EPA-660/2-75-001
FEBRUARY 1975
Environmental Protection Technology Series
Waste Citrus Activated Sludge
as a Poultry Feed Ingredient
National Environmental Research Center
Office of Resejvch and Development
U.S. Environmental Protection Agency
Corvallis, Oregon 97330
-------
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. Socioecononric Environmental Studies
This report has been assigned to the ENVIRONMENTAL PROTECTION
TECHNOLOGY STUDIES 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 report has been reviewed by the Office of Research and
Development, EPA, and approved for publication. Approval does
not signify that the contents necessarily reflect the views and
policies of the Environmental Protection Agency, nor does mention
of trade names or commercial products constitute endorsement or
recommendation for use.
-------
EPA-660/2-75-001
February 1975
TCASTE CITRUS ACTIVATED SLUDGE
AS A POULTRY FEED INGREDIEOT
By
Richard H. Jones
John T. White
B. L. Damron
Grant No. S-801432
Program Element 1BB037
ROAP/TASK No. 21 BAE/030
Project Officer
Harold V. Thompson
Pacific Northwest Environmental Research Laboratory
National Environmental Research Center
Corvallis, Oregon 97330
NATIONAL ENVIRONMENTAL RESEARCH CENTER
OFFICE OF RESEARCH & DEVELOPMENT
u.s. ENirEPQ^iENTAL PROTECTION AGEHCY
CORVALLIS, OREGON 97330
-------
ABSTRACT
This report presents an evaluation of the potential of utilizing waste
activated sludge as a poultry feed supplement. The sludge used in this
study was obtained from an activated sludge process treating concentrated
citrus waste containing no sanitary wastewater. The sludge was thickened,
dewatered and dried using full-scale and pilot-scale equipment. The dried
sludge was then analyzed for protein, fiber, amino acids, nutrients and
moisture. Poultry feeds containing varying concentrations of sludge were
prepared. Two experiments with broiler chicks, each of three weeks dura-
tion, one 8-week broiler study, and a six-month laying hen study were con-
ducted to determine the effect of the inclusion of sludge in poultry diets
on performance and quality.
It is shown in this report that the inclusion of sludge in properly for-
mulated diets up to 7.5 percent did not significantly affect poultry per-
formance or meat or egg quality. The value of the sludge was calculated
based on the reduction in feed ingredients resulting from the inclusion
of sludge. It was found that the value of the recovered sludge signifi-
cantly reduced the total cost of sludge handling.
This report was submitted in fulfillment of Grant Number S-801432 by
Winter Garden Citrus Products Cooperative under the partial sponsorship
of the Envirorroental Protection Agency. Work was completed as of November,
1974.
11
-------
CONTENTS
Abstract ii
List of Figures iv
List of Tables v
Acknowledgements
Sections
I Conclusions 1
II Recommendations 3
III Introduction 4
IV Experimental Equipment and Procedures 7
V Results 16
VI Discussion 45
VII References 56
111
-------
FIGURES
No. Page
1 V&stewater Treatment System 8
2 Schematic Diagram of Test Centrifuges 10
3 Influent and Effluent BOD and COD, 1972-1973 Season 18
4 Percent Recovery Versus Feed Eate for a Basket 25
Centrifuge (SST-900)
5 Percent Recovery Versus Feed Rate for a Basket 49
Centrifuge (SST-1600)
IV
-------
TABLES
**>» Page
1 Chemical Analyses for the 1972-1973 Operating Season 17
(monthly averages)
2 Average Chemical Analysis of Aeration Tank, 1972-1973 19
Operating Season
3 Chemical Analyses of Waste Activated Sludge 20
(clarifier underflow)
4 Chemical Analyses of Sludge Thickener Underflow and 23
Sludge Surge Tank Underflow (percent)
5 Typical Results for the Nestfalia Centrifuge 26
6 Pilot Plant Kiln Data 29
7 Pilot Plant Flash Evaporator Data 30
8 Composition of Dried Activated Sludge 31
9 Composition of Basal and Sludge Diets 32
10 Chick Performance Data (Experiment 1) 34
11 Chick Performance Data (Experiment 2) 35
12 Data From Broiler Study 37
13 Average Dressed Carcass Weight for Broilers Fed Various 38
Dietary Levels of Sludge
14 Average and Mean Palatability Scores of Dark and White 39
Neat Fran Cooked Male and Female Broilers
15 Laying Hen Sludge Diet Composition 39
16 Average Laying Een Performance (6 months) 40
17 Average Laying Hen Performance (6 months) 41
18 Average Laying Hen Performance (6 months) 41
19 Interrelationship of Dietary Sludge and Heiman-Carver 42
Color Rotor Numbers
v
-------
TABLES
(cxsntijTued)
No.
20 Color Oiaracteristics of Egg Yolk 43
21 Taste Panel Evaluation of Eggs Fran Control and 44
20.0 Percent Sludge Diets
22 Yearly Costs for Sludge Recovery ($/year) 50
23 Ccnposition of Feed (percent) 52
24 Changes in Ingredient Costs Resulting From Sludge 53
Addition
-------
ACKNOWLEDGEMENTS
Mr. James W. Hayes, Production Manager, Winter Garden Citrus Products
Cooperative, is acknowledged for his close cooperation throughout the
project.
Dr. Richard H. Jones of Jones, Olson & Associates, Inc., who served as
Project Manager, and Mr. John T. White also of Jones, Olson & Associates,
Inc., who compiled the report, are acknowledged.
Dr. B. L. Dararon of the Poultry Sciences Department, University of
Florida, is acknowledged for his efforts in conducting the poultry test-
ing program.
Mr. Harold W. Thompson of the U. S. Environmental Protection Agency
served as Project Officer and is acknowledged for his cooperation and
assistance.
Vll
-------
SECTION I
CONCLUSIONS
The activated sludge process is a viable treatment alternative for the
citrus industry and its application can be expected to increase in the
future. One of the major problems associated with the activated sludge
process is the production of excess sludge which must be handled in some
manner. The handling of excess sludge is both a technical difficulty and
an economic burden.
It has been demonstrated through this study that waste activated sludge
can be handled by a system consisting of gravity thickening and centrifu-
gation. The unit cost of dewatering sludge in this manner, to a solids
concentration of 8 percent, is approximately $119/kkg ($108/ton) of dry
solids. This cost does not include the cost of final disposal which,
for the Winter Garden Citrus Products Cooperative, is estimated to be
$6/kkg ($5.45/ton) for land disposal.
One method of off-setting the cost of sludge dewatering and final dis-
posal would be to develop a use for the sludge. It has been demonstrated
through this study that the use of dried sludge as an ingredient in a
properly formulated poultry diet may be a viable means of reducing the
cost of sludge handling. In this study, dried activated sludge was in-
cluded in the diets of broiler chicks and laying hens in amounts varying
from 0.0 to 20.0 percent. Above levels of approximately 10 percent, the
inclusion of sludge resulted in a significant depression in final body
weight, feed efficiency and other performance factors. • The addition of
less than 10 percent sludge did not adversely affect poultry performance
and, in fact, provided some improvement in performance.
The inclusion of dried sludge in poultry diets allowed for a reduction
in the percentage of yellow corn, soybean meal and phosphate required,
-------
while increasing the percentage requirement of animal fat and sulfur amino
acids. The inclusion of 7.5 percent (by weight) dried sludge in a poultry
diet resulted in a savings in feed ingredients valued at $8.00/kkg ($7.26/
ton) of feed. Thus, the apparent value of the dried sludge was $107/kkg
($97/ton) , while the cost of drying previously dewatered sludge was approx-
imately $79/kkg ($72/ton) . Thus, the cost of final disposal would be re-
placed by an apparent profit of $28/kkg ($25/ton) .
total cost of sludge handling has been shown to be approximately
$119/kkg ($108/ton) for dewatering plus $6/kkg ($5.45/ton) for ultimate
disposal by landfilling. Recovery of the sludge for poultry feed re-
duces the total cost of sludge handling by about 27 percent to $91/kkg
($83/ton) . Because of the seasonal nature of the Florida citrus industry,
these cost figures apply only to Winter Garden Citrus Products Cooperative
or similar facilities.
-------
SECTION II
REJCXMIENDftTICNS
It is reconroended that further study be conducted with the objective of
isolating the factor or factors which depressed poultry performance at
higher sludge dietary levels. Additional work should be conducted to
pursue the findings of pilot trials which indicated that sludge might
have value as a pigment source for egg yolk coloration.
It is reconroended that further study be conducted to develop improved
sludge handling technology. Investigation of alternative sludge drying
methods should be undertaken.
The use of dried sludge as a poultry feed ingredient should be reccmmended
to poultry producers in order to provide a market for the sludge. Incen-
tive should be provided to industry and poultry producers to encourage
utilization of sludge as a feed ingredient.
-------
SECTION III
H7TRODUCTICN
Since its discovery in 1914,1 the activated sludge process has been
utilized in a wide variety of applications; and, with increasingly
stringent effluent limitations, the use of the activated sludge process
can be expected to increase. In the Florida citrus industry, there are
several biological treatment alternatives which are available to meet
the effluent limitation requirements. However, for many citrus pro-
cessors the lack of suitable land prohibits the use of alternatives
other than the activated sludge process.
One of the major problems associated with this process is the production
of excess activated sludge. The handling and disposal of excess activated
sludge results in one of the largest operating expenses in the activated
sludge process. The purpose of this project was to demonstrate a system
for handling waste activated sludge and to study the potential of utili-
zing the recovered sludge as a poultry feed supplement, thereby reducing
the financial burden of final sludge disposal.
SCOPE AND PURPOSE
The primary objective of this project was to demonstrate the potential of
using waste activated sludge as a chicken feed supplement. This objec-
tive was to be accomplished by using waste activated sludge from an exist-
ing activated sludge system treating concentrated citrus processing waste
containing no sanitary waste. The activated sludge was to be dewatered
and dried by a system consisting of a gravity thickener, a centrifuge,
and a rotary kiln dryer. The potential of using waste activated sludge
as a chicken feed supplement was to be determined through actual chicken
feeding studies, including evaluation of produce quality (both meat and
egg) and post mortem examinations. This research was not designed to
assay nutrients or determine biological availability, but rather to gain
-------
basic information about what practical levels of sludge could be utilized,
the level of toxicity, and taste iinpartation to meat or eggs.
