600286014
FACTORS AFFECTING COMPOSTING OF MUNICIPAL
SLUDGE IN A BIOREACTOR
H. A. J. Holtlnk and G. A. Kuter
The Ohio State University
Ohio Agricultural Research and Development Center
Wooster, Ohio 44691
CR-807791-01-0
Project Officer
Atal E. Eralp
Wastewater Research Division
Water Engineering Research Laboratory
Cincinnati, Ohio 45268
WATER ENGINEERING RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNTI, OHIO 45268
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DISCLAIMER
Although the Information described 1n this document has been funded
wholly or 1n part by the United States Environmental Protection Agency through
assistance agreement number CR-807791-01-0, The Ohio State University, Ohio
Agricultural Research and Development Center, Wooster, Ohio, 1t has not been
subjected to the Agency's required peer and administrative review and there-
fore does not necessarily reflect the views of the Agency and no official
endorsement should be Inferred.
11
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FOREWORD
The U.S. Environmental Protection Agency 1s charged by Congress with
protecting the Nation's land, air, and water systems. Under a mandate of
national environmental laws, the agency strives to formulate and implement
actions leading to a compatible balance between human activities and the
ability of natural systems to support and nurture life. The Clean Water
Act, the Safe Drinking Water Act, and the Toxics Substances Control Act
are three of the major congressional laws that provide the framework for re-
storing and maintaining the integrity of our Nation's water, for preserving
and enhancing the water we drink, and for protecting the environment from
toxic substances. These laws direct the EPA to perform research to
define our environmental problems, measure the Impacts, and search for
solutions.
The Water Engineering Research Laboratory 1s that component of EPA's
Research and Development program concerned with preventing, treating, and
managing municipal and industrial wastewater discharges; establishing prac-
tices to control and remove contaminants from drinking water and to prevent
Its deterioration during storage and distribution; and assessing the nature
and controllability of releases of toxic substances to thei £ir, water, and
land from manufacturing processes and subsequent product uses. This publica-
tion is one of the products of that research and provides a vital communica-
tion link between the researcher and the user community.
Composting is one of the alternatives available in the treatment of
municipal sludges. This report details the research aimed at developing
optimum operation strategies by means of temperature control.
Francis T. Mayo, Director
Water Engineering Research Laboratory
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ABSTRACT
This research was Initiated to determine the feasibility of composting
municipal sludge in an aerated tank bioreactor system and to develop
baseline data for the rational operation and design of enclosed reactor
composting systems. A section of the reactor (24 m) was used for replicated
composting trials. A variety of conditions were tested and various mixtures
of recycled compost, bark and sawdust were used as bulking agents. The mean
temperature of the compost was regulated through programmed rates of airflow.
Material balances were determined from accurate measurements of the
weights of solids and water in the reactor feed and reactor product. In
addition, temperature, aeration and carbon dioxide evolution were monitored
continuously.
Losses of water and solids experienced in this system were significantly
greater than those published for the static aerated pile system. Measure-
ments of carbon dioxide evolution appeared to accurately reflect the
destruction of volatile solids and indicated that activity was at an optimum
when the mean temperature of the compost was maintained at 38-55 C under
high rates of aeration. Experiments with a puamill mixer indicated that
thorough mixing of the reactor feed resulted in increased rates of drying
and loss of solids over front-end loader mixing. ' Data collected on this
system are in general agreement with those of others based on bench-scale
reactors.
This report was submitted in fulfillment of Agreement No. CR-807791-01-0
by the Department of Plant Pathology, OARDC, OSU, Wooster, under the
sponsorship of U.S. Environmental Protection Agency. This report covers the
period of September 22, 1980 to July 21, 1983.
iv
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CONTENTS
Foreword iii
Abstract iv
Figures vi
Tables ix
Acknowledgment xi
Introduction ...... 1
Description of the Reactor Vessels 3
Data acquisition center 7
C02 and 02 measurements 9
Data processing . . 10
Samping Procedures 12
Temperature gradients in the reactor vessel 12
Distribution of dry solids in the reactor vessel 15
Distribution of volatile solids in the reactor ........ 15
Determination of free air space .. . . . . 25
Chemical analyses . ...../ 28
Materials Balances for Seven Composting Trials 29
Introduction . . . 29
Materials balance '. - 30
Pugmill mixing versus FEL mixing of reactor feed 40
Specific Activity of the Compost Biota 43
Fate of Fecal Pathogens .' . 58
Bulking Agents 72
Discussion . . . . 74
References
Appendices
I. Calculations for the determination of airflow, mass (Kg)
of dry air entering the reactor and mass (Kg) of carbon
dioxide produced during each four hour interval 81
II. Interpolation of temperature data 83
III. Paygro system process performance summary 87
IV. Survival of fecal pathogens I
V. Survival of fecal pathogens II 93
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FIGURES
Number
Schematic diagram of composting facilities at Paygro Inc.,
11000 Huntington Rd., South Charleston, OH 45368
Aeration equipment: l*air intake, 2«fan and gates, 3«port
where air enters plenum under the compost, 4*averaging pitot
tube, 5*differential pressure transducer, 6-outside wall
of building in which reactors are located, and 7*reactor
vessel wall 8
Temperature distributions for reactor sections maintained
at 65 and 42 C during preliminary summer trial . 13
View of tank showing temperature probe positions, x
indicates probe position (two in center, one each at 30
and 60 cm) from the wall in each section. Thermocouples are
attached to probes in the center at depths of 15, 30, 80,
115, 135, 210, and 240 cm; near the wall thermocouples
are attached at 15, 135, and 240 cm depths ,./.-. . . . 14
Percent dry solids distribution with depth in the reactor:
2*Trial 2, distribution on March 23 after 34 days and
3«Trial 3, distribution on June 18 after 18 days in the
reactor. Mean percent dry solids for reactor products
of Trials 2 and 3 were 46.9 and 58.5, respectively 19
Temperature at various depths from surface in compost
during a winter trial (2/26/81-3/3/81) with anaerobically
digested sludge after the second turn: 1, 2, 3, and 4 are
7.5, 90, 150, 245 cm from the surface, respectively. 5 and
6 are daily ambient maximum and minimum temperatures,
respectively 26
Aeration (#2 evolution and temperature data for the "cool"
(43 C) section of Trial 2. Aeration and C02 evolution are
given for each 4 hour interval. Mean temperature and % of
Reactor Volume>55 C are based on readings from 20 thermocouples.
The compost was turned once after 9 days and removed from the
reactor 6 days later 44
hit
Aeration, CO, evolution and temperature data for the "hot1
(65 C) section of Trial 2. Aeration and C02 evolution are
(continued)
vi
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FIGURES (continued)
Number
•
given for each 4 hour interval . Mean temperature and % of
Reactor Volume > 55 C are based on readings from 20 thermo-
couples. The compost was turned once after 9 days and removed
from the reactor 6 days later
9 Relationship between C02 evolution and mean compost temperature
in Trial II. ="cool" section before turn, 0="cool" section
after turn, ="hot" section before turn, ="hot" section after
turn .............................. 47
10 Aeration, C02 evolution, and temperature data for "cool" section
of reactor before first turn in Trial VII ..... ....... 49
11 Aeration, C02 evoluiton, and temperature data for "cool" section
of reactor after turn in Trial VII ... ............ 50
12 Aeration, C02 evolution, and temperature data for "hot" section
of reactor before turn in Trial VII ............... 51
13 Aeration, C02 evolution, and temperature data for "hot" section
of reactor after turn in Trial VII ............... 52
14 From page 316 in_ Haug, R. T. , 1980, Compost Engineering.
Principles and Practice. Ann Arbor Science. Publishers, .Inc.,
The Butterworth Group, P. 0. Box 1425, Ann. Arbor, MI 48*160 ... 57
15 Mean temperature (C) and percent of compost above 55 C during
Trial VII. Circled numbers indicate times for which temperature
distributions were plotted (Figs. 16-22) .... ........ 60
16 Temperature distribution at hour 8. Mean tempera ture= 26. 3 C.
Percent of compost above 55 C=0.0% ............... 61
17 Temperature distribution at hour 24. Mean temperature^S^ c.
Percent of compost above 55 C=0.0% ...... . ........ 62
18 Temperature distribution at hour 52. Mean temperature=65 . 9 C.
Percent of compost above 55 C=69.8% ............... 63
19 Temperature distribution at hour 136. Mean temperature=65 C.
Percent of compost above 55 C=69.8% ............... 64
20 Temperature distribution at hour 148. Mean temperature3 76. 5 C.
Percent of compost above 55 C=100% ............... 66
(continued)
VI1
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FIGURES (continued)
Number Page
21 Temperature distribution at hour 176. Mean tenperature-64.9 C.
Percent of compost above 55 080.3% 67
22 Temperature distribution at hour 212. Mean temperature*54.0 C.
Percent volume above 55 O53.7 68
23 Mean temperture and percent of compost. 55 C for two sections
(2, 3) of reactor vessel during Trial III 70
viii
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TABLES
Number
1 Arrangement of data contained in working files. Missing
data are indicated by -0000. 0 11
2 Mean percent solids distribution in the reactor after
34 days of composting for a winter trial 16
3 Mean percent solids distribution in the reactor at time
of second turn (day 11) for a summer trial 17
4 Mean percent solids distribution in the reactor at time
of removal (day 18) for a summer trial 18
5 Description of components and reactor feed mixture for a
preliminary summer trial 20
6 Materials balance for a preoliminary summer composting trial . 21
7 Mean percent volatile solids distribution in the reactor at
time of second turn (day 11) for a summer trial .;/".... 22
8 Mean percent volatile solids distribution in the reactor at
time of compost removal (day 18) for a summer trial 23
9 Mean tempertures of compost in various thermocouple positions
for selected time periods for a summer trial 24
10 Mean percent volatile solids distribution in the reactor after
34 days of composting for a winter trial 27
11 Materials balance for Trial I. Compost retention time=12.6
days. Volume of reactor feed=473 cubic yards 31
12 . Materials balance for Trial II. Compost retention time=14.75
days. Volume of reactor feed=473 cubic yards 32
13 Materials balance for Trial III. Compost retention time=15
days. Volume of reactor feed=673 cubic yards 33
14 Materials balance for Trial IV. Compost retention time=20.25
days. Volume of reactor feed=663 cubic yards 34
(continued)
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TABLES (continued)
Number Page
15 Materials balance for Trial V. Compost retention time«21.7
days. Volume of reactor feed«S81 cubic yards 35
16 Materials balance for Trial VI. Congest retention time«15.3
days. Volume of reactor feed«473 cubic yards 35
17 Materials balance for Trial VII. Compost retention time«12.6
days. Volume of reactor feed»473 cubic yards 37
18 Mean dry solids (% DS) and volatile solids (% VS) of
components, reactor feed and reactor product for seven
composting trials. Mean compost retention time»16.0 days . . 38
19 Percentage loss of wet weight, weight dry solids and weight
water. Number of days retention and mean high and low
ambient air tempertures for compost Trials I-VII 39
20 Dry solids (%) obtained in Trial V using front end loader
(PEL) and pugmill mixed (speed flow) 42
21 Percent dry solids (% DS), percent volatile solids (% VS) and
percent loss of initial weight of dry solids for "cool" and
"hot" sections of Trial VII 48
/ '
22 Comparison between carbon dioxide evolution values and
calculated values based on stiochiometric formulae for
Trial VII S3
23 Carbon dioxide production and oxygen uptake determinations for
"cool" and "hot" sections of Trial VII 56
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ACKNOWLEDGMENTS
The cooperation and leadership of C. Kip, Vice President, Paygro, Inc.,
P. 0. Box W, 11000 Huntington Road, South Charleston, OH 45368 in the
operation of the reactor is gratefully acknolwedged. Ve are endebted to D.
Entler for providing technical assistance throughout this project. We also
thank R. H. Ryan, General Manager, R. G. Gossett and D. Lerma from Compost
Systems Company, 8403 Kenwood Road, Cincinnati, OR 45242 for coordination of
experiments and providing other helpful assistance. We thank Prof. J. R.
Vestal and V. KcKinley, Department of Biological Sciences, University of
Cincinnati, OH 45221 for many helpful suggestions throughout this project.
The cooperation and assistance of Dr. T. Hayes, W. C. Baytos and R. G. Luce
from Battelle Columbus Laboratories, 505 King Ave., Columbus, OH 43201 in
the design of the automated data acquisition and analysis system for this
project is gratefully acknowledged. We thank Dr. R. D. Fox, Department of
Agricultural Engineering, OARDC, OSU, Wooster, OH 44691 for calibrating the
airflow monitoring system. Special thanks are offered to Dr. L. Rossman,
HERL, USEPA, Cincinnati, OH 45268 for writing computer programs for analysis
of the data and to Dr. A. E. Eralp, also of HERL for his helpful suggestions
for this research program. Finally we thank R. A. Honteith, Bureau of
Engineering, 701 Municipal Building, Akron, OH 44311 and R. C. Smith, City
of Columbus, 90 West Broad Street, Columbus, OH 43215 for providing
municipal sludge for these experiments.
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INTRODUCTION
During the past decade composting has become of increasing importance
for the ultimate treatment of municipal sludges in the United States.
Vindrov composting is used successfully in the arid parts of the Southwest
and the aerated static pile has been adopted widely in the Northeast (1, 4,
12, 16). In both systems, during wet weather, there are significant levels
of anaerobic and microaerophilic metabolism which may result in serious odor
problems.
Present trends in the U.S. are to install enclosed systems to avoid
nuisances associated with exposed systems and reduce labor and operating
costs through mechanized materials handling. In Europe a variety of
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enclosed composting systems have been in use for several years. Although
several types of silo systems predominate in Europe, none are in operation
s
in the U.S. However several of these systems are in the planning stage at
this time.
At the present time, research on various composting systems is based on
a small number of studies using laboratory or bench-scale composters (2, 3,
5, 8, 9, 10, 14, 15)* Engineering principles have been developed from such
data (6) however there have been few studies on large scale or pilot scale
composting. Furthermore, there are no published studies which have examined
composting in a full scale enclosed reactor. Thus rational guidelines for
the operation and engineering of these systems must be derived from studies
of other systems.
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Recently valuable Information has been published from Rutgers
University on parameters affecting the performance of the aerated static
pile. For example, rates of drying and apparently decomposition were
highest when temperatures within the compost were maintained at between
35-55 C (11). These results, obtained in a pilot scale study, have
important implications for all composting systems.
It is the purpose of this study to present quantitative data on
composting of municipal sludge in a full scale reactor vessel. Four
sections of an existing tank system used to compost cow manure were modified
for experimentation. Quantitative data are presented on drying, loss of dry
and volatile solids, and rates of aeration and carbon dioxide evolution.
The performance of the system is evaluated by measuring the rates of carbon
dioxide evolution in the reactor and by examining the effects of various
temperature conditions on these rates.
/ "
The report also presents- detailed analyses of the temperature gradients
within the reactor. The significance of the temperature distribution in
terms of pathogen reduction is discussed. In addition, the effects of using
various bulking agents, the continued use of recycled compost as bulking
agent and the impact of different compost mixing procedures are discussed.
The information presented in this report serves as a sound quantitative
basis for the rational design and operation of enclosed reactor systems.
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DESCRIPTION OF THE REACTOR VESSELS
A schematic drawing of the Paygro system located at Paygro, Inc., 11000
Huntington Rd., South Charleston, OH 45363, is presented in Fig. 1. It
consists of two reactors each 121.9 i 6.1 m (400 z 20 ft). The reactors are
3 m (10 ft) deep. The base consists of a perforated metal floor below which
is an air space. Air is forced by fans through an opening in one wall into
the airspace and up through the perforated floor into the reactor.
Centazial tubular centrifugal fans (7 1/2 HP motors) made by Aerovent Inc.,
Piqua, OH, are located at 12.1 m (40 ft) distances along the base of each
reactor. A layer of pea gravel is positioned permanently on top of the
perforated floor. A layer of compost remains in the reactor each time that
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it is emptied by the extractoveyor (see Fig. 1).
Sludge and bulking agent were mixed on an outdoor concrete pad with
front end loaders (FEL). In one trial a pugmill mixer was used for further
blending. The reactor feed was loaded by FEL into a live-bottom feed hopper
and moved into the reactors via a continuous belt, tripper car and indexing
conveyor. The compost was turned or removed by the extractoveyor, loaded
into trucks, weighed and stored in curing piles or mixed into the reactor
feed of the following trial as recycled compost (Fig. 1).
In preliminary experiments it was observed that air moved between
sections of the reactor aerated by adjacent fans. In the 24 H (80 ft)
experimental section of the reactor therefore, modifications were made which
significantly reduced air leakage from the one vessel to the next. It was
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Fig. l.
Schematic dlagra* of composting facilities
•t Paygro Inc.. 11000 Muntlngton Mil..
South Charleston, (HI 4S36S.
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' also discovered that fans did not supply enough air to maintain low
temperatures in the compost in each 12 M section during summer trials. This
problem only occurred during the first two days after compost was loaded
into the reactor. Two additional fans, therefore, were installed so that
four vessels were available, each 6 m long, 6 m wide and 3 m deep (108
m/vessel). The total depth of compost that could be loaded into the
reactor was 290 cm.
A plank was positioned on top of each buffer zone in the base of the
reactor between each vessel section. During loading, sheets of polyethylene
were attached to the plank, so that sections were separated from each other
to the top of the reactor by "polyethylene walls" buried in the compost.
The extractoveyor cut vertically through the compost up to the "wall" so
that all compost placed into each section could be recovered with a minimum
of contamination from the adjacent vessel.
- / "
The two vessels in the middle of the experimental section functioned
independently from each other. However air leaks still existed in the outer
vessels. All experiments therefore, were performed in the center vessels.
The outer vessels served as buffers with treatments as similar to the center
vessels as possible.
Two systems for regulation of airflow were tested in preliminary
trials. In one system thermocouples activated fans via a controller to
supply air. Gates on the air intake end could be closed manually to
decrease airflow. In the other system the controller regulated a gate so
that airflow was reduced rather than stopped entirely, until temperatures
rose over a set point and the gate was opened automatically to increase
airflow and therefore cool the compost. Significant problems occurred with
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the automatic system because small gate openings interfered with pitot tube
readings. Furthermore constant low rates of airflow caused freezing in the
base of the reactor during cold weather, whereas sudden bursts of airflow
did not. It was decided to-regulate airflow by an all or no-air system in
which fans were turned on automatically once temperatures exceeded the
programmed temperature.
Airflow sensing equipment was calibrated by H. D. Fox, Professor,
Department of Agricultural Engineering, USDA, OSU, Vooster, OH 44691*
Averaging pitot tubes (PSE, Inc., 41227-I94I-Vay Service Dr., Vanfiuren
Township, Belleville, HI 48111; Series 100 PAB70, standard flow sensor) were
installed in 40.6 cm (16 inch) diameter 7.3 m long (24 ft) ducts ahead of
the intake end of each fan (Fig. 2). Nagnehelic differential pressure
transducers calibrated with an inclined manometer provided a signal output
which was interfaced with a data acquisition center. The magnehelic
pressure transducers were mounted in heated chambers to avoid interference
caused by low ambient temperatures in the winter. Pitot tubes were
calibrated by comparing readings with those of a heated thermocouple
anemometer (Hastings model). Airflow in the duct could be estimated by
Vave-0.9 x velocity at the center of the tube. The velocity profile across
the duct was nearly uniform. Gate position (just ahead of the fan) had a
slight effect on air velocity measurement. At the 1/4 flow poation, the
pitot tube air velocity measurements were somewhat greater than heated
thermocouple values. This probably was due to disturbance in airflow at the
pitot tube in the duct which changed air velocity profiles across the duct.
Gates, therefore, were not closed to less than the 1/3 flow position in
experiments. It was concluded that a constant factor could be used to
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correct pitot tube readings to yield accurate measurements on the quantity
of air entering the reactor.
Relative humidity of air entering the reactor was measured twice daily
with a sling psychrometer (dry-wet bulb type) so that the amount of dry air
entering the reactor could be calculated.
Fans generally were controlled through feed back from thermocouples by
a Kaye Instruments data logger/controller (Kaye Instruments, 15 DeAngelo
Drive, Bedford, HA 01730). This system equipped with a RAMP processor could
be programmed to activate fans separately and maintain preset temperatures
in each of the four vessels. During start up of a given test fans were
operated by 10 min or 30 min timers which could be set to provide 1 min
increments of aeration. Once a mean preset temperature point was reached,
the data logger/controller took over automatically and controlled the fans.
Data acquisition center. An automated system for monitoring process
temperature, airflow and CO. production in each of four vessels was designed
and installed by Battelle Columbus Laboratories, 505 King Avenue, Columbus,
OH 43201. The entire system was installed in a mobile laboratory (trailer)
directly adjacent to the experimental vessel section. Temperature in the
trailer was maintained at 18-20 C. The Kaye RAMP/processor, a Beckman C02
analyzer, a pump, solenoid valves, timers, a balance and a forced air oven
were located in the trailer. The RAHP/processor was programmed at the
beginning of each trial to record temperature measurements from 80 locations
in the vessels, the ambient temperature and the temperature of the air
entering the fans. In some experiments additional temperature mesurements
were made at various locations in the exhaust air above the compost.
Readings were recorded hourly by a paper printer and every 4 hr on magnetic
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-Fig. 2. Aeration equipment: l*air intake, 2»fan and gates, 3*port
where air enters plenum under the compost, 4*averaging
pilot tube, 5«differential pressure transducer, 6»outside
wall of building in which reactors are located, and 7>
reactor vessel wall.
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tape with an HFE model 2500 tape deck (MFE Corp., Keewaydin Dr., Salem, NH
03079) that was interfaced with the RAMP/processor. The mean temperature of
20 thermocouples in each section was monitored continuously and used to
regulate aeration. Temperature set points were programmed for each section
and alarm relays were used to turn fans on and off. Each time the fans were
activated the event was recorded in Julian date and time of day. From this
data the number of minutes that fans were supplying air to the compost could
be determined accurately. Readings from the pressure transducers were
recorded hourly on paper tape and every 4 hr on magnetic tape. In addition
manual readings were taken twice daily to check the values.
Facilities in the trailer were used to determine percent dry solids by
oven drying of pre-weighed samples. Other analyses were performed at OSU,
OAEDC in Wooster.
COg and 0,, measurement. Five two-liter beakers were buried upside down
^ .
45 cm deep inside each vessel and connected via a manifold, condensate flask
and dryer (Dryrite) to a Beckman infrared CO. analyzer. Air was pulled
under vacuum out of each vessel, dried and analyzed for CO- concentration
after a constant C02 value was reached in the dry air moving through the
analyzer. Readings for each vessel were taken automatically every 4 hours
and printed on paper tape. The CO- system was calibrated routinely by
introducing 10? C02 from a standard pressurized cylinder into the manifold
on the compost pile. The oxygen concentration in exhaust air was measured
manually with a Teledyne 0. electrode. Periodically manual 0_ and CO-
readings were made with a Fyrite gas analyzer. The sum of 0? and CO- values
varied from 18 to 2\%.
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Data processing. The data recorded on magnetic tapes was processed
with * Hewlett-Packard 8? computer and programs written by Dr. L. Rossman,
Vaatewater Research Division, KEEL, US-EPA, Cincinnati, OH 45268. The data
were first transferred from the tapes to raw data files on computer discs.
From the raw data files the data were transformed into working files. In
these working files 'the data were tabulated for each of the four reactor
sections (l-IV) for 4 hr time intervals. The data in the working files
(Table 1 ) included the following: the temperature of the air entering the
fans (AMB TEMP), the relative humidity (REL HUMID), temperature at 13
locations within each section [T(-1 )-T(-13)], the mean of 20 thermocouples
in each section used to regulate fans (AVG TEMP) , the differential pressure
measured in the fan duct (FAN PRESS), the amount of time that the fans were
running during the 4 hr period (?AH OH HRS) , and the percent carbon dioxide
in the air moving out of the compost (CO^). These data were then checked
against the paper printouts and manual records and all necessary corrections
were made. Data in the working files were then used to determine the air
flow (CFM and kg dry air) and the C02 produced (kg COp) for each section
during each four hour interval. The formulae used to calculate these values
are given in Appendix I. In addition, the temperature distribution data
were used to calculate a weighted mean temperature which more accurately
reflected the temperature in the compost and the percentage of the compost
that was between .selected temperature intervals. The formulae used in these
determinations are included in Appendix II.
10
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Table 1 . Arrangement of data contained in working files.
Missing data are indicated by -9999. 0.
RECORD 1 4 mm
Section
T( 1)
T( 2)
7( 3)
Tl 4)
T( 5)
T( 6)
T( 7)
Tl 8)
T( 9)
T(10)
7(11)
TI12)
1(13)
AVS TEHP
FAN PRESS
FAN ON HRS
CD2
HOUR 8
I
50.9
37.8
-9999.0
58.7
58.3
38. &
. 34.2
37.0
48.5
30. &
31.3
3i.6
56.7
41.8
.489
4.000
9.450
mm AKB TEHP
II
46.4
43.9
31.0
46.1
60.9
40.3
30.5
40.0
43.9
27.7
29.0
32.0
50.7
38.3
.095
.800
14.220
7.9 mttt REL HUHID
III
49.9
46.6
31.0
50.1
62.3
56.7
30.1
40.1
55.3
27.4
25.1
23.2
66.3
40.8
.082
.300
14.600
86.00
IV
. 36.8
36.9
17.2
* 37.2
30.3
/54'.6
26.9
26.2
' 57.5
27.8
25.2
24.5
64.6
35.3
.464
.300
13.230
11
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SAMPLING PROCEDURES
Six preliminary trials were performed in the winter and summer of 1981.
The objectives of these trials were to determine 1) whether municipal
sludge could be composted effectively in the Paygro system, 2) procedures
for sampling of the compost in the reactor and 3) procedures for monitoring
the rate of composting. It was observed early that significant vertical
gradients existed in the reactor which complicated sampling procedures.
Each is discussed separately.
Temperature gradients in the reactor vessel. Preliminary mid-winter
and summer trials (1981) showed that temperature readings at a depth of 50
cm were uniform across the entire reactor up to a 50 cm distance from either
/ "
side wall. However, temperatures varied greatly with depth and particularly
in the center of the reactor. Since temperature variation was symmetric,
all probes were positioned in one half of the reactor. Examples of
temperature gradients are presented in Fig. 3« Isotemps are based on means
of all readings throughout a 14 day trial (Sept., 1981) for 40 thermocouple
positions in each vessel. Based on this temperature distribution data it
was decided to place two probes with seven thermocouples each in the center
of the reactor (thermocouple depths of 15* 30, 80, 115, 135, 210 and 240 cm)
and one probe with three thermocouples (depths of 15. 135, and 240 cm) at 30
cm from the wall and another with three at a 60 cm distance from the wall.
A total of 20 thermocouples therefore were placed in each of four reactor
vessels as illustrated in Fig. 4*
12
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TOP
cc
OJ
UJ
o
en MEAN
£ TEMPERATURE
o
<
LU
CC
65° C
2
N.
CM
TOP
-3M
cc
LU
B MEAN
n: TEMPERATURE
£ 42°C
LU
OL
Fig.3 . Temperature distributions for reactor sections maintained
at 65 and 42C during preliminary summer trial.
13
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6 m
6 rn
Length of tank 24m
6..m
6 rn
T3
ctf
H
Section 4
X X
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Section 3
X X
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Section 2
x x
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f-
Sectlon 1
* X
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^
Fan
an
Fan
Fan"
Fig. 4. View of tank showing temperature probe positions, x indicates
probe position (two In center, one each at 30 and 60 cm) from
the wall In each section. Thermocouples are attached to probes
in the center at depths of 15.30.80.115,135,210, and 240cm;
near the wall thermocouples are attached at 15, 135, and 240 cm depths.
-------
Distribution of dry solids in the reactor vessel. Distribution of dry
solids was examined in both winter and summer trials. This was accomplished
by removing samples from a vertical cut made by the extractoveyer through
the compost. Horizontal dry solids gradients were not detected at any depth
in either winter or summer trials (Table 2, 3 and 4) which supports symmetry
found for horizontal temperature readings. However samples removed from
various depths in the reactor vessels differed significantly (P-0.05).
During winter trials the top 50 cm layer in the reactor had the lowest dry
solids level. During summer trials this top wet layer usually was 15 cm
deep or less. A comparison of dry solids gradients for a summer and winter
trial are presented in Fig. 5- A description of the reactor feed and a
materials balance for this summer trial are presented in Tables 5 and 6.
Distribution of volatile solids in the reactor. Samples removed from
the face of vertical cuts in the ractor vessels for determination of dry
/ "
solids were also analyzed for volatile solids. After drying, samples were
ground to a fine powder in a Viley mill. Percent volatile solids was then
determined by ashing 1 g oven dry subsamples (minimum of 1 hr at 550 C). In
a summer trial samples were removed at day 11 (Table 7) and at day 18 (Table
8). A slight vertical gradient in volatile solids levels was detected in
the summer test (Table 8) after 18 days of composting. No evidence of
horizontal volatile solids gradients was detected at either time..
Temperature distribution data within the compost are presented in Table 9
for this 18 day summer trial.
In a preliminary winter trial compost was left without turning in the
reactor for 34 days to examine long range effects. Highly significant
differences in levels of volatile solids were found among samples from
15
-------
TABLE 2. Mean percent solids distribution in the reactor after 34 days
of composting for a winter trial.
