&EPA
I mited States
•..TiriH.T't.'il PrOt!"
Agency
Roberts Kerr Environmental Research EPA-600/2-78-1 S3
I ytxiratory ju|y 1975
)K 74820
Research and Development
Water Quality
Renovation
of Anima! Waste
Lagoons Utilizing
Aquatic Plants
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been ouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. “Special” Reports
9. Miscellaneous Reports
This report has been assigned: to the ENVIRONMENTAL PROTECTION TECH-
NOLOGY series. This series describes research performed to develop and dem-
onstrate instrumentation, equipment, and methodology to repair or prevent en-
vironmental degradation from point and non-point sources of pollution. This work
provides the new or improved technology required for the control and treatment
of pollution sources to meet environmental quality standards.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/2-78-153
July 1978
WATER QUALITY RENOVATION OF ANIMAL
WASTE LAGOONS UTILIZING AQUATIC PLANTS
by
Dudley D. Culley, Jr.
James H. Gholson
Tom S. Chisholm
Leon C. Standifer
Ernest A. Epps
Louisiana State Agricultural
Experiment Station
Louisiana State University
and Agricultural and Mechanical College
Baton Rouge, Louisiana 70803
Grant No. R-803326
Project Officer
R. Douglas Kreis
Source Management Branch
Robert S. Kerr .Environmental Research Laboratory
Ada, Oklahoma 74820
ROBERT S. KERR ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
ADA, OKLAHOMA 74820
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DISCLAThER
This report has been reviewed by the Robert S. Kerr Environmental
Research Laboratory, U.S. Environmental Protection Agency, and approved
for publication. Approval does not signify that the contents necessarily
reflect the views and policies of the U.S. Environmental Protection
Agency, nor does mention of trade names or commercial products constitute
endorsement or recommendation for use.
11
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FOREWORD
The Environmental Protection Agency was established to coordinate
administration of the major Federal programs designed to protect the
quality of our environment.
An important part of the Agency’s effort involves the search for
information about environmental problems, management techniques and new
technologies through which optimum use of the nation’s land and water
resources can be assured and the threat pollution poses to the welfare
of the American people can be minimized.
EPA’s Office of Research and Development conducts this search
through a nationwide network of research facilities.
As one of these facilities, the Robert S. Kerr Environmental
Research Laboratory is responsible for the management of programs to:
(a) investigate the nature, transport, fate and management of pollutants
in groundwater; (b) develop and demonstrate methods for treating waste-
waters with soil and other natural systems; (c) develop and demonstrate
pollution control technologies for irrigation return flows, (d) develop
and demonstrate pollution control technologies for animal production
wastes; (e) develop and demonstrate technologies to prevent, control
or abate pollution from the petroleum refining and petrochemical in-
dustries, and (f) develop and demonstrate technologies to manage pollution
resulting from combinations of industrial wastewaters or industrial!
municipal wastewaters.
This report is a contribution to the Agency’s overall effort in ful-
filling its mission to improve and protect the nation’s environment for
the benefit of the American public.
C) € C
William C. Galegar, Director
Robert S. Kerr Environmental
Research Laboratory
111
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ABSTRACT
Duckweeds, Lemnaceae, were grown on a two stage dairy waste lagoon
system. Sp irodela oligorhiza exhibited greater growth than S. p lyrhiza in
spring and early fall, while the opposite occurred during the summer.
Lenina gibba (Clone G3) grew best during the fall, winter, and early spring.
Mixed cultures performed equally well compared to single clone cultures,
under static and mixing conditions.
Estimated annual yield on a per hectare basis indicated 22,023 kg
(dry weight) theoretically could have been produced based on demonstrated
highest treatment yields for each three month period. However, this
production is not as high as laboratory studies.
Nutrient content of duckweeds increases when grown on water containing
high nutrient co icentrations. Mean crude protein content of duckweeds
(irrespective of species and treatment) was 36%, but a high of 42% was
recorded. Duckweeds compare favorably with ingredients of high protein
supplements used in livestock rations. Results indicate that duckweeds
may be economical to use as a replacement for some common protein supple-
ment ingredients used in dairy cattle rations.
Based on the estimated annual yield and values of nutrients excreted
by dairy cattle, duckweeds recovered the nitrogen of 15.5 head, phosphorus
of 34.0 head, and potassium of 8.8 head on a per hectare basis.
Reductions in Total Kjeldahl Nitrogen, ammonium, and phosphorus were
significantly greater (P < .05) in duckweed covered test channels than in
controls. Summer reduction rates of Total Kjeldahl Nitrogen were 0.91 mg/il
day for test channels supporting stands of S. oligorhiza and 0.74 mg/i/day
for controls. Total Kjeldahl Nitrogen declined during the winter under
aerated conditions at rates of 1.27 mg/i/day and 0.82 mg/i/day on
S. oligorhiza covered channels and controls respectively. Ammonium
decline under aerated winter conditions showed rates of 0.035 mg/l/t 3 and
0.019 mg/l/t 3 for S. oligorhiza and controls respectively.
This report was submitted In fulfillment of Grant No. R803326 to
Louisiana State University and the Louisiana Agricultural Experiment
Station under the partial sponsorship of the U. S. Environmental Protection
Agency. This report covers the period July 1, 1975 to December 31, 1977,
and the work was completed as of December 28, 1977.
iv
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Foreword
Abstract
Figures
Tables
List of Metric Conversions
Acknowledgements
1. Introduction
2. Conclusions
3. Recommendations
4. Technical Background
5. Objectives
6. Methods
7. Results
Plant Screening
Waste Treatment Studies
Preliminary Feeding Trials
8. Discussion
9. References
10. Bibliography
CONTENTS
111
iv
vi
viii
xv
xvi
1
3
5
7
15
16
20
20
20
125
126
137
141
V
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FIGURES
Number Page
1 Campus dairy—herd facility showing location of feedlot
and milking parlor 17
2 Biochemical oxygen demand, chemical oxygen demand, total
residue, volatile residue, and fixed residue in static
dairy waste lagoon water with and wJthout duckweed
(S. oligorhiza) , spring, 1976 (Test lagoon 1) . . . . 31
3 TKN reduction and pH in static dairy waste lagoons with
and without stands of duckweeds, spring, 1976 (Test
lagoon 1)
4 5—day biochemical oxygen demand in static dairy waste
lagoons with and without stands of duckweeds, summer,
1976 48
5 Chemical oxygen demand in static dairy waste lagoons
with and without stands of duckweeds, summer, 1976 . . 49
6 Total residue In static dairy waste lagoons with and
without stands of duckweeds, summer, 1976 50
7 Volatile residue in static dairy waste lagoons with and
without stands of duckweeds, sununer, 1976 51
8 Fixed residue in static dairy waste lagoons with and
without stands of duckweeds, summer, 1976 52
9 Total suspended matter in static dairy waste lagoons
with and without stands of duckweeds, summer, 1976 . . 53
10 TKN reduction in test channels covered with duckweed,
and controls, summer, 1976 54
11 TOC reduction in test channels covered with duckweed,
and controls, summer, 1976 55
12 Standard bacteria plate count and anaerobic counts per
ml of composite samples of the test channels covered
with duckweed, and controls, summer, 1976 . . 60
vi
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Number ____
13 Fecal coliform per ml of composite samples of test
channels covered with duckweed, and controls,
summer, 1976 61
14 Fecal streptococci count per ml of composite
samples of test channels covered with duckweed,
and controls, summer, 1976 62
15 A schematic plan of an aquacultural waste treatment
system involving duckweed 135
vii
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TABLES
Number Page
1 NUMBER OF ANIMALS MAINTAINED UNDER FEEDLOT CONDITIONS 8
2 CHEMICAL COMPOSITION OF PARTIALLY DRIED Ricciocarpus
natans AND Azolla caroliniana GROWN ON DAIRY WASTE
LAGOONS UNDER WINTER CONDITIONS, JANUARY, 1976 21
3 CHEMICAL COMPOSITION OF DUCKWEED MAINTAINED IN LOW
NUTRIENT PONDS BEFORE USE IN LAGOONS RECEIVING
DAIRY CATTLE WASTE 22
4 CHEMICAL ANALYSIS OF CITY WATER, LAGOON SOILS, AND
23
5 BIOCHEMICAL OXYGEN DEMAND, CHEMICAL OXYGEN DEMAND,
TOTAL RESIDUE, VOLATILE RESIDUE, AND FIXED RESIDUE
OF STAGE 1 ANAEROBIC DAIRY LAGOON EFFLUENT AFTER
LOADING BEGAN (FEBRUARY 19, 1976) 25
6 STAGE 1 ANAEROBIC LAGOON TEN AND pH VALUES . 26
7 STANDARD PLATE COUNT, ANAEROBIC COUNT, FECAL COLIFORN,
AND FECAL STREPTOCOCCI COUNTS OF THE STAGE 1 ANAEROBIC
LAGOON EFFLUENT 27
8 RAINFALL DATA FOR TEST 1 STUDY PERIOD (CM) 29
9 BIOCHEMICAL OXYGEN DEMAND, CHEMICAL OXYGEN DEMAND,
TOTAL RESIDUE, VOLATILE RESIDUE, AND FIXED RESIDUE
IN mg/i OF STATIC DAIRY WASTE LAGOONS WITH AND
WITHOUT DUCKWEED (S. oligorhiza) , SPRING, 1976
(TESTLAG00N 1) 30
10 STANDARD PLATE COUNT, ANAEROBIC COUNT, FECAL COLIFOR14,
AND FECAL STREPTOCOCCI COUNTS IN STATIC DAIRY WASTE
LAGOONS WITH AND WITHOUT DUCKWEED ( . oligorhiza) ,
SPRING, 1976 (TEST LAGOON 1) 32
11 5. oligorhiza BIOMASS HARVESTED FROM STATIC TEST
CHANNELS RECEIVING DAIRY WASTE, SPRING,1976 34
viii
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Number Page
12 PARTIAL CHEMICAL ANALYSIS OF S. oligorhiza GROWN ON
STATIC TEST CHANNELS RECEIVING DAIRY WASTE, SPRING,
1976 35
13 PARTIAL CHEMICAL ANALYSIS OF S. polyrhiza GROWN ON
TEST CHANNELS RECEIVING A CONT.INTJOUS FLOW OF DAIRY
WASTE FROM THE STAGE 1 ANAEROBIC LAGOON, SPRING, 1976 37
14 BIOCHEMICAL OXYGEN DEMAND, CHEMICAL OXYGEN DEMAND,
TOTAL RESIDUE, VOLATILE RESIDUE, AND FIXED RESIDUE
OF THE STAGE 1 ANAEROBIC DAIRY LAGOON EFFLUENT . . . . . . . 39
15 STAGE 1 ANAEROBIC LAGOON WATER QUALITY 40
16 STANDARD PLATE COUNT, ANAEROBIC COUNT, FECAL COLIFORN,
AND FECAL STREPTOCOCCI COUNTS OF THE STAGE 1 ANAEROBIC
LAGOON EFFLUENT 41
17 RAINFALL DATA FOR TEST 2 STUDY PERIOD (CM) 42
18 BIOCHEMICAL OXYGEN DEMAND, CHEMICAL OXYGEN DEMAND,
TOTAL RESIDUE, VOLATILE RESIDUE, FIXED RESIDUE,
AND TOTAL SUSPENDED MATTER OF THE S. oligorhiza
TEST CHANNELS, SUMMER, 1976 43
19 BIOCHEMICAL OXYGEN DEMAND, CHEMICAL OXYGEN DEMAND,
TOTAL RESIDUE, VOLATILE RESIDUE, FIXED RESIDUE,
AND TOTAL SUSPENDED MATTER OF COMPOSITE SAMPLE
OF THE S. polyrhiza TEST CHANNELS, SUMMER, 1976 . 44
20 BIOCHEMICAL OXYGEN DEMAND, CHEMI AL OXYGEN DEMAND,
TOTAL RESIDUE, VOLATILE RESIDUE, FIXED RESIDUE,
AND TOTAL SUSPENDED MATTER OF THE COMPOSITE SAMPLE
FROM THE CONTROL CHANNELS, SUMMER, 1976 45
21 TKN, POTASSIUM, CALCIUM, TOC, pH AND WATER TEMPERATURE
OF TEST AND CONTROL CHANNELS, SUMMER, 1976 46
22 STANDARD PLATE COUNT OF COMPOSITE SAMPLES OF TEST
CHANNELS COVERED WITH DUCKWEED, AND CONTROLS,
SUMMER, 1976 56
23 ANAEROBIC COUNT OF COMPOSITE SAMPLES OF TEST
CHANNELS COVERED WITH DUCKWEED, AND CONTROLS,
SUMMER, 1976 57
24 FECAL COLIFORM COUNT OF COMPOSITE SAMPLES OF TEST
CHANNELS COVERED WITH DUCKWEED, AND CONTROLS,
SUMMER, 1976 58
ix
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Number Page
25 FECAL STREPTOCOCCI COUNT OF COMPOSITE SAMPLES OF TEST
CHANNELS COVERED WITH DUCKWEED, AND CONTROLS,
SUMMER, 1976 . . 59
26 PERCENT REDUCTION IN TEST AND CONTROL CHANNEL WATER
QUALITY AND BACTERIAL COUNTS, SUMMER, 1976 63
27 S. oligorhiza BIOMASS HARVESTED FROM STATIC TEST
CHANNELS RECEIVING DAIRY WASTE, SUMMER, 1976 65
28 S. o1yrhiza BIONASS HARVESTED FROM STATIC TEST
— CHANNELS RECEIVING DAIRY WASTE, SUNMER,1976 . . . . 66
29 PARTIAL CHEMICAL ANALYSIS OF S. oligorhiza GROWN ON
STATIC TEST CHANNELS RECEIVING DAIRY WASTE, SUMMER,
1976 67
30 PARTIAL CHEMICAL ANALYSIS OF S. p 1yrhiza GROWN ON
STATIC TEST CHANNELS RECEIVING DAIRY WASTE, SUMMER,
1976 68
31 WATER QUALITY OF TEST AND CONTROL CHANNELS UNDER
MIXED AND NON-MIXED CONDITIONS 70
32 CHEMICAL OXYGEN DEMAND (COD), TOTAL RESIDUE (TR),
VOLATILE RESIDUE (VR), FIXED RESIDUE (FR), AND
TOTAL SUSPENDED MATTER (TSM) OF MIXED AND NON-
MIXED CHANNELS 73
33 BIOMASS HARVEST OF S. oligorhiza AND S. polyrhiza
GROWN ON MIXED AND NON-MIXED TEST CHANNELS, SUMMER,
1976 74
34 CHEMICAL COMPOSITION OF S. oligorhiza AND S. polyrhiza
GROWN ON MIXED AND NON-MIXED TEST CHANNELS, SUMMER,
1976 75
35 WATER QUALITY OF TEST AND CONTROL CHANNELS WITH AND
WITHOUT THE ADDITION OF DAIRY WASTE EFFLUENT . . . . 77
36 CHEMICAL OXYGEN DEMAND (COD), TOTAL RESIDUE (TR),
VOLATILE RESIDUE (VR), FIXED RESIDUE (FR), AND
TOTAL SUSPENDED MATTER (TSM) OF TEST LAGOON 1
RECEIVING DAIRY WASTE EFFLUENT 79
37 CHEMICAL OXYGEN DEMAND (COD), TOTAL RESIDUE (TR),
VOLATILE RESIDUE (VR), FIXED RESIDUE (FR), AND
TOTAL SUSPENDED MATTER (TsN) OF TEST LAGOON 2
HELD STATIC 80
x
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Number Page
38 STANDARD PLATE COUNT (SPC), ANAEROBIC COUNT(AC), FECAL
COLIFORM (PC), AND FECAL STREPTOCOCCI COUNTS (FSC)
OF TEST LAGOON 1 RECEIVING DAIRY WASTE EFFLUENT 81
39 STANDARD PLATE COUNT (SPC), ANAEROBIC COUNT (AC), FECAL
COLIFORM (FC), AND FECAL STREPTOCOCCI COUNTS (FSC)
OF TEST LAGOON 2 HELD STATIC 82
40 S. oligorhiza BIOMASS HARVESTED FROM FLOODED AND STATIC
TEST CHANNELS RECEIVING DAIRY WASTE, SUMMER,1976 . . 83
41 S. p 1yrhiza BIOMASS HARVESTED PROM FLOODED AND STATIC
TEST CHANNELS RECEIVING DAIRY WASTE, SUMMER, 1976 . . 84
42 CHEMICAL COMPOSITION OF S. oligorhiza GROWN ON FLOODED
AND STATIC TEST CHANNELS, SUMNER, 1976 85
43 CHEMICAL COMPOSITION OF S. p yrhiza GROWN ON FLOODED
AND STATIC TEST CHANNELS, SUMMER, 1976 86
44 WATER QUALITY OF TEST LAGOON 2 RECEIVING DAIRY WASTE
EFFLUENT INTERMITTENTLY AND SUPPORTING A STAND OF
S. polyrhiza AND A MIXED STAND OF S. polyrhiza AND
S. oligorhiza, LATE SUMMER, 1976 . . . . 88
45 CHEMICAL OXYGEN DEMAND (COD), TOTAL RESIDUE (TR),
VOLATILE RESIDUE (VR), FIXED RESIDUE FR), AND
TOTAL SUSPENDED MATTER (TSM) OF TEST LAGOON 2,
FLOODED INTERMITTENTLY WITH DAIRY WASTE EFFLUENT,
LATE SUMMER, 1976 89
46 BIOMASS OF S. p yrhiza AND A MIXED CULTURE OF
S. pç yrhiza AND S. oligorhiza HARVESTED FROM TEST
LAGOON 2 FLOODED INTERMITTENTLY WITH DAIRY WASTE
EFFLUENT, LATE SUMMER, 1976 . . . . 90
47 CHEMICAL ANALYSIS OF S. p ].yrhiza GROWN ON TEST
CHANNELS PERIODICALLY FLOODED WITH DAIRY WASTE
EFFLUENT, LATE SUMMER, 1976 91
48 CHEMICAL ANALYSIS OF A MIXED STAND OF S. oligorhiza
AND S. pp yrhiza GROWN ON TEST CHANNELS PERIODICALLY
FLOODED WITH DAIRY WASTE EFFLUENT, LATE, SUMMER 1976 . 92
49 WATER QUALITY OF AERATED, STATIC LAGOON TEST CHANNELS
SUPPORTING STANDS OF S. polyrhiza , LATE FALL, 1976 . 93
50 WATER QUALITY OF AERATED STATIC LAGOON TEST CHANNELS
SUPPORTING A STAND OF S. oligorhiza , LATE FALL, 1976 . 94
xi
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Number Page
51 WATER QUALITY OF AERATED STATIC LAGOON TEST CHANNELS
SUPPORTING A MIXED STAND OF S. oligorhiza AND
S. p 1yrhiza , LATE FALL, 1976 95
52 WATER QUALITY OF AERATED STATIC LAGOON CONTROL
CHANNELS,LATEFALL,1976 96
53 BIOCHEMICAL OXYGEN DEMAND (BOD), CHEMICAL OXYGEN
DEMAND (COD), TOTAL RESIDUE (TR), VOLATILE
RESIDUE (VR), FIXED RESIDUE (FR), AND TOTAL
SUSPENDED MATTER (TSM) OF COMPOSITE SAMPLES OF
TESTLAGOONS1AND2 97
54 BIOMASS OF S. oligorhiza , S. polyrhiza , AND A MIXED (N)
CULTURE OF THE IWO HARVESTED FROM AERATED STATIC TEST
LAGOONS, LATE FALL, 1976 99
55 CHEMICAL ANALYSIS OF S. oligorhiza AN]) S. p 1yrhiza
GROWN ON AERATED STATIC TEST CHANNELS RECEIVING
DAIRYWASTE,LATEFALL,1976 100
56 WATER QUALITY OF AERATED, STATIC LAGOON TEST CHANNELS
SUPPORTING STANDS OF S. oligorhiza , WINTER, 1976—77 101
57 WATER QUALITY OF AERATED, STATIC LAGOON TEST CHANNELS,
CONTROLS, WINTER, 1976—77 . . . 102
58 WATER QUALITY OF AERATED, STATIC TEST CHANNELS
SUPPORTING STANDS OF L. g Lbba , WINTER,1976—77 . . . . . 103
59 WATER QUALITY OP AERATED, STATIC TEST CHANNELS,
CONTROLS, WINTER, 1976—77 104
60 BIOMASS OF S. oligorhiza AND L. gibba HARVESTED FROM
AERATED, STATIC TEST LAGOONS, WINTER, 1976—77 106
61 CHEMICAL ANALYSIS OP S. oligorhiza AND L. bba GROWN
ON AERATED STATIC TEST CHANNELS RECEIVING DAIRY
WASTE, WINTER, 1976—77 107
62 YIELD OF L. gibba , COVERED AND NON—COVERED AND A MIXED
CULTURE (M) OP L. g bba AN]) S. oligorhiza FROM STATIC
TEST CHANNELS RECEIVING DAIRY WASTE, WINTER,
1977 109
63 PARTIAL CHEMICAL COMPOSITION OF L. gibba (G3) AN]) A
MIXED CULTURE (M) OF L. bba AND S oligorhiza GROWN
ON STATIC TEST CHANNEL RECEIVING DAIRY WASTE,
WINTER, 1977 110
xii
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Number Page
64 WATER QUALITY OF STATIC AND AERATED TEST CHANNELS
SUPPORTING A MIXTURE OF S. rhi a AND L. gibba ,
WINTER,1977 111
65 WATER QUALITY OF STATIC AND AERATED CONTROL CHANNELS,
WINTER, 1977 . 112
66 BIOCHEMICAL OXYGEN DEMAND (BUD), CHEMICAL OXYGEN
DEMAND (COD), TOTAL RESIDUE (TR), VOLATILE RESIDUE
(VR), FIXED RESIDUE (FR), AND TOTAL SUSPENDED
MATTER (TSM), OF COMPOSITE SAMPLES FROM MIXED
SPECIES IN STATIC TEST CHANNELS, WINTER,1977 . . . 114
67 BIOCHEMICAL OXYGEN DEMAND (BOB), CHEMICAL OXYGEN
DEMAND (COD), TOTAL RESIDUE (TR), VOLATILE RESIDUE
(VR), FIXED RESIDUE (FR), AND TOTAL SUSPENDED
MATTER (TSM) OF COMPOSITE SAMPLES FROM STATIC CONTROL
CHANNELS, WINTER, 1977 114
68 STANDARD PLATE COUNT, FECAL COLIFORM, AND FECAL
STREPTOCOCCI COUNTS OF THE MIXED SPECIES IN
STATIC TEST CHANNELS, WINTER, 1977 115
69 STANDARD PLATE COUNT, FECAL COLIFORN, AND FECAL
STREPTOCOCCI COUNTS OF COMPOSITE SAMPLES FROM
CONTROL CHANNELS, WINTER, 1977 . . . . . 115
70 WATER QUALITY OF COVERED, AERATED AN]) STATIC TEST
CHANNELS SUPPORTING L. gibba , WINTER, 1977 116
71 WATER QUALITY OF NON-COVERED, AERATED AND STATIC
TEST CHANNELS SUPPORTING L. gibba , WINTER, 1977 117
72 BIOCHEMICAL OXYGEN DEMAND (BUD), CHEMICAL OXYGEN
DEMAND (COD), TOTAL RESIDUE (TR), VOLATILE RESIDUE
(VR), FIXED RESIDUE (FR), AND TOTAL SUSPENDED
MATTER (TSM) OF COMPOSITE SAMPLES FROM L.
STATIC, COVERED TEST CHANNELS, WINTER, 1977 . . . 118
73 BIOCHEMICAL OXYGEN DEMAND (BUD), CHEMICAL OXYGEN
DEMAND (COD), TOTAL RESIDUE (TR), VOLATILE RESIDUE
(VR), FIXED RESIDUE (FR), AND TOTAL SUSPENDED
MATTER (TSM) OF COMPOSITE SAMPLES FROM L. gibba
STATIC, NON—COVERED TEST CHANNELS, WINTER,1977 . 118
74 STANDARD PLATE COUNT, FECAL COLIFORN, AND FECAL
STREPTOCOCCI COUNTS OF COMPOSITE SAMPLES FROM
L. STATIC, COVERED CHANNELS, WINTER, 1977 - 119
xiii
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Number Page
75 STANDARD PLATE COUNT, FECAL COLIFORM, AND FECAL
STREPTOCOCCI COUNTS OF COMPOSITE SAMPLES FROM
L. gibba STATIC, NON—COVERED TEST CHANNELS,
WINTER, 1977 119
76 WATER QUALITY OF DIJCKWEED COVERED TEST (AERATED)
AND CONTROL (STATIC) CHANNELS, SUMMER,1977 121
77 YIELD OF A MIXTURE OF L. gibba AND S. oligorhiza
UNDER AERATION IN STATIC TEST CHANNELS FLOODED
WITHDAIRYWASTE,STJHMER,1977 123
78 CHEMICAL COMPOSITION OF A MIXTURE OF S. oligorhiza
AND L. gibba UNDER LOW NUTRIENT AND AERATED
CONDITIONS, SUMMER, 1977 124
79 ESTIMATED ANNUAL DRY WEIGHT YIELD PER HECTARE OF
DUCKWEEDS PRODUCED ON LAGOONS RECEIVING DAIRY
CATTLE WASTES, 1976—77 127
80 PARTIAL CHEMICAL COMPOSITION AND YIELD COMPARISONS
OF SOME COMMON ANIMAL FEED PROTEIN SUPPLEMENTS
ANDDUCKWEEDS 130
xiv
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LIST OF HETRIC CONVERSIONS
Length
1 centimeter = 0.3937 inch 1 inch = 2.540 centimeters
1 meter 3.281 feet 1 foot = 0.305 meter
1 meter 1.094 yard 1 yard = 0.914 meter
Area
1 sq. meter = 10.76 sq. feet 1 sq. foot 0.0929 sq. meter
1 hectare = 2.47 acres 1 acre = 0.405 hectare
Weight
1 kilogram = 2.205 pounds 1 pound = .453 kilogram
1 metric ton = 2,204 pounds 1 short ton (2,000 pounds) =
.907 metric ton
xv
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ACKNOWLEDGEMENTS
Many people were involved in this study, and made significant contri-
butions to the successful completion of the project. They are deserving
of recognition for their time and research contribution.
