficiency in terms of influent and
effluent waste characteristics.
Sn - S,
E =-n- L (100) (18)
^o
where E = treatment efficiency, percent
S = influent waste characteristic
o
S, = effluent waste characteristic
In a completely mixed system, the mixed liquor and effluent should have
the same characteristics and either concentration can be used. This
equation can be used in several ways. The most common is to express
S and Sn as concentrations, mass per unit volume. A second approach
is a total mass balance with S and S, representing total mass in and
out of the treatment system. A third method is based on the ratio of
any given parameter such as total and volatile solids, organic nitrogen
and COD to a constant factor such as fixed solids in both raw and stabilized
waste. The latter was the approach used for the calculation of treatment
efficiencies in this study.
The following is an example of this method of calculation of treatment
efficiency. Ratios of a given parameter to fixed solids in the raw
53
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wastes and mixed liquor were calculated from analyses to determine
concentration per unit volume of both the parameter and fixed solids
in each sample. The fixed solids ratio was then calculated as follows:
Concentration of parameter,
Fixed solids ratio, _ mass/volume /ig^
mass/mass Concentration of fixed solids ^ '
mass/volume
The ratio calculated from raw manure analyses represented S in Equation
18 while S-| was the ratio calculated from results of mixed liquor analyses.
The difference between S and S-, represents biological removal from the
system.
Either the first or third method could have been used to estimate treat-
ment efficiency. The inability to accurately determine losses via sedi-
mentation eliminated the total mass balance approach. The fixed solid
ratio approach was selected because it was similar to the means of SRT
estimation in that both are based on fixed solids. This approach provided
a simple and rapid method of monitoring system performance.
ECONOMICS
Capital costs, building modifications and equipment were amortized at an
interest rate of 9 percent to determine annual costs. Time periods used
are as follows:
Structures 20 years
Aeration Equipment 10 years
Energy consumption was continually measured for each electric motor in
order to determine energy costs. Where operating conditions resulted
in motor loadings that were below values which produced peak motor
efficiency, corrections in measured energy consumption were made to de-
termine energy consumption at peak motor efficiency. This was done when
operating conditions were such that the electric motor was significantly
underloaded and could have been replaced with a smaller size motor. The
motor performance curves (Appendix, Figures 1 through 4) were used for
54
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this purpose. The measured input energy was used to determine energy
output. This value was then used to calculate energy consumption at
the peak motor efficiency for that motor as indicated in the performance
curves. The variable speed D.C. motor for the propeller drive had a low
peak efficiency, 62 percent, in comparison to an A.C. motor. Since a
variable speed D.C. motor normally would not be used, the value of 70
percent, which is realistic for an A.C. motor, was used in the case of
the propeller. The electrical energy cost to Manorcrest Farms through-
out the study remained constant at $0.0201 per kilowatt hour. This
included the fuel adjustment charge as well as the base rate.
55
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SECTION VI
SYSTEM PERFORMANCE RESULTS
INTRODUCTION
The project "Demonstration of Aeration Systems for Poultry Wastes"
covered the period from March 1973 through June 1975. Details of the
major phases of the study are contained in Table 11.
Table 11. AN OUTLINE OF THE MANORCREST DEMONSTRATION ACTIVITIES
Time Period Activities
March - May 1973 System design and equipment
selection and acquisition
June - August 1973 Construction, electrical work
and equipment installation
August 1973 Oxygen transfer studies
September 1973 - System operation for demonstration
March 1975 and evaluation
March - June 1975 Detailed analyses of data;
preparation of final report
It was necessary to integrate the construction activities and the oxygen
transfer studies with the replacement schedule for the chickens located
in Building No. 1. This resulted in the extended period for design
and construction.
The initial operating conditions for each oxidation ditch are presented
in Table 12.
56
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Table 12. SUMMARY OF INITIAL OPERATING CONDITIONS,
SEPTEMBER 1973
Ditch I Ditch II
Bird number 4,000 4,000
Volume 105,980 i 105,980 a
(28,000 gal) (28,000 gal)
Liquid depth 50.8 cm 50.8 cm
(20 in) (20.1n)
Aeration unit
Speed 252 rpm 100 rpm
Immersion depth 15.2 cm 12.7 cm
(6 in) (5 in)
Propeller speed 232 rpm
Oxygen transfer 1403 gms Op/hr 3360 gms 02/hr
capacity
Over the 19 months that the aeration systems were monitored, several
changes in operating conditions were instituted. These changes are
listed in Table 13. The aerator speed in Ditch I was increased to
evaluate system performance at a higher level of oxygen transfer. The
resulting increase in mixed liquor velocity due to increased pumping
by the aerator made the propeller expendable. Since the propeller
housing was impending foam movement and causing a significant sediment
accumulation, it was removed. The reason for the reduction in liquid
depth was to increase mixed liquor velocity to reduce sedimentation.
This problem will be discussed in greater detail at a later point.
This section contains the experimental results of the study. Included
are results of the oxygen transfer and velocity studies, system
performance, system costs, and identification of problem areas.
57
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Table 13. CHANGES IN OPERATING CONDITIONS
Date Change
1/7/74 Aerator speed in Ditch I increased
to 310 rpm. Immersion depth decreased
to 11.4 cm (4.5 in.).
1/17/74 Propeller in Ditch I was removed
9/1/74 Volume of each ditch reduced to
68,887 £ (18,200 gal.). New liquid
depth was 33 cm (13 in.).
OXYGEN TRANSFER STUDIES
Oxygen transfer studies were conducted in both ditches following the
completion of construction and equipment installation. The specific
objectives of these studies were to:
1) establish baseline oxygen transfer data
2) evaluate the brush aerator-propeller combination as
an alternative aeration approach
The scope of these studies was restricted by two factors. First, the
cages were empty during construction and only a limited time period was
available prior to the housing of new birds. Second, the flow rate of
the farm water supply was limited. Therefore, it was necessary to
purchase water to run these tests. Thus, only one filling of each ditch
was possible. The results reported were limited to the data obtained
from the first 10 trials, although 12 tests were conducted in each
ditch. The data collected during the llth and 12th trials were of poor
quality. Accumulation of salts or other contaminants was the probable
cause of this phenomenon. Problems resulting from poor mixing of the
chemicals with the tap waterand leakage in Ditch II reduced the usable
data to that collected during 4 of the 12 trials.
58
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Ditch I
The aeration system in this ditch was the experimental brush aerator and
the propeller mixer. The relationship of two variables, brush aerator
speed and velocity of ditch contents, to oxygenation efficiency was
examined in this ditch. The test conditions included two brush aerator
speeds, 126 and 252 rpm at a constant immersion depth of 15.2 cm (6 in).
Propeller speeds included 0, 115, and 232 rpm. Cavitation limited the
maximum propeller speed to 232 rpm. Both oxygen transfer and velocity
measurements are presented in Tables 14 and 15 respectively. Shaft
power, kilowatts, or horsepower were obtained from energy consumption
data and motor efficiency curves.
The results presented in Tables 14 and 15 show the relative impact of
each device on both oxygenation and pumping efficiencies. The propeller
did not perform any aeration. Increased propeller speed, and therefore
ditch velocity, decreased the oxygenation efficiency per unit of power
utilized. Peak pumping efficiency did not occur when the propeller was
used alone. Although the data indicates that the propeller was more
efficient than the brush aerator for pumping, the most effective situa-
tion was the combination of the 126 rpm aerator speed and the 115 rpm
propeller speed. This combination also had the highest oxygenation
efficiency, 1684 gms 02 per kw-hr.
However, oxygen transfer was only 527 gms 02 per hour or 132 gms 02 per
1000 bird-hours for 4000 birds. This value was significantly below value
for odor control of 470 gms 02 per 1000 bird-hours (Table 8). Consequently,
the combination of the 252 rpm aerator speed and the 232 rpm propeller
speed which provided 351 gms 02/1000 bird-hours was used for initial
phase of Ditch I operation.
59
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Table 14. RESULTS OF OXYGEN TRANSFER MEASUREMENTS - DITCH I
Test Condi
RPM
Aerator -
Propeller
Aerator -
Propeller
Aerator -
Propeller
Aerator -
Propeller
Aerator -
Propeller
tions,
252
- 232
252
- 0
126
- 232
126
- 115
0
- 232
K, a^Q Gms Op/
Min-1 Hr.
.024 1403
.024 1403
.011 616
.009 527
- 0
Shaft Power, Gms 02/
Watts KwHr
.947 918
.582
.947 1482
0
.306 694
.582
.306 1684
.700
.582
Ditch II
Rotor immersion depth was the variable examined in this oxygen transfer
study of the cage rotor. Trials were conducted at two immersion depths,
7.3 and 12.7 cm (2.9 and 5 in.). The results of these trials are noted
in Tables 16 and 17. The cage rotor had a greater oxygenation and pump-
ing capacity than the system in Ditch I. However, both oxygenation and
pumping efficiencies were lower. Therefore, higher operating costs per
unit oxygen transferred could be expected for this system.
The results of cage rotor oxygen transfer measurements are compared to
results of other studies in Figure 11. The other studies also involved
Thrive Centers cage rotors of the same design as the Manorcrest unit.
As shown in the Figure, there is good general agreement between the
Manorcrest results and those of the other investigations. It appears
60
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Table 15. RESULTS OF VELOCITY MEASUREMENTS - DITCH I
Aerator
Speed,
RPM
126
126
126
252
252
0
Propeller
Speed,
RPM
0
115
232
0
232
232
Average
Velocity,*
m/sec
0.06
0.12
0.24
0.15
0.26
0.11
Pumping
Capacity,
a/sec
71
142
285
178
309
130
Shaft
Power,
Watts
306
313
887
947
1529
582
Efficiency
£/sec/watt-hr
.232
.454
.321
.188
.202
.223
*Average of velocities measured at locations 1 and 2 (Figure 9)
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Table 16. RESULTS OF OXYGEN TRANSFER MEASUREMENTS - DITCH II
Immersion Depth,
cm (in.)
7.3 (2.9)
12.7 (5)
KLa2Q Gins 02/hr Gms 07/meter
m1-n-l of rotor length
0.036 1925 1148
0.062 3360 2005
Table 17. RESULTS OF VELOCITY MEASUREMENTS -
Shaft Power,
watts
1678
2759
DITCH II
Efficiency
Gms 02/KwHr
1147
1218
Immersion Depth,
cm (in.)
Average Velocity, Pumping Capacity
m/sec £/sec
Shaft Power,
watts
Efficiency,
^/sec/watt
12.7 (5)
0.38
458
2759
.166
-------
167.6 cm ROTOR, MANORCREST FARMS
66 cm ROTOR , JONES, et a I. (45 )
55.9 cm ROTOR, MARTIN (46)
116.8 cm ROTOR, JONES, et. al. (45)
O
QC
O
(T
L_
O
I
QC
LJ
2600
2400
2200
2000
1800
O 1600
bJ
"* 1400
1200
1000
6 800
o
600
400
1
I
5.08 10.16 15.24 20.32
IMMERSION DEPTH , cm
Figure 11. Comparison of oxygen transfer characteristics,
Thrive Centers cage rotors
63
-------
that the differences are due to factors such as ditch size and geometry
which varied.
At the 12.7 cm (5 in.) rotor immersion depth, oxygen transfer was 3360
gms Op per hour or 840 gm Op per 1000 bird-hours for 4000 birds. This
value was comparable to the design value of 860 gms Op/1000 bird-hours
for odor control plus nitrification (Table 8). Therefore, this
immersion depth was used under operating conditions.
RAW WASTE QUANTITIES AND CHARACTERISTICS
The laying hens involved in this study were a commercially available
breed white leghorn chickens, the Shaver strain. The period of oxida-
tion ditch operation exceeded one laying cycle. Since these birds were
replaced at the end of the first cycle, 12 months, two groups of birds
were involved in this study. The first group was housed in September
1973, concurrent with the start operation of the oxidation ditches, and
the second in September 1974. The birds were 20 weeks of age and had
started egg production when placed in the cages over the oxidation ditches,
There was no major change in the mass or characteristics of the manure
with increasing bird age. Therefore, each year's results were averaged
and are presented in Table 18. Only small changes in waste characteris-
tics occurred between the two years. These variations could have been
due to changes in feed. No feed analysis information was available,
since most of the feed is manufactured on the farm from home grown grains.
Noticeable changes were the 11.4 percent increase in COD and the 12
percent increase in fixed solid production per bird-day in 1974-75.
The observed quantities and characteristics of the raw manure are signi-
ficantly lower than the values assumed for design (Table 5). Due to the
lower loading rates, the design safety factor was greater than that
originally estimated. Precise reasons for the difference in raw waste
characteristics are unclear. Two factors are possible differences in
64
-------
Table 18. RAW MANURE CHARACTERISTICS, MANORCREST FARMS
gms TS
bird-day
gms VS
bird- day
gms FS
bird- day
0/ vs
/0 TS
gms COD
bird- day
gms TKN
bird -day
gms BOD5
bird-day
BOD5
COD
% Soluble COD
mg COD
gm FS
mg TKN
gm FS
3ms VS
gms FS
1973-74
29.6
22.1
7.5
74.8
19.2
2.3
4.9
.26
24.5
2565
307
2.9
1974-75
29.0
20.6
8.4
72.0
21.4
2.2
23.3
2544
263
2.4
65
-------
diet and the strain of bird. The values used for design were obtained
from Babcock white leghorn chickens.
