PB-222
PHOTOSYNTHETIC RECLAMATION OF AGRICULTURAL SOLID
AND LIQUID WASTES
CALIFORNIA UNIVERSITY
PREPARED FOR
ENVIRONMENTAL PROTECTION AGENCY
AUGUST 1973
Distributed By:
National Technical Information Service
U. S. DEPARTMENT OF COMMERCE
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EPA-R3-73-031
Ecological Research Series
August 1973
PHOTOSYNTHETIC RECLAMATION
OF AGRICULTURAL
SOLID AND LIQUID WASTES
by
Clarence G. Golueke, William J. Oswald, Gordon L. Dugan,
Charles E. Rixford, and Stanley Scher
Sanitary Engineering Research Laboratory
College of Engineering and School of Public Health
University of California
Berkeley, California
Grant No. EP-U0272
Program Element 1D2314
Project Officer
C. J. Rogers
Solid Waste Research Laboratory
National Environmental Research Center
Cincinnati, Ohio 45268
Prepared for
Office of Research & Development
U.S. Environmental Protection Agency
Washington, D.C. 20460
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! BIBLIOGRAPHIC DATA '• Report No. 2-
1 >HEET EPA-R3-73-031
Title and Subtitle
Photosynthetic Reclamation of Agricultural Solid
and Liquid Wastes
Author(s) c. G. Golueke, W. J. Oswald, G. L. Dugan,
C. E. Rixford, and S. Scher
Performing Organization Name and Address
Sanitary Engineering Research Laboratory
College of Engineering & School of Public Health
University of California
Berkeley, California
Sponsoring Organization Name and Address
U . S .. Environmental Protection Agency
National Environmental Research Center
Office of Research &
Cincinnati, Ohio 45268
3. Recipient's Accession Nn.
PB-222 454
$• Report Date '
1973-issuing date
6.
8' Performing Organization Kept.
No.
10. Program Element
1D231A
11. Contract/Grant No.
EP-00272
13. Type of Report & Period
Covered
Final Report
14.
Supplementary Notes
Abstracts
The
ith which
ndustries could
overall objective of this study was to develop a system
a large fraction of the wastes produced by agricultural
converted into a useful material without imposing
n unacceptable burden on the environment. Specifically, the project
nvolved a detailed study of the basic characteristics of an integrated
naerobic fermentation and algae growth system for agricultural solid
nd liquid wastes on a laboratory and small pilot plant scale, with
pecial attention being devoted to the reaction kinetics of the systeny-
substantial degree of nutrient recovery and recycle was also attained
n the system.
Key Words and Document Analysis. 17a. Descriptors
Laboratories, Pilot plants, *Wastes, *Waste disposal, *Animals,
Anaerobic conditions, Aerobic processes, Recycling, Water, Reclamation
Poultry, Hydraulic equipment, Digesters, Algae, Sedimentation, Ponds,
Potatoes, *Agricultural wastes
Identifiers/Open-Ended Terms
*Animal waste management, Solid waste disposal, Resource recovery,
Lytic properties, Photosynthetic bacteria
COSATI Field/Group 13-B, 2-A
'.variability Statement
Release to public
19.. Security Class (This
Report)
UNCLASSIFIED
20. Security Class (This
Page
UNCLASSIFIED
21. No. of Pages
22.. Price,
1 NTIS-35 (REV. 3-72)
USCOMb-DC' 14952-P72
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REVIEW NOTICE
The Solid Waste Research Laboratory of
the National Environmental Research Center,
Cincinnati, U.S. Environmental Protection
Agency, has reviewed this report and approved
its publication. Approval does not signify
that the contents necessarily reflect the
views and policies of this laboratory or of
the U.S. Environmental Protection Agency, nor
does mention of trade names or commercial
products constitute endorsement or recommen-
dation for use. The text of this report is
reproduced in the form received from the
Grantee; new preliminary pages have been
supplied.
-ii-
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FOREWORD
Man and his environment must be protected from the
adverse effects of pesticides, radiation, noise and other
forms of pollution, and the unwise management of solid
waste. Efforts to protect the environment require a
focus that recognizes the interplay between the com-
ponents of our physical environment--air, water, and
land. The National Environmental Research Centers
provide this multidisciplinary focus through programs
engaged in
• studies on the effects of environmental
contaminants on man and the biosphere, and
• a search for ways to prevent contamina-
tion and to recycle valuable resources.
In an attempt to solve the problems involved in
solid waste disposal, this study attempted to develop
a partially closed system for animal waste management
based on the integration of an anaerobic and aerobic
phase, the recycling of water, and the reclamation
of usuable products.
A. W. Breidenbach, Ph.D.
Director
National Environmental
Research Center, Cincinnati
-iii-
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PREFACE
The report herein presented is of the nature of a final report
covering the three year grant period, supported in part by USPHS Grant
No. 5 R01 UI 00566-03 and in part by the College of Engineering and
School of Public Health, University of California, Berkeley,
The research plan on which the grant was based called for labora-
tory and pilot plant studies to develop a partially closed system of
animal waste management based on the integration of an anaerobic and
aerobic phase, the recycling of water, and the reclamation of usable
products. Contained herein are summaries of the first and second pro-
gress reports, and an account of experiments performed in the final
three-four-month period of the research. The first and second reports
covered the first two and one-half year period of the research. The
pilot plant included a poultry enclosure, a hydraulic system for handling
the wastes, a heated anaerobic digester with ancillary equipment, and
an algae-production pond.
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TABLE OF CONTENTS
Page
PREFACE • • • iv
LIST OF TABLES viii
LIST OF FIGURES ix
I. INTRODUCTION 1
NEED FOR THE STUDY 1
OBJECTIVES OF THE STUDY 3
NATURE AND RATIONALE OF STUDY A
ORGANIZATION FOR THE STUDY 4
ACKNOWLEDGMENTS 5
II. SUMMARY OF RESEARCH DESCRIBED IN PROGRESS
REPORTS I AND II 5
INTRODUCTORY REMARKS e . „ . „ 5
PRE-PILOT PLANT STUDIES 6
PILOT PLANT STUDIES 11
Sedimentation Tank 13
Digester 15
Pond 15
The Integrated System 17
III. STUDIES CONDUCTED FOLLOWING PUBLICATION OF
PROGRESS REPORTS 18
INTRODUCTORY REMARKS ."...a..,."...... 18
PILOT PLANT STUDIES „ „ „ „ . „ „ <, . . 8 . „ . . 20
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TABLE OF CONTENTS (cent.)
Page
Mechanical Aeration of the Pond . . . . . ..... 20
Inorganic Carbon as Related to Phot osyn thesis in
the Algae Pond ................. 29
Introduction ... ............ .. 29
Methods .................... 29
Results . ...... ............. 30
Discussion ............. . ..... 32
Inorganic Carbon and Dissolved Oxygen
Responses ......... . ...... 34
Summary and Conclusions ..... . ...... 36
Lytic Pf op~ertf ies of Photosynthetic Bacteria in
the Algae Pond ................. 37
Introduction .......... ........ 37
Materials and Methods . ....... ..... 37
Results . ............... .... 38
Discussion .... ............... 40
Approaches to Inactivation and Control of
Lytic Activity ............... 41
Summary ........ * ........... 42
Discussion of Pilot Plant Studies ......... 42
Design Considerations ......... .... 42
Roof Ponds ..... . ........... 43
Harvesting Algae ..... o ..... ... 44
Practical Scale Systems ....... .... 45
Economics ................... 47
Overall Evaluation of the System ..... ... 52
TREATMENT OF POTATO WASTES THROUGH ALGAL CULTURE ... 53
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TABLE OF CONTENTS (cont.)
Page
Introduction . . . . . 53
Experimental . <> . . o <, . o . 55
Discussion o . , 61
Conclusions 63
IV. POTENTIAL OF PHOTOSYNTHESIS IN WASTE TREATMENT
SYSTEMS 63
GENERAL CHARACTERISTICS 63
TYPES OF APPLICABLE PHOTOSYNTHETIC SYSTEMS .... 65
V. RECOMMENDATIONS 67
APPENDIX As DESIGN OF AN ALGAL REGENERATIVE SYSTEM
FOR SINGLE FAMILY FARMS AND VILLAGES .... 72
REFERENCES 82
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LIST OF TABLES
No. Title Page
1 Diurnal Changes in pH, Alkalinity, Dissolved Oxygen,
and Inorganic Carbon Uptake ....... 31
2 Estimated Capital and Maintenance Costs of the Waste
Handling Facilities of a 100,000 Egg-Laying Poultry
Operation Utilizing Photosynthetic Reclamation and
Hydraulic Transport ..... 49
3 Comparison of Domestic Sewage, Beet Flume Water, and
Potato Waste with Standard Algae Nutrient . 54
4 Photosynthetic Oxygen Production in Potato Waste .... 56
5 Concentration of Algae (Cc) and Theoretical Oxygen
Production (TOP) Under Phosphate Addition, Car-
bonation, and Dilution 59
6 Odor Endurance at Various Dilutions of Potato Wastes
in Domestic Sewage ...... 60
7 Design Specifications for a 4000-Bird Demonstration
Facility 69
-viii-
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LIST OF FIGURES
No. Title
Frontispiece - Eggs from Chickens Fed Algae Grown on Chicken
Waste x
1 Settling Time Characteristics of Diluted Cow Manure 8
2 Generalized Pilot Plant Flow Chart 12
3 Total and Suspended Solids Concentration of the Pond
During Mechanical Aeration 22
4 Concentration of Volatile Suspended Solids During
Mechanical Aeration « 24
5 Concentration of Unoxidized Nitrogen in the Pond During
Mechanical Aeration 25
6 Concentration of NH^-N in the Pond During Mechanical
Aeration 26
7 Percentage of Total Solids in the Form of Unoxidized
Nitrogen During Mechanical Aeration 27
8 Interrelationship Between Photosynthesis Related Phenomena. . 33
9 Schematic Diagram of a Single-family Microbiological
Organic Waste Recycle System 73
10 Schematic Diagram of a Dwelling Unit for a Family and
their Livestock which Incorporates a Microbiological
Recycle System for Water, Nutrients and Energy in a
Convenient and Hygenic Environment 79
-ix-
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I
•X
I
TO
m
0 i
<=» I
cz
o
CO
FRONTISPIECE: EGGS FROM CHICKENS FED 5 PERCENT, 10 PERCENT AND 15 PERCENT
ALGAE GROWN ON CHICKEN WASTE PLUS 15 PERCENT, 10 PERCENT AND 5 PERCENT
SOYBEAN OIL MEAL. THE EGG ON THE RIGHT WAS FROM A CHICKEN FED A 20
PERCENT SOYBEAN MEAL AS A CONTROL
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!„ INTRODUCTION
NEED FOR THE STUDY
The expanded urbanization of our population, attended as it is
by a decentralization of the majority of the metropolitan areas in the
United States, leads to an increasing degree of encroachment on the
agricultural lands surrounding urbanised regions* In turn, the multi-
plication of uses and augmentation of demands for these agricultural
lands inevitably is accompanied by an increase in the monetary value of
the land and a concomitant increment in taxation. The result is that the
agricultural enterprises located in these areas must intensify their
operations if they are to survive. The intensification of agricultural
industries leads to a corresponding step-up in waste production by these
industries. The increase in the volume of the waste production is not
the only problem, however. More serious is the fact that inasmuch as
agricultural wastes generally are highly putrescible in nature, their
disposal in an acceptable manner becomes an urgent necessity. The problem
is aggravated by the marginal nature of the economics of the agricultural
industry in general, and its consequent inability to expend the money
needed to treat its wastes satisfactorily. The general unavailability
of land area plus the prohibitive costs of the land make the formerly
acceptable method of disposal by spreading on land no longer feasible
in many areas. Thus, the sequence of events triggered by the expansion
of urbanization leads to the need for research directed at developing
new systems of waste management consonant with modern conditions.
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The situation described above is especially typified in the poultry
(shell-egg) industry. Even a relatively small operation of 10,000
chickens results in the production of at least two tons of wet manure per
day* (The term "chicken manure" denotes mainly manure with small quanti-
ties of spill-feed, broken eggs, feathers, etc.). Unless carefully managed,
this manure can lead to the production of very objectionable odors and
the generation of huge populations of flies. The manure usually cannot
be spread on land because land is either unavailable, too expensive, or
too wet. It cannot be sold as a fertilizer, at least in sufficient
quantities, because large-scale crop producers are unwilling to use the
less convenient organic fertilisers when chemical fertilizers are at
hand. Even if the operations were located so that they could be connected
to municipal sewerage systems, discharging the wastes into the sewer
undoubtedly would be forbidden by the affected municipality. The added
burden of treating wastes from one or more large-scale poultry operations
would probably overtax the capacity of the existing facilities most of
which are already inadequate. Thus, in all probability, increasing the
capacity of the facilities to meet the added burden would necessitate
expenditures on a scale unacceptable to the taxpayers.
Since the presently practiced methods of disposal of animal wastes
are becoming unsuitable, it is imperative that new methods be found which
are sanitarily and aesthetically acceptable and yet economically feasible.
Ideally, the method or methods should involve some type of reclamation,
not only to conserve resources, but to utilize solar energy. Photo-
synthetic reclamation of manures in the form of algae production is one - -
possibility.
The photosynthetic reclamation system proposed in this study
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incorporates the hydraulic handling of animal wastes. A brief description
of the system is as follows: The animals9 wastes are trapped on a flat
wet surface then quickly flushed to a holding tank in which settleable
solids are separated from the liquid phase. The supernatant is pumped
directly to an algae pond and the settled solids are discharged into an
anaerobic digester* Digester supernatant is pumped directly to the algae
pond; and the settleable, stabilized sludge (dewatered and greatly
reduced in volume)is wasted. Depending upon the algae concentration,
pond effluent either is recycled directly to the animal quarters for
flushing, or the wastes can be processed so that the algae are removed.
A portion of the supernatant from the separation process is pumped to the
animal quarters for waste flushing. The algae are dried for use as an
animal feedstuff. As the description indicates, the system is "closed"
so far as water is concerned. However, in practice, some water is
naturally lost due to product removal» evaporation and spillage. This
can ba compensated for by discharging the necessary overflow from the
animals9 drinking water supply into the system.