Dr. 3. B. Frye, Head of the Department of Dairy Science, certainly
encouraged the study and made sure the project proceeded smoothly. His
continued interest is appreciated. Dr. Delmer Evans coordinated the
research with the dairy farm daily operations. Without this help, it would
have been difficult to schedule some of our activities.
Drs. Louis Rusoff and Antonio Achacoso, with the help of Dave Williams
and Debra Kelly were responsible for the preliminary studies on the effect
of duckweed on palatability, milk quality, and growth. Their contributions
are appreciated.
Dr. Ronald Gough and Ms. Kelly conducted the bacteriological phase of
the study, in addition to several water quality parameters. They spent many
hours in the laboratory, and are commended for their diligence.
Mr. Robert Myers and Steve Boney, graduate students in Fisheries, were
responsible for the duckweed production and water quality analyses. They
also became country—fair construction engineers. With the help of
Agricultural Engineering associates Gordon Newton and George Baskin the
lagoons were maintained in operating condition. The maintenance provided
by these four men was instrumental in keeping the research aspects of the
project functional.
The water and plant chemical analyses were supported by a team of five
people, employed in the Wilson Feed and Fertilizer Laboratory. These
gentlemen; Joe Kowalezuk, Pete Keller, Leonard Devoid, Pedro Carasco, and
Austin Harold, are appreciated. Their quality and efficient work helped
keep this project on schedule.
The project was obviously a team effort, involving five separate
departments on the campus, and 23 personnel. Two persons were instrumental
in keeping this large group coordinated. Miss Jennifer Achee and
Mrs. Elaine Saucier, the Fisheries secretaries, handled the many secretarial
requirements for the project. Mrs. Saucier deserves recognition for
coordinating the financial affairs, and Miss Achee for typing this report,
which was no easy task.
xvi
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This multidisciplinary research involved the Departments of Agricultural
Engineering, Dairy Science, and Horticulture, the School of Forestry and
Wildlife Management, and the Wilson Feed and Fertilizer Laboratory with the
support from the Louisiana Agricultural Experiment Station.
Guidance and assistance was provided by personnel of the Robert S. Kerr
Environmental Research Laboratory, U.S. Environmental Protection Agency, Ada,
Oklahoma. This included total organic carbon analysis and analytical quality
control monitoring by Mr. Don A. Clark and project guidance by Mr. R. Douglas
Kreis, Project Officer.
xvii
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SECTION 1
INTRODUCTION
The increased production of meat, poultry, and dairy products in the
United States and the world has been paralleled by an increase in energy use
and waste generation at a time of declining fossil fuel resources, increasing
demand for water and air pollution control, and rapid world population
expansion. Efforts to control population growth and develop additional
energy sources are underway, but it is questionable at this time whether or
not these programs will be achieved in time to thwart world—wide human
starvation and serious deterioration of our environment. Many approaches
are needed to obtain energy and increased food production to meet human
demands. Of particular interest is the concept of energy production and
nutrient reclamation through recycling of animal wastes to offset limited
energy availability and to increase food resources. Development of a treat-
ment system to economically generate energy and food from organic wastes
should be applicable to livestock feedlot operations, and the food processing
industry. With the increased confinement of animals into feedlots, the
economics of extracting energy and nutrients from wastes becomes more
attractive. The energy could be used in transportation of food and wastes,
lighting, heating and cooling of air and water, refrigeration, etc. The
nutrients could be easily made available for crop production, particularly
if the crop is grown on lagoon systems adjacent to the feedlot.
In waste treatment emphasis has been placed upon breakdown of organic
matter, but another equally significant aspect is that a very large percen-
tage of the nutritive value of the feed remains in the manure. Recovery of
these nutrients could be of considerable significance.
The use of aquatic plants to recover waste nutrients, though not a
new concept, is in the early stages of development. Emphasis in lagoon—
aquatic plant systems is not so much on treatment, as management. The
management concept holds that a variety of products are available within
the manure, or can be produced from proper manure management. Methane, of
course, can be derived directly from the manure. Feeds can be derived both
directly (refeeding of sludge) and indirectly (production of crops utilizing
manures as fertilizers). Use of high—nutrient aquatic systems (lagoons)
offers possibilities for developing a variety of products, but awaits the
imagination of aquatic biologists for development.
1
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This study reports on the use of duckweeds (family Lemnaceae) as part
of a waste management system for a dairy farm. Emphasis was placed on
evaluation of the plants in waste water renovation and as a feed ingredient
for dairy cows. The rapid growth, high feed value, ease in harvest, cold
tolerance, and ability to culture the plants adjacent to the feedlot offer
several advantages over other aquatic plants as part of a waste management
scheme.
The value of lagoon systems over land application in high rainfall
areas are evaluated in this study, and a proposed scheme for an integrated
waste management — energy efficient system is presented.
2
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SECTION 2
CONCLUS IONS
WATER QUALITY
Even under high manure loading rates duckweed covered channels showed
greater reductions in Total Kjeldahl Nitrogen (TKN), ammonium (N4) and
phosphorus (P) than controls. Under proper lagoon management where loading
rates are controlled to minimize solids flow into lagoons duckweeds appear
to offer treatment advantages.
Removal of phosphorus by duckweeds, though superior to control lagoons,
was sufficiently low to consider another mechanism of removal. If duckweeds
are to be used in the treatment, clonal selection for phosphorus concentra—
tion may be required.
With a multistage lagoon system and better control of loading rates
than in our study, duckweeds should be capable of removing most nitrogen (N).
Under the conditions of this study, duckweed—covered lagoons averaged about
20% greater nitrogen removal than controls. Arnmonium was apparently the
dominant form of N available to duckweeds.
DUCKWEED PRODUCTION
The clones of Spirodela oligorhiza used in this study exhibited greater
growth in the spring and fall, S. polyrhiza in the sujimier, and Leinna gibba
(clone G3)* grew best during the fall, winter, and spring. Use of other
clones within each species may not perform equally well. Mixed cultures of
the species grew as well as the monoclonal cultures. The average and
maximum annual yield projected to a per hectare basis was 17,577 kg and
22,023 kg (dry weight) respectively. Aeration and circulation of the lagoon
water did not increase growth, and there was some evidence that growth may
be reduced under aerobic conditions.
Nutrient content of the duckweeds increased when lagoon nutrients were
increased, particularly when the TKN in lagoons exceeded ca 20—30 mg/i.
Mean crude protein content (dry weight) was 36%, and a maximum of 42.6% was
recorded. The plants compare favorably with ingredients of high protein
*Clone identification number for L. gibba . Plant supplied by Dr. William
Hiliman, Brookhaven National Laboratory, Upton, L.I., N.Y. 11973. Referred
to as L. gibba throughout this paper.
3
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feeds and appear economical to use. Preliminary studies on cattle growth,
palatability, and milk quality utilizing duckweed showed no adverse effects.
Further study is needed.
On an annual per hectare basis, nutrient uptake by duckweed showed
removal of N from the manure of 15.5 mature dairy cows, P from 34 cows, and
potassium (K) from 8.8 cows. L. gibba showed the ability to concentrate K.
TKN decline in duckweed lagoons averages ca 1 mg/l/day.
Duckweeds performed well under apparent anaerobic conditions, but the
layer of water associated with the duckweed may have been aerobic. Year
round production appears possible, particularly if the water temperature
can be maintained above freezing. High loading rates reduced duckweed
growth only when solids appeared on the lagoon surface. Surface algae
blooms occasionally appeared to affect duckweed growth, but the problem was
not serious. There was little evidence of pests affecting duckweed produc-
tion. Mosquito larvae (unidentified) were frequently associated with the
duckweed, but were more prevalent when harvest was not routine and complete
cover was not achieved. Higher growth rates were suggested under continuous
flow conditions as compared to static, and higher yields (current study)
under daily harvest as compared to intervals exceeding three days.
BACTERIOLOGICAL
Due to overloading of the system with waste, fecal coliform and fecal
streptococci were relatively high. The major genera of bacteria were
Proteus, Bacillus, Achromobacter, Flavobacterium, Escherichia, Enterobacter,
Micrococcus , and Pseudomonas. Salmonella organisms were isolated from
surface samples only twice, and each time were associated with a turtle
infestation. During aeration studies in which the sludge was suspended in
the water column Salmonella was not recovered. Pathogenic bacteria were not
found in the effluent (surface overflow) other than mentioned above.
Further study is needed as it is possible the bacteria attached to the
duckweed. However, preliminary feeding tests for growth, palatability, and
milk quality failed to show symptoms of pathogen infection. In all cases
the duckweed was washed with chlorinated water, or dried before feeding.
FEEDING TRIALS
Duckweed is a high quality feed material and acceptable to dairy cattle
when fresh or dried. The cattle consumed up to 75% duckweed in the diet.
Washing apparently improved the palatability response, as did mixing with
other feeds. No adverse effect was noted on growth and milk quality. The
acceptability of the wet duckweed by cows will greatly enhance energy
conservation in processing the plant, which requires only washing. Further
study is needed, however, as these tests involved only 1 to 4 cows.
4
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SECTION 3
RECOMMENDATIONS
The primary goal of this study was to obtain information on the value
of duckweeds as part of a waste management system. Particular emphasis was
placed on: (1) the growth performance and nutrient uptake of these plants
under the worst possible lagoon conditions, e.g. extreme overloading of the
system; (2) chemical, physical, and microbiological characteristics of
duckweed—covered lagoons in comparison with conventional lagoons; and
(3) the usefulness of duckweeds as an animal feed. Based on these studies
the following factors were evident: Some duckweeds adapted easily to
waste lagoons, grew rapidly, concentrated nutrients, improved waste treat-
ment, and appeared to be useful as a feed ingredient. These results support
the following recommendations.
1. Research should continue to define the lagoon management require-
ments for maximum duckweed production and nutrient extracting.
2. Although few pathogenic bacteria were associated with the harvested
duckweed and surface water, they were present in the deeper water and sludge.
Therefore, bacteriological studies should continue, with emphasis on
controlling the loading rate and washing of duckweed with chlorinated water
before feeding.
3. Research should be undertaken to develop a duckweed harvesting and
transportation system, as current studies indicate that daily harvest will
result in higher yields than harvesting at intervals longer than three days.
4. Studies should be initiated to genetically engineer clones of
duckweed with higher growth rates and nutrient value, cold tolerance,
reduced water content and other desired characteristics for various uses.
5. The concept of agricultural waste management should emphasize
nutrient recovery and utilization, energy production, development of
marketable products and the production of acceptable quality water.
6. Lagooning of wastes for nutrient extraction and product development
should take priority over land application in high rainfall areas, both for
waste treatment and crop production. It is doubtful that yields of land—
based protein crops will compete with aquatic plants such as duckweed.
7. Economic evaluations are needed for integrated waste management —
food production schemes suggested in this study.
5
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8. TKN decline during the study averaged ca 1 mg/l/day. Based on
this study lagoons with 40—50 mg/i TKN should be reduced to less than
10 mg/i by the duckweed system within 30 to 40 days. However, shallow
lagoons (< 0.3 m) and their management should be considered in a waste
management scheme with duckweeds and other aquatic plants. Retention times
could be greatly reduced, treatment improved, and plant yield increased.
9. Phosphorus reduction needs further study, as the uptake by duck—
weeds was not sufficient to meet strict water quality standards (of about
0.1 mg/l). Proper lagoon management may improve upon removal of this plant
nutrient.
6
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SECTION 4
TECHNICAL BACKGROUND
The needs to provide food for a hungry world and curb pollution are
becoming increasingly difficult to achieve due to the human population
growth, consumption, and limited available energy sources. Animal waste
utilization offers good potential for generating energy and food.
TABLE 1 shows the estimated number of animal stocks grown under
confinement in the United States which could be utilized to meet energy,
food, and product demands. Development of our renewable waste resources
through integrated recycling and use systems may well improve the economics
of water and air pollution control.
Public reaction to water pollution and the general deterioration of
the environment makes it mandatory that new technology be developed to
resolve the ever growing mountains of pollutants caused by the increasing
needs for food production. Waste resulting from heavily populated urban
areas, mass production and the crowding of livestock and food processing
plants near these areas has exceeded the capacity of present waste disposal
systems. This aspect becomes even more graphic when one considers that
livestock alone presently generates an estimated 2 billion tons* of wastes
yearly (Anonymous, 1970).
Livestock has become highly concentrated in that some beef feedlots
may contain up to 50,000 animals, dairy farms may have 5,000—8,000 animals
on very limited acreage, poultry farms up to 1,000,000 birds and swine
operations as many as 1,500. These wastes were formerly returned to the
land, but the associated costs weremore expensive than utilization of
commercial fertilizers. In addition there is not sufficient available land
near these concentrations of livestock to absorb the wastes produced without
causing excessive pollution of waterways from runoff. The net result often
is excessive nutrification and rapid eutrophication of surface and ground
waters.
There is a current interest in land application of livestock waste
rather than using lagoons for biological treatment of these animal wastes.
Most of the research work on lagoons has been on the engineering aspects of
*See LIST OF METRIC CONVERSIONS. In order to insure accuracy of the
referenced authors, conversion of the reference data to metric system was
not made.
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TABLE 1. NUMBER OF ANIMALS MAINTAINED UNDER FEEDLOT CONDITIONSa
Animal Number of aniinalsb
Dairy 11 x 106
Poultry (layers) 478 x io6
Poultry (broilers) 1,000 x lO
Swine 61 x
Turkey 90 x io6
Beef 14 x i0 6
Sheep 4.2 x io6
Ducks 1.9 x io6
Horses 0.3 x io6
aExtracted from data compiled by Hamilton Standard (1973) for the EPA
to serve as a guide for effluent management for the feedlot industry.
bThese figures do not include animals in pasture.
eData on poultry obtained from Louisiana State University Poultry
Science Department.
8
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the system, a carry—over from municipal lagoon design, but biological
factors related to microbial activity have not been studied in detail.
Unfortunately, the acceptance of lagoons and their use on farms has
preceded definitive studies on their ability to adequately degrade animal
waste and produce an acceptable effluent. This lack of knowledge of lagoon
function, and how to control the system may have stimulated recent interest
in land application. Lagoons are often extolled for the efficiency of
biochemical oxygen demand (BOD 5 ) reduction (as high as 85%), but little
mention is made of the fact that there frequently will be effluent flow,
or the volume of effluent and its pollutional load. In high rainfall areas
runoff and effluent flow is the rule, not the exception. The discharge
contains organic and inorganic nutrients.
It is general knowledge that the primary means of handling livestock
waste has been to return the waste to its original source —— the soil.
Experiments (Russell, 1961; Whie and Holben, 1921; Wiancke, Walker, and
Mulvey, 1935) have been conducted in which animal wastes were shown to be
satisfactory sources of plant nutrients. The application of wastes on
certain soils has proved to be an effective filter in removing pollution
from water supplies. Overman, Hortenstine, and Wing (1970) have reported
that the use of soil to reclaim dairy waste waters before discharge into
receiving streams resulted in a stabilized effluent. McCaskey, Little, and
Rollins (1971) reporting on the application of liquid and dry manure to soil
indicated that a slightly higher BOD than the suggested maximum of 30 ppm
for runoff was present when 2.4 tons of raw wet solids were applied per acre
per month. When dry wastes were applied 1.5 to 2.3 times the recommended
BOD was observed in the runoff from the application of 12.8 tons of wastes
per acre per month. These studies were made on sandy type soils which are
open soils that would provide filtering action. However, soils in the
Mississippi River flood plain and Gulf coast areas, are mainly clay type
soils and filtering rates are greatly reduced. High rainfall further compli-
cates the tight soIl problem.
In the incorporation of vascular aquatic plants into the biological
treatment process, three distince advantages are evident: (1) An additional
biological system is added to existing biological processes and should
further augment waste treatment. (2) Since most chemicals in animal waste
lagoons that impair water quality are in solution, large quantities leave
the lagoon in the effluent. Those that are trapped in the bottom sediments
must ultimately be removed by dredging, processing and transportation to
another location. Utilization of aquatic plants could provide a method of
removing these nutrients continuously and possibly reduce or eliminate the
need for periodic dredging. (3) The lagoon owner receives no economic
benefits from lagoon systems at present. Due to the high nutritional value
of some aquatic plants and the ease of harvesting, the owner could receive
economic benefits by utilizing these plants as animal feeds and reduce the
labor and cost of spreading waste on land. It is imperative that the long—
range research goals be designed to continue to refine and improve on waste
treatment processes to insure continued multiple use of water resources
and to provide economic benefits from the treatment process.
9
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In Louisiana, over 200 lagoons are now in operation. Nine other
southern states probably have similar numbers. The design recommendations
allow for overflow. Redesign of these lagoons to prevent overflow will be
expensive. A treatment process utilizing aquatic plants may improve the
water quality sufficiently to allow the existing lagoons to remain unchanged.
The overflow water may be of acceptable quality to recycle as wash water,
or if used in irrigation (at certain times of the year) be of such quality
that no contamination of surface waters will occur. However, these ten
states have high annual rainfall with much of it coming in a few months.
In Louisiana it is not uncommon to have from 25 to 40 cm in one month. The
use of lagoon water for irrigation is of little value as a waste treatment
technique during rainy seasons as is land application of manure. The
alternatives are to redesign each lagoon to have no overflow, or use a
combination of irrigation (during dry periods) and recycling of the effluent
as wash water during the rainy season. The latter approach may be economi-
cally more desirable, particularly if the aquatic plants can be economically
utilized.
The use of lagoons has been of three types, based on biological
activity, namely, anaerobic, aerobic, and a combination of the two. Most
of the research on these systems to date have been conducted on swine and
poultry wastes.
Anaerobic plus aerobic lagoons have been under considerable study by
several investigators (Anthony, 1969; Foree and O’Dell, 1969; Shmid and
Lipper, 1969; Sobel, 1969; Vickers and Genetelle, 1969) and appear to offer
excellent possibilities for livestock waste disposal. Loading rates,
separation methods, microbiological characteristics, climate and design
details are under preliminary study, but must be examined in detail to
provide efficient economical operational procedures.
It is conceivable that a combination system of waste screening,
anaerobic and aerobic breakdown may offer possibilities for the requirements
needed for a non—polluting stabilized effluent. Continued research will be
necessary to define the specific problems associated with collection, treat-
ment and nutrient losses. The ultimate goal is to design systems that will
stabilize the undesirable materials and allow re—use of valuable nutrients
at a low cost to the farmer.
It has been emphasized that research on more effective techniques to
remove and/or recovery of mineral nutrients from effluents prior to release
in natural waters is needed (American Chemical Society, 1969). Animal and
municipal waste lagoons convert large quantities of organic nutrients to
inorganic nutrients and minerals. Great quantities of inorganic nutrients
leave the lagoon system with the effluent and no practical or economically
beneficial method of extraction has been developed. Inorganics that are
trapped in the sludge must ultimately be disposed of as it is necessary to
periodically dredge out the sludge. Processing or disposal of sludge is
expensive. Incorporation of aquatic plants into lagoon systems may reduce
the sludge load and remove large quantities of nutrients dissolved in the
water column.
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Although considerable research has been conducted on the use of aquatic
plants in waste treatment, biomass production, and as an animal feed, little
success has been realized in developing an economically feasible system for
any of these uses. However, use of aquatic plants in the family Lemnaceae
(duckweeds) has been largely ignored as a food source until recently
(Bhanthuxnnarin and McGarry, 1971; Culley and Epps, 1973; Truax et al., 1972;
Sutton and Ornes, 1975; Harvey and Fox, 1973). These studies suggest that
duckweeds hold high potential as an animal feed. Growth rates in the
laboratory and under field conditions exceed traditional agricultural crops
in biomass production, and have a high nutrient quality (up to 45% protein).
Water content of certain duckweeds varies from 90—94%, harvest techniques are
available, and some plants tolerate light freezes and actively grow during
mild winters. The several criteria listed below for selecting specific
aquatic plants for waste treatment are best fulfilled by duckweeds. Aquatic
plants should (1) be easily harvested, (2) be low in water content,
(3) possess a high protein content, (4) have a low fiber and lignin content,
(5) have a high mineral absorption capability, (6) have an extended growing
and harvesting period, (7) be non—toxic to human and domestic stocks,
(8) be easily processed, and (9) few pests. Based on the studies by Truax
et al. (1972) and Culley and Epps (1973), duckweeds fulfill criteria 1, 3,
4, 5, 6, and 9 and partially fulfill criteria 7 and 8. Based on the
criteria it is evident that not only can duckweeds be used for extended
periods to take up nutrients, but they can also be harvested and the energy
and nutrients in the plants recycled back into animal feeds. The possibility
of economic benefits resulting from utilizing duckweeds makes them extremely
attractive in water treatment processes.
Joy (1969) and Hiliman (1957; 1961) state that a variety of organic
compounds have been used as duckweed culture media, indicating their
ability to utilize organic compounds for growth, even in the absence of
photosynthetic light levels. Joy obtained greatest growth rates in medias
consisting of minerals, sucrose, and hydrolyzed casein. Thus, duckweed may
function not only to tie up inorganic fractions in a lagoon system, but may
aid bacteria by removing organics. Therefore, it may be possible to load
a lagoon system with organic wastes at a higher rate than could be afforded
with present biological systems in use.
Utilization of duckweeds should be applicable to a variety of waste
lagoons, particularly those involving treatment of (1) all types of animal
excrement, (2) food processing plants such as canning, meat and poultry,
sugar mills, rendering and leather plants, paper mills, etc., and (3) indus-
tries involved with release of metal wastes, radioactive materials,
fertilizers, and possibly insecticides.
LAGOONING VS. LAND APPLICATION
The agricultural industry faces a need for an environmentally
acceptable method of livestock waste disposal. Due to high labor and land
cost, livestock operations are moving to more confined systems. The concen-
trating of larger groups of animals into smaller areas causes increased
problems in waste management.
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In 1969 there were 604 dairies in Louisiana with 20—30 cows. These
farms accounted for approximately 35% of all dairy farms in the state.
There were 835 producers with herds of 50—100 cows, representing 49% of the
total statewide. From 1964 to 1969, nationally, the farms in the range of
50—100 head increased from 37,601 farms (16% of the total cows) to 38,457
farms (22.6% of total cows). In the range of 100—more head per farm, in
1964 there were 8,846 farms (0.8% of total cows), nationally. In Louisiana
farms of 100—more head, the increase was from 235 farms (18.6% of total cows)
in 1964 to 275 farms (33.0% of total cows) in 1969. In 1965 the average
herd in Louisiana was 68 cows; by 1975 this figure had increased to 92 cows.
The forecast f or the future is a movement to herds of 300—500 cows being
housed in concentrated feedlot situations with little cropland or pasture
available for waste disposal.
Because of growing concern over pollution, the development of an
acceptable waste disposal system is of high priority. The waste produced
by one cow equals that of 16.4 humans, similarly 100,000 layers produce
waste equivalent to that of 1,500 people (Eby, 1962). Each person is
supported by 2 laying hens, 4 broilers, one—half turkey, one—half cow,
one—third pig, one—tenth sheep, and several other smaller animals too
numerous to mention, producing in excess of 6 million tons of manure
daily (Turner, 1970).
Scrape and Spread Method
The conventional system of handling waste requires that the confinement
area be scraped daily and manure loaded directly into the manure spreader.
When the spreader is fully loaded, manure is spread in fields adjacent to
the dairy. Daily manure production of a 1400 pound dairy cow was reported
by a North Carolina study, Drigger et al. (1973), as 118 pounds per day.
For a 150 cow herd two loads of a manure spreader is required daily to
remove the waste (ca 4.5 metric tons per load). This requires two persons
about three hours each day in good weather and field conditions. During
inclimate weather the procedure quickly becomes restrictive due to the
inability to move the manure, stockpiling, etc. Efforts to spread the
manure frequently result in damage to pasture drainage contours. Not only
is a health hazard produced by stockpiling, but when weather conditions
improve, personnel are tied up an excessive amount of time to remove the
stockpile. In short, the scrape and spread method is not very efficient.
The amount of manure/hectare that can be applied varies with the type
of soil, the crop, and the area of the United States. Soils with a high
percentage of clay, such as those in Louisiana, do not lend themselves to
high levels of manure application due to low percolation capacity resulting
in soil saturation and runoff. The amount of N that can be utilized by a
crop also places a limit on the quantity of waste than can be applied to a
given soil. Some average values include: feedlot manure on grain sorghum
is 25 metric tons/hectare every 3 years while that for irrigated corn silage
is 250—320 metric tons/hectare. Since irrigation water decreases the
amnionium and salt concentrations in soils, larger amounts of manure may be
added under these conditions, but irrigated crops are impractical in certain
high rainfall areas of the nation (Loehr, 1977).