SYSTEM PERFORMANCE
Introduction
The rationale of using SRT as a design and operational parameter for
slurry type biological treatment systems was discussed in Section III
and used in the design of these aeration systems. In order to confirm
or nullify the validity of this approach, system performance was evaluated
at several different SRT's. In addition, the differences in oxygenation
capacity of the two aeration systems (Table 12) provided comparison of
two different levels of oxygen transfer. The increase of the brush
aerator speed (Table 13) provided a third level of oxygen transfer. The
relationships between quantity of oxygen supplied to both waste stabiliza-
tion and nitrogen transformations were examined.
Physical design and mechanical difficulties limited the number, and in
some cases, the length of equilibrium SRT conditions. Accumulation of
sediments in both ditches was one serious problem. It was necessary to
completely empty each ditch on two occasions. This will be discussed
later in greater detail. Mechanical problems resulted in the stopping
of the Thrive rotor for periods exceeding 24 hours on at least eight
occasions. Operation of the brush aerator was also interrupted several
times. These occurrences either interrupted equilibrium conditions or
prolonged the time period necessary to reach steady-state.
General
Throughout the course of the study, both aeration systems provided a
high degree of odor control. This was true at all three levels of oxygena-
tion and the various SRT's evaluated. At the lowest level of oxygen
transfer, 351 gms OM per 1000 bird-hours, the odor of ammonia due to
ammonia stripping was detectable in the immediate vicinity of the
66
-------
aeration unit. No waste associated odors were present in other areas
of the building or in the ventilation exhaust air streams when continuous
aeration was provided. Malodors did occur following restart of aeration
units after mechanical problems. However, reestablishment of odor control
was accomplished within approximately three to six hours depending on
the length of aerator shutdown. The longest breakdown period was four
days. No other vermin problems were observed.
The only point in these two systems where trial odors were generated was
in the settling and sludge storage tanks. Although odors were evident
when sludge was being removed for ultimate disposal, the intensity was
not of sufficient magnitude to create any problems during pumping or
field spreading. In addition to door control, the presence of house flies,
Musca domestica, which breed in animal manures, was essentially eliminated.
There was no need to use any fly control measures through the course of
the study.
Relationship erf SRT tp^ Treatment Efficiency
To demonstrate and quantify the relationship between SRT and treatment
efficiency with respect to aerated poultry wastes, treatment efficiencies
at six different SRT's were determined. SRT was varied by controlling
the rate of solids removal in the settling system. Precise selection
of SRT was not possible due to problems in liquid-solids separation
which will be discussed later. This accounts for the non-uniform distri-
bution of SRT's which ranged from 10.5 to 36.5 days. However, it was
possible to establish steady-state conditions at six different SRT's.
Removals of total and volatile solids, COD, and organic nitrogen were
calculated for each period.
Relationships between SRT and the percentage removal of each parameter
are presented in Figures 12 and 13. These results show that as SRT
increased, removal of each parameter also increased. Details of each
equilibrium period are given in Table 1 of the Appendix.
67
-------
60 r
50
< 40
O
30
(T
20
10
TOTAL SOLIDS
* VOLATILE SOLIDS
10 20 30
SRT, days
40
Figure 12.
Observed relationships between SRT and removal of
total and volatile solids
70
60
<
> 50
Id
or
o**
40
30
20
10
10
* ORGANIC NITROGEN
COD
I I I
20 30
SRT, days
40
Figure 13. Observed relationships between SRT and removal of
organic nitrogen and COD
68
-------
Relationship of_ Oxygen Supply tp_ Process Performance
The Manorcrest oxidation ditches were operated at three different levels
of oxygen transfer in order to develop a relationship between oxygen
supply and process performance. The three levels were 350, 520, and
840 gms 02 per 1000 bird-hours. For purposes of simplicity, these three
levels of oxygen transfer capacity will be referred to as Levels I, II,
and III. Due to the relationship of mixed liquor total solids concentra-
tions to a (Figure 2), estimated oxygen transfer for the three SRT's at
Level III were less than the tap water value of 840 gms 02 per 1000 bird-
hours. This was not due to any changes in system operation. These
Levels were examined concurrently with SRT in order to correlate oxygen
input with treatment efficiency.
The absence of malodors indicated that the exerted carbonaceous oxygen
demand was satisfied aerobically even at the lowest level of oxygen in-
put. Comparison of carbonaceous oxygen demand satisfied expressed as
COD removed with the oxygen transferred under process conditions is
presented in Table 19. Oxygen transferred under process conditions was
calculated using the relationship between mixed liquor total solids
concentrations and a presented earlier (Figure 2). The quantity of COD
removed was based on the calculated treatment efficiency for each
detention time.
The conclusion that the exerted carbonaceous oxygen demand was being
satisfied as indicated by odor control is substantiated by these values.
In all cases, the rate of oxygen transfer exceeded the rate of COD
removal. These data indicate that treatment efficiency, i.e., total and
volatile solids, COD, and organic nitrogen removal, was not limited at
any time by the lack of available oxygen. The variations in the rates
of COD removal appear to be related to changes in SRT.
Average dissolved oxygen concentrations (DO) for the range of conditions
studied are given in Table 20. The designations 1/4 and 3/4 point
69
-------
Table 19. COMPARISON OF COD REMOVED WITH OXYGEN SUPPLY
Level of
Oxygen Transfer
I
II
III
SRT,
Days
15
21
10.5
18
27
36.5
Total Solids
Concentration,
mg/£
9,960
13,550
13,760
21,570
19,800
23,830
a
Factor
1
1
1
0.95
0.97
0.94
Oxygen*
Transferred
gms/1000 bird-hr
351
520
520
798
815
790
gms COD Removed/**
1000 bird-hrs
263
250
200
322
251
280
* Calculated oxygen transfer under process conditions
**Calculated from raw waste characteristics and removal results
-------
Table 20. DISSOLVED OXYGEN CONCENTRATIONS
Average dissolved oxygen
concentration, mg/£
Level of
Oxygen transfer
gms 02/1QOO bird-hrs
350
520
520
798
815
790
SRT
Days
15
21
10.5
18
27
36.5
1/4
(0.7
(0.5
(0.6
(1.0
(1-4
(1.4
Point
1-0
- 1.55)*
1.0
- 1.6)
1.1
- 1.5)
1.5
- 1.8)
4.5
- 7.3)
2.6
- 4.8)
3/4
(0.1
(0.1
(0.2
(0.3
(0.4
(0.4
Poi nt
0.25
- 0.4)
0.3
- 0.5)
0.2
- 0.3)
0.4
- 0.6)
3.9
- 6.9)
1.4
- 3.2)
Temp.
°C
13
12
13
16
13
13
*Range of values
71
-------
indicate the distance downstream from the aeration unit at which the DO
measurements were made (Figure 8). The relatively high DO levels at the
3/4 point for the 27 and 36.5 day SRT suggest that the DO of the mixed
liquor entering the rotor may not have been zero. Therefore, the quantity
of oxygen transferred would have been less than the values stated in
Table 20. The calculated quantities of oxygen transferred were based
upon a maximum oxygen deficit, C<. - C. , where C, is zero. This indicates
that the total oxygen demand, carbonaceous and nitrogenous, was less
than the maximum potential oxygen supply from the aeration unit.
Removal of Soluble COD
The removal of the soluble fraction of total COD in poultry wastes by
aeration was examined at four different SRT's. As shown in Table 21,
observed removals varied but always exceeded 85 percent. These data
indicate that the major portion of soluble COD removal from poultry
wastes in aeration systems will occur at SRT's of 10.5 days or less and
corroborated the data shown in Table 2 and Figure 1.
Table 21. OBSERVED REMOVAL OF SOLUBLE COD
Level of SRT, Removal of Soluble
Oxygen Transfer Days COD, Percent
I 15 86.8
II 10.5 93.8
21 95.7
III 27 92.5
36.5 90.4
72
-------
RESULTS
Nitrogen
The systems design identified nitrogen removal as a necessary design
objective for Manorcrest Farm No. 2. Two areas involving nitrogen re-
moval were examined. The first concerned the determination of whether
or not seeding is necessary to establish a population of nitrifying
organisms. Included in this area were patterns of nitrification. The
second was to compare nitrogen removal at different levels of oxygen
transfer. Comparison included both method and extent of nitrogen removal.
Seeding and Patterns of_ Nitrification -
Each oxidation ditch was thoroughly cleaned to remove any residue from
previous manure accumulations before the oxygen transfer studies. Neither
ditch was intentionally seeded with nitrifying organisms prior to commence-
ment of operation under process conditions. In Ditch II, nitrification,
as indicated by the presence of nitrites (NCU-NK was first observed on
the Nth day of operation (Figure 14). Sweeping of material on the
building floors into both ditches during routine cleaning may have intro-
duced the nitrifying organisms.
During the start-up period, days 0 through 74, Ditch II was operated as
a continuously loaded, batch reactor to build the microbial population
and to reach the desired mixed liquor total solids concentration. Mixed
liquor concentrations of ammonia (NH,-N), nitrite (NO?-N), and nitrate
(NOo-N), plus pH for this time period are presented in Figure 14.
Following the onset of nitrification, this period was characterized by
high concentrations of NCL-N in comparison to NO--N. Nitrification
reduced the initial accumulation of NH,-N, but NH.-N concentrations
-------
8.0
7.0
6.0
600
10
20
30 40
TIME, doys
50
60
70
Figure 14. Nitrogen transformations during the start-up
period, Ditch II
-------
NOp-N accumulation reoccurred (Figure 15). Solids removal to achieve
equilibrium conditions started on day 81. Therefore, Ditch II was no
longer a continuously loaded batch system. Aeration was again inter-
rupted on two occasions as noted. Significant denitrification was not
observed during or after either of these latter non-aerated periods.
Only data from two periods of nitrite accumulation are presented here.
However, the same phenomenon was observed on several other occasions
following aerator breakdowns and when Ditch II was restarted for the
second year. Unfortunately, aeration could not be continuously
maintained for a sufficiently long time period to determine if complete
nitrification, accumulation of NOo-N, would occur. Aerator mechanical
O
problems were the cause for the frequent interruptions in aeration.
Nitrogen Removal
The removal of total nitrogen was examined in relation to the three
levels of oxygen transfer previously described. Comparison of removal
of total versus organic nitrogen and the details of operating conditions
for four steady-state periods are presented in Table 22. Losses of
total nitrogen ranged between 48.8 and 63.3 percent under the various
conditions. Both ammonia desorption and nitrification-denitrification
were observed as mechanisms of nitrogen removal. Desorption occurred
at the lowest level of oxygen input with nitrification-denitrification
occurring at the higher levels. The following sections contain the
results obtained at each level of oxygen input.
a_ - Nitrogen removal at 351 grns CL per 1000 bird-hours - At this level of
oxygen input, significant nitrification, as identified by measurements of
NO£-N or NOo-N concentrations above trace levels, was not observed. Active
mass determinations established that both Nitrosomonas and Nitrobacter
were present although in low numbers. Insufficient oxygen, as evidenced
by low mixed liquor dissolved oxygen concentrations (Figure 16) and not
75
-------
8.0]
7.0
6.0
600
NO AERATION
BALANCE PERIOD
II 121
TIME, days
Figure 15. Reoccurrence of nitrite accumulation in Ditch II
-------
- 2.0|
61
71 81
TIME, days
91
101
Figure 16. Dissolved oxygen concentrations in Ditch I at the
oxygen transfer capacity of 351 gms 02/1000 bird-hours
-------
the absence of the microorganisms, was the probable cause for the lack of
significant nitrification.
During this time period, the average mixed liquor ammonia concentration
was 1265 mg/£ at an average pH of 8.1. The average free ammonia (NHg-N)
concentration was 43.7 mg/£. This relatively high free NHg-N concentra-
tion and the strong odor of ammonia in the immediate vicinity of the
aeration unit suggests that ammonia stripping was the major method of
nitrogen removal at this level of oxygen input. Mixed liquor concentra-
tions of total and free ammonia plus pH are presented in Figure 17.
Table 22. RELATIONSHIPS BETWEEN OXYGEN TRANSFERRED AND
REMOVAL EFFICIENCIES OF ORGANIC AND TOTAL NITROGEN
Removal Efficiencies, %
Oxygen Transfer
Capacity
gms/1000-bird-hrs.
351
520
815
790
SRT, days
15
21
27
36.5
Organic
Nitrogen
55.0
60.4
64.7
63.3
Total
Nitrogen
48.8
60.4
47.7
63.3
As shown in Table 22, the removal of total nitrogen was less than that
for organic nitrogen during the balance period. The difference was due
to the increase of ammonia in the total system, oxidation ditch plus
settling tanks, over the balance period. This was due to increased
ammonia concentration in the contents of both the ditch and settling
tanks. Refilling the settling tanks with tap water following sludge
removal on day 78 added to the ammonia storage capacity. Table 23
shows the increase in mass of ammonia in the total system with time.
78
-------
X
Q.