OBJECTIVES OF THE STUDY
The overall objective of the study was to develop a system with
which a large fraction of the wastes produced by agricultural industries
can be converted into a useful material without imposing an unacceptable
burden on the environment. Specifically, the project involved a detailed
study of the basic characteristics of an integrated anaerobic fermenta-
tion and algae growth system for agricultural solid and liquid wastes
on a laboratory and small pilot plant scale, with special attention
being devoted to the reaction kinetics of the system.
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f-
As will be documented, a substantial degree of nutrient recovery
and recycle was also attained in the systemo
NATURE AND RATIONALE OF THE STUDY
To attain the objectives of the study, it was not enough to
establish tentative design and operational parameters of the constituents
of the proposed system by way of experimentation. To complete the study,
the applicability of the design and operational parameters had to be
tested by way of the construction and use and operation of a pilot plant
of meaningful size which incorporated these design and operational
parameters.
The activities which took place in the laboratory phase included
preliminary studies concerned with establishing guidelines with respect
to the planning of experiments to be conducted with the pilot plant,
with determining the characteristics of manure for use in laboratory
experimentation in terms of source of study, and with evaluating
methods for collecting and storing the manure. Pre-pilot plant
activities were directed at refurbishing existing facilities to be
used in the investigation, and at conducting preliminary pilot plant
studies. The pilot plant phase took up the greater part of the total
research period.
ORGANIZATION FOR THE STUDY
The organization of the study is indicated by the information
given in the Preface. The organization of the report is indicative of
the chronology of the research effort. The laboratory studies were
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conducted during the first year of the grant period. The pre-pilot
plant phase of the research began toward the end of the first year and
continued into the second. The pilot plant phasef naturally» began
with the completion of the pre-pilot phase and continued up to the
termination of the project.
ACKNOWLEDGMENTS
The research reported herein was supported in part by a Public
O
Health Service Research Grant (UI 00566-01, 023 03) from the Bureau of
Solid Waste Management, U.S. Dept. of Health, Education, and Welfare
(presently Solid Waste Researchs U.S. Environmental Protection Agency)
to the Regents of the University of California.
II. SUMMARY OF RESEARCH DESCRIBED IN PROGRESS REPORTS I & II
INTRODUCTORY REMARKS
The experimental effort in the research project "Photosynthetic
Reclamation of Agricultural Solid and Liquid Wastes" was directed towards
the finding of ways of converting into useful materials the agricultural
wastes now causing severe environmental problems. Specifically, the
work involved making determinations of the energy, organic loadings,
balance of water and nutrientss and overall performance of an animal
waste treatment system consisting of an anaerobic reactor preceding an
algae growth pond.
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Because the problem of manure disposal is especially critical in
the poultry industry, and because at the time facilities available at
the Richmond Field Station were best suited to the use of poultry
manure for the study, the major effort of the research was concerned
with chicken manure.
PRE-PILOT PLANT STUDIES
Because the proposed system had as one of its components, the
anaerobic digestion of poultry manure, laboratory studies on the factors
involved in poultry manure digestion were indicated. To develop the
necessary cultures, cultures of digesting sewage (domestic) sludge were
adapted to the use of manure as a nutrient source. In these studies
the existence of a very critical concentration of volatile solids with
respect to satisfactory digestion of poultry manure was demonstrated.
This level was found to be about 50% of the dry weight of the manure
as volatile solids (VS). In the experiments, the manure digested readily
when its volatile solids were 62% or above; and very poorly, when the
volatile solids were less than 50%.
To determine the optimum operating conditions for the algae pro-
duction pond, it was necessary to know the algal growth potential (AGP)
of the liquids discharged into it, namely, of the supernatant from the
anaerobic reactor (digester) and the supernatant produced as a result
of the incorporation of the flush method and accompanying settling tank
to store the flushings. Tests showed that in terms of AGP, the optimum
ratio of digester effluent supernatant to settled manure trough-flushings
was from U10 to 1:20.
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In terms of the objectives of the research, the most practical of
the various methods of handling chicken manure vas one based on hydraulic
transport. To design the hydraulic system, information was needed on
the relation between settleability and solids content of aqueous sus-
pensions of the manure,, Results of experiments involving poultry manure
suspensions having solids concentration ranging from 0.1% to 30% wet
weight indicated that: a) approximately 70% of the solids settle out;
b) the higher the initial concentration, the slower the rate of settling;
and c) that at the most probable maximum wet weight of solids concentra-
tion to be encountered in the system, namely, from 1% to 3%, most of the
settling would take place in less than 15 minutes.
The experiments on the rate of settling to solids concentration
of slurry were later repeated with the use of cow manure instead of
poultry manure. Rates of settling of slurries of cow manure paralleled
those for poultry manure slurries, and are plotted in Figure 1 as a
function of solids content. The results indicate that the acceleration
accompanying increase in amount of dilution also is applicable to
slurries of cow manure.
A hydraulic manure-handling system incorporating a program of
frequent flushing appeared to be the practical solution for wastes re-
moval and transport in the contemplated operation. To arrive at a design
for the flushing system, two model tipping buckets, one having a capacity
of 1 gal, and the other of 2 gal, were mounted on a trough (12 in by 96
in long) designed to be adjustable to any desired slope. The 2-gal bucket
with the trough at a slope of 1:16 supplied enough flushing action to
transport the manure when an equivalent of approximately two hours of
manure production was placed in the trough. A critical fact brought out
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1000
TOTAL SOLIDS- 14.6%
VOLATILE SOLIDS-86.3%
20
40 60 80
TIME ,min.
100
FIG. i.- SETTLING TIME CHARACTERISTICS OF DILUTED COW
MANURE'
I. Fecal matter only
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in the test was the importance of not allowing the manure to dry oh the
trough surface, since it took a considerable force of water to dislodge
dried material. Also drying of manure is accompanied by loss of CO2
and ammonia* a factor which was decreased by prompt and frequent flushing.
Prior to the completion of the integrated pilot plant system, a
closely controlled heated digester (3 ft in diameter, 8 ft in depth;
culture volume 45.4 cu ft) was constructed. To arrive at parameters for
later operation, a series of preliminary experiments were conducted with
the use of the new digester* Operation of the digester was initiated
by introducing well-digested sewage sludge into the digester and adapting
it to chicken manure by starting with an initial average low loading of
0.021 Ib VS cu ft-day. The pH ranged from 7.2 to 7.8. At detention
times ranging from 28 to 65 days (mean 40 days), digester gas production
at loading intervals of four to six days per week ranged from 5.0 to
11.25 cu ft/lb VS introduced.
The algae growth pond was in existence prior to the initiation of
the present project. The planned culture depth in the pond was 7 in. At
this level, the surface area of the culture was 737 sq ft, and the culture
volume about 3,200 gal. Arrangement was made to mix the pond for 10-
minute periods at hourly intervals by recirculating the liquid such that
it acquired a velocity of 2 ft/sec. Such mixing is essential to prevent
stratification and anaerobiosis in the sludge phase of the algae ponding
system.
Two methods of algae harvesting were used, namely, settling and
centrifugation. In harvesting by settling, pond effluent was passed
through a cyclindrical settling tank having a conical bottom at a rate
such that the detention time of the pond effluent in the tank was 38
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io
hours. The settled algae were drawn off periodically. A Westphalia
centrifuge and a laboratory basket-type centrifuge were used in the
centrifuge operation.
Because of the rapid decomposition of volatile solids occurring
under normal storage conditions and of the difficulty in procuring a
constant and uniform supply of manure from nearby outside sources, the
need for establishing a chicken colony at the site was demonstrated early
in the study. Accordingly, a 14 ft by 14 ft poultry enclosure was de-
signed and constructed, and was stocked with a flock of 113 twenty-week
old white leghorn pullets. The birds were caged in batteries, each of
which held four hens (except one cage with five hens during the initial
part of the study) with a space allotment of about 0.45 sq ft/hen.
Directly beneath each row of chicken batteries was a fiberglass
coated plywood trough to catch the chicken excreta. Once each hour, a
tipping bucket (8.3 gal capacity) mounted at the end of each trough
automatically discharged its contents into the trough to flush the excreta
down the trough, through the disposal unit, and into a sedimentation tank.
The working depth of the sedimentation tank was about 4 ft. A submerged
sump pump moved the supernatant in the sedimentation tank to the algae
pond, and a sludge pump moved the settled chicken manure hopper for cali-
bration prior to discharge into the digester.
One of the more significant outcomes of the study was the success
attending the functioning of the manure flushing and hydraulic transport
subsystems. The success was evidenced by the practically complete lack
of objectionable odors and the absence of fly breeding in the area.
A thin layer of slime did build up on the surface of the troughs.
However, extensive buildup of the layer was prevented by scraping approxi-
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11
mately every tvo weeks with a "squeegee05<= Perhaps this periodic scraping
may have been unnecessary, inasmuch as the layer might have sloughed off
after reaching a critical depth, much as do the slime accumulations on
the media of trickling filters. The biological composition of the slime
layer was much the same as that of coatings on rocks in trickling filters,
except that the former had a dense population of deep pink-colored or-
gan isms --probably a species of red spirillae A thin layer of algae de-
veloped in those portions of the troughs exposed to sunlight. Undoubtedly,
the organisms in the slime layer were responsible for some decomposition
of the manure in the troughs in the intervals between flushings and effected
some loss of nutrients in the system.
PILOT PLANT STUDIES
Upon completion of the poultry enclosure, the enclosure, sedi-
mentation tank, digester, and algae pond were integrated to form the
pilot plant diagrammed in Figure 2. The flow arrangement may be briefly
described as follows: wastes excreted by the chickens drop into manure
troughs. The excreta are then flushed down the manure troughs into a
sedimentation tank. Supernatant in the sedimentation tank is pumped to
an algae pond, while the settled solids are measured and introduced into
a digester. Digested stable sludge periodically is wasted to the environ-
ment when necessary to provide volume for newly admitted solids. Super-
natant from the digester is discharged into the algae pond. Effluent
from the algae pond either may be passed through an algae separation
process or may be pumped directly to the manure troughs and recycled
through the system. If the effluent is passed through an algae-separa-
tion process, the harvested algae are removed from the system and a
portion of the supernatant is pumped to the manure troughs for use as
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I Poultry Enclosure \
Chicken Batteries
Tipping Flush Buckets
Flush Water Outlets
Digester Feed Line
•
Depth Probe
Mixing-Effluent Line
Sludge Extraction Line
Water Seal
Wet Gas Meter^ Hof Wattf Mf/
Mixing Pump
v>lsTj-f33*s£L.-'j&g2
;--mv>:^^M5*W^'^-=;'-
/ '"•^••Ki^i^s^y-" )
Manure Supernatant
Effluent Pump
Pond Overflow
Pipe
Pond Mixing
Pump
£W
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13
!
flushing water, thus completing the cycle. Supernatant not diverted for
flushing is returned to the pond. Physical dimensions, construction and
equipment details as well as operational features of each of the units
mentioned in the flow chart were given in the progress reports.
The operation of the pilot plant progressed without any major
problems throughout the course of the study. Out of the 113 chickens at
the start of the study, 88 remained at the end of the first run. Of
the 25 chickens that were removed due to mortality or morbidity* 12 were
killed by marauding dogs that gained access to the pens. Egg production
ranged from 68.7% to 81.4%. Feed consumption averaged 0.258 lb/chicken/
day* Manure output averaged 0.418 lb/chicken/day (189.7 gm/chicken/day)
with an average solids content of 25.4% of the wet weight, and a volatile
solids content of 67.7% of the dry weight. The population equivalent was
9.2 chickens per capita. No difficulties were encountered in the manure
flushing operation. The quantity of flushing water (i.e. recycled pond
water) was approximately 12,000 liters per week and the drinking water
around 4000 liters per week.
The systems approach was used to analyze the pilot plant phase.
A "balance" of the major inputs, outputs, concentration changes within the
system, and A system changes (not accounted for in the measurements)
was performed for total solids, volatile solids, total unoxidized nitrogen,
and energy for the system components, chickens, sedimentation tank, di-
gester, and algae pond. The balances were performed weekly. The digester
operation was terminated at the conclusion of week 24.
Sedimentation Tank;
The sedimentation tank received 1053 kg of manure total solids
from the chicken component. The supernatant was pumped directly to the
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14
algae pond and the settled solids were pumped to the digester from the
start of the study through week 24. Thereafter, the settled solids were
dewatered, dried, and stored for use in feed studies. From week 5 through
24, the distribution of the sedimentation tank contents was 57% sedi-
mentation tank supernatant to the algae pond, 34% settled solids to the
digester, and 9% "grit" was removed from the settled solids before it
entered the digester. The A outputs were: A total solids 24%; A
volatile solids 28%, A total unoxidized nitrogen 15%; and 4 energy 32%.
The settling efficiency obtained in the sedimentation tank was
not as high as might have been expected on the basis of the laboratory
studies. About 57% of the supernatant discharged from the sedimentation
tank was in the form of dissolved and suspended manure solids* Using a
manure slurry of the same concentration (1% manure solids, wet weight)
as in the sedimentation tank, only about 33% of the manure solids remained
in the supernatant of slurry placed in an Imhoff cone. This difference
would lead one to conclude that through better designing, the efficiency
of a manure sedimentation tank could be increased from the observed 43%
to highs of 60% or 65%. The desirability of increasing the settling
efficiency in a practical operation would depend upon the design capacity
and mode of operation of the aerobic and anaerobic constituents of the
plant.
The grinder unit which was installed in the sedimentation tank to
intercept and grind feathers discharged with the manure did not function
as well as was expected. Because of the structure of chicken feathers
and, more likely because of the spacing between the grinding surfaces of
the machine, many of the feathers passed through the grinder unground.
Although the obvious solution would be to reduce the spacing between the
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grinding surfaces, doing so could only lead to a more serious problem,
namely clogging. Since feathers float, a more likely solution would be
to install some type of a skimming device at the surface level of the
liquid in the sedimentation tank, or in & large operation to utilize a
feather screen which is available commercialIy0
Digesters
The loading to the digester component ranged from 0.040 to 0.054
Ib VS/cu ft-day (mean 0.043) with an average detention time of 22.9 days.