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Lag ooning
A basic lagoon waste handling system consists of an aerobic pond and an
anaerobic pond. These ponds should be designed to meet specifications
recommended by the Soil Conservation Service (SCS) if treatment only is
desired. The lagoon as a natural waste oxidizing system has been used for
many years, and today its use as a primary method of waste disposal is
widespread. This use of lagooning is attributable to low cost of construc-
tion, ease of operation, and low maintenance. Manure is usually scraped
once each day from the holding area into the anaerobic lagoon. Anaerobic
lagoons may be loaded in excess of 448 kg BOD/ha/day. The aerobic or
facultative pond is usually designed for loading of 56 kg/BOD/ha/day with
effluents from the aerobic pond having a BOD concentration of 20—40 mg/i.
Lagoons normally achieve 50—90% BOD removal, depending on loading, retention
time, and whether or not solids are removed prior to discharge (Loehr, 1977).
Incorporation of aquatic plants into the system should improve treatment.
However, in terms of waste management, optimum recommended lagoon designs
are unknown. The use of SCS recommendations on existing farms should
probably be utilized until management techniques are defined.
Cost Review
A study was undertaken at Michigan State University by Hogland et al.
(1972) to determine manure handling practices in use and to develop
investment and cost data. Investments in complete manure handling systems
ranged from $80 per cow for gutter—spreader system to $190 per cow for a
liquid manure—handling system.
Buxton and Zeigler (1974) estimated added investment and annual cost
dairy operators would incur in controlling runoff, wash water, and added
water from major storms. It was concluded that the cost of pollution
control would be borne by the dairy farmer in the short run. Small farms
might be forced out of production or forced to expand and adopt more
efficient housing and milking technology.
In a study of Louisiana dairymen conducted by Hromadka (1976), it was
found with an average herd size of 110 cows the investment per cow was
$21.38 for a lagoon system (ramp, anaerobic lagoon, and aerobic lagoon)
vs. $47.98 per cow for a scraper—loader—spreader system.
Alternative waste handling systems were examined in a study at the
University of Tennessee conducted by Henderson and Bauer (1973). Labor
requirements for liquid, conventional, and irrigation systems were similar.
The lagoon system required no labor beyond scraping the loafing area.
Miner (1975) states that, “Currently, most animal waste is applied to
agricultural land; liquids are irrigated, and solids or slurries applied by
a spreader. The term, disposal area, has gained undesirable currency. If
long—term pollution of surface or ground water is to be avoided, rates of
manure application must match the assimilation capacity of the site; that
is, capacity that minimizes release of pollutants. In some arid areas of
the country, this matching may allow very high manure application for one
13
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year, followed by several resting years for assimilation. Humid areas with
regular rainfall will not be able to follow such a practice because of
nutrient infiltration or runoff. The concept of disposal areas is not
compatible with the maintenance of soil productivity.”
The use of manure for land application has specific disadvantages in
certain areas of the United States, such as Louisiana. Due to the high
annual rainfall (approximately 150 cm/year) it would be impossible at
certain periods of the year to spread manure and the quantity would be
limited, also there would be a high percentage of runoff. The need for
holding areas brings with it the need for least cost operation. A lagoon
system offers the best of alternatives, with a large holding capacity for
manure and runoff, low investment, ease of operation, and ability to
irrigate or fertilize with the effluent, if the producer has the need or
desire to do so. Catching of surface runoff water from the confinement
area can not be over emphasized due to the large volumes of water involved
from rainfall. A lagoon system seems to be the easiest method for the
average producer to comply with regulations. In confinement operations the
use of water from the aerobic lagoon for washing down the loafing area
offers a “closed system” alternative, bringing the producer in full
compliance with existing regulations of “no point discharge.”
14
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SECTION 5
OBJECTIVES
The long—term goals of this research at Louisiana State University are
to determine if efficient methods of livestock waste treatment and reduc-
tion in the use of energy can be achieved by recycling waste nutrients from
lagoon systems back into animal feeds. Dairy cattle wastes are being used
as the model for treatment of livestock waste.
This particular study was designed to incorporate duckweeds into the
lagoon treatment process to determine if (1) waste treatment could be
enhanced, and (2) a sufficient quantity of duckweeds with acceptable
nutritional feed value could be produced on the system. The following
objectives were considered.
1. Determine the chemical, physical and microbiological composition
of lagoon waters receiving dairy cattle wastes.
2. Determine the effluent water quality of lagoons with and without
duckweed cover throughout the year.
3. Determine the chemical composition, rate of production, and harvest
rate of duckweeds, and relate these values to changes in water
quality.
4. Obtain information to establish optimum loading rates for maximum
growth and nutrient removal by aquatic plants.
15
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SECTION 6
METHODS
CHARACTERISTICS OF STUDY AREA AND HERD
This study was conducted at the Dairy Product Teaching and Research
Center, a research unit of the Department of Dairy Science and the Louisiana
Agricultural Experiment Station in Baton Rouge, Louisiana. A 370 acre
(150 ha) farm, located off campus is used to house and care for approxi—
mately 350 animals (115 milking cows). The lactating herd is maintained
in a dry lot adjacent to a four lagoon complex. The lagoons (Figure 1)
receive liquid wastes from the milking parlor, wash—down from the holding
areas, and solid waste and rainfall on the loafing area. Solid waste was
added as needed.
Solid wastes were pushed into the lagoon via the loading ramp. Liquid
wastes flowed by gravity to the collection sump, where fibrous materials
were screened from the liquid. A two horsepower sewage pump conveyed the
liquid through a 4—inch (10 cm) PVC plastic pipe to the stage 1 anaerobic
lagoon where some solids settle—out and biological activity initiates
break—down of the waste. Retention time was only a few days. Effluent
passed by gravity through a 2—inch (5 cm) PVC pipe to test lagoons 1 and 2,
or the collection pit. Each test lagoon was subdivided into 8 test channels.
Effluent flow could be individually directed into and diverted from each of
these channels.
Each test channel was ca 2.7 in wide and when fully flooded up to 10 m
in length. Surface area for each channel when full was about 26 in 2 .
Maximum water depth was about 1.3 in. Movable vertical drain lines at the
opposite end from the valves could be adjusted to control the water depth.
Partitions dividing each test channel (8/lagoon) were made of wooden
fencing material and lined with nylon reinforced plastic and embedded in the
lagoon floor. Walkways were constructed over each partition to allow
sampling at various locations within each lagoon.
In order to control harvesting of duckweed within each test channel a
plastic partition was placed midway across each channel. This partition
rested on the floor of the lagoon and was simply raised to the surface so
only one—half of the duckweed could be removed, leaving the other half for
regrowth.
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HOLDING PENS—I
T -65
65’
ii
MILKING PARLOR
COLLECTION SUMP
WITH PUMP
CLOSED DRAIN TO CANAL
-- --- ----- -
//
/ / LAGOON
/
I
/STA E I
‘ANAEROB!
/ LAGOON
P
EFFLUENT
COLLECTION
PIT
I 70
TEST
LAGOON
2
EMERGENCY OVERFLOW DRAIN TO CANAL
Figure 1. Campus dairy—herd facility showing location of feedlot and milking parlor.
Scale 1” = 100’.
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Thermocouples were placed in each test channel to monitor temperatures
at various depths.
An aeration system was installed in the test lagoons. Pressurized air
for this system was supplied by a 3/4 horsepower electrically—operated
compressor, and the air was conveyed through a 1—inch (2.54 cm) PVC plastic
pipe along the bottom of each channel. The air line in the channel had
ca 1 i holes spaced 0.5 m apart. All tests were conducted under aerated
and non—aerated conditions.
Each cow was fed approximately 2.3 metric tons of hay, 6.4 metric tons
of silage, and 2.7 metric tons of grain (feed concentrate) per year to
produce an average of 5,578 kg of milk/year. Estimated energy requirements
to maintain the herd were 794.2 x lO cal/yr, 561 x io cal/yr, and
21.9 x cal/yr for feed; production and harvest of feed; and waste
removal respectively. These figures are low as all energy expenditures
could not be accurately estimated. An estimated 419.4 x cal/yr are
produced in the milk. The energy input—output ratio for the dairy herd is
about 4 to 1 if the energy requirements for building operations are
included.
TECHNIQUES
All three lagoons were initially filled with city water. Samples were
taken after several days to determine the physical and chemical character-
istics of water exposed only to soil within the lagoon.
Chemical, physical, and microbial analyses was monitored using
standard analytical techniques (Horwitz, 1975) and Standard Methods
(American Public Health Association, 1971). Analytical quality control was
periodically monitored by the Animal Production Section of the USEPA
Robert S. Kerr Environmental Research Laboratory at Ada, Oklahoma. Water
analyses included pH, temperature, total Kjeldahl Nitrogen (TKN), phosphorus
(P), potassium (K), calcium (Ca), nitrate (No 3 ), ammonium (NH 4 ), total
suspended matter (TSM), volatile, fixed, and total residue (VR, FR, and TR),
dissolved oxygen (DO), biochemical oxygen demand (BOD 5 ), chemical oxygen
demand (COD), and total organic carbon (TOC).
The lagoons were monitored bacteriologically. Test channel samples
were taken from the outlet which received surface water overflow. Micro-
biological analyses included standart plate counts (SPC) at 20°C and 32°C,
anaerobic counts (AC), fecal coliform (FC) and streptococci counts (FC).
Deatiled methods as outlined by Bergey, Breed, and Murray (1957) and the
Society of American Bacteriologists (1957) were utilized in characterization
of micro—organisms.
Chemical analysis of the plants included such determinations as total
N, P, K, Ca, fats, fiber, ash, moisture, nitrogen—free extract (NFE), and
TOC following the techniques of Horwitz (1975), with periodic analytical
quality control monitoring by the Animal Production Section located at
Ada, Oklahoma.
18
-------
Throughout the study, several tests were conducted under maximum
loading rates of manure. The stage 1 anaerobic lagoon was deliberately
overloaded to create as high a nutrient load as possible in order to
determine duckweed performance under the most adverse conditions. Under
these conditions, several species of Leinnaceae were initially introduced
to determine their ability to adapt to the system. The criteria used in
selecting the species for additional study were: (1) recovery response
of the plants after collecting, transporting, and stocking on water with
chemical characteristics quite different from collection sites; (2) rate of
recovery; (3) evidence of rapid growth; (4) chemical characteristics; and
(5) evidence of cold tolerance, based on growth during winter months. The
duckweeds evaluated were species of Lemna, Spirodela , and Wolf fia . Two
other plants with similar growth forms, Azolla caroliniana (Salviniaceae
family) and a liverwort, Ricciocarpus natans (Ricciaceae family) were
evaluated. The former was selected because species within the genus are
known to have a symbiotic relationship with a blue—green algae that fixes
nitrogen (Ashton arid Walmsley, 1976), and could possibly enhance nitrogen
recovery or protein content of the Azolla .
Cultures of the various duckweeds were maintained at the experimental
fisheries research station in earthen ponds. A sufficient quantity of a
species was stocked on each test channel to allow rapid covering. When
full coverage was achieved, one—half of the plants were removed, allowed to
drain for 24 hours in perforated plastic buckets and then weighed. Samples
were then washed, oven dried for 18 hours at 95°C and then chemically
analyzed. Monthly harvest rates were estimates based on the quantity of
plants (wet and dry weight) removed from each test channel.
Tests were conducted under static conditions, i.e. each test channel
was filled to capacity with waste water and then the valves cut off.
Each channel was flooded from two to four days in order to insure similar
chemical characteristics existed in each channel before testing. Water
quality samples were taken and then the duckweed stocked. Control channels
without duckweed were used to compare performance. Records were maintained
on changes in surface area due to evaporation and figured into the calcula-
tions of total harvest per channel. Volume changes in the channels were
also calculated and related to changing water quality. Chemical, physical,
and microbial analyses were conducted at each harvest or more frequently.
Tests were conducted during each season through the year. During winter
some channels were covered with clear plastic and duckweed growth was
compared with that in non—covered channels.
Preliminary feeding trials were conducted with dairy cattle depending
on the quantity of material available. Emphasis was placed on the
palatability and digestibility of duckweed (wet and dry).
19
-------
SECTION 7
RESULTS
PLANT SCREENING
Studies involving the use of duckweeds were initiated July 1975.
Initial studies involved screening species of duckweed and other plants with
similar growth forms. Clones of the following duckweeds were evaluated:
Spriodela oligorhiza , S. yrhiza, Lemna rpusilla , L. g bba , and
Wolf fia spp. In addition, Azolla caroliniana and Ricäiocarpus natans were
evaluated.
The latter two species and L. gibba showed evidence under field
conditions of cold tolerance, but growth of the water fern and liverwort
was sporadic over a two month period. Spirodela oligorhiza and S. pplyrhiza
were selected for further study due to high animal feed quality character-
istics, apparent rapid growth, some evidence of cold tolerance, and their
ability to adapt quickly after considerable abuse in collei ting and
transporting. Sustained growth appeared to occur through the summer and
fall months. L. gibba was selected also, primarily due to its active growth
during winter months. Little growth was evident during the summer.
L. rpusilla and Wolf fia adapted poorly to the system and the former
gradually disappeared. Wolf f Ia maintained itself in low numbers and showed
evidence of sporadic rapid growth, particularly in cool weather. Both
L. p erpusilla and Wolff ia were dropped due to their slow adaptation to the
system.
TABLE 2 shows some chemical vlues obtained from the Ricciocarpus and
Azolla grown under lagoon conditions, indicating possible value as an animal
feed ingredient. Due to sporadic growth further study was terminated.
Values for the species used in followup studies are shown in other tables.
WASTE TREATMENT STUDIES
Characteristics of Various Components Used in the Stu y
Chemical values were obtained for the lagoon water and soils, animal
waste and duckweeds prior to the introduction of waste. Periodic sampling
of the animal waste was continued throughout the study. TABLE 3 shows the
chemical content of two duckweeds maintained in low nutrient systems before
culture. TABLE 4 shows water, soil, and manure when the lagoons were
completed and ready for loading.
20
-------
TABLE 2. CHEMICAL COMPOSITiON OF PARTIAL.LY DRIED o rpus natans AND
Azolla caroliniana GROWN ON DAIRY ASTE LAGOONS UNDER WINTER
CONDITIONS, JANUAPSY, 1976
Ricciocarpus
Crude
Proteina
Fat
Fiber
7
°
1oisture
Ash
N
P
K
Ca
Lignth
30.0
4.0
8.2
6.4
9.5
4.8
0.69
2.0
0
.83
11.9
Azolla
30.2
3.8
9.8
5.9
18.6
4.8
0.74
5.6
1
.1
5.1
aprotein equals N x 6.25.
-------
TABLE 3. CHEMICAL CHARACTERISTICS OF DUCKWEED MAINTAINED IN LOW NUTRIENT
PONDS BEFORE USE IN LAGOONS RECEIVING DAIRY CATTLE WASTE
a
Crude
%
of dry matter
Spirodela
oligorhiza
Protein
Fat
Fiber
Ash
N
P
K
13.5
2.3
12.5
16.3
2.11
0.56
2.0
Spirodela
polyrhiza
12.9
2.5
18.2
12.7
2.07
0.54
2.4
aNitrogen x 6.25.
-------
TABLE 4. CHEMICAL ANALYSI? OF CITY WATER, LAGOON SOILS,
AND MANURE
Water
(mg/i)
Soil (mg/kg)
Manure (mg/kg)
6/14/76
9/1/76
dry
6/14/76 9/1/76
6/14/76
COD < 5 < 5 1.2 x io6
TKN .70 .70 3 x 1O
Phosphorus .28 .24 8200
Calcium .50 1.20 5600 8400 22 io
Magnesium 4.50 .06 2400 2500 6200
Sodium 88.0 76.0 330 410 950
Potassium .40 .30 2800 3200 4600
Chloride 9.80 7.40 3500
Cobalt < .01 < .01 4.90 7.30 .80
Copper .02 .02 5.10 3.50 11.0
Iron .10 .00 11000 8700 1900
Manganese < .05 .00 260 240 110
Zinc .03 < .02 64 66 82
Aluminum 9600 9300 3400
Nitrate .03 .12 < 7.50
Nitrite < .03 < .03 9.00
aAverage of several composite samples taken throughout the study.
23
-------
From February 26 to April 6 two samples from the stage 1 anaerobic
lagoon were analyzed, one a composite sample taken at three points in the
lagoon and the second at the outlet. Analyses of these two samples
indicated there was little difference between the, thus the outlet was
sampled as an accurate measure of the water quality of the stage 1 anaerobic
lagoon and the effluent entering the test channels.
TABLE 5 presents BOD 5 , COD, total, volatile, and fixed residue of the
stage 1 anaerobic lagoon outlet. The general trend was an increase in all
values as the lagoon became loaded with organic matter. The range of BOD5
values was 415 mg/i on March 3 to 814 rag/i on April 4 and the COD range was
1180 mg/i on February 25 to 2701 mg/i on March 24. The totai residue,
volatile residue, and fixed residue showed the same general trend of
increase until loading of manure was stopped. The total residue ranged from
937 mg/i on March 3 to 2730 mg/i on April 14, volatile residue from 595 mg/i
on February 26 to 1504 mg/i on March 17, and the fixed residue from 220 mg/i
on March 3 to 1278 mg/l on March 10. Variation may be attributed to the
building and breakdown of the anaerobic lagoon crust.
TABLE 6 gives TKN and pH values in the stage 1 lagoon. The TKN suddenly
increased with loading of manure, but the pH changed little. Over time, the
TKN gradually increased while the pH declined but stabilized betwe n 6.5 and
7.0.
The Standard Plate Count, Anaerobic Count, Fecal Coliform, and Fecal
Streptococci counts are shown in TABLE 7. Little variation occurred in
these counts during the entire testing period. The average values were:
SPC, 2.8 x 10 6 /ml; AC, 2.1 x i0 6 /ml; FC, 2.6 x 106/100 ml; and FS, 2.0 x 106/
100 ml.
Test 1, Spring Treatment, 1976
To initiate the study, the test lagoons were filled with tap water in
early January. Duckweeds were stocked February 24 and then waste water was
introduced beginning March 10 and continued for 3 days until TKN values
approximated values in the stage 1 anaerobic lagoon (Figure 1). Duckweed
harvest and water quality analysis was initiated after the plants fuily
covered the test channels.
Preliminary tests showed that growth slowed once fuil coverage was
achieved. Thus, duckweeds in channels that were slow in achieving full
cover, in afew days would catch up with those that covered quickly. When
similar plant biomass was observed one—half of the duckweed from each test
channel was harvested by seining (April 8). Routine water quality, micro-
bial, and duckweed analyses began on the day of harvest. The control
channels did not contain duckweed. As we did not know how the system
would perform, complete chemical analyses were not run. Each channel was
sampled to obtain an idea of variability using TKN and pH as the standards.
Samples were taken about 12 cm below the surface. Other values were from
pooled samples. The data reflects water quality changes in channels tested
only with S. oligorhiza . S. p lyrhiza did not achieve full coverage, and
was therefore excluded.
24
-------
TABLE 5. BIOCHEMICAL OXYGEN DEMAND, CHEMICAL OXYGEN DEMAND,
TOTAL RESIDUE, VOLATILE RESIDUE, AND FIXED RESIDUE
OF STAGE 1 ANAEROBIC DAIRY LAGOON EFFLUENT AFTER
LOADING BEGAN (FEBRUARY 19, 1976)
Date
Chemical
Biochemical Oxygen Total Volatile Fixed
Oxygen Demand Demand Residue Residue Residue
mg/i — —
2/25/76
——— 1180 1195 723 472
2/26
——— 1162 944 595 349
3/3
415 2105 937 717 220
3110 a
540 2047 2714 1436 1278
3/17
483 2546 2728 1504 1224
3/24
585 2701 2624 1492 1132
3/31
678 2016 1912 1242 670
4/6
814 2320 2084 1422 662
4/14
667 2202 2740 1422 1318
4/22
533 1936 2416 1492 924
4/29
467 1665 2098 1440 658
5/6
557 1790 2013 1063 950
aF1OW to test channels initiated and continued for three days.
25
-------
TABLE 6. STAGE 1 ANAEROBIC LAGOON TKN AND pH VALUES
Date TKN (mg/i) pH
2/3 4.2 7.60
2/11 4.1 7.75
2/18 (manure loading 55.7 7.55
initiated)a
2/24 80.5 7.35
3/1 122.0 7.45
3/6 179.0 7.45
3/16 209.9 7.15
3/22 196.3 6.90
3/30 (manure loading 123.5 7.00
ceased)
4/4 129.1 6.55
4/15 123.5 6.55
4/27 119.4 6.80
5/s 105.9 6.80
aApproximately 3,651 kg added/day. Washvater from the loafing area
and milking parlor were added daily throughout most of the year.
26
-------
TABLE 7. STANDARD PLATE COUNT, ANAEROBIC COUNT, FECAL COLIFORN,
AND FECAL STREPTOCOCCI COUNTS OF THE STAGE 1 ANAEROBIC
LAGOON EFFLUENT
Fecal
Fecal
Standard
Plate
Anaerobic
Coliform
Streptococci
Date Count per ml
Count
per
ml
per 100
nil
per 100
ml
x io 6 —
2/26/76 3.9 2.5 4.9 3.3
3/3 2.1 43 3.3 1.8
3/10 2.3 1.6 3.5 3.3
3/17 2.3 1.5 3.1 1.7
3/24 3.4 1.5 3.3 2.3
3/31 3.5 1.5 2.3 1.7
4.6 2.3 2.5 1.1 1.8
4/14 2.9 1.8
4/22 2.0 1.8 1.8 1.2
4/29 3.0 1.9 1.3 1.4
5/6 2.6 1.8 1.2 1.4
Average
Value 2.8 2.1 2.6 2.0
27
-------
During the test, we received 1.1 cm of rain (TABLE 8), thus water
levels declined during the study. Water quality values shown in other
tables have not been corrected for evaporation. Normal rainfall for April
and May is 13.9 and 10.9 cm respectively. Had we received this much rain
the water would have remained at about the original depth and water quality
values would have been about 20% lower than shown. TABLE 9 shows the change
in BOD5, COD, total, fixed and volatile residue for duckweed covered and
control channels. The data show that the control and duckweed—covered
channels varied in their response to the values measured. However, since
only one control channel was available for comparison, care should be
excercised in concluding a significant difference existed for any parameter.
The data indicate that the duckweed—covered channels showed approximately
the performance of control channels. Figure 2 depicts the changes graphi-
cally.
TABLE 10 shows bacterial counts for the duckweed and control lagoons.
Data was not available when the test was initiated so the percent change
could not be determined. Based on the final counts it appears that the
duckweed—covered lagoons had lower bacterial levels than the control
channels. These values were a little surprising due to the apparent lower
phytoplankton levels in the duckweed channels. Reduced competition for
nutrients by the phytoplankton in the test channels could result in higher
bacterial levels, but the data shows higher bacterial counts occurred in
control channels with higher phytoplankton levels.
The TKN reduction was similar in the test and control channels
(Figure 3). Reduction in the control channel was 30%, and 29.5% for the
test channel. The TKN declined at a rate of 1.26 mg/i/day under both
conditions. However evaporation would serve to concentrate the TKN so
the quantity removed daily was actually higher. Correction for water loss
(ca 20% of the water volume) shows that about 41 mg/i of TKN was removed.
Under normal rainfall at this Jime of year, this reduction would be
expected.
At nutrient levels where the TKN values exceeded 110 mg/l it would
require about 90—100 days retention time for nitrogen to be reduced to
acceptable levels for release under static lagoons with no circulation,
assuming the rate of decline was linear. However, chemical stratification
was evident in the test channels and the lower values near the surface
could have reduced the rate of duckweed growth.
Based on these data, loading rates for lagoons should be lower than
used here. The question of immediate importance, however, is what happens
to the nitrogen in both systems? All channels were anaerobic, indicating
that much of the nitrogen was in the ammonium form or tied up in the biota.
Since water samples were not filtered we were unable to determine the
quantity in solution, and therefore available to the duckweeds. It is also
conceivable that the top 2 or 3 cm of the duckweed channels were low in
nutrients. Based on the rate of harvest and the quantity of nutrients in
the plants (see TABLES 11 and 12) it is possible that excellent treatment
occurred near the surface.
28
-------
TABLE 8. RAINFALL DATA FOR TEST 1 STUDY PERIOD (CM)a
March, 1976 Apr11, 1976 May, 1976
3/8 1.52
3/14 ———— 1.50
3/15 0.46
3/16 0.64
3/20 0.25
3/21 0.76
3/26 6.10
3/30 1.14
3/31 0.89
Total 12.34
4/3 0.33
4/25 1.09
Total 1.42
0
5/8 2.97
a x .3937 for inches.
-------
TABLE 9. BIOCHEMICAL OXYGEN DEMAND, CHEMICAL OXYGEN DEMAND, TOTAL RESIDUE, VOLATILE RESIDUE,
AND FIXED RESIDUE IN mg/i OF STATIC DAIRY WASTE LAGOONS WITH AND WITHOUT DUCKWEED
(S. oligorhiza) , SPRING, 1976 (TEST LAGOON 1)
Date
Biochemical
Oxygen
Demand
Chemical
Oxygen
Demand
Total
Residue
Fixed
Residue
Volatile
Residue
C 8 T
C T
C T
C T
C T
4/8
385 475
1888 2096
1658 1586
698 590
960 996
4/22
334 480
1382 1512
2370 2182
1044 704
1326 1478
4/29
294 358
978 978
1740 1576
596 756
1144 820
5/6
188 269
891 979
1181 1229
474 346
707 883
% reductlonb
51 43
53 53
29 23
32 41
26 11
8 Control (C)
Test (T), average of 3 channels.
corrected for evaporation.