8.5
7.5
St
-------
Table 23. CHANGE IN MASS OF AMMONIA NITROGEN IN DITCH I
AT 351 QMS 0 TRANSFERRED/1000 BIRD-HRS
Day
51
55
62
6b
69
75
78
83
87
92
99
106
Mixed Liquor
Ammonia-Nitrogen,
kg.
131.3
133.5
1 31 . 3
126.1
133.5
141.4
136.5
128.3
135.3
127.6
141.4
141.7
Settling Tank
Ammonia-Nitrogen,
kg.
37.1
41.6
45.0
45.8
48.2
50.5
0*
44.5
46.6
46.6
48.0
51.4
Total Mass,
kg.
168.4
175.1
176.3
171.3
181.7
191.9
136.5
172.8
182.4
174.2
189.7
192.8
*Settling tanks emptied and refilled with tap water
80
-------
]D - Nitrogen removal at 520 gms 02 per 1000 bird-hours - Following the
period of lowest oxygen input, the level of oxygen transfer in Ditch I
was increased from 351 to 520 gms 02 per 1000 bird-hours. Significant
nitrification occurred, as evidenced by a continuous reduction of the
mixed liquor ammonia concentration (Figure 18). Trace amounts of NO?-N
were present in the mixed liquor throughout this period but NO,-N was
O
not observed.
Although some of the nitrogen loss can be attributed to ammonia stripping,
the potential for desorption decreased with time as the free ammonia con-
centration decreased (Figure 18). Mixed liquor dissolved oxygen concen-
trations (Figure 19) did not significantly differ from those during the
period of lower oxygen transfer (Figure 16). One factor which may explain
the low DO levels is the additional nitrogenous oxygen demand (NOD) from
the residual ammonia in the system. Combining the quantity of ammonia
produced from the degradation of organic nitrogen added during this period
with the reduction of the ammonia residual, it was calculated that 150
percent of the NOD was satisfied.
c_- Nitrogen removal at higher oxygen inputs - Nitrogen losses were
determined for two separate time periods at higher levels of oxygen
transfer in Ditch II. The oxygen inputs were 815 and 790 gms 02 per
1000 bird-hrs. during the first and second balance periods:
During the first mass balance period at 815 gms 02 per 1000 bird-hrs.,
the loss of total nitrogen was less than that of organic nitrogen
(Table 22). Accumulation of inorganic nitrogen in the system as ammonia,
nitrite, and nitrate was responsible for the difference. Mixed liquor
concentrations of these compounds are presented in the segment of
Figure 15 denoted balance period (days 91 to 124). Both NH4-N and N02-N
concentrations representing unsatisfied nitrogenous oxygen demand, in-
creased during the balance period. Concurrently, mixed liquor dissolved
oxygen concentrations also increased (Figure 20).
81
-------
8.5
I
o.
7.5
110
FREE AMMONIA
TOTAL AMMONIA
120
130 140
TIME, days
150
Figure 18. Mixed liquor concentrations of total and free ammonia plus
pH at the oxygen transfer capacity of 520 gms 02/1000 bird-hours
82
-------
QO
00
2.0r
120
130 140
TIME, days
150
160
Figure 19. Dissolved oxygen concentrations in Ditch I at the oxygen transfer
capacity of 520 gms CL/IOOO bird-hours
-------
Z oğ
uj £
o
<^ *ğ
si
o5
UJ CC
o ^
crt U
0)
o
Q O
Z 2 ~
91
101
Figure 20.
Ill
TIME, days
121
131
Dissolved oxygen concentrations in Ditch II at the oxygen
transfer capacity of 520 gms 02/1000 bird-hours
199
209
TIME, doys
219
229
Figure 21. Dissolved oxygen concentrations in Ditch II at the 'oxygen
transfer capacity of 790 gms 02/1000 bird-hours
84
-------
During the second mass balance period, 790 gms 02 per 1000 bird-hours,
removal of organic and total nitrogen was equal (Table 22). No accumu-
lation of inorganic nitrogen occurred and concentrations of NH.-N, NO?-N,
and NO^-N remained near zero throughout the balance period. Mixed liquor
dissolved oxygen concentrations are presented in Figure 21.
Liquid-Solids Separation -
A key aspect of the systems design approach used at Manorcrest was the
removal of residual solids in order to control mixed liquor total solids
(MLTS) concentrations. The settling system did permit maintenance of
MLTS concentrations at levels below 25,000 mg/a and provided equilibrium
conditions to examine the relationship between SRT and treatment efficiency.
However, overall performance of the settling system was not satisfactory.
It was not possible to develop any clear relationship between overflow
rates and removal of solids due to variation in performance.
a_ - Gravitational settling - The poor settling performance was due in
part to the combination of liquid solids separation and sludge storage.
Gasification from denitrification and/or anaerobic processes resulted in
a floating layer of solids and pin floe. Since the settling tank overflow
pipe was 0.6 m (2 ft.) below the liquid surface, the floating solids did
not present any problems with respect to clarification. However, these
floating solids including feathers formed a mat which was extremely dif-
ficult to remove when the tanks were emptied. The pin floes were carried
in the overflow reducing the solids removal efficiency.
Although these problems were significant, observations indicated that
the cause of the poor performance was more fundamental in nature, speci-
fically the liquid-solid separation characteristics of aerated poultry
wastes. Comparison of settling efficiency at two different mixed liquor
total solids concentrations (MLTS) indicated the existence of a relation-
ship between total solids concentrations and settling characteristics.
85
-------
Comparisons of mixed liquor and settling tank overflow total solids con-
centrations at two different MLTS concentrations are presented in
Figures 22 and 23. In both instances, the settling tanks had been in
operation for 3 days prior to the first data point presented. At MLTS
concentrations below 12,000 mg/fc, the total solids concentrations in the
settling tank overflow remained low over the first 20 days of operation
(Figure 22). In contrast at MLTS concentrations above 18,000 mg/£,
settling tank overflow total solids concentrations increased rapidly
(Figure 23).
In order to gain a clearer understanding of the settling characteristics
of aerated poultry wastes, the relationship of settling velocity to MLTS
was examined over a wide range of MLTS concentrations. This study was
conducted at the AWML using aerated poultry wastes from the pilot plant
scale oxidation ditch located in that facility.
The range of MLTS concentrations evaluated in the settling tests was
3000 to 13,000 mg/£. Both flocculent settling and zone settling were
observed. Flocculent settling occurred at MLTS concentrations below
6,000 mg/£. No attempt was made to quantify the flocculent settling
characteristics of the wastewater. At MLTS concentrations greater than
6,000 mg/£, classical zone settling occurred with a distinct interface
between the clarified supernatant and the sludge. A typical batch
settling curve is presented in Figure 24. The zone settling velocity
(ZSV) for each batch settling test was determined by calculating the
slope of the steepest portion of the curve as indicated in the Figure.
The combined results of the individual batch settling tests are presented
in Figure 25. As shown, ZSV decreased dramatically at MLTS concentrations
greater than 11,000 mg/Ji. These values were less than 1 cm/hr. The
data exhibited significant scatter. Possible explanations for the
scatter are wall effects since a 1000 ml graduated cylinder was used
for the tests and the absence of stirring to break up bridged solids that
may have occurred during settling.
86
-------
MIXED LIQUOR
SETTLING TANK
OVERFLOW
61 66
TIME, days
Figure 22. Comparison of mixed liquor and settling tank overflow total
solids concentrations at MLTS concentration below 12,000 mg/a
_ 22,000r-
MIXED LIQUOR
SETTLING TANK
OVERFLOW
94 99
TIME, days
Figure 23. Comparison of mixed liquor and settling tank overflow total
solids concentrations at MLTS concentration above 18,000 mg/4
87
-------
00
00
E
o
MIXED LIQUOR TOTAL SOLIDS
CONCENTRATION, 9565 mg/l
10
20
30 40
TIME, minutes
50
Figure 24. Typical results from a batch settling test, aerated poultry wastes
-------
160
w 140
.c
e
O
*
H
O
O
LJ
2
O
N
120
100
80
z 60
_i
I-
ui 40|
en
20
I
I
1
I
5,000 5,000
7,000
9,000
11,000
MIXED LIQUOR TOTAL SOLIDS
CONCENTRATION, mg/l
13,000
Figure 25- Zone settling velocity versus total solids concentration
in aerated poultry wastes
89
-------
The settling data collected also permitted the calculation of sludge
volume indices (SVI) at various MLTS concentrations. Total solids
were used in place of total suspended solids in the calculation. The
lowest SVI's were observed between 6,000 and 11,000 mg/£ MLTS (Figure 26).
The results from both the SVI and ZSV determinations indicated that the
range for optimum gravitational liquid-solids separation of aerated
poultry wastes lies between 6,000 and 11,000 mg/£ MLTS.
JD - Screening and centrifugation - Two mechanical liquid-solid separation
devices were examined as alternatives to gravitational settling. They
were a basket type centrifuge and a vibrating screen. Since both items
were obtained on a loan basis from the respective manufacturers, the
extent of these tests was limited.
The centrifuge tested was a DeLaval 30.5 cm (12 in.) basket type unit.
The unit was operated 2750 rpm and the flow rate was 3.8 £ per minute
(1 gal. per minute). The test results are presented in Table 24.
Table 24. RESULTS OF CENTRIFUGE TEST
Total solids
Volatile solids
Influent,
mg/£
14,150
9,078
Effluent,
nig/*
3,530
1,652
%
Removal
75.0
81.8
Under flow
solids, %
15.8
11.7
The underflow solids were semi-solid, and it appeared that they could be
handled with solid manure handling equipment.
The vibrating screen tested was a 46 cm (18 in.) Sweco Vibro-Energy
Separator that can be operated in a single or multiple stage mode with
screens placed in series. The vibrational motion of this unit is derived
90
-------
100
90
80
x
LJ
O
LJ
O
O
D
_l
V)
70
60
LJ __
5 50
O 40
30
20
3000 5000 7000 9000 11000 13000
TOTAL SOLIDS CONCENTRATION, mg/I
Figure 26. Sludge volume Index versus total solids concentration
in aerated poultry wastes
91
-------
from the interaction of suspension springs and rotating weights.
Figure 27 is a vertical section of the unit.
Three different mesh size screens; 200, 250, and 325 were evaluated.
In addition to the screen size, the Sweco unit has two other operating
variables. One is the number of additional weight plates attached to
the lower motor weight. This controls the vertical movement of the
material as it travels horizontally across the screen cloth. The manu-
facturer recommends several plates for heavy, coarse, or wet material.
The maximum number, four, were used throughout this study. The second
variable is the degree of lead of the bottom with respect to the top
motor weight, i.e., the lead angle. This controls the horizontal
pattern of travel across the screen. Examples of average material travel
patterns are presented in Figure 28.
The initial phase of this study investigated the relationship of lead
angle to performance for a constant screen size, 200 mesh. The test
results are presented in Table 25. At the higher lead angles, 45°
and 60°, flow was restricted to a maximum of 6.7 a per minute. When
flow was increased beyond this amount, the rate of solids loading to
the screen was greater than the rate of solids discharge. The result
was an accumulation of solids which blocked the flow of filtrate through
the screen. Therefore, a major portion of the flow was short circuited
through the solids discharge spout (Figure 27). As the lead angle was
decreased, maximum permisible flow rate increased. At all lead angles,
the total solids content of the cake decreased with increasing flow
rates. Subsequent tests were conducted at a constant lead angle of 0°
and flow rate of 13.3 £ (3.5 gal.) per minute.
The objectives of these subsequent tests were to examine the relationships
of total suspended solids (TSS) concentrations to performance and the
effect of screen size on TSS removal. Performance was evaluated in terms
of TSS removal and the dry matter content of the separated solids. The
results of these tests are presented in Table 26. Single stage screening
92
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FEED
BUCKET TYPE
VELOCITY REDUCER
INTERCHANGEABLE
SIEVE -
LIQUID DISCHARGE
SPOUT-
SOLIDS
DISCHARGE
SPOUT
Figure 27.
Vertical section through a basic single deck, 18 inch
Sweco Vibrating Screen Separator
0° Lead-average material
may be thrown straight
and may give insufficient
separation
40° Lead-may give average
dry material maximum
efficient screening pattern
Maximum lead may keep oversize
material from being discharged
and assist in receiving maximum
thruput of minus material which
tends to "ball"
15° Lead-average material
may begin to spiral
60° Lead-may give average
wet material maximum
effecient screening pattern
DISCHARGE
SPOUT
ROPE OF
MATERIAL
SCREEN SURFACE
Roping pattern on the screen
Figure 28. Illustration of average material travel on the screen
93
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Table 25. RELATIONSHIP BETWEEN LEAD ANGLE AND PERFORMANCE
200 MESH SCREEN, 0.074 mm
Average Lead Flow Rate,
Influent Angle Ji/min.
Total Suspended
Solids Concentration,
1970 60° 2.5
4.0
6.7
45° 2.5
4.0
6.7
2800 30° 5.7
13.3
4890 15° 2.0
13.3
0° 4.0
8.0
13.3
Percent Removal
Total Suspended
Solids
23.5
24.8
17.6
29.3
34.0
22.1
37.1
36.2
34.8
34.5
27.4
22.9
24.8
Cake
Percent Total
Solids
11.9
10.6
9.0
11.7
10.7
9.0
13.3
10.7
12.2
11.4
13.2
11.5
11.1
-------
Table 26. RESULTS OF SINGLE AND TWO STAGE SCREENING TRIALS
Feed Solids
Concentration, mg/£ .