BACKGROUND
This demonstration project was a supplement to a previous project funded
by a grant from the U. S. Environmental Protection Agency.2 The purpose
of that grant was to demonstrate the use of the complete mix activated
sludge process for treatment of citrus process wastes at the Winter Garden
Citrus Products Cooperative (WGCP) citrus processing plant in Winter
Garden, Florida. The resulting treatment system was the first approved
system of its type in the State of Florida. It was designed to treat
88 I/sec (2.0 MGD) at an average BOD concentration of 2,000 mg/1 and can
consistently achieve a BOD reduction of 98 to 99 percent.
As with most activated sludge processes, one of the major costs of treat-
ing the WGCP wastewater is the cost of sludge handling. The complete mix
system produces 0.5 to 0.6 kg TSS/kg BOD5 removed per day.3 At Winter
Garden Citrus the production of total solids is 5,400 to 6,400 kg/day
(6 to 7 tons/day) on a dry weight basis at the design loading rate. The
original design for sludge handling consisted of sludge dewatering using
a solid bowl, scroll type centrifuge followed by drying in existing rotary
kiln dryers along with citrus peel. The citrus peel and dried sludge
were then to be sold as a cattle feed supplement. The determination of
the value of the sludge as an animal feed supplement was not part of the
initial grant. Uhf ortunately , the centrifuge failed to operate properly
causing the kiln dryers to become overloaded. This required that the
portion of the waste sludge which could not be handled in the kiln dryers
be disposed of by land spreading. Thus, the objective of this project
was to determine the value of the sludge as a 'chicken feed additive and
simultaneously develop a suitable sludge handling method for the Coop-
erative.
The program consisted of pilot testing tWD centrifuges, a solid bowl
basket type and a disc type, in order to select a full-scale centrifuge
-------
A full-scale system was then operated consisting of a gravity thickener
and a disc type centrifuge in order to dewater sludge prior to drying
along with citrus peel in existing rotary kiln dryers. A pilot plant
rotary kiln dryer and a sand bed were utilized to dry sludge for chicken
feeding tests. The potential of the dried sludge as a chicken feed sup-
plement was determined by a series of feeding tests conducted by the
Department of Poultry Science at the University of Florida.
-------
SECTION IV
EXPERIMENTAL EQUIPMENT AND PROCEDURES
This report describes two fundamentally different types of ejqperimentation.
One section is sludge recovery by thickening, dewatering, and drying. The
second section of experimentation concerns the feeding of dried sludge to
chickens. Obviously, the equipment, procedures, techniques and terminolo-
gy for these toro types of experimentation differ widely. "For this reason,
the materials and methods used will be described in two separate sections.
SLUDGE RECOVERY
The treatment system utilized at the VCCP is shown schematically in Figure
1. The pre-screened wastewater enters the aeration basins following nu-
trient addition and pH control. Nutrients are added in the form of phos-
phoric acid and anhydrous ammonia. The aeration basins are circular, con-
crete tanks, 44 meters (144 feet) in diameter with a side water depth of
3.6 meters (12 feet). Each tank, equipped with three 75 H.P. floating
mechanical aerators, can be operated in series or parallel. Effluent from
the aeration basins flews to a clarifier f ran which return sludge is pumped
back into the influent pipe to the aeration basins. The supernatant liquor
from the clarifier is either returned to the citrus processing plant for
reuse as cooling water or discharged.
Excess activated sludge is pumped from the bottom of the clarifier to a
gravity thickener from which supernatant is returned to the aeration
basins, and thickened sludge is discharged to a sludge holding tank. The
thickened sludge was then centrifuged, with the centrate returned to the
aeration tanks.
The equipment used for sludge recovery in this study was all full-scale
equipment with the exception of a pilot scale rotary kiln dryer and a
pilot-scale flash evaporator. Sludge was thickened in a gravity thickener
-------
NUTRIENTS
pH ADJUSTMENT
INFLUENT
IN PLANT REUSE
EFFLUENT OVERFLOW
RETURN SLUDGE
EXCESS
SLUDGE
SUPERNATANT
SUPERNATANT
CENTRATE
1. COMPLETE MIXED ACTIVATED SLUDGE TANKS
2.CLARIFIER
3. GRAVITY SLUDGE THICKENER
4. SLUDGE HOLDING TANK
5. CENTRIFUGE
6. WET WELL
7. ROTARY KILN DRYER
DRIED SLUDGE
Figure 1. Wastewater treatment system
-------
which had been converted from a line treatment unit. The thickener has
a 17-meter (55-foot) diameter and a side water depth of 4.6 meters (15
feet). Since the tank was originally designed as a lime treatment tank,
the sludge rake mechanism was actually typical of a standard lime water
softening mechanism. The thickened sludge was raked to a center trough
and removed with a Moyno pump. Supernatant was returned to the activated
sludge units while thickened sludge was pumped to a conical surge tank.
Sludge was pumped with ffoyno pumps from the surge tank to the subsequent
dewatering units.
The thickener and surge tank were operated on a continuous basis as an
integral part of the treatment system during the testing period. Thus,
influent solids concentration and surface loading rate varied depending
on the treatment plant operation. The only analyses performed on the
thickened solids were total suspended and volatile suspended solids.
These analyses were performed on-site in accordance with Standard Methods.'
The equipment used for dewatering was two types of centrifuges and a
pilot-scale flash evaporator. The first type was a Fletcher Sharpies
basket centrifuge manufactured by the Pennwalt Corporation shown sche-
matically in Figure 2. The unit tested was a production size unit, the
102 cm by 61 cm (40-inch by 24-inch) SST-900. This centrifuge was tested
at various loading rates with and without polymer addition. The feed to
the centrifuge and the centrate were analyzed on-site for suspended
solids. The cake was analyzed for total solids.
The second centrifuge tested was a Westfalia disc type unit. The unit
tested was a full-scale centrifuge. Figure 2 also illustrates the inter-
nal configuration of this type of centrifuge. The Wsstfalia unit was
operated at various loading rates with and without polymer addition.
A pilot flash evaporator was tested to determine its efficiency for
sludge thickening and to determine if it could replace the centrifuga-
tion process. The flash evaporator was a pilot-scale unit consisting
-------
UNUOADER
KNIFE
BASKET
FEED
^Jl »_*. CENTRATE
DISC TYPE
,-.
|1B=B*t>!SCHARGE
DISCHARGE
BASKET TYPE
Figure 2. Schematic diagram of test centrifuaes
-------
of a propane gas fired torch, a rotary fan for heated air-sludge mixing
prior to wet sludge-air separation in a separation chamber. The unit was
also equipped with a product storage tank and a feed sludge holding tank.
Sludge was recycled by the use of a rotary vane pump. Sludge was pumped
from the sludge holding tank into the rotary fan. The hot air and sludge
were mixed by the fan and blown into the separator. Exhaust gases were
vented through the top of the separator and thickened material collected
at the bottom.
After dewatering in a centrifuge, the sludge had to be dried to provide
material for the feeding studies. Two methods of drying were tested—a
rotary kiln dryer and sand beds. The rotary kiln was a pilot-scale three-
pass drum dryer constructed of two concentric rotating drums inside a
third stationary insulated drum. The overall dimensions of the drum were
76 cm (30 inches) in diameter and 1.8 meters (6 feet) long. Heat was
supplied by a propane torch and the kiln was operated at 590°C (1100°F)
to 760°C (1400°F) inlet temperature and 65°C (150°F) to 95°C (200°F) out-
let temperature. The rotating drums were operated at 15 rpm, and the
kiln was hand fed. Material transport within the kiln was achieved by
sets of parallel longitudinal baffles attached inside all three drums.
After the third pass in the dryer, the dried material was pulled into a
two-stage, single fan cyclone and dropped into a collection bucket.
Material fed into the dryer was maintained at 30 to 40 percent moisture
by mixing with recycled dried material.
The sand beds used were conventional sludge drying beds located at the
City of Winter Park's sewage treatment plant. Thickened sludge was
placed on the beds and left until dried. The dried sludge was removed
by hand. Extraneous sand was removed by a shaker screen.
POULTRY FEED
Prior to beginning the poultry feeding tests, a composite sample of the
sludge produced via the above drying methods was analyzed to determine
moisture, protein, crude fiber, calcium and phosphorus content. Amino
11
-------
acid content was taken from the work of Hackler.5 Metabolizable energy
value was estimated. Based on this analysis, a series of diet composi-
tions containing various levels of sludge were formulated, with the diets
in each experiment containing equal levels of protein, calcium, phosphorus,
total sulfur araino acids and metabolizable energy. The composition of
each diet is presented in Section V.
The poultry feeding tests consisted of two series of broiler chick evalu-
ations each of three weeks duration, a broiler study of eight weeks dura-
tion, and a six-month laying hen trial.
Broiler Chick Trials
The broiler chick trials were conducted in Petersime electrically heated
battery brooders with raised wire floors. Pour pens, each containing
five male and five female broiler type chicks were used in each trial.
Mortality was recorded on a daily basis and all birds were group weighed
by sex at the end of the three-week test period. The specific diet com-
positions utilized are discussed in Section V.
Broiler Study
The broiler study was conducted over an eight-week period which is the
standard growirxj period for conmercial broilers. Twelve replicate floor
pens, each containing 10 male and 10 female day-old broiler chicks, re-
ceived each dietary treatment over the 56-day feeding period in three
replications. The daily feed intake and final body weight of the birds
was determined.
At the end of the eight-week feeding period, the individual groups were
kept separate, sacrificed, and processed. A scalding temperature of
60°C for 40 seconds was used. For future identification, each pen of
birds was wing banded as to sex and treatment following picking. The
evicerated carcasses were then rapidly chilled to 5°C in ice slush and
held six hours. The birds were graded as chilled carcasses following
12
-------
the standards established by the USD& Poultry Grading Manual6 for flesh-
ing. Each bird was then individually packaged in 2-mil polyethylene bags
(10 cm by 15 cm by 40 on) and stored at -18°C.