-------
2500 —
2000
1500
mg / I
1000
500—
0
APRIL 8
Figure 2.
5
Control channels
Test channels
TR
I I I
22 29MAY6
Biochemical oxygen demand (BOD 5 ), chemical
oxygen demand (COD), total residue (TR),
volatile residue (VR), and fixed residue (PR)
in static dairy waste lagoon water with and
without duckweed ( . oligorhiza) , spring,
1976 (Test lagoon 1).
COD
VR
FR
/
/
,
—
— — — — — — — —
8005
31
-------
TABLE 10. STANDARD PLATE COUNT, ANAEROBIC COUNT, FECAL COLIFORN,
AND FECAL STREPTOCOCCI COUNTS IN STATIC DAIRY WASTE
LAGOONS WITH AND WITHOUT DUCKWEED (S. oligorhiza),
SPRING, 1976 (TEST LAGOON 1)
Date
Standard Plate
Count per ml
Fecal Fecal
Anaerobic Coliform Streptococci
Count per ml per 100 ml per 100 ml
io 6
———x lO - ——————-———
C
T
C T C T C T
4/22
2.1
2.5
4.3 4.5 3.3 3.1 4.9 1.8
4/29
2.1
2.3
5.7 5.1 2.3 2.3 3.3 1.1
5/6
2.5
1.4
3.9 3.3 3.3 3.3 3.3 2.3
32
-------
20 —
110-
100—
mg / I
90—
80—
Control
S. oligorhizo
\
7.05
7.15
6.98 6.99
8.10 8.10 8.10 Control
7.65 7.43 7.55 Test
I I I I I
APRIL 8
15 22
29 MAY 6
Figure 3.
TKN reduction and pH in static dairy waste lagoons
with and without stands of duckweeds, spring, 1976
(Test lagoon 1).
L
pH
33
-------
c )
TABLE 11. S. olig 1 orhiza BIOMASS HARVESTEDa FROM STATIC TEST CHANNELS RECEIVING
DAIRY WASTE, SPRING, 1976
aHarvest data reflects actual biomass removed/rn 2 from one—half (12.5 m 2 ) of each test channel.
Only half would be harvested in order to leave duckweed stock for regrowth.
bAverage of 4 test channels.
CTotal harvest values in kg/ha/mo and lbs/acre/mo are based on one—half hectare or acre being
harvested.
Harvest
dateb
Total/27
days
Harvest/moC
kg/ha
lbs/acre
4/15
4/22
4/29
5/5
kg
harvested/rn 2
wet
.66
.485
.389
.487
2.02
dry (9.2%)
.06
• .045
.035
.045
.185
2056
1836
-------
TABLE 12. PARTIAL CHEMICAL ANALYSIS OF S. oligorhiza
GROWN ON STATIC TEST CHANNELS RECEIVING
DAIRY WASTE, SPRING, 1976
Sample
date
moisture
%
of dry mattera
4-9
92
TKN
Fiber
Ash
Fats
TOC
Crude
proteinb
———
———
———
———
———
4—13
90
——--
———
6.8
———
———
4—21
90
5.15
7.18
9.1
———
O.5
32.19
4—29
90
4.92
8.28
7.0
———
32.3
30.75
5—5
92
5.10
6.68
1
0.3
———
36.3
31.88
aAverage of
bNitrogen x
four
6.25.
channels.
35
-------
Undoubtedly fallout of organic matter accounted for some decline in
the TKN, but how much is difficult to tell. Attempts to quantitatively
measure the depth of the sludge layer were not successful as incoming
suspended matter at the start of the test contributed an unknown amount
of detritus to the channel bottom.
The TOC values were obtained for the lagoon water near the end of the
study. The control channel TOC value was 210 and 200 mg!l for the last two
sample periods, while the composited duckweed channels averaged 328 and
283 mg/i. The C:N ratio on May 5 was 2.5 to 1 for the control and 3.58 to 1
for the combined test channels for water sampled about 25 cm below the
surface.
The test channels appeared to show higher buffering capacity than the
control channels as the pH increased less (Figure 3) in the test channels.
However, the duckweed cover undoubtedly reduced the incoming light, coupled
with lower phytoplankton levels, the quantity of C02 produced could have
been altered considerably.
TABLE 11 shows the kg wet duckweed harvested from one—half of each test
channel at estimated doubling times for S. oligorhiza . The average dry
biomass harvested/rn 2 was .185 kg over the 27 day period. Projecting this
figure to a hectare or acre basis, the total dry biomass that would have
been harvested would be 2056 kg and 1851 lbs respectively. Based on
nutrient analysis (TABLE 12) the duckweed averaged 31.6% crude protein,
or 585 lbs of the biornass was protein. The low fiber and ash values shown
in TABLE 12 show that the duckweed is a high quality feed material. The
water content was low compared to later tests as will be seen. Duplication
of drying showed these values to be accurate. Reasons for the high dry
matter in this test are not known.
It is evident from TABLE 13 that protein values can be higher than
reported in TABLE 12, and also in previous work where values exceeded 40%
(Culley and Epps, 1973).
TABLE 13 shows growth of duckweed under continuous flow of effluent
into test channels. These data were obtained in order to determine if the
chemical content of duckweed was affected by a static vs. flowing system
in which high nutrient levels could be maintained. Water and ash content
of plants grown on the two systems were similar. Nitrogen, fiber, TOC,
and crude protein gradually increased over time. It appears that a constant
flowing system may improve duckweed feed value, but will also tend to
complicate treatment as the retention time must be increased as waste
treatment is offset by incoming effluent.
During this test water temperatures were recorded just under the water
surface and 25 cm from the bottom. Surface temperatures ranged from 170 to
20°C and bottom temperatures from 16° to 18°C. Thermal stratification was
evident in all channels. No temperature difference could be detected
between test and control channels at the surface or bottom. Temperature
differences between the surface and bottom ranged from .5 to 2.5°C. The
36
-------
TABLE 13. PARTIAL CHEMICAL ANALYSIS OF S. p lyrhiza
GROWN ON TEST CHANNELS RECEIVING A CONTINUOUS
FLOW OF DAIRY WASTE FROM THE STAGE 1 ANAEROBIC
LAGOON, SPRING, 1976
Sample
date
%
moisture
% of dry mattera
4—9
90
TKN
Fiber
Ash
Fats
TOC
Crude
proteinb
5.13
5.7
9.6
———
34
32.06
4—13
90
———
———
8.0
———
———
———
4—2 1
———
———
———
———
———
———
———
4—29
91
5.40
9.8
5.8
———
35
33.75
5—5
93
5.91
9.1
9.6
———
44
36.94
aAverage of six channels.
bNitrogen x 6.25.
37
-------
stage 1 anaerobic lagoon consistently had 2 to 5°C higher temperature
and no vertical stratification.
This initial test indicated that the duckweed treatment performed
equally to the control channels when the system received a high load of
organic waste. The major difference indicated by harvesting the duckweed
was that a considerable quantity of nutrients were removed by the duckweed
whereas in the control channels many of these nutrients would remain in the
bottom sediments or leave with the effluent.
Test 2, Summer Treatment, 1976
The same basic procedures used In Test 1 were repeated here. Test
lagoons 1 and 2 were flooded with the stage 1 anaerobic lagoon effluent,
but at a lower nutrient level. Twelve channels were used, four each for
S. oligorhiza , S. polyrhiza , and controls. Equal quantities of both plants
were stocked (taken from previous test) on May 17 when the channels were
reflooded. First harvest date was May 26 and was based on an average
surface area of 25 m 2 /channel. Water quality data was not corrected for
evaporation, and collected about 12 cm below the surface. Productivity and
nutrient content was again determined for the duckweeds.
Only washwater from the holding pens and milking parlor was allowed to
enter the stage 1 anaerobic lagoon. Data on the lagoon are presented in
TABLES 14, 15, and 16. A crust formed on the lagoon before the study was
initiated and the continual build up and breakdown of this crust along with
daily loading undoubtedly caused variation in the outlet sample. The
general increase in bacterial counts (TABLE 16) is due to increasing
temperature and continued high nutrient conditions. TABLES 18 through 21
and Figures 4 through 11 show water quality changes during this study and
TABLE 17 shows rainfall. Water quality values were not corrected for
evaporation. Although nearly 17 cm of rain occurred during the 50 days,
evaporation still exceeded rainfall. Water quality values would have been
about 202 lower had evaporation equaled rainfall.
It is clearly evident from all water quality values recorded in
TABLES 18 through 21 that the duckweed—covered channels performed as well
as the control channels in water quality renovation. Although there was
considerable fluctuation on specific sampling days for several parameters,
by the end of the test most values were similar, and the actual value change
for each parameter was similar.
TABLES 22 through 25 and Figures 12 through 14 show surface water
bacterial population changes with treatment. Responses again show t est and
control channels performed similarly In bacterial reduction. Bacteria
counts were lower In two of the four categories at the end of the test, but
the differences were slight. It is pertinent to point out again, that
results obtained should not be taken as expected values under a well managed
system in which large quantities of insoluble matter would not enter
duckweed—covered lagoons. TABLE 26 shows the average percent reduction of
chemical and microbial parameters for combined channels. Calcium was not
38
-------
TABLE 14. BIOCHEMICAL OXYGEN DEMAND, CHEMICAL OXYGEN
DEMAND, TOTAL RESIDUE, VOLATILE RESIDUE, AND
FIXED RESIDUE OF THE STAGE 1 ANAEROBIC DAIRY
LAGOON EFFLUENT
Biochemical Chemical Total
Oxygen Oxygen Total Volatile Fixed Suspended
Date Demand Demand Residue Residue Residue Matter
— ——mg/i
5/17/76 498 2149 2382 1642 740 800
5/26 317 1984 2116 1376 740 400
6/4 256 1052 1864 1290 874
6/14 ——— 1767 2044 1350 694 770
6/18 ——— 2450 3148 1576 1572 2140
6/24 ——— 1656 2570 1540 1030 1160
7/1 495 1842 2434 1932 502 1140
Average
Value 392 1843 2365 1529 879 1068
39
-------
TABLE 15. STAGE 1 ANAEROBIC LAGOON WATER QuALITYa
Date TKN(mg/1) K(mgIl) Ca(uig/1) pH Temperature(°C)
5/27 89.9 97.7 54.6 6.80 24.4
5/31 105.9 97.7 50.4 6.85 25.0
6/6 112.4 102.0 43.1 7.02 25.6
6/14 90.8 101.3 38.0 6.61 26.7
6/18 116.2 6.84 27.2
6/24 117.5 74.3 64.1 6.98 27.8
7/1 128.1 6.85 27.8
7/8 126.7 150.8 67.5 6.61 28.3
7/15 125.9 138.1 69.9 6.75
7/22 104.3 152.8 56.9 6.85
7/29 111.7 14L4 60.1 6.68 26.7
8/5 101.9 143.0 55.4 6.86 26.7
9/1 69.2 84.5 45.5 6.62
9/8 80.4 79.6 43.9 6.65
aReceived only wash water from the loafing area and milking parlor.
Considerable manure loaded in February and March was still present.
40
-------
TABLE 16. STANDARD PLATE COUNT, ANAEROBIC COUNT,
FECAL COLIFORN, AND FECAL STREPTOCOCCI
COUNTS OF THE STAGE 1 ANAEROBIC LAGOON
EFFLUENT
Date
Standard Anaerobic
Plate Count Count
per nil per ml
Fecal Fecal
Coliform Streptococci
per 100 ml per 100 ml
io 6
x
5/17/76
3.2 2.2
1.8 1.3
5/26
2.5 2.0
2.2 2.0
6/4
2.6 5.5
2.8 2.0
6/14
4.9 3.9
4.7 3.8
6/18
2.7 4.4
4.8 4.1
6/24
2.1 3.1
5.1 4.8
7/1
3.2 3.0
4.1 3.7
Average
Value
3.0 3.4
3.6 3.1
41
-------
TABLE 17. RAINFALL DATA FOR TEST 2 STUDY pERIODa (( )b
May 1976
June 1976
July 1976
5/25 ———
0.89
611
—1.91
7/ ]. 1.37
5/28
1.40
6/5
1.14
7/5 4.01
Total
2.29
6/19
— 1.60
7/17 ———————— 3.12
6/29
5.21
7/20 2.49
6/30
0 .15
7/23 1.09
Total
10.01
7/24 2.21
7/25 2.62
7/26 0.13
Total 17.04
aS UdY initiated May 17 and terminated July 15.
bX 39 31 for inches.
42
-------
TABLE 18. BIOCHEMiCAL OXYGEN DEMAND, CHEMICAL OXYGEN DEMAND,
TOTAL RESIDUE, VOLATILE RESIDUE, FIXED RESIDUE,
AND TOTAL SUSPENDED MATTER OF THE S. oligorhiza
TEST CHANNELS, SUMMER, 1976
Date
Biochemical Chemical Total
Oxygen Oxygen Total Volatile Fixed Suspended
Demand Demand Residue esidue Residue Matter
mg/i
5/17/76
278 782 934 643 291 620
5/26
91 732 1078 908 170 300
6/4
47 341 724 386 338
6/14
——— 293 922 552 370 100
6/18
——— 304 742 400 342 86
6/24
——— 266 892 645 247 84
7/1
20 217 735 436 299 94
7/8
——— 279 668 442 226 108
7/15
——— 180 382 198 184 93
43
-------
TABLE 19. BIOCHEMICAL OXYGEN DEMAND, CHEMICAL OXYGEN DEMAND,
TOTAL RESIDUE, VOLATILE RESIDUE, FIXED RESIDUE,
AND TOTAL SUSPENDED MATTER OF COMPOSITE SAMPLE
OF THE S. p 1yrhiza TEST CHANNELS, SU *(ER, 1976
Date
Biochemical Chemical Total
Oxygen Oxygen Total Volatile Fixed Suspended
Demand Demand Residue Residue Residue Matter
————————mg/l————————————-—-— —---———-
5/17/76
236 807 1087 743 344 690
5/26
60 516 980 718 262 330
6/4
51 403 794 432 362
6/14
——— 301 1078 590 488 170
6/18
——— 316 714 392 322 114
6/24
——— 216 939 735 204 108
7/1
18 202 683 388 295 104
7/8
—— 271 584 358 226 109
7/15
——— 184 596 460 136 91
44
-------
TABLE 20. BIOCHEMICAL OXYGEN DEMAND, CHEMICAL OXYGEN DEMAND,
TOTAL RESIDUE, VOLATILE RESIDUE, FIXED RESIDUE,
AND TOTAL SUSPENDED MATTER OF TfIE COMPOSITE SAMPLE
FROM THE CONTROL CHANNELS, SUMMER, 1976
Date
Biochemical Chemical Total
Oxygen Oxygen Total Volatile Fixed Suspended
Demand Demand Residue Residue Residue Matter
— mg/i
5/17/76
248 861 938 600 338 630
5/26
52 616 893 597 296 320
6/4
33 263 692 472 220
6/14
——— 274 790 516 274 110
6/18
——— 336 773 450 323 122
6/24
——— 230 857 587 270 104
7/1
17 209 769 489 280 104
7/8
——— 271 722 484 238 111
7/15
——— 209 550 352 198 101
45
-------
0 ’
TABLE 21. TXN, POTASSIUM, CALCIUM, TOC, pH AND WATER TEMPERATURE OF TEST AND CONTROL
CIIANNELSa SUMMER, 1976
Date
TKN(mg/1)
bs.o. S.p.
K(nig/1)
Ca(mg/1)
TOc(mg/1)
pH
C
S.o. S.p. C
S.o.
S.p.
C
S.o.
S.p.
C
S.o.
S.p.
C
5/17/76
82.2
75.0
76.8
—
7.1
7.3
7.4
5/27
69.6
60.1
63.8
91.1 92.7 94.3
63.0
63.0
64.2
155
125
120
7.6
7.8
8.0
5/31
63.9
64.0
61.7
88.9 90.1 96.0
60.3
62.0
64.7
120
150
135
7.6
7.7
8.0
6/6
59.9
58.9
59.4
90.3 91.9 93.6
66.4
65.5
69.3
225
220
225
7.7
7.6
8.0
6/14
53.5
54.7
53.1
91.4 94.0 96.9
59.4
62.4
64.0
———
———
———
7.5
7. 3
7.8
6/18
50.1
53.3
49.7
L06.6 103.5 108.8
61.9
60.9
61.0
———
———
———
7.7
7.5
8.0
6/24
43.8
47.0
45.1
96.0 95.4 96.8
77.7
77.4
86.0
110
98
99
7.9
7.7
7.9
7/1
34.4
33.9
36.5
——— ——— ———
———
———
———
84
81
85
7.7
7.7
7.8
7 / 8 c
24.0
26.0
28.5
80.1 84.4 93.4
56.3
61.3
68.1
83
84
85
7.7
7.5
8.1
7/15
23.3
17.1
20.7
75.4 72.6 81.0
55.1
60.2
58.3
———
———
———
7.8
7.6
7.8
(Continued).
-------
TABLE 21 (continued).
Date
Water temperature
So.
and
S.p.
Control
Top
Bottom
Top
Bottom
5/17
20.2
19.5
21.4
19.5
5/27
21.3
19.1
21.5
19.5
5/31
22.8
19.3
25.0
19.4
6/6
24.0
20.2
25.5
20.3
6/14
25.0
20.7
25.9
20.6
6/18
25.9
21.6
26.3
21.4
6/24
26.7
21.9
26.9
21.8
7/2
27.4
22.2
27.4
22.2
7/8
27.5
22.3
27.4
22.2
7/29
26.8
25.9
———
———
8/5
26.9
25.8
———
———
aAverage of 4 channels.
bs. 0 . ( Spirodela oligorhiza) , S.p. ( !p4 de1a polyrhiza) , C (control).
CAverage of 2 channels beginning on 7/8.
-------
300—
I _____________
I
250— 1
I
1
1
1
200—
II
I
150— 1
mg/I
100 —
50
0
MAY 17 26 JUNE 4 14 8 24 JULY I
Figure 4. 5—day biochemical oxygen demand in static dairy
waste lagoons with and without stands of duckweeds,
summer, 1976.
Control
—— — —. S. oligorhizo
S. polyrhizo
‘4
‘4
\
I I
I I
48
-------
300—
_L _ _i i i i i i i
4 I a JULY I
4 24
a
‘5
Figure 5.
Chemical oxygen demand in static dairy waste
lagoons with and without stands of duckweeds,
summer, 1976.
‘
Control
—‘——— S oligorhiza
————-—S. polyrhiza
I
I
I
‘I
I
I
mq / I
700
500
300—
100—
MAY I?
JUNE
26
49
-------
1050 —
950
850 —
750-
650-
550—
450—
I
—
NAY 17 JUNE 4
26
I I i I i
8 JULY I 15
4 24 8
Figure 6.
Total residue in
with and without
sunnner, 1976.
static dairy waste lagoons
stands of duckweeds,
It
It I
/ I
I
Control
.————s S. oligorhlza
————— S. polyrhlzo
mg /I
St
St
I-
50
-------
Control
I’
I’
I
I’
It
I
— I
I
I
‘%
‘I
600—
400—
200—
I I
MAY 17 JUNE 4
26
1—— S. oligorhizo
S 1 polyrhizo
I II I I I
lB JULY I 15
14 24 8
Figure 7.
Volatile residue
with and without
1976.
in static dairy waste lagoons
stands of duckweeds, sunmier,
1000
800
mg/I
/
/
51
-------
500
400 —
300—
200—
\
‘I
I
A
I’
I’
/ I
/
I
I
I A
I,’
Control
.‘————.s. oligorhiza
S. polyrhiZa
I
MAY 17
26
I II I I I
JUNE 4 18 JULY I 15
4 24 8
Figure 8.
Fixed residue in static dairy waste lagoons
with and without stands of duckweeds, summer,
1976.
mg/I
‘I
Iv ’ )
52
-------
700—
600—
500 —
400—
300—
200-
I
II I
MAY 17 JUNE 4 18 JULY I 15
26 4 24
8
Figure 9.
Total suspended matter in static dairy waste
lagoons with and without stands of duckweeds,
summer, 1976.
Control
.——————-. S. oligorhizo
S. polyrhizo
mg/I
100-
-
0
53
-------
90-
I II I Ii I V I I
17 31 (4 24 8
27 JUNE 6 18 JULY I
‘5
Figure 10.
TKN reduction in test channels covered with
duckweed, and controls, sunuer, 1976.
80-
Control
——- ——--S S oligorbizo
S. polyrhizo
mg/I
70—
60-
50-
40-
30 —
20-
10-
0
MAY
54
-------
220-
ft I ft
27 JUNE 6
31
I I I
24
JULY I
$
Figure 11. TOC reduction in test channels covered with
duckweed, and controls, summer, 1976.
Control
..————--. S. oligorhizo
S. polyrhiza
mg / I
200 -
(80 -
(60
140 -
120 -
100
80-
—
MAY
55
-------
TABLE 22. STANDARD PLATE COUNT OF COMPOSITE SAMPLES OF
TEST CHANNELS COVERED WITH DUCKWEED, AND
CONTROLS, SUMMER, 1976
Date
Standard Plate Count per ml
s. oligorhiza S. pçlyrhiza Control
——————-----——-—x10 6
3.0 2.6 2.5
5/17/76
5/26
2.5 1.7 1.5
6/4
4.9 4.6 1.7
6/14
1.7 1.1 1.9
6/18
1.3 1.6 1.7
6/24
1.5 1.3 1.3
711
2.3 1.6 1.9
56
-------
TABLE 23. ANAEROBIC COUNT OF COMPOSITE SAMPLES OF TEST
CHANNELS COVERED WITh DUCKWEED, AND CONTROLS,
SUMMER, 1976
Date
Anaerobic
Count per ml
S. ollgorhiza S.
polyrhiza Control
x l0
5/17/76
3.3
3.8 3.4
5/26
3.1
3.1 3.3
6/4
4.8
3.3 4.6
6/14
4.6
5.3 4.1
6/18
1.2
1.8 1.5
6/24
1.4
1.2 1.5
7/1
1.4
1.7 1.4
57
-------
TABLE 24. FECAL COLIFORM COUNT OF COMPOSITE SAMPLES
OF TEST CHANNELS COVERED WITH DUCKWEED,
AND CONTROLS, SUMMER, 1976
Date
Fecal Coliform per 100 ml.
S. oligorhiza S. polyrhiza
—— — —— — —————x10 5 ————
2.0 2.5
Control
5/17/76
2.1
5/26
3.3 3.0
2.4
6/4
3.5 5.0
3.4
6/14
3.6 4.4
1.4
6/18
3.7 4.1
2.0
6/24
2.3 2.7
2.3
7/1
1.9 1.6
1.2
58
-------
TABLE 25. FECAL STREPTOCOCCI COUNT OF CO 1POSITE SAMPLES
OF TEST CHANNELS COVERED WITH DUCKWEED, AND
CONTROLS, SUMMER, 1976
Date
Fecal Streptococci per 100 ml
S. ol.lgorhiza S. p 1yrhiza Control
x1 0 5
1.7 1.8 1.5
5/17/76
5/26
1.9 2.6 1.4
6/4
2.1 2.3 2.0
6/14
2.1 3.0 1.0
6/18
2.0 2.6 1.1
6/24
2.4 2.6 2.2
7/1
1.6 1.4 0.9
59
-------
STANDARD PLATE COUNT
Control
— -• S.oligorhizo
—— ——— S.polyrhizo
I II I I
17 26 4 1418 24 I
ANAEROBIC COUNT
I II
(7 26 4 141824
JUNE
JULY
Figure 12.
Standard bacteria plate count and anaerobic
counts per ml of composite samples of the
test channels covered with duckweed, and
controls, summer, 1976.
6
5
x io6
4-
3-
2—
0
6
5
X 106
4-
3—
2—
I—
0
MAY
60
-------
6—
Control
I-— — — - S. ollgorhizo
\
-‘
I I
I? 26 4 141824
JUNE
MAY
Fecal coliform per ml
test channels covered
summer, 1976.
of composite samples of
with duckweed, and controls,
5
4
S. polyrhizo
I
/
II
/
/
I
I
x
3—
2
V
Figure 13.
JULY
61
-------
Control
—— — —. S. oligorhiza
/ ‘ ————— S. polyrhiza
‘St
I I I II I
17 26 4 1418 24 I
JUNE
JULY
Figure 14. Pecal streptococci count per ml of composite
samples of test channels covered with duckweed,
and controls, summer, 1976.
/
/
/
\ /
/
I
I
I
—I
x 103
/
V
‘4
3—
2
I—
0
MAY
62
-------
TABLE 26. PERCENT REDUCTION IN TEST AND CONTROL CHANNEL WATER QUALITY AND BACTERIAL
COUNTS, SUMMER, 1976
0 ’
Biochemical
Oxygen
Demand
Chemical
Oxygen
Demand
Total
Residue
Volatile Fixed
Residue Residue
Total
Suspended
Matter
Total
Kjeldahl
Nitrogen
S. oligorhiza
92
77
59
69 37
85
72
S. polyrhiza
93
77
45
38 60
87
77
Controls
93
76
41
41 41
84
73
Potassium
Total
Organic
Carbon
Standard
Plate
Count
Anaerobic
Count
Fecal
Coliform
Count
Fecal
Streptococci
S. oligorhiza
18
46
23
58
5
6
S. polyrhiza
22
33
38
55
.6
22
Controls
14
29
24
59
43
40
-------
included as a decline was not clearly evident. Potassium did show a little
decline. Both of these elements were not expected to decline because of
their abundance in the soil.