Screen
Mesh No.
1 Stage
200
Size, Total
mm. Solids
0.074 4,512
5,228
9,575
23,625
2 Stage
200
plus
250
200
plus
325
0.074 9,:
0.062
0.074
0.044
525
Total
Suspended
Solids
1,974
2,425
5,015
17,676
4,763
Total
Suspended
Solids, mg/&
1,302
1,811
3,865
13,364
3,748
3,678
3,758
3,249
Filtrate
% Removal of
Total Suspended
Solids
34.0
35.4
22.9
24.8
21.3
22.8
21.1
31.8
Cake
Dry Matter
Content
Percent
10.6
10.2
11.5
11.1
15.4
11.0
15.4
2.7
-------
trials were conducted with 200, 250, and 325 mesh screens over a range
of TSS from 1,302 to 13,364 mg/fc. Performance of the 250 and 325 mesh
screens individually were unsatisfactory since the flow was limited to
low rates with these screens. The results from the single stage trials
(Table 26) indicate that removal of TSS decreased as influent TS and TSS
concentrations increased. The separated solids consisted of coarse
materials such as seed coats, feed, and feather parts. The cake was
semi-solid similar to wet sawdust and appeared amenable to handling as
a solid.
Two stage screening tests were conducted using combinations of 200 plus
250 and 200 plus 325 mesh screens in series. The addition of the 250
mesh screen only nominally increased TSS removal (Table 26). Although
the dry matter content of the cake from the 250 mesh screen, 11.0 percent
was similar to that of the separated solids from the single stage 200
mesh tests, the physical appearance differed. The 325 mesh screen in-
creased TSS removal by 11.2 percent over the first stage 200 mesh screen
with a total TSS removal of 31.8 percent.
PROBLEMS IDENTIFIED
Introduction
One of the objectives of this study was to identify problem areas in
the design and operation of aeration systems for poultry wastes. During
the course of the investigation, several problems were encountered.
They include equipment breakdowns, sedimentation of solids in both ditches,
foaming, feathers, and excess water leakage from the bird watering system.
The first two items placed constraints on the evaluation of the system
performance.
Equipment Problems
The major equipment problem involved the Thrive Centers cage rotor in
Ditch II. The most frequent problem was failure of connection 1 to 2
between the paddle bar and wheel plate assembly (Figure 29).
96
-------
BEARING
SO
WHEEL PLATE
ASSEM
CONNECTING
BRACKETS
BOLT
PADDLE BAR
Figure 29. Assembly diagram of a Thrive Center Cage Rotor
-------
Two types of failure occurred. They involved shearing of the connecting
brackets, which were flat plates butt welded to the wheel plate assembly,
and failure of the connecting bolt. The initial type of failure was shear-
ing of the connecting brackets.
Following the third failure of this type, it was concluded that the bracket
shear problem was not an isolated problem but involved inadequate design.
Upon informing Thrive Centers, Inc. of the difficulties, they replaced both
wheel plate assemblies. On the new units, the flat plate bracket was re-
placed by an angle iron bracket. At this point, shearing of the brackets
was replaced by failure of the connecting bolts. The cause of the bolt
failures is not clear. However, it may be related to over tightening of
certain bolts during reassembly following replacement of the wheel plates.
The problem of bracket shearing was due to a design change by Thrive which
has been rectified. Bolt failure appears to be isolated to the Manorcrest
unit. Discussion with other owners of the Thrive rotors indicates that
this is not a common problem. However, these and other problems such
as drive belt breakage caused aeration to be interrupted for periods
exceeding 24 hours, on eight separate occasions during the 19 months of
system monitoring.
The bearings of both aerators were replaced due to deterioration following
the first eight months of operation. During this period, lubrication was
performed weekly. A daily lubrication schedule was instituted following
bearing replacement. No further problems were encountered in the remainder
of the study period.
Sediment Accumulations
The accumulation of a significant quantity of solids in the bottom of
both oxidation ditches was a major problem in this study. As the accumu-
lation of sediments increased, the velocity of the mixed liquor decreased
98
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to the point of a complete stoppage of circulation. This occurred
several times in Ditch II requiring the complete removal of the ditch
contents. Conversely, circulation in Ditch I was always maintained
although velocity did decrease with sediment accumulation.
Sediment accumulations were first measured in April 1974, when Ditch II
velocities were approaching zero. At this time, Ditch II had been in
operation for 8 months. A profile of the measured sediments is presented
in Figure 30. Based upon the sediment measurements, it was calculated
that 30 percent of the ditch liquid volume was occupied by settled
solids. At this time, it was necessary to empty the ditch to facilitate
the replacement of the Thrive rotor wheel assemblies. At this time,
accumulated sediments were removed. This permitted reestablishment of
ditch circulation through the end of the laying cycle, August 1974.
Sediment accumulation was measured in Ditch I after 10.5 months of opera-
tion. The sediment profile is presented in Figure 31. The volume of
accumulated solids was 22 percent of the liquid volume. This indicates
that Ditch I had a lower rate of solids deposition since the accumulated
quantity was less than that in Ditch II and period of operation was
longer.
Prior to the beginning of the second year of operation, the accumulated
sediments in both ditches were completely removed. The liquid depth was
reduced from 50.8 cm (20 in.) to 33 cm (13 in.). The objective was to
reduce the cross-sectional area of the liquid. It was assumed that with
a constant aerator depth and therefore pumping capacity, the result would
be a substantial increase in mixed liquor velocity, since the cross-sec-
tional liquid area was reduced by 35 percent. This reduced the mixed
liquor volume from 105,980 £ (28,000 gal.) to 68,887 a (18,200 gal.).
Initial velocities under these conditions were 0.36 m/sec (1.2 ft/sec)
and 0.43 m/sec (1.4 ft/sec) for Ditches I and II. A comparison of
initial velocities for years I and II are presented in Table 27.
99
-------
o
o
- io
FLOW
40
40
80
240
120 160 200
DITCH LENGTH, ft.
Figure 30. Sediment profile in Oxidation Ditch II, 1973-74
FLOW
280
320
80
120 160 200
DITCH LENGTH, ft.
240
280
320
Figure 31. Sediment profile in Oxidation Ditch I, 1973-74
-------
Table 27. COMPARISON OF INITIAL DITCH VELOCITIES AT
VOLUMES OF 68,887 £ AND 105,980 £
Year I (105,980 £) Year II (68,887 a)
Ditch I
Ditch II
0.26 m/sec.
0.38 m/sec.
0.36 m/sec.
0.43 m/sec.
The problem of sediment accumulation and reduced mix liquor velocity
reoccurred under the new operating conditions. Figures 32 and 33 show
the profiles of the settled solids at two points in time in each ditch.
The profiles indicate a pattern of initial solids accumulation immediately
downstream from the aeration unit followed by deposition further down-
stream. It was necessary to again remove the sediments from Ditch II
after 5 months of operation since the mixed liquor circulation had
ceased at that time.
Composite samples of the accumulated solids were taken from each ditch
when the last sediment measurements were made. The samples were analyzed
to characterize their composition. The results of the analyses and
comparison to raw manure are given in Table 28.
Table 28. SEDIMENT CHARACTERISTICS
% TS
y VS
7° TS
mg COD
mg FS
Ditch I
30.3
30.6
729
Ditch II
19.4
49.0
1760
Raw Manure,
1974-1975
--
72
2544
101
-------
FLOW
o
tc
AFTER 2MONTHS of OPERATION
AFTER 4MONTHS of OPERATION
Q.
LJ
Q
LU
S
Q
Ixl
CO
120 160 200
DITCH LENGTH, ft.
Figure 32. Sediment profile in Oxidation Ditch I, 1974-75
240
280 320
FLOW
AFTER 2 MONTHS of OPERATION
A AFTER 4 MONTHS of OPERATION
120 160 200
DITCH LENGTH, ft.
240
280
320
Figure 33. Sediment profile in Oxidation Ditch II, 1974-75
-------
The differences in the sediment characteristics of the two ditches
appear to be related to mixed liquor velocities prior to sampling. The
velocity of Ditch II was approaching zero at the time of sampling. Raw
manure was accumulating on top of the initial sediment layer and was
included in the sample. This could account for the higher percentage
of volatile solids and the larger COD to fixed solids ratio. The
analytical results indicate that sediment in Ditch I consisted primarily
of inorganic material.
Foaming, Feathers, and Excess Mater
Foaming problems were encountered during this study. However, these
problems were of a nuisance rather than a serious nature. No endanger-
ment of the animals or workers in the building ever occurred. Excessive
foaming occurred in Ditch II but not in Ditch I. Therefore, inadequate
oxygen supply was discounted as the cause of foaming. Ditch I was a
minimally aerated system.
The cause of the foaming problem appeared to be related to the movement
of the foam around the ditch. Foam was usually present on this surface
of Ditch I in a thin layer or in patches. However, surface velocity
was always adequate to maintain continuous movement. Therefore, a
constant cycle of foam generation and breakdown by the aerator occurred.
The foaming problems encountered in Ditch II appeared to be related to
the interruption of this cycle due to a stoppage in the movement of the
foam layer. The principle factor responsible for cessation of foam
layer movement was reduction in mixed liquor velocity due to sediment
accumulation. Because of minimal friction between the foam layer and
the mixed liquor surface, the ditch sidewalls were adequate to stop
foam movement as mixed liquor velocities decreased. Therefore, the
cycle of foam generation and breakdown was interrupted. Generation of
foam continued with the resulting accumulation causing an overflow
onto the service aisles on several occasions. Used motor oil was added
103
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to Ditch II to control foam during the first year. When the liquid
depth was decreased to 33 cm (13 in.) at the beginning of the second
year, freeboard increased to 41 cm (16 in.). This was adequate to
contain the foam, and oil additions were not necessary.
The role of the accumulated sediments to the foaming problem is unclear.
Both ditches had significant accumulations of these sediments, but
foaming problems only occurred in Ditch II.
Feathers were another problem. Initially, the feathers were allowed to
move through the overflow standpipes into the settling tanks. However,
they accumulated in the first settling tank and formed a floating mat.
On several occasions, this mat blocked flow through the standpipes.
When the settling tanks were emptied, it was necessary to remove the
feathers manually using rakes and shovels.
To eliminate the reoccurrence of this problem, baffles were installed
around the standpipes to exclude the feathers from the settling tanks.
This was possible since most of the feathers were on the surface.
However, this resulted in the accumulation of large mats of floating
feathers which would be stopped by obstructions such as the overflow
standpipes or the propeller housing in Ditch I prior to its removal.
It was necessary to remove these mats with a rake. This was done in
response to accumulation which varied from daily to weekly depending
on the rate of feather loss.
Excessive leakage from the bird watering system was greater than
evaporative losses. This caused a small overflow from the settling
tanks onto the corn fields behind Building No. 1. The frequency and
quantity varied due to variation in amount of leakage and changes in
evaporative conditions. The watering system consisted of individual
watering units known as Hart Cups. Figure 34 is a schematic drawing of
a Hart Cup. Operation of the on-off valve, which consisted of a rubber
104'
-------
RUBBER
SEAL.
A
VALVE SEAT
Figure 34. Cross section of a Hart Cup
105
-------
seal and seat, is dependent on water pressure. Variations in water
pressure caused the units to overflow. Since dilution water was
necessary to liquify the manure with the previous management system,
leakage was desirable. Therefore, no pressure regulators had been
used. Following recognition of the problem, pressure regulators were
installed. This reduced but did not completely eliminate the problem.
Overflow of the Hart Cups also occurred when particles, primarily feed,
lodged between the rubber seal and seat. This held the valve open
causing a drop in water pressure in the line. Then other cups would
overflow due to the drop in water pressure. Although the cups were
checked daily and repaired when necessary, this was not adequate to
control the excess leakage.
CAPITAL AND OPERATING COSTS
One of the study objectives was the evaluation of the economic impact
of utilizing aeration systems for poultry wastes. In keeping with this
objective, the major capital and operating costs were determined.
Capital and operating costs were not constant due to differences in
aeration equipment and methods of operation. Each situation was examined
individually.
The capital costs for the two oxidation ditches included costs for the
modification of the existing pits, settling and storage tanks, and
aeration equipment. The modification costs were the labor and materials
for the conversion of the existing manure collection pits into two
oxidation ditch channels and the equipment installation including
necessary electrical modifications. Settling tank costs included labor
for excavation, tank placement, and backfilling. The cost of the industrial
propeller originally used in Ditch I was excluded since it was found to
be ineffective and was removed from the system.
106
-------
Table 29 contains the initial cost, estimated useful life, and annual
cost for each capital item. These figures were used to determine the
total and annual capital costs for each oxidation ditch which are
presented in Table 30. Construction costs were equal for each ditch.
The difference in aerator costs is responsible for the overall differences
between the two ditches.