Gas production was nearly 12 cu ft/lb volatile solids introduced. Di-
gester gas composition was grouped into CH^, (X>2, and nonidentif ied gas.
The CH^ content ranged from 13% to 45% and C(>2 ranged from 41% to 67%.
The CH^tCOj ratio increased from 0.18 in week 7 to 0.96 in week 24. Non-
defined gas averaged about 20% of the total* Overall volatile solids
destruction was approximately 55%. Out of the 185 kg of digest influent
total solids content, 120 kg were released as digester gas.
Judging from the information given in the preceding paragraph,
the digester functioned with an efficiency comparable to that charact-
eristic of municipal digesters. Although the volume of gas produced was
greater than that generally encountered in the digestion of raw sewage
sludge, the methane content was correspondingly lowere It started at
12% CH4, but by the end of the 24-week period in which the digester
was operated it had reached 40%. In view of the steady increase, there
is good reason for believing that with continued operation, the percentage
of CH^ would have reached the conventional 60% to 65%.
Pond;
The installation and operation of an algae pond in a photosynthetic
-------
16
reclamation system such as described herein can serve many useful pur-
poses. It can provide: 1) an effective and odor-free treatment for the
solids (dissolved and suspended) coining from the sedimentation tank
and for the digester supernatant; 2) a supply of water for the flushers;
and 3) a highly proteinaceous plant crop* As a waste treatment device,
it functions much as an activated sludge system, differing from conven-
tional activated sludge systems in that much of the oxygen comes from
algal activity rather than by mechanical induction of atmospheric oxygen.
The hydraulic detention time of the algae pond for the 36-week
period ranged from 9 days to infinity. Excluding the one infinity value,
the average detention time was 22 days. The algae pond received a total
solids loading of 1151 kg from the sedimentation tank supernatant (in-
cluding recycled flushing water) and digester supernatant. The measured
total solids outputs as•percentages of input were: centrifuged harvested
algae, 3%; settled harvested algae, 5%; sump output, 17%; and recycled
flushing water, 55%. The ratios pertaining to the other parameters,
namely, volatile solids, total unoxidieed nitrogen, and energy were quite
similar to those for total solids. The A outputs were: total solids,
20%; volatile solids, 21%; total unoxidized nitrogen, 17%; and energy
12%. The A energy did not include solar energy input directly. Photo-
synthetic efficiency as measured by the harvested algae and the visible
solar energy input averaged 0.64%, with a high of 2*8%. Low efficiency
was primarily due to long detention time in the reactor. A study of the
diurnal changes in pH, alkalinity, dissolved oxygen, and calculated in-
organic carbon uptake produced results that were within 1% of values
calculated according to the classical photosynthesis formula.
An interesting development in the study was the apparent absence
-------
17
of a detectable accumulation of dissolved solids in the algae pond. When
the operation was initiated, it was taken for granted that the dissolved
solids concentration would increase because the system was closed to some
extent. Under such a circumstance, with salts coming in as manure solids
and the small amount with the tap water,- coupled with loss of water
through evaporation should have led to some concentrating of dissolved
solids. Although there was some effluent from the pond by way of sump
overflow, the amount of solids discharged in this manner was only 18%
of the input of solids into the system. Solids removed as algae from
the system amounted to only an additional 8%. About the only explanation
for the lack of accumulation would be one involving a biological con-
version of a large fraction of the incoming solids to gaseous volatile
substances. This apparently occurred. In view of the absence of accum-
ulation, it would seem feasible to operate the system as a closed.one or
a nearly closed one until the salt buildup reached a level at which algae
and bacteria would be seriously affected. Of course, there remains the
possibility that in a closed system an accumulation of some toxic meta-
bolite of one of the microbial groups may reach inhibitory proportions
long before .that from an inorganic salt buildup, but such information
can only be obtained through a more sustained operation of a pilot plant
than was possible in this study.
The Integrated Systems
An analysis of the integrated system reveals that biological
activity in the sedimentation tank; digester j, and algee pond decreased
the total solids by 60%; the volatile solids by 62%; the total unoxidized
nitrogen by 45%; and the energy by 56%. The extent of the biological
destruction of incoming solids was substantial.,, An overall analysis
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18
of the integrated system for a 31-week period revealed a loss of about
60% of the incoming total solids. The most likely explanation for the
loss is conversion to gas through biological decomposition, both aerobic
and anaerobic. In addition to the loss attributable to gasification,
settled solids accounted for 13%; sump outflow, 18%; harvested algae, 8%;
and grit, 7%. (Settled solids were those solids routinely removed from
the sedimentation tank after the digester was discontinued.) Had the
digester been continued throughout the run, the loss attributable to
settled solids would have been correspondingly higher. The grit is
mainly the inert material found in chicken feed. Since it is inert,
disposal of it would pose only a mechanical problem. If a more effective
algae harvesting system had been available during the run, the solid
conversion to algae would have been appreciably greater. The conversion
of solids to algal cells is the reclamation feature of the integrated
system, since waste solids are converted to algae which can be used as a
highly proteinaceous feedstuff.
III. STUDIES CONDUCTED FOLLOWING PUBLICATION OF THE PROGRESS REPORTS
INTRODUCTORY REMARKS
At the time the second progress report was written, the authors
had good reason for assuming that the project would be funded for an
additional year or two so that certain questions concerning the present
and future performance of the system could be explored. Consequently,
it was planned to follow the solids that must surely accompany the con-
tinued operation of the plant as a "closed system1*, and thus determine
the rates required for repletion of necessary elements and removal of
undesirable elements to assure the continued successful operation of the
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19
system. Another question to be answered was that of the minimum surface
area of pond per bird. As was pointed out in the second progress report,
the pond area could be reduced to 2 sq ft/bird without any adverse effects.
Although intuition would indicate a limitation somewhere between 1.5 and
2 sq ft, this important question requires an answer more firmly based
than intuition. Another projected study was to determine the utility of
the dewatered sedimentation tank settled solids as a feedstuff for
ruminants0 Unfortunately, plans to study these important questions had
to be laid aside when it was learned that the needed funding would not
be available. The few months remaining until the imposed termination of
the project did not allow the time needed for a meaningful exploration
of the questions.
Inasmuch as a study on the use of mechanical aeration to supply
the oxygen needed for oxidation of the organic wastes in the pond was in
progress at the time the second progress report was written, it was de-
cided to continue that study. The successful utilization of artificial
aeration would expand the geographical application of the integrated system
by providing a means of oxygenation during those seasons when environ-
mental factors were not conducive to algal growth and oxygen production.
In addition, the pilot plant studies included two special investigations.
They were: 1. a study of inorganic carbon metabolism in the pond as
related to the photosynthesis reaction in the pond portion of the system;
and 2. & determination of the lytic properties of photosynthetic bacteria
in the algae ponde The scope of the overall study was broadened to examine
a vegetable solid waste by including a study on the treatability of potato
wastes through algal culture. The study was made a part of continuing
effort to apply photosynthesis to the treatment of agricultural wastes--
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20
both plant and animal. Potato wastes have the high carbon content
characteristic of most cannery wastes and are of special interest in the
projected integrated systems for communities.
PI1DT PLANT STUDIES
Mechanical Aeration of the Pond;
The method of supplying aeration and preliminary results were
described in the second progress report (p. 134) as follows:
"Inasmuch as the season (i.e. winter) was patently unfavorable for
growing algae in the concentration needed to meet the increased loading,
it was decided to try mechanical aeration as a means of supplying the
oxygen needed in stabilizing the organic loading. Accordingly, three
float-activated 1/3 hp sump pumps were pressed into service to act as
aerators by installing a 2-ft vertical pipe into the discharge point of
the pump and capping the pipe with a "T" fitting such that the liquid
was discharged horizontally into the air and cascaded back into the pond.
This closely simulated the type of aeration attained with floating
surface aerators.
With continuous operation of 3 aeration pumps, the dissolved oxygen
concentration of the pond remained >7 mg/liter. Reducing the number of
pumps to two resulted in a small decrease in the average dissolved oxygen
concentration to -6.5 mg/liter. A further reduction to one pump resulted
in an average dissolved oxygen value of slightly less than 6 rag/liter.
The power cost of an aeration system equivalent to one pump operated
continuously on a year-round basis would be about 0.1^/doz eggs."
The research reported herein was concentrated principally on the
solids build-up and the carbon and nitrogen relationships during the time
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21
the pond was mechanically aerated. The tin® period elapsed during the
study was from Feb. A to April ll--a period of about 63 days. The time
period encompassed the transition from the San Francisco Bay Area winter;
slightly frosty, foggy or rainy season to spring.
An important feature of the run was the fact that no water was
wasted from the system, excepting that lost through spillage, evapora-
tion, etc., indicating the aerators were effective in enhancing evapora-
tion. The total and suspended solid concentration of the pond culture
during the course of the run are plotted in Figure 3. According to the
slope of the curves in the figure, the solids content of the pond in-
creased gradually during the run. The exception was the very sharp in-
crease during the last couple of weeks of the run. Judging from the
difference between the numerical value of the total solids and those of
the suspended solids, the sharp increase in the suspended solids con-
centration was not accompanied by a comparably sharp rise in total dis-
solved solids. The variation was within the range of 613 rag to 783 mg/
liter or about 21% of the highest concentration of suspended solids.
Consequently, the increase in total solids was solely a function of in-
crease in suspended solids concentration.
Reasons for the buildup in suspended solids concentration could
have been an increase in bacterial population--or one in algal numbers.
The buildup in bacterial population could be expected because of the
increased oxygen supply and the heavy concentration of nutrient. The
algal buildup would come as an accompaniment of the rising temperature
and increase in solar irradiation attendant upon the change in season
from winter to spring. An examination of the bottom sludge showed it to
have a biota characteristic of conventional activated sludge.
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22
2600
240& —
2200
1
£
en
o
o
to
2000
1800
1600
1400
1200
1000
800
600
I I I I I I
POND OPERATED AS "ACTIVATED SLUDGE SYSTEM"
O TOTAL SOLIDS
A SUSPENDED SOLIDS
D TOTAL DISSOLVED SOLIDS
D 1
10
A—
. D
_L
20 30 40 50 60
DAYS AFTER START OF RUN
FIGURE 3. TOTAL, SUSPENDED, AND DISSOLVED SOLIDS OF POND
CULTURE DURING MECHANICAL AERATION
-------
24
1100
1000 —
9OO —
o»
^800
o
o
to
o
UJ TOO
o
UJ
Q.
en
en
UJ
o
600
500
400
300
O
O
I
I
I
I
10
20 30 40 50
DAYS AFTER START OF RUN
60
FIGURE 4. CONCENTRATIOM OF VOLATILE SUSPENDED SOLIDS DURING
MECHANICAL AERATION
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23
The final abrupt rise In total and suspended solids cannot be
attributed solely to increase in cell mass--algal or bacterial--becaus«!
the percentage of the suspended solids In a volatile form dropped equally
abruptly. Whereas throughout the run, the volatile fraction of the
suspended solids ranged between 70 and 79%, on the 63rd day it dropped
to only 45%0 However, as is shown in Figure 4, the actual concentration
of volatile suspended solids rose from about 436 rag/liter to about 767
mg/liter. On the last day of the run (63rd day), it was 767 mg/liter.
It is unlikely that the final spurt in total solids is an artifact
(arising from experimental or analytical error in that the total and sus-
pended solids and nitrogen all showed an abrupt increase at the same time*
The phenomenon was probably caused by a burst of algal growth with the
coming of spring. Algal growth was followed by a rise in pH and pre-
cipitation of soluble complexes accumulated during the long period of
aeration.
The slope of the curves for unoxidized nitrogen concentration and
NH^-N concentration of the pond culture, as plotted respectively in
Figures 5 and 6 fairly closely approximate those for total and sus-
pended solids in the pond. Although the total concentration of unoxidixed
nitrogen in the pond rose quite steeply in the last 20 or more days of
the run, the percentage of total solids in the form of unoxidized nitrogen
dropped sharply. This drop in percentage nitrogen is shown in Figure 7.
At the start of the run, unoxidized nitrogen accounted for slightly more
than 7.5% of the total solids. This percentage soon dropped to 4 to 57,
and remained there until the end of the run. The drop in percentage
probably is symptomatic of the shift from algal to bacterial predominance
in the biota that began with the application of mechanical aeration.
-------
25
220
210
200
g1 190
Q
UJ
tJ ISO
O
X
O
< 170
O
160
ISO
140
I
I
I
24 2 nig/?/
6 3 DAYS
I
10 20 30 40 50
DAYS AFTER START OF RUN
60
FIGURE 5. THE CONCENTRATION OF UNOXIDIZED NITROGEN IN THE
POND DURING MECHANICAL AERATION
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26
160
150
140
130
01
e
Z
120
110
100
90
80
PROBABLE TRUE SLOPE
I
APRIL II
I
10
20 30 40 50
DAYS AFTER START OF RUN
60
FIGURE 6. CONCENTRATION OF NH4-N IN THE POND DURING MECHANICAL
AERATION
-------
27
7.0 —
;o
~o
-------
28
The type of unicellular alga generally encountered in ponds almost always
has a nitrogen content of at least 6%. Visual and random observation
with a microscope confirmed the decline in number of algae.
Another piece of evidence, or even a symptom of decline in the
algal population, was the high concentration of NH^-N which prevailed
in the pond. As is shown by the curve in Figure 6, in which is plotted
the change in concentration of NH^-N, the NH4-N concentration remained
above 100 mg/liter throughout the run excepting for an apparent drop to
about 85 mg/liter on one occasion. Inasmuch as a rule, algae preferen-
tially use NH^-N as a nitrogen source, the high NH^-N content would in-
dicate either a sparse or an inactive algal population. Interestingly,
the slope of the curve showing percentage of total solids as NH^-N
(cf Figure 7) fairly well reflects that for percentage unoxidized-N.
The concentration began with a high of 6.8% and ended at 5%. The high
ammonia content could--and probably did--have a significant effect on
amount and rate of nitrogen loss from the system. The concentration was
at a level at which it was toxic for fish. Carp ("goldfish") placed in
the pond expired in less than a day.