The frozen carcasses were thawed overnight as needed in a walk-in
refrigerator (6°C) and weighed prior to cooking. The carcasses were
cooked, five to a pan, with breast up and two pans at a time in a con-
ventional oven to an internal thigh temperature of 90°C. The internal
temperature was measured by copper-constantan thermocouples inserted
into four thigh muscles and attached to a Leeds & Nbrthrup Speedomax H
Potentiometer recorder. The carcasses were cooled to room temperature
following cooking and weighed. The percent cooking loss was calculated.
Analysis of variance was calculated to determine the significance of the
dressed carcass weight according to sex and treatment.
Flavor, juiciness and texture of cooked light and dark meat were evalu-
ated on five birds from each treatment-sex group for a total of 20 birds
per day. The meat was evaluated by a semi-trained taste panel using a
five point hedonic scale. Samples of dark meat, m. semitendinosus and
m. s^emimembranosus, were excised together from the thigh at the coccygeal
vertebra and caudal part of the ilium. The light meat sample was the
large inner breast muscle, m. pectoralis superficialis (minor).
These muscles were removed only from the right side after the carcass
had cooled to room temperature (27°C) and held for taste panel evaluation.
The meat was cut into four pieces and the same relative section of meat
was given to the same panel member for each of the four treatments on
that day. The number of panelists available each day varied from 18 to
20. Each panelist was separated from others by dividers. Water was pro-
vided between sanples. No attempt was made -to alter the normal fluores-
cent room lighting. Analysis of variance was performed comparing differ-
ences between muscle, sex and treatment for flavor, juiciness and texture.
The remainder of the carcasses were removed from the refrigerator after
24 hours in order to determine tenderness using the Food Technology
13
-------
Texture Press. The m. pectoralis superficialis (minor) was excised from
the left side and wrapped to prevent moisture loss. All samples were
allowed to reach room temperature and trimmed to a length of 6 cm and
weighed to the nearest 0.1 gram. Each piece was placed perpendicular to
the slots of the shear cell and the force recorded in 0.45 kg increments
by a 136 kg force deformation ring, This force was converted to kg/gram
of muscle tissue. An analysis of variance performed comparing signifi-
cant differences between muscle, sex and treatment.
Hen Trials
The last experiment involved the feeding of various levels of sludge to
White Leghorn hens over a six-month period. As in the previous experi-
ments, each feed was formulated to be isonitrogenous and isocaloric with
each feed also containing equal levels of calcium, phosphorus and sulfur-
containing amino acids. The specific diets are described in Section V.
Eight replicate groups of five individually caged hens were assigned to
each of the dietary treatments. Evaluation criteria were hen-day egg
production, daily feed intake, feed required to produce a dozen eggs,
mortality and egg weights.
Qrganoleptic evaluations were also conducted on the eggs produced during
the above laying hen trials. Initially, two eggs (1 to 6 hours after
lay) from each sludge treatment level were collected and broken open
into plastic petri dishes, without breaking the yolks, and the yoUc
color scored by conparison with the Heiman-Carver color rotor. Yolk
color measurements were subsequently made with a reflectance colorimeter,
the U3L COLOR-EYE*'. The COLOR-EYE values were converted to dominant
wavelength, excitation, purity and luminosity which represent a mathe-
matical description of the egg yolk color, all possible biases and human
judgement being removed.
Pour eggs (1- and 2-day old), held at 18.3°C and 75 percent room humidity,
were selected from each replication and broken out to obtain a pooled
14
-------
yolk sample. After removal of the majority of the albumen, each yolk was
rolled on a dampened paper towel to remove all adhering albumen. The
yolk was held over a beaker, the vitelline membrane ruptured and the yolk
contents collected. The yolk material was hand-stirred, care being taken
to keep the incorporation of air bubbles to a minimum. Lucite sample
holders were used and analyses made on the IDL COLOR-EYE. Two additional
color determinations were made at 10-day intervals using the above pro-
cedure.
Flavor comparisons were made on eggs collected from, hens receiving the
0.0 percent (control) and the 20.0 percent (treatment) levels of citrus
sludge. The eggs were held for five days at 18.3°C and 75 percent room
humidity to permit optimum peelability, as these eggs were to be hard
cooked by the cold water method as per Irmiter.7 The paired-comparison
test suggested by Dawson8 et. al., was used to select the best sample.
The eggs were hard cooked, cooled in ice water, peeled and quartered.
Untrained panelists from the Poultry Science Department sampled three
pairs each day with only one pair compared at a time. The eggs were
served at room temperature on a 23-cm plate with a quarter-slice placed
on the extreme left and a quarter-slice of the other (either the control
or treatment) on the extreme right. Each pair of samples was placed on
the plate before serving and coded to prevent the panelists from knowing
beforehand the serving sequence. The panelists were asked to select
separately the egg which had: 1) the darker colored yolk, 2) the greater
degree of albumen off-flavor, and 3) the greater degree of yolk off-
flavor. A minimum of 80-paired comparisons was necessary for the bino-
mial distribution statistics of Dawson8 and calculations performed as
per Wilks.9
All statements of probability throughout the poultry feeding tests are
based on the analysis of variance as described by Snedecor,10 and sig-
nificant differences being determined by the multiple range test of Duncan.11
15
-------
SECTION V
RESULTS
The sludge recovery portion of this study was performed on-site at the
WQCP citrus plant in Winter Garden, Florida. As a portion of the equip-
ment being evaluated was full-scale equipment operated as an integral
part of the treatment system, the operation of the activated sludge pro-
cess during this period affected the results of the study. Therefore,
the treatment plant operating data collected during the study period
will be presented. Following the presentation of treatment plant oper-
ating data, the performance of the sludge recovery units will be presented.
Finally, the results of the various poultry feeding tests will be pre-
sented.
OPERATION OF THE ACTIVATED SLUDGE PROCESS (1972-1973 SEASON)
The period of interest in this study is the 1972-1973 citrus processing
season which lasted fron December 1972 through August 1973. The chemical
data collected during the season is tabulated in Table 1. The consis-
tently high reduction in BOD and GOD and the variation in influent con-
centration are also illustrated in Figure 3. Table 2 is a cotpilation
of the average aeration tank operating data for the season.
The quantity of sludge wasted during the 1972-1973 season averaged approx-
imately 1.8 to 2.7 kkg/day (2 to 3 tons/day). Table 3 shows typical
chemical analyses of the waste activated sludge. The waste sludge volume
varied fron 246 to 734 K*/day (65,000 to 194,000 gpd) with a clarifier
underflow solids concentration of approximately 8,000 mg/1. The quantity
of sludge wasted appears excessive because sludge was wasted to the sludge
thickener and sludge holding tanks at a relatively constant rate. During
periods when all of the waste sludge could not be handled by the centri-
fuge or kiln dryer, the excess overflowed the sludge holding tank back
into the wastewater treatment plant.
16
-------
Table 1. CHEMICAL ANALYSES FOR THE 1972-1973 OPERATING SEASON
(monthly averages)
Month
December, 1972
January, 1973
February
March
April
May
June
July
August
Average flow,
M3/daya
4,540
6,060
5,680
5,680
5,300
6,810
6,060
4,540
3,790
Sanpling
point
Influent
Effluent
% Reduction
Influent
Effluent
% Reduction
Influent
Effluent
% Reduction
Influent
Effluent
% Reduction
influent
Effluent
% Reduction
Influent
Effluent
% Reduction
Influent
Effluent
% Reduction
Influent
Effluent
% Reduction
Influent
Effluent
% Reduction
BOD,
630
15
97.6
980
28
97.1
1100
20
98.2
1040
20
98.1
930
34
96.2
480
16
96.5
530
57
89.2
600
12
98.0
400
4
99.0
ODD,
rag/1
1960
97
95.0
3080
432
86.0
3310
159
95.2
3110
204
93.4
2570
105
96.0
2820
199
93.0
2160
219
89.9
1870
69
96.3
1170
65
94.4
pti mg/1
8.4
7.4 0.5
—
8.5
7.4 0.6
-
8.2
7.0 2.2
-
8.7
7.1 2.1
-
9.1
7.4 1.1
—
9.4
7.5 0.7
—
9.3
7.4 0.7
-
9.1
7.5 0.6
_
9.6
7.6 3.0
—
NH3,
_
0.9
—
-
1.4
-
-
0.9
—
-
1.4
—
-
1.3
—
—
1.0
—
_
1.2
—
-
1.8
—
-
2.0
—
= M3/day (2.642 x 10~4)
Median value
-------
1100 ,
1000 _
3OOO
20OO
BOD INFLUENT
COD INFLUENT
COD EFFLUENT
BOD EFFLUENT
DEC JAN FEB MAR APR MAY JUN JUL AUG
Q
O
O
ooo
Figure 3. Influent and effluent BOD and COD, 1972-1973 season
18
-------
Table 2. AVERAGE CHEMICAL ANALYSIS OF AERATION TANK,
1972-1973 OPERATING SEASON
Mixed liquor
suspended solids,
Month nig/1
December, 1972
January, 1973
February
March
April
May
June
July
August
3830
4140
5400
5400
4230
4250
3900
3960
3520
Dissolved oxygen,
ng/1
4.2
1.8
1.3
1.2
3.6
2.4
1.6
2.5
3.7
PHS
7.4
7.4
7.0
7.1
7.3
7.4
7.3
7.5
7.5
aMedian value
19
-------
Table 3. CHEMICN* MffiLYSES OF WASTE ACTIVATED SLUDGE
(clarifier underflow)
Test3
no.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
Flow,
M3/dayk
708
708
708
708
246
492
708
708
708
708
246
708
708
708
674
367
674
674
674
674
613
Total
solids,
mg/1
6,390
7,320
8,750
8,130
7,290
9,870
10,970
9,360
6,670
9,040
2,360
7,250
7,560
7,940
7,660
6,770
8,700
8,420
8,160
11,290
16,290
Volatile
solids,
irg/i
5,490
6,440
7,800
7,250
6,430
8,890
9,670
8,190
5,600
6,260
6,540
6,850
7,600
8,070
7,780
10,110
14,720
Waste
sludge,
kg TS/day0
4,520
5,180
6,200
5,760
1,790
4,860
7,770
6,630
4,720
6,400
582
5,130
5,350
5,620
5,160
2,480
5,860
5,680
5,500
7,610
9,980
20
-------
Table 3 (continued). CHEMICAL ANALYSES OF WASTE ACTIVATED SLUDGE
(clarifier underflow)
Testa
no.