The operating costs examined included power, maintenance and repairs,
and taxes and insurance. Power costs varied with the level of oxygen
transfer and each situation was examined independently. The numerous
mechanical problems encountered in this study made estimation of
maintenance and repair costs extremely difficult. The number of
mechanical problems encountered in this study do not appear to be
representative. Therefore, maintenance and repair costs were estimated
at 2 percent of the total initial investment for each ditch. This appears
reasonable since daily maintenance was minimal consisting only of bear-
ing lubrication which was done during feeding or egg collection. Yearly
bearing replacement has been shown to be the major repair item in other
experiences with similar systems. Taxes and insurance were estimated
to be 3 1/2 percent of the annual capital cost.
Energy costs at the three different levels of oxygen transfer examined
in this study are presented in Table 31. A summary of the overall
operating costs are presented in Table 32. As shown, energy is the
major operating cost, comprising 60 to 73 percent of total operating
costs. Differences in maintenance and repair costs and insurance and
taxes betweeen the two ditches were small. Problems in the area of
liquid-solids separation precluded a realistic assessment of ultimate
disposal costs.
Table 33 contains a total .cost summary for aeration of poultry wastes
at Manorcrest Farms. As shown, aeration systems are capital intensive .
with capital costs responsible for 58 to 66 percent of total costs
depending on level of oxygen transfer and therefore energy consumption.
107
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Table 29. INITIAL AND ANNUAL CAPITAL COSTS - MANORCREST PROJECT
AERATION SYSTEMS COMPONENTS
Total Cost* Estimated Annual Cost**
Useful Life
Years
Construction
Oxidation Ditches
Settling Tanks
Equipment
Thrive Center
Cage Rotor
Montair Brush
Aerator
8,735 20 958
3,040 20 333
2,120 10 346
1,500 10 244
* 1973 prices
** Amortized at 9 percent per year over the estimated useful life, no
salvage value
108
-------
Table 30. TOTAL AND ANNUAL CAPITAL COSTS FOR THE
MANORCREST AERATION SYSTEMS
Item Ditch I Ditch II
Capital Costs
Total $ 7,388 $8,008
Per 1,000 hens 1,847 2,002
Annual cost per year 890 992
Annual cost/1,000 hens/year 222 248
Cost per dozen eggs* .0111 .0124
*Assumes 4,000 hens per ditch and 20 dozen eggs per hen/yr.
109
-------
Table 31. ENERGY COSTS* FOR AERATION IN RELATION TO
THE LEVEL OF OXYGEN TRANSFER
Level of Oxygen
Transfer Capacity,
gms 02/1000 bird-hrs.
351
520
790 &
815
Ditch Aeration Unit kwhr/ Cost/ Cost/**
No. 1000 hens/yr 1000 hens/yr Dozen Eggs
i
I Brush Aerator 3,328 $ 66.89 $.0033
I Brush Aerator 4,558 91.62 .0046
II Cage Rotor 6,524 131.14 .0067
* Energy cost of $.0201 per kilowatt-hour
**Assumes 4,000 hens per ditch and 20 dozen eggs per hen-year
-------
Table 32. OPERATING COSTS FOK MANORCREST AERATION SYSTEMS
PER 1,000 HENS PER YEAR
Energy Costs
Maintenance and Repairs
Taxes and Insurance
Total
Cost per Dozen* Eggs
Ditch I
Oxygen Transfer
351
66.89
36.94
7.78
111.61
.0056
Capacity,
520
91.62
36.94
7.78
136.34
.0068
Ditch II
Gms 02/1000 bird-hrs.
790 & 815
131.14
40.04
8.68
179.86
.0090
*Assumes 20 dozen eggs per hen-year
111
-------
Table 33. COST SUMMARY OF AERATION OF POULTRY
WASTES, MANORCREST FARMS
Ditch I
Oxygen Transfer Capacity, Gms
Costs/1,000 hens/year
Annual capital
Operating
Total
Costs/dozen eggs*
Annual capital
Operating
Total
351
$ 222
112
$ 334
$.0111
.0056
$.0167
520
$ 222
136
$ 358
$.0111
.0068
$.0179
Ditch II
02/1,000 Bird-hrs.
790 & 815
$ 248
180
$ 428
$.0124
.0090
$-0214
*Assumes 20 dozen eggs per hen-year
112
-------
SECTION VII
DISCUSSION OF EXPERIMENTAL RESULTS
GENERAL
The primary objective of this investigation was to demonstrate and
evaluate the potential of aerobic treatment to reduce the air and water
pollution potential of poultry wastes when employed under commercial
conditions. The concepts used in the design and operation of the Manor-
crest aeration systems were derived from the results of smaller scale
studies. Although the specific goals of odor control, waste stabiliza-
tion and nitrogen management were achieved, overall system performance
was not as perfect as desired. The problems encountered were primarily
related to the physical system design. This identified a shortcoming
in the design approach which was process oriented.
The problems of sediment accumulation and poor liquid solids separation
as well as equipment failures hindered but did not eliminate the demon-
stration of the process design parameters for aeration systems for
poultry wastes..
This section will discuss the results in terms of the process design
concepts employed as well as the physical problems encountered and their
role in overall systems design. Also included is an evaluation of the
economic impact of utilizing aeration systems for waste management in
egg production.
ODOR CONTROL
An objective of this study was to demonstrate the odor control capabilities
of the aeration process. Malodors emanating from ventilation systems
and wastes spread on the land have been a major point of conflict between
egg producers and other rural residents. Elimination of odor problems
was demonstrated in this study.
113
-------
The additional benefit of improved environmental conditions within the
building should also be recognized. The elimination of malodors, flies,
and other vermin greatly improved the working conditions for the people
caring for the birds. This point was frequently cited in discussions
about the study with Manorcrest employees. Similar observations were
made by members of the Cornell Agricultural Waste Management Program
who had visited the site prior to conversion to the aeration systems.
The high rise house, Building No. 2, provided some basis for comparisons.
Although environmental conditions in that building were superior to the
anaerobic liquid manure system previously in Building 1, they were not
as good as the conditions in Building No. 1 with aeration. Both employees
and visitors to the demonstration site commented on this fact. The
additional benefit of improved working conditions appears to be signi-
ficant in that poor working conditions due to odors, etc., are often
identified as a major problem area in attracting good farm labor.
DESIGN PARAMETERS
The relationship between oxygen transfer and mixed liquor total solids
(MLTS) concentration formed the basis for the Manorcrest aeration systems
design. The objective was to maximize oxygen transfer by restricting
the MLTS concentration to a maximum of 20,000 mg/£. This would maintain
a values at or approaching unity. This required removal of residual
solids and the use of SRT as a design and operational parameter.
Although the design SRT was based on maintenance of nitrifying conditions,
relationships between the degree of stabilization and SRT in aerobically
treated poultry wastes had been previously developed (11,16). Variations
in SRT due to inconsistent solids removal permitted confirmation of the
earlier observations. The results from this study have been presented
in Figure 12 through 13. These results were combined with results obtained
in a previous study and are presented in Figures 35 through 38.
114
-------
_J
o
LJ
or
0s-
50
40
30
20
10
0
A
^^^'*
A^>- A*" * A
THIS STUDY
_ A MARTIN et al (16)
1 1
0 10 20 30 40
F
O
LJ
or
SRT, days
igun
70
60
50
40
30
20
10
C
2 35. Observed relationship between SRT and removal
of total solids in aerated poultry wastes
A
O^M^
* ^^^^
"A A
A
THIS STUDY
A MARTIN et al ( 16)
^mmmm
1 1
) 10 20 30 40
SRT, days
Figure 36. Observed relationship between SRT and removal
of volatile solids in aerated poultry wastes
115
-------
60
50
§
O 40
UJ
cc
30
20
10
THIS STUDY
* MARTIN etal (16)
10 20 30
SRT, days
40
Figure 37. Observed relationship between SRT and removal
of COD in aerated poultry wastes
80
70
5 60
£ 50
40
30
10
THIS STUDY
MARTIN et ol (16)
1
20
SRT, days
30
40
Figure 38. Observed relationship between SRT and removal
of organic nitrogen in aerated poultry wastes
116
-------
There is good agreement between the results of these separate studies.
These data serve to define the relationship between removals of total
solids, volatile solids, COD, and organic nitrogen and SRT and show
that removal increases with SRT. Therefore, regulation of SRT provides
a mechanism for control of the degree of stabilization to meet specific
objectives. With proper design, it should be possible to limit oxygen
requirements necessary to meet exerted carbonaceous oxygen demand and
provide odor control. Oxygen requirements for nitrogenous oxygen demand,
if nitrification or nitrification-denitrification are part of the overall
stabilization objectives,also could be developed using a similar approach.
Oxygen supply was always greater than the exerted carbonaceous oxygen
demand in this study (Table 19). No odor problems were encountered
even at the lowest level of oxygen transfer, 350 gm 02/1,000 bird-hours.
However, the rate of oxygen transfer exceeded the rate of COD removal
by 25 percent. Satisfactory odor control has been reported when the
estimated rate of oxygen transfer exceeded COD removed by only 2
percent (16). That study also involved the evaluation of aeration of
poultry wastes under commercial conditions. Based upon the combined
results presented in Figure 37, reduction of SRT from 36.5 to 30 days
should reduce oxygen requirements, expressed as COD removed for odor
control, by about 19 percent. As shown in Figure 38, the exerted nitroge-
nous oxygen demand from ammonification of organic nitrogen will also
decrease with decreases in SRT.
Due to the interrelationships between SRT and waste stabilization as
well as those between SRT and nitrification, it is not possible to
specify a single SRT for all aeration systems. Individual situations
and waste management objectives must be considered. However, the
results of this study (Table 21) and those of a previous study (11)
show that most of the soluble COD is removed at an SRT of 10 days.
Therefore, a minimum SRT of 10 days should significantly reduce the water
pollution potential from soluble carbonaceous compounds. These compounds
117
-------
have the greatest potential for contamination of surface waters via
overland flow. Increased removal of total solids, volatile solids,
and COD can be achieved by increasing SRT beyond 10 days (Figures 35
through 37). Increase in SRT beyond 10 days will increase oxygen
requirements but will also provide a greater degree of waste stabilization.
This may be necessary if storage occurs following aerobic treatment and
odorous end products from anaerobic processes can result from remaining
unstabilized wastes. It was not possible to determine a clear relation-
ship between ma!odors generated from the stored sludge and the degree of
stabilization in this study. It was observed that the nature of the
odors generated during storage differed from those common to untreated,
liquid poultry manure. The intensity of the malodors from the stored
sludge was significantly lower and diffused rapidly. In contrast,
untreated liquid poultry manure continues to be a source of odors for
an extended period of time following field spreading. This comparison
shows that aeration is effective in controlling odors following field
spreading even if storage follows aeration.
If nitrification is desired, provision of an adequate SRT to maintain a
nitrifying population will be the constraining factor in determining
the minimum SRT. The increased SRT for nitrification, particularly at
low temperature, will increase oxygen requirements to meet both the addi-
tional exerted carbonaceous oxygen demand and the nitrogenous demand.
The end result will be an increased degree of stabilization as well as
nitrification.
NITROGEN
The decision to remove or conserve nitrogen from poultry wastes is
directly related to the opportunities to recycle this element through
crop production. Although animal production not accompanied by cropping
activities has the most stringent nitrogen removal requirements, the
Manorcrest system design identified the need for nitrogen removal when
crop production is limited.
118
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The potential for nitrogen removal is limited by the ammonification
process which is a function of SRT (Figures 13 and 38). The degree of
nitrogen removal via ammonia stripping in oxidation ditches was shown
to be substantial when nitrification was inhibited by the lack of available
oxygen. Therefore, it appears that inhibition of nitrification is not
an effective method of nitrogen conservation in aeration systems for
poultry wastes. In addition, the disadvantages of the odor of ammonia
in the building in the case of an in-house oxidation ditch and the potential
adverse environmental impact from the discharge of ammonia into the
atmosphere should be recognized.
It is necessary to meet the total exerted carbonaceous and nitrogenous
oxygen demand to achieve nitrification. Based upon the mass balance
results, it was calculated that the total exerted oxygen demand was
514 gms 02/1000 bird-hours. Oxygen transferred was 520 gms 0^/1000
bird-hours. This demonstrates the validity of the method used to cal-
culate oxygen demand, Equation 8. Since the oxygen supply was equal to
the demand, no residual dissolved oxygen should have been present in the
mixed liquor. As shown in Figure 19, residual dissolved oxygen concen-
trations were minimal during this period.
The potential for nitrogen conservation by maintenance of an adequate
residual dissolved oxygen concentration could not be evaluated due to
opportunities for denitrification in the settling tanks. At the highest
levels of oxygen transfer, oxygen transfer capacity was 142 and 153
percent of the total exerted demand based on calculations from the mass
balance results. This indicated that residual dissolved oxygen concen-
trations should have been maintained. Dissolved oxygen measurements,
(Figures 20 and 21) confirm this conclusion. However, results of pilot
plant studies (20) have shown that a 30 percent loss of nitrogen via denitri-
fication can occur even at high dissolved oxygen levels. It is necessary to
examine the value of the nitrogen conserved in comparison to the additional
equipment and energy costs to determine the feasibility of this approach.