The percent decline in bacterial counts were low. The values were
calculated from the counts on the first and last day. However, the counts
increased up to the third to fifth sampling period and then declined.
Percent decline for the fecal coliform under S. oligorhiza , S. p lyrhiza , and
control would have been 49%, 68%, and 65% respectively had the highest count
been used. Similar increases in the percent decline were evident in other
bacterial counts. High copepod populations developed as the bacterial
counts peaked. They may have contributed significantly to the bacterial
decline as they feed on the bacteria.
In the control channels the pH drifted up to a value of 8, while In the
test channels it remained between 7.5 to 7.7. As the water quality improved
in all channels, the pH stabilized between 7.6 to 7.8. The higher values
in the control probably related to photosynthetic activity by phytoplankton
in the water column. As the nutrients became depleted phytoplankton biomass
decreased as did the photosynthetic rate, and therefore the pH.
During the 59 days of the test TKN reduction averaged 1 mg/i/day, not
taking into account that evaporation served to concentrate TKN. This daily
redution is less than the TKN reduction observed in Test 1 where higher
nutrients were recorded.
In developing a management scheme for lagoons, with or without duckweed,
nutrient loading where TKN is less than 100 mg/i may be more efficient in
achieving acceptable water quality as the total percent reduction was
greater at the lower level. Further analysis is needed however, because
the sludge layer on the lagoon floor may have contributed to the nutrients
in the water column. Because in the initial study and Test 2, the lagoons
were flooded with an effluent high i; nutrients and suspended matter, a
nutrient reservoir developed on the bottom. Under a controlled system, flow
of soluble nutrients into the aquatic plant lagoons should be maximized,
and flow of suspended organic matter minimized. In an effort to evaluate
the effect of nutrient—laden sludge on the nutrients in the water column, a
test was set up to resuspend the sludge by mixing. This study (Test 3) is
discussed in the next section.
The growth response and chemical content of the two duckweeds are shown
in TABLES 27, 28, 29, and 30. Compared to Test 1 (spring) S. oligorhiza had
reduced growth. S. 2 yrhiza developed rapidly and showed excellent growth.
It is not known if our clone of S. oligorhiza was affected by the increased
temperature, daylength, or nutrients. Previous to this project both species
had grown well under cool temperatures and a shorter daylength. However,
in the spring test the S. p lyrhiza clone developed slowly, but grew rapidly
as summer conditions appeared. Factors other than genetics and nutrients
complicate the growth of duckweeds and this study was not designed to deter-
mine these various factors. For example, duckweeds are known to show
periodicity in growth unrelated to temperature. With this knowledge,
management schemes should give proper consideration to utilizing mixed
64
-------
TABLE 27. S. oligorhiza BIOMASS HARVESTEDa FROM STATIC TEST CHANNELS
RECEIVING DAIRY WASTE, SUMMER, 1976
Harvest
dateb
Total/59
days
Harvest/moC
5/26
6/6
6/14
6/18
6/24
711
7/8
7/15
kg/ha
lbs/acre
kg
harvested/rn 2
wet
.51
.26
.45
.50
.29
.43
.36
.41
3.21
———
dry (7.96%)
.041
.021
.036
.040
.023
.034
.029
.033
0.257
1307
1167
avalues show the average amount removed (½) from a m 2 .
bAverage of 4 test channels except for 7/8 and 7/15 which are the average of 2 channels.
CTotal harvest values are based on one—half hectare or acre being harvested. One—half remains for
regrowth.
0 ’
U i
-------
a.’
0 ’
TABLE 28. S. polyrhiza BIOMASS HARVESTEDa FROM STATIC TEST CHANNELS RECEIVING
DAIRY WASTE, SUNMER, 1976
avalues show the average biomass removed (½) from a m 2 .
bAverage of 4 test channels except for 7/8 and 7/15 which are averages of 2 channels.
CTota] . harvest values are based on one—half hectare or acre being harvested. One—half remains for
regrowth.
Harvest
dateb
Total/59
days
Harvest/moC
kg/ha lbs/acre
5/26
6/6
6/14
6/18
6/24
7/1
7/8
7/15
kg
harvested/rn 2
wet
———
.82
.73
.64
.50
.52
.50
.79
4.50
dry
———
.048
.043
.038
.030
.031
.030
.047
.267
1358
1213
-------
TABLE 29. PARTIAL CHEMICAL ANALYSIS OF S. oligorhiza
GROWN ON STATIC TEST CHANNELS RECEIVING
DAIRY WASTE, SUMMER, 1976
Sample
Date
% Moisture
% of dry mattera
Crude —
TKN
Fiber
Ash
TOC
Silica
Proteinb
5/25
91.1
5.87
8.1
9.4
35.8
.65
36.7
5/31
92.9
5.46
7.9
10.9
34.5
.83
34.1
6/6
92.0
5.96
7.9
12.0
36.5
———
37.3
6/18
91.8
5.92
———
12.3
32.5
———
37.0
6/24
92.2
5.53
7.3
13.0
34.0
———
34.6
7/1
92.6
5.58
8.6
14.0
32.0
———
34.9
7/8
91.5
5.77
8.8
13.9
36.5
———
36.1
7/15
92.2
5.25
10.0
37.5
———
32.8
aAverages of 4 channels except for 7/8 and 7/15 which are an average of
2.
bNitrogen x 6.25.
67
-------
TABLE 30. PARTIAL CHEMICAL ANALYSIS OF S. polyrhiza
GROWN ON STATIC TEST CHANNELS RECEIVING
DAIRY WASTE, SUMMER, 1976
Sample
Date
%
Moisture
% of
dry mattera
TKN
Fiber
Ash
TOC
Silica
Crude
proteinb
5/25
———
———
———
———
———
———
———
5/31
94.3
5.38
9.5
13.1
34.3
1.25
33.6
6/6
94.2
6.55
8.6
12.9
34.3
———
40.9
6/18
94.9
5.51
———
13.0
33.8
———
34.4
6/24
94.3
5.76
8.0
12.5
34.8
———
36.0
7/1
94.7
5.95
9.4
12.6
34.8
———
37.2
7/8
93.4
5.70
9.3
14.2
36.0
———
35.6
7/15
93.0
5.44
9.6
12.9
32.5
———
34.0
aAverage of 4 channels except for 7/8 and 7/15 which are an average
of 2.
bNitrogen x 6.25.
68
-------
species as well as several clones of a species so that some plants will be
actively growing at all times.
With the reduction in growth in Test 2, the channels were ref boded
with effluent from the stage 1 anaerobic lagoon to determine if the addition
of nutrients would restimulate growth, and thereby improve treatment of the
waste water. This study is shown in Test 4.
Test 3, Mixing Treatment, Summer, 1976
Due to the low biomass of duckweed harvested during Test 2 and the
reduced nutrient levels in the lagoon water, a test was set up to determine
if mixing of the bottom sediments into the water column would revive duck—
weed growth. Analysis of the sludge TICN showed that 1300 to 1400 mg/l
was present. Channels in test lagoon 2 were thoroughly mixed manually on
alternate days and test lagoon 1 served as a non—mixed control. TABLES 31
and 32 show little change in water quality between the mixed and non—mixed
channels. The TKN was the only value that showed a consistent increase in
all channels as a result of mixing. However, the increase was modest, and
by the end of two weeks the TKN values for the mixed and non—mixed channels
had declined. Channels containing S. oligorhiza had similar TKN values
under both conditions. S. olyrhiza and control channels were rapidly
declining but the mixed channels showed higher TKN values. Values before
mixing were not available for K and Ca. Potassium appeared a little higher
in the non—mixed channel after the test started. Calcium was initially
higher in the non—mixed channel but values were similar at the end.
The total suspended matter showed little change throughout the test.
During the test, the sludge layer was thoroughly mixed throughout the water
column, but rapidly settled. It is apparent that the sludge does not
decompose rapidly as evidenced by little change in water quality values.
The TKN in the sludge was about 30 X that in the water column, yet little
change occurred due to mixing.
TABLES 33 and 34 show little change in biomass harvested as a result of
mixing. In view of small nutrient change in the water, the lack of a biomass
increase was not surprising. Chemical analysis of the duckweeds showed
similar values as in Tests 1 and 2.
Because increased growth of the duckweeds failed to materialize, and
nutrients did not increase in the water significantly, another test was set
up to see if the addition of nutrients from the stage 1 anaerobic lagoon
would stimulate growth. Test 4, below, describes the results.
Test 4, Nutrient Addition and Growth, Summer, 1976
The objective of Test 4 was to determine if a nutrient increase would
result in a growth improvement of duckweeds. It was thought that summer
conditions should have resulted in higher growth than was achieved on the
lagoons. Mixing of the bottom sediments failed to increase nutrients
significantly and an improvement in growth was not evidenced. Thus effluent
from the stage 1 lagoon, which received fresh water daily, was introduced
69
-------
TABLE 31. WATER QUALITYa OF TEST AND CONTROL CHANNELS UNDER MIXED 1 ’ AND NON-MIXED CONDITIONS
TKN (mg/i)
mixed
TKN (mg/i)
non—mixed
K (mg/i)
mixed
K(mg/1)
non—mixed
Date
S.o.C
S.p.
C
S.o.
S.p.
C
S.o.
S.p.
C
S.o.
S.p.
C
711 d
38.7
39.0
38.9
30.1
28.8
34.5
———
———
———
———
———
———
7/2
43.0
43.5
43.1
33.8
33.5
35.5
77.6
73,7
79.6
88.1
83.8
96.2
7/8
33.6
37.1
37.4
24.0
26.0
28.5
81.0
73.3
84.4
80.i
84.4
93.4
7/15
23.4
29.5
27.8
23.3
17.i
20.7
69.8
63.6
74.3
75.4
72.6
81.0
%
fr
reduction
om 7/2
46
32
36
31
42
42
10
14
7
14
13
16
—I
0
(Continued)
-------
TABLE 31 (continued).
-4
Ca(mg/1)
mixed
Ca(mg/1)
— non—mixed
pH
mixed
pH
non—mixed
Date
S.o.
S.p.
C
S.o.
S.p.
C
S.o.
S.p.
C
S.o.
S.p.
C
7/1
—— —
———
———
———
———
———
7.7
7.7
7.8
7.8
7.7
7.8
7/1
62.4
63.3
63.9
70.3
65.0
76.3
7.6
7.5
7.7
7.9
7.7
7.8
7/8
59.1
59.1
59.7
56.3
61.3
683
7.7
7.5
7.9
7.7
7.5
8.].
7/15
55.8
55.8
57.5
55.1
60.2
58.3
7.7
7.6
8.1
7.8
7.6
7.8
% reduction
from 7/2
11
12
10
22
7
24
———
———
———
———
—
———
(Continued)
-------
TABLE 31 (continued).
Date
TOC
mixed
TOC
non—mixed
S.o.
S.p.
C
S.o.
S.p.
C
7/2
85
83
83
82
78
85
7/8
———
———
———
———
———
———
7/15
78
88
76
83
84
85
% reduction
from 7/2
8
———
8
avalueg are averages of 2 channels.
bChannels were mixed manually every other day.
CS.O. (S. oligorhiza) , Sp. (S. lyrhiza) , C (Control).
dSample taken prior to mixing.
-------
TABLE 32. CHEMICAL OXYGEN DEMAND (COD), TOTAL RESIDUE (TR), VOLATILE RESIDUE
(VR), FIXED RESIDUE (FR), AND TOTAL SUSPENDED MATTER (TSM) OF MIXED
AND NON-MIXED CRANNELSa
Date
S. po yrhiza S. oligorhiza
1976
COD TR VR FR TSM COD TR VR FR TSM COD TR VR FR TSM
—-mg/i
Mixed
7/1
202 683 388 295 104 217 735 436 299 94 209 769 489 280 104
7/8
267 566 336 230 107 359 866 564 302 118 271 708 436 272 106
7/15
230 576 384 192 107 360 606 420 186 113 238 568 394 174 110
Non—mixed
7/1
202 683 388 295 104 217 735 436 299 94 209 769 489 280 104
7/8
271 584 358 226 109 279 668 442 226 108 271 722 484 238 111
7/15
184 596 460 136 91 180 382 198 184 93 209 550 352 198 101
aValues on 7/1/76 are averages of 4 channels for each species and controls in test lagoons 1 and 2 prIor
to mixing. Values for 7/8 and 7/15 are averages of 2 channels each. Test lagoon 1. was non—mixed and
test lagoon 2 was mixed.
-------
Harvest
datea
Total/13
days
Harvest/moC
7/8
7/15
lcg/ha
lbs/acre
k.g
harvested/m2b
S.o.
S.p.
S.o.
S.p.
S.o.
S.p.
S.o.
S.p.
S.o. S.p.
wet mixed
.32
.64
.38
.73
.70
1.37
non—mixed
.35
.50
.41
.79
.76
1.29
———
———
———
dry( 25%)mjxe
.026
.044
.031
.050
.057
.094
1315
2169
1174 1937
(8.90%)non—mixed
.031
.035
.037
.055
.068
.090
1569
2077
1401 1855
avalues are averages of two test channels for each species under mixed and non—mixed conditions.
bVaiues show the average biomass removed (½) from a m 2 .
CTotal harvest values are based on one—half hectare or acre being harvested. One—half remains for
regrowth.
TABLE 33. BIOMASS HARVEST OF S. hiza AND S. polyrhiza GROWN ON MIXED
AND NON—MIXED TEST CHANNELS, SUMMER, T976
-4
-------
U ’
TABLE 34. CHEMICAL COMPOSITION OF S. oligorhiza AND S. polyrhiza GROWN ON MIXED
AND NON—MIXED TEST CHANNELS, SUMMER, 1976 a
aAverage of
bNitrogen x
2 channels.
6.25.
Sample
Date
% moisture
% of dry matter
S.o.
S.p.
S.o.
TKN
Fiber
Ash
TOC
Crude
Proteinb
S.p.
S.o. S.p.
So.
S.p.
S.o.
S.p.
S.o. S.p.
7/8
Mix
91.3
93.4
5.77
5.70
8.8 9.3
14.0
14.2
36.5
36.0
36.1 35.6
Non—mixed
90.8
92.9
5.86
5.85
7.9 8.2
15.7
14.9
35.5
34.5
36.6 36.6
7/15
Mix
92.2
93.0
5.25
5.44
10.0 9.55
13.9
12.9
37.5
32.5
32.8 34.0
Non—mixed
91.4
93.0
5.55
5.72
8.6 9.35
16.7
13.5
35.0
36.0
34.7 35.8
-------
in an effort to increase the nutrients in the test channels. Test lagoon 1
was ref boded with stage 1 lagoon effluent on July 19 and 29. Test lagoon 2
was held static as a control.
TABLES 35, 36, 37, 38 and 39 show the chemical and bacteriological
characteristics of the test and control channels during this test. It is
evident that flooding the channels with waste effluent restulted in a
nutrient increase. Data in these tables are primarily presented to show the
extent of increase for comparison with duckweed growth. However, values for
the static test channels provides some information on treatment at low water
quality values. Under static conditions duckweed—covered channels showed a
TKN reduction of 23% for S. oligorhiza , 52% for S. p lyrhiza , and 24% in the
control. Potassium, calcium, and pH changes were similar to previous tests.
TKN reduction was less than 1 mg/i/day, which was less than previous
reductions at higher nutrient levels. In TABLE 37 total, volatile, and fixed
residues again are variable. These parameters have not appeared very useful
in determining lagoon performance due to widely fluctuating values. The COD
and total suspended matter, however, are less variable and may be useful in
characterizing lagoon waste treatment along with TKN. Phosphorus, which has
not been measured, may also prove useful and is evaluated in later tests.
TABLE 39 shows bacterial changes under the static condition at low
nutrient levels. Although the values do fluctuate somewhat the trend to
decline is evident, and thus are considered useful in evaluating lagoon
performance.
TABLES 40 and 41 show that duckweed biomass between mixed and static
channels were similar. Differences in biomass between species were insigni-
ficant. S. oligorhiza , which showed the lower harvest in Test 3 (mixing vs.
non—mixing) increased considerably in Test 4. However, the controls which
did not receive nutrients increased considerably as welL S. polyrhiza had
the higher biomass harvested in Test 3, but declined in Test 4 when fresh
waste effluent was introduced into the test channels.
TABLES 42 and 43 indicate a different picture from the biomass change.
Both species of duckweed had higher TKN values in the flooded channels . than
the static. Phosphorus appeared to increase also, while potassium, fiber,
and ash declined. Thus it appears that with a nutrient increase in the
lagoon water the plants accumulate higher levels of nutrients, but growth
rates do not necessary change. The data in TABLES 34 and 21 indicate that
less nitrogen is picked up when TKN in the waste water is below 25 to 30
mg/i. The ratio is dissolved nutrients may also affect plant nutrients and
growth.
Management of lagoons for maximum uptake of nutrients by duckweeds must
include consideration of nutrient quantity and possibly ratios of various
nutrients. Further study is needed to relate plant growth and nutrient
uptake with available nutrients before an effective management system can be
recommended.
76
-------
TABLE 35. WATER QUALITYa OF TEST AND CONTROL CHANNELS WITH AND WITHOUT THE ADDITION
OF DAIRY WASTE EFFLUENTb
TKN (mg/i)
flooded
TKN(mg/1)
static
K(rng/l)
flooded
K
(mg/i)
static
Date
S.o.c S.p. C
S.o. S.p.
C
S.o.
S.p.
C
S.o. S.p. C
7115 d
23.6 17.2 20.7
23.4 29.5 27.8
75.4 72.6
81
69.8
63.6
74.3
7/22
51.4 55.3 53.8
22.0 22.3 24.8
98.5 100.7
107.5
70.9
63.9
68.7
7/29
63.8 61.2 62.2
19.9 17.5 21.8
110.3 109.7
111.4
62.4
57.4
64.9
8/5
51.6 51.8 49.4
18.0 14.3 20.8
110.3 108.1
111.4
64.8
54.6
65.4
Date
Ca(mg/l)
flooded
Ca(mg/1)
static
p 1 1
flooded
pH
static
S.o.
S.p.
C
S.o. S.p.
C
S.o. S.p.
C
S.o. S.p. C
7/15
55.1 60.2
58.3
55.8 55.8 57.5
7.8 7.6
7.8
7.7
7.6
8.1
7/22
49.1 48.5
48.5
49.5 48.5 48.5
7.3 7.2
7.5
7.7
7.7
8.1
7/29
54.0 57.7
56.8
51.2 51.8 54.0
7.1 7.2
7.4
7.6
7.5
8.1
8/5
55.7 58.0
58.0
48.9 49.5 52.9
7.5 7.6
7.8
7.6
7.4
7.9
-4
-4
(Continued)
-------
TABLE 35 (continued).
avalues are averages of two channels.
bEff1 nt was introduced on July 19 and 29.
CS.o. (S. oligorhiza) ; S.p. (S. polyrhiza) ; C (Control).
dsampie taken prior to addition of effluent.
—I
Date
TOC(mg/l)
flooded
TOC(mg/l)
static
S.o.
S.p.
C
S.o.
S.p.
C
7/15
———
———
———
———
———
———
7/22
72
75
120
69
73
83
7/29
100
100
110
69
57
77
8/5
92
96
93
63
48
67
-------
TABLE 36. CHEMICAL OXYGEN DEMAND (COD), TOTAL RESIDUE (TR), VOLATILE RESIDUE (VR),
FIXED RESIDUE (FR), AND TOTAL SUSPENDED MATTER (TSM) OF TEST LAGOON 1
RECEIVING DAIRY WASTE EFFLUENT
Date
S.
polyrhiza
S.
o1i orhiza
Control
COD TR VR FR TSM
1976
COD TR
VR FR TSM
COD TR
yR FR TSM
7/15
230
576
384
192
107
360
606
g/l
420
186
113
238
568
394
174
110
‘° 7/22
322
948
581
367
146
385
916
710
206
136
322
860
652
208
144
7/29
353
998
580
418
90
288
852
614
238
80
346
1012
612
400
85
8/5
360
1048
606
442
60
338
1058
628
430
52
360
1116
698
418
68
8/13
187
798
444
354
51
166
729
428
301
48
187
782
441
341
53
-------
TABLE 37. CHEMICAL OXYGEN DEMAND (COD), TOTAL RESIDUE (TR), VOLATILE RESIDUE (VR),
FIXED RESIDUE (FR), AND TOTAL SUSPENDED MATTER (TSM) OF TEST LAGOON 2
HELD STATIC
S. pplyrhiza __________
COD TR VR FR TSM
mg/i.
Control
COD TR VR FR TSM
7/22
7/29
8/5
8/13
184 596 460 136
188 760 666 94
187 752 556 196
266 810 492 318
108 770 404 366
91 180 382 198 184 93
78 200 808 702 106 128
22 180 732 388 344 27
32 216 806 440 366 60
31 94 604 392 212 26
209 550 352 198 101
220 764 560 204 88
169 794 400 394 39
230 958 500 458 84
94 594 388 206 32
Date
1976
S. oligorhiza
COD TR VR FR TSM
-------
TABLE 38. STANDARD PLATE COUNT (SPC), ANAEROBIC COUNT (AC), FECAL COLIFORN (FC),
AND FECAL STREPTOCOCCI COUNTS (FSC) OF TEST LAGOON 1 RECEIVING DAIRY
WASTE EFFLUENT
S. polyrhiza S. olig
orhiza Control
Date
1976
SPC/ AC! FC/ FSC/ SPC/ AC!
ml ml 100 ml 100 ml ml ml
FC/ FSC/ SPC/ Ad FC/ FSC/
100 ml 100 ml ml ml 100 In]. 100 ml
x
10
7/22
2.7 2.6 1.7 1.7 2.4 2.9
2.1 2.0 2.9 2.8 1.6 1.4
7/29
4.6 5.2 1.8 1.6 3.7 3.2
1.8 1.5 3.8 4.1 1.4 1.1
8/5
3.1 3.0 2.4 2.1 2.9 2.7
2.1 1.9 2.9 2.8 2.0 1.8
8/13
2.5 2.3 1.6 1.4 2.7 2.6
1.9 1.5 2.7 2.4 1.6 1.2
-------
TABLE 39. STANDARD PLATE COUNT (SPC), ANAEROBIC COUNT (AC), FECAL COLIFORN (FC),
AND FECAL STREPTOCOCCI COUNTS (FSC) OF TEST LAGOON 2 HELD STATIC
S. polyrhiza S. olig
orhiza Control
Date
1976
- FCI FSCI SPC/ Ac! FC/ FSC/
100 ml 100 ml ml ml 100 ml 100 ml
SPC/ AC! FC/ FSC/ SPC/ ACt
ml ml 100 ml 100 ml nil ml
x
io 5
7/22
1.7 1.5 1.7 1.4 1.3 1.1
2.3 1.9 1.1 1.0 1.8 1.6
7/29
1.7 1.6 1.6 1.3 1.3 1.3
1.8 1.6 1.4 1.2 1.9 1.4
8/5
1.5 1.3 1.2 1.1 1.7 1.2
2.7 2.4 1.3 1.2 2.2 1.9
8/13
0.7 0.6 1.1 1.1 0.8 0.9
1.9 1.4 0.8 0.7 1.5 1.3
03
-------
cc
( j
TABLE 40. S. oligorhiza BIOMASS HARVESTED FROM FLOODED AND STATIC TEST CHANNELS
RECEIVING DAIRY WASTE, SUMMER, 1976
aValues as averages of 2 test channels for each species under flooded and static conditions.
bvaiues show the average biomass removed (½) from a m 2 .
CTotal harvest values are based on one—half hectare or acre being harvested. One—half remains for
regrowth.
Harvest
datea
Total) 16
days
Harvest/moC
7/30
8/4
kg/ha
lbs/acre
kg
harvested/zn2 ’
wet flooded
.66
.65
1.31
———
———
static
.50
.61
1.11
———
—— —
dry(7.95%)flooded
.053
.052
.105
1969
1758
(8.78%)static
.044
.054
.098
1838
1641
-------
TABLE 41. S. polyrhiza BIOMASS HARVESTED FROM FLOODED AND STATIC TEST CHANNELS
RECEIVING DAIRY WASTE, SUMNER, 1976
Harvest
datea
Total! 16
days
Harvest/moC
kg/ha
lbs/acre
7/30
8/4
kg
b
harvested/rn 2
wet flooded
.67
.63
1.30
static
.64
.71
1.35
——
dry (6.36%)flooded
.043
.040
.083
1556
1390
(6.89%)static
.044
.049
.049
1744
1557
avalues as averages of 2 test channels for each species under flooded and static conditions.
bvaiues show the average biomass removed (½) from a m 2 .
cTotal harvest values are based on one—half hectare or acre being harvested. One—half remains for
regrowth.
-------
TABLE 42. CHEMICAL COMPOSITION OF S. oligorhiza GROWN ON FLOODED AND STATIC
TEST CHANNELS, SUMMER, i976
Sle
Date
% moisture
% of dry matter
7/30
TKN
P
K
Fiber
Ash
TOC
Crude
proteinb
Flooded
92.05
6.19
1.49
1.75
7.30
7.5
33.5
38.9
Static
91.17
4.84
1.46
2.00
7.35
8.9
32.5
30.1
8/4
Flooded
92.06
5.78
1.45
1.85
5.90
7.9
35.0
36.1
Static
91.28
5.19
1.49
2.34
8.25
9.4
31.0
32.4
aAverage of 2 channels.
bNitrogen x 6.25.