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
Flow,
613
446
734
734
734
734
734
734
734
458
734
734
734
734
734
734
734
Total
solids,
mg/1
11,510
10,410
10,000
11,000
9,400
9,100
11,000
9,000
10,000
7,000
7,000
11,000
7,000
10,000
8,000
6,000
7,000
Volatile
solids,
rag/1
10,340
9,400
9,000
9,900
8,460
8,190
9,900
8,100
9,000
6,230
6,230
9,570
5,950
9,200
7,200
5,400
6,300
Waste
sludge,
kg TS/dayc
7,060
4,640
7,340
8,070
6,900
6,680
8,080
6,610
7,340
3,210
5,140
8,070
5,140
7,340
5,870
4,400
5,140
aEach test nunfcer represents a 24-hour sattpling period
bgpd = M3/day x 264.2
Clbs/day = kg/day x 2.20
21
-------
SLUDGE RECOVERY
Vario\as sludge recovery techniques were tested. In all cases the waste
sludge was thickened prior to further recovery attenpts. The efficiency
of the thickener is shown in Table 4. The average total solids of the
thickener underflow was 2.8 percent; however, with proper control a sludge
concentration of 3.0 to 3.5 percent could be obtained. Assuming an influ-
ent and effluent total solids of 0.8 and 3.2 percent/ respectively/ the
sludge thickener was able to decrease sludge volume by 75 percent.
Also shown in Table 4 is the effect on solids concentration of sludge
storage in the holding tank. As can be seen, a well designed surge or
holding tank can provide significant additional thickening.
The thickened sludge was dewatered by centrifugation, followed by rotary
kiln drying, by drying without centrifugation, and by sand bed drying on
open beds. Two centrifuges were tested at various feed rates and influ-
ent concentrations. Figure 4 shows the predicted capacity of a Fletcher-
Sharpies basket centrifuge. The SST-900 has a 102 cm bowl. Figure 4 was
developed from data collected through the operation of an SST-900 at MGCP.
The solids in the cake varied from approximately 7 to 10 percent depend-
ing upon the feed rate to the centrifuge.
Table 5 shows the results of 37 different tests using a Vfestfalia disc
type centrifuge. Tests 1 through 31 were conducted without polymer and
tests 32 through 37 were conducted with the addition of polymer (Herco-
floc). The main effect of polymer addition was to increase the percent
solids recovery; but it had little effect on cake dryness. At an aver-
age feed rate of 29 1/min (7.6 gpm) and a feed solids of 1.9 percent,
the disc centrifuge was capable of producing a cake of approximately 7.2
percent solids with an 87 percent recovery efficiency.
As can be seen both types of centrifuge produced good recovery of acti-
vated sludge. Based on these results and in consideration of other
22
-------
Table 4. CHEMICAL ANALYSES OF SLUDGE THICKENER UNDERFLOW
AND SLUDGE SURGE TANK UNDERFLOW
(percent)
Thickener Underflow
Testa
no.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
Total
solids
1.2
2.2
2.7
1.7
1.4
1.2
1.1
1.6
2.9
2.9
2.4
2.6
2.9
2.5
2.6
3.5
4.2
3.5
3.7
Volatile
solids
0.9
1.9
2.5
1.5
1.2
0.7
0.8
1.3
2.6
-
-
2.3
2.5
2.2
2.2
-
-
3.1
3.1
Sludge Surge Tank Underflow
Total
solids
1.7
2.4
2.8
4.0
2.0
1.6
1.9
2.5
2.8
1.5
3.3
2.5
3.0
4.1
2.8
3.5
' 3.7
-
Volatile
solids
1.4
2.1
2.5
3.0
1.8
1.2
1.7
2.2
2.5
-
-
2.1
2.6
3.7
2.5
-
3.2
-
23
-------
Table 4 (continued).
CHEMICAL ANALYSES OF SLUDGE THICKENER UNDERFLOW
AND SLUDGE SURGE TANK UNDERFLOW
(percent)
Thickener Underflow Sludge Surge Tank Underflow
Testa
no.
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
Total
solids
4.4
3.7
2.8
3.0
3.9
3.1
3.0
2.3
3.2
3.9
3.0
3.0
3.1
3.5
3.7
2.6
2.6
Volatile Total
solids solids
3.9
3.1
2.6
2.6
3.1
2.7
2.7
2.1
2.9
3.5
2.7
2.7
2.5
3.1
3.3
2.3
2.3
Volatile
solids
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
aEach test nunfoer represents a 24-hour composite sample
24
-------
to
94
92
s
Q
UJ
95
z>
V)
90
ct 84
u.
a
ui
a.
80
FEED: 2.5*/.
FEED.:1.5'/..
122cm x 61cm
SST - 900 ,
i_J LJ L
I I I I I
0.7 0.8 0.9 1.0
1.1 1.2 1.3 1.4 1.5 1.6
(NET) FEED RATE, I /sec
1.7 1.8 1.9 2.0 2.1
Fiqure 4. Percent recovery versus feed rate for a basket centrifuge
(SST-900)
-------
Table 5. TYPICAL RESULTS FOR THE WESTFKLIA CENTRIFUGE
Total Solids
Testa
no.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Feed rate,
l/Mir0
34
34
34
34
21
21
21
21
57
57
34
34
34
-
19
19
19
19
23
23
Feed,
percent
1.2
1.2
1.2
1.2
0.9
0.9
1.4
1.4
1.4
1.4
2.2
2.2
2.2
-
2.2
2.2
2.4
2.4
2.4
2.4
Cake,
percent
7.6
7.7
5.5
8.2
8.1
5.9
9.7
8.4
6.4
6.8
8.2
6.9
7.6
-
9.2
7.4
8.7
8.3
8.1
9.0
Effluent,
percent
0.14
0.12
0.12
0.23
0.12
0.12
0.29
0.11
0.14
0.18
0.72
0.19
0.37
-
0.14
0.07
0.08
0.11
0.61
0.52
Recovery,
percent
89
90
90
81
86
86
80
92
90
87
67
92
83
-
94
97
97
96
75
79
26
-------
Table 5 (continued) . TYPICAL RESULTS FOR THE WESTFALIA CENTRIFUGE
Total Solids
Testa
no.
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
Feed rate/
l/min33
34
30
17
30
26
17
30
30
30
26
28
26
26
26
30
30
28
Feed,
percent
2.3
2.1
2.1
1.9
1.9
2.2
2.2
2.2
2.6
2.1
2.2
2.2
1.5
2.4
2.4
2.2
2.2
Cake,
percent
6.8
7.2
6.9
6.3
6.4
5.5
7.0
7.2
6.0
5.7
6.4
6.3
5.7
6.6
6.2
6.7
7.1
Effluent,
percent
0.13
0.48
0.29
0.25
0.24
0.15
0.27
0.78
1.00
0.40
0.12
0.10
0.08
0.13
0.14
0.12
0.11
Recovery,
percent
94
77
86
87
88
93
88
65
62
82
95
96
95
94
94
95
95
t numbers 1-33 with "open foot," 34-37 with "closed foot"
Test numbers 32-35 with 2.5 qms HereoflocA^ dry solids
Test numbers 33-36 with 5.0 gms HereofIoc/k.q dry solids
gpm = I/tain x 0.2642
27
-------
factors, a full-scale Vfestfalia centrifuge was installed to operate full-
tine for sludge recovery. The factor influencing this choice was WGCP's
previous experience with a solid bowl centrifuge which was not favorable.
If the Vfestfalia unit failed to perform adequately for sludge recovery,
it could be used in the oil mill for liquid-liquid separation, whereas
the basket centrifuge would have no such application. The engineer's
reconmendation was against the use of the Westfalia unit because of the
known effects of abrasive materials on the discs. No provision for grit
removal was available in the activated sludge plant; therefore, quantities
of sand resulting from the fruit washing operation found their way into
the waste sludge. Sand had an abrasive effect on various parts of the
disc centrifuge resulting in the centrifuge having to be taken out of ser-
vice for repair. Unless sand or other abrasive material is removed from
the waste sludge, it is questionable if this type machine can be utilized
for sludge dewatering.
In order to provide a dry material for the chicken feeding studies and to
provide needed operational data on sludge drying, a pilot rotary kiln
dryer was tested. Itotary kiln dryers cannot function on a feed with as
low a solids content as results from the gravity sludge thickener or the
centrifuge. Therefore, it was necessary to recycle dried sludge to mix
with the feed sludge to maintain an input solids content of approximately
40 percent.
Table 6 shows the results of 20 separate pilot plant "runs" using the
rotary kiln dryer. Each run represents a successful operating day when
the pilot plant was kept in continuous operation from 10 to 12 hours.
There were numerous days that either mechanical failure or weather con-
ditions (the plant was not covered) required a "run" to be terminated.
In an attempt to increase the production rate of the pilot plant kiln
dryer, a pilot plant flash evaporator was installed to help remove a por-
tion of the water from the gravity thickened sludge. Table 7 shows
typical results obtained by drying sludge in the flash evaporator.
28
-------
Table 6. PHOT PIANT KUN DATA
Run
no.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Temperature,
°C
Inlet
650-760
650-760
650-760
650-760
590-700
590-700
590-700
590-700
590-700
650-700
650-700
650-700
650-700
590-650
590-650
590-650
590-650
620-650
540-650
590-650
Outlet
66-79
66-79
74-85
80-93
80-93
80-93
80-93
80-93
80-93
80-93
80-93
80-93
80-93
80-93
80-93
80-93
80-93
80-93
80-93
80-93
Total solids,
percent
Influent
3.5
4.2
2.6
2.3
3.3
3.2
3.2
4.9
3.7
3.8
3.6
2.4
2.6
4.8
3.9
4.8
4.6
6.5
4.6
5.8
Cake
74
89
90
94
94
91
92
92
93
93
95
98
98
96
94
92
95
95
96
94
Total
volatile solids,
percent
Influent
—
89
90
90
90
86
92
93
91
84
96
86
93
92
87
90
88
91
87
90
Cake
—
74
74
75
66
72
70
69
69
69
73
75
70
71
69
70
76
79
76
77
Cake
produced,
kg
6.4
3.2
4.5
1.8
2.3
3.6
2.7
2.3
1.8
1.8
1.8
0.9
1.4
1.8
1.8
1.8
1.8
0.9
3.2
2.3
29
-------
Table 7. PILOT PLANT FLASH EVAPORATOR DATA
Total solids, Total volatile solids,
percent percent
Run no.