119
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The observed removal of nitrogen via nitrification-denitrification
even at relatively long SRT's (Table 22) demonstrated that the addition
of an organic carbon source such as methanol is unnecessary for deni-
trification with these wastes. In comparison, the addition of an organic
carbon source is commonly required for denitrification of nitrified
domestic and industrial wastes.
t v
The observation of NO^-N on the 14th day of operation of Ditch II, demon-
strated that seeding is not necessary to introduce nitrifying organisms
into these systems. However, nitrification patterns indicating inhibi-
tion were observed on several occasions (Figures 14 and 15). Un-ionized
ammonia (NH-) and un-ionized nitrous acid (HN02) could have been the
inhibitory compounds. Inhibition of nitrification by these compounds
in poultry and other wastewaters has been reported (55). Free ammonia
concentrations from 0.1 to 150 mg/£ were noted to be inhibitory. Free
ammonia inhibition to Nitrobacter occurred at concentrations lower than
those that inhibited Nitrosomonas. The inhibitory range for free nitrous
acid was 0.2 to 2.8 mg/£.
During the first 14 days of operation, the free ammonia concentration
reached a maximum of 21.3 mg/£. This is well within the above inhibitory
range. Complete inhibition did not occur. However, comparison of NO~-N
and NO--N concentrations indicates that the inhibition to Nitrobacter
was greater than that to Nitrosomonas. With the accumulation of nitrite,
free nitrous acid levels increased and reached a maximum of 2.2 mg/£ on
day 42 which is also well within the suggested inhibitory range.
The accumulation of NO^-N affected system performance in several ways.
First, complete nitrification did not occur. Significant mixed liquor
ammonia residuals remained (Figures 14 and 15). It was observed that
residual dissolved oxygen levels increased with increased NCL-N concen-
trations (Figure 20). This indicates a reduction in exerted oxygen demand
as N0~N concentrations increased.
120
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The results of this study demonstrates that it is not necessary to seed
these systems in order to introduce nitrifying organisms. However, it
may be desirable to prevent an initial ammonia accumulation and the
resulting free ammonia inhibition. This would, in turn, prevent the
free nitrous acid inhibition from developing.
LIQUID-SOLIDS SEPARATION
The process design concepts of a controlled mixed liquor total solids
concentration and SRT are dependent on the removal of residual solids.
Continuous dilution does not appear practical and an effective mechanism
for liquid-solid separation is required. This study examined three alter-
native approaches; gravitational settling, screening, and centrifugation.
Gravitational Settling
It does not appear that the poor performance of the gravitational liquid
solids separation system at Manorcrest is a true indicator of the potential
of this approach. The zone settling velocity studies suggest that at
MLTS concentrations below 11,000 mg/£, aerated poultry wastes have good
settling characteristics. Therefore, this approach should not be entirely
discounted. However, it is clear that the clarification and storage
functions should be separated to prevent solids flotation in the clarifi-
cation unit due to gas production from denitrification and other anaerobic
processes.
In order to access feasibility in terms of clarifier size requirements,
preliminary surface area requirements based on the ZSV test were calcu-
lated. The design approach presented by Lawrence (56) which is based
upon the batch flux method (57) was used. The clarifier surface area
2 2
requirements were calculated to be 929 cm (1 ft ) per 1000 birds. The
design conditions were as follows:
Mixed liquor total solids concentration - 8,000 mg/Ji
Solids retention time - 15 days
Underflow solids concentration - 70,000 mg/Ğ.
Flow through the clarifier - 2440 A/day
121
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This indicates that a large clarification unit would not be required and
that surface area was not an independent limiting factor in the Manorcrest
settling units.
Using the specified design conditions, sludge production was calculated
to be 287 a per 1000 birds per day (76gal./1000 birds/day). The volume
of sludge requiring ultimate disposal would be 104 a per bird per year
(28gal./bird/yr). Assuming the use of a 9462 £ (2500gal.) manure spreader
and an estimated time requirement of 30 minutes per load for loading,
transportation, and spreading, the estimated time required to dispose of
the yearly sludge production from 1000 birds would be 5.5 hours per year.
Caution should be used in utilizing the zone settling velocity results
reported here as a basis for design. Further investigation is warranted
to confirm these preliminary results and evaluate the effects of variation
in methods of treatment system operation before using the reported data
for actual design.
Screening and Centrifugation
The results of the screening tests indicate that this process has only
limited potential for liquid-solids separation in aerated poultry wastes.
The major problem is that the mixed liquor suspended solids are very
small. The results of the 200 mesh screening test indicated that 60 to
80 percent of the suspended solids were less than 0.074 mm in diameter.
Based upon sieve analyses of fresh poultry wastes, 49 percent of the manure
solids were reported (58) to be finer than 0.074 mm. Therefore, it appears
that aerobic treatment changes the particle size distribution in these
wastes. This fact is important not only with respect to screening but
also to gravitational settling and possibly other separation processes.
A possible application of screening would be as the first step before
aeration where it would be desirable to handle coarse solids separately.
122
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Another possibility would be removal of coarse solids following aeration
in a batch system. This could increase the time period to reach a
selected maximum mixed liquor total solids concentration and thus increase
storage time by 15 to 30 percent.
The centrifuge test results (Table 24) indicate that this process is
capable of a high degree of solids removal from oxidation ditch mixed
liquor. Also, it results in a concentrated sludge which can reduce the
volume of material requiring ultimate disposal in comparison to direct
disposal of mixed liquor. The supernatant can be recycled back into the
aeration systems. Production of thickened solids containing 16 percent
total solids would reduce sludge volume to approximately that of the
original raw waste. This best can be understood by considering the follow-
ing example. Fresh poultry manure contains roughly 25 percent total
solids. If biological solids destruction occurred without dilution for
aeration, 36 percent total solids destruction would result in the reduc-
tion in total solids to 16 percent. This is without any dilution to
increase volume. Therefore, following dilution for and solids destruction
during aeration, removal of dilution water by centrifugation to attain
a sludge total solids concentration of 16 percent would result in a
waste volume equal to the original volume of the raw waste. This
suggests that increased waste volume requiring ultimate disposal is not
necessarily a characteristic of aeration. This would serve to overcome
a commonly cited disadvantage of aeration systems; increase in volume of
the waste material due to dilution.
The tests results suggest that the use of centrifugation for liquid-
solids separation has significant potential. However, due to the
limited extent of the testing, comment on the practicality of the
process is not possible at this time. Factors such as cost and ease
of operation need to be evaluated along with more detailed testing
before the total potential of centrifugation can be realistically
evaluated.
123
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SEDIMENT ACCUMULATION
The problem of sediment accumulation encountered in this study indicates
that the Manorcrest oxidation ditch design was inadequate in the area
of hydraulics. The observed reduction of mixed liquor velocity as
sediment accumulation occurred decreased mixing which is important to
the biological process. Although biological process failure due to
inadequate mixing did not occur, neither ditch was allowed to operate
over an extended time period at mixed liquor velocities approaching
zero. If sediment removal to increase velocity had not occurred, it
appears reasonable to assume that failure would occur due to inadequate
mixing and dissolved oxygen transport. This indicates that there is
an interdependence between process and physical design. In addition,
sediment removal was a time consuming and labor intensive operation.
The cause of the sediment accumulation was inadequate initial mixed
liquor velocity. The accumulation of some sediment was not unexpected
in that oxygen transfer and not pumping capacity was the primary
consideration in aerator sizing. However, the design calculations and
initial velocity measurements for Ditch II compared favorably with the
recommended minimum velocity for oxidation ditches of 0.38 m/sec
(1.25 ft/sec) (21).
Sedimentation was a major problem in both ditches, but it had a greater
adverse impact in Ditch II. Accumulations of sediment were greater
and the secondary effects more pronounced in Ditch II even though
Ditch I had lower mixed liquor velocities. The reason for this
phenomenon is not clear although it appears to be related to the
type of aeration unit. This was the only physical difference between
the two ditches.
Although accumulation of some sediment was not totally unexpected,
it was assumed that the accumulations would reach an equilibrium. It
124
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was theorized that as the sediments reduced the channel cross-sectional
area, velocity would increase until scour occurred. In fact, the
reverse occurred. As sediment accumulation increased, velocity
decreased thereby causing more settling. This process continued
until the velocity approached zero as was demonstrated on several
occasions in Ditch II. Use of the Manning uniform equation for open
channel flow, Equation 20, to describe flow in an oxidation ditch
provides a possible explanation for the effect of the sediments on
mixed liquor velocity.
V , L486 R2/3 sl/2 (2fl)
where V = velocity
N = coefficient of roughness
R = hydraulic radius, cross-sectional area
divided by the wetted perimeter
S = slope
Assuming a constant pumping capacity and therefore a constant equivalent
to the energy line slope, the equation predicts velocity will decrease
as the coefficient of roughness increases and/or as the hydraulic
radius decreases. Sediment accumulations caused both to occur. The
accumulation of 25.4 cm (10 in.) of sediment as occurred in Ditch II
during 1973-74 reduced the hydraulic radius by 41 percent. Assuming
both S and N remained constant, it was calculated that the resultant
velocity reduction would be 29 percent.
Several factors affect the coefficient of roughness in the Manning
equation (59). Included are surface roughness and channel irregu-
larity. Surface roughness is a function of the shape and size of the
grains of material forming the wetted perimeter. A significant difference
should not exist between concrete and poultry manure solids. The
sediment accumulations did significantly increase channel irregularity
125
-------
as shown in Figures 30 through 33. Irregularity can increase the
value of N as much as 0.02 above the value for a smooth channel (59).
Assuming an initial value of N of 0.016 for a concrete channel and an
increase of 0.02 for irregularity, the effect of the increase coefficient
of roughness and decreased hydraulic radius was calculated for Ditch II.
The results of this calculation predicted that the initial velocity of
0.38 m/sec (1.25 ft/sec) would decrease to 0.12 m/sec (0.39 ft/sec)
which agrees reasonably well with observed performance. The problem
with the original theory, which assumed that scour would cause sedi-
ment accumulations to reach an equilibrium, lies in the failure to
recognize that friction losses are not constant.
It is clear that sedimentation in oxidation ditches should be prevented.
Therefore, mixed liquor design velocities in these systems should
equal or exceed the scour velocity necessary to keep the heaviest
manure particles in suspension. The scour velocity for poultry manure
was calculated to be 0.53 m/sec (1.74 ft/sec) using the following
relationship:
where Vu = horizontal velocity that will produce scour
n
s = specific gravity of particles
d = diameter of particles
k = constant dependent on type of material
being scoured
f = Darcy - Weisbach friction factor
The values used in this calculation and their sources are as follows:
s = 2 gms/cm3 (58)
d = 1.19 mm maximum (58)
126
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k = 0.06 (60)
f = 0.02 (60)
This indicates that the currently recommended minimum design velocity
of 0.38 m/sec (1.25 ft/sec) is not adequate for poultry wastes.
This conclusion has a significant impact on the design of these
systems. Analysis of results has shown that the Thrive rotor's oxygen
transfer capacity was excessive in comparison to the combined carbona-
ceous and nitrogenous oxygen demand. However, the results of this
analysis also indicate that the unit was under-sized in terms of pump-
ing capacity. Two methods of increasing pumping capacity exist. They
are increasing the size of the aeration unit or using a supplemental pumping
device. Both solutions will increase capital and operating costs and
may make aeration economically unattractive.
An alternative solution may lie in improvement of the hydraulic design
of oxidation ditch channels to reduce friction losses, as suggested by
Simons (61). This would result in velocity increases without increasing
energy input. Opportunities exist to reduce friction losses through
improvement of cross-section channel geometry and the geometry of the
semi-circular curves connecting the two linear channels. As can be seen
in the Manning equation, increasing the hydraulic radius will increase
velocity. This can be achieved by decreasing the wetted perimeter in
relation to the liquid cross-sectional area. However, the potential for
increasing velocity by this approach is small.
Based upon a comparison of velocity in Manorcrest Ditch II and an oxida-
tion ditch discussed by Windt, et al. (62), it appears that significant
increases in velocity at a fixed energy input can be achieved by in-
creasing the radius of curvature of the semi-circular connecting channels.
Details of both ditches are presented in Table 34. Although volume per
127
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Table 34. COMPARISON OF THE PHYSICAL DETAILS OF
MANORCREST DITCH II AND AN OXIDATION
DITCH DISCUSSED BY WINDT, et al
Manorcrest Oxidation Ditch'
Ditch II Discussed by
Windt, et al. (62)
Length of straight
channel section
Channel width
Liquid depth
Radius of curvature
of senri -circular sections
Volume
Rotor
Rotor length
Immersion depth
Volume per unit
rotor length
Velocity
39.6 m
2.3 m
51 cm
1.6 m
106 m3
Thrive H-805
r
1.7 m
13 cm
62.4
0.38 m/sec
27.7 m
2.4 m
56 cm
3.8 m
93.5 m3
Thrive H-805
1.7 m
15 cm
55
0.61 m/sec
128
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unit length of rotor and therefore energy input was less in the Manorcrest
ditch, it does not appear that this factor alone is responsible for the
significant difference in liquid velocity.
The greatest geometrical difference between the two ditches was the
radius of curvature of the semi-circular sections. In a discussion of
energy loss resulting from curve resistance, Chow (59) states that the
coefficient of curve resistance, f , is a function of several factors.