The percentage carbon content remained quite constant throughout
the run, ranging from 34 to 39% of the total solids. The percentage did
not change drastically even during the final surge in solids concentra-
tion. The fact that the percentage carbon never exceeded 39% would in-
dicate that some of the solids were not organic in nature, since most
organic material averages about 50% carbon.
It is unfortunate that the study could not have been extended
long enough to determine at what level the buildup of solids would con-
tinue, or whether the final sharp surge was a single event or would have
-------
29
i
continued. All in all, the pond functioned much as a conventional acti-
vated sludge or extended aeration unit during the run* Tests did show
that under the constant turbidity prevailing in the pond because of the
mechanical aeration, algal growth was greatly inhibited except possibly
during the final weeks when spring weather occurred*
Inorganic Carbon as Related to Photosynthesis in the Algae Pond;
Introduction; The purpose of this phase of the study was to ascertain
with reference to the algae pond, the relationship of photosynthesis
with the diurnal parameters of pH, alkalinity, dissolved oxygen (DO),
water temperature, and inorganic carbon uptake; inasmuch as the extent
of diurnal variation is an excellent indicator of intensity of photo-
synthetic activity in an outdoor algal culture. With information gained
by measuring the diurnal shift, it should be possible to evaluate the
performance of the algae pond. Alkalinity measurements could be used to
establish the amount of carbon available to the algae from alkalinity.
To determine the diurnal variation in photosynthetic related
factors, ideally a 24-hour period of monitoring is needed. Less ideally,
the period of observation could be confined to that time of the day during
which photosynthesis occurs. Because of a manpower shortage and the lack
of a mechanical sampling system, only one extended observation was made
of the diurnal variations in the study discussed herein although several
short-term observations were also made.
Methods; The mixing usually applied to the pond was suspended during
the time in which the actual studies were made. Although mixing was held
in abeyance during the period of observation, some minimal disturbance
of the pond contents did take place when the flush water was discharged
into the pond each hour, since recycling was maintained at all times.
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30
Alkalinity, pH, temperature and dissolved oxygen were analyzed
at hourly Intervals immediately after sampling during.the extended period
of observation of the diurnal shift. Analyses were made according to
Standard Methods (!)• Inorganic carbon content was determined from a
table compiled by Saunders, et al. 1962 (2). Saunders* table is based
on equilibrium calculations for the different carbon chemical species*
The period of observation was begun at 0500 hours. It was terminated at
2400 hours because the dissolved oxygen content had dropped to zero at
2000 hours and remained at that level thereafter. Moreover, during that
same time period (2000-2400 hrs), pH and alkalinity levels also remained
almost constant.
Results: According to Table 1 in which are listed data obtained in the
run, the solar energy input was at its maximum at 1300 hours. The pond
temperature rose from 9.0°C at 0700 hours to 27°C at 1500 hours. Judging
from the solar energy level and the high pond temperature, the day was
an excellent one as far as algal growth was concerned. The period of
highest pH level (pH 10.85), came about two hours after the peak of the
solar energy input had been reached. The level of pH at 0500 hours was
7.82; and at 2400 hours, 8.40. As would be expected, the high, pH levels
were accompanied by high phenolphthalein alkalinities, namely, 160 and
165 mg/liter as CaCO^. Maximum variation in total alkalinity was only
a matter of 65 mg/liter as CaC03. The lowest level of total alkalinity,
268 mg/liter as CaCO-j, occurred at 1500 hours; and the highest, 333 mg/
liter, at 0500 hours. The concentration of dissolved oxygen was greatest
(37.5 mg/liter) at 1100 hours. On the other hand, it was zero from 0500
and 0600 hours, and from 2100 hours to 2400 hours.
At pH levels from 5.0 to 9.4 the inorganic carbon uptake was a
-------
TABI£ 1. DIURNAL CHANGES IN pH, ALKALINITY, DISSOLVED OXYGEN, AND INORGANIC CARBON UPTAKE6
Time
(hr)
0500
0600
0700
0800
0900
1000
1100
1200
1300
1600
1500
1600
1700
1800
1900
2000
2100
2200
2300
2400
Solarb
(amp-hr]
Base
0..00
0.03
0.11
0.18
0.34
0.32
0.33
0.43
0.34
0.29
0.25
0.20
0.08
0.00
0.00
0.00
0.00
0.00
0.00
Temperature
Ambient
(°C)
6.0
6.0
8.5
10.5
12.0
18.0
19.0
18.0
19.0
21.0
20.0
20.0
19.0
16.0
14.0
12.2
12.0
12.8
12.5
12.0
Pond
(°C)
9.0
9.0
9.0
11.0
13.0
19.5
23.0
18.0
22.0
24.0
27.0
26.0
22.0
20.0
18.5
17.5
17.0
16.0
15.0
14.5
PH
7.82
8.07
8.07
9.27
9.10
9.57
9.80
9.04
9.59
9.88
10.85
10.85
9.21
..«
8.95
8.74
8.52
8.49
8.45
8.40
Alkalinity0
Phenol -
phthalein
(mg/1)
0
0
0
60
48
75
98
45
80
95
160
165
58
._
28
18
8
8
3
3
Total
(mg/1)
333
328
330
315
298
288
278
300
290
278
268
273
298
300
285
290
295
303
295
308
Dissolved
Oxygen
(mg/D
0.00
0.00
0.95
11.55
10.25
20.50
37.50
12.80
22.30
33.10
33.20
31.90
4.10
2.25
...
2.60
0.00
0.00
0.00
0.00
Calculated
Inorganic
Carbon
(mg/1)
83.3
78.7
79.2
72.5
68.5
5l.ld
42. 2d
66.0
50. 4d
43. &
25. 9*1
25. 9d
68.5
72.0
65.6
69.6
70.8
72.7
70.8
73.9
Carbon
(mg/1)
Base
- 4.6
+ 0.5
- 6.8
- 4.0
-17.4
- 7.9
+22.8
-15.6
- 6.5
-18.0
0.0
+42.6
+ 3.5
- 6.4
+ 4.0
+ 1.2
+ 1.9
- 1.9
+ 3.1
Remarks
Mild north wind
Mild north wind
Mild north wind
Mild north wind
Mild north wind
Calm
Calm
Moderate west wind
Calm
Calm
Mild west wind
Mild west wind
Mild west wind
Mild west wind
Mild west wind
Mild west wind
Mild west wind
Mild west wind
Mild west wind
Mild west wind
«Run made on April 25, 1969.
bSolar meter calibrated for 1.0 amp-hr to equal about 0.190 k-cal/cm2 hr.
cPhenolphthalein alkalinity titrated to pH 8.3. Total alkalinity to pH 4.3.
dDetermined as follows: Inorganic carbon « 0.24 (total alkalinity-phenolphthalein alkalinity)
when the pH level is above 9.4.
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32
function of temperature and total alkalinity,. At pH levels above 9.4,
the inorganic carbon uptake was simply the difference between the total
and the phenolphthole in alkalinities multiplied by 0.24 (Saunders, et al.
1962). Although these calculations are dependent on the assumption that
equilibria exist in a system having relatively high concentrations of
only C02, HC03~, C03", and OH", this assumption would not lead to
erroneous conclusions because the conclusions are based on relative
values or on differences, thus cancelling out any errors with respect
to inorganic carbon.
In arriving at the values given in Table 1, it was assumed that
there was no interchange of Oj and COg between the pond and the atmos-
phere and this appeared quite probable because of the persistence of
a noticeable but thin scum observed on the surface of the pond which
would probably impede significant gas transfer unless the scum were
disturbed. This assumption appeared reasonable because the great
decreases in dissolved oxygen levels were observed only after a wind
had occurred and disturbed the water surface.
Discussion; The interrelationships between the photosynthesis-related
phenomena are shown in Figure 8, in which values for the different
variables are plotted as functions of time of day. The interrelation-
ships are demonstrated by the simultaneity of the sharp responses of
the four variables which took place at 0700 hours, again at 1200 hours,
and finally at 1600 hours. The nature of the response in terms of
inorganic carbon was the inverse of those for pH, phenolphthalein
alkalinity, and dissolved oxygen.
The initial rise in level of response for pH, alkalinity, and
DO, and the dip in inorganic carbon corresponded with the beginning of
-------
I I
I I I
(25 APRIL 1969)
TEMPERATURE
DISSOLVED OXYGEN
INORGANIC
CARBON
PHENOLPHTHALEIN
ALKALINITY
I I
175
150
125
100 * O
75
50
25
O.
Q.
0500 0700 0900 1100 1300 1500 1700 1900 2100 2300 0100 0300 0500
TIME OF DAY, hr.
FIGURE 8. INTERRELATIONSHIP BETWEEN PHOTOSYNTHESIS AND RELATED PHENOMENA
CO
u
-------
34
the daylight period, i.e., the beginning of the input of solar energy.
Thus, as would be expected, ©11 of the responses mark the beginning
of photosynthetic activity in the pond. This relationship between the
four parameters and photosynthetic activity continued throughout the
daylight period.
The dip in pond temperature as wall as in the levels of pH,
phenolphthalein alkalinity, and DO which took place at 1200 hours
coincided with a brief period of moderate west wind. The sharpness
of the response of the three parameters seems to have been out of
proportion to the extent of the temperature drop. Perhaps the tempera-
ture-related effects may have been enhanced by those due to wind action.
For example, the rate of 0~ loss to the atmosphere may have been in-
creased, inasmuch as the pond culture was supersaturated with 02 at the
time. Similarly, some CO- may also have been lost.
The abruptness of the change in all four parameters which took
place at 1600 to 1700 hours was out of proportion to the drop in pond
temperature and to the amount of solar energy available to the pond
culture at the time, if the two factors are taken individually. On
the other hand, if temperature and solar energy are considered together
and added to the effects from wind action which took place at that
time, then the responses would have been cumulative and hence abrupt
in their expression.
Inorganic Carbon and Dissolved Oxygen Responses; This analysis is
based upon the classical formula for photosynthesis, namely:
C02 + 2H20 enegqy, (CH20)X + 02 + H20
The quantity of oxygen produced during the period of observation, as
determined by integrating the area under the DO curve from Figure 8
-------
35
amounted to 235.6 mg/l-day. Accordingly, the total amount produced
by the entire algae pond culture for the day was 2.85 kg of 0_ (41.6 g
0_/m • day). The inorganic carbon uptake was considered to be the
summation of the negative values given in the A carbon column in Table 1.
Calculated on this basisf the inorganic uptake was 89.0 mg/1 as C or
326.3 mg/liter as C02 which equals 3.95 kg of C02 (57.7 g C02/m2 • day)
for the entire algae pond culture.
According to the formula for photosynthesis, for every gram of
C(>2 reduced in the photosynthetic process, 1.375 g of 02 are produced.
If this be true, the total C0_ uptake by the pond during the day should
have been 3.92 kg (1.375 x 2.85 kg of C02)0 Thus, the difference between
the observed amount (3.95 kg) and the expected theoretical value (3.92
kg) was only 0.03 kg, or less than 1 percent.
The small difference between the observed and the theoretical
values does not necessarily mean that the observed value reflected
reality equally closely. Two possible sources of error, other than
experimental and mathematical, may have influenced results. The first
could have resulted from making the assumption that no net loss or gain
in CO. or 0- took place between the pond culture and the atmosphere.
Perhaps there may have been a loss or gain. A second source could stem
from the assumption that the CO- uptake was only the summation of the
negative values for inorganic carbon. Some CO. uptake undoubtedly
occurred during the hours when the net change in inorganic carbon may
have had a positive value. Nevertheless, the extent of the error, if
any, introduced from these sources must be small, since a high degree
of fortunate coincidence would have to have been involved in arriving
at a set of observed values so closely identical with the theoretical
values.
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36
The correlation between theoretical and measured carbon utili-
zation in the system was not unexpected (e.g., Odum - References 3 and
4)o Similar cycles have been described by Bartsch and Allum (5). Not
only are relatively copious amounts of carbon available for algal photo-
synthesis from carbon sources in alkalinity but dissolved oxygen can be
accumulated to relatively high concentrations (>30 mg/1) without in-
hibiting the photosynthetic reactions.
Although this method of determining respiration-photosynthesis
may not be simply applicable to lakes or larger ponds, by dealing with
entire systems it has considerable value over previous methods based
on enclosed polyethylene bags (e.g., Goldman, Ref. 6) or open cylinders
(Kemmerer and Newhold, Ref. 7). In the system described herein, plank-
tonic and benthic production are measured and wall interference caused
by confinement are avoided. Measurements are simple and easy to make
and diurnal measurements can be replicated as necessary to provide valid
statistical analysis. Also, in a pond system such as this, the pro-
duction rates are quite high, a factor of 100 greater than for a eutro-
phic lake and changes are more easily measured. However, more attention
should be devoted to gas diffusion effects, even though they probably
are minor in relative magnitude in an algae pond. (In lakes, diffusion
would be extremely important Q.e.g., Hutchinson, Ref. 8].) Thus, it is
a valuable method for analyzing the balanced operation of a pond system
in waste treatment.
Summary and Conclusions: l) Agreement between the theoretical carbon
change and measured carbon change in the algae pond was within 1 percent.
Oxygen production was calculated to be 41.6 g Op/m • day and carbon
2
dioxide uptake as 57.7 g C02/m • day. 2) Sufficient carbon was avail-
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37
able for algal growth, almost all of which was derived from carbon
chemical species measured in alkalinity. 3) The rather simple measure-
ment of alkalinity, pH, temperature, and dissolved oxygen provided in-
formation, which could be of considerable value in interpreting the
operation of algae ponds.
Lytic Properties of Photosynthetic Bacteria in the Algae Pond
Introduction! Considerable research has been focused on the role of
algae in natural and artificial ecosystems where large quantities of
organic compounds are decomposed. In contrast* the involvement of
photosynthetic bacteria in heterotrophic environments is poorly under-
stood. Cooper and others (9, 10) have noted that ponds receiving do-
mestic, industrial or agricultural wastes frequently develop conspicuous
populations of photosynthetic bacteria. Other reports attest to the
ubiquity of such bacteria in eutrophic environments.