1
2
3
4
5
6
Inlet
3.4
3.4
3.3
2.2
2.5
2.9
Outlet
4.6
4.6
5.8
4.8
4.6
6.5
Inlet
-
-
-
98
97
97
Outlet
-
-
-
95
95
94
POULTRY FEEDING STODIES
In order to evaluate the potential of waste activated sludge as a poultry
feed supplement, three experiments were conducted. The experimentation
consisted of two short-term chick trials, an eight-week broiler study,
and a six-month feeding period with laying hens.
Prior to beginning these studies, the basic nutrient composition of the
material was determined and is presented in Table 8. On an analytical
basis, the dried sludge appears to be a good source of protein and phos-
phorus. It also contains substantial quantities of lysine and the sulfur
containing amino acids—methionine and cystine. These are the amino acids
which are normally in shortest supply in poultry feeds where corn and
soybean meal are the staple ingredients. The relatively high level of
fiber was of concern since chickens do not have the enzymes necessary to
digest fiber. The metabolizable energy value which is estimated is approx-
imately one-half that found in yellow corn.
30
-------
Table 8. COMPOSITION OF DRIED ACTIVATED SLUDGE
Ingredient
Moisture
Protein
Crude fiber
Calcium
Phosphorus
Methionine
Cystine
Lysine
Metabolizable calories/kilogram b
Percent
6.30
38.6
12.6
1.49
1.59
0.50
0.20
1.30
1760
aThese values taken from Hackler5
^Estimate based on chemical analysis of sludge (protein, fat and
NFE multiplied by appropriate calories/kg)
Broiler Chick Studies
The first two experiments were conducted in electrically heated battery
brooders with raised wire floors to prevent fecal recycling. In each of
the two experiments four replicate pens, each containing five male and
five female day-old broiler type chicks, received dietary treatments con-
sisting of various levels of sludge for a three-week feeding period. In
the first experiment the birds received diets containing 0, 2.5, 5, 10,
15 or 20 percent sludge. The diets were composed primarily of yellow
corn and soybean meal in combination with other ingredients commonly em-
ployed in poultry feeding. These diets and their composition are sham
in Table 9.
All of the diets in the series were calculated to contain 23 percent
protein, 1.1 percent calcium, 0.755 percent total phosphorus, 0.88 per-
cent total sulfur amino acids, and 3,012 kilocalories of metabolizable
31
-------
Table 9. COMPOSITION OF BASAL AND SLUDGE DIETS
u>
to
Ingredient
Yellow corn
Soybean meal (48.5 percent)
Alfalfa meal (20 percent)
Sludge
Ground limestone (38 percent Ca)
Def luorinated phosphate
(18 percent P, 32 percent Ca)
Iodized salt
Vitamin pre-mbca
Animal fat
DL-methionine
Basal
%
54.97
36.50
2.50
0.00
0.74
2.11
0.40
0.50
2.15
0.13
Sludge
2.5 %
53.81
34.71
2.50
2.50
0.79
1.95
0.40
0.50
2.70
0.14
5.0 %
52.71
32.87
2.50
5.00
0.82
1.81
0.40
0.50
3.23
0.16
10.0 %
50.40
29.28
2.50
10.00
0.89
1.52
0.40
0.50
4.33
0.18
20.0 %
45.94
21.98
2.50
20.00
1.05
0.92
0.40
0.50
6.47
0.25
Supplied per kilogram of diet: 6,600 I.U. vitamin A; 2f200 I.C.U. vitamin 03; 499.4 mg choline
chloride; 39.6 mg niacin; 13.2 mg pantothenic acid; 4.4 mg riboflavin; 2.2 mg menadione dimethyl-
pyrimidinol bisulfite; 0.125 mg ethoxyguin; and 22 yg vitamin
-------
energy per kilogram. The inclusion of citrus sludge allowed for corres-
ponding decreases in the amounts of yellow corn, soybean meal and defluori-
nated phosphate necessary to maintain equivalent diets; however, large
increases in the amounts of animal fat and DL-methionine were required in
order to maintain energy and sulfur amino acid levels.
Since previous work12 has indicated that sludge tends to cause the destruc-
tion of unstabilized vitamin D sources, a supplemental level of 2,200
International Chick Units of vitamin D^ per kilogram of diet was eitployed.
This level of fortification was approximately 10 times greater than the
requirement level of the starting chick as defined by the National Research
Council.13
As previously mentioned, the chick performance tests were performed in
two short-term experimental phases. The chick performance data for
Experiment 1 are shown in Table 10. The daily consumption of feed did
not vary significantly with different levels of sludge. However, the
efficiency of the feed did vary significantly. Feed efficiency is mea-
sured as grams of feed consumed per gram of body weight and, obviously,
the best efficiency is the least ratio of feed to final body weight. In
Experiment 1, the best efficiency was obtained at the 2.5 and 5.0 percent
sludge levels, and the inclusion of sludge up to 10 percent in the chicks'
diet did not significantly affect the feed efficiency. The feed effici-
ency value for birds fed a diet containing 15 percent sludge was not sig-
nificantly different from the value for the 10 percent sludge diet, but
was different from values obtained for all other diets. Birds receiving
a diet containing 20 percent sludge had a feed efficiency significantly
lower than all other treatments or, in other words, a feed to body weight
ratio significantly higher than any other sludge treatment level.
The final body weight for the broiler chicks in Experiment 1 at the end
of the three week test is also given in Table 10. As can be seen, there
was a trend to lower final body weight at higher sludge levels. The in-
clusion of sludge at levels above 10 percent resulted in a significant
33
-------
Table 10. CHICK PERFORMANCE DATA (Experiment 1)
Treatment,
percent sludge
0.0
2.5
5.0
10.0
15.0
20.0
Feed/bird/day ,
grams/day
30.4
29.6
29.6
30.5
31.0
31.6
Feed/body weight3
1.48A
1.45&
1.45A
1.51*°
1.59s
1.74C
Body weight,5
grams
4UAB
413*
409ABC
403ABCD
390°°
365E
without common letters are significantly different according to
Duncan's multiple range test (P <0.05)
difference in final body weight. The 20.0 percent level of sludge re-
sulted in a final body weight significantly lighter than that obtained
at any other level of sludge treatment.
From the data obtained in the first experiment it was evident that some
change in treatments should be made before the next study was initiated.
It was felt that the growth depression associated with the 20 percent
sludge diet might have been due to the low availability of sulfur amino
acids, or because the dietary lysine level was slightly below the National
Research Council's suggested requirement. Therefore, in the second ex-
periment the amounts of methionine and lysine supplied in the first ex-
periment by the inclusion of 20 percent citrus sludge were added back to
this diet in purified form, resulting in total supplemental levels of
0.38 percent methionine and 0.26 percent lysine. Thus, the dietary
treatments of the second experiment consisted of 0, 2.5, 5, 10, or 20
percent sludge, with a sixth treatment of 20 percent sludge plus addi-
tional methionine and lysine. The latter diet will subsequently be re-
ferred to as the "20 percent plus" diet. As in the first experiment,
34
-------
all but the "20 percent plus" diet were calculated to be isonitrogenous,
isocaloric and meet all other requirements of the starting chick.
Table 11 presents the results of the second experiment with broiler chicks.
As in the first three-week experiment, no significant difference in daily
feed intake values resulted at any of the sludge levels tested. Feed
efficiency did not differ significantly from the basal diet up to the in-
clusion of 5.0 percent dried sludge in the chicks' diet. Also, efficiency
values for birds receiving diets containing 10, 20 or the "20 percent
plus" diets did not differ significantly. From a numerical standpoint,
it appeared that levels in excess of 5 percent sludge adversely affected
feed efficiency.
Table 11. CHICK PEKFOEMANCE DATA (Experiment 2)
Treatment, Feed/bird/day,
percent sludge grams/day
0.0
2.5
5.0
10.0
20.0
20.0 + Lysine &
Methionine
35.8
35.6
37.3
34.4
37.2
35.3
Feed/body weight3
1.64ABC
1.62A
i.ee^
1.75P
1.83°
1.74BCD
Body weight,3
grams
455^
460^
472A
414C
423C
425C
aMeans without common letters are significantly different (P <0.05)
according to Duncan's multiple range test
As shown in Table 11, there were no significant differences among the
body weights of birds receiving either 0, 2.5 or 5 percent sludge; how-
ever, there was some trend towards parallel sludge and body weight in-
creases for this group. Weights of treatment groups receiving above 5
35
-------
percent sludge were all significantly below those of the lower sludge
levels previously mentioned, but did not differ statistically from each
other.
Mortality was not a factor in either experiment, as mortality records
indicated that only one bird died in each trial. Throughout all experi-
ments, the addition of sludge had no effect upon feed or dropping condi-
tion, other than to impart a dark color to both.
These data indicate that levels of between 5 and 10 percent sludge could
be included in the diet of starting broiler chicks without adversely
affecting growth or other performance criteria. The exact level tolerated
would be dependent upon feed intake, as evidenced by the fact that birds
of the second experiment tolerated a lower dietary percentage because
their feed intake was higher than that of the birds utilized in the first
experiment.
Broiler Studies
The next phase of experimentation was a broiler study of eight weeks
duration in which broiler chicks were fed a control diet supplemented
with either 2.5, 5.0 or 10 percent citrus sludge. The diets used were
identical in composition to those shown for previous experiments, with
the exception of the inclusion of 0.05 percent Amprol, a coccidiostat,
in place of an equal amount of yellow corn. Table 12 presents the final
body weight, feed consumption and feed efficiency of the broilers at the
various sludge levels. In this experiment there was no significant dif-
ference in final body weights at any level of sludge treatment. However,
as seen in the chick trials, body weights tended to increase through the
5 percent level of supplementation with the weights of the birds receiv-
ing 10 percent sludge being somewhat lower than those of controls.