\f
They are:
R = Reynolds number
y/b = ratio of liquid depth to channel width
a/1800 = ratio of angle of curvature to 180°
r /b = ratio of radius of curvature to channel width
\f
Assuming a constant velocity and therefore Reynolds number, the only
parameter that varies significantly between the two ditches is rc/b.
The value of this ratio is 0.7 for the Manorcrest ditch and 1.6 for the
oxidation ditch discussed by Windt. The effect of this difference on
f can not be calculated. However, experiment results reported by Shukry
w
(63) showed a decrease in f from 0.91 to 0.32 when r /b increased from
0.5 to 1.0. Values of the other parameters in the study where:
R = 7.5 x 10"4
y/b = 1
a/1800 = 0.5
While this result does not directly apply to the comparison under
consideration, it does illustrate the effect of the radius of curva-
ture in a nonlinear channel on f . The effect of f on energy loss due
c "-
to curve resistance in terms of velocity head can be expressed as follows:
*f - fc £ <22)
129
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where hf = velocity head
V = mean velocity in the section
g = acceleration due to gravity
It can be seen that as f increases, hf to maintain a constant velocity
\* *
also increases.
Unfortunately, precise relationships concerning flow in nonlinear open
channels have not been defined. However, it appears that velocity in
oxidation ditches can be increased without increasing energy input by
improving hydraulic design. This suggests that the current practice
of adapting oxidation ditches to animal housing patterns such as placing
channels below cages may need revision.
FOAMING AND EXCESS WATER
As indicated in the results section, foaming problems of a nuisance
nature were encountered in this study. The causes of the foaming are
not clear. Inadequate oxygen supply resulting in anaerobic conditions is
often cited as the cause of foam. However, foaming problems did not
occur in Ditch l, which was the minimally aerated system, but rather
in Ditch II where residual dissolved oxygen concentrations were maintained.
Accumulated sediments have also been suggested as a causative agent of
foaming in a study of aerobic treatment of swine wastes (47). However,
sediment accumulations were present in both Manorcrest ditches but
foaming only occurred in Ditch II. Based upon the observations during
this study and from previous experience, it appears that there are
several factors which will cause foaming. However, relationships are
not clear. With the exception of an overloaded condition, it appears
that adequate velocity to maintain continuous foam movement can prevent
foam from becoming a problem.
130
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In a pilot plant study, it was reported that no overflow occurred from
an oxidation ditch treating poultry wastes (6). In this study, it was
necessary to add water to offset evaporative losses. It appears that
the same situation should occur under commercial conditions if leakage
from the bird watering system is eliminated. This can be accomplished
through the use of a trough type watering system. Water addition via
manure is low and was calculated to be approximately 79 £ per 1000
birds per day (21 gal per 1000 birds per day) at Manorcrest. Evaporative
losses should offset the quantity of water added as manure.
ECONOMIC IMPACT
The practicality of aeration as a poultry waste management tool will
depend heavily on economic impact. Since the price the producer receives
for eggs is determined by the market forces of supply and demand, there
is not opportunity to pass the cost of pollution control measures. The
economic impact of any waste management system on net income is a logical
criteria for the economic assessment of that system. However, a 1973
survey (64) of 40 New York State poultry farms showed that labor and
management incomes varied widely. Income ranged from minus values to
over $30,000 per operator. Similar variations were reported in 1971
and 1972 (65,66,). Differences in management skills among producers appear
to be the major factor responsible for this variability.
As an alternative, capital investment and production costs were used
as baselines for economic assessment. This procedure allows determination
of economic impact in terms of efficient production resulting from
skillful management. Egg production costs in New York State for the
years 1971-73 are presented in Table 35. The values noted are average
values reported for New York State except for feed costs. Feed costs
were based on 1.91 kg (4.2 Ibs) of feed per dozen eggs and 20 dozen eggs
marketed per hen year. The effect of good management is reflected
in the selected feed conversion efficiency and production values which
are above average for the three years evaluated.
131
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Table 35. NEW YORK STATE EGG PRODUCTION COSTS
(64,65,66)
Cost /hen-year
Return to capital @9%
Labor*
Feed
Hen**
Building repairs
Electricity
Taxes
Insurance
Total
Production cost/
dozen eggs
1973
$ .67
.94
5.12
1.75
.03
.11
.07
.11
$8.80
0.44
1972
$ .56
.87
3.23
1.75
.04
.10
.06
.09
$6.70
0.335
1971
$ .62
1.05
3.56
1.75
.04
.09
.07
.09
$7.27
0.364
* Includes operator's labor
**Estimated cost $2.00/bird, less salvage value of $.25/bird
132
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The capital costs of the Manorcrest aeration systems, Table 30, are
high in comparison to those previously reported for another application
of oxidation ditches for poultry waste treatment. That system,
Houghton's, was also evaluated by personnel from the Cornell Agricultural
Waste Management Program (16). An itemized comparison of the capital
costs for both systems per 1000 birds is presented in Table 36.
As shown, the major factor in the high capital cost of the Manorcrest
systems is the construction cost for conversion of the four manure
collection pits into two oxidation ditches. One factor contributing
to the higher costs at Manorcrest was the smaller number of birds, 8,000,
in comparison to the 15,000 birds at the Houghton Farm. Both conversions
were similar requiring the connection of four manure collection pits
to form two oxidation ditches. Since the Houghton system served more
birds, the result was a lower unit cost.
However, this does not account for the total difference. Another factor
was the decision to place the connecting channels beyond the ends of the
cage rows at Manorcrest which increased construction costs. This placed
these channels in the service alleys at each end of the cage rows and
necessitated the construction of a floor system capable of supporting
workers and feed and egg carts over the connecting channels. Conversely,
the connecting channels were placed under the cages at the Houghton Farm.
The use of precast concrete settling and storage tanks also increased
the capital cost of the Manorcrest systems. Estimation of costs for
alternative approaches to liquid-solid separation and storage awaits
the results of more detail investigation into this area.
The energy costs for aeration determined in this study, Table 31, were
significantly lower than those previously reported. Power costs of
two to four cents per dozen eggs have been reported for a pilot plant
scale oxidation ditch (67). and one cent per dozen for a full scale,
15,000 bird, oxidation ditch system (16). The impact of energy costs
133
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Table 36. COMPARISON OF CAPITAL COSTS PER 1,000 BIRDS,
MANORCREST FARMS AMD HOUGHTUN'S POULTRY FARM
Manorcrest Houghton
Ditch I Ditch II
Construction $1,092 $1,092 $187
Settling tanks 380 380
Aeration units 375 530 480
$1,847 $2,002 $667
Annual capital cost
per 1,000 hens $ 222 $ 248 $ 95
Annual capital cost
per dozen eggs .0111 .0124 .0047
134
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for the four levels of oxygen transfer evaluated in this study on
production costs are presented in Table 37. For three years 1971-73,
energy costs of aeration for odor control would have increased production
costs by a maximum of one percent. Even at the highest level of oxygen
transfer where transfer capacity exceeded calculated total demand by
approximately 45 percent, the maximum increase in production costs
would have been only two percent.
The total economic impact of the use of aeration for the different
designs and modes of operation on egg production costs, for the years
1971-73, are summarized in Table 38. The increased total cost of
aeration for odor control never exceeded 5 percent even with the high
capital costs characteristic of this study. The cost of electricity
was $.0201 per kwhr for this study and may differ elsewhere.
This study has demonstrated that process design based on fundamental
concepts of the biological waste treatment process and oxygen transfer
can reduce energy costs for aeration. This point is illustrated by
comparison Of the energy costs between the Houghton system and Manorcrest.
The design and operation of the Houghton system was based on empirical
parameters where as a more fundamental approach was used for Manorcrest.
Energy cost per dozen eggs for odor control at Houghton's was reported
to be $0.0100 (16) in comparison to $0.0056 per dozen eggs at Manorcrest
(Table 31).
In evaluating these energy costs, it is important to realize that energy
costs are also a function of the aerator oxygen transfer efficiency.
Both aeration units in this study delivered approximately 1500 gms 02 per
kwhr (2.5 Ibs 02 per hp-hr). Other types of surface aeration equipment
with higher efficiencies, 2400 gms 02 per kwhr (4 Ibs 02 per hp-hr) are
available (60). A turbine aeration system evaluated in a pilot plant
scale study of poultry wastes has been reported to have an oxygen
transfer efficiency of approximately 3000 gms 02 per kwhr (5 Ibs 02 per
135
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Table 37. EFFECT OF POWER COSTS FOK AEROBIC STABILIZATION
ON EGG PRODUCTION COSTS
Level
of Oxygen
Transfer Capacity,
gms Op/I
000 bird-hrs.
351
520
790 &
815
Degree of
Stabilization
Odor control
Nitrification-
denitrifi cation
Potential
nitrogen
conservation
Percentage
Increase In
Egg Production
1973 1
0.8
1.1
1.6
972
1.0
1.4
2.0
Costs
1971
0.9
1.3
1.8
Table 38. EFFECT OF TOTAL COSTS FOR AEROBIC STABILIZATION
ON EGG PRODUCTION COSTS
Level of Oxygen
Transfer Capacity
gms 02/1000 bird-hrs.
351
520
790 &
815
Degree of
Stabilization
Odor control
Ni trifi cation-
den itrifi cati on
Potential
nitrogen
conservation
Percentage Increase In
Egg Production Costs
1973
3.8
4.1
4.9
1972
5.0
5.3
6.4
1971
4.6
4.9
5.9
136
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hp-hr) (42). The use of more efficient aeration equipment would reduce
operating costs but may require a system different from the oxidation
ditch.
The differences in capital costs between Manorcrest and the Houghton
farm suggest that opportunities for cost reduction are available. The
location of the semi-circular connecting channels beyond the end of the
cage rows in the service alleys at Manorcrest necessitated excavation
and construction of a floor system which increased construction costs.
In contrast, these channels were placed under the cages and reduced
construction costs for the Houghton system. Use of an earthen lagoon
in place of precast concrete tanks would also reduce capital costs.
Realization of these lower capital costs along with the low power costs
demonstrated in this study should result in further improvements in
what appear to be reasonable costs.
137
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15. Converse, J.C., D.L. Day, J.T. Pfeffer and B.A. Jones, Jr. Aeration
with ORP Control to Suppress Odors Emitted from Liquid Swine Manure
Systems. In: Livestock Waste Management and Pollution Abatement.
ASAE. St. Joseph, Michigan. 1971. p. 267-271.
139
-------
16. Martin, J.H., R.C. Loehr, A.C. Anthonisen, and S.P. Nieswand.
Aerobic Treatment of Poultry Wastes. ASAE Paper No. 74-4029.
St. Joseph, Michigan. 1974. 35 p.
17. Holmes, B.J. Effect of Drying on the Losses of Nitrogen and
Total Solids from Poultry Manure. Unpublished M.S. Thesis, Cornell
University. 1973. 97 p.
18. Hashimoto, A.G. Aeration Under Caged Laying Hens. ASAE Paper
No. NAR-71-428. St. Joseph, Michigan. 15:1119-1123, 1972.
19. Dunn, G.G. and Robinson, J.B. Nitrogen Losses through Denitrification
and Other Changes in Continuously Aerated Poultry Manure. Proc.
Agric. Waste Management Conference, Cornell University, Ithaca,
New York. 1972. pp. 545-554. Ğ
20. Prakasam, T.B.S., E.G. Srinath, A.C. Anthonisen, J.H. Martin, Jr.,
and R.C. Loehr. Approaches for the Control of Nitrogen with an
Oxidation Ditch. Proc. Agric. Waste Management Conference, Cornell
University, Ithaca, New York. 1974. p. 421-435.
21. Jones, D.D., D.L. Day, and A.C. Dale. Aerobic Treatment of
Livestock Wastes. Bulletin 737, University of Illinois at
Urbana-Champaign. 1970. 55 p.
22. Agricultural Engineers Digest. Oxidation Ditch for Treating Hog
Wastes. AED-14, Midwest Plan Service, Iowa State University.
Ames, Iowa. 1970.
23. Canada Department of Agriculture. Canada Animal Waste Management
Guide. Publication 1534. Ottawa, Ontario. 1974.
24. Fair, G.M. and J.C. Geyer. Elements of Water Supply and Waste-Water
Disposal. John Wiley and Sons, New York 1958. p. 418-420.
140
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25. Owens, J.D., M.R. Evans, F.E. Thuder, R. Hlssett, and S. Baines.
Aerobic Treatment of Piggery Wastes. Water Research 7:1745-1766,
1973.
26. Monod, 0. The Growth of Bacterial Cultures. Ann. Rev. Microbiology.
3:371-394, 1949.
27. Lawrence, A.H. and P.L. McCarty. Unified Basis for Biological Treat-
ment Design and Operation. J. Sanitary Eng. Div., ASCE, 96:757-778,
1970.
28. Stensel, H.D. and 6.L. Shell. Two Methods of Biological Treatment
Design. J. Water Poll. Control Fed. 46:271-283, 1974.
29. Woods, J.L. and J.R. O'Callaghan. Mathematical Modelling of
Animal Waste Treatment. J. Agric. Eng. Res. 19:245-258, 1974.