During the course of observations on the algae pond, the char-
acteristic pink color of photosynthetic bacteria was noted in samples
of algae harvested from the pond. Several species were isolated from
the pond,and their physiological properties were examined in the labora-
tory. Herein are summarized the results of studies concerned with lytic
properties of facultative heterotrophic photosynthetic bacteria that
relate to the use of algae as a protein supplement.
Materials and Methods8 For laboratory studies, samples of the pilot
chicken waste pond material were collected from several sites in the
hydraulic transport system, from the sides of the pond, and from algae
harvested by centrifugation from the pilot plant. These samples served
as inoculum for preparing enrichment cultures and for direct plating
experiments. The media, general procedures and conditions for establishing
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38
enrichment cultures of photosynthetic bacteria have been described by
van Niel (11).
Pure cultures were obtained by means of the shake-tube technique
previously described (12). In experiments concerned with lysin pro-
duction, the bacterial strains were streaked on sheep-blood agar and
incubated under either anaerobic conditions using the gaspak technique,
or aerobic conditions. Plates were stored at room temperature in the
light unless otherwise indicated.
Resultst Enrichment cultures incubated under anaerobic conditions
with incandescent lamps as a source of illumination developed turbidity
i
and pigmentation characteristic of the non-sulfur photosynthetic bacteria
(Athiorhodaceae) within 3-5 days. Although no experiments were under-
taken to specifically determine the numbers of photosynthetic bacteria
in the algae pond at the time of sampling* from serial dilution of shake-
tube cultures it is possible to make an estimate of approximately 10°-
10'/ml. Using the shake-tube method* several strains of Rhodopseudomonas
and Rhodspirillum were established in pure culture.
Experiments with sheep-blood agar plates streaked with inoculum
taken directly from pond samples prior to establishing enrichment
cultures yielded large numbers of colonies ringed with a clear colorless
zone. When such cleared areas were examined under the microscope* no
red blood cells were detected. These results suggested that microor-
ganisms in the algae pond were producing a diffusible agent capable of
lysing red blood cells. The lytic reaction was characteristic of BETA-
hemolysis.
Pure cultures of Rhodopseudomonas and Rhodospirilium isolated
from the algae pond were tested for hemolytic activity on sheep-blood
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39
agar plates. All strains tested were found to exhibit hemolytic activity
when cells were grown under aerobic conditions. No detectable activity
was observed when growth occurred under anaerobic conditions. These
results provide evidence that lysis of red blood cells is strictly de-
pendent upon the presence of oxygen.
In subsequent studiess strains of Rhodopseudomonas and Rhodo-
spirillum isolated from the algae pond were compared with reference
strains obtained from the University of California Department of
Bacteriology culture collection. These experiments served to confirm
earlier findings that hemolytic activity is a common feature of the
facultative strains of Rhodoseudomonas and Rhodospirillum, and that the
production of the lytic agent requires molecular oxygen.
Other experiments were performed to obtain additional informa-
tion concerning the process of lysin production* and to study some
properties of the lysin. The results can be summarized as followss
1. Using sheep-blood agar plates to assay for hemolytic activity,
it was noted that the lytic reaction was detectable after two days at
30°C and reached a maximum between three to four days after incubation.
2, When plates containing fully grown colonies of photosynthetic
bacteria were shifted from anaerobic to aerobic conditions, a lag was
detected in the appearance of lytic activity. These observations are
consistent with the hypothesis that synthesis of the lysin is inducible
by oxygen.. The lag period that precedes the detection of lytic activity
argues against the idea that the lytic agent preexists in the bacterial
cells and requires oxygen for activation.
3. The regulation of lysin synthesis is coordinated in a nega-
tive fashion with the formation of photosynthetic pigments such as
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40
bacteriochlorophyll and spirillaxanthin. Oxygen appears to serve two
functions in regulation: a) As a corepressor to induce transcription
of a specific messenger RNA coding for lysin synthesis; and 2) As a
represser of photosynthetic pigment synthesis.
4<, On the basis of dialysis experiments, a rough estimate of
the molecular weight of the lysin has been obtained. The lysin appears
to be of the order of 40,000 M.W.$. it is apparently excreted from the
bacterial cells into the surrounding medium, and is readily diffusible
in agar.
Discussions The discovery that non-sulfur photosynthetic bacteria such
as Rhodopseudomonas and Rhodospirillum produce a lytic agent capable
of destroying red blood cells raises a number of questions concerning
the ecological importance of such lysins in eutrophic environments. In
this paper, the discussion is limited to the significance of this finding
for algae production in photosynthetic reclamation systems.
If the properties of the lysin produced by photosynthetic bacteria
are compared with other bacterial lysins, it becomes apparent they have
much in common. The lytic agent produced by Rhodopseudomonas or Rhodo-
spirillum is a high molecular weight compound that is excreted into the
medium—non-dialyzable but diffusible in agar. The hemolytic exotoxins
of certain Streptococci and Clostridia are soluble enzymes that hydrolize
phospholipids of cell membranes. Such enzymes are capable of lysing
other types of cells besides red blood cells.
The inducibility of lysin synthesis by oxygen represents the
first case of a non-constitutitive lytic factor. Either the inducibility
of lysins in other bacteria has been overlooked, or lysin synthesis in
non-photosynthetic bacteria is normally constituitive.
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Approaches to Inactivation and Control of Lytic Activity? If the large
molecular weight compound is a protein, then lytic activity should be
abolished by thermal denaturation. Although we have not as yet deter-
mined thermal decay kinetics for the lysin, preliminary experiments
indicate that virtually all activity is destroyed within 5 minutes at
100 C. Accordingly, one solution to the problem of lysins in algae
to be used as a protein supplement in animal feed is to pasteurize the
algal product. Alternatively, there may be a decay, albeit less rapid,
of lytic activity during storage at ambient temperatures.
The potential contamination of algae by hemoiytic photosynthetic
bacteria poses the question* Do hemoiytic strains represent possible
pathogens for man or domestic animals? Again, if it is assumed that the
lysin is a protein, then it is likely that it will be degraded by pro-
teolytic enzymes in the digestive tract.
It seems important to keep in mind that photosynthetic bacteria
are not the only potentially hemoiytic microorganisms in algae ponds.
It is highly likely that a large number of non-photosynthetic bacteria
are also present in such ponds, and that a fraction of these may also
produce lysins.
One way of looking at the problem of photosynthetic bacteria in
algae ponds is to consider the pond as an enrichment culture. The high
concentrations of organic hydrogen donors and ammonium nitrogen favors
the growth of photosynthetic bacteria over other microorganisms in the
pond, bacterial photosynthesis competes with algal photosynthesis for
CO-s finally, the growth rate for photosynthetic bacteria is probably
two or three fold more rapid than that of most algae.
Cooper (9) has noted that the population of photosynthetic
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42
bacteria in waste treatment ponds seems to depend upon the organic
loading rate. At high loading rates, the ponds become anaerobic and the
photosynthetic bacteria become conspicuous| at low loading rates, the
algae are favored, the pond becomes aerobic, and the photosynthetic
bacteria are suppressed. Cooper has commented that regardless of load
rate, the ponds that he studied functioned well. These observations
suggest that the photosynthetic bacterial population in algae ponds can
be controlled by maintaining the loading rate below the level that
favors the enrichment of these bacteria over the algae.
Summary« Non-sulfur photosynthetic bacteria were isolated from the
algae pond. When pure cultures were isolated, and tested on sheep-
blood agar plates, all strains of Rhodopseudomonas and Rhodospirillum
were capable of lysing red blood cells. The lytic reaction is produced
only in the presence of oxygen. Such lytic activity may have a bearing
on the feed value of recycled algae from the system.
Discussion of Pilot Plant Studiest
Design Considerationsi Pond area required per bird is a determining
factor with respect to the economic feasibility of incorporating an
algae production pond into a system of the type described in the study
reported herein. In the experiments, a pond surface area of 7 sq ft
was originally alloted per bird. However, the loading to the pond
resulting from this large surface area allotment proved to be far less
than the capacity of the pond to treat the wastes. Through successive
partitioning of the pond, it was found that a surface area of - 2 sq
ft/bird was as adequate as 7 sq ft per bird. As stated in the opening
paragraphs of this report, the project unfortunately had to be terminated
before the minimum permissible area per bird could be determined. However,
-------
the closer the minimum surface area is approached^ the less the safety
factor becomes in terms of satisfactory waste treatment. There is the
possibility;, or even likelihood* that during seasons of the year un-
favorable to algae growth, the 2 sq ft/bird may be less than adequate.
However, as the studies showed, the deficiency can be easily met by
resorting to a simple form of mechanical aeration. An economic analysis
would have to be made to determine the trade-off point at which cost of
land area balances cost of purchase and operation of equipment for
mechanical aeration. All things considered, the 2 sq ft of pond area/
bird dimension probably will prove to be generally applicable.
Water requirements for flushing need not be the limiting factor
in reducing areal requirements, since only about two-thirds of a gallon
(about 2.5 liters) of water per chicken per day is required to clean
the troughs and provide a 1% (wet weight) manure slurry. This water
could be supplied to the system by way of overflow from the chickens'
drinking water troughs.
Roof Pondst A portion of the land area required for the algae pond could
be reduced by constructing an algae pond on the roof of the poultry
enclosure. (By coincidence in the study reported herein, the surface
area of the partitioned (i.e. active) portion of the pond proved to be
about the same as the floor area of the poultry enclosure.) The design
load of the substructure of the poultry enclosure would have to be in-
creased to accommodate the added weight load of the pond and its contents
(62.4 Ib/sq ft-12 in water), as well as the impulse loads attending the
recirculation of the algal culture. Moreover, the roof also would have
to be curbed and waterproofed to a greater degree than is practiced in
normal construction. However, the increased design loading would be
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44
no greater than that generally made for snow and wind in many parts of
the U.S. The head provided by the elevated culture would permit flushing
of the manure by simple systems, as for example electrically activated
valves connected to timers <, The pond would serve as an insulation for
the poultry enclosure, thus providing some degree of cooling in the
summer and reducing heat loss during the winter. Heat lost into the
culture from the poultry enclosure during winter would raise the tempera-
ture of the pond culture somewhat, and thus the efficiency of the culture.
Heat exchange between the enclosure and the pond might be sufficient to
diminish or eliminate freezing in areas where sustained freezing normally
occurs.
Harvesting Algaet There is no need for an extensive dissertation on
the uses of harvested algae in this report, since the use of algae as
a feedstuff is well documented in the literature. According to Grau and
Klein (13) and Hintz and Heitman (14), algae in either the dried state
or as a dewatered paste can be used with good results as a protein sup-
plement in the diet of chickens, ruminants, and swine. If a market for
the algae as a feedstuff should fail to develop, the product could be
used as a high-grade fertilizer. If used as a fertilizer, the algae
could be pumped to the fields directly after the initial removal, there-
by eliminating the cost of dewatering and drying steps. Yet another fate
for the harvested algae could be digestion in the enclosed digester.
Regardless of the ultimate use of algae removed from the pond, some
harvesting will probably have to be done in a practical operation to
provide a detention period for the algal population. Experience with
algal cultures, as well as with any microbial culture, has shown that
once an optimum population density of the organism in question is
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45
exceeded; the activity of the population as a whole declines quite
rapidly. Consequently to maintain the pond at its peak oxygen production
efficiency, some algae would have to be harvested.
Neither the need for algae removal nor the amounts needed to be
removed were fully explored in the present study. Obviously, the amount
to be removed would depend upon the rate of algal growth. Hence, more
would have to be harvested in the summer than in the winter. The study
showed that algae could be removed from the pond culture either by
centrifugation or by natural settling. The slurry resulting from either
method of separation could be easily air dried. The authors estimate
that in a large-scale operation, dried sewage-grown algae could be
produced for about $0.04/lb. Feeding the algae as a wet paste, i.e.
directly after the dewatering step, would lower the cost of production
by an estimated 3#/lb.
If the algae product is to be used as a fertilizer, then undoubtedly
separation by natural settling would be indicated. Nonalgal solids also
could be removed in this manner by operating the pond mixing pumps while
the pond effluent is being discharged to the harvesting settling tank.
An alternative to the use of a separate settling tank for harvesting
algae through natural settling would be to construct in the algae pond
a narrow, deep pit having a cross-sectional design comparable to that
of an Imhoff tank. Algal and nonalgal solids settled in this pit could
be periodically or continuously removed and pumped directly to the
digester, or to the fields, or to dewatering and drying units. The
settling tank as well as the anaerobic digester could be located below
the chicken house, resulting in a saving of land.
Practical Scale Systems; Findings made thus far are sufficiently
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advanced to make it possible to directly adapt portions of the pilot
plant system to a large-scale egg-laying operation without undue dif-
ficulty. The manure troughs and flushing units could be easily formed
of sheet metal and be fabricated into a conventional poultry battery
arrangement. The manure trough scheme would be especially suitable in
a multi-storied operation, in which at present a barrier has to be
interposed between each story of poultry batteries to shield the birds
in the lower cages from the droppings of those in the upper cages. The
manure trough would serve that function.
The sedimentation tank could be a conventional open tank. A
substantial part of the required culture volume could be ponded on the
roof of the poultry shelter. Depending upon the market, algae either
could be harvested by flocculation (or centrifugation) or by simple
settling.
If the.system is to include an anaerobic phase, this phase could
consist either of a closed digester or of an anaerobic lagoon system.
The utilization of an enclosed heated digester probably would be justi-
fied only in an extremely large enterprise, or where land use must be
kept at an irreducible minimum because of high land costs, or where even
a low level of odor emanation would not be tolerated. Although the
gas wasted from the digester in the experiments had some odor, odor
problems would not plague a practical operation because the waste gases
would be combusted. In cases where a digester would not be warranted,
an anaerobic or facultative lagoon might be used to receive the settled
solids from the sedimentation tank. This would be especially attractive
in situations in which the solids could be discharged into irrigation
pipes during the crop-growing season. The settled solid could also be
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47
dewatered, dried? and used as a low-protein feedstuff for ruminants.
One might feel that even in operations somewhat smaller than the
type named above, the use of a closed digester would be justified if the
gas were burned and the heat used to heat the digester and to dry algae.
The applicability of this assumption would depend on the market value of
combustible gases, i.e. would the savings in gas purchase outweigh the
expenses involved in constructing and operating the digester.