Daily feed intake values were rather variable within this experiment,
but increased levels of intake did appear to be correlated with dietary
36
-------
Table 12. DATA FROM BROILER STUDY
Sludge,
percent
0.0
2.5
5.0
10.0
Body weight,
grams
1750
1772
1800
1732
Feed/bird/day , a
grams/day
66AB
63^
67B
6S5
Feed/body weight
2.16
2.08
2.16
2.25
without common letters are significantly different (P <0.05)
according to Duncan's multiple range test
sludge content. Again, feed required per unit of body weight was not
significantly influenced by treatment and, in general, these values re-
flected the trends of body weight and daily feed intake. These data
tend to substantiate other trials in that a level of sludge somewhere
between 5 and 10 percent appeared to support best performance.
In addition to determining feed efficiency levels for the broilers, taste
panel evaluations of muscle tissue from these birds were also conducted.
At the end of the eight-week feeding study, the birds were sacrificed,
picked and frozen as previously described. The frozen carcasses were
thawed overnight and weighed prior to cooking. The average dressed car-
cass weights are shown in Table 13. A significant difference in weights
was observed between sexes at the 0.01 level of significance. Bcwever,
there were no significant effects attributable to sludge levels.
The carcasses were then cooked in a conventional oven to an internal
thigh temperature of 90°C. The cooked birds were then weighed to deter-
mine the percent cooking loss. No significant difference in cooking
loss due to sludge treatment levels was found. The mean cooking loss
was 25.57 percent and the standard deviation was 3.87 percent.
37
-------
Table 13. AVERAGE DRESSED CARCASS WEIGHT FOR BROILERS FED
VARIOUS DIETARY LEVELS OF SLUDGE
Sludge,
percent
Basal
2.5
5.0
10.0
Average3
Dressed
Male
1228
1126
1238
1212
1202
carcass weight,
grains
Female
984
1042
1024
970
1005
aOverall average, 1102; standard deviation, 103
Flavor, juiciness and texture of cooked light and dark meat were evaluated
by a semi-trained taste panel. Palatability was graded on a five-point
hedonic scale. While there was a significant difference in preference
between dark and white meat, as shown in Table 14, there was no signifi-
cant difference due to sludge treatment level. There was also no signi-
ficant difference in shear strength in the muscle tissue of birds fed
different levels of sludge.
Laying Hen Studies
The last phase of experimentation involved the feeding of 0, 2.5, 5.0,
7.5 or 20 percent sludge to laying hens over a six-month period. The
composition of the basal diet and the diet containing the 20 percent
sludge addition are shown in Table 15.
These sludge additions were made while maintaining a constant level of
protein at 15 percent, calcium at 3.25 percent, 0.65 percent phosphorus,
0.59 percent sulfur containing amino acids, and 2,860 kilocalories of
metabolizable energy per kilogram of diet. As noted before, sludge
38
-------
Table 14. AVERAGE AND MEM PALATABILITY SCORES OF DARK AND WHITE MEAT
FROM COOKED MALE AND FEMALE BROILERS3
Sludge,
percent
Basal
2.5
5.0
10.0
Type
meat
Dark
Light
Dark
Light
Dark
Light
Dark
Light
Flavor
0.58
0.85
0.57
0.85
0.63
0.84
0.51
0.96
Juiciness
0.33
-0.08
0.33
-0.12
0.40
-0.15
0.32
0.04
Texture
0.32
0.89
0.38
0.84
0.64
0.81
0.43
0.84
Mean
0.42
0.56
0.43
0.52
0.56
0.50
0.42
0.61
a-2 is for very unacceptable, dry or tough and +2 is for very acceptable,
moist or tender
Table 15. LAYING HEN SLUDGE DIET COMPOSITION
Ingredient
Yellow corn
Soybean meal (48.5%)
Alfalfa meal (20%)
Sludge
Limestone (38% Ca)
Defluorinated K>4 (18% P, 32% Ca)
Iodized salt
Microingredients
Animal fat
DL-Methionine
Filler
Basal
66.50
17.96
2.50
—
6.77
1.94
0.40
0.50
1.10
0.06
2.27
Percent
20% sludge
58.00
3.34
2.50
20.00
6.98
0.80
0.40
0.50
5.22
0.17
2.09
39
-------
additions allowed for the removal of yellow corn, almost all of the soy-
bean meal, and a large portion of the defluorinated phosphate, with corres-
ponding increases of animal fat and DL-methionine. Evaluation criteria
included egg production, daily feed intake, feed required to produce a
dozen eggs, mortality and egg measurements of average weight, specific
gravity and Haugh units. In addition, organoleptic evaluations were con-
ducted on the eggs produced and the differences in yolk color evaluated.
Eight replicate groups of White Leghorn hens held in individual laying
cages were assigned to each dietary treatment through 7.5 percent sludge.
Pour replicate groups received the 20 percent level.
Egg production was not affected by the addition of levels of sludge
through 7.5 percent as shown in Table 16; however, the 20 percent level
did cause a significant depression of egg production.
Table 16. AVERAGE LAYING HEN PERFORMANCE (6 months)
Treatment,
percent sludge
0.0
2.5
5.0
7.5
20.0
Average egg
production,3
percent
69.61A
68.32A
67.01A
69.21A
42.12s
Egg weight,3
grams
62.^
63. 4A
63.6A
63.3*
59. 0B
aMeans without common letters are significantly different (P <0.05)
according to Duncan's multiple range test
The average weight of eggs produced followed exactly the same trends as
egg production.
There was no significant effect upon daily feed intake until the 20 per-
cent level of sludge was reached, as shown in Table 17.
40
-------
Table 17. AVERAGE LAYING HEN PERFORMANCE (6 months)
Treatment,
percent sludge
0.0
2.5
5.0
7.5
20.0
Feed/bird/day ra
grams/day
113A
109A
114A
112A
92B
Feed/dozen eggs,a
kilograms
2.00A
1.98A
2.13*
2.01A
2.86B
without oontnon letters are significantly different (P <0.05)
according to Duncan's multiple range test
This feed intake trend is very definitely related to egg production rate;
however, it is very difficult to determine whether the intake depression
resulted in lowered production or whether the lowered production resulted
in reduced feed intake. As expected, the amount of feed required to pro-
duce a dozen eggs was also a function of the egg production and feed in-
take trend.
Specific gravity is a measurement of eggshell quality made by moving each
egg through a graded series of salt solution. No significant differences
due to treatment were found, as illustrated in Table 18.
Table 18. AVERAGE LAYING HEN PERFORMANCE (6 months)
Treatment,
percent sludge
0.0
2.5
5.0
7.5
20.0
Specific gravity
1.0792
1.0801
1.0787
1.0780
1.0781
Haugh unitsa
64. 3A
67. 4^'
69. 4B
68. 9B
82. 0C
aMeans without common letters are significantly different (P <0.05)
according to Duncan's multiple range test
41
-------
Haugh units are a measure of interior egg quality arrived at through an
integration of egg weight and albumen height. A trend towards improving
Haugh unit scores is seen as the level of sludge increased through 7.5
percent. The scores of eggs from hens receiving either 5 or 7.5 percent
citrus sludge were significantly better than those of control birds. The
extremely high value from hens receiving 20 percent sludge was anticipated
since interior egg quality is normally inversely related to the bird's
level of egg production.
Proper egg yolk color is a very important commercial consideration and,
due to the possibility of off-flavors developing from the feeding of
citrus sludge, a further investigation of the effect of sludge upon these
parameters was initiated.
Initially, two eggs from each treatment group were collected and broken
open into plastic petri dishes, without breaking the yolks, and the yolk
color scored by comparison with a color rotor which carries a graded
series of standard color spots. The scores ranged from 12 for the yolks
of eggs from control hens to 18 for those receiving 20 percent citrus
sludge (Table 19). This score increase represents a definite increase
of yolk color intensity, with a higher number indicating the darker color.
Table 19. IMEERREUffilCNSHIP OF DIETARY SLUDGE AND
HEIMSN-CARVER COLOR ROTOR NUMBERS
Sludge, Heiman-Carver color
percent rotor numbers
0.0 12
2.5 14
5.0 15
7.5 16
20.0 18
42
-------
Subsequent yolk color measurements were made with reflectance colorimeter,
the IDL COLOR-EYE®. The COLOR-EYE values represent a mathematical descrip-
tion of egg yolk color with all possible biases and human judgement being re-
ceived. For this evaluation, eggs were collected from hens in four repli-
cations of each dietary treatment. Pour eggs from each replication were
then broken out to obtain a pooled yolk sample and prepared for COLOR-EYE
evaluation. The results of these COLOR-EYE determinations are summarized
in Table 20.
Table 20. COIOR CHARACTERISTICS OF EGG YOLK
Sludge ,
percent
0.0
2.5
5.0
7.5
20.0
Dominant wavelength,
nm
578.5
579.3
579.5
580.8
583.5
As the level of dietary citrus sludge increased the dominant wavelength,
which is the color or hue of the egg yolk, also increased. This numeri-
cal improvement represents a change in color from yellow to a yellowish-
orange hue. Increasing sludge levels dictated the removal of both yellow
corn and soybean meal. Yellow corn is normally a prime source of egg
yolk coloration. The removal of 12.8 percent yellow corn from the basal
diet in order to formulate the 20 percent level of citrus sludge resulted
in a lower contribution of yellow corn to dietary pigmentation; however,
the addition of citrus sludge more than compensated for this reduction.
Flavor and color comparisons were also made by untrained taste panelists
from the Department of Poultry Science, University of Florida, on eggs
collected from hens receiving either the control or the 20 percent sludge
43
-------
diet. The eggs wee held for five days to permit optimum peelability and
then hard-cooked for sampling. A paired-comparison test was used with
each panelist sampling three pairs each day, but only one pair at a time.
They were asked to select separately the egg which had the darker colored
yolk, the greater degree of albumen off-flavor and the greater degree of
yolk off-flavor. The evaluation of 86 separate pairs (Table 21) showed
that a level of 20 percent citrus sludge resulted in significantly darker
yolks than the control.