-------
TABLE 43. CHEMICAL COMPOSITION OF S. lyrhiza GROWN ON FLOODED AND STATIC TEST
CHANNELS, SUMNER, 1976 a
Sample
Date
% moisture
% of dry
matter
7/30
TKN
P
K
Fiber
Ash
TOC
Crude
Protei&’
Flooded
93.49
630
1.44
1.75
7.70
8.25
34.0
39.4
Static
93.09
5.02
1.22
2.70
9.00
8.70
34.0
31.4
8/4
Flooded
93.79
6.08
1.35
1.83
7.45
8.90
32.0
38.0
Static
93.13
5.49
1.23
2.78
8.50
9.10
33.0
34.3
aAverage of 2 channels.
bNitrogen x 6.25.
-------
Test 5, Duckweed Growth and Nutrient U take, Late Summer—Early Fall, 1976
As a follow—up to test 4 to determine if the addition of fresh effluent
would stimulate duckweed growth and nutrient uptake, test lagoon 2 was
stocked with two duckweed cultures on three channels each. S. p lyrhiza
had a mixed culture of S. olyrhiza and S. oliforhiza were tested. Data was
useful for comparison with spring data (Test 1) as air temperatures were
similar. Test channels were flooded once weekly.
TABLES 44 and 45 show chemical analysis of test channel water throughout
the study. Due to the addition of effluent from the stage 1 lagoon water
quality values tended to fluctuate, depending on changes with the stage 1
lagoon.
TABLE 46 shows growth of S. polyrhiza and the mixed culture for only a
7 day period. Two harvests were taken, on September 1 and 8. However, the
second harvest was not weighed, as they were accidentally removed for
feeding before weights were taken. Growth during the second week appeared
similar to the first. Samples for chemical analysis were taken however.
Biomass harvested equaled or exceeded previous harvest data and
strengthens the indication that continuous or periodic flooding improves
growth.
TABLES 47 and 48 show chemical content of the duckweed cultures. Boron
was included in the analysis as it is an ingredient in detergents used in
the milking operation. It was picked up by the duckweeds as evidenced in
the tables, but in low concentration, and should pose no problems to animal
utilizing duckweed as part of a standard diet.
Phosphorus, TKN, K and fats increased over the test, while calcium
declined, and fiber, ash, and TOC fluctuated slightly. The data again shows
that periodic flooding with nutrient—rich effluent results in an increase
in TKN and protein.
Test 6, Waste Treatment and Duckweed Growth Under Aeration, Fall, 1976
In September, 1976, unseasonably cool weather developed. Duckweed
growth declined significantly, but the plants remained on the surface. In
order to obtain information on waste treatment in lagoons and plant growth
during winter—time conditions a test was set up November 3 and carried to
December 4. Three channels were used for each: S. oligorhiza , S. polyrhiza ,
a mixture of the two, and controls. The system was aerated on alternate
days to obtain information on treatment characteristics under aerobic low
temperature conditions with and without duckweed.
TABLES 49 through 53 show water quality conditions during this study.
Several days of below freezing temperatures occurred, but not sufficiently
low to freeze over the lagoons. The channels were slow in responding to
aeration, as most channels showed little oxygen increase until near the end
of the test. Some of the channels were well oxygenated for 15 to 20 days
but the conversion of ammonium to nitrites and nitrates was not clearly
87
-------
TABLE 44. WATER QUALITYa OF TEST LAGOON 2 RECEIVING DAIRY WASTE EFFLUENT INTER-
MITTENTLYb AND SUPPORTING A STAND OF S. polyrhiza AND A MIXED STAND OF
S. polyrhiza AND S. oligorhiza , LATE SUMMER, 1976
DateC
TKN
(mg/i)
K
(mg/i)
Ca (mg/i)
pH
S.p.
mixed
S.p.
mixed
S.p.
mixed
S.p.
mixed
8/26
31.0
33.7
75.0
78.0
56.3
54.4
7.2
7.2
9/1
28.8
29.4
63.0
67.5
45.0
47.3
———
———
9/8
41.2
35.0
69.8
66.4
47.3
47.3
7.1
7.2
avalues are averages of 3 channels.
bEf fluent was added August 26, 31, and September 7.
CSampie taken after effluent added.
-------
TABLE 45. CHEMICAL OXYGEN DEMAND (COD), TOTAL RESIDUE (TR), VOLATILE RESIDUE (VR),
FIXED RESIDUE (FR), AND TOTAL SUSPENDED MATTER (TSM) OF TEST LAGOON 2,
FLOODED INTERMITTENTLYa WITH DAIRY WASTE EFFLUENT, LATE SUMMER, 1976
DateC
S. pçlyrhlza Mixed Culture
bCOD TR VR FR TSM COD TR VR FR TSM
mg/i
8/26
97 406 301 105 63 117 419 311 108 70
9/1
186 431 257 174 40 198 551 428 123 50
9/8
232 760 560 200 59 199 753 511 242 64
aEf fluent added August 26, 31, and September 7.
bvalues represent 3 channels combined.
CSample taken after effluent added.
-------
TABLE 46.
BIOMASS OFS. polyrhiza AND A MIXED CULTURE OF S. polyrhiza AND S. oligorhiza
HARVESTEDa FROM TEST LAGOON 2 FLOODED INTERMITTENTLY WITH DAIRY WASTE EFFLUENTb,
LATE SUMMER, 1976
0
Harvest
9/1
date
Total harvested!
7 days
kg/ha
Harvest/mo/
lbs/acre
S.p.
mixed
S.p.
mixed
S.p.
mixed
S.p.
mixed
kg
harvested/m2C
wet
.69
.69
.69
.69
———
——
dry
(7.3%)
.05
———
.05
———
2156
———
1925
———
(7.3%)
———
.05
———
.05
———
2156
———
1925
aAverage of 3 channels.
bEf fluent added August 26, 31, and September 7.
CValues show the average biømass removed (½) from a m 2 .
-------
TABLE 47. CHEMICAL ANALYSIS OF S. pplyrhiza GROWN ON TEST CHANNELS PERIODICALLY
FLOODED WITH DAIRY WASTE EFFLUENT, LATE SUMMER, 1976 a
Sample
Date % nxisture % of dry matter
Crude
TKN P K Ca Fiber Ash Fat TOC Bb ProteinC
8125 d 92.0 4.87 1.10 1.90 2.38 8.6 20.7 4.2 34.3 .022 30.4
9/1 93.4 5.64 1.21 1.98 2.42 8.9 17.2 7.8 33.7 .029 35.3
9/8 92.7 5.84 1.37 2.08 2.17 8.7 17.2 8.6 .024 36.5
aAverage of 3 channels.
bBoron
CT x 6.25.
dmi 8 sample taken prior to adding effluent (August 26, 31 and September 7).
-------
TABLE 48. CHEMICAL ANALYSIS OF A MIXED STAND OF S. 2 !iza AND S. polyrhiza
GROWN ON TEST CHANNELS PERIODICALLY FLOODED WITH DAIRY WASTE EFFLUENT,
LATE SUMMER, 1976 a
Sample
Date 2 moisture 2 of dry matter
- ru e
TKN P K Ca Fiber Ash Fat TOC Bb Protein C
8125 d 92.4 5.44 1.28 2.03 2.18 8.0 18.0 6.4 32.2 .028 34.0
9/1 93.0 5.64 1.38 2.43 1.69 9.1 15.9 9.2 32.7 .034 35.3
9/8 93.4 6.07 1.68 2.50 1.67 8.8 17.8 8.3 .034 38.0
aAverage of 3 channels.
bBoron
CTv x 6.25.
dmi 8 sample taken prior to adding effluent (August 26, 31 and September 7).
-------
TABLE 49. WATER QuALITya OF AERATED, STATIC LAGOON TEST CHANNELS SUPPORTING STANDS
OF S. p lyrhiza , LATE FALL, 1976
Sample
Date
mg/i
pH
Surface
Temp
°C
TKN
NO 3
NO 2
NH 4
P—ortho
as P0 4
02
11/3
47.9
<
.25
<.1
26.0
31.9
0
7.4
14
11/4
———
“
“
30 4
33 6
0
———
“
11/6
———
“
‘
29 0
———
0 3
———
“
11/8
———
“
“
32 6
———
0
———
———
11/10
———
“
“
29 6
32 3
0.1
———
19
11/15
———
“
.3
29.6
———
5.5
———
8
11/20
34.6
“
1.1
29.3
31.8
1.6
7.9
9
11/30
29.1
.25
2.0
29.4
26.2
7.9
7.9
———
12/4
26.7
.82
1.0
24.0
24.1
7.4
———
———
aAverage of 2 or 3 channels.
-------
TABLE 50. WATER QUAL1TYa OF AERATED STATIC LAGOON TEST CHANNELS SUPPORTING A
STAND OF S. oligorhiza , LATE FALL, 1976
Sample
Date
mg/i
PH
Surface
Temp
0 C
TKN
NO 3 —
NO 2 -
N H 4
P—ortho
as P0 4
02
11/3
54.9
<
.25
<.1
32.5
34.5
0
7.3
14
11/4
———
“
“
31.2
34.8
0
———
“
11/6
———
“
•
“
33.6
———
0
“
11/8
———
“
“
———
34.0
2.3
———
11/10
———
“
“
30.4
34,3
0.13
———
19
11/15
“
“
———
32.6
0.9
———
8
11/20
39.6
“
.1
29.9
35.3
0.9
7.8
9
11/30
32.5
“
.15
30.4
28.6
4.4
7.8
———
12/4
32.6
“
.1
———
24.7
3.4
———
———
aAverage of 2 or 3 channels.
-------
TABLE 51. WATER QUALITYa OF AERATED STATIC LAGOON TEST CHANNELS SUPPORTING A MIXED
STAND OF S. oligorhiza AND S. polyrhiza , LATE FALL, 1976
“I
Sample
Date
mg/i
pH
Surface
Temp
°C —
TKN
NO 3
NO 2
NH 4
P—ortho
as P0 4
02
11/3
51.1
<.25
<.1
27.3
34.3
0
7.4
14
11/4
———
‘I
30.5
35.0
0
———
“
11/6
———
“
“
29.5
———
0
———
“
11/8
———
H
H
34.4
.1
11/10
———
“
“
28 5
34 0
1.2
———
19
11/15
———
“
“
———
31.6
.3
———
8
11/20
37.3
“
.2
29.0
31.4
1.3
———
9
11/30
31.5
“
.3
29.1
24.6
3.8
7.9
———
12 / 4
27. 9
. 35
. 75
———
———
7. 3
———
———
aAverage of 2 or 3 channels.
-------
TABLE 52. WATER QUALITya OF AERATED STATIC LAGOON CONTROL CHANNELS, LATE FALL, 1976
a’
Sample
Date
mg/i
Surface
Temp
°C
TKN
NO 3
NO 2
N}1 4
P—ortho
as P0 4
02
11/3
51.3
<.25
<.1
31.1
32.3
0
7.4
14
11/4
———
“
“
29.2
34.4
0
———
“
11/6
———
‘
“
30.6
———
0
———
“
11/8
———
“
“
———
34.5
.15
———
11/10
—
“
“
28.2
33.1
0
———
19
11/15
“
“
334
2.9
———
8
11/20
38.9
.04
.15
28.2
33.2
1.9
7.9
9
11/30
33.3
.3
.35
28.4
27.2
8.1
7.9
———
12/4
30.8
.41
.15
———
26.1
6.8
———
———
aAverage of 2 or 3 channels.
-------
TABLE 53. BIOCHEMICAL OXYGEN DEMAND (BOD), CHEMICAL OXYGEN DEMAND (COD), TOTAL
RESIDUE (TR), VOLATILE RESIDUE (VR), FIXED RESIDUE (FR), AND TOTAL
SUSPENDED MATTER (TSM) OF CONPOSITEa SAMPLES OF TEST LAGOONS 1 AND 2
Date
S. polyrhiza S. oligorhiza Mixed Culture Control
BOD COD TSM BOD COD TSM BOD COD TSM BOD COD TSM
1976
mg/i -
11/4
68 267 198 69 273 194 63 319 201 59 261 173
11/24
48 206 340 28 170 186 18 174 184 48 206 226
11/30
32 182 162 29 186 155 30 192 156 36 193 181
Date
1976
S. polyrhiza S. oiigorhiza Mixed Culture Control
— —
TR VR FR TR VR FR TR VR FR TR VR FR
11/4
1027 566 461 1022 556 466 1046 491 555 1006 563 443
11/24
988 514 474 944 520 424 798 458 340 954 486 468
11/30
704 273 431 721 323 398 819 472 347 816 470 346
aAverage of 3 channels.
-------
evident. Control and test channels had similar TKN, BOD, COD, TR, VR, FR,
and TSM values. TKN decline in the test channels averaged 43% while the
controls showed a decline of 41%. Nitrates and Nitrites showed small
increases throughout the test period indicating the conversion of anunonium
was slow. Phosphorus values indicate that the duckweed—covered channels may
have an effect on phsophorus decline, as these channels showed an average
decline of 27% while the controls averaged 19% decline. However, due to the
lack of growth of the plants the decline is probably not related to
phosphorus uptake. Considering the low temperatures and lower metabolic
activity, the decline in all channels was rather sharp.
TABLE 54 shows the duckweed biotnass harvested. Due to freezing
temperatures biomass increase did not occur. Thus harvest indicates only
what was removed and should not be taken as an indication of biomass
replacement.
TABLE 55 shows the nutrient content in the plants. In spite of the low
growth rate nutrient values remained similar to previous values.
Test 7, Winter Growth of Duckweeds, Covered and Non—covered, Winter, 1976—
1977
During the fall of 1976 S. oliporhiza growth declined greatly. From
December 10, 1976 through January 7, 1977 a preliminary study was set up
to compare growth of S. oligorhiza under covered channels as growth had
declined in Test 6 due to freezing temperatures. Three channels of
S. oligorhiza were covered with .006 mm clear polyethylene plastic and four
channels (not covered) served as non—stocked controls to compare treatment
effects. The clone of L. gibba which had been stocked during the sunmier
showed rapid growth during the fall. Three channels of L. gibba , non—
covered, .were added to obtain information on growth of this species under
winter conditions. All channels were aerated to insure nutrient mixing.
Tests 3, 4, 5, and 6, which involved circulation of nutrients in the
lagoons, failed to stimulate significant growth of duckweeds, except possibly
in channels where the C:N ratio was 2:1 less. Aeration in the fall, when
cooler temperatures prevailed did not produce a significant growth Increase.
Temperature, rather than low nutrients, seemed to be in the factor most
likely affecting growth. By covering the test channels in Test 7, we hoped
to determine if elevation of temperature would result in a growth increase,
and be reflected in waste treatment.
TABLES 56, 57, 58 and 59 show the water quality of the test and control
channels for S. oligorhiza covered channels was 1 to 2°C higher than
controls. Air temperatures under the cover were variable but exceeded
21°C on several occasions and did not drop below freezing as did the ambient
temperature on several occasions during the study. Reduction in TKN, NHt,
and P was greater in the test channels for both species.
98
-------
TABLE 54. BIOMASS OF S. oligorhiza , S. polyrhiza , AND A MIXED (M) CULTURE OF
TIlE TWO HARVESTED FROM AERATEDa STATIC TEST LAGOONS, LATE FALL, 1976
Harvest
11/25
dateb
12/4
Total
31
harves
days
tf
Harvest/moC
kg/ha lbs/acre
S.o.
S.p.
M
S.o.
S.p.
M
S.o.
S.p.
M
S.o.
S.p.
M
S.o. S.p.
M
kg
harvested/zn 2
wet
.29
.38
.51
.19
.17
.27
.48
.55
.78
———
———
dry (8%)
.023
.015
.038
368
328
(6%)
.023
.014
.037
358
320
(7%)
.036
.019
.055
532
475
aChannels aerated every other day.
bAverage of 3 channels, stocked 11/3/76.
CTotal harvest values are based on one—half hectare or acre being harvested. One—half remains for
regrowth.
dvaiues show the average biomass removed (½) from a nz 2 .
-------
TABLE 55. CHEMICAL ANALYSIS OF S. oli&orhiza AND S. po yrhiza GROWN ON AERATED
STATIC TEST CHANNELS RECEIVING DAIRY WASTE, LATE FALL, 1976
TKN Fiber Ash
Crude
P K Ca Fats proteinb
0
0
Sample
Date % moisture
°‘ f dry mattera
/00
12/4
S.
oligorhiza
92.0
5.97
8.8
10.8
1.32
1.77
.12
4.0
37.3
S.
polyrhiza
94.0
5.62
6.7
18.2
1.50
1.48
.15
3.5
35.1
mIxed
93.0
5.51
6.8
18.3
1.42
1.68
.11
3.8
34.4
aAverage of 3 channels.
bNitrogen x 6.25.
-------
I-
0
TABLE 56. WATER QUALITY OF AERATED, STATIC LAGOON TEST CHANNELS SUPPORTING
STANDS OF S. oligorhizaa , WINTER, 1976—77
Sample
Date
mg/i
pH
Surface
Temp
°C
TKN
NO 3
NO 2
N i l 4
P—ortho
as P0 4
02
12/10
59.8
<.25
.1
41.7
28.8
———
7.5
———
12/16
———
“
———
41.3
27.6
———
7.6
———
12/23
44.0
“
.7
35.4
26.9
1.6
7.8
10.3
12/29
37.0
“
2.0
28.9
25.8
.93
7.8
10.5
% change
—38
———
+1900
—31
—10
acovered with clear plastic, average of 3 channels.
-------
I —
0
TABLE 57. WATER QUALITY OF AERATED, STATIC LAGOON TEST CHANNELS, CONTROLSa,
WINTER, 1976—77
Sample
Date
- mg/ I.
pH
Surface
Temp
°C
TKN
NO 3
NO 2
NH 4
P—ortho
as P0 4
02
12/1.0
54.9
<.25
.13
38.6
28.8
———
7.6
———
12/16
“
———
38.3
28.6
———
7.8
———
12/23
43.6
“
.23
35.6
28.7
2.2
7.9
8.0
12/29
40.6
“
.33
31.5
28.3
2.5
8.0
9.6
% change
—26
———
+154
—18
—2
aNon_covered, average of 3 channels.
-------
Sample
Date
mg/i
pH
Surface
Temp
0 C
TKN
NO
NO 2
NH 4
P—ortho
as PG 4
02
12/10
48.7
<
.25
<.1
37.5
21.8
———
7.5
———
12/16
———
“
———
35.8
22.3
———
7.6
———
12/23
30.9
“
<.1
21.0
22.3
.8
7.8
7.8
12/29
23.8
“
.3
17.1
20.5
.7
7.8
7.8
% change
—51
———
+200
—54
—6
aNon_covered, average of 3 channels; from Dr. William human, Brookhaven National Laboratory,
Upton, N.Y., clone designation (G—3).
TABLE 58.
WATER QUALITY OF AERATED, STATIC TEST CHANNELS SUPPORTING STANDS OF
L. gibbaa , WINTER, 1976—77
I— .
0
-------
TABLE 59. WATER QUALITY OF AERATED, STATIC TEST CHANNELS, CONTROLSa, WINTER, 1976-77
I-
0
Sample
Date
TKN
mgi 1
_
°2
pH
Surface
Temp
°C
NO 3
NO 2
NH 4
P—ortho
as P0 4
12/10
39.8
<.25
<.1
28.0
24.3
———
7.5
———
12/16
———
H
28.5
25.0
———
7.5
———
12123
40.8
“
<.1
40.0
28.5
.2
7.5
7.5
12/29
43.3
“
.3
29.7
26.3
.5
7.8
7.8
% change
+9
—-—
+200
+6
+8
aNon_covered, average of 3 channels.
-------
The higher temperature under cover was associated with an increase in
growth (TABLE 60) for S. oligorhiza over previous data (Test 6). The
greater inprovement in water quality under the plastic—covered channels
appeared unusual if temperature related, because of the slight differences
between test and control channels. L. gibba channels showed a performance
similar to S. oligorhiza with greater TKN, N4, and P reductions than
controls. L. gibba , exposed to lower temperatures than S. oligorhiza , had
as rapid growth, indicating the plant is more cold tolerant.
TKN reduction for the S. oligorhiza channels average 1.2 mg/i/day for
19 days, and L. gibba channels averaged 1.3 mg/i/day. These values equal or
exceed the rate of decline in previous tests, and exceed the controls which
respectively increased in one case (TABLE 59) and declined .75 mg/i/day in
the second (TABLE 57).
Harvest data (TABLE 60) show that the addition of minimal amount of heat
can improve growth of S. oligorhiza during winter, and the growth may be due
to increased air temperature under the cover rather than in water tempera-
ture. Growth of L. g ba without being covered equaled that of
S. oligorhiza , indicating this plant is cold tolerant, and can be utilized
during winter months if maintained in lagoons free of ice cover. Estimated
harvest for both species/hectare was sufficient to warrant further study
on winter growth, particularly since the winter of 1976—77 was one of the
most severe on record.
TABLE 61 shows that the nutrient content of both plants was similar to
previous values. The ash values were in part due to silica. It is not
known if the silica was taken up by the plants or due to inadequate washing
before analysis. L. gibba appears to concentrate potassium, which could
limit its use as a cattle feed. The increased productivity over Test 6
shows the potential for 12 month production by selecting appropriate
clones, or protection from low temperatures.
Test 8, Duckweed Growth and Water Quality in Covered and Non—covered
Channels, Winter, 1977
Results of Test 7 showed that growth of L. gibba exposed to normal
winter air temperatures equaled S. oligorhiza which was covered with clear
polyethelene. During Test 7 several freezes caused the non—covered ponds to
ice over. Test 8 was set up to determine if L. g J J was offered protection
from freezing temperatures, would an increase in growth occur. Three test
channels with the plant were covered as in Test 7 and three remained open.
All six channels were stocked with 9.09 kg of the plant on February 8, 1977
and continued until March 21. Three non—covered channels with a mixture of
L. gibba and S. oligorhiza were included to provide further information on
the growth of mixed cultures. Three non—stocked, open channels served as
controls. Aeration was applied to all channels, but failure of the air pump
after the first harvest date terminated aerated—nonaerated comparisons except
for the first harvest. All data collected up to the first harvest period are
averages of the two non—aerated channels; thereafter results are the average
of three channels, all non—aerated.
105
-------
TABLE 60. BIOMASS OF S. oligQrhlzaa AND L. g bbab HARVESTED FROM AERATED, STATIC
TEST LAGOONS, WINTER, 1976—77 —
Stocked/rn 2
12/10/76
S.o. L.g.
Total /harvest
28 days
1/7/77
S.o. L.g.
lbs/acre
S.o. L.g.
aCovered with clear plastic.
hNon...covered, see Table 58 for source of plant.
CTotal harvest values are based on one—half hectare or acre being harvested. One—half remains for
regrowth.
dAverage of 3 channels; values show the blomass stocked and removed (½) from a m 2 .
d
kg
0
0 ’
dry (8%)
(6%)
wet .35 .33 .89 .93
Harvest/moC
kg/ha
S.o. L.g.
.071
.056
760.7 679.3
611.0
545.6
-------
TABLE 61. CHEMICAL ANALYSIS OF S. oligorhizaa AND
L. gibba 1 ’ GROWN ON AERATED STATiC TEST
CHANNELS RECEIVING DAIRY WASTE, WINTER,
19 76—7 7
% of dry matter
TKt
Ash
Moisture
S.o.
6.04
S.o. 15.7
S.o.
92
L.g.
6.16
L.g. 16.4
L.g.
94
P
Fat
So.
1.45
S.o. 3.8
L.g.
1.55
L.g. 3.0
K
Silica
S.o.
2.86
S.o. 5.4
L.g.
4.19
L.g. 4.6
Ca
Crude proteind
S.o.
1.3
S.o. 37.8
L.g.
1.0
L.g. 38.5
Fiber
So.
7.3
L.g.
9.4
aCovered with clear plastic.
hNon covered
CBased on plants collected (1/7/77), the last day of testing. Test
began December 10, 1976. Values are averages of 3 channels.
dNftrogen x 6.25.
107
-------
Although not shown in the tables, plant growth between aerated and
non—aerated channels at the first harvest date agreed with previous tests
that aeration offered no advantage and may reduce plant growth.
Yield data are presented in TABLE 62. Both L. gibba treatments yielded
approximately 1400 kg/ha/mo. Thus covering of the plant was of little value
during this experiment. The mixed culture did not show as high an estimated
yield, but analysis of variance confirmed that the difference was not
significant (P < .05).
The fact that no significant difference of yield was observed between
the mixed culture and monoculture treatments is of potential importance to
management of lagoon systems using aquatic plants as part of the treatment
process. By utilizing a mixture of clones selected for optimal growth
(seasonally) and nutrient content, one species and/or clone would become
dominant or less active for any given set of environmental conditions.
Chemical composition of the plants for the test period are shown in
TABLE 63. It appears that there are differences in values as compared to
previous experiments. Ash content is noticeably higher and is most likely
due to the samples having not been thoroughly washed.
Water content in L. gibba Increased somewhat over previous tests. We
think this may be accounted for by the less active growth, and evidence of
slight deterioration of some individual plants. This species contains
large air cells on the lower surface. There was evidence of cell wall
deterioration and the cells were found to contain water.
Duckweeds, during winter, frequently become dormant. In so doing they
show an increase in starch and each frond separates from the present plant
and sinks to the bottom. These dormant fronds (called turions) sink due to
the accumulation of starch. The reduction in carbohydrate, as estimated
from the nitrogen free extract (NFE), through study is puzzling as just the
opposite would be expected. More curious is the increase In lipids as this
would tend to make the plant more bouyant.
Reduction in TKN through the test, based on previous work, can be
explained by the low nutrient content in the lagoon, as earlier tests
indicated a drop in plant nitrogen when lagoon TKN was less than 20—30 mg/i.