Outflow from the sump (i.e. discharge to the environment) can be
set at any desired level, even to the point of closing the system. Should
an extensive prolongation of the operation of the integrated system as
a closed system eventually prove to be unfeasible, even then effluent
discharged to the environment would require no further treatment. The
reason is that the sump outflow would be passed through the algae har-
vesting subcomponent of the system, with the result that algae would be
removed, and the effluent, now devoid of algae and most of the nutrients
conducive to algal regrowth, would have received the equivalent of
secondary and tertiary treatment.
Economics» While it would be somewhat presumptious to attribute a. high
degree of accuracy to projections made at this time on the economics of
the process, one should be made so that a basis for a judgment can be
had with respect to the order of magnitude of the economic feasibility
of such a system. Moreover, by being aware of the factors which limit
the firmness of the analysis, one can arrive at a reliable conclusion
as to the degree of the accuracy of the analysis. One factor which would
detract from the firmness of an economic analysis at this time is the
fact that the present study had not progressed far enough to supply the
firm data needed in making an analysis. Insufficiently known variables
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are the actual pond area requirements9 the actual market value of the
algal product, the food and Barket value of manure processed for use as
a feedstuff for other animals» and certain of the operating conditions.
Other variables9 unknown for specific situations, but for which ranges
of values can be set up are climatological factors (temperature, solar
radiation^ wind, rainfall, etc.), land use, and costs, market value of
the products other than algae and processed manure (e.g. eggs, fryers,
etc.), economics of manure use, disposal, labor, and equipment costs.
An analysis made as a part of this study for a 100,000-bird
operation is summarized in the information given in Table 2. The
analysis was made in order to arrive at the maximum practical cost of a
system which would include a heated digester, hard-surfaced algae pond,
and algae-removal equipment. If desired, the digester could be replaced
by a facultative pond. If this were done, no hard surface would be
applied to the facultative portion. Algae removal could be by settling
rather than by centrifugation.
The poultry enclosure additions under the heading "Construction
and Equipment Costs" in Table 2. include those required for the hydraulic
system, namely, manure troughs, flushing mechanisms, etc. The incorpora-
tion of the manure troughs, flushing mechanisms, etc., into the chicken
battery assemblies at the time of fabrication would undoubtedly save a
considerable portion of the $5,000 allotted for these items. The capacity
of the sedimentation tank was designed for a 2-hour detention time. For
practical purposes two tanks should be used, so that one can be by-passed
for maintenance. The estimate was based on two rectangular shaped re-
inforced concrete tanks with sloping bottoms. Sludge and supernatant
pumps, as well as the necessary plumbing were included in the estimate.
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TABLE 2
Estimated Capital and Maintenance Costs of the Waste Handling
Facilities of a 100,000 Egg-Laying Poultry Operation Utilizing
Photosynthetic Reclamation and Hydraulic Transport
Construction and Equipment Costs* Estimated Costsa
Poultry Enclosure Additions $ 5,000
Sedimentation Tank + Pumps, etc 5,000
Digester(s) + Appurtenances .. 50,000
Algae Pond (including land, pumps, etc.) 100,000
Algae Removal Equipment (Batch Centrifuge
and Drying Facilities) ... 10,000
TOTAL $170,000
Fixed Costs*
Depreciation (10 yr - straight line) $ 17,000
Working Capital - 7% 11,900
TOTAL $ 28,900
Utilities and Maintenances
Utilities and Repair of Equipment $ 5,000
Additional Labor 5.000
TOTAL $ 10,000
Total Estimated Annual Cost $ 38,900
Total Estimated Cost per Chicken per Year .39
Total Estimated Cost per Dozen Eggs .02
'1970-dollars*
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50
The digester cost was based on unit prices developed by
Taiganides et al. (15) for animal manures with the capacity based on the
approximate organic loading of 0.09 Ib VS/cu ft. The design utilized
for developing the unit prices was based on the fairly sophisticated
type of digester typically found in municipal sewage treatment plants.
It was assumed that the digester gas would be utilized as the fuel for
heating the digester contents.
Although it is not considered likely that expensive surfacing
would be required, nevertheless the cost of a hard-surfaced algae pond
(i.e. asphalt, gunite, etc.) including medium-priced agricultural and
mixing equipment, transfer pumps, etc., is estimated to be $10,000/acre.
At the pilot p'lant loading based on approximately 7 sq ft/chicken, 16
acres would be required. However, since the performance of the pilot
plant pond indicated that the area required per chicken could be safely
reduced to 2 sq ft, it would be excessively conservative for evaluation
purposes to extrapolate from the full 7 sq ft/chicken. On the basis of
2 sq ft/bird, the pond area would be 5 acres. Therefore, in making the
evaluation, the range of indicated areas was taken into consideration
and the safe operational pond area was assumed to be 10 acres (4.36 sq
ft/bird). The unit price for the pond area would be the same regardless
of whether the pond was installed on the roof of the poultry enclosure
or on the ground.
The $10,000 allotted for algae removal leaves considerable latitude
in the size and type of batch centrifuge and drying facilities used.
The production of saleable high-protein algae suitable for animal feed
supplements is an ancillary benefit that was not included in the economic
analysis given in Table 2. Depreciation was calculated on a straight
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line for a period of ten years. Working capital was assumed to be 7%.
Utilities and repair of equipment will vary with the region* however,
$5,000 should cover most regions for the anticipated type of equipment.
The $5,000 allotted for additional labor was assumed to cover the wages
of a laborer on a one-half time basis.
The total estimated annual cost was $38,900 or 39Cifchicken for the
100,000-bird operation. Based on the expected average egg production,
this would amount to 2$/dozen eggs. If the cost benefits of algae pro-
duction were taken into consideration, the net annual cost would be
reduced by at least $9,800. This figure is based on a value derived
from only that fraction of the algae actually harvested by centrifugation
in the experiments, and hence is much lower than would be the case in
an operation in which algae production was emphasized. The bases for
the $9,800 estimate are on algal yield of 6 tons/acre-yr and a market
value of $100/ton. (The harvesting costs were included in the overall
$38,900 estimate—see Table 2). The quoted market value is based on a
compromise between the two demonstrated potential uses of the algal
product, namely as a substitute for fish meal or for soybean oil meal.
Fish meal sells for about $150/ton, and soybean oil meal for approximately
$80/ton (16). As was stated earlier, in the experimental run, harvest-
ing was carried on only for about 6 hrs/day and 5 days/week. Experience
with algae production on waste waters indicates that the annual yield
could well be 20 tons/acre-yr. Assuming a more realistic and yet con-
servative yield of 12/tons acre-yr, the market value of the algal crop
then would be $19,600/100,000 hens, or an annual cost of about 20$/bird-
yr. This reduces the wastes handling costs to approximately one cent
per dozen eggs.
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52
Linton (17) reported in 1966 for two rural New York counties an
average manure handling cost of 0.75
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53
mental enhancement, closed systems for conveyance, treatment and re-
generation of animal manure should be considered as a major alternative
to other methods in the design of wastes systems for the future.
TREATMENT OF POTATO WASTES THROUGH ALGAL CULTURE
Introduction
The possibility that micro-algae could be produced on potato
processing wastes had been suggested during a presentation before the
potato industry at Sun Valley in 1963 (18). At that time, there was
no information to indicate whether or not algal growth on potato wastes
was a feasible concept; and indeed it was unknown whether algae culti-
vation could be practiced economically with any waste but sewage. In
the intervening years, however, algae culture studies have been extended
to include beet sugar flume wastes, Steffens waste, and chicken manure.
Moreover, two studies have been made on growing algae in potato wastes.
The first involved the potential of potato wastes to support algae in
an aerobic system, and the second involved anaerobic fermentation of
potato wastes as a step toward algal growth.
The literature on potato wastes reports little concern to date
for the problem of plant nutrients (19, 20). However, analyses showing
the major characteristics of the wastes do exist. The data listed in
Table 3 give an idea of the nutritional quality of potato wastes as
compared to that of other wastes. As is now well known, carbonates,
nitrates, phosphates, and other oxides are produced in the bacteriological
decomposition of all wastes, including those from potato processes.
Based upon the nitrogen content, the algal growth potential (AGP)
of the potato waste listed in Table 3 is 1,800 mg per liter. As based
on phosphorus, it is 2,000 mg per liter. Using BOD as a basis, there
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TABLE 3
Comparison of Domestic Sewage, Beet Flume Hater*
and Potato Waste With Standard Algae Nutrient
Character is tics
Total Solids
Volatile
Total N
Organic N
Ammonia N
Nitrate N
Phosphorus (P)
Sulfur
Potassium
Alk. mg/liter
as CaC03
5-day 20°C BOD
pH
Magnesium
Calcium
Trace Minerals
Domestic
Sewage
800
500
60
28
30
2
20
8
12
200
350
7-8
18
7
Pres.
Beet Sugar
Wastes
3000
1500
50
20
30
5
100
80
500
1000
9-11
—
—
Prob. pres.
Standard Algae
Pilot Plant
(inorganic)
6250
—
315
—
—
315
300
300
1690
—
00
6
492
Must be add.
Potato
Wastes
4000
2500
180
170
10
1
20
—
100
2500
9-11
Prob. pres.
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55
is sufficient carbon in the waste to yield an algal crop of about 1,500
mg per liter of waste. Thus, it appears that carbon may limit algal
growth in some potato waste. Since potato wastes are of organic origin,
it is logical to assume that all trace elements are present although
this could be erroneous if precipitation of polyvalent metals were to
occur due to the high pH of the wastes.
Experimental»
To determine how much of the algal nutrients in potato wastes
actually are available for algal growth, experimental work was initiated
which involved the use of bioassays as the major experimental procedure.
The assays were carried out in accordance with procedures for
AGP determinations, which are currently under standardization by EPA
(21). Essentially, the tests involved serial dilutions of the waste
with water and inoculation of the dilutions with bacteria and algae.
The inoculated samples were then incubated in the light and at tempera-
tures such that bacterial and algal growth occurred freely. The tubes
were mixed and sniffed daily for odor. If found to be odorous, the
indication was that algae growth in the dilution at hand was insufficient
to meet the oxygen demand of the bacteria at that time. In samples that
were fresh-smelling, the algae were evidently meeting the oxygen demand
of the bacteria. At the end of the incubation period indicated by
no further increase in algae growth, and in this case in 10 days, the
dry weight of algae was determined and its oxygen equivalent compared
with the BOD. The oxygen equivalent or theoretical oxygen production
(TOP) was computed by multiplying the algae concentration (C ) by 1.6.
Results of a typical experiment are listed in Table 4. Judging
from the amount of nitrogen and phosphorus removed from the waste, the
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56
TABLE 4
Photosynthetic Oxygen Production in Potato Waste
No.
1
2
3
4
5
6
Algae
ml
2
2
2
2
2
2
Water
ml
0
50
66
85
91
98
Potato Waste
ml
100
50
33
16
9
2
BODb
mg/1
1980
990
660
396
200
40
'CC
mg/1
— •
875
800
437
138
50
TOP
mg/1
—
1400
1270
700
220
80
TOP
BOD
—
1.42
1.89
1.76
1.10
2.00
aN = 150 mg/1; P = 12 mg/1
Based on 60% depletion of 02
Concentration of algae in mg/1
TOP - theoretical oxygen production
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57
AGP of the waste was 1500 mg/liter for N and 1200 mg/liter for P. Based
on the actual AGP attained, the 50% dilution produced 875 mg/liter of
algae„ Thus, it appears that following bacterial action, most of the
nitrogen and phosphorus became available to algae, and in addition algae
growth was stimulated to an extent wherein the actual concentration of
nitrogen in the cells fell below 10% and the concentration of phosphorus
in the cells fell below 1%. For example, assuming that phosphorus was
a limiting factor in the test, the ratio of phosphorus in the cells must
have been 600/875 x .01 = .0069%. A shortage of phosphorus in the waste
would account for the decreased TOP/BOD ratio in the 10% dilution.
It is significant that in all cases where growth occurred the
TOP/BOD was greater than 1. Failure of algae to grow in the undiluted
waste in this test was attributed to pH level in excess of that favorable
to bacterial action. However, at the end of 10 days, some green became
apparent in the undiluted samples; and after 20 days, they too became
green. It was concluded that a stronger inoculum of algae adapted to
potato wastes might grow rapidly in pure potato waste with adjusted pH.
This was found to be the case. Accordingly, algal cell material from
previous growth experiments was conserved and used for inoculum in sub-
sequent experiments. This proved to be practical since adapted algal
inoculum was found to grow very rapidly in full-strength potato waste.
The possibility that phosphorus or pH limited the growth of
algae on potato waste was tested by assays similar to those described
above. Growth in pure waste following phosphate addition and carbonation
was to be compared with growth in the pure waste attained in a HI dilution.
The pH of potato waste was lowered from pH 10 to 6 by bubbling CO- through
the waste for two minutes. The rate of bubbling was about 0.2 SCUF pure
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58
C0_ per minute in a 1-liter vessel of waste. After the waste had attained
a pH of 6.0, triplicate flasks were inoculated with 5 ml of adapted
inoculum and incubated for 8 days. The mean growth is indicated by the
data in Table 5.
Similarly in testing the effects of phosphate addition, H PO^
was added to give a final concentration increment of 8 mg per liter of
available phosphorus as P. Again, triplicate samples were incubated and
the concentrations of algae determined as a function of time. Mean growths
are listed in Table 5. To further test the efficiency of HI dilution
of the potato wastes in tap water, triplicate samples were made up and
incubated as above. The concentrations of algae are shown in Table 5.
The results show that algae grow vigorously in raw undiluted potato waste
if either phosphate is added at the 8 rag/liter level, if carbonation is
applied, or if the waste is diluted HI. In each case the 8-day growth
represented a theoretical oxygen production greater than the BOD of the
waste. Early in the test some odors were noted but they became negligible
by the third or fourth day. The TOP/BOD ratio was 1.3 for phosphate
addition, 1.23 for carbonation, and 1.46 for dilution. Thus, although
carbonation and phosphate addition resulted in higher growth rates,
simple dilution resulted in superior oxygenation and a shorter period
of odor production.