Table 21. TASTE PANEL EVALUATION OF EGGS FROM CONTROL AND
20.0 PERCENT SLUDGE DIETS
Preference
Attribute
Yolk color
Yolk flavor
Albumen flavor
Control
5
42
40
Sludge
81
44
46
Significant
difference3
yes
no
no
aAcceptance range (52.3 - 33.8) at P <0.05
Eighty-one of the 86 panelists found the citrus sludge eggs to have a
darker yolk color, which is well outside of the acceptable range of 33
to 52. No significant off-flavor was detected for either the albumen
or the yolk, as these twD parameters fall within the acceptable range.
44
-------
SECTION VI
DISCUSSION
In Section V, the data collected during this study were presented and
briefly discussed. The purpose of this section is to discuss the signi-
ficant results of this study, to develop a prototype design for the re-
covery of sludge for subsequent use as a poultry feed, and to discuss the
value of the sludge as a poultry feed supplement.
DISCUSSION OF THE RESULTS
The primary objectives of this project were to determine the value of
waste activated sludge as a poultry feed supplement and to determine the
feasibility of recovering sludge for this purpose. In order to accom-
plish these objectives, the value of the sludge had to first be deter-
mined through feeding tests. Subsequently, it had to be determined
whether or not it is possible to thicken, dewater, and dry activated
sludge at a cost commensurate with the value of the sludge as a feed
material.
The characteristics of activated sludge are directly related to the
operating conditions of the system from which the sludge is wasted.
Therefore, the results of this study are not necessarily of general
application. For this particular sludge, it was shown conclusively
that approximately 75 percent of the water can be removed, by gravity
thickening. In a properly designed and operated gravity thickener,
solids concentration can be increased fron about 0.8 percent to greater
than 3 percent.
Two types of centrifuges were tested on a pilot basis and one, a disc-
type centrifuge, was installed as a production unit. Both types were
tested at various feed rates, concentrations, and with and without
45
-------
polymer addition. It was found that both types could provide a recovery
of 90 percent of the feed solids and produce a cake with a solids concen-
tration of 7.0 to 8.0 percent. Thus, sludge thickening, followed by de-
watering by centrifugation, reduced the volume of sludge by approximately
90 percent. However, the moisture content of the sludge cake was still
in excess of 90 percent.
Although a flash evaporator was utilized for a short period of time,
sufficient data were not gathered to determine its cost effectiveness.
In order to provide a dry material suitable for use as an ingredient in
poultry feed, the sludge had to be dried further. The methods utilized
for sludge drying in this study were rotary kiln drying and sand bed
drying. The primary problem encountered while drying the activated
sludge was that the sludge is highly volatile. In general, at 600°C
activated sludge is about 80 to 90 percent volatile material. The inlet
temperature usually utilized in rotary kiln drying is between 600°C and
800°C (1100°F to 1400°F), while the outlet temperature is usually around
93°C (200°F). The average temperature is between these two extremes and,
obviously, a portion of the sludge can be expected to volatilize. Sludge
dried by the rotary kiln dryer to a moisture content of approximately 4.0
percent and sludge dried on sand beds to approximately 35 percent mois-
ture proved to be stable and an effective poultry feed additive.
The results of the various poultry feeding studies were thoroughly dis-
cussed in Section V. The most significant conclusion from these tests
was that, with the possible exception of the second chick trial, a sludge
level of up to 7.5 percent in a properly formulated feed did not signi-
ficantly affect poultry performance levels. The inclusion of dried
sludge allowed for a reduction in other protein sources such as yellow
corn and soybean meal, and also allowed for a reduction in the amount of
defluorinated phosphate which had to be added to the feed. However, the
amounts of animal fat and DIrfnethionine had to be substantially increased
to maintain energy and sulfur amino acid levels.
46
-------
It was found that inclusion of sludge at levels exceeding about 10 per-
cent resulted in significant decreases in feed efficiency values and sig-
nificantly lighter final body weights in the broiler chicks tested. The
addition of sludge to the diet of broilers did not affect the palatability
or texture of the meat.
Sludge addition to properly formulated laying hen feed did not signifi-
cantly affect egg weight, egg production or feed required to produce a
dozen eggs at levels up to 7.5 percent. The addition of sludge to laying
hen diet provided a significant improvement in egg yolk color, but did
not affect the flavor of either the yolk or albumen.
In summary, it would appear that the inclusion of sludge at a level of
up to 7.5 percent in a properly formulated diet would not affect the
performance or quality of poultry. In some cases, the inclusion of sludge
at low levels appeared to improve performance such as by producing a
slight increase in feed efficiency. The characteristic of sludge to im-
prove egg yolk color could be significant in that the percentage of yellow
corn or other color producing agents may be reduced. If the factor in
the sludge which resulted in a depression in performance at sludge levels
above 7.5 to 10 percent could be identified and compensated for or re-
moved, then the percentage of sludge which could be included in the feed
might be increased significantly.
PROTOTYPE DESIQJ
For the purpose of determining an approximate cost of production of
dried sludge for poultry feed, a prototype design based on the require-
ments of the W3CP is given below. The. equipment for this project was,
in several instances, used because of its availability. Other alterna-
tives for sludge recovery and drying could have been used and may have
been more efficient. The costs developed below assume the use of the
same types of equipment as were used in this study. The equipment sizes
are based on an average flow rate of 88 I/sec (2 MGD) of wastewater
47
-------
containing 2,000 mg/1 of BCD. It is assumed that 0.5 kg of waste
activated sludge, as total solids, is produced per kilogram of influent
BCD removed. Thus, the amount of sludge to be handled is 7.57 kkg/day
(16,680 pounds) of dry solids. Assuming the solids concentration in the
return sludge from the existing clarifier is 0.8 percent, then the daily
volume of sludge to be handled is 946 M3/day (250,000 gallons).
Sludge would be handled in this prototype system by wasting activated
sludge from the return sludge line to a gravity thickener. Based on a
solids loading rate of approximately 29 kg/M2/cJay/ the gravity thickener
would be about 18 meters in diameter. The underflow solids which have
a projected concentration of 3.0 percent would be pumped to a surge tank
from which the thickened sludge could be fed as needed to centrifugation.
Three Fletcher Sharpies SST-1600 basket centrifuges would be required, as
can be determined from Figure 5 which is a scale-up of actual pilot data
collected at W3CP. Dewatered sludge would drop from the centrifuges to
a conveyor belt and then be transferred to a rotary kiln dryer. Centrate
from the centrifuges would be pumped back to the activated sludge aera-
tion tanks. The rotary kiln dryer would be a gas fired, three pass
cylindrical dryer with the capacity to evaporate 4,100 kg (9,000 Ibs) of
water per hour and would be equipped with a cyclone to capture fine
sludge particles. It is assumed that approximately 75 percent of input
solids will be recovered through the dryer. The specified equipment for
this sludge recovery system is given below along with the estimated in-
stalled cost. Operating and maintenance cost estimates are presented
in Table 22.
Installed Cost
1. Gravity Thickener (18-meter diameter) $175,000
2. Surge Tank (132,000 liters) 40,000
3. Centrifuge (three 122 cm x 76 cm basket tvpe) 210,000
4. Rotary Kiln Dryer (4,100 kg/hr capacity) 60,000
5. Pumps, Piping, Valves, etc. 50,000
TOTAL $535,000
48
-------
94
!«
G
O
Q 90
Q
UJ, 88
UJ
ft
UJ
8 84
a:
ul
U
a:
LU
Q.
82
80
78
0.5
FEED : 2.5°/o
122cm x 76cm
5ST - 1 6OO
FEED: 1.5°/o-
1.0 1.5 2.0
(NET) FEED RATE , l
2.5
3.0
3.5
Fiqure 5. Percent recovery versus feed rate for a basket centrifuge
(SST-1600)
-------
(Jl
o
Table 22. YEARLY COSTS FOR SLUDGE
($/year)
Item
Gravity thickener
Surge tank
Centrifuges {3)
Rotary kiln dryer
"Pi imr \c r5"i Twiner . stc .
TOTALS
Operation3
$ 2,100
1,050
12,600
50,750
3,150
$69,650
b
Maintenance
$ 5,000
1,000
21,000
3,000
5,000
$35,000
Amortization
$20,600
4,700
39,400°
7,000
5,900
$77,600
Total
yearly cost
$ 27,700
6,750
73,000
60,750
14 , 050
$182,250
alt is assumed that one man is required full-tine 24 hours/day, 175 days/year to operate all equip-
ment and to perform routine maintenance and that 60 percent of all labor cost is due to the cen-
trifuges, lO^ercent is due to the dryer, 15 percent is due to the pumps, pipes, etc., 10 percent
is due to the'gravity thickener, and 5 percent is due to the surge tank
bAnnual maintenance expenditures are assumed at 2.8, 2.5, 10, 5 and 10 percent of installed costs
respectively for the thickener, surge tank, centrifuges, dryer, and pumps, piping, etc.
°Amortized over 8 years; other equipment amortized over 20 years
-------
These cost estimates are based upon present (October 1974) prices and
upon the following assumptions:
1. Maximum sludge volume to be handled is 946 M3/day at
0.8 percent solids
2. Fuel cost = $0.90/106 Btu
3. Dryer efficiency = 56 percent
4. Dryer yield = 75 percent of input solids
5. Operating days = 150t maintenance days = 25
6. 20-year amortization on all equipment except that the
centrifuges are amortized over an 8-year period
7. 10 percent interest on borrowed money
8. Labor required is 24 man-hours/day at $5/hour
ECONOMIC ANALYSIS
At this point, two significant facts have been established; one is that
it is technically feasible to recover waste activated sludge and, second,
the recovered sludge has value as a poultry feed ingredient. The final
point to be discussed is whether or not it is economically feasible to
recover the sludge for use as a chicken feed.