TABLES 64 and 65 show the water quality for the non—covered mixed
duckweed and control channels. Test channels performed significantly better
than controls as In other tests. Comparisons between the aerated and static
channels after February 25 cannot be made due to the breakdown of the
aeration system. Little differences were noted on February 25 after twelve
days of aeration, except for TKN, in which the static test and control
channels showed greater TKN reductions. These data, again point out the
questionable value of aeration as a treatment technique. As a management
technique for increasing duckweed growth, aeration alone doesn’t appear to
offer any advantages.
108
-------
TABLE 62. YIELDa OF L. COVERED AND NON—COVERED AND A MIXED CULTURE (M) OF L. gibba AND
S. oligorhiza HARVESTED FROM STATIC TEST CHANNELS RECEIVING DAIRY WASTE,
WINTER, 1977
0
Harvest
dateb
Total/41
days
L.g.
d
Harvest/mo
kg/hae
L.g.3 M
2/25/77
3/7/77
3/16/77
3/21/77
L.g.
L.g.3
M
L.g.
L.g.3
M
L.g.
L.g.3
H
L.g.
L.g.3°
M
L.g.
L.g.3
M
wet
0.673
0.573
0.391
0.624
0.833
0.573
1.182
1.124
1.085
0.824
0.745
0.776
3.303
3.275
2.825
dry (5.83%) 0.039
0.033
0.023
0.036
0.049
0.033
0.069
0.066
0.063
0.048
0.043
0.045
0.192
0.191
0.164
1405
1398 1200
ayield data reflects biomass removed per m 2 from one—half (12.5 m 2 ) of each test channel, one half was left for regrowth.
bMeans of 3 test channels except for 2/25/77 which is the mean of two channels.
CChannels covered with polyethelene plastic.
dHarvest/mo based on 30 day month and represents Kg harvested from one—half of a hectare.
eMultiply by 0.893 to obtain lbs/ac/mo.
-------
0
Composite samples.
TABLE 63. PARTIAL CHEMICAL COMPOSITION OF L. gibba (G3) AND A MIXED
CULTURE (N) OF L. gibba AND S. oligorhiza GROWN ON STATIC
TEST CHANNEL RECEIVING DAIRY WASTE, WINTER, 1977
hNitrogen free extract.
Sample
datea
% moisture
% of
dry matter
Stocked 2/8/77
TKN
P
K
Ca
Fiber
Ash
Fats
NFEb
Crude
proteinC
L. gibba
94.0
6.82
1.82
———
2.79
10.5
13.8
2.4
30.7
42.6
M
92.0
5.84
1.42
———
2.78
9.7
9.3
2.0
42.6
36.5
3/22/ 77
L. gibba
(covered)
94.0
5.70
———
———
———
10.4
21.8
7.5
22.5
35.6
L. gibba
(non—covered)
94.0
5.67
———
———
11.2
20.3
7.3
23.4
35.4
H
92.5
5.50
———
———
———
10.9
20.9
7.2
24.4
34.3
1KN x 6.25.
-------
TABLE 64. WATER QUALITY OF STATIC AND AERATEDa TEST CHANNELS SUPPORTING
A MIXTURE OF S. oligorhiza AND L. gibba , WINTER, 1977
‘-I
I -I
Sample
date
mg/i
2/10/77
Aeratedb
StaticC
TKN
P0 4
K
Ca
02
pH
33.2
37.0
20.3
18.6
39.4
37.9
28.5
30.9
4.7
7.4
7.8
7.7
2/15/77
Aerated
Static
29.3
32.0
21.0
18.6
39.5
36.2
26.5
28.1
4.5
0.6
7.7
7.6—7.7
2/25/77
Aerated
Static
26.4
25.9
18.3
17.1
39.2
36.0
23.5
26.8
4.6
0.4
7.7
7.7
3/2/77
Aerated
Static
21.4
21.5
———
———
40.6
35.9
30.0
30.7
7.7
7.7
3/16/77
Aerated
Static
9.7
11.8
9•3
6.7
31.9
28.1
23.3
24.2
7.5
7.2
3/31/77
Aerated
Static
8.4
8.2
8.8
6.5
27.9
24.2
24.5
27.3
———
7.8
7.5—7.9
%
reduction
Aerated
Static
74.7
77.8
56.7
65.1
29.2
35.4
14.0
11.7
———
———
———
———
apump failure on February 25 terminated aerated vs. static comparisons. Separate values are shown
however throughout the test.
bData from one channel.
CMean of two channels, excluding pH which shows actual values.
-------
TABLE 65. WATER QUALITY OF STATIC AI D AERATEDa CONTROL CHANNELS, WINTER; 1977
Sample
_date mg/i
TKN P0 4 K Ca 02 pH
2/10/77 Aeratedb 33.5 17.8 35.1 31.8 6.6 8.0
StaticC 40.0 21.2 42.3 31.9 7.8 7.8—8.3
2/15/77 Aerated 31.2 18.0 37.9 31.3 5.8 7.9
Static 33.9 21.8 42.2 30.2 1.6 7.8—8.0
2/25/77 Aerated 29.3 17.0 37.7 31.1 4.9 7.9
Static 28.1 21.3 42.3 28.1 0.7 7.7
3/2/77 Aerated 26.2 16.0 38.0 31.3 7.8
Static 23.7 21.8 44.0 32.9 7.6—7.8
3/16/77 Aerated 16.5 6.8 31.2 25.3 7.8
Static 13.9 14.8 36.1 25.7 7.2—7.4
3/31/77 Aerated 9.7 6.4 29.5 26.9 7.8
Static 12.9 13.0 36.9 28.8 7.8
%
Aerated
71.0
64.4
22.4
15.4
———
———
reduction
Static
67.8
40.4
16.1
12.5
———
———
aPump failure on February 25 terminated aerated vs. static comparisons. Separate values are shown
however throughout the test.
bData from one channel.
cMean of two channels, excluding pH which shows actual values.
-------
Tha reduction rates for TKN and P04 were rapid through March 16 until
the values dropped below 10 mg/i. Thereafter the rate of decline slowed,
indicating a need to develop management techniques if water quality Is to
be further improved without an excessive retention time, It is possible
that the duckweed system should be replaced by other biological treatment
techniques when the TKN drops below 10 mg/i.
TABLES 66 and 67 show changes in BOD, COD, TR, VR, FR, and TSM for
the mixed species and control channels. Similar ending values were noted
for test and control channels. Throughout the total study we detected
little differences between the duckweed and control channels for the above
parameters. Under a well managed system where loading rates are controlled,
and a high percent of soluble components are added and insoluble materials
minimized, the duckweed lagoons may show improved performance over conven-
tional lagoons. It is clear that under the conditions of the various tests,
duckweeds are not detrimental to waste water renovation.
Standard plate counts showed little variation throughout Test 8 between
test and controls (TABLES 68 and 69) and were similar to previous studies.
Fecal counts in the test channels were less than in the controls. The
reduced decline In bacterial counts over previous tests was due to the
cooler temperatures.
Comparison of lagoon water quality from L. gibba covered and non—covered
test channels showed that TKN and K reductions were greatest in channels
under cover while Ca and P0 4 reductions were greatest in the non—covered
channels (TABLES 70 and 71). Partial aeration (through February 25)
appeared, again, to offer no advantage over static conditions, at least
under the conditions of this and previous tests.
The non—covered controls (TABLE 65) and L. gibba (TABLE 71) showed
similar water quality, while the covered L. gibba channels (TABLE 70) showed
greater reductions than controls except for calcium. This suggested that
L. gibba , when given protection from winter conditions, might be responsible
for the water quality improvement as compared to the non—covered controls.
However, growth of the plant under the two conditions was equal (TABLE 62).
Therefore the better water treatment in the covered channels is best
explained by the higher (though only 2 to 3°C) water temperatures and
presumably the greater bacterial activity.
Compared to previous studies, reductions in P0 4 , K, and Ca were
surprisingly high. The reason is unclear at this time.
TABLES 72 and 73 show that BOD, COD, and other values in the covered
test channels were similar to the non—covered test channels and controls
(TABLE 67). The protection from ambient winter conditions was apparently
insufficient to Induce temperature—related differences in treatment.
Standard plate counts were similar in numbers and rate of decline
(TABLES 74 and 75). However, fecal bacteria were Initially lower in the
covered channels and increased, while in the non—covered channels the reverse
113
-------
TABLE 66.
BIOCHEMICAL OXYGEN DEMAND (BOD), CHEMICAL OXYGEN
DEMAND (COD), TOTAL RESIDUE (TR), VOLATILE RESIDUE
(VR), FIXED RESIDUE (FR), AND TOTAL SUSPENDED
MATTER (TSM), OF COMPOSITE SAMPLES FROM MIXED
SpECIESa IN STATICb TEST CHANNELS, WINTER, 1977
Date
aAverage of two channels.
I .,
FR TSM
BOO COD TR VR
LU I
2/10/77
43 176 795 624 171 88
2/24/77
42 138 685 376 309 32
3/3/77
—— 125 728 447 281 47
3/7/77
—— 139 762 463 299 104
3/16/77
23 106 551 302 249 26
aS. oligorhiza
and L. gibba.
channels.
bAverage of two
TABLE 67.
BIOCHEMICAL OXYGEN DEMAND (BOD), CHEMICAL OXYGEN
DEMAND (COD), TOTAL RESIDUE (TR), VOLATILE RESIDUE
(VR), FIXED RESIDUE (FR), AND TOTAL SUSPENDED
MATTER (TsM) OF COMpOSITEa SAMPLES FROM STATIC
CHANNELS, WINTER, 1977
BOO COD TR VR FR TSM
Date
——— —————————————mg/1
2/10/77
39 168 783 628 155 104
2/24/77
30 166 777 571 206 40
3/3/77
—— 115 683 486 196 51
3/7/77
— — 146 701 490 211 100
3/16/77
21 98 546 279 267 24
114
-------
TABLE 68. STANDARD PLATE COUNT, FECAL COLIFORN, AND
FECAL STREPTOCOCCI COUNTS OF THE MIXED
SpECIESa IN STATICb TEST CHANNELS, WINTER,
1977
Date
SPC/ml FC/100 ml FS/100 ml
x x io6 x io6
2/10/77
1.6 4.7 3.1
2/24/77
2.1 5.8 4.3
3/3/77
3/7/77
2.2 6.3 5.6
2.1 5.9 5.1
3/16/77
1.8 4.9 4.7
a 5 • oligorhiza
and L. gibba.
bAverage of two
channels.
TABLE
69. STANDARD PLATE COUNT, FECAL COLIFORN, AND
FECAL STREPTOCOCCI COUNTS OF COMPOSITE 5
SAMPLES FROM CONTROL CHANNELS, WINTER, 1977
Date
SPC/ml FC/100 ml FS/100
N iü x io6 x io6
ml
2/10/77
2.6 4.7 3.7
2/24/77
2.1 6.3 5.7
3/3/77
2.4 7.6 6.9
3/7/77
1.9 5.4 5.3
3/16/77
1.8 5.7 5.1
aAverage of two channels.
115
-------
TABLE 70. WATER QUALITY OF COVERED, AERATED AND STATIC TEST CHANNELS SUPPORTING
L. gibba , WINTER, 1977
Sample
date mg/i
TKN P0 4 K Ca 02 pH
2/10/77 Aerateda 35.9 18.8 35.6 30.4 5.7 7.9
Staticb 37.4 19.4 37.2 31.9 6.5 7.7—7.8
2/15/77 Aerated 33.0 19.0 41.8 32.0 2.9 7.9
Static 33.5 19.6 40.8 28.9 0.5 7.5—7.8
2/25/77 Aerated 29.6 18.0 35.8 30.4 3.7 7.8
Static 28.9 17.0 38.0 24.8 0.6 7.7
3/2/77 Aerated 24.5 17.3 39.1 31.0 7.8
Static 24.2 14.8 38.7 31.7 7.7
3/16/77 Aerated 12.5 8.6 34.3 28.5 7.4
Static 11.5 8.2 31.7 27.3 7.2—7.4
3/31/77 Aerated 7.6 8.0 29.8 29.6 7.8
Static 8.0 7.8 26.8 28.7 7.5
%
Aerated
78.8
57.9
28.7
7.5
———
———
reduction
Static
78.6
60.2
34.3
10.0
———
———
aAerated, data from one channel. Pump failure on February 25 terminated aerated vs. static
comp aris on&.
bStatic, mean of 2 channels excluding pH.
-------
TABLE 71. WATER QUALITY OF NON—COVERED, AERATED AND STATIC TEST CHANNELS SUPPORTING
L. gibba , WINTER, 1977
Sample
date mg/i
TKN P0 4 K Ca 02 pH
2/10/77 Aerateda 32.6 18.3 33.6 30.6 5.8 7.9
Staticb 32.9 17.3 32.5 30.7 6.7 7.8—8.1
2/15/77 Aerated 30.5 18.3 36.1 29.4 4.4 7.9
Static 29.9 17.4 34,9 29.5 0.8 7.7—8.0
2/25/77 Aerated 28.4 16.4 35.2 27.8 4.7 7.8
Static 25.6 15.1 33.0 27.7 0.6 7.7—7.9
3/2/77 Aerated 25.8 15.8 37.6 31.9 7.7
Static 21.6 13.8 33.5 29.2 7.7—7.9
3/16/77 Aerated 15.8 7.1 31.4 25.8 7.4
Static 14.2 5.5 28.3 24.6 7.2—7.4
3/31/77 Aerated 10.3 6.8 31.6 26.8 7.8
Static 9.2 5.2 28.8 25.0 7.5—7.6
%
Aerated
68.4
62.8
15.9
15.9
———
———
reduction
Static
72.0
70.1
17.5
18.6
———
———
aAerated, data from one channel. Pump failure on February 25 terminated aerated vs. static
comparisons.
bStatic, mean of 2 channels excluding pH.
-------
TABLE 72. BIOCHEMICAL OXYGEN DEMAND (BOD), CHEMICAL
OXYGEN DEMAND (COD), TOTAL RESIDUE (TR),
VOLATILE RESIDUE (VR), FIXED RESIDUE (FR),
AND TOTAL SUSPENDED MATTER (TsM) OF COMPOSITEa
SAMPLES FROM L. gibba STATIC, COVERED TEST
CHANNELS, WINTER, 1977
Date
BOD COD TR yR FR TSM
————— mg/i
2/10177
42 176 867 666 201 80
2/24/77
18 95 500 335 165 36
3/3/77
—— 123 731 440 291 43
317177
—— 147 782 476 306 88
3/16/77
21 96 526 284 242 28
aAverage
of two
channels.
TABLE
73. BIOCHEMICAL OXYGEN DEMAND (BOD), CHEMICAL
OXYGEN DEMAND (COD), TOTAL RESIDUE (TR),
VOLATILE RESIDUE (VR), FIXED RESIDUE (FR),
AND TOTAL SUSPENDED MATTER (TSM), OF COMpOSITEa
SAMPLES FROM L. gibba STATIC, NON-COVERED
TEST CHANNELS, WINTER, 1977
BOD COD TR VR FR TSM
Date
— mg/i
2/10/77
46 216 884 736 148 88
2/24/77
18 115 717 350 367 22
3/3/77
—— 117 720 403 317 39
3/7/77
—— 132 743 501 242 118
3/16/77
23 101 548 280 268 34
aAverage of two channels.
118
-------
TABLE 74. STANDARD PLATE COUNT, FECAL COLIFORM, AND
FECAL STREPTOCOCCI COUNTS OF COMPOSITEa
SAMPLES FROM L. gibba STATIC, COVERED
CHANNELS, WINTER, 1977
Date
SPC/ml FC/100 ml
X i0 x 106
FS/lOO ml
x lo6
2/10/77
2.6 4.4
3.6
2/24/77
1.9 4.3
3.8
3/3/77
2.4 5.1
4.2
3/7/77
1.9 4.1
3.7
3/16/77
2.1 4.9
4.1
aAverage
of two
channels.
TABLE
75. STANDARD PLATE COUNT, FECAL COLIFORM, AND
FECAL STREPTOCOCCI COUNTS OF CONpOSITEa
SAMPLES FROM L. gibba STATIC, NON-COVERED
TEST CHANNELS, WINTER, 1977
Date
SPC/ml FC/lOO ml
X iO x io 6
FS/lOO
x io6
ml
2/10/77
2.6 8.0
7.9
2/24/77
1.8 6.3
5.9
3/3/77
2.0 6.1
5.9
3/7/77
1.9 5.4
5.3
3/16/77
2.2 7.0
6.8
aAverage of two channels.
119
-------
occurred. The bacterial increase under the covered channels suggests that
the TKN values showed greater decline in the covered channels due to the
slightly higher temperatures which could have enhanced bacterial action.
Test 9, Water Quality of Static Control Channels and Duckweed Covered
Aerated Channels, Summer, 1977
This test was conducted to evaluate growth of a mixture S. oligorhiza
and L. gibba aerated under summer conditions and to compare water quality
changes of duckweed aerated channels with static controls. Aeration under
su uner conditions had not been tested. No differences were detected
between aeration and static conditions during the winter months.
Six text channels were used for this study. All channels were flooded
with water from the anaerobic lagoon to raise nutrient levels prior to plant
stocking. On June 17, 1977 three channels were seeded with 9.09 kg of the
duckweed mixture and aeration was initiated. Three channels (without
duckweed) remained static and served as controls. Harvesting began on
July 3 when channels were covered with the duckweed.
Chemical analysis of lagoon water in previous tests indicated that TKN
and P0 4 were the best indicators of treatment. Oxygen, also useful, was
measured through the study primarily to indicate whether or not the lagoons
were aerobic. NO 3 and NO 2 were monitored to determine if nitrification was
active.
TABLE 76 shows that TKN reduction in the aerated duckweed channels (87%)
was greater than the static control (76.8%). However, during the first 24
days TKN reduction in the aerated channel was 85% and the static 67%. In the
last 20 days of the study the aerated channel showed 13% reduction compared
to 30% for the static channel. The slower decline in the test channels
the last 20 days may be explained by the oxidation of the more difficult to
degrade organic compounds, and thus replacing TKN being removed by the
duckweed. In the static channels, the more rapid decline the last 20 days
may be explained by the settling of organic compounds, and the possible
absence of a nitrification—denitrification sequence. Due to the low oxygen
and with a pH of less than 10, NHt should form and stay in solution. With—
out nitrifying and denitrifying bacteria the conversion of NH 4 ions to
nitrogen gas is greatly reduced. Settling of organic material offers a
feasible explanation for the control channels in the absence of a
nitrification—denitrification sequence.
During the first 24 days TKN reduction in the aerated channels
averaged 1.53 mg/i/day. Uptake by the duckweed accounted for .162 mg/l/day
or 11% of the TKN. Dissolved oxygen levels were high enough to permit
nitrification to occur. Undoubtedly less oxygen was present in the lower
portions of the channel, and denitrification could occur, resulting in the
loss of nitrogen as a gas. However, during the last 20 days, oxygen was
quite high, and denitrification may not have followed nitrification. The
only way significant nitrogen could be lost from the system would be through
uptake by duckweed which averaged .141 mg/l/day. The nitrogen reduction was
120
-------
TABLE 76. WATER QUALITY OF DUCKWEED COVERED TEST (AERATED) AND CONTROL (STATIC)
CHANNELS, SUMMER, 1977
Sample
date mg/i
TKN NO 3 NO 2 P0 4 DOb
6/25/77 Aeratedd 43.1 <.5 <.25 31.9 .9 7.5-7.6
Static 45.6 <.5 <.25 31.7 0 7.6—7.7
7/2/77 Aerated 33.5 <.5 <.25 30.6 .8 7.5—7.6
Static 35.7 <.5 <.25 32.2 0 7.6—7.9
7/9/77 Aerated 22.3 <.5 <.25 29.4 .9 7.4—7.5
Static 26.9 <.5 <.25 32.0 .1 7.8—7.9
7/13/77 Aerated 13.5 <1.4 <.50 30.7 1.0 7.47.5
Static 20.2 <.5 <.25 32.4 .2 7.9—8.0
7/19/77 Aerated 6.4 <2.0 <.90 24.3 2.5 7.4—7.7
Static 15.2 <.5 <.25 32.2 .7 7.8—8.0
7/27/77 Aerated 6.6 <.5 <1.60 31.8 3.1 7.4—7.6
Static 14.2 <.5 <.25 24.6 0 7.8—8.0
8/2/77 Aerated 6.5 <.5 <.90 29.5 2.9 7.4—7.5
Static 12.1 <.5 <.25 23.5 0 7.9—8.1
/8/77 Aerated 5.6 <.5 <.50 30.0 7.4
Static 10.6 <.5 <.25 24.1 7.9—8.1
% reduction Aerated
87.0
———
——
5.9
Static
76.8
———
———
23.9
——
aMeans of 3 channels, water temperature 28 ± .5°C.
bTaken between 1200-1400 hour.
CRange of 3 channels.
dCovered with a mixture of L. gibba and S. oligorhiza ; static controls without duckweed.
-------
only .04 mg/i/day. Nitrogen was probably being moved into the water column
from the sludge zone to replace that removed by the duckweed.
Nitrogen conservation may best be achieved by maintaining a complete
aerobic system, or anaerobic system with a pH of less than 10. A facultative
system in which nitrification—denitrification can occur, will result in
nitrogen loss, which is acceptable for a waste treatment scheme, but
undesirable for waste management, in which maximum utilization of nutrients
are desired.
Under the static system, phosphorus reduction (23.9%) exceeded the
aerated system (5.9%). Duckweeds do not remove high quantities of
phosphorus, and the aeration most likely kept phosphorus somewhat suspended
in the water column. The low reduction in phosphorus was seen throughout
this project and removal by duckweeds was not very effective. The develop—
ment of clones capable of concentrating phosphorus is desirable, or alternate
management schemes must be developed.
The pH of the static lagoons in this test, and others, has been
conducive to maintaining nitrogen within the system as NHI. Thus the
opportunity for extraction for use is optimized. If removal only is desired,
ammonification or a nitrification—denitrificatiott sequence would be needed.
TABLE 77 shows the yield of duckveed on the aerated system. The yield
was one of the lowest recorded, and corresponded only with winter yields.
During the summer of 1976 we also had yields lower than spring and fall
studies, but the 1976 summer yields under static conditions were over 3 fold
the 1977 summer yield.
It is interesting to note that higher yields were obtained when the
test channels were near anaerobic conditions (up to July 19). Thereafter
the yield declined. It appears that the duckweed we studied may give best
growth under anaerobic conditions. Previous tests indicated that S. oligor—
hiza and L. g ba had highest growth rates in cooler months. S. p lyrhiza ,
which performed best in sunm er temperatures, may have been a more desirable
plant. The placement of aerators in the duckweed channels created open
areas where the air surfaced. Even though this area was small, it increased
crowding of the duckweed and may have reduced growth. Further studies may
be warranted to evaluate duckweed growth and waste trearutnet under aerobic
conditions.
Chemical analysis of the duckweed (TABLE 78) agrees with previous tests.
The low TKN values were expected on the low nutrient system. The high K
levels can be accounted for by the presence of L. gibba . It is not known
if aeration reduced the TKN uptake. With the reduced growth rate N
utilization may have diminished.
122
-------
TABLE 77. YIELD OF A MIXTURE OF L. gibba AND S. oli rhiza UNDER AERATION IN
STATIC TEST CHANNELS FLOODED WITH DAIRY WASTE, SUMMER, 1977
Harvest
datea
Total/44
days
Harvest/moC
kg/ha
lbs/acre
7/3
7/19
7/26
8/1
kg
harvested/rn 2
b
wet
.582
.655
.455
.473
2.165
———
———
dry (6.8%)
.040
.045
.031
.032
.147
405
361
aMeans of 3 test channels.
bMean biomass removed from
CTotal harvest values are based on one—half hectare or acre being harvested. One—half remains for
regrowth.
-------
TABLE 78. CHEMICAL COMPOSITION OF A MIXTURE OF S. oligorhiza D L. gibba UNDER
LOW NUTRIENT A1 D AERATED CONDITIONS, SUMMER, 1977
Sample
date
% of dry
mattera
7/19/77
TKN
P
K
Ca
Fiber
Ash
Fat
NFE
Crude
protein
5.33
1.12
3.30
.
1.57
10.0
15.1
6.7
27.4
33.3
7/25/77
5.15
1.03
3.42
1.41
8.9
12.9
6.9
37.5
32.2
8/1/77
5.23
1.04
3.39
1.67
8.0
14.2
5.5
35.9
32.7
8/8/77
5.31
1.10
4.13
1.65
8.1
15.1
6.9
33.2
33.2
8/15/77
4.59
1.01
4.40
1.64
9.3
15.1
6.6
34.5
28.7
aNn of 3 channels.
bT X 6.25.
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PRELIMINARY FEEDING TRIALS
Palatabi liiy
S. polyrhiza and S. oligorhiza were presented to young dairy cows
(204—227 kg). The plants were grown on dairy waste lagoons, harvested,
rinsed and presented wet or dry alone or in c,ombination with a feed concen-
trate (corn meal). Duckweed ranged from 0 (controls) to 100% of the diet.
The duckweed was palatable whether or not it was mixed with a feed
concentrate. However, at the 100% duckweed diet the cows were reluctant
to feed on it unless washed. Animals consumed up to 75% duckweed ration
readily for a period of 26 days and gained in weight. The animals on the
diet showed no external signs of health disorders such as extreme weight
loss, loss of appetite, diarrhea, or nervousness.