A study of odor emission was made concurrently with all other
tests. A more precise experiment was subsequently conducted. To assure
that odor-forming organisms would be present, a weak domestic sewage
having a BOD less than 100 mg/liter was used as dilution water. As is
evident from the data on odor production given in Table 6, odors persisted
in the concentrated wastes up to 7 or 8 days, whereas the HI diluted
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59
TABLE 5
Concentration of Algae (C ) and Theoretical Oxygen Production
(TOP)a Under Phosphate Addition, Carbonation, and Dilution1*
Time
Days
1
2
3
4
5
6
7
8
100 ml PW
8 mg/1 P
C
c
(mg/1)
490
840
1090
1340
1470
1540
1580
1600
100 ml PW
CO to pH 6
* C
c
(mg/1)
250
512
700
870
1060
1230
1400
1520
50 ml PW
50 ml water
C
c
(mg/1)
210
420
615
755
850
880
910
910
obtain theoretical oxygen production, multiply C x 1.6
Inoculum - 5 ml algal suspension
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60
TABLE 6
Odor Endurance at Various Dilutions of
Potato Wastes in Domestic Sewage
Sewage
ml
90
85
80
75
70
65
63
58
53
48
43
38
33
28
23
18
13
8
3
0
Potato
Waste
ml
»
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
Algae
Seed
ml
5
5
5
5
5
5
2
2
2
2
2
2
2
2
2
2
2
2
2
2
Days
123456789 10
+ 4-0000000 0
+ + 0000000 0
+ + -000000 0
+ + + 000000 0
+ + + 000000 0
+ + + 00 0-0 00-0
+ + + -00000 0
+ + + + 00000 0
+ + + + 00000 0
+ + + + -0000 0
+ + + + 00 000.0
+ + + + 00-000 0
+ + + + + 0000 0
+ + + + + 0000 0
+ + + + + -000 0
+ + + + + + 000 0
+ + + + + + + 00 0
+ + + + + + + 00 0
+ + + + + + + -0 0
+ + + + + + + 00 0
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61
waste became odorless in about A days. The indication here is that in
any system* detention periods of at least 5 days should be used, and
treated waste should be recycled at least HI in order to avoid odors.
Preliminary studies on the anaerobic fermentation of potato
wastes indicate that although potato wastes are subject to methane fer-
mentation* extended continuous fermentation will not sustain itself
without provision for pH and odor control. Thus* in any system in which
anaerobic fermentation is applied to pretreat potato wastes for subsequent
algal growth* recirculation and dilution of the waste with buffered final
effluent water would be desirable.
Discussion*
From the preliminary data presented herein, it is evident that
the potato wastes contain the nutrients needed for algal culture, and
that a system can be designed in which algae provide all of the oxygen
required for oxygenation and complete treatment. If the entire algal
growth potential of the waste were exerted* production would be on the
order of 1*200 rag of algae per liter* or about 5 tons per million gallons
of waste processed. At 5 cents per pound* the value of the algae would
be on the order of $500 per million gallons of potato waste.
To obtain such quantities of algae* a completely controlled
system would be required and could be obtained only with a substantial
capital investment. The problems of inclement weather would have to be
compensated and complete mixing of the system would be required. However,
it seems likely that if a suitable market could be found for the algal
product, such an investment would be justified. There is a new system
for growing algae in greenhouse fashion, but it remains to be seen
whether such a complex system would be justified for by-product recovery
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62
from potato wastes. One such system is the algatron (22) in which cul-
tures of algae as dense as 6 grams per liter can be produced in as little
as 12 hours' detention period. If such a system could be justified
economically* there is little doubt that complete in-house treatment and
reclamation of potato wastes could be attained essentially independently
of weather.
The beneficial effects one might hope to attain from the utiliza-
tion of algae culture in treating potato wastes would be an improved
effluent, reduced aeration costs resulting from economic production of
oxygen, reduction in odors of holding ponds, production of by-product
algae, and nutrient stripping. Theoretically at least, use of a waste
for algae production is comparable to use of wastes for irrigation of
crops with two exceptions. Algae production per unit of area is 10-
to 20-fold that of crop production; and with algae production, most of
the water is not consumed and hence can be used for irrigation directly,
or reused in the plant following algae removal. From a production stand-
point, intensive algae culture on potato waste would yield algae aes-
thetically suitable for human consumption.
A major deterrent to growth of algae on potato wastes is climate.
Potato production in northern latitudes from mid-September to early May
bridges the winter months when algae growth is most limited. Thus algae
culture on potato wastes must be applied during early fall and late
spring, with alternate methods used during the winter. The alternative
is to store the wastes for processing during the summer. Another al-
ternative is greenhouse culture applied the year around. The latter would
be expensive and hence only economically feasible if algae could be solid
in large volumes at moderately high prices. The cost of greenhouse algae
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63
production would most likely be 20 to 30 cents per pound—a cost greatly
exceeding that of production in outdoor ponds. Because the greenhouse-
produced algae would be a pure by-product of a vegetable processing system,
the product might command a price of 50 cents per Ib on the open market,
which would offset the high production cost. The benefits of waste treat-
ment, nutrient stripping, and water recovery would also accrue to the
industry if greenhouse culture were practiced.
Conclusions
The results reported herein indicate that large quantities of
edible algae can be produced from potato wastes concurrently with com-
plete oxidation of the waste and removal of algae nutrients. More in-
tensive investigation of the kinetics of algae growth in potato wastes
should be carried out in the near future. Studies should also be under-
taken to examine the benefits and disadvantages of combining vegetable
and animal wastes in integrated regenerative systems.
IV. POTENTIAL OF PHOTOSYNTHESIS IN WASTE TREATMENT SYSTEMS
GENERAL CHARACTERISTICS
As is well known today, conventional waste treatment systems which
were suitable a very few years ago to the preservation of a healthful and
aesthetically satisfactory environment, no longer are adequate to meet
the burden imposed upon them under present-day conditions, nor would
they be able to do so under the forecasted future conditions. Conven-
tional waste treatment processes traditionally have been designed around
the concept of the biostabilization of degradable organic wastes to
decrease their oxygen consumption capacity (BOD). In general, these
processes have been concerned mainly with providing some means of
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64
oxidizing organic products, and very little with the products of this
oxidation or of the minor nutrients not affected by the treatment process.
The situation now has changed* and attention is being devoted not
only to the problem of oxidizing the organic wastes, but also to that of
preventing from entering receiving waters those substances in municipal
and agricultural wastes which could support undesirable aquatic growth
in the receiving waters. As a consequence, more and more waste water
treatment plants are being modified or new ones constructed to have the
capacity not only of decreasing the BOD of the waste waters but also of
reducing the concentration of nitrogen and phosphorus in the waters. The
difficulty is that although carbon, nitrogen, and phosphorus are essential
to aquatic growths, merely removing even a large percentage of the sub-
stances from organic wastes does not always sufficiently decrease the
algal growth potential (AGP) of the waste waters so treated (23).
Apparently, in organic wastes an unassessed concentration of vitamins,
certain amino acids, and trace elements, remain in the effluent in
quantities sufficient to stimulate a leisurely growth of algae in the
natural environment.
It is in the removal not only of oxygen-demanding substances and
of nitrogen, phosphorus, and carbon, but also of the biostimulants that
treatment systems involving the culture of algae are especially useful.
Hence, the wastes management system described herein is especially valuable
in those situations in which complete (i.e., primary, secondary, and
I
tertiary treatment is demanded. This function is served regardless of
whether the system is operated.as a closed or an open system. If
operated as a closed system, the effect is obvious; there is no effluent
and hence no discharge of nutrient to receiving waters. If operated as
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65
an open system, the effluent will have been subjected not only to con-
vential treatment but also algal culture, and hence the greater part of
the AGP will have been removed.,
TYPES OF APPLICABLE PHOTOSYKTHETIC SYSTEMS
Although the potential combinations of systems are many, four
types of photosynthetic systems stand out. They aret l) systems design
primarily for waste treatment} 2) regenerative agro-industrial complexes
designed as protein factories? 3) operation designed to convert solar
energy to the chemical energy of methane; and 4) small-scale regenerative
systems for family farms or small villages.
The first system is one in which wastes from a community or
industry are converted into algae in a line process, designed to take
only those wastes which require disposal. All algae produced in a plant
would be sold on the open market as a protein supplement, the water
recycled, and the values received would be used to defray a part or
perhaps all of the cost of waste disposal.
In the second system—agro-industrial complex designed as a pro-
tein factory—all animal wastes would be recycled in the system, and
exports consisting of animal products, rather than of algae, would be the
output of system. A hypothetical system of this type was described in
1962 (24), and the present report described a pilot plant application
of the type,,
The third system, namely a process for converting light (solar)
energy to the chemical energy of methane seemed rather exotic to the
authors in 1959, the time they conceived and developed the process
(25, 26)| but today, in view of the increasing concern over the con-
servation of energy, its approach to everyday practicability has been
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66
advanced considerably* The process involves an approach to solar power
that goes back to nature's sequence, namely solar energy to plant life,
to fuel by way of growing algae on wastes and digesting the algae to
produce methane* The algae fix the visible light spectrum of solar
energy into algal protoplasm. The algae are killed and subjected to
conventional anaerobic digestion. Through the digestion stage, the
chemical energy of cellular protoplasm is transformed into the chemical
energy of methane.
Although the fourth type of system appears to be feasible today,
it has not been demonstrated as a miniature regenerative system of sub-
sistence size designed to be incorporated in family farms or small
villages. Only excess animal products would be exported from the system,
and essential food, feed, and water would be imported. Such a system has
a substantial potential for decentralized waste disposal and recycle in
tropical countries having rural or semirural populations currently
existing at a lower than minimum standard of living. Geographically,
the system would find its most immediate and practical application in
countries characterized by the possession of a tropical climate. Cer-
tain key components of these regenerative systems were demonstrated as
being technically feasible on an experimental basis in the studies re-
ported herein. There is a high probability that they would perform much
better in tropical areas. This is because temperature, more frequently
than too little light, is the limiting factor to algal growth and bacterial
decomposition in the temperate zone. Temperature would always be near
optimum in many areas of India, and light would be more than adequate
except perhaps during the Monsoon season. Thus Bombay, Nagpur, or Kanpur
should be excellent locations for trying the system.
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67
A detailed description of the design for an application of the
fourth system is given in Appendix A.
V. RECOMMENDATIONS
Inasmuch as the advantages accompanying the application of photo-
synthesis to agricultural waste treatment, as was demonstrated by the
work reported herein, it is imperative that the additional research and
development needed to ensure its successful utilization in general practice
be given a high priority. The research remaining to be done was outlined
in the introductory remarks to Part III of this report. For the sake of
emphasis, they are repeated here» l) Determine the rate and extent of
solids (sludge and salts) build-up when the hydraulic portion of the
system is maintained as a "closed" system. ("Closed" is meant in the
sense that no water other than overflow from the animals' drinking water
supply is added to the system.) 2) Determine the required rate of
repletion of desired elements and removal of inhibitory substances.
3) Determine the minimum pond area requirements per bird or animal.
4) Assess the utility of dewatered settled solids residue as a feedstuff
for ruminants, especially with the protein content enhanced by adding
harvested algae to the material. 5) Try the system with animals other
than poultry—for example, dairy cattle or steers. 6) Determine the
effects of "scale-up" in questions 1 through 5 by conducting a demon-
stration-sized operation. 7) Determine the ability of animal wastes to
increase the treatability of vegetable wastes.
An appropriately sized demonstration operation for conduct at the
University's Richmond Field Station would be one geared to a pond having
an area of two-thirds acrej inasmuch as such a pond already is in
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68
existence at the Station* a pond area of that size would warrant a
facility having a capacity for 4000 hens.
The design specifications for such a facility are given in Table 7.
Information in the table covers all of the data pertinent to arriving
at the dimensions named therein, and is self-explanatory.
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69
TABLE 7
Design Specifications for a 4000-Bird Demonstration Facility
A, Equipment Available
1. Two-thirds acre high-rate algae pond
2. Algae removal equipment (continuous centrifuge; batch centrifuge;
drum dryer)
3. One-quarter acre anaerobic-facultative pond; bottom needs to be
cleaned of sulfur deposits and/or lined with plastic (visqueen).
4. Complete chemical laboratory, maintenance shop, etc.
B. Chicken Feed and Water
0.25 Ibs/bird-day (av feed consumption). 1000 Ibs/day = 30,000 Ibs/
mo = 15 tons/mo.
Assume feed costs $4.50/100 Ib or $90/ton. .*. 15 tons/mo x $90/ton =
$1350/mo Feed cost per month.
1. Feed Storage
3
Assume feed to weigh 50 Ib/ft , . °. one-months supply required
min. of 600 ft-* Net months feed storage requirements.
Farm agent and/or literature should be consulted for proper feed
storage construction.
2. Water Supply
Water troughs or pressure release valves. Farm agent or poultry
growers should be consulted for the amount of maintenance required
for each. Adequate quantity of water available at SERL.
C. Ejgg Production
Assume a maximum egg production of 75% of the original number.
.*. 4000 x 0.75 = 3000 eggs/day = 250 dozen/day.
For convenience in handling and marketing the eggs? could be sent to
a processor for cleaning^, candle ing, etc», except for eggs used in
analyses. The eggs should be counted and weighed.
Return on eggs may defray some operational costs of the project.
D. Manure Production
Assume wet manure production is 0.4 Ibs/day-bird. 4000 x 0.4 =
1600 Ibs/day.
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70
TABLE 7 (cont.)
Design Specifications for a 4000-Bird Demonstration Facility
Eo Expected Fatality Rate
Assume 1%% month. 4000 x 0.015 « 60 birds/month.
F. Chickens
Assume 20 week old pullets - cost $1.70/ea. 4000 x $1.70 = $6,800.
G0 Building
Assume bird density @ 0.5 ft /bird.
Assume aisle required© 0.5 ft2/bird.
.*. 1 tier - 1 bird/ft2 of floor area
2 tieis- 2 birds/ft2 of floor area
3 tiers- 3 birds/ft2 of floor area.
Assume the use of flushing manure troughs at a slope of 6 in per 10 ft.
For convenience, assume 2 tiers.
. *. 4000 birds 7 2 birds/ft2 = 2000 ft2 building.