In any activated sludge system, waste sludge must be handled in some
manner. If one assumes that the system described here—i.e., gravity
thickening followed by centrifugaticai—is as cost effective a method to
dewater sludge as any other method available, then the cost of dewatering
sludge to a solids concentration of 8.0 percent can be calculated. Assum-
ing a 90 percent yield through the centrifuges, the daily production of
dewatered sludge is 6.8 kkg (7.5 tons) on a dry weight basis. From Table
22, the total yearly cost for dewatering is $121,500 which is equivalent
to $119/kkg ($108/ton). This cost is assumed to be incurred whether the
dewatered sludge is subsequently utilized as chicken feed or is disposed
of by landfill. The actual cost to produce dried sludge for chicken feed
therefore, is assumed not to be the total cost of sludge disposal, but
only the cost of sludge drying beyond 8.0 percent. From Table 22, the
51
-------
total yearly cost associated with sludge drying is approximately $60,750.
Assuming 75 percent recovery of input solids through the dryer, the daily
production of dried sludge would be 5,112 kg (11,259 Ibs). The unit cost
of dried sludge then would be about $79/kkg ($72/ton).
In order to determine the value of the dried sludge, one must consider
the value of the feed ingredients which are no longer required because
of the addition of the sludge. For this purpose, the composition of feed
shown in Table 23 is assumed to be a typical diet. Also shown in Table
23 is the composition of a feed which contains 7.5 percent dried activated
sludge which is the maximum sludge level used with success in the poultry
feeding studies. Table 24 gives estimated unit costs for the ingredients
in the diets which are affected by the addition of sludge.14
Table 23. COMPOSITION OF FEED
(percent)
Ingredient
Yellow corn
Soybean meal (48.5%)
Alfalfa meal (20%)
Citrus sludge
Ground limestone (38% Ca)
Defluorinated phosphate
(18% P and 32% Ca)
Iodized salt
Vitamin pre-mix
Animal fat
DL-Methionine
Basal
54.97
36.50
2.50
0.00
0.74
2.11
0.40
0.50
2.15
0.13
7.5% sludge
51.55
31.08
2.50
7.50
0.86
1.67
0.40
0.50
3.78
0.17
Change
-3.42
-5.42
-
+7.50
+0.12
-0.44
-
-
+1.63
+0.04
Thus, from Table 23 it can be seen that a reduction of 3.42 percent in
the amount of yellow corn required results from the addition of the dried
sludge. The value of the yellow corn which is saved is about $4.92/kkg
52
-------
Table 24. CHANGES IN INGREDIENT COSTS RESULTING FROM SLUDGE ADDITION
Ln
Ingredient
Yellow corn
Soybean meal
Ground limestone
Defluorinated phosphate
Animal fat
DL-Methionine
Unit costa $/kkg
$3
.66/bushel
$170/kkg
$1
.80/100 kg
$176/kkg
$0
$3
.34/kg
.30Ag
$
$
$
$
$
$3
144
170
18
176
341
,300
% Change Savings or cost/kkg
+3
+5
-0
+0
-1
-0
.42
.42
.12
.44
.63
.04
FEED INGREDIENT SAVINGS
Dried activated sludge
$7
9/kkg
$
79
-7
.50
ACTUAL SAVINGS IN FEED COSTS
+$4
+$9
-$o
+$0
-$5
-$1
+$8
-$5
+$2
.92
.21
.02
.77
.56
.32
.00
.92
.08
dt costs are from Feedstuffs1 ** for November 1974, F.O.B. Atlanta or nearest inarket to Winter
Garden, Florida
Table 23
-------
of feed. By similarly calculatiiig the value of the ingredients which are
no longer required and subtracting the value of the ingredients which must
be added, a resultant savings of $2.08/kkg ($1.89/ton) of feed is obtained
as shown in Table 24.
The savings in feed ingredient costs may be interpreted to be the value
of the dried sludge as a feed ingredient. For the feed composition shown,
the addition of 7.5 percent sludge, or 75 kg of sludge per kkg of feed,
results in a savings of $8.00/kkg in feed ingredients and the value of
the added sludge is then $107/kkg ($97/ton). The cost of drying the
sludge is $79/kkg ($72/ton) of dried sludge F.O.B. the citrus plant,
which results in an apparent profit of $28/kkg ($25/ton) of dried sludge.
Thus, recovering the sludge for poultry feed results in a net profit
whereas ultimate disposal of the sludge cake by landfilling would cost an
additional $6/kkg ($5.45/ton).
In summary, it would appear that the recovery of activated sludge for
subsequent use as an animal feed material is both technically feasible
and economically attractive. Even if the total cost of dewatering and
drying of sludge is considered rather than just the cost of drying, it
is apparent that the recovery of sludge for poultry feed could signifi-
cantly off-set the cost of sludge handling. The total cost of handling
sludge by thickening, centrifuging and hauling to landfill for ultimate
disposal is $125/kkg ($113/ton), whereas the net cost for recovering the
sludge as poultry feed is $91Akg ($83/ton). This is a reduction in
sludge handling costs of 27 percent.
It should be noted that the above economic analysis is based on one given
set of conditions and assumptions. The cost of capital equipment, labor,
fuel and feed ingredients will vary widely with location and market con-
ditions. It should also be noted that the cost of sludge recovery would
be substantially reduced for an industry which operated year round rather
than on a seasonal basis, as equipment would be utilized continuously,
increasing the yearly production of dried sludge by a factor of 2.4.
54
-------
The total yearly costs would be increased by a factor of only 1.5 The
result is a net decrease in the unit cost of sludge recovered of approxi-
mately 38 percent.
55
-------
SECTICN VII
REFERENCES
1. Arden, E. and W. T. Lockett. Experiments on the Oxidation of Sewage
Without the Aid of Filters, Part I. J. Soc. Shem. (London). 33:523,
1914. —
2. Complete Mix Activated Sludge Treatment of Citrus Process Wastes.
Environmental Protection Agency. Grant No. 12060 EZY. August 1971.
120 p.
3. Stewart, M. J. Activated Sludge Process Variations—The Complete
Spectnm. Water and Sewage Works, Reference Number. 1964.
4. Standard Methods for the Examination of Water and Waste Water, 13th
Edition. New York, American Public Health Association, 1971. 871 p.
5. Hackler, L. R., A. L. Neumann and B. C. Johnson. Feed From Sewage,
III. Dried Activated Sewage Sludge as a Nitrogen Source for Sheep.
Journal of Animal Science. 16:125-129, 1954.
6. Poultry Grading Manual. Washington, D.C., Department of Agriculture,
1971.
7. Irmiter, T. F., L. E. Dawson and J. G. Keagan. Methods of Preparing
Hard Cooked Eggs. Poultry Science. 490:1232-1236, 1970.
8. Dawson, E. H. Sensory Testing Guide for Panel Evaluation of Foods
and Beverages. Food Technology. 18_: 25-31, 1964.
9. WiUcs, S. S. Elementary Statistical Analysis, 13th Edition.
Princeton, Princeton University Press, 1966.
10. Snedecor, G. W. Statistical Methods, 5th Edition. Ames, Iowa
State University Press, 1956.
11. Duncan, D. B. Multiple Range and Multiple F Test. Biometrics.
11:1-42, 1955.
12. Hurwitz, E. The Use of Activated Sludge as an Adjuvant to Animal
Feeds, In: 12th Industrial Waste Conference. Purdue University,
1957. p. 395-414.
13. National Research Council. Nutrient Requirements for Poultry.
National Academy for Sciences. Washington, D.C., 1971.
14. Feedstuffs. Minneapolis, Minnesota. 4£:46-48. November 1974.
56
-------
TECHNICAL REPORT DATA
(I'lrasc read Instructions on the reverse before completing)
RLPOHT NO.
EPA-660/2-75-001
4. TITLE ANO SUflTfTLE
2.
Waste Citrus Activated Sludge
as a Poultry Feed Ingredient
3. RECIPIENT'S ACCESSION-NO.
5. REPORT DATE
February 1975
6. PERFORMING ORGANIZATION CODE
Richard H. Jones and John T. White (Jones,
Olson & Associates, Inc.), B. L. Damron (University
of Florida)
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORG •WIZATION NAME AND ADDRESS
Winter Garden Citrus Products Cooperative
Post Office Box 399
Winter Garden, Florida 32787
10. PROGRAM ELEMENT NO.
1BB037
11. CONTRACT/GRANT NO.
S-801432
12. SPONSORING AGENCY NAME AND ADORES?
Environmental Protection Agency
Office of Research and Development
National Environmental Research Center
Corvallis, Oregon 97330
13. TYPE OF REPORT AND PERIOD COVERED
Final Report
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
18. ABSTRACT
This report presents an evaluation of the potential of utilizing waste activated
sludge as a poultry feed supplement. The sludge used in this study was obtained
from an activated sludge process treating concentrated citrus waste containing
no sanitary wastewater. The sludge was thickened, dewatered and dried using full-
scale and pilot-scale equipment. The dried sludge was then analyzed for protein,
fiber, amino acids, nutrients and moisture. Poultry feeds containing varying
concentrations of sludge were prepared. Two experiments with broiler chicks, each
of three weeks duration, one 8-week broiler study, and a six-month laying hen study
were conducted to determine the effect of the inclusion of sludge in poultry diets
on performance.
It is shown in this report that the inclusion of sludge in properly formulated diets
up to 7.5 percent did not significantly affect poultry performance or meat or egg
quality. The value of the sludge was calculated based on the reduction in feed in-
gredients resulting from the inclusion of sludge. It was found that the value of
the recovered sludge significantly reduced the total cost of sludge handling.
This report was submitted in fulfillment of Grant Number S-801432 by Winter Garden
Citrus Products Cooperative under the partial sponsorship of the Environmental
1Q74
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
*S1udge Disposal, *Byproducts, *Food
Processing Industry, industrial Wastes,
Ultimate Disposal, Sludge Treatment,
Activated Sludge, Poultry, Citrus
Fruit, Feeds, Organic Wastes
b.lDENTIFIERS/OPEN ENDED TERMS C. COS AT I Field/Group
Byproducts recovery
13/13B
19. DISTRIBUTION STATEMENT
19. SECURITY CLASS (This Report!
21. NO. OF PAGES
64
20. SECURITY CLASS (Thispage)
22. PRICE
EPA Form 2220-1 (9-73)
* U.S. GOVERNMENT PRINTING OFFICE 1975-698-090 IC5
------- |