Milk Quality
In a preliminary test to determine if any serious problems were evident
with milk quality from cows fed duckweed, a single lactating cow was given
a diet containing a combination of duckweeds (ca 25% of diet on dry weight
basis) for 7 days. No significant change in milk flavor other than a
possible increase in fat acid degree value was detected.
Digestibility
Separate “in vitro” digestibility studies with S. oligorhiza ,
S. polyrhiza , and L. gibba , showed digestibility of about 70%. This is
within the range of current rations. Wolf fia sp. showed “in vitro”
digestibility of 97%. This value exceeds typical cattle feeds, suggesting
a high quality of feed. Further nutritional research is needed before
duckweeds can be recommended as a feed source.
125
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SECTION 8
DISCUSSION
SPECIES COMPOSITION
As noted in Tests 5, 6, and 8, mixed culture treatments exhibited no
significantly different yields than treatments containing one species or
clone. It is a broadly accepted dogma of ecologists that diversity promotes
stability. The utilization of mixed cultures of several species and/or
clones has two potential advantages. Seasonal dominance of one or more
clones would alter the relative composition of the plant biomass. This
would tend to even out yield over the entire year and allow a more reliable
feed supply—utilization scheme, perhaps lessening the need for storage.
The second potential advantage of mixed cultures is the stability
expected against pests and/or disease. Pests of duckweeds are few, but
Scotland (1934; 1940) dIscusses and reviews obligate and facultative
relationships between aquatic insects and species of Lemna . Since clones
inherently have only small amounts of genetic variability, an infestation
or disease could have devastating and rapid effects on the plant stand.
Polyclonal cultures would theoretically be less susceptible to such
hazards. Though few diseases or pests of duckweeds are known, it is
important to recognize the possibility of their existence, and to manage
duckweed cultures accordingly.
ANNUAL AND SEASONAL YIELD
Utilizing yield estimates calculated for each experiment two estimates
of total annual yield (dry weight) per hectare were determined. One
estimate was based on mean yield (irrespective of species and treatment)
as shown in TABLE 79. The second estimate was based on the highest yield
during each 3—month period (also irrespective of species and treatments).
Yield was estimated to be 17,577 kg/ha/yr (mean) and 22,023 kg/ha/yr (high).
The former value indicates the average yield that would have been produced
annually if grown on a one hectare lagoon. The latter value is an estimate
of the best annual yield obtained (for the prevailing conditions during the
study) on a one hectare basis.
Seasonal variation of yield (mean) was dramatic. Winter yield was
approximately 25% of fall yield while spring and summer yields were
approximately 75% of the yield during the fall months. This variation
could be decreased if duckweed clones are found to be optimally suited
to each season, thus stabilizing supply for the utilization of the plants.
126
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TABLE 79. ESTIMATED ANNUAL DRY WEIGHT YIELD PER
RECTARE OF DUCKWEEDS PRODUCED ON LAGOONS
RECEIVING DAIRY CATTLE WASTES, 1976 _ 77 a
Tn—monthly basis
mean yield highest yield
(single estimate)
Yield May — July 1663 kg/mo 2215 kg/mo
X 3 months X 3 months
subtotal 4989 kg 6645 kg
Yield Aug. — Oct. 2122 kg/mo 2143 kg/mo
X 3 months X 3 months
subtotal 6366 kg 6429 kg
Yelid Nov. — Jan. 518 kg/mo 761 kg/mo
X 3 months X 3 months
subtotal 1554 kg 2283 kg
Yield Feb. — April 1556 kg/mo 2222 kg/mo
X 3 months X 3 months
subtotal 4668 kg 6666 kg
Totaib 17,577 kg/ha/yr 22,023 kg/ha/yr
aVai s are irrespective of species and treatment.
bTo obtain lb/ac/yr multiply by 0.893.
127
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Further research should include plant screening and selective breeding
studies to obtain clones which are adapted (seasonally) to remove or reduce
the variation of yield.
Based on the mean chemical content of the plants; 1,019 kg N, 248 kg P,
and 353 kg K would have been removed via harvest from one hectare. Each
454 kg cow excretes 0.18 kg of N, 0.02 kg of P, and 0.11 kg of K daily
(Loehr, 1969). Based on these values, the duckweeds harvested per hectare
effectively removed N of 15.5 cows, P of 34.0 cows, and K of 8.8 cows. It
should be noted that the lagoon system was overloaded during the study and
the dynamics of nutrient removal under lower nutrient concentrations may
differ substantially from this.
Though duckweeds in this system were grown on cattle wastes, growth has
been demonstrated on swine wastes (Culley and Epps, 1973; Stanley and
Madewell, 1975) and should be applicable to other animal waste lagoon
systems. Duckweeds may find application as part of municipal, chemical
plant, and food processing plant waste treatment systems as well.
NUTRIENT PLASTICITY
Duckweeds show the ability to increase dry weight percentages of
nutrients when placed on waters containing high concentrations of nutrients
or upon periodic reflooding. An optimum dilution rate for growth of L. minor
on swine wastes was determined by Stanley and Madewell (1975). It appears
that separate optima for growth and nutrient content of duckweed clones are
likely to exist. Also, It is probable that there exists an optimum range
for water rennovation efficiency. During the study, growth rate did not seem
to decline until TKN of the water was below ca 20 mg/i. To validate this
statistically simultaneous studies need to be performed under different
nutrient regimes. This was unfortunately obviated by physical limitations
of the lagoon system in this study.
Further research involving long term growth and nutrient content studies
in relation to water chemistry are needed, as this system frequently was
operated at overloaded conditions and in an unusually low rainfall year.
Clearly, if stable economic benefits are to be derived from the waste
rennovation system, lagoon management schemes must attempt to optimize:
(1) plant nutrient content, (2) growth, and (3) water rennovation efficiency.
Thus, further study is needed to delineate optimum concentrations of bovine
wastes in relation to the above criteria.
POTENTIAL ECONOMIC BENEFITS
As stated by Wolverton, Barlow, and McDonald (1975) and NAS (1976),
aquatic plants are potentially useful as feed, energy, and fertilizer
sources. If one of these potentials could be exploited, utilization of a
waste treatment system for producing aquatic plant crops might prove economi-
cal to agricultural operations and improve waste treatment.
128
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Nutrient content of unprocessed duckweeds compare favorably with
processed high protein crops, used as livestock feed protein supplements,
as shown in TABLE 80. Mean crude protein content during this study
(irrespective of species and treatments) was 36%. Duckweeds, however,
have been shown to contain 40 to 45% (dry weight) crude protein (Truax
et al., 1972; Culley and Epps, 1973). This indicates the potential value
of duckweeds as a protein supplement (NAS, 1971). As a feed for cattle
duckweeds have been shown to be palatable. The only potentially harmful
nutrient, observed in this study, was the potassium content of L. gibba
(4.2%) which could possibly upset the cation balance in dairy cattle. The
concentration may be compensated for by “dilution” with other plant materials
containing lower amounts of potassium. Some duckweeds contain calcium
oxalate crystals but it is not detrimental to cattle.
Yield of duckweeds exceeds those of the high protein crops shown in
TABLE 80. Yield estimates (high and mean) of duckweeds are from TABLE 79.
Multiplying yield (kg/ha) by the percentage of crude protein represents
the total protein yield (TPY). From these values, hectare equivalents were
determined by dividing TPY for each crop into the TPY of duckweeds. Thus,
for example, one hectare of duckweed would produce the equivalent protein of
26 and 32 hectares of cotton (seed, mech—extd.), using the mean and high
duckweed estimates respectively.
The economic feasibility of using duckweeds as an ingredient in a
protein supplement for dairy cattle was determined by using Feedmix, a
computer program (Just et al., 1968 as modified by Pope). Various feed
sources (including those shown in TABLE 80) were entered at fixed prices
(average prices for the first six months of 1977) and duckweed was entered
at variable price. Results indicate that the value of duckweed would vary
between $3.50 and $5.57 per hundred weight depending on the particular
formulation. For example, one possible formulation containing 18.69%
duckweed would be economically feasible if the cost of duckweed did not
exceed $3.79 per hundred weight. Thus, cost of production, transportation,
and processing of duckweeds could not exceed $3.79 per hundred weight for
this particular formulation to be economical. Considering the yield per
hectare and the close proximity of the plant source to the point of
consumption; if on site processing .was feasible, the above price constraints
were met, and the total yield (high) were utilized as protein supplement
ingredients for this particular ration, the producer would save an estimated
$745.38 per acre—year ($1841.09 per hectare—year).
Hromadka (1976) found that the predominant method of waste management
for Louisiana dairymen was lagooning. For herds with greater than 100 head,
he determined average investment cost for lagooning was $3,266.67 or
$17.49 per head. If duckweeds are grown and utilized on a lagoon waste
treatment system, it appears that the investment and operating costs could
be recovered while still providing the necessary waste treatment, based on
the above figures. It should be clear, however, that the economic efficiency
of agriculture is due to the low cost of fossil fuels. United States agri—
culture is energy intensive and any increase in fuel costs will have an
adverse impact on feed costs. Duckweeds may be a low energy cost crop, and
may become an even more attractive alternative in the future.
129
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TAZLE 80.. PARTIAL CHEMICAL COMPOSITION AND YIELD COMPARISONS OF SOME COMMON ANIMAL FEED PROTEIN SUPPLEMENTS 5 AND DUCKWEEDS
Yie ldb
Plant material kg/ha
%
dry weight
Crude
protein
yield
kg/ha
Hectare
equivalents
Cotton, seed w some hulls
mech—extd. grnd
448
Crude
protein
N
P
K
Ash
Fiber
Ca
Fat
200
mean
32 40
44.7
7.2
1.18
1.35
6.6
11.8
.20
6.0
Soybean, seeds, solv—extd.
5—04—604 1263
52.4
•
8.4
.73
2.15
6.6
5.9
.33
1.3
662
10 12
Peanut, kernels, solv-extd.
5—03—650 1792
51.8
8.3
.71
———
4.9
14.3
.22
1.3
928
7 9
Corn, gluten w bran
5—02—903 1630
28.6
4.6
.86
.63
7.3
8.1
.49
2.9
466
14 17
Duckweedsd 17577
22023
(mean)
(high)
36
5.8
1.41
2.01 13.7
8.3
1.7
4.8
6328
7928
(mean)
(high)
1
1
aSource: Atlas of Nutr. Data on U.S. and Can. Feeds . NAS. Wash., D. C. 1971.
bAll values except duckweed based on data from: Louisiana Crop Production , USDA, La. Crop and Livestock Reporting Service, Alexandria,
La., 1975.
CNational Academy of Science feed reference number.
d ans during this study irrespective of treatments and species.
I-
0
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LAGOON MANAGEMENT
Although lagoon systems have been used in agricultural operations for
many years, we located no research data concerning management of lagoons
to optimize aquatic plant production. This study elucidated several points
for future research in this regard.
Optimum water nutrient content for the use of bovine wastes in aquatic
plant production is not known. As indicated earlier, separate optima of
different clones in relation to growth, nutrient content, and water
rennovation efficiency may exist. Polyclonal cultures will also need to be
considered in further detail in regard to lagoon management. If efficiency
of a waste treatment system utilizing aquatic plants is to be achieved,
then comparative studies of lagoon management schemes are needed.
As shown in several of our experiments, duckweeds exhibited increased
nutrient content when grown on high nutrient waters. Periodic addition of
nutrients may prove valuable in producing a better quality plant for feed.
Covering duckweed channels during cold weather was shown to be
partially effective; however, further work is needed. Screening of duck—
weeds and selective breeding to obtain cold—tolerant clones is needed.
If winter growth could be increased, by obtaining cold—tolerant clones or
increasing lagoon temperatures, water renovation efficiency could possibly
be increased during the winter season.
WATER QUALITY
Of the several chemical and physical parameters measured through this
study, TKN and P appeared most useful in evaluating water quality. Phos-
phorus may be the best single measure of water quality due to its slow
removal over time and its importance in contributing to eutrophication in
receiving waters. The TKN, due to its value as a plant nutrient and rather
consistent decline over time in all tests, also proved useful in evaluating
water quality. However, the TKN value includes many nitrogen sources which
vary considerably. 1’ hile the total TKN may be declining, readily available
plant nutrient components may be increasing, and stimulate plant growth in
receiving waters. A measurement of the TKN alone would not elucidate the
cause.
Phosphorus removal may or may not be accelerated in aerobic treatment as
compared to anaerobic. Tables of Test 6 (49 to 51) indicated greater
removal, but was refuted in Test 9 (TABLE 76).
There was a discrepancy between the rates of phosphorus decline we
observed and the phosphorus removed by plant growth. Phosphorus content
of the duckweeds ranged from 1.32% to 1.55% (dry weight) for the Test 6
study. Calculations based on plant harvest during this period show that
the quantity of phosphorus removed as plant material would reduce orthophos—
phate concentration in the test channels by approximately 0.6 mg/i (0.02 mgI
i/day). This rate is considered low. Sutton and Ornes (1975) gave
131
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phosphorus rate at approximately 0.09 mg/i/day for a 28 day retention time in
their work with a mixed culture of L. gibba and L. minor grown on static
sewage effluent.
Phosphorus may have been removed by the sludge layer. Wells (1969)
found that certain acclimated sludges were capable of removing phosphorus
from waste waters at rates of 65 mg/i/hr. Wells also found that 50% of
the phosphorus moved between the sludge layer and the water column. The
reaction was oxygen dependent, but he was unable to characterize the sludge
further. Such a mechanism may have been operative in our test channels.
Minimizing the sludge zone would tend to keep phosphorus in solution and
facilitate uptake by duckweeds. In our system, which had high loading rates,
the sludge layer approached 15 cm at times. This layer could have accounted
for the variation in percent phosphorus reduction between duckweed and
control channels.
Removal of phosphorus from animal waste water systems may be the most
difficult problem of all. We encountered greater than 30 mg/i phosphorus
concentrations in the effluent. The possibility of obtaining a clone of
duckweed that concentrates phosphorus cannot be ruled out. However, until
a mechanism for phosphorus removal is developed for lagoon systems, the only
realistic means of reducing phosphorus is an effluent is by decreasing
loading rates.
Nitrogen uptake during plant growth accounted for only part of the
nitrogen leaving the duckweed channels and did not explain nitrogen loss
from control channels. Approximately 5.05 kg (dry matter) of S. oligorhiza /
channel was harvested during the summer study. Based on a mean TKN content
of 5.72%, approximately 0.29 kg of TKN was removed as plant material. When
corrected for water loss of 16 cm, the concentration of TKN removed from the
system was calculated to be 48.1 mg/i. Of the 48.1 mg TKN/l removed,
11.0 mg TKN/l or 23% was accounted for by plant harvest. Similar calcula-
tions showed nitrogen removed as plant material accounted for 10.4% and
19.8% of the total nitrogen reductions for the Test 6 and 7 studies
respectively. Settling or organic matter was undoubtedly responsible for
a part of the observed decline, but nitrification—denitrification processes
may have been important since the system was facultative at times.
Other workers attributed nitrogen losses to volatilization of ammonia
but ammonia stripping requires a pH near 10 and a high air/liquid ratio.
The pH requirement is based on the equilibrium of molecular ammonia and
aninonium ions In water and Is represented by the following equation:
NHX +0H+N} 1 3 +H 2 0
Below a pH of 10, ainmonium ion predominates and little stripping should
occur. The pH of the test channels ranged from 7.0 to 8.5 for all studies.
Samples (1967) and Painter (1970) give the following conditions as
favorable to nitrification:
132
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Dissolved Oxygen > 0.5 mg/i
Temperature 50 to 45°C
Detention Time 8 hours
pH 6.5 to 9.5
BOD/VS < 0.4 mg/i
Previous data indicated that the temperature, detention time, PH, and BOD/VS
ratio criteria were satisfied throughout the three studies. Oxygen levels
were sufficient during part of both winter studies, and presence of phyto—
planton blooms at and slightly below the surface, and the continued
appearance of zooplankton populations indicated that the test channels
were slightly aerobic in the upper few cm. Conditions for nitrification
to occur, at least in the upper few cm, were probably satisfied. Thus
complex nitrogen compounds could be degraded to ammonium ions and further
oxidized to nitrites and nitrates.
Conversion of the nitrites and nitrates to nitrogen gas (denitrifica—
tion) takes place under anaerobic and near—anaerobic (0.5 mg/i oxygen)
conditions (Wheatland, Barrett, and Bruce, 1959). Nitrification—
denitrification along a vertical oxygen gradient (as in our system) in a
pig manure lagoon was, however, conclusively demonstrated by van Fassen
and Dijk (1974), and Patrick et al., 1976 with flooded soils. Thus it was
likely that some nitrogen loss occurred in our system through nitrification—
denitrification, but we do not know if a significant amount was removed.
Potassium is seldom regarded as a pollutant and is generally overlooked
in discussions of animal waste treatment operations. We monitored potassium
since it is a plant nutrient and of vital importance in cattle feeds.
Duckweeds remove potassium, and could affect the quantity of duckweeds
blended with cattle rations. The slow decline of potassium was likely due
to leaching from the sludge layer, as in laboratory tests rapid leaching
of P0 4 from sludge was demonstrated.
The difference in calcium levels between lagoons results from different
loading rates and soil content. The mean concentrations of calcium were
71.3 mg/l and 62.7 mg/i for test lagoons 1 and 2 respectively. Calcium
levels varied in like manner for both duckweed channels and controls. We
expected plant uptake to reduce calcium levels in the duckweed channels, but
it was apparently offset by leaching from the soil and sludge layer.
Further analysis of data may show some useful relationships between
TOC, TSM, TKN, COD, TR, and P in evaluating effluent quality. Should there
be a fixed ratio between TOC, COD, TR, or TSM and TKN or P, then a single
measurement may prove useful in monitoring waste water effluent involving
macronutrients.
Total suspended solids was useful in indicating a potential settleable
load, or a reduction in light penetration. However, it tells nothing of the
associated nutrient load or nutrients in solution. The total residue
includes both the volatile and fixed residue. There may be a useful ratio
index between the TR and TKN or phosphorus. Further analysis is needed to
make these determinations.
133
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BACTERIOLOGICAL IMPLICATIONS
Although considerable effort was placed on bacterial analysis in this
study, it must be remembered that the system was overloaded with waste
material. In evaluating the performance of duckweed at high nutrient levels,
high concentrations of bacteria were introduced into the system. The
declines observed were expected, as well as the high concentrations.
Although pathogenic bacteria were evident in the lagoons, they were
confined primarily near the floor. Overflow from the lagoons was from
surface waters associated with the duckweed. Pathogenic bacteria were not
found in the effluent. In addition, studies on the palatability, growth,
and milk quality failed to show evidence of disease transmission, though
further studies are needed. When using duckweed as a feed ingredient, it
was always washed with chlorinated water. This practice should be
continued as a safety precaution.
LAGOONS AND LAND APPLICATION
Throughout this study, it became clearly evident that land application
of manure was labor intensive and expensive as compared to lagooning. In
high rainfall areas, such as the southeastern section of the country, dry
seasons are unpredictable. Planned irrigation of waste water from our
lagoons was difficult. For example, during August 1977 our study area
received over 35.6 cm of rain. This month is normally one of our drier
months. Irrigation was out of the question. Manure spreading resulted in
increased man hours, damage to pasture surface and drainage, and an increase
in energy consumption. Stockpiling the manure during wet days resulted in
odor and potential health problems. Five to ten cm rains are not uncommon
in the southeast, and runoff simply removes nutrients before assimilation.
Regarding our system, in which we are interested in waste management
(nutrient recovery and use), with an effective waste treatment process also
being achieved, the nitrification—denitrification process posed a problem.
Because inorganic nitrogen fertilizers require a high energy input to
manufacture, maximum recovery of nitrogen from the lagoon system is
desirable. Denitrification, which probably is most active at night, and in
the lower portion of the lagoons, could result in a considerable loss of
nitrogen as gas. Maintaining the system under complete anaerobic conditions
and a pH of less than 10 or complete aerobic conditions should reduce the
nitrogen loss and optimize the chance of recovery through the duckweed
system. One particular advantage in using duckweeds is their capability of
absorbing complex molecules (amino acids, sugars, etc.), thus having
heterotrophic growth characteristics (Hillman, 1961). Not only can they
remove complex organic nitrogen compounds, but the plants will continue to
assimilate nutrients in the absence of light.
Through proper clonal selection strains of duckweeds may well be
developed that greatly enhance nitrogen recovery. The addition of other
nutrient—consuming organisms, with a marketable value, placed In a series
of connecting lagoons could then provide for additional nutrient recovery
and help offset or pay for the treatment facility. Figure 15 depicts such a
134
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1 Two-acre lagoons
2 Skimmer
3 Harvesting canal
4 Washwater line
5 Conveyor/strainer
6 Washwater collection pit
7 Feed trailer
9 Feeding trough 17 Gas scrubber
10 Feedlot covered with solar collector 18 Methane gas stomge
system 19 Generator
11 Duct drawing heated air from roof 20 Waste sludge to lagoons via heat
12 Heat storage exchange in waste pit
13 Drying tunnel 21 Final stage lagoon treatment
14 Waste pit 22 Aquaculture system
15 Milking center 23 Orchard
16 Fermentation unit 24 Pasture
8 Feeding alley
I- .
LA)
U i
DRAWING BY DOUG REED
11*) COOPERATIVE EXTENSION SERVICE ART STUDIO
Figure 15. A schematic plan of an aquacultural waste treatment system involving duckweed.
-------
schematic plan. In this system, emphasis is also given to energy recovery
through the installation of a manure fermentation unit and solar collector
system. Evidence presented in this study indicates that the proposed
system shown in Figure 15 would be superior to land application.
ANIMAL FEEDS
The “in vitro” digestibility of Wolf fia sp. indicates a need for further
study in culturing this plant. The clone was slow in adapting to lagoon
conditions, but once established production appeared high. In preliminary
trials for selecting the species for this study, a crude protein level of
30% was obtained for Woiffia . Under controlled nutrient systems the protein
may approach other duckweeds.
The greatest disadvantage of Wolf f Ia is its high water content, about
96%. Clonal selection should improve the condition however. If production
and crude protein content approaches those of other duckweeds, then, due to
its high digestibility more usable bioinass will be realized. The high
digestibility, Indicating little fibrous tissue, places it as a potential
human food.
136
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SECTION 9
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TECHNICAL REPORT DATA
(l’leaSe read Jn&z.ruetions on the reverse before comple ring)
1. REPORT NO. 2.
EPA—600/2—78—153
3. RECIPIENT’S ACCESSIOI’#NO.
4. TITLE AND SUBTITLE
WATER QUALITY RENOVATION OF ANIMAL WASTE LAGOONS
UTILIZING AQUATIC PLANTS
5. REPORT DATE
July 1978 issuing date
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
D. D. Culley, Jr., J. H. Gholson, T. S. Chishoirn,
L. C. Standifer, and E. A. Epps
8. PERFORMING ORGANIZATION REPORT NO.
. PERFORMING ORGANIZATION NAME AND ADDRESS
Louisiana Agricultural Experirnentf Station
Louisiana State University and Agricultural and
Mechanical College
Baton Rouge, Louisiana 70803
10. PROGRAM ELEMENT NO.
1BB77O
11. CONTRACT/GRANT NO.
R—803326
12. SPONSORING AGENCY NAME AND ADDRESS
Robert S. Kerr Environmental Research Lab. — Ada, OK
Off ice of Research and Development
U.S. Environmental Protection Agency
Ada, Oklahoma 74820
13. TYPE OF REPORT AND PERIOD COVERED
Final (7/75 — 12/77)
14. SPONSORING AGENCY CODE
EPA/600/l5
15. SUPPLEMENTARY NOTES
16. ABSTRACT
Duckweeds Spirodela oligorhiza , S. polyrhiza , and Lernna gibba (clone G3) grown on
dairy waste lagoons gave an estimated maximum annual yield of 22,023 kg dry wt./ha.
S. oligorhiza and L. gibba had higher growth rates in the spring, fall, and winter,
with L. gibba growing throughout most of the winter. Nutrient content of the plants
increased with increasing nutrients in the lagoons. Mean crude protein of dry duck—
weeds was 36%, to a maximum of 42%. Maximum protein yield/rn 2 exceeded protein
produced by peanuts, soybeans, and cottonseed 9, 12, and 40 fold respectively. The
duckweeds recovered on a hectare basis the N, F, and K of 15.5, 34, and 8.8 lactating
COWS respectively. Reductions in lagoon TKN, NHt, and P were significantly greater
in the duckweed lagoons than controls. Reduction of TKN averaged 0.91 mg/i/day in
summer for duckweed—covered lagoons and 0.74 mg/i/day for controls. During the winter
the rate was 1.27 mg/i/day (duckweed lagoons) and 0.82 mg/i/day for controls.
Ammonium reduction was 84% greater in the duckweed lagoons during winter. Phosphorus
reduction in duckweed lagoons, though significantly different from controls, was
insufficient to meet water quality standards.
17. KEY WORDS AND DOCUMENT ANALYSIS
a. DESCRIPTORS b.IDENTIFIERS/OPEF ’J ENDED TERMS C. COSATI Field/Group
Aquaculture, Hydroponics, Dairy cattle,
Agricultural wastes, Materials recovery
Duckweed, Clones,
Manure, Animal feed,
Culture lagoons
43F
57C
57H
6 8D
9 8A
9 8F
18. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (ThisReport)
UNCLASSIFIED
21. NO. OF PAGES
166
20. SECURITY CLASS (This page)
UNCLASSIFIED
22. PRICE
EPA Form 2220.1 (9.73)
149
U.S. GOVERNMENT PRINTING OFFICE 1978—757—140/1428 Region No. 5—fl
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