30. Loehr, R.C., T.B.S. Prakasam, E.G. Srinath, and Y.D. Joo. Development
and Demonstration of Nutrient Removal From Animal Wastes. Environ-
mental Protection Technology Series Report No. EPA-R2-73-095, U.S.
Environmental Protection Agency. 1973. 340 p.
31. Downing, A.L., H.A. Painter, and G. Knowles. Nitrification in the
Activated Sludge Process. Journal Institute of Sewage Purification.
Part 2. 1964. p. 130-158.
32. Loehr, R.C. Agricultural Waste Management. New York, Academic
Press, 1974. 242 p.
33. Cullen, E.J. and J.F. Davidson. The Effect of Surface Active Agents
on the Rate of Adsorption of Carbon Dioxide by Water. Chemical
Engineering Science. 6:2, 49-50, 1956.
141
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34. Downing, A.L. and A.G. Boon. Oxygen Transfer in the Activated
Sludge Process. Air and Water Pollution 5:131-148, 1963.
35. O'Connor, D.J. Effects of Surface Active Agents on Reaeration.
Air and Hater Pollution 5:123-130, 1963.
36. Gaden, E.L., Jr. Aeration and Oxygen Transport in Biological
Systems - Basic Considerations. In: Biological Treatment of
Sewage and Industrial Wastes. New York, Reinhold Publishing
Corp., 1956. p. 172.
37. Baker, D.R., R.C. Loehr, and A.C. Anthonisen. Oxygen Transfer
at High Solids Concentrations. J. Environ. Eng. Div., ASCE.
101:759-774. 1975.
38. Gameson, A.L. and K.G. Robertson. The Solubility of Oxygen in
Pure Water and Sea Water. Journal of Applied Chemistry. 5:502,
1955.
39. Water Pollution Control Federation. Aeration in Hastewater
Treatment - Manual of Practice No. 5. Washington, D.C. 1970.
40. Anderson, D.R. and M. Kurd. Study of Complete Mixing Activated
Sludge. J. Water Poll. Control Fed. 43:422-432, 1971.
41. Pfeffer, J.T., F.C. Hart, and L.A. Schmid. Field Evaluation of
Aerators in Activated Sludge Systems. Proc. 23rd Industrial Waste
Conference, Purdue University, 183-194, 1968.
42. Hashimoto, A.G. and Y.R. Chen. Turbine-Air Aeration System for
Poultry Wastes. In: Managing Livestock Wastes. ASAE. St. Joseph,
Michigan. 1975. p. 530-534.
142
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43. Stratton, F.E. and P.L. Mccarty. Prediction of Nitrification
Effects on the Dissolved Oxygen Balance of Streams. Environ-
mental Science and Technology. 1:405-410, 1972.
44. Terashima, S., K. Koyama, and Y. Mazara. In: Biological Sewage
Treatment in a Cold Climate Area. (R.S. Murphy and D. Nyguist,
eds.). College, Alaska. EPA Report 16100 EXH. University of
Alaska, 1971. p. 263-385.
45. Fair, G.M. and J.C. Geyer. Elements of Water Supply and Waste-
water Disposal. John Wiley and Sons, New York, 1958. p. 329.
46. Jones, D.D., D.L. Day, and J.C. Converse. Oxygenation Capacities
of Oxidation Ditch Rotors for Confinement Livestock Buildings.
In: Proc. of the 24th Annual Purdue Industrial Waste Conference,
Lafayette, Indiana, Purdue University, 1969. p. 191-208.
47. Martin, J.H. Unpublished Data. Cornell University Agricultural
Waste Management Program. 1972.
48. McKinney, R.E. and R. Bella. Water Quality Changes in Confined
Hog Waste Treatment. Project Report: Kansas Hater Resources
Research Institute. University of Kansas, Lawrence, Kansas.
1967. 88 p.
49. American Public Health Association. Standard Methods for the
Examination of Water and Wastewater. 13th ed. New York, 1971.
50. McKenzie, H.A. and H.S. Wallace. The Kjeldahl Determination of
Nitrogen: A Critical Study of Digestion Conditions, Temperature,
Catalyst, and Oxidizing Agent. Aust. J. Chem (Sidney) 7:55-71. 1954.
143
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51. Prakasam, T.B.S., E.G. Srinath, P.Y. Yang, and R.C. Loehr.
Analyzing Physical and Chemical Properties of Liquid Waste.
In: Standardizing Properties and Analytical Methods Related
to Animal Waste Research. ASAE. St. Joseph, Michigan. 1975.
p. 114-166.
52. Montgomery, H.A.C. and J.F. Dymock. The Determination of Nitrite
in Water. Analyst 86:414-416. 1961.
53. Jeris, J.S. A Rapid COD Test. Water and Wastes Engineering.
4:89-91, 1967.
54. Srinath, E.G., R.C. Loehr, and T.B.S. Prakasam. Nitrifying Organism
Concentrations and Activity. Accepted for Publication. J. Environ.
Eng. Div., ASCE.
55. Anthonisen, A.C., R.C. Loehr, T.B.S. Prakasam, and E.G. Srinath.
Inhibition of Nitrification by Ammonia and Nitrous Acid. (Presented
at the 47th Annual Conf., Water Pollution Control Federation, Denver,
Colorado, October 1974) and accepted for publication by the J. Water
Poll. Control Fed.
56. Lawrence, A.W. Modeling and Simulation of Slurry Biological Reactors.
In: Mathematical Modeling and Environmental Engineering. Association
of Environmental Engineering Professors. 8th Annual Workshop, Nassau
Bahamas. 1972. p. 216-255.
57. Dick, R.I. Role of Activated Sludge Final Settling Tanks. J. Sanitary
Eng. Div., ASCE 96:423-436, 1970.
58. Sobel, A.T. Physical Properties of Animal Manures Associated with
Handling. In: Farm Animal Wastes. ASAE. St. Joseph, Michigan.
1966. p. 27-32.
144
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59. Chow, V.T. Open-Channel Hydraulics. New York, McGraw-Hill Book
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60. Metcalf and Eddy, Inc. Wastewater Engineering. New York, McGraw-
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61. Simons, D., D.D. Jones, and A.C. Dale. Oxidation Ditch Analysis
and Field Evaluation of the Aerob-A-Jet. Proc. Agricultural Haste
Management Conference, Cornell University, Ithaca, New York. 1974.
p. 436-454.
62. Windt, T.A., N.R. Bulley, and L.M. Staley. Design, Installation,
and Biological Assessment of a Pasveer Oxidation Ditch on a Large
British Columbia Swine Farm. In: Livestock Waste Management and
Pollution Abatement. ASAE. St. Joseph, Michigan. 1971. p. 213-^16.
63. Shukry, A. Flow Around Bonds in an Open Flume. Transactions, ASCE.
115:751-779, 1950.
64. Bratton, C.A., and G.H. Thacker. 1973 Poultry Farm Business Summary.
Dept. of Agricultural Economics, Cornell University, Ithaca, New York.
1974. 34 p-
65. Bratton, C.A., and G.H. Thacker. 1972 Poultry Farm Business Summary.
Dept. of Agricultural Economics, Cornell University, Ithaca, New York.
1973. 34 p.
66. Bratton, C.A., and G.H. Thacker. 1971 Poultry Farm Business Summary.
Dept. of Agricultural Economics, Cornell University, Ithaca, New York.
1972. 34 p.
67. Ludington, D.C., A.T. Sobel, R.C. Loehr, and A.G. Hashimoto. Pilot
Plant Comparison of Liquid and Dry Waste Management Systems for
Poultry Manure. Proc. Agric. Waste Management Conf., Cornell
University, Ithaca, New York. 1972. p. 569-580.
145
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SECTION IX
APPENDICES
FIGURE TITLE PAGE
Al Motor performance data for the brush
aeration unit 147
A2 Motor performance data for the Thrive
Center Aeration Unit 148
A3 Motor performance data for the propeller
drive unit, 115 rpm 149
A4 Motor performance data for the propeller
drive unit, 230 rpm 150
TABLE TITLE PAGE
Al Relationships Between SRT and Treatment
Effeciencies 151
146
-------
2.2
2.Q_
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
KILOWATTS,
EFFICIENCY
ELECTRA MOTORS OIV -
JEFFERY MANUF. CO.
2 HP, 10, 60 Hz, 230 VOLTS,
345 RPM. GEARHEAD MOTOR
60
50
40
30
20
UJ
0 .2 4 .6 .8 1.0 1.2 1.4 1.6 1.8 2.0
SHAFT HORSEPOWER
10
Figure Al. Motor Performance data for the brush aeration unit
-------
oo
CENTURY ELECTRIC COMPANY
5 HP, 10, 60HzM 230 VOLTS,
1750 RPM, TYPE CS,
FRAME 2I3T.
40
o
LtJ
O
iZ
LL
LU
§*
20
2 3
SHAFT HORSEPOWER
Figure A2. Motor performance data for the Thrive Center Aeration Unit
-------
800
6OO
ID
Q.
400
200
WATTS
U.S. MOTORS *S.M.3030 D.C. PKG.
UNIT with BROWNING 107 SM 05
SHAFT MOUNTED REDUCER. 3 HP,
60 Hz, I 0 , 230 VOLTS, 115 RPM.
40
30
>
o
UJ
20 y
U.
UJ
$5
10
O.I 0.2 0.3
SHAFT HORSEPOWER
0.4
Figure A3. Motor performance data for the propeller
drive unit, 115 rpm
149
-------
en
o
2,000
1300
1,600
1,400
H-
£ '>2°o
z
> 1,000
800
600
400
200
EFFICIENCY
U.S. MOTORS *SM-3030 D.C.Pkg. UNIT
with BROWNING I07SM05 SHAFT
MOUNTED REDUCER. 3 HP, 10,
60 Hz, 230 VOLTS, 230 RPM
I
I
60
50
40
o
o
bJ
30 0s
20
0.4 0.8 1.2
SHAFT HORSEPOWER
1.6
Figure A4. Motor performance data for the propeller drive unit, 230 rpm
-------
Table Al. RELATIONSHIPS BETWEEN SRT AND TREATMENT EFFICIENCIES
Ditch
No.
I
I
II
I
II
II
Length of
Equilibrium
Period
(Days)
25
56
14
56
34
36
Average Total
Solids Concentration,
13,
9,
21,
13,
19,
23,
760
960
570
550
800
830
Removal Efficiencies (%)
SRT
Days
10.5
15.0
18.0
21.0
27.0
36.5
Total
26.
38.
33.
37.
35.
40.
5
9
0
9
4
8
Solids
Volatile
37.
50.
46.
49.
47.
54.
5
8
5
1
7
3
COD
22.
32.
36.
31.
31.
35.
4
9
2
2
4
0
Organic
Nitrogen
49.0
55.0
58.5
60.4
64.7
63.3
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/2-76-186
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
Demonstration of Aeration Systems for Poultry Wastes
5. REPORT DATE
October 1975 (Issuing
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
8. PERFORMING ORGANIZATION REPORT NO.
J.H. Martin, Jr. and R.C. Loehr, Cornell University,
Ithaca, NPW Ynrk
9. PERFORMING ORGANIZATION NAME AND ADDRESS
flanorcrest Farms
5322 Munro Road
Camillus, NY 13031
10. PROGRAM ELEMENT NO.
1HB617
11. CONTRACT/GRANT NO.
5800863
12. SPONSORING AGENCY NAME AND ADDRESS
Environmental Research Laboratory - Athens, GA
Office of Research and Development
U.S. Environmental Protection Agency
Athens, Georgia 30601
13. TYPE OF REPORT AND PERIOD COVERED
Final Report
14. SPONSORING AGENCY CODE
EPA/600/01
15. SUPPLEMENTARY NOTES
16. ABSTRACT
A full scale study demonstrated the potential of aeration systems to reduce the water
and air pollution potential of poultry wastes under commercial conditions. The
nerformance of two oxidation ditches, each receiving the wastes from approximately
4000 layinn hens, was monitored and evaluated.
The relationships between two design and operational variables and system performance
were examined. The variables were level of oxygen supply and solids retention time.
It was observed that an oxygen input equivalent to the exerted carbonaceous oxynen
demand provided a high degree of odor control. Increase in oxynen supply to also
satisfy the exerted nitrogenous oxygen demand resulted in nitrification which termi-
nated ammonia desorotion. Subsequent nitrogen losses were the result of denitrifica-
tion relationships between removals of total solids, volatile solids, COD, and organic
nitrogen in aerated poultry wastes were developed.
Two major problem areas were identified and examined. The first was the removal and
concentration of residual solids to maximize oxygen transfer efficiency and minimize
the volume of material requiring ultimate disposal. The second was sedimentation of
solids in the oxidation ditch channel which reduced and in several instances stopped
nixed liquor circulation.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
Capitalized Cost, Oxidation, Odor Control,
Operating Costs, Waste Treatment, Poultry
b.lDENTIFIERS/OPEN ENDED TERMS
Poultry manure, Oxida~
tion ditch, Nitrogen
transformations, nitrogeji
losses, liquid-solids
separation, liquid aera-
tion systems, COD
removal.
COSATI Field/Group
02/C/E
3. DISTRIBUTION STATEMENT
Release Unlimited
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
164
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
152
r U. S. GOVERNMENT PRINTING OFflCE. 1977-757-056/5529 Region No. 5-1
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