Depth
(cm from
surface)
7.5
IS
60
120
150
210
245
Mean for
distance ,
from wall
Distance
15
36
49
45
48
47
57
53
48
.92
.4
.1
.9
.3
.0
.3
.3
150
38.0
39.7
46.6
50.2
53.8
52.8
52.1
47.6
230
36.1
40.8
47.5
49.9
49.7
55.8
53.7
47.6
from wall (cm)
300
37.8
38.9
46.2
49.8
49.8
57.2
52.5
47.5
380
35.3
37.1
51.3
50.0
49.4
55.3
50.2
46.9
460
35
37
46
50
49
54
SO
46
.6
.8
.1
.2
.9
.3
.4
.3
580
35
42
48
48
46
48
48
45
.3
.6
.1
.3
.8
.2
.6
.4
Means
for
depth
36.41
40.91
47.2
49.6 I
49.5 1
54.3 1
51. 5
1
Mean (of 14-samples) joined by a common line are not significantly
different according to Duncan's new multiple range test. LSD Q «2.6.
Mean of two samples.
Means of 14 samples. No significant, differences (P-.05).
-------
TABLE 3. Mean percent solids distribu tion in the reactor at
time of second turn (day 11) for a summer trial.
Depth
(cm from
surface)
5
7.5
80
130
185
240
Means for
distance _
from wall
Distance from
15
38
SO
52
51
49
50
48
.o2
.9
.4
.9
.9
.3
.8
60
39
53
52
50
49
54
49
.3
.1
.9
.0
.7
.0
.8
200
36.9
47.4
50.6
51.1
52.1
53.0
48.5
wall
275
40.5
47.0
51.7
51.7
54.6
52.2
49.6
(cm)
340
40.4
46.4
50.0
52.2
52.3
52.0
48.9
Means
for ,
500
37.
45.
49.
51.
51.
55.
48.
depth*
6
3
6
4
8
0
S"
38
48
51
51
51
52
.81
.3|
.2
.4
.6
.7
Means (of 24 samples each) joined by a common line are
not significantly different according to Duncan's new
multiple range test LSD .-=1.5.
• U j
Means of four values.
No significant difference among means (P=0.05).
17
-------
TABLE 4. Mean percent solids distribution in the reactor at
time of removal (day 18) for a summer trial.
Depth
(on from
surface)
5
7.5
80
130
185
240
Mean for
distance .
from wall
15
41.
59.
60.
62.
58.
57.
56.
22
6
5
7
6
2
6
Distance from wall (cm)
60
40
54
58
60
60
55
54
.8
.3
.1
.2
.1
.1
.8
200
41.9
50.6
56.7
57.6
60.1
60.0
54.6
275
41.3
50.0
56.0
56.3
57.7
62.6
54.0
340
41.0
54.9
56.6
57.6
56.7
61.2
54.7
500
40
54
57
55
58
60
54
.6
.6
.5
.9
.3
.3
.6
Means
for
depth
41
54
57
58
58
59
.11
.o|
.6
.4
.6
.4
Means (of 24 samples each) joined by a common line are
not significantly different according to Duncan's new
multiple range test LSD Q «1.6.
Mean of four values.
Means (of 24 samples) joined by a common "line are not
significantly different according to Duncan's new
multiple range test. LSD Q-»1.6.
18
-------
60
50
8
oc
o
40-
30
_L
J_
10 30 50 70
DEPTH FROM SURFACE CINCHES)
90
Figure 5. Percent dry solids distribution with depth in the reactor:
2=Trial 2, distribution on March 23 after 34 days and 3=Trial
3, distribution on June 18 after 18 days in the reactor. Mean
percent dry solids for reactor products of Trials 2 and 3 were
46.9 and 58.5, respectively.
19
-------
It
Table 5. Description of components and reactor feed mixture for a
preliminary summer trial
Component
Raw sludge
Recycled compost
Bark
A
Reactor feed
Mixing ratio
(volumes)
1
2.8
1.6
-
Bulk density
kg/m5
1063
605
414
679
Mean %
solids
14.5
SI. 8
57.2
40.8
Mean *
volatile
solids2
72.7
65.3
84.5
72.9
Determined by compacting (0.7 kg/cm , 10 Ibs/sq in) samples into
a 28.3 liter (1 cu ft) square box.
Mean of 10 or more samples of approximately 100 gm wet weight each.
/ "
Raw municipal sludge (98.4 M tons net weight) was obtained
(5/26/81) from the Southerly Treatment Plant, Columbus, OH.
Total volume-439 m (error <4%).
20
-------
TABLE 6. Materials balance for a preliminary summer composting trial.
. Bulk2
Volume density
(m3) (kg/m3)
Reactor feed
Reactor product
Loss during
composting**
% loss
439
341
98
22
.4 678. 5
.0 517.7
.4
.4
Wet3 .
weight % Dry
(M tons) solids
298.2 40.8
176. S 58.5
121.7
40.8
. Weight dry5
\ Volatile* solids
solids (H tons)
72.9 121.
67.8 103.
18.
IS.
7
3
4
1
Weight5 Height5
water volatile solids
(H tons) (M tons)
176.5
73.2
103.3
58. 5
88
70
18
21
.7
.0
.7
.1
1
Measurements were wade in the reactor (error 4%).
See Table 1 for explanation.
Calculated from bulk density and volume.
Means of a •inimun of 10 samples of approximately lOOg wet weight each.
Calculated from we weight and percent solids or volatile solids.
After 18 days in the reactor.
-------
TABLE 7. Mean percent volatile solids distribution in the
reactor at time of second turn (day 11) for a summer trial.
Depth
(cm from
surface)
5
7.5
80
130
185
240
Mean for
distance ,
from wall
Distance from wall (cm)
15
69
69
72
67
70
75
70
.72
.6
.9
.9
.4
.1
.9
60
70
69
71
72
70
69
70
.1
.5
.5
.1
.1
.6
.6
200
69.9
67.6
67.1
70.6
70.5
68.3
68.5
275
69.8
68.7
71.9
69.8
67.6
67.4
69.2
340
69.8
70.1
67.7
70.2
69.9
69.6
69.6
500
67.9
70.6
71.6
72.3
72.8
68.7
70.7
Means
for ,
depth
69
69
70
70
70
69
"
.2
.3
.5
.5
.2
.8
Means (of 24 samples each) joined by a common line are
not significantly different according to Duncan's new
multiple range test (P«0.05).
Mean of four values.
3
22
-------
TABLE 8. Mean percent volatile solids distribution in the
reactor at time of compost removal (day 18) for a summer
trial.
Depth
(cm from
surface)
5
7.5
80
130
185
240
Mean for
distance ,
from wall
Distance from wall (cm)
62
74
64
65
63
64
63
IS
.9*
.6
.1
.3
.7
.6
.8
60
66
65
61
65
65
63
64
.9
.2
.8
.3
.0
.1
.5
200
65.0
63.6
62.6
65.3
65.2
66.8
64.7
275
68.3
63.4
64.0
65.2
63.1
63.7
64.6
340
66.2
63.7
61.8
63.8
63.7
63.1
63.7
500
66.0
62.4
64.3
63.7
62.5
64.9
64.0
Means
for
depth1
65
64
64
63
63
63
.91
.4
.4
.9
.9
.1
Means joined by' a common line are not significantly
different according to Duncan's new multiple range test
LSD0.05-1.4.
2
Mean of four values.
No significant difference among means (P=0.05).
23
-------
TABLE 9. Mean temperatures of compost in various thermo-
couple positions for selected time periods of a summer
trial.
Total hours
elapsed
A A
88
First Turn
184
Second Turn
160
Removal
432 (total)
Depth
(cm)
7.5
80
130
240
7.5
80
130
240
7.5
80
130
240
7.5
80
130
240
Distance
Wall
_2
_
31.4
20.3
34.3
—
32.9
22.4
45.7
—
39.4
25.3
39.1
34.4
22.7
15
•
33.5
22.2
47.8
—
36.0
18.4
53.0
_
41.5
26.4
49.7
36.9
21.5
from wall (cm)
30
.
_
41.7
24.6
49.9
_
34.7
24.6
53.6
„
41.8
24.0
51.2
38.3
25.7
60
.
_
44.0
35.2
51.1
—
49.4
30.9
54.6
_
4<5.~3
29.3
52.4
45.7
31.5
200
73.1
71.4
59.3
58.9
59.0
54.5
34.9
59.2
59.5
56.5
37.0
59.0
62.5
.59.0
41.3
Means of readings taken every 4 hr in four locations
for the wall, 15, 30 and 60 cm positions. Means of
eight locations for the 200 cm position.
Missing data.
24
-------
various depths but not among samples removed from the same depth (Table 10).
The lowest levels were in the bottom of the reactor (Table 6) suggesting
that more decomposition had occurred in this lower temperature location of
the reactor (Fig. 6). However because dry solids and other factors also
varied significantly along this vertical gradient, no causal relationship
between temperature and volatile solids destruction could be determined from
this data. The distribution of volatile solids data however further support
horizontal symmetry in the reactor.
To reduce sampling error caused by the vertical gradients for the
determination of dry and volatile solids levels of the compost for each
vessel section, samples were taken after compost was removed and had been
mixed thoroughly with the extractoveyor. A total of eight 125-150 g (wet
wt.) samples were taken at constant intervals per vessel. Compost from each
section was loaded onto eight trucks, weighed and sampled before it was
returned to the reactor during turning. One sample was taken per truck
load. Samples were dried in a 104 C forced air oven to constant weight to
determine percent dry solids.
Determination of free air space. In preliminary trials several
procedures were tested, including core samples typically used for the Learner
and Shaw desorption apparatus and an air pycnometer. Neither system
provided reproducible data probably because the reactor feed was plastic
whereas the product was solid. The reactor feed compacted ahead of the core
sampler as it was forced into the compost, thus reducing air-filled pore
space. The procedure which did produce reliable results is known as the
procedure for determining "air-filled pore space levels" in container media
used in horticulture. In this technique, samples of known bulk density are
25
-------
AERATION - MINUTES OUT Of TEN THAT EAN WAS ON
I
• n
«•
19
a
8
10 •
HOURS
Fig. 6. Traperatur* at vtrious depths fro* surf act in covpost during
• winter trial (2/26/81-3/3/81) with anacrobically digested
sludge after the second turn: 1, 2, 3 and 4 are 7.5, 90, ISO,
24S tm fron the surf ace. respectively. S and 6 are daily artient
' Mxisusi and miniauB testieratures. respectively.
26
-------
K)
TABLE 10 . Mean percent volatile solids distribution in the reactor after
34 days of composting for a winter trial.
Depth
(cm from
surface)
7.5
15
60
120
150
210
245
Mean for
distance ,
from wall
Distance
15
71
69
70
70
69
58
56
66
.22
.5
.0
.0
.8
.3
.7
.5
150
70
68
69
71
70
62
60
67
.4
.7
.2
.0
.1
.5
.0
.3
230
73.
70.
70.
70.
70.
64.
61.
68.
6
4
6
6
2
2
1
7
from wall (cm)
300
67.7
71.5
69.9
67.9
70.2
61.9
62.0
67.2
380
74.0
73.4
72.6
69.5
72.2
67.0
60.2
69.9
460
69.2
70.0
70.5
68.9
73.3
64.0
58.1
67.7
Means
for ,
580 depth*
66.
66.
68.
66.
69.
62.
57.
65.
3 70.3
7 70.1
1 70.1
6 69.5
0 70.7
5 62.9 |
1 59.1 |
5
,
1
different according to Duncan's new multiple range test. LSD .05=2.9.
Means of two samples.
f '.
Means of 14 samples, no significant differences (Pa.05).
-------
packed to the appropriate density in a 1 liter glaaa graduate cylinder. It
ia accurate for batchea of composts of known bulk density. Since reactor
feed and product for seven trials in 1982 and 1983 were weighed and total
volumes in the reactor could be determined accurately, precise bulk density
values were available. After the weights of the empty and packed cylinder
were determined, water was allowed to drain via a tube along the inside wall
of the cylinder to the base of the cylinder where air was forced upwards, as
water entered. Water was added during a 10 min period while the aidewalls
of the cylinder were tapped with a rubber stopper. Addition of water was
stopped once the surface of the compost glistened. All air bubbles were
removed from the compost in this fashion. The compost used in this work did
not float in water. Sludge particles did not rearrange during the 10 min
time period. The cylinder was then reweighed and the increase in weight of
the cylinder contents represented the volume of air replaced by water and
/
was used to calculate percent Free Air Space. Compost samples, which were
drier than "55% moisture did not wet well when water was added. Air pockets
could be seen in the vessel. To avoid this a wetting agent was added to the
water which removed air from the dry sample. Means were calculated from a
minimum of three samples.
Chemical analyses. Total Kjeldahl nitrogen, total organic carbon,
carbon-nitrogen ratio and pH of reactor feed and product were determined on
three samples per treatment by T. J. Logan, Professor, Department of
Agronomy, Kottman Kail, OSU, Columbus, OH. Conductivity in a saturated
paste extract, pH, total H, P, and K, as well concentrations of heavy metals
were determined on cured compost of seven trials by the sludge laboratory of
the Research Extension and Analytical Laboratory (REAL) of OSU, OARDC,
Wooster, OH 44691.
28
-------
MATERIALS BALANCES FOR SEVEN COMPOSTING TRIALS
Introduction. Several parameters were examined in seven composting
trials performed from October 15, 1982 to Aprl 10, 198?. Factors affecting
the rate of composting and drying were evaluated. In trials I and II, the
effect of process temperature on the composting process was examined. Trial
I basically served to test all equipment. Attempts were made to maintain
high (mean of 63 C) and low (mean of 43 C) temperatures throughout each
trial. In trial III and IV the effects of a high process temperature early
in the composting process followed by a low temperature later in the process
were compared with the reverse of these temperature regimes. The purpose of
these trials was to establish whether reduction in fecal pathogens could be
accomplished early and/or late in the process. In trial V the effect of
blending reactor feed^with a pugmill mixer on the rate of composting was
compared with that of front-end-loader (PEL) mixing. In trial VII high and
low process temperatures were combined with reverse airflow to expose
compost in the bottom of the vessels to high temperatures. From January to
October 1982, 10 composting trials were performed by Compost Systems Co.,
9403 Kenwood Rd., Cincinnati, OH 45242 under a City of Akron, EPA grant to
Burgess and Niple, Limited, 46 South Summit St., Akron, OH. The testing
laboratory was used during these trials and the general procedures used to
determine a materials balance were based on sampling methods developed
during preliminary trials. As a result of this work, a summary of which is
presented in Appendix III, a data base was established for composting of
municipal sludge in the Paygro reactor.
29
-------
Materials balance. Detailed materials balances of trials 1-VII are
presented in Tables 11-17. The mean percentage dry solids (% DS) of the
sludges received from the City of Akron used in these trials was 21.6 (Table
18). Raw primary sludge was used in all trials, except in trial VI, for
which a mixture of primary and waste-activated sludge was used.
The top 30-40 cm layer of the reactor product usually was higher in
moisture content than the lower part. Therefore the top layer was removed
separately and placed into a curing pile. The bottom layer in the reactor
product was recycled into the following trial as bulking agent. It is
referred to as "recycled compost" in this report. The mean % DS of the
recycled compost in these trials was 58.6 (Table 18). Bark and sawdust made
up the remainder of the bulking agent with % DS values of 53.9 and 50.0
respectively.
Sludge, bark, sawdust and recycled compost were mixed at a volumetric
/ "
ratio of 1.0, 0.4, 0.3, and 2.8, respectively, to yield 46.3$ DS in the
reactor feed. The mean % DS of the reactor product, which was moved to the
curing piles, was 53«0. The overall % DS of the reactor product after 16.0
days of composting was 56.9. The mean percentage volatile solids (% VS) for
each component is also listed in Table 18.
Decomposition rates as measured by 1) CO. evolution, 2) loss in weight
of dry solids per trial and 3) by a reduction in % VS, varied from trial to
trial. The mean ambient high and low temperatures were 9*9 and 3-0 C.
Means of water loss and volatile solids destruction for trials I-VII are
presented in Table 19* The mean percentages loss in wet weight and dry
solids were 25*7 and 9.3, respectively during a mean of 16 days of
composting. During this time period the mean percentage of water evaporated
30
-------
TABLE LI MATERIALS BALANCE FOR TRIAL I. COMPOST RETENTION TIME -12.6
DAYS. VOLUME OF REACTOR FEED - 473 CUBIC YARDS.
COMPONENT
RECYCLE
BARK
SAWDUST
SLUDGE
TOTALS
REACTOR FEED
REACTOR PRODUCT2
RECYCLE
CURING
DESTROYED
WET WT
(LBS)
329,920
33,000
31,680
316,520
711,120
53.5031
657,617
438,460
367,790
70,480
219,157
Z SOLIDS
67.4
57.0
56.0
22.0
46.2
46.2
61.9
62.1
61;9
WT SOLIDS
(LBS)
222,366
18,810
17,741
69,634
328,551
303,819
271,407
228,516
43,627
32,412
WT WATER
(LBS)
107,554
14,190
13,939
246,886
382,569
353,798
••/" 167,053
139,464
26,853
186,745
1 EXCESS MATERIAL NOT PLACED IN REACTOR
2 REACTOR PRODUCT USED IN SUBSEQUENT TRIALS DESIGNATED AS RECYCLE
WITH REMAINDER PLACED IN CURING PILE
31
-------
TABLE 12. MATERIALS BALANCE FOR TRIAL II. COMPOST RETENTION TIME - 14.75
DAYS. VOLUME OF REACTOR FEED - 473 CUBIC YARDS.
COMPONENT
RECYCLE
BARK
SAWDUST
SLUDGE
TOTALS
REACTOR FEED
REACTOR PRODUCT1
RECYCLE
CURING
DESTROYED
WET WT
(LBS)
367,980
48,580
28,560
289,920
735,040
735,040
535.800
437,000
98,800
199,240
Z SOLIDS
62.1
48.4
61.1
19.0
44.2
44.2
56.4
57.8
50.0
WT SOLIDS
(LBS)
228,516
23,513
17,450
55,085
324,888
324,888
301,986
252,586
49,400
22,902
WT WATER
(LBS)
139,464
25,067
11,110
234,835
410,152
410,152
223,814
'/" 184,414
49,400
186,338
1 REACTOR PRODUCT USED IN SUBSEQUENT TRIALS DESIGNATED AS RECYCLE WITH
REMAINDER PLACED IN CURING PILE
32
-------
TABLE 13. MATERIALS BALANCE FOR TRIAL III. COMPOST RETENTION TIME - 15
DAYS. VOLUME OF REACTOR FEED - 673 CUBIC YARDS.
COMPONENT
RECYCLE
(AKR 18)
BARK
SAWDUST
SLUDGE
TOTALS
REACTOR FEED
REACTOR PRODUCT1
RECYCLE
CURING
DESTROYED
WET WT
(LBS)
437,000
108,720
32,080
32,340
297,280
907,420
907,420
716,780
541,540
175,240
190,640
Z SOLIDS
57.8
60.0
65.3
59.6
19.1
45.7
55.4
57.5
48.9
WT SOLIDS
(LBS)
252,586
65,232
20,948
19,275
56,780
414,821
414,821
397,096
311,386
85,710
17,725
WT WATER
(LBS)
184,414
43,488
11,132
13,065
240,500
492,599
492,599
319,684
230,154
89,530
172,915
1 REACTOR PRODUCT USED IN SUBSEQUENT TRIALS DESIGNATED AS
RECYCLE WITH REMAINDER PLACED IN CURING PILE
33
-------
TABLE 14. MATERIALS BALANCE FOR TRIAL IV. COMPOST RETENTION TIME - 20.25
DAYS. VOLUME OF REACTOR FEED - 663 CUBIC YARDS.
COMPONENT
RECYCLE
AKE III
AKR X
BARK
SAWDUST
SLUDGE
TOTALS
REACTOR FEED
REACTOR PRODUCT1
RECYCLE
CURING
DESTROYED
WET WT
OBS)
541,540
27,840
27,340
51,880
39,380
249,300
937,280
937,280
709,860
535,080
174,780
227,420
Z SOLIDS
57.5
74.8
66.1
54.0
47.4
18.5
47.3
47.3
53.5
53.7
53.2
WT SOLIDS
(LBS)
311,386
20,824
18,072
28,015
18,666
46,121
443,089
443,084
379,775 •/ "
287,338
92,983
63,309
WT WATER
(LBS)
230,154
7,016
9,268
23,865
20,714
203,179
494,195
494.195
330,085
247,742
81,797
164,110
1 REACTOR PRODUCT USED IN SUBSEQUENT TRIALS DESIGNATED AS
RECYCLE WITH REMAINDER PLACED IN CURING PILE
34
-------
TABLE 15. MATERIALS BALANCE FOR TRIAL V. COMPOST RETENTION TIME - 21.7
DAYS. VOLUME OF REACTOR FEED - 581 CUBIC YARDS.
COMPONENT
RECYCLE
BARK
SAWDUST
SLUDGE
TOTALS
REACTOR FEED
REACTOR PRODUCT2
RECYCLE
CURING
DESTROYED
WET WT
(LBS)
535,080
45,280
45,000
187,740
813,100
64.0801
749,080
579,820
388,740
191,080
169,260
Z SOLIDS
53.7
50.0
47.0
21.2
45.6
45.6
.53.22
53.91
51.83
WT SOLIDS
(LBS)
287,338
22,640
21,150
39,801
370,929
341,580
. 308,580
209,570
99,010
33,000
WT WATER
(LBS)
247,742
22,640
23,850
147,939
442,171
407,500
271,240
179,170
92,070
136,260
1 EXCESS MATERIAL NOT PLACED IN REACTOR
2 REACTOR PRODUCT USED IN SUBSEQUENT TRIALS DESIGNATED AS RECYCLE
WITH REMAINDER PLACED IN CORING PILE
35
-------
TABLE L6. Materials balance for Trial VI. Compost retention time * 15.3
days. Volume of reactor feed » 473 cubic yards.
Component
Recycle
Bark/sawdust
Sludge
Totals
Reactor feed
Reactor product
Recycle
Curing
Destroyed
Wet wt
(Ibs)
388,740
83,920
165,800
638,460
638,460
498,400
381,560
116,840
140.060
% Solids
53.9
51.6
27.2
46.7
56.4
58.1
50.7
Wt solids
(Ibs)
209,570
43,336
45,116
298,022
298,022
280,936
221,760
59,176
17,086
Wt water
(Ibs)
179,170
40,584
120,684
340,438
340,438
217,464
- 159,000
57,664
122,974
Reactor product used in subsequent trials designated as recycle
with remainder placed in curing pile.
36
-------
TABLE 17. Materials balance for Trial VII. Compost retention time = 12.6
days. Volume of reactor feed g 473 cubic yards.
Component
Recycle
Bark/ sawdust
Sludge
Totals
Reactor feed
Reactor product
Destroyed
Wet wt
(Ibs)
381,560
87,760
166,240
635,560
34.7401
600,820
442,700
158,120
% Solids
58.1
51.7
23.9
48.3
57.6
Wt solids
(Ibs)
221,760
45,387
39,765
306,912
290,137
254,983
35,154
Wt water
(Ibs)
159,800
42,373
126,475
328,648
310,683
187,717
122,966
/ "
Excess material not placed in reactor.
37
-------
Table 18. Mean dry solids (% DS) and volatile
solids (% VS) of components, reactor feed and
reactor product for seven composting trials.
Mean compost retention time * 16.0 days.
Component
Sludge
Bark
Sawdust
Recycle
Reactor Feed
Reactor Product
\ DS
21.6
S3.9
50.0
58.6
46.3
56.9
% VS
58.9
86.5
95.0
57.0
58.9
56.3
Volume
ratio
1.0
.4
.3
2.8
38
-------
TABLE 19. Percentage loss of wet weight, weight dry solids and weight water:
Number of days retention and neon high and low ambient air temperatures for
compost Trials I-VII. _______^_^__________________
Trial Mean
I II III IV V VI VII (I-VII)
% Loss in:
Net Height 33.3 28.2 21.0 24.3 22.6 21.9 26.3 2S.7
Weight Dry
solids 10.4 3.5 4.1 14.S 9.7 5.7 12.1 9.3
Height water 52.9 43.7 35.3 33.0 33.S 36.1 39.6 39.2
Days Retention 12.6 14.8 15.0 20.3 21.7 15.3 12.6 16.0
Mean temperature ' '
(C) of ambient air
High 24.8 12.S 7.3 3.7 1.0 12.2 7.5 9.9
Low 14.1 4.7 3.3 -3.7 -1.5 2.9 1.2 - 3.0
39
-------
*
was 39*2. This loss In water does not include water liberated through
biological activity. A limited attempt was made to determine a water
balance for the system. Direct measurements were not possible within the
scope of this study, therefore, only calculations of biological water
liberated based on stoichiometric formulae and loss in dry solids can be
made.
Air flow through the compost (CPU) changed markedly over the course of
a given trial. Rates were lowest (1,000-1,500 CPM) at the beginning of a
trial when the % solids was lowest. After the compost was turned the
highest rates (2,000-3,200 CFN) were observed. Static head pressures varied
at any given time among sections and with time within sections. The static
head pressure measured just past the fan, where air entered the plenum under
the reactor, ranged from 1.3-2.0 inches of water when reactor vessels were
empty. Static head pressures (inches of water) for fully loaded vessels
ranged from 5-7 inches. Readings were generally lowest after turning (as
low as 4"). Increases occurred thereafter as compost settled (from the full
\
height of 290 cm to as low as 240 cm).
Results of chemical analyses of the reactor product of all seven trials
indicated that heavy metals were not being concentrated with the bulking
agent ratios used in these trials. The percent nitrogen (T.K.N.) ranged
from 1.7-2.0 with the greater portion (1.3-1*8£) existing as organic
nitrogen. There was no appreciable change in pH (7.0-7.5) or increase in
conductivity (6.8-11.0 MKHOS) in the reactor product.
Fugmill mixing versus PEL mixing of reactor feed. In trial V a
Speed flow pugmill mixer was tested for the Paygro system. The reactor feed
was mixed by PEL and part of it was then fed through the pugmill during the
40
-------
*
tank loading process. Two sections were filled vith reactor feed produced
by each of the tvo procedures. Mean % PAS (free air space) readings in the
FBL sections were significantly (P-0.05) higher (45.2) than those in the
pugmill-mixed sections (42.3) at the beginning of the trial. After 21.5
days when the reactor product was removed the mean % FAS values in the PEL
and pugmill sections were significantly lower (42.6 and 38.5 respectively).
In spite of higher FAS readings in the FEL-mized sections, airflow was
higher in pugmill sections. Bates of airflow in the PEL sections ranged
from 1000-2000 CFM whereas airflow in the pugmill sections were 2000-3000
CFM.
Samples of the reactor feed were removed from both sections before the
first turn. In the FEL-mized sections "balls" of sludge were found. After
the sludge balls were cut in half putrifactive odors escaped. Ho bulking
agent was present inside these sludge balls. In the pugmill-mized sections
balls also were found. However when these were broken open, putrifactive
odors were not detected and bulking agent was present uniformly throughout.
The low airflow rates in the FEL-mdjced sections therefore may have been due
to the presence of "flattened" sludge balls in the base of the reactor, thus
decreasing % FAS and restricting airflow in that area, resulting in some
anaerobic metabolism.
Rates of drying for the two treatments are presented in Table 20.
After the first turn (14 days) the % DS of the compost in the apeedflow
section was significantly higher (P-0.01) than that in the FEL section after
21 days. Drying therefore was significantly better in the pugmill-raixed
sections than in the FEL-mized sections. Data on CO- evolution were not
obtained in this mid-January trial since ice accumulated in lines (ahead of
the condenser) and interfered with airflow to the CO- analyzer.
41
-------
TABLE 20. DRY SOLIDS (Z) OBTAINED IN TRIAL V
USING FRONT END LOADER (PEL) AND PUGMILL MIXER
(SPEED FLOW).
METHOD OF MIXING
FEL SPEED FLOW
REACTOR FEED 46.21 47.4
TORN
(14 DAYS RETENTION) 50.5 54.6**
REACTOR PRODUCT
(21 DAYS RETENTION) 52.7 58.8**
LSD (P - .01) - 3.48
** DIFFERENCES BETWEEN MIXING TREATMENTS
ARE. SIGNIFICANT (P • .01)
42
-------
SPECIFIC ACTIVITY OF THE COMPOST BIOTA
MacGregor et al. (11) found that low process temperatures appeared to
favor C0_ production and drying during composting. In a preliminary summer
trial during 1931 similar observations were made with the Paygro System.
However measurements on actual amounts of air forced through the compost
piles and therefore measurements on actual levels of CO- produced were
lacking in both studies.
In trials II and VII carbon dioxide evolution was measured for sections
of the reactor maintained at "low" (40 C) and "high" (60 C) temperatures.
Temperature was controlled by regulating the amount of air entering each
section. In trial II a continuous flow was maintained and the volume of air
varied by opening or closing gat'es. The total weight of carbon-dioxide
evolved during this trial was abnormally high and did not correspond to the
calculated weight of carbon dioxide lost based on measured losses of dry
solids. These calculations assumed that glucose was the primary carbon
source metabolized and thus each kg of dry solids yielded approximately 1.5
kg carbon dioxide. However there were appreciable differences in the
weights of carbon dioxide evolved from the "hot" and "cool" sections which
corresponded to the differences in losses of dry solids and volatile solids.
Thus the amounts of carbon dioxide produced during trial II were expressed
as arbitrary quantitative units.
CO- evolution and airflow for the "hot" and "cool" sections in trial
II, as well as mean temperatures and the percent of reactor volume above 55
43
-------
10
Kg. Dry Air x I.OOO/M Mr
Units C02
ZO
10
IOO
80
IOO
80
fiO
40
20
Mean Temp. C
% of Reactor Volume > 55 C
TIME, DAYS v
Fig. 7. Aeration, CO. evolution and temperature, data for the "cool" (43C) section of Trial 2:
Aeration and CO. evolution are given for each 4 hour Interval. Mean temperature and
X of Reactor Volume > 55C are based on readings from 20 thermocouples. The compost
was turned once after 9 days and removed from the reactor 6 days later.
-------
20
10
- Kg Dry Air x I.OOO/t/Hr
---- Units C02../HHr
20
IO
too
eo
so
40
20
60
20
VN
>_ _^N /-
Mean Temp. C
% of Reactor Volume > 55 C
TIME, DAYS
Fig. 8. Aeration, C02 evolution and temperature data for the "hot" (65C) section of Trial 2.
Aeration and CO. evolution are glvenMor each A hour interval. Mean temperature and
" % of Reactor Volume^ S5C are based . on 'readings from 20 thermocouples. The compost
was turned once after 9 days and removed from the reactor 6 days later.
-------
C, are presented in Figs. 7 and 8. The highest levels of CO. evolution and
airflow occurred in the "cool" section. Mean temperature and % volume above
55C appeared to be negatively correlated with CO. evolution and airflow.
The highest level of CO. evolution in the "cool" section occurred within a
temperature range of 38-55 C (Fig. 9). Levels of CO. evolution before the
turn were considerably higher than those after the turn.
In trial VII temperatures were controlled by automatically turning the
fans on or off when the mean temperature reached or fell below a set value.
As observed in trial II, "cool" sections dried more rapidly and lost more
volatile solids than "hot" sections. Aa shown in Table 21, there already
were significant differences (P-0.05) between sections in the percent dry
solids by the time the compost was turned (5*6 days). Differences in the
percent volatile solids between sections were not evident until the end of
the trial (12.6 days). In addition, differential rates of activity between
"cool" and "hot" sections were evident when the percent losses of dry solids.
were compared. Approximately 15£ of the dry solids of the reactor feed was
lost in 12.6 days in the "cool" section in contrast to only 10$ in the "hot"
section.
The relationships between air volumes, carbon dioxide evolution, mean
temperature and % of compost >55 C are shown in Figs. 10-13* Before the
turn, the mean temperatures in the "cool" sections were maintained between
36 and 46 C (Fig. 10) whereas the mean temperatures in the "hot" sections
were held to between 50 and 86 C (Fig. 12). After the turn (day 6.6-13.3),
the temperatures in the "cool" sections were maintained at 32-36 C (Fig.
11). Mechanical problems with one of the fans in one of the "hot" sections
resulted in poor temperature control after day 9 (Fig. 13). Differences in
46
-------
350
300
250
<
CM
O
u
z
D
200
150
100
50
0 s* ••
:'•; '
00
20 30 40 50 60 70
MEAN TEMPERATURE °C
80
Fig. 9. Relationship between C02 evolution and mean compost temperature
in trial II. • ="cool" section before turn, 0="cool" section
after turn,A ="hot" section before turn, .A ="hot section after
turn.
4-7
-------
Table 21. Percent dry solids (* OS), percent volatile solids (\ VS) and
percent loss of initial weight of dry solids for "cool" and "hot" sections
of trial VII
\ DS
Reactor Feed
Turn (5.6 days)
Reactor Product
(12.6 days)
"Cool"
48.2
54.9
60.8
"Hot"
48.3
52.3*
55.4**
% Loss of initial
% VS weight DS
"Cool"
57.4
59.4
55.5
"Hot" "Cool"
59.4
59.2 8.6
59.6* 14.8
"Hot"
—
5.3
10.0
Difference between "cool" and "hot" sections significant at P-.05
Difference between "cool" and "hot" sections significant at P».01
48
-------
9: - ... •
BO
70
80
SO
40
30
20
10
0
^^ ••
Mean Temperature C
i*
% Compost > 55C
10
Kg. Dry Air (X1000) / 4 Hr
Kg. CO2 (X100)/4Hr.
x ^ ^
TJHE. DAYS
Fig. 10. Aeration, CO2 evolution, and Temperature data for "cool"
section of reactor before first turn in Trial VII.
49
-------
JO
ID
70
Mean Temperature C
• % Compost >55C
»r /
\
10
II
13
10
Kg. Dry Air (X1000)/ 4 Hr.
-Kg, CO2 (X100)/ 4Hr.
7 • • 10 II U II
nic. o*n
Fig. 11 • Aeration. COj •volution and temperature data for "cool"
••ction of reactor after torn In Trial VU.
50
-------
90
ac
70
60
so
40
30
zo
:o
o
~- Mean Temperature C
— — % Compost^ 55C
Kg. Dry Air(XlOOO)/ 4 Hr.
Kg. CO- -(X100)/ 4 Hr.
TIME. OMS
Fig. 12.Aeration. COj evolution and temperature data for "hot"
section of reactor before turn in Trial VII.
51
-------
•0
70
ao
so
40
»
20
10
0
10
——— Mean Temperature C
— — - % Compost > 55C
10
13
—— Kg. Dir Air (X1000)/ 4 Hr.
Kg. CO2 (X100) / 4 Hr.
a 10 u
TIME. OATS
12
u
Fig. 13. Aeration. COj evolution and Temperature data fot "hot"
•ection of reactor after turn in Trial VII.
52
-------
the mean temperatures and % of compost >55 C were due to differences in the
amounts of air supplied to the sections. Air was forced through "cool"
sections at 14,000-2500 kg dry air/4 hr and through "hot" sections at
7500-500 kg dry air/4 hr. During the period of mechanical failure it was
assumed that the air flow through the "hot" section from the adjacent "hot"
section was 500 kg dry air/4 hr. Readings of the percent carbon dioxide
were available throughout this period and calculations of carbon dioxide
evolved were based on this assumption.
Within each section variations in mean temperature during the trial
were principally due to variations in amounts of air supplied. For example,
in the "cool" section between day 1 and 4 airflow was reduced from 14,500 kg
to 2500 kg dry air/4 hr (Fig. 10). During this period the mean temperature
increased slowly. The mean temperature was next reduced sharply on day 4 by
increasing airflow. After the turn, temperature was maintained at a nearly
constant level from day 8 through 13 (Fig. 11). The amount of air supplied
during this period declined steadily. This reduction in air may have been
due to reduced microbial activity and thus heat output due to gradual
depletion of the most readily available energy sources over this time
period. However during this period there was a drop in ambient temperature
which may also have been partially responsible for this trend.
The amount of carbon dioxide evolved each 4 hour interval was generally
higher in the "cool" section than in the "hot" section. In addition, in
both "cool" and "hot" sections carbon dioxide evolution was greatest at the
beginning of the trial and tended to decline with time. For example in the
"cool" section amounts declined from 250 to 50 kg C02/4 hr from day 0.6 to
day 6 (Fig. 10). This drop in CO evolution appeared to be independent of
S3
-------
variations in the volume of air supplied during this period and was the
reault of a decrease in the percent C02 values measured. The decline in
carbon dioxide evolution from day 1 to 4 corresponds with an increase in the
mean temperature and percent of the compost >55C. After the turn the
amounts of CO. evolved in the "cool" section vere greater than those
observed immediately prior to the turn. This difference reflects lover
temperatures during this time and possibly the release of available
nutrients as a result of the turning process.
The measured weight of carbon dioxide lost (metric tons) from the
"cool" and "hot" sections corresponded closely to the calculated losses
assuming glucose as the primary carbon source (Table 22). Values based on
the stoichiometric formula (1) for sludge did not correspond as closely.
Thus for this trial the air measurement data and carbon dioxide measurements
appear to be accurate and therefore, meaningful calculations of the overall
/
respiration rates for this system can be made.
for comparison with other studies the measured rates of carbon dioxide
evolution (kg/4- hr) vere converted to mg C0./g VS-hr (Table 23). Bates of
CO. production in the Paygro system for the 108 ar "cool" sections ranged
from 5*9 mg C02/g VS-Hr at the beginning of the trial to 0.6 mg C0_/g VS-Hr
just before the turn. In the "hot" section these rates vere much lover.
Also oxygen uptake rates vere calculated (mg 0_/g VS-Hr) for selected times
during trial VII (Table 23). Rates of oxygen uptake vere based on the •
assumption that glucose was the primary source of carbon and that aerobic
respiration prevailed* These values are very similar to rates published for
various pilot-scale composting systems as shown in Fig. 14 (from Haug, R.
T., Compost Engineering, Principles and Practice, Ann Arbor Science, Ann
Arbor, HI. p. 316, Fig. 7).
SA.
-------
in
in
Table 22. Comparison between carbon dioxide evolution values and calculated values
based on stiochiometric formulae for trial VII
Time Period
Before turn
After turn
Total
Section
"Cool"
"Hot"
"Cool"
"Hot"
"Cool"
"Hot"
Observed loss
of C02
(metric tons)
4.2
2.5
5.6
2.6
9.8
5.1
Measured loss
of dry solids
(metric tons)
3.3
2.0
2.4
1.6
5.7
3.6
Calculated weight of C02
for equal weight loss of:
Sludge
(metric tons)
7.2
4.4
5.3
3.5
12.5
7.9
Glucose
(metric tons)
4.9
3.0
3.5
2.4
8.4
5.4
1
Stiochiometric calculations based on the following formulae:
Sludge: C1()H1903N+12.5 02 *• 10 CO,, + 8H20 + NHj
Glucose: CJL.O.. + 60_ > 6 C0_ + 6H-0
o L£ o i it
-------
1/1
01
Table 23. Carbon dioxide production and oxygen uptake determinations for "cool" and "hot"
sections of trial VII
Section
"Cool"
"Hot"
Time
(HR from
start of trial)
14
122
14
122
Mean
temperature
39.3
36,6
46.0
54.5
Aeration rates
M3/ton VS-hr *
160
51
30
11
Kg C02/
4 hr
520
50
230
10
Mg C02/
g VS-hr
5.9
0.6
2.6
0.1
Mg 02/2
g VS-hr
4.3
0.4
1.9
0.1
1
Calculated from measured air volumes (Kg dry air/4 hr).
0- calculated on the assumption that glucose is the primary carbon source.
-------
316 COMPOST ENGINEERING
to
a.
m
O u
O
ui
O
> OJ
x
O
oe
at
JIMS, «c
-------
FATE OF FECAL PATHOGENS
Rules and regulations published in Federal Register Vol. 44, #179,
Thursday, September 13, 1979, page # 53464 mandate that solid waste
composted in within-veaael systems be maintained at operating conditions of
55 C or greater for three days to further reduce pathogens. In one of the
preliminary summer trials, in a section maintained at 63 C and turned twice
with an 18 day retention time, more than 99£ of the compost was exposed to
55 C continuous for three days or more. During normal aeration procedures
however, significant vertical and horizontal temperature gradients exist
within the Paygro reactor (Fig. 3). Obviously not all compost produced in
the Paygro system meets these conditions if it were to be operated without
turning and maintained at low (43 C) temperatures by high rates of aeration.
For example in trial VII in the "cool" section compost was turned once and
only 32$ of the compost was exposed to a mean process temperature >55 C for
three continuous days. In the "hot" section only 36/J met the criteria.
One solution to meeting the 55 C requirement for all sections of the
Paygro rector is to reverse airflow. During reverse airflow [negative
pressure aeration, (HPA)], heat accumulates in the bottom of the reactor.
This could solve the 55 C exposure problem. However during HPA with
composts of low percent dry solids, moisture migrates to the base of the
reactor resulting in water logging, drainage, poor aeration and problems
with freezing in the winter and the production of metabolites of
anaerobiosis. All these problems can be avoided by first applying positive
58
-------
pressure aeration (PFA) followed by UFA during the last week of a 3 vk
retention time period. These principles were tested at the end of trial
VII. After a 12.6 day retention time and one turn with PPA, the compost was
turned again and aerated by HPA for 5.6 days followed by an additional 3-5
days of PPA. The total retention time for trial VII therefore was 21.7
days. The mean temperature of the compost and the percentage of the compost
<55 C during SPA and PPA are presented in Fig. 15.
During the first 16 hr after the second turn when the compost was
incubated without forced aeration temperatures increased gradually (Fig. 16)
but were below 40 C. After 16 hr, when NPA was applied (5 min/30 min) a
sharp increase in temperature was observed (Fig. 15). After 24 hr (4 hr
HPA) temperatures across the entire reactor still were low (24.2-45.1 C with
a mean of 33.9 C) but the higher temperatures were located in the bottom
center part of the reactor (Fig. 17). No part of the reactor was above 55
C. Aeration was increased to 10 min/30 min after 28 hr (20.00 hr on day 2
in Fig. 15). At the end of that day the mean temperature (65.9 C).
stabilized. At this time (52 hr, Fig. 18) 69.8? of the compost was above 55
C. Compost in a large area in the base and center of the reactor was above
80 C. This incubation temperature rapidly kills all known forms of
microbial life in compost (3). Temperatures of the compost near the wall in
the lower 2 m section also were above 55 C. After this time period,
temperatures gradually declined. At 136 hr the weighted mean temperature of
the compost was 65 C and 69.8$ of the volume was >55 C. The temperature
distribution (Fig. 19) was different from that at 52 hr (Fig. 18).
Temperatures in the center were lower but higher near the top suggesting
that more heat was produced in the cooler top part of the reactor and less
in the hot center part.
59 .
-------
g
100
00
00
70
60
50
40
30
20
10
NEGATIVE AIR PUESSUHE
POSITIVE AIR
PRESSURE
I
a
TIME. DAYS
Fig. IS Mean temperature (C) and percent of compost above 55C during Trial VII . Circled number*
indicate time* for which temperature distribution* were plotted (Fig*. 16- 22).
-------
DISTANCE FROM OUTSIDE WALL (M)
0 .46
0 r—
.23
«"
2.
82 -
Q * ^^
O
2
o
e
w
u
fc 1.71
H
13
r^ ,
Q
2.24
1
} t * TTfTi > ! J t
1 J
> 4
» 22.0 •-
\ i
ft i
I * * * * .{: 4 t >: 1 1
f t
ft 4
.' *
• 22.7 *
»: 4
) !
r 1
>44t*4*4444
> ' 4
{ 4
> 24.3 1
f * » 1 i i 1 1 4 1 :
f 4r
2,80 fern *:**»**. 1
.92
1
99 9 *
,• \frt, ?, \ -\ t * * *
t
t
22.7 ';
* p.
4
* * 4 ' * * 1 4 ! 4 :f 4
t
*
t
22.2 *
t
ft
*
* 4 4 ' * 4 4 1 1 4 4 4
t
-4
24.9 4
* 4 - * 4 * 4 * * » 4 4:
4.
4 4: 4*4 4*444: 4
•| T '* 7 * 1
22.7
;; 4 4 # 4 4
24.0
4. * 4 4 4 4
26.6
4*4144
**%?*
1.68
|
7 7. t t T "f 3' !f t
t
:} 4: 4 4 + * * » 4
t
4
4
4
4
* * * * 4 4. 4.4 1
4
4
*
4
4'
4
t
4 4 4 4 4 4 4 * 4
t
*
t :
4 -t 1 4 4 4 4> *
t;
-T
•» 4 * 4 4. 4: 4' 4 *
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nig. 16. Temperature distribution at hour 8. Mean Temperature =26. 3 C. Percent of
compost above 55 C = 0. 0%.
-------
DISTANCE FROM OUTSIDE WALL (M)
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Pig. 17. Temperature distribution at hour 24. Mean temperatures 33. 9. Percent
compost above 55 C = 0. 0%.
-------
DISTANCE FROM OUTSIDE WALL, (M)
to •
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^BWMBMM
.23-
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Fig. 18. Temperature distribution at hour 52. Mean temperature = 65.9. Percent of
compost above 55 C = 69. 8%.
-------
DISTANCE FROM OUTSIDE WALL (M)
en
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U
ig. 19. Temperature distribution at hour 136. Mean temperature = 65 C. Percent
of compost above 55C = 69. 8 % .
-------
Airflow was reversed on day 5*6. The mean temperature increased
sharply and 100£ of the compost was >55 C for a brief period (Fig. 20). A
steady drop in temperatures occurred thereafter (Figs. 21, 22) and under PPA
the highest temperatures once again were near the top of the compost. Thus
during this entire reverse airflow procedure 100/5 of the compost in the
reactor had been exposed to 55 C for at least three continuous days. This
data shows therefore that the Paygro system can be operated at an efficient
temperature for destruction of volatile solids early in the process,
followed by a reverse in airflow for pathogen kill purposes.
Although analysis of the fate of fecal pathogens and parasites was not
an objective of this research initially, a few standardized tests for
survival of coliforms, Salmonella, and parasites were performed. The fate
of fecal viruses was not examined.
In a preliminary trial during June, 1981, some analyses were performed
by J. Robie Vestal, Professor, University of Cincinnati, CiJJcinnati, OH
45221. Raw municipal sludge was received from the Columbus, Ohio, Southerly
Q
Treatment Plant on May 26 and 27, 1981. The reactor feed contained 1 x 10
and 2 x 10 c.f.u. coliforma and Salmonella-Shigella/g dry wt.,
respectively. No appreciable numbers of coliforms or Salmonella were
present in the reactor product after 18 days composting. Details of
pathogen assays in this preliminary trial are presented in Appendix IV.
In a second trial in November-December, 1982 (Trial III) analyses were
performed by Belmonte Park Laboratories, Div. Elam Testing Co., 1415 Salem
Ave., Dayton, OH 45406. Raw primary sludge from the City of Akron was mixed
with bulking agents and sampled for pathogens before loading of the reactor.
Attempts were made to maintain high temperatures (60C) before the turn in
65
-------
DISTANCE FROM OUTSIDE
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l:ig. 20Temperature distribution at hour 148. Mean temperature = 76.5 C. Percent of
compost above 55 C= 100%.
-------
0
DISTANCE FROM OUTSIDE WALL, (M)
.46 .92 1.68
2.44
3.05
en
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7 •>
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l!ig. 21. Temperature distribution at hour 176. Mean temperature = 64.9. Percerittof
compost above 55 C = 80. 3 %.
-------
o-
00
0
DISTANCE FROM OUTSIDE WALL (M)
.46 .92 1.66
2.44
3.05
0 —
.23 —
DISTANCE FROM TOP
Is* r*
* •
* rw -o
7 f r
4,
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4
r
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t
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III 1 i
*********ii*»**»»»*************************»***|i*y*****»*»»V
46.6 * 60.3 * 74.9 * 75.7 * 68 9 *
t**********************************************************
* * * *
t * * *
46.6 J 60.0 1 74.9 74.3 * 65.3 *
t * * *
* * * *«
* * *y
* * *.£
42.1 * 58.7 J 70.1 66.2 60.0 Jg
44 4
* * 4
»***4*» 44*** ********* ********** ***************** **********
« * * 4
30.4 J 40.0 * 51.0 49.6 J 44.6 J
4*444*»»*4»4*4»*»*****4*************************»*********4
23.3 » 31.3 * 41.1 * 40V3 * 34,5 '
Fig. 22. Temperature cliatribution at hour 212. Mean temperature = 54.0 C, t» volume above
55 C = 53.7
-------
sections 1 and 2 and lower temperatures (45 C) sections 3 and 4. After the
turn temperature conditions were reversed with the low temperatures in
sections 1 and 2. A materials balance for Trial III is presented in Table
13. Comparison of percent losses in dry solids for all trials (Table 19)
shows that trial 3 had the lowest rate of decomposition of all trials even
though ambient temperatures were not lowest values for that winter season.
Comparison of mean temperature data for trial 3 (Fig. 23) shows that
temperatures rose slowly as compared in other trials (e.g. Fig. 9-13)• In
summary, trial 3 had the worst performance of any trial in this study.
Samples for pathogen testing were processed within 2 hr after they were
collected. The most probable number (MPN) of coliforms in the reactor feed
ranged from 1.5 to 46.0 x 10 /gm compost. The M.P.N. for Salmonella ranged
from 40-230/gm compost. Details of parasites detected and methods used are
presented in Appendix Va. After a 15 day compost retention time and one
/
turn,.compost was removed from the reactor. The top wet layer in each
section -(identified as 1-20, 2-19, 3-18 and 4-17 "recycle top" in Appendix
Vb) was removed first and sampled. The dryer bottom layer was used as
recycle for trial VI and sampled separately (identified as 1-20, etc.,
"recycle bottom" in Appendix Vb). The H.P.H. for coliforms in the reactor
product ranged from 0.9-15 x 10 /g compost. No Salmonella were detected.
Some parasites were detected in the reactor product..
The top wet layer was moved into a curing pile out of doors.
Temperatures (taken once per week) in the center of the curing pile ranged
from 60-70 C during the first three weeks and stabilized at 50-55 C. After
2 months of curing duplicate samples were removed from the center, and from
the outer 15 cm layer as well as from two sites 30 cm deep into the pile.
69
-------
Htan Ttmp. C
*/o of Rt«tor>55C
Stcttoh
234
TIME, DAYS
K>
M««n Ttmp.C
• o of Bt«ctor > 55 C
StcMona
234 50 I 2345676910
, TIME, DAYS
Fig. 23. Mean temperature and % of compost 55 C for two sections (2, 3)
of reactor vessel during trial III.
-------
Temperatures in the outer 15 cm layer ranged from 0-30 C whereas those in
the 30 cm deep layer ranged from 30-50 C. Coliforas isolated (Appendix Vc)
were identified as E»_ eoli, Enterobacter sp. and Klebaiella sp. Paeudomonas
isolates also vere found. Samples from the outer 15 cm layer are identified
in Appendix Vc as Storage #1 and #2; those from the 30 cm deep layer as #3
and #4 and those from the center as #5 and #6. The highest coliform counts
were detected in the 30 cm deep layer. Counts in the outer layer and center
were lowest. No Salmonella were detected. Some parasites were found in the
outer 30 cm layer. They were dessicated and probably non-viable. No
parasite ova were found in samples from the center of the curing pile.
After 4 months of curing additional duplicate samples were removed from
the three locations in the curing pile (Appendix Vd). Samples were mixed
and divided in half (v/v). One-half (1 liter) of each sample was analyzed
by Belmonte Park Laboratories. The other half was analyzed by A.
/
Ottolenghi, Professor, Department of Medical Microbiology, The Ohio State
University, Columbus, OH. No potential pathogens were detected in any of
the samples (Appendices Vd and e). No evidence for regrowth of Salmonella
was detected in any of these studies. These results show that pathogens did
not survive in those parts of the curing pile where temperatures <55 C
occurred over a several week period.
-------
BULKING AGENTS
In the original proposal considerable emphasis was placed on bulking
agent needs for composting of municipal sludge in the Paygro reactor. Much
of this work was completed in preliminary trials before complete monitoring
equipment was available. A summary of this work is presented here.
Initially coarse bark and fine potting bark were compared as bulking
agents.- The coarse bark (mostly red oak) was received from sawmills
equipped with Hosmer head debarkers. It contained particle sizes ranging
from dust to pieces 30 cm long. Potting bark represents the fines screened
(rectangular screen, 3/8-3/4 inch opening) out of Hosmer head-debarked bark.
During the first preliminary composting trial, in which these bulking agents
/ '
were compared (January 1981) it was discovered that sludge amended with fine
bark did not dry well. In fact the surface layer of compost in the reactor
froze, whereas the batch mixed with coarse bark did not freeze. It was
decided therefore, to use coarse unprocessed bark as a bulking agent in
futher work.
In preliminary trials it was observed that coarse bark mixed with
sludges low in dry solids (11-14$ DS) did not retain adequate moisture.
Therefore, sawdust (mostly from hardwoods) was added to the mixture, which
solved this drainage problem. A volumetric ratio of 3 sawdust to 4 bark was
eventually chosen as most effective. This mixture was prepared and weighed
in advance and added to recycled compost at a mean volumetric ratio of 1
bark-sawdust:4 recycled compost. Sludge was then added to yield a final %
-------
DS of 38-45^ in the reactor feed. Since adequate mixing equipment was
available for only one trial, the % DS of reactor feed usually ranged from
42-45. This explains the high total bulking agent ratio used in this
research as compared in the City of Akron study (Appendix III).
Sawdust added to the compost did not cause nitrogen deficiency on
plants produced even in container media amended with 60$ composted municipal
sludge (CHS). The batch of CMS prepared with bark and sawdust as bulking
agents had been cured for only 30 days suggesting that all the sawdust had
been decomposed adequately to prevent N deficiency (V. ?aber, Department of
Horticulture, The Ohio State University, Columbus, OH 43210). This high
level of decomposition may also account for the apparent lack of Salmonella
regrowth in the compost produced by this system.
Voodchips were used as bulking agents in one trial. The raw
sludge-woodchip mixture was prepared at the City of Columbus, OH Southerly
Treatment Plant composting facility. The woodchip mixture was loaded into
two sections and compared with a bark-sawdust-raw sludge mixture prepared
the same day. Severe ammonia losses occurred in the sections of the tank
where woodchips were used as bulking agent. This problem did not occur in
the l>ark-sawdust mixture. Probably the total surface area of bulking agent
available in the woodchip mixture was inadequate for this highly aerated
system. This resulted in carbon deficiency for the microbiota. Therefore
deamination occurred and ammonia losses resulted. Voodchips therefore, were
not evaluated further as a bulking agent. However a mixture of woodchips,
sawdust, ground corn cobs or another finely ground carbon source should be
evaluated to verify the possible explanation for the observed phenomenon and
to develop other bulking agent combinations for this system.
73
-------
DISCUSSION
The rate of composting In the Paygro system, even under winter
conditions, is very high as compared in other published systems. For
example, approximately 30$ and 10$ of the vet and dry weights, respectively,
typically are lost during 42 days of composting (21 days of aeration, 21
days of curing) in the static pile system (13)* In the Paygro system in
this winter study 25.7 and 9*3$ of the wet and dry weights, respectively,
were lost but in a mean composting period of only 16.0 days (Table 19).
Much higher rates of wet and dry wt losses (40.8 and 15*1$ respectively)
were found in a 1981 summer trial and in 10 trials performed during 1982 in
the Paygro reactor during a City of Akron composting contract (Appendix
III).
s
The metabolism of the microflora in the Paygro reactor seems to be
largely aerobic or microaerophilic in nature. Strong odors were not
encountered in any of the trials. Although a acentometer was present at the
site, it could not be used satisfactorily since minor odors could not be
separated from those produced by the feedlot manure system.
The rate of respiration (C02 evolution) in the Paygro system was
highest over a temperature range of 38-55 C. This specific activity of the
compost biota within this temperature range corresponds with that found by
J. R. Vestal, University of Cincinnati, for the microflora in this reactor
and also with that of continuous composting of mixed refuse in a pilot scale
reactor (8, 9, 10).
74
-------
In the Paygro system the temperature of the compost is regulated by
controlling aeration. Experimental results clearly demonstrated more rapid
drying (indicated by change in percent D.S.) and stabilization (change in
percent volatile solids) when low temperature (40.95) were maintained with
high rates of airflow. In one trial (trial VII) low temperature composting
resulted in a 14? loss of the initial weight dry solids in 15 days, whereas
high temperature composting produced only a 10£ loss. Losses of water and
solids given in Table 19 represent averages of a range of composting
conditions and are not representative of what could be achieved by
temperature control.
Observations made on effects of temperature on rates of composting
support those described for various pilot scale systems (8, 9, 10, 15) and
the work of MacGregor et al. (11). In the field-scale static pile system of
MacGregor et al. (11) airflow was described in terms of "blower demand."
This represented the percent of time that blowers (fans) were on. We found
trends in "blower demand" and process temperature similar to those published
in MacGregor et al. (11) with the highest "demands" at low temperatures.
However over the course of a trial, as compost dried and settled marked
changes in actual rates of airflow occurred. "Blower demand" therefore does
not represent actual quantities of air entering a system. Furthermore,
percent CO. values in air in a compost pile also do not reflect accurate
quantities of CO. being exhausted out of a pile. The C02 data provided by
MacGregor et al. indicate whether the compost microbiota is being supplied
with adequate levels of aeration however as MacGregor et al indicated it is
not indicative of metabolic activity.
7S
-------
In this study quantitative measurements of airflow were made and thus
quantitative measurements on CO. evolution were available. In addition the
veight of compost in each section was determined during loading at turning
and during unloading. In fact measured losses of C0_ and calculations based
on stoichiometric formulae agreed closely (Table 22). Therefore,
quantitative comparisons with other published systems indeed are possible.
Haug recently reviewed oxygen consumption rates for various composting
mixtures and reaction types as a function of temperature (6). Calculated 0.
consumption values for the Paygro reactor (Table 23) were comparable to
rates for bench-scale compostars containing a variety of materials (6 mg)
(Fig. 14). Bates of CO. evolution and of 0. consumption have not been
published for large scale or field-scale composting systems. Many studies
on pilot scale systems do not lend themselves to quantitative interpretation
since CO- balances frequently are not presented. However our data can be
compared with data generated for the aerated static pile (7, 14)* Their
maximum rates (approximately 0.18 mg CO^/gm VS-hr) are much lower than those
in the Paygro system (5.9 mg CO-Xgrn VS-hr, Table 23).
A critical aspect of composting ia the fate of fecal pathogens. In the
aerated static pile an insulating layer is placed over the entire pile so
that all parts of the compost are exposed to temperatures >55 C for three
continuous days (12). Bates of aeration in that systems are low, resulting
in low rates of composting. On the other hand in the Paygro. system high
rates of decomposition and negligible odor problems are obtained by the high
aeration rates. Therefore, under these conditions significant volumes of
compost at any one time do not meet the criteria for "further reduction of
pathogens." Compost in the Paygro System however, can be turned, so that
76
-------
all compost eventually meets the criteria• Furthermore data presented in
this work clearly show that reversing the direction of airflow effectively
exposes all compost in the reactor to the >55 C conditions. Thus high
temperature was applied successfully after low temperature treatment showing
that maximum rates of stabilization indeed could be paired with adequate
levels of pathogen destruction and yet maintain aerobic conditions to avoid
odors.
All of the reactor feed used in this study was mixed by FEL, with the
exception of parts of trial V. High rates of drying were observed during
mid-winter (January) in the pugmill-mixed compost. The importance of
preparing a "homogeneous mix has been stressed in the literature (7, 17).
In all except this trial compost,was not mixed adequately until after the
first turn, when the extractoveyor removed the compost from the reactors.
Estimates on drying obtained in this study (Table 19) therefore are
/
conservative as compared with-results which could be obtained in.a Faygro
system specifically designed for sludge. In the manure system at Faygro,
excrement is mixed with bedding by the "walking" of the cattle on the
mixture in the pens. A specific mixing system other than FEL therefore is
not necessary at the facility where this research was performed.
77
-------
REFERENCES
1. Epstein, E., G. 5. Willson, V. D. Surge, D. C. Mullen, and N. K.
Eakiri. 1976. A forced aeration system for composting waste water
sludge. J. Water Pollut. Control Fed. 48:688-694.
2. Finatein, M. S. 1978. Composting process temperature: Conflict
between the fastest possible disinfection and organic matter
stabilization. Workshop on the Health Effects and Legal
Implications of Sewage Sludge Composting. Cambridge, Haas.,
December 18, 19, and 20, 1978. p. 1-12.
3. Finatein, H. S., and H. L. Morris. 1975* Microbiology of municipal
solid waste composting. Adv. Appl. Microbiol. 19:113-151-
• / "
4* Finstein, M. S., and M. L. Morris. 1979* Anaerobitic digestion and
composting: Microbiological alternatives for sewage sludge
treatment. ASM Hews (Amer. Soc. Microbiol) 45:44-48.
5. Frankoa, H. H., L. J., Sikora, and F. Gouin. 1983. Using woodchips of
specific species in composting of sewage sludge. Biocycle 23:38-40.
6. Haug, R. T. 1980. Compost Engineering: Principles and Practice. Ann
Arbor Science. Publishers Inc., The Butterworth Group, P. o. Box
1425, Ann Arbor, MI 48106.
7. Higgins, A. J., V. Kasper, Jr., D. A. Derr, M. E. Singley, and A.
Singh. 1981. Mixing systems for sludge composting. Biocycle
Sept.-Oct. 18-22.
78
-------
8. Jeris, J. S.| and R. V..Regan. 1973' Controlling environmental
parameters for optimum composting. I. Experimental procedures and
temperature. Compost Sci. 14:10-15*
9* Jeris, J. S., and R. V. Regan. 1973* Controlling environmental
parameters for optimum composting. II. Moisture, free air space
and recycle. Compost Sci. 14:8-15.
10. Jeris, J. S., and R. V. Regan. 1973* Controlling environmental
parameters for optimum composting. III. Effect of pH, nutrient
storage and paper content. Compost Sci. 14:16-22.
11. MacGregor, S. T., C. F. Miller, K. M. Psarianos and M. S. Finstein.
1981. Composting process control based on interaction between
microbial heat output and temperature. Appl. Env. Microbiol.
4:1321-330. ..,-
12. Parr, J. P., E. Epstein, and G. B. Willson. 1978. Composting sewage
sludge for land application. Agric. Environm. 4:123-127.
13.- Sikora, L. J., 6. B. Willson, D. Collacicco, and J. F. Parr. 1981.
Materials balance in static pile composting. J. Vater Poll. Cont.
Fed. 53:1702-1707.
14. Sikora, L. J., M. A. Ramirez, and T. A. Troeschel. 1983* Laboratory
composter for simulation studies. J. Environ. Qual. 12:
15. Suler, D. J., and M. S. Finstein. 1977. Effect of temperature,
aeration, and moisture on CO formation in bench-scale, continuously
thermophilic composting of solid waste. Appl. Environm. Microbiol.
33:345-350. 79
-------
16. Walker, J. X., N. S. Pinstein, and J. S. Hall. 1979* A oritieal
review of the performance of sewage sludge composting operations.
Presented at the National Conference on Municipal and Industrial
Sludge Composting, Sponsor—Information Transfer, Inc., Hew
Carrollton, ND. Nov. 1979.
80
-------
Appendix I. Calculations for the determination of airflow, mass (Kg)
of dry air entering the reactor and mass (Kg) of carbon
dioxide produced during each four hour interval.
The airflow through the ducts is a function of the size of the opening
of the duct and air velocity and can be determined by the formula:
(1) Q (cubic ft./min.=FCM) = V*A
where V=air velocity
A=cross sectional area of duct
The velocity of the air was determined from the differential pressure
measured by the averaging pitot tubes inserted in each fan duct using
the formula:
(2) V (feet/sec)= / 225.43* h * T
where h=differential pressure, inches of water
T=air temperature, K(=273.16 + C)
P=atmospheric air pressure, 30 inches Hg
Combining equations 1 and 2 and 'knowing the diameter of the duct (16"),
Q in cubic feet/min was determined from the formula:
(3)
Q= 83.7 / 225.43 T\
Since airflow is a function of atmospheric conditions, Q at standard
temperature and pressure conditions was determined using the following
relationship:
(4) Q (std) = Q f P \ X / 294.27\
81
-------
Equations 3 and 4 were combined to yield the following formula for
determination of the airflow:
(5) Q (std) - 12,359.3
Conversion to metric units (cubic meters/min) was achieved by multiplying
by the constant .0283.
Using the Q(std) it was then possible to determine the mass of air (Kg)
that passed through the reactor. The Kg of dry air was determined using
relationships for ideal gases. The derivation of the following formula
is given by T. Haug on pp. 385-388 in Compost Engineering, Ann Arbor
Science, Inc., Ann Arbor, MI.
(6) Dry Air (Kg/min)
1.0.X105 /*760-PV\ Q
\ 760 ;
287.0 *T
where Q»cubic meters/min
T*air temperature in degrees K /
PV»actual water vapor pressure (calculated using relative
humidity and temperature readings)
The amount of time that the fans were on during each 4 hr interval was
recorded (FON) and was used in the following formula to determine the Kg
of dry air that entered the reactor during a 4 hr time period:
{7) Dry Air (Kg/4 hr) » Dry Air (Kg/min) f T* FON* .06\
\,ZS7~J
Given that the air leaving the reactor was equal to that entering the
reactor, the mass of carbon dioxide produced during each 4 hr interval
was determined using the relationship:
(8) C02 (Kg/4 hr) » (* C02-.OS) (Kg dry air/4 hr)/100
82
-------
Appendix II . Interpolation of temperature data
the following problem is the subject of this meno. Temperature readings .
are available at H locations over a rectangular area. The i«Ch, location has
coordinates (x^ , y^> and its temperature is T. . He wish to assign a temp*
erature value to any arbitrary point (x*,y*l in the plane. This will allow
one to compute such items 'as (a) spatially averaged temperature. Obi isotherm
contours, or (c) percent of the area within a given temperature range.
Problems of this type are similar to those of mapping areal rainfall in
hydrology. Reviews of techniques applicable to these problems ha^e been
written by Ball and Barclay (19751 and Creutin and Obled (1.9321, The simplest
class of techniques to use is known as surface fitting. It assumes that temp-
erature can be expressed as some known function of x and y,
T - f te,y)
The function f will contain certain parameters or coefficients whose values
are derived from the known measurements according to a particular leasti-squares
fitting or interpolating criterion. Two such .techniques, each with different
surface functions and parameter estimation criteria, will now be discussed.
Quadratic Interpolation (Oiidley and Keys, 1970)
tee T be described by the following function
* • «j» * «2* * a-jxy •»• a4y2 * a5y + afi
where a, to ag are coefficients. Their values are determined as follows.
From the H observed values of T we have the following set of equations
83
-------
-2-
\ «x Vx *i *i *
*2 *2 *2*2 *2 '2 X
*« «J VM yJ *« \
•x"
•a
••.
™
*x~
T2
.V
me ia
Since • will usually bo gr»«t«r than 6 this *y*tM of equations la
in«d. ^ can b« a*ciawtad by a laaar
eritarioo. i.«. , by
» •
,t
can ba
tto qoaaclty W » - T) . Thi« laada to UM solutioa
fita spatially ar«x«9«d t*sv«ratux«, T ,
«*•
3H/3 * «3>»2H/4 * a4«3/3
«bax« N <• width of area ia tha x direction and B • height of the area
la the y direction.
Spline InterpTla^lqp (Creutia and °Med. 1982)
Oa» pxoblea aaaoeiated with quadratic interpolation im the tesdaaey for
the reapennire function to oscillate wildly between the •oaMreBaas pointat
To overcome this pseblea it has been caagened that a spline fnactica be used
a* an interpolaat. subject to certain eaoothness criteria. One suci sxiterion
<« to sdniatize the foUwoiao; functiooal
where 7f (a.y) » •1TOt.y)/ax2 + 23*TU.yl/3x3y * 9xT(x,y)/3Yx.
This ia a first approxioation of the average curvature or ftendiac esarey of
84
-------
-J-
• thin elastic sheet «pr««d over the »-y region R with height T, «t the
point* <*!>*£>•
The unique function th»t satisfi«» such a criterion is given by
H
f (x.y) - »0 •*• 4jX + *jy * E CjKte^.y^y)
liter* KCa^.x.y^y) - (tej-x)* + (y^)1 }log{ (jet-«) * * Qfj.Ti* }-
Th« co«erici«nts •„, ^, »2, c^, i- 1 to H, «r» dataraiMd by solving tbs -
following Mt of H*3
H " .
^"fri-wv" Ti l •l:
N
EC. - 0
3-1 3
H
£ c « - 0
J-l 3 3
E c.y ' - 0
j-l 3 3
This method gives most satisfactory results when the statistical errors
in the observed T values are small. An extension of the method that includes
a smoothing criterion seeks to mintmi re
H
1 (Vf<*,y)>* dR + p E { T. - fbe,.yt) }*
R i-1
where p is an appropriately chosen weighting parameter.
the computational effort in using the spline technique is greater than
for quadratic interpolation. 1*«*« also applies to the effort required to
evaluate the temperature function fbc.y). This makes additional computations.
such as finding spatial averages or contour plotting, more difficult.
References
Chidley and Keys, 'A rapid method of computing area rainfall*. J..Hydrol.»
12.15 (1970).
85
-------
Croatia. J.O. aad Oblad. C., "Objocti** analyaia and sappta* tachniqoM for
rainfall fialdat An objective coapariaoB*. «at«r liaaoureaa Haaoagch. lSt413.
UN2).
tall, A.J. Md MrelKf. ».*..Itothod* of dMMBiaia* mxMl z»latall «ro»
«t«". ia tw«ictiaa to Otcl^«it Brdrelogy, •dlti*d tor T.C.
••d r.X. OoBia. ftutraliw tautmy of Set«te« a»731.
86
-------
Appendix III
Paygro System
Process Performance Summary
Summarized from Akron Composting Demonstration Project, City of
Akron, March, 1983. Burgess and Niple, Limited, 46 South Summit Street,
Akron, OH
Shown in Table 1 are the average characteristics of the components used
during the composting trials along with the volumetric mix ratios utilized.
Also shown are the dry solids, volatile solids and bulk weights of the
average reactor feed and reactor product during the evaluation.
Trials 1 thru 3 were designated as a "start-up" phase since a high
ratio of bark and sawdust was required to produce sufficient recycle for
subsequent trials. During this start-up phase the volumetric mix ratios
averaged 1.0 sludge to 1.06 bark and sawdust to 1.46 recycled compost.
Steady state conditions were achieved during Trials 4 thru' 8. At
steady state the volumetric mix ratios averaged 1.0 sludge to 0.39 bark
and sawdust to 1.21 recycle.
Trials 9 and 10 were designated "re-start" because a large amount of
finished product was shipped following Trial 8 to meet the requirements of
a marketing evaluation. This shipment of finished product left insufficient
compost available for use as a bulking agent during Trial 9. Compost
generated during Trials 9 and 10 was utilized as the recycle component for
subsequent studies conducted by OARDC. The volumetric mix ratios for the
re-start phase averaged 1.0 sludge to 0.82 bark and sawdust to 1.07 recycle.
Detailed materials balances for two representative trials are
presented in Tables 2 and 3. Trial 4 represents cold weather operation
at an average ambient temperature of approximately S°C while Trial 7 was
conducted at warmer temperatures averaging about 20°C.
Table 4 summarized Paygro System performance for all 10 trials. For
steady state conditions, represented by Trials 4 thru 8, the reactor feed
averaged 41.9% OS and the system yielded a reactor product which averaged
61.4% DS. At a mean retention time of 16.7 days the Paygro System resulted
in a total weight loss of 47.2%, a dry solids weight loss of 22.8%, a volatile
solids weight loss of 28.1% and a moisture reduction of 64.8% (excluding
water generated through biological activity).
87
-------
TABLE 1
CDMP01
iERT CH/
UACTEKISTIC:
i AND MIX RATIOS
VOUMETKIC MIX RATIOS
OOMPmmn
Sludg*
Bark 6 Swdtuc
••cycle
Kaactor F«ad
&Metor Produce
1^
26.7
66.2
60.2
41.9
61.4
LSI
64.7
90.0
63.9
68.4
63.6
LBS/cn.rt.
56.7
21.7
33.6
40.8
33.6
TPIfllr*
1-3 4-8
STAXT-U? STUDY STATE
1.0 1.0
1.06 0.39
1.46 1.21
9-10
USTATT
1.0
0.82
1.07
88
-------
TABLE 2
TRIAL |4 MATERIALS BALANCE. AKRON. OHIO SLUDGE AT 221 DS
COMPOST. RETENTION TIME IS.
PEED COMPONENT
SLUDGE
RECYCLE
BARK
PEED MIXTURE
FINISHED COMPOST
Oo
10 LOSS DURING TRIAL
X LOSS
WEIGHT
(TONS)
169.6
169.6
37.0
376.2
207.4
16B.8
44.9
VOLUME
(CU.FT.)
5.653
9.975
3.365
18,993
12.200
6,793
35.8
BULK
WEIGHT X DRY
(LB/CU.FT.) SOLIDS
60.0 22.0
34.0 53.4
22.0 62.0
39.6 40. 5
34.0 56. 7
25 DAYS, APRIL 1982
Z VOLATILE
SOLIDS
70.0
69.8
90.0
72.9
66.3
WEIGHT
DS
(TONS)
39.0
90.6
23.0
152.6
117.7
34.9
22.8
WEIGHT
VS
(TONS)
27.3
63.2
20.7
111.2
78.0
33.2
29.8
WEIGHT
WATER
(TONS)
130.6
79.0
14.0
223.6
89.7
133.9
59.9
-------
TABLE 3
FEED COMPONENT
SLUDGE
KECTCLE
IAKK
FEED MIXTURE
FINISHED COMPOST
LOSS PUKING TRIAL
< LOSS
TRIAL
WEIGHT
(TONS)
220.2
73.4
23.7
317.3
170.1
147.2
46.4
17 MATERIALS BALANCE. AKRON.
COMPOST
VOLUME
(CU.FT.)
f
8.007
4.590
2.155
14.752
9.720
5,032
Jill
RETENTION
MILK
WEIGHT
(LI/CU.FT.
55.0
32.0
22.0
43.0
33.0
OHIO SLUDGE
AT 31. 91
DS
TIME 17 DAYS. JUNE 1982
Z DRY
) SOLIDS
31.9
67.7
64.0
.42.6
56.6
Z VOLATILE
SOLIDS
62.4
66.1
90.0
66.8
62.0
WEIGHT
OS
(TOMS)
70.2
49.7
15.2
135.1
96.3
38.8
28.7
WEIGHT
VS
(TONS)
43.8
32.9
13.6
90.3
59.7
30.6
33.9
WEIGHT
WATER
(TONS)
150.0
23.7
8.5
182.2
73.8
108.4
59.5
-------
TABLE
<£>
PAYGRO SYSTEM
DRY SOLIDS (X) OPi
REACTOR FEED
i REACTOR PRODUCT
i
X LOSS IN:
WET WEIGHT
WEIGHT DS
WEIGHT VS
WEIGHT H20
DAYS RETENTION
MEAN TEMPERATURE
OF AMBIENT AIR (*C)
HIGH
LOW
1-3
36.8
48.1
34.9
15.0
22.2
46.6
32.8
1.1
-4.4
AKRON.
4
40.5
56.7
44.9
22.8
29.8.
59.9
15.3
9.7
2.5
PERFORMANCE SUMMARY.
10 TRIALS
OHIO RAW PRIMARY SLUDGE
5
42.2
58.8
49.8
30.0
35.1
64.3
17.5
20.4
10.2
TRIAL
6
42.0
67.7
48.1
16.3
22.3
71.0
21.8
23.3
16.3
7
42.6
56.6
46.4
28.7
33.9
59.5
17.0
23.9
IS. 6
8
42.3
66.6
46.7
16.0
19.3
69.1
11.8
28.5
20.1
9-10
45.0
67.2
40.8
11.5
. 17.6
64.7
19.8
25.9
17.1
MEAN
4-8
41.9
61.4
47.2
22.8
28.1
64.8
16.7
21.2
12.9
-------
The results of the tea Akron sludge Rial*, from • process design standpoint!
Indicated that:
I. A 14 day retention parted la sufficient except during severely
cold weather.
2. felunetrlc mix ratio* of fresh bulking agent, i.e. bark aad sawdust,
of as low aa 0.26 are adequate aa long as sufficient recycled eovpost
la utilised to produce a reactor feed solids concentration of 40X.
3. Moisture reductions of 60 to 70Z (excluding water generated by
biological activity) can be expected for steady state operating
conditions.
4. the taygro Syataa can generate a product with dry solids concentration
in excess of 62Z in a 14 day retention period.
92
-------
Appendix IV.
UrtvettttyolOncinnatl CoUegeof Arts and Science*
Cincinnati, Ohio 49221
September 22. 1981
Or. Harry Hoitink
Department of Plant Pathology
OAHDC
Hooster, Ohio 44691
Dear Harry:
W« checked the 'cured* 'compost tram the last run of Columbus sludge for
collforms and Salaonella-Shigella. The procedine and results are as
follows:
Sg wet weight - (3.55g dry wt.) into 100ml of sterile
buffer, blended for 30 sec, allowed to settle for 10 min,
plated 0.5 and O.lml onto EMB and SS agar in triplicate. y *
While there were a lot of bacteria, there were no pathogens detected.
If there ware appreciable numbers of pathogens, I an sure they would have
been detected. This means that there were less than 281 pathogens per
gram dry weight of eosport.
I hope that these data will be useful to you.
See you soon.
Sincerely ,> • .
J. Robie Vestal 7 Ph.D.
Associate Professor of
Biological Sciences
JRV:mk
cc: Dr. Atal Eralp
93
-------
Appendix Va
(Be/mooi* [Paf* •Laoo/ato/Mt
DIVISION Of ILMtt TtSTINO COMPANY
Or. Marry Holt Ink, Ph. 0.
Professor of Plant Pathologeforms
O.A.R.O.C.
Uooster, Ohio
REPORT TOt
REPORT ON!
PROJECT NOt
Or. Harry HoltInk, Ph. 0.
Sludge analysis collected at tha Paygro Plant, South Charleston,
Ohio.
HHB2001
Date receivedt
Oata reported!
H>12-82
RESULTS t
1.
2.
3.
SAMPLE 1.0.
» 1
* 2
93
<».
#«»
SALHONELLA
MPNt 9,300.000/gm
MPNt t.500,000/ gm
MPNt d6,000,000/ gm
Kttt «»,300,000/ gm
« it
1 ifnlf,
MPNt
MPNt 230/ gm
MPNt 90/gm
MPNt ISO/ gm
, OlahvUobothrlum
ASCARIS
No ova found
/ No ova found
No Ascarls ova
found.
e1et
No ova found
Tha results for Selannella and eolifonn are reported t.
J. A% Elan, 8.L.O.
President » Director
R. Oaneman
Chief Mlcroblologlst
94
-------
Appendix Vb
{Par* jLaooratones
DIVISION Of IIAM TCSTINO COMPANY
Or. Harry Hoilink, •
Professor of Plant Pathologeforms
O.A.R.O.C.
Uooster. Ohio
REPORT T0<
REPORT OH:
PROJECT NOt
RESULTS »
SAMPLE 1.0.
- ^— — -^
Or. Harry Koltlnk, Ph. 0.
Sludge analysis collected at
Charleston, Ohio
HH82002
PACE 1 of 2 PAGES
1. Section f-20
recycle top
2. Section #1-20
recycle bottom
3. Section # 2-19
recycle top
It. Section » 2-19
recycle bottom
5. Section # 3-18
recycle top
MPN« 9.300/ gm
the Paygro Plant, South
'- .; Date received! 12-6-82
6*t< reported: 12-15-82
COUFORM
MPNt U.300/ gm
MPNi 900/ gm
\
MPHi 1.500/ gm
"MPNI is.ooo/ gm :.''.'
'Negative
\\
* \\
i. * \\
ASCARIS
No ova found
; Negative *• .. . , \ Ite ova found
* . * *. •"•>»*
Negative
. Negative
Negative
One ovum of:
Taenla species
T-o (2)
. rhabditiform larvi
Stromavloidet
stercoralis
OneTH
cyst Entamoeba co
One (1) •
ovum Ascaris
lumbricoides
OneU)
ovum Taenla $peci«
Three (3)
rhabditiform larvt
Stronpyloides
stercoral»s
•c taua o» Ktnei • <
ni-acu. nmoucim
lucnorunu •oeinr. one ntuc KOI.TII Auocunon. MCICTT or UMuncnnuNC ciMCUTionariia>ii>i.T«r.MUtic<.>iAMacuTiaiter«c«<»iou>cuTiioiiioMUNCm-uiuuc
-------
Appendix Vb cent. '
\Bflmontt (Park ^Laboratories
DIVISION o» CLAM TUTINC COM»*MV
7.
8.
Section » J-18
recycle bottoB
Section # <»-17
recycle top
Section * aaples. rosltlve
results are confirmed by further testing and the numbers of positives at different decimal
dilutions leed to the production of the MW result by statistical methods.
RCFCRENCEi "STANDARD METHODS FOR THE EXAMINATION OF WATER AND UASTEWATER, 15th. edition"
Respectfully submitted.
JA A. Elim, B.L.O. '
President * Director
Chief Micrebiologist
-------
Appendix Vc
\Belmonte (Park J~aboratori.es
DIVISION Of ELAM TESTING COMPANY
Dr. Harry Boitiok
Profaaaor of Plant Pathologeforaa
O.a.a.D.C.
Uooater, OB 44641
Page 1 of 2 pages
REPORT TO: Or. Harry Hoitink
REPORT OH: Sludge analysis collected at the Paygro Plant, S. Charleston, '
PROJECT HO: HH83001 Data Received: 2-22-83 Data Reported: 3-1-6
DEPTH IN
RESULTS
SAMPLE I.D.
1. Trial III,
Storage #1
2. Trial III,
Storage *2
3. Trial III,
Storage 13 30
4. Trial III,
Storage »4 30
5. Trial III,
Storage #5 Center
6. Trial III,
Storage #6 Center
SALMONELLA
MPH: 460/ gn Negative
MPH: 2407 gm Negative
MPH: 1,1007 go Negative
MPH: 1,1007 gffl Negative
MPH: 237 ga negative
MPH: 937 gn negative
ASCARI5
No ova seen
Two (2) ova
Enterobius
vermicularis
Four (4) ova
Ascaris lumbricoidi
One (1)
Enterobiua
vermicularis
No ova seen
Ho ova seen
Ho ova'seen
The results for coliforo are reported in terms of "Most probable number"
(HPH) and result from multiple-portion decimal dilutions of the sludge
samples. Positive results are confirmed by further^ testing and the number:
of positives at different decimal dilutions lead to'the production of tne
MPH result by statistical methods. On re-isolation, coliforms were
found to include E. Coll. Enterobacter species, and Klebsiella species.
Pseudomonas were also found.
•Parasite ova seen were in desaicated form and probably non-viable.
97
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Appendix Vc com.
Coe/monto [Park jLaoeratOftts DIVISION OP ILAM TISTINC COMPANY
2
Dr. larry Hoitlnk
3-1-13
iirixuci: "STAJIDA»D MSTHOOS roi THE EXAMXVATXOH or VATII AMD
HA3TXVATIX, 15th •dttiea".
l«ip«ctfullr *ub»itt«4,
Freaitfeat ft Director Chief Microbiolociat
98
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Appendix Vd
oratoriu
DIVISION 0' SLAM TESTING
Dr. Barry Holtink
Professor of Plant PaCholog*fora*
O.A.R.D.C.
Booster Ohio 44641
REPORT 70: Dr. Harry Roitlnk
REPORT OH: Compote gaoplas for pathogens
PROJECT HO: HH 83002 Data Received: 4-13-83 Dace Reported: 4-21-H3
RESULTS
SAMPLE I
1.
2.
3.
4.
5.
6.
Trial
Trial
Trial
Trial
Trial
Trial
in
III
III
III
III
III
.0.
11
#2
n
H
n
16
COLITORM
MPN:
MPN:
MPN:
MPN:
MPN
MPN:
1
>2
>2
>2
460 /
43 /
.1007
,400/
,4007
,4007
gm
g»
ga
gm.
SB
gm
SALMONTJ.I.*
Negative
Negative
Negative
Negative
Negative
Negative
ASCARIS
/
No
No
No
No
No
ova
ova
ova
ova
ova
ova
seen
seen
seen
seen
seen
seen
The results for Salmonella and coliform are reported in terns of "Most probable
number" (MPN) and results froa multiple-portion decimal dilution of the compost
samples. Positive results are confirmed by further testing and the numbers of
positives at different decimal dilutions lead to the production of the MPN result
by statistical methods.
REFERENCE: "STANDARD METHODS FOR THE EXAMINATION OF WATER AND- WASTEWATER,15th.edition"
Respectfully submitted,
' \ HAAI^A Cx. c Qflj
Jaiae*. A. Elam, B.L.D.
President & Director
R. Daneman
Chief Mierobiologist
.99
-------
Appendix V«
Tto OMt SW* UMMfvAy
Oh» 43210
RESULTS OF THE EXAMINATION OF SLUDGE COnWST FROM
TRIM. Ill
Samples numbered 1-6
Received 4/13/83
ExMlnation started 4/14/83
MOISTURE CONTENTS
Sample i 1 2 3 45 6
I moisture 40* 401 601 C4X 64$. • 541
EXAMINATION FOR SALMONEUA
No SalaontlUt found In any sptcfMfl. 8 gn». Mt wtlght of tich
MS susp«ndt4 In 32 «I of sttrili Mttr. Final conctntritlon 201.
Htthod sensitivity: (Rteovtry of sctdtd Stlnontllat) ea. 35 CFU/wl of
suspension.
EXAMINATION FOR PARASITES.
A saapli of approximately 20 gram (dry might equivalent) of the compost
was examined. Following treatment with hypochlotlte, detergent and
washing the eggs were floated on zinc sulfate (sp. 9-1.2).
No Ascarts nor other huaan paraslts eggs were seen, treat numbers
of mite eggs were recovered.
EXAMINATION FOR COLIFORMS.
An attempt was made to count coll form by the filter meobrane method
(Standard Methods (14th Ed.)). Because of the relative high number of
non-col 1 form present the results are not considered to be reliable. No
conforms were seen at a dilution of 4 x 10"* In sanples 3 and 4, the
first dilution giving a readable membrane. No coll form were seen In
samples 1.2.S and 6 at a dilution of 4 x 1Q-*.
100
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TECHNICAL REPORT DATA
(Pleat read Insmicrions OH the revene before completing)
RBPORT NO.
2.
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
FACTORS AFFECTING COMPOSTING OF MUNICIPAL SLUDGE IN A
BIOREACTOR
8. REPORT DATE
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
H. A. J. Hoitlnk and G. A. Kuter
8. PERFORMING ORGANIZATION REPORT NO.
. PERFORMING ORGANIZATION NAME AND ADDRESS
The Ohio State University
Ohio Agricultural Research and Development Center
Wooster, Ohio 44691
10. PROGRAM ELEMENT NO.
CAZB1B
11. CONTRACT/GRANTNO.
CR-807791-01-0
12. SPONSORING AGENCY NAME AND ADDRESS
Water Engineering Research Laboratory, Cin., OH
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, OH 45268
13. TYPE OF REPORT AND PERIOD COVERED
Final Project Report
14. SPONSORING AGENCY CODE
EPA/600/14
IS. SUPPLEMENTARY NOTES
Project Officer: Atal E. Eralp (513) 684-2621
10. ABSTRACT
This research was Initiated to determine the feasibility of composting munici-
pal sludge 1n an aerated tank bloreactor system and to develop baseline data for the
rational operation and design of enclosed reactor composting systems. A variety of
conditions was teste^J and various mixtures of recycled compost, tfark, and sawdust
were used as bulking agents. The mean temperature of the compost was regulated
through programmed rates of airflow.- • •
Material balances were determined from accurate measurements of the weights
of solids and water In the reactor feed and reactor product. In addition, tempera-
ture, aeration and carbon dioxide evolution were monitored continuously.
Losses of water and solIds experienced In this system were significantly
greater than those published for the static aerated pile system. Measurements of *
carbon dioxide evolution appeared to accurately reflect the destruction of volatile
sol Ids and Indicated that activity was at an optimum when the mean temperature of
the compost was maintained at 38-55°C under high rates of aeration.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
18. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (This Report I
UNCLASSIFIED
21. NO. OP PAGES
20. SECURITY CLASS fTI>i3 page/
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (R«». 4-77) PREVIOUS EDITION is OBSOLETE
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