Minimum feed storage 600 ft3. Assume feed storage @ 4 ft.
600 ft3 i 4 ft = 150 ft2.
Total area 2,000 ft2 + 150 ft2 = 2,150 ft2.
Assume 40 ft width. 2150 ft2 7 40 ft « 53.75 ft.
For building convenience, design structure 40 ft x 60 ft x 10 ft hieh.
1
)
'
10 ft high
3 0 13 El D 13 C
Metal roof, fiberglass
sides
Suggest construction
similar to pilot plant
_fi£L
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71
TABLE 7 (cont.)
Design Specifications for a 4000-Bird Demonstration Facility
H. Sedimentation Tank
Two 6 ft x 6 ft x 10 ft high cone, pits or two circular 8 ft dia x
8 ft concrete cyclinders. Two turbine pumps similar to the present
pilot plant one should be adequate, -v $600-$800 ea.
I. Misc. Equipment (depending on final design)
Pumps
Gauges
Metering devices
Centrifuges (manure solids separation).
Overhaul existing units as required.
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72
APPENDIX A
DESIGN OF AN ALGAL REGENERATIVE SYSTEM FOR
SINGLE FAMILY FARMS AND VILLAGES
A schematic diagram of a typical small-scale algal regenerative
system is shown in Figure A-l. In addition to its living occupants, the
system would involve an anaerobic digester, a series of algal growth
chambers9 a sedimentation chamber, sand beds, a solar still, and a gas
exchanger. Inasmuch as it is combined with a residence needing gas for
cooking, the anaerobic digester should be covered so that combustible
gas would accumulate under the cover at a pressure sufficiently above
atmospheric, to permit its conveyance. Excess gas, which would be rich
in methane, (i.e. 55 to 65%) would be conveyed from the gas dome through
conduits into the residence, where it could be used for household pur-
poses. Digested solids would be periodically drawn from the digester
to be used for soil conditioner or fertilizer in the growth of vegetables
on a soil plot nearby.
The hypothetical minimum sized system described above would pro-
vide waste disposal and nutrient recycle for 4 humans, 1 cow, and 50
chickens. Such a system was arbitrarily selected as the most elementary
that could be operated. Because of its small size it would be most
economical for research studies. Based upon design data collected for
a single family system, larger units could be made for larger populations.
The manner in which the size of the components of this family-
sized system was estimated, was as follows» The algae production unit
-------
SOIL CONDITIONER (CROPS)
DRY
ALGAE
EXCESS
SOLD
FEED
CARBOHYDRATE
AND OTHER
ANIMAL FEEDS
COW (I)
URINE 8
MANURE
CHIC KENS (50)
MANURE
URINE 8
MANURE
WASTED
FOOD
DIGESTED SOLIDS
ANAEROBIC
FERMENTATION
SUPERNATANT
MILK AND EGGS
WATER
CLOSET
HAND
PUMP
1
SURPLUS
SOLD
(™*\
I STORAGE I
COOKING
SYSTEM
REFRIGERATION
ILLUMINATION
CO,
RAIN
FLUSH WATER
URINE 8 FECES
MAKE-UP
WATER
ALGAE
GROWTH
SYSTEM
HUMANS
(4)
MILK AND EGGS
EXCESS RAIN
OVERFLOW
ALGAE
WATER
VAPOR
SEDIMENTATION
SOLAR STILL
DISTILLED
WATER
DISTILLED
WATER
STORAGE
FOOD
PREPARATION
DRINKING
RICE, CEREALS, VEGETABLES 8
SPICES (PURCHASED)
CO
FIGURE 9. SCHEMATIC DIAGRAM OF SINGLE-FAMILY MICROBIOLOGICAL ORGANIC WASTE
RECYCLE SYSTEM
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74
which is the most crucial part of the system was sized on the basis of
waste nitrogen from the contributing populationo For example, an
efficient milk cow may process 120 grams of nitrogen daily* excreting
20 grams in milk and 100 grams in feces and urine. An efficient laying
hen may process 3 grams of nitrogen daily, excreting 0.6 grams in eggs
and 2.4 grams in feces. With one cow and 50 chickens, the animal contri-
bution in waste would be 2,220 grams (4.9 Ibs) of nitrogen per day.
Each human excretes about 12 grains of nitrogen daily? therefore four
persons would waste about 48 grams of nitrogen per day. The aggregate
amount of waste nitrogen would then be 268 grams daily. Past experience
indicates that in such a system, nitrogen, phosphorous and other elements
would always be in excess with respect to carbon. It also indicates that
under such conditions the composition of the algae may be assumed to be
10% nitrogen, as compared with 6 to 8% nitrogen found in less nitrogen-
rich waters. Thus, if all waste nitrogen were to be recycled, the amount
of algae grown each day would be 2,680 grams (5.9 Ibs). If the pro-
duction rate is assumed to be 0.33 grams per gram of algae per day, the
standing biomass of algae required would be 8,130 grains (18 Ibs).
Assuming a concentration of 500 mg per liter, the culture volume re-
quired would be 16,250 liters (4294 gal).
In determining the design depth for a culture, experience has
shown that algal cultures which are adequately mixed will attain a con-
centration such that light penetrates to 1/3 the culture depth. Light
of daylight intensity will penetrate about 12 cm into a culture having
a concentration of 500 mg per liter, therefore the culture depth should
2
be 36 cm. A 36-cm deep culture occupies 28 cm /liter. Therefore to
contain about 16,250 liters one would need an area of 58 meters2
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75
(623.5 sq ft). This would be provided by a circular pond about 8.6
meters (28.2 ft) in diameter, but for structural uniformity, the dia-
meter selected should be about 9 meters. Thus a total area of about 64
sq meters (688 sq ft) would be provided by adding a small factor of
safety to the computed 58 sq meters. Thus a circular culture 64 meters
in area» 9 meters in diameter, and 36 cm deep is required. Practically
speaking, a culture of this volume and dimensions in India should pro-
duce between 2 and 5 pounds dry weight of 50% protein algae per day,
depending on temperature and light.
The size of the digestion element of the system was based on an
established microbiological minimum per capita criterion of 1 ft (0.028 m3)
for humans, 10 ft3 for cattle, and % ft3 for chickens. The minimum
aggregate volumetric digester requirement for a population of 4 humans,
50 laying hens, and one milk cow is 26 ft (0.736 m3). The minimum
manageable digester, however, should be 1 meter in diameter and 2.5
meters deep. This would provide an active volume of 55 ft3 (1.56 m3)*
which is almost twice the computed minimum requirement. Such an oversize
digester should provide superior fermentation and excellent gas con-
version.
The digester, as noted previously, should be provided with an
inverted dome-type cover for gas pressurization. It should also be
equipped with a charging chute through which the manures and night soil
and food and feed waste could be introduced to the liquid digestion
phase without permitting gas to escape. This may be accomplished by
constructing the recharge chutes with a side entrance below the water
lineo For most efficient use, the digester should be at the center of
the ponding system and living area so that overflow supernatant would
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76
move directly into the algal pond system, so that heat may be con-
served.
Although the algae culture would only be about 0.36 meters deep,
the algae pond walls should ba 0.5 maters high to provide freeboard.
The culture floor should slope slightly outward from the center so that
any settled algae would be moved away from the digester during mixing.
The pond system itself should actually be 3 concentric ponds in series,
offering protection against transfer to or survival of pathogens in the
final pond. Three or more ponds in series insures an excellent degree
of treatment.
In the outer final section of the pond system, a collector hopper
% meter wide and 1/3 meter deep would be provided as a sump in which
settleable algae could be collected. The algae would be drawn periodi-
cally through a valve into a watering system for the cow or onto sand
beds for drying. A total of 8 sq meters of sand beds involving 4 beds
of 2 sq meters each would be required. The sand beds should be under-
drained so that water could be collected and returned to the system if
needs be.
The human occupants of the system will require fresh potable, low
solids water. This would be provided by a 20 ft2 (1.86 m2) solar dis-
tilling apparatus mounted so that it captures vapor from the algal
culture. A 20 ft2 solar still would yield about 10 gallons (37.85
liters) of distilled water per day, which should be adequate for drinking
and cooking for 4 humans. During the monsoon, the solar still would be
used as a catchment area for rain water to be used in lieu of distilled
water. During the dry season of the year, evaporation would be exten-
sive from the algal culture surface, and on the hottest, windiest days
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77
could be as much as 757 liters (200 gallons) per day from the 64 sq
meters of surface. A source of makeup water will therefore be required.
«
Ground or surface water may be used, but it will have to be piped or
carried manually into the system each day. This water would be used
for bathing, for drinking water for the chickens (chickens are not
tolerant to salt), and for cleansing purposes. The quality of this
water should be carefully controlled lest excess spillage lead to un-
sanitary conditions. If the system were covered with transparent materials
to admit light but prevent evaporation, excess heating of the culture
probably would occur. However, the possibility of utilizing high-
temperature strains of algae in a system with transparent cover should
be investigated, since in a covered system the need to import large
amounts of water would be reduced. During heavy rains, the overflow
from the final pond of an open system would be suitable for disposal
to surface or ground waters.
Mixing of the algal system is essential and may be accomplished by
brooms or paddles. The floor of the pond should be constructed of
sufficient strength that individuals in boots could wade freely about
the bottom during the mixing process.
By placing the algal culture above the house, the entire digestion
and algal growth system could be located on a plot of land 10 meters by
10 meters; and should it be feasible to support the culture above the
ground, it would provide shelter and living space beneath it for the
animals and for the humans as well. While from a management standpoint
there would be large economic advantages to having larger than single-
family units, individual units would have the advantage that each family
could take personal responsibility for its own system, and those most
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78
diligent would benefit greatly from their own efforts.
A typical family unit of the size designed above and incorporated
in the shelter complex is shown in Figure A-2. In operation of the
system as shown, all manure, urine, wasted food, night soil; and clean-
up water would be charged into the digester shortly after it is produced*
or at least once daily. In the digester, fermentation once established
would occur steadily and gas would be produced. Operationally, par-
ticular care would have to be exercized to avoid the unnecessary loss
of any useful component; hence, providion should be made for all solids,
liquids, and gases to be recycled or consumed. In the digester, complex
substances would be decomposed in the form of organic acids, ammonia,
C02, and methane. The methane would be burned. With the addition of
the nutrients to the digester, soluble substances would be displaced
into the algae culture, where they would provide substrate for algal
growth. The methane, under slight pressure, would be available for
gas cooking} and the gases from the gas-fired burners would be vented
by convection to the algae culture, where a part of C(>2 content of the
gases would be absorbed by the growing algae. Algal slurry would be
provided to the cow as its sole source of drinking water, thus forcing
it to consume algal protein in the wet form. Excess algae in the trough
would be drawn onto sand beds and dried for use as cow or chicken feed,
or for sale.
If living space were provided below the algal culture, it would
provide shelter from the elements for both the humans and animals. The
algal culture and digester would provide a buffer against rapid changes
in temperature for the occupants, and the occupants would in turn to
some extent warm the algae culture and digester during cool periods.
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Area "\Entry
1
Digester
Overflow to Well Rain Collector
Excess Gas Exchange
Manifold"
Access Walkway and Ladder^
Settling Tank
Chicken Pens
'echarge Supply Well
and Pump
Overflow
to Sandbeds
from Digester
and Trough '
Potable Water Storage
Anaerobic Digester
with Charging Chute
Algae Cultures
Kitchen Area
with Gas Refrigerator,
Lighting and Burner
Stall with • ' »"
Water and Food Troughs
Bedrooms
Toilet and Shower
FIGURE 10. SCHEMATIC DIAGRAM OF A DWELLING UNIT FOR A FAMILY OF 4 AND THEIR
LIVESTOCK WHICH INCORPORATES A MICROBIOLOGICAL RECYCLE SYSTEM
FOR WATER, NUTRIENTS AND ENERGY IN A CONVENIENT AND HYGIENIC
ENVIRONMENT
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The system schematically shown in Figure A-2 is an advanced form
of unite ^frich theoretically could provide an ample and hygienic environ-
ment for a family and its essential livestock. Such a unit could be
bult of local materials or perhaps prefabricated for import. Because it
is largely powered by sunlight energy, the feasibility of such a system
should be greatest in tropical regions of the world, but it would be of
use in other areas during the summer period,, The advantages of such a
system would be provision of a highly livable system for its occupants,
provision of efficient decentralization of algal culture, efficient and
hygienic waste management, and the recovery of valuable nutrients and
water from wastes. Its major disadvantage would be the need for a sub-
stantial capital investment, a factor lacking for most impoverished
families. However, through experimental studies with prototype units,
functions and materials can be experimentally tested and, if required,
modified in such a way that costs can be minimized, and operations
perfected to a point at which the systems would be economically self-
supporting. If this were possible, an economic incentive would exist
for investors or for governmental agencies to provide such units on a
long-term loan basis. The economic base for repayments of loans would
come from maximizing production of milk, eggs, vegetables, and surplus
algae, and minimizing the cost of essential inputs to the system such
as supplementary feeds. Surplus eggs, milk, vegetables, and algae would
be sold or bartered, and a portion of the money used to repay the capital
investment for the system. A preliminary economic analysis indicates
that a gross income of between $250 and $1,000 per year could be realized
with such systems. Operationsl costs would be from $50 to $100 per year.
If the higher income level could be attained, such units would probably
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become economically attractive. On the other handy if only the lower
levels were reached, the use of such systems probably would be economically
infeasible or would require substantial subsidies*
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REFERENCES
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of a modified d4 technique for estimation of photosynthesis in large
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3. Odum, H. T0 1956. "Primary Production in Flowing Waters," Limnol.
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4. Odum, H. T., 1957. "Primary Production Measurements in Eleven
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7. Kemmerer, A. J. and Newhold, J. M. g 1969. A method for gross pri-
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13. Grau, C. R. and Klein* N. W., 1957. "Sewage-grown algae as a feed-
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14. Hintz, F. F. and Heitman, H. Jr., 1965. "Nutritive value of algae
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Fredericton, New Brunswick, Canada.
20. Keuneman, R. W.} Discussion of treatment of Idaho potato processing
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23. McGauhey, P.H. et al., May 1969. Eutrophication of surface Waters